PURPOSE: Investigate the effects of an experimental peptide supplement in conjunction with an acute bout of lower body resistance exercise on serum insulin and insulin like growth factor 1 (IGF-1) and skeletal muscle insulin receptor substrate 1 (IRS-1), AKT, p70S6Kinase (p70S6K) and eIF4E-binding protein 1 (eIF4E-BP1) signaling pathways in recreationally active males.
METHODS: In a randomized, double-blind, cross-over design, 10 males (21 ± 2.18 yr, 78.04 ± 11.77 kg) ingested 1 week apart, either a placebo (10 grams of matodextrose) and/or the Peptide (10 grams of protein), 30 minutes prior to a lower body resistance exercise bout. Both supplements were isocaloric and independently prepared in individually blinded packages (Glanbia Nutritionals, Twin Falls, ID, USA). The resistance exercise bout consisted of 4 sets of 8-10 reps on both the angled leg press and knee extension at 80% of participant 1 RM. Rest periods of 2.5 minutes were given between both sets and exercises. Blood samples were obtained prior to, and 30 minutes following supplement ingestion and 15 and 120 minutes post exercise. Muscle biopsies from the vastus lateralis were obtained prior to supplementation, and 15 and 120 minutes post exercise. Data was analyzed using multivariate analysis of variance (MANOVA).
RESULTS: A significant main effect for time was observed for serum insulin (Baseline: 13.4±6.6 vs. 30 min post supplement ingestion: 48.4±26.4 ulU/ml, p<0.01), with no group or group by time interactions. No time, group or group by time effects were observed for serum IGF concentration. A significant main effect for time was observed for phosphorylated concentrations of IRS-1 (Baseline: 17.4±7.8 vs. 15 min post exercise: 25.6±12.6 U/ml/mg, p<0.01), AKT (Baseline: 5.9±1.5 vs. 120 min post exercise: 4.6±1.7 U/ml/mg, p<0.05), eIF4E-BP1 (Baseline: 4.8±1.9 vs. 15 min post exercise: 2.5±1.1 U/ml/mg, p=0.005). However, no significant group or group x time interaction was observed for all skeletal muscle phosphorylated variables.
CONCLUSIONS: The experimental peptide supplement had no significant effect on systemic and cellular mechanisms involved in skeletal muscle hypertrophy following an acute bout of lower body resistance exercise in untrained individuals. This study was sponsored by Glanbia Nutritionals, Twin Falls, ID, USA.