Serum and urine vitamin D metabolite analysis in early preeclampsia

Abstract

Vitamin D deficiency is common in pregnant women and may contribute to adverse events in pregnancy such as preeclampsia (PET). To date, studies of vitamin D and PET have focused primarily on serum concentrations vitamin D, 25-hydroxyvitamin D3 (25(OH)D3) later in pregnancy. The aim here was to determine whether a more comprehensive analysis of vitamin D metabolites earlier in pregnancy could provide predictors of PET. Using samples from the SCOPE pregnancy cohort, multiple vitamin D metabolites were quantified by liquid chromatography-tandem mass spectrometry in paired serum and urine prior to the onset of PET symptoms. Samples from 50 women at pregnancy week 15 were analysed, with 25 (50%) developing PET by the end of the pregnancy and 25 continuing with uncomplicated pregnancy. Paired serum and urine from non-pregnant women (n = 9) of reproductive age were also used as a control. Serum concentrations of 25(OH)D3, 25(OH)D2, 1,25(OH)₂D3, 24,25(OH)₂D3 and 3-epi-25(OH)D3 were measured and showed no significant difference between women with uncomplicated pregnancies and those developing PET. As previously reported, serum 1,25(OH)₂D3 was higher in all pregnant women (in the second trimester), but serum 25(OH)D2 was also higher compared to non-pregnant women. In urine, 25(OH)D3 and 24,25(OH)₂D3 were quantifiable, with both metabolites demonstrating significantly lower (P < 0.05) concentrations of both of these metabolites in those destined to develop PET. These data indicate that analysis of urinary metabolites provides an additional insight into vitamin D and the kidney, with lower urinary 25(OH)D3 and 24,25(OH)₂D3 excretion being an early indicator of a predisposition towards developing PET.

Keywords: biomarker; preeclampsia; pregnancy; serum and urine; vitamin D.

Figure 1

Serum vitamin D metabolites in non-pregnant women and pregnant women at 15-week gestation. Serum concentrations of (A) 25-hydroxyvitamin D3 (25(OH)D3) nmol/L; (B) 25-hydroxyvitamin D2 (25(OH)D2) nmol/L; (C) 3-epi-25(OH)D3 nmol/L; (D) 1,25-dihydroxyvitamin D3 (1,25(OH)₂D3) pmol/L; (E) 24,25-dihydroxyvitamin D3 (24,25(OH)₂D3) nmol/L. Sample groups were non-pregnant (black; n = 9), normotensive pregnancies (red; n = 25) and those who later developed pre-eclampsia (blue; n = 25). Median with interquartile range are shown. Statistically significant variations are indicated, *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001.

Figure 2

Effect of maternal vitamin D status (serum 25-hydroyxvitamin D3) upon other serum vitamin D metabolites at 15-week gestation; comparative analysis in healthy pregnant controls and prospective PET cases. Serum concentrations of 25-hydroxyvitamin D3 (25(OH)D3) were correlated with C3-epi-25(OH)D3 (nmol/L), 1,25-dihydroxyvitamin D3 (1,25(OH)₂D3)(pmol/L) and 24,25-dihydroxyvitamin D3 (24,25(OH)₂D3) (nmol/L) in healthy pregnant controls (A) and prospective pre-eclampsia (PET) cases (B). Statistically significant correlations are indicated as P values, with Pearson R values shown.

Figure 3

Relationship between excreted urinary vitamin D metabolites. Urine concentrations 25(OH)D3 were correlated with 24,25(OH)₂D3 (nmol/L) in non-pregnant (A), healthy pregnant controls (B) and prospective pre-eclampsia (PET) cases (C). All nmol/L. Statistically significant correlations are indicated as P values, with Pearson R values shown.

Figure 4

Urine vitamin D metabolite analysis in pregnant women at 15-week gestation. Urinary concentrations of (A) 25-hydroxyvitamin D3 (25(OH)D3) nmol/L and (B) 24,25-dihydroxyvitamin D3 (24,25(OH)₂D3) nmol/L normalised for urinary creatinine (ng/g creatinine) for matched normotensive pregnancies (red) and those who later developed pre-eclampsia (PET; blue). Median with interquartile range values is shown. Statistically significant variations are indicated, *P < 0.05.