Effect of glutamine supplementation on protein metabolism and glutathione in tumor-bearing rats.
The effect of glutamine (GLN)-supplemented total parenteral nutrition (TPN) on tumor growth and protein metabolism was investigated in tumor-bearing rats. Six days after implantation of AH109A hepatoma, rats received isonitrogenous TPN without or with alanyl-glutamine (25% of total N) for a period of 6 days. Protein turnover was assessed by continuous infusion of l4C-leucine and levels of GLN and glutathione were determined in muscle, jejunum and liver. Diet had no effect on tumor parameters: weight (mean = 4.4 g), GLN and glutathione concentrations, protein synthesis rate and bromodeoxyuridine-labeling index. Body weight loss was less pronounced in the GLN group (-5.5 +/- 1.2 vs. -9.4 +/- 1.4 g/5d). Decrease in plasma and muscle GLN concentrations (-30% and -17% vs. healthy controls, respectively) was limited in tumor-bearing rats receiving GLN-enriched TPN (-15% and +3%). GLN-supplemented TPN increased muscle and jejunum fractional synthesis rates (36% and 25% vs. standard TPN, respectively) and reduced body protein breakdown in tumor-bearing animals (303 +/- 33 vs. 421 +/- 66 mumol Leu/Kg/h). Decrease in jejunum glutathione levels was partially abolished in the GLN group: -50% vs. -64% in the standard TPN group; no effect was noticed in other tissues. The authors conclude that GLN-supplemented TPN improves protein metabolism at both the whole body and the tissue level, and prevents GLN and glutathione deficiencies associated with tumor implantation.
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Laboratoire de Biochimie A, Hôpital Saint-Louis1, Avenue Claude Vellefaux, 75010 Paris, France.