Protein synthesis in skeletal muscle of uremic patients: effect of low-protein diet and supplementation with ketoacids.

The purpose of this study was to investigate the modifications of muscle protein synthesis activity in uremic patients fed a low-protein diet and a low-protein diet supplemented with a keto acid-amino acid mixture. The protein synthesis activity was evaluated in vitro on isolated muscle ribosomes incubated in a cell-free medium with tritiated leucine. Simultaneously, nitrogen kinetics and amino acid patterns were examined. Protein synthesis activity is correlated with the protein content of the diet in uremic patients. The keto acid-amino acid supplementation enhances protein synthesis. Variations of protein synthesis can be correlated with the variations of nitrogen balance which implies a major role of protein synthesis activity in muscle protein metabolism. Variations in plasma levels of the essential amino acids, mainly leucine and valine, can be correlated with the variations of protein synthesis activity, and these amino acids seem therefore to be mediators of the dietary effects on protein synthesis in uremia.