title: Dietary protein level alters oxidative phosphorylation in heart and liver mitochondria of chicks.
abstract: 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:O) 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:O ratios to protein level in hepatic mitochondria showed more dependency on protein level than in heart muscle; at all feeding periods the ADP:O 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:O 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.
authors.affiliation: Department of Animal Science, Kagoshima University, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Toyomizu
authors.forename: D
authors.initials: D
authors.lastname: Kirihara
authors.forename: M
authors.initials: M
authors.lastname: Tanaka
authors.forename: K
authors.initials: K
authors.lastname: Hayashi
authors.forename: Y
authors.initials: Y
authors.lastname: Tomita
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000818:Animals; D001823:Body Composition / Q000502:physiology; D002645:Chickens / Q000378:metabolism*; D004044:Dietary Proteins / Q000378:metabolism*; D008297:Male; D008929:Mitochondria, Heart / Q000378:metabolism*; D008930:Mitochondria, Liver / Q000378:metabolism*; D010085:Oxidative Phosphorylation; D010100:Oxygen / Q000378:metabolism; D013997:Time Factors
chemical_list: D004044:Dietary Proteins; D000244:Adenosine Diphosphate; D010100:Oxygen