Rationale: Vitamin D and its metabolites have potent immunomodulatory effects in vitro, including up-regulation of cathelicidin, a critical antimicrobial protein.
Objectives: We investigated whether administration of 1,25-dihydroxyvitamin D (calcitriol) to critically ill patients with sepsis would have beneficial effects on markers of innate immunity, inflammation, and kidney injury.
Methods: We performed a double-blind, randomized, placebo-controlled, physiologic study among 67 critically ill patients with severe sepsis or septic shock. Patients were randomized to receive a single dose of calcitriol (2 μg intravenously) versus placebo. The primary outcome was plasma cathelicidin protein levels assessed 24 hours after study drug administration. Secondary outcomes included leukocyte cathelicidin mRNA expression, plasma cytokine levels (IL-10, IL-6, tumor necrosis factor-α, IL-1β, and IL-2), and urinary kidney injury markers.
Measurements and main results: Patients randomized to calcitriol (n = 36) versus placebo (n = 31) had similar plasma cathelicidin protein levels at 24 hours (P = 0.16). Calcitriol-treated patients had higher cathelicidin (P = 0.04) and IL-10 (P = 0.03) mRNA expression than placebo-treated patients 24 hours after study drug administration. Plasma cytokine levels (IL-10, IL-6, tumor necrosis factor-α, IL-1β, and IL-2) and urinary kidney injury markers were similar in calcitriol- versus placebo-treated patients (P > 0.05 for all comparisons). Calcitriol had no effect on clinical outcomes nor were any adverse effects observed.
Conclusions: Calcitriol administration did not increase plasma cathelicidin protein levels in critically ill patients with sepsis and had mixed effects on other immunomodulatory markers. Additional phase II trials investigating the dose and timing of calcitriol as a therapeutic agent in specific sepsis phenotypes may be warranted. Clinical trial registered with www.clinicaltrials.gov (NCT 01689441).
Trial registration: ClinicalTrials.gov NCT01689441.
Keywords: 1,25-dihydroxyvitamin D; cathelicidin; critical illness; innate immunity; vitamin D.