Equal atherosclerosis in rabbits fed cholesterol-free, low-fat diet or cholesterol-supplemented diet

This study compares the atherogenicity of a cholesterol-free, low fat, semisynthetic diet and a cholesterol-supplemented chow diet. Rabbits fed the semisynthetic cholesterol-free diet developed endogenous hypercholesterolemia with cholesterol concentrations of 240-650 mg/dl plasma during a 182-250 day study. When equal plasma cholesterol concentrations were maintained in pairs of rabbits with either cholesterol-induced hypercholesterolemia or endogenous hypercholesterolemia, no differences in atherosclerotic disease, as judged by visual grading or by aortic cholesterol concentrations were found. Microscopic examination of aortas also failed to show differences in atherosclerosis produced by these diets. Lipoproteins from rabbits fed semisynthetic diet or cholesterol-supplemented chow diet showed similarities: both had elevated cholesterol to triglyceride ratios, and very low density lipoproteins which migrated electrophoretically as β-lipoproteins. Rabbits fed the semisynthetic diet transported relatively more cholesterol in low density lipoproteins (putative very low density lipoprotein remnants), whereas rabbits fed cholesterol transported more in β-migrating very low density lipoproteins (chylomicron remnants). This suggests that, at the same level of plasma cholesterol, the partially degraded endogenous very low density lipoproteins and chylomicron remnants are equally atherogenic, and that the total β-migrating lipoprotein cholesterol is a better index of atherogenic potential of serum than is the low density lipoprotein (1.019 < d < 1.063) fraction.