The relationship of hypovitaminosis D and IL-6 in preeclampsia

OBJECTIVE: Vitamin D deficiency has been linked to the pathogenesis of preeclampsia. Given the demonstrated antiinflammatory function of vitamin D in multiple organ systems including trophoblast cells and placenta, we hypothesized that vitamin D deficiency contributes to the development of preeclampsia through increased inflammation, as indicated by elevated interleukin (IL)-6 concentrations. STUDY DESIGN: Plasma samples from a large preeclampsia cohort study were examined in 100 preeclamptic and 100 normotensive pregnant women. Comparisons of vitamin D and IL-6 concentrations used Student t test and chi(2) test or their nonparametric counterparts. A logistic regression model assessed the association among vitamin D, IL-6 concentrations, and preeclampsia risk. RESULTS: The mean concentration of 25-hydroxyvitamin D was 49.4 +/- 22.6 nmol/L in normotensives and 42.3 +/- 17.3 nmol/L in preeclamptic women (P = .01). The median (interquartile range: Q1, Q3) concentrations of IL-6 were 2.0 (1.3, 3.4) pg/mL and 4.4 (2.2, 10.0) pg/mL in the control and preeclampsia groups, respectively (P < .01). We observed a significant association between IL-6 elevation and preeclampsia (odds ratio, 4.4; 95% confidence interval, 1.8-10.8; P < .01) and between vitamin D deficiency and preeclampsia (odds ratio, 4.2; 95% confidence interval, 1.4-12.8; P = .04). However, there was no association between vitamin D deficiency and IL-6 elevation. CONCLUSION: Third-trimester IL-6 elevation and vitamin D deficiency were independently associated with the risk of preeclampsia. We found no evidence to support the hypothesis that vitamin D deficiency alters the pathogenesis of preeclampsia by activation of inflammation as assessed by IL-6 concentration.