Effect of dietary protein on hepatic mitochondrial function and cardiac muscle protein turnover in uremic rats

Abstract To define the metabolic consequences of diets low in protein in chronic renal failure, young uremic and sham operated rats were fed isoenergetic diets for three weeks varying in protein content from 22% to 8% casein at the expense of carbohydrate. The results indicate that reducing casein content from 22% (control) to either 16%, 12% or 8% in uremic rats did not result in gross differences in renal function or decreases in liver weight, mitochondrial content or respiration. Atrial muscle protein synthesis was increased 26% while degradation was slightly, but not significantly, decreased in uremic and sham-operated rats fed the 8% casein diet compared to control. In both uremic and sham-operated rats fed the 8% casein diet, serum triiodothyronine (T 3 ) concentrations and hepatic mitochondrial glycerolphosphate (GP) shuttle activity were significantly increased while malate-aspartate shuttle activity was decreased compared to all other diet groups. The increased serum T 3 level and GP shuttle activity produced by feeding the 8% casein diet suggests a diet induced alteration in hepatic mitochondrial intermediary metabolism which may be of benefit in protecting against the potentially serious consequences of lowered thyroid hormone levels in chronic renal insufficiency.