17 beta-estradiol but not the phytoestrogen naringenin attenuates aortic cholesterol accumulation in WHHL rabbits

The effects of 17 beta -estradiol (17 beta -E-2) or the phytoestrogen narin genin on spontaneous atherosclerosis were studied in 36 ovariectomized homo zygous Watanabe heritable hyperlipidemic (WHHL) rabbits receiving a semisyn thetic control diet; this diet added 0.0040% 17 beta -E-2, or 0.20% naringe nin, for 16 weeks. The uterine weight was increased (P < 0.001) and the con centration of estrogen receptor alpha was decreased (P < 0.001) in the 17 b eta -E-2 group compared with the controls. Total plasma cholesterol and tri glycerides were not different from those in the controls, In lipoproteins, HDL cholesterol was increased (P < 0.01), and LDL triglyceride and IDL trig lyceride were lowered (P < 0.05), The oxidation (as concentration of malond ialdehyde) was increased in LDL (P < 0.05) but not in plasma. The cholester ol accumulation was decreased (P < 0.05) in the ascending aorta and in the total aorta but the ratio of intima to media and area of intima in ascendin g, thoracic, and abdominal aorta were not significantly different. In the n aringenin group the only differences, compared with the control group, were increased LDL cholesterol (P < 0.001) and decreased activity of glutathion e reductase (P < 0.05) In conclusion, 17 beta -E-2, but not naringenin, att enuated aortic cholesterol accumulation independently of plasma and LDL cho lesterol, Further, these results support previously suggested pro-oxidant a bility of 17 beta -E-2 toward LDL and a possible connection between the pro -oxidant nature of 17 beta -E-2 and its antiatherogenic effect. - Mortensen , A., V. Breinholt, T. Dalsgaard, H. Frandsen, S. T. Lauridsen, J. Laigaard , B. Ottesen, and J-J. Larsen. 17 beta -Estradiol but not the phytoestrogen naringenin attenuates aortic cholesterol accumulation in WHHL rabbits.