Gut Microbiota Regulates Brain-Bone Axis to Influence Osteoporosis Pathogenesis and Treatment.

Osteoporosis is a systemic skeletal disorder characterized by reduced bone mass, impaired microarchitecture, and increased fracture risk, primarily resulting from dysregulated bone remodeling. Increasing evidence highlights a close interaction between bone metabolism and the gut microbiota. Alterations in bone mineral density can influence gut microbial composition. Conversely, microbial dysbiosis disrupts bone homeostasis through multiple pathways, including microbial metabolites, immune regulation, and neuroendocrine signaling. Short-chain fatty acids suppress osteoclast differentiation and enhance intestinal calcium absorption, while gut dysbiosis promotes bone loss by impairing intestinal barrier integrity and increasing proinflammatory cytokines such as tumor necrosis factor-α and interleukin-6. The gut-brain-bone axis represents an important regulatory network linking the central nervous system, gut-derived signals, and skeletal remodeling. Chronic stress and neurodegenerative conditions activate the hypothalamic-pituitary-adrenal axis and bone-derived extracellular vesicle signaling, thereby favoring bone resorption. Estrogen deficiency further disrupts the receptor activator of nuclear factor κΒ ligand/osteoprotegerin signaling pathway and alters gut microbial composition, contributing to postmenopausal bone loss. Therapeutic strategies targeting this axis, including probiotics, prebiotics, fecal microbiota transplantation, dietary fiber supplementation, and pharmacological or natural compounds, show potential in restoring microbial balance and improving bone metabolism. Future studies integrating multiomics approaches and well-designed clinical trials are needed to clarify microbiome-bone interactions and support the development of targeted interventions for osteoporosis.