Alanyl-glutamine Counteracts the Depletion of Free Glutamine and the Postoperative Decline in Protein Synthesis in Skeletal Muscle

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Abstract
Skeletal muscle protein and amino acid metabolism change after surgical trauma during a period characterized by skeletal muscle protein catabolism. Available total parenteral nutrition (TPN) not containing glutamine does not prevent these changes, while TPN enriched with glutamine has been shown to have beneficial effects on postoperative skeletal muscle protein metabolism. Glutamine, in the form of a dipeptide, alanyl-glutamine, was added to TPN. Patients undergoing elective cholecystectomy were given postoperative TPN. Two groups received isocaloric and isonitrogenous conventional TPN, one group with (n = 8) and the other without an addition of alanyl-glutamine (n = 8). Skeletal muscle protein metabolism was studied in muscle biopsy specimens from which the muscle free amino acid pattern and the concentration and size distribution of ribosomes, serving as a measure of protein synthesis, were determined. In the control group, muscle free glutamine decreased by 38.8% .+-. 6.6% and the polyribosome concentration per mg of DNA decreased by 21% .+-. 5.2% after operation. In the group given TPN supplemented with alanyl-glutamine, these two parameters of muscle protein and amino acid metabolism did not change significantly. Compared to the control group, whole body nitrogen balance was improved after operation by the addition of alanyl-glutamine to TPN (p < 0.01). Muscle free glutamine and muscle protein synthesis were preserved after operation and the whole-body nitrogen balance was improved by adding glutamine in the form of alanyl-glutamine to TPN. The dipeptide alanyl-glutamine seems to be a suitable means of providing glutamine in a stable form.

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