Sitagliptin (SN), an orally active, potent dipeptidyl-peptidase inhibitor [DPP-4 inhibitor (Figure 1(A)) has recently been approved (listed in top 20 drugs in 2017) for the therapy of type 2 diabetes (Zerilli & Pyon, 2007). This evidence concerns the gene DPP4 and type 2 diabetes mellitus.