In a previous study, in rats with tacrolimus-induced diabetes, the dipeptidyl peptidase-4 (DPP4) inhibitor, MK-0626, decreased the levels of 8-OHdG (a marker of oxidative DNA damage) and increased the levels of manganese superoxide dismutase and heme oxygenase-1 (41). This evidence concerns the gene HMOX1 and diabetes mellitus.