Intermittent hypoxia–driven gut microbial and metabolic remodeling in obstructive sleep apnea: mechanisms and evidence across target organs

Obstructive sleep apnea (OSA) exposes tissues to recurrent intermittent hypoxia (IH) and is associated with multisystem morbidity. Growing evidence implicates the gut microbiota and microbial metabolism in these consequences, but their contribution to target-organ injury remains uncertain. This narrative review examines how IH remodels the intestinal environment and evaluates the evidence linking these changes to systemic injury, distinguishing preclinical experimental findings from human clinical observations. IH can disturb intestinal oxygen homeostasis, impair epithelial barrier function, and alter microbial and host–microbial metabolic pathways involving short-chain fatty acids, bile acids, and trimethylamine N-oxide. These changes may influence distant tissues through metabolic signaling and immune activation. Preclinical studies support a functional microbial contribution to selected cardiovascular, metabolic, and neurocognitive phenotypes, but mechanistic resolution and applicability vary with exposure conditions, diet, and host background. Human studies remain predominantly observational and do not establish microbial mediation of OSA-related organ injury. Overall, the gut microbiota is best regarded as a context-dependent contributor and amplifier of IH-related injury, rather than a universal mediator. A focus on microbial function and host–microbial co-metabolism may be more informative than inconsistent taxonomic signatures. Longitudinal studies and targeted interventions are needed to establish clinical relevance and determine whether microbiome-directed approaches can complement established OSA treatment.