COL18A1 and chronic kidney disease: Moreover, we have recently shown that asymmetric dimethyl arginine (ADMA), a key, competitive inhibitor of endothelial nitric oxide synthase, and related circulating angiogenesis inhibitors endostatin (END), thrombospondin-2 (TSP), and angiopoietin-2 (ANG) are increased in patients with chronic kidney disease, a patient population at increased risk for coronary artery disease.