DPP4 and diabetic kidney disease: DPP-4, also known as CD26, is a peptidase expressed on the cell surface of most hematopoietic cells.[13] DPP-4 cleaves a wide variety of substrates, including the chemokine stromal cell-derived factor-1 and, more importantly, the N-terminal of erythropoietin.[14] A previous study showed that hematopoiesis after radiation or chemotherapy was enhanced in DPP-4 knock-out mice or mice receiving an orally active DPP-4 inhibitor.[14] However, to the best of our knowledge, there is no human study on the relation between DPP-4 inhibitor therapy and anemia in DKD patients.