The Role of the Intraplaque Vitamin D System in Atherogenesis

Table 3

Observational studies investigating the relationship between vitamin D and endothelial dysfunction.

Author	Year	Study design; (sample size)	Country; (ethnicity); Age	Correlation; (lower range of 25(OH)D)	Findings
Jablonski et al. [65]	2011	Cross-sectional; (75 subjects)	U.S.; (Caucasian, Hispanic and Asian); 50–79 years	Yes; (<50 nmol/L)	Brachial FMD was lower in vitamin D-deficient group (𝑃<0.01), showing a linear correlation with 25(OH)D (𝑃<0.01). Moreover, 25(OH)D showed a significant inverse correlation with IL-6 (𝑃<0.01) and CYP27B1 (𝑃<0.05).
Yiu et al. [66]	2011	Cross-sectional; (280 TDM2 and 73 matched healthy subjects)	Hong Kong; (not provided); Stratified	Yes; (<50 nmol/L)	Vitamin D-deficient group showed lower brachial FMD (𝑃=0.003). In addition, there was a significant linear correlation between low 25(OH)D levels and CD133+/KDR+ EPC (𝑃<0.001).
Al Mheid et al. [67]	2011	Cross-sectional; (554 healthy subjects)	U.S.; (Caucasian, African Americans and Hispanic); Mean 47 years	Yes; (linear correlation)	25(OH)D was independently correlated with brachial FMD (𝑃=0.03) and PWV (𝑃=0.04).
Chitalia et al. [68]	2012	Cross-sectional; (50 CKD patients)	U.K.; (not provided); 15–85 years	Yes; (linear correlation)	This study showed a linear correlation between 25(OH)D and brachial FMD (𝑃=0.007).
Syal et al. [69]	2012	Cross-sectional; (100 patients undergoing coronary angiography)	India; (Indian); Mean 56 years	Yes; (<50 nmol/L)	25(OH)D was independently correlated with brachial FMD (𝑃=0.002).
Karohl et al. [71]	2013	Cross-sectional; (368 soldiers from the Vietnam Era Registry)	U.S.; (Caucasian 93.5%); Mean 55 years	Yes; (<75 nmol/L)	CFR assessed with PET [^13N]ammonia was lower in vitamin D-deficiency group (𝑃=0.007).
Oz et al. [60]	2013	Cross-sectional; (222 patients undergoing coronary angiography)	Turkey; (Turkish); Stratified	Yes; (<75 nmol/L)	Patients with vitamin D deficiency has slower coronary flow (RR 3.5 (CI 95% 1.1–10.5); 𝑃=0.01). In addition, 25(OH)D deficiency correlated independently with FMD (𝑃<0.001)
Kuloglu et al. [70]	2013	Cross-sectional; (133 hypertensive patients)	Turkey; (Caucasian); Mean 62 years	Yes; (not available)	In this cohort 25(OH)D showed a signficant correlation with PWV (𝑟=−0.432; 𝑃<0.001)
Sypniewska et al. [62]	2014	Cross-sectional; (98 hypertensive patients)	Poland; (Caucasian); 42–58 years	Yes; (<52.5 nmol/L)	In this cohort 25(OH)D showed a signficant correlation with PWV (𝑟=−0.33; 𝑃=0.03)

FMD: flow-mediated dilation; IL: interleukin; CYP27B1: 25-hydroxyvitamin D-1-α hydroxylase; TDM2: type 2 diabetes mellitus; PWV: pulse wave velocity; CKD: chronic kidney disease; CFR: coronary flow reserve.