The mechanism of dietary cholesterol effects on lipids metabolism in rats

The serum triglyceride and high density lipoprotein cholesterol levels were significantly decreased but the total cholesterol and non high density lipoprotein cholesterol levels were significantly increased in the cholesterol-fed rats compared with the control rats. And the concentrations of the hepatic total cholesterol and triglyceride increased about 4-fold and 20-fold separately by dietary cholesterol. The activities of hepatic malic enzyme, glucose-6-phosphate dehydrogenase, fatty acid synthase, phosphatidate phophatase and carnitine palmitoyl transferase were depressed by the cholesterol feeding (40%, 70%, 50%, 15% and 25% respectively). The results of mRNA expression showed that fatty acid synthase, carnitine palmitoyl transferase 1, carnitine palmitoyl transferase 2, and HMG-CoA reductase were down-regulated (35%, 30%, 50% and 25% respectively) and acyl-CoA: cholesterol acyltransferase and cholesterol 7α-hydroxylase were up regulated (1.6 and 6.5 folds) in liver by the cholesterol administration.The dietary cholesterol increased the triglyceride accumulation in liver, but did not stimulate the activity and the gene expression of hepatic enzymes related to triglyceride and fatty acid biosynthesis.The high dietary cholesterol was concerned with the increasing concentrations of serum and hepatic total cholesterol(TC), especially the level of very low density lipoprotein (VLDL) and low density lipoprotein (LDL) in serum, which is considered to be a primary risk factor of cardiovascular disease. Hypercholesterolemia rat model is represented for cardiovascular and cerebrovascular disease research, which can be established by feeding with 0.5%-1.0% cholesterol-supplement diet for several weeks. Dietary 0.5%-1.0% cholesterol can increase serum VLDL and LDL levels dramatically in rats. In this case, dietary cholesterol remarkably disturbed triglyceride (TG) metabolism, the hepatic TG content increased in folds until hepatic steatosis forms. Thereby, it has been devel