Effect of Acute Exercise on Skeletal Muscle Exosome Biogenesis

Abstract

Exercise training promotes a wide range of beneficial adaptations. Skeletal muscle is now considered an endocrine organ. Exosomes, small microvesicles, are produced by and participate in the endocrine function of skeletal muscle. Exosome biogenesis is regulated in part by components of the multivesicular body (MVB) processing pathway: hepatocyte growth factor-regulated tyrosine kinase substrate (HGS), signal transducing adapter molecule 1 (STAM), VTA1 homolog (VTA1), and vacuolar protein sorting-associated protein 4A (VPS4a). PURPOSE: Determine if exercise induces skeletal muscle exosome biogenesis. METHODS: Twelve lean, young men completed acute aerobic cycling at 55% VO2Max for 45 minutes followed immediately by single leg knee extensor resistance exercise (3 sets, 8-12 reps, 55% 1-RM). Vastus lateralis biopsies were obtained prior to (PRE) and 1-hour post aerobic (AEX) and aerobic+resistance (A+REX) exercise. Gene expression for proteins in the MVB pathway was analyzed using rt- PCR. RESULTS: There was no effect of exercise on STAM (PRE: 1.0; AEX: 1.03; A+REX: 1.28, AU), VTA1 (PRE: 1.0; AEX: 0.93; A+REX: 1.14, AU), or VPS4a (PRE: 1.0; AEX: 0.93; A+REX: 1.06, AU) . There was a trend for an increase in HGS at 1 hr post-exercise (PRE: 1.0; AEX: 0.97; A+REX: 1.27, AU). CONCLUSIONS: There was no effect of acute exercise on the gene expression of components of the exosome biogenesis pathway. However, activation of exosome biogenesis may be evident at different time points post exercise or with greater exercise intensities.