Macrophage metabolic reprogramming via HIF-1α-glycolysis drives osteoblast ferroptosis and bone loss through an IL-6-STAT3-dependent redox axis.

BACKGROUND

Postmenopausal osteoporosis (PMOP) is characterized by exacerbated bone resorption and inadequate bone formation, with macrophage-driven inflammation playing a key role. However, how immunometabolic reprogramming of macrophages modulates osteoblast fate remains unknown.

METHODS

Using integrated single-cell and bulk transcriptomics, we identified a hypermetabolic macrophage subpopulation in PMOP marrow reliant on HIF-1α-glycolysis. We pharmacologically disrupted this axis with the HDAC inhibitor valproic acid (VPA) and validated its function using the HIF-1α stabilizer DMOG. The paracrine effects on osteoblasts were assessed via conditioned medium, focusing on ferroptosis and differentiation. Therapeutic efficacy was tested in ovariectomized rats.

RESULTS

VPA upregulated HIF1AN, enhancing its binding to HIF-1α and promoting its degradation. This suppressed glycolytic flux and M1 polarization, reducing IL-6 secretion. The altered secretome protected osteoblasts from ferroptosis by inhibiting the IL-6/p-STAT3/HIF-1α/TFRC axis and rebalancing GPX4/ACSL4. Osteogenic differentiation was restored. In OVX rats, VPA improved bone mass and microstructure, effects abolished by DMOG.

CONCLUSION

We unveil a macrophage-centric immunometabolic checkpoint that is linked to osteoblast ferroptosis via IL-6/STAT3 signaling. Targeting this HIF-1α-glycolysis axis, exemplified by VPA, represents a novel therapeutic strategy for PMOP.