title: Ingestion of a protein hydrolysate is accompanied by an accelerated in vivo digestion and absorption rate when compared with its intact protein.
abstract: BACKGROUND
  It has been suggested that a protein hydrolysate, as opposed to its intact protein, is more easily digested and absorbed from the gut, which results in greater plasma amino acid availability and a greater muscle protein synthetic response.
  
  
  OBJECTIVE
  We aimed to compare dietary protein digestion and absorption kinetics and the subsequent muscle protein synthetic response to the ingestion of a single bolus of protein hydrolysate compared with its intact protein in vivo in humans.
  
  
  METHODS
  Ten elderly men (mean +/- SEM age: 64 +/- 1 y) were randomly assigned to a crossover experiment that involved 2 treatments in which the subjects consumed a 35-g bolus of specifically produced L-[1-(13)C]phenylalanine-labeled intact casein (CAS) or hydrolyzed casein (CASH). Blood and muscle-tissue samples were collected to assess the appearance rate of dietary protein-derived phenylalanine in the circulation and subsequent muscle protein fractional synthetic rate over a 6-h postprandial period.
  
  
  RESULTS
  The mean (+/-SEM) exogenous phenylalanine appearance rate was 27 +/- 6% higher after ingestion of CASH than after ingestion of CAS (P < 0.001). Splanchnic extraction was significantly lower in CASH compared with CAS treatment (P < 0.01). Plasma amino acid concentrations increased to a greater extent (25-50%) after the ingestion of CASH than after the ingestion of CAS (P < 0.01). Muscle protein synthesis rates averaged 0.054 +/- 0.004% and 0.068 +/- 0.006%/h in the CAS and CASH treatments, respectively (P = 0.10).
  
  
  CONCLUSIONS
  Ingestion of a protein hydrolysate, as opposed to its intact protein, accelerates protein digestion and absorption from the gut, augments postprandial amino acid availability, and tends to increase the incorporation rate of dietary amino acids into skeletal muscle protein.
authors.affiliation: Department of Human Movement Sciences, Nutrition and Toxicology Research Institute Maastricht, Maastricht, Netherlands.
authors.forename: René
authors.initials: R
authors.lastname: Koopman
authors.forename: Nico
authors.initials: N
authors.lastname: Crombach
authors.forename: Annemie P
authors.initials: AP
authors.lastname: Gijsen
authors.forename: Stéphane
authors.initials: S
authors.lastname: Walrand
authors.forename: Jacques
authors.initials: J
authors.lastname: Fauquant
authors.forename: Arie K
authors.initials: AK
authors.lastname: Kies
authors.forename: Sophie
authors.initials: S
authors.lastname: Lemosquet
authors.forename: Wim H M
authors.initials: WH
authors.lastname: Saris
authors.forename: Yves
authors.initials: Y
authors.lastname: Boirie
authors.forename: Luc J C
authors.initials: LJ
authors.lastname: van Loon
mesh_terms: D001786:Blood Glucose / Q000378:metabolism; D002247:Carbon Isotopes / Q000378:metabolism; D002364:Caseins / Q000378:metabolism*; D018592:Cross-Over Studies; D003922:Diabetes Mellitus, Type 1 / Q000097:blood; D004044:Dietary Proteins / Q000378:metabolism*; D004063:Digestion / Q000502:physiology*; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000097:blood; D007408:Intestinal Absorption / Q000502:physiology*; D007700:Kinetics; D007930:Leucine / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism; D010649:Phenylalanine / Q000097:blood* / Q000378:metabolism; D011492:Protein Hydrolysates / Q000378:metabolism*
chemical_list: D001786:Blood Glucose; D002247:Carbon Isotopes; D002364:Caseins; D004044:Dietary Proteins; D007328:Insulin; D011492:Protein Hydrolysates; D010649:Phenylalanine; D007930:Leucine