Shift of metabolism in rats with ventromedial hypothalamic lesions with respect to changes in daily rhythms of enzyme activity.
Metabolic alterations in ventromedial hypothalamus (VMH)-lesioned rats were investigated by examining daily changes of enzyme activities and urea concentrations three weeks after the operation. VMH-lesions in female adult rats caused a significant elevation in the activity of acetyl-CoA carboxylase in the liver and parametrial adipose tissue. These changes suggest an increased lipogenesis. VMH-lesions also elicited an increase in activities of glucokinase (GK), pyruvate kinase (PK) and fructose 1,6-bisphosphatase (FBPase), and a decrease in activities of phosphofructokinase (PFK), glucose-6-phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase (PEPCK) in the liver. The apparently inconsistent changes in activities of key glycolytic enzymes, GK, PK and PFK, and key gluconeogenic enzymes, G6Pase, PEPCK and FBPase in the liver may be explained by the fact that they were favorable for glucose oxidation through pentose phosphate cycle and provide NADPH for lipogenesis in the liver. Furthermore, VMH-lesions induced an increase in urea contents of the liver and serum, and elicited an increase in activity of liver tyrosine aminotransferase (TAT) and a decrease in activity of liver histidase. These changes suggest an accelerated amino acid and protein catabolism, and favor an increment in the supply of the substrate for lipogenesis. Daily rhythms of TAT, histidase activities and serum urea concentration observed in the control rats were abolished by VMH-lesions. These findings suggest that VMH-lesions elicit the loss of these daily rhythms, probably through the disturbance of the circadian rhythm of feeding behavior at this dynamic phase (three weeks after operation) of obesity.
D000103:Acetyl-CoA Carboxylase / Q000378:metabolism; D000273:Adipose Tissue / Q000201:enzymology / Q000473:pathology; D000818:Animals; D001835:Body Weight; D002940:Circadian Rhythm; D005260:Female; D005943:Gluconeogenesis; D005954:Glucosephosphate Dehydrogenase / Q000378:metabolism; D006019:Glycolysis; D006638:Histidine Ammonia-Lyase / Q000378:metabolism; D007027:Hypothalamic Diseases / Q000378:metabolism*; D007033:Hypothalamus, Middle / Q000378:metabolism; D007668:Kidney / Q000473:pathology; D008099:Liver / Q000201:enzymology / Q000473:pathology; D051381:Rats; D011919:Rats, Inbred Strains; D014444:Tyrosine Transaminase / Q000378:metabolism; D014508:Urea / Q000378:metabolism
D014508:Urea; D005954:Glucosephosphate Dehydrogenase; D014444:Tyrosine Transaminase; D006638:Histidine Ammonia-Lyase; D000103:Acetyl-CoA Carboxylase