Glutamine: An essential amino acid for the gut
Glutamine is the most abundant free amino acid in the circulation. It is a primary fuel for rapidly dividing cells and plays a key role in the transport of nitrogen between organs. Although glutamine is absent from conventional regimens aimed at nutritional support, glutamine deficiency can occur during periods of metabolic stress; this has led to the reclassification of glutamine as a conditionally essential amino acid. Experiments with various animal models have demonstrated that the provision of glutamine can result in better nitrogen homoeostasis, with conservation of skeletal muscle. There is also considerable evidence that glutamine can enhance the barrier function of the gut. This review concludes by discussing the clinical evidence that supports the inclusion of stable forms of glutamine in solutions of nutrients(1).
Glutamine is a non-essential amino acid which is produced in sufficient amount by the healthy human body. From experimental work it is known that glutamine is an important nutrient for rapidly dividing cells such as cells from the immune system and the gut. During several conditions a lack of glutamine may occur. This will result in functional disturbances of the immune system and/or the gut. Glutamine is produced mainly by the muscle tissue.
A decrease in muscle mass during nutritional depletion may result in decreased glutamine production capacity. Furthermore during critical illness, there is an increased demand for glutamine probably as a result of an increased utilisation by the immune system. In addition, patients receiving standard parenteral nutrition do not receive glutamine, until recently, commercial parenteral nutrition did not contain glutamine because of instability of this amino acid during prolonged storage.
One of the important functions of the gut is to prevent migration of bacteria and/or toxins from the gut lumen into the systemic circulation. A lack of glutamine may result in deterioration of this intestinal barrier. Supplementation of glutamine to certain patients could be essential. The relation between glutamine and the gut in several situations (nutritional depletion, critical illness, parenteral nutrition) is discussed in this paper(2).
1. Hall, J.C., K., Heel, and R., McCauley. (1996). Glutamine. British Journal of Surgery, vol. 83, sup. 3, pp. 305 – 312.
2. Van der Hulst, R.R., M.F., von Meyenfeldt and P.B., Soeters. (1996). Glutamine: an essential amino acid for the gut. Nutrition, vol. 12, sup. 11-12, pp. S78-81.