GCG and type 2 diabetes mellitus: Moreover, the higher the abundance and diversity of SCFA-producing bacteria are, the more improvement observed in the hemoglobin A1c levels of the subjects, which can be partly attributed to the SCFA-mediated increase in glucagon-like peptide-1 (GLP-1) production.47 However, this study is not sufficient to highlight the causal metabolic links between certain SCFAs and type 2 diabetes.