Eucommia ulmoides extract and soy isoflavones attenuate postmenopausal osteoporosis by modulating bone-specific transcription factors and inflammatory signaling pathways

Postmenopausal osteoporosis (PMO) is driven by estrogen deficiency, enhanced osteoclastic activity, impaired osteoblast function, and persistent inflammatory signaling. Eucommia ulmoides extract (EUE) and soy isoflavones (Isf) are known to possess phytoestrogenic and anti-inflammatory properties, but their combined molecular effects on PMO remain unclear.

An ovariectomy-induced PMO rat model was used to assess the therapeutic efficacy of EUE, Isf, and their combination. Bone strength and mineral content were evaluated together with serum indicators of bone turnover, including type I procollagen N-terminal propeptide, alkaline phosphatase, C-terminal telopeptide of type I collagen, and tartrate-resistant acid phosphatase. Serum calcium, phosphorus, superoxide dismutase, and malondialdehyde levels were also measured. Trabecular microarchitecture was assessed histologically. In vitro, osteoblast differentiation was examined by Alizarin Red staining and proliferative activity by EdU incorporation, while osteoclast formation and apoptosis were analyzed by tartrate-resistant acid phosphatase staining and flow cytometry. Mechanistic evaluation focused on bone-related transcriptional regulators such as Runx2 and alkaline phosphatase, key mediators of osteoclastogenesis including RANKL, RANK, OPG, and TRAP, and inflammatory cytokines including tumor necrosis factor-α, interleukin-6, interleukin-1β, and interleukin-10.

The combined EUE and Isf treatment significantly improved biomechanical performance of the femur and restored bone mineral content in ovariectomized rats. Levels of bone formation markers were elevated, whereas indices of bone resorption were reduced. Serum calcium-phosphorus homeostasis and oxidative stress were markedly corrected, accompanied by substantial improvement in trabecular structure. In vitro, the combination enhanced osteoblast mineralization and proliferation, suppressed osteoclast formation, and increased osteoclast apoptosis. Mechanistically, the combined treatment increased the expression of osteogenic regulators Runx2, alkaline phosphatase, and osteoprotegerin, while reducing the expression of RANKL, RANK, and TRAP. Pro-inflammatory cytokines were lowered, whereas interleukin-10 was upregulated.

EUE combined with soy isoflavones effectively attenuates postmenopausal osteoporosis by enhancing osteoblast function, suppressing osteoclastogenesis, and rebalancing bone-related transcriptional and inflammatory pathways. This botanical combination represents a promising therapeutic strategy for the management of PMO.