The renin–angiotensin system is closely involved in the pathophysiology of CKD via overproduction of ROS,25 and renin–angiotensin system blockers such as ACE-I and ARB are reported to improve the prognosis of CKD.26 By contrast, few clinical trials have demonstrated the beneficial effects of direct antioxidant therapies not only for CKD patients but also for CAD patients. This evidence concerns the gene REN and chronic kidney disease.