ADAPTIVE RESPONSES TO VERY-LOW PROTEIN DIETS - THE FIRST COMPARISON OF KETOACIDS TO ESSENTIAL AMINO-ACIDS

Eight patients with chronic renal failure (GFR 18.8 +/- 2.7 ml/min) we re randomized to a crossover comparison of a very low protein diet (VL PD) containing 0.28 g protein and 35 kcal per kg per day, plus an isom olar mixture of either ketoacids (KA) or essential amino acids (EAA). Subjects initiated the diets 14 days before hospital admission and fol lowing a four-day equilibration, a five-day nitrogen balance (BN) was performed. Whole-body protein turnover (WBPT) was measured during fast ing and feeding using intravenous [1-C-13]leucine and intragastric [5, 5,5-H-2(3)]leucine. Even though the VLPD/KA regimen contained 15% less nitrogen, B-N was neutral and did not differ between the regimens. Ni trogen conservation with KA was due to a reduction in urea nitrogen ap pearance. Rates of WBPT measured during fasting and feeding did not di ffer between the KA or EAA regimens. During both regimens, feeding dec reased protein degradation, whereas protein synthesis was unchanged. A lthough feeding stimulated leucine oxidation, rates were 50 to 100% lo wer than reported in CRF patients consuming 0.6 or 1.0 g protein/kg/da y. Thus, neutral B-N with the VLPD regimen is achieved by a marked red uction in amino acid oxidation and a postprandial inhibition of protei n degradation.