Effects of dietary N-3 fatty acid supplementation on lipoproteins and intimal foam cell accumulation in the casein-fed rabbit.

This study was undertaken to evaluate the effects of dietary N-3 fatty acid supplementation on lipoprotein profiles and intimal foam cell accumulation in rabbits fed a cholesterol-free semipurified casein diet for 10 weeks. Diets were supplemented with a low-cholesterol fish oil preparation (MaxEPA) or a mixture of corn, palm, and safflower oils with a polyunsaturated/saturated (P/S) fatty acid ratio equivalent to the MaxEPA. Plasma cholesterol levels in both groups doubled after two weeks on diet and remained elevated throughout the study. Plasma triglycerides of both groups decreased uniformly from baseline, reaching at sacrifice a mean concentration that was 52% of baseline values. Neither of these plasma measures were affected by the type of oil supplement. Concentrations of low density lipoprotein (LDL) cholesterol, triglyceride, phospholipid, and protein measured at sacrifice were significantly elevated in MaxEPA treated rabbits. Plasma concentrations of thiobarbituric acid reactive substances (TBARS), indicators of lipid peroxidation, were not significantly different between groups. A macroscopic survey of the thoracic aortas revealed that lesions were restricted to the aortic arch regions in both groups. Microscopically it was determined that these intimal lesions were primarily comprised of oil red O positive foam cell aggregates. N-3 fatty acids did not have an effect on the number of intimal foam cells within these lesions. These data suggest that dietary fish oils may exacerbate an LDL hypercholesterolemia, but not the atherosclerotic process in the casein-fed rabbit model of atherosclerosis.