A recent combined in vivo and in vitro study demonstrated that metformin could improve metabolic disorders such as hyperglycemia via reducing the gut level of Bacteroides fragilis, which then increased specific BAs, inhibited intestinal farnesoid X receptor signals, and increased blood glucagon-like peptide 1 (GLP-1), and these actions together could improve blood sugar homeostasis (11). The gene discussed is GCG; the disease is metabolic disease.