VEGFA-mediated role of estradiol on angiogenesis/adipogenesis process in the adipose tissue

Abstract

Adipogenesis and angiogenesis are two closely related processes. It is believed that a low angiogenic capacity may decrease the adipogenic potential and consequently promotes adipocyte hypertrophy, which in turn, is closely related to insulin resistance (IR). In this context, the vascular endothelial growth factor A (VEGFA) plays an important role, since changes on its expression and on the expression of its signaling machinery components may affect the development of obesity and, consequently, on IR. Estradiol (E2) is considered a protector against obesity and a regulator of the VEGF gene. In fat cells, E2 increases the expression of the glucose transporter GLUT4 (encoded by SLC2A4 gene) as well as glucose uptake, increasing insulin sensitivity. However nothing is known about the E2 effects on VEGF adipocyte production, and its consequence for cellular sensibility and much less about the adjacent molecular mechanisms. Our hypothesis is that E2 regulation in the adipogenesis/insulin sensibility is intrinsically related to angiogenesis, in a process that VEGF is a key regulator. Thus, the aim of the present work is to investigate the role of E2 on angiogenesis/adipogenesis interplay, determining the involvement of VEGF in this process and establishing some molecular mechanisms involved as: 1) Estrogen receptors mediation; 2) Glucose transporter 4 expression, and; 3) Transcriptional regulation by HIF1A and NFºB. For that, in vitro studies will be performed using 3T3-L1 adipocytes to investigate the effect of 17²-estradiol on Vefga and Slc2a4 expression during and after differentiation, in different doses and time points by real time PCR and Western Blotting. In the conditions in which important effects are observed, we will analyze the participation of the estrogens receptors, ESR1 and ESR2, by using specific agonist and antagonist, as well as the participation of NFºB and HIF1A factors by evaluating the binding activity in the promoter of target genes by Electrophoretic Mobility Assay (EMSA). In parallel, in vivo, we will investigate the vascularization and the expression of VEGF and its receptors, FLT1 and KDR, and GLUT4 in adipose tissue of ESR1 or ESR2 selective knockout mice (study in cooperation with Dr. Rodrigo P. Barros, University of Houston, USA). Furthermore, we will analyze the expression of CEBP-± and PPAR-³, intermediate markers of adipogenesis, in cells and in adipose tissue of transgenic mice. With these studies, we expected to elucidate the role of 17²-estradiol and VEGF on adipogenesis as well as on adipose cells insulin sensitivity, identifying new targets for preventive and / or therapeutic for obesity and insulin resistance.