Myostatin mRNA Levels Research Articles

Acute resistance exercise reduces increased gene expression in muscle atrophy of ovariectomised arthritic rats.

ObjectiveWe studied the effect of resistance exercise (RE) on mRNA levels of atrogin-1, MuRF-1, and myostatin in the gastrocnemius muscle of arthritic rats after loss of ovarian function (LOF).Material and methodsThirty female Wistar rats (nine weeks old, 195.3 ±17.4 grams) were randomly allocated into five groups: control group (CT-Sham; n = 6); group with rheumatoid arthritis (RA; n = 6); group with rheumatoid arthritis subjected to RE (RAEX; n = 6); ovariectomy group with rheumatoid arthritis (RAOV; n = 6); and an ovariectomy group with rheumatoid arthritis subjected to RE (RAOVEX; n = 6). After 15 days of intra-articular injections with Met-BSA the animals were subjected to RE and six hours after workout were euthanised.ResultsThe rheumatoid arthritis provoked reduction in the cross-sectional area (CSA) of muscle fibres, but the CSA was lower in the RAOV when compared to the RA groups. Skeletal muscle atrogin-1 mRNA level was increased in arthritic rats (RA and RAOV), but the atrogin-1 level was higher in RAOV group when compared to other arthritic groups. The Muscle MuRF-1 mRNA level was also increased in the RAOV group. The increased atrogin-1 and MuRF-1 mRNA levels were lower in the RAOVEX group than in the RAOV group. The myostatin mRNA level was similar in all groups, except for the RAOVEX group, in which it was lower than the other groups.ConclusionsLOF results in increased loss of skeletal muscle-related ubiquitin ligases (atrogin-1 and MuRF-1). However, the RE reduces the atrogin-1, MuRF-1, and myostatin mRNA levels in muscle of arthritic rats affected by LOF.

Myostatin mRNA expression and its association with body weight and carcass traits in Yunnan Wuding chicken.

Myostatin (MSTN) is expressed in the myotome and developing skeletal muscles, and acts to regulate the number of muscle fibers. Wuding chicken large body, developed muscle, high disease resistance, and tender, delicious meat, and are not selected for fast growth. Broiler chickens (Avian broiler) are selected for fast growth and have a large body size and high muscle mass. Here, 240 one-day-old chickens (120 Wuding chickens and 120 broilers) were examined. Twenty chickens from each breed were sacrificed at days 1, 30, 60, 90, 120, and 150. Breast and leg muscle samples were collected within 20 min of sacrifice to investigate the effects of MSTN gene expression on growth performance and carcass traits. Body weight, carcass traits, and skeletal muscle mass in Wuding chickens were significantly (P < 0.05) lower than those in broiler chickens at all time points. Breast muscle MSTN mRNA was lower in Wuding chickens than in broilers before day 30 (P < 0.05). After day 30, breast muscle MSTN expression was higher in Wuding chicken than in broilers (P < 0.05). Leg muscle MSTN mRNA expression was higher in Wuding chicken than in broilers at all ages except for day 60 (P < 0.05). Correlation analysis revealed that breast muscle MSTN expression has a greater effect in slow growing Wuding chickens than in the fast growing broilers. In contract, leg muscle MSTN mRNA level has a greater effect in broilers than in Wuding chickens. MSTN regulates growth performance and carcass traits in chickens.

Efficient Generation of Myostatin Mutations in Pigs Using the CRISPR/Cas9 System.

Genetically modified pigs are increasingly used for biomedical and agricultural applications. The efficient CRISPR/Cas9 gene editing system holds great promise for the generation of gene-targeting pigs without selection marker genes. In this study, we aimed to disrupt the porcine myostatin (MSTN) gene, which functions as a negative regulator of muscle growth. The transfection efficiency of porcine fetal fibroblasts (PFFs) was improved to facilitate the targeting of Cas9/gRNA. We also demonstrated that Cas9/gRNA can induce non-homologous end-joining (NHEJ), long fragment deletions/inversions and homology-directed repair (HDR) at the MSTN locus of PFFs. Single-cell MSTN knockout colonies were used to generate cloned pigs via somatic cell nuclear transfer (SCNT), which resulted in 8 marker-gene-free cloned pigs with biallelic mutations. Some of the piglets showed obvious intermuscular grooves and enlarged tongues, which are characteristic of the double muscling (DM) phenotype. The protein level of MSTN was decreased in the mutant cloned pigs compared with the wild-type controls, and the mRNA levels of MSTN and related signaling pathway factors were also analyzed. Finally, we carefully assessed off-target mutations in the cloned pigs. The gene editing platform used in this study can efficiently generate genetically modified pigs with biological safety.

Myostatin, follistatin and activin type II receptors are highly expressed in adenomyosis

To evaluate the expression pattern of activins and related growth factor messenger RNA (mRNA) levels in adenomyotic nodules and in their endometrium. Prospective study. University hospital. Symptomatic premenopausal women scheduled to undergo hysterectomy for adenomyosis. Samples from adenomyotic nodules and homologous endometria were collected. Endometrial tissue was also obtained from a control group. Quantitative real-time polymerase chain reaction (PCR) analysis and immunohistochemical localization of activin-related growth factors (activin A, activin B, and myostatin), binding protein (follistatin), antagonists (inhibin-α, cripto), and receptors (ActRIIa, ActRIIb) were performed. Myostatin mRNA levels in adenomyotic nodule were higher than in eutopic endometrium and myostatin, activin A, and follistatin concentrations were higher than in control endometrium. No difference was observed for inhibin-α, activin B, and criptomRNA levels. Increased mRNA levels of ActRIIa and ActRIIb were observed in adenomyotic nodules compared with eutopic endometrium and control endometrium. Immunofluorescent staining for myostatin and follistatin confirmed higher protein expression in both glands and stroma of patients with adenomyosis than in controls. The present study showed for the first time that adenomyotic tissues express high levels of myostatin, follistatin, and activin A (growth factors involved in proliferation, apoptosis, and angiogenesis). Increased expression of their receptors supports the hypothesis of a possible local effect of these growth factors in adenomyosis. The augmented expression of ActRIIa, ActRIIb, and follistatin in the endometrium of these patients may play a role in adenomyosis-related infertility.

The relative expression levels of insulin-like growth factor 1 and myostatin mRNA in the asynchronous development of skeletal muscle in ducks during early development

Genetic selection is a powerful tool for modifying poultry muscle yield. Insulin-like growth factor I (IGF-I) and myostatin (MSTN) are important regulators of muscle growth, especially in the myogenesis stage. This study compared the developmental pattern of the pectoralis major (PM) and lateral gastrocnemius (LM) muscles, mRNA expression characterization of IGF-I and MSTN-A and their correlation between 14days in ovo and 1week post-hatch in two Chinese local duck breeds. During early development, the growth of duck PM and LM followed an asynchronous pattern. Variations in PM growth rate observed with development followed the relative variations of MSTN and IGF-I expression; however, the same behavior was not observed in LM. Moreover, the profile of IGF-I expression in duck skeletal muscles indicated that genetic selection for high meat-yield poultry has altered the temporal expression of IGF-I and affected cellular characteristics and mass by hatch in a PM-specific manner. The MSTN-A expression profile showed synchronization with the growth of skeletal muscle and peaks of myofiber proliferation. The expression patterns of IGF-I and MSTN suggest that duck pectoralis fibers are prioritized for proliferation in embryogenesis. The IGF-1/MSTN-A mRNA ratios in PM and LM presented very similar trends in the changes of myofiber characteristics, and differences in the IGF-1/MSTN-A mRNA ratio in PM between the two breeds corresponded to the timing of differences in PM mass between the varieties. Our results support the hypothesis that relative levels of IGF-I and MSTN mRNA may participate in ordering muscle growth rates with selected development.

Effect of Training on PPARGC1A and FNDC5 Gene Expression in Thoroughbred Horses

IntroductionPGC‐1α and irisin, encoded by the PPARGC1A and FNDC5 genes, play key roles in mediating the beneficial effects of exercise. PPARGC1A gene expression is induced by exercise and has been shown to upregulate FNDC5 expression. Higher levels of FNDC5 have been observed in young male human athletes compared to sedentary controls. FNDC5 gene expression has also been shown in some species to be modulated by myostatin (MSTN), a growth factor that limits muscle hypertrophy. In horses MSTN variation (g.66493737C&gt;T) affects gene expression and racing performance. Thoroughbreds homozygous for the C‐allele have significantly higher levels of MSTN mRNA than homozygous T : T horses. The aim of this study was to investigate the responses of PPARGC1A and FNDC5 in skeletal muscle to exercise and investigate the relationship with MSTN genotype.MethodsSkeletal muscle (gluteus medius) biopsies were taken from untrained yearling Thoroughbreds (n = 27) at rest and after a ten month period of training at two‐years‐old. Skeletal muscle gene expression was measured using real‐time qRT‐PCR assays and data was analysed using qBase software.ResultsA significant increase in both PPARGC1A (P = 0.0001, FC = 1.82) and FNDC5 (P = 0.039, FC = 1.72) was observed post‐training. A significant positive correlation was found between FNDC5 and PPARGC1A expression levels post training (P = 0.01, R2 = 0.22). There was no relationship between PPARGC1A or FNDC5 gene expression and MSTN genotype.ConclusionsThese data indicate a coordinated role for PGC‐1α and irisin in the skeletal muscle response to exercise in Thoroughbred horses. Their known roles in mitochondrial biogenesis and brown fat metabolism suggest important roles in the adaptive response to exercise, which is independent of MSTN‐determined muscle type.Ethical Animal ResearchInstitutional Animal Research Ethics Committee approval was obtained. Explicit owner informed consent for participation in this study is not stated. Sources of funding: Science Foundation Ireland under Grant Number 11/PI/1166. Competing interests: Dr Hill is a co‐founder and Chairman of Equinome Ltd.

The effects of exogenous cortisol on myostatin transcription in rainbow trout, Oncorhynchus mykiss

Glucocorticoids (GCs) strongly regulate myostatin expression in mammals via glucocorticoid response elements (GREs), and bioinformatics methods suggest that this regulatory mechanism is conserved among many vertebrates. However, the multiple myostatin genes found in some fishes may be an exception. In silico promoter analyses of the three putative rainbow trout (Oncorhynchus mykiss) myostatin promoters have failed to identify putative GREs, suggesting a divergence in myostatin function. Therefore, we hypothesized that myostatin mRNA expression is not regulated by glucocorticoids in rainbow trout. In this study, both juvenile rainbow trout and primary trout myoblasts were treated with cortisol to examine the effects on myostatin mRNA expression. Results suggest that exogenous cortisol does not regulate myostatin-1a and -1b expression in vivo, as myostatin mRNA levels were not significantly affected by cortisol treatment in either red or white muscle tissue. In red muscle, myostatin-2a levels were significantly elevated in the cortisol treatment group relative to the control, but not the vehicle control, at both 12h and 24h post-injection. As such, it is unclear if cortisol was acting alone or in combination with the vehicle. Cortisol increased myostatin-1b expression in a dose-dependent manner in vitro. Further work is needed to determine if this response is the direct result of cortisol acting on the myostatin-1b promoter or through an alternative mechanism. These results suggest that regulation of myostatin by cortisol may not be as highly conserved as previously thought and support previous work that describes potential functional divergence of the multiple myostatin genes in fishes.

Mechanisms of cisplatin-induced muscle atrophy

Fatigue is the most common side effect of chemotherapy. However, the mechanisms of “muscle fatigue” induced by anti-cancer drugs are not fully understood. We therefore investigated the muscle-atrophic effect of cisplatin, a platinum-based anti-cancer drug, in mice. C57BL/6J mice were treated with cisplatin (3mg/kg, i.p.) or saline for 4 consecutive days. On Day 5, hindlimb and quadriceps muscles were isolated from mice. The loss of body weight and food intake under the administration of cisplatin was the same as those in a dietary restriction (DR) group. Under the present conditions, the administration of cisplatin significantly decreased not only the muscle mass of the hindlimb and quadriceps but also the myofiber diameter, compared to those in the DR group. The mRNA expression levels of muscle atrophy F-box (MAFbx), muscle RING finger-1 (MuRF1) and forkhead box O3 (FOXO3) were significantly and further increased by cisplatin treated group, compared to DR. Furthermore, the mRNA levels of myostatin and p21 were significantly upregulated by the administration of cisplatin, compared to DR. On the other hand, the phosphorylation of Akt and FOXO3a, which leads to the blockade of the upregulation of MuRF1 and MAFbx, was significantly and dramatically decreased by cisplatin. These findings suggest that the administration of cisplatin increases atrophic gene expression, and may lead to an imbalance between protein synthesis and protein degradation pathways, which would lead to muscle atrophy. This phenomenon could, at least in part, explain the mechanism of cisplatin-induced muscle fatigue.

Expression Profiles of Myostatin, Myogenin, and Myosin Heavy Chain in Skeletal Muscles of Two Rabbit Breeds Differing in Growth Rate

The purpose of the present study was to compare mRNA levels of myostatin (MSTN), myogenin (MyoG), and fiber type compositions in terms of myosin heavy chain (MyHC) in skeletal muscles of two rabbit breeds with different body sizes and growth rates. Longissimus dorsi and biceps femoris muscles of 16 Californian rabbits (CW) and 16 Germany great line of ZIKA rabbits (GZ) were collected at the ages of 35d and 84d (slaughter age). The results showed that the live weights of GZ rabbits of 35d and 84d old were approximately 36% and 26% greater than those of CW rabbits, respectively. Quantitative real-time PCR analysis revealed that at the age of 84d GZ rabbits contained significantly lower MSTN mRNA level and higher MyoG mRNA level in both longissimus dorsi and biceps femoris muscles than CW rabbits, and mRNA levels of MSTN and MyoG exhibited opposite changes from the age of 35d to 84d, suggesting that GZ rabbits were subjected to less growth inhibition from MSTN at slaughter age, which occurred most possibly in skeletal muscles. Four types of fiber were identified by real-time PCR in rabbit muscles, with MyHC-1 and MyHC-2D, MyHC-2B were the major types in biceps femoris and longissimus dorsi muscles, respectively. At the age of 84d, GZ rabbits contained greater proportion of MyHC-1 and decreased proportion of MyHC-2D and decreased lactate dehydrogenase activity in biceps femoris than CW rabbits, and the results were exactly opposite in longissimus dorsi, suggesting that GZ rabbits show higher oxidative capacity in biceps femoris muscle than CW rabbits. In conclusion, the trends of mRNA levels of MSTN and fiber types in GZ rabbits' skeletal muscles might be consistent with the putative fast growth characteristic of GZ rabbits compared to CW rabbits.

Characterization of muscle morphology and satellite cells, and expression of muscle-related genes in skeletal muscle of juvenile and adult Megalobrama amblycephala

Hyperplasia and hypertrophy are two distinct processes of skeletal muscle growth regulated by four myogenic regulatory factors (MRFs, contains MyoD, Myf5, Mrf4 and myogenin (MyoG)) and myostatin (MSTN). In this study, characterization of muscle morphology and satellite cells in juvenile (1-year-old) and adult (2-year-old) Megalobrama amblycephala was described. Compared with 1-year-old M. amblycephala, the diameter scope of epaxial, horizontal septum and hypaxial muscle fibers including red and white muscle in 2-year-old fish exhibited broader with dramatic reduction in frequency distribution of <20μm diameter, nevertheless observable increase in frequency distribution of >50μm diameter. Intermyofibrillar (IM) nuclei were also found except numerous subsarcolemmal (SS) nuclei in 2-year-old fish, whereas only SS nuclei were observed in 1-year-old fish. Immunofluorescence results showed that more satellite cells existed in red muscle than white muscle in 1-year-old fish, rather than 2-year-old fish. Moreover, we observed predominant increase in the mRNA levels of MyoD, Myf5, Mrf4, and MSTN during muscle development of fish in 2-year-old fish except MyoG.

Non‐uniform myostatin transcription in the acute response to a myocardial infarction (699.7)

Myostatin, a negative regulator of skeletal muscle growth, is transcriptionally upregulated in the heart following myocardial infarction (MI). Investigations have largely focused on myostatin production in the left ventricle (LV) during development of LV dysfunction. However, MI causes significant right ventricle (RV) dysfunction along with greater re‐expression of fetal genes as compared to LV. Our objective was to examine relative RV and LV myostatin expression following MI. Methods. Mice were sacrificed following MI and the infarct, peri‐infarct and RV were separated. Myostatin mRNA levels were determined via qPCR. Results. Baseline myostatin expression was statistically similar between the LV and RV. One‐hour post‐MI, a 10 and 2.3 fold increase in myostatin mRNA was observed in the RV and peri‐infarct tissue, respectively. Myostatin mRNA levels peaked 12h post‐MI with a 30 and 7.5 fold increase in RV and peri‐infarct regions, respectively. Out to 1 week, myostatin levels remain significantly higher in the RV than in the peri‐infarct tissue. Conclusion. Myostatin transcription in response to a MI is 4‐5 times greater in the RV than in other regions of the heart. Determining the mechanism behind this region specific increase in myostatin transcription may provide key details in understanding the role of myostatin expression in cardiac pathology.Grant Funding Source: Canadian Institute of Health and Research

Androgenic and estrogenic regulation of Atrogin-1, MuRF1 and myostatin expression in different muscle types of male mice

The molecular factors targeted by androgens and estrogens on muscle mass are not fully understood. The current study aimed to explore gene and protein expression of Atrogin-1, MuRF1, and myostatin in an androgen deprivation-induced muscle atrophy model. We examined the effects of Orx either with or without testosterone (T) or estradiol (E2) administration on Atrogin-1 gene expression, and MuRF1 and myostatin gene and protein expression. Measurements were made in soleus (SOL), extensor digitorum longus (EDL) and levator ani/bulbocavernosus (LA/BC) of male C57BL/6 mice. Thirty days of Orx resulted in a reduction in weight gain and muscle mass. These effects were prevented by T. In LA/BC, Atrogin-1 and MuRF1 mRNA was increased throughout 30 days of Orx, which was fully reversed by T and partially by E2 administration. In EDL and SOL, a less pronounced upregulation of both genes was only detectable at the early stages of Orx. Myostatin mRNA levels were downregulated in LA/BC and upregulated in EDL following Orx. T, but not E2, reversed these effects. No changes in protein levels of MuRF1 and myostatin were found in EDL at any time point following Orx. The atrophy in SOL and EDL in response to androgen deprivation, and its restoration by T, is accompanied by only minimal changes in atrogenes and myostatin gene expression. The marked differences in muscle atrophy and atrogene and myostatin mRNA between LA/BC and the locomotor muscles suggest that the murine LA/BC is not an optimal model to study Orx-induced muscle atrophy.

Gene expression profile of IGF1 and MSTN mRNA and their correlation with carcass traits in different breeds of geese at 70 d of age

1. The expression of insulin-like growth factor-1 (IGF1) and myostatin (MSTN) mRNA in breast and leg muscle was quantified in 70-d-old Taihu and Wanxi geese by using a Multiplex Competitive Fluorescent–PCR method and the correlations between mRNA levels and carcass traits were analysed.2. IGF1 mRNA expression in breast muscle in Taihu geese was significantly higher than that in Wanxi geese and the MSTN mRNA level in leg muscle in Taihu geese was significantly higher than that in Wanxi geese.3. There was no significant difference in breast muscle MSTN or leg muscle IGF1 mRNA expression between the two breeds.4. Within the same breed, the IGF1 mRNA expression in leg muscle of male geese was significantly higher than that in female geese, and MSTN mRNA expression in leg muscle was significantly higher than that in breast muscle.5. There was no difference in the IGF1 mRNA expression between tissues.6. There was a positive correlation between IGF1 mRNA and MSTN mRNA and a negative correlation between IGF1 mRNA expression of breast muscle and leg muscle ratio.7. In Wanxi geese, MSTN mRNA expression in leg muscle was negatively associated with body weight and leg muscle weight.

Rearing temperature induces changes in muscle growth and gene expression in juvenile pacu (Piaractus mesopotamicus)

Pacu (Piaractus mesopotamicus) is a fast-growing fish that is extensively used in Brazilian aquaculture programs and shows a wide range of thermal tolerance. Because temperature is an environmental factor that influences the growth rate of fish and is directly related to muscle plasticity and growth, we hypothesized that different rearing temperatures in juvenile pacu, which exhibits intense muscle growth by hyperplasia, can potentially alter the muscle growth patterns of this species. The aim of this study was to analyze the muscle growth characteristics together with the expression of the myogenic regulatory factors MyoD and myogenin and the growth factor myostatin in juvenile pacu that were submitted to different rearing temperatures. Juvenile fish (1.5 g weight) were distributed in tanks containing water and maintained at 24°C (G24), 28 °C (G28) and 32 °C (G32) (three replicates for each group) for 60 days. At days 30 and 60, the fish were anesthetized and euthanized, and muscle samples (n=12) were collected for morphological, morphometric and gene expression analyses. At day 30, the body weight and standard length were lower for G24 than for G28 and G32. Muscle fiber frequency in the <25 μm class was significantly higher in G24, and the >50 μm class was lower in G24. MyoD gene expression was higher in G24 compared with that in G28 and G32, and myogenin and myostatin mRNA levels were higher in G24 than G28. At day 60, the body weight and the standard length were higher in G32 but lower in G24. The frequency distribution of the <25 μm diameter muscle fibers was higher in G24, and that of the >50 μm class was lower in G24. MyoD mRNA levels were higher in G24 and G32, and myogenin mRNA levels were similar between G24 and G28 and between G24 and G32 but were higher in G28 compared to G32. The myostatin mRNA levels were similar between the studied temperatures. In light of our results, we conclude that low rearing temperature altered the expression of muscle growth-related genes and induced a delay in muscle growth in juvenile pacu (P. mesopotamicus). Our study provides a clear example of thermally induced phenotypic plasticity in pacu fish and shows that changing the rearing temperature during the juvenile stage can have a considerable effect on gene expression and muscle growth in this species.

Acute molecular responses in untrained and trained muscle subjected to aerobic and resistance exercise training versus resistance training alone

This study assessed and compared acute muscle molecular responses before and after 5-week training, employing either aerobic (AE) and resistance exercise (RE) or RE only. Ten men performed one-legged RE, while the contralateral limb performed AE followed by RE 6 h later (AE+RE). Before (untrained) and after (trained) the intervention, acute bouts of RE were performed with or without preceding AE. Biopsies were obtained from m. vastus lateralis of each leg pre- and 3 h post-RE to determine mRNA levels of VEGF, PGC-1α, MuRF-1, atrogin-1, myostatin and phosphorylation of mTOR, p70S6K, rpS6 and eEF2. PGC-1α and VEGF expression increased (P < 0.05) after acute RE in the untrained, but not the trained state. These markers showed greater response after AE+RE than RE in either condition. Myostatin was lower after AE+RE than RE, both before and after training. AE+RE showed higher MuRF-1 and atrogin-1 expression than RE in the untrained, not the trained state. Exercise increased (P < 0.05) p70S6K phosphorylation both before and after training, yet this increase tended to be more prominent for AE+RE than RE before training. Phosphorylation of p70S6K was greater in trained muscle. Changes in these markers did not correlate with exercise-induced alterations in strength or muscle size. Concurrent exercise in untrained skeletal muscle prompts global molecular responses consistent with resulting whole muscle adaptations. Yet, training blunts the more robust anabolic response shown after AE+RE compared with RE. This study challenges the concept that single molecular markers could predict training-induced changes in muscle size or strength.

Sparing of the Dystrophin-Deficient Cranial Sartorius Muscle Is Associated with Classical and Novel Hypertrophy Pathways in GRMD Dogs

Both Duchenne and golden retriever muscular dystrophy (GRMD) are caused by dystrophin deficiency. The Duchenne muscular dystrophy sartorius muscle and orthologous GRMD cranial sartorius (CS) are relatively spared/hypertrophied. We completed hierarchical clustering studies to define molecular mechanisms contributing to this differential involvement and their role in the GRMD phenotype. GRMD dogs with larger CS muscles had more severe deficits, suggesting that selective hypertrophy could be detrimental. Serial biopsies from the hypertrophied CS and other atrophied muscles were studied in a subset of these dogs. Myostatin showed an age-dependent decrease and an inverse correlation with the degree of GRMD CS hypertrophy. Regulators of myostatin at the protein (AKT1) and miRNA (miR-539 and miR-208b targeting myostatin mRNA) levels were altered in GRMD CS, consistent with down-regulation of myostatin signaling, CS hypertrophy, and functional rescue of this muscle. mRNA and proteomic profiling was used to identify additional candidate genes associated with CS hypertrophy. The top-ranked network included α-dystroglycan and like-acetylglucosaminyltransferase. Proteomics demonstrated increases in myotrophin and spectrin that could promote hypertrophy and cytoskeletal stability, respectively. Our results suggest that multiple pathways, including decreased myostatin and up-regulated miRNAs, α-dystroglycan/like-acetylglucosaminyltransferase, spectrin, and myotrophin, contribute to hypertrophy and functional sparing of the CS. These data also underscore the muscle-specific responses to dystrophin deficiency and the potential deleterious effects of differential muscle involvement.

The cAMP Response Element Binding protein (CREB) is activated by Insulin-like Growth Factor-1 (IGF-1) and regulates myostatin gene expression in skeletal myoblast

Myostatin, a member of the Transforming Growth Factor beta (TGF-β) superfamily, plays an important role as a negative regulator of skeletal muscle growth and differentiation. We have previously reported that IGF-1 induces a transient myostatin mRNA expression, through the activation of the Nuclear Factor of Activated T cells (NFAT) in an IP3/calcium-dependent manner. Here we examined the activation of CREB transcription factor as downstream targets of IGF-1 during myoblast differentiation and its role as a regulator of myostatin gene expression.In cultured skeletal myoblast, IGF-1 induced the phosphorylation and transcriptional activation of CREB via IGF-1 Receptor/Phosphatidylinositol 3-Kinase (PI3K)/Phospholipase C gamma (PLC γ), signaling pathways. Also, IGF-1 induced calcium-dependent molecules such as Calmodulin Kinase II (CaMK II), Extracellular signal-regulated Kinases (ERK), Protein Kinase C (PKC). Additionally, we examined myostatin mRNA levels and myostatin promoter activity in differentiated myoblasts stimulated with IGF-1. We found a significant increase in mRNA contents of myostatin and its reporter activity after treatment with IGF-1. The expression of myostatin in differentiated myoblast was downregulated by the transfection of siRNA–CREB and by pharmacological inhibitors of the signaling pathways involved in CREB activation. By using pharmacological and genetic approaches together these data demonstrate that IGF-1 regulates the myostatin gene expression via CREB transcription factor during muscle cell differentiation.

Immobility and diminished skeletal muscle recovery with age: the sedentary myoblast.

Immobility and diminished skeletal muscle recovery with age: the sedentary myoblast.

Early changes of muscle insulin‐like growth factor‐1 and myostatin gene expression in gastric cancer patients

Cachexia increases morbidity and mortality of cancer patients. The progressive loss of muscle mass negatively affects physical function and quality of life. We previously showed reduced muscle insulin-like growth factor-1 (IGF-1) expression and enhanced myostatin signaling in tumor-bearing animals. This study was aimed at investigating whether similar perturbations occur in gastric cancer patients. Early perturbations of myostatin and IGF-1 signaling (including the expression of muscle-specific ubiquitin ligases) were investigated in 16 gastric cancer patients and in 6 controls by analyzing muscle mRNA expression with semiquantitative reverse transcriptase polymerase chain reaction (PCR) and real-time PCR. In gastric cancer patients, muscle mRNA levels for IGF-1, myostatin, and atrogin-1 were reduced irrespective of weight loss (≤5% or >5%), whereas MuRF1 expression was unchanged. IGF-1 and myostatin mRNA levels are downregulated in gastric cancer patients who have minimal or no weight loss. These early alterations are particularly relevant in order to devise preventive and therapeutic strategies for cancer cachexia.

Effect of tibiotarsal joint inflammation on gene expression and cross-sectional area in rat soleus muscle

Joint inflammation is a common clinical problem in patients treated by physical therapists. The hypothesis of this study is that joint inflammation induces molecular and structural changes in the soleus muscle, which is composed mainly of slow-twitch muscle fibers. To study the effect of tibiotarsal joint inflammation on muscle fiber cross-sectional area (CSA), gene expression levels (atrogin-1, MuRF1, MyoD, myostatin, p38MAPK, NFκB, TNF-alpha), and TNF-alpha protein in the soleus muscle. Wistar rats were randomly divided into 3 periods (2, 7 and 15 days) and assigned to 4 groups (control, sham, inflammation, and immobilization). In the inflammation group at 2 days, MuRF1 and p38MAPK expression had increased, and NFκB mRNA levels had decreased. At 7 days, myostatin expression had decreased. At 7 and 15 days, this group had muscle fiber CSA reduction. At 2 days, the immobilization group showed increased atrogin-1, MuRF1, NFκB, MyoD, and p38MAPK expressions and reduced muscle fiber CSA. At 7 and 15 days, myostatin mRNA levels had increased, and the CSA had decreased. The sham group showed increased p38MAPK and myostatin expressions at 2 and 7 days, respectively. No changes occurred in TNF-alpha gene or protein expression. Acute joint inflammation induces gene expression related to the proteolytic pathway without reduction in muscle fiber CSA. Chronic joint inflammation induced muscle atrophy without up-regulation of important genes belonging to the proteolytic pathway. Thus, muscle adaptation may differ according to the stage of joint inflammation, which suggests that the therapeutic modalities used by physical therapists at each stage should also be different.