Abstract
We have developed a method to quantitate hepatic apolipoprotein (apo) B, LDL receptor, 3-hyddroxy-3-methylglutary coenzyme A reductase (HMG-CoA reductase) and cholesterol 7α-hydroxylase mRNA expression in rats fed a cholesterol-enriched diet after long-term feeding using competitive RT-RCR. Rats (8 wk of age) fed a conventional diet were shifted to diets containing 10% perilla oil (PEO, oleic acid+linoleic acid+α-linolenic acid), borage oil (BRO, oleic acid+linoleic acid+γ-linolenic acid), evening primrose oil (EPO, linoleic acid+γ-linolenic acid), mixed oil (MIO, oleic acid+linoleic acid+γ-linolenic acid+α-linolenic acid), or palm oil (PLO, palmitic acid+oleic acid+linoleic acid) With 0.5% cholesterol 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 cholesterol and very low density lipoprotein (VLDL)+intermediate density lipoprotein (IDL)+low density lipoprotein (LDL)-cholesterol concentrations were consistently higher in PLO group than in the other groups. The serum high density lipoprotein cholesterol concentration was significantly lower in the PEO group than in the other groups. The liver cholesterol concentration group was significantly higher in the PEO than in the other groups. There were no significant differences in the hepatic LDL receptor mRNA level among the groups. Hepatic apo B, HMG-CoA reductase and cholesterol 7α-hydroxylase mRNA levels were not affected by the experimental conditions. However, hepatic cholesterol 7α-hydroxylase mRNA level in the PEO and MIO groups tended to be higher than in the other groups. The fecal cholesterol extraction 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 γ-linolenic acid and α-linolenic acid lowered serum total cholesterol and VLDL+IDL+LDL-cholesterol concentrations of rats in the presence of excess cholesterol in the diet compared with dietary saturated fatty acid.
