Alanyl-glutamine-supplemented parenteral nutrition increases luminal mucus gel and decreases permeability in the rat small intestine

Background: Effect of supplemental alanyl-glutamine in standard TPN (S-TPN) on luminal mucus gel and small intestinal permeability was investigated. Methods: Thirty Sprague-Dawley rats were divided into group I (n = 10), receiving standard rat diet; group II (n = 10), receiving S-TPN; and group III (n = 10), receiving alanyl-glutamine-supplemented TPN for 1 week. After 1 week, fluorescein isothiocyanate (FITC)-dextran was injected into the small intestine of the rats, and they were killed. A small intestinal sample and portal blood were obtained for morphologic and functional analysis of mucus gel and intestinal permeability. Results: In group II, thickness and optical density of mucus gel per millimeter serosal length of intestine were significantly lower than group I (p < .001) and were significantly higher in group III than in group II (p < .001). The number of goblet cells in the villi and in the crypt of the small intestine was significantly lower in group II than in group I (p < .001) and was significantly higher in group III than in group II (p < .001), with the exception of the villi of jejunum. Villous and crypt surface area per millimeter serosal length of intestine was significantly lower in group II than in group I (p < .001) and was significantly higher in group III than in group II (p < .001). Small intestinal permeability to FITC-dextran was significantly higher in group TT than in group I (p < .001) and was significantly lower in group III than in group II (p < .001). Glucosamine synthetase level was significantly higher in group III than in group I and ileum of group II (p < .001). Conclusions: Alanyl-glutamine-supplemented TPN prevents a decrease in mucus gel and an increase in small intestinal permeability associated with S-TPN.