Endothelial progenitor cell status in metabolic syndrome

Dysfunctional endothelial progenitor cells in metabolic syndrome

The metabolic syndrome (MetS) is highly prevalent and confers an increased risk of diabetes and cardiovascular disease. A key early event in atherosclerosis is endothelial dysfunction. Numerous groups have reported endothelial dysfunction in MetS. However, the measurement of endothelial function is far from optimum. There has been much interest recently in a subtype of progenitor cells, termed endothelial progenitor cells (EPCs), that can circulate, proliferate, and dfferentiate into mature endothelial cells. EPCs can be characterized by the assessment of surface markers, CD34 and vascular endothelial growth factor receptor-2, VEGFR-2 (KDR). The CD34(+)KDR(+) phenotype has been demonstrated to be an independent predictor of cardiovascular outcomes. MetS patients without diabetes or cardiovascular diseases have decreased EPC number and functionality as evidenced by decreased numbers of colony forming units, decreased adhesion and migration, and decreased tubule formation. Strategies that have been shown to upregulate and enhance EPC number and functionality include statins, angiotensin converting enzyme inhibitors, angiotensin receptor blockers, and peroxisome-proliferator-activating-receptor gamma agonists. Mechanisms by which they affect EPC number and functionality need to be studied. Thus, EPC number and/or functionality could emerge as novel cellular biomarkers of endothelial dysfunction and cardiovascular disease risk in MetS.

Circulating levels of endothelial progenitor cell mobilizing factors in the metabolic syndrome

Endothelial progenitor cells (EPCs) are an emerging biomarker of vascular health. However, there are few data on the biology and mobilizing factors of EPCs in metabolic syndrome (MS). The aim of this study was to assay EPC mobilizing factors, including granulocyte colony-stimulating factor, stem cell factor/c-kit ligand (SCF), vascular endothelial growth factor, and stromal cell-derived factor-1 levels, in patients with MS (n = 36) and age- and gender-matched controls (n = 38). There was a significant reduction of 83% in granulocyte colony-stimulating factor levels in patients with MS. Also, there were decreases in SCF and SCF soluble receptor levels. However, there was no significant difference in stromal cell-derived factor-1 levels, and paradoxically, vascular endothelial growth factor levels were increased, consistent with resistance. In conclusion, in addition to progenitor cell exhaustion as a mechanism for the decrease in EPCs in patients with MS, they also have a mobilization defect, as manifested by decreased levels of granulocyte colony-stimulating factor and SCF, resulting in a decrease in EPCs.