Mechanistic Insights into Kaempferol's Therapeutic Effects on Postmenopausal Osteoporosis: A Proteomic and Experimental Validation in Ovariectomized Rats.

Background: Postmenopausal Osteoporosis (PMOP) is characterized by decreased bone mass and deterioration of bone microarchitecture, leading to increased fracture risk. Current treatments often have adverse effects, necessitating safer alternatives. Kaempferol, a flavonoid identified as a key active component of the traditional Chinese medicine Yishen Gushu formula, has shown promise in improving bone health, but its mechanisms in PMOP treatment remain unclear.

Objective: The aim of this study was to investigate the therapeutic effects and underlying mechanisms of kaempferol in the treatment of PMOP.

Methods: A bilateral ovariectomized (OVX) rat model was established to simulate PMOP. Sixty female Sprague-Dawley rats were divided into six groups: Sham operation, OVX control, OVX with alendronate (ALN), and OVX with kaempferol at doses of 10, 20, and 40 mg/kg. Treatments were administered orally once daily for 12 weeks. Assessments included Bone Mineral Density (BMD), trabecular microarchitecture via histopathology, organ morphology, organ indices, and serum levels of bone metabolism markers (TRACP-5b, BALP, ALP, Ca, P, and Fe) as well as liver and kidney function indicators (ALT, AST, CREA, and urea). Tandem Mass Tag (TMT) quantitative proteomics and bioinformatics analyses were conducted on femur samples to identify differentially expressed proteins (DEPs). Key DEPs were validated using parallel reaction monitoring (PRM), immunohistochemistry, and molecular docking.

Results: Kaempferol significantly improved BMD and enhanced trabecular microarchitecture in OVX rats in a dose-dependent manner, comparable to ALN, without causing hepatic, renal, or estrogen- like side effects. Serum bone metabolism markers were normalized with kaempferol treatment. Proteomic analysis identified 902 DEPs associated with kaempferol treatment, involved in processes such as bone remodeling, skeletal system development, and osteoclast function. Key signaling pathways affected included NF-κB, PI3K-AKT, and HIF-1. Notably, kaempferol downregulated five key DEPs-Rac2, Ddb1, Cdc42, Rpl19, and Hist2h4-in the femur, which are crucial for osteoclast resorptive activity, migration, adhesion, and cell cycle progression.

Conclusion: Kaempferol exerts therapeutic effects on PMOP by inhibiting key proteins involved in osteoclast function, thereby reducing bone resorption and promoting bone health. These findings suggested that kaempferol is a potential safer alternative for PMOP treatment. Further research is recommended to explore its clinical applications and elucidate detailed mechanisms.