title: Leucine-enriched amino acid ingestion after resistance exercise prolongs myofibrillar protein synthesis and amino acid transporter expression in older men.
abstract: BACKGROUND
  Postexercise protein or amino acid ingestion restores muscle protein synthesis in older adults and represents an important therapeutic strategy for aging muscle. However, the precise nutritional factors involved are unknown.
  
  
  OBJECTIVE
  The purpose of this study was to determine the role of increased postexercise Leu ingestion on skeletal muscle myofibrillar protein synthesis (MyoPS), mammalian/mechanistic target of rapamycin complex 1 signaling, and amino acid transporter (AAT) mRNA expression in older men over a 24-h post-resistance exercise (RE) time course.
  
  
  METHODS
  During a stable isotope infusion trial (l-[ring-(13)C6]Phe; l-[1-(13)C]Leu), older men performed RE and, at 1 h after exercise, ingested 10 g of essential amino acids (EAAs) containing either a Leu content similar to quality protein (control, 1.85 g of Leu, n = 7) or enriched Leu (LEU; 3.5 g of Leu, n = 8). Muscle biopsies (vastus lateralis) were obtained at rest and 2, 5, and 24 h after exercise.
  
  
  RESULTS
  p70 S6 kinase 1 phosphorylation was increased in each group at 2 h (P < 0.05), whereas 4E binding protein 1 phosphorylation increased only in the LEU group (P < 0.05). MyoPS was similarly increased (∼90%) above basal in each group at 5 h (P < 0.05) and remained elevated (∼90%) at 24 h only in the LEU group (P < 0.05). The mRNA expression of select AATs was increased at 2 and 5 h in each group (P < 0.05), but AAT expression was increased at 24 h only in the LEU group (P < 0.05).
  
  
  CONCLUSIONS
  Leu-enriched EAA ingestion after RE may prolong the anabolic response and sensitivity of skeletal muscle to amino acids in older adults. These data emphasize the potential importance of adequate postexercise Leu ingestion to enhance the response of aging muscle to preventive or therapeutic exercise-based rehabilitation programs. This trial was registered at clinicaltrials.gov as NCT00891696.
authors.affiliation: Departments of Nutrition and Metabolism and Division of Rehabilitation Sciences, and Sealy Center on Aging, University of Texas Medical Branch, Galveston, TX; and School of Nutrition and Health Promotion, Healthy Lifestyles Research Center, Exercise Science and Health Promotion, Arizona State University, Phoenix, AZ jared.dickinson@asu.edu.
authors.forename: Jared M
authors.initials: JM
authors.lastname: Dickinson
authors.affiliation: Departments of Nutrition and Metabolism and Division of Rehabilitation Sciences, and.
authors.forename: David M
authors.initials: DM
authors.lastname: Gundermann
authors.affiliation: Division of Rehabilitation Sciences, and.
authors.forename: Dillon K
authors.initials: DK
authors.lastname: Walker
authors.affiliation: Departments of Nutrition and Metabolism and Division of Rehabilitation Sciences, and.
authors.forename: Paul T
authors.initials: PT
authors.lastname: Reidy
authors.affiliation: Departments of Nutrition and Metabolism and Division of Rehabilitation Sciences, and.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Borack
authors.affiliation: Departments of Nutrition and Metabolism and Division of Rehabilitation Sciences, and Sealy Center on Aging, University of Texas Medical Branch, Galveston, TX; and.
authors.forename: Micah J
authors.initials: MJ
authors.lastname: Drummond
authors.affiliation: Sealy Center on Aging, University of Texas Medical Branch, Galveston, TX; and.
authors.forename: Mohit
authors.initials: M
authors.lastname: Arora
authors.affiliation: Internal Medicine-Geriatrics Division of Rehabilitation Sciences, and Sealy Center on Aging, University of Texas Medical Branch, Galveston, TX; and.
authors.forename: Elena
authors.initials: E
authors.lastname: Volpi
authors.affiliation: Departments of Nutrition and Metabolism and Division of Rehabilitation Sciences, and Sealy Center on Aging, University of Texas Medical Branch, Galveston, TX; and.
authors.forename: Blake B
authors.initials: BB
authors.lastname: Rasmussen
mesh_terms: D000368:Aged; D026905:Amino Acid Transport Systems / Q000235:genetics / Q000378:metabolism*; D000596:Amino Acids / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*; D015444:Exercise / Q000502:physiology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D007930:Leucine / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*; D008297:Male; D009210:Myofibrils / Q000235:genetics / Q000378:metabolism*
chemical_list: D026905:Amino Acid Transport Systems; D000596:Amino Acids; D007930:Leucine