Portal de Periódicos da CAPES

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

1973; Elsevier BV; Volume: 103; Issue: 1 Linguagem: Inglês

10.1093/jn/103.1.93

1541-6100

Alan C. Tsai, I. A. Dyer,

Pancreatic function and diabetes

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, phosphogluco- mutase and NADP-isocitrate dehydrogenase and the rate of in vitro liver cholestero- genesis 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 metabo lism enzymes probably through some mechanism secondary to elevation in the concen tration of liver cholesterol or expansion of bile acid pool. J. Nutr. 103: 93-101, 1973. Dietary cholesterol and cholic acid sup- gested carbohydrates or the processes of plementation has been shown to depress hpogenesis. In this study, experiments were the activity of liver glucokinase, glucose-6- conducted to examine the response of cer- phosphate dehydrogenase and NADP-malic tain liver enzymes following cholesterol and enzyme in rats ( 1). Glucokinase is an im- cholic acid feeding, portant enzyme for the phosphorylation of glucose in the liver and this reaction prob- METHOD, ably is the primary rate-limiting step in the Experimental diet and animals. Rats of utilization of glucose (2-5). In the rat, the the Holtzman strain were used for all ex- activity of this enzyme has been shown to periments in this study. Rats were indi- be correlated with glucose tolerance (6). vidually housed in stainless steel cages at a Glucose-6-phosphate dehydrogenase and constant room temperature of 24°.Food NADP-malic enzyme are important in pro- and water were provided for ad libitum viding reduced nicotinamide adenine di- consumption in all experiments. Individual nucleotide phosphate (NADPH) for lipo- body weight and food consumption were genesis (7-10). The activity of these two recorded. The basal diet contained 25% enzymes is correlated with the rate of lipo- Received for pllbucation June 12.1972.