EFFECT OF DIETARY OMEGA-3 EICOSAPENTAENOIC ACID SUPPLEMENTS ON CHOLESTERYL ESTER TRANSFER FROM HDL IN CHOLESTEROL-FED RABBITS

We investigated the reactivities of cholesteryl ester transfer protein (CETP) in Japanese white rabbits fed either a low-cholesterol diet co ntaining 0.1% cholesterol (Control group) or a diet containing 0.1% ch olesterol plus 17.5% omega-3 eicosapentaenoic acid (omega-3 20:5, EPA) of 4.5% (w/w) total lipid (EPA group) for 6 weeks. The plasma total a nd LDL cholesterol levels and aortic cholesterol content were all sign ificantly higher in the EPA group than in the control group. The aorti c cholesterol content significantly correlated with LDL cholesterol(r = 0.81). HDL cholesterol levels tended to be lower in the EPA group co mpared with control group, which was not statistically significant. Th e plasma VLDL cholesterol levels did not differ significantly between the groups. In addition, no significant differences were observed in t he plasma CETP activity or lecithin:cholesterol acyltransferase (LCAT) activity between the groups. However, the cholesteryl ester (CE) mass transfer from fractionated HDL in the EPA group to excess VLDL and/or LDL as accepters by purified CETP increased significantly compared wi th the control group, even if the accepters were fractionated from eit her the EPA or the control group. Fatty acid analyses of CE showed tha t the omega-3 18:3, 20:4 or omega-3 20:5 fatty acid acyl groups in CE of HDL were significantly more transferred to apo B-containing lipopro teins compared with the 14:0, 16:0, 18:0, 18:1 or 18:2 fatty acid acyl groups in CE of HDL during the incubation period. The amount of CE in HDL containing omega-3 18:3 and omega-3 20:5 fatty acid acyl groups w as greater, while the amount of CE containing 18:2 fatty acid acyl gro ups was smaller in the EPA group than in the control group. These resu lts show that although CETP itself did not change, the transfer of CE in HDL to apo B-containing lipoproteins by CETP increased in the rabbi ts fed a diet containing EPA as the HDL is modified by the diet, which may partly explain why atherogenicity was thus found to progress in t he rabbits fed a cholesterol plus EPA diet. (C) 1997 Elsevier Science B.V.