Abstract 17140: Nitric Oxide Production is Decreased in the Left Ventricle of Diabetic Subjects Undergoing Coronary Artery Bypass Grafting

Abstract

Introduction: Dysregulation of endothelial nitric oxide synthase (eNOS) and generation of nitric oxide (NO) are critical early indicators for diabetes-induced endothelial dysfunction and cardiovascular complications. We hypothesize that levels of NO production and eNOS expression by endothelial cells are decreased in DM subjects when compared to non-DM subjects. Methods: The study cohort consisted of 9 non-DM subjects and 6 DM subjects undergoing myocardial biopsy at the time of coronary artery bypass grafting surgery. The non-myocyte cell suspensions from the left ventricle (LV), right atrial appendages (RAA), and skeletal muscle (SKM) tissue were analyzed by flow cytometry to measure production of nitric oxide in subpopulations of endothelial and non-endothelial cells. Cells in suspension were incubated with DAF-2DA in the presence or absence of NO synthase inhibitor, L-NAME. Flow cytometry was used to determine production of NO in subpopulations of endothelial and non-endothelial cells from biopsies. Measurements of eNOS and phospho-eNOS (ser1177) were performed using western blot. Results: Basal Nitric oxide production was measurable in non-diabetic subjects \ in 55%, 80% and 65% of unstimulated endothelial cells obtained from RAA, LV and SKM biopsies, compared to 40%, 40%, and 66%, respectively in diabetic subjects ( P < 0.02, DM vs Non-DM). No differences were found in the number of NO-producing non-endothelial cells between DM and non-DM subjects. The level of eNOS showed a trend towards decreased protein expression in DM subjects compared to non-DM. Conclusions: Generation of NO by endothelial cells and level of eNOS expression are decreased in left ventricular endothelial cells of DM patients compared to non-DM. Left ventricular biopsies can be used safely for assessment of NO dysregulation and endothelial dysfunction, and whether these can be improved with interventions targeting diabetic cardiovascular disease.