Resistance exercise decreases eIF2B[epsilon] phosphorylation and potentiates the feeding-induced stimulation of [p70.sup.S6K1] and rpS6 in young men

We investigated the effect of resistance exercise and feeding on the activation of signaling proteins involved in translation initiation. Nine young men (23.7 [+ or -] 0.41 yr; BMI = 25.5 [+ or -] 1.0 kg/[m.sup.2]; means [+ or -] SE) were tested twice after they performed a strenuous bout of unilateral resistance exercise, such that their contralateral leg acted as a nonexercised comparator, in either the fasted and fed [1,000 kJ, each 90 min (3 doses): 10 g protein, 41 g carbohydrate, 4 g fat] states. Muscle biopsies were obtained 6 h postexercise from both legs, resulting in four experimental conditions: rest-fasted, rest-fed, exercise-fasted, and exercise-fed. Feeding increased PKB/Akt (Ser473) phosphorylation (P < 0.05), while exercise increased the phosphorylation of Akt and the downstream 70 kDa $6 protein kinase ([p70.sup.S6K1], Thr389) and ribosomal protein $6 (rpS6, Ser235/236, Ser240/244; all P < 0.05). The combination of resistance exercise and feeding increased the phosphorylation of [p70.sup.S6Kl] (Thr389) and rpS6 (Ser240/244) above exercise alone (P < 0.05). Exercise also reduced phosphorylation of the catalytic epsilon subunit of eukaryotic initiation factor 2B (elF2B[epsilon], Ser540; P < 0.05). Mammalian target of rapamycin (mTOR, Ser2448), glycogen synthase kinase-3[beta] (GSK-3[beta], Ser9), and focal adhesion kinase (FAK, [Tyr.sup.576/577]) phosphorylation were unaffected by either feeding or resistance exercise (all P > 0.14). In summary, feeding resulted in phosphorylation of Akt, while resistance exercise stimulated phosphorylation of Akt, [p70.sup.S6K1], rpS6, and dephosphorylation elF2B[epsilon] with a synergistic effect of feeding and exercise on [p70.sup.S6K1] and its downstream target rpS6. We conclude that resistance exercise potentiates the effect of feeding on the phosphorylation and presumably activation of critical proteins involved in the regulation of muscle protein synthesis in young men. hypertrophy; lean body mass; protein accretion; weightlifting