title: Combined enteral infusion of glutamine, carbohydrates, and antioxidants modulates gut protein metabolism in humans.
abstract: BACKGROUND
  Available data suggest that nutrients can affect intestinal protein metabolism, which contributes to the regulation of gut barrier function.
  
  
  OBJECTIVE
  We aimed to assess whether an oral nutritional supplement (ONS) containing glutamine (as the dipeptide Ala-Gln), carbohydrates, and antioxidants would modulate duodenal protein metabolism in healthy humans.
  
  
  METHODS
  Thirty healthy control subjects were included and, over a period of 5 h, received by nasogastric tube either saline or ONS providing 11.7 kcal/kg as 0.877 g Ala-Gln/kg, 3.9 g carbohydrates/kg, and antioxidants (29.25 mg vitamin C/kg, 9.75 mg vitamin E/kg, 195 microg beta-carotene/kg, 5.85 mg Se/kg, and 390 microg Zn/kg) or glutamine (0.585 g/kg, 2.34 kcal/kg). Simultaneously, a continuous intravenous infusion of l-[1-(13)C]-leucine was done until endoscopy. Leucine enrichment was assessed by using gas chromatography-mass spectrometric analysis, and mucosal fractional synthesis rate was calculated by using intracellular amino acid enrichment as precursor. Mucosal proteolytic pathways were also evaluated.
  
  
  RESULTS
  ONS infusion resulted in a doubling increase (P < 0.01) of duodenal fractional synthesis rate and a significant (P < 0.05) decrease in cathepsin D-mediated proteolysis compared with saline, whereas proteasome and Ca(2+)-dependent activities were unaffected. ONS infusion significantly (P < 0.01) decreased duodenal glutathione but not glutathione disulfide concentrations or the ratio of glutathione to glutathione disulfide. Insulinemia increased after ONS infusion, whereas plasma essential amino acids decreased. Infusion of glutamine alone did not reproduce ONS effects.
  
  
  CONCLUSIONS
  ONS infusion improves duodenal protein balance in healthy humans. Further investigations are needed to study the origin of these effects and to evaluate ONS supply in stressed persons.
authors.affiliation: Appareil Digestif Environnement Nutrition EA4311, the Institute for Biomedical Research, the European Institute for Peptide Research, and Clinical Investigation Center 0204, Rouen University and Rouen University Hospital, Rouen, France.
authors.forename: Moïse
authors.initials: M
authors.lastname: Coëffier
authors.forename: Sophie
authors.initials: S
authors.lastname: Claeyssens
authors.forename: Stéphane
authors.initials: S
authors.lastname: Lecleire
authors.forename: Jonathan
authors.initials: J
authors.lastname: Leblond
authors.forename: Aude
authors.initials: A
authors.lastname: Coquard
authors.forename: Christine
authors.initials: C
authors.lastname: Bôle-Feysot
authors.forename: Alain
authors.initials: A
authors.lastname: Lavoinne
authors.forename: Philippe
authors.initials: P
authors.lastname: Ducrotté
authors.forename: Pierre
authors.initials: P
authors.lastname: Déchelotte
mesh_terms: D000328:Adult; D000975:Antioxidants / Q000008:administration & dosage* / Q000378:metabolism; D002154:Calpain / Q000378:metabolism; D002247:Carbon Isotopes; D002402:Cathepsin D / Q000378:metabolism; D004040:Dietary Carbohydrates / Q000008:administration & dosage* / Q000378:metabolism; D004386:Duodenum / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D004750:Enteral Nutrition; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D005973:Glutamine / Q000008:administration & dosage* / Q000378:metabolism; D006801:Humans; D007413:Intestinal Mucosa / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D007441:Intubation, Gastrointestinal; D007930:Leucine / Q000008:administration & dosage / Q000032:analysis; D008297:Male; D009752:Nutritional Status; D014176:Protein Biosynthesis / Q000187:drug effects* / Q000502:physiology
chemical_list: D000975:Antioxidants; D002247:Carbon Isotopes; D004040:Dietary Carbohydrates; D005973:Glutamine; D002154:Calpain; D002402:Cathepsin D; D007930:Leucine