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Effect of Soy‐Dairy Protein Blend Ingestion on Post‐Exercise Muscle mTORC1 Signaling and Protein Synthesis in Older Adults
Author(s) -
Borack Michael,
Reidy Paul,
Husaini Syed,
Markofski Melissa,
Deer Rachel,
Richison Abigail,
Lambert Bradley,
Cope Mark,
Mukherjea Ratna,
Jennings Kristofer,
Volpi Elena,
Rasmussen Blake
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.678.5
Subject(s) - mtorc1 , anabolism , soy protein , medicine , endocrinology , p70 s6 kinase 1 , leucine , whey protein , ingestion , chemistry , casein , valine , food science , amino acid , biology , biochemistry , pi3k/akt/mtor pathway , signal transduction
Purpose Our previous work demonstrated that a soy‐dairy protein blend can prolong aminoacidemia and muscle protein synthesis in young adults following high intensity resistance exercise. The current work investigated the effect of the same soy‐dairy protein blend in older individuals who commonly develop anabolic resistance and sarcopenia. We hypothesized that a soy‐dairy protein blend (whey, soy and casein) would prolong aminoacidemia resulting in enhanced mTORC1 signaling and muscle protein anabolism as compared to a whey protein isolate (WPI) alone. Methods The study population for this double‐blind randomized controlled trial included recreationally active men 55–75 years of age. The subjects consumed 30g of WPI or 30g of a soy‐dairy protein blend (25% soy, 25% whey, and 50% casein) one hour following leg extension exercise (8 sets of 10 repetitions at 70% 1RM). Amino acid concentrations as well as basal and post‐exercise muscle protein turnover (breakdown and synthesis) were measured using stable isotopic methods. In addition, skeletal muscle mTORC1 signaling was assessed via western blotting. Results There were no differences between the two protein groups for aminoacidemia, mTORC1 signaling or muscle protein turnover following resistance exercise and supplementation. Both groups showed similar blood branched‐chain amino acid profiles following protein ingestion (i.e., leucine, isoleucine, and valine remained elevated (p<0.001) for 240 min) and blood phenylalanine was increased for 185 min in both groups (p<0.001) post‐ingestion. Activation of the mTORC1 pathway (i.e., increased phosphorylation of mTOR, S6K1, and rpS6) was increased to a similar extent in both groups post‐exercise at early (0–2 hrs post‐supplement) and late (2–4 hrs post‐supplement) periods (p<0.05). FBR was significantly reduced post‐exercise for the WPI group (p=0.002) and tended to be reduced in the soy‐dairy protein blend group (P=0.077); however, no difference in post‐exercise FBR was observed between the two groups when controlling for resting FBR and age (p=0.31). Post‐exercise FSR was significantly elevated early for the WPI group (p=0.032), however, post‐exercise FSR did not differ between groups after controlling for resting FSR and age (p=0.38). Conclusion Soy‐dairy protein blend induced an increase in aminoacidemia, muscle protein synthesis and mTORC1 signaling to a similar extent as whey protein in older adults when 30 g of protein was ingested after exercise. This data adds new evidence for the use of soy‐dairy protein blends as targeted nutritional interventions that may help overcome anabolic resistance in an effort to counteract sarcopenia. Support or Funding Information Grant support provided by DuPont Nutrition & Health