NOX4 and type 1 diabetes mellitus: It was reported that the expression of NADPH oxidase subunits, p22phox and Nox4 was significantly increased in the heart of diabetic mice and rats [13,14,45,46], indicating that Nox4 was an important source of ROS in the left ventricle and Nox4-derived ROS contribute to cardiomyopathy at early stages of type 1 diabetes [45].