Puerarin improves OVX-induced osteoporosis by regulating phospholipid metabolism and biosynthesis of unsaturated fatty acids based on serum metabolomics

Background: Postmenopausal osteoporosis (PMOP) is a serious problem for the women over 50 years old. Natural product puerarin (PUE) has been proven to improve PMOP with high safety. PMOP is a metabolic disorder affecting bone metabolism, indicating that endogenous metabolites amelioration may be a novel strategy for PMOP therapy. However, what the metabolic profile of POMP will be after PUE treatment is still obscure.

Purpose: We purpose to figure out the metabolic characteristics of PMOP and to explore the intrinsic mechanism on the anti-osteoporosis efficacy after PUE treatment based on the serum metabolomics.

Methods: We established OVX rats as osteoporosis model, and the animals were distributed into Sham, OVX, and OVX+PUE (100 mg/kg/d) group. The femurs were analyzed by μ-CT and three-point bending test. Serum metabolomics was performed by UPLC/Q-TOF-MS. We also determined the body weight, liver weight, and the levels of serum TC, TG, LDL-C, and HDL-C. The key proteins of the PPARγ pathway and Wnt pathway were analyzed by Western blot and qPCR experiments.

Results: PUE treatment for 14 weeks both improved the bone structure and ameliorated lipid metabolism in ovariectomized rats. By determination and further analysis of serum metabolomics, we revealed that the endogenous metabolites was significantly changed in ovariectomized rats, and PUE treatment adjusted 23 differential metabolites, which were involved in phospholipid metabolism metabolism and PUFAs metabolic pathways. Close correlationships were futher found between the indexes of bone metabolism, lipid metabolism and the differential metabolites, particularly LysoPA, S1P and n-3/n-6 PUFAs. Further, we discovered that PUE regulated differentiation of BMSCs to elicit anti-osteoporosis efficacy, attributing to Wnt/β-catenin signaling activation and PPARγ pathway inhibition initiated by metabolomics.

Conclusion: PUE improves OVX-induced osteoporosis and lipid metabolism by regulating phospholipid metabolism and biosynthesis of PUFAs, resulting in reducing the adipogenic differentiation and promoting osteogenic differentiation of BMSCs via Wnt pathway activation and PPARγ pathway inhibition in ovariectomized rats. The study provides us a novel mechanism to explain the improvement of osteoporosis by PUE, depicts a metabolic profile of PMOP, and gives us another point cut for further exploring the pathogenesis of PMOP and looking for biomarkers of osteoporosis.