Investigation of gene expressions related to cholesterol metabolism in rats fed diets enriched in n-6 or n-3 fatty acid with a cholesterol after long-term feeding using quantitative-competitive RT-PCR analysis

We have developed a method to quantitate hepatic apolipoprotein (apo) B, LD L receptor, 3-hyddroxy-3-methylglutary coenzyme A reductase (HMG-CoA reduct ase) and cholesterol 7 alpha -hydroxylase mRNA expression in rats fed a cho lesterol-enriched diet after long-term feeding using competitive RT-RCR. Ra ts (8 wk of age) fed a conventional diet were shifted to diets containing 1 0%, perilla oil (PEO, oleic acid + linoleic acid + alpha -linolenic acid), borage oil (BRO, oleic acid + linoleic acid + gamma -linolenic acid), eveni ng primrose oil (EPO, linoleic acid + gamma -linolenic acid), mixed oil (MI O, oleic acid+linoleic acid+ gamma -linolenic acid+ alpha -linolenic acid), or palm oil (PLO, palmitic acid +oleic acid+ linoleic acid) with 0.5% chol esterol for 15 wk. There were no significant differences in the food intake and body weight gain among the groups. The liver weight in the PEO and PLO groups was significantly higher than other groups. The serum total cholest erol and very low density lipoprotein (VLDL) + intermediate density lipopro tein (IDL)+ low density lipoprotein (LDL)-cholesterol concentrations were c onsistently higher in PLO group than in the other groups. The serum high de nsity lipoprotein cholesterol concentration was significantly lower in the PEO group than in the other groups. The liver cholesterol concentration gro up was significantly higher in the PEO than in the other groups. There were no significant differences in the hepatic LDL receptor mRNA level among th e groups. Hepatic apo B. HMG-CoA reductase and cholesterol 7 alpha -hydroxy lase mRNA levels were not affected by the experimental conditions. However, hepatic cholesterol 7 alpha -hydroxylase mRNA level in the PEO and MIO gro ups tended to be higher than in the other groups. The fecal cholesterol ext raction was significantly higher in the MIO and PLO groups than in the PEO and EPO groups and the total bile acid extraction was significantly higher in the PEO and MIO groups than in the PLO group. The results of this study demonstrated that both n-6 fatty acid and n-3 fatty acids such as gamma -li nolenic acid and alpha -linolenic acid lowered serum total cholesterol and VLDL+IDL+LDL-cholesterol concentrations of rats in the presence of excess c holesterol in the diet compared with dietary saturated fatty acid.