The hypoxia–gut microbiota–bile acid axis: mechanistic crosstalk and therapeutic opportunities

Hypoxia is a central feature of a wide range of pathological conditions; however, the metabolic regulatory networks underlying hypoxic adaptation remain incompletely understood. In recent years, accumulating evidence suggests that bile acids, traditionally regarded as metabolic end products, also function as signaling molecules and may participate in hypoxia-related regulation. Nevertheless, this association is largely indirect and context-dependent. In this context, the gut microbiota has emerged as a key intermediary. It is highly sensitive to fluctuations in oxygen tension and plays a dominant role in shaping bile acid composition, including the generation of secondary and microbially conjugated bile acids. Collectively, these observations raise the possibility that hypoxic signaling, microbial dynamics, and bile acid metabolism are functionally interconnected within an integrated regulatory network that remains to be fully defined. In this review, we propose a hypoxia–microbiota–bile acid axis as one of a central regulatory hub in hypoxic adaptation. Hypoxia-inducible factors regulate bile acid synthesis and transport while reshaping gut microbial composition, thereby altering the bile acid pool. In turn, bile acids feed back on hypoxia signaling, modulating oxidative stress, inflammation, and metabolic homeostasis. Microbiota-derived bile acids further amplify these effects through receptor-mediated pathways. Notably, these interactions are highly tissue- and context-dependent, leading to both protective and detrimental outcomes. Within this framework, we further delineate how host HIF signaling may selectively enrich MCBA-competent bacterial taxa and activate their biosynthetic machinery at the host–microbial interface, thereby connecting hypoxic sensing to a structurally distinct class of microbial metabolites. Elucidating this network may advance our understanding of hypoxia-related diseases and uncover therapeutic opportunities targeting the microbiota–bile acid interface. Oxygen shortage (also called hypoxia) is common in many diseases, such as heart problems, stroke, and chronic inflammation. When oxygen levels drop, the body must adjust how it produces energy and maintains balance. One important but often overlooked part of this response involves the gut, where trillions of microbes help regulate many processes that keep us healthy. These gut microbes play a key role in transforming bile acids—natural substances made by the liver that not only help digest food but also act as signals controlling metabolism, immunity, and stress responses. Recent research shows that low oxygen levels can reshape the gut microbial community, which in turn changes how bile acids are modified. This creates a close link between oxygen levels, gut microbes, and bile acid activity. In this review, we explain how this interconnected system works and how it influences the body’s response to stress. Some bile acids produced by microbes can help protect tissues, reduce inflammation, and support energy balance. However, under certain conditions, they may also contribute to cell damage and disease. Overall, this system acts like a double-edged sword. A better understanding of these interactions may lead to new treatments for diseases linked to low oxygen, metabolic disorders, and inflammation by targeting gut microbes or bile acid pathways.