title: Rapid aminoacidemia enhances myofibrillar protein synthesis and anabolic intramuscular signaling responses after resistance exercise.
abstract: BACKGROUND
  Ingestion of whey or casein yields divergent patterns of aminoacidemia that influence whole-body and skeletal muscle myofibrillar protein synthesis (MPS) after exercise. Direct comparisons of the effects of contrasting absorption rates exhibited by these proteins are confounded by their differing amino acid contents.
  
  
  OBJECTIVE
  Our objective was to determine the effect of divergent aminoacidemia by manipulating ingestion patterns of whey protein alone on MPS and anabolic signaling after resistance exercise.
  
  
  METHODS
  In separate trials, 8 healthy men consumed whey protein either as a single bolus (BOLUS; 25-g dose) or as repeated, small, "pulsed" drinks (PULSE; ten 2.5-g drinks every 20 min) to mimic a more slowly digested protein. MPS and phosphorylation of signaling proteins involved in protein synthesis were measured at rest and after resistance exercise.
  
  
  RESULTS
  BOLUS increased blood essential amino acid (EAA) concentrations above those of PULSE (162% compared with 53%, P < 0.001) 60 min after exercise, whereas PULSE resulted in a smaller but sustained increase in aminoacidemia that remained elevated above BOLUS amounts later (180-220 min after exercise, P < 0.05). Despite an identical net area under the EAA curve, MPS was elevated to a greater extent after BOLUS than after PULSE early (1-3 h: 95% compared with 42%) and later (3-5 h: 193% compared with 121%) (both P < 0.05). There were greater changes in the phosphorylation of the Akt-mammalian target of rapamycin pathway after BOLUS than after PULSE.
  
  
  CONCLUSIONS
  Rapid aminoacidemia in the postexercise period enhances MPS and anabolic signaling to a greater extent than an identical amount of protein fed in small pulses that mimic a more slowly digested protein. A pronounced peak aminoacidemia after exercise enhances protein synthesis. This trial was registered at clinicaltrials.gov as NCT01319513.
authors.affiliation: Exercise Metabolism Research Group, Department of Kinesiology, McMaster University, Hamilton, Canada.
authors.forename: Daniel W D
authors.initials: DW
authors.lastname: West
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Burd
authors.forename: Vernon G
authors.initials: VG
authors.lastname: Coffey
authors.forename: Steven K
authors.initials: SK
authors.lastname: Baker
authors.forename: Louise M
authors.initials: LM
authors.lastname: Burke
authors.forename: John A
authors.initials: JA
authors.lastname: Hawley
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Moore
authors.forename: Trent
authors.initials: T
authors.lastname: Stellingwerff
authors.forename: Stuart M
authors.initials: SM
authors.lastname: Phillips
mesh_terms: D000601:Amino Acids, Essential / Q000097:blood*; D015444:Exercise / Q000502:physiology*; D006801:Humans; D008297:Male; D008894:Milk Proteins / Q000008:administration & dosage / Q000494:pharmacology*; D009210:Myofibrils / Q000378:metabolism*; D010766:Phosphorylation; D014176:Protein Biosynthesis; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D055070:Resistance Training; D015398:Signal Transduction / Q000187:drug effects; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D014891:Weight Lifting / Q000502:physiology*; D000067816:Whey Proteins; D055815:Young Adult
chemical_list: D000601:Amino Acids, Essential; D008894:Milk Proteins; D000067816:Whey Proteins; C546842:MTOR protein, human; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases