| Abstract: | The effects of diets enriched with cholesterol and different fats upon plasma lipoproteins and hepatic low density lipoprotein (LDL) receptor mRNA levels were studied in a group of 18 normal baboons. Animals were fed diets containing 1% cholesterol and 25% fat as either coconut oil, peanut oil, or olive oil for a period of 20 weeks. Plasma total cholesterol, high density lipoprotein (HDL) cholesterol, beta-lipoprotein (LDL + very low density lipoprotein) cholesterol, apolipoprotein B and apolipoprotein A-I were measured in samples obtained at 4-week intervals. All three diet groups demonstrated a statistically significant increase in plasma cholesterol as compared to base line throughout the experiment. Hepatic LDL receptor (LDL-R) mRNA levels were quantified by dot blot hybridization in serial liver biopsies. Animals fed saturated fat sustained a significant reduction in hepatic LDL-R mRNA as compared to those fed either monounsaturated or polyunsaturated fat. A strong negative correlation between LDL-R mRNA and plasma total cholesterol (r = -0.71), HDL cholesterol (r = -0.76), and plasma apo A-I (r = -0.77) was observed only in those animals fed coconut oil. Weak negative correlations between LDL-R mRNA and other plasma parameters did not achieve statistical significance. We conclude that saturated and unsaturated oils may influence plasma cholesterol levels in part through differential effects on LDL receptor biosynthesis in baboons. |
