Maternal vitamin D and markers of glycaemia during pregnancy in the Belfast centre of the Hyperglycaemia and Adverse Pregnancy Outcome study

Maternal, umbilical arterial metabolic levels and placental Nrf2/CBR1 expression in pregnancies with and without 25-hydroxyvitamin D deficiency

BACKGROUND

The aim of this case-control study was to document maternal, umbilical arterial metabolic levels and correlations in pregnancies with and without 25-hydroxyvitamin D [25(OH)D] deficiency, while, also investigating the expression of nuclear factor erythroid 2 related factor 2 (Nrf2) and carbonyl reductase 1 (CBR1) in the placenta.

METHODS

One hundred participants, 50 deficient for 25(OH)D and 50 normal, were recruited from among hospitalized single-term pregnant women who had elected for cesarean section. Umbilical arterial and placental samples were collected during cesarean section. Metabolic levels were assessed for the 25(OH)D deficiency and control groups' maternal, umbilical arterial samples. Nrf2 and CBR1 expression levels were investigated in the placentas of 12 pregnant women with 25(OH)D deficiency and 12 controls.

RESULTS

Compared with the control participants, the 25(OH)D deficient women had significantly higher triglyceride (TG) levels (3.80 ± 2.11 vs. 2.93 ± 1.16 mmol/L, 3.64 ± 1.84 vs. 2.81 ± 1.16 mmol/L, p < .01, .001); lower high density lipoprotein cholesterol (HDL-C) levels (1.54 ± 0.32 vs. 1.82 ± 0.63 mmol/L, 1.41 ± 0.72 vs. 2.44 ± 1.68 mmol/L, p < .001, .01) in both material blood and the umbilical artery. In addition, Nrf2 and CBR1 expression levels were lower in the maternal 25(OH)D deficient placenta.

CONCLUSION

25(OH)D deficient pregnant women have higher TG levels and lower HDL-C levels in both material blood and the umbilical artery. TG level is negatively correlated with 25(OH)D in both the maternal serum and infant umbilical artery. 25(OH)D deficiency also lowers placental expression of Nrf2 and CBR1.

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Association between Gene Polymorphisms of Vitamin D Receptor and Gestational Diabetes Mellitus: A Systematic Review and Meta-Analysis

(1) Background: Studies on the association between Vitamin D receptor gene polymorphism and gestational diabetes mellitus have been inconsistent. The aim of this study was to summarize available evidence on the association between polymorphisms of Vitamin D receptor genes and susceptibility to gestational diabetes mellitus. (2) Methods: We searched databases of PubMed, Web of Science, Embase, China national knowledge infrastructure (CNKI), China science and technology journal database (VIP), and Wanfang Data for relevant articles. A systematic review and a meta-analysis were done to compare the distribution of Vitamin D receptor gene polymorphisms in gestational diabetes mellitus patients with those in controls using allelic, codominant, dominant, and recessive models. (3) Results: A total of eight eligible articles were included in the systematic review and of them, six articles were included in the meta-analysis. The vitamin D receptor gene rs7975232 polymorphism was associated with gestational diabetes mellitus under the allelic model (odds ratio = 1.28, 95% confidence interval 1.06–1.56), codominant model (CC vs. AA odds ratio = 1.97, 95% confidence interval 1.28–3.05), and recessive model (odds ratio = 1.83, 95% confidence interval 1.27–2.64) in the case of low heterogeneity. High heterogeneity existed in studies on the association of vitamin D receptor genes rs1544410, rs2228570, and rs731236 with gestational diabetes mellitus, and the most common sources of heterogeneity were the year of publication and matching. (4) Conclusion: Polymorphism of the vitamin D receptor gene rs7975232 may be associated with risk of developing gestational diabetes mellitus. Future studies should be designed to include standardized data collection and matching for important confounding factors such as body mass index, age, and race.

Evaluation of the efficacy of two doses of vitamin D supplementation on glycemic, lipidemic and oxidative stress biomarkers during pregnancy: a randomized clinical trial

BACKGROUND

Vitamin D deficiency during pregnancy is common and is likely to be associated with metabolic complications in the mother. The aim of this study was to assess the efficacy of two doses of vitamin D supplementation during pregnancy on maternal and cord blood vitamin D status and metabolic and oxidative stress biomarkers.

METHODS

The eligible pregnant women (n = 84) invited to participate in the study and randomly allocated to one of the two supplementation groups (1000 IU/d vitamin D and 2000 IU/d). Biochemical assessments of mothers including serum concentrations of 25(OH)D, calcium, phosphate, iPTH, fasting serum sugar (FBS), insulin, triglyceride, total cholesterol, LDL-C, HDL-C, malondialdehyde (MDA) and total antioxidant capacity (TAC) were done at the beginning and 34 weeks of gestation. Cord blood serum concentrations of 25(OH)D, iPTH, MDA and TAC were assessed at delivery as well. To determine the effects of vitamin D supplementation on metabolic markers 1-factor repeated-measures analysis of variance (ANOVA) was used. Between groups comparisons was done by using Independent-samples Student's t-test or Mann-Whitney test. P < 0.05 was considered as significant.

RESULTS

Supplementation with 1000 IU/d and 2000 IU/d vitamin D resulted in significant changes in vitamin D status over pregnancy (24.01 ± 21.7, P < 0.001 in 1000 IU/d group and 46.7 ± 30.6 nmol/L, P < 0.001 in 2000 IU/d group). Daily intake of 2000 compared with 1000 IU/d tended to increase the serum concentration of HDL-C (10 ± 8.37, P < 0.001 in 1000 IU/d group and 9.52 ± 11.39 mg/dL, P < 0.001 in 2000 IU/d group). A significant decrement in serum concentration of iPTH observed in both groups (- 4.18 ± 7.5, P = 0.002 in 1000 IU/d group and - 8.36 ± 14.17, P = 0.002 in 2000 IU/d group).

CONCLUSIONS

Supplementation with 2000 IU/d vitamin D as compared with 1000 IU/d, is more effective in promoting vitamin D status and HDL-C serum concentration and in decreasing iPTH over pregnancy.

TRIAL REGISTRATION

This trial is registered at clinicaltrials.gov ( NCT03308487 ). Registered 12 October 2017 'retrospectively registered'.

The role of vitamin D in perinatology. An up-to-date review

The role of vitamin D in perinatology is a subject of major interest in current medicine. There is growing evidence about the role of maternal vitamin D levels in pregnancy outcomes. The aim of this review is to summarize the current literature about the role of vitamin D in perinatology. Evidence from this review suggests associations between low levels of maternal vitamin D and higher risk of certain obstetrical complications. Vitamin D has been found to be related to preeclampsia, gestational diabetes mellitus, low birth weight, and preterm birth. The current literature supports vitamin D supplementation in pregnant women, but more high-quality data are necessary. The problem that remains is how to achieve an optimal 25-hydroxyvitamin D level. To determine the real benefits of vitamin D supplementation in pregnancy, we need high-quality trials in larger groups.

VDR Variants rather than Early Pregnancy Vitamin D Concentrations Are Associated with the Risk of Gestational Diabetes: The Ma'anshan Birth Cohort (MABC) Study

AIM

This study investigated the associations among early pregnancy vitamin D concentrations, seasonality, and vitamin D metabolic gene variants and how these variables related alone and in interaction with the risk of gestational diabetes mellitus (GDM).

METHODS

Research participants were women from the Ma'anshan birth cohort study in China. The overall study included 3110 women to explore the association between early pregnancy vitamin D concentrations and the risk of GDM. In the current analysis, a nested case-control study of 274 GDM cases and 380 controls was conducted to investigate seven vitamin D metabolic gene variants and the risk of GDM. Vitamin D concentrations were measured by radioimmunoassay. Genotypes were determined by improved multiple ligase detection reaction. Interactions between genetic variants and vitamin D as predictors of the risk of GDM were evaluated by a pair-wise analysis under a multiplicative interaction model.

RESULTS

Vitamin D concentrations were not significantly associated with the risk of GDM (OR = 0.79, 95% CI = 0.55-1.13) after adjusting for seasonality. Fall-winter conceptions had a 37% decreased risk of GDM compared with spring-summer conceptions (OR = 0.63, 95% CI = 0.49-0.81), independent of vitamin D concentrations. Two VDR gene variants rs1544410 (OR = 2.03, 95% CI = 1.17-3.51 for CT versus CC) and rs731236 (OR = 2.42, 95% CI = 1.29-4.55 for GA versus AA) were significantly associated with the risk of GDM. No interactions among genetic variants and vitamin D concentrations were detected.

CONCLUSION

Early pregnancy vitamin D insufficiency or deficiency was not significantly associated with the risk of GDM. The results of this study emphasize the importance of genetic variants in VDR and conception season as factors that affect the risk of GDM.