It is clear that Glutamine (GLN) controls the proliferative effects of immunologic tissue and also enhances function. These effects are concentration dependent. Higher concentrations will initiate greater or more balanced immune responses, and these responses will presumably be translated into improved outcome. GLN will also enhance bowel mucosal proliferation and thereby repair intestinal mucosal defects and maintain bowel barrier function. Because the role of the bowel as the vector for infection following critical illness is unknown in human disease, this specific contribution to overall host defense is only speculative at this time.
However, the positive effects observed in premature infants with an immature intestinal tract and the bone marrow transplant patients following chemotherapy and total body irradiation suggests that this benefit may enhance recovery in selected patient groups. GLN stimulates growth hormone elaboration, and this hormone can effectively upregulate the immune system, through direct and indirect effects, the latter occurring because of receptor homologies with interleukin-2. The support of glutathione synthesis by GLN is another example of how this amino acid participates in protection of the host, in this case through the maintenance of the antioxidant system.
The contributions of GLN to protein anabolism and through acid-base homeostasis must contribute to the defense of the host, but the specific role of these functions to the host defense have not been quantitated. A wide variety of effects can be observed following GLN administration. Patients will greatly benefit as we learn to prevent GLN deficiency through the provision of this important nutrient.
Wilmore, D.W. and J.K. Shabert. (1998). Role of Glutamine in Immunologic Responses. Nutrition, vol. 14, no. 7/8, pp. 618 – 626.