Glutamine Protects GI Epithelial Tight Junctions
l-Glutamine is the most abundant amino acid in blood stream accounting for 30–35 % of the amino acid nitrogen in plasma. It was classified as a non-essential amino acid because it can be readily synthesized in the body from glutamate by glutamine synthetase, which is expressed at high levels in skeletal muscle, liver, brain and stomach tissue. Intracellular concentration of l-glutamine ranges from 2 to 20 mM, and its concentration in the extracellular fluid varies from 0.5 to 0.8 mM. Under conditions of extreme physical exertion, trauma and severe infections, the rate of utilization of glutamine is more than its rate of synthesis, resulting in a significant decline in plasma glutamine concentration. Glutamine is an essential fuel for the gastrointestinal tract. It is required for the synthesis of proteins, nucleic acids and antioxidants, such as glutathione, and involved in the maintenance of acid–base balance with the release of ammonia during its metabolism. Under conditions of reduced plasma glutamine concentration, body depends on the exogenous glutamine to meet its requirements. Therefore, l-glutamine now is reclassified as a conditionally essential amino acid.
KeywordsGlutamine Intestine Barrier function Epithelium Tight junction Burn injury Total parenteral nutrition Enteral nutrition Endotoxemia Bacterial translocation
Preparation of this article and some of the studies discussed in it are supported by the National Institutes of Health grants: DK55532 and AA12307.
- 6.Tannuri U, Carrazza FR, Iriya K. The effects of glutamine-supplemented diet on the intestinal mucosa of the malnourished growing rat. Rev Hosp Clin Fac Med (SP). 2000;55(3):87–92.Google Scholar
- 14.Nakamura E, Hagen S. Role of glutamine and arginase in protection against ammonia-induced cell death in gastric epithelial cells. Am J Physiol Gastrointest Liver Physiol. 2002;283(6):75.Google Scholar