REN and chronic kidney disease: It is well known that the incidence of cardiovascular events and mortality is much higher in patients with chronic kidney disease (CKD) [1], because such patients, not only have classical risk factors for cardiovascular disease (CVD), such as hypertension, diabetes mellitus, dyslipidemia, and hyperuricemia, etc., but also have many non-classical CKD-specific risk factors for CVD, including anemia, volume over-load, mineral bone disorders, inflammation, malnutrition, and activation of the sympathetic nervous system and renin-angiotensin-aldosterone systems, among others [2].