ABSTRACT
Glutamine is recognized as a crucial and versatile amino acid for cell survival and growth, playing an important role in metabolism. This chapter discusses the mechanisms underlying the diverse actions of glutamine. Glutamine is considered as a "fuel for the immune system", and a low concentration may impact on defense mechanisms, resulting in poor clinical outcomes and increased risk of mortality. Glutamine is clearly an important metabolic substrate of rapidly proliferating cells and has multiple effects on the immune system, on intestinal function, and on protein metabolism. Lymphocytes, macrophages, and neutrophils play crucial roles in the immune and inflammatory responses. Crucial experiments performed at the University of Oxford demonstrated the unique roles and properties of glutamine with respect to immune cell metabolism and function. Subsequent studies revealed that glutamine deficiency increased the mortality of animals subjected to bacterial stress. In critically ill patients, parenteral glutamine reduced both nitrogen loss and mortality.
