To determine the effects of dietary protein level on cardiac and hepatic mitochondrial’ oxidative phosphorylation, chicks were fed on semi-purified diets of different protein levels (7, 25, 43 and 61 % of metabolizable energy content) for 7, 14 and 21 d. All diets were formulated to contain equivalent fat, mineral and vitamin contents on a gross energy basis. Cardiac and hepatic mitochondrial oxidative phosphorylation rates were assessed polarographically with pyruvate and malate as substrates. Cardiac mitochondria isolated from chicks fed on a 43 or 61 % protein-energy diet for 7 d exhibited significantly reduced ADP:oxygen (ADP:0) ratios when compared with mitochondria isolated from chicks fed on a lower-protein-energy diet. Feeding low- (7%) protein-energy diets for 14 d resulted in a relatively increased ADP: O ratio in the heart. Responses of ADP:0 ratios to protein level in hepatic mitochondria showed more dependency on protein level than in heart muscle; at all feeding periods the ADP:0 ratio decreased with an increase in protein level. As a result, ATP synthesized in the liver, expressed as nmol/mg mitochondrial protein per min, significantly decreased with increased dietary protein level. A parallel correlation was observed, in chicks fed on diets with different levels of protein, between ADP:0 ratio for liver mitochondria and body fat. These results suggest that the reduction in oxidative phosphorylation in the heart and liver of animals fed on a higher protein-energy diet may partly contribute to the depression of body fat.
- Dietary protein
- Oxidative phosphorylation: Liver and heart mitochondria: Body fat: Chicken
ASJC Scopus subject areas
- Medicine (miscellaneous)
- Nutrition and Dietetics