Treating endothelial dysfunction with vitamin D in chronic kidney disease: a meta-analysis

Background: Vitamin D deficiency is common in patients with chronic kidney disease (CKD), and is associated with endothelial dysfunction and cardiovascular disease. We performed a meta-analysis to assess the effect of vitamin D treatment on flow mediated vasodilation (FMD) in CKD patients. Methods: PubMed/Medline, Web of Science, Embase and Cochrane trials and reviews were searched systematically for randomized controlled trials (RCT:s) using any vitamin D compound, at any stage of CKD, with FMD as outcome. Fixed and random effects models were performed using the standardized mean difference effect size post treatment for each trial. Heterogeneity was assessed by I-2 statistics. Results: 4 trials were included, comprising 305 patients. One used both 1 and 2 mu g for two intervention groups and was therefore split in two during the analysis. Patients in the included trials had a mean age of 44-65 years and were all in CKD 3 to 4. One study used cholecalciferol, the others all used paricalcitol as treatment. Study duration was 12-16 weeks. Intervention with vitamin D was associated with ameliorated FMD (STANDmean ES 0.78, 95% CI 0.55-1.01) in a fixed model. Heterogeneity was substantial (I-2 = 84%). Secondary analysis with random model analysis also showed significant results. Conclusions: Short term intervention with vitamin D is associated with improvements in endothelial function, as measured by FMD. This indicates positive effects of vitamin D on vascular disease in CKD. Limitations of this metaanalysis are the small number of studies performed, and the short duration of intervention.