title: Soy-Dairy Protein Blend or Whey Protein Isolate Ingestion Induces Similar Postexercise Muscle Mechanistic Target of Rapamycin Complex 1 Signaling and Protein Synthesis Responses in Older Men.
abstract: BACKGROUND
  Previous work demonstrated that a soy-dairy protein blend (PB) prolongs hyperaminoacidemia and muscle protein synthesis in young adults after resistance exercise.
  
  
  OBJECTIVE
  We investigated the effect of PB in older adults. We hypothesized that PB would prolong hyperaminoacidemia, enhancing mechanistic target of rapamycin complex 1 (mTORC1) signaling and muscle protein anabolism compared with a whey protein isolate (WPI).
  
  
  METHODS
  This double-blind, randomized controlled trial studied men 55-75 y of age. Subjects consumed 30 g protein from WPI or PB (25% soy, 25% whey, and 50% casein) 1 h after leg extension exercise (8 sets of 10 repetitions at 70% one-repetition maximum). Blood and muscle amino acid concentrations and basal and postexercise muscle protein turnover were measured by using stable isotopic methods. Muscle mTORC1 signaling was assessed by immunoblotting.
  
  
  RESULTS
  Both groups increased amino acid concentrations (P < 0.05) and mTORC1 signaling after protein ingestion (P < 0.05). Postexercise fractional synthesis rate (FSR; P ≥ 0.05), fractional breakdown rate (FBR; P ≥ 0.05), and net balance (P = 0.08) did not differ between groups. WPI increased FSR by 67% (mean ± SEM: rest: 0.05% ± 0.01%; postexercise: 0.09% ± 0.01%; P < 0.05), decreased FBR by 46% (rest: 0.17% ± 0.01%; postexercise: 0.09% ± 0.03%; P < 0.05), and made net balance less negative (P < 0.05). PB ingestion did not increase FSR (rest: 0.07% ± 0.03%; postexercise: 0.09% ± 0.01%; P ≥ 0.05), tended to decrease FBR by 42% (rest: 0.25% ± 0.08%; postexercise: 0.15% ± 0.08%; P = 0.08), and made net balance less negative (P < 0.05). Within-group percentage of change differences were not different between groups for FSR, FBR, or net balance (P ≥ 0.05).
  
  
  CONCLUSIONS
  WPI and PB ingestion after exercise in older men induced similar responses in hyperaminoacidemia, mTORC1 signaling, muscle protein synthesis, and breakdown. These data add new evidence for the use of whey or soy-dairy PBs as targeted nutritional interventions to counteract sarcopenia. This trial was registered at clinicaltrials.gov as NCT01847261.
authors: Division of Rehabilitation Sciences.
authors: Michael S
authors: MS
authors: Borack
authors: Division of Rehabilitation Sciences.
authors: Paul T
authors: PT
authors: Reidy
authors: Sealy Center on Aging.
authors: Syed H
authors: SH
authors: Husaini
authors: Sealy Center on Aging.
authors: Melissa M
authors: MM
authors: Markofski
authors: Sealy Center on Aging.
authors: Rachel R
authors: RR
authors: Deer
authors: Department of Nutrition and Metabolism.
authors: Abigail B
authors: AB
authors: Richison
authors: Division of Rehabilitation Sciences.
authors: Bradley S
authors: BS
authors: Lambert
authors: DuPont Nutrition and Health, St. Louis, MO.
authors: Mark B
authors: MB
authors: Cope
authors: DuPont Nutrition and Health, St. Louis, MO.
authors: Ratna
authors: R
authors: Mukherjea
authors: Department of Preventive Medicine and Community Health, University of Texas Medical Branch, Galveston, TX; and.
authors: Kristofer
authors: K
authors: Jennings
authors: Sealy Center on Aging.|Department of Internal Medicine/Geriatrics, and.
authors: Elena
authors: E
authors: Volpi
authors: Division of Rehabilitation Sciences, blrasmus@utmb.edu.|Department of Nutrition and Metabolism.|Sealy Center on Aging.
authors: Blake B
authors: BB
authors: Rasmussen
mesh_terms: D000368:Aged; D000375:Aging; D001628:Beverages / Q000032:analysis; D004311:Double-Blind Method; D015444:Exercise; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D006801:Humans; D008297:Male; D000076222:Mechanistic Target of Rapamycin Complex 1; D008875:Middle Aged; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D030262:Soybean Proteins / Q000737:chemistry / Q000494:pharmacology*; D058570:TOR Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D000067816:Whey Proteins / Q000494:pharmacology*
chemical_list: D046912:Multiprotein Complexes; D030262:Soybean Proteins; D000067816:Whey Proteins; D000076222:Mechanistic Target of Rapamycin Complex 1; D058570:TOR Serine-Threonine Kinases
keywords: aging; leucine; muscle protein turnover; protein supplementation; sarcopenia