Short-term enteral glutamine does not enhance protein accretion in burned children: a stable isotope study.

Abstract

Glutamine is a nonessential amino acid that, in recent years, has been found to play important roles in several metabolic and immunologic processes. It has been theorized that, in a stressed state, it may become "conditionally essential" because the patient's ability to manufacture glutamine may not be adequate to meet their needs under this condition. We chose to evaluate the ability of 48 hours of enteral glutamine to enhance immediate nitrogen accretion in stressed pediatric burn patients. Nine children with serious burns who were tolerating tube feedings were enrolled in a human studies committee-approved protocol in which they received 48 hours of enteral feedings with glutamine replacing 20% of essential and nonessential amino acids and 48 hours of isonitrogenous, isocaloric standard enteral feedings. This interval was chosen to help ensure that the study periods were comparable from a metabolic perspective. At the end of each period, protein kinetics were determined by a primed constant infusion of L-[1-(13)C] leucine tracer. The order of the studies was randomized. Seven children completed both phases of the study. Results were compared by paired t test and are presented as mean +/- standard error of the mean. During the glutamine feeding period, the leucine flux and leucine oxidation rate were significantly lower than those in the conventional feeding period. This reflects a reduction in total leucine intake from 80 +/- 11 to 62 +/- 10 micromol/kg per hour. However, there was no significant difference in the net balance of leucine accretion into proteins between these 2 dietary periods, which indicated that enriched glutamine feeding for 48 hours did not result in an immediate whole body protein gain in this group of pediatric patients. In addition, plasma glutamine concentration showed a moderate increase after 48 hours of supplementation but did not reach significance. Rapid protein accretion does not occur with short-term enteral glutamine supplementation. Several days of glutamine supplementation may be required to restore plasma glutamine levels and stimulate protein synthesis.