GLUTAMINE-METABOLISM IN HEALTHY ADULT MEN - RESPONSE TO ENTERAL AND INTRAVENOUS-FEEDING

To assess the effect of feeding on glutamine kinetics, six healthy men received 4-h intravenous infusions of L-[2-N-15]glutamine and L-[1-C- 13]leucine on 3 separate days: 1) in the postabsorptive state, 2) over the course of an 8-h nasogastric infusion of a small peptide-based nu trient mixture, and 3) during an 8-h isonitrogenous, isoenergetic intr avenous infusion (1.5 g amino acid.kg(-1).d(-1); 130 kJ.kg(-1).d(-1), or 31 kcal.kg(-1).d(-1); 58% carbohydrate and 42% fat). Regardless of the route, nutrition increased leucine appearance rate (Ra) and oxidat ion, stimulated protein synthesis, and improved leucine balance; appar ent rates of protein breakdown decreased during enteral nutrition only . Glutamine Ra increased 16.8% (NS) and 26.2% (P < 0.01) with parenter al and enteral feeding, respectively, over postabsorptive values. The present findings are consistent with a major role of glutamine in inte rorgan nitrogen transport in the fed state and further suggest that in creased availability of precursors may stimulate glutamine synthesis d e novo, and enteral infusion of peptide-bound amino acids may be an ef fective route to provide free glutamine to the rest of the body.