Vitamin D supplementation improves pathophysiology in a rat model of preeclampsia

Both endothelial mineralocorticoid receptor expression and hyperleptinemia are required for clinical characteristics of placental ischemia in mice

One of the initiating events in preeclampsia (PE) is placental ischemia. Rodent models of placental ischemia do not present with vascular endothelial dysfunction, a hallmark of PE. We previously demonstrated a role for leptin in endothelial dysfunction in pregnancy in the absence of placental ischemia. We hypothesized that placental ischemia requires hyperleptinemia and endothelial mineralocorticoid receptor (ECMR) expression to induce PE-associated endothelial dysfunction in pregnant mice. We induced placental ischemia via the reduced uterine perfusion pressure (RUPP) procedure in pregnant ECMR-intact (ECMR+/+) and ECMR deletion (ECMR-/-) mice at gestational day (GD) 13. ECMR+/+ RUPP pregnant mice also received concurrent leptin infusion via miniosmotic pump (0.9 mg/kg/day). RUPP increased blood pressure via radiotelemetry and decreased fetal growth in ECMR+/+ pregnant mice. Both increases in blood pressure and reduced fetal growth were abolished in RUPP ECMR-/- mice. Placental ischemia did not decrease endothelial-dependent relaxation to acetylcholine (ACh) but increased phenylephrine (Phe) contraction in mesenteric arteries of pregnant mice, which was ablated by ECMR deletion. Addition of leptin to RUPP mice significantly reduced ACh relaxation in ECMR+/+ pregnant mice, accompanied by an increase in soluble FMS-like tyrosine kinase-1 (sFlt-1)/placental growth factor (PLGF) ratio. In conclusion, our data indicate that high leptin levels drive endothelial dysfunction in PE and that ECMR is required for clinical characteristics of hypertension and fetal growth restriction in placental ischemia PE. Collectively, we show that both ECMR and leptin play a role to mediate PE.NEW & NOTEWORTHY Leptin is a key feature of preeclampsia that initiates vascular endothelial dysfunction in preeclampsia characterized by placental ischemia. Endothelial mineralocorticoid receptor (ECMR) deletion in placental ischemia protects pregnant mice from elevations in blood pressure and fetal growth restriction in pregnancy. Increases in leptin production mediate the key pathological feature of endothelial dysfunction in preeclampsia in rodents. ECMR activation contributes to the increase in blood pressure and fetal growth restriction in preeclampsia.

Reduced uterine perfusion pressure as a model for preeclampsia and fetal growth restriction in murine: a systematic review and meta-analysis

The reduced uterine perfusion pressure (RUPP) model is frequently used to study preeclampsia and fetal growth restriction. An improved understanding of influential factors might improve reproducibility and reduce animal use considering the variability in RUPP phenotype. We performed a systematic review and meta-analysis by searching Medline and Embase (until 28 March, 2023) for RUPP studies in murine. Primary outcomes included maternal blood pressure (BP) or proteinuria, fetal weight or crown-rump length, fetal reabsorptions, or antiangiogenic factors. We aimed to identify influential factors by meta-regression analysis. We included 155 studies. Our meta-analysis showed that the RUPP procedure results in significantly higher BP (MD = 24.1 mmHg; [22.6; 25.7]; n = 148), proteinuria (SMD = 2.3; [0.9; 3.8]; n = 28), fetal reabsorptions (MD = 50.4%; [45.5; 55.2]; n = 42), circulating soluble FMS-like tyrosine kinase-1 (sFlt-1) (SMD = 2.6; [1.7; 3.4]; n = 34), and lower fetal weight (MD = -0.4 g; [-0.47; -0.34]; n = 113. The heterogeneity (variability between studies) in primary outcomes appeared ≥90%. Our meta-regression identified influential factors in the method and time point of BP measurement, randomization in fetal weight, and type of control group in sFlt-1. The RUPP is a robust model considering the evident differences in maternal and fetal outcomes. The high heterogeneity reflects the observed variability in phenotype. Because of underreporting, we observed reporting bias and a high risk of bias. We recommend standardizing study design by optimal time point and method chosen for readout measures to limit the variability. This contributes to improved reproducibility and thereby eventually improves the translational value of the RUPP model.

Cochlear pathology in preeclamptic rats: protective effects of vitamin D and magnesium sulfate

Background/aim

This study investigated the possible degeneration in cochlear morphology induced by preeclampsia (PE) and the therapeutic/preventive effect of vitamin D (Vit D) and magnesium sulfate (MgSO4) used separately and together on feto-maternal outcomes.

Materials and methods

We created PE in rats using a reduced uterine perfusion pressure (RUPP) animal model and recorded blood pressure (BP), embryonic survival (ES), and embryonic weight (EW) and evaluated cochlear morphology by electron microscopy.

Results

The PE group had elevated BP, a decreased number and weight of live pups, and significant degeneration in the cochlea compared to the sham group. In the PEV group, we observed significant beneficial effects of Vit D supplementation at 14.5 and 19.5 dpc in terms of BP (p < 0.05), EW (p < 0.001), and cochlear degeneration compared to the PE group. In the PEM group, BP (p < 0.05) and cochlear degeneration nearly reached the level found in the sham group. However, although the EW was statistically different in the PE group, it did not reach sham group levels. We also observed that BP returned to sham level (p < 0.01) and noticed significant increases in the EW (p < 0.0001) and ES (p = 0.017) in the PEMV group compared to the PE group. According to the scanning electron microscope results, combined administration of VitD and MgSO4 is more effective than separate administration in improving cochlear degeneration induced by PE.

Conclusion

The administration of Vit D and MgSO4 during pregnancy has beneficial effects on PE pathology and may play a significant role in preventing PE-related complications, including cochlear degeneration.

1,25(OH)2D3 alleviates LPS-induced preeclampsia-like rats impairment in the protective effect by TLR4/NF-kB pathway

INTRODUCTION

Accumulating epidemiological studies support that Vitamin D deficiency is associated with the pathogenesis of preeclampsia. However, it is unknown whether vitamin D can be used as a treatment for preeclampsia. This study aimed to explore whether vitamin D supplementation could improve the rat model of preeclampsia.

METHODS

LPS was used to establish a rat model of preeclampsia. Inflammatory cytokines were examined by QRT-PCR and ELISA assays, and the concentration of sfit-1 and NO was assessed by ELISA. Analyzing the pathological features of the placenta with hematoxylin-eosin. The spatial learning and memory abilities of offspring were evaluated by the Morris water maze. Immune histology and western blot were performed to evaluate the expression levels of inflammatory pathway-associated Factor and vascular endothelium-associated Factor in the placenta.

RESULTS

Vitamin D treatment reduced the blood pressure and urine protein of PE model rats, alleviated pathological damage to the placenta and pregnancy outcomes, and protected PE offspring from impaired memory and learning abilities. Moreover, TLR4 signaling pathway in the placenta was inhibited. Furthermore, vitamin D supplementation increased the expression of endothelial growth factor and vascular relaxing factor, and there was no significant difference compared with the control group.

DISCUSSION

We generated the result that Vitamin D supplementation significantly improved the phenotype of preeclampsia and adverse pregnancy outcome caused by an abnormal inflammatory reaction and endothelial dysfunction in the placenta, and improved the learning and cognitive ability of offspring.

miR-2115-3p inhibits ferroptosis by downregulating the expression of glutamic-oxaloacetic transaminase in preeclampsia

INTRODUCTION

Recently, ferroptosis has been reported to be closely related to preeclampsia (PE). However, the mechanisms associated with ferroptosis in PE have been poorly studied.

METHODS

A PE rat model was established via reduced uterine perfusion pressure (RUPP) surgery. A Ferroptosis inhibitor was used to treat the model rats. Blood pressure, urine protein, sFlt-1, GSH, GSH-PX, MDA, total Fe, Fe (II), and Fe (Ⅲ) levels were detected. Placenta morphological changes and fetal survival rate were observed and counted, respectively. miRNA sequencing and bioinformatical analysis were conducted to establish the ferroptosis-related interaction network of miRNAs-mRNAs in PE. After hypoxia treatment, cells were silenced glutamic-oxaloacetic transaminase1 (GOT1) or overexpressed miR-2115-3p/GOT1. Cellular proliferation, invasion, and reactive oxygen species (ROS) were determined. The ferroptosis-related factors levels (ACSL4, TfR1, GPX4, SCL7A11, GSH, GSH-PX, Fe (II), and MDA) were quantified.

RESULTS

In vivo, ferrostatin-1 attenuated ferroptosis in the PE models, significantly increasing fetal survivability. The miR-2115-3p/GOT1 pathway was screened for possible association with abnormal ferroptosis in PE. miR-2115-3p was discovered to interact with the mRNA of GOT1. Inhibition of GOT1 and overexpression of miR-2115-3p reversed the decrease in cell proliferation capacity, GSH, GSH-PX, and GPX4 levels, and the increase in ROS, ACSL4, TfR1, MDA, total Fe, and Fe (II) levels induced by hypoxia. However, simultaneous overexpression of miR-2115-3p and GOT1 reversed the above results of overexpression of miR-2115-3p.

DISCUSSION

miR-2115-3p might interact with the GOT1 mRNA to downregulate its expression, further inhibiting the hypoxia-promoted ferroptosis in a PE model.

Relationship between Maternal Vitamin D Levels and Adverse Outcomes

Vitamin D (VD), a fat-soluble vitamin, has a variety of functions that are important for growth and development, including regulation of cell differentiation and apoptosis, immune system development, and brain development. As such, VD status during pregnancy is critical for maternal health, fetal skeletal growth, and optimal pregnancy outcomes. Studies have confirmed that adverse pregnancy outcomes, such as preeclampsia, low birth weight, neonatal hypocalcemia, poor postnatal growth, skeletal fragility, and increased incidence of autoimmune diseases, can be associated with low VD levels during pregnancy and infancy. Thus, there is growing interest in the role of VD during pregnancy. This review summarizes the potential adverse health outcomes of maternal VD status during pregnancy for both mother and offspring (gestational diabetes mellitus, hypertensive gestational hypertension, intrauterine growth restriction, miscarriage, stillbirth, and preterm birth) and discusses the underlying mechanisms (regulation of cytokine pathways, immune system processing, internal secretion, placental function, etc.) of VD in regulating each of the outcomes. This review aims to provide a basis for public health intervention strategies to reduce the incidence of adverse pregnancies.

Animal models of preeclampsia: investigating pathophysiology and therapeutic targets

Animal models have been critical in investigating the pathogenesis, mediators, and even therapeutic options for a number of diseases, including preeclampsia. Preeclampsia is the leading cause of maternal and fetal morbidity and mortality worldwide. The placenta is thought to play a central role in the pathogenesis of this disease because it releases antiangiogenic and proinflammatory factors into the maternal circulation, resulting in the maternal syndrome. Despite the deleterious effects preeclampsia has been shown to have on the mother and baby during pregnancy and postpartum, there is still no effective treatment for this disease. Although clinical studies in patients are crucial to identify the involvement of pathogenic factors in preeclampsia, there are obvious limitations that prevent detailed investigation of the quantitative importance of time-dependent mechanisms involved in this syndrome. Animal models allow investigators to perform proof-of-concept studies and examine whether certain factors found in women with preeclampsia mediate hypertension and other manifestations of this disease. In this brief review, we summarize some of the more widely studied models used to investigate pathophysiological mechanisms that are thought to be involved in preeclampsia. These include models of placental ischemia, angiogenic imbalance, and maternal immune activation. Infusion of preeclampsia-related factors into animals has been widely studied to understand the specific mediators of this disease. These models have been included, in addition to a number of genetic models involved in overexpression of the renin-angiotensin system, complement activation, and trophoblast differentiation. Together, these models cover multiple mechanisms of preeclampsia from trophoblast dysfunction and impaired placental vascularization to the excess circulating placental factors and clinical manifestation of this disease. Most animal studies have been performed in rats and mice; however, we have also incorporated nonhuman primate models in this review. Preclinical animal models not only have been instrumental in understanding the pathophysiology of preeclampsia but also continue to be important tools in the search for novel therapeutic options for the treatment of this disease.

Soluble guanylate cyclase stimulation in late gestation does not mitigate asymmetric intrauterine growth restriction or cardiovascular risk induced by placental ischemia in the rat

Stimulation of soluble guanylate cyclase (sGC) improves fetal growth at gestational day 20 in the reduced uterine perfusion pressure (RUPP) rat model of placental ischemia suggesting a role for sGC in the etiology of intrauterine growth restriction (IUGR). This study tested the hypothesis that stimulation of sGC until birth attenuates asymmetric IUGR mitigating increased cardiovascular risk in offspring. Sham or RUPP surgery was performed at gestational day 14 (G14); vehicle or the sGC stimulator Riociguat (10 mg/kg/day sc) was administered G14 until birth. Birth weight was reduced in offspring from RUPP [intrauterine growth restricted (IUGR)], sGC RUPP (sGC IUGR), and sGC Sham (sGC Control) compared with Sham (Control). Crown circumference was maintained, but abdominal circumference was reduced in IUGR and sGC IUGR compared with Control indicative of asymmetrical growth. Gestational length was prolonged in sGC RUPP, and survival at birth was reduced in sGC IUGR. Probability of survival to postnatal day 2 was also significantly reduced in IUGR and sGC IUGR versus Control and in sGC IUGR versus IUGR. At 4 mo of age, blood pressure was increased in male IUGR and sGC IUGR but not male sGC Control born with symmetrical IUGR. Global longitudinal strain was increased and stroke volume was decreased in male IUGR and sGC IUGR compared with Control. Thus late gestational stimulation of sGC does not mitigate asymmetric IUGR or increased cardiovascular risk in male sGC IUGR. Furthermore, late gestational stimulation of sGC is associated with symmetrical growth restriction in sGC Control implicating contraindications in normal pregnancy.NEW & NOTEWORTHY The importance of the soluble guanylate cyclase-cGMP pathway in a rat model of placental ischemia differs during critical windows of development, implicating other factors may be critical mediators of impaired fetal growth in the final stages of gestation. Moreover, increased blood pressure at 4 mo of age in male intrauterine growth restriction offspring is associated with impaired cardiac function including an increase in global longitudinal strain in conjunction with a decrease in stroke volume, ejection fraction, and cardiac output.

Preeclampsia: Linking Placental Ischemia with Maternal Endothelial and Vascular Dysfunction

Preeclampsia (PE), a hypertensive disorder, occurs in 3% to 8% of pregnancies in the United States and affects over 200,000 women and newborns per year. The United States has seen a 25% increase in the incidence of PE, largely owing to increases in risk factors, including obesity and cardiovascular disease. Although the etiology of PE is not clear, it is believed that impaired spiral artery remodeling of the placenta reduces perfusion, leading to placental ischemia. Subsequently, the ischemic placenta releases antiangiogenic and pro-inflammatory factors, such as cytokines, reactive oxygen species, and the angiotensin II type 1 receptor autoantibody (AT1-AA), among others, into the maternal circulation. These factors cause widespread endothelial activation, upregulation of the endothelin system, and vasoconstriction. In turn, these changes affect the function of multiple organ systems including the kidneys, brain, liver, and heart. Despite extensive research into the pathophysiology of PE, the only treatment option remains early delivery of the baby and importantly, the placenta. While premature delivery is effective in ameliorating immediate risk to the mother, mounting evidence suggests that PE increases risk of cardiovascular disease later in life for both mother and baby. Notably, these women are at increased risk of hypertension, heart disease, and stroke, while offspring are at risk of obesity, hypertension, and neurological disease, among other complications, later in life. This article aims to discuss the current understanding of the diagnosis and pathophysiology of PE, as well as associated organ damage, maternal and fetal outcomes, and potential therapeutic avenues. © 2021 American Physiological Society. Compr Physiol 11:1315-1349, 2021.

The relationship among vitamin D, TLR4 pathway and preeclampsia

Preeclampsia is a pregnancy-specific syndrome that has been the greatest cause of maternal and fetal morbidity and mortality. The impaired outcomes are related to maternal and the offspring healthy in the short and long-term. Although preeclampsia origins remain unclear, it is well known that there is impaired trophoblast invasion with culminant abnormal immune response. The early and late-onset preeclampsia have been studied, the subtypes have the same difference in the placentation and inflammatory features. Dietary compounds can stimulate or inhibit the activation of immune cells. Low vitamin D intake has been linked to impaired fetal development, intrauterine growth restriction, and preeclampsia. Vitamin D has been described as an anti-inflammatory effect. It can downregulate pro-inflammatory cytokines expression by the inhibition of the Nuclear Factor-ĸB pathway signaling cascade. High vitamin D levels could attenuate the immune response. On the other hand, vitamin D deficiency may contribute to increasing pro-inflammatory state. In preeclampsia, there is a reduced expression of vitamin D receptor and its metabolism is disrupted. In this review, we aimed to discuss the role of vitamin D as an anti-inflammatory agent in relation to the pro-inflammatory process of preeclampsia through the activation of the TLR4 pathway. Although there are limited studies showing the relation between vitamin D and lower risk of preeclampsia, the maternal status of vitamin D seems to influence the risk of PE development. Therefore, vitamin D supplementation in women may be a strategy to improve pregnancy outcomes.

The Influence of Vitamin D on Neurodegeneration and Neurological Disorders: A Rationale for its Physio-pathological Actions

Vitamin D is a steroid hormone implicated in the regulation of neuronal integrity and many brain functions. Its influence, as a nutrient and a hormone, on the physiopathology of the most common neurodegenerative diseases is continuously emphasized by new studies. This review addresses what is currently known about the action of vitamin D on the nervous system and neurodegenerative diseases such as Multiple Sclerosis, Alzheimer's disease, Parkinson's disease and Amyotrophic Lateral Sclerosis. Further vitamin D research is necessary to understand how the action of this "neuroactive" steroid can help to optimize the prevention and treatment of several neurological diseases.

Co-targeting of endothelin-A and vitamin D receptors: a novel strategy to ameliorate cisplatin-induced nephrotoxicity

BACKGROUND

Although modulation of the vitamin D receptor (VDR) and endothelin-A receptor (ETAR) has previously been reported to offer renoprotection against cisplatin-induced nephrotoxicity, the possible interaction between the ET-1 and vitamin D pathways remains obscure. Therefore, the present study addressed the possible interaction between these signalling pathways using BQ-123 (a selective ETAR blocker) and alfacalcidol (a vitamin D3 analogue) separately or in combination.

METHODS

Male Sprague-Dawley rats were divided into the following groups: control (DMSO orally), cisplatin (single dose of 6 mg/kg ip; nephrotoxicity model), cisplatin + BQ-123 (1 mg/kg BQ-123 ip 1 h before and 1 day after cisplatin), cisplatin + alfacalcidol (50 ng/kg alfacalcidol orally 5 days before and 14 days after cisplatin), and cisplatin + BQ-123+alfacalcidol. Nephrotoxicity was evaluated 96 h and 14 days following cisplatin administration.

RESULTS

Both BQ-123 and alfacalcidol counteracted cisplatin-induced nephrotoxic changes. Specifically, they reduced serum creatinine and urea levels; renal tumour necrosis factor-alpha (TNF-α), transforming growth factor-beta1 (TGF-β1), and phosphorylated nuclear factor-kappa B (pNF-κB) content; and caspase-3 activity. They downregulated ET-1 and ETAR expression and ameliorated cisplatin-induced acute tubular necrosis. In addition, the treatments have increased VDR and endothelin-B receptor (ETBR) expression; however, BQ-123 did not affect ETBR. The effect of the combination regimen surpassed that of each drug alone.

CONCLUSION

These findings highlight the potential cross-talk between vitamin D and ET-1 pathways and pave the way for future preclinical/clinical studies to explore further mechanisms involved in this cross-talk.

Characterisation of the Selective Reduced Uteroplacental Perfusion (sRUPP) Model of Preeclampsia

Preeclampsia is a complication of pregnancy characterised by gestational hypertension, proteinuria and/or end organ disease. The reduced uteroplacental perfusion (RUPP) model, via partial occlusion of the lower abdominal aorta, mimics insufficient placental perfusion as a primary causal characteristic of preeclampsia. However, a major limitation of the RUPP model is that perfusion is reduced to the entire hindquarters of the rat resulting in hindlimb ischemia. We hypothesised that clipping the uterine and ovarian arteries in the selective (s)RUPP model would provoke signs of preeclampsia while avoiding systemic ischemia. Sham, RUPP or sRUPP procedures were performed in pregnant Sprague Dawley rats on gestational day (GD)14. On GD21 uterine blood flow was significantly reduced in both the RUPP and sRUPP models while aortic flow was reduced only in RUPP. Both models resulted in increased MAP, increased vascular oxidative stress (superoxide generation), increased pro-inflammatory (RANTES) and reduced pro-angiogenic (endoglin) mediators. Vascular compliance and constriction were unaltered in either RUPP or sRUPP groups. In summary, refinements to the RUPP model simultaneously maintain the characteristic phenotype of preeclampsia and avoid peripheral ischemia; providing a useful tool which may be used to increase our knowledge and bring us closer to a solution for women affected by preeclampsia.

The Implications of Vitamin D Status During Pregnancy on Mother and her Developing Child

Pregnancy is a time of tremendous growth and physiological changes for mother and her developing fetus with lifelong implications for the child. The concert of actions that must occur so mother does not reject the foreign tissue of the fetus is substantial. There must be exquisite balance between maternal tolerance to these foreign proteins of paternal origin but also immune surveillance and function such that the mother is not immunocompromised. When this process goes awry, the mother may experience such pregnancy complications as preeclampsia and infections. Vitamin D deficiency affects these processes. Controversy continues with regard to the optimal daily intake of vitamin D, when sunlight exposure should be taken into account, and how to define sufficiency during such vulnerable and critical periods of development. The importance of vitamin D supplementation during pregnancy in preventing some of the health risks to the mother and fetus appears linked to achieving 25(OH)D concentrations >40 ng/mL, the beginning point of the plateau where conversion of the vitamin D metabolite 25(OH)D, the pre-hormone, to 1,25(OH)2D, the active hormone, is optimized. Throughout pregnancy, the delivery of adequate vitamin D substrate-through sunlight or supplement-is required to protect both mother and fetus, and when in sufficient supply, favorably impacts the epigenome of the fetus, and in turn, long term health. There is a growing need for future research endeavors to focus not only on critical period(s) from pre-conception through pregnancy, but throughout life to prevent certain epigenetic changes that adversely affect health. There is urgency based on emerging research to correct deficiency and maintain optimal vitamin D status. The impact of vitamin D and its metabolites on genetic signaling during pregnancy in both mother and fetus is an area of great activity and still in its early stages. While vitamin D repletion during pregnancy minimizes the risk of certain adverse outcomes (e.g., preterm birth, asthma, preeclampsia, and gestational diabetes), the mechanisms of how these processes occur are not fully understood. As we intensify our research efforts in these areas. it is only a matter of time that such mechanisms will be defined.

Increases in placental nitric oxide, but not nitric oxide-mediated relaxation, underlie the improvement in placental efficiency and antihypertensive effects of hydrogen sulphide donor in hypertensive pregnancy

Dysregulation of hydrogen sulphide (H₂ S) producing enzymes has been related to hypertensive pregnancy, and H₂ S donor, sodium hydrosulphide (NaHS) exerts antihypertensive effects, modulates angiogenic factors production and acts as an antioxidant. Moreover, reduction in nitric oxide (NO) bioavailability is related to hypertensive pregnancy and H₂ S may interact with NO, modulating its production. We aimed to investigate the NaHS effects in hypertension-in-pregnancy and also in feto-placental parameters. Female Wistar rats (200-250 g) were mated and desoxycorticosterone acetate injections followed by replacement of water by 0.9% saline solution were used to induce hypertensive pregnancy. Rats were divided into four groups: normal pregnant (Norm-Preg), pregnant + NaHS (Preg+NaHS), hypertensive pregnant (HTN-Preg) and HTN-Preg+NaHS. Systolic blood pressure was increased in HTN-Preg and this increase was blunted in HTN-Preg+NaHS. Fetal and placental weights were decreased in HTN-Preg animals, while fetal growth restriction was improved in HTN-Preg+NaHS. Placental weight was lower in HTN-Preg+NaHS than in HTN-Preg; however, placental efficiency was re-established in HTN-Preg+NaHS rats. We observed that a partial contribution of placental NO, but not changes in anti-angiogenic factors may mediate the increases in placental efficiency in HTN-Preg+NaHS. HTN-Preg presented thoracic aorta hyperreactivity to phenylephrine while NaHS treatment blunted this hyperreactivity, which seems not to be related to NO-mediated relaxation induced by acetylcholine. Therefore, changes in vascular responsiveness promoted by NaHS treatment may underlie the beneficial effects in systolic blood pressure and feto-placental parameters in our study.

Impact of vitamin D on pregnancy-related disorders and on offspring outcome

Observational studies from all over the world continue to find high prevalence rates of vitamin D insufficiency and deficiency in many populations, including pregnant women. Beyond its classical function as a regulator of calcium and phosphate metabolism, vitamin D elicits numerous effects in the human body. Current evidence highlights a vital role of vitamin D in mammalian gestation. During pregnancy, adaptations in maternal vitamin D metabolism lead to a physiologic increase of vitamin D levels, mainly because of an increased renal production, although other potential sources like the placenta are being discussed. A sufficient supply of mother and child with calcium and vitamin D during pregnancy ensures a healthy bone development of the fetus, whereas lack of either of these nutrients can lead to the development of rickets in the child. Moreover, vitamin D insufficiency during pregnancy has consistently been associated with adverse maternal and neonatal pregnancy outcomes. In multitudinous studies, low maternal vitamin D status was associated with a higher risk for preeclampsia, gestational diabetes mellitus and other gestational diseases. Likewise, several negative consequences for the fetus have been reported, including fetal growth restriction, increased risk of preterm birth and a changed susceptibility for later-life diseases. However, study results are diverging and causality has not been proven so far. Meta-analyses on the relationship between maternal vitamin D status and pregnancy outcomes revealed a wide heterogeneity of studied populations and the applied methodology in vitamin D assessment. Until today, clinical guidelines for supplementation cannot be based on high-quality evidence and it is not clear if the required intake for pregnant women differs from non-pregnant women. Long-term safety data of vitamin D supplementation in pregnant women has not been established and overdosing of vitamin D might have unfavorable effects, especially in mothers and newborns with mutations of genes involved in vitamin D metabolism. Reliable data from large observational and interventional randomized control trials are urgently needed as a basis for any detailed and safe recommendations for supplementation in the general population and, most importantly, in pregnant women. This is of utmost importance, as ensuring a sufficient vitamin D-supply of mother and child implies a great potential for the prevention of birth complications and development of diseases.

Vitamin D Supplementation Prevents Placental Ischemia Induced Endothelial Dysfunction by Downregulating Placental Soluble FMS-Like Tyrosine Kinase-1

Maternal vitamin D deficiency in pregnancy has been associated with an increased risk of preeclampsia. Vascular endothelial dysfunction is a major phenotype of pregnancies with preeclampsia, contributing to increased maternal hypertension and proteinuria. We sought to determine whether vitamin D supplementation would alleviate preeclampsia associated endothelial dysfunction and explore the underlying mechanism using the reduced uterine perfusion pressure (RUPP) rat model. RUPP operated rats were supplemented with 1,25(OH)₂D (RUPP+VD) on day 1, 7, and 14 of pregnancy by subcutaneous injection. On day 19 of pregnancy, after the measurement of blood pressure and urine collection, maternal blood serum and placenta samples were collected. 1,25(OH)₂D treatment significantly improved endothelial dysfunction by reducing apoptosis and increasing nitric oxide (NO) production in blood vessels of RUPP operated rats compared to untreated RUPP rats. 1,25(OH)₂D significantly down-regulated the expression of placental soluble FMS-like tyrosine kinase-1 (sFlt-1) in RUPP rats. Furthermore, the circulating sFlt-1 levels in maternal serum were positively correlated with the expression of placental sFlt-1 and were restored to a normal pregnant level by 1,25(OH)₂D treatment in RUPP rats. Incubation of endothelial cell line with rat serum from RUPP+VD group significantly increased NO production and decreased caspase-3 activity compared with serum from untreated RUPP rats. Moreover, neutralization of sFlt-1 using the specific antibody mimicked the effect of 1,25(OH)₂D, which abolished the deleterious effect of RUPP rat's serum on NO production and apoptosis. These results suggest that vitamin D supplementation is protective against RUPP induced endothelial dysfunction by downregulating placental sFlt-1, which can possibly alleviate preeclampsia associated symptoms.

Vitamin D supplementation during pregnancy: Improvements in birth outcomes and complications through direct genomic alteration

Pregnancy represents a time of rapid change, including dramatic shifts in vitamin D metabolism. Circulating concentrations of the active form of vitamin D-1,25(OH)2D skyrocket early in pregnancy to levels that would be toxic to a nonpregnant adult, signaling a decoupling of vitamin D from the classic endocrine calcium metabolic pathway, likely serving an immunomodulatory function in the mother and her developing fetus. In this review, we summarize the unique aspects of vitamin D metabolism and the data surrounding vitamin D requirements during this important period. Both observational and clinical trials are reviewed in the context of vitamin D's health effects during pregnancy that include preeclampsia, preterm birth, and later disease states such as asthma and multiple sclerosis. With enhanced knowledge about vitamin D's role as a preprohormone, it is clear that recommendations about supplementation must mirror what is clinically relevant and evidence-based. Future research that focuses on the critical period(s) leading up to conception and during pregnancy to correct deficiency or maintain optimal vitamin D status remains to be studied. In addition, what effects vitamin D has on genetic signatures that minimize the risk to the mother and her developing fetus have not been elucidated. Clearly, while there is much more research that needs to be performed, our understanding of vitamin D requirements during pregnancy has advanced significantly during the last few decades.

Vitamin D administration during pregnancy as prevention for pregnancy, neonatal and postnatal complications

Pregnancy represents a time of rapid bodily change, which includes physical proportions, physiology and responsibility. At this context, maternal vitamin D stores have been the objective of extensive scientific research during the last decades, focusing on their potential effects on maternal an neonatal health. A growing body of observational studies indicated that maternal hypovitaminosis D (as defined by maternal 25-hydroxyvitamin D [25(OH)D] levels <20 ng/ml or <50 nmol/l) is a significant risk factor for adverse neonatal outcomes including asthma, multiple sclerosis and other neurological disorders. On that basis, this review aims to provide to the reader new insights into the vitamin D requirements and function during pregnancy supported by recent data and will not discuss the classical roles of vitamin D and skeletal function during pregnancy. In addition, we will focus on recent results that demonstrate that maternal vitamin D supplementation could reduce neonatal respiratory and neurological complications, suggesting that available guidelines should be updated, since it remains unclear why these recommendations are not updated according to recent results. Also, with regard to randomized controlled trials (RCT's) for vitamin D, we consider that they are largely doomed to fail. The reasons for this are many and specific cases of this failure will be presented in this text.

New insights into the vitamin D requirements during pregnancy

Pregnancy represents a dynamic period with physical and physiological changes in both the mother and her developing fetus. The dramatic 2–3 fold increase in the active hormone 1,25(OH)₂D concentrations during the early weeks of pregnancy despite minimal increased calcium demands during that time of gestation and which are sustained throughout pregnancy in both the mother and fetus suggests an immunomodulatory role in preventing fetal rejection by the mother. While there have been numerous observational studies that support the premise of vitamin D's role in maintaining maternal and fetal well-being, until recently, there have been few randomized clinical trials with vitamin D supplementation. One has to exhibit caution, however, even with RCTs, whose results can be problematic when analyzed on an intent-to-treat basis and when there is high non-adherence to protocol (as if often the case), thereby diluting the potential good or harm of a given treatment at higher doses. As such, a biomarker of a drug or in this case “vitamin” or pre-prohormone is better served. For these reasons, the effect of vitamin D therapies using the biomarker circulating 25(OH)D is a far better indicator of true “effect.” When pregnancy outcomes are analyzed using the biomarker 25(OH)D instead of treatment dose, there are notable differences in maternal and fetal outcomes across diverse racial/ethnic groups, with improved health in those women who attain a circulating 25(OH)D concentration of at least 100 nmol·L⁻¹ (40 ng·mL⁻¹). Because an important issue is the timing or initiation of vitamin D treatment/supplementation, and given the potential effect of vitamin D on placental gene expression and its effects on inflammation within the placenta, it appears crucial to start vitamin D treatment before placentation (and trophoblast invasion); however, this question remains unanswered. Additional work is needed to decipher the vitamin D requirements of pregnant women and the optimal timing of supplementation, taking into account a variety of lifestyles, body types, baseline vitamin D status, and maternal and fetal vitamin D receptor (VDR) and vitamin D binding protein (VDBP) genotypes. Determining the role of vitamin D in nonclassical, immune pathways continues to be a challenge that once answered will substantiate recommendations and public health policies.

Meta-analysis of the effect of the maternal vitamin D level on the risk of spontaneous pregnancy loss

BACKGROUND

The association between vitamin D deficiency and early spontaneous pregnancy loss (SPL) is unclear.

OBJECTIVES

To assess the association of serum 25-hydroxyvitamin D (25(OH)D) and SPL.

SEARCH STRATEGY

Embase, PubMed, and Web of Science were searched for relevant papers published before February 20, 2016, using search terms including "vitamin D" and "pregnancy loss."

SELECTION CRITERIA

Case-control and cohort studies investigating the relationship of maternal serum 25(OH)D and SPL were included.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted original data from the selected papers. The DerSimonian-Laird random-effects model was used to perform the meta-analysis. Heterogeneity was assessed by calculating I² .

MAIN RESULTS

Five studies, including 10 630 pregnant women, met the inclusion criteria. There was no significant association between a low 25(OH)D level and an increased risk of SPL. In a subgroup analysis, an extremely low 25(OH)D level (<20 ng/mL) was significantly associated with an increased risk of SPL in the first trimester (relative risk 2.24, 95% confidence interval 1.15-4.37); the heterogeneity across studies was not significant (I² =0.0%, P=0.355).

CONCLUSIONS

Severe Vitamin D deficiency could be detrimental to early embryonic development and increase the risk of early SPL.

Vitamin D supplementation reduces some AT1-AA-induced downstream targets implicated in preeclampsia including hypertension

Autoantibodies to the ANG II type I receptor (AT₁-AA) are associated with preeclampsia (PE). We found that vitamin D supplementation reduced AT₁-AA and blood pressure (MAP) in the RUPP rat model of PE. However, it was undetermined whether the decrease in AT₁-AA was the mechanism whereby vitamin D lowered MAP or if it were through factors downstream of AT₁-AA. Uterine artery resistance index, placental ET-1, and soluble FMS-like tyrosine kinase-1 are increased with AT₁-AA-induced hypertension and are considered markers of PE in pregnant women. Therefore, we hypothesized that vitamin D would reduce PE factors during AT₁-AA-induced hypertension and could lower blood pressure in a model of hypertension during pregnancy without PE features. Either ANG II (50 ng·kg^-1·day) or AT₁-AA (1:40) was infused from gestational day (GD) 12-19. vitamin D₂ (VD2, 270 IU/day) or vitamin D₃ (VD3, 15 IU/day) was administered orally from GD14-GD18. MAP (mmHg) increased in AT₁-AA (121 ± 4) and ANG II (113 ± 1)-infused pregnant rats compared with normal pregnant rats (NP) (101 ± 2) but was lower in AT₁-AA+VD2 (105 ± 2), AT₁-AA+VD3 (109 ± 2), ANG II+VD2 (104 ± 4), and ANG II+VD3 (104 ± 3). VD2 and/or VD3 improved PE features associated with AT₁-AA during pregnancy, while ANG II did not induce such features, supporting the hypothesis that AT₁-AA induces PE features during pregnancy, and these are improved with vitamin D. In this study, we demonstrate that vitamin D improved many factors associated with PE and reduced blood pressure in a hypertensive model without PE features, indicating that vitamin D could be beneficial for various hypertensive disorders of pregnancy.

Vitamin D restores angiogenic balance and decreases tumor necrosis factor-α in a rat model of pre-eclampsia

AIM

Deficiency of vitamin D is correlated with pre-eclampsia (PE), a hypertensive disorder of pregnancy, and is characterized by angiogenic imbalance and inflammation. The aim of this study was to investigate whether vitamin D supplementation can restore the angiogenic balance and ameliorate inflammation in a rat model of PE.

METHODS

PE was induced using l-nitroarginine methylester. Normal pregnant and PE-induced rats were supplemented with vitamin D on gestation days 14-19.

RESULTS

Blood pressure was significantly increased in PE-induced rats compared with normal pregnant rats (P < 0.05), and vitamin D supplementation ameliorated this difference. In addition, rats from the PE group had lower vascular endothelial growth factor (VEGF; P < 0.01), and higher plasma-soluble FMS-like tyrosine kinase-1 (sFlt-1) and tumor necrosis factor-α (TNF-α; P < 0.01 for both) compared with the normal pregnant group. The vitamin D treatment group had significantly increased VEGF, and reduced sFlt-1 and TNF-α compared with the untreated PE group. Moreover, vitamin D supplementation was able to reduce the oxidative stress by lowering the plasma oxidative stress marker malondialdehyde.

CONCLUSION

Vitamin D supplementation plays an important role in restoring angiogenic balance and reducing inflammation in pregnancy-induced hypertension.

Vitamin D depletion does not affect key aspects of the preeclamptic phenotype in a transgenic rodent model for preeclampsia

Maternal vitamin D deficiency is proposed as a risk factor for preeclampsia in humans. We tested the hypothesis that vitamin D depletion aggravates and high supplementation ameliorates the preeclampsia phenotype in an established transgenic rat model of human renin-angiotensin system-mediated preeclampsia. Adult rat dams, transgenic for human angiotensinogen (hAGT) and mated with male rats transgenic for human renin (hREN), were fed either vitamin D-depleted chow (VDd) or enriched chow (VDh) 2 weeks before mating and during pregnancy. Mean blood pressure was recorded by tail-cuff, and 24-hour urine samples were collected in metabolic cages at days 6 and 18 of gestation. Rats were sacrificed at day 21 of gestation. Depleted dams (VDd) had negligible serum 25-hydroxyvitamin D2+3 levels (mean ± SEM; 2.95 ± 0.45 nmol/l vs. VDh 26.20 ± 2.88 nmol/l, P = .01), but in both groups, levels of 1,25(OH)2D3 remained below detection level of 25 pmol/l. Dietary vitamin D depletion did not aggravate hypertension (mean ± SEM BP, day 20 of gestation: 151.38 ± 5.65 mmHg VDd vs. 152.00 ± 4.10 mmHg VDh) or proteinuria. Fetal anthropometrics were similar between the groups, whereas VDd displayed lower placental:fetal weight ratios (0.15 vs. 0.16 g/g, P = .01) and increased sFlt-1/PlGF ratio. Expression of hREN was lower in placenta of VDd dams (0.82 ± 0.44 AU vs. 1.52 ± 0.15 AU, P = .04). Expression of key vitamin D metabolizing enzymes was unchanged. Dietary vitamin D intervention did not alter key aspects of the preeclampsia phenotype using the transgenic rodent model of human renin-angiotensin system-mediated pre-eclampsia, plausibly due to altered vitamin D metabolism or excretion in the transgenic rats.

Reduced Uterine Perfusion Pressure (RUPP) Model of Preeclampsia in Mice

Preeclampsia (PE) is a pregnancy-induced hypertension with proteinuria that typically develops after 20 weeks of gestation. A reduction in uterine blood flow causes placental ischemia and placental release of anti-angiogenic factors such as sFlt-1 followed by PE. Although the reduced uterine perfusion pressure (RUPP) model is widely used in rats, investigating the role of genes on PE using genetically engineered animals has been problematic because it has been difficult to make a useful RUPP model in mice. To establish a RUPP model of PE in mice, we bilaterally ligated ovarian vessels distal to ovarian branches, uterine vessels, or both in ICR-strain mice at 14.5 days post coitum (dpc). Consequently, these mice had elevated BP, increased urinary albumin excretion, severe endotheliosis, and mesangial expansion. They also had an increased incidence of miscarriage and premature delivery. Embryonic weight at 18.5 dpc was significantly lower than that in sham mice. The closer to the ligation site the embryos were, the higher the resorption rate and the lower the embryonic weight. The phenotype was more severe in the order of ligation at the ovarian vessels < uterine vessels < both. Unlike the RUPP models described in the literature, this model did not constrict the abdominal aorta, which allowed BP to be measured with a tail cuff. This novel RUPP model in mice should be useful for investigating the pathogenesis of PE in genetically engineered mice and for evaluating new therapies for PE.