Mysotatin Gene Expression In Response To Acute Resistance Exercise With Amino Acids And Carbohydrate Supplementation

Abstract

PURPOSE: To determine if co-ingestion of carbohydrate (CHO) with branched-chain amino acids (BCAA) or leucine (Leu) downregulates the myostatin expression and upregulates the makers of myogenesis to an extent greater than that which resistance exercise elicits alone. METHODS: 41 males (20.4 yrs; 81.4kg) were randomly assigned to 1 of 4 groups: Control (placebo, 450 ml Crystal Light®), CHO-BCAA (maltodextrin 1.5 g/kg/bw, BCAA 120mg/kg/bw), CHO-Leucine (maltodextrin 1.5 g/kg/bw, Leu 60mg/kg/bw) and CHO alone (maltodextrin 1.5 g/kg/bw). Subjects performed 4 sets of leg press and leg extension at 80% 1RM to failure. Supplementation was ingested at 3 time points: 30 minutes prior to exercise, and immediately pre- and post-exercise. Venous blood and muscle biopsies were sampled at baseline, 30min post, 2hr post, and 6hr post-exercise for myostatin, ActRIIB, myoD, myf-5, myogenin and MRF-4 mRNA expression (expressed as CT ratio). Serum and muscle variables were analyzed via a 4 (group) × 4 (time points) repeated measures MANOVA, followed by univariate ANOVAs. RESULTS: Compared with control, CHO-BCAA (112.0±22.4 vs. 94.7±10.7 mg/dL, p<0.05), CHO-Leu (122.4±19.1 vs. 94.7±10.7mg/dL, p<0.05) and CHO (128.0±23.0 vs. 94.7±10.7 mg/dL, p<0.05) alone significantly increased blood glucose levels at 30min post RE. Serum insulin was significantly elevated at 30min post in CHO-BCAA (144.1±67.1 vs. 24.1±8.7 uIU/mL, p<0.05), CHO-Leu (156.8±60.8 vs. 24.1±8.7 uIU/mL, p<0.05) and CHO (124.9±38.6 vs. 24.1±8.7 uIU/mL, p<0.05) alone, compared with control. A univariate group × time interaction relative to myogenin mRNA expression indicated that the CHO-Leu group was significantly upregulated at the 6hr post time point in comparison with the Placebo group (0.96±0.1 vs. 0.90±0.02, p <.05). No group × time interactions were observed for the myostain signaling molecules and other myogenic regulatory factors. CONCLUSIONS: CHO-Leu supplementation upregulated the myogenin mRNA expression in conjunction with resistance exercise at 6hr post-exercise. Co-ingestion of BCAA or Leu had no effect on the inhibition of myostatin signaling at pre- and post-translational level.