Peri-exercise co-ingestion of branched-chain amino acids and carbohydrate in men does not preferentially augment resistance exercise- induced increases in PI3K/Akt-mTOR pathway markers indicative of muscle protein synthesis

The effects of a single bout of resistance exercise (RE) in conjunction with peri-exercise branched chain amino acid (BCAA) and carbohydrate (CHO) ingestion on skeletal muscle signaling markers indicative of muscle protein synthesis (MPS) were determined. It was hypothesized that CHO + BCAA would elicit a more profound effect on these signaling markers compared to CHO. Twenty-seven males were randomly assigned to CHO, CHO + BCAA, or placebo (PLC) groups. Four sets of leg presses and leg extensions were performed at 80% 1RM. Supplements were ingested 30 min and immediately prior to and after RE. Venous blood and muscle biopsy samples were obtained immediately prior to supplement ingestion and 0.5 hr, 2 hr, and 6 hr after RE. Serum insulin and glucose and phosphorylated levels of muscle insulin receptor substrate 1 (IRS1), protein kinase B (Akt), mammalian target of rapamycin (mTOR), p70S6 kinase (p70S6K), and 4E binding protein 1 (4E-BP1) were assessed. Data were analyzed by two-way repeated measures ANOVA. Significant group x time interactions were observed for glucose and insulin (p < 0.05) showing that CHO and CHO + BCAA were significantly greater than PLC. Significant time main effects were observed for IRS1 (p = 0.001), Akt (p = 0.031), mTOR (p = 0.003), and p70S6K (p = 0.001). CHO and CHO + BCAA supplementation significantly increased IRS-1 compared to PLC (p = 0.002). However, peri-exercise co-ingestion of CHO and BCAA did not augment RE-induced increases in skeletal muscle signaling markers indicative of MPS when compared to CHO.