Glutamine-enriched total parenteral nutrition maintains intestinal interleukin-4 and mucosal immunoglobulin A levels

Background: Total parenteral nutrition (TPN) prevents progressive malnutrit ion but fails to maintain intestinal gut-associated lymphoid tissue (GALT) or established respiratory antiviral or antibacterial mucosal immunity. Our previous work demonstrated that decreases in intestinal immunoglobulin A ( IgA) were associated with decreases in Th2-type IgA-stimulating cytokines, interleukin (IL)-4 and IL-10. Because glutamine supplementation of TPN part ially preserves respiratory defenses and normalizes GALT, we investigated t he ability of parenteral glutamine to normalize respiratory and intestinal IgA levels and measured Th2 cytokines in intestinal homogenates. Methods: A nimals were cannulated and randomly assigned to receive chow (n = 17), TPN (n = 18), or an isonitrogenous, isocaloric TPN solution formulated by remov ing the appropriate amount of amino acids and replacing them with 2% glutam ine (n = 18) for 5 days. Respiratory tract and intestinal washings were obt ained for IgA and the intestine homogenized and analyzed for IL-4 and IL-10 . Results: TPN decreased intestinal and respiratory IgA in association with decreases in intestinal IL-4 and IL-10 compared with chow-fed animals. Glu tamine significantly improved respiratory and intestinal IgA levels, signif icantly improved IL-4 compared with TPN animals, and maintained IL-10 level s midway between chow-fed and TPN animals. Conclusions: Glutamine-enriched TPN preserved both extraintestinal and intestinal IgA levels and had a norm alizing effect on Th2-type IgA-stimulating cytokines.