Betaine alleviates renal osteodystrophy by stabilizing ABCG1 mRNA to inhibit HMOX1-mediated ferroptosis in BMSCs.

Renal osteodystrophy is a debilitating complication of chronic kidney disease characterized by deteriorated bone microarchitecture and impaired bone formation, leading to increased fracture risk. Despite the pressing need for anabolic therapies, the cellular mechanisms by which uremic stress compromises osteoprogenitor function remain poorly defined. Here, metabolomic profiling of renal osteodystrophy patient cohorts revealed a profound depletion of circulating betaine. We show that betaine supplementation not only rescued the osteogenic differentiation of bone marrow-derived mesenchymal stem cells challenged with the uremic toxin indoxyl sulfate but also ameliorated skeletal deterioration in a rat model of chronic kidney disease. Mechanistically, we demonstrated that indoxyl sulfate triggered ferroptosis in bone marrow-derived mesenchymal stem cells-characterized by iron-dependent lipid peroxidation and aberrant HMOX1 up-regulation-thereby arresting osteogenesis. Betaine mitigates this ferroptotic stress through a novel post-transcriptional mechanism. Specifically, betaine down-regulated the RNA-binding protein hnRNP A1, preventing the recruitment of the CNOT1 deadenylase complex. This inhibition stabilized Abcg1 mRNA, leading to restored ABCG1 expression. Functional perturbation studies confirmed that the ABCG1-HMOX1 axis was indispensable for the anti-ferroptotic and osteoprotective effects of betaine. Collectively, our findings delineate a Betaine-hnRNP A1/CNOT1-ABCG1-HMOX1 signaling cascade that links metabolic deficiency to ferroptosis-driven osteogenic failure, positioning betaine as a promising anabolic therapeutic strategy for renal osteodystrophy.