Leucine supplementation affects mTORC1 signaling following moderate endurance exercise

Abstract

Effects of leucine‐enriched amino acid supplementation during moderate intensity endurance exercise on translational control of skeletal muscle protein synthesis are not well documented. This study examined how essential amino acid (EAA) supplementation, of varying leucine content, affected components of the mTORC1 signaling pathway following exercise (60 min, 60% VO2peak). Ten adults (23 ± 2 yr) completed two separate bouts of cycle ergometry. Isonitrogenous (10 g EAA) drinks of varying leucine content (L‐EAA; 34% leucine, vs. EAA, 18% leucine) were consumed during exercise. Phosphorylation of mTORC1 signaling proteins was quantified by multiplex analysis of muscle samples obtained at baseline, 30 min and 210 min post‐exercise. Phosphorylation of mTOR and GSKa at 210 min post‐exercise was 113% and 54% greater (P < 0.05), respectively for L‐EAA compared to EAA. Regardless of the drink consumed, IRS1, Akt, and TSC2 phosphorylation was greater (P < 0.05) 30 min versus 210 min post‐exercise. Similarly, p70S6K and rpS6 phosphorylation was greater (P < 0.05) post‐exercise relative to baseline but not different between drinks. The phosphorylation of mTOR coupled with changes in key translational regulators of muscle protein synthesis suggests that L‐EAA supplementation may enhance skeletal muscle protein synthesis following moderate endurance exercise.