Lack of effect of acute enteral arginine infusion on whole-body and intestinal protein metabolism in humans.
Arginine is a conditionally essential amino acid and exerts anabolic effects. We studied the effects of enteral arginine on whole-body and duodenal protein metabolism. Eight healthy fasted volunteers received randomly a 5-hr enteral infusion of either arginine (Arg; 20 g) or an isonitrogenous amino acid mixture (AA) and an IV infusion of [13C]leucine. Duodenal biopsies were performed. Whole-body protein turnover and duodenal protein synthesis (FSR) were calculated from GC/MS-assessed enrichment. The mRNA levels for major components of proteolytic pathways, ubiquitin, cathepsin D, and m-calpain, were evaluated by RT-PCR. Results were compared using paired Wilcoxon test. Endogenous, oxidative, and nonoxidative leucine fluxes were not different after Arg and AA infusions, respectively. Duodenal mucosal protein FSR (71% +/- 26% vs 81% +/- 30%/day) and mRNA levels of ubiquitin, cathepsin D, and m-calpain were also similar after Arg and AA infusions. We conclude that in healthy subjects, arginine infusion exerts no effect on whole-body and duodenal protein metabolism. Whether arginine might specifically affect these parameters in catabolic or inflammatory situations remains to be determined.
Claeyssens
Sophie
S
Appareil Digestif, Environnement et Nutrition (ADEN EA 3234), Institut Fédératif de Recherche Multidisciplinaire sur les Peptides, and CIC-INSERM-CHU, Rouen, France.
Lecleire
Stéphane
S
Leblond
Jonathan
J
Marion
Rachel
R
Hecketsweiler
Bernadette
B
Lavoinne
Alain
A
Ducrotté
Philippe
P
Déchelotte
Pierre
P
Coëffier
Moïse
M
D000328:Adult; D000596:Amino Acids / Q000097:blood; D001120:Arginine / Q000008:administration & dosage / Q000494:pharmacology*; D002154:Calpain / Q000235:genetics; D002250:Carbon Radioisotopes; D002403:Cathepsins / Q000235:genetics; D004386:Duodenum / Q000378:metabolism; D005260:Female; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism*; D007930:Leucine / Q000378:metabolism; D008297:Male; D011506:Proteins / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D025801:Ubiquitin / Q000235:genetics
D000596:Amino Acids; D002250:Carbon Radioisotopes; D011506:Proteins; D012333:RNA, Messenger; D025801:Ubiquitin; D001120:Arginine; D002403:Cathepsins; D002154:Calpain; C449000:m-calpain; D007930:Leucine