Randomized controlled trial of vitamin D supplement on endothelial function in patients with type 2 diabetes
Yuen-Fung Yiu, Kai-Hang Yiu, Chung-Wah Siu, Yap-Hang Chan, Sheung-Wai Li, Lai-Yung Wong, Stephen W.L. Lee, Sidney Tam, Eric W.K. Wong, Chu-Pak Lau, Bernard M.Y. Cheung bernardmycheung at gmail.com, Hung-Fat Tse
Received 29 July 2012; received in revised form 2 December 2012; accepted 16 December 2012. published online 07 January 2013.
Suboptimal vitamin D status is associated with endothelial dysfunction and an increased risk of cardiovascular diseases but it is unclear whether vitamin D supplementation is beneficial. The aim was to investigate the effect of vitamin D supplementation on endothelial function in patients with type 2 diabetes mellitus (DM).
In a double-blind, placebo-controlled trial, we randomized 100 type 2 DM patients to vitamin D supplement (5000 IU/day, n = 50) or placebo (controls, n = 50) for 12 weeks. Assessment of vascular function with brachial artery flow-mediated dilatation (FMD), circulating levels of endothelial progenitor cells (EPCs) and brachial-ankle pulse wave velocity, and metabolic parameter, high-sensitivity C-reactive protein (hsCRP) and oxidative stress markers were performed before and after the supplementation.
After 12 weeks, vitamin D treated patients had significant increases in serum 25-hydroxyvitamin D [25(OH)D] concentration (treatment effect 34.7 ng/mL, 95% CI 26.4–42.9, P < 0.001) and serum ionized calcium (treatment effect 0.037 mmol/L, 95% CI 0.007–0.067, P = 0.018); decreased serum parathyroid hormone concentration (treatment effect −0.55 pmol/L, 95% CI −1.08 to −0.02, P = 0.042) compared to patients who received placebo.
Nevertheless, vitamin D supplementation did not improve vascular function as determined by FMD, circulating EPC count or baPWV (all P > 0.05). Furthermore, hsCRP, oxidative stress markers, low- and high-density lipoprotein and glycated hemoglobin were also similar between two groups (all P > 0.05).
In patients with type 2 DM, 12 weeks oral supplementation of vitamin D did not significantly affect vascular function or serum biomarkers of inflammation and oxidative stress.
Clinical trial number: HKCTR-867, www.hkclinicaltrials.com.