Whey Hydrolysate Supplementation Following Resistance Exercise Elicits Similar Anabolic Responses in Both Young and Older Adults

Abstract

Skeletal muscle sensitivity to dietary protein and exercise typically declines during aging. However, previous data presented by our group indicates that whey protein hydrolysate (WH, di- and tri-peptide mixture) may be able to stimulate muscle anabolism at lower dosages than observed with intact whey protein in older adults. PURPOSE: To compare the effect of a minimal dose (10 g) of WH provided after resistance exercise (REx) on skeletal muscle anabolism in young and older adults. METHODS: Twenty healthy recreationally active adults (YOUNG: M=8, F=2; 25±4yr, 25±4 kg[BULLET OPERATOR]m2 | OLD: M=7, F=3; 65±4yr, 25±4 kg[BULLET OPERATOR]m2) were studied pre- and post-ingestion (PI) of 10 g of WH 1 h after high-intensity REx ([email protected]~70% 1RM, leg ext). We measured mixed-muscle protein fractional synthetic rate (FSR) and plasma BCAA concentrations by stable isotopic methods. Western-blotting was used to asses anabolic signaling and the presence of peptide transporters in muscle. Muscle biopsies from the vastus lateralis were collected at rest and during the early (0–2 h) and late (2–4 h) PI periods. Mixed muscle FSR and anabolic signaling was analyzed using a 2(group) x 3(time) mixed model ANOVA repeated across time. BCAA concentrations were modeled separately per time point using a 2 (group) x 2 (time) mixed-model ANOVA. Type I error for all analyses was set at α=0.05.Table: No title available.RESULTS: Compared with rest, increases in p-mTOR (Young: +2.0 fold, Old: +2.5 fold) and p-4E-BP1 (Young: +1.5 fold, Old: +1.4 fold) were observed in both groups at 4h PI (p<0.05). Increases in p-S6K1 were observed in both groups at 2h PI but to a greater extent in the OLD group (p <0.05). Peptide transporter-1 (PEPT1) expression was found in muscle samples from both groups. CONCLUSION: WH provided after Rex enhances muscle anabolism in older adults at a dose previously shown to be ineffective with intact whey isolate. Future studies will be required to determine if WH may aid in the long-term preservation of muscle in this population.