Dietary glutamine enhances cytokine production by murine macrophages

To examine the effects of dietary glutamine on cytokine production by macro phages, mice were fed for 2 wk on a control diet that included 200.0 g case in/kg providing 19.6 g glutamine/kg ora glutamine-enriched diet that provid ed 54.8 g glutamine/kg partly at the expense of casein. There were no diffe rences in weight gain between animals fed the two diets. The plasma concent rations of a number of amino acids differed according to the diet fed; this variation largely reflected the variation in the levels of the different a mino acids in the diets. Plasma glutamine concentration was not significant ly affected by dietary glutamine level. The production of three cytokines, tumor necrosis factor-alpha, interleukin-1 beta, and interleukin-6, was gre ater for lipopolysaccharide-stimulated macrophages from mice fed the glutam ine-enriched diet. Thus, increasing the amount of glutamine in the murine d iet enhances the ability of macrophages to respond to stimulation, at least in terms of cytokine production. These observations suggest that increasin g the availability of glutamine orally could promote immune responses invol ving macrophage-derived cytokines. (C) Elsevier Science Inc. 1999.