SCFAs, especially acetic acid, butyric acid, and propionic acid, have the function of improving glucose regulation and insulin sensitivity in T2DM patients by triggering glucagon-like peptide-1 (GLP-1) and peptide YY (PYY) production, inhibiting β-cell apoptosis, and stimulating insulin secretion [48,49]. This evidence concerns the gene GCG and type 2 diabetes mellitus.