Branched-chain amino acids administration suppresses endurance exercise-related activation of ubiquitin proteasome signaling in trained human skeletal muscle

We tested whether post exercise ingestion of branched-chain amino acids (BCAA < 10 g) is sufficient to activate signaling associated with muscle protein synthesis and suppress exercise-induced activation of mechanisms associated with proteolysis in endurance-trained human skeletal muscle. Nine endurance-trained athletes performed a cycling bout with and without BCAA ingestion (0.1 g/kg). Post exercise ACC(Ser79/222) phosphorylation (endogenous marker of AMPK activity) was increased (similar to 3-fold, P < 0.05) in both sessions. No changes were observed in IGF1 mRNA isoform expression or phosphorylation of the key anabolic markers - p70S6K1(Thr389) and eEF2(Thr56) - between the sessions. BCAA administration suppressed exercise-induced expression of mTORC1 inhibitor DDIT4 mRNA, eliminated activation of the ubiquitin proteasome system, detected in the control session as decreased FOXO1(Ser256) phosphorylation (0.83-fold change, P < 0.05) and increased TRIM63 (MURF1) expression (2.4-fold, P < 0.05). Therefore, in endurance-trained human skeletal muscle, post exercise BCAA ingestion partially suppresses exercise-induced expression of PGC-1a mRNA, activation of ubiquitin proteasome signaling, and suppresses DDIT4 mRNA expression.