MaxEPA fish oil enhances cholesterol-induced intimal foam cell formation in rabbits

In this study, the cholesterol-fed rabbit model was used to test the hypothesis that fish oil supplementation can influence the initiation and development of atherosclerotic lesions. Rabbits were fed one of two diets for a period of 30 days: a nonatherogenic diet with corn oil as the sole fat source, or an atherogenic diet containing beef tallow and cholesterol. In addition, animals received a daily supplement of either MaxEPA fish oil or corn oil (0.5 ml/kg body weight). Terminal blood samples were drawn and the cholesterol and triglyceride levels determined for both plasma and very low-density (VLDL), intermediate-density (IDL), low-density (LDL), and high-density (HDL) lipoproteins. Thiobarbituric acid-reacting substance (TBARS), an indicator of lipid peroxidation, was measured in the plasma samples. Besides these biochemical parameters of atherogenesis, the number of intimal foam cells in the descending thoracic aorta of each animal was determined by microscopic examination of the vessels en face. In rabbits fed the nonatherogenic diet, fish oil supplementation did not significantly affect any of the biochemical parameters that were measured. In contrast, fish oil supplementation of the atherogenic diet led to a significant increase in the LDL- and HDL-cholesterol as well as the HDL-triglyceride levels. Plasma TBARS also increased more than four times. Morphologic analysis of the vessels from rabbits fed the atherogenic diet indicated that fish oil supplementation led to a threefold increase in the number of intimal foam cells, a result that may be linked to increases in both LDL-cholesterol and plasma TBARS. The results of these experiments do not support the hypothesis that dietary fish oil will inhibit the initiation or progression of lesion formation in the cholesterol-fed rabbit.