title: A protein-leucine supplement increases branched-chain amino acid and nitrogen turnover but not performance.
abstract: OBJECTIVE
  This study aimed to determine the effect of postexercise protein-leucine coingestion with CHO-lipid on subsequent high-intensity endurance performance and to investigate candidate mechanisms using stable isotope methods and metabolomics.
  
  
  METHODS
  In this double-blind, randomized, crossover study, 12 male cyclists ingested a leucine/protein/CHO/fat supplement (LEUPRO 7.5/20/89/22 g · h(-1), respectively) or isocaloric CHO/fat control (119/22 g · h(-1)) 1-3 h after exercise during a 6-d training block (intense intervals, recovery, repeated-sprint performance rides). Daily protein intake was clamped at 1.9 g · kg(-1) · d(-1) (LEUPRO) and 1.5 g · kg(-1) · d(-1) (control). Stable isotope infusions (1-(13)C-leucine and 6,6-(2)H2-glucose), mass spectrometry-based metabolomics, and nitrogen balance methods were used to determine the effects of LEUPRO on whole-body branched-chain amino acid (BCAA) and glucose metabolism and protein turnover.
  
  
  RESULTS
  After exercise, LEUPRO increased BCAA levels in plasma (2.6-fold; 90% confidence limits = ×/÷ 1.1) and urine (2.8-fold; ×/÷ 1.2) and increased products of BCAA metabolism plasma acylcarnitine C5 (3.0-fold; ×/÷ 0.9) and urinary leucine (3.6-fold; ×/÷ 1.3) and β-aminoisobutyrate (3.4-fold; ×/÷ 1.4), indicating that ingesting ~10 g leucine per hour during recovery exceeds the capacity to metabolize BCAA. Furthermore, LEUPRO increased leucine oxidation (5.6-fold; ×/÷ 1.1) and nonoxidative disposal (4.8-fold; ×/÷ 1.1) and left leucine balance positive relative to control. With the exception of day 1 (LEUPRO = 17 ± 20 mg N · kg(-1), control = -90 ± 44 mg N · kg(-1)), subsequent (days 2-5) nitrogen balance was positive for both conditions (LEUPRO = 130 ± 110 mg N · kg(-1), control = 111 ± 86 mg N · kg(-1)). Compared with control feeding, LEUPRO lowered the serum creatine kinase concentration by 21%-25% (90% confidence limits = ± 14%), but the effect on sprint power was trivial (day 4 = 0.4% ± 1.0%, day 6 = -0.3% ± 1.0%).
  
  
  CONCLUSIONS
  Postexercise protein-leucine supplementation saturates BCAA metabolism and attenuates tissue damage, but effects on subsequent intense endurance performance may be inconsequential under conditions of positive daily nitrogen balance.
authors.affiliation: School of Sport and Exercise, Massey University, Wellington, New Zealand.
authors.forename: Andre R
authors.initials: AR
authors.lastname: Nelson
authors.forename: Stuart M
authors.initials: SM
authors.lastname: Phillips
authors.forename: Trent
authors.initials: T
authors.lastname: Stellingwerff
authors.forename: Serge
authors.initials: S
authors.lastname: Rezzi
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Bruce
authors.forename: Isabelle
authors.initials: I
authors.lastname: Breton
authors.forename: Anita
authors.initials: A
authors.lastname: Thorimbert
authors.forename: Philippe A
authors.initials: PA
authors.lastname: Guy
authors.forename: Jim
authors.initials: J
authors.lastname: Clarke
authors.forename: Suzanne
authors.initials: S
authors.lastname: Broadbent
authors.forename: David Stephen
authors.initials: DS
authors.lastname: Rowlands
mesh_terms: D000328:Adult; D000597:Amino Acids, Branched-Chain / Q000097:blood / Q000378:metabolism* / Q000652:urine; D000621:Aminoisobutyric Acids / Q000652:urine; D054874:Athletic Performance / Q000502:physiology*; D003402:Creatine Kinase / Q000097:blood; D018592:Cross-Over Studies; D004040:Dietary Carbohydrates / Q000008:administration & dosage / Q000378:metabolism; D004044:Dietary Proteins / Q000008:administration & dosage* / Q000378:metabolism; D019587:Dietary Supplements; D004311:Double-Blind Method; D006801:Humans; D007930:Leucine / Q000008:administration & dosage* / Q000378:metabolism / Q000652:urine; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000187:drug effects / Q000502:physiology; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D009584:Nitrogen / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology; D012420:Running / Q000502:physiology
chemical_list: D000597:Amino Acids, Branched-Chain; D000621:Aminoisobutyric Acids; D004040:Dietary Carbohydrates; D004044:Dietary Proteins; D003402:Creatine Kinase; D007930:Leucine; D009584:Nitrogen; C033435:3-aminoisobutyric acid