Protein, amino acid metabolism and therapy: Edited by Erich Roth and Paul B. PencharzEffect of physical activity on glutamine metabolismAgostini, Francesco; Biolo, GianniAuthor Information Department of Medical, Technological and Translational Sciences, Division of Internal Medicine, University of Trieste, Trieste, Italy Correspondence to Gianni Biolo, Department of Medical, Technological and Translational Sciences, Division of Internal Medicine, University of Trieste, Str. di Fiume 447, 34149 Trieste, Italy Tel: +39 040 399 4532; e-mail: [email protected] Current Opinion in Clinical Nutrition and Metabolic Care: January 2010 - Volume 13 - Issue 1 - p 58-64 doi: 10.1097/MCO.0b013e328332f946 Buy Metrics Abstract Purpose of review Glutamine is largely synthesized in skeletal muscles and provides fuel to rapidly dividing cells of the immune system and precursors to gluconeogenesis in the liver. Physical exercise is known to affect glutamine synthesis and to modulate glutamine uptake. Overtraining is frequently associated with reduced availability of glutamine and decreased immunocompetence. Inactivity affects glutamine metabolism, but this subject was poorly investigated. Recent findings Strenuous physical exercise as well as exhaustive training programs lead to glutamine depletion due to lowered synthesis and enhanced uptake by liver and immune cells. Evidence suggests that postexercise glutamine depletion is associated with immunodepression. Counterwise, moderate training leads to improved glutamine availability due to a positive balance between muscle synthesis and peripheral clearance. Physical inactivity, as investigated by experimental bed rest in healthy volunteers, reduced glutamine synthesis and availability. Summary After exercise, a reduced glutamine availability may be considered as a marker of overtraining. An increased glutamine availability may contribute to decreased inflammation and health benefits associated with optimal training. Thus, glutamine supplementation may enhance immunocompetence after strenuous exercise. The potential of glutamine supplementation during physical inactivity needs to be explored. © 2010 Lippincott Williams & Wilkins, Inc.