Differential effects of n-3 fatty acids on the regression of atherosclerosis in coronary arteries and the aorta of the pig

Atherosclerosis was induced in 13 Yorkshire pigs (4 weeks; 7-10 kg) by endothelial balloon denudation of the aorta and left arterior descending coronary artery and a diet containing 2% (wt/wt) of cholesterol, 8% (wt/wt) of lard fat and 0.5% (wt/wt) of bile acids. After 8 months 7 animals (group I) were sacrificed to determine the extent to which atherosclerosis had developed. The other 6 animals (group R) received a diet (no cholesterol, 5% (wt/wt) of lard fat and 5% (wt/wt) of fish oil) for 4 months. In I plasma cholesterol increased from 2.29 to 9.02 mmol l^-1 after 8 months and in R it returned to 1.89 mmol l^-1 after 12 months. Less marked changes occurred in plasma HDL cholesterol and triglycerides. ADP-induced platelet aggregation and the number of platelets remained constant in I whereas both parameters were reduced in R after 12 months. In the lesions of the abdominal aorta of I, cholesterol, cholesterol ester, phospholipid and triglyceride contents were 4.97, 2.08, 4.20 and 0.77 μg g^-1 wet wt, respectively, whereas in R these values (3.02, 0.47, 2.70 and 0.44 μg g^-1 wet wt, respectively), were close to the values measured in non-abraded vessel wall specimens. The Sudan IV-positive area of the aorta was 34 ± 9% in I and 10 ± 4% in R (P < 0.05). Luminal encroachment of the denudated left anterior descending coronary artery was 11 ± 3% in I and 13 ± 3% in R (P < 0.05). We conclude that addition of n-3 fatty acids to a low cholesterol diet resulted in regression of atherosclerosis in the aorta but not in the coronary arteries.