A standardized Humulus lupulus (L.) ethanol extract partially prevents ovariectomy-induced bone loss in the rat without induction of adverse effects in the uterus

Abstract Background Hops ( Humulus lupulus (L.)) dietary supplements are of interest as herbal remedies to alleviate menopausal symptoms, such as hot flushes, depression and anxiety. So far, the evidence regarding estrogenic and related properties of hops preparations has been considered insufficient for a market authorization for menopausal indications. Purpose The study aims to investigate a chemically standardized hops extract regarding its safety in the uterus, as wells as its efficacy to prevent bone loss in the ovariectomized rat model. Study Design/Methods Female Wistar rats were ovariectomized and divided into a control group receiving phytoestrogen-free diet, a group treated with E 2 benzoate (0.93 mg/kg body weight/d) and a group treated with the standardized hops extract (60 mg/kg body weight/d) for 8 weeks. Micro-computed tomography of the tibiae and vertebrae, as wells as histological changes in the uterus and tibia were analyzed. Results Neither uterotrophic nor proliferative effects were observed in the endometrium in response to the oral 8-week administration of the hops extract. However, site-dependent skeletal effects were observed. The hops extract significantly decreased the number of osteoclasts in the tibial metaphysis and prevented reduction of the trabecular thickness that resulted from estradiol depletion. In contrast, the hops extract did not prevent the ovariectomy-induced micro-architectural changes in the lumbar vertebra. Certain parameters ( e.g. thickness and number of trabeculae) were even found to be below the values determined in the ovariectomized control group. Conclusion Taken together, the results provide evidence for the safety of the standardized hops extract and point to a weak bone type-specific, protective effect on bone loss following estradiol depletion.