DPP4 and type 1 diabetes mellitus: In the above-described murine model of type 1 diabetes studied by the author and collaborators [64], immunohistochemical and Western blot analyses revealed that DPP-4 was up-regulated in the glomerular basement membrane, tubules, and peritubular vascular cells of the kidneys of diabetic mice compared with control mice; however, linagliptin reduced the expression and enzymatic activity of DPP-4 as well as the expression of TGF-β1 and TGF-β2 [64].