Inhibition of atherosclerosis by fish oil in cholesterol-fed rabbits

Abstract

To evaluate the effects of dietary fish oil on cholesterol-induced atherosclerosis, 36 New Zealand rabbits in four groups were fed a 0.3% cholesterol diet for 10 weeks. One group served as control, whereas groups I, II and III received 1, 2 and 3 ml/day, respectively, of fish oil (Protochol, eicosapentaenoic acid, 180 mg, and docosahexaenoic acid [DHA], 120 mg/ml). The percent of aortic and pulmonary atherosclerosis was measured by planimetry of sudanophilic lesions. The percent of aortic lesions in the control group was 59 ± 22%. The two higher dose fish oil groups showed a significant reduction in aortic lesions: group I (40 ± 26%, p = NS), group II (18 ± 11%, p < 0.01) and group III (36 ± 22%, p < 0.05). Area of pulmonary artery lesions was significantly higher in the control group (48 ± 22%) as compared with group I (15 ± 13%, p < 0.01), group II (4 ± 3%, p < 0.01) and group III (8 ± 9%, p < 0.01).The high cholesterol diet in the control group decreased bleeding time from 82 ± 17 to 59 ± 22 s (p < 0.05). Groups II and III showed an increased bleeding time (62 ± 15 to 84 ± 17 s and 66 ± 22 to 95 ± 27 s; p < 0.05, respectively). Fish oil did not signifcantly alter total serum cholesterol and high density lipoprotein (HDL cholesterol. In group II triglyceride decreased from 128 ± 22 to 64 ± 25 mg/dl (p < 0.001). Plasma thromboxane B2levels decreased to the same extent in all four groups. There was no correlation between thromboxane B2levels and percent of aortic or pulmonary atherosclerosis. However, there was a modest correlation between percent lesions in the pulmonary artery and aorta (r = 0.6).This study shows that dietary fish oil can attenuate the development of aortic and pulmonary atherosclerosis in cholesterol-fed rabbits. The increased bleeding time appears to confirm the known antiplatelet effects of fish oil.