Gut-bone axis crosstalk: Microbiota-driven immune-metabolic-neural networks in bone disorders and precision interventions.

The gut microbiota regulates bone metabolism via a complex gut-bone axis involving short-chain fatty acids (SCFAs), immune modulation, and neuroendocrine signals. However, the precise mechanisms remain unclear, and microbiota-targeted interventions (probiotics, prebiotics, fecal microbiota transplantation) are not yet optimized for clinical use. This review systematically synthesizes the immune-metabolic-neural interaction network within the gut-bone axis, highlighting non-linear crosstalk among SCFAs, bile acids, tryptophan derivatives, immune cells (macrophages, Treg/Th17), and vagus nerve signaling. We critically assess translational hurdles, including heterogeneous study designs, confounding factors, and lack of causal evidence. Based on this network perspective, we propose a framework for future research that prioritizes multi-omics approaches, stratified interventions, and rigorous trials. This synthesis advances understanding of how gut dysbiosis drives bone disorders and paves the way for precision skeletal medicine. Translational potential statement: This review identifies microbial markers for risk stratification of bone metabolic disorders and discusses SCFA-based strategies and fecal microbiota transplantation (FMT) in conditions including osteoporosis, impaired fracture healing, rheumatoid arthritis, and glucocorticoid-associated osteonecrosis. It provides testable hypotheses for large-scale randomized controlled trials (RCTs), directly supporting translation of microbiome research into clinical practice for bone disorders.