Influence of Dietary Cholesterol and Cholic Acid on Liver Carbohydrate Metabolism Enzymes in Rats

Abstract

The effects of dietary cholesterol and cholic acid on the activity of several carbohydrate metabolism enzymes were examined in the liver or adipose tissue of rats. The activity of liver and adipose tissue glucose-6-phosphate dehydrogenase and NADP-malic enzyme, the activity of liver glucokinase, pyruvate kinase, phosphoglucomutase and NADP-isocitrate dehydrogenase and the rate of in vitro liver cholesterogenesis were determined. Cholesterol-cholic acid feeding significantly depressed the activity of glucose-6-phosphate dehydrogenase and NADP-malic enzyme in the liver but not in the adipose tissue. Liver glucokinase was also depressed, but to a lesser degree. Liver pyruvate kinase was depressed only during the first few days of the feeding. The depression in the activity of these enzymes was inversely correlated with an increase in the concentration of liver cholesterol. Unlike liver enzymes which were depressed only after 2 to 3 days of cholesterol-cholic acid feeding, liver cholesterogenesis was severely depressed within the first day of the feeding. These observations suggest that liver enzyme depression is probably related to certain metabolic changes secondary to elevation of liver cholesterol or expansion of bile acid pool. Feeding of cholic acid has effects on liver enzymes similar to the feeding of cholesterol. The study shows that dietary cholesterol plays a role in the control of several hepatic carbohydrate metabolism enzymes probably through some mechanism secondary to elevation in the concentration of liver cholesterol or expansion of bile acid pool.