Circulating endothelial progenitor cells in type 1 diabetic patients with erectile dysfunction

Circulating endothelial progenitor cells (EPCs) are bone marrow-derived stem cells able to migrate to sites of damaged endothelium and differentiate into endothelial cells, thereby contributing to vascular repair. Recent studies demonstrated a reduction of EPCs in patients with diabetes mellitus or erectile dysfunction (ED). The aim of this study was to evaluate the circulating levels of different EPCs phenotypes and their relation with testosterone levels in young type 1 diabetic patients with ED. We studied 118 consecutively type 1 diabetic patients and 60 age-matched healthy controls. Erectile function was assessed by completing the International Index of Erectile Function (IIEF-5) and EPCs levels by flow cytometry. Testosterone concentrations were evaluated in all the study population. We identified 38 diabetic patients with ED (Group 1) and 80 patients without ED (Group 2). CD34+KDR+CD133+ cells were significantly lower in patients in Group 1 as compared with those in Group 2 [median and interquartile range, n/106 events, 12 (6–16) vs. 18 (13–22), P < 0.001)]. In all participants in the study, there was a significant correlation between circulating CD34+KDR+CD133+ cells and testosterone levels (r = 0.410, P < 0.001), which was highest in Group 1, intermediate in Group 2, and lowest in Group 3 (controls). There was a significant correlation between IIEF-5 score and both CD34+KDR+ (r = 0.459, P = 0.003) and CD34+KDR+CD133+ (r = 0.316, P = 0.050) cells among patients of Group 1, as well as between testosterone levels and most of the EPCs phenotypes. Finally, multivariate regression analysis identified levels of circulating CD34+KDR+ cells as an independent risk factor for ED (β-coefficient 0.348, P = 0.007). In conclusion, type 1 diabetic patients with ED show reduced levels of CD34+KDR+CD133+ cells, whose number correlates with IIEF. Further studies are needed to fully understand the exact mechanisms by which testosterone regulates vascular homeostasis.