Myostatin, a potent negative regulator of skeletal muscle growth, play important role in the regulation of muscle mass. However, the mechanisms by which muscle myostatin production is regulated have not been fully understood. The purpose of this study was to determine the effect of eight weeks resistance training on changes of serum myostatin, cortisol and testosterone levels, muscle strength and lean body mass in untrained young men. Sixteen young men (age: 22.5±2.9 yr) were assigned to resistance training (n=8) or control (n=8) groups. The training protocol consisted of thrice weekly using three sets of eight to ten repetition at 60-70% of 1RM for whole-body exercise, whereas control group performed no resistance training. Blood sampling, muscular strength test and body composition analysis (DEXA), were performed at 0, 4th and 8th weeks. One-way ANOVA with repeated measurement and bivariate correlation showed that resistance training caused significant increase in muscular strength, lean body mass and testosterone, whereas cortisol and myostatin were decreased (P<0.05), and there were also negative and positive correlations (r=-0.69, P<0.05) between changes of serum myostatin with testosterone and myostatin with cortisol after resistance training, respectively. These data demonstrate that serum myostatin levels are reduced in response to resistance training, and resistance training-iduced alterations in myostatin, testosterone and cortisol levels may have a role in increases muscle strength and mass.

Genome scan to map quantitative trait loci (QTL) is one of the efficient strategies for molecular dissection of complex traits. QTL mapping is the first step toward the detection of genes responsible for quantitative traits variation. The objective of the present research was to identify QTL influencing carcass weight in cattle. Six Limousin x Jersey crossbred sires were mated to both Jersey and Limousin dams producing 782 backcross progeny. Six sires and all the progeny were genotyped for 189 microsattelite markers. Carcass weight (CWT) was pre-adjusted to account for known fixed effects including, slaughter group, sex, year, herd, dam breed, birth type and age of dam. Residuals were stored after standardization by dividing by the phenotypic standard deviation (sp), Linkage with standardized CWT was tested, using interval-mapping regression procedure. Three genome-wide significant QTL located on BT A3, 5 and 14 and two chromosome-wide significant QTL resided on BTA 10 and 17 were identified for CWT. QTL located on BT A 14 was segregating in all the six families. The QTL effects raged from 0.4 to 0.8 in units of phenotypic standard deviation, thus the experiment had only a power to detect medium to large QTL.

The purpose of this study was to determine the effect of eight weeks resistance training on muscle strength, lean body mass, serum myostatin, GASP-1, IGF-I and IGFBP-3 in untrained young men. Sixteen young men (19-26 years) were assigned to resistance training (n=8) or control (n=8) groups. The training protocol consisted of thrice weekly using three sets of eight to ten repetitions at 60-70% of 1RM for whole-body exercises, whereas control group performed no resistance training. Blood sampling, muscular strength test and body composition analysis (DEXA), were performed at 0, 4th and 8th weeks. Myostatin, GASP-1, and IGFBP-3 measured by enzyme immuno assay, wherease IGF-I was determined via immunoradiometric. Result showed that resistance training caused significant increases in muscular strength [between weeks 0 and 4 (P<0.05), and weeks 4 and 8 (P<0.05)], lean body mass [between weeks 0 and 8 (P<0.05)] and GASP-1 [between weeks 0 and 8 (P<0.05)], whereas myostatin were decreased [between weeks 0 and 4 (P<0.05), and weeks 4 and 8 (P<0.05)]. But significant change in serum levels of IGF-I and IGFBP-3 did not observe. The findings of this study suggest that 8 weeks resistance training does not alter serum levels of IGF-I and IGFBP-3, and decreasing myostatin production and inhabitation of its function by GASP-1 may play important role in increasing muscle strength and muscle mass which induced by resistance training.

Background: Muscle mass is known to be a significant predictor of bone mineral density (BMD), and myostatin is a negative regulator of muscle growth. The aim of present study was investigate the effects of resistance training on bone mineral density and serum myostatin in healthy young men.Methods and Materials: In this clinical trial thirty young men were assigned to resistance training (n=15) and control (n=15) groups. The training group participated in 6 mounths of progressive whole-body resistance training. Total body fat, lean body mass, total body BMD, femoral neck BMD and L2-L4 spine BMD were determined by Dual-Energy X-ray Absorptiometry (DEXA) before and after 6 mounths of resistance training. Serum level myostatin measured by enzyme immnoassay.Results: Resistance training caused significant increases in chest press (52.36±6.36 vs 62.20±8.96 kg), leg press (135.24±13.77 vs 146.91±17.66 kg), lean body mass (61.00±0.96 vs 62.58±2.08 kg) and femoral neck BMD (1.115±0.078 vs 1.131±0.088 g/cm2), whereas myostatin were decreased (102.91±10.18 vs 94.03±13.93 ng/ml) (P<0.05). Total body BMD and L2-L4 spine BMD did not change with 6 months resistance training.Conclusion: A 6 month resistance training program increases muscle mass, power and improves BMD of the femoral neck in young men, and myostatin inhibition may play an important role in increasing BMD which is induced by resistance training.

The aim of this study was to determine the effect of resistance training for 10 weeks on muscle strength, lean body mass, serum myostatin, and insulin resistance in obese-overweight men. Seventeen obsess-overweight men (age:=43.1±4.7 yr, body mass index=29.1±2.17 kg/m2) participated in the study The subjects were randomly assigned to resistance training (n=9) and control (n=8) groups. Resistance training was performed 3 times weekly for 10 weeks. Body composition, metabolic parameters, and myostatin were measured prior to and after the intervention. After a 10 week resistance training, insulin resistance index (HOMAIR) was significantly decreased (P<0.05), but without changes in adiposity parameter such as body weight, body mass index, fat percent and waist circumference (P>0.05). Also, following the resistance training, muscle strength and lean body mass were significantly increased (P<0.05). Concurrently, myostatin concentration were significantly decreased in response to resistance training (P<0.05). In conclusion, this study demonstrate that 10 weeks of resistance training caused an improvement in insulin resistance in obeseoverweight men, independent of changes in body fat, and this improvement was associated with decreased myostatin levels. These data suggest that resistance training–induced alterations in myostatin levels may have role in resistance training–induced insulin sensitivity improvement.

Myostatin (MSTN), also known as growth and differentiation factor-8 (GDF8), is a member of the transforming growth factor beta (TGF-b) superfamily that decreases growth in mammals. A single nucleotide polymorphism (SNP) in the myostatin (GDF8) 3'UTR of OAR2 has been known as responsible for muscular hypertrophy in foreign breeds. In this study, in order to identify single nucleotide polymorphisms (SNP) in the myostatin (GDF8) gene, blood samples were collected from a population set of Chaal (n=20), Zandi (n=24) and Zel sheep (n=17) lambs. Genomic DNA was extracted from the whole blood samples and polymerase chain reaction (PCR) was carried out in order to amplify a 1003 bp fragment of the target gene and PCR products sequenced to detect single nucleotide polymorphism (SNP). Comparison of the sequence of the target gene in Gene Bank with our results of sequencing showed all animals had the g.+6223G allele in the 3'UTR of myostatin which do not cause double muscle (DM) phenotype.