Background:

Vitamin D receptor (VDR) activation is associated with cardiovascular and survival benefits in chronic kidney disease patients. Calcifediol, also known as calcidiol, is a prehormone that is produced in the liver by hydroxylation of vitamin D3.

In vitro: Calcifediol induced CYP24A1 expression with EC50 at 70 nM. Calcifediol stimulated the expression of thrombomodulin with EC50 at 10-100 nM. Confocal microscopy revealed that calcifediol at 0.1 - 10 μM induced VDR translocation into the nucleus dose-dependently; the VDR localization pattern was similar in cells treated with calcitriol [1].

In vivo: Spontaneously hypertensive rats and normotensive Wistar-Kyoto (WKY) rats were injected with either 50 ng/d calcifediol or vehicle alone for 3 days. Decreased calbindin-D9K and cellular Ca2+ flux were observed in control SHR. Calcifediol increased total cell and brush border calbindin-D9K. In contrast, Ca2+ flux, which increased in vit-D animals, remained lower in SHR for plasma calcitriol levels similar to those in WKY rats [2].

Clinical trial: Calcifediol given daily, weekly, or as a single bolus is about 2-3 times more potent in increasing plasma 25(OH)D3 concentrations than vitamin D3. Plasma 25(OH)D3 concentrations of 30 ng/mL were reached more rapidly and reliably with calcifediol [3].

Reference:
[1] Wu-Wong JR, Chen YW, Nakane M, Wolf M.  Differential effects of vitamin d receptor agonists on gene expression in neonatal rat cardiomyocytes. Cardiovasc Drugs Ther. 2011 Jun;25(3):215-22.
[2] Roullet CM, Roullet JB, Martin AS, McCarron DA.  In vivo effect of calcitriol on calcium transport and calcium binding proteins in the spontaneously hypertensive rat. Hypertension. 1994 Aug;24(2):176-82.
[3] Jetter A, Egli A, Dawson-Hughes B, Staehelin HB, Stoecklin E, Goessl R, Henschkowski J, Bischoff-Ferrari HA.  Pharmacokinetics of oral vitamin D(3) and calcifediol. Bone. 2014 Feb;59:14-9.