Nutrition and chronic renal failure in rats: What if is an optimal dietaryprotein?

In chronic uremia (CRF), malnutrition is an important determinant of morbid ity in adults and impaired growth in children. Causes of malnutrition inclu de anorexia and abnormal protein and amino acid metabolism. To determine ho w different levels of dietary protein and CRF interact to influence growth and nutritional status, CRF and sham-operated, pair-fed control rats were f ed isocaloric diets containing 8, 17, or 30% protein for 21 d to mimic diet ary regimens recommended for CRF patients: the minimum daily requirement; t he recommended daily allowance; or an excess of dietary protein. Serum crea tinine did not differ between groups of CRF rats but blood urea nitrogen wa s lowest in CRF rats fed 8% protein (P < 0.001). CRF rats eating 30% protei n gained less weight and length compared to their controls or CRF rats fed 8 or 17% protein (P < 0.05); they also had acidemia. CRF rats fed 8% protei n had the highest efficiency of utilization of protein for growth, while 17 % protein promoted the highest efficiency of utilization of food and calori es for growth. Notably, CRF rats eating 30% protein had the lowest protein efficiency; their calorie intake was also the lowest because of anorexia. P lasma branched-chain amino acids were progressively higher in control rats eating 8, 17, or 30% protein. CRF rats fed 8 or 17% protein had lower branc hed-chain amino acid concentrations compared with CRF rats fed 30% protein. In CRF, it is concluded that excessive dietary protein impairs growth but a law-protein diet does not impair nutritional responses and permits utiliz ation of protein for growth if calories are sufficient.