In vitro and in vivo experiments have confirmed that the absence of A. muciniphila is a primary feature of metabolic and inflammatory diseases, and supplementing with live or pasteurized bacteria, or A. muciniphila extracellular vesicles (AmEVs), can reverse obesity, improve glucose tolerance and insulin resistance (Cani et al., 2022), reduce epithelial permeability, and thicken the mucus layer. The gene discussed is INS; the disease is obesity due to melanocortin 4 receptor deficiency.