Effects of parenteral nutrition supplemented with glutamine or glutamine dipeptides on liver antioxidant and detoxication systems in rats

Our aim was to determine the effects of glutamine or alanyl glutamine paren teral supplementation on the liver oxidant/antioxidant balance and on cytoc hrome-P450-mediated detoxication in rats. Animals were infused for 5 d with standard total parenteral nutrition (TPN), glutamine-enriched TPN, or alan yl glutamine-enriched TPN. The hepatic concentration of glutathione was red uced, and the levels of thiobarbituric-acid-reactive substances (TBARS) wer e increased in animals receiving standard TPN. Both glutamine and alanyl gl utamine supplementation normalized glutathione, but thiobarbituric-acid-rea ctive substance concentration was only decreased by alanyl glutamine. This effect was parallel to a partial recovery of the activity of antioxidant en zymes. Cytochrome-P450 Liver content, cytochrome-P450-dependent monooxygena ses, and antipyrine clearance were not modified by glutamine or alanyl glut amine. Our data suggest a better protection against free radicals by alanyl glutamine supplementation and an absence of effects of both glutamine and alanyl glutamine on liver oxidative metabolism. Nutrition 2000;16:125-128. (C) Elsevier Science Inc. 2000.