Exercise Enhances The Overnight Muscle Protein Synthetic Response To Pre-sleep Protein Feeding In Older Males

Abstract

PURPOSE: The age-related decline in skeletal muscle mass is, at least partly, attributed to anabolic resistance to food intake. To compensate for anabolic resistance, we recently introduced the ingestion of dietary protein prior to sleep as a nutritional strategy to increase overnight muscle protein synthesis rates. Here we aimed to assess whether resistance-type exercise performed in the evening can further augment the overnight muscle protein synthetic response to pre-sleep protein ingestion in older males. METHODS: In a parallel group design, twenty-three healthy older men (71±1 y) were randomly assigned to ingest 40 g casein protein before going to sleep with (PRO+EX: n=11) or without (PRO: n=12) performing resistance-type exercise earlier that evening. Overnight protein digestion and absorption kinetics, whole body protein metabolism and muscle myofibrillar protein synthesis rates were assessed using primed, continuous infusions of L-[ring-2H5]-phenylalanine and L-[ring-2H2]-tyrosine with the ingestion of intrinsically L-[1-13C]-phenylalanine labeled casein protein. RESULTS: Exogenous phenylalanine appearance rates expressed over time did not differ between treatments. A total of 53±2 vs 55±2% of the ingested protein-derived phenylalanine appeared in the circulation during overnight sleep in the PRO+EX and PRO treatment, respectively (P=0.49). Myofibrillar protein synthesis rates were 31% higher during overnight sleep when exercise was performed earlier that day (0.058±0.002 vs 0.044±0.003 %·h-1 in PRO+EX and PRO, respectively; P<0.01; L-[ring-2H5]-phenylalanine). In line, 27% more L-[1-13C]-phenylalanine was incorporated into myofibrillar protein in PRO+EX compared with PRO (0.042±0.002 vs 0.033±0.002 MPE, respectively; P<0.05; L-[1-13C]-phenylalanine). CONCLUSIONS: Resistance-type exercise augments the overnight muscle protein synthetic response to pre-sleep protein ingestion and allows more of the ingested protein to be directed towards de novo muscle protein synthesis during overnight sleep in older males. Funding: Top Institute Food and Nutrition (TIFN)