Activation of signaling pathways regulating translation initiation in human skeletal muscle with feeding and resistance exercise

The regulation of the muscle mass is acutely controlled by the processes of muscle protein synthesis and breakdown. Feeding and resistance exercise stimulate muscle protein synthesis independently and synergistically. Our aim was to investigate the activation of important signaling proteins involved in the regulation of translation initiation in humans in four conditions: fasted, fed, rested and post‐resistance exercise. Seven males completed two heavy unilateral resistance leg exercise trials, with their contralateral leg acting as non‐exercised (rested) comparator, 1wk apart. One trial was in the fasted condition while the other was in the fed state – consumption of a mixed‐meal drink (1000kJ, 10g protein) q90min. Biopsies were taken from both legs 6h post‐exercise. Exercise increased Akt, P70s6k, and rps6 phosphorylation (P<0.05). Feeding increased phosphorylation of Focal adhesion kinase (FAK; P<0.05). Phosphorylation of GSK3β tended to increase with exercise and feeding (P=0.068). There was no significant change in mTOR phosphorylation status. Heavy resistance exercise increases the active phosphorylated forms of key members of the Akt pathway, while feeding appears to affect FAK activation. There was a tendency for feeding and exercise to increase GSK3β phosphorylation, which may reduce its inhibitory effect on translation initiation. Supported by NSERC.