Impact of 4-methylbenzylidene camphor, daidzein, and estrogen on intact and osteotomized bone in osteopenic rats

The study investigated the influence of 4-methylbenzylidene camphor (4-MBC), daidzein, and estradiol-17β-benzoate (E 2 ) on either intact or osteotomized cancellous bone in ovariectomized (Ovx) rats. Three-month old Ovx rats were fed with soy-free (SF) diet over 8 weeks; thereafter, bilateral transverse metaphyseal osteotomy of tibia was performed and rats were divided into groups: rats fed with SF diet and SF diet supplemented with 4-MBC (200 mg), daidzein (50 mg), or E 2 (0.4 mg) per kilogram body weight. After 5 or 10 weeks, computed tomographical, biomechanical, histological, and ashing analyses were performed in lumbar spine and tibia of 12 rats from each group. 4-MBC and E 2 improved bone parameters in lumbar spine and tibia, were not favorable for osteotomy healing, and decreased serum osteocalcin level. However, daidzein improved bone parameters to a lesser extent and facilitated osteotomy healing. For lumbar spine, the bone mineral density was 338±9, 346±5, 361±6, and 360±5 mg/cm 3 in SF, daidzein, 4-MBC, and E 2 , respectively, after 10 weeks. For tibia, the yield load was 98±5, 114±3, 90±2, and 52±4 N in SF, daidzein, 4-MBC, and E 2 , respectively, after 10 weeks. Serum daidzein was 54±6 ng/ml in daidzein group and equol was not detected. Alp and Igf1 genes were down-regulated in callus after daidzein and E 2 compared with 4-MBC (week 5). The response of bone tissue and serum markers of bone metabolism could be ordered: daidzein<4-MBC<E 2 . Treatments were more effective after 5 vs 10 weeks. In SF group, bone structure was impaired after 5 weeks and improved after 10 weeks probably due to adaptation mechanisms to osteoporosis. In conclusion, it is conceivable that 4-MBC may improve bone tissue in osteoporotic organisms; osteoporotic patients with fractures could benefit from daidzein treatment.