Uridine inhibits ROS-mediated osteoclast differentiation and alleviates osteoporosis via modulation of PI3K/Akt–FoxO signaling

Background: Osteoporosis is a metabolic bone disease characterized by dysregulated osteoclast activity, resulting in increased bone degradation and compromised bone microarchitecture. While the interconnection between osteoclast differentiation and cellular energy metabolism has become increasingly recognized, the role of pyrimidine metabolism in this process remains largely undefined. Methods: Integrative multi-omics analyses were performed to characterize transcriptional and metabolic alterations during receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast differentiation. The effects of uridine (UD) on osteoclast development and resorptive function were assessed in vitro using RAW264.7 cells and bone marrow-derived macrophages (BMMs). In vivo effects of UD on bone loss were evaluated in an ovariectomized (OVX) mouse model. Results: Integrative analyses revealed distinct metabolic remodeling during osteoclast differentiation and identified UD as a pivotal metabolite that showed a significant decline upon RANKL stimulation. Experimental evidence indicated that exogenous UD supplementation significantly suppressed osteoclast development and resorptive function, along with a reduction in the expression of nuclear factor of activated T cells c1 (NFATc1) and cathepsin K (CTSK). In OVX mice, UD administration improved trabecular microarchitecture, reduced osteoclast burden, and mitigated bone loss. Mechanistically, UD inhibited phosphoinositide 3-kinase/protein kinase B (PI3K/Akt) phosphorylation, facilitated Forkhead box O (FoxO) nuclear translocation, and suppressed reactive oxygen species (ROS) accumulation, thereby preventing NFATc1 activation and nuclear import. Conclusion: Collectively, this research identifies a novel metabolic-signaling interplay linking pyrimidine metabolism with osteoclast differentiation and highlights UD as a promising metabolic regulator for the treatment and prevention of osteoporosis.