Effect of exogenous cholesterol on plasma lipids and hepatic enzymes in rabbits fed different carbohydrate diets

Abstract

In order to understand the mechanism by which exogenous cholesterol lowers plasma triglycerides in sucrose-fed animals, levels of certain key enzymes in liver, namely glucose: ATP phosphotransferases, pyruvate kinase, glycerokinase, and α-glycerophosphate dehydrogenase activities, were studied along with plasma and hepatic tissue lipids in rabbits fed sucrose and starch diets with and without cholesterol. Four groups of male rabbits (six animals per group) were fed semisynthetic diets containing either high starch or sucrose (69%, w/w) with or without cholesterol for 16 days. Sucrose diet significantly increased the levels of fasting plasma triglycerides and free fatty acids when compared with a starch diet (34 and 48%, respectively, P < 0.05). Cholesterol supplementation significantly lowered both plasma and hepatic levels of triglycerides and free fatty acids by 45 ( P < 0.01) and 46% ( P < 0.01), respectively, only in sucrose-diet-fed animals. As expected, a sucrose diet resulted in marked increase in glucokinase, pyruvate kinase, glycerokinase, and α-glycerophosphate dehydrogenase activities when compared with a starch diet ( P < 0.05). However, among sucrose and starch diets, cholesterol supplementation reduced glucokinase (25%, P < 0.05) and pyruvate kinase (30%, P < 0.05) and increased α-glycerophosphate dehydrogenase (36%, P < 0.01) only when added to sucrose diet. These results suggest that depending upon the nature of the dietary carbohydrate, exogenous cholesterol alters the levels of hepatic enzymes and hepatic and plasma lipid parameters.