Naringin inhibits the osteoblast-osteoclast pyroptosis cascade reaction mediated by accumulated bone marrow adipose tissue in the treatment of postmenopausal osteoporosis

Background: Excessive expansion of bone marrow adipose tissue (BMAT) is considered to be a crucial factor leading to postmenopausal osteoporosis (PMOP). Conventional osteoporosis drugs mainly focus on inhibiting bone resorption, promoting bone formation or calcium absorption, with less emphasis on regulating BM adiposity. Potential therapeutic agents need to be screened. The objective of this study is to explore the potential mechanisms by which naringin (NG), abundant in citrus fruits, regulates lipid metabolism and exerts bone-protective activities.

Methods: Key pathways and molecular mechanisms underlying NG's amelioration of PMOP symptoms in mice were investigated using RNA Sequencing. Molecular docking and surface plasmon resonance were employed to identify the direct targets of NG. The roles of key molecules identified were validated in PMOP through in vivo overexpression or pharmacological inhibition.

Results: NG treatment improved ovariectomy-induced bone loss and reduced bone marrow fat accumulation. Correspondingly, the co-culture system of adipocytes/osteoblasts suggested impaired osteoblast functionality and alterations in mitochondrial dynamics, which was reversed by NG through its antioxidative effect to restore mitochondrial fission and fusion balance. Furthermore, RNA Sequencing results revealed that adipocytes induced osteoblast Pyroptosis mediated by NLRP3 inflammasomes. This osteoblast Pyroptosis was alleviated following NG to clear ROS or target TLR2 to inhibit MyD88/NF-κB pathway activation. Subsequently, a strong M1 macrophage polarization tendency was observed, as well as accelerated early osteoclast differentiation induced by RANKL, in a co-culture system of pyroptosis-affected osteoblasts and macrophages. However, these changes were reversed by early NG in osteoblasts. Finally, anti-PMOP effect of NG was attenuated in PMOP mice with overexpressed NLRP3, and pharmacological inhibition of NLRP3 alleviated the PMOP symptoms.

Conclusion: NG can regulate osteoblast mitochondrial dynamics disorder through suppression of BMAT-mediated lipotoxicity, and can modulate the MyD88/NF-κB signaling pathway via direct targeting of TLR2, thereby inhibiting the adipocyte-osteoblast-osteoclast Pyroptosis cascade.

The translational potential of this article: This study highlights the pivotal role of BMAT-triggered Pyroptosis cascades in PMOP pathogenesis and demonstrates NG's therapeutic potential. Our findings position bone marrow adiposity modulation as a promising anti-PMOP strategy, emphasizing the importance of developing natural adiposity regulators like NG for targeted intervention.

NLRP3; Naringin; Postmenopausal osteoporosis; Pyroptosis; TLR2/MyD88/NF-κB.