Enteral Nutrition and Keratinocyte Growth Factor Regulate Expression of Glutathione‐Related Enzyme Messenger RNAs in Rat Intestine

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Abstract
Background: Malnutrition is associated with increased reactive oxygen species (ROS) formation and depletion of the critical antioxidant glutathione (GSH) in the intestine. The malnutrition‐induced decrease in gut GSH levels is prevented by recombinant keratinocyte growth factor (KGF) administration. We investigated whether enzymes that are induced by oxidants and modulate tissue GSH supply are regulated by enteral nutrients or KGF at the messenger RNA (mRNA) level. Methods: Adult rats were fasted for 3 days alone or fasted for 3 days then refed ad libitum. In a second model, rats were fasted for 3 days and then refed ad libitum or 25% of ad libitum intake with daily intraperitoneal saline or recombinant KGF (5 mg/kg/d) for 3 subsequent days. mRNA levels for γ‐glutamylcysteine synthetase (γ‐GCS), γ‐glutamyl transpeptidase (γ‐GT), glutathione‐S‐transferase Ya‐subunit, gastrointestinal glutathione peroxidase (GI‐GPx), and non‐selenium‐dependent glutathione peroxidase (ns‐GPx) were determined in ileum and colon by ribonuclease protection assay. Results: Fasting increased ileal γ‐GCS, ns‐GPx, and glutathione‐S‐transferase mRNAs (by 36%, 165%, and 130% of controls) and decreased GI‐GPx mRNA (to 55% of controls). In the colon, mRNAs for GSH‐related enzymes were unchanged by fasting or refeeding. Prolonged enteral nutrient restriction (25% refeeding after a 3‐day fast) increased γ‐GCS and glutathione‐S‐transferase mRNAs (by >270% of controls), decreased GI‐GPx mRNA (to 200% of controls). Conclusions: Enteral nutrient intake regulates GSH‐related enzyme mRNA levels in the intestine, which may contribute to the decrease in mucosal GSH during malnutrition. Increased ns‐GPx and glutathione‐S‐transferase mRNA levels during malnutrition and with KGF administration may increase detoxifying functions in the gut under these conditions. (Journal of Parenteral and Enteral Nutrition 24:67–75, 2000)