Olive oil exhibits osteoprotection in ovariectomized rats without estrogenic effects

The present study was designed to evaluate the effect of olive oil on bone and uterus in ovariectomized rats. A total of 34 surgically ovariectomized or sham-operated virgin Sprague-Dawley rats were divided into four groups: i) Sham-operated control rats (sham group); ii) Ovariectomized rats (OVX group); iii) Olive oil-supplemented ovariectomized rats (olive group); and iv) Diethylstilbestrol-supplemented ovariectomized rats (E₂ group). At 12 weeks following left ventricular blood sacrificed to detect plasma estradiol (E₂), interleukin-1β (IL-1β) and IL-6 levels. Bone mineral density (BMD) of the lumbar spine was evaluated using dual-energy X-ray absorptiometry, and the left femur proximal 1/3 slices were observed using transmission electron microscopy. Uterine wet weight and the uterus index (ratio of uterine wet weight and body weight) were compared, and the uterine endometrium was observed using a light microscope. In the OVX group, serum E₂ was significantly lower and IL-1β and IL-6 levels were significantly higher compared with the sham group. By contrast, serum E₂ levels increased and IL-1β levels decreased in the olive group, but showed no significant difference compared with the sham group. The lumbar spine BMD in the olive group was increased compared with OVX group. Electron microscopy revealed sparse collagen fibers in the OVX group, with decreased density and multi-cavity, showing pathological features of osteoporosis. By contrast, the situation was improved in the E₂ and olive groups, in which organelles such as the rough endoplasmic reticulum, mitochondria and Golgi apparatus were visible and active. Compared with the sham group rats, the uterine wet weight and uterine index decreased in the OVX and olive groups; however, no statistically significant difference was observed in the E₂ group. Furthermore, endometrial hyperplasia was not observed in the olive group, which were apparently different from E₂ group. The present results suggest that olive oil can effectively reduce bone loss in ovariectomized rats, and with no or only mild effects on the uterine endothelium.