Providing nutrients after endurance exercise stimulates mTOR-dependent protein translation signaling pathways in rats

To examine the role of both endurance exercise and nutrient supplementation on the activation of protein translation signaling pathways post-exercise, rats were subjected to a three-hour swimming protocol. Immediately following exercise, the rats were provided with a solution containing either carbohydrates (CHO), protein (PRO), carbohydrates and protein (CP), or a placebo (EX). The rats were then sacrificed at 0, 30, and 90 minutes post-exercise, and phosphorylation states of mammalian target of rapamycin (mTOR), ribosomal S6 kinase (p70S6K), ribosomal protein S6 (RPS6), and 4E-binding protein 1 (4E-BP1), were analyzed by immunoblot analysis in the red (RQ) and white (WQ) quadricep muscle. Results demonstrated that rat groups provided with any of the three nutritional supplements (CHO, PRO, CP) transiently increased the phosphorylation states of mTOR, 4E-BP1, RPS6, and p70S6K compared to EX rats. Among the CHO, PRO, and CP supplements, only CP showed a consistently elevated activation of mTOR pathway enzymes in both RQ and WQ tissue. Furthermore, the stimulation of the mTOR pathway observed in the CP groups was correlated to an increased insulin concentration above the EX group. This study is the first to compare both the interaction of endurance exercise and of supplementation on the mTOR-dependent signaling pathway in the postprandial state. These results suggest that CP supplementation may be most effective in activating protein synthesis post exercise.