A randomised controlled trial evaluating the impact of targeted vitamin D supplementation on endothelial function in type 2 diabetes mellitus: The DIMENSION trial
What this study found
Targeted vitamin D repletion raised 25(OH)D to the intended range but did not produce a statistically significant improvement in the primary endothelial function outcome after adjustment. Reactive hyperemia index increased within the vitamin D arm from 0.65 (0.42) to 0.73 (0.36), but the between-group result was not significant after adjustment (p = 0.07), despite an unadjusted p = 0.02. Mean 25(OH)D rose from 17.3 ± 5.2 ng/mL at baseline to 31.3 ± 9.0 ng/mL at 8 weeks and 31.6 ± 9.5 ng/mL at 16 weeks; 16/33 (49%) achieved >30 ng/mL at 8 weeks and 23/33 (70%) at 16 weeks. Other…
- Study & population
- Randomized, double-blind, placebo-controlled trial in adults with type 2 diabetes mellitus and hypovitaminosis D at a single tertiary centre in Singapore.
- Intervention
- In the active arm, participants received oral cholecalciferol for 16 weeks using a targeted dosing strategy based on baseline 25(OH)D: 4000 IU daily if baseline 25(OH)D was ≤20 ng/mL, or 2000 IU daily if baseline 25(OH)D was 21-30 ng/mL.
- Key limitation
- The trial was relatively small, single-centre, and short duration, which limits power to detect modest cardiovascular effects.
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Open PDFOriginal abstract
We sought to determine if vitamin D supplementation, to target 25(OH)D concentrations of 30–40 ng/mL, improves endothelial function in Singapore’s multi-ethnic type 2 diabetes mellitus population. We randomised 64 type 2 diabetes mellitus patients with hypovitaminosis D to cholecalciferol 4000 International Unit/matching placebo [baseline 25(OH)D < 20 ng/mL] or cholecalciferol 2000 International Unit/matching placebo [baseline 25(OH)D: 20–30 ng/mL] daily for 16 weeks with a down titration at 8 weeks if 25(OH)D > 30 ng/mL. Endothelial function was assessed by peripheral tonometry (reactive hyperaemia index–endothelial peripheral arterial tonometry) and vascular biomarkers: E-selectin, von-Willebrand factor and high-sensitivity C-reactive protein. We compared the change from baseline parameters in the two groups using Student’s t-test or Kruskal–Wallis test. A log-normal multivariate regression analysis was used to adjust for relevant baseline variables. The median reactive hyperaemia index in the vitamin D group increased from 0.65 (interquartile range: 0.42) to 0.73 (interquartile range: 0.36), whereas it decreased from 0.73 (interquartile range: 0.65) to 0.65 (interquartile range: 0.38) (p = 0.02) in the placebo group. After adjustment for baseline variables, the change was not statistically significant for reactive hyperaemia index (p = 0.07) and for other vascular biomarkers (p > 0.05). Targeted vitamin D supplementation for 16 weeks resulted in a small but non-significant improvement in endothelial function in a type 2 diabetes mellitus cohort.