Low circulating levels of vitamin D may contribute to the occurrence of preeclampsia through deregulation of Treg /Th17 cell ratio

PROBLEM: Studies assessing the association between vitamin D deficiency and preeclampsia (PE) have not reached a consensus. The study aimed to investigate the role of vitamin D in the occurrence of PE through its immune-modulatory effects on Treg/Th17 cell ratio. METHOD OF STUDY: This is a case-control study of third-trimester pregnant women. Peripheral blood 25(OH)D, TGF-β1, IL-6, and Treg/Th17 cells were analyzed. RESULTS: One hundred and sixty-three pregnant women were recruited, and 100 women (59 with a normal pregnancy (NP) and 41 with PE) were included in the study. The prevalence of vitamin D deficiency was 69.3%. Vitamin D-deficient pregnant women (25(OH) D < 20 ng/mL) had fivefold higher risk to develop PE than those with 25(OH)D level ≥20 ng/mL (OR = 5.29, CI 95% = 1.81-15.41). PE patients had lower circulating levels of 25(OH)D (12.83 ± 5.37 ng/mL vs 20.76 ± 9.63 ng/mL, P < .0001) and Treg/Th17 cell ratio (1.61 ± 0.71% vs 2.94 ± 1.35%, P < .0001), compared to women with NP. In patients with PE, 25(OH)D level correlated negatively with IL-6 levels (r = -.60, P < .0001) and positively with Treg/Th17 cell ratio (r = .89, P < .0001). We also observed a negative relationship between IL-6 levels and Treg/Th17 cell ratio (r = -.54, P = .0002). CONCLUSION: Our study demonstrated the correlation between low plasma vitamin D level and altered immune parameters in PE. We propose that, through its effects on Treg/Th17 cell ratio, vitamin D might influence the occurrence of PE.