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Sample records for insulin promoter activity

  1. Acute activation of GLP-1-expressing neurons promotes glucose homeostasis and insulin sensitivity.

    Science.gov (United States)

    Shi, Xuemei; Chacko, Shaji; Li, Feng; Li, Depei; Burrin, Douglas; Chan, Lawrence; Guan, Xinfu

    2017-11-01

    Glucagon-like peptides are co-released from enteroendocrine L cells in the gut and preproglucagon (PPG) neurons in the brainstem. PPG-derived GLP-1/2 are probably key neuroendocrine signals for the control of energy balance and glucose homeostasis. The objective of this study was to determine whether activation of PPG neurons per se modulates glucose homeostasis and insulin sensitivity in vivo. We generated glucagon (Gcg) promoter-driven Cre transgenic mice and injected excitatory hM3Dq-mCherry AAV into their brainstem NTS. We characterized the metabolic impact of PPG neuron activation on glucose homeostasis and insulin sensitivity using stable isotopic tracers coupled with hyperinsulinemic euglycemic clamp. We showed that after ip injection of clozapine N-oxide, Gcg-Cre lean mice transduced with hM3Dq in the brainstem NTS downregulated basal endogenous glucose production and enhanced glucose tolerance following ip glucose tolerance test. Moreover, acute activation of PPG neurons NTS enhanced whole-body insulin sensitivity as indicated by increased glucose infusion rate as well as augmented insulin-suppression of endogenous glucose production and gluconeogenesis. In contrast, insulin-stimulation of glucose disposal was not altered significantly. We conclude that acute activation of PPG neurons in the brainstem reduces basal glucose production, enhances intraperitoneal glucose tolerance, and augments hepatic insulin sensitivity, suggesting an important physiological role of PPG neurons-mediated circuitry in promoting glycemic control and insulin sensitivity. Copyright © 2017 The Authors. Published by Elsevier GmbH.. All rights reserved.

  2. Acute activation of GLP-1-expressing neurons promotes glucose homeostasis and insulin sensitivity

    Directory of Open Access Journals (Sweden)

    Xuemei Shi

    2017-11-01

    Conclusions: We conclude that acute activation of PPG neurons in the brainstem reduces basal glucose production, enhances intraperitoneal glucose tolerance, and augments hepatic insulin sensitivity, suggesting an important physiological role of PPG neurons-mediated circuitry in promoting glycemic control and insulin sensitivity.

  3. mTORC2 promotes type I insulin-like growth factor receptor and insulin receptor activation through the tyrosine kinase activity of mTOR.

    Science.gov (United States)

    Yin, Yancun; Hua, Hui; Li, Minjing; Liu, Shu; Kong, Qingbin; Shao, Ting; Wang, Jiao; Luo, Yuanming; Wang, Qian; Luo, Ting; Jiang, Yangfu

    2016-01-01

    Mammalian target of rapamycin (mTOR) is a core component of raptor-mTOR (mTORC1) and rictor-mTOR (mTORC2) complexes that control diverse cellular processes. Both mTORC1 and mTORC2 regulate several elements downstream of type I insulin-like growth factor receptor (IGF-IR) and insulin receptor (InsR). However, it is unknown whether and how mTOR regulates IGF-IR and InsR themselves. Here we show that mTOR possesses unexpected tyrosine kinase activity and activates IGF-IR/InsR. Rapamycin induces the tyrosine phosphorylation and activation of IGF-IR/InsR, which is largely dependent on rictor and mTOR. Moreover, mTORC2 promotes ligand-induced activation of IGF-IR/InsR. IGF- and insulin-induced IGF-IR/InsR phosphorylation is significantly compromised in rictor-null cells. Insulin receptor substrate (IRS) directly interacts with SIN1 thereby recruiting mTORC2 to IGF-IR/InsR and promoting rapamycin- or ligand-induced phosphorylation of IGF-IR/InsR. mTOR exhibits tyrosine kinase activity towards the general tyrosine kinase substrate poly(Glu-Tyr) and IGF-IR/InsR. Both recombinant mTOR and immunoprecipitated mTORC2 phosphorylate IGF-IR and InsR on Tyr1131/1136 and Tyr1146/1151, respectively. These effects are independent of the intrinsic kinase activity of IGF-IR/InsR, as determined by assays on kinase-dead IGF-IR/InsR mutants. While both rictor and mTOR immunoprecitates from rictor(+/+) MCF-10A cells exhibit tyrosine kinase activity towards IGF-IR and InsR, mTOR immunoprecipitates from rictor(-/-) MCF-10A cells do not induce IGF-IR and InsR phosphorylation. Phosphorylation-deficient mutation of residue Tyr1131 in IGF-IR or Tyr1146 in InsR abrogates the activation of IGF-IR/InsR by mTOR. Finally, overexpression of rictor promotes IGF-induced cell proliferation. Our work identifies mTOR as a dual-specificity kinase and clarifies how mTORC2 promotes IGF-IR/InsR activation.

  4. Insulin promotes diacylglycerol kinase activation by different mechanisms in rat cerebral cortex synaptosomes.

    Science.gov (United States)

    Zulian, Sandra E; Ilincheta de Boschero, Mónica G; Giusto, Norma M

    2006-10-01

    The mechanism by which insulin increases diacylglycerol kinase (DAGK) activity has been studied in cerebral cortex (CC) synaptosomes from adult (3-4 months of age) rats. The purpose of this study was to identify the role of phospholipases C and D (PLC and PLD) in DAGK activation by insulin. Neomycin, an inhibitor of PLC phosphatidylinositol-bisphosphate (PIP2) specific; ethanol, an inhibitor of phosphatidic acid (PA) formation by the promotion of a transphosphatidyl reaction of phosphatidylcholine phospholipase D (PC-PLD); and DL propranolol, an inhibitor of phosphatidate phosphohydrolase (PAP), were used in this study. Insulin (0.1 microM) shielded an increase in PA synthesis by [32P] incorporation using [gamma-32P]ATP as substrate and endogenous diacylglycerol (DAG) as co-substrate. This activated synthesis was strongly inhibited either by ethanol or DL propranolol. Pulse chase experiments also showed a PIP2-PLC activation within 1 min exposure to insulin. When exogenous unsaturated 18:0-20:4 DAG was present, insulin increased PA synthesis significantly. However, this stimulatory effect was not observed in the presence of exogenous saturated (di-16:0). In the presence of R59022, a selective DAGK inhibitor, insulin exerted no stimulatory effect on [32P]PA formation, suggesting a strong relationship between increased PA formation by insulin and DAGK activity. These data indicate that the increased synthesis of PA by insulin could be mediated by the activation of both a PC-PLD pathway to provide DAG and a direct DAGK activation that is associated to the use of 18:0-20:4 DAG species. PIP2-PLC activation may contribute at least partly to the insulin effect on DAGK activity. Copyright 2006 Wiley-Liss, Inc.

  5. Insulin induces a transcriptional activation of epiregulin, HB-EGF and amphiregulin, by a PI3K-dependent mechanism: Identification of a specific insulin-responsive promoter element

    International Nuclear Information System (INIS)

    Ornskov, Dorthe; Nexo, Ebba; Sorensen, Boe S.

    2007-01-01

    Previously we have shown that insulin-stimulation of RT4 bladder cancer cells leads to increased proliferation, which require HER1 activation, and is accompanied by increased mRNA expression of the EGF-ligands heparin-binding EGF-like growth factor (HB-EGF), amphiregulin (AR), and epiregulin (EPI) [D. Ornskov, E. Nexo, B.S. Sorensen, Insulin-induced proliferation of bladder cancer cells is mediated through activation of the epidermal growth factor system, FEBS J. 273 (2006) 5479-5489]. In the present paper, we have investigated the molecular mechanism leading to this insulin-induced expression. We monitored the decay of mRNA after inhibiting transcription with Actinomycin D and demonstrated that the insulin-mediated increase was not caused by enhanced mRNA stability. In untreated cells, HB-EGF mRNA was the least stable, whereas AR and EPI mRNA decayed with slower kinetics. However, promoter analysis of HB-EGF and EPI demonstrated that insulin stimulated transcription. Studies on the EPI promoter identified the insulin-responsive element to be located in the region -564 to -365 bp. This region contains potential binding sites for the transcription factors SP1, AP1, and NF-κB. Interestingly, all three transcription factors can be activated by PI3K. We demonstrate that the insulin-induced expression of HB-EGF, AR, and EPI mRNA is completely prevented by the specific PI3K inhibitor Wortmannin, suggesting an involvement of the PI3K

  6. Acute activation of GLP-1-expressing neurons promotes glucose homeostasis and insulin sensitivity

    OpenAIRE

    Xuemei Shi; Shaji Chacko; Feng Li; Depei Li; Douglas Burrin; Lawrence Chan; Xinfu Guan

    2017-01-01

    Objective: Glucagon-like peptides are co-released from enteroendocrine L cells in the gut and preproglucagon (PPG) neurons in the brainstem. PPG-derived GLP-1/2 are probably key neuroendocrine signals for the control of energy balance and glucose homeostasis. The objective of this study was to determine whether activation of PPG neurons per se modulates glucose homeostasis and insulin sensitivity in vivo. Methods: We generated glucagon (Gcg) promoter-driven Cre transgenic mice and injected...

  7. Insulin promotes cell migration by regulating PSA-NCAM

    Energy Technology Data Exchange (ETDEWEB)

    Monzo, Hector J.; Coppieters, Natacha [Centre for Brain Research, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag, 92019, Auckland (New Zealand); Department of Anatomy and Medical Imaging, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag, 92019, Auckland (New Zealand); Park, Thomas I.H. [Centre for Brain Research, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag, 92019, Auckland (New Zealand); Department of Pharmacology, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag, 92019, Auckland (New Zealand); Dieriks, Birger V.; Faull, Richard L.M. [Centre for Brain Research, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag, 92019, Auckland (New Zealand); Department of Anatomy and Medical Imaging, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag, 92019, Auckland (New Zealand); Dragunow, Mike [Centre for Brain Research, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag, 92019, Auckland (New Zealand); Department of Pharmacology, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag, 92019, Auckland (New Zealand); Curtis, Maurice A., E-mail: m.curtis@auckland.ac.nz [Centre for Brain Research, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag, 92019, Auckland (New Zealand); Department of Anatomy and Medical Imaging, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag, 92019, Auckland (New Zealand)

    2017-06-01

    Cellular interactions with the extracellular environment are modulated by cell surface polysialic acid (PSA) carried by the neural cell adhesion molecule (NCAM). PSA-NCAM is involved in cellular processes such as differentiation, plasticity, and migration, and is elevated in Alzheimer's disease as well as in metastatic tumour cells. Our previous work demonstrated that insulin enhances the abundance of cell surface PSA by inhibiting PSA-NCAM endocytosis. In the present study we have identified a mechanism for insulin-dependent inhibition of PSA-NCAM turnover affecting cell migration. Insulin enhanced the phosphorylation of the focal adhesion kinase leading to dissociation of αv-integrin/PSA-NCAM clusters, and promoted cell migration. Our results show that αv-integrin plays a key role in the PSA-NCAM turnover process. αv-integrin knockdown stopped PSA-NCAM from being endocytosed, and αv-integrin/PSA-NCAM clusters co-labelled intracellularly with Rab5, altogether indicating a role for αv-integrin as a carrier for PSA-NCAM during internalisation. Furthermore, inhibition of p-FAK caused dissociation of αv-integrin/PSA-NCAM clusters and counteracted the insulin-induced accumulation of PSA at the cell surface and cell migration was impaired. Our data reveal a functional association between the insulin/p-FAK-dependent regulation of PSA-NCAM turnover and cell migration through the extracellular matrix. Most importantly, they identify a novel mechanism for insulin-stimulated cell migration. - Highlights: • Insulin modulates PSA-NCAM turnover through upregulation of p-FAK. • P-FAK modulates αv-integrin/PSA-NCAM clustering. • αv-integrin acts as a carrier for PSA-NCAM endocytosis. • Cell migration is promoted by cell surface PSA. • Insulin promotes PSA-dependent migration in vitro.

  8. Insulin promotes cell migration by regulating PSA-NCAM

    International Nuclear Information System (INIS)

    Monzo, Hector J.; Coppieters, Natacha; Park, Thomas I.H.; Dieriks, Birger V.; Faull, Richard L.M.; Dragunow, Mike; Curtis, Maurice A.

    2017-01-01

    Cellular interactions with the extracellular environment are modulated by cell surface polysialic acid (PSA) carried by the neural cell adhesion molecule (NCAM). PSA-NCAM is involved in cellular processes such as differentiation, plasticity, and migration, and is elevated in Alzheimer's disease as well as in metastatic tumour cells. Our previous work demonstrated that insulin enhances the abundance of cell surface PSA by inhibiting PSA-NCAM endocytosis. In the present study we have identified a mechanism for insulin-dependent inhibition of PSA-NCAM turnover affecting cell migration. Insulin enhanced the phosphorylation of the focal adhesion kinase leading to dissociation of αv-integrin/PSA-NCAM clusters, and promoted cell migration. Our results show that αv-integrin plays a key role in the PSA-NCAM turnover process. αv-integrin knockdown stopped PSA-NCAM from being endocytosed, and αv-integrin/PSA-NCAM clusters co-labelled intracellularly with Rab5, altogether indicating a role for αv-integrin as a carrier for PSA-NCAM during internalisation. Furthermore, inhibition of p-FAK caused dissociation of αv-integrin/PSA-NCAM clusters and counteracted the insulin-induced accumulation of PSA at the cell surface and cell migration was impaired. Our data reveal a functional association between the insulin/p-FAK-dependent regulation of PSA-NCAM turnover and cell migration through the extracellular matrix. Most importantly, they identify a novel mechanism for insulin-stimulated cell migration. - Highlights: • Insulin modulates PSA-NCAM turnover through upregulation of p-FAK. • P-FAK modulates αv-integrin/PSA-NCAM clustering. • αv-integrin acts as a carrier for PSA-NCAM endocytosis. • Cell migration is promoted by cell surface PSA. • Insulin promotes PSA-dependent migration in vitro.

  9. Sulfatide promotes the folding of proinsulin, preserves insulin crystals, and mediates its monomerization.

    Science.gov (United States)

    Osterbye, T; Jørgensen, K H; Fredman, P; Tranum-Jensen, J; Kaas, A; Brange, J; Whittingham, J L; Buschard, K

    2001-06-01

    Sulfatide is a glycolipid that has been associated with insulin-dependent diabetes mellitus. It is present in the islets of Langerhans and follows the same intracellular route as insulin. However, the role of sulfatide in the beta cell has been unclear. Here we present evidence suggesting that sulfatide promotes the folding of reduced proinsulin, indicating that sulfatide possesses molecular chaperone activity. Sulfatide associates with insulin by binding to the insulin domain A8--A10 and most likely by interacting with the hydrophobic side chains of the dimer-forming part of the insulin B-chain. Sulfatide has a dual effect on insulin. It substantially reduces deterioration of insulin hexamer crystals at pH 5.5, conferring stability comparable to those in beta cell granules. Sulfatide also mediates the conversion of insulin hexamers to the biological active monomers at neutral pH, the pH at the beta-cell surface. Finally, we report that inhibition of sulfatide synthesis with chloroquine and fumonisine B1 leads to inhibition of insulin granule formation in vivo. Our observations suggest that sulfatide plays a key role in the folding of proinsulin, in the maintenance of insulin structure, and in the monomerization process.

  10. FTO Inhibits Insulin Secretion and Promotes NF-κB Activation through Positively Regulating ROS Production in Pancreatic β cells.

    Directory of Open Access Journals (Sweden)

    Hong-Qi Fan

    Full Text Available FTO (Fat mass and obesity-associated is associated with increased risk of obesity and type 2 diabetes incurrence. Pancreas islet β cells dysfunction and insulin resistance are major causes of type 2 diabetes. However, whether FTO plays an important functional role in pancreatic β cells as well as the related molecular mechanism is still unclear. In the present study, the tissue expression profile of FTO was firstly determined using quantitative PCR and western blot. FTO is widely expressed in various tissues and presented with relative high expression in pancreas tissue, especially in endocrine pancreas. FTO overexpression in MIN6 cells achieved by lentivirus delivery significantly inhibits insulin secretion in the presence of glucose stimulus as well as KCl. FTO silence has no effect on insulin secretion of MIN6 cells. However, FTO overexpression doesn't affect the transcription of insulin gene. Furthermore, reactive oxygen species (ROS production and NF-κB activation are significantly promoted by FTO overexpression. Inhibition of intracellular ROS production by N-acetyl-L-cysteine (NAC can alleviate NF-κB activation and restore the insulin secretion mediated by FTO overexpression. A whole transcript-microarray is employed to analyze the differential gene expression mediated by FTO overexpression. The genes which are modulated by FTO are involved in many important biological pathways such as G-protein coupled receptor signaling and NF-κB signaling. Therefore, our study indicates that FTO may contribute to pancreas islet β cells dysfunction and the inhibition of FTO activity is a potential target for the treatment of diabetes.

  11. Interleukin-33-Activated Islet-Resident Innate Lymphoid Cells Promote Insulin Secretion through Myeloid Cell Retinoic Acid Production.

    Science.gov (United States)

    Dalmas, Elise; Lehmann, Frank M; Dror, Erez; Wueest, Stephan; Thienel, Constanze; Borsigova, Marcela; Stawiski, Marc; Traunecker, Emmanuel; Lucchini, Fabrizio C; Dapito, Dianne H; Kallert, Sandra M; Guigas, Bruno; Pattou, Francois; Kerr-Conte, Julie; Maechler, Pierre; Girard, Jean-Philippe; Konrad, Daniel; Wolfrum, Christian; Böni-Schnetzler, Marianne; Finke, Daniela; Donath, Marc Y

    2017-11-21

    Pancreatic-islet inflammation contributes to the failure of β cell insulin secretion during obesity and type 2 diabetes. However, little is known about the nature and function of resident immune cells in this context or in homeostasis. Here we show that interleukin (IL)-33 was produced by islet mesenchymal cells and enhanced by a diabetes milieu (glucose, IL-1β, and palmitate). IL-33 promoted β cell function through islet-resident group 2 innate lymphoid cells (ILC2s) that elicited retinoic acid (RA)-producing capacities in macrophages and dendritic cells via the secretion of IL-13 and colony-stimulating factor 2. In turn, local RA signaled to the β cells to increase insulin secretion. This IL-33-ILC2 axis was activated after acute β cell stress but was defective during chronic obesity. Accordingly, IL-33 injections rescued islet function in obese mice. Our findings provide evidence that an immunometabolic crosstalk between islet-derived IL-33, ILC2s, and myeloid cells fosters insulin secretion. Copyright © 2017 Elsevier Inc. All rights reserved.

  12. Growth hormone-induced insulin resistance in human subjects involves reduced pyruvate dehydrogenase activity

    DEFF Research Database (Denmark)

    Nellemann, B.; Vendelbo, M.H.; Nielsen, Thomas Svava

    2014-01-01

    Insulin resistance induced by growth hormone (GH) is linked to promotion of lipolysis by unknown mechanisms. We hypothesized that suppression of the activity of pyruvate dehydrogenase in the active form (PDHa) underlies GH-induced insulin resistance similar to what is observed during fasting....

  13. Insulin-induced decrease in protein phosphorylation in rat adipocytes not explained by decreased A-kinase activity

    International Nuclear Information System (INIS)

    Egan, J.J.; Greenberg, A.S.; Chang, M.K.; Londos, C.

    1987-01-01

    In isolated rat adipocytes, insulin inhibits lipolysis to a greater extent than would be predicted by the decrease in (-/+)cAMP activity ratio of cAMP-dependent protein kinase [A-kinase], from which it was speculated that insulin promotes the dephosphorylation of hormone-sensitive lipase. They have examined the phosphorylation state of cellular proteins under conditions of varying A-kinase activities in the presence and absence of insulin. Protein phosphorylation was determined by SDS-PAGE electrophoresis of extracts from 32 P-loaded cells; glycerol and A-kinase activity ratios were measured in the cytosolic extracts from control, non-radioactive cells. Increased protein phosphorylation in general occurred over the same range of A-kinase activity ratios, 0.1-0.3, associated with increased glycerol release. The insulin-induced decrease in lipolysis was associated with a decrease in the 32 P content of several proteins, an effect not explained by the modest reduction in A-kinase activity by insulin. This effect of insulin on protein phosphorylation was lost as the A-kinase activity ratios exceeded 0.5. The results suggest that insulin promotes the dephosphorylation of those adipocyte proteins which are subject to phosphorylation by A-kinase

  14. Hepatic Insulin Resistance Following Chronic Activation of the CREB Coactivator CRTC2

    DEFF Research Database (Denmark)

    Hogan, Meghan F; Ravnskjaer, Kim; Matsumura, Shigenobu

    2015-01-01

    and dephosphorylation of the cAMP regulated CREB coactivators CRTC2 and CRTC3. In parallel, decreases in circulating insulin also increase gluconeogenic gene expression via the de-phosphorylation and activation of the forkhead transcription factor FOXO1. Hepatic gluconeogenesis is increased in insulin resistance where...... increased gluconeogenic gene expression under fasting as well as feeding conditions. Circulating glucose concentrations were constitutively elevated in CRTC2S171,275A expressing mice, leading to compensatory increases in circulating insulin concentrations that enhance FOXO1 phosphorylation. Despite...... accompanying decreases in FOXO1 activity, hepatic gluconeogenic gene expression remained elevated in CRTC2S171,275A mice demonstrating that chronic increases in CRTC2 activity in the liver are indeed sufficient to promote hepatic insulin resistance and to disrupt glucose homeostasis....

  15. Estradiol represses Insulin-like 3 expression and promoter activity in MA-10 Leydig cells

    International Nuclear Information System (INIS)

    Lague, Eric; Tremblay, Jacques J.

    2009-01-01

    There are increasing evidence in the literature reporting the detrimental effects of endocrine disruptors on the development and function of the male reproductive system. One example is cryptorchidism, or undescended testis, caused by exposure to excessive estrogens. Estrogens, acting through the estrogen receptor α (ERα), have been shown to repress expression of the gene encoding insulin-like 3 (INSL3), a small peptide produced by testicular Leydig cells that is essential for normal testis descent. The molecular mechanism of estrogen/ER action on Insl3 expression, however, remains poorly understood. Here we report estradiol (E 2 ) represses Insl3 mRNA levels in MA-10 cells, a Leydig cell line model. We also found that E 2 represses the activity of the human and mouse Insl3 promoter in these cells. The E 2 -responsive region of the human INSL3 promoter was located to the proximal INSL3 promoter. This region does not contain a consensus estrogen response element indicating an indirect mechanism of action. In agreement with this, we found that E 2 -responsiveness was lost when two previously characterized binding sites for the nuclear receptors NUR77 and SF1 were mutated. Finally we show that the E 2 repressive effect could be overcome by cotreatment with testosterone, a positive regulator of Insl3 transcription. Collectively our data provide important new insights into the molecular mechanism of estrogen action in Insl3 transcription in Leydig cells

  16. Reductive methylation of insulin. Production of a biologically active tritiated insulin

    Energy Technology Data Exchange (ETDEWEB)

    Marsh, J W; Nahum, A; Steiner, D F [Department of Biochemistry, University of Chicago, Illinois, USA

    1983-01-01

    Reductive methylation of the three amino groups of porcine insulin was accomplished by incubation with formaldehyde and sodium cyanoborohydride. The two amino termini and the epsilon amino group of B29 lysine were each dimethylated within 1 h of incubation. The fully methylated insulin bound more tightly to a reverse phase column than did native insulin, had a slightly more acid isoelectric point, and maintained approximately 50% biological activity when examined with an insulin sensitive cultured cell line. Reductive methylation with sodium cyanoboro (/sup 3/H) hydride resulted in a (/sup 3/H) methylated insulin with a specific activity of 6 Ci/mmol.

  17. Glucose metabolism in pigs expressing human genes under an insulin promoter.

    Science.gov (United States)

    Wijkstrom, Martin; Bottino, Rita; Iwase, Hayoto; Hara, Hidetaka; Ekser, Burcin; van der Windt, Dirk; Long, Cassandra; Toledo, Frederico G S; Phelps, Carol J; Trucco, Massimo; Cooper, David K C; Ayares, David

    2015-01-01

    Xenotransplantation of porcine islets can reverse diabetes in non-human primates. The remaining hurdles for clinical application include safe and effective T-cell-directed immunosuppression, but protection against the innate immune system and coagulation dysfunction may be more difficult to achieve. Islet-targeted genetic manipulation of islet-source pigs represents a powerful tool to protect against graft loss. However, whether these genetic alterations would impair islet function is unknown. On a background of α1,3-galactosyltransferase gene-knockout (GTKO)/human (h)CD46, additional genes (hCD39, human tissue factor pathway inhibitor, porcine CTLA4-Ig) were inserted in different combinations under an insulin promoter to promote expression in islets (confirmed by immunofluorescence). Seven pigs were tested for baseline and glucose/arginine-challenged levels of glucose, insulin, C-peptide, and glucagon. This preliminary study did not show definite evidence of β-cell deficiencies, even when three transgenes were expressed under the insulin promoter. Of seven animals, all were normoglycemic at fasting, and five of seven had normal glucose disposal rates after challenge. All animals exhibited insulin, C-peptide, and glucagon responses to both glucose and arginine challenge; however, significant interindividual variation was observed. Multiple islet-targeted transgenic expression was not associated with an overtly detrimental effect on islet function, suggesting that complex genetic constructs designed for islet protection warrants further testing in islet xenotransplantation models. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  18. Tau deletion promotes brain insulin resistance.

    Science.gov (United States)

    Marciniak, Elodie; Leboucher, Antoine; Caron, Emilie; Ahmed, Tariq; Tailleux, Anne; Dumont, Julie; Issad, Tarik; Gerhardt, Ellen; Pagesy, Patrick; Vileno, Margaux; Bournonville, Clément; Hamdane, Malika; Bantubungi, Kadiombo; Lancel, Steve; Demeyer, Dominique; Eddarkaoui, Sabiha; Vallez, Emmanuelle; Vieau, Didier; Humez, Sandrine; Faivre, Emilie; Grenier-Boley, Benjamin; Outeiro, Tiago F; Staels, Bart; Amouyel, Philippe; Balschun, Detlef; Buee, Luc; Blum, David

    2017-08-07

    The molecular pathways underlying tau pathology-induced synaptic/cognitive deficits and neurodegeneration are poorly understood. One prevalent hypothesis is that hyperphosphorylation, misfolding, and fibrillization of tau impair synaptic plasticity and cause degeneration. However, tau pathology may also result in the loss of specific physiological tau functions, which are largely unknown but could contribute to neuronal dysfunction. In the present study, we uncovered a novel function of tau in its ability to regulate brain insulin signaling. We found that tau deletion leads to an impaired hippocampal response to insulin, caused by altered IRS-1 and PTEN (phosphatase and tensin homologue on chromosome 10) activities. Our data also demonstrate that tau knockout mice exhibit an impaired hypothalamic anorexigenic effect of insulin that is associated with energy metabolism alterations. Consistently, we found that tau haplotypes are associated with glycemic traits in humans. The present data have far-reaching clinical implications and raise the hypothesis that pathophysiological tau loss-of-function favors brain insulin resistance, which is instrumental for cognitive and metabolic impairments in Alzheimer's disease patients. © 2017 Marciniak et al.

  19. Insulin Promotes the Proliferation of Human Umbilical Cord Matrix-Derived Mesenchymal Stem Cells by Activating the Akt-Cyclin D1 Axis

    Directory of Open Access Journals (Sweden)

    Peng Li

    2017-01-01

    Full Text Available Background. The functions of insulin in mesenchymal stem cells (MSC remain poorly understood. Methods. MSC from human umbilical cord matrix (UCM cultured in serum-free media (SFM with or without insulin were subjected to various molecular biological analyses to determine their proliferation and growth states, expression levels of Akt-cyclin D1 signaling molecules, and in vitro differentiation capacities. Results. Insulin accelerated the G1-S cell cycle progression of UCM-MSC and significantly stimulated their proliferation and growth in SFM. The pro-proliferative action of insulin was associated with augmented cyclin D1 and phosphorylated Akt expression levels. Akt inactivation remarkably abrogated insulin-induced increases in cyclin D1 expression and cell proliferation, indicating that insulin enhances the proliferation of UCM-MSC via acceleration of the G1-S transition mediated by the Akt-cyclin D1 pathway. Additionally, the UCM-MSC propagated in SFM supplemented with insulin exhibited similar specific surface antigen profiles and differentiation capacities as those generated in conventional media containing fetal bovine serum. Conclusions. These findings suggest that insulin acts solely to promote UCM-MSC proliferation without affecting their immunophenotype and differentiation potentials and thus have important implications for utilizing insulin to expand clinical-grade MSC in vitro.

  20. Imidacloprid Promotes High Fat Diet-Induced Adiposity and Insulin Resistance in Male C57BL/6J Mice.

    Science.gov (United States)

    Sun, Quancai; Xiao, Xiao; Kim, Yoo; Kim, Daeyoung; Yoon, Kyoon Sup; Clark, John M; Park, Yeonhwa

    2016-12-14

    Imidacloprid, a neonicotinoid insecticide widely used in agriculture worldwide, has been reported to promote adipogenesis and cause insulin resistance in vitro. The purpose of the current study was to determine the effects of imidacloprid and its interaction with dietary fat in the development of adiposity and insulin resistance using male C57BL/6J mice. Imidacloprid (0.06, 0.6, or 6 mg/kg bw/day) was mixed in a low-fat (4% w/w) or high-fat (20% w/w) diet and given to mice ad libitum for 12 weeks. Imidacloprid significantly promoted high fat diet-induced body weight gain and adiposity. In addition, imidacloprid treatment with the high fat diet resulted in impaired glucose metabolism. Consistently, there were significant effects of imidacloprid on genes regulating lipid and glucose metabolisms, including the AMP-activated protein kinase-α (AMPKα) pathway in white adipose tissue and liver. These results suggest that imidacloprid may potentiate high fat diet-induced adiposity and insulin resistance in male C57BL/6J mice.

  1. Zinc promotes proliferation and activation of myogenic cells via the PI3K/Akt and ERK signaling cascade

    Energy Technology Data Exchange (ETDEWEB)

    Ohashi, Kazuya, E-mail: asuno10k@yahoo.co.jp [Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo (Japan); Nagata, Yosuke, E-mail: cynagata@mail.ecc.u-tokyo.ac.jp [Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo (Japan); Wada, Eiji, E-mail: gacchu1@yahoo.co.jp [Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo (Japan); Zammit, Peter S., E-mail: peter.zammit@kcl.ac.uk [Randall Division of Cell and Molecular Biophysics, King' s College London, London SE1 1UL (United Kingdom); Shiozuka, Masataka, E-mail: cmuscle@mail.ecc.u-tokyo.ac.jp [Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo (Japan); Matsuda, Ryoichi, E-mail: cmatsuda@mail.ecc.u-tokyo.ac.jp [Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo (Japan)

    2015-05-01

    Skeletal muscle stem cells named muscle satellite cells are normally quiescent but are activated in response to various stimuli, such as injury and overload. Activated satellite cells enter the cell cycle and proliferate to produce a large number of myogenic progenitor cells, and these cells then differentiate and fuse to form myofibers. Zinc is one of the essential elements in the human body, and has multiple roles, including cell growth and DNA synthesis. However, the role of zinc in myogenic cells is not well understood, and is the focus of this study. We first examined the effects of zinc on differentiation of murine C2C12 myoblasts and found that zinc promoted proliferation, with an increased number of cells incorporating EdU, but inhibited differentiation with reduced myogenin expression and myotube formation. Furthermore, we used the C2C12 reserve cell model of myogenic quiescence to investigate the role of zinc on activation of myogenic cells. The number of reserve cells incorporating BrdU was increased by zinc in a dose dependent manner, with the number dramatically further increased using a combination of zinc and insulin. Akt and extracellular signal-regulated kinase (ERK) are downstream of insulin signaling, and both were phosphorylated after zinc treatment. The zinc/insulin combination-induced activation involved the phosphoinositide 3-kinase (PI3K)/Akt and ERK cascade. We conclude that zinc promotes activation and proliferation of myogenic cells, and this activation requires phosphorylation of PI3K/Akt and ERK as part of the signaling cascade. - Highlights: • Zinc has roles for promoting proliferation and inhibition differentiation of C2C12. • Zinc promotes activation of reserve cells. • Insulin and zinc synergize activation of reserve cells. • PI3K/Akt and ERK cascade affect zinc/insulin-mediated activation of reserve cells.

  2. Evidence that phosphatidylcholine-specific phospholipase C is a key molecule mediating insulin-induced enhancement of gene expression from human cytomegalovirus promoter in CHO cells

    OpenAIRE

    Zhang, Yingpei; Katakura, Yoshinori; Seto, Perry; Shirahata, Sanetaka

    1997-01-01

    The signal transduction from insulin to its receptors and Ras has been extensively studied, while little has been reported beyond these steps. We found that the expression of human interleukin 6 gene under the control of immediate early gene promoter of human cytomegalovirus was enhanced by insulin sitmulation in Chinese hamster ovary cells. The induction effect of insulin was not significantly affected by inhibitors or activators of conventional protein kinase C, cAMP dependent protein kinas...

  3. TLR4 and Insulin Resistance

    Directory of Open Access Journals (Sweden)

    Jane J. Kim

    2010-01-01

    Full Text Available Chronic inflammation is a key feature of insulin resistance and obesity. Toll-Like Receptor 4 (TLR4, involved in modulating innate immunity, is an important mediator of insulin resistance and its comorbidities. TLR4 contributes to the development of insulin resistance and inflammation through its activation by elevated exogenous ligands (e.g., dietary fatty acids and enteric lipopolysaccharide and endogenous ligands (e.g., free fatty acids which are elevated in obese states. TLR4, expressed in insulin target tissues, activates proinflammatory kinases JNK, IKK, and p38 that impair insulin signal transduction directly through inhibitory phosphorylation of insulin receptor substrate (IRS on serine residues. TLR4 activation also leads to increased transcription of pro-inflammatory genes, resulting in elevation of cytokine, chemokine, reactive oxygen species, and eicosanoid levels that promote further insulin-desensitization within the target cell itself and in other cells via paracrine and systemic effects. Increased understanding of cell type-specific TLR4-mediated effects on insulin action present the opportunity and challenge of developing related therapeutic approaches for improving insulin sensitivity while preserving innate immunity.

  4. Dipalmitoleoylphosphoethanolamine as a PP2A enhancer obstructs insulin signaling by promoting Ser/Thr dephosphorylation of Akt.

    Science.gov (United States)

    Tsuchiya, Ayako; Kanno, Takeshi; Nishizaki, Tomoyuki

    2014-01-01

    The phospholipid phosphatidylethanolamine is implicated in the regulation of a variety of cellular processes. The present study investigated the effect of phosphatidylethanolamines such as 1,2-diarachidonoyl-sn-glycero-3-phosphoethanolamine (DAPE), 1,2-dilinoleoyl-sn-glycero-3-phosphoethanolamine (DLPE), 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), and 1,2-dipalmitoleoyl-sn-glycero-3-phosphoethanolamine (DPPE) on protein phosphatases, Akt1/2 activity, GLUT4 mobilizations, and glucose uptake into cells. Activity of protein phosphatase 2A (PP2A) was assayed under the cell-free conditions, and Western blotting, intracellular GLUT4 trafficking, and glucose uptake into cells were monitored using differentiated 3T3-L1-GLUT4myc adipocytes. Of the investigated phosphatidylethanolamines, DLPE and DPPE significantly enhanced PP2A activity. DPPE inhibited insulin-induced phosphorylation of Akt1/2 at Thr308/309 and Ser473/474 in differentiated 3T3-L1-GLUT4myc adipocytes. DPPE also inhibited insulin-stimulated GLUT4 translocation to the cell surface and reduced insulin-stimulated glucose uptake into adipocytes. The results of the present study indicate that the PP2A enhancer DPPE obstructs insulin signaling by promoting serine/threonine dephosphorylation of Akt1/2, resulting in the suppression of GLUT4 translocation to the cell surface and glucose uptake into adipocytes. © 2014 S. Karger AG, Basel.

  5. Dipalmitoleoylphosphoethanolamine as a PP2A Enhancer Obstructs Insulin Signaling by Promoting Ser/Thr Dephosphorylation of Akt

    Directory of Open Access Journals (Sweden)

    Ayako Tsuchiya

    2014-08-01

    Full Text Available Background/Aims: The phospholipid phosphatidylethanolamine is implicated in the regulation of a variety of cellular processes. The present study investigated the effect of phosphatidylethanolamines such as 1,2-diarachidonoyl-sn-glycero-3-phosphoethanolamine (DAPE, 1,2-dilinoleoyl-sn-glycero-3-phosphoethanolamine (DLPE, 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE, and 1,2-dipalmitoleoyl-sn-glycero-3-phosphoethanolamine (DPPE on protein phosphatases, Akt1/2 activity, GLUT4 mobilizations, and glucose uptake into cells. Methods: Activity of protein phosphatase 2A (PP2A was assayed under the cell-free conditions, and Western blotting, intracellular GLUT4 trafficking, and glucose uptake into cells were monitored using differentiated 3T3-L1-GLUT4myc adipocytes. Results: Of the investigated phosphatidylethanolamines, DLPE and DPPE significantly enhanced PP2A activity. DPPE inhibited insulin-induced phosphorylation of Akt1/2 at Thr308/309 and Ser473/474 in differentiated 3T3-L1-GLUT4myc adipocytes. DPPE also inhibited insulin-stimulated GLUT4 translocation to the cell surface and reduced insulin-stimulated glucose uptake into adipocytes. Conclusion: The results of the present study indicate that the PP2A enhancer DPPE obstructs insulin signaling by promoting serine/threonine dephosphorylation of Akt1/2, resulting in the suppression of GLUT4 translocation to the cell surface and glucose uptake into adipocytes.

  6. Receptor-like protein-tyrosine phosphatase alpha specifically inhibits insulin-increased prolactin gene expression

    DEFF Research Database (Denmark)

    Jacob, K K; Sap, J; Stanley, F M

    1998-01-01

    A physiologically relevant response to insulin, stimulation of prolactin promoter activity in GH4 pituitary cells, was used as an assay to study the specificity of protein-tyrosine phosphatase function. Receptor-like protein-tyrosine phosphatase alpha (RPTPalpha) blocks the effect of insulin...... is specific by two criteria. A number of potential RPTPalpha targets were ruled out by finding (a) that they are not affected or (b) that they are not on the pathway to insulin-increased prolactin-CAT activity. The negative effect of RPTPalpha on insulin activation of the prolactin promoter is not due...... to reduced phosphorylation or kinase activity of the insulin receptor or to reduced phosphorylation of insulin receptor substrate-1 or Shc. Inhibitor studies suggest that insulin-increased prolactin gene expression is mediated by a Ras-like GTPase but is not mitogen-activated protein kinase dependent...

  7. Early growth response-1 negative feedback regulates skeletal muscle postprandial insulin sensitivity via activating Ptp1b transcription.

    Science.gov (United States)

    Wu, Jing; Tao, Wei-Wei; Chong, Dan-Yang; Lai, Shan-Shan; Wang, Chuang; Liu, Qi; Zhang, Tong-Yu; Xue, Bin; Li, Chao-Jun

    2018-03-15

    Postprandial insulin desensitization plays a critical role in maintaining whole-body glucose homeostasis by avoiding the excessive absorption of blood glucose; however, the detailed mechanisms that underlie how the major player, skeletal muscle, desensitizes insulin action remain to be elucidated. Herein, we report that early growth response gene-1 ( Egr-1) is activated by insulin in skeletal muscle and provides feedback inhibition that regulates insulin sensitivity after a meal. The inhibition of the transcriptional activity of Egr-1 enhanced the phosphorylation of the insulin receptor (InsR) and Akt, thus increasing glucose uptake in L6 myotubes after insulin stimulation, whereas overexpression of Egr-1 decreased insulin sensitivity. Furthermore, deletion of Egr-1 in the skeletal muscle improved systemic insulin sensitivity and glucose tolerance, which resulted in lower blood glucose levels after refeeding. Mechanistic analysis demonstrated that EGR-1 inhibited InsR phosphorylation and glucose uptake in skeletal muscle by binding to the proximal promoter region of protein tyrosine phosphatase-1B (PTP1B) and directly activating transcription. PTP1B knockdown largely restored insulin sensitivity and enhanced glucose uptake, even under conditions of EGR-1 overexpression. Our results indicate that EGR-1/PTP1B signaling negatively regulates postprandial insulin sensitivity and suggest a potential therapeutic target for the prevention and treatment of excessive glucose absorption.-Wu, J., Tao, W.-W., Chong, D.-Y., Lai, S.-S., Wang, C., Liu, Q., Zhang, T.-Y., Xue, B., Li, C.-J. Early growth response-1 negative feedback regulates skeletal muscle postprandial insulin sensitivity via activating Ptp1b transcription.

  8. Synapses of Amphids Defective (SAD-A) Kinase Promotes Glucose-stimulated Insulin Secretion through Activation of p21-activated Kinase (PAK1) in Pancreatic β-Cells*

    Science.gov (United States)

    Nie, Jia; Sun, Chao; Faruque, Omar; Ye, Guangming; Li, Jia; Liang, Qiangrong; Chang, Zhijie; Yang, Wannian; Han, Xiao; Shi, Yuguang

    2012-01-01

    The p21-activated kinase-1 (PAK1) is implicated in regulation of insulin exocytosis as an effector of Rho GTPases. PAK1 is activated by the onset of glucose-stimulated insulin secretion (GSIS) through phosphorylation of Thr-423, a major activation site by Cdc42 and Rac1. However, the kinase(s) that phosphorylates PAK1 at Thr-423 in islet β-cells remains elusive. The present studies identified SAD-A (synapses of amphids defective), a member of AMP-activated protein kinase-related kinases exclusively expressed in brain and pancreas, as a key regulator of GSIS through activation of PAK1. We show that SAD-A directly binds to PAK1 through its kinase domain. The interaction is mediated by the p21-binding domain (PBD) of PAK1 and requires both kinases in an active conformation. The binding leads to direct phosphorylation of PAK1 at Thr-423 by SAD-A, triggering the onset of GSIS from islet β-cells. Consequently, ablation of PAK1 kinase activity or depletion of PAK1 expression completely abolishes the potentiating effect of SAD-A on GSIS. Consistent with its role in regulating GSIS, overexpression of SAD-A in MIN6 islet β-cells significantly stimulated cytoskeletal remodeling, which is required for insulin exocytosis. Together, the present studies identified a critical role of SAD-A in the activation of PAK1 during the onset of insulin exocytosis. PMID:22669945

  9. Synapses of amphids defective (SAD-A) kinase promotes glucose-stimulated insulin secretion through activation of p21-activated kinase (PAK1) in pancreatic β-Cells.

    Science.gov (United States)

    Nie, Jia; Sun, Chao; Faruque, Omar; Ye, Guangming; Li, Jia; Liang, Qiangrong; Chang, Zhijie; Yang, Wannian; Han, Xiao; Shi, Yuguang

    2012-07-27

    The p21-activated kinase-1 (PAK1) is implicated in regulation of insulin exocytosis as an effector of Rho GTPases. PAK1 is activated by the onset of glucose-stimulated insulin secretion (GSIS) through phosphorylation of Thr-423, a major activation site by Cdc42 and Rac1. However, the kinase(s) that phosphorylates PAK1 at Thr-423 in islet β-cells remains elusive. The present studies identified SAD-A (synapses of amphids defective), a member of AMP-activated protein kinase-related kinases exclusively expressed in brain and pancreas, as a key regulator of GSIS through activation of PAK1. We show that SAD-A directly binds to PAK1 through its kinase domain. The interaction is mediated by the p21-binding domain (PBD) of PAK1 and requires both kinases in an active conformation. The binding leads to direct phosphorylation of PAK1 at Thr-423 by SAD-A, triggering the onset of GSIS from islet β-cells. Consequently, ablation of PAK1 kinase activity or depletion of PAK1 expression completely abolishes the potentiating effect of SAD-A on GSIS. Consistent with its role in regulating GSIS, overexpression of SAD-A in MIN6 islet β-cells significantly stimulated cytoskeletal remodeling, which is required for insulin exocytosis. Together, the present studies identified a critical role of SAD-A in the activation of PAK1 during the onset of insulin exocytosis.

  10. Independent Benefits of Meeting the 2008 Physical Activity Guidelines to Insulin Resistance in Obese Latino Children

    Directory of Open Access Journals (Sweden)

    Nazrat Mirza

    2012-01-01

    Full Text Available We examined the independent association between moderate-to-vigorous physical activity (MVPA and insulin resistance (IR among obese Latino children (N=113; 7–15 years who were enrolled in a community-based obesity intervention. Baseline information on physical activity was gathered by self-report. Clinical assessments of body composition, resting energy expenditure (REE, as well as glucose and insulin responses to an oral glucose tolerance test (OGTT were performed after an overnight fast. Insulin resistance was defined as a 2 h insulin concentration >57 μU·mL-1. We observed that those obese children who met the 2008 Guidelines for MVPA (≥60 min/day experienced a significantly lower odds of IR compared with those not meeting the Guidelines (OR=0.29; 95% CI: (0.10–0.92 and these findings were independent of age, sex, pubertal stage, acculturation, fasting insulin, and 2 h glucose concentrations. Efforts to promote 60 min or more of daily MVPA among children from ethnic minority and high-risk communities should assume primary public health importance.

  11. Induction of insulin and islet amyloid polypeptide production in pancreatic islet glucagonoma cells by insulin promoter factor 1

    DEFF Research Database (Denmark)

    Serup, P; Jensen, J; Andersen, F G

    1996-01-01

    Insulin promoter factor 1 (IPF1), a member of the homeodomain protein family, serves an early role in pancreas formation, as evidenced by the lack of pancreas formation in mice carrying a targeted disruption of the IPF1 gene [Jonsson, J., Carlsson, L., Edlund, T. & Edlund, H. (1994) Nature (London...

  12. Insulin-like activity in the retina

    International Nuclear Information System (INIS)

    Das, A.

    1986-01-01

    A number of studies have recently demonstrated that insulin or a homologous peptide may be synthesized outside the pancreas also. The present study was designed to investigate whether insulin-like activity exists in the retina, and if it exists, whether it is due to local synthesis of insulin or a similar peptide in the retina. To determine whether the insulin-like immunoreactivity in retinal glial cells is due to binding and uptake or local synthesis of insulin, a combined approach of immunocytochemistry and in situ DNA-RNA hybridization techniques was used on cultured rat retinal glial cells. Insulin-like immunoreactivity was demonstrated in the cytoplasma of these cells. In situ hybridization studies using labeled rat insulin cDNA indicated that these cells contain the mRNA necessary for de novo synthesis of insulin or a closely homologous peptide. Since human retinal cells have, as yet, not been conveniently grown in culture, an ocular tumor cell line, human Y79 retinoblastoma was used as a model to extend these investigations. The presence of insulin-like immunoreactivity as well as insulin-specific mRNA was demonstrated in this cell line. Light microscopic autoradiography following incubation of isolated rat retinal cells with 125 I-insulin showed the presence of insulin binding sites on the photoreceptors and amarcine cells. On the basis of these observations that rat retina glial cells, including Muller cells are sites of synthesis of insulin or a similar peptide, a model for the pathogenesis of dabetic retinopathy is proposed

  13. Hyperglycemia- and hyperinsulinemia-induced insulin resistance causes alterations in cellular bioenergetics and activation of inflammatory signaling in lymphatic muscle.

    Science.gov (United States)

    Lee, Yang; Fluckey, James D; Chakraborty, Sanjukta; Muthuchamy, Mariappan

    2017-07-01

    Insulin resistance is a well-known risk factor for obesity, metabolic syndrome (MetSyn) and associated cardiovascular diseases, but its mechanisms are undefined in the lymphatics. Mesenteric lymphatic vessels from MetSyn or LPS-injected rats exhibited impaired intrinsic contractile activity and associated inflammatory changes. Hence, we hypothesized that insulin resistance in lymphatic muscle cells (LMCs) affects cell bioenergetics and signaling pathways that consequently alter contractility. LMCs were treated with different concentrations of insulin or glucose or both at various time points to determine insulin resistance. Onset of insulin resistance significantly impaired glucose uptake, mitochondrial function, oxygen consumption rates, glycolysis, lactic acid, and ATP production in LMCs. Hyperglycemia and hyperinsulinemia also impaired the PI3K/Akt while enhancing the ERK/p38MAPK/JNK pathways in LMCs. Increased NF-κB nuclear translocation and macrophage chemoattractant protein-1 and VCAM-1 levels in insulin-resistant LMCs indicated activation of inflammatory mechanisms. In addition, increased phosphorylation of myosin light chain-20, a key regulator of lymphatic muscle contraction, was observed in insulin-resistant LMCs. Therefore, our data elucidate the mechanisms of insulin resistance in LMCs and provide the first evidence that hyperglycemia and hyperinsulinemia promote insulin resistance and impair lymphatic contractile status by reducing glucose uptake, altering cellular metabolic pathways, and activating inflammatory signaling cascades.-Lee, Y., Fluckey, J. D., Chakraborty, S., Muthuchamy, M. Hyperglycemia- and hyperinsulinemia-induced insulin resistance causes alterations in cellular bioenergetics and activation of inflammatory signaling in lymphatic muscle. © FASEB.

  14. Phosphorylation-dependent down-regulation of apolipoprotein A5 by insulin

    Energy Technology Data Exchange (ETDEWEB)

    Nowak, Maxine; Helleboid-Chapman, Audrey; Jakel, Heidelinde; Rommens, Corinne; Martin, Genevieve; Duran-Sandoval, Daniel; Staels, Bart; Rubin, Edward M.; Pennacchio, Len A.; Taskinen, Marja-Riitta; Fruchart-Najib, Jamila; Fruchart, Jean-Charles

    2004-02-15

    The apolipoprotein A5 (APOA5) gene has been shown to be important in lowering plasma triglyceride levels. Since several studies have shown that hyperinsulinemia is associated with hypertriglyceridemia, we sought to determine whether APOA5 gene is regulated by insulin. We show here that cell and mouse treatments with insulin down-regulated APOA5 expression in a dose-dependent manner. Furthermore, we determined that insulin decreases APOA5 promoter activity and subsequent deletion analyses revealed an E-box-containing fragment. We showed that Upstream Stimulatory Factors, USF1/USF2, bind to the identified E-box in the APOA5 promoter. Moreover, in cotransfection studies, USF1 stimulates APOA5 promoter activity. The treatment with insulin reduces the binding of USF1/USF2 to APOA5 promoter. The inhibition of PI3K pathway with wortmannin abolished the insulin s effect on APOA5 gene transcription. Using oligoprecipitation method of USF from nuclear extracts, we demonstrated that phosphorylated USF1 failed to bind to APOA5 promoter. This indicates that the APOA5 gene transrepression by insulin involves a phosphorylation of USF through PI3K, that modulate their binding to APOA5 promoter and results in APOA5 down-regulation. The effect of exogenous hyperinsulinemia in healthy men shows a decrease of the plasma ApoAV level. These data suggest a potential mechanism involving APOA5 gene in hypertriglyceridemia associated with hyperinsulinemia.

  15. Insulin resistance in uremia: Insulin receptor kinase activity in liver and muscle from chronic uremic rats

    International Nuclear Information System (INIS)

    Cecchin, F.; Ittoop, O.; Sinha, M.K.; Caro, J.F.

    1988-01-01

    The authors have studied the structure and function of the partially purified insulin receptors from liver and skeletal muscle in a rat model of severe chronic uremia. 125 I-insulin binding was higher in the liver from uremic rats when compared with ad libitum- and pair-fed controls. Furthermore, the ability of insulin to stimulate the autophosphorylation of the β-subunit and insulin receptor kinase activity using Glu 80 , Tyr 20 as exogenous phosphoacceptor was increased in the liver of the uremic animals. The structural characteristics of the receptors, as determined by electrophoretic mobilities of affinity labeled α-subunit and the phosphorylated β-subunit, were normal in uremia. 125 I-insulin binding and insulin receptor kinase activity were similar in the skeletal muscle from uremic and pair- and ad libitum-fed animals. Thus the data are supportive of the hypothesis that in liver and muscle of chronic uremic rats, insulin resistance is due to a defect(s) distal to the insulin receptor kinase

  16. Insulin stimulates choline acetyltransferase activity in cultured embryonic chicken retina neurons

    International Nuclear Information System (INIS)

    Kyriakis, J.M.; Hausman, R.E.; Peterson, S.W.

    1987-01-01

    The effect of insulin on the appearance of the enzyme choline acetyltransferase in embryonic chicken retina neurons cultured in defined medium was studied. In the presence of a minimal level of insulin (1 ng/ml), ChoAcT activity increased with time in culture. A correspondence between the insulin concentration in the defined medium (1-100 ng/ml) and both the rate of increase and maximum attained level of ChoAcT activity was observed. Maximal ChoAcT activity was 2- to 3-fold greater in cells cultured in the presence of 100 ng of insulin per ml than in cells cultured in the presence of 1 ng of insulin per ml. To elicit maximum ChoAcT activity, insulin at 100 ng/ml was required in the medium for only the first 4 days of the culture period, at which time insulin could be reduced to maintenance levels (10 ng/ml) without affecting ChoAcT activity. Insulin binding assays performed during a 7-day culture period revealed that irrespective of the 125 I-insulin concentration in the medium during culture, cell-surface insulin receptors decreased by ≅ 90% between 4 and 7 days in culture. This decrease in insulin binding corresponded to the observed decrease in the sensitivity of ChoAcT activity to insulin. The findings suggest that insulin plays a role in mediating cholinergic differentiation in the embryonic chicken retina

  17. Ubiquitinated CD36 sustains insulin-stimulated Akt activation by stabilizing insulin receptor substrate 1 in myotubes.

    Science.gov (United States)

    Sun, Shishuo; Tan, Pengcheng; Huang, Xiaoheng; Zhang, Wei; Kong, Chen; Ren, Fangfang; Su, Xiong

    2018-02-16

    Both the magnitude and duration of insulin signaling are important in executing its cellular functions. Insulin-induced degradation of insulin receptor substrate 1 (IRS1) represents a key negative feedback loop that restricts insulin signaling. Moreover, high concentrations of fatty acids (FAs) and glucose involved in the etiology of obesity-associated insulin resistance also contribute to the regulation of IRS1 degradation. The scavenger receptor CD36 binds many lipid ligands, and its contribution to insulin resistance has been extensively studied, but the exact regulation of insulin sensitivity by CD36 is highly controversial. Herein, we found that CD36 knockdown in C2C12 myotubes accelerated insulin-stimulated Akt activation, but the activated signaling was sustained for a much shorter period of time as compared with WT cells, leading to exacerbated insulin-induced insulin resistance. This was likely due to enhanced insulin-induced IRS1 degradation after CD36 knockdown. Overexpression of WT CD36, but not a ubiquitination-defective CD36 mutant, delayed IRS1 degradation. We also found that CD36 functioned through ubiquitination-dependent binding to IRS1 and inhibiting its interaction with cullin 7, a key component of the multisubunit cullin-RING E3 ubiquitin ligase complex. Moreover, dissociation of the Src family kinase Fyn from CD36 by free FAs or Fyn knockdown/inhibition accelerated insulin-induced IRS1 degradation, likely due to disrupted IRS1 interaction with CD36 and thus enhanced binding to cullin 7. In summary, we identified a CD36-dependent FA-sensing pathway that plays an important role in negative feedback regulation of insulin activation and may open up strategies for preventing or managing type 2 diabetes mellitus. © 2018 by The American Society for Biochemistry and Molecular Biology, Inc.

  18. Insulin-increased L-arginine transport requires A(2A adenosine receptors activation in human umbilical vein endothelium.

    Directory of Open Access Journals (Sweden)

    Enrique Guzmán-Gutiérrez

    Full Text Available Adenosine causes vasodilation of human placenta vasculature by increasing the transport of arginine via cationic amino acid transporters 1 (hCAT-1. This process involves the activation of A(2A adenosine receptors (A(2AAR in human umbilical vein endothelial cells (HUVECs. Insulin increases hCAT-1 activity and expression in HUVECs, and A(2AAR stimulation increases insulin sensitivity in subjects with insulin resistance. However, whether A(2AAR plays a role in insulin-mediated increase in L-arginine transport in HUVECs is unknown. To determine this, we first assayed the kinetics of saturable L-arginine transport (1 minute, 37°C in the absence or presence of nitrobenzylthioinosine (NBTI, 10 µmol/L, adenosine transport inhibitor and/or adenosine receptors agonist/antagonists. We also determined hCAT-1 protein and mRNA expression levels (Western blots and quantitative PCR, and SLC7A1 (for hCAT-1 reporter promoter activity. Insulin and NBTI increased the extracellular adenosine concentration, the maximal velocity for L-arginine transport without altering the apparent K(m for L-arginine transport, hCAT-1 protein and mRNA expression levels, and SLC7A1 transcriptional activity. An A2AAR antagonist ZM-241385 blocked these effects. ZM241385 inhibited SLC7A1 reporter transcriptional activity to the same extent in cells transfected with pGL3-hCAT-1(-1606 or pGL3-hCAT-1(-650 constructs in the presence of NBTI + insulin. However, SLC7A1 reporter activity was increased by NBTI only in cells transfected with pGL3-hCAT-1(-1606, and the ZM-241385 sensitive fraction of the NBTI response was similar in the absence or in the presence of insulin. Thus, insulin modulation of hCAT-1 expression and activity requires functional A(2AAR in HUVECs, a mechanism that may be applicable to diseases associated with fetal insulin resistance, such as gestational diabetes.

  19. Endothelial Fcγ Receptor IIB Activation Blunts Insulin Delivery to Skeletal Muscle to Cause Insulin Resistance in Mice

    Science.gov (United States)

    Tanigaki, Keiji; Chambliss, Ken L.; Yuhanna, Ivan S.; Sacharidou, Anastasia; Ahmed, Mohamed; Atochin, Dmitriy N.; Huang, Paul L.

    2016-01-01

    Modest elevations in C-reactive protein (CRP) are associated with type 2 diabetes. We previously revealed in mice that increased CRP causes insulin resistance and mice globally deficient in the CRP receptor Fcγ receptor IIB (FcγRIIB) were protected from the disorder. FcγRIIB is expressed in numerous cell types including endothelium and B lymphocytes. Here we investigated how endothelial FcγRIIB influences glucose homeostasis, using mice with elevated CRP expressing or lacking endothelial FcγRIIB. Whereas increased CRP caused insulin resistance in mice expressing endothelial FcγRIIB, mice deficient in the endothelial receptor were protected. The insulin resistance with endothelial FcγRIIB activation was due to impaired skeletal muscle glucose uptake caused by attenuated insulin delivery, and it was associated with blunted endothelial nitric oxide synthase (eNOS) activation in skeletal muscle. In culture, CRP suppressed endothelial cell insulin transcytosis via FcγRIIB activation and eNOS antagonism. Furthermore, in knock-in mice harboring constitutively active eNOS, elevated CRP did not invoke insulin resistance. Collectively these findings reveal that by inhibiting eNOS, endothelial FcγRIIB activation by CRP blunts insulin delivery to skeletal muscle to cause insulin resistance. Thus, a series of mechanisms in endothelium that impairs insulin movement has been identified that may contribute to type 2 diabetes pathogenesis. PMID:27207525

  20. Fibronectin and laminin promote differentiation of human mesenchymal stem cells into insulin producing cells through activating Akt and ERK

    Directory of Open Access Journals (Sweden)

    Chiou Shih-Hwa

    2010-07-01

    Full Text Available Abstract Background Islet transplantation provides a promising cure for Type 1 diabetes; however it is limited by a shortage of pancreas donors. Bone marrow-derived multipotent mesenchymal stem cells (MSCs offer renewable cells for generating insulin-producing cells (IPCs. Methods We used a four-stage differentiation protocol, containing neuronal differentiation and IPC-conversion stages, and combined with pellet suspension culture to induce IPC differentiation. Results Here, we report adding extracellular matrix proteins (ECM such as fibronectin (FN or laminin (LAM enhances pancreatic differentiation with increases in insulin and Glut2 gene expressions, proinsulin and insulin protein levels, and insulin release in response to elevated glucose concentration. Adding FN or LAM induced activation of Akt and ERK. Blocking Akt or ERK by adding LY294002 (PI3K specific inhibitor, PD98059 (MEK specific inhibitor or knocking down Akt or ERK failed to abrogate FN or LAM-induced enhancement of IPC differentiation. Only blocking both of Akt and ERK or knocking down Akt and ERK inhibited the enhancement of IPC differentiation by adding ECM. Conclusions These data prove IPC differentiation by MSCs can be modulated by adding ECM, and these stimulatory effects were mediated through activation of Akt and ERK pathways.

  1. Interleukin-1β inhibits insulin signaling and prevents insulin-stimulated system A amino acid transport in primary human trophoblasts.

    Science.gov (United States)

    Aye, Irving L M H; Jansson, Thomas; Powell, Theresa L

    2013-12-05

    Interleukin-1β (IL-1β) promotes insulin resistance in tissues such as liver and skeletal muscle; however the influence of IL-1β on placental insulin signaling is unknown. We recently reported increased IL-1β protein expression in placentas of obese mothers, which could contribute to insulin resistance. In this study, we tested the hypothesis that IL-1β inhibits insulin signaling and prevents insulin-stimulated amino acid transport in cultured primary human trophoblast (PHT) cells. Cultured trophoblasts isolated from term placentas were treated with physiological concentrations of IL-1β (10pg/ml) for 24h. IL-1β increased the phosphorylation of insulin receptor substrate-1 (IRS-1) at Ser307 (inhibitory) and decreased total IRS-1 protein abundance but did not affect insulin receptor β expression. Furthermore, IL-1β inhibited insulin-stimulated phosphorylation of IRS-1 (Tyr612, activation site) and Akt (Thr308) and prevented insulin-stimulated increase in PI3K/p85 and Grb2 protein expression. IL-1β alone stimulated cRaf (Ser338), MEK (Ser221) and Erk1/2 (Thr202/Tyr204) phosphorylation. The inflammatory pathways nuclear factor kappa B and c-Jun N-terminal kinase, which are involved in insulin resistance, were also activated by IL-1β treatment. Moreover, IL-1β inhibited insulin-stimulated System A, but not System L amino acid uptake, indicating functional impairment of insulin signaling. In conclusion, IL-1β inhibited the insulin signaling pathway by inhibiting IRS-1 signaling and prevented insulin-stimulated System A transport, thereby promoting insulin resistance in cultured PHT cells. These findings indicate that conditions which lead to increased systemic maternal or placental IL-1β levels may attenuate the effects of maternal insulin on placental function and consequently fetal growth. Published by Elsevier Ireland Ltd.

  2. The IGFBP7 homolog Imp-L2 promotes insulin signaling in distinct neurons of the Drosophila brain.

    Science.gov (United States)

    Bader, R; Sarraf-Zadeh, L; Peters, M; Moderau, N; Stocker, H; Köhler, K; Pankratz, M J; Hafen, E

    2013-06-15

    In Drosophila, Insulin-like peptide 2 (Dilp-2) is expressed by insulin-producing cells in the brain, and is secreted into the hemolymph to activate insulin signaling systemically. Within the brain, however, a more local activation of insulin signaling may be required to couple behavioral and physiological traits to nutritional inputs. We show that a small subset of neurons in the larval brain has high Dilp-2-mediated insulin signaling activity. This local insulin signaling activation is accompanied by selective Dilp-2 uptake and depends on the expression of the Imaginal morphogenesis protein-late 2 (Imp-L2) in the target neurons. We suggest that Imp-L2 acts as a licensing factor for neuronal IIS activation through Dilp-2 to further increase the precision of insulin activity in the brain.

  3. IGF-1 and insulin exert opposite actions on ClC-K2 activity in the cortical collecting ducts.

    Science.gov (United States)

    Zaika, Oleg; Mamenko, Mykola; Boukelmoune, Nabila; Pochynyuk, Oleh

    2015-01-01

    Despite similar stimulatory actions on the epithelial sodium channel (ENaC)-mediated sodium reabsorption in the distal tubule, insulin promotes kaliuresis, whereas insulin-like growth factor-1 (IGF-1) causes a reduction in urinary potassium levels. The factors contributing to this phenomenon remain elusive. Electrogenic distal nephron ENaC-mediated Na(+) transport establishes driving force for Cl(-) reabsorption and K(+) secretion. Using patch-clamp electrophysiology, we document that a Cl(-) channel is highly abundant on the basolateral plasma membrane of intercalated cells in freshly isolated mouse cortical collecting duct (CCD) cells. The channel has characteristics attributable to the ClC-K2: slow gating kinetics, conductance ∼10 pS, voltage independence, Cl(-)>NO3 (-) anion selectivity, and inhibition/activation by low/high pH, respectively. IGF-1 (100 and 500 nM) acutely stimulates ClC-K2 activity in a reversible manner. Inhibition of PI3-kinase (PI3-K) with LY294002 (20 μM) abrogates activation of ClC-K2 by IGF-1. Interestingly, insulin (100 nM) reversibly decreases ClC-K2 activity in CCD cells. This inhibitory action is independent of PI3-K and is mediated by stimulation of a mitogen-activated protein kinase-dependent cascade. We propose that IGF-1, by stimulating ClC-K2 channels, promotes net Na(+) and Cl(-) reabsorption, thus reducing driving force for potassium secretion by the CCD. In contrast, inhibition of ClC-K2 by insulin favors coupling of Na(+) reabsorption with K(+) secretion at the apical membrane contributing to kaliuresis. Copyright © 2015 the American Physiological Society.

  4. Differential Effects of Camel Milk on Insulin Receptor Signaling – Towards Understanding the Insulin-like Properties of Camel Milk

    Directory of Open Access Journals (Sweden)

    Abdulrasheed O Abdulrahman

    2016-01-01

    Full Text Available Previous studies on the Arabian camel (Camelus dromedarius showed beneficial effects of its milk reported in diverse models of human diseases including a substantial hypoglycemic activity. However, the cellular and molecular mechanisms involved in such effects remain completely unknown. In this study, we hypothesized that camel milk may act at the level of human insulin receptor (hIR and its related intracellular signaling pathways. Therefore, we examined the effect of camel milk on the activation of hIR transiently expressed in human embryonic kidney 293 (HEK293 cells using bioluminescence resonance energy transfer (BRET technology. BRET was used to assess, in live cells and real-time, the physical interaction between hIR and insulin receptor signaling proteins (IRS1 and the growth factor receptor-bound protein 2 (Grb2. Our data showed that camel milk did not promote any increase in the BRET signal between hIR and IRS1 or Grb2 in the absence of insulin stimulation. However, it significantly potentiated the maximal insulin-promoted BRET signal between hIR and Grb2 but not IRS1. Interestingly, camel milk appears to differentially impact the downstream signaling since it significantly activated ERK1/2 and potentiated the insulin-induced ERK1/2 but not Akt activation. These observations are to some extent consistent with the BRET data since ERK1/2 and Akt activation are known to reflect the engagement of Grb2 and IRS1 pathways, respectively. The preliminary fractionation of camel milk suggests the peptide/protein nature of the active component in camel milk. Together, our study demonstrates for the first time an allosteric effect of camel milk on insulin receptor conformation and activation with differential effects on its intracellular signaling. These findings should help to shed more light on the hypoglycemic activity of camel milk with potential therapeutic applications.

  5. Association between GRB2/Sos and insulin receptor substrate 1 is not sufficient for activation of extracellular signal-regulated kinases by interleukin-4: implications for Ras activation by insulin.

    Science.gov (United States)

    Pruett, W; Yuan, Y; Rose, E; Batzer, A G; Harada, N; Skolnik, E Y

    1995-03-01

    Insulin receptor substrate 1 (IRS-1) mediates the activation of a variety of signaling pathways by the insulin and insulin-like growth factor 1 receptors by serving as a docking protein for signaling molecules with SH2 domains. We and others have shown that in response to insulin stimulation IRS-1 binds GRB2/Sos and have proposed that this interaction is important in mediating Ras activation by the insulin receptor. Recently, it has been shown that the interleukin (IL)-4 receptor also phosphorylates IRS-1 and an IRS-1-related molecule, 4PS. Unlike insulin, however, IL-4 fails to activate Ras, extracellular signal-regulated kinases (ERKs), or mitogen-activated protein kinases. We have reconstituted the IL-4 receptor into an insulin-responsive L6 myoblast cell line and have shown that IRS-1 is tyrosine phosphorylated to similar degrees in response to insulin and IL-4 stimulation in this cell line. In agreement with previous findings, IL-4 failed to activate the ERKs in this cell line or to stimulate DNA synthesis, whereas the same responses were activated by insulin. Surprisingly, IL-4's failure to activate ERKs was not due to a failure to stimulate the association of tyrosine-phosphorylated IRS-1 with GRB2/Sos; the amounts of GRB2/Sos associated with IRS-1 were similar in insulin- and IL-4-stimulated cells. Moreover, the amounts of phosphatidylinositol 3-kinase activity associated with IRS-1 were similar in insulin- and IL-4-stimulated cells. In contrast to insulin, however, IL-4 failed to induce tyrosine phosphorylation of Shc or association of Shc with GRB2. Thus, ERK activation correlates with Shc tyrosine phosphorylation and formation of an Shc/GRB2 complex. Thus, ERK activation correlates with Shc tyrosine phosphorylation and formation of an Shc/GRB2 complex. Previous studies have indicated that activation of ERks in this cell line is dependent upon Ras since a dominant-negative Ras (Asn-17) blocks ERK activation by insulin. Our findings, taken in the context

  6. Nasal insulin changes peripheral insulin sensitivity simultaneously with altered activity in homeostatic and reward-related human brain regions.

    Science.gov (United States)

    Heni, M; Kullmann, S; Ketterer, C; Guthoff, M; Linder, K; Wagner, R; Stingl, K T; Veit, R; Staiger, H; Häring, H-U; Preissl, H; Fritsche, A

    2012-06-01

    Impaired insulin sensitivity is a major factor leading to type 2 diabetes. Animal studies suggest that the brain is involved in the regulation of insulin sensitivity. We investigated whether insulin action in the human brain regulates peripheral insulin sensitivity and examined which brain areas are involved. Insulin and placebo were given intranasally. Plasma glucose, insulin and C-peptide were measured in 103 participants at 0, 30 and 60 min. A subgroup (n = 12) was also studied with functional MRI, and blood sampling at 0, 30 and 120 min. For each time-point, the HOMA of insulin resistance (HOMA-IR) was calculated as an inverse estimate of peripheral insulin sensitivity. Plasma insulin increased and subsequently decreased. This excursion was accompanied by slightly decreased plasma glucose, resulting in an initially increased HOMA-IR. At 1 h after insulin spray, the HOMA-IR subsequently decreased and remained lower up to 120 min. An increase in hypothalamic activity was observed, which correlated with the increased HOMA-IR at 30 min post-spray. Activity in the putamen, right insula and orbitofrontal cortex correlated with the decreased HOMA-IR at 120 min post-spray. Central insulin action in specific brain areas, including the hypothalamus, may time-dependently regulate peripheral insulin sensitivity. This introduces a potential novel mechanism for the regulation of peripheral insulin sensitivity and underlines the importance of cerebral insulin action for the whole organism.

  7. Sustained Treatment with Insulin Detemir in Mice Alters Brain Activity and Locomotion.

    Directory of Open Access Journals (Sweden)

    Tina Sartorius

    Full Text Available Recent studies have identified unique brain effects of insulin detemir (Levemir®. Due to its pharmacologic properties, insulin detemir may reach higher concentrations in the brain than regular insulin. This might explain the observed increased brain stimulation after acute insulin detemir application but it remained unclear whether chronic insulin detemir treatment causes alterations in brain activity as a consequence of overstimulation.In mice, we examined insulin detemir's prolonged brain exposure by continuous subcutaneous (s.c. application using either micro-osmotic pumps or daily s.c. injections and performed continuous radiotelemetric electrocorticography and locomotion recordings.Acute intracerebroventricular injection of insulin detemir activated cortical and locomotor activity significantly more than regular insulin in equimolar doses (0.94 and 5.63 mU in total, suggesting an enhanced acute impact on brain networks. However, given continuously s.c., insulin detemir significantly reduced cortical activity (theta: 21.3±6.1% vs. 73.0±8.1%, P<0.001 and failed to maintain locomotion, while regular insulin resulted in an increase of both parameters.The data suggest that permanently-increased insulin detemir levels in the brain convert its hyperstimulatory effects and finally mediate impairments in brain activity and locomotion. This observation might be considered when human studies with insulin detemir are designed to target the brain in order to optimize treatment regimens.

  8. Insulin-induced activation of glycerol-3-phosphate acyltransferase by a chiro-inositol-containing insulin mediator is defective in adipocytes of insulin-resistant, type II diabetic, Goto-Kakizaki rats.

    Science.gov (United States)

    Farese, R V; Standaert, M L; Yamada, K; Huang, L C; Zhang, C; Cooper, D R; Wang, Z; Yang, Y; Suzuki, S; Toyota, T

    1994-11-08

    Type II diabetic Goto-Kakizaki (GK) rats were insulin-resistant in euglycemic-hyperinsulinemic clamp studies. We therefore examined insulin signaling systems in control Wistar and diabetic GK rats. Glycerol-3-phosphate acyltransferase (G3PAT), which is activated by headgroup mediators released from glycosyl-phosphatidylinositol (GPI), was activated by insulin in intact and cell-free adipocyte preparations of control, but not diabetic, rats. A specific chiro-inositol-containing inositol phosphoglycan (IPG) mediator, prepared from beef liver, bypassed this defect and comparably activated G3PAT in cell-free adipocyte preparations of both diabetic GK and control rats. A myo-inositol-containing IPG mediator did not activate G3PAT. Relative to control adipocytes, labeling of GPI by [3H]glucosamine was diminished by 50% and insulin failed to stimulate GPI hydrolysis in GK adipocytes. In contrast to GPI-dependent G3PAT activation, insulin-stimulated hexose transport was intact in adipocytes and soleus and gastrocnemius muscles of the GK rat, as was insulin-induced activation of mitogen-activated protein kinase and protein kinase C. We conclude that (i) chiro-inositol-containing IPG mediator activates G3PAT during insulin action, (ii) diabetic GK rats have a defect in synthesizing or releasing functional chiro-inositol-containing IPG, and (iii) defective IPG-regulated intracellular glucose metabolism contributes importantly to insulin resistance in diabetic GK rats.

  9. Palmitate-induced inflammatory pathways in human adipose microvascular endothelial cells promote monocyte adhesion and impair insulin transcytosis.

    Science.gov (United States)

    Pillon, Nicolas J; Azizi, Paymon M; Li, Yujin E; Liu, Jun; Wang, Changsen; Chan, Kenny L; Hopperton, Kathryn E; Bazinet, Richard P; Heit, Bryan; Bilan, Philip J; Lee, Warren L; Klip, Amira

    2015-07-01

    Obesity is associated with inflammation and immune cell recruitment to adipose tissue, muscle and intima of atherosclerotic blood vessels. Obesity and hyperlipidemia are also associated with tissue insulin resistance and can compromise insulin delivery to muscle. The muscle/fat microvascular endothelium mediates insulin delivery and facilitates monocyte transmigration, yet its contribution to the consequences of hyperlipidemia is poorly understood. Using primary endothelial cells from human adipose tissue microvasculature (HAMEC), we investigated the effects of physiological levels of fatty acids on endothelial inflammation and function. Expression of cytokines and adhesion molecules was measured by RT-qPCR. Signaling pathways were evaluated by pharmacological manipulation and immunoblotting. Surface expression of adhesion molecules was determined by immunohistochemistry. THP1 monocyte interaction with HAMEC was measured by cell adhesion and migration across transwells. Insulin transcytosis was measured by total internal reflection fluorescence microscopy. Palmitate, but not palmitoleate, elevated the expression of IL-6, IL-8, TLR2 (Toll-like receptor 2), and intercellular adhesion molecule 1 (ICAM-1). HAMEC had markedly low fatty acid uptake and oxidation, and CD36 inhibition did not reverse the palmitate-induced expression of adhesion molecules, suggesting that inflammation did not arise from palmitate uptake/metabolism. Instead, inhibition of TLR4 to NF-κB signaling blunted palmitate-induced ICAM-1 expression. Importantly, palmitate-induced surface expression of ICAM-1 promoted monocyte binding and transmigration. Conversely, palmitate reduced insulin transcytosis, an effect reversed by TLR4 inhibition. In summary, palmitate activates inflammatory pathways in primary microvascular endothelial cells, impairing insulin transport and increasing monocyte transmigration. This behavior may contribute in vivo to reduced tissue insulin action and enhanced tissue

  10. AgRP Neurons Control Systemic Insulin Sensitivity via Myostatin Expression in Brown Adipose Tissue.

    Science.gov (United States)

    Steculorum, Sophie M; Ruud, Johan; Karakasilioti, Ismene; Backes, Heiko; Engström Ruud, Linda; Timper, Katharina; Hess, Martin E; Tsaousidou, Eva; Mauer, Jan; Vogt, Merly C; Paeger, Lars; Bremser, Stephan; Klein, Andreas C; Morgan, Donald A; Frommolt, Peter; Brinkkötter, Paul T; Hammerschmidt, Philipp; Benzing, Thomas; Rahmouni, Kamal; Wunderlich, F Thomas; Kloppenburg, Peter; Brüning, Jens C

    2016-03-24

    Activation of Agouti-related peptide (AgRP) neurons potently promotes feeding, and chronically altering their activity also affects peripheral glucose homeostasis. We demonstrate that acute activation of AgRP neurons causes insulin resistance through impairment of insulin-stimulated glucose uptake into brown adipose tissue (BAT). AgRP neuron activation acutely reprograms gene expression in BAT toward a myogenic signature, including increased expression of myostatin. Interference with myostatin activity improves insulin sensitivity that was impaired by AgRP neurons activation. Optogenetic circuitry mapping reveals that feeding and insulin sensitivity are controlled by both distinct and overlapping projections. Stimulation of AgRP → LHA projections impairs insulin sensitivity and promotes feeding while activation of AgRP → anterior bed nucleus of the stria terminalis (aBNST)vl projections, distinct from AgRP → aBNSTdm projections controlling feeding, mediate the effect of AgRP neuron activation on BAT-myostatin expression and insulin sensitivity. Collectively, our results suggest that AgRP neurons in mice induce not only eating, but also insulin resistance by stimulating expression of muscle-related genes in BAT, revealing a mechanism by which these neurons rapidly coordinate hunger states with glucose homeostasis. Copyright © 2016 Elsevier Inc. All rights reserved.

  11. Loss of Interdependent Binding by the FoxO1 and FoxA1/A2 Forkhead Transcription Factors Culminates in Perturbation of Active Chromatin Marks and Binding of Transcriptional Regulators at Insulin-sensitive Genes*

    OpenAIRE

    Yalley, Akua; Schill, Daniel; Hatta, Mitsutoki; Johnson, Nicole; Cirillo, Lisa Ann

    2016-01-01

    FoxO1 binds to insulin response elements located in the promoters of insulin-like growth factor-binding protein 1 (IGFBP1) and glucose-6-phosphatase (G6Pase), activating their expression. Insulin-mediated phosphorylation of FoxO1 promotes cytoplasmic translocation, inhibiting FoxO1-mediated transactivation. We have previously demonstrated that FoxO1 opens and remodels chromatin assembled from the IGFBP1 promoter via a highly conserved winged helix motif. This finding, which established FoxO1 ...

  12. GQ-16, a Novel Peroxisome Proliferator-activated Receptor gamma (PPAR gamma) Ligand, Promotes Insulin Sensitization without Weight Gain

    NARCIS (Netherlands)

    Amato, Angelica A.; Rajagopalan, Senapathy; Lin, Jean Z.; Carvalho, Bruno M.; Figueira, Ana C. M.; Lu, Jenny; Ayers, Stephen D.; Mottin, Melina; Silveira, Rodrigo L.; Telles de Souza, Paulo; Mourao, Rosa H. V.; Saad, Mario J. A.; Togashi, Marie; Simeoni, Luiz A.; Abdalla, Dulcineia S. P.; Skaf, Munir S.; Polikparpov, Igor; Lima, Maria C. A.; Galdino, Suely L.; Brennan, Richard G.; Baxter, John D.; Pitta, Ivan R.; Webb, Paul; Phillips, Kevin J.; Neves, Francisco A. R.

    2012-01-01

    The recent discovery that peroxisome proliferator-activated receptor gamma (PPAR gamma) targeted anti-diabetic drugs function by inhibiting Cdk5-mediated phosphorylation of the receptor has provided a new viewpoint to evaluate and perhaps develop improved insulin-sensitizing agents. Herein we report

  13. Insulin receptor substrates 1 and 2 but not Shc can activate the insulin receptor independent of insulin and induce proliferation in CHO-IR cells

    International Nuclear Information System (INIS)

    Niessen, Markus; Jaschinski, Frank; Item, Flurin; McNamara, Morgan P.; Spinas, Giatgen A.; Trueb, Thomas

    2007-01-01

    Ligand-activated insulin receptor (IR) attracts and phosphorylates various substrates such as insulin receptor substrates 1-4 (IRS) and Shc. To investigate how binding affinity for substrate affects signalling we generated chimeric receptors with the β-chain of the insulin receptor containing NPXY motives with different affinities for receptor substrates. We found that the extent of receptor tyrosine phosphorylation positively correlates with binding affinity towards IRS1/2 but not towards Shc. Moreover, overexpression of IRS1 or IRS2 but not of Shc increased IR tyrosine phosphorylation in a dose-dependent manner, also independent of insulin. Molecular truncations of IRS1 revealed that neither the isolated PH and PTB domains nor the C-terminus with the tyrosine phosphorylation sites alone are sufficient for substrate-dependent receptor activation. Overexpression of IRS1 and IRS2 impaired insulin-induced internalization of the IR in a dose-dependent manner suggesting that IRS proteins prevent endosome-associated receptor dephosphorylation/inactivation. IRS1 and IRS2 could therefore target the activated IR to different cellular compartments. Overexpression of IRS1 and IRS2 inhibited insulin-stimulated activation of the MAP kinases Erk1/2 while it increased/induced activation of Akt/PKB. Finally, overexpression of IRS1 and IRS2 but not of Shc induced DNA synthesis in starved CHO-IR cells independent of exogenous growth factors. Our results demonstrate that variations in cellular IRS1 and IRS2 concentration affect insulin signalling both upstream and downstream and that IRS proteins could play instructive rather than just permissive roles in signal transmission

  14. Insulin regulation of Na/K pump activity in rat hepatoma cells

    International Nuclear Information System (INIS)

    Gelehrter, T.D.; Shreve, P.D.; Dilworth, V.M.

    1984-01-01

    Insulin rapidly increases Na/K pump activity in HTC rat hepatoma cells in tissue culture, as measured by the ouabain-sensitive influx of the potassium analogue 86Rb+. Increased influx is observed within minutes and is maximal (70% above control) within 1-2 h. The effect appears to be mediated by the insulin receptors, as: the concentration dependence on insulin is identical to that for insulin induction of tyrosine aminotransferase and stimulation of 2-aminoisobutyric acid transport, proinsulin is 6% as potent as insulin, and the effect is blocked by anti-receptor antibodies. The early stimulation of potassium influx is not blocked by cycloheximide and is not associated with an increased number of pump sites as measured by 3 H-ouabain binding. The insulin effect is blocked by amiloride, which blocks sodium influx, and is mimicked by the sodium ionophore monensin, which increases sodium influx and intracellular accumulation. Insulin also rapidly increases the initial rate of 22 Na+ influx, suggesting that insulin may enhance Na/K pump activity, in part, by increasing intracellular sodium concentration. Incubation of HTC cells with insulin for 24 h causes complete unresponsiveness to the insulin induction of transaminase and stimulation of amino acid transport, a phenomenon mediated by postbinding mechanisms. In contrast, similar incubation with insulin does not cause unresponsiveness to the insulin stimulation of Na/K pump activity. Therefore, the site of regulation of responsiveness to insulin must be distal to, or separate from, those events causing stimulation of ion fluxes

  15. Akt/PKB activation and insulin signaling: a novel insulin signaling pathway in the treatment of type 2 diabetes

    Directory of Open Access Journals (Sweden)

    Mackenzie RWA

    2014-02-01

    Full Text Available Richard WA Mackenzie, Bradley T Elliott Department of Human and Health Sciences, Facility of Science and Technology, University of Westminster, London, UK Abstract: Type 2 diabetes is a metabolic disease categorized primarily by reduced insulin sensitivity, β-cell dysfunction, and elevated hepatic glucose production. Treatments reducing hyperglycemia and the secondary complications that result from these dysfunctions are being sought after. Two distinct pathways encourage glucose transport activity in skeletal muscle, ie, the contraction-stimulated pathway reliant on Ca2+/5′-monophosphate-activated protein kinase (AMPK-dependent mechanisms and an insulin-dependent pathway activated via upregulation of serine/threonine protein kinase Akt/PKB. Metformin is an established treatment for type 2 diabetes due to its ability to increase peripheral glucose uptake while reducing hepatic glucose production in an AMPK-dependent manner. Peripheral insulin action is reduced in type 2 diabetics whereas AMPK signaling remains largely intact. This paper firstly reviews AMPK and its role in glucose uptake and then focuses on a novel mechanism known to operate via an insulin-dependent pathway. Inositol hexakisphosphate (IP6 kinase 1 (IP6K1 produces a pyrophosphate group at the position of IP6 to generate a further inositol pyrophosphate, ie, diphosphoinositol pentakisphosphate (IP7. IP7 binds with Akt/PKB at its pleckstrin homology domain, preventing interaction with phosphatidylinositol 3,4,5-trisphosphate, and therefore reducing Akt/PKB membrane translocation and insulin-stimulated glucose uptake. Novel evidence suggesting a reduction in IP7 production via IP6K1 inhibition represents an exciting therapeutic avenue in the treatment of insulin resistance. Metformin-induced activation of AMPK is a key current intervention in the management of type 2 diabetes. However, this treatment does not seem to improve peripheral insulin resistance. In light of this

  16. SH2-B promotes insulin receptor substrate 1 (IRS1)- and IRS2-mediated activation of the phosphatidylinositol 3-kinase pathway in response to leptin.

    Science.gov (United States)

    Duan, Chaojun; Li, Minghua; Rui, Liangyou

    2004-10-15

    Leptin regulates energy homeostasis primarily by binding and activating its long form receptor (LRb). Deficiency of either leptin or LRb causes morbid obesity. Leptin stimulates LRb-associated JAK2, thus initiating multiple pathways including the Stat3 and phosphatidylinositol (PI) 3-kinase pathways that mediate leptin biological actions. Here we report that SH2-B, a JAK2-interacting protein, promotes activation of the PI 3-kinase pathway by recruiting insulin receptor substrate 1 (IRS1) and IRS2 in response to leptin. SH2-B directly bound, via its PH and SH2 domain, to both IRS1 and IRS2 both in vitro and in intact cells and mediated formation of a JAK2/SH2-B/IRS1 or IRS2 tertiary complex. Consequently, SH2-B dramatically enhanced leptin-stimulated tyrosine phosphorylation of IRS1 and IRS2 in HEK293 cells stably expressing LRb, thus promoting association of IRS1 and IRS2 with the p85 regulatory subunit of PI 3-kinase and phosphorylation and activation of Akt. SH2-B mutants with lower affinity for IRS1 and IRS2 exhibited reduced ability to promote association of JAK2 with IRS1, tyrosine phosphorylation of IRS1, and association of IRS1 with p85 in response to leptin. Moreover, deletion of the SH2-B gene impaired leptin-stimulated tyrosine phosphorylation of endogenous IRS1 in mouse embryonic fibroblasts (MEF), which was reversed by reintroduction of SH2-B. Similarly, SH2-B promoted growth hormone-stimulated tyrosine phosphorylation of IRS1 in both HEK293 and MEF cells. Our data suggest that SH2-B is a novel mediator of the PI 3-kinase pathway in response to leptin or other hormones and cytokines that activate JAK2.

  17. Insulin Promoter Factor 1 variation is associated with type 2 diabetes in African Americans

    Directory of Open Access Journals (Sweden)

    Wang Xiaoqin

    2005-10-01

    Full Text Available Abstract Background Defective insulin secretion is a key defect in the pathogenesis of type 2 diabetes (T2DM. The β-cell specific transcription factor, insulin promoter factor 1 gene (IPF1, is essential to pancreatic development and the maintenance of β-cell mass. We hypothesized that regulatory or coding variants in IPF1 contribute to defective insulin secretion and thus T2DM. Methods We screened 71 Caucasian and 69 African American individuals for genetic variants in the promoter region, three highly conserved upstream regulatory sequences (PH1, PH2 and PH3, the human β-cell specific enhancer, and the two exons with adjacent introns. We tested for an association of each variant with T2DM Caucasians (192 cases and 192 controls and African Americans (341 cases and 186 controls. Results We identified 8 variants in the two populations, including a 3 bp insertion in exon 2 (InsCCG243 in African Americans that resulted in an in-frame proline insertion in the transactivation domain. No variant was associated with T2DM in Caucasians, but polymorphisms at -3766 in the human β-cell enhancer, at -2877 bp in the PH1 domain, and at -108 bp in the promoter region were associated with T2DM in African American subjects (p Conculsion The common alleles of regulatory variants in the 5' enhancer and promoter regions of the IPF1 gene increase susceptibility to type 2 diabetes among African American individuals, likely as a result of gene-gene or gene-environment interactions. In contrast, IPF1 is not a cause of type 2 diabetes in Caucasians. A previously described InsCCG243 variant may contribute to diabetes susceptibility in African American individuals, but is of low penetrance.

  18. Alteration of brain insulin and leptin signaling promotes energy homeostasis impairment and neurodegenerative diseases

    Directory of Open Access Journals (Sweden)

    Taouis Mohammed

    2011-09-01

    cerebrospinal fluid of AD patients is diminished. Taken together, these data clearly links deficiency of leptin and insulin signaling to both alterations of energy homeostasis control and predisposition to AD. Furthermore, environment changes leading to insulin and leptin-resistance may promote these defects, such as high fat diet.

  19. Fucosterol activates the insulin signaling pathway in insulin resistant HepG2 cells via inhibiting PTP1B.

    Science.gov (United States)

    Jung, Hyun Ah; Bhakta, Himanshu Kumar; Min, Byung-Sun; Choi, Jae Sue

    2016-10-01

    Insulin resistance is a characteristic feature of type 2 diabetes mellitus (T2DM) and is characterized by defects in insulin signaling. This study investigated the modulatory effects of fucosterol on the insulin signaling pathway in insulin-resistant HepG2 cells by inhibiting protein tyrosine phosphatase 1B (PTP1B). In addition, molecular docking simulation studies were performed to predict binding energies, the specific binding site of fucosterol to PTP1B, and to identify interacting residues using Autodock 4.2 software. Glucose uptake was determined using a fluorescent D-glucose analogue and the glucose tracer 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl) amino]-2-deoxyglucose, and the signaling pathway was detected by Western blot analysis. We found that fucosterol enhanced insulin-provoked glucose uptake and conjointly decreased PTP1B expression level in insulin-resistant HepG2 cells. Moreover, fucosterol significantly reduced insulin-stimulated serine (Ser307) phosphorylation of insulin receptor substrate 1 (IRS1) and increased phosphorylation of Akt, phosphatidylinositol-3-kinase, and extracellular signal- regulated kinase 1 at concentrations of 12.5, 25, and 50 µM in insulin-resistant HepG2 cells. Fucosterol inhibited caspase-3 activation and nuclear factor kappa B in insulin-resistant hepatocytes. These results suggest that fucosterol stimulates glucose uptake and improves insulin resistance by downregulating expression of PTP1B and activating the insulin signaling pathway. Thus, fucosterol has potential for development as an anti-diabetic agent.

  20. Thylakoids promote release of the satiety hormone cholecystokinin while reducing insulin in healthy humans

    DEFF Research Database (Denmark)

    Köhnke, Rickard; Lindbo, Agnes; Larsson, Therese

    2009-01-01

    (CCK, leptin and ghrelin), insulin and blood metabolites (glucose and free fatty acids). RESULTS: The CCK level increased, in particular between the 120 min time-point and onwards, the ghrelin level was reduced at 120 min and leptin level increased at 360 min after intake of the thylakoid-enriched meal....... The insulin level was reduced, whereas glucose concentrations were unchanged. Free fatty acids were reduced between time-point 120 min and onwards after the thylakoid meal. CONCLUSIONS: The addition of thylakoids to energy-dense food promotes satiety signals and reduces insulin response during a single meal......OBJECTIVE: The effects of a promising new appetite suppressor named "thylakoids" (membrane proteins derived from spinach leaves) were examined in a single meal in man. Thylakoids inhibit the lipase/colipase hydrolysis of triacylglycerols in vitro and suppress food intake, decrease body-weight gain...

  1. Short-term fasting promotes insulin expression in rat hypothalamus.

    Science.gov (United States)

    Dakic, Tamara B; Jevdjovic, Tanja V; Peric, Mina I; Bjelobaba, Ivana M; Markelic, Milica B; Milutinovic, Bojana S; Lakic, Iva V; Jasnic, Nebojsa I; Djordjevic, Jelena D; Vujovic, Predrag Z

    2017-07-01

    In the hypothalamus, insulin takes on many roles involved in energy homoeostasis. Therefore, the aim of this study was to examine hypothalamic insulin expression during the initial phase of the metabolic response to fasting. Hypothalamic insulin content was assessed by both radioimmunoassay and Western blot. The relative expression of insulin mRNA was examined by qPCR. Immunofluorescence and immunohistochemistry were used to determine the distribution of insulin immunopositivity in the hypothalamus. After 6-h fasting, both glucose and insulin levels were decreased in serum but not in the cerebrospinal fluid. Our study showed for the first time that, while the concentration of circulating glucose and insulin decreased, both insulin mRNA expression and insulin content in the hypothalamic parenchyma were increased after short-term fasting. Increased insulin immunopositivity was detected specifically in the neurons of the hypothalamic periventricular nucleus and in the ependymal cells of fasting animals. These novel findings point to the complexity of mechanisms regulating insulin expression in the CNS in general and in the hypothalamus in particular. © 2017 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

  2. Protein Kinase Mitogen-activated Protein Kinase Kinase Kinase Kinase 4 (MAP4K4) Promotes Obesity-induced Hyperinsulinemia.

    Science.gov (United States)

    Roth Flach, Rachel J; Danai, Laura V; DiStefano, Marina T; Kelly, Mark; Menendez, Lorena Garcia; Jurczyk, Agata; Sharma, Rohit B; Jung, Dae Young; Kim, Jong Hun; Kim, Jason K; Bortell, Rita; Alonso, Laura C; Czech, Michael P

    2016-07-29

    Previous studies revealed a paradox whereby mitogen-activated protein kinase kinase kinase kinase 4 (Map4k4) acted as a negative regulator of insulin sensitivity in chronically obese mice, yet systemic deletion of Map4k4 did not improve glucose tolerance. Here, we report markedly reduced glucose-responsive plasma insulin and C-peptide levels in whole body Map4k4-depleted mice (M4K4 iKO) as well as an impaired first phase of insulin secretion from islets derived from M4K4 iKO mice ex vivo After long-term high fat diet (HFD), M4K4 iKO mice pancreata also displayed reduced β cell mass, fewer proliferating β cells and reduced islet-specific gene mRNA expression compared with controls, although insulin content was normal. Interestingly, the reduced plasma insulin in M4K4 iKO mice exposed to chronic (16 weeks) HFD was not observed in response to acute HFD challenge or short term treatment with the insulin receptor antagonist S961. Furthermore, the improved insulin sensitivity in obese M4K4 iKO mice was abrogated by high exogenous insulin over the course of a euglycemic clamp study, indicating that hypoinsulinemia promotes insulin sensitivity in chronically obese M4K4 iKO mice. These results demonstrate that protein kinase Map4k4 drives obesity-induced hyperinsulinemia and insulin resistance in part by promoting insulin secretion from β cells in mice. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

  3. BPN, a marine-derived PTP1B inhibitor, activates insulin signaling and improves insulin resistance in C2C12 myotubes.

    Science.gov (United States)

    Xu, Qi; Luo, Jiao; Wu, Ning; Zhang, Renshuai; Shi, Dayong

    2018-01-01

    Insulin resistance is a key feature of type 2 diabetes mellitus (T2DM) and is characterized by defects in insulin signaling. Protein tyrosine phosphatase 1B (PTP1B) is a major negative regulator of insulin signaling cascade and has attracted intensive investigation in recent T2DM therapy study. BPN, a marine-derived bromophenol compound, was isolated from the red alga Rhodomela confervoides. This study investigated the effects of BPN on the insulin signaling pathway in insulin-resistant C2C12 myotubes by inhibiting PTP1B. Molecular docking study and analysis of small- molecule interaction with PTP1B all showed BPN inhibited PTP1B activity via binding to the catalytic site through hydrogen bonds. We then found that BPN permeated into C2C12 myotubes, on the one hand, activated insulin signaling in an insulin-independent manner in C2C12 cells; on the other hand, ameliorated palmitate-induced insulin resistance through augmenting insulin sensitivity. Moreover, our studies also showed that PTP1B inhibition by BPN increased glucose uptake in normal and insulin-resistant C2C12 myotubes through glucose transporter 4 (GLUT4) translocation. Taken together, BPN activates insulin signaling and alleviates insulin resistance and represents a potential candidate for further development as an antidiabetic agent. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Genetic variants in promoters and coding regions of the muscle glycogen synthase and the insulin-responsive GLUT4 genes in NIDDM

    DEFF Research Database (Denmark)

    Bjørbaek, C; Echwald, Søren Morgenthaler; Hubricht, P

    1994-01-01

    To examine the hypothesis that variants in the regulatory or coding regions of the glycogen synthase (GS) and insulin-responsive glucose transporter (GLUT4) genes contribute to insulin-resistant glucose processing of muscle from non-insulin-dependent diabetes mellitus (NIDDM) patients, promoter...... volunteers. By applying inverse polymerase chain reaction and direct DNA sequencing, 532 base pairs (bp) of the GS promoter were identified and the transcriptional start site determined by primer extension. SSCP scanning of the promoter region detected five single nucleotide substitutions, positioned at 42......'-untranslated region, and the coding region of the GLUT4 gene showed four polymorphisms, all single nucleotide substitutions, positioned at -581, 1, 30, and 582. None of the three changes in the regulatory region of the gene had any major influence on expression of the GLUT4 gene in muscle. The variant at 582...

  5. E4orf1 induction in adipose tissue promotes insulin-independent signaling in the adipocyte

    Directory of Open Access Journals (Sweden)

    Christine M. Kusminski

    2015-10-01

    Conclusion: We conclude that E4orf1 expression in the adipocyte leads to enhanced baseline activation of the distal insulin signaling node, yet impaired insulin receptor stimulation in the presence of insulin, with important implications for the regulation of adiponectin secretion. The resulting systemic phenotype is complex, yet highlights the powerful nature of manipulating selective branches of the insulin signaling network within the adipocyte.

  6. E4orf1 induction in adipose tissue promotes insulin-independent signaling in the adipocyte.

    Science.gov (United States)

    Kusminski, Christine M; Gallardo-Montejano, Violeta I; Wang, Zhao V; Hegde, Vijay; Bickel, Perry E; Dhurandhar, Nikhil V; Scherer, Philipp E

    2015-10-01

    Type 2 diabetes remains a worldwide epidemic with major pathophysiological changes as a result of chronic insulin resistance. Insulin regulates numerous biochemical pathways related to carbohydrate and lipid metabolism. We have generated a novel mouse model that allows us to constitutively activate, in an inducible fashion, the distal branch of the insulin signaling transduction pathway specifically in adipocytes. Using the adenoviral 36 E4orf1 protein, we chronically stimulate locally the Ras-ERK-MAPK signaling pathway. At the whole body level, this leads to reduced body-weight gain under a high fat diet challenge. Despite overlapping glucose tolerance curves, there is a reduced requirement for insulin action under these conditions. The mice further exhibit reduced circulating adiponectin levels that ultimately lead to impaired lipid clearance, and inflamed and fibrotic white adipose tissues. Nevertheless, they are protected from diet-induced hepatic steatosis. As we observe constitutively elevated p-Akt levels in the adipocytes, even under conditions of low insulin levels, this pinpoints enhanced Ras-ERK-MAPK signaling in transgenic adipocytes as a potential alternative route to bypass proximal insulin signaling events. We conclude that E4orf1 expression in the adipocyte leads to enhanced baseline activation of the distal insulin signaling node, yet impaired insulin receptor stimulation in the presence of insulin, with important implications for the regulation of adiponectin secretion. The resulting systemic phenotype is complex, yet highlights the powerful nature of manipulating selective branches of the insulin signaling network within the adipocyte.

  7. Osteoinductive activity of insulin-functionalized cell culture surfaces obtained using diazonium chemistry

    Science.gov (United States)

    Mikulska, Anna; Filipowska, Joanna; Osyczka, Anna; Nowakowska, Maria; Szczubiałka, Krzysztof

    2014-12-01

    Polymeric surfaces suitable for cell culture (DR/Pec) were constructed from diazoresin (DR) and pectin (Pec) in a form of ultrathin films using the layer-by-layer (LbL) technique. The surfaces were functionalized with insulin using diazonium chemistry. Such functionalized surfaces were used to culture human mesenchymal stem cells (hMSCs) to assess their suitability for bone tissue engineering and regeneration. The activity of insulin immobilized on the surfaces (DR/Pec/Ins) was compared to that of insulin dissolved in the culture medium. Human MSC grown on insulin-immobilized DR/Pec surfaces displayed increased proliferation and higher osteogenic activity. The latter was determined by means of alkaline phosphatase (ALP) activity, which increases at early stages of osteoblasts differentiation. Insulin dissolved in the culture medium did not stimulate cell proliferation and its osteogenic activity was significantly lower. Addition of recombinant human bone morphogenetic protein 2 (rhBMP-2) to the culture medium further increased ALP activity in hMSCs indicating additive osteogenic action of immobilized insulin and rhBMP-2

  8. Osteoinductive activity of insulin-functionalized cell culture surfaces obtained using diazonium chemistry

    Directory of Open Access Journals (Sweden)

    Anna eMikulska

    2015-01-01

    Full Text Available Polymeric surfaces suitable for cell culture (DR/Pec were constructed from diazoresin (DR and pectin (Pec in a form of ultrathin films using the layer-by-layer (LbL technique. The surfaces were functionalized with insulin using diazonium chemistry. Such functionalized surfaces were used to culture human mesenchymal stem cells (hMSCs to assess their suitability for bone tissue engineering and regeneration. The activity of insulin immobilized on the surfaces (DR/Pec/Ins was compared to that of insulin dissolved in the culture medium. Human MSC grown on insulin-immobilized DR/Pec surfaces displayed increased proliferation and higher osteogenic activity. The latter was determined by means of alkaline phosphatase (ALP activity, which increases at early stages of osteoblasts differentiation. Insulin dissolved in the culture medium did not stimulate cell proliferation and its osteogenic activity was significantly lower. Addition of recombinant human bone morphogenetic protein 2 (rhBMP-2 to the culture medium further increased ALP activity in hMSCs indicating additive osteogenic action of immobilized insulin and rhBMP-2

  9. Influence of Adiposity, Physical Activity, Fitness, and Screen Time on Insulin Dynamics Over 2 Years in Children.

    Science.gov (United States)

    Henderson, Mélanie; Benedetti, Andrea; Barnett, Tracie A; Mathieu, Marie-Eve; Deladoëy, Johnny; Gray-Donald, Katherine

    2016-03-01

    Despite extensive evidence showing that lifestyle habits play a critical role in preventing or delaying the onset of type 2 diabetes in adults, little is known regarding the impact of lifestyle habits on type 2 diabetes risk in childhood. To assess whether adiposity, fitness, moderate-to-vigorous physical activity, and screen time predict insulin sensitivity or insulin secretion during a 2-year period in children with a family history of obesity. This is a prospective longitudinal cohort study of 630 children, having at least 1 obese parent, recruited from schools in Quebec, Canada, between July 2005 and December 2008 in the Quebec Adipose and Lifestyle Investigation in Youth (QUALITY) cohort. Children were assessed at baseline (ages 8-10 years) and 2 years later. Fitness was measured by peak oxygen consumption, percentage of body fat (adiposity) by dual-energy x-ray absorptiometry, moderate-to-vigorous physical activity using accelerometry, and screen time by average daily hours of self-reported television, video game, or computer use. Regression models were adjusted for age, sex, season, and pubertal stage. The current analysis was completed in October 2015. Insulin sensitivity was measured by the homeostatic model assessment of insulin resistance and an oral glucose tolerance test-based index (Matsuda insulin sensitivity index). Insulin secretion was measured using the area under the curve of insulin to glucose during the first 30 minutes of the oral glucose tolerance test and using the area under the curve of insulin to glucose over 2 hours. Of 630 children evaluated at baseline (mean [SD] age, 9.6 [0.9] years; 54.4% male; 56.2% normal weight, 19.2% overweight, and 22.7% obese), 564 were evaluated at 2-year follow-up. Adiposity and changes in adiposity were the central predictors of insulin dynamics over time. Every additional 1% of body fat at ages 8 to 10 years decreased insulin sensitivity by 2.9% (95% CI, -3.3% to -2.5%; P effect on adiposity levels

  10. Insulin resistance in non-obese subjects is associated with activation of the JNK pathway and impaired insulin signaling in skeletal muscle.

    Directory of Open Access Journals (Sweden)

    Umesh B Masharani

    2011-05-01

    Full Text Available The pathogenesis of insulin resistance in the absence of obesity is unknown. In obesity, multiple stress kinases have been identified that impair the insulin signaling pathway via serine phosphorylation of key second messenger proteins. These stress kinases are activated through various mechanisms related to lipid oversupply locally in insulin target tissues and in various adipose depots.To explore whether specific stress kinases that have been implicated in the insulin resistance of obesity are potentially contributing to insulin resistance in non-obese individuals, twenty healthy, non-obese, normoglycemic subjects identified as insulin sensitive or resistant were studied. Vastus lateralis muscle biopsies obtained during euglycemic, hyperinsulinemic clamp were evaluated for insulin signaling and for activation of stress kinase pathways. Total and regional adipose stores and intramyocellular lipids (IMCL were assessed by DXA, MRI and (1H-MRS. In muscle of resistant subjects, phosphorylation of JNK was increased (1.36±0.23 vs. 0.78±0.10 OD units, P<0.05, while there was no evidence for activation of p38 MAPK or IKKβ. IRS-1 serine phosphorylation was increased (1.30±0.09 vs. 0.22±0.03 OD units, P<0.005 while insulin-stimulated tyrosine phosphorylation decreased (10.97±0.95 vs. 0.89±0.50 OD units, P<0.005. IMCL levels were twice as high in insulin resistant subjects (3.26±0.48 vs. 1.58±0.35% H(2O peak, P<0.05, who also displayed increased total fat and abdominal fat when compared to insulin sensitive controls.This is the first report demonstrating that insulin resistance in non-obese, normoglycemic subjects is associated with activation of the JNK pathway related to increased IMCL and higher total body and abdominal adipose stores. While JNK activation is consistent with a primary impact of muscle lipid accumulation on metabolic stress, further work is necessary to determine the relative contributions of the various mediators of impaired

  11. Identification of SH2B2β as an Inhibitor for SH2B1- and SH2B2α-Promoted Janus Kinase-2 Activation and Insulin Signaling

    OpenAIRE

    Li, Minghua; Li, Zhiqin; Morris, David L.; Rui, Liangyou

    2007-01-01

    The SH2B family has three members (SH2B1, SH2B2, and SH2B3) that contain conserved dimerization (DD), pleckstrin homology, and SH2 domains. The DD domain mediates the formation of homo- and heterodimers between members of the SH2B family. The SH2 domain of SH2B1 (previously named SH2-B) or SH2B2 (previously named APS) binds to phosphorylated tyrosines in a variety of tyrosine kinases, including Janus kinase-2 (JAK2) and the insulin receptor, thereby promoting the activation of JAK2 or the ins...

  12. DsbA-L prevents obesity-induced inflammation and insulin resistance by suppressing the mtDNA release-activated cGAS-cGAMP-STING pathway.

    Science.gov (United States)

    Bai, Juli; Cervantes, Christopher; Liu, Juan; He, Sijia; Zhou, Haiyan; Zhang, Bilin; Cai, Huan; Yin, Dongqing; Hu, Derong; Li, Zhi; Chen, Hongzhi; Gao, Xiaoli; Wang, Fang; O'Connor, Jason C; Xu, Yong; Liu, Meilian; Dong, Lily Q; Liu, Feng

    2017-11-14

    Chronic inflammation in adipose tissue plays a key role in obesity-induced insulin resistance. However, the mechanisms underlying obesity-induced inflammation remain elusive. Here we show that obesity promotes mtDNA release into the cytosol, where it triggers inflammatory responses by activating the DNA-sensing cGAS-cGAMP-STING pathway. Fat-specific knockout of disulfide-bond A oxidoreductase-like protein (DsbA-L), a chaperone-like protein originally identified in the mitochondrial matrix, impaired mitochondrial function and promoted mtDNA release, leading to activation of the cGAS-cGAMP-STING pathway and inflammatory responses. Conversely, fat-specific overexpression of DsbA-L protected mice against high-fat diet-induced activation of the cGAS-cGAMP-STING pathway and inflammation. Taken together, we identify DsbA-L as a key molecule that maintains mitochondrial integrity. DsbA-L deficiency promotes inflammation and insulin resistance by activating the cGAS-cGAMP-STING pathway. Our study also reveals that, in addition to its well-characterized roles in innate immune surveillance, the cGAS-cGAMP-STING pathway plays an important role in mediating obesity-induced metabolic dysfunction.

  13. Effects of insulin on messenger RNA activities in rat liver

    International Nuclear Information System (INIS)

    Hill, R.E.; Lee, K.L.; Kenney, F.T.

    1981-01-01

    Liver poly(A) RNA, isolated from adrenalectomized rats after insulin treatment, was translated in a nuclease-treated lysate of rabbit reticulocytes and quantitated for both total activity and the capacity to synthesize the insulin-inducible enzyme tyrosine amino-transferase. Analysis of the translated products from poly(A) RNA isolated 1 h after insulin treatment showed a 2.7-fold increase in activity of tyrosine aminotransferase mRNA. During the same interval, the capacity of poly(A) RNA to direct the synthesis of total protein in lysates also changed, showing a 30 to 40% increase in translational activity/unit of RNA. Increased translatability was apparent in all fractions of poly(A) RNA separated by centrifugation on sucrose gradients. Insulin thus appears to mediated a generalized changed in mRNAs leading to increased capacity for translation; induction of tyrosine aminotransferase may reflect unusual sensitivity to this effect of the hormone

  14. Activated α2-macroglobulin binding to human prostate cancer cells triggers insulin-like responses.

    Science.gov (United States)

    Misra, Uma Kant; Pizzo, Salvatore Vincent

    2015-04-10

    Ligation of cell surface GRP78 by activated α2-macroglobulin (α2M*) promotes cell proliferation and suppresses apoptosis. α2M*-treated human prostate cancer cells exhibit a 2-3-fold increase in glucose uptake and lactate secretion, an effect similar to insulin treatment. In both α2M* and insulin-treated cells, the mRNA levels of SREBP1-c, SREBP2, fatty-acid synthase, acetyl-CoA carboxylase, ATP citrate lyase, and Glut-1 were significantly increased together with their protein levels, except for SREBP2. Pretreatment of cells with α2M* antagonist antibody directed against the carboxyl-terminal domain of GRP78 blocks these α2M*-mediated effects, and silencing GRP78 expression by RNAi inhibits up-regulation of ATP citrate lyase and fatty-acid synthase. α2M* induces a 2-3-fold increase in lipogenesis as determined by 6-[(14)C]glucose or 1-[(14)C]acetate incorporation into free cholesterol, cholesterol esters, triglycerides, free fatty acids, and phosphatidylcholine, which is blocked by inhibitors of fatty-acid synthase, PI 3-kinase, mTORC, or an antibody against the carboxyl-terminal domain of GRP78. We also assessed the incorporation of [(14)CH3]choline into phosphatidylcholine and observed similar effects. Lipogenesis is significantly affected by pretreatment of prostate cancer cells with fatostatin A, which blocks sterol regulatory element-binding protein proteolytic cleavage and activation. This study demonstrates that α2M* functions as a growth factor, leading to proliferation of prostate cancer cells by promoting insulin-like responses. An antibody against the carboxyl-terminal domain of GRP78 may have important applications in prostate cancer therapy. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  15. Identification of a growth hormone-responsive STAT5-binding element in the rat insulin 1 gene

    DEFF Research Database (Denmark)

    Galsgaard, E D; Gouilleux, F; Groner, B

    1996-01-01

    promoter activity 2-fold, and this stimulation was abolished by introduction of a block mutation in a gamma-interferon-activated sequence (GAS)-like element (GLE) with the sequence 5'-TTCTGGGAA-3' located in the rat insulin 1 enhancer at position -330 to -322. This element, termed Ins-GLE, was able...... transfected with STAT5 and GH receptor cDNAs, it was found that expression of STAT5 was necessary for GH induction of these two DNA-binding complexes. These results suggest that GH stimulates insulin 1 promoter activity by inducing the binding of STAT5 to Ins-GLE.......GH and PRL stimulate both proliferation and insulin production in pancreatic beta-cells as well as in the rat insulinoma cell line RIN-5AH, We report here that human GH increases insulin mRNA levels in RIN-5AH cells via both somatogenic and lactogenic receptors. GH stimulated the rat insulin 1...

  16. The insulin and IGF1 receptor kinase domains are functional dimers in the activated state

    Science.gov (United States)

    Cabail, M. Zulema; Li, Shiqing; Lemmon, Eric; Bowen, Mark E.; Hubbard, Stevan R.; Miller, W. Todd

    2015-03-01

    The insulin receptor (IR) and insulin-like growth factor-1 receptor (IGF1R) are highly related receptor tyrosine kinases with a disulfide-linked homodimeric architecture. Ligand binding to the receptor ectodomain triggers tyrosine autophosphorylation of the cytoplasmic domains, which stimulates catalytic activity and creates recruitment sites for downstream signalling proteins. Whether the two phosphorylated tyrosine kinase domains within the receptor dimer function independently or cooperatively to phosphorylate protein substrates is not known. Here we provide crystallographic, biophysical and biochemical evidence demonstrating that the phosphorylated kinase domains of IR and IGF1R form a specific dimeric arrangement involving an exchange of the juxtamembrane region proximal to the kinase domain. In this dimer, the active position of α-helix C in the kinase N lobe is stabilized, which promotes downstream substrate phosphorylation. These studies afford a novel strategy for the design of small-molecule IR agonists as potential therapeutic agents for type 2 diabetes.

  17. Insulin VNTR and IGF-1 promoter region polymorphisms are not associated with body composition in early childhood: The generation R study

    NARCIS (Netherlands)

    J.A.J.B.M. Maas (Janneke); D.O. Mook-Kanamori (Dennis); L. Ay (Lamise); R.P.M. Steegers-Theunissen (Régine); P. Tikka-Kleemola (Päivi); A. Hofman (Albert); A.C.S. Hokken-Koelega (Anita); V.W.V. Jaddoe (Vincent)

    2010-01-01

    textabstractObjective: The objective of this study was to examine the associations between insulin gene variable number of tandem repeats (INS VNTR) and insulin-like growth factor 1 (IGF1) gene promoter region polymorphisms with body composition in early childhood. Methods: This study was embedded

  18. Insulin treatment promotes tyrosine phosphorylation of PKR and inhibits polyIC induced PKR threonine phosphorylation.

    Science.gov (United States)

    Swetha, Medchalmi; Ramaiah, Kolluru V A

    2015-11-01

    Tyrosine phosphorylation of insulin receptor beta (IRβ) in insulin treated HepG2 cells is inversely correlated to ser(51) phosphorylation in the alpha-subunit of eukaryotic initiation factor 2 (eIF2α) that regulates protein synthesis. Insulin stimulates interaction between IRβ and PKR, double stranded RNA-dependent protein kinase, also known as EIF2AK2, and phosphorylation of tyrosine residues in PKR, as analyzed by immunoprecipitation and pull down assays using anti-IRβ and anti-phosphotyrosine antibodies, recombinant IRβ and immunopurified PKR. Further polyIC or synthetic double stranded RNA-induced threonine phosphorylation or activation of immunopurified and cellular PKR is suppressed in the presence of insulin treated purified IRβ and cell extracts. Acute, but not chronic, insulin treatment enhances tyrosine phosphorylation of IRβ, its interaction with PKR and tyrosine phosphorylation of PKR. In contrast, lipopolysaccharide that stimulates threonine phosphorylation of PKR and eIF2α phosphorylation and AG 1024, an inhibitor of the tyrosine kinase activity of IRβ, reduces PKR association with the receptor, IRβ in HepG2 cells. These findings therefore may suggest that tyrosine phosphorylated PKR plays a role in the regulation of insulin induced protein synthesis and in maintaining insulin sensitivity, whereas, suppression of polyIC-mediated threonine phosphorylation of PKR by insulin compromises its ability to fight against virus infection in host cells. Copyright © 2015 Elsevier Inc. All rights reserved.

  19. Insulin and TOR signal in parallel through FOXO and S6K to promote epithelial wound healing

    Science.gov (United States)

    Kakanj, Parisa; Moussian, Bernard; Grönke, Sebastian; Bustos, Victor; Eming, Sabine A.; Partridge, Linda; Leptin, Maria

    2016-01-01

    The TOR and Insulin/IGF signalling (IIS) network controls growth, metabolism and ageing. Although reducing TOR or insulin signalling can be beneficial for ageing, it can be detrimental for wound healing, but the reasons for this difference are unknown. Here we show that IIS is activated in the cells surrounding an epidermal wound in Drosophila melanogaster larvae, resulting in PI3K activation and redistribution of the transcription factor FOXO. Insulin and TOR signalling are independently necessary for normal wound healing, with FOXO and S6K as their respective effectors. IIS is specifically required in cells surrounding the wound, and the effect is independent of glycogen metabolism. Insulin signalling is needed for the efficient assembly of an actomyosin cable around the wound, and constitutively active myosin II regulatory light chain suppresses the effects of reduced IIS. These findings may have implications for the role of insulin signalling and FOXO activation in diabetic wound healing. PMID:27713427

  20. Measuring phospholipase D activity in insulin-secreting pancreatic beta-cells and insulin-responsive muscle cells and adipocytes.

    Science.gov (United States)

    Cazzolli, Rosanna; Huang, Ping; Teng, Shuzhi; Hughes, William E

    2009-01-01

    Phospholipase D (PLD) is an enzyme producing phosphatidic acid and choline through hydrolysis of phosphatidylcholine. The enzyme has been identified as a member of a variety of signal transduction cascades and as a key regulator of numerous intracellular vesicle trafficking processes. A role for PLD in regulating glucose homeostasis is emerging as the enzyme has recently been identified in events regulating exocytosis of insulin from pancreatic beta-cells and also in insulin-stimulated glucose uptake through controlling GLUT4 vesicle exocytosis in muscle and adipose tissue. We present methodologies for assessing cellular PLD activity in secretagogue-stimulated insulin-secreting pancreatic beta-cells and also insulin-stimulated adipocyte and muscle cells, two of the principal insulin-responsive cell types controlling blood glucose levels.

  1. Insulin-induced activation of glycerol-3-phosphate acyltransferase by a chiro-inositol-containing insulin mediator is defective in adipocytes of insulin-resistant, type II diabetic, Goto-Kakizaki rats.

    OpenAIRE

    Farese, R V; Standaert, M L; Yamada, K; Huang, L C; Zhang, C; Cooper, D R; Wang, Z; Yang, Y; Suzuki, S; Toyota, T

    1994-01-01

    Type II diabetic Goto-Kakizaki (GK) rats were insulin-resistant in euglycemic-hyperinsulinemic clamp studies. We therefore examined insulin signaling systems in control Wistar and diabetic GK rats. Glycerol-3-phosphate acyltransferase (G3PAT), which is activated by headgroup mediators released from glycosyl-phosphatidylinositol (GPI), was activated by insulin in intact and cell-free adipocyte preparations of control, but not diabetic, rats. A specific chiro-inositol-containing inositol phosph...

  2. Insulin receptor binding and protein kinase activity in muscles of trained rats

    International Nuclear Information System (INIS)

    Dohm, G.L.; Sinha, M.K.; Caro, J.F.

    1987-01-01

    Exercise has been shown to increase insulin sensitivity, and muscle is quantitatively the most important tissue of insulin action. Since the first step in insulin action is the binding to a membrane receptor, the authors postulated that exercise training would change insulin receptors in muscle and in this study they have investigated this hypothesis. Female rats initially weighing ∼ 100 g were trained by treadmill running for 2 h/day, 6 days/wk for 4 wk at 25 m/min (0 grade). Insulin receptors from vastus intermedius muscles were solubilized by homogenizing in a buffer containing 1% Triton X-100 and then partially purified by passing the soluble extract over a wheat germ agglutinin column. The 4 wk training regimen resulted in a 65% increase in citrate synthase activity in red vastus lateralis muscle, indicating an adaptation to exercise [ 125 I]. Insulin binding by the partially purified receptor preparations was approximately doubled in muscle of trained rats at all insulin concentrations, suggesting an increase in the number of receptors. Training did not alter insulin receptor structure as evidenced by electrophoretic mobility under reducing and nonreducing conditions. Basal insulin receptor protein kinase activity was higher in trained than untrained animals and this was likely due to the greater number of receptors. However, insulin stimulation of the protein kinase activity was depressed by training. These results demonstrate that endurance training does alter receptor number and function in muscle and these changes may be important in increasing insulin sensitivity after exercise training

  3. Glycogen Synthase Kinase-3 regulates IGFBP-1 gene transcription through the Thymine-rich Insulin Response Element

    Directory of Open Access Journals (Sweden)

    Marquez Rodolfo

    2004-09-01

    Full Text Available Abstract Background Hepatic expression of several gene products involved in glucose metabolism, including phosphoenolpyruvate carboxykinase (PEPCK, glucose-6-phosphatase (G6Pase and insulin-like growth factor binding protein-1 (IGFBP-1, is rapidly and completely inhibited by insulin. This inhibition is mediated through the regulation of a DNA element present in each of these gene promoters, that we call the Thymine-rich Insulin Response Element (TIRE. The insulin signalling pathway that results in the inhibition of these gene promoters requires the activation of phosphatidylinositol 3-kinase (PI 3-kinase. However, the molecules that connect PI 3-kinase to these gene promoters are not yet fully defined. Glycogen Synthase Kinase 3 (GSK-3 is inhibited following activation of PI 3-kinase. We have shown previously that inhibitors of GSK-3 reduce the activity of two TIRE-containing gene promoters (PEPCK and G6Pase, whose products are required for gluconeogenesis. Results In this report we demonstrate that in H4IIE-C3 cells, four distinct classes of GSK-3 inhibitor mimic the effect of insulin on a third TIRE-containing gene, IGFBP-1. We identify the TIRE as the minimum requirement for inhibition by these agents, and demonstrate that the target of GSK-3 is unlikely to be the postulated TIRE-binding protein FOXO-1. Importantly, overexpression of GSK-3 in cells reduces the insulin regulation of TIRE activity as well as endogenous IGFBP-1 expression. Conclusions These results implicate GSK-3 as an intermediate in the pathway from the insulin receptor to the TIRE. Indeed, this is the first demonstration of an absolute requirement for GSK-3 inhibition in insulin regulation of gene transcription. These data support the potential use of GSK-3 inhibitors in the treatment of insulin resistant states such as Type 2 diabetes mellitus, but suggest that it will be important to identify all TIRE-containing genes to assess potential side effects of these agents.

  4. PKB/Akt phosphorylation of ERRγ contributes to insulin-mediated inhibition of hepatic gluconeogenesis.

    Science.gov (United States)

    Kim, Don-Kyu; Kim, Yong-Hoon; Hynx, Debby; Wang, Yanning; Yang, Keum-Jin; Ryu, Dongryeol; Kim, Kyung Seok; Yoo, Eun-Kyung; Kim, Jeong-Sun; Koo, Seung-Hoi; Lee, In-Kyu; Chae, Ho-Zoon; Park, Jongsun; Lee, Chul-Ho; Biddinger, Sudha B; Hemmings, Brian A; Choi, Hueng-Sik

    2014-12-01

    Insulin resistance, a major contributor to the pathogenesis of type 2 diabetes, leads to increased hepatic glucose production (HGP) owing to an impaired ability of insulin to suppress hepatic gluconeogenesis. Nuclear receptor oestrogen-related receptor γ (ERRγ) is a major transcriptional regulator of hepatic gluconeogenesis. In this study, we investigated insulin-dependent post-translational modifications (PTMs) altering the transcriptional activity of ERRγ for the regulation of hepatic gluconeogenesis. We examined insulin-dependent phosphorylation and subcellular localisation of ERRγ in cultured cells and in the liver of C57/BL6, leptin receptor-deficient (db/db), liver-specific insulin receptor knockout (LIRKO) and protein kinase B (PKB) β-deficient (Pkbβ (-/-)) mice. To demonstrate the role of ERRγ in the inhibitory action of insulin on hepatic gluconeogenesis, we carried out an insulin tolerance test in C57/BL6 mice expressing wild-type or phosphorylation-deficient mutant ERRγ. We demonstrated that insulin suppressed the transcriptional activity of ERRγ by promoting PKB/Akt-mediated phosphorylation of ERRγ at S179 and by eliciting translocation of ERRγ from the nucleus to the cytoplasm through interaction with 14-3-3, impairing its ability to promote hepatic gluconeogenesis. In addition, db/db, LIRKO and Pkbβ (-/-) mice displayed enhanced ERRγ transcriptional activity due to a block in PKBβ-mediated ERRγ phosphorylation during refeeding. Finally, the phosphorylation-deficient mutant ERRγ S179A was resistant to the inhibitory action of insulin on HGP. These results suggest that ERRγ is a major contributor to insulin action in maintaining hepatic glucose homeostasis.

  5. Insulin-like growth factors: assay methods and their implications

    International Nuclear Information System (INIS)

    Guyda, H.J.; Posner, B.I.; Schiffrin, A.; Rappaport, R.; Postel-Vinay, M.C.; Corvol, M.T.

    1981-01-01

    The insulin-like growth factors (IGF's) are small molecular weight peptides (6-10 x 10 3 daltons) that circulate in blood plasma almost entirely bound to macromolecular carrier proteins. The growth-promoting and insulin-like activities of IGF's can be explained by the observed ability of these peptides to interact with the IGF receptor on the one hand and with the insulin receptor on the other. These observations have led to the establishment of radioreceptor assays (RRA's), competitive protein binding assays (CPBA's), and more recently radioimmunoassays (RIA's) for the IGF's that have different specificities. Because of their ease of performance and sensitivity, the radioligand assays have largely supplanted the biological assays originally utilized to identify and characterize these anabolic peptides. In this report the authors' studies are summarised which utilize a slightly acidic IGF which has been purified on the basis of its insulin-like activity in an insulin RRA and which was termed ILAs. They refer to purified insulin-like peptides that have the properties of a somatomedin by the generic term insulin-like growth factor (IGF). Somatomedin (SM) activity will be utilized to connote that activity in plasma or serum determined by bioassay. The competitive dose-response curves for IGF peptides in the insulin RRA as well as those in the ILAs RRA are presented. A combination of bioassays, RRA and RIA were employed to assess somatomedin activity and IGF peptide levels in a number of clinical circumstances. The correlations are discussed. (Auth.)

  6. Defective insulin signaling pathway and increased glycogen synthase kinase-3 activity in the brain of diabetic mice: parallels with Alzheimer's disease and correction by insulin.

    Science.gov (United States)

    Jolivalt, C G; Lee, C A; Beiswenger, K K; Smith, J L; Orlov, M; Torrance, M A; Masliah, E

    2008-11-15

    We have evaluated the effect of peripheral insulin deficiency on brain insulin pathway activity in a mouse model of type 1 diabetes, the parallels with Alzheimer's disease (AD), and the effect of treatment with insulin. Nine weeks of insulin-deficient diabetes significantly impaired the learning capacity of mice, significantly reduced insulin-degrading enzyme protein expression, and significantly reduced phosphorylation of the insulin-receptor and AKT. Phosphorylation of glycogen synthase kinase-3 (GSK3) was also significantly decreased, indicating increased GSK3 activity. This evidence of reduced insulin signaling was associated with a concomitant increase in tau phosphorylation and amyloid beta protein levels. Changes in phosphorylation levels of insulin receptor, GSK3, and tau were not observed in the brain of db/db mice, a model of type 2 diabetes, after a similar duration (8 weeks) of diabetes. Treatment with insulin from onset of diabetes partially restored the phosphorylation of insulin receptor and of GSK3, partially reduced the level of phosphorylated tau in the brain, and partially improved learning ability in insulin-deficient diabetic mice. Our data indicate that mice with systemic insulin deficiency display evidence of reduced insulin signaling pathway activity in the brain that is associated with biochemical and behavioral features of AD and that it can be corrected by insulin treatment.

  7. Functional characterization of autophosphorylation sites of the activated insulin receptor-tyrosine kinase

    International Nuclear Information System (INIS)

    Flores-Riveros, J.R.; Lane, M.D.

    1987-01-01

    Insulin receptor, solubilized from 3T3-L1 cellular membranes and then purified, was autophosphorylated with [γ- 32 P]ATP in the absence or presence of insulin. Specific phosphopeptides generated by trypsin digestion of the 32 P-labeled β-subunit were identified and separated by reverse phase HPLC. In the absence of insulin, radioactivity of the phosphopeptides is evenly distributed among four major peaks designated as sites I, II, III and IV, according to their order of elution. This pattern is maintained for at least the first 30 min of autophosphorylation. When the reaction is carried out in the presence of insulin, > 50% of the total 32 P radioactivity is found in site I and the rate of 32 P incorporation into this site is markedly higher than into sites II, III and IV. Maximal activation of tyrosine kinase activity, as estimated by substrate phosphorylation, is coincident with the nearly complete phosphorylation of site I. Delayed activation of previously autophosphorylated receptor by insulin, but not by EGF or IGF-I, produced a similar pattern where phosphorylated site I predominates. These observations indicate that one major insulin-regulated autophosphorylation site in the β-subunit is responsible for activation of the insulin receptor tyrosine kinase. The isolation of this phosphopeptide on a preparative scale and its characterization are now in progress

  8. Insulin Treatment Cannot Promote Lipogenesis in Rat Fetal Lung in Gestational Diabetes Mellitus Because of Failure to Redress the Imbalance Among SREBP-1, SCAP, and INSIG-1.

    Science.gov (United States)

    Li, Jinyan; Qian, Guanhua; Zhong, Xiaocui; Yu, Tinghe

    2018-03-01

    Gestational diabetes mellitus (GDM) has a higher incidence of neonatal respiratory distress syndrome, and lipogenesis is required for the synthesis of pulmonary surfactants. The aim of this study was to determine the effect of insulin treatment in GDM on the production of lipids in the lungs of fetal rats. GDM was induced by streptozotocin, and insulin was used to manage diabetes. Type II alveolar epithelial cells (AEC II), bronchoalveolar lavage fluid (BALF), and lung tissues of the neonatal rats were sampled for analyses. Insulin treatment could not decrease plasma glucose to normal level at a later gestational stage. Lipids/phospholipids in AEC II, BALF, and lung tissues decreased in GDM, and insulin treatment could not increase the levels; quantitative PCR and western blotting demonstrated a lower level of sterol regulator element-binding protein 1 (SREBP-1), SREBP cleavage-activating protein (SCAP), and insulin-induced gene 1 (INSIG-1) in GDM, but insulin treatment upregulated only SREBP-1. Nuclear translocation of the SREBP-1 protein in AEC II was impaired in GDM, which could not be ameliorated by insulin treatment. These findings indicated that insulin treatment in GDM cannot promote lipogenesis in the fetal lung because of failure to redress the imbalance among SREBP-1, SCAP, and INSIG-1.

  9. Dipeptidyl peptidase-4 impairs insulin signaling and promotes lipid accumulation in hepatocytes

    International Nuclear Information System (INIS)

    Rufinatscha, Kerstin; Radlinger, Bernhard; Dobner, Jochen; Folie, Sabrina; Bon, Claudia; Profanter, Elisabeth; Ress, Claudia; Salzmann, Karin; Staudacher, Gabriele; Tilg, Herbert; Kaser, Susanne

    2017-01-01

    Dipeptidyl-peptidase 4 [DPP-4) has evolved into an important target in diabetes therapy due to its role in incretin hormone metabolism. In contrast to its systemic effects, cellular functions of membranous DPP-4 are less clear. Here we studied the role of DPP-4 in hepatic energy metabolism. In order to distinguish systemic from cellular effects we established a cell culture model of DPP-4 knockdown in human hepatoma cell line HepG2. DPP-4 suppression was associated with increased basal glycogen content due to enhanced insulin signaling as shown by increased phosphorylation of insulin-receptor substrate 1 (IRS-1), protein kinase B/Akt and mitogen-activated protein kinases (MAPK)/ERK, respectively. Additionally, glucose-6-phosphatase cDNA expression was significantly decreased in DPP-4 deficiency. Reduced triglyceride content in DPP-4 knockdown cells was paralleled by enhanced expressions of peroxisome proliferator-activated receptor alpha (PPARα) and carnitine palmitoyltransferase −1 (CPT-1) while sterol regulatory element-binding protein 1c (SREBP-1c) expression was significantly decreased. Our data suggest that hepatic DPP-4 induces a selective pathway of insulin resistance with reduced glycogen storage, enhanced glucose output and increased lipid accumulation in the liver. Hepatic DPP-4 might be a novel target in fatty liver disease in patients with glucose intolerance. - Highlights: • DPP-IV knockdown results in increased insulin signaling in hepatocytes. • Increased fatty acid oxidation and decreased lipogenesis result in reduced hepatic triglyceride content in DPP-IV deficiency. • Hepatic DPP-IV induces a selective pathway of insulin resistance with increased triglyceride accumulation in the liver.

  10. DsbA-L prevents obesity-induced inflammation and insulin resistance by suppressing the mtDNA release-activated cGAS-cGAMP-STING pathway

    Science.gov (United States)

    Chronic inflammation in adipose tissue plays a key role in obesity-induced insulin resistance. However, the mechanisms underlying obesity-induced inflammation remain elusive. Here we show that obesity promotes mtDNA release into the cytosol, where it triggers inflammatory responses by activating the...

  11. Polyethyleneglycol RIA (radioimmunoassay) insulin

    International Nuclear Information System (INIS)

    1988-01-01

    Insulin is a polypeptide hormone of M.W. 6,000 composed of two peptide chains, A and B, jointed by two cross-linked disulphide bonds and synthesized by the beta-cells of the islets of Langerhans of the pancreas. Insulin influences most of the metabolic functions of the body. Its best known action is to lower the blood glucose concentration by increasing the rate at which glucose is converted to glycogen in the liver and muscles and to fat in adipose tissue, by stimulating the rate of glucose metabolism and by depressing gluconeogenesis. Insulin stimulates the synthesis of proteins, DNA and RNA in cells generally, and promotes the uptake of aminoacids and their incorporation into muscle protein. It increases the uptake of glucose in adipose tissue and its conversion into fat and inhibits lipolysis. Insulin primary action is on the cell membrane, where it probably facilitates the transport of glucose and aminoacids into the cells. At the same time it may activate intracellular enzymes such as glycogen synthetase, concerned with glycogen synthesis. (Author) [es

  12. Interaction between the p21ras GTPase activating protein and the insulin receptor

    NARCIS (Netherlands)

    Pronk, G.J.; Medema, R.H.; Burgering, B.M.T.; Clark, R.; McCormick, F.; Bos, J.L.

    1992-01-01

    We investigated the involvement of the p21ras-GTPase activating protein (GAP) in insulin-induced signal transduction. In cells overexpressing the insulin receptor, we did not observe association between GAP and the insulin receptor after insulin treatment nor the phosphorylation of GAP on tyrosine

  13. Pancreatic β-Cell Electrical Activity and Insulin Secretion: of Mice and Men

    Science.gov (United States)

    Rorsman, Patrik; Ashcroft, Frances M

    2018-01-01

    The pancreatic β-cell plays a key role in glucose homeostasis by secreting insulin, the only hormone capable of lowering the blood glucose concentration. Impaired insulin secretion results in the chronic hyperglycaemia that characterizes type 2 diabetes (T2DM), which currently afflicts >450 million people worldwide. The healthy β-cell acts as a glucose sensor matching its output to the circulating glucose concentration. It does so via metabolically induced changes in electrical activity, which culminate in an increase in the cytoplasmic Ca2+ concentration and initiation of Ca2+-dependent exocytosis of insulin-containing secretory granules. Here, we review recent advances in our understanding of the β-cell transcriptome, electrical activity and insulin exocytosis. We highlight salient differences between mouse and human β-cells, provide models of how the different ion channels contribute to their electrical activity and insulin secretion, and conclude by discussing how these processes become perturbed in T2DM. PMID:29212789

  14. Aβ-Induced Insulin Resistance and the Effects of Insulin on the Cholesterol Synthesis Pathway and Aβ Secretion in Neural Cells.

    Science.gov (United States)

    Najem, Dema; Bamji-Mirza, Michelle; Yang, Ze; Zhang, Wandong

    2016-06-01

    Alzheimer's disease (AD) is characterized by amyloid-β (Aβ) toxicity, tau pathology, insulin resistance, neuroinflammation, and dysregulation of cholesterol homeostasis, all of which play roles in neurodegeneration. Insulin has polytrophic effects on neurons and may be at the center of these pathophysiological changes. In this study, we investigated possible relationships among insulin signaling and cholesterol biosynthesis, along with the effects of Aβ42 on these pathways in vitro. We found that neuroblastoma 2a (N2a) cells transfected with the human gene encoding amyloid-β protein precursor (AβPP) (N2a-AβPP) produced Aβ and exhibited insulin resistance by reduced p-Akt and a suppressed cholesterol-synthesis pathway following insulin treatment, and by increased phosphorylation of insulin receptor subunit-1 at serine 612 (p-IRS-S612) as compared to parental N2a cells. Treatment of human neuroblastoma SH-SY5Y cells with Aβ42 also increased p-IRS-S612, suggesting that Aβ42 is responsible for insulin resistance. The insulin resistance was alleviated when N2a-AβPP cells were treated with higher insulin concentrations. Insulin increased Aβ release from N2a-AβPP cells, by which it may promote Aβ clearance. Insulin increased cholesterol-synthesis gene expression in SH-SY5Y and N2a cells, including 24-dehydrocholesterol reductase (DHCR24) and 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMGCR) through sterol-regulatory element-binding protein-2 (SREBP2). While Aβ42-treated SH-SY5Y cells exhibited increased HMGCR expression and c-Jun phosphorylation as pro-inflammatory responses, they also showed down-regulation of neuro-protective/anti-inflammatory DHCR24. These results suggest that Aβ42 may cause insulin resistance, activate JNK for c-Jun phosphorylation, and lead to dysregulation of cholesterol homeostasis, and that enhancing insulin signaling may relieve the insulin-resistant phenotype and the dysregulated cholesterol-synthesis pathway to promote A

  15. Mechanism by which arylamine N-acetyltransferase 1 ablation causes insulin resistance in mice

    DEFF Research Database (Denmark)

    Camporez, João Paulo; Wang, Yongliang; Faarkrog, Kasper

    2017-01-01

    A single-nucleotide polymorphism in the human arylamine N-acetyltransferase 2 (Nat2) gene has recently been identified as associated with insulin resistance in humans. To understand the cellular and molecular mechanisms by which alterations in Nat2 activity might cause insulin resistance, we...... examined murine ortholog Nat1 knockout (KO) mice. Nat1 KO mice manifested whole-body insulin resistance, which could be attributed to reduced muscle, liver, and adipose tissue insulin sensitivity. Hepatic and muscle insulin resistance were associated with marked increases in both liver and muscle...... adipose tissue, and hepatocytes. Taken together, these studies demonstrate that Nat1 deletion promotes reduced mitochondrial activity and is associated with ectopic lipid-induced insulin resistance. These results provide a potential genetic link among mitochondrial dysfunction with increased ectopic lipid...

  16. Insulin at pH 2: structural analysis of the conditions promoting insulin fibre formation.

    Science.gov (United States)

    Whittingham, Jean L; Scott, David J; Chance, Karen; Wilson, Ashley; Finch, John; Brange, Jens; Guy Dodson, G

    2002-04-26

    When insulin solutions are subjected to acid, heat and agitation, the normal pattern of insulin assembly (dimers-->tetramers-->hexamers) is disrupted; the molecule undergoes conformational changes allowing it to follow an alternative aggregation pathway (via a monomeric species) leading to the formation of insoluble amyloid fibres. To investigate the effect of acid pH on the conformation and aggregation state of the protein, the crystal structure of human insulin at pH 2.1 has been determined to 1.6 A resolution. The structure reveals that the native fold is maintained at low pH, and that the molecule is still capable of forming dimers similar to those found in hexameric insulin structures at higher pH. Sulphate ions are incorporated into the molecule and the crystal lattice where they neutralise positive charges on the protein, stabilising its structure and facilitating crystallisation. The sulphate interactions are associated with local deformations in the protein, which may indicate that the structure is more plastic at low pH. Transmission electron microscopy analysis of insulin fibres reveals that the appearance of the fibres is greatly influenced by the type of acid employed. Sulphuric acid produces distinctive highly bunched, truncated fibres, suggesting that the sulphate ions have a sophisticated role to play in fibre formation, rather as they do in the crystal structure. Analytical ultracentrifugation studies show that in the absence of heating, insulin is predominantly dimeric in mineral acids, whereas in acetic acid the equilibrium is shifted towards the monomer. Hence, the effect of acid on the aggregation state of insulin is also complex. These results suggest that acid conditions increase the susceptibility of the molecule to conformational change and dissociation, and enhance the rate of fibrillation by providing a charged environment in which the attractive forces between the protein molecules is increased. (c) 2002 Elsevier Science Ltd.

  17. Anti-diabetic activity of insulin-degrading enzyme inhibitors mediated by multiple hormones.

    Science.gov (United States)

    Maianti, Juan Pablo; McFedries, Amanda; Foda, Zachariah H; Kleiner, Ralph E; Du, Xiu Quan; Leissring, Malcolm A; Tang, Wei-Jen; Charron, Maureen J; Seeliger, Markus A; Saghatelian, Alan; Liu, David R

    2014-07-03

    Despite decades of speculation that inhibiting endogenous insulin degradation might treat type-2 diabetes, and the identification of IDE (insulin-degrading enzyme) as a diabetes susceptibility gene, the relationship between the activity of the zinc metalloprotein IDE and glucose homeostasis remains unclear. Although Ide(-/-) mice have elevated insulin levels, they exhibit impaired, rather than improved, glucose tolerance that may arise from compensatory insulin signalling dysfunction. IDE inhibitors that are active in vivo are therefore needed to elucidate IDE's physiological roles and to determine its potential to serve as a target for the treatment of diabetes. Here we report the discovery of a physiologically active IDE inhibitor identified from a DNA-templated macrocycle library. An X-ray structure of the macrocycle bound to IDE reveals that it engages a binding pocket away from the catalytic site, which explains its remarkable selectivity. Treatment of lean and obese mice with this inhibitor shows that IDE regulates the abundance and signalling of glucagon and amylin, in addition to that of insulin. Under physiological conditions that augment insulin and amylin levels, such as oral glucose administration, acute IDE inhibition leads to substantially improved glucose tolerance and slower gastric emptying. These findings demonstrate the feasibility of modulating IDE activity as a new therapeutic strategy to treat type-2 diabetes and expand our understanding of the roles of IDE in glucose and hormone regulation.

  18. Corydalis edulis Maxim. Promotes Insulin Secretion via the Activation of Protein Kinase Cs (PKCs) in Mice and Pancreatic β Cells.

    Science.gov (United States)

    Zheng, Jiao; Zhao, Yunfang; Lun, Qixing; Song, Yuelin; Shi, Shepo; Gu, Xiaopan; Pan, Bo; Qu, Changhai; Li, Jun; Tu, Pengfei

    2017-01-16

    Corydalis edulis Maxim., a widely grown plant in China, had been proposed for the treatment for type 2 diabetes mellitus. In this study, we found that C. edulis extract (CE) is protective against diabetes in mice. The treatment of hyperglycemic and hyperlipidemic apolipoprotein E (ApoE)-/- mice with a high dose of CE reduced serum glucose by 28.84% and serum total cholesterol by 17.34% and increased insulin release. We also found that CE significantly enhanced insulin secretion in a glucose-independent manner in hamster pancreatic β cell (HIT-T15). Further investigation revealed that CE stimulated insulin exocytosis by a protein kinase C (PKC)-dependent signaling pathway and that CE selectively activated novel protein kinase Cs (nPKCs) and atypical PKCs (aPKCs) but not conventional PKCs (cPKCs) in HIT-T15 cells. To the best of our knowledge, our study is the first to identify the PKC pathway as a direct target and one of the major mechanisms underlying the antidiabetic effect of CE. Given the good insulinotropic effect of this herbal medicine, CE is a promising agent for the development of new drugs for treating diabetes.

  19. Peroxisome Proliferator-Activated Receptors and Hepatitis C Virus-Induced Insulin Resistance

    Directory of Open Access Journals (Sweden)

    Francesco Negro

    2009-01-01

    Full Text Available Insulin resistance and type 2 diabetes are associated with hepatitis C virus infection. A wealth of clinical and experimental data suggests that the virus is directly interfering with the insulin signalling in hepatocytes. In the case of at least one viral genotype (the type 3a, insulin resistance seems to be directly mediated by the downregulation of the peroxisome proliferator-activated receptor γ. Whether and how this interaction may be manipulated pharmacologically, in order to improve the responsiveness to antivirals of insulin resistant chronic hepatitis C, patients remain to be fully explored.

  20. P21-activated kinase 2 (PAK2) regulates glucose uptake and insulin sensitivity in neuronal cells.

    Science.gov (United States)

    Varshney, Pallavi; Dey, Chinmoy Sankar

    2016-07-05

    P21-activated kinases (PAKs) are recently reported as important players of insulin signaling and glucose homeostasis in tissues like muscle, pancreas and liver. However, their role in neuronal insulin signaling is still unknown. Present study reports the involvement of PAK2 in neuronal insulin signaling, glucose uptake and insulin resistance. Irrespective of insulin sensitivity, insulin stimulation decreased PAK2 activity. PAK2 downregulation displayed marked enhancement of GLUT4 translocation with increase in glucose uptake whereas PAK2 over-expression showed its reduction. Treatment with Akti-1/2 and wortmannin suggested that Akt and PI3K are mediators of insulin effect on PAK2 and glucose uptake. Rac1 inhibition demonstrated decreased PAK2 activity while inhibition of PP2A resulted in increased PAK2 activity, with corresponding changes in glucose uptake. Taken together, present study demonstrates an inhibitory role of insulin signaling (via PI3K-Akt) and PP2A on PAK2 activity and establishes PAK2 as a Rac1-dependent negative regulator of neuronal glucose uptake and insulin sensitivity. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  1. Insulin resistance enhances the mitogen-activated protein kinase signaling pathway in ovarian granulosa cells.

    Directory of Open Access Journals (Sweden)

    Linghui Kong

    Full Text Available The ovary is the main regulator of female fertility. Granulosa cell dysfunction may be involved in various reproductive endocrine disorders. Here we investigated the effect of insulin resistance on the metabolism and function of ovarian granulosa cells, and dissected the functional status of the mitogen-activated protein kinase signaling pathway in these cells. Our data showed that dexamethasone-induced insulin resistance in mouse granulosa cells reduced insulin sensitivity, accompanied with an increase in phosphorylation of p44/42 mitogen-activated protein kinase. Furthermore, up-regulation of cytochrome P450 subfamily 17 and testosterone and down-regulation of progesterone were observed in insulin-resistant mouse granulosa cells. Inhibition of p44/42 mitogen-activated protein kinase after induction of insulin resistance in mouse granulosa cells decreased phosphorylation of p44/42 mitogen-activated protein kinase, downregulated cytochrome P450 subfamily 17 and lowered progesterone production. This insulin resistance cell model can successfully demonstrate certain mechanisms such as hyperandrogenism, which may inspire a new strategy for treating reproductive endocrine disorders by regulating cell signaling pathways.

  2. PLASMA INSULIN AND IGF-1 AND HEPATIC ACTIVITY IN SAANEN GOAT KIDS, AROUND WEANING

    Directory of Open Access Journals (Sweden)

    Damiano Magistrelli

    2009-02-01

    Full Text Available Weaning is a crucial event in the life of young ruminants. At weaning ruminal and digestive activity are still incomplete, so weaning may coincide with a period of growth stasis. Since insulin and insulin-like growth factor 1 (IGF-1 can play a fundamental role in post-natal development, the aim of the present study was to evaluate plasma variations of insulin and IGF-1 levels and their relationships with the hepatic activity, around weaning.For this purpose, eleven 3-days-old Saanen goat kids were randomly divided into MILK (6 animals and WMIX (5 animals groups. All kids were fed goat milk to age 29 days. After that, MILK kids continued to receive milk, while WMIX ones underwent weaning, based on the progressive replacement of milk with solid feed. WMIX kids were completely weaned on day 48. Blood samples were weekly analyzed for metabolic traits, insulin and IGF-1 levels, alanine aminotransferase (ALT and aspartate aminotransferase (AST activities. On day 50, all animals were slaughtered, liver weight was recorded and liver samples were analyzed for DNA, RNA, phospholipids, glicogen and soluble protein content, ALT and AST activity.On day 50, plasma insulin and IGF-1 were lower in WMIX group, as possible consequence of the lower plasma glucose and amino acids levels. Liver weight was not different between groups, but liver weight expressed as percentage of body weight was lower in WMIX kids and highly correlated to plasma IGF-1. Liver glycogen was also lower in WMIX kids, as possible consequence of the lower plasma glucose.Hepatic ALT and AST activities were not different between groups and both were strongly correlated to plasma insulin. Moreover, insulin was positively correlated to the proteosynthetic capability per cell (RNA/DNA of the liver.Our results indicate that the adopted livestock practice permitted the normal development of the animal used, avoiding growth stasis. Anyway, weaning altered plasma insulin and IGF-1, without affecting

  3. Molecular mechanism of insulin resistance

    Indian Academy of Sciences (India)

    Free fatty acids are known to play a key role in promoting loss of insulin sensitivity, thereby causing insulin resistance and type 2 diabetes. However, the underlying mechanism involved is still unclear. In searching for the cause of the mechanism, it has been found that palmitate inhibits insulin receptor (IR) gene expression, ...

  4. Relationship between Inflammation markers, Coagulation Activation and Impaired Insulin Sensitivity in Obese Healthy Women

    International Nuclear Information System (INIS)

    Soliman, S.Et; Shousha, M.A.

    2011-01-01

    Obesity, insulin resistance syndrome, and atherosclerosis are closely linked phenomena, often connected with a chronic low grade inflammatory state and pro thrombotic hypo fibrinolytic condition. This study investigated the relationship between impaired insulin sensitivity and selected markers of inflammation and thrombin generation in obese healthy women. The study included 36 healthy obese women (body mass index ≥ 30), with normal insulin sensitivity (NIS, n = 18) or impaired insulin sensitivity (IIS, n 18), and 10 non obese women (body mass index < 25).Impaired insulin sensitivity patients had significantly higher levels of high sensitivity C-reactive protein (hs-CRP), transforming growth factor -β1(TGF-β1), plasminogen activator inhibitor-1 (PAI-1), activated factor VII (VIIa), and prothrombin fragments 1 + 2 (F1 + 2) compared with either control subjects or normal insulin sensitivity patients. On the other hand, NIS patients had higher hs-CRP, TGF-β1, PAI-1, and factor VIIa, but not F1 + 2, levels than controls. Significant inverse correlations were observed between the insulin sensitivity index and TGF-β1, hs-CRP, PAI-1; factor VIIa, and F1 + 2 levels. Moreover, significant direct correlations were noted between TGF-β1 and CRP, PAI-1, factor VIIa, and F1 + 2 concentrations. Finally, multiple regressions revealed that TGF-β1 and the insulin sensitivity index were independently related to F1 + 2. These results document an in vivo relationship between insulin sensitivity and coagulation activation in obesity. Here we report that obesity is associated with higher TGF-β, PAI-1, prothrombin fragments 1 and 2 (F1 + 2), and activated factor VII (VIIa) plasma levels, and that insulin resistance exacerbates these alterations. The elevated TGF-β1 levels detected in the obese population may provide a biochemical link between insulin resistance and an increased risk for cardiovascular disease

  5. Fumosorinone, a novel PTP1B inhibitor, activates insulin signaling in insulin-resistance HepG2 cells and shows anti-diabetic effect in diabetic KKAy mice

    International Nuclear Information System (INIS)

    Liu, Zhi-Qin; Liu, Ting; Chen, Chuan; Li, Ming-Yan; Wang, Zi-Yu; Chen, Ruo-song; Wei, Gui-xiang; Wang, Xiao-yi; Luo, Du-Qiang

    2015-01-01

    Insulin resistance is a characteristic feature of type 2 diabetes mellitus (T2DM) and is characterized by defects in insulin signaling. Protein tyrosine phosphatase 1B (PTP1B) is a key negative regulator of the insulin signaling pathways, and its increased activity and expression are implicated in the pathogenesis of insulin resistance. Therefore, the inhibition of PTP1B is anticipated to become a potential therapeutic strategy to treat T2DM. Fumosorinone (FU), a new natural product isolated from insect fungi Isaria fumosorosea, was found to inhibit PTP1B activity in our previous study. Herein, the effects of FU on insulin resistance and mechanism in vitro and in vivo were investigated. FU increased the insulin-provoked glucose uptake in insulin-resistant HepG2 cells, and also reduced blood glucose and lipid levels of type 2 diabetic KKAy mice. FU decreased the expression of PTP1B both in insulin-resistant HepG2 cells and in liver tissues of diabetic KKAy mice. Furthermore, FU increased the phosphorylation of IRβ, IRS-2, Akt, GSK3β and Erk1/2 in insulin-resistant HepG2 cells, as well as the phosphorylation of IRβ, IRS-2, Akt in liver tissues of diabetic KKAy mice. These results showed that FU increased glucose uptake and improved insulin resistance by down-regulating the expression of PTP1B and activating the insulin signaling pathway, suggesting that it may possess antidiabetic properties. - Highlights: • Fumosorinone is a new PTP1B inhibitor isolated from insect pathogenic fungi. • Fumosorinone attenuated the insulin resistance both in vitro and in vivo. • Fumosorinone decreased the expression of PTP1B both in vitro and in vivo. • Fumosorinone activated the insulin signaling pathway both in vitro and in vivo

  6. Fumosorinone, a novel PTP1B inhibitor, activates insulin signaling in insulin-resistance HepG2 cells and shows anti-diabetic effect in diabetic KKAy mice

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Zhi-Qin [College of Life Sciences, Key Laboratory of Medicinal Chemistry and Molecular Diagnosis of Ministry of Education, Hebei University, Baoding 071002 (China); College of Pharmaceutical Sciences, key laboratory of pharmaceutical quality control of Hebei province, Hebei University, Baoding 071002 (China); Liu, Ting; Chen, Chuan [College of Life Sciences, Key Laboratory of Medicinal Chemistry and Molecular Diagnosis of Ministry of Education, Hebei University, Baoding 071002 (China); Li, Ming-Yan; Wang, Zi-Yu; Chen, Ruo-song; Wei, Gui-xiang; Wang, Xiao-yi [College of Pharmaceutical Sciences, key laboratory of pharmaceutical quality control of Hebei province, Hebei University, Baoding 071002 (China); Luo, Du-Qiang, E-mail: duqiangluo999@126.com [College of Life Sciences, Key Laboratory of Medicinal Chemistry and Molecular Diagnosis of Ministry of Education, Hebei University, Baoding 071002 (China)

    2015-05-15

    Insulin resistance is a characteristic feature of type 2 diabetes mellitus (T2DM) and is characterized by defects in insulin signaling. Protein tyrosine phosphatase 1B (PTP1B) is a key negative regulator of the insulin signaling pathways, and its increased activity and expression are implicated in the pathogenesis of insulin resistance. Therefore, the inhibition of PTP1B is anticipated to become a potential therapeutic strategy to treat T2DM. Fumosorinone (FU), a new natural product isolated from insect fungi Isaria fumosorosea, was found to inhibit PTP1B activity in our previous study. Herein, the effects of FU on insulin resistance and mechanism in vitro and in vivo were investigated. FU increased the insulin-provoked glucose uptake in insulin-resistant HepG2 cells, and also reduced blood glucose and lipid levels of type 2 diabetic KKAy mice. FU decreased the expression of PTP1B both in insulin-resistant HepG2 cells and in liver tissues of diabetic KKAy mice. Furthermore, FU increased the phosphorylation of IRβ, IRS-2, Akt, GSK3β and Erk1/2 in insulin-resistant HepG2 cells, as well as the phosphorylation of IRβ, IRS-2, Akt in liver tissues of diabetic KKAy mice. These results showed that FU increased glucose uptake and improved insulin resistance by down-regulating the expression of PTP1B and activating the insulin signaling pathway, suggesting that it may possess antidiabetic properties. - Highlights: • Fumosorinone is a new PTP1B inhibitor isolated from insect pathogenic fungi. • Fumosorinone attenuated the insulin resistance both in vitro and in vivo. • Fumosorinone decreased the expression of PTP1B both in vitro and in vivo. • Fumosorinone activated the insulin signaling pathway both in vitro and in vivo.

  7. Cost-effectiveness of healthy eating and/or physical activity promotion in pregnant women at increased risk of gestational diabetes mellitus

    DEFF Research Database (Denmark)

    Broekhuizen, Karen; Simmons, David; Devlieger, Roland

    2018-01-01

    for pregnant women at increased risk for GDM. The purpose of this study was to evaluate the cost-effectiveness of the healthy eating and/or physical activity promotion intervention compared to usual care among pregnant women at increased risk of GDM from a societal perspective. Methods: An economic evaluation...... was performed alongside a European multicenter-randomized controlled trial. A total of 435 pregnant women at increased risk of GDM in primary and secondary care settings in nine European countries, were recruited and randomly allocated to a healthy eating and physical activity promotion intervention (HE + PA...... intervention), a healthy eating promotion intervention (HE intervention), or a physical activity promotion intervention (PA intervention). Main outcome measures were gestational weight gain, fasting glucose, insulin resistance (HOMA-IR), quality adjusted life years (QALYs), and societal costs. Results: Between...

  8. Insulin/IGF-I regulation of necdin and brown adipocyte differentiation via CREB- and FoxO1-associated pathways

    DEFF Research Database (Denmark)

    Cypess, Aaron M; Zhang, Hongbin; Schulz, Tim J

    2011-01-01

    is regulated by the phosphoinositide 3 kinase-Akt pathway, increased necdin promoter activity. Based on reporter gene assays using truncations of the necdin promoter and chromatin immunoprecipitation studies, we demonstrated that CREB and FoxO1 are recruited to the necdin promoter, likely interacting......Brown adipose tissue plays an important role in obesity, insulin resistance, and diabetes. We have previously shown that the transition from brown preadipocytes to mature adipocytes is mediated in part by insulin receptor substrate (IRS)-1 and the cell cycle regulator protein necdin. In this study...... with specific consensus sequences in the proximal region. Based on these results, we propose that insulin/IGF-I act through IRS-1 phosphorylation to stimulate differentiation of brown preadipocytes via two complementary pathways: 1) the Ras-ERK1/2 pathway to activate CREB and 2) the phosphoinositide 3 kinase-Akt...

  9. Body fat related to daily physical activity and insulin concentrations in non-diabetic children

    DEFF Research Database (Denmark)

    Dencker, Magnus; Thorsson, Ola; Karlsson, Magnus K

    2007-01-01

    This study explored the associations between body fat versus daily physical activity and insulin concentrations in non-diabetic young children in a cross-sectional study of 172 children (93 boys and 79 girls) aged 8-11 years. Blood samples were analysed for serum insulin and daily physical activity......%). Body fat distribution was calculated as AFM/TBF. Body fat distribution was independently linked to both insulin concentrations and physical activity. In contrast, TBF, AFM, and BF% were linked to physical activity only and not to insulin concentrations. In conclusion in this population of non-diabetic...... was measured by accelerometers. Time spent performing vigorous activity was estimated from accelerometer data by using established cut-off points. Dual-energy x-ray absorptiometry (DXA) was used to quantify abdominal fat mass (AFM) and total body fat (TBF), also calculated as percentage of body weight (BF...

  10. Phorbol ester-induced serine phosphorylation of the insulin receptor decreases its tyrosine kinase activity.

    Science.gov (United States)

    Takayama, S; White, M F; Kahn, C R

    1988-03-05

    The effect of 12-O-tetradecanoylphorbol-13-acetate (TPA) on the function of the insulin receptor was examined in intact hepatoma cells (Fao) and in solubilized extracts purified by wheat germ agglutinin chromatography. Incubation of ortho[32P]phosphate-labeled Fao cells with TPA increased the phosphorylation of the insulin receptor 2-fold after 30 min. Analysis of tryptic phosphopeptides from the beta-subunit of the receptor by reverse-phase high performance liquid chromatography and determination of their phosphoamino acid composition suggested that TPA predominantly stimulated phosphorylation of serine residues in a single tryptic peptide. Incubation of the Fao cells with insulin (100 nM) for 1 min stimulated 4-fold the phosphorylation of the beta-subunit of the insulin receptor. Prior treatment of the cells with TPA inhibited the insulin-stimulated tyrosine phosphorylation by 50%. The receptors extracted with Triton X-100 from TPA-treated Fao cells and purified on immobilized wheat germ agglutinin retained the alteration in kinase activity and exhibited a 50% decrease in insulin-stimulated tyrosine autophosphorylation and phosphotransferase activity toward exogenous substrates. This was due primarily to a decrease in the Vmax for these reactions. TPA treatment also decreased the Km of the insulin receptor for ATP. Incubation of the insulin receptor purified from TPA-treated cells with alkaline phosphatase decreased the phosphate content of the beta-subunit to the control level and reversed the inhibition, suggesting that the serine phosphorylation of the beta-subunit was responsible for the decreased tyrosine kinase activity. Our results support the notion that the insulin receptor is a substrate for protein kinase C in the Fao cell and that the increase in serine phosphorylation of the beta-subunit of the receptor produced by TPA treatment inhibited tyrosine kinase activity in vivo and in vitro. These data suggest that protein kinase C may regulate the function

  11. Role of AMP-activated protein kinase for regulating post-exercise insulin sensitivity

    DEFF Research Database (Denmark)

    Kjøbsted, Rasmus; Wojtaszewski, Jørgen; Treebak, Jonas Thue

    2016-01-01

    Skeletal muscle insulin resistance precedes development of type 2 diabetes (T2D). As skeletal muscle is a major sink for glucose disposal, understanding the molecular mechanisms involved in maintaining insulin sensitivity of this tissue could potentially benefit millions of people that are diagno......Skeletal muscle insulin resistance precedes development of type 2 diabetes (T2D). As skeletal muscle is a major sink for glucose disposal, understanding the molecular mechanisms involved in maintaining insulin sensitivity of this tissue could potentially benefit millions of people...... that are diagnosed with insulin resistance. Regular physical activity in both healthy and insulin-resistant individuals is recognized as the single most effective intervention to increase whole-body insulin sensitivity and thereby positively affect glucose homeostasis. A single bout of exercise has long been known...... to increase glucose disposal in skeletal muscle in response to physiological insulin concentrations. While this effect is identified to be restricted to the previously exercised muscle, the molecular basis for an apparent convergence between exercise- and insulin-induced signaling pathways is incompletely...

  12. Mechanisms of action of brain insulin against neurodegenerative diseases.

    Science.gov (United States)

    Ramalingam, Mahesh; Kim, Sung-Jin

    2014-06-01

    Insulin, a pancreatic hormone, is best known for its peripheral effects on the metabolism of glucose, fats and proteins. There is a growing body of evidence linking insulin action in the brain to neurodegenerative diseases. Insulin present in central nervous system is a regulator of central glucose metabolism nevertheless this glucoregulation is not the main function of insulin in the brain. Brain is known to be specifically vulnerable to oxidative products relative to other organs and altered brain insulin signaling may cause or promote neurodegenerative diseases which invalidates and reduces the quality of life. Insulin located within the brain is mostly of pancreatic origin or is produced in the brain itself crosses the blood-brain barrier and enters the brain via a receptor-mediated active transport system. Brain Insulin, insulin receptor and insulin receptor substrate-mediated signaling pathways play important roles in the regulation of peripheral metabolism, feeding behavior, memory and maintenance of neural functions such as neuronal growth and differentiation, neuromodulation and neuroprotection. In the present review, we would like to summarize the novel biological and pathophysiological roles of neuronal insulin in neurodegenerative diseases and describe the main signaling pathways in use for therapeutic strategies in the use of insulin to the cerebral tissues and their biological applications to neurodegenerative diseases.

  13. Why were "starvation diets" promoted for diabetes in the pre-insulin period?

    Directory of Open Access Journals (Sweden)

    Mazur Allan

    2011-03-01

    Full Text Available Abstract In the decade before the discovery of insulin, the prominent American physicians Frederick Allen and Elliott Joslin advocated severe fasting and undernutrition to prolong the lives of diabetic patients. Detractors called this "starvation dieting," and some patients did indeed starve to death. Allen and Joslin promoted the therapy as a desperate application of animal experimentation to clinical treatment, and texts still describe it that way. This justification was exaggerated. The public record contains only the briefest account of relevant animal experiments, and clinical experience at the time provided little indication that severe undernutrition had better outcomes than low carbohydrate diets then in use.

  14. A two-week reduction of ambulatory activity attenuates peripheral insulin sensitivity

    DEFF Research Database (Denmark)

    Krogh-Madsen, Rikke; Thyfault, John P; Broholm, Christa

    2009-01-01

    after step reduction, with a post hoc analysis revealing the most pronounced effect after 4 h of insulin infusion. In addition, the two-week period induced a 7% decline in VO2max (ml/min; cardiovascular fitness). Lean mass of legs, but not arms and truck, decreased concurrently. Taken together, one...... possible biological cause for the public health problem of type 2 diabetes has been identified. Reduced ambulatory activity for two weeks in healthy, non-exercising young men significantly reduced peripheral insulin sensitivity, cardiovascular fitness, and lean leg mass. Key words: Inactivity, Insulin...... number of daily steps induced a significant reduction of 17% in the glucose infusion rate (GIR) during the clamp. This reduction was due to a decline in peripheral insulin sensitivity with no effect on hepatic endogenous glucose production. The insulin-stimulated ratio of pAkt(thr308)/total Akt decreased...

  15. Hydrogen peroxide induces activation of insulin signaling pathway via AMP-dependent kinase in podocytes

    International Nuclear Information System (INIS)

    Piwkowska, Agnieszka; Rogacka, Dorota; Angielski, Stefan; Jankowski, Maciej

    2012-01-01

    Highlights: ► H 2 O 2 activates the insulin signaling pathway and glucose uptake in podocytes. ► H 2 O 2 induces time-dependent changes in AMPK phosphorylation. ► H 2 O 2 enhances insulin signaling pathways via AMPK activation. ► H 2 O 2 stimulation of glucose uptake is AMPK-dependent. -- Abstract: Podocytes are cells that form the glomerular filtration barrier in the kidney. Insulin signaling in podocytes is critical for normal kidney function. Insulin signaling is regulated by oxidative stress and intracellular energy levels. We cultured rat podocytes to investigate the effects of hydrogen peroxide (H 2 O 2 ) on the phosphorylation of proximal and distal elements of insulin signaling. We also investigated H 2 O 2 -induced intracellular changes in the distribution of protein kinase B (Akt). Western blots showed that H 2 O 2 (100 μM) induced rapid, transient phosphorylation of the insulin receptor (IR), the IR substrate-1 (IRS1), and Akt with peak activities at 5 min (Δ 183%, P 2 O 2 >. Furthermore, H 2 O 2 inhibited phosphorylation of the phosphatase and tensin homologue (PTEN; peak activity at 10 min; Δ −32%, P 2 O 2 on IR phosphorylation by about 40% (from 2.07 ± 0.28 to 1.28 ± 0.12, P 2 O 2 increased glucose uptake in podocytes (from 0.88 ± 0.04 to 1.29 ± 0.12 nmol/min/mg protein, P 2 O 2 activated the insulin signaling pathway and glucose uptake via AMPK in cultured rat podocytes. This signaling may play a potential role in the prevention of insulin resistance under conditions associated with oxidative stress.

  16. Guava leaf extracts promote glucose metabolism in SHRSP.Z-Leprfa/Izm rats by improving insulin resistance in skeletal muscle.

    Science.gov (United States)

    Guo, Xiangyu; Yoshitomi, Hisae; Gao, Ming; Qin, Lingling; Duan, Ying; Sun, Wen; Xu, Tunhai; Xie, Peifeng; Zhou, Jingxin; Huang, Liansha; Liu, Tonghua

    2013-03-01

    Metabolic syndrome (MS) and type 2 diabetes mellitus (T2DM) have been associated with insulin-resistance; however, the effective therapies in improving insulin sensitivity are limited. This study is aimed at investigating the effect of Guava Leaf (GL) extracts on glucose tolerance and insulin resistance in SHRSP.Z-Leprfa/Izm rats (SHRSP/ZF), a model of spontaneously metabolic syndrome. Male rats at 7 weeks of age were administered with vehicle water or treated by gavage with 2 g/kg GL extracts daily for six weeks, and their body weights, water and food consumption, glucose tolerance, and insulin resistance were measured. Compared with the controls, treatment with GL extracts did not modulate the amounts of water and food consumption, but significantly reduced the body weights at six weeks post treatment. Treatment with GL extracts did not alter the levels of fasting plasma glucose and insulin, but significantly reduced the levels of plasma glucose at 60 and 120 min post glucose challenge, also reduced the values of AUC and quantitative insulin sensitivity check index (QUICKI) at 42 days post treatment. Furthermore, treatment with GL extracts promoted IRS-1, AKT, PI3Kp85 expression, then IRS-1, AMKP, and AKT308, but not AKT473, phosphorylation, accompanied by increasing the ratios of membrane to total Glut 4 expression and adiponectin receptor 1 transcription in the skeletal muscles. These data indicated that GL extracts improved glucose metabolism and insulin sensitivity in the skeletal muscles of rats by modulating the insulin-related signaling.

  17. Hepatocyte DACH1 Is Increased in Obesity via Nuclear Exclusion of HDAC4 and Promotes Hepatic Insulin Resistance

    Directory of Open Access Journals (Sweden)

    Lale Ozcan

    2016-06-01

    Full Text Available Defective insulin signaling in hepatocytes is a key factor in type 2 diabetes. In obesity, activation of calcium/calmodulin-dependent protein kinase II (CaMKII in hepatocytes suppresses ATF6, which triggers a PERK-ATF4-TRB3 pathway that disrupts insulin signaling. Elucidating how CaMKII suppresses ATF6 is therefore essential to understanding this insulin resistance pathway. We show that CaMKII phosphorylates and blocks nuclear translocation of histone deacetylase 4 (HDAC4. As a result, HDAC4-mediated SUMOylation of the corepressor DACH1 is decreased, which protects DACH1 from proteasomal degradation. DACH1, together with nuclear receptor corepressor (NCOR, represses Atf6 transcription, leading to activation of the PERK-TRB3 pathway and defective insulin signaling. DACH1 is increased in the livers of obese mice and humans, and treatment of obese mice with liver-targeted constitutively nuclear HDAC4 or DACH1 small hairpin RNA (shRNA increases ATF6, improves hepatocyte insulin signaling, and protects against hyperglycemia and hyperinsulinemia. Thus, DACH1-mediated corepression in hepatocytes emerges as an important link between obesity and insulin resistance.

  18. Fructose induced neurogenic hypertension mediated by overactivation of p38 MAPK to impair insulin signaling transduction caused central insulin resistance.

    Science.gov (United States)

    Cheng, Pei-Wen; Lin, Yu-Te; Ho, Wen-Yu; Lu, Pei-Jung; Chen, Hsin-Hung; Lai, Chi-Cheng; Sun, Gwo-Ching; Yeh, Tung-Chen; Hsiao, Michael; Tseng, Ching-Jiunn; Liu, Chun-Peng

    2017-11-01

    Type 2 diabetes are at a high risk of complications related to hypertension, and reports have indicated that insulin levels may be associated with blood pressure (BP). Fructose intake has recently been reported to promote insulin resistance and superoxide formation. The aim of this study is to investigate whether fructose intake can enhance superoxide generation and impair insulin signaling in the NTS and subsequently elevate BP in rats with fructose-induced hypertension. Treatment with fructose for 4 weeks increased the BP, serum fasting insulin, glucose, homeostatic model assessment-insulin resistance, and triglyceride levels and reduced the serum direct high-density lipoprotein level in the fructose group. The Tempol treatment recovered the fructose-induced decrease in nitric oxide production in the NTS. Immunoblotting and immunofluorescence analyses further showed that fructose increased the p38- and fructose-induced phosphorylation of insulin receptor substrate 1 (IRS1 S307 ) and suppressed Akt S473 and neuronal nitric oxide synthase phosphorylation. Similarly, fructose was able to impair insulin sensitivity and increase insulin levels in the NTS. Fructose intake also increased the production of superoxide in the NTS. The results of this study suggest that fructose might induce central insulin resistance and elevate BP by enhancing superoxide production and activating p38 phosphorylation in the NTS. Copyright © 2017 Elsevier Inc. All rights reserved.

  19. Extrinsic factors promoting insulin producing cell-differentiation and insulin expression enhancement-hope for diabetics.

    Science.gov (United States)

    Dave, Shruti

    2013-11-01

    Diabetes mellitus (DM) is considered to be an autoimmune disorder leading to destruction of beta-cells resulting in to a loss of blood sugar control. Attempts using many pharmacological compositions including exogenous insulin have failed to show tight control of glycemia and associated manifestations. Stem cells are considered a potential tool for the supply of insulin-producing cells (IPC) generation in vitro. Stem cell differentiation in to pancreatic lineages requires influence of both intrinsic and extrinsic factors. Application of islet growth factors is considered to be potential for enhancement of beta-cell replication, function and survival. Use of certain extrinsic factors is known to facilitate expression of transcription factors known to be important for beta-cell differentiation and production of insulin enabling IPC generation. Hierarchies of secreted signals and transcription factors have been identified by studies from several laboratories that guide cell differentiation in to IPC. This knowledge provides insights for in vitro IPC differentiation from stem cells. Current advancement in medical knowledge promises an insulin independency for DM patients. The review sheds light on few specific extrinsic factors which facilitate differentiation of stem cells in to IPC in vitro have been discussed; which can be proven as a potential therapeutic option for treatment of DM and associated diseases.

  20. PGBR extract ameliorates TNF-α induced insulin resistance in hepatocytes

    Directory of Open Access Journals (Sweden)

    Fu-Chih Chen

    2018-01-01

    Full Text Available Pre-germinated brown rice (PGBR could ameliorate metabolic syndrome, however, not much research estimates the effect of PGBR extract on insulin resistance. The aim of this study is to examine the effects of PGBR extract in TNF-α induced insulin resistance. HepG2 cells, hepatocytes, were cultured in DMEM medium and added with 5 μM insulin or with insulin and 30 ng/ml TNF-α or with insulin, TNF-α and PGBR extract (50, 100, 300 μg/ml. The glucose levels of the medium were decreased by insulin, demonstrating insulin promoted glucose uptake into cell. However, TNF-α inhibited glucose uptake into cells treated with insulin. Moreover, insulin increased the protein expressions of AMP-activated protein kinase (AMPK, insulin receptor substrate-1 (IRS-1, phosphatidylinositol-3-kinase-α (PI3K-α, serine/threonine kinase PI3K-linked protein kinase B (Akt/PKB, glucose transporter-2 (GLUT-2, glucokinase (GCK, peroxisome proliferator activated receptor-α (PPAR-α and PPAR-γ. TNF-α activated p65 and MAPKs (JNK1/2 and ERK1/2 which worsened the expressions of AMPK, IRS-1, PI3K-α, Akt/PKB, GLUT-2, GCK, glycogen synthase kinase-3 (GSK-3, PPAR-α and PPAR-γ. Once this relationship was established, we added PGBR extract to cell with insulin and TNF-α. We found glucose levels of medium were lowered and that the protein expressions of AMPK, IRS-1, PI3K-α, Akt/PKB, GLUT-2, GCK, GSK-3, PPAR-α, PPAR-γ and p65, JNK1/2 were also recovered. In conclusion, this study found that TNF-α inhibited insulin stimulated glucose uptake and aggravated related proteins expressions, suggesting that it might cause insulin resistance. PGBR extract was found to ameliorate this TNF-α induced insulin resistance, suggesting that it might be used in the future to help control insulin resistance.

  1. Insulin-sensitive phospholipid signaling systems and glucose transport. Update II.

    Science.gov (United States)

    Farese, R V

    2001-04-01

    Insulin provokes rapid changes in phospholipid metabolism and thereby generates biologically active lipids that serve as intracellular signaling factors that regulate glucose transport and glycogen synthesis. These changes include: (i) activation of phosphatidylinositol 3-kinase (PI3K) and production of PIP3; (ii) PIP3-dependent activation of atypical protein kinase Cs (PKCs); (iii) PIP3-dependent activation of PKB; (iv) PI3K-dependent activation of phospholipase D and hydrolysis of phosphatidylcholine with subsequent increases in phosphatidic acid (PA) and diacylglycerol (DAG); (v) PI3K-independent activation of glycerol-3-phosphate acylytansferase and increases in de novo synthesis of PA and DAG; and (vi) activation of DAG-sensitive PKCs. Recent findings suggest that atypical PKCs and PKB serve as important positive regulators of insulin-stimulated glucose metabolism, whereas mechanisms that result in the activation of DAG-sensitive PKCs serve mainly as negative regulators of insulin signaling through PI3K. Atypical PKCs and PKB are rapidly activated by insulin in adipocytes, liver, skeletal muscles, and other cell types by a mechanism requiring PI3K and its downstream effector, 3-phosphoinositide-dependent protein kinase-1 (PDK-1), which, in conjunction with PIP3, phosphorylates critical threonine residues in the activation loops of atypical PKCs and PKB. PIP3 also promotes increases in autophosphorylation and allosteric activation of atypical PKCs. Atypical PKCs and perhaps PKB appear to be required for insulin-induced translocation of the GLUT 4 glucose transporter to the plasma membrane and subsequent glucose transport. PKB also appears to be the major regulator of glycogen synthase. Together, atypical PKCs and PKB serve as a potent, integrated PI3K/PDK-1-directed signaling system that is used by insulin to regulate glucose metabolism.

  2. Insulin signaling regulates fatty acid catabolism at the level of CoA activation.

    Directory of Open Access Journals (Sweden)

    Xiaojun Xu

    2012-01-01

    Full Text Available The insulin/IGF signaling pathway is a highly conserved regulator of metabolism in flies and mammals, regulating multiple physiological functions including lipid metabolism. Although insulin signaling is known to regulate the activity of a number of enzymes in metabolic pathways, a comprehensive understanding of how the insulin signaling pathway regulates metabolic pathways is still lacking. Accepted knowledge suggests the key regulated step in triglyceride (TAG catabolism is the release of fatty acids from TAG via the action of lipases. We show here that an additional, important regulated step is the activation of fatty acids for beta-oxidation via Acyl Co-A synthetases (ACS. We identify pudgy as an ACS that is transcriptionally regulated by direct FOXO action in Drosophila. Increasing or reducing pudgy expression in vivo causes a decrease or increase in organismal TAG levels respectively, indicating that pudgy expression levels are important for proper lipid homeostasis. We show that multiple ACSs are also transcriptionally regulated by insulin signaling in mammalian cells. In sum, we identify fatty acid activation onto CoA as an important, regulated step in triglyceride catabolism, and we identify a mechanistic link through which insulin regulates lipid homeostasis.

  3. Bavachin from Psoralea corylifolia Improves Insulin-Dependent Glucose Uptake through Insulin Signaling and AMPK Activation in 3T3-L1 Adipocytes

    Directory of Open Access Journals (Sweden)

    Hyejin Lee

    2016-04-01

    Full Text Available The fruit of Psoralea corylifolia L. (Fabaceae (PC, known as “Bo-Gol-Zhee” in Korea has been used as traditional medicine. Ethanol and aqueous extracts of PC have an anti-hyperglycemic effect by increasing plasma insulin levels and decreasing blood glucose and total plasma cholesterol levels in type 2 diabetic rats. In this study, we purified six compounds from PC and investigated their anti-diabetic effect. Among the purified compounds, bavachin most potently accumulated lipids during adipocyte differentiation. Intracellular lipid accumulation was measured by Oil Red-O (ORO cell staining to investigate the effect of compounds on adipogenesis. Consistently, bavachin activated gene expression of adipogenic transcriptional factors, proliferator-activated receptorγ (PPARγ and CCAAT/enhancer binding protein-α (C/EBPα. Bavachin also increased adiponectin expression and secretion in adipocytes. Moreover, bavachin increased insulin-induced glucose uptake by differentiated adipocytes and myoblasts. In differentiated adipocytes, we found that bavachin enhanced glucose uptake via glucose transporter 4 (GLUT4 translocation by activating the Akt and 5′AMP-activated protein kinase (AMPK pathway in the presence or absence of insulin. These results suggest that bavachin from Psoralea corylifolia might have therapeutic potential for type 2 diabetes by activating insulin signaling pathways.

  4. Mechanical stress regulates insulin sensitivity through integrin-dependent control of insulin receptor localization.

    Science.gov (United States)

    Kim, Jung; Bilder, David; Neufeld, Thomas P

    2018-01-15

    Insulin resistance, the failure to activate insulin signaling in the presence of ligand, leads to metabolic diseases, including type 2 diabetes. Physical activity and mechanical stress have been shown to protect against insulin resistance, but the molecular mechanisms remain unclear. Here, we address this relationship in the Drosophila larval fat body, an insulin-sensitive organ analogous to vertebrate adipose tissue and livers. We found that insulin signaling in Drosophila fat body cells is abolished in the absence of physical activity and mechanical stress even when excess insulin is present. Physical movement is required for insulin sensitivity in both intact larvae and fat bodies cultured ex vivo. Interestingly, the insulin receptor and other downstream components are recruited to the plasma membrane in response to mechanical stress, and this membrane localization is rapidly lost upon disruption of larval or tissue movement. Sensing of mechanical stimuli is mediated in part by integrins, whose activation is necessary and sufficient for mechanical stress-dependent insulin signaling. Insulin resistance develops naturally during the transition from the active larval stage to the immotile pupal stage, suggesting that regulation of insulin sensitivity by mechanical stress may help coordinate developmental programming with metabolism. © 2018 Kim et al.; Published by Cold Spring Harbor Laboratory Press.

  5. Cytokines and their association with insulin resistance in obese pregnant women with different levels of physical activity.

    Science.gov (United States)

    Nayak, Minakshi; Eekhoff, Marelise E W; Peinhaupt, Miriam; Heinemann, Akos; Desoye, Gernot; van Poppel, Mireille N M

    2016-01-01

    Cytokines contribute to insulin resistance in pregnancy, but the role of distinct cytokines is not fully understood. To study whether cytokines produced by tissues other than skeletal muscle are associated with glucose and insulin metabolism activity in overweight and obese women and to study whether these associations can be modified by physical activity. A longitudinal study with 44 overweight and obese pregnant women was conducted. Changes in cytokines levels (IFN-γ, IP-10, IL1-α, MIP1-α, adiponectin and leptin) and ICAM1 from early (15wk) to late (32wk) pregnancy were determined. Physical activity was measured objectively with accelerometers. In linear regression models, the associations between (changes in) cytokine levels and fasting glucose, fasting insulin and HOMA-IR were studied. Both IFN-γ and IP-10 levels increased from early to late pregnancy, and adiponectin levels decreased. IFN-γ and IP-10 were positively associated with fasting glucose, whereas IL-1α, ICAM1 and adiponectin were inversely associated with insulin and insulin resistance. The association of IL-1α with insulin and insulin resistance was only found in women with low levels of physical activity. IFN-γ, IP-10, IL1-α, ICAM1, and adiponectin may play a role in glucose and insulin metabolism in pregnancy. The relationship of IL-1α with insulin and insulin resistance might be moderated by levels of physical activity. Further studies are required to confirm the role of these cytokines in glucose and insulin metabolism in obese pregnant women. Copyright © 2015 Elsevier Ltd. All rights reserved.

  6. Activation of transmembrane bile acid receptor TGR5 stimulates insulin secretion in pancreatic {beta} cells

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Divya P.; Rajagopal, Senthilkumar; Mahavadi, Sunila [Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, VA (United States); Mirshahi, Faridoddin [Division of Gastroenterology, Hepatology and Nutrition, Department of Internal Medicine, Virginia Commonwealth University School of Medicine, Richmond, VA (United States); Grider, John R. [Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, VA (United States); Murthy, Karnam S., E-mail: skarnam@vcu.edu [Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, VA (United States); Sanyal, Arun J., E-mail: asanyal@mcvh-vcu.edu [Division of Gastroenterology, Hepatology and Nutrition, Department of Internal Medicine, Virginia Commonwealth University School of Medicine, Richmond, VA (United States)

    2012-10-26

    Highlights: Black-Right-Pointing-Pointer G protein coupled receptor TGR5 is expressed in mouse and human islets. Black-Right-Pointing-Pointer TGR5 is coupled to activation of Gs and Ca{sup 2+} release via cAMP/Epac/PLC-{epsilon} pathway. Black-Right-Pointing-Pointer Activation of TGR5 by bile salts and selective ligands causes insulin secretion. Black-Right-Pointing-Pointer TGR5 could be a potential therapeutic target to treat diabetes. -- Abstract: Bile acids act as signaling molecules and stimulate the G protein coupled receptor, TGR5, in addition to nuclear farnesoid X receptor to regulate lipid, glucose and energy metabolism. Bile acid induced activation of TGR5 in the enteroendocrine cells promotes glucagon like peptide-1 (GLP-1) release, which has insulinotropic effect in the pancreatic {beta} cells. In the present study, we have identified the expression of TGR5 in pancreatic {beta} cell line MIN6 and also in mouse and human pancreatic islets. TGR5 selective ligands, oleanolic acid (OA) and INT-777 selectively activated G{alpha}{sub s} and caused an increase in intracellular cAMP and Ca{sup 2+}. OA and INT-777 also increased phosphoinositide (PI) hydrolysis and the increase was blocked by NF449 (a selective G{alpha}{sub s} inhibitor) or (U73122) (PI hydrolysis inhibitor). OA, INT-777 and lithocholic acid increased insulin release in MIN6 and human islets and the increase was inhibited by treatment with NF449, (U73122) or BAPTA-AM (chelator of calcium), but not with myristoylated PKI (PKA inhibitor), suggesting that the release is dependent on G{sub s}/cAMP/Ca{sup 2+} pathway. 8-pCPT-2 Prime -O-Me-cAMP, a cAMP analog, which activates Epac, but not PKA also stimulated PI hydrolysis. In conclusion, our study demonstrates that the TGR5 expressed in the pancreatic {beta} cells regulates insulin secretion and highlights the importance of ongoing therapeutic strategies targeting TGR5 in the control of glucose homeostasis.

  7. Activation of transmembrane bile acid receptor TGR5 stimulates insulin secretion in pancreatic β cells

    International Nuclear Information System (INIS)

    Kumar, Divya P.; Rajagopal, Senthilkumar; Mahavadi, Sunila; Mirshahi, Faridoddin; Grider, John R.; Murthy, Karnam S.; Sanyal, Arun J.

    2012-01-01

    Highlights: ► G protein coupled receptor TGR5 is expressed in mouse and human islets. ► TGR5 is coupled to activation of Gs and Ca 2+ release via cAMP/Epac/PLC-ε pathway. ► Activation of TGR5 by bile salts and selective ligands causes insulin secretion. ► TGR5 could be a potential therapeutic target to treat diabetes. -- Abstract: Bile acids act as signaling molecules and stimulate the G protein coupled receptor, TGR5, in addition to nuclear farnesoid X receptor to regulate lipid, glucose and energy metabolism. Bile acid induced activation of TGR5 in the enteroendocrine cells promotes glucagon like peptide-1 (GLP-1) release, which has insulinotropic effect in the pancreatic β cells. In the present study, we have identified the expression of TGR5 in pancreatic β cell line MIN6 and also in mouse and human pancreatic islets. TGR5 selective ligands, oleanolic acid (OA) and INT-777 selectively activated Gα s and caused an increase in intracellular cAMP and Ca 2+ . OA and INT-777 also increased phosphoinositide (PI) hydrolysis and the increase was blocked by NF449 (a selective Gα s inhibitor) or (U73122) (PI hydrolysis inhibitor). OA, INT-777 and lithocholic acid increased insulin release in MIN6 and human islets and the increase was inhibited by treatment with NF449, (U73122) or BAPTA-AM (chelator of calcium), but not with myristoylated PKI (PKA inhibitor), suggesting that the release is dependent on G s /cAMP/Ca 2+ pathway. 8-pCPT-2′-O-Me-cAMP, a cAMP analog, which activates Epac, but not PKA also stimulated PI hydrolysis. In conclusion, our study demonstrates that the TGR5 expressed in the pancreatic β cells regulates insulin secretion and highlights the importance of ongoing therapeutic strategies targeting TGR5 in the control of glucose homeostasis.

  8. FoxO6 Integrates Insulin Signaling With Gluconeogenesis in the Liver

    Science.gov (United States)

    Kim, Dae Hyun; Perdomo, German; Zhang, Ting; Slusher, Sandra; Lee, Sojin; Phillips, Brett E.; Fan, Yong; Giannoukakis, Nick; Gramignoli, Roberto; Strom, Stephen; Ringquist, Steven; Dong, H. Henry

    2011-01-01

    OBJECTIVE Excessive endogenous glucose production contributes to fasting hyperglycemia in diabetes. This effect stems from inept insulin suppression of hepatic gluconeogenesis. To understand the underlying mechanisms, we studied the ability of forkhead box O6 (FoxO6) to mediate insulin action on hepatic gluconeogenesis and its contribution to glucose metabolism. RESEARCH DESIGN AND METHODS We characterized FoxO6 in glucose metabolism in cultured hepatocytes and in rodent models of dietary obesity, insulin resistance, or insulin-deficient diabetes. We determined the effect of FoxO6 on hepatic gluconeogenesis in genetically modified mice with FoxO6 gain- versus loss-of-function and in diabetic db/db mice with selective FoxO6 ablation in the liver. RESULTS FoxO6 integrates insulin signaling to hepatic gluconeogenesis. In mice, elevated FoxO6 activity in the liver augments gluconeogenesis, raising fasting blood glucose levels, and hepatic FoxO6 depletion suppresses gluconeogenesis, resulting in fasting hypoglycemia. FoxO6 stimulates gluconeogenesis, which is counteracted by insulin. Insulin inhibits FoxO6 activity via a distinct mechanism by inducing its phosphorylation and disabling its transcriptional activity, without altering its subcellular distribution in hepatocytes. FoxO6 becomes deregulated in the insulin-resistant liver, accounting for its unbridled activity in promoting gluconeogenesis and correlating with the pathogenesis of fasting hyperglycemia in diabetes. These metabolic abnormalities, along with fasting hyperglycemia, are reversible by selective inhibition of hepatic FoxO6 activity in diabetic mice. CONCLUSIONS Our data uncover a FoxO6-dependent pathway by which the liver orchestrates insulin regulation of gluconeogenesis, providing the proof-of-concept that selective FoxO6 inhibition is beneficial for curbing excessive hepatic glucose production and improving glycemic control in diabetes. PMID:21940782

  9. Long term rebaudioside A treatment does not alter circadian activity rhythms, adiposity, or insulin action in male mice.

    Directory of Open Access Journals (Sweden)

    Thomas H Reynolds

    Full Text Available Obesity is a major public health problem that is highly associated with insulin resistance and type 2 diabetes, two conditions associated with circadian disruption. To date, dieting is one of the only interventions that result in substantial weight loss, but restricting caloric intake is difficult to maintain long-term. The use of artificial sweeteners, particularly in individuals that consume sugar sweetened beverages (energy drinks, soda, can reduce caloric intake and possibly facilitate weight loss. The purpose of the present study was to examine the effects of the artificial sweetener, rebaudioside A (Reb-A, on circadian rhythms, in vivo insulin action, and the susceptibility to diet-induced obesity. Six month old male C57BL/6 mice were assigned to a control or Reb-A (0.1% Reb-A supplemented drinking water group for six months. Circadian wheel running rhythms, body weight, caloric intake, insulin action, and susceptibility to diet-induced obesity were assessed. Time of peak physical activity under a 12:12 light-dark (LD cycle, mean activity levels, and circadian period in constant dark were not significantly different in mice that consumed Reb-A supplemented water compared to normal drinking water, indicating that circadian rhythms and biological clock function were unaltered. Although wheel running significantly reduced body weight in both Reb-A and control mice (P = 0.0001, consuming Reb-A supplemented water did not alter the changes in body weight following wheel running (P = 0.916. In vivo insulin action, as assessed by glucose, insulin, and pyruvate tolerance tests, was not different between mice that consumed Reb-A treated water compared to normal drinking water. Finally, Reb-A does not appear to change the susceptibility to diet-induced obesity as both groups of mice gained similar amounts of body weight when placed on a high fat diet. Our results indicate that consuming Reb-A supplemented water does not promote circadian disruption

  10. Alternate Phosphorylation/O-GlcNAc Modification on Human Insulin IRSs: A Road towards Impaired Insulin Signaling in Alzheimer and Diabetes

    Directory of Open Access Journals (Sweden)

    Zainab Jahangir

    2014-01-01

    Full Text Available Impaired insulin signaling has been thought of as important step in both Alzheimer’s disease (AD and type 2 diabetes mellitus (T2DM. Posttranslational modifications (PTMs regulate functions and interaction of insulin with insulin receptors substrates (IRSs and activate insulin signaling downstream pathways via autophosphorylation on several tyrosine (TYR residues on IRSs. Two important insulin receptor substrates 1 and 2 are widely expressed in human, and alternative phosphorylation on their serine (Ser and threonine (Thr residues has been known to block the Tyr phosphorylation of IRSs, thus inhibiting insulin signaling and promoting insulin resistance. Like phosphorylation, O-glycosylation modification is important PTM and inhibits phosphorylation on same or neighboring Ser/Thr residues, often called Yin Yang sites. Both IRS-1 and IRS-2 have been shown to be O-glycosylated; however exact sites are not determined yet. In this study, by using neuronal network based prediction methods, we found more than 50 Ser/Thr residues that have potential to be O-glycosylated and may act as possible sites as well. Moreover, alternative phosphorylation and O-glycosylation on IRS-1 Ser-312, 984, 1037, and 1101 may act as possible therapeutic targets to minimize the risk of AD and T2DM.

  11. Elevation of serum insulin concentration during euglycemic hyperinsulinemic clamp studies leads to similar activation of insulin receptor kinase in skeletal muscle of subjects with and without NIDDM

    DEFF Research Database (Denmark)

    Klein, H H; Vestergaard, H; Kotzke, G

    1995-01-01

    The role of skeletal muscle insulin receptor kinase in the pathogenesis of non-insulin-dependent diabetes mellitus (NIDDM) was investigated. Muscle biopsies from 13 patients with NIDDM and 10 control subjects at fasting serum insulin concentrations and approximately 1,000 pmol/l steady-state serum...... insulin during euglycemic hyperinsulinemic clamps were immediately frozen. The biopsies were then solubilized, and the receptors were immobilized to anti-insulin receptor antibody-coated microwells. Receptor kinase and binding activities were consecutively measured in these wells. The increase in serum...... and control groups, respectively). Moreover, by selecting only the receptors that bound to anti-phosphotyrosine antibody, we found similar hyperinsulinemia-induced increases of this receptor fraction and its kinase activity in both study groups. In vitro activation of the immobilized receptors with 2 mmol...

  12. Periodontitis contributes to adipose tissue inflammation through the NF-B, JNK and ERK pathways to promote insulin resistance in a rat model.

    Science.gov (United States)

    Huang, Yanli; Zeng, Jin; Chen, Guoqing; Xie, Xudong; Guo, Weihua; Tian, Weidong

    2016-12-01

    This study aimed to investigate the mechanism by which periodontitis affects the inflammatory response and systemic insulin resistance in the white adipose and liver tissues in an obese rat model. The obese model was generated by feeding rats a high fat diet. The periodontitis model was induced by ligatures and injection of "red complex", which consisted of Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia, for two weeks. When compared with rats without periodontitis, fasting glucose levels and homeostasis model assessment index were significantly increased in rats with periodontitis, suggesting that periodontitis promotes the development of insulin resistance in obese rats. Gene and protein expression analysis in white adipose and liver tissue revealed that experimental periodontitis stimulated the expression of inflammatory cytokines, such as tumor necrosis factors-alpha, interleukin-1 beta, toll-like receptor 2 and toll-like receptor 4. Signals associated with inflammation and insulin resistance, including nuclear factor- B, c-Jun amino-terminal kinase and extracellular-signal regulated kinase were significantly activated in the white adipose tissue from obese rats with periodontitis compared to obese rats without periodontitis. Taken together, these findings suggest that periodontitis plays an important role in aggravating the development of local white adipose inflammation and systemic insulin resistance in rat models. Copyright © 2016 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.

  13. Associations of objective physical activity with insulin sensitivity and circulating adipokine profile

    DEFF Research Database (Denmark)

    Spartano, N L; Stevenson, M D; Xanthakis, V

    2017-01-01

    The purpose of this study was to explore the relation of physical activity (PA) and sedentary time (SED) to insulin sensitivity and adipokines. We assessed PA and SED using Actical accelerometers and insulin resistance (HOMA-IR) in 2109 participants (free of type 1 and 2 diabetes mellitus) from...

  14. Oral insulin improves metabolic parameters in high fat diet fed rats

    Directory of Open Access Journals (Sweden)

    LEANDRO C. LIPINSKI

    2017-08-01

    Full Text Available ABSTRACT Introduction/Aim: The gut has shown to have a pivotal role on the pathophysiology of metabolic disease. Food stimulation of distal intestinal segments promotes enterohormones secretion influencing insulin metabolism. In diabetic rats, oral insulin has potential to change intestinal epithelium behavior. This macromolecule promotes positive effects on laboratorial metabolic parameters and decreases diabetic intestinal hypertrophy. This study aims to test if oral insulin can influence metabolic parameters and intestinal weight in obese non-diabetic rats. Methods: Twelve weeks old Wistar rats were divided in 3 groups: control (CTRL standard chow group; high fat diet low carbohydrates group (HFD and HFD plus daily oral 20U insulin gavage (HFD+INS. Weight and food consumption were weekly obtained. After eight weeks, fasting blood samples were collected for laboratorial analysis. After euthanasia gut samples were isolated. Results: Rat oral insulin treatment decreased body weight gain (p<0,001, fasting glucose and triglycerides serum levels (p<0,05 an increased intestinal weight of distal ileum (P<0,05. Animal submitted to high fat diet presented higher levels of HOMA-IR although significant difference to CT was not achieved. HOMA-beta were significantly higher (p<0.05 in HFD+INS. Visceral fat was 10% lower in HFD+INS but the difference was not significant. Conclusions: In non-diabetic obese rats, oral insulin improves metabolic malfunction associated to rescue of beta-cell activity.

  15. Knockout of Vasohibin-1 Gene in Mice Results in Healthy Longevity with Reduced Expression of Insulin Receptor, Insulin Receptor Substrate 1, and Insulin Receptor Substrate 2 in Their White Adipose Tissue

    Directory of Open Access Journals (Sweden)

    Eichi Takeda

    2017-01-01

    Full Text Available Vasohibin-1 (Vash1, originally isolated as an endothelium-derived angiogenesis inhibitor, has a characteristic of promoting stress tolerance in endothelial cells (ECs. We therefore speculated that the lack of the vash1 gene would result in a short lifespan. However, to our surprise, vash1−/− mice lived significantly longer with a milder senescence phenotype than wild-type (WT mice. We sought the cause of this healthy longevity and found that vash1−/− mice exhibited mild insulin resistance along with reduced expression of the insulin receptor (insr, insulin receptor substrate 1 (irs-1, and insulin receptor substrate 2 (irs-2 in their white adipose tissue (WAT but not in their liver or skeletal muscle. The expression of vash1 dominated in the WAT among those 3 organs. Importantly, vash1−/− mice did not develop diabetes even when fed a high-fat diet. These results indicate that the expression of vash1 was required for the normal insulin sensitivity of the WAT and that the target molecules for this activity were insr, irs1, and irs2. The lack of vash1 caused mild insulin resistance without the outbreak of overt diabetes and might contribute to healthy longevity.

  16. Activation of hypothalamic RIP-Cre neurons promotes beiging of WAT via sympathetic nervous system.

    Science.gov (United States)

    Wang, Baile; Li, Ang; Li, Xiaomu; Ho, Philip Wl; Wu, Donghai; Wang, Xiaoqi; Liu, Zhuohao; Wu, Kelvin Kl; Yau, Sonata Sy; Xu, Aimin; Cheng, Kenneth Ky

    2018-04-01

    Activation of brown adipose tissue (BAT) and beige fat by cold increases energy expenditure. Although their activation is known to be differentially regulated in part by hypothalamus, the underlying neural pathways and populations remain poorly characterized. Here, we show that activation of rat-insulin-promoter-Cre (RIP-Cre) neurons in ventromedial hypothalamus (VMH) preferentially promotes recruitment of beige fat via a selective control of sympathetic nervous system (SNS) outflow to subcutaneous white adipose tissue (sWAT), but has no effect on BAT Genetic ablation of APPL2 in RIP-Cre neurons diminishes beiging in sWAT without affecting BAT, leading to cold intolerance and obesity in mice. Such defects are reversed by activation of RIP-Cre neurons, inactivation of VMH AMPK, or treatment with a β3-adrenergic receptor agonist. Hypothalamic APPL2 enhances neuronal activation in VMH RIP-Cre neurons and raphe pallidus, thereby eliciting SNS outflow to sWAT and subsequent beiging. These data suggest that beige fat can be selectively activated by VMH RIP-Cre neurons, in which the APPL2-AMPK signaling axis is crucial for this defending mechanism to cold and obesity. © 2018 The Authors.

  17. Insulin resistance in vascular endothelial cells promotes intestinal tumour formation

    DEFF Research Database (Denmark)

    Wang, X; Häring, M-F; Rathjen, Thomas

    2017-01-01

    in vascular endothelial cells. Strikingly, these mice had 42% more intestinal tumours than controls, no change in tumour angiogenesis, but increased expression of vascular cell adhesion molecule-1 (VCAM-1) in primary culture of tumour endothelial cells. Insulin decreased VCAM-1 expression and leukocyte...... adhesion in quiescent tumour endothelial cells with intact insulin receptors and partly prevented increases in VCAM-1 and leukocyte adhesion after treatment with tumour necrosis factor-α. Knockout of insulin receptors in endothelial cells also increased leukocyte adhesion in mesenteric venules...

  18. Covalent glycoinositolphospholipid (GPI binding to hemoglobin is associated with insulin-activation of erythrocyte membrane protease

    Directory of Open Access Journals (Sweden)

    VESNA NIKETIC

    2004-05-01

    Full Text Available Recently, it was demonstrated that prolonged hyperinsulinism associated with hypoglycemia, both in vivo and in vitro, caused covalent glycoinositolphospholipid (GPI binding to the C termini of both hemoglobin b-chains, which resulted in the formation of a novel, hitherto unrecognized, minor hemoglobin fraction (GPI-Hb (Niketic et al., Biochem. Biophys. Res. Commun. 239 (1997 435. In this study it was demonstrated that exposure of erythrocyte membranes to insulin causes the activation of membrane protease as well as that the formation of GPI-Hb parallels its activity. It is suggested that the insulin-activated protease is able to catalyze, albeit slowly, the transpeptidation, i.e., the replacement of the carboxy-terminal amino acid(s residues of the Hb b-chains with GPI as an exogenous nucleophile. To our knowledge the present results show for the first time that insulin stimulates protease activity in erythrocyte membranes, as well as that insulin-activated protease may be involved in post-translational GPI binding to proteins.

  19. Branched-chain amino acids in metabolic signalling and insulin resistance

    Science.gov (United States)

    Lynch, Christopher J.; Adams, Sean H.

    2015-01-01

    Branched-chain amino acids (BCAAs) are important nutrient signals that have direct and indirect effects. Frequently, BCAAs have been reported to mediate antiobesity effects, especially in rodent models. However, circulating levels of BCAAs tend to be increased in individuals with obesity and are associated with worse metabolic health and future insulin resistance or type 2 diabetes mellitus (T2DM). A hypothesized mechanism linking increased levels of BCAAs and T2DM involves leucine-mediated activation of the mammalian target of rapamycin complex 1 (mTORC1), which results in uncoupling of insulin signalling at an early stage. A BCAA dysmetabolism model proposes that the accumulation of mitotoxic metabolites (and not BCAAs per se) promotes β-cell mitochondrial dysfunction, stress signalling and apoptosis associated with T2DM. Alternatively, insulin resistance might promote aminoacidaemia by increasing the protein degradation that insulin normally suppresses, and/or by eliciting an impairment of efficient BCAA oxidative metabolism in some tissues. Whether and how impaired BCAA metabolism might occur in obesity is discussed in this Review. Research on the role of individual and model-dependent differences in BCAA metabolism is needed, as several genes (BCKDHA, PPM1K, IVD and KLF15) have been designated as candidate genes for obesity and/or T2DM in humans, and distinct phenotypes of tissue-specific branched chain ketoacid dehydrogenase complex activity have been detected in animal models of obesity and T2DM. PMID:25287287

  20. [Molecular mechanism for ET-1-induced insulin resistance in skeletal muscle cells].

    Science.gov (United States)

    Horinouchi, Takahiro; Mazaki, Yuichi; Terada, Koji; Miwa, Soichi

    2018-01-01

    Insulin resistance is a condition where the sensitivity to insulin of the tissues expressing insulin receptor (InsR) is decreased due to a functional disturbance of InsR-mediated intracellular signaling. Insulin promotes the entry of glucose into the tissues and skeletal muscle is the most important tissue responsible for the insulin's action of decreasing blood glucose levels. Endothelin-1 (ET-1), a potent vasoconstrictor and pro-inflammatory peptide, induces insulin resistance through a direct action on skeletal muscle. However, the signaling pathways of ET-1-induced insulin resistance in skeletal muscle remain unclear. Here we show molecular mechanism underlying the inhibitory effect of ET-1 on insulin-stimulated Akt phosphorylation and glucose uptake in myotubes of rat L6 skeletal muscle cell line. mRNA expression levels of differentiation marker genes, MyoD and myogenin, were increased during L6 myoblasts differentiation into myotubes. Some of myotubes possessed the ability to spontaneously contract. In myotubes, insulin promoted Akt phosphorylation at Thr 308 and Ser 473 , and [ 3 H]-labelled 2-deoxy-D-glucose ([ 3 H]2-DG) uptake. The insulin-facilitated Akt phosphorylation and [ 3 H]2-DG uptake were inhibited by ET-1. The inhibitory effect of ET-1 was counteracted by blockade of ET type A receptor (ET A R), inhibition of G q/11 protein, and siRNA knockdown of G protein-coupled receptor kinase 2 (GRK2). The exogenously overexpressed GRK2 directly bound to endogenous Akt and their association was facilitated by ET-1. In summary, activation of ET A R with ET-1 inhibits insulin-induced Akt phosphorylation and [ 3 H]2-DG uptake in a G q/11 protein- and GRK2-dependent manner in skeletal muscle. These findings indicate that ET A R and GRK2 are potential targets for insulin resistance.

  1. Dietary fat and insulin resistance: a connection through leptin and PPARγ activation

    Directory of Open Access Journals (Sweden)

    Doaa Nader Al-Jada

    2016-06-01

    Full Text Available Insulin resistance refers to reduced insulin action in peripheral tissues and impaired suppression of endogenous glucose production, a state which is critical for maintaining normal glucose homeostasis. Insulin resistance is partly explained by genetic factors and is strongly influenced by the individual's habitual lifestyle. Investigating factors that may influence the development of insulin resistance and their mechanisms of action is highly significant; one of these factors include dietary fat. Both quantitative and qualitative terms of dietary fat have been known to play an important role in the development of insulin resistance, although the mechanism underlying this effect is not fully understood. In this regard, the classical view has been that dietary fat quality mainly affects cell membrane fatty acid composition and consequently the membrane function. Recently, the relationship between dietary fat and insulin resistance has entered an advanced level due to the discovery that different fatty acids can regulate gene expression, transcriptional activity and adipocytokines secretion. In essence, this provides new mechanisms by which fatty acids exert their cellular effects. The present review critically assesses the effect of dietary fat quality on the development of insulin resistance in relation to the adipocytokine, leptin and the activation of the transcription factor, peroxisome proliferator-activated receptor gamma (PPARγ. It is evident that fat quality influences the development of insulin resistance and has a more important role than quantity. Leptin and PPARγ prove to be potential candidates linking dietary fat with insulin resistance. However, the exact role or mechanism of action of various types of dietary fat in the development of insulin resistance is still uncertain. Further well-controlled studies in humans are necessary to establish better evidence-based dietary fat recommendations for diabetes prevention and its

  2. Association of an APOC3 promoter variant with type 2 diabetes risk and need for insulin treatment in lean persons

    NARCIS (Netherlands)

    M. van Hoek (Mandy); T.W. van Herpt (Thijs); A. Dehghan (Abbas); A. Hofman (Albert); A. Lieverse (Aloysius); C.M. van Duijn (Cornelia); J.C.M. Witteman (Jacqueline); E.J.G. Sijbrands (Eric)

    2011-01-01

    textabstractAims/hypothesis: An APOC3 promoter haplotype has been previously associated with type 1 diabetes. In this population-based study, we investigated whether APOC3 polymorphisms increase type 2 diabetes risk and need for insulin treatment in lean participants. Methods: In the Rotterdam

  3. Decreased 11β-Hydroxysteroid Dehydrogenase 1 Level and Activity in Murine Pancreatic Islets Caused by Insulin-Like Growth Factor I Overexpression.

    Directory of Open Access Journals (Sweden)

    Subrata Chowdhury

    Full Text Available We have reported a high expression of IGF-I in pancreatic islet β-cells of transgenic mice under the metallothionein promoter. cDNA microarray analysis of the islets revealed that the expression of 82 genes was significantly altered compared to wild-type mice. Of these, 11β-hydroxysteroid dehydrogenase 1 (11β-HSD1, which is responsible for the conversion of inert cortisone (11-dehydrocorticosterone, DHC in rodents to active cortisol (corticosterone in the liver and adipose tissues, has not been identified previously as an IGF-I target in pancreatic islets. We characterized the changes in its protein level, enzyme activity and glucose-stimulated insulin secretion. In freshly isolated islets, the level of 11β-HSD1 protein was significantly lower in MT-IGF mice. Using dual-labeled immunofluorescence, 11β-HSD1 was observed exclusively in glucagon-producing, islet α-cells but at a lower level in transgenic vs. wild-type animals. MT-IGF islets also exhibited reduced enzymatic activities. Dexamethasone (DEX and DHC inhibited glucose-stimulated insulin secretion from freshly isolated islets of wild-type mice. In the islets of MT-IGF mice, 48-h pre-incubation of DEX caused a significant decrease in insulin release, while the effect of DHC was largely blunted consistent with diminished 11β-HSD1 activity. In order to establish the function of intracrine glucocorticoids, we overexpressed 11β-HSD1 cDNA in MIN6 insulinoma cells, which together with DHC caused apoptosis and a significant decrease in proliferation. Both effects were abolished with the treatment of an 11β-HSD1 inhibitor. Our results demonstrate an inhibitory effect of IGF-I on 11β-HSD1 expression and activity within the pancreatic islets, which may mediate part of the IGF-I effects on cell proliferation, survival and insulin secretion.

  4. Light-intensity physical activity is associated with insulin resistance in elderly Japanese women independent of moderate-to vigorous-intensity physical activity.

    Science.gov (United States)

    Gando, Yuko; Murakami, Haruka; Kawakami, Ryoko; Tanaka, Noriko; Sanada, Kiyoshi; Tabata, Izumi; Higuchi, Mitsuru; Miyachi, Motohiko

    2014-02-01

    It is unclear whether light physical activity is beneficially associated with insulin resistance, similar to moderate and/or vigorous physical activity. This cross-sectional study was performed to determine the relationship between the amount of light physical activity, as determined with a triaxial accelerometer, and insulin resistance. A total of 807 healthy men and women participated in this study. Physical activity was measured using a triaxial accelerometer worn for 28 days and summarized as light intensity (1.1-2.9 METs) or moderate to vigorous intensity (≥ 3.0 METs). Insulin resistance was evaluated by HOMA_R (FPG [mg/dL] × IRI [μU/mL]/405). The daily time spent in light physical activity was inversely associated with HOMA_R (r = -0.173, P physical activity and HOMA_R remained statistically significant (β = -0.119, P physical activity remained significantly associated with HOMA_R following further adjustment for moderate to vigorous intensity activity (β = -0.125, P physical activity was modeled as quartiles, especially in elderly women. These cross-sectional data suggest that light-intensity physical activity is beneficially associated with insulin resistance in elderly Japanese women.

  5. A 2-wk reduction of ambulatory activity attenuates peripheral insulin sensitivity

    DEFF Research Database (Denmark)

    Krogh-Madsen, Rikke; Thyfault, John P; Broholm, Christa

    2010-01-01

    decreased after step reduction, with a post hoc analysis revealing the most pronounced effect after 4 h of insulin infusion. In addition, the 2-wk period induced a 7% decline in VO2 max (ml/min; cardiovascular fitness). Lean mass of legs, but not arms and trunk, decreased concurrently. Taken together, one...... possible biological cause for the public health problem of Type 2 diabetes has been identified. Reduced ambulatory activity for 2 wk in healthy, nonexercising young men significantly reduced peripheral insulin sensitivity, cardiovascular fitness, and lean leg mass........ A reduced number of daily steps induced a significant reduction of 17% in the glucose infusion rate (GIR) during the clamp. This reduction was due to a decline in peripheral insulin sensitivity with no effect on hepatic endogenous glucose production. The insulin-stimulated ratio of pAktthr308/total Akt...

  6. Anti-hyperglycemic and insulin sensitizer effects of turmeric and its principle constituent curcumin.

    Science.gov (United States)

    Ghorbani, Zeinab; Hekmatdoost, Azita; Mirmiran, Parvin

    2014-10-01

    Turmeric is obtained from the plant Curcuma longa L; its major constituent, curcumin, is a polyphenol with multiple effects which can modulate some signaling pathways. Insulin resistance is a major risk factor for chronic diseases such as type 2 diabetes, atherosclerotic, metabolic syndrome and cardiovascular disease. In addition, Insulin resistance in peripheral tissue is one of the most important reasons of hyperglycemia which can cause global or systemic effects. The present study reviewed studies published in PubMed from 1998 to 2013, indicating the role of curcumin in attenuation of many pathophysiological processes involved in development and progression of hyperglycemia and insulin resistance. Curcumin can reduce blood glucose level by reducing the hepatic glucose production, suppression of hyperglycemia-induced inflammatory state, stimulation of glucose uptake by up-regulation of GLUT4, GLUT2 and GLUT3 genes expressions, activation of AMP kinase, promoting the PPAR ligand-binding activity, stimulation of insulin secretion from pancreatic tissues, improvement in pancreatic cell function, and reduction of insulin resistance. Curcumin has antihyperglycemic and insulin sensitizer effects. Thereby, more studies evaluating the effects of curcumin on hyperglycemic state and insulin resistance in related disorders such as diabetes are recommended.

  7. Systemic insulin sensitivity is regulated by GPS2 inhibition of AKT ubiquitination and activation in adipose tissue.

    Science.gov (United States)

    Cederquist, Carly T; Lentucci, Claudia; Martinez-Calejman, Camila; Hayashi, Vanessa; Orofino, Joseph; Guertin, David; Fried, Susan K; Lee, Mi-Jeong; Cardamone, M Dafne; Perissi, Valentina

    2017-01-01

    Insulin signaling plays a unique role in the regulation of energy homeostasis and the impairment of insulin action is associated with altered lipid metabolism, obesity, and Type 2 Diabetes. The main aim of this study was to provide further insight into the regulatory mechanisms governing the insulin signaling pathway by investigating the role of non-proteolytic ubiquitination in insulin-mediated activation of AKT. The molecular mechanism of AKT regulation through ubiquitination is first dissected in vitro in 3T3-L1 preadipocytes and then validated in vivo using mice with adipo-specific deletion of GPS2, an endogenous inhibitor of Ubc13 activity (GPS2-AKO mice). Our results indicate that K63 ubiquitination is a critical component of AKT activation in the insulin signaling pathway and that counter-regulation of this step is provided by GPS2 preventing AKT ubiquitination through inhibition of Ubc13 enzymatic activity. Removal of this negative checkpoint, through GPS2 downregulation or genetic deletion, results in sustained activation of insulin signaling both in vitro and in vivo . As a result, the balance between lipid accumulation and utilization is shifted toward storage in the adipose tissue and GPS2-AKO mice become obese under normal laboratory chow diet. However, the adipose tissue of GPS2-AKO mice is not inflamed, the levels of circulating adiponectin are elevated, and systemic insulin sensitivity is overall improved. Our findings characterize a novel layer of regulation of the insulin signaling pathway based on non-proteolytic ubiquitination of AKT and define GPS2 as a previously unrecognized component of the insulin signaling cascade. In accordance with this role, we have shown that GPS2 presence in adipocytes modulates systemic metabolism by restricting the activation of insulin signaling during the fasted state, whereas in absence of GPS2, the adipose tissue is more efficient at lipid storage, and obesity becomes uncoupled from inflammation and insulin

  8. Drosophila insulin release is triggered by adipose Stunted ligand to brain Methuselah receptor.

    Science.gov (United States)

    Delanoue, Renald; Meschi, Eleonora; Agrawal, Neha; Mauri, Alessandra; Tsatskis, Yonit; McNeill, Helen; Léopold, Pierre

    2016-09-30

    Animals adapt their growth rate and body size to available nutrients by a general modulation of insulin-insulin-like growth factor signaling. In Drosophila, dietary amino acids promote the release in the hemolymph of brain insulin-like peptides (Dilps), which in turn activate systemic organ growth. Dilp secretion by insulin-producing cells involves a relay through unknown cytokines produced by fat cells. Here, we identify Methuselah (Mth) as a secretin-incretin receptor subfamily member required in the insulin-producing cells for proper nutrient coupling. We further show, using genetic and ex vivo organ culture experiments, that the Mth ligand Stunted (Sun) is a circulating insulinotropic peptide produced by fat cells. Therefore, Sun and Mth define a new cross-organ circuitry that modulates physiological insulin levels in response to nutrients. Copyright © 2016, American Association for the Advancement of Science.

  9. New twist on neuronal insulin receptor signaling in health, disease, and therapeutics.

    Science.gov (United States)

    Wada, Akihiko; Yokoo, Hiroki; Yanagita, Toshihiko; Kobayashi, Hideyuki

    2005-10-01

    Long after the pioneering studies documenting the existence of insulin (year 1967) and insulin receptor (year 1978) in brain, the last decade has witnessed extraordinary progress in the understanding of brain region-specific multiple roles of insulin receptor signalings in health and disease. In the hypothalamus, insulin regulates food intake, body weight, peripheral fat deposition, hepatic gluconeogenesis, reproductive endocrine axis, and compensatory secretion of counter-regulatory hormones to hypoglycemia. In the hippocampus, insulin promotes learning and memory, independent of the glucoregulatory effect of insulin. Defective insulin receptor signalings are associated with the dementia in normal aging and patients with age-related neurodegenerative diseases (e.g., Alzheimer's disease); the cognitive impairment can be reversed with systemic administration of insulin in the euglycemic condition. Intranasal administration of insulin enhances memory and mood and decreases body weight in healthy humans, without causing hypoglycemia. In the hypothalamus, insulin-induced activation of the phosphoinositide 3-kinase pathway followed by opening of ATP-sensitive K+ channel has been shown to be related to multiple effects of insulin. However, the precise molecular mechanisms of insulin's pleiotropic effects still remain obscure. More importantly, much remains unknown about the quality control mechanisms ensuring correct conformational maturation of the insulin receptor, and the cellular mechanisms regulating density of cell surface functional insulin receptors.

  10. Metabolism and insulin signaling in common metabolic disorders and inherited insulin resistance.

    Science.gov (United States)

    Højlund, Kurt

    2014-07-01

    muscle in vivo by activation of the insulin signaling cascade to glucose transport through the enzymes IRS1, PI3K, Akt2, AS160/TBC1D4 and RAC1, and to glycogen synthesis through Akt2, inhibition of GSK3 and activation of glycogen synthase (GS) via dephosphorylation of serine residues in both the NH2-terminal (site 2+2a) and the COOH-terminal end (site 3a+3b). In type 2 diabetes, obesity and PCOS, there is, although with some variation from study to study, defects in insulin signaling through IRS1, PI3K, Akt2 and AS160/TBC1D4, which can explain reduced insulin action on glucose transport. In type 2 diabetes an altered intracellular distribution of SNAP23 and impaired activation of RAC1 also seem to play a role for reduced insulin action on glucose transport. In all common metabolic disorders, we observed an impaired insulin activation of GS, which seems to be caused by attenuated dephosphorylation of GS at site 2+2a, whereas as the inhibition of GSK3 and the dephosphorylation of GS at its target sites, site 3a+3a, appeared to be completely normal. In individuals with inherited insulin resistance, we observed largely the same defects in insulin action on IRS1, PI3K, Akt2 and GS, as well as a normal inhibition of GSK3 and dephosphorylation of GS at site 3a+3b. In these individuals, however, a markedly reduced insulin clearance seems to partially rescue insulin signaling to glucose transport and GS. Adiponectin is thought to improve insulin sensitivity primarily by increasing lipid oxidation through activation of the enzyme AMPK, and possibly via cross-talking of adiponectin with insulin signaling, and hence glucose transport and glycogen synthesis. We demonstrated a strong correlation between plasma adiponectin and insulin action on glucose disposal and glycogen synthesis in obesity, type 2 diabetes and PCOS. In individuals with inherited insulin resistance, plasma adiponectin was normal, but the correlation of adiponectin with insulin-stimulated glucose uptake and glycogen

  11. Calcium phosphate-PEG-insulin-casein (CAPIC) particles as oral delivery systems for insulin.

    Science.gov (United States)

    Morçöl, T; Nagappan, P; Nerenbaum, L; Mitchell, A; Bell, S J D

    2004-06-11

    An oral delivery system for insulin was developed and functional activity was tested in a non-obese diabetic (NOD) mice model. Calcium phosphate particles containing insulin was synthesized in the presence of PEG-3350 and modified by aggregating the particles with caseins to obtain the calcium phosphate-PEG-insulin-casein (CAPIC) oral insulin delivery system. Single doses of CAPIC formulation were tested in NOD mice under fasting or fed conditions to evaluate the glycemic activity. The blood glucose levels were monitored every 1-2h for 12h following the treatments using an ACCU CHECK blood glucose monitoring system. Orally administered and subcutaneously injected free insulin solution served as controls in the study. Based on the results obtained we propose that: (1). the biological activity of insulin is preserved in CAPIC formulation; (2). insulin in CAPIC formulations, but not the free insulin, displays a prolonged hypoglycemic effect after oral administration to diabetic mice; (3). CAPIC formulation protects insulin from degradation while passing through the acidic environment of the GI track until it is released in the less acidic environment of the intestines where it can be absorbed in its biologically active form; (4). CAPIC formulation represents a new and unique oral delivery system for insulin and other macromolecules.

  12. [Hypertension and insulin treatment in type 2 diabetes].

    Science.gov (United States)

    Ben Salem Hachmi, L; Bouguerra, R; Maatki, O; Smadhi, H; Turki, Z; Hraoui, S; Ben Slama, C

    2007-08-01

    Insulin resistance and endogenous hyperinsulinemia are associated with blood hypertension. The aim of this analysis is to estimate the prevalence of blood hypertension one year after insulin treatment in type 2 diabetic patients. and methods: This is a retrospective clinical study of 178 type 2 diabetic patients (57 men and 121 women) insulin treated since at least one year. Mean age is 62 +/- 10 years and mean duration of diabetes is ten years. All patients had a clinical and biological control before treatment with insulin and at least three controls during the first year of insulin treatment (anthropometric measurements, blood pressure, fasting plasma glucose, HbA1C). WHO definition of hypertension is used (blood pressure >or=140 / 90 mmHg). At baseline, 48% of patients have hypertension. After insulin treatment, the prevalence of hypertension significantly increase to 53% (94 / 178) three months later (p=0.008), to 54.5% (98 / 178) six months later (p=0.001) and to 55.6% (99 / 178) twelve months later. This increase in hypertension frequency is associated with a significant weight gain and a better blood glucose control. Insulin therapy may contribute to the development of blood hypertension. It promotes renal sodium retention and increases sympathetic nervous system activity. In the UKPDS intensive blood glucose control with insulin is not associated with an increase of macro vascular complications. These observational data suggest the need for further study of the relationship between exogenous insulin and hypertension.

  13. Bcl10 links saturated fat overnutrition with hepatocellular NF-kB activation and insulin resistance

    NARCIS (Netherlands)

    Beek, M.H. van; Oravecz-Wilson, K.I.; Delekta, P.C.; Gu, S.; Li, X.; Jin, X.; Apel, I.J.; Konkle, K.S.; Feng, Y.; Teitelbaum, D.H.; Ruland, J.; McAllister-Lucas, L.M.; Lucas, P.C.

    2012-01-01

    Excess serum free fatty acids (FFAs) are fundamental to the pathogenesis of insulin resistance. With high-fat feeding, FFAs activate NF-kB in target tissues, initiating negative crosstalk with insulin signaling. However, the mechanisms underlying FFA-dependent NF-kB activation remain unclear. Here,

  14. Modern basal insulin analogs: An incomplete story

    OpenAIRE

    Singh, Awadhesh Kumar; Gangopadhyay, Kalyan Kumar

    2014-01-01

    The currently available basal insulin does not completely mimic the endogenous insulin secretion. This has continued to promote the search for ideal basal insulin. The newer basal insulin have primarily focused on increasing the duration of action, reducing variability, and reducing the incidence of hypoglycemia, particularly nocturnal. However, the changing criteria of hypoglycemia within a short span of a few years along with the surprising introduction of major cardiac events as another ou...

  15. Plasma lipid fatty acid composition, desaturase activities and insulin sensitivity in Amerindian women.

    Science.gov (United States)

    Vessby, B; Ahrén, B; Warensjö, E; Lindgärde, F

    2012-03-01

    Two Amerindian populations--Shuar women living in the Amazonian rain forest under traditional conditions and urbanized women in a suburb of Lima were studied. The fatty acid composition in plasma lipids and the relationships between fatty acid composition and metabolic variables were studied, as well as in a reference group of Swedish women. Fasting plasma was used for analyses of glucose, insulin, leptin and fatty acid composition. Women in Lima had more body fat, higher fasting insulin and leptin and lower insulin sensitivity than the Shuar women, who had insulin sensitivity similar to Swedish women. Shuar women had very high proportions (mean; SD) of palmitoleic (13.2; 3.9%) and oleic (33.9; 3.7%) acids in the plasma cholesteryl esters with very low levels of linoleic acid (29.1; 6.1 3%), as expected on a low fat, high carbohydrate diet. The estimated activity of delta 9 (SCD-1) desaturase was about twice as high in the Shuar compared with Lima women, suggesting neo lipogenesis, while the delta 5 desaturase activity did not differ. The Lima women, as well as the Swedish, showed strong positive correlations between SCD-1 activity on the one hand and fasting insulin and HOMA index on the other. These associations were absent in the Shuar women. The high SCD-1 activity in the Shuar women may reflect increased lipogenesis in adipose tissue. It also illustrates how a low fat diet rich in non-refined carbohydrates can be linked to a good metabolic situation. Copyright © 2010. Published by Elsevier B.V.

  16. Synthetic (+)-antroquinonol exhibits dual actions against insulin resistance by triggering AMP kinase and inhibiting dipeptidyl peptidase IV activities.

    Science.gov (United States)

    Hsu, C Y; Sulake, R S; Huang, P-K; Shih, H-Y; Sie, H-W; Lai, Y-K; Chen, C; Weng, C F

    2015-01-01

    The fungal product (+)-antroquinonol activates AMP kinase (AMPK) activity in cancer cell lines. The present study was conducted to examine whether chemically synthesized (+)-antroquinonol exhibited beneficial metabolic effects in insulin-resistant states by activating AMPK and inhibiting dipeptidyl peptidase IV (DPP IV) activity. Effects of (+)-antroquinonol on DPP IV activity were measured with a DPPIV Assay Kit and effects on GLP-1-induced PKA were measured in AR42J cells. Translocation of the glucose transporter 4, GLUT4, induced either by insulin-dependent PI3K/AKT signalling or by insulin-independent AMPK activation, was assayed in differentiated myotubes. Glucose uptake and GLUT4 translocation were assayed in L6 myocytes. Mice with diet-induced obesity were used to assess effects of acute and chronic treatment with (+)-antroquinonol on glycaemic control in vivo. The results showed that of (+)-antroquinonol (100 μM ) inhibited the DPP IV activity as effectively as the clinically used inhibitor, sitagliptin. The phosphorylation of AMPK Thr(172) in differentiated myotubes was significantly increased by (+)-antroquinonol. In cells simultaneously treated with S961 (insulin receptor antagonist), insulin and (+)-antroquinonol, the combination of (+)-antroquinonol plus insulin still increased both GLUT4 translocation and glucose uptake. Further, (+)-antroquinonol and sitagliptin reduced blood glucose, when given acutely or chronically to DIO mice. Chemically synthesized (+)-antroquinonol exhibits dual effects to ameliorate insulin resistance, by increasing AMPK activity and GLUT4 translocation, along with inhibiting DPP IV activity. © 2014 The British Pharmacological Society.

  17. Cost-effectiveness of healthy eating and/or physical activity promotion in pregnant women at increased risk of gestational diabetes mellitus

    DEFF Research Database (Denmark)

    Broekhuizen, Karen; Simmons, David; Devlieger, Roland

    2018-01-01

    was performed alongside a European multicenter-randomized controlled trial. A total of 435 pregnant women at increased risk of GDM in primary and secondary care settings in nine European countries, were recruited and randomly allocated to a healthy eating and physical activity promotion intervention (HE + PA...... intervention), a healthy eating promotion intervention (HE intervention), or a physical activity promotion intervention (PA intervention). Main outcome measures were gestational weight gain, fasting glucose, insulin resistance (HOMA-IR), quality adjusted life years (QALYs), and societal costs. Results: Between...... intervention strategy. At 35-37 weeks, it depends on the decision-makers' willingness to pay per kilogram reduction in gestational weight gain whether the HE + PA intervention is cost-effective for gestational weight gain, whereas it was not cost-effective for fasting glucose and HOMA-IR. After delivery...

  18. PPARγ transcriptionally regulates the expression of insulin-degrading enzyme in primary neurons

    International Nuclear Information System (INIS)

    Du, Jing; Zhang, Lang; Liu, Shubo; Zhang, Chi; Huang, Xiuqing; Li, Jian; Zhao, Nanming; Wang, Zhao

    2009-01-01

    Insulin-degrading enzyme (IDE) is a protease that has been demonstrated to play a key role in degrading both Aβ and insulin and deficient in IDE function is associated with Alzheimer's disease (AD) and type 2 diabetes mellitus (DM2) pathology. However, little is known about the cellular and molecular regulation of IDE expression. Here we show IDE levels are markedly decreased in DM2 patients and positively correlated with the peroxisome proliferator-activated receptor γ (PPARγ) levels. Further studies show that PPARγ plays an important role in regulating IDE expression in rat primary neurons through binding to a functional peroxisome proliferator-response element (PPRE) in IDE promoter and promoting IDE gene transcription. Finally, we demonstrate that PPARγ participates in the insulin-induced IDE expression in neurons. These results suggest that PPARγ transcriptionally induces IDE expression which provides a novel mechanism for the use of PPARγ agonists in both DM2 and AD therapies.

  19. Protein Kinase-C Beta Contributes to Impaired Endothelial Insulin Signaling in Humans with Diabetes Mellitus

    Science.gov (United States)

    Tabit, Corey E; Shenouda, Sherene M; Holbrook, Monica; Fetterman, Jessica L; Kiani, Soroosh; Frame, Alissa A; Kluge, Matthew A; Held, Aaron; Dohadwala, Mustali; Gokce, Noyan; Farb, Melissa; Rosenzweig, James; Ruderman, Neil; Vita, Joseph A; Hamburg, Naomi M

    2013-01-01

    Background Abnormal endothelial function promotes atherosclerotic vascular disease in diabetes. Experimental studies indicate that disruption of endothelial insulin signaling through the activity of protein kinase C-β (PKCβ) and nuclear factor κB (NFκB) reduces nitric oxide availability. We sought to establish whether similar mechanisms operate in the endothelium in human diabetes mellitus. Methods and Results We measured protein expression and insulin response in freshly isolated endothelial cells from patients with Type 2 diabetes mellitus (n=40) and non-diabetic controls (n=36). Unexpectedly, we observed 1.7-fold higher basal endothelial nitric oxide synthase (eNOS) phosphorylation at serine 1177 in patients with diabetes (P=0.007) without a difference in total eNOS expression. Insulin stimulation increased eNOS phosphorylation in non-diabetic subjects but not in diabetic patients (P=0.003) consistent with endothelial insulin resistance. Nitrotyrosine levels were higher in diabetic patients indicating endothelial oxidative stress. PKCβ expression was higher in diabetic patients and was associated with lower flow-mediated dilation (r=−0.541, P=0.02) Inhibition of PKCβ with LY379196 reduced basal eNOS phosphorylation and improved insulin-mediated eNOS activation in patients with diabetes. Endothelial NFκB activation was higher in diabetes and was reduced with PKCβ inhibition. Conclusions We provide evidence for the presence of altered eNOS activation, reduced insulin action and inflammatory activation in the endothelium of patients with diabetes. Our findings implicate PKCβ activity in endothelial insulin resistance. PMID:23204109

  20. Liraglutide increases FGF-21 activity and insulin sensitivity in high fat diet and adiponectin knockdown induced insulin resistance.

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    Mengliu Yang

    Full Text Available BACKGROUND: Liraglutide is a glucagon-like peptide-1 analogue that stimulates insulin secretion and improves β-cell function. However, it is not clear whether liraglutide achieves its glucose lowering effect only by its known effects or whether other as yet unknown mechanisms are involved. The aim of this study was to examine the effects of liraglutide on Fibroblast growth factor-21 (FGF-21 activity in High-fat diet (HFD fed ApoE(-/- mice with adiponectin (Acrp30 knockdown. METHOD: HFD-fed ApoE(-/- mice were treated with adenovirus vectors expressing shAcrp30 to produce insulin resistance. Hyperinsulinemic-euglycemic clamp studies were performed to evaluate insulin sensitivity of the mouse model. QRT-PCR and Western blot were used to measure the mRNA and protein expression of the target genes. RESULTS: The combination of HFD, ApoE deficiency, and hypoadiponectinemia resulted in an additive effect on insulin resistance. FGF-21 mRNA expressions in both liver and adipose tissues were significantly increased while FGF-21 receptor 1 (FGFR-1 and β-Klotho mRNA levels in adipose tissue, as well as FGFR-1-3 and β-Klotho mRNA levels in liver were significantly decreased in this model. Liraglutide treatment markedly improved insulin resistance and increased FGF-21 expression in liver and FGFR-3 in adipose tissue, restored β-Klotho mRNA expression in adipose tissue as well as FGFR-1-3, β-Klotho levels and phosphorylation of FGFR1 up to the levels observed in control mice in liver. Liraglutide treatment also further increased FGF-21 proteins in liver and plasma. In addition, as shown by hyperinsulinemic-euglycemic clamp, liraglutide treatment also markedly improved glucose metabolism and insulin sensitivity in these animals. CONCLUSION: These findings demonstrate an additive effect of HFD, ApoE deficiency, and adiponectin knockdown on insulin resistance and unveil that the regulation of glucose metabolism and insulin sensitivity by liraglutide may be

  1. The Proton-Activated Receptor GPR4 Modulates Glucose Homeostasis by Increasing Insulin Sensitivity

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    Luca Giudici

    2013-11-01

    Full Text Available Background: The proton-activated G protein-coupled receptor GPR4 is expressed in many tissues including white adipose tissue. GPR4 is activated by extracellular protons in the physiological pH range (i.e. pH 7.7 - 6.8 and is coupled to the production of cAMP. Methods: We examined mice lacking GPR4 and examined glucose tolerance and insulin sensitivity in young and aged mice as well as in mice fed with a high fat diet. Expression profiles of pro- and anti-inflammatory cytokines in white adipose tissue, liver and skeletal muscle was assessed. Results: Here we show that mice lacking GPR4 have an improved intraperitoneal glucose tolerance test and increased insulin sensitivity. Insulin levels were comparable but leptin levels were increased in GPR4 KO mice. Gpr4-/- showed altered expression of PPARα, IL-6, IL-10, TNFα, and TGF-1β in skeletal muscle, white adipose tissue, and liver. High fat diet abolished the differences in glucose tolerance and insulin sensitivity between Gpr4+/+ and Gpr4-/- mice. In contrast, in aged mice (12 months old, the positive effect of GPR4 deficiency on glucose tolerance and insulin sensitivity was maintained. Liver and adipose tissue showed no major differences in the mRNA expression of pro- and anti-inflammatory factors between aged mice of both genotypes. Conclusion: Thus, GPR4 deficiency improves glucose tolerance and insulin sensitivity. The effect may involve an altered balance between pro- and anti-inflammatory factors in insulin target tissues.

  2. Potentiation of insulin release in response to amino acid methyl esters correlates to activation of islet glutamate dehydrogenase activity

    DEFF Research Database (Denmark)

    Kofod, Hans; Lernmark, A; Hedeskov, C J

    1986-01-01

    Column perifusion of mouse pancreatic islets was used to study the ability of amino acids and their methyl esters to influence insulin release and activate islet glutamate dehydrogenase activity. In the absence of L-glutamine, L-serine and the methyl ester of L-phenylalanine, but neither L...... glutamate dehydrogenase activity showed that only the two methyl esters of L-phenylalanine and L-serine activated the enzyme. It is concluded that the mechanism by which methyl esters of amino acids potentiate insulin release is most likely to be mediated by the activation of pancreatic beta-cell glutamate...

  3. Dithiothreitol activation of the insulin receptor/kinase does not involve subunit dissociation of the native α2β2 insulin receptor subunit complex

    International Nuclear Information System (INIS)

    Sweet, L.J.; Wilden, P.A.; Pessin, J.E.

    1986-01-01

    The subunit composition of the dithiothreitol- (DTT) activated insulin receptor/kinase was examined by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis and gel filtration chromatography under denaturing or nondenaturing conditions. Pretreatment of 32 P-labeled insulin receptors with 50 mM DTT followed by gel filtration chromatography in 0.1% SDS demonstrated the dissociation of the α 2 β 2 insulin receptor complex (M/sub r/ 400,000) into the monomeric 95,000 β subunit. In contrast, pretreatment of the insulin receptors with 1-50 mM DTT followed by gel filtration chromatography in 0.1% Triton X-100 resulted in no apparent alteration in mobility compared to the untreated insulin receptors. Resolution of this complex by nonreducing SDS-polyacrylamide gel electrophoresis and autoradiography demonstrated the existence of the α 2 β 2 heterotetrameric complex with essentially no αβ heterodimeric or free monomeric β subunit species present. This suggests that the insulin receptor can reoxidize into the M/sub r/ 400,000 complex after the removal of DTT by gel filtration chromatography. To prevent reoxidation, the insulin receptors were pretreated with 50 mM DTT. Under the conditions the insulin receptors migrated as the M/sub r/ 400,000 α 2 β 2 complex. These results demonstrate that treatment of the insulin receptors with high concentrations of DTT, followed by removal of DTT by gel filtration, results in reoxidation of the reduced α 2 β 2 insulin receptor complex. Further, these results document that although the DTT stimulation of the insulin receptor/kinase does involve reduction of the insulin receptor subunits, it does not result in dissociation of the native α 2 β 2 insulin receptor subunit complex

  4. Insulin-like Growth Factor 1 Regulates the Expression of ATP-Binding Cassette Transporter A1 in Pancreatic Beta Cells.

    Science.gov (United States)

    Lyu, J; Imachi, H; Iwama, H; Zhang, H; Murao, K

    2016-05-01

    ATP-binding cassette transporter A1 (ABCA1) in pancreatic beta cells influences insulin secretion and cholesterol homeostasis. The present study investigates whether insulin-like growth factor 1 (IGF-1), which mediates stimulation of ABCA1 gene expression, could also interfere with the phosphatidylinositol 3-kinase (PI3-K) cascade.ABCA1 expression was examined by real-time polymerase chain reaction (PCR), Western blot analysis, and a reporter gene assay in rat insulin-secreting INS-1 cells incubated with IGF-1. The binding of forkhead box O1 (FoxO1) protein to the ABCA1 promoter was assessed by a chromatin immunoprecipitation (ChIP) assay. ABCA1 protein levels increased in response to rising concentrations of IGF-1. Real-time PCR analysis showed a significant increase in ABCA1 mRNA expression. However, both effects were suppressed after silencing the IGF-1 receptor. In parallel with its effect on endogenous ABCA1 mRNA levels, IGF-1 induced the activity of a reporter construct containing the ABCA1 promoter, while it was abrogated by LY294002, a specific inhibitor of PI3-K. Constitutively active Akt stimulated activity of the ABCA1 promoter, and a dominant-negative mutant of Akt or mutagenesis of the FoxO1 response element in the ABCA1 promoter abolished the ability of IGF-1 to stimulate promoter activity. A ChIP assay showed that FoxO1 mediated its transcriptional activity by directly binding to the ABCA1 promoter region. The knockdown of FoxO1 disrupted the effect of IGF-1 on ABCA1 expression. Furthermore, IGF-1 promoted cholesterol efflux and reduced the pancreatic lipotoxicity. These results demonstrate that the PI3-K/Akt/FoxO1 pathway contributes to the regulation of ABCA1 expression in response to IGF-1 stimulation. © Georg Thieme Verlag KG Stuttgart · New York.

  5. Cerebral insulin, insulin signaling pathway, and brain angiogenesis.

    Science.gov (United States)

    Zeng, Yi; Zhang, Le; Hu, Zhiping

    2016-01-01

    Insulin performs unique non-metabolic functions within the brain. Broadly speaking, two major areas of these functions are those related to brain endothelial cells and the blood-brain barrier (BBB) function, and those related to behavioral effects, like cognition in disease states (Alzheimer's disease, AD) and in health. Recent studies showed that both these functions are associated with brain angiogenesis. These findings raise interesting questions such as how they are linked to each other and whether modifying brain angiogenesis by targeting certain insulin signaling pathways could be an effective strategy to treat dementia as in AD, or even to help secure healthy longevity. The two canonical downstream pathways involved in mediating the insulin signaling pathway, the phosphoinositide-3 kinase (PI3K), and mitogen-activated protein kinase (MAPK) cascades, in the brain are supposed to be similar to those in the periphery. PI3K and MAPK pathways play important roles in angiogenesis. Both are involved in stimulating hypoxia inducible factor (HIF) in angiogenesis and could be activated by the insulin signaling pathway. This suggests that PI3K and MAPK pathways might act as cross-talk between the insulin signaling pathway and the angiogenesis pathway in brain. But the cerebral insulin, insulin signaling pathway, and the detailed mechanism in the connection of insulin signaling pathway, brain angiogenesis pathway, and healthy aging or dementias are still mostly not clear and need further studies.

  6. cGMP and NHR signaling co-regulate expression of insulin-like peptides and developmental activation of infective larvae in Strongyloides stercoralis.

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    Jonathan D Stoltzfus

    2014-07-01

    Full Text Available The infectious form of the parasitic nematode Strongyloides stercoralis is a developmentally arrested third-stage larva (L3i, which is morphologically similar to the developmentally arrested dauer larva in the free-living nematode Caenorhabditis elegans. We hypothesize that the molecular pathways regulating C. elegans dauer development also control L3i arrest and activation in S. stercoralis. This study aimed to determine the factors that regulate L3i activation, with a focus on G protein-coupled receptor-mediated regulation of cyclic guanosine monophosphate (cGMP pathway signaling, including its modulation of the insulin/IGF-1-like signaling (IIS pathway. We found that application of the membrane-permeable cGMP analog 8-bromo-cGMP potently activated development of S. stercoralis L3i, as measured by resumption of feeding, with 85.1 ± 2.2% of L3i feeding in 200 µM 8-bromo-cGMP in comparison to 0.6 ± 0.3% in the buffer diluent. Utilizing RNAseq, we examined L3i stimulated with DMEM, 8-bromo-cGMP, or the DAF-12 nuclear hormone receptor (NHR ligand Δ7-dafachronic acid (DA--a signaling pathway downstream of IIS in C. elegans. L3i stimulated with 8-bromo-cGMP up-regulated transcripts of the putative agonistic insulin-like peptide (ILP -encoding genes Ss-ilp-1 (20-fold and Ss-ilp-6 (11-fold in comparison to controls without stimulation. Surprisingly, we found that Δ7-DA similarly modulated transcript levels of ILP-encoding genes. Using the phosphatidylinositol-4,5-bisphosphate 3-kinase inhibitor LY294002, we demonstrated that 400 nM Δ7-DA-mediated activation (93.3 ± 1.1% L3i feeding can be blocked using this IIS inhibitor at 100 µM (7.6 ± 1.6% L3i feeding. To determine the tissues where promoters of ILP-encoding genes are active, we expressed promoter::egfp reporter constructs in transgenic S. stercoralis post-free-living larvae. Ss-ilp-1 and Ss-ilp-6 promoters are active in the hypodermis and neurons and the Ss-ilp-7 promoter is active in the

  7. Improved insulin sensitivity after exercise: focus on insulin signaling

    DEFF Research Database (Denmark)

    Frøsig, Christian; Richter, Erik

    2009-01-01

    After a single bout of exercise, the ability of insulin to stimulate glucose uptake is markedly improved locally in the previously active muscles. This makes exercise a potent stimulus counteracting insulin resistance characterizing type 2 diabetes (T2D). It is believed that at least part...... of the mechanism relates to an improved ability of insulin to stimulate translocation of glucose transporters (GLUT4) to the muscle membrane after exercise. How this is accomplished is still unclear; however, an obvious possibility is that exercise interacts with the insulin signaling pathway to GLUT4...... translocation allowing for a more potent insulin response. Parallel to unraveling of the insulin signaling cascade, this has been investigated within the past 25 years. Reviewing existing studies clearly indicates that improved insulin action can occur independent of interactions with proximal insulin signaling...

  8. Cinnamon extract improves insulin sensitivity in the brain and lowers liver fat in mouse models of obesity.

    Science.gov (United States)

    Sartorius, Tina; Peter, Andreas; Schulz, Nadja; Drescher, Andrea; Bergheim, Ina; Machann, Jürgen; Schick, Fritz; Siegel-Axel, Dorothea; Schürmann, Annette; Weigert, Cora; Häring, Hans-Ulrich; Hennige, Anita M

    2014-01-01

    Treatment of diabetic subjects with cinnamon demonstrated an improvement in blood glucose concentrations and insulin sensitivity but the underlying mechanisms remained unclear. This work intends to elucidate the impact of cinnamon effects on the brain by using isolated astrocytes, and an obese and diabetic mouse model. Cinnamon components (eugenol, cinnamaldehyde) were added to astrocytes and liver cells to measure insulin signaling and glycogen synthesis. Ob/ob mice were supplemented with extract from cinnamomum zeylanicum for 6 weeks and cortical brain activity, locomotion and energy expenditure were evaluated. Insulin action was determined in brain and liver tissues. Treatment of primary astrocytes with eugenol promoted glycogen synthesis, whereas the effect of cinnamaldehyde was attenuated. In terms of brain function in vivo, cinnamon extract improved insulin sensitivity and brain activity in ob/ob mice, and the insulin-stimulated locomotor activity was improved. In addition, fasting blood glucose levels and glucose tolerance were greatly improved in ob/ob mice due to cinnamon extracts, while insulin secretion was unaltered. This corresponded with lower triglyceride and increased liver glycogen content and improved insulin action in liver tissues. In vitro, Fao cells exposed to cinnamon exhibited no change in insulin action. Together, cinnamon extract improved insulin action in the brain as well as brain activity and locomotion. This specific effect may represent an important central feature of cinnamon in improving insulin action in the brain, and mediates metabolic alterations in the periphery to decrease liver fat and improve glucose homeostasis.

  9. Non-autonomous Regulation of Neuronal Migration by Insulin Signaling, DAF-16/FOXO and PAK-1

    Science.gov (United States)

    Kennedy, Lisa M.; Pham, Steven C.D.L.; Grishok, Alla

    2013-01-01

    SUMMARY Neuronal migration is essential for nervous system development in all organisms and is regulated in the nematode, C. elegans, by signaling pathways that are conserved in humans. Here, we demonstrate that the Insulin/IGF-1-PI3K signaling pathway modulates the activity of the DAF-16/FOXO transcription factor to promote the anterior migrations of the hermaphrodite-specific neurons (HSNs) during embryogenesis of C. elegans. When signaling is reduced, DAF-16 is activated and promotes migration, conversely, when signaling is enhanced, DAF-16 is inactivated and migration is inhibited. We show that DAF-16 acts non-autonomously in the hypodermis to promote HSN migration. Furthermore, we identify PAK-1, a p21-activated kinase, as a downstream mediator of Insulin/IGF-1-DAF-16 signaling in the non-autonomous control of HSN migration. As a FOXO-Pak1 pathway was recently shown to regulate mammalian neuronal polarity, our findings indicate that the roles of FOXO and Pak1 in neuronal migration are likely conserved from C. elegans to higher organisms. PMID:23994474

  10. Insulin and insulin signaling play a critical role in fat induction of insulin resistance in mouse

    Science.gov (United States)

    Ning, Jie; Hong, Tao; Yang, Xuefeng; Mei, Shuang; Liu, Zhenqi; Liu, Hui-Yu

    2011-01-01

    The primary player that induces insulin resistance has not been established. Here, we studied whether or not fat can cause insulin resistance in the presence of insulin deficiency. Our results showed that high-fat diet (HFD) induced insulin resistance in C57BL/6 (B6) mice. The HFD-induced insulin resistance was prevented largely by the streptozotocin (STZ)-induced moderate insulin deficiency. The STZ-induced insulin deficiency prevented the HFD-induced ectopic fat accumulation and oxidative stress in liver and gastrocnemius. The STZ-induced insulin deficiency prevented the HFD- or insulin-induced increase in hepatic expression of long-chain acyl-CoA synthetases (ACSL), which are necessary for fatty acid activation. HFD increased mitochondrial contents of long-chain acyl-CoAs, whereas it decreased mitochondrial ADP/ATP ratio, and these HFD-induced changes were prevented by the STZ-induced insulin deficiency. In cultured hepatocytes, we observed that expressions of ACSL1 and -5 were stimulated by insulin signaling. Results in cultured cells also showed that blunting insulin signaling by the PI3K inhibitor LY-294002 prevented fat accumulation, oxidative stress, and insulin resistance induced by the prolonged exposure to either insulin or oleate plus sera that normally contain insulin. Finally, knockdown of the insulin receptor prevented the oxidative stress and insulin resistance induced by the prolonged exposure to insulin or oleate plus sera. Together, our results show that insulin and insulin signaling are required for fat induction of insulin resistance in mice and cultured mouse hepatocytes. PMID:21586696

  11. The road to the first, fully active and more stable human insulin variant with an additional disulfide bond

    DEFF Research Database (Denmark)

    Vinther, Tine N.; Kjeldsen, Thomas B.; Jensen, Knud Jørgen

    2015-01-01

    Insulin, a small peptide hormone, is crucial in maintaining blood glucose homeostasis. The stability and activity of the protein is directed by an intricate system involving disulfide bonds to stabilize the active monomeric species and by their non-covalent oligomerization. All known insulin...... variants in vertebrates consist of two peptide chains and have six cysteine residues, which form three disulfide bonds, two of them link the two chains and a third is an intra-chain bond in the A-chain. This classical insulin fold appears to have been conserved over half a billion years of evolution. We...... addressed the question whether a human insulin variant with four disulfide bonds could exist and be fully functional. In this review, we give an overview of the road to engineering four-disulfide bonded insulin analogs. During our journey, we discovered several active four disulfide bonded insulin analogs...

  12. Unaltered Prion Pathogenesis in a Mouse Model of High-Fat Diet-Induced Insulin Resistance.

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    Caihong Zhu

    Full Text Available Epidemiological, clinical, and experimental animal studies suggest a strong correlation between insulin resistance and Alzheimer's disease. In fact, type-2 diabetes is considered an important risk factor of developing Alzheimer's disease. In addition, impaired insulin signaling in the Alzheimer's disease brain may promote Aβ production, impair Aβ clearance and induce tau hyperphosphorylation, thereby leading to deterioration of the disease. The pathological prion protein, PrPSc, deposits in the form of extracellular aggregates and leads to dementia, raising the question as to whether prion pathogenesis may also be affected by insulin resistance. We therefore established high-fat diet-induced insulin resistance in tga20 mice, which overexpress the prion protein. We then inoculated the insulin-resistant mice with prions. We found that insulin resistance in tga20 mice did not affect prion disease progression, PrPSc deposition, astrogliosis or microglial activation, and had no effect on survival. Our study demonstrates that in a mouse model, insulin resistance does not significantly contribute to prion pathogenesis.

  13. Maternal insulin sensitivity is associated with oral glucose-induced changes in fetal brain activity.

    Science.gov (United States)

    Linder, Katarzyna; Schleger, Franziska; Ketterer, Caroline; Fritsche, Louise; Kiefer-Schmidt, Isabelle; Hennige, Anita; Häring, Hans-Ulrich; Preissl, Hubert; Fritsche, Andreas

    2014-06-01

    Fetal programming plays an important role in the pathogenesis of type 2 diabetes. The aim of the present study was to investigate whether maternal metabolic changes during OGTT influence fetal brain activity. Thirteen healthy pregnant women underwent an OGTT (75 g). Insulin sensitivity was determined by glucose and insulin measurements at 0, 60 and 120 min. At each time point, fetal auditory evoked fields were recorded with a fetal magnetoencephalographic device and response latencies were determined. Maternal insulin increased from a fasting level of 67 ± 25 pmol/l (mean ± SD) to 918 ± 492 pmol/l 60 min after glucose ingestion and glucose levels increased from 4.4 ± 0.3 to 7.4 ± 1.1 mmol/l. Over the same time period, fetal response latencies decreased from 297 ± 99 to 235 ± 84 ms (p = 0.01) and then remained stable until 120 min (235 ± 84 vs 251 ± 91 ms, p = 0.39). There was a negative correlation between maternal insulin sensitivity and fetal response latencies 60 min after glucose ingestion (r = 0.68, p = 0.02). After a median split of the group based on maternal insulin sensitivity, fetuses of insulin-resistant mothers showed a slower response to auditory stimuli (283 ± 79 ms) than those of insulin-sensitive mothers (178 ± 46 ms, p = 0.03). Lower maternal insulin sensitivity is associated with slower fetal brain responses. These findings provide the first evidence of a direct effect of maternal metabolism on fetal brain activity and suggest that central insulin resistance may be programmed during fetal development.

  14. Role of insulin in regulation of Na+-/K+-dependent ATPase activity and pump function in corneal endothelial cells.

    Science.gov (United States)

    Hatou, Shin; Yamada, Masakazu; Akune, Yoko; Mochizuki, Hiroshi; Shiraishi, Atsushi; Joko, Takeshi; Nishida, Teruo; Tsubota, Kazuo

    2010-08-01

    The Na(+)-/K(+)-dependent ATPase (Na,K-ATPase) expressed in the basolateral membrane of corneal endothelial cells plays an important role in the pump function of the corneal endothelium. The role of insulin in the regulation of Na,K-ATPase activity and pump function in corneal endothelial cells was investigated. Confluent monolayers of mouse corneal endothelial cells were exposed to insulin. ATPase activity was evaluated by spectrophotometric measurement of phosphate released from ATP with the use of ammonium molybdate; Na,K-ATPase activity was defined as the portion of total ATPase activity sensitive to ouabain. Pump function was measured with the use of a Ussing chamber; pump function attributable to Na,K-ATPase activity was defined as the portion of the total short-circuit current sensitive to ouabain. Western blot analysis and immunocytochemistry were performed to measure the expression of the Na,K-ATPase alpha(1)-subunit. Insulin increased the Na,K-ATPase activity and pump function of cultured corneal endothelial cells. These effects were blocked by protein kinase C (PKC) inhibitors and protein phosphatases 1 and 2A inhibitor. Western blot analysis indicated that insulin decreased the ratio of the inactive Na,K-ATPase alpha(1)-subunit. Immunocytochemistry indicated that insulin increased the cell surface expression of the Na,K-ATPase alpha(1)-subunit. These results suggest that insulin increases the Na,K-ATPase activity and pump function of cultured corneal endothelial cells. The effect of insulin is mediated by PKC and presumably results in the activation of PP1, 2A, or both, which are essential for activating Na,K-ATPase by alpha(1)-subunit dephosphorylation.

  15. Repression of COUP-TFI Improves Bone Marrow-Derived Mesenchymal Stem Cell Differentiation into Insulin-Producing Cells

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    Tao Zhang

    2017-09-01

    Full Text Available Identifying molecular mechanisms that regulate insulin expression in bone marrow-derived mesenchymal stem cells (bmMSCs can provide clues on how to stimulate the differentiation of bmMSCs into insulin-producing cells (IPCs, which can be used as a therapeutic approach against type 1 diabetes (T1D. As repression factors may inhibit differentiation, the efficiency of this process is insufficient for cell transplantation. In this study, we used the mouse insulin 2 (Ins2 promoter sequence and performed a DNA affinity precipitation assay combined with liquid chromatography-mass spectrometry to identify the transcription factor, chicken ovalbumin upstream promoter transcriptional factor I (COUP-TFI. Functionally, bmMSCs were reprogrammed into IPCs via COUP-TFI suppression and MafA overexpression. The differentiated cells expressed higher levels of genes specific for islet endocrine cells, and they released C-peptide and insulin in response to glucose stimulation. Transplantation of IPCs into streptozotocin-induced diabetic mice caused a reduction in hyperglycemia. Mechanistically, COUP-TFI bound to the DR1 (direct repeats with 1 spacer element in the Ins2 promoter, thereby negatively regulating promoter activity. Taken together, the data provide a novel mechanism by which COUP-TFI acts as a negative regulator in the Ins2 promoter. The differentiation of bmMSCs into IPCs could be improved by knockdown of COUP-TFI, which may provide a novel stem cell-based therapy for T1D. Keywords: siRNAs, differentiation, stem cell transplantation, diabetes, mesenchymal stem cells

  16. Data in support of fumosorinone, a novel PTP1B inhibitor, activates insulin signaling in insulin-resistance HepG2 cells and shows anti-diabetic effect in diabetic KKAy mice

    Directory of Open Access Journals (Sweden)

    Du-Qiang Luo

    2015-09-01

    Full Text Available This data article contains data related to the research article entitled “Fumosorinone, a novel PTP1B inhibitor, activates insulin signaling in insulin-resistance HepG2 cells and shows anti-diabetic effect in diabetic KKAy mice” in the Toxicology and Applied Pharmacology [1]. Fumosorinone (FU is a new inhibitor of protein phosphatase 1B inhibitor, which was isolated from insect pathogenic fungi Isaria fumosorosea. FU was found to inhibit PTP1B activity in our previous study [2]. PTP1B is the physiological antagonist of the insulin signalling pathway. Inhibition of PTP 1B may increase insulin sensitivity [3]. PTP1B has been considered promising as an insulin-sensitive drug target for the prevention and the treatment of insulin-based diseases [4]. We determined the effect of FU on the glucose consumption of IR HepG2 cells. FU caused significant enhancement in glucose consumption by insulin-resistant HepG2 cells compared with control cells.

  17. Possible Involvement of Insulin Resistance in the Progression of Cancer Cachexia in Mice.

    Science.gov (United States)

    Ohsawa, Masahiro; Murakami, Tomoyasu; Kume, Kazuhiko

    2016-01-01

    Malnutrition is a common problem among cancer patients, affecting up to 85% of patients with certain cancers. In severe cases, malnutrition can progress to cachexia, a specific form of malnutrition characterized by loss of lean body mass and muscle wasting. Although this muscle wasting might be a product of enhanced protein degradation, the precise mechanisms of cancer cachexia are not fully elucidated. Based on basic and clinical research, glucose intolerance and insulin resistance have been postulated to be associated with cancer cachexia. Since insulin in the skeletal muscle inhibits protein degradation and promotes protein synthesis, insulin resistance could be a possible cause of cancer cachexia. Therefore, we investigated the involvement of insulin resistance in the development of cancer cachexia in tumor-bearing mice. The signaling protein in the insulin cascade was attenuated in the skeletal muscle and hypothalamus from tumor-bearing mice. We identified Chrysanthemum morifolium RAMAT., known as Kikuka, as a peroxisome proliferator-activated receptor γ (PPARγ) ligand. Treatment with Kikuka attenuates the skeletal muscle changes in tumor-bearing mice. These results suggest that this natural PPARγ activator might be an attractive candidate for the treatment of cancer cachexia. In the symposium, we presented the PPARγ activator-induced improvement of cancer cachexia.

  18. RFX6 Regulates Insulin Secretion by Modulating Ca2+ Homeostasis in Human β Cells

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    Vikash Chandra

    2014-12-01

    Full Text Available Development and function of pancreatic β cells involve the regulated activity of specific transcription factors. RFX6 is a transcription factor essential for mouse β cell differentiation that is mutated in monogenic forms of neonatal diabetes. However, the expression and functional roles of RFX6 in human β cells, especially in pathophysiological conditions, are poorly explored. We demonstrate the presence of RFX6 in adult human pancreatic endocrine cells. Using the recently developed human β cell line EndoC-βH2, we show that RFX6 regulates insulin gene transcription, insulin content, and secretion. Knockdown of RFX6 causes downregulation of Ca2+-channel genes resulting in the reduction in L-type Ca2+-channel activity that leads to suppression of depolarization-evoked insulin exocytosis. We also describe a previously unreported homozygous missense RFX6 mutation (p.V506G that is associated with neonatal diabetes, which lacks the capacity to activate the insulin promoter and to increase Ca2+-channel expression. Our data therefore provide insights for understanding certain forms of neonatal diabetes.

  19. Raman optical activity study on insulin amyloid- and prefibril intermediate

    Czech Academy of Sciences Publication Activity Database

    Yamamoto, Shigeki; Watarai, H.

    2012-01-01

    Roč. 24, č. 2 (2012), s. 97-103 ISSN 0899-0042 Institutional research plan: CEZ:AV0Z40550506 Keywords : raman optical activity * amyloid * fibril * intermediate * insulin Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.718, year: 2012

  20. Activation and regulation of the pattern recognition receptors in obesity-induced adipose tissue inflammation and insulin resistance.

    Science.gov (United States)

    Watanabe, Yasuharu; Nagai, Yoshinori; Takatsu, Kiyoshi

    2013-09-23

    Obesity-associated chronic tissue inflammation is a key contributing factor to type 2 diabetes mellitus, and a number of studies have clearly demonstrated that the immune system and metabolism are highly integrated. Recent advances in deciphering the various immune cells and signaling networks that link the immune and metabolic systems have contributed to our understanding of the pathogenesis of obesity-associated inflammation. Other recent studies have suggested that pattern recognition receptors in the innate immune system recognize various kinds of endogenous and exogenous ligands, and have a crucial role in initiating or promoting obesity-associated chronic inflammation. Importantly, these mediators act on insulin target cells or on insulin-producing cells impairing insulin sensitivity and its secretion. Here, we discuss how various pattern recognition receptors in the immune system underlie the etiology of obesity-associated inflammation and insulin resistance, with a particular focus on the TLR (Toll-like receptor) family protein Radioprotective 105 (RP105)/myeloid differentiation protein-1 (MD-1).

  1. Activation and Regulation of the Pattern Recognition Receptors in Obesity-Induced Adipose Tissue Inflammation and Insulin Resistance

    Directory of Open Access Journals (Sweden)

    Kiyoshi Takatsu

    2013-09-01

    Full Text Available Obesity-associated chronic tissue inflammation is a key contributing factor to type 2 diabetes mellitus, and a number of studies have clearly demonstrated that the immune system and metabolism are highly integrated. Recent advances in deciphering the various immune cells and signaling networks that link the immune and metabolic systems have contributed to our understanding of the pathogenesis of obesity-associated inflammation. Other recent studies have suggested that pattern recognition receptors in the innate immune system recognize various kinds of endogenous and exogenous ligands, and have a crucial role in initiating or promoting obesity-associated chronic inflammation. Importantly, these mediators act on insulin target cells or on insulin-producing cells impairing insulin sensitivity and its secretion. Here, we discuss how various pattern recognition receptors in the immune system underlie the etiology of obesity-associated inflammation and insulin resistance, with a particular focus on the TLR (Toll-like receptor family protein Radioprotective 105 (RP105/myeloid differentiation protein-1 (MD-1.

  2. Insulin resistance, insulin sensitization and inflammation in polycystic ovarian syndrome

    Directory of Open Access Journals (Sweden)

    Dhindsa G

    2004-04-01

    Full Text Available It is estimated that 5-10% of women of reproductive age have polycystic ovarian syndrome (PCOS. While insulin resistance is not part of the diagnostic criteria for PCOS, its importance in the pathogenesis of PCOS cannot be denied. PCOS is associated with insulin resistance independent of total or fat-free body mass. Post-receptor defects in the action of insulin have been described in PCOS which are similar to those found in obesity and type 2 diabetes. Treatment with insulin sensitizers, metformin and thiazolidinediones, improve both metabolic and hormonal patterns and also improve ovulation in PCOS. Recent studies have shown that PCOS women have higher circulating levels of inflammatory mediators like C-reactive protein, tumour necrosis factor- , tissue plasminogen activator and plasminogen activator inhibitor-1 (PAI-1 . It is possible that the beneficial effect of insulin sensitizers in PCOS may be partly due to a decrease in inflammation.

  3. Glycosides from Stevia rebaudiana Bertoni Possess Insulin-Mimetic and Antioxidant Activities in Rat Cardiac Fibroblasts

    Directory of Open Access Journals (Sweden)

    Cecilia Prata

    2017-01-01

    Full Text Available Stevia rebaudiana Bertoni is a shrub having a high content of sweet diterpenoid glycosides in its leaves, mainly stevioside and rebaudioside A, which are used as noncaloric, natural sweeteners. The aim of this study was to deepen the knowledge about the insulin-mimetic effect exerted by four different mixtures of steviol glycosides, rich in stevioside and rebaudioside A, in neonatal rat cardiac fibroblasts. The potential antioxidant activity of these steviol glycosides was also assessed, as oxidative stress is associated with diabetes. Likewise the insulin effect, steviol glycosides caused an increase in glucose uptake into rat fibroblasts by activating the PI3K/Akt pathway, thus inducing Glut4 translocation to the plasma membrane. The presence of S961, an insulin antagonist, completely abolished these effects, allowing to hypothesize that steviol glycosides could act as ligands of the same receptor engaged by insulin. Moreover, steviol glycosides counteracted oxidative stress by increasing reduced glutathione intracellular levels and upregulating expression and activity of the two antioxidant enzymes superoxide dismutase and catalase. The present work unravels the insulin-mimetic effect and the antioxidant property exerted by steviol glycosides, suggesting their potential beneficial role in the cotreatment of diabetes and in health maintenance.

  4. Glycosides from Stevia rebaudiana Bertoni Possess Insulin-Mimetic and Antioxidant Activities in Rat Cardiac Fibroblasts

    Science.gov (United States)

    Prata, Cecilia; Zambonin, Laura; Rizzo, Benedetta; Vieceli Dalla Sega, Francesco

    2017-01-01

    Stevia rebaudiana Bertoni is a shrub having a high content of sweet diterpenoid glycosides in its leaves, mainly stevioside and rebaudioside A, which are used as noncaloric, natural sweeteners. The aim of this study was to deepen the knowledge about the insulin-mimetic effect exerted by four different mixtures of steviol glycosides, rich in stevioside and rebaudioside A, in neonatal rat cardiac fibroblasts. The potential antioxidant activity of these steviol glycosides was also assessed, as oxidative stress is associated with diabetes. Likewise the insulin effect, steviol glycosides caused an increase in glucose uptake into rat fibroblasts by activating the PI3K/Akt pathway, thus inducing Glut4 translocation to the plasma membrane. The presence of S961, an insulin antagonist, completely abolished these effects, allowing to hypothesize that steviol glycosides could act as ligands of the same receptor engaged by insulin. Moreover, steviol glycosides counteracted oxidative stress by increasing reduced glutathione intracellular levels and upregulating expression and activity of the two antioxidant enzymes superoxide dismutase and catalase. The present work unravels the insulin-mimetic effect and the antioxidant property exerted by steviol glycosides, suggesting their potential beneficial role in the cotreatment of diabetes and in health maintenance. PMID:28947927

  5. APPL1 potentiates insulin sensitivity by facilitating the binding of IRS1/2 to the insulin receptor.

    Science.gov (United States)

    Ryu, Jiyoon; Galan, Amanda K; Xin, Xiaoban; Dong, Feng; Abdul-Ghani, Muhammad A; Zhou, Lijun; Wang, Changhua; Li, Cuiling; Holmes, Bekke M; Sloane, Lauren B; Austad, Steven N; Guo, Shaodong; Musi, Nicolas; DeFronzo, Ralph A; Deng, Chuxia; White, Morris F; Liu, Feng; Dong, Lily Q

    2014-05-22

    Binding of insulin receptor substrate proteins 1 and 2 (IRS1/2) to the insulin receptor (IR) is essential for the regulation of insulin sensitivity and energy homeostasis. However, the mechanism of IRS1/2 recruitment to the IR remains elusive. Here, we identify adaptor protein APPL1 as a critical molecule that promotes IRS1/2-IR interaction. APPL1 forms a complex with IRS1/2 under basal conditions, and this complex is then recruited to the IR in response to insulin or adiponectin stimulation. The interaction between APPL1 and IR depends on insulin- or adiponectin-stimulated APPL1 phosphorylation, which is greatly reduced in insulin target tissues in obese mice. appl1 deletion in mice consistently leads to systemic insulin resistance and a significant reduction in insulin-stimulated IRS1/2, but not IR, tyrosine phosphorylation, indicating that APPL1 sensitizes insulin signaling by acting at a site downstream of the IR. Our study uncovers a mechanism regulating insulin signaling and crosstalk between the insulin and adiponectin pathways. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

  6. PEDF expression is inhibited by insulin treatment in adipose tissue via suppressing 11β-HSD1.

    Directory of Open Access Journals (Sweden)

    Yinli Zhou

    Full Text Available Early intensive insulin therapy improves insulin sensitivity in type 2 diabetic patients; while the underlying mechanism remains largely unknown. Pigment epithelium-derived factor (PEDF, an anti-angiogenic factor, is believed to be involved in the pathogenesis of insulin resistance. Here, we hypothesize that PEDF might be down regulated by insulin and then lead to the improved insulin resistance in type 2 diabetic patients during insulin therapy. We addressed this issue by investigating insulin regulation of PEDF expression in diabetic conditions. The results showed that serum PEDF was reduced by 15% in newly diagnosed type 2 diabetic patients after insulin therapy. In adipose tissue of diabetic Sprague-Dawley rats, PEDF expression was associated with TNF-α elevation and it could be decreased both in serum and in adipose tissue by insulin treatment. In adipocytes, PEDF was induced by TNF-α through activation of NF-κB. The response was inhibited by knockdown and enhanced by over expression of NF-κB p65. However, PEDF expression was indirectly, not directly, induced by NF-κB which promoted 11β-hydroxysteroid dehydrogenase 1 (11β-HSD1 expression in adipocytes. 11β-HSD1 is likely to stimulate PEDF expression through production of active form of glucocorticoids as dexamethasone induced PEDF expression in adipose tissue. Insulin inhibited PEDF by down-regulating 11β-HSD1 expression. The results suggest that PEDF activity is induced by inflammation and decreased by insulin through targeting 11β-HSD1/glucocorticoid pathway in adipose tissue of diabetic patients.

  7. Hydrogen peroxide induces activation of insulin signaling pathway via AMP-dependent kinase in podocytes

    Energy Technology Data Exchange (ETDEWEB)

    Piwkowska, Agnieszka, E-mail: apiwkowska@cmdik.pan.pl [Mossakowski Medical Research Centre, Polish Academy of Sciences, Laboratory of Molecular and Cellular Nephrology, Gdansk (Poland); Rogacka, Dorota; Angielski, Stefan [Mossakowski Medical Research Centre, Polish Academy of Sciences, Laboratory of Molecular and Cellular Nephrology, Gdansk (Poland); Jankowski, Maciej [Mossakowski Medical Research Centre, Polish Academy of Sciences, Laboratory of Molecular and Cellular Nephrology, Gdansk (Poland); Medical University of Gdansk, Department of Therapy Monitoring and Pharmacogenetics (Poland)

    2012-11-09

    Highlights: Black-Right-Pointing-Pointer H{sub 2}O{sub 2} activates the insulin signaling pathway and glucose uptake in podocytes. Black-Right-Pointing-Pointer H{sub 2}O{sub 2} induces time-dependent changes in AMPK phosphorylation. Black-Right-Pointing-Pointer H{sub 2}O{sub 2} enhances insulin signaling pathways via AMPK activation. Black-Right-Pointing-Pointer H{sub 2}O{sub 2} stimulation of glucose uptake is AMPK-dependent. -- Abstract: Podocytes are cells that form the glomerular filtration barrier in the kidney. Insulin signaling in podocytes is critical for normal kidney function. Insulin signaling is regulated by oxidative stress and intracellular energy levels. We cultured rat podocytes to investigate the effects of hydrogen peroxide (H{sub 2}O{sub 2}) on the phosphorylation of proximal and distal elements of insulin signaling. We also investigated H{sub 2}O{sub 2}-induced intracellular changes in the distribution of protein kinase B (Akt). Western blots showed that H{sub 2}O{sub 2} (100 {mu}M) induced rapid, transient phosphorylation of the insulin receptor (IR), the IR substrate-1 (IRS1), and Akt with peak activities at 5 min ({Delta} 183%, P < 0.05), 3 min ({Delta} 414%, P < 0.05), and 10 min ({Delta} 35%, P < 0.05), respectively. Immunostaining cells with an Akt-specific antibody showed increased intensity at the plasma membrane after treatment with H{sub 2}O{sub 2}>. Furthermore, H{sub 2}O{sub 2} inhibited phosphorylation of the phosphatase and tensin homologue (PTEN; peak activity at 10 min; {Delta} -32%, P < 0.05) and stimulated phosphorylation of the AMP-dependent kinase alpha subunit (AMPK{alpha}; 78% at 3 min and 244% at 10 min). The stimulation of AMPK was abolished with an AMPK inhibitor, Compound C (100 {mu}M, 2 h). Moreover, Compound C significantly reduced the effect of H{sub 2}O{sub 2} on IR phosphorylation by about 40% (from 2.07 {+-} 0.28 to 1.28 {+-} 0.12, P < 0.05). In addition, H{sub 2}O{sub 2} increased glucose uptake in podocytes

  8. The relationship between bone turnover and insulin sensitivity and secretion

    DEFF Research Database (Denmark)

    Frost, Morten; Balkau, Beverley; Hatunic, Mensud

    2018-01-01

    Bone metabolism appears to influence insulin secretion and sensitivity, and insulin promotes bone formation in animals, but similar evidence in humans is limited. The objectives of this study are to explore if bone turnover markers were associated with insulin secretion and sensitivity and to det...

  9. Heparanase augments insulin receptor signaling in breast carcinoma

    Science.gov (United States)

    Goldberg, Rachel; Sonnenblick, Amir; Hermano, Esther; Hamburger, Tamar; Meirovitz, Amichay; Peretz, Tamar; Elkin, Michael

    2017-01-01

    Recently, growing interest in the potential link between metabolic disorders (i.e., diabetes, obesity, metabolic syndrome) and breast cancer has mounted, including studies which indicate that diabetic/hyperinsulinemic women have a significantly higher risk of bearing breast tumors that are more aggressive and associated with higher death rates. Insulin signaling is regarded as a major contributor to this phenomenon; much less is known about the role of heparan sulfate-degrading enzyme heparanase in the link between metabolic disorders and cancer. In the present study we analyzed clinical samples of breast carcinoma derived from diabetic/non-diabetic patients, and investigated effects of heparanase on insulin signaling in breast carcinoma cell lines, as well as insulin-driven growth of breast tumor cells. We demonstrate that heparanase activity leads to enhanced insulin signaling and activation of downstream tumor-promoting pathways in breast carcinoma cells. In agreement, heparanase enhances insulin-induced proliferation of breast tumor cells in vitro. Moreover, analyzing clinical data from diabetic breast carcinoma patients, we found that concurrent presence of both diabetic state and heparanase in tumor tissue (as opposed to either condition alone) was associated with more aggressive phenotype of breast tumors in the patient cohort analyzed in our study (two-sided Fisher's exact test; p=0.04). Our findings highlight the emerging role of heparanase in powering effect of hyperinsulinemic state on breast tumorigenesis and imply that heparanase targeting, which is now under intensive development/clinical testing, could be particularly efficient in a growing fraction of breast carcinoma patients suffering from metabolic disorders. PMID:28038446

  10. Activation of AMPK improves inflammation and insulin resistance in adipose tissue and skeletal muscle from pregnant women.

    Science.gov (United States)

    Liong, Stella; Lappas, Martha

    2015-12-01

    Gestational diabetes mellitus (GDM) is characterised by maternal peripheral insulin resistance and inflammation. Sterile inflammation and bacterial infection are key mediators of this enhanced inflammatory response. Adenosine monophosphate (AMP)-activated kinase (AMPK), which is decreased in insulin resistant states, possesses potent pro-inflammatory actions. There are, however, no studies on the role of AMPK in pregnancies complicated by GDM. Thus, the aims of this study were (i) to compare the expression of AMPK in adipose tissue and skeletal muscle from women with GDM and normal glucose-tolerant (NGT) pregnant women; and (ii) to investigate the effect of AMPK activation on inflammation and insulin resistance induced by the bacterial endotoxin lipopolysaccharide (LPS) and the pro-inflammatory cytokine IL-1β. When compared to NGT pregnant women, AMPKα activity was significantly lower in women with GDM as evidenced by a decrease in threonine phosphorylation of AMPKα. Activation of AMPK, using two pharmacologically distinct compounds, AICAR or phenformin, significantly suppressed LPS- or IL-1β-induced gene expression and secretion of pro-inflammatory cytokine IL-6, the chemokines IL-8 and MCP-1, and COX-2 and subsequent prostaglandin release from adipose tissue and skeletal muscle. In addition, activators of AMPK decreased skeletal muscle insulin resistance induced by LPS or IL-1β as evidenced by increased insulin-stimulated phosphorylation of IRS-1, GLUT-4 expression and glucose uptake. These findings suggest that AMPK may play an important role in inflammation and insulin resistance.

  11. Bariatric surgery in morbidly obese insulin resistant humans normalises insulin signalling but not insulin-stimulated glucose disposal.

    Directory of Open Access Journals (Sweden)

    Mimi Z Chen

    Full Text Available Weight-loss after bariatric surgery improves insulin sensitivity, but the underlying molecular mechanism is not clear. To ascertain the effect of bariatric surgery on insulin signalling, we examined glucose disposal and Akt activation in morbidly obese volunteers before and after Roux-en-Y gastric bypass surgery (RYGB, and compared this to lean volunteers.The hyperinsulinaemic euglycaemic clamp, at five infusion rates, was used to determine glucose disposal rates (GDR in eight morbidly obese (body mass index, BMI=47.3 ± 2.2 kg/m(2 patients, before and after RYGB, and in eight lean volunteers (BMI=20.7 ± 0.7 kg/m2. Biopsies of brachioradialis muscle, taken at fasting and insulin concentrations that induced half-maximal (GDR50 and maximal (GDR100 GDR in each subject, were used to examine the phosphorylation of Akt-Thr308, Akt-473, and pras40, in vivo biomarkers for Akt activity.Pre-operatively, insulin-stimulated GDR was lower in the obese compared to the lean individuals (P<0.001. Weight-loss of 29.9 ± 4 kg after surgery significantly improved GDR50 (P=0.004 but not GDR100 (P=0.3. These subjects still remained significantly more insulin resistant than the lean individuals (p<0.001. Weight loss increased insulin-stimulated skeletal muscle Akt-Thr308 and Akt-Ser473 phosphorylation, P=0.02 and P=0.03 respectively (MANCOVA, and Akt activity towards the substrate PRAS40 (P=0.003, MANCOVA, and in contrast to GDR, were fully normalised after the surgery (obese vs lean, P=0.6, P=0.35, P=0.46, respectively.Our data show that although Akt activity substantially improved after surgery, it did not lead to a full restoration of insulin-stimulated glucose disposal. This suggests that a major defect downstream of, or parallel to, Akt signalling remains after significant weight-loss.

  12. Free radical activity during development of insulin-dependent diabetes mellitus in the rat

    Energy Technology Data Exchange (ETDEWEB)

    Pitkaenen, O.M.; Akerblom, H.K.; Sariola, H.; Andersson, S.M. (Univ. of Helsinki (Finland)); Martin, J.M. (Hospital for Sick Children, Toronto, Ontario (Canada)); Hallman, M. (Univ. of California, Irvine (United States))

    1991-01-01

    Free radical-induced lipid peroxidation was quantified by measuring expired pentane from diabetic prone BB Wistar rats of 45-90 d of age. Insulin-dependent diabetes mellitus was manifest at the age of 71 {plus minus} 8 d. Expired pentane increased from 2.1 {plus minus} 0.7 to 5.0 {plus minus}3.0 pmol/100g/min (p <0.01) at manifestation of the disease and remained high throughout the test period. In healthy age-matched control rats it persisted low. In rats made diabetic with streptozotocin, expired pentane remained low. The changes in expired pentane suggest that the development of endogenous insulin-dependent diabetes mellitus in BB rats is associated with increased free radical activity. This is not due to hyperglycemia or ketosis per se, and reflects a fundamental difference in the free radical activity between the spontaneously diabetic BB rats and the disease produced by streptozotocin. Development of spontaneous insulin-dependent diabetes in BB rats is associated with increased free radical activity that persists after the manifestation of the disease.

  13. Insulin resistance and improvements in signal transduction.

    Science.gov (United States)

    Musi, Nicolas; Goodyear, Laurie J

    2006-02-01

    Type 2 diabetes and obesity are common metabolic disorders characterized by resistance to the actions of insulin to stimulate skeletal muscle glucose disposal. Insulin-resistant muscle has defects at several steps of the insulin-signaling pathway, including decreases in insulin-stimulated insulin receptor and insulin receptor substrate-1 tyrosine phosphorylation, and phosphatidylinositol 3-kinase (PI 3-kinase) activation. One approach to increase muscle glucose disposal is to reverse/improve these insulin-signaling defects. Weight loss and thiazolidinediones (TZDs) improve glucose disposal, in part, by increasing insulin-stimulated insulin receptor and IRS-1 tyrosine phosphorylation and PI 3-kinase activity. In contrast, physical training and metformin improve whole-body glucose disposal but have minimal effects on proximal insulin-signaling steps. A novel approach to reverse insulin resistance involves inhibition of the stress-activated protein kinase Jun N-terminal kinase (JNK) and the protein tyrosine phosphatases (PTPs). A different strategy to increase muscle glucose disposal is by stimulating insulin-independent glucose transport. AMP-activated protein kinase (AMPK) is an enzyme that works as a fuel gauge and becomes activated in situations of energy consumption, such as muscle contraction. Several studies have shown that pharmacologic activation of AMPK increases glucose transport in muscle, independent of the actions of insulin. AMPK activation is also involved in the mechanism of action of metformin and adiponectin. Moreover, in the hypothalamus, AMPK regulates appetite and body weight. The effect of AMPK to stimulate muscle glucose disposal and to control appetite makes it an important pharmacologic target for the treatment of type 2 diabetes and obesity.

  14. Histone deacetylase regulates insulin signaling via two pathways in pancreatic β cells.

    Directory of Open Access Journals (Sweden)

    Yukina Kawada

    Full Text Available Recent studies demonstrated that insulin signaling plays important roles in the regulation of pancreatic β cell mass, the reduction of which is known to be involved in the development of diabetes. However, the mechanism underlying the alteration of insulin signaling in pancreatic β cells remains unclear. The involvement of epigenetic control in the onset of diabetes has also been reported. Thus, we analyzed the epigenetic control of insulin receptor substrate 2 (IRS2 expression in the MIN6 mouse insulinoma cell line. We found concomitant IRS2 up-regulation and enhanced insulin signaling in MIN6 cells, which resulted in an increase in cell proliferation. The H3K9 acetylation status of the Irs2 promoter was positively associated with IRS2 expression. Treatment of MIN6 cells with histone deacetylase inhibitors led to increased IRS2 expression, but this occurred in concert with low insulin signaling. We observed increased IRS2 lysine acetylation as a consequence of histone deacetylase inhibition, a modification that was coupled with a decrease in IRS2 tyrosine phosphorylation. These results suggest that insulin signaling in pancreatic β cells is regulated by histone deacetylases through two novel pathways affecting IRS2: the epigenetic control of IRS2 expression by H3K9 promoter acetylation, and the regulation of IRS2 activity through protein modification. The identification of the histone deacetylase isoform(s involved in these mechanisms would be a valuable approach for the treatment of type 2 diabetes.

  15. Meal-induced platelet activation in diabetes mellitus type 1 or type 2 is related to postprandial insulin rather than glucose levels.

    Science.gov (United States)

    Spectre, Galia; Stålesen, Ragnhild; Östenson, Claes-Göran; Hjemdahl, Paul

    2016-05-01

    Postprandial platelet activation was related to postprandial insulin rather than glucose levels in a previous meal insulin study in type 2 diabetes mellitus (T2DM). We therefore compared postprandial platelet activation in type 1 (T1DM) patients without insulin secretion and T2DM patients with high postprandial insulin levels. Patients with T1DM (n=11) and T2DM (n=12) were studied before and 90min after a standardized meal without premeal insulin. Five T1DM patients volunteered for a restudy with their regular premeal insulin. Platelet activation was assessed by flow cytometry, with and without the thromboxane analogue U46619 or ADP, and by whole blood aggregometry (Multiplate®). Effects of insulin (100μU/mL) in vitro were also studied. Before the meal, glucose, insulin and platelet activation markers other than platelet-leukocyte aggregates (PLAs) were similar in T1DM and T2DM; PLAs were higher in T1DM. Postprandial glucose levels increased more markedly in T1DM (to 22.1±1.4 vs. 11.2±0.6mmol/L) while insulin levels increased only in T2DM (from 24.4±4.4 to 68.8±12.3μU/mL). Platelet P-selectin expression, fibrinogen binding and PLA formation stimulated by U46619 were markedly enhanced (approximately doubled) and whole blood aggregation stimulated by U46619 was increased (pinsulin in T1DM patients showed postprandial platelet activation when postprandial insulin levels increased. In vitro insulin mildly activated platelets in both groups. Postprandial platelet activation via the thromboxane pathway is related to postprandial hyperinsulinemia and not to postprandial hyperglycaemia in patients with diabetes. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. Insulin resistance predicts early cardiovascular morbidity in men without diabetes mellitus, with effect modification by physical activity.

    Science.gov (United States)

    Hellgren, Margareta I; Daka, Bledar; Jansson, Per-Anders; Lindblad, Ulf; Larsson, Charlotte A

    2015-07-01

    to assess how well insulin resistance predicts cardiovascular disease (CVD) in non-diabetic men and women and to explore the influence of physical activity. in this prospective study 2563 men and women without diabetes were examined with an oral glucose tolerance test, anthropometric measurements and blood pressure assessment. Questionnaires about lifestyle and physical activity were completed. Insulin resistance was estimated by fasting concentrations of plasma insulin and by HOMA index for insulin resistance. Participants were followed up for cardiovascular morbidity and mortality during an 8-year period, using information from the National Swedish Inpatient and Mortality registers. at follow-up, HOMAir predicted CVD morbidity in males (50 events) and females (28 events) combined (HRage/sex-adj 1.4, 95% CI 1.1-1.7); however, when stratified by gender HOMAir was predictive solely in men (HRage-adj 1.8, 95% CI 1.3-2.4), whereas no association was found in women (HRage-adj 1.1, 95% CI 0.8-1.5). When stratifying the data for high and low physical activity, the predictive value of insulin resistance became stronger in sedentary men (HRage-adj 2.3, 95% CI 1.5-3.4) but was abolished in men performing moderate to vigorous physical activity (HRage-adj 1.0, 95% CI 0.6-1.6). The results remained when step-wise adjusted also for BMI, ApoB/ApoA1 and hypertension, as well as for smoking, alcohol consumption and education. Outcome for fasting plasma insulin was similar to HOMAir. insulin resistance predicts CVD in the general population; however, men may be more vulnerable to increased insulin resistance than women, and physically inactive men seem to be at high risk. © The European Society of Cardiology 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

  17. Insulin deficiency exacerbates cerebral amyloidosis and behavioral deficits in an Alzheimer transgenic mouse model

    Directory of Open Access Journals (Sweden)

    Teng Wei-Ping

    2010-11-01

    Full Text Available Abstract Background Although increasing evidence has indicated that brain insulin dysfunction is a risk factor for Alzheimer disease (AD, the underlying mechanisms by which insulin deficiency may impact the development of AD are still obscure. Using a streptozotocin (STZ-induced insulin deficient diabetic AD transgenic mouse model, we evaluated the effect of insulin deficiency on AD-like behavior and neuropathology. Results Our data showed that administration of STZ increased the level of blood glucose and reduced the level of serum insulin, and further decreased the phosphorylation levels of insulin receptors, and increased the activities of glycogen synthase kinase-3α/β and c-Jun N-terminal kinase in the APP/PS1 mouse brain. We further showed that STZ treatment promoted the processing of amyloid-β (Aβ precursor protein resulting in increased Aβ generation, neuritic plaque formation, and spatial memory deficits in transgenic mice. Conclusions Our present data indicate that there is a close link between insulin deficient diabetes and cerebral amyloidosis in the pathogenesis of AD.

  18. Therapeutic actions of an insulin receptor activator and a novel peroxisome proliferator-activated receptor gamma agonist in the spontaneously hypertensive obese rat model of metabolic syndrome X.

    Science.gov (United States)

    Velliquette, Rodney A; Friedman, Jacob E; Shao, J; Zhang, Bei B; Ernsberger, Paul

    2005-07-01

    Insulin resistance clusters with hyperlipidemia, impaired glucose tolerance, and hypertension as metabolic syndrome X. We tested a low molecular weight insulin receptor activator, demethylasterriquinone B-1 (DMAQ-B1), and a novel indole peroxisome proliferator-activated receptor gamma agonist, 2-(2-(4-phenoxy-2-propylphenoxy)ethyl)indole-5-acetic acid (PPEIA), in spontaneously hypertensive obese rats (SHROB), a genetic model of syndrome X. Agents were given orally for 19 days. SHROB showed fasting normoglycemia but impaired glucose tolerance after an oral load, as shown by increased glucose area under the curve (AUC) [20,700 mg x min/ml versus 8100 in lean spontaneously hypertensive rats (SHR)]. Insulin resistance was indicated by 20-fold excess fasting insulin and increased insulin AUC (6300 ng x min/ml versus 990 in SHR). DMAQ-B1 did not affect glucose tolerance (glucose AUC = 21,300) but reduced fasting insulin 2-fold and insulin AUC (insulin AUC = 4300). PPEIA normalized glucose tolerance (glucose AUC = 9100) and reduced insulin AUC (to 3180) without affecting fasting insulin. PPEIA also increased food intake, fat mass, and body weight gain (81 +/- 12 versus 45 +/- 8 g in untreated controls), whereas DMAQ-B1 had no effect on body weight but reduced subscapular fat mass. PPEIA but not DMAQ-B1 reduced blood pressure. In skeletal muscle, insulin-stimulated phosphorylation of the insulin receptor and insulin receptor substrate protein 1-associated phosphatidylinositol 3-kinase activity were decreased by 40 to 55% in SHROB relative to lean SHR. PPEIA, but not DMAQ-B1, enhanced both insulin actions. SHROB also showed severe hypertriglyceridemia (355 +/- 42 mg/dl versus 65 +/- 3 in SHR) attenuated by both agents (DMAQ-B1, 228 +/- 18; PPEIA, 79 +/- 3). Both these novel antidiabetic agents attenuate insulin resistance and hypertriglyceridemia associated with metabolic syndrome but via distinct mechanisms.

  19. Insulin receptors mediate growth effects in cultured fetal neurons. II. Activation of a protein kinase that phosphorylates ribosomal protein S6

    International Nuclear Information System (INIS)

    Heidenreich, K.A.; Toledo, S.P.

    1989-01-01

    As an initial attempt to identify early steps in insulin action that may be involved in the growth responses of neurons to insulin, we investigated whether insulin receptor activation increases the phosphorylation of ribosomal protein S6 in cultured fetal neurons and whether activation of a protein kinase is involved in this process. When neurons were incubated for 2 h with 32Pi, the addition of insulin (100 ng/ml) for the final 30 min increased the incorporation of 32Pi into a 32K microsomal protein. The incorporation of 32Pi into the majority of other neuronal proteins was unaltered by the 30-min exposure to insulin. Cytosolic extracts from insulin-treated neurons incubated in the presence of exogenous rat liver 40S ribosomes and [gamma-32P]ATP displayed a 3- to 8-fold increase in the phosphorylation of ribosomal protein S6 compared to extracts from untreated cells. Inclusion of cycloheximide during exposure of the neurons to insulin did not inhibit the increased cytosolic kinase activity. Activation of S6 kinase activity by insulin was dose dependent (seen at insulin concentration as low as 0.1 ng/ml) and reached a maximum after 20 min of incubation. Addition of phosphatidylserine, diolein, and Ca2+ to the in vitro kinase reaction had no effect on the phosphorylation of ribosomal protein S6. Likewise, treatment of neurons with (Bu)2cAMP did not alter the phosphorylation of ribosomal protein S6 by neuronal cytosolic extracts. We conclude that insulin activates a cytosolic protein kinase that phosphorylates ribosomal S6 in neurons and is distinct from protein kinase-C and cAMP-dependent protein kinase. Stimulation of this kinase may play a role in insulin signal transduction in neurons

  20. Activity restriction, impaired capillary function, and the development of insulin resistance in lean primates.

    Science.gov (United States)

    Chadderdon, Scott M; Belcik, J Todd; Smith, Elise; Pranger, Lindsay; Kievit, Paul; Grove, Kevin L; Lindner, Jonathan R

    2012-09-01

    Insulin produces capillary recruitment in skeletal muscle through a nitric oxide (NO)-dependent mechanism. Capillary recruitment is blunted in obese and diabetic subjects and contributes to impaired glucose uptake. This study's objective was to define whether inactivity, in the absence of obesity, leads to impaired capillary recruitment and contributes to insulin resistance (IR). A comprehensive metabolic and vascular assessment was performed on 19 adult male rhesus macaques (Macaca mulatta) after sedation with ketamine and during maintenance anesthesia with isoflurane. Thirteen normal-activity (NA) and six activity-restricted (AR) primates underwent contrast-enhanced ultrasound to determine skeletal muscle capillary blood volume (CBV) during an intravenous glucose tolerance test (IVGTT) and during contractile exercise. NO bioactivity was assessed by flow-mediated vasodilation. Although there were no differences in weight, basal glucose, basal insulin, or truncal fat, AR primates were insulin resistant compared with NA primates during an IVGTT (2,225 ± 734 vs. 5,171 ± 3,431 μg·ml⁻¹·min⁻¹, P < 0.05). Peak CBV was lower in AR compared with NA primates during IVGTT (0.06 ± 0.01 vs. 0.12 ± 0.02 ml/g, P < 0.01) and exercise (0.10 ± 0.02 vs. 0.20 ± 0.02 ml/g, P < 0.01), resulting in a lower peak skeletal muscle blood flow in both circumstances. The insulin-mediated changes in CBV correlated inversely with the degree of IR and directly with activity. Flow-mediated dilation was lower in the AR primates (4.6 ± 1.0 vs. 9.8 ± 2.3%, P = 0.01). Thus, activity restriction produces impaired skeletal muscle capillary recruitment during a carbohydrate challenge and contributes to IR in the absence of obesity. Reduced NO bioactivity may be a pathological link between inactivity and impaired capillary function.

  1. Characterization of dFOXO binding sites upstream of the Insulin Receptor P2 promoter across the Drosophila phylogeny.

    Directory of Open Access Journals (Sweden)

    Dorcas J Orengo

    Full Text Available The insulin/TOR signal transduction pathway plays a critical role in determining such important traits as body and organ size, metabolic homeostasis and life span. Although this pathway is highly conserved across the animal kingdom, the affected traits can exhibit important differences even between closely related species. Evolutionary studies of regulatory regions require the reliable identification of transcription factor binding sites. Here we have focused on the Insulin Receptor (InR expression from its P2 promoter in the Drosophila genus, which in D. melanogaster is up-regulated by hypophosphorylated Drosophila FOXO (dFOXO. We have finely characterized this transcription factor binding sites in vitro along the 1.3 kb region upstream of the InR P2 promoter in five Drosophila species. Moreover, we have tested the effect of mutations in the characterized dFOXO sites of D. melanogaster in transgenic flies. The number of experimentally established binding sites varies across the 1.3 kb region of any particular species, and their distribution also differs among species. In D. melanogaster, InR expression from P2 is differentially affected by dFOXO binding sites at the proximal and distal halves of the species 1.3 kb fragment. The observed uneven distribution of binding sites across this fragment might underlie their differential contribution to regulate InR transcription.

  2. Complement activation, endothelial dysfunction, insulin resistance and chronic heart failure

    DEFF Research Database (Denmark)

    Bjerre, M.; Kistorp, C.; Hansen, T.K.

    2010-01-01

    CRP), endothelial activation (soluble E-selectin, sEsel)), endothelial damage/dysfunction (von Willebrand factor, vWf) and insulin resistance (IR) and prognosis in CHF remains unknown. Design. We investigated the association(s) between plasma sMAC, hsCRP, sEsel, vWf and IR (assessed by homeostatic model assessment...

  3. Fatty acid represses insulin receptor gene expression by impairing HMGA1 through protein kinase Cε

    International Nuclear Information System (INIS)

    Dey, Debleena; Bhattacharya, Anirban; Roy, SibSankar; Bhattacharya, Samir

    2007-01-01

    It is known that free fatty acid (FFA) contributes to the development of insulin resistance and type2 diabetes. However, the underlying mechanism in FFA-induced insulin resistance is still unclear. In the present investigation we have demonstrated that palmitate significantly (p < 0.001) inhibited insulin-stimulated phosphorylation of PDK1, the key insulin signaling molecule. Consequently, PDK1 phosphorylation of plasma membrane bound PKCε was also inhibited. Surprisingly, phosphorylation of cytosolic PKCε was greatly stimulated by palmitate; this was then translocated to the nuclear region and associated with the inhibition of insulin receptor (IR) gene transcription. A PKCε translocation inhibitor peptide, εV1, suppressed this inhibitory effect of palmitate, suggesting requirement of phospho-PKCε migration to implement palmitate effect. Experimental evidences indicate that phospho-PKCε adversely affected HMGA1. Since HMGA1 regulates IR promoter activity, expression of IR gene was impaired causing reduction of IR on cell surface and that compromises with insulin sensitivity

  4. Effects of heparin on insulin binding and biological activity

    International Nuclear Information System (INIS)

    Kriauciunas, K.M.; Grigorescu, F.; Kahn, C.R.

    1987-01-01

    The effect of heparin, a polyanionic glycosaminoglycan known to alter the function of many proteins, on insulin binding and bioactivity was studied. Cultured human lymphocytes (IM-9) were incubated with varying concentrations of heparin, then extensively washed, and 125 I-labeled insulin binding was measured. Heparin at concentrations used clinically for anticoagulation (1-50 U/ml) inhibited binding in a dose-dependent manner; 50% inhibition of binding occurred with 5-10 U/ml. Scatchard analysis indicated that the decrease in binding was due to a decrease in both the affinity and the apparent number of available insulin receptors. The effect occurred within 10 min at 22 degrees C and persisted even after the cells were extensively washed. Inhibition of insulin binding also occurred when cells were preincubated with heparinized plasma or heparinized serum but not when cells were incubated with normal serum or plasma from blood anticoagulated with EDTA. By contrast, other polyanions and polycations, e.g., poly-L-glutamic acid, poly-L-lysine, succinylated poly-L-lysine, and histone, did not inhibit binding. Heparin also inhibited insulin binding in Epstein-Barr (EB) virus-transformed lymphocytes but had no effect on insulin binding to isolated adipocytes, human erythrocytes, or intact hepatoma cells. When isolated adipocytes were incubated with heparin, there was a dose-dependent inhibition of insulin-stimulated glucose oxidation and, to a lesser extent, of basal glucose oxidation. Although heparin has no effect on insulin binding to intact hepatoma cells, heparin inhibited both insulin binding and insulin-stimulated autophosphorylation in receptors solubilized from these cells

  5. Insulin and the Brain

    Directory of Open Access Journals (Sweden)

    Grosu Cristina

    2017-12-01

    Full Text Available The brain represents an important site for the action of insulin. Besides the traditionally known importance in glucoregulation, insulin has significant neurotrophic properties and influences the brain activity: insulin influences eating behavior, regulates the storage of energy and several aspects concerning memory and knowledge. Insulin resistance and hyperinsulinism could be associated with brain aging, vascular and metabolic pathologies. Elucidating the pathways and metabolism of brain insulin could have a major impact on future targeted therapies.

  6. Insulin-like peptide 5 is a microbially regulated peptide that promotes hepatic glucose production

    DEFF Research Database (Denmark)

    Lee, Ying Shiuan; De Vadder, Filipe; Tremaroli, Valentina

    2016-01-01

    expression in the brain was higher in CONV-R versus GF mice. We also observed that colonic Insl5 expression was suppressed by increasing the energy supply in GF mice by colonization or high-fat feeding. We did not observe any differences in food intake, gut transit or oral glucose tolerance between Insl5......-/- and wild-type mice. However, we showed impaired intraperitoneal glucose tolerance in Insl5-/- mice. We also observed improved insulin tolerance and reduced hepatic glucose production in Insl5-/- mice. CONCLUSIONS: We have shown that colonic Insl5 expression is regulated by the gut microbiota and energy...... availability. We propose that INSL5 is a hormone that could play a role in promoting hepatic glucose production during periods of energy deprivation....

  7. Palmitate and insulin synergistically induce IL-6 expression in human monocytes

    Directory of Open Access Journals (Sweden)

    Lumpkin Charles K

    2010-11-01

    Full Text Available Abstract Background Insulin resistance is associated with a proinflammatory state that promotes the development of complications such as type 2 diabetes mellitus (T2DM and atherosclerosis. The metabolic stimuli that initiate and propagate proinflammatory cytokine production and the cellular origin of proinflammatory cytokines in insulin resistance have not been fully elucidated. Circulating proinflammatory monocytes show signs of enhanced inflammation in obese, insulin resistant subjects and are thus a potential source of proinflammatory cytokine production. The specific, circulating metabolic factors that might stimulate monocyte inflammation in insulin resistant subjects are poorly characterized. We have examined whether saturated nonesterified fatty acids (NEFA and insulin, which increase in concentration with developing insulin resistance, can trigger the production of interleukin (IL-6 and tumor necrosis factor (TNF-α in human monocytes. Methods Messenger RNA and protein levels of the proinflammatory cytokines IL-6 and TNF-α were measured by quantitative real-time PCR (qRT-PCR and Luminex bioassays. Student's t-test was used with a significance level of p Results Esterification of palmitate with coenzyme A (CoA was necessary, while β-oxidation and ceramide biosynthesis were not required, for the induction of IL-6 and TNF-α in THP-1 monocytes. Monocytes incubated with insulin and palmitate together produced more IL-6 mRNA and protein, and more TNF-α protein, compared to monocytes incubated with palmitate alone. Incubation of monocytes with insulin alone did not affect the production of IL-6 or TNF-α. Both PI3K-Akt and MEK/ERK signalling pathways are important for cytokine induction by palmitate. MEK/ERK signalling is necessary for synergistic induction of IL-6 by palmitate and insulin. Conclusions High levels of saturated NEFA, such as palmitate, when combined with hyperinsulinemia, may activate human monocytes to produce

  8. A novel PTP1B inhibitor extracted from Ganoderma lucidum ameliorates insulin resistance by regulating IRS1-GLUT4 cascades in the insulin signaling pathway.

    Science.gov (United States)

    Yang, Zhou; Wu, Fan; He, Yanming; Zhang, Qiang; Zhang, Yuan; Zhou, Guangrong; Yang, Hongjie; Zhou, Ping

    2018-01-24

    Insulin resistance caused by the overexpression of protein tyrosine phosphatase 1 B (PTP1B) as well as the dephosphorylation of its target is one of the main causes of type 2 diabetes (T2D). A newly discovered proteoglycan, Fudan-Yueyang Ganoderma lucidum (FYGL) extracted from Ganoderma lucidum, was first reported to be capable of competitively inhibiting PTP1B activity in vitro in our previous work. In the present study, we sought to reveal the mechanism of PTP1B inhibition by FYGL at the animal and cellular levels. We found that FYGL can decrease blood glucose, reduce body weight and ameliorate insulin resistance in ob/ob mice. Decrease of PTP1B expression and increase of the phosphorylation of PTP1B targets in the insulin signaling pathway of skeletal muscles were observed. In order to clearly reveal the underlying mechanism of the hypoglycemic effect caused by FYGL, we further investigated the effects of FYGL on the PTP1B-involved insulin signaling pathway in rat myoblast L6 cells. We demonstrated that FYGL had excellent cell permeability by using a confocal laser scanning microscope and a flow cytometer. We found that FYGL had a positive effect on insulin-stimulated glucose uptake by using the 2-deoxyglucose (2-DG) method. FYGL could inhibit PTP1B expression at the mRNA level, phosphorylating insulin receptor substrate-1 (IRS1), as well as activating phosphatidylinositol-3 kinase (PI3K) and protein kinase B (Akt). Finally, FYGL increased the phosphorylation of adenosine monophosphate-activated protein kinase (AMPK) and consequently up-regulated the expression of glucose transporter type 4 (GLUT4), promoting GLUT4 transportation to the plasma membrane in PTP1B-transfected L6 cells. Our study provides theoretical evidence for FYGL to be potentially used in T2D management.

  9. Growth hormone, interferon-gamma, and leukemia inhibitory factor promoted tyrosyl phosphorylation of insulin receptor substrate-1

    DEFF Research Database (Denmark)

    Argetsinger, L S; Hsu, G W; Myers, M G

    1995-01-01

    ), the principle substrate of the insulin receptor. Tyrosyl phosphorylation of IRS-1 is a critical step in insulin signaling and provides binding sites for proteins with the appropriate Src homology 2 domains, including the 85-kDa regulatory subunit of phosphatidylinositol (PI) 3'-kinase. In 3T3-F442A fibroblasts......., Campbell, G. S., Allevato, G., Billestrup, N., Norstedt, G., and Carter-Su, C. (1994) J. Biol. Chem. 269, 21709-21717). When other cytokines that activate JAK2 were tested for the ability to stimulate the tyrosyl phosphorylation of IRS-1, stimulation was detected with interferon-gamma and leukemia...... to JAK2. GH is also shown to stimulate binding of IRS-1 to the 85-kDa regulatory subunit of PI 3'-kinase. The ability of GH to stimulate tyrosyl phosphorylation of IRS-1 and its association with PI 3'-kinase provides a biochemical basis for responses shared by insulin and GH including the well...

  10. Studies on interaction of insulin and insulin receptor in rat liver cell membranes

    Energy Technology Data Exchange (ETDEWEB)

    Sakai, Y; Hara, H; Kawate, R; Kawasaki, T [Hiroshima Univ. (Japan). School of Medicine

    1975-07-01

    Rat liver was homogenized with a Polytron PT 20 ST and fractionated by differential centrifugation. Prepared plasma membranes (100 ..mu..g protein) were incubated with enzymatically iodinated /sup 125/I-insulin (0.3 ng, specific activity 107 ..mu..Ci/..mu..g) in 25 mM Tris-HCl buffer, pH 7.5, containing 0.9% NaCl and 1% bovine serum albumin. The 12,000xg- and 17,000xg-sediments obtained after subfractionation of liver homogenates showed almost equally high specific binding activity with /sup 125/I-insulin and less activity was detected in the 600 g-, 5,000 g- and 40,000 g- sediments and the 40,000 g- supernatant. Specific binding of insulin with the membrane fraction was time-, temperature- and ionic strength-dependent. The highest binding was obtained under conditions in which the membrane fraction was incubated with insulin for 24 hours at 4/sup 0/C in the buffer containing 1 M NaCl. Under these conditions, specific binding of /sup 125/I-insulin was 26.8% of the total radioactivity. The effect of native insulin on the binding of /sup 125/I-insulin with the membrane fraction was studied in the range of 0--6.4 x 10/sup 5/ ..mu..U/ml of unlabeled insulin and a distinct competitive displacement of /sup 125/I-insulin with native insulin was observed between 10 and 10/sup 4/ ..mu..U/ml. Kinetic studies by Scatchard plot analysis of the above results revealed heterogeneity in insulin receptors or receptor sites, one with a high affinity of 10/sup 9/ M/sup -1/ order and the other with a low affinity of 10/sup 8/ M/sup -1/ order. Both affinities were also affected by temperature and ionic strength.

  11. Nonautonomous Regulation of Neuronal Migration by Insulin Signaling, DAF-16/FOXO, and PAK-1

    Directory of Open Access Journals (Sweden)

    Lisa M. Kennedy

    2013-09-01

    Full Text Available Neuronal migration is essential for nervous system development in all organisms and is regulated in the nematode, C. elegans, by signaling pathways that are conserved in humans. Here, we demonstrate that the insulin/IGF-1-PI3K signaling pathway modulates the activity of the DAF-16/FOXO transcription factor to regulate the anterior migrations of the hermaphrodite-specific neurons (HSNs during embryogenesis of C. elegans. When signaling is reduced, DAF-16 is activated and promotes migration; conversely, when signaling is enhanced, DAF-16 is inactivated, and migration is inhibited. We show that DAF-16 acts nonautonomously in the hypodermis to promote HSN migration. Furthermore, we identify PAK-1, a p21-activated kinase, as a downstream mediator of insulin/IGF-1-DAF-16 signaling in the nonautonomous control of HSN migration. Because a FOXO-Pak1 pathway was recently shown to regulate mammalian neuronal polarity, our findings indicate that the roles of FOXO and Pak1 in neuronal migration are most likely conserved from C. elegans to higher organisms.

  12. Alteration in insulin action

    DEFF Research Database (Denmark)

    Tanti, J F; Gual, P; Grémeaux, T

    2004-01-01

    Insulin resistance, when combined with impaired insulin secretion, contributes to the development of type 2 diabetes. Insulin resistance is characterised by a decrease in insulin effect on glucose transport in muscle and adipose tIssue. Tyrosine phosphorylation of insulin receptor substrate 1 (IRS......-1) and its binding to phosphatidylinositol 3-kinase (PI 3-kinase) are critical events in the insulin signalling cascade leading to insulin-stimulated glucose transport. Modification of IRS-1 by serine phosphorylation could be one of the mechanisms leading to a decrease in IRS-1 tyrosine...... to phosphorylate these serine residues have been identified. These exciting results suggest that serine phosphorylation of IRS-1 is a possible hallmark of insulin resistance in biologically insulin responsive cells or tIssues. Identifying the pathways by which "diabetogenic" factors activate IRS-1 kinases...

  13. Serum Is Not Necessary for Prior Pharmacological Activation of AMPK to Increase Insulin Sensitivity of Mouse Skeletal Muscle

    Directory of Open Access Journals (Sweden)

    Nicolas O. Jørgensen

    2018-04-01

    Full Text Available Exercise, contraction, and pharmacological activation of AMP-activated protein kinase (AMPK by 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR have all been shown to increase muscle insulin sensitivity for glucose uptake. Intriguingly, improvements in insulin sensitivity following contraction of isolated rat and mouse skeletal muscle and prior AICAR stimulation of isolated rat skeletal muscle seem to depend on an unknown factor present in serum. One study recently questioned this requirement of a serum factor by showing serum-independency with muscle from old rats. Whether a serum factor is necessary for prior AICAR stimulation to increase insulin sensitivity of mouse skeletal muscle is not known. Therefore, we investigated the necessity of serum for this effect of AICAR in mouse skeletal muscle. We found that the ability of prior AICAR stimulation to improve insulin sensitivity of mouse skeletal muscle did not depend on the presence of serum during AICAR stimulation. Although prior AICAR stimulation did not enhance proximal insulin signaling, insulin-stimulated phosphorylation of Tre-2/BUB2/CDC16- domain family member 4 (TBC1D4 Ser711 was greater in prior AICAR-stimulated muscle compared to all other groups. These results imply that the presence of a serum factor is not necessary for prior AMPK activation by AICAR to enhance insulin sensitivity of mouse skeletal muscle.

  14. Biological activity of alligator, avian, and mammalian insulin in juvenile alligators: plasma glucose and amino acids.

    Science.gov (United States)

    Lance, V A; Elsey, R M; Coulson, R A

    1993-02-01

    The biological activity of alligator, turkey, and bovine insulin on plasma glucose and plasma amino acids was tested in fasted juvenile alligators. Preliminary experiments showed that the stress associated with taking the initial blood sample resulted in a hyperglycemic response lasting more than 24 hr. Despite repeated bleedings no additional hyperglycemic events occurred, and blood glucose declined slowly over the next 7 days. Under these conditions the smallest dose of insulin eliciting a hypoglycemic response was 40 micrograms/kg body wt. A dose of 400 micrograms/kg body wt of either alligator or bovine insulin caused a pronounced hypoglycemia by 12 hr postinjection. Maximum decline in plasma glucose occurred at 24 to 36 hr with a slow return to control levels by 120 hr. There were no significant differences in the hypoglycemic responses to any of the three insulins tested. The decline in plasma amino acids was much more rapid than the decline in plasma glucose in response to insulin. Even at the 40 micrograms/kg body wt dose a significant difference from saline-injected control was seen at 2 hr postinjection. Maximum decline in plasma amino acids occurred at 8 to 12 hr with a return to baseline by 36 hr. These results show that the relatively conservative changes in the sequence of alligator insulin (three amino acid substitutions in the B-chain compared with that of chicken) have little effect on biological activity and that alligator insulin receptors do not appear to discriminate among the three insulins.

  15. Insulin and insulin-like growth factor receptors and responses

    International Nuclear Information System (INIS)

    Roth, R.A.; Steele-Perkins, G.; Hari, J.; Stover, C.; Pierce, S.; Turner, J.; Edman, J.C.; Rutter, W.J.

    1988-01-01

    Insulin is a member of a family of structurally related hormones with diverse physiological functions. In humans, the best-characterized members of this family include insulin, insulin-like growth factor (IGF)-I, and IGF-II. Each of these three polypeptide hormones has its own distinct receptor. The structures of each of these receptors have now been deduced from analyses of isolated cDNA clones. To study further the responses mediated through these three different receptors, the authors have been studying cells expressing the proteins encoded by these three cDNAs. The isolated cDNAs have been transfected into Chinese hamster ovary (CHO) cells, and the resulting transfected cell lines have been characterized as to the ligand-binding activities and signal-transducing activities of the expressed proteins

  16. OPA1 deficiency promotes secretion of FGF21 from muscle that prevents obesity and insulin resistance.

    Science.gov (United States)

    Pereira, Renata Oliveira; Tadinada, Satya M; Zasadny, Frederick M; Oliveira, Karen Jesus; Pires, Karla Maria Pereira; Olvera, Angela; Jeffers, Jennifer; Souvenir, Rhonda; Mcglauflin, Rose; Seei, Alec; Funari, Trevor; Sesaki, Hiromi; Potthoff, Matthew J; Adams, Christopher M; Anderson, Ethan J; Abel, E Dale

    2017-07-14

    Mitochondrial dynamics is a conserved process by which mitochondria undergo repeated cycles of fusion and fission, leading to exchange of mitochondrial genetic content, ions, metabolites, and proteins. Here, we examine the role of the mitochondrial fusion protein optic atrophy 1 (OPA1) in differentiated skeletal muscle by reducing OPA1 gene expression in an inducible manner. OPA1 deficiency in young mice results in non-lethal progressive mitochondrial dysfunction and loss of muscle mass. Mutant mice are resistant to age- and diet-induced weight gain and insulin resistance, by mechanisms that involve activation of ER stress and secretion of fibroblast growth factor 21 (FGF21) from skeletal muscle, resulting in increased metabolic rates and improved whole-body insulin sensitivity. OPA1-elicited mitochondrial dysfunction activates an integrated stress response that locally induces muscle atrophy, but via secretion of FGF21 acts distally to modulate whole-body metabolism. © 2017 The Authors.

  17. Relationships between thermic effect of food, insulin resistance and autonomic nervous activity.

    Science.gov (United States)

    Watanabe, Tomonori; Nomura, Masahiro; Nakayasu, Kimiko; Kawano, Tomohito; Ito, Susumu; Nakaya, Yutaka

    2006-02-01

    The thermic effect of food (TEF) is higher in lean than in obese human subjects. Relationships between TEF and insulin resistance during meals, from the point of view of autonomic nervous activity, were evaluated. Autonomic nervous activity was evaluated in 20 young adults using the spectral analysis of heart rate variability from one hour before to two hours after a meal. Heart rate data were analyzed based on low frequency components (LF power, 0.04-0.15 Hz), high frequency components (HF power, 0.15-0.40 Hz), and LF/HF ratios. Energy expenditure and the TEF were measured 30 min after a meal. Homeostasis model of insulin resistance index (HOMA-IR) was also measured. The LF/HF ratio was significantly increased 30 min after a meal (pinsulin sensitivity induces a poor response of sympathetic nervous activity in the postprandial phase and a reduction in postprandial energy expenditure.

  18. Aerobic exercise regulates blood lipid and insulin resistance via the toll‑like receptor 4‑mediated extracellular signal‑regulated kinases/AMP‑activated protein kinases signaling pathway.

    Science.gov (United States)

    Wang, Mei; Li, Sen; Wang, Fubaihui; Zou, Jinhui; Zhang, Yanfeng

    2018-06-01

    ІІ diabetes mellitus. The activity of ERK and AMPK, and the function of islet β‑cells were observed to be improved in experimental mice treated with aerobic exercise. Furthermore, blood lipid metabolism and insulin resistance were improved by treatment with aerobic exercise. Body weight and glucose concentration of serology was markedly improved in mouse models of type‑ІІ diabetes mellitus. Furthermore, TLR‑4 inhibition markedly promoted ERK and AMPK expression levels and activity. Thus, these results indicate that aerobic exercise may improve blood lipid metabolism, insulin resistance and glucose plasma concentration in mouse models of type‑ІІ diabetes mellitus. Thus indicating aerobic exercise is beneficial for improvement of blood lipid and insulin resistance via the TLR‑4‑mediated ERK/AMPK signaling pathway in the progression of type‑ІІ diabetes mellitus.

  19. Vitamin D receptor gene polymorphisms, dietary promotion of insulin resistance, and colon and rectal cancer.

    Science.gov (United States)

    Murtaugh, Maureen A; Sweeney, Carol; Ma, Khe-Ni; Potter, John D; Caan, Bette J; Wolff, Roger K; Slattery, Martha L

    2006-01-01

    Modifiable risk factors in colorectal cancer etiology and their interactions with genetic susceptibility are of particular interest. Functional vitamin D receptor (VDR) gene polymorphisms may influence carcinogenesis through modification of cell growth, protection from oxidative stress, cell-cell matrix effects, or insulin and insulin-like growth factor pathways. We investigated interactions between foods (dairy products, red and processed meat, and whole and refined grains) and dietary patterns (sucrose-to-fiber ratio and glycemic index) associated with insulin resistance with the FokI polymorphism of the VDR gene and colon and rectal cancer risk. Data (diet, anthropometrics, and lifestyle) and DNA came from case-control studies of colon (1,698 cases and 1,861 controls) and rectal cancer (752 cases and 960 controls) in northern California, Utah, and the Twin Cities metropolitan area, Minnesota (colon cancer study only). Unconditional logistic regression models were adjusted for smoking, race, sex, age, body mass index, physical activity, energy intake, dietary fiber, and calcium. The lowest colon cancer risk was observed with the Ff/ff FokI genotypes and a low sucrose-to-fiber ratio. Rectal cancer risk decreased with greater consumption of dairy products and increased with red or processed meat consumption and the FF genotype. Modifiable dietary risk factors may be differentially important among individuals by VDR genotype and may act through the insulin pathway to affect colon cancer risk and through fat, calcium, or other means to influence rectal cancer risk.

  20. Potential Roles of Stevia rebaudiana Bertoni in Abrogating Insulin Resistance and Diabetes: A Review

    Directory of Open Access Journals (Sweden)

    Nabilatul Hani Mohd-Radzman

    2013-01-01

    Full Text Available Insulin resistance is a key factor in metabolic disorders like hyperglycemia and hyperinsulinemia, which are promoted by obesity and may later lead to Type II diabetes mellitus. In recent years, researchers have identified links between insulin resistance and many noncommunicable illnesses other than diabetes. Hence, studying insulin resistance is of particular importance in unravelling the pathways employed by such diseases. In this review, mechanisms involving free fatty acids, adipocytokines such as TNFα and PPARγ and serine kinases like JNK and IKKβ, asserted to be responsible in the development of insulin resistance, will be discussed. Suggested mechanisms for actions in normal and disrupted states were also visualised in several manually constructed diagrams to capture an overall view of the insulin-signalling pathway and its related components. The underlying constituents of medicinal significance found in the Stevia rebaudiana Bertoni plant (among other plants that potentiate antihyperglycemic activities were explored in further depth. Understanding these factors and their mechanisms may be essential for comprehending the progression of insulin resistance towards the development of diabetes mellitus.

  1. Insulin receptor binding and tyrosine kinase activity in skeletal muscle from normal pregnant women and women with gestational diabetes

    DEFF Research Database (Denmark)

    Damm, P.; Handberg, A.; Kühl, C.

    1993-01-01

    OBJECTIVE: To ascertain whether the decreased glucose tolerance and insulin resistance found in normal and gestational diabetic pregnancy might be associated with changes in insulin receptor function. METHODS: Eight nonpregnant healthy women (nonpregnant controls), eight healthy pregnant women...... (pregnant controls), and eight women with gestational diabetes were investigated. All were non-obese. Muscle biopsies were obtained from the vastus lateralis muscle, and insulin binding and tyrosine kinase activities in partially purified skeletal muscle insulin receptors were studied. The pregnant controls...... with gestational diabetes compared to nonpregnant controls (P pregnant women did not differ from the other two groups. Postpartum, no differences in insulin binding were found between the groups. Basal and maximal tyrosine kinase activities toward the exogenous substrate poly(Glu4Tyr1) were...

  2. Insulin Resistance and Cancer Risk: An Overview of the Pathogenetic Mechanisms

    Directory of Open Access Journals (Sweden)

    Biagio Arcidiacono

    2012-01-01

    Full Text Available Insulin resistance is common in individuals with obesity or type 2 diabetes (T2D, in which circulating insulin levels are frequently increased. Recent epidemiological and clinical evidence points to a link between insulin resistance and cancer. The mechanisms for this association are unknown, but hyperinsulinaemia (a hallmark of insulin resistance and the increase in bioavailable insulin-like growth factor I (IGF-I appear to have a role in tumor initiation and progression in insulin-resistant patients. Insulin and IGF-I inhibit the hepatic synthesis of sex-hormone binding globulin (SHBG, whereas both hormones stimulate the ovarian synthesis of sex steroids, whose effects, in breast epithelium and endometrium, can promote cellular proliferation and inhibit apoptosis. Furthermore, an increased risk of cancer among insulin-resistant patients can be due to overproduction of reactive oxygen species (ROS that can damage DNA contributing to mutagenesis and carcinogenesis. On the other hand, it is possible that the abundance of inflammatory cells in adipose tissue of obese and diabetic patients may promote systemic inflammation which can result in a protumorigenic environment. Here, we summarize recent progress on insulin resistance and cancer, focusing on various implicated mechanisms that have been described recently, and discuss how these mechanisms may contribute to cancer initiation and progression.

  3. Systemic insulin sensitivity is regulated by GPS2 inhibition of AKT ubiquitination and activation in adipose tissue

    Directory of Open Access Journals (Sweden)

    Carly T. Cederquist

    2017-01-01

    Conclusions: Our findings characterize a novel layer of regulation of the insulin signaling pathway based on non-proteolytic ubiquitination of AKT and define GPS2 as a previously unrecognized component of the insulin signaling cascade. In accordance with this role, we have shown that GPS2 presence in adipocytes modulates systemic metabolism by restricting the activation of insulin signaling during the fasted state, whereas in absence of GPS2, the adipose tissue is more efficient at lipid storage, and obesity becomes uncoupled from inflammation and insulin resistance.

  4. Interleukin-18 activates skeletal muscle AMPK and reduces weight gain and insulin resistance in mice

    DEFF Research Database (Denmark)

    Madsen, Birgitte Lindegaard; Matthews, Vance B; Brandt, Claus

    2013-01-01

    Circulating interleukin (IL)-18 is elevated in obesity, but paradoxically causes hypophagia. We hypothesized that IL-18 may attenuate high fat diet induced insulin resistance by activating AMP activated protein kinase (AMPK). We studied mice with a global deletion of the α isoform of the IL-18...... receptor (IL-18R(-/-)), fed a standard chow or high fat diet (HFD). We next performed gain of function experiments in skeletal muscle, in vitro, ex vivo and in vivo. We show that IL-18 is implicated in metabolic homeostasis, inflammation and insulin resistance via mechanisms involving the activation...

  5. Altered insulin distribution and metabolism in type I diabetics assessed by [123I]insulin scanning

    International Nuclear Information System (INIS)

    Hachiya, H.L.; Treves, S.T.; Kahn, C.R.; Sodoyez, J.C.; Sodoyez-Goffaux, F.

    1987-01-01

    Scintigraphic scanning with [ 123 I]insulin provides a direct and quantitative assessment of insulin uptake and disappearance at specific organ sites. Using this technique, the biodistribution and metabolism of insulin were studied in type 1 diabetic patients and normal subjects. The major organ of [ 123 I]insulin uptake in both diabetic and normal subjects was the liver. After iv injection in normal subjects, the uptake of [ 123 I]insulin by the liver was rapid, with peak activity at 7 min. Activity declined rapidly thereafter, consistent with rapid insulin degradation and clearance. Rapid uptake of [ 123 I]insulin also occurred in the kidneys, although the uptake of insulin by the kidneys was about 80% of that by liver. In type 1 diabetic patients, uptake of [ 123 I]insulin in these organ sites was lower than that in normal subjects; peak insulin uptakes in liver and kidneys were 21% and 40% lower than those in normal subjects, respectively. The kinetics of insulin clearance from the liver was comparable in diabetic and normal subjects, whereas clearance from the kidneys was decreased in diabetics. The plasma clearance of [ 123 I]insulin was decreased in diabetic patients, as was insulin degradation, assessed by trichloroacetic acid precipitability. Thirty minutes after injection, 70.9 +/- 3.8% (+/- SEM) of [ 123 I]insulin in the plasma of diabetics was trichloroacetic acid precipitable vs. only 53.9 +/- 4.0% in normal subjects. A positive correlation was present between the organ uptake of [123I]insulin in the liver or kidneys and insulin degradation (r = 0.74; P less than 0.001)

  6. Intranasal Insulin Restores Metabolic Parameters and Insulin Sensitivity in Rats with Metabolic Syndrome.

    Science.gov (United States)

    Derkach, K V; Ivantsov, A O; Chistyakova, O V; Sukhov, I B; Buzanakov, D M; Kulikova, A A; Shpakov, A O

    2017-06-01

    We studied the effect of 10-week treatment with intranasal insulin (0.5 IU/day) on glucose tolerance, glucose utilization, lipid metabolism, functions of pancreatic β cells, and insulin system in the liver of rats with cafeteria diet-induced metabolic syndrome. The therapy reduced body weight and blood levels of insulin, triglycerides, and atherogenic cholesterol that are typically increased in metabolic syndrome, normalized glucose tolerance and its utilization, and increased activity of insulin signaling system in the liver, thus reducing insulin resistance. The therapy did not affect the number of pancreatic islets and β cells. The study demonstrates prospects of using intranasal insulin for correction of metabolic parameters and reduction of insulin resistance in metabolic syndrome.

  7. The phosphatidylinositol 3-kinase inhibitor, wortmannin, inhibits insulin-induced activation of phosphatidylcholine hydrolysis and associated protein kinase C translocation in rat adipocytes.

    Science.gov (United States)

    Standaert, M L; Avignon, A; Yamada, K; Bandyopadhyay, G; Farese, R V

    1996-02-01

    We questioned whether phosphatidylinositol 3-kinase (PI 3-kinase) and protein kinase C (PKC) function as interrelated signalling mechanisms during insulin action in rat adipocytes. Insulin rapidly activated a phospholipase D that hydrolyses phosphatidylcholine (PC), and this activation was accompanied by increases in diacylglycerol and translocative activation of PKC-alpha and PKC-beta in the plasma membrane. Wortmannin, an apparently specific PI 3-kinase inhibitor, inhibited insulin-stimulated, phospholipase D-dependent PC hydrolysis and subsequent translocation of PKC-alpha and PKC-beta to the plasma membrane. Wortmannin did not inhibit PKC directly in vitro, or the PKC-dependent effects of phorbol esters on glucose transport in intact adipocytes. The PKC inhibitor RO 31-8220 did not inhibit PI 3-kinase directly or its activation in situ by insulin, but inhibited both insulin-stimulated and phorbol ester-stimulated glucose transport. Our findings suggest that insulin acts through PI 3-kinase to activate a PC-specific phospholipase D and causes the translocative activation of PKC-alpha and PKC-beta in plasma membranes of rat adipocytes.

  8. Insulin receptor internalization defect in an insulin-resistant mouse melanoma cell line

    International Nuclear Information System (INIS)

    Androlewicz, M.J.; Straus, D.S.; Brandenburg, D.F.

    1989-01-01

    Previous studies from this laboratory demonstrated that the PG19 mouse melanoma cell line does not exhibit a biological response to insulin, whereas melanoma x mouse embryo fibroblast hybrids do respond to insulin. To investigate the molecular basis of the insulin resistance of the PG19 melanoma cells, insulin receptors from the insulin-resistant melanoma cells and insulin-sensitive fibroblast x melanoma hybrid cells were analyzed by the technique of photoaffinity labeling using the photoprobe 125 I-NAPA-DP-insulin. Photolabeled insulin receptors from the two cell types have identical molecular weights as determined by SDS gel electrophoresis under reducing and nonreducing conditions, indicating that the receptors on the two cell lines are structurally similar. Insulin receptor internalization studies revealed that the hybrid cells internalize receptors to a high degree at 37 degree C, whereas the melanoma cells internalize receptors to a very low degree or not at all. The correlation between ability to internalize insulin receptors and sensitivity to insulin action in this system suggests that uptake of the insulin-receptor complex may be required for insulin action in these cells. Insulin receptors from the two cell lines autophosphorylate in a similar insulin-dependent manner both in vitro and in intact cells, indicating that insulin receptors on the melanoma and hybrid cells have functional tyrosine protein kinase activity. Therefore, the block in insulin action in the PG19 melanoma cells appears to reside at a step beyond insulin-stimulated receptor autophosphorylation

  9. Insulin receptor substrate-3, interacting with Bcl-3, enhances p50 NF-{kappa}B activity

    Energy Technology Data Exchange (ETDEWEB)

    Kabuta, Tomohiro [Departments of Animal Sciences and Applied Biological Chemistry, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Tokyo 113-8657 (Japan); Department of Degenerative Neurological Diseases, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Tokyo 187-8502 (Japan); Hakuno, Fumihiko; Cho, Yoshitake; Yamanaka, Daisuke; Chida, Kazuhiro [Departments of Animal Sciences and Applied Biological Chemistry, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Tokyo 113-8657 (Japan); Asano, Tomoichiro [Graduate School of Biomedical Science, Hiroshima University, Hiroshima 734-8551 (Japan); Wada, Keiji [Department of Degenerative Neurological Diseases, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Tokyo 187-8502 (Japan); Takahashi, Shin-Ichiro, E-mail: atkshin@mail.ecc.u-tokyo.ac.jp [Departments of Animal Sciences and Applied Biological Chemistry, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Tokyo 113-8657 (Japan)

    2010-04-09

    The insulin receptor substrate (IRS) proteins are major substrates of both insulin receptor and insulin-like growth factor (IGF)-I receptor tyrosine kinases. Previously, we reported that IRS-3 is localized to both cytosol and nucleus, and possesses transcriptional activity. In the present study, we identified Bcl-3 as a novel binding protein to IRS-3. Bcl-3 is a nuclear protein, which forms a complex with the homodimer of p50 NF-{kappa}B, leading to enhancement of transcription through p50 NF-{kappa}B. We found that Bcl-3 interacts with the pleckstrin homology domain and the phosphotyrosine binding domain of IRS-3, and that IRS-3 interacts with the ankyrin repeat domain of Bcl-3. In addition, IRS-3 augmented the binding activity of p50 to the NF-{kappa}B DNA binding site, as well as the tumor necrosis factor (TNF)-{alpha}-induced transcriptional activity of NF-{kappa}B. Lastly, IRS-3 enhanced NF-{kappa}B-dependent anti-apoptotic gene induction and consequently inhibited TNF-{alpha}-induced cell death. This series of results proposes a novel function for IRS-3 as a transcriptional regulator in TNF-{alpha} signaling, distinct from its function as a substrate of insulin/IGF receptor kinases.

  10. Bioluminescence imaging of β cells and intrahepatic insulin gene activity under normal and pathological conditions.

    Directory of Open Access Journals (Sweden)

    Tokio Katsumata

    Full Text Available In diabetes research, bioluminescence imaging (BLI has been applied in studies of β-cell impairment, development, and islet transplantation. To develop a mouse model that enables noninvasive imaging of β cells, we generated a bacterial artificial chromosome (BAC transgenic mouse in which a mouse 200-kbp genomic fragment comprising the insulin I gene drives luciferase expression (Ins1-luc BAC transgenic mouse. BLI of mice was performed using the IVIS Spectrum system after intraperitoneal injection of luciferin, and the bioluminescence signal from the pancreatic region analyzed. When compared with MIP-Luc-VU mice [FVB/N-Tg(Ins1-lucVUPwrs/J] expressing luciferase under the control of the 9.2-kbp mouse insulin I promoter (MIP, the bioluminescence emission from Ins1-luc BAC transgenic mice was enhanced approximately 4-fold. Streptozotocin-treated Ins1-luc BAC transgenic mice developed severe diabetes concomitant with a sharp decline in the BLI signal intensity in the pancreas. Conversely, mice fed a high-fat diet for 8 weeks showed an increase in the signal, reflecting a decrease or increase in the β-cell mass. Although the bioluminescence intensity of the islets correlated well with the number of isolated islets in vitro, the intensity obtained from a living mouse in vivo did not necessarily reflect an absolute quantification of the β-cell mass under pathological conditions. On the other hand, adenovirus-mediated gene transduction of β-cell-related transcription factors in Ins1-luc BAC transgenic mice generated luminescence from the hepatic region for more than 1 week. These results demonstrate that BLI in Ins1-luc BAC transgenic mice provides a noninvasive method of imaging islet β cells and extrapancreatic activity of the insulin gene in the liver under normal and pathological conditions.

  11. Analysis of IRS-1-mediated phosphatidylinositol 3-kinase activation in the adipose tissue of polycystic ovary syndrome patients complicated with insulin resistance

    Energy Technology Data Exchange (ETDEWEB)

    Yongli, Chu [Yantai Yuhuangding Hospital, Yantai (China). Dept. of Obstetrics and Gynecology; Hongyu, Qiu; Yongyu, Sun; Min, Li; Hongfa, Li

    2004-04-01

    Objective: To investigate the insulin receptor substance-1 (IRS-1)-mediated phosphatidylinositol-3 (PI-3) kinase activity in adipose tissue of polycystic ovary syndrome (PCOS) patients, and to explore molecular mechanisms of insulin resistance of PCOS. Methods: Blood and adipose tissue samples from patients with PCOS with insulin resistance (n=19), PCOS without insulin resistance (n=10) and controls (n=15) were collected. Serum luteinizing hormone (LH), follicle stimulating hormone (FSH), testosterone (T) were measured by chemiluminescence assay. Fasting insulin (FIN) was measured by radioimmunoassay. Fasting plasma glucose (FPG) was measured by oxidase assay. Insulin resistance index (IR) was calculated using homeostasis model assessment (HOMA) to analyze the relationship between these markers and insulin resistance. The tyrosine phosphorylation of IRS-1 was measured by immunoprecipitation and enhanced chemiluminescent immunoblotting technique. PI-3 kinase activity was detected by immunoprecipitation, thin-layer chromatography and gamma scintillation counting. The results were analyzed by statistical methods. Results: 1) The levels of serum LH, LH/FSH, T, FIN and HOMA-IR in PCOS without insulin resistance were significantly higher than those of control group (all P<0.05); the levels of serum LH, LH/FSH, T, FIN and HOMA-IR in PCOS with insulin resistance were significantly higher than those of PCOS without insulin resistance (all P<0.05). 2) The tyrosine phosphorylation analysis of IRS-1 showed that IRS-1 tyrosine phosphorylation was significantly decreased in PCOS with insulin resistance compared to that of PCOS without insulin resistance and control groups (P<0.01). 3) PI-3 kinase activity was significantly decreased (P<0.01) and negatively correlated with HOMA-IR. Conclusion: In consequence of the weaker signal caused by the change of upper stream signal molecule IRS-1 tyrosine phosphorylation, PI-3 kinase activity decreased, it affects the insulin signal

  12. Analysis of IRS-1-mediated phosphatidylinositol 3-kinase activation in the adipose tissue of polycystic ovary syndrome patients complicated with insulin resistance

    International Nuclear Information System (INIS)

    Chu Yongli; Qiu Hongyu; Sun Yongyu; Li Min; Li Hongfa

    2004-01-01

    Objective: To investigate the insulin receptor substance-1 (IRS-1)-mediated phosphatidylinositol-3 (PI-3) kinase activity in adipose tissue of polycystic ovary syndrome (PCOS) patients, and to explore molecular mechanisms of insulin resistance of PCOS. Methods: Blood and adipose tissue samples from patients with PCOS with insulin resistance (n=19), PCOS without insulin resistance (n=10) and controls (n=15) were collected. Serum luteinizing hormone (LH), follicle stimulating hormone (FSH), testosterone (T) were measured by chemiluminescence assay. Fasting insulin (FIN) was measured by radioimmunoassay. Fasting plasma glucose (FPG) was measured by oxidase assay. Insulin resistance index (IR) was calculated using homeostasis model assessment (HOMA) to analyze the relationship between these markers and insulin resistance. The tyrosine phosphorylation of IRS-1 was measured by immunoprecipitation and enhanced chemiluminescent immunoblotting technique. PI-3 kinase activity was detected by immunoprecipitation, thin-layer chromatography and gamma scintillation counting. The results were analyzed by statistical methods. Results: 1) The levels of serum LH, LH/FSH, T, FIN and HOMA-IR in PCOS without insulin resistance were significantly higher than those of control group (all P<0.05); the levels of serum LH, LH/FSH, T, FIN and HOMA-IR in PCOS with insulin resistance were significantly higher than those of PCOS without insulin resistance (all P<0.05). 2) The tyrosine phosphorylation analysis of IRS-1 showed that IRS-1 tyrosine phosphorylation was significantly decreased in PCOS with insulin resistance compared to that of PCOS without insulin resistance and control groups (P<0.01). 3) PI-3 kinase activity was significantly decreased (P<0.01) and negatively correlated with HOMA-IR. Conclusion: In consequence of the weaker signal caused by the change of upper stream signal molecule IRS-1 tyrosine phosphorylation, PI-3 kinase activity decreased, it affects the insulin signal

  13. The adipose renin-angiotensin system modulates sysemic markers of insulin sensitivity activates the intrarenal renin-angiotensin system

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Suyeon [University of Tennessee, Knoxville (UTK); Soltani-Bejnood, Morvarid [University of Tennessee, Knoxville (UTK); Quignard-Boulange, Annie [Centre Biomedical des Cordeliers, Paris, France; Massiera, Florence [Centre de Biochimie, Nice, France; Teboul, Michele [Centre de Biochimie, Nice, France; Ailhaud, Gerard [Centre de Biochimie, Nice, France; Kim, Jung [University of Tennessee, Knoxville (UTK); Moustaid-Moussa, Naima [University of Tennessee, Knoxville (UTK); Voy, Brynn H [ORNL

    2006-07-01

    BACKGROUND: A growing body of data provides increasing evidence that the adipose tissue renin-angiotensin system (RAS) contributes to regulation of fat mass. Beyond its paracrine actions within adipose tissue, adipocyte-derived angiotensin II (Ang II) may also impact systemic functions such as blood pressure and metabolism. METHODS AND RESULTS: We used a genetic approach to manipulate adipose RAS activity in mice and then study the consequences on metabolic parameters and on feedback regulation of the RAS. The models included deletion of the angiotensinogen (Agt) gene (Agt-KO), its expression solely in adipose tissue under the control of an adipocyte-specific promoter (aP2-Agt/ Agt-KO), and overexpression in adipose tissue of wild type mice (aP2-Agt). Total body weight, epididymal fat pad weight, and circulating levels of leptin, insulin and resistin were significantly decreased in Agt-KO mice, while plasma adiponectin levels were increased. Overexpression of Agt in adipose tissue resulted in increased adiposity and plasma leptin and insulin levels compared to wild type (WT) controls. Angiotensinogen and type I Ang II receptor protein levels were also markedly elevated in kidney of aP2-Agt mice, suggesting that hypertension in these animals may be in part due to stimulation of the intrarenal RAS. CONCLUSIONS: Taken together, the results from this study demonstrate that alterations in adipose RAS activity significantly alter both local and systemic physiology in a way that may contribute to the detrimental health effects of obesity.

  14. RNA helicase HEL-1 promotes longevity by specifically activating DAF-16/FOXO transcription factor signaling in Caenorhabditis elegans

    Science.gov (United States)

    Seo, Mihwa; Seo, Keunhee; Hwang, Wooseon; Koo, Hee Jung; Hahm, Jeong-Hoon; Yang, Jae-Seong; Han, Seong Kyu; Hwang, Daehee; Kim, Sanguk; Jang, Sung Key; Lee, Yoontae; Nam, Hong Gil; Lee, Seung-Jae V.

    2015-01-01

    The homeostatic maintenance of the genomic DNA is crucial for regulating aging processes. However, the role of RNA homeostasis in aging processes remains unknown. RNA helicases are a large family of enzymes that regulate the biogenesis and homeostasis of RNA. However, the functional significance of RNA helicases in aging has not been explored. Here, we report that a large fraction of RNA helicases regulate the lifespan of Caenorhabditis elegans. In particular, we show that a DEAD-box RNA helicase, helicase 1 (HEL-1), promotes longevity by specifically activating the DAF-16/forkhead box O (FOXO) transcription factor signaling pathway. We find that HEL-1 is required for the longevity conferred by reduced insulin/insulin-like growth factor 1 (IGF-1) signaling (IIS) and is sufficient for extending lifespan. We further show that the expression of HEL-1 in the intestine and neurons contributes to longevity. HEL-1 enhances the induction of a large fraction of DAF-16 target genes. Thus, the RNA helicase HEL-1 appears to promote longevity in response to decreased IIS as a transcription coregulator of DAF-16. Because HEL-1 and IIS are evolutionarily well conserved, a similar mechanism for longevity regulation via an RNA helicase-dependent regulation of FOXO signaling may operate in mammals, including humans. PMID:26195740

  15. Central GLP-2 enhances hepatic insulin sensitivity via activating PI3K signaling in POMC neurons

    Science.gov (United States)

    Shi, Xuemei; Zhou, Fuguo; Li, Xiaojie; Chang, Benny; Li, Depei; Wang, Yi; Tong, Qingchun; Xu, Yong; Fukuda, Makoto; Zhao, Jean J.; Li, Defa; Burrin, Douglas G.; Chan, Lawrence; Guan, Xinfu

    2013-01-01

    Glucagon-like peptides (GLP-1/2) are co-produced and highlighted as key modulators to improve glucose homeostasis and insulin sensitivity after bariatric surgery. However, it is unknown if CNS GLP-2 plays any physiological role in the control of glucose homeostasis and insulin sensitivity. We show that mice lacking GLP-2 receptor (GLP-2R) in POMC neurons display glucose intolerance and hepatic insulin resistance. GLP-2R activation in POMC neurons is required for GLP-2 to enhance insulin-mediated suppression of hepatic glucose production (HGP) and gluconeogenesis. GLP-2 directly modulates excitability of POMC neurons in GLP-2R- and PI3K-dependent manners. GLP-2 initiates GLP-2R-p85α interaction and facilitates PI3K-Akt-dependent FoxO1 nuclear exclusion in POMC neurons. Central GLP-2 suppresses basal HGP and enhances insulin sensitivity, which are abolished in POMC-p110α KO mice. Thus, CNS GLP-2 plays a key physiological role in the control of hepatic glucose production through activating PI3K-dependent modulation of membrane excitability and nuclear transcription of POMC neurons in the brain. PMID:23823479

  16. Central GLP-2 enhances hepatic insulin sensitivity via activating PI3K signaling in POMC neurons.

    Science.gov (United States)

    Shi, Xuemei; Zhou, Fuguo; Li, Xiaojie; Chang, Benny; Li, Depei; Wang, Yi; Tong, Qingchun; Xu, Yong; Fukuda, Makoto; Zhao, Jean J; Li, Defa; Burrin, Douglas G; Chan, Lawrence; Guan, Xinfu

    2013-07-02

    Glucagon-like peptides (GLP-1/GLP-2) are coproduced and highlighted as key modulators to improve glucose homeostasis and insulin sensitivity after bariatric surgery. However, it is unknown if CNS GLP-2 plays any physiological role in the control of glucose homeostasis and insulin sensitivity. We show that mice lacking GLP-2 receptor (GLP-2R) in POMC neurons display glucose intolerance and hepatic insulin resistance. GLP-2R activation in POMC neurons is required for GLP-2 to enhance insulin-mediated suppression of hepatic glucose production (HGP) and gluconeogenesis. GLP-2 directly modulates excitability of POMC neurons in GLP-2R- and PI3K-dependent manners. GLP-2 initiates GLP-2R-p85α interaction and facilitates PI3K-Akt-dependent FoxO1 nuclear exclusion in POMC neurons. Central GLP-2 suppresses basal HGP and enhances insulin sensitivity, which are abolished in POMC-p110α KO mice. Thus, CNS GLP-2 plays a key physiological role in the control of HGP through activating PI3K-dependent modulation of membrane excitability and nuclear transcription of POMC neurons in the brain. Copyright © 2013 Elsevier Inc. All rights reserved.

  17. Employer's information and promotion-seeking activities

    OpenAIRE

    Epstein, Gil S.

    2012-01-01

    This paper presents a model in which promotion of employees within the internal firm hierarchy is determined by the individuals' allocation of time between promotion/rent-seeking and productive activity. We consider the effect of an increase in the employer's knowledge (information) regarding the employees' productivity levels on the total time spent by the workers in non-productive promotion-seeking activities.

  18. Effect of insulin on the mitotic activity of bone marrow cells after irradiation. [Gamma radiation, rats

    Energy Technology Data Exchange (ETDEWEB)

    Barkalaya, A I

    1976-02-01

    A total of 236 white rats were given a whole-body gamma dose of 750 R. Part of the rats were given a subcutaneous insulin injection of 0.2 units/kg. After 10, 20, 30 min, 1, 2, 3, 5, 8, 10 and 12 hours the mitotic index was determined in both groups of rats in the bone marrow of the femur. The content of glucose and insulin in the blood was determined. The mitotic index was found to be higher on administering insulin. The use of insulin in radiation sickness intensifies the mitotic activity of bone marrow cells and stimulates the recovery of bone marrow hematopoiesis. 5 references.

  19. Physical activity and diabetes mellitus.

    Science.gov (United States)

    Bhaskarabhatla, Krishna V; Birrer, Richard

    2005-01-01

    Diabetes mellitus (DM), a metabolic syndrome consisting of two main groups, type 1 and 2, is characterized by absolute or relative insulin deficiency or insulin resistance. Individuals with DM take part in physical activity for health promotion, disease management, and or recreational or competitive sports. Several studies confirm the beneficial role of physical activity in favorably altering the prognosis of DM. Exercise as a therapeutic strategy has potential risks, too. Hence, sports medicine physicians caring for athletes with diabetes have several important responsibilities. Diabetic education; pre-participatory evaluation for vascular, neurological, retinal or joint disease; diabetic status and control; promotion of blood glucose self-monitoring; and individualized dietary, medication, and physical activity plans are essential to achieve safe and enjoyable outcomes in individuals with diabetes who are embarking on physical activity.

  20. Plasma phospholipid transfer protein activity is related to insulin resistance : impaired acute lowering by insulin in obese Type II diabetic patients

    NARCIS (Netherlands)

    Riemens, SC; van Tol, A; Sluiter, WJ; Dullaart, RPF

    Cholesteryl ester transfer protein (CETP) and phospholipid transfer protein (PLTP) have important functions in high density lipoprotein (HDL) metabolism. We determined the association of plasma CETP and PLTP activities (measured with exogenous' substrate assays) with insulin resistance, plasma

  1. Promotional activities of banks in Serbia

    Directory of Open Access Journals (Sweden)

    Zelenović Vera

    2008-01-01

    Full Text Available The paper is focused on banking sector in Serbia, particulary on promotional activities of banks in public and on media. The authors of paper tried to find cause and effect relationship between business success and working quality on the one hand and investment in promotion activities of bank on the other hand, like important instrument of bank's business policy realization. Promotional activities appear like successful instrument in order to increase satisfaction of the bank's clients, which effect the increase of successfulness of banks' business.

  2. Effect of resistance exercise under conditions of reduced blood insulin on AMPKα Ser485/491 inhibitory phosphorylation and AMPK pathway activation.

    Science.gov (United States)

    Kido, Kohei; Yokokawa, Takumi; Ato, Satoru; Sato, Koji; Fujita, Satoshi

    2017-08-01

    Insulin stimulates skeletal muscle glucose uptake via activation of the protein kinase B/Akt (Akt) pathway. Recent studies suggest that insulin downregulates AMP-activated protein kinase (AMPK) activity via Ser485/491 phosphorylation of the AMPK α-subunit. Thus lower blood insulin concentrations may induce AMPK signal activation. Acute exercise is one method to stimulate AMPK activation; however, no study has examined the relationship between blood insulin levels and acute resistance exercise-induced AMPK pathway activation. Based on previous findings, we hypothesized that the acute resistance exercise-induced AMPK pathway activation would be augmented by disruptions in insulin secretion through a decrease in AMPKα Ser485/491 inhibitory phosphorylation. To test the hypothesis, 10-wk-old male Sprague-Dawley rats were administered the toxin streptozotocin (STZ; 55 mg/kg) to destroy the insulin secreting β-cells. Three days postinjection, the right gastrocnemius muscle from STZ and control rats was subjected to resistance exercise by percutaneous electrical stimulation. Animals were killed 0, 1, or 3 h later; activation of the Akt/AMPK and downstream pathways in the muscle tissue was analyzed by Western blotting and real-time PCR. Notably, STZ rats showed a significant decrease in basal Akt and AMPKα Ser485/491 phosphorylation, but substantial exercise-induced increases in both AMPKα Thr172 and acetyl-CoA carboxylase (ACC) Ser79 phosphorylation were observed. Although no significant impact on resistance exercise-induced Akt pathway activation or glucose uptake was found, resistance exercise-induced peroxisome proliferator-activated receptor (PPAR)-γ coactivator-1 α (PGC-1α) gene expression was augmented by STZ treatment. Collectively, these data suggest that circulating insulin levels may regulate acute resistance exercise-induced AMPK pathway activation and AMPK-dependent gene expression relating to basal AMPKα Ser485/491 phosphorylation. Copyright © 2017

  3. Antidiabetic activity of Kalanchoe pinnata in streptozotocin-induced diabetic rats by glucose independent insulin secretagogue action.

    Science.gov (United States)

    Patil, Swapnil B; Dongare, Vandana R; Kulkarni, Chaitanya R; Joglekar, Madhav M; Arvindekar, Akalpita U

    2013-11-01

    Kalanchoe pinnata Lam. (Crassulaceae) is used as a traditional medicine worldwide to treat several ailments, including diabetes. However, the mechanism for the antihyperglycemic action is unknown. The present study evaluates the antihyperglycemic and insulin secretagogue potential of Kalanchoe pinnata and assessment of the probable mechanism of action. Steam distillate of Kalanchoe pinnata leaves was subjected to solvent fractionation and antidiabetic activity was detected in dichloromethane (DCM) fraction. In the in vivo studies, rats were treated with 5 and 10 mg/kg body weight of DCM fraction for 45 days orally. Lipid profile and other biochemical parameters were estimated. The probable mechanism for insulin secretagogue action was evaluated through studies using diazoxide and nifedipine. The bioactive component from DCM fraction was studied using HPTLC, GCMS and IR. Fasting blood glucose values were reduced to 116 mg/dl from 228 mg/dl on treatment with 10 mg/kg body weight of DCM fraction, while glycated hemoglobin improved to 8.4% compared with 12.9% in diabetic controls. The insulin level and lipid profile values were close to normal values. In vitro studies demonstrated a dose-dependent insulin secretagogue action. Insulin secretion was 3.29-fold higher at 10 µg/ml as compared to the positive control. The insulin secretagogue activity was glucose independent and K(+)-ATP channel dependent. The bioactive component of the DCM fraction was identified to be a phenyl alkyl ether derivative. The DCM fraction of Kalanchoe pinnata demonstrates excellent insulin secretagogue action and can be useful in treatment of diabetes mellitus.

  4. The effects of two-week program of individually measured physical activity on insulin resistance in obese non-insulin-dependent diabetes mellitus

    Directory of Open Access Journals (Sweden)

    Čizmić Milica

    2003-01-01

    Full Text Available It is well known that under the influence of regular, individually measured aerobic physical activity, it is possible to raise the biological efficiency of insulin by several mechanisms: by increasing the number of insulin receptors, their sensitivity and efficiency, as well as by increasing glucose transporters GLUT-4 on the level of cell membrane. The aim of this research was to examine whether decreased insulin resistance could be achieved under the influence of the program of individually measured aerobic physical activity in the 2-week period, in the obese type 2 diabetes patients with the increased aerobic capacity (VO2max. In 10 type 2 diabetes patients 47.6 ± 4.6 years of age (group E, in the 14-days period, program of aerobic training was applied (10 sessions - 35 min session of walking on treadmill, intensity 60.8 ± 5.7% (VO2max, frequency 5 times a week , as well as 1 600 kcal diet. At the same time, other 10 type 2 diabetes patients 45.9 ± 5.5 years of age (group C were on 1 600 kcal diet. Before and after this period the following was measured in both groups: insulin sensitivity (M/I by the method of hyperinsulin euglycemic clamp, and (VO2max by Astrand test on ergocycle. In contrast to the group C, in the second testing of E group subjects a significant increase was obtained in M/I (1.23 ± 0.78 vs. 2.42 ± 0.95 mg/kg/min/mU p<0.001, 96.75% as well as the increase of (VO2max (26.34 ± 4.26 vs. 29.16 ± 5.01 ml/kg/min p<0.05, 10.7%. The results had shown that 2-week program of aerobic training had had significant influence on the increased aerobic capacity and insulin sensitivity in the tested patients.

  5. Insulin action in denervated skeletal muscle

    International Nuclear Information System (INIS)

    Smith, R.L.

    1987-01-01

    The goal of this study was to determine the mechanisms responsible for reduced insulin response in denervated muscle. Denervation for 3 days of rat muscles consisting of very different compositions of fiber types decreased insulin stimulated [U- 14 C]glucose incorporation into glycogen by 80%. Associated with the reduction in glycogen synthesis was a decreased activation of glycogen synthase. Denervation of hemidiaphragms for 1 day decreased both the basal and insulin stimulated activity ratios of glycogen synthase and the rate of insulin stimulated [U- 14 C[glucose incorporation into glycogen by 50%. Insulin stimulation of 2-deoxy[ 3 H]glucose uptake was not decreased until 3 days after denervation. Consistent with the effects on glucose transport,insulin did not increase the intracellular concentration of glucose-6-P in muscles 3 days after denervation. Furthermore, since the Ka for glucose-6-P activation of glycogen synthase was not decreased by insulin in denervated hemidiaphragms, the effects of denervation on glycogen synthase and glucose transport were synergistic resulting in the 80% decrease in glycogen synthesis rates

  6. Autophagy downregulation contributes to insulin resistance mediated injury in insulin receptor knockout podocytes in vitro

    Directory of Open Access Journals (Sweden)

    Ying Xu

    2016-04-01

    Full Text Available It is unknown whether autophagy activity is altered in insulin resistant podocytes and whether autophagy could be a therapeutic target for diabetic nephropathy (DN. Here we used shRNA transfection to knockdown the insulin receptor (IR gene in cultured human immortalized podocytes as an in vitro insulin resistant model. Autophagy related proteins LC3, Beclin, and p62 as well as nephrin, a podocyte injury marker, were assessed using western blot and immunofluorescence staining. Our results show that autophagy is suppressed when podocytes lose insulin sensitivity and that treatment of rapamycin, an mTOR specific inhibitor, could attenuate insulin resistance induced podocytes injury via autophagy activation. The present study deepens our understanding of the role of autophagy in the pathogenesis of DN.

  7. Progranulin causes adipose insulin resistance via increased autophagy resulting from activated oxidative stress and endoplasmic reticulum stress.

    Science.gov (United States)

    Guo, Qinyue; Xu, Lin; Li, Huixia; Sun, Hongzhi; Liu, Jiali; Wu, Shufang; Zhou, Bo

    2017-01-31

    Progranulin (PGRN) has recently emerged as an important regulator for insulin resistance. However, the direct effect of progranulin in adipose insulin resistance associated with the autophagy mechanism is not fully understood. In the present study, progranulin was administered to 3T3-L1 adipocytes and C57BL/6 J mice with/without specific inhibitors of oxidative stress and endoplasmic reticulum stress, and metabolic parameters, oxidative stress, endoplasmic reticulum stress and autophagy markers were assessed. Progranulin treatment increased iNOS expression, NO synthesis and ROS generation, and elevated protein expressions of CHOP, GRP78 and the phosphorylation of PERK, and caused a significant increase in Atg7 and LC3-II protein expression and a decreased p62 expression, and decreased insulin-stimulated tyrosine phosphorylation of IRS-1 and glucose uptake, demonstrating that progranulin activated oxidative stress and ER stress, elevated autophagy and induced insulin insensitivity in adipocytes and adipose tissue of mice. Interestingly, inhibition of iNOS and ER stress both reversed progranulin-induced stress response and increased autophagy, protecting against insulin resistance in adipocytes. Furthermore, the administration of the ER stress inhibitor 4-phenyl butyric acid reversed the negative effect of progranulin in vivo. Our findings showed the clinical potential of the novel adipokine progranulin in the regulation of insulin resistance, suggesting that progranulin might mediate adipose insulin resistance, at least in part, by inducing autophagy via activated oxidative stress and ER stress.

  8. Obestatin regulates adipocyte function and protects against diet-induced insulin resistance and inflammation.

    Science.gov (United States)

    Granata, Riccarda; Gallo, Davide; Luque, Raul M; Baragli, Alessandra; Scarlatti, Francesca; Grande, Cristina; Gesmundo, Iacopo; Córdoba-Chacón, Jose; Bergandi, Loredana; Settanni, Fabio; Togliatto, Gabriele; Volante, Marco; Garetto, Stefano; Annunziata, Marta; Chanclón, Belén; Gargantini, Eleonora; Rocchietto, Stefano; Matera, Lina; Datta, Giacomo; Morino, Mario; Brizzi, Maria Felice; Ong, Huy; Camussi, Giovanni; Castaño, Justo P; Papotti, Mauro; Ghigo, Ezio

    2012-08-01

    The metabolic actions of the ghrelin gene-derived peptide obestatin are still unclear. We investigated obestatin effects in vitro, on adipocyte function, and in vivo, on insulin resistance and inflammation in mice fed a high-fat diet (HFD). Obestatin effects on apoptosis, differentiation, lipolysis, and glucose uptake were determined in vitro in mouse 3T3-L1 and in human subcutaneous (hSC) and omental (hOM) adipocytes. In vivo, the influence of obestatin on glucose metabolism was assessed in mice fed an HFD for 8 wk. 3T3-L1, hSC, and hOM preadipocytes and adipocytes secreted obestatin and showed specific binding for the hormone. Obestatin prevented apoptosis in 3T3-L1 preadipocytes by increasing phosphoinositide 3-kinase (PI3K)/Akt and extracellular signal-regulated kinase (ERK)1/2 signaling. In both mice and human adipocytes, obestatin inhibited isoproterenol-induced lipolysis, promoted AMP-activated protein kinase phosphorylation, induced adiponectin, and reduced leptin secretion. Obestatin also enhanced glucose uptake in either the absence or presence of insulin, promoted GLUT4 translocation, and increased Akt phosphorylation and sirtuin 1 (SIRT1) protein expression. Inhibition of SIRT1 by small interfering RNA reduced obestatin-induced glucose uptake. In HFD-fed mice, obestatin reduced insulin resistance, increased insulin secretion from pancreatic islets, and reduced adipocyte apoptosis and inflammation in metabolic tissues. These results provide evidence of a novel role for obestatin in adipocyte function and glucose metabolism and suggest potential therapeutic perspectives in insulin resistance and metabolic dysfunctions.

  9. Physical activity and health promotion strategies among ...

    African Journals Online (AJOL)

    EB

    out information regarding physical activity were most common methods used in promotion of physical activity. Policies on ... highlighted. Conclusion: Although physiotherapists experience barriers to promoting physical activity, they have good physical activity .... workplace tended to vary from lack of books or articles on.

  10. Variations in insulin responsiveness in rat fat cells are due to metabolic differences rather than insulin binding

    DEFF Research Database (Denmark)

    Hansen, Finn Mølgård; Nilsson, Poul; Sonne, Ole

    1983-01-01

    -insulin to fat cells. Insulin binding was not correlated to the plasma insulin level which however was reflected in the lipoprotein lipase activity in the adipose tissue. In conclusion, these results indicate that variations in insulin responsiveness in fat cells are due to alterations in cellular metabolism...

  11. Insulin-like growth factor-I, physical activity, and control of cellular anabolism.

    Science.gov (United States)

    Nindl, Bradley C

    2010-01-01

    The underlying mechanisms responsible for mediating the beneficial outcomes of exercise undoubtedly are many, but the insulin-like growth factor-I (IGF-I) system is emerging as an important and central hormonal axis that plays a significant role concerning cellular anabolism. This introductory article summarizes the intent and the content for papers presented as part of a 2008 American College of Sports Medicine national symposium entitled "Insulin-like Growth Factor-I, Physical Activity, and Control of Cellular Anabolism." The individual authors and their papers are as follows: Jan Frystyk authoring "The relationship between exercise and the growth hormone/insulin-like growth factor-I axis," Greg Adams authoring "IGF-I signaling in skeletal muscle and the potential for cytokine interactions," and Brad Nindl authoring "Insulin-like growth factor-I as a biomarker of health, fitness, and training status." These papers focus on 1) different assay methodologies for IGF-I within the paradigm of exercise studies, 2) research demonstrating that intracellular signaling components associated with several proinflammatory cytokines have the potential to interact with anabolic signaling processes in skeletal muscle, and 3) an overview of IGF-I as a biomarker related to exercise training, muscle and bone remodeling, body composition, cognition, and cancer. When summed in total, the contribution that these papers will make will undoubtedly involve bringing attention to the vast regulatory complexity of the IGF-I system and will hopefully convince the reader that the IGF-I system warrants further detailed scientific inquiry to resolve many unanswered questions and paradoxical experimental findings. The IGF-I system remains one of the most intriguing and captivating marvels of human physiology that seems central in mediating numerous adaptations from physical activity.

  12. An upstream activation element exerting differential transcriptional activation on an archaeal promoter

    DEFF Research Database (Denmark)

    Peng, Nan; Xia, Qiu; Chen, Zhengjun

    2009-01-01

    S gene encoding an arabinose binding protein was characterized using an Sulfolobus islandicus reporter gene system. The minimal active araS promoter (P(araS)) was found to be 59 nucleotides long and harboured four promoter elements: an ara-box, an upstream transcription factor B-responsive element (BRE......), a TATA-box and a proximal promoter element, each of which contained important nucleotides that either greatly decreased or completely abolished promoter activity upon mutagenesis. The basal araS promoter was virtually inactive due to intrinsically weak BRE element, and the upstream activating sequence...... (UAS) ara-box activated the basal promoter by recruiting transcription factor B to its BRE. While this UAS ensured a general expression from an inactive or weak basal promoter in the presence of other tested carbon resources, it exhibited a strong arabinose-responsive transcriptional activation. To our...

  13. Sustained activation of the mammalian target of rapamycin nutrient sensing pathway is associated with hepatic insulin resistance, but not with steatosis, in mice

    NARCIS (Netherlands)

    Korsheninnikova, E.; van der Zon, G. C. M.; Voshol, P. J.; Janssen, G. M.; Havekes, L. M.; Grefhorst, A.; Kuipers, F.; Reijngoud, D.-J.; Romijn, J. A.; Ouwens, D. M.; Maassen, J. A.

    2006-01-01

    Activation of nutrient sensing through mammalian target of rapamycin (mTOR) has been linked to the pathogenesis of insulin resistance. We examined activation of mTOR-signalling in relation to insulin resistance and hepatic steatosis in mice. Chronic hepatic steatosis and hepatic insulin resistance

  14. Effects of Ursodeoxycholic Acid and Insulin on Palmitate-Induced ROS Production and Down-Regulation of PI3K/Akt Signaling Activity.

    Science.gov (United States)

    Yokoyama, Kunihiro; Tatsumi, Yasuaki; Hayashi, Kazuhiko; Goto, Hidemi; Ishikawa, Tetsuya; Wakusawa, Shinya

    2017-01-01

    In obese and diabetic patients, plasma free fatty acid (FFA) levels are often elevated and may play a causal role in insulin resistance and reactive oxygen species (ROS) production. We have previously shown that ursodeoxycholic acid (UDCA) has antioxidative activity through the phosphatidylinositol 3-kinase (PI3K)/Akt signaling-mediated glutathione production. In this study, we investigated the effects of UDCA on insulin response by analyzing intracellular ROS and the activation of the PI3K/Akt signaling pathway in HepG2 cells treated with palmitate. The level of ROS was quantified using 2',7'-dichlorodihydrofluorescein diacetate (H 2 DCFDA), and the activation of the PI3K/Akt signaling pathway was determined by Western blotting assay using appropriate antibodies. The intracellular ROS levels were increased by palmitate but were reduced by treatment with UDCA and insulin. Furthermore, insulin significantly stimulated the phosphorylation of Akt. When the cells were pre-treated with palmitate, insulin-induced Akt-phosphorylation was markedly inhibited. However, when the cells were treated with palmitate and UDCA, the effects of insulin were partially restored. UDCA may have protective effects against palmitate-induced decreases in responsiveness to insulin.

  15. The phosphatidylinositol 3-kinase inhibitor, wortmannin, inhibits insulin-induced activation of phosphatidylcholine hydrolysis and associated protein kinase C translocation in rat adipocytes.

    OpenAIRE

    Standaert, M L; Avignon, A; Yamada, K; Bandyopadhyay, G; Farese, R V

    1996-01-01

    We questioned whether phosphatidylinositol 3-kinase (PI 3-kinase) and protein kinase C (PKC) function as interrelated signalling mechanisms during insulin action in rat adipocytes. Insulin rapidly activated a phospholipase D that hydrolyses phosphatidylcholine (PC), and this activation was accompanied by increases in diacylglycerol and translocative activation of PKC-alpha and PKC-beta in the plasma membrane. Wortmannin, an apparently specific PI 3-kinase inhibitor, inhibited insulin-stimulat...

  16. Ghrelin differentially affects hepatic and peripheral insulin sensitivity in mice

    NARCIS (Netherlands)

    Heijboer, A. C.; van den Hoek, A. M.; Parlevliet, E. T.; Havekes, L. M.; Romijn, J. A.; Pijl, H.; Corssmit, E. P. M.

    2006-01-01

    This study was conducted to evaluate the effects of ghrelin on insulin's capacity to suppress endogenous glucose production and promote glucose disposal in mice. To establish whether the growth hormone secretagogue (GHS) receptor can mediate the putative effect of ghrelin on the action of insulin,

  17. Zn2+ chelation by serum albumin improves hexameric Zn2+-insulin dissociation into monomers after exocytosis.

    Directory of Open Access Journals (Sweden)

    José A G Pertusa

    Full Text Available β-cells release hexameric Zn2+-insulin into the extracellular space, but monomeric Zn2+-free insulin appears to be the only biologically active form. The mechanisms implicated in dissociation of the hexamer remain unclear, but they seem to be Zn2+ concentration-dependent. In this study, we investigate the influence of albumin binding to Zn2+ on Zn2+-insulin dissociation into Zn2+-free insulin and its physiological, methodological and therapeutic relevance. Glucose and K+-induced insulin release were analyzed in isolated mouse islets by static incubation and perifusion experiments in the presence and absence of albumin and Zn2+ chelators. Insulin tolerance tests were performed in rats using different insulin solutions with and without Zn2+ and/or albumin. Albumin-free buffer does not alter quantification by RIA of Zn2+-free insulin but strongly affects RIA measurements of Zn2+-insulin. In contrast, accurate determination of Zn2+-insulin was obtained only when bovine serum albumin or Zn2+ chelators were present in the assay buffer solution. Albumin and Zn2+ chelators do not modify insulin release but do affect insulin determination. Preincubation with albumin or Zn2+ chelators promotes the conversion of "slow" Zn2+-insulin into "fast" insulin. Consequently, insulin diffusion from large islets is ameliorated in the presence of Zn2+ chelators. These observations support the notion that the Zn2+-binding properties of albumin improve the dissociation of Zn2+-insulin into subunits after exocytosis, which may be useful in insulin determination, insulin pharmacokinetic assays and islet transplantation.

  18. The relationship between vitamin D status, physical activity and insulin resistance in overweight and obese subjects

    Directory of Open Access Journals (Sweden)

    Gülis Kavadar

    2015-05-01

    Full Text Available Type 2 diabetes mellitus (T2DM incidence has been increasing worldwide along with the rise of obesity and sedantery lifestyle. Decreased physical activity (PA and obesity have also been associated with the low vitamin D levels. We aimed to determine the association between PA, vitamin D status and insulin resistance in overweight and obese subjects. A total of 294 (186 female, 108 male overweight or obese subjects were included in this cross-sectional study. 25-hydroxy vitamin D (25(OHD, insulin, fasting plasma glucose (FPG and HbA1c levels were measured in blood samples. Body mass index (BMI, HOMA-index and total score of International Physical Activity Questionnaire-long form (IPAQ were calculated. Insulin resistant subjects were compared with the non-resistant group. The mean age of the participants was 45±12.25 and 41.39±10.32; 25(OHD levels were 8.91 ± 4.30 and 17.62 ± 10.47 ng/dL; BMIs were 31.29 ± 4.48  and 28.2 ± 3.16 kg/m², IPAQ total scores were 548.71±382.81 and 998±486.21 in the insulin resistant and nonresistant subjects, respectively. There was a statistically significant difference in terms of 25(OHD, FPG, insulin levels, IPAQ  total score and BMI between the two groups (p = 0.001, p = 0.001, p = 0.001, p = 0.001, p = 0.001.Significantly low 25(OHD levels, high BMI and low PA in insulin resistant subjects confirm the importance of active lifestyle and the maintenance of normal vitamin D levels in overweight and obese subjects in prevention of T2DM.

  19. Akt kinase C-terminal modifications control activation loop dephosphorylation and enhance insulin response.

    Science.gov (United States)

    Chan, Tung O; Zhang, Jin; Tiegs, Brian C; Blumhof, Brian; Yan, Linda; Keny, Nikhil; Penny, Morgan; Li, Xue; Pascal, John M; Armen, Roger S; Rodeck, Ulrich; Penn, Raymond B

    2015-10-01

    The Akt protein kinase, also known as protein kinase B, plays key roles in insulin receptor signalling and regulates cell growth, survival and metabolism. Recently, we described a mechanism to enhance Akt phosphorylation that restricts access of cellular phosphatases to the Akt activation loop (Thr(308) in Akt1 or protein kinase B isoform alpha) in an ATP-dependent manner. In the present paper, we describe a distinct mechanism to control Thr(308) dephosphorylation and thus Akt deactivation that depends on intramolecular interactions of Akt C-terminal sequences with its kinase domain. Modifications of amino acids surrounding the Akt1 C-terminal mTORC2 (mammalian target of rapamycin complex 2) phosphorylation site (Ser(473)) increased phosphatase resistance of the phosphorylated activation loop (pThr(308)) and amplified Akt phosphorylation. Furthermore, the phosphatase-resistant Akt was refractory to ceramide-dependent dephosphorylation and amplified insulin-dependent Thr(308) phosphorylation in a regulated fashion. Collectively, these results suggest that the Akt C-terminal hydrophobic groove is a target for the development of agents that enhance Akt phosphorylation by insulin. © 2015 Authors; published by Portland Press Limited.

  20. Computational study of the activity, dynamics, energetics and conformations of insulin analogues using molecular dynamics simulations: Application to hyperinsulinemia and the critical residue B26

    Directory of Open Access Journals (Sweden)

    Anastasios Papaioannou

    2017-09-01

    Full Text Available Due to the increasing prevalence of diabetes, finding therapeutic analogues for insulin has become an urgent issue. While many experimental studies have been performed towards this end, they have limited scope to examine all aspects of the effect of a mutation. Computational studies can help to overcome these limitations, however, relatively few studies that focus on insulin analogues have been performed to date. Here, we present a comprehensive computational study of insulin analogues—three mutant insulins that have been identified with hyperinsulinemia and three mutations on the critical B26 residue that exhibit similar binding affinity to the insulin receptor—using molecular dynamics simulations with the aim of predicting how mutations of insulin affect its activity, dynamics, energetics and conformations. The time evolution of the conformers is studied in long simulations. The probability density function and potential of mean force calculations are performed on each insulin analogue to unravel the effect of mutations on the dynamics and energetics of insulin activation. Our conformational study can decrypt the key features and molecular mechanisms that are responsible for an enhanced or reduced activity of an insulin analogue. We find two key results: 1 hyperinsulinemia may be due to the drastically reduced activity (and binding affinity of the mutant insulins. 2 Y26BS and Y26BE are promising therapeutic candidates for insulin as they are more active than WT-insulin. The analysis in this work can be readily applied to any set of mutations on insulin to guide development of more effective therapeutic analogues.

  1. PON1 promoter polymorphisms contribute to PCOS susceptibility and phenotypic outcomes in Indian women.

    Science.gov (United States)

    Dadachanji, Roshan; Shaikh, Nuzhat; Patil, Anushree; Shah, Nalini; Mukherjee, Srabani

    2018-06-30

    Polycystic ovary syndrome is a common endocrinopathy characterized by anovulatory infertility, hyperandrogenism, insulin resistance and oxidative stress, which predisposes affected women to reproductive and cardiometabolic complications in later life. We have investigated the association of PON1 promoter polymorphisms with PCOS susceptibility, PON1 activity and its related traits in Indian women. The genotypic and allelic frequency distribution of only -907G/C polymorphism in PON1 promoter showed significant difference between non-hyperandrogenic control and PCOS women, and was significantly associated with reduced susceptibility to PCOS, considering the recessive model. PON1 lactonase and arylesterase activities were also significantly decreased in women with PCOS compared to controls. Further, PON1 promoter polymorphisms were linked to altered insulin and testosterone levels in hyperandrogenic and non-hyperandrogenic women with PCOS. This study highlights PON1 as an important candidate gene influencing genetic pathophysiology of PCOS. Copyright © 2018 Elsevier B.V. All rights reserved.

  2. Reconstructing Dynamic Promoter Activity Profiles from Reporter Gene Data.

    Science.gov (United States)

    Kannan, Soumya; Sams, Thomas; Maury, Jérôme; Workman, Christopher T

    2018-03-16

    Accurate characterization of promoter activity is important when designing expression systems for systems biology and metabolic engineering applications. Promoters that respond to changes in the environment enable the dynamic control of gene expression without the necessity of inducer compounds, for example. However, the dynamic nature of these processes poses challenges for estimating promoter activity. Most experimental approaches utilize reporter gene expression to estimate promoter activity. Typically the reporter gene encodes a fluorescent protein that is used to infer a constant promoter activity despite the fact that the observed output may be dynamic and is a number of steps away from the transcription process. In fact, some promoters that are often thought of as constitutive can show changes in activity when growth conditions change. For these reasons, we have developed a system of ordinary differential equations for estimating dynamic promoter activity for promoters that change their activity in response to the environment that is robust to noise and changes in growth rate. Our approach, inference of dynamic promoter activity (PromAct), improves on existing methods by more accurately inferring known promoter activity profiles. This method is also capable of estimating the correct scale of promoter activity and can be applied to quantitative data sets to estimate quantitative rates.

  3. THE PROMOTIONAL ACTIVITY IN THE TOURISTIC SECTOR

    Directory of Open Access Journals (Sweden)

    Costel Iliuta Negricea

    2008-05-01

    Full Text Available The promotion as one of the components of the marketing mix, laying stress, în this regard,on its role în the deployment of the tourism companies’ activity, the structure of the promotional activity în thetouristic sector as well as the use of the promotional strategies în the attainment of the development targets ofthe tourism companies.So, în the paper there have been mentioned the three levels at which it is made the touristic promotionîn Romania, respectively nationally, by the Ministry of the Tourism, under whose subordination it is theTourism National Authority, the second level is the regional/local one, concerning the activity carried out bythe Centers/Offices of Touristic Information from a series of localities, and the last level refers to the microone, respectively at the level of the tourism companies, which promote their offer individually (the most often.The important role of the promotion în the deployment of the activity of the tourism companies isbeing highlighted by the fact that this makes the connection between the activity of an organization and itscustomers (effective or potential, and, în the touristic field, the content of the promotional activity is stronglystressed by the features of this type of services and of the system of creation and delivery, as well as of thepurchasing behaviour.

  4. Scoparia dulcis (SDF7) endowed with glucose uptake properties on L6 myotubes compared insulin.

    Science.gov (United States)

    Beh, Joo Ee; Latip, Jalifah; Abdullah, Mohd Puad; Ismail, Amin; Hamid, Muhajir

    2010-05-04

    Insulin stimulates glucose uptake and promotes the translocation of glucose transporter 4 (Glut 4) to the plasma membrane on L6 myotubes. The aim of this study is to investigate affect of Scoparia dulcis Linn water extracts on glucose uptake activity and the Glut 4 translocation components (i.e., IRS-1, PI 3-kinase, PKB/Akt2, PKC and TC 10) in L6 myotubes compared to insulin. Extract from TLC fraction-7 (SDF7) was used in this study. The L6 myotubes were treated by various concentrations of SDF7 (1 to 50 microg/ml) and insulin (1 to 100 nM). The glucose uptake activities of L6 myotubes were evaluated using 2-Deoxy-D-glucose uptake assay in with or without fatty acid-induced medium. The Glut 4 translocation components in SDF7-treated L6 myotubes were detected using immunoblotting and quantified by densitometry compared to insulin. Plasma membrane lawn assay and glycogen colorimetry assay were carried out in SDF7- and insulin-treated L6 myotubes in this study. Here, our data clearly shows that SDF7 possesses glucose uptake properties on L6 myotubes that are dose-dependent, time-dependent and plasma membrane Glut 4 expression-dependent. SDF7 successfully stimulates glucose uptake activity as potent as insulin at a maximum concentration of 50 microg/ml at 480 min on L6 myotubes. Furthermore, SDF7 stimulates increased Glut 4 expression and translocation to plasma membranes at equivalent times. Even in the insulin resistance stage (free fatty acids-induced), SDF7-treated L6 myotubes were found to be more capable at glucose transport than insulin treatment. Thus, we suggested that Scoparia dulcis has the potential to be categorized as a hypoglycemic medicinal plant based on its good glucose transport properties. (c) 2010 Elsevier Ireland Ltd. All rights reserved.

  5. Visceral adiposity, insulin resistance and cancer risk

    LENUS (Irish Health Repository)

    Donohoe, Claire L

    2011-06-22

    Abstract Background There is a well established link between obesity and cancer. Emerging research is characterising this relationship further and delineating the specific role of excess visceral adiposity, as opposed to simple obesity, in promoting tumorigenesis. This review summarises the evidence from an epidemiological and pathophysiological perspective. Methods Relevant medical literature was identified from searches of PubMed and references cited in appropriate articles identified. Selection of articles was based on peer review, journal and relevance. Results Numerous epidemiological studies consistently identify increased risk of developing carcinoma in the obese. Adipose tissue, particularly viscerally located fat, is metabolically active and exerts systemic endocrine effects. Putative pathophysiological mechanisms linking obesity and carcinogenesis include the paracrine effects of adipose tissue and systemic alterations associated with obesity. Systemic changes in the obese state include chronic inflammation and alterations in adipokines and sex steroids. Insulin and the insulin-like growth factor axis influence tumorigenesis and also have a complex relationship with adiposity. There is evidence to suggest that insulin and the IGF axis play an important role in mediating obesity associated malignancy. Conclusions There is much evidence to support a role for obesity in cancer progression, however further research is warranted to determine the specific effect of excess visceral adipose tissue on tumorigenesis. Investigation of the potential mechanisms underpinning the association, including the role of insulin and the IGF axis, will improve understanding of the obesity and cancer link and may uncover targets for intervention.

  6. NUCKS Is a Positive Transcriptional Regulator of Insulin Signaling

    Directory of Open Access Journals (Sweden)

    Beiying Qiu

    2014-06-01

    Full Text Available Although much is known about the molecular players in insulin signaling, there is scant information about transcriptional regulation of its key components. We now find that NUCKS is a transcriptional regulator of the insulin signaling components, including the insulin receptor (IR. Knockdown of NUCKS leads to impaired insulin signaling in endocrine cells. NUCKS knockout mice exhibit decreased insulin signaling and increased body weight/fat mass along with impaired glucose tolerance and reduced insulin sensitivity, all of which are further exacerbated by a high-fat diet (HFD. Genome-wide ChIP-seq identifies metabolism and insulin signaling as NUCKS targets. Importantly, NUCKS is downregulated in individuals with a high body mass index and in HFD-fed mice, and conversely, its levels increase upon starvation. Altogether, NUCKS is a physiological regulator of energy homeostasis and glucose metabolism that works by regulating chromatin accessibility and RNA polymerase II recruitment to the promoters of IR and other insulin pathway modulators.

  7. Cardiac Insulin Resistance and MicroRNA Modulators

    Directory of Open Access Journals (Sweden)

    Lakshmi Pulakat

    2012-01-01

    Full Text Available Cardiac insulin resistance is a metabolic and functional disorder that is often associated with obesity and/or the cardiorenal metabolic syndrome (CRS, and this disorder may be accentuated by chronic alcohol consumption. In conditions of over-nutrition, increased insulin (INS and angiotensin II (Ang II activate mammalian target for rapamycin (mTOR/p70 S6 kinase (S6K1 signaling, whereas chronic alcohol consumption inhibits mTOR/S6K1 activation in cardiac tissue. Although excessive activation of mTOR/S6K1 induces cardiac INS resistance via serine phosphorylation of INS receptor substrates (IRS-1/2, it also renders cardioprotection via increased Ang II receptor 2 (AT2R upregulation and adaptive hypertrophy. In the INS-resistant and hyperinsulinemic Zucker obese (ZO rat, a rodent model for CRS, activation of mTOR/S6K1signaling in cardiac tissue is regulated by protective feed-back mechanisms involving mTOR↔AT2R signaling loop and profile changes of microRNA that target S6K1. Such regulation may play a role in attenuating progressive heart failure. Conversely, alcohol-mediated inhibition of mTOR/S6K1, down-regulation of INS receptor and growth-inhibitory mir-200 family, and upregulation of mir-212 that promotes fetal gene program may exacerbate CRS-related cardiomyopathy.

  8. p38 MAPK activation upregulates proinflammatory pathways in skeletal muscle cells from insulin-resistant type 2 diabetic patients

    DEFF Research Database (Denmark)

    Brown, Audrey E; Palsgaard, Jane; Borup, Rehannah

    2015-01-01

    Skeletal muscle is the key site of peripheral insulin resistance in type 2 diabetes. Insulin-stimulated glucose uptake is decreased in differentiated diabetic cultured myotubes, which is in keeping with a retained genetic/epigenetic defect of insulin action. We investigated differences in gene...... expression during differentiation between diabetic and control muscle cell cultures. Microarray analysis was performed using skeletal muscle cell cultures established from type 2 diabetic patients with a family history of type 2 diabetes and clinical evidence of marked insulin resistance and nondiabetic...... significantly, it did not improve insulin-stimulated glucose uptake. Increased cytokine expression driven by increased p38 MAPK activation is a key feature of cultured myotubes derived from insulin-resistant type 2 diabetic patients. p38 MAPK inhibition decreased cytokine expression but did not affect...

  9. Psychological insulin resistance in type 2 diabetes patients regarding oral antidiabetes treatment, subcutaneous insulin injections, or inhaled insulin.

    Science.gov (United States)

    Petrak, Frank; Herpertz, Stephan; Stridde, Elmar; Pfützner, Andreas

    2013-08-01

    "Psychological insulin resistance" (PIR) is an obstacle to insulin treatment in type 2 diabetes, and patients' expectations regarding alternative ways of insulin delivery are poorly understood. PIR and beliefs regarding treatment alternatives were analyzed in patients with type 2 diabetes (n=532; mean glycated hemoglobin, 68±12 mmol/mol [8.34±1.5%]) comparing oral antidiabetes treatment, subcutaneous insulin injections, or inhaled insulin. Questionnaires were used to assess barriers to insulin treatment (BIT), generic and diabetes-specific quality of life (Short Form 36 and Problem Areas in Diabetes, German version), diabetes knowledge, locus of control (Questionnaire for the Assessment of Diabetes-Specific Locus of Control, in German), coping styles (Freiburg Questionnaire of Illness Coping, 15-Items Short Form), self-esteem (Rosenberg Self-Esteem Scale, German version), and mental disorders (Patient Health Questionnaire, German version). Patients discussed treatment optimization options with a physician and were asked to make a choice about future diabetes therapy options in a two-step treatment choice scenario. Step 1 included oral antidiabetes drugs or subcutaneous insulin injection (SCI). Step 2 included an additional treatment alternative of inhaled insulin (INH). Subgroups were analyzed according to their treatment choice. Most patients perceived their own diabetes-related behavior as active, problem-focused, internally controlled, and oriented toward their doctors' recommendations, although their diabetes knowledge was limited. In Step 1, rejection of the recommended insulin was 82%, and in Step 2, it was 57%. Fear of hypoglycemia was the most important barrier to insulin treatment. Patients choosing INH (versus SCI) scored higher regarding fear of injection, expected hardship from insulin therapy, and BIT-Sumscore. The acceptance of insulin is very low in type 2 diabetes patients. The option to inhale insulin increases the acceptability for some but

  10. Drosophila insulin and target of rapamycin (TOR pathways regulate GSK3 beta activity to control Myc stability and determine Myc expression in vivo

    Directory of Open Access Journals (Sweden)

    Parisi Federica

    2011-09-01

    Full Text Available Abstract Background Genetic studies in Drosophila melanogaster reveal an important role for Myc in controlling growth. Similar studies have also shown how components of the insulin and target of rapamycin (TOR pathways are key regulators of growth. Despite a few suggestions that Myc transcriptional activity lies downstream of these pathways, a molecular mechanism linking these signaling pathways to Myc has not been clearly described. Using biochemical and genetic approaches we tried to identify novel mechanisms that control Myc activity upon activation of insulin and TOR signaling pathways. Results Our biochemical studies show that insulin induces Myc protein accumulation in Drosophila S2 cells, which correlates with a decrease in the activity of glycogen synthase kinase 3-beta (GSK3β a kinase that is responsible for Myc protein degradation. Induction of Myc by insulin is inhibited by the presence of the TOR inhibitor rapamycin, suggesting that insulin-induced Myc protein accumulation depends on the activation of TOR complex 1. Treatment with amino acids that directly activate the TOR pathway results in Myc protein accumulation, which also depends on the ability of S6K kinase to inhibit GSK3β activity. Myc upregulation by insulin and TOR pathways is a mechanism conserved in cells from the wing imaginal disc, where expression of Dp110 and Rheb also induces Myc protein accumulation, while inhibition of insulin and TOR pathways result in the opposite effect. Our functional analysis, aimed at quantifying the relative contribution of Myc to ommatidial growth downstream of insulin and TOR pathways, revealed that Myc activity is necessary to sustain the proliferation of cells from the ommatidia upon Dp110 expression, while its contribution downstream of TOR is significant to control the size of the ommatidia. Conclusions Our study presents novel evidence that Myc activity acts downstream of insulin and TOR pathways to control growth in Drosophila. At

  11. Drosophila insulin and target of rapamycin (TOR) pathways regulate GSK3 beta activity to control Myc stability and determine Myc expression in vivo.

    Science.gov (United States)

    Parisi, Federica; Riccardo, Sara; Daniel, Margaret; Saqcena, Mahesh; Kundu, Nandini; Pession, Annalisa; Grifoni, Daniela; Stocker, Hugo; Tabak, Esteban; Bellosta, Paola

    2011-09-27

    Genetic studies in Drosophila melanogaster reveal an important role for Myc in controlling growth. Similar studies have also shown how components of the insulin and target of rapamycin (TOR) pathways are key regulators of growth. Despite a few suggestions that Myc transcriptional activity lies downstream of these pathways, a molecular mechanism linking these signaling pathways to Myc has not been clearly described. Using biochemical and genetic approaches we tried to identify novel mechanisms that control Myc activity upon activation of insulin and TOR signaling pathways. Our biochemical studies show that insulin induces Myc protein accumulation in Drosophila S2 cells, which correlates with a decrease in the activity of glycogen synthase kinase 3-beta (GSK3β ) a kinase that is responsible for Myc protein degradation. Induction of Myc by insulin is inhibited by the presence of the TOR inhibitor rapamycin, suggesting that insulin-induced Myc protein accumulation depends on the activation of TOR complex 1. Treatment with amino acids that directly activate the TOR pathway results in Myc protein accumulation, which also depends on the ability of S6K kinase to inhibit GSK3β activity. Myc upregulation by insulin and TOR pathways is a mechanism conserved in cells from the wing imaginal disc, where expression of Dp110 and Rheb also induces Myc protein accumulation, while inhibition of insulin and TOR pathways result in the opposite effect. Our functional analysis, aimed at quantifying the relative contribution of Myc to ommatidial growth downstream of insulin and TOR pathways, revealed that Myc activity is necessary to sustain the proliferation of cells from the ommatidia upon Dp110 expression, while its contribution downstream of TOR is significant to control the size of the ommatidia. Our study presents novel evidence that Myc activity acts downstream of insulin and TOR pathways to control growth in Drosophila. At the biochemical level we found that both these pathways

  12. Insulin/insulin like growth factors in cancer: new roles for the aryl hydrocarbon receptor, tumor resistance mechanisms and new blocking strategies

    Directory of Open Access Journals (Sweden)

    Travis B Salisbury

    2015-02-01

    Full Text Available The insulin-like growth factor 1 receptor (IGF1R and the insulin receptor (IR are receptor tyrosine kinases (RTKs that are expressed in cancer cells. The results of different studies indicate that tumor proliferation and survival is dependent on the IGF1R and IR, and that their inhibition leads to reductions in proliferation and increases in cell death. Molecular targeting therapies that have been used in solid tumors include: anti-IGF1R antibodies, anti-IGF1/IGF2 antibodies and small molecule inhibitors that suppress IGF1R and IR kinase activity. New advances in the molecular basis of anti-IGF1R blocking antibodies reveal they are biased agonists and promote the binding of IGF1 to integrin β3 receptors in some cancer cells. Our recent reports indicate that pharmacological aryl hydrocarbon receptor (AHR ligands inhibit breast cancer cell responses to IGFs, suggesting that targeting AHR may have benefit in cancers whose proliferation and survival are dependent on insulin/IGF signaling. Novel aspects of IGF1R/IR in cancer, such as biased agonism, integrin β3 signaling, AHR and new therapeutic targeting strategies will be discussed.

  13. Current understanding of increased insulin sensitivity after exercise - emerging candidates

    DEFF Research Database (Denmark)

    Maarbjerg, Stine Just; Sylow, Lykke; Richter, Erik

    2011-01-01

    signaling component in the insulin signaling pathway such as aPKC, Rac1, TBC1D4 and TBC1D1 have been described. These are all affected by both insulin and exercise which means that they are likely converging points in promoting GLUT4 translocation and therefore possible candidates for regulating insulin...... sensitivity after exercise. Whereas TBC1D1 does not appear to regulate insulin sensitivity after exercise, correlative evidence in contrast suggests TBC1D4 to be a relevant candidate. Little is known about aPKC and Rac1 in relation to insulin sensitivity after exercise. Besides mechanisms involved...

  14. Data describing the effect of DRD4 promoter polymorphisms on promoter activity

    Directory of Open Access Journals (Sweden)

    Shoin Tei

    2016-06-01

    Full Text Available This data article tested whether polymorphisms within the dopamine D4 receptor (DRD4 gene promoter can lead to differences in the promoter activity. The variants, a 120-bp variable number tandem repeat (VNTR, −906 T/C, −809 G/A, −616G/C, and −521C/T, were introduced into the DRD4 promoter and the promoter activity was measured in a neural cell line using the luciferase assay. However, no differences were detected among the haplotypes investigated, and the in vitro data obtained from our protocol could not support the involvement of DRD4 promoter polymorphisms in heritable human traits.

  15. Insulin-secretagogue activity and cytoprotective role of the traditional antidiabetic plant Scoparia dulcis (Sweet Broomweed).

    Science.gov (United States)

    Latha, Muniappan; Pari, Leelavinothan; Sitasawad, Sandhya; Bhonde, Ramesh

    2004-09-03

    Scoparia dulcis (Sweet Broomweed) has been documented as a traditional treatment of diabetes. The administration of an aqueous extract of Scoparia dulcis at a dose of 200 mg/kg body weight significantly decreased the blood glucose with significant increase in plasma insulin level in streptozotocin diabetic rats at the end of 15 days treatment. The insulin secretagogue action of Scoparia dulcis plant extract (SPEt) was further investigated using isolated pancreatic islets from mice. SPEt at a dose of 10 microg/ml evoked 6.0 fold stimulation of insulin secretion from isolated islets indicating its insulin secretagogue activity. In addition the effect of SPEt on streptozotocin induced cell death and nitric oxide (NO) in terms of nitrite production were also examined. SPEt protected against streptozotocin- mediated cytotoxicity (88%) and NO production in rat insulinoma cell line (RINm5F). Above results suggest the glucose lowering effect of SPEt to be associated with potentiation of insulin release from pancreatic islets. Our results revealed the possible therapeutic value of Scoparia dulcis for the better control, management and prevention of diabetes mellitus progression.

  16. The inability of phosphatidylinositol 3-kinase activation to stimulate GLUT4 translocation indicates additional signaling pathways are required for insulin-stimulated glucose uptake.

    Science.gov (United States)

    Isakoff, S J; Taha, C; Rose, E; Marcusohn, J; Klip, A; Skolnik, E Y

    1995-10-24

    Recent experimental evidence has focused attention to the role of two molecules, insulin receptor substrate 1 (IRS-1) and phosphatidylinositol 3-kinase (PI3-kinase), in linking the insulin receptor to glucose uptake; IRS-1 knockout mice are insulin resistant, and pharmacological inhibitors of PI3-kinase block insulin-stimulated glucose uptake. To investigate the role of PI3-kinase and IRS-1 in insulin-stimulated glucose uptake we examined whether stimulation of insulin-sensitive cells with platelet-derived growth factor (PDGF) or with interleukin 4 (IL-4) stimulates glucose uptake; the activated PDGF receptor (PDGFR) directly binds and activates PI3-kinase, whereas the IL-4 receptor (IL-4R) activates PI3-kinase via IRS-1 or the IRS-1-related molecule 4PS. We found that stimulation of 3T3-L1 adipocytes with PDGF resulted in tyrosine phosphorylation of the PDGFR and activation of PI3-kinase in these cells. To examine whether IL-4 stimulates glucose uptake, L6 myoblasts were engineered to overexpress GLUT4 as well as both chains of the IL-4R (L6/IL-4R/GLUT4); when these L6/IL-4R/GLUT4 myoblasts were stimulated with IL-4, IRS-1 became tyrosine phosphorylated and associated with PI3-kinase. Although PDGF and IL-4 can activate PI3-kinase in the respective cell lines, they do not possess insulin's ability to stimulate glucose uptake and GLUT4 translocation to the plasma membrane. These findings indicate that activation of PI3-kinase is not sufficient to stimulate GLUT4 translocation to the plasma membrane. We postulate that activation of a second signaling pathway by insulin, distinct from PI3-kinase, is necessary for the stimulation of glucose uptake in insulin-sensitive cells.

  17. Rac1 Activation Caused by Membrane Translocation of a Guanine Nucleotide Exchange Factor in Akt2-Mediated Insulin Signaling in Mouse Skeletal Muscle.

    Directory of Open Access Journals (Sweden)

    Nobuyuki Takenaka

    Full Text Available Insulin-stimulated glucose uptake in skeletal muscle is mediated by the glucose transporter GLUT4, which is translocated to the plasma membrane following insulin stimulation. Several lines of evidence suggested that the protein kinase Akt2 plays a key role in this insulin action. The small GTPase Rac1 has also been implicated as a regulator of insulin-stimulated GLUT4 translocation, acting downstream of Akt2. However, the mechanisms whereby Akt2 regulates Rac1 activity remain obscure. The guanine nucleotide exchange factor FLJ00068 has been identified as a direct regulator of Rac1 in Akt2-mediated signaling, but its characterization was performed mostly in cultured myoblasts. Here, we provide in vivo evidence that FLJ00068 indeed acts downstream of Akt2 as a Rac1 regulator by using mouse skeletal muscle. Small interfering RNA knockdown of FLJ00068 markedly diminished GLUT4 translocation to the sarcolemma following insulin administration or ectopic expression of a constitutively activated mutant of either phosphoinositide 3-kinase or Akt2. Additionally, insulin and these constitutively activated mutants caused the activation of Rac1 as shown by immunofluorescent microscopy using a polypeptide probe specific to activated Rac1 in isolated gastrocnemius muscle fibers and frozen sections of gastrocnemius muscle. This Rac1 activation was also abrogated by FLJ00068 knockdown. Furthermore, we observed translocation of FLJ00068 to the cell periphery following insulin stimulation in cultured myoblasts. Localization of FLJ00068 in the plasma membrane in insulin-stimulated, but not unstimulated, myoblasts and mouse gastrocnemius muscle was further affirmed by subcellular fractionation and subsequent immunoblotting. Collectively, these results strongly support a critical role of FLJ00068 in Akt2-mediated Rac1 activation in mouse skeletal muscle insulin signaling.

  18. Studies on insulin receptor, 1

    International Nuclear Information System (INIS)

    Sakai, Yukio

    1979-01-01

    The present study was designed for the purpose of establishing a method of insulin radioreceptor assay using plasma membranes of guinea pigs as receptor sites. The results obtained are as follows: 1) Insulin receptor in the renal plasma membranes of guinea pigs showed a significantly high affinity to porcine insulin compared with that in the plasma membranes of guinea pig liver or rat kidney and liver. 2) In the insulin radioreceptor assay, an optimum condition was observed by the incubation at 4 0 C for 24 - 48 hours with 100 μg membrane protein of guinea pig kidney and 0.08 ng of 125 I-insulin. This assay method was specific for insulin and showed an accurate biological activity of insulin. 3) The recovery rate of insulin radioreceptor assay was 98.4% and dilution check up to 16 times did not influence on the result. An average of coefficient variation was 3.92% within assay. All of these results indicated the method to be satisfactory. 4) Glucose induced insulin release by perfusion method in isolated Langerhans islets of rats showed an identical pattern of reaction curves between radioreceptor assay and radioimmunoassay, although the values of radioreceptor assay was slightly low. 5) Insulin free serum produced by ultra filtration method was added to the standard assay medium. By this procedure, direct measurement of human serum by radioreceptor assay became possible. 6) The value of human serum insulin receptor binding activity by the radioreceptor assay showed a high correlation with that of insulin radioimmunoassay in sera of normal, borderline or diabetic type defined by glucose tolerance test. (author)

  19. Insulin stimulates the expression of the SHARP-1 gene via multiple signaling pathways.

    Science.gov (United States)

    Takagi, K; Asano, K; Haneishi, A; Ono, M; Komatsu, Y; Yamamoto, T; Tanaka, T; Ueno, H; Ogawa, W; Tomita, K; Noguchi, T; Yamada, K

    2014-06-01

    The rat enhancer of split- and hairy-related protein-1 (SHARP-1) is a basic helix-loop-helix transcription factor. An issue of whether SHARP-1 is an insulin-inducible transcription factor was examined. Insulin rapidly increased the level of SHARP-1 mRNA both in vivo and in vitro. Then, signaling pathways involved with the increase of SHARP-1 mRNA by insulin were determined in H4IIE rat hepatoma cells. Pretreatments with LY294002, wortmannin, and staurosporine completely blocked the induction effect, suggesting the involvement of both phosphoinositide 3-kinase (PI 3-K) and protein kinase C (PKC) pathways. In fact, overexpression of a dominant negative form of atypical protein kinase C lambda (aPKCλ) significantly decreased the induction of the SHARP-1 mRNA. In addition, inhibitors for the small GTPase Rac or Jun N-terminal kinase (JNK) also blocked the induction of SHARP-1 mRNA by insulin. Overexpression of a dominant negative form of Rac1 prevented the activation by insulin. Furthermore, actinomycin D and cycloheximide completely blocked the induction of SHARP-1 mRNA by insulin. Finally, when a SHARP-1 expression plasmid was transiently transfected with various reporter plasmids into H4IIE cells, the promoter activity of PEPCK reporter plasmid was specifically decreased. Thus, we conclude that insulin induces the SHARP-1 gene expression at the transcription level via a both PI 3-K/aPKCλ/JNK- and a PI 3-K/Rac/JNK-signaling pathway; protein synthesis is required for this induction; and that SHARP-1 is a potential repressor of the PEPCK gene expression. © Georg Thieme Verlag KG Stuttgart · New York.

  20. Evaluation of insulin expression and secretion in genetically engineered gut K and L-cells

    Directory of Open Access Journals (Sweden)

    Ahmad Zalinah

    2012-09-01

    Full Text Available Abstract Background Gene therapy could provide an effective treatment of diabetes. Previous studies have investigated the potential for several cell and tissue types to produce mature and active insulin. Gut K and L-cells could be potential candidate hosts for gene therapy because of their special features. Results In this study, we isolated gut K and L-cells to compare the potential of both cell types to produce insulin when exposed to similar conditions. The isolated pure K and L-cells were transfected with recombinant plasmids encoding insulin and with specific promoters for K or L-cells. Insulin expression was studied in response to glucose or meat hydrolysate. We found that glucose and meat hydrolysate efficiently induced insulin secretion from K and L-cells. However, the effects of meat hydrolysate on insulin secretion were more potent in both cells compared with glucose. Results of enzyme-linked immunosorbent assays showed that L-cells secreted more insulin compared with K-cells regardless of the stimulator, although this difference was not statistically significant. Conclusion The responses of K and L-cells to stimulation with glucose or meat hydrolysate were generally comparable. Therefore, both K and L-cells show similar potential to be used as surrogate cells for insulin gene expression in vitro. The potential use of these cells for diabetic gene therapy warrants further investigation.

  1. TET1-GPER-PI3K/AKT pathway is involved in insulin-driven endometrial cancer cell proliferation

    International Nuclear Information System (INIS)

    Xie, Bing-ying; Lv, Qiao-ying; Ning, Cheng-cheng; Yang, Bing-yi; Shan, Wei-wei; Cheng, Ya-li; Gu, Chao; Luo, Xue-zhen; Zhang, Zhen-bo; Chen, Xiao-jun; Xi, Xiao-wei; Feng, You-ji

    2017-01-01

    Large amount of clinical evidence has demonstrated that insulin resistance is closely related to oncogenesis of endometrial cancer (EC). Despite recent studies showed the up-regulatory role of insulin in G protein-coupled estrogen receptor (GPER/GPR30) expression, GPER expression was not decreased compared to control when insulin receptor was blocked even in insulin treatment. The purpose of this study was to explore the possible mechanism by which insulin up-regulates GPER that drives EC cell proliferation. For this purpose, we first investigated the GPER expression in tissues of endometrial lesions, further explored the effect of GPER on EC cell proliferation in insulin resistance context. Then we analyzed the role of Ten-Eleven Translocation 1 (TET1) in insulin-induced GEPR expression and EC cell proliferation. The results showed that GPER was highly expressed in endometrial atypical hyperplasia and EC tissues. Mechanistically, insulin up-regulated TET1 expression and the latter played an important role in up-regulating GPER expression and activating PI3K/AKT signaling pathway. TET1 mediated GPER up-regulation was another mechanism that insulin promotes EC cell proliferation. - Highlights: • GPER acts as an oncogene to drive EC cell growth in insulin resistance context. • TET1 is associated with insulin-induced GPER expression. • Insulin resistance contributed to EC through TET1-GPER-PI3K/AKT pathway.

  2. Activation of SF1 Neurons in the Ventromedial Hypothalamus by DREADD Technology Increases Insulin Sensitivity in Peripheral Tissues.

    Science.gov (United States)

    Coutinho, Eulalia A; Okamoto, Shiki; Ishikawa, Ayako Wendy; Yokota, Shigefumi; Wada, Nobuhiro; Hirabayashi, Takahiro; Saito, Kumiko; Sato, Tatsuya; Takagi, Kazuyo; Wang, Chen-Chi; Kobayashi, Kenta; Ogawa, Yoshihiro; Shioda, Seiji; Yoshimura, Yumiko; Minokoshi, Yasuhiko

    2017-09-01

    The ventromedial hypothalamus (VMH) regulates glucose and energy metabolism in mammals. Optogenetic stimulation of VMH neurons that express steroidogenic factor 1 (SF1) induces hyperglycemia. However, leptin acting via the VMH stimulates whole-body glucose utilization and insulin sensitivity in some peripheral tissues, and this effect of leptin appears to be mediated by SF1 neurons. We examined the effects of activation of SF1 neurons with DREADD (designer receptors exclusively activated by designer drugs) technology. Activation of SF1 neurons by an intraperitoneal injection of clozapine- N -oxide (CNO), a specific hM3Dq ligand, reduced food intake and increased energy expenditure in mice expressing hM3Dq in SF1 neurons. It also increased whole-body glucose utilization and glucose uptake in red-type skeletal muscle, heart, and interscapular brown adipose tissue, as well as glucose production and glycogen phosphorylase a activity in the liver, thereby maintaining blood glucose levels. During hyperinsulinemic-euglycemic clamp, such activation of SF1 neurons increased insulin-induced glucose uptake in the same peripheral tissues and tended to enhance insulin-induced suppression of glucose production by suppressing gluconeogenic gene expression and glycogen phosphorylase a activity in the liver. DREADD technology is thus an important tool for studies of the role of the brain in the regulation of insulin sensitivity in peripheral tissues. © 2017 by the American Diabetes Association.

  3. Interactive roles of Ras, insulin receptor substrate-1, and proteins with Src homology-2 domains in insulin signaling in Xenopus oocytes.

    Science.gov (United States)

    Chuang, L M; Hausdorff, S F; Myers, M G; White, M F; Birnbaum, M J; Kahn, C R

    1994-11-04

    Insulin receptor substrate-1 (IRS-1) serves as the major immediate substrate of insulin/insulin-like growth factor (IGF)-1 receptors and following tyrosine phosphorylation binds to specific Src homology-2 (SH2) domain-containing proteins including the p85 subunit of phosphatidylinositol (PI) 3-kinase and GRB2, a molecule believed to link IRS-1 to the Ras pathway. To investigate how these SH2-containing signaling molecules interact to regulate insulin/IGF-1 action, IRS-1, glutathione S-transferase (GST)-SH2 domain fusion proteins and Ras proteins were microinjected into Xenopus oocytes. We found that pleiotropic insulin actions are mediated by IRS-1 through two independent, but convergent, pathways involving PI 3-kinase and GRB2. Thus, microinjection of GST-fusion proteins of either p85 or GRB2 inhibited IRS-1-dependent activation of mitogen-activated protein (MAP) and S6 kinases and oocyte maturation, although only the GST-SH2 of p85 reduced insulin-stimulated PI 3-kinase activation. Co-injection of a dominant negative Ras (S17N) with IRS-1 inhibited insulin-stimulated MAP and S6 kinase activation. Micro-injection of activated [Arg12,Thr59]Ras increased basal MAP and S6 kinase activities and sensitized the oocytes to insulin-stimulated maturation without altering insulin-stimulated PI 3-kinase. The Ras-enhanced oocyte maturation response, but not the elevated basal level of MAP and S6 kinase, was partially blocked by the SH2-p85, but not SH2-GRB2. These data strongly suggest that IRS-1 can mediate many of insulin's actions on cellular enzyme activation and cell cycle progression requires binding and activation of multiple different SH2-domain proteins.

  4. Interleukin-Driven Insulin-Like Growth Factor Promotes Prostatic Inflammatory Hyperplasia

    Science.gov (United States)

    Hahn, Alana M.; Myers, Jason D.; McFarland, Eliza K.; Lee, Sanghee

    2014-01-01

    Prostatic inflammation is of considerable importance to urologic research because of its association with benign prostatic hyperplasia and prostate cancer. However, the mechanisms by which inflammation leads to proliferation and growth remain obscure. Here, we show that insulin-like growth factors (IGFs), previously known as critical developmental growth factors during prostate organogenesis, are induced by inflammation as part of the proliferative recovery to inflammation. Using genetic models and in vivo IGF receptor blockade, we demonstrate that the hyperplastic response to inflammation depends on interleukin-1–driven IGF signaling. We show that human prostatic hyperplasia is associated with IGF pathway activation specifically localized to foci of inflammation. This demonstrates that mechanisms of inflammation-induced epithelial proliferation and hyperplasia involve the induction of developmental growth factors, further establishing a link between inflammatory and developmental signals and providing a mechanistic basis for the management of proliferative diseases by IGF pathway modulation. PMID:25292180

  5. Nature and regulation of the insulin receptor: structure and function

    International Nuclear Information System (INIS)

    Czech, M.P.

    1985-01-01

    Native, cell-surface insulin receptor consists of two glycoprotein subunit types with apparent masses of about 125,000 daltons (alpha subunit) and 90,000 daltons (beta subunit). The alpha and beta insulin-receptor subunits seem to have distinct functions such that alpha appears to bind hormone whereas beta appears to possess intrinsic tyrosine kinase activity. In detergent extracts, insulin activates receptor autophosphorylation of tyrosine residues on its beta subunit, whereas in the presence of reductant, the alpha subunit is also phosphorylated. In intact cells, insulin activates serine/threonine phosphorylation of insulin receptor beta subunit as well as tyrosine phosphorylation. The biological role of the receptor-associated tyrosine kinase is not known. The insulin receptor kinase is regulated by beta-adrenergic agonists and other agents that elevate cAMP in adipocytes, presumably via the cAMP-dependent protein kinase. Such agents decrease receptor affinity for insulin and partially uncouple receptor tyrosine kinase activity from activation by insulin. These effects appear to contribute to the biological antagonism between insulin and beta-agonists. These data suggest the hypothesis that a complex network of tyrosine and serine/threonine phosphorylations on the insulin receptor modulate its binding and kinase activities in an antagonistic manner

  6. G protein-coupled receptors (GPCRs) That Signal via Protein Kinase A (PKA) Cross-talk at Insulin Receptor Substrate 1 (IRS1) to Activate the phosphatidylinositol 3-kinase (PI3K)/AKT Pathway.

    Science.gov (United States)

    Law, Nathan C; White, Morris F; Hunzicker-Dunn, Mary E

    2016-12-30

    G protein-coupled receptors (GPCRs) activate PI3K/v-AKT thymoma viral oncoprotein (AKT) to regulate many cellular functions that promote cell survival, proliferation, and growth. However, the mechanism by which GPCRs activate PI3K/AKT remains poorly understood. We used ovarian preantral granulosa cells (GCs) to elucidate the mechanism by which the GPCR agonist FSH via PKA activates the PI3K/AKT cascade. Insulin-like growth factor 1 (IGF1) is secreted in an autocrine/paracrine manner by GCs and activates the IGF1 receptor (IGF1R) but, in the absence of FSH, fails to stimulate YXXM phosphorylation of IRS1 (insulin receptor substrate 1) required for PI3K/AKT activation. We show that PKA directly phosphorylates the protein phosphatase 1 (PP1) regulatory subunit myosin phosphatase targeting subunit 1 (MYPT1) to activate PP1 associated with the IGF1R-IRS1 complex. Activated PP1 is sufficient to dephosphorylate at least four IRS1 Ser residues, Ser 318 , Ser 346 , Ser 612 , and Ser 789 , and promotes IRS1 YXXM phosphorylation by the IGF1R to activate the PI3K/AKT cascade. Additional experiments indicate that this mechanism also occurs in breast cancer, thyroid, and preovulatory granulosa cells, suggesting that the PKA-dependent dephosphorylation of IRS1 Ser/Thr residues is a conserved mechanism by which GPCRs signal to activate the PI3K/AKT pathway downstream of the IGF1R. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

  7. Insulin and Insulin-Sensitizing Drugs in Neurodegeneration: Mitochondria as Therapeutic Targets

    Directory of Open Access Journals (Sweden)

    Paula I. Moreira

    2009-12-01

    Full Text Available Insulin, besides its glucose lowering effects, is involved in the modulation of lifespan, aging and memory and learning processes. As the population ages, neurodegenerative disorders become epidemic and a connection between insulin signaling dysregulation, cognitive decline and dementia has been established. Mitochondria are intracellular organelles that despite playing a critical role in cellular metabolism are also one of the major sources of reactive oxygen species. Mitochondrial dysfunction, oxidative stress and neuroinflammation, hallmarks of neurodegeneration, can result from impaired insulin signaling. Insulin-sensitizing drugs such as the thiazolidinediones are a new class of synthetic compounds that potentiate insulin action in the target tissues and act as specific agonists of the peroxisome proliferator-activated receptor gamma (PPAR-γ. Recently, several PPAR agonists have been proposed as novel and possible therapeutic agents for neurodegenerative disorders. Indeed, the literature shows that these agents are able to protect against mitochondrial dysfunction, oxidative damage, inflammation and apoptosis. This review discusses the role of mitochondria and insulin signaling in normal brain function and in neurodegeneration. Furthermore, the potential protective role of insulin and insulin sensitizers in Alzheimer´s, Parkinson´s and Huntington´s diseases and amyotrophic lateral sclerosis will be also discussed.

  8. Dietary Sodium Restriction Decreases Insulin Secretion Without Affecting Insulin Sensitivity in Humans

    Science.gov (United States)

    Byrne, Loretta M.; Yu, Chang; Wang, Thomas J.; Brown, Nancy J.

    2014-01-01

    Context: Interruption of the renin-angiotensin-aldosterone system prevents incident diabetes in high-risk individuals, although the mechanism remains unclear. Objective: To test the hypothesis that activation of the endogenous renin-angiotensin-aldosterone system or exogenous aldosterone impairs insulin secretion in humans. Design: We conducted a randomized, blinded crossover study of aldosterone vs vehicle and compared the effects of a low-sodium versus a high-sodium diet. Setting: Academic clinical research center. Participants: Healthy, nondiabetic, normotensive volunteers. Interventions: Infusion of exogenous aldosterone (0.7 μg/kg/h for 12.5 h) or vehicle during low or high sodium intake. Low sodium (20 mmol/d; n = 12) vs high sodium (160 mmol/d; n = 17) intake for 5–7 days. Main Outcome Measures: Change in acute insulin secretory response assessed during hyperglycemic clamps while in sodium balance during a low-sodium vs high-sodium diet during aldosterone vs vehicle. Results: A low-sodium diet increased endogenous aldosterone and plasma renin activity, and acute glucose-stimulated insulin (−16.0 ± 5.6%; P = .007) and C-peptide responses (−21.8 ± 8.4%; P = .014) were decreased, whereas the insulin sensitivity index was unchanged (−1.0 ± 10.7%; P = .98). Aldosterone infusion did not affect the acute insulin response (+1.8 ± 4.8%; P = .72) or insulin sensitivity index (+2.0 ± 8.8%; P = .78). Systolic blood pressure and serum potassium were similar during low and high sodium intake and during aldosterone infusion. Conclusions: Low dietary sodium intake reduces insulin secretion in humans, independent of insulin sensitivity. PMID:25029426

  9. Suppression of Ghrelin Exacerbates HFCS-Induced Adiposity and Insulin Resistance.

    Science.gov (United States)

    Ma, Xiaojun; Lin, Ligen; Yue, Jing; Wu, Chia-Shan; Guo, Cathy A; Wang, Ruitao; Yu, Kai-Jiang; Devaraj, Sridevi; Murano, Peter; Chen, Zheng; Sun, Yuxiang

    2017-06-19

    High fructose corn syrup (HFCS) is widely used as sweetener in processed foods and soft drinks in the United States, largely substituting sucrose (SUC). The orexigenic hormone ghrelin promotes obesity and insulin resistance; ghrelin responds differently to HFCS and SUC ingestion. Here we investigated the roles of ghrelin in HFCS- and SUC-induced adiposity and insulin resistance. To mimic soft drinks, 10-week-old male wild-type (WT) and ghrelin knockout ( Ghrelin -/- ) mice were subjected to ad lib. regular chow diet supplemented with either water (RD), 8% HFCS (HFCS), or 10% sucrose (SUC). We found that SUC-feeding induced more robust increases in body weight and body fat than HFCS-feeding. Comparing to SUC-fed mice, HFCS-fed mice showed lower body weight but higher circulating glucose and insulin levels. Interestingly, we also found that ghrelin deletion exacerbates HFCS-induced adiposity and inflammation in adipose tissues, as well as whole-body insulin resistance. Our findings suggest that HFCS and SUC have differential effects on lipid metabolism: while sucrose promotes obesogenesis, HFCS primarily enhances inflammation and insulin resistance, and ghrelin confers protective effects for these metabolic dysfunctions.

  10. Suppression of Ghrelin Exacerbates HFCS-Induced Adiposity and Insulin Resistance

    Directory of Open Access Journals (Sweden)

    Xiaojun Ma

    2017-06-01

    Full Text Available High fructose corn syrup (HFCS is widely used as sweetener in processed foods and soft drinks in the United States, largely substituting sucrose (SUC. The orexigenic hormone ghrelin promotes obesity and insulin resistance; ghrelin responds differently to HFCS and SUC ingestion. Here we investigated the roles of ghrelin in HFCS- and SUC-induced adiposity and insulin resistance. To mimic soft drinks, 10-week-old male wild-type (WT and ghrelin knockout (Ghrelin−/− mice were subjected to ad lib. regular chow diet supplemented with either water (RD, 8% HFCS (HFCS, or 10% sucrose (SUC. We found that SUC-feeding induced more robust increases in body weight and body fat than HFCS-feeding. Comparing to SUC-fed mice, HFCS-fed mice showed lower body weight but higher circulating glucose and insulin levels. Interestingly, we also found that ghrelin deletion exacerbates HFCS-induced adiposity and inflammation in adipose tissues, as well as whole-body insulin resistance. Our findings suggest that HFCS and SUC have differential effects on lipid metabolism: while sucrose promotes obesogenesis, HFCS primarily enhances inflammation and insulin resistance, and ghrelin confers protective effects for these metabolic dysfunctions.

  11. The Evolution of Physical Activity Promotion.

    Science.gov (United States)

    Richards, Elizabeth Ann

    2015-08-01

    A physically active lifestyle has numerous physical and mental health benefits for patients of all ages. Despite these significant benefits, a majority of Americans do not meet current physical activity guidelines. Health care providers, especially nurses, play a vital role in physical activity promotion. Over the past several decades, exercise and physical activity guidelines have evolved from a focus on structured, vigorous exercise to a focus on moderate-intensity "lifestyle" physical activity. The author updates nurses on physical activity guidelines and provides tips for promoting physical activity, with a focus on lifestyle activities such as walking to work. This article also addresses new research findings on the importance of decreasing sedentary and sitting time, even in physically active people.

  12. Insulin effect on [14C]-valine incorporation and its relation to hexokinase activity in developing brain

    International Nuclear Information System (INIS)

    Pal, N.; Bessman, S.P.

    1988-01-01

    Using minced brain cortex from fetal and postnatal rats, we studied the incorporation of [ 14 C]-valine into protein in the presence of insulin. We also assayed the particle bound and soluble hexokinase in these tissues. Insulin significantly stimulated the incorporation of [ 14 C]-valine into brain proteins from fetal stage upto 2 days of life. After this period the insulin effect was minimal, with no effect by day 5. The particle bound (40,000g pellet) brain hexokinase, on the other hand, remained low till about 2 days of life and then increased to almost adult level by 5 days. Our results show that there is an inverse relation between this anabolic effect of insulin and the particle bound hexokinase activity in the cortex of developing rat brain

  13. Small Molecule Kaempferol Promotes Insulin Sensitivity and Preserved Pancreatic β-Cell Mass in Middle-Aged Obese Diabetic Mice

    Science.gov (United States)

    Alkhalidy, Hana; Moore, William; Zhang, Yanling; Wang, Aihua; Ali, Mostafa; Suh, Kyung-Shin; Zhen, Wei; Cheng, Zhiyong; Jia, Zhenquan; Hulver, Matthew

    2015-01-01

    Insulin resistance and a progressive decline in functional β-cell mass are hallmarks of developing type 2 diabetes (T2D). Thus, searching for natural, low-cost compounds to target these two defects could be a promising strategy to prevent the pathogenesis of T2D. Here, we show that dietary intake of flavonol kaempferol (0.05% in the diet) significantly ameliorated hyperglycemia, hyperinsulinemia, and circulating lipid profile, which were associated with the improved peripheral insulin sensitivity in middle-aged obese mice fed a high-fat (HF) diet. Kaempferol treatment reversed HF diet impaired glucose transport-4 (Glut4) and AMP-dependent protein kinase (AMPK) expression in both muscle and adipose tissues from obese mice. In vitro, kaempferol increased lipolysis and prevented high fatty acid-impaired glucose uptake, glycogen synthesis, AMPK activity, and Glut4 expression in skeletal muscle cells. Using another mouse model of T2D generated by HF diet feeding and low doses of streptozotocin injection, we found that kaempferol treatment significantly improved hyperglycemia, glucose tolerance, and blood insulin levels in obese diabetic mice, which are associated with the improved islet β-cell mass. These results demonstrate that kaempferol may be a naturally occurring anti-diabetic agent by improving peripheral insulin sensitivity and protecting against pancreatic β-cell dysfunction. PMID:26064984

  14. A novel cell growth-promoting factor identified in a B cell leukemia cell line, BALL-1

    International Nuclear Information System (INIS)

    Dao, T.; Holan, V.; Minowada, J.

    1993-01-01

    A novel leukemia cell growth-promoting activity has been identified in the culture supernatant from a human B cell leukemia cell line, BALL-1. The supernatant from unstimulated cultures of the BALL-1 cells significantly promoted the growth of 16 out of 24 leukemia/lymphoma cell lines of different lineages (T, B and non-lymphoid) in a minimal concentration of fetal bovine serum (FBS), and 5 out of 12 cases of fresh leukemia cells in FBS-free medium. The growth-promoting sieve filtration and dialysis. The MW of the factor was less than 10 kDa. The growth-promoting activity was heat and acid stable and resistant to trypsin treatment. The factor isolated from the BALL-1 supernatant was distinct from known polypeptide growth factors with MW below 10 kDa, such as epidermal growth factor, transforming growth factor α, insulin-like growth factor I (IGF-I), IGF-II and insulin, as determine by specific antibodies and by cell-growth-promoting tests. The factor is the BALL-1 supernatant did not promote the proliferation of normal human fresh peripheral blood lymphocytes or mouse fibroblast cell line, BALB/C 3T3. In addition to the BALL-1 supernatant, a similar growth-promoting activity was found in the culture supernatant from 13 of 17 leukemia/lymphoma cell lines tested. The activity in these culture supernatant promoted the growth of leukemia/lymphoma cell lines in autocrine and/or paracrine fashions. These observations suggest that the low MW cell growth-promoting activity found in the BALL-1 culture supernatant is mediated by a novel factor which may be responsible for the clonal expansion of particular leukemic clones. (author)

  15. Coordinated balancing of muscle oxidative metabolism through PGC-1{alpha} increases metabolic flexibility and preserves insulin sensitivity

    Energy Technology Data Exchange (ETDEWEB)

    Summermatter, Serge [Biozentrum, Division of Pharmacology/Neurobiology, University of Basel, Klingelbergstrasse 50-70, CH-4056 Basel (Switzerland); Troxler, Heinz [Division of Clinical Chemistry and Biochemistry, Department of Pediatrics, University Children' s Hospital, University of Zurich, Steinwiesstrasse 75, CH-8032 Zurich (Switzerland); Santos, Gesa [Biozentrum, Division of Pharmacology/Neurobiology, University of Basel, Klingelbergstrasse 50-70, CH-4056 Basel (Switzerland); Handschin, Christoph, E-mail: christoph.handschin@unibas.ch [Biozentrum, Division of Pharmacology/Neurobiology, University of Basel, Klingelbergstrasse 50-70, CH-4056 Basel (Switzerland)

    2011-04-29

    Highlights: {yields} PGC-1{alpha} enhances muscle oxidative capacity. {yields} PGC-1{alpha} promotes concomitantly positive and negative regulators of lipid oxidation. {yields} Regulator abundance enhances metabolic flexibility and balances oxidative metabolism. {yields} Balanced oxidation prevents detrimental acylcarnitine and ROS generation. {yields} Absence of detrimental metabolites preserves insulin sensitivity -- Abstract: The peroxisome proliferator-activated receptor {gamma} coactivator 1{alpha} (PGC-1{alpha}) enhances oxidative metabolism in skeletal muscle. Excessive lipid oxidation and electron transport chain activity can, however, lead to the accumulation of harmful metabolites and impair glucose homeostasis. Here, we investigated the effect of over-expression of PGC-1{alpha} on metabolic control and generation of insulin desensitizing agents in extensor digitorum longus (EDL), a muscle that exhibits low levels of PGC-1{alpha} in the untrained state and minimally relies on oxidative metabolism. We demonstrate that PGC-1{alpha} induces a strictly balanced substrate oxidation in EDL by concomitantly promoting the transcription of activators and inhibitors of lipid oxidation. Moreover, we show that PGC-1{alpha} enhances the potential to uncouple oxidative phosphorylation. Thereby, PGC-1{alpha} boosts elevated, yet tightly regulated oxidative metabolism devoid of side products that are detrimental for glucose homeostasis. Accordingly, PI3K activity, an early phase marker for insulin resistance, is preserved in EDL muscle. Our findings suggest that PGC-1{alpha} coordinately coactivates the simultaneous transcription of gene clusters implicated in the positive and negative regulation of oxidative metabolism and thereby increases metabolic flexibility. Thus, in mice fed a normal chow diet, over-expression of PGC-1{alpha} does not alter insulin sensitivity and the metabolic adaptations elicited by PGC-1{alpha} mimic the beneficial effects of endurance training

  16. Coordinated balancing of muscle oxidative metabolism through PGC-1α increases metabolic flexibility and preserves insulin sensitivity

    International Nuclear Information System (INIS)

    Summermatter, Serge; Troxler, Heinz; Santos, Gesa; Handschin, Christoph

    2011-01-01

    Highlights: → PGC-1α enhances muscle oxidative capacity. → PGC-1α promotes concomitantly positive and negative regulators of lipid oxidation. → Regulator abundance enhances metabolic flexibility and balances oxidative metabolism. → Balanced oxidation prevents detrimental acylcarnitine and ROS generation. → Absence of detrimental metabolites preserves insulin sensitivity -- Abstract: The peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) enhances oxidative metabolism in skeletal muscle. Excessive lipid oxidation and electron transport chain activity can, however, lead to the accumulation of harmful metabolites and impair glucose homeostasis. Here, we investigated the effect of over-expression of PGC-1α on metabolic control and generation of insulin desensitizing agents in extensor digitorum longus (EDL), a muscle that exhibits low levels of PGC-1α in the untrained state and minimally relies on oxidative metabolism. We demonstrate that PGC-1α induces a strictly balanced substrate oxidation in EDL by concomitantly promoting the transcription of activators and inhibitors of lipid oxidation. Moreover, we show that PGC-1α enhances the potential to uncouple oxidative phosphorylation. Thereby, PGC-1α boosts elevated, yet tightly regulated oxidative metabolism devoid of side products that are detrimental for glucose homeostasis. Accordingly, PI3K activity, an early phase marker for insulin resistance, is preserved in EDL muscle. Our findings suggest that PGC-1α coordinately coactivates the simultaneous transcription of gene clusters implicated in the positive and negative regulation of oxidative metabolism and thereby increases metabolic flexibility. Thus, in mice fed a normal chow diet, over-expression of PGC-1α does not alter insulin sensitivity and the metabolic adaptations elicited by PGC-1α mimic the beneficial effects of endurance training on muscle metabolism in this context.

  17. Comparison on hypoglycemic and antioxidant activities of the fresh and dried Portulaca oleracea L. in insulin-resistant HepG2 cells and streptozotocin-induced C57BL/6J diabetic mice.

    Science.gov (United States)

    Gu, Jun-Fei; Zheng, Zhi-Yin; Yuan, Jia-Rui; Zhao, Bing-Jie; Wang, Chun-Fei; Zhang, Li; Xu, Qing-Yu; Yin, Guo-Wen; Feng, Liang; Jia, Xiao-Bin

    2015-02-23

    Fresh Portulaca oleracea L. (family: Portulacaceae; POL) has been used as a folk medicine for the treatment of diabetes mellitus for a long time. More bioactive components with higher activity could be retained in fresh medicinal herbs compared to the dried ones. The present study was conducted to compare different antidiabetic activity between fresh and dried POL, including hypoglycemic and antioxidant activities both in vivo and in vitro. Furthermore, in order to explore which components were responsible for the antidiabetic activity, the difference on chemical components between fresh and dried POL was analyzed and compared. Insulin-resistant HepG2 cells induced by insulin were used to evaluate the promoting effect of the fresh and dried POL on glucose utilization in vitro. Streptozotocin (STZ)-induced C57BL/6J diabetic mice were used to compare the differences on hypoglycemic and antioxidant activities of fresh and dried POL, including the fasting blood glucose, glucose tolerance, serum insulin level, malondialdehyde (MDA) level and superoxide dismutase (SOD) activity in vivo. UPLC/Q-TOF-MS method was performed to analyze the difference of antidiabetic components between fresh and dried POL. Compared with the dried POL extract, the fresh POL extract significantly increased the consumption of extracellular glucose in insulin-resistant HepG2 cells (P<0.05). In STZ-induced C57BL/6J diabetic mice, both fresh and dried extracts decreased markedly the fasting blood glucose (FBG) levels, and improved significantly oral glucose tolerance test (OGTT), as well as enhanced significantly insulin secretion and antioxidative activities (P<0.05; P<0.01). Furthermore, the fresh extract showed stronger antidiabetic activity (P<0.05). The UPLC/Q-TOF-MS analysis results also revealed that the relative contents of polyphenols and alkaloids in the fresh herbs were more abundant than those in the dried POL. Our results indicated that both fresh and dried POL possessed antidiabetic

  18. Sequence-specific 1H-NMR assignments for the aromatic region of several biologically active, monomeric insulins including native human insulin.

    Science.gov (United States)

    Roy, M; Lee, R W; Kaarsholm, N C; Thøgersen, H; Brange, J; Dunn, M F

    1990-06-12

    The aromatic region of the 1H-FT-NMR spectrum of the biologically fully-potent, monomeric human insulin mutant, B9 Ser----Asp, B27 Thr----Glu has been investigated in D2O. At 1 to 5 mM concentrations, this mutant insulin is monomeric above pH 7.5. Coupling and amino acid classification of all aromatic signals is established via a combination of homonuclear one- and two-dimensional methods, including COSY, multiple quantum filters, selective spin decoupling and pH titrations. By comparisons with other insulin mutants and with chemically modified native insulins, all resonances in the aromatic region are given sequence-specific assignments without any reliance on the various crystal structures reported for insulin. These comparisons also give the sequence-specific assignments of most of the aromatic resonances of the mutant insulins B16 Tyr----Glu, B27 Thr----Glu and B25 Phe----Asp and the chemically modified species des-(B23-B30) insulin and monoiodo-Tyr A14 insulin. Chemical dispersion of the assigned resonances, ring current perturbations and comparisons at high pH have made possible the assignment of the aromatic resonances of human insulin, and these studies indicate that the major structural features of the human insulin monomer (including those critical to biological function) are also present in the monomeric mutant.

  19. AMPK and insulin action

    DEFF Research Database (Denmark)

    Frøsig, Christian; Jensen, Thomas Elbenhardt; Jeppesen, Jacob

    2013-01-01

    The 5'-AMP-activated protein kinase (AMPK) is considered "a metabolic master-switch" in skeletal muscle reducing ATP- consuming processes whilst stimulating ATP regeneration. Within recent years, AMPK has also been proposed as a potential target to attenuate insulin resistance, although the exact...... role of AMPK is not well understood. Here we hypothesized that mice lacking a2AMPK activity in muscle would be more susceptible to develop insulin resistance associated with ageing alone or in combination with high fat diet. Young (~4 month) or old (~18 month) wild type and muscle specific a2AMPK...... kinase-dead mice on chow diet as well as old mice on 17 weeks of high fat diet were studied for whole body glucose homeostasis (OGTT, ITT and HOMA-IR), insulin signaling and insulin-stimulated glucose uptake in muscle. We demonstrate that high fat diet in old mice results in impaired glucose homeostasis...

  20. Adipocyte-specific blockade of gamma-secretase, but not inhibition of Notch activity, reduces adipose insulin sensitivity

    Directory of Open Access Journals (Sweden)

    David P. Sparling

    2016-02-01

    Full Text Available Objective: As the obesity pandemic continues to expand, novel molecular targets to reduce obesity-related insulin resistance and Type 2 Diabetes (T2D continue to be needed. We have recently shown that obesity is associated with reactivated liver Notch signaling, which, in turn, increases hepatic insulin resistance, opening up therapeutic avenues for Notch inhibitors to be repurposed for T2D. Herein, we tested the systemic effects of γ-secretase inhibitors (GSIs, which prevent endogenous Notch activation, and confirmed these effects through creation and characterization of two different adipocyte-specific Notch loss-of-function mouse models through genetic ablation of the Notch transcriptional effector Rbp-Jk (A-Rbpj and the obligate γ-secretase component Nicastrin (A-Nicastrin. Methods: Glucose homeostasis and both local adipose and systemic insulin sensitivity were examined in GSI-treated, A-Rbpj and A-Nicastrin mice, as well as vehicle-treated or control littermates, with complementary in vitro studies in primary hepatocytes and 3T3-L1 adipocytes. Results: GSI-treatment increases hepatic insulin sensitivity in obese mice but leads to reciprocal lowering of adipose glucose disposal. While A-Rbpj mice show normal body weight, adipose development and mass and unchanged adipose insulin sensitivity as control littermates, A-Nicastrin mice are relatively insulin-resistant, mirroring the GSI effect on adipose insulin action. Conclusions: Notch signaling is dispensable for normal adipocyte function, but adipocyte-specific γ-secretase blockade reduces adipose insulin sensitivity, suggesting that specific Notch inhibitors would be preferable to GSIs for application in T2D. Keywords: Notch, γ-secretase complex, Insulin resistance

  1. Loss of insulin-induced activation of TRPM6 magnesium channels results in impaired glucose tolerance during pregnancy

    Science.gov (United States)

    Nair, Anil V.; Hocher, Berthold; Verkaart, Sjoerd; van Zeeland, Femke; Pfab, Thiemo; Slowinski, Torsten; Chen, You-Peng; Schlingmann, Karl Peter; Schaller, André; Gallati, Sabina; Bindels, René J.; Konrad, Martin; Hoenderop, Joost G.

    2012-01-01

    Hypomagnesemia affects insulin resistance and is a risk factor for diabetes mellitus type 2 (DM2) and gestational diabetes mellitus (GDM). Two single nucleotide polymorphisms (SNPs) in the epithelial magnesium channel TRPM6 (V1393I, K1584E) were predicted to confer susceptibility for DM2. Here, we show using patch clamp analysis and total internal reflection fluorescence microscopy, that insulin stimulates TRPM6 activity via a phosphoinositide 3-kinase and Rac1-mediated elevation of cell surface expression of TRPM6. Interestingly, insulin failed to activate the genetic variants TRPM6(V1393I) and TRPM6(K1584E), which is likely due to the inability of the insulin signaling pathway to phosphorylate TRPM6(T1391) and TRPM6(S1583). Moreover, by measuring total glycosylated hemoglobin (TGH) in 997 pregnant women as a measure of glucose control, we demonstrate that TRPM6(V1393I) and TRPM6(K1584E) are associated with higher TGH and confer a higher likelihood of developing GDM. The impaired response of TRPM6(V1393I) and TRPM6(K1584E) to insulin represents a unique molecular pathway leading to GDM where the defect is located in TRPM6. PMID:22733750

  2. Insulin analog with additional disulfide bond has increased stability and preserved activity

    DEFF Research Database (Denmark)

    Vinther, Tine N.; Norrman, Mathias; Ribel, Ulla

    2013-01-01

    Insulin is a key hormone controlling glucose homeostasis. All known vertebrate insulin analogs have a classical structure with three 100% conserved disulfide bonds that are essential for structural stability and thus the function of insulin. It might be hypothesized that an additional disulfide...... bond may enhance insulin structural stability which would be highly desirable in a pharmaceutical use. To address this hypothesis, we designed insulin with an additional interchain disulfide bond in positions A10/B4 based on Cα-Cα distances, solvent exposure, and side-chain orientation in human insulin...... (HI) structure. This insulin analog had increased affinity for the insulin receptor and apparently augmented glucodynamic potency in a normal rat model compared with HI. Addition of the disulfide bond also resulted in a 34.6°C increase in melting temperature and prevented insulin fibril formation...

  3. Calycosin promotes lifespan in Caenorhabditis elegans through insulin signaling pathway via daf-16, age-1 and daf-2.

    Science.gov (United States)

    Lu, Lulu; Zhao, Xuan; Zhang, Jianyong; Li, Miao; Qi, Yonghao; Zhou, Lijun

    2017-07-01

    The naturally occurring calycosin is a known antioxidant that prevents redox imbalance in organisms. However, calycosin's effect on lifespan and its physiological molecular mechanisms are not yet well understood. In this study, we demonstrated that calycosin could prolong the lifespan of Caenorhabditis elegans, and that such extension was associated with its antioxidant capability as well as its ability to enhance stress resistance and reduce ROS (reactive oxygen species) accumulation. To explore mechanisms of this longevity effect, we assessed the impact of calycosin on lifespans of insulin-signaling impaired worms: daf-2, age-1, and daf-16 mutants. We found that calycosin did not alter the lifespan of all three mutants, thereby suggesting that calycosin requires insulin signaling to promote lifespan extension. On the other hand, we observed that calycosin could enhance the nuclear translocation of the core transcription factor DAF-16/FoXO instead of the conserved stress-responsive transcription factor SKN-1/Nrf-2. This observation is consistent with the understanding that the nuclear localized DAF-16 up-regulates its downstream targets sod-3, ctl-1, and hsp-16.2. Lastly, it is also noteworthy that the longevity effect of calycosin is likely not associated with the calorie restriction mechanism. Collectively, our results strongly suggest that calycosin could function as an antioxidant to extend the lifespan of C. elegans by enhancing nucleus translocation of DAF-16 through the insulin-signaling pathway. Copyright © 2017 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  4. Hematopoietic-Derived Galectin-3 Causes Cellular and Systemic Insulin Resistance.

    Science.gov (United States)

    Li, Pingping; Liu, Shuainan; Lu, Min; Bandyopadhyay, Gautum; Oh, Dayoung; Imamura, Takeshi; Johnson, Andrew M F; Sears, Dorothy; Shen, Zhufang; Cui, Bing; Kong, Lijuan; Hou, Shaocong; Liang, Xiao; Iovino, Salvatore; Watkins, Steven M; Ying, Wei; Osborn, Olivia; Wollam, Joshua; Brenner, Martin; Olefsky, Jerrold M

    2016-11-03

    In obesity, macrophages and other immune cells accumulate in insulin target tissues, promoting a chronic inflammatory state and insulin resistance. Galectin-3 (Gal3), a lectin mainly secreted by macrophages, is elevated in both obese subjects and mice. Administration of Gal3 to mice causes insulin resistance and glucose intolerance, whereas inhibition of Gal3, through either genetic or pharmacologic loss of function, improved insulin sensitivity in obese mice. In vitro treatment with Gal3 directly enhanced macrophage chemotaxis, reduced insulin-stimulated glucose uptake in myocytes and 3T3-L1 adipocytes and impaired insulin-mediated suppression of glucose output in primary mouse hepatocytes. Importantly, we found that Gal3 can bind directly to the insulin receptor (IR) and inhibit downstream IR signaling. These observations elucidate a novel role for Gal3 in hepatocyte, adipocyte, and myocyte insulin resistance, suggesting that Gal3 can link inflammation to decreased insulin sensitivity. Inhibition of Gal3 could be a new approach to treat insulin resistance. Copyright © 2016 Elsevier Inc. All rights reserved.

  5. Liver insulinase and insulin-like activity of the blood plasma in irradiated rats

    Energy Technology Data Exchange (ETDEWEB)

    Zhikhareva, A I; Dokshina, G A [Tomskij Gosudarstvennyj Univ. (USSR)

    1975-05-01

    Comparative quantitative analysis of the functional effect of radiation on the activity of liver insulinase of irradiated rats has shown that the insulinase activity of the blood plasma decreases (21-45%) one to three days after the exposure at betatron. Insulinase activity of the liver extracts is also inhibited (16-22%) as compared to intact liver extracts. Twelve days after the exposure and later, insulin-like activity of the plasma and the enzyme activity increase up to 37 per cent.

  6. Insulin as a model to teach three-dimensional structure of proteins

    Directory of Open Access Journals (Sweden)

    João Batista Teixeira da Rocha

    2018-02-01

    Proteins are the most ubiquitous macromolecules found in the living cells and have innumerous physiological functions. Therefore, it is fundamental to build a solid knowledge about the proteins three dimensional structure to better understand the living state. The hierarchical structure of proteins is usually studied in the undergraduate discipline of Biochemistry. Here we described pedagogical interventions designed to increase the preservice teacher chemistry students’ knowledge about protein structure. The activities were made using alternative and cheap materials to encourage the application of these simple methodologies by the future teachers in the secondary school. From the primary structure of insulin chains, students had to construct a three-dimensional structure of insulin. After the activities, the students highlighted an improvement of their previous knowledge about proteins structure. The construction of a tridimensional model together with other activities seems to be an efficient way to promote the learning about the structure of proteins to undergraduate students. The methodology used was inexpensiveness and simple and it can be used both in the university and in the high-school.

  7. Olive Component Oleuropein Promotes β-Cell Insulin Secretion and Protects β-Cells from Amylin Amyloid-Induced Cytotoxicity.

    Science.gov (United States)

    Wu, Ling; Velander, Paul; Liu, Dongmin; Xu, Bin

    2017-09-26

    Oleuropein, a natural product derived from olive leaves, has reported anti-diabetic functions. However, detailed molecular mechanisms for how it affects β-cell functions remain poorly understood. Here, we present evidence that oleuropein promotes glucose-stimulated insulin secretion (GSIS) in β-cells. The effect is dose-dependent and stimulates the ERK/MAPK signaling pathway. We further demonstrated that oleuropein inhibits the cytotoxicity induced by amylin amyloids, a hallmark feature of type 2 diabetes. We demonstrated that these dual functions are structure-specific: we identified the 3-hydroxytyrosol moiety of oleuropein as the main functional entity responsible for amyloid inhibition, but the novel GSIS function requires the entire structure scaffold of the molecule.

  8. Characterization of the chicken muscle insulin receptor

    International Nuclear Information System (INIS)

    Adamo, M.; Simon, J.; Rosebrough, R.W.; McMurtry, J.P.; Steele, N.C.; LeRoith, D.

    1987-01-01

    Insulin receptors are present in chicken skeletal muscle. Crude membrane preparations demonstrated specific 125 I-insulin binding. The nonspecific binding was high (36-55% of total binding) and slightly lower affinity receptors were found than are typically observed for crude membrane insulin binding in other chicken tissues. Affinity crosslinking of 125 I-insulin to crude membranes revealed insulin receptor alpha-subunits of Mr 128K, intermediate between those of liver (134K) and brain (124K). When solubilized and partially purified on wheat germ agglutinin (WGA) affinity columns, chicken muscle insulin receptors exhibited typical high affinity binding, with approximately 10(-10) M unlabeled insulin producing 50% inhibition of the specific 125 I-insulin binding. WGA purified chicken muscle insulin receptors also exhibited insulin-stimulated autophosphorylation of the beta-subunit, which appeared as phosphorylated bands of 92- and 81K. Both bands were immunoprecipitated by anti-receptor antiserum (B10). WGA purified membranes also demonstrated dose-dependent insulin-stimulated phosphorylation of the exogenous substrate poly(Glu,Tyr)4:1. However, unlike chicken liver, chicken muscle insulin receptor number and tyrosine kinase activity were unaltered by 48 hr of fasting or 48 hr of fasting and 24 hr of refeeding. Thus, despite the presence of insulin receptors in chicken muscle showing normal coupling to receptor tyrosine kinase activity, nutritional alterations modulate these parameters in a tissue-specific manner in chickens

  9. Mechanisms of insulin resistance in obesity

    Science.gov (United States)

    Ye, Jianping

    2014-01-01

    Obesity increases the risk for type 2 diabetes through induction of insulin resistance. Treatment of type 2 diabetes has been limited by little translational knowledge of insulin resistance although there have been several well-documented hypotheses for insulin resistance. In those hypotheses, inflammation, mitochondrial dysfunction, hyperinsulinemia and lipotoxicity have been the major concepts and have received a lot of attention. Oxidative stress, endoplasmic reticulum (ER) stress, genetic background, aging, fatty liver, hypoxia and lipodystrophy are active subjects in the study of these concepts. However, none of those concepts or views has led to an effective therapy for type 2 diabetes. The reason is that there has been no consensus for a unifying mechanism of insulin resistance. In this review article, literature is critically analyzed and reinterpreted for a new energy-based concept of insulin resistance, in which insulin resistance is a result of energy surplus in cells. The energy surplus signal is mediated by ATP and sensed by adenosine monophosphate-activated protein kinase (AMPK) signaling pathway. Decreasing ATP level by suppression of production or stimulation of utilization is a promising approach in the treatment of insulin resistance. In support, many of existing insulin sensitizing medicines inhibit ATP production in mitochondria. The effective therapies such as weight loss, exercise, and caloric restriction all reduce ATP in insulin sensitive cells. This new concept provides a unifying cellular and molecular mechanism of insulin resistance in obesity, which may apply to insulin resistance in aging and lipodystrophy. PMID:23471659

  10. Mactosylceramide Prevents Glial Cell Overgrowth by Inhibiting Insulin and Fibroblast Growth Factor Receptor Signaling

    DEFF Research Database (Denmark)

    Gerdøe-Kristensen, Stine; Lund, Viktor K; Wandall, Hans H

    2017-01-01

    , in which the mannosyltransferase Egghead controls conversion of glucosylceramide (GlcCer) to mactosylceramide (MacCer). Lack of elongated GSL in egghead (egh) mutants causes overgrowth of subperineurial glia (SPG), largely due to aberrant activation of phosphatidylinositol 3-kinase (PI3K). However, to what...... of the Drosophila Insulin Receptor (InR) and the FGFR homolog Heartless (Htl) in wild type SPG, and is suppressed by inhibiting Htl and InR activity in egh. Knockdown of GlcCer synthase in the SPG fails to suppress glial overgrowth in egh nerves, and slightly promotes overgrowth in wild type, suggesting that RTK...... hyperactivation is caused by absence of MacCer and not by GlcCer accumulation. We conclude that an early product in GSL biosynthesis, MacCer, prevents inappropriate activation of Insulin and Fibroblast Growth Factor Receptors in Drosophila glia. This article is protected by copyright. All rights reserved....

  11. Effects of soybean oligosaccharides on antioxidant enzyme activities and insulin resistance in pregnant women with gestational diabetes mellitus.

    Science.gov (United States)

    Fei, Bei-bei; Ling, Li; Hua, Chen; Ren, Shu-yan

    2014-09-01

    The effects of soybean oligosaccharides (SBOS) on antioxidant enzyme activities and insulin resistance in pregnant women with gestational diabetes mellitus (GDM) were investigated. Ninety-seven pregnant women with GDM were randomly divided into two groups, the control group (51 cases) and the SBOS group (46 cases). Before the group separation, the blood sugar level in patients was maintained stable by regular diet and insulin treatment. The control group was continued with the insulin treatment, while the SBOS group was treated with the combination of insulin and SBOS. Results showed that SBOS were able to reduce oxidative stress and alleviate insulin resistance in pregnant women with GDM, which indicates that SBOS may play an important role in the control of GDM complications. Copyright © 2014 Elsevier Ltd. All rights reserved.

  12. Study of NSILA-s (nonsuppressible insulin-like activity soluble in acid ethanol) by a new radio-receptor assay

    International Nuclear Information System (INIS)

    Megyeri, K.

    1977-01-01

    The insulin-like activity nonsuppressible with insulin-antibodies (NSILA) accounts for 90% of the insulin activity of the blood plasma. A peptid, soluble in acid ethanol, was purified (NSILA-s) and specific NSILA-s receptors were found on the plasma membrane of liver cells. The specificity, kinetics, affinity and pH-optimum of NSILA-s receptors significantly differed from those of insulin-receptors. A new, highly specific radio-receptor assay was developed, applying 125 I NSILA-s and liver cell membranes or lymphocytes. By this means the NSILA-s concentration of blood plasma was determined under normal and pathological (hypoglycaemizing tumours, hypopituritarism, acromegaly, anorexia nervosa, etc.) conditions. It is concluded that, 90% of the NSILA-s concentration of blood plasma is bound. In cases of hypoglycaemizing tumours increased NSILA-s activity was demonstrated both in blood serum and in the extracts of the tumour-tissue. Pharmacological doses of growth hormon (GH) increased plasma NSILA-s concentration, however, in the case of stimulation- and inhibition-tests carried out in normal patients, no unambiguous relationship could be demonstrated between plasma GH- and NSILA-s-levels. (L.E.)

  13. Effects of turtle oil on insulin sensitivity and glucose metabolism in insulin resistant cell model

    International Nuclear Information System (INIS)

    Bai Jing; Tian Yaping; Guo Duo

    2007-01-01

    To evaluate the effects of turtle oil on insulin sensitivity and glucose metabolism in an insulin-resistant (IR) cell model which was established by the way of high concentration of insulin induction with HepG 2 cell in vitro culture. The IR cells were treated by turtle oil, the glucose consumption and 3 H-D-glucose incorporation rate in IR cells were detected by the way of glucose oxidase and 3 H-D-glucose incorporation assay respectively. The state of cell proliferation was tested by MTT method. The results showed that the incorporation rate of 3 H-D-glucose in IR cells was significantly lower than that in the control cells(P 3 H-D-glucose incorporation rate in either IR cells or control cells was increased with the increase of insulin concentration. Moreover, the 3 H-D-glucose incorporation rate of IR cells increased slower than that of control cells. The MTT assay showed that turtle oil can promote the proliferation of IR cell and control cell. The glucose uptake and glucose consumption in IR cell which treated with turtle oil was significantly increase than that in the control cells (P<0.05). Turtle oil can improve the insulin sensitivity and glucose metabolism in the IR cell model. (authors)

  14. Intestine-targeted DGAT1 inhibition improves obesity and insulin resistance without skin aberrations in mice.

    Directory of Open Access Journals (Sweden)

    Naoto Tsuda

    Full Text Available OBJECTIVE: Diacylglycerol O-acyltransferase 1 (DGAT1 catalyzes the final committed step in triglyceride biosynthesis. DGAT1 null mice are known to be resistant to diet-induced obesity, and more insulin sensitive relative to the wild-type; however, the mice exhibit abnormalities in the skin. This work determined whether the intestine-targeted DGAT1 inhibitor could improve obesity and insulin resistance without skin aberrations in mice. DESIGN AND METHODS: We synthesized 2 DGAT1 inhibitors: Compound A, described in the patent application from the Japan Tobacco, and Compound B (A-922500, reported by Abbott Laboratories. Both compounds were evaluated for inhibitory activities against DGAT1 enzymes and effects on the skin in mice in vivo. Compound B was further investigated for effects on obesity and insulin resistance in diet-induced-obese (DIO mice. RESULTS: The 2 compounds comparably inhibited the DGAT1 enzyme activity and the cellular triglyceride synthesis in vitro, while they showed different distribution patterns in mice in vivo. Compound A, which distributed systemically, caused skin aberrations, while Compound B, which preferentially distributed to the intestine, improved obesity and insulin resistance without skin aberrations in DIO mice. CONCLUSIONS: Our results suggest that the intestine is the key tissue in which DGAT1 plays a role in promoting obesity and insulin resistance.

  15. Mechanisms for greater insulin-stimulated glucose uptake in normal and insulin-resistant skeletal muscle after acute exercise

    Science.gov (United States)

    2015-01-01

    Enhanced skeletal muscle and whole body insulin sensitivity can persist for up to 24–48 h after one exercise session. This review focuses on potential mechanisms for greater postexercise and insulin-stimulated glucose uptake (ISGU) by muscle in individuals with normal or reduced insulin sensitivity. A model is proposed for the processes underlying this improvement; i.e., triggers initiate events that activate subsequent memory elements, which store information that is relayed to mediators, which translate memory into action by controlling an end effector that directly executes increased insulin-stimulated glucose transport. Several candidates are potential triggers or memory elements, but none have been conclusively verified. Regarding potential mediators in both normal and insulin-resistant individuals, elevated postexercise ISGU with a physiological insulin dose coincides with greater Akt substrate of 160 kDa (AS160) phosphorylation without improved proximal insulin signaling at steps from insulin receptor binding to Akt activity. Causality remains to be established between greater AS160 phosphorylation and improved ISGU. The end effector for normal individuals is increased GLUT4 translocation, but this remains untested for insulin-resistant individuals postexercise. Following exercise, insulin-resistant individuals can attain ISGU values similar to nonexercising healthy controls, but after a comparable exercise protocol performed by both groups, ISGU for the insulin-resistant group has been consistently reported to be below postexercise values for the healthy group. Further research is required to fully understand the mechanisms underlying the improved postexercise ISGU in individuals with normal or subnormal insulin sensitivity and to explain the disparity between these groups after similar exercise. PMID:26487009

  16. Influence of Gut Microbiota on Subclinical Inflammation and Insulin Resistance

    Directory of Open Access Journals (Sweden)

    Bruno Melo Carvalho

    2013-01-01

    Full Text Available Obesity is the main condition that is correlated with the appearance of insulin resistance, which is the major link among its comorbidities, such as type 2 diabetes, nonalcoholic fatty liver disease, cardiovascular and neurodegenerative diseases, and several types of cancer. Obesity affects a large number of individuals worldwide; it degrades human health and quality of life. Here, we review the role of the gut microbiota in the pathophysiology of obesity and type 2 diabetes, which is promoted by a bacterial diversity shift mediated by overnutrition. Whole bacteria, their products, and metabolites undergo increased translocation through the gut epithelium to the circulation due to degraded tight junctions and the consequent increase in intestinal permeability that culminates in inflammation and insulin resistance. Several strategies focusing on modulation of the gut microbiota (antibiotics, probiotics, and prebiotics are being experimentally employed in metabolic derangement in order to reduce intestinal permeability, increase the production of short chain fatty acids and anorectic gut hormones, and promote insulin sensitivity to counteract the inflammatory status and insulin resistance found in obese individuals.

  17. Caffeine and contraction synergistically stimulate 5′-AMP-activated protein kinase and insulin-independent glucose transport in rat skeletal muscle

    Science.gov (United States)

    Tsuda, Satoshi; Egawa, Tatsuro; Kitani, Kazuto; Oshima, Rieko; Ma, Xiao; Hayashi, Tatsuya

    2015-01-01

    5′-Adenosine monophosphate-activated protein kinase (AMPK) has been identified as a key mediator of contraction-stimulated insulin-independent glucose transport in skeletal muscle. Caffeine acutely stimulates AMPK in resting skeletal muscle, but it is unknown whether caffeine affects AMPK in contracting muscle. Isolated rat epitrochlearis muscle was preincubated and then incubated in the absence or presence of 3 mmol/L caffeine for 30 or 120 min. Electrical stimulation (ES) was used to evoke tetanic contractions during the last 10 min of the incubation period. The combination of caffeine plus contraction had additive effects on AMPKα Thr172 phosphorylation, α-isoform-specific AMPK activity, and 3-O-methylglucose (3MG) transport. In contrast, caffeine inhibited basal and contraction-stimulated Akt Ser473 phosphorylation. Caffeine significantly delayed muscle fatigue during contraction, and the combination of caffeine and contraction additively decreased ATP and phosphocreatine contents. Caffeine did not affect resting tension. Next, rats were given an intraperitoneal injection of caffeine (60 mg/kg body weight) or saline, and the extensor digitorum longus muscle was dissected 15 min later. ES of the sciatic nerve was performed to evoke tetanic contractions for 5 min before dissection. Similar to the findings from isolated muscles incubated in vitro, the combination of caffeine plus contraction in vivo had additive effects on AMPK phosphorylation, AMPK activity, and 3MG transport. Caffeine also inhibited basal and contraction-stimulated Akt phosphorylation in vivo. These findings suggest that caffeine and contraction synergistically stimulate AMPK activity and insulin-independent glucose transport, at least in part by decreasing muscle fatigue and thereby promoting energy consumption during contraction. PMID:26471759

  18. Interplay between lipids and branched-chain amino acids in development of insulin resistance

    Science.gov (United States)

    Newgard, Christopher B.

    2013-01-01

    Summary Fatty acids (FA) and FA-derived metabolites have long been implicated in the development of insulin resistance and type 2 diabetes. Surprisingly, application of metabolomics technologies has revealed that branched-chain amino acids (BCAA) and related metabolites are more strongly associated with insulin resistance than many common lipid species. Moreover, the BCAA-related signature is predictive of incident diabetes and intervention outcomes, and uniquely responsive to therapeutic interventions. Nevertheless, in animal feeding studies, BCAA supplementation requires the background of a high-fat diet to promote insulin resistance. This article develops a model to explain how lipids and BCAA may synergize to promote metabolic diseases. PMID:22560213

  19. Mechanical stretch augments insulin-induced vascular smooth muscle cell proliferation by insulin-like growth factor-1 receptor

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Gang [Department of Pharmacology, Faculty of Medicine, Kagawa University, Kagawa (Japan); Department of Anesthesiology, First Affiliated Hospital of China Medical University, Shenyang (China); Hitomi, Hirofumi, E-mail: hitomi@kms.ac.jp [Department of Pharmacology, Faculty of Medicine, Kagawa University, Kagawa (Japan); Hosomi, Naohisa [Department of Cardiorenal and Cerebrovascular Medicine, Faculty of Medicine, Kagawa University, Kagawa (Japan); Lei, Bai; Nakano, Daisuke [Department of Pharmacology, Faculty of Medicine, Kagawa University, Kagawa (Japan); Deguchi, Kazushi; Mori, Hirohito; Masaki, Tsutomu [Department of Gastroenterology and Neurology, Faculty of Medicine, Kagawa University, Kagawa (Japan); Ma, Hong [Department of Anesthesiology, First Affiliated Hospital of China Medical University, Shenyang (China); Griendling, Kathy K. [Department of Medicine, Division of Cardiology, Emory University School of Medicine, Atlanta, GA (United States); Nishiyama, Akira [Department of Pharmacology, Faculty of Medicine, Kagawa University, Kagawa (Japan)

    2011-10-15

    Insulin resistance and hypertension have been implicated in the pathogenesis of cardiovascular disease; however, little is known about the roles of insulin and mechanical force in vascular smooth muscle cell (VSMC) remodeling. We investigated the contribution of mechanical stretch to insulin-induced VSMC proliferation. Thymidine incorporation was stimulated by insulin in stretched VSMCs, but not in un-stretched VSMCs. Insulin increased 2-deoxy-glucose incorporation in both stretched and un-stretched VSMCs. Mechanical stretch augmented insulin-induced extracellular signal-regulated kinase (ERK) and Akt phosphorylation. Inhibitors of epidermal growth factor (EGF) receptor tyrosine kinase and Src attenuated insulin-induced ERK and Akt phosphorylation, as well as thymidine incorporation, whereas 2-deoxy-glucose incorporation was not affected by these inhibitors. Moreover, stretch augmented insulin-like growth factor (IGF)-1 receptor expression, although it did not alter the expression of insulin receptor and insulin receptor substrate-1. Insulin-induced ERK and Akt activation, and thymidine incorporation were inhibited by siRNA for the IGF-1 receptor. Mechanical stretch augments insulin-induced VSMC proliferation via upregulation of IGF-1 receptor, and downstream Src/EGF receptor-mediated ERK and Akt activation. Similar to in vitro experiment, IGF-1 receptor expression was also augmented in hypertensive rats. These results provide a basis for clarifying the molecular mechanisms of vascular remodeling in hypertensive patients with hyperinsulinemia. -- Highlights: {yields} Mechanical stretch augments insulin-induced VSMC proliferation via IGF-1 receptor. {yields} Src/EGFR-mediated ERK and Akt phosphorylation are augmented in stretched VSMCs. {yields} Similar to in vitro experiment, IGF-1 receptor is increased in hypertensive rats. {yields} Results provide possible mechanisms of vascular remodeling in hypertension with DM.

  20. Elevated TCA cycle function in the pathology of diet-induced hepatic insulin resistance and fatty liver.

    Science.gov (United States)

    Satapati, Santhosh; Sunny, Nishanth E; Kucejova, Blanka; Fu, Xiaorong; He, Tian Teng; Méndez-Lucas, Andrés; Shelton, John M; Perales, Jose C; Browning, Jeffrey D; Burgess, Shawn C

    2012-06-01

    The manner in which insulin resistance impinges on hepatic mitochondrial function is complex. Although liver insulin resistance is associated with respiratory dysfunction, the effect on fat oxidation remains controversial, and biosynthetic pathways that traverse mitochondria are actually increased. The tricarboxylic acid (TCA) cycle is the site of terminal fat oxidation, chief source of electrons for respiration, and a metabolic progenitor of gluconeogenesis. Therefore, we tested whether insulin resistance promotes hepatic TCA cycle flux in mice progressing to insulin resistance and fatty liver on a high-fat diet (HFD) for 32 weeks using standard biomolecular and in vivo (2)H/(13)C tracer methods. Relative mitochondrial content increased, but respiratory efficiency declined by 32 weeks of HFD. Fasting ketogenesis became unresponsive to feeding or insulin clamp, indicating blunted but constitutively active mitochondrial β-oxidation. Impaired insulin signaling was marked by elevated in vivo gluconeogenesis and anaplerotic and oxidative TCA cycle flux. The induction of TCA cycle function corresponded to the development of mitochondrial respiratory dysfunction, hepatic oxidative stress, and inflammation. Thus, the hepatic TCA cycle appears to enable mitochondrial dysfunction during insulin resistance by increasing electron deposition into an inefficient respiratory chain prone to reactive oxygen species production and by providing mitochondria-derived substrate for elevated gluconeogenesis.

  1. Function of insulin in snail brain in associative learning.

    Science.gov (United States)

    Kojima, S; Sunada, H; Mita, K; Sakakibara, M; Lukowiak, K; Ito, E

    2015-10-01

    Insulin is well known as a hormone regulating glucose homeostasis across phyla. Although there are insulin-independent mechanisms for glucose uptake in the mammalian brain, which had contributed to a perception of the brain as an insulin-insensitive organ for decades, the finding of insulin and its receptors in the brain revolutionized the concept of insulin signaling in the brain. However, insulin's role in brain functions, such as cognition, attention, and memory, remains unknown. Studies using invertebrates with their open blood-vascular system have the promise of promoting a better understanding of the role played by insulin in mediating/modulating cognitive functions. In this review, the relationship between insulin and its impact on long-term memory (LTM) is discussed particularly in snails. The pond snail Lymnaea stagnalis has the ability to undergo conditioned taste aversion (CTA), that is, it associatively learns and forms LTM not to respond with a feeding response to a food that normally elicits a robust feeding response. We show that molluscan insulin-related peptides are up-regulated in snails exhibiting CTA-LTM and play a key role in the causal neural basis of CTA-LTM. We also survey the relevant literature of the roles played by insulin in learning and memory in other phyla.

  2. Caffeine and contraction synergistically stimulate 5'-AMP-activated protein kinase and insulin-independent glucose transport in rat skeletal muscle.

    Science.gov (United States)

    Tsuda, Satoshi; Egawa, Tatsuro; Kitani, Kazuto; Oshima, Rieko; Ma, Xiao; Hayashi, Tatsuya

    2015-10-01

    5'-Adenosine monophosphate-activated protein kinase (AMPK) has been identified as a key mediator of contraction-stimulated insulin-independent glucose transport in skeletal muscle. Caffeine acutely stimulates AMPK in resting skeletal muscle, but it is unknown whether caffeine affects AMPK in contracting muscle. Isolated rat epitrochlearis muscle was preincubated and then incubated in the absence or presence of 3 mmol/L caffeine for 30 or 120 min. Electrical stimulation (ES) was used to evoke tetanic contractions during the last 10 min of the incubation period. The combination of caffeine plus contraction had additive effects on AMPKα Thr(172) phosphorylation, α-isoform-specific AMPK activity, and 3-O-methylglucose (3MG) transport. In contrast, caffeine inhibited basal and contraction-stimulated Akt Ser(473) phosphorylation. Caffeine significantly delayed muscle fatigue during contraction, and the combination of caffeine and contraction additively decreased ATP and phosphocreatine contents. Caffeine did not affect resting tension. Next, rats were given an intraperitoneal injection of caffeine (60 mg/kg body weight) or saline, and the extensor digitorum longus muscle was dissected 15 min later. ES of the sciatic nerve was performed to evoke tetanic contractions for 5 min before dissection. Similar to the findings from isolated muscles incubated in vitro, the combination of caffeine plus contraction in vivo had additive effects on AMPK phosphorylation, AMPK activity, and 3MG transport. Caffeine also inhibited basal and contraction-stimulated Akt phosphorylation in vivo. These findings suggest that caffeine and contraction synergistically stimulate AMPK activity and insulin-independent glucose transport, at least in part by decreasing muscle fatigue and thereby promoting energy consumption during contraction. © 2015 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological

  3. Using Virtual Pets to Promote Physical Activity in Children: An Application of the Youth Physical Activity Promotion Model.

    Science.gov (United States)

    Ahn, Sun Joo Grace; Johnsen, Kyle; Robertson, Tom; Moore, James; Brown, Scott; Marable, Amanda; Basu, Aryabrata

    2015-01-01

    A virtual pet was developed based on the framework of the youth physical activity promotion model and tested as a vehicle for promoting physical activity in children. Children in the treatment group interacted with the virtual pet for three days, setting physical activity goals and teaching tricks to the virtual pet when their goals were met. The virtual pet became more fit and learned more sophisticated tricks as the children achieved activity goals. Children in the control group interacted with a computer system presenting equivalent features but without the virtual pet. Physical activity and goal attainment were evaluated using activity monitors. Results indicated that children in the treatment group engaged in 1.09 more hours of daily physical activity (156% more) than did those in the control group. Physical activity self-efficacy and beliefs served as mediators driving this increase in activity. Children that interacted with the virtual pet also expressed higher intentions than children in the control group to continue physical activity in the future. Theoretical and practical potentials of using a virtual pet to systematically promote physical activity in children are discussed.

  4. Ligand binding affinity at the insulin receptor isoform A (IR-A and subsequent IR-A tyrosine phosphorylation kinetics are important determinants of mitogenic biological outcomes.

    Directory of Open Access Journals (Sweden)

    Harinda eRajapaksha

    2015-07-01

    Full Text Available The insulin receptor (IR is a tyrosine kinase receptor that can mediate both metabolic and mitogenic biological actions. The IR isoform-A (IR-A arises from alternative splicing of exon 11 and has different ligand binding and signalling properties compared to the IR isoform-B. The IR-A not only binds insulin but also insulin-like growth factor-II (IGF-II with high affinity. IGF-II acting through the IR-A promotes cancer cell proliferation, survival and migration by activating some unique signalling molecules compared to those activated by insulin. This observation led us to investigate whether the different IR-A signalling outcomes in response to IGF-II and insulin could be attributed to phosphorylation of a different subset of IR-A tyrosine residues or to the phosphorylation kinetics. We correlated IR-A phosphorylation to activation of molecules involved in mitogenic and metabolic signalling (MAPK and Akt and receptor internalisation rates (related to mitogenic signalling. We also extended this study to incorporate two ligands that are known to promote predominantly mitogenic ([His4, Tyr15, Thr49, Ile51] IGF-I, qIGF-I or metabolic (S597 peptide biological actions, to see if common mechanisms can be used to define mitogenic or metabolic signalling through the IR-A. The 3-fold lower mitogenic action of IGF-II compared to insulin was associated with a decreased potency in activation of Y960, Y1146, Y1150, Y1151, Y1316 and Y1322, in MAPK phosphorylation and in IR-A internalization. With the poorly mitogenic S597 peptide it was a decreased rate of tyrosine phosphorylation rather than potency that was associated with a low mitogenic potential. We conclude that both decreased affinity of IR-A binding and the kinetics of IR-A phosphorylation can independently lead to a lower mitogenic activity. None of the studied parameters could account for the lower metabolic activity of qIGF-I.

  5. Suppression of Adaptive Immune Cell Activation Does Not Alter Innate Immune Adipose Inflammation or Insulin Resistance in Obesity.

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    Manikandan Subramanian

    Full Text Available Obesity-induced inflammation in visceral adipose tissue (VAT is a major contributor to insulin resistance and type 2 diabetes. Whereas innate immune cells, notably macrophages, contribute to visceral adipose tissue (VAT inflammation and insulin resistance, the role of adaptive immunity is less well defined. To address this critical gap, we used a model in which endogenous activation of T cells was suppressed in obese mice by blocking MyD88-mediated maturation of CD11c+ antigen-presenting cells. VAT CD11c+ cells from Cd11cCre+Myd88fl/fl vs. control Myd88fl/fl mice were defective in activating T cells in vitro, and VAT T and B cell activation was markedly reduced in Cd11cCre+Myd88fl/fl obese mice. However, neither macrophage-mediated VAT inflammation nor systemic inflammation were altered in Cd11cCre+Myd88fl/fl mice, thereby enabling a focused analysis on adaptive immunity. Unexpectedly, fasting blood glucose, plasma insulin, and the glucose response to glucose and insulin were completely unaltered in Cd11cCre+Myd88fl/fl vs. control obese mice. Thus, CD11c+ cells activate VAT T and B cells in obese mice, but suppression of this process does not have a discernible effect on macrophage-mediated VAT inflammation or systemic glucose homeostasis.

  6. The brain modulates insulin sensitivity in multiple tissues

    NARCIS (Netherlands)

    Parlevliet, Edwin T.; Coomans, Claudia P.; Rensen, Patrick C. N.; Romijn, Johannes A.

    2014-01-01

    Insulin sensitivity is determined by direct effects of circulating insulin on metabolically active tissues in combination with indirect effects of circulating insulin, i.e. via the central nervous system. The dose-response effects of insulin differ between the various physiological effects of

  7. Reconstructing Dynamic Promoter Activity Profiles from Reporter Gene Data

    DEFF Research Database (Denmark)

    Kannan, Soumya; Sams, Thomas; Maury, Jérôme

    2018-01-01

    activity despite the fact that the observed output may be dynamic and is a number of steps away from the transcription process. In fact, some promoters that are often thought of as constitutive can show changes in activity when growth conditions change. For these reasons, we have developed a system......Accurate characterization of promoter activity is important when designing expression systems for systems biology and metabolic engineering applications. Promoters that respond to changes in the environment enable the dynamic control of gene expression without the necessity of inducer compounds......, for example. However, the dynamic nature of these processes poses challenges for estimating promoter activity. Most experimental approaches utilize reporter gene expression to estimate promoter activity. Typically the reporter gene encodes a fluorescent protein that is used to infer a constant promoter...

  8. Stimulation of muscle protein synthesis by somatotropin in pigs is independent of the somatotropin-induced increase in circulating insulin.

    Science.gov (United States)

    Wilson, Fiona A; Orellana, Renán A; Suryawan, Agus; Nguyen, Hanh V; Jeyapalan, Asumthia S; Frank, Jason; Davis, Teresa A

    2008-07-01

    Chronic treatment of growing pigs with porcine somatotropin (pST) promotes protein synthesis and doubles postprandial levels of insulin, a hormone that stimulates translation initiation. This study aimed to determine whether the pST-induced increase in skeletal muscle protein synthesis was mediated through an insulin-induced stimulation of translation initiation. After 7-10 days of pST (150 microg x kg(-1) x day(-1)) or control saline treatment, pancreatic glucose-amino acid clamps were performed in overnight-fasted pigs to reproduce 1) fasted (5 microU/ml), 2) fed control (25 microU/ml), and 3) fed pST-treated (50 microU/ml) insulin levels while glucose and amino acids were maintained at baseline fasting levels. Fractional protein synthesis rates and indexes of translation initiation were examined in skeletal muscle. Effectiveness of pST treatment was confirmed by reduced urea nitrogen and elevated insulin-like growth factor I levels in plasma. Skeletal muscle protein synthesis was independently increased by both insulin and pST. Insulin increased the phosphorylation of protein kinase B and the downstream effectors of the mammalian target of rapamycin, ribosomal protein S6 kinase, and eukaryotic initiation factor (eIF)4E-binding protein-1 (4E-BP1). Furthermore, insulin reduced inactive 4E-BP1.eIF4E complex association and increased active eIF4E.eIF4G complex formation, indicating enhanced eIF4F complex assembly. However, pST treatment did not alter translation initiation factor activation. We conclude that the pST-induced stimulation of skeletal muscle protein synthesis in growing pigs is independent of the insulin-associated activation of translation initiation.

  9. Implications of compound heterozygous insulin receptor mutations in congenital muscle fibre type disproportion myopathy for the receptor kinase activation

    DEFF Research Database (Denmark)

    Klein, H H; Müller, R; Vestergaard, H

    1999-01-01

    We studied insulin receptor kinase activation in two brothers with congenital muscle fibre type disproportion myopathy and compound heterozygous mutations of the insulin receptor gene, their parents, and their unaffected brother. In the father who has a heterozygote Arg1174-->Gln mutation, in sit...

  10. Dietary fat drives whole-body insulin resistance and promotes intestinal inflammation independent of body weight gain

    DEFF Research Database (Denmark)

    Jensen, Benjamin Anderschou Holbech; Nielsen, Thomas Svava; Fritzen, Andreas Mæchel

    2016-01-01

    body glucose homeostasis was evaluated by insulin and glucose tolerance tests as well as by a hyperinsulinemic euglycemic clamp experiment. RESULTS: Compared with LFD-fed reference mice, HFD-fed mice, irrespective of protein:carbohydrate ratio, exhibited impaired glucose tolerance, whereas...... no differences were observed during insulin tolerance tests. The hyperinsulinemic euglycemic clamp revealed tissue-specific effects on glucose homeostasis in all HFD-fed groups. HFD-fed mice exhibited decreased insulin-stimulated glucose uptake in white but not in brown adipose tissue, and sustained endogenous...... glucose production under insulin-stimulated conditions. We observed no impairment of insulin-stimulated glucose uptake in skeletal muscles of different fiber type composition. HFD-feeding altered the gut microbiota composition paralleled by increased expression of pro-inflammatory cytokines and genes...

  11. Binding of the Ras activator son of sevenless to insulin receptor substrate-1 signaling complexes.

    Science.gov (United States)

    Baltensperger, K; Kozma, L M; Cherniack, A D; Klarlund, J K; Chawla, A; Banerjee, U; Czech, M P

    1993-06-25

    Signal transmission by insulin involves tyrosine phosphorylation of a major insulin receptor substrate (IRS-1) and exchange of Ras-bound guanosine diphosphate for guanosine triphosphate. Proteins containing Src homology 2 and 3 (SH2 and SH3) domains, such as the p85 regulatory subunit of phosphatidylinositol-3 kinase and growth factor receptor-bound protein 2 (GRB2), bind tyrosine phosphate sites on IRS-1 through their SH2 regions. Such complexes in COS cells were found to contain the heterologously expressed putative guanine nucleotide exchange factor encoded by the Drosophila son of sevenless gene (dSos). Thus, GRB2, p85, or other proteins with SH2-SH3 adapter sequences may link Sos proteins to IRS-1 signaling complexes as part of the mechanism by which insulin activates Ras.

  12. Adipokines and Hepatic Insulin Resistance

    Science.gov (United States)

    Hassan, Waseem

    2013-01-01

    Obesity is a major risk factor for insulin resistance and type 2 diabetes. Adipose tissue is now considered to be an active endocrine organ that secretes various adipokines such as adiponectin, leptin, resistin, tumour necrosis factor-α, and interleukin-6. Recent studies have shown that these factors might provide a molecular link between increased adiposity and impaired insulin sensitivity. Since hepatic insulin resistance plays the key role in the whole body insulin resistance, clarification of the regulatory processes about hepatic insulin resistance by adipokines in rodents and human would seem essential in order to understand the mechanism of type 2 diabetes and for developing novel therapeutic strategies to treat it. PMID:23762871

  13. Concentrated insulins: the new basal insulins

    Directory of Open Access Journals (Sweden)

    Lamos EM

    2016-03-01

    Full Text Available Elizabeth M Lamos,1 Lisa M Younk,2 Stephen N Davis3 1Division of Endocrinology, Diabetes and Nutrition, 2Department of Medicine, University of Maryland School of Medicine, 3Department of Medicine, University of Maryland Medical Center, Baltimore, MD, USA Introduction: Insulin therapy plays a critical role in the treatment of type 1 and type 2 diabetes mellitus. However, there is still a need to find basal insulins with 24-hour coverage and reduced risk of hypoglycemia. Additionally, with increasing obesity and insulin resistance, the ability to provide clinically necessary high doses of insulin at low volume is also needed. Areas covered: This review highlights the published reports of the pharmacokinetic (PK and glucodynamic properties of concentrated insulins: Humulin-R U500, insulin degludec U200, and insulin glargine U300, describes the clinical efficacy, risk of hypoglycemic, and metabolic changes observed, and finally, discusses observations about the complexity of introducing a new generation of concentrated insulins to the therapeutic market. Conclusion: Humulin-R U500 has a similar onset but longer duration of action compared with U100 regular insulin. Insulin glargine U300 has differential PK/pharmacodynamic effects when compared with insulin glargine U100. In noninferiority studies, glycemic control with degludec U200 and glargine U300 is similar to insulin glargine U100 and nocturnal hypoglycemia is reduced. Concentrated formulations appear to behave as separate molecular entities when compared with earlier U100 insulin analog compounds. In the review of available published data, newer concentrated basal insulins may offer an advantage in terms of reduced intraindividual variability as well as reducing the injection burden in individuals requiring high-dose and large volume insulin therapy. Understanding the PK and pharmacodynamic properties of this new generation of insulins is critical to safe dosing, dispensing, and administration

  14. Insulin like growth factor-1/insulin bypasses Pref-1/FA1-mediated inhibition of adipocyte differentiation

    DEFF Research Database (Denmark)

    Zhang, Hongbin; Nøhr, Jane; Jensen, Charlotte Harken

    2003-01-01

    that forced expression of the soluble form, FA1, or full-length Pref-1 did not inhibit adipocyte differentiation of 3T3-L1 cells when differentiation was induced by standard treatment with methylisobutylxanthine, dexamethasone, and high concentrations of insulin. However, forced expression of either form...... of Pref-1/FA1 in 3T3-L1 or 3T3-F442A cells inhibited adipocyte differentiation when insulin or insulin-like growth factor-1 (IGF-1) was omitted from the differentiation mixture. We demonstrate that the level of the mature form of the IGF-1 receptor is reduced and that IGF-1-dependent activation of p42/p44...... mitogen-activated protein kinases (MAPKs) is compromised in preadipocytes with forced expression of Pref-1. This is accompanied by suppression of clonal expansion and terminal differentiation. Accordingly, supplementation with insulin or IGF-1 rescued p42/p44 MAPK activation, clonal expansion...

  15. Insulin analogues and cancer: a note of caution

    Directory of Open Access Journals (Sweden)

    Joseph A.M.J.L. eJanssen

    2014-05-01

    Full Text Available Abstract In view of the lifelong exposure and large patient populations involved, insulin analogues with an increased mitogenic effect in comparison to human insulin may potentially constitute a major health problem, since these analogues may possibly induce the growth of pre-existing neoplasms. At present, the available data suggest that insulin analogues are safe. In line with these findings, we observed that serum of diabetic patients treated with insulin analogues, compared to that of diabetic patients treated with human insulin, did not induce an increased phosphorylation of tyrosine residues of the insulin-like growth factor-I receptor (IGF-IR. However, the classical model of the IGF-IR signaling may be insufficient to explain (all mitogenic effects of insulin analogues since also non-canonical signaling pathways of the IGF-IR may play a major role in this respect. Although phosphorylation of tyrosine residues of the IGF-IR is generally considered to be the initial activation step within the intracellular IGF-IR signaling pathway, it has been found that cells undergo a signaling switch under hyperglycemic conditions. After this switch, a completely different mechanism is utilized to activate the mitogenic (mitogen-activated protein kinase (MAPK pathways of the IGF-IR that is independent from tyrosine phosphorylation of the IGF-IR. At present it is unknown whether activation of this alternative intracellular pathway of the IGF-IR occurs during hyperglycemia in vivo and whether it is stronger in patients treated with (some insulin analogues than in patients treated with human insulin. In addition, it is unknown whether the insulin receptors (IRs also undergo a signaling switch during hyperglycemia. This should be investigated in future studies. Finally, relative overexpression of IR isoform A (IR-A in (pre cancer tissues may play a key role in the development and progression of human cancers during treatment with insulin (analogues. Further

  16. Insulin Signaling and Heart Failure

    Science.gov (United States)

    Riehle, Christian; Abel, E. Dale

    2016-01-01

    Heart failure is associated with generalized insulin resistance. Moreover, insulin resistant states such as type 2 diabetes and obesity increases the risk of heart failure even after adjusting for traditional risk factors. Insulin resistance or type 2 diabetes alters the systemic and neurohumoral milieu leading to changes in metabolism and signaling pathways in the heart that may contribute to myocardial dysfunction. In addition, changes in insulin signaling within cardiomyocytes develop in the failing heart. The changes range from activation of proximal insulin signaling pathways that may contribute to adverse left ventricular remodeling and mitochondrial dysfunction to repression of distal elements of insulin signaling pathways such as forkhead (FOXO) transcriptional signaling or glucose transport which may also impair cardiac metabolism, structure and function. This article will review the complexities of insulin signaling within the myocardium and ways in which these pathways are altered in heart failure or in conditions associated with generalized insulin resistance. The implications of these changes for therapeutic approaches to treating or preventing heart failure will be discussed. PMID:27034277

  17. Activated AKT/PKB signaling in C. elegans uncouples temporally distinct outputs of DAF-2/insulin-like signaling

    Directory of Open Access Journals (Sweden)

    Hanselman Keaton B

    2006-10-01

    Full Text Available Abstract Background In the nematode, Caenorhabditis elegans, a conserved insulin-like signaling pathway controls larval development, stress resistance and adult lifespan. AGE-1, a homolog of the p110 catalytic subunit of phosphoinositide 3-kinases (PI3K comprises the major known effector pathway downstream of the insulin receptor, DAF-2. Phospholipid products of AGE-1/PI3K activate AKT/PKB kinase signaling via PDK-1. AKT/PKB signaling antagonizes nuclear translocation of the DAF-16/FOXO transcription factor. Reduced AGE-1/PI3K signaling permits DAF-16 to direct dauer larval arrest and promote long lifespan in adult animals. In order to study the downstream effectors of AGE-1/PI3K signaling in C. elegans, we conducted a genetic screen for mutations that suppress the constitutive dauer arrest phenotype of age-1(mg109 animals. Results This report describes mutations recovered in a screen for suppressors of the constitutive dauer arrest (daf-C phenotype of age-1(mg109. Two mutations corresponded to alleles of daf-16. Two mutations were gain-of-function alleles in the genes, akt-1 and pdk-1, encoding phosphoinositide-dependent serine/threonine kinases. A fifth mutation, mg227, located on chromosome X, did not correspond to any known dauer genes, suggesting that mg227 may represent a new component of the insulin pathway. Genetic epistasis analysis by RNAi showed that reproductive development in age-1(mg109;akt-1(mg247 animals was dependent on the presence of pdk-1. Similarly, reproductive development in age-1(mg109;pdk-1(mg261 animals was dependent on akt-1. However, reproductive development in age-1(mg109; mg227 animals required only akt-1, and pdk-1 activity was dispensable in this background. Interestingly, while mg227 suppressed dauer arrest in age-1(mg109 animals, it enhanced the long lifespan phenotype. In contrast, akt-1(mg247 and pdk-1(mg261 did not affect lifespan or stress resistance, while both daf-16 alleles fully suppressed these

  18. Activated AKT/PKB signaling in C. elegans uncouples temporally distinct outputs of DAF-2/insulin-like signaling.

    Science.gov (United States)

    Gami, Minaxi S; Iser, Wendy B; Hanselman, Keaton B; Wolkow, Catherine A

    2006-10-04

    In the nematode, Caenorhabditis elegans, a conserved insulin-like signaling pathway controls larval development, stress resistance and adult lifespan. AGE-1, a homolog of the p110 catalytic subunit of phosphoinositide 3-kinases (PI3K) comprises the major known effector pathway downstream of the insulin receptor, DAF-2. Phospholipid products of AGE-1/PI3K activate AKT/PKB kinase signaling via PDK-1. AKT/PKB signaling antagonizes nuclear translocation of the DAF-16/FOXO transcription factor. Reduced AGE-1/PI3K signaling permits DAF-16 to direct dauer larval arrest and promote long lifespan in adult animals. In order to study the downstream effectors of AGE-1/PI3K signaling in C. elegans, we conducted a genetic screen for mutations that suppress the constitutive dauer arrest phenotype of age-1(mg109) animals. This report describes mutations recovered in a screen for suppressors of the constitutive dauer arrest (daf-C) phenotype of age-1(mg109). Two mutations corresponded to alleles of daf-16. Two mutations were gain-of-function alleles in the genes, akt-1 and pdk-1, encoding phosphoinositide-dependent serine/threonine kinases. A fifth mutation, mg227, located on chromosome X, did not correspond to any known dauer genes, suggesting that mg227 may represent a new component of the insulin pathway. Genetic epistasis analysis by RNAi showed that reproductive development in age-1(mg109);akt-1(mg247) animals was dependent on the presence of pdk-1. Similarly, reproductive development in age-1(mg109);pdk-1(mg261) animals was dependent on akt-1. However, reproductive development in age-1(mg109); mg227 animals required only akt-1, and pdk-1 activity was dispensable in this background. Interestingly, while mg227 suppressed dauer arrest in age-1(mg109) animals, it enhanced the long lifespan phenotype. In contrast, akt-1(mg247) and pdk-1(mg261) did not affect lifespan or stress resistance, while both daf-16 alleles fully suppressed these phenotypes. A screen for suppressors of PI3K

  19. 4PS/insulin receptor substrate (IRS)-2 is the alternative substrate of the insulin receptor in IRS-1-deficient mice.

    Science.gov (United States)

    Patti, M E; Sun, X J; Bruening, J C; Araki, E; Lipes, M A; White, M F; Kahn, C R

    1995-10-20

    Insulin receptor substrate-1 (IRS-1) is the major cytoplasmic substrate of the insulin and insulin-like growth factor (IGF)-1 receptors. Transgenic mice lacking IRS-1 are resistant to insulin and IGF-1, but exhibit significant residual insulin action which corresponds to the presence of an alternative high molecular weight substrate in liver and muscle. Recently, Sun et al. (Sun, X.-J., Wang, L.-M., Zhang, Y., Yenush, L. P., Myers, M. G., Jr., Glasheen, E., Lane, W.S., Pierce, J. H., and White, M. F. (1995) Nature 377, 173-177) purified and cloned 4PS, the major substrate of the IL-4 receptor-associated tyrosine kinase in myeloid cells, which has significant structural similarity to IRS-1. To determine if 4PS is the alternative substrate of the insulin receptor in IRS-1-deficient mice, we performed immunoprecipitation, immunoblotting, and phosphatidylinositol (PI) 3-kinase assays using specific antibodies to 4PS. Following insulin stimulation, 4PS is rapidly phosphorylated in liver and muscle, binds to the p85 subunit of PI 3-kinase, and activates the enzyme. Insulin stimulation also results in the association of 4PS with Grb 2 in both liver and muscle. In IRS-1-deficient mice, both the phosphorylation of 4PS and associated PI 3-kinase activity are enhanced, without an increase in protein expression. Immunodepletion of 4PS from liver and muscle homogenates removes most of the phosphotyrosine-associated PI 3-kinase activity in IRS-1-deficient mice. Thus, 4PS is the primary alternative substrate, i.e. IRS-2, which plays a major role in physiologic insulin signal transduction via both PI 3-kinase activation and Grb 2/Sos association. In IRS-1-deficient mice, 4PS/IRS-2 provides signal transduction to these two major pathways of insulin signaling.

  20. Relationships between thermic effect of food, insulin resistance and autonomic nervous activity

    OpenAIRE

    Watanabe, Tomonori; Nomura, Masahiro; Nakayasu, Kimiko; Kawano, Tomohito; Ito, Susumu; Nakaya, Yutaka

    2006-01-01

    Background: The thermic effect of food (TEF) is higher in lean than in obese human subjects. Objective: Relationships between TEF and insulin resistance during meals, from the point of view of autonomic nervous activity, were evaluated. Methods : Autonomic nervous activity was evaluated in 20 young adults using the spectral analysis of heart rate variability from one hour before to two hours after a meal. Heart rate data were analyzed based on low frequency components (LF power, 0.04 - 0.15Hz...

  1. Insulin Clearance Is Associated with Hepatic Lipase Activity and Lipid and Adiposity Traits in Mexican Americans.

    Directory of Open Access Journals (Sweden)

    Artak Labadzhyan

    Full Text Available Reduction in insulin clearance plays an important role in the compensatory response to insulin resistance. Given the importance of this trait to the pathogenesis of diabetes, a deeper understanding of its regulation is warranted. Our goal was to identify metabolic and cardiovascular traits that are independently associated with metabolic clearance rate of insulin (MCRI. We conducted a cross-sectional analysis of metabolic and cardiovascular traits in 765 participants from the Mexican-American Coronary Artery Disease (MACAD project who had undergone blood sampling, oral glucose tolerance test, euglycemic-hyperinsulinemic clamp, dual-energy X-ray absorptiometry, and carotid ultrasound. We assessed correlations of MCRI with traits from seven domains, including anthropometry, biomarkers, cardiovascular, glucose homeostasis, lipase activity, lipid profile, and liver function tests. We found inverse independent correlations between MCRI and hepatic lipase (P = 0.0004, insulin secretion (P = 0.0002, alanine aminotransferase (P = 0.0045, total fat mass (P = 0.014, and diabetes (P = 0.03. MCRI and apolipoprotein A-I exhibited a positive independent correlation (P = 0.035. These results generate a hypothesis that lipid and adiposity associated traits related to liver function may play a role in insulin clearance.

  2. Food image-induced brain activation is not diminished by insulin infusion.

    Science.gov (United States)

    Belfort-DeAguiar, R; Seo, D; Naik, S; Hwang, J; Lacadie, C; Schmidt, C; Constable, R T; Sinha, R; Sherwin, R

    2016-11-01

    The obesity epidemic appears to be driven in large part by our modern environment inundated by food cues, which may influence our desire to eat. Although insulin decreases food intake in both animals and humans, the effect of insulin on motivation for food in the presence of food cues is not known. Therefore, the aim of this study was to evaluate the effect of an intravenous insulin infusion on the brain response to visual food cues, hunger and food craving in non-obese human subjects. Thirty-four right-handed healthy non-obese subjects (19F/15M, age: 29±8 years.; BMI: 23.1±2.1 kg m -2 ) were divided in two groups matched by age and BMI; the insulin group (18 subjects) underwent a hyperinsulinemic-euglycemic-clamp, and the control group (16 subjects) received an intravenous saline infusion, while viewing high and low-calorie food and non-food pictures during a functional MRI scan. Motivation for food was determined via analog scales for hunger, wanting and liking ratings. Food images induced brain responses in the hypothalamus, striatum, amygdala, insula, ventromedial prefrontal cortex (PFC), dorsolateral PFC and occipital lobe (whole brain correction, Pinsulin and saline infusion groups. Hunger ratings increased throughout the MRI scan and correlated with preference for high-calorie food pictures (r=0.70; Pbrain activity nor food cravings were affected by hyperinsulinemia or hormonal status (leptin and ghrelin levels) (P=NS). Our data demonstrate that visual food cues induce a strong response in motivation/reward and cognitive-executive control brain regions in non-obese subjects, but that these responses are not diminished by hyperinsulinemia per se. These findings suggest that our modern food cue saturated environment may be sufficient to overpower homeostatic hormonal signals, and thus contribute to the current obesity epidemic.

  3. Elevated TCA cycle function in the pathology of diet-induced hepatic insulin resistance and fatty liver[S

    Science.gov (United States)

    Satapati, Santhosh; Sunny, Nishanth E.; Kucejova, Blanka; Fu, Xiaorong; He, Tian Teng; Méndez-Lucas, Andrés; Shelton, John M.; Perales, Jose C.; Browning, Jeffrey D.; Burgess, Shawn C.

    2012-01-01

    The manner in which insulin resistance impinges on hepatic mitochondrial function is complex. Although liver insulin resistance is associated with respiratory dysfunction, the effect on fat oxidation remains controversial, and biosynthetic pathways that traverse mitochondria are actually increased. The tricarboxylic acid (TCA) cycle is the site of terminal fat oxidation, chief source of electrons for respiration, and a metabolic progenitor of gluconeogenesis. Therefore, we tested whether insulin resistance promotes hepatic TCA cycle flux in mice progressing to insulin resistance and fatty liver on a high-fat diet (HFD) for 32 weeks using standard biomolecular and in vivo 2H/13C tracer methods. Relative mitochondrial content increased, but respiratory efficiency declined by 32 weeks of HFD. Fasting ketogenesis became unresponsive to feeding or insulin clamp, indicating blunted but constitutively active mitochondrial β-oxidation. Impaired insulin signaling was marked by elevated in vivo gluconeogenesis and anaplerotic and oxidative TCA cycle flux. The induction of TCA cycle function corresponded to the development of mitochondrial respiratory dysfunction, hepatic oxidative stress, and inflammation. Thus, the hepatic TCA cycle appears to enable mitochondrial dysfunction during insulin resistance by increasing electron deposition into an inefficient respiratory chain prone to reactive oxygen species production and by providing mitochondria-derived substrate for elevated gluconeogenesis. PMID:22493093

  4. Insulin-induced translocation of IR to the nucleus in insulin responsive cells requires a nuclear translocation sequence.

    Science.gov (United States)

    Kesten, Dov; Horovitz-Fried, Miriam; Brutman-Barazani, Tamar; Sampson, Sanford R

    2018-04-01

    Insulin binding to its cell surface receptor (IR) activates a cascade of events leading to its biological effects. The Insulin-IR complex is rapidly internalized and then is either recycled back to the plasma membrane or sent to lysosomes for degradation. Although most of the receptor is recycled or degraded, a small amount may escape this pathway and migrate to the nucleus of the cell where it might be important in promulgation of receptor signals. In this study we explored the mechanism by which insulin induces IR translocation to the cell nucleus. Experiments were performed cultured L6 myoblasts, AML liver cells and 3T3-L1 adipocytes. Insulin treatment induced a rapid increase in nuclear IR protein levels within 2 to 5 min. Treatment with WGA, an inhibitor of nuclear import, reduced insulin-induced increases nuclear IR protein; IR was, however, translocated to a perinuclear location. Bioinformatics tools predicted a potential nuclear localization sequence (NLS) on IR. Immunofluorescence staining showed that a point mutation on the predicted NLS blocked insulin-induced IR nuclear translocation. In addition, blockade of nuclear IR activation in isolated nuclei by an IR blocking antibody abrogated insulin-induced increases in IR tyrosine phosphorylation and nuclear PKCδ levels. Furthermore, over expression of mutated IR reduced insulin-induced glucose uptake and PKB phosphorylation. When added to isolated nuclei, insulin induced IR phosphorylation but had no effect on nuclear IR protein levels. These results raise questions regarding the possible role of nuclear IR in IR signaling and insulin resistance. Copyright © 2018 Elsevier B.V. All rights reserved.

  5. Clinical study on insulin receptors of mononuclear cells in diabetes

    Energy Technology Data Exchange (ETDEWEB)

    Dalimunthe, D [Hiroshima Univ. (Japan). School of Medicine

    1980-12-01

    /sup 125/I-insulin binding activity to mononuclear cells was studied in 75 noninsulin-dependent diabetic subjects and 31 normal subjects and the following results were obtained. 1. /sup 125/I-insulin binding is directly proportional to the mononuclear cell concentrations. There is a linear increase of specific /sup 125/I-insulin binding. 2. The binding of /sup 125/I-insulin to mononuclear cells is displaced by the increasing concentration of native insulin. 3. The /sup 125/I-insulin degradation in the incubation medium after incubation of mononuclear cells for 24 hours at 4/sup 0/C was almost 5% in this study. 4. The insulin binding activity in diabetic subjects was lower than that in normal subjects (P < 0.001) without any significant difference in affinity constant. 5. The relationship of binding activity to age of diabetics (r = 0.06, N.S), relative body weitht (r = 0.06, N.S) and duration of diabetes from onset was not significant. 6. In untreated noninsulin-dependent diabetics the insulin binding activity was inversely correlated to fasting blood glucose level (r = 0.78, P < 0.001) and slightly inversely correlated to serum insulin level (r = 0.47, P < 0.01). A slight inverse correlation was also observed in serum triglyceride level (r = 0.53, P < 0.01) and in total cholesterol level (r = 0.29, P < 0.05). 7. No significant difference between the binding activity was observed by grade of diabetic retinopathy. 8. After treatment with diet and/or sulfonylurea, the diabetics exhibited a significant increase in insulin binding activity (P < 0.005) but no significant difference in plasma insulin level, body weight and plasma lipid levels was observed.

  6. [Severe type A insulin resistance syndrome due to a mutation in the insulin receptor gene].

    Science.gov (United States)

    Ros, P; Colino-Alcol, E; Grasso, V; Barbetti, F; Argente, J

    2015-01-01

    Insulin resistance syndromes without lipodystrophy are an infrequent and heterogeneous group of disorders with variable clinical phenotypes, associated with hyperglycemia and hyperinsulinemia. The three conditions related to mutations in the insulin receptor gene are leprechaunism or Donohue syndrome, Rabson-Mendenhall syndrome, and Type A syndrome. A case is presented on a patient diagnosed with type A insulin resistance, defined by the triad of extreme insulin resistance, acanthosis nigricans, and hyperandrogenism, carrying a heterozygous mutation in exon 19 of the insulin receptor gene coding for its tyrosine kinase domain that is crucial for the catalytic activity of the receptor. The molecular basis of the syndrome is reviewed, focusing on the structure-function relationships of the insulin receptor, knowing that the criteria for survival are linked to residual insulin receptor function. It is also pointed out that, although type A insulin resistance appears to represent a somewhat less severe condition, these patients have a high morbidity and their treatment is still unsatisfactory. Copyright © 2014 Asociación Española de Pediatría. Published by Elsevier Espana. All rights reserved.

  7. Amino Acids Attenuate Insulin Action on Gluconeogenesis and Promote Fatty Acid Biosynthesis via mTORC1 Signaling Pathway in trout Hepatocytes

    Directory of Open Access Journals (Sweden)

    Weiwei Dai

    2015-06-01

    Full Text Available Background/Aims: Carnivores exhibit poor utilization of dietary carbohydrates and glucose intolerant phenotypes, yet it remains unclear what are the causal factors and underlying mechanisms. We aimed to evaluate excessive amino acids (AAs-induced effects on insulin signaling, fatty acid biosynthesis and glucose metabolism in rainbow trout and determine the potential involvement of mTORC1 and p38 MAPK pathway. Methods: We stimulated trout primary hepatocytes with different AA levels and employed acute administration of rapamycin to inhibit mTORC1 activation. Results: Increased AA levels enhanced the phosphorylation of ribosomal protein S6 kinase (S6K1, S6, and insulin receptor substrate 1 (IRS-1 on Ser302 but suppressed Akt and p38 phosphorylation; up-regulated the expression of genes related to gluconeogenesis and fatty acid biosynthesis. mTORC1 inhibition not only inhibited the phosphorylation of mTORC1 downstream targets, but also blunted IRS-1 Ser302 phosphorylation and restored excessive AAs-suppressed Akt phosphorylation. Rapamycin also inhibited fatty acid biosynthetic and gluconeogenic gene expression. Conclusion: High levels of AAs up-regulate hepatic fatty acid biosynthetic gene expression through an mTORC1-dependent manner, while attenuate insulin-mediated repression of gluconeogenesis through elevating IRS-1 Ser302 phosphorylation, which in turn impairs Akt activation and thereby weakening insulin action. We propose that p38 MAPK probably also involves in these AAs-induced metabolic changes.

  8. Exercise, pregnancy, and insulin sensitivity--what is new?

    DEFF Research Database (Denmark)

    Damm, Peter; Breitowicz, Bettina; Hegaard, Hanne Kristine

    2007-01-01

    Pregnancy is characterized by a marked physiological insulin resistance. Overweight and obesity or lack of physical activity can aggravate this reduced insulin sensitivity further. Increased insulin resistance has been associated with serious pregnancy complications, such as gestational diabetes...... mellitus (GDM) and pre-eclampsia. Recent studies clearly indicate that physical activity before and during pregnancy can reduce the risk of GDM and pre-eclampsia....

  9. Roles of mitochondrial fragmentation and reactive oxygen species in mitochondrial dysfunction and myocardial insulin resistance

    International Nuclear Information System (INIS)

    Watanabe, Tomoyuki; Saotome, Masao; Nobuhara, Mamoru; Sakamoto, Atsushi; Urushida, Tsuyoshi; Katoh, Hideki; Satoh, Hiroshi; Funaki, Makoto; Hayashi, Hideharu

    2014-01-01

    Purpose: Evidence suggests an association between aberrant mitochondrial dynamics and cardiac diseases. Because myocardial metabolic deficiency caused by insulin resistance plays a crucial role in heart disease, we investigated the role of dynamin-related protein-1 (DRP1; a mitochondrial fission protein) in the pathogenesis of myocardial insulin resistance. Methods and Results: DRP1-expressing H9c2 myocytes, which had fragmented mitochondria with mitochondrial membrane potential (ΔΨ m ) depolarization, exhibited attenuated insulin signaling and 2-deoxy-D-glucose (2-DG) uptake, indicating insulin resistance. Treatment of the DRP1-expressing myocytes with Mn(III)tetrakis(1-methyl-4-pyridyl)porphyrin pentachloride (TMPyP) significantly improved insulin resistance and mitochondrial dysfunction. When myocytes were exposed to hydrogen peroxide (H 2 O 2 ), they increased DRP1 expression and mitochondrial fragmentation, resulting in ΔΨ m depolarization and insulin resistance. When DRP1 was suppressed by siRNA, H 2 O 2 -induced mitochondrial dysfunction and insulin resistance were restored. Our results suggest that a mutual enhancement between DRP1 and reactive oxygen species could induce mitochondrial dysfunction and myocardial insulin resistance. In palmitate-induced insulin-resistant myocytes, neither DRP1-suppression nor TMPyP restored the ΔΨ m depolarization and impaired 2-DG uptake, however they improved insulin signaling. Conclusions: A mutual enhancement between DRP1 and ROS could promote mitochondrial dysfunction and inhibition of insulin signal transduction. However, other mechanisms, including lipid metabolite-induced mitochondrial dysfunction, may be involved in palmitate-induced insulin resistance. - Highlights: • DRP1 promotes mitochondrial fragmentation and insulin-resistance. • A mutual enhancement between DRP1 and ROS ipromotes insulin-resistance. • Palmitate increases DRP1 expression and induces insulin-resistance. • Inhibition of DRP or ROS

  10. Roles of mitochondrial fragmentation and reactive oxygen species in mitochondrial dysfunction and myocardial insulin resistance

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, Tomoyuki [Internal Medicine III, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu 431-3192 (Japan); Saotome, Masao, E-mail: msaotome@hama-med.ac.jp [Internal Medicine III, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu 431-3192 (Japan); Nobuhara, Mamoru; Sakamoto, Atsushi; Urushida, Tsuyoshi; Katoh, Hideki; Satoh, Hiroshi [Internal Medicine III, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu 431-3192 (Japan); Funaki, Makoto [Clinical Research Center for Diabetes, Tokushima University Hospital, 2-50-1 Kuramoto-cho, Tokushima 770-8503 (Japan); Hayashi, Hideharu [Internal Medicine III, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu 431-3192 (Japan)

    2014-05-01

    Purpose: Evidence suggests an association between aberrant mitochondrial dynamics and cardiac diseases. Because myocardial metabolic deficiency caused by insulin resistance plays a crucial role in heart disease, we investigated the role of dynamin-related protein-1 (DRP1; a mitochondrial fission protein) in the pathogenesis of myocardial insulin resistance. Methods and Results: DRP1-expressing H9c2 myocytes, which had fragmented mitochondria with mitochondrial membrane potential (ΔΨ{sub m}) depolarization, exhibited attenuated insulin signaling and 2-deoxy-D-glucose (2-DG) uptake, indicating insulin resistance. Treatment of the DRP1-expressing myocytes with Mn(III)tetrakis(1-methyl-4-pyridyl)porphyrin pentachloride (TMPyP) significantly improved insulin resistance and mitochondrial dysfunction. When myocytes were exposed to hydrogen peroxide (H{sub 2}O{sub 2}), they increased DRP1 expression and mitochondrial fragmentation, resulting in ΔΨ{sub m} depolarization and insulin resistance. When DRP1 was suppressed by siRNA, H{sub 2}O{sub 2}-induced mitochondrial dysfunction and insulin resistance were restored. Our results suggest that a mutual enhancement between DRP1 and reactive oxygen species could induce mitochondrial dysfunction and myocardial insulin resistance. In palmitate-induced insulin-resistant myocytes, neither DRP1-suppression nor TMPyP restored the ΔΨ{sub m} depolarization and impaired 2-DG uptake, however they improved insulin signaling. Conclusions: A mutual enhancement between DRP1 and ROS could promote mitochondrial dysfunction and inhibition of insulin signal transduction. However, other mechanisms, including lipid metabolite-induced mitochondrial dysfunction, may be involved in palmitate-induced insulin resistance. - Highlights: • DRP1 promotes mitochondrial fragmentation and insulin-resistance. • A mutual enhancement between DRP1 and ROS ipromotes insulin-resistance. • Palmitate increases DRP1 expression and induces insulin

  11. Subcellular localization, mobility, and kinetic activity of glucokinase in glucose-responsive insulin-secreting cells.

    Science.gov (United States)

    Stubbs, M; Aiston, S; Agius, L

    2000-12-01

    We investigated the subcellular localization, mobility, and activity of glucokinase in MIN6 cells, a glucose-responsive insulin-secreting beta-cell line. Glucokinase is present in the cytoplasm and a vesicular/granule compartment that is partially colocalized with insulin granules. The granular staining of glucokinase is preserved after permeabilization of the cells with digitonin. There was no evidence for changes in distribution of glucokinase between the cytoplasm and the granule compartment during incubation of the cells with glucose. The rate of release of glucokinase and of phosphoglucoisomerase from digitonin-permeabilized cells was slower when cells were incubated at an elevated glucose concentration (S0.5 approximately 15 mmol/l). This effect of glucose was counteracted by competitive inhibitors of glucokinase (5-thioglucose and mannoheptulose) but was unaffected by fructose analogs and may be due to changes in cell shape or conformation of the cytoskeleton that are secondary to glucose metabolism. Based on the similar release of glucokinase and phosphoglucoisomerase, we found no evidence for specific binding of cytoplasmic digitonin-extractable glucokinase. The affinity of beta-cells for glucose is slightly lower than that in cell extracts and, unlike that in hepatocytes, is unaffected by fructose, tagatose, or a high-K+ medium, which is consistent with the lack of change in glucokinase distribution or release. We conclude that glucokinase is present in two locations, cytoplasm and the granular compartment, and that it does not translocate between them. This conclusion is consistent with the lack of adaptive changes in the glucose phosphorylation affinity. The glucokinase activity associated with the insulin granules may have a role in either direct or indirect coupling between glucose phosphorylation and insulin secretion.

  12. Comparison Between Individually and Group-Based Insulin Pump Initiation by Time-Driven Activity-Based Costing.

    Science.gov (United States)

    Ridderstråle, Martin

    2017-07-01

    Depending on available resources, competencies, and pedagogic preference, initiation of insulin pump therapy can be performed on either an individual or a group basis. Here we compared the two models with respect to resources used. Time-driven activity-based costing (TDABC) was used to compare initiating insulin pump treatment in groups (GT) to individual treatment (IT). Activities and cost drivers were identified, timed, or estimated at location. Medical quality and patient satisfaction were assumed to be noninferior and were not measured. GT was about 30% less time-consuming and 17% less cost driving per patient and activity compared to IT. As a batch driver (16 patients in one group) GT produced an upward jigsaw-shaped accumulative cost curve compared to the incremental increase incurred by IT. Taking the alternate cost for those not attending into account, and realizing the cost of opportunity gained, suggested that GT was cost neutral already when 5 of 16 patients attended, and that a second group could be initiated at no additional cost as the attendance rate reached 15:1. We found TDABC to be effective in comparing treatment alternatives, improving cost control and decision making. Everything else being equal, if the setup is available, our data suggest that initiating insulin pump treatment in groups is far more cost effective than on an individual basis and that TDABC may be used to find the balance point.

  13. Insulin Sensitivity Determines Effects of Insulin and Meal Ingestion on Systemic Vascular Resistance in Healthy Subjects.

    Science.gov (United States)

    Woerdeman, Jorn; Meijer, Rick I; Eringa, Etto C; Hoekstra, Trynke; Smulders, Yvo M; Serné, Erik H

    2016-01-01

    In addition to insulin's metabolic actions, insulin can dilate arterioles which increase blood flow to metabolically active tissues. This effect is blunted in insulin-resistant subjects. Insulin's effect on SVR, determined by resistance arterioles, has, however, rarely been examined directly. We determined the effects of both hyperinsulinemia and a mixed meal on SVR and its relationship with insulin sensitivity. Thirty-seven lean and obese women underwent a hyperinsulinemic-euglycemic clamp, and 24 obese volunteers underwent a mixed-meal test. SVR was assessed using CPP before and during hyperinsulinemia as well as before and 60 and 120 minutes after a meal. SVR decreased significantly during hyperinsulinemia (-13%; p Insulin decreased SVR more strongly in insulin-sensitive individuals (standardized β: -0.44; p = 0.01). In addition, SVR at 60 minutes after meal ingestion was inversely related to the Matsuda index (β: -0.39; p = 0.04) and the change in postprandial SVR was directly related to postprandial glycemia (β: 0.53; p insulin resistance. This suggests that resistance to insulin-induced vasodilatation contributes to regulation of vascular resistance. © 2015 John Wiley & Sons Ltd.

  14. Insulin secretion enhancing activity of roselle calyx extract in normal and streptozotocin-induced diabetic rats

    Science.gov (United States)

    Wisetmuen, Eamruthai; Pannangpetch, Patchareewan; Kongyingyoes, Bunkerd; Kukongviriyapan, Upa; Yutanawiboonchai, Wiboonchai; Itharat, Arunporn

    2013-01-01

    Background and Objective: Our recent study revealed the antihyperglycemic activity of an ethanolic extract of roselle calyxes (Hibiscus sabdariffa) in diabetic rats. The present study had, therefore, an objective to investigate the mechanism underlying this activity. Materials and Methods: Male Sprague Dawley rats were induced to be diabetes by intraperitoneal injection of 45 mg/kg streptozotocin (STZ). Normal rats as well as diabetic rats were administered with the ethanolic extract of H. sabdariffa calyxes (HS-EE) at 0.1 and 1.0 g/kg/day, respectively, for 6 weeks. Then, blood glucose and insulin levels, at basal and glucose-stimulated secretions, were measured. The pancreas was dissected to examine histologically. Results: HS-EE 1.0 g/kg/day significantly decreased the blood glucose level by 38 ± 12% in diabetic rats but not in normal rats. In normal rats, treatment with 1.0 g/kg HS-EE increased the basal insulin level significantly as compared with control normal rats (1.28 ± 0.25 and 0.55 ± 0.05 ng/ml, respectively). Interestingly, diabetic rats treated with 1.0 g/kg HS-EE also showed a significant increase in basal insulin level as compared with the control diabetic rats (0.30 ± 0.05 and 0.15 ± 0.01 ng/ml, respectively). Concerning microscopic histological examination, HS-EE 1.0 g/kg significantly increased the number of islets of Langerhans in both normal rats (1.2 ± 0.1 and 2.0 ± 0.1 islet number/10 low-power fields (LPF) for control and HS-EE treated group, respectively) and diabetic rats (1.0 ± 0.3 and 3.9 ± 0.6 islet number/10 LPF for control and HS-EE treated group, respectively). Conclusion: The antidiabetic activity of HS-EE may be partially mediated via the stimulating effect on insulin secretion. PMID:23798879

  15. Insulin Resistance in Alzheimer's Disease

    Science.gov (United States)

    Dineley, Kelly T; Jahrling, Jordan B; Denner, Larry

    2014-01-01

    Insulin is a key hormone regulating metabolism. Insulin binding to cell surface insulin receptors engages many signaling intermediates operating in parallel and in series to control glucose, energy, and lipids while also regulating mitogenesis and development. Perturbations in the function of any of these intermediates, which occur in a variety of diseases, cause reduced sensitivity to insulin and insulin resistance with consequent metabolic dysfunction. Chronic inflammation ensues which exacerbates compromised metabolic homeostasis. Since insulin has a key role in learning and memory as well as directly regulating ERK, a kinase required for the type of learning and memory compromised in early Alzheimer's disease (AD), insulin resistance has been identified as a major risk factor for the onset of AD. Animal models of AD or insulin resistance or both demonstrate that AD pathology and impaired insulin signaling form a reciprocal relationship. Of note are human and animal model studies geared toward improving insulin resistance that have led to the identification of the nuclear receptor and transcription factor, peroxisome proliferator-activated receptor gamma (PPARγ) as an intervention tool for early AD. Strategic targeting of alternate nodes within the insulin signaling network has revealed disease-stage therapeutic windows in animal models that coalesce with previous and ongoing clinical trial approaches. Thus, exploiting the connection between insulin resistance and AD provides powerful opportunities to delineate therapeutic interventions that slow or block the pathogenesis of AD. PMID:25237037

  16. Deletion of G-protein-coupled receptor 55 promotes obesity by reducing physical activity.

    Science.gov (United States)

    Meadows, A; Lee, J H; Wu, C-S; Wei, Q; Pradhan, G; Yafi, M; Lu, H-C; Sun, Y

    2016-03-01

    Cannabinoid receptor 1 (CB1) is the best-characterized cannabinoid receptor, and CB1 antagonists are used in clinical trials to treat obesity. Because of the wide range of CB1 functions, the side effects of CB1 antagonists pose serious concerns. G-protein-coupled receptor 55 (GPR55) is an atypical cannabinoid receptor, and its pharmacology and functions are distinct from CB1. GPR55 regulates neuropathic pain, gut, bone, immune functions and motor coordination. GPR55 is expressed in various brain regions and peripheral tissues. However, the roles of GPR55 in energy and glucose homeostasis are unknown. Here we have investigated the roles of GPR55 in energy balance and insulin sensitivity using GPR55-null mice (GPR55(-/-)). Body composition of the mice was measured by EchoMRI. Food intake, feeding behavior, energy expenditure and physical activity of GPR55(-/-) mice were determined by indirect calorimetry. Muscle function was assessed by forced treadmill running test. Insulin sensitivity was evaluated by glucose and insulin tolerance tests. Adipose inflammation was assessed by flow cytometry analysis of adipose tissue macrophages. The expression of inflammatory markers in adipose tissues and orexigenic/anorexigenic peptides in the hypothalamus was also analyzed by real-time PCR. GPR55(-/-) mice had normal total energy intake and feeding pattern (i.e., no changes in meal size, meal number or feeding frequency). Intriguingly, whereas adult GPR55(-/-) mice only showed a modest increase in overall body weight, they exhibited significantly increased fat mass and insulin resistance. The spontaneous locomotor activity of GPR55(-/-) mice was dramatically decreased, whereas resting metabolic rate and non-shivering thermogenesis were unchanged. Moreover, GPR55(-/-) mice exhibited significantly decreased voluntary physical activity, showing reduced running distance on the running wheels, whereas muscle function appeared to be normal. GPR55 has an important role in energy

  17. Vitamin C and E chronic supplementation differentially affect hepatic insulin signaling in rats.

    Science.gov (United States)

    Ali, Mennatallah A; Eid, Rania M H M; Hanafi, Mervat Y

    2018-02-01

    Vitamin C and vitamin E supplementations and their beneficial effects on type 2 diabetes mellitus (T2DM) have been subjected to countless controversial data. Hence, our aim is to investigate the hepatic molecular mechanisms of any diabetic predisposing risk of the chronic administration of different doses of vitamin E or vitamin C in rats. The rats were supplemented with different doses of vitamin C or vitamin E for eight months. Vitamin C and vitamin E increased fasting blood glucose, insulin, and homeostasis model assessment index for insulin resistance (HOMA). Vitamin C disrupted glucose tolerance by attenuating upstream hepatic insulin action through impairing the phosphorylation and activation of insulin receptor and its subsequent substrates; however, vitamin E showed its effect downstream insulin receptor in the insulin signaling pathway, reducing hepatic glucose transporter-2 (GLUT2) and phosphorylated protein kinase (p-Akt). Moreover, both vitamins showed their antioxidant capabilities [nuclear factor-erythroid-2-related factor 2 (Nrf2), total and reduced glutathione] and their negative effect on Wnt pathway [phosphorylated glycogen synthase kinase-3β (p-GSK-3β)], by altering the previously mentioned parameters, inevitably leading to severe reduction of reactive oxygen species (ROS) below the physiological levels. In conclusion, a detrimental effect of chronic antioxidant vitamins supplementation was detected; leading to insulin resistance and impaired glucose tolerance obviously through different mechanisms. Overall, these findings indicate that the conventional view that vitamins promote health benefits and delay chronic illnesses and aging should be modified or applied with caution. Copyright © 2017. Published by Elsevier Inc.

  18. Anaesthesia generates neuronal insulin resistance by inducing hypothermia

    Directory of Open Access Journals (Sweden)

    Sutherland Calum

    2008-10-01

    Full Text Available Abstract Background Anaesthesia is commonly employed prior to surgical investigations and to permit icv injections in rodents. Indeed it is standard practise in many studies examining the subsequent actions of hormones and growth factors on the brain. Recent evidence that the basal activity of specific intracellular signalling proteins can be affected by anaesthesia prompted us to examine the effect of anaesthesia not only on the basal activity but also the insulin sensitivity of the major insulin signalling pathways. Results We find that urethane- and ketamine-induced anaesthesia results in rapid activation of the phosphatidylinositol (PI 3-kinase-protein kinase B (PKB signalling pathway in the brain, increases tau phosphorylation while at the same time reducing basal activity of the Ras-ERK pathway. Subsequent injection of insulin does not alter the activity of either the PI 3-kinase or ERK signalling pathways, indicating a degree of neuronal molecular insulin resistance. However, if body temperature is maintained during anaesthesia then there is no alteration in the basal activity of these signalling molecules. Subsequent response of both pathways to insulin injection is restored. Conclusion The data is consistent with a hypothermia related alteration in neuronal signalling following anaesthesia, and emphasises the importance of maintaining the body temperature of rodents when monitoring insulin (or growth factor/neurotrophic agent action in the brain of anesthetised rodents.

  19. Peripheral insulin resistance in ILK-depleted mice by reduction of GLUT4 expression.

    Science.gov (United States)

    Hatem-Vaquero, Marco; Griera, Mercedes; García-Jerez, Andrea; Luengo, Alicia; Álvarez, Julia; Rubio, José A; Calleros, Laura; Rodríguez-Puyol, Diego; Rodríguez-Puyol, Manuel; De Frutos, Sergio

    2017-08-01

    The development of insulin resistance is characterized by the impairment of glucose uptake mediated by glucose transporter 4 (GLUT4). Extracellular matrix changes are induced when the metabolic dysregulation is sustained. The present work was devoted to analyze the possible link between the extracellular-to-intracellular mediator integrin-linked kinase (ILK) and the peripheral tissue modification that leads to glucose homeostasis impairment. Mice with general depletion of ILK in adulthood (cKD-ILK) maintained in a chow diet exhibited increased glycemia and insulinemia concurrently with a reduction of the expression and membrane presence of GLUT4 in the insulin-sensitive peripheral tissues compared with their wild-type littermates (WT). Tolerance tests and insulin sensitivity indexes confirmed the insulin resistance in cKD-ILK, suggesting a similar stage to prediabetes in humans. Under randomly fed conditions, no differences between cKD-ILK and WT were observed in the expression of insulin receptor (IR-B) and its substrate IRS-1 expressions. The IR-B isoform phosphorylated at tyrosines 1150/1151 was increased, but the AKT phosphorylation in serine 473 was reduced in cKD-ILK tissues. Similarly, ILK-blocked myotubes reduced their GLUT4 promoter activity and GLUT4 expression levels. On the other hand, the glucose uptake capacity in response to exogenous insulin was impaired when ILK was blocked in vivo and in vitro , although IR/IRS/AKT phosphorylation states were increased but not different between groups. We conclude that ILK depletion modifies the transcription of GLUT4, which results in reduced peripheral insulin sensitivity and glucose uptake, suggesting ILK as a molecular target and a prognostic biomarker of insulin resistance. © 2017 Society for Endocrinology.

  20. Globular adiponectin ameliorates metabolic insulin resistance via AMPK-mediated restoration of microvascular insulin responses

    Science.gov (United States)

    Zhao, Lina; Fu, Zhuo; Wu, Jing; Aylor, Kevin W; Barrett, Eugene J; Cao, Wenhong; Liu, Zhenqi

    2015-01-01

    Abstract Hypoadiponectinaemia is closely associated with endothelial dysfunction and insulin resistance, and microvasculature plays a critical role in the regulation of insulin action in muscle. Here we tested whether adiponectin replenishment could improve metabolic insulin sensitivity in male rats fed a high-fat diet (HFD) via the modulation of microvascular insulin responses. Male Sprague–Dawley rats were fed either a HFD or low-fat diet (LFD) for 4 weeks. Small resistance artery myograph changes in tension, muscle microvascular recruitment and metabolic response to insulin were determined. Compared with rats fed a LFD, HFD feeding abolished the vasodilatory actions of globular adiponectin (gAd) and insulin on pre-constricted distal saphenous arteries. Pretreatment with gAd improved insulin responses in arterioles isolated from HFD rats, which was blocked by AMP-activated protein kinase (AMPK) inhibition. Similarly, HFD abolished microvascular responses to either gAd or insulin and decreased insulin-stimulated glucose disposal by ∼60%. However, supplementing gAd fully rescued insulin’s microvascular action and significantly improved the metabolic responses to insulin in HFD male rats and these actions were abolished by inhibition of either AMPK or nitric oxide production. We conclude that HFD induces vascular adiponectin and insulin resistance but gAd administration can restore vascular insulin responses and improve insulin’s metabolic action via an AMPK- and nitric oxide-dependent mechanism in male rats. Key points Adiponectin is an adipokine with anti-inflammatory and anti-diabetic properties. Hypoadiponectinaemia is closely associated with endothelial dysfunction and insulin resistance in obesity and diabetes. Insulin resistance is present in muscle microvasculature and this may contribute to decreased insulin delivery to, and action in, muscle. In this study we examined whether adiponectin ameliorates metabolic insulin resistance by affecting muscle

  1. The interleukin-6 (-174) G/C promoter polymorphism is associated with type-2 diabetes mellitus in Native Americans and Caucasians

    DEFF Research Database (Denmark)

    Vozarova, Barbora; Fernández-Real, José-Manuel; Knowler, William C

    2003-01-01

    Chronic low-grade activation of the immune system may play a role in the pathogenesis of type-2 diabetes mellitus (T2DM). Interleukin-6 (IL6), a powerful inducer of hepatic acute phase response, has been implicated in the etiology of insulin resistance and T2DM. Recently, an IL6 promoter...... polymorphism (G/C) at position -174 was found to be associated with measures of insulin sensitivity. Because we have previously found an association between high IL6 levels and insulin resistance in both Pima Indians - a population with high rates of insulin resistance and T2DM - and Caucasians, we aimed...... to assess whether the IL6 promoter polymorphism is associated with T2DM in these populations. We genotyped the IL6 (-174) G/C polymorphism using pyrosequencing in 463 Native Americans and by PCR-RFLP in 329 Spanish Caucasians. Among the Spanish Caucasian subjects, there was a significant difference...

  2. Rebelling against the (Insulin Resistance: A Review of the Proposed Insulin-Sensitizing Actions of Soybeans, Chickpeas, and Their Bioactive Compounds

    Directory of Open Access Journals (Sweden)

    Jaime L. Clark

    2018-03-01

    Full Text Available Insulin resistance is a major risk factor for diseases such as type 2 diabetes and metabolic syndrome. Current methods for management of insulin resistance include pharmacological therapies and lifestyle modifications. Several clinical studies have shown that leguminous plants such as soybeans and pulses (dried beans, dried peas, chickpeas, lentils are able to reduce insulin resistance and related type 2 diabetes parameters. However, to date, no one has summarized the evidence supporting a mechanism of action for soybeans and pulses that explains their ability to lower insulin resistance. While it is commonly assumed that the biological activities of soybeans and pulses are due to their antioxidant activities, these bioactive compounds may operate independent of their antioxidant properties and, thus, their ability to potentially improve insulin sensitivity via alternative mechanisms needs to be acknowledged. Based on published studies using in vivo and in vitro models representing insulin resistant states, the proposed mechanisms of action for insulin-sensitizing actions of soybeans, chickpeas, and their bioactive compounds include increasing glucose transporter-4 levels, inhibiting adipogenesis by down-regulating peroxisome proliferator-activated receptor-γ, reducing adiposity, positively affecting adipokines, and increasing short-chain fatty acid-producing bacteria in the gut. Therefore, this review will discuss the current evidence surrounding the proposed mechanisms of action for soybeans and certain pulses, and their bioactive compounds, to effectively reduce insulin resistance.

  3. Overproduction of altered VLDL in an insulin-resistance rat model: Influence of SREBP-1c and PPAR-α.

    Science.gov (United States)

    Lucero, Diego; Miksztowicz, Verónica; Macri, Vanesa; López, Gustavo H; Friedman, Silvia; Berg, Gabriela; Zago, Valeria; Schreier, Laura

    2015-01-01

    In insulin-resistance, VLDL presents alterations that increase its atherogenic potential. The mechanism by which insulin-resistance promotes the production of altered VLDL is still not completely understood. The aim of this study was to evaluate the relationship between the expression of sterol regulatory element binding protein 1c (SREBP-1c) and of peroxisome proliferator-activated receptor-α (PPAR-α), with the features of composition and size of VLDL in an insulin-resistance rat model induced by a sucrose rich diet (SRD). The study was conducted on 12 male Wistar rats (180g) receiving SRD (12 weeks) and 12 controls. Lipid profile, free fatty acids, glucose, and insulin were measured. Lipid content in liver and visceral fat were assessed. Isolated VLDL (d<1.006g/ml) was characterized by its chemical composition and size by HPLC. The respective hepatic expression of SREBP-1c and PPAR-α was determined (Western blot). As expected, SRD had elevated triglycerides (TG), free fatty acids and insulin levels, and decreased HDL-cholesterol (p<0.05), together with augmented hepatic and visceral fat (p<0.05). SRD showed higher VLDL total mass - with increased TG content - and predominance of large VLDL (p<0.05). SRD showed an increase in SREBP-1c (precursor and mature forms) and decreased PPAR-α expression (p<0.045). SREBP-1c forms were positively associated with VLDL total mass (p<0.04), VLDL-TG% (p<0.019), and large VLDL% (p<0.002). On the other hand, PPAR-α correlated negatively with VLDL total mass (p=0.05), VLDL-TG% (p=0.005), and large VLDL% (p=0.002). Insulin-resistance, by coordinated activation of SREBP-1c and reduction of PPAR-α, could promote the secretion of larger and TG over-enriched VLDL particles, with greater atherogenic capacity. Copyright © 2014 Sociedad Española de Arteriosclerosis. Published by Elsevier España. All rights reserved.

  4. Fuel-Stimulated Insulin Secretion Depends upon Mitochondria Activation and the Integration of Mitochondrial and Cytosolic Substrate Cycles

    Directory of Open Access Journals (Sweden)

    Gary W. Cline

    2011-10-01

    Full Text Available The pancreatic islet β-cell is uniquely specialized to couple its metabolism and rates of insulin secretion with the levels of circulating nutrient fuels, with the mitochondrial playing a central regulatory role in this process. In the β-cell, mitochondrial activation generates an integrated signal reflecting rates of oxidativephosphorylation, Kreb's cycle flux, and anaplerosis that ultimately determines the rate of insulin exocytosis. Mitochondrial activation can be regulated by proton leak and mediated by UCP2, and by alkalinization to utilize the pH gradient to drive substrate and ion transport. Converging lines of evidence support the hypothesis that substrate cycles driven by rates of Kreb's cycle flux and by anaplerosis play an integral role in coupling responsive changes in mitochondrial metabolism with insulin secretion. The components and mechanisms that account for the integrated signal of ATP production, substrate cycling, the regulation of cellular redox state, and the production of other secondary signaling intermediates are operative in both rodent and human islet β-cells.

  5. Estradiol Protects Proopiomelanocortin Neurons Against Insulin Resistance.

    Science.gov (United States)

    Qiu, Jian; Bosch, Martha A; Meza, Cecilia; Navarro, Uyen-Vy; Nestor, Casey C; Wagner, Edward J; Rønnekleiv, Oline K; Kelly, Martin J

    2018-02-01

    Insulin resistance is at the core of the metabolic syndrome, and men exhibit a higher incidence of metabolic syndrome than women in early adult life, but this sex advantage diminishes sharply when women reach the postmenopausal state. Because 17β-estradiol (E2) augments the excitability of the anorexigenic proopiomelanocortin (POMC) neurons, we investigated the neuroprotective effects of E2 against insulin resistance in POMC neurons from diet-induced obese (DIO) female and male mice. The efficacy of insulin to activate canonical transient receptor potential 5 (TRPC5) channels and depolarize POMC neurons was significantly reduced in DIO male mice but not in DIO female mice. However, the insulin response in POMC neurons was abrogated in ovariectomized DIO females but restored with E2 replacement. E2 increased T-type calcium channel Cav3.1 messenger RNA (mRNA) expression and whole-cell currents but downregulated stromal-interaction molecule 1 mRNA, which rendered POMC neurons more excitable and responsive to insulin-mediated TRPC5 channel activation. Moreover, E2 prevented the increase in suppressor of cytokine signaling-3 mRNA expression with DIO as seen in DIO males. As proof of principle, insulin [intracerebroventricular injection into the third ventricle (ICV)] decreased food intake and increased metabolism in female but not male guinea pigs fed a high-fat diet. The uncoupling of the insulin receptor from its downstream effector system was corroborated by the reduced expression of phosphorylated protein kinase B in the arcuate nucleus of male but not female guinea pigs following insulin. Therefore, E2 protects female POMC neurons from insulin resistance by enhancing POMC neuronal excitability and the coupling of insulin receptor to TRPC5 channel activation. Copyright © 2018 Endocrine Society.

  6. AZD5363 inhibits inflammatory synergy between interleukin-17 and insulin/insulin-like growth factor 1

    Directory of Open Access Journals (Sweden)

    Chong eChen

    2014-12-01

    Full Text Available In the United States, one third of population is affected by obesity and almost 29 million people are suffering from type 2 diabetes. Obese people have elevated serum levels of insulin, insulin-like growth factor 1 (IGF1 and interleukin-17 (IL-17. Insulin and IGF1 are known to enhance IL-17-induced expression of inflammatory cytokines and chemokines, which may contribute to the chronic inflammatory status observed in obese people. We have previously demonstrated that insulin/IGF1 signaling pathway crosstalks with IL-17-activated nuclear factor-kappa B (NF-κB pathway through inhibiting glycogen synthase kinase 3β (GSK3β activity. However, it is unclear whether GSK3α also plays a role and whether this crosstalk can be manipulated by AZD5363, a novel pan-Akt inhibitor that has been shown to increase GSK3 activity through reducing phosphorylation of GSK3α and GSK3β. In this study, we investigated IL-17-induced expression of C-X-C motif ligand 1 (Cxcl1, C-C motif ligand 20 (Ccl20 and interleukin-6 (Il-6 in wild-type, GSK3α-/-, and GSK3β-/- mouse embryonic fibroblast (MEF cells as well as in mouse prostate tissues by real-time quantitative PCR. We examined the proteins involved in the signaling pathways by Western blot analysis. We found that insulin and IGF1 enhanced IL-17- induced expression of Cxcl1, Ccl20 and Il-6, which was associated with increased phosphorylation of GSK3α and GSK3β in the presence of insulin and IGF1. AZD5363 inhibited the synergy between IL-17 and insulin/IGF1 through reducing phosphorylation of GSK3α and GSK3β by inhibiting Akt function. These findings imply that the cooperative crosstalk of IL-17 and insulin/IGF1 in initiating inflammatory responses may be alleviated by AZD5363.

  7. Cyclodextrin-insulin complex encapsulated polymethacrylic acid based nanoparticles for oral insulin delivery.

    Science.gov (United States)

    Sajeesh, S; Sharma, Chandra P

    2006-11-15

    Present investigation was aimed at developing an oral insulin delivery system based on hydroxypropyl beta cyclodextrin-insulin (HPbetaCD-I) complex encapsulated polymethacrylic acid-chitosan-polyether (polyethylene glycol-polypropylene glycol copolymer) (PMCP) nanoparticles. Nanoparticles were prepared by the free radical polymerization of methacrylic acid in presence of chitosan and polyether in a solvent/surfactant free medium. Dynamic light scattering (DLS) experiment was conducted with particles dispersed in phosphate buffer (pH 7.4) and size distribution curve was observed in the range of 500-800 nm. HPbetaCD was used to prepare non-covalent inclusion complex with insulin and complex was analyzed by Fourier transform infrared (FTIR) and fluorescence spectroscopic studies. HPbetaCD complexed insulin was encapsulated into PMCP nanoparticles by diffusion filling method and their in vitro release profile was evaluated at acidic/alkaline pH. PMCP nanoparticles displayed good insulin encapsulation efficiency and release profile was largely dependent on the pH of the medium. Enzyme linked immunosorbent assay (ELISA) study demonstrated that insulin encapsulated inside the particles was biologically active. Trypsin inhibitory effect of PMCP nanoparticles was evaluated using N-alpha-benzoyl-L-arginine ethyl ester (BAEE) and casein as substrates. Mucoadhesive studies of PMCP nanoparticles were conducted using freshly excised rat intestinal mucosa and the particles were found fairly adhesive. From the preliminary studies, cyclodextrin complexed insulin encapsulated mucoadhesive nanoparticles appear to be a good candidate for oral insulin delivery.

  8. Exposures to arsenite and methylarsonite produce insulin resistance and impair insulin-dependent glycogen metabolism in hepatocytes.

    Science.gov (United States)

    Zhang, Chongben; Fennel, Emily M J; Douillet, Christelle; Stýblo, Miroslav

    2017-12-01

    Environmental exposure to inorganic arsenic (iAs) has been shown to disturb glucose homeostasis, leading to diabetes. Previous laboratory studies have suggested several mechanisms that may underlie the diabetogenic effects of iAs exposure, including (i) inhibition of insulin signaling (leading to insulin resistance) in glucose metabolizing peripheral tissues, (ii) inhibition of insulin secretion by pancreatic β cells, and (iii) dysregulation of the methylation or expression of genes involved in maintenance of glucose or insulin metabolism and function. Published studies have also shown that acute or chronic iAs exposures may result in depletion of hepatic glycogen stores. However, effects of iAs on pathways and mechanisms that regulate glycogen metabolism in the liver have never been studied. The present study examined glycogen metabolism in primary murine hepatocytes exposed in vitro to arsenite (iAs 3+ ) or its methylated metabolite, methylarsonite (MAs 3+ ). The results show that 4-h exposures to iAs 3+ and MAs 3+ at concentrations as low as 0.5 and 0.2 µM, respectively, decreased glycogen content in insulin-stimulated hepatocytes by inhibiting insulin-dependent activation of glycogen synthase (GS) and by inducing activity of glycogen phosphorylase (GP). Further investigation revealed that both iAs 3+ and MAs 3+ inhibit insulin-dependent phosphorylation of protein kinase B/Akt, one of the mechanisms involved in the regulation of GS and GP by insulin. Thus, inhibition of insulin signaling (i.e., insulin resistance) is likely responsible for the dysregulation of glycogen metabolism in hepatocytes exposed to iAs 3+ and MAs 3+ . This study provides novel information about the mechanisms by which iAs exposure impairs glucose homeostasis, pointing to hepatic metabolism of glycogen as one of the targets.

  9. Loss of renal SNX5 results in impaired IDE activity and insulin resistance in mice.

    Science.gov (United States)

    Li, Fengmin; Yang, Jian; Villar, Van Anthony M; Asico, Laureano D; Ma, Xiaobo; Armando, Ines; Sanada, Hironobu; Yoneda, Minoru; Felder, Robin A; Jose, Pedro A; Wang, Xiaoyan

    2018-03-01

    We hypothesised that renal sorting nexin 5 (SNX5) regulates the insulin-degrading enzyme (IDE) and, thus, circulating insulin levels. We therefore studied the dynamic interaction between SNX5 and IDE in human renal proximal tubule cells (hRPTCs), as well as in rat and mouse kidneys. The regulation of IDE by SNX5 expressed in the kidney was studied in vitro and in vivo. Snx5 or mock siRNA was added to immortalised hRPTCs (passage <20) in culture or selectively infused, via osmotic mini-pump, into the remnant kidney of uninephrectomised mice and rats. SNX5 co-localised with IDE at the plasma membrane and perinuclear area of hRPTCs and in the brush border membrane of proximal tubules of human, rat, and mouse kidneys. Insulin increased the co-localisation and co-immunoprecipitation of SNX5 and IDE in hRPTCs. Silencing SNX5 in hRPTCs decreased IDE expression and activity. Renal-selective silencing of Snx5 (SNX5 protein: 100 ± 25 vs 29 ± 10, p < 0.05 [% of control]) in C57Bl/6J mice decreased IDE protein (100 ± 13 vs 57 ± 6, p < 0.05 [% of control]) and urinary insulin excretion, impaired the responses to insulin and glucose, and increased blood insulin and glucose levels. Spontaneously hypertensive rats (SHRs) had increased blood insulin and glucose levels and decreased renal SNX5 (100 ± 27 vs 29 ± 6, p < 0.05 [% of control]) and IDE (100 ± 5 vs 75 ± 4, p < 0.05 [% of control]) proteins, compared with normotensive Wistar-Kyoto (WKY) rats. Kidney Snx5-depleted WKY rats also had increased blood insulin and glucose levels. The expression of SNX5 and IDE was decreased in RPTCs from SHRs and hypertensive humans compared with cells from normotensive volunteers, indicating a common cause for hyperinsulinaemia and hypertension. Renal SNX5 positively regulates IDE expression and function. This study is the first to demonstrate the novel and crucial role of renal SNX5 in insulin and glucose metabolism.

  10. Sustained activation of the mammalian target of rapamycin nutrient sensing pathway is associated with hepatic insulin resistance, but not with steatosis, in mice

    NARCIS (Netherlands)

    Korsheninnikova, E.; van der Zon, G. C. M.; Voshol, P. J.; Janssen, G. M.; Havekes, L. M.; Grefhorst, A.; Kuipers, F.; Reijngoud, D. -J.; Romijn, J. A.; Ouwens, D. M.; Maassen, J. A.

    2006-01-01

    Aims/hypothesis Activation of nutrient sensing through mammalian target of rapamycin (mTOR) has been linked to the pathogenesis of insulin resistance. We examined activation of mTOR-signalling in relation to insulin resistance and hepatic steatosis in mice. Materials and methods Chronic hepatic

  11. Neurotrophin Signaling Is Required for Glucose-Induced Insulin Secretion.

    Science.gov (United States)

    Houtz, Jessica; Borden, Philip; Ceasrine, Alexis; Minichiello, Liliana; Kuruvilla, Rejji

    2016-11-07

    Insulin secretion by pancreatic islet β cells is critical for glucose homeostasis, and a blunted β cell secretory response is an early deficit in type 2 diabetes. Here, we uncover a regulatory mechanism by which glucose recruits vascular-derived neurotrophins to control insulin secretion. Nerve growth factor (NGF), a classical trophic factor for nerve cells, is expressed in pancreatic vasculature while its TrkA receptor is localized to islet β cells. High glucose rapidly enhances NGF secretion and increases TrkA phosphorylation in mouse and human islets. Tissue-specific deletion of NGF or TrkA, or acute disruption of TrkA signaling, impairs glucose tolerance and insulin secretion in mice. We show that internalized TrkA receptors promote insulin granule exocytosis via F-actin reorganization. Furthermore, NGF treatment augments glucose-induced insulin secretion in human islets. These findings reveal a non-neuronal role for neurotrophins and identify a new regulatory pathway in insulin secretion that can be targeted to ameliorate β cell dysfunction. Copyright © 2016 Elsevier Inc. All rights reserved.

  12. The relationship between the connecting peptide of recombined single chain insulin and its biological function

    Institute of Scientific and Technical Information of China (English)

    HUANG; Yiding; (

    2001-01-01

    . et al., The role of C-terminus of insulin B chain and the amino group of B29Lys side chain in the growth promoting activities of insulin, Acta Biochim. Biophys. Sin., 1999, 31: 274-278.[24]Yang, J. T., Wu, C. S., Martinez, H. M., Calculation of protein conformation from circular dichroism, Meth. Enzym., 1986, 130: 208-269.[25]Mirmira, R. G., Tager, H. S., Role of the phenylalanine B24 side chain in directing insulin interaction with its receptor, Importance of main chain conformation, J. Biol. Chem., 1989, 264: 6349-6354.[26]Inouye, M., Intramolecular chaperone: the role of the pro-peptide in protein folding, Enzyme, 1991, 45: 314-321.[27]Murray-Rust, J., McLeod, A. N., Blundell, T. L. et al., Structure and evolution of insulins: Implications for receptor binding, Bioassays, 1992, 14: 325-331.[28]Cheng, S. G., Kim, D. Y., Chio, K. D. et al., Human insulin production from a novel miniproinsulin which has high receptor-binding activity, Biochem. J., 1998, 329: 631-635.

  13. Mulberry (Morus alba L.) Fruit Extract Containing Anthocyanins Improves Glycemic Control and Insulin Sensitivity via Activation of AMP-Activated Protein Kinase in Diabetic C57BL/Ksj-db/db Mice.

    Science.gov (United States)

    Choi, Kyung Ha; Lee, Hyun Ah; Park, Mi Hwa; Han, Ji-Sook

    2016-08-01

    The effect of mulberry (Morus alba L.) fruit extract (MFE) on hyperglycemia and insulin sensitivity in an animal model of type 2 diabetes was evaluated. C57BL/Ksj-diabetic db/db mice were divided into three groups: diabetic control, rosiglitazone, and MFE groups. Blood glucose, plasma insulin, and intraperitoneal glucose were measured, and an insulin tolerance test was performed after MFE supplementation in db/db mice. In addition, the protein levels of various targets of insulin signaling were measured by western blotting. The blood levels of glucose and HbA1c were significantly lower in the MFE-supplemented group than in the diabetic control group. Moreover, glucose and insulin tolerance tests showed that MFE treatment increased insulin sensitivity. The homeostatic index of insulin resistance significantly decreased in the MFE-supplemented group relative to the diabetic control group. MFE supplementation significantly stimulated the levels of phosphorylated (p)-AMP-activated protein kinase (pAMPK) and p-Akt substrate of 160 kDa (pAS160) and enhanced the level of plasma membrane-glucose transporter 4 (GLUT4) in skeletal muscles. Further, dietary MFE significantly increased pAMPK and decreased the levels of glucose 6-phosphatase and phosphoenolpyruvate carboxykinase in the liver. MFE may improve hyperglycemia and insulin sensitivity via activation of AMPK and AS160 in skeletal muscles and inhibition of gluconeogenesis in the liver.

  14. Insulin Resistance Induced by Hyperinsulinemia Coincides with a Persistent Alteration at the Insulin Receptor Tyrosine Kinase Domain

    Science.gov (United States)

    Catalano, Karyn J.; Maddux, Betty A.; Szary, Jaroslaw; Youngren, Jack F.; Goldfine, Ira D.; Schaufele, Fred

    2014-01-01

    Insulin resistance, the diminished response of target tissues to insulin, is associated with the metabolic syndrome and a predisposition towards diabetes in a growing proportion of the worldwide population. Under insulin resistant states, the cellular response of the insulin signaling pathway is diminished and the body typically responds by increasing serum insulin concentrations to maintain insulin signaling. Some evidence indicates that the increased insulin concentration may itself further dampen insulin response. If so, insulin resistance would worsen as the level of circulating insulin increases during compensation, which could contribute to the transition of insulin resistance to more severe disease. Here, we investigated the consequences of excess insulin exposure to insulin receptor (IR) activity. Cells chronically exposed to insulin show a diminished the level of IR tyrosine and serine autophosphorylation below that observed after short-term insulin exposure. The diminished IR response did not originate with IR internalization since IR amounts at the cell membrane were similar after short- and long-term insulin incubation. Förster resonance energy transfer between fluorophores attached to the IR tyrosine kinase (TK) domain showed that a change in the TK domain occurred upon prolonged, but not short-term, insulin exposure. Even though the altered ‘insulin refractory’ IR TK FRET and IR autophosphorylation levels returned to baseline (non-stimulated) levels after wash-out of the original insulin stimulus, subsequent short-term exposure to insulin caused immediate re-establishment of the insulin-refractory levels. This suggests that some cell-based ‘memory’ of chronic hyperinsulinemic exposure acts directly at the IR. An improved understanding of that memory may help define interventions to reset the IR to full insulin responsiveness and impede the progression of insulin resistance to more severe disease states. PMID:25259572

  15. Insulin resistance induced by hyperinsulinemia coincides with a persistent alteration at the insulin receptor tyrosine kinase domain.

    Directory of Open Access Journals (Sweden)

    Karyn J Catalano

    Full Text Available Insulin resistance, the diminished response of target tissues to insulin, is associated with the metabolic syndrome and a predisposition towards diabetes in a growing proportion of the worldwide population. Under insulin resistant states, the cellular response of the insulin signaling pathway is diminished and the body typically responds by increasing serum insulin concentrations to maintain insulin signaling. Some evidence indicates that the increased insulin concentration may itself further dampen insulin response. If so, insulin resistance would worsen as the level of circulating insulin increases during compensation, which could contribute to the transition of insulin resistance to more severe disease. Here, we investigated the consequences of excess insulin exposure to insulin receptor (IR activity. Cells chronically exposed to insulin show a diminished the level of IR tyrosine and serine autophosphorylation below that observed after short-term insulin exposure. The diminished IR response did not originate with IR internalization since IR amounts at the cell membrane were similar after short- and long-term insulin incubation. Förster resonance energy transfer between fluorophores attached to the IR tyrosine kinase (TK domain showed that a change in the TK domain occurred upon prolonged, but not short-term, insulin exposure. Even though the altered 'insulin refractory' IR TK FRET and IR autophosphorylation levels returned to baseline (non-stimulated levels after wash-out of the original insulin stimulus, subsequent short-term exposure to insulin caused immediate re-establishment of the insulin-refractory levels. This suggests that some cell-based 'memory' of chronic hyperinsulinemic exposure acts directly at the IR. An improved understanding of that memory may help define interventions to reset the IR to full insulin responsiveness and impede the progression of insulin resistance to more severe disease states.

  16. Glucose, other secretagogues, and nerve growth factor stimulate mitogen-activated protein kinase in the insulin-secreting beta-cell line, INS-1

    DEFF Research Database (Denmark)

    Frödin, M; Sekine, N; Roche, E

    1995-01-01

    The signaling pathways whereby glucose and hormonal secretagogues regulate insulin-secretory function, gene transcription, and proliferation of pancreatic beta-cells are not well defined. We show that in the glucose-responsive beta-cell line INS-1, major secretagogue-stimulated signaling pathways...... converge to activate 44-kDa mitogen-activated protein (MAP) kinase. Thus, glucose-induced insulin secretion was found to be associated with a small stimulatory effect on 44-kDa MAP kinase, which was synergistically enhanced by increased levels of intracellular cAMP and by the hormonal secretagogues......-1. Phorbol ester, an activator of protein kinase C, stimulated 44-kDa MAP kinase by both Ca(2+)-dependent and -independent pathways. Nerve growth factor, independently of changes in cytosolic Ca2+, efficiently stimulated 44-kDa MAP kinase without causing insulin release, indicating that activation...

  17. Selenium Supranutrition: Are the Potential Benefits of Chemoprevention Outweighed by the Promotion of Diabetes and Insulin Resistance?

    Science.gov (United States)

    Rocourt, Caroline R. B.; Cheng, Wen-Hsing

    2013-01-01

    Selenium was considered a toxin until 1957, when this mineral was shown to be essential in the prevention of necrotic liver damage in rats. The hypothesis of selenium chemoprevention is principally formulated by the observations that cancer incidence is inversely associated with selenium status. However, recent clinical and epidemiological studies demonstrate a role for some selenoproteins in exacerbating or promoting other disease states, specifically type 2 diabetes, although other data support a role of selenium in stimulating insulin sensitivity. Therefore, it is clear that our understanding in the role of selenium in glucose metabolism and chemoprevention is inadequate and incomplete. Research exploring the role of selenium in individual healthcare is of upmost importance and possibly will help explain how selenium is a double-edged sword in the pathologies of chronic diseases. PMID:23603996

  18. Pre-gravid physical activity and reduced risk of glucose intolerance in pregnancy: the role of insulin sensitivity.

    Science.gov (United States)

    Retnakaran, Ravi; Qi, Ying; Sermer, Mathew; Connelly, Philip W; Zinman, Bernard; Hanley, Anthony J G

    2009-04-01

    Pre-gravid physical activity has been associated with a reduced risk of gestational diabetes mellitus (GDM), although neither the types of exercise nor the physiologic mechanisms underlying this protective effect have been well-studied. Thus, we sought to study the relationships between types of pre-gravid physical activity and metabolic parameters in pregnancy, including glucose tolerance, insulin sensitivity and beta-cell function. A total of 851 women underwent a glucose challenge test (GCT) and a 3-h oral glucose tolerance test (OGTT) in late pregnancy, yielding four glucose tolerance groups: (i) GDM; (ii) gestational impaired glucose tolerance (GIGT); (iii) abnormal GCT with normal glucose tolerance on OGTT (abnormal GCT NGT); and (iv) normal GCT with NGT on OGTT (normal GCT NGT). Pre-gravid physical activity was assessed using the Baecke questionnaire, which measures (i) total physical activity and (ii) its three component domains: work, nonsport leisure-time, and vigorous/sports activity. Glucose tolerance status improved across increasing quartiles of pre-gravid total physical activity (P = 0.0244). Whereas neither work nor nonsport leisure-time activity differed between glucose tolerance groups, pre-gravid vigorous/sports activity was significantly higher in women with normal GCT NGT compared to women with (i) abnormal GCT NGT (P = 0.0018) (ii) GIGT (P = 0.0025), and (iii) GDM (P = 0.0044). In particular, vigorous/sports activity correlated with insulin sensitivity (measured by IS(OGTT)) (r = 0.21, P sports activity emerged as a significant independent predictor of IS(OGTT) in pregnancy (t = 4.97, P sports activity is associated with a reduced risk of glucose intolerance in pregnancy, an effect likely mediated by enhanced insulin sensitivity.

  19. Potensi Terapeutik Fibroblast Growth Factor 21 terhadap Resistensi Insulin

    Directory of Open Access Journals (Sweden)

    Kurniasari Kurniasari

    2015-12-01

    Full Text Available Fibroblast growth factor 21 (FGF21 merupakan salah satu dari anggota FGF yang berperansebagai faktor endokrin. Hepar dan jaringan adiposa merupakan tempat kerja utama FGF21.Ekspresi FGF21 di hepar diatur oleh peroxisome proliferator activated receptor alpha (PPARαsedangkan di jaringan adiposa diatur oleh peroxisome proliferator activated receptor gamma(PPARγ. Kedua faktor transkripsi tersebut terlibat dalam metabolisme karbohidrat dan lipid. Padaresistensi insulin terdapat hiperglikemia, hiperinsulinemia, dan dislipidemia. Pemberian FGF21pada berbagai studi in vivo dan in vitro telah menunjukan potensi FGF21 dalam mengatasi kelainanakibat resistensi insulin sekaligus meningkatkan sensitivitas jaringan terhadap insulin. Kata kunci: FGF21, PPARγ, PPARα, resistensi insulin Fibroblast Growth Factor 21 (FGF21 Potension in InsulinResistance Treatment Abstract Fibroblast growth factor 21 (FGF21 is a member of FGF family that plays a role as endocrinefactor. Liver and adipose tissue are major target of FGF21. The expression of FGF21 in liveris regulated by peroxisome proliferator activated receptor alpha (PPARα, while peroxisomeproliferator activated receptor gamma (PPARγ regulate FGF21 expression in adipose tissue.Both transcription factors are involved in carbohydrate and lipid metabolism. Hyperglycemia,hyperinsulinemia, and dyslipidemia are observed in insulin resistance. Treatment with FGF21 inin vitro and in vivo study showed that FGF21 have the potential to overcome insulin resistance aswell as increasing tissue’s sensitivity towards insulin. Keywords: FGF21, PPARγ, PPARα, insulin resistance Normal 0 false false false IN X-NONE X-NONE

  20. A new variation in the promoter region, the -604 C>T, and the Leu72Met polymorphism of the ghrelin gene are associated with protection to insulin resistance.

    Science.gov (United States)

    Zavarella, S; Petrone, A; Zampetti, S; Gueorguiev, M; Spoletini, M; Mein, C A; Leto, G; Korbonits, M; Buzzetti, R

    2008-04-01

    Previous studies suggested that polymorphisms in the coding region of the preproghrelin were involved in the etiology of obesity and might modulate glucose-induced insulin secretion. We evaluated the association of a new variation, -604C>T, in the promoter region of the ghrelin gene, of Leu72Met (247C>A) and of Gln90Leu (265A>T), all haplotype-tagging single nucleotide polymorphisms (SNPs), with measures of insulin sensitivity in 1420 adult individuals. The three SNPs were genotyped using ABI PRISM 7900 HT Sequence Detection System. We used multiple linear regression analysis for quantitative traits and THESIAS software for haplotype analysis. We observed a protective effect exerted by Met72 variant of Leu72Met SNP on insulin resistance parameters; a significant decreasing trend from Leu/Leu to Leu/Met and to Met/Met homozygous subjects in triglycerides, fasting insulin levels and HOMA-IR index (P=0.02, 0.01 and 0.003, respectively), and, consistently, an increase in ghrelin levels (P=0.003) was found. A significant decrease from CC to TC and to TT genotypes in insulin levels and HOMA-IR index was also detected (P=0.00l for both), but only in subjects homozygous for Leu72, where the protective effect of Met72 was not present. The haplotype analysis results supported the data obtained by the evaluation of each single SNP, showing the highest value of insulin levels and HOMA-IR index in the -604(c)247(c) haplotype intermediate value in -604(T)247(C) and lowest value in -604(C)247(A). Our observations suggest a protective role of the Met72 variant and of -604 T allele in modulating insulin resistance. These SNPs or an unknown functional variant in linkage disequilibrium could increase ghrelin levels and probably insulin sensitivity.

  1. β cell membrane remodelling and procoagulant events occur in inflammation-driven insulin impairment: a GLP-1 receptor dependent and independent control.

    Science.gov (United States)

    Gleizes, Céline; Kreutter, Guillaume; Abbas, Malak; Kassem, Mohamad; Constantinescu, Andrei Alexandru; Boisramé-Helms, Julie; Yver, Blandine; Toti, Florence; Kessler, Laurence

    2016-02-01

    Inflammation and hyperglycaemia are associated with a prothrombotic state. Cell-derived microparticles (MPs) are the conveyors of active procoagulant tissue factor (TF) and circulate at high concentration in diabetic patients. Liraglutide, a glucagon-like peptide (GLP)-1 analogue, is known to promote insulin secretion and β-cell preservation. In this in vitro study, we examined the link between insulin impairment, procoagulant activity and plasma membrane remodelling, under inflammatory conditions. Rin-m5f β-cell function, TF activity mediated by MPs and their modulation by 1 μM liraglutide were examined in a cell cross-talk model. Methyl-β-cyclodextrine (MCD), a cholesterol depletor, was used to evaluate the involvement of raft on TF activity, MP shedding and insulin secretion as well as Soluble N-éthylmaleimide-sensitive-factor Attachment protein Receptor (SNARE)-dependent exocytosis. Cytokines induced a two-fold increase in TF activity at MP surface that was counteracted by liraglutide. Microparticles prompted TF activity on the target cells and a two-fold decrease in insulin secretion via protein kinase A (PKA) and p38 signalling, that was also abolished by liraglutide. Large lipid raft clusters were formed in response to cytokines and liraglutide or MCD-treated cells showed similar patterns. Cells pre-treated by saturating concentration of the GLP-1r antagonist exendin (9-39), showed a partial abolishment of the liraglutide-driven insulin secretion and liraglutide-decreased TF activity. Measurement of caspase 3 cleavage and MP shedding confirmed the contribution of GLP-1r-dependent and -independent pathways. Our results confirm an integrative β-cell response to GLP-1 that targets receptor-mediated signalling and membrane remodelling pointing at the coupling of insulin secretion and inflammation-driven procoagulant events. © 2015 The Authors. Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and

  2. Exercise, pregnancy, and insulin sensitivity--what is new?

    DEFF Research Database (Denmark)

    Damm, Peter; Breitowicz, Bettina; Hegaard, Hanne

    2007-01-01

    Pregnancy is characterized by a marked physiological insulin resistance. Overweight and obesity or lack of physical activity can aggravate this reduced insulin sensitivity further. Increased insulin resistance has been associated with serious pregnancy complications, such as gestational diabetes...

  3. Design of insulin analogues for meal-related therapy.

    Science.gov (United States)

    Brange, J

    1993-01-01

    The human insulin in replacement therapy has a hexameric structure. Hexamerization of the insulin molecule facilitates biosynthesis and beta-cell storage of insulin, but is unnecessary for biologic activity and appears to contribute to delayed absorption of exogenous insulin from the subcutis. Insulin analogues with reduced self-association that are produced through recombinant DNA techniques have been shown to have in vivo activity comparable to that of human insulin and absorption kinetics characterized by higher and more constant rates of disappearance from the subcutaneous injection site. In preliminary studies in patients receiving insulin therapy, monomeric insulin analogues have been found to provide glycemic control in the postprandial period that is at least equivalent to that of human insulin. Findings in these studies suggest that the use of such analogues may provide meal-related insulin effects closer to those observed in the physiologic state by limiting excessive postprandial glucose excursions and decreasing the risk of late hypoglycemia. Banting and Best revolutionized diabetes therapy 70 years ago with the extraction of insulin from animal pancreas glands (J Lab Clin Med 7:464-472, 1922). Since that time, many refinements of the therapeutic properties of pharmaceutical preparations of the hormone have been introduced. Until recently, however, such advances have been limited to improvements in insulin purity, insulin species, and adjustment of the composition of the vehicle with respect to auxiliary substances and other additives. With the advent of recombinant DNA techniques, it has become possible to optimize the insulin molecule itself for purposes of replacement therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

  4. Insulin induces a shift in lipid and primary carbon metabolites in a model of fasting-induced insulin resistance

    Science.gov (United States)

    Olmstead, Keedrian I.; La Frano, Michael R.; Fahrmann, Johannes; Grapov, Dmitry; Viscarra, Jose A.; Newman, John W.; Fiehn, Oliver; Crocker, Daniel E.; Filipp, Fabian V.; Ortiz, Rudy M.

    2017-01-01

    Introduction Prolonged fasting in northern elephant seals (NES) is characterized by a reliance on lipid metabolism, conservation of protein, and reduced plasma insulin. During early fasting, glucose infusion previously reduced plasma free fatty acids (FFA); however, during late-fasting, it induced an atypical elevation in FFA despite comparable increases in insulin during both periods suggestive of a dynamic shift in tissue responsiveness to glucose-stimulated insulin secretion. Objective To better assess the contribution of insulin to this fasting-associated shift in substrate metabolism. Methods We compared the responses of plasma metabolites (amino acids (AA), FFA, endocannabinoids (EC), and primary carbon metabolites (PCM)) to an insulin infusion (65 mU/kg) in early- and late-fasted NES pups (n = 5/group). Plasma samples were collected prior to infusion (T0) and at 10, 30, 60, and 120 min post-infusion, and underwent untargeted and targeted metabolomics analyses utilizing a variety of GC-MS and LC-MS technologies. Results In early fasting, the majority (72%) of metabolite trajectories return to baseline levels within 2 h, but not in late fasting indicative of an increase in tissue sensitivity to insulin. In late-fasting, increases in FFA and ketone pools, coupled with decreases in AA and PCM, indicate a shift toward lipolysis, beta-oxidation, ketone metabolism, and decreased protein catabolism. Conversely, insulin increased PCM AUC in late fasting suggesting that gluconeogenic pathways are activated. Insulin also decreased FFA AUC between early and late fasting suggesting that insulin suppresses triglyceride hydrolysis. Conclusion Naturally adapted tolerance to prolonged fasting in these mammals is likely accomplished by suppressing insulin levels and activity, providing novel insight on the evolution of insulin during a condition of temporary, reversible insulin resistance. PMID:28757815

  5. Endonucleolysis in the turnover of insulin-like growth factor II mRNA

    DEFF Research Database (Denmark)

    Nielsen, F C; Christiansen, Jan

    1992-01-01

    The overlapping transcription units constituting the rat insulin-like growth factor II (IGF-II) locus generate multiple mRNAs by using different promoters. Three promoters have been identified, giving rise to 4.6-, 3.8-, and 3.6-kilobase mRNAs. The latter, originating from promoter P3, is the most...

  6. Elevated insulin and reduced insulin like growth factor binding protein-3/prostate specific antigen ratio with increase in prostate size in Benign Prostatic Hyperplasia.

    Science.gov (United States)

    Sreenivasulu, Karli; Nandeesha, Hanumanthappa; Dorairajan, Lalgudi Narayanan; Rajappa, Medha; Vinayagam, Vickneshwaran

    2017-06-01

    Insulin and insulin like growth factor-1 (IGF-1) have growth promoting effects, while insulin like growth factor binding protein-3 (IGFBP-3) has growth inhibitory effects. The present study was designed to assess the concentrations of insulin, IGF-1, IGFBP-3 and their association with prostate size in patients with BPH. Ninety 90 BPH cases and 90 controls were enrolled in the study. Insulin, IGF-1, IGFBP-3, PSA, testosterone and estradiol were estimated in both the groups. Insulin, IGF-1 and estradiol were increased and IGFBP-3/PSA was decreased in BPH cases when compared with controls. Insulin (r=0.64, p=0.001) and IGF-1 (r=0.22, p=0.03) were positively correlated and IGFBP-3/PSA (r=-0.316, p=0.002) were negatively correlated with prostate size in BPH. Multivariate analysis showed that insulin (p=0.001) and IGFBP-3/PSA (p=0.004) predicts the prostate size in patients with BPH. Insulin was increased and IGFBP-3/PSA was reduced in BPH patients with increased prostate size. At a cutoff concentration of 527.52, IGFBP-3/PSA ratio was found to differentiate benign growth of prostate from normal prostate with 96% sensitivity and 96% specificity. Insulin is elevated and IGFBP-3/PSA is reduced with increase prostate size in BPH cases. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Absorption of protamine-insulin in diabetic patients. Part 1. Preparation and characterization of protamine-/sup 125/I-insulin

    Energy Technology Data Exchange (ETDEWEB)

    Hansen, B; Linde, S; Koelendorf, K; Jensen, F [Steno Memorial Hospital and Nordisk Insulinlaboratorium, Gentofte (Denmark). Research Lab.

    1979-02-01

    Protamine-/sup 125/I-insulin with low specific radioactivity was prepared using /sup 125/,/sup 127/I-insulin, 0.2 I/mole. The preparations were characterized by disc electrophoresis, isoelectric focusing and analytical gel chromatography in order to evaluate the suitability of /sup 125/I-insulin as marker for insulin in protamine-insulin. The stability of the preparations was followed up to 90 days at 4/sup 0/C. The biological and immunological activity was determined in mice, isolated rat fat cells and by radioimmunoassay. It was concluded that both from a chemical and a biological point of view, the protamine-/sup 125/I-insulin is a satisfactory preparation that might be used in absorption studies.

  8. Alkali pH directly activates ATP-sensitive K+ channels and inhibits insulin secretion in beta-cells.

    Science.gov (United States)

    Manning Fox, Jocelyn E; Karaman, Gunce; Wheeler, Michael B

    2006-11-17

    Glucose stimulation of pancreatic beta-cells is reported to lead to sustained alkalization, while extracellular application of weak bases is reported to inhibit electrical activity and decrease insulin secretion. We hypothesize that beta-cell K(ATP) channel activity is modulated by alkaline pH. Using the excised patch-clamp technique, we demonstrate a direct stimulatory action of alkali pH on recombinant SUR1/Kir6.2 channels due to increased open probability. Bath application of alkali pH similarly activates native islet beta-cell K(ATP) channels, leading to an inhibition of action potentials, and hyperpolarization of membrane potential. In situ pancreatic perfusion confirms that these cellular effects of alkali pH are observable at a functional level, resulting in decreases in both phase 1 and phase 2 glucose-stimulated insulin secretion. Our data are the first to report a stimulatory effect of a range of alkali pH on K(ATP) channel activity and link this to downstream effects on islet beta-cell function.

  9. Expression of an insulin/interleukin-1 receptor antagonist hybrid gene in insulin-producing cell lines (HIT-T15 and NIT-1) confers resistance against interleukin-1-induced nitric oxide production.

    Science.gov (United States)

    Welsh, N; Bendtzen, K; Welsh, M

    1995-01-01

    A hybrid gene consisting of the insulin gene enhancer/promoter region, the signal sequence, the insulin B- and C-chains, and the human interleukin-1 receptor antagonist (IL-1ra) gene was constructed. This hybrid gene was transfected together with the pSV2-neo construct into the insulin-producing cell lines HIT-T15 and NIT-1. One of the geneticin-selected clones, HITra2, expressed a 1.4-kb mRNA, which hybridized both to insulin and IL-1ra-cDNA in Northern blot analysis. Three proteins, with the mol wt 23, 17, and 14 kD, were immunoprecipitated with anti-IL-1ra antibodies from [35S]methionine-labeled HITra2 cells. Both at a low and at a high glucose concentration, 4-5 ng of IL-1ra/10(6) cells (ELISA) was released from these cells. On the other hand, a high glucose concentration evoked a three-fold increase in the release of insulin, suggesting that IL-1ra was released constitutively. Measured by nitrite production, transfected HIT, and NIT-1 cells exhibited a more than 10-fold decrease in IL-1 beta sensitivity. Since the conditioned culture media from the HITra2 cells exhibited an anti-IL-1 beta activity of only 0.5 U/ml, and mixed culture of HITra2 cells and isolated rat islets prevented IL-1 beta induced inhibition of insulin release, it is likely that IL-1ra acts locally at the cell surface. It is concluded that expression of a hybrid insulin/IL-1ra gene confers resistance to IL-1 and that this technique may be used to elucidate the role of IL-1 in autoimmune disorders such as insulin-dependent diabetes mellitus. Images PMID:7706480

  10. IGF-1 and insulin as growth hormones.

    Science.gov (United States)

    Laron, Zvi

    2004-01-01

    IGF-1 generated in the liver is the anabolic effector and linear growth promoting hormone of the pituitary growth hormone (GH). This is evidenced by dwarfism in states of congenital IGF-1 deficiency, Igf1 gene mutation/deletions or knockouts, and in Laron syndrome (LS), due to GH receptor gene mutations/deletions or IGF-1 receptor blocking. In a positive way, daily IGF-1 administration to stunted patients with LS or hGH gene deletion accelerates linear growth velocity. IGF-1 acts on the proliferative cells of the epiphyseal cartilage. IGF-1 also induces organ and tissue growth; its absence causing organomicria. Insulin shares a common ancestry with IGF-1 and with 45% amino acid homology, as well as very close relationships in the structure of its receptors and post-receptor cascade, also acts as a growth hormone. It has protein anabolic activity and stimulates IGF-1 synthesis. Pancreas agenesis causes short babies, and obese children with hyperinsulinism, with or without pituitary GH, have an accelerated growth rate and skeletal maturation; so do babies with macrosomia. Whether the insulin growth effect is direct, or mediated by IGF-1 or leptin is controversial.

  11. THE INFLUENCE OF THYROID FUNCTION AND BONE TURNOVER ON LIPOPROTEIN PROFILE IN YOUNG PHYSICALLY ACTIVE MEN WITH DIFFERENT INSULIN SENSITIVITY

    Directory of Open Access Journals (Sweden)

    A. Kęska

    2014-07-01

    Full Text Available Physical activity induces changes in the endocrine system. Previous data indicated that changes in insulin secretion and the tissue response to this hormone are very important for energy metabolism. It is believed that they are accompanied by changes in lipid metabolism, but factors contributing to this process are still disputed. The aim of this study was to assess interactions among insulin sensitivity, thyroid function, a bone turnover marker and serum lipid profile in young physically active men. Eighty-seven physical education students, aged 18-23 years, participated in the study. We measured serum levels of glucose, lipids, insulin, thyroid-stimulating hormone (TSH, osteocalcin and anthropometric parameters. Insulin sensitivity was determined using homeostatic model assessment for insulin resistance (HOMA-IR. The median value of HOMA-IR (1.344 was used to divide the study population into Group A (above the median and Group B (below the median. Men from both groups did not differ in anthropometric parameters or in daily physical activity. Triglycerides (TG, total cholesterol (TC and high-density lipoprotein cholesterol (HDL-C levels were higher in Group A (P<0.05. TSH and osteocalcin levels were similar in males with different HOMA-IR. Multiple regression analysis for TSH and osteocalcin showed that in Group A these hormones had no effect on plasma lipoproteins. However, in Group B they significantly determined the variation of plasma TC and low-density lipoprotein cholesterol (LDL-C levels (in about 28% and 29%, respectively. We concluded that TSH and osteocalcin are involved in determination of a more healthy lipid profile at a certain level of insulin sensitivity.

  12. Studies of gene expression and activity of hexokinase, phosphofructokinase and glycogen synthase in human skeletal muscle in states of altered insulin-stimulated glucose metabolism

    DEFF Research Database (Denmark)

    Vestergaard, H

    1999-01-01

    been reported to increase the basal concentration of muscle GS mRNA in NIDDM patients to a level similar to that seen in control subjects although insulin-stimulated glucose disposal rates remain reduced in NIDDM patients. In the insulin resistant states examined so far, basal and insulin-stimulated......When whole body insulin-stimulated glucose disposal rate is measured in man applying the euglycaemic, hyperinsulinaemic clamp technique it has been shown that approximately 75% of glucose is taken up by skeletal muscle. After the initial transport step, glucose is rapidly phosphorylated to glucose...... critical roles in glucose oxidation/glycolysis and glucose storage, respectively. Glucose transporters and glycogen synthase activities are directly and acutely stimulated by insulin whereas the activities of hexokinases and phosphofructokinase may primarily be allosterically regulated. The aim...

  13. Archaeal promoter architecture and mechanism of gene activation

    DEFF Research Database (Denmark)

    Peng, Nan; Ao, Xiang; Liang, Yun Xiang

    2011-01-01

    element named ara box directing arabinose-inducible expression and the basal promoter element TATA, serving as the binding site for the TATA-binding protein. Strikingly, these promoters possess a modular structure that allows an essentially inactive basal promoter to be strongly activated. The invoked...... mechanisms include TFB (transcription factor B) recruitment by the ara-box-binding factor to activate gene expression and modulation of TFB recruitment efficiency to yield differential gene expression....

  14. A clinical study on insulin receptors of mononuclear cells in diabetes

    International Nuclear Information System (INIS)

    Dalimunthe, D.

    1980-01-01

    125 I-insulin binding activity to mononuclear cells was studied in 75 noninsulin-dependent diabetic subjects and 31 normal subjects and the following results were obtained. 1. 125 I-insulin binding is directly proportional to the mononuclear cell concentrations. There is a linear increase of specific 125 I-insulin binding. 2. The binding of 125 I-insulin to mononuclear cells is displaced by the increasing concentration of native insulin. 3. The 125 I-insulin degradation in the incubation medium after incubation of mononuclear cells for 24 hours at 4 0 C was almost 5% in this study. 4. The insulin binding activity in diabetic subjects was lower than that in normal subjects (P < 0.001) without any significant difference in affinity constant. 5. The relationship of binding activity to age of diabetics (r = 0.06, N.S), relative body weitht (r = 0.06, N.S) and duration of diabetes from onset was not significant. 6. In untreated noninsulin-dependent diabetics the insulin binding activity was inversely correlated to fasting blood glucose level (r = 0.78, P < 0.001) and slightly inversely correlated to serum insulin level (r = 0.47, P < 0.01). A slight inverse correlation was also observed in serum triglyceride level (r = 0.53, P < 0.01) and in total cholesterol level (r = 0.29, P < 0.05). 7. No significant difference between the binding activity was observed by grade of diabetic retinopathy. 8. After treatment with diet and/or sulfonylurea, the diabetics exhibited a significant increase in insulin binding activity (P < 0.005) but no significant difference in plasma insulin level, body weight and plasma lipid levels was observed. (author)

  15. Chelation of intracellular calcium blocks insulin action in the adipocyte

    International Nuclear Information System (INIS)

    Pershadsingh, H.A.; Shade, D.L.; Delfert, D.M.; McDonald, J.M.

    1987-01-01

    The hypothesis that intracellular Ca 2+ is an essential component of the intracellular mechanism of insulin action in the adipocyte was evaluated. Cells were loaded with the Ca 2+ chelator quin-2, by preincubating them with quin-2 AM, the tetrakis(acetoxymethyl) ester of quin-2. Quin-2 loading inhibited insulin-stimulated glucose transport without affecting basal activity. The ability of insulin to stimulate glucose uptake in quin-2-loaded cells could be partially restored by preincubating cells with buffer supplemented with 1.2 mM CaCl 2 and the Ca 2+ ionophore A23187. These conditions had no effect on basal activity and omission of CaCl 2 from the buffer prevented the restoration of insulin-stimulated glucose uptake by A23187. Quin-2 loading also inhibited insulin-stimulated glucose oxidation and the ability of insulin to inhibit cAMP-stimulated lipolysis without affecting their basal activities. Incubation of cells with 100 μM quin-2 or quin-2 AM had no effect on intracellular ATP concentration or the specific binding of 125 I=labeled insulin to adipocytes. These findings suggest that intracellular Ca 2+ is an essential component in the coupling of the insulin-activated receptor complex to cellular physiological/metabolic machinery. Furthermore, differing quin-2 AM dose-response profiles suggest the presence of dual Ca 2+ -dependent pathways in the adipocyte. One involves insulin stimulation of glucose transport and oxidation, whereas the other involves the antilipolytic action of insulin

  16. Insulin sensitizers prevent fine particulate matter-induced vascular insulin resistance and changes in endothelial progenitor cell homeostasis.

    Science.gov (United States)

    Haberzettl, Petra; McCracken, James P; Bhatnagar, Aruni; Conklin, Daniel J

    2016-06-01

    Exposure to fine particular matter (PM2.5) increases the risk of developing cardiovascular disease and Type 2 diabetes. Because blood vessels are sensitive targets of air pollutant exposure, we examined the effects of concentrated ambient PM2.5 (CAP) on vascular insulin sensitivity and circulating levels of endothelial progenitor cells (EPCs), which reflect cardiovascular health. We found that CAP exposure for 9 days decreased insulin-stimulated Akt phosphorylation in the aorta of mice maintained on control diet. This change was accompanied by the induction of IL-1β and increases in the abundance of cleaved IL-18 and p10 subunit of Casp-1, consistent with the activation of the inflammasome pathway. CAP exposure also suppressed circulating levels of EPCs (Flk-1(+)/Sca-1(+) cells), while enhancing the bone marrow abundance of these cells. Although similar changes in vascular insulin signaling and EPC levels were observed in mice fed high-fat diet, CAP exposure did not exacerbate diet-induced changes in vascular insulin resistance or EPC homeostasis. Treatment with an insulin sensitizer, metformin or rosiglitazone, prevented CAP-induced vascular insulin resistance and NF-κB and inflammasome activation and restored peripheral blood and bone marrow EPC levels. These findings suggest that PM2.5 exposure induces diet-independent vascular insulin resistance and inflammation and prevents EPC mobilization, and that this EPC mobilization defect could be mediated by vascular insulin resistance. Impaired vascular insulin sensitivity may be an important mechanism underlying PM2.5-induced vascular injury, and pharmacological sensitization to insulin action could potentially prevent deficits in vascular repair and mitigate vascular inflammation due to exposure to elevated levels of ambient air pollution. Copyright © 2016 the American Physiological Society.

  17. The insulin secretory action of novel polycyclic guanidines: discovery through open innovation phenotypic screening, and exploration of structure-activity relationships.

    Science.gov (United States)

    Shaghafi, Michael B; Barrett, David G; Willard, Francis S; Overman, Larry E

    2014-02-15

    We report the discovery of the glucose-dependent insulin secretogogue activity of a novel class of polycyclic guanidines through phenotypic screening as part of the Lilly Open Innovation Drug Discovery platform. Three compounds from the University of California, Irvine, 1-3, having the 3-arylhexahydropyrrolo[1,2-c]pyrimidin-1-amine scaffold acted as insulin secretagogues under high, but not low, glucose conditions. Exploration of the structure-activity relationship around the scaffold demonstrated the key role of the guanidine moiety, as well as the importance of two lipophilic regions, and led to the identification of 9h, which stimulated insulin secretion in isolated rat pancreatic islets in a glucose-dependent manner. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

  18. Insulin and GLP-1 infusions demonstrate the onset of adipose-specific insulin resistance in a large fasting mammal: potential glucogenic role for GLP-1.

    Science.gov (United States)

    Viscarra, Jose A; Rodriguez, Ruben; Vazquez-Medina, Jose Pablo; Lee, Andrew; Tift, Michael S; Tavoni, Stephen K; Crocker, Daniel E; Ortiz, Rudy M

    2013-08-01

    Prolonged food deprivation increases lipid oxidation and utilization, which may contribute to the onset of the insulin resistance associated with fasting. Because insulin resistance promotes the preservation of glucose and oxidation of fat, it has been suggested to be an adaptive response to food deprivation. However, fasting mammals exhibit hypoinsulinemia, suggesting that the insulin resistance-like conditions they experience may actually result from reduced pancreatic sensitivity to glucose/capacity to secrete insulin. To determine whether fasting results in insulin resistance or in pancreatic dysfunction, we infused early- and late-fasted seals (naturally adapted to prolonged fasting) with insulin (0.065 U/kg), and a separate group of late-fasted seals with low (10 pM/kg) or high (100 pM/kg) dosages of glucagon-like peptide-1 (GLP-1) immediately following a glucose bolus (0.5g/kg), and measured the systemic and cellular responses. Because GLP-1 facilitates glucose-stimulated insulin secretion, these infusions provide a method to assess pancreatic insulin-secreting capacity. Insulin infusions increased the phosphorylation of insulin receptor and Akt in adipose and muscle of early and late fasted seals; however the timing of the signaling response was blunted in adipose of late fasted seals. Despite the dose-dependent increases in insulin and increased glucose clearance (high dose), both GLP-1 dosages produced increases in plasma cortisol and glucagon, which may have contributed to the glucogenic role of GLP-1. Results suggest that fasting induces adipose-specific insulin resistance in elephant seal pups, while maintaining skeletal muscle insulin sensitivity, and therefore suggests that the onset of insulin resistance in fasting mammals is an evolved response to cope with prolonged food deprivation.

  19. In situ detection of the activation of Rac1 and RalA small GTPases in mouse adipocytes by immunofluorescent microscopy following in vivo and ex vivo insulin stimulation.

    Science.gov (United States)

    Takenaka, Nobuyuki; Nihata, Yuma; Ueda, Sho; Satoh, Takaya

    2017-11-01

    Rac1 has been implicated in insulin-dependent glucose uptake by mechanisms involving plasma membrane translocation of the glucose transporter GLUT4 in skeletal muscle. Although the uptake of glucose is also stimulated by insulin in adipose tissue, the role for Rac1 in adipocyte insulin signaling remains controversial. As a step to reveal the role for Rac1 in adipocytes, we aimed to establish immunofluorescent microscopy to detect the intracellular distribution of activated Rac1. The epitope-tagged Rac1-binding domain of a Rac1-specific target was utilized as a probe that specifically recognizes the activated form of Rac1. Rac1 activation in response to ex vivo and in vivo insulin stimulations in primary adipocyte culture and mouse white adipose tissue, respectively, was successfully observed by immunofluorescent microscopy. These Rac1 activations were mediated by phosphoinositide 3-kinase. Another small GTPase RalA has also been implicated in insulin-stimulated glucose uptake in skeletal muscle and adipose tissue. Similarly to Rac1, immunofluorescent microscopy using an activated RalA-specific polypeptide probe allowed us to detect intracellular distribution of insulin-activated RalA in adipocytes. These novel approaches to visualize the activation status of small GTPases in adipocytes will largely contribute to the understanding of signal transduction mechanisms particularly for insulin action. Copyright © 2017 Elsevier Inc. All rights reserved.

  20. Fat-Specific DsbA-L Overexpression Promotes Adiponectin Multimerization and Protects Mice From Diet-Induced Obesity and Insulin Resistance

    Science.gov (United States)

    Liu, Meilian; Xiang, Ruihua; Wilk, Sarah Ann; Zhang, Ning; Sloane, Lauren B.; Azarnoush, Kian; Zhou, Lijun; Chen, Hongzhi; Xiang, Guangda; Walter, Christi A.; Austad, Steven N.; Musi, Nicolas; DeFronzo, Ralph A.; Asmis, Reto; Scherer, Philipp E.; Dong, Lily Q.; Liu, Feng

    2012-01-01

    The antidiabetic and antiatherosclerotic effects of adiponectin make it a desirable drug target for the treatment of metabolic and cardiovascular diseases. However, the adiponectin-based drug development approach turns out to be difficult due to extremely high serum levels of this adipokine. On the other hand, a significant correlation between adiponectin multimerization and its insulin-sensitizing effects has been demonstrated, suggesting a promising alternative therapeutic strategy. Here we show that transgenic mice overexpressing disulfide bond A oxidoreductase-like protein in fat (fDsbA-L) exhibited increased levels of total and the high-molecular-weight form of adiponectin compared with wild-type (WT) littermates. The fDsbA-L mice also displayed resistance to diet-induced obesity, insulin resistance, and hepatic steatosis compared with WT control mice. The protective effects of DsbA-L overexpression on diet-induced insulin resistance, but not increased body weight and fat cell size, were significantly decreased in adiponectin-deficient fDsbA-L mice (fDsbA-L/Ad−/−). In addition, the fDsbA-L/Ad−/− mice displayed greater activity and energy expenditure compared with adiponectin knockout mice under a high-fat diet. Taken together, our results demonstrate that DsbA-L protects mice from diet-induced obesity and insulin resistance through adiponectin-dependent and independent mechanisms. In addition, upregulation of DsbA-L could be an effective therapeutic approach for the treatment of obesity and its associated metabolic disorders. PMID:22807031

  1. Fasting and Systemic Insulin Signaling Regulate Phosphorylation of Brain Proteins That Modulate Cell Morphology and Link to Neurological Disorders*

    Science.gov (United States)

    Li, Min; Quan, Chao; Toth, Rachel; Campbell, David G.; MacKintosh, Carol; Wang, Hong Yu; Chen, Shuai

    2015-01-01

    Diabetes is strongly associated with cognitive decline, but the molecular reasons are unknown. We found that fasting and peripheral insulin promote phosphorylation and dephosphorylation, respectively, of specific residues on brain proteins including cytoskeletal regulators such as slit-robo GTPase-activating protein 3 (srGAP3) and microtubule affinity-regulating protein kinases (MARKs), in which deficiency or dysregulation is linked to neurological disorders. Fasting activates protein kinase A (PKA) but not PKB/Akt signaling in the brain, and PKA can phosphorylate the purified srGAP3. The phosphorylation of srGAP3 and MARKs were increased when PKA signaling was activated in primary neurons. Knockdown of PKA decreased the phosphorylation of srGAP3. Furthermore, WAVE1, a protein kinase A-anchoring protein, formed a complex with srGAP3 and PKA in the brain of fasted mice to facilitate the phosphorylation of srGAP3 by PKA. Although brain cells have insulin receptors, our findings are inconsistent with the down-regulation of phosphorylation of target proteins being mediated by insulin signaling within the brain. Rather, our findings infer that systemic insulin, through a yet unknown mechanism, inhibits PKA or protein kinase(s) with similar specificity and/or activates an unknown phosphatase in the brain. Ser858 of srGAP3 was identified as a key regulatory residue in which phosphorylation by PKA enhanced the GAP activity of srGAP3 toward its substrate, Rac1, in cells, thereby inhibiting the action of this GTPase in cytoskeletal regulation. Our findings reveal novel mechanisms linking peripheral insulin sensitivity with cytoskeletal remodeling in neurons, which may help to explain the association of diabetes with neurological disorders such as Alzheimer disease. PMID:26499801

  2. Voluntary exercise improves insulin sensitivity and adipose tissue inflammation in diet-induced obese mice

    OpenAIRE

    Bradley, Richard L.; Jeon, Justin Y.; Liu, Fen-Fen; Maratos-Flier, Eleftheria

    2008-01-01

    Exercise promotes weight loss and improves insulin sensitivity. However, the molecular mechanisms mediating its beneficial effects are not fully understood. Obesity correlates with increased production of inflammatory cytokines, which in turn, contributes to systemic insulin resistance. To test the hypothesis that exercise mitigates this inflammatory response, thereby improving insulin sensitivity, we developed a model of voluntary exercise in mice made obese by feeding of a high fat/high suc...

  3. Quercetin suppresses insulin receptor signaling through inhibition of the insulin ligand–receptor binding and therefore impairs cancer cell proliferation

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Feng [Department of Gastroenterology, The Tenth People’s Hospital of Shanghai, Tongji University, Shanghai 200072 (China); Department of Nanomedicine, Houston Methodist Research Institute, Houston, TX 77030 (United States); Yang, Yong, E-mail: yyang@houstonmethodist.org [Department of Nanomedicine, Houston Methodist Research Institute, Houston, TX 77030 (United States); Department of Medicine, Weill Cornell Medical College, New York, NY 10065 (United States)

    2014-10-03

    Graphical abstract: - Highlights: • Quercetin inhibits insulin ligand–receptor interactions. • Quercetin reduces downstream insulin receptor signaling. • Quercetin blocks insulin induced glucose uptake. • Quercetin suppresses insulin stimulated cancer cell proliferation and tumor growth. - Abstract: Although the flavonoid quercetin is known to inhibit activation of insulin receptor signaling, the inhibitory mechanism is largely unknown. In this study, we demonstrate that quercetin suppresses insulin induced dimerization of the insulin receptor (IR) through interfering with ligand–receptor interactions, which reduces the phosphorylation of IR and Akt. This inhibitory effect further inhibits insulin stimulated glucose uptake due to decreased cell membrane translocation of glucose transporter 4 (GLUT4), resulting in impaired cancer cell proliferation. The effect of quercetin in inhibiting tumor growth was also evident in an in vivo model, indicating a potential future application for quercetin in the treatment of cancers.

  4. Quercetin suppresses insulin receptor signaling through inhibition of the insulin ligand–receptor binding and therefore impairs cancer cell proliferation

    International Nuclear Information System (INIS)

    Wang, Feng; Yang, Yong

    2014-01-01

    Graphical abstract: - Highlights: • Quercetin inhibits insulin ligand–receptor interactions. • Quercetin reduces downstream insulin receptor signaling. • Quercetin blocks insulin induced glucose uptake. • Quercetin suppresses insulin stimulated cancer cell proliferation and tumor growth. - Abstract: Although the flavonoid quercetin is known to inhibit activation of insulin receptor signaling, the inhibitory mechanism is largely unknown. In this study, we demonstrate that quercetin suppresses insulin induced dimerization of the insulin receptor (IR) through interfering with ligand–receptor interactions, which reduces the phosphorylation of IR and Akt. This inhibitory effect further inhibits insulin stimulated glucose uptake due to decreased cell membrane translocation of glucose transporter 4 (GLUT4), resulting in impaired cancer cell proliferation. The effect of quercetin in inhibiting tumor growth was also evident in an in vivo model, indicating a potential future application for quercetin in the treatment of cancers

  5. Shared Genetic Control of Brain Activity During Sleep and Insulin Secretion: A Laboratory-Based Family Study.

    Science.gov (United States)

    Morselli, Lisa L; Gamazon, Eric R; Tasali, Esra; Cox, Nancy J; Van Cauter, Eve; Davis, Lea K

    2018-01-01

    Over the past 20 years, a large body of experimental and epidemiologic evidence has linked sleep duration and quality to glucose homeostasis, although the mechanistic pathways remain unclear. The aim of the current study was to determine whether genetic variation influencing both sleep and glucose regulation could underlie their functional relationship. We hypothesized that the genetic regulation of electroencephalographic (EEG) activity during non-rapid eye movement sleep, a highly heritable trait with fingerprint reproducibility, is correlated with the genetic control of metabolic traits including insulin sensitivity and β-cell function. We tested our hypotheses through univariate and bivariate heritability analyses in a three-generation pedigree with in-depth phenotyping of both sleep EEG and metabolic traits in 48 family members. Our analyses accounted for age, sex, adiposity, and the use of psychoactive medications. In univariate analyses, we found significant heritability for measures of fasting insulin sensitivity and β-cell function, for time spent in slow-wave sleep, and for EEG spectral power in the delta, theta, and sigma ranges. Bivariate heritability analyses provided the first evidence for a shared genetic control of brain activity during deep sleep and fasting insulin secretion rate. © 2017 by the American Diabetes Association.

  6. Regulation of ALF promoter activity in Xenopus oocytes.

    Directory of Open Access Journals (Sweden)

    Dan Li

    Full Text Available BACKGROUND: In this report we evaluate the use of Xenopus laevis oocytes as a matched germ cell system for characterizing the organization and transcriptional activity of a germ cell-specific X. laevis promoter. PRINCIPAL FINDINGS: The promoter from the ALF transcription factor gene was cloned from X. laevis genomic DNA using a PCR-based genomic walking approach. The endogenous ALF gene was characterized by RACE and RT-PCR for transcription start site usage, and by sodium bisulfite sequencing to determine its methylation status in somatic and oocyte tissues. Homology between the X. laevis ALF promoter sequence and those from human, chimpanzee, macaque, mouse, rat, cow, pig, horse, dog, chicken and X. tropicalis was relatively low, making it difficult to use such comparisons to identify putative regulatory elements. However, microinjected promoter constructs were very active in oocytes and the minimal promoter could be narrowed by PCR-mediated deletion to a region as short as 63 base pairs. Additional experiments using a series of site-specific promoter mutants identified two cis-elements within the 63 base pair minimal promoter that were critical for activity. Both elements (A and B were specifically recognized by proteins present in crude oocyte extracts based on oligonucleotide competition assays. The activity of promoter constructs in oocytes and in transfected somatic Xenopus XLK-WG kidney epithelial cells was quite different, indicating that the two cell types are not functionally equivalent and are not interchangeable as assay systems. CONCLUSIONS: Overall the results provide the first detailed characterization of the organization of a germ cell-specific Xenopus promoter and demonstrate the feasibility of using immature frog oocytes as an assay system for dissecting the biochemistry of germ cell gene regulation.

  7. Chitosan nanofibers for transbuccal insulin delivery.

    Science.gov (United States)

    Lancina, Michael G; Shankar, Roopa Kanakatti; Yang, Hu

    2017-05-01

    In this work, they aimed at producing chitosan based nanofiber mats capable of delivering insulin via the buccal mucosa. Chitosan was electrospun into nanofibers using poly(ethylene oxide) (PEO) as a carrier molecule in various feed ratios. The mechanical properties and degradation kinetics of the fibers were measured. Insulin release rates were determined in vitro using an ELISA assay. The bioactivity of released insulin was measured in terms of Akt activation in pre-adipocytes. Insulin permeation across the buccal mucosa was measured in an ex-vivo porcine transbuccal model. Fiber morphology, mechanical properties, and in vitro stability were dependent on PEO feed ratio. Lower PEO content blends produced smaller diameter fibers with significantly faster insulin release kinetics. Insulin showed no reduction in bioactivity due to electrospinning. Buccal permeation of insulin facilitated by high chitosan content blends was significantly higher than that of free insulin. Taken together, the work demonstrates that chitosan-based nanofibers have the potential to serve as a transbuccal insulin delivery vehicle. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1252-1259, 2017. © 2017 Wiley Periodicals, Inc.

  8. Insulin delivery route for the artificial pancreas: subcutaneous, intraperitoneal, or intravenous? Pros and cons.

    Science.gov (United States)

    Renard, Eric

    2008-07-01

    Insulin delivery is a crucial component of a closed-loop system aiming at the development of an artificial pancreas. The intravenous route, which has been used in the bedside artificial pancreas model for 30 years, has clear advantages in terms of pharmacokinetics and pharmacodynamics, but cannot be used in any ambulatory system so far. Subcutaneous (SC) insulin infusion benefits from the broad expansion of insulin pump therapy that promoted the availability of constantly improving technology and fast-acting insulin analog use. However, persistent delays of insulin absorption and action, variability and shortterm stability of insulin infusion from SC-inserted catheters generate effectiveness and safety issues in view of an ambulatory, automated, glucose-controlled, artificial beta cell. Intraperitoneal insulin delivery, although still marginally used in diabetes care, may offer an interesting alternative because of its more-physiological plasma insulin profiles and sustained stability and reliability of insulin delivery.

  9. Studies on insulin secretion and insulin resistance in non-insulin-dependent diabetes in young Indians

    International Nuclear Information System (INIS)

    Naidoo, C.

    1986-01-01

    Patients with Non-insulin-dependent diabetes mellitus (NIDDM) have defects in insulin secretion and insulin action. In the discrete genetic syndrome of NIDDY (non-insulin-dependent diabetes in the young), the situation is less clear and these aspects is the subject of this thesis. This study included Indian pasients with three generation transmission of NIDDM via one parent. The insulin and C-peptide responses to oral and intravenous glucose in patients with NIDDY were studied. The insulin and glucose responses to non-glucose secretogogues glucagon, tolbutamide and arginine, in NIDDY were also investigated. The following aspects with regard to insulin resistance in NIDDY were examined: glucose and free fatty acid response to intravenous insulin administration, insulin binding to circulating erythrocytes and monocytes, 125 I-insulin binding to the solubilized erythrocyte membrane receptor and 125 I-insulin binding to fibroblasts in culture

  10. Studies on insulin secretion and insulin resistance in non-insulin-dependent diabetes in young Indians

    Energy Technology Data Exchange (ETDEWEB)

    Naidoo, C

    1986-01-01

    Patients with Non-insulin-dependent diabetes mellitus (NIDDM) have defects in insulin secretion and insulin action. In the discrete genetic syndrome of NIDDY (non-insulin-dependent diabetes in the young), the situation is less clear and these aspects is the subject of this thesis. This study included Indian pasients with three generation transmission of NIDDM via one parent. The insulin and C-peptide responses to oral and intravenous glucose in patients with NIDDY were studied. The insulin and glucose responses to non-glucose secretogogues glucagon, tolbutamide and arginine, in NIDDY were also investigated. The following aspects with regard to insulin resistance in NIDDY were examined: glucose and free fatty acid response to intravenous insulin administration, insulin binding to circulating erythrocytes and monocytes, /sup 125/I-insulin binding to the solubilized erythrocyte membrane receptor and /sup 125/I-insulin binding to fibroblasts in culture.

  11. Impaired insulin activation and dephosphorylation of glycogen synthase in skeletal muscle of women with polycystic ovary syndrome is reversed by pioglitazone treatment

    DEFF Research Database (Denmark)

    Glintborg, Dorte; Højlund, Kurt; Andersen, Nicoline Resen

    2008-01-01

    CONTEXT: Insulin resistance is a major risk factor for type 2 diabetes in women with polycystic ovary syndrome (PCOS). The molecular mechanisms underlying reduced insulin-mediated glycogen synthesis in skeletal muscle of patients with PCOS have not been established. SUBJECTS AND METHODS: We...... metabolically characterized by euglycemic-hyperinsulinemic clamps and indirect calorimetry. RESULTS: Reduced insulin-mediated glucose disposal (P .... No significant abnormalities in GSK-3alpha or -3beta were found in PCOS subjects. Pioglitazone treatment improved insulin-stimulated glucose metabolism and GS activity in PCOS (all P

  12. Long-Term Consumption of Platycodi Radix Ameliorates Obesity and Insulin Resistance via the Activation of AMPK Pathways

    Directory of Open Access Journals (Sweden)

    Chae Eun Lee

    2012-01-01

    Full Text Available This study was designed to evaluate the effects and mechanism of Platycodi radix, having white balloon flower (Platycodon grandiflorum for. albiflorum (Honda H. Hara on obesity and insulin resistance. The extracts of Platycodi radix with white balloon flower were tested in cultured cells and administered into mice on a high-fat diet. The Platycodi radix activated the AMPK/ACC phosphorylation in C2C12 myotubes and also suppressed adipocyte differentiation in 3T3-L1 cells. In experimental animal, it suppressed the weight gain of obese mice and ameliorated obesity-induced insulin resistance. It also reduced the elevated circulating mediators, including triglyceride (TG, T-CHO, leptin, resistin, and monocyte chemotactic protein (MCP-1 in obesity. As shown in C2C12 myotubes, the administration of Platycodi radix extracts also recovered the AMPK/ACC phosphorylation in the muscle of obese mice. These results suggest that Platycodi radix with white balloon flower ameliorates obesity and insulin resistance in obese mice via the activation of AMPK/ACC pathways and reductions of adipocyte differentiation.

  13. S961, an insulin receptor antagonist causes hyperinsulinemia, insulin-resistance and depletion of energy stores in rats

    Energy Technology Data Exchange (ETDEWEB)

    Vikram, Ajit [Department of Pharmacology and Toxicology, National Institute of Pharmaceutical Education and Research (NIPER), SAS Nagar, Mohali, Punjab 160 062 (India); Jena, Gopabandhu, E-mail: gbjena@gmail.com [Department of Pharmacology and Toxicology, National Institute of Pharmaceutical Education and Research (NIPER), SAS Nagar, Mohali, Punjab 160 062 (India)

    2010-07-23

    Research highlights: {yields}Insulin receptor antagonist S961 causes hyperglycemia, hyperinsulinemia and insulin resistance in rats. {yields}Peroxysome-proliferator-activated-receptor-gamma agonist pioglitazone improves S961 induced hyperglycemia and glucose intolerance. {yields}Long term treatment with insulin receptor antagonist S961 results in the decreased adiposity and hepatic glycogen content. {yields}Improvement in the hyperglycemia and glucose intolerance by pioglitazone clearly demonstrates that S961 treated rats can be successfully used to screen the novel therapeutic interventions having potential to improve glucose disposal through receptor independent mechanisms. -- Abstract: Impairment in the insulin receptor signaling and insulin mediated effects are the key features of type 2 diabetes. Here we report that S961, a peptide insulin receptor antagonist induces hyperglycemia, hyperinsulinemia ({approx}18-fold), glucose intolerance and impairment in the insulin mediated glucose disposal in the Sprague-Dawley rats. Further, long-term S961 treatment (15 day, 10 nM/kg/day) depletes energy storage as evident from decrease in the adiposity and hepatic glycogen content. However, peroxysome-proliferator-activated-receptor-gamma (PPAR{gamma}) agonist pioglitazone significantly (P < 0.001) restored S961 induced hyperglycemia (196.73 {+-} 16.32 vs. 126.37 {+-} 27.07 mg/dl) and glucose intolerance ({approx}78%). Improvement in the hyperglycemia and glucose intolerance by pioglitazone clearly demonstrates that S961 treated rats can be successfully used to screen the novel therapeutic interventions having potential to improve glucose disposal through receptor independent mechanisms. Further, results of the present study reconfirms and provide direct evidence to the crucial role of insulin receptor signaling in the glucose homeostasis and fuel metabolism.

  14. Aegeline inspired synthesis of novel β3-AR agonist improves insulin sensitivity in vitro and in vivo models of insulin resistance.

    Science.gov (United States)

    Rajan, Sujith; Satish, Sabbu; Shankar, Kripa; Pandeti, Sukanya; Varshney, Salil; Srivastava, Ankita; Kumar, Durgesh; Gupta, Abhishek; Gupta, Sanchita; Choudhary, Rakhi; Balaramnavar, Vishal M; Narender, Tadigoppula; Gaikwad, Anil N

    2018-03-07

    In our drug discovery program of natural product, earlier we have reported Aegeline that is N-acylated-1-amino-2- alcohol, which was isolated from the leaves of Aeglemarmelos showed anti-hyperlipidemic activity for which the QSAR studies predicted the compound to be the β3-AR agonist, but the mechanism of its action was not elucidated. In our present study, we have evaluated the β3-AR activity of novel N-acyl-1-amino-3-arylopropanol synthetic mimics of aegeline and its beneficial effect in insulin resistance. In this study, we have proposed the novel pharmacophore model using reported molecules for antihyperlipidemic activity. The reported pharmacophore features were also compared with the newly developed pharmacophore model for the observed biological activity. Based on 3D pharmacophore modeling of known β3AR agonist, we screened 20 synthetic derivatives of Aegeline from the literature. From these, the top scoring compound 10C was used for further studies. The in-slico result was further validated in HEK293T cells co-trransfected with human β3-AR and CRE-Luciferase reporter plasmid for β3-AR activity.The most active compound was selected and β3-AR activity was further validated in white and brown adipocytes differentiated from human mesenchymal stem cells (hMSCs). Insulin resistance model developed in hMSC derived adipocytes was used to study the insulin sensitizing property. 8 week HFD fed C57BL6 mice was given 50 mg/Kg of the selected compound and metabolic phenotyping was done to evaluate its anti-diabetic effect. As predicted by in-silico 3D pharmacophore modeling, the compound 10C was found to be the most active and specific β3-AR agonist with EC 50 value of 447 nM. The compound 10C activated β3AR pathway, induced lipolysis, fatty acid oxidation and increased oxygen consumption rate (OCR) in human adipocytes. Compound 10C induced expression of brown adipocytes specific markers and reverted chronic insulin induced insulin resistance in white

  15. Reduced plasma adiponectin concentrations may contribute to impaired insulin activation of glycogen synthase in skeletal muscle of patients with type 2 diabetes

    DEFF Research Database (Denmark)

    Højlund, K.; Frystyk, J.; Levin, K.

    2006-01-01

    AIMS/HYPOTHESIS: Circulating levels of adiponectin are negatively associated with multiple indices of insulin resistance, and the concentration is reduced in humans with insulin resistance and type 2 diabetes. However, the mechanisms by which adiponectin improves insulin sensitivity remain unclear...... (ten lean, 21 obese and 20 with type 2 diabetes). RESULTS: Plasma adiponectin was significantly reduced in type 2 diabetic compared with obese and lean subjects. In lean and obese subjects, insulin significantly reduced plasma adiponectin, but this response was blunted in patients with type 2 diabetes...... by improving the capacity to switch from lipid to glucose oxidation and to store glucose as glycogen in response to insulin, and that low adiponectin may contribute to impaired insulin activation of GS in skeletal muscle of patients with type 2 diabetes....

  16. Effect of iodination site on binding of radiolabeled ligand by insulin antibodies and insulin autoantibodies

    International Nuclear Information System (INIS)

    Diaz, J.L.; Wilkin, T.J.

    1988-01-01

    Four human insulins and four porcine insulins, each monoiodinated to the same specific activity at one of the four tyrosine residues (A14, A19, B16, B26) and purified by reversed-phase liquid chromatography, were tested in a radiobinding assay against a panel of insulin-antibody (IA)-positive sera from 10 insulin-treated diabetics and insulin-autoantibody-positive (IAA) sera from 10 nondiabetics. Of the 10 IAA-positive sera, five were fully cross reactive with both insulin species, and five were specific for human insulin. The rank order of binding of sera with the four ligands from each species was random for IA (mean rank values of 1.9 for A14, 2.0 for A19, 2.5 for B16, and 3.6 for B26 from a possible ranking range of 1 to 4), but more consistent for non-human-insulin-specific IAA (mean rank values 1.3 for A14, 3.8 for A19, 1.7 for B16, and 3.2 for B26 for labeled human insulins; 1.2 for A14, 4.0 for A19, 1.8 for B16, and 3.0 for B26 for labeled porcine insulins). The rank order of binding was virtually uniform for human-insulin-specific IAA (mean values 1.2 for A14, 3.0 for A19, 1.8 for B16, and 4.0 for B26). The influence of iodination site on the binding of labeled insulin appears to be dependent on the proximity of the labeled tyrosine to the antibody binding site and the clonal diversity, or restriction, of insulin-binding antibodies in the test serum. When IA and IAA are measured, the implications of this study regarding the choice of assay ligand may be important

  17. Prediagnostic circulating concentrations of plasma insulin-like growth factor-I and risk of lymphoma in the European Prospective Investigation into Cancer and Nutrition

    NARCIS (Netherlands)

    Perez-Cornago, Aurora; Appleby, Paul N.; Tipper, Sarah; Key, Timothy J.; Allen, Naomi E.; Nieters, Alexandra; Vermeulen, Roel; Roulland, Sandrine; Casabonne, Delphine; Kaaks, Rudolf; Fortner, Renee T.; Boeing, Heiner; Trichopoulou, Antonia; La Vecchia, Carlo; Klinaki, Eleni; Hansen, Louise; Tjønneland, Anne; Bonnet, Fabrice; Fagherazzi, Guy; Boutron-Ruault, Marie Christine; Pala, Valeria; Masala, Giovanna; Sacerdote, Carlotta; Peeters, Petra H.; Bueno-de-Mesquita, H. Bas; Weiderpass, Elisabete; Dorronsoro, Miren; Quirós, J. Ramón; Barricarte, Aurelio; Gavrila, Diana; Agudo, Antonio; Borgquist, Signe; Rosendahl, Ann H.; Melin, Beatrice; Wareham, Nick; Khaw, Kay Tee; Gunter, Marc; Riboli, Elio; Vineis, Paolo; Travis, Ruth C.

    2017-01-01

    Insulin-like growth factor (IGF)-I has cancer promoting activities. However, the hypothesis that circulating IGF-I concentration is related to risk of lymphoma overall or its subtypes has not been examined prospectively. IGF-I concentration was measured in pre-diagnostic plasma samples from a nested

  18. Mechanisms linking brain insulin resistance to Alzheimer's disease

    Science.gov (United States)

    Matioli, Maria Niures P.S.; Nitrini, Ricardo

    2015-01-01

    Several studies have indicated that Diabetes Mellitus (DM) can increase the risk of developing Alzheimer's disease (AD). This review briefly describes current concepts in mechanisms linking DM and insulin resistance/deficiency to AD. Insulin/insulin-like growth factor (IGF) resistance can contribute to neurodegeneration by several mechanisms which involve: energy and metabolism deficits, impairment of Glucose transporter-4 function, oxidative and endoplasmic reticulum stress, mitochondrial dysfunction, accumulation of AGEs, ROS and RNS with increased production of neuro-inflammation and activation of pro-apoptosis cascade. Impairment in insulin receptor function and increased expression and activation of insulin-degrading enzyme (IDE) have also been described. These processes compromise neuronal and glial function, with a reduction in neurotransmitter homeostasis. Insulin/IGF resistance causes the accumulation of AβPP-Aβ oligomeric fibrils or insoluble larger aggregated fibrils in the form of plaques that are neurotoxic. Additionally, there is production and accumulation of hyper-phosphorylated insoluble fibrillar tau which can exacerbate cytoskeletal collapse and synaptic disconnection. PMID:29213950

  19. Mechanisms linking brain insulin resistance to Alzheimer's disease

    Directory of Open Access Journals (Sweden)

    Maria Niures P.S. Matioli

    Full Text Available Several studies have indicated that Diabetes Mellitus (DM can increase the risk of developing Alzheimer's disease (AD. This review briefly describes current concepts in mechanisms linking DM and insulin resistance/deficiency to AD. Insulin/insulin-like growth factor (IGF resistance can contribute to neurodegeneration by several mechanisms which involve: energy and metabolism deficits, impairment of Glucose transporter-4 function, oxidative and endoplasmic reticulum stress, mitochondrial dysfunction, accumulation of AGEs, ROS and RNS with increased production of neuro-inflammation and activation of pro-apoptosis cascade. Impairment in insulin receptor function and increased expression and activation of insulin-degrading enzyme (IDE have also been described. These processes compromise neuronal and glial function, with a reduction in neurotransmitter homeostasis. Insulin/IGF resistance causes the accumulation of AβPP-Aβ oligomeric fibrils or insoluble larger aggregated fibrils in the form of plaques that are neurotoxic. Additionally, there is production and accumulation of hyper-phosphorylated insoluble fibrillar tau which can exacerbate cytoskeletal collapse and synaptic disconnection.

  20. Mangiferin ameliorates insulin resistance by inhibiting inflammation and regulatiing adipokine expression in adipocytes under hypoxic condition.

    Science.gov (United States)

    Yang, Chao-Qiang; Xu, Jing-Hua; Yan, Dan-Dan; Liu, Bao-Lin; Liu, Kang; Huang, Fang

    2017-09-01

    Adipose tissue hypoxia has been recognized as the initiation of insulin resistance syndromes. The aim of the present study was to investigate the effects of mangiferin on the insulin signaling pathway and explore whether mangiferin could ameliorate insulin resistance caused by hypoxia in adipose tissue. Differentiated 3T3-L1 adipocytes were incubated under normal and hypoxic conditions, respectively. Protein expressions were analyzed by Western blotting. Inflammatory cytokines and HIF-1-dependent genes were tested by ELISA and q-PCR, respectively. The glucose uptake was detected by fluorescence microscopy. HIF-1α was abundantly expressed during 8 h of hypoxic incubation. Inflammatory reaction was activated by up-regulated NF-κB phosphorylation and released cytokines like IL-6 and TNF-α. Glucose uptake was inhibited and insulin signaling pathway was damaged as well. Mangiferin substantially inhibited the expression of HIF-1α. Lactate acid and lipolysis, products released by glycometabolism and lipolysis, were also inhibited. The expression of inflammatory cytokines was significantly reduced and the damaged insulin signaling pathway was restored to proper functional level. The glucose uptake of hypoxic adipocytes was promoted and the dysfunction of adipocytes was relieved. These results showed that mangiferin could not only improve the damaged insulin signaling pathway in hypoxic adipocytes, but also ameliorate inflammatory reaction and insulin resistance caused by hypoxia. Copyright © 2017 China Pharmaceutical University. Published by Elsevier B.V. All rights reserved.

  1. A chimeric receptor of the insulin-like growth factor receptor type 1 (IGFR1) and a single chain antibody specific to myelin oligodendrocyte glycoprotein activates the IGF1R signalling cascade in CG4 oligodendrocyte progenitors.

    Science.gov (United States)

    Annenkov, Alexander; Rigby, Anne; Amor, Sandra; Zhou, Dun; Yousaf, Nasim; Hemmer, Bernhard; Chernajovsky, Yuti

    2011-08-01

    In order to generate neural stem cells with increased ability to survive after transplantation in brain parenchyma we developed a chimeric receptor (ChR) that binds to myelin oligodendrocyte glycoprotein (MOG) via its ectodomain and activates the insulin-like growth factor receptor type 1 ‎‎(IGF1R) signalling cascade. Activation of this pro-survival pathway in response to ligand broadly available in the brain might increase neuroregenerative potential of transplanted precursors. The ChR was produced by fusing a MOG-specific single ‎chain antibody with the extracellular boundary of the IGF1R transmembrane segment. The ChR is expressed on the cellular surface, predominantly as a monomer, and is not N-glycosylated. To show MOG-dependent functionality of the ChR, neuroblastoma cells B104 expressing this ChR were stimulated with monolayers of cells expressing recombinant MOG. The ChR undergoes MOG-dependent tyrosine phosphorylation and homodimerisation. It promotes insulin and IGF-independent growth of the oligodendrocyte progenitor cell line CG4. The proposed mode of the ChR activation is by MOG-induced dimerisation which promotes kinase domain transphosphorylation, by-passing the requirement of conformation changes known to be important for IGF1R activation. Another ChR, which contains a segment of the β-chain ectodomain, was produced in an attempt to recapitulate some of these conformational changes, but proved non-functional. 2011 Elsevier B.V. All rights reserved.

  2. Impact of intensive insulin treatment on the development and consequences of oxidative stress in insulin-dependent diabetes mellitus

    Directory of Open Access Journals (Sweden)

    Kocić Radivoj

    2007-01-01

    Full Text Available Background/Aim. The aim of this study, which included patients with insulin-dependent diabetes mellitus, was to determine the influence of the application of various treatment modalities (intensive or conventional on the total plasma antioxidative capacity and lipid peroxidation intensity expressed as malondialdehyde (MDA level, catalase and xanthine oxidase activity, erythrocyte glutatione reduced concentration (GSH RBC, erythrocyte MDA level (MDA RBC, as well as susceptibility of erythrocyte to H2O2-induced oxidative stress. Methods. This study included 42 patients with insulin-dependent diabetes mellitus. In 24 of the patients intensive insulin treatment was applied using the model of short-acting insulin in each meal and medium- acting insulin before going to bed, while in 18 of the patients conventional insulin treatment was applied in two (morning and evening doses. In the examined patients no presence of diabetes mellitus complications was recorded. The control group included 20 healthy adults out of a blood doner group. The plasma and erythrocytes taken from the blood samples were analyzed immediately. Results. This investigation proved that the application of intensive insulin treatment regime significantly improves total antioxidative plasma capacity as compared to the application of conventional therapy regime. The obtained results showed that the both plasma and lipoproteines apo B MDA increased significantly more in the patients on conventional therapy than in the patients on intensive insulin therapy, most probably due to intensified xanthine oxidase activity. The level of the MDA in fresh erythrocytes did not differ significantly between the groups on intensive and conventional therapy. The level of GSH and catalase activity, however, were significantly reduced in the patients on conventional therapy due to the increased susceptibility to H2O2-induced oxidative stress . Conclusion. The presented study confirmed positive effect of

  3. Peripheral nervous system insulin resistance in ob/ob mice

    Science.gov (United States)

    2013-01-01

    Background A reduction in peripheral nervous system (PNS) insulin signaling is a proposed mechanism that may contribute to sensory neuron dysfunction and diabetic neuropathy. Neuronal insulin resistance is associated with several neurological disorders and recent evidence has indicated that dorsal root ganglion (DRG) neurons in primary culture display altered insulin signaling, yet in vivo results are lacking. Here, experiments were performed to test the hypothesis that the PNS of insulin-resistant mice displays altered insulin signal transduction in vivo. For these studies, nondiabetic control and type 2 diabetic ob/ob mice were challenged with an intrathecal injection of insulin or insulin-like growth factor 1 (IGF-1) and downstream signaling was evaluated in the DRG and sciatic nerve using Western blot analysis. Results The results indicate that insulin signaling abnormalities documented in other “insulin sensitive” tissues (i.e. muscle, fat, liver) of ob/ob mice are also present in the PNS. A robust increase in Akt activation was observed with insulin and IGF-1 stimulation in nondiabetic mice in both the sciatic nerve and DRG; however this response was blunted in both tissues from ob/ob mice. The results also suggest that upregulated JNK activation and reduced insulin receptor expression could be contributory mechanisms of PNS insulin resistance within sensory neurons. Conclusions These findings contribute to the growing body of evidence that alterations in insulin signaling occur in the PNS and may be a key factor in the pathogenesis of diabetic neuropathy. PMID:24252636

  4. Degludec insulin: A novel basal insulin

    OpenAIRE

    Kalra, Sanjay; Unnikrishnan, Ambika Gopalakrishnan; Baruah, Manash; Kalra, Bharti

    2011-01-01

    This paper reviews a novel insulin analogue, degludec, which has the potential to emerge as an ideal basal insulin. It reviews the limitations of existing basal insulin and analogues, and highlights the need for a newer molecule. The paper discusses the potential advantages of degludec, while reviewing its pharmacologic and clinical studies done so far. The paper assesses the potential role of insulin degludec and degludec plus in clinical diabetes practice.

  5. Exocrine cell-derived microparticles in response to lipopolysaccharide promote endocrine dysfunction in cystic fibrosis.

    Science.gov (United States)

    Constantinescu, Andrei Alexandru; Gleizes, Céline; Alhosin, Mahmoud; Yala, Elhassan; Zobairi, Fatiha; Leclercq, Alexandre; Stoian, Gheorghe; Mitrea, Ioan Liviu; Prévost, Gilles; Toti, Florence; Kessler, Laurence

    2014-03-01

    Diabetes in cystic fibrosis (CF) is a result of exocrine pancreas alteration followed by endocrine dysfunction at a later stage. Microparticles (MPs) are plasma membrane fragments shed from stimulated or damaged cells that act as cellular effectors. Our aim was to identify a new form of interaction between exocrine and endocrine pancreatic cells mediated by exocrine MPs, in the context of recurrent infection in CF. MPs from either human exocrine CFTRΔF508-mutated (CFPAC-1) cells or exocrine normal pancreatic (PANC-1) cells were collected after treatment by LPS from Pseudomonas aeruginosa and applied to rat endocrine normal insulin-secreting RIN-m5F cells. MP membrane integration in target cells was established by confocal microscopy and flow cytometry using PKH26 lipid probe. Apoptosis, lysosomal activity, insulin secretion were measured after 18 h. MP-mediated NF-κB activation was measured in HEK-Blue reporter cells by SEAP reporter gene system and in RIN-m5F cells by Western blot. In endocrine normal cells, CFTR inhibition was achieved using Inhibitor-172. Compared to PANC-1, MPs from CFPAC-1 significantly reduced insulin secretion and lysosomal activity in RIN-m5F. MPs induced NF-κB activation by increasing the level of IκB phosphorylation. Moreover, the inhibition of NF-κB activation using specific inhibitors was associated with a restored insulin secretion. Interestingly, CFTR inhibition in normal RIN-m5F cells promoted apoptosis and decreased insulin secretion. During recurrent infections associated with CF, exocrine MPs may contribute to endocrine cell dysfunction via NF-κB pathways. Membrane CFTR dysfunction is associated with decreased insulin secretion. © 2013. Published by Elsevier B.V. on behalf of European Cystic Fibrosis Society. All rights reserved.

  6. Activation of PPARd and RXRa stimulates fatty acid oxidatin and insulin secretion inpancreatic beta-cells

    DEFF Research Database (Denmark)

    Børgesen, Michael; Ravnskjær, Kim; Frigerio, Francesca

    as a central effector of unsaturated fatty acids in pancreatic ß-cells. Interestingly, activation of PPARd increases basal as well as glucose-stimulated insulin secretion of INS-1E cells. This increase is further potentiated by RXR agonists. This observation suggests that PPARd may mediate some of the positive......ACTIVATION OF PPARd AND RXRa STIMULATES FATTY ACID OXIDATION AND INSULIN SECRETION IN PANCREATIC b-CELLS Michael Boergesen1, Kim Ravnskjaer2, Francesca Frigerio3, Allan E. Karlsen4, Pierre Maechler3 and Susanne Mandrup1 1 Department of Biochemistry and Molecular Biology, University of Southern...... of genes as PPARd specific agonists and stimulates ß-oxidation. Importantly, oleate-induction of gene expression and ß-oxidation in INS-1E cells is abolished by knock-down of PPARd using adenoviral transfer of shRNA. Thus, PPARd appears to be a central regulator of fatty acid metabolism as well...

  7. Targeted deletion of C1q/TNF-related protein 9 increases food intake, decreases insulin sensitivity, and promotes hepatic steatosis in mice.

    Science.gov (United States)

    Wei, Zhikui; Lei, Xia; Petersen, Pia S; Aja, Susan; Wong, G William

    2014-04-01

    Transgenic overexpression of CTRP9, a secreted hormone downregulated in obesity, confers striking protection against diet-induced obesity and type 2 diabetes. However, the physiological relevance of this adiponectin-related plasma protein remains undefined. Here, we used gene targeting to establish the metabolic function of CTRP9 in a physiological context. Mice lacking CTRP9 were obese and gained significantly more body weight when fed standard laboratory chow. Increased food intake, due in part to upregulated expression of hypothalamic orexigenic neuropeptides, contributed to greater adiposity in CTRP9 knockout mice. Although the frequency of food intake remained unchanged, CTRP9 knockout mice increased caloric intake by increasing meal size and decreasing satiety ratios. The absence of CTRP9 also resulted in peripheral tissue insulin resistance, leading to increased fasting insulin levels, impaired hepatic insulin signaling, and reduced insulin tolerance. Increased expression of lipogenic genes, combined with enhanced caloric intake, contributed to hepatic steatosis in CTRP9 knockout mice. Loss of CTRP9 also resulted in reduced skeletal muscle AMPK activation and mitochondrial content. Together, these results provide the genetic evidence for a physiological role of CTRP9 in controlling energy balance via central and peripheral mechanisms.

  8. Insulin promotes Rip11 accumulation at the