Interestingly, plasma concentrations of DPP-4 protein increased after a single dose and after 12 weeks of treatment with the DPP-4 inhibitor, sitagliptin, in patients with type 2 diabetes, while plasma DPP-4 enzymatic activity decreased by more than 80% for the entire duration of DPP-4 inhibitor therapy [42]. The gene discussed is DPP4; the disease is type 2 diabetes mellitus.