Resistance Exercise and Low Dose Protein Ingestion Augments Anabolic Signaling Mechanisms In Older Women

Abstract

Resistance exercise enhances skeletal muscle anabolic signaling responses to the ingestion of sub-optimal amounts of protein in young men. However, the effectiveness of resistance exercise to potentiate the phosphorylation of the mechanistic target of rapamycin (mTORC1) to the ingestion of minimal amount of protein in aging women has not been well characterized. PURPOSE: We compared the phosphorylated-state ofmTORC1 before and after ingestion of ~14 g whey protein or water at rest and after resistance exercise in middle-aged and older women. METHODS: 10 women (59±2 y; BMI: 25±1 kg/m2; LBM: 46±2 kg) performed a bout of unilateral leg extension exercise (3 sets × 12 repetitions at 60% estimated 1RM) prior to ingesting whey protein (0.3g/kg LBM; WHEY, n=5) or water (WATER n=5). Blood and skeletal muscle biopsies were used to measure plasma amino acids and insulin concentrations and phosphorylation of mTORC1 at Ser2448 at 2 and 4 h of the postprandial phase in both exercise (EX) and non-exercised (CON) legs. RESULTS: Plasma branched chain amino acid concentrations were increased from basal (2.5-fold) in WHEY (P<0.05), but not in WATER condition (P>0.05). Plasma insulin concentrations increased after WHEY (2.3±0.8 fold change from basal, P=0.02), but not after WATER ingestion (1.0 ± 0.1 fold-change, P=0.45). WHEY ingestion increased mTORC1 phosphorylation at 2 h (3.4±0.6 and 1.7±0.3 fold-change in EX and CON, respectively P<0.05). There were no changes in mTORC1 phosphorylation after WATER ingestion at any time point (P>0.05). CONCLUSION: Our data demonstrated that consuming a minimal amount of protein immediately after resistance exercise resulted in a greater, but transient, phosphorylation of anabolic signaling mechanisms involved in protein translation over that induced by feeding or resistance exercise alone.