Effects of dietary equol on body weight gain, intra-abdominal fat accumulation, plasma lipids, and glucose tolerance in ovariectomized Sprague-Dawley rats

Abstract

Objective: To evaluate the effects of dietary equol, a metabolite of the phytoestrogen daidzein, on body weight gain, intra-abdominal fat accumulation, plasma leptin, lipids, and glucose tolerance in ovariectomized rats and to compare them to the effects of 17beta-estradiol.

Design: Twenty-eight female Sprague-Dawley rats were ovariectomized and fed soy-free chow with the addition of estradiol-3 benzoate (E2B) (10 mg/kg, n=10) or equol (400 mg/kg, n=10). The control group (n=8) received soy-free chow only. Weight and food intake were recorded once weekly. After 6 weeks, intra-abdominal fat was measured using computed tomography, and the intraperitoneal glucose tolerance test was performed. In the seventh week, the animals were killed, blood was collected for plasma, and uteri were removed.

Results: Dietary equol significantly increased uterine mass. This effect was, however, 3.5 times lower in magnitude compared to E2B. Similar to E2B, dietary equol decreased weight gain, intra-abdominal fat accumulation, and plasma leptin levels. Equol-treated animals had also lower plasma total cholesterol and triglyceride levels compared to controls. E2B treatment also decreased plasma total cholesterol as well as high-density lipoprotein and low-density lipoprotein cholesterol. In the glucose tolerance test, the area under the curve was significantly smaller in the E2B- and equol-treated animals compared to controls. Also, E2B-treated animals had lower fasting plasma insulin levels.

Conclusions: In ovariectomized rats, dietary equol administration attenuates weight gain and shows favorable metabolic effects. However, because of its mild uterotrophic activity, its use in the prevention of postmenopausal weight gain and related metabolic disorders in women with an intact uterus is questionable in terms of safety and warrants further studies.