Role of glutamine administration on cellular immunity after total parenteral nutrition enriched with glutamine in patients with systemic inflammatory response syndrome

Glutamine is an important substrate for enterocyte and other rapidly proliferating cells. Low plasma and tissue levels present in glutamine in critically ill patients suggest that demand may exceed endogenous supply. Because commercially available amino acid solutions do not contain glutamine because of its instability in aqueous solution, conventional total parenteral nutrition (TPN) does not prevent stress-induced glutamine depletion. In this study, we administered intravenous glutamine-supplemented TPN to patients with systemic inflammatory response syndrome (SIRS) to investigate the effect of glutamine supplementation on immune states. This study is a prospective, randomized clinical trial. All patients received TPN given continuously for 6 days. Thirty patients with SIRS were allocated to either a glutamine group (l-glutamine 0.4g/[kg d]) (n = 15) or a control group (n = 15). Blood samples were collected on day 1 and day 6 after admission for C-reactive protein, immunoglobulin (Ig) M, IgG, IgA, C₃, C4, and lymphocyte analysis. The Acute Physiologic and Chronic Health Evaluation II score and the Simplified Acute Physiologic II (SAPS II) score were used to evaluate the patients after admission. Although there was a tendency for decreased T cytotoxic cells and natural killer cells in the control group, no significant difference was observed between the 2 groups. However, an increase in lymphocyte and lymphocyte subgroups in the glutamine group was observed; but there was no difference between the groups. A low SAPS II score was observed on the sixth day in the glutamine group, whereas no difference in SAPS II and Acute Physiologic and Chronic Health Evaluation II scores was observed between the 2 groups. There was no difference in IgM, IgG, IgA, C₃, and C4 levels and numbers of B-lymphocytes between the groups. Glutamine-added TPN significantly decreases leukocyte and natural killer cell count and therefore suppresses inflammation. Furthermore, total lymphocyte count, B- and T-lymphocytes, and their subgroups (helper T-lymphocytes, cytotoxic T-lymphocytes) are increased; although not statistically significant, these increases might be playing a role in improving the immune system.