| Purpose. To determine if activity of the MAPK-ERK or PI3K-mTOR insulin signaling pathway is increased in response to an acute lower body resistance exercise (RE) bout and supplemental BCAA + CHO or CHO ingestion. Methods. 27 recreationally trained males (20.9 y; 81.8 kg) were randomly assigned to a group: BCAA (30g) + CHO (350g), CHO (350g), or placebo CON. Participants performed 4 sets of leg press and extensions at 80% 1RM to failure. Supplements were ingested at 3 time points: 30 min prior to RE, and immediately pre- and post-RE. Venous blood was sampled at baseline (Pre-); 30 min post-RE; 2 h post-RE, and 6 h post-RE for serum glucose and insulin. Blood variables were transformed to percent change values and analyzed by a 3 x 4 repeated measures MANOVA. Muscle biopsies were obtained at baseline, 30 min post-RE, 2 h post-RE, and 6 h post-RE for ERK1/2, IRS, Akt/PKB, GSK, mTOR, 4E-BPI, and p70S6K. Skeletal muscle variables were transformed to percent change values and analyzed by 3 x 4 repeated measures MANOVA. Univariate ANOVAs were utilized as follow-up tests to the MANOVA for select variables. Results. MANOVA results demonstrate a significant group x time interaction for insulin and glucose (p<.05). Despite a nearly 3-fold increase of insulin over fasting baseline measures in the CHO groups as compared to the placebo group, neither BCAA + CHO or CHO significantly increased any of the muscle variables. Univariate analysis demonstrated a significant group x time interaction for Akt/PKB phosphorylation (p=.039), suggesting a group effect. Several muscle variables demonstrated by MANOVA a significant time effect: IRS (p=.054); Akt/PKB (p=.011); ERK1/2 (p=.026); p70S6K (p=.038). A time trend for mTOR (p=.089) was noted. No significant effects were found for GSK and 4E-BP above baseline or among groups. Summary. Results indicate that RE, not BCAA + CHO or CHO, increased the phosphorylation status of IRS, Akt/PKB, p70S6K, and ERK above baseline levels (p<.05) with a group x time interaction trend for Akt/PKB and a time trend for mTOR activation. Phosphorylation of GSK and 4E-BP were not influenced by the RE and supplementation protocol. |
