The effects of heavy resistance exercise in combination with orally administered branched-chain amino acids or leucine on insulin signaling and Akt/mTOR pathway activity in active males.

Purpose: To determine if activity of the insulin signaling pathway is increased during lower body resistance exercise due to supplemental BCAA or leucine ingestion. Methods: 30 recreationally trained males (22.5yrs; 81.1kg) were randomly assigned to 1 of 3 groups: Leucine (60mg/kg/bw), BCAA (120mg/kg/bw), or non-caloric placebo. Participants performed 4 sets of leg press and leg extension at 80% 1RM to failure (at least 8 reps). Supplements were ingested at 3 time points: 30 minutes prior to RE, and immediately pre- and post-RE. Venous blood was sampled at baseline (Pre); immediate pre- and post-exercise, 30 minutes post-exercise; 2hours post-exercise, and 6 hours post-exercise for serum glucose, insulin, GH, and IGF-1. Muscle biopsies were obtained at baseline, and 30 minutes post, and 2 and 6 hours post-exercise for IRS-1, Akt, mTOR, 4E-BP1, and P70-S6K. Skeletal muscle variables were transformed to delta values and analyzed using a 3 (group) x 4 (time points) repeated measures MANOVA. Univariate ANOVAs (Bonferroni adjusted) were utilized as follow-up tests to the MANOVA. Post-hoc tests of the interaction effects demonstrated in the ANOVA were analyzed using independent samples T-tests. Results: Neither BCAA or leucine significantly increased any of the 4 serum variables. A group x time interaction for IRS-1 phosphorylation demonstrated that the leucine group was significantly elevated at 2hr post and 6hr post when compared to the BCAA group (p < .05). A group x time interaction for 4E-BP1 phosphorylation demonstrated that the leucine and BCAA groups were both elevated at the 2hr post in comparison with the placebo (p < .05). BCAA was significantly greater than leucine at 6 hours (p < .05) as well. No interactions were observed for Akt, mTOR, or P70-S6K. Summary: The results indicate that BCAA and leucine supplementation with RE increased the phosphorylation status of 4E-BP1 at 2 hours post-exercise and the BCAA group increased the phosphorylation of 4E-BP1 greater than leucine (p < .05) at 6 hours post-exercise.