Dietary Protein Level and Uric Acid Metabolism in Normal Man ,

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Abstract
The influence of different dietary levels of protein and yeast ribonucleic acid (RNA) on uric acid metabolism was studied in six healthy young men living in a metabolic unit for 60 days. Four liquid formula diets provided daily 0.9, 13 and 62 g nitrogen or 13 g nitrogen plus 4 g RNA. Urinary excretion of urea, uric acid, alpha amino nitrogen and ammonia varied directly with protein intake but the percentage contribution of individual compounds to total nitrogen excretion differed at each dietary nitrogen level. The high protein and RNA diets produced identical urinary uric acid excretion but only RNA increased serum urate levels. The miscible pool size and turnover rate of uric acid with different dietary treatments were determined with the aid of isotopic (15N-labeled) uric acid. The increased uric acid excretion with the high protein diet was the result of a two-fold increase in uric acid turnover rate without alteration of urate pool size, whereas a similarly increased uric acid excretion with RNA feeding was the result of a very slight increase in turnover rate and a 100% expansion of miscible pool size. The role of dietary changes in altering uric acid production and excretion is discussed with respect to postulated feedback controls on purine metabolism.