title: Leucine supplementation of a low-protein mixed macronutrient beverage enhances myofibrillar protein synthesis in young men: a double-blind, randomized trial.
abstract: BACKGROUND
  Leucine is a key amino acid involved in the regulation of skeletal muscle protein synthesis.
  
  
  OBJECTIVE
  We assessed the effect of the supplementation of a lower-protein mixed macronutrient beverage with varying doses of leucine or a mixture of branched chain amino acids (BCAAs) on myofibrillar protein synthesis (MPS) at rest and after exercise.
  
  
  METHODS
  In a parallel group design, 40 men (21 ± 1 y) completed unilateral knee-extensor resistance exercise before the ingestion of 25 g whey protein (W25) (3.0 g leucine), 6.25 g whey protein (W6) (0.75g leucine), 6.25 g whey protein supplemented with leucine to 3.0 g total leucine (W6+Low-Leu), 6.25 g whey protein supplemented with leucine to 5.0 g total leucine (W6+High-Leu), or 6.25 g whey protein supplemented with leucine, isoleucine, and valine to 5.0 g total leucine. A primed continuous infusion of l-[ring-(13)C6] phenylalanine with serial muscle biopsies was used to measure MPS under baseline fasted and postprandial conditions in both a rested (response to feeding) and exercised (response to combined feeding and resistance exercise) leg.
  
  
  RESULTS
  The area under the blood leucine curve was greatest for the W6+High-Leu group compared with the W6 and W6+Low-Leu groups (P < 0.001). In the postprandial period, rates of MPS were increased above baseline over 0-1.5 h in all treatments. Over 1.5-4.5 h, MPS remained increased above baseline after all treatments but was greatest after W25 (∼267%) and W6+High-Leu (∼220%) treatments (P = 0.002).
  
  
  CONCLUSIONS
  A low-protein (6.25 g) mixed macronutrient beverage can be as effective as a high-protein dose (25 g) at stimulating increased MPS rates when supplemented with a high (5.0 g total leucine) amount of leucine. These results have important implications for formulations of protein beverages designed to enhance muscle anabolism. This trial was registered at clinicaltrials.gov as NCT 1530646.
authors.affiliation: Exercise Metabolism Research Group, Departments of Kinesiology (TAC-V, LB, DMDD, AJH, CJM, and SMP) and Neurology (SKB), McMaster University, Hamilton, Canada, and the Nestlé Research Centre, Nestec Ltd, Lausanne, Switzerland (DRM, TS, DB, and EAO).
authors.forename: Tyler A
authors.initials: TA
authors.lastname: Churchward-Venne
authors.forename: Leigh
authors.initials: L
authors.lastname: Breen
authors.forename: Danielle M
authors.initials: DM
authors.lastname: Di Donato
authors.forename: Amy J
authors.initials: AJ
authors.lastname: Hector
authors.forename: Cameron J
authors.initials: CJ
authors.lastname: Mitchell
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Moore
authors.forename: Trent
authors.initials: T
authors.lastname: Stellingwerff
authors.forename: Denis
authors.initials: D
authors.lastname: Breuille
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Offord
authors.forename: Steven K
authors.initials: SK
authors.lastname: Baker
authors.forename: Stuart M
authors.initials: SM
authors.lastname: Phillips
mesh_terms: D000293:Adolescent; D000328:Adult; D000597:Amino Acids, Branched-Chain / Q000008:administration & dosage; D001628:Beverages; D001786:Blood Glucose / Q000378:metabolism; D018753:Diet, Protein-Restricted; D004044:Dietary Proteins / Q000008:administration & dosage; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D006801:Humans; D007328:Insulin / Q000097:blood; D007930:Leucine / Q000008:administration & dosage* / Q000097:blood; D016014:Linear Models; D008297:Male; D008894:Milk Proteins / Q000008:administration & dosage; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism; D009210:Myofibrils / Q000187:drug effects* / Q000378:metabolism; D010649:Phenylalanine / Q000008:administration & dosage / Q000097:blood; D014176:Protein Biosynthesis / Q000187:drug effects*; D055070:Resistance Training; D012146:Rest / Q000502:physiology; D000067816:Whey Proteins; D055815:Young Adult
chemical_list: D000597:Amino Acids, Branched-Chain; D001786:Blood Glucose; D004044:Dietary Proteins; D007328:Insulin; D008894:Milk Proteins; D000067816:Whey Proteins; D010649:Phenylalanine; D007930:Leucine