ET-1 is a potent vasoconstrictor mainly produced by mesangial cells in the kidneys, and renal microcirculation is particularly susceptible to ET-1 [35], which may explain why plasma ET-1 levels were found to be elevated in diabetic patients with microalbuminuria [36], but not elevated in our patients with normoalbuminuric renal insufficiency. The gene discussed is EDN1; the disease is Renal insufficiency.