DPP4 and type 1 diabetes mellitus: From a therapeutic point of view, considering the burden of the pathology, insulin continues to be an agent of ordinary and necessary use in the pharmacological treatment of diabetes, especially in T1DM and despite the various pharmacological alternatives for the treatment of T2DM [GLP1-RA, sodium-glucose co-transporter-2 inhibitors (SGLT2i), Dipeptidyl peptidase 4 (DPP4)], often as an add-on to other molecules, in order to achieve the pre-established glycemic objectives [11,57,60].