Experimental atherosclerosis in rabbits fed cholesterol-free diets: 5. Comparison of Peanut, Corn, Butter, and Coconut Oils

Abstract

Four groups of Dutch belted rabbits were fed a semipurified diet containing 40% sucrose, 25% casein, and 14% fat for 10 months (without added cholesterol). The fats were peanut oil (PNO), corn oil (CO), butter oil (BO), and coconut oil (CNO). All diets were hyperlipidemic and hyperlipoproteinemic. The highest serum cholesterol and triglyceride levels were observed in the CNO groups, 330 and 286 mgm/dl, respectively. Serum cholesterol and triglyceride levels in the other groups (mgm/dl) were: PNO-205 and 51; CO-152 and 28; BO-292 and 48. The serum of α β lipoprotein cholesterol ratios were: PNO-0.28; CO-0.28; BO-0.19, and CNO-0.13. This ratio is about 0.35–0.40 in normal Dutch belted rabbits. Liver cholesterol levels were similar in all groups (1.35 ± 0.5 gm/100 gm). Liver triglyceride levels were (gm/100 gm): PNO-0.37; CO-0.55; BO-0.66; CNO-0.39. The most severe gross atherosclerosis was observed in the CNO group (25% of surface area) and the least in the CO group (2%). The involved surface area in the other two groups was: PNO-10% and BO-14%. Microscopic evaluation of the severity of the aortic lesions indicated that the rabbits fed CNO, BO, and PNO had the most frequent and severe lesions. In contrast, the animals fed CO consistently showed much less aortic disease. Gross aortic examination revealed distinct differences in the characteristics of atherosclerotic lesions induced by the four dietary fats. The most extensive lesions, observed in rabbits fed CNO, were characterized by intimal proliferation spread over the area of lipid deposition. BO tended to produce aortic lesions rich in lipid but a relatively small number of cells and little collagen deposition. The aortic lesions in rabbits fed PNO contained relatively little lipid and were characterized by thick fibrous plaques due to prominent intimal proliferation and a high proportion of collagen. The rabbits fed CO developed few aortic lesions, with minimal intimal proliferation and very little lipid. The relative atherogenicity of PNO was an unexpected finding.