The study by Smits et al. in 2021 enrolled 51 DM patients treated with GLP1 agonists (glucagon-like peptide-1 receptor agonists, such as Liraglutide) or DPP-4 inhibitors (dipeptidyl peptidase-4 inhibitors, such as Sitagliptin) to analyze any changes in microbiota and found that there were no statistically significant changes [189]. This evidence concerns the gene DPP4 and diabetes mellitus.