Strontium fructose 1,6-diphosphate prevents bone loss in a rat model of postmenopausal osteoporosis via the OPG/RANKL/RANK pathway

Aim: To evaluate the protective effects of strontium fructose 1,6-diphosphate (FDP-Sr), a novel strontium salt that combined fructose 1,6-diphosphate (FDP) with strontium, on bone in an ovariectomy-induced model of bone loss. Methods: Eighty female Sprague-Dawley rats were ovariectomized (OVX) or sham-operated. Three months later, the rats were assigned to six groups (10 for each): sham-operated, OVX control, OVX+FDP-Sr (110, 220, or 440 mg/kg), or OVX+strontium ranelate (SR, 180 mg/kg). Drugs were administered orally for 3 months. When the treatment was terminated, the following parameters were assessed: bone mineral density (BMD), the biomechanical properties of the femur and lumbar vertebrae, trabecular histomorphology, serum phosphorus, calcium, bone-specific alkaline phosphatase (B-ALP), tartrate-resistant acid phosphatase 5b (TRACP5b), N-telopeptide of type I collagen (NTx) and a series of markers for oxidative stress. Receptor activator of NF-κB ligand (RANKL) and osteoprotegerin (OPG) levels in serum were measured using ELISA and their gene expression levels in the bone were measured using R-T PCR. Results: Treatment with FDP-Sr (220 or 440 mg/kg) or SR (180 mg/kg) significantly increased the BMD and improved the bone microarchitecture and bone strength in OVX rats. The treatments also decreased in the levels of H ₂O ₂ and MDA, restored the CAT level in serum and bone marrow, increased the serum B-ALP and decreased NTx and TRACP 5b in OVX rats. Treatment with FDP-Sr decreased the RANKL level, and increased the OPG level in serum in a dose-dependent manner. It also significantly down-regulated the RANKL expression and up-regulated OPG expression in bone marrow. Conclusion: FDP-Sr may be an effectve treatment for postmenopausal osteoporosis that acts, in part, via a decrease in osteoclastogenesis through the OPG\RANKL\RANK pathway.