Combined enteral infusion of glutamine, carbohydrates, and antioxidants modulates gut protein metabolism in humans.
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.
Coëffier
Moïse
M
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.
Claeyssens
Sophie
S
Lecleire
Stéphane
S
Leblond
Jonathan
J
Coquard
Aude
A
Bôle-Feysot
Christine
C
Lavoinne
Alain
A
Ducrotté
Philippe
P
Déchelotte
Pierre
P
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
D000975:Antioxidants; D002247:Carbon Isotopes; D004040:Dietary Carbohydrates; D005973:Glutamine; D002154:Calpain; D002402:Cathepsin D; D007930:Leucine