Glutamine-Supplemented Parenteral Nutrition Improves Gut Mucosa Integrity and Function in Endotoxemic Rats

The effects of glutamine-supplemented parenteral nutrition on protein metabolism, small intestinal mucosal metabolism, morphology, and barrier function were studied in endotoxin-treated rats. Forty-six male Wistar rats were randomized to two groups of 23 animals each and received total parenteral nutrition solutions supplemented with either glutamine (GLN group) or glycine (GLY group) at 2% wt/vol. Endotoxemia was induced by continuous intravenous infusion of endotoxin at a dose of 2 mg/kg per day throughout the 4-day study period. The GLN group had a less-negative cumulative nitrogen balance (-14.0 ± 132.8 mg of nitrogen in the GLN group and -86.8 ± 161.7 mg of nitrogen in the GLY group, p < .05) and less cumulative excretion of urinary 3-methylhistidine (2910 ± 593 nmol) than the GLY group (4447 ± 933 nmol, p < .01). Jejunal mucosal glutaminase activity and the arterio-portal venous blood glutamine concentration differences were significantly higher in the GLN group compared with the GLY group (15.6 ± 2.3 vs 11.1 ± 1.9 μmol/g per minute, p < .05, and 181 ± 52 vs 147 ± 36 nmol/mL, p < .05, respectively). The morphology of the jejunal mucosa in the GLN group was significant for having greater mucosal weight (23.4 ± 3.1 vs 17.6 ± 2.5 mg/cm), villus height (445 ± 75 vs 357 ± 57 μm), crypt depth (197 ± 34 vs 161 ± 28 μm), and wall thickness (751 ± 77 vs 648 ± 102 μm) than the GLY group (p < .05). In the GLN group, the arterio-portal venous endotoxin difference was less negative (-31 ± 137 vs -480 ± 672 pg/mL), suggesting that the absorption of endotoxin across the gut was partially reversed. We conclude that glutamine supplementation can improve gut metabolism, decrease the extent of mucosal atrophy, and thereby assist in the maintenance of the mucosal barrier function in endotoxemia. (Journal of Parenteral and Enteral Nutrition 18:167-171, 1994)