In failing hearts obtained from patients with dilated cardiomyopathy (compared to donors with normal hearts), the level of NOX4 was significantly higher, whereas the level of NOX4 phosphorylated at Y566 was lower, resulting in a decreased ratio of phosphorylated NOX4 to total NOX4 in dilated cardiomyopathy (DCM) hearts [49]. Here, NOX4 is linked to dilated cardiomyopathy.