Effects of 17β-estradiol and isoflavones on movement drive, body weight, and bone density in ovariectomised female rats

Reduced estrogen levels occurring during menopause in women, are accompanied by a variety of disorders, e.g. hot flushes, depressions, osteoporosis, increase of body weight and reduced movement drive. To study effects of estradiol and phytoestrogens on such disorders in an animal model, ovariectomised (OVX) female Wistar rats were either fed with an isoflavone rich diet (IRD) (daily exposure was 10mg/kg b.wt./d daidzein and 10mg/kg b.wt.d genistein) or substituted with 4µg kg b.wt./d estradiol (E2 pellet), for 3 months. Sham operated rats and vehicle treated OVX animals served as controls. Movement activity, changes of body weight and of bone density in the tibia (determined by quantitative computer tomography) were analysed and correlated to uterine wet weights and the height of the vaginal epithelium. Uterine wet weights were stimulated significantly by E2 substitution, but only marginally in animals fed IRD. OVX rats display an 8-times lower movement activity than sham animals. E2 treatment, but not IRD, significantly increased the movement activity of OVX rats. During 3 months, the lowest increase of body weight was observed in sham animals, the highest rate in OVX animals. E2 treatment, but not IRD, lowers the increase of body weight significantly compared to OVX animals. E2 substitution also lowers the increase of body weight in animals with no access to running training, which demonstrates the involvement of metabolic changes under the control of E2. Bone mineral density was strongly reduced in OVX rats compared to sham animals. E2 substitution, but not IRD, resulted in an increase of bone density compared to OVX animals.

In conclusion, our data demonstrate that body weight, movement drive and bone density are positively influenced by E2. E2 acts in the trabecular area of the tibia in a bone-protective manner and strongly decreases the decline of movement drive and the body weight increase seen after ovariectomy. In contrast, these effects were not observed in animals fed with an IRD.