Nutritional energy in the regulation of human muscle mTOR signaling following resistance exercise

Resistance exercise (Ex) stimulates the mammalian target of rapamycin (mTOR) signaling pathway. The ingestion of leucine‐enriched essential amino acids and carbohydrate (EAA+CHO) 1 hr following Ex further stimulates mTOR signaling. The purpose of this study was to determine whether the addition of nutritional energy to a EAA+CHO stimulus following Ex enhances mTOR signaling. Sixteen male subjects were randomized to two groups containing an equivalent amount of EAA (∼20g) but different amounts of CHO. Both groups ingested the nutrient solution 1 hr after a bout of Ex. mTOR signaling was assessed by immunoblotting from muscle biopsy samples at baseline, immediately following, and 1 and 2 hr post‐Ex. There were no differences between groups for any proteins measured prior to nutrient ingestion. At 2 hr post‐Ex (following nutrient ingestion) the phosphorylation status of mTOR and its downstream effectors S6K1 and 4E‐BP1 increased with no differences between groups (P>0.05). However, Akt/PKB phosphorylation was higher in the extra energy group, likely due to increased blood insulin concentration (P<0.05). We conclude that mTOR signaling is not further enhanced, despite increased Akt activation, by the availability of additional energy (carbohydrates) following Ex as compared to a stimulus containing the same amount of EAA and approximately half the caloric energy. Funded by NIH Grant # 5R01AR049877