Clostridium butyricum Promotes Bone Remodeling by Activating Inflammatory Genes in Mice

Clostridium butyricum (CB), a commensal gut bacterium with established probiotic properties, has demonstrated therapeutic potential in diverse human and animal pathologies. Despite its recognized benefits, the precise mechanisms underlying its influence on bone metabolism remain poorly understood. This study investigates the effects of CB on bone metabolism in murine models and elucidates the involved molecular pathways. Intragastric administration of CB to juvenile female mice significantly elevated osteogenic and osteoclastogenic gene expression profiles, correlating with increased bone mineral content (BMC) and bone mineral density (BMD). GC-MS metabolomic profiling identified butyric acid and acetic acid as primary bacterial metabolites. Subsequent in vitro analyses revealed that sodium butyrate (SB), sodium acetate (SA), and their combination (SB + SA) potently upregulated osteogenic/osteoclastogenic markers in total bone marrow adherent cells (BMCs). Concordant results were observed in vivo, where dietary supplementation with these metabolites enhanced bone remodeling. Notably, flow cytometry demonstrated significant expansion of CD45⁺/CD11b⁺ myeloid populations in bone marrow following CB or metabolite treatments, coinciding with upregulated pro-inflammatory gene such as Il-6 expression. Crucially, the bone remodeling effects of both CB and its metabolites were substantially diminished in Il-6-knockout (Il-6-KO) mice. These findings establish that CB enhances bone remodeling through butyrate- and acetate-dependent activation of inflammatory signaling pathways, particularly IL-6-mediated mechanisms. This study provides novel insights into microbiota-bone axis interactions and proposes probiotic interventions as potential therapeutic strategies for metabolic bone disorders.