Comparisons of isonitrogenous supplements (1.2 g N) of essential amino acids and five keto acid analogues with four essential amino acids were made in seven patients with stable chronic renal failure (creatinine clearance, 4.6 to 16 ml/min) on moderately protein-restricted diets (4.60 to 7.8 g N per day). Full nitrogen balance data on the four patients who have already completed studies lasting 24 weeks are presented. No benefits of keto acid over amino acid supplements were observed. Two transient episodes of hypercalcemia occurred during keto acid treatment. There was no improvement of renal function with keto acids. Also, no carry-over effects were seen after keto acid treatment. It is concluded that any beneficial effects of keto acids in patients with chronic renal failure are only likely to occur in those taking a diet of less than 30 g protein daily.

Five patients with chronic renal failure taking a diet containing approximately 5 g N throughout were studied during two periods of 1 month each. Nitrogen balance, urea metabolism, and incorporation of 15N from urea into albumin on diet alone or with a keto acid/essential amino acid supplement were measured. Keto acids produced a reduction of plasma urea, urea synthesis, and urea excretion and an improvement in nitrogen balance. In patients who demonstrated the greatest change on ketoacids, 15N incorporation also increased, but their total incorporation of urea nitrogen was not nearly sufficient to account for the improvement in nitrogen balance. The role of keto acids in protein anabolism is not solely or even mainly explained by promotion of nonprotein nitrogen reutilization.

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