Hypovitaminosis D is Associated with Endothelial Dysfunction in Patients with Metabolic Syndrome

Objectives: Recent research has shown that hypovitaminosis D may increase the risk of hypertension, vascular disease, diabetes mellitus, obesity and Metabolic Syndrome (MetS). Endothelial Dysfunction (ED) is one of the key components of MetS which is associated with an imbalance between vasoactive substances such as Nitric Oxide (NO) and Endothelins (ET). In this study, we assessed the association of 25(OH) D3 level with endothelial dysfunction and subclinical atherosclerosis in MetS patients. Design and Methods: 105 MetS patients and 48 controls were included. 25(OH) D3 levels were measured using Ultra-High Performance Liquid Chromatography (UHPLC). NOx (NO 2 plus NO 3 ) and Endothelin- 1(ET-1) concentrations were determined along with routine biochemical tests. Flow-Mediated Dilatation (FMD) and carotid Intima-Media Thickness (cIMT) were measured by ultrasonography. Results: In MetS patients, vitamin D and NOx levels were significantly lower (p<0.001), while ET-1 levels were higher than controls (p<0.005). MetS patients with ED exhibited significantly lower vitamin D levels than their counterparts free of ED. Vitamin D levels were correlated positively with FMD and NOx, and negatively with systolic blood pressure and body mass index. Subclinical atherosclerosis as assessed by the cIMT did not associate with low vitamin D levels. Conclusion: Vitamin D deficiency seen in MetS patients is more prominent in the presence of ED. Hypovitaminosis D may affect endothelial cells, and participate in the development of hypertension.