“To evaluate the effects of the dipeptidyl peptidase-4 (DPP-4) inhibitor linagliptin on aortic pulse wave velocity (PWV) as a surrogate [endpoint] marker of arterial stiffness and early atherosclerosis in people with early type 2 diabetes.”39 (We recommend the use of the term “surrogate endpoint” rather than “marker”). Here, DPP4 is linked to type 2 diabetes mellitus.