Abstract 4363338: B-type Natriuretic Peptide Reverses Vascular Endothelial Insulin Resistance and Ameliorates Oxidative Stress in Human Atherosclerosis

Abstract

Aim: Patients with atherosclerosis and type 2 diabetes (T2DM) on aggressive insulin therapy have poor cardiovascular outcomes. Atherosclerosis patients with and without T2DM exhibit vascular endothelial insulin resistance. When exposed to insulin, pathological endothelial signalling activates NADPH oxidase (NOX) and uncouples endothelial nitric oxide synthase (eNOS), resulting in excess superoxide production and consequently, vasoconstriction, inflammation, and oxidative stress. DPPIV inhibitors ameliorate this effect ex vivo but do not confer prognostic clinical benefits. B-type natriuretic peptide (BNP) is a DPPIV substrate that may modulate endothelial insulin and redox signalling. Methods: Blood, internal mammary artery (IMA) and saphenous vein (SV) were collected from 391 adults undergoing coronary bypass surgery. Plasma BNP was measured by ELISA. DNA was extracted from whole blood and sequenced. Sequential vessel rings were incubated in 4 conditions (control, insulin, BNP, insulin&BNP). Baseline, NOX-derived and LNAME-delta superoxide production were measured in IMAs via chemiluminescent luminometry. Endothelial function was quantified in SVs via vasomotor studies. Western blotting quantified activation of endothelial signalling molecules (AKT, ERK, eNOS, IRS1, RAC1). Patients were followed up for 10 years. Results: Insulin impairs endothelium-dependent vasorelaxation (p=0.01) whilst BNP with insulin improves endothelium-dependent vasorelaxation (p=0.04)(1A-C). Insulin increases IMA resting (p<0.001) and NOX-derived (p<0.001) superoxide production and uncouples eNOS (p=0.027)(2A-D). BNP combined with insulin restores these to normal levels (2A-D). BNP with and without insulin recouples eNOS (p=0.037)(2D). Insulin alone increases endothelial ERK (p=0.004)(3B) and IRS1 (p=0.03)(3D) phosphorylation and RAC1 activation (p=0.03)(3E) but does not activate AKT or eNOS (3A&C). BNP with insulin increases AKT (P=0.004)(3A) and eNOS (p=0.03)(3C) phosphorylation and reduces IRS1 phosphorylation (p=0.008)(3D) and RAC1 activation (p=0.01)(3E). A SNP causing increased nppb expression and plasma BNP (rs198983) is associated with increased NOX-derived superoxide (p<0.05)(3F) and increased major adverse cardiovascular event rates (p=0.03)(1D). Conclusion: BNP sensitises the arterial wall to insulin and ameliorates pathological redox signalling related to vascular insulin resistance. BNP could be used to reverse the pro-atherogenic profile of insulin treatment in T2DM.