title: The impact of postexercise essential amino acid ingestion on the ubiquitin proteasome and autophagosomal-lysosomal systems in skeletal muscle of older men.
abstract: Essential amino acid (EAA) ingestion enhances postexercise muscle protein synthesis, and, in particular, the anabolic response of older adults appears sensitive to the quantity of ingested leucine. The effect of leucine ingestion on muscle breakdown following resistance exercise (RE) is less understood. The purpose of this study was to identify the impact of postexercise leucine ingestion on the ubiquitin proteasome and autophagosomal-lysosomal systems following acute RE in older men. Subjects (72 ± 2 yr) performed RE and 1 h postexercise ingested 10 g of EAA containing a leucine quantity similar to quality protein (control, 1.8 g leucine,n= 7) or enriched in leucine (leucine, 3.5 g leucine,n= 8). Stable isotope infusion and muscle biopsies (vastus lateralis) obtained at rest and 2, 5, and 24 h postexercise were used to examine protein content (Western blot), mRNA expression (RT-quantitative PCR), and muscle protein fractional breakdown rate (FBR). Muscle-specific RING finger 1 mRNA increased in both groups at 2 and 5 h (P< 0.05). LC3 mRNA increased, and the LC3BII-to-LC3BI ratio decreased at all postexercise time points in control (P< 0.05). Conversely, LC3 mRNA only increased at 2 h, and the LC3BII-to-LC3BI ratio only decreased at 2 and 5 h in leucine (P< 0.05). Tumor necrosis factor receptor-associated factor-6 mRNA increased (P< 0.05) in control at 5 h. FBR was not statistically different between groups or from basal 24 h postexercise (P> 0.05). These data indicate that ingesting a larger quantity of leucine following RE may further reduce postexercise skeletal muscle autophagy in older men; however, it does not appear to influence the acute postexercise elevation in markers of the ubiquitin proteasome system or the breakdown of intact proteins.NEW & NOTEWORTHYThe impact of postexercise leucine ingestion on processes of skeletal muscle breakdown in older adults is not well understood. Additional postexercise leucine ingestion appears to further reduce autophagy, but it does not interfere with the increase in ubiquitin proteasome system markers or the breakdown of intact proteins in skeletal muscle of older men. Postexercise leucine ingestion may promote a healthier protein pool and favorable muscle adaptations in older adults through greater accretion of myofibrillar proteins.
authors: School of Nutrition and Health Promotion, Healthy Lifestyles Research Center, Exercise Science and Health Promotion, Arizona State University, Phoenix, Arizona; jared.dickinson@asu.edu.|Department of Nutrition and Metabolism, University of Texas Medical Branch, Galveston, Texas.|Sealy Center on Aging, University of Texas Medical Branch, Galveston, Texas.|Division of Rehabilitation Sciences, University of Texas Medical Branch, Galveston, Texas; and.
authors: Jared M
authors: JM
authors: Dickinson
authors: Department of Nutrition and Metabolism, University of Texas Medical Branch, Galveston, Texas.|Division of Rehabilitation Sciences, University of Texas Medical Branch, Galveston, Texas; and.
authors: Paul T
authors: PT
authors: Reidy
authors: Department of Nutrition and Metabolism, University of Texas Medical Branch, Galveston, Texas.|Division of Rehabilitation Sciences, University of Texas Medical Branch, Galveston, Texas; and.
authors: David M
authors: DM
authors: Gundermann
authors: Department of Nutrition and Metabolism, University of Texas Medical Branch, Galveston, Texas.|Division of Rehabilitation Sciences, University of Texas Medical Branch, Galveston, Texas; and.
authors: Michael S
authors: MS
authors: Borack
authors: Department of Nutrition and Metabolism, University of Texas Medical Branch, Galveston, Texas.
authors: Dillon K
authors: DK
authors: Walker
authors: School of Nutrition and Health Promotion, Healthy Lifestyles Research Center, Exercise Science and Health Promotion, Arizona State University, Phoenix, Arizona.
authors: Andrew C
authors: AC
authors: D'Lugos
authors: Department of Nutrition and Metabolism, University of Texas Medical Branch, Galveston, Texas.|Sealy Center on Aging, University of Texas Medical Branch, Galveston, Texas.|Division of Rehabilitation Sciences, University of Texas Medical Branch, Galveston, Texas; and.|Department of Internal Medicine-Geriatrics, University of Texas Medical Branch, Galveston, Texas.
authors: Elena
authors: E
authors: Volpi
authors: Department of Nutrition and Metabolism, University of Texas Medical Branch, Galveston, Texas.|Sealy Center on Aging, University of Texas Medical Branch, Galveston, Texas.|Division of Rehabilitation Sciences, University of Texas Medical Branch, Galveston, Texas; and.
authors: Blake B
authors: BB
authors: Rasmussen
mesh_terms: D000284:Administration, Oral; D000368:Aged; D000375:Aging / Q000502:physiology; D000071182:Autophagosomes / Q000187:drug effects* / Q000502:physiology; D004435:Eating / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D006801:Humans; D007930:Leucine / Q000008:administration & dosage / Q000494:pharmacology*; D008247:Lysosomes / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000502:physiology / Q000648:ultrastructure; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism*
chemical_list: D025801:Ubiquitin; D046988:Proteasome Endopeptidase Complex; D007930:Leucine
keywords: autophagy; fractional breakdown rate; leucine; protein breakdown; skeletal muscle