DPP4 and diabetes mellitus: Our findings indicated that DM significantly increased plasma DPP4 activity in the nonCAD control subjects (8.0 ± 2.9 vs. 6.4 ± 3.1 ng/L, P<0.01), whereas it tended to increase the blood DPP4 activity levels in the CAD patients (12.2 ± 4.4 vs. 10.9 ± 4.9 ng/L, P>0.05) (Tables 3 and 4).