RAC1 and diabetes mellitus: The small GTP‐binding protein Rac1 might represent a suitable target to inhibit maladaptive NOX activity.17, 18 Rac1 was previously found to activate NOX in endothelial cells and to promote ROS production in response to stress.17, 18 Rac1 increases vascular permeability and inflammation.17, 18 In addition, we previously found that Rac1 inhibition rescues both diabetes mellitus‐induced and high blood pressure–induced arterial endothelial dysfunction.19, 20 However, the role of Rac1 in the development of human endothelial dysfunction, particularly in veins, is unknown.