THE OVARIAN HORMONE DEFICIENCY-INDUCED HYPERCHOLESTEROLEMIA IS REVERSED BY SOY PROTEIN AND THE SYNTHETIC ISOFLAVONE, IPRIFLAVONE

The purpose of this study was to compare the effects of soy protein is olate with normal isoflavone content (soy) and with reduced isoflavone content (soy-), ipriflavone (IP), a synthetic isoflavone; and 17 beta -estradiol (E(2)) on lipid metabolism in ovariectomized (ovx) rats. Se venty-two 95-day old Sprague-Dawley rats were assigned to six groups: sham operated (sham), ovx, ovx+soy, ovx+soy-, ovx+IP, and ovx+E(2). Ra ts in the sham, ovx, ovx+IP, and ovx+E(2) groups were fed a casein-bas ed diet, whereas the soy and soy- groups were fed diets in which casei n was replaced with soy or soy-. Animals were pair-fed to the mean foo d intake of ovx+E(2) for 35 days. At the end of the study, animals wer e sacrificed in a nonfasted state and blood was collected via abdomina l aorta. The ovx-induced increase in serum total cholesterol was rever sed by all the treatments including ipriflavone and soy. Serum triglyc eride levels were not significantly affected by any of the treatments. Liver cholesterol (mu mol/g) in animals receiving IP or fed soy were significantly (p<0.01) lower than the ovx, ovx+soy-, and ovx+E(2) grou ps. Liver lipids (mg/g) were significantly (p<0.05) lower in the anima ls that received E(2) or fed soy, but not those which were fed soy- or given IF. The ovx-induced increase in abdominal fat was completely re versed by soy and E(2) treatments but not by soy- or ipriflavone treat ments. Soy, soy-, and IP had no uterotrophic activity as compared to E (2). Ovariectomy significantly increased body weight gains which were not suppressed by any of the treatments except E(2). These data indica te that ipriflavone is effective in preventing the unfavorable changes in serum and liver cholesterol associated with ovarian hormone defici ency in this animal model. Moreover, the consumption of synthetic or n atural isoflavones may offer a potential alternative therapy in the tr eatment of hypercholesterolemia in ovarian hormone-deficient women. (C ) 1997 Elsevier Science Inc.