ACAT1 inhibitor Avasimibe suppresses osteoclastogenesis and alleviates ovariectomy-induced bone loss via CKB/PI3K-AKT signaling

Excessive osteoclast-mediated bone resorption is central to osteoporosis pathogenesis. We initially observed that Acyl-CoA Cholesterol Acyltransferase-1 (ACAT1) is significantly upregulated during receptor activator of nuclear factor kappa-B ligand (RANKL)-induced osteoclastogenesis, and its knockdown potently inhibited osteoclastogenesis. This prompted us to investigate the therapeutic potential of Avasimibe (AVA), a specific ACAT1 Inhibitor, originally developed for atherosclerosis due to its suppression of Cholesterol esterification and anti-inflammatory effects, for osteoporosis treatment. In vitro, AVA markedly suppressed RANKL-induced osteoclastogenesis without cytotoxicity, as demonstrated by tartrate-resistant Acid Phosphatase (TRAP) staining, immunofluorescence, quantitative Real-Time PCR (qRT-PCR), and western blot analysis. In vivo, AVA administration effectively attenuated bone loss in ovariectomized (OVX) mice, significantly improving bone mineral density, preserving trabecular microarchitecture. Mechanistically, RNA Sequencing (RNA-seq) and bioinformatic analysis revealed that AVA downregulates Creatine Kinase B (CKB), a key mediator identified as upregulated during osteoclastogenesis, consequently inhibiting the phosphatidylinositol 3-kinase-protein kinase B (PI3K-AKT) signaling pathway. Critically, the inhibitory effects of AVA on osteoclast differentiation and PI3K-AKT activation were reversed by exogenous phosphocreatine (PCr). Collectively, our data demonstrate that AVA attenuates osteoclastogenesis and bone resorption by targeting the CKB/PI3K-AKT axis, identifying it as a promising novel therapeutic candidate for osteoporosis.