While negative or very weakly iNOS-immunostained cells were found in the control group (Figure 5A), immunohistochemical staining for iNOS in cardiac sections of the untreated diabetic group (T2DM) showed numerous iNOS-positive cells (Figure 5B,D), whose presence was significantly (p < 0.0001) reduced by metformin in the Met + T2DM group (Figure 5C,D). Here, NOS2 is linked to type 2 diabetes mellitus.