Effects of glutamine-supplemented total parenteral nutrition on cytokine production and T cell population in septic rats

Background: This study was designed to investigate the effects of total parenteral nutrition (TPN) enriched with glutamine (GLN) on in vivo cytokine production and cellular immune response in early and late septic stages of rats. Methods: Male Wistar rats were divided into 2 experimental groups and received TPN solution at an energy level of 270 kcal/kg body weight. The TPN solutions were isonitrogenous and identical in nutrients composition except for differences in amino acid content. One group received 2% GLN, whereas the other group received glycine (Gly) instead. TPN was maintained for 5 or 6 days according to the sacrifice schedule of the rats. On day 5, sepsis was induced by cecal ligation and puncture (CLP). Respective groups of rats were sacrificed 2, 4, 6, and 24 hours after CLP. Results: Sepsis resulted in a negative nitrogen balance in both groups, and nitrogen loss was significantly lower in the GLN than the Gly group. Interleukin (IL)-2 and interferon (IFN)-γ in most of the samples collected at various time points were not detectable in plasma or peritoneal lavage fluid. No differences in plasma IL-6 and TNF-α concentrations were observed between the GLN and Gly groups. Also, there were no significant differences in IL-1β, IL-6, and TNF-α concentrations in peritoneal lavage fluid between the 2 groups at various time points. The CD4+/CD8+ ratio was significantly higher in the GLN group than in the Gly group only at 4 hours after CLP, and no difference was observed at 24 hours after CLP. Conclusions: TPN preinfused with a GLN-supplemented solution had a beneficial effect in ameliorating the extent of negative nitrogen balance in septic rats. However, parenterally administered GLN did not reduce the production of inflammatory mediators systemically or at the site of injury, and the influence on enhancing cellular immunity was not obvious.