The Role of Dietary Supplementation with L-Glutamine in Inflammatory Mediator Release and Intestinal Injury in Hypoxia/Reoxygenation-Induced Experimental Necrotizing Enterocolitis

Abstract

Background/Aims: Necrotizing enterocolitis (NEC) is a multifactorial syndrome in the neonate. Enteral feeding practices are an important component of gastrointestinal injury in neonatal NEC. In the present study, we examined the protective effect of oral supplementation with L-glutamine, an important specific fuel for the enterocytes, against hypoxia-reoxygenation (H/R)-induced NEC in young mice. Methods: Young mice were divided into four groups: group 1 mice (untreated) underwent H/R; group 2 mice were supplemented with L-glutamine in drinking water (0.5 g/dl) for 3 days, and group 3 mice were supplemented with L-glutamine (3 g/dl) for 10 days. Group 4 mice served as control. Hypoxia was induced by placing the young mice in a 100% CO₂ chamber for 5 min. After hypoxia, they were reoxygenated for 10 min with 100% oxygen. We examined the intestinal lesions with light microscopy and measured intestinal generation of PAF and TNF-α in the H/R-induced model of NEC. Results: In group 3 mice, NEC-induced intestinal tissue damage was greatly attenuated with necrosis limited partially to the mucosa. Both intestinal tissue PAF and TNF-α concentrations were significantly higher in the untreated group than in controls (p < 0.001). Group 3 mice (3 g/dl supplemented) showed a significant decrease in intestinal TNF-α concentration compared with young group 1 and group 2 mice (p < 0.05 and p < 0.05, respectively). On the other hand, no significant difference was observed in the intestinal generation of PAF between H/R groups (p > 0.05). Conclusion: The present study suggests that H/R plays an important role in the pathogenesis of NEC and supports the hypothesis that especially PAF and TNF-α are involved in the pathophysiological mechanism of H/R-induced NEC. This study also demonstrates that dietary supplementation with L-glutamine reduces the histologic evidence of H/R-induced intestinal injury. Based on these findings, beneficial effects of L-glutamine in this model of NEC are mediated via mechanisms inhibiting intestinal cytokine release.