Abstract
This study was designed to investigate the effects of a fat- and cholesterol-enriched diet on gene expression related to cholesterol metabolism in rats. Rats were fed a cholesterol-free diet with 50 g/kg corn oil or a fat- and cholesterol-enriched diet containing 5 g/kg cholesterol and 100 g/kg palm oil for 2 weeks. There were no significant differences in food intake, final body weight and liver weight among the groups. The serum total cholesterol and very low-density lipoprotein + intermediate-density lipoprotein + LDL-cholesterol concentrations in the cholesterol-free diet group were significantly lower than those in the fat- and cholesterol-enriched diet group throughout the experimental period. The serum HDL-cholesterol concentration in the fat- and cholesterol-enriched diet group was significantly lower than that in the cholesterol-free diet at week 1, but there was no significant difference between the groups at week 2. There was no significant difference in the serum triglyceride concentration between the groups throughout the experimental period. The hepatic ADD1/SREBP-1c (adipocyte determination differentiation-dependent factor 1/ sterol regulatory element binding protein), PPARγ (peroxisome proliferator-activated receptor), LDL receptor, scavenger receptor class B type 1, and HMG-CoA reductase mRNA levels in the fat- and cholesterol-enriched diet group were significantly lower that those in the cholesterol-free diet group. However, there were no significant differences in the hepatic fatty acid synthase and cholesterol 7α-hydroxylase mRNA levels between the groups. The results of this study demonstrate that ADD1/SREBP-1c and PPARγ are regulated by food fat in the rat liver and that the decline in nuclear ADD1/SREBP-1c and PPARγ upon feeding the fat- and cholesterol-enriched diet may in part explain the decrease in mRNAs encoding enzymes of the cholesterol biosynthetic pathway.
