Obesity and the regulation of phosphofructokinase in heart: an apparent insensitivity to adrenergic activation in mature-age genetically obese rats.
The activity ratio of phosphofructokinase in perfused rat heart and its activation by epinephrine was examined in non-obese, fat-fed obese, and genetically obese rats. For non-obese colony rats there was an age-dependent increase in the activity ratio of phosphofructokinase from 0.2 at 40 days to 0.4 at mature age (greater than 200 days). Epinephrine (10 microM) treatment of the heart for 5 min increased the ratio at all ages but the proportional increase diminished with age. For mature-age lean Zucker rats carrying the genetic determinant for obesity the results were similar to those obtained for comparable non-obese colony rats. For fat-fed obese rats the activity ratio of phosphofructokinase at 200 days of age was 0.2 and was increased to 0.6 by epinephrine treatment. For mature-age obese Zucker rats the activity ratio was 0.2 and no significant response to epinephrine occurred. The activity ratio of glycogen phosphorylase and its response to epinephrine (beta-adrenergic receptor mediated) in heart was unaffected by age, diet or the gene for obesity. The present findings indicate a specific defect in the adrenergic regulatory mechanism for phosphofructokinase in genetically obese rats.
D000375:Aging; D000818:Animals; D004040:Dietary Carbohydrates / Q000494:pharmacology; D004041:Dietary Fats / Q000494:pharmacology; D004789:Enzyme Activation; D004837:Epinephrine / Q000502:physiology*; D005260:Female; D008297:Male; D009206:Myocardium / Q000201:enzymology*; D009765:Obesity / Q000201:enzymology* / Q000235:genetics; D010732:Phosphofructokinase-1 / Q000378:metabolism*; D006005:Phosphorylases / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011924:Rats, Zucker; D011943:Receptors, Adrenergic, beta / Q000502:physiology
D004040:Dietary Carbohydrates; D004041:Dietary Fats; D011943:Receptors, Adrenergic, beta; D006005:Phosphorylases; D010732:Phosphofructokinase-1; D004837:Epinephrine