Glutamine Enhancement of Structure and Function in Transplanted Small Intestine in the Rat

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Abstract
Total parenteral nutrition is required by all patients in need of small bowel transplantation. Untoward side effects of total parenteral nutrition include atrophy and hypofunction of the small intestine. Glutamine, the preferred fuel for the enterocyte, is presumably present in insufficient amounts in diets given to patients with intestinal dysfunction. In a rat model of total parenteral nutrition and small bowel transplantation, this study investigated the following: (1) whether glutamine improves graft structure and function, (2) the optimal route of glutamine delivery (intravenous vs direct infusion into the graft), and (3) the effect of glutamine on ultrastructure of the graft enterocyte. Lewis rats underwent small bowel transplantation as a Thiry‐Vella graft and received total parenteral nutrition for 14 days while assigned to one of four infusion groups: 2% intravenous glutamine; 2% intravenous isonitrogenous mixture, nonessential amino acids (control); 2% glutamine into the graft; or 2% nonessential amino acids into the graft (control). Graft mucosal villous height, villous surface area, crypt depth, weight, protein, deoxyribonucleic acid content, glucose absorption, and enterocyte ultrastructure were then evaluated. Infusion of glutamine directly into the graft significantly increased mucosal villous height (p =.045), surface area (p =.029), and glucose absorption (p =.004) when compared with controls. Intravenous glutamine infusion significantly increased mucosal villous height (p =.002), surface area (p =.001), weight (p =.005), and glucose absorption (p =.04) when compared with controls. Most enterotrophic and functional benefits of glutamine were not significantly different between intravenous infusions and direct administration into the graft. Intravenous glutamine maintained normal enterocyte ultrastructure of the graft when compared with intravenous combined nonessential amino acids. These results indicate that glutamine supplementation improves structure and function in a rat model of total parenteral nutrition and small bowel transplantation. (Journal of Parenteral and Enteral Nutrition 17:47–55, 1993)