Mysotatin Gene Expression In Response To Acute Resistance Exercise With Amino Acids And Carbohydrate Supplementation
Rui Li1, Maria P. Ferreira2, Matthew B. Cooke1, Paul LaBounty1, Bill Campbell3, Mike Greenwood, FACSM4, Darryn S. Willoughby, FACSM4,
Richard B. Kreider, FACSM5. 1Northeastern University, Boston, MA. 2Haskell Indian Nations University/University of Kansas, Lawrence, KS.
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) x 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.
