Diminished hepatic insulin removal in obesity

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Cano, I; Salvador, J; Rodriguez, R; Arraiza, M C; Goena, M; Barberia, J J; Moncada, E

1986-01-01

Peripheral insulin and C-peptide levels during oral glucose load were measured in 20 obese and 23 normal weight nondiabetic subjects. The fasting C-peptide to insulin molar ratios (Cp/I), as well as the relation between incremental areas of the two polypeptides (ACp-AI)/ACp, were used as relative measures of the hepatic insulin extraction (HIE). The insulin and C-peptide basal levels as well as incremental areas under plasma curves were higher in the obese subjects (P<0.001). HIE was lower in obeses than in controls assessed in the fasting state (P<0.05), as well as after glucose load (P<0.001). Nevertheless, obeses and controls with similar insulin fasting levels showed identical hepatic insulin extraction in fasting or after glucose load. HIE was independent of obesity degree, but was related to insulin basal levels (r=-0.60, P<0.01). This study suggests the hypothesis that the decreased hepatic insulin extraction in obeses is a result of the chronically increased insulin delivery to the liver and is not a consequence of obesity, although a contributory role cannot be ruled out.

Brain insulin lowers circulating BCAA levels by inducing hepatic BCAA catabolism

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Shin, Andrew C.; Fasshauer, Martin; Filatova, Nika; Grundell, Linus A.; Zielinski, Elizabeth; Zhou, Jian-Ying; Scherer, Thomas; Lindtner, Claudia; White, Phillip J.; Lapworth, Amanda L.; Ilkayeva, Olga; Knippschild, Uwe; Wolf, Anna M.; Scheja, Ludger; Grove, Kevin L.

2014-01-01

Circulating branched-chain amino acid (BCAA) levels are elevated in obesity/diabetes and are a sensitive predictor for type 2 diabetes. Here we show in rats that insulin dose-dependently lowers plasma BCAA levels through induction of hepatic protein expression and activity of branched-chain α keto-acid dehydrogenase (BCKDH), the rate-limiting enzyme in the BCAA degradation pathway. Selective induction of hypothalamic insulin signaling in rats and genetic modulation of brain insulin receptors ...

Insulin resistance, adipokine profile and hepatic expression of SOCS-3 gene in chronic hepatitis C.

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Wójcik, Kamila; Jabłonowska, Elżbieta; Omulecka, Aleksandra; Piekarska, Anna

2014-08-14

To analyze adipokine concentrations, insulin resistance and hepatic expression of suppressor of cytokine signaling 3 (SOCS-3) in patients with chronic hepatitis C genotype 1 with normal body weight, glucose and lipid profile. The study group consisted of 31 patients with chronic hepatitis C and 9 healthy subjects. Total levels of adiponectin, leptin, resistin, visfatin, omentin, osteopontin and insulin were measured using an ELISA kit. The hepatic expression of SOCS-3 was determined by the use of the reverse transcription polymerase chain reaction method. Homeostasis model assessment for insulin resistance (HOMA-IR) values were significantly higher in hepatitis C virus (HCV) infected patients without metabolic disorders compared to healthy controls (2.24 vs 0.59, P = 0.0003). Hepatic steatosis was observed in 32.2% of patients with HCV infection and was found in patients with increased HOMA-IR index (2.81 vs 1.99, P = 0.05) and reduced adiponectin level (5.96 vs 8.37, P = 0.04). Inflammatory activity (G ≥ 2) was related to increased osteopontin concentration (34.04 vs 23.35, P = 0.03). Advanced liver fibrosis (S ≥ 2) was associated with increased levels of omentin and osteopontin (436.94 vs 360.09, P = 0.03 and 32.84 vs 20.29, P = 0.03) and reduced resistin concentration (1.40 vs 1.74, P = 0.047). No correlations were reported between adipokine profile, HOMA-IR values and hepatic expression of the SOCS-3 gene. We speculated that no relationship between adipokines and HOMA-IR values may indicate that HCV can induce insulin resistance itself. Some adipokines appear to be biochemical markers of steatosis, inflammation and fibrosis in patients with chronic HCV infection. © 2014 Baishideng Publishing Group Inc. All rights reserved.

FoxO6 Integrates Insulin Signaling With Gluconeogenesis in the Liver

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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

Signal Transducer and Activator of Transcription 3 (STAT3) Mediates Amino Acid Inhibition of Insulin Signaling through Serine 727 Phosphorylation*

OpenAIRE

Kim, Jeong-Ho; Yoon, Mee-Sup; Chen, Jie

2009-01-01

Nutrient overload is associated with the development of obesity, insulin resistance, and type II diabetes. High plasma concentrations of amino acids have been found to correlate with insulin resistance. At the cellular level, excess amino acids impair insulin signaling, the mechanisms of which are not fully understood. Here, we report that STAT3 plays a key role in amino acid dampening of insulin signaling in hepatic cells. Excess amino acids inhibited insulin-stimulated Akt phosphorylation a...

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

Postprandial regulation of hepatic microRNAs predicted to target the insulin pathway in rainbow trout.

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Jan A Mennigen

Full Text Available Rainbow trout are carnivorous fish and poor metabolizers of carbohydrates, which established this species as a model organism to study the comparative physiology of insulin. Following the recent characterisation of key roles of several miRNAs in the insulin action on hepatic intermediary metabolism in mammalian models, we investigated the hypothesis that hepatic miRNA expression is postprandially regulated in the rainbow trout and temporally coordinated in the context of insulin-mediated regulation of metabolic gene expression in the liver. To address this hypothesis, we used a time-course experiment in which rainbow trout were fed a commercial diet after short-term fasting. We investigated hepatic miRNA expression, activation of the insulin pathway, and insulin regulated metabolic target genes at several time points. Several miRNAs which negatively regulate hepatic insulin signaling in mammalian model organisms were transiently increased 4 h after the meal, consistent with a potential role in acute postprandial negative feed-back regulation of the insulin pathway and attenuation of gluconeogenic gene expression. We equally observed a transient increase in omy- miRNA-33 and omy-miRNA-122b 4 h after feeding, whose homologues have potent lipogenic roles in the liver of mammalian model systems. A concurrent increase in the activity of the hepatic insulin signaling pathway and the expression of lipogenic genes (srebp1c, fas, acly was equally observed, while lipolytic gene expression (cpt1a and cpt1b decreased significantly 4 h after the meal. This suggests lipogenic roles of omy-miRNA-33 and omy-miRNA-122b may be conserved between rainbow trout and mammals and that these miRNAs may furthermore contribute to acute postprandial regulation of de novo hepatic lipid synthesis in rainbow trout. These findings provide a framework for future research of miRNA regulation of hepatic metabolism in trout and will help to further elucidate the metabolic

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

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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

Interaction Between the Central and Peripheral Effects of Insulin in Controlling Hepatic Glucose Metabolism in the Conscious Dog

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Ramnanan, Christopher J.; Kraft, Guillaume; Smith, Marta S.; Farmer, Ben; Neal, Doss; Williams, Phillip E.; Lautz, Margaret; Farmer, Tiffany; Donahue, E. Patrick; Cherrington, Alan D.; Edgerton, Dale S.

2013-01-01

The importance of hypothalamic insulin action to the regulation of hepatic glucose metabolism in the presence of a normal liver/brain insulin ratio (3:1) is unknown. Thus, we assessed the role of central insulin action in the response of the liver to normal physiologic hyperinsulinemia over 4 h. Using a pancreatic clamp, hepatic portal vein insulin delivery was increased three- or eightfold in the conscious dog. Insulin action was studied in the presence or absence of intracerebroventricularly mediated blockade of hypothalamic insulin action. Euglycemia was maintained, and glucagon was clamped at basal. Both the molecular and metabolic aspects of insulin action were assessed. Blockade of hypothalamic insulin signaling did not alter the insulin-mediated suppression of hepatic gluconeogenic gene transcription but blunted the induction of glucokinase gene transcription and completely blocked the inhibition of glycogen synthase kinase-3β gene transcription. Thus, central and peripheral insulin action combined to control some, but not other, hepatic enzyme programs. Nevertheless, inhibition of hypothalamic insulin action did not alter the effects of the hormone on hepatic glucose flux (production or uptake). These data indicate that brain insulin action is not a determinant of the rapid (<4 h) inhibition of hepatic glucose metabolism caused by normal physiologic hyperinsulinemia in this large animal model. PMID:23011594

Kaempferol alleviates insulin resistance via hepatic IKK/NF-κB signal in type 2 diabetic rats.

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Luo, Cheng; Yang, Hui; Tang, Chengyong; Yao, Gaoqiong; Kong, Lingxi; He, Haixia; Zhou, Yuanda

2015-09-01

Recent studies show that inflammation underlies the metabolic disorders of insulin resistance and type 2 diabetes mellitus. Since kaempferol, a naturally occurring flavonoid, has been described to have potent anti-inflammatory properties, we investigated whether kaempferol could ameliorate insulin resistance through inhibiting inflammatory responses. The model of diabetic rat was induced by 6-week high-fat diet plus streptozotocin. Animals were orally treated with kaempferol (50 or 150 mg/kg) and aspirin (100mg/kg) for 10 weeks. The results showed that kaempferol ameliorated blood lipids and insulin in an dose-dependent manner. Kaempferol effectively restored insulin resistance induced alteration of glucose disposal by using an insulin tolerance test and the euglycemic-hyperinsulinemic clamp method. Western blotting results showed that KPF inhibited the phosphorylation of insulin receptor substrate-1 (IRS-1), IkB kinase α (IKKα) and IkB kinase β (IKKβ). These effects were accompanied with reduction in nucleic and cytosol levels of nuclear factor kappa-β (NF-κB), and further tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) levels. Aspirin had similar effects. These results provide in vivo evidence that kaempferol-mediated down-regulation of IKK and subsequent inhibition of NF-κB pathway activation may be associated with the reduction of hepatic inflammatory lesions, which is contributing to the improvement of insulin signaling defect in diabetes. Copyright © 2015 Elsevier B.V. All rights reserved.

Brain insulin action augments hepatic glycogen synthesis without suppressing glucose production or gluconeogenesis in dogs

Science.gov (United States)

Ramnanan, Christopher J.; Saraswathi, Viswanathan; Smith, Marta S.; Donahue, E. Patrick; Farmer, Ben; Farmer, Tiffany D.; Neal, Doss; Williams, Philip E.; Lautz, Margaret; Mari, Andrea; Cherrington, Alan D.; Edgerton, Dale S.

2011-01-01

In rodents, acute brain insulin action reduces blood glucose levels by suppressing the expression of enzymes in the hepatic gluconeogenic pathway, thereby reducing gluconeogenesis and endogenous glucose production (EGP). Whether a similar mechanism is functional in large animals, including humans, is unknown. Here, we demonstrated that in canines, physiologic brain hyperinsulinemia brought about by infusion of insulin into the head arteries (during a pancreatic clamp to maintain basal hepatic insulin and glucagon levels) activated hypothalamic Akt, altered STAT3 signaling in the liver, and suppressed hepatic gluconeogenic gene expression without altering EGP or gluconeogenesis. Rather, brain hyperinsulinemia slowly caused a modest reduction in net hepatic glucose output (NHGO) that was attributable to increased net hepatic glucose uptake and glycogen synthesis. This was associated with decreased levels of glycogen synthase kinase 3β (GSK3β) protein and mRNA and with decreased glycogen synthase phosphorylation, changes that were blocked by hypothalamic PI3K inhibition. Therefore, we conclude that the canine brain senses physiologic elevations in plasma insulin, and that this in turn regulates genetic events in the liver. In the context of basal insulin and glucagon levels at the liver, this input augments hepatic glucose uptake and glycogen synthesis, reducing NHGO without altering EGP. PMID:21865644

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.

Selenite exacerbates hepatic insulin resistance in mouse model of type 2 diabetes through oxidative stress-mediated JNK pathway

Energy Technology Data Exchange (ETDEWEB)

Zhou, Jun, E-mail: hustzhj@hust.edu.cn; Xu, Gang; Bai, Zhaoshuai; Li, Kaicheng; Yan, Junyan; Li, Fen; Ma, Shuai; Xu, Huibi; Huang, Kaixun, E-mail: hxxzrf@hust.edu.cn

2015-12-15

Recent evidence suggests a potential pro-diabetic effect of selenite treatment in type 2 diabetics; however, the underlying mechanisms remain elusive. Here we investigated the effects and the underlying mechanisms of selenite treatment in a nongenetic mouse model of type 2 diabetes. High-fat diet (HFD)/streptozotocin (STZ)-induced diabetic mice were orally gavaged with selenite at 0.5 or 2.0 mg/kg body weight/day or vehicle for 4 weeks. High-dose selenite treatment significantly elevated fasting plasma insulin levels and insulin resistance index, in parallel with impaired glucose tolerance, insulin tolerance and pyruvate tolerance. High-dose selenite treatment also attenuated hepatic IRS1/Akt/FoxO1 signaling and pyruvate kinase gene expressions, but elevated the gene expressions of phosphoenolpyruvate carboxyl kinase (PEPCK), glucose 6-phosphatase (G6Pase), peroxisomal proliferator-activated receptor-γ coactivator 1α (PGC-1α) and selenoprotein P (SelP) in the liver. Furthermore, high-dose selenite treatment caused significant increases in MDA contents, protein carbonyl contents, and a decrease in GSH/GSSG ratio in the liver, concurrent with enhanced ASK1/MKK4/JNK signaling. Taken together, these findings suggest that high-dose selenite treatment exacerbates hepatic insulin resistance in mouse model of type 2 diabetes, at least in part through oxidative stress-mediated JNK pathway, providing new mechanistic insights into the pro-diabetic effect of selenite in type 2 diabetes. - Highlights: • Selenite exacerbates hepatic insulin resistance in HFD/STZ-induced diabetic mice. • Selenite elevates hepatic gluconeogenesis and reduces glycolysis in diabetic mice. • Selenite exacerbates hepatic oxidative stress and triggers JNK signaling pathway. • Selenite elevates hepatic selenoprotein P expression in diabetic mice.

Selenite exacerbates hepatic insulin resistance in mouse model of type 2 diabetes through oxidative stress-mediated JNK pathway

International Nuclear Information System (INIS)

Zhou, Jun; Xu, Gang; Bai, Zhaoshuai; Li, Kaicheng; Yan, Junyan; Li, Fen; Ma, Shuai; Xu, Huibi; Huang, Kaixun

2015-01-01

Recent evidence suggests a potential pro-diabetic effect of selenite treatment in type 2 diabetics; however, the underlying mechanisms remain elusive. Here we investigated the effects and the underlying mechanisms of selenite treatment in a nongenetic mouse model of type 2 diabetes. High-fat diet (HFD)/streptozotocin (STZ)-induced diabetic mice were orally gavaged with selenite at 0.5 or 2.0 mg/kg body weight/day or vehicle for 4 weeks. High-dose selenite treatment significantly elevated fasting plasma insulin levels and insulin resistance index, in parallel with impaired glucose tolerance, insulin tolerance and pyruvate tolerance. High-dose selenite treatment also attenuated hepatic IRS1/Akt/FoxO1 signaling and pyruvate kinase gene expressions, but elevated the gene expressions of phosphoenolpyruvate carboxyl kinase (PEPCK), glucose 6-phosphatase (G6Pase), peroxisomal proliferator-activated receptor-γ coactivator 1α (PGC-1α) and selenoprotein P (SelP) in the liver. Furthermore, high-dose selenite treatment caused significant increases in MDA contents, protein carbonyl contents, and a decrease in GSH/GSSG ratio in the liver, concurrent with enhanced ASK1/MKK4/JNK signaling. Taken together, these findings suggest that high-dose selenite treatment exacerbates hepatic insulin resistance in mouse model of type 2 diabetes, at least in part through oxidative stress-mediated JNK pathway, providing new mechanistic insights into the pro-diabetic effect of selenite in type 2 diabetes. - Highlights: • Selenite exacerbates hepatic insulin resistance in HFD/STZ-induced diabetic mice. • Selenite elevates hepatic gluconeogenesis and reduces glycolysis in diabetic mice. • Selenite exacerbates hepatic oxidative stress and triggers JNK signaling pathway. • Selenite elevates hepatic selenoprotein P expression in diabetic mice.

Hepatic Diacylglycerol-Associated Protein Kinase Cε Translocation Links Hepatic Steatosis to Hepatic Insulin Resistance in Humans

NARCIS (Netherlands)

ter Horst, Kasper W.; Gilijamse, Pim W.; Versteeg, Ruth I.; Ackermans, Mariette T.; Nederveen, Aart J.; la Fleur, Susanne E.; Romijn, Johannes A.; Nieuwdorp, Max; Zhang, Dongyan; Samuel, Varman T.; Vatner, Daniel F.; Petersen, Kitt F.; Shulman, Gerald I.; Serlie, Mireille J.

2017-01-01

Hepatic lipid accumulation has been implicated in the development of insulin resistance, but translational evidence in humans is limited. We investigated the relationship between liver fat and tissue-specific insulin sensitivity in 133 obese subjects. Although the presence of hepatic steatosis in

Whole-Body and Hepatic Insulin Resistance in Obese Children

Science.gov (United States)

Ibarra-Reynoso, Lorena del Rocío; Pisarchyk, Liudmila; Pérez-Luque, Elva Leticia; Garay-Sevilla, Ma. Eugenia; Malacara, Juan Manuel

2014-01-01

Background Insulin resistance may be assessed as whole body or hepatic. Objective To study factors associated with both types of insulin resistance. Methods Cross-sectional study of 182 obese children. Somatometric measurements were registered, and the following three adiposity indexes were compared: BMI, waist-to-height ratio and visceral adiposity. Whole-body insulin resistance was evaluated using HOMA-IR, with 2.5 as the cut-off point. Hepatic insulin resistance was considered for IGFBP-1 level quartiles 1 to 3 (HOMA-IR was negatively associated with IGFBP-1 and positively associated with BMI, triglycerides, leptin and mother's BMI. Girls had increased HOMA-IR. IGFBP-1 was negatively associated with waist-to-height ratio, age, leptin, HOMA-IR and IGF-I. We did not find HOMA-IR or IGFBP-1 associated with fatty liver. Conclusion In school-aged children, BMI is the best metric to predict whole-body insulin resistance, and waist-to-height ratio is the best predictor of hepatic insulin resistance, indicating that central obesity is important for hepatic insulin resistance. The reciprocal negative association of IGFBP-1 and HOMA-IR may represent a strong interaction of the physiological processes of both whole-body and hepatic insulin resistance. PMID:25411786

The Role of PTP1B O-GlcNAcylation in Hepatic Insulin Resistance

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Yun Zhao

2015-09-01

Full Text Available Protein tyrosine phosphatase 1B (PTP1B, which can directly dephosphorylate both the insulin receptor and insulin receptor substrate 1 (IRS-1, thereby terminating insulin signaling, reportedly plays an important role in insulin resistance. Accumulating evidence has demonstrated that O-GlcNAc modification regulates functions of several important components of insulin signal pathway. In this study, we identified that PTP1B is modified by O-GlcNAcylation at three O-GlcNAc sites (Ser104, Ser201, and Ser386. Palmitate acid (PA impaired the insulin signaling, indicated by decreased phosphorylation of both serine/threonine-protein kinase B (Akt and glycogen synthase kinase 3 beta (GSK3β following insulin administration, and upregulated PTP1B O-GlcNAcylation in HepG2 cells. Compared with the wild-type, intervention PTP1B O-GlcNAcylation by site-directed gene mutation inhibited PTP1B phosphatase activity, resulted in a higher level of phosphorylated Akt and GSK3β, recovered insulin sensitivity, and improved lipid deposition in HepG2 cells. Taken together, our research showed that O-GlcNAcylation of PTP1B can influence insulin signal transduction by modulating its own phosphatase activity, which participates in the process of hepatic insulin resistance.

The role of insulin receptor signaling in the brain.

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Plum, Leona; Schubert, Markus; Brüning, Jens C

2005-03-01

The insulin receptor (IR) is expressed in various regions of the developing and adult brain, and its functions have become the focus of recent research. Insulin enters the central nervous system (CNS) through the blood-brain barrier by receptor-mediated transport to regulate food intake, sympathetic activity and peripheral insulin action through the inhibition of hepatic gluconeogenesis and reproductive endocrinology. On a molecular level, some of the effects of insulin converge with those of the leptin signaling machinery at the point of activation of phosphatidylinositol 3-kinase (PI3K), resulting in the regulation of ATP-dependent potassium channels. Furthermore, insulin inhibits neuronal apoptosis via activation of protein kinase B in vitro, and it regulates phosphorylation of tau, metabolism of the amyloid precursor protein and clearance of beta-amyloid from the brain in vivo. These findings indicate that neuronal IR signaling has a direct role in the link between energy homeostasis, reproduction and the development of neurodegenerative diseases.

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.

Tartary buckwheat flavonoids ameliorate high fructose-induced insulin resistance and oxidative stress associated with the insulin signaling and Nrf2/HO-1 pathways in mice.

Science.gov (United States)

Hu, Yuanyuan; Hou, Zuoxu; Yi, Ruokun; Wang, Zhongming; Sun, Peng; Li, Guijie; Zhao, Xin; Wang, Qiang

2017-08-01

The present study was conducted to explore the effects of a purified tartary buckwheat flavonoid fraction (TBF) on insulin resistance and hepatic oxidative stress in mice fed high fructose in drinking water (20%) for 8 weeks. The results indicated that continuous administration of TBF dose-dependently improved the insulin sensitivity and glucose intolerance in high fructose-fed mice. TBF treatment also reversed the reduced level of insulin action on the phosphorylation of insulin receptor substrate-1 (IRS-1), protein kinase B (Akt) and phosphatidylinositol 3-kinase (PI3K), as well as the translocation of glucose transporter type 4 (GLUT4) in the insulin-resistant liver. Furthermore, TBF was found to exert high antioxidant capacity as it acts as a shield against oxidative stress induced by high fructose by restoring the antioxidant status, and modulating nuclear factor E2 related factor 2 (Nrf2) translocation to the nucleus with subsequently up-regulated antioxidative enzyme protein expression. Histopathological examinations revealed that impaired pancreatic/hepatic tissues were effectively restored in high fructose-fed mice following TBF treatment. Our results show that TBF intake is effective in preventing the conversion of high fructose-induced insulin resistance and hepatic oxidative stress in mice by improving the insulin signaling molecules and the Nrf2 signal pathway in the liver.

3,5 Diiodo-L-Thyronine (T2 Does Not Prevent Hepatic Steatosis or Insulin Resistance in Fat-Fed Sprague Dawley Rats.

Directory of Open Access Journals (Sweden)

Daniel F Vatner

Full Text Available Thyroid hormone mimetics are alluring potential therapies for diseases like dyslipidemia, nonalcoholic fatty liver disease (NAFLD, and insulin resistance. Though diiodothyronines are thought inactive, pharmacologic treatment with 3,5- Diiodo-L-Thyronine (T2 reportedly reduces hepatic lipid content and improves glucose tolerance in fat-fed male rats. To test this, male Sprague Dawley rats fed a safflower-oil based high-fat diet were treated with T2 (0.25 mg/kg-d or vehicle. Neither 10 nor 30 days of T2 treatment had an effect on weight, adiposity, plasma fatty acids, or hepatic steatosis. Insulin action was quantified in vivo by a hyperinsulinemic-euglycemic clamp. T2 did not alter fasting plasma glucose or insulin concentration. Basal endogenous glucose production (EGP rate was unchanged. During the clamp, there was no difference in insulin stimulated whole body glucose disposal. Insulin suppressed EGP by 60% ± 10 in T2-treated rats as compared with 47% ± 4 suppression in the vehicle group (p = 0.32. This was associated with an improvement in hepatic insulin signaling; insulin stimulated Akt phosphorylation was ~2.5 fold greater in the T2-treated group as compared with the vehicle-treated group (p = 0.003. There was no change in expression of genes thought to mediate the effect of T2 on hepatic metabolism, including genes that regulate hepatic lipid oxidation (ppara, carnitine palmitoyltransferase 1a, genes that regulate hepatic fatty acid synthesis (srebp1c, acetyl coa carboxylase, fatty acid synthase, and genes involved in glycolysis and gluconeogenesis (L-pyruvate kinase, glucose 6 phosphatase. Therefore, in contrast with previous reports, in Sprague Dawley rats fed an unsaturated fat diet, T2 administration failed to improve NAFLD or whole body insulin sensitivity. Though there was a modest improvement in hepatic insulin signaling, this was not associated with significant differences in hepatic insulin action. Further study will be

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.

In nondiabetic, human immunodeficiency virus-infected patients with lipodystrophy, hepatic insulin extraction and posthepatic insulin clearance rate are decreased in proportion to insulin resistance

DEFF Research Database (Denmark)

Haugaard, Steen B; Andersen, Ove; Hansen, Birgitte R

2005-01-01

In healthy, nondiabetic individuals with insulin resistance, fasting insulin is inversely correlated to the posthepatic insulin clearance rate (MCRi) and the hepatic insulin extraction (HEXi). We investigated whether similar early mechanisms to facilitate glucose homeostasis exist in nondiabetic...... endogenous insulin secretion, which was estimated by deconvolution of C-peptide concentrations. Hepatic extraction of insulin was calculated as 1 minus the ratio of fasting posthepatic insulin delivery rate to fasting endogenous insulin secretion rate. Compared with controls, LIPO displayed increased fasting...... insulin (130%, P Hepatic extraction of insulin was similar between groups (LIPO, 55%; controls, 57%; P > .8). In LIPO, HEXi and MCRi correlated inversely with fasting insulin (r = -0.56, P

Regulation of leptin and insulin signaling by the t cell protein tyrosine phosphatase

OpenAIRE

Loh, Kim Yong

2017-01-01

The prevalence of obesity and diabetes are increasing at alarming rates. Both are major health concerns worldwide. Food intake, energy expenditure and hepatic glucose production are regulated by hypothalamic neuronal circuits that respond to peripheral signals including leptin and insulin. Leptin is produced by adipose tissue and acts in the hypothalamus via the JAK2/STAT3 signaling pathway to decrease food intake and increase energy expenditure. It is now also widely appreciated that insulin...

A novel surrogate index for hepatic insulin resistance.

LENUS (Irish Health Repository)

Vangipurapu, J

2011-03-01

In epidemiological and genetic studies surrogate indices are needed to investigate insulin resistance in different insulin-sensitive tissues. Our objective was to develop a surrogate index for hepatic insulin resistance.

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

Heterozygous deficiency of endoglin decreases insulin and hepatic triglyceride levels during high fat diet.

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Daniel Beiroa

Full Text Available Endoglin is a transmembrane auxiliary receptor for transforming growth factor-beta (TGF-beta that is predominantly expressed on proliferating endothelial cells. It plays a wide range of physiological roles but its importance on energy balance or insulin sensitivity has been unexplored. Endoglin deficient mice die during midgestation due to cardiovascular defects. Here we report for first time that heterozygous endoglin deficiency in mice decreases high fat diet-induced hepatic triglyceride content and insulin levels. Importantly, these effects are independent of changes in body weight or adiposity. At molecular level, we failed to detect relevant changes in the insulin signalling pathway at basal levels in liver, muscle or adipose tissues that could explain the insulin-dependent effect. However, we found decreased triglyceride content in the liver of endoglin heterozygous mice fed a high fat diet in comparison to their wild type littermates. Overall, our findings indicate that endoglin is a potentially important physiological mediator of insulin levels and hepatic lipid metabolism.

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

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

Hepatic steatosis does not cause insulin resistance in people with familial hypobetalipoproteinaemia

NARCIS (Netherlands)

Visser, M. E.; Lammers, N. M.; Nederveen, A. J.; van der Graaf, M.; Heerschap, A.; Ackermans, M. T.; Sauerwein, H. P.; Stroes, E. S.; Serlie, M. J.

2011-01-01

Hepatic steatosis is strongly associated with hepatic and whole-body insulin resistance. It has proved difficult to determine whether hepatic steatosis itself is a direct cause of insulin resistance. In patients with familial hypobetalipoproteinaemia (FHBL), hepatic steatosis is a direct consequence

TCPTP Regulates Insulin Signalling in AgRP Neurons to Coordinate Glucose Metabolism with Feeding.

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Dodd, Garron T; Lee-Young, Robert S; Brüning, Jens C; Tiganis, Tony

2018-04-30

Insulin regulates glucose metabolism by eliciting effects on peripheral tissues as well as the brain. Insulin receptor (IR) signalling inhibits AgRP-expressing neurons in the hypothalamus to contribute to the suppression of hepatic glucose production (HGP) by insulin, whereas AgRP neuronal activation attenuates brown adipose tissue (BAT) glucose uptake. The tyrosine phosphatase TCPTP suppresses IR signalling in AgRP neurons. Hypothalamic TCPTP is induced by fasting and degraded after feeding. Here we assessed the influence of TCPTP in AgRP neurons in the control of glucose metabolism. TCPTP deletion in AgRP neurons ( Agrp -Cre; Ptpn2 fl/fl ) enhanced insulin sensitivity as assessed by the increased glucose infusion rates and reduced HGP during hyperinsulinemic-euglycemic clamps, accompanied by increased [ 14 C]-2-deoxy-D-glucose uptake in BAT and browned white adipose tissue. TCPTP deficiency in AgRP neurons promoted the intracerebroventricular insulin-induced repression of hepatic gluconeogenesis in otherwise unresponsive food-restricted mice yet had no effect in fed/satiated mice where hypothalamic TCPTP levels are reduced. The improvement in glucose homeostasis in Agrp -Cre; Ptpn2 fl/fl mice was corrected by IR heterozygosity ( Agrp -Cre; Ptpn2 fl/fl ; Insr fl/+ ), causally linking the effects on glucose metabolism with the IR signalling in AgRP neurons. Our findings demonstrate that TCPTP controls IR signalling in AgRP neurons to coordinate HGP and brown/beige adipocyte glucose uptake in response to feeding/fasting. © 2018 by the American Diabetes Association.

Erythrocytes 125I-Insulin Binding Studies in Viral Hepatitis and Schistosomiasis Patients

International Nuclear Information System (INIS)

Ahmed, A.M.

2003-01-01

The present study aims to evaluate the alterations of insulin binding sites in human erythrocytes in patients with chronic viral B and C hepatitis and in schistosomiasis. Fifty men with ages ranged from 20-45 years were diagnosed into five groups; hepatitis B virus, hepatitis C virus, mixed hepatitis B and C, schistosomiasis and normal healthy volunteers as a control group. Biochemical analyses as erythrocyte insulin radioreceptor, plasma insulin estimation, fasting and post prandial blood glucose levels and liver function tests were performed. The results revealed significant decrease in insulin binding sites/cell in patients with hepatitis C virus, mixed B and C viruses and in schistosomiasis compared to the control group. There were significant increase in fasting plasma glucose levels in groups of hepatitis C virus mixed B and C viruses, while there were highly significant increase in post prandial plasma glucose levels in patients with mixed B and C viruses and in schistosomiasis groups compared to the normal control. Also, fasting plasma insulin levels were significantly elevated in groups of hepatitis C mixed B and C viruses and in schistosomiasis group. The obtained results revealed the importance of laboratory follow up of glucose and insulin levels in patients with chronic liver diseases

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.

Supplementation with Vitis vinifera L. skin extract improves insulin resistance and prevents hepatic lipid accumulation and steatosis in high-fat diet-fed mice.

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Santos, Izabelle Barcellos; de Bem, Graziele Freitas; Cordeiro, Viviane Silva Cristino; da Costa, Cristiane Aguiar; de Carvalho, Lenize Costa Reis Marins; da Rocha, Ana Paula Machado; da Costa, Gisele França; Ognibene, Dayane Teixeira; de Moura, Roberto Soares; Resende, Angela Castro

2017-07-01

Nonalcoholic fatty liver disease is one of the most common complications of obesity. The Vitis vinifera L. grape skin extract (ACH09) is an important source of polyphenols, which are related to its antioxidant and antihyperglycemic activities. We hypothesized that ACH09 could also exert beneficial effects on metabolic disorders associated with obesity and evaluated ACH09's influence on high-fat (HF) diet-induced hepatic steatosis and insulin resistance in C57BL/6 mice. The animals were fed a standard diet (10% fat, control) or an HF diet (60% fat, HF) with or without ACH09 (200mg/[kg d]) for 12weeks. Our results showed that ACH09 reduced HF diet-induced body weight gain, prevented hepatic lipid accumulation and steatosis, and improved hyperglycemia and insulin resistance. The underlying mechanisms of these beneficial effects of ACH09 may involve the activation of hepatic insulin-signaling pathway because the expression of phosphorylated insulin receptor substrate-1, phosphatidylinositol 3-kinase, phosphorylated Akt serine/threonine kinase 1, and glucose transporter 2 was increased by ACH09 and correlated with improvement of hyperglycemia, hyperinsulinemia, and insulin resistance. ACH09 reduced the expression of the lipogenic factor sterol regulatory-element binding protein-1c in the liver and upregulated the lipolytic pathway (phosphorylated liver kinase B1/phosphorylated adenosine-monophosphate-activated protein kinase), which was associated with normal hepatic levels of triglyceride and cholesterol and prevention of steatosis. ACH09 prevented the hepatic oxidative damage in HF diet-fed mice probably by restoration of antioxidant activity. In conclusion, ACH09 protected mice from HF diet-induced obesity, insulin resistance, and hepatic steatosis. The regulation of hepatic insulin signaling pathway, lipogenesis, and oxidative stress may contribute to ACH09's protective effect. Copyright © 2017 Elsevier Inc. All rights reserved.

Insulin Signaling in Liver and Adipose Tissues in Periparturient Dairy Cows Supplemented with Dietary Nicotinic Acid.

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Kinoshita, Asako; Kenéz, Ákos; Locher, Lena; Meyer, Ulrich; Dänicke, Sven; Rehage, Jürgen; Huber, Korinna

2016-01-01

The glucose homeostasis in dairy cattle is very well controlled, in line with the metabolic adaptation during the periparturient period. Former studies showed that nicotinic acid (NA) lowered plasma non-esterified fatty acids (NEFA) concentrations and increased insulin sensitivity in dairy cows. Thus, the purpose of this study was to investigate whether the expression of proteins involved in hepatic and adipose insulin signaling and protein expression of hepatic glucose transporter 2 (GLUT2) were affected by dietary NA and dietary concentrate intake in periparturient dairy cows. Twenty pluriparous German Holstein cows were fed with the same diet from about 21 days before the expected calving date (d-21) to calving. After calving, cows were randomly assigned in 4 groups and fed with diets different in concentrate proportion ("HC" with 60:40% or "LC" with 30:70% concentrate-to-roughage ratio) and supplemented with NA (24 g/day) (NA) or without (CON) until d21. Biopsy samples were taken from the liver, subcutaneous (SCAT) and retroperitoneal (RPAT) adipose tissues at d-21 and d21. Protein expression of insulin signaling molecules (insulin receptor (INSR), phosphatidylinositol-3-kinase (PI3K), protein kinase Cζ (PKCζ)) and hepatic GLUT2 was measured by Western Blotting. The ratio of protein expression at d21/at d-21 was calculated and statistically evaluated for the effects of time and diet. Cows in HC had significantly higher dietary energy intake than cows in LC. In RPAT a decrease in PI3K and PKCζ expression was found in all groups, irrespectively of diet. In the liver, the GLUT2 expression was significantly lower in cows in NA compared with cows in CON. In conclusion, insulin signaling might be decreased in RPAT over time without any effect of diet. NA was able to modulate hepatic GLUT2 expression, but its physiological role is unclear.

Insulin Signaling in Liver and Adipose Tissues in Periparturient Dairy Cows Supplemented with Dietary Nicotinic Acid.

Directory of Open Access Journals (Sweden)

Asako Kinoshita

Full Text Available The glucose homeostasis in dairy cattle is very well controlled, in line with the metabolic adaptation during the periparturient period. Former studies showed that nicotinic acid (NA lowered plasma non-esterified fatty acids (NEFA concentrations and increased insulin sensitivity in dairy cows. Thus, the purpose of this study was to investigate whether the expression of proteins involved in hepatic and adipose insulin signaling and protein expression of hepatic glucose transporter 2 (GLUT2 were affected by dietary NA and dietary concentrate intake in periparturient dairy cows. Twenty pluriparous German Holstein cows were fed with the same diet from about 21 days before the expected calving date (d-21 to calving. After calving, cows were randomly assigned in 4 groups and fed with diets different in concentrate proportion ("HC" with 60:40% or "LC" with 30:70% concentrate-to-roughage ratio and supplemented with NA (24 g/day (NA or without (CON until d21. Biopsy samples were taken from the liver, subcutaneous (SCAT and retroperitoneal (RPAT adipose tissues at d-21 and d21. Protein expression of insulin signaling molecules (insulin receptor (INSR, phosphatidylinositol-3-kinase (PI3K, protein kinase Cζ (PKCζ and hepatic GLUT2 was measured by Western Blotting. The ratio of protein expression at d21/at d-21 was calculated and statistically evaluated for the effects of time and diet. Cows in HC had significantly higher dietary energy intake than cows in LC. In RPAT a decrease in PI3K and PKCζ expression was found in all groups, irrespectively of diet. In the liver, the GLUT2 expression was significantly lower in cows in NA compared with cows in CON. In conclusion, insulin signaling might be decreased in RPAT over time without any effect of diet. NA was able to modulate hepatic GLUT2 expression, but its physiological role is unclear.

Association of hepatitis C virus with insulin resistance: evidences from animal studies and clinical studies.

Science.gov (United States)

Badar, Sadaf; Khubaib, Bushra; Idrees, Muhammad; Hussain, Abrar; Awan, Zunaira; Butt, Sadia; Afzal, Samia; Akram, Madeeha; Fatima, Zareen; Aftab, Mahwish; Saleem, Sana; Munir, Sara; Rauff, Bisma; Naudhani, Mahrukh; Ali, Liaquat; Ali, Muhammaad; Rehman, Irshadul

2012-01-01

HCV infection is strongly associated with development of insulin resistance and type-2 diabetes, however molecular mechanism of these associations is not known. The aim of this review was to conduct a comprehensive literature search to understand the nature of the association between hepatitis C virus (HCV) infection and insulin resistance (IR). We also explored the role of HCV core protein and NS5a in modulating the course of the insulin-signaling pathway. We searched Directory of Open Access Journals (DOAJ) Google Scholar, Pubmed (NLM), LISTA (EBSCO), Web of Science (TS and PakMediNet). Emerging evidence suggests an association between HCV infection and carotid/coronary vascular disease. IR appears to be a dominant underlying cause of accelerated atherosclerosis in patients with chronic hepatitis C (CHC). HCV can induce IR directly through the stimulation of SOCS3 and PPA2, and both of these molecules have been shown to inhibit interferon-α signaling. Improvement of insulin sensitivity may increase the response rate to antiviral treatment and prevent IR complications, including vascular diseases. The results of several clinical trials that have used insulin sensitizers (metformin and PPAR-γ agonists) have been inconclusive. Beside the association between HCV and IR, the published data also have showed the possible association of HCV core and NS5A protein with IR.

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.

The association between insulin resistance and hepatic fibrosis in patients with chronic hepatitis C: an observational, multicenter study in Turkey.

Science.gov (United States)

Dökmeci, Abdulkadir; Ustündağ, Yücel; Hulagu, Saadettin; Tuncer, Ilyas; Akdoğan, Meral; Demirsoy, Hüseyin; Köklü, Seyfettin; Güzelbulut, Fatih; Doğan, Ibrahim; Demir, Ali; Akarsu, Mesut; Yüceyar, Hakan; Ozdoğan, Osman Cavit; Ozdener, Fatih; Erdoğan, Seda

2014-10-01

To evaluate the association between insulin resistance and hepatic fibrosis in patients with chronic hepatitis C. A total of 104 chronic hepatitis C patients were included in this non-interventional, open-label, observational, multicenter, cross-sectional study conducted at 20 gastroenterology clinics in Turkey. The primary end point was the correlation between stage of hepatic fibrosis and insulin resistance evaluated via the homeostasis model of assessment-insulin resistance index. Confounders of hepatic fibrosis and insulin resistance were the secondary end points. The mean age of patients was 52.8 years; 65.4% were female. Type 2 diabetes was present in 6.8% and insulin resistance noted in 38.0% of patients. Further, 45.7% of the patients had mild (A0/A1) and the remaining had moderate/severe (A2/A3) hepatic necroinflammatory activity. Patient distribution according to Metavir fibrosis stage was as follows: F0/F1 (57.0%); F2 (6.5%); F3 (23.7%); and F4 (12.9%). A univariate analysis revealed significant positive correlations between Metavir fibrosis stage and insulin resistance (r=0.297; p=0.007). Logistic regression analysis showed that significant predictors of insulin resistance were high alanine transaminase levels (odds ratio, 0.97; 95% confidence interval, 0.944-0.997) and liver fibrosis stage (odds ratio, 0.114; 95% confidence interval, 0.021-0.607). Our findings revealed significant associations between insulin resistance and hepatic fibrosis.

The transcription factor Prep1 controls hepatic insulin sensitivity and gluconeogenesis by targeting nuclear localization of FOXO1

International Nuclear Information System (INIS)

Kulebyakin, Konstantin; Penkov, Dmitry; Blasi, Francesco; Akopyan, Zhanna; Tkachuk, Vsevolod

2016-01-01

Liver plays a key role in controlling body carbohydrate homeostasis by switching between accumulation and production of glucose and this way maintaining constant level of glucose in blood. Increased blood glucose level triggers release of insulin from pancreatic β-cells. Insulin represses hepatic glucose production and increases glucose accumulation. Insulin resistance is the main cause of type 2 diabetes and hyperglycemia. Currently thiazolidinediones (TZDs) targeting transcriptional factor PPARγ are used as insulin sensitizers for treating patients with type 2 diabetes. However, TZDs are reported to be associated with cardiovascular and liver problems and stimulate obesity. Thus, it is necessary to search new approaches to improve insulin sensitivity. A promising candidate is transcriptional factor Prep1, as it was shown earlier it could affect insulin sensitivity in variety of insulin-sensitive tissues. The aim of the present study was to evaluate a possible involvement of transcriptional factor Prep1 in control of hepatic glucose accumulation and production. We created mice with liver-specific Prep1 knockout and discovered that hepatocytes derived from these mice are much more sensitive to insulin, comparing to their WT littermates. Incubation of these cells with 100 nM insulin results in almost complete inhibition of gluconeogenesis, while in WT cells this repression is only partial. However, Prep1 doesn't affect gluconeogenesis in the absence of insulin. Also, we observed that nuclear content of gluconeogenic transcription factor FOXO1 was greatly reduced in Prep1 knockout hepatocytes. These findings suggest that Prep1 may control hepatic insulin sensitivity by targeting FOXO1 nuclear stability. - Highlights: • A novel model of liver-specific Prep1 knockout is established. • Ablation of Prep1 in hepatocytes increases insulin sensitivity. • Prep1 controls hepatic insulin sensitivity by regulating localization of FOXO1. • Prep1 regulates

Histidine augments the suppression of hepatic glucose production by central insulin action.

Science.gov (United States)

Kimura, Kumi; Nakamura, Yusuke; Inaba, Yuka; Matsumoto, Michihiro; Kido, Yoshiaki; Asahara, Shun-Ichiro; Matsuda, Tomokazu; Watanabe, Hiroshi; Maeda, Akifumi; Inagaki, Fuyuhiko; Mukai, Chisato; Takeda, Kiyoshi; Akira, Shizuo; Ota, Tsuguhito; Nakabayashi, Hajime; Kaneko, Shuichi; Kasuga, Masato; Inoue, Hiroshi

2013-07-01

Glucose intolerance in type 2 diabetes is related to enhanced hepatic glucose production (HGP) due to the increased expression of hepatic gluconeogenic enzymes. Previously, we revealed that hepatic STAT3 decreases the expression of hepatic gluconeogenic enzymes and suppresses HGP. Here, we show that increased plasma histidine results in hepatic STAT3 activation. Intravenous and intracerebroventricular (ICV) administration of histidine-activated hepatic STAT3 reduced G6Pase protein and mRNA levels and augmented HGP suppression by insulin. This suppression of hepatic gluconeogenesis by histidine was abolished by hepatic STAT3 deficiency or hepatic Kupffer cell depletion. Inhibition of HGP by histidine was also blocked by ICV administration of a histamine H1 receptor antagonist. Therefore, histidine activates hepatic STAT3 and suppresses HGP via central histamine action. Hepatic STAT3 phosphorylation after histidine ICV administration was attenuated in histamine H1 receptor knockout (Hrh1KO) mice but not in neuron-specific insulin receptor knockout (NIRKO) mice. Conversely, hepatic STAT3 phosphorylation after insulin ICV administration was attenuated in NIRKO but not in Hrh1KO mice. These findings suggest that central histidine action is independent of central insulin action, while both have additive effects on HGP suppression. Our results indicate that central histidine/histamine-mediated suppression of HGP is a potential target for the treatment of type 2 diabetes.

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

Dynamics of insulin signalling in liver during hyperinsulinemic euglycaemic clamp conditions in vivo and the effects of high-fat feeding in male mice

NARCIS (Netherlands)

Korsheninnikova, E.; Voshol, P.J.; Baan, B.; Zon, G.C.M. van der; Havekes, L.M.; Romijn, J.A.; Maassen, J.A.; Ouwens, D.M.

2007-01-01

Insulin is an important regulator of hepatic carbohydrate, lipid, and protein metabolism, and the regulation of these processes by insulin is disturbed under conditions of insulin resistance and type 2 diabetes. Despite these alterations, the impact of insulin resistance on insulin signalling in the

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.

Intrahepatic detection of insulin receptor substrate 2 in chronic hepatitis c patients

International Nuclear Information System (INIS)

Ahmed, N.; Rashid, A.; Bashir, Q.; Majeed, A.

2017-01-01

To detect hepatic insulin receptor substrate 2 in chronic hepatitis C patients. Study Design: Comparative study. Place and Duration of Study: Center for research in experimental and applied medicine (CREAM), Department of Biochemistry and Molecular Biology, Army Medical College and Holy Family Hospital Rawalpindi, from Dec 2011 to Nov 2012. Diagnosed patients of chronic hepatitis C were included in the study. Known cases of diabetes mellitus, patients with pancreatic disease and liver pathology other than hepatitis C were excluded from the study. Material and Methods: Twenty seropositive non diabetic HCV infected patients and 10 control subjects were recruited. Liver biopsy specimen was obtained from seropositive HCV patients while blood samples were obtained from controls as biopsy sample was not possible from normal controls. Both types of speciens were studied for detection of insulin receptor substrate 2 (IRS-2). Results: No alteration in the content of insulin receptor substrate 2 in both seropositive patients and control samples were detected. Conclusion: Hepatitis C virus has no effect on insulin receptor substrate 2 content thus indicating absence of hepatic insulin resistance in patients with HCV infection. (author)

Insulin resistance, hepatic lipid and adipose tissue distribution in HIV infected men

Science.gov (United States)

He, Qing; Engelson, Ellen S.; Ionescu, Gabriel; Glesby, Marshall J.; Albu, Jeanine B.; Kotler, Donald P.

2010-01-01

Background A large proportion of HIV-infected subjects on antiretroviral medication develop insulin resistance, especially in the context of fat redistribution. This study investigates the interrelationships among fat distribution, hepatic lipid content, and insulin resistance in HIV-infected men. Design and methods We performed a cross-sectional analysis of baseline data from twenty-three HIV-infected participants in 3 prospective clinical studies. Magnetic resonance spectroscopy was applied to quantify hepatic lipid concentrations. Magnetic resonance imaging was used to quantify whole body adipose tissue compartments, i.e., subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) volumes as well as inter-muscular adipose tissue (IMAT) subcompartment, and omental-mesenteric adipose tissue (OMAT) and retroperitoneal adipose tissue (RPAT) subcompartments of VAT. Homeostasis model for assessment of insulin resistance (HOMA-IR) was calculated from fasting glucose and insulin concentrations. Results Hepatic lipid content correlated significantly with total VAT (r=0.62, p=0.0014) but not with SAT (r=0.053, p=0.81). In univariate analysis, hepatic lipid content was associated with the OMAT (r=0.67, p=0.0004) and RPAT (r=0.53, p=0.009) subcompartments; HOMA-IR correlated with both VAT and hepatic lipid contents (r=0.61, p=0.057 and 0.68, p=0.0012, respectively). In stepwise linear regression models, hepatic lipid had the strongest associations with OMAT and with HOMA-IR. Conclusion Hepatic lipid content is associated with VAT volume, especially the omental-mesenteric subcompartment, in HIV-infected men. Hepatic lipid content is associated with insulin resistance in HIV-infected men. Hepatic lipid content might mediate the relationship between VAT and insulin resistance among treated, HIV-infected men. PMID:18572755

Insulin resistance, hepatic lipid and adipose tissue distribution in HIV-infected men.

Science.gov (United States)

He, Qing; Engelson, Ellen S; Ionescu, Gabriel; Glesby, Marshall J; Albu, Jeanine B; Kotler, Donald P

2008-01-01

A large proportion of HIV-infected patients on antiretroviral medication develop insulin resistance, especially in the context of fat redistribution. This study investigates the interrelationships among fat distribution, hepatic lipid content, and insulin resistance in HIV-infected men. We performed a cross-sectional analysis of baseline data from 23 HIV-infected participants in three prospective clinical studies. Magnetic resonance spectroscopy was used to quantify hepatic lipid concentrations. Magnetic resonance imaging was used to quantify whole-body adipose tissue compartments: that is, subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) volumes, as well as the intermuscular adipose tissue (IMAT) subcompartment and the omental-mesenteric adipose tissue (OMAT) and retroperitoneal adipose tissue (RPAT) subcompartments of VAT. The homeostasis model for assessment of insulin resistance (HOMA-IR) was calculated from fasting glucose and insulin concentrations. Hepatic lipid content correlated significantly with total VAT (r = 0.62, P = 0.0014), but not with SAT (r = 0.053, P = 0.81). In univariate analysis, hepatic lipid content was associated with the OMAT (r = 0.67, P = 0.0004) and RPAT (r = 0.53, P = 0.009) subcompartments; HOMA-IR correlated with both VAT and hepatic lipid contents (r = 0.61, P = 0.057 and r = 0.68, P = 0.0012, respectively). In stepwise linear regression models, hepatic lipid had the strongest associations with OMAT and with HOMA-IR. Hepatic lipid content is associated with VAT volume, especially the OMAT subcompartment, in HIV-infected men. Hepatic lipid content is associated with insulin resistance in HIV-infected men. Hepatic lipid content might mediate the relationship between VAT and insulin resistance among treated, HIV-infected men.

Nutrigenomic effects of edible bird’s nest on insulin signaling in ovariectomized rats

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Hou ZP

2015-08-01

Full Text Available Zhiping Hou,1,2 Mustapha Umar Imam,1 Maznah Ismail,1,3 Der Jiun Ooi,1 Aini Ideris,4 Rozi Mahmud5 1Laboratory of Molecular Biomedicine, Institute of Bioscience, Universiti Putra Malaysia, Serdang, Malaysia; 2Department of Pathology, Chengde Medical University, Chengde, People’s Republic of China; 3Department of Nutrition and Dietetics, Universiti Putra Malaysia, Serdang, Malaysia; 4Department of Veterinary Clinical Studies, Faculty of Veterinary Medicine, Universiti Putra Malaysia, Serdang, Malaysia; 5Department of Imaging, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, Serdang, Malaysia Abstract: Estrogen deficiency alters quality of life during menopause. Hormone replacement therapy has been used to improve quality of life and prevent complications, but side effects limit its use. In this study, we evaluated the use of edible bird’s nest (EBN for prevention of cardiometabolic problems in rats with ovariectomy-induced menopause. Ovariectomized female rats were fed for 12 weeks with normal rat chow, EBN, or estrogen and compared with normal non-ovariectomized rats. Metabolic indices (insulin, estrogen, superoxide dismutase, malondialdehyde, oral glucose tolerance test, and lipid profile were measured at the end of the experiment from serum and liver tissue homogenate, and transcriptional levels of hepatic insulin signaling genes were measured. The results showed that ovariectomy worsened metabolic indices and disrupted the normal transcriptional pattern of hepatic insulin signaling genes. EBN improved the metabolic indices and also produced transcriptional changes in hepatic insulin signaling genes that tended toward enhanced insulin sensitivity, and glucose and lipid homeostasis, even better than estrogen. The data suggest that EBN could meliorate estrogen deficiency-associated increase in risk of cardiometabolic disease in rats, and may in fact be useful as a functional food for the prevention of such a problem in

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

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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.

Phosphatidylcholine Transfer Protein Interacts with Thioesterase Superfamily Member 2 to Attenuate Insulin Signaling

OpenAIRE

Ersoy, Baran A.; Tarun, Akansha; D’Aquino, Katharine; Hancer, Nancy J.; Ukomadu, Chinweike; White, Morris F.; Michel, Thomas; Manning, Brendan D.; Cohen, David E.

2013-01-01

Phosphatidylcholine transfer protein (PC-TP) is a phospholipid-binding protein that is enriched in liver and that interacts with thioesterase superfamily member 2 (THEM2). Mice lacking either protein exhibit improved hepatic glucose homeostasis and are resistant to diet-induced diabetes. Insulin receptor substrate 2 (IRS2) and mammalian target of rapamycin complex 1 (mTORC1) are key effectors of insulin signaling, which is attenuated in diabetes. We found that PC-TP inhibited IRS2, as evidenc...

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...

Eradicating hepatitis C virus ameliorates insulin resistance without change in adipose depots.

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Milner, K-L; Jenkins, A B; Trenell, M; Tid-Ang, J; Samocha-Bonet, D; Weltman, M; Xu, A; George, J; Chisholm, D J

2014-05-01

Chronic hepatitis C (CHC) is associated with lipid-related changes and insulin resistance; the latter predicts response to antiviral therapy, liver disease progression and the risk of diabetes. We sought to determine whether insulin sensitivity improves following CHC viral eradication after antiviral therapy and whether this is accompanied by changes in fat depots or adipokine levels. We compared 8 normoglycaemic men with CHC (genotype 1 or 3) before and at least 6 months post viral eradication and 15 hepatitis C antibody negative controls using an intravenous glucose tolerance test and two-step hyperinsulinaemic-euglycaemic clamp with [6,6-(2) H2 ] glucose to assess peripheral and hepatic insulin sensitivity. Magnetic resonance imaging and spectroscopy quantified abdominal fat compartments, liver and intramyocellular lipid. Peripheral insulin sensitivity improved (glucose infusion rate during high-dose insulin increased from 10.1 ± 1.6 to 12 ± 2.1 mg/kg/min/, P = 0.025), with no change in hepatic insulin response following successful viral eradication, without any accompanying change in muscle, liver or abdominal fat depots. There was corresponding improvement in incremental glycaemic response to intravenous glucose (pretreatment: 62.1 ± 8.3 vs post-treatment: 56.1 ± 8.5 mm, P = 0.008). Insulin sensitivity after viral clearance was comparable to matched controls without CHC. Post therapy, liver enzyme levels decreased but, interestingly, levels of glucagon, fatty acid-binding protein and lipocalin-2 remained elevated. Eradication of the hepatitis C virus improves insulin sensitivity without alteration in fat depots, adipokine or glucagon levels, consistent with a direct link of the virus with insulin resistance. © 2013 John Wiley & Sons Ltd.

Keratin 8/18 regulation of glucose metabolism in normal versus cancerous hepatic cells through differential modulation of hexokinase status and insulin signaling

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Mathew, Jasmin; Loranger, Anne; Gilbert, Stéphane [Centre de recherche en cancérologie de l' Université Laval and Centre de recherche du CHUQ (L' Hôtel-Dieu de Québec), 9 McMahon, Québec, Qc, Canada G1R 2J6 (Canada); Faure, Robert [Département de Pédiatrie, Université Laval and Centre de recherche du CHUQ (Centre Mère-Enfant), Québec, Qc, Canada G1V 4G2 (Canada); Marceau, Normand, E-mail: normand.marceau@crhdq.ulaval.ca [Centre de recherche en cancérologie de l' Université Laval and Centre de recherche du CHUQ (L' Hôtel-Dieu de Québec), 9 McMahon, Québec, Qc, Canada G1R 2J6 (Canada)

2013-02-15

As differentiated cells, hepatocytes primarily metabolize glucose for ATP production through oxidative phosphorylation of glycolytic pyruvate, whereas proliferative hepatocellular carcinoma (HCC) cells undergo a metabolic shift to aerobic glycolysis despite oxygen availability. Keratins, the intermediate filament (IF) proteins of epithelial cells, are expressed as pairs in a lineage/differentiation manner. Hepatocyte and HCC (hepatoma) cell IFs are made solely of keratins 8/18 (K8/K18), thus providing models of choice to address K8/K18 IF functions in normal and cancerous epithelial cells. Here, we demonstrate distinctive increases in glucose uptake, glucose-6-phosphate formation, lactate release, and glycogen formation in K8/K18 IF-lacking hepatocytes and/or hepatoma cells versus their respective IF-containing counterparts. We also show that the K8/K18-dependent glucose uptake/G6P formation is linked to alterations in hexokinase I/II/IV content and localization at mitochondria, with little effect on GLUT1 status. In addition, we find that the insulin-stimulated glycogen formation in normal hepatocytes involves the main PI-3 kinase-dependent signaling pathway and that the K8/K18 IF loss makes them more efficient glycogen producers. In comparison, the higher insulin-dependent glycogen formation in K8/K18 IF-lacking hepatoma cells is associated with a signaling occurring through a mTOR-dependent pathway, along with an augmentation in cell proliferative activity. Together, the results uncover a key K8/K18 regulation of glucose metabolism in normal and cancerous hepatic cells through differential modulations of mitochondrial HK status and insulin-mediated signaling.

An Intestinal Farnesoid X Receptor–Ceramide Signaling Axis Modulates Hepatic Gluconeogenesis in Mice

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Xie, Cen; Shi, Jingmin; Gao, Xiaoxia; Sun, Dongxue; Sun, Lulu; Wang, Ting; Takahashi, Shogo; Anitha, Mallappa; Krausz, Kristopher W.; Patterson, Andrew D.

2017-01-01

Increasing evidence supports the view that intestinal farnesoid X receptor (FXR) is involved in glucose tolerance and that FXR signaling can be profoundly impacted by the gut microbiota. Selective manipulation of the gut microbiota–FXR signaling axis was reported to significantly impact glucose intolerance, but the precise molecular mechanism remains largely unknown. Here, caffeic acid phenethyl ester (CAPE), an over-the-counter dietary supplement and an inhibitor of bacterial bile salt hydrolase, increased levels of intestinal tauro-β-muricholic acid, which selectively suppresses intestinal FXR signaling. Intestinal FXR inhibition decreased ceramide levels by suppressing expression of genes involved in ceramide synthesis specifically in the intestinal ileum epithelial cells. The lower serum ceramides mediated decreased hepatic mitochondrial acetyl-CoA levels and pyruvate carboxylase (PC) activities and attenuated hepatic gluconeogenesis, independent of body weight change and hepatic insulin signaling in vivo; this was reversed by treatment of mice with ceramides or the FXR agonist GW4064. Ceramides substantially attenuated mitochondrial citrate synthase activities primarily through the induction of endoplasmic reticulum stress, which triggers increased hepatic mitochondrial acetyl-CoA levels and PC activities. These results reveal a mechanism by which the dietary supplement CAPE and intestinal FXR regulates hepatic gluconeogenesis and suggest that inhibiting intestinal FXR is a strategy for treating hyperglycemia. PMID:28223344

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....

Dapper1 attenuates hepatic gluconeogenesis and lipogenesis by activating PI3K/Akt signaling.

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Kuang, Jian-Ren; Zhang, Zhi-Hui; Leng, Wei-Ling; Lei, Xiao-Tian; Liang, Zi-Wen

2017-05-15

Studies have shown that hepatic insulin resistance, a disorder of glucose and lipid metabolism, plays a vital role in type 2 diabetes (T2D). To clarify the function of Dapper1 in glucose and lipid metabolism in the liver, we investigated the relationships between Dapper1 and adenosine triphosphate (ATP)- and Ca 2+ -mediated activation of PI3K/Akt. We observed a reduction in hepatic Dapper1 in db/db (mice that are homozygous for a spontaneous diabetes mutation) and HFD-induced diabetic mice with T2D. Hepatic overexpression of Dapper1 improved hyperglycemia, insulin resistance, and fatty liver. It also increased Akt (pAkt) signaling and repressed both gluconeogenesis and lipogenesis. Conversely, Ad-shDapper1-induced knockdown of hepatic Dapper1 promoted gluconeogenesis and lipogenesis. Furthermore, Dapper1 activated PI3K p110α/Akt in an insulin-independent manner by inducing ATP production and secretion in vitro. Blockade of P2 ATP receptors, the downstream phospholipase C (PLC), or the inositol triphosphate receptor (IP3R all reduced the Dapper1-induced increase in cytosolic free calcium and Dapper1-mediated PI3K/Akt activation, as did removal of calcium in the medium. In conclusion, Dapper1 attenuates hepatic gluconeogenesis and lipogenesis in T2D. Copyright © 2017 Elsevier B.V. All rights reserved.

Ingestion of a natural mineral-rich water in an animal model of metabolic syndrome: effects in insulin signalling and endoplasmic reticulum stress.

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Pereira, Cidália D; Passos, Emanuel; Severo, Milton; Vitó, Isabel; Wen, Xiaogang; Carneiro, Fátima; Gomes, Pedro; Monteiro, Rosário; Martins, Maria J

2016-05-01

High-fructose and/or low-mineral diets are relevant in metabolic syndrome (MS) development. Insulin resistance (IR) represents a central mechanism in MS development. Glucocorticoid signalling dysfunction and endoplasmic reticulum (ER) and oxidative stresses strongly contribute to IR and associate with MS. We have described that natural mineral-rich water ingestion delays fructose-induced MS development, modulates fructose effects on the redox state and glucocorticoid signalling and increases sirtuin 1 expression. Here, we investigated mineral-rich water ingestion effects on insulin signalling and ER homeostasis of fructose-fed rats. Adult male Sprague-Dawley rats had free access to standard-chow diet and different drinking solutions (8 weeks): tap water (CONT), 10%-fructose/tap water (FRUCT) or 10%-fructose/mineral-rich water (FRUCTMIN). Hepatic and adipose (visceral, VAT) insulin signalling and hepatic ER homeostasis (Western blot or PCR) as well as hepatic lipid accumulation were evaluated. Hepatic p-IRS1Ser307/IRS1 (tendency), p-IRS1Ser307, total JNK and (activated IRE1α)/(activated JNK) decreased with fructose ingestion, while p-JNK tended to increase; mineral-rich water ingestion, totally or partially, reverted all these effects. Total PERK, p-eIF2α (tendency) and total IRS1 (tendency) decreased in both fructose-fed groups. p-ERK/ERK and total IRE1α increasing tendencies in FRUCT became significant in FRUCTMIN (similar pattern for lipid area). Additionally, unspliced-XBP1 increased with mineral-rich water. In VAT, total ERK fructose-induced increase was partially prevented in FRUCTMIN. Mineral-rich water modulation of fructose-induced effects on insulin signalling and ER homeostasis matches the better metabolic profile previously reported. Increased p-ERK/ERK, adding to decreased IRE1α activation, and increased unspliced-XBP1 and lipid area may protect against oxidative stress and IR development in FRUCTMIN.

The role of exogenous insulin in the complex of hepatic lipidosis and ketosis associated with insulin resistance phenomenon in postpartum dairy cattle.

Science.gov (United States)

Hayirli, A

2006-10-01

As a result of a marked decline in dry matter intake (DMI) prior to parturition and a slow rate of increase in DMI relative to milk production after parturition, dairy cattle experience a negative energy balance. Changes in nutritional and metabolic status during the periparturient period predispose dairy cattle to develop hepatic lipidosis and ketosis. The metabolic profile during early lactation includes low concentrations of serum insulin, plasma glucose, and liver glycogen and high concentrations of serum glucagon, adrenaline, growth hormone, plasma beta-hydroxybutyrate and non-esterified fatty acids, and liver triglyceride. Moreover, during late gestation and early lactation, flow of nutrients to fetus and mammary tissues are accorded a high degree of metabolic priority. This priority coincides with lowered responsiveness and sensitivity of extrahepatic tissues to insulin, which presumably plays a key role in development of hepatic lipidosis and ketosis. Hepatic lipidosis and ketosis compromise production, immune function, and fertility. Cows with hepatic lipidosis and ketosis have low tissue responsiveness to insulin owing to ketoacidosis. Insulin has numerous roles in metabolism of carbohydrates, lipids and proteins. Insulin is an anabolic hormone and acts to preserve nutrients as well as being a potent feed intake regulator. In addition to the major replacement therapy to alleviate severity of negative energy balance, administration of insulin with concomitant delivery of dextrose increases efficiency of treatment for hepatic lipidosis and ketosis. However, data on use of insulin to prevent these lipid-related metabolic disorders are limited and it should be investigated.

Deregulation of brain insulin signaling in Alzheimer's disease.

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Chen, Yanxing; Deng, Yanqiu; Zhang, Baorong; Gong, Cheng-Xin

2014-04-01

Contrary to the previous belief that insulin does not act in the brain, studies in the last three decades have demonstrated important roles of insulin and insulin signal transduction in various functions of the central nervous system. Deregulated brain insulin signaling and its role in molecular pathogenesis have recently been reported in Alzheimer's disease (AD). In this article, we review the roles of brain insulin signaling in memory and cognition, the metabolism of amyloid β precursor protein, and tau phosphorylation. We further discuss deficiencies of brain insulin signaling and glucose metabolism, their roles in the development of AD, and recent studies that target the brain insulin signaling pathway for the treatment of AD. It is clear now that deregulation of brain insulin signaling plays an important role in the development of sporadic AD. The brain insulin signaling pathway also offers a promising therapeutic target for treating AD and probably other neurodegenerative disorders.

Hepatitis C and insulin resistance: steatosis, fibrosis and non-response Hepatitis C y resistencia a la insulina: esteatosis, fibrosis y no respuesta

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M. Romero-Gómez

2006-08-01

Full Text Available Insulin resistance is more often seen in hepatitis C than in other liver diseases, including non-alcoholic steatohepatitis. The Homeostasis Model for Assessment [HOMA= fasting insulin (mUI/ml * fasting glucose (mmol/L / 22.5] has proved useful in the measurement of insulin sensitivity in euglycemic patients. Cross-sectional and case-cohort studies support a role for hepatitis C as a factor implied in the development of type-2 diabetes in high-risk patients (male patients, older than 40 years, and overweight. In transgenic mice models the HCV core protein has been found to induce insulin resistance via TNF production. Insulin resistance has been associated with steatosis development and fibrosis progression in a genotype-dependent manner. In genotype-1 patients, the mechanisms by which insulin resistance promotes fibrosis progression include: a steatosis; b hyperleptinemia; c increased TNF production; and d impaired expression of PPARγ receptors. Indeed, insulin resistance has been found as a common denominator to the majority of features associated with difficult-to-treat patients. Patients with cirrhosis, obesity, coinfected with HIV, and Afro-American, all of them showed insulin resistance. Insulin resistance strongly influences sustained response rates, at least in genotype-1 patients. Insulin resistance decreases during and after treatment in patients that achieved virus C clearance. Moreover, the incidence of type-2 diabetes seems to be lower in responders than in non-responders. In summary, hepatitis C promotes insulin resistance and insulin resistance induces steatosis, fibrosis, and interferon resistance. The treatment of insulin resistance by decreasing hyperinsulinemia could improve sustained response rates in patients with chronic hepatitis C treated with peginterferon plus ribavirin.

Hepatitis C virus E2 protein involve in insulin resistance through an impairment of Akt/PKB and GSK3β signaling in hepatocytes

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Hsieh Ming-Ju

2012-06-01

Full Text Available Abstract Background Hepatitis C virus (HCV infection may cause liver diseases of various severities ranging from primary acute infection to life-threatening diseases, such as cirrhosis or hepatocellular carcinoma with poor prognosis. According to clinical findings, HCV infection may also lead to some extra-hepatic symptoms, including type 2 diabetes mellitus (DM. Since insulin resistance is the major etiology for type 2 DM and numerous evidences showed that HCV infection associated with insulin resistance, the involvement of E2 in the pathogenesis of type 2 DM and underlying mechanisms were investigated in this study. Methods Reverse transcription and real-time PCR, Western blot assay, Immunoprecipitation, Glucose uptake assay and analysis of cellular glycogen content. Results Results showed that E2 influenced on protein levels of insulin receptor substrate-1 (IRS-1 and impaired insulin-induced Ser308 phosphorylation of Akt/PKB and Ser9 phosphorylation of GSK3β in Huh7 cells, leading to an inhibition of glucose uptake and glycogen synthesis, respectively, and eventually insulin resistance. Conclusions Therefore, HCV E2 protein indeed involved in the pathogenesis of type 2 DM by inducing insulin resistance.

GLP-1 Elicits an Intrinsic Gut-Liver Metabolic Signal to Ameliorate Diet-Induced VLDL Overproduction and Insulin Resistance.

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Khound, Rituraj; Taher, Jennifer; Baker, Christopher; Adeli, Khosrow; Su, Qiaozhu

2017-12-01

Perturbations in hepatic lipid and very-low-density lipoprotein (VLDL) metabolism are involved in the pathogenesis of obesity and hepatic insulin resistance. The objective of this study is to delineate the mechanism of subdiaphragmatic vagotomy in preventing obesity, hyperlipidemia, and insulin resistance. By subjecting the complete subdiaphragmatic vagotomized mice to various nutritional conditions and investigating hepatic de novo lipogenesis pathway, we found that complete disruption of subdiaphragmatic vagal signaling resulted in a significant decrease of circulating VLDL-triglyceride compared with the mice obtained sham procedure. Vagotomy further prevented overproduction of VLDL-triglyceride induced by an acute fat load and a high-fat diet-induced obesity, hyperlipidemia, hepatic steatosis, and glucose intolerance. Mechanistic studies revealed that plasma glucagon-like peptide-1 was significantly raised in the vagotomized mice, which was associated with significant reductions in mRNA and protein expression of SREBP-1c (sterol regulatory element-binding protein 1c), SCD-1 (stearoyl-CoA desaturase-1), and FASN (fatty acid synthase), as well as enhanced hepatic insulin sensitivity. In vitro, treating mouse primary hepatocytes with a glucagon-like peptide-1 receptor agonist, exendin-4, for 48 hours inhibited free fatty acid, palmitic acid treatment induced de novo lipid synthesis, and VLDL secretion from hepatocytes. Elevation of glucagon-like peptide-1 in vagotomized mice may prevent VLDL overproduction and insulin resistance induced by high-fat diet. These novel findings, for the first time, delineate an intrinsic gut-liver regulatory circuit that is mediated by glucagon-like peptide-1 in regulating hepatic energy metabolism. © 2017 American Heart Association, Inc.

Deletion of hepatic carbohydrate response element binding protein (ChREBP impairs glucose homeostasis and hepatic insulin sensitivity in mice

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Tara Jois

2017-11-01

Conclusions: Overall, hepatic ChREBP is protective in regards to hepatic insulin sensitivity and whole body glucose homeostasis. Hepatic ChREBP action can influence other peripheral tissues and is likely essential in coordinating the body's response to different feeding states.

Proximity to Delivery Alters Insulin Sensitivity and Glucose Metabolism in Pregnant Mice.

Science.gov (United States)

Musial, Barbara; Fernandez-Twinn, Denise S; Vaughan, Owen R; Ozanne, Susan E; Voshol, Peter; Sferruzzi-Perri, Amanda N; Fowden, Abigail L

2016-04-01

In late pregnancy, maternal insulin resistance occurs to support fetal growth, but little is known about insulin-glucose dynamics close to delivery. This study measured insulin sensitivity in mice in late pregnancy at day 16 (D16) and near term at D19. Nonpregnant (NP) and pregnant mice were assessed for metabolite and hormone concentrations, body composition by DEXA, tissue insulin signaling protein abundance by Western blotting, glucose tolerance and utilization, and insulin sensitivity using acute insulin administration and hyperinsulinemic-euglycemic clamps with [(3)H]glucose infusion. Whole-body insulin resistance occurred in D16 pregnant dams in association with basal hyperinsulinemia, insulin-resistant endogenous glucose production, and downregulation of several proteins in hepatic and skeletal muscle insulin signaling pathways relative to NP and D19 values. Insulin resistance was less pronounced at D19, with restoration of NP insulin concentrations, improved hepatic insulin sensitivity, and increased abundance of hepatic insulin signaling proteins. At D16, insulin resistance at whole-body, tissue, and molecular levels will favor fetal glucose acquisition, while improved D19 hepatic insulin sensitivity will conserve glucose for maternal use in anticipation of lactation. Tissue sensitivity to insulin, therefore, alters differentially with proximity to delivery in pregnant mice, with implications for human and other species. © 2016 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.

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

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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

Berberine Protects against NEFA-Induced Impairment of Mitochondrial Respiratory Chain Function and Insulin Signaling in Bovine Hepatocytes

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Zhen Shi

2018-06-01

Full Text Available Fatty liver is a major lipid metabolic disease in perinatal dairy cows and is characterized by high blood levels of non-esterified fatty acid (NEFA and insulin resistance. Berberine (BBR has been reported to improve insulin sensitivity in mice with hepatic steatosis. Mitochondrial dysfunction is considered a causal factor that induces insulin resistance. This study investigates the underlying mechanism and the beneficial effects of BBR on mitochondrial and insulin signaling in bovine hepatocytes. Revised quantitative insulin sensitivity check index (RQUICKI of cows with fatty liver was significantly lower than that of healthy cows. Importantly, the Akt and GSK3β phosphorylation levels, protein levels of PGC-1α and four of the five representative subunits of oxidative phosphorylation (OXPHOS were significantly decreased in cows with fatty liver using Western Blot analysis. In bovine hepatocytes, 1.2 mmol/L NEFA reduced insulin signaling and mitochondrial respiratory chain function, and 10 and 20 umol/L BBR restored these changes. Furthermore, activation of PGC-1α played the same beneficial effects of BBR on hepatocytes treated with NEFA. BBR treatment improves NEFA-impaired mitochondrial respiratory chain function and insulin signaling by increasing PGC-1α expression in hepatocytes, which provides a potential new strategy for the prevention and treatment of fatty liver in dairy cows.

Hepatic 123I-insulin binding kinetics in non-insulin-dependent (Type 2) diabetic patients after i.v. bolus administration

International Nuclear Information System (INIS)

Oolbekkink, M.; Veen, E.A. van der; Heine, R.J.; Hollander, W. den; Nauta, J.J.P.

1989-01-01

Insulin binding kinetics in the liver were studied in non insulin dependent (Type 2) diabetic patients, by i.v. bolus administration of 123 I-insulin. Eight Type 2 diabetic patients were compared with six male volunteers. Uptake of 123 I-insulin by liver and kidneys was measured by dynamic scintigraphy with a gamma camera during 30 min. Images of liver and kidneys appeared within 2-3 min after administration of 123 I-insulin at a dose of 1 mCi (37 MBq). Peak radioactivity for the liver was found 7.5±0.2 and 6.9±0.3 min after injection for the healthy and the diabetic subjects, respectively (N.S.). The percentage 123 I-insulin hepatic uptake was not significantly different for the diabetic and the healthy subjects. Although a large variation exists for maximal uptake of radioactivity within both groups, the data suggest that binding differences in the liver in Type 2 diabetic patients, as compared to healthy subjects, may not account for hepatic insulin resistance. (orig.)

Evaluated the Up –regulation in Gene ‎Expression of Hepatic Insulin Gene and ‎Hepatic Insulin Receptor Gene in Type 1 ‎Diabetic Rats Treated with Cuscuta chinesis ‎Lam.‎

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Fadia ‎ H. Al-Sultany

2018-02-01

Full Text Available         This research was conducted to study the hypoglycemic activity of C. chinesis Lam on type 1 diabetic disease and investigate the  molecular and histological mechanism of  its action .many parameters was investigated , Fasting blood glucose (FBG, Fasting serum insulin,Hepatic Insulin Gene Expression, pancreas Insulin Gene Expression ,Hepatic Insulin  Receptors Gene expression  and histological sections of pancrease and liver.54 Rattus rattus male rats weighting(180 -200g were divided into 3 groups: A normal control daily administrated with Dw, B Diabetic control daily administrated with Dw  and C  diabetic group daily administrated with 400 mg/Kg body weight of C. chinesis  Lam. methanolic extract, each group consisted of  18 rats and further divided into (3 sub- groups 1 ,2  and 3. According to the period of administration  30, 60 and  90 days respectively. The results showing  the daily administration of 400 mg/Kg body weight of C. chinesis  Lam. methanolic extract for 60 day causing significance  decrease  in FBG and In the other hand each of fasting serum insulin, hepatic Insulin gene expression,pancreas Insulin gene expression and hepatic Insulin receptor gene expression was increased in group C in compare to B group and return all studied parameters involving pancrease and liver texture to the normal state ,which were statically morphologically  not appeared any significant difference from A group .this study concluded that the daily administration type 1 diabetic rats with 400 mg/Kg body weight of C. chinesis  Lam. extract for 60 day was return  fasting serum insulin and FBG to normal value by  upregulated  the gene expression of hepatic INS Gene ,INSR gene , pancreas INS Gene ,regenerate pancreatic beta- cell and returnthe texture of both liver and pancrease to the normal state

Phosphatidylcholine transfer protein interacts with thioesterase superfamily member 2 to attenuate insulin signaling.

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Ersoy, Baran A; Tarun, Akansha; D'Aquino, Katharine; Hancer, Nancy J; Ukomadu, Chinweike; White, Morris F; Michel, Thomas; Manning, Brendan D; Cohen, David E

2013-07-30

Phosphatidylcholine transfer protein (PC-TP) is a phospholipid-binding protein that is enriched in liver and that interacts with thioesterase superfamily member 2 (THEM2). Mice lacking either protein exhibit improved hepatic glucose homeostasis and are resistant to diet-induced diabetes. Insulin receptor substrate 2 (IRS2) and mammalian target of rapamycin complex 1 (mTORC1) are key effectors of insulin signaling, which is attenuated in diabetes. We found that PC-TP inhibited IRS2, as evidenced by insulin-independent IRS2 activation after knockdown, genetic ablation, or chemical inhibition of PC-TP. In addition, IRS2 was activated after knockdown of THEM2, providing support for a role for the interaction of PC-TP with THEM2 in suppressing insulin signaling. Additionally, we showed that PC-TP bound to tuberous sclerosis complex 2 (TSC2) and stabilized the components of the TSC1-TSC2 complex, which functions to inhibit mTORC1. Preventing phosphatidylcholine from binding to PC-TP disrupted interactions of PC-TP with THEM2 and TSC2, and disruption of the PC-TP-THEM2 complex was associated with increased activation of both IRS2 and mTORC1. In livers of mice with genetic ablation of PC-TP or that had been treated with a PC-TP inhibitor, steady-state amounts of IRS2 were increased, whereas those of TSC2 were decreased. These findings reveal a phospholipid-dependent mechanism that suppresses insulin signaling downstream of its receptor.

Accretion of visceral fat and hepatic insulin resistance in pregnant rats.

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Einstein, Francine H; Fishman, Sigal; Muzumdar, Radhika H; Yang, Xiao Man; Atzmon, Gil; Barzilai, Nir

2008-02-01

Insulin resistance (IR) is a hallmark of pregnancy. Because increased visceral fat (VF) is associated with IR in nonpregnant states, we reasoned that fat accretion might be important in the development of IR during pregnancy. To determine whether VF depots increase in pregnancy and whether VF contributes to IR, we studied three groups of 6-mo-old female Sprague-Dawley rats: 1) nonpregnant sham-operated rats (Nonpreg; n = 6), 2) pregnant sham-operated rats (Preg; n = 6), and 3) pregnant rats in which VF was surgically removed 1 mo before mating (PVF-; n = 6). VF doubled by day 19 of pregnancy (Nonpreg 5.1 +/- 0.3, Preg 10.0 +/- 1.0 g, P Insulin sensitivity was measured by hyperinsulinemic-euglycemic clamp in late gestation in chronically catheterized unstressed rats. Glucose IR (mg.kg(-1).min(-1)) was highest in Nonpreg (19.4 +/- 2.0), lowest in Preg (11.1 +/- 1.4), and intermediate in PVF- (14.7 +/- 0.6; P insulin sensitivity than Preg [hepatic glucose production (HGP): Nonpreg 4.5 +/- 1.3, Preg 9.3 +/- 0.5 mg.kg(-1).min(-1); P insulin sensitivity was similar to nonpregnant levels in PVF- (HGP 4.9 +/- 0.8 mg.kg(-1).min(-1)). Both pregnant groups had lower peripheral glucose uptake compared with Nonpreg. In parallel with hepatic insulin sensitivity, hepatic triglyceride content was increased in pregnancy (Nonpreg 1.9 +/- 0.4 vs. Preg 3.2 +/- 0.3 mg/g) and decreased with removal of VF (PVF- 1.3 +/- 0.4 mg/g; P insulin action in pregnancy.

Chronic hepatitis C infection is associated with insulin resistance and lipid profiles.

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Dai, Chia-Yen; Yeh, Ming-Lun; Huang, Chung-Feng; Hou, Chen-Hsiu; Hsieh, Ming-Yen; Huang, Jee-Fu; Lin, I-Ling; Lin, Zu-Yau; Chen, Shinn-Chern; Wang, Liang-Yen; Chuang, Wan-Long; Yu, Ming-Lung; Tung, Hung-Da

2015-05-01

Chronic hepatitis C virus (HCV) infection has been suggested to be associated with non-insulin-dependent diabetes mellitus and lipid profiles. This study aimed to investigate the possible relationships of insulin resistance (IR) and lipid profiles with chronic hepatitis C (CHC) patients in Taiwan. We enrolled 160 hospital-based CHC patients with liver biopsy and the 480 controlled individuals without CHC and chronic hepatitis B from communities without known history of non-insulin-dependent diabetes mellitus. Fasting plasma glucose, total cholesterol, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), triglycerides (TGs), alanine aminotransferase, and serum insulin levels, and homeostasis model assessment (HOMA-IR) were tested. When comparing factors between CHC patients, and sex- and age-matched controls who had no HCV infection, patients with HCV infection had a significantly higher alanine aminotransferase level, fasting plasma glucose level, insulin level, and HOMA-IR (P C and LDL-C levels (all P  2.5]), a high body mass index, TGs, and HCV RNA level are independent factors significantly associated with high HOMA-IR in multivariate logistic analyses. Chronic HCV infection was associated with metabolic characteristics including IR and lipid profile. IR was also associated with virological characteristics. © 2013 Journal of Gastroenterology and Hepatology Foundation and Wiley Publishing Asia Pty Ltd.

In nondiabetic, human immunodeficiency virus-infected patients with lipodystrophy, hepatic insulin extraction and posthepatic insulin clearance rate are decreased in proportion to insulin resistance

DEFF Research Database (Denmark)

Haugaard, Steen B; Andersen, Ove; Hansen, Birgitte R

2005-01-01

In healthy, nondiabetic individuals with insulin resistance, fasting insulin is inversely correlated to the posthepatic insulin clearance rate (MCRi) and the hepatic insulin extraction (HEXi). We investigated whether similar early mechanisms to facilitate glucose homeostasis exist in nondiabetic...... > .1). Our data suggest that HEXi and MCRi are decreased in proportion to the degree of insulin resistance in nondiabetic HIV-infected patients with lipodystrophy....... insulin clearance rate was estimated as the ratio of posthepatic insulin appearance rate to steady-state plasma insulin concentration during a euglycemic hyperinsulinemic clamp (40 mU.m-2 .min-1). Posthepatic insulin appearance rate during the clamp was calculated, taking into account the remnant...

High alanine aminotransferase is associated with decreased hepatic insulin sensitivity and predicts the development of type 2 diabetes

DEFF Research Database (Denmark)

Vozarova, Barbora; Stefan, Norbert; Lindsay, Robert S

2002-01-01

-sectionally associated with obesity and whole-body and hepatic insulin resistance and prospectively associated with a decline in hepatic insulin sensitivity and the development of type 2 diabetes. Our findings indicate that high ALT is a marker of risk for type 2 diabetes and suggest a potential role of the liver...... with prospective changes in liver or whole-body insulin sensitivity and/or insulin secretion and whether these elevated enzymes predict the development of type 2 diabetes in Pima Indians. We measured ALT, AST, and GGT in 451 nondiabetic (75-g oral glucose tolerance test) Pima Indians (aged 30 +/- 6 years, body fat...... 33 +/- 8%, ALT 45 +/- 29 units/l, AST 34 +/- 18 units/l, and GGT 56 +/- 40 units/l [mean +/- SD]) who were characterized for body composition (hydrodensitometry or dual-energy X-ray absorptiometry), whole-body insulin sensitivity (M), and hepatic insulin sensitivity (hepatic glucose output [HGO...

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

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Højlund, Kurt

2014-07-01

Type 2 diabetes, obesity and polycystic ovary syndrome (PCOS) are common metabolic disorders which are observed with increasing prevalences, and which are caused by a complex interplay between genetic and environmental factors, including increased calorie intake and physical inactivity. These metabolic disorders are all characterized by reduced plasma adiponectin and insulin resistance in peripheral tissues. Quantitatively skeletal muscle is the major site of insulin resistance. Both low plasma adiponectin and insulin resistance contribute to an increased risk of type 2 diabetes and cardiovascular disease. In several studies, we have investigated insulin action on glucose and lipid metabolism, and at the molecular level, insulin signaling to glucose transport and glycogen synthesis in skeletal muscle from healthy individuals and in obesity, PCOS and type 2 diabetes. Moreover, we have described a novel syndrome characterized by postprandial hyperinsulinemic hypoglycemia and insulin resistance. This syndrome is caused by a mutation in the tyrosine kinase domain of the insulin receptor gene (INSR). We have studied individuals with this mutation as a model of inherited insulin resistance. Type 2 diabetes, obesity and PCOS are characterized by pronounced defects in the insulin-stimulated glucose uptake, in particular glycogen synthesis and to a lesser extent glucose oxidation, and the ability of insulin to suppress lipid oxidation. In inherited insulin resistance, however, only insulin action on glucose uptake and glycogen synthesis is impaired. This suggests that the defects in glucose and lipid oxidation in the common metabolic disorders are secondary to other factors. In young women with PCOS, the degree of insulin resistance was similar to that seen in middle-aged patients with type 2 diabetes. This supports the hypothesis of an unique pathogenesis of insulin resistance in PCOS. Insulin in physiological concentrations stimulates glucose uptake in human skeletal

Insulin signaling pathways in lepidopteran steroidogenesis

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Wendy eSmith

2014-02-01

Full Text Available Molting and metamorphosis are stimulated by the secretion of ecdysteroid hormones from the prothoracic glands. Insulin-like hormones have been found to enhance prothoracic gland activity, providing a mechanism to link molting to nutritional state. In silk moths (Bombyx mori, the prothoracic glands are directly stimulated by insulin and the insulin-like hormone bombyxin. Further, in Bombyx , the neuropeptide prothoracicotropic hormone (PTTH appears to act at least in part through the insulin-signaling pathway. In the prothoracic glands of Manduca sexta, while insulin stimulates the phosphorylation of the insulin receptor and Akt, neither insulin nor bombyxin II stimulate ecdysone secretion. Involvement of the insulin-signaling pathway in Manduca prothoracic glands was explored using two inhibitors of phosphatidylinositol-3-kinase (PI3K, LY294002 and wortmannin. PI3K inhibitors block the phosphorylation of Akt and 4EBP but have no effect on ecdysone secretion, or on the phosphorylation of the MAPkinase, ERK. Inhibitors that block phosphorylation of ERK, including the MEK inhibitor U0126, and high doses of the RSK inhibitor SL0101, effectively inhibit ecdysone secretion. The results highlight differences between the two lepidopteran insects most commonly used to directly study ecdysteroid secretion. In Bombyx, the PTTH and insulin-signaling pathways intersect; both insulin and PTTH enhance the phosphorylation of Akt and stimulate ecdysteroid secretion, and inhibition of PI3K reduces ecdysteroid secretion. By contrast, in Manduca, the action of PTTH is distinct from insulin. The results highlight species differences in the roles of translational regulators such as 4EBP, and members of the MAPkinase pathway such as ERK and RSK, in the effects of nutritionally-sensitive hormones such as insulin on ecdysone secretion and molting.

Endothelial activation markers (VCAM-1, vWF in patients with chronic hepatitis C and insulin resistance

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T. V. Antonova

2012-01-01

Full Text Available Blood markers of endothelial activation (sVCAM-1, vWF: Ag in patients with chronic hepatitis C in the presence of insulin resistance, metabolic syndrome and its components had been evaluated. The study included 69 patients with chronic hepatitis C with oligosymptomatic the disease. In one third of cases of chronic hepatitis C (33.3% showed improvement in the blood content of sVCAM-1 and / or vWF: Ag. In patients with chronic hepatitis C with insulin resistance, metabolic syndrome significantly more often found signs adhesion of endothelial dysfunction (increased blood concentrations of sVCAM-1 than in patients without these disorders. Found that in patients with severe hepatic fibrosis in patients with chronic hepatitis C blood concentration sVCAM-1 is significantly higher compared to patients with early stages of fibrosis (F0-F2, including those in patients without insulin resistance. These data suggest the multivariate development of endothelial dysfunction in chronic hepatitis C.

Insulin resistance in obesity as the underlying cause for the metabolic syndrome.

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Gallagher, Emily J; Leroith, Derek; Karnieli, Eddy

2010-01-01

The metabolic syndrome affects more than a third of the US population, predisposing to the development of type 2 diabetes and cardiovascular disease. The 2009 consensus statement from the International Diabetes Federation, American Heart Association, World Heart Federation, International Atherosclerosis Society, International Association for the Study of Obesity, and the National Heart, Lung, and Blood Institute defines the metabolic syndrome as 3 of the following elements: abdominal obesity, elevated blood pressure, elevated triglycerides, low high-density lipoprotein cholesterol, and hyperglycemia. Many factors contribute to this syndrome, including decreased physical activity, genetic predisposition, chronic inflammation, free fatty acids, and mitochondrial dysfunction. Insulin resistance appears to be the common link between these elements, obesity and the metabolic syndrome. In normal circumstances, insulin stimulates glucose uptake into skeletal muscle, inhibits hepatic gluconeogenesis, and decreases adipose-tissue lipolysis and hepatic production of very-low-density lipoproteins. Insulin signaling in the brain decreases appetite and prevents glucose production by the liver through neuronal signals from the hypothalamus. Insulin resistance, in contrast, leads to the release of free fatty acids from adipose tissue, increased hepatic production of very-low-density lipoproteins and decreased high-density lipoproteins. Increased production of free fatty acids, inflammatory cytokines, and adipokines and mitochondrial dysfunction contribute to impaired insulin signaling, decreased skeletal muscle glucose uptake, increased hepatic gluconeogenesis, and β cell dysfunction, leading to hyperglycemia. In addition, insulin resistance leads to the development of hypertension by impairing vasodilation induced by nitric oxide. In this review, we discuss normal insulin signaling and the mechanisms by which insulin resistance contributes to the development of the metabolic

Mincle Signaling Promotes Con-A Hepatitis

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Greco, Stephanie H.; Torres-Hernandez, Alejandro; Kalabin, Aleksandr; Whiteman, Clint; Rokosh, Rae; Ravirala, Sushma; Ochi, Atsuo; Gutierrez, Johana; Salyana, Muhammad Atif; Mani, Vishnu R.; Nagaraj, Savitha V.; Deutsch, Michael; Seifert, Lena; Daley, Donnele; Barilla, Rocky; Hundeyin, Mautin; Nikifrov, Yuriy; Tejada, Karla; Gelb, Bruce E.; Katz, Steven C.; Miller, George

2016-01-01

Concanavalin-A (Con-A) hepatitis is regarded as a T cell-mediated model of acute liver injury. Mincle is a C-type lectin receptor (CLR) that is critical in the immune response to mycobacteria and fungi, but does not have a well-defined role in pre-clinical models of non-pathogen mediated inflammation. Since Mincle can ligate the cell death ligand SAP130, we postulated that Mincle signaling drives intrahepatic inflammation and liver injury in Con-A hepatitis. Acute liver injury was assessed in the murine Con-A hepatitis model using C57BL/6, Mincle−/−, and Dectin-1−/− mice. The role of C/EBPβ and HIF-1α signaling was assessed using selective inhibitors. We found that Mincle was highly expressed in hepatic innate inflammatory cells and endothelial cells in both mice and humans. Furthermore, sterile Mincle ligands and Mincle signaling intermediates were increased in the murine liver in Con-A hepatitis. Most significantly, Mincle deletion or blockade protected against Con-A hepatitis whereas Mincle ligation exacerbated disease. Bone marrow chimeric and adoptive transfer experiments suggested that Mincle signaling in infiltrating myeloid cells dictates disease phenotype. Conversely, signaling via other CLRs did not alter disease course. Mechanistically, we found that Mincle blockade decreased the NF-κβ related signaling intermediates, C/EBPβ and HIF-1α, both of which are necessary in macrophage-mediated inflammatory responses. Accordingly, Mincle deletion lowered production of nitrites in Con-A hepatitis and inhibition of both C/EBPβ and HIF1-α reduced the severity of liver disease. Our work implicates a novel innate immune driver of Con-A hepatitis and, more broadly, suggests a potential role for Mincle in diseases governed by sterile inflammation. PMID:27559045

Mincle Signaling Promotes Con A Hepatitis.

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Greco, Stephanie H; Torres-Hernandez, Alejandro; Kalabin, Aleksandr; Whiteman, Clint; Rokosh, Rae; Ravirala, Sushma; Ochi, Atsuo; Gutierrez, Johana; Salyana, Muhammad Atif; Mani, Vishnu R; Nagaraj, Savitha V; Deutsch, Michael; Seifert, Lena; Daley, Donnele; Barilla, Rocky; Hundeyin, Mautin; Nikifrov, Yuriy; Tejada, Karla; Gelb, Bruce E; Katz, Steven C; Miller, George

2016-10-01

Con A hepatitis is regarded as a T cell-mediated model of acute liver injury. Mincle is a C-type lectin receptor that is critical in the immune response to mycobacteria and fungi but does not have a well-defined role in preclinical models of non-pathogen-mediated inflammation. Because Mincle can ligate the cell death ligand SAP130, we postulated that Mincle signaling drives intrahepatic inflammation and liver injury in Con A hepatitis. Acute liver injury was assessed in the murine Con A hepatitis model using C57BL/6, Mincle(-/-), and Dectin-1(-/-) mice. The role of C/EBPβ and hypoxia-inducible factor-1α (HIF-1α) signaling was assessed using selective inhibitors. We found that Mincle was highly expressed in hepatic innate inflammatory cells and endothelial cells in both mice and humans. Furthermore, sterile Mincle ligands and Mincle signaling intermediates were increased in the murine liver in Con A hepatitis. Most significantly, Mincle deletion or blockade protected against Con A hepatitis, whereas Mincle ligation exacerbated disease. Bone marrow chimeric and adoptive transfer experiments suggested that Mincle signaling in infiltrating myeloid cells dictates disease phenotype. Conversely, signaling via other C-type lectin receptors did not alter disease course. Mechanistically, we found that Mincle blockade decreased the NF-κβ-related signaling intermediates C/EBPβ and HIF-1α, both of which are necessary in macrophage-mediated inflammatory responses. Accordingly, Mincle deletion lowered production of nitrites in Con A hepatitis and inhibition of both C/EBPβ and HIF-1α reduced the severity of liver disease. Our work implicates a novel innate immune driver of Con A hepatitis and, more broadly, suggests a potential role for Mincle in diseases governed by sterile inflammation. Copyright © 2016 by The American Association of Immunologists, Inc.

Biochanin A improves hepatic steatosis and insulin resistance by regulating the hepatic lipid and glucose metabolic pathways in diet-induced obese mice.

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Park, Hee-Sook; Hur, Haeng Jeon; Kim, Soon-Hee; Park, Su-Jin; Hong, Moon Ju; Sung, Mi Jeong; Kwon, Dae Young; Kim, Myung-Sunny

2016-09-01

Natural compounds that regulate peroxisome proliferator-activated receptor alpha (PPARα) have been reported to have beneficial effects in obesity-mediated metabolic disorders. In this study, we demonstrated that biochanin A (BA), an agonist of PPAR-α, improved hepatic steatosis and insulin resistance by regulating hepatic lipid and glucose metabolism. C57BL/6 mice were fed a normal chow diet, a high-fat diet (HFD), and an HFD supplemented with 0.05% BA for 12 weeks. Histological and biochemical examinations indicated that BA prevented obesity-induced hepatic steatosis and insulin resistance in HFD-fed mice. BA stimulated the transcriptional activation of PPAR-α in vitro and increased the expression of PPAR-α and its regulatory proteins in the liver. CE-TOF/MS analyses indicated that BA administration promoted the recovery of metabolites involved in phosphatidylcholine synthesis, lipogenesis, and beta-oxidation in the livers of obese mice. BA also suppressed the levels of gluconeogenesis-related metabolites and the expression of the associated enzymes, glucose 6-phosphatase and pyruvate kinase. Taken together, these results showed that BA ameliorated metabolic disorders such as hepatic steatosis and insulin resistance by modulating lipid and glucose metabolism in diet-induced obesity. Thus, BA may be a potential therapeutic agent for the prevention of obesity-mediated hepatic steatosis and insulin resistance. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

NUCKS Is a Positive Transcriptional Regulator of Insulin Signaling

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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.

Control of Hepatic Glucose Metabolism by Islet and Brain

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Rojas, Jennifer M.; Schwartz, Michael W.

2014-01-01

Dysregulation of hepatic glucose uptake (HGU) and inability of insulin to suppress hepatic glucose production (HGP), both contribute to hyperglycemia in patients with type 2 diabetes (T2D). Growing evidence suggests that insulin can inhibit HGP not only through a direct effect on the liver, but also via a mechanism involving the brain. Yet the notion that insulin action in the brain plays a physiological role in the control of HGP continues to be controversial. Although studies in dogs suggest that the direct hepatic effect of insulin is sufficient to explain day-to-day control of HGP, a surprising outcome has been revealed by recent studies in mice investigating whether the direct hepatic action of insulin is necessary for normal HGP: when hepatic insulin signaling pathway was genetically disrupted, HGP was maintained normally even in the absence of direct input from insulin. Here we present evidence that points to a potentially important role of the brain in the physiological control of both HGU and HGP in response to input from insulin as well as other hormones and nutrients. PMID:25200294

The triglyceride content in skeletal muscle is associated with hepatic but not peripheral insulin resistance in elderly twins

DEFF Research Database (Denmark)

Grunnet, L G; Laurila, Esa; Hansson, Ola

2012-01-01

Total muscle triglyceride (MT) content has been associated with insulin resistance. We investigated the predictors and impact of MT on relevant metabolic parameters including peripheral and hepatic insulin resistance in elderly twins.......Total muscle triglyceride (MT) content has been associated with insulin resistance. We investigated the predictors and impact of MT on relevant metabolic parameters including peripheral and hepatic insulin resistance in elderly twins....

Insulin Action in Brain Regulates Systemic Metabolism and Brain Function

OpenAIRE

Kleinridders, Andr?; Ferris, Heather A.; Cai, Weikang; Kahn, C. Ronald

2014-01-01

Insulin receptors, as well as IGF-1 receptors and their postreceptor signaling partners, are distributed throughout the brain. Insulin acts on these receptors to modulate peripheral metabolism, including regulation of appetite, reproductive function, body temperature, white fat mass, hepatic glucose output, and response to hypoglycemia. Insulin signaling also modulates neurotransmitter channel activity, brain cholesterol synthesis, and mitochondrial function. Disruption of insulin action in t...

Epigenetic programming at the Mogat1 locus may link neonatal overnutrition with long-term hepatic steatosis and insulin resistance.

Science.gov (United States)

Ramon-Krauel, Marta; Pentinat, Thais; Bloks, Vincent W; Cebrià, Judith; Ribo, Silvia; Pérez-Wienese, Ricky; Vilà, Maria; Palacios-Marin, Ivonne; Fernández-Pérez, Antonio; Vallejo, Mario; Téllez, Noèlia; Rodríguez, Miguel Àngel; Yanes, Oscar; Lerin, Carles; Díaz, Rubén; Plosch, Torsten; Tietge, Uwe J F; Jimenez-Chillaron, Josep C

2018-05-29

Postnatal overfeeding increases the risk of chronic diseases later in life, including obesity, insulin resistance, hepatic steatosis, and type 2 diabetes. Epigenetic mechanisms might underlie the long-lasting effects associated with early nutrition. Here we aimed to explore the molecular pathways involved in early development of insulin resistance and hepatic steatosis, and we examined the potential contribution of DNA methylation and histone modifications to long-term programming of metabolic disease. We used a well-characterized mouse model of neonatal overfeeding and early adiposity by litter size reduction. Neonatal overfeeding led to hepatic insulin resistance very early in life that persisted throughout adulthood despite normalizing food intake. Up-regulation of monoacylglycerol O-acyltransferase ( Mogat) 1 conceivably mediates hepatic steatosis and insulin resistance through increasing intracellular diacylglycerol content. Early and sustained deregulation of Mogat1 was associated with a combination of histone modifications that might favor Mogat1 expression. In sum, postnatal overfeeding causes extremely rapid derangements of hepatic insulin sensitivity that remain relatively stable until adulthood. Epigenetic mechanisms, particularly histone modifications, could contribute to such long-lasting effects. Our data suggest that targeting hepatic monoacylglycerol acyltransferase activity during early life might provide a novel strategy to improve hepatic insulin sensitivity and prevent late-onset insulin resistance and fatty liver disease.-Ramon-Krauel, M., Pentinat, T., Bloks, V. W., Cebrià, J., Ribo, S., Pérez-Wienese, R., Vilà, M., Palacios-Marin, I., Fernández-Pérez, A., Vallejo, M., Téllez, N., Rodríguez, M. À., Yanes, O., Lerin, C., Díaz, R., Plosch, T., Tietge, U. J. F., Jimenez-Chillaron, J. C. Epigenetic programming at the Mogat1 locus may link neonatal overnutrition with long-term hepatic steatosis and insulin resistance.

Insulin suppresses the AMPK signaling pathway to regulate lipid metabolism in primary cultured hepatocytes of dairy cows.

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Li, Xinwei; Li, Yu; Ding, Hongyan; Dong, Jihong; Zhang, Renhe; Huang, Dan; Lei, Lin; Wang, Zhe; Liu, Guowen; Li, Xiaobing

2018-05-01

Dairy cows with type II ketosis display hepatic fat accumulation and hyperinsulinemia, but the underlying mechanism is not completely clear. This study aimed to clarify the regulation of lipid metabolism by insulin in cow hepatocytes. In vitro, cow hepatocytes were treated with 0, 1, 10, or 100 nm insulin in the presence or absence of AICAR (an AMP-activated protein kinase alpha (AMPKα) activator). The results showed that insulin decreased AMPKα phosphorylation. This inactivation of AMPKα increased the gene and protein expression levels of carbohydrate responsive element-binding protein (ChREBP) and sterol regulatory element-binding protein-1c (SREBP-1c), which downregulated the expression of lipogenic genes, thereby decreasing lipid biosynthesis. Furthermore, AMPKα inactivation decreased the gene and protein expression levels of peroxisome proliferator-activated receptor-α (PPARα), which upregulated the expression of lipid oxidation genes, thereby increasing lipid oxidation. In addition, insulin decreased the very low density lipoprotein (VLDL) assembly. Consequently, triglyceride content was significantly increased in insulin treated hepatocytes. Activation of AMPKα induced by AICAR could reverse the effect of insulin on PPARα, SREBP-1c, and ChREBP, thereby decreasing triglyceride content. These results indicate that insulin inhibits the AMPKα signaling pathway to increase lipid synthesis and decrease lipid oxidation and VLDL assembly in cow hepatocytes, thereby inducing TG accumulation. This mechanism could partly explain the causal relationship between hepatic fat accumulation and hyperinsulinemia in dairy cows with type II ketosis.

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.

Regulation of insect behavior via the insulin-signaling pathway

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Renske eErion

2013-12-01

Full Text Available The insulin/insulin-like growth factor signaling (IIS pathway is well established as a critical regulator of growth and metabolic homeostasis across the animal kingdom. Insulin-like peptides (ILPs, the functional analogs of mammalian insulin, were initially discovered in the silkmoth Bombyx mori and subsequently identified in many other insect species. Initial research focused on the role of insulin signaling in metabolism, cell proliferation, development, reproduction and aging. More recently however, increasing attention has been given to the role of insulin in the regulation of neuronal function and behavior. Here we review the role of insulin signaling in two specific insect behaviors: feeding and locomotion.

Sexual dimorphism in hepatic, adipose tissue and peripheral tissue insulin sensitivity in obese humans

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Kasper W. ter Horst

2015-11-01

Full Text Available Glucose and lipid metabolism differ between men and women, and women tend to have better whole-body or muscle insulin sensitivity. This may be explained, in part, by differences in sex hormones and adipose tissue distribution. Few studies have investigated gender differences in hepatic, adipose tissue and whole-body insulin sensitivity between severely obese men and women. In this study, we aimed to determine the differences in glucose metabolism between severely obese men and women using tissue-specific measurements of insulin sensitivity. Insulin sensitivity was compared between age and body mass index (BMI-matched obese men and women by a two-step euglycemic hyperinsulinemic clamp with infusion of [6,6-2H2]glucose. Basal endogenous glucose production and insulin sensitivity of the liver, adipose tissue and peripheral tissues were assessed. Liver fat content was assessed by proton magnetic resonance spectroscopy in a subset of included subjects. We included 46 obese men and women (age, 48±2 vs 46±2 years, p=0.591; BMI, 41±1 vs 41±1 kg/m2, p=0.832. There was no difference in basal endogenous glucose production (14.4±1.0 vs 15.3±0.5 µmol•kg fat-free mass-1•min-1, p=0.410, adipose tissue insulin sensitivity (insulin-mediated suppression of free fatty acids, 71.6±3.6 vs 76.1±2.6%, p=0.314 or peripheral insulin sensitivity (insulin-stimulated rate of disappearance of glucose, 26.2±2.1 vs 22.7±1.7 µmol•kg-1•min-1, p=0.211. Obese men were characterized by lower hepatic insulin sensitivity (insulin-mediated suppression of endogenous glucose production, 61.7±4.1 vs 72.8±2.5% in men vs women, resp., p=0.028. Finally, these observations could not be explained by differences in liver fat content (men vs women, 16.5±3.1 vs 16.0±2.5%, p=0.913, n=27.We conclude that obese men have lower hepatic, but comparable adipose tissue and peripheral tissue, insulin sensitivity compared to similarly obese women. Hepatic insulin resistance may

Intermittent fasting reduces body fat but exacerbates hepatic insulin resistance in young rats regardless of high protein and fat diets.

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Park, Sunmin; Yoo, Kyung Min; Hyun, Joo Suk; Kang, Suna

2017-02-01

Intermittent fasting (IMF) is a relatively new dietary approach to weight management, although the efficacy and adverse effects have not been full elucidated and the optimal diets for IMF are unknown. We tested the hypothesis that a one-meal-per-day intermittent fasting with high fat (HF) or protein (HP) diets can modify energy, lipid, and glucose metabolism in normal young male Sprague-Dawley rats with diet-induced obesity or overweight. Male rats aged 5 weeks received either HF (40% fat) or HP (26% protein) diets ad libitum (AL) or for 3 h at the beginning of the dark cycle (IMF) for 5 weeks. Epidydimal fat pads and fat deposits in the leg and abdomen were lower with HP and IMF. Energy expenditure at the beginning of the dark cycle, especially from fat oxidation, was higher with IMF than AL, possibly due to greater activity levels. Brown fat content was higher with IMF. Serum ghrelin levels were higher in HP-IMF than other groups, and accordingly, cumulative food intake was also higher in HP-IMF than HF-IMF. HF-IMF exhibited higher area under the curve (AUC) of serum glucose at the first part (0-40 min) during oral glucose tolerance test, whereas AUC of serum insulin levels in both parts were higher in IMF and HF. During intraperitoneal insulin tolerance test, serum glucose levels were higher with IMF than AL. Consistently, hepatic insulin signaling (GLUT2, pAkt) was attenuated and PEPCK expression was higher with IMF and HF than other groups, and HOMA-IR revealed significantly impaired attenuated insulin sensitivity in the IMF groups. However, surprisingly, hepatic and skeletal muscle glycogen storage was higher in IMF groups than AL. The higher glycogen storage in the IMF groups was associated with the lower expression of glycogen phosphorylase than the AL groups. In conclusion, IMF especially with HF increased insulin resistance, possibly by attenuating hepatic insulin signaling, and lowered glycogen phosphorylase expression despite decreased fat mass in young

SOCS2 deletion protects against hepatic steatosis but worsens insulin resistance in high-fat-diet-fed mice

DEFF Research Database (Denmark)

Zadjali, Fahad; Santana-Farre, Ruyman; Vesterlund, Mattias

2012-01-01

in the development of diet-induced hepatic steatosis and insulin resistance. SOCS2-knockout (SOCS2(-/-)) mice and wild-type littermates were fed for 4 mo with control or high-fat diet, followed by assessment of insulin sensitivity, hepatic lipid content, and expression of inflammatory cytokines. SOCS2(-/-) mice...

White Pitaya (Hylocereus undatus) Juice Attenuates Insulin Resistance and Hepatic Steatosis in Diet-Induced Obese Mice.

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Song, Haizhao; Zheng, Zihuan; Wu, Jianan; Lai, Jia; Chu, Qiang; Zheng, Xiaodong

2016-01-01

Insulin resistance and hepatic steatosis are the most common complications of obesity. Pitaya is an important source of phytochemicals such as polyphenols, flavonoid and vitamin C which are related to its antioxidant activity. The present study was conducted to evaluate the influence of white pitaya juice (WPJ) on obesity-related metabolic disorders (e.g. insulin resistance and hepatic steatosis) in high-fat diet-fed mice. Forty-eight male C57BL/6J mice were assigned into four groups and fed low-fat diet with free access to water or WPJ, or fed high-fat diet with free access to water or WPJ for 14 weeks. Our results showed that administration of WPJ improved high-fat diet-induced insulin resistance, hepatic steatosis and adipose hypertrophy, but it exerted no influence on body weight gain in mice. Hepatic gene expression analysis indicated that WPJ supplement not only changed the expression profile of genes involved in lipid and cholesterol metabolism (Srebp1, HMGCoR, Cpt1b, HL, Insig1 and Insig2) but also significantly increased the expression levels of FGF21-related genes (Klb, FGFR2, Egr1 and cFos). In conclusion, WPJ protected from diet-induced hepatic steatosis and insulin resistance, which was associated with the improved FGF21 resistance and lipid metabolism.

Free fatty acid-induced hepatic insulin resistance is attenuated following lifestyle intervention in obese individuals with impaired glucose tolerance.

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Haus, Jacob M; Solomon, Thomas P J; Marchetti, Christine M; Edmison, John M; González, Frank; Kirwan, John P

2010-01-01

The objective of the study was to examine the effects of an exercise/diet lifestyle intervention on free fatty acid (FFA)-induced hepatic insulin resistance in obese humans. Obese men and women (n = 23) with impaired glucose tolerance were randomly assigned to either exercise training with a eucaloric (EU; approximately 1800 kcal; n = 11) or hypocaloric (HYPO; approximately 1300 kcal; n = 12) diet for 12 wk. Hepatic glucose production (HGP; milligrams per kilogram fat-free mass(-1) per minute(-1)) and hepatic insulin resistance were determined using a two-stage sequential hyperinsulinemic (40 mU/m(2) . min(-1)) euglycemic (5.0 mm) clamp with [3-(3)H]glucose. Measures were obtained at basal, during insulin infusion (INS; 120 min), and insulin plus intralipid/heparin infusion (INS/FFA; 300 min). At baseline, basal HGP was similar between groups; hyperinsulinemia alone did not completely suppress HGP, whereas INS/FFA exhibited less suppression than INS (EU, 4.6 +/- 0.8, 2.0 +/- 0.5, and 2.6 +/- 0.4; HYPO, 3.8 +/- 0.5, 1.2 +/- 0.3, and 2.3 +/- 0.4, respectively). After the intervention the HYPO group lost more body weight (P HYPO: -50 +/- 20%, before vs. after, P = 0.02). In contrast, the ability of insulin to overcome FFA-induced hepatic insulin resistance and HGP was improved only in the HYPO group (EU: -15 +/- 24% vs. HYPO: -58 +/- 19%, P = 0.02). Both lifestyle interventions are effective in reducing hepatic insulin resistance under basal and hyperinsulinemic conditions. However, the reversal of FFA-induced hepatic insulin resistance is best achieved with a combined exercise/caloric-restriction intervention.

Ebselen pretreatment attenuates ischemia/reperfusion injury and prevents hyperglycemia by improving hepatic insulin signaling and β-cell survival in gerbils.

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Park, S; Kang, S; Kim, D S; Shin, B K; Moon, N R; Daily, J W

2014-08-01

Transient carotid artery occlusion causes ischemia/reperfusion (I/R) injury resulting in neuron and pancreatic β-cell death with consequential post-stroke hyperglycemia, which can lead to diabetes and may accelerate the development of Alzheimer's disease. Antioxidants have been shown to protect against the I/R injury and destruction of neurons. However, it is unknown whether the protection against I/R injury extends to the pancreatic β-cells. Therefore, we investigated whether treatment with ebselen, a glutathione peroxidase mimic, prevents neuronal and β-cell death following I/R in gerbils susceptible to stroke. After 28 days post artery occlusion, there was widespread neuronal cell death in the CA1 of the hippocampus and elevated IL-1β and TNF-α levels. Pretreatment with ebselen prevented the death by 56% and attenuated neurological damage (abnormal eyelid drooping, hair bristling, muscle tone, flexor reflex, posture, and walking patterns). Ischemic gerbils also exhibited impaired glucose tolerance and insulin sensitivity which induced post-stroke hyperglycemia associated with decreased β-cell mass due to increased β-cell apoptosis. Ebselen prevented the increased β-cell apoptosis, possibly by decreasing IL-1β and TNF-α in islets. Ischemia also attenuated hepatic insulin signaling, and expression of GLUT2 and glucokinase, whereas ebselen prevented the attenuation and suppressed gluconeogenesis by decreasing PEPCK expression. In conclusion, antioxidant protection by ebselen attenuated I/R injury of neurons and pancreatic β-cells and prevented subsequent impairment of glucose regulation that could lead to diabetes and Alzheimer's disease.

Targeted deletion of C1q/TNF-related protein 9 increases food intake, decreases insulin sensitivity, and promotes hepatic steatosis in mice.

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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.

Chronic hepatitis c genotype-4 infection: role of insulin resistance in hepatocellular carcinoma

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M Hashem Abdel

2011-11-01

Full Text Available Abstract Background Hepatitis C virus (HCV is a major cause of chronic hepatitis and hepatocellular carcinoma (HCC and different HCV genotypes show characteristic variations in their pathological properties. Insulin resistance (IR occurs early in HCV infection and may synergize with viral hepatitis in HCC development. Egypt has the highest reported rates of HCV infection (predominantly genotype 4 in the world; this study investigated effects of HCV genotype-4 (HCV-4 on prevalence of insulin resistance in chronic hepatitis C (CHC and HCC in Egyptian patients. Methods Fifty CHC patients, 50 HCC patients and 20 normal subjects were studied. IR was estimated using HOMA-IR index and HCV-4 load determined using real-time polymerase chain reaction. Hepatitis B virus was excluded by enzyme-linked immunosorbent assay. Standard laboratory and histopathological investigations were undertaken to characterize liver function and for grading and staging of CHC; HCC staging was undertaken using intraoperative samples. Results HCC patients showed higher IR frequency but without significant difference from CHC (52% vs 40%, p = 0.23. Multivariate logistic regression analysis showed HOMA-IR index and International Normalization Ratio independently associated with fibrosis in CHC; in HCC, HbA1c, cholesterol and bilirubin were independently associated with fibrosis. Fasting insulin and cholesterol levels were independently associated with obesity in both CHC and HCC groups. Moderate and high viral load was associated with high HOMA-IR in CHC and HCC (p Conclusions IR is induced by HCV-4 irrespective of severity of liver disease. IR starts early in infection and facilitates progression of hepatic fibrosis and HCC development.

Insulin signaling disruption in male mice due to perinatal bisphenol A exposure: Role of insulin signaling in the brain.

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Fang, Fangfang; Gao, Yue; Wang, Tingwei; Chen, Donglong; Liu, Jingli; Qian, Wenyi; Cheng, Jie; Gao, Rong; Wang, Jun; Xiao, Hang

2016-03-14

Bisphenol A (BPA), an environmental estrogenic endocrine disruptor, is widely used for producing polycarbonate plastics and epoxy resins. Available data have shown that perinatal exposure to BPA contributes to peripheral insulin resistance, while in the present study, we aimed to investigate the effects of perinatal BPA exposure on insulin signaling and glucose transport in the cortex of offspring mice. The pregnant mice were administrated either vehicle or BPA (100 μg/kg/day) at three perinatal stages. Stage I: from day 6 of gestation until parturition (P6-PND0 fetus exposure); Stage II: from lactation until delactation (PND0-PND21 newborn exposure) and Stage III: from day 6 of pregnancy until delactation (P6-PND21 fetus and newborn exposure). At 8 months of age for the offspring mice, the insulin signaling pathways and glucose transporters (GLUTs) were detected. Our data indicated that the insulin signaling including insulin, phosphorylated insulin receptor (IR), phosphorylated protein kinase B (p-AKT), phosphorylated glycogen synthase kinase 3β (p-GSK3β) and phosphorylated extracellular signal regulated protein kinase (p-ERK) were significantly decreased in the brain. In parallel, GLUTs (GLUT1/3/4) were obviously decreased as well in BPA-treated group in mice brain. Noteworthily, the phosphorylated tau (p-tau) and amyloid precursor protein (APP) were markedly up-regulated in all BPA-treated groups. These results, taken together, suggest the adverse effects of BPA on insulin signaling and GLUTs, which might subsequently contribute to the increment of p-tau and APP in the brain of adult offspring. Therefore, perinatal BPA exposure might be a risk factor for the long-term neurodegenerative changes in offspring male mice. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

White Pitaya (Hylocereus undatus Juice Attenuates Insulin Resistance and Hepatic Steatosis in Diet-Induced Obese Mice.

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Haizhao Song

Full Text Available Insulin resistance and hepatic steatosis are the most common complications of obesity. Pitaya is an important source of phytochemicals such as polyphenols, flavonoid and vitamin C which are related to its antioxidant activity. The present study was conducted to evaluate the influence of white pitaya juice (WPJ on obesity-related metabolic disorders (e.g. insulin resistance and hepatic steatosis in high-fat diet-fed mice. Forty-eight male C57BL/6J mice were assigned into four groups and fed low-fat diet with free access to water or WPJ, or fed high-fat diet with free access to water or WPJ for 14 weeks. Our results showed that administration of WPJ improved high-fat diet-induced insulin resistance, hepatic steatosis and adipose hypertrophy, but it exerted no influence on body weight gain in mice. Hepatic gene expression analysis indicated that WPJ supplement not only changed the expression profile of genes involved in lipid and cholesterol metabolism (Srebp1, HMGCoR, Cpt1b, HL, Insig1 and Insig2 but also significantly increased the expression levels of FGF21-related genes (Klb, FGFR2, Egr1 and cFos. In conclusion, WPJ protected from diet-induced hepatic steatosis and insulin resistance, which was associated with the improved FGF21 resistance and lipid metabolism.

Skeletal muscle and hepatic insulin signaling is maintained in heat-stressed lactating Holstein cows.

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Xie, G; Cole, L C; Zhao, L D; Skrzypek, M V; Sanders, S R; Rhoads, M L; Baumgard, L H; Rhoads, R P

2016-05-01

period, but the phosphorylation ratio (abundance of phosphorylated protein:abundance of total protein) of AKT was decreased in P2 for TNPF animals, but not during WFHS. These results indicate that mild systemic insulin resistance during HS may be related to reduced nutrient intake but skeletal muscle and liver insulin signaling remains unchanged. Copyright © 2016 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

E4orf1 Enhances Glucose Uptake Independent of Proximal Insulin Signaling.

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Na, Ha-Na; Hegde, Vijay; Dubuisson, Olga; Dhurandhar, Nikhil V

2016-01-01

Impaired proximal insulin signaling is often present in diabetes. Hence, approaches to enhance glucose disposal independent of proximal insulin signaling are desirable. Evidence indicates that Adenovirus-derived E4orf1 protein may offer such an approach. This study determined if E4orf1 improves insulin sensitivity and downregulates proximal insulin signaling in vivo and enhances cellular glucose uptake independent of proximal insulin signaling in vitro. High fat fed mice were injected with a retrovirus plasmid expressing E4orf1, or a null vector. E4orf1 significantly improved insulin sensitivity in response to a glucose load. Yet, their proximal insulin signaling in fat depots was impaired, as indicated by reduced tyrosine phosphorylation of insulin receptor (IR), and significantly increased abundance of ectonucleotide pyrophosphatase/phosphodiesterase-1 (ENPP1). In 3T3-L1 pre-adipocytes E4orf1 expression impaired proximal insulin signaling. Whereas, treatment with rosiglitazone reduced ENPP1 abundance. Unaffected by IR-KD (insulin receptor knockdown) with siRNA, E4orf1 significantly up-regulated distal insulin signaling pathway and enhanced cellular glucose uptake. In vivo, E4orf1 impairs proximal insulin signaling in fat depots yet improves glycemic control. This is probably explained by the ability of E4orf1 to promote cellular glucose uptake independent of proximal insulin signaling. E4orf1 may provide a therapeutic template to enhance glucose disposal in the presence of impaired proximal insulin signaling.

E4orf1 Enhances Glucose Uptake Independent of Proximal Insulin Signaling.

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Ha-Na Na

Full Text Available Impaired proximal insulin signaling is often present in diabetes. Hence, approaches to enhance glucose disposal independent of proximal insulin signaling are desirable. Evidence indicates that Adenovirus-derived E4orf1 protein may offer such an approach. This study determined if E4orf1 improves insulin sensitivity and downregulates proximal insulin signaling in vivo and enhances cellular glucose uptake independent of proximal insulin signaling in vitro. High fat fed mice were injected with a retrovirus plasmid expressing E4orf1, or a null vector. E4orf1 significantly improved insulin sensitivity in response to a glucose load. Yet, their proximal insulin signaling in fat depots was impaired, as indicated by reduced tyrosine phosphorylation of insulin receptor (IR, and significantly increased abundance of ectonucleotide pyrophosphatase/phosphodiesterase-1 (ENPP1. In 3T3-L1 pre-adipocytes E4orf1 expression impaired proximal insulin signaling. Whereas, treatment with rosiglitazone reduced ENPP1 abundance. Unaffected by IR-KD (insulin receptor knockdown with siRNA, E4orf1 significantly up-regulated distal insulin signaling pathway and enhanced cellular glucose uptake. In vivo, E4orf1 impairs proximal insulin signaling in fat depots yet improves glycemic control. This is probably explained by the ability of E4orf1 to promote cellular glucose uptake independent of proximal insulin signaling. E4orf1 may provide a therapeutic template to enhance glucose disposal in the presence of impaired proximal insulin signaling.

Superior Glycemic Control with a Glucose-Responsive Insulin Analog: Hepatic and Nonhepatic Impacts.

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Moore, Mary Courtney; Kelley, David E; Camacho, Raul C; Zafian, Peter; Ye, Tian; Lin, Songnian; Kaarsholm, Niels C; Nargund, Ravi; Kelly, Terri M; Van Heek, Margaret; Previs, Stephen F; Moyes, Christopher; Smith, Marta S; Farmer, Ben; Williams, Phil; Cherrington, Alan D

2018-03-14

We evaluated the hepatic and nonhepatic responses to glucose-responsive insulin (GRI). Eight dogs received GRI or regular human insulin (HI) in random order. A primed, continuous intravenous infusion of [3- 3 H]glucose began at -120 min. Basal sampling (-30 to 0 min) was followed by 2 study periods (150 min each), P1 and P2. At 0 min, somatostatin and GRI (36±3 pmol/kg/min) or HI (1.8 pmol/kg/min) were infused IV; basal glucagon was replaced intraportally. Glucose was infused intravenously to clamp plasma glucose at 80 mg/dL (P1) and 240 mg/dL (P2). Whole body insulin clearance (WBIC) and insulin concentrations were not different in P1 vs P2 with HI, but WBIC was 23% higher and arterial insulin 16% lower in P1 vs P2 with GRI. Net hepatic glucose output was similar between treatments in P1. In P2, both treatments induced net hepatic glucose uptake (2.1±0.5 [HI] vs 3.3±0.4 [GRI] mg/kg/min). Nonhepatic glucose uptake (nonHGU, mg/kg/min) in P1 and P2, respectively, differed between treatments (2.6±0.3 and 7.4±0.6 with HI; 2.0±0.2 and 8.1±0.8 with GRI). Thus, glycemia impacted GRI but not HI clearance, with resultant differential effects on HGU and nonHGU. GRI holds promise for decreasing hypoglycemia risk while enhancing glucose uptake under hyperglycemic conditions. © 2018 by the American Diabetes Association.

Protein source in a high-protein diet modulates reductions in insulin resistance and hepatic steatosis in fa/fa Zucker rats.

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Wojcik, Jennifer L; Devassy, Jessay G; Wu, Yinghong; Zahradka, Peter; Taylor, Carla G; Aukema, Harold M

2016-01-01

High-protein diets are being promoted to reduce insulin resistance and hepatic steatosis in metabolic syndrome. Therefore, the effect of protein source in high-protein diets on reducing insulin resistance and hepatic steatosis was examined. Fa/fa Zucker rats were provided normal-protein (15% of energy) casein, high-protein (35% of energy) casein, high-protein soy, or high-protein mixed diets with animal and plant proteins. The high-protein mixed diet reduced area under the curve for insulin during glucose tolerance testing, fasting serum insulin and free fatty acid concentrations, homeostatic model assessment index, insulin to glucose ratio, and pancreatic islet cell area. The high-protein mixed and the high-protein soy diets reduced hepatic lipid concentrations, liver to body weight ratio, and hepatic steatosis rating. These improvements were observed despite no differences in body weight, feed intake, or adiposity among high-protein diet groups. The high-protein casein diet had minimal benefits. A high-protein mixed diet was the most effective for modulating reductions in insulin resistance and hepatic steatosis independent of weight loss, indicating that the source of protein within a high-protein diet is critical for the management of these metabolic syndrome parameters. © 2015 The Obesity Society.

Isothiocyanate-rich Moringa oleifera extract reduces weight gain, insulin resistance, and hepatic gluconeogenesis in mice.

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Waterman, Carrie; Rojas-Silva, Patricio; Tumer, Tugba Boyunegmez; Kuhn, Peter; Richard, Allison J; Wicks, Shawna; Stephens, Jacqueline M; Wang, Zhong; Mynatt, Randy; Cefalu, William; Raskin, Ilya

2015-06-01

Moringa oleifera (moringa) is tropical plant traditionally used as an antidiabetic food. It produces structurally unique and chemically stable moringa isothiocyanates (MICs) that were evaluated for their therapeutic use in vivo. C57BL/6L mice fed very high fat diet (VHFD) supplemented with 5% moringa concentrate (MC, delivering 66 mg/kg/d of MICs) accumulated fat mass, had improved glucose tolerance and insulin signaling, and did not develop fatty liver disease compared to VHFD-fed mice. MC-fed group also had reduced plasma insulin, leptin, resistin, cholesterol, IL-1β, TNFα, and lower hepatic glucose-6-phosphatase (G6P) expression. In hepatoma cells, MC and MICs at low micromolar concentrations inhibited gluconeogenesis and G6P expression. MICs and MC effects on lipolysis in vitro and on thermogenic and lipolytic genes in adipose tissue in vivo argued these are not likely primary targets for the anti-obesity and anti-diabetic effects observed. Data suggest that MICs are the main anti-obesity and anti-diabetic bioactives of MC, and that they exert their effects by inhibiting rate-limiting steps in liver gluconeogenesis resulting in direct or indirect increase in insulin signaling and sensitivity. These conclusions suggest that MC may be an effective dietary food for the prevention and treatment of obesity and type 2 diabetes. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Influence of Unweighting on Insulin Signal Transduction in Muscle

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Tischler, Marc E.

2002-01-01

Unweighting of the juvenile soleus muscle is characterized by an increased binding capacity for insulin relative to muscle mass due to sparing of the receptors during atrophy. Although carbohydrate metabolism and protein degradation in the unweighted muscle develop increased sensitivity to insulin in vivo, protein synthesis in vivo and system A amino acid transport in vitro do not appear to develop such an enhanced response. The long-term goal is to identify the precise nature of this apparent resistance in the insulin signal transduction pathway and to consider how reduced weight-bearing may elicit this effect, by evaluating specific components of the insulin signalling pathway. Because the insulin-signalling pathway has components in common with the signal transduction pathway for insulin-like growth factor (IGF-1) and potentially other growth factors, the study could have important implications in the role of weight-bearing function on muscle growth and development. Since the insulin signalling pathway diverges following activation of insulin receptor tyrosine kinase, the immediate specific aims will be to study the receptor tyrosine kinase (IRTK) and those branches, which lead to phosphorylation of insulin receptor substrate-1 (IRS-1) and of Shc protein. To achieve these broader objectives, we will test in situ, by intramuscular injection, the responses of glucose transport, system A amino acid transport and protein synthesis to insulin analogues for which the receptor has either a weaker or much stronger binding affinity compared to insulin. Studies will include: (1) estimation of the ED(sub 50) for each analogue for these three processes; (2) the effect of duration (one to four days) of unweighting on the response of each process to all analogues tested; (3) the effect of unweighting and the analogues on IRTK activity; and (4) the comparative effects of unweighting and analogue binding on the tyrosine phosphorylation of IRTK, IRS-1, and Shc protein.

Impact of 9 days of bed rest on hepatic and peripheral insulin action, insulin secretion, and whole-body lipolysis in healthy young male offspring of patients with type 2 diabetes

DEFF Research Database (Denmark)

Alibegovic, Amra C; Højbjerre, Lise; Sonne, Mette P

2009-01-01

decrease in whole-body insulin sensitivity in both groups. Hepatic insulin resistance was elevated in FDR subjects prior to bed rest and was significantly augmented by bed rest in FDR (P ... deteriorates with 9 days of bed rest, converging toward similar degrees of whole-body insulin resistance. FDR subjects exhibit hepatic insulin resistance (HIR), which, in contrast to CON subjects, deteriorates in response to physical inactivity. FDR subjects exhibit reduced insulin secretion when seen...... subjects, with no significant differences between the groups. Insulin resistance induced by bed rest was fully accounted for by the impairment of nonoxidative glucose metabolism in both groups (overall P resistant FDR and healthy CON subjects...

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

OpenAIRE

Mackenzie, Richard WA; Elliott, Bradley T

2014-01-01

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 tr...

Rat Strain Differences in Susceptibility to Alcohol-Induced Chronic Liver Injury and Hepatic Insulin Resistance

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Sarah M. DeNucci

2010-01-01

Full Text Available The finding of more severe steatohepatitis in alcohol fed Long Evans (LE compared with Sprague Dawley (SD and Fisher 344 (FS rats prompted us to determine whether host factors related to alcohol metabolism, inflammation, and insulin/IGF signaling predict proneness to alcohol-mediated liver injury. Adult FS, SD, and LE rats were fed liquid diets containing 0% or 37% (calories ethanol for 8 weeks. Among controls, LE rats had significantly higher ALT and reduced GAPDH relative to SD and FS rats. Among ethanol-fed rats, despite similar blood alcohol levels, LE rats had more pronounced steatohepatitis and fibrosis, higher levels of ALT, DNA damage, pro-inflammatory cytokines, ADH, ALDH, catalase, GFAP, desmin, and collagen expression, and reduced insulin receptor binding relative to FS rats. Ethanol-exposed SD rats had intermediate degrees of steatohepatitis, increased ALT, ADH and profibrogenesis gene expression, and suppressed insulin receptor binding and GAPDH expression, while pro-inflammatory cytokines were similarly increased as in LE rats. Ethanol feeding in FS rats only reduced IL-6, ALDH1–3, CYP2E1, and GAPDH expression in liver. In conclusion, susceptibility to chronic steatohepatitis may be driven by factors related to efficiency of ethanol metabolism and degree to which ethanol exposure causes hepatic insulin resistance and cytokine activation.

Hepatitis C virus nonstructural protein 5A favors upregulation of gluconeogenic and lipogenic gene expression leading towards insulin resistance: a metabolic syndrome.

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Parvaiz, Fahed; Manzoor, Sobia; Iqbal, Jawed; McRae, Steven; Javed, Farrakh; Ahmed, Qazi Laeeque; Waris, Gulam

2014-05-01

Chronic hepatitis C is a lethal blood-borne infection often associated with a number of pathologies such as insulin resistance and other metabolic abnormalities. Insulin is a key hormone that regulates the expression of metabolic pathways and favors homeostasis. In this study, we demonstrated the molecular mechanism of hepatitis C virus (HCV) nonstructural protein 5A (NS5A)-induced metabolic dysregulation. We showed that transient expression of HCV NS5A in human hepatoma cells increased lipid droplet formation through enhanced lipogenesis. We also showed increased transcriptional expression of peroxisome proliferator-activated receptor gamma coactivator (PGC)-1α and diacylglycerol acyltransferase-1 (DGAT-1) in NS5A-expressing cells. On the other hand, there was significantly reduced transcriptional expression of microsomal triglyceride transfer protein (MTP) and peroxisome proliferator-activated receptor γ (PPARγ) in cells expressing HCV NS5A. Furthermore, increased gluconeogenic gene expression was observed in HCV-NS5A-expressing cells. In addition, it was also shown that HCV-NS5A-expressing hepatoma cells show serine phosphorylation of IRS-1, thereby hampering metabolic activity and contributing to insulin resistance. Therefore, this study reveals that HCV NS5A is involved in enhanced gluconeogenic and lipogenic gene expression, which triggers metabolic abnormality and impairs insulin signaling pathway.

Insulin action in brain regulates systemic metabolism and brain function.

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Kleinridders, André; Ferris, Heather A; Cai, Weikang; Kahn, C Ronald

2014-07-01

Insulin receptors, as well as IGF-1 receptors and their postreceptor signaling partners, are distributed throughout the brain. Insulin acts on these receptors to modulate peripheral metabolism, including regulation of appetite, reproductive function, body temperature, white fat mass, hepatic glucose output, and response to hypoglycemia. Insulin signaling also modulates neurotransmitter channel activity, brain cholesterol synthesis, and mitochondrial function. Disruption of insulin action in the brain leads to impairment of neuronal function and synaptogenesis. In addition, insulin signaling modulates phosphorylation of tau protein, an early component in the development of Alzheimer disease. Thus, alterations in insulin action in the brain can contribute to metabolic syndrome, and the development of mood disorders and neurodegenerative diseases. © 2014 by the American Diabetes Association.

Dietary Chromium Restriction of Pregnant Mice Changes the Methylation Status of Hepatic Genes Involved with Insulin Signaling in Adult Male Offspring.

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Zhang, Qian; Sun, Xiaofang; Xiao, Xinhua; Zheng, Jia; Li, Ming; Yu, Miao; Ping, Fan; Wang, Zhixin; Qi, Cuijuan; Wang, Tong; Wang, Xiaojing

2017-01-01

Maternal undernutrition is linked with an elevated risk of diabetes mellitus in offspring regardless of the postnatal dietary status. This is also found in maternal micro-nutrition deficiency, especial chromium which is a key glucose regulator. We investigated whether maternal chromium restriction contributes to the development of diabetes in offspring by affecting DNA methylation status in liver tissue. After being mated with control males, female weanling 8-week-old C57BL mice were fed a control diet (CON, 1.19 mg chromium/kg diet) or a low chromium diet (LC, 0.14 mg chromium/kg diet) during pregnancy and lactation. After weaning, some offspring were shifted to the other diet (CON-LC, or LC-CON), while others remained on the same diet (CON-CON, or LC-LC) for 29 weeks. Fasting blood glucose, serum insulin, and oral glucose tolerance test was performed to evaluate the glucose metabolism condition. Methylation differences in liver from the LC-CON group and CON-CON groups were studied by using a DNA methylation array. Bisulfite sequencing was carried out to validate the results of the methylation array. Maternal chromium limitation diet increased the body weight, blood glucose, and serum insulin levels. Even when switched to the control diet after weaning, the offspring also showed impaired glucose tolerance and insulin resistance. DNA methylation profiling of the offspring livers revealed 935 differentially methylated genes in livers of the maternal chromium restriction diet group. Pathway analysis identified the insulin signaling pathway was the main process affected by hypermethylated genes. Bisulfite sequencing confirmed that some genes in insulin signaling pathway were hypermethylated in livers of the LC-CON and LC-LC group. Accordingly, the expression of genes in insulin signaling pathway was downregulated. There findings suggest that maternal chromium restriction diet results in glucose intolerance in male offspring through alterations in DNA methylation which

Dietary Chromium Restriction of Pregnant Mice Changes the Methylation Status of Hepatic Genes Involved with Insulin Signaling in Adult Male Offspring.

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Qian Zhang

Full Text Available Maternal undernutrition is linked with an elevated risk of diabetes mellitus in offspring regardless of the postnatal dietary status. This is also found in maternal micro-nutrition deficiency, especial chromium which is a key glucose regulator. We investigated whether maternal chromium restriction contributes to the development of diabetes in offspring by affecting DNA methylation status in liver tissue. After being mated with control males, female weanling 8-week-old C57BL mice were fed a control diet (CON, 1.19 mg chromium/kg diet or a low chromium diet (LC, 0.14 mg chromium/kg diet during pregnancy and lactation. After weaning, some offspring were shifted to the other diet (CON-LC, or LC-CON, while others remained on the same diet (CON-CON, or LC-LC for 29 weeks. Fasting blood glucose, serum insulin, and oral glucose tolerance test was performed to evaluate the glucose metabolism condition. Methylation differences in liver from the LC-CON group and CON-CON groups were studied by using a DNA methylation array. Bisulfite sequencing was carried out to validate the results of the methylation array. Maternal chromium limitation diet increased the body weight, blood glucose, and serum insulin levels. Even when switched to the control diet after weaning, the offspring also showed impaired glucose tolerance and insulin resistance. DNA methylation profiling of the offspring livers revealed 935 differentially methylated genes in livers of the maternal chromium restriction diet group. Pathway analysis identified the insulin signaling pathway was the main process affected by hypermethylated genes. Bisulfite sequencing confirmed that some genes in insulin signaling pathway were hypermethylated in livers of the LC-CON and LC-LC group. Accordingly, the expression of genes in insulin signaling pathway was downregulated. There findings suggest that maternal chromium restriction diet results in glucose intolerance in male offspring through alterations in DNA

E4orf1 Enhances Glucose Uptake Independent of Proximal Insulin Signaling

OpenAIRE

Na, Ha-Na; Hegde, Vijay; Dubuisson, Olga; Dhurandhar, Nikhil V.

2016-01-01

Impaired proximal insulin signaling is often present in diabetes. Hence, approaches to enhance glucose disposal independent of proximal insulin signaling are desirable. Evidence indicates that Adenovirus-derived E4orf1 protein may offer such an approach. This study determined if E4orf1 improves insulin sensitivity and downregulates proximal insulin signaling in vivo and enhances cellular glucose uptake independent of proximal insulin signaling in vitro. High fat fed mice were injected with a ...

Acupuncture Alters Expression of Insulin Signaling Related Molecules and Improves Insulin Resistance in OLETF Rats

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Xin-Yu Huang

2016-01-01

Full Text Available To determine effect of acupuncture on insulin resistance in Otsuka Long-Evans Tokushima Fatty (OLETF rats and to evaluate expression of insulin signaling components. Rats were divided into three groups: Sprague-Dawley (SD rats, OLETF rats, and acupuncture+OLETF rats. Acupuncture was subcutaneously applied to Neiguan (PC6, Zusanli (ST36, and Sanyinjiao (SP6; in contrast, acupuncture to Shenshu (BL23 was administered perpendicularly. For Neiguan (PC6 and Zusanli (ST36, needles were connected to an electroacupuncture (EA apparatus. Fasting blood glucose (FPG was measured by glucose oxidase method. Plasma fasting insulin (FINS and serum C peptide (C-P were determined by ELISA. Protein and mRNA expressions of insulin signaling molecules were determined by Western blot and real-time RT-PCR, respectively. OLETF rats exhibit increased levels of FPG, FINS, C-P, and homeostasis model assessment-estimated insulin resistance (HOMA-IR, which were effectively decreased by acupuncture treatment. mRNA expressions of several insulin signaling related molecules IRS1, IRS2, Akt2, aPKCζ, and GLUT4 were decreased in OLETF rats compared to SD controls. Expression of these molecules was restored back to normal levels upon acupuncture administration. PI3K-p85α was increased in OLETF rats; this increase was also reversed by acupuncture treatment. Acupuncture improves insulin resistance in OLETF rats, possibly via regulating expression of key insulin signaling related molecules.

Hepatitis C virus induces a prediabetic state by directly impairing hepatic glucose metabolism in mice.

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Lerat, Hervé; Imache, Mohamed Rabah; Polyte, Jacqueline; Gaudin, Aurore; Mercey, Marion; Donati, Flora; Baudesson, Camille; Higgs, Martin R; Picard, Alexandre; Magnan, Christophe; Foufelle, Fabienne; Pawlotsky, Jean-Michel

2017-08-04

Virus-related type 2 diabetes is commonly observed in individuals infected with the hepatitis C virus (HCV); however, the underlying molecular mechanisms remain unknown. Our aim was to unravel these mechanisms using FL-N/35 transgenic mice expressing the full HCV ORF. We observed that these mice displayed glucose intolerance and insulin resistance. We also found that Glut-2 membrane expression was reduced in FL-N/35 mice and that hepatocyte glucose uptake was perturbed, partly accounting for the HCV-induced glucose intolerance in these mice. Early steps of the hepatic insulin signaling pathway, from IRS2 to PDK1 phosphorylation, were constitutively impaired in FL-N/35 primary hepatocytes via deregulation of TNFα/SOCS3. Higher hepatic glucose production was observed in the HCV mice, despite higher fasting insulinemia, concomitant with decreased expression of hepatic gluconeogenic genes. Akt kinase activity was higher in HCV mice than in WT mice, but Akt-dependent phosphorylation of the forkhead transcription factor FoxO1 at serine 256, which triggers its nuclear exclusion, was lower in HCV mouse livers. These findings indicate an uncoupling of the canonical Akt/FoxO1 pathway in HCV protein-expressing hepatocytes. Thus, the expression of HCV proteins in the liver is sufficient to induce insulin resistance by impairing insulin signaling and glucose uptake. In conclusion, we observed a complete set of events leading to a prediabetic state in HCV-transgenic mice, providing a valuable mechanistic explanation for HCV-induced diabetes in humans. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

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

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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.

Coordinated defects in hepatic long chain fatty acid metabolism and triglyceride accumulation contribute to insulin resistance in non-human primates.

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Subhash Kamath

Full Text Available Non-alcoholic fatty liver disease (NAFLD is characterized by accumulation of triglycerides (TG in hepatocytes, which may also trigger cirrhosis. The mechanisms of NAFLD are not fully understood, but insulin resistance has been proposed as a key determinant.To determine the TG content and long chain fatty acyl CoA composition profile in liver from obese non-diabetic insulin resistant (IR and lean insulin sensitive (IS baboons in relation with hepatic and peripheral insulin sensitivity.Twenty baboons with varying grades of adiposity were studied. Hepatic (liver and peripheral (mainly muscle insulin sensitivity was measured with a euglycemic clamp and QUICKI. Liver biopsies were performed at baseline for TG content and LCFA profile by mass spectrometry, and histological analysis. Findings were correlated with clinical and biochemical markers of adiposity and insulin resistance.Obese IR baboons had elevated liver TG content compared to IS. Furthermore, the concentration of unsaturated (LC-UFA was greater than saturated (LC-SFA fatty acyl CoA in the liver. Interestingly, LC-FA UFA and SFA correlated with waist, BMI, insulin, NEFA, TG, QUICKI, but not M/I. Histological findings of NAFLD ranging from focal to diffuse hepatic steatosis were found in obese IR baboons.Liver TG content is closely related with both hepatic and peripheral IR, whereas liver LC-UFA and LC-SFA are closely related only with hepatic IR in non-human primates. Mechanisms leading to the accumulation of TG, LC-UFA and an altered UFA: LC-SFA ratio may play an important role in the pathophysiology of fatty liver disease in humans.

Cross-talk between insulin and Wnt signaling in preadipocytes

DEFF Research Database (Denmark)

Palsgaard, Jane; Emanuelli, Brice; Winnay, Jonathon N

2012-01-01

and appears to be due to an inducible interaction between LRP5 and the insulin receptor as demonstrated by co-immunoprecipitation. These data demonstrate that Wnt and insulin signaling pathways exhibit cross-talk at multiple levels. Wnt induces phosphorylation of Akt, ERK1/2, and GSK3β, and this is dependent...... and LRP6 and with and without knock-out of insulin and IGF-1 receptors. We find that Wnt stimulation leads to phosphorylation of insulin signaling key mediators, including Akt, GSK3β, and ERK1/2, although with a lower fold stimulation and slower time course than observed for insulin. These Wnt effects...... are insulin/IGF-1 receptor-dependent and are lost in insulin/IGF-1 receptor double knock-out cells. Conversely, in LRP5 knockdown preadipocytes, insulin-induced phosphorylation of IRS1, Akt, GSK3β, and ERK1/2 is highly reduced. This effect is specific to insulin, as compared with IGF-1, stimulation...

Low Prevalence of Insulin Resistance among Iranian Patients with Chronic Hepatitis C Virus Infection: A Case-Control Study.

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Eshraghian, Kavous; Lankarani, Kamran B; Fattahi, Mohammad Reza; Esmailnejad, Atefeh; Peymani, Payam

2017-07-14

Association between chronic hepatitis C virus (CHC) infection and type 2 diabetes mellitus has been challenging in recent decades. Despite of extensive research in this area, there is no general agreement on the direct effect of HCV infection on insulin resistance. The study was performed in 52 CHC patients (mean age = 39.48) and 52 and sex‑matched healthy Iranian controls, referred to the Hepatitis Clinic, Department of Gastroenterohepatology, Shiraz University of medical sciences, Shiraz, Iran, from 2012 to 2015. Fasting blood glucose level, fasting insulin level and insulin resistance defined as a homeostasis model assessment of insulin resistance (HOMA-IR) index were determined and compared between two groups. Insulin resistance was present in 26.9% of CHC patients and 34.62% of healthy controls. Mean HOMA index was 1.93 in patients and 2.18 in controls. There were no statistically significant differences between patient and control groups with regard to fasting insulin level, fasting blood glucose, HOMA index and insulin resistance. HOMA index and fasting insulin level were significantly higher in IR CHC patients relative to IR controls. Fasting blood glucose was also significantly higher in controls younger than 40 years. Results obtained in this study showed that chronic hepatitis C cannot be considered as a risk factor for insulin resistance and diabetes in Iranian population. However, regular screening for insulin resistance is recommended in CHC patients with age ≥ 40 years and fasting blood glucose ≥ 100 mg/dl. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Insulin signaling in various equine tissues under basal conditions and acute stimulation by intravenously injected insulin.

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Warnken, Tobias; Brehm, Ralph; Feige, Karsten; Huber, Korinna

2017-10-01

The aim of the study was to analyze key proteins of the equine insulin signaling cascade and their extent of phosphorylation in biopsies from muscle tissue (MT), liver tissue (LT), and nuchal AT, subcutaneous AT, and retroperitoneal adipose tissues. This was investigated under unstimulated (B1) and intravenously insulin stimulated (B2) conditions, which were achieved by injection of insulin (0.1 IU/kg bodyweight) and glucose (150 mg/kg bodyweight). Twelve warmblood horses aged 15 ± 6.8 yr (yr), weighing 559 ± 79 kg, and with a mean body condition score of 4.7 ± 1.5 were included in the study. Key proteins of the insulin signaling cascade were semiquantitatively determined using Western blotting. Furthermore, modulation of the cascade was assessed. The basal expression of the proteins was only slightly influenced during the experimental period. Insulin induced a high extent of phosphorylation of insulin receptor in LT (P < 0.01) but not in MT. Protein kinase B and mechanistic target of rapamycin expressed a higher extent of phosphorylation in all tissues in B2 biopsies. Adenosine monophosphate protein kinase, as a component related to insulin signaling, expressed enhanced phosphorylation in MT (P < 0.05) and adipose tissues (nuchal AT P < 0.05; SCAT P < 0.01; retroperitoneal adipose tissue P < 0.05), but not in LT at B2. Tissue-specific variations in the acute response of insulin signaling to intravenously injected insulin were observed. In conclusion, insulin sensitivity in healthy horses is based on a complex concerted action of different tissues by their variations in the molecular response to insulin. Copyright © 2017 Elsevier Inc. All rights reserved.

Insulin signaling in Caenorhabditis elegans regulates both endocrine-like and cell-autonomous outputs.

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Iser, Wendy B; Gami, Minaxi S; Wolkow, Catherine A

2007-03-15

In C. elegans, insulin signaling affects development, lifespan and stress resistance. Several studies have shown that insulin signaling affects lifespan in an endocrine-like manner from different cells, while the major downstream target of insulin, the FOXO transcription factor encoded by daf-16, may act preferentially in intestinal cells to prolong lifespan. This discrepancy raised the possibility that insulin may have both endocrine and cell-intrinsic outputs. Here, we further investigated the types of cells capable of producing endocrine outputs of insulin and also identified a new cell-intrinsic insulin output. We found that insulin signaling within groups of neurons promoted wildtype lifespan, showing that the endocrine outputs of insulin were not restricted to specific cells. In contrast, DAF-16 appeared to have a greater effect on lifespan when expressed in a combination of tissues. These results suggest that insulin signaling may regulate DAF-16 through cell-intrinsic and endocrine pathways. We also found that an insulin-dependent response to fasting in intestinal cells was preferentially regulated by intestinal insulin signaling and was less responsive to insulin signaling from non-intestinal cells. Together, these results show that C. elegans insulin signaling has endocrine as well as tissue-specific outputs which could influence lifespan in a combinatorial fashion.

Gamma-glutamyltransferase, fatty liver index and hepatic insulin resistance are associated with incident hypertension in two longitudinal studies.

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Bonnet, Fabrice; Gastaldelli, Amalia; Pihan-Le Bars, Florence; Natali, Andrea; Roussel, Ronan; Petrie, John; Tichet, Jean; Marre, Michel; Fromenty, Bernard; Balkau, Beverley

2017-03-01

We hypothesized that liver markers and the fatty liver index (FLI) are predictive of incident hypertension and that hepatic insulin resistance plays a role. The association between liver markers and incident hypertension was analysed in two longitudinal studies of normotensive individuals, 2565 from the 9-year data from an epidemiological study on the insulin resistance cohort and the 321 from the 3-year 'Relationship between Insulin Sensitivity and Cardiovascular disease' cohort who had a measure of endogenous glucose production. The FLI is calculated from BMI, waist circumference, triglycerides and gamma-glutamyltransferase (GGT) and the hepatic insulin resistance index from endogenous glucose production and fasting insulin. The incidence of hypertension increased across the quartiles groups of both baseline GGT and alanine aminotransferase. After adjustment for sex, age, waist circumference, fasting glucose, smoking and alcohol intake, only GGT was significantly related with incident hypertension [standardized odds ratio: 1.21; 95% confidence interval (1.10-1.34); P = 0.0001]. The change in GGT levels over the follow-up was also related with an increased risk of hypertension, independently of changes in body weight. FLI analysed as a continuous value, or FLI at least 60 at baseline were predictive of incident hypertension in the multivariable model. In the RISC cohort, the hepatic insulin resistance index was positively related with the risk of 3-year incident hypertension [standardized odds ratio: 1.54 (1.07-2.22); P = 0.02]. Baseline GGT and FLI, as well as an increase in GGT over time, were associated with the risk of incident hypertension. Enhanced hepatic insulin resistance predicted the onset of hypertension and may be a link between liver markers and hypertension.

Insulin-dependent signaling: regulation by amino acids and energy

NARCIS (Netherlands)

Meijer, A. J.

2004-01-01

Recent research has indicated that amino acids stimulate a signal-transduction pathway that is also used by insulin. Moreover, for insulin to exert its anabolic and anticatabolic effects on protein, there is an absolute requirement for amino acids. This signaling pathway becomes inhibited by

The transcription factor Prep1 controls hepatic insulin sensitivity and gluconeogenesis by targeting nuclear localization of FOXO1.

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Kulebyakin, Konstantin; Penkov, Dmitry; Blasi, Francesco; Akopyan, Zhanna; Tkachuk, Vsevolod

2016-12-02

Liver plays a key role in controlling body carbohydrate homeostasis by switching between accumulation and production of glucose and this way maintaining constant level of glucose in blood. Increased blood glucose level triggers release of insulin from pancreatic β-cells. Insulin represses hepatic glucose production and increases glucose accumulation. Insulin resistance is the main cause of type 2 diabetes and hyperglycemia. Currently thiazolidinediones (TZDs) targeting transcriptional factor PPARγ are used as insulin sensitizers for treating patients with type 2 diabetes. However, TZDs are reported to be associated with cardiovascular and liver problems and stimulate obesity. Thus, it is necessary to search new approaches to improve insulin sensitivity. A promising candidate is transcriptional factor Prep1, as it was shown earlier it could affect insulin sensitivity in variety of insulin-sensitive tissues. The aim of the present study was to evaluate a possible involvement of transcriptional factor Prep1 in control of hepatic glucose accumulation and production. We created mice with liver-specific Prep1 knockout and discovered that hepatocytes derived from these mice are much more sensitive to insulin, comparing to their WT littermates. Incubation of these cells with 100 nM insulin results in almost complete inhibition of gluconeogenesis, while in WT cells this repression is only partial. However, Prep1 doesn't affect gluconeogenesis in the absence of insulin. Also, we observed that nuclear content of gluconeogenic transcription factor FOXO1 was greatly reduced in Prep1 knockout hepatocytes. These findings suggest that Prep1 may control hepatic insulin sensitivity by targeting FOXO1 nuclear stability. Copyright © 2016 Elsevier Inc. All rights reserved.

Hepatic Cholesterol-25-Hydroxylase Overexpression Improves Systemic Insulin Sensitivity in Mice

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Britta Noebauer

2017-01-01

Full Text Available Obesity is a major risk factor for several diseases including diabetes, heart disease, and some forms of cancer and due to its rapidly increasing prevalence it has become one of the biggest problems medicine is facing today. All the more surprising, a substantial percentage of obese patients are metabolically healthy when classified based on insulin resistance and systemic inflammation. Oxysterols are naturally occurring molecules that play important role in various metabolic and inflammatory processes and their levels are elevated in patients suffering from obesity and diabetes. 25-Hydroxycholesterol (25-OHC is produced in cells from cholesterol by the enzyme cholesterol 25-hydroxylase (Ch25h and is involved in lipid metabolism, inflammatory processes, and cell proliferation. Here, we investigated the role of hepatic Ch25h in the transition from metabolically healthy obesity to insulin resistance and diabetes. Using several different experimental approaches, we demonstrated the significance of Ch25h on the border of “healthy” and “diseased” states of obesity. Adenovirus-mediated Ch25h overexpression in mice improved glucose tolerance and insulin sensitivity and lowered HOMA-IR. Our data suggest that low hepatic Ch25h levels could be considered a risk marker for unhealthy obesity.

Ursodeoxycholic acid improves insulin sensitivity and hepatic steatosis by inducing the excretion of hepatic lipids in high-fat diet-fed KK-Ay mice.

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Tsuchida, Takuma; Shiraishi, Muneshige; Ohta, Tetsuya; Sakai, Kaoru; Ishii, Shinichi

2012-07-01

Type 2 diabetes mellitus is frequently accompanied by fatty liver/nonalcoholic fatty liver disease. Hence, accumulation of lipids in the liver is considered to be one of the risk factors for insulin resistance and metabolic syndrome. Ursodeoxycholic acid (UDCA) is widely used for the treatment of liver dysfunction. We investigated the therapeutic effects of UDCA on type 2 diabetes mellitus exacerbating hepatic steatosis and the underlying mechanisms of its action using KK-A(y) mice fed a high-fat diet. KK-A(y) mice were prefed a high-fat diet; and 50, 150, and 450 mg/kg of UDCA was orally administered for 2 or 3 weeks. Administration of UDCA decreased fasting hyperglycemia and hyperinsulinemia. Hyperinsulinemic-euglycemic clamp analyses showed that UDCA improved hepatic (but not peripheral) insulin resistance. Hepatic triglyceride and cholesterol contents were significantly reduced by treatment with UDCA, although the genes involved in the synthesis of fatty acids and cholesterol, including fatty acid synthase and 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase, were upregulated. Fecal levels of bile acids, neutral sterols, fatty acids, and phospholipids were significantly increased by UDCA treatment. The gene expression levels and protein phosphorylation levels of endoplasmic reticulum stress markers were not changed by UDCA treatment. These results indicate that UDCA ameliorates hyperglycemia and hyperinsulinemia by improving hepatic insulin resistance and steatosis in high-fat diet-fed KK-A(y) mice. Reduction of hepatic lipids might be due to their excretion in feces, followed by enhanced utilization of glucose for the synthesis of fatty acids and cholesterol. Ursodeoxycholic acid should be effective for the treatment of type 2 diabetes mellitus accompanying hepatic steatosis. Copyright © 2012 Elsevier Inc. All rights reserved.

Bezafibrate ameliorates diabetes via reduced steatosis and improved hepatic insulin sensitivity in diabetic TallyHo mice

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Andras Franko

2017-03-01

Full Text Available Objective: Recently, we have shown that Bezafibrate (BEZ, the pan-PPAR (peroxisome proliferator-activated receptor activator, ameliorated diabetes in insulin deficient streptozotocin treated diabetic mice. In order to study whether BEZ can also improve glucose metabolism in a mouse model for fatty liver and type 2 diabetes, the drug was applied to TallyHo mice. Methods: TallyHo mice were divided into an early (ED and late (LD diabetes progression group and both groups were treated with 0.5% BEZ (BEZ group or standard diet (SD group for 8 weeks. We analyzed plasma parameters, pancreatic beta-cell morphology, and mass as well as glucose metabolism of the BEZ-treated and control mice. Furthermore, liver fat content and composition as well as hepatic gluconeogenesis and mitochondrial mass were determined. Results: Plasma lipid and glucose levels were markedly reduced upon BEZ treatment, which was accompanied by elevated insulin sensitivity index as well as glucose tolerance, respectively. BEZ increased islet area in the pancreas. Furthermore, BEZ treatment improved energy expenditure and metabolic flexibility. In the liver, BEZ ameliorated steatosis, modified lipid composition and increased mitochondrial mass, which was accompanied by reduced hepatic gluconeogenesis. Conclusions: Our data showed that BEZ ameliorates diabetes probably via reduced steatosis, enhanced hepatic mitochondrial mass, improved metabolic flexibility and elevated hepatic insulin sensitivity in TallyHo mice, suggesting that BEZ treatment could be beneficial for patients with NAFLD and impaired glucose metabolism. Keywords: Bezafibrate, Glucose metabolism, Insulin resistance, Lipid metabolism, NAFLD

Decreased hepatic RBP4 secretion is correlated with reduced hepatic glucose production but is not associated with insulin resistance in patients with liver cirrhosis

NARCIS (Netherlands)

Bahr, Matthias J.; Boeker, Klaus H. W.; Manns, Michael P.; Tietge, Uwe J. F.

Patients with liver cirrhosis have a high incidence of insulin resistance and diabetes. This study was designed to determine circulating levels and hepatic production of retinol-binding protein 4 (RBP4) in relation to parameters of hepatic and systemic metabolism in patients with liver cirrhosis.

Deepure Tea Improves High Fat Diet-Induced Insulin Resistance and Nonalcoholic Fatty Liver Disease

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Jing-Na Deng

2015-01-01

Full Text Available This study was to explore the protective effects of Deepure tea against insulin resistance and hepatic steatosis and elucidate the potential underlying molecular mechanisms. C57BL/6 mice were fed with a high fat diet (HFD for 8 weeks to induce the metabolic syndrome. In the Deepure tea group, HFD mice were administrated with Deepure tea at 160 mg/kg/day by gavage for 14 days. The mice in HFD group received water in the same way over the same period. The age-matched C57BL/6 mice fed with standard chow were used as normal control. Compared to the mice in HFD group, mice that received Deepure tea showed significantly reduced plasma insulin and improved insulin sensitivity. Deepure tea increased the expression of insulin receptor substrate 2 (IRS-2, which plays an important role in hepatic insulin signaling pathway. Deepure tea also led to a decrease in hepatic fatty acid synthesis and lipid accumulation, which were mediated by the downregulation of sterol regulatory element binding protein 1c (SREBP-1c, fatty acid synthesis (FAS, and acetyl-CoA carboxylase (ACC proteins that are involved in liver lipogenesis. These results suggest that Deepure tea may be effective for protecting against insulin resistance and hepatic steatosis via modulating IRS-2 and downstream signaling SREBP-1c, FAS, and ACC.

Immune and Metabolic Regulation Mechanism of Dangguiliuhuang Decoction against Insulin Resistance and Hepatic Steatosis

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Hui Cao

2017-07-01

Full Text Available Dangguiliuhuang decoction (DGLHD is a traditional Chinese medicine (TCM formula, which mainly consists of angelica, radix rehmanniae, radix rehmanniae praeparata, scutellaria baicalensis, coptis chinensis, astragalus membranaceus, and golden cypress, and used for the treatment of diabetes and some autoimmune diseases. In this study, we explored the potential mechanism of DGLHD against insulin resistance and fatty liver in vivo and in vitro. Our data revealed that DGLHD normalized glucose and insulin level, increased the expression of adiponectin, diminished fat accumulation and lipogenesis, and promoted glucose uptake. Metabolomic analysis also demonstrated that DGLHD decreased isoleucine, adenosine, and cholesterol, increased glutamine levels in liver and visceral adipose tissue (VAT of ob/ob mice. Importantly, DGLHD promoted the shift of pro-inflammatory to anti-inflammatory cytokines, suppressed T lymphocytes proliferation, and enhanced regulatory T cells (Tregs differentiation. DGLHD also inhibited dendritic cells (DCs maturation, attenuated DCs-stimulated T cells proliferation and secretion of IL-12p70 cytokine from DCs, and promoted the interaction of DCs with Tregs. Further studies indicated that the changed PI3K/Akt signaling pathway and elevated PPAR-γ expression were not only observed with the ameliorated glucose and lipid metabolism in adipocytes and hepatocytes, but also exhibited in DCs and T cells by DGLHD. Collectively, our results suggest that DGLHD exerts anti-insulin resistant and antisteatotic effects by improving abnormal immune and metabolic homeostasis. And DGLHD may be a novel approach to the treatment of obesity-related insulin resistance and hepatic steatosis.

Tribbles 3 inhibits brown adipocyte differentiation and function by suppressing insulin signaling

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Jeong, Ha-Won; Choi, Ran Hee; McClellan, Jamie L. [Division of Applied Physiology, Department of Exercise Science, University of South Carolina, Columbia, SC 29208 (United States); Piroli, Gerardo G.; Frizzell, Norma [Department of Pharmacology, Physiology & Neuroscience, University of South Carolina School of Medicine, Columbia, SC 29208 (United States); Tseng, Yu-Hua; Goodyear, Laurie J. [Research Division, Joslin Diabetes Center and Department of Medicine, Harvard Medical School, Boston, MA 02215 (United States); Koh, Ho-Jin, E-mail: kohh@mailbox.sc.edu [Division of Applied Physiology, Department of Exercise Science, University of South Carolina, Columbia, SC 29208 (United States)

2016-02-19

Recent studies have demonstrated that adult humans have substantial amounts of functioning brown adipose tissue (BAT). Since BAT has been implicated as an anti-obese and anti-diabetic tissue, it is important to understand the signaling molecules that regulate BAT function. There has been a link between insulin signaling and BAT metabolism as deletion or pharmaceutical inhibition of insulin signaling impairs BAT differentiation and function. Tribbles 3 (TRB3) is a pseudo kinase that has been shown to regulate metabolism and insulin signaling in multiple tissues but the role of TRB3 in BAT has not been studied. In this study, we found that TRB3 expression was present in BAT and overexpression of TRB3 in brown preadipocytes impaired differentiation and decreased expression of BAT markers. Furthermore, TRB3 overexpression resulted in significantly lower oxygen consumption rates for basal and proton leakage, indicating decreased BAT activity. Based on previous studies showing that deletion or pharmaceutical inhibition of insulin signaling impairs BAT differentiation and function, we assessed insulin signaling in brown preadipocytes and BAT in vivo. Overexpression of TRB3 in cells impaired insulin-stimulated IRS1 and Akt phosphorylation, whereas TRB3KO mice displayed improved IRS1 and Akt phosphorylation. Finally, deletion of IRS1 abolished the function of TRB3 to regulate BAT differentiation and metabolism. These data demonstrate that TRB3 inhibits insulin signaling in BAT, resulting in impaired differentiation and function. - Highlights: • TRB3 is expressed in brown adipose tissue and its expression is increased during differentiation. • Overexpression of TRB3 inhibits differentiation and its activity. • Overexpression of TRB3 in brown preadipocytes inhibits insulin signaling. • TRB3KO mice displays improved insulin signaling in brown adipose tissue. • Insulin signaling is required for the effects of TRB3 to regulate brown adipose tissue differentiation and

Tribbles 3 inhibits brown adipocyte differentiation and function by suppressing insulin signaling

International Nuclear Information System (INIS)

Jeong, Ha-Won; Choi, Ran Hee; McClellan, Jamie L.; Piroli, Gerardo G.; Frizzell, Norma; Tseng, Yu-Hua; Goodyear, Laurie J.; Koh, Ho-Jin

2016-01-01

Recent studies have demonstrated that adult humans have substantial amounts of functioning brown adipose tissue (BAT). Since BAT has been implicated as an anti-obese and anti-diabetic tissue, it is important to understand the signaling molecules that regulate BAT function. There has been a link between insulin signaling and BAT metabolism as deletion or pharmaceutical inhibition of insulin signaling impairs BAT differentiation and function. Tribbles 3 (TRB3) is a pseudo kinase that has been shown to regulate metabolism and insulin signaling in multiple tissues but the role of TRB3 in BAT has not been studied. In this study, we found that TRB3 expression was present in BAT and overexpression of TRB3 in brown preadipocytes impaired differentiation and decreased expression of BAT markers. Furthermore, TRB3 overexpression resulted in significantly lower oxygen consumption rates for basal and proton leakage, indicating decreased BAT activity. Based on previous studies showing that deletion or pharmaceutical inhibition of insulin signaling impairs BAT differentiation and function, we assessed insulin signaling in brown preadipocytes and BAT in vivo. Overexpression of TRB3 in cells impaired insulin-stimulated IRS1 and Akt phosphorylation, whereas TRB3KO mice displayed improved IRS1 and Akt phosphorylation. Finally, deletion of IRS1 abolished the function of TRB3 to regulate BAT differentiation and metabolism. These data demonstrate that TRB3 inhibits insulin signaling in BAT, resulting in impaired differentiation and function. - Highlights: • TRB3 is expressed in brown adipose tissue and its expression is increased during differentiation. • Overexpression of TRB3 inhibits differentiation and its activity. • Overexpression of TRB3 in brown preadipocytes inhibits insulin signaling. • TRB3KO mice displays improved insulin signaling in brown adipose tissue. • Insulin signaling is required for the effects of TRB3 to regulate brown adipose tissue differentiation and

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.

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

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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.

High fat diet-induced modifications in membrane lipid and mitochondrial-membrane protein signatures precede the development of hepatic insulin resistance in mice.

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Kahle, M; Schäfer, A; Seelig, A; Schultheiß, J; Wu, M; Aichler, M; Leonhardt, J; Rathkolb, B; Rozman, J; Sarioglu, H; Hauck, S M; Ueffing, M; Wolf, E; Kastenmueller, G; Adamski, J; Walch, A; Hrabé de Angelis, M; Neschen, S

2015-01-01

Excess lipid intake has been implicated in the pathophysiology of hepatosteatosis and hepatic insulin resistance. Lipids constitute approximately 50% of the cell membrane mass, define membrane properties, and create microenvironments for membrane-proteins. In this study we aimed to resolve temporal alterations in membrane metabolite and protein signatures during high-fat diet (HF)-mediated development of hepatic insulin resistance. We induced hepatosteatosis by feeding C3HeB/FeJ male mice an HF enriched with long-chain polyunsaturated C18:2n6 fatty acids for 7, 14, or 21 days. Longitudinal changes in hepatic insulin sensitivity were assessed via the euglycemic-hyperinsulinemic clamp, in membrane lipids via t-metabolomics- and membrane proteins via quantitative proteomics-analyses, and in hepatocyte morphology via electron microscopy. Data were compared to those of age- and litter-matched controls maintained on a low-fat diet. Excess long-chain polyunsaturated C18:2n6 intake for 7 days did not compromise hepatic insulin sensitivity, however, induced hepatosteatosis and modified major membrane lipid constituent signatures in liver, e.g. increased total unsaturated, long-chain fatty acid-containing acyl-carnitine or membrane-associated diacylglycerol moieties and decreased total short-chain acyl-carnitines, glycerophosphocholines, lysophosphatidylcholines, or sphingolipids. Hepatic insulin sensitivity tended to decrease within 14 days HF-exposure. Overt hepatic insulin resistance developed until day 21 of HF-intervention and was accompanied by morphological mitochondrial abnormalities and indications for oxidative stress in liver. HF-feeding progressively decreased the abundance of protein-components of all mitochondrial respiratory chain complexes, inner and outer mitochondrial membrane substrate transporters independent from the hepatocellular mitochondrial volume in liver. We assume HF-induced modifications in membrane lipid- and protein-signatures prior to and

Higher intramuscular triacylglycerol in women does not impair insulin sensitivity and proximal insulin signaling

DEFF Research Database (Denmark)

Høeg, Louise; Roepstorff, Carsten; Thiele, Maja

2009-01-01

that despite 47% higher IMTG levels in women in the follicular phase whole body as well as leg insulin sensitivity are higher than in matched men. This was not explained by sex differences in proximal insulin signalling in women. In women it seems that a high capillary density and type 1 muscle fiber...... expression may be important for insulin action. Key words: Muscle Triglycerides, gender, insulin action, sex paradox....

Dissection of the insulin signaling pathway via quantitative phosphoproteomics

DEFF Research Database (Denmark)

Krüger, Marcus; Kratchmarova, Irina; Blagoev, Blagoy

2008-01-01

spectrum of the tyrosine phosphorylation cascade, we have defined the tyrosine-phosphoproteome of the insulin signaling pathway, using high resolution mass spectrometry in combination with phosphotyrosine immunoprecipitation and stable isotope labeling by amino acids in cell culture (SILAC......The insulin signaling pathway is of pivotal importance in metabolic diseases, such as diabetes, and in cellular processes, such as aging. Insulin activates a tyrosine phosphorylation cascade that branches to create a complex network affecting multiple biological processes. To understand the full...

Role of chrysin on expression of insulin signaling molecules

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Kottireddy Satyanarayana

2015-01-01

Full Text Available Background: Currently available drugs are unsuccessful for the treatment of tye-2 diabetes due to their adverseside-effects. Hence, a search for novel drugs, especially ofplant origin, continues. Chrysin (5,7-dihydroxyflavone is a flavonoid, natural component of traditional medicinal herbs, present in honey, propolis and many plant extracts that hasbeen used in traditional medicine around the world to treat numerous ailments. Objective: The present study was aimed to identify the protective role of chrysin on the expression of insulin-signaling molecules in the skeletal muscle of high fat and sucrose-induced type-2 diabetic adult male rats. Materials and Methods: The oral effective dose of chrysin (100 mg/kg body weight was given once a day until the end of the study (30 days post-induction of diabetes to high fat diet-induced diabetic rats.At the end of the experimental period, fasting blood glucose, oral glucose tolerance, serum lipid profile, lipid peroxidation (LPO and free radical generation, as well as the levels of insulin signaling molecules and tissue glycogen in the gastrocnemius muscle were assessed. Results: Diabetic rats showed impaired glucose tolerance and impairment in insulin signaling molecules (IR, IRS-1, p-IRS-1Tyr 632 , p- Akt Thr308 , glucose transporter subtype 4 [GLUT4] proteins and glycogen concentration. Serum insulin, lipid profile, LPO and free radical generation were found to be increased in diabetic control rats.The treatment with chrysin normalized the altered levels of blood glucose, serum insulin, lipid profile, LPO and insulin signaling molecules as well as GLUT4 proteins. Conclusion: Our present findings indicate that chrysin improves glycemic control through activation of insulin signal transduction in the gastrocnemius muscle of high fat and sucrose-induced type-2 diabetic male rats.

Exposures to arsenite and methylarsonite produce insulin resistance and impair insulin-dependent glycogen metabolism in hepatocytes.

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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.

Meju, unsalted soybeans fermented with Bacillus subtilis and Aspergilus oryzae, potentiates insulinotropic actions and improves hepatic insulin sensitivity in diabetic rats.

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Yang, Hye Jeong; Kwon, Dae Young; Kim, Min Jung; Kang, Suna; Park, Sunmin

2012-05-02

Although soybeans have the ability to attenuate insulin resistance, it is insufficient to alleviate type 2 diabetic symptoms and different types of fermented soybeans may have even better anti-diabetic effects. Meju, unsalted fermented soybeans exhibited better insulin sensitizing and insulinotropic actions than unfermented cooked soybeans (CSB). We investigated whether meju fermented in the traditional (TMS) manner for 60 days and meju fermented in the standardized (MMS) method inoculating Bacillus subtilis and Aspergillus oryzae for 6 days modulated insulin resistance, insulin secretion, and pancreatic β-cell growth and survival in 90% pancreatectomized (Px) diabetic rats, a moderate and non-obese type 2 diabetic animal model. Diabetic rats were divided into 3 groups: 1) TMS (n = 20), 2) MMS (n = 20) or 3) casein (control; n = 20). Rats were provided with a high fat diet (40 energy % fat) containing assigned 10% meju for 8 weeks. At the end of experiment insulin resistance and insulin secretion capacity were measured by euglycemic hyperinsulinemic clamp and by hyperglycemic clamp, respectively. Additionally, β-cell mass and islet morphohometry were determined by immunohistochemistry and insulin signaling in the liver was measured by western blot. TMS and MMS increased isoflavonoid aglycones much more than CSB. CSB and TMS/MMS improved glucose tolerance in diabetic rats but the mechanism was different between treatments (P MMS enhanced only hepatic insulin sensitivity through activating insulin signaling in diabetic rats (P MMS, but not CSB, potentiated glucose-stimulated insulin secretion and β-cell mass (P MMS had better insulinotropic actions than the control (P MMS, especially when fermented with Bacillus subtilis and Aspergillus oryzae, was superior to CSB by increasing isoflavonoid aglycones and small peptides with regard to type 2 diabetic rats.

Nutrient Restriction Increases Circulating and Hepatic Ceramide in Dairy Cows Displaying Impaired Insulin Tolerance.

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Davis, Amanda N; Clegg, J L; Perry, C A; McFadden, J W

2017-09-01

The progression of insulin resistance in dairy cows represents a maternal adaptation to support milk production during heightened energy demand; however, excessive adipose tissue lipolysis can develop. In diabetic non-ruminants, the mechanisms that mediate insulin resistance involve the sphingolipid ceramide. We tested the hypothesis that ceramide accumulates in dairy cows experiencing lipolysis and insulin resistance. Nine dairy cows were utilized in a replicated 3 × 3 Latin square design. Cows were ad libitum fed, nutrient-restricted (NR), or NR with nicotinic acid (NA; 5 mg of NA/h per kg BW; delivered i.v.) for 34 h. When provided access, cows were ad libitum fed a mixed ration of grass hay and ground corn to meet requirements. Intake for NR cows was limited to vitamins and minerals. Nicotinic acid was administered to suppress lipolysis. Saline was infused in cows not provided NA. At 32 and 33 h of treatment, a liver biopsy and insulin tolerance test were performed, respectively. Samples were analyzed using colorimetry, immunoassay, and mass spectrometry. Nutrient restriction increased serum fatty acids and ceramide levels, and impaired insulin sensitivity; however, NA infusion was unable to prevent these responses. We also show that NR increases hepatic ceramide accumulation, a response that was positively associated with serum ceramide supply. Our data demonstrate that circulating and hepatic 24:0-Cer are inversely associated with systemic insulin tolerance, an effect not observed for the 16:0 moiety. In conclusion, our results suggest that ceramide accrual represents a metabolic adaptation to nutrient restriction and impaired insulin action in dairy cows.

Changes in insulin and insulin signaling in Alzheimer’s disease: cause or consequence?

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Stanley, Molly; Macauley, Shannon L.

2016-01-01

Individuals with type 2 diabetes have an increased risk for developing Alzheimer’s disease (AD), although the causal relationship remains poorly understood. Alterations in insulin signaling (IS) are reported in the AD brain. Moreover, oligomers/fibrils of amyloid-β (Aβ) can lead to neuronal insulin resistance and intranasal insulin is being explored as a potential therapy for AD. Conversely, elevated insulin levels (ins) are found in AD patients and high insulin has been reported to increase Aβ levels and tau phosphorylation, which could exacerbate AD pathology. Herein, we explore whether changes in ins and IS are a cause or consequence of AD. PMID:27432942

INSULIN SIGNALING AND THE REGULATION OF INSECT DIAPAUSE

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Cheolho eSim

2013-07-01

Full Text Available A rich chapter in the history of insect endocrinology has focused on hormonal control of diapause, especially the major roles played by juvenile hormones (JHs, ecdysteroids, and the neuropeptides that govern JH and ecdysteroid synthesis. More recently, experiments with adult diapause in Drosophila melanogaster and the mosquito Culex pipiens, and pupal diapause in the flesh fly Sarcophaga crassipalpis provide strong evidence that insulin signaling is also an important component of the regulatory pathway leading to the diapause phenotype. Insects produce many different insulin-like peptides (ILPs, and not all are involved in the diapause response; ILP-1 appears to be the one most closely linked to diapause in C. pipiens. Many steps in the pathway leading from perception of daylength (the primary environmental cue used to program diapause to generation of the diapause phenotype remain unknown, but the role for insulin signaling in mosquito diapause appears to be upstream of JH, as evidenced by the fact that application of exogenous JH can rescue the effects of knocking down expression of ILP-1 or the Insulin Receptor. Fat accumulation, enhancement of stress tolerance, and other features of the diapause phenotype are likely linked to the insulin pathway through the action of a key transcription factor, FOXO. This review highlights many parallels for the role of insulin signaling as a regulator in insect diapause and dauer formation in the nematode Caenorhabditis elegans.

High density lipoproteins improve insulin sensitivity in high-fat diet-fed mice by suppressing hepatic inflammation[S

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McGrath, Kristine C.; Li, Xiao Hong; Whitworth, Phillippa T.; Kasz, Robert; Tan, Joanne T.; McLennan, Susan V.; Celermajer, David S.; Barter, Philip J.; Rye, Kerry-Anne; Heather, Alison K.

2014-01-01

Obesity-induced liver inflammation can drive insulin resistance. HDL has anti-inflammatory properties, so we hypothesized that low levels of HDL would perpetuate inflammatory responses in the liver and that HDL treatment would suppress liver inflammation and insulin resistance. The aim of this study was to investigate the effects of lipid-free apoAI on hepatic inflammation and insulin resistance in mice. We also investigated apoAI as a component of reconstituted HDLs (rHDLs) in hepatocytes to confirm results we observed in vivo. To test our hypothesis, C57BL/6 mice were fed a high-fat diet (HFD) for 16 weeks and administered either saline or lipid-free apoAI. Injections of lipid-free apoAI twice a week for 2 or 4 weeks with lipid-free apoAI resulted in: i) improved insulin sensitivity associated with decreased systemic and hepatic inflammation; ii) suppression of hepatic mRNA expression for key transcriptional regulators of lipogenic gene expression; and iii) suppression of nuclear factor κB (NF-κB) activation. Human hepatoma HuH-7 cells exposed to rHDLs showed suppressed TNFα-induced NF-κB activation, correlating with decreased NF-κB target gene expression. We conclude that apoAI suppresses liver inflammation in HFD mice and improves insulin resistance via a mechanism that involves a downregulation of NF-κB activation. PMID:24347528

Regulation of brain insulin signaling: A new function for tau.

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Gratuze, Maud; Planel, Emmanuel

2017-08-07

In this issue of JEM, Marciniak et al. (https://doi.org/10.1084/jem.20161731) identify a putative novel function of tau protein as a regulator of insulin signaling in the brain. They find that tau deletion impairs hippocampal response to insulin through IRS-1 and PTEN dysregulation and suggest that, in Alzheimer's disease, impairment of brain insulin signaling might occur via tau loss of function. © 2017 Gratuze and Planel.

Preventive effects of chronic exogenous growth hormone levels on diet-induced hepatic steatosis in rats

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Tian Ya-ping

2010-07-01

Full Text Available Abstract Background Non-alcoholic fatty liver disease (NAFLD, which is characterized by hepatic steatosis, can be reversed by early treatment. Several case reports have indicated that the administration of recombinant growth hormone (GH could improve fatty liver in GH-deficient patients. Here, we investigated whether chronic exogenous GH levels could improve hepatic steatosis induced by a high-fat diet in rats, and explored the underlying mechanisms. Results High-fat diet-fed rats developed abdominal obesity, fatty liver and insulin resistance. Chronic exogenous GH improved fatty liver, by reversing dyslipidaemia, fat accumulation and insulin resistance. Exogenous GH also reduced serum tumour necrosis factor-alpha (TNF-alpha levels, and ameliorated hepatic lipid peroxidation and oxidative stress. Hepatic fat deposition was also reduced by exogenous GH levels, as was the expression of adipocyte-derived adipokines (adiponectin, leptin and resistin, which might improve lipid metabolism and hepatic steatosis. Exogenous GH seems to improve fatty liver by reducing fat weight, improving insulin sensitivity and correcting oxidative stress, which may be achieved through phosphorylation or dephosphorylation of a group of signal transducers and activators of hepatic signal transduction pathways. Conclusions Chronic exogenous GH has positive effects on fatty liver and may be a potential clinical application in the prevention or reversal of fatty liver. However, chronic secretion of exogenous GH, even at a low level, may increase serum glucose and insulin levels in rats fed a standard diet, and thus increase the risk of insulin resistance.

S961, an insulin receptor antagonist causes hyperinsulinemia, insulin-resistance and depletion of energy stores in rats

International Nuclear Information System (INIS)

Vikram, Ajit; Jena, Gopabandhu

2010-01-01

Research highlights: →Insulin receptor antagonist S961 causes hyperglycemia, hyperinsulinemia and insulin resistance in rats. →Peroxysome-proliferator-activated-receptor-gamma agonist pioglitazone improves S961 induced hyperglycemia and glucose intolerance. →Long term treatment with insulin receptor antagonist S961 results in the decreased adiposity and hepatic glycogen content. →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 (∼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 (PPARγ) agonist pioglitazone significantly (P < 0.001) restored S961 induced hyperglycemia (196.73 ± 16.32 vs. 126.37 ± 27.07 mg/dl) and glucose intolerance (∼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.

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

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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.

High fructose-mediated attenuation of insulin receptor signaling does not affect PDGF-induced proliferative signaling in vascular smooth muscle cells.

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Osman, Islam; Poulose, Ninu; Ganapathy, Vadivel; Segar, Lakshman

2016-11-15

Insulin resistance is associated with accelerated atherosclerosis. Although high fructose is known to induce insulin resistance, it remains unclear as to how fructose regulates insulin receptor signaling and proliferative phenotype in vascular smooth muscle cells (VSMCs), which play a major role in atherosclerosis. Using human aortic VSMCs, we investigated the effects of high fructose treatment on insulin receptor substrate-1 (IRS-1) serine phosphorylation, insulin versus platelet-derived growth factor (PDGF)-induced phosphorylation of Akt, S6 ribosomal protein, and extracellular signal-regulated kinase (ERK), and cell cycle proteins. In comparison with PDGF (a potent mitogen), neither fructose nor insulin enhanced VSMC proliferation and cyclin D1 expression. d-[ 14 C(U)]fructose uptake studies revealed a progressive increase in fructose uptake in a time-dependent manner. Concentration-dependent studies with high fructose (5-25mM) showed marked increases in IRS-1 serine phosphorylation, a key adapter protein in insulin receptor signaling. Accordingly, high fructose treatment led to significant diminutions in insulin-induced phosphorylation of downstream signaling components including Akt and S6. In addition, high fructose significantly diminished insulin-induced ERK phosphorylation. Nevertheless, high fructose did not affect PDGF-induced key proliferative signaling events including phosphorylation of Akt, S6, and ERK and expression of cyclin D1 protein. Together, high fructose dysregulates IRS-1 phosphorylation state and proximal insulin receptor signaling in VSMCs, but does not affect PDGF-induced proliferative signaling. These findings suggest that systemic insulin resistance rather than VSMC-specific dysregulation of insulin receptor signaling by high fructose may play a major role in enhancing atherosclerosis and neointimal hyperplasia. Copyright © 2016 Elsevier B.V. All rights reserved.

Cross talk between insulin and bone morphogenetic protein signaling systems in brown adipogenesis

DEFF Research Database (Denmark)

Zhang, Hongbin; Schulz, Tim J; Espinoza, Daniel O

2010-01-01

Both insulin and bone morphogenetic protein (BMP) signaling systems are important for adipocyte differentiation. Analysis of gene expression in BMP7-treated fibroblasts revealed a coordinated change in insulin signaling components by BMP7. To further investigate the cross talk between insulin...... BMP7's suppressive effect on pref-1 transcription. Together, these data suggest cross talk between the insulin and BMP signaling systems by which BMP7 can rescue brown adipogenesis in cells with insulin resistance....

The effects of diet-induced obesity on hepatocyte insulin signaling pathways and induction of non-alcoholic liver damage

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Sameer Fatani

2011-03-01

Full Text Available Sameer Fatani1, Imose Itua2, Paul Clark3, Christopher Wong3, Ebrahim K Naderali21Obesity Biology Unit, School of Clinical Sciences, University of Liverpool, Liverpool, UK; 2Department of Health and Applied Social Sciences, Liverpool Hope University, Hope Park, Liverpool UK; 3Aintree University Hospital NHS Foundation Trust, Longmoor Lane, Liverpool, UKAbstract: The prevalence of diet-induced obesity is increasing amongst adults and children worldwide, predisposing millions of people to an array of health problems that include metabolic syndrome, non-alcoholic fatty liver disease and non-alcoholic steatohepatitis. In this study we used experimental animals to investigate the effects of dietary obesity on markers of hepatic insulin signaling as well as structural changes in hepatocytes. Adult male Wistar rats were randomized and assigned to either a control group or a test group. Controls were fed standard laboratory pelleted diet (chow-fed, while the test group had free access to a highly-palatable diet (HPD. After eight weeks, the HPD-fed animals were subdivided into three subgroups and their diets altered as follows: HPD-to-chow, HPD with the addition of fenofibrate given by oral gavage for a further seven weeks, or HPD with vehicle (1% carboxymethylcellulose at 1 mL/kg body weight given by oral gavage for a further seven weeks, respectively. Untreated diet-fed animals had significantly higher body weight, liver weight, and all measured metabolic profiles compared with chow-fed and treated diet-fed groups. Expression of kinases IRβ, IRS-1, AKt, eNOS, Shc and ERK1/2 were unaffected by obesity, while IRS-2 and P I3 kinase levels were significantly reduced in untreated HPD animals. Compared with chow-fed animals, steatosis and steatohepatitis were almost doubled in animals from untreated HPD, while removal of HPD and fenofibrate-treatment reduced steatosis by 40% and 80% respectively. These data suggest that diet-induced obesity affects

Nutrient sensing and insulin signaling in neuropeptide-expressing immortalized, hypothalamic neurons: A cellular model of insulin resistance.

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Fick, Laura J; Belsham, Denise D

2010-08-15

Obesity and type 2 diabetes mellitus represent a significant global health crisis. These two interrelated diseases are typified by perturbed insulin signaling in the hypothalamus. Using novel hypothalamic cell lines, we have begun to elucidate the molecular and intracellular mechanisms involved in the hypothalamic control of energy homeostasis and insulin resistance. In this review, we present evidence of insulin and glucose signaling pathways that lead to changes in neuropeptide gene expression. We have identified some of the molecular mechanisms involved in the control of de novo hypothalamic insulin mRNA expression. And finally, we have defined key mechanisms involved in the etiology of cellular insulin resistance in hypothalamic neurons that may play a fundamental role in cases of high levels of insulin or saturated fatty acids, often linked to the exacerbation of obesity and diabetes.

Brain insulin signaling and Alzheimer's disease: current evidence and future directions.

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Schiöth, Helgi B; Craft, Suzanne; Brooks, Samantha J; Frey, William H; Benedict, Christian

2012-08-01

Insulin receptors in the brain are found in high densities in the hippocampus, a region that is fundamentally involved in the acquisition, consolidation, and recollection of new information. Using the intranasal method, which effectively bypasses the blood-brain barrier to deliver and target insulin directly from the nose to the brain, a series of experiments involving healthy humans has shown that increased central nervous system (CNS) insulin action enhances learning and memory processes associated with the hippocampus. Since Alzheimer's disease (AD) is linked to CNS insulin resistance, decreased expression of insulin and insulin receptor genes and attenuated permeation of blood-borne insulin across the blood-brain barrier, impaired brain insulin signaling could partially account for the cognitive deficits associated with this disease. Considering that insulin mitigates hippocampal synapse vulnerability to amyloid beta and inhibits the phosphorylation of tau, pharmacological strategies bolstering brain insulin signaling, such as intranasal insulin, could have significant therapeutic potential to deter AD pathogenesis.

Activin signaling targeted by insulin/dFOXO regulates aging and muscle proteostasis in Drosophila.

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Hua Bai

2013-11-01

Full Text Available Reduced insulin/IGF signaling increases lifespan in many animals. To understand how insulin/IGF mediates lifespan in Drosophila, we performed chromatin immunoprecipitation-sequencing analysis with the insulin/IGF regulated transcription factor dFOXO in long-lived insulin/IGF signaling genotypes. Dawdle, an Activin ligand, is bound and repressed by dFOXO when reduced insulin/IGF extends lifespan. Reduced Activin signaling improves performance and protein homeostasis in muscles of aged flies. Activin signaling through the Smad binding element inhibits the transcription of Autophagy-specific gene 8a (Atg8a within muscle, a factor controlling the rate of autophagy. Expression of Atg8a within muscle is sufficient to increase lifespan. These data reveal how insulin signaling can regulate aging through control of Activin signaling that in turn controls autophagy, representing a potentially conserved molecular basis for longevity assurance. While reduced Activin within muscle autonomously retards functional aging of this tissue, these effects in muscle also reduce secretion of insulin-like peptides at a distance from the brain. Reduced insulin secretion from the brain may subsequently reinforce longevity assurance through decreased systemic insulin/IGF signaling.

Brain Insulin Signaling Is Increased in Insulin-Resistant States and Decreases in FOXOs and PGC-1α and Increases in Aβ1–40/42 and Phospho-Tau May Abet Alzheimer Development

Science.gov (United States)

Sajan, Mini; Hansen, Barbara; Ivey, Robert; Sajan, Joshua; Ari, Csilla; Song, Shijie; Braun, Ursula; Leitges, Michael; Farese-Higgs, Margaret

2016-01-01

Increased coexistence of Alzheimer disease (AD) and type 2 diabetes mellitus (T2DM) suggests that insulin resistance abets neurodegenerative processes, but linkage mechanisms are obscure. Here, we examined insulin signaling factors in brains of insulin-resistant high-fat–fed mice, ob/ob mice, mice with genetically impaired muscle glucose transport, and monkeys with diet-dependent long-standing obesity/T2DM. In each model, the resting/basal activities of insulin-regulated brain protein kinases, Akt and atypical protein kinase C (aPKC), were maximally increased. Moreover, Akt hyperactivation was accompanied by hyperphosphorylation of substrates glycogen synthase kinase-3β and mammalian target of rapamycin and FOXO proteins FOXO1, FOXO3A, and FOXO4 and decreased peroxisome proliferator–activated receptor γ coactivator-1α (PGC-1α) expression. Akt hyperactivation was confirmed in individual neurons of anterocortical and hippocampal regions that house cognition/memory centers. Remarkably, β-amyloid (Aβ1–40/42) peptide levels were as follows: increased in the short term by insulin in normal mice, increased basally in insulin-resistant mice and monkeys, and accompanied by diminished amyloid precursor protein in monkeys. Phosphorylated tau levels were increased in ob/ob mice and T2DM monkeys. Importantly, with correction of hyperinsulinemia by inhibition of hepatic aPKC and improvement in systemic insulin resistance, brain insulin signaling normalized. As FOXOs and PGC-1α are essential for memory and long-term neuronal function and regeneration and as Aβ1–40/42 and phospho-tau may increase interneuronal plaques and intraneuronal tangles, presently observed aberrations in hyperinsulinemic states may participate in linking insulin resistance to AD. PMID:26895791

Significance of glucagon for insulin secretion and hepatic glycogenolysis during exercise in rats

DEFF Research Database (Denmark)

Richter, Erik; Galbo, H; Holst, J J

1981-01-01

The significance of glucagon and of the sympatho-adrenal system for insulin secretion and hepatic glycogen depletion during exercise was studied. Male rats were either adrenodemedullated and chemically sympathectomized with 6-hydroxydopamine (SX) or sham-treated (C). During light ether anesthesia......, cardiac blood for glucose analysis and a biopsy of the liver were obtained, and either antigen-stripped glucagon antibodies (A) or control gamma globulins (N) in saline were injected through the cardiac cannula. Subsequently, the rats swam in tepid water (33-34 degree C) for 100 minutes with a tail weight...... attached (2% of body weight). Then cardiac blood was drawn for analysis of glucose, insulin and glucagon, and a sample of the liver was collected. In both CA and CN rats, the blood glucose concentration tended to increase (p less than 0.1) during exercise, whereas hepatic glycogen depletion and the plasma...

Insulin and C peptide response, and antibody levels in hepatitis C related chronic liver disease

International Nuclear Information System (INIS)

Abbas, Z.; Tariq, N.; Iqbal, M.; Shah, M.A.

2002-01-01

Objective: Patients with cirrhosis due to hepatitis C (HC) have an increased prevalence of diabetes mellitus. The pathogenic mechanism by which HC predisposes to DM is not clear. The objective of this study was to determine the insulin and C-peptide response to 75 gram oral glucose load and measure anti phospholipid antibody levels in patients with chronic liver disease due to HC. Design: a prospective study. Place and duration of study: This study was conducted at the department of medicine, Jinnah postgraduate medical centre over period of three months. Subjects and methods: An analytical case control study was carried out on 37 patients (m-18,f=19); none of these patients had received interferon. They were divided into four groups: (a) HC cirrhosis with DM (n=9 ), (b) HC cirrhosis without DM (n=11), (c) hepatitis B (HB) cirrhosis without DM (n=7), (d) chronic hepatitis C without DM (n=10). Group C and D were taken as controls. Fasting blood samples were taken and repeated after 2 hours of 75 gram oral glucose load (2 h PG). Result: mean ages of group A,B,C and D were (yr +- SD) 51.3 +- 7.6,48.9 +- 2.4, 33.7 +-10.8 and 31.7 +- 8.8 respectively. There was no statistically significant difference in the age, Pugh score and body mass index of HC cirrhotic patients with and without DM. Patients of group A had higher fasting and 2 h PG glucose levels (P=0.003 and 0.000) and higher fasting insulin level (p=0.045). However, increments in insulin and c peptide levels 2 h PG were much less (p=0.048 and 0.003). HB cirrhotics without diabetes (group C behaved just like HC cirrhotic without diabetes (group B). Patients of group D had normal glucose tolerance and insulin and C peptide levels. All four groups had normal anti phospholipid antibody levels. Conclusion: Patients with cirrhosis due to HC nd HB show evidence of glucose intolerance in spite of hyperinsulinaemia probably due to insulin resistance. HC cirrhotics with diabetes have fasting hyperglycemia in spite of

Strength Exercise Improves Muscle Mass and Hepatic Insulin Sensitivity in Obese Youth

NARCIS (Netherlands)

Van Der Heijden, Gert-Jan; Wang, Zhiyue J.; Chu, Zili; Toffolo, Gianna; Manesso, Erica; Sauer, Pieter J. J.; Sunehag, Agneta L.

VAN DER HEIJDEN, G.-J., Z. J. WANG, Z. CHU, G. TOFFOLO, E. MANESSO, P. J. J. SAUER, and A. L. SUNEHAG. Strength Exercise Improves Muscle Mass and Hepatic Insulin Sensitivity in Obese Youth. Med. Sci. Sports Exerc., Vol. 42, No. 11, pp. 1973-1980, 2010. Introduction: Data on the metabolic effects of

Strength Exercise Improves Muscle Mass and Hepatic Insulin Sensitivity in Obese Youth

NARCIS (Netherlands)

Van Der Heijden, Gert-Jan; Wang, Zhiyue J.; Chu, Zili; Toffolo, Gianna; Manesso, Erica; Sauer, Pieter J. J.; Sunehag, Agneta L.

2010-01-01

VAN DER HEIJDEN, G.-J., Z. J. WANG, Z. CHU, G. TOFFOLO, E. MANESSO, P. J. J. SAUER, and A. L. SUNEHAG. Strength Exercise Improves Muscle Mass and Hepatic Insulin Sensitivity in Obese Youth. Med. Sci. Sports Exerc., Vol. 42, No. 11, pp. 1973-1980, 2010. Introduction: Data on the metabolic effects of

Insulin Signaling in the Aging of Healthy and Proteotoxically Stressed Mechanosensory Neurons

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Courtney eScerbak

2014-07-01

Full Text Available Insulin signaling is central to cellular metabolism and organismal aging. However, the role of insulin signaling in natural and proteotoxically stressed aging neurons has yet to be fully described. We studied aging of Caenorbaditis elegans mechanosensory neurons expressing a neurotoxic expanded polyglutamine transgene (polyQ128, or lacking this proteotoxicity stressor (polyQ0, under conditions in which the insulin signaling pathway was disrupted by RNA interference (RNAi. We describe specific changes in lifespan, mechanosensory neuronal morphologies, and mechansensory function following RNAi treatment targeting the insulin signaling pathway. Overall, we confirmed that transcription factor DAF-16 is neuroprotective in the proteotoxically stressed model, though not strikingly in the naturally aging model. Decreased insulin signaling through daf-2 RNAi improved mechanosensory function in both models and decreased protein aggregation load in polyQ128, yet showed opposing effects on accumulation of neuronal aberrations in both strains. Decreased daf-2 signaling slightly enhanced mechanosensation while greatly enhancing branching of the mechanosensory neuron axons and dendrites in polyQ0 animals, suggesting that branching is an adaptive response in natural aging. These effects in polyQ0 did not appear to involve DAF-16, suggesting the existence of a non-canonical DAF-2 pathway for the modulation of morphological adaptation. However, in polyQ128 animals, decreased daf-2 signaling significantly enhanced mechanosensation while decreasing neuronal aberrations. Unlike other interventions that reduce the strength of insulin signaling, daf-2 RNAi dramatically redistributed large polyQ128 aggregates to the cell body, away from neuronal processes. Our results suggest that insulin signaling strength can differentially affect specific neurons aging naturally or under proteotoxic stress.

A maternal high-fat, high-sucrose diet alters insulin sensitivity and expression of insulin signalling and lipid metabolism genes and proteins in male rat offspring: effect of folic acid supplementation.

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Cuthbert, Candace E; Foster, Jerome E; Ramdath, D Dan

2017-10-01

A maternal high-fat, high-sucrose (HFS) diet alters offspring glucose and lipid homoeostasis through unknown mechanisms and may be modulated by folic acid. We investigated the effect of a maternal HFS diet on glucose homoeostasis, expression of genes and proteins associated with insulin signalling and lipid metabolism and the effect of prenatal folic acid supplementation (HFS/F) in male rat offspring. Pregnant Sprague-Dawley rats were randomly fed control (CON), HFS or HFS/F diets. Offspring were weaned on CON; at postnatal day 70, fasting plasma insulin and glucose and liver and skeletal muscle gene and protein expression were measured. Treatment effects were assessed by one-way ANOVA. Maternal HFS diet induced higher fasting glucose in offspring v. HFS/F (P=0·027) and down-regulation (Pinsulin resistance v. CON (P=0·030) and HFS/F was associated with higher insulin (P=0·016) and lower glucose (P=0·025). Maternal HFS diet alters offspring insulin sensitivity and de novo hepatic lipogenesis via altered gene and protein expression, which appears to be potentiated by folate supplementation.

Black Seed Thymoquinone Improved Insulin Secretion, Hepatic Glycogen Storage, and Oxidative Stress in Streptozotocin-Induced Diabetic Male Wistar Rats

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Heba M. A. Abdelrazek

2018-01-01

Full Text Available Diabetes mellitus is one of the metabolic diseases having several complications. Nigella sativa oil (NSO might have beneficial effects in the treatment of diabetic complications. Thirty-two mature male Wistar rats were equally divided into four experimental groups: control, control NSO 2 mL/kg, streptozotocin- (STZ- induced diabetic, and diabetic (STZ-induced treated with oral NSO 2 mg/kg for 30 days. Fasting blood glucose (FBG, insulin, and lipid profile levels were determined. Pancreatic and hepatic tissues were used for catalase and GSH. Histopathology, hepatic glycogen contents, insulin immunohistochemistry, and pancreatic islet morphometry were performed. NSO 2 mL/kg was noticed to decrease (P<0.05 FBG and increase (P<0.05 insulin levels in diabetic rats than in diabetic nontreated animals. Lipid profile showed significant (P<0.5 improvement in diabetic rats that received NSO 2 mL/kg than in the diabetic group. Both pancreatic and hepatic catalase and GSH activities revealed a significant (P<0.05 increment in the diabetic group treated with NSO than in the diabetic animals. NSO improved the histopathological picture and hepatic glycogen contents of the diabetic group as well as increased (P<0.05 insulin immunoreactive parts % and mean pancreatic islet diameter. NSO exerts ameliorative and therapeutic effects on the STZ-induced diabetic male Wistar rats.

Hepatic Expression of Adenovirus 36 E4ORF1 Improves Glycemic Control and Promotes Glucose Metabolism Through AKT Activation.

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McMurphy, Travis B; Huang, Wei; Xiao, Run; Liu, Xianglan; Dhurandhar, Nikhil V; Cao, Lei

2017-02-01

Considering that impaired proximal insulin signaling is linked with diabetes, approaches that enhance glucose disposal independent of insulin signaling are attractive. In vitro data indicate that the E4ORF1 peptide derived from human adenovirus 36 (Ad36) interacts with cells from adipose tissue, skeletal muscle, and liver to enhance glucose disposal, independent of proximal insulin signaling. Adipocyte-specific expression of Ad36E4ORF1 improves hyperglycemia in mice. To determine the hepatic interaction of Ad36E4ORF1 in enhancing glycemic control, we expressed E4ORF1 of Ad36 or Ad5 or fluorescent tag alone by using recombinant adeno-associated viral vector in the liver of three mouse models. In db/db or diet-induced obesity (DIO) mice, hepatic expression of Ad36E4ORF1 but not Ad5E4ORF1 robustly improved glycemic control. In normoglycemic wild-type mice, hepatic expression of Ad36E4ORF1 lowered nonfasting blood glucose at a high dose of expression. Of note, Ad36E4ORF1 significantly reduced insulin levels in db/db and DIO mice. The improvement in glycemic control was observed without stimulation of the proximal insulin signaling pathway. Collectively, these data indicate that Ad36E4ORF1 is not a typical sensitizer, mimetic, or secretagogue of insulin. Instead, it may have insulin-sparing action, which seems to reduce the need for insulin and, hence, to reduce insulin levels. © 2017 by the American Diabetes Association.

Brain Insulin Signaling Is Increased in Insulin-Resistant States and Decreases in FOXOs and PGC-1α and Increases in Aβ1-40/42 and Phospho-Tau May Abet Alzheimer Development.

Science.gov (United States)

Sajan, Mini; Hansen, Barbara; Ivey, Robert; Sajan, Joshua; Ari, Csilla; Song, Shijie; Braun, Ursula; Leitges, Michael; Farese-Higgs, Margaret; Farese, Robert V

2016-07-01

Increased coexistence of Alzheimer disease (AD) and type 2 diabetes mellitus (T2DM) suggests that insulin resistance abets neurodegenerative processes, but linkage mechanisms are obscure. Here, we examined insulin signaling factors in brains of insulin-resistant high-fat-fed mice, ob/ob mice, mice with genetically impaired muscle glucose transport, and monkeys with diet-dependent long-standing obesity/T2DM. In each model, the resting/basal activities of insulin-regulated brain protein kinases, Akt and atypical protein kinase C (aPKC), were maximally increased. Moreover, Akt hyperactivation was accompanied by hyperphosphorylation of substrates glycogen synthase kinase-3β and mammalian target of rapamycin and FOXO proteins FOXO1, FOXO3A, and FOXO4 and decreased peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) expression. Akt hyperactivation was confirmed in individual neurons of anterocortical and hippocampal regions that house cognition/memory centers. Remarkably, β-amyloid (Aβ1-40/42) peptide levels were as follows: increased in the short term by insulin in normal mice, increased basally in insulin-resistant mice and monkeys, and accompanied by diminished amyloid precursor protein in monkeys. Phosphorylated tau levels were increased in ob/ob mice and T2DM monkeys. Importantly, with correction of hyperinsulinemia by inhibition of hepatic aPKC and improvement in systemic insulin resistance, brain insulin signaling normalized. As FOXOs and PGC-1α are essential for memory and long-term neuronal function and regeneration and as Aβ1-40/42 and phospho-tau may increase interneuronal plaques and intraneuronal tangles, presently observed aberrations in hyperinsulinemic states may participate in linking insulin resistance to AD. © 2016 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.

Intracellular compartmentalization of skeletal muscle glycogen metabolism and insulin signalling

DEFF Research Database (Denmark)

Prats Gavalda, Clara; Gomez-Cabello, Alba; Vigelsø Hansen, Andreas

2011-01-01

The interest in skeletal muscle metabolism and insulin signalling has increased exponentially in recent years as a consequence of their role in the development of type 2 diabetes mellitus. Despite this, the exact mechanisms involved in the regulation of skeletal muscle glycogen metabolism...... and insulin signalling transduction remain elusive. We believe that one of the reasons is that the role of intracellular compartmentalization as a regulator of metabolic pathways and signalling transduction has been rather ignored. This paper briefly reviews the literature to discuss the role of intracellular...... compartmentalization in the regulation of skeletal muscle glycogen metabolism and insulin signalling. As a result, a hypothetical regulatory mechanism is proposed by which cells could direct glycogen resynthesis towards different pools of glycogen particles depending on the metabolic needs. Furthermore, we discuss...

Exenatide improves both hepatic and adipose tissue insulin resistance: A dynamic positron emission tomography study.

Science.gov (United States)

Gastaldelli, Amalia; Gaggini, Melania; Daniele, Giuseppe; Ciociaro, Demetrio; Cersosimo, Eugenio; Tripathy, Devjit; Triplitt, Curtis; Fox, Peter; Musi, Nicolas; DeFronzo, Ralph; Iozzo, Patricia

2016-12-01

Glucagon-like peptide 1 (GLP-1) receptor agonists (GLP-1-RAs) act on multiple tissues, in addition to the pancreas. Recent studies suggest that GLP-1-RAs act on liver and adipose tissue to reduce insulin resistance (IR). Thus, we evaluated the acute effects of exenatide (EX) on hepatic (Hep-IR) and adipose (Adipo-IR) insulin resistance and glucose uptake. Fifteen male subjects (age = 56 ± 8 years; body mass index = 29 ± 1 kg/m 2 ; A1c = 5.7 ± 0.1%) were studied on two occasions, with a double-blind subcutaneous injection of EX (5 μg) or placebo (PLC) 30 minutes before a 75-g oral glucose tolerance test (OGTT). During OGTT, we measured hepatic (HGU) and adipose tissue (ATGU) glucose uptake with [ 18 F]2-fluoro-2-deoxy-D-glucose/positron emission tomography, lipolysis (RaGly) with [U- 2 H 5 ]-glycerol, oral glucose absorption (RaO) with [U- 13 C 6 ]-glucose, and hepatic glucose production (EGP) with [6,6- 2 H 2 ]-glucose. Adipo-IR and Hep-IR were calculated as (FFA 0-120min ) × (Ins 0-120min ) and (EGP 0-120min ) × (Ins 0-120min ), respectively. EX reduced RaO, resulting in reduced plasma glucose and insulin concentration from 0 to 120 minutes postglucose ingestion. EX decreased Hep-IR (197 ± 28 to 130 ± 37; P = 0.02) and increased HGU of orally administered glucose (23 ± 4 to 232 ± 89 [μmol/min/L]/[μmol/min/kg]; P = 0.003) despite lower insulin (23 ± 5 vs. 41 ± 5 mU/L; P < 0.02). EX enhanced insulin suppression of RaGly by decreasing Adipo-IR (23 ± 4 to 13 ± 3; P = 0.009). No significant effect of insulin was observed on ATGU (EX = 1.16 ± 0.15 vs. PLC = 1.36 ± 0.13 [μmol/min/L]/[μmol/min/kg]). Acute EX administration (1) improves Hep-IR, decreases EGP, and enhances HGU and (2) reduces Adipo-IR, improves the antilipolytic effect of insulin, and reduces plasma free fatty acid levels during OGTT. (Hepatology 2016;64:2028-2037). © 2016 by the American Association for the Study of Liver Diseases.

Peripheral insulin resistance and impaired insulin signaling contribute to abnormal glucose metabolism in preterm baboons.

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Blanco, Cynthia L; McGill-Vargas, Lisa L; Gastaldelli, Amalia; Seidner, Steven R; McCurnin, Donald C; Leland, Michelle M; Anzueto, Diana G; Johnson, Marney C; Liang, Hanyu; DeFronzo, Ralph A; Musi, Nicolas

2015-03-01

Premature infants develop hyperglycemia shortly after birth, increasing their morbidity and death. Surviving infants have increased incidence of diabetes as young adults. Our understanding of the biological basis for the insulin resistance of prematurity and developmental regulation of glucose production remains fragmentary. The objective of this study was to examine maturational differences in insulin sensitivity and the insulin-signaling pathway in skeletal muscle and adipose tissue of 30 neonatal baboons using the euglycemic hyperinsulinemic clamp. Preterm baboons (67% gestation) had reduced peripheral insulin sensitivity shortly after birth (M value 12.5 ± 1.5 vs 21.8 ± 4.4 mg/kg · min in term baboons) and at 2 weeks of age (M value 12.8 ± 2.6 vs 16.3 ± 4.2, respectively). Insulin increased Akt phosphorylation, but these responses were significantly lower in preterm baboons during the first week of life (3.2-fold vs 9.8-fold). Preterm baboons had lower glucose transporter-1 protein content throughout the first 2 weeks of life (8%-12% of term). In preterm baboons, serum free fatty acids (FFAs) did not decrease in response to insulin, whereas FFAs decreased by greater than 80% in term baboons; the impaired suppression of FFAs in the preterm animals was paired with a decreased glucose transporter-4 protein content in adipose tissue. In conclusion, peripheral insulin resistance and impaired non-insulin-dependent glucose uptake play an important role in hyperglycemia of prematurity. Impaired insulin signaling (reduced Akt) contributes to the defect in insulin-stimulated glucose disposal. Counterregulatory hormones are not major contributors.

Vitamin D Signaling Through Induction of Paneth Cell Defensins Maintains Gut Microbiota and Improves Metabolic Disorders and Hepatic Steatosis in Animal Models

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Danmei Su

2016-11-01

Full Text Available Metabolic syndrome (MetS, characterized as obesity, insulin resistance, and non-alcoholic fatty liver diseases (NAFLD，is associated with vitamin D insufficiency/deficiency in epidemiological studies, while the underlying mechanism is poorly addressed. On the other hand, disorder of gut microbiota, namely dysbiosis, is known to cause MetS and NAFLD. It is also known that systemic inflammation blocks insulin signaling pathways, leading to insulin resistance and glucose intolerance, which are the driving force for hepatic steatosis. Vitamin D receptor (VDR is highly expressed in the ileum of the small intestine，which prompted us to test a hypothesis that vitamin D signaling may determine the enterotype of gut microbiota through regulating the intestinal interface. Here, we demonstrate that high-fat-diet feeding (HFD is necessary but not sufficient, while additional vitamin D deficiency (VDD as a second hit is needed, to induce robust insulin resistance and fatty liver. Under the two hits (HFD+VDD, the Paneth cell-specific alpha-defensins including α-defensin 5 (DEFA5, MMP7 which activates the pro-defensins, as well as tight junction genes, and MUC2 are all suppressed in the ileum, resulting in mucosal collapse, increased gut permeability, dysbiosis, endotoxemia, systemic inflammation which underlie insulin resistance and hepatic steatosis. Moreover, under the vitamin D deficient high fat feeding (HFD+VDD, Helicobacter hepaticus, a known murine hepatic-pathogen, is substantially amplified in the ileum, while Akkermansia muciniphila, a beneficial symbiotic, is diminished. Likewise, the VD receptor (VDR knockout mice exhibit similar phenotypes, showing down regulation of alpha-defensins and MMP7 in the ileum, increased Helicobacter hepaticus and suppressed Akkermansia muciniphila. Remarkably, oral administration of DEFA5 restored eubiosys, showing suppression of Helicobacter hepaticus and increase of Akkermansia muciniphila in association with

The Effects of Peripheral and Central High Insulin on Brain Insulin Signaling and Amyloid-β in Young and Old APP/PS1 Mice.

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Stanley, Molly; Macauley, Shannon L; Caesar, Emily E; Koscal, Lauren J; Moritz, Will; Robinson, Grace O; Roh, Joseph; Keyser, Jennifer; Jiang, Hong; Holtzman, David M

2016-11-16

Hyperinsulinemia is a risk factor for late-onset Alzheimer's disease (AD). In vitro experiments describe potential connections between insulin, insulin signaling, and amyloid-β (Aβ), but in vivo experiments are needed to validate these relationships under physiological conditions. First, we performed hyperinsulinemic-euglycemic clamps with concurrent hippocampal microdialysis in young, awake, behaving APP swe /PS1 dE9 transgenic mice. Both a postprandial and supraphysiological insulin clamp significantly increased interstitial fluid (ISF) and plasma Aβ compared with controls. We could detect no increase in brain, ISF, or CSF insulin or brain insulin signaling in response to peripheral hyperinsulinemia, despite detecting increased signaling in the muscle. Next, we delivered insulin directly into the hippocampus of young APP/PS1 mice via reverse microdialysis. Brain tissue insulin and insulin signaling was dose-dependently increased, but ISF Aβ was unchanged by central insulin administration. Finally, to determine whether peripheral and central high insulin has differential effects in the presence of significant amyloid pathology, we repeated these experiments in older APP/PS1 mice with significant amyloid plaque burden. Postprandial insulin clamps increased ISF and plasma Aβ, whereas direct delivery of insulin to the hippocampus significantly increased tissue insulin and insulin signaling, with no effect on Aβ in old mice. These results suggest that the brain is still responsive to insulin in the presence of amyloid pathology but increased insulin signaling does not acutely modulate Aβ in vivo before or after the onset of amyloid pathology. Peripheral hyperinsulinemia modestly increases ISF and plasma Aβ in young and old mice, independent of neuronal insulin signaling. The transportation of insulin from blood to brain is a saturable process relevant to understanding the link between hyperinsulinemia and AD. In vitro experiments have found direct connections

Quercetin suppresses insulin receptor signaling through inhibition of the insulin ligand–receptor binding and therefore impairs cancer cell proliferation

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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.

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

Gallic acid ameliorates hyperglycemia and improves hepatic carbohydrate metabolism in rats fed a high-fructose diet.

Science.gov (United States)

Huang, Da-Wei; Chang, Wen-Chang; Wu, James Swi-Bea; Shih, Rui-Wen; Shen, Szu-Chuan

2016-02-01

Herein, we investigated the hypoglycemic effect of plant gallic acid (GA) on glucose uptake in an insulin-resistant cell culture model and on hepatic carbohydrate metabolism in rats with a high-fructose diet (HFD)-induced diabetes. Our hypothesis is that GA ameliorates hyperglycemia via alleviating hepatic insulin resistance by suppressing hepatic inflammation and improves abnormal hepatic carbohydrate metabolism by suppressing hepatic gluconeogenesis and enhancing the hepatic glycogenesis and glycolysis pathways in HFD-induced diabetic rats. Gallic acid increased glucose uptake activity by 19.2% at a concentration of 6.25 μg/mL in insulin-resistant FL83B mouse hepatocytes. In HFD-induced diabetic rats, GA significantly alleviated hyperglycemia, reduced the values of the area under the curve for glucose in an oral glucose tolerance test, and reduced the scores of the homeostasis model assessment of insulin resistance index. The levels of serum C-peptide and fructosamine and cardiovascular risk index scores were also significantly decreased in HFD rats treated with GA. Moreover, GA up-regulated the expression of hepatic insulin signal transduction-related proteins, including insulin receptor, insulin receptor substrate 1, phosphatidylinositol-3 kinase, Akt/protein kinase B, and glucose transporter 2, in HFD rats. Gallic acid also down-regulated the expression of hepatic gluconeogenesis-related proteins, such as fructose-1,6-bisphosphatase, and up-regulated expression of hepatic glycogen synthase and glycolysis-related proteins, including hexokinase, phosphofructokinase, and aldolase, in HFD rats. Our findings indicate that GA has potential as a health food ingredient to prevent diabetes mellitus. Copyright © 2016 Elsevier Inc. All rights reserved.

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

Interaction between leucine and phosphodiesterase 5 inhibition in modulating insulin sensitivity and lipid metabolism

Directory of Open Access Journals (Sweden)

Fu L

2015-05-01

Full Text Available Lizhi Fu,1 Fenfen Li,1 Antje Bruckbauer,2 Qiang Cao,1 Xin Cui,1 Rui Wu,1 Hang Shi,1 Bingzhong Xue,1 Michael B Zemel21Department of Biology, Center for Obesity Reversal, Georgia State University, Atlanta, GA, 2NuSirt Biopharma Inc., Nashville, TN, USA Purpose: Leucine activates SIRT1/AMP-activated protein kinase (AMPK signaling and markedly potentiates the effects of other sirtuin and AMPK activators on insulin signaling and lipid metabolism. Phosphodiesterase 5 inhibition increases nitric oxide–cGMP signaling, which in turn exhibits a positive feedback loop with both SIRT1 and AMPK, thus amplifying peroxisome proliferator-activated receptor γ co-activator α (PGC1α-mediated effects. Methods: We evaluated potential synergy between leucine and PDE5i on insulin sensitivity and lipid metabolism in vitro and in diet-induced obese (DIO mice. Results: Leucine (0.5 mM exhibited significant synergy with subtherapeutic doses (0.1–10 nM of PDE5-inhibitors (sildenafil and icariin on fat oxidation, nitric oxide production, and mitochondrial biogenesis in hepatocytes, adipocytes, and myotubes. Effects on insulin sensitivity, glycemic control, and lipid metabolism were then assessed in DIO-mice. DIO-mice exhibited fasting and postprandial hyperglycemia, insulin resistance, and hepatic steatosis, which were not affected by the addition of leucine (24 g/kg diet. However, the combination of leucine and a subtherapeutic dose of icariin (25 mg/kg diet for 6 weeks reduced fasting glucose (38%, P<0.002, insulin (37%, P<0.05, area under the glucose tolerance curve (20%, P<0.01, and fully restored glucose response to exogenous insulin challenge. The combination also inhibited hepatic lipogenesis, stimulated hepatic and muscle fatty acid oxidation, suppressed hepatic inflammation, and reversed high-fat diet-induced steatosis. Conclusion: These robust improvements in insulin sensitivity, glycemic control, and lipid metabolism indicate therapeutic potential for

Relationship between adiponectin and hepatic fibrosis markers expressions as well as insulin resistance index in patients with non-alcoholic fatty liver disease

International Nuclear Information System (INIS)

Cui Jianhe; Pan Feng; Zhou Chuanwen; Ren Jianguo; Li Donghai

2009-01-01

Objective: To investigate the retationship between expressions of adiponectin and hepatic fibrosis markers as well as insulin resistance index in patients with non-alcoholic fatty liver disease. Methods: Serum adiponectin, type III pro-collagen (PCIII), hyaluronic acid (HA), type IV collagen (CIV), laminin levels (with ELISA) and insulin resistance index (IRI) (calculated from homeostasis model assessment) were determined in 46 patients with non-alcoholic fatty liver disease (NAFLD) and 46 controls. Results The serum adiponectin levels in patients with NAFLD were significantly lower than those in controls while the serum hepatic fibrosis markers (PCIII, HA, CIV, LN) levels and IRI were significantly higher than those in controls (P<0.05). IRI was significantly positively correlated with the hepatic fibrosis markers levels (P<0.05). Serum adiponectin levels were significantly negatively correlated with WHR, RMI, HOMA-IRI and levels of FRG, TG, FINS hepatic fibrosis markers (P<0.05 or P<0.01). Conclusion: Serum adiponectin levels were greatly reduced in patients with NAFLD, which might play important role in the increase of insulin resistance and development of hepatic fibrosis. (authors)

Interaction of IFNL3 with insulin resistance, steatosis and lipid metabolism in chronic hepatitis C virus infection.

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Eslam, Mohammed; Booth, David R; George, Jacob; Ahlenstiel, Golo

2013-11-07

Metabolic changes are inextricably linked to chronic hepatitis C (CHC). Recently polymorphisms in the IFNL3 (IL28B) region have been shown to be strongly associated with spontaneous and treatment induced recovery from hepatitis C virus (HCV) infection. Further, circumstantial evidence suggests a link between IFNL3 single nucleotide polymorphisms and lipid metabolism, steatosis and insulin resistance in CHC. The emerging picture suggests that the responder genotypes of IFNL3 polymorphisms are associated with a higher serum lipid profile, and less frequent steatosis and insulin resistance. This review analyzes the current data regarding this interaction and its meaning for HCV pathogenesis and disease progression.

Dissociation of hepatic insulin resistance from susceptibility of nonalcoholic fatty liver disease induced by a high-fat and high-carbohydrate diet in mice.

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Asai, Akihiro; Chou, Pauline M; Bu, Heng-Fu; Wang, Xiao; Rao, M Sambasiva; Jiang, Anthony; DiDonato, Christine J; Tan, Xiao-Di

2014-03-01

Liver steatosis in nonalcoholic fatty liver disease is affected by genetics and diet. It is associated with insulin resistance (IR) in hepatic and peripheral tissues. Here, we aimed to characterize the severity of diet-induced steatosis, obesity, and IR in two phylogenetically distant mouse strains, C57BL/6J and DBA/2J. To this end, mice (male, 8 wk old) were fed a high-fat and high-carbohydrate (HFHC) or control diet for 16 wk followed by the application of a combination of classic physiological, biochemical, and pathological studies to determine obesity and hepatic steatosis. Peripheral IR was characterized by measuring blood glucose level, serum insulin level, homeostasis model assessment of IR, glucose intolerance, insulin intolerance, and AKT phosphorylation in adipose tissues, whereas the level of hepatic IR was determined by measuring insulin-triggered hepatic AKT phosphorylation. We discovered that both C57BL/6J and DBA/2J mice developed obesity to a similar degree without the feature of liver inflammation after being fed an HFHC diet for 16 wk. C57BL/6J mice in the HFHC diet group exhibited severe pan-lobular steatosis, a marked increase in hepatic triglyceride levels, and profound peripheral IR. In contrast, DBA/2J mice in the HFHC diet group developed only a mild degree of pericentrilobular hepatic steatosis that was associated with moderate changes in peripheral IR. Interestingly, both C57BL/6J and DBA/2J developed severe hepatic IR after HFHC diet treatment. Collectively, these data suggest that the severity of diet-induced hepatic steatosis is correlated to the level of peripheral IR, not with the severity of obesity and hepatic IR. Peripheral rather than hepatic IR is a dominant factor of pathophysiology in nonalcoholic fatty liver disease.

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

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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.

Metformin attenuates olanzapine-induced hepatic, but not peripheral insulin resistance.

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Remington, Gary J; Teo, Celine; Wilson, Virginia; Chintoh, Araba; Guenette, Melanie; Ahsan, Zohra; Giacca, Adria; Hahn, Margaret K

2015-11-01

Antipsychotics (APs) are linked to diabetes, even without weight gain. Whether anti-diabetic drugs are efficacious in reversing the direct effects of APs on glucose pathways is largely undetermined. We tested two metformin (Met) doses to prevent impairments seen following a dose of olanzapine (Ola) (3 mg/kg); glucokinetics were measured using the hyperinsulinemic-euglycemic clamp (HIEC). Met (150 mg/kg; n=13, or 400 mg/kg; n=11) or vehicle (Veh) (n=11) was administered through gavage preceding an overnight fast, followed by a second dose prior to the HIEC. Eleven additional animals were gavaged with Veh and received a Veh injection during the HIEC (Veh/Veh); all others received Ola. Basal glucose was similar across treatment groups. The Met 400 group had significantly greater glucose appearance (Ra) in the basal period (i.e., before Ola, or hyperinsulinemia) vs other groups. During hyperinsulinemia, glucose infusion rate (GINF) to maintain euglycemia (reflective of whole-body insulin sensitivity) was higher in Veh/Veh vs other groups. Met 150/Ola animals demonstrated increased GINF relative to Veh/Ola during early time points of the HIEC. Glucose utilization during hyperinsulinemia, relative to basal conditions, was significantly higher in Veh/Veh vs other groups. The change in hepatic glucose production (HGP) from basal to hyperinsulinemia demonstrated significantly greater decreases in Veh/Veh and Met 150/Ola groups vs Veh/Ola. Given the increase in basal Ra with Met 400, we measured serum lactate (substrate for HGP), finding increased levels in Met 400 vs Veh and Met 150. In conclusion, Met attenuates hepatic insulin resistance observed with acute Ola administration, but fails to improve peripheral insulin resistance. Use of supra-therapeutic doses of Met may mask metabolic benefits by increasing lactate. © 2015 Society for Endocrinology.

Clearance of Hepatitis C Virus Improves Insulin Resistance During and After Peginterferon and Ribavirin Therapy.

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Chien, Cheng-Hung; Lin, Chih-Lang; Hu, Ching-Chih; Chang, Jia-Jang; Chien, Rong-Nan

2015-12-01

Patients with chronic hepatitis C virus (HCV) infection are at a greater risk of developing insulin resistance (IR). However, little is known about when insulin sensitivity may improve during or after treatment for hepatitis C. In this study, we examined the effect of combination therapy with pegylated interferon-α and ribavirin on IR in patients with chronic HCV infection. We also analyzed factors associated with changes in insulin sensitivity. IR was estimated by homeostasis model assessment (HOMA-IR). HOMA-IR was measured before therapy, during therapy (12 and 24 weeks), and at the end of therapy (EOT; 24 or 48 weeks). We analyzed 78 HCV patients receiving combination therapy. Twenty-two patients (28.2%) exhibited pretreatment IR (HOMA-IR >2.5). In all patients, HOMA-IR was not significantly different from baseline values at 12 weeks (P = 0.823), 24 weeks (P = 0.417), or at EOT (P = 0.158). In patients with pretreatment IR, a significant decrease in HOMA-IR was observed at 12 weeks (P = 0.023), 24 weeks (P = 0.008), and at EOT (P = 0.002). Multivariate analysis using a logistic regression model showed that baseline HOMA-IR is the only factor associated with the decline in HOMA-IR during and after therapy. The eradication of HCV infection was associated with improved insulin sensitivity among patients with pretreatment IR. This significant improvement in insulin sensitivity may occur as early as 12 weeks after the initiation of antiviral therapy.

Genetic ablation or chemical inhibition of phosphatidylcholine transfer protein attenuates diet-induced hepatic glucose production.

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Shishova, Ekaterina Y; Stoll, Janis M; Ersoy, Baran A; Shrestha, Sudeep; Scapa, Erez F; Li, Yingxia; Niepel, Michele W; Su, Ya; Jelicks, Linda A; Stahl, Gregory L; Glicksman, Marcie A; Gutierrez-Juarez, Roger; Cuny, Gregory D; Cohen, David E

2011-08-01

Phosphatidylcholine transfer protein (PC-TP, synonym StARD2) is a highly specific intracellular lipid binding protein that is enriched in liver. Coding region polymorphisms in both humans and mice appear to confer protection against measures of insulin resistance. The current study was designed to test the hypotheses that Pctp-/- mice are protected against diet-induced increases in hepatic glucose production and that small molecule inhibition of PC-TP recapitulates this phenotype. Pctp-/- and wildtype mice were subjected to high-fat feeding and rates of hepatic glucose production and glucose clearance were quantified by hyperinsulinemic euglycemic clamp studies and pyruvate tolerance tests. These studies revealed that high-fat diet-induced increases in hepatic glucose production were markedly attenuated in Pctp-/- mice. Small molecule inhibitors of PC-TP were synthesized and their potencies, as well as mechanism of inhibition, were characterized in vitro. An optimized inhibitor was administered to high-fat-fed mice and used to explore effects on insulin signaling in cell culture systems. Small molecule inhibitors bound PC-TP, displaced phosphatidylcholines from the lipid binding site, and increased the thermal stability of the protein. Administration of the optimized inhibitor to wildtype mice attenuated hepatic glucose production associated with high-fat feeding, but had no activity in Pctp-/- mice. Indicative of a mechanism for reducing glucose intolerance that is distinct from commonly utilized insulin-sensitizing agents, the inhibitor promoted insulin-independent phosphorylation of key insulin signaling molecules. These findings suggest PC-TP inhibition as a novel therapeutic strategy in the management of hepatic insulin resistance. Copyright © 2011 American Association for the Study of Liver Diseases.

Fibroblast Growth Factor 21 Mediates Glycemic Regulation by Hepatic JNK

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Santiago Vernia

2016-03-01

Full Text Available The cJun NH2-terminal kinase (JNK-signaling pathway is implicated in metabolic syndrome, including dysregulated blood glucose concentration and insulin resistance. Fibroblast growth factor 21 (FGF21 is a target of the hepatic JNK-signaling pathway and may contribute to the regulation of glycemia. To test the role of FGF21, we established mice with selective ablation of the Fgf21 gene in hepatocytes. FGF21 deficiency in the liver caused marked loss of FGF21 protein circulating in the blood. Moreover, the protective effects of hepatic JNK deficiency to suppress metabolic syndrome in high-fat diet-fed mice were not observed in mice with hepatocyte-specific FGF21 deficiency, including reduced blood glucose concentration and reduced intolerance to glucose and insulin. Furthermore, we show that JNK contributes to the regulation of hepatic FGF21 expression during fasting/feeding cycles. These data demonstrate that the hepatokine FGF21 is a key mediator of JNK-regulated metabolic syndrome.

Diabetes mellitus, insulin resistance and hepatitis C virus infection: A contemporary review.

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Desbois, Anne-Claire; Cacoub, Patrice

2017-03-07

To summarise the literature data on hepatitis C virus (HCV)-infected patients concerning the prevalence of glucose abnormalities and associated risk. We conducted a PubMed search and selected all studies found with the key words "HCV" or "hepatitis C virus" and "diabetes" or "insulin resistance". We included only comparative studies written in English or in French, published from January 2000 to April 2015. We collected the literature data on HCV-infected patients concerning the prevalence of glucose abnormalities [diabetes mellitus (DM) and insulin resistance (IR)] and associated risk [ i.e ., severe liver fibrosis, response to antivirals, and the occurrence of hepatocellular carcinoma (HCC)]. HCV infection is significantly associated with DM/IR compared with healthy volunteers and patients with hepatitis B virus infection. Glucose abnormalities were associated with advanced liver fibrosis, lack of sustained virologic response to interferon alfa-based treatment and with a higher risk of HCC development. As new antiviral therapies may offer a cure for HCV infection, such data should be taken into account, from a therapeutic and preventive point of view, for liver and non-liver consequences of HCV disease. The efficacy of antidiabetic treatment in improving the response to antiviral treatment and in decreasing the risk of HCC has been reported by some studies but not by others. Thus, the effects of glucose abnormalities correction in reducing liver events need further studies. Glucose abnormalities are strongly associated with HCV infection and show a negative impact on the main liver related outcomes.

Dietary fat and carbohydrates differentially alter insulin sensitivity during caloric restriction.

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Kirk, Erik; Reeds, Dominic N; Finck, Brian N; Mayurranjan, S Mitra; Mayurranjan, Mitra S; Patterson, Bruce W; Klein, Samuel

2009-05-01

We determined the effects of acute and chronic calorie restriction with either a low-fat, high-carbohydrate (HC) diet or a low-carbohydrate (LC) diet on hepatic and skeletal muscle insulin sensitivity. Twenty-two obese subjects (body mass index, 36.5 +/- 0.8 kg/m2) were randomized to an HC (>180 g/day) or LC (vs 8.9% +/- 1.4%; P vs 7.2% +/- 1.4%; P vs 7.9% +/- 1.2%; P < .05). Insulin-mediated glucose uptake did not change at 48 hours but increased similarly in both groups after 7% weight loss (48.4% +/- 14.3%; P < .05). In both groups, insulin-stimulated phosphorylation of c-Jun-N-terminal kinase decreased by 29% +/- 13% and phosphorylation of Akt and insulin receptor substrate 1 increased by 35% +/- 9% and 36% +/- 9%, respectively, after 7% weight loss (all P < .05). Moderate calorie restriction causes temporal changes in liver and skeletal muscle metabolism; 48 hours of calorie restriction affects the liver (IHTG content, hepatic insulin sensitivity, and glucose production), whereas moderate weight loss affects muscle (insulin-mediated glucose uptake and insulin signaling).

Hepatic and extrahepatic responses to insulin in NIDDM and nondiabetic humans. Assessment in absence of artifact introduced by tritiated nonglucose contaminants

International Nuclear Information System (INIS)

Butler, P.C.; Kryshak, E.J.; Schwenk, W.F.; Haymond, M.W.; Rizza, R.A.

1990-01-01

It is well established that patients with non-insulin-dependent diabetes mellitus (NIDDM) are resistant to insulin. However, the contribution of hepatic and extrahepatic tissues to insulin resistance remains controversial. The uncertainty may be at least in part due to errors introduced by the unknowing use in previous studies of impure isotopes to measure glucose turnover. To determine hepatic and extrahepatic responses to insulin in the absence of these errors, steady-state glucose turnover was measured simultaneously with [6-3H]- and [6-14C]glucose during sequential 5- and 4-h infusions of insulin at rates of 0.4 and 10 mU.kg-1.min-1 in diabetic and nondiabetic subjects. At low insulin concentrations, [6-3H]- and [6-14C]glucose gave similar estimates of glucose turnover. Hepatic glucose release was equal to but not below zero in the nondiabetic subjects, but persistent glucose release (P less than 0.001) and decreased glucose uptake (P less than 0.001) was observed in the diabetic patients. At high insulin concentrations, both isotopes underestimated glucose turnover during the 1st h after initiation of the high-dose insulin infusion. More time (P less than 0.05) was required to reachieve steady state in NIDDM than nondiabetic subjects. At steady state, [6-3H]- but not [6-14C]glucose systematically underestimated (P less than 0.05) glucose turnover in both groups due to the presence of a tritiated nonglucose contaminant. The percentage of radioactivity in plasma due to tritiated contaminants was linearly related to turnover

Alternative translation initiation of Caveolin-2 desensitizes insulin signaling through dephosphorylation of insulin receptor by PTP1B and causes insulin resistance.

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Kwon, Hayeong; Jang, Donghwan; Choi, Moonjeong; Lee, Jaewoong; Jeong, Kyuho; Pak, Yunbae

2018-06-01

Insulin resistance, defined as attenuated sensitivity responding to insulin, impairs insulin action. Direct causes and molecular mechanisms of insulin resistance have thus far remained elusive. Here we show that alternative translation initiation (ATI) of Caveolin-2 (Cav-2) regulates insulin sensitivity. Cav-2β isoform yielded by ATI desensitizes insulin receptor (IR) via dephosphorylation by protein-tyrosine phosphatase 1B (PTP1B), and subsequent endocytosis and lysosomal degradation of IR, causing insulin resistance. Blockage of Cav-2 ATI protects against insulin resistance by preventing Cav-2β-PTP1B-directed IR desensitization, thereby normalizing insulin sensitivity and glucose uptake. Our findings show that Cav-2β is a negative regulator of IR signaling, and identify a mechanism causing insulin resistance through control of insulin sensitivity via Cav-2 ATI. Copyright © 2018 Elsevier B.V. All rights reserved.

Astrocytic Insulin Signaling Couples Brain Glucose Uptake with Nutrient Availability

NARCIS (Netherlands)

García-Cáceres, Cristina; Quarta, Carmelo; Varela, Luis; Gao, Yuanqing; Gruber, Tim; Legutko, Beata; Jastroch, Martin; Johansson, Pia; Ninkovic, Jovica; Yi, Chun-Xia; Le Thuc, Ophelia; Szigeti-Buck, Klara; Cai, Weikang; Meyer, Carola W.; Pfluger, Paul T.; Fernandez, Ana M.; Luquet, Serge; Woods, Stephen C.; Torres-Alemán, Ignacio; Kahn, C. Ronald; Götz, Magdalena; Horvath, Tamas L.; Tschöp, Matthias H.

2016-01-01

We report that astrocytic insulin signaling co-regulates hypothalamic glucose sensing and systemic glucose metabolism. Postnatal ablation of insulin receptors (IRs) in glial fibrillary acidic protein (GFAP)-expressing cells affects hypothalamic astrocyte morphology, mitochondrial function, and

Visceral fat dominant distribution in male type 2 diabetic patients is closely related to hepatic insulin resistance, irrespective of body type

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Miyazaki Yoshinori

2009-08-01

Full Text Available Abstract Background All previous studies that investigated the association between abdominal fat distribution and insulin resistance evaluated subcutaneous and visceral fat area and/or volume, but these values were not related to the body type of each subject. In the present study we have examined the association between abdominal fat distribution and peripheral (muscle/hepatic sensitivity to insulin using the visceral to abdominal subcutaneous fat area ratio (VF/SF ratio in male patients with type 2 diabetes mellitus. This ratio defines the predominancy of visceral or subcutaneous abdominal adiposity, independent of the body type of each individual. Methods Thirty-six type 2 diabetic male patients underwent a euglycemic insulin clamp (insulin infusion rate = 40 mU/m2·min with 3-3H-glucose to measure insulin-mediated total body (primarily reflects muscle glucose disposal (TGD and suppression of endogenous (primarily reflects liver glucose production (EGP in response to a physiologic increase in plasma insulin concentration. Abdominal subcutaneous (SF and intraabdominal visceral fat (VF areas were quantitated with magnetic resonance imaging (MRI at the level of L4–5. Results TGD and TGD divided by steady state plasma insulin concentration during the insulin clamp (TGD/SSPI correlated inversely with body mass index (BMI, total fat mass (FM measured by 3H2O, SF and VF areas, while VF/SF ratio displayed no significant relationship with TGD or TGD/SSPI. In contrast, EGP and the product of EGP and SSPI during the insulin clamp (an index hepatic insulin resistance correlated positively with VF/SF ratio, but not with BMI, FM, VF or SF. Conclusion We conclude that, independent of the individual's body type, visceral fat dominant accumulation as opposed to subcutaneous fat accumulation is associated with hepatic insulin resistance, whereas peripheral (muscle insulin resistance is more closely related to general obesity (i.e. higher BMI and total FM

Roles of circulating WNT-signaling proteins and WNT-inhibitors in human adiposity, insulin resistance, insulin secretion, and inflammation.

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Almario, R U; Karakas, S E

2015-02-01

Wingless-type MMTV integration site family member (WNT) signaling and WNT-inhibitors have been implicated in regulation of adipogenesis, insulin resistance, pancreatic function, and inflammation. Our goal was to determine serum proteins involved in WNT signaling (WNT5 and WISP2) and WNT inhibition (SFRP4 and SFRP5) as they relate to obesity, serum adipokines, insulin resistance, insulin secretion, and inflammation in humans. Study population comprised 57 insulin resistant women with polycystic ovary syndrome (PCOS) and 27 reference women. In a cross-sectional study, blood samples were obtained at fasting, during oral, and frequently sampled intravenous glucose tolerance tests. Serum WNT5, WISP2, and SFRP4 concentrations did not differ between PCOS vs. reference women. Serum WNT5 correlated inversely with weight both in PCOS and reference women, and correlated directly with insulin response during oral glucose tolerance test in PCOS women. Serum WISP2 correlated directly with fatty acid binding protein 4. Serum SFRP5 did not differ between obese (n=32) vs. nonobese (n=25) PCOS women, but reference women had lower SFRP5 (pPCOS groups). Serum SFRP5 correlated inversely with IL-1β, TNF-α, cholesterol, and apoprotein B. These findings demonstrated that WNT5 correlated inversely with adiposity and directly with insulin response, and the WNT-inhibitor SFRP5 may be anti-inflammatory. Better understanding of the role of WNT signaling in obesity, insulin resistance, insulin secretion, lipoprotein metabolism, and inflammation is important for prevention and treatment of metabolic syndrome, diabetes and cardiovascular disease. © Georg Thieme Verlag KG Stuttgart · New York.

Role of IRS-2 in insulin and cytokine signalling.

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Sun, X J; Wang, L M; Zhang, Y; Yenush, L; Myers, M G; Glasheen, E; Lane, W S; Pierce, J H; White, M F

1995-09-14

The protein IRS-1 acts as an interface between signalling proteins with Src-homology-2 domains (SH2 proteins) and the receptors for insulin, IGF-1, growth hormone, several interleukins (IL-4, IL-9, IL-13) and other cytokines. It regulates gene expression and stimulates mitogenesis, and appears to mediate insulin/IGF-1-stimulated glucose transport. Thus, survival of the IRS-1-/- mouse with only mild resistance to insulin was surprising. This dilemma is provisionally resolved with our discovery of a second IRS-signalling protein. We purified and cloned a likely candidate called 4PS from myeloid progenitor cells and, because of its resemblance to IRS-1, we designate it IRS-2. Alignment of the sequences of IRS-2 and IRS-1 revealed a highly conserved amino terminus containing a pleckstrin-homology domain and a phosphotyrosine-binding domain, and a poorly conserved carboxy terminus containing several tyrosine phosphorylation motifs. IRS-2 is expressed in many cells, including tissues from IRS-1-/- mice, and may be essential for signalling by several receptor systems.

The ontogeny of insulin signaling in the preterm baboon model.

Science.gov (United States)

Blanco, Cynthia L; Liang, Hanyu; Joya-Galeana, Joaquin; DeFronzo, Ralph A; McCurnin, Donald; Musi, Nicolas

2010-05-01

Hyperglycemia, a prevalent condition in premature infants, is thought to be a consequence of incomplete suppression of endogenous glucose production and reduced insulin-stimulated glucose disposal in peripheral tissues. However, the molecular basis for these conditions remains unclear. To test the hypothesis that the insulin transduction pathway is underdeveloped with prematurity, fetal baboons were delivered, anesthetized, and euthanized at 125 d gestational age (GA), 140 d GA, or near term at 175 d GA. Vastus lateralis muscle and liver tissues were obtained, and protein content of insulin signaling molecules [insulin receptor (IR)-beta, IR substate-1, p85 subunit of phosphatidylinositol 3-kinase, Akt, and AS160] and glucose transporters (GLUT)-1 and GLUT4 was measured by Western blotting. Muscle from 125 d GA baboons had markedly reduced GLUT1 protein content (16% of 140 d GA and 9% of 175 d GA fetuses). GLUT4 and AS160 also were severely reduced in 125 d GA fetal muscle (43% of 175 d GA and 35% of 175 d GA, respectively). In contrast, the protein content of IR-beta, IR substate-1, and Akt was elevated by 1.7-, 5.2-, and 1.9-fold, respectively, in muscle from 125 d GA baboons when compared with 175 d GA fetuses. No differences were found in the content of insulin signaling proteins in liver. In conclusion, significant gestational differences exist in the protein content of several insulin signaling proteins in the muscle of fetal baboons. Reduced muscle content of key glucose transport-regulating proteins (GLUT1, GLUT4, AS160) could play a role in the pathogenesis of neonatal hyperglycemia and reduced insulin-stimulated glucose disposal.

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

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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.

SOCS-1 deficiency does not prevent diet-induced insulin resistance

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Emanuelli, Brice; Macotela, Yazmin; Boucher, Jérémie

2008-01-01

Obesity is associated with inflammation and increased expression of suppressor of cytokine signaling (SOCS) proteins, which inhibit cytokine and insulin signaling. Thus, reducing SOCS expression could prevent the development of obesity-induced insulin resistance. Using SOCS-1 knockout mice, we...... investigated the contribution of SOCS-1 in the development of insulin resistance induced by a high-fat diet (HFD). SOCS-1 knockout mice on HFD gained 70% more weight, displayed a 2.3-fold increase in epididymal fat pads mass and increased hepatic lipid content. This was accompanied by increased mRNA expression...... of leptin and the macrophage marker CD68 in white adipose tissue and of SREBP1c and FAS in liver. HFD also induced hyperglycemia in SOCS-1 deficient mice with impairment of glucose and insulin tolerance tests. Thus, despite the role of SOCS proteins in obesity-related insulin resistance, SOCS-1 deficiency...

Effects of Bisphenol A on glucose homeostasis and brain insulin signaling pathways in male mice.

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Fang, Fangfang; Chen, Donglong; Yu, Pan; Qian, Wenyi; Zhou, Jing; Liu, Jingli; Gao, Rong; Wang, Jun; Xiao, Hang

2015-02-01

The potential effects of Bisphenol A (BPA) on peripheral insulin resistance have recently gained more attention, however, its functions on brain insulin resistance are still unknown. The aim of the present study was to investigate the effects of BPA on insulin signaling and glucose transport in mouse brain. The male mice were administrated of 100 μg/kg/day BPA or vehicle for 15 days then challenged with glucose and insulin tolerance tests. The insulin levels were detected with radioimmunoassay (RIA), and the insulin signaling pathways were investigated by Western blot. Our results revealed that BPA significantly increased peripheral plasma insulin levels, and decreased the insulin signals including phosphorylated insulin receptor (p-IR), phosphorylated insulin receptor substrate 1 (p-IRS1), phosphorylated protein kinase B (p-AKT), phosphorylated glycogen synthase kinase 3β (p-GSK3β) and phosphorylated extracellular regulated protein kinases (p-ERK1/2) in the brain, though insulin expression in both hippocampus and profrontal cortex was increased. In parallel, BPA exposure might contribute to glucose transport disturbance in the brain since the expression of glucose transporters were markedly decreased. In conclusion, BPA exposure perturbs the insulin signaling and glucose transport in the brain, therefore, it might be a risk factor for brain insulin resistance. Copyright © 2015 Elsevier Inc. All rights reserved.

Exercise Protects Against Defective Insulin Signaling and Insulin Resistance of Glucose Transport in Skeletal Muscle of Angiotensin II-Infused Rat

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Juthamard Surapongchai

2018-04-01

Full Text Available Objectives: The present study investigated the impact of voluntary exercise on insulin-stimulated glucose transport and the protein expression and phosphorylation status of the signaling molecules known to be involved in the glucose transport process in the soleus muscle as well as other cardiometabolic risks in a rat model with insulin resistance syndrome induced by chronic angiotensin II (ANGII infusion.Materials and Methods: Male Sprague-Dawley rats were assigned to sedentary or voluntary wheel running (VWR groups. Following a 6-week period, rats in each group were subdivided and subcutaneously administered either normal saline or ANGII at 100 ng/kg/min for 14 days. Blood pressure, glucose tolerance, insulin-stimulated glucose transport and signaling proteins, including insulin receptor (IR, insulin receptor substrate 1 (IRS-1, Akt, Akt substrate of 160 kDa (AS160, AMPKα, c-Jun NH2-terminal kinase (JNK, p38 MAPK, angiotensin converting enzyme (ACE, ANGII type 1 receptor (AT1R, ACE2, Mas receptor (MasR and oxidative stress marker in the soleus muscle, were evaluated.Results: Exercise protected against the insulin resistance of glucose transport and defective insulin signaling molecules in the soleus muscle; this effect was associated with a significant increase in AMPK Thr172 (43% and decreases in oxidative stress marker (31% and insulin-induced p38 MAPK Thr180/Tyr182 (45% and SAPK/JNK Thr183/Tyr185 (25%, without significant changes in expression of AT1R, AT2R, ACE, ACE2, and MasR when compared to the sedentary rats given ANGII infusion. At the systemic level, VWR significantly decreased body weight, fat weight, and systolic blood pressure as well as improved serum lipid profiles.Conclusion: Voluntary exercise can alleviate insulin resistance of glucose transport and impaired insulin signaling molecules in the soleus muscle and improve whole-body insulin sensitivity in rats chronically administered with ANGII.

Early enhancements of hepatic and later of peripheral insulin sensitivity combined with increased postprandial insulin secretion contribute to improved glycemic control after Roux-en-Y gastric bypass

DEFF Research Database (Denmark)

Bojsen-Møller, Kirstine N; Dirksen, Carsten; Jørgensen, Nils Bruun

2014-01-01

after RYGB. Participants were included after a preoperative diet induced total weight loss of -9.2±1.2%. Hepatic and peripheral insulin sensitivity were assessed using the hyperinsulinemic euglycemic clamp combined with glucose tracer technique and beta-cell function evaluated in response...... after surgery. Insulin mediated glucose disposal and suppression of fatty acids did not improve immediately after surgery but increased at 3 months and 1 year likely related to the reduction in body weight. Insulin secretion increased after RYGB, but only in patients with type 2 diabetes and only...

Physical inactivity affects skeletal muscle insulin signaling in a birth weight-dependent manner

DEFF Research Database (Denmark)

Mortensen, Brynjulf; Friedrichsen, Martin; Andersen, Nicoline Resen

2014-01-01

We investigated whether physical inactivity could unmask defects in insulin and AMPK signaling in low birth weight (LBW) subjects.......We investigated whether physical inactivity could unmask defects in insulin and AMPK signaling in low birth weight (LBW) subjects....

Distinct signalling properties of insulin receptor substrate (IRS)-1 and IRS-2 in mediating insulin/IGF-1 action.

Science.gov (United States)

Rabiee, Atefeh; Krüger, Marcus; Ardenkjær-Larsen, Jacob; Kahn, C Ronald; Emanuelli, Brice

2018-07-01

Insulin/IGF-1 action is driven by a complex and highly integrated signalling network. Loss-of-function studies indicate that the major insulin/IGF-1 receptor substrate (IRS) proteins, IRS-1 and IRS-2, mediate different biological functions in vitro and in vivo, suggesting specific signalling properties despite their high degree of homology. To identify mechanisms contributing to the differential signalling properties of IRS-1 and IRS-2 in the mediation of insulin/IGF-1 action, we performed comprehensive mass spectrometry (MS)-based phosphoproteomic profiling of brown preadipocytes from wild type, IRS-1 -/- and IRS-2 -/- mice in the basal and IGF-1-stimulated states. We applied stable isotope labeling by amino acids in cell culture (SILAC) for the accurate quantitation of changes in protein phosphorylation. We found ~10% of the 6262 unique phosphorylation sites detected to be regulated by IGF-1. These regulated sites included previously reported substrates of the insulin/IGF-1 signalling pathway, as well as novel substrates including Nuclear Factor I X and Semaphorin-4B. In silico prediction suggests the protein kinase B (PKB), protein kinase C (PKC), and cyclin-dependent kinase (CDK) as the main mediators of these phosphorylation events. Importantly, we found preferential phosphorylation patterns depending on the presence of either IRS-1 or IRS-2, which was associated with specific sets of kinases involved in signal transduction downstream of these substrates such as PDHK1, MAPK3, and PKD1 for IRS-1, and PIN1 and PKC beta for IRS-2. Overall, by generating a comprehensive phosphoproteomic profile from brown preadipocyte cells in response to IGF-1 stimulation, we reveal both common and distinct insulin/IGF-1 signalling events mediated by specific IRS proteins. Copyright © 2018 Elsevier Inc. All rights reserved.

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

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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.

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

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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.

Insulin signaling displayed a differential tissue-specific response to low-dose dihydrotestosterone in female mice.

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Andrisse, Stanley; Billings, Katelyn; Xue, Ping; Wu, Sheng

2018-04-01

Hyperandrogenemia and hyperinsulinemia are believed to play prominent roles in polycystic ovarian syndrome (PCOS). We explored the effects of low-dose dihydrotestosterone (DHT), a model of PCOS, on insulin signaling in metabolic and reproductive tissues in a female mouse model. Insulin resistance in the energy storage tissues is associated with type 2 diabetes. Insulin signaling in the ovaries and pituitary either directly or indirectly stimulates androgen production. Energy storage and reproductive tissues were isolated and molecular assays were performed. Livers and white adipose tissue (WAT) from DHT mice displayed lower mRNA and protein expression of insulin signaling intermediates. However, ovaries and pituitaries of DHT mice exhibited higher expression levels of insulin signaling genes/proteins. Insulin-stimulated p-AKT levels were blunted in the livers and WAT of the DHT mice but increased or remained the same in the ovaries and pituitaries compared with controls. Glucose uptake decreased in liver and WAT but was unchanged in pituitary and ovary of DHT mice. Plasma membrane GLUTs were decreased in liver and WAT but increased in ovary and pituitary of DHT mice. Skeletal muscle insulin-signaling genes were not lowered in DHT mice compared with control. DHT mice did not display skeletal muscle insulin resistance. Insulin-stimulated glucose transport increased in skeletal muscles of DHT mice compared with controls. DHT mice were hyperinsulinemic. However, the differential mRNA and protein expression pattern was independent of hyperinsulinemia in cultured hepatocytes and pituitary cells. These findings demonstrate a differential effect of DHT on the insulin-signaling pathway in energy storage vs. reproductive tissues independent of hyperinsulinemia.

Insulin-induced CARM1 upregulation facilitates hepatocyte proliferation

Energy Technology Data Exchange (ETDEWEB)

Yeom, Chul-gon; Kim, Dong-il; Park, Min-jung; Choi, Joo-hee [College of Veterinary Medicine, Chonnam National University, Gwangju 500-757 (Korea, Republic of); Jeong, Jieun; Wi, Anjin; Park, Whoashig [Jeollanamdo Forest Resources Research Institute, Naju 520-833 (Korea, Republic of); Han, Ho-jae [College of Veterinary Medicine, Seoul National University, Seoul 151-741 (Korea, Republic of); Park, Soo-hyun, E-mail: parksh@chonnam.ac.kr [College of Veterinary Medicine, Chonnam National University, Gwangju 500-757 (Korea, Republic of)

2015-06-05

Previously, we reported that CARM1 undergoes ubiquitination-dependent degradation in renal podocytes. It was also reported that CARM1 is necessary for fasting-induced hepatic gluconeogenesis. Based on these reports, we hypothesized that treatment with insulin, a hormone typically present under the ‘fed’ condition, would inhibit gluconeogenesis via CARM1 degradation. HepG2 cells, AML-12 cells, and rat primary hepatocytes were treated with insulin to confirm CARM1 downregulation. Surprisingly, insulin treatment increased CARM1 expression in all cell types examined. Furthermore, treatment with insulin increased histone 3 methylation at arginine 17 and 26 in HepG2 cells. To elucidate the role of insulin-induced CARM1 upregulation, the HA-CARM1 plasmid was transfected into HepG2 cells. CARM1 overexpression did not increase the expression of lipogenic proteins generally increased by insulin signaling. Moreover, CARM1 knockdown did not influence insulin sensitivity. Insulin is known to facilitate hepatic proliferation. Like insulin, CARM1 overexpression increased CDK2 and CDK4 expression. In addition, CARM1 knockdown reduced the number of insulin-induced G2/M phase cells. Moreover, GFP-CARM1 overexpression increased the number of G2/M phase cells. Based on these results, we concluded that insulin-induced CARM1 upregulation facilitates hepatocyte proliferation. These observations indicate that CARM1 plays an important role in liver pathophysiology. - Highlights: • Insulin treatment increases CARM1 expression in hepatocytes. • CARM1 overexpression does not increase the expression of lipogenic proteins. • CARM1 knockdown does not influence insulin sensitivity. • Insulin-induced CARM1 upregulation facilitates hepatocyte proliferation.

Insulin-induced CARM1 upregulation facilitates hepatocyte proliferation

International Nuclear Information System (INIS)

Yeom, Chul-gon; Kim, Dong-il; Park, Min-jung; Choi, Joo-hee; Jeong, Jieun; Wi, Anjin; Park, Whoashig; Han, Ho-jae; Park, Soo-hyun

2015-01-01

Previously, we reported that CARM1 undergoes ubiquitination-dependent degradation in renal podocytes. It was also reported that CARM1 is necessary for fasting-induced hepatic gluconeogenesis. Based on these reports, we hypothesized that treatment with insulin, a hormone typically present under the ‘fed’ condition, would inhibit gluconeogenesis via CARM1 degradation. HepG2 cells, AML-12 cells, and rat primary hepatocytes were treated with insulin to confirm CARM1 downregulation. Surprisingly, insulin treatment increased CARM1 expression in all cell types examined. Furthermore, treatment with insulin increased histone 3 methylation at arginine 17 and 26 in HepG2 cells. To elucidate the role of insulin-induced CARM1 upregulation, the HA-CARM1 plasmid was transfected into HepG2 cells. CARM1 overexpression did not increase the expression of lipogenic proteins generally increased by insulin signaling. Moreover, CARM1 knockdown did not influence insulin sensitivity. Insulin is known to facilitate hepatic proliferation. Like insulin, CARM1 overexpression increased CDK2 and CDK4 expression. In addition, CARM1 knockdown reduced the number of insulin-induced G2/M phase cells. Moreover, GFP-CARM1 overexpression increased the number of G2/M phase cells. Based on these results, we concluded that insulin-induced CARM1 upregulation facilitates hepatocyte proliferation. These observations indicate that CARM1 plays an important role in liver pathophysiology. - Highlights: • Insulin treatment increases CARM1 expression in hepatocytes. • CARM1 overexpression does not increase the expression of lipogenic proteins. • CARM1 knockdown does not influence insulin sensitivity. • Insulin-induced CARM1 upregulation facilitates hepatocyte proliferation

Curcumin ameliorates insulin signalling pathway in brain of Alzheimer's disease transgenic mice.

Science.gov (United States)

Feng, Hui-Li; Dang, Hui-Zi; Fan, Hui; Chen, Xiao-Pei; Rao, Ying-Xue; Ren, Ying; Yang, Jin-Duo; Shi, Jing; Wang, Peng-Wen; Tian, Jin-Zhou

2016-12-01

Deficits in glucose, impaired insulin signalling and brain insulin resistance are common in the pathogenesis of Alzheimer's disease (AD); therefore, some scholars even called AD type 3 diabetes mellitus. Curcumin can reduce the amyloid pathology in AD. Moreover, it is a well-known fact that curcumin has anti-oxidant and anti-inflammatory properties. However, whether or not curcumin could regulate the insulin signal transduction pathway in AD remains unclear. In this study, we used APPswe/PS1dE9 double transgenic mice as the AD model to investigate the mechanisms and the effects of curcumin on AD. Immunohistochemical (IHC) staining and a western blot analysis were used to test the major proteins in the insulin signal transduction pathway. After the administration of curcumin for 6 months, the results showed that the expression of an insulin receptor (InR) and insulin receptor substrate (IRS)-1 decreased in the hippocampal CA1 area of the APPswe/PS1dE9 double transgenic mice, while the expression of phosphatidylinositol-3 kinase (PI3K), phosphorylated PI3K (p-PI3K), serine-threonine kinase (AKT) and phosphorylated AKT (p-AKT) increased. Among the curcumin groups, the medium-dose group was the most effective one. Thus, we believe that curcumin may be a potential therapeutic agent that can regulate the critical molecules in brain insulin signalling pathways. Furthermore, curcumin could be adopted as one of the AD treatments to improve a patient's learning and memory ability. © The Author(s) 2016.

Insulin signaling mediates sexual attractiveness in Drosophila.

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Tsung-Han Kuo

Full Text Available Sexually attractive characteristics are often thought to reflect an individual's condition or reproductive potential, but the underlying molecular mechanisms through which they do so are generally unknown. Insulin/insulin-like growth factor signaling (IIS is known to modulate aging, reproduction, and stress resistance in several species and to contribute to variability of these traits in natural populations. Here we show that IIS determines sexual attractiveness in Drosophila through transcriptional regulation of genes involved in the production of cuticular hydrocarbons (CHC, many of which function as pheromones. Using traditional gas chromatography/mass spectrometry (GC/MS together with newly introduced laser desorption/ionization orthogonal time-of-flight mass spectrometry (LDI-MS we establish that CHC profiles are significantly affected by genetic manipulations that target IIS. Manipulations that reduce IIS also reduce attractiveness, while females with increased IIS are significantly more attractive than wild-type animals. IIS effects on attractiveness are mediated by changes in CHC profiles. Insulin signaling influences CHC through pathways that are likely independent of dFOXO and that may involve the nutrient-sensing Target of Rapamycin (TOR pathway. These results suggest that the activity of conserved molecular regulators of longevity and reproductive output may manifest in different species as external characteristics that are perceived as honest indicators of fitness potential.

Study of prevalence and effects of insulin resistance in patients with chronic hepatitis C genotype 4.

Science.gov (United States)

Amer, A F; Baddour, M M; Elshazly, M A; Fadally, G; Hanafi, N F; Assar, S L

2016-02-01

There is strong epidemiological evidence linking hepatitis C virus (HCV) infection and diabetes. Our aim was to evaluate the prevalence of insulin resistance in Egyptian patients with chronic HCV genotype 4 infection, to assess factors associated with insulin resistance and to test the impact of insulin resistance on outcomes of treatment with pegylated interferon/ribavirin. Insulin resistance [homeostasis model assessmentinsulin resistance (HOMA-IR) score > 3.0] was detected in 31 of 100 nondiabetic patients. The relationship between elevated HOMA-IR and baseline viral load and degree of fibrosis was statistically significant (r = 0.218 and r = 0.223). Follow-up of patients with complete early virological response until the end of treatment showed a statistically significant decrease in HOMA-IR score. Out of 29 liver tissue sections examined, 14 had a low level of expression of insulin receptor type 1 by immunohistochemical studies. This study confirms that insulin resistance affects treatment outcome, and thus HOMA-IR testing before initiation of therapy may be a cost-effective tool.

Differential insulin and steroidogenic signaling in insulin resistant and non-insulin resistant human luteinized granulosa cells-A study in PCOS patients.

Science.gov (United States)

Belani, Muskaan; Deo, Abhilash; Shah, Preeti; Banker, Manish; Singal, Pawan; Gupta, Sarita

2018-04-01

Insulin resistance (IR) is one of the significant aberrations in polycystic ovarian syndrome (PCOS), however is only observed in 70%-80% of obese PCOS and 20%-25% of lean PCOS. Hyperinsulinemia accompanies PCOS-IR along with hyperandrogenemia against normal insulin and androgen levels in PCOS-non insulin resistance (NIR). This could possibly be due to defects in the downstream signaling pathways. The study thus aims to unravel insulin and steroidogenic signaling pathways in luteinized granulosa cells isolated from PCOS-IR and NIR vs matched controls. Luteinized granulosa cells from 30 controls and 39 PCOS were classified for IR based on a novel method of down regulation of protein expression of insulin receptor-β (INSR- β) as shown in our previous paper. We evaluated expression of molecules involved in insulin, steroidogenic signaling and lipid metabolism in luteinized granulosa cells followed by analysis of estradiol, progesterone and testosterone in follicular fluid. Protein expression of INSR- β, pIRS (ser 307), PI(3)K, PKC-ζ, pAkt, ERK1/2, pP38MAPK and gene expression of IGF showed differential expression in the two groups. Increased protein expression of PPAR-γ was accompanied by up regulation in SREBP1c, FAS, CPT-1 and ACC-1 genes in PCOS-IR group. Expression of StAR, CYP19A1, 17 β- HSD and 3 β- HSD demonstrated significant decrease along with increase in CYP11A1, FSH-R and LH-R in both the groups. Follicular fluid testosterone increased and progesterone decreased in PCOS-IR group. This study shows how candidate molecules that were differentially expressed, aid in designing targeted therapy against the two phenotypes of PCOS. Copyright © 2018 Elsevier Ltd. All rights reserved.

Fructose downregulates miR-330 to induce renal inflammatory response and insulin signaling impairment: Attenuation by morin.

Science.gov (United States)

Gu, Ting-Ting; Song, Lin; Chen, Tian-Yu; Wang, Xing; Zhao, Xiao-Juan; Ding, Xiao-Qin; Yang, Yan-Zi; Pan, Ying; Zhang, Dong-Mei; Kong, Ling-Dong

2017-08-01

Fructose induces insulin resistance with kidney inflammation and injury. MicroRNAs are emerged as key regulators of insulin signaling. Morin has insulin-mimetic effect with the improvement of insulin resistance and kidney injury. This study investigated the protective mechanisms of morin against fructose-induced kidney injury, with particular focus on miR-330 expression change, inflammatory response, and insulin signaling impairment. miR-330, sphingosine kinase 1 (SphK1)/sphingosine-1-phosphate (S1P)/S1P receptor (S1PR)1/3 signaling, nuclear factor-κB (NF-κB)/NOD-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome, and insulin signaling were detected in kidney cortex of fructose-fed rats and fructose-exposed HK-2 cells, respectively. Whether miR-330 mediated inflammatory response to affect insulin signaling was examined using SphK1 inhibitor, S1PR1/3 short interfering RNA, or miR-330 mimic/inhibitor, respectively. Fructose was found to downregulate miR-330 expression to increase SphK1/S1P/S1PR1/3 signaling, and then activate NF-κB/NLRP3 inflammasome to produce IL-1β, causing insulin signaling impairment. Moreover, morin upregulated miR-330 and partly attenuated inflammatory response and insulin signaling impairment to alleviate kidney injury. These findings suggest that morin protects against fructose-induced kidney insulin signaling impairment by upregulating miR-330 to reduce inflammatory response. Morin may be a potential therapeutic agent for the treatment of kidney injury associated with fructose-induced inflammation and insulin signaling impairment. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Distinct signalling properties of insulin receptor substrate (IRS)-1 and IRS-2 in mediating insulin/IGF-1 action

DEFF Research Database (Denmark)

Rabiee, Atefeh; Krüger, Marcus; Ardenkjær-Larsen, Jacob

2018-01-01

Insulin/IGF-1 action is driven by a complex and highly integrated signalling network. Loss-of-function studies indicate that the major insulin/IGF-1 receptor substrate (IRS) proteins, IRS-1 and IRS-2, mediate different biological functions in vitro and in vivo, suggesting specific signalling...... properties despite their high degree of homology. To identify mechanisms contributing to the differential signalling properties of IRS-1 and IRS-2 in the mediation of insulin/IGF-1 action, we performed comprehensive mass spectrometry (MS)-based phosphoproteomic profiling of brown preadipocytes from wild type......, IRS-1-/-and IRS-2-/-mice in the basal and IGF-1-stimulated states. We applied stable isotope labeling by amino acids in cell culture (SILAC) for the accurate quantitation of changes in protein phosphorylation. We found ~10% of the 6262 unique phosphorylation sites detected to be regulated by IGF-1...

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.

Racl Signaling Is Required for Insulin-Stimulated Glucose Uptake and Is Dysregulated in Insulin-Resistant Murine and Human Skeletal Muscle

DEFF Research Database (Denmark)

Sylow, L.; Jensen, T. E.; Kleinert, M.

2013-01-01

The actin cytoskeleton-regulating GTPase Racl is required for insulin-stimulated GLUT4 translocation in cultured muscle cells. However, involvement of Racl and its downstream signaling in glucose transport in insulin-sensitive and insulin-resistant mature skeletal muscle has not previously been i...

Impact of embryo number and maternal undernutrition around the time of conception on insulin signaling and gluconeogenic factors and microRNAs in the liver of fetal sheep.

Science.gov (United States)

Lie, Shervi; Morrison, Janna L; Williams-Wyss, Olivia; Suter, Catherine M; Humphreys, David T; Ozanne, Susan E; Zhang, Song; MacLaughlin, Severence M; Kleemann, David O; Walker, Simon K; Roberts, Claire T; McMillen, I Caroline

2014-05-01

This study aimed to determine whether exposure of the oocyte and/or embryo to maternal undernutrition results in the later programming of insulin action in the liver and factors regulating gluconeogenesis. To do this, we collect livers from singleton and twin fetal sheep that were exposed to periconceptional (PCUN; -60 to 7 days) or preimplantation (PIUN; 0-7 days) undernutrition at 136-138 days of gestation (term = 150 days). The mRNA and protein abundance of insulin signaling and gluconeogenic factors were then quantified using qRT-PCR and Western blotting, respectively, and global microRNA expression was quantified using deep sequencing methodology. We found that hepatic PEPCK-C mRNA (P < 0.01) and protein abundance and the protein abundance of IRS-1 (P < 0.01), p110β (P < 0.05), PTEN (P < 0.05), CREB (P < 0.01), and pCREB (Ser(133); P < 0.05) were decreased in the PCUN and PIUN singletons. In contrast, hepatic protein abundance of IRS-1 (P < 0.01), p85 (P < 0.01), p110β (P < 0.001), PTEN (P < 0.01), Akt2 (P < 0.01), p-Akt (Ser(473); P < 0.01), and p-FOXO-1 (Thr24) (P < 0.01) was increased in twins. There was a decrease in PEPCK-C mRNA (P < 0.01) but, paradoxically, an increase in PEPCK-C protein (P < 0.001) in twins. Both PCUN and PIUN altered the hepatic expression of 23 specific microRNAs. We propose that the differential impact of maternal undernutrition in the presence of one or two embryos on mRNAs and proteins involved in the insulin signaling and gluconeogenesis is explained by changes in the expression of a suite of specific candidate microRNAs.

Partial rescue of in vivo insulin signalling in skeletal muscle by impaired insulin clearance in heterozygous carriers of a mutation in the insulin receptor gene

DEFF Research Database (Denmark)

Højlund, K.; Wojtaszewski, Jørgen; Birk, Jesper Bratz

2006-01-01

AIMS/HYPOTHESIS: Recently we reported the coexistence of postprandial hypoglycaemia and moderate insulin resistance in heterozygous carriers of the Arg1174Gln mutation in the insulin receptor gene (INSR). Controlled studies of in vivo insulin signalling in humans with mutant INSR are unavailable,...

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

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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.

The Mediterranean diet improves hepatic steatosis and insulin sensitivity in individuals with non-alcoholic fatty liver disease.

Science.gov (United States)

Ryan, Marno C; Itsiopoulos, Catherine; Thodis, Tania; Ward, Glenn; Trost, Nicholas; Hofferberth, Sophie; O'Dea, Kerin; Desmond, Paul V; Johnson, Nathan A; Wilson, Andrew M

2013-07-01

Non-alcoholic fatty liver disease (NAFLD) affects up to 30% of the population and signifies increased risk of liver fibrosis and cirrhosis, type 2 diabetes, and cardiovascular disease. Therapies are limited. Weight loss is of benefit but is difficult to maintain. We aimed at examining the effect of the Mediterranean diet (MD), a diet high in monounsaturated fatty acids, on steatosis and insulin sensitivity, using gold standard techniques. Twelve non-diabetic subjects (6 Females/6 Males) with biopsy-proven NAFLD were recruited for a randomised, cross-over 6-week dietary intervention study. All subjects undertook both the MD and a control diet, a low fat-high carbohydrate diet (LF/HCD), in random order with a 6-week wash-out period in- between. Insulin sensitivity was determined with a 3-h hyperinsulinemic-euglycemic clamp study and hepatic steatosis was assessed with localized magnetic resonance (1)H spectroscopy ((1)H-MRS). At baseline, subjects were abdominally obese with elevated fasting concentrations of glucose, insulin, triglycerides, ALT, and GGT. Insulin sensitivity at baseline was low (M=2.7 ± 1.0 mg/kg/min(-1)). Mean weight loss was not different between the two diets (p=0.22). There was a significant relative reduction in hepatic steatosis after the MD compared with the LF/HCD: 39 ± 4% versus 7 ± 3%, as measured by (1)H-MRS (p=0.012). Insulin sensitivity improved with the MD, whereas after the LF/HCD there was no change (p=0.03 between diets). Even without weight loss, MD reduces liver steatosis and improves insulin sensitivity in an insulin-resistant population with NAFLD, compared to current dietary advice. This diet should be further investigated in subjects with NAFLD. Copyright © 2013 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.

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.

Crosstalk between insulin and dopamine signaling: A basis for the metabolic effects of antipsychotic drugs.

Science.gov (United States)

Nash, Abigail I

2017-10-01

In the setting of rising rates of obesity and metabolic syndrome, characterized in part by hyperinsulinemia, it is increasingly important to understand the mechanisms that contribute to insulin dysregulation. The higher risk for metabolic syndrome imparted by antipsychotic medication use highlights one such mechanism. Though there is great variation in the number and types of signaling pathways targeted by these medications, the one common mechanism of action is through dopamine. Dopamine's effects on insulin signaling begin at the level of insulin secretion from the pancreas and continue through the central nervous system. In a reciprocal fashion, insulin also affects dopamine signaling, with specific effects on dopamine reuptake from the synapse. This review probes the dopamine-insulin connection to provide a comprehensive examination of how antipsychotics may contribute towards insulin resistance. Published by Elsevier B.V.

Insulin induces suppressor of cytokine signaling-3 tyrosine phosphorylation through janus-activated kinase

NARCIS (Netherlands)

Peraldi, P; Filloux, C; Emanuelli, B; Hilton, DJ; Van Obberghen, E

2001-01-01

Suppressor of cytokine signaling (SOCS) proteins were originally described as cytokine-induced molecules involved in negative feedback loops. We have shown that SOCS-3 is also a component of the insulin signaling network (1), Indeed, insulin leads to SOCS-3 expression in 3T3-L1 adipocytes. Once

Role of altered insulin signaling pathways in the pathogenesis of podocyte malfunction and microalbuminuria

Science.gov (United States)

Jauregui, Alexandra; Mintz, Daniel H; Mundel, Peter; Fornoni, Alessia

2010-01-01

Purpose of review In diabetic nephropathy (DN), insulin resistance and hyperinsulinemia correlate with the development of albuminuria. The possibility that altered insulin signaling in glomerular cells and particularly podocytes contributes to the development of DN will be discussed. Recent findings While normal podocytes uptake glucose in response to insulin, diabetic podocytes become insulin resistant in experimental DN prior to the development of significant albuminuria. Both clinical and experimental data suggest that insulin sensitizers may be renoprotective independently of their systemic effects on the metabolic control of diabetes. Summary We will review the clinical and experimental evidence that altered insulin signaling correlates with the development of DN in both type 1 and type 2 diabetes, and that insulin sensitizers may be superior to other hypoglycemic agents in the prevention of DN. We will then review potential mechanisms by which altered podocyte insulin signaling may contribute to the development of DN. Understanding the role of podocyte in glucose metabolism is important because it may lead to the discovery of novel pathogenetic mechanisms of DN, it may affect current strategies for prevention and treatment of DN, and it may allow for the identification of novel therapeutic targets. PMID:19724224

Aging and insulin signaling differentially control normal and tumorous germline stem cells.

Science.gov (United States)

Kao, Shih-Han; Tseng, Chen-Yuan; Wan, Chih-Ling; Su, Yu-Han; Hsieh, Chang-Che; Pi, Haiwei; Hsu, Hwei-Jan

2015-02-01

Aging influences stem cells, but the processes involved remain unclear. Insulin signaling, which controls cellular nutrient sensing and organismal aging, regulates the G2 phase of Drosophila female germ line stem cell (GSC) division cycle in response to diet; furthermore, this signaling pathway is attenuated with age. The role of insulin signaling in GSCs as organisms age, however, is also unclear. Here, we report that aging results in the accumulation of tumorous GSCs, accompanied by a decline in GSC number and proliferation rate. Intriguingly, GSC loss with age is hastened by either accelerating (through eliminating expression of Myt1, a cell cycle inhibitory regulator) or delaying (through mutation of insulin receptor (dinR) GSC division, implying that disrupted cell cycle progression and insulin signaling contribute to age-dependent GSC loss. As flies age, DNA damage accumulates in GSCs, and the S phase of the GSC cell cycle is prolonged. In addition, GSC tumors (which escape the normal stem cell regulatory microenvironment, known as the niche) still respond to aging in a similar manner to normal GSCs, suggesting that niche signals are not required for GSCs to sense or respond to aging. Finally, we show that GSCs from mated and unmated females behave similarly, indicating that female GSC-male communication does not affect GSCs with age. Our results indicate the differential effects of aging and diet mediated by insulin signaling on the stem cell division cycle, highlight the complexity of the regulation of stem cell aging, and describe a link between ovarian cancer and aging. © 2014 The Authors. Aging Cell published by the Anatomical Society and John Wiley & Sons Ltd.

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

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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.

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

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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.

A 12-Week Aerobic Exercise Program Reduces Hepatic Fat Accumulation and Insulin Resistance in Obese, Hispanic Adolescents

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van der Heijden, Gert-Jan; Wang, Zhiyue J.; Chu, Zili D.; Sauer, Pieter J. J.; Haymond, Morey W.; Rodriguez, Luisa M.; Sunehag, Agneta L.

2010-01-01

The rise in obesity-related morbidity in children and adolescents requires urgent prevention and treatment strategies. Currently, only limited data are available on the effects of exercise programs on insulin resistance, and visceral, hepatic, and intramyocellular fat accumulation. We hypothesized

Neurotrophin Signaling Is Required for Glucose-Induced Insulin Secretion.

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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.

A genome-wide siRNA screen to identify modulators of insulin sensitivity and gluconeogenesis.

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Ruojing Yang

Full Text Available BACKGROUND: Hepatic insulin resistance impairs insulin's ability to suppress hepatic glucose production (HGP and contributes to the development of type 2 diabetes (T2D. Although the interests to discover novel genes that modulate insulin sensitivity and HGP are high, it remains challenging to have a human cell based system to identify novel genes. METHODOLOGY/PRINCIPAL FINDINGS: To identify genes that modulate hepatic insulin signaling and HGP, we generated a human cell line stably expressing beta-lactamase under the control of the human glucose-6-phosphatase (G6PC promoter (AH-G6PC cells. Both beta-lactamase activity and endogenous G6PC mRNA were increased in AH-G6PC cells by a combination of dexamethasone and pCPT-cAMP, and reduced by insulin. A 4-gene High-Throughput-Genomics assay was developed to concomitantly measure G6PC and pyruvate-dehydrogenase-kinase-4 (PDK4 mRNA levels. Using this assay, we screened an siRNA library containing pooled siRNA targeting 6650 druggable genes and identified 614 hits that lowered G6PC expression without increasing PDK4 mRNA levels. Pathway analysis indicated that siRNA-mediated knockdown (KD of genes known to positively or negatively affect insulin signaling increased or decreased G6PC mRNA expression, respectively, thus validating our screening platform. A subset of 270 primary screen hits was selected and 149 hits were confirmed by target gene KD by pooled siRNA and 7 single siRNA for each gene to reduce G6PC expression in 4-gene HTG assay. Subsequently, pooled siRNA KD of 113 genes decreased PEPCK and/or PGC1alpha mRNA expression thereby demonstrating their role in regulating key gluconeogenic genes in addition to G6PC. Last, KD of 61 of the above 113 genes potentiated insulin-stimulated Akt phosphorylation, suggesting that they suppress gluconeogenic gene by enhancing insulin signaling. CONCLUSIONS/SIGNIFICANCE: These results support the proposition that the proteins encoded by the genes identified in

Differential interaction of Apolipoprotein-E isoforms with insulin receptors modulates brain insulin signaling in mutant human amyloid precursor protein transgenic mice.

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Chan, Elizabeth S; Chen, Christopher; Cole, Gregory M; Wong, Boon-Seng

2015-09-08

It is unclear how human apolipoprotein E4 (ApoE4) increases the risk for Alzheimer's disease (AD). Although Aβ levels can lead to insulin signaling impairment, these experiments were done in the absence of human ApoE. To examine ApoE role, we crossed the human ApoE-targeted replacement mice with mutant human amyloid precursor protein (APP) mice. In 26 week old mice with lower Aβ levels, the expression and phosphorylation of insulin signaling proteins remained comparable among APP, ApoE3xAPP and ApoE4xAPP mouse brains. When the mice aged to 78 weeks, these proteins were markedly reduced in APP and ApoE4xAPP mouse brains. While Aβ can bind to insulin receptor, how ApoE isoforms modulate this interaction remains unknown. Here, we showed that ApoE3 had greater association with insulin receptor as compared to ApoE4, regardless of Aβ42 concentration. In contrast, ApoE4 bound more Aβ42 with increasing peptide levels. Using primary hippocampal neurons, we showed that ApoE3 and ApoE4 neurons are equally sensitive to physiological levels of insulin. However, in the presence of Aβ42, insulin failed to elicit a downstream response only in ApoE4 hippocampal neurons. Taken together, our data show that ApoE genotypes can modulate this Aβ-mediated insulin signaling impairment.

Nitric oxide agents impair insulin-mediated signal transduction in rat skeletal muscle

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Ragoobirsingh Dalip

2006-05-01

Full Text Available Abstract Background Evidence demonstrates that exogenously administered nitric oxide (NO can induce insulin resistance in skeletal muscle. We have investigated the modulatory effects of two NO donors, S-nitroso-N-acetyl-D, L-penicillamine (SNAP and S-nitrosoglutathione (GSNO on the early events in insulin signaling in rat skeletal myocytes. Results Skeletal muscle cells from 6–8 week old Sprague-Dawley rats were treated with SNAP or GSNO (25 ng/ml in the presence or absence of glucose (25 mM and insulin (100 nM. Cellular insulin receptor-β levels and tyrosine phosphorylation in IRS-1 were significantly reduced, while serine phosphorylation in IRS-1 was significantly increased in these cells, when compared to the insulin-stimulated control. Reversal to near normal levels was achieved using the NO scavenger, 2-(4-carboxyphenyl-4, 4, 5, 5-tetramethylimidazoline-1-oxyl 3-oxide (carboxy-PTIO. Conclusion These data suggest that NO is a potent modulator of insulin-mediated signal transduction and may play a significant role in the pathogenesis of type 2 diabetes mellitus.

Insulin resistance and liver steatosis in chronic hepatitis C infection genotype 3.

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Abenavoli, Ludovico; Masarone, Mario; Peta, Valentina; Milic, Natasa; Kobyliak, Nazarii; Rouabhia, Samir; Persico, Marcello

2014-11-07

Hepatitis C virus (HCV) infection is a common chronic liver disease worldwide. Non-alcoholic fatty liver disease and insulin resistance (IR) are the major determinants of fibrosis progression and response to antiviral therapy. The pathogenetic link between IR and chronic HCV infection is complex, and is associated with HCV genotype. Liver steatosis is the most common in the patients infected with genotype 3 virus, possibly due to direct effects of genotype 3 viral proteins. To the contrary, hepatic steatosis in the patients infected with other genotypes is thought to be mostly due to the changes in host metabolism, involving IR. In HCV genotype 3, liver steatosis correlates with viral load, reverts after reaching the sustained virologic response and reoccurs in the relapsers. A therapeutic strategy to improve IR and liver steatosis and subsequently the response to antiviral treatment in these patients is warranted.

Pre‐natal undernutrition and post‐natal overnutrition are associated with permanent changes in hepatic metabolism markers and fatty acid composition in sheep

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Hou, L.; Hellgren, Lars; Kongsted, A. H.

2014-01-01

was associated with increased hepatic triglyceride, ceramide and free fatty acid content in adulthood (not observed in lambs), which was accompanied by up‐regulated early‐stage insulin signalling as reflected by increased INSRβ and PI3K‐p110 protein expression. The HCHF diet increased hepatic triglyceride...... content in lambs, associated with down‐regulated expressions of energy‐metabolism‐related genes (GLUT1, PPARα, SREBP1c, PEPCK). These post‐natal effects were not observed in adult HCHF sheep, after they had received a moderate (body‐fat correcting) diet for 1.5 years. Interestingly, pre‐natal LOW...... nutrition induced permanent alterations in hepatic phospholipids’ fatty acid composition. Thus, the amount of linoleic acid (C18 : 2 ∆9,12) was significantly increased and composition of rumen‐derived fatty acids were altered, indicating changed composition of rumenal microbiota. Hepatic insulin signalling...

Insulin Signaling, Resistance, and the Metabolic Syndrome: Insights from Mouse Models to Disease Mechanisms

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Guo, Shaodong

2014-01-01

Insulin resistance is a major underlying mechanism for the “metabolic syndrome”, which is also known as insulin resistance syndrome. Metabolic syndrome is increasing at an alarming rate, becoming a major public and clinical problem worldwide. Metabolic syndrome is represented by a group of interrelated disorders, including obesity, hyperglycemia, hyperlipidemia, and hypertension. It is also a significant risk factor for cardiovascular disease and increased morbidity and mortality. Animal studies demonstrate that insulin and its signaling cascade normally control cell growth, metabolism and survival through activation of mitogen-activated protein kinases (MAPKs) and phosphotidylinositide-3-kinase (PI3K), of which activation of PI-3K-associated with insulin receptor substrate-1 and -2 (IRS1, 2) and subsequent Akt→Foxo1 phosphorylation cascade has a central role in control of nutrient homeostasis and organ survival. Inactivation of Akt and activation of Foxo1, through suppression IRS1 and IRS2 in different organs following hyperinsulinemia, metabolic inflammation, and over nutrition may provide the underlying mechanisms for metabolic syndrome in humans. Targeting the IRS→Akt→Foxo1 signaling cascade will likely provide a strategy for therapeutic intervention in the treatment of type 2 diabetes and its complications. This review discusses the basis of insulin signaling, insulin resistance in different mouse models, and how a deficiency of insulin signaling components in different organs contributes to the feature of the metabolic syndrome. Emphasis will be placed on the role of IRS1, IRS2, and associated signaling pathways that couple to Akt and the forkhead/winged helix transcription factor Foxo1. PMID:24281010

Insulin regulates multiple signaling pathways leading to monocyte/macrophage chemotaxis into the wound tissue

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Yan Liu

2018-01-01

Full Text Available Wound healing is a complex process that involves sequential phases that overlap in time and space and affect each other dynamically at the gene and protein levels. We previously showed that insulin accelerates wound healing by stimulating faster and regenerative healing. One of the processes that insulin stimulates is an increase in monocyte/macrophage chemotaxis. In this study, we performed experiments in vivo and in vitro to elucidate the signaling transduction pathways that are involved in insulin-induced monocyte/macrophage chemotaxis. We found that insulin stimulates THP-1 cell chemotaxis in a dose-dependent and insulin receptor-dependent manner. We also show that the kinases PI3K-Akt, SPAK/JNK, and p38 MAPK are key molecules in the insulin-induced signaling pathways that lead to chemoattraction of the THP-1 cell. Furthermore, both PI3K-Akt and SPAK/JNK signaling involve Rac1 activation, an important molecule in regulating cell motility. Indeed, topical application of Rac1 inhibitor at an early stage during the healing process caused delayed and impaired healing even in the presence of insulin. These results delineate cell and molecular mechanisms involved in insulin-induced chemotaxis of monocyte/macrophage, cells that are critical for proper healing.

Higher protein kinase C ζ in fatty rat liver and its effect on insulin actions in primary hepatocytes.

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Wei Chen

Full Text Available We previously showed the impairment of insulin-regulated gene expression in the primary hepatocytes from Zucker fatty (ZF rats, and its association with alterations of hepatic glucose and lipid metabolism. However, the molecular mechanism is unknown. A preliminary experiment shows that the expression level of protein kinase C ζ (PKCζ, a member of atypical PKC family, is higher in the liver and hepatocytes of ZF rats than that of Zucker lean (ZL rats. Herein, we intend to investigate the roles of atypical protein kinase C in the regulation of hepatic gene expression. The insulin-regulated hepatic gene expression was evaluated in ZL primary hepatocytes treated with atypical PKC recombinant adenoviruses. Recombinant adenovirus-mediated overexpression of PKCζ, or the other atypical PKC member PKCι/λ, alters the basal and impairs the insulin-regulated expressions of glucokinase, sterol regulatory element-binding protein 1c, the cytosolic form of phosphoenolpyruvate carboxykinase, the catalytic subunit of glucose 6-phosphatase, and insulin like growth factor-binding protein 1 in ZL primary hepatocytes. PKCζ or PKCι/λ overexpression also reduces the protein level of insulin receptor substrate 1, and the insulin-induced phosphorylation of AKT at Ser473 and Thr308. Additionally, PKCι/λ overexpression impairs the insulin-induced Prckz expression, indicating the crosstalk between PKCζ and PKCι/λ. We conclude that the PKCζ expression is elevated in hepatocytes of insulin resistant ZF rats. Overexpressions of aPKCs in primary hepatocytes impair insulin signal transduction, and in turn, the down-stream insulin-regulated gene expression. These data suggest that elevation of aPKC expression may contribute to the hepatic insulin resistance at gene expression level.

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

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Taouis Mohammed

2011-09-01

Full Text Available The central nervous system (CNS controls vital functions, by efficiently coordinating peripheral and central cascades of signals and networks in a coordinated manner. Historically, the brain was considered to be an insulin-insensitive tissue. But, new findings demonstrating that insulin is present in different regions of themammalian brain, in particular the hypothalamus and the hippocampus. Insulin acts through specific receptors and dialogues with numerous peptides, neurotransmitters and adipokines such as leptin. The cross-talk between leptin and insulin signaling pathways at the hypothalamic level is clearly involved in the control of energy homeostasis. Both hormones are anorexigenic through their action on hypothalamic arcuate nucleus by inducing the expression of anorexigenic neuropetides such as POMC (pro-opiomelanocortin, the precursor of aMSH and reducing the expression of orexigenic neuropeptide such as NPY (Neuropeptide Y. Central defect of insulin and leptin signaling predispose to obesity (leptin-resistant state and type-2 diabetes (insulin resistant state. Obesity and type-2 diabetes are associated to deep alterations in energy homeostasis control but also to other alterations of CNS functions as the predisposition to neurodegenerative diseases such as Alzheimer’s disease (AD. AD is a neurodegenerative disorder characterized by distinct hallmarks within the brain. Postmortem observation of AD brains showed the presence of parenchymal plaques due to the accumulation of the amyloid beta (AB peptide and neurofibrillary tangles. These accumulations result from the hyperphosphorylation of tau (a mictrotubule-interacting protein. Both insulin and leptin have been described to modulate tau phosphorylation and therefore in leptin and insulin resistant states may contribute to AD. The concentrations of leptin and insulin cerebrospinal fluid are decreased type2 diabetes and obese patients. In addition, the concentration of insulin in the

Tobacco Smoke Exposure Impairs Brain Insulin/IGF Signaling: Potential Co-Factor Role in Neurodegeneration.

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Deochand, Chetram; Tong, Ming; Agarwal, Amit R; Cadenas, Enrique; de la Monte, Suzanne M

2016-01-01

Human studies suggest tobacco smoking is a risk factor for cognitive impairment and neurodegeneration, including Alzheimer's disease (AD). However, experimental data linking tobacco smoke exposures to underlying mediators of neurodegeneration, including impairments in brain insulin and insulin-like growth factor (IGF) signaling in AD are lacking. This study tests the hypothesis that cigarette smoke (CS) exposures can impair brain insulin/IGF signaling and alter expression of AD-associated proteins. Adult male A/J mice were exposed to air for 8 weeks (A8), CS for 4 or 8 weeks (CS4, CS8), or CS8 followed by 2 weeks recovery (CS8+R). Gene expression was measured by qRT-PCR analysis and proteins were measured by multiplex bead-based or direct binding duplex ELISAs. CS exposure effects on insulin/IGF and insulin receptor substrate (IRS) proteins and phosphorylated proteins were striking compared with the mRNA. The main consequences of CS4 or CS8 exposures were to significantly reduce insulin R, IGF-1R, IRS-1, and tyrosine phosphorylated insulin R and IGF-1R proteins. Paradoxically, these effects were even greater in the CS8+R group. In addition, relative levels of S312-IRS-1, which inhibits downstream signaling, were increased in the CS4, CS8, and CS8+R groups. Correspondingly, CS and CS8+R exposures inhibited expression of proteins and phosphoproteins required for signaling through Akt, PRAS40, and/or p70S6K, increased AβPP-Aβ, and reduced ASPH protein, which is a target of insulin/IGF-1 signaling. Secondhand CS exposures caused molecular and biochemical abnormalities in brain that overlap with the findings in AD, and many of these effects were sustained or worsened despite short-term CS withdrawal.

Expression of insulin signalling components in the sensory epithelium of the human saccule

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Degerman, Eva; Rauch, Uwe; Lindberg, Sven

2013-01-01

signalling components in the inner ear is sparce. Our immunohistochemistry approach has shown that the insulin receptor, insulin receptor substrate 1 (IRS1), protein kinase B (PKB) and insulin-sensitive glucose transporter (GLUT4) are expressed in the sensory epithelium of the human saccule, which also...

Maternal periodontal disease in rats decreases insulin sensitivity and insulin signaling in adult offspring.

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Shirakashi, Daisy J; Leal, Rosana P; Colombo, Natalia H; Chiba, Fernando Y; Garbin, Cléa A S; Jardim, Elerson G; Antoniali, Cristina; Sumida, Doris H

2013-03-01

Periodontal disease during pregnancy has been recognized as one of the causes of preterm and low-birth-weight (PLBW) babies. Several studies have demonstrated that PLBW babies are prone to developing insulin resistance as adults. Although there is controversy over the association between periodontal disease and PLBW, the phenomenon known as programming can translate any stimulus or aggression experienced during intrauterine growth into physiologic and metabolic alterations in adulthood. The purpose of the present study is to investigate whether the offspring of rats with periodontal disease develop insulin resistance in adulthood. Ten female Wistar rats were divided into periodontal disease (PED) and control (CN) groups. All rats were mated at 7 days after induction of periodontal disease. Male offspring were divided into two groups: 1) periodontal disease offspring (PEDO; n = 24); and 2) control offspring (CNO; n = 24). Offspring body weight was measured from birth until 75 days. When the offspring reached 75 days old, the following parameters were measured: 1) plasma concentrations of glucose, insulin, fructosamine, lipase, amylase, and tumor necrosis factor-α (TNF-α); 2) insulin sensitivity (IS); and 3) insulin signal transduction (IST) in insulin-sensitive tissues. Low birth weight was not detected in the PEDO group. However, plasma concentrations of glucose, insulin, fructosamine, lipase, amylase, and TNF-α were increased and IS and IST were reduced (P PEDO group compared with the CNO group. Maternal periodontal disease may induce insulin resistance and reduce IST in adult offspring, but such alterations are not attributable to low birth weight.

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

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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

Responses of the insulin signaling pathways in the brown adipose tissue of rats following cold exposure.

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Wang, Xiaofei; Wahl, Richard

2014-01-01

The insulin signaling pathway is critical for the control of blood glucose levels. Brown adipose tissue (BAT) has also been implicated as important in glucose homeostasis. The effect of short-term cold exposure on this pathway in BAT has not been explored. We evaluated the effect of 4 hours of cold exposure on the insulin pathway in the BAT of rats. Whole genomic microarray chips were used to examine the transcripts of the pathway in BAT of rats exposed to 4°C and 22°C for 4 hours. The 4 most significantly altered pathways following 4 hours of cold exposure were the insulin signaling pathway, protein kinase A, PI3K/AKT and ERK/MAPK signaling. The insulin signaling pathway was the most affected. In the documented 142 genes of the insulin pathway, 42 transcripts (29.6%) responded significantly to this cold exposure with the least false discovery rate (Benjamini-Hochberg Multiple Testing: -log10 (p-value)  = 7.18). Twenty-seven genes (64%) were up-regulated, including the insulin receptor (Insr), insulin substrates 1 and 2 (Irs1 and Irs2). Fifteen transcripts (36%) were down-regulated. Multiple transcripts of the primary target and secondary effector targets for the insulin signaling were also up-regulated, including those for carbohydrate metabolism. Using western blotting, we demonstrated that the cold induced higher Irs2, Irs1, and Akt-p protein levels in the BAT than in the BAT of controls maintained at room temperature, and higher Akt-p protein level in the muscle. this study demonstrated that 4 hours of cold exposure stimulated the insulin signaling pathway in the BAT and muscle of overnight fasted rats. This raises the possibility that acute cold stimulation may have potential to improve glucose clearance and insulin sensitivity.

Delta-like Ligand-4-Notch Signaling Inhibition Regulates Pancreatic Islet Function and Insulin Secretion

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Fabienne Billiard

2018-01-01

Full Text Available Although Notch signaling has been proposed as a therapeutic target for type-2 diabetes, liver steatosis, and atherosclerosis, its direct effect on pancreatic islets remains unknown. Here, we demonstrated a function of Dll4-Notch signaling inhibition on the biology of insulin-producing cells. We confirmed enhanced expression of key Notch signaling genes in purified pancreatic islets from diabetic NOD mice and showed that treatment with anti-Dll4 antibody specifically abolished Notch signaling pathway activation. Furthermore, we showed that Notch inhibition could drive proliferation of β-islet cells and confer protection from the development of STZ-induced diabetes. Importantly, inhibition of the Dll4 pathway in WT mice increased insulin secretion by inducing the differentiation of pancreatic β-islet cell progenitors, as well as the proliferation of insulin-secreting cells. These findings reveal a direct effect of Dll4-blockade on pancreatic islets that, in conjunction with its immunomodulatory effects, could be used for unmet medical needs hallmarked by inefficient insulin action.

Branched-chain amino acids in metabolic signalling and insulin resistance

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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

In type 1 diabetics, high-dose biotin may compensate for low hepatic insulin exposure, promoting a more normal expression of glycolytic and gluconeogenic enyzymes and thereby aiding glycemic control.

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McCarty, Mark F

2016-10-01

In type 1 diabetics, hepatic exposure to insulin is chronically subnormal even in the context of insulin therapy; as a result, expression of glycolytic enzymes is decreased, and that of gluconeogenic enzymes is enhanced, resulting in a physiologically inappropriate elevation of hepatic glucose output. Subnormal expression of glucokinase (GK) is of particular importance in this regard. Possible strategies for correcting this perturbation of hepatic enzyme expression include administration of small molecule allosteric activators of GK, as well as a procedure known as chronic intermittent intravenous insulin therapy (CIIIT); however, side effects accompany the use of GK activators, and CIIIT is time and labor intensive. Alternatively, administration of high-dose biotin has potential for modulating hepatic enzyme expression in a favorable way. Studies in rodents and in cultured hepatocytes demonstrate that, in the context of low insulin exposure, supra-physiological levels of biotin induce increased expression of GK while suppressing that of the key gluconeogenic enzyme phosphoenolpyruvate carboxykinase. These effects may be a downstream consequence of the fact that biotin down-regulates mRNA expression of FOXO1; insulin's antagonism of the activity of this transcription factor is largely responsible for its modulatory impact on hepatic glycolysis and gluconeogenesis. Hence, high-dose biotin may compensate for subnormal insulin exposure by suppressing FOXO1 levels. High-dose biotin also has the potential to oppose hepatic steatosis by down-regulating SREBP-1 expression. Two pilot trials of high-dose biotin (16 or 2mg per day) in type 1 diabetics have yielded promising results. There is also some reason to suspect that high-dose biotin could aid control of diabetic neuropathy and nephropathy via its stimulatory effect on cGMP production. Owing to the safety, good tolerance, moderate expense, and current availability of high-dose biotin, this strategy merits more

Spatial memory impairment is associated with hippocampal insulin signals in ovariectomized rats.

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Wang, Fang; Song, Yan-Feng; Yin, Jie; Liu, Zi-Hua; Mo, Xiao-Dan; Wang, De-Gui; Gao, Li-Ping; Jing, Yu-Hong

2014-01-01

Estrogen influences memory formation and insulin sensitivity. Meanwhile, glucose utilization directly affects learning and memory, which are modulated by insulin signals. Therefore, this study investigated whether or not the effect of estrogen on memory is associated with the regulatory effect of this hormone on glucose metabolism. The relative expression of estrogen receptor β (ERβ) and glucose transporter type 4 (GLUT4) in the hippocampus of rats were evaluated by western blot. Insulin level was assessed by ELISA and quantitative RT-PCR, and spatial memory was tested by the Morris water maze. Glucose utilization in the hippocampus was measured by 2-NBDG uptake analysis. Results showed that ovariectomy impaired the spatial memory of rats. These impairments are similar as the female rats treated with the ERβ antagonist tamoxifen (TAM). Estrogen blockade by ovariectomy or TAM treatment obviously decreased glucose utilization. This phenomenon was accompanied by decreased insulin level and GLUT4 expression in the hippocampus. The female rats were neutralized with hippocampal insulin with insulin antibody, which also impaired memory and local glucose consumption. These results indicated that estrogen blockade impaired the spatial memory of the female rats. The mechanisms by which estrogen blockade impaired memory partially contributed to the decline in hippocampal insulin signals, which diminished glucose consumption.

Living without insulin: the role of leptin signaling in the hypothalamus

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Teppei eFujikawa

2015-03-01

Full Text Available Since its discovery in 1922, insulin has been thought to be required for normal metabolic homeostasis and survival. However, this view would need to be revised as recent results from different laboratories have convincingly indicated that life without insulin is possible in rodent models. These data indicate that particular neuronal circuitries, which include hypothalamic leptin-responsive neurons, are empowered with the capability of permitting life in complete absence of insulin. Here, we review the neuronal and peripheral mechanisms by which leptin signaling in the central nervous system (CNS regulates glucose metabolism in an insulin-independent manner.

Cardiac Development and Transcription Factors: Insulin Signalling, Insulin Resistance, and Intrauterine Nutritional Programming of Cardiovascular Disease

Science.gov (United States)

Govindsamy, Annelene; Naidoo, Strinivasen

2018-01-01

Programming with an insult or stimulus during critical developmental life stages shapes metabolic disease through divergent mechanisms. Cardiovascular disease increasingly contributes to global morbidity and mortality, and the heart as an insulin-sensitive organ may become insulin resistant, which manifests as micro- and/or macrovascular complications due to diabetic complications. Cardiogenesis is a sequential process during which the heart develops into a mature organ and is regulated by several cardiac-specific transcription factors. Disrupted cardiac insulin signalling contributes to cardiac insulin resistance. Intrauterine under- or overnutrition alters offspring cardiac structure and function, notably cardiac hypertrophy, systolic and diastolic dysfunction, and hypertension that precede the onset of cardiovascular disease. Optimal intrauterine nutrition and oxygen saturation are required for normal cardiac development in offspring and the maintenance of their cardiovascular physiology. PMID:29484207

A common variation of the PTEN gene is associated with peripheral insulin resistance

DEFF Research Database (Denmark)

Grinder-Hansen, L; Ribel-Madsen, R; Wojtaszewski, Jørgen

2016-01-01

. RESULTS: The minor G allele of PTEN rs11202614 was associated with elevated fasting plasma insulin levels and a decreased peripheral glucose disposal rate, but not with the hepatic insulin resistance index or insulin secretion measured as the first-phase insulin response and disposition index. The single...... nucleotide polymorphism was not associated with either PI3K or Akt activities. CONCLUSION: A common PTEN variation is associated with peripheral insulin resistance and subsequent risk of developing T2D. However, the association with insulin resistance is not explained by decreased proximal insulin signalling......AIM: Phosphatase and tensin homologue (PTEN) reduces insulin sensitivity by inhibiting the phosphatidylinositol 3-kinase (PI3K)/v-akt murine thymoma viral oncogene homologue (Akt) pathway. This study investigated how a common single nucleotide polymorphism near PTEN, previously associated...

Astrocytic Insulin Signaling Couples Brain Glucose Uptake with Nutrient Availability.

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García-Cáceres, Cristina; Quarta, Carmelo; Varela, Luis; Gao, Yuanqing; Gruber, Tim; Legutko, Beata; Jastroch, Martin; Johansson, Pia; Ninkovic, Jovica; Yi, Chun-Xia; Le Thuc, Ophelia; Szigeti-Buck, Klara; Cai, Weikang; Meyer, Carola W; Pfluger, Paul T; Fernandez, Ana M; Luquet, Serge; Woods, Stephen C; Torres-Alemán, Ignacio; Kahn, C Ronald; Götz, Magdalena; Horvath, Tamas L; Tschöp, Matthias H

2016-08-11

We report that astrocytic insulin signaling co-regulates hypothalamic glucose sensing and systemic glucose metabolism. Postnatal ablation of insulin receptors (IRs) in glial fibrillary acidic protein (GFAP)-expressing cells affects hypothalamic astrocyte morphology, mitochondrial function, and circuit connectivity. Accordingly, astrocytic IR ablation reduces glucose-induced activation of hypothalamic pro-opio-melanocortin (POMC) neurons and impairs physiological responses to changes in glucose availability. Hypothalamus-specific knockout of astrocytic IRs, as well as postnatal ablation by targeting glutamate aspartate transporter (GLAST)-expressing cells, replicates such alterations. A normal response to altering directly CNS glucose levels in mice lacking astrocytic IRs indicates a role in glucose transport across the blood-brain barrier (BBB). This was confirmed in vivo in GFAP-IR KO mice by using positron emission tomography and glucose monitoring in cerebral spinal fluid. We conclude that insulin signaling in hypothalamic astrocytes co-controls CNS glucose sensing and systemic glucose metabolism via regulation of glucose uptake across the BBB. Copyright © 2016 Elsevier Inc. All rights reserved.

NGA/Insulin receptor scanning

International Nuclear Information System (INIS)

Kurtaran, A.; Virgolini, I.

1994-01-01

Tc-99m-galactosyl-neoglycoalbumin (NGA) is one of the first receptor-based radiopharmaceuticals which specifically recognizes the hepatic binding protein (HBP) located on the surface of the hepatocytes. The exclusive interactin of NGA with HBP provided the basis for a kinetic model for the evaluation hepatocellular function. During the last years we have used NGA in more than 300 patients with various liver diseases including liver cirrhosis (Stages Child A to Child C), viral hepatitis, and carcinomas. In these studies, the calculated HBP densities, after i.v.-injection of Tc-99m-NGA, significantly correlated with the clinical course of the diseases. Furthermore, similar to conventional Tc-colloid, NGA provided excellent demonstration of 'cold spots' for hepatic masses. In a further approach we used another hepatocyte receptor-seeking radioligand, I-123-Tyr-A14- insulin, and found, that its in vitro-binding to hepatocellular carcinomas is greatly enhanced over normal hepatic tissue. On this basis, we developed a double-tracer method using NGA and insulin in a single study. Thus, areas of 'cold spots' identifying hepatic masses on NGA scans, take up I-123-Tyr-A14-insulin immediately after i.v.-injection. This was true for hepatocellular hepatomas, but not for adenocarcinomas. In conclusion, NGA/insulin receptor scanning could be a novel and save method for the demonstration of hepatocellular hepatomas. (author)

NGA/Insulin receptor scanning

Energy Technology Data Exchange (ETDEWEB)

Kurtaran, A; Virgolini, I [Vienna Univ. (Austria). Abt. fuer Nuklearmedizin; Angelberger, P [Ludwig Boltzmann-Institut fuer Nuklearmedizin, Vienna (Austria)

1994-10-01

Tc-99m-galactosyl-neoglycoalbumin (NGA) is one of the first receptor-based radiopharmaceuticals which specifically recognizes the hepatic binding protein (HBP) located on the surface of the hepatocytes. The exclusive interactin of NGA with HBP provided the basis for a kinetic model for the evaluation hepatocellular function. During the last years we have used NGA in more than 300 patients with various liver diseases including liver cirrhosis (Stages Child A to Child C), viral hepatitis, and carcinomas. In these studies, the calculated HBP densities, after i.v.-injection of Tc-99m-NGA, significantly correlated with the clinical course of the diseases. Furthermore, similar to conventional Tc-colloid, NGA provided excellent demonstration of `cold spots` for hepatic masses. In a further approach we used another hepatocyte receptor-seeking radioligand, I-123-Tyr-A14- insulin, and found, that its in vitro-binding to hepatocellular carcinomas is greatly enhanced over normal hepatic tissue. On this basis, we developed a double-tracer method using NGA and insulin in a single study. Thus, areas of `cold spots` identifying hepatic masses on NGA scans, take up I-123-Tyr-A14-insulin immediately after i.v.-injection. This was true for hepatocellular hepatomas, but not for adenocarcinomas. In conclusion, NGA/insulin receptor scanning could be a novel and save method for the demonstration of hepatocellular hepatomas. (author).

Neuronal LRP1 regulates glucose metabolism and insulin signaling in the brain.

Science.gov (United States)

Liu, Chia-Chen; Hu, Jin; Tsai, Chih-Wei; Yue, Mei; Melrose, Heather L; Kanekiyo, Takahisa; Bu, Guojun

2015-04-08

Alzheimer's disease (AD) is a neurological disorder characterized by profound memory loss and progressive dementia. Accumulating evidence suggests that Type 2 diabetes mellitus, a metabolic disorder characterized by insulin resistance and glucose intolerance, significantly increases the risk for developing AD. Whereas amyloid-β (Aβ) deposition and neurofibrillary tangles are major histological hallmarks of AD, impairment of cerebral glucose metabolism precedes these pathological changes during the early stage of AD and likely triggers or exacerbates AD pathology. However, the mechanisms linking disturbed insulin signaling/glucose metabolism and AD pathogenesis remain unclear. The low-density lipoprotein receptor-related protein 1 (LRP1), a major apolipoprotein E receptor, plays critical roles in lipoprotein metabolism, synaptic maintenance, and clearance of Aβ in the brain. Here, we demonstrate that LRP1 interacts with the insulin receptor β in the brain and regulates insulin signaling and glucose uptake. LRP1 deficiency in neurons leads to impaired insulin signaling as well as reduced levels of glucose transporters GLUT3 and GLUT4. Consequently, glucose uptake is reduced. By using an in vivo microdialysis technique sampling brain glucose concentration in freely moving mice, we further show that LRP1 deficiency in conditional knock-out mice resulted in glucose intolerance in the brain. We also found that hyperglycemia suppresses LRP1 expression, which further exacerbates insulin resistance, glucose intolerance, and AD pathology. As loss of LRP1 expression is seen in AD brains, our study provides novel insights into insulin resistance in AD. Our work also establishes new targets that can be explored for AD prevention or therapy. Copyright © 2015 the authors 0270-6474/15/355851-09$15.00/0.

Variants of Insulin-Signaling Inhibitor Genes in Type 2 Diabetes and Related Metabolic Abnormalities

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Carlo de Lorenzo

2013-01-01

Full Text Available Insulin resistance has a central role in the pathogenesis of several metabolic diseases, including type 2 diabetes, obesity, glucose intolerance, metabolic syndrome, atherosclerosis, and cardiovascular diseases. Insulin resistance and related traits are likely to be caused by abnormalities in the genes encoding for proteins involved in the composite network of insulin-signaling; in this review we have focused our attention on genetic variants of insulin-signaling inhibitor molecules. These proteins interfere with different steps in insulin-signaling: ENPP1/PC-1 and the phosphatases PTP1B and PTPRF/LAR inhibit the insulin receptor activation; INPPL1/SHIP-2 hydrolyzes PI3-kinase products, hampering the phosphoinositide-mediated downstream signaling; and TRIB3 binds the serine-threonine kinase Akt, reducing its phosphorylation levels. While several variants have been described over the years for all these genes, solid evidence of an association with type 2 diabetes and related diseases seems to exist only for rs1044498 of the ENPP1 gene and for rs2295490 of the TRIB3 gene. However, overall the data recapitulated in this Review article may supply useful elements to interpret the results of novel, more technically advanced genetic studies; indeed it is becoming increasingly evident that genetic information on metabolic diseases should be interpreted taking into account the complex biological pathways underlying their pathogenesis.

Effect of insulin resistance on intracellular signal transduction of vessels in diabetic

International Nuclear Information System (INIS)

Cen Rongguang; Wei Shaoying; Mo Xingju

2003-01-01

To investigate the relationship between the insulin resistance (IR) and the intracellular signal transduction of vessels, changes in fasting blood glucose (FBG), fasting insulin (FINS), triglyceride (TG), total cholesterol (TC), inositol triphosphate (IP 3 ), protein kinase C(PKC) and intracellular total calcium concentration in 31 diabetic patients were compared with those of 39 normal controls. The levels of FBG, FINS, TG and TC in diabetic patients were significantly higher than those of normal controls (P 3 and PKC in diabetic patients were significantly lower than those of normal controls (P<0.01). The results suggest that there is a causal relation between insulin resistance and abnormalities of cellular calcium metabolism and intracellular signal transduction of vessels

Central Nervous Insulin Signaling in Sleep-Associated Memory Formation and Neuroendocrine Regulation

OpenAIRE

Feld, Gordon B; Wilhem, Ines; Benedict, Christian; Rüdel, Benjamin; Klameth, Corinna; Born, Jan; Hallschmid, Manfred

2016-01-01

The neurochemical underpinnings of sleep's contribution to the establishment and maintenance of memory traces are largely unexplored. Considering that intranasal insulin administration to the CNS improves memory functions in healthy and memory-impaired humans, we tested whether brain insulin signaling and sleep interact to enhance memory consolidation in healthy participants. We investigated the effect of intranasal insulin on sleep-associated neurophysiological and neuroendocrine parameters ...

Lipid metabolism disturbances contribute to insulin resistance and decrease insulin sensitivity by malathion exposure in Wistar rat.

Science.gov (United States)

Lasram, Mohamed Montassar; Bouzid, Kahena; Douib, Ines Bini; Annabi, Alya; El Elj, Naziha; El Fazaa, Saloua; Abdelmoula, Jaouida; Gharbi, Najoua

2015-04-01

Several studies showed that organophosphorus pesticides disturb glucose homeostasis and can increase incidence of metabolic disorders and diabetes via insulin resistance. The current study investigates the influence of malathion on glucose metabolism regulation, in vivo, during subchronic exposure. Malathion was administered orally (200 mg/kg), once a day for 28 consecutive days. Plasma glucose, insulin and Glycated hemoglobin levels were significantly increased while hepatic glycogen content was decreased in intoxicated animals compared with the control group. Furthermore, there was a significant disturbance of lipid content in subchronic treated and post-treated rats deprived of malathion for one month. In addition, we used the homeostasis model assessment (HOMA) to assess insulin resistance (HOMA-IR) and pancreatic β-cell function (HOMA-β). Our results show that malathion increases insulin resistance biomarkers and decreases insulin sensitivity indices. Statistical analysis demonstrates that there was a positive and strong significant correlation between insulin level and insulin resistance indices, HOMA-IR, HOMA-β. Similarly, a negative and significant correlation was also found between insulin level and insulin sensitivity indices. For the first time, we demonstrate that malathion induces insulin resistance in vivo using homeostasis model assessment and these changes were detectable one month after the end of exposure. To explain insulin resistance induced by malathion we focus on lipid metabolism disturbances and their interaction with many proteins involved in insulin signaling pathways.

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

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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

Central insulin-like growth factor-1 (IGF-1) restores whole-body insulin action in a model of age-related insulin resistance and IGF-1 decline.

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Huffman, Derek M; Farias Quipildor, Gabriela; Mao, Kai; Zhang, Xueying; Wan, Junxiang; Apontes, Pasha; Cohen, Pinchas; Barzilai, Nir

2016-02-01

Low insulin-like growth factor-1 (IGF-1) signaling is associated with improved longevity, but is paradoxically linked with several age-related diseases in humans. Insulin-like growth factor-1 has proven to be particularly beneficial to the brain, where it confers protection against features of neuronal and cognitive decline. While aging is characterized by central insulin resistance in the face of hyperinsulinemia, the somatotropic axis markedly declines in older humans. Thus, we hypothesized that increasing IGF-1 in the brain may prove to be a novel therapeutic alternative to overcome central insulin resistance and restore whole-body insulin action in aging. Utilizing hyperinsulinemic-euglycemic clamps, we show that old insulin-resistant rats with age-related declines in IGF-1 level demonstrate markedly improved whole-body insulin action, when treated with central IGF-1, as compared to central vehicle or insulin (P IGF-1, but not insulin, suppressed hepatic glucose production and increased glucose disposal rates in aging rats (P IGF-1 action in the brain and periphery provides a 'balance' between its beneficial and detrimental actions. Therefore, we propose that strategies aimed at 'tipping the balance' of IGF-1 action centrally are the optimal approach to achieve healthy aging and longevity in humans. © 2015 The Authors. Aging Cell published by the Anatomical Society and John Wiley & Sons Ltd.

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....

Regulation of energy substrate utilization and hepatic insulin sensitivity by phosphatidylcholine transfer protein/StarD2.

Science.gov (United States)

Scapa, Erez F; Pocai, Alessandro; Wu, Michele K; Gutierrez-Juarez, Roger; Glenz, Lauren; Kanno, Keishi; Li, Hua; Biddinger, Sudha; Jelicks, Linda A; Rossetti, Luciano; Cohen, David E

2008-07-01

Phosphatidylcholine transfer protein (PC-TP, also known as StarD2) is a highly specific intracellular lipid binding protein with accentuated expression in oxidative tissues. Here we show that decreased plasma concentrations of glucose and free fatty acids in fasting PC-TP-deficient (Pctp(-/-)) mice are attributable to increased hepatic insulin sensitivity. In hyperinsulinemic-euglycemic clamp studies, Pctp(-/-) mice exhibited profound reductions in hepatic glucose production, gluconeogenesis, glycogenolysis, and glucose cycling. These changes were explained in part by the lack of PC-TP expression in liver per se and in part by marked alterations in body fat composition. Reduced respiratory quotients in Pctp(-/-) mice were indicative of preferential fatty acid utilization for energy production in oxidative tissues. In the setting of decreased hepatic fatty acid synthesis, increased clearance rates of dietary triglycerides and increased hepatic triglyceride production rates reflected higher turnover in Pctp(-/-) mice. Collectively, these data support a key biological role for PC-TP in the regulation of energy substrate utilization.

Insulin secretion and signaling in response to dietary restriction and subsequent re-alimentation in cattle.

Science.gov (United States)

Keogh, Kate; Kenny, David A; Kelly, Alan K; Waters, Sinéad M

2015-08-01

The objectives of this study were to examine systemic insulin response to a glucose tolerance test (GTT) and transcript abundance of genes of the insulin signaling pathway in skeletal muscle, during both dietary restriction and re-alimentation-induced compensatory growth. Holstein Friesian bulls were blocked to one of two groups: 1) restricted feed allowance for 125 days (period 1) (RES, n = 15) followed by ad libitum feeding for 55 days (period 2) or 2) ad libitum access to feed throughout (periods 1 and 2) (ADLIB, n = 15). On days 90 and 36 of periods 1 and 2, respectively, a GTT was performed. M. longissimus dorsi biopsies were harvested from all bulls on days 120 and 15 of periods 1 and 2, respectively, and RNA-Seq analysis was performed. RES displayed a lower growth rate during period 1 (RES: 0.6 kg/day, ADLIB: 1.9 kg/day; P alimentation (RES: 2.5 kg/day, ADLIB: 1.4 kg/day; P alimentation (P > 0.05). Genes differentially expressed in the insulin signaling pathway suggested a greater sensitivity to insulin in skeletal muscle, with pleiotropic effects of insulin signaling interrupted during dietary restriction. Collectively, these results indicate increased sensitivity to glucose clearance and skeletal muscle insulin signaling during dietary restriction; however, no overall role for insulin was apparent in expressing compensatory growth. Copyright © 2015 the American Physiological Society.

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

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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.

Delivery of circulating lipoproteins to specific neurons in the Drosophila brain regulates systemic insulin signaling.

Science.gov (United States)

Brankatschk, Marko; Dunst, Sebastian; Nemetschke, Linda; Eaton, Suzanne

2014-10-02

The Insulin signaling pathway couples growth, development and lifespan to nutritional conditions. Here, we demonstrate a function for the Drosophila lipoprotein LTP in conveying information about dietary lipid composition to the brain to regulate Insulin signaling. When yeast lipids are present in the diet, free calcium levels rise in Blood Brain Barrier glial cells. This induces transport of LTP across the Blood Brain Barrier by two LDL receptor-related proteins: LRP1 and Megalin. LTP accumulates on specific neurons that connect to cells that produce Insulin-like peptides, and induces their release into the circulation. This increases systemic Insulin signaling and the rate of larval development on yeast-containing food compared with a plant-based food of similar nutritional content.

Hepatic insulin-like growth-factor binding protein (igfbp) responses tofood restriction in Atlantic salmon smolts

Science.gov (United States)

Breves, Jason P.; Phipps-Costin, Silas K.; Fujimoto, Chelsea K.; Einarsdottir, Ingibjörg E.; Regish, Amy M.; Björnsson, Björn Thrandur; McCormick, Stephen

2016-01-01

The growth hormone (Gh)/insulin-like growth-factor (Igf) system plays a central role in the regulation of growth in fishes. However, the roles of Igf binding proteins (Igfbps) in coordinating responses to food availability are unresolved, especially in anadromous fishes preparing for seaward migration. We assayed plasma Gh, Igf1, thyroid hormones and cortisol along with igfbp mRNA levels in fasted and fed Atlantic salmon ( Salmo salar ). Fish were fasted for 3 or 10 days near the peak of smoltification (late April to early May). Fasting reduced plasma glucose by 3 days and condition factor by 10 days. Plasma Gh, cortisol, and thyroxine (T 4 ) were not altered in response to fasting, whereas Igf1 and 3,5,3′-triiodo- l -thyronine (T 3 ) were slightly higher and lower than controls, respectively. Hepatic igfbp1b1 , - 1b2 , - 2a , - 2b1 and - 2b2 mRNA levels were not responsive to fasting, but there were marked increases in igfbp1a1 following 3 and 10 days of fasting. Fasting did not alter hepatic igf1or igf2 ; however, muscle igf1 was diminished by 10 days of fasting. There were no signs that fasting compromised branchial ionoregulatory functions, as indicated by unchanged Na + /K + -ATPase activity and ion pump/transporter mRNA levels. We conclude that dynamic hepatic igfbp1a1 and muscle igf1 expression participate in the modulation of Gh/Igf signaling in smolts undergoing catabolism.

Hepcidin is directly regulated by insulin and plays an important role in iron overload in streptozotocin-induced diabetic rats.

Science.gov (United States)

Wang, Heyang; Li, Hongxia; Jiang, Xin; Shi, Wencai; Shen, Zhilei; Li, Min

2014-05-01

Iron overload is frequently observed in type 2 diabetes mellitus (DM2), but the underlying mechanisms remain unclear. We hypothesize that hepcidin may be directly regulated by insulin and play an important role in iron overload in DM2. We therefore examined the hepatic iron content, serum iron parameters, intestinal iron absorption, and liver hepcidin expression in rats treated with streptozotocin (STZ), which was given alone or after insulin resistance induced by a high-fat diet. The direct effect of insulin on hepcidin and its molecular mechanisms were furthermore determined in vitro in HepG2 cells. STZ administration caused a significant reduction in liver hepcidin level and a marked increase in intestinal iron absorption and serum and hepatic iron content. Insulin obviously upregulated hepcidin expression in HepG2 cells and enhanced signal transducer and activator of transcription 3 protein synthesis and DNA binding activity. The effect of insulin on hepcidin disappeared when the signal transducer and activator of transcription 3 pathway was blocked and could be partially inhibited by U0126. In conclusion, the current study suggests that hepcidin can be directly regulated by insulin, and the suppressed liver hepcidin synthesis may be an important reason for the iron overload in DM2.

Fluoxetine increases insulin action in obese type II (non-insulin dependent) diabetic patients

NARCIS (Netherlands)

Potter van Loon, B. J.; Radder, J. K.; Froelich, M.; Krans, H. Michiel J.; Zwinderman, A. H.; Meinders, A. E.

1992-01-01

Insulin resistance contributes to the metabolic defects in non-insulin dependent diabetes mellitus (NIDDM). Anorectic agents have been shown to improve insulin action in NIDDM, irrespective of weight reduction. In a double-blind placebo-controlled cross-over study, we examined hepatic and peripheral

Berberine inhibits hepatic gluconeogenesis via the LKB1-AMPK-TORC2 signaling pathway in streptozotocin-induced diabetic rats.

Science.gov (United States)

Jiang, Shu-Jun; Dong, Hui; Li, Jing-Bin; Xu, Li-Jun; Zou, Xin; Wang, Kai-Fu; Lu, Fu-Er; Yi, Ping

2015-07-07

To investigate the molecular mechanisms of berberine inhibition of hepatic gluconeogenesis in a diabetic rat model. The 40 rats were randomly divided into five groups. One group was selected as the normal group. In the remaining groups (n = 8 each), the rats were fed on a high-fat diet for 1 mo and received intravenous injection of streptozotocin for induction of the diabetic models. Berberine (156 mg/kg per day) (berberine group) or metformin (184 mg/kg per day) (metformin group) was intragastrically administered to the diabetic rats and 5-aminoimidazole-4-carboxamide1-β-D-ribofuranoside (AICAR) (0.5 mg/kg per day) (AICAR group) was subcutaneously injected to the diabetic rats for 12 wk. The remaining eight diabetic rats served as the model group. Fasting plasma glucose and insulin levels as well as lipid profile were tested. The expressions of proteins were examined by western blotting. The nuclear translocation of CREB-regulated transcription co-activator (TORC)2 was observed by immunohistochemical staining. Berberine improved impaired glucose tolerance and decreased plasma hyperlipidemia. Moreover, berberine decreased fasting plasma insulin and homeostasis model assessment of insulin resistance (HOMA-IR). Berberine upregulated protein expression of liver kinase (LK)B1, AMP-activated protein kinase (AMPK) and phosphorylated AMPK (p-AMPK). The level of phophorylated TORC2 (p-TORC2) protein in the cytoplasm was higher in the berberine group than in the model group, and no significant difference in total TORC2 protein level was observed. Immunohistochemical staining revealed that more TORC2 was localized in the cytoplasm of the berberine group than in the model group. Moreover, berberine treatment downregulated protein expression of the key gluconeogenic enzymes (phosphoenolpyruvate carboxykinase and glucose-6-phosphatase) in the liver tissues. Our findings revealed that berberine inhibited hepatic gluconeogenesis via the regulation of the LKB1-AMPK-TORC2

Implication of inflammatory signaling pathways in obesity-induced insulin resistance

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Jean-François eTANTI

2013-01-01

Full Text Available Obesity is characterized by the development of a low-grade chronic inflammatory state in different metabolic tissues including adipose tissue and liver. This inflammation develops in response to an excess of nutrient flux and is now recognized as an important link between obesity and insulin resistance. Several dietary factors like saturated fatty acids and glucose as well as changes in gut microbiota have been proposed as triggers of this metabolic inflammation through the activation of pattern-recognition receptors, including Toll-like receptors, inflammasome and NOD. The consequences are the production of pro-inflammatory cytokines and the recruitment of immune cells such as macrophages and T lymphocytes in metabolic tissues. Inflammatory cytokines activate several kinases like IKKbeta, mTOR/S6 kinase and MAP kinases as well as SOCS proteins that interfere with insulin signaling and action in adipocytes and hepatocytes. In this review, we summarize recent studies demonstrating that pattern recognition receptors and stress kinases are important integrators of metabolic and inflammatory stress signals in metabolic tissues leading to peripheral and central insulin resistance and metabolic dysfunction. We discuss recent data obtained with genetically modified mice and pharmacological approaches suggesting that these inflammatory pathways are potential novel pharmacological targets for the management of obesity-associated insulin resistance.

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

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

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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.

Impaired Insulin/IGF Signaling in Experimental Alcohol-Related Myopathy

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Elizabeth Silbermann

2012-08-01

Full Text Available Alcohol-related myopathy (Alc-M is highly prevalent among heavy drinkers, although its pathogenesis is not well understood. We hypothesize that Alc-M is mediated by combined effects of insulin/IGF resistance and oxidative stress, similar to the effects of ethanol on liver and brain. We tested this hypothesis using an established model in which adult rats were pair-fed for 8 weeks with isocaloric diets containing 0% (N = 8 or 35.5% (N = 13 ethanol by caloric content. Gastrocnemius muscles were examined by histology, morphometrics, qRT-PCR analysis, and ELISAs. Chronic ethanol feeding reduced myofiber size and mRNA expression of IGF-1 polypeptide, insulin, IGF-1, and IGF-2 receptors, IRS-1, and IRS-2. Multiplex ELISAs demonstrated ethanol-associated inhibition of insulin, IRS-1, Akt, and p70S6K signaling, and increased activation of GSK-3β. In addition, ethanol-exposed muscles had increased 4-hydroxy-2-nonenal immunoreactivity, reflecting lipid peroxidation, and reduced levels of mitochondrial Complex IV, Complex V, and acetylcholinesterase. These results demonstrate that experimental Alc-M is associated with inhibition of insulin/IGF/IRS and downstream signaling that mediates metabolism and cell survival, similar to findings in alcoholic liver and brain degeneration. Moreover, the increased oxidative stress, which could be mediated by mitochondrial dysfunction, may have led to inhibition of acetylcholinesterase, which itself is sufficient to cause myofiber atrophy and degeneration.

Akt and Rac1 signalling are jointly required for insulin-stimulated glucose uptake in skeletal muscle and downregulated in insulin resistance

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Sylow, Lykke; Kleinert, Maximilian; Pehmøller, Christian

2014-01-01

Skeletal muscle plays a major role in regulating whole body glucose metabolism. Akt and Rac1 are important regulators of insulin-stimulated glucose uptake in skeletal muscle. However the relative role of each pathway and how they interact is not understood. Here we delineate how Akt and Rac1...... pathways signal to increase glucose transport independently of each other and are simultaneously downregulated in insulin resistant muscle. Pharmacological inhibition of Rac1 and Akt signalling was used to determine the contribution of each pathway to insulin-stimulated glucose uptake in mouse muscles....... The actin filament-depolymerizing agent LatrunculinB was combined with pharmacological inhibition of Rac1 or Akt, to examine whether either pathway mediates its effect via the actin cytoskeleton. Akt and Rac1 signalling were investigated under each condition, as well as upon Akt2 knockout and in ob/ob mice...

Chronic hepatitis B associated with hepatic steatosis, insulin ...

African Journals Online (AJOL)

Objectives: The aim of this study was to investigate the viral and host causes of ... Homeostasis Model Assessment- Insulin Resistance (HOMA-IR), viral load, ... those diagnosed with diabetes and cirrhosis, patients ... insulin (µU/ml) × fasting glucose (mmol/L))/22.514. ..... ic steatosis B virus infected patients: meta-analysis of.

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

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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

Coordinated Regulation of Insulin Signaling by the Protein Tyrosine Phosphatases PTP1B and TCPTP

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Galic, Sandra; Hauser, Christine; Kahn, Barbara B.; Haj, Fawaz G.; Neel, Benjamin G.; Tonks, Nicholas K.; Tiganis, Tony

2005-01-01

The protein tyrosine phosphatase PTP1B is a negative regulator of insulin signaling and a therapeutic target for type 2 diabetes. Our previous studies have shown that the closely related tyrosine phosphatase TCPTP might also contribute to the regulation of insulin receptor (IR) signaling in vivo (S. Galic, M. Klingler-Hoffmann, M. T. Fodero-Tavoletti, M. A. Puryer, T. C. Meng, N. K. Tonks, and T. Tiganis, Mol. Cell. Biol. 23:2096-2108, 2003). Here we show that PTP1B and TCPTP function in a coordinated and temporally distinct manner to achieve an overall regulation of IR phosphorylation and signaling. Whereas insulin-induced phosphatidylinositol 3-kinase/Akt signaling was prolonged in both TCPTP−/− and PTP1B−/− immortalized mouse embryo fibroblasts (MEFs), mitogen-activated protein kinase ERK1/2 signaling was elevated only in PTP1B-null MEFs. By using phosphorylation-specific antibodies, we demonstrate that both IR β-subunit Y1162/Y1163 and Y972 phosphorylation are elevated in PTP1B−/− MEFs, whereas Y972 phosphorylation was elevated and Y1162/Y1163 phosphorylation was sustained in TCPTP−/− MEFs, indicating that PTP1B and TCPTP differentially contribute to the regulation of IR phosphorylation and signaling. Consistent with this, suppression of TCPTP protein levels by RNA interference in PTP1B−/− MEFs resulted in no change in ERK1/2 signaling but caused prolonged Akt activation and Y1162/Y1163 phosphorylation. These results demonstrate that PTP1B and TCPTP are not redundant in insulin signaling and that they act to control both common as well as distinct insulin signaling pathways in the same cell. PMID:15632081

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.

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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.

Insulin Clearance Is Associated with Hepatic Lipase Activity and Lipid and Adiposity Traits in Mexican Americans.

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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.

Circulating Glucagon 1-61 Regulates Blood Glucose by Increasing Insulin Secretion and Hepatic Glucose Production

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Nicolai J. Wewer Albrechtsen

2017-11-01

Full Text Available Glucagon is secreted from pancreatic α cells, and hypersecretion (hyperglucagonemia contributes to diabetic hyperglycemia. Molecular heterogeneity in hyperglucagonemia is poorly investigated. By screening human plasma using high-resolution-proteomics, we identified several glucagon variants, among which proglucagon 1-61 (PG 1-61 appears to be the most abundant form. PG 1-61 is secreted in subjects with obesity, both before and after gastric bypass surgery, with protein and fat as the main drivers for secretion before surgery, but glucose after. Studies in hepatocytes and in β cells demonstrated that PG 1-61 dose-dependently increases levels of cAMP, through the glucagon receptor, and increases insulin secretion and protein levels of enzymes regulating glycogenolysis and gluconeogenesis. In rats, PG 1-61 increases blood glucose and plasma insulin and decreases plasma levels of amino acids in vivo. We conclude that glucagon variants, such as PG 1-61, may contribute to glucose regulation by stimulating hepatic glucose production and insulin secretion.

Dihydrotestosterone deteriorates cardiac insulin signaling and glucose transport in the rat model of polycystic ovary syndrome.

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Tepavčević, Snežana; Vojnović Milutinović, Danijela; Macut, Djuro; Žakula, Zorica; Nikolić, Marina; Božić-Antić, Ivana; Romić, Snježana; Bjekić-Macut, Jelica; Matić, Gordana; Korićanac, Goran

2014-05-01

It is supposed that women with polycystic ovary syndrome (PCOS) are prone to develop cardiovascular disease as a consequence of multiple risk factors that are mostly related to the state of insulin resistance and consequent hyperinsulinemia. In the present study, we evaluated insulin signaling and glucose transporters (GLUT) in cardiac cells of dihydrotestosterone (DHT) treated female rats as an animal model of PCOS. Expression of proteins involved in cardiac insulin signaling pathways and glucose transporters, as well as their phosphorylation or intracellular localization were studied by Western blot analysis in DHT-treated and control rats. Treatment with DHT resulted in increased body mass, absolute mass of the heart, elevated plasma insulin concentration, dyslipidemia and insulin resistance. At the molecular level, DHT treatment did not change protein expression of cardiac insulin receptor and insulin receptor substrate 1, while phosphorylation of the substrate at serine 307 was increased. Unexpectedly, although expression of downstream Akt kinase and its phosphorylation at threonine 308 were not altered, phosphorylation of Akt at serine 473 was increased in the heart of DHT-treated rats. In contrast, expression and phosphorylation of extracellular signal regulated kinases 1/2 were decreased. Plasma membrane contents of GLUT1 and GLUT4 were decreased, as well as the expression of GLUT4 in cardiac cells at the end of androgen treatment. The obtained results provide evidence for alterations in expression and especially in functional characteristics of insulin signaling molecules and glucose transporters in the heart of DHT-treated rats with PCOS, indicating impaired cardiac insulin action. Copyright © 2014 Elsevier Ltd. All rights reserved.

Signal transduction through the IL-4 and insulin receptor families.

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Wang, L M; Keegan, A; Frankel, M; Paul, W E; Pierce, J H

1995-07-01

Activation of tyrosine kinase-containing receptors and intracellular tyrosine kinases by ligand stimulation is known to be crucial for mediating initial and subsequent events involved in mitogenic signal transduction. Receptors for insulin and insulin-like growth factor 1 (IGF-1) contain cytoplasmic tyrosine kinase domains that undergo autophosphorylation upon ligand stimulation. Activation of these receptors also leads to pronounced and rapid tyrosine phosphorylation of insulin receptor substrate 1 (IRS-1) in cells of connective tissue origin. A related substrate, designated 4PS, is similarly phosphorylated by insulin and IGF-1 stimulation in many hematopoietic cell types. IRS-1 and 4PS possess a number of tyrosine phosphorylation sites that are within motifs that bind specific SH2-containing molecules known to be involved in mitogenic signaling such as PI-3 kinase, SHPTP-2 (Syp) and Grb-2. Thus, they appear to act as docking substrates for a variety of signaling molecules. The majority of hematopoietic cytokines bind to receptors that do not possess intrinsic kinase activity, and these receptors have been collectively termed as members of the hematopoietin receptor superfamily. Despite their lack of tyrosine kinase domains, stimulation of these receptors has been demonstrated to activate intracellular kinases leading to tyrosine phosphorylation of multiple substrates. Recent evidence has demonstrated that activation of different members of the Janus family of tyrosine kinases is involved in mediating tyrosine phosphorylation events by specific cytokines. Stimulation of the interleukin 4 (IL-4) receptor, a member of the hematopoietin receptor superfamily, is thought to result in activation of Jak1, Jak3, and/or Fes tyrosine kinases.(ABSTRACT TRUNCATED AT 250 WORDS)

Action of Phytochemicals on Insulin Signaling Pathways Accelerating Glucose Transporter (GLUT4 Protein Translocation

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Abu Sadat Md Sayem

2018-01-01

Full Text Available Diabetes is associated with obesity, generally accompanied by a chronic state of oxidative stress and redox imbalances which are implicated in the progression of micro- and macro-complications like heart disease, stroke, dementia, cancer, kidney failure and blindness. All these complications rise primarily due to consistent high blood glucose levels. Insulin and glucagon help to maintain the homeostasis of glucose and lipids through signaling cascades. Pancreatic hormones stimulate translocation of the glucose transporter isoform 4 (GLUT4 from an intracellular location to the cell surface and facilitate the rapid insulin-dependent storage of glucose in muscle and fat cells. Malfunction in glucose uptake mechanisms, primarily contribute to insulin resistance in type 2 diabetes. Plant secondary metabolites, commonly known as phytochemicals, are reported to have great benefits in the management of type 2 diabetes. The role of phytochemicals and their action on insulin signaling pathways through stimulation of GLUT4 translocation is crucial to understand the pathogenesis of this disease in the management process. This review will summarize the effects of phytochemicals and their action on insulin signaling pathways accelerating GLUT4 translocation based on the current literature.

Elevated toll-like receptor 4 expression and signaling in muscle from insulin-resistant subjects.

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Reyna, Sara M; Ghosh, Sangeeta; Tantiwong, Puntip; Meka, C S Reddy; Eagan, Phyllis; Jenkinson, Christopher P; Cersosimo, Eugenio; Defronzo, Ralph A; Coletta, Dawn K; Sriwijitkamol, Apiradee; Musi, Nicolas

2008-10-01

OBJECTIVE- Tall-like receptor (TLR)4 has been implicated in the pathogenesis of free fatty acid (FFA)-induced insulin resistance by activating inflammatory pathways, including inhibitor of kappaB (IkappaB)/nuclear factor kappaB (NFkappaB). However, it is not known whether insulin-resistant subjects have abnormal TLR4 signaling. We examined whether insulin-resistant subjects have abnormal TLR4 expression and TLR4-driven (IkappaB/NFkappaB) signaling in skeletal muscle. RESEARCH DESIGN AND METHODS- TLR4 gene expression and protein content were measured in muscle biopsies in 7 lean, 8 obese, and 14 type 2 diabetic subjects. A primary human myotube culture system was used to examine whether FFAs stimulate IkappaB/NFkappaB via TLR4 and whether FFAs increase TLR4 expression/content in muscle. RESULTS- Obese and type 2 diabetic subjects had significantly elevated TLR4 gene expression and protein content in muscle. TLR4 muscle protein content correlated with the severity of insulin resistance. Obese and type 2 diabetic subjects also had lower IkappaBalpha content, an indication of elevated IkappaB/NFkappaB signaling. The increase in TLR4 and NFkappaB signaling was accompanied by elevated expression of the NFkappaB-regulated genes interleukin (IL)-6 and superoxide dismutase (SOD)2. In primary human myotubes, acute palmitate treatment stimulated IkappaB/NFkappaB, and blockade of TLR4 prevented the ability of palmitate to stimulate the IkappaB/NFkappaB pathway. Increased TLR4 content and gene expression observed in muscle from insulin-resistant subjects were reproduced by treating myotubes from lean, normal-glucose-tolerant subjects with palmitate. Palmitate also increased IL-6 and SOD2 gene expression, and this effect was prevented by inhibiting NFkappaB. CONCLUSIONS- Abnormal TLR4 expression and signaling, possibly caused by elevated plasma FFA levels, may contribute to the pathogenesis of insulin resistance in humans.

Lipid induced insulin resistance affects women less than men and is not accompanied by inflammation or impaired proximal insulin signaling

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Høeg, Louise D; Sjøberg, Kim Anker; Jeppesen, Jacob

2011-01-01

than men. We therefore hypothesized that women would be less prone to lipid induced insulin resistance. Research and design methods: Insulin sensitivity of whole body and leg glucose disposal was studied in 16 young well matched healthy men and women infused with intralipid or saline for 7h. Muscle...... ratio was decreased by intralipid. Conclusion: Intralipid infusion causes less insulin resistance of muscle glucose uptake in women than in men. This insulin resistance is not due to decreased canonical insulin signaling, accumulation of lipid intermediates, inflammation or direct inhibition of glucose......AbstractObjective: We have previously shown that overnight fasted women have higher insulin stimulated whole body and leg glucose uptake despite a higher intramyocellular triacylglycerol concentration than men. Women also express higher muscle mRNA levels of proteins related to lipid metabolism...

Entada phaseoloides extract suppresses hepatic gluconeogenesis via activation of the AMPK signaling pathway.

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Zheng, Tao; Hao, Xincai; Wang, Qibin; Chen, Li; Jin, Si; Bian, Fang

2016-12-04

The seed of Entada phaseoloides (L.) Merr. (Entada phaseoloides) has been long used as a folk medicine for the treatment of Diabetes mellitus by Chinese ethnic minorities. Recent reports have demonstrated that total saponins from Entada phaseoloides (TSEP) could reduce fasting blood glucose in type 2 diabetic rats. However, the mechanism has not been fully elucidated. The aim of this study was to explore the underlying mechanisms of TSEP on type 2 Diabetes mellitus (T2DM). Primary mouse hepatocytes and HepG2 cells were used to investigate the effects of TSEP on gluconeogenesis. After treatment with TSEP, glucose production, genes expression levels of Glucose-6-phosphatase (G6pase) and Phosphoenoylpyruvate carboxykinase (Pepck) were detected. The efficacy and underlying mechanism of TSEP on AMP-activated protein kinase (AMPK) signaling pathway were determinated. TSEP significantly inhibited glucose production and the gluconeogenic gene expression. Treatment with TSEP elevated the phosphorylation of AMPK, which in turn promoted the phosphorylation of acetyl coenzyme A (ACC) and Akt/glycogen synthase kinase 3β (GSK3β), respectively. Furthermore, TSEP reduced lipid accumulation and improved insulin sensitivity in hepatocytes. These findings provide evidence that TSEP exerts an antidiabetic effect by suppressing hepatic gluconeogenesis via the AMPK signaling pathway. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

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

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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

Decreased insulin response in dairy cows following a four-day fast to induce hepatic lipidosis.

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Oikawa, S; Oetzel, G R

2006-08-01

Negative energy balance has been implicated in the development of fatty liver, insulin resistance, and impaired health in dairy cows. A 4-d fasting model previously was reported to increase liver triglycerides more than 2.5-fold. The purpose of the present study was to evaluate insulin response in this fasting model. Nonlactating, nonpregnant Holstein cows were fasted for 4 d (6 cows) or fed continuously as control cows (4 cows). Samples were collected 5 d before fasting, during fasting, and immediately after the 4-d fast, 8 d after the fast, and 16 d after the fast. Fasted cows had greater liver triglyceride content (49.4 vs. 16.2 mg/g, wet-weight basis) at the end of the fasting period compared with control cows. Fasted cows also had increased plasma nonesterified fatty acid (NEFA) concentrations (1.24 vs. 0.21 mmol/L) and increased plasma beta-hydroxybutyrate (BHBA) concentrations at the end of the fasting period. Liver triglyceride, plasma NEFA, and plasma BHBA in fasted cows returned to prefasting concentrations by the end of the experiment. Plasma glucose concentrations were not affected by fasting. Plasma insulin concentrations were decreased (6.3 vs. 14.1 microU/mL) and insulin-stimulated blood glucose reduction was decreased (24.9 vs. 48.6%) in the fasted cows compared with control cows at the end of the fast, indicating reduced insulin response. Insulin response was negatively correlated with plasma NEFA and liver triglycerides. Decreased insulin response may be an important complication of negative energy balance and hepatic lipidosis.

Ethanolic Extract of Butea monosperma Leaves Elevate Blood Insulin Level in Type 2 Diabetic Rats, Stimulate Insulin Secretion in Isolated Rat Islets, and Enhance Hepatic Glycogen Formation

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Mehdi Bin Samad

2014-01-01

Full Text Available We measured a vast range of parameters, in an attempt to further elucidate previously claimed antihyperglycemic activity of Butea monosperma. Our study clearly negates the possibility of antidiabetic activity by inhibited gastrointestinal enzyme action or by reduced glucose absorption. Reduction of fasting and postprandial glucose level was reconfirmed (P<0.05. Improved serum lipid profile via reduced low density lipoprotein (LDL, cholesterol, triglycerides (TG, and increased high density lipoprotein (HDL was also reestablished (P<0.05. Significant insulin secretagogue activity of B. monosperma was found in serum insulin assay of B. monosperma treated type 2 diabetic rats (P<0.01. This was further ascertained by our study on insulin secretion on isolated rat islets (P<0.05. Improved sensitivity of glucose was shown by the significant increase in hepatic glycogen deposition (P<0.05. Hence, we concluded that antihyperglycemic activity of B. monosperma was mediated by enhanced insulin secretion and enhanced glycogen formation in the liver.

Role of necroptosis in autophagy signaling during hepatic ischemia and reperfusion

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Hong, Jeong-Min; Kim, Seok-Joo; Lee, Sun-Mee, E-mail: sunmee@skku.edu

2016-10-01

Ischemia and reperfusion (I/R) is a complex phenomenon involving massive inflammation and cell death. Necroptosis refers to a newly described cell death as “programmed necrosis” that is controlled by receptor-interacting protein kinase (RIP) 1 and RIP3, which is involved in the pathogenesis of several inflammatory diseases. Autophagy is an essential cytoprotective system that is rapidly activated in response to various stimuli and involves crosstalk between different modes of cell death and inflammation. In this study, we investigated pattern changes in necroptosis and its role in autophagy signaling during hepatic I/R. Male C57BL/6 mice were subjected to 60 min of ischemia followed by 3 h reperfusion. Necrostatin-1 (Nec-1, a necroptosis inhibitor; 1.65 mg/kg) was administered intraperitoneally 5 min before reperfusion. Hepatic I/R significantly increased the level of RIP3, phosphorylated RIP1 and RIP3 protein expression, and RIP1/RIP3 necrosome formation, which were attenuated by Nec-1. I/R also significantly increased serum levels of alanine aminotransferase, tumor necrosis factor-α, and interleukin-6, which were attenuated by Nec-1. Meanwhile, hepatic I/R activated autophagy and mitophagy, as evidenced by increased LC3-II, PINK1, and Parkin, and decreased sequestosome 1/p62 protein expression. Nec-1 attenuated these changes and attenuated the increased levels of autophagy-related protein (ATG) 3, ATG7, Rab7, and cathepsin B protein expression during hepatic I/R. Moreover, hepatic I/R activated the extracellular signal-regulated kinase (ERK) pathway, and Nec-1 attenuated this increase. Taken together, our findings suggest that necroptosis contributes to hepatic damage during I/R, which induces autophagy via ERK activation. - Highlights: • Hepatic I/R induces RIP1/RIP3-dependent necroptosis. • Necroptosis contributes to hepatic I/R injury. • Necroptosis activates autophagic flux via ERK activation during hepatic I/R.

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

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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.

Differential Role of Insulin/IGF-1 Receptor Signaling in Muscle Growth and Glucose Homeostasis

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Brian T. O’Neill

2015-05-01

Full Text Available Insulin and insulin-like growth factor 1 (IGF-1 are major regulators of muscle protein and glucose homeostasis. To determine how these pathways interact, we generated mice with muscle-specific knockout of IGF-1 receptor (IGF1R and insulin receptor (IR. These MIGIRKO mice showed >60% decrease in muscle mass. Despite a complete lack of insulin/IGF-1 signaling in muscle, MIGIRKO mice displayed normal glucose and insulin tolerance. Indeed, MIGIRKO mice showed fasting hypoglycemia and increased basal glucose uptake. This was secondary to decreased TBC1D1 resulting in increased Glut4 and Glut1 membrane localization. Interestingly, overexpression of a dominant-negative IGF1R in muscle induced glucose intolerance in MIGIRKO animals. Thus, loss of insulin/IGF-1 signaling impairs muscle growth, but not whole-body glucose tolerance due to increased membrane localization of glucose transporters. Nonetheless, presence of a dominant-negative receptor, even in the absence of functional IR/IGF1R, induces glucose intolerance, indicating that interactions between these receptors and other proteins in muscle can impair glucose homeostasis.

Insulin resistance in obesity can be reliably identified from fasting plasma insulin.

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ter Horst, K W; Gilijamse, P W; Koopman, K E; de Weijer, B A; Brands, M; Kootte, R S; Romijn, J A; Ackermans, M T; Nieuwdorp, M; Soeters, M R; Serlie, M J

2015-12-01

Insulin resistance is the major contributor to cardiometabolic complications of obesity. We aimed to (1) establish cutoff points for insulin resistance from euglycemic hyperinsulinemic clamps (EHCs), (2) identify insulin-resistant obese subjects and (3) predict insulin resistance from routinely measured variables. We assembled data from non-obese (n=112) and obese (n=100) men who underwent two-step EHCs using [6,6-(2)H2]glucose as tracer (insulin infusion dose 20 and 60 mU m(-2) min(-1), respectively). Reference ranges for hepatic and peripheral insulin sensitivity were calculated from healthy non-obese men. Based on these reference values, obese men with preserved insulin sensitivity or insulin resistance were identified. Cutoff points for insulin-mediated suppression of endogenous glucose production (EGP) and insulin-stimulated glucose disappearance rate (Rd) were 46.5% and 37.3 μmol kg(-)(1) min(-)(1), respectively. Most obese men (78%) had EGP suppression within the reference range, whereas only 12% of obese men had Rd within the reference range. Obese men with Rd obese men in age, body mass index (BMI), body composition, fasting glucose or cholesterol, but did have higher fasting insulin (110±49 vs 63±29 pmol l(-1), Pobese men could be identified with good sensitivity (80%) and specificity (75%) from fasting insulin >74 pmol l(-1). Most obese men have hepatic insulin sensitivity within the range of non-obese controls, but below-normal peripheral insulin sensitivity, that is, insulin resistance. Fasting insulin (>74 pmol l(-1) with current insulin immunoassay) may be used for identification of insulin-resistant (or metabolically unhealthy) obese men in research and clinical settings.

Myrcia bella Leaf Extract Presents Hypoglycemic Activity via PI3k/Akt Insulin Signaling Pathway

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Priscilla Maria Ponce Vareda

2014-01-01

Full Text Available Species of Myrcia are used by indigenous people and in traditional communities in Brazil for the treatment of Diabetes mellitus. We investigated the hypoglycemic effect of the extract of leaves of Myrcia bella in diabetic mice. The chemical fingerprinting of the 70% EtOH extract characterized as main constituents flavonoid aglycones, flavonoid-O-glycosides, and acylated flavonoid-O-glycosides derivatives of quercetin and myricetin. Mice were treated with saline or extract of M. bella (300 or 600 mg/Kg b.w. for 14 days. Body weight and water and food intake were measured every day. Fasting blood glucose was measured weekly. At the end of the treatment, blood insulin, triglycerides, total cholesterol, and protein were measured. Glycogen content and expression of proteins of the insulin signaling pathway were measured in liver. The treatment with 600 mg/Kg reduced the fasting blood glucose in diabetic mice of the 7th day as water and food intake and increased hepatic glycogen. Total cholesterol and triglycerides were reduced in diabetic treated mice. The treatment increased the expression of IRS-1, PI3-K, and AKT in the livers of diabetic treated mice. The results indicate that the extract of the leaves of Myrcia bella has hypoglycemic properties and possibly acts to regulate glucose uptake by the liver.

Jinlida reduces insulin resistance and ameliorates liver oxidative stress in high-fat fed rats.

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Liu, Yixuan; Song, An; Zang, Shasha; Wang, Chao; Song, Guangyao; Li, Xiaoling; Zhu, Yajun; Yu, Xian; Li, Ling; Wang, Yun; Duan, Liyuan

2015-03-13

Jinlida (JLD) is a compound preparation formulated on the basis of traditional Chinese medicine and is officially approved for the treatment of type 2 diabetes (T2DM) in China. We aimed to elucidate the mechanism of JLD treatment, in comparison to metformin treatment, on ameliorating insulin sensitivity in insulin resistant rats and to reveal its anti-oxidant properties. Rats were fed with standard or high-fat diet for 6 weeks. After 6 weeks, the high-fat fed rats were subdivided into five groups and orally fed with JLD or metformin for 8 weeks. Fasting blood glucose (FBG), fasting blood insulin, blood lipid and antioxidant enzymes were measured. Intraperitoneal glucose tolerance test (IPGTT) and hyperinsulinemic euglycemic clamp technique were carried out to measure insulin sensitivity. Gene expression of the major signaling pathway molecules that regulate glucose uptake, including insulin receptor (INSR), insulin receptor substrate-1 (IRS-1), phosphoinositide-3-kinase (PI3K), protein kinase beta (AKT), and glucose transporter type 2 (GLUT2), were assessed by quantitative RT-PCR. The totle and phosphorylation expression of IRS-1, AKT, JNK and p38MAPK were determined by Western blot. Treatment with JLD effectively ameliorated the high-fat induced hyperglycemia, hyperinsulinemia and hyperlipidemia. Similar to metformin, the high insulin resistance in high-fat fed rats was significantly decreased by JLD treatment. JLD displayed anti-oxidant effects, coupled with up-regulation of the insulin signaling pathway. The attenuation of hepatic oxidative stress by JLD treatment was associated with reduced phosphorylation protein levels of JNK and p38MAPK. Treatment with JLD could moderate glucose and lipid metabolism as well as reduce hepatic oxidative stress, most likely through the JNK and p38MAPK pathways. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Inter-domain tagging implicates caveolin-1 in insulin receptor trafficking and Erk signaling bias in pancreatic beta-cells

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Tobias Boothe

2016-05-01

Full Text Available Objective: The role and mechanisms of insulin receptor internalization remain incompletely understood. Previous trafficking studies of insulin receptors involved fluorescent protein tagging at their termini, manipulations that may be expected to result in dysfunctional receptors. Our objective was to determine the trafficking route and molecular mechanisms of functional tagged insulin receptors and endogenous insulin receptors in pancreatic beta-cells. Methods: We generated functional insulin receptors tagged with pH-resistant fluorescent proteins between domains. Confocal, TIRF and STED imaging revealed a trafficking pattern of inter-domain tagged insulin receptors and endogenous insulin receptors detected with antibodies. Results: Surprisingly, interdomain-tagged and endogenous insulin receptors in beta-cells bypassed classical Rab5a- or Rab7-mediated endocytic routes. Instead, we found that removal of insulin receptors from the plasma membrane involved tyrosine-phosphorylated caveolin-1, prior to trafficking within flotillin-1-positive structures to lysosomes. Multiple methods of inhibiting caveolin-1 significantly reduced Erk activation in vitro or in vivo, while leaving Akt signaling mostly intact. Conclusions: We conclude that phosphorylated caveolin-1 plays a role in insulin receptor internalization towards lysosomes through flotillin-1-positive structures and that caveolin-1 helps bias physiological beta-cell insulin signaling towards Erk activation. Author Video: Author Video Watch what authors say about their articles Keywords: Insulin receptor internalization, Insulin resistance, Pancreatic islet beta-cells, Autocrine insulin signaling

Insulin sensitivity and metabolic flexibility following exercise training among different obese insulin-resistant phenotypes.

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Malin, Steven K; Haus, Jacob M; Solomon, Thomas P J; Blaszczak, Alecia; Kashyap, Sangeeta R; Kirwan, John P

2013-11-15

Impaired fasting glucose (IFG) blunts the reversal of impaired glucose tolerance (IGT) after exercise training. Metabolic inflexibility has been implicated in the etiology of insulin resistance; however, the efficacy of exercise on peripheral and hepatic insulin sensitivity or substrate utilization in adults with IFG, IGT, or IFG + IGT is unknown. Twenty-four older (66.7 ± 0.8 yr) obese (34.2 ± 0.9 kg/m(2)) adults were categorized as IFG (n = 8), IGT (n = 8), or IFG + IGT (n = 8) according to a 75-g oral glucose tolerance test (OGTT). Subjects underwent 12-wk of exercise (60 min/day for 5 days/wk at ∼85% HRmax) and were instructed to maintain a eucaloric diet. A euglycemic hyperinsulinemic clamp (40 mU·m(2)·min(-1)) with [6,6-(2)H]glucose was used to determine peripheral and hepatic insulin sensitivity. Nonoxidative glucose disposal and metabolic flexibility [insulin-stimulated respiratory quotient (RQ) minus fasting RQ] were also assessed. Glucose incremental area under the curve (iAUCOGTT) was calculated from the OGTT. Exercise increased clamp-derived peripheral and hepatic insulin sensitivity more in adults with IFG or IGT alone than with IFG + IGT (P work is required to assess the molecular mechanism(s) by which chronic hyperglycemia modifies insulin sensitivity following exercise training.

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

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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 sho...

Exercise increases human skeletal muscle insulin sensitivity via coordinated increases in microvascular perfusion and molecular signaling

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Sjøberg, Kim Anker; Frøsig, Christian; Kjøbsted, Rasmus

2017-01-01

and increased similarly in both legs during the clamp and L-NMMA had no effect on these insulin-stimulated signaling pathways. Therefore, acute exercise increases insulin sensitivity of muscle by a coordinated increase in insulin-stimulated microvascular perfusion and molecular signaling at the level of TBC1D4...... and glycogen synthase in muscle. This secures improved glucose delivery on the one hand and increased ability to take up and dispose of the delivered glucose on the other hand....

Beneficial Effects of Phyllanthus amarus Against High Fructose Diet Induced Insulin Resistance and Hepatic Oxidative Stress in Male Wistar Rats.

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Putakala, Mallaiah; Gujjala, Sudhakara; Nukala, Srinivasulu; Desireddy, Saralakumari

2017-11-01

Insulin resistance (IR) is a characteristic feature of obesity, type 2 diabetes mellitus, and cardiovascular diseases. Emerging evidence suggests that the high-fructose consumption is a potential and important factor responsible for the rising incidence of IR. The present study investigates the beneficial effects of aqueous extract of Phyllanthus amarus (PAAE) on IR and oxidative stress in high-fructose (HF) fed male Wistar rats. HF diet (66% of fructose) and PAAE (200 mg/kg body weight/day) were given concurrently to the rats for a period of 60 days. Fructose-fed rats showed weight gain, hyperglycemia, hyperinsulinemia, impaired glucose tolerance, impaired insulin sensitivity, dyslipidemia, hyperleptinemia, and hypoadiponectinemia (P diet significantly ameliorated all these alterations. Regarding hepatic antioxidant status, higher lipid peroxidation and protein oxidation, lower reduced glutathione levels and lower activities of enzymatic antioxidants, and the histopathological changes like mild to severe distortion of the normal architecture as well as the prominence and widening of the liver sinusoids observed in the HF diet-fed rats were significantly prevented by PAAE treatment. These findings indicate that PAAE is beneficial in improving insulin sensitivity and attenuating metabolic syndrome and hepatic oxidative stress in fructose-fed rats.

Chardonnay grape seed flour ameliorates hepatic steatosis and insulin resistance via altered hepatic gene expression for oxidative stress, inflammation, and lipid and ceramide synthesis in diet-induced obese mice

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Diet-induced obese (DIO) mice were fed high-fat (HF) diets containing either partially defatted flavonoid-rich Chardonnay grape seed flour (ChrSd) or microcrystalline cellulose (MCC, control) for 5 weeks in order to determine whether ChrSd improved insulin resistance and the pathogenesis of hepatic ...

A hepatic amino acid/mTOR/S6K-dependent signalling pathway modulates systemic lipid metabolism via neuronal signals.

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Uno, Kenji; Yamada, Tetsuya; Ishigaki, Yasushi; Imai, Junta; Hasegawa, Yutaka; Sawada, Shojiro; Kaneko, Keizo; Ono, Hiraku; Asano, Tomoichiro; Oka, Yoshitomo; Katagiri, Hideki

2015-08-13

Metabolism is coordinated among tissues and organs via neuronal signals. Levels of circulating amino acids (AAs), which are elevated in obesity, activate the intracellular target of rapamycin complex-1 (mTORC1)/S6kinase (S6K) pathway in the liver. Here we demonstrate that hepatic AA/mTORC1/S6K signalling modulates systemic lipid metabolism via a mechanism involving neuronal inter-tissue communication. Hepatic expression of an AA transporter, SNAT2, activates the mTORC1/S6K pathway, and markedly elevates serum triglycerides (TGs), while downregulating adipose lipoprotein lipase (LPL). Hepatic Rheb or active-S6K expression have similar metabolic effects, whereas hepatic expression of dominant-negative-S6K inhibits TG elevation in SNAT2 mice. Denervation, pharmacological deafferentation and β-blocker administration suppress obesity-related hypertriglyceridemia with adipose LPL upregulation, suggesting that signals are transduced between liver and adipose tissue via a neuronal pathway consisting of afferent vagal and efferent sympathetic nerves. Thus, the neuronal mechanism uncovered here serves to coordinate amino acid and lipid levels and contributes to the development of obesity-related hypertriglyceridemia.

Replacing Fish Oil with Vegetable Oils in Salmon Feed Increases Hepatic Lipid Accumulation and Reduces Insulin Sensitivity in Mice

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Midtbø, Lisa Kolden

Background: Due to a growing global aquaculture production, fish oil (FO) and fish meal (FM) are partly replaced with vegetable ingredients in aqua feed for Atlantic salmon. These replacements in the feed lead to an altered fatty acid composition in the salmon fillet. We aimed to investigate how...... these changes affects obesity development and insulin sensitivity in mice eating the salmon. In addition, we wanted to investigate how the background diet affects the antiobesity effect of FO. Results: Western diets (WDs) were produced containing salmon fed either FO (WD-FO), or with partly replacement (80......%) of FO with different vegetable oils (VOs); rape seed oil (WDRO), olive oil (WD-OO) or soybean oil (WD-SO). These diets were given to C57BL/6J mice, and mice had higher hepatic lipid accumulation and lower insulin sensitivity when given WD-SO compared with WD-FO. Mice given WD-SO had higher hepatic...

Dexras1 links glucocorticoids to insulin-like growth factor-1 signaling in adipogenesis

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Kim, Hyo Jung; Cha, Jiyoung Y.; Seok, Jo Woon; Choi, Yoonjeong; Yoon, Bo Kyung; Choi, Hyeonjin; Yu, Jung Hwan; Song, Su Jin; Kim, Ara; Lee, Hyemin; Kim, Daeun; Han, Ji Yoon; Kim, Jae-woo

2016-01-01

Glucocorticoids are associated with obesity, but the underlying mechanism by which they function remains poorly understood. Previously, we showed that small G protein Dexras1 is expressed by glucocorticoids and leads to adipocyte differentiation. In this study, we explored the mechanism by which Dexras1 mediates adipogenesis and show a link to the insulin-like growth factor-1 (IGF-1) signaling pathway. Without Dexras1, the activation of MAPK and subsequent phosphorylation of CCAAT/enhancer binding protein β (C/EBPβ) is abolished, thereby inhibiting mitotic clonal expansion and further adipocyte differentiation. Dexras1 translocates to the plasma membrane upon insulin or IGF-1 treatment, for which the unique C-terminal domain (amino acids 223–276) is essential. Dexras1-dependent MAPK activation is selectively involved in the IGF-1 signaling, because another Ras protein, H-ras localized to the plasma membrane independently of insulin treatment. Moreover, neither epidermal growth factor nor other cell types shows Dexras1-dependent MAPK activation, indicating the importance of Dexras1 in IGF-1 signaling in adipogenesis. Dexras1 interacts with Shc and Raf, indicating that Dexras1-induced activation of MAPK is largely dependent on the Shc-Grb2-Raf complex. These results suggest that Dexras1 is a critical mediator of the IGF-1 signal to activate MAPK, linking glucocorticoid signaling to IGF-1 signaling in adipogenesis. PMID:27345868

Insulin and Leptin Signaling Interact in the Mouse Kiss1 Neuron during the Peripubertal Period.

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Xiaoliang Qiu

Full Text Available Reproduction requires adequate energy stores for parents and offspring to survive. Kiss1 neurons, which are essential for fertility, have the potential to serve as the central sensors of metabolic factors that signal to the reproductive axis the presence of stored calories. Paradoxically, obesity is often accompanied by infertility. Despite excess circulating levels of insulin and leptin, obese individuals exhibit resistance to both metabolic factors in many neuron types. Thus, resistance to insulin or leptin in Kiss1 neurons could lead to infertility. Single deletion of the receptors for either insulin or the adipokine leptin from Kiss1 neurons does not impair adult reproductive dysfunction. However, insulin and leptin signaling pathways may interact in such a way as to obscure their individual functions. We hypothesized that in the presence of genetic or obesity-induced concurrent insulin and leptin resistance, Kiss1 neurons would be unable to maintain reproductive function. We therefore induced a chronic hyperinsulinemic and hyperleptinemic state in mice lacking insulin receptors in Kiss1 neurons through high fat feeding and examined the impact on fertility. In an additional, genetic model, we ablated both leptin and insulin signaling in Kiss1 neurons (IR/LepRKiss mice. Counter to our hypothesis, we found that the addition of leptin insensitivity did not alter the reproductive phenotype of IRKiss mice. We also found that weight gain, body composition, glucose and insulin tolerance were normal in mice of both genders. Nonetheless, leptin and insulin receptor deletion altered pubertal timing as well as LH and FSH levels in mid-puberty in a reciprocal manner. Our results confirm that Kiss1 neurons do not directly mediate the critical role that insulin and leptin play in reproduction. However, during puberty kisspeptin neurons may experience a critical window of susceptibility to the influence of metabolic factors that can modify the onset of

Effect of TNF-Alpha on Caveolin-1 Expression and Insulin Signaling During Adipocyte Differentiation and in Mature Adipocytes

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Sara Palacios-Ortega

2015-07-01

Full Text Available Background/Aims: Tumor necrosis factor-α (TNF-α-mediated chronic low-grade inflammation of adipose tissue is associated with obesity and insulin resistance. Caveolin-1 (Cav-1 is the central component of adipocyte caveolae and has an essential role in the regulation of insulin signaling. The effects of TNF-α on Cav-1 expression and insulin signaling during adipocyte differentiation and in mature adipocytes were studied. Methods: 3T3-L1 cells were differentiated (21 days in the presence TNF-α (10 ng/mL and mature adipocytes were also treated with TNF-α for 48 hours. Cav-1 and insulin receptor (IR gene methylation were determined as well as Cav-1, IR, PKB/AKT-2 and Glut-4 expression and activation by real time RT-PCR and western blot. Baseline and insulin-induced glucose uptake was measured by the 2-[C14]-deoxyglucose uptake assay. Results: TNF-α slowed down the differentiation program, hindering the expression of some insulin signaling intermediates without fully eliminating insulin-mediated glucose uptake. In mature adipocytes, TNF-α did not compromise lipid-storage capacity, but downregulated the expression of the insulin signaling intermediates, totally blocking insulin-mediated glucose uptake. Insulin sensitivity correlated with the level of activated phospho-Cav-1 in both situations, strongly suggesting the direct contribution of Cav-1 to the maintenance of this physiological response. Conclusion: Cav-1 activation by phosphorylation seems to be essential for the maintenance of an active and insulin-sensitive glucose uptake.

Role of sialic acid in insulin action and the insulin resistance of diabetes mellitus

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Salhanick, A.I.; Amatruda, J.M.

1988-01-01

Adipocytes treated with neuraminidase show markedly reduced responsiveness to insulin without any alteration in insulin binding. In addition, several studies have separately demonstrated both insulin resistance and decreases in membrane sialic acid content and associated biosynthetic enzymes in diabetes mellitus. In the present study, the authors investigated the role that sialic acid residues may play in insulin action and in the hepatic insulin resistance associated with nonketotic diabetes. Primary cultures of hepatocytes from normal rats treated with neuraminidase demonstrated a dose-dependent decrease in insulin-stimulated lipogenesis. At a concentration of neuraminidase that decreases insulin action by 50%, 23% of total cellular sialic acid content was released. Neuraminidase-releasable sialic acid was significantly decreased in hepatocytes from diabetic rats and this was associated with significant insulin resistance. Treatment of hepatocytes from diabetic rats with cytidine 5'-monophospho-N-acetylneuraminic acid (CMP-NANA) enhanced insulin responsiveness 39%. The enhanced insulin responsiveness induced by CMP-NANA was blocked by cytidine 5'-monophosphate (CMP) suggesting that the CMP-NANA effect was catalyzed by a cell surface sialyl-transferase. CMP reduced neuraminidase-releasable [ 14 C]sialic acid incorporation into hepatocytes by 43%. The data demonstrate a role for cell surface sialic acid residues in hepatic insulin action and support a role for decreased cell surface sialic acid residues in the insulin resistance of diabetes mellitus

Potential role of insulin signaling on vascular smooth muscle cell migration, proliferation, and inflammation pathways.

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Cersosimo, Eugenio; Xu, Xiaojing; Musi, Nicolas

2012-02-15

To investigate the role of insulin signaling pathways in migration, proliferation, and inflammation of vascular smooth muscle cells (VSMCs), we examined the expression of active components of the phosphatidyl inositol 3 (PI-3) kinase (p-Akt) and mitogen-activated protein kinase (MAPK) (p-Erk) in primary cultures of VSMCs from human coronary arteries. VSMCs were treated in a dose-response manner with insulin (0, 1, 10, and 100 nM) for 20 min, and Akt and Erk phosphorylation were measured by Western blot analysis. In separate experiments, we evaluated the effect of 200 μM palmitate, in the presence and absence of 8 μM pioglitazone, on insulin-stimulated (100 nM for 20 min) Akt and Erk phosphorylation. The phosphorylation of Akt and Erk in VSMCs exhibited a dose dependency with a three- to fourfold increase, respectively, at the highest dose (100 nM). In the presence of palmitate, insulin-induced Akt phosphorylation was completely abolished, and there was a threefold increase in p-Erk. With addition of pioglitazone, the phosphorylation of Akt by insulin remained unchanged, whereas insulin-stimulated Erk phosphorylation was reduced by pioglitazone. These data in VSMCs indicate that high palmitate decreases insulin-stimulated Akt phosphorylation and stimulates MAPK, whereas preexposure peroxisome proliferator-activated receptor-γ agonist pioglitazone preserves Akt phosphorylation and simultaneously attenuates MAPK signaling. Our results suggest that metabolic and mitogenic insulin signals have different sensitivity, are independently regulated, and may play a role in arterial smooth muscle cells migration, proliferation, and inflammation in conditions of acute hyperinsulinemia.

Inactivation of the Class II PI3K-C2β Potentiates Insulin Signaling and Sensitivity

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Samira Alliouachene

2015-12-01

Full Text Available In contrast to the class I phosphoinositide 3-kinases (PI3Ks, the organismal roles of the kinase activity of the class II PI3Ks are less clear. Here, we report that class II PI3K-C2β kinase-dead mice are viable and healthy but display an unanticipated enhanced insulin sensitivity and glucose tolerance, as well as protection against high-fat-diet-induced liver steatosis. Despite having a broad tissue distribution, systemic PI3K-C2β inhibition selectively enhances insulin signaling only in metabolic tissues. In a primary hepatocyte model, basal PI3P lipid levels are reduced by 60% upon PI3K-C2β inhibition. This results in an expansion of the very early APPL1-positive endosomal compartment and altered insulin receptor trafficking, correlating with an amplification of insulin-induced, class I PI3K-dependent Akt signaling, without impacting MAPK activity. These data reveal PI3K-C2β as a critical regulator of endosomal trafficking, specifically in insulin signaling, and identify PI3K-C2β as a potential drug target for insulin sensitization.

Effect of hypophysectomy and insulin on lipogenesis in cockerels

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Kompiang, I P; Gibson, W R [Monash Univ., Clayton (Australia). Dept. of Physiology

1976-09-01

Hypophysectomy increases hepatic lipogenesis in cockerels. In an attempt to find the possible hormonal mechanism for this we have examined the effects of hypophysectomy, insulin and pituitary homogenates on hepatic lipogenesis. Insulin (5 U/kg) injected intravenously, simultaneously with glucose-/sup 14/C tracer, increased the amount of /sup 14/C found in liver lipids at 30 min after the injection. Similarly, insulin injected 5 min before killing increased the incorporation of glucose-/sup 14/C and acetate-/sup 14/C by liver slices during a 30 min incubation. Hypophysectomy increased lipogenesis within 24 hours. The effect of insulin was most pronounced in hypophysectomized cockerels. The activity of the lipogenic enzyme, acetyl CoA carboxylase was similarly affected. A homogenate of chicken pituitaries added to the medium reduced lipid synthesis from glucose-/sup 14/C by liver slices. This effect was larger in liver slices in which lipogenesis had been stimulated by insulin. The increased rate of hepatic lipogenesis in hypophysectomized cockerels may be caused partly by increased hepatic sensitivity to the lipogenic action of insulin or by the removal of a direct inhibition by pituitary hormones.

Defective insulin signaling and the protective effects of dimethyldiguanide during follicular development in the ovaries of polycystic ovary syndrome.

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Wang, Fan; Wang, Shaobing; Zhang, Zhenghong; Lin, Qingqiang; Liu, Yiping; Xiao, Yijun; Xiao, Kaizhuan; Wang, Zhengchao

2017-12-01

It is established that the physiological effects of insulin are primarily mediated by the insulin signaling pathway. However, a defective insulin signaling is closely associated with the clinical manifestations of polycystic ovary syndrome (PCOS), which include excess androgen levels, insulin resistance and anovulation, and is involved in the pathophysiology of PCOS at the molecular level. Dimethyldiguanide (DMBG) has been widely employed to alleviate reproduction dysfunction in women with PCOS, however, the exact mechanism of this effect remains unclear. The objective of the present study was to investigate the effects of DMBG on the expression of the insulin signaling pathway in the ovaries of rats with PCOS, and to identify the potential underlying molecular mechanisms of these effects in PCOS. In the present study, a PCOS rat model was induced by letrozole, and successful establishment of the model was confirmed by examining ovarian histology and determining serum testosterone levels, by hematoxylin and eosin staining and ELISA, respectively. Subsequently, the expression of two key elements of insulin signaling, insulin receptor substrate (IRS)‑2 and phosphatidylinositol 3‑kinase (PI3K), was determined by immunohistochemistry and western blot analysis. The results demonstrated that IRS‑2 and PI3K expression was markedly decreased in PCOS ovaries, which was rescued by DMBG treatment. These results indicate that IRS‑2/PI3K signaling may be involved in the development of PCOS and the therapeutic effects of DMBG on PCOS. To further confirm the effects of DMBG on insulin signaling expression during this process, the expression of an additional two downstream proteins, phosphoinositide‑dependent kinase‑1 (PDK‑1) and the mammalian target of rapamycin (mTOR), was also investigated in the present study, and the results demonstrated that the expression of PDK‑1 and mTOR was significantly reduced in PCOS ovaries and increased following DMBG treatment

Acute High-intensity Interval Exercise-induced Redox Signaling is Associated with Enhanced Insulin Sensitivity in Obese Middle-aged Men.

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Lewan Parker

2016-09-01

Full Text Available Background. Obesity and ageing are associated with increased oxidative stress, activation of stress and mitogen activated protein kinases (SAPK, and the development of insulin resistance and metabolic disease. In contrast, acute exercise also increases oxidative stress and SAPK signaling, yet is reported to enhance insulin sensitivity and reduce the risk of metabolic disease. This study explored this paradox by investigating the effect of a single session of high-intensity interval-exercise (HIIE on redox status, muscle SAPK and insulin protein signaling in eleven middle-aged obese men. Methods. Participants completed a 2 hour hyperinsulinaemic-euglycaemic clamp at rest, and 60 minutes after HIIE (4x4 mins at 95% HRpeak; 2 min recovery periods, separated by 1-3 weeks. Results. Irrespective of exercise-induced changes to redox status, insulin stimulation both at rest and after HIIE similarly increased plasma superoxide dismutase activity, plasma catalase activity, and skeletal muscle 4-HNE; and significantly decreased plasma TBARS and hydrogen peroxide. The SAPK signaling pathways of p38 MAPK, NF-κB p65, and JNK, and the distal insulin signaling protein AS160Ser588, were activated with insulin stimulation at rest and to a greater extent with insulin stimulation after a prior bout of HIIE. Higher insulin sensitivity after HIIE was associated with higher insulin-stimulated SAPK phosphorylation (JNK, p38 MAPK and NF-κB and SOD activity (p<0.05. Conclusion. These findings support a role for redox homeostasis and SAPK signaling in insulin-stimulated glucose uptake which may contribute to the enhancement of insulin sensitivity in obese men 3 hours after HIIE.

Studies of insulin resistance in congenital generalized lipodystrophy

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Søvik, O; Vestergaard, H; Trygstad, O

1996-01-01

suppressed lipid oxidation in the controls. It is concluded that patients with congenital generalized lipodystrophy may present severe insulin resistance with regard to hepatic glucose production as well as muscle glycogen synthesis and lipid oxidation. The results suggest a postreceptor defect in the action......, immunoreactive protein and mRNA levels. The patients had fasting hyperinsulinaemia, and the rate of total glucose disposal was severely impaired, primarily due to a decreased non-oxidative glucose metabolism. In the patient studied with muscle biopsy, the expected activation of glycogen synthase by insulin did...... not occur. In both patients there was severely increased hepatic glucose output in the basal state, suggesting a failure of insulin to suppress hepatic gluconeogenesis. During insulin infusion a substantially elevated rate of lipid oxidation remained in the patients, in contrast to the almost completely...

Prolonged Treatment with Free Fatty Acids has Post Receptor Effect in Hepatic Insulin Resistance: Evidence that Fatty Acids, Oleate and Palmitate have Insignificant Effect on the Insulin Receptor Beta In Vivo and Ex Vivo Primary Hepatocytes

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Rafik Ragheb

2009-01-01

Full Text Available In the current study, we used immunoprecipitation and immunoblotting to examine the levels and phosphorylation status of the insulin receptor-beta subunit (IR-β, as well as the down stream target in PI3K pathway, total PKB/Akt as well as their phosphorylated forms. The assessment of FFAs treatment showed no direct and significant effect on the PI3K stimulation, specifically the IR-β in primary hepatic control cells treated with insulin. Cells treated with either oleate or palmitate (360 µM showed no statistically significant values following insulin stimulation (P > 0.05. To further investigate the effect of both FFAs and high insulin (1 µg, we examined the effects of oleate and palmitate at 360 µM concentration on IR-β as well as PKB. There was no significant difference in the total protein levels and their phosphorylated forms in cells treated with or without oleate or plamitate. Interestingly, IR-β tyrosine phosphorylation showed a similar insignificant effect in vivo and ex vivo hepatic cells treated with oleate or palmitate in comparison to their controls in the fructose fed hamsters.

Amino Acids Attenuate Insulin Action on Gluconeogenesis and Promote Fatty Acid Biosynthesis via mTORC1 Signaling Pathway in trout Hepatocytes

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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.

Hepatitis C virus eradication by direct antiviral agents improves glucose tolerance and reduces post-load insulin resistance in nondiabetic patients with genotype 1.

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Salomone, Federico; Catania, Maurizio; Montineri, Arturo; Bertino, Gaetano; Godos, Justyna; Rizzo, Leonardo; Magrì, Giovanni; Li Volti, Giovanni

2017-12-19

Genotype 1 chronic hepatitis C is associated with an impairment of glucose homoeostasis, especially in the advanced stages of the disease. Glucose tolerance is an independent predictor of liver-related mortality in patients with cirrhosis because of chronic hepatitis C. However, no study has demonstrated so far weather hepatitis C virus clearance affects glucose tolerance. To this aim, we performed a prospective study assessing the effects of direct antiviral agents treatment in nondiabetic cirrhotic patients with genotypes 1a/1b and impaired glucose tolerance based on a 75-g oral glucose tolerance test. Impaired glucose tolerance was diagnosed by a 2-hour plasma glucose between 140 and 199 mg/dL. Insulin resistance was estimated by the oral glucose insulin sensitivity index, an oral glucose tolerance test-derived measure. After meeting the inclusion criteria, the study population included 32 outpatients (26/6 genotypes 1b/1a; age 62 ± 7.4 years; 18 males) with compensated Child-A cirrhosis. All patients achieved a sustained virological response following direct antiviral agents treatment. After viral eradication, we did not observe change in fasting plasma glucose (103.5 ± 7.1 vs 102.8 ± 7.2 mg/dL, P = .15) but 2-hour plasma glucose was reduced (165.2 ± 22.7 vs 138.5 ± 21.3 mg/dL, P Hepatitis C virus eradication led also to a significant reduction in HbA1c (6.1 ± 0.2% vs 5.7 ± 0.3%, P resistance as assessed by the oral glucose insulin sensitivity index (6.92 ± 1.56 vs 9.52 ± 1.39 mg/kg/min, P  .5). Our results indicate that hepatitis C virus eradication may early improve glucose tolerance in patients with hepatitis C virus-related cirrhosis. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Complement component 1, q subcomponent binding protein (C1QBP) in lipid rafts mediates hepatic metastasis of pancreatic cancer by regulating IGF-1/IGF-1R signaling.

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Shi, Haojun; Fang, Winston; Liu, Minda; Fu, Deliang

2017-10-01

Pancreatic cancer shows a remarkable predilection for hepatic metastasis. Complement component 1, q subcomponent binding protein (C1QBP) can mediate growth factor-induced cancer cell chemotaxis and distant metastasis by activation of receptor tyrosine kinases. Coincidentally, insulin-like growth factor-1 (IGF-1) derived from the liver and cancer cells itself has been recognized as a critical inducer of hepatic metastasis. However, the mechanism underlying IGF-1-dependent hepatic metastasis of pancreatic cancer, in which C1QBP may be involved, remains unknown. In the study, we demonstrated a significant association between C1QBP expression and hepatic metastasis in patients with pancreatic cancer. IGF-1 induced the translocation of C1QBP from cytoplasm to lipid rafts and further drove the formation of CD44 variant 6 (CD44v6)/C1QBP complex in pancreatic cancer cells. C1QBP interacting with CD44v6 in lipid rafts promoted phosphorylation of IGF-1R and thus activated downstream PI3K and MAPK signaling pathways which mediated metastatic potential of pancreatic cancer cells including proliferation, apoptosis, invasion, adhesion and energy metabolism. Furthermore, C1QBP knockdown suppressed hepatic metastasis of pancreatic cancer cells in nude mice. We therefore conclude that C1QBP in lipid rafts serves a key regulator of IGF-1/IGF-1R-induced hepatic metastasis from pancreatic cancer. Our findings about C1QBP in lipid rafts provide a novel strategy to block IGF-1/IGF-1R signaling in pancreatic cancer and a reliable premise for more efficient combined modality therapies. © 2017 UICC.

Degradation of PHLPP2 by KCTD17, via a Glucagon-Dependent Pathway, Promotes Hepatic Steatosis.

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Kim, KyeongJin; Ryu, Dongryeol; Dongiovanni, Paola; Ozcan, Lale; Nayak, Shruti; Ueberheide, Beatrix; Valenti, Luca; Auwerx, Johan; Pajvani, Utpal B

2017-12-01

Obesity-induced nonalcoholic fatty liver disease (NAFLD) develops, in part, via excess insulin-stimulated hepatic de novo lipogenesis, which increases, paradoxically, in patients with obesity-induced insulin resistance. Pleckstrin homology domain leucine-rich repeat protein phosphatase 2 (PHLPP2) terminates insulin signaling by dephosphorylating Akt; levels of PHLPP2 are reduced in livers from obese mice. We investigated whether loss of hepatic PHLPP2 is sufficient to induce fatty liver in mice, mechanisms of PHLPP2 degradation in fatty liver, and expression of genes that regulate PHLPP2 in livers of patients with NAFLD. C57BL/6J mice (controls), obese db/db mice, and mice with liver-specific deletion of PHLPP2 (L-PHLPP2) fed either normal chow or high-fat diet (HFD) were analyzed for metabolic phenotypes, including glucose tolerance and hepatic steatosis. PHLPP2-deficient primary hepatocytes or CRISPR/Cas9-mediated PHLPP2-knockout hepatoma cells were analyzed for insulin signaling and gene expression. We performed mass spectrometry analyses of liver tissues from C57BL/6J mice transduced with Ad-HA-Flag-PHLPP2 to identify posttranslational modifications to PHLPP2 and proteins that interact with PHLPP2. We measured levels of mRNAs by quantitative reverse transcription polymerase chain reaction in liver biopsies from patients with varying degrees of hepatic steatosis. PHLPP2-knockout hepatoma cells and hepatocytes from L-PHLPP2 mice showed normal initiation of insulin signaling, but prolonged insulin action. Chow-fed L-PHLPP2 mice had normal glucose tolerance but hepatic steatosis. In HFD-fed C57BL/6J or db/db obese mice, endogenous PHLPP2 was degraded by glucagon and PKA-dependent phosphorylation of PHLPP2 (at Ser1119 and Ser1210), which led to PHLPP2 binding to potassium channel tetramerization domain containing 17 (KCTD17), a substrate-adaptor for Cul3-RING ubiquitin ligases. Levels of KCTD17 mRNA were increased in livers of HFD-fed C57BL/6J or db/db obese mice

Insulin signaling inhibits the 5-HT2C receptor in choroid plexus via MAP kinase

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Guan Kunliang

2003-06-01

Full Text Available Abstract Background G protein-coupled receptors (GPCRs interact with heterotrimeric GTP-binding proteins (G proteins to modulate acute changes in intracellular messenger levels and ion channel activity. In contrast, long-term changes in cellular growth, proliferation and differentiation are often mediated by tyrosine kinase receptors and certain GPCRs by activation of mitogen-activated protein (MAP kinases. Complex interactions occur between these signaling pathways, but the specific mechanisms of such regulatory events are not well-understood. In particular it is not clear whether GPCRs are modulated by tyrosine kinase receptor-MAP kinase pathways. Results Here we describe tyrosine kinase receptor regulation of a GPCR via MAP kinase. Insulin reduced the activity of the 5-HT2C receptor in choroid plexus cells which was blocked by the MAP kinase kinase (MEK inhibitor, PD 098059. We demonstrate that the inhibitory effect of insulin and insulin-like growth factor type 1 (IGF-1 on the 5-HT2C receptor is dependent on tyrosine kinase, RAS and MAP kinase. The effect may be receptor-specific: insulin had no effect on another GPCR that shares the same G protein signaling pathway as the 5-HT2C receptor. This effect is also direct: activated MAP kinase mimicked the effect of insulin, and removing a putative MAP kinase site from the 5-HT2C receptor abolished the effect of insulin. Conclusion These results show that insulin signaling can inhibit 5-HT2C receptor activity and suggest that MAP kinase may play a direct role in regulating the function of a specific GPCR.

Intrahippocampal Administration of Amyloid-β1–42 Oligomers Acutely Impairs Spatial Working Memory, Insulin Signaling, and Hippocampal Metabolism

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Pearson-Leary, Jiah; McNay, Ewan C.

2017-01-01

Increasing evidence suggests that abnormal brain accumulation of amyloid-β1–42 (Aβ1–42) oligomers plays a causal role in Alzheimer’s disease (AD), and in particular may cause the cognitive deficits that are the hallmark of AD. In vitro, Aβ1–42 oligomers impair insulin signaling and suppress neural functioning. We previously showed that endogenous insulin signaling is an obligatory component of normal hippocampal function, and that disrupting this signaling led to a rapid impairment of spatial working memory, while delivery of exogenous insulin to the hippocampus enhanced both memory and metabolism; diet-induced insulin resistance both impaired spatial memory and prevented insulin from increasing metabolism or cognitive function. Hence, we tested the hypothesis that Aβ1–42 oligomers could acutely impair hippocampal metabolic and cognitive processes in vivo in the rat. Our findings support this hypothesis: Aβ1–42 oligomers impaired spontaneous alternation behavior while preventing the task-associated dip in hippocampal ECF glucose observed in control animals. In addition, Aβ1–42 oligomers decreased plasma membrane translocation of the insulin-sensitive glucose transporter 4 (GluT4), and impaired insulin signaling as measured by phosphorylation of Akt. These data show in vivo that Aβ1–42 oligomers can rapidly impair hippocampal cognitive and metabolic processes, and provide support for the hypothesis that elevated Aβ1–42 leads to cognitive impairment via interference with hippocampal insulin signaling. PMID:22430529

Insulin sensitivity and metabolic flexibility following exercise training among different obese insulin resistant phenotypes

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Malin, Steven K; Haus, Jacob M; Solomon, Thomas

2013-01-01

Impaired fasting glucose (IFG) blunts the reversal of impaired glucose tolerance (IGT) after exercise training. Metabolic inflexibility has been implicated in the etiology of insulin resistance, however, the efficacy of exercise on peripheral and hepatic insulin sensitivity or substrate utilizati...

Long-term dietary supplementation with low-dose nobiletin ameliorates hepatic steatosis, insulin resistance, and inflammation without altering fat mass in diet-induced obesity.

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Kim, Young-Je; Choi, Myung-Sook; Woo, Je Tae; Jeong, Mi Ji; Kim, Sang Ryong; Jung, Un Ju

2017-08-01

We evaluated the long-term effect of low-dose nobiletin (NOB), a polymethoxylated flavone, on diet-induced obesity and related metabolic disturbances. C57BL/6J mice were fed a high-fat diet (HFD, 45 kcal% fat) with or without NOB (0.02%, w/w) for 16 weeks. NOB did not alter food intake or body weight. Despite increases in fatty acid oxidation-related genes expression and enzymes activity in adipose tissue, NOB did not affect adipose tissue weight due to simultaneous increases in lipogenic genes expression and fatty acid synthase activity. However, NOB significantly decreased not only pro-inflammatory genes expression in adipose tissue but also proinflammatory cytokine levels in plasma. NOB-supplemented mice also showed improved glucose tolerance and insulin resistance, along with decreased levels of plasma insulin, free fatty acids, total cholesterol, non-HDL-cholesterol, and apolipoprotein B. In addition, NOB caused significant decreases in hepatic lipid droplet accumulation and triglyceride content by activating hepatic fatty acid oxidation-related enzymes. Hepatic proinflammatory TNF-α mRNA expression, collagen accumulation, and plasma levels of aminotransferases, liver damage indicators, were also significantly lower in NOB-supplemented mice. These findings suggest that long-term supplementation with low-dose NOB can protect against HFD-induced inflammation, insulin resistance, dyslipidemia, and nonalcoholic fatty liver disease, without ameliorating adiposity. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The role of insulin C-peptide in the coevolution analyses of the insulin signaling pathway: a hint for its functions.

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Shuai Wang

Full Text Available As the linker between the A chain and B chain of proinsulin, C-peptide displays high variability in length and amino acid composition, and has been considered as an inert byproduct of insulin synthesis and processing for many years. Recent studies have suggested that C-peptide can act as a bioactive hormone, exerting various biological effects on the pathophysiology and treatment of diabetes. In this study, we analyzed the coevolution of insulin molecules among vertebrates, aiming at exploring the evolutionary characteristics of insulin molecule, especially the C-peptide. We also calculated the correlations of evolutionary rates between the insulin and the insulin receptor (IR sequences as well as the domain-domain pairs of the ligand and receptor by the mirrortree method. The results revealed distinctive features of C-peptide in insulin intramolecular coevolution and correlated residue substitutions, which partly supported the idea that C-peptide can act as a bioactive hormone, with significant sequence features, as well as a linker assisting the formation of mature insulin during synthesis. Interestingly, the evolution of C-peptide exerted the highest correlation with that of the insulin receptor and its ligand binding domain (LBD, implying a potential relationship with the insulin signaling pathway.

Acute effects of different diet compositions on skeletal muscle insulin signalling in obese individuals during caloric restriction

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Wang, Cecilia C.L.; Adochio, Rebecca L.; Leitner, J. Wayne; Abeyta, Ian M.; Draznin, Boris; Cornier, Marc-Andre

2012-01-01

Objective The cellular effects of restricting fat versus carbohydrate during a low-calorie diet are unclear. The aim of this study was to examine acute effects of energy and macronutrient restriction on skeletal muscle insulin signalling in obesity. Materials/Methods Eighteen obese individuals without diabetes underwent euglycemic-hyperinsulinemic clamp and skeletal muscle biopsy after: (a) 5 days of eucaloric diet (30% fat, 50% carbohydrate), and (b) 5 days of a 30% calorie-restricted diet, either low fat/high carbohydrate (LF/HC: 20% fat, 60% carbohydrate) or high-fat/low carbohydrate (HF/LC: 50% fat, 30% carbohydrate). Results Weight, body composition, and insulin sensitivity were similar between groups after eucaloric diet. Weight loss was similar between groups after hypocaloric diet, 1.3 ± 1.3 kg (pdiet. Skeletal muscle of the LF/HC group had increased insulin-stimulated tyrosine phosphorylation of IRS-1, decreased insulin-stimulated Ser 307 phosphorylation of IRS-1, and increased IRS-1-associated phosphatidylinositol (PI)3-kinase activity. Conversely, insulin stimulation of tyrosine phosphorylated IRS-1 was absent and serine 307 phosphorylation of IRS-1 was increased on HF/LC, with blunting of IRS-1-associated PI3-kinase activity. Conclusion Acute caloric restriction with a LF/HC diet alters skeletal muscle insulin signalling in a way that improves insulin sensitivity, while acute caloric restriction with a HF/LC diet induces changes compatible with insulin resistance. In both cases, ex vivo changes in skeletal muscle insulin signalling appear prior to changes in whole body insulin sensitivity. PMID:23174405

Opuntia ficus indica (nopal) attenuates hepatic steatosis and oxidative stress in obese Zucker (fa/fa) rats.

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Morán-Ramos, Sofía; Avila-Nava, Azalia; Tovar, Armando R; Pedraza-Chaverri, José; López-Romero, Patricia; Torres, Nimbe

2012-11-01

Nonalcoholic fatty liver disease (NAFLD) is associated with multiple factors such as obesity, insulin resistance, and oxidative stress. Nopal, a cactus plant widely consumed in the Mexican diet, is considered a functional food because of its antioxidant activity and ability to improve biomarkers of metabolic syndrome. The aim of this study was to assess the effect of nopal consumption on the development of hepatic steatosis and hepatic oxidative stress and on the regulation of genes involved in hepatic lipid metabolism. Obese Zucker (fa/fa) rats were fed a control diet or a diet containing 4% nopal for 7 wk. Rats fed the nopal-containing diet had ∼50% lower hepatic TG than the control group as well as a reduction in hepatomegaly and biomarkers of hepatocyte injury such as alanine and aspartate aminotransferases. Attenuation of hepatic steatosis by nopal consumption was accompanied by a higher serum concentration of adiponectin and a greater abundance of mRNA for genes involved in lipid oxidation and lipid export and production of carnitine palmitoyltransferase-1 and microsomal TG transfer proteins in liver. Hepatic reactive oxygen species and lipid peroxidation biomarkers were significantly lower in rats fed nopal compared with the control rats. Furthermore, rats fed the nopal diet had a lower postprandial serum insulin concentration and a greater liver phosphorylated protein kinase B (pAKT):AKT ratio in the postprandial state. This study suggests that nopal consumption attenuates hepatic steatosis by increasing fatty acid oxidation and VLDL synthesis, decreasing oxidative stress, and improving liver insulin signaling in obese Zucker (fa/fa) rats.