The effects of essential and non-essential amino acids on post-exercise anabolic signaling and transcriptional regulators of the intramuscular extracellular matrix in young males : a randomized controlled trial

Skeletal muscle is composed of myofibers surrounded by an extracellular matrix (ECM) primarily containing collagen. Essential amino acid (EAA) consumption is known to increase post-exercise myofiber anabolism, but it is unknown if post-exercise ECM remodeling is nutrient-sensitive. Seventeen males (21.1±3.3 years) completed combined plyometric and resistance exercise and received biopsies of the vastus lateralis collected before, 2 and 4 hours post-exercise to assess the mechanistic target of rapamycin (mTOR) pathway activation and transcriptional regulators of ECM turnover. Blood was also drawn from an antecubital vein to measure plasma amino acid concentrations prior to and following supplement consumption and resistance exercise. Immediately after exercise, participants consumed 15g of either a carbohydrate placebo, EAA, or a vitamin C enriched collagen peptide (enriched in non-essential amino acids) supplement; each participant completed two of the three randomized conditions. EAA supplementation increased plasma amino acid concentrations of EAAs and leucine (p ≤ 0.001), whereas collagen peptide supplementation increased concentrations of non-essential amino acids (NEAA), glycine, proline, and hydroxyproline (p ≤ 0.018), there was no effect of carbohydrate consumption on plasma amino acid concentrations. rpS6Ser235/236 and rpS6Ser240/244 phosphorylation following EAA supplementation resulted in a larger and more prolonged anabolic signaling response, at 2 and 4 hours post-exercise, respectively, compared to the collagen peptide and placebo conditions (p ≤ 0.036). Anabolic signaling increased in the collagen peptide and placebo conditions similarly post-exercise. There was no effect of exercise or nutrition on mRNA expression of ECM regulators; however, a main effect of time for connected tissue growth factor (CTGF) demonstrated an increased expression from 0 to 2 hours (p = 0.014). These findings suggest that mTOR pathway activation is upregulated post-exercise and further increased with EAA supplementation, while the acute transcriptional ECM regulators are independent of exercise and plasma amino acid availability in the hours following exercise. Further analysis will directly measure the effects of post-exercise nutrition on myofibrillar and skeletal muscle ECM protein synthesis.Education, Faculty ofKinesiology, School ofGraduat