Daidzin-rich Soy Isoflavone Extracts Promote Estrous Cycling in VCD- induced Menopause Mouse Model

By 2025 postmenopausal women will make up to 20% of the US population. Since traditional hormone replacement therapies (HRT) increase the risk of breast cancer, alternative strategies are needed to delay and manage menopause. With this intention, recent studies in our laboratory screened isoflavone (phytoestrogens) extracts of fifty-four commercially grown soybean cultivars in a bioassay and identified extracts from three cultivars with high daidzin to genistin ratio as highly estrogenic. Based these results, we hypothesized that soy isoflavone extracts with a high daidzin to genistin ratio will promote estrous cycling in menopausal mice. In a VCD-induced menopause mouse model, the number of estrous cycles was significantly increased in mice receiving a soy isoflavone supplemented diet compared to VCD-treated mice receiving an unfortified diet (p=0.0004). Moreover, soy isoflavone extracts that promoted estrous cycling had a high daidzin to genistin ratio. There was no significant difference in percentage weight change between the control mice receiving unfortified diets and mice receiving a soy isoflavone fortified diet (p=0.2). In addition there were no palpable mammary tumors detected in mice. Taken together, our study suggests that the composition of soy isoflavone extracts determines their effectiveness in delaying menopause. Soy isoflavone extracts with a high daidzin to genistin ratio may delay the onset of menopause by increasing functional estrogen activity during menopause transition.