Metabolic effects of glutamine on insulin sensitivity

Glutamine, the most abundant free amino acid in human plasma, has outstanding nutritional and non-nutritional properties. Glutamine regulates immune function and modulates cell metabolism. In particular, its administration showed a positive effect on glucose oxidation and on insulin resistance in different experimental and clinical studies. In humans, glutamine acts as both a substrate and modulator of its metabolism to glucose. In trauma patients and in critical illness, parenteral glutamine supplementation improved insulin sensitivity and enhanced the release of insulin by pancreatic β-cells. In a recent clinical study, also, oral L-glutamine supplementation ameliorated the glucose profile in obese patients and those with type 2 diabetes. The mechanisms underlying these specific effects are still unknown. Further clinical trials investigating the role of glutamine on glucose/insulin metabolism are needed. Several diseases, such as obesity and diabetes, may receive important benefits from glutamine supplementation, possibly in association with conventional therapy. (Nutritional Therapy & Metabolism 2010; 28: 7-11)