Abstract 9717: Reduction in Arnt/hif1 Beta Mediates Vascular Dysfunction in Mice with Type 2 Diabetes Mellitus

Abstract

Introduction: Endothelial dysfunction, especially at the microvasculature level, is one of the most deleterious events in diabetes. ARNT is a transcription factor that functions as a master regulator of glucose homeostasis, but its role in diabetic vascular complications is poorly understood Hypothesis: Aberrations in ARNT expression might contribute to the vascular deficiencies associated with diabetes Methods and Results: We found a reduction in ARNT expression in microvascular endothelial cells (MVECs) derived from type 2 diabetic mice (db/db). Thus, we generated an inducible, EC-specific ARNT-knockout mutation (ArntΔEC, ERT2) to address the hypothesis that aberrations in ARNT expression might contribute to the vascular deficiencies associated with diabetes. We show here that loss of ARNT in the endothelium mimics diabetic phenotypes, such as impairs blood flow recovery after hindlimb ischemia (n=8-12, p<0.01 vs Control group), delays wound healing, and exacerbates infiltration of pro-inflammatory neutrophils after myocardial infarction. Interestedly, the degree of these impairments in the KO mice was more remarkable in diabetic animals induced with high-fat chow (n=10, P<0.01vs Control) In addition, the siRNA-mediated knockdown of ARNT activity reduced tube formation and cell viability measurements in HUVECs cultured under high-glucose conditions. The ArntΔEC, ERT2 mutation also reduced measures of cell viability while increasing the production of reactive oxygen species (ROS) in MVECs isolated from mouse skeletal muscle, and the viability of ArntΔEC, ERT2 MVECs under high-glucose concentrations increased when the cells were treated with a ROS inhibitor. Conclusions: Collectively, these observations suggest that declines in endothelial ARNT expression contribute to the suppressed angiogenic phenotype in diabetic mice, and that the cytoprotective effect of ARNT expression in ECs is at least partially mediated by declines in ROS production. Endothelial ARNT might be a critical mediator of endothelial function and could serve as a therapeutic target for diabetic complications.