25-Hydroxyvitamin D status, arterial stiffness and the renin-angiotensin system in healthy humans

Vitamin D deficiency is associated with increased arterial stiffness. We sought to clarify the influence of vitamin D in modulating angiotensin II-dependent arterial stiffness. Thirty-six healthy subjects (33 +/- 2 years, 67% female, mean 25-hydroxyvitamin D 69 +/- 4 nmol/L) were studied in high salt balance. Arterial stiffness, expressed as brachial pulse wave velocity (bPWV) and aortic augmentation index (AIx), was measured by tonometry at baseline and in response to angiotensin II infusion (3 ng/kg/min x 30 min then 6 ng/kg/min x 30 min). The primary outcome was change in bPWV after an angiotensin II challenge. Results were analyzed according to plasma 25-hydroxyvitamin D status: deficient (<50 nmol/L) and sufficient (>= 50 nmol/L). There were no differences in baseline arterial stiffness between vitamin D deficient (25-hydroxyvitamin D 40 +/- 2 nmol/L) and sufficient (25-hydroxyvitamin D 80 +/- 4 nmol/L) groups. Compared with sufficient vitamin D status, vitamin D deficiency was associated with a decreased arterial response to angiotensin II challenge (Delta brachial pulse wave velocity: 0.48 +/- 0.44 m/s versus 1.95 +/- 0.22 m/s, p = 0.004; Daortic augmentation index: 9.4 +/- 3.4% versus 14.2 +/- 2.7%, p = 0.3), which persisted for brachial pulse wave velocity response after adjustment for covariates (p = 0.03). Vitamin D deficiency is associated with increased arterial stiffness in healthy humans, possibly through an angiotensin II-dependent mechanism.