Soy isoflavones mitigate long-term femoral and lumbar vertebral bone loss in middle-aged ovariectomized mice

We evaluated the protective effects of soy isoflavones (SIF) against osteoporosis in middle-aged ovariectomized (OVX) mice. SIF (30mg/kg or 60>mg/kg) or 17β-estradiol (E₂) was administered to OVX mice for 4 months after bilateral ovariectomy. We observed the biochemical markers of bone turnover, e.g., alkaline phosphatase (ALP) and tartrate-resistant acid phosphatase (TRAP), in serum. We also observed the bone mineral density (BMD) in femurs and lumbar vertebrae. In addition, we examined trabecular bone and interstitial cells in the femur using hematoxylin and eosin staining. The decrease in ALP levels and the increase in TRAP levels normally resulting from ovariectomy were suppressed by administration of 60mg/kg SIF or E₂. Administration of 60>mg/kg SIF or E₂ also maintained the BMD, trabecular bone, and interstitial cells in OVX mice compared to those in pre-OVX mice. These results suggest that 60mg/kg SIF effectively mitigates ovariectomy-induced osteoporosis in middle-aged mice.