We have recently demonstrated that whole egg ingestion induces a greater muscle protein synthetic (MPS) response when compared with isonitrogenous egg white ingestion after resistance exercise in young men. Our aim was to determine whether whole egg or egg white ingestion differentially influenced colocalization of key regulators of mechanistic target of rapamycin complex 1 (mTORC1) as means to explain our previously observed divergent postexercise MPS response. In crossover trials, 10 healthy resistance-trained men (21 ± 1 yr; 88 ± 3 kg; body fat: 16 ± 1%; means ± SE) completed lower body resistance exercise before ingesting whole eggs (18 g protein, 17 g fat) or egg whites (18 g protein, 0 g fat). Muscle biopsies were obtained before exercise and at 120 and 300 min after egg ingestion to assess, by immunofluorescence, protein colocalization of key anabolic signaling molecules. After resistance exercise, tuberous sclerosis 2-Ras homolog enriched in brain (Rheb) colocalization decreased ( P < 0.01) at 120 and 300 min after whole egg and egg white ingestion with concomitant increases ( P < 0.01) in mTOR-Rheb colocalization. After resistance exercise, mTOR-lysosome-associated membrane protein 2 (LAMP2) colocalization significantly increased at 120 and 300 min only after whole egg ingestion ( P < 0.01), and mTOR-LAMP2 colocalization correlated with rates of MPS at rest and after exercise ( r = 0.40, P < 0.05). We demonstrated that the greater postexercise MPS response with whole egg ingestion is related in part to an enhanced recruitment of mTORC1-Rheb complexes to the lysosome during recovery. These data suggest nonprotein dietary factors influence the postexercise regulation of mRNA translation in human skeletal muscle.
Keywords: Rheb; TSC2; anabolic signaling; immunofluorescence; muscle protein synthesis.