Impact of high-dose vitamin D3 on plasma free 25-hydroxyvitamin D concentrations and antimicrobial peptides in critically ill mechanically ventilated adults.

OBJECTIVES: High-dose vitamin D3 increases plasma total 25-hydroxyvitamin D [25(OH)D] in critically ill, ventilated patients; however, to our knowledge, the effect on plasma levels of free (nonprotein-bound) 25(OH)D has not been investigated in critical illness. Moreover, the relationship of free 25(OH)D and the regulation of endogenous antimicrobial peptides (AMPs) remains unknown. The aims of this study were to determine in critically ill adults with respiratory failure the effect of previous high-dose regimens of vitamin D3 on free 25(OH)D concentrations, the relationship of free 25(OH)D with circulating cathelicidin (LL-37) and human beta-defensin-2 (hBD-2), and the associations between plasma levels of free 25(OH)D and these AMPs to alveolar macrophage phagocytosis function. METHODS: In a double blind, randomized controlled trial, critically ill ventilator-dependent adults (N = 30) received enteral vitamin D3 (250,000 or 500,000 IU total over 5 d) or placebo. Plasma was obtained serially for concentrations of free 25(OH)D, LL-37, hBD-2, and expression of peripheral blood mononuclear cell human cationic antimicrobial protein (hCAP18) mRNA. Total 25(OH)D and LL-37 concentrations and alveolar macrophage phagocytosis were determined in bronchoalveolar lavage fluid. RESULTS: Plasma concentrations of free 25(OH)D over time were correlated with total 25(OH)D levels (r= 0.82; P < 0.001). The increase in free 25(OH)D was greater with the 500 000 IU vitamin D3 dose than with the lower dose. The percent change in mRNA expression of hCAP18 was positively associated with percent change in free 25(OH)D at days 7 and 14 (ρ = 0.48; P = 0.04 and ρ = 0.59; P = 0.03, respectively). Additionally, plasma LL-37 levels correlated with the percentage of alveolar macrophages exhibiting phagocytosis (ρ = 0.51; P = 0.04). CONCLUSIONS: The present study found a dose-related increase in plasma free-25(OH)D levels, which was associated with increasing circulating mRNA expression of hCAP18 over time. There were no correlations between changes in total and free 25(OH)D against plasma LL-37 and hBD-2 concentrations. Larger studies appear warranted to determine the impact of high-dose vitamin D3 administration on endogenous AMPs.

High Dose Vitamin D Administration in Ventilated Intensive Care Unit Patients: A Pilot Double Blind Randomized Controlled Trial.

BACKGROUND: There is a high prevalence of vitamin D deficiency in the critically ill patient population. Several intensive care unit studies have demonstrated an association between vitamin D deficiency [25-hydroxyvitamin D (25(OH)D) < 20 ng/mL] and increased hospital length of stay (LOS), readmission rate, sepsis and mortality. MATERIAL AND METHODS: Pilot, double blind randomized control trial conducted on mechanically ventilated adult ICU patients. Subjects were administered either placebo, 50,000 IU vitamin D3 or 100,000 IU vitamin D3 daily for 5 consecutive days enterally (total vitamin D3 dose = 250,000 IU or 500,000 IU, respectively). The primary outcome was plasma 25(OH)D concentration 7 days after oral administration of study drug. Secondary outcomes were plasma levels of the antimicrobial peptide cathelicidin (LL37), hospital LOS, SOFA score, duration of mechanical ventilation, hospital mortality, mortality at 12 weeks, and hospital acquired infection. RESULTS: A total of 31 subjects were enrolled with 13 (43%) being vitamin D deficient at entry (25(OH)D levels < 20 ng/mL). The 250,000 IU and 500,000 IU vitamin D3 regimens each resulted in a significant increase in mean plasma 25(OH)D concentrations from baseline to day 7; values rose to 45.7±19.6 ng/mL and 55.2 ± 14.4 ng/mL, respectively, compared to essentially no change in the placebo group (21±11.2 ng/mL), p<0.001. There was a significant decrease in hospital length of stay over time in the 250,000 IU and the 500,000 IU vitamin D3 group, compared to the placebo group (25 ± 14 and 18 ± 11 days compared to 36 ± 19 days, respectively; p=0.03). There was no statically significant change in plasma LL-37 concentrations or other clinical outcomes by group over time. CONCLUSIONS: In this pilot study, high-dose vitamin D3 safely increased plasma 25(OH)D concentrations into the sufficient range and was associated with decreased hospital length of stay without altering other clinical outcomes. CLINICAL TRIAL REGISTRATION: www.clinicaltrials.gov (NCT01372995).