Enteral glutamine stimulates protein synthesis and decreases ubiquitin mRNA level in human gut mucosa.
Effects of glutamine on whole body and intestinal protein synthesis and on intestinal proteolysis were assessed in humans. Two groups of healthy volunteers received in a random order enteral glutamine (0.8 mmol.kg body wt(-1)x h(-1)) compared either to saline or isonitrogenous amino acids. Intravenous [2H5]phenylalanine and [13C]leucine were simultaneously infused. After gas chromatography-mass spectrometry analysis, whole body protein turnover was estimated from traced plasma amino acid fluxes and the fractional synthesis rate (FSR) of gut mucosal protein was calculated from protein and intracellular phenylalanine and leucine enrichments in duodenal biopsies. mRNA levels for ubiquitin, cathepsin D, and m-calpain were analyzed in biopsies by RT-PCR. Glutamine significantly increased mucosal protein FSR compared with saline. Glutamine and amino acids had similar effects on FSR. The mRNA level for ubiquitin was significantly decreased after glutamine infusion compared with saline and amino acids, whereas cathepsin D and m-calpain mRNA levels were not affected. Enteral glutamine stimulates mucosal protein synthesis and may attenuate ubiquitin-dependent proteolysis and thus improve protein balance in human gut.
Coëffier
Moïse
M
Appareil Digestif, Environnement et Nutrition, Institut Fédératif de Recherche Multidisciplinaire sur les Peptides, Centre d' Investigation Clinique, Rouen, France.
Claeyssens
Sophie
S
Hecketsweiler
Bernadette
B
Lavoinne
Alain
A
Ducrotté
Philippe
P
Déchelotte
Pierre
P
D000328:Adult; D000596:Amino Acids / Q000097:blood; D002154:Calpain / Q000235:genetics; D002247:Carbon Isotopes; D002402:Cathepsin D / Q000235:genetics; D003903:Deuterium; D004386:Duodenum / Q000737:chemistry; D004750:Enteral Nutrition; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D005973:Glutamine / Q000008:administration & dosage*; D006801:Humans; D007328:Insulin / Q000097:blood; D007413:Intestinal Mucosa / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D007441:Intubation, Gastrointestinal; D007930:Leucine / Q000008:administration & dosage / Q000032:analysis; D008297:Male; D010649:Phenylalanine / Q000008:administration & dosage / Q000032:analysis; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000032:analysis*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D025801:Ubiquitin / Q000235:genetics*
D000596:Amino Acids; D002247:Carbon Isotopes; D007328:Insulin; D012333:RNA, Messenger; D025801:Ubiquitin; D005973:Glutamine; D010649:Phenylalanine; D003903:Deuterium; D002154:Calpain; C449000:m-calpain; D002402:Cathepsin D; D007930:Leucine