The role of Akkermansia muciniphila in human disease: a friend or a foe?

Akkermansia muciniphila ( A. muciniphila ) was isolated and identified about two decades ago. It has drawn great attention due to its close association with diseases, such as obesity, diabetes, inflammatory bowel disease (IBD), liver steatosis, asthma and cardiovascular diseases. Research on the biological functions of A. muciniphila in human diseases has made it a potential probiotic with several therapeutic properties: it helps maintain gut barrier function, reduce brain atrophy, release inflammatory responses, and improve bone health. Its abundance and activity, however, are shaped by a complex interplay of environmental and host factors, including diet, medication, oxygen, bile acids, and microbial interactions. Here we review the genotypic diversity of A. muciniphila and its involvement in oral, atopic, respiratory, intestinal, metabolic, cardiovascular, rheumatic, skeletal, and neurological diseases, with particular attention to its bioactive components—such as the outer membrane protein Amuc_1100, extracellular vesicles, and the GLP-1-inducing protein P9—and the mechanisms through which they act. We also weigh the evidence that, in certain host contexts or in the presence of specific pathogens, A. muciniphila may aggravate rather than alleviate disease. A clearer, strain-level understanding of these context-dependent effects will be essential if A. muciniphila is to move from a promising commensal to a safe and effective therapy. The isolation, identification of A. muciniphila strains with beneficial effects and the large-scale industrial production challenges the translational applications.