GCG and diabetes mellitus: The combination of SCFAs and G protein-coupled receptor (GRP) can induce the secretion of glucagon-like peptide-1 (GLP-1) (Yao et al., 2020), while GLP-1 can protect the organism’s islet β cells, improve insulin resistance, ultimately improve the symptoms of DM (Hwang et al., 2015; Wang et al., 2019).