Enteral glutamine feeding and some aspects of immune function in intensive care patients

Glutamine-enriched total parenteral nutrition (TPN) is beneficial in reducing both infective complications and mortality of critically ill patients. Similar results were observed in bone marrow transplant patients, as well as increased circulating numbers of lymphocytes, in particular T-cell subsets. An increase was observed in T-cell DNA synthesis in colorectal cancer patients receiving glutamine-enriched TPN. However, TPN is associated with complications such as intestinal atrophy, and enteral nutrition is now the preferred route.

The present study assessed the effects of feeding glutamine enterally in 14 intensive care patients who were not immunosuppressed. Blood samples were analysed for plasma glutamine concentration (enzymatically), lymphocyte proliferation via ³H thymidine incorporation into DNA (counts per minute — CPM) with and without mitogenic stimulation (Concanavalin-A), neutrophil activity (using an oxidative burst technique) and cytokine production in culture medium (IL-2 and IL-8). Patients were randomly divided into two groups and fed 15-g bolus doses in water of either glutamine (n = 7; 60 ± 8 years) or placebo (n = 7; 60 ± 6 years) for 5 days. Nasogastric nutrition was discontinued daily at midday and a blood sample was taken; 1 hour later, a bolus dose of glutamine/placebo was administered via the tube; 2 hours later total nutrition was started again.

Lymphocyte proliferation increased in the glutamine group (P < 0.04) compared with the placebo, as measured by CPM and the stimulation index. IL-2 production increased in culture medium from Day 0 to Day 5 for patients receiving glutamine (P < 0.02) compared with the placebo group. IL-8 production, neutrophil numbers or activity, and plasma glutamine did not change. Our results suggest that glutamine is able to induce an IL-2 mediated increase in the proliferative ability of T-cells, and we hypothesise that these changes may underlie previously observed clinical benefits from glutamine administration in critically ill patients.