MAOA and type 2 diabetes mellitus: In the first stage of GSE13270, according to the analysis of MaoA and MaoB protein expression in the islets of Type 2 diabetes mellitus in mice and humans, it can be found that the amount of MaoB in β cells of Type 2 diabetes mellitus is significantly reduced, which shows that the loss of Mao causes dysfunction of β cells, resulting in Type 2 diabetes [56].