ABSTRACT: Protein-leucine supplement ingestion following strenuous endurance exercise accentuates skeletal-muscle protein synthesis and adaptive molecular responses, but the underlying transcriptome is uncharacterized. In a randomized single-blind triple-crossover design, 12 trained men completed 100 min of high-intensity cycling then ingested either 70/15/180/30g protein/leucine/carbohydrate/fat (15LEU), 23/5/180/30g (5LEU) or 0/0/274/30g (CON) beverages during the first 90 min of a 240-min recovery period. Vastus lateralis muscle samples (30 and 240-min post-exercise) underwent transcriptome analysis by microarray followed by bioinformatic analysis. Gene expression was regulated by Protein-leucine in a dose-dependent manner impacting the inflammatory response, muscle growth and development. At 30 min, 15LEU and 5LEU vs. CON activated transcriptome networks with geneset functions involving cell-cycle arrest (Z-score 2.0-2.7; P<0.01), leukocyte maturation (1.7; P=0.007), cell viability (2.4; P=0.005), promyogenic networks encompassing myocyte differentiation and myogenin (MYOD1, MYOG), and a proteinaceous extracellular matrix, adhesion, and development programme correlated with plasma lysine, arginine, tyrosine, taurine, glutamic acid, and asparagine concentrations. High protein-leucine dose (15LEU-5LEU) activated an IL1b-centered proinflammatory network and leukocyte migration, differentiation, and survival functions (2.0-2.6; <0.001). By 240 min, the protein-leucine transcriptome was anti-inflammatory and promyogenic (IL-6, NF-kβ, SMAD, STAT3 network inhibition), with overrepresented functions including decreased leukocyte migration and connective tissue development (-1.8-2.4; P<0.01), increased apoptosis of myeloid and muscle cells (2.2-3.0; P<0.002) and cell metabolism (2.0-2.4; P<0.01). The analysis suggests protein-leucine ingestion modulates inflammatory-myogenic regenerative processes during skeletal muscle recovery from endurance exercise. Further cellular and translational research is warranted to validate amino acid-mediated myeloid and myocellular mechanisms within skeletal-muscle functional plasticity.
