Vitamin D effects on pregnancy and the placenta

Vitamin D stimulates multiple microRNAs to inhibit CRH and other pro-labor genes in human placenta

Maternal vitamin D deficiency is linked to adverse pregnancy outcomes including spontaneous preterm birth (SPB). Placental corticotropin-releasing hormone (CRH) has been proposed to be part of a clock that governs the length of gestation in humans, with elevated maternal serum levels predicting early delivery. In this study, we test the hypothesis that vitamin D could contribute to the prevention of preterm labor by inhibiting CRH and other pro-labor mediators. The biological activity of vitamin D occurs via two pathways: non-genomic and genomic responses, both of which involve binding of 1,25-dihydroxyvitamin D (1,25(OH)2D), the active metabolite of vitamin D binding to the vitamin D receptor (VDR). By using chromatin immunoprecipitation followed by sequencing (ChIP-seq), we found that 1,25(OH)2D stimulates association of VDR with a number of miRNA genes including MIR181B2 and MIR26B, and their mature products miR-181b-5p and miR-26b-5p are predicted to target CRH and cyclooxygenase-2 (COX-2) mRNA at 3'-untranslated region (UTR), respectively. We performed RT-qPCR analysis to validate that expression of mature miR-181b-5p and miR-26b-5p in term human syncytiotrophoblast increased in response to treatment with 1,25(OH)2D. miR-181b-5p- or miR-26b-5p-mediated inhibition of CRH or COX-2 was further assessed by the use of miRNA mimics/inhibitors and a luciferase reporter assay. Taken together, this study has identified novel mechanisms by which vitamin D downregulates pro-labor genes and could lower the risk of preterm delivery.

Longitudinal Maternal Vitamin D Status during Pregnancy Is Associated with Neonatal Anthropometric Measures

Findings on maternal 25-hydroxyvitamin D (25[OH]D) and neonatal anthropometry are inconsistent, and may at least be partly due to variations in gestational week (GW) of 25(OH)D measurement and the lack of longitudinal 25(OH)D measurements across gestation. The aim of the current study was to examine the associations of longitudinal measures of maternal 25(OH)D and neonatal anthropometry at birth. This study included 321 mother–offspring pairs enrolled in the Eunice Kennedy Shriver National Institute of Child Health and Human Development Fetal Growth Studies–Singletons. This study was a prospective cohort design without supplementation and without data on dietary supplementation. Nevertheless, measurement of plasma 25(OH)D reflects vitamin D from different sources, including supplementation. Maternal concentrations of total 25(OH)D were measured at 10–14, 15–26, 23–31, and 33–39 GW and categorized as <50 nmol/L, 50–75 nmol/L, and >75 nmol/L. Generalized linear models were used to examine associations of 25(OH)D at each time-point with neonate birthweight z-score, length, and sum of skinfolds at birth. At 10–14 GW, 16.8% and 49.2% of women had 25(OH)D <50 nmol/L and between 50–75 nmol/L, respectively. The association of maternal 25(OH)D with neonatal anthropometry differed by GW and women’s prepregnancy BMI (normal (<25.0 kg/m²), overweight/obese (25.0–44.9 kg/m²)). All analyses were stratified by prepregnancy BMI status. Among women with an overweight/obese BMI, 25(OH)D <50 nmol/L at 10–14 GW was associated with lower birthweight z-score (0.56; 95% CI: −0.99, −0.13) and length (−1.56 cm; 95% CI: −3.07, −0.06), and at 23–31 GW was associated with shorter length (−2.77 cm; 95% CI: −13.38, −4.98) and lower sum of skinfolds (−9.18 mm; 95% CI: −13.38, −4.98). Among women with a normal BMI, 25(OH)D <50 nmol/L at 10–14 GW was associated with lower sum of skinfolds (−2.64 mm; 95% CI: −5.03, −0.24), at 23–31 GW was associated with larger birthweight z-scores (0.64; 95% CI: 0.03, 1.25), and at 33-39 GW with both higher birthweight z-score (1.22; 95% CI: 0.71, 1.73) and longer length (1.94 cm; 95% CI: 0.37, 3.52). Maternal 25(OH)D status during pregnancy was associated with neonatal anthropometric measures, and the associations were specific to GW of 25(OH)D measurement and prepregnancy BMI.

Systematic review and meta-analysis of Spanish studies regarding the association between maternal 25-hydroxyvitamin D levels and perinatal outcomes

Objective: This systematic review and meta-analysis of Spanish studies assessed the association of maternal 25-hydroxyvitamin D [25(OH)D] levels on perinatal outcomes. Methods: PubMed, Cochrane Library, Embase, Scielo, Scopus, and Web of Science research databases were searched from inception through December 30 2017 using the terms 'vitamin D', 'pregnancy', and 'Spain'. Studies that compared first or second half of pregnancy normal 25(OH)D (≥30.0 ng/mL) versus insufficient (20.0-29.9 ng/mL) or deficient (<20.0 ng/mL) circulating levels and perinatal outcomes were systematically extracted. Data are presented as pooled odds ratios and their 95% confidence intervals (CIs) for categorical variables or mean differences and CIs for continuous variables. Risk of bias was evaluated with the Newcastle-Ottawa Scale. Results: Five cohort studies met inclusion criteria. The risk of gestational diabetes mellitus, preeclampsia, preterm birth, and small-for-gestational-age infants, and birthweight was not influenced by first half of pregnancy maternal 25(OH)D levels. In addition, second half of pregnancy 25(OH) levels did not affect birthweight. Conclusion: Maternal 25(OH)D levels during pregnancy did not affect studied perinatal outcomes and birthweight.

Vitamin D levels in children and adolescents with attention-deficit hyperactivity disorder (ADHD): a meta-analysis

The aim of this article was to assess the differences in serum 25(OH)D levels between children and adolescents with attention-deficit/hyperactivity disorder (ADHD) and healthy controls. We used the PubMed (1966-2017), Scopus (2004-2017), ClinicalTrials.gov (2008-2017), Cochrane Central Register of Controlled Trials CENTRAL (2000-2017), and Google Scholar (2004-2017) databases. Statistical meta-analysis was performed with RevMan 5.3. Εight studies were finally included in the present meta-analysis with a total number of 11,324 children. Among them, 2655 were diagnosed with ADHD, while the remaining 8669 were recruited as healthy controls. All eight trials reported significantly lower serum concentrations of 25(OH)D in patients diagnosed with ADHD compared to healthy controls. The pooled data showed that there was a significant difference between the ADHD group and the control group (SMD = - 0.73, 95% CI [- 1.00, - 0.46]). The systematic review and meta-analysis of observational studies demonstrated an inverse association between serum 25(OH)D and young patients with ADHD. Large cohort studies are required to investigate whether vitamin D-deficient infants are more likely to develop ADHD in the future. Also, whether children with ADHD should be supplemented with higher doses of vitamin D3 remains to be confirmed through long-term controlled clinical trials.

Differential and Overlapping Effects of 20,23(OH)₂D3 and 1,25(OH)₂D3 on Gene Expression in Human Epidermal Keratinocytes: Identification of AhR as an Alternative Receptor for 20,23(OH)₂D3

A novel pathway of vitamin D activation by CYP11A has previously been elucidated. To define the mechanism of action of its major dihydroxy-products, we tested the divergence and overlap between the gene expression profiles of human epidermal keratinocytes treated with either CYP11A1-derived 20,23(OH)₂D3 or classical 1,25(OH)₂D3. Both secosteroids have significant chemical similarity with the only differences being the positions of the hydroxyl groups. mRNA was isolated and examined by microarray analysis using Illumina’s HumanWG-6 chip/arrays and subsequent bioinformatics analyses. Marked differences in the up- and downregulated genes were observed between 1,25(OH)₂D3- and 20,23(OH)₂D3-treated cells. Hierarchical clustering identified both distinct, opposite and common (overlapping) gene expression patterns. CYP24A1 was a common gene strongly activated by both compounds, a finding confirmed by qPCR. Ingenuity pathway analysis identified VDR/RXR signaling as the top canonical pathway induced by 1,25(OH)₂D3. In contrast, the top canonical pathway induced by 20,23(OH)₂D3 was AhR, with VDR/RXR being the second nuclear receptor signaling pathway identified. QPCR analyses validated the former finding by revealing that 20,23(OH)₂D3 stimulated CYP1A1 and CYP1B1 gene expression, effects located downstream of AhR. Similar stimulation was observed with 20(OH)D3, the precursor to 20,23(OH)₂D3, as well as with its downstream metabolite, 17,20,23(OH)₃D3. Using a Human AhR Reporter Assay System we showed marked activation of AhR activity by 20,23(OH)₂D3, with weaker stimulation by 20(OH)D3. Finally, molecular modeling using an AhR LBD model predicted vitamin D3 hydroxyderivatives to be good ligands for this receptor. Thus, our microarray, qPCR, functional studies and molecular modeling indicate that AhR is the major receptor target for 20,23(OH)₂D3, opening an exciting area of investigation on the interaction of different vitamin D3-hydroxyderivatives with AhR and the subsequent downstream activation of signal transduction pathways in a cell-type-dependent manner.

Global prevalence and disease burden of vitamin D deficiency: a roadmap for action in low- and middle-income countries

Vitamin D is an essential nutrient for bone health and may influence the risks of respiratory illness, adverse pregnancy outcomes, and chronic diseases of adulthood. Because many countries have a relatively low supply of foods rich in vitamin D and inadequate exposure to natural ultraviolet B (UVB) radiation from sunlight, an important proportion of the global population is at risk of vitamin D deficiency. There is general agreement that the minimum serum/plasma 25-hydroxyvitamin D concentration (25(OH)D) that protects against vitamin D deficiency-related bone disease is approximately 30 nmol/L; therefore, this threshold is suitable to define vitamin D deficiency in population surveys. However, efforts to assess the vitamin D status of populations in low- and middle-income countries have been hampered by limited availability of population-representative 25(OH)D data, particularly among population subgroups most vulnerable to the skeletal and potential extraskeletal consequences of low vitamin D status, namely exclusively breastfed infants, children, adolescents, pregnant and lactating women, and the elderly. In the absence of 25(OH)D data, identification of communities that would benefit from public health interventions to improve vitamin D status may require proxy indicators of the population risk of vitamin D deficiency, such as the prevalence of rickets or metrics of usual UVB exposure. If a high prevalence of vitamin D deficiency is identified (>20% prevalence of 25(OH)D < 30 nmol/L) or the risk for vitamin D deficiency is determined to be high based on proxy indicators (e.g., prevalence of rickets >1%), food fortification and/or targeted vitamin D supplementation policies can be implemented to reduce the burden of vitamin D deficiency-related conditions in vulnerable populations.

Polymorphisms and haplotypes in VDR gene are associated with female idiopathic infertility

Unexplained infertility refers to the absence of a definable cause of reproductive failure. Vitamin D receptor (VDR) acts as a transcription factor and regulates a number of vitamin D-responsive genes, including those involved in the immune system. Recent finding that VDR is expressed in reproductive tissues suggests a possible importance of vitamin D in pregnancy. We conducted a case-control study to examine the association of polymorphisms in VDR gene with reproductive success. DNA from 117 female patients with unexplained infertility and 130 fertile controls was isolated from peripheral blood and VDR genotypes (FokI, BsmI, ApaI and TaqI) were detected by PCR-RFLP. Haplotypes were determined using Haploview software. Our results show significant association of FokI and BsmI polymorphisms with infertility (p < 0.05). The haplotype analysis confirmed strong linkage disequilibrium between closely positioned BsmI, ApaI and TaqI polymorphisms. Two haplotypes were associated with infertility: (i) haplotype bAT was increasing the risk for secondary infertility; while (ii) haplotype BAT had a protective role against primary infertility (p < 0.05). By changing the expression and the activity of VDR gene, which leads to the change in expression of vitamin D-responsive genes, these polymorphisms and haplotypes could possibly have an effect on immune system in the female reproductive tract.

Role of vitamin D in pregnancy and Toll-like receptor pathway

There is a growing concern about the impacts of hypovitaminosis D on the health of pregnant woman, fetal development, childhood, and adult life. Variations in maternal nutrition during gestation and/or lactation play a critical role in the physiological and metabolic development of the fetus and neonate, which can induce phenotypic changes and trigger important consequences throughout life, such as type 2 diabetes, cardiovascular disease, obesity, and hypertension. Vitamin D plays a role in regulating cell proliferation and differentiation and in modulating the innate and adaptive immune response. Also, vitamin D correlates with changes in cytokines, anti and proinflammatory, as well as prevents inflammation induced by changes in myometrial cells mediated by the nuclear factor kappa B pathway. Further investigation is required regarding these relationship.

Understanding vitamin D metabolism in pregnancy: From physiology to pathophysiology and clinical outcomes

This critical time frame of intrauterine life development is considered of major importance on the metabolic imprinting of overall health of the offspring, in later life. This requires a delicate immune balance that nurtures the allogeneic fetus, while maintaining reactivity against pathogens. Dysregulation of these tightly controlled biophenomena at a systemic and placental level, have been considered as a potential mechanism mediating pathogenesis of preeclampsia and spontaneous birth. In this context, vitamin D has been considered as a significant regulator of both innate and adaptive immunity by regulating cell proliferation, differentiation and apoptosis. Vitamin D metabolism during pregnancy manifests striking differences as compared to the non-pregnant state. Calcitriol is increasing >2-3 fold in the first weeks of pregnancy whereas maternal 25-hydroxyvitamin D crosses the placental barrier and represents the main pool of vitamin D in the fetus. Moreover, during pregnancy, vitamin D receptor and regulatory metabolic enzymes are expressed in the placenta and decidua, indicating a potential critical point in the immunomodulation at the maternal-fetal interface. Considering these effects, maternal hypovitaminosis D during pregnancy has been associated with pregnancy related disorders. This review focuses on the mechanistic basis of these adaptive changes, as a background for the development of pregnancy related disorders, with a discourse on the pathophysiology relating hypovitaminosis D and clinical outcomes.

Single Nucleotide Polymorphisms in Vitamin D Receptor Gene Affect Birth Weight and the Risk of Preterm Birth: Results From the "Mamma & Bambino" Cohort and A Meta-Analysis

The effect of vitamin D receptor gene (VDR) polymorphisms on adverse pregnancy outcomes—including preterm birth (PTB), low birth weight and small for gestational age—is currently under debate. We investigated 187 mother-child pairs from the Italian “Mamma & Bambino” cohort to evaluate the association of maternal VDR polymorphisms—BsmI, ApaI, FokI and TaqI—with neonatal anthropometric measures and the risk of PTB. To corroborate our results, we conducted a meta-analysis of observational studies. For the FokI polymorphism, we showed that gestational duration and birth weight decreased with increasing number of A allele (p = 0.040 and p = 0.010, respectively). Compared to the GG and GA genotypes, mothers who carried the AA genotype exhibited higher PTB risk (OR = 12.049; 95% CI = 2.606–55.709; p = 0.001) after adjusting for covariates. The meta-analysis confirmed this association under the recessive model (OR = 3.67, 95%CI 1.18–11.43), and also pointed out the protective effect of BsmI polymorphism against the risk of PTB under the allelic (A vs. G: OR = 0.74; 95%CI 0.59–0.93) and recessive (AA vs. GG + AG: OR = 0.62; 95%CI 0.43–0.89) models. Our results suggest the association between some maternal VDR polymorphisms with neonatal anthropometric measures and the risk of PTB.

Vitamin D levels, brain volume, and genetic architecture in patients with psychosis

BACKGROUND

Lower vitamin D levels are found in people with schizophrenia and depressive disorders, and also associated with neuroimaging abnormalities such as reduced brain volume in both animals and humans. Reduced whole brain and increased ventricular volume are also systematically reported in schizophrenia. Even though vitamin D deficiency has been proposed as a risk mechanism for schizophrenia there exist no studies to date of the association between vitamin D levels and brain volume in this population. Therefore, we investigated the relationship between vitamin D levels and brain phenotypes in psychotic disorders, and assessed possible interactions with genetic variants in vitamin D receptor (VDR) and other genetic variants that play a role in vitamin D levels in the body.

METHODS

Our sample consisted of 83 psychosis patients and 101 healthy controls. We measured vitamin D levels as serum 25-hydroxyvitamin D. All participants were genotyped and neuroimaging conducted by structural magnetic resonance imaging.

RESULTS

Vitamin D levels were significantly positively associated with peripheral grey matter volume in patients (β 860.6; 95% confidence interval (CI) 333.4-1466, p < .003). A significant interaction effect of BSML marker (rs1544410) was observed to mediate the association between patient status and both white matter volume (β 23603.3; 95% CI 2732.8-48708.6, p < .05) and whole brain volume (β 46670.6, 95% CI 8817.8-93888.3, p < .04). Vitamin D did not predict ventricular volume, which rather was associated with patient status (β 4423.3, 95% CI 1583.2-7267.8p < .002) and CYP24A1 marker (rs6013897) (β 2491.5, 95% CI 269.7-4978.5, p < .04).

CONCLUSIONS

This is the first study of the association between vitamin D levels and brain volume in patients with psychotic disorders that takes into account possible interaction with genetic polymorphisms. The present findings warrant replication in independent samples.

Placental Vascular Calcification and Cardiovascular Health: It Is Time to Determine How Much of Maternal and Offspring Health Is Written in Stone

Vascular calcification is the deposition of calcium phosphate minerals in vascular tissue. Vascular calcification occurs by both active and passive processes. Extent and tissue-specific patterns of vascular calcification are predictors of cardiovascular morbidity and mortality. The placenta is a highly vascularized organ with specialized vasculature that mediates communication between two circulatory systems. At delivery the placenta often contains calcified tissue and calcification can be considered a marker of viral infection, but the mechanisms, histoanatomical specificity, and pathophysiological significance of placental calcification are poorly understood. In this review, we outline the current understanding of vascular calcification mechanisms, biomedical consequences, and therapeutic interventions in the context of histoanatomical types. We summarize available placental calcification data and clinical grading systems for placental calcification. We report on studies that have examined the association between placental calcification and acute adverse maternal and fetal outcomes. We then review the intersection between placental dysfunction and long-term cardiovascular health, including subsequent occurrence of maternal vascular calcification. Possible maternal phenotypes and trigger mechanisms that may predispose for calcification and cardiovascular disease are discussed. We go on to highlight the potential diagnostic value of placental calcification. Finally, we suggest avenues of research to evaluate placental calcification as a research model for investigating the relationship between placental dysfunction and cardiovascular health, as well as a biomarker for placental dysfunction, adverse clinical outcomes, and increased risk of subsequent maternal and offspring cardiovascular events.

Update of the tolerable upper intake level for vitamin D for infants

Following a request from the European Commission, the Panel on Dietetic Products, Nutrition and Allergies (NDA) was asked to revise the tolerable upper intake level (UL) for vitamin D for infants (≤ 1 year) set in 2012. From its literature review, the Panel concluded that the available evidence on daily vitamin D intake and the risk of adverse health outcomes (hypercalciuria, hypercalcaemia, nephrocalcinosis and abnormal growth patterns) cannot be used alone for deriving the UL for infants. The Panel conducted a meta-regression analysis of collected data, to derive a dose-response relationship between daily supplemental intake of vitamin D and mean achieved serum 25(OH)D concentrations. Considering that a serum 25(OH)D concentration of 200 nmol/L or below is unlikely to pose a risk of adverse health outcomes in infants, the Panel estimated the percentage of infants reaching a concentration above this value at different intakes of vitamin D. Based on the overall evidence, the Panel kept the UL of 25 μg/day for infants aged up to 6 months and set a UL of 35 μg/day for infants 6-12 months. The Panel was also asked to advise on the safety of the consumption of infant formulae with an increased maximum vitamin D content of 3 μg/100 kcal (Commission Delegated Regulation (EU) 2016/127 repealing Directive 2006/141/EC in 2020). For infants aged up to 4 months, the intake assessment showed that the use of infant formulae containing vitamin D at 3 μg/100 kcal may lead some infants to receive an intake above the UL of 25 μg/day from formulae alone without considering vitamin D supplemental intake. For infants aged 4-12 months, the 95th percentile of vitamin D intake (high consumers) estimated from formulae and foods fortified or not with vitamin D does not exceed the ULs, without considering vitamin D supplemental intake.

Association Between Vitamin D Supplementation During Pregnancy and Offspring Growth, Morbidity, and Mortality: A Systematic Review and Meta-analysis

IMPORTANCE

Whether vitamin D supplementation during pregnancy is beneficial and safe for offspring is unclear.

OBJECTIVE

To systematically review studies of the effects of vitamin D supplementation during pregnancy on offspring growth, morbidity, and mortality.

DATA SOURCES

Searches of Medline, Embase, and the Cochrane Database of Systematic Reviews were conducted up to October 31, 2017. Key search terms were vitamin D, pregnancy, randomized controlled trials, and offspring outcomes.

STUDY SELECTION

Randomized clinical trials of vitamin D supplementation during pregnancy and offspring outcomes.

DATA EXTRACTION AND SYNTHESIS

Two authors independently extracted data, and the quality of the studies was assessed. Summary risk ratio (RR), risk difference (RD) or mean difference (MD), and 95% CI were calculated using fixed-effects or random-effects meta-analysis.

MAIN OUTCOMES AND MEASURES

Main outcomes were fetal or neonatal mortality, small for gestational age (SGA), congenital malformation, admission to a neonatal intensive care unit, birth weight, Apgar scores, neonatal 25-hydroxyvitamin D (25[OH]D) and calcium concentrations, gestational age, preterm birth, infant anthropometry, and respiratory morbidity during childhood.

RESULTS

Twenty-four clinical trials involving 5405 participants met inclusion criteria. Vitamin D supplementation during pregnancy was associated with a lower risk of SGA (RR, 0.72; 95% CI, 0.52 to 0.99; RD, -5.60%; 95% CI, -0.86% to -10.34%) without risk of fetal or neonatal mortality (RR, 0.72; 95% CI, 0.47 to 1.11) or congenital abnormality (RR, 0.94; 95% CI, 0.61 to 1.43). Neonates with prenatal vitamin D supplementation had higher 25(OH)D levels (MD, 13.50 ng/mL; 95% CI, 10.12 to 16.87 ng/mL), calcium levels (MD, 0.19 mg/dL; 95% CI, 0.003 to 0.38 mg/dL), and weight at birth (MD, 75.38 g; 95% CI, 22.88 to 127.88 g), 3 months (MD, 0.21 kg; 95% CI, 0.13 to 0.28 kg), 6 months (MD, 0.46 kg; 95% CI, 0.33 to 0.58 kg), 9 months (MD, 0.50 kg; 95% CI, 0.01 to 0.99 kg), and 12 months (MD, 0.32 kg; 95% CI, 0.12 to 0.52 kg). Subgroup analysis by doses showed that low-dose vitamin D supplementation (≤2000 IU/d) was associated with a reduced risk of fetal or neonatal mortality (RR, 0.35; 95% CI, 0.15 to 0.80), but higher doses (>2000 IU/d) did not reduce this risk (RR, 0.95; 95% CI, 0.59 to 1.54).

CONCLUSIONS AND RELEVANCE

Vitamin D supplementation during pregnancy is associated with a reduced risk of SGA and improved infant growth without risk of fetal or neonatal mortality or congenital abnormality. Vitamin D supplementation with doses of 2000 IU/d or lower during pregnancy may reduce the risk of fetal or neonatal mortality.

Vitamin D levels in an Australian and New Zealand cohort and the association with pregnancy outcome

BACKGROUND

Pregnant women are at increased susceptibility to vitamin D deficiency. Hence, there is continuing interest in determining how vitamin D influences pregnancy health. We aimed to compare vitamin D status in two distinct populations of pregnant women in Australia and New Zealand and to investigate the relationship between vitamin D status and pregnancy outcome. This included evaluating possible effect measure modifications according to fetal sex.

METHODS

Serum 25-hydroxy vitamin D (25(OH)D) was measured at 15 ± 1 weeks' gestation in 2800 women from Adelaide and Auckland who participated in the multi-centre, prospective cohort SCreening fOr Pregnancy Endpoints (SCOPE) study.

RESULTS

Mean serum 25(OH)D in all women was 68.1 ± 27.1 nmol/L and 28% (n = 772) were considered vitamin D deficient (< 50 nmol/L). Serum 25(OH)D was lower in the women recruited in Adelaide when compared to the women recruited in Auckland and remained lower after adjusting for covariates including maternal body mass index and socioeconomic index (Adelaide: 58.4 ± 50.3 vs. Auckland: 70.2 ± 54.5 nmol/L, P < 0.001). A 53% decreased risk for gestational diabetes mellitus (GDM) was observed with high (> 81 nmol/L) "standardised" vitamin D status when compared to moderate-high (63-81 nmol/L, aRR, 0.47; 95% CI: 0.23, 0.96). Marginal sex-specific differences occurred between vitamin D status and GDM: women carrying a female fetus had a 56% decreased risk for GDM in those with low-moderate levels of standardised vitamin D (44-63 nmol/L) compared to moderate-high levels (aRR: 0.44; 95% CI: 0.20, 0.97), whilst in women carrying a male fetus, a 55% decreased risk of GDM was found with high standardised vitamin D when compared to moderately-high vitamin D, but this was not statistically significant (aRR: 0.45; 95% CI: 0.15, 1.38).

CONCLUSIONS

High serum 25(OH)D at 15 ± 1 weeks' gestation was shown to be protective against the development of GDM. A possible association between fetal sex, vitamin D status and GDM provides further questions and encourages continual research and discussion into the role of vitamin D in pregnancy, particularly in vitamin D replete populations.

Longitudinal measures of maternal vitamin D and neonatal body composition

Background/Objectives

Vitamin D status has been associated with fetal growth and offspring’s bone mass in some observational studies. We characterize the trajectory of total maternal serum 25-hydroxyvitamin D [25(OH)D] concentration by race and examine whether vitamin D status is associated with neonatal anthropometry and body composition as assessed by dual energy X-ray absorptiometry (DXA).

Methods

Three longitudinal pregnancy samples from the Memphis site of the Calcium for Preeclampsia Prevention trial (1992-1995) were used. Racial differences in total 25(OH)D trajectories (n=343 women) were tested using an interaction term between blood draw gestational week and race in linear mixed-effects models. Linear regression and linear mixed-effects models estimated adjusted associations between total 25(OH)D concentration with neonatal anthropometry and body composition (n=252 with DXA), including interactions with infant sex and serum calcium.

Results

Total 25(OH)D concentration increased with gestational age but its trajectory over pregnancy did not differ between African-American and Caucasian women. Deficient maternal vitamin D (25(OH)D concentration <20 ng/ml) was associated with lower neonatal total bone mineral density (β −0.009 g/cm²; 95% CI −0.016, −0.002). Among male newborns, deficiency was also associated with lower lean mass (−217 g; −391, −43) and birthweight (−308 g; −540, −76). Deficient maternal vitamin D was also associated with lower ponderal index (β –2.3 kg/m³; 95% CI −4.0, −0.5) among those in the lowest calcium tertile.

Conclusion

Vitamin D deficiency during pregnancy is associated with lower bone density and smaller size at birth in certain subgroups suggesting its importance in fetal development.

Vitamin D: Effects on human reproduction, pregnancy, and fetal well-being

Pregnancy places exceptional demands on vitamin D and calcium availability; thus, their deficiencies during pregnancy threaten the woman and her fetus. Globally, vitamin D and other micronutrient deficiencies are common during pregnancy, especially in developing countries where pregnant women have less access to nutritional supplements. Vitamin D deficiency has been reported to be as high as 40% among pregnant women. As a pregnancy progresses, the requirements for vitamin D increase and thus, can worsen preexisting hypovitaminosis D. Consequently, hypovitaminosis D is increasingly associated with a higher incidence of fetal miscarriage, preeclampsia, gestational diabetes, bacterial vaginosis, and impaired fetal and childhood growth and development. This review explores the recent advances in the understanding of vitamin D and the pivotal role it plays in human reproduction, with an emphasis on pregnancy and its outcomes. Given the seriousness of the issue, there is a pressing need for clinicians to become aware of the risks associated with not identifying and correcting vitamin D deficiency. Identifying and correcting vitamin D deficiency, including safe exposure to sunlight, is particularly relevant for those who seek assistance with fertility issues or prenatal counseling, and those in the beginning of their pregnancy. The data point to a significant protective effects of vitamin D during pregnancy when the 25(OH)D serum level exceeds 30 ng/mL before pregnancy and during the first trimester and, sufficient levels are maintained throughout the pregnancy.

Effects of micronutrients on placental function: evidence from clinical studies to animal models

Micronutrient deficiencies are common in pregnant women due to low dietary intake and increased requirements for fetal development. Low maternal micronutrient status is associated with a range of pregnancy pathologies involving placental dysfunction, including fetal growth restriction (FGR), small-for-gestational age (SGA), pre-eclampsia and preterm birth. However, clinical trials commonly fail to convincingly demonstrate beneficial effects of supplementation of individual micronutrients, attributed to heterogeneity and insufficient power, potential interactions and lack of mechanistic knowledge of effects on the placenta. We aimed to provide current evidence of relationships between selected micronutrients (vitamin D, vitamin A, iron, folate, vitamin B12) and adverse pregnancy outcomes, combined with understanding of actions on the placenta. Following a systematic literature search, we reviewed data from clinical, in vitro and in vivo studies of micronutrient deficiency and supplementation. Key findings are potential effects of micronutrient deficiencies on placental development and function, leading to impaired fetal growth. Studies in human trophoblast cells and rodent models provide insights into underpinning mechanisms. Interestingly, there is emerging evidence that deficiencies in all micronutrients examined induce a pro-inflammatory state in the placenta, drawing parallels with the inflammation detected in FGR, pre-eclampsia, stillbirth and preterm birth. Beneficial effects of supplementation are apparent in vitro and in animal models and for combined micronutrients in clinical studies. However, greater understanding of the roles of these micronutrients, and insight into their involvement in placental dysfunction, combined with more robust clinical studies, is needed to fully ascertain the potential benefits of supplementation in pregnancy.

Effect of vitamin D3 supplementation in pregnancy on risk of pre-eclampsia - Randomized controlled trial

BACKGROUND

Vitamin D plays pivotal role in decidualization and implantation of the placenta. Recent researches have shown that low level of vitamin D3 "25-hydroxyvitamin D (25[OH]D)" in serum is a risk factor for pre-eclampsia. Latest evidence supports role of vitamin D3 deficiency treatment in reducing the risk of pre-eclampsia. The aim of this study is to determine the effect of antenatal supplementation of vitamin D3 on the risk of pre-eclampsia and to explore the dose effect in attaining the vitamin D3 normal level.

METHOD

An open labelled randomized controlled study was conducted on 179 pregnant women presenting in King Fahad Medical City antenatal clinic from Oct 2012-Oct 2015. Patients with age less than 20 years or more than 40 years, pregnancy with fetal anomalies, history of hypertension, pre-eclampsia, recurrent miscarriage, chronic renal or hepatic disease and malignancy were excluded from the study. Serum 25[OH]D was analysed during the first trimester (between 6 and 12 weeks of pregnancy). Patients with vitamin D3 deficiency (serum levels <25 nmol/L) were included in the study and randomized for vitamin D3 supplementation 400 IU (Group 1) versus 4000 IU (Group 2). Both groups were compared for the prevalence of pre-eclampsia and dose effect on vitamin D level.

RESULTS

Of 179 gravidae enrolled, 164 completed the trial. Mean maternal 25[OH]D was significantly increased in group 2 from 16.3 ± 5 nmol/mL to 72.3 ± 30.9 nmol/mL compared with group 1 from 17.5 ± 6.7 nmol/mL to 35.3 ± 20.7 nmol/mL (p > 0.0001). The relative risk reduction (RRR) for attaining ≥75 nmol/L before delivery was significantly higher (RRR 93.2 [CI 79-98] when treated with 4000 IU. The total incidence of pre-eclampsia in the study population was 4.3%. In comparison to group 1, the group 2 reported fewer pre-eclampsia events during the study period (8.6% versus 1.2%; p < 0.05). The total number of IUGRs was lesser in the group 2 (9.6%) versus group 1 (22.2%); p = 0.027. However, other obstetric outcomes were comparable between both groups.

CONCLUSION

Vitamin D supplementation in the deficient group reduces the risk of pre-eclampsia and IUGR in a dose dependant manner. However larger clinical trials are essential to investigate optimum dosage of vitamin D3 in this group.

Systematic Review of Vitamin D and Hypertensive Disorders of Pregnancy

This narrative systematic review evaluates growing evidence of an association between low maternal vitamin D status and increased risk of hypertensive disorders. The inclusion of interventional, observational, and dietary studies on vitamin D and all hypertensive disorders of pregnancy is a novel aspect of this review, providing a unique contribution to an intensively-researched area that still lacks a definitive conclusion. To date, trial evidence supports a protective effect of combined vitamin D and calcium supplementation against preeclampsia. Conflicting data for an association of vitamin D with gestational hypertensive disorders in observational studies arises from a number of sources, including large heterogeneity between study designs, lack of adherence to standardized perinatal outcome definitions, variable quality of analytical data for 25-hydroxyvitamin D (25(OH)D), and inconsistent data reporting of vitamin D status. While evidence does appear to lean towards an increased risk of gestational hypertensive disorders at 25(OH)D concentrations <50 nmol/L, caution should be exercised with dosing in trials, given the lack of data on long-term safety. The possibility that a fairly narrow target range for circulating 25(OH)D for achievement of clinically-relevant improvements requires further exploration. As hypertension alone, and not preeclampsia specifically, limits intrauterine growth, evaluation of the relationship between vitamin D status and all terms of hypertension in pregnancy is a clinically relevant area for research and should be prioritised in future randomised trials.

Prenatal vitamin D status and offspring's growth, adiposity and metabolic health: a systematic review and meta-analysis

In this systematic review and meta-analysis of observational studies, we aimed to estimate the associations between prenatal vitamin D status and offspring growth, adiposity and metabolic health. We searched the literature in human studies on prenatal vitamin D status and offspring growth in PubMed, up to July 2017. Studies were selected according to their methodological quality and outcomes of interest (anthropometry, fat mass and diabetes in offspring). The inverse variance method was used to calculate the pooled mean difference (MD) with 95 % CI for continuous outcomes, and the Mantel-Haenszel method was used to calculate the pooled OR with 95 % CI for dichotomous outcomes. In all, thirty observational studies involving 35 032 mother-offspring pairs were included. Vitamin D status was evaluated by circulating 25-hydroxyvitamin D (25(OH)D) level. Low vitamin D status was based on each study's cut-off for low 25(OH)D levels. Low prenatal vitamin D levels were associated with lower birth weight (g) (MD -100·69; 95 % CI -162·25, -39·13), increased risk of small-for-gestational-age (OR 1·55; 95 % CI 1·16, 2·07) and an elevated weight (g) in infant at the age of 9 months (g) (MD 119·75; 95 % CI 32·97, 206·52). No associations were observed between prenatal vitamin D status and other growth parameters at birth, age 1 year, 4-6 years or 9 years, nor with diabetes type 1. Prenatal vitamin D may play a role in infant adiposity and accelerated postnatal growth. The effects of prenatal vitamin D on long-term metabolic health outcomes in children warrant future studies.

Altered downstream target gene expression of the placental Vitamin D receptor in human idiopathic fetal growth restriction

Fetal growth restriction (FGR) affects up to 5% of pregnancies and is associated with significant perinatal complications. Maternal deficiency of vitamin D, a secosteroid hormone, is common in FGR-affected pregnancies. We recently demonstrated that decreased expression of the vitamin D receptor (VDR) in idiopathic FGR placentae could impair trophoblast growth. As strict regulation of cell-cycle genes in trophoblast cells is critical for optimal feto-placental growth, we hypothesised that pathologically decreased placental VDR contributes to aberrant regulation of cell-cycle genes. The study aims were to (i) identify the downstream cell-cycle regulatory genes of VDR in trophoblast cells, and (ii) determine if expression was changed in cases of FGR. Targeted cell-cycle gene cDNA arrays were used to screen for downstream targets of VDR in VDR siRNA-transfected BeWo and HTR-8/SVneo trophoblast-derived cell lines, and in third trimester placentae from FGR and gestation-matched control pregnancies (n = 25 each). The six candidate genes identified were CDKN2A, CDKN2D, HDAC4, HDAC6, TGFB2 and TGFB3. TGFB3 was prioritised for further validation, as its expression is largely unknown in FGR. Significantly reduced mRNA and protein expression of TGFB3 was verified in FGR placentae and the BeWo and HTR-8/SVneo trophoblast cell lines, using real-time PCR and immunoblotting respectively. In summary, decreased placental VDR expression alters the expression of regulatory cell-cycle genes in FGR placentae. Aberrant regulation of cell-cycle genes in the placental trophoblast cells may constitute a mechanistic pathway by which decreased placental VDR reduces feto-placental growth.

Maternal early pregnancy vitamin D status in relation to low birth weight and small-for-gestational-age offspring

Maternal vitamin D deficiency is an independent risk factor for fetal growth. We examined the associations between maternal vitamin D status (defined by 25-hydroxyvitamin D [25(OH)D]) at the first prenatal visit and measures of newborn and placental weight, in a large China cohort of singleton, term, live births. From July 2015 to June 2016, women delivering singleton, term, live births with 25(OH)D measured at a first prenatal visit (N=747). Birth weight, placental weight, the placental to fetal weight ratio, and small for gestational age (SGA) were measured. The relationship between levels of 25(OH)D and SGA were evaluated using univariate and multivariate regression analysis. Vitamin D deficiency was defined as 25(OH)D less than 20ng/ml. In those women, 76.9% (95%CI: 74%-78%) were defined as vitamin D deficiency. Incidence of SGA was also high (13.3%; 95%CI: 10.8%-15.7%). We found a nonlinear relation between 25(OH)D and birth weight as well as head circumference (P<0.01). Birth weight and head circumference increased by 69 [95%CI: 38-122] g and 0.31 (0.22-0.40) cm, respectively, per 1ng/ml increase in maternal 25(OH)D up to 20ng/ml and then leveled off thereafter. The SGA distribution across the 25(OH)D quartiles ranged between 3.7% (fourth quartile) to 24.1% (first quartile). For each 1 unit decrease of plasma concentration of 25(OH)D, the unadjusted and adjusted risk of SGA increased by 19% (odds ratio 1.19 [95% CI 1.13-1.25], P<0.001) and 9% (1.08 [1.03-1.16], P=0.009), respectively. In a multivariate model using the vitamin D deficiency vs. other together with the clinical variables, the adjusted risk of SGA increased by 205% (odds ratio 3.05 [95% CI 2.24-4.40], P=0.001). Maternal vitamin D insufficiency is common during pregnancy and is independently associated with low birth weight and high risk of SGA in term infants.

Calcitriol regulates immune genes CD14 and CD180 to modulate LPS responses in human trophoblasts

We assessed the response of primary cultures of placental villous mononucleated trophoblasts and multinucleated syncytiotrophoblast to calcitriol, the most biologically active form of vitamin D. Whole-genome microarray data showed that calcitriol modulates the expression of many genes in trophoblasts within 6 hours of exposure and RT-qPCR revealed similar responses in cytotrophoblasts, syncytiotrophoblasts and villous explants. Both cytotrophoblasts and syncytiotrophoblasts expressed genes for the vitamin D receptor, for LRP2 and CUBN that mediate internalization of calcidiol, forCYP27B1that encodes the enzyme that converts calcidiol into active calcitriol, and forCYP24A1that encodes the enzyme that modifies calcitriol and calcidiol to inactive calcitetrol. Notably, we found an inverse effect of calcitriol on expression of CD14 and CD180/RP105, proteins that differentially regulate toll-like receptor 4-mediated immune responses. Supported by gene ontology analysis, we tested the hypothesis that CD14 and CD180 modulate the inflammatory response of syncytiotrophoblast to bacterial lipopolysaccharide (LPS). These cells showed a robust response to a wide range of LPS concentrations, with induction of active NF-κB and increased secretion of IL-6 and IL-8. SiRNA-mediated knockdown ofCD14reduced the secretion of IL-6 and IL-8 in response to LPS. Collectively, our data showed that calcitriol has a rapid and widespread effect on villous trophoblast gene expression in general, and a specific effect on the innate immune response by syncytiotrophoblast.

Vitamin D metabolic loci and vitamin D status in Black and White pregnant women

BACKGROUND

Several candidate genes and genome wide association studies have reported significant associations between vitamin D metabolism genes and 25-hydroxyvitamin D. Few studies have examined these relationships in pregnancy.

OBJECTIVE

We evaluated the relationship between maternal allelic variants in three vitamin D metabolism genes and 25-hydroxyvitamin D (25(OH)D) concentration in pregnancy.

STUDY DESIGN

In two case-control studies, samples were drawn from women who delivered at Magee Womens Hospital in Pittsburgh, PA from 1999 to 2010 and twelve recruiting sites across the United States from 1959 to 65. For 882 Black and 1796 White pregnant women from these studies, 25(OH)D concentration was measured and single nucleotide polymorphisms (SNPs) were genotyped 50 kilobases up- and down-stream in three genes (VDR, GC, and CYP27B1). Using multivariable linear regression, we estimated the associations between allelic variation of each locus and log-transformed 25(OH)D concentration separately by race and study group. Meta-analysis was used to estimate the association across the four groups for each SNP.

RESULTS

Minor alleles of several variants in VDR, GC, and CYP27B1 were associated with differences in log-transformed 25(OH)D concentration compared to the corresponding major alleles [beta, 95% confidence intervals (CI)]. The meta-analysis confirmed the associations for differences in log-transformed 25(OH)D by allelic loci for one intron VDR variant [rs2853559 0.08 (0.02, 0.13), p<0.01] and a variant in the GC flanking region [rs13150174: 0.04 (0.02, 0.07), p<0.01], and a GC missense mutation [rs7041 0.05 (0.01, 0.09), p<0.01]. The meta-analysis also revealed possible associations for SNPs in linkage disequilibrium with variants in the VDR 3-prime untranslated region, another GC missense variant (rs4588), and a variant of the 3-prime untranslated region of CYP27B1.

CONCLUSION

We observed associations between VDR, GC, and CYP27B1 variants and maternal 25-hydroxyvitamin D concentration. Our results provide additional support for a possible role of genetic variation in vitamin D metabolism genes on vitamin D status during pregnancy.

Role of Placental VDR Expression and Function in Common Late Pregnancy Disorders

Vitamin D, besides its classical role in bone metabolism, plays a distinct role in multiple pathways of the feto-maternal unit. Calcitriol is the major active ligand of the nuclear vitamin D receptor (VDR). The vitamin D receptor (VDR) is expressed in different uteroplacental parts and exerts a variety of functions in physiologic pregnancy. It regulates decidualisation and implantation, influences hormone secretion and placental immune modulations. This review highlights the role of the vitamin D receptor in physiologic and disturbed pregnancy, as preeclampsia, fetal growth restriction, gestational diabetes and preterm birth. We discuss the existing literature regarding common VDR polymorphisms in these pregnancy disorders.

Lower maternal and fetal vitamin D status and higher placental and umbilical vitamin D receptor expression in preeclamptic pregnancies

OBJECTIVE

To explore associations between maternal and fetal vitamin D status in preeclamptic pregnancies.

METHODS

A case-control experiment was carried out with proportion ratio of 1:1 (controls: n = 60 vs cases: n = 60). Blood collection of both maternal and cord were performed before and during delivery, respectively, and 25(OH)D measurement was conducted. Difference analysis was performed according to returned data. Immunohistochemical analysis, together with semi-quantitative Western blot, was also performed to determine protein expression of vitamin D receptor in placenta and cord tissues of ESPE.

RESULTS

Mean ± SD values of maternal 25(OH)D in control and PE group were 38.06 ± 6.28 and 33.05 ± 4.10, respectively, and significant differences with P < 0.0001 were found between control and PE in both continuous and categorical variables, especially in ESPE subtype (32.96 ± 4.49). The deficiency category (< 30 nmol/L) showed increased odds of PE (OR, 2.83, 95% CI, 1.32-6.08) in both maternal 25(OH)D and cord 25(OH)D in multivariable logistic regression. Semi-quantitative analysis showed that expression of placenta VDR in the ESPE subgroup was significantly higher than that in control group with P < 0.001, while expression of umbilical vein VDR in ESPE subgroup was significantly higher than that in control group with P < 0.05.

CONCLUSIONS

The present study finds that lowest maternal and fetal vitamin D status in ESPE existed in the preeclampsia subsets. The VDR expression in placenta and fetus in ESPE were higher than that of normal pregnancy, which indicated that it might be related to placenta compensatory mechanism and is worthy of further research.

Vitamin D-metabolic enzymes and related molecules: Expression at the maternal-conceptus interface and the role of vitamin D in endometrial gene expression in pigs

Vitamin D is a secosteroid hormone with many varied functions including regulation of blood calcium levels, cell proliferation, immunity, and reproduction in mammals. Vitamin D is activated by 25-hydroxylase (CYP2R1) and 1-alpha-hydroxylase (CYP27B1) and is degraded by 24-hydroxylase (CYP24A1). Vitamin D is transported by vitamin D-binding protein (group-specific component, GC) through the bloodstream and regulates cellular actions by binding to vitamin D receptor (VDR). In this study, we determined the expression and regulation of vitamin D-related molecules and the role of vitamin D at the maternal-conceptus interface in pigs. Vitamin D-metabolizing enzymes CYP2R1, CYP27B1, and CYP24A1, vitamin D binding protein GC, and vitamin D receptor VDR were expressed in the endometrium in a pregnancy stage-specific manner as well as in conceptus and chorioallantoic tissues during pregnancy. VDR protein was localized to endometrial and trophoblastic cells. Concentrations of calcitriol, the active form of vitamin D, in the endometrial tissues were higher during early pregnancy than in mid- to late pregnancy, while plasma concentrations of calcitriol were highest during late pregnancy. Furthermore, calcitriol affected the expression of several genes related to conceptus implantation, vitamin D metabolism, calcium ion regulation, PG metabolism, and calcium-binding proteins in endometrial tissue explants. These results show that CYP2R1, CYP27B1, CYP24A1, GC, and VDR were expressed at the maternal-conceptus interface, endometrial calcitriol levels were regulated during pregnancy, and calcitriol modulated the expression of endometrial genes, suggesting that calcitriol may play an important role in the establishment and maintenance of pregnancy by regulating endometrial function in pigs.

Non-skeletal health effects of vitamin D supplementation: A systematic review on findings from meta-analyses summarizing trial data

BACKGROUND

A large number of observational studies have reported harmful effects of low 25-hydroxyvitamin D (25OHD) levels on non-skeletal outcomes. We performed a systematic quantitative review on characteristics of randomized clinical trials (RCTs) included in meta-analyses (MAs) on non-skeletal effects of vitamin D supplementation.

METHODS AND FINDINGS

We identified systematic reviews (SR) reporting summary data in terms of MAs of RCTs on selected non-skeletal outcomes. For each outcome, we summarized the results from available SRs and scrutinized included RCTs for a number of predefined characteristics. We identified 54 SRs including data from 210 RCTs. Most MAs as well as the individual RCTs reported null-findings on risk of cardiovascular diseases, type 2 diabetes, weight-loss, and malignant diseases. Beneficial effects of vitamin D supplementation was reported in 1 of 4 MAs on depression, 2 of 9 MAs on blood pressure, 3 of 7 MAs on respiratory tract infections, and 8 of 12 MAs on mortality. Most RCTs have primarily been performed to determine skeletal outcomes, whereas non-skeletal effects have been assessed as secondary outcomes. Only one-third of the RCTs had low level of 25OHD as a criterion for inclusion and a mean baseline 25OHD level below 50 nmol/L was only present in less than half of the analyses.

CONCLUSIONS

Published RCTs have mostly been performed in populations without low 25OHD levels. The fact that most MAs on results from RCTs did not show a beneficial effect does not disprove the hypothesis suggested by observational findings on adverse health outcomes of low 25OHD levels.

1,25-Dihydroxy vitamin D3 stimulates system A amino acid transport in primary human trophoblast cells

Vitamin D deficiency during pregnancy is linked to adverse perinatal outcomes such as small for gestational age infants. Recent evidence suggests that changes in placental amino acid transport contribute to altered fetal growth. We tested the hypothesis that 1,25-dihydroxy vitamin D3 increases the gene expression of System A and L amino acid transporter isoforms and stimulates placental amino acid transport activity in cultured primary human trophoblast cells mediated by mTOR signaling. Treatment with 1,25-dihydroxy vitamin D3 significantly increased mRNA expression of the System A isoform SNAT2 and System A activity, but had no effect on System L and did not affect mTOR signaling. siRNA silencing of the vitamin D receptor prevented 1,25-dihydroxy vitamin D3-stimulated System A transport. In conclusion, 1,25-dihydroxy vitamin D3 regulates System A activity through increased mRNA expression of SNAT2 transporters. Effects on placental amino acid transport may be the mechanism underlying the association between maternal vitamin D status and fetal growth.

Placental Vitamin D-Binding Protein Expression in Human Idiopathic Fetal Growth Restriction

Vitamin D-binding protein is a multifunctional serum protein with multiple actions related to normal health. Vitamin D-binding protein transports vitamin D and influences the metabolism of this key hormone but it also has additional immunomodulatory and actin-clearing properties. We investigated whether vitamin D-binding protein expression is altered in fetal growth restriction-associated placental dysfunction. Protein was extracted from 35 placentae derived from 17 healthy control subjects and 18 gestation-matched subjects with fetal growth restriction (FGR). FGR subjects were further subdivided as idiopathic (n = 9) and nonidiopathic (n = 9). Vitamin D-binding protein and 25(OH) vitamin D were measured by ELISA and normalized to protein concentration. The results showed significantly reduced levels of placental vitamin D-binding protein (control versus FGR, p < 0.05, Student's t-test) that were strongly associated with idiopathic fetal growth restriction (p < 0.01, Kruskal-Wallis), whereas levels of vitamin D-binding protein were not associated with placental 25(OH) vitamin D stores (p = 0.295, Pearson's correlation). As such, vitamin D-binding protein may be a factor in unexplained placental dysfunction associated with idiopathic fetal growth restriction and may potentially serve as a biomarker of this disease.

Maternal Vitamin D Status in the Late Second Trimester and the Risk of Severe Preeclampsia in Southeastern China

The association between maternal vitamin D deficiency and the risk of severe preeclampsia is still debated. In the present study, we aimed to evaluate vitamin D status in Chinese pregnant women and investigate its correlation with the odds of developing severe preeclampsia. A cohort study was performed on 13,806 pregnant women who routinely visited the antenatal care clinics and subsequently delivered at the Wuxi Maternity and Child Health Hospital. All the subjects in the cohort had their serum 25-hydroxyvitamin D (25(OH)D) concentrations measured during pregnancy. A high prevalence of maternal vitamin D deficiency (25(OH)D < 50 nmol/L) was found. Pregnant women who had different BMIs before pregnancy had significantly different serum concentrations of 25(OH)D. There was also a significant difference in the serum 25(OH)D concentration among pregnant women of different ages. The serum 25(OH)D concentration was significantly lower in pregnant women who subsequently developed severe preeclampsia compared with those who did not. Maternal vitamin D deficiency at 23-28 weeks of gestation was strongly associated with increased odds for severe preeclampsia after adjusting for relevant confounders (adjusted OR, 3.16; 95% CI, 1.77-5.65). Further studies are required to investigate whether vitamin D supplementation would reduce the risk of severe preeclampsia and improve pregnancy outcomes.

Altered metabolic homeostasis between vitamin D and long chain polyunsaturated fatty acids in preeclampsia

Sub-optimal maternal nutrition may result in pregnancy complications like preeclampsia. Preeclampsia is known to be of placental origin and a major cause of maternal morbidity and mortality worldwide. Our earlier studies suggest that altered metabolism of folic acid, vitamin B₁₂ and long chain polyunsaturated fatty acid (LCPUFAs) in the one carbon cycle increases homocysteine levels in preeclampsia. Recent reports indicate that vitamin D deficiency may also have a role in preeclampsia, although the mechanisms are unclear. A disturbed one carbon cycle can influence methylation patterns of various genes involved in placental development. Altered expression of cystathionine beta synthase (CBS) gene can result in hyperhomocystenemia. Higher homocysteine levels are known to increase reactive oxygen species (ROS) production which in turn leads to increased expression of phospholipase A2 (PLA2) and cyclooxygenase-2 (COX-2). Higher expression of PLA2 and COX-2 can influence the release of arachidonic acid (AA) from membrane phospholipid and result in increased conversion to thromboxane. Vitamin D [1,25(OH)₂D₃] is known to induce the CBS gene expression while it can suppress the oxidative stress-induced COX-2 up-regulation and thromboxane production. Based on this, we propose a novel hypothesis that a disturbed vitamin D and LCPUFA metabolism influence the regulation of the one carbon cycle which will trigger inflammation through oxidative stress in preeclampsia. This may lead to altered feto-placental growth and development in preeclampsia.

Women with Recurrent Miscarriage Have Decreased Expression of 25-Hydroxyvitamin D3-1α-Hydroxylase by the Fetal-Maternal Interface

Background

Effects of vitamin D deficiency in pregnancy have been associated with some adverse pregnancy outcomes. The 25-hydroxyvitamin D₃-1α-hydroxylase (CYP27B1) is integral to the vitamin D metabolic pathway. The enzyme catalyzes localized conversion of pro-hormone 25-hydroxyvitamin D₃ to active 1,25-dihydroxyvitamin D₃. Our aim was to investigate the expression of CYP27B1 at the fetal-maternal interface in the first trimester pregnancy and to determine whether CYP27B1 was associated with recurrent miscarriage (RM).

Methods

Expressions of CYP27B1 mRNA and protein in villi and decidua from 20 women undergoing primary miscarriage, 20 women with RM and 20 women with normal pregnancy were evaluated by western blot, and quantitative real-time PCR. The co-localization of CYP27B1 and certain cytokines including IL-10, IFN-γ, TNF-α, and IL-2 expression were examined using immunohistochemistry and confocal microscopy.

Results

Women with RM had a significantly lower expression of CYP27B1 mRNA and protein in villous and decidual tissues compared with the normal pregnant women (P = 0.000 in villus, P = 0.002 in decidua for mRNA; P = 0.036 in villus, P = 0.007 in decidua for protein.). Compared with the normal pregnancy, immunostaining for CYP27B1 was significantly decreased in villous trophoblasts and decidual glandular epithelial cells in RM women. No significant differences in the localization of CYP27B1, IL-10, IFN-γ, TNF-α, and IL-2 expression were identified between the normal pregnant and RM women.

Conclusions

Women with RM have a lower level of CYP27B1 expression in chorionic villi and decidua compared with normal pregnant women, suggesting that reduced CYP27B1 expression may be associated with RM. The consistent localization of CYP27B1 and IL-10, IFN-γ, TNF-α, and IL-2 expression in villous and decidual tissues suggests the importance of the local production of 1,25(OH)₂D₃ at the fetal-maternal interface to regulate cytokine responses.

Placental genetic variations in vitamin D metabolism and birthweight

INTRODUCTION

Vitamin D has pleiotropic functions that regulate fetal growth and development. We investigated associations of common placental genetic variations in vitamin D metabolism with birthweight.

METHODS

The study was conducted among participants (506 maternal-infant pairs) of a pregnancy cohort study. Data were collected using interviewer-administered questionnaires and post-delivery medical record abstraction. DNA, extracted from placental samples collected at delivery, was genotyped for eight single nucleotide polymorphisms (SNPs) in five vitamin D metabolism genes (CUBN, LRP2, VDR, GC, and CYP2R1). Linear and logistic regression models were used to evaluate associations of SNPs with birthweight and risk of low birthweight, respectively. Effect modification of associations by infant sex was examined using stratified analyses and interaction terms in regression models.

RESULTS

Mean (standard-deviation) birthweight among all, male, and female infants was 3482.1 (549.9), 3544.6 (579.0) and 3419.2 (512.5) grams, respectively. Each copy of the minor allele of rs2282679 (GC) was associated with a 68.6 g (95%CI:3.1134.7 g) increase in birthweight overall. Sex-specific associations were observed for SNP rs4667591 (LRP2) (p-value for interaction < 0.001). Each copy of the minor allele of rs4667591 was associated with a 124.7 g (95%CI:20.1229.0 g) increase in birthweight among female infants, and a suggested 81.6 g decrease in birthweight among male infants (95%CI:-183.7,20.5 g).

DISCUSSION

Our study identified overall and sex-specific associations between placental genetic variations in vitamin D metabolism and birthweight. If confirmed by larger replication studies, observed associations may provide insight into mechanistic underpinnings of the relationships between placental vitamin D metabolism and birth size.

Role of Vitamin D in the Hygiene Hypothesis: The Interplay between Vitamin D, Vitamin D Receptors, Gut Microbiota, and Immune Response

The hygiene hypothesis postulates that higher levels of cleanliness and improper exposure to microorganisms early in childhood could disturb the intestinal microbiome resulting in abnormal immune responses. Recently, more attention has been put on how a lack of sun exposure and consequently vitamin D deficiency could lead to less immune tolerance and aberrant immune responses. Moreover, vitamin D receptor (VDR) function has been positioned to be a critical aspect of immune response and gut homeostasis. Therefore, this review focuses on the role that the interaction between vitamin D, VDR function, and gut microbiome might have on autoimmune diseases in the context of the hygiene hypothesis. Literature shows that there is a high correlation between vitamin D deficiency, VDR dysfunction, gut microbiota composition, and autoimmune diseases. The biologically active form of vitamin D, 1,25(OH)₂D₃, serves as the primary ligand for VDRs, which have been shown to play a fundamental role in reducing autoimmune disease symptoms. Although the biological functions of VDR, the effects of its genetic variants, and the effects of epigenetic profiles in its promoter region are largely unknown in humans, studies in murine models are increasingly demonstrating that VDRs play a crucial role in attenuating autoimmune disease symptoms by regulating autophagy and the production of antimicrobial peptides, such cathelicidin and β-defensin, which are responsible for modifying the intestinal microbiota to a healthier composition. Remarkably, evidence shows that hormonal compounds and byproducts of the microbiota such as secondary bile acids might also activate VDR. Therefore, understanding the interaction between VDR and gut microbiota is of the utmost importance toward understanding the rise in autoimmune diseases in Western countries. We have gained insights on how the VDR functions affects inflammation, autophagy, and microbiota composition that could lead to the development of pathogenesis of autoimmune diseases, while confirming the role vitamin D and VDRs have in the context of hygiene hypothesis.

Maternal Vitamin D Status and Adverse Birth Outcomes in Children from Rural Western Kenya

Maternal plasma 25-hydroxyvitamin D (25(OH)D) status and its association with pregnancy outcomes in malaria holoendemic regions of sub-Saharan Africa is poorly defined. We examined this association and any potential interaction with malaria and helminth infections in an ongoing pregnancy cohort study in Kenya. The association of maternal plasma 25(OH)D status with pregnancy outcomes and infant anthropometric measurements at birth was determined in a subset of women (n = 63). Binomial and linear regression analyses were used to examine associations between maternal plasma 25(OH)D and adverse pregnancy outcomes. Fifty-one percent of the women had insufficient (<75 nmol/L) and 21% had deficient (<50 nmol/L) plasma 25(OH)D concentration at enrollment. At birth, 74.4% of the infants had insufficient and 30% had deficient plasma 25(OH)D concentrations, measured in cord blood. Multivariate analysis controlling for maternal age and body mass index (BMI) at enrollment and gestational age at delivery found that deficient plasma 25(OH)D levels were associated with a four-fold higher risk of stunting in neonates (p = 0.04). These findings add to the existing literature about vitamin D and its association with linear growth in resource-limited settings, though randomized clinical trials are needed to establish causation.

Early pregnancy vitamin D status and risk of preeclampsia

BACKGROUND

Low vitamin D status in pregnancy was proposed as a risk factor of preeclampsia.

METHODS

We assessed the effect of vitamin D supplementation (4,400 vs. 400 IU/day), initiated early in pregnancy (10-18 weeks), on the development of preeclampsia. The effects of serum vitamin D (25-hydroxyvitamin D [25OHD]) levels on preeclampsia incidence at trial entry and in the third trimester (32-38 weeks) were studied. We also conducted a nested case-control study of 157 women to investigate peripheral blood vitamin D-associated gene expression profiles at 10 to 18 weeks in 47 participants who developed preeclampsia.

RESULTS

Of 881 women randomized, outcome data were available for 816, with 67 (8.2%) developing preeclampsia. There was no significant difference between treatment (N = 408) or control (N = 408) groups in the incidence of preeclampsia (8.08% vs. 8.33%, respectively; relative risk: 0.97; 95% CI, 0.61-1.53). However, in a cohort analysis and after adjustment for confounders, a significant effect of sufficient vitamin D status (25OHD ≥30 ng/ml) was observed in both early and late pregnancy compared with insufficient levels (25OHD <30 ng/ml) (adjusted odds ratio, 0.28; 95% CI, 0.10-0.96). Differential expression of 348 vitamin D-associated genes (158 upregulated) was found in peripheral blood of women who developed preeclampsia (FDR <0.05 in the Vitamin D Antenatal Asthma Reduction Trial [VDAART]; P < 0.05 in a replication cohort). Functional enrichment and network analyses of this vitamin D-associated gene set suggests several highly functional modules related to systematic inflammatory and immune responses, including some nodes with a high degree of connectivity.

CONCLUSIONS

Vitamin D supplementation initiated in weeks 10-18 of pregnancy did not reduce preeclampsia incidence in the intention-to-treat paradigm. However, vitamin D levels of 30 ng/ml or higher at trial entry and in late pregnancy were associated with a lower risk of preeclampsia. Differentially expressed vitamin D-associated transcriptomes implicated the emergence of an early pregnancy, distinctive immune response in women who went on to develop preeclampsia.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00920621.

FUNDING

Quebec Breast Cancer Foundation and Genome Canada Innovation Network. This trial was funded by the National Heart, Lung, and Blood Institute. For details see Acknowledgments.

The Role of Vitamin D in the Transcriptional Program of Human Pregnancy

Background

Patterns of gene expression of human pregnancy are poorly understood. In a trial of vitamin D supplementation in pregnant women, peripheral blood transcriptomes were measured longitudinally on 30 women and used to characterize gene co-expression networks.

Objective

Studies suggest that increased maternal Vitamin D levels may reduce the risk of asthma in early life, yet the underlying mechanisms have not been examined. In this study, we used a network-based approach to examine changes in gene expression profiles during the course of normal pregnancy and evaluated their association with maternal Vitamin D levels.

Design

The VDAART study is a randomized clinical trial of vitamin D supplementation in pregnancy for reduction of pediatric asthma risk. The trial enrolled 881 women at 10–18 weeks of gestation. Longitudinal gene expression measures were obtained on thirty pregnant women, using RNA isolated from peripheral blood samples obtained in the first and third trimesters. Differentially expressed genes were identified using significance of analysis of microarrays (SAM), and clustered using a weighted gene co-expression network analysis (WGCNA). Gene-set enrichment was performed to identify major biological pathways.

Results

Comparison of transcriptional profiles between first and third trimesters of pregnancy identified 5839 significantly differentially expressed genes (FDR<0.05). Weighted gene co-expression network analysis clustered these transcripts into 14 co-expression modules of which two showed significant correlation with maternal vitamin D levels. Pathway analysis of these two modules revealed genes enriched in immune defense pathways and extracellular matrix reorganization as well as genes enriched in notch signaling and transcription factor networks.

Conclusion

Our data show that gene expression profiles of healthy pregnant women change during the course of pregnancy and suggest that maternal Vitamin D levels influence transcriptional profiles. These alterations of the maternal transcriptome may contribute to fetal immune imprinting and reduce allergic sensitization in early life.

Trial Registration

clinicaltrials.gov NCT00920621

Racial disparities in cord blood vitamin D levels and its association with small-for-gestational-age infants

OBJECTIVE

To examine the relationship of race and maternal characteristics and their association with cord blood vitamin D levels and small-for-gestational-age (SGA) status.

STUDY DESIGN

Cord blood vitamin D levels were measured in 438 infants (276 black and 162 white). Multivariable logistic regression models were used to evaluate associations between maternal characteristics, vitamin D status and SGA.

RESULTS

Black race, Medicaid status, mean body mass index at delivery and lack of prenatal vitamin use were associated with vitamin D deficiency. Black infants had 3.6 greater adjusted odds (95% confidence interval (CI): 2.4, 5.6) of vitamin D deficiency when compared with white infants. Black infants with vitamin D deficiency had 2.4 greater adjusted odds (95% CI: 1.0, 5.8) of SGA. Vitamin D deficiency was not significantly associated with SGA in white infants.

CONCLUSION

Identification of risk factors (black race, Medicaid status, obesity and lack of prenatal vitamin use) can lead to opportunities for targeted prenatal vitamin supplementation to reduce the risk of neonatal vitamin D deficiency and SGA status.

Global "omics" evaluation of human placental responses to preeclamptic conditions

BACKGROUND

Preeclampsia (PE) is a leading cause of maternal death. Its cause is still debated but there is general agreement that the placenta plays a central role. Perhaps the most commonly proposed contributors to PE include placental hypoxia, oxidative stress, and increased proinflammatory cytokines. How the placenta responds to these abnormalities has been considered but not as part of a comprehensive analysis of low-molecular-weight biomolecules and their responses to these accepted PE conditions.

OBJECTIVE

Using a peptidomic approach, we sought to identify a set of molecules exhibiting differential expression in consequence of provocative agents/chemical mediators of PE applied to healthy human placental tissue.

STUDY DESIGN

Known PE conditions were imposed on normal placental tissue from 13 uncomplicated pregnancies and changes in the low-molecular-weight peptidome were evaluated. A t test was used to identify potential markers for each imposed stress. These markers were then submitted to a least absolute shrinkage and selection operator multinomial logistic regression model to identify signatures specific to each stressor. Estimates of model performance on external data were obtained through internal validation.

RESULTS

A total of 146 markers were increased/decreased as a consequence of exposure to proposed mediators of PE. Of these 75 changed with hypoxia; 23 with hypoxia-reoxygenation/oxidative stress and 48 from exposure to tumor necrosis factor-α. These markers were chemically characterized using tandem mass spectrometry. Identification rates were: hypoxia, 34%; hypoxia-reoxygenation, 60%; and tumor necrosis factor-α, 50%. Least absolute shrinkage and selection operator modeling specified 16 markers that effectively distinguished all groups, ie, the 3 abnormal conditions and control. Bootstrap estimates of misclassification rates, multiclass area under the curve, and Brier score were 0.108, 0.944, and 0.160, respectively.

CONCLUSION

Using this approach we found previously unknown molecular changes in response to individual PE conditions that allowed development biomolecular signatures for exposure to each accepted pathogenic condition.

Decreased expression of the vitamin D receptor in women with recurrent pregnancy loss

The multiple functions of vitamin D3 have stimulated interest in the role that this vitamin may play during pregnancy. The present study investigated the expression of the vitamin D receptor (VDR) in women during the first trimester of pregnancy in order to determine whether VDR is associated with recurrent pregnancy loss (RPL). Forty women at 7-10 weeks gestation with RPL and 40 women of similar gestational age with a healthy pregnancy were recruited. VDR mRNA and protein in chorionic villi and decidua were evaluated by immunohistochemistry, confocal laser scanning microscopy (CLSM), western blot, and quantitative real-time polymerase chain reaction. The serum levels of VDR were measured by an enzyme-linked immunosorbent assay. Women with RPL had a significantly weaker expression of VDR mRNA in villi and decidual tissues compared with the control women (both p < 0.0001). Western blot analysis showed an approximately 46% decrease in VDR expression in villi and a 52% decrease in decidua in the RPL vs. the controls. Serum VDR levels were also significantly lower in the RPL group than in the control group (p = 0.003). Compared with the controls, immunohistochemical and CLSM analysis revealed significantly lower VDR expression in villous cytotrophoblasts and stromal cells, as well as in decidual glandular epithelial and stromal cells (all p < 0.05). In conclusion, these observations show that women with RPL have lower levels of VDR expression in chorionic villi, decidua and serum compared with normal pregnant women, suggesting that decreased VDR expression in the first trimester pregnancy may be associated with RPL.