Insulin decreases atherosclerosis by inducing endothelin receptor B expression.

Abstract

Endothelial cell (EC) insulin resistance and dysfunction, caused by diabetes, accelerates atherosclerosis. It is unknown whether specifically enhancing EC-targeted insulin action can decrease atherosclerosis in diabetes. Accordingly, overexpressing insulin receptor substrate-1 (IRS1) in the endothelia of <i>Apoe</i>^-/- mice (<i>Irs1/Apoe</i>^-/-) increased insulin signaling and function in the aorta. Atherosclerosis was significantly reduced in <i>Irs1/ApoE</i>^-/- mice on diet-induced hyperinsulinemia and hyperglycemia. The mechanism of insulin's enhanced antiatherogenic actions in EC was related to remarkable induction of NO action, which increases endothelin receptor B (EDNRB) expression and intracellular [Ca²⁺]. Using the mice with knockin mutation of eNOS, which had Ser1176 mutated to alanine (AKI), deleting the only known mechanism for insulin to activate eNOS/NO pathway, we observed that IRS1 overexpression in the endothelia of <i>Aki/ApoE</i>^-/- mice significantly decreased atherosclerosis. Interestingly, endothelial EDNRB expression was selectively reduced in intima of arteries from diabetic patients and rodents. However, endothelial EDNRB expression was upregulated by insulin via P13K/Akt pathway. Finally EDNRB deletion in EC of <i>Ldlr</i>^-/- and <i>Irs1/Ldlr^-/-</i> mice decreased NO production and accelerated atherosclerosis, compared with <i>Ldlr^-/-</i> mice. Accelerated atherosclerosis in diabetes may be reduced by improving insulin signaling selectively via IRS1/Akt in the EC by inducing EDNRB expression and NO production.