Abstract 3698: Decreased Circulating Endothelial Progenitor Cells and Endothelial Dysfunction: a Novel Mechanism of Atherogenesis in Obesity.
Underlying mechanisms of endothelial dysfunction in obesity are not fully understood. Circulating Endothelial Progenitor Cells (EPCs) are known to promote endothelial repair. Our aim was to assess the number/function of EPCs in morbid obese individuals and its correlation with endothelial function and inflammatory markers. EPCs were isolated from 33 morbid obese patients (age 47±1.8 y; men=34%; BMI=49±2.1 kg/m2, metabolic syndrome=84%) and 20 lean controls. Peripheral blood EPC number was significantly reduced in obese patients both with flow cytometry (KDR+/CD34+; 0.041±0.04 vs 0.074±0.05 %events, p<0.001) and fluorescence analysis after short-term culture (49±4 vs 28±2 cells/field, p<0.001). The plasma number of primitive CD 133+ cells, and concentrations of VEGF (Elisa) and nitrogen oxides (which potentially recruit EPCs), were similar to control, suggesting that reduction of EPCs occurs distally to early cell differentiation. Importantly, C-Reactive Protein (CRP), robustly increased in obese patients (0.15±0.04 vs 1.3±0.3; p=0.003), was a strong predictor of reduced EPC number at multivariate analysis (r=0.623; p < 0.001). Likewise, the migratory response of EPCs to VEGF in vitro was significantly impaired in obese vs controls, despite similar VEGF receptor numbers. Multivariate analysis suggested potential roles of metabolic syndrome and leptin in such effect. Endothelial function at flow-mediated brachial artery reactivity was markedly reduced (by 60%) in obese patients, and had a significant inverse correlation with EPC number (r= 0.678; p< 0.001). Carotid intimal thickness was also increased in obese patients (0.68±0.02 vs 0.58±0.08; p=0.001). On the other hand, the number of circulating endothelial cells (CD31+/CD106+) was similar in both groups, suggesting that apoptosis was not enhanced in the obese. These results suggest for the first time that reduced number and migratory capacity of EPCs correlate with endothelial dysfunction or increased CRP and may be a key underlying mechanism of vascular complications and atherosclerosis in obesity.