Shin et al. showed that treatment with metformin significantly improved the high-fiber diet-fed mice’s glycemic status and showed higher abundance of the mucin-degrading bacterium A. muciniphila than controls, emphasizing that drugs favoring A. muciniphila species may be a potential therapeutic approach for type 2 diabetes (Shin et al., 2014). This evidence concerns the gene MUC5AC and type 2 diabetes mellitus.