REN and chronic kidney disease: Deterioration of renal function could promote increased arterial stiffness due to the presence of risk factors for CVD or through hemodynamic and metabolic mechanisms, such as hypervolemia secondary to CKD, abnormal calcium and phosphorus metabolism—leading to calcification of vessel walls, the direct effect of uremic toxins, and hyperactivation of the renin-angiotensin system [3,4,7].