ACE2 and type 2 diabetes mellitus: Sitagliptin, 35 potential targets, 20 key signaling pathways and T2DM were imported into Cytoscape software to show the relationship between drug―target―signaling pathway―disease in the form of network topology (Figure 7), and further to study the molecular mechanism of sitagliptin in the treatment of T2DM, and to explore the role of ACE2.