The effect of glutamine administration on intestinal glutamine content

The small intestine has been identified as an important site of metabolism of glutamine. The impairment of gut mucosa integrity during total parenteral nutrition (TPN) has been ascribed to a diminished supply of glutamine, due to the lack of glutamine in standard TPN. In addition, nutritional depletion diminishes glutamine availability in the intestine. The uptake of glutamine in the gut is dependent on the plasma glutamine concentration. This study was performed to observe changes in plasma and mucosa amino acid content during infusion of standard TPN and during infusion of TPN supplemented with glutamine. Twenty patients were randomly allocated to an experimental group (GTPN, TPN containing 0.23 g glutamine/kg.day) and a control group (CTPN, standard TPN). Patients received the iso-nitrogenous and isocaloric TPN during 10-14 days. After an overnight fast, before TPN was started, biopsies were taken from the duodenum. Amino acid concentrations were determined in the biopsies. Blood was taken for routine laboratory measurements and amino acid determination. This procedure was repeated on the last day of TPN infusion. Plasma glutamine in the GTPN group rose about 25% whereas plasma glutamine concentrations in the CTPN group remained unchanged. Mucosa glutamine rose with about 75% in the GTPN group whereas in the CTPN group no increase was observed. The rise of total plasma and mucosa amino acids was equal in both groups. The rise in plasma and mucosa glutamine was limited to nutritionally depleted patients. In conclusion, parenteral glutamine administration increases plasma and subsequently mucosa glutamine, specifically in depleted patients.