Myostatin In Skeletal Muscle Research Articles

Skeletal muscle myostatin mRNA expression is upregulated in aged human adults with excess adiposity but is not associated with insulin resistance and ageing.

Myostatin negatively regulates skeletal muscle growth and appears upregulated in human obesity and associated with insulin resistance. However, observations are confounded by ageing, and the mechanisms responsible are unknown. The aim of thisstudy wasto delineate between the effects of excess adiposity, insulin resistance and ageing on myostatin mRNA expression in human skeletal muscle and to investigate causative factors using in vitro models. An in vivo cross-sectional analysis of human skeletal muscle was undertaken to isolate effects of excess adiposity and ageing per se on myostatin expression. In vitro studies employed human primary myotubes to investigate the potential involvement of cross-talk between subcutaneous adipose tissue (SAT) and skeletal muscle, and lipid-induced insulin resistance. Skeletal muscle myostatin mRNA expression was greater in aged adults with excess adiposity than age-matched adults with normal adiposity (2.0-fold higher; P < 0.05) and occurred concurrently with altered expression of genes involved in the maintenance of muscle mass but did not differ between younger and aged adults with normal adiposity. Neither chronic exposure to obese SAT secretome nor acute elevation of fatty acid availability (which induced insulin resistance) replicated the obesity-mediated upregulation of myostatin mRNA expression in vitro. In conclusion,skeletal muscle myostatin mRNA expression is uniquely upregulated in aged adults with excess adiposity and insulin resistance but not by ageing alone. This does not appear to be mediated by the SAT secretome or by lipid-induced insulin resistance. Thus, factors intrinsic to skeletal muscle may be responsible for the obesity-mediated upregulation of myostatin, and future work to establish causality is required.

Histological and chronological study of myostatin (MSTN) role on muscles growth in domestic broiler chicken

Chicken meat have a low-cholesterol levels, low-fat with a high unsaturation amount of fatty acids, which moreover be considered as functional foods, which provide bioactive ingredients with advantageous effects on human health like vitamins and antioxidants. Therefore, this project was designed to focusing on the relationship between increased the growth curve of skeletal muscles and the role of Myostatin (MSTN) in local domestic broiler chicken. The 50 birds of male domestic broiler chicken were collected from commercial field of Al -Kut, and according ages, the birds were divided into five groups (1day, 8 day, 15 day, 22day, and 30day). The samples of skeletal muscles were taken from the breast and leg areas. All samples were exposed to histological investigation by H&amp;E stains, as well as immunohistochemical technique by a primary and secondary antibody of MSTN through paraffin-embedded sections. Histological results apparent a general structure of skeletal muscles at different ages through synchronous growth development of chicken. Immunohistochemical investigation appeared the different attribution of MSTN reactive in the skeletal muscle sections at sequence ages of chicken. Surface blots analysis of MSTN in skeletal muscle at the five experimental stages was (3.096, 10.049, 12.927, 18.453, 22.744) respectively.

Development of Myostatin Inhibitory d-Peptides to Enhance the Potency, Increasing Skeletal Muscle Mass in Mice.

Myostatin is a key negative regulator of skeletal muscle growth, and myostatin inhibitors are attractive tools for the treatment of muscular atrophy. Previously, we reported a series of 14-29-mer peptide myostatin inhibitors, including a potent derivative, MIPE-1686, a 16-mer N-terminal-free l-peptide with three unnatural amino acids and a propensity to form β-sheets. However, the in vivo biological stability of MIPE-1686 is a concern for its development as a drug. In the present study, to develop a more stable myostatin inhibitory d-peptide (MID), we synthesized various retro-inverso versions of a 16-mer peptide. Among these, an arginine-containing derivative, MID-35, shows a potent and equivalent in vitro myostatin inhibitory activity equivalent to that of MIPE-1686 and considerable stability against biodegradation. The in vivo potency of MID-35 to increase the tibialis anterior muscle mass in mice is significantly enhanced over that of MIPE-1686, and MID-35 can serve as a new entity for the prolonged inactivation of myostatin in skeletal muscle.

Regulation of Myostatin on the Growth and Development of Skeletal Muscle.

Myostatin (MSTN), a member of the transforming growth factor-β superfamily, can negatively regulate the growth and development of skeletal muscle by autocrine or paracrine signaling. Mutation of the myostatin gene under artificial or natural conditions can lead to a significant increase in muscle quality and produce a double-muscle phenotype. Here, we review the similarities and differences between myostatin and other members of the transforming growth factor-β superfamily and the mechanisms of myostatin self-regulation. In addition, we focus extensively on the regulation of myostatin functions involved in myogenic differentiation, myofiber type conversion, and skeletal muscle protein synthesis and degradation. Also, we summarize the induction of reactive oxygen species generation and oxidative stress by myostatin in skeletal muscle. This review of recent insights into the function of myostatin will provide reference information for future studies of myostatin-regulated skeletal muscle formation and may have relevance to agricultural fields of study.

Summer season induced heat stress associated changes on meat production and quality characteristics, myostatin and HSP70 gene expression patterns in indigenous goat

The study was conducted to assess the effect of heat stress on the meat production and quality variables in indigenous Malabari breed goats. The study was conducted during 45 days using twelve 10 months to one year old Malabari goats. The goats were randomly allocated into two groups: MC (n = 6; Malabari control) and MHS (n = 6; Malabari Heat stress). The MC group animals were housed inside the shed without exposure to outside environment while the MHS group animals were exposed to summer heat stress by keeping them outside the shed from 10:00 h to 16:00 h. At the end of the study, animals were slaughtered and their meat characteristics were assessed. The findings from the study revealed that heat stress caused significant reduction in live weight (P < 0.05), pre-slaughter weight (P < 0.01), hot carcass weight (P < 0.05), loin eye area (LEA) (P < 0.01), and fat score (P < 0.01). Fore saddle is the only primal cut which was significantly (P < 0.05) lower in weight in MHS as compared to MC group. Further, meat quality variables such as ultimate meat pH, water holding capacity (WHC) and shear force significantly (P < 0.01) increased during heat stress. Among the sensory characteristics, appearance (P < 0.01) and flavour (P < 0.05) reduced significantly in MHS group. However, plasma leptin level was significantly (P < 0.01) higher in MHS group. In addition, the skeletal muscle myostatin gene expression pattern was significantly (P < 0.05) lower while HSP70 gene expression was significantly (P < 0.05) higher in MHS as compared to MC group. Thus, it may be concluded from the study that indigenous Malabari goats possessed the inherent ability to maintain meat production by overcoming the adverse effects of heat stress. However, the severity of heat stress was reflected on the meat quality variables in this breed.

Skeletal muscle myostatin gene expression and sarcopenia in overweight and obese middle‐aged and older adults

BackgroundMyostatin (MSTN) is a key negative regulator of muscle mass in humans and animals, having direct and indirect influences on molecular regulators of atrophy and hypertrophy, thus potentially impacting fitness and physical function. We have shown that myostatin is elevated in conditions of chronic disability (e.g. paretic limb of stroke). Our hypothesis is that myostatin would be elevated in older adults with sarcopenia. The purpose of this study was to examine the role of skeletal muscle myostatin in sarcopenia.MethodsSixty-four overweight to obese aged 45–81 years underwent a maximal aerobic capacity (VO2max) test, dual-energy X-ray absorptiometry (DXA) scan to determine appendicular lean tissue (ALM), and vastus lateralis muscle biopsy to determine myostatin mRNA expression by quantitative real time PCR (Q-RT-PCR). Rates of sarcopenia were determined using (ALM/BMI), and sarcopenia was defined as <0.789 in men and <0.512 in women. Subjects had low fitness (VO2max: 22.7 ± 0.7 mL/kg/min) and on average 40.9 ± 1% body fat.ResultsThe prevalence of sarcopenia in this cohort was 16%. BMI, % body fat, and fat mass were higher in adults with sarcopenia than those without sarcopenia (all P < 0.001). Myostatin mRNA expression was lower in those without sarcopenia than those with sarcopenia (P < 0.05) and higher in men than women (P < 0.001). Myostatin expression was associated with BMI (r = 0.36, P < 0.01) and mid-thigh intramuscular fat (r = 0.29, P < 0.05).ConclusionGiven that myostatin is important in muscle atrophy, fat accumulation, and sarcopenia, further work could address its implication in other aging cohorts of disability and chronic disease.

Myostatin inhibitor YK11 as a preventative health supplement for bacterial sepsis

Muscle wasting caused by catabolic reactions in skeletal muscle is commonly observed in patients with sepsis. Myostatin, a negative regulator of muscle mass, has been reported to be upregulated in diseases associated with muscle atrophy. However, the behavior of myostatin during sepsis is not well understood. Herein, we sought to investigate the expression and regulation of myostatin in skeletal muscle in mice inoculated with gram-negative bacteria. Interestingly, the protein level of myostatin was found to increase in the muscle of septic mice simultaneously with an increase in the levels of follistatin, NF-κΒ, myogenin, MyoD, p- FOXO3a, and p-Smad2. Furthermore, the inhibition of myostatin by YK11 repressed the levels of pro-inflammatory cytokines and organ damage markers in the bloodstream and in the major organs of mice, which originally increased in sepsis; thus, myostatin inhibition by YK11 decreased the mortality rate due to sepsis. The results of this study suggest that YK11 may help revert muscle wasting during sepsis and subdue the inflammatory environment, thereby highlighting its potential as a preventive agent for sepsis-related muscle wasting.

Irisin Acts via the PGC-1α and BDNF Pathway to Improve Depression-like Behavior.

Depression is the most prevalent psychiatric disorder experienced by the world's population. Mechanisms associated with depression-like behavior have not been fully investigated. Among the therapeutic solution for depression, exercise is considered an important regulator attenuating depressive neuropathology. Exercise has been reported to boost the secretion of myokines such as irisin and myostatin in skeletal muscles. Myokines secreted during exercise are involved in various cellular responses including the endocrine and autocrine systems. Especially, irisin as a cleaved version of fibronectin domain-containing protein 5 has multiple functions such as white fat-browning, energy expenditure increase, anti-inflammatory effects, and mitochondrial function improvement in both systemic circulation and central nervous system. Furthermore, irisin activates energy metabolism-related signaling peroxisome proliferator-activated receptor-gamma coactivator-1 alpha and memory formation-related signaling brain-derived neurotrophic factor involved in depression. However, the role and mechanism of irisin in depression disorder is not obvious until now. Here, we review recent evidences regarding the therapeutic effect of irisin in depression disorder. We suggest that irisin is a key molecule that suppresses several neuropathological mechanisms involved in depression.

Effects Of Adipose Mesenchymal Stem Cells Injected Intramuscularly On Myostatin Signaling Skeletal Muscle In Rats After Eccentric Exercise

PURPOSE: To observe the effect of adipose mesenchymal stem cells (ASCs) on myostatin signal of skeletal muscle in rats at different time points after eccentric exercise, and to explore the mechanism of ASCs injection on skeletal muscle injury and repair after eccentric exercise. METHODS: Phosphate buffer saline (PBS) were injected into the gastrocnemius muscle in the left leg, and ASCs were injected into the gastrocnemius muscle of the right leg of SD rats after eccentric exercise. The rats were randomly divided into four groups: one day D1, three days D3, seven days W1 and fourteen days W2 after exercise. Skeletal muscle ultrastructure was observed by electron microscopic. The content of serum creatine kinase (CK), skeletal muscle troponin I (sTnI), myostatin (MSTN), follistatin (FST) were measured by ELISA. Real-time PCR was used to detect the expressions of MSTN, ACVR2B, FST mRNA in skeletal muscle. The expression of MSTN, ACVR2B, FST, p-Smad2/3 were detected by Western Blot. RESULTS: Compared with group PBS, adipose mesenchymal stem cell injection significantly promoted the repair of muscle fibers. Compared with group D1, the level of CK in group W2 was significantly decreased, the content of sTnI level in group D3 and group W1 were remarkably increased, the serum MSTN contents in group W1 were significantly decreased, which in group W2 was remarkably increased. Compared with group PBS, the relative expression quantities of MSTN mRNA were significantly decreased at time point D3 and which were extremely significantly down-regulated at time point W2. Compared with group PBS, the expression of MSTN protein were significantly decreased at time point D3, the expression of ACVR2B protein were remarkably increased at time point D1,D3 and W1, however, which was significantly decreased at time point W2. Compared with group PBS, the phosphorylation of Smad2/3 shown significantly decreased at the time point W2 of group ASCs. CONCLUSIONS: After eccentric exercise, allogeneic adipose mesenchymal stem cells injected intramuscularly can decreased the transcription of MSTN in skeletal muscle. Adipose mesenchymal stem cells injected intramuscularly may improve the regeneration and repair of skeletal muscle after eccentric exercise through affecting the downstream signaling pathway of MSTN.

Exogenous miR-29a Attenuates Muscle Atrophy and Kidney Fibrosis in Unilateral Ureteral Obstruction Mice.

Renal fibrosis leads to end-stage renal disease, but antifibrotic drugs are difficult to develop. Chronic kidney disease often results in muscle wasting, and thereby increases morbidity and mortality. In this work, adeno-associated virus (AAV)-mediated overexpressing miR-29a was hypothesized to counteract renal fibrosis and muscle wasting through muscle-kidney crosstalk in unilateral ureteral obstruction (UUO) mice. miR-29a level was downregulated in the kidney and skeletal muscle of UUO mice. The secretion of exosome-encapsulated miR-29a increased in cultured skeletal muscle satellite cells and HEK293 renal cells after stimulation with serum from UUO mice. This result was confirmed by qPCR and microRNA deep sequencing in the serum exosomes of mice with obstructed ureters. A recombinant AAV-miR-29a was generated to overexpress miR-29a and injected into the tibialis anterior muscle of the mice 2 weeks before UUO surgery. AAV-miR-29a abrogated the UUO-induced upregulation of YY1 and myostatin in skeletal muscles. Renal fibrosis was also partially improved in the UUO mice with intramuscular AAV-miR-29a transduction. AAV-miR-29a overexpression reversed the increase in transforming growth factor β, fibronectin, alpha-smooth muscle actin, and collagen 1A1 and 4A1 levels in the kidney of UUO mice. AAV-green fluorescent protein was applied to trace the AAV route in vivo, and fluorescence was significantly visible in the injected/uninjected muscles and in the kidneys. In conclusion, intramuscular AAV-miR-29a injection attenuates muscle wasting and ameliorates renal fibrosis by downregulating several fibrotic-related proteins in UUO mice.

Chronic Alcohol Consumption Enhances Skeletal Muscle Wasting in Mice Bearing Cachectic Cancers: The Role of TNFα/Myostatin Axis.

Chronic alcohol consumption enhances cancer-associated cachexia, which is one of the major causes of decreased survival. The precise molecular mechanism of how alcohol consumption enhances cancer-associated cachexia, especially skeletal muscle loss, remains to be elucidated. We used a mouse model of chronic alcohol consumption, in which 20% (w/v) alcohol was provided as sole drinking fluid, and Lewis lung carcinoma to study the underlying mechanisms. We found that alcohol consumption up-regulated the expression of MAFbx, MuRF-1, and LC3 in skeletal muscle, suggesting that alcoholenhanced ubiquitin-mediated proteolysis and LC3-mediated autophagy. Alcohol consumption enhanced phosphorylation of Smad2/3, p38, and ERK and decreased the phosphorylation of FOXO1. These are the signaling molecules governing protein degradation pathways. Moreover, alcohol consumption slightly up-regulated the expression of insulin receptor substrate-1, did not affect phosphatidylinositol-3 kinase, but decreased the phosphorylation of Akt and mammalian target of rapamycin (mTOR), and down-regulated the expression of Raptor and p70 ribosomal kinase S6 kinase, suggesting that alcohol impaired protein synthesis signaling pathway in skeletal muscle of tumor-bearing mice. Alcohol consumption enhanced the expression of myostatin in skeletal muscle, plasma, and tumor, but did not affect the expression of myostatin in non-tumor-bearing mice. In TNFα knockout mice, the effects of alcohol-enhanced expression of myostatin and protein degradation-related signaling molecules, and decreased protein synthesis signaling in skeletal muscle were abolished. Consequently, alcohol consumption neither affected cancer-associated cachexia nor decreased the survival of TNFα KO mice bearing cachectic cancer. Chronic alcohol consumption enhances cancer-associated skeletal muscle loss through suppressing Akt/mTOR-mediated protein synthesis pathway and enhancing protein degradation pathways. This process is initiated by TNFα and mediated by myostatin.

FGF-2 targets sclerostin in bone and myostatin in skeletal muscle to mitigate the deleterious effects of glucocorticoid on musculoskeletal degradation

AimMyokines are associated with regulation of bone and muscle mass. However, limited information is available regarding the impact of myokines on glucocorticoid (GC) mediated adverse effects on the musculoskeletal system. This study investigates the role of myokine fibroblast growth factor-2 (FGF-2) in regulating GC-induced deleterious effects on bone and skeletal muscle. MethodsPrimary osteoblast cells and C2C12 myoblast cell line were treated with FGF-2 and then exposed to dexamethasone (GC). FGF-2 mediated attenuation of the inhibitory effect of GC on osteoblast and myoblast differentiation and muscle atrophy was assessed through quantitative PCR and western blot analysis. Further, FGF-2 was administered subcutaneously to dexamethasone treated mice to collect bone and skeletal muscle tissue for in vivo analysis of bone microarchitecture, mechanical strength, histomorphometry and for histological alterations in treated tissue samples. Key findingsFGF-2 abrogated the dexamethasone induced inhibitory effect on osteoblast differentiation by modulating BMP-2 pathway and inhibiting Wnt antagonist sclerostin. Further, dexamethasone induced atrophy in C2C12 cells was mitigated by FGF-2 as evident from down regulation of atrogenes expression. FGF-2 prevented GC-induced impairment of mineral density, biomechanical strength, trabecular bone volume, cortical thickness and bone formation rate in mice. Additionally, skeletal muscle tissue from GC treated mice displayed weak myostatin immunostaining and reduced expression of atrogenes following FGF-2 treatment. SignificanceFGF-2 mitigated GC induced effects through inhibition of sclerostin and myostatin expression in bone and muscle respectively. Taken together, this study exhibited the role of exogenous FGF-2 in sustaining osteoblastogenesis and inhibiting muscle atrophy in presence of glucocorticoid.

Myostatin alters with exercise training in diabetic rats; possible interaction with glycosylated hemoglobin and inflammatory cytokines

The role of myostatin (MSTN) in the regulation of energy homeostasis has been known and that MSTN inhibition can attenuate the development of diabetes. However, the response of MSTN to exercise in type 1 diabetes (T1DM) is unknown. This study aimed to investigate the alteration of MSTN following aerobic exercise training in diabetic rats and its possible interaction with glycosylated hemoglobin (HbA1c) and inflammatory cytokines. Forty-eight male Wistar rats were divided into non-diabetic untrained, non-diabetic trained, diabetic untrained and diabetic trained groups. To induce T1DM, rats received an intraperitoneal injection of STZ (60 mg·kg−1). Treadmill exercise was performed for six weeks, five days/week. HbA1c was estimated, MSTN mRNA expression in skeletal muscle was measured, and plasma MSTN and inflammatory cytokines including interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α) and interleukin-1 beta (IL-1β) were determined. Results revealed a significant decrease of HbA1c and plasma inflammatory cytokines (IL-6, TNF-α and IL-1β) followed by a significant decrease of plasma and skeletal muscle MSTN in diabetic trained rats versus non-diabetic untrained and diabetic untrained rats after the experimental period. Moreover, in diabetic untrained and diabetic trained rats, a significantly positive correlation (change versus change) of plasma MSTN with HbA1c and plasma IL-6, TNF-α and IL-1β was found. In conclusion, this study indicated that aerobic exercise training by a decrease of HbA1c and plasma IL-6, TNF-α and IL-1β could decrease MSTN levels in plasma and skeletal muscle in T1DM. Furthermore, the effective influence of exercise may be reflected by changes of MSTN in diabetic rats.

Anterior Cruciate Ligament Tear Promotes Skeletal Muscle Myostatin Expression, Fibrogenic Cell Expansion, and a Decline in Muscle Quality

Background: Anterior cruciate ligament (ACL) tears result in significant quadriceps muscle atrophy that is resistant to recovery despite extensive rehabilitation. Recent work suggests an elevated fibrotic burden in the quadriceps muscle after the injury, which may limit recovery. Elucidating the mechanisms and cell types involved in the progression of fibrosis is critical for developing new treatment strategies. Purpose: To identify factors contributing to the elevated fibrotic burden found after the injury. Study Design: Descriptive laboratory study. Methods: After an ACL injury, muscle biopsy specimens were obtained from the injured and noninjured vastus lateralis of young adults (n = 14, mean ± SD: 23 ± 4 years). The expression of myostatin, transforming growth factor β, and other regulatory factors was measured, and immunohistochemical analyses were performed to assess turnover of extracellular matrix components. Results: Injured limb skeletal muscle demonstrated elevated myostatin gene (P < .005) and protein (P < .0005) expression, which correlated (R2 = 0.38, P < .05) with fibroblast cell abundance. Immunohistochemical analysis showed that human fibroblasts express the activin type IIB receptor and that isolated primary human muscle-derived fibroblasts increased proliferation after myostatin treatment in vitro (P < .05). Collagen 1 and fibronectin, primary components of the muscle extracellular matrix, were significantly higher in the injured limb (P < .05). The abundance of procollagen 1–expressing cells as well as a novel index of collagen remodeling was also elevated in the injured limb (P < .05). Conclusion: These findings support a role for myostatin in promoting fibrogenic alterations within skeletal muscle after an ACL injury. Clinical Relevance: The current work shows that the cause of muscle quality decline after ACL injury likely involves elevated myostatin expression, and future studies should explore therapeutic inhibition of myostatin to facilitate improvements in muscle recovery and return to sport.

Exogenous miR-29a Attenuates Muscle Atrophy and Kidney Fibrosis in UUO Mice

Our previous study found that miR-29a was decreased in skeletal muscle of mice with renal disease. However, the cause of decreasing miR-29a and the influence other organs is less known. We hypothesized that adeno-associated virus (AAV)-mediated overexpressing miR-29a would counteract unilateral ureteral obstruction (UUO)-induced muscle wasting and renal fibrosis via muscle-kidney crosstalk. The expression of miR-29a was decreased in skeletal muscle and kidney of UUO mice. Serum from UUO mice enhanced secretion of exosome-encapsulated miR-29a from cultured skeletal muscle satellite cells and HEK293 renal cells. This was confirmed by qPCR and microRNA deep sequencing in serum exosomes of mice with obstructed ureters. We generated a recombinant adeno-associated virus (AAV-miR29a) to overexpress miR-29a and injected it into the tibialis anterior (TA) muscle of UUO mice for 14-days. The AAV-miR-29a decreased UUO-induced upregulation of YY1 and myostatin in skeletal muscle. In addition, renal fibrosis was partially depressed in the UUO mice with intramuscular transduction with AAV-miR-29a. We found that TGF, alpha-smooth muscle actin (SMA), fibronectin, collagen 1A1 and 4A1 were increased in the kidney of UUO mice, overexpressing by AAV-miR-29a reversed these changes. When we used AAV-GFP to trace the AAV route in vivo we found that fluorescence was significantly visible in both injected and un-injected muscle and in kidneys. We conclude that intramuscular injection of AAV-miR-29a not only ameliorates skeletal protein metabolism, but also attenuates UUO-induced kidney fibrosis by down-regulating TGF- pathway cascade proteins and extracellular matrix components. Funding Statement: Research reported in this publication was supported by grants from the National Natural Science Foundation of China (Nos. 81700650, 81700618, 31772690), and the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) of the National Institutes of Health under Award Number R01 AR060268 and American Heart Association Discover and Innovation Grants (17IBDG33780000) to X.H.W. and the Natural Science Foundation of Jiangsu Province (BK20181487), China Young Nephrologist Research Project, and Southeast University High Level Thesis Project to B. W. Declaration of Interests: The authors state no conflicts of interest. Ethics Approval Statement: These experiments were approved by the Emory University IACUC (protocol 141-2008).

(-)-Epicatechin Supplementation Inhibits Aerobic Adaptations to Cycling Exercise in Humans.

The purpose of the study was to determine if cycling exercise combined with (–)-epicatechin supplementation was more effective at increasing training adaptations than cycling combined with a placebo. Blood and muscle samples were obtained at rest before and after training to determine the effects of (–)-epicatechin supplementation on total serum antioxidant capacity, skeletal muscle mitochondrial protein content, and skeletal muscle myostatin gene expression. Participants (n = 20) completed two testing sessions separated by 4 weeks of cycle training, with supplementation of 100 mg (200 mg total daily) of (–)-epicatechin or a placebo, twice daily. Data were analyzed using a two-way mixed model ANOVA for each variable and the alpha level was set at p ≤ 0.05. A significant increase was observed for time for relative peak anaerobic power (p < 0.01), relative anaerobic capacity (p < 0.01), and fatigue index (p < 0.01). A significant increase was observed for time for absolute peak VO2 (p < 0.01) and peak power output obtained during the peak VO2 test (p < 0.01). A significant interaction between group and time for relative peak VO2 was observed (p = 0.04). Relative peak VO2 significantly increased over time in the placebo group (p < 0.01), but not in the (–)-epicatechin group (p = 0.21). A significant increase was observed for time for total serum antioxidant capacity (p = 0.01). No interaction or main effect of time was observed for myostatin (p > 0.05). Likewise, no interaction or main effect of time was observed for cytochrome C or citrate synthase (p > 0.05). A significant interaction effect was observed for succinate dehydrogenase (SDH; p = 0.02). SDH content increased significantly for the placebo group (p = 0.03, partial η2 = 0.59), but not for the (–)-epicatechin group (p = 0.81). Further, whereas no difference existed between the groups for SDH at baseline (p = 0.23), SDH content was significantly greater in the placebo group at the post time point (p = 0.01). Results indicate that (–)-epicatechin supplementation does not affect myostatin gene expression or anaerobic training adaptations but inhibits aerobic and mitochondrial SDH adaptations to cycle exercise training.

Comparative assessment of heat stress induced changes in carcass traits, plasma leptin profile and skeletal muscle myostatin and HSP70 gene expression patterns between indigenous Osmanabadi and Salem Black goat breeds

The primary objective of the study was to compare the impact of heat stress on meat production characteristics of Osmanabadi and Salem Black breed goats based on changes in carcass characteristics, meat quality attributes, plasma leptin concentration, skeletal muscle myostatin and heat shock protein 70 (HSP70) gene expression patterns. The goats were randomly distributed into four groups: OSC (n = 6; Osmanabadi Control), OSHS (n = 6; Osmanabadi Heat Stress), SBC (n = 6; Salem Black Control) and SBHS (n = 6; Salem Black Heat Stress). The animals were slaughtered at the end of the study and their meat characteristics were assessed. This study established the impact of heat stress on a wide variety of carcass and meat quality characteristics in OS and SB goat breeds. The results from the study also provided some crucial evidence for a better resilience capacity of Salem Black breed as compared to Osmanabadi goats in maintaining the meat production during heat stress. The study also established plasma leptin and HSP70 genes to be the ideal biomarkers to reflect the impact of heat stress on meat characteristics in indigenous goats.

Prevention of chemotherapy-induced cachexia by ACVR2B ligand blocking has different effects on heart and skeletal muscle.

BackgroundToxicity of chemotherapy on skeletal muscles and the heart may significantly contribute to cancer cachexia, mortality, and decreased quality of life. Doxorubicin (DOX) is an effective cytostatic agent, which unfortunately has toxic effects on many healthy tissues. Blocking of activin receptor type IIB (ACVR2B) ligands is an often used strategy to prevent skeletal muscle loss, but its effects on the heart are relatively unknown.MethodsThe effects of DOX treatment with or without pre‐treatment with soluble ACVR2B‐Fc (sACVR2B‐Fc) were investigated. The mice were randomly assigned into one of the three groups: (1) vehicle (PBS)‐treated controls, (2) DOX‐treated mice (DOX), and (3) DOX‐treated mice administered with sACVR2B‐Fc during the experiment (DOX + sACVR2B‐Fc). DOX was administered with a cumulative dose of 24 mg/kg during 2 weeks to investigate cachexia outcome in the heart and skeletal muscle. To understand similarities and differences between skeletal and cardiac muscles in their responses to chemotherapy, the tissues were collected 20 h after a single DOX (15 mg/kg) injection and analysed with genome‐wide transcriptomics and mRNA and protein analyses. The combination group was pre‐treated with sACVR2B‐Fc 48 h before DOX administration. Major findings were also studied in mice receiving only sACVR2B‐Fc.ResultsThe DOX treatment induced similar (~10%) wasting in skeletal muscle and the heart. However, transcriptional changes in response to DOX were much greater in skeletal muscle. Pathway analysis and unbiased transcription factor analysis showed that p53‐p21‐REDD1 is the main common pathway activated by DOX in both skeletal and cardiac muscles. These changes were attenuated by blocking ACVR2B ligands especially in skeletal muscle. Tceal7 (3‐fold to 5‐fold increase), transferrin receptor (1.5‐fold increase), and Ccl21 (0.6‐fold to 0.9‐fold decrease) were identified as novel genes responsive to blocking ACVR2B ligands. Overall, at the transcriptome level, ACVR2B ligand blocking had only minor influence in the heart while it had marked effects in skeletal muscle. The same was also true for the effects on tissue wasting. This may be explained in part by about 18‐fold higher gene expression of myostatin in skeletal muscle compared with the heart.ConclusionsCardiac and skeletal muscles display similar atrophy after DOX treatment, but the mechanisms for this may differ between the tissues. The present results suggest that p53‐p21‐REDD1 signalling is the main common DOX‐activated pathway in these tissues and that blocking activin receptor ligands attenuates this response, especially in skeletal muscle supporting the overall stronger effects of this treatment in skeletal muscles.

Mice overexpressing growth hormone exhibit increased skeletal muscle myostatin and MuRF1 with attenuation of muscle mass

BackgroundIn contrast to the acute effects of growth hormone (GH) on skeletal muscle protein synthesis, long-term GH treatment appears to have negligible effects on muscle mass. Despite this knowledge, little is known regarding the chronic effects of GH on skeletal muscle protein synthesis and atrophy signaling pathways. The purpose of this study was to determine if protein synthesis pathways are attenuated and/or muscle atrophy intracellular signaling pathways are altered in the skeletal muscle of transgenic bovine GH (bGH) mice.MethodsThe gastrocnemius and soleus from 5-month-old male bGH mice (n = 9) and wild type (WT) controls (n = 9) were harvested and analyzed for proteins involved in the protein synthesis (Akt/mTOR), growth and proliferation (MAPK), and muscle atrophy (MuRF1 and myostatin) pathways.ResultsTotal body mass was significantly increased in bGH mice compared to WT controls (49%, P < 0.0001). When expressed relative to total body mass, the gastrocnemius (− 28%, P < 0.0001), but not the soleus, was significantly lower in mice overexpressing GH, compared to controls. Transgenic bGH mice had elevated phosphorylation levels of protein kinase b (Akt1), 4E-binding protein 1 (4E-BP1), p70 S6 kinase, p42/44, and p38 (P < 0.05) compared to WT littermates. Mature myostatin (26 kDa), premature myostatin (52 kDa), and activin receptor type IIB (AcvR2B) protein levels were increased in bGH mice (P < 0.05), along with elevated phosphorylation levels of mothers against decapentaplegic homolog (Smad2) (59%, P < 0.0001). Mice overexpressing GH had increased MuRF1 expression (30%, P < 0.05) and insulin receptor substrate 1 (IRS1) serine phosphorylation (44%, P < 0.05) in the gastrocnemius, but not the soleus, when compared to controls.ConclusionsThese findings demonstrate that chronic elevations in circulating GH have a critical impact on signaling pathways involved in skeletal muscle protein synthesis and atrophy, and suggest that MuRF1, myostatin, and IRS1 serine phosphorylation may act to inhibit exaggerated glycolytic muscle growth, in environments of chronic GH/IGF-1 excess.

THE ROLE OF SKELETAL MUSCLE MYOSTATIN IN SARCOPENIA IN OLDER ADULTS

Myostatin is a key negative regulator of muscle mass in humans and animals, having direct and indirect influences on molecular regulators of atrophy and hypertrophy, thus may impact fitness and physical function. We have shown that myostatin is elevated in conditions of chronic disability (e.g. paretic limb of stroke). Our hypothesis is that myostatin would be elevated in older adults with sarcopenia The purpose of this study was to examine the role of skeletal muscle myostatin in sarcopenia. Thirty-eight normal-weight to obese (BMI: 33 ± 5 kg/m2, X±SEM, range 21–45 kg/m2) men (n=21) and women (n=17) aged 45–81 years underwent a VO2max test, DXA scan to determine appendicular lean tissue (ALM), and vastus lateralis muscle biopsy. Quantitative real time PCR (Q-RT-PCR) was performed using Taqman probes with 36B4 as a reference to determine myostatin mRNA expression. Rates of sarcopenia were determined using (ALM/BMI) and sarcopenia was defined as < 0.789 in men and < 0.512 in women. Subjects had low fitness (VO2max: 24 ± 1 ml/kg/min) and on average 41 ± 1% body fat. The prevalence of sarcopenia in this cohort was 16%. Myostatin mRNA expression tended to be lower (29%) in those without sarcopenia than those with sarcopenia (68 ± 6 vs. 96 ± 18 AU, P=0.09). Myostatin expression was not related to age or VO2max. While myostatin may be important in muscle atrophy and sarcopenia, further work could address it’s implication in other aging cohorts of disability and chronic disease.