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 (NO2 plus NO3) 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.