Head-head interactions of resting myosin crossbridges in intact frog skeletal muscles, revealed by synchrotron x-ray fiber diffraction.

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Kanji Oshima

Full Text Available The intensities of the myosin-based layer lines in the x-ray diffraction patterns from live resting frog skeletal muscles with full thick-thin filament overlap from which partial lattice sampling effects had been removed were analyzed to elucidate the configurations of myosin crossbridges around the thick filament backbone to nanometer resolution. The repeat of myosin binding protein C (C-protein molecules on the thick filaments was determined to be 45.33 nm, slightly longer than that of myosin crossbridges. With the inclusion of structural information for C-proteins and a pre-powerstroke head shape, modeling in terms of a mixed population of regular and perturbed regions of myosin crown repeats along the filament revealed that the myosin filament had azimuthal perturbations of crossbridges in addition to axial perturbations in the perturbed region, producing pseudo-six-fold rotational symmetry in the structure projected down the filament axis. Myosin crossbridges had a different organization about the filament axis in each of the regular and perturbed regions. In the regular region that lacks C-proteins, there were inter-molecular interactions between the myosin heads in axially adjacent crown levels. In the perturbed region that contains C-proteins, in addition to inter-molecular interactions between the myosin heads in the closest adjacent crown levels, there were also intra-molecular interactions between the paired heads on the same crown level. Common features of the interactions in both regions were interactions between a portion of the 50-kDa-domain and part of the converter domain of the myosin heads, similar to those found in the phosphorylation-regulated invertebrate myosin. These interactions are primarily electrostatic and the converter domain is responsible for the head-head interactions. Thus multiple head-head interactions of myosin crossbridges also characterize the switched-off state and have an important role in the regulation

Smooth muscle myosin light chain kinase efficiently phosphorylates serine 15 of cardiac myosin regulatory light chain

International Nuclear Information System (INIS)

Josephson, Matthew P.; Sikkink, Laura A.; Penheiter, Alan R.; Burghardt, Thomas P.; Ajtai, Katalin

2011-01-01

Highlights: ► Cardiac myosin regulatory light chain (MYL2) is phosphorylated at S15. ► Smooth muscle myosin light chain kinase (smMLCK) is a ubiquitous kinase. ► It is a widely believed that MYL2 is a poor substrate for smMLCK. ► In fact, smMLCK efficiently and rapidly phosphorylates S15 in MYL2. ► Phosphorylation kinetics measured by novel fluorescence method without radioactivity. -- Abstract: Specific phosphorylation of the human ventricular cardiac myosin regulatory light chain (MYL2) modifies the protein at S15. This modification affects MYL2 secondary structure and modulates the Ca 2+ sensitivity of contraction in cardiac tissue. Smooth muscle myosin light chain kinase (smMLCK) is a ubiquitous kinase prevalent in uterus and present in other contracting tissues including cardiac muscle. The recombinant 130 kDa (short) smMLCK phosphorylated S15 in MYL2 in vitro. Specific modification of S15 was verified using the direct detection of the phospho group on S15 with mass spectrometry. SmMLCK also specifically phosphorylated myosin regulatory light chain S15 in porcine ventricular myosin and chicken gizzard smooth muscle myosin (S20 in smooth muscle) but failed to phosphorylate the myosin regulatory light chain in rabbit skeletal myosin. Phosphorylation kinetics, measured using a novel fluorescence method eliminating the use of radioactive isotopes, indicates similar Michaelis–Menten V max and K M for regulatory light chain S15 phosphorylation rates in MYL2, porcine ventricular myosin, and chicken gizzard myosin. These data demonstrate that smMLCK is a specific and efficient kinase for the in vitro phosphorylation of MYL2, cardiac, and smooth muscle myosin. Whether smMLCK plays a role in cardiac muscle regulation or response to a disease causing stimulus is unclear but it should be considered a potentially significant kinase in cardiac tissue on the basis of its specificity, kinetics, and tissue expression.

Smooth muscle myosin light chain kinase efficiently phosphorylates serine 15 of cardiac myosin regulatory light chain

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Josephson, Matthew P.; Sikkink, Laura A. [Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905 (United States); Penheiter, Alan R. [Molecular Medicine Program, Mayo Clinic, Rochester, MN 55905 (United States); Burghardt, Thomas P., E-mail: burghardt@mayo.edu [Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905 (United States); Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905 (United States); Ajtai, Katalin [Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905 (United States)

2011-12-16

Highlights: Black-Right-Pointing-Pointer Cardiac myosin regulatory light chain (MYL2) is phosphorylated at S15. Black-Right-Pointing-Pointer Smooth muscle myosin light chain kinase (smMLCK) is a ubiquitous kinase. Black-Right-Pointing-Pointer It is a widely believed that MYL2 is a poor substrate for smMLCK. Black-Right-Pointing-Pointer In fact, smMLCK efficiently and rapidly phosphorylates S15 in MYL2. Black-Right-Pointing-Pointer Phosphorylation kinetics measured by novel fluorescence method without radioactivity. -- Abstract: Specific phosphorylation of the human ventricular cardiac myosin regulatory light chain (MYL2) modifies the protein at S15. This modification affects MYL2 secondary structure and modulates the Ca{sup 2+} sensitivity of contraction in cardiac tissue. Smooth muscle myosin light chain kinase (smMLCK) is a ubiquitous kinase prevalent in uterus and present in other contracting tissues including cardiac muscle. The recombinant 130 kDa (short) smMLCK phosphorylated S15 in MYL2 in vitro. Specific modification of S15 was verified using the direct detection of the phospho group on S15 with mass spectrometry. SmMLCK also specifically phosphorylated myosin regulatory light chain S15 in porcine ventricular myosin and chicken gizzard smooth muscle myosin (S20 in smooth muscle) but failed to phosphorylate the myosin regulatory light chain in rabbit skeletal myosin. Phosphorylation kinetics, measured using a novel fluorescence method eliminating the use of radioactive isotopes, indicates similar Michaelis-Menten V{sub max} and K{sub M} for regulatory light chain S15 phosphorylation rates in MYL2, porcine ventricular myosin, and chicken gizzard myosin. These data demonstrate that smMLCK is a specific and efficient kinase for the in vitro phosphorylation of MYL2, cardiac, and smooth muscle myosin. Whether smMLCK plays a role in cardiac muscle regulation or response to a disease causing stimulus is unclear but it should be considered a potentially significant

The structure of the actin-smooth muscle myosin motor domain complex in the rigor state.

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Banerjee, Chaity; Hu, Zhongjun; Huang, Zhong; Warrington, J Anthony; Taylor, Dianne W; Trybus, Kathleen M; Lowey, Susan; Taylor, Kenneth A

2017-12-01

Myosin-based motility utilizes catalysis of ATP to drive the relative sliding of F-actin and myosin. The earliest detailed model based on cryo-electron microscopy (cryoEM) and X-ray crystallography postulated that higher actin affinity and lever arm movement were coupled to closure of a feature of the myosin head dubbed the actin-binding cleft. Several studies since then using crystallography of myosin-V and cryoEM structures of F-actin bound myosin-I, -II and -V have provided details of this model. The smooth muscle myosin II interaction with F-actin may differ from those for striated and non-muscle myosin II due in part to different lengths of important surface loops. Here we report a ∼6 Å resolution reconstruction of F-actin decorated with the nucleotide-free recombinant smooth muscle myosin-II motor domain (MD) from images recorded using a direct electron detector. Resolution is highest for F-actin and the actin-myosin interface (3.5-4 Å) and lowest (∼6-7 Å) for those parts of the MD at the highest radius. Atomic models built into the F-actin density are quite comparable to those previously reported for rabbit muscle actin and show density from the bound ADP. The atomic model of the MD, is quite similar to a recently published structure of vertebrate non-muscle myosin II bound to F-actin and a crystal structure of nucleotide free myosin-V. Larger differences are observed when compared to the cryoEM structure of F-actin decorated with rabbit skeletal muscle myosin subfragment 1. The differences suggest less closure of the 50 kDa domain in the actin bound skeletal muscle myosin structure. Copyright © 2017 Elsevier Inc. All rights reserved.

Enhanced protein electrophoresis technique for separating human skeletal muscle myosin heavy chain isoforms

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Bamman, M. M.; Clarke, M. S.; Talmadge, R. J.; Feeback, D. L.

1999-01-01

Talmadge and Roy (J. Appl. Physiol. 1993, 75, 2337-2340) previously established a sodium dodecyl sulfate - polyacrylamide gel electrophoresis (SDS-PAGE) protocol for separating all four rat skeletal muscle myosin heavy chain (MHC) isoforms (MHC I, IIa, IIx, IIb); however, when applied to human muscle, the type II MHC isoforms (Ila, IIx) are not clearly distinguished. In this brief paper we describe a modification of the SDS-PAGE protocol which yields distinct and consistent separation of all three adult human MHC isoforms (MHC I, IIa, IIx) in a minigel system. MHC specificity of each band was confirmed by Western blot using three monoclonal IgG antibodies (mAbs) immunoreactive against MHCI (mAb MHCs, Novacastra Laboratories), MHCI+IIa (mAb BF-35), and MHCIIa+IIx (mAb SC-71). Results provide a valuable SDS-PAGE minigel technique for separating MHC isoforms in human muscle without the difficult task of casting gradient gels.

Drastic increase of myosin light chain MLC-2 in senescent skeletal muscle indicates fast-to-slow fibre transition in sarcopenia of old age.

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Gannon, Joan; Doran, Philip; Kirwan, Anne; Ohlendieck, Kay

2009-11-01

The age-dependent decline in skeletal muscle mass and function is believed to be due to a multi-factorial pathology and represents a major factor that blocks healthy aging by increasing physical disability, frailty and loss of independence in the elderly. This study has focused on the comparative proteomic analysis of contractile elements and revealed that the most striking age-related changes seem to occur in the protein family representing myosin light chains (MLCs). Comparative screening of total muscle extracts suggests a fast-to-slow transition in the aged MLC population. The mass spectrometric analysis of the myofibril-enriched fraction identified the MLC2 isoform of the slow-type MLC as the contractile protein with the most drastically changed expression during aging. Immunoblotting confirmed an increased abundance of slow MLC2, concomitant with a switch in fast versus slow myosin heavy chains. Staining of two-dimensional gels of crude extracts with the phospho-specific fluorescent dye ProQ-Diamond identified the increased MLC2 spot as a muscle protein with a drastically enhanced phosphorylation level in aged fibres. Comparative immunofluorescence microscopy, using antibodies to fast and slow myosin isoforms, confirmed a fast-to-slow transformation process during muscle aging. Interestingly, the dramatic increase in slow MLC2 expression was restricted to individual senescent fibres. These findings agree with the idea that aged skeletal muscles undergo a shift to more aerobic-oxidative metabolism in a slower-twitching fibre population and suggest the slow MLC2 isoform as a potential biomarker for fibre type shifting in sarcopenia of old age.

Thick filament mechano-sensing is a calcium-independent regulatory mechanism in skeletal muscle.

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Fusi, L; Brunello, E; Yan, Z; Irving, M

2016-10-31

Recent X-ray diffraction studies on actively contracting fibres from skeletal muscle showed that the number of myosin motors available to interact with actin-containing thin filaments is controlled by the stress in the myosin-containing thick filaments. Those results suggested that thick filament mechano-sensing might constitute a novel regulatory mechanism in striated muscles that acts independently of the well-known thin filament-mediated calcium signalling pathway. Here we test that hypothesis using probes attached to the myosin regulatory light chain in demembranated muscle fibres. We show that both the extent and kinetics of thick filament activation depend on thick filament stress but are independent of intracellular calcium concentration in the physiological range. These results establish direct control of myosin motors by thick filament mechano-sensing as a general regulatory mechanism in skeletal muscle that is independent of the canonical calcium signalling pathway.

Effects of BTS (N-benzyl-p-toluene sulphonamide), an inhibitor for myosin-actin interaction, on myofibrillogenesis in skeletal muscle cells in culture.

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Kagawa, Maiko; Sato, Naruki; Obinata, Takashi

2006-11-01

Actin filaments align around myosin filaments in the correct polarity and in a hexagonal arrangement to form cross-striated structures. It has been postulated that this myosin-actin interaction is important in the initial phase of myofibrillogenesis. It was previously demonstrated that an inhibitor of actin-myosin interaction, BDM (2,3-butanedione monoxime), suppresses myofibril formation in muscle cells in culture. However, further study showed that BDM also exerts several additional effects on living cells. In this study, we further examined the role of actin-myosin interaction in myofibril assembly in primary cultures of chick embryonic skeletal muscle by applying a more specific inhibitor, BTS (N-benzyl-p-toluene sulphonamide), of myosin ATPase and actin-myosin interaction. The assembly of sarcomeric structures from myofibrillar proteins was examined by immunocytochemical methods with the application of BTS to myotubes just after fusion. Addition of BTS (10-50 microM) significantly suppressed the organization of actin and myosin into cross-striated structures. BTS also interfered in the organization of alpha-actinin, C-protein (or MyBP-C), and connectin (or titin) into ordered striated structures, though the sensitivity was less. Moreover, when myotubes cultured in the presence of BTS were transferred to a control medium, sarcomeric structures were formed in 2-3 days, indicating that the inhibitory effect of BTS on myotubes is reversible. These results show that actin-myosin interaction plays a critical role in the process of myofibrillogenesis.

The importance of subfragment 2 and C-terminus of myosin heavy chain for thick filament assembly in skeletal muscle cells.

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Ojima, Koichi; Oe, Mika; Nakajima, Ikuyo; Shibata, Masahiro; Muroya, Susumu; Chikuni, Koichi; Hattori, Akihito; Nishimura, Takanori

2015-04-01

In skeletal muscle cells, myofibrillar proteins are highly organized into sarcomeres in which thick filaments interdigitate with thin filaments to generate contractile force. The size of thick filaments, which consist mainly of myosin molecules, is strictly controlled. However, little is known about the mechanisms by which myosin molecules assemble into thick filaments. Here, we assessed the ability of each domain of myosin heavy chain (Myh) to form thick filaments. We showed that exogenously expressed subfragment 2 (S2) + light meromyosin (LMM) of Myh was efficiently incorporated into thick filaments in muscle cells, although neither solely expressed S2 nor LMM targeted to thick filaments properly. In nonmuscle COS7 cells, S2+LMM formed more enlarged filaments/speckles than LMM. These results suggest that Myh filament formation is induced by S2 accompanying LMM. We further examined the effects of Myh C-terminus on thick filament assembly. C-terminal deletion mutants were incorporated not into entire thick filaments but rather into restricted regions of thick filaments. Our findings suggest that the elongation of myosin filaments to form thick filaments is regulated by S2 as well as C-terminus of LMM. © 2014 Japanese Society of Animal Science.

PLASTICITY OF SKELETAL MUSCLE STUDIED BY STEREOLOGY

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Ida Eržen

2011-05-01

Full Text Available The present contribution provides an overview of stereological methods applied in the skeletal muscle research at the Institute of Anatomy of the Medical Faculty in Ljubljana. Interested in skeletal muscle plasticity we studied three different topics: (i expression of myosin heavy chain isoforms in slow and fast muscles under experimental conditions, (ii frequency of satellite cells in young and old human and rat muscles and (iii capillary supply of rat fast and slow muscles. We analysed the expression of myosin heavy chain isoforms within slow rat soleus and fast extensor digitorum longus muscles after (i homotopic and heterotopic transplantation of both muscles, (ii low frequency electrical stimulation of the fast muscle and (iii transposition of the fast nerve to the slow muscle. The models applied were able to turn the fast muscle into a completely slow muscle, but not vice versa. One of the indicators for the regenerative potential of skeletal muscles is its satellite cell pool. The estimated parameters, number of satellite cells per unit fibre length, corrected to the reference sarcomere length (Nsc/Lfib and number of satellite cells per number of nuclei (myonuclei and satellite cell nuclei (Nsc/Nnucl indicated that the frequency of M-cadherin stained satellite cells declines in healthy old human and rat muscles compared to young muscles. To access differences in capillary densities among slow and fast muscles and slow and fast muscle fibres, we have introduced Slicer and Fakir methods, and tested them on predominantly slow and fast rat muscles. Discussing three different topics that require different approach, the present paper reflects the three decades of the development of stereological methods: 2D analysis by simple point counting in the 70's, the disector in the 80's and virtual spatial probes in the 90's. In all methods the interactive computer assisted approach was utilised.

Smitin, a novel smooth muscle titin-like protein, interacts with myosin filaments in vivo and in vitro.

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Kim, Kyoungtae; Keller, Thomas C S

2002-01-07

Smooth muscle cells use an actin-myosin II-based contractile apparatus to produce force for a variety of physiological functions, including blood pressure regulation and gut peristalsis. The organization of the smooth muscle contractile apparatus resembles that of striated skeletal and cardiac muscle, but remains much more poorly understood. We have found that avian vascular and visceral smooth muscles contain a novel, megadalton protein, smitin, that is similar to striated muscle titin in molecular morphology, localization in a contractile apparatus, and ability to interact with myosin filaments. Smitin, like titin, is a long fibrous molecule with a globular domain on one end. Specific reactivities of an anti-smitin polyclonal antibody and an anti-titin monoclonal antibody suggest that smitin and titin are distinct proteins rather than differentially spliced isoforms encoded by the same gene. Smitin immunofluorescently colocalizes with myosin in chicken gizzard smooth muscle, and interacts with two configurations of smooth muscle myosin filaments in vitro. In physiological ionic strength conditions, smitin and smooth muscle myosin coassemble into irregular aggregates containing large sidepolar myosin filaments. In low ionic strength conditions, smitin and smooth muscle myosin form highly ordered structures containing linear and polygonal end-to-end and side-by-side arrays of small bipolar myosin filaments. We have used immunogold localization and sucrose density gradient cosedimentation analyses to confirm association of smitin with both the sidepolar and bipolar smooth muscle myosin filaments. These findings suggest that the titin-like protein smitin may play a central role in organizing myosin filaments in the contractile apparatus and perhaps in other structures in smooth muscle cells.

Response of slow and fast muscle to hypothyroidism: maximal shortening velocity and myosin isoforms

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Caiozzo, V. J.; Herrick, R. E.; Baldwin, K. M.

1992-01-01

This study examined both the shortening velocity and myosin isoform distribution of slow- (soleus) and fast-twitch (plantaris) skeletal muscles under hypothyroid conditions. Adult female Sprague-Dawley rats were randomly assigned to one of two groups: control (n = 7) or hypothyroid (n = 7). In both muscles, the relative contents of native slow myosin (SM) and type I myosin heavy chain (MHC) increased in response to the hypothyroid treatment. The effects were such that the hypothyroid soleus muscle expressed only the native SM and type I MHC isoforms while repressing native intermediate myosin and type IIA MHC. In the plantaris, the relative content of native SM and type I MHC isoforms increased from 5 to 13% and from 4 to 10% of the total myosin pool, respectively. Maximal shortening velocity of the soleus and plantaris as measured by the slack test decreased by 32 and 19%, respectively, in response to hypothyroidism. In contrast, maximal shortening velocity as estimated by force-velocity data decreased only in the soleus (-19%). No significant change was observed for the plantaris.

Myosin Binding Protein-C Slow Phosphorylation is Altered in Duchenne Dystrophy and Arthrogryposis Myopathy in Fast-Twitch Skeletal Muscles.

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Ackermann, Maegen A; Ward, Christopher W; Gurnett, Christina; Kontrogianni-Konstantopoulos, Aikaterini

2015-08-19

Myosin Binding Protein-C slow (sMyBP-C), encoded by MYBPC1, comprises a family of regulatory proteins of skeletal muscles that are phosphorylated by PKA and PKC. MYBPC1 missense mutations are linked to the development of Distal Arthrogryposis-1 (DA-1). Although structure-function details for this myopathy are evolving, function is undoubtedly driven by sequence variations and post-translational modifications in sMyBP-C. Herein, we examined the phosphorylation profile of sMyBP-C in mouse and human fast-twitch skeletal muscles. We used Flexor Digitorum Brevis (FDB) isolated from young (~2-months old) and old (~14-months old) wild type and mdx mice, and human Abductor Hallucis (AH) and gastrocnemious muscles carrying the DA-1 mutations. Our results indicate both constitutive and differential phosphorylation of sMyBP-C in aged and diseased muscles. We report a 7-35% reduction in the phosphorylation levels of select sites in old wild type and young or old mdx FDB mouse muscles, compared to young wild type tissue. Similarly, we observe a 30-70% decrease in the phosphorylation levels of all PKA and PKC phospho-sites in the DA-1 AH, but not gastrocnemius, muscle. Overall, our studies show that the phosphorylation pattern of sMyBP-C is differentially regulated in response to age and disease, suggesting that phosphorylation plays important roles in these processes.

Expression of developmental myosin and morphological characteristics in adult rat skeletal muscle following exercise-induced injury.

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Smith, H K; Plyley, M J; Rodgers, C D; McKee, N H

1999-07-01

The extent and stability of the expression of developmental isoforms of myosin heavy chain (MHCd), and their association with cellular morphology, were determined in adult rat skeletal muscle fibres following injury induced by eccentrically-biased exercise. Adult female Wistar rats [274 (10) g] were either assigned as non-exercised controls or subjected to 30 min of treadmill exercise (grade, -16 degrees; speed, 15 m x min(-1)), and then sacrificed following 1, 2, 4, 7, or 12 days of recovery (n = 5-6 per group). Histologically and immunohistologically stained serial, transverse cryosections of the soleus (S), vastus intermedius (VI), and tibialis anterior (TA) muscles were examined using light microscopy and digital imaging. Fibres staining positively for MHCd (MHCd+) were seldom detected in the TA. In the VI and S, higher proportions of MHCd+ fibres (0.8% and 2.5%, respectively) were observed in rats at 4 and 7 days post-exercise, in comparison to all other groups combined (0.2%, 1.2%; P < or = 0.01). In S, MHCd+ fibres were observed less frequently by 12 days (0.7%) than at 7 days (2.6%) following exercise. The majority (85.1%) of the MHCd+ fibres had morphological characteristics indicative of either damage, degeneration, repair or regeneration. Most of the MHCd+ fibres also expressed adult slow, and/or fast myosin heavy chain. Quantitatively, the MHCd+ fibres were smaller (< 2500 microm2) and more angular than fibres not expressing MHCd. Thus, there was a transient increase in a small, but distinct population of MHCd+ fibres following unaccustomed, functional exercise in adult rat S and VI muscles. The observed close coupling of MHCd expression with morphological changes within muscle fibres suggests that these characteristics have a common, initial exercise-induced injury-related stimulus.

Association of expression levels in skeletal muscle and a SNP in the ...

Indian Academy of Sciences (India)

dicted breeding value for rib eye area in two experiments using 100 sires (P ... In the real-time PCR-based analysis, we used skeletal muscle tissues of eight JB .... mediates recruitment of muscle-type creatine kinase (CK) to myosin. Biochem.

Passive Repetitive Stretching for a Short Duration within a Week Increases Myogenic Regulatory Factors and Myosin Heavy Chain mRNA in Rats' Skeletal Muscles

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Yurie Kamikawa

2013-01-01

Full Text Available Stretching is a stimulation of muscle growth. Stretching for hours or days has an effect on muscle hypertrophy. However, differences of continuous stretching and repetitive stretching to affect muscle growth are not well known. To clarify the difference of continuous and repetitive stretching within a short duration, we investigated the gene expression of muscle-related genes on stretched skeletal muscles. We used 8-week-old male Wistar rats ( for this study. Animals medial gastrocnemius muscle was stretched continuously or repetitively for 15 min daily and 4 times/week under anesthesia. After stretching, muscles were removed and total RNA was extracted. Then, reverse transcriptional quantitative real-time PCR was done to evaluate the mRNA expression of MyoD, myogenin, and embryonic myosin heavy chain (MyHC. Muscles, either stretched continuously or repetitively, increased mRNA expression of MyoD, myogenin, and embryonic MyHC more than unstretched muscles. Notably, repetitive stretching resulted in more substantial effects on embryonic MyHC gene expression than continuous stretching. In conclusion, passive stretching for a short duration within a week is effective in increasing myogenic factor expression, and repetitive stretching had more effects than continuous stretching for skeletal muscle on muscle growth. These findings are applicable in clinical muscle-strengthening therapy.

Thyroid Hormone Signaling in Male Mouse Skeletal Muscle Is Largely Independent of D2 in Myocytes

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Werneck-de-Castro, Joao P.; Fonseca, Tatiana L.; Ignacio, Daniele L.; Fernandes, Gustavo W.; Andrade-Feraud, Cristina M.; Lartey, Lattoya J.; Ribeiro, Marcelo B.; Ribeiro, Miriam O.; Gereben, Balazs

2015-01-01

The type 2 deiodinase (D2) activates the prohormone T4 to T3. D2 is expressed in skeletal muscle (SKM), and its global inactivation (GLOB-D2KO mice) reportedly leads to skeletal muscle hypothyroidism and impaired differentiation. Here floxed Dio2 mice were crossed with mice expressing Cre-recombinase under the myosin light chain 1f (cre-MLC) to disrupt D2 expression in the late developmental stages of skeletal myocytes (SKM-D2KO). This led to a loss of approximately 50% in D2 activity in neonatal and adult SKM-D2KO skeletal muscle and about 75% in isolated SKM-D2KO myocytes. To test the impact of Dio2 disruption, we measured soleus T3 content and found it to be normal. We also looked at the expression of T3-responsive genes in skeletal muscle, ie, myosin heavy chain I, α-actin, myosin light chain, tropomyosin, and serca 1 and 2, which was preserved in neonatal SKM-D2KO hindlimb muscles, at a time that coincides with a peak of D2 activity in control animals. In adult soleus the baseline level of D2 activity was about 6-fold lower, and in the SKM-D2KO soleus, the expression of only one of five T3-responsive genes was reduced. Despite this, adult SKM-D2KO animals performed indistinguishably from controls on a treadmill test, running for approximately 16 minutes and reached a speed of about 23 m/min; muscle strength was about 0.3 mN/m·g body weight in SKM-D2KO and control ankle muscles. In conclusion, there are multiple sources of D2 in the mouse SKM, and its role is limited in postnatal skeletal muscle fibers. PMID:26214036

Coexistence of potentiation and fatigue in skeletal muscle

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D.E. Rassier

2000-05-01

Full Text Available Twitch potentiation and fatigue in skeletal muscle are two conditions in which force production is affected by the stimulation history. Twitch potentiation is the increase in the twitch active force observed after a tetanic contraction or during and following low-frequency stimulation. There is evidence that the mechanism responsible for potentiation is phosphorylation of the regulatory light chains of myosin, a Ca2+-dependent process. Fatigue is the force decrease observed after a period of repeated muscle stimulation. Fatigue has also been associated with a Ca2+-related mechanism: decreased peak Ca2+ concentration in the myoplasm is observed during fatigue. This decrease is probably due to an inhibition of Ca2+ release from the sarcoplasmic reticulum. Although potentiation and fatigue have opposing effects on force production in skeletal muscle, these two presumed mechanisms can coexist. When peak myoplasmic Ca2+ concentration is depressed, but myosin light chains are relatively phosphorylated, the force response can be attenuated, not different, or enhanced, relative to previous values. In circumstances where there is interaction between potentiation and fatigue, care must be taken in interpreting the contractile responses.

Regulation of Contraction by the Thick Filaments in Skeletal Muscle.

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Irving, Malcolm

2017-12-19

Contraction of skeletal muscle cells is initiated by a well-known signaling pathway. An action potential in a motor nerve triggers an action potential in a muscle cell membrane, a transient increase of intracellular calcium concentration, binding of calcium to troponin in the actin-containing thin filaments, and a structural change in the thin filaments that allows myosin motors from the thick filaments to bind to actin and generate force. This calcium/thin filament mediated pathway provides the "START" signal for contraction, but it is argued that the functional response of the muscle cell, including the speed of its contraction and relaxation, adaptation to the external load, and the metabolic cost of contraction is largely determined by additional mechanisms. This review considers the role of the thick filaments in those mechanisms, and puts forward a paradigm for the control of contraction in skeletal muscle in which both the thick and thin filaments have a regulatory function. The OFF state of the thick filament is characterized by helical packing of most of the myosin head or motor domains on the thick filament surface in a conformation that makes them unavailable for actin binding or ATP hydrolysis, although a small fraction of the myosin heads are constitutively ON. The availability of the majority fraction of the myosin heads for contraction is controlled in part by the external load on the muscle, so that these heads only attach to actin and hydrolyze ATP when they are required. This phenomenon seems to be the major determinant of the well-known force-velocity relationship of muscle, and controls the metabolic cost of contraction. The regulatory state of the thick filament also seems to control the dynamics of both muscle activation and relaxation. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Skeletal muscle contraction in protecting joints and bones by absorbing mechanical impacts

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Rudenko, O. V.; Tsyuryupa, S.; Sarvazyan, A.

2016-09-01

We have previously hypothesized that the dissipation of mechanical energy of external impact is a fundamental function of skeletal muscle in addition to its primary function to convert chemical energy into mechanical energy. In this paper, a mathematical justification of this hypothesis is presented. First, a simple mechanical model, in which the muscle is considered as a simple Hookean spring, is considered. This analysis serves as an introduction to the consideration of a biomechanical model taking into account the molecular mechanism of muscle contraction, kinetics of myosin bridges, sarcomere dynamics, and tension of muscle fibers. It is shown that a muscle behaves like a nonlinear and adaptive spring tempering the force of impact and increasing the duration of the collision. The temporal profiles of muscle reaction to the impact as functions of the levels of muscle contraction, durations of the impact front, and the time constants of myosin bridges closing, are obtained. The absorption of mechanical shock energy is achieved due to the increased viscoelasticity of the contracting skeletal muscle. Controlling the contraction level allows for the optimization of the stiffness and viscosity of the muscle necessary for the protection of the joints and bones.

TGF-β receptors, in a Smad-independent manner, are required for terminal skeletal muscle differentiation

International Nuclear Information System (INIS)

Droguett, Rebeca; Cabello-Verrugio, Claudio; Santander, Cristian; Brandan, Enrique

2010-01-01

Skeletal muscle differentiation is strongly inhibited by transforming growth factor type β (TGF-β), although muscle formation as well as regeneration normally occurs in an environment rich in this growth factor. In this study, we evaluated the role of intracellular regulatory Smads proteins as well as TGF-β-receptors (TGF-β-Rs) during skeletal muscle differentiation. We found a decrease of TGF-β signaling during differentiation. This phenomenon is explained by a decline in the levels of the regulatory proteins Smad-2, -3, and -4, a decrease in the phosphorylation of Smad-2 and lost of nuclear translocation of Smad-3 and -4 in response to TGF-β. No change in the levels and inhibitory function of Smad-7 was observed. In contrast, we found that TGF-β-R type I (TGF-β-RI) and type II (TGF-β-RII) increased on the cell surface during skeletal muscle differentiation. To analyze the direct role of the serine/threonine kinase activities of TGF-β-Rs, we used the specific inhibitor SB 431542 and the dominant-negative form of TGF-β-RII lacking the cytoplasmic domain. The TGF-β-Rs were important for successful muscle formation, determined by the induction of myogenin, creatine kinase activity, and myosin. Silencing of Smad-2/3 expression by specific siRNA treatments accelerated myogenin, myosin expression, and myotube formation; although when SB 431542 was present inhibition in myosin induction and myotube formation was observed, suggesting that these last steps of skeletal muscle differentiation require active TGF-β-Rs. These results suggest that both down-regulation of Smad regulatory proteins and cell signaling through the TGF-β receptors independent of Smad proteins are essential for skeletal muscle differentiation.

TGF-{beta} receptors, in a Smad-independent manner, are required for terminal skeletal muscle differentiation

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Droguett, Rebeca; Cabello-Verrugio, Claudio; Santander, Cristian [Centro de Regulacion Celular y Patologia, Centro de Regeneracion y Envejecimiento (CARE), Departamento de Biologia Celular y Molecular, MIFAB, Pontificia Universidad Catolica de Chile, Santiago (Chile); Brandan, Enrique, E-mail: ebrandan@bio.puc.cl [Centro de Regulacion Celular y Patologia, Centro de Regeneracion y Envejecimiento (CARE), Departamento de Biologia Celular y Molecular, MIFAB, Pontificia Universidad Catolica de Chile, Santiago (Chile)

2010-09-10

Skeletal muscle differentiation is strongly inhibited by transforming growth factor type {beta} (TGF-{beta}), although muscle formation as well as regeneration normally occurs in an environment rich in this growth factor. In this study, we evaluated the role of intracellular regulatory Smads proteins as well as TGF-{beta}-receptors (TGF-{beta}-Rs) during skeletal muscle differentiation. We found a decrease of TGF-{beta} signaling during differentiation. This phenomenon is explained by a decline in the levels of the regulatory proteins Smad-2, -3, and -4, a decrease in the phosphorylation of Smad-2 and lost of nuclear translocation of Smad-3 and -4 in response to TGF-{beta}. No change in the levels and inhibitory function of Smad-7 was observed. In contrast, we found that TGF-{beta}-R type I (TGF-{beta}-RI) and type II (TGF-{beta}-RII) increased on the cell surface during skeletal muscle differentiation. To analyze the direct role of the serine/threonine kinase activities of TGF-{beta}-Rs, we used the specific inhibitor SB 431542 and the dominant-negative form of TGF-{beta}-RII lacking the cytoplasmic domain. The TGF-{beta}-Rs were important for successful muscle formation, determined by the induction of myogenin, creatine kinase activity, and myosin. Silencing of Smad-2/3 expression by specific siRNA treatments accelerated myogenin, myosin expression, and myotube formation; although when SB 431542 was present inhibition in myosin induction and myotube formation was observed, suggesting that these last steps of skeletal muscle differentiation require active TGF-{beta}-Rs. These results suggest that both down-regulation of Smad regulatory proteins and cell signaling through the TGF-{beta} receptors independent of Smad proteins are essential for skeletal muscle differentiation.

Calcium ion in skeletal muscle: its crucial role for muscle function, plasticity, and disease

DEFF Research Database (Denmark)

Berchtold, M W; Brinkmeier, H; Müntener, M

2000-01-01

in the sarcoplasmic reticulum. In addition, a multitude of Ca(2+)-binding proteins is present in muscle tissue including parvalbumin, calmodulin, S100 proteins, annexins, sorcin, myosin light chains, beta-actinin, calcineurin, and calpain. These Ca(2+)-binding proteins may either exert an important role in Ca(2......Mammalian skeletal muscle shows an enormous variability in its functional features such as rate of force production, resistance to fatigue, and energy metabolism, with a wide spectrum from slow aerobic to fast anaerobic physiology. In addition, skeletal muscle exhibits high plasticity that is based...... on the potential of the muscle fibers to undergo changes of their cytoarchitecture and composition of specific muscle protein isoforms. Adaptive changes of the muscle fibers occur in response to a variety of stimuli such as, e.g., growth and differentition factors, hormones, nerve signals, or exercise...

The expression of HSP in human skeletal muscle. Effects of muscle fiber phenotype and training background

DEFF Research Database (Denmark)

Folkesson, Mattias; Mackey, Abigail L; Langberg, Henning

2013-01-01

AIM: Exercise-induced adaptations of skeletal muscle are related to training mode and can be muscle fibre type specific. This study aimed to investigate heat shock protein expression in type I and type II muscle fibres in resting skeletal muscle of subjects with different training backgrounds...... myosin heavy chain I and IIA, αB-crystallin, HSP27, HSP60 and HSP70. RESULTS: In ACT and RES, but not in END, a fibre type specific expression with higher staining intensity in type I than type II fibres was seen for αB-crystallin. The opposite (II>I) was found for HSP27 in subjects from ACT (6 of 12...... HSPs in human skeletal muscle is influenced by muscle fibre phenotype. The fibre type specific expression of HSP70 is influenced by resistance and endurance training whereas those of αB-crystallin and HSP27 are influenced only by endurance training suggesting the existence of a training...

Polymorphism of myofibrillar proteins of rabbit skeletal-muscle fibres. An electrophoretic study of single fibres.

OpenAIRE

Salviati, G; Betto, R; Danieli Betto, D

1982-01-01

Rabbit predominantly fast-twitch-fibre and predominantly slow-twitch-fibre skeletal muscles of the hind limbs, the psoas, the diaphragm and the masseter muscles were fibre-typed by one-dimensional polyacrylamide-gel electrophoresis of the myofibrillar proteins of chemically skinned single fibres. Investigation of the distribution of fast-twitch-fibre and slow-twitch-fibre isoforms of myosin light chains and the type of myosin heavy chains, based on peptide 'maps' published in Cleveland. Fisch...

Skeletal muscle myosin heavy chain isoform content in relation to gonadal hormones and anabolic-catabolic balance in trained and untrained men.

Science.gov (United States)

Grandys, Marcin; Majerczak, Joanna; Karasinski, Janusz; Kulpa, Jan; Zoladz, Jerzy A

2012-12-01

Gonadal hormones and anabolic-catabolic hormone balance have potent influence on skeletal muscle tissue, but little is known about their action with regard to myosin heavy chain (MHC) transformation in humans. We investigated the relationship between skeletal muscle MHC isoform content in the vastus lateralis muscle and basal testosterone (T) concentration in 3 groups of subjects: endurance trained (E), sprint/strength trained (S), and untrained (U) young men. We have also determined basal sex hormone-binding globulin and cortisol (C) concentrations in untrained subjects to examine the relationship between MHC composition and the anabolic-catabolic hormone balance. Moreover, basal free testosterone (fT) and bioavailable testosterone (bio-T) concentrations were calculated for this subgroup. Despite significant differences in MHC isoform content (69.4 ± 2.39%, 61.4 ± 8.04%, and 37.5 ± 13.80% of MHC-2 for groups S, U, and E, respectively, Kruskal-Wallis: H = 18.58, p 0.5). We have also found that in the U group, type 2 MHC in the vastus lateralis muscle is positively correlated with basal fT:C ratio (r = 0.63, p = 0.01). It is concluded that the differences in the training history and training specificity can be distinguished with regard to the MHC composition but not with regard to the basal T concentration. Simultaneously, it has been shown that MHC isoform content in human vastus lateralis muscle may be related to basal anabolic-catabolic hormone balance, and this hypothesis needs further investigation.

Ca2+-Dependent Regulations and Signaling in Skeletal Muscle: From Electro-Mechanical Coupling to Adaptation

Science.gov (United States)

Gehlert, Sebastian; Bloch, Wilhelm; Suhr, Frank

2015-01-01

Calcium (Ca2+) plays a pivotal role in almost all cellular processes and ensures the functionality of an organism. In skeletal muscle fibers, Ca2+ is critically involved in the innervation of skeletal muscle fibers that results in the exertion of an action potential along the muscle fiber membrane, the prerequisite for skeletal muscle contraction. Furthermore and among others, Ca2+ regulates also intracellular processes, such as myosin-actin cross bridging, protein synthesis, protein degradation and fiber type shifting by the control of Ca2+-sensitive proteases and transcription factors, as well as mitochondrial adaptations, plasticity and respiration. These data highlight the overwhelming significance of Ca2+ ions for the integrity of skeletal muscle tissue. In this review, we address the major functions of Ca2+ ions in adult muscle but also highlight recent findings of critical Ca2+-dependent mechanisms essential for skeletal muscle-regulation and maintenance. PMID:25569087

Age- and Activity-Related Differences in the Abundance of Myosin Essential and Regulatory Light Chains in Human Muscle

Directory of Open Access Journals (Sweden)

James N. Cobley

2016-04-01

Full Text Available Traditional methods for phenotyping skeletal muscle (e.g., immunohistochemistry are labor-intensive and ill-suited to multixplex analysis, i.e., assays must be performed in a series. Addressing these concerns represents a largely unmet research need but more comprehensive parallel analysis of myofibrillar proteins could advance knowledge regarding age- and activity-dependent changes in human muscle. We report a label-free, semi-automated and time efficient LC-MS proteomic workflow for phenotyping the myofibrillar proteome. Application of this workflow in old and young as well as trained and untrained human skeletal muscle yielded several novel observations that were subsequently verified by multiple reaction monitoring (MRM. We report novel data demonstrating that human ageing is associated with lesser myosin light chain 1 content and greater myosin light chain 3 content, consistent with an age-related reduction in type II muscle fibers. We also disambiguate conflicting data regarding myosin regulatory light chain, revealing that age-related changes in this protein more closely reflect physical activity status than ageing per se. This finding reinforces the need to control for physical activity levels when investigating the natural process of ageing. Taken together, our data confirm and extend knowledge regarding age- and activity-related phenotypes. In addition, the MRM transitions described here provide a methodological platform that can be fine-tuned to suite multiple research needs and thus advance myofibrillar phenotyping.

Ferulic Acid Promotes Hypertrophic Growth of Fast Skeletal Muscle in Zebrafish Model.

Science.gov (United States)

Wen, Ya; Ushio, Hideki

2017-09-26

As a widely distributed and natural existing antioxidant, ferulic acid and its functions have been extensively studied in recent decades. In the present study, hypertrophic growth of fast skeletal myofibers was observed in adult zebrafish after ferulic acid administration for 30 days, being reflected in increased body weight, body mass index (BMI), and muscle mass, along with an enlarged cross-sectional area of myofibers. qRT-PCR analyses demonstrated the up-regulation of relative mRNA expression levels of myogenic transcriptional factors (MyoD, myogenin and serum response factor (SRF)) and their target genes encoding sarcomeric unit proteins involved in muscular hypertrophy (skeletal alpha-actin, myosin heavy chain, tropomyosin, and troponin I). Western blot analyses detected a higher phosphorylated level of zTOR (zebrafish target of rapamycin), p70S6K, and 4E-BP1, which suggests an enhanced translation efficiency and protein synthesis capacity of fast skeletal muscle myofibers. These changes in transcription and translation finally converge and lead to higher protein contents in myofibers, as confirmed by elevated levels of myosin heavy chain (MyHC), and an increased muscle mass. To the best of our knowledge, these findings have been reported for the first time in vivo and suggest potential applications of ferulic acid as functional food additives and dietary supplements owing to its ability to promote muscle growth.

Radiation injury to skeletal muscle

International Nuclear Information System (INIS)

Persons, C.C.M.; Wondergem, J.; Leer, J.W.H.

1997-01-01

Radiotherapy of neoplasia has increased the mean life expectancy of cancer patients. On the other hand, more reports are published on morbidity of the treatment with regard to normal tissue. Studies on skeletal muscle injury specifically are scarce, but many clinical long term follow-up studies make note of side effects as muscle atrophy, fibrosis and limited function. Furthermore it is suggested that skeletal muscles of children are more prone to radiation injury than those of adult subjects. Effects of radiation on skeletal muscle were studied in rats. On hind limb of young (100 g) and adult (350 g) rats was irradiated with single doses (15-30 Gy), while the other served as control. Follow-up was up to 12 months post treatment. Muscular function in young rats was decreased significantly at 6 months post irradiation, but did not further decrease in the following 6 months. The amount of collagen, on the other hand, was not increased at 6 months, but became highly elevated at 12 months past treatment. This suggests that at 6 months, impaired muscular function may not be explained by increased fibrotic tissues. This is an agreement with results obtained in adult rats, where function was also impaired, without concomitant increase in collagen. In an earlier study, mitochondrial oxygen consumption was dose dependently decreased after irradiation, at 12 months, but not at 6 months post treatment. Furthermore, myosin-actin interaction was measured in skinned fibers. The first results of this study indicate changes in the interaction of contraction proteins, as early as 6 months post treatment. (authors)

Skeletal muscle morphology, protein synthesis and gene expression in Ehlers Danlos Syndrome

DEFF Research Database (Denmark)

Nygaard, Rie H; Jensen, Jacob K; Voermans, Nicol C

2017-01-01

skeletal muscle biopsies in patients with classic EDS (cEDS, n=5 (Denmark)+ 8 (The Netherlands)) and vascular EDS (vEDS, n=3) and analyzed muscle fiber morphology and content (Western blotting and muscle fiber type/area distributions) and muscle mRNA expression and protein synthesis rate (RT-PCR and stable...... isotope technique). RESULTS: The cEDS patients did not differ from healthy controls (n = 7-11) with regard to muscle fiber type/area, myosin/α-actin ratio, muscle protein synthesis rate or mRNA expression. In contrast, the vEDS patients demonstrated higher expression of matrix proteins compared to c......EDS patients (fibronectin and MMP-2). DISCUSSION: The cEDS patients had surprisingly normal muscle morphology and protein synthesis, whereas vEDS patients demonstrated higher mRNA expression for extracellular matrix remodeling in skeletal musculature compared to cEDS patients....

Immunolabelling, histochemistry and in situ hybridisation in human skeletal muscle fibres to detect myosin heavy chain expression at the protein and mRNA level

Science.gov (United States)

SERRANO, A. L.; PÉREZ, MARGARITA; LUCÍA, A.; CHICHARRO, J. L.; QUIROZ-ROTHE, E.; RIVERO, J. L. L.

2001-01-01

The distribution of muscle fibres classified on the basis of their content of different myosin heavy chain (MHC) isoforms was analysed in vastus lateralis muscle biopsies of 15 young men (with an average age of 22 y) by correlating immunohistochemistry with specific anti-MHC monoclonal antibodies, myofibrillar ATPase (mATPase) histochemistry and in situ hybridisation with probes specific for MHC β-slow, MHC-IIA and MHC-IIX. The characterisation of a large number of individual fibres was compared and correlated on a fibre-to-fibre basis. The panel of monoclonal antibodies used in the study allowed classification of human skeletal muscle fibres into 5 categories according to the MHC isoform they express at the protein level, types I, I+IIA, IIA, IIAX and IIX. Hybrid fibres coexpressing two isoforms represented a considerable proportion of the fibre composition (about 14%) and were clearly underestimated by mATPase histochemistry. For a very high percentage of fibres there was a precise correspondence between the MHC protein isoforms and mRNA transcripts. The integrated methods used demonstrate a high degree of precision of the immunohistochemical procedure used for the identification and quantification of human skeletal muscle fibre types. The monoclonal antibody S5-8H2 is particularly useful for identifying hybrid IIAX fibres. This protocol offers new prospects for muscle fibre classification in human experimental studies. PMID:11554510

Myosin light chain kinase phosphorylation in tracheal smooth muscle

International Nuclear Information System (INIS)

Stull, J.T.; Hsu, L.C.; Tansey, M.G.; Kamm, K.E.

1990-01-01

Purified myosin light chain kinase from smooth muscle is phosphorylated by cyclic AMP-dependent protein kinase, protein kinase C, and the multifunctional calmodulin-dependent protein kinase II. Because phosphorylation in a specific site (site A) by any one of these kinases desensitizes myosin light chain kinase to activation by Ca2+/calmodulin, kinase phosphorylation could play an important role in regulating smooth muscle contractility. This possibility was investigated in 32 P-labeled bovine tracheal smooth muscle. Treatment of tissues with carbachol, KCl, isoproterenol, or phorbol 12,13-dibutyrate increased the extent of kinase phosphorylation. Six primary phosphopeptides (A-F) of myosin light chain kinase were identified. Site A was phosphorylated to an appreciable extent only with carbachol or KCl, agents which contract tracheal smooth muscle. The extent of site A phosphorylation correlated to increases in the concentration of Ca2+/calmodulin required for activation. These results show that cyclic AMP-dependent protein kinase and protein kinase C do not affect smooth muscle contractility by phosphorylating site A in myosin light chain kinase. It is proposed that phosphorylation of myosin light chain kinase in site A in contracting tracheal smooth muscle may play a role in the reported desensitization of contractile elements to activation by Ca2+

CaMKII content affects contractile, but not mitochondrial, characteristics in regenerating skeletal muscle

NARCIS (Netherlands)

Eilers, W.; Jaspers, R.T.; de Haan, A.; Ferrié, C.; Valdivieso, P.; Flueck, M.

2014-01-01

Background: The multi-meric calcium/calmodulin-dependent protein kinase II (CaMKII) is the main CaMK in skeletal muscle and its expression increases with endurance training. CaMK family members are implicated in contraction-induced regulation of calcium handling, fast myosin type IIA expression and

Interaction of thyroid state and denervation on skeletal myosin heavy chain expression

Science.gov (United States)

Haddad, F.; Arnold, C.; Zeng, M.; Baldwin, K.

1997-01-01

The goal of this study was to examine the effects of altered thyroid state and denervation (Den) on skeletal myosin heavy chain (MHC) expression in the plantaris and soleus muscles. Rats were subjected to unilateral denervation (Den) and randomly assigned to one of three groups: (1) euthyroid; (2) hyperthyroid; (3) and hypothyroid. Denervation caused severe muscle atrophy and muscle-type specific MHC transformation. Denervation transformed the soleus to a faster muscle, and its effects required the presence of circulating thyroid hormone. In contrast, denervation transformed the plantaris to a slower muscle independently of thyroid state. Furthermore, thyroid hormone effects did not depend upon innervation status in the soleus, while they required the presence of the nerve in the plantaris. Collectively, these findings suggest that both thyroid hormone and intact nerve (a) differentially affect MHC transformations in fast and slow muscle; and (b) are important factors in regulating the optimal expression of both type I and IIB MHC genes. This research suggests that for patients with nerve damage and/or paralysis, both muscle mass and biochemical properties can also be affected by the thyroid state.

Bifunctional Rhodamine Probes of Myosin Regulatory Light Chain Orientation in Relaxed Skeletal Muscle Fibers

Science.gov (United States)

Brack, Andrew S.; Brandmeier, Birgit D.; Ferguson, Roisean E.; Criddle, Susan; Dale, Robert E.; Irving, Malcolm

2004-01-01

The orientation of the regulatory light chain (RLC) region of the myosin heads in relaxed skinned fibers from rabbit psoas muscle was investigated by polarized fluorescence from bifunctional rhodamine (BR) probes cross-linking pairs of cysteine residues introduced into the RLC. Pure 1:1 BR-RLC complexes were exchanged into single muscle fibers in EDTA rigor solution for 30 min at 30°C; ∼60% of the native RLC was removed and stoichiometrically replaced by BR-RLC, and >85% of the BR-RLC was located in the sarcomeric A-bands. The second- and fourth-rank order parameters of the orientation distributions of BR dipoles linking RLC cysteine pairs 100-108, 100-113, 108-113, and 104-115 were calculated from polarized fluorescence intensities, and used to determine the smoothest RLC orientation distribution—the maximum entropy distribution—consistent with the polarized fluorescence data. Maximum entropy distributions in relaxed muscle were relatively broad. At the peak of the distribution, the “lever” axis, linking Cys707 and Lys843 of the myosin heavy chain, was at 70–80° to the fiber axis, and the “hook” helix (Pro830–Lys843) was almost coplanar with the fiber and lever axes. The temperature and ionic strength of the relaxing solution had small but reproducible effects on the orientation of the RLC region. PMID:15041671

Lessons from a tarantula: new insights into muscle thick filament and myosin interacting-heads motif structure and function.

Science.gov (United States)

Alamo, Lorenzo; Koubassova, Natalia; Pinto, Antonio; Gillilan, Richard; Tsaturyan, Andrey; Padrón, Raúl

2017-10-01

The tarantula skeletal muscle X-ray diffraction pattern suggested that the myosin heads were helically arranged on the thick filaments. Electron microscopy (EM) of negatively stained relaxed tarantula thick filaments revealed four helices of heads allowing a helical 3D reconstruction. Due to its low resolution (5.0 nm), the unambiguous interpretation of densities of both heads was not possible. A resolution increase up to 2.5 nm, achieved by cryo-EM of frozen-hydrated relaxed thick filaments and an iterative helical real space reconstruction, allowed the resolving of both heads. The two heads, "free" and "blocked", formed an asymmetric structure named the "interacting-heads motif" (IHM) which explained relaxation by self-inhibition of both heads ATPases. This finding made tarantula an exemplar system for thick filament structure and function studies. Heads were shown to be released and disordered by Ca 2+ -activation through myosin regulatory light chain phosphorylation, leading to EM, small angle X-ray diffraction and scattering, and spectroscopic and biochemical studies of the IHM structure and function. The results from these studies have consequent implications for understanding and explaining myosin super-relaxed state and thick filament activation and regulation. A cooperative phosphorylation mechanism for activation in tarantula skeletal muscle, involving swaying constitutively Ser35 mono-phosphorylated free heads, explains super-relaxation, force potentiation and post-tetanic potentiation through Ser45 mono-phosphorylated blocked heads. Based on this mechanism, we propose a swaying-swinging, tilting crossbridge-sliding filament for tarantula muscle contraction.

Direct photoaffinity labeling by nucleotides of the apparent catalytic site on the heavy chains of smooth muscle and Acanthamoeba myosins

International Nuclear Information System (INIS)

Maruta, H.; Korn, E.D.

1981-01-01

The heavy chains of Acanthamoeba myosins, IA, IB and II, turkey gizzard myosin, and rabbit skeletal muscle myosin subfragment-1 were specifically labeled by radioactive ATP, ADP, and UTP, each of which is a substrate or product of myosin ATPase activity, when irradiated with uv light at 0 0 C. With UTP, as much as 0.45 mol/mol of Acanthamoeba myosin IA heavy chain and 1 mol/mol of turkey gizzard myosin heavy chain was incorporated. Evidence that the ligands were associated with the catalytic site included the observations that reaction occurred only with nucleotides that are substrates or products of the ATPase activity; that the reaction was blocked by pyrophosphate which is an inhibitor of the ATPase activity; that ATP was bound as ADP; and that label was probably restricted to a single peptide following limited subtilisin proteolysis of labeled Acanthamoeba myosin IA heavy chain and extensive cleavage with CNBr and trypsin of labeled turkey gizzard myosin heavy chain

Determination of the source of SHG verniers in zebrafish skeletal muscle

Science.gov (United States)

Dempsey, William P.; Hodas, Nathan O.; Ponti, Aaron; Pantazis, Periklis

2015-12-01

SHG microscopy is an emerging microscopic technique for medically relevant imaging because certain endogenous proteins, such as muscle myosin lattices within muscle cells, are sufficiently spatially ordered to generate detectable SHG without the use of any fluorescent dye. Given that SHG signal is sensitive to the structural state of muscle sarcomeres, SHG functional imaging can give insight into the integrity of muscle cells in vivo. Here, we report a thorough theoretical and experimental characterization of myosin-derived SHG intensity profiles within intact zebrafish skeletal muscle. We determined that “SHG vernier” patterns, regions of bifurcated SHG intensity, are illusory when sarcomeres are staggered with respect to one another. These optical artifacts arise due to the phase coherence of SHG signal generation and the Guoy phase shift of the laser at the focus. In contrast, two-photon excited fluorescence images obtained from fluorescently labeled sarcomeric components do not contain such illusory structures, regardless of the orientation of adjacent myofibers. Based on our results, we assert that complex optical artifacts such as SHG verniers should be taken into account when applying functional SHG imaging as a diagnostic readout for pathological muscle conditions.

CHARACTERIZATION OF TIGHTLY-ASSOCIATED SMOOTH MUSCLE MYOSIN-MYOSIN LIGHT CHAIN KINASE-CALMODULIN COMPLEXES*

OpenAIRE

Hong, Feng; Haldeman, Brian D.; John, Olivia A.; Brewer, Paul D.; Wu, Yi-Ying; Ni, Shaowei; Wilson, David P.; Walsh, Michael P.; Baker, Jonathan E.; Cremo, Christine R.

2009-01-01

A current popular model to explain phosphorylation of smooth muscle myosin (SMM) by smooth muscle myosin light chain kinase (MLCK) proposes that MLCK is bound tightly to actin but weakly to SMM. We found that MLCK and calmodulin (CaM) co-purify with unphosphorylated SMM (up-SMM) from chicken gizzard, suggesting that they are tightly bound. Although the MLCK:SMM molar ratio in SMM preparations was well below stoichiometric (1:73 ± 9), the ratio was ~ 23–37% of that in gizzard tissue. Fifteen t...

Primary skeletal muscle cells cultured on gelatin bead microcarriers develop structural and biochemical features characteristic of adult skeletal muscle.

Science.gov (United States)

Kubis, Hans-Peter; Scheibe, Renate J; Decker, Brigitte; Hufendiek, Karsten; Hanke, Nina; Gros, Gerolf; Meissner, Joachim D

2016-04-01

A primary skeletal muscle cell culture, in which myoblasts derived from newborn rabbit hindlimb muscles grow on gelatin bead microcarriers in suspension and differentiate into myotubes, has been established previously. In the course of differentiation and beginning spontaneous contractions, these multinucleated myotubes do not detach from their support. Here, we describe the development of the primary myotubes with respect to their ultrastructural differentiation. Scanning electron microscopy reveals that myotubes not only grow around the surface of one carrier bead but also attach themselves to neighboring carriers, forming bridges between carriers. Transmission electron microscopy demonstrates highly ordered myofibrils, T-tubules, and sarcoplasmic reticulum. The functionality of the contractile apparatus is evidenced by contractile activity that occurs spontaneously or can be elicited by electrostimulation. Creatine kinase activity increases steadily until day 20 of culture. Regarding the expression of isoforms of myosin heavy chains (MHC), we could demonstrate that from day 16 on, no non-adult MHC isoform mRNAs are present. Instead, on day 28 the myotubes express predominantly adult fast MHCIId/x mRNA and protein. This MHC pattern resembles that of fast muscles of adult rabbits. In contrast, primary myotubes grown on matrigel-covered culture dishes express substantial amounts of non-adult MHC protein even on day 21. To conclude, primary myotubes grown on microcarriers in their later stages exhibit many features of adult skeletal muscle and characteristics of fast type II fibers. Thus, the culture represents an excellent model of adult fast skeletal muscle, for example, when investigating molecular mechanisms of fast-to-slow fiber-type transformation. © 2015 International Federation for Cell Biology.

A novel three-filament model of force generation in eccentric contraction of skeletal muscles.

Directory of Open Access Journals (Sweden)

Gudrun Schappacher-Tilp

Full Text Available We propose and examine a three filament model of skeletal muscle force generation, thereby extending classical cross-bridge models by involving titin-actin interaction upon active force production. In regions with optimal actin-myosin overlap, the model does not alter energy and force predictions of cross-bridge models for isometric contractions. However, in contrast to cross-bridge models, the three filament model accurately predicts history-dependent force generation in half sarcomeres for eccentric and concentric contractions, and predicts the activation-dependent forces for stretches beyond actin-myosin filament overlap.

Distinct functional interactions between actin isoforms and nonsarcomeric myosins.

Directory of Open Access Journals (Sweden)

Mirco Müller

Full Text Available Despite their near sequence identity, actin isoforms cannot completely replace each other in vivo and show marked differences in their tissue-specific and subcellular localization. Little is known about isoform-specific differences in their interactions with myosin motors and other actin-binding proteins. Mammalian cytoplasmic β- and γ-actin interact with nonsarcomeric conventional myosins such as the members of the nonmuscle myosin-2 family and myosin-7A. These interactions support a wide range of cellular processes including cytokinesis, maintenance of cell polarity, cell adhesion, migration, and mechano-electrical transduction. To elucidate differences in the ability of isoactins to bind and stimulate the enzymatic activity of individual myosin isoforms, we characterized the interactions of human skeletal muscle α-actin, cytoplasmic β-actin, and cytoplasmic γ-actin with human myosin-7A and nonmuscle myosins-2A, -2B and -2C1. In the case of nonmuscle myosins-2A and -2B, the interaction with either cytoplasmic actin isoform results in 4-fold greater stimulation of myosin ATPase activity than was observed in the presence of α-skeletal muscle actin. Nonmuscle myosin-2C1 is most potently activated by β-actin and myosin-7A by γ-actin. Our results indicate that β- and γ-actin isoforms contribute to the modulation of nonmuscle myosin-2 and myosin-7A activity and thereby to the spatial and temporal regulation of cytoskeletal dynamics. FRET-based analyses show efficient copolymerization abilities for the actin isoforms in vitro. Experiments with hybrid actin filaments show that the extent of actomyosin coupling efficiency can be regulated by the isoform composition of actin filaments.

Blockades of mitogen-activated protein kinase and calcineurin both change fibre-type markers in skeletal muscle culture

DEFF Research Database (Denmark)

Higginson, James; Wackerhage, Henning; Woods, Niall

2002-01-01

A and mitogen-activated protein kinase kinase (MEK1/2) blockade with U0126 upon myosin heavy chain (MHC) isoform mRNA levels and activities of metabolic enzymes after 1 day, 3 days and 7 days of treatment in primary cultures of spontaneously twitching rat skeletal muscle. U0126 treatment significantly decreased......Activation of either the calcineurin or the extracellular signal-regulated kinase (ERK1/2) pathway increases the percentage of slow fibres in vivo suggesting that both pathways can regulate fibre phenotypes in skeletal muscle. We investigated the effect of calcineurin blockade with cyclosporin...

Muscle Contraction.

Science.gov (United States)

Sweeney, H Lee; Hammers, David W

2018-02-01

SUMMARYMuscle cells are designed to generate force and movement. There are three types of mammalian muscles-skeletal, cardiac, and smooth. Skeletal muscles are attached to bones and move them relative to each other. Cardiac muscle comprises the heart, which pumps blood through the vasculature. Skeletal and cardiac muscles are known as striated muscles, because the filaments of actin and myosin that power their contraction are organized into repeating arrays, called sarcomeres, that have a striated microscopic appearance. Smooth muscle does not contain sarcomeres but uses the contraction of filaments of actin and myosin to constrict blood vessels and move the contents of hollow organs in the body. Here, we review the principal molecular organization of the three types of muscle and their contractile regulation through signaling mechanisms and discuss their major structural and functional similarities that hint at the possible evolutionary relationships between the cell types. Copyright © 2018 Cold Spring Harbor Laboratory Press; all rights reserved.

Growth Factors and Tension-Induced Skeletal Muscle Growth

Science.gov (United States)

Vandenburgh, Herman H.

1994-01-01

The project investigated biochemical mechanisms to enhance skeletal muscle growth, and developed a computer based mechanical cell stimulator system. The biochemicals investigated in this study were insulin/(Insulin like Growth Factor) IGF-1 and Steroids. In order to analyze which growth factors are essential for stretch-induced muscle growth in vitro, we developed a defined, serum-free medium in which the differentiated, cultured avian muscle fibers could be maintained for extended periods of time. The defined medium (muscle maintenance medium, MM medium) maintains the nitrogen balance of the myofibers for 3 to 7 days, based on myofiber diameter measurements and myosin heavy chain content. Insulin and IGF-1, but not IGF-2, induced pronounced myofiber hypertrophy when added to this medium. In 5 to 7 days, muscle fiber diameters increase by 71 % to 98% compared to untreated controls. Mechanical stimulation of the avian muscle fibers in MM medium increased the sensitivity of the cells to insulin and IGF-1, based on a leftward shift of the insulin dose/response curve for protein synthesis rates. (54). We developed a ligand binding assay for IGF-1 binding proteins and found that the avian skeletal muscle cultures produced three major species of 31, 36 and 43 kD molecular weight (54) Stretch of the myofibers was found to have no significant effect on the efflux of IGF-1 binding proteins, but addition of exogenous collagen stimulated IGF-1 binding protein production 1.5 to 5 fold. Steroid hormones have a profound effect on muscle protein turnover rates in vivo, with the stress-related glucocorticoids inducing rapid skeletal muscle atrophy while androgenic steroids induce skeletal muscle growth. Exercise in humans and animals reduces the catabolic effects of glucocorticoids and may enhance the anabolic effects of androgenic steroids on skeletal muscle. In our continuing work on the involvement of exogenrus growth factors in stretch-induced avian skeletal muscle growth, we

Adult fast myosin pattern and Ca2+-induced slow myosin pattern in primary skeletal muscle culture

Science.gov (United States)

Kubis, Hans-Peter; Haller, Ernst-August; Wetzel, Petra; Gros, Gerolf

1997-01-01

A primary muscle cell culture derived from newborn rabbit muscle and growing on microcarriers in suspension was established. When cultured for several weeks, the myotubes in this model develop the completely adult pattern of fast myosin light and heavy chains. When Ca2+ ionophore is added to the culture medium on day 11, raising intracellular [Ca2+] about 10-fold, the myotubes develop to exhibit properties of an adult slow muscle by day 30, expressing slow myosin light as well as heavy chains, elevated citrate synthase, and reduced lactate dehydrogenase. The remarkable plasticity of these myotubes becomes apparent, when 8 days after withdrawal of the ionophore a marked slow-to-fast transition, as judged from the expression of isomyosins and metabolic enzymes, occurs. PMID:9108130

Functional evaluation of artificial skeletal muscle tissue constructs fabricated by a magnetic force-based tissue engineering technique.

Science.gov (United States)

Yamamoto, Yasunori; Ito, Akira; Fujita, Hideaki; Nagamori, Eiji; Kawabe, Yoshinori; Kamihira, Masamichi

2011-01-01

Skeletal muscle tissue engineering is currently applied in a variety of research fields, including regenerative medicine, drug screening, and bioactuator development, all of which require the fabrication of biomimic and functional skeletal muscle tissues. In the present study, magnetite cationic liposomes were used to magnetically label C2C12 myoblast cells for the construction of three-dimensional artificial skeletal muscle tissues by an applied magnetic force. Skeletal muscle functions, such as biochemical and contractile properties, were evaluated for the artificial tissue constructs. Histological studies revealed that elongated and multinucleated myotubes were observed within the tissue. Expression of muscle-specific markers, such as myogenin, myosin heavy chain and tropomyosin, were detected in the tissue constructs by western blot analysis. Further, creatine kinase activity increased during differentiation. In response to electric pulses, the artificial tissue constructs contracted to generate a physical force (the maximum twitch force, 33.2 μN [1.06 mN/mm2]). Rheobase and chronaxie of the tissue were determined as 4.45 V and 0.72 ms, respectively. These results indicate that the artificial skeletal muscle tissue constructs fabricated in this study were physiologically functional and the data obtained for the evaluation of their functional properties may provide useful information for future skeletal muscle tissue engineering studies.

Double phosphorylation of the myosin regulatory light chain during rigor mortis of bovine Longissimus muscle.

Science.gov (United States)

Muroya, Susumu; Ohnishi-Kameyama, Mayumi; Oe, Mika; Nakajima, Ikuyo; Shibata, Masahiro; Chikuni, Koichi

2007-05-16

To investigate changes in myosin light chains (MyLCs) during postmortem aging of the bovine longissimus muscle, we performed two-dimensional gel electrophoresis followed by identification with matrix-assisted laser desorption ionization time-of-flight mass spectrometry. The results of fluorescent differential gel electrophoresis showed that two spots of the myosin regulatory light chain (MyLC2) at pI values of 4.6 and 4.7 shifted toward those at pI values of 4.5 and 4.6, respectively, by 24 h postmortem when rigor mortis was completed. Meanwhile, the MyLC1 and MyLC3 spots did not change during the 14 days postmortem. Phosphoprotein-specific staining of the gels demonstrated that the MyLC2 proteins at pI values of 4.5 and 4.6 were phosphorylated. Furthermore, possible N-terminal region peptides containing one and two phosphoserine residues were detected in each mass spectrum of the MyLC2 spots at pI values of 4.5 and 4.6, respectively. These results demonstrated that MyLC2 became doubly phosphorylated during rigor formation of the bovine longissimus, suggesting involvement of the MyLC2 phosphorylation in the progress of beef rigor mortis. Bovine; myosin regulatory light chain (RLC, MyLC2); phosphorylation; rigor mortis; skeletal muscle.

Fluorescent modification and orientation of myosin sulfhydryl 2 in skeletal muscle fibers

International Nuclear Information System (INIS)

Ajtai, K.; Burghardt, T.P.

1989-01-01

The authors describe a protocol for the selective covalent labeling of the sulfhydryl 2 (SH2) on the myosin cross-bridge in glycerinated muscle fibers using the sulfhydryl-selective label 4-[N-[(iodoacetoxy)ethyl]-N-methylamino]-7-nitrobenz-2-oxa-1,3-diazole (IANBD). The protocol promotes the specificity of IANBD by using the ability to protect sulfhydryl 1 (SH1) from modification by binding the cross-bridge to the actin filament and using cross-bridge-bound MgADP to promote the accessibility of SH2. They determined the specificity of the probe using fluorescence gel scanning of fiber-extracted proteins to isolate the probe on myosin subfragment 1 (S1), limited proteolysis of the purified S1 to isolate the probe on the 20-kilodalton fragment of S1, and titration of the free SH1's on purified S1 using the radiolabeled SH1-specific reagent [ 14 C]iodoacetamide or enzymatic activity measurements. They characterized the angular distribution of the IANBD on cross-bridges in fibers when the fibers are in rigor, in relaxation, in the presence of MgADP, and in isometric contraction using wavelength-dependent fluorescence polarization. They find that the SH2 probe distinguishes the different states of the fiber such that rigor and MgADP are ordered and maintain a similar orientation throughout the excitation wavelength domain. The relaxed cross-bridge is ordered and has an orientation that is distinct from the orientation of the cross-bridge in rigor and MgADP over the entire wavelength domain. The active isometric cross-bridge is also oriented differently from the other states, suggesting the presence of a predominant actin-bound cross-bridge state that precedes the power stroke during muscle contraction

Adipophilin distribution and colocalization with lipid droplets in skeletal muscle.

LENUS (Irish Health Repository)

Shaw, Christopher S

2009-05-01

Intramyocellular lipids (IMCL) are stored as discrete lipid droplets which are associated with a number of proteins. The lipid droplet-associated protein adipophilin (the human orthologue of adipose differentiation-related protein) is ubiquitously expressed and is one of the predominant lipid droplet-proteins in skeletal muscle. The aim of this study was to investigate the subcellular distribution of adipophilin in human muscle fibres and to measure the colocalization of adipophilin with IMCL. Muscle biopsies from six lean male cyclists (BMI 23.4 +\\/- 0.4, aged 31 +\\/- 2 years, W (max) 346 +\\/- 8) were stained for myosin heavy chain type 1, IMCL, adipophilin and mitochondria using immunofluorescence and viewed with widefield and confocal fluorescence microscopy. The present study shows that like IMCL, the adipophilin content is ~twofold greater in type I skeletal muscle fibres and is situated in the areas between the mitochondrial network. Colocalization analysis demonstrated that 61 +\\/- 2% of IMCL contain adipophilin. Although the majority of adipophilin is contained within IMCL, 36 +\\/- 4% of adipophilin is not associated with IMCL. In conclusion, this study indicates that the IMCL pool is heterogeneous, as the majority but not all IMCL contain adipophilin.

The Kinetics of Myosin Light Chain Kinase Activation of Smooth Muscle Myosin in an In Vitro Model System

OpenAIRE

Hong, Feng; Facemyer, Kevin C.; Carter, Michael S.; Jackson, Del R.; Haldeman, Brian D.; Ruana, Nick; Sutherland, Cindy; Walsh, Michael P.; Cremo, Christine R.; Baker, Josh E.

2013-01-01

During activation of smooth muscle contraction, one myosin light chain kinase (MLCK) molecule rapidly phosphorylates many smooth muscle myosin (SMM) molecules, suggesting that muscle activation rates are influenced by the kinetics of MLCK-SMM interactions. To determine the rate-limiting step underlying activation of SMM by MLCK, we measured the kinetics of calcium-calmodulin (Ca2+-CaM)-MLCK-mediated SMM phosphorylation and the corresponding initiation of SMM-based F-actin motility in an in vi...

Muscle protein analysis. II. Two-dimensional electrophoresis of normal and diseased human skeletal muscle

Energy Technology Data Exchange (ETDEWEB)

Giometti, C.S. (Argonne National Lab., IL); Barany, M.; Danon, M.J.; Anderson, N.G.

1980-07-01

High-resolution two-dimensional electrophoresis was used to analyze the major proteins of normal and pathological human-muscle samples. The normal human-muscle pattern contains four myosin light chains: three that co-migrate with the myosin light chains from rabbit fast muscle (extensor digitorum longus), and one that co-migrates with the light chain 2 from rabbit slow muscle (soleus). Of seven Duchenne muscular dystrophy samples, four yielded patterns with decreased amounts of actin and myosin relative to normal muscle, while three samples gave patterns comparable to that for normal muscle. Six samples from patients with myotonic dystrophy also gave normal patterns. In nemaline rod myopathy, in contrast, the pattern was deficient in two of the fast-type myosin light chains.

Twitchin can regulate the ATPase cycle of actomyosin in a phosphorylation-dependent manner in skinned mammalian skeletal muscle fibres.

Science.gov (United States)

Avrova, Stanislava V; Rysev, Nikita A; Matusovsky, Oleg S; Shelud'ko, Nikolay S; Borovikov, Yurii S

2012-05-01

The effect of twitchin, a thick filament protein of molluscan muscles, on the actin-myosin interaction at several mimicked sequential steps of the ATPase cycle was investigated using the polarized fluorescence of 1.5-IAEDANS bound to myosin heads, FITC-phalloidin attached to actin and acrylodan bound to twitchin in the glycerol-skinned skeletal muscle fibres of mammalian. The phosphorylation-dependent multi-step changes in mobility and spatial arrangement of myosin SH1 helix, actin subunit and twitchin during the ATPase cycle have been revealed. It was shown that nonphosphorylated twitchin inhibited the movements of SH1 helix of the myosin heads and actin subunits and decreased the affinity of myosin to actin by freezing the position and mobility of twitchin in the muscle fibres. The phosphorylation of twitchin reverses this effect by changing the spatial arrangement and mobility of the actin-binding portions of twitchin. In this case, enhanced movements of SH1 helix of the myosin heads and actin subunits are observed. The data imply a novel property of twitchin incorporated into organized contractile system: its ability to regulate the ATPase cycle in a phosphorylation-dependent fashion by changing the affinity and spatial arrangement of the actin-binding portions of twitchin. Copyright © 2012 Elsevier Inc. All rights reserved.

Effects of hypothyroidism on myosin heavy chain composition and fibre types of fast skeletal muscles in a small marsupial, Antechinus flavipes.

Science.gov (United States)

Zhong, Wendy W H; Withers, Kerry W; Hoh, Joseph F Y

2010-04-01

Effects of drug-induced hypothyroidism on myosin heavy chain (MyHC) content and fibre types of fast skeletal muscles were studied in a small marsupial, Antechinus flavipes. SDS-PAGE of MyHCs from the tibialis anterior and gastrocnemius revealed four isoforms, 2B, 2X, 2A and slow, in that order of decreasing abundance. After 5 weeks treatment with methimazole, the functionally fastest 2B MyHC significantly decreased, while 2X, 2A and slow MyHCs increased. Immunohistochemistry using monospecific antibodies to each of the four MyHCs revealed decreased 2b and 2x fibres, and increased 2a and hybrid fibres co-expressing two or three MyHCs. In the normally homogeneously fast superficial regions of these muscles, evenly distributed slow-staining fibres appeared, resembling the distribution of slow primary myotubes in fast muscles during development. Hybrid fibres containing 2A and slow MyHCs were virtually absent. These results are more detailed but broadly similar to the earlier studies on eutherians. We hypothesize that hypothyroidism essentially reverses the effects of thyroid hormone on MyHC gene expression of muscle fibres during myogenesis, which differ according to the developmental origin of the fibre: it induces slow MyHC expression in 2b fibres derived from fast primary myotubes, and shifts fast MyHC expression in fibres of secondary origin towards 2A, but not slow, MyHC.

Proteomics of Skeletal Muscle

DEFF Research Database (Denmark)

Deshmukh, Atul

2016-01-01

, of altered protein expressions profiles and/or their posttranslational modifications (PTMs). Mass spectrometry (MS)-based proteomics offer enormous promise for investigating the molecular mechanisms underlying skeletal muscle insulin resistance and exercise-induced adaptation; however, skeletal muscle......Skeletal muscle is the largest tissue in the human body and plays an important role in locomotion and whole body metabolism. It accounts for ~80% of insulin stimulated glucose disposal. Skeletal muscle insulin resistance, a primary feature of Type 2 diabetes, is caused by a decreased ability...... of muscle to respond to circulating insulin. Physical exercise improves insulin sensitivity and whole body metabolism and remains one of the most promising interventions for the prevention of Type 2 diabetes. Insulin resistance and exercise adaptations in skeletal muscle might be a cause, or consequence...

MURC, a muscle-restricted coiled-coil protein, is involved in the regulation of skeletal myogenesis.

Science.gov (United States)

Tagawa, Masashi; Ueyama, Tomomi; Ogata, Takehiro; Takehara, Naofumi; Nakajima, Norio; Isodono, Koji; Asada, Satoshi; Takahashi, Tomosaburo; Matsubara, Hiroaki; Oh, Hidemasa

2008-08-01

Skeletal myogenesis is a multistep process by which multinucleated mature muscle fibers are formed from undifferentiated, mononucleated myoblasts. However, the molecular mechanisms of skeletal myogenesis have not been fully elucidated. Here, we identified muscle-restricted coiled-coil (MURC) protein as a positive regulator of myogenesis. In skeletal muscle, MURC was localized to the cytoplasm with accumulation in the Z-disc of the sarcomere. In C2C12 myoblasts, MURC expression occurred coincidentally with myogenin expression and preceded sarcomeric myosin expression during differentiation into myotubes. RNA interference (RNAi)-mediated knockdown of MURC impaired differentiation in C2C12 myoblasts, which was accompanied by impaired myogenin expression and ERK activation. Overexpression of MURC in C2C12 myoblasts resulted in the promotion of differentiation with enhanced myogenin expression and ERK activation during differentiation. During injury-induced muscle regeneration, MURC expression increased, and a higher abundance of MURC was observed in immature myofibers compared with mature myofibers. In addition, ERK was activated in regenerating tissue, and ERK activation was detected in MURC-expressing immature myofibers. These findings suggest that MURC is involved in the skeletal myogenesis that results from modulation of myogenin expression and ERK activation. MURC may play pivotal roles in the molecular mechanisms of skeletal myogenic differentiation.

Skeletal muscle atrophy in bioengineered skeletal muscle: a new model system.

Science.gov (United States)

Lee, Peter H U; Vandenburgh, Herman H

2013-10-01

Skeletal muscle atrophy has been well characterized in various animal models, and while certain pathways that lead to disuse atrophy and its associated functional deficits have been well studied, available drugs to counteract these deficiencies are limited. An ex vivo tissue-engineered skeletal muscle offers a unique opportunity to study skeletal muscle physiology in a controlled in vitro setting. Primary mouse myoblasts isolated from adult muscle were tissue engineered into bioartificial muscles (BAMs) containing hundreds of aligned postmitotic muscle fibers expressing sarcomeric proteins. When electrically stimulated, BAMs generated measureable active forces within 2-3 days of formation. The maximum isometric tetanic force (Po) increased for ∼3 weeks to 2587±502 μN/BAM and was maintained at this level for greater than 80 days. When BAMs were reduced in length by 25% to 50%, muscle atrophy occurred in as little as 6 days. Length reduction resulted in significant decreases in Po (50.4%), mean myofiber cross-sectional area (21.7%), total protein synthesis rate (22.0%), and noncollagenous protein content (6.9%). No significant changes occurred in either the total metabolic activity or protein degradation rates. This study is the first in vitro demonstration that length reduction alone can induce skeletal muscle atrophy, and establishes a novel in vitro model for the study of skeletal muscle atrophy.

Skeletal myogenic differentiation of human urine-derived cells as a potential source for skeletal muscle regeneration.

Science.gov (United States)

Chen, Wei; Xie, Minkai; Yang, Bin; Bharadwaj, Shantaram; Song, Lujie; Liu, Guihua; Yi, Shanhong; Ye, Gang; Atala, Anthony; Zhang, Yuanyuan

2017-02-01

Stem cells are regarded as possible cell therapy candidates for skeletal muscle regeneration. However, invasive harvesting of those cells can cause potential harvest-site morbidity. The goal of this study was to assess whether human urine-derived stem cells (USCs), obtained through non-invasive procedures, can differentiate into skeletal muscle linage cells (Sk-MCs) and potentially be used for skeletal muscle regeneration. In this study, USCs were harvested from six healthy individuals aged 25-55. Expression profiles of cell-surface markers were assessed by flow cytometry. To optimize the myogenic differentiation medium, we selected two from four different types of myogenic differentiation media to induce the USCs. Differentiated USCs were identified with myogenic markers by gene and protein expression. USCs were implanted into the tibialis anterior muscles of nude mice for 1 month. The results showed that USCs displayed surface markers with positive staining for CD24, CD29, CD44, CD73, CD90, CD105, CD117, CD133, CD146, SSEA-4 and STRO-1, and negative staining for CD14, CD31, CD34 and CD45. After myogenic differentiation, a change in morphology was observed from 'rice-grain'-like cells to spindle-shaped cells. The USCs expressed specific Sk-MC transcripts and protein markers (myf5, myoD, myosin, and desmin) after being induced with different myogenic culture media. Implanted cells expressed Sk-MC markers stably in vivo. Our findings suggest that USCs are able to differentiate into the Sk-MC lineage in vitro and after being implanted in vivo. Thus, they might be a potential source for cell injection therapy in the use of skeletal muscle regeneration. Copyright © 2014 John Wiley & Sons, Ltd. Copyright © 2014 John Wiley & Sons, Ltd.

Cytoskeletal Tropomyosin Tm5NM1 Is Required for Normal Excitation–Contraction Coupling in Skeletal Muscle

Science.gov (United States)

Vlahovich, Nicole; Kee, Anthony J.; Van der Poel, Chris; Kettle, Emma; Hernandez-Deviez, Delia; Lucas, Christine; Lynch, Gordon S.; Parton, Robert G.; Gunning, Peter W.

2009-01-01

The functional diversity of the actin microfilaments relies in part on the actin binding protein tropomyosin (Tm). The muscle-specific Tms regulate actin-myosin interactions and hence contraction. However, there is less known about the roles of the numerous cytoskeletal isoforms. We have shown previously that a cytoskeletal Tm, Tm5NM1, defines a Z-line adjacent cytoskeleton in skeletal muscle. Recently, we identified a second cytoskeletal Tm in this region, Tm4. Here we show that Tm4 and Tm5NM1 define separate actin filaments; the former associated with the terminal sarcoplasmic reticulum (SR) and other tubulovesicular structures. In skeletal muscles of Tm5NM1 knockout (KO) mice, Tm4 localization was unchanged, demonstrating the specificity of the membrane association. Tm5NM1 KO muscles exhibit potentiation of T-system depolarization and decreased force rundown with repeated T-tubule depolarizations consistent with altered T-tubule function. These results indicate that a Tm5NM1-defined actin cytoskeleton is required for the normal excitation–contraction coupling in skeletal muscle. PMID:19005216

Cytoskeletal tropomyosin Tm5NM1 is required for normal excitation-contraction coupling in skeletal muscle.

Science.gov (United States)

Vlahovich, Nicole; Kee, Anthony J; Van der Poel, Chris; Kettle, Emma; Hernandez-Deviez, Delia; Lucas, Christine; Lynch, Gordon S; Parton, Robert G; Gunning, Peter W; Hardeman, Edna C

2009-01-01

The functional diversity of the actin microfilaments relies in part on the actin binding protein tropomyosin (Tm). The muscle-specific Tms regulate actin-myosin interactions and hence contraction. However, there is less known about the roles of the numerous cytoskeletal isoforms. We have shown previously that a cytoskeletal Tm, Tm5NM1, defines a Z-line adjacent cytoskeleton in skeletal muscle. Recently, we identified a second cytoskeletal Tm in this region, Tm4. Here we show that Tm4 and Tm5NM1 define separate actin filaments; the former associated with the terminal sarcoplasmic reticulum (SR) and other tubulovesicular structures. In skeletal muscles of Tm5NM1 knockout (KO) mice, Tm4 localization was unchanged, demonstrating the specificity of the membrane association. Tm5NM1 KO muscles exhibit potentiation of T-system depolarization and decreased force rundown with repeated T-tubule depolarizations consistent with altered T-tubule function. These results indicate that a Tm5NM1-defined actin cytoskeleton is required for the normal excitation-contraction coupling in skeletal muscle.

Stretch activates myosin light chain kinase in arterial smooth muscle

International Nuclear Information System (INIS)

Barany, K.; Rokolya, A.; Barany, M.

1990-01-01

Stretching of porcine carotid arterial muscle increased the phosphorylation of the 20 kDa myosin light chain from 0.23 to 0.68 mol [32P]phosphate/mol light chain, whereas stretching of phorbol dibutyrate treated muscle increased the phosphorylation from 0.30 to 0.91 mol/mol. Two-dimensional gel electrophoresis followed by two-dimensional tryptic phosphopeptide mapping was used to identify the enzyme involved in the stretch-induced phosphorylation. Quantitation of the [32P]phosphate content of the peptides revealed considerable light chain phosphorylation by protein kinase C only in the phorbol dibutyrate treated arterial muscle, whereas most of the light chain phosphorylation was attributable to myosin light chain kinase. Upon stretch of either the untreated or treated muscle, the total increment in [32P]phosphate incorporation into the light chain could be accounted for by peptides characteristic for myosin light chain kinase catalyzed phosphorylation, demonstrating that the stretch-induced phosphorylation is caused by this enzyme exclusively

Aerobic exercise training induces skeletal muscle hypertrophy and age-dependent adaptations in myofiber function in young and older men

Science.gov (United States)

Konopka, Adam R.; Undem, Miranda K.; Hinkley, James M.; Minchev, Kiril; Kaminsky, Leonard A.; Trappe, Todd A.; Trappe, Scott

2012-01-01

To examine potential age-specific adaptations in skeletal muscle size and myofiber contractile physiology in response to aerobic exercise, seven young (YM; 20 ± 1 yr) and six older men (OM; 74 ± 3 yr) performed 12 wk of cycle ergometer training. Muscle biopsies were obtained from the vastus lateralis to determine size and contractile properties of isolated slow [myosin heavy chain (MHC) I] and fast (MHC IIa) myofibers, MHC composition, and muscle protein concentration. Aerobic capacity was higher (P 0.05) with training. Training reduced (P aerobic capacity are similar between YM and OM, while adaptations in myofiber contractile function showed a general improvement in OM. Training-related increases in MHC I and MHC IIa peak power reveal that skeletal muscle of OM is responsive to aerobic exercise training and further support the use of aerobic exercise for improving cardiovascular and skeletal muscle health in older individuals. PMID:22984247

Myosin heavy chain expression in rabbit masseter muscle during postnatal development

NARCIS (Netherlands)

Bredman, J. J.; Weijs, W. A.; Korfage, H. A.; Brugman, P.; Moorman, A. F.

1992-01-01

The expression of isoforms of myosin heavy chain (MHC) during postnatal development was studied in the masseter muscle of the rabbit. Evidence is presented that in addition to adult fast and slow myosin, the rabbit masseter contains neonatal and 'cardiac' alpha-MHC. During postnatal growth myosin

Protective Effects of Clenbuterol against Dexamethasone-Induced Masseter Muscle Atrophy and Myosin Heavy Chain Transition.

Directory of Open Access Journals (Sweden)

Daisuke Umeki

Full Text Available Glucocorticoid has a direct catabolic effect on skeletal muscle, leading to muscle atrophy, but no effective pharmacotherapy is available. We reported that clenbuterol (CB induced masseter muscle hypertrophy and slow-to-fast myosin heavy chain (MHC isoform transition through direct muscle β2-adrenergic receptor stimulation. Thus, we hypothesized that CB would antagonize glucocorticoid (dexamethasone; DEX-induced muscle atrophy and fast-to-slow MHC isoform transition.We examined the effect of CB on DEX-induced masseter muscle atrophy by measuring masseter muscle weight, fiber diameter, cross-sectional area, and myosin heavy chain (MHC composition. To elucidate the mechanisms involved, we used immunoblotting to study the effects of CB on muscle hypertrophic signaling (insulin growth factor 1 (IGF1 expression, Akt/mammalian target of rapamycin (mTOR pathway, and calcineurin pathway and atrophic signaling (Akt/Forkhead box-O (FOXO pathway and myostatin expression in masseter muscle of rats treated with DEX and/or CB.Masseter muscle weight in the DEX-treated group was significantly lower than that in the Control group, as expected, but co-treatment with CB suppressed the DEX-induced masseter muscle atrophy, concomitantly with inhibition of fast-to-slow MHC isoforms transition. Activation of the Akt/mTOR pathway in masseter muscle of the DEX-treated group was significantly inhibited compared to that of the Control group, and CB suppressed this inhibition. DEX also suppressed expression of IGF1 (positive regulator of muscle growth, and CB attenuated this inhibition. Myostatin protein expression was unchanged. CB had no effect on activation of the Akt/FOXO pathway. These results indicate that CB antagonizes DEX-induced muscle atrophy and fast-to-slow MHC isoform transition via modulation of Akt/mTOR activity and IGF1 expression. CB might be a useful pharmacological agent for treatment of glucocorticoid-induced muscle atrophy.

Human skeletal muscle fibroblasts stimulate in vitro myogenesis and in vivo muscle regeneration.

Science.gov (United States)

Mackey, Abigail L; Magnan, Mélanie; Chazaud, Bénédicte; Kjaer, Michael

2017-08-01

Accumulation of skeletal muscle extracellular matrix is an unfavourable characteristic of many muscle diseases, muscle injury and sarcopenia. The extent of cross-talk between fibroblasts, as the source of matrix protein, and satellite cells in humans is unknown. We studied this in human muscle biopsies and cell-culture studies. We observed a strong stimulation of myogenesis by human fibroblasts in cell culture. In biopsies collected 30 days after a muscle injury protocol, fibroblast number increased to four times control levels, where fibroblasts were found to be preferentially located immediately surrounding regenerating muscle fibres. These novel findings indicate an important role for fibroblasts in supporting the regeneration of muscle fibres, potentially through direct stimulation of satellite cell differentiation and fusion, and contribute to understanding of cell-cell cross-talk during physiological and pathological muscle remodelling. Accumulation of skeletal muscle extracellular matrix is an unfavourable characteristic of many muscle diseases, muscle injury and sarcopenia. In addition to the indispensable role satellite cells play in muscle regeneration, there is emerging evidence in rodents for a regulatory influence on fibroblast activity. However, the influence of fibroblasts on satellite cells and muscle regeneration in humans is unknown. The purpose of this study was to investigate this in vitro and during in vivo regeneration in humans. Following a muscle injury protocol in young healthy men (n = 7), the number of fibroblasts (TCF7L2+), satellite cells (Pax7+), differentiating myogenic cells (myogenin+) and regenerating fibres (neonatal/embryonic myosin+) was determined from biopsy cross-sections. Fibroblasts and myogenic precursor cells (MPCs) were also isolated from human skeletal muscle (n = 4) and co-cultured using different cell ratios, with the two cell populations either in direct contact with each other or separated by a permeable

An Antibody Blocking Activin Type II Receptors Induces Strong Skeletal Muscle Hypertrophy and Protects from Atrophy

Science.gov (United States)

Minetti, Giulia C.; Sheppard, KellyAnn; Ibebunjo, Chikwendu; Feige, Jerome N.; Hartmann, Steffen; Brachat, Sophie; Rivet, Helene; Koelbing, Claudia; Morvan, Frederic; Hatakeyama, Shinji

2014-01-01

The myostatin/activin type II receptor (ActRII) pathway has been identified to be critical in regulating skeletal muscle size. Several other ligands, including GDF11 and the activins, signal through this pathway, suggesting that the ActRII receptors are major regulatory nodes in the regulation of muscle mass. We have developed a novel, human anti-ActRII antibody (bimagrumab, or BYM338) to prevent binding of ligands to the receptors and thus inhibit downstream signaling. BYM338 enhances differentiation of primary human skeletal myoblasts and counteracts the inhibition of differentiation induced by myostatin or activin A. BYM338 prevents myostatin- or activin A-induced atrophy through inhibition of Smad2/3 phosphorylation, thus sparing the myosin heavy chain from degradation. BYM338 dramatically increases skeletal muscle mass in mice, beyond sole inhibition of myostatin, detected by comparing the antibody with a myostatin inhibitor. A mouse version of the antibody induces enhanced muscle hypertrophy in myostatin mutant mice, further confirming a beneficial effect on muscle growth beyond myostatin inhibition alone through blockade of ActRII ligands. BYM338 protects muscles from glucocorticoid-induced atrophy and weakness via prevention of muscle and tetanic force losses. These data highlight the compelling therapeutic potential of BYM338 for the treatment of skeletal muscle atrophy and weakness in multiple settings. PMID:24298022

Characterisation of L-Type Amino Acid Transporter 1 (LAT1 Expression in Human Skeletal Muscle by Immunofluorescent Microscopy

Directory of Open Access Journals (Sweden)

Nathan Hodson

2017-12-01

Full Text Available The branch chain amino acid leucine is a potent stimulator of protein synthesis in skeletal muscle. Leucine rapidly enters the cell via the L-Type Amino Acid Transporter 1 (LAT1; however, little is known regarding the localisation and distribution of this transporter in human skeletal muscle. Therefore, we applied immunofluorescence staining approaches to visualise LAT1 in wild type (WT and LAT1 muscle-specific knockout (mKO mice, in addition to basal human skeletal muscle samples. LAT1 positive staining was visually greater in WT muscles compared to mKO muscle. In human skeletal muscle, positive LAT1 staining was noted close to the sarcolemmal membrane (dystrophin positive staining, with a greater staining intensity for LAT1 observed in the sarcoplasmic regions of type II fibres (those not stained positively for myosin heavy-chain 1, Type II—25.07 ± 5.93, Type I—13.71 ± 1.98, p < 0.01, suggesting a greater abundance of this protein in these fibres. Finally, we observed association with LAT1 and endothelial nitric oxide synthase (eNOS, suggesting LAT1 association close to the microvasculature. This is the first study to visualise the distribution and localisation of LAT1 in human skeletal muscle. As such, this approach provides a validated experimental platform to study the role and regulation of LAT1 in human skeletal muscle in response to various physiological and pathophysiological models.

NRIP is newly identified as a Z-disc protein, activating calmodulin signaling for skeletal muscle contraction and regeneration.

Science.gov (United States)

Chen, Hsin-Hsiung; Chen, Wen-Pin; Yan, Wan-Lun; Huang, Yuan-Chun; Chang, Szu-Wei; Fu, Wen-Mei; Su, Ming-Jai; Yu, I-Shing; Tsai, Tzung-Chieh; Yan, Yu-Ting; Tsao, Yeou-Ping; Chen, Show-Li

2015-11-15

Nuclear receptor interaction protein (NRIP, also known as DCAF6 and IQWD1) is a Ca(2+)-dependent calmodulin-binding protein. In this study, we newly identify NRIP as a Z-disc protein in skeletal muscle. NRIP-knockout mice were generated and found to have reduced muscle strength, susceptibility to fatigue and impaired adaptive exercise performance. The mechanisms of NRIP-regulated muscle contraction depend on NRIP being downstream of Ca(2+) signaling, where it stimulates activation of both 'calcineurin-nuclear factor of activated T-cells, cytoplasmic 1' (CaN-NFATc1; also known as NFATC1) and calmodulin-dependent protein kinase II (CaMKII) through interaction with calmodulin (CaM), resulting in the induction of mitochondrial activity and the expression of genes encoding the slow class of myosin, and in the regulation of Ca(2+) homeostasis through the internal Ca(2+) stores of the sarcoplasmic reticulum. Moreover, NRIP-knockout mice have a delayed regenerative capacity. The amount of NRIP can be enhanced after muscle injury and is responsible for muscle regeneration, which is associated with the increased expression of myogenin, desmin and embryonic myosin heavy chain during myogenesis, as well as for myotube formation. In conclusion, NRIP is a novel Z-disc protein that is important for skeletal muscle strength and regenerative capacity. © 2015. Published by The Company of Biologists Ltd.

Life without double-headed non-muscle myosin II motor proteins

Science.gov (United States)

Betapudi, Venkaiah

2014-07-01

Non-muscle myosin II motor proteins (myosin IIA, myosin IIB, and myosin IIC) belong to a class of molecular motor proteins that are known to transduce cellular free-energy into biological work more efficiently than man-made combustion engines. Nature has given a single myosin II motor protein for lower eukaryotes and multiple for mammals but none for plants in order to provide impetus for their life. These specialized nanomachines drive cellular activities necessary for embryogenesis, organogenesis, and immunity. However, these multifunctional myosin II motor proteins are believed to go awry due to unknown reasons and contribute for the onset and progression of many autosomal-dominant disorders, cataract, deafness, infertility, cancer, kidney, neuronal, and inflammatory diseases. Many pathogens like HIV, Dengue, hepatitis C, and Lymphoma viruses as well as Salmonella and Mycobacteria are now known to take hostage of these dedicated myosin II motor proteins for their efficient pathogenesis. Even after four decades since their discovery, we still have a limited knowledge of how these motor proteins drive cell migration and cytokinesis. We need to enrich our current knowledge on these fundamental cellular processes and develop novel therapeutic strategies to fix mutated myosin II motor proteins in pathological conditions. This is the time to think how to relieve the hijacked myosins from pathogens in order to provide a renewed impetus for patients’ life. Understanding how to steer these molecular motors in proliferating and differentiating stem cells will improve stem cell based-therapeutics development. Given the plethora of cellular activities non-muscle myosin motor proteins are involved in, their importance is apparent for human life.

Life without double-headed non-muscle myosin II motor proteins

Directory of Open Access Journals (Sweden)

Venkaiah eBetapudi

2014-07-01

Full Text Available Non-muscle myosin II motor proteins (myosin IIA, myosin IIB, and myosin IIC belong to a class of molecular motor proteins that are known to transduce cellular free-energy into biological work more efficiently than man-made combustion engines. Nature has given a single myosin II motor protein for lower eukaryotes and multiple for mammals but none for plants in order to provide impetus for their life. These specialized nanomachines drive cellular activities necessary for embryogenesis, organogenesis, and immunity. However, these multifunctional myosin II motor proteins are believed to go awry due to unknown reasons and contribute for the onset and progression of many autosomal-dominant disorders, cataract, deafness, infertility, cancer, kidney, neuronal, and inflammatory diseases. Many pathogens like HIV, Dengue, hepatitis C, and Lymphoma viruses as well as Salmonella and Mycobacteria are now known to take hostage of these dedicated myosin II motor proteins for their efficient pathogenesis. Even after four decades since their discovery, we still have a limited knowledge of how these motor proteins drive cell migration and cytokinesis. We need to enrich our current knowledge on these fundamental cellular processes and develop novel therapeutic strategies to fix mutated myosin II motor proteins in pathological conditions. This is the time to think how to relieve the hijacked myosins from pathogens in order to provide a renewed impetus for patients’ life. Understanding how to steer these molecular motors in proliferating and differentiating stem cells will improve stem cell based-therapeutics development. Given the plethora of cellular activities non-muscle myosin motor proteins are involved in, their importance is apparent for human life.

Nitrosative stress in human skeletal muscle attenuated by exercise countermeasure after chronic disuse.

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Salanova, Michele; Schiffl, Gudrun; Gutsmann, Martina; Felsenberg, Dieter; Furlan, Sandra; Volpe, Pompeo; Clarke, Andrew; Blottner, Dieter

2013-01-01

Activity-induced nitric oxide (NO) imbalance and "nitrosative stress" are proposed mechanisms of disrupted Ca(2+) homeostasis in atrophic skeletal muscle. We thus mapped S-nitrosylated (SNO) functional muscle proteins in healthy male subjects in a long-term bed rest study (BBR2-2 Study) without and with exercise as countermeasure in order to assess (i) the negative effects of chronic muscle disuse by nitrosative stress, (ii) to test for possible attenuation by exercise countermeasure in bed rest and (iii) to identify new NO target proteins. Muscle biopsies from calf soleus and hip vastus lateralis were harvested at start (Pre) and at end (End) from a bed rest disuse control group (CTR, n=9) and two bed rest resistive exercise groups either without (RE, n=7) or with superimposed vibration stimuli (RVE, n=7). At subcellular compartments, strong anti-SNO-Cys immunofluorescence patterns in control muscle fibers after bed rest returned to baseline following vibration exercise. Total SNO-protein levels, Nrf-2 gene expression and nucleocytoplasmic shuttling were changed to varying degrees in all groups. Excess SNO-protein levels of specific calcium release/uptake proteins (SNO-RyR1, -SERCA1 and -PMCA) and of contractile myosin heavy chains seen in biopsy samples of chronically disused skeletal muscle were largely reduced by vibration exercise. We also identified NOS1 as a novel NO target in human skeletal muscle controlled by activity driven auto-nitrosylation mechanisms. Our findings suggest that aberrant levels of functional SNO-proteins represent signatures of uncontrolled nitrosative stress management in disused human skeletal muscle that can be offset by exercise as countermeasure.

Nitrosative stress in human skeletal muscle attenuated by exercise countermeasure after chronic disuse

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Michele Salanova

2013-01-01

Full Text Available Activity-induced nitric oxide (NO imbalance and “nitrosative stress” are proposed mechanisms of disrupted Ca2+ homeostasis in atrophic skeletal muscle. We thus mapped S-nitrosylated (SNO functional muscle proteins in healthy male subjects in a long-term bed rest study (BBR2-2 Study without and with exercise as countermeasure in order to assess (i the negative effects of chronic muscle disuse by nitrosative stress, (ii to test for possible attenuation by exercise countermeasure in bed rest and (iii to identify new NO target proteins. Muscle biopsies from calf soleus and hip vastus lateralis were harvested at start (Pre and at end (End from a bed rest disuse control group (CTR, n=9 and two bed rest resistive exercise groups either without (RE, n=7 or with superimposed vibration stimuli (RVE, n=7. At subcellular compartments, strong anti-SNO-Cys immunofluorescence patterns in control muscle fibers after bed rest returned to baseline following vibration exercise. Total SNO-protein levels, Nrf-2 gene expression and nucleocytoplasmic shuttling were changed to varying degrees in all groups. Excess SNO-protein levels of specific calcium release/uptake proteins (SNO-RyR1, –SERCA1 and –PMCA and of contractile myosin heavy chains seen in biopsy samples of chronically disused skeletal muscle were largely reduced by vibration exercise. We also identified NOS1 as a novel NO target in human skeletal muscle controlled by activity driven auto-nitrosylation mechanisms. Our findings suggest that aberrant levels of functional SNO-proteins represent signatures of uncontrolled nitrosative stress management in disused human skeletal muscle that can be offset by exercise as countermeasure.

Fnip1 regulates skeletal muscle fiber type specification, fatigue resistance, and susceptibility to muscular dystrophy

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Reyes, Nicholas L.; Banks, Glen B.; Tsang, Mark; Margineantu, Daciana; Gu, Haiwei; Djukovic, Danijel; Chan, Jacky; Torres, Michelle; Liggitt, H. Denny; Hirenallur-S, Dinesh K.; Hockenbery, David M.; Raftery, Daniel; Iritani, Brian M.

2015-01-01

Mammalian skeletal muscle is broadly characterized by the presence of two distinct categories of muscle fibers called type I “red” slow twitch and type II “white” fast twitch, which display marked differences in contraction strength, metabolic strategies, and susceptibility to fatigue. The relative representation of each fiber type can have major influences on susceptibility to obesity, diabetes, and muscular dystrophies. However, the molecular factors controlling fiber type specification remain incompletely defined. In this study, we describe the control of fiber type specification and susceptibility to metabolic disease by folliculin interacting protein-1 (Fnip1). Using Fnip1 null mice, we found that loss of Fnip1 increased the representation of type I fibers characterized by increased myoglobin, slow twitch markers [myosin heavy chain 7 (MyH7), succinate dehydrogenase, troponin I 1, troponin C1, troponin T1], capillary density, and mitochondria number. Cultured Fnip1-null muscle fibers had higher oxidative capacity, and isolated Fnip1-null skeletal muscles were more resistant to postcontraction fatigue relative to WT skeletal muscles. Biochemical analyses revealed increased activation of the metabolic sensor AMP kinase (AMPK), and increased expression of the AMPK-target and transcriptional coactivator PGC1α in Fnip1 null skeletal muscle. Genetic disruption of PGC1α rescued normal levels of type I fiber markers MyH7 and myoglobin in Fnip1-null mice. Remarkably, loss of Fnip1 profoundly mitigated muscle damage in a murine model of Duchenne muscular dystrophy. These results indicate that Fnip1 controls skeletal muscle fiber type specification and warrant further study to determine whether inhibition of Fnip1 has therapeutic potential in muscular dystrophy diseases. PMID:25548157

Quantitative evaluation of skeletal muscle defects in second harmonic generation images

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Liu, Wenhua; Raben, Nina; Ralston, Evelyn

2013-02-01

Skeletal muscle pathologies cause irregularities in the normally periodic organization of the myofibrils. Objective grading of muscle morphology is necessary to assess muscle health, compare biopsies, and evaluate treatments and the evolution of disease. To facilitate such quantitation, we have developed a fast, sensitive, automatic imaging analysis software. It detects major and minor morphological changes by combining texture features and Fourier transform (FT) techniques. We apply this tool to second harmonic generation (SHG) images of muscle fibers which visualize the repeating myosin bands. Texture features are then calculated by using a Haralick gray-level cooccurrence matrix in MATLAB. Two scores are retrieved from the texture correlation plot by using FT and curve-fitting methods. The sensitivity of the technique was tested on SHG images of human adult and infant muscle biopsies and of mouse muscle samples. The scores are strongly correlated to muscle fiber condition. We named the software MARS (muscle assessment and rating scores). It is executed automatically and is highly sensitive even to subtle defects. We propose MARS as a powerful and unbiased tool to assess muscle health.

Cytoskeletal Tropomyosin Tm5NM1 Is Required for Normal Excitation–Contraction Coupling in Skeletal Muscle

OpenAIRE

Vlahovich, Nicole; Kee, Anthony J.; Van der Poel, Chris; Kettle, Emma; Hernandez-Deviez, Delia; Lucas, Christine; Lynch, Gordon S.; Parton, Robert G.; Gunning, Peter W.; Hardeman, Edna C.

2009-01-01

The functional diversity of the actin microfilaments relies in part on the actin binding protein tropomyosin (Tm). The muscle-specific Tms regulate actin-myosin interactions and hence contraction. However, there is less known about the roles of the numerous cytoskeletal isoforms. We have shown previously that a cytoskeletal Tm, Tm5NM1, defines a Z-line adjacent cytoskeleton in skeletal muscle. Recently, we identified a second cytoskeletal Tm in this region, Tm4. Here we show that Tm4 and Tm5N...

Stretch-stimulated glucose transport in skeletal muscle is regulated by Rac1.

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Sylow, Lykke; Møller, Lisbeth L V; Kleinert, Maximilian; Richter, Erik A; Jensen, Thomas E

2015-02-01

Rac1 regulates stretch-stimulated (i.e. mechanical stress) glucose transport in muscle. Actin depolymerization decreases stretch-induced glucose transport in skeletal muscle. Rac1 is a required part of the mechanical stress-component of the contraction-stimulus to glucose transport in skeletal muscle. An alternative to the canonical insulin signalling pathway for glucose transport is muscle contraction/exercise. Mechanical stress is an integrated part of the muscle contraction/relaxation cycle, and passive stretch stimulates muscle glucose transport. However, the signalling mechanism regulating stretch-stimulated glucose transport is not well understood. We recently reported that the actin cytoskeleton regulating GTPase, Rac1, was activated in mouse muscle in response to stretching. Rac1 is a regulator of contraction- and insulin-stimulated glucose transport, however, its role in stretch-stimulated glucose transport and signalling is unknown. We therefore investigated whether stretch-induced glucose transport in skeletal muscle required Rac1 and the actin cytoskeleton. We used muscle-specific inducible Rac1 knockout mice as well as pharmacological inhibitors of Rac1 and the actin cytoskeleton in isolated soleus and extensor digitorum longus muscles. In addition, the role of Rac1 in contraction-stimulated glucose transport during conditions without mechanical load on the muscles was evaluated in loosely hanging muscles and muscles in which cross-bridge formation was blocked by the myosin ATPase inhibitors BTS and Blebbistatin. Knockout as well as pharmacological inhibition of Rac1 reduced stretch-stimulated glucose transport by 30-50% in soleus and extensor digitorum longus muscle. The actin depolymerizing agent latrunculin B similarly decreased glucose transport in response to stretching by 40-50%. Rac1 inhibition reduced contraction-stimulated glucose transport by 30-40% in tension developing muscle but did not affect contraction-stimulated glucose transport in

in Skeletal Muscle

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Espen E. Spangenburg

2011-01-01

Full Text Available Triglyceride storage is altered across various chronic health conditions necessitating various techniques to visualize and quantify lipid droplets (LDs. Here, we describe the utilization of the BODIPY (493/503 dye in skeletal muscle as a means to analyze LDs. We found that the dye was a convenient and simple approach to visualize LDs in both sectioned skeletal muscle and cultured adult single fibers. Furthermore, the dye was effective in both fixed and nonfixed cells, and the staining seemed unaffected by permeabilization. We believe that the use of the BODIPY (493/503 dye is an acceptable alternative and, under certain conditions, a simpler method for visualizing LDs stored within skeletal muscle.

The exercised skeletal muscle: a review

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Marina Marini

2010-09-01

Full Text Available The skeletal muscle is the second more plastic tissue of the body - second to the nervous tissue only. In fact, both physical activity and inactivity contribute to modify the skeletal muscle, by continuous signaling through nerve impulses, mechanical stimuli and humoral clues. In turn, the skeletal muscle sends signals to the body, thus contributing to its homeostasis. We'll review here the contribute of physical exercise to the shaping of skeletal muscle, to the adaptation of its mass and function to the different needs imposed by different physical activities and to the attainment of the health benefits associated with active skeletal muscles. Focus will primarily be on the molecular pathways and on gene regulation that result in skeletal muscle adaptation to exercise.

Colocalization properties of elementary Ca(2+) release signals with structures specific to the contractile filaments and the tubular system of intact mouse skeletal muscle fibers.

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Georgiev, Tihomir; Zapiec, Bolek; Förderer, Moritz; Fink, Rainer H A; Vogel, Martin

2015-12-01

Ca(2+) regulates several important intracellular processes. We combined second harmonic generation (SHG) and two photon excited fluorescence microscopy (2PFM) to simultaneously record the SHG signal of the myosin filaments and localized elementary Ca(2+) release signals (LCSs). We found LCSs associated with Y-shaped structures of the myosin filament pattern (YMs), so called verniers, in intact mouse skeletal muscle fibers under hypertonic treatment. Ion channels crucial for the Ca(2+) regulation are located in the tubular system, a system that is important for Ca(2+) regulation and excitation-contraction coupling. We investigated the tubular system of intact, living mouse skeletal muscle fibers using 2PFM and the fluorescent Ca(2+) indicator Fluo-4 dissolved in the external solution or the membrane dye di-8-ANEPPS. We simultaneously measured the SHG signal from the myosin filaments of the skeletal muscle fibers. We found that at least a subset of the YMs observed in SHG images are closely juxtaposed with Y-shaped structures of the transverse tubules (YTs). The distances of corresponding YMs and YTs yield values between 1.3 μm and 4.1 μm including pixel uncertainty with a mean distance of 2.52±0.10 μm (S.E.M., n=41). Additionally, we observed that some of the linear-shaped areas in the tubular system are colocalized with linear-shaped areas in the SHG images. Copyright © 2015 Elsevier Inc. All rights reserved.

Why muscle is an efficient shock absorber.

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Michael A Ferenczi

Full Text Available Skeletal muscles power body movement by converting free energy of ATP hydrolysis into mechanical work. During the landing phase of running or jumping some activated skeletal muscles are subjected to stretch. Upon stretch they absorb body energy quickly and effectively thus protecting joints and bones from impact damage. This is achieved because during lengthening, skeletal muscle bears higher force and has higher instantaneous stiffness than during isometric contraction, and yet consumes very little ATP. We wish to understand how the actomyosin molecules change their structure and interaction to implement these physiologically useful mechanical and thermodynamical properties. We monitored changes in the low angle x-ray diffraction pattern of rabbit skeletal muscle fibers during ramp stretch compared to those during isometric contraction at physiological temperature using synchrotron radiation. The intensities of the off-meridional layer lines and fine interference structure of the meridional M3 myosin x-ray reflection were resolved. Mechanical and structural data show that upon stretch the fraction of actin-bound myosin heads is higher than during isometric contraction. On the other hand, the intensities of the actin layer lines are lower than during isometric contraction. Taken together, these results suggest that during stretch, a significant fraction of actin-bound heads is bound non-stereo-specifically, i.e. they are disordered azimuthally although stiff axially. As the strong or stereo-specific myosin binding to actin is necessary for actin activation of the myosin ATPase, this finding explains the low metabolic cost of energy absorption by muscle during the landing phase of locomotion.

Fiber type effects on contraction-stimulated glucose uptake and GLUT4 abundance in single fibers from rat skeletal muscle.

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Castorena, Carlos M; Arias, Edward B; Sharma, Naveen; Bogan, Jonathan S; Cartee, Gregory D

2015-02-01

To fully understand skeletal muscle at the cellular level, it is essential to evaluate single muscle fibers. Accordingly, the major goals of this study were to determine if there are fiber type-related differences in single fibers from rat skeletal muscle for: 1) contraction-stimulated glucose uptake and/or 2) the abundance of GLUT4 and other metabolically relevant proteins. Paired epitrochlearis muscles isolated from Wistar rats were either electrically stimulated to contract (E-Stim) or remained resting (No E-Stim). Single fibers isolated from muscles incubated with 2-deoxy-d-[(3)H]glucose (2-DG) were used to determine fiber type [myosin heavy chain (MHC) isoform protein expression], 2-DG uptake, and abundance of metabolically relevant proteins, including the GLUT4 glucose transporter. E-Stim, relative to No E-Stim, fibers had greater (P contraction-stimulated glucose uptake. Copyright © 2015 the American Physiological Society.

Skeletal muscle performance and ageing.

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Tieland, Michael; Trouwborst, Inez; Clark, Brian C

2018-02-01

The world population is ageing rapidly. As society ages, the incidence of physical limitations is dramatically increasing, which reduces the quality of life and increases healthcare expenditures. In western society, ~30% of the population over 55 years is confronted with moderate or severe physical limitations. These physical limitations increase the risk of falls, institutionalization, co-morbidity, and premature death. An important cause of physical limitations is the age-related loss of skeletal muscle mass, also referred to as sarcopenia. Emerging evidence, however, clearly shows that the decline in skeletal muscle mass is not the sole contributor to the decline in physical performance. For instance, the loss of muscle strength is also a strong contributor to reduced physical performance in the elderly. In addition, there is ample data to suggest that motor coordination, excitation-contraction coupling, skeletal integrity, and other factors related to the nervous, muscular, and skeletal systems are critically important for physical performance in the elderly. To better understand the loss of skeletal muscle performance with ageing, we aim to provide a broad overview on the underlying mechanisms associated with elderly skeletal muscle performance. We start with a system level discussion and continue with a discussion on the influence of lifestyle, biological, and psychosocial factors on elderly skeletal muscle performance. Developing a broad understanding of the many factors affecting elderly skeletal muscle performance has major implications for scientists, clinicians, and health professionals who are developing therapeutic interventions aiming to enhance muscle function and/or prevent mobility and physical limitations and, as such, support healthy ageing. © 2017 The Authors. Journal of Cachexia, Sarcopenia and Muscle published by John Wiley & Sons Ltd on behalf of the Society on Sarcopenia, Cachexia and Wasting Disorders.

Spot light on skeletal muscles: optogenetic stimulation to understand and restore skeletal muscle function.

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van Bremen, Tobias; Send, Thorsten; Sasse, Philipp; Bruegmann, Tobias

2017-08-01

Damage of peripheral nerves results in paralysis of skeletal muscle. Currently, the only treatment option to restore proper function is electrical stimulation of the innervating nerve or of the skeletal muscles directly. However this approach has low spatial and temporal precision leading to co-activation of antagonistic muscles and lacks cell-type selectivity resulting in pain or discomfort by stimulation of sensible nerves. In contrast to electrical stimulation, optogenetic methods enable spatially confined and cell-type selective stimulation of cells expressing the light sensitive channel Channelrhodopsin-2 with precise temporal control over the membrane potential. Herein we summarize the current knowledge about the use of this technology to control skeletal muscle function with the focus on the direct, non-neuronal stimulation of muscle fibers. The high temporal flexibility of using light pulses allows new stimulation patterns to investigate skeletal muscle physiology. Furthermore, the high spatial precision of focused illumination was shown to be beneficial for selective stimulation of distinct nearby muscle groups. Finally, the cell-type specific expression of the light-sensitive effector proteins in muscle fibers will allow pain-free stimulation and open new options for clinical treatments. Therefore, we believe that direct optogenetic stimulation of skeletal muscles is a very potent method for basic scientists that also harbors several distinct advantages over electrical stimulation to be considered for clinical use in the future.

Redox Control of Skeletal Muscle Regeneration.

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Le Moal, Emmeran; Pialoux, Vincent; Juban, Gaëtan; Groussard, Carole; Zouhal, Hassane; Chazaud, Bénédicte; Mounier, Rémi

2017-08-10

Skeletal muscle shows high plasticity in response to external demand. Moreover, adult skeletal muscle is capable of complete regeneration after injury, due to the properties of muscle stem cells (MuSCs), the satellite cells, which follow a tightly regulated myogenic program to generate both new myofibers and new MuSCs for further needs. Although reactive oxygen species (ROS) and reactive nitrogen species (RNS) have long been associated with skeletal muscle physiology, their implication in the cell and molecular processes at work during muscle regeneration is more recent. This review focuses on redox regulation during skeletal muscle regeneration. An overview of the basics of ROS/RNS and antioxidant chemistry and biology occurring in skeletal muscle is first provided. Then, the comprehensive knowledge on redox regulation of MuSCs and their surrounding cell partners (macrophages, endothelial cells) during skeletal muscle regeneration is presented in normal muscle and in specific physiological (exercise-induced muscle damage, aging) and pathological (muscular dystrophies) contexts. Recent advances in the comprehension of these processes has led to the development of therapeutic assays using antioxidant supplementation, which result in inconsistent efficiency, underlying the need for new tools that are aimed at precisely deciphering and targeting ROS networks. This review should provide an overall insight of the redox regulation of skeletal muscle regeneration while highlighting the limits of the use of nonspecific antioxidants to improve muscle function. Antioxid. Redox Signal. 27, 276-310.

Increased expression of Myosin binding protein H in the skeletal muscle of amyotrophic lateral sclerosis patients

KAUST Repository

Conti, Antonio; Riva, Nilo; Pesca, Mariasabina Sabina; Iannaccone, Sandro; Cannistraci, Carlo; Corbo, Massimo; Previtali, Stefano Carlo; Quattrini, Angelo; Alessio, Massimo

2014-01-01

Amyotrophic lateral sclerosis (ALS) is a severe and fatal neurodegenerative disease of still unknown pathogenesis. Recent findings suggest that the skeletal muscle may play an active pathogenetic role. To investigate ALS's pathogenesis and to seek

Muscle fiber type specific induction of slow myosin heavy chain 2 gene expression by electrical stimulation

International Nuclear Information System (INIS)

Crew, Jennifer R.; Falzari, Kanakeshwari; DiMario, Joseph X.

2010-01-01

Vertebrate skeletal muscle fiber types are defined by a broad array of differentially expressed contractile and metabolic protein genes. The mechanisms that establish and maintain these different fiber types vary throughout development and with changing functional demand. Chicken skeletal muscle fibers can be generally categorized as fast and fast/slow based on expression of the slow myosin heavy chain 2 (MyHC2) gene in fast/slow muscle fibers. To investigate the cellular and molecular mechanisms that control fiber type formation in secondary or fetal muscle fibers, myoblasts from the fast pectoralis major (PM) and fast/slow medial adductor (MA) muscles were isolated, allowed to differentiate in vitro, and electrically stimulated. MA muscle fibers were induced to express the slow MyHC2 gene by electrical stimulation, whereas PM muscle fibers did not express the slow MyHC2 gene under identical stimulation conditions. However, PM muscle fibers did express the slow MyHC2 gene when electrical stimulation was combined with inhibition of inositol triphosphate receptor (IP3R) activity. Electrical stimulation was sufficient to increase nuclear localization of expressed nuclear-factor-of-activated-T-cells (NFAT), NFAT-mediated transcription, and slow MyHC2 promoter activity in MA muscle fibers. In contrast, both electrical stimulation and inhibitors of IP3R activity were required for these effects in PM muscle fibers. Electrical stimulation also increased levels of peroxisome-proliferator-activated receptor-γ co-activator-1 (PGC-1α) protein in PM and MA muscle fibers. These results indicate that MA muscle fibers can be induced by electrical stimulation to express the slow MyHC2 gene and that fast PM muscle fibers are refractory to stimulation-induced slow MyHC2 gene expression due to fast PM muscle fiber specific cellular mechanisms involving IP3R activity.

NO-sGC Pathway Modulates Ca2+ Release and Muscle Contraction in Zebrafish Skeletal Muscle.

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Xiyuan, Zhou; Fink, Rainer H A; Mosqueira, Matias

2017-01-01

Vertebrate skeletal muscle contraction and relaxation is a complex process that depends on Ca 2+ ions to promote the interaction of actin and myosin. This process can be modulated by nitric oxide (NO), a gas molecule synthesized endogenously by (nitric oxide synthase) NOS isoforms. At nanomolar concentrations NO activates soluble guanylate cyclase (sGC), which in turn activates protein kinase G via conversion of GTP into cyclic GMP. Alternatively, NO post-translationally modifies proteins via S-nitrosylation of the thiol group of cysteine. However, the mechanisms of action of NO on Ca 2+ homeostasis during muscle contraction are not fully understood and we hypothesize that NO exerts its effects on Ca 2+ homeostasis in skeletal muscles mainly through negative modulation of Ca 2+ release and Ca 2+ uptake via the NO-sGC-PKG pathway. To address this, we used 5-7 days-post fecundation-larvae of zebrafish, a well-established animal model for physiological and pathophysiological muscle activity. We evaluated the response of muscle contraction and Ca 2+ transients in presence of SNAP, a NO-donor, or L-NAME, an unspecific NOS blocker in combination with specific blockers of key proteins of Ca 2+ homeostasis. We also evaluate the expression of NOS in combination with dihydropteridine receptor, ryanodine receptor and sarco/endoplasmic reticulum Ca 2+ ATPase. We concluded that endogenous NO reduced force production through negative modulation of Ca 2+ transients via the NO-sGC pathway. This effect could be reversed using an unspecific NOS blocker or sGC blocker.

Muscle Bioenergetic Considerations for Intrinsic Laryngeal Skeletal Muscle Physiology

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Sandage, Mary J.; Smith, Audrey G.

2017-01-01

Purpose: Intrinsic laryngeal skeletal muscle bioenergetics, the means by which muscles produce fuel for muscle metabolism, is an understudied aspect of laryngeal physiology with direct implications for voice habilitation and rehabilitation. The purpose of this review is to describe bioenergetic pathways identified in limb skeletal muscle and…

Skeletal muscle tissue engineering: methods to form skeletal myotubes and their applications.

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Ostrovidov, Serge; Hosseini, Vahid; Ahadian, Samad; Fujie, Toshinori; Parthiban, Selvakumar Prakash; Ramalingam, Murugan; Bae, Hojae; Kaji, Hirokazu; Khademhosseini, Ali

2014-10-01

Skeletal muscle tissue engineering (SMTE) aims to repair or regenerate defective skeletal muscle tissue lost by traumatic injury, tumor ablation, or muscular disease. However, two decades after the introduction of SMTE, the engineering of functional skeletal muscle in the laboratory still remains a great challenge, and numerous techniques for growing functional muscle tissues are constantly being developed. This article reviews the recent findings regarding the methodology and various technical aspects of SMTE, including cell alignment and differentiation. We describe the structure and organization of muscle and discuss the methods for myoblast alignment cultured in vitro. To better understand muscle formation and to enhance the engineering of skeletal muscle, we also address the molecular basics of myogenesis and discuss different methods to induce myoblast differentiation into myotubes. We then provide an overview of different coculture systems involving skeletal muscle cells, and highlight major applications of engineered skeletal muscle tissues. Finally, potential challenges and future research directions for SMTE are outlined.

Expression of smooth muscle and non-muscle myosin heavy chain isoforms in cultured vascular smooth muscle cells

International Nuclear Information System (INIS)

Rovner, A.S.; Murphy, R.A.; Owens, G.K.

1986-01-01

Immunocytochemical studies of cultured smooth muscle cells (SMCs) have disagreed on the nature of myosin expression. This investigation was undertaken to test for the presence of heterogeneous myosin heavy chain (MHC) isoforms in cell culture as a possible explanation for these results. Previously, Rovner et al. detected two MHCs in intact smooth muscles which differed in molecular weight by ca. 4000 daltons (SM1 and SM2) using a 3-4% acrylamide gradient SDS gel system. When sub-confluent primary cultures of rat aorta SMCs were assayed by this system, SM1 and SM2 were seen, along with large amounts of a third, unique MHC, NM, which closely resembled the MHC from human platelet in size and antigenicity. Data from 35 S-methionine autoradiograms showed that the log growth phase SMC cultures were producing almost exclusively NM, but the growth arrest, post-confluent cultures synthesized increased relative amounts of the SM MHC forms and contained comparable amounts of SM1, SM2, and NM. The same patterns of MHC synthesis were seen in sub-passaged SMCs. The expression of the SM-specific forms of myosin in quiescent, post-confluent cultures parallels that of smooth muscle actin suggesting that density induced growth arrest promotes cytodifferentiation in cultured vascular SMCs

Skeletal muscle myofilament adaptations to aging, disease and disuse and their effects on whole muscle performance in older adult humans

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Mark Stuart Miller

2014-09-01

Full Text Available Skeletal muscle contractile function declines with aging, disease and disuse. In vivo muscle contractile function depends on a variety of factors, but force, contractile velocity and power generating capacity ultimately derive from the summed contribution of single muscle fibers. The contractile performance of these fibers are, in turn, dependent upon the isoform and function of myofilament proteins they express, with myosin protein expression and its mechanical and kinetic characteristics playing a predominant role. Alterations in myofilament protein biology, therefore, may contribute to the development of functional limitations and disability in these conditions. Recent studies suggest that these conditions are associated with altered single fiber performance due to decreased expression of myofilament proteins and/or changes in myosin-actin cross-bridge interactions. Furthermore, cellular and myofilament-level adaptations are related to diminished whole muscle and whole body performance. Notably, the effect of these various conditions on myofilament and single fiber function tends to be larger in older women compared to older men, which may partially contribute to their higher rates of disability. To maintain functionality and provide the most appropriate and effective countermeasures to aging, disease and disuse in both sexes, a more thorough understanding is needed of the contribution of myofilament adaptations to functional disability in older men and women and their contribution to tissue level function and mobility impairment.

Effects of different activity and inactivity paradigms on myosin heavy chain gene expression in striated muscle

Science.gov (United States)

Baldwin, K. M.; Haddad, F.

2001-01-01

The goal of this mini-review is to summarize findings concerning the role that different models of muscular activity and inactivity play in altering gene expression of the myosin heavy chain (MHC) family of motor proteins in mammalian cardiac and skeletal muscle. This was done in the context of examining parallel findings concerning the role that thyroid hormone (T(3), 3,5,3'-triiodothyronine) plays in MHC expression. Findings show that both cardiac and skeletal muscles of experimental animals are initially undifferentiated at birth and then undergo a marked level of growth and differentiation in attaining the adult MHC phenotype in a T(3)/activity level-dependent fashion. Cardiac MHC expression in small mammals is highly sensitive to thyroid deficiency, diabetes, energy deprivation, and hypertension; each of these interventions induces upregulation of the beta-MHC isoform, which functions to economize circulatory function in the face of altered energy demand. In skeletal muscle, hyperthyroidism, as well as interventions that unload or reduce the weight-bearing activity of the muscle, causes slow to fast MHC conversions. Fast to slow conversions, however, are seen under hypothyroidism or when the muscles either become chronically overloaded or subjected to intermittent loading as occurs during resistance training and endurance exercise. The regulation of MHC gene expression by T(3) or mechanical stimuli appears to be strongly regulated by transcriptional events, based on recent findings on transgenic models and animals transfected with promoter-reporter constructs. However, the mechanisms by which T(3) and mechanical stimuli exert their control on transcriptional processes appear to be different. Additional findings show that individual skeletal muscle fibers have the genetic machinery to express simultaneously all of the adult MHCs, e.g., slow type I and fast IIa, IIx, and IIb, in unique combinations under certain experimental conditions. This degree of

Muscle plasticity related to changes in tubulin and αB-crystallin levels induced by eccentric contraction in rat skeletal muscles.

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Jee, H; Ochi, E; Sakurai, T; Lim, J-Y; Nakazato, K; Hatta, H

2016-09-01

We used the model of eccentric contraction of the hindlimb muscle by Ochi et al. to examine the role of eccentric contraction in muscle plasticity. This model aims to focus on stimulated skeletal muscle responses by measuring tissue weights and tracing the quantities of αB-crystallin and tubulin. The medial gastrocnemius muscle (GCM) responded to electrically induced eccentric contraction (EIEC) with significant increases in tissue weight (p muscle weight after EIEC. EIEC in the GCM caused contractile-induced sustenance of the traced proteins, but the soleus muscle exhibited a remarkable decrease in α-tubulin and a 19% decrease in αB-crystallin. EIEC caused fast-to-slow myosin heavy chain (MHC) isoform type-oriented shift within both the GCM and soleus muscle. These results have shown that different MHC isoform type-expressing slow and fast muscles commonly undergo fast-to-slow type MHC isoform transformation. This suggests that different levels of EIEC affected each of the slow and fast muscles to induce different quantitative changes in the expression of αB-crystallin and α-tubulin.

Skeletal muscle and fetal alcohol spectrum disorder.

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Myrie, Semone B; Pinder, Mark A

2018-04-01

Skeletal muscle is critical for mobility and many metabolic functions integral to survival and long-term health. Alcohol can affect skeletal muscle physiology and metabolism, which will have immediate and long-term consequences on health. While skeletal muscle abnormalities, including morphological, biochemical, and functional impairments, are well-documented in adults that excessively consume alcohol, there is a scarcity of information about the skeletal muscle in the offspring prenatally exposed to alcohol ("prenatal alcohol exposure"; PAE). This minireview examines the available studies addressing skeletal muscle abnormalities due to PAE. Growth restriction, fetal alcohol myopathy, and abnormalities in the neuromuscular system, which contribute to deficits in locomotion, are some direct, immediate consequences of PAE on skeletal muscle morphology and function. Long-term health consequences of PAE-related skeletal abnormalities include impaired glucose metabolism in the skeletal muscle, resulting in glucose intolerance and insulin resistance, leading to an increased risk of type 2 diabetes. In general, there is limited information on the morphological, biochemical, and functional features of skeletal abnormalities in PAE offspring. There is a need to understand how PAE affects muscle growth and function at the cellular level during early development to improve the immediate and long-term health of offspring suffering from PAE.

Analysis of myofibrillar proteins and transcripts in adult skeletal muscles of the American lobster Homarus americanus: variable expression of myosins, actin and troponins in fast, slow-twitch and slow-tonic fibres.

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Medler, Scott; Mykles, Donald L

2003-10-01

Skeletal muscles are diverse in their contractile properties, with many of these differences being directly related to the assemblages of myofibrillar isoforms characteristic of different fibers. Crustacean muscles are similar to other muscles in this respect, although the majority of information about differences in muscle organization comes from vertebrate species. In the present study, we examined the correlation between myofibrillar protein isoforms and the patterns of myofibrillar gene expression in fast, slow-phasic (S(1)) and slow-tonic (S(2)) fibers of the American lobster Homarus americanus. SDS-PAGE and western blotting were used to identify isoform assemblages of myosin heavy chain (MHC), P75, troponin T (TnT) and troponin I (TnI). RT-PCR was used to monitor expression of fast and slow (S(1)) MHC, P75 and actin in different fiber types, and the MHC and actin levels were quantified by real-time PCR. Fast and slow fibers from the claw closers predominantly expressed fast and S(1) MHC, respectively, but also lower levels of the alternate MHC. By contrast, fast fibers from the deep abdominal muscle expressed fast MHC exclusively. In addition, slow muscles expressed significantly higher levels of actin than fast fibers. A distal bundle of fibers in the cutter claw closer muscle was found to be composed of a mixture of S(1) and S(2) fibers, many of which possessed a mixture of S(1) and S(2) MHC isoforms. This pattern supports the idea that S(1) and S(2) fibers represent extremes in a continuum of slow muscle phenotype. Overall, these patterns demonstrate that crustacean skeletal muscles cannot be strictly categorized into discrete fiber types, but a muscle's properties probably represent a point on a continuum of fiber types. This trend may result from differences in innervation pattern, as each muscle is controlled by a unique combination of phasic, tonic or both phasic and tonic motor nerves. In this respect, future studies examining how muscle phenotype

Human skeletal muscle releases leptin in vivo

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Wolsk, Emil; Grøndahl, Thomas Sahl; Pedersen, Bente Klarlund

2012-01-01

Leptin is considered an adipokine, however, cultured myocytes have also been found to release leptin. Therefore, as proof-of-concept we investigated if human skeletal muscle synthesized leptin by measuring leptin in skeletal muscle biopsies. Following this, we quantified human skeletal muscle...... was unaltered. During saline infusion the adipose tissue release averaged 0.8 ± 0.3 ng min(-1) 100g tissue(-1) whereas skeletal muscle release was 0.5 ± 0.1 ng min(-1) 100g tissue(-1). In young healthy humans, skeletal muscle contribution to whole body leptin production could be substantial given the greater...

AMPK in skeletal muscle function and metabolism

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Kjøbsted, Rasmus; Hingst, Janne Rasmuss; Fentz, Joachim

2018-01-01

Skeletal muscle possesses a remarkable ability to adapt to various physiologic conditions. AMPK is a sensor of intracellular energy status that maintains energy stores by fine-tuning anabolic and catabolic pathways. AMPK's role as an energy sensor is particularly critical in tissues displaying...... highly changeable energy turnover. Due to the drastic changes in energy demand that occur between the resting and exercising state, skeletal muscle is one such tissue. Here, we review the complex regulation of AMPK in skeletal muscle and its consequences on metabolism (e.g., substrate uptake, oxidation......, and storage as well as mitochondrial function of skeletal muscle fibers). We focus on the role of AMPK in skeletal muscle during exercise and in exercise recovery. We also address adaptations to exercise training, including skeletal muscle plasticity, highlighting novel concepts and future perspectives...

Exercise training during chemotherapy preserves skeletal muscle fiber area, capillarization, and mitochondrial content in patients with breast cancer.

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Mijwel, Sara; Cardinale, Daniele A; Norrbom, Jessica; Chapman, Mark; Ivarsson, Niklas; Wengström, Yvonne; Sundberg, Carl Johan; Rundqvist, Helene

2018-05-11

Exercise has been suggested to ameliorate the detrimental effects of chemotherapy on skeletal muscle. The aim of this study was to compare the effects of different exercise regimens with usual care on skeletal muscle morphology and mitochondrial markers in patients being treated with chemotherapy for breast cancer. Specifically, we compared moderate-intensity aerobic training combined with high-intensity interval training (AT-HIIT) and resistance training combined with high-intensity interval training (RT-HIIT) with usual care (UC). Resting skeletal muscle biopsies were obtained pre- and postintervention from 23 randomly selected women from the OptiTrain breast cancer trial who underwent RT-HIIT, AT-HIIT, or UC for 16 wk. Over the intervention, citrate synthase activity, muscle fiber cross-sectional area, capillaries per fiber, and myosin heavy chain isoform type I were reduced in UC, whereas RT-HIIT and AT-HIIT were able to counteract these declines. AT-HIIT promoted up-regulation of the electron transport chain protein levels vs. UC. RT-HIIT favored satellite cell count vs. UC and AT-HIIT. There was a significant association between change in citrate synthase activity and self-reported fatigue. AT-HIIT and RT-HIIT maintained or improved markers of skeletal muscle function compared with the declines found in the UC group, indicating a sustained trainability in addition to the preservation of skeletal muscle structural and metabolic characteristics during chemotherapy. These findings highlight the importance of supervised exercise programs for patients with breast cancer during chemotherapy.-Mijwel, S., Cardinale, D. A., Norrbom, J., Chapman, M., Ivarsson, N., Wengström, Y., Sundberg, C. J., Rundqvist, H. Exercise training during chemotherapy preserves skeletal muscle fiber area, capillarization, and mitochondrial content in patients with breast cancer.

Myonuclear domain size and myosin isoform expression in muscle fibres from mammals representing a 100,000-fold difference in body size.

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Liu, Jing-Xia; Höglund, Anna-Stina; Karlsson, Patrick; Lindblad, Joakim; Qaisar, Rizwan; Aare, Sudhakar; Bengtsson, Ewert; Larsson, Lars

2009-01-01

This comparative study of myonuclear domain (MND) size in mammalian species representing a 100,000-fold difference in body mass, ranging from 25 g to 2500 kg, was undertaken to improve our understanding of myonuclear organization in skeletal muscle fibres. Myonuclear domain size was calculated from three-dimensional reconstructions in a total of 235 single muscle fibre segments at a fixed sarcomere length. Irrespective of species, the largest MND size was observed in muscle fibres expressing fast myosin heavy chain (MyHC) isoforms, but in the two smallest mammalian species studied (mouse and rat), MND size was not larger in the fast-twitch fibres expressing the IIA MyHC isofom than in the slow-twitch type I fibres. In the larger mammals, the type I fibres always had the smallest average MND size, but contrary to mouse and rat muscles, type IIA fibres had lower mitochondrial enzyme activities than type I fibres. Myonuclear domain size was highly dependent on body mass in the two muscle fibre types expressed in all species, i.e. types I and IIA. Myonuclear domain size increased in muscle fibres expressing both the beta/slow (type I; r = 0.84, P fast IIA MyHC isoform (r = 0.90; P muscle fibre type, independent of species. However, myosin isoform expression is not the sole protein determining MND size, and other protein systems, such as mitochondrial proteins, may be equally or more important determinants of MND size.

Skeletal Muscle Na+ Channel Disorders

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Dina eSimkin

2011-10-01

Full Text Available Five inherited human disorders affecting skeletal muscle contraction have been traced to mutations in the gene encoding the voltage-gated sodium channel Nav1.4. The main symptoms of these disorders are myotonia or periodic paralysis caused by changes in skeletal muscle fiber excitability. Symptoms of these disorders vary from mild or latent disease to incapacitating or even death in severe cases. As new human sodium channel mutations corresponding to disease states become discovered, the importance of understanding the role of the sodium channel in skeletal muscle function and disease state grows.

Park7 expression influences myotube size and myosin expression in muscle.

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Hui Yu

Full Text Available Callipyge sheep exhibit postnatal muscle hypertrophy due to the up-regulation of DLK1 and/or RTL1. The up-regulation of PARK7 was identified in hypertrophied muscles by microarray analysis and further validated by quantitative PCR. The expression of PARK7 in hypertrophied muscle of callipyge lambs was confirmed to be up-regulated at the protein level. PARK7 was previously identified to positively regulate PI3K/AKT pathway by suppressing the phosphatase activity of PTEN in mouse fibroblasts. The purpose of this study was to investigate the effects of PARK7 in muscle growth and protein accretion in response to IGF1. Primary myoblasts isolated from Park7 (+/+ and Park7 (-/- mice were used to examine the effect of differential expression of Park7. The Park7 (+/+ myotubes had significantly larger diameters and more total sarcomeric myosin expression than Park7 (-/- myotubes. IGF1 treatment increased the mRNA abundance of Myh4, Myh7 and Myh8 between 20-40% in Park7 (+/+ myotubes relative to Park7 (-/-. The level of AKT phosphorylation was increased in Park7 (+/+ myotubes at all levels of IGF1 supplementation. After removal of IGF1, the Park7 (+/+ myotubes maintained higher AKT phosphorylation through 3 hours. PARK7 positively regulates the PI3K/AKT pathway by inhibition of PTEN phosphatase activity in skeletal muscle. The increased PARK7 expression can increase protein synthesis and result in myotube hypertrophy. These results support the hypothesis that elevated expression of PARK7 in callipyge muscle would increase levels of AKT activity to cause hypertrophy in response to the normal IGF1 signaling in rapidly growing lambs. Increasing expression of PARK7 could be a novel mechanism to increase protein accretion and muscle growth in livestock or help improve muscle mass with disease or aging.

[Molecular mechanisms of skeletal muscle hypertrophy].

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Astratenkova, I V; Rogozkin, V A

2014-06-01

Enzymes Akt, AMPK, mTOR, S6K and PGC-1a coactivator take part in skeletal muscles in the regulation of synthesis of proteins. The expression of these proteins is regulated by growth factors, hormones, nutrients, mechanical loading and leads to an increase in muscle mass and skeletal muscle hypertrophy. The review presents the results of studies published in the past four years, which expand knowledge on the effects of various factors on protein synthesis in skeletal muscle. The attention is focused on the achievements that reveal and clarify the signaling pathways involved in the regulation of protein synthesis in skeletal muscle. The central place is taken by mTOR enzyme which controls and regulates the main stages of the cascade of reactions of muscle proteins providing synthesis in the conditions of human life. coactivator PGC-1a.

Skeletal muscle lymphoma: observations at MR imaging

International Nuclear Information System (INIS)

Eustace, S.; Winalski, C.S.; McGowen, A.; Lan, H.; Dorfman, D.

1996-01-01

We present the MR appearances of three patients with biopsy-proven primary lymphoma of skeletal muscle. In each case lymphoma resulted in bulky expansion of the involved muscle, homogeneously isointense to skeletal muscle on T1-weighted images, homogeneously hyperintense to skeletal muscle on T2-weighted images and diffusely enhancing following intravenous administration of gadopentate dimeglumine. (orig.)

IMP metabolism in human skeletal muscle after exhaustive exercise

DEFF Research Database (Denmark)

Tullson, P. C.; Bangsbo, Jens; Hellsten, Ylva

1995-01-01

This study addressed whether AMP deaminase (AMPD)myosin binding occurs with deamination during intense exercise in humans and the extent of purine loss from muscle during the initial minutes of recovery. Male subjects performed cycle exercise (265 +/- 2 W for 4.39 +/- 0.04 min) to stimulate muscle...... inosine 5'-monophosphate (IMP) formation. After exercise, blood flow to one leg was occluded. Muscle biopsies (vastus lateralis) were taken before and 3.6 +/- 0.2 min after exercise from the occluded leg and 0.7 +/- 0.0, 1.1 +/- 0.0, and 2.9 +/- 0.1 min postexercise in the nonoccluded leg. Exercise...... activated AMPD; at exhaustion IMP was 3.5 +/- 0.4 mmol/kg dry muscle. Before exercise, 16.0 +/- 1.6% of AMPD cosedimented with the myosin fraction; the extent of AMPD:myosin binding was unchanged by exercise. Inosine content increased about threefold during exercise and twofold more during recovery; by 2...

Myosin heavy chain and Na+,K+-ATPase isoforms in equine skeletal muscle : Comparison of mRNA and protein expression profiles

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van den Burg, M.M.M.

2009-01-01

Adaptations to training and exercise can be measured in blood, muscle, and bones and are also reflected in behavior. Since equine total muscle mass represents approximately 42% of total body weight, a major role for skeletal muscle in adaptation to training can be expected. The plasticity of

Role of cyclic AMP sensor Epac1 in masseter muscle hypertrophy and myosin heavy chain transition induced by β2-adrenoceptor stimulation.

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Ohnuki, Yoshiki; Umeki, Daisuke; Mototani, Yasumasa; Jin, Huiling; Cai, Wenqian; Shiozawa, Kouichi; Suita, Kenji; Saeki, Yasutake; Fujita, Takayuki; Ishikawa, Yoshihiro; Okumura, Satoshi

2014-12-15

The predominant isoform of β-adrenoceptor (β-AR) in skeletal muscle is β2-AR and that in the cardiac muscle is β1-AR. We have reported that Epac1 (exchange protein directly activated by cAMP 1), a new protein kinase A-independent cAMP sensor, does not affect cardiac hypertrophy in response to pressure overload or chronic isoproterenol (isoprenaline) infusion. However, the role of Epac1 in skeletal muscle hypertrophy remains poorly understood. We thus examined the effect of disruption of Epac1, the major Epac isoform in skeletal muscle, on masseter muscle hypertrophy induced by chronic β2-AR stimulation with clenbuterol (CB) in Epac1-null mice (Epac1KO). The masseter muscle weight/tibial length ratio was similar in wild-type (WT) and Epac1KO at baseline and was significantly increased in WT after CB infusion, but this increase was suppressed in Epac1KO. CB treatment significantly increased the proportion of myosin heavy chain (MHC) IIb at the expense of that of MHC IId/x in both WT and Epac1KO, indicating that Epac1 did not mediate the CB-induced MHC isoform transition towards the faster isoform. The mechanism of suppression of CB-mediated hypertrophy in Epac1KO is considered to involve decreased activation of Akt signalling. In addition, CB-induced histone deacetylase 4 (HDAC4) phosphorylation on serine 246 mediated by calmodulin kinase II (CaMKII), which plays a role in skeletal muscle hypertrophy, was suppressed in Epac1KO. Our findings suggest that Epac1 plays a role in β2-AR-mediated masseter muscle hypertrophy, probably through activation of both Akt signalling and CaMKII/HDAC4 signalling. © 2014 The Authors. The Journal of Physiology © 2014 The Physiological Society.

Skeletal muscle ATP turnover and muscle fiber conduction velocity are elevated at higher muscle temperatures during maximal power output development in humans.

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Gray, Stuart R; De Vito, Giuseppe; Nimmo, Myra A; Farina, Dario; Ferguson, Richard A

2006-02-01

The effect of temperature on skeletal muscle ATP turnover and muscle fiber conduction velocity (MFCV) was studied during maximal power output development in humans. Eight male subjects performed a 6-s maximal sprint on a mechanically braked cycle ergometer under conditions of normal (N) and elevated muscle temperature (ET). Muscle temperature was passively elevated through the combination of hot water immersion and electric blankets. Anaerobic ATP turnover was calculated from analysis of muscle biopsies obtained before and immediately after exercise. MFCV was measured during exercise using surface electromyography. Preexercise muscle temperature was 34.2 degrees C (SD 0.6) in N and 37.5 degrees C (SD 0.6) in ET. During ET, the rate of ATP turnover for phosphocreatine utilization [temperature coefficient (Q10) = 3.8], glycolysis (Q10 = 1.7), and total anaerobic ATP turnover [Q10 = 2.7; 10.8 (SD 1.9) vs. 14.6 mmol x kg(-1) (dry mass) x s(-1) (SD 2.3)] were greater than during N (P < 0.05). MFCV was also greater in ET than in N [3.79 (SD 0.47) to 5.55 m/s (SD 0.72)]. Maximal power output (Q10 = 2.2) and pedal rate (Q10 = 1.6) were greater in ET compared with N (P < 0.05). The Q10 of maximal and mean power were correlated (P < 0.05; R = 0.82 and 0.85, respectively) with the percentage of myosin heavy chain type IIA. The greater power output obtained with passive heating was achieved through an elevated rate of anaerobic ATP turnover and MFCV, possibly due to a greater effect of temperature on power production of fibers, with a predominance of myosin heavy chain IIA at the contraction frequencies reached.

Localization of sarcomeric proteins during myofibril assembly in cultured mouse primary skeletal myotubes

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White, Jennifer; Barro, Marietta V.; Makarenkova, Helen P.; Sanger, Joseph W.; Sanger, Jean M.

2014-01-01

It is important to understand how muscle forms normally in order to understand muscle diseases that result in abnormal muscle formation. Although the structure of myofibrils is well understood, the process through which the myofibril components form organized contractile units is not clear. Based on the staining of muscle proteins in avian embryonic cardiomyocytes, we previously proposed that myofibrils formation occurred in steps that began with premyofibrils followed by nascent myofibrils and ending with mature myofibrils. The purpose of this study was to determine whether the premyofibril model of myofibrillogenesis developed from studies developed from studies in avian cardiomyocytes was supported by our current studies of myofibril assembly in mouse skeletal muscle. Emphasis was on establishing how the key sarcomeric proteins, F-actin, non-muscle myosin II, muscle myosin II, and α-actinin were organized in the three stages of myofibril assembly. The results also test previous reports that non-muscle myosins II A and B are components of the Z-Bands of mature myofibrils, data that are inconsistent with the premyofibril model. We have also determined that in mouse muscle cells, telethonin is a late assembling protein that is present only in the Z-Bands of mature myofibrils. This result of using specific telethonin antibodies supports the approach of using YFP-tagged proteins to determine where and when these YFP-sarcomeric fusion proteins are localized. The data presented in this study on cultures of primary mouse skeletal myocytes are consistent with the premyofibril model of myofibrillogenesis previously proposed for both avian cardiac and skeletal muscle cells. PMID:25125171

Myosin heavy chain profile of equine gluteus medius muscle following prolonged draught-exercise training and detraining.

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Serrano, A L; Rivero, J L

2000-04-01

Fourteen 4-year old Andalusian mares were used to examine the plasticity of myosin heavy chain (MHC) composition in horse skeletal muscle with heavy draught-exercise training and detraining. Seven horses underwent a training programme based on carriage exercises for 8 months. Afterwards, they were kept in paddocks for 3 months. The remaining seven animals were used as control horses. Three gluteus medius muscle biopsies were removed at depths of 20, 40 and 60 mm from each horse before (month 0), during the training (months 3 and 8) and after detraining (month 11). Myosin heavy chain composition was analysed by electrophoresis and immunohistochemically with anti-MHC monoclonal antibodies. Fibre areas, oxidative capacity and capillaries were studied histochemically. After 8 months of training, MHC-IIX and IIX fibres decreased whereas MHC-I and type I and I + IIA fibres increased. Neither MHC-IIA nor the percentage of IIA fibres changed when the data were considered as a whole, but the proportion of MHC-IIA increased in the superficial region of the muscle after 8 months of training. Mean areas of type II fibres were not affected by training and detraining, but the cross-sectional of type I fibres increased after 3 month of training and not further increases were recorded afterward. The percentage of high-oxidative capacity fibres and the number of capillaries per mm2 increased with training. Most of these muscular adaptations reverted after detraining. These results indicate that long term draught-exercise training induces a reversible transition of MHC composition in equine muscle in the order IIX --> IIA --> I. The physiological implication of these changes is an impact on the velocity of shortening and fatigue resistance of muscle fibres.

Ontogenetic changes in skeletal muscle fiber type, fiber diameter and myoglobin concentration in the Northern elephant seal (Mirounga angustirostris

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Colby eMoore

2014-06-01

Full Text Available Northern elephant seals (Mirounga angustirostris (NES are known to be deep, long-duration divers and to sustain long-repeated patterns of breath-hold, or apnea. Some phocid dives remain within the bounds of aerobic metabolism, accompanied by physiological responses inducing lung compression, bradycardia and peripheral vasoconstriction. Current data suggest an absence of type IIb fibers in pinniped locomotory musculature. To date, no fiber type data exist for NES, a consummate deep diver. In this study, NES were biopsied in the wild. Ontogenetic changes in skeletal muscle were revealed through succinate dehydrogenase (SDH based fiber typing. Results indicated a predominance of uniformly shaped, large type I fibers and elevated myoglobin (Mb concentrations in the longissimus dorsi (LD muscle of adults. No type II muscle fibers were detected in any adult sampled. This was in contrast to the juvenile animals that demonstrated type II myosin in Western Blot analysis, indicative of an ontogenetic change in skeletal muscle with maturation. These data support previous hypotheses that the absence of type II fibers indicates reliance on aerobic metabolism during dives, as well as a depressed metabolic rate and low energy locomotion. We also suggest that the lack of type IIb fibers (adults may provide a protection against ischemia reperfusion (IR injury in vasoconstricted peripheral skeletal muscle.

Skeletal muscle contraction-induced vasodilation in the microcirculation.

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Hong, Kwang-Seok; Kim, Kijeong

2017-10-01

Maximal whole body exercise leads skeletal muscle blood flow to markedly increase to match metabolic demands, a phenomenon termed exercise hyperaemia that is accomplished by increasing vasodilation. However, local vasodilatory mechanisms in response to skeletal muscle contraction remain uncertain. This review highlights metabolic vasodilators released from contracting skeletal muscle, endothelium, or blood cells. As a considerable skeletal muscle vasodilation potentially results in hypotension, sympathetic nerve activity needs to be augmented to elevate cardiac output and blood pressure during dynamic exercise. However, since the enhanced sympathetic vasoconstriction restrains skeletal muscle blood flow, intramuscular arteries have an indispensable ability to blunt sympathetic activity for exercise hyperaemia. In addition, we discuss that mechanical compression of the intramuscular vasculature contributes to causing the initial phase of increasing vasodilation following a single muscle contraction. We have also chosen to focus on conducted (or ascending) electrical signals that evoke vasodilation of proximal feed arteries to elevate blood flow in the microcirculation of skeletal muscle. Endothelial hyperpolarization originating within distal arterioles ascends into the proximal feed arteries, thereby increasing total blood flow in contracting skeletal muscle. This brief review summarizes molecular mechanisms underlying the regulation of skeletal muscle blood flow to a single or sustained muscle contraction.

* Tissue-Specific Extracellular Matrix Enhances Skeletal Muscle Precursor Cell Expansion and Differentiation for Potential Application in Cell Therapy.

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Zhang, Deying; Zhang, Yong; Zhang, Yuanyuan; Yi, Hualin; Wang, Zhan; Wu, Rongpei; He, Dawei; Wei, Guanghui; Wei, Shicheng; Hu, Yun; Deng, Junhong; Criswell, Tracy; Yoo, James; Zhou, Yu; Atala, Anthony

2017-08-01

Skeletal muscle precursor cells (MPCs) are considered a key candidate for cell therapy in the treatment of skeletal muscle dysfunction due to injury, disease, or age. However, expansion of a sufficient number of functional skeletal muscle cells in vitro from a small tissue biopsy has been challenging due to changes in phenotypic expression of these cells under traditional culture conditions. Thus, the aim of the study was to develop a better culture system for the expansion and myo-differentiation of MPCs that could further be used for therapy. For this purpose, we developed an ideal method of tissue decellularization and compared the ability of different matrices to support MPC growth and differentiation. Porcine-derived skeletal muscle and liver and kidney extracellular matrix (ECM) were generated by decellularization methods consisting of distilled water, 0.2 mg/mL DNase, or 5% fetal bovine serum. Acellular matrices were further homogenized, dissolved, and combined with a hyaluronic acid-based hydrogel decorated with heparin (ECM-HA-HP). The cell proliferation and myogenic differentiation capacity of human MPCs were assessed when grown on gel alone, ECM, or each ECM-HA-HP substrate. Human MPC proliferation was significantly enhanced when cultured on the ECM-HA-HP substrates compared to the other substrates tested, with the greatest proliferation on the muscle ECM-HA-HP (mECM-HA-HP) substrate. The number of differentiated myotubes was significantly increased on the mECM-HA-HP substrate compared to the other gel-ECM substrates, as well as the numbers of MPCs expressing specific myogenic cell markers (i.e., myosin, desmin, myoD, and myf5). In conclusion, skeletal mECM-HA-HP as a culture substrate provided an optimal culture microenvironment potentially due to its similarity to the in vivo environment. These data suggest a potential use of skeletal muscle-derived ECM gel for the expansion and differentiation of human MPCs for cell-based therapy for skeletal muscle

Myo/Nog cells: targets for preventing the accumulation of skeletal muscle-like cells in the human lens.

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Jacquelyn Gerhart

Full Text Available Posterior capsule opacification (PCO is a vision impairing condition that arises in some patients following cataract surgery. The fibrotic form of PCO is caused by myofibroblasts that may emerge in the lens years after surgery. In the chick embryo lens, myofibroblasts are derived from Myo/Nog cells that are identified by their expression of the skeletal muscle specific transcription factor MyoD, the bone morphogenetic protein inhibitor Noggin, and the epitope recognized by the G8 monoclonal antibody. The goal of this study was to test the hypothesis that depletion of Myo/Nog cells will prevent the accumulation of myofibroblasts in human lens tissue. Myo/Nog cells were present in anterior, equatorial and bow regions of the human lens, cornea and ciliary processes. In anterior lens tissue removed by capsulorhexis, Myo/Nog cells had synthesized myofibroblast and skeletal muscle proteins, including vimentin, MyoD and sarcomeric myosin. Alpha smooth muscle actin (α-SMA was detected in a subpopulation of Myo/Nog cells. Areas of the capsule denuded of epithelial cells were surrounded by Myo/Nog cells. Some of these cell free areas contained a wrinkle in the capsule. Depletion of Myo/Nog cells eliminated cells expressing skeletal muscle proteins in 5-day cultures but did not affect cells immunoreactive for beaded filament proteins that accumulate in differentiating lens epithelial cells. Transforming growth factor-betas 1 and 2 that mediate an epithelial-mesenchymal transition, did not induce the expression of skeletal muscle proteins in lens cells following Myo/Nog cell depletion. This study demonstrates that Myo/Nog cells in anterior lens tissue removed from cataract patients have undergone a partial differentiation to skeletal muscle. Myo/Nog cells appear to be the source of skeletal muscle-like cells in explants of human lens tissue. Targeting Myo/Nog cells with the G8 antibody during cataract surgery may reduce the incidence of PCO.

Calcineurin regulates slow myosin, but not fast myosin or metabolic enzymes, during fast-to-slow transformation in rabbit skeletal muscle cell culture

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Meißner, Joachim D; Gros, Gerolf; Scheibe, Renate J; Scholz, Michael; Kubis, Hans-Peter

2001-01-01

The addition of cyclosporin A (500 ng ml−1) - an inhibitor of the Ca2+-calmodulin-regulated serine/threonine phosphatase calcineurin - to primary cultures of rabbit skeletal muscle cells had no influence on the expression of fast myosin heavy chain (MHC) isoforms MHCIIa and MHCIId at the level of protein and mRNA, but reduced the expression of slow MHCI mRNA. In addition, no influence of cyclosporin A on the expression of citrate synthase (CS) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA was found. The level of enzyme activity of CS was also not affected. When the Ca2+ ionophore A23187 (4 × 10−7m) was added to the medium, a partial fast-to-slow transformation occurred. The level of MHCI mRNA increased, and the level of MHCIId mRNA decreased. Cotreatment with cyclosporin A was able to prevent the upregulation of MHCI at the level of mRNA as well as protein, but did not reverse the decrease in MHCIId expression. The expression of MHCIIa was also not influenced by cyclosporin A. Cyclosporin A was not able to prevent the upregulation of CS mRNA under Ca2+ ionophore treatment and failed to reduce the increased enzyme activity of CS. The expression of GAPDH mRNA was reduced under Ca2+ ionophore treatment and was not altered under cotreatment with cyclosporin A. When the myotubes in the primary muscle culture were electrostimulated at 1 Hz for 15 min periods followed by pauses of 30 min, a partial fast-to-slow transformation was induced. Again, cotreatment with cyclosporin A prevented the upregulation of MHCI at the level of mRNA and protein without affecting MHCIId expression. The nuclear translocation of the calcineurin-regulated transcription factor nuclear factor of activated thymocytes (NFATc1) during treatment with Ca2+ ionophore, and the prevention of the translocation in the presence of cyclosporin A, were demonstrated immunocytochemically in the myotubes of the primary culture. The effects of cyclosporin A demonstrate the involvement of

Mechanical modeling of skeletal muscle functioning

NARCIS (Netherlands)

van der Linden, B.J.J.J.

1998-01-01

For movement of body or body segments is combined effort needed of the central nervous system and the muscular-skeletal system. This thesis deals with the mechanical functioning of skeletal muscle. That muscles come in a large variety of geometries, suggest the existence of a relation between muscle

Structural changes during contraction in vertebrate skeletal muscle as studied by time-resolved X-ray diffraction technique

International Nuclear Information System (INIS)

Sugi, H.; Tanaka, H.; Kobayashi, T.; Iwamoto, H.; Wakabayashi, K.; Hamanaka, T.; Mitsui, T.; Amemiya, Y.

1986-01-01

To obtain information about the structural changes in vertebrate skeletal muscle during contraction, time-resolved X-ray diffraction studies were performed on the intensity changes of the 59 A and 51 A actin layer lines from bullfrog sartorius muscle during the isometric force development, and the intensity changes of the 143 A and 215 A myosin meridional reflections and of the 1,0 and 1,1 equatorial reflections when isometrically contracting muscle was subjected to sinusoidal length changes (1%, 5-10Hz) with the following results. The integrated intensities of the 59 A and 51 A actin layer lines increased during the force development by 30-50% for the 59 A reflection, and by about 70% for the 51 A reflection compard to their respective resting values. These intensity changes were greater than those taking place during the transition from rest to rigor state, and observed to precede the intensity changes of the 429 A myosin off-meridional reflection and of equatorial reflections. When sinusoidal length changes were applied to the muscle generating steady isometric force, the resulting periodic intensity changes in the 1,0 and 1,1 equatorial reflections were in phase and in antiphase with the length changes, respectively. On the other hand, the 143 A myosin reflection exhibited a characteristic periodic change; its intensity reached a maximum at each boundary between the stretch and release phases of the length changes. These results are discussed in connection with the behavior of the cross-bridges during contraction. (author)

A role for Insulin-like growth factor 2 in specification of the fast skeletal muscle fibre

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Ting Tao

2007-06-01

Full Text Available Abstract Background Fibre type specification is a poorly understood process beginning in embryogenesis in which skeletal muscle myotubes switch myosin-type to establish fast, slow and mixed fibre muscle groups with distinct function. Growth factors are required to establish slow fibres; it is unknown how fast twitch fibres are specified. Igf-2 is an embryonically expressed growth factor with established in vitro roles in skeletal muscle. Its localisation and role in embryonic muscle differentiation had not been established. Results Between E11.5 and E15.5 fast Myosin (FMyHC localises to secondary myotubes evenly distributed throughout the embryonic musculature and gradually increasing in number so that by E15.5 around half contain FMyHC. The Igf-2 pattern closely correlates with FMyHC from E13.5 and peaks at E15.5 when over 90% of FMyHC+ myotubes also contain Igf-2. Igf-2 lags FMyHC and it is absent from muscle myotubes until E13.5. Igf-2 strongly down-regulates by E17.5. A striking feature of the FMyHC pattern is its increased heterogeneity and attenuation in many fibres from E15.5 to day one after birth (P1. Transgenic mice (MIG which express Igf-2 in all of their myotubes, have increased FMyHC staining, a higher proportion of FMyHC+ myotubes and loose their FMyHC staining heterogeneity. In Igf-2 deficient mice (MatDi FMyHC+ myotubes are reduced to 60% of WT by E15.5. In vitro, MIG induces a 50% excess of FMyHC+ and a 30% reduction of SMHyC+ myotubes in C2 cells which can be reversed by Igf-2-targeted ShRNA resulting in 50% reduction of FMyHC. Total number of myotubes was not affected. Conclusion In WT embryos the appearance of Igf-2 in embryonic myotubes lags FMyHC, but by E15.5 around 45% of secondary myotubes contain both proteins. Forced expression of Igf-2 into all myotubes causes an excess, and absence of Igf-2 suppresses, the FMyHC+ myotube component in both embryonic muscle and differentiated myoblasts. Igf-2 is thus required, not for

Retraction: Myostatin Induces Degradation of Sarcomeric Proteins through a Smad3 Signaling Mechanism During Skeletal Muscle Wasting

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Lokireddy, Sudarsanareddy; McFarlane, Craig; Ge, Xiaojia; Zhang, Huoming; Sze, Siu Kwan; Sharma, Mridula

2011-01-01

Ubiquitination-mediated proteolysis is a hallmark of skeletal muscle wasting manifested in response to negative growth factors, including myostatin. Thus, the characterization of signaling mechanisms that induce the ubiquitination of intracellular and sarcomeric proteins during skeletal muscle wasting is of great importance. We have recently characterized myostatin as a potent negative regulator of myogenesis and further demonstrated that elevated levels of myostatin in circulation results in the up-regulation of the muscle-specific E3 ligases, Atrogin-1 and muscle ring finger protein 1 (MuRF1). However, the exact signaling mechanisms by which myostatin regulates the expression of Atrogin-1 and MuRF1, as well as the proteins targeted for degradation in response to excess myostatin, remain to be elucidated. In this report, we have demonstrated that myostatin signals through Smad3 (mothers against decapentaplegic homolog 3) to activate forkhead box O1 and Atrogin-1 expression, which further promotes the ubiquitination and subsequent proteasome-mediated degradation of critical sarcomeric proteins. Smad3 signaling was dispensable for myostatin-dependent overexpression of MuRF1. Although down-regulation of Atrogin-1 expression rescued approximately 80% of sarcomeric protein loss induced by myostatin, only about 20% rescue was seen when MuRF1 was silenced, implicating that Atrogin-1 is the predominant E3 ligase through which myostatin manifests skeletal muscle wasting. Furthermore, we have highlighted that Atrogin-1 not only associates with myosin heavy and light chain, but it also ubiquitinates these sarcomeric proteins. Based on presented data we propose a model whereby myostatin induces skeletal muscle wasting through targeting sarcomeric proteins via Smad3-mediated up-regulation of Atrogin-1 and forkhead box O1. PMID:21964591

The mRNA expression profile of metabolic genes relative to MHC isoform pattern in human skeletal muscles

DEFF Research Database (Denmark)

Plomgaard, Peter; Penkowa, Milena; Leick, Lotte

2006-01-01

The metabolic profile of rodent muscle is generally reflected in the myosin heavy chain (MHC) fiber-type composition. The present study was conducted to test the hypothesis that metabolic gene expression is not tightly coupled with MHC fiber-type composition for all genes in human skeletal muscle....... Triceps brachii, vastus lateralis quadriceps, and soleus muscle biopsies were obtained from normally physically active, healthy, young male volunteers, because these muscles are characterized by different fiber-type compositions. As expected, citrate synthase and 3-hydroxyacyl dehydrogenase activity...... of a broad range of metabolic genes. The triceps muscle had two- to fivefold higher MHC IIa, phosphofructokinase, and LDH A mRNA content and two- to fourfold lower MHC I, lipoprotein lipase, CD36, hormone-sensitive lipase, and LDH B and hexokinase II mRNA than vastus lateralis or soleus. Interestingly...

Overexpression of IGF-1 attenuates skeletal muscle damage and accelerates muscle regeneration and functional recovery after disuse

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Ye, Fan; Mathur, Sunita; Liu, Min; Borst, Stephen E.; Walter, Glenn A.; Sweeney, H. Lee; Vandenborne, Krista

2014-01-01

Skeletal muscle is a highly dynamic tissue that responds to endogenous and external stimuli, including alterations in mechanical loading and growth factors. In particular, the antigravity soleus muscle experiences significant muscle atrophy during disuse and extensive muscle damage upon reloading. Since insulin-like growth factor-1 (IGF-1) has been implicated as a central regulator of muscle repair and modulation of muscle size, we examined the effect of viral mediated overexpression of IGF-1 on the soleus muscle following hindlimb cast immobilization and upon reloading. Recombinant IGF-1 cDNA virus was injected into one of the posterior hindlimbs of the mice, while the contralateral limb was injected with saline (control). At 20 weeks of age, both hindlimbs were immobilized for two weeks to induce muscle atrophy in the soleus and ankle plantar flexor muscle group. Subsequently, the mice were allowed to reambulate and muscle damage and recovery was monitored over a period of 2 to 21 days. The primary finding of this study was that IGF-1 overexpression attenuated reloading-induced muscle damage in the soleus muscle, and accelerated muscle regeneration and force recovery. Muscle T2 assessed by MRI, a nonspecific marker of muscle damage, was significantly lower in IGF-1 injected, compared to contralateral soleus muscles at 2 and 5 days reambulation (P<0.05). The reduced prevalence of muscle damage in IGF-1 injected soleus muscles was confirmed on histology, with a lower fraction area of abnormal muscle tissue in IGF-I injected muscles at 2 days reambulation (33.2±3.3%vs 54.1±3.6%, P<0.05). Evidence of the effect of IGF-1 on muscle regeneration included timely increases in the number of central nuclei (21% at 5 days reambulation), paired-box transcription factor 7 (36% at 5 days), embryonic myosin (37% at 10 days), and elevated MyoD mRNA (7-fold at 2 days) in IGF-1 injected limbs (P<0.05). These findings demonstrate a potential role of IGF-1 in protecting unloaded

Electron Microscopic Recording of the Power and Recovery Strokes of Individual Myosin Heads Coupled with ATP Hydrolysis: Facts and Implications

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Haruo Sugi

2018-05-01

Full Text Available The most straightforward way to get information on the performance of individual myosin heads producing muscle contraction may be to record their movement, coupled with ATP hydrolysis, electron-microscopically using the gas environmental chamber (EC. The EC enables us to visualize and record ATP-induced myosin head movement in hydrated skeletal muscle myosin filaments. When actin filaments are absent, myosin heads fluctuate around a definite neutral position, so that their time-averaged mean position remains unchanged. On application of ATP, myosin heads are found to move away from, but not towards, the bare region, indicating that myosin heads perform a recovery stroke (average amplitude, 6 nm. After exhaustion of ATP, myosin heads return to their neutral position. In the actin–myosin filament mixture, myosin heads form rigor actin myosin linkages, and on application of ATP, they perform a power stroke by stretching adjacent elastic structures because of a limited amount of applied ATP ≤ 10 µM. The average amplitude of the power stroke is 3.3 nm and 2.5 nm at the distal and the proximal regions of the myosin head catalytic domain (CAD, respectively. The power stroke amplitude increases appreciably at low ionic strength, which is known to enhance Ca2+-activated force in muscle. In both the power and recovery strokes, myosin heads return to their neutral position after exhaustion of ATP.

Enhanced contractile force generation by artificial skeletal muscle tissues using IGF-I gene-engineered myoblast cells.

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Sato, Masanori; Ito, Akira; Kawabe, Yoshinori; Nagamori, Eiji; Kamihira, Masamichi

2011-09-01

The aim of this study was to investigate whether insulin-like growth factor (IGF)-I gene delivery to myoblast cells promotes the contractile force generated by hydrogel-based tissue-engineered skeletal muscles in vitro. Two retroviral vectors allowing doxycycline (Dox)-inducible expression of the IGF-I gene were transduced into mouse myoblast C2C12 cells to evaluate the effects of IGF-I gene expression on these cells. IGF-I gene expression stimulated the proliferation of C2C12 cells, and a significant increase in the growth rate was observed for IGF-I-transduced C2C12 cells with Dox addition, designated C2C12/IGF (Dox+) cells. Quantitative morphometric analyses showed that the myotubes induced from C2C12/IGF (Dox+) cells had a larger area and a greater width than control myotubes induced from normal C2C12 cells. Artificial skeletal muscle tissues were prepared from the respective cells using hydrogels composed of type I collagen and Matrigel. Western blot analyses revealed that the C2C12/IGF (Dox+) tissue constructs showed activation of a skeletal muscle hypertrophy marker (Akt) and enhanced expression of muscle-specific markers (myogenin, myosin heavy chain and tropomyosin). Moreover, the creatine kinase activity was increased in the C2C12/IGF (Dox+) tissue constructs. The C2C12/IGF (Dox+) tissue constructs contracted in response to electrical pulses, and generated a significantly higher physical force than the control C2C12 tissue constructs. These findings indicate that IGF-I gene transfer has the potential to yield functional skeletal muscle substitutes that are capable of in vivo restoration of the load-bearing function of injured muscle or acting as in vitro electrically-controlled bio-actuators. Copyright © 2011 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Myosin heavy chain composition of single fibres from m. biceps brachii of male body builders

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Klitgaard, H; Zhou, M.-Y.; Richter, Erik

1990-01-01

The myosin heavy chain (MHC) composition of single fibres from m. biceps brachii of young sedentary men (28 +/- 0.4 years, mean +/- SE, n = 4) and male body builders (25 +/- 2.0 years, n = 4) was analysed with a sensitive one-dimensional electrophoretic technique. Compared with sedentary men...... expression of MHC isoforms within histochemical type II fibres of human skeletal muscle with body building. Furthermore, in human skeletal muscle differences in expression of MHC isoforms may not always be reflected in the traditional histochemical classification of types I, IIa, IIb and IIc fibres....

Skeletal Muscle Contraction Time and Tone Decrease After 8 Weeks of Plyometric Training.

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Zubac, Damir; Šimunič, Boštjan

2017-06-01

The aim of the study was to examine whether an improvement in jumping performance after 8 weeks of plyometric training (PT) runs in parallel with changes in lower-limb skeletal muscle contractile properties. Using noninvasive tensiomyography (TMG), we assessed contraction time (Tc) and the maximal amplitude of radial displacement (Dm) in 20 subjects (50% men; age 22.4 ± 4.7 years of age), randomly divided in PT group (N = 10; PLYO) and a control group (N = 10; CTRL). The PLYO performed 8 weeks of PT. Tensiomyography was measured in 5 leg skeletal muscles: vastus lateralis (VL), biceps femoris (BF), tibialis anterior (TA), gastrocnemius medialis (GM), and gastrocnemius lateralis (GL). Additionally, we evaluated countermovement jump (CMJ) height improvement on a ground force plate. Assessments were repeated before and after PT. After 8 weeks of PT, CMJ height increased by 12.2% in PLYO (p = 0.015), but not in CRTL. Contraction time, which is related to myosin heavy-chain type 1 (MHC-1) proportion, decreased in VL (-8.7%; p muscle tone, decreased in BF (-26.5%; p = 0.032), GM (-14.9%; p = 0.017), GL (-31.5%; p = 0.017), but not in TA (-16.8%; p = 0.113) and VL (-6.0%; p = 0.654). After PT, jumping performance increased, which was paralleled by decreased Tc and decreased muscle tone. Additionally, adaptations to contractile properties were muscle specific, which is important for future studies. It seems that adjustments were dose dependent, being higher in muscles with lower habitual load.

Peripheral endocannabinoids regulate skeletal muscle development and maintenance

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Dongjiao Zhao

2010-12-01

Full Text Available As a principal tissue responsible for insulin-mediated glucose uptake, skeletal muscle is important for whole-body health. The role of peripheral endocannabinoids as regulators of skeletal muscle metabolism has recently gained a lot of interest, as endocannabinoid system disorders could cause peripheral insulin resistance. We investigated the role of the peripheral endocannabinoid system in skeletal muscle development and maintenance. Cultures of C2C12 cells, primary satellite cells and mouse skeletal muscle single fibers were used as model systems for our studies. We found an increase in cannabinoid receptor type 1 (CB1 mRNA and endocannabinoid synthetic enzyme mRNA skeletal muscle cells during differentiation. We also found that activation of CB1 inhibited myoblast differentiation, expanded the number of satellite cells, and stimulated the fast-muscle oxidative phenotype. Our findings contribute to understanding of the role of the endocannabinoid system in skeletal muscle metabolism and muscle oxygen consumption, and also help to explain the effects of the peripheral endocannabinoid system on whole-body energy balance.

Myosin isoform switching during assembly of the Drosophila flight muscle thick filament lattice.

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Orfanos, Zacharias; Sparrow, John C

2013-01-01

During muscle development myosin molecules form symmetrical thick filaments, which integrate with the thin filaments to produce the regular sarcomeric lattice. In Drosophila indirect flight muscles (IFMs) the details of this process can be studied using genetic approaches. The weeP26 transgenic line has a GFP-encoding exon inserted into the single Drosophila muscle myosin heavy chain gene, Mhc. The weeP26 IFM sarcomeres have a unique MHC-GFP-labelling pattern restricted to the sarcomere core, explained by non-translation of the GFP exon following alternative splicing. Characterisation of wild-type IFM MHC mRNA confirmed the presence of an alternately spliced isoform, expressed earlier than the major IFM-specific isoform. The two wild-type IFM-specific MHC isoforms differ by the presence of a C-terminal 'tailpiece' in the minor isoform. The sequential expression and assembly of these two MHCs into developing thick filaments suggest a role for the tailpiece in initiating A-band formation. The restriction of the MHC-GFP sarcomeric pattern in weeP26 is lifted when the IFM lack the IFM-specific myosin binding protein flightin, suggesting that it limits myosin dissociation from thick filaments. Studies of flightin binding to developing thick filaments reveal a progressive binding at the growing thick filament tips and in a retrograde direction to earlier assembled, proximal filament regions. We propose that this flightin binding restricts myosin molecule incorporation/dissociation during thick filament assembly and explains the location of the early MHC isoform pattern in the IFM A-band.

Prior acetaminophen consumption impacts the early adaptive cellular response of human skeletal muscle to resistance exercise.

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D'Lugos, Andrew C; Patel, Shivam H; Ormsby, Jordan C; Curtis, Donald P; Fry, Christopher S; Carroll, Chad C; Dickinson, Jared M

2018-04-01

Resistance exercise (RE) is a powerful stimulus for skeletal muscle adaptation. Previous data demonstrate that cyclooxygenase (COX)-inhibiting drugs alter the cellular mechanisms regulating the adaptive response of skeletal muscle. The purpose of this study was to determine whether prior consumption of the COX inhibitor acetaminophen (APAP) alters the immediate adaptive cellular response in human skeletal muscle after RE. In a double-blinded, randomized, crossover design, healthy young men ( n = 8, 25 ± 1 yr) performed two trials of unilateral knee extension RE (8 sets, 10 reps, 65% max strength). Subjects ingested either APAP (1,000 mg/6 h) or placebo (PLA) for 24 h before RE (final dose consumed immediately after RE). Muscle biopsies (vastus lateralis) were collected at rest and 1 h and 3 h after exercise. Mammalian target of rapamycin (mTOR) complex 1 signaling was assessed through immunoblot and immunohistochemistry, and mRNA expression of myogenic genes was examined via RT-qPCR. At 1 h p-rpS6 Ser240/244 was increased in both groups but to a greater extent in PLA. At 3 h p-S6K1 Thr389 was elevated only in PLA. Furthermore, localization of mTOR to the lysosome (LAMP2) in myosin heavy chain (MHC) II fibers increased 3 h after exercise only in PLA. mTOR-LAMP2 colocalization in MHC I fibers was greater in PLA vs. APAP 1 h after exercise. Myostatin mRNA expression was reduced 1 h after exercise only in PLA. MYF6 mRNA expression was increased 1 h and 3 h after exercise only in APAP. APAP consumption appears to alter the early adaptive cellular response of skeletal muscle to RE. These findings further highlight the mechanisms through which COX-inhibiting drugs impact the adaptive response of skeletal muscle to exercise. NEW & NOTEWORTHY The extent to which the cellular reaction to acetaminophen impacts the mechanisms regulating the adaptive response of human skeletal muscle to resistance exercise is not well understood. Consumption of acetaminophen before

A simplified immunohistochemical classification of skeletal muscle fibres in mouse

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M. Kammoun

2014-06-01

Full Text Available The classification of muscle fibres is of particular interest for the study of the skeletal muscle properties in a wide range of scientific fields, especially animal phenotyping. It is therefore important to define a reliable method for classifying fibre types. The aim of this study was to establish a simplified method for the immunohistochemical classification of fibres in mouse. To carry it out, we first tested a combination of several anti myosin heavy chain (MyHC antibodies in order to choose a minimum number of antibodies to implement a semi-automatic classification. Then, we compared the classification of fibres to the MyHC electrophoretic pattern on the same samples. Only two anti MyHC antibodies on serial sections with the fluorescent labeling of the Laminin were necessary to classify properly fibre types in Tibialis Anterior and Soleus mouse muscles in normal physiological conditions. This classification was virtually identical to the classification realized by the electrophoretic separation of MyHC. This immunohistochemical classification can be applied to the total area of Tibialis Anterior and Soleus mouse muscles. Thus, we provide here a useful, simple and time-efficient method for immunohistochemical classification of fibres, applicable for research in mouse

Structure–function relationship of skeletal muscle provides inspiration for design of new artificial muscle

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Gao, Yingxin; Zhang, Chi

2015-01-01

A variety of actuator technologies have been developed to mimic biological skeletal muscle that generates force in a controlled manner. Force generation process of skeletal muscle involves complicated biophysical and biochemical mechanisms; therefore, it is impossible to replace biological muscle. In biological skeletal muscle tissue, the force generation of a muscle depends not only on the force generation capacity of the muscle fiber, but also on many other important factors, including muscle fiber type, motor unit recruitment, architecture, structure and morphology of skeletal muscle, all of which have significant impact on the force generation of the whole muscle or force transmission from muscle fibers to the tendon. Such factors have often been overlooked, but can be incorporated in artificial muscle design, especially with the discovery of new smart materials and the development of innovative fabrication and manufacturing technologies. A better understanding of the physiology and structure–function relationship of skeletal muscle will therefore benefit the artificial muscle design. In this paper, factors that affect muscle force generation are reviewed. Mathematical models used to model the structure–function relationship of skeletal muscle are reviewed and discussed. We hope the review will provide inspiration for the design of a new generation of artificial muscle by incorporating the structure–function relationship of skeletal muscle into the design of artificial muscle. (topical review)

Structure-function relationship of skeletal muscle provides inspiration for design of new artificial muscle

Science.gov (United States)

Gao, Yingxin; Zhang, Chi

2015-03-01

A variety of actuator technologies have been developed to mimic biological skeletal muscle that generates force in a controlled manner. Force generation process of skeletal muscle involves complicated biophysical and biochemical mechanisms; therefore, it is impossible to replace biological muscle. In biological skeletal muscle tissue, the force generation of a muscle depends not only on the force generation capacity of the muscle fiber, but also on many other important factors, including muscle fiber type, motor unit recruitment, architecture, structure and morphology of skeletal muscle, all of which have significant impact on the force generation of the whole muscle or force transmission from muscle fibers to the tendon. Such factors have often been overlooked, but can be incorporated in artificial muscle design, especially with the discovery of new smart materials and the development of innovative fabrication and manufacturing technologies. A better understanding of the physiology and structure-function relationship of skeletal muscle will therefore benefit the artificial muscle design. In this paper, factors that affect muscle force generation are reviewed. Mathematical models used to model the structure-function relationship of skeletal muscle are reviewed and discussed. We hope the review will provide inspiration for the design of a new generation of artificial muscle by incorporating the structure-function relationship of skeletal muscle into the design of artificial muscle.

Myosin Va Plays a Role in Nitrergic Smooth Muscle Relaxation in Gastric Fundus and Corpora Cavernosa of Penis

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Carew, Josephine A.; Goyal, Raj K.; Sullivan, Maryrose P.

2014-01-01

The intracellular motor protein myosin Va is involved in nitrergic neurotransmission possibly by trafficking of neuronal nitric oxide synthase (nNOS) within the nerve terminals. In this study, we examined the role of myosin Va in the stomach and penis, proto-typical smooth muscle organs in which nitric oxide (NO) mediated relaxation is critical for function. We used confocal microscopy and co-immunoprecipitation of tissue from the gastric fundus (GF) and penile corpus cavernosum (CCP) to localize myosin Va with nNOS and demonstrate their molecular interaction. We utilized in vitro mechanical studies to test whether smooth muscle relaxations during nitrergic neuromuscular neurotransmission is altered in DBA (dilute, brown, non-agouti) mice which lack functional myosin Va. Myosin Va was localized in nNOS-positive nerve terminals and was co-immunoprecipitated with nNOS in both GF and CCP. In comparison to C57BL/6J wild type (WT) mice, electrical field stimulation (EFS) of precontracted smooth muscles of GF and CCP from DBA animals showed significant impairment of nitrergic relaxation. An NO donor, Sodium nitroprusside (SNP), caused comparable levels of relaxation in smooth muscles of WT and DBA mice. These normal postjunctional responses to SNP in DBA tissues suggest that impairment of smooth muscle relaxation resulted from inhibition of NO synthesis in prejunctional nerve terminals. Our results suggest that normal physiological processes of relaxation of gastric and cavernosal smooth muscles that facilitate food accommodation and penile erection, respectively, may be disrupted under conditions of myosin Va deficiency, resulting in complications like gastroparesis and erectile dysfunction. PMID:24516539

Dietary fat influences the expression of contractile and metabolic genes in rat skeletal muscle.

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Wataru Mizunoya

Full Text Available Dietary fat plays a major role in obesity, lipid metabolism, and cardiovascular diseases. To determine whether the intake of different types of dietary fats affect the muscle fiber types that govern the metabolic and contractile properties of the skeletal muscle, we fed male Wistar rats with a 15% fat diet derived from different fat sources. Diets composed of soybean oil (n-6 polyunsaturated fatty acids (PUFA-rich, fish oil (n-3 PUFA-rich, or lard (low in PUFAs were administered to the rats for 4 weeks. Myosin heavy chain (MyHC isoforms were used as biomarkers to delineate the skeletal muscle fiber types. Compared with soybean oil intake, fish oil intake showed significantly lower levels of the fast-type MyHC2B and higher levels of the intermediate-type MyHC2X composition in the extensor digitorum longus (EDL muscle, which is a fast-type dominant muscle. Concomitantly, MyHC2X mRNA levels in fish oil-fed rats were significantly higher than those observed in the soybean oil-fed rats. The MyHC isoform composition in the lard-fed rats was an intermediate between that of the fish oil and soybean oil-fed rats. Mitochondrial uncoupling protein 3, pyruvate dehydrogenase kinase 4, and porin mRNA showed significantly upregulated levels in the EDL of fish oil-fed rats compared to those observed in soybean oil-fed and lard-fed rats, implying an activation of oxidative metabolism. In contrast, no changes in the composition of MyHC isoforms was observed in the soleus muscle, which is a slow-type dominant muscle. Fatty acid composition in the serum and the muscle was significantly influenced by the type of dietary fat consumed. In conclusion, dietary fat affects the expression of genes related to the contractile and metabolic properties in the fast-type dominant skeletal muscle, where the activation of oxidative metabolism is more pronounced after fish oil intake than that after soybean oil intake.

Overexpression of SMPX in adult skeletal muscle does not change skeletal muscle fiber type or size.

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Einar Eftestøl

Full Text Available Mechanical factors such as stretch are thought to be important in the regulation of muscle phenotype. Small muscle protein X-linked (SMPX is upregulated by stretch in skeletal muscle and has been suggested to serve both as a transcription factor and a mechanosensor, possibly giving rise to changes in both fiber size and fiber type. We have used in vivo confocal imaging to study the subcellular localization of SMPX in skeletal muscle fibers of adult rats using a SMPX-EGFP fusion protein. The fusion protein was localized predominantly in repetitive double stripes flanking the Z-disc, and was excluded from all nuclei. This localization would be consistent with SMPX being a mechanoreceptor, but not with SMPX playing a role as a transcription factor. In vivo overexpression of ectopic SMPX in skeletal muscle of adult mice gave no significant changes in fiber type distribution or cross sectional area, thus a role of SMPX in regulating muscle phenotype remains unclear.

Omega-3 Fatty Acids and Skeletal Muscle Health

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Stewart Jeromson

2015-11-01

Full Text Available Skeletal muscle is a plastic tissue capable of adapting and mal-adapting to physical activity and diet. The response of skeletal muscle to adaptive stimuli, such as exercise, can be modified by the prior nutritional status of the muscle. The influence of nutrition on skeletal muscle has the potential to substantially impact physical function and whole body metabolism. Animal and cell based models show that omega-3 fatty acids, in particular those of marine origin, can influence skeletal muscle metabolism. Furthermore, recent human studies demonstrate that omega-3 fatty acids of marine origin can influence the exercise and nutritional response of skeletal muscle. These studies show that the prior omega-3 status influences not only the metabolic response of muscle to nutrition, but also the functional response to a period of exercise training. Omega-3 fatty acids of marine origin therefore have the potential to alter the trajectory of a number of human diseases including the physical decline associated with aging. We explore the potential molecular mechanisms by which omega-3 fatty acids may act in skeletal muscle, considering the n-3/n-6 ratio, inflammation and lipidomic remodelling as possible mechanisms of action. Finally, we suggest some avenues for further research to clarify how omega-3 fatty acids may be exerting their biological action in skeletal muscle.

Pathogenesis of Insulin Resistance in Skeletal Muscle

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Muhammad A. Abdul-Ghani

2010-01-01

Full Text Available Insulin resistance in skeletal muscle is manifested by decreased insulin-stimulated glucose uptake and results from impaired insulin signaling and multiple post-receptor intracellular defects including impaired glucose transport, glucose phosphorylation, and reduced glucose oxidation and glycogen synthesis. Insulin resistance is a core defect in type 2 diabetes, it is also associated with obesity and the metabolic syndrome. Dysregulation of fatty acid metabolism plays a pivotal role in the pathogenesis of insulin resistance in skeletal muscle. Recent studies have reported a mitochondrial defect in oxidative phosphorylation in skeletal muscle in variety of insulin resistant states. In this review, we summarize the cellular and molecular defects that contribute to the development of insulin resistance in skeletal muscle.

Exercise Promotes Healthy Aging of Skeletal Muscle.

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Cartee, Gregory D; Hepple, Russell T; Bamman, Marcas M; Zierath, Juleen R

2016-06-14

Primary aging is the progressive and inevitable process of bodily deterioration during adulthood. In skeletal muscle, primary aging causes defective mitochondrial energetics and reduced muscle mass. Secondary aging refers to additional deleterious structural and functional age-related changes caused by diseases and lifestyle factors. Secondary aging can exacerbate deficits in mitochondrial function and muscle mass, concomitant with the development of skeletal muscle insulin resistance. Exercise opposes deleterious effects of secondary aging by preventing the decline in mitochondrial respiration, mitigating aging-related loss of muscle mass and enhancing insulin sensitivity. This review focuses on mechanisms by which exercise promotes "healthy aging" by inducing modifications in skeletal muscle. Copyright © 2016 Elsevier Inc. All rights reserved.

Skeletal Muscle-specific G Protein-coupled Receptor Kinase 2 Ablation Alters Isolated Skeletal Muscle Mechanics and Enhances Clenbuterol-stimulated Hypertrophy.

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Woodall, Benjamin P; Woodall, Meryl C; Luongo, Timothy S; Grisanti, Laurel A; Tilley, Douglas G; Elrod, John W; Koch, Walter J

2016-10-14

GRK2, a G protein-coupled receptor kinase, plays a critical role in cardiac physiology. Adrenergic receptors are the primary target for GRK2 activity in the heart; phosphorylation by GRK2 leads to desensitization of these receptors. As such, levels of GRK2 activity in the heart directly correlate with cardiac contractile function. Furthermore, increased expression of GRK2 after cardiac insult exacerbates injury and speeds progression to heart failure. Despite the importance of this kinase in both the physiology and pathophysiology of the heart, relatively little is known about the role of GRK2 in skeletal muscle function and disease. In this study we generated a novel skeletal muscle-specific GRK2 knock-out (KO) mouse (MLC-Cre:GRK2 fl/fl ) to gain a better understanding of the role of GRK2 in skeletal muscle physiology. In isolated muscle mechanics testing, GRK2 ablation caused a significant decrease in the specific force of contraction of the fast-twitch extensor digitorum longus muscle yet had no effect on the slow-twitch soleus muscle. Despite these effects in isolated muscle, exercise capacity was not altered in MLC-Cre:GRK2 fl/fl mice compared with wild-type controls. Skeletal muscle hypertrophy stimulated by clenbuterol, a β 2 -adrenergic receptor (β 2 AR) agonist, was significantly enhanced in MLC-Cre:GRK2 fl/fl mice; mechanistically, this seems to be due to increased clenbuterol-stimulated pro-hypertrophic Akt signaling in the GRK2 KO skeletal muscle. In summary, our study provides the first insights into the role of GRK2 in skeletal muscle physiology and points to a role for GRK2 as a modulator of contractile properties in skeletal muscle as well as β 2 AR-induced hypertrophy. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Skeletal Muscle-specific G Protein-coupled Receptor Kinase 2 Ablation Alters Isolated Skeletal Muscle Mechanics and Enhances Clenbuterol-stimulated Hypertrophy*

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Woodall, Benjamin P.; Woodall, Meryl C.; Luongo, Timothy S.; Grisanti, Laurel A.; Tilley, Douglas G.; Elrod, John W.; Koch, Walter J.

2016-01-01

GRK2, a G protein-coupled receptor kinase, plays a critical role in cardiac physiology. Adrenergic receptors are the primary target for GRK2 activity in the heart; phosphorylation by GRK2 leads to desensitization of these receptors. As such, levels of GRK2 activity in the heart directly correlate with cardiac contractile function. Furthermore, increased expression of GRK2 after cardiac insult exacerbates injury and speeds progression to heart failure. Despite the importance of this kinase in both the physiology and pathophysiology of the heart, relatively little is known about the role of GRK2 in skeletal muscle function and disease. In this study we generated a novel skeletal muscle-specific GRK2 knock-out (KO) mouse (MLC-Cre:GRK2fl/fl) to gain a better understanding of the role of GRK2 in skeletal muscle physiology. In isolated muscle mechanics testing, GRK2 ablation caused a significant decrease in the specific force of contraction of the fast-twitch extensor digitorum longus muscle yet had no effect on the slow-twitch soleus muscle. Despite these effects in isolated muscle, exercise capacity was not altered in MLC-Cre:GRK2fl/fl mice compared with wild-type controls. Skeletal muscle hypertrophy stimulated by clenbuterol, a β2-adrenergic receptor (β2AR) agonist, was significantly enhanced in MLC-Cre:GRK2fl/fl mice; mechanistically, this seems to be due to increased clenbuterol-stimulated pro-hypertrophic Akt signaling in the GRK2 KO skeletal muscle. In summary, our study provides the first insights into the role of GRK2 in skeletal muscle physiology and points to a role for GRK2 as a modulator of contractile properties in skeletal muscle as well as β2AR-induced hypertrophy. PMID:27566547

Skeletal Muscle Cell Induction from Pluripotent Stem Cells

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Yusaku Kodaka

2017-01-01

Full Text Available Embryonic stem cells (ESCs and induced pluripotent stem cells (iPSCs have the potential to differentiate into various types of cells including skeletal muscle cells. The approach of converting ESCs/iPSCs into skeletal muscle cells offers hope for patients afflicted with the skeletal muscle diseases such as the Duchenne muscular dystrophy (DMD. Patient-derived iPSCs are an especially ideal cell source to obtain an unlimited number of myogenic cells that escape immune rejection after engraftment. Currently, there are several approaches to induce differentiation of ESCs and iPSCs to skeletal muscle. A key to the generation of skeletal muscle cells from ESCs/iPSCs is the mimicking of embryonic mesodermal induction followed by myogenic induction. Thus, current approaches of skeletal muscle cell induction of ESCs/iPSCs utilize techniques including overexpression of myogenic transcription factors such as MyoD or Pax3, using small molecules to induce mesodermal cells followed by myogenic progenitor cells, and utilizing epigenetic myogenic memory existing in muscle cell-derived iPSCs. This review summarizes the current methods used in myogenic differentiation and highlights areas of recent improvement.

Effect of Increased Cyclic AMP Concentration on Muscle Protein Synthesis and Beta-Adrenergic Receptor Expression in Chicken Skeletal Muscle Cells in Culture

Science.gov (United States)

Young, R. B.; Vaughn, J. R.; Bridge, K. Y.; Smith, C. K.

1998-01-01

Analogies of epinephrine are known to cause hypertrophy of skeletal muscle when fed to animals. These compounds presumably exert their physiological action through interaction with the P-adrenergic receptor. Since the intracellular signal generated by the Beta-adrenergic receptor is cyclic AMP (cAMP), experiments were initiated in cell culture to determine if artificial elevation of cAMP by treatment with forskolin would alter muscle protein metabolism and P-adrenergic receptor expression. Chicken skeletal muscle cells after 7 days in culture were treated with 0.2-30 micrometers forskolin for a total of three days. At the end of the treatment period, both the concentration of cAMP and the quantity of myosin heavy chain (MHC) were measured. Concentration of cAMP in forskolin-treated cells increased up to 10-fold in a dose dependent manner. In contrast, the quantity of MHC was increased approximately 50% above control cells at 0.2 micrometers forskolin, but exhibited a gradual decline at higher levels of forskolin so that the quantity of MHC in cells treated with 30 micrometers forskolin was not significantly different from controls. Curiously, the intracellular concentration of cAMP which elicited the maximum increase in the quantity of MHC was only 40% higher than cAMP concentration in control cells.

Electron Tomography of Cryofixed, Isometrically Contracting Insect Flight Muscle Reveals Novel Actin-Myosin Interactions

International Nuclear Information System (INIS)

Wu, Shenping; Liu, Jun; Reedy, Mary C.; Tregear, Richard T.; Winkler, Hanspeter; Franzini-Armstrong, Clara; Sasaki, Hiroyuki; Lucaveche, Carmen; Goldman, Yale E.; Reedy, Michael K.; Taylor, Kenneth A.

2010-01-01

Isometric muscle contraction, where force is generated without muscle shortening, is a molecular traffic jam in which the number of actin-attached motors is maximized and all states of motor action are trapped with consequently high heterogeneity. This heterogeneity is a major limitation to deciphering myosin conformational changes in situ. We used multivariate data analysis to group repeat segments in electron tomograms of isometrically contracting insect flight muscle, mechanically monitored, rapidly frozen, freeze substituted, and thin sectioned. Improved resolution reveals the helical arrangement of F-actin subunits in the thin filament enabling an atomic model to be built into the thin filament density independent of the myosin. Actin-myosin attachments can now be assigned as weak or strong by their motor domain orientation relative to actin. Myosin attachments were quantified everywhere along the thin filament including troponin. Strong binding myosin attachments are found on only four F-actin subunits, the 'target zone', situated exactly midway between successive troponin complexes. They show an axial lever arm range of 77 o /12.9 nm. The lever arm azimuthal range of strong binding attachments has a highly skewed, 127 o range compared with X-ray crystallographic structures. Two types of weak actin attachments are described. One type, found exclusively in the target zone, appears to represent pre-working-stroke intermediates. The other, which contacts tropomyosin rather than actin, is positioned M-ward of the target zone, i.e. the position toward which thin filaments slide during shortening. We present a model for the weak to strong transition in the myosin ATPase cycle that incorporates azimuthal movements of the motor domain on actin. Stress/strain in the S2 domain may explain azimuthal lever arm changes in the strong binding attachments. The results support previous conclusions that the weak attachments preceding force generation are very different from

Electron tomography of cryofixed, isometrically contracting insect flight muscle reveals novel actin-myosin interactions.

Directory of Open Access Journals (Sweden)

Shenping Wu

2010-09-01

Full Text Available Isometric muscle contraction, where force is generated without muscle shortening, is a molecular traffic jam in which the number of actin-attached motors is maximized and all states of motor action are trapped with consequently high heterogeneity. This heterogeneity is a major limitation to deciphering myosin conformational changes in situ.We used multivariate data analysis to group repeat segments in electron tomograms of isometrically contracting insect flight muscle, mechanically monitored, rapidly frozen, freeze substituted, and thin sectioned. Improved resolution reveals the helical arrangement of F-actin subunits in the thin filament enabling an atomic model to be built into the thin filament density independent of the myosin. Actin-myosin attachments can now be assigned as weak or strong by their motor domain orientation relative to actin. Myosin attachments were quantified everywhere along the thin filament including troponin. Strong binding myosin attachments are found on only four F-actin subunits, the "target zone", situated exactly midway between successive troponin complexes. They show an axial lever arm range of 77°/12.9 nm. The lever arm azimuthal range of strong binding attachments has a highly skewed, 127° range compared with X-ray crystallographic structures. Two types of weak actin attachments are described. One type, found exclusively in the target zone, appears to represent pre-working-stroke intermediates. The other, which contacts tropomyosin rather than actin, is positioned M-ward of the target zone, i.e. the position toward which thin filaments slide during shortening.We present a model for the weak to strong transition in the myosin ATPase cycle that incorporates azimuthal movements of the motor domain on actin. Stress/strain in the S2 domain may explain azimuthal lever arm changes in the strong binding attachments. The results support previous conclusions that the weak attachments preceding force generation are very

Characterization of disuse skeletal muscle atrophy and the efficacy of a novel muscle atrophy countermeasure during spaceflight and simulated microgravity

Science.gov (United States)

Hanson, Andrea Marie

Humans are an integral part of the engineered systems that will enable return to the Moon and eventually travel to Mars. Major advancements in countermeasure development addressing deleterious effects of microgravity and reduced gravity on the musculoskeletal system need to be made to ensure mission safety and success. The primary objectives of this dissertation are to advance the knowledge and understanding of skeletal muscle atrophy, and support development of novel countermeasures for disuse atrophy to enable healthy long-duration human spaceflight. Models simulating microgravity and actual spaceflight were used to examine the musculoskeletal adaptations during periods of unloading. Myostatin inhibition, a novel anti-atrophy drug therapy, and exercise were examined as a means of preventing and recovering from disuse atrophy. A combination of assays was used to quantify adaptation responses to unloading and examine efficacy of the countermeasures. Body and muscle masses were collected to analyze systemic changes due to treatments. Hindlimb strength and individual muscle forces were measured to demonstrate functional adaptations to treatments. Muscle fiber morphology and myosin heavy chain (MHC) expression was examined to identify adaptations at the cellular level. Protein synthesis signals insulin-like growth factor-1 (IGF-1), Akt, and p70s6 kinase; and the degradation signals Atrogin-1 and MuRF-1 were examined to identify adaptations at the molecular level that ultimately lead to muscle hypertrophy and atrophy. A time course study provided a thorough characterization of the adaptation of skeletal muscle during unloading in C57BL/6 mice, and baseline data for comparison to and evaluation of subsequent studies. Time points defining the on-set and endpoints of disuse muscle atrophy were identified to enable characterization of rapid vs. long-term responses of skeletal muscle to hindlimb suspension. Unloading-induced atrophy primarily resulted from increased protein

Purinergic receptors expressed in human skeletal muscle fibres

DEFF Research Database (Denmark)

Bornø, A; Ploug, Thorkil; Bune, L T

2012-01-01

distribution of purinergic receptors in skeletal muscle fibres. We speculate that the intracellular localization of purinergic receptors may reflect a role in regulation of muscle metabolism; further studies are nevertheless needed to determine the function of the purinergic system in skeletal muscle cells.......Purinergic receptors are present in most tissues and thought to be involved in various signalling pathways, including neural signalling, cell metabolism and local regulation of the microcirculation in skeletal muscles. The present study aims to determine the distribution and intracellular content...... of purinergic receptors in skeletal muscle fibres in patients with type 2 diabetes and age-matched controls. Muscle biopsies from vastus lateralis were obtained from six type 2 diabetic patients and seven age-matched controls. Purinergic receptors were analysed using light and confocal microscopy...

Skeletal muscle proteomic signature and metabolic impairment in pulmonary hypertension.

Science.gov (United States)

Malenfant, Simon; Potus, François; Fournier, Frédéric; Breuils-Bonnet, Sandra; Pflieger, Aude; Bourassa, Sylvie; Tremblay, Ève; Nehmé, Benjamin; Droit, Arnaud; Bonnet, Sébastien; Provencher, Steeve

2015-05-01

Exercise limitation comes from a close interaction between cardiovascular and skeletal muscle impairments. To better understand the implication of possible peripheral oxidative metabolism dysfunction, we studied the proteomic signature of skeletal muscle in pulmonary arterial hypertension (PAH). Eight idiopathic PAH patients and eight matched healthy sedentary subjects were evaluated for exercise capacity, skeletal muscle proteomic profile, metabolism, and mitochondrial function. Skeletal muscle proteins were extracted, and fractioned peptides were tagged using an iTRAQ protocol. Proteomic analyses have documented a total of 9 downregulated proteins in PAH skeletal muscles and 10 upregulated proteins compared to healthy subjects. Most of the downregulated proteins were related to mitochondrial structure and function. Focusing on skeletal muscle metabolism and mitochondrial health, PAH patients presented a decreased expression of oxidative enzymes (pyruvate dehydrogenase, p metabolism in PAH skeletal muscles. We provide evidences that impaired mitochondrial and metabolic functions found in the lungs and the right ventricle are also present in skeletal muscles of patients. • Proteomic and metabolic analysis show abnormal oxidative metabolism in PAH skeletal muscle. • EM of PAH patients reveals abnormal mitochondrial structure and distribution. • Abnormal mitochondrial health and function contribute to exercise impairments of PAH. • PAH may be considered a vascular affliction of heart and lungs with major impact on peripheral muscles.

Dynamics of the Skeletal Muscle Secretome during Myoblast Differentiation

DEFF Research Database (Denmark)

Henningsen, Jeanette; Rigbolt, Kristoffer T G; Blagoev, Blagoy

2010-01-01

During recent years, increased efforts have focused on elucidating the secretory function of skeletal muscle. Through secreted molecules, skeletal muscle affects local muscle biology in an auto/paracrine manner as well as having systemic effects on other tissues. Here we used a quantitative...... proteomics platform to investigate the factors secreted during the differentiation of murine C2C12 skeletal muscle cells. Using triple encoding stable isotope labeling by amino acids in cell culture, we compared the secretomes at three different time points of muscle differentiation and followed the dynamics...... of the skeletal muscle as a prominent secretory organ. In addition to previously reported molecules, we identified many secreted proteins that have not previously been shown to be released from skeletal muscle cells nor shown to be differentially released during the process of myogenesis. We found 188...

Molecular Signals and Skeletal Muscle Adaptation to Exercise

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Mark Wilson

2013-09-01

Full Text Available The phenotypic plasticity of skeletal muscle affords a considerable degree of adaptability not seen in other bodily tissues. The mechanical properties of skeletal muscle are highly dependent on loading conditions. The extent of skeletal muscle plasticity is distinctly highlighted by a loss of muscle mass, or atrophy, after a period of reduced weight-bearing activity, for example during periods of extended bed rest, space flight and in spinal cord injury. On the other hand, increased mechanical loading, or resistance training, induces muscle growth, or hypertrophy. Endurance exercise performance is also dependent on the adaptability of skeletal muscle, especially muscles that contribute to posture, locomotion and the mechanics of breathing.  However, the molecular pathways governing skeletal muscle adaptations are yet to be satisfactorily delineated and require further investigation. Researchers in the areas of exercise physiology, physiotherapy and sports medicine are endeavoring to translate experimental knowledge into effective, innovative treatments and regimens in order to improve physical performance and health in both elite athletes and the general community. The efficacy of the translation of molecular biological paradigms in experimental exercise physiology has long been underappreciated. Indeed, molecular biology tools can now be used to answer questions regarding skeletal muscle adaptation in response to exercise and provide new frameworks to improve physical performance. Furthermore, transgenic animal models, knockout animal models and in vivo studies provide tools to test questions concerned with how exercise initiates adaptive changes in gene expression. In light of these perceived deficiencies, an attempt is made here to elucidate the molecular mechanisms of skeletal muscle adaptation to exercise. An examination will be made of the functional capacity of skeletal muscle to respond to a variety of exercise conditions, namely

Molecular Signals and Skeletal Muscle Adaptation to Exercise

Directory of Open Access Journals (Sweden)

Mark Wilson

2013-08-01

Full Text Available The phenotypic plasticity of skeletal muscle affords a considerable degree of adaptability not seen in other bodily tissues. The mechanical properties of skeletal muscle are highly dependent on loading conditions. The extent of skeletal muscle plasticity is distinctly highlighted by a loss of muscle mass, or atrophy, after a period of reduced weight-bearing activity, for example during periods of extended bed rest, space flight and in spinal cord injury. On the other hand, increased mechanical loading, or resistance training, induces muscle growth, or hypertrophy. Endurance exercise performance is also dependent on the adaptability of skeletal muscle, especially muscles that contribute to posture, locomotion and the mechanics of breathing. However, the molecular pathways governing skeletal muscle adaptations are yet to be satisfactorily delineated and require further investigation. Researchers in the areas of exercise physiology, physiotherapy and sports medicine are endeavoring to translate experimental knowledge into effective, innovative treatments and regimens in order to improve physical performance and health in both elite athletes and the general community. The efficacy of the translation of molecular biological paradigms in experimental exercise physiology has long been underappreciated. Indeed, molecular biology tools can now be used to answer questions regarding skeletal muscle adaptation in response to exercise and provide new frameworks to improve physical performance. Furthermore, transgenic animal models, knockout animal models and in vivo studies provide tools to test questions concerned with how exercise initiates adaptive changes in gene expression. In light of these perceived deficiencies, an attempt is made here to elucidate the molecular mechanisms of skeletal muscle adaptation to exercise. An examination will be made of the functional capacity of skeletal muscle to respond to a variety of exercise conditions, namely

Treatment with the anti-IL-6 receptor antibody attenuates muscular dystrophy via promoting skeletal muscle regeneration in dystrophin-/utrophin-deficient mice.

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Wada, Eiji; Tanihata, Jun; Iwamura, Akira; Takeda, Shin'ichi; Hayashi, Yukiko K; Matsuda, Ryoichi

2017-10-27

Chronic increases in the levels of the inflammatory cytokine interleukin-6 (IL-6) in serum and skeletal muscle are thought to contribute to the progression of muscular dystrophy. Dystrophin/utrophin double-knockout (dKO) mice develop a more severe and progressive muscular dystrophy than the mdx mice, the most common murine model of Duchenne muscular dystrophy (DMD). In particular, dKO mice have smaller body sizes and muscle diameters, and develop progressive kyphosis and fibrosis in skeletal and cardiac muscles. As mdx mice and DMD patients, we found that IL-6 levels in the skeletal muscle were significantly increased in dKO mice. Thus, in this study, we aimed to analyze the effects of IL-6 receptor (IL-6R) blockade on the muscle pathology of dKO mice. Male dKO mice were administered an initial injection (200 mg/kg intraperitoneally (i.p.)) of either the anti-IL-6R antibody MR16-1 or an isotype-matched control rat IgG at the age of 14 days, and were then given weekly injections (25 mg/kg i.p.) until 90 days of age. Treatment of dKO mice with the MR16-1 antibody successfully inhibited the IL-6 pathway in the skeletal muscle and resulted in a significant reduction in the expression levels of phosphorylated signal transducer and activator of transcription 3 in the skeletal muscle. Pathologically, a significant increase in the area of embryonic myosin heavy chain-positive myofibers and muscle diameter, and reduced fibrosis in the quadriceps muscle were observed. These results demonstrated the therapeutic effects of IL-6R blockade on promoting muscle regeneration. Consistently, serum creatine kinase levels were decreased. Despite these improvements observed in the limb muscles, degeneration of the diaphragm and cardiac muscles was not ameliorated by the treatment of mice with the MR16-1 antibody. As no adverse effects of treatment with the MR16-1 antibody were observed, our results indicate that the anti-IL-6R antibody is a potential therapy for muscular dystrophy

Exercise Promotes Healthy Aging of Skeletal Muscle

DEFF Research Database (Denmark)

Cartee, Gregory D; Hepple, Russell T; Bamman, Marcas M

2016-01-01

caused by diseases and lifestyle factors. Secondary aging can exacerbate deficits in mitochondrial function and muscle mass, concomitant with the development of skeletal muscle insulin resistance. Exercise opposes deleterious effects of secondary aging by preventing the decline in mitochondrial...... respiration, mitigating aging-related loss of muscle mass and enhancing insulin sensitivity. This review focuses on mechanisms by which exercise promotes "healthy aging" by inducing modifications in skeletal muscle....

Measurement of skeletal muscle collagen breakdown by microdialysis

DEFF Research Database (Denmark)

Miller, B F; Ellis, D; Robinson, M M

2011-01-01

Exercise increases the synthesis of collagen in the extracellular matrix of skeletal muscle. Breakdown of skeletal muscle collagen has not yet been determined because of technical limitations. The purpose of the present study was to use local sampling to determine skeletal muscle collagen breakdown...... collagen breakdown 17–21 h post-exercise, and our measurement of OHP using GC–MS was in agreement with traditional assays....

Intraurethral Injection of Autologous Minced Skeletal Muscle

DEFF Research Database (Denmark)

Gräs, Søren; Klarskov, Niels; Lose, Gunnar

2014-01-01

noted. CONCLUSIONS: Intraurethral injection of minced autologous muscle tissue is a simple surgical procedure that appears safe and moderately effective in women with uncomplicated stress urinary incontinence. It compares well to a more complicated regenerative strategy using in vitro expanded muscle......PURPOSE: Intraurethral injection of in vitro expanded autologous skeletal muscle derived cells is a new regenerative therapy for stress urinary incontinence. We examined the efficacy and safety of a simpler alternative strategy using freshly harvested, minced autologous skeletal muscle tissue...... with its inherent content of regenerative cells. MATERIALS AND METHODS: A total of 20 and 15 women with uncomplicated and complicated stress urinary incontinence, respectively, received intraurethral injections of minced autologous skeletal muscle tissue and were followed for 1 year. Efficacy was assessed...

Disease-Induced Skeletal Muscle Atrophy and Fatigue

NARCIS (Netherlands)

Powers, Scott K.; Lynch, Gordon S.; Murphy, Kate T.; Reid, Michael B.; Zijdewind, Inge

2016-01-01

Numerous health problems including acute critical illness, cancer, diseases associated with chronic inflammation, and neurological disorders often result in skeletal muscle weakness and fatigue. Disease-related muscle atrophy and fatigue is an important clinical problem because acquired skeletal

A metabolic link to skeletal muscle wasting and regeneration

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René eKoopman

2014-02-01

Full Text Available Due to its essential role in movement, insulating the internal organs, generating heat to maintain core body temperature, and acting as a major energy storage depot, any impairment to skeletal muscle structure and function may lead to an increase in both morbidity and mortality. In the context of skeletal muscle, altered metabolism is directly associated with numerous pathologies and disorders, including diabetes, and obesity, while many skeletal muscle pathologies have secondary changes in metabolism, including cancer cachexia, sarcopenia and the muscular dystrophies. Furthermore, the importance of cellular metabolism in the regulation of skeletal muscle stem cells is beginning to receive significant attention. Thus, it is clear that skeletal muscle metabolism is intricately linked to the regulation of skeletal muscle mass and regeneration. The aim of this review is to discuss some of the recent findings linking a change in metabolism to changes in skeletal muscle mass, as well as describing some of the recent studies in developmental, cancer and stem-cell biology that have identified a role for cellular metabolism in the regulation of stem cell function, a process termed ‘metabolic reprogramming’.

Skeletal Muscle Angiogenesis and Its Relation to Insulin Sensitivity

DEFF Research Database (Denmark)

Lindqvist, Anna Maria Charlotte K

mediator of angiogenesis) are reduced in insulin resistant individuals. Exercise training can improve skeletal muscle capillarization and the angiogenic potential and physical activity has also been proven to enhance muscle insulin sensitivity. Increased skeletal muscle capillarization is associated......) or by overexpression of VEGF-A in the tibialis anterior muscle (transfection; study II) and the effect of the increased muscle capillarization on muscle insulin sensitivity was examined. In study I skeletal muscle specific angiogenesis was induced by administering an α1-adrenergic antagonist (prazosin) to healthy...

Deer Antler Extract Improves Fatigue Effect through Altering the Expression of Genes Related to Muscle Strength in Skeletal Muscle of Mice

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Jaw-Chyun Chen

2014-01-01

Full Text Available Deer antler is a well-known traditional Chinese medicine used in Asian countries for the tonic and the improvement of aging symptoms. The present study was designed to investigate the antifatigue effect and mechanism of Formosan sambar deer tip antler extract (FSDTAE. The swimming times to exhaustion of mice administered FSDTAE (8.2 mg/day for 28 days were apparently longer than those of the vehicle-treated mice in forced swim test. However, the indicators of fatigue, such as the reduction in glucose level and the increases in blood urea nitrogen and lactic acid levels, were not significantly inhibited by FSDTAE. Therefore, microarray analysis was further used to examine the anti-fatigue mechanism of FSDTAE. We selected genes with fold changes >2 or <−2 in skeletal muscle for pathway analysis. FSDTAE-affected genes were involved in 9 different signaling pathways, such as GnRH signaling pathway and insulin signaling pathway. All of the significantly expressed genes were classified into 8 different categories by their functions. The most enriched category was muscular system, and 6 upregulated genes, such as troponin I, troponin T1, cysteine and glycine-rich protein 2, myosin heavy polypeptide 7, tropomyosin 2, and myomesin family member 3, were responsible for the development and contraction of muscle. Real-time PCR analysis indicated that FSDTAE increased troponins mRNA expression in skeletal muscle. In conclusion, our findings suggested that FSDTAE might increase the muscle strength through the upregulation of genes responsible for muscle contraction and consequently exhibited the anti-fatigue effect in mice.

Effects of the belt electrode skeletal muscle electrical stimulation system on lower extremity skeletal muscle activity: Evaluation using positron emission tomography.

Science.gov (United States)

Numata, Hitoaki; Nakase, Junsuke; Inaki, Anri; Mochizuki, Takafumi; Oshima, Takeshi; Takata, Yasushi; Kinuya, Seigo; Tsuchiya, Hiroyuki

2016-01-01

Lower-extremity muscle weakness in athletes after lower limb trauma or surgery can hinder their return to sports, and the associated muscle atrophy may lead to deterioration in performance after returning to sports. Recently, belt electrode skeletal muscle electrical stimulation (B-SES) which can contract all the lower limb skeletal muscles simultaneously was developed. However, no study has evaluated skeletal muscle activity with B-SES. Since only superficial muscles as well as a limited number of muscles can be investigated using electromyography, we investigated whether positron emission tomography (PET) can evaluate the activity of all the skeletal muscles in the body simultaneously. The purpose of this study was to evaluate the effectiveness of the B-SES system using PET. Twelve healthy males (mean age, 24.3 years) were divided into two groups. The subjects in the control group remained in a sitting position for 10 min, and [(18)F] fluorodeoxyglucose (FDG) was intravenously injected. In the exercise group, subjects exercised using the B-SES system for 20 min daily for three consecutive days as a pre-test exercise. On the measurement day, they exercised for 10 min, received an injection of FDG, and exercised for another 10 min. PET-computed tomography images were obtained in each group 60 min after the FDG injection. Regions of interest were drawn in each lower-extremity muscle. We compared each skeletal muscle metabolism using the standardized uptake value. In the exercise group, FDG accumulation in the gluteus maximus, gluteus medius, gluteus minimus, quadriceps femoris, sartorius, and hamstrings was significantly higher than the muscles in the control (P skeletal muscle activity of the gluteal muscles as well as the most lower-extremity muscles simultaneously. Copyright © 2015 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved.

Regulation of an antisense RNA with the transition of neonatal to IIb myosin heavy chain during postnatal development and hypothyroidism in rat skeletal muscle.

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Pandorf, Clay E; Jiang, Weihua; Qin, Anqi X; Bodell, Paul W; Baldwin, Kenneth M; Haddad, Fadia

2012-04-01

Postnatal development of fast skeletal muscle is characterized by a transition in expression of myosin heavy chain (MHC) isoforms, from primarily neonatal MHC at birth to primarily IIb MHC in adults, in a tightly coordinated manner. These isoforms are encoded by distinct genes, which are separated by ∼17 kb on rat chromosome 10. The neonatal-to-IIb MHC transition is inhibited by a hypothyroid state. We examined RNA products [mRNA, pre-mRNA, and natural antisense transcript (NAT)] of developmental and adult-expressed MHC genes (embryonic, neonatal, I, IIa, IIx, and IIb) at 2, 10, 20, and 40 days after birth in normal and thyroid-deficient rat neonates treated with propylthiouracil. We found that a long noncoding antisense-oriented RNA transcript, termed bII NAT, is transcribed from a site within the IIb-Neo intergenic region and across most of the IIb MHC gene. NATs have previously been shown to mediate transcriptional repression of sense-oriented counterparts. The bII NAT is transcriptionally regulated during postnatal development and in response to hypothyroidism. Evidence for a regulatory mechanism is suggested by an inverse relationship between IIb MHC and bII NAT in normal and hypothyroid-treated muscle. Neonatal MHC transcription is coordinately expressed with bII NAT. A comparative phylogenetic analysis also suggests that bII NAT-mediated regulation has been a conserved trait of placental mammals for most of the eutherian evolutionary history. The evidence in support of the regulatory model implicates long noncoding antisense RNA as a mechanism to coordinate the transition between neonatal and IIb MHC during postnatal development.

An optimized histochemical method to assess skeletal muscle glycogen and lipid stores reveals two metabolically distinct populations of type I muscle fibers

DEFF Research Database (Denmark)

Prats Gavalda, Clara; Gomez-Cabello, Alba; Nordby, Pernille

2013-01-01

Skeletal muscle energy metabolism has been a research focus of physiologists for more than a century. Yet, how the use of intramuscular carbohydrate and lipid energy stores are coordinated during different types of exercise remains a subject of debate. Controversy arises from contradicting data...... preservation of muscle energy stores, air drying cryosections or cycles of freezing-thawing need to be avoided. Furthermore, optimization of the imaging settings in order to specifically image intracellular lipid droplets stained with oil red O or Bodipy-493/503 is shown. When co-staining lipid droplets...... distinct myosin heavy chain I expressing fibers: I-1 fibers have a smaller crossectional area, a higher density of lipid droplets, and a tendency to lower glycogen content compared to I-2 fibers. Type I-2 fibers have similar lipid content than IIA. Exhaustive exercise lead to glycogen depletion in type IIA...

Role of skeletal muscle in lung development.

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Baguma-Nibasheka, Mark; Gugic, Dijana; Saraga-Babic, Mirna; Kablar, Boris

2012-07-01

Skeletal (striated) muscle is one of the four basic tissue types, together with the epithelium, connective and nervous tissues. Lungs, on the other hand, develop from the foregut and among various cell types contain smooth, but not skeletal muscle. Therefore, during earlier stages of development, it is unlikely that skeletal muscle and lung depend on each other. However, during the later stages of development, respiratory muscle, primarily the diaphragm and the intercostal muscles, execute so called fetal breathing-like movements (FBMs), that are essential for lung growth and cell differentiation. In fact, the absence of FBMs results in pulmonary hypoplasia, the most common cause of death in the first week of human neonatal life. Most knowledge on this topic arises from in vivo experiments on larger animals and from various in vitro experiments. In the current era of mouse mutagenesis and functional genomics, it was our goal to develop a mouse model for pulmonary hypoplasia. We employed various genetically engineered mice lacking different groups of respiratory muscles or lacking all the skeletal muscle and established the criteria for pulmonary hypoplasia in mice, and therefore established a mouse model for this disease. We followed up this discovery with systematic subtractive microarray analysis approach and revealed novel functions in lung development and disease for several molecules. We believe that our approach combines elements of both in vivo and in vitro approaches and allows us to study the function of a series of molecules in the context of lung development and disease and, simultaneously, in the context of lung's dependence on skeletal muscle-executed FBMs.

Satellite cells in human skeletal muscle plasticity

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Tim eSnijders

2015-10-01

Full Text Available Skeletal muscle satellite cells are considered to play a crucial role in muscle fiber maintenance, repair and remodelling. Our knowledge of the role of satellite cells in muscle fiber adaptation has traditionally relied on in vitro cell and in vivo animal models. Over the past decade, a genuine effort has been made to translate these results to humans under physiological conditions. Findings from in vivo human studies suggest that satellite cells play a key role in skeletal muscle fiber repair/remodelling in response to exercise. Mounting evidence indicates that aging has a profound impact on the regulation of satellite cells in human skeletal muscle. Yet, the precise role of satellite cells in the development of muscle fiber atrophy with age remains unresolved. This review seeks to integrate recent results from in vivo human studies on satellite cell function in muscle fiber repair/remodelling in the wider context of satellite cell biology whose literature is largely based on animal and cell models.

Satellite cells in human skeletal muscle plasticity.

Science.gov (United States)

Snijders, Tim; Nederveen, Joshua P; McKay, Bryon R; Joanisse, Sophie; Verdijk, Lex B; van Loon, Luc J C; Parise, Gianni

2015-01-01

Skeletal muscle satellite cells are considered to play a crucial role in muscle fiber maintenance, repair and remodeling. Our knowledge of the role of satellite cells in muscle fiber adaptation has traditionally relied on in vitro cell and in vivo animal models. Over the past decade, a genuine effort has been made to translate these results to humans under physiological conditions. Findings from in vivo human studies suggest that satellite cells play a key role in skeletal muscle fiber repair/remodeling in response to exercise. Mounting evidence indicates that aging has a profound impact on the regulation of satellite cells in human skeletal muscle. Yet, the precise role of satellite cells in the development of muscle fiber atrophy with age remains unresolved. This review seeks to integrate recent results from in vivo human studies on satellite cell function in muscle fiber repair/remodeling in the wider context of satellite cell biology whose literature is largely based on animal and cell models.

Leucine stimulation of skeletal muscle protein synthesis

International Nuclear Information System (INIS)

Layman, D.K.; Grogan, C.K.

1986-01-01

Previous work in this laboratory has demonstrated a stimulatory effect of leucine on skeletal muscle protein synthesis measured in vitro during catabolic conditions. Studies in other laboratories have consistently found this effect in diaphragm muscle, however, studies examining effects on nitrogen balance or with in vivo protein synthesis in skeletal muscle are equivocal. This experiment was designed to determine the potential of leucine to stimulate skeletal muscle protein synthesis in vivo. Male Sprague-Dawley rats weighing 200 g were fasted for 12 hrs, anesthetized, a jugular cannula inserted, and protein synthesis measured using a primed continuous infusion of 14 C-tyrosine. A plateau in specific activity was reached after 30 to 60 min and maintained for 3 hrs. The leucine dose consisted of a 240 umole priming dose followed by a continuous infusion of 160 umoles/hr. Leucine infusion stimulated protein synthesis in the soleus muscle (28%) and in the red (28%) and white portions (12%) of the gastrocnemius muscle compared with controls infused with only tyrosine. The increased rates of protein synthesis were due to increased incorporation of tyrosine into protein and to decreased specific activity of the free tyrosine pool. These data indicate that infusion of leucine has the potential to stimulate in vivo protein synthesis in skeletal muscles

Cardiac, Skeletal, and smooth muscle mitochondrial respiration

DEFF Research Database (Denmark)

Park, Song-Young; Gifford, Jayson R; Andtbacka, Robert H I

2014-01-01

, skeletal, and smooth muscle was harvested from a total of 22 subjects (53±6 yrs) and mitochondrial respiration assessed in permeabilized fibers. Complex I+II, state 3 respiration, an index of oxidative phosphorylation capacity, fell progressively from cardiac, skeletal, to smooth muscle (54±1; 39±4; 15......±1 pmol•s(-1)•mg (-1), prespiration rates were normalized by CS (respiration...... per mitochondrial content), oxidative phosphorylation capacity was no longer different between the three muscle types. Interestingly, Complex I state 2 normalized for CS activity, an index of non-phosphorylating respiration per mitochondrial content, increased progressively from cardiac, skeletal...

Skeletal muscle myotubes of the severely obese exhibit altered ubiquitin-proteasome and autophagic/lysosomal proteolytic flux

Science.gov (United States)

Bollinger, Lance M.; Powell, Jonathan J. S.; Houmard, Joseph A.; Witczak, Carol A.; Brault, Jeffrey J.

2015-01-01

Objective Whole-body protein metabolism is dysregulated with obesity. Our goal was to determine if activity and expression of major protein degradation pathways are compromised specifically in human skeletal muscle with obesity. Methods We utilized primary Human Skeletal Muscle cell (HSkM) cultures since cellular mechanisms can be studied absent of hormones and contractile activity that could independently influence metabolism. HSkM from 10 lean (BMI ≤ 26.0 kg/m2) and 8 severely obese (BMI ≥ 39.0) women were examined basally and when stimulated to atrophy (serum and amino acid starvation). Results HSkM from obese donors had a lower proportion of type I myosin heavy chain and slower flux through the autophagic/lysosomal pathway. During starvation, flux through the ubiquitin-proteasome system diverged according to obesity status, with a decrease in the lean and an increase in HSkM from obese subjects. HSkMC from the obese also displayed elevated proteasome activity despite no difference in proteasome content. Atrophy-related gene expression and myotube area were similar in myotubes derived from lean and obese individuals under basal and starved conditions. Conclusions Our data indicate that muscle cells of the lean and severely obese have innate differences in management of protein degradation, which may explain their metabolic differences. PMID:26010327

The effect of transcutaneous application of carbon dioxide (CO2) on skeletal muscle

International Nuclear Information System (INIS)

Oe, Keisuke; Ueha, Takeshi; Sakai, Yoshitada; Niikura, Takahiro; Lee, Sang Yang; Koh, Akihiro; Hasegawa, Takumi; Tanaka, Masaya; Miwa, Masahiko; Kurosaka, Masahiro

2011-01-01

Highlights: → PGC-1α is up-regulated as a result of exercise such as mitochondrial biogenesis and muscle fiber-type switching, and up-regulation of VEGF. → We demonstrated transcutaneous application of CO 2 up-regulated the gene expression of PGC-1α, SIRT1 and VEGF, and instance of muscle fiber switching. → Transcutaneous application of CO 2 may cause similar effect to aerobic exercise in skeletal muscle. -- Abstract: In Europe, carbon dioxide therapy has been used for cardiac disease and skin problems for a long time. However there have been few reports investigating the effects of carbon dioxide therapy on skeletal muscle. Peroxisome proliferators-activated receptor (PPAR)-gamma coactivator-1 (PGC-1α) is up-regulated as a result of exercise and mediates known responses to exercise, such as mitochondrial biogenesis and muscle fiber-type switching, and neovascularization via up-regulation of vascular endothelial growth factor (VEGF). It is also known that silent mating type information regulation 2 homologs 1 (SIRT1) enhances PGC-1α-mediated muscle fiber-type switching. Previously, we demonstrated transcutaneous application of CO 2 increased blood flow and a partial increase of O 2 pressure in the local tissue known as the Bohr effect. In this study, we transcutaneously applied CO 2 to the lower limbs of rats, and investigated the effect on the fast muscle, tibialis anterior (TA) muscle. The transcutaneous CO 2 application caused: (1) the gene expression of PGC-1α, silent mating type information regulation 2 homologs 1 (SIRT1) and VEGF, and increased the number of mitochondria, as proven by real-time PCR and immunohistochemistry, (2) muscle fiber switching in the TA muscle, as proven by isolation of myosin heavy chain and ATPase staining. Our results suggest the transcutaneous application of CO 2 may have therapeutic potential for muscular strength recovery resulting from disuse atrophy in post-operative patients and the elderly population.

Erythropoietin receptor in human skeletal muscle and the effects of acute and long-term injections with recombinant human erythropoietin on the skeletal muscle

DEFF Research Database (Denmark)

Lundby, Carsten; Hellsten, Ylva; Jensen, Mie B. F.

2008-01-01

The presence and potential physiological role of the erythropoietin receptor (Epo-R) were examined in human skeletal muscle. In this study we demonstrate that Epo-R is present in the endothelium, smooth muscle cells, and in fractions of the sarcolemma of skeletal muscle fibers. To study...... the potential effects of Epo in human skeletal muscle, two separate studies were conducted: one to study the acute effects of a single Epo injection on skeletal muscle gene expression and plasma hormones and another to study the effects of long-term (14 wk) Epo treatment on skeletal muscle structure. Subjects...... was studied in subjects (n = 8) who received long-term Epo administration, and muscle biopsies were obtained before and after. Epo treatment did not alter mean fiber area (0.84 +/- 0.2 vs. 0.72 +/- 0.3 mm(2)), capillaries per fiber (4.3 +/- 0.5 vs. 4.4 +/- 1.3), or number of proliferating endothelial cells...

Comparative decline of the protein profiles of nebulin in response to denervation in skeletal muscle

Energy Technology Data Exchange (ETDEWEB)

Wei, Jih-Hua [Department of Internal Medicine, Min-Sheng General Hospital, Taoyuan, Taiwan (China); Chang, Nen-Chung [Division of Cardiology, Department of Internal Medicine, College of Medicine, Taipei Medical University Hospital, Taipei, Taiwan (China); Chen, Sy-Ping [Department of Nursing, Chang Gung University of Science and Technology, Taoyuan, Taiwan (China); Geraldine, Pitchairaj [Department of Animal Science, School of Life Sciences, Bharathidasan University, Tiruchirappalli, Tamil Nadu (India); Jayakumar, Thanasekaran, E-mail: tjaya_2002@yahoo.co.in [Department of Pharmacology and Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan (China); Fong, Tsorng-Harn, E-mail: thfong@tmu.edu.tw [Department of Anatomy and Cell Biology, College of Medicine, Taipei Medical University, Taipei, Taiwan (China)

2015-10-09

The sliding filament model of the sarcomere was developed more than half a century ago. This model, consisting only of thin and thick filaments, has been efficacious in elucidating many, but not all, features of skeletal muscle. Work during the 1980s revealed the existence of two additional filaments: the giant filamentous proteins titin and nebulin. Nebulin, a giant myofibrillar protein, acts as a protein ruler to maintain the lattice arrays of thin filaments and plays a role in signal transduction and contractile regulation. However, the change of nebulin and its effect on thin filaments in denervation-induced atrophic muscle remains unclear. The purpose of this study is to examine the content and pattern of nebulin, myosin heavy chain (MHC), actin, and titin in innervated and denervated tibialis anterior (TA) muscles of rats using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), densitometry and electron microscopic (EM) analyses. The results revealed that denervation induced muscle atrophy is accompanied by decreased nebulin content in a time-dependent manner. For instant, the levels of nebulin in denervated muscles were markedly (P < 0.05) decreased, about 24.6% and 40.2% in comparison with innervated muscle after denervation of 28 and 56 days, respectively. The nebulin/MHC, nebulin/actin, and nebulin/titin ratios were decreased, suggesting a concomitant reduction of nebulin in denervated muscle. Moreover, a western blotting assay proved that nebulin declined faster than titin on 28 and 56 days of denervated muscle. In addition, EM study revealed that the disturbed arrangements of myofilaments and a disorganized contractile apparatus were also observed in denervated muscle. Overall, the present study provides evidence that nebulin is more sensitive to the effect of denervation than MHC, actin, and titin. Nebulin decline indeed resulted in disintegrate of thin filaments and shortening of sarcomeres. - Highlights: • We successfully

Alternative S2 Hinge Regions of the Myosin Rod Affect Myofibrillar Structure and Myosin Kinetics

Energy Technology Data Exchange (ETDEWEB)

Miller, Mark S.; Dambacher, Corey M.; Knowles, Aileen F.; Braddock, Joan M.; Farman, Gerrie P.; Irving, Thomas C.; Swank, Douglas M.; Bernstein, Sanford I.; Maughan, David W.; (RPI); (IIT); (SDSU); (Vermont)

2009-07-01

The subfragment 2/light meromyosin 'hinge' region has been proposed to significantly contribute to muscle contraction force and/or speed. Transgenic replacement of the endogenous fast muscle isovariant hinge A (exon 15a) in Drosophila melanogaster indirect flight muscle with the slow muscle hinge B (exon 15b) allows examination of the structural and functional changes when only this region of the myosin molecule is different. Hinge B was previously shown to increase myosin rod length, increase A-band and sarcomere length, and decrease flight performance compared to hinge A. We applied additional measures to these transgenic lines to further evaluate the consequences of modifying this hinge region. Structurally, the longer A-band and sarcomere lengths found in the hinge B myofibrils appear to be due to the longitudinal addition of myosin heads. Functionally, hinge B, although a significant distance from the myosin catalytic domain, alters myosin kinetics in a manner consistent with this region increasing myosin rod length. These structural and functional changes combine to decrease whole fly wing-beat frequency and flight performance. Our results indicate that this hinge region plays an important role in determining myosin kinetics and in regulating thick and thin filament lengths as well as sarcomere length.

Photothermal imaging of skeletal muscle mitochondria.

Science.gov (United States)

Tomimatsu, Toru; Miyazaki, Jun; Kano, Yutaka; Kobayashi, Takayoshi

2017-06-01

The morphology and topology of mitochondria provide useful information about the physiological function of skeletal muscle. Previous studies of skeletal muscle mitochondria are based on observation with transmission, scanning electron microscopy or fluorescence microscopy. In contrast, photothermal (PT) microscopy has advantages over the above commonly used microscopic techniques because of no requirement for complex sample preparation by fixation or fluorescent-dye staining. Here, we employed the PT technique using a simple diode laser to visualize skeletal muscle mitochondria in unstained and stained tissues. The fine mitochondrial network structures in muscle fibers could be imaged with the PT imaging system, even in unstained tissues. PT imaging of tissues stained with toluidine blue revealed the structures of subsarcolemmal (SS) and intermyofibrillar (IMF) mitochondria and the swelling behavior of mitochondria in damaged muscle fibers with sufficient image quality. PT image analyses based on fast Fourier transform (FFT) and Grey-level co-occurrence matrix (GLCM) were performed to derive the characteristic size of mitochondria and to discriminate the image patterns of normal and damaged fibers.

TAK1 regulates skeletal muscle mass and mitochondrial function

Science.gov (United States)

Hindi, Sajedah M.; Sato, Shuichi; Xiong, Guangyan; Bohnert, Kyle R.; Gibb, Andrew A.; Gallot, Yann S.; McMillan, Joseph D.; Hill, Bradford G.

2018-01-01

Skeletal muscle mass is regulated by a complex array of signaling pathways. TGF-β–activated kinase 1 (TAK1) is an important signaling protein, which regulates context-dependent activation of multiple intracellular pathways. However, the role of TAK1 in the regulation of skeletal muscle mass remains unknown. Here, we report that inducible inactivation of TAK1 causes severe muscle wasting, leading to kyphosis, in both young and adult mice.. Inactivation of TAK1 inhibits protein synthesis and induces proteolysis, potentially through upregulating the activity of the ubiquitin-proteasome system and autophagy. Phosphorylation and enzymatic activity of AMPK are increased, whereas levels of phosphorylated mTOR and p38 MAPK are diminished upon inducible inactivation of TAK1 in skeletal muscle. In addition, targeted inactivation of TAK1 leads to the accumulation of dysfunctional mitochondria and oxidative stress in skeletal muscle of adult mice. Inhibition of TAK1 does not attenuate denervation-induced muscle wasting in adult mice. Finally, TAK1 activity is highly upregulated during overload-induced skeletal muscle growth, and inactivation of TAK1 prevents myofiber hypertrophy in response to functional overload. Overall, our study demonstrates that TAK1 is a key regulator of skeletal muscle mass and oxidative metabolism. PMID:29415881

Primary sacrococcygeal chordoma with unusual skeletal muscle metastasis

Directory of Open Access Journals (Sweden)

Lisa Vu, MD

2014-01-01

Full Text Available Chordomas are rare neoplasms that do not often metastasize. Of the small percent that do metastasize, they very infrequently involve skeletal muscle. Only a few cases of skeletal muscle metastases have been reported in the literature. We report an unusual case of a patient with a primary sacrococcygeal chordoma who experienced a long period of remission but who subsequently developed recurrence and multiple metastatic lesions to skeletal muscles including the deltoid, triceps, and pectineus.

mTOR as a Key Regulator in Maintaining Skeletal Muscle Mass

Directory of Open Access Journals (Sweden)

Mee-Sup Yoon

2017-10-01

Full Text Available Maintenance of skeletal muscle mass is regulated by the balance between anabolic and catabolic processes. Mammalian target of rapamycin (mTOR is an evolutionarily conserved serine/threonine kinase, and is known to play vital roles in protein synthesis. Recent findings have continued to refine our understanding of the function of mTOR in maintaining skeletal muscle mass. mTOR controls the anabolic and catabolic signaling of skeletal muscle mass, resulting in the modulation of muscle hypertrophy and muscle wastage. This review will highlight the fundamental role of mTOR in skeletal muscle growth by summarizing the phenotype of skeletal-specific mTOR deficiency. In addition, the evidence that mTOR is a dual regulator of anabolism and catabolism in skeletal muscle mass will be discussed. A full understanding of mTOR signaling in the maintenance of skeletal muscle mass could help to develop mTOR-targeted therapeutics to prevent muscle wasting.

Angiotensin II Infusion Induces Marked Diaphragmatic Skeletal Muscle Atrophy

Science.gov (United States)

Rezk, Bashir M.; Yoshida, Tadashi; Semprun-Prieto, Laura; Higashi, Yusuke; Sukhanov, Sergiy; Delafontaine, Patrice

2012-01-01

Advanced congestive heart failure (CHF) and chronic kidney disease (CKD) are characterized by increased angiotensin II (Ang II) levels and are often accompanied by significant skeletal muscle wasting that negatively impacts mortality and morbidity. Both CHF and CKD patients have respiratory muscle dysfunction, however the potential effects of Ang II on respiratory muscles are unknown. We investigated the effects of Ang II on diaphragm muscle in FVB mice. Ang II induced significant diaphragm muscle wasting (18.7±1.6% decrease in weight at one week) and reduction in fiber cross-sectional area. Expression of the E3 ubiquitin ligases atrogin-1 and muscle ring finger-1 (MuRF-1) and of the pro-apoptotic factor BAX was increased after 24 h of Ang II infusion (4.4±0.3 fold, 3.1±0.5 fold and 1.6±0.2 fold, respectively, compared to sham infused control) suggesting increased muscle protein degradation and apoptosis. In Ang II infused animals, there was significant regeneration of injured diaphragm muscles at 7 days as indicated by an increase in the number of myofibers with centralized nuclei and high expression of embryonic myosin heavy chain (E-MyHC, 11.2±3.3 fold increase) and of the satellite cell marker M-cadherin (59.2±22.2% increase). Furthermore, there was an increase in expression of insulin-like growth factor-1 (IGF-1, 1.8±0.3 fold increase) in Ang II infused diaphragm, suggesting the involvement of IGF-1 in diaphragm muscle regeneration. Bone-marrow transplantation experiments indicated that although there was recruitment of bone-marrow derived cells to the injured diaphragm in Ang II infused mice (267.0±74.6% increase), those cells did not express markers of muscle stem cells or regenerating myofibers. In conclusion, Ang II causes marked diaphragm muscle wasting, which may be important for the pathophysiology of respiratory muscle dysfunction and cachexia in conditions such as CHF and CKD. PMID:22276172

Angiotensin II infusion induces marked diaphragmatic skeletal muscle atrophy.

Directory of Open Access Journals (Sweden)

Bashir M Rezk

Full Text Available Advanced congestive heart failure (CHF and chronic kidney disease (CKD are characterized by increased angiotensin II (Ang II levels and are often accompanied by significant skeletal muscle wasting that negatively impacts mortality and morbidity. Both CHF and CKD patients have respiratory muscle dysfunction, however the potential effects of Ang II on respiratory muscles are unknown. We investigated the effects of Ang II on diaphragm muscle in FVB mice. Ang II induced significant diaphragm muscle wasting (18.7±1.6% decrease in weight at one week and reduction in fiber cross-sectional area. Expression of the E3 ubiquitin ligases atrogin-1 and muscle ring finger-1 (MuRF-1 and of the pro-apoptotic factor BAX was increased after 24 h of Ang II infusion (4.4±0.3 fold, 3.1±0.5 fold and 1.6±0.2 fold, respectively, compared to sham infused control suggesting increased muscle protein degradation and apoptosis. In Ang II infused animals, there was significant regeneration of injured diaphragm muscles at 7 days as indicated by an increase in the number of myofibers with centralized nuclei and high expression of embryonic myosin heavy chain (E-MyHC, 11.2±3.3 fold increase and of the satellite cell marker M-cadherin (59.2±22.2% increase. Furthermore, there was an increase in expression of insulin-like growth factor-1 (IGF-1, 1.8±0.3 fold increase in Ang II infused diaphragm, suggesting the involvement of IGF-1 in diaphragm muscle regeneration. Bone-marrow transplantation experiments indicated that although there was recruitment of bone-marrow derived cells to the injured diaphragm in Ang II infused mice (267.0±74.6% increase, those cells did not express markers of muscle stem cells or regenerating myofibers. In conclusion, Ang II causes marked diaphragm muscle wasting, which may be important for the pathophysiology of respiratory muscle dysfunction and cachexia in conditions such as CHF and CKD.

Glucose transporter expression in human skeletal muscle fibers

DEFF Research Database (Denmark)

Gaster, M; Handberg, A; Beck-Nielsen, H

2000-01-01

, but its expression is markedly reduced around birth and is further reduced to undetectable levels within the first year of life; 2) GLUT-3 protein expression appears at 18 wk of gestation and disappears after birth; and 3) GLUT-4 protein is diffusely expressed in muscle cells throughout gestation, whereas...... after birth, the characteristic subcellular localization is as seen in adult muscle fibers. Our results show that GLUT-1, GLUT-3, and GLUT-4 seem to be of importance during muscle fiber growth and development. GLUT-5 protein was undetectable in fetal and adult skeletal muscle fibers. In adult muscle...... amplification (TSA) technique to detect the localization of glucose transporter expression in human skeletal muscle. We found expression of GLUT-1, GLUT-3, and GLUT-4 in developing human muscle fibers showing a distinct expression pattern. 1) GLUT-1 is expressed in human skeletal muscle cells during gestation...

The adipokine leptin increases skeletal muscle mass and significantly alters skeletal muscle miRNA expression profile in aged mice

International Nuclear Information System (INIS)

Hamrick, Mark W.; Herberg, Samuel; Arounleut, Phonepasong; He, Hong-Zhi; Shiver, Austin; Qi, Rui-Qun; Zhou, Li; Isales, Carlos M.

2010-01-01

Research highlights: → Aging is associated with muscle atrophy and loss of muscle mass, known as the sarcopenia of aging. → We demonstrate that age-related muscle atrophy is associated with marked changes in miRNA expression in muscle. → Treating aged mice with the adipokine leptin significantly increased muscle mass and the expression of miRNAs involved in muscle repair. → Recombinant leptin therapy may therefore be a novel approach for treating age-related muscle atrophy. -- Abstract: Age-associated loss of muscle mass, or sarcopenia, contributes directly to frailty and an increased risk of falls and fractures among the elderly. Aged mice and elderly adults both show decreased muscle mass as well as relatively low levels of the fat-derived hormone leptin. Here we demonstrate that loss of muscle mass and myofiber size with aging in mice is associated with significant changes in the expression of specific miRNAs. Aging altered the expression of 57 miRNAs in mouse skeletal muscle, and many of these miRNAs are now reported to be associated specifically with age-related muscle atrophy. These include miR-221, previously identified in studies of myogenesis and muscle development as playing a role in the proliferation and terminal differentiation of myogenic precursors. We also treated aged mice with recombinant leptin, to determine whether leptin therapy could improve muscle mass and alter the miRNA expression profile of aging skeletal muscle. Leptin treatment significantly increased hindlimb muscle mass and extensor digitorum longus fiber size in aged mice. Furthermore, the expression of 37 miRNAs was altered in muscles of leptin-treated mice. In particular, leptin treatment increased the expression of miR-31 and miR-223, miRNAs known to be elevated during muscle regeneration and repair. These findings suggest that aging in skeletal muscle is associated with marked changes in the expression of specific miRNAs, and that nutrient-related hormones such as leptin

The adipokine leptin increases skeletal muscle mass and significantly alters skeletal muscle miRNA expression profile in aged mice

Energy Technology Data Exchange (ETDEWEB)

Hamrick, Mark W., E-mail: mhamrick@mail.mcg.edu [Department of Cellular Biology and Anatomy, Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, GA (United States); Department of Orthopaedic Surgery, Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, GA (United States); Herberg, Samuel; Arounleut, Phonepasong [Department of Cellular Biology and Anatomy, Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, GA (United States); Department of Orthopaedic Surgery, Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, GA (United States); He, Hong-Zhi [Henry Ford Immunology Program, Henry Ford Health System, Detroit, MI (United States); Department of Dermatology, Henry Ford Health System, Detroit, MI (United States); Shiver, Austin [Department of Cellular Biology and Anatomy, Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, GA (United States); Department of Orthopaedic Surgery, Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, GA (United States); Qi, Rui-Qun [Henry Ford Immunology Program, Henry Ford Health System, Detroit, MI (United States); Department of Dermatology, Henry Ford Health System, Detroit, MI (United States); Zhou, Li [Henry Ford Immunology Program, Henry Ford Health System, Detroit, MI (United States); Department of Dermatology, Henry Ford Health System, Detroit, MI (United States); Department of Internal Medicine, Henry Ford Health System, Detroit, MI (United States); Isales, Carlos M. [Department of Cellular Biology and Anatomy, Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, GA (United States); Department of Orthopaedic Surgery, Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, GA (United States); others, and

2010-09-24

Research highlights: {yields} Aging is associated with muscle atrophy and loss of muscle mass, known as the sarcopenia of aging. {yields} We demonstrate that age-related muscle atrophy is associated with marked changes in miRNA expression in muscle. {yields} Treating aged mice with the adipokine leptin significantly increased muscle mass and the expression of miRNAs involved in muscle repair. {yields} Recombinant leptin therapy may therefore be a novel approach for treating age-related muscle atrophy. -- Abstract: Age-associated loss of muscle mass, or sarcopenia, contributes directly to frailty and an increased risk of falls and fractures among the elderly. Aged mice and elderly adults both show decreased muscle mass as well as relatively low levels of the fat-derived hormone leptin. Here we demonstrate that loss of muscle mass and myofiber size with aging in mice is associated with significant changes in the expression of specific miRNAs. Aging altered the expression of 57 miRNAs in mouse skeletal muscle, and many of these miRNAs are now reported to be associated specifically with age-related muscle atrophy. These include miR-221, previously identified in studies of myogenesis and muscle development as playing a role in the proliferation and terminal differentiation of myogenic precursors. We also treated aged mice with recombinant leptin, to determine whether leptin therapy could improve muscle mass and alter the miRNA expression profile of aging skeletal muscle. Leptin treatment significantly increased hindlimb muscle mass and extensor digitorum longus fiber size in aged mice. Furthermore, the expression of 37 miRNAs was altered in muscles of leptin-treated mice. In particular, leptin treatment increased the expression of miR-31 and miR-223, miRNAs known to be elevated during muscle regeneration and repair. These findings suggest that aging in skeletal muscle is associated with marked changes in the expression of specific miRNAs, and that nutrient

The essence of biophysical cues in skeletal muscle tissue engineering

NARCIS (Netherlands)

Langelaan, M.L.P.

2010-01-01

Skeletal muscle is an appealing topic for tissue engineering because of its variety in applications. Evidently, tissue engineered skeletal muscle can be used in the field of regenerative medicine to repair muscular defects or dystrophies. Engineered skeletal muscle constructs can also be used as a

Action of Obestatin in Skeletal Muscle Repair: Stem Cell Expansion, Muscle Growth, and Microenvironment Remodeling

Science.gov (United States)

Gurriarán-Rodríguez, Uxía; Santos-Zas, Icía; González-Sánchez, Jessica; Beiroa, Daniel; Moresi, Viviana; Mosteiro, Carlos S; Lin, Wei; Viñuela, Juan E; Señarís, José; García-Caballero, Tomás; Casanueva, Felipe F; Nogueiras, Rubén; Gallego, Rosalía; Renaud, Jean-Marc; Adamo, Sergio; Pazos, Yolanda; Camiña, Jesús P

2015-01-01

The development of therapeutic strategies for skeletal muscle diseases, such as physical injuries and myopathies, depends on the knowledge of regulatory signals that control the myogenic process. The obestatin/GPR39 system operates as an autocrine signal in the regulation of skeletal myogenesis. Using a mouse model of skeletal muscle regeneration after injury and several cellular strategies, we explored the potential use of obestatin as a therapeutic agent for the treatment of trauma-induced muscle injuries. Our results evidenced that the overexpression of the preproghrelin, and thus obestatin, and GPR39 in skeletal muscle increased regeneration after muscle injury. More importantly, the intramuscular injection of obestatin significantly enhanced muscle regeneration by simulating satellite stem cell expansion as well as myofiber hypertrophy through a kinase hierarchy. Added to the myogenic action, the obestatin administration resulted in an increased expression of vascular endothelial growth factor (VEGF)/vascular endothelial growth factor receptor 2 (VEGFR2) and the consequent microvascularization, with no effect on collagen deposition in skeletal muscle. Furthermore, the potential inhibition of myostatin during obestatin treatment might contribute to its myogenic action improving muscle growth and regeneration. Overall, our data demonstrate successful improvement of muscle regeneration, indicating obestatin is a potential therapeutic agent for skeletal muscle injury and would benefit other myopathies related to muscle regeneration. PMID:25762009

Determining the impact of oxidation on the motility of single muscle-fibres expressing different myosin isoforms

DEFF Research Database (Denmark)

Spanos, Dimitrios; Li, M.; Baron, Caroline P.

2013-01-01

heavy chain (MyHC) isoforms has not been previously investigated. Oxidation of myosin isolated from muscle fibres originating from various porcine muscles with a different metabolic profile was studied using a single muscle fibre in-vitro motility assay, allowing measurements of catalytic properties...... (motility speed) and force-generation capacity of specific MyHC isoforms. In the experimental procedure, single muscle fibres were split in different segments and each segment was exposed to a different concentration of hydrogen peroxide. Speed and force measurements were recorded and compared, to assess...... the effect of myosin oxidation on motility and force. The MyHC isoform expression in the single muscle fibre was subsequently determined on silver-stained gel SDS-PAGE. Preliminary results indicate a decrease of directionality and speed of the in-vitro motility as a result of an oxidative environment...

Heterogeneity among muscle precursor cells in adult skeletal muscles with differing regenerative capacities.

Science.gov (United States)

Pavlath, G K; Thaloor, D; Rando, T A; Cheong, M; English, A W; Zheng, B

1998-08-01

Skeletal muscle has a remarkable capacity to regenerate after injury, although studies of muscle regeneration have heretofore been limited almost exclusively to limb musculature. Muscle precursor cells in skeletal muscle are responsible for the repair of damaged muscle. Heterogeneity exists in the growth and differentiation properties of muscle precursor cell (myoblast) populations throughout limb development but whether the muscle precursor cells differ among adult skeletal muscles is unknown. Such heterogeneity among myoblasts in the adult may give rise to skeletal muscles with different regenerative capacities. Here we compare the regenerative response of a masticatory muscle, the masseter, to that of limb muscles. After exogenous trauma (freeze or crush injuries), masseter muscle regenerated much less effectively than limb muscle. In limb muscle, normal architecture was restored 12 days after injury, whereas in masseter muscle, minimal regeneration occurred during the same time period. Indeed, at late time points, masseter muscles exhibited increased fibrous connective tissue in the region of damage, evidence of ineffective muscle regeneration. Similarly, in response to endogenous muscle injury due to a muscular dystrophy, widespread evidence of impaired regeneration was present in masseter muscle but not in limb muscle. To explore the cellular basis of these different regenerative capacities, we analyzed the myoblast populations of limb and masseter muscles both in vivo and in vitro. From in vivo analyses, the number of myoblasts in regenerating muscle was less in masseter compared with limb muscle. Assessment of population growth in vitro indicated that masseter myoblasts grow more slowly than limb myoblasts under identical conditions. We conclude that the impaired regeneration in masseter muscles is due to differences in the intrinsic myoblast populations compared to limb muscles.

Androgen interacts with exercise through the mTOR pathway to induce skeletal muscle hypertrophy.

Science.gov (United States)

Zeng, Fanxing; Zhao, Hua; Liao, Jingwen

2017-12-01

This study was designed to investigate the effects of exogenous androgen and resistance exercise on skeletal muscle hypertrophy and the role of the mammalian target of rapamycin (mTOR) signalling during the process. A total of 24 male Sprague-Dawley rats were randomly assigned to sham operation and dihydrotestosterone (DHT) implantation groups with subgroups subjected to sedentary conditions or resistance exercise (SHAM+SED, SHAM+EX, DHT+SED, and DHT+EX). The experimental procedure lasted for 10 days. The mRNA expression of androgen receptor (AR) and insulin-like growth factor I (IGF-I), the expression of myosin heavy chain (MHC), as well as the phosphorylation statuses of AR, mTOR, p70 ribosomal S6 kinase (p70 S6K ), and eukaryotic translation initiation factor 4E-binding protein 1 (4EBP1) were determined in the white gastrocnemius muscle. The cross sectional area and wet mass of the muscle were also measured. The cross sectional area and MHC expression were significantly higher in SHAM+EX, DHT+SED, and DHT+EX than in SHAM+SED. There was no significant difference among groups in muscle mass. The mRNA expression of AR and IGF-I and the phosphorylation of mTOR, p70 S6K , and 4EBP1 were significantly increased in DHT+SED and SHAM+EX and were significantly enhanced in DHT+EX compared with either DHT or exercise alone. These data show that DHT causes hypertrophy in skeletal muscle and that exercise has a synergistic effect on DHT-induced hypertrophy. Exercise enhances androgen-induced rapid anabolic action, which involves activation of the mTOR pathway.

Could a functional artificial skeletal muscle be useful in muscle wasting?

Science.gov (United States)

Fuoco, Claudia; Cannata, Stefano; Gargioli, Cesare

2016-05-01

Regardless of the underlying cause, skeletal muscle wasting is detrimental for a person's life quality, leading to impaired strength, locomotion, and physiological activity. Here, we propose a series of studies presenting tissue engineering-based approaches to reconstruct artificial muscle in vitro and in vivo. Skeletal muscle tissue engineering is attracting more and more attention from scientists, clinicians, patients, and media, thanks to the promising results obtained in the last decade with animal models of muscle wasting. The use of novel and refined biomimetic scaffolds mimicking three-dimensional muscle environment, thus supporting cell survival and differentiation, in combination with well characterized myogenic stem/progenitor cells, revealed the noteworthy potential of these technologies for creating artificial skeletal muscle tissue. In vitro, the production of three-dimensional muscle structures offer the possibility to generate a drug-screening platform for patient-specific pharmacological treatment, opening new frontiers in the development of new compounds with specific therapeutic actions. In vivo, three-dimensional artificial muscle biomimetic constructs offer the possibility to replace, in part or entirely, wasted muscle by means of straight reconstruction and/or by enhancing endogenous regeneration. Reports of tissue engineering approaches for artificial muscle building appeared in large numbers in the specialized press lately, advocating the suitability of this technology for human application upon scaling up and a near future applicability for medical care of muscle wasting. http://links.lww.com/COCN/A9

Effect of repeated forearm muscle cooling on the adaptation of skeletal muscle metabolism in humans

Science.gov (United States)

Wakabayashi, Hitoshi; Nishimura, Takayuki; Wijayanto, Titis; Watanuki, Shigeki; Tochihara, Yutaka

2017-07-01

This study aimed to investigate the effect of repeated cooling of forearm muscle on adaptation in skeletal muscle metabolism. It is hypothesized that repeated decreases of muscle temperature would increase the oxygen consumption in hypothermic skeletal muscle. Sixteen healthy males participated in this study. Their right forearm muscles were locally cooled to 25 °C by cooling pads attached to the skin. This local cooling was repeated eight times on separate days for eight participants (experimental group), whereas eight controls received no cold exposure. To evaluate adaptation in skeletal muscle metabolism, a local cooling test was conducted before and after the repeated cooling period. Change in oxy-hemoglobin content in the flexor digitorum at rest and during a 25-s isometric handgrip (10% maximal voluntary construction) was measured using near-infrared spectroscopy at every 2 °C reduction in forearm muscle temperature. The arterial blood flow was occluded for 15 s by upper arm cuff inflation at rest and during the isometric handgrip. The oxygen consumption in the flexor digitorum muscle was evaluated by a slope of the oxy-hemoglobin change during the arterial occlusion. In the experimental group, resting oxygen consumption in skeletal muscle did not show any difference between pre- and post-intervention, whereas muscle oxygen consumption during the isometric handgrip was significantly higher in post-intervention than in pre-test from thermoneutral baseline to 31 °C muscle temperature ( P cooling might facilitate oxidative metabolism in the skeletal muscle. In summary, skeletal muscle metabolism during submaximal isometric handgrip was facilitated after repeated local muscle cooling.

Immunology Guides Skeletal Muscle Regeneration

Directory of Open Access Journals (Sweden)

F. Andrea Sass

2018-03-01

Full Text Available Soft tissue trauma of skeletal muscle is one of the most common side effects in surgery. Muscle injuries are not only caused by accident-related injuries but can also be of an iatrogenic nature as they occur during surgical interventions when the anatomical region of interest is exposed. If the extent of trauma surpasses the intrinsic regenerative capacities, signs of fatty degeneration and formation of fibrotic scar tissue can occur, and, consequentially, muscle function deteriorates or is diminished. Despite research efforts to investigate the physiological healing cascade following trauma, our understanding of the early onset of healing and how it potentially determines success or failure is still only fragmentary. This review focuses on the initial physiological pathways following skeletal muscle trauma in comparison to bone and tendon trauma and what conclusions can be drawn from new scientific insights for the development of novel therapeutic strategies. Strategies to support regeneration of muscle tissue after injury are scarce, even though muscle trauma has a high incidence. Based on tissue specific differences, possible clinical treatment options such as local immune-modulatory and cell therapeutic approaches are suggested that aim to support the endogenous regenerative potential of injured muscle tissues.

Skeletal muscle weakness in osteogenesis imperfecta mice.

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Gentry, Bettina A; Ferreira, J Andries; McCambridge, Amanda J; Brown, Marybeth; Phillips, Charlotte L

2010-09-01

Exercise intolerance, muscle fatigue and weakness are often-reported, little-investigated concerns of patients with osteogenesis imperfecta (OI). OI is a heritable connective tissue disorder hallmarked by bone fragility resulting primarily from dominant mutations in the proα1(I) or proα2(I) collagen genes and the recently discovered recessive mutations in post-translational modifying proteins of type I collagen. In this study we examined the soleus (S), plantaris (P), gastrocnemius (G), tibialis anterior (TA) and quadriceps (Q) muscles of mice expressing mild (+/oim) and moderately severe (oim/oim) OI for evidence of inherent muscle pathology. In particular, muscle weight, fiber cross-sectional area (CSA), fiber type, fiber histomorphology, fibrillar collagen content, absolute, relative and specific peak tetanic force (P(o), P(o)/mg and P(o)/CSA respectively) of individual muscles were evaluated. Oim/oim mouse muscles were generally smaller, contained less fibrillar collagen, had decreased P(o) and an inability to sustain P(o) for the 300-ms testing duration for specific muscles; +/oim mice had a similar but milder skeletal muscle phenotype. +/oim mice had mild weakness of specific muscles but were less affected than their oim/oim counterparts which demonstrated readily apparent skeletal muscle pathology. Therefore muscle weakness in oim mice reflects inherent skeletal muscle pathology. Copyright © 2010 Elsevier B.V. All rights reserved.

PGC-1α-mediated adaptations in skeletal muscle

DEFF Research Database (Denmark)

Olesen, Jesper; Kiilerich, Kristian; Pilegaard, Henriette

2010-01-01

multiple pathways and functions underline the potential importance of PGC-1alpha in skeletal muscle adaptations in humans. The absence of exercise-induced PGC-1alpha-mediated gene regulation during a physical inactive lifestyle is suggested to lead to reduced oxidative capacity of skeletal muscle...... involved in angiogenesis and the anti-oxidant defence as well as to affect expression of inflammatory markers. Exercise increases PGC-1alpha transcription and potentially PGC-1alpha activity through post-translational modifications, and concomitant PGC-1alpha-mediated gene regulation is suggested...... to be an underlying mechanism for adaptations in skeletal muscle, when exercise is repeated. The current review presents some of the key findings in PGC-1alpha-mediated regulation of metabolically related, anti-oxidant and inflammatory proteins in skeletal muscle in the basal state and in response to exercise...

Standardization of metachromatic staining method of myofibrillar ATPase activity of myosin to skeletal striated muscle of mules and donkeys

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Flora H.F. D'Angelis

2014-09-01

Full Text Available This study aims at standardizing the pre-incubation and incubation pH and temperature used in the metachromatic staining method of myofibrillar ATPase activity of myosin (mATPase used for asses and mules. Twenty four donkeys and 10 mules, seven females and three males, were used in the study. From each animal, fragments from the Gluteus medius muscle were collected and percutaneous muscle biopsy was performed using a 6.0-mm Bergström-type needle. In addition to the metachromatic staining method of mATPase, the technique of nicotinamide adenine dinucleotide tetrazolium reductase (NADH-TR was also performed to confirm the histochemical data. The histochemical result of mATPase for acidic pre-incubation (pH=4.50 and alkaline incubation (pH=10.50, at a temperature of 37ºC, yielded the best differentiation of fibers stained with toluidine blue. Muscle fibers were identified according to the following colors: type I (oxidative, light blue, type IIA (oxidative-glycolytic, intermediate blue and type IIX (glycolytic, dark blue. There are no reports in the literature regarding the characterization and distribution of different types of muscle fibers used by donkeys and mules when performing traction work, cargo transportation, endurance sports (horseback riding and marching competitions. Therefore, this study is the first report on the standardization of the mATPase technique for donkeys and mules.

Regulatory mechanisms of skeletal muscle protein turnover during exercise

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Rose, Adam John; Richter, Erik

2009-01-01

Skeletal muscle protein turnover is a relatively slow metabolic process that is altered by various physiological stimuli such as feeding/fasting and exercise. During exercise, catabolism of amino acids contributes very little to ATP turnover in working muscle. With regards to protein turnover......, there is now consistent data from tracer studies in rodents and humans showing that global protein synthesis is blunted in working skeletal muscle. Whether there is altered skeletal muscle protein breakdown during exercise remains unclear. The blunting of protein synthesis is believed to be mediated...... downstream of changes in intracellular Ca(2+) and energy turnover. In particular, a signaling cascade involving Ca(2+)-calmodulin-eEF2 kinase-eEF2 is implicated. The possible functional significance of altered protein turnover in working skeletal muscle during exercise is discussed. Further work...

Cryopreservation of human skeletal muscle impairs mitochondrial function

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Larsen, Steen; Wright-Paradis, C; Gnaiger, E

2012-01-01

functionality after long term cryopreservation (1 year). Skeletal muscle samples were preserved in dimethyl sulfoxide (DMSO) for later analysis. Human skeletal muscle fibres were thawed and permeabilised with saponin, and mitochondrial respiration was measured by high-resolution respirometry. The capacity...

Spectroscopic Studies of the Super Relaxed State of Skeletal Muscle.

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Leonardo Nogara

Full Text Available In the super-relaxed state of myosin, ATPase activity is strongly inhibited by binding of the myosin heads to the core of the thick filament in a structure known as the interacting-heads motif. In the disordered relaxed state myosin heads are not bound to the core of the thick filament and have an ATPase rate that is 10 fold greater. In the interacting-heads motif the two regulatory light chains appear to bind to each other. We have made single cysteine mutants of the regulatory light chain, placed both paramagnetic and fluorescent probes on them, and exchanged them into skinned skeletal muscle fibers. Many of the labeled light chains tended to disrupt the stability of the super-relaxed state, and showed spectral changes in the transition from the disordered relaxed state to the super-relaxed state. These data support the putative interface between the two regulatory light chains identified by cryo electron microscopy and show that both the divalent cation bound to the regulatory light chain and the N-terminus of the regulatory light chain play a role in the stability of the super-relaxed state. One probe showed a shift to shorter wavelengths in the super-relaxed state such that a ratio of intensities at 440nm to that at 520nm provided a measure of the population of the super-relaxed state amenable for high throughput screens for finding potential pharmaceuticals. The results provide a proof of concept that small molecules that bind to this region can destabilize the super-relaxed state and provide a method to search for small molecules that do so leading to a potentially effective treatment for Type 2 diabetes and obesity.

Protein and amino acid metabolism in skeletal muscle

Energy Technology Data Exchange (ETDEWEB)

Wu, Guoyao.

1989-01-01

Isolated chick extensor digitorum communis (EDC) muscles and, in some experiments, rat skeletal muscles were used to study a number of aspects of protein and amino acid metabolism. (1) Chick EDC muscles synthesize and release large amounts of alanine and glutamine, which indirectly obtain their amino groups from branched-chain amino acids (BCAA). (2) Acetoacetate or DL-{beta}-hydroxybutyrate (4 mM) decrease (P < 0.01) alanine synthesis and BCAA transamination in EDC muscles from 24-h fasted chicks by decreasing (P < 0.01) intracellular concentrations of pyruvate due to inhibition of glycolysis. (3) Glutamine is extensively degraded in skeletal muscles from both chicks and rats, thus challenging the traditional view that glutamine oxidation is negligible in skeletal muscle. The cytosolic glutamine aminotransferases L and K in the rat and the mitochondrial phosphate-activated glutaminase in the chick play important roles in the conversion of glutamine to {alpha}-ketoglutarate for further oxidation. (4) Although methionine has been reported to be extensively transaminated in rat skeletal muscle preparations in the absence of other amino acids, transamination of methionine is absent or negligible in chick and rat skeletal muscles in the presence of physiological concentrations of amino acids. (5) Glutamine at 1.0-15 mM increases (P < 0.01) protein synthesis ({sup 3}H-phenylalanine incorporation), and at 10.0-15.0 mM decreases (P < 0.05) protein degradation ({sup 3}H-phenylalanine release from prelabelled protein in vivo) in EDC muscles from fed chicks as compared to muscles incubated in the absence of glutamine. (6) Acetoacetate or DL-{beta}-hydroxybutyrate (4 mM) has a small but significant inhibitory effect (P < 0.05) on the rate of protein synthesis, but has no effect (P > 0.05) on the rate of protein degradation in EDC muscles from fed chicks.

Dihydrotestosterone activates the MAPK pathway and modulates maximum isometric force through the EGF receptor in isolated intact mouse skeletal muscle fibres.

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Hamdi, M M; Mutungi, G

2010-02-01

It is generally believed that steroid hormones have both genomic and non-genomic (rapid) actions. Although the latter form an important component of the physiological response of these hormones, little is known about the cellular signalling pathway(s) mediating these effects and their physiological functions in adult mammalian skeletal muscle fibres. Therefore, the primary aim of this study was to investigate the non-genomic actions of dihydrotestosterone (DHT) and their physiological role in isolated intact mammalian skeletal muscle fibre bundles. Our results show that treating the fibre bundles with physiological concentrations of DHT increases both twitch and tetanic contractions in fast twitch fibres. However, it decreases them in slow twitch fibres. These changes in force are accompanied by an increase in the phosphorylation of MAPK/ERK1/2 in both fibre types and that of regulatory myosin light chains in fast twitch fibres. Both effects were insensitive to inhibitors of Src kinase, androgen receptor, insulin-like growth factor 1 receptor and platelet-derived growth factor receptor. However, they were abolished by the MAPK/ERK1/2 kinase inhibitor PD98059 and the epidermal growth factor (EGF) receptor inhibitor tyrphostin AG 1478. In contrast, testosterone had no effect on force and increased the phosphorylation of ERK1/2 in slow twitch fibres only. From these results we conclude that sex steroids have non-genomic actions in isolated intact mammalian skeletal muscle fibres. These are mediated through the EGF receptor and one of their main physiological functions is the enhancement of force production in fast twitch skeletal muscle fibres.

Plasticity of human skeletal muscle: gene expression to in vivo function.

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Harridge, Stephen D R

2007-09-01

Human skeletal muscle is a highly heterogeneous tissue, able to adapt to the different challenges that may be placed upon it. When overloaded, a muscle adapts by increasing its size and strength through satellite-cell-mediated mechanisms, whereby protein synthesis is increased and new nuclei are added to maintain the myonuclear domain. This process is regulated by an array of mechanical, hormonal and nutritional signals. Growth factors, such as insulin-like growth factor I (IGF-I) and testosterone, are potent anabolic agents, whilst myostatin acts as a negative regulator of muscle mass. Insulin-like growth factor I is unique in being able to stimulate both the proliferation and the differentiation of satellite cells and works as part of an important local repair and adaptive mechanism. Speed of movement, as characterized by maximal velocity of shortening (V(max)), is regulated primarily by the isoform of myosin heavy chain (MHC) contained within a muscle fibre. Human fibres can express three MHCs: MHC-I, -IIa and -IIx, in order of increasing V(max) and maximal power output. Training studies suggest that there is a subtle interplay between the MHC-IIa and -IIx isoforms, with the latter being downregulated by activity and upregulated by inactivity. However, switching between the two main isoforms appears to require significant challenges to a muscle. Upregulation of fast gene programs is caused by prolonged disuse, whilst upregulation of slow gene programs appears to require significant and prolonged activity. The potential mechanisms by which alterations in muscle composition are mediated are discussed. The implications in terms of contractile function of altering muscle phenotype are discussed from the single fibre to the whole muscle level.

Cardiac troponin T and fast skeletal muscle denervation in ageing.

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Xu, Zherong; Feng, Xin; Dong, Juan; Wang, Zhong-Min; Lee, Jingyun; Furdui, Cristina; Files, Daniel Clark; Beavers, Kristen M; Kritchevsky, Stephen; Milligan, Carolanne; Jin, Jian-Ping; Delbono, Osvaldo; Zhang, Tan

2017-10-01

Ageing skeletal muscle undergoes chronic denervation, and the neuromuscular junction (NMJ), the key structure that connects motor neuron nerves with muscle cells, shows increased defects with ageing. Previous studies in various species have shown that with ageing, type II fast-twitch skeletal muscle fibres show more atrophy and NMJ deterioration than type I slow-twitch fibres. However, how this process is regulated is largely unknown. A better understanding of the mechanisms regulating skeletal muscle fibre-type specific denervation at the NMJ could be critical to identifying novel treatments for sarcopenia. Cardiac troponin T (cTnT), the heart muscle-specific isoform of TnT, is a key component of the mechanisms of muscle contraction. It is expressed in skeletal muscle during early development, after acute sciatic nerve denervation, in various neuromuscular diseases and possibly in ageing muscle. Yet the subcellular localization and function of cTnT in skeletal muscle is largely unknown. Studies were carried out on isolated skeletal muscles from mice, vervet monkeys, and humans. Immunoblotting, immunoprecipitation, and mass spectrometry were used to analyse protein expression, real-time reverse transcription polymerase chain reaction was used to measure gene expression, immunofluorescence staining was performed for subcellular distribution assay of proteins, and electromyographic recording was used to analyse neurotransmission at the NMJ. Levels of cTnT expression in skeletal muscle increased with ageing in mice. In addition, cTnT was highly enriched at the NMJ region-but mainly in the fast-twitch, not the slow-twitch, muscle of old mice. We further found that the protein kinase A (PKA) RIα subunit was largely removed from, while PKA RIIα and RIIβ are enriched at, the NMJ-again, preferentially in fast-twitch but not slow-twitch muscle in old mice. Knocking down cTnT in fast skeletal muscle of old mice: (i) increased PKA RIα and reduced PKA RIIα at the NMJ; (ii

Skeletal Muscle Regeneration, Repair and Remodelling in Aging: The Importance of Muscle Stem Cells and Vascularization.

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Joanisse, Sophie; Nederveen, Joshua P; Snijders, Tim; McKay, Bryon R; Parise, Gianni

2017-01-01

Sarcopenia is the age-related loss of skeletal muscle mass and strength. Ultimately, sarcopenia results in the loss of independence, which imposes a large financial burden on healthcare systems worldwide. A critical facet of sarcopenia is the diminished ability for aged muscle to regenerate, repair and remodel. Over the years, research has focused on elucidating underlying mechanisms of sarcopenia and the impaired ability of muscle to respond to stimuli with aging. Muscle-specific stem cells, termed satellite cells (SC), play an important role in maintaining muscle health throughout the lifespan. It is well established that SC are essential in skeletal muscle regeneration, and it has been hypothesized that a reduction and/or dysregulation of the SC pool, may contribute to accelerated loss of skeletal muscle mass that is observed with advancing age. The preservation of skeletal muscle tissue and its ability to respond to stimuli may be impacted by reduced SC content and impaired function observed with aging. Aging is also associated with a reduction in capillarization of skeletal muscle. We have recently demonstrated that the distance between type II fibre-associated SC and capillaries is greater in older compared to younger adults. The greater distance between SC and capillaries in older adults may contribute to the dysregulation in SC activation ultimately impairing muscle's ability to remodel and, in extreme circumstances, regenerate. This viewpoint will highlight the importance of optimal SC activation in addition to skeletal muscle capillarization to maximize the regenerative potential of skeletal muscle in older adults. © 2016 S. Karger AG, Basel.

Increased skeletal muscle capillarization enhances insulin sensitivity

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Åkerström, Thorbjörn; Laub, Lasse; Vedel, Kenneth

2014-01-01

Increased skeletal muscle capillarization is associated with improved glucose tolerance and insulin sensitivity. However, a possible causal relationship has not previously been identified. We therefore investigated whether increased skeletal muscle capillarization increases insulin sensitivity....... Skeletal muscle specific angiogenesis was induced by adding the α1-adrenergic receptor antagonist Prazosin to the drinking water of Sprague Dawley rats (n=33) while 34 rats served as controls. Insulin sensitivity was measured ≥40 h after termination of the 3-week Prazosin treatment, which ensured...... that Prazosin was cleared from the blood stream. Whole-body insulin sensitivity was measured in conscious, unrestrained rats by hyperinsulinemic euglycemic clamp. Tissue specific insulin sensitivity was assessed by administration of 2-deoxy-[(3)H]-Glucose during the plateau phase of the clamp. Whole...

Rotator cuff tear state modulates self-renewal and differentiation capacity of human skeletal muscle progenitor cells.

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Thomas, Kelsey A; Gibbons, Michael C; Lane, John G; Singh, Anshuman; Ward, Samuel R; Engler, Adam J

2017-08-01

Full thickness rotator cuff tendon (RCT) tears have long-term effects on RC muscle atrophy and fatty infiltration, with lasting damage even after surgical tendon repair. Skeletal muscle progenitor cells (SMPs) are critical for muscle repair in response to injury, but the inability of RC muscles to recover from chronic RCT tear indicates possible deficits in repair mechanisms. Here we investigated if muscle injury state was a crucial factor during human SMP expansion and differentiation ex vivo. SMPs were isolated from muscles in patients with no, partial-thickness (PT), or full-thickness (FT) RCT tears. Despite using growth factors, physiological niche stiffness, and muscle-mimetic extracellular matrix (ECM) proteins, we found that SMPs isolated from human RC muscle with RCT tears proliferated slower but fused into myosin heavy chain (MHC)-positive myotubes at higher rates than SMPs from untorn RCTs. Proteomic analysis of RC muscle tissue revealed shifts in muscle composition with pathology, as muscle from massive RCT tears had increased ECM deposition compared with no tear RC muscle. Together these data imply that the remodeled niche in a torn RCT primes SMPs not for expansion but for differentiation, thus limiting longer-term self-renewal necessary for regeneration after surgical repair. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1816-1823, 2017. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Comprehensive analysis of tropomyosin isoforms in skeletal muscles by top-down proteomics.

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Jin, Yutong; Peng, Ying; Lin, Ziqing; Chen, Yi-Chen; Wei, Liming; Hacker, Timothy A; Larsson, Lars; Ge, Ying

2016-04-01

Mammalian skeletal muscles are heterogeneous in nature and are capable of performing various functions. Tropomyosin (Tpm) is a major component of the thin filament in skeletal muscles and plays an important role in controlling muscle contraction and relaxation. Tpm is known to consist of multiple isoforms resulting from different encoding genes and alternative splicing, along with post-translational modifications. However, a systematic characterization of Tpm isoforms in skeletal muscles is still lacking. Therefore, we employed top-down mass spectrometry (MS) to identify and characterize Tpm isoforms present in different skeletal muscles from multiple species, including swine, rat, and human. Our study revealed that Tpm1.1 and Tpm2.2 are the two major Tpm isoforms in swine and rat skeletal muscles, whereas Tpm1.1, Tpm2.2, and Tpm3.12 are present in human skeletal muscles. Tandem MS was utilized to identify the sequences of the major Tpm isoforms. Furthermore, quantitative analysis revealed muscle-type specific differences in the abundance of un-modified and modified Tpm isoforms in rat and human skeletal muscles. This study represents the first systematic investigation of Tpm isoforms in skeletal muscles, which not only demonstrates the capabilities of top-down MS for the comprehensive characterization of skeletal myofilament proteins but also provides the basis for further studies on these Tpm isoforms in muscle-related diseases.

Deletion of skeletal muscle SOCS3 prevents insulin resistance in obesity

DEFF Research Database (Denmark)

Beck Jørgensen, Sebastian; O'Neill, Hayley M; Sylow, Lykke

2013-01-01

Obesity is associated with chronic low-grade inflammation that contributes to defects in energy metabolism and insulin resistance. Suppressor of cytokine signaling (SOCS)-3 expression is increased in skeletal muscle of obese humans. SOCS3 inhibits leptin signaling in the hypothalamus and insulin...... of hyperinsulinemia and insulin resistance because of enhanced skeletal muscle insulin receptor substrate 1 (IRS1) and Akt phosphorylation that resulted in increased skeletal muscle glucose uptake. These data indicate that skeletal muscle SOCS3 does not play a critical role in regulating muscle development or energy...... expenditure, but it is an important contributing factor for inhibiting insulin sensitivity in obesity. Therapies aimed at inhibiting SOCS3 in skeletal muscle may be effective in reversing obesity-related glucose intolerance and insulin resistance....

Modulation effects of cordycepin on the skeletal muscle contraction of toad gastrocnemius muscle.

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Yao, Li-Hua; Meng, Wei; Song, Rong-Feng; Xiong, Qiu-Ping; Sun, Wei; Luo, Zhi-Qiang; Yan, Wen-Wen; Li, Yu-Ping; Li, Xin-Ping; Li, Hai-Hang; Xiao, Peng

2014-03-05

Isolated toad gastrocnemius muscle is a typical skeletal muscle tissue that is frequently used to study the motor system because it is an important component of the motor system. This study investigates the effects of cordycepin on the skeletal muscle contractile function of isolated toad gastrocnemius muscles by electrical field stimulation. Results showed that cordycepin (20 mg/l to 100 mg/l) significantly decreased the contractile responses in a concentration-dependent manner. Cordycepin (50 mg/l) also produced a rightward shift of the contractile amplitude-stimulation intensity relationship, as indicated by the increases in the threshold stimulation intensity and the saturation stimulation intensity. However, the most notable result was that the maximum amplitude of the muscle contractile force was significantly increased under cordycepin application (122±3.4% of control). This result suggests that the skeletal muscle contractile function and muscle physical fitness to the external stimulation were improved by the decreased response sensitivity in the presence of cordycepin. Moreover, cordycepin also prevented the repetitive stimulation-induced decrease in muscle contractile force and increased the recovery amplitude and recovery ratio of muscle contraction. However, these anti-fatigue effects of cordycepin on muscle contraction during long-lasting muscle activity were absent in Ca2+-free medium or in the presence of all Ca2+ channels blocker (0.4 mM CdCl2). These results suggest that cordycepin can positively affect muscle performance and provide ergogenic and prophylactic benefits in decreasing skeletal muscle fatigue. The mechanisms involving excitation-coupled Ca2+ influxes are strongly recommended.

Calprotectin is released from human skeletal muscle tissue during exercise

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Mortensen, Ole Hartvig; Andersen, Kasper; Fischer, Christian

2008-01-01

Skeletal muscle has been identified as a secretory organ. We hypothesized that IL-6, a cytokine secreted from skeletal muscle during exercise, could induce production of other secreted factors in skeletal muscle. IL-6 was infused for 3 h into healthy young males (n = 7) and muscle biopsies obtained...... in skeletal muscle following IL-6 infusion compared to controls. Furthermore, S100A8 and S100A9 mRNA levels were up-regulated 5-fold in human skeletal muscle following cycle ergometer exercise for 3 h at approximately 60% of in young healthy males (n = 8). S100A8 and S100A9 form calprotectin, which is known...... as an acute phase reactant. Plasma calprotectin increased 5-fold following acute cycle ergometer exercise in humans, but not following IL-6 infusion. To identify the source of calprotectin, healthy males (n = 7) performed two-legged dynamic knee extensor exercise for 3 h with a work load of approximately 50...

A Drosophila model of dominant inclusion body myopathy type 3 shows diminished myosin kinetics that reduce muscle power and yield myofibrillar defects.

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Suggs, Jennifer A; Melkani, Girish C; Glasheen, Bernadette M; Detor, Mia M; Melkani, Anju; Marsan, Nathan P; Swank, Douglas M; Bernstein, Sanford I

2017-06-01

Individuals with inclusion body myopathy type 3 (IBM3) display congenital joint contractures with early-onset muscle weakness that becomes more severe in adulthood. The disease arises from an autosomal dominant point mutation causing an E706K substitution in myosin heavy chain type IIa. We have previously expressed the corresponding myosin mutation (E701K) in homozygous Drosophila indirect flight muscles and recapitulated the myofibrillar degeneration and inclusion bodies observed in the human disease. We have also found that purified E701K myosin has dramatically reduced actin-sliding velocity and ATPase levels. Since IBM3 is a dominant condition, we now examine the disease state in heterozygote Drosophila in order to gain a mechanistic understanding of E701K pathogenicity. Myosin ATPase activities in heterozygotes suggest that approximately equimolar levels of myosin accumulate from each allele. In vitro actin sliding velocity rates for myosin isolated from the heterozygotes were lower than the control, but higher than for the pure mutant isoform. Although sarcomeric ultrastructure was nearly wild type in young adults, mechanical analysis of skinned indirect flight muscle fibers revealed a 59% decrease in maximum oscillatory power generation and an approximately 20% reduction in the frequency at which maximum power was produced. Rate constant analyses suggest a decrease in the rate of myosin attachment to actin, with myosin spending decreased time in the strongly bound state. These mechanical alterations result in a one-third decrease in wing beat frequency and marginal flight ability. With aging, muscle ultrastructure and function progressively declined. Aged myofibrils showed Z-line streaming, consistent with the human heterozygote phenotype. Based upon the mechanical studies, we hypothesize that the mutation decreases the probability of the power stroke occurring and/or alters the degree of movement of the myosin lever arm, resulting in decreased in vitro

A Drosophila model of dominant inclusion body myopathy type 3 shows diminished myosin kinetics that reduce muscle power and yield myofibrillar defects

Directory of Open Access Journals (Sweden)

Jennifer A. Suggs

2017-06-01

Full Text Available Individuals with inclusion body myopathy type 3 (IBM3 display congenital joint contractures with early-onset muscle weakness that becomes more severe in adulthood. The disease arises from an autosomal dominant point mutation causing an E706K substitution in myosin heavy chain type IIa. We have previously expressed the corresponding myosin mutation (E701K in homozygous Drosophila indirect flight muscles and recapitulated the myofibrillar degeneration and inclusion bodies observed in the human disease. We have also found that purified E701K myosin has dramatically reduced actin-sliding velocity and ATPase levels. Since IBM3 is a dominant condition, we now examine the disease state in heterozygote Drosophila in order to gain a mechanistic understanding of E701K pathogenicity. Myosin ATPase activities in heterozygotes suggest that approximately equimolar levels of myosin accumulate from each allele. In vitro actin sliding velocity rates for myosin isolated from the heterozygotes were lower than the control, but higher than for the pure mutant isoform. Although sarcomeric ultrastructure was nearly wild type in young adults, mechanical analysis of skinned indirect flight muscle fibers revealed a 59% decrease in maximum oscillatory power generation and an approximately 20% reduction in the frequency at which maximum power was produced. Rate constant analyses suggest a decrease in the rate of myosin attachment to actin, with myosin spending decreased time in the strongly bound state. These mechanical alterations result in a one-third decrease in wing beat frequency and marginal flight ability. With aging, muscle ultrastructure and function progressively declined. Aged myofibrils showed Z-line streaming, consistent with the human heterozygote phenotype. Based upon the mechanical studies, we hypothesize that the mutation decreases the probability of the power stroke occurring and/or alters the degree of movement of the myosin lever arm, resulting in

Effect of experimental hyperthyroidism on protein turnover in skeletal and cardiac muscle.

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Carter, W J; Van Der Weijden Benjamin, W S; Faas, F H

1980-10-01

Since experimental hyperthyroidism reduces skeletal muscle mass while simultaneously increasing cardiac muscle mass, the effect of hyperthyroidism on muscle protein degradation was compared in skeletal and cardiac muscle. Pulse-labeling studies using (3H) leucine and (14C) carboxyl labeled aspartate and glutamate were carried out. Hyperthyroidism caused a 25%-29% increase in protein breakdown in both sarcoplasmic and myofibrillar fractions of skeletal muscle. Increased muscle protein degradation may be a major factor in the development of skeletal muscle wasting and weakness in hyperthyroidism. In contrast, protein breakdown appeared to be reduced 22% in the sarcoplasmic fraction of hyperthyroid heart muscle and was unchanged in the myofibrillar fraction. Possible reasons for the contrasting effects of hyperthyroidism on skeletal and cardiac muscle include increased sensitivity of the hyperthyroid heart to catecholamines, increased cardiac work caused by the hemodynamic effects of hyperthyroidism, and a different direct effect of thyroid hormone at the nuclear level in cardiac as opposed to skeletal muscle.

Generation of skeletal muscle from transplanted embryonic stem cells in dystrophic mice

International Nuclear Information System (INIS)

Bhagavati, Satyakam; Xu Weimin

2005-01-01

Embryonic stem (ES) cells have great therapeutic potential because of their capacity to proliferate extensively and to form any fully differentiated cell of the body, including skeletal muscle cells. Successful generation of skeletal muscle in vivo, however, requires selective induction of the skeletal muscle lineage in cultures of ES cells and following transplantation, integration of appropriately differentiated skeletal muscle cells with recipient muscle. Duchenne muscular dystrophy (DMD), a severe progressive muscle wasting disease due to a mutation in the dystrophin gene and the mdx mouse, an animal model for DMD, are characterized by the absence of the muscle membrane associated protein, dystrophin. Here, we show that co-culturing mouse ES cells with a preparation from mouse muscle enriched for myogenic stem and precursor cells, followed by injection into mdx mice, results occasionally in the formation of normal, vascularized skeletal muscle derived from the transplanted ES cells. Study of this phenomenon should provide valuable insights into skeletal muscle development in vivo from transplanted ES cells

Skeletal muscle wasting: new role of nonclassical renin-angiotensin system.

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Cabello-Verrugio, Claudio; Rivera, Juan C; Garcia, Dominga

2017-05-01

Skeletal muscle can be affected by many physiological and pathological conditions that contribute to the development of muscle weakness, including skeletal muscle loss, inflammatory processes, or fibrosis. Therefore, research into therapeutic treatment alternatives or alleviation of these effects on skeletal muscle is of great importance. Recent studies have shown that angiotensin (1-7) [Ang-(1-7)] - a vasoactive peptide of the nonclassical axis in the renin-angiotensin system (RAS) - and its Mas receptor are expressed in skeletal muscle. Ang-(1-7), through its Mas receptor, prevents or diminishes deleterious effects induced by skeletal muscle disease or injury. Specifically, the Ang-(1-7)-Mas receptor axis modulates molecular mechanisms involved in muscle mass regulation, such as the ubiquitin proteasome pathway, the insulin-like growth factor type 1/Akt (protein kinase B) pathway, or myonuclear apoptosis, and also inflammation and fibrosis pathways. Although further research into this topic and the possible side effects of Ang-(1-7) is necessary, these findings are promising, and suggest that the Ang-(1-7)-Mas axis can be considered a possible therapeutic target for treating patients with muscular disorders.

State of Skeletal Muscle Tissue in Women in the Ukrainian Population

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V.V. Povoroznyuk

2015-10-01

Full Text Available Today among geriatric syndromes, world scientists pay much attention to the study of sarcopenia. It was found that the evaluation of skeletal muscle strength has a significant correlation with the risk of falls, disability, deterioration in the quality of life, duration of hospitalization. It is proved that measurements of skeletal muscle strength, but not the determination of skeletal muscles mass, are strong and independent predictors of mortality in the elderly. Further researches are needed to study the characteristics of weight loss, strength and function of skeletal muscle with age in individuals of different sex and age. The objective of this study was to explore the features of strength and functionality of skeletal muscle tissue in women of all ages. The study involved 248 women, who were divided into groups by decades depending on age: 20–29, 30–39, 40–49, 50–59, 60–69, 70–79, 80–89 years. Skeletal muscle strength was evaluated using spring carpal dynamometer. Functions of skeletal muscles and the risk of falls were assessed using special tests. Fat-free mass of the whole body, upper and lower extremities was evaluated by means of dual-energy X-ray absorptiometry (Prodigy, GEHC Lunar, Madison, WI, USA. The study found that maximal values of strength and functional capacity of skeletal muscles were observed in women in the age group of 20–29 years. The significant loss of skeletal muscle strength is being detected in individuals from the age group of 60–69 years and older. When determining the functional capacity of skeletal muscles and risk of falls, significantly worse performance was established in women older than 50 years compared to those in women in the age group of 20–29 years.

Potential of laryngeal muscle regeneration using induced pluripotent stem cell-derived skeletal muscle cells.

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Dirja, Bayu Tirta; Yoshie, Susumu; Ikeda, Masakazu; Imaizumi, Mitsuyoshi; Nakamura, Ryosuke; Otsuki, Koshi; Nomoto, Yukio; Wada, Ikuo; Hazama, Akihiro; Omori, Koichi

2016-01-01

Conclusion Induced pluripotent stem (iPS) cells may be a new potential cell source for laryngeal muscle regeneration in the treatment of vocal fold atrophy after recurrent laryngeal nerve paralysis. Objectives Unilateral vocal fold paralysis can lead to degeneration, atrophy, and loss of force of the thyroarytenoid muscle. At present, there are some treatments such as thyroplasty, arytenoid adduction, and vocal fold injection. However, such treatments cannot restore reduced mass of the thyroarytenoid muscle. iPS cells have been recognized as supplying a potential resource for cell transplantation. The aim of this study was to assess the effectiveness of the use of iPS cells for the regeneration of laryngeal muscle through the evaluation of both in vitro and in vivo experiments. Methods Skeletal muscle cells were generated from tdTomato-labeled iPS cells using embryoid body formation. Differentiation into skeletal muscle cells was analyzed by gene expression and immunocytochemistry. The tdTomato-labeled iPS cell-derived skeletal muscle cells were transplanted into the left atrophied thyroarytenoid muscle. To evaluate the engraftment of these cells after transplantation, immunohistochemistry was performed. Results The tdTomato-labeled iPS cells were successfully differentiated into skeletal muscle cells through an in vitro experiment. These cells survived in the atrophied thyroarytenoid muscle after transplantation.

Activation of the skeletal alpha-actin promoter during muscle regeneration.

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Marsh, D R; Carson, J A; Stewart, L N; Booth, F W

1998-11-01

Little is known concerning promoter regulation of genes in regenerating skeletal muscles. In young rats, recovery of muscle mass and protein content is complete within 21 days. During the initial 5-10 days of regeneration, mRNA abundance for IGF-I, myogenin and MyoD have been shown to be dramatically increased. The skeletal alpha-actin promoter contains E box and serum response element (SRE) regulatory regions which are directly or indirectly activated by myogenin (or MyoD) and IGF-I proteins, respectively. We hypothesized that the skeletal alpha-actin promoter activity would increase during muscle regeneration, and that this induction would occur before muscle protein content returned to normal. Total protein content and the percentage content of skeletal alpha-actin protein was diminished at 4 and 8 days and re-accumulation had largely occurred by 16 days post-bupivacaine injection. Skeletal alpha-actin mRNA per whole muscle was decreased at day 8, and thereafter returned to control values. During regeneration at day 8, luciferase activity (a reporter of promoter activity) directed by -424 skeletal alpha-actin and -99 skeletal alpha-actin promoter constructs was increased by 700% and 250% respectively; however, at day 16, skeletal alpha-actin promoter activities were similar to control values. Thus, initial activation of the skeletal alpha-actin promoter is associated with regeneration of skeletal muscle, despite not being sustained during the later stages of regrowth. The proximal SRE of the skeletal alpha-actin promoter was not sufficient to confer a regeneration-induced promoter activation, despite increased serum response factor protein binding to this regulatory element in electrophoretic mobility shift assays. Skeletal alpha-actin promoter induction during regeneration is due to a combination of regulatory elements, at least including the SRE and E box.

Severe energy deficit upregulates leptin receptors, leptin signaling, and PTP1B in human skeletal muscle.

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Perez-Suarez, Ismael; Ponce-González, Jesús Gustavo; de La Calle-Herrero, Jaime; Losa-Reyna, Jose; Martin-Rincon, Marcos; Morales-Alamo, David; Santana, Alfredo; Holmberg, Hans-Christer; Calbet, Jose A L

2017-11-01

In obesity, leptin receptors (OBR) and leptin signaling in skeletal muscle are downregulated. To determine whether OBR and leptin signaling are upregulated with a severe energy deficit, 15 overweight men were assessed before the intervention (PRE), after 4 days of caloric restriction (3.2 kcal·kg body wt -1 ·day -1 ) in combination with prolonged exercise (CRE; 8 h walking + 45 min single-arm cranking/day) to induce an energy deficit of ~5,500 kcal/day, and following 3 days of control diet (isoenergetic) and reduced exercise (CD). During CRE, the diet consisted solely of whey protein ( n = 8) or sucrose ( n = 7; 0.8 g·kg body wt -1 ·day -1 ). Muscle biopsies were obtained from the exercised and the nonexercised deltoid muscles and from the vastus lateralis. From PRE to CRE, serum glucose, insulin, and leptin were reduced. OBR expression was augmented in all examined muscles associated with increased maximal fat oxidation. Compared with PRE, after CD, phospho-Tyr 1141 OBR, phospho-Tyr 985 OBR, JAK2, and phospho-Tyr 1007/1008 JAK2 protein expression were increased in all muscles, whereas STAT3 and phospho-Tyr 705 STAT3 were increased only in the arms. The expression of protein tyrosine phosphatase 1B (PTP1B) in skeletal muscle was increased by 18 and 45% after CRE and CD, respectively ( P < 0.05). Suppressor of cytokine signaling 3 (SOCS3) tended to increase in the legs and decrease in the arm muscles (ANOVA interaction: P < 0.05). Myosin heavy chain I isoform was associated with OBR protein expression ( r  = -0.75), phospho-Tyr 985 OBR ( r  = 0.88), and phospho-Tyr 705 STAT3/STAT3 ( r = 0.74). In summary, despite increased PTP1B expression, skeletal muscle OBR and signaling are upregulated by a severe energy deficit with greater response in the arm than in the legs likely due to SOCS3 upregulation in the leg muscles. NEW & NOTEWORTHY This study shows that the skeletal muscle leptin receptors and their corresponding signaling cascade are upregulated in

The Effects of Hsp90α1 Mutations on Myosin Thick Filament Organization.

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He, Qiuxia; Liu, Kechun; Tian, Zhenjun; Du, Shao Jun

2015-01-01

Heat shock protein 90α plays a key role in myosin folding and thick filament assembly in muscle cells. To assess the structure and function of Hsp90α and its potential regulation by post-translational modification, we developed a combined knockdown and rescue assay in zebrafish embryos to systematically analyze the effects of various mutations on Hsp90α function in myosin thick filament organization. DNA constructs expressing the Hsp90α1 mutants with altered putative ATP binding, phosphorylation, acetylation or methylation sites were co-injected with Hsp90α1 specific morpholino into zebrafish embryos. Myosin thick filament organization was analyzed in skeletal muscles of the injected embryos by immunostaining. The results showed that mutating the conserved D90 residue in the Hsp90α1 ATP binding domain abolished its function in thick filament organization. In addition, phosphorylation mimicking mutations of T33D, T33E and T87E compromised Hsp90α1 function in myosin thick filament organization. Similarly, K287Q acetylation mimicking mutation repressed Hsp90α1 function in myosin thick filament organization. In contrast, K206R and K608R hypomethylation mimicking mutations had not effect on Hsp90α1 function in thick filament organization. Given that T33 and T87 are highly conserved residues involved post-translational modification (PTM) in yeast, mouse and human Hsp90 proteins, data from this study could indicate that Hsp90α1 function in myosin thick filament organization is potentially regulated by PTMs involving phosphorylation and acetylation.

Myosin heavy chain expression in cranial, pectoral fin, and tail muscle regions of zebrafish embryos.

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Peng, Mou-Yun; Wen, Hui-Ju; Shih, Li-Jane; Kuo, Ching-Ming; Hwang, Sheng-Ping L

2002-12-01

To investigate whether different myosin heavy chain (MHC) isoforms may constitute myofibrils in the trunk and tail musculature and if their respective expression may be regulated by spadetail (spt) and no tail (brachyury), we identified and characterized mRNA expression patterns of an embryonic- and tail muscle-specific MHC gene (named myhz2) during zebrafish development in wild type, spt, and ntl mutant embryos. The identified myhz2 MHC gene encodes a polypeptide containing 1,935 amino acids. Deduced amino acid comparisons showed that myhz2 MHC shared 92.6% sequence identity with that of carp fast skeletal MHC. Temporal and spatial myhz2 MHC mRNA expression patterns were analyzed by quantitative RT-PCR and whole-mount in situ hybridization using primer pairs and probes designed from the 3'-untranslated region (UTR). Temporally myhz2 MHC mRNA appears in pharyngula embryos and peaks in protruding-mouth larvae. The expression level decreased in 7-day-old hatching larvae, and mRNA expression was not detectable in adult fish. Spatially in pharyngula embryos, mRNA was localized only in the tail somite region, while in long-pec embryos, transcripts were also expressed in the two cranial muscle elements of the adductor mandibulae and medial rectus, as well as in pectoral fin muscles and the tail muscle region. Myhz2 MHC mRNA was expressed in most cranial muscle elements, pectoral fin muscles, and the tail muscle region of 3-day-old hatching larvae. In contrast, no expression of myhz2 MHC mRNA could be observed in spt prim-15 mutant embryos. In spt long-pec mutant embryos, transcripts were expressed in two cranial muscle elements and the tail muscle region, but not in pectoral fin muscles, while only trace amounts of myhz2 MHC mRNA were expressed in the remaining tail muscle region of 38 hpf and long-pec ntl mutant embryos. Copyright 2002 Wiley-Liss, Inc.

The effects of space flight on the contractile apparatus of antigravity muscles: implications for aging and deconditioning

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Baldwin, K. M.; Caiozzo, V. J.; Haddad, F.; Baker, M. J.; Herrick, R. E.

1994-01-01

Previous studies have shown that the unloading of skeletal muscle, as occurring during exposure to space flight, exerts a profound effect on both the mass (cross sectional area) of skeletal muscle fibers and the relative expression of protein isoforms comprising the contractile system. Available information suggests that slow (type I) fibers, comprising chiefly the antigravity muscles of experimental animals, in addition to atrophying, undergo alterations in the type of myosin heavy chain (MHC) expressed such that faster isoforms become concomitantly expressed in a sub-population of slow fibers when insufficient force-bearing activity is maintained on the muscle. Consequently, these transformations in both mass and myosin heavy chain phenotype could exert a significant impact on the functional properties of skeletal muscle as manifest in the strength, contractile speed, and endurance scope of the muscle. To further explore these issues, a study was performed in which young adult male rats were exposed to zero gravity for six days, following which, the antigravity soleus muscle was examined for a) contractile properties, determined in situ and b) isomyosin expression, as studied using biochemical, molecular biology, and histochemical/immunohistochemical techniques.

Proteomics of Skeletal Muscle: Focus on Insulin Resistance and Exercise Biology

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Atul S. Deshmukh

2016-02-01

Full Text Available Skeletal muscle is the largest tissue in the human body and plays an important role in locomotion and whole body metabolism. It accounts for ~80% of insulin stimulated glucose disposal. Skeletal muscle insulin resistance, a primary feature of Type 2 diabetes, is caused by a decreased ability of muscle to respond to circulating insulin. Physical exercise improves insulin sensitivity and whole body metabolism and remains one of the most promising interventions for the prevention of Type 2 diabetes. Insulin resistance and exercise adaptations in skeletal muscle might be a cause, or consequence, of altered protein expressions profiles and/or their posttranslational modifications (PTMs. Mass spectrometry (MS-based proteomics offer enormous promise for investigating the molecular mechanisms underlying skeletal muscle insulin resistance and exercise-induced adaptation; however, skeletal muscle proteomics are challenging. This review describes the technical limitations of skeletal muscle proteomics as well as emerging developments in proteomics workflow with respect to samples preparation, liquid chromatography (LC, MS and computational analysis. These technologies have not yet been fully exploited in the field of skeletal muscle proteomics. Future studies that involve state-of-the-art proteomics technology will broaden our understanding of exercise-induced adaptations as well as molecular pathogenesis of insulin resistance. This could lead to the identification of new therapeutic targets.

High Fat Diet-Induced Skeletal Muscle Wasting Is Decreased by Mesenchymal Stem Cells Administration: Implications on Oxidative Stress, Ubiquitin Proteasome Pathway Activation, and Myonuclear Apoptosis

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Johanna Abrigo

2016-01-01

Full Text Available Obesity can lead to skeletal muscle atrophy, a pathological condition characterized by the loss of strength and muscle mass. A feature of muscle atrophy is a decrease of myofibrillar proteins as a result of ubiquitin proteasome pathway overactivation, as evidenced by increased expression of the muscle-specific ubiquitin ligases atrogin-1 and MuRF-1. Additionally, other mechanisms are related to muscle wasting, including oxidative stress, myonuclear apoptosis, and autophagy. Stem cells are an emerging therapy in the treatment of chronic diseases such as high fat diet-induced obesity. Mesenchymal stem cells (MSCs are a population of self-renewable and undifferentiated cells present in the bone marrow and other mesenchymal tissues of adult individuals. The present study is the first to analyze the effects of systemic MSC administration on high fat diet-induced skeletal muscle atrophy in the tibialis anterior of mice. Treatment with MSCs reduced losses of muscle strength and mass, decreases of fiber diameter and myosin heavy chain protein levels, and fiber type transitions. Underlying these antiatrophic effects, MSC administration also decreased ubiquitin proteasome pathway activation, oxidative stress, and myonuclear apoptosis. These results are the first to indicate that systemically administered MSCs could prevent muscle wasting associated with high fat diet-induced obesity and diabetes.

Effects of Nandrolone in the Counteraction of Skeletal Muscle Atrophy in a Mouse Model of Muscle Disuse: Molecular Biology and Functional Evaluation.

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Giulia Maria Camerino

Full Text Available Muscle disuse produces severe atrophy and a slow-to-fast phenotype transition in the postural Soleus (Sol muscle of rodents. Antioxidants, amino-acids and growth factors were ineffective to ameliorate muscle atrophy. Here we evaluate the effects of nandrolone (ND, an anabolic steroid, on mouse skeletal muscle atrophy induced by hindlimb unloading (HU. Mice were pre-treated for 2-weeks before HU and during the 2-weeks of HU. Muscle weight and total protein content were reduced in HU mice and a restoration of these parameters was found in ND-treated HU mice. The analysis of gene expression by real-time PCR demonstrates an increase of MuRF-1 during HU but minor involvement of other catabolic pathways. However, ND did not affect MuRF-1 expression. The evaluation of anabolic pathways showed no change in mTOR and eIF2-kinase mRNA expression, but the protein expression of the eukaryotic initiation factor eIF2 was reduced during HU and restored by ND. Moreover we found an involvement of regenerative pathways, since the increase of MyoD observed after HU suggests the promotion of myogenic stem cell differentiation in response to atrophy. At the same time, Notch-1 expression was down-regulated. Interestingly, the ND treatment prevented changes in MyoD and Notch-1 expression. On the contrary, there was no evidence for an effect of ND on the change of muscle phenotype induced by HU, since no effect of treatment was observed on the resting gCl, restCa and contractile properties in Sol muscle. Accordingly, PGC1α and myosin heavy chain expression, indexes of the phenotype transition, were not restored in ND-treated HU mice. We hypothesize that ND is unable to directly affect the phenotype transition when the specialized motor unit firing pattern of stimulation is lacking. Nevertheless, through stimulation of protein synthesis, ND preserves protein content and muscle weight, which may result advantageous to the affected skeletal muscle for functional recovery.

[Myosin B ATPase activity of the intestinal smooth muscle in intestinal obstruction].

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Takamatsu, H

1983-06-01

Intestinal smooth myosin B was prepared from muscle layers around the lesion in dogs with experimental colonic stenosis and in patients with congenital intestinal obstruction. Mg2+-ATPase activity of the myosin B was compared between the proximal dilated segment and distal segment to obstruction. Experimental colonic stenosis: In early period after surgery, proximal colons showed higher activity of myosin B ATPase than distal colons, decreasing to less than distal colon as time passed. Congenital intestinal obstruction: In three cases, whose atresia might have occurred at earlier period of gestation, proximal bowels showed less activity of myosin B ATPase than distal bowels. However, in two cases, whose atresia might have occurred at later period of gestation, and two cases with intestinal stenosis, proximal bowels indicated higher activity of myosin B ATPase than distal bowels. These data suggested that the contractibility of the proximal intestine was depending on the duration of obstruction, and it was depressed in the former patients and was accelerated in the latter patients. These results suggested that the extensive resection of dilated proximal bowel in the congenital atresia is not always necessary to obtain good postoperative intestinal dynamics at the operation of the atresial lesions which may be induced at later period of gestation. They also suggested that surgery for intestinal obstruction should be performed before the depression of intestinal contractibility to get good bowel function.

L-Citrulline Supplementation-Increased Skeletal Muscle PGC-1α Expression is Associated With Exercise Performance and Increased Skeletal Muscle Weight.

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Villareal, Myra O; Matsukawa, Toshiya; Isoda, Hiroko

2018-05-24

L-citrulline has recently been reported as a more effective supplement for promoting intracellular NO production compared to L-arginine. Here, the effect of L-citrulline on skeletal muscle and its influence on exercise performance were investigated. The underlying mechanism of its effect, specifically on the expression of skeletal muscle peroxisome proliferator-activated receptor-gamma coactivator-1α (PGC-1α), was also elucidated. Six-week-old ICR mice were orally supplemented with L-citrulline (250 mg kg -1 ) daily, and their performance in weight-loaded swimming exercise every other day for 15 days, was evaluated. In addition, mice muscles were weighed and evaluated for the expression of PGC-1α and PGC-1α-regulated genes. Mice orally supplemented with L-citrulline had significantly higher gastrocnemius and biceps femoris muscle mass. Although not statistically significant, L-citrulline prolonged the swimming time to exhaustion. PGC-1α upregulation was associated with vascular endothelial growth factor α (VEGFα) and insulin-like growth factor 1 (IGF1) upregulation. VEGFα and IGF1 are important for angiogenesis and muscle growth, respectively, and are regulated by PGC-1α. Treatment with L-NAME, a nitric oxide synthesis inhibitor, suppressed the L-citrulline-induced PGC-1α upregulation in-vitro. Supplementation with L-citrulline upregulates skeletal muscle PGC-1α levels resulting to higher skeletal muscle weight that improves time to exhaustion during exercise. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Comparative Statistical Mechanics of Muscle and Non-Muscle Contractile Systems: Stationary States of Near-Equilibrium Systems in A Linear Regime

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Yves Lecarpentier

2017-10-01

Full Text Available A. Huxley’s equations were used to determine the mechanical properties of muscle myosin II (MII at the molecular level, as well as the probability of the occurrence of the different stages in the actin–myosin cycle. It was then possible to use the formalism of statistical mechanics with the grand canonical ensemble to calculate numerous thermodynamic parameters such as entropy, internal energy, affinity, thermodynamic flow, thermodynamic force, and entropy production rate. This allows us to compare the thermodynamic parameters of a non-muscle contractile system, such as the normal human placenta, with those of different striated skeletal muscles (soleus and extensor digitalis longus as well as the heart muscle and smooth muscles (trachea and uterus in the rat. In the human placental tissues, it was observed that the kinetics of the actin–myosin crossbridges were considerably slow compared with those of smooth and striated muscular systems. The entropy production rate was also particularly low in the human placental tissues, as compared with that observed in smooth and striated muscular systems. This is partly due to the low thermodynamic flow found in the human placental tissues. However, the unitary force of non-muscle myosin (NMII generated by each crossbridge cycle in the myofibroblasts of the human placental tissues was similar in magnitude to that of MII in the myocytes of both smooth and striated muscle cells. Statistical mechanics represents a powerful tool for studying the thermodynamics of all contractile muscle and non-muscle systems.

Skeletal muscle inflammation and insulin resistance in obesity

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Wu, Huaizhu; Ballantyne, Christie M.

2017-01-01

Obesity is associated with chronic inflammation, which contributes to insulin resistance and type 2 diabetes mellitus. Under normal conditions, skeletal muscle is responsible for the majority of insulin-stimulated whole-body glucose disposal; thus, dysregulation of skeletal muscle metabolism can strongly influence whole-body glucose homeostasis and insulin sensitivity. Increasing evidence suggests that inflammation occurs in skeletal muscle in obesity and is mainly manifested by increased immune cell infiltration and proinflammatory activation in intermyocellular and perimuscular adipose tissue. By secreting proinflammatory molecules, immune cells may induce myocyte inflammation, adversely regulate myocyte metabolism, and contribute to insulin resistance via paracrine effects. Increased influx of fatty acids and inflammatory molecules from other tissues, particularly visceral adipose tissue, can also induce muscle inflammation and negatively regulate myocyte metabolism, leading to insulin resistance. PMID:28045398

Skeletal muscle as a gene regulatory endocrine organ

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Karstoft, Kristian; Pedersen, Bente K.

2016-01-01

Purpose of review Skeletal muscle is gaining increased attention as an endocrine organ. Recently, novel myokines and new effects of already established myokines have been identified. The objective of this review is to give an update on the recent advances in the field. Recent findings Several...... hundred putative myokines have been described, some of which are induced by contraction and differentially regulated between healthy and metabolically diseased individuals. Interleukin-6 (IL-6) is the prototype myokine, which was identified as a muscle-derived cytokine 15 years ago. Recently, IL-6 has...... on training status. IL-15 has been established as a cytokine mediating cross-talk between skeletal muscle and skin tissue, and decorin has been characterized as a contraction-induced myokine which apparently is differentially regulated between healthy and dysglycemic individuals. Summary Skeletal muscle...

Tetanic contraction induces enhancement of fatigability and sarcomeric damage in atrophic skeletal muscle and its underlying molecular mechanisms.

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Yu, Zhi-Bin

2013-11-01

Muscle unloading due to long-term exposure of weightlessness or simulated weightlessness causes atrophy, loss of functional capacity, impaired locomotor coordination, and decreased resistance to fatigue in the antigravity muscles of the lower limbs. Besides reducing astronauts' mobility in space and on returning to a gravity environment, the molecular mechanisms for the adaptation of skeletal muscle to unloading also play an important medical role in conditions such as disuse and paralysis. The tail-suspended rat model was used to simulate the effects of weightlessness on skeletal muscles and to induce muscle unloading in the rat hindlimb. Our series studies have shown that the maximum of twitch tension and the twitch duration decreased significantly in the atrophic soleus muscles, the maximal tension of high-frequency tetanic contraction was significantly reduced in 2-week unloaded soleus muscles, however, the fatigability of high-frequency tetanic contraction increased after one week of unloading. The maximal isometric tension of intermittent tetanic contraction at optimal stimulating frequency did not alter in 1- and 2-week unloaded soleus, but significantly decreased in 4-week unloaded soleus. The 1-week unloaded soleus, but not extensor digitorum longus (EDL), was more susceptible to fatigue during intermittent tetanic contraction than the synchronous controls. The changes in K+ channel characteristics may increase the fatigability during high-frequency tetanic contraction in atrophic soleus muscles. High fatigability of intermittent tetanic contraction may be involved in enhanced activity of sarcoplasmic reticulum Ca(2+)-ATPase (SERCA) and switching from slow to fast isoform of myosin heavy chain, tropomyosin, troponin I and T subunit in atrophic soleus muscles. Unloaded soleus muscle also showed a decreased protein level of neuronal nitric oxide synthase (nNOS), and the reduction in nNOS-derived NO increased frequency of calcium sparks and elevated

Poorly Understood Aspects of Striated Muscle Contraction

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Alf Månsson

2015-01-01

Full Text Available Muscle contraction results from cyclic interactions between the contractile proteins myosin and actin, driven by the turnover of adenosine triphosphate (ATP. Despite intense studies, several molecular events in the contraction process are poorly understood, including the relationship between force-generation and phosphate-release in the ATP-turnover. Different aspects of the force-generating transition are reflected in the changes in tension development by muscle cells, myofibrils and single molecules upon changes in temperature, altered phosphate concentration, or length perturbations. It has been notoriously difficult to explain all these events within a given theoretical framework and to unequivocally correlate observed events with the atomic structures of the myosin motor. Other incompletely understood issues include the role of the two heads of myosin II and structural changes in the actin filaments as well as the importance of the three-dimensional order. We here review these issues in relation to controversies regarding basic physiological properties of striated muscle. We also briefly consider actomyosin mutation effects in cardiac and skeletal muscle function and the possibility to treat these defects by drugs.

Identification of telocytes in skeletal muscle interstitium: implication for muscle regeneration.

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Popescu, L M; Manole, Emilia; Serboiu, Crenguţa S; Manole, C G; Suciu, Laura C; Gherghiceanu, Mihaela; Popescu, B O

2011-06-01

Skeletal muscle interstitium is crucial for regulation of blood flow, passage of substances from capillaries to myocytes and muscle regeneration. We show here, probably, for the first time, the presence of telocytes (TCs), a peculiar type of interstitial (stromal) cells, in rat, mouse and human skeletal muscle. TC features include (as already described in other tissues) a small cell body and very long and thin cell prolongations-telopodes (Tps) with moniliform appearance, dichotomous branching and 3D-network distribution. Transmission electron microscopy (TEM) revealed close vicinity of Tps with nerve endings, capillaries, satellite cells and myocytes, suggesting a TC role in intercellular signalling (via shed vesicles or exosomes). In situ immunolabelling showed that skeletal muscle TCs express c-kit, caveolin-1 and secrete VEGF. The same phenotypic profile was demonstrated in cell cultures. These markers and TEM data differentiate TCs from both satellite cells (e.g. TCs are Pax7 negative) and fibroblasts (which are c-kit negative). We also described non-satellite (resident) progenitor cell niche. In culture, TCs (but not satellite cells) emerge from muscle explants and form networks suggesting a key role in muscle regeneration and repair, at least after trauma. © 2011 The Authors Journal of Cellular and Molecular Medicine © 2011 Foundation for Cellular and Molecular Medicine/Blackwell Publishing Ltd.

Clinical assessment of serum myosin light chain I in patients with dilated cardiomyopathy

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Tsuda, Takashi; Izumi, Tohru; Shibata, Akira (Niigata Univ. (Japan). School of Medicine)

1992-08-01

Serum cardiac myosin light chain I (LCI) levels were quantitated using a radioimmunoassay kit in patients suspected of dilated cardiomyopathy (DCM). In this study, 55 patients were evaluated between 1986 and 1991. They were composed of 40 males and 15 females, and their age was 27-75 years (51[+-]11 years). The patients with renal dysfunction were excluded due to their serum creatinine levels (>2.0 mg/dl). After cardiac catheterization, endomyocardial biopsy and echocardiography, 44 patients were diagnosed as DCM, 2 as ischemic heart disease, 2 as chronic myocarditis, 1 as restrictive cardiomyopathy, 1 as dilated hypertrophic cardiomyopathy, 1 as cardiac amyloidosis, 2 as myopathy, 1 as polymyositis and 1 as hypothyroidism. Only two patients with DCM had elevated LCI. Besides, two patients with myopathy or hypothyroidism had elevated LCI. In the follow-up, one patient died suddenly 6 months later and another showed normal value of LCI four years later. LCI elevation in DCM was not related to either the severity of heart failure or cardiac function and it showed no finding of [sup 201]Tl myocardial defect or elevated CPK. The mechanism for elevated LCI in myopathy is related to a crossreaction with myosin light chain in the skeletal muscle. In hypothyroidism, it may be related to decreased clearance of normal LCI concentration or increased myosin light chain from damaged skeletal muscle. In conclusion, it is evident that the measurement of LCI is not helpful in clinical assessment of patients with DCM, but may be useful in detection of secondary cardiomyopathy. (author).

Clinical assessment of serum myosin light chain I in patients with dilated cardiomyopathy

International Nuclear Information System (INIS)

Tsuda, Takashi; Izumi, Tohru; Shibata, Akira

1992-01-01

Serum cardiac myosin light chain I (LCI) levels were quantitated using a radioimmunoassay kit in patients suspected of dilated cardiomyopathy (DCM). In this study, 55 patients were evaluated between 1986 and 1991. They were composed of 40 males and 15 females, and their age was 27-75 years (51±11 years). The patients with renal dysfunction were excluded due to their serum creatinine levels (>2.0 mg/dl). After cardiac catheterization, endomyocardial biopsy and echocardiography, 44 patients were diagnosed as DCM, 2 as ischemic heart disease, 2 as chronic myocarditis, 1 as restrictive cardiomyopathy, 1 as dilated hypertrophic cardiomyopathy, 1 as cardiac amyloidosis, 2 as myopathy, 1 as polymyositis and 1 as hypothyroidism. Only two patients with DCM had elevated LCI. Besides, two patients with myopathy or hypothyroidism had elevated LCI. In the follow-up, one patient died suddenly 6 months later and another showed normal value of LCI four years later. LCI elevation in DCM was not related to either the severity of heart failure or cardiac function and it showed no finding of 201 Tl myocardial defect or elevated CPK. The mechanism for elevated LCI in myopathy is related to a crossreaction with myosin light chain in the skeletal muscle. In hypothyroidism, it may be related to decreased clearance of normal LCI concentration or increased myosin light chain from damaged skeletal muscle. In conclusion, it is evident that the measurement of LCI is not helpful in clinical assessment of patients with DCM, but may be useful in detection of secondary cardiomyopathy. (author)

How is AMPK activity regulated in skeletal muscles during exercise?

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Jørgensen, Sebastian Beck; Rose, Adam John

2008-01-01

AMPK is a metabolic "master" controller activated in skeletal muscle by exercise in a time and intensity dependent manner, and has been implicated in regulating metabolic pathways in muscle during physical exercise. AMPK signaling in skeletal muscle is regulated by several systemic...... and intracellular factors and the regulation of skeletal muscle AMPK in response to exercise is the focus of this review. Specifically, the role of LKB1 and phosphatase PP2C in nucleotide-dependent activation of AMPK, and ionized calcium in CaMKK-dependent activation of AMPK in working muscle is discussed. We also...

Localization of 3H-diethylstilbestrol in skeletal muscle

International Nuclear Information System (INIS)

Gruber, B.; Cohen, L.

1981-01-01

The localization of diethylstilbestrol (DES) in skeletal muscle was studied in CF1 mice and perfused rat hindlimbs. There was a slow accumulation of 3H-DES in mouse muscle from 4 to 24 hours following i.p. injection even though plasma DES was decreasing. Twenty-four hours after injection of 50 microCi 3H-DES (714 pmole) mouse gastrocnemius contained 8.9 x 10(-17) mole unaltered 3H-DES per mg muscle. Extrapolating to the entire skeletal muscle mass of the animal, this represents 0.15% of the radioactivity injected. The radioactivity in muscle was completely extracted with 95% ethanol or ether: ethanol (3:1), and both unaltered DES and DES-metabolites were present in the extracts. The fraction of radioactivity due to unaltered DES 4 hours after injection was 0.51 +/- 0.09 in muscle and 0.30 +/- 0.11 in plasma. Significant extrahepatic metabolism of DES was demonstrated in perfused isolated rat hindlimbs by the presence of DES-metabolites in the perfusate. The radioactivity extracted from the perfused muscle itself was unaltered DES. These results indicate that skeletal muscle is an important site of DES localization in rodents

Regulation of the skeletal muscle blood flow in humans

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Mortensen, Stefan; Saltin, Bengt

2014-01-01

In humans, skeletal muscle blood flow is regulated by an interaction between several locally formed vasodilators including nitric oxide (NO) and prostaglandins. In plasma, ATP is a potent vasodilator that stimulates the formation of NO and prostaglandins and very importantly can offset local...... concentration does not increase during exercise. In the skeletal muscle interstitium, there is a marked increase in the concentration of ATP and adenosine and this increase is tightly coupled to the increase in blood flow. The sources of interstitial ATP and adenosine are thought to be skeletal muscle cells...... hyperaemia whereas the role of ATP remains uncertain due to lack of specific purinergic receptor blockers for human use. The purpose of this review is to address the interaction between vasodilator systems and to discuss the multiple proposed roles of ATP in human skeletal muscle blood flow regulation...

Skeletal muscle apolipoprotein B expression reduces muscular triglyceride accumulation

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Bartels, Emil D; Ploug, Thorkil; Størling, Joachim

2014-01-01

Abstract Background. Lipid accumulation in skeletal muscle is associated with impaired insulin sensitivity in type 2 diabetes. In cardiac myocytes, lipoprotein secretion controlled by apolipoproteinB (apoB) and microsomal triglyceride transfer protein (MTP) affects lipid homeostasis. Design. In t...... accumulation and attenuates peripheral insulin resistance in obese mice........ In this study, we investigated whether expression of a human apoB transgene affects triglyceride accumulation and insulin sensitivity in skeletal muscle in fat fed obese mice. Results. Expression of apoB and MTP mRNA and the human apoB transgene was seen in skeletal muscle of the transgene mice. Human apo......Abstract Background. Lipid accumulation in skeletal muscle is associated with impaired insulin sensitivity in type 2 diabetes. In cardiac myocytes, lipoprotein secretion controlled by apolipoproteinB (apoB) and microsomal triglyceride transfer protein (MTP) affects lipid homeostasis. Design...

ALDH2 restores exhaustive exercise-induced mitochondrial dysfunction in skeletal muscle

International Nuclear Information System (INIS)

Zhang, Qiuping; Zheng, Jianheng; Qiu, Jun; Wu, Xiahong; Xu, Yangshuo; Shen, Weili; Sun, Mengwei

2017-01-01

Background: Mitochondrial aldehyde dehydrogenase 2 (ALDH2) is highly expressed in heart and skeletal muscles, and is the major enzyme that metabolizes acetaldehyde and toxic aldehydes. The cardioprotective effects of ALDH2 during cardiac ischemia/reperfusion injury have been recognized. However, less is known about the function of ALDH2 in skeletal muscle. This study was designed to evaluate the effect of ALDH2 on exhaustive exercise-induced skeletal muscle injury. Methods: We created transgenic mice expressing ALDH2 in skeletal muscles. Male wild-type C57/BL6 (WT) and ALDH2 transgenic mice (ALDH2-Tg), 8-weeks old, were challenged with exhaustive exercise for 1 week to induce skeletal muscle injury. Animals were sacrificed 24 h post-exercise and muscle tissue was excised. Results: ALDH2-Tg mice displayed significantly increased treadmill exercise capacity compared to WT mice. Exhaustive exercise caused an increase in mRNA levels of the muscle atrophy markers, Atrogin-1 and MuRF1, and reduced mitochondrial biogenesis and fusion in WT skeletal muscles; these effects were attenuated in ALDH2-Tg mice. Exhaustive exercise also enhanced mitochondrial autophagy pathway activity, including increased conversion of LC3-I to LC3-II and greater expression of Beclin1 and Bnip3; the effects of which were mitigated by ALDH2 overexpression. In addition, ALDH2-Tg reversed the increase of an oxidative stress biomarker (4-hydroxynonenal) and decreased levels of mitochondrial antioxidant proteins, including manganese superoxide dismutase and NAD(P)H:quinone oxidoreductase 1, in skeletal muscle induced by exhaustive exercise. Conclusion: ALDH2 may reverse skeletal muscle mitochondrial dysfunction due to exhaustive exercise by regulating mitochondria dynamic remodeling and enhancing the quality of mitochondria. - Highlights: • Skeletal muscle ALDH2 expression and activity declines during exhaustive exercise. • ALDH2 overexpression enhances physical performance and restores muscle

Skeletal muscle metastases: primary tumours, prevalence, and radiological features

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Surov, Alexey; Spielmann, Rolf Peter; Behrmann, Curd; Hainz, Michael; Holzhausen, Hans-Juergen; Arnold, Dirk; Katzer, Michaela; Schmidt, Joerg

2010-01-01

Although skeletal muscles comprise nearly 50% of the total human body mass and are well vascularised, metastases in the musculature are rare. The reported prevalence of skeletal muscle metastases from post-mortem studies of patients with cancer is inconstant and ranges from 0.03 to 17.5%. Of 5,170 patients with metastasised cancer examined and treated at our institution during the period from January 2000 to December 2007, 61 patients with muscle metastases (80 lesions) were identified on computed tomography (CT). Genital tumours (24.6%) were the most frequent malignancies metastasising into the skeletal musculature, followed by gastrointestinal tumours (21.3%), urological tumours (16.4%), and malignant melanoma (13.1%). Other primary malignancies were rarer, including bronchial carcinoma (8.2%), thyroid gland carcinoma (4.9%), and breast carcinoma (3.3%). In 8.2%, carcinoma of unknown primary was diagnosed. Skeletal muscle metastases (SMM) were located in the iliopsoas muscle (27.5%), paravertebral muscles (25%), gluteal muscles (16.3%), lower extremity muscles (12.5%), abdominal wall muscles (10%), thoracic wall muscles (5%), and upper extremity muscles (3.8%). Most (76.3%) of the 80 SMM were diagnosed incidentally during routine staging CT examinations, while 23.7% were symptomatic. Radiologically, SMM presented with five different types of lesions: focal intramuscular masses (type I, 52.5% of SMM), abscess-like intramuscular lesions (type II, 32.5%), diffuse metastatic muscle infiltration (type III, 8.8%), multifocal intramuscular calcification (type IV, 3.7%) and intramuscular bleeding (type V, 2.5%). (orig.)

Skeletal muscle metastases: primary tumours, prevalence, and radiological features

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Surov, Alexey; Spielmann, Rolf Peter; Behrmann, Curd [Martin-Luther-University Halle-Wittenberg, Department of Radiology, Halle (Germany); Hainz, Michael; Holzhausen, Hans-Juergen [Martin-Luther-University Halle-Wittenberg, Department of Pathology, Halle (Germany); Arnold, Dirk [Martin-Luther-University Halle-Wittenberg, Department of Haematology/Oncology, Halle (Germany); Katzer, Michaela [Martin-Luther-University Halle-Wittenberg, Department of Urology, Halle (Germany); Schmidt, Joerg [Martin-Luther-University Halle-Wittenberg, Department of Medical Statistics and Controlling, Halle (Germany)

2010-03-15

Although skeletal muscles comprise nearly 50% of the total human body mass and are well vascularised, metastases in the musculature are rare. The reported prevalence of skeletal muscle metastases from post-mortem studies of patients with cancer is inconstant and ranges from 0.03 to 17.5%. Of 5,170 patients with metastasised cancer examined and treated at our institution during the period from January 2000 to December 2007, 61 patients with muscle metastases (80 lesions) were identified on computed tomography (CT). Genital tumours (24.6%) were the most frequent malignancies metastasising into the skeletal musculature, followed by gastrointestinal tumours (21.3%), urological tumours (16.4%), and malignant melanoma (13.1%). Other primary malignancies were rarer, including bronchial carcinoma (8.2%), thyroid gland carcinoma (4.9%), and breast carcinoma (3.3%). In 8.2%, carcinoma of unknown primary was diagnosed. Skeletal muscle metastases (SMM) were located in the iliopsoas muscle (27.5%), paravertebral muscles (25%), gluteal muscles (16.3%), lower extremity muscles (12.5%), abdominal wall muscles (10%), thoracic wall muscles (5%), and upper extremity muscles (3.8%). Most (76.3%) of the 80 SMM were diagnosed incidentally during routine staging CT examinations, while 23.7% were symptomatic. Radiologically, SMM presented with five different types of lesions: focal intramuscular masses (type I, 52.5% of SMM), abscess-like intramuscular lesions (type II, 32.5%), diffuse metastatic muscle infiltration (type III, 8.8%), multifocal intramuscular calcification (type IV, 3.7%) and intramuscular bleeding (type V, 2.5%). (orig.)

Catch-slip bonds can be dispensable for motor force regulation during skeletal muscle contraction

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Dong, Chenling; Chen, Bin

2015-07-01

It is intriguing how multiple molecular motors can perform coordinated and synchronous functions, which is essential in various cellular processes. Recent studies on skeletal muscle might have shed light on this issue, where rather precise motor force regulation was partly attributed to the specific stochastic features of a single attached myosin motor. Though attached motors can randomly detach from actin filaments either through an adenosine triphosphate (ATP) hydrolysis cycle or through "catch-slip bond" breaking, their respective contribution in motor force regulation has not been clarified. Here, through simulating a mechanical model of sarcomere with a coupled Monte Carlo method and finite element method, we find that the stochastic features of an ATP hydrolysis cycle can be sufficient while those of catch-slip bonds can be dispensable for motor force regulation.

Maintenance of muscle myosin levels in adult C. elegans requires both the double bromodomain protein BET-1 and sumoylation

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Kate Fisher

2013-10-01

Attenuation of RAS-mediated signalling is a conserved process essential to control cell proliferation, differentiation, and apoptosis. Cooperative interactions between histone modifications such as acetylation, methylation and sumoylation are crucial for proper attenuation in C. elegans, implying that the proteins recognising these histone modifications could also play an important role in attenuation of RAS-mediated signalling. We sought to systematically identify these proteins and found BET-1. BET-1 is a conserved double bromodomain protein that recognises acetyl-lysines on histone tails and maintains the stable fate of various lineages. Unexpectedly, adults lacking both BET-1 and SUMO-1 are depleted of muscle myosin, an essential component of myofibrils. We also show that this muscle myosin depletion does not occur in all animals at a specific time, but rather that the penetrance of the phenotype increases with age. To gain mechanistic insights into this process, we sought to delay the occurrence of the muscle myosin depletion phenotype and found that it requires caspase activity and MEK-dependent signalling. We also performed transcription profiling on these mutants and found an up-regulation of the FGF receptor, egl-15, a tyrosine kinase receptor acting upstream of MEK. Consistent with a MEK requirement, we could delay the muscle phenotype by systemic or hypodermal knock down of egl-15. Thus, this work uncovered a caspase- and MEK-dependent mechanism that acts specifically on ageing adults to maintain the appropriate net level of muscle myosin.

Characteristics of myosin profile in human vastus lateralis muscle in relation to training background.

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Zawadowska, B; Majerczak, J; Semik, D; Karasinski, J; Kolodziejski, L; Kilarski, W M; Duda, K; Zoladz, J A

2004-01-01

Twenty-four male volunteers (mean +/- SD: age 25.4+/-5.8 years, height 178.6+/-5.5 cm, body mass 72.1+/-7.7 kg) of different training background were investigated and classified into three groups according to their physical activity and sport discipline: untrained students (group A), national and sub-national level endurance athletes (group B, 7.8+/-2.9 years of specialised training) and sprint-power athletes (group C, 12.8+/-8.7 years of specialised training). Muscle biopsies of vastus lateralis were analysed histochemically for mATPase and SDH activities, immunohistochemically for fast and slow myosin, and electrophoretically followed by Western immunoblotting for myosin heavy chain (MyHC) composition. Significant differences (Pski-jumping, volleyball, soccer and modern dance. Furthermore, the relative amount of the fastest MyHCIIX isoform in vastus lateralis muscle was significantly lower in the athletes from group C than in students (group A). We conclude that the myosin profile in the athletes belonging to group C was unfavourable for their sport disciplines. This could be the reason why those athletes did not reach international level despite of several years of training.

Dissemination of Walker 256 carcinoma cells to rat skeletal muscle

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Ueoka, H.; Hayashi, K.; Namba, T.; Grob, D.

1986-01-01

After injection of 10 6 Walker 256 carcinoma cells labelled with 125 I-5-iodo-2'-deoxyuridine into the tail vein, peak concentration in skeletal muscle was 46 cells/g at 60 minutes, which was lower than 169202, 1665, 555, 198 and 133 cells/g, respectively, at 30 or 60 minutes in lung, liver, spleen, kidney and heart. Because skeletal muscle constitutes 37.4% of body weight, the total number of tumor cells was 2323 cells, which was much greater than in spleen, kidney and heart with 238, 271, and 85 cells, respectively, and only less than in lung and liver, at 222857 and 11700 cells, respectively. The total number in skeletal muscle became greater than in liver at 4 hours and than in lung at 24 hours. Ten minutes after injection of 7.5 x 10 6 Walker 256 carcinoma cells into the abdominal aorta of rats, a mean of 31 colony-forming cells were recovered from the gastrocnemius, while 106 cells were recovered from the lung after injection into the tail vein. These results indicate that a large number of viable tumor cells can be arrested in skeletal muscle through circulation. The rare remote metastasis of malignancies into skeletal muscle despite constantly circulating tumor cells does not appear to be due to poor dissemination of tumor cells into muscle but due to unhospitable environment of skeletal muscle

Insulin Increases Ceramide Synthesis in Skeletal Muscle

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M. E. Hansen

2014-01-01

Full Text Available Aims. The purpose of this study was to determine the effect of insulin on ceramide metabolism in skeletal muscle. Methods. Skeletal muscle cells were treated with insulin with or without palmitate for various time periods. Lipids (ceramides and TAG were isolated and gene expression of multiple biosynthetic enzymes were quantified. Additionally, adult male mice received daily insulin injections for 14 days, followed by muscle ceramide analysis. Results. In muscle cells, insulin elicited an increase in ceramides comparable to palmitate alone. This is likely partly due to an insulin-induced increase in expression of multiple enzymes, particularly SPT2, which, when knocked down, prevented the increase in ceramides. In mice, 14 days of insulin injection resulted in increased soleus ceramides, but not TAG. However, insulin injections did significantly increase hepatic TAG compared with vehicle-injected animals. Conclusions. This study suggests that insulin elicits an anabolic effect on sphingolipid metabolism in skeletal muscle, resulting in increased ceramide accumulation. These findings reveal a potential mechanism of the deleterious consequences of the hyperinsulinemia that accompanies insulin resistance and suggest a possible novel therapeutic target to mitigate its effects.

Insulin binding to individual rat skeletal muscles

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Koerker, D.J.; Sweet, I.R.; Baskin, D.G.

1990-01-01

Studies of insulin binding to skeletal muscle, performed using sarcolemmal membrane preparations or whole muscle incubations of mixed muscle or typical red (soleus, psoas) or white [extensor digitorum longus (EDL), gastrocnemius] muscle, have suggested that red muscle binds more insulin than white muscle. We have evaluated this hypothesis using cryostat sections of unfixed tissue to measure insulin binding in a broad range of skeletal muscles; many were of similar fiber-type profiles. Insulin binding per square millimeter of skeletal muscle slice was measured by autoradiography and computer-assisted densitometry. We found a 4.5-fold range in specific insulin tracer binding, with heart and predominantly slow-twitch oxidative muscles (SO) at the high end and the predominantly fast-twitch glycolytic (FG) muscles at the low end of the range. This pattern reflects insulin sensitivity. Evaluation of displacement curves for insulin binding yielded linear Scatchard plots. The dissociation constants varied over a ninefold range (0.26-2.06 nM). Binding capacity varied from 12.2 to 82.7 fmol/mm2. Neither binding parameter was correlated with fiber type or insulin sensitivity; e.g., among three muscles of similar fiber-type profile, the EDL had high numbers of low-affinity binding sites, whereas the quadriceps had low numbers of high-affinity sites. In summary, considerable heterogeneity in insulin binding was found among hindlimb muscles of the rat, which can be attributed to heterogeneity in binding affinities and the numbers of binding sites. It can be concluded that a given fiber type is not uniquely associated with a set of insulin binding parameters that result in high or low binding

A leucine-supplemented diet improved protein content of skeletal muscle in young tumor-bearing rats

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Gomes-Marcondes M.C.C.

2003-01-01

Full Text Available Cancer cachexia induces host protein wastage but the mechanisms are poorly understood. Branched-chain amino acids play a regulatory role in the modulation of both protein synthesis and degradation in host tissues. Leucine, an important amino acid in skeletal muscle, is higher oxidized in tumor-bearing animals. A leucine-supplemented diet was used to analyze the effects of Walker 256 tumor growth on body composition in young weanling Wistar rats divided into two main dietary groups: normal diet (N, 18% protein and leucine-rich diet (L, 15% protein plus 3% leucine, which were further subdivided into control (N or L or tumor-bearing (W or LW subgroups. After 12 days, the animals were sacrificed and their carcass analyzed. The tumor-bearing groups showed a decrease in body weight and fat content. Lean carcass mass was lower in the W and LW groups (W = 19.9 ± 0.6, LW = 23.1 ± 1.0 g vs N = 29.4 ± 1.3, L = 28.1 ± 1.9 g, P < 0.05. Tumor weight was similar in both tumor-bearing groups fed either diet. Western blot analysis showed that myosin protein content in gastrocnemius muscle was reduced in tumor-bearing animals (W = 0.234 ± 0.033 vs LW = 0.598 ± 0.036, N = 0.623 ± 0.062, L = 0.697 ± 0.065 arbitrary intensity, P < 0.05. Despite accelerated tumor growth, LW animals exhibited a smaller reduction in lean carcass mass and muscle myosin maintenance, suggesting that excess leucine in the diet could counteract, at least in part, the high host protein wasting in weanling tumor-bearing rats.

Alterations of cAMP-dependent signaling in dystrophic skeletal muscle

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Rüdiger eRudolf

2013-10-01

Full Text Available Autonomic regulation processes in striated muscles are largely mediated by cAMP/PKA-signaling. In order to achieve specificity of signaling its spatial-temporal compartmentation plays a critical role. We discuss here how specificity of cAMP/PKA-signaling can be achieved in skeletal muscle by spatio-temporal compartmentation. While a microdomain containing PKA type I in the region of the neuromuscular junction is important for post-synaptic, activity-dependent stabilization of the nicotinic acetylcholine receptor, PKA type I and II microdomains in the sarcomeric part of skeletal muscle are likely to play different roles, including the regulation of muscle homeostasis. These microdomains are due to specific A-kinase anchoring proteins, like rapsyn and myospryn. Importantly, recent evidence indicates that compartmentation of the cAMP/PKA-dependent signaling pathway and pharmacological activation of cAMP production are aberrant in different skeletal muscles disorders. Thus, we discuss here their potential as targets for palliative treatment of certain forms of dystrophy and myasthenia. Under physiological conditions, the neuropeptide, α-calcitonin-related peptide, as well as beta-adrenergic agonists are the most-mentioned natural triggers for activating cAMP/PKA signaling in skeletal muscle. While the precise domains and functions of these first messengers are still under investigation, agonists of β2-adrenoceptors clearly exhibit anabolic activity under normal conditions and reduce protein degradation during atrophic periods. Past and recent studies suggest direct sympathetic innervation of skeletal muscle fibers. In summary, the organization and roles of cAMP-dependent signaling in skeletal muscle are increasingly understood, revealing crucial functions in processes like nerve-muscle interaction and muscle trophicity.

Skeletal muscle digoxin concentration during digitalization and during withdrawal of digoxin treatment.

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Jogestrand, T; Ericsson, F; Sundqvist, K

1981-01-01

Blood samples and skeletal muscle biopsies (m. quadriceps femoris, vastus lateralis) were taken from 15 patients during digitalization or during withdrawal of digoxin treatment for analysis of serum and skeletal muscle digoxin concentrations. A percutaneous needle biopsy technique was used for muscle sampling and digoxin was analysed by radioimmunoassay. During "slow" digitalization with 0.25 mg digoxin daily the skeletal muscle digoxin concentrations after 2 and 4 days were 45% (range 19%--62%; n = 3) and 78% (range 56%--92%; n= 3) respectively, of the steady state concentration (defined as the digoxin concentration after 25--40 days of treatment). After 9 and 11 days of treatment the skeletal muscle digoxin concentrations were 106% (range 84%--133%; n = 5) and 116% (range 72%--164%; n = 3) respectively, of the steady state concentration. A doubling of the digoxin dose gave a proportional increase in skeletal muscle digoxin concentration (three patients). The magnitude of the estimated half-life of skeletal muscle digoxin was the same as previously reportedly in healthy subjects. No significant correlations were found between changes in systolic time intervals and steady state serum or skeletal muscle digoxin concentrations.

Beneficial effects of GH/IGF-1 on skeletal muscle atrophy and function in experimental heart failure.

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Dalla Libera, Luciano; Ravara, Barbara; Volterrani, Maurizio; Gobbo, Valerio; Della Barbera, Mila; Angelini, Annalisa; Danieli Betto, Daniela; Germinario, Elena; Vescovo, Giorgio

2004-01-01

Muscle atrophy is a determinant of exercise capacity in heart failure (CHF). Myocyte apoptosis, triggered by tumor necrosis factor-alpha (TNF-alpha) or its second messenger sphingosine (SPH), is one of the causes of atrophy. Growth hormone (GH) improves hemodynamic and cardiac trophism in several experimental models of CHF, but its effect on skeletal muscle in CHF is not yet clear. We tested the hypothesis that GH can prevent skeletal muscle apoptosis in rats with CHF. CHF was induced by injecting monocrotaline. After 2 wk, 2 groups of rats were treated with GH (0.2 mg.kg(-1).day(-1) and 1.0 mg.kg(-1).day(-1)) subcutaneously. A third group of controls had saline. After 2 additional weeks, rats were killed. Tibialis anterior cross-sectional area, myosin heavy chain (MHC) composition, and a study on myocyte apoptosis and serum levels of TNF-alpha and SPH were carried out. The number of apoptotic nuclei, muscle atrophy, and serum levels of TNF-alpha and SPH were decreased with GH at high but not at low doses compared with CHF rats. Bcl-2 was increased, whereas activated caspases and bax were decreased. The MHC pattern in GH-treated animals was similar to that of controls. Monocrotaline slowed down both contraction and relaxation but did not affect specific tetanic force, whereas absolute force was decreased. GH treatment restored contraction and relaxation to control values and brought muscle mass and absolute twitch and tetanic tension to normal levels. These findings may provide an insight into the therapeutic strategy of GH given to patients with CHF to improve exercise capacity.

Diffuse metastatic infiltration of a carcinoma into skeletal muscle

International Nuclear Information System (INIS)

Hundt, W.; Braunschweig, R.; Reiser, M.

1999-01-01

Skeletal muscle is one of the most unusual sites of metastasis from any malignancy. We report a patient with rapidly progressive contractures due to metastatic infiltration of a carcinoma of unknown origin into the skeletal muscle. This 61-year-old man presented with a 1-month history of rapidly evolving, painful restriction of mobility of his right arm and his legs. Computed tomography showed diffuse metastatic nodules in all muscles, particularly in the hip abductors. Muscle biopsy revealed extensive infiltration of the muscle with carcinoma cells. (orig.)

The role of skeletal muscle in the pathophysiology and management of knee osteoarthritis.

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Krishnasamy, Priathashini; Hall, Michelle; Robbins, Sarah R

2018-05-01

The role of skeletal muscle in the pathophysiology of knee OA is poorly understood. To date, the majority of literature has focused on the association of muscle strength with OA symptoms, disease onset and progression. However, deficits or improvements in skeletal muscle strength do not fully explain the mechanisms behind outcome measures in knee OA, such as pain, function and structural disease. This review aims to summarize components of skeletal muscle, providing a holistic view of skeletal muscle mechanisms that includes muscle function, quality and composition and their interactions. Similarly, the role of skeletal muscle in the management of knee OA will be discussed.

Diabetic Myopathy: Impact of Diabetes Mellitus on Skeletal Muscle Progenitor Cells

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Donna M D'Souza

2013-12-01

Full Text Available Diabetes mellitus is defined as a group of metabolic diseases that are associated with the presence of a hyperglycemic state due to impairments in insulin function. While the development of each form of diabetes (Type 1 or Type 2 drastically differs, resultant pathologies often overlap. In each diabetic condition a failure to maintain healthy muscle is often observed, and is termed diabetic myopathy. This significant, but often overlooked, complication is believed to contribute to the progression of additional diabetic pathologies due to the vital importance of skeletal muscle for our physical and metabolic well-being. While studies have investigated the link between changes to skeletal muscle metabolic health following diabetes mellitus onset (particularly Type 2 diabetes mellitus, few have examined the negative impact of diabetes mellitus on the growth and reparative capacities of skeletal muscle that often coincides with disease development. Importantly, evidence is accumulating that the muscle progenitor cell population (particularly the muscle satellite cell population is also negatively affected by the diabetic environment, and as such, likely contributes to the declining skeletal muscle health observed in diabetes mellitus. In this review, we summarize the current knowledge surrounding the influence of diabetes mellitus on skeletal muscle growth and repair, with a particular emphasis on the impact of diabetes mellitus on the progenitor cell population of skeletal muscle.

Selenium regulates gene expression of selenoprotein W in chicken skeletal muscle system.

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Ruan, Hongfeng; Zhang, Ziwei; Wu, Qiong; Yao, Haidong; Li, Jinlong; Li, Shu; Xu, Shiwen

2012-01-01

Selenoprotein W (SelW) is abundantly expressed in skeletal muscles of mammals and necessary for the metabolism of skeletal muscles. However, its expression pattern in skeletal muscle system of birds is still uncovered. Herein, to investigate the distribution of SelW mRNA in chicken skeletal muscle system and its response to different selenium (Se) status, 1-day-old chickens were exposed to various concentrations of Se as sodium selenite in the feed for 35 days. In addition, myoblasts were treated with different concentrations of Se in the medium for 72 h. Then the levels of SelW mRNA in skeletal muscles (wing muscle, pectoral muscle, thigh muscle) and myoblasts were determined on days 1, 15, 25, and 35 and at 0, 24, 48, and 72 h, respectively. The results showed that SelW was detected in all these muscle components and it increased both along with the growth of organism and the differentiation process of myoblasts. The thigh muscle is more responsive to Se intake than the other two skeletal muscle tissues while the optimal Se supplementation for SelW mRNA expression in chicken myoblasts was 10(-7) M. In summary, Se plays important roles in the development of chicken skeletal muscles. To effect optimal SelW gene expression, Se must be provided in the diet and the media in adequate amounts and neither at excessive nor deficient levels.

Characterization of human cardiac myosin heavy chain genes

International Nuclear Information System (INIS)

Yamauchi-Takihara, K.; Sole, M.J.; Liew, J.; Ing, D.; Liew, C.C.

1989-01-01

The authors have isolated and analyzed the structure of the genes coding for the α and β forms of the human cardiac myosin heavy chain (MYHC). Detailed analysis of four overlapping MYHC genomic clones shows that the α-MYHC and β-MYHC genes constitute a total length of 51 kilobases and are tandemly linked. The β-MYHC-encoding gene, predominantly expressed in the normal human ventricle and also in slow-twitch skeletal muscle, is located 4.5 kilobases upstream of the α-MYHC-encoding gene, which is predominantly expressed in normal human atrium. The authors have determined the nucleotide sequences of the β form of the MYHC gene, which is 100% homologous to the cardiac MYHC cDNA clone (pHMC3). It is unlikely that the divergence of a few nucleotide sequences from the cardiac β-MYHC cDNA clone (pHMC3) reported in a MYHC cDNA clone (PSMHCZ) from skeletal muscle is due to a splicing mechanism. This finding suggests that the same β form of the cardiac MYHC gene is expressed in both ventricular and slow-twitch skeletal muscle. The promoter regions of both α- and β-MYHC genes, as well as the first four coding regions in the respective genes, have also been sequenced. The sequences in the 5'-flanking region of the α- and β-MYHC-encoding genes diverge extensively from one another, suggesting that expression of the α- and β-MYHC genes is independently regulated

Dynamic changes in the mouse skeletal muscle proteome during denervation-induced atrophy

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Franziska Lang

2017-07-01

Full Text Available Loss of neuronal stimulation enhances protein breakdown and reduces protein synthesis, causing rapid loss of muscle mass. To elucidate the pathophysiological adaptations that occur in atrophying muscles, we used stable isotope labelling and mass spectrometry to quantify protein expression changes accurately during denervation-induced atrophy after sciatic nerve section in the mouse gastrocnemius muscle. Additionally, mice were fed a stable isotope labelling of amino acids in cell culture (SILAC diet containing 13C6-lysine for 4, 7 or 11 days to calculate relative levels of protein synthesis in denervated and control muscles. Ubiquitin remnant peptides (K-ε-GG were profiled by immunoaffinity enrichment to identify potential substrates of the ubiquitin-proteasomal pathway. Of the 4279 skeletal muscle proteins quantified, 850 were differentially expressed significantly within 2 weeks after denervation compared with control muscles. Moreover, pulse labelling identified Lys6 incorporation in 4786 proteins, of which 43 had differential Lys6 incorporation between control and denervated muscle. Enrichment of diglycine remnants identified 2100 endogenous ubiquitination sites and revealed a metabolic and myofibrillar protein diglycine signature, including myosin heavy chains, myomesins and titin, during denervation. Comparative analysis of these proteomic data sets with known atrogenes using a random forest approach identified 92 proteins subject to atrogene-like regulation that have not previously been associated directly with denervation-induced atrophy. Comparison of protein synthesis and proteomic data indicated that upregulation of specific proteins in response to denervation is mainly achieved by protein stabilization. This study provides the first integrated analysis of protein expression, synthesis and ubiquitin signatures during muscular atrophy in a living animal.

Engineered matrices for skeletal muscle satellite cell engraftment and function.

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Han, Woojin M; Jang, Young C; García, Andrés J

2017-07-01

Regeneration of traumatically injured skeletal muscles is severely limited. Moreover, the regenerative capacity of skeletal muscle declines with aging, further exacerbating the problem. Recent evidence supports that delivery of muscle satellite cells to the injured muscles enhances muscle regeneration and reverses features of aging, including reduction in muscle mass and regenerative capacity. However, direct delivery of satellite cells presents a challenge at a translational level due to inflammation and donor cell death, motivating the need to develop engineered matrices for muscle satellite cell delivery. This review will highlight important aspects of satellite cell and their niche biology in the context of muscle regeneration, and examine recent progresses in the development of engineered cell delivery matrices designed for skeletal muscle regeneration. Understanding the interactions of muscle satellite cells and their niche in both native and engineered systems is crucial to developing muscle pathology-specific cell- and biomaterial-based therapies. Copyright © 2016 International Society of Matrix Biology. Published by Elsevier B.V. All rights reserved.

Sarcomere lattice geometry influences cooperative myosin binding in muscle.

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Bertrand C W Tanner

2007-07-01

Full Text Available In muscle, force emerges from myosin binding with actin (forming a cross-bridge. This actomyosin binding depends upon myofilament geometry, kinetics of thin-filament Ca(2+ activation, and kinetics of cross-bridge cycling. Binding occurs within a compliant network of protein filaments where there is mechanical coupling between myosins along the thick-filament backbone and between actin monomers along the thin filament. Such mechanical coupling precludes using ordinary differential equation models when examining the effects of lattice geometry, kinetics, or compliance on force production. This study uses two stochastically driven, spatially explicit models to predict levels of cross-bridge binding, force, thin-filament Ca(2+ activation, and ATP utilization. One model incorporates the 2-to-1 ratio of thin to thick filaments of vertebrate striated muscle (multi-filament model, while the other comprises only one thick and one thin filament (two-filament model. Simulations comparing these models show that the multi-filament predictions of force, fractional cross-bridge binding, and cross-bridge turnover are more consistent with published experimental values. Furthermore, the values predicted by the multi-filament model are greater than those values predicted by the two-filament model. These increases are larger than the relative increase of potential inter-filament interactions in the multi-filament model versus the two-filament model. This amplification of coordinated cross-bridge binding and cycling indicates a mechanism of cooperativity that depends on sarcomere lattice geometry, specifically the ratio and arrangement of myofilaments.

Changes in skeletal muscle gene expression following clenbuterol administration

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McIntyre Lauren M

2006-12-01

Full Text Available Abstract Background Beta-adrenergic receptor agonists (BA induce skeletal muscle hypertrophy, yet specific mechanisms that lead to this effect are not well understood. The objective of this research was to identify novel genes and physiological pathways that potentially facilitate BA induced skeletal muscle growth. The Affymetrix platform was utilized to identify gene expression changes in mouse skeletal muscle 24 hours and 10 days after administration of the BA clenbuterol. Results Administration of clenbuterol stimulated anabolic activity, as indicated by decreased blood urea nitrogen (BUN; P P Conclusion Global evaluation of gene expression after administration of clenbuterol identified changes in gene expression and overrepresented functional categories of genes that may regulate BA-induced muscle hypertrophy. Changes in mRNA abundance of multiple genes associated with myogenic differentiation may indicate an important effect of BA on proliferation, differentiation, and/or recruitment of satellite cells into muscle fibers to promote muscle hypertrophy. Increased mRNA abundance of genes involved in the initiation of translation suggests that increased levels of protein synthesis often associated with BA administration may result from a general up-regulation of translational initiators. Additionally, numerous other genes and physiological pathways were identified that will be important targets for further investigations of the hypertrophic effect of BA on skeletal muscle.

FDG-PET/CT in Skeletal Muscle: Pitfalls and Pathologies.

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Parida, Girish Kumar; Roy, Shambo Guha; Kumar, Rakesh

2017-07-01

FDG-PET/CT is an integral part of modern-day practice of medicine. By detecting increased cellular metabolism, FDG-PET/CT can help us detect infection, inflammatory disorders, or tumors, and also help us in prognostication of patients. However, one of the most important challenges is to correctly differentiate the abnormal uptake that is potentially pathologic from the physiological uptake. So while interpreting a PET/CT, one must be aware of normal biodistribution and different physiological variants of FDG uptake. Skeletal muscles constitute a large part of our body mass and one of the major users of glucose. Naturally, they are often the site of increased FDG uptake in a PET study. We as a nuclear medicine physician must be aware of all the pitfalls of increased skeletal muscle uptake to differentiate between physiological and pathologic causes. In this review, we have discussed the different causes and patterns of physiological FDG uptake in skeletal muscles. This knowledge of normal physiological variants of FDG uptake in the skeletal muscles is essential for differentiating pathologic uptake from the physiological ones. Also, we reviewed the role of FDG-PET/CT in various benign and malignant diseases involving skeletal muscle. Copyright © 2017 Elsevier Inc. All rights reserved.

Probing muscle myosin motor action: x-ray (m3 and m6) interference measurements report motor domain not lever arm movement.

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Knupp, Carlo; Offer, Gerald; Ranatunga, K W; Squire, John M

2009-07-10

The key question in understanding how force and movement are produced in muscle concerns the nature of the cyclic interaction of myosin molecules with actin filaments. The lever arm of the globular head of each myosin molecule is thought in some way to swing axially on the actin-attached motor domain, thus propelling the actin filament past the myosin filament. Recent X-ray diffraction studies of vertebrate muscle, especially those involving the analysis of interference effects between myosin head arrays in the two halves of the thick filaments, have been claimed to prove that the lever arm moves at the same time as the sliding of actin and myosin filaments in response to muscle length or force steps. It was suggested that the sliding of myosin and actin filaments, the level of force produced and the lever arm angle are all directly coupled and that other models of lever arm movement will not fit the X-ray data. Here, we show that, in addition to interference across the A-band, which must be occurring, the observed meridional M3 and M6 X-ray intensity changes can all be explained very well by the changing diffraction effects during filament sliding caused by heads stereospecifically attached to actin moving axially relative to a population of detached or non-stereospecifically attached heads that remain fixed in position relative to the myosin filament backbone. Crucially, and contrary to previous interpretations, the X-ray interference results provide little direct information about the position of the myosin head lever arm; they are, in fact, reporting relative motor domain movements. The implications of the new interpretation are briefly assessed.

Diffuse metastatic infiltration of a carcinoma into skeletal muscle

Energy Technology Data Exchange (ETDEWEB)

Hundt, W.; Braunschweig, R.; Reiser, M. [Dept. of Diagnostic Radiology, Ludwig-Maximilians-Univ., Muenchen (Germany)

1999-03-01

Skeletal muscle is one of the most unusual sites of metastasis from any malignancy. We report a patient with rapidly progressive contractures due to metastatic infiltration of a carcinoma of unknown origin into the skeletal muscle. This 61-year-old man presented with a 1-month history of rapidly evolving, painful restriction of mobility of his right arm and his legs. Computed tomography showed diffuse metastatic nodules in all muscles, particularly in the hip abductors. Muscle biopsy revealed extensive infiltration of the muscle with carcinoma cells. (orig.) With 4 figs., 21 refs.

The Skeletal Muscle Satellite Cell

Science.gov (United States)

2011-01-01

The skeletal muscle satellite cell was first described and named based on its anatomic location between the myofiber plasma and basement membranes. In 1961, two independent studies by Alexander Mauro and Bernard Katz provided the first electron microscopic descriptions of satellite cells in frog and rat muscles. These cells were soon detected in other vertebrates and acquired candidacy as the source of myogenic cells needed for myofiber growth and repair throughout life. Cultures of isolated myofibers and, subsequently, transplantation of single myofibers demonstrated that satellite cells were myogenic progenitors. More recently, satellite cells were redefined as myogenic stem cells given their ability to self-renew in addition to producing differentiated progeny. Identification of distinctively expressed molecular markers, in particular Pax7, has facilitated detection of satellite cells using light microscopy. Notwithstanding the remarkable progress made since the discovery of satellite cells, researchers have looked for alternative cells with myogenic capacity that can potentially be used for whole body cell-based therapy of skeletal muscle. Yet, new studies show that inducible ablation of satellite cells in adult muscle impairs myofiber regeneration. Thus, on the 50th anniversary since its discovery, the satellite cell’s indispensable role in muscle repair has been reaffirmed. PMID:22147605

McArdle disease does not affect skeletal muscle fibre type profiles in humans

Directory of Open Access Journals (Sweden)

Tertius Abraham Kohn

2014-11-01

Full Text Available Patients suffering from glycogen storage disease V (McArdle disease were shown to have higher surface electrical activity in their skeletal muscles when exercising at the same intensity as their healthy counterparts, indicating more muscle fibre recruitment. To explain this phenomenon, this study investigated whether muscle fibre type is shifted towards a predominance in type I fibres as a consequence of the disease. Muscle biopsies from the Biceps brachii (BB (n = 9 or Vastus lateralis (VL (n = 8 were collected over a 13-year period from male and female patients diagnosed with McArdle disease, analysed for myosin heavy chain (MHC isoform content using SDS-PAGE, and compared to healthy controls (BB: n = 3; VL: n = 10. All three isoforms were expressed and no difference in isoform expression in VL was found between the McArdle patients and healthy controls (MHC I: 33±19% vs. 43±7%; MHC IIa: 52±9% vs. 40±7%; MHC IIx: 15±18% vs. 17±9%. Similarly, the BB isoform content was also not different between the two groups (MHC I: 33±14% vs. 30±11%; MHC IIa: 46±17% vs. 39±5%; MHC IIx: 21±13% vs. 31±14%. In conclusion, fibre type distribution does not seem to explain the higher surface EMG in McArdle patients. Future studies need to investigate muscle fibre size and contractility of McArdle patients.

Effective fiber hypertrophy in satellite cell-depleted skeletal muscle

Science.gov (United States)

McCarthy, John J.; Mula, Jyothi; Miyazaki, Mitsunori; Erfani, Rod; Garrison, Kelcye; Farooqui, Amreen B.; Srikuea, Ratchakrit; Lawson, Benjamin A.; Grimes, Barry; Keller, Charles; Van Zant, Gary; Campbell, Kenneth S.; Esser, Karyn A.; Dupont-Versteegden, Esther E.; Peterson, Charlotte A.

2011-01-01

An important unresolved question in skeletal muscle plasticity is whether satellite cells are necessary for muscle fiber hypertrophy. To address this issue, a novel mouse strain (Pax7-DTA) was created which enabled the conditional ablation of >90% of satellite cells in mature skeletal muscle following tamoxifen administration. To test the hypothesis that satellite cells are necessary for skeletal muscle hypertrophy, the plantaris muscle of adult Pax7-DTA mice was subjected to mechanical overload by surgical removal of the synergist muscle. Following two weeks of overload, satellite cell-depleted muscle showed the same increases in muscle mass (approximately twofold) and fiber cross-sectional area with hypertrophy as observed in the vehicle-treated group. The typical increase in myonuclei with hypertrophy was absent in satellite cell-depleted fibers, resulting in expansion of the myonuclear domain. Consistent with lack of nuclear addition to enlarged fibers, long-term BrdU labeling showed a significant reduction in the number of BrdU-positive myonuclei in satellite cell-depleted muscle compared with vehicle-treated muscle. Single fiber functional analyses showed no difference in specific force, Ca2+ sensitivity, rate of cross-bridge cycling and cooperativity between hypertrophied fibers from vehicle and tamoxifen-treated groups. Although a small component of the hypertrophic response, both fiber hyperplasia and regeneration were significantly blunted following satellite cell depletion, indicating a distinct requirement for satellite cells during these processes. These results provide convincing evidence that skeletal muscle fibers are capable of mounting a robust hypertrophic response to mechanical overload that is not dependent on satellite cells. PMID:21828094

Human skeletal muscle digitalis glycoside receptors (Na,K-ATPase)--importance during digitalization.

Science.gov (United States)

Schmidt, T A; Holm-Nielsen, P; Kjeldsen, K

1993-02-01

The aims of the present study were to evaluate in humans the putative importance of skeletal muscle digitalis glycoside receptors (Na,K-ATPase) in the volume of distribution of digoxin and to assess whether therapeutic digoxin exposure might cause digitalis receptor upregulation in skeletal muscle. Samples of the vastus lateralis were obtained postmortem from 11 long-term (9 months to 9 years) digitalized (125-187.5 micrograms daily) and eight undigitalized subjects. In intact samples from digitalized patients, vanadate-facilitated 3H-ouabain binding increased 15% (p 0.30) before and after washing in specific digoxin antibody fragments, respectively. Thus, the present study indicates a approximately 13% occupancy of skeletal muscle digitalis glycoside receptors with digoxin during digitalization. In light of the large skeletal muscle contribution to body mass, this indicates that the skeletal muscle Na,K-ATPase pool constitutes a major volume of distribution for digoxin during digitalization. The results gave no indication of skeletal muscle digitalis glycoside receptor upregulation in response to digoxin treatment. On the contrary, there was evidence of significantly lower (37%, p digitalized patients, which may be of importance for skeletal muscle incapacity in heart failure.

Branched-chain amino acid-rich diet improves skeletal muscle wasting caused by cigarette smoke in rats.

Science.gov (United States)

Tomoda, Koichi; Kubo, Kaoru; Hino, Kazuo; Kondoh, Yasunori; Nishii, Yasue; Koyama, Noriko; Yamamoto, Yoshifumi; Yoshikawa, Masanori; Kimura, Hiroshi

2014-04-01

Cigarette smoke induces skeletal muscle wasting by a mechanism not yet fully elucidated. Branched-chain amino acids (BCAA) in the skeletal muscles are useful energy sources during exercise or systemic stresses. We investigated the relationship between skeletal muscle wasting caused by cigarette smoke and changes in BCAA levels in the plasma and skeletal muscles of rats. Furthermore, the effects of BCAA-rich diet on muscle wasting caused by cigarette smoke were also investigated. Wistar Kyoto (WKY) rats that were fed with a control or a BCAA-rich diet were exposed to cigarette smoke for four weeks. After the exposure, the skeletal muscle weight and BCAA levels in plasma and the skeletal muscles were measured. Cigarette smoke significantly decreased the skeletal muscle weight and BCAA levels in both plasma and skeletal muscles, while a BCAA-rich diet increased the skeletal muscle weight and BCAA levels in both plasma and skeletal muscles that had decreased by cigarette smoke exposure. In conclusion, skeletal muscle wasting caused by cigarette smoke was related to the decrease of BCAA levels in the skeletal muscles, while a BCAA-rich diet may improve cases of cigarette smoke-induced skeletal muscle wasting.

Intercellular adhesion molecule-1 expression by skeletal muscle cells augments myogenesis

International Nuclear Information System (INIS)

Goh, Qingnian; Dearth, Christopher L.; Corbett, Jacob T.; Pierre, Philippe; Chadee, Deborah N.; Pizza, Francis X.

2015-01-01

We previously demonstrated that the expression of intercellular adhesion molecule-1 (ICAM-1) by skeletal muscle cells after muscle overload contributes to ensuing regenerative and hypertrophic processes in skeletal muscle. The objective of the present study is to reveal mechanisms through which skeletal muscle cell expression of ICAM-1 augments regenerative and hypertrophic processes of myogenesis. This was accomplished by genetically engineering C2C12 myoblasts to stably express ICAM-1, and by inhibiting the adhesive and signaling functions of ICAM-1 through the use of a neutralizing antibody or cell penetrating peptide, respectively. Expression of ICAM-1 by cultured skeletal muscle cells augmented myoblast–myoblast adhesion, myotube formation, myonuclear number, myotube alignment, myotube–myotube fusion, and myotube size without influencing the ability of myoblasts to proliferate or differentiate. ICAM-1 augmented myotube formation, myonuclear accretion, and myotube alignment through a mechanism involving adhesion-induced activation of ICAM-1 signaling, as these dependent measures were reduced via antibody and peptide inhibition of ICAM-1. The adhesive and signaling functions of ICAM-1 also facilitated myotube hypertrophy through a mechanism involving myotube–myotube fusion, protein synthesis, and Akt/p70s6k signaling. Our findings demonstrate that ICAM-1 expression by skeletal muscle cells augments myogenesis, and establish a novel mechanism through which the inflammatory response facilitates growth processes in skeletal muscle. - Highlights: • We examined mechanisms through which skeletal muscle cell expression of ICAM-1 facilitates events of in vitro myogenesis. • Expression of ICAM-1 by cultured myoblasts did not influence their ability to proliferate or differentiate. • Skeletal muscle cell expression of ICAM-1 augmented myoblast fusion, myotube alignment, myotube–myotube fusion, and myotube size. • ICAM-1 augmented myogenic processes through

Intercellular adhesion molecule-1 expression by skeletal muscle cells augments myogenesis

Energy Technology Data Exchange (ETDEWEB)

Goh, Qingnian; Dearth, Christopher L.; Corbett, Jacob T. [Department of Kinesiology, The University of Toledo, Toledo, OH (United States); Pierre, Philippe [Centre d’Immunologie de Marseille-Luminy U2M, Aix-Marseille Université, Marseille (France); INSERM U631, Institut National de la Santé et Recherche Médicale, Marseille (France); CNRS UMR6102, Centre National de la Recherche Scientifique, Marseille (France); Chadee, Deborah N. [Department of Biological Sciences, The University of Toledo, Toledo, OH (United States); Pizza, Francis X., E-mail: Francis.Pizza@utoledo.edu [Department of Kinesiology, The University of Toledo, Toledo, OH (United States)

2015-02-15

We previously demonstrated that the expression of intercellular adhesion molecule-1 (ICAM-1) by skeletal muscle cells after muscle overload contributes to ensuing regenerative and hypertrophic processes in skeletal muscle. The objective of the present study is to reveal mechanisms through which skeletal muscle cell expression of ICAM-1 augments regenerative and hypertrophic processes of myogenesis. This was accomplished by genetically engineering C2C12 myoblasts to stably express ICAM-1, and by inhibiting the adhesive and signaling functions of ICAM-1 through the use of a neutralizing antibody or cell penetrating peptide, respectively. Expression of ICAM-1 by cultured skeletal muscle cells augmented myoblast–myoblast adhesion, myotube formation, myonuclear number, myotube alignment, myotube–myotube fusion, and myotube size without influencing the ability of myoblasts to proliferate or differentiate. ICAM-1 augmented myotube formation, myonuclear accretion, and myotube alignment through a mechanism involving adhesion-induced activation of ICAM-1 signaling, as these dependent measures were reduced via antibody and peptide inhibition of ICAM-1. The adhesive and signaling functions of ICAM-1 also facilitated myotube hypertrophy through a mechanism involving myotube–myotube fusion, protein synthesis, and Akt/p70s6k signaling. Our findings demonstrate that ICAM-1 expression by skeletal muscle cells augments myogenesis, and establish a novel mechanism through which the inflammatory response facilitates growth processes in skeletal muscle. - Highlights: • We examined mechanisms through which skeletal muscle cell expression of ICAM-1 facilitates events of in vitro myogenesis. • Expression of ICAM-1 by cultured myoblasts did not influence their ability to proliferate or differentiate. • Skeletal muscle cell expression of ICAM-1 augmented myoblast fusion, myotube alignment, myotube–myotube fusion, and myotube size. • ICAM-1 augmented myogenic processes through

Three-dimensional optical coherence micro-elastography of skeletal muscle tissue

OpenAIRE

Chin, Lixin; Kennedy, Brendan F.; Kennedy, Kelsey M.; Wijesinghe, Philip; Pinniger, Gavin J.; Terrill, Jessica R.; McLaughlin, Robert A.; Sampson, David D.

2014-01-01

In many muscle pathologies, impairment of skeletal muscle function is closely linked to changes in the mechanical properties of the muscle constituents. Optical coherence micro-elastography (OCME) uses optical coherence tomography (OCT) imaging of tissue under a quasi-static, compressive mechanical load to map variations in tissue mechanical properties on the micro-scale. We present the first study of OCME on skeletal muscle tissue. We show that this technique can resolve features of muscle t...

Current opportunities and challenges in skeletal muscle tissue engineering

NARCIS (Netherlands)

Koning, Merel; Harmsen, Martin C; van Luyn, Marja J A; Werker, Paul M N

The purpose of this article is to give a concise review of the current state of the art in tissue engineering (TE) of skeletal muscle and the opportunities and challenges for future clinical applicability. The endogenous progenitor cells of skeletal muscle, i.e. satellite cells, show a high

SwissProt search result: AK104031 [KOME

Lifescience Database Archive (English)

Full Text Available AK104031 001-020-D10 (P02604) Myosin light chain 1, skeletal muscle isoform (A1 cat...alytic) (Alkali myosin light chain 1) (MLC-1) (Myosin light chain 1f) (Skeletal-muscle myosin L-1 light chain) MLE1_CHICK 2e-20 ...

SwissProt search result: AK070889 [KOME

Lifescience Database Archive (English)

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SwissProt search result: AK104031 [KOME

Lifescience Database Archive (English)

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Lifescience Database Archive (English)

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SwissProt search result: AK119956 [KOME

Lifescience Database Archive (English)

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SwissProt search result: AK104159 [KOME

Lifescience Database Archive (English)

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SwissProt search result: AK059756 [KOME

Lifescience Database Archive (English)

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SwissProt search result: AK111834 [KOME

Lifescience Database Archive (English)

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SwissProt search result: AK062496 [KOME

Lifescience Database Archive (English)

Full Text Available AK062496 001-104-A02 (P02605) Myosin light chain 3, skeletal muscle isoform (A2 cat...alytic) (Alkali myosin light chain 3) (MLC-3) (Myosin light chain 3f) (Skeletal-muscle myosin L-4 light chain) MLE3_CHICK 2e-29 ...

SwissProt search result: AK111834 [KOME

Lifescience Database Archive (English)

Full Text Available AK111834 J023133G18 (P02605) Myosin light chain 3, skeletal muscle isoform (A2 catalytic) (Alkali myosin lig...ht chain 3) (MLC-3) (Myosin light chain 3f) (Skeletal-muscle myosin L-4 light chain) MLE3_CHICK 3e-22 ...

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Lifescience Database Archive (English)

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SwissProt search result: AK104159 [KOME

Lifescience Database Archive (English)

Full Text Available AK104159 006-211-A05 (P02605) Myosin light chain 3, skeletal muscle isoform (A2 cat...alytic) (Alkali myosin light chain 3) (MLC-3) (Myosin light chain 3f) (Skeletal-muscle myosin L-4 light chain) MLE3_CHICK 2e-12 ...

SwissProt search result: AK059534 [KOME

Lifescience Database Archive (English)

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Lifescience Database Archive (English)

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SwissProt search result: AK119956 [KOME

Lifescience Database Archive (English)

Full Text Available AK119956 002-184-C10 (P02605) Myosin light chain 3, skeletal muscle isoform (A2 cat...alytic) (Alkali myosin light chain 3) (MLC-3) (Myosin light chain 3f) (Skeletal-muscle myosin L-4 light chain) MLE3_CHICK 2e-22 ...

Skeletal muscle tissue transcriptome differences in lean and obese female beagle dogs.

Science.gov (United States)

Grant, R W; Vester Boler, B M; Ridge, T K; Graves, T K; Swanson, K S

2013-08-01

Skeletal muscle is a large and insulin-sensitive tissue that is an important contributor to metabolic homeostasis and energy expenditure. Many metabolic processes are altered with obesity, but the contribution of muscle tissue in this regard is unclear. A limited number of studies have compared skeletal muscle gene expression of lean and obese dogs. Using microarray technology, our objective was to identify genes and functional classes differentially expressed in skeletal muscle of obese (14.6 kg; 8.2 body condition score; 44.5% body fat) vs. lean (8.6 kg; 4.1 body condition score; 22.9% body fat) female beagle adult dogs. Alterations in 77 transcripts was observed in genes pertaining to the functional classes of signaling, transport, protein catabolism and proteolysis, protein modification, development, transcription and apoptosis, cell cycle and differentiation. Genes differentially expressed in obese vs. lean dog skeletal muscle indicate oxidative stress and altered skeletal muscle cell differentiation. Many genes traditionally associated with lipid, protein and carbohydrate metabolism were not altered in obese vs. lean dogs, but genes pertaining to endocannabinoid metabolism, insulin signaling, type II diabetes mellitus and carnitine transport were differentially expressed. The relatively small response of skeletal muscle could indicate that changes are occurring at a post-transcriptional level, that other tissues (e.g., adipose tissue) were buffering skeletal muscle from metabolic dysfunction or that obesity-induced changes in skeletal muscle require a longer period of time and that the length of our study was not sufficient to detect them. Although only a limited number of differentially expressed genes were detected, these results highlight genes and functional classes that may be important in determining the etiology of obesity-induced derangement of skeletal muscle function. © 2013 The Authors, Animal Genetics © 2013 Stichting International Foundation

Lipolysis in Skeletal Muscle

DEFF Research Database (Denmark)

Serup, Annette Karen Lundbeck

chemical structure of DAG. We took advantage of the fact that insulin sensitivity is increased after exercise, and that mice knocked out (KO) of HSL accumulate DAG after exercise, and measured insulin stimulated glucose uptake after treadmill running in skeletal muscle from HSL KO mice and wildtype control...

Aberrant mitochondrial homeostasis in the skeletal muscle of sedentary older adults.

Directory of Open Access Journals (Sweden)

Adeel Safdar

Full Text Available The role of mitochondrial dysfunction and oxidative stress has been extensively characterized in the aetiology of sarcopenia (aging-associated loss of muscle mass and muscle wasting as a result of muscle disuse. What remains less clear is whether the decline in skeletal muscle mitochondrial oxidative capacity is purely a function of the aging process or if the sedentary lifestyle of older adult subjects has confounded previous reports. The objective of the present study was to investigate if a recreationally active lifestyle in older adults can conserve skeletal muscle strength and functionality, chronic systemic inflammation, mitochondrial biogenesis and oxidative capacity, and cellular antioxidant capacity. To that end, muscle biopsies were taken from the vastus lateralis of young and age-matched recreationally active older and sedentary older men and women (N = 10/group; female symbol = male symbol. We show that a physically active lifestyle is associated with the partial compensatory preservation of mitochondrial biogenesis, and cellular oxidative and antioxidant capacity in skeletal muscle of older adults. Conversely a sedentary lifestyle, associated with osteoarthritis-mediated physical inactivity, is associated with reduced mitochondrial function, dysregulation of cellular redox status and chronic systemic inflammation that renders the skeletal muscle intracellular environment prone to reactive oxygen species-mediated toxicity. We propose that an active lifestyle is an important determinant of quality of life and molecular progression of aging in skeletal muscle of the elderly, and is a viable therapy for attenuating and/or reversing skeletal muscle strength declines and mitochondrial abnormalities associated with aging.

Stretching skeletal muscle: chronic muscle lengthening through sarcomerogenesis.

Directory of Open Access Journals (Sweden)

Alexander M Zöllner

Full Text Available Skeletal muscle responds to passive overstretch through sarcomerogenesis, the creation and serial deposition of new sarcomere units. Sarcomerogenesis is critical to muscle function: It gradually re-positions the muscle back into its optimal operating regime. Animal models of immobilization, limb lengthening, and tendon transfer have provided significant insight into muscle adaptation in vivo. Yet, to date, there is no mathematical model that allows us to predict how skeletal muscle adapts to mechanical stretch in silico. Here we propose a novel mechanistic model for chronic longitudinal muscle growth in response to passive mechanical stretch. We characterize growth through a single scalar-valued internal variable, the serial sarcomere number. Sarcomerogenesis, the evolution of this variable, is driven by the elastic mechanical stretch. To analyze realistic three-dimensional muscle geometries, we embed our model into a nonlinear finite element framework. In a chronic limb lengthening study with a muscle stretch of 1.14, the model predicts an acute sarcomere lengthening from 3.09[Formula: see text]m to 3.51[Formula: see text]m, and a chronic gradual return to the initial sarcomere length within two weeks. Compared to the experiment, the acute model error was 0.00% by design of the model; the chronic model error was 2.13%, which lies within the rage of the experimental standard deviation. Our model explains, from a mechanistic point of view, why gradual multi-step muscle lengthening is less invasive than single-step lengthening. It also explains regional variations in sarcomere length, shorter close to and longer away from the muscle-tendon interface. Once calibrated with a richer data set, our model may help surgeons to prevent muscle overstretch and make informed decisions about optimal stretch increments, stretch timing, and stretch amplitudes. We anticipate our study to open new avenues in orthopedic and reconstructive surgery and enhance

Adaptation of Mouse Skeletal Muscle to Long-Term Microgravity in the MDS Mission

Science.gov (United States)

Camerino, Giulia M.; Bianchini, Elisa; Ciciliot, Stefano; Danieli-Betto, Daniela; Dobrowolny, Gabriella; Furlan, Sandra; Germinario, Elena; Goto, Katsumasa; Gutsmann, Martina; Kawano, Fuminori; Nakai, Naoya; Ohira, Takashi; Ohno, Yoshitaka; Picard, Anne; Salanova, Michele; Schiffl, Gudrun; Blottner, Dieter; Musarò, Antonio; Ohira, Yoshinobu; Betto, Romeo; Conte, Diana; Schiaffino, Stefano

2012-01-01

The effect of microgravity on skeletal muscles has so far been examined in rat and mice only after short-term (5–20 day) spaceflights. The mice drawer system (MDS) program, sponsored by Italian Space Agency, for the first time aimed to investigate the consequences of long-term (91 days) exposure to microgravity in mice within the International Space Station. Muscle atrophy was present indistinctly in all fiber types of the slow-twitch soleus muscle, but was only slightly greater than that observed after 20 days of spaceflight. Myosin heavy chain analysis indicated a concomitant slow-to-fast transition of soleus. In addition, spaceflight induced translocation of sarcolemmal nitric oxide synthase-1 (NOS1) into the cytosol in soleus but not in the fast-twitch extensor digitorum longus (EDL) muscle. Most of the sarcolemmal ion channel subunits were up-regulated, more in soleus than EDL, whereas Ca2+-activated K+ channels were down-regulated, consistent with the phenotype transition. Gene expression of the atrophy-related ubiquitin-ligases was up-regulated in both spaceflown soleus and EDL muscles, whereas autophagy genes were in the control range. Muscle-specific IGF-1 and interleukin-6 were down-regulated in soleus but up-regulated in EDL. Also, various stress-related genes were up-regulated in spaceflown EDL, not in soleus. Altogether, these results suggest that EDL muscle may resist to microgravity-induced atrophy by activating compensatory and protective pathways. Our study shows the extended sensitivity of antigravity soleus muscle after prolonged exposition to microgravity, suggests possible mechanisms accounting for the resistance of EDL, and individuates some molecular targets for the development of countermeasures. PMID:22470446

Adaptation of mouse skeletal muscle to long-term microgravity in the MDS mission.

Directory of Open Access Journals (Sweden)

Dorianna Sandonà

Full Text Available The effect of microgravity on skeletal muscles has so far been examined in rat and mice only after short-term (5-20 day spaceflights. The mice drawer system (MDS program, sponsored by Italian Space Agency, for the first time aimed to investigate the consequences of long-term (91 days exposure to microgravity in mice within the International Space Station. Muscle atrophy was present indistinctly in all fiber types of the slow-twitch soleus muscle, but was only slightly greater than that observed after 20 days of spaceflight. Myosin heavy chain analysis indicated a concomitant slow-to-fast transition of soleus. In addition, spaceflight induced translocation of sarcolemmal nitric oxide synthase-1 (NOS1 into the cytosol in soleus but not in the fast-twitch extensor digitorum longus (EDL muscle. Most of the sarcolemmal ion channel subunits were up-regulated, more in soleus than EDL, whereas Ca(2+-activated K(+ channels were down-regulated, consistent with the phenotype transition. Gene expression of the atrophy-related ubiquitin-ligases was up-regulated in both spaceflown soleus and EDL muscles, whereas autophagy genes were in the control range. Muscle-specific IGF-1 and interleukin-6 were down-regulated in soleus but up-regulated in EDL. Also, various stress-related genes were up-regulated in spaceflown EDL, not in soleus. Altogether, these results suggest that EDL muscle may resist to microgravity-induced atrophy by activating compensatory and protective pathways. Our study shows the extended sensitivity of antigravity soleus muscle after prolonged exposition to microgravity, suggests possible mechanisms accounting for the resistance of EDL, and individuates some molecular targets for the development of countermeasures.

Microgenomic analysis in skeletal muscle: expression signatures of individual fast and slow myofibers.

Directory of Open Access Journals (Sweden)

Francesco Chemello

Full Text Available BACKGROUND: Skeletal muscle is a complex, versatile tissue composed of a variety of functionally diverse fiber types. Although the biochemical, structural and functional properties of myofibers have been the subject of intense investigation for the last decades, understanding molecular processes regulating fiber type diversity is still complicated by the heterogeneity of cell types present in the whole muscle organ. METHODOLOGY/PRINCIPAL FINDINGS: We have produced a first catalogue of genes expressed in mouse slow-oxidative (type 1 and fast-glycolytic (type 2B fibers through transcriptome analysis at the single fiber level (microgenomics. Individual fibers were obtained from murine soleus and EDL muscles and initially classified by myosin heavy chain isoform content. Gene expression profiling on high density DNA oligonucleotide microarrays showed that both qualitative and quantitative improvements were achieved, compared to results with standard muscle homogenate. First, myofiber profiles were virtually free from non-muscle transcriptional activity. Second, thousands of muscle-specific genes were identified, leading to a better definition of gene signatures in the two fiber types as well as the detection of metabolic and signaling pathways that are differentially activated in specific fiber types. Several regulatory proteins showed preferential expression in slow myofibers. Discriminant analysis revealed novel genes that could be useful for fiber type functional classification. CONCLUSIONS/SIGNIFICANCE: As gene expression analyses at the single fiber level significantly increased the resolution power, this innovative approach would allow a better understanding of the adaptive transcriptomic transitions occurring in myofibers under physiological and pathological conditions.

Muscle specific microRNAs are regulated by endurance exercise in human skeletal muscle

DEFF Research Database (Denmark)

Nielsen, Søren; Scheele, Camilla; Yfanti, Christina

2010-01-01

Muscle specific miRNAs, myomiRs, have been shown to control muscle development in vitro and are differentially expressed at rest in diabetic skeletal muscle. Therefore, we investigated the expression of these myomiRs, including miR-1, miR-133a, miR-133b and miR-206 in muscle biopsies from vastus...... lateralis of healthy young males (n = 10) in relation to a hyperinsulinaemic–euglycaemic clamp as well as acute endurance exercise before and after 12 weeks of endurance training. The subjects increased their endurance capacity, VO2max (l min-1) by 17.4% (P improved insulin sensitivity by 19......, but their role in regulating human skeletal muscle adaptation remains unknown....

Structural, biochemical, cellular, and functional changes in skeletal muscle extracellular matrix with aging

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Kragstrup, T W; Kjaer, M; Mackey, A L

2011-01-01

The extracellular matrix (ECM) of skeletal muscle is critical for force transmission and for the passive elastic response of skeletal muscle. Structural, biochemical, cellular, and functional changes in skeletal muscle ECM contribute to the deterioration in muscle mechanical properties with aging....... Structural changes include an increase in the collagen concentration, a change in the elastic fiber system, and an increase in fat infiltration of skeletal muscle. Biochemical changes include a decreased turnover of collagen with potential accumulation of enzymatically mediated collagen cross...

Selection, processing and clinical application of muscle-skeletal tissue

International Nuclear Information System (INIS)

Luna Z, D.; Reyes F, M.L.; Lavalley E, C.; Castaneda J, G.

2007-01-01

Due to the increase in the average of the world population's life, people die each time to more age, this makes that the tissues of support of the human body, as those muscle-skeletal tissues, when increasing the individual's age go weakening, this in turn leads to the increment of the illnesses like the osteoporosis and the arthritis, that undoubtedly gives as a result more injure of the muscle-skeletal tissues joined a greater number of traffic accidents where particularly these tissues are affected, for that the demand of tissues muscle-skeletal for transplant every day will be bigger. The production of these tissues in the Bank of Radio sterilized Tissues, besides helping people to improve its quality of life saved foreign currencies because most of the muscle-skeletal tissues transplanted in Mexico are of import. The use of the irradiation to sterilize tissues for transplant has shown to be one of the best techniques with that purpose for what the International Atomic Energy Agency believes a Technical cooperation program to establish banks of tissues using the nuclear energy, helping mainly to countries in development. In this work the stages that follows the bank of radio sterilized tissues of the National Institute of Nuclear Research for the cadaverous donor's of muscle-skeletal tissue selection are described, as well as the processing and the clinical application of these tissues. (Author)

Quantitative sonoelastography for the in vivo assessment of skeletal muscle viscoelasticity

International Nuclear Information System (INIS)

Hoyt, Kenneth; Kneezel, Timothy; Castaneda, Benjamin; Parker, Kevin J

2008-01-01

A novel quantitative sonoelastography technique for assessing the viscoelastic properties of skeletal muscle tissue was developed. Slowly propagating shear wave interference patterns (termed crawling waves) were generated using a two-source configuration vibrating normal to the surface. Theoretical models predict crawling wave displacement fields, which were validated through phantom studies. In experiments, a viscoelastic model was fit to dispersive shear wave speed sonoelastographic data using nonlinear least-squares techniques to determine frequency-independent shear modulus and viscosity estimates. Shear modulus estimates derived using the viscoelastic model were in agreement with that obtained by mechanical testing on phantom samples. Preliminary sonoelastographic data acquired in healthy human skeletal muscles confirm that high-quality quantitative elasticity data can be acquired in vivo. Studies on relaxed muscle indicate discernible differences in both shear modulus and viscosity estimates between different skeletal muscle groups. Investigations into the dynamic viscoelastic properties of (healthy) human skeletal muscles revealed that voluntarily contracted muscles exhibit considerable increases in both shear modulus and viscosity estimates as compared to the relaxed state. Overall, preliminary results are encouraging and quantitative sonoelastography may prove clinically feasible for in vivo characterization of the dynamic viscoelastic properties of human skeletal muscle

Chiral Orientation of Skeletal Muscle Cells Requires Rigid Substrate

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Ninghao Zhu

2017-06-01

Full Text Available Reconstitution of tissue morphology with inherent left–right (LR asymmetry is essential for tissue/organ functions. For skeletal muscle, the largest tissue in mammalian organisms, successful myogenesis requires the regulation of the LR asymmetry to form the appropriate muscle alignment. However, the key factor for reproducing the LR asymmetry of skeletal tissues in a controllable, engineering context remains largely unknown. Recent reports indicate that cell chirality may underlie the LR development in tissue morphogenesis. Here, we report that a rigid substrate is required for the chirality of skeletal muscle cells. By using alternating micropatterned cell-adherent and cell-repellent stripes on a rigid substrate, we found that C2C12 skeletal muscle myoblasts exhibited a unidirectional tilted orientation with respect to the stripe boundary. Importantly, such chiral orientation was reduced when soft substrates were used instead. In addition, we demonstrated the key role of actin stress fibers in the formation of the chiral orientation. This study reveals that a rigid substrate is required for the chiral pattern of myoblasts, paving the way for reconstructing damaged muscle tissue with inherent LR asymmetry in the future.

Simvastatin effects on skeletal muscle

DEFF Research Database (Denmark)

Larsen, Steen; Stride, Nis; Hey-Mogensen, Martin

2013-01-01

Glucose tolerance and skeletal muscle coenzyme Q(10) (Q(10)) content, mitochondrial density, and mitochondrial oxidative phosphorylation (OXPHOS) capacity were measured in simvastatin-treated patients (n = 10) and in well-matched control subjects (n = 9)....

Human skeletal muscle fibroblasts stimulate in vitro myogenesis and in vivo muscle regeneration

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Mackey, Abigail L.; Magnan, Mélanie; Chazaud, Bénédicte

2017-01-01

Accumulation of skeletal muscle extracellular matrix is an unfavourable characteristic of many muscle diseases, muscle injury and sarcopenia. In addition to the indispensable role satellite cells play in muscle regeneration, there is emerging evidence in rodents for a regulatory influence...

The Human Skeletal Muscle Proteome Project

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Gonzalez-Freire, Marta; Semba, Richard D.; Ubaida-Mohien, Ceereena

2017-01-01

Skeletal muscle is a large organ that accounts for up to half the total mass of the human body. A progressive decline in muscle mass and strength occurs with ageing and in some individuals configures the syndrome of ‘sarcopenia’, a condition that impairs mobility, challenges autonomy, and is a ri...

Molecular Mechanisms for Age-Associated Mitochondrial Deficiency in Skeletal Muscle

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Akira Wagatsuma

2012-01-01

Full Text Available The abundance, morphology, and functional properties of mitochondria decay in skeletal muscle during the process of ageing. Although the precise mechanisms remain to be elucidated, these mechanisms include decreased mitochondrial DNA (mtDNA repair and mitochondrial biogenesis. Mitochondria possess their own protection system to repair mtDNA damage, which leads to defects of mtDNA-encoded gene expression and respiratory chain complex enzymes. However, mtDNA mutations have shown to be accumulated with age in skeletal muscle. When damaged mitochondria are eliminated by autophagy, mitochondrial biogenesis plays an important role in sustaining energy production and physiological homeostasis. The capacity for mitochondrial biogenesis has shown to decrease with age in skeletal muscle, contributing to progressive mitochondrial deficiency. Understanding how these endogenous systems adapt to altered physiological conditions during the process of ageing will provide a valuable insight into the underlying mechanisms that regulate cellular homeostasis. Here we will summarize the current knowledge about the molecular mechanisms responsible for age-associated mitochondrial deficiency in skeletal muscle. In particular, recent findings on the role of mtDNA repair and mitochondrial biogenesis in maintaining mitochondrial functionality in aged skeletal muscle will be highlighted.

Physiological aspects of the subcellular localization of glycogen in skeletal muscle

DEFF Research Database (Denmark)

Nielsen, Joachim; Ørtenblad, Niels

2013-01-01

Glucose is stored in skeletal muscle fibers as glycogen, a branched-chain polymer observed in electron microscopy images as roughly spherical particles (known as β-particles of 10-45 nm in diameter), which are distributed in distinct localizations within the myofibers and are physically associated...... investigated the role and regulation of these distinct deposits of glycogen. In this report, we review the available literature regarding the subcellular localization of glycogen in skeletal muscle as investigated by electron microscopy studies and put this into perspective in terms of the architectural......, topological, and dynamic organization of skeletal muscle fibers. In summary, the distribution of glycogen within skeletal muscle fibers has been shown to depend on the fiber phenotype, individual training status, short-term immobilization, and exercise and to influence both muscle contractility...

Cardiac, skeletal, and smooth muscle mitochondrial respiration: are all mitochondria created equal?

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Park, Song-Young; Gifford, Jayson R; Andtbacka, Robert H I; Trinity, Joel D; Hyngstrom, John R; Garten, Ryan S; Diakos, Nikolaos A; Ives, Stephen J; Dela, Flemming; Larsen, Steen; Drakos, Stavros; Richardson, Russell S

2014-08-01

Unlike cardiac and skeletal muscle, little is known about vascular smooth muscle mitochondrial respiration. Therefore, the present study examined mitochondrial respiratory rates in smooth muscle of healthy human feed arteries and compared with that of healthy cardiac and skeletal muscles. Cardiac, skeletal, and smooth muscles were harvested from a total of 22 subjects (53 ± 6 yr), and mitochondrial respiration was assessed in permeabilized fibers. Complex I + II, state 3 respiration, an index of oxidative phosphorylation capacity, fell progressively from cardiac to skeletal to smooth muscles (54 ± 1, 39 ± 4, and 15 ± 1 pmol·s(-1)·mg(-1), P respiration rates were normalized by CS (respiration per mitochondrial content), oxidative phosphorylation capacity was no longer different between the three muscle types. Interestingly, complex I state 2 normalized for CS activity, an index of nonphosphorylating respiration per mitochondrial content, increased progressively from cardiac to skeletal to smooth muscles, such that the respiratory control ratio, state 3/state 2 respiration, fell progressively from cardiac to skeletal to smooth muscles (5.3 ± 0.7, 3.2 ± 0.4, and 1.6 ± 0.3 pmol·s(-1)·mg(-1), P respiration highlight the existence of intrinsic functional differences between these muscle mitochondria. This likely influences the efficiency of oxidative phosphorylation and could potentially alter ROS production.

Direct effects of doxorubicin on skeletal muscle contribute to fatigue

NARCIS (Netherlands)

Norren, van K.; Helvoort, van A.; Argiles, J.M.; Tuijl, van S.; Arts, K.; Gorselink, M.; Laviano, A.; Kegler, D.; Haagsman, H.P.; Beek, E.M.

2009-01-01

Chemotherapy-induced fatigue is a multidimensional symptom. Oxidative stress has been proposed as a working mechanism for anthracycline-induced cardiotoxicity. In this study, doxorubicin (DOX) was tested on skeletal muscle function. Doxorubicin induced impaired ex vivo skeletal muscle relaxation

Immunohistochemical detection of interleukin-6 in human skeletal muscle fibers following exercise

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Penkowa, Milena; Keller, Charlotte; Keller, Pernille

2003-01-01

individuals. The IL-6 immunostainings of skeletal muscle cells were homogeneous and without difference between muscle fiber types. The IL-6 mRNA peaked immediately after the exercise, and, in accordance, the IL-6 protein expression within muscle cells was most pronounced around 3 h post-exercise. However......, the finding that plasma IL-6 concentration peaked in the end of exercise indicates a high turnover of muscle-derived IL-6. In conclusion, the finding of marked IL-6 protein expression exclusively within skeletal muscle fibers following exercise demonstrates that skeletal muscle fibers of all types...

Phosphorylated peptides occur in a non-helical portion of the tail of a catch muscle myosin

International Nuclear Information System (INIS)

Castellani, L.; Elliott, B.W. Jr.; Cohen, C.

1987-01-01

Myosin from a molluscan catch muscle (the Anterior Byssus Retractor (ABRM) of Mytilus edulis) is unusual in being phosphorylated in the rod by an endogenous heavy-chain kinase. This phosphorylation enhances myosin solubility at low ionic strength and induces molecular folding of the myosin tail. Papain and chymotryptic cleavage of this myosin, phosphorylated with [γ- 32 P]ATP, indicates that the phosphorylated residues are associated with the carboxy-terminal end of the light meromyosin. Ion-exchange and reverse-phase HPLC of radiolabeled chymotryptic peptides allow the isolation of two different peptides with high specific activity. One of these peptides is rich in lysine and arginine residues, a finding consistent with the observation that basic residues often determine the substrate specificity of protein kinases. The second peptide contains proline residues. Taken together, these results suggest that, as in the case of Acanthamoeba myosin, phosphorylation occurs in a nonhelical portion of the rod that may also control solubility. Identification of the residues that are phosphorylated and their location in the rod may reveal how the phosphorylation-dependent changes observed in the myosin in vitro are related to changes in intermolecular interactions in the thick filaments in vivo

MicroRNA in Skeletal Muscle: Its Crucial Roles in Signal Proteins, Mus cle Fiber Type, and Muscle Protein Synthesis.

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Zhang, Jing; Liu, Yu Lan

2017-01-01

Pork is one of the most economical sources of animal protein for human consumption. Meat quality is an important economic trait for the swine industry, which is primarily determined by prenatal muscle development and postnatal growth. Identification of the molecular mechanisms underlying skeletal muscle development is a key priority. MicroRNAs (miRNAs) are a class of small noncoding RNAs that have emerged as key regulators of skeletal muscle development. A number of muscle-related miRNAs have been identified by functional gain and loss experiments in mouse model. However, determining miRNA-mRNA interactions involved in pig skeletal muscle still remains a significant challenge. For a comprehensive understanding of miRNA-mediated mechanisms underlying muscle development, miRNAome analyses of pig skeletal muscle have been performed by deep sequencing. Additionally, porcine miRNA single nucleotide polymorphisms have been implicated in muscle fiber types and meat quality. The present review provides an overview of current knowledge on recently identified miRNAs involved in myogenesis, muscle fiber type and muscle protein metabolism. Undoubtedly, further systematic understanding of the functions of miRNAs in pig skeletal muscle development will be helpful to expand the knowledge of basic skeletal muscle biology and be beneficial for the genetic improvement of meat quality traits. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Cold exposure increases slow-type myosin heavy chain 1 (MyHC1) composition of soleus muscle in rats.

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Mizunoya, Wataru; Iwamoto, Yohei; Sato, Yusuke; Tatsumi, Ryuichi; Ikeuchi, Yoshihide

2014-03-01

The aim of this study was to examine the effects of cold exposure on rat skeletal muscle fiber type, according to myosin heavy chain (MyHC) isoform and metabolism-related factors. Male Wistar rats (7 weeks old) were housed individually at 4 ± 2°C as a cold-exposed group or at room temperature (22 ± 2°C) as a control group for 4 weeks. We found that cold exposure significantly increased the slow-type MyHC1 content in the soleus muscle (a typical slow-type fiber), while the intermediate-type MyHC2A content was significantly decreased. In contrast to soleus, MyHC composition of extensor digitorum longus (EDL, a typical fast-type fiber) and gastrocnemius (a mix of slow-type and fast-type fibers) muscle did not change from cold exposure. Cold exposure increased mRNA expression of mitochondrial uncoupling protein 3 (UCP3) in both the soleus and EDL. Cold exposure also increased mRNA expression of myoglobin, peroxisome proliferator-activated receptor gamma coactivator 1α (PGC1α) and forkhead box O1 (FOXO1) in the soleus. Upregulation of UCP3 and PGC1α proteins were observed with Western blotting in the gastrocnemius. Thus, cold exposure increased metabolism-related factors in all muscle types that were tested, but MyHC isoforms changed only in the soleus. © 2013 Japanese Society of Animal Science.

Androgens regulate gene expression in avian skeletal muscles.

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Matthew J Fuxjager

Full Text Available Circulating androgens in adult reproductively active male vertebrates influence a diversity of organ systems and thus are considered costly. Recently, we obtained evidence that androgen receptors (AR are expressed in several skeletal muscles of three passeriform birds, the golden-collared manakin (Manacus vitellinus, zebra finch (Taenopygia guttata, and ochre-bellied flycatcher (Mionectes oleagieus. Because skeletal muscles that control wing movement make up the bulk of a bird's body mass, evidence for widespread effects of androgen action on these muscles would greatly expand the functional impact of androgens beyond their well-characterized effects on relatively discrete targets throughout the avian body. To investigate this issue, we use quantitative PCR (qPCR to determine if androgens alter gene mRNA expression patterns in wing musculature of wild golden-collared manakins and captive zebra finches. In manakins, the androgen testosterone (T up-regulated expression of parvalbumin (PV and insulin-like growth factor I (IGF-I, two genes whose products enhance cellular Ca(2+ cycling and hypertrophy of skeletal muscle fibers. In T-treated zebra finches, the anti-androgen flutamide blunted PV and IGF-I expression. These results suggest that certain transcriptional effects of androgen action via AR are conserved in passerine skeletal muscle tissue. When we examined wing muscles of manakins, zebra finches and ochre-bellied flycatchers, we found that expression of PV and IGF-I varied across species and in a manner consistent with a function for AR-dependent gene regulation. Together, these findings imply that androgens have the potential to act on avian muscle in a way that may enhance the physicality required for successful reproduction.

Skeletal muscle stem cells from animals I. Basic cell biology

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Skeletal muscle stem cells from food-producing animals have been of interest to agricultural life scientists seeking to develop a better understanding of the molecular regulation of lean tissue (skeletal muscle protein hypertrophy) and intramuscular fat (marbling) development. Enhanced understanding...

Oxidative proteome alterations during skeletal muscle ageing

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Sofia Lourenço dos Santos

2015-08-01

Full Text Available Sarcopenia corresponds to the degenerative loss of skeletal muscle mass, quality, and strength associated with ageing and leads to a progressive impairment of mobility and quality of life. However, the cellular and molecular mechanisms involved in this process are not completely understood. A hallmark of cellular and tissular ageing is the accumulation of oxidatively modified (carbonylated proteins, leading to a decreased quality of the cellular proteome that could directly impact on normal cellular functions. Although increased oxidative stress has been reported during skeletal muscle ageing, the oxidized protein targets, also referred as to the ‘oxi-proteome’ or ‘carbonylome’, have not been characterized yet. To better understand the mechanisms by which these damaged proteins build up and potentially affect muscle function, proteins targeted by these modifications have been identified in human rectus abdominis muscle obtained from young and old healthy donors using a bi-dimensional gel electrophoresis-based proteomic approach coupled with immunodetection of carbonylated proteins. Among evidenced protein spots, 17 were found as increased carbonylated in biopsies from old donors comparing to young counterparts. These proteins are involved in key cellular functions such as cellular morphology and transport, muscle contraction and energy metabolism. Importantly, impairment of these pathways has been described in skeletal muscle during ageing. Functional decline of these proteins due to irreversible oxidation may therefore impact directly on the above-mentioned pathways, hence contributing to the generation of the sarcopenic phenotype.

Bone marrow mesenchymal cells improve muscle function in a skeletal muscle re-injury model.

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Bruno M Andrade

Full Text Available Skeletal muscle injury is the most common problem in orthopedic and sports medicine, and severe injury leads to fibrosis and muscle dysfunction. Conventional treatment for successive muscle injury is currently controversial, although new therapies, like cell therapy, seem to be promise. We developed a model of successive injuries in rat to evaluate the therapeutic potential of bone marrow mesenchymal cells (BMMC injected directly into the injured muscle. Functional and histological assays were performed 14 and 28 days after the injury protocol by isometric tension recording and picrosirius/Hematoxilin & Eosin staining, respectively. We also evaluated the presence and the fate of BMMC on treated muscles; and muscle fiber regeneration. BMMC treatment increased maximal skeletal muscle contraction 14 and 28 days after muscle injury compared to non-treated group (4.5 ± 1.7 vs 2.5 ± 0.98 N/cm2, p<0.05 and 8.4 ± 2.3 vs. 5.7 ± 1.3 N/cm2, p<0.05 respectively. Furthermore, BMMC treatment increased muscle fiber cross-sectional area and the presence of mature muscle fiber 28 days after muscle injury. However, there was no difference in collagen deposition between groups. Immunoassays for cytoskeleton markers of skeletal and smooth muscle cells revealed an apparent integration of the BMMC within the muscle. These data suggest that BMMC transplantation accelerates and improves muscle function recovery in our extensive muscle re-injury model.