title: Protein-leucine fed dose effects on muscle protein synthesis after endurance exercise.
abstract: Protein-leucine ingestion after strenuous endurance exercise accentuates muscle protein synthesis and improves recovery of muscle performance.
  
  
  OBJECTIVE
  The objective of this study is to determine whether a low-dose protein-leucine blend ingested after endurance exercise enhances skeletal muscle myofibrillar protein fractional synthetic rate (FSR).
  
  
  METHODS
  In a crossover design, 12 trained men completed 100 min of high-intensity cycling, then ingested either 70/15/180/30 g of protein/leucine/carbohydrate/fat (15LEU), 23/5/180/30 g of 5LEU, or 0/0/274/30 g of CON beverages in randomized order in four servings during the first 90 min of a 240-min recovery period. Muscle biopsies were collected at 30 and 240 min into recovery with FSR determined by L-[ring-13C6]phenylalanine incorporation and mTORC1 pathway phosphorylation by Western blot.
  
  
  RESULTS
  The 33% (90% CL, ±12%) increase in FSR with 5LEU (mean, SD: 0.080, 0.014%·h(-1)) versus CON (0.060, 0.012%·h(-1)) represented near-maximal FSR stimulation. Tripling protein-leucine dose (15LEU: 0.090, 0.11%·h(-1)) negligibly increased FSR (13%, ±12% vs 5LEU). Despite similar FSR, mTORC1(Ser2448) phosphorylation only increased with 15LEU at 30 min, whereas p70S6K(Thr389), rpS6(Ser240/244), and 4E-BP1γ(Ser112) phosphorylation increased with protein-leucine quantity at one or both time points. Plasma leucine and essential amino acid concentrations decreased during recovery in CON but increased with protein-leucine dose. Serum insulin was increased in 15LEU versus CON (60%, ±20%) but was unaffected relative to 5LEU. Regression analysis revealed p70S6K-rpS6 phosphorylation moderately predicted FSR, but the associations with plasma leucine and essential amino acids were small.
  
  
  CONCLUSIONS
  Ingesting 23 g of protein with 5 g of added leucine achieved near-maximal FSR after endurance exercise, an effect unlikely attributable to mTORC1-S6K-rpS6 signaling, insulin, or amino acids. Translating the effects of protein-leucine quantity on protein synthesis to optimizing adaptation and performance requires further research.
authors.affiliation: 1School of Sport and Exercise, Massey University, Wellington, NEW ZEALAND; 2Institute of Sport, Exercise and Active Living, Victoria University, Melbourne, AUSTRALIA; 3Kinesiology, McMaster University, Hamilton, CANADA; 4The Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Urbana, IL; 5Nestle Research Centre, Lausanne, SWITZERLAND; 6Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, ON, CANADA; and 7Canadian Sport Institute-Pacific, Victoria, BC, CANADA.
authors.forename: David S
authors.initials: DS
authors.lastname: Rowlands
authors.forename: Andre R
authors.initials: AR
authors.lastname: Nelson
authors.forename: Stuart M
authors.initials: SM
authors.lastname: Phillips
authors.forename: James A
authors.initials: JA
authors.lastname: Faulkner
authors.forename: Jim
authors.initials: J
authors.lastname: Clarke
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Burd
authors.forename: Daniel
authors.initials: D
authors.lastname: Moore
authors.forename: Trent
authors.initials: T
authors.lastname: Stellingwerff
mesh_terms: D000328:Adult; D000601:Amino Acids, Essential / Q000097:blood; D001628:Beverages; D001786:Blood Glucose / Q000378:metabolism; D018592:Cross-Over Studies; D004040:Dietary Carbohydrates / Q000008:administration & dosage; D004041:Dietary Fats / Q000008:administration & dosage; D004044:Dietary Proteins / Q000008:administration & dosage* / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000097:blood; D007930:Leucine / Q000008:administration & dosage* / Q000097:blood; D008297:Male; D000076222:Mechanistic Target of Rapamycin Complex 1; D046912:Multiprotein Complexes / Q000378:metabolism; D009124:Muscle Proteins / Q000096:biosynthesis*; D018482:Muscle, Skeletal / Q000378:metabolism; D009210:Myofibrils / Q000378:metabolism; D010807:Physical Endurance / Q000502:physiology*; D016037:Single-Blind Method; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism
chemical_list: D000601:Amino Acids, Essential; D001786:Blood Glucose; D004040:Dietary Carbohydrates; D004041:Dietary Fats; D004044:Dietary Proteins; D007328:Insulin; D046912:Multiprotein Complexes; D009124:Muscle Proteins; D000076222:Mechanistic Target of Rapamycin Complex 1; D058570:TOR Serine-Threonine Kinases; D007930:Leucine