Serum 1,25-Dihydroxyvitamin D: An Outcome Prognosticator in Human Sepsis

In sepsis, the vitamin D active metabolite 1,25-dihydroxyvitamin D (1,25(OH)(2)D) may play a crucial role by its action to produce cathelicidin and improve endothelial barrier function, such that a deficiency in 1,25(OH)(2)D is associated with poor outcome. To test our hypothesis, we performed analysis of stored plasma samples from a prospective observational study in 91 patients with sepsis, age of 59.1+/−2.0 years, 52.7% females, and 11.0% deaths at 30 days. Vitamin D status, including 25-hydroxyvitamin D (25(OH)D), 1,25(OH)(2)D, 24,25-dihydroxyvitamin D (24,25(OH)(2)D), and parathyroid hormone (PTH), were measured daily over 3 days after hospital admission. At baseline, 1,25(OH)(2)D was significantly different between survivors vs. non-survivors. But there was no significant difference in 25(OH)D, 24,25(OH)(2)D, and PTH. In a multivariable binomial logistic regression model, age, total calcium and 1,25(OH)(2)D were significant predictors of 30-day mortality. Kaplan Meier analysis showed that patients with mean 1,25(OH)(2)D measured over 3 days of < = 13.6 pg/mL had 57.1% 30-day survival compared to 91.7% in patients with 1,25 (OH)(2)D level >13.6 pg/mL (p<0.01). From repeated measures regression analysis, there was significant increase in 1,25(OH)(2)D for increases in 25(OH)D in both survivors and non-survivors. However, compared to survivors, the low 25(OH)D in non-survivors was insufficient to account for the larger decrease in 1,25(OH)(2)D, indicating a dysfunctional 1α-hydroxylase. Additionally, there was a significant negative correlation between PTH and 1,25(OH)(2)D in both survivors and non-survivors, suggesting a severe impairment in the effect of PTH to increase renal 1α-hydroxylase activity. In conclusion, low 1,25(OH)(2)D levels are associated with increased 30-day mortality in sepsis patients, likely due to impaired 25(OH)D hydroxylation and PTH insensitivity. Our data also suggest that the active metabolite 1,25(OH)(2)D may be an important therapeutic target in the design of sepsis clinical trials.