Health Questions and Answers

Question: What is the role of glutamine in the immune system?

Answer:

Glutamine is a unique amino acid. It has at least two distinct functions in the body, both of which are important for the immune system. First, it is a preferred energy source for rapidly proliferating cells. It supplies nearly as much adenosine triphosphate (ATP) as glucose when metabolized completely and is preferred to glucose in such tissues as the gut mucosa. It helps to maintain bowel mucosal integrity and prevent atrophy. The functional result is that translocation of bacteria from the bowel to the tissues and vessels is lessened or prevented. The gut mucosal barrier is one of the body’s “outer wall” defenses against infection. If glutamine is not provided to the gut mucosa, then the barrier begins to fail and the internal components of the immune system must deal with bacterial invasion of the portal circulation. While the normal route of glutamine into the mucosa cells is through the intestinal lumen, glutamine is also taken up by the mucosa if given intravenously. It appears likely that intravenous glutamine is sufficient to maintain the gut mucosal barrier.

Second, glutamine is a nitrogen donor in protein, purine, and pyrimidine synthesis. It seems to be essential for cellular replication. It acts as a “nitrogen carrier” between cells. It is a precursor to the synthesis of DNA and RNA. The need for glutamine is particularly acute when metabolism is increased, as in surgical stress, sepsis, injury and burns. This is especially true in the immune system, with its high level of protein synthesis and its rapid cellular turn-over.

Increasing evidence suggests that glutamine is a crucial substrate for cells of the immune system. Glutamine depletion in lymphocytes prevents late activation. Glutamine deprivation in monocytes lowers surface antigens responsible for phagocytosis. Clinical studies demonstrated lower nitrogen losses, fewer infections, and shorter hospital stays in bone marrow transplantation patients who were supplemented with glutamine. The use of glutamine appeared to lower the mortality rate.

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