Effect of gamma-oryzanol on atheroma formation in hypercholesterolemic rabbits

The anti-oxidant action of ferulic acid in gamma-oryzanol was tested in hypercholesterolemic rabbits to determine its effects on the development of atherosclerosis. Eighteen male New Zealand white rabbits were fed a diet containing 1% cholesterol with or without 1% gamma-oryzanol for 10 weeks. The anti-oxidant effect was assessed by the degree of resistance of low density lipoprotein (LDL) to oxidation by copper sulfate and the effect of the copper oxidized LDL on the incorporation of oleate into cholesteryl ester by mouse peritoneal macrophages. In addition, the levels of plasma cholesterol, triglyceride and lipid peroxide were measured before, during and at the end of cholesterol loading. The amount of free ferulic acid and gamma-oryzanol in plasma and LDL and the area of aortic atherosclerotic plaques were determined. It was found that oleate incorporation into cholesteryl ester by macrophages was significantly reduced in the gamma-oryzanol-treated group compared to the non-treated group, and that the reduction was via a mechanism independent of anti-oxidant action. However, no differences were found in the levels of plasma cholesterol, triglyceride, lipid peroxide or in the areas of atherosclerotic plaques between the two groups. It was concluded that gamma-oryzanol has little or no preventive effects on atherosclerosis in rabbits.