An Investigation of the Effects of Formononetin on Hypothalamic Gonadotropin-releasing Hormone, Kisspeptin and Tachykinin 2 Gene Expression in Rats

Background: Red clover and its main derivative, formononetin, belong to the phytoestrogens. They are clinically used to alleviate mood disorders, anxiety, and hot flashes. Formononetin may interfere with the reproductive axis due to its estrogenic potency and its ability to bind estrogen receptors. To find some molecular mechanisms mediating the effects of formononetin on the hypothalamus-pituitary-gonadal (HPG) axis, this research aimed to investigate the effects of formononetin on the hypothalamic mRNA levels of gonadotropin-releasing hormone (Gnrh), kisspeptin1(Kiss1) and tachykinin 2 (Tac2). Materials and Methods: Fifteen male Wistar rats weighing 200±10 g were divided into three groups (n=5). Group 1 as the control group, received saline. Groups 2 and 3 received 20 and 40 µg of formononetin via the third cerebral ventricle. The hypothalamic samples were dissected. The Gnrh, Kiss1 and Tac2 gene expression was measured by real-time PCR. Results: Injection of 20 µg formononetin did not significantly decrease the mRNA levels of Gnrh and Tac2 compared to the control group. However, injection of 40 µg formononetin significantly reduced the mRNA levels of Gnrh and Tac2 compared to the control group. Injection of 20 and 40 µg formononetin, significantly declined the mRNA levels of Kiss1 compared to the control group.Conclusion: Present results indicated that formononetin may be involved in the regulation of the reproductive axis via reducing the activity of hypothalamic GnRH neurons and downregulation of the kisspeptin and neurokinin B signaling pathways upstream of GnRH neurons.