title: Leucine-enriched essential amino acid supplementation during moderate steady state exercise enhances postexercise muscle protein synthesis.
abstract: BACKGROUND
  The effects of essential amino acid (EAA) supplementation during moderate steady state (ie, endurance) exercise on postexercise skeletal muscle metabolism are not well described, and the potential role of supplemental leucine on muscle protein synthesis (MPS) and associated molecular responses remains to be elucidated.
  
  
  OBJECTIVE
  This randomized crossover study examined whether EAA supplementation with 2 different concentrations of leucine affected post-steady state exercise MPS, whole-body protein turnover, and mammalian target of rapamycin 1 (mTORC1) intracellular signaling.
  
  
  METHODS
  Eight adults completed 2 separate bouts of cycle ergometry [60 min, 60% VO(2)peak (peak oxygen uptake)]. Isonitrogenous (10 g EAA) drinks with different leucine contents [leucine-enriched (l)-EAA, 3.5 g leucine; EAA, 1.87 g leucine] were consumed during exercise. MPS and whole-body protein turnover were determined by using primed continuous infusions of [(2)H(5)]phenylalanine and [1-(13)C]leucine. Multiplex and immunoblot analyses were used to quantify mTORC1 signaling.
  
  
  RESULTS
  MPS was 33% greater (P < 0.05) after consumption of L-EAA (0.08 ± 0.01%/h) than after consumption of EAA (0.06 ± 0.01%/h). Whole-body protein breakdown and synthesis were lower (P < 0.05) and oxidation was greater (P < 0.05) after consumption of L-EAA than after consumption of EAA. Regardless of dietary treatment, multiplex analysis indicated that Akt and mammalian target of rapamycin phosphorylation were increased (P < 0.05) 30 min after exercise. Immunoblot analysis indicated that phosphorylation of ribosomal protein S6 and extracellular-signal regulated protein kinase increased (P < 0.05) and phosphorylation of eukaryotic elongation factor 2 decreased (P < 0.05) after exercise but was not affected by dietary treatment.
  
  
  CONCLUSIONS
  These findings suggest that increasing the concentration of leucine in an EAA supplement consumed during steady state exercise elicits a greater MPS response during recovery. This trial is registered at clinicaltrials.gov as NCT01366924.
authors.affiliation: Military Nutrition Division, US Army Research Institute of Environmental Medicine, Natick, MA, USA. stefan.pasiakos@us.army.mil
authors.forename: Stefan M
authors.initials: SM
authors.lastname: Pasiakos
authors.forename: Holly L
authors.initials: HL
authors.lastname: McClung
authors.forename: James P
authors.initials: JP
authors.lastname: McClung
authors.forename: Lee M
authors.initials: LM
authors.lastname: Margolis
authors.forename: Nancy E
authors.initials: NE
authors.lastname: Andersen
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Cloutier
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Pikosky
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Rood
authors.forename: Roger A
authors.initials: RA
authors.lastname: Fielding
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Young
mesh_terms: D000328:Adult; D001642:Bicycling / Q000502:physiology*; D018592:Cross-Over Studies; D019587:Dietary Supplements; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005260:Female; D006801:Humans; D007554:Isotopes; D007930:Leucine / Q000494:pharmacology*; D008297:Male; D009124:Muscle Proteins / Q000096:biosynthesis*; D010084:Oxidation-Reduction; D010766:Phosphorylation; D014176:Protein Biosynthesis / Q000187:drug effects*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D038601:Ribosomal Protein S6 / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013194:Staining and Labeling; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D055815:Young Adult
chemical_list: D007554:Isotopes; D009124:Muscle Proteins; D038601:Ribosomal Protein S6; C546842:MTOR protein, human; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D007930:Leucine