25-hydroxyvitamin D, biomarkers of endothelial dysfunction and subclinical organ damage in adults with hypertension

The mechanism that underlies the association between low 25-hydroxyvitamin D [25(OH)D] and hypertension is not well understood; it seems to involve regulation of the renin-angiotensin-aldosterone system and the impact on endothelial function, cardiac remodeling, and subclinical organ damage. Vitamin D supplementation presents an ambiguous effect on endothelial function and arterial stiffness. We assess serum 25(OH)D3, biomarkers of endothelial dysfunction (soluble intercellular adhesion molecule [sICAM], C-reactive protein [CRP], homocysteine [Hcy]) and subclinical organ damage in adults with newly diagnosed untreated hypertension. Patients were classified based on ambulatory blood pressure monitoring: 98 had hypertension, whereas in 60 persons BP was normal. Laboratory assays including serum 25(OH)D3, hsCRP, Hcy, sICAM, glucose, insulin, lipids, echocardiography, pulse wave velocity (PWV), intima-media thickness (IMT), and left-ventricular mass (LVM) measurements were performed. 25(OH)D3 was significantly lower in hypertensive patients. The logistic regression analysis indicated that 25(OH)D3 reduced the probability of hypertension occurrence after adjusting for body mass index (BMI). 25(OH)D3 in those with hypertension correlated significantly with systolic BP (SBP; r = -0.39), PWV, IMT (r = -0.33), and diastolic BP (r = -0.26). Multiple regression analysis in patients with hypertension revealed that 25(OH)D3 and sICAM accounted for up to 27% of SBP variation after adjusting for age, BMI, and smoking. 25(OH)D3 and either PWV or IMT accounted for 23% of SBP variation. The impact of 25(OH)D3 was 10%. The impact of 25(OH)D3 on SBP variation, mediated by its effect on endothelial dysfunction and subclinical organ damage, is modest but significant.