Maternal myo-inositol, glucose, and zinc status is associated with the risk of offspring with spina bifida

Inositols and female reproduction disorders: a consensus statement from the working group of the Club of the Italian Society of Endocrinology (SIE)-Women's Endocrinology

PURPOSE

To provide the latest scientific knowledge on the efficacy of inositols for improving reproductive disorders in women with and without polycystic ovary syndrome (PCOS) and to reach a consensus on their potential use through a Delphi-like process.

METHODS

A panel of 17 endocrinologists and 1 gynecologist discussed 4 key domains: menses irregularity and anovulation, fertility, pregnancy outcomes, and neonatal outcomes.

RESULTS

A total of eight consensus statements were drafted. Myo-inositol (Myo) supplementation can be used to improve menses irregularities and anovulation in PCOS. Myo supplementation can be used in subfertile women with or without PCOS to reduce the dose of r-FSH for ovarian stimulation during IVF, but it should not be used to increase the clinical pregnancy rate or live birth rate. Myo supplementation can be used in the primary prevention of gestational diabetes mellitus (GDM), but should not be used to improve pregnancy outcomes in women with GDM. Myo can be preconceptionally added to folic acid in women with a previous neural tube defects (NTD)-complicated pregnancy to reduce the risk of NTDs in newborns. Myo can be used during pregnancy to reduce the risk of macrosomia and neonatal hypoglycemia in mothers at risk of GDM.

CONCLUSION

This consensus statement provides recommendations aimed at guiding healthcare practitioners in the use of inositols for the treatment or prevention of female reproductive disorders. More evidence-based data are needed to definitively establish the usefulness of Myo, the appropriate dosage, and to support the use of D-chiro-inositol (DCI) or a definitive Myo/DCI ratio.

Association of embryonic inositol status with susceptibility to neural tube defects, metabolite profile, and maternal inositol intake

Maternal nutrition contributes to gene-environment interactions that influence susceptibility to common congenital anomalies such as neural tube defects (NTDs). Supplemental myo-inositol (MI) can prevent NTDs in some mouse models and shows potential for prevention of human NTDs. We investigated effects of maternal MI intake on embryonic MI status and metabolism in curly tail mice, which are genetically predisposed to NTDs that are inositol-responsive but folic acid resistant. Dietary MI deficiency caused diminished MI in maternal plasma and embryos, showing that de novo synthesis is insufficient to maintain MI levels in either adult or embryonic mice. Under normal maternal dietary conditions, curly tail embryos that developed cranial NTDs had significantly lower MI content than unaffected embryos, revealing an association between diminished MI status and failure of cranial neurulation. Expression of inositol-3-phosphate synthase 1, required for inositol biosynthesis, was less abundant in the cranial neural tube than at other axial levels. Supplemental MI or d-chiro-inositol (DCI) have previously been found to prevent NTDs in curly tail embryos. Here, we investigated the metabolic effects of MI and DCI treatments by mass spectrometry-based metabolome analysis. Among inositol-responsive metabolites, we noted a disproportionate effect on nucleotides, especially purines. We also found altered proportions of 5-methyltetrahydrolate and tetrahydrofolate in MI-treated embryos suggesting altered folate metabolism. Treatment with nucleotides or the one-carbon donor formate has also been found to prevent NTDs in curly tail embryos. Together, these findings suggest that the protective effect of inositol may be mediated through the enhanced supply of nucleotides during neural tube closure.

BMP/Smad Pathway Is Involved in Lithium Carbonate-Induced Neural-Tube Defects in Mice and Neural Stem Cells

Neural-tube defects (NTDs) are one type of the most serious birth defects. Studies have shown that inositol deficiency is closely related to the occurrence of NTDs. Bone morphogenetic protein (BMP)-mediated Smad signaling pathways have been implicated in neurogenesis and neural-tube closure. However, the role of the BMP/Smad pathway in inositol-deficiency-induced NTDs remains unclear. Inositol-deficiency models in C57 mice and mouse neural stem cells (mNSCs) were induced with Li₂CO₃ treatment or inositol withdrawal. The role of the BMP/Smad pathway in the regulation of cell proliferation and the development of NTDs was determined utilizing qRT-PCR, HE staining, Western blot, immunostaining, MTT assay, EdU staining, and flow cytometry. The intraperitoneal injection of Li₂CO₃ at Embryonic Day 7.5 induced the occurrence of NTDs. The mRNA levels of Bmp2, Bmp4, Smad1, Smad5, Smad8 and Runx2, the phosphorylation of Smad1/5/8, and the nuclear translocation of Runx2 were significantly increased in NTD embryonic brain tissues and mNSCs exposed to Li₂CO₃ or an inositol-free medium, which were suppressed by BMP receptor selective inhibitor LDN-193189. The Li₂CO₃-induced phosphorylation of Smad1/5/8 was inhibited by inositol supplementation. Cell proliferation was significantly promoted by Li₂CO₃ exposure or the absence of inositol in mNSCs, which was reversed by LDN-193189. These results suggest that the activation of the BMP/Smad signaling pathway might play an important role in the development of NTDs induced by maternal Li₂CO₃ exposure via inositol deficiency.

Genetic Effects of ITPK1 Polymorphisms on the Risk of Neural Tube Defects: a Population-Based Study

Inositol is closely related to the occurrence of neural tube defects (NTDs). Inositol 1, 3, 4-trisphosphate 5/6-kinase (ITPK1) gene encoded an essential regulatory enzyme ITPK1, which is involved in inositol metabolism and has a critical role in the development of neural tube and axial mesoderm. It had been reported that some polymorphisms of critical genes in inositol pathways, including ITPK1, were associated with NTDs in Chinese pregnant women; however, the association between fetus ITPK1 polymorphisms and NTDs had not been reported. In a high incidence of NTDs region of China, a case-control study was performed to evaluate the association between fetal ITPK1 polymorphisms and NTDs. The ITPK1 polymorphisms were genotyped by iPLEX® Gold assay. Inositol levels in fetus brain tissues were analyzed. Three genetic polymorphisms of fetus ITPK1's, including rs3818175, rs2295394, and rs4586354, were statistically associated with spina bifida (NTD subtypes). A higher risk of spina bifida was associated with genotype GG of rs3818175, genotype CC of rs4586354, and genotype TT of rs2295394 (OR = 2.66, 95% CI [1.17-6.05], P = 0.017; OR = 2.22, 95% CI [1.02-4.80], P = 0.041; and OR = 2.33, 95% CI [1.00-5.48], P = 0.047), when compared with the other wild-type genotypes CC, TT, and CC, respectively. Decreased brain inositol level was found in NTDs fetuses, compared to normal controls. Inositol levels were found to significantly decrease with rs2295394 (CC genotype), rs4586354 (TT genotype), and rs3818175 (GC genotype) (P < 0.05). The polymorphisms of fetus ITPK1 were associated with the incidence of NTDs and might be a genetic risk factor for spina bifida.

Inositols: From Established Knowledge to Novel Approaches

Myo-inositol (myo-Ins) and D-chiro-inositol (D-chiro-Ins) are natural compounds involved in many biological pathways. Since the discovery of their involvement in endocrine signal transduction, myo-Ins and D-chiro-Ins supplementation has contributed to clinical approaches in ameliorating many gynecological and endocrinological diseases. Currently both myo-Ins and D-chiro-Ins are well-tolerated, effective alternative candidates to the classical insulin sensitizers, and are useful treatments in preventing and treating metabolic and reproductive disorders such as polycystic ovary syndrome (PCOS), gestational diabetes mellitus (GDM), and male fertility disturbances, like sperm abnormalities. Moreover, besides metabolic activity, myo-Ins and D-chiro-Ins deeply influence steroidogenesis, regulating the pools of androgens and estrogens, likely in opposite ways. Given the complexity of inositol-related mechanisms of action, many of their beneficial effects are still under scrutiny. Therefore, continuing research aims to discover new emerging roles and mechanisms that can allow clinicians to tailor inositol therapy and to use it in other medical areas, hitherto unexplored. The present paper outlines the established evidence on inositols and updates on recent research, namely concerning D-chiro-Ins involvement into steroidogenesis. In particular, D-chiro-Ins mediates insulin-induced testosterone biosynthesis from ovarian thecal cells and directly affects synthesis of estrogens by modulating the expression of the aromatase enzyme. Ovaries, as well as other organs and tissues, are characterized by a specific ratio of myo-Ins to D-chiro-Ins, which ensures their healthy state and proper functionality. Altered inositol ratios may account for pathological conditions, causing an imbalance in sex hormones. Such situations usually occur in association with medical conditions, such as PCOS, or as a consequence of some pharmacological treatments. Based on the physiological role of inositols and the pathological implications of altered myo-Ins to D-chiro-Ins ratios, inositol therapy may be designed with two different aims: (1) restoring the inositol physiological ratio; (2) altering the ratio in a controlled way to achieve specific effects.

Myo-Inositol as a Key Supporter of Fertility and Physiological Gestation

Pregnancy is a complex process, featuring several necessary changes in women’s physiology. Most women undergo healthy pregnancies; even so, several women experience reduced fertility or pathologies related to the pregnancy. In the last years, researchers investigated several molecules as promoters of fertility. Among all, myo-inositol (myo-ins) represents a safe compound that proved useful in issues related to fertility and pregnancy. In fact, myo-ins participates in several signaling processes, including the pathways of insulin and gonadotropins, and, therefore, it is likely to positively affect fertility. In particular, several clinical trials demonstrate that its administration can have therapeutic effects in infertile women, and that it can also be useful as a preventive treatment during pregnancy. Particularly, myo-ins could prevent the onset of neural tube defects and the occurrence of gestational diabetes mellitus, promoting a trouble-free gestation. Due to the safety and efficiency of myo-ins, such a treatment may also substitute several pharmaceuticals, which are contraindicated in pregnancy.

Down-Regulation of Inpp5e Associated With Abnormal Ciliogenesis During Embryonic Neurodevelopment Under Inositol Deficiency

The inositol polyphosphate-5-phosphatase E (Inpp5e) gene is located on chromosome 9q34.3. The enzyme it encodes mainly hydrolyzes the 5-phosphate groups of phosphatidylinositol (3,4,5)-trisphosphate (PtdIns (3,4,5) P3) and phosphatidylinositol (4,5)-bisphosphate (PtdIns (4,5)P2), which are closely related to ciliogenesis and embryonic neurodevelopment, through mechanisms that are largely unknown. Here we studied the role of Inpp5e gene in ciliogenesis during embryonic neurodevelopment using inositol-deficiency neural tube defects (NTDs) mouse and cell models. Confocal microscopy and scanning electron microscope were used to examine the number and the length of primary cilia. The dynamic changes of Inpp5e expression in embryonic murine brain tissues were observed during Embryonic Day 10.5-13.5 (E 10.5-13.5). Immunohistochemistry, western blot, polymerase chain reaction (PCR) arrays were applied to detect the expression of Inpp5e and cilia-related genes of the embryonic brain tissues in inositol deficiency NTDs mouse. Real-time quantitative PCR (RT-qPCR) was used to validate the candidate genes in cell models. The levels of inositol and PtdIns(3,4) P2 were measured using gas chromatography-mass spectrometry (GC-MS) and enzyme linked immunosorbent assay (ELISA), respectively. Our results showed that the expression levels of Inpp5e gradually decreased in the forebrain tissues of the control embryos, but no stable trend was observed in the inositol deficiency NTDs embryos. Inpp5e expression in inositol deficiency NTDs embryos was significantly decreased compared with the control tissues. The expression levels of Inpp5e gene and the PtdIns (3,4) P2 levels were also significantly decreased in the inositol deficient cell model. A reduced number and length of primary cilia were observed in NIH3T3 cells when inositol deficient. Three important cilia-related genes (Ift80, Mkks, Smo) were down-regulated significantly in the inositol-deficient NTDs mouse and cell models, and Smo was highly involved in NTDs. In summary, these findings suggested that down-regulation of Inpp5e might be associated with abnormal ciliogenesis during embryonic neurodevelopment, under conditions of inositol deficiency.

Epidemiology and (Patho)Physiology of Folic Acid Supplement Use in Obese Women before and during Pregnancy

Preconception folic acid supplement use is a well-known method of primary prevention of neural tube defects (NTDs). Obese women are at a higher risk for having a child with a NTD. As different international recommendations on folic acid supplement use for obese women before and during pregnancy exist, this narrative review provides an overview of epidemiology of folate deficiency in obese (pre)pregnant women, elaborates on potential mechanisms underlying folate deficiency, and discusses considerations for the usage of higher doses of folic acid supplements. Women with obesity more often suffer from an absolute folate deficiency, as they are less compliant to periconceptional folic acid supplement use recommendations. In addition, their dietary folate intake is limited due to an unbalanced diet (relative malnutrition). The association of obesity and NTDs also seems to be independent of folate intake, with studies suggesting an increased need of folate (relative deficiency) due to derangements involved in other pathways. The relative folate deficiency, as a result of an increased metabolic need for folate in obese women, can be due to: (1) low-grade chronic inflammation (2) insulin resistance, (3) inositol, and (4) dysbiotic gut microbiome, which plays a role in folate production and uptake. In all these pathways, the folate-dependent one-carbon metabolism is involved. In conclusion, scientific evidence of the involvement of several folate-related pathways implies to increase the recommended folic acid supplementation in obese women. However, the physiological uptake of synthetic folic acid is limited and side-effects of unmetabolized folic acid in mothers and offspring, in particular variations in epigenetic (re)programming with long-term health effects, cannot be excluded. Therefore, we emphasize on the urgent need for further research and preconception personalized counseling on folate status, lifestyle, and medical conditions.

Maternal serum zinc concentration and neural tube defects in offspring: a meta-analysis

OBJECTIVE

This study was to assess the relationship between maternal serum zinc concentration and NTDs in offspring by conducting a meta-analysis.

METHODS

We searched Pubmed, Medline and Web of Science for all English studies about the relationship between maternal serum zinc level and NTDs in offspring (published between 1 January 1975 and 1 January 2020). Pooled effect sizes with corresponding 95% CIs were calculated using a random-effect model by Revman 5.3 and Stata 15.1 software.

RESULTS

Eight articles met our selection criteria and a total of 187 cases and 894 controls were included in this meta-analysis. Our results showed that mothers with NTDs infants had lower serum zinc concentration than those with healthy infants (SMD= -0.77, 95%CI [-1.16, -0.37], p = .0001, I ² = 73%).

CONCLUSIONS

Compared with mothers with healthy infants, mothers with NTDs infants have lower serum zinc levels, suggesting that low maternal serum zinc level during pregnancy is probably associated with the risk of NTDs in offspring. But the mechanism of the association remains to be ascertained by large-scale cohort studies.

A review of the role of inositols in conditions of insulin dysregulation and in uncomplicated and pathological pregnancy

Inositols, a group of 6-carbon polyols, are highly bioactive molecules derived from diet and endogenous synthesis. Inositols and their derivatives are involved in glucose and lipid metabolism and participate in insulin-signaling, with perturbations in inositol processing being associated with conditions involving insulin resistance, dysglycemia and dyslipidemia such as polycystic ovary syndrome and diabetes. Pregnancy is similarly characterized by substantial and complex changes in glycemic and lipidomic regulation as part of maternal adaptation and is also associated with physiological alterations in inositol processing. Disruptions in maternal adaptation are postulated to have a critical pathophysiological role in pregnancy complications such as gestational diabetes and pre-eclampsia. Inositol supplementation has shown promise as an intervention for the alleviation of symptoms in conditions of insulin resistance and for gestational diabetes prevention. However, the mechanisms behind these affects are not fully understood. In this review, we explore the role of inositols in conditions of insulin dysregulation and in pregnancy, and identify priority areas for research. We particularly examine the role and function of inositols within the maternal-placental-fetal axis in both uncomplicated and pathological pregnancies. We also discuss how inositols may mediate maternal-placental-fetal cross-talk, and regulate fetal growth and development, and suggest that inositols play a vital role in promoting healthy pregnancy.

An update on the use of inositols in preventing gestational diabetes mellitus (GDM) and neural tube defects (NTDs)

INTRODUCTION

Obstetric history and maternal body composition and lifestyle may be associated with serious complications both for the mother, such as gestational diabetes mellitus (GDM), and for the fetus, including congenital malformations such as neural tube defects (NTDs).

AREAS COVERED

In view of the recent knowledge, changes in nutritional and physical activity habits ameliorate glycemic control during pregnancy and in turn improve maternal and neonatal health outcomes. Recently, a series of small clinical and experimental studies indicated that supplemenation with inositols, a family of insulin sensitizers, was associated with beneficial impact for both GDM and NTDs.

EXPERT OPINION

Herein, we discuss the most significant scientific evidence supporting myo-inositol administration as a prophylaxis for the above-mentioned conditions.

Essential trace elements in umbilical cord tissue and risk for neural tube defects

Deficient or excessive quantities of essential trace elements (ETEs)¹ in the fetal environment can compromise developmental processes. We investigated whether concentrations of zinc (Zn), manganese (Mn), selenium (Se), cobalt (Co), molybdenum (Mo), and nickel (Ni) in umbilical cord tissue are associated with risk for neural tube defects (NTDs). Umbilical cord tissues from 166 cases of NTD cases and 166 matched controls were collected and element concentrations were measured using inductively coupled plasma-mass spectrometry. Associations between ETE concentrations and the risk for NTDs were estimated using multivariate logistic regression while adjusting for potential confounders. Bayesian kernel machine regression (BKMR) was used to examine the joint effects of these ETEs. We found that median concentrations of Ni were higher but those of Mo and Co were lower in the NTD group than in the control group. Co was the only element that was associated with NTD risk after adjusting for confounders (OR 0.31, 95 % CI 0.12-0.79 for the second and OR 0.37, 95 % CI 0.15-0.91 for the top tertile relative to the lowest tertile). The association between Co and NTD risk was confirmed with the BKMR model. In addition, a joint effect of the six ETE mixture on NTD risk was observed: the risk decreased with the levels of the mixture from 25th percentile through 75th percentile. In conclusion, higher levels of Co were associated with lower risk for NTDs, and NTD risk decreased with the levels of the six ETEs as a co-exposure mixture, suggesting a protective effect.

Maternal Inositol Status and Neural Tube Defects: A Role for the Human Yolk Sac in Embryonic Inositol Delivery?

Supplementation with myo-inositol during the periconceptional period of pregnancy may ameliorate the recurrence risk of having a fetus affected by a neural tube defect (NTD; e.g., spina bifida). This could be of particular importance in providing a means for preventing NTDs that are unresponsive to folic acid. This review highlights the characteristics of inositol and describes the role of myo-inositol in the prevention of NTDs in rodent studies and the evidence for its efficacy in reducing NTD risk in human pregnancy. The possible reduction in NTD risk by maternal myo-inositol implies functional and developmentally important maternal-embryonic inositol interrelationships and also suggests that embryonic uptake of myo-inositol is crucial for embryonic development. The establishment of active myo-inositol cellular uptake mechanisms in the embryonic stages of human pregnancy, when the neural tube is closing, is likely to be an important determinant of normal development. We draw attention to the generation of materno-fetal inositol concentration gradients and relationships, and outline a transport pathway by which myo-inositol may be delivered to the early developing human embryo. These considerations provide novel insights into the mechanisms that may underpin inositol's ability to confer embryonic developmental benefit.

Preconception telomere length as a novel maternal biomarker to assess the risk of spina bifida in the offspring

BACKGROUND

Periconception interactions between maternal conditions and environmental and genetic factors are involved in the pathogenesis and prevention of neural tube defects (NTD), such as spina bifida. These factors have in common that they can impair the oxidative pathway, resulting in excessive (chronic) oxidative stress and inflammation.

METHODS

Review of the literature concerning underlying mechanisms and biomarkers of aging particularly during reproduction. A number of molecular markers for biological aging have been identified, including telomere length (TL). Excessive telomere shortening is an index of senescence, causes genomic instability and is associated with a higher risk of age-related diseases. Furthermore, TL shortening is associated with the similar environmental and lifestyle exposures associated with NTD risk.

RESULTS

Embryonic mice deficient in the telomerase gene show shorter TL and failure of closure of the neural tube as the main defect, suggesting that this developmental process is among the most sensitive to telomere loss and chromosomal instability.

CONCLUSIONS

From this background, we hypothesize that preconceptional long term exposure to harmful environmental and lifestyle risk factors accelerates a woman's aging process, which can be measured by TL, and thereby her underlying risk of NTD offspring. Alternatively, it might be that women with an increased NTD risk already exhibit a more advanced biological age before the onset of pregnancy compared to women of identical calendar age.

Mouse Models of Neural Tube Defects

During embryonic development, the central nervous system forms as the neural plate and then rolls into a tube in a complex morphogenetic process known as neurulation. Neural tube defects (NTDs) occur when neurulation fails and are among the most common structural birth defects in humans. The frequency of NTDs varies greatly anywhere from 0.5 to 10 in 1000 live births, depending on the genetic background of the population, as well as a variety of environmental factors. The prognosis varies depending on the size and placement of the lesion and ranges from death to severe or moderate disability, and some NTDs are asymptomatic. This chapter reviews how mouse models have contributed to the elucidation of the genetic, molecular, and cellular basis of neural tube closure, as well as to our understanding of the causes and prevention of this devastating birth defect.

The Effects of Inositol Metabolism in Pregnant Women on Offspring in the North and South of China

Background

Inositol is an essential nutrient for cell growth, survival and embryonic development. Myo-inositol is the predominant form in natural. To investigate the correlation between inositol metabolism and embryonic development, we assessed the metabolic characteristics of myo-inositol, phosphatidylinositol 4,5-bisphosphate (PI(4,5)P₂) and phosphatidylinositol 3,4,5-trisphosphate (PI(3,4,5)P₃) of pregnant women in the North China (Yangquan and Weihai) and South China (Nanchang and Haikou) China.

Material/Methods

All data were collected by face-to-face interview during pregnant women health visits using a questionnaire. Plasma levels of myo-inositol, PI(4,5)P₂ and PI(3,4,5)P₃ from 89 randomly collected pregnant women were detected by gas chromatography-mass spectrometry and enzyme linked immunosorbent assay.

Results

A total of 400 pregnant women were included in this survey. The plasma levels of myo-inositol and PI(4,5)P₂ in the North China group of pregnant women were significantly higher than that in the South China group (P<0.01). The birth weight of fetuses in the North China group was heavier than that in the South China group (P<0.01). The birth length of fetuses in Yangquan was the longest among the 4 cities (P<0.01). The incidence rate of birth defects was 3.05% in the North China group, and 0.0% in the South China group. In bivariate linear correlation analysis, the body weight correlated with myo-inositol (r=0.5044, P<0.0001), PI(4,5)P₂ (r=0.5950, P<0.0001) and PI(3,4,5)P₃ (r=0.4710, P<0.0001), the body length was correlated with PI(4,5)P₂ (r=0.3114, P=0.0035) and PI(3,4,5)P₃ (r=0.2638, P<0.0130).

Conclusions

The plasma levels of myo-inositol and PI(4,5)P₂ in pregnant women had significant difference between the North and the South of China, which might be correlated with fetal development and birth defects.

Zinc deficiency causes neural tube defects through attenuation of p53 ubiquitylation

Micronutrition is essential for neural tube closure, and zinc deficiency is associated with human neural tube defects. Here, we modeled zinc deficiency in mouse embryos, and used live imaging and molecular studies to determine how zinc deficiency affects neural tube closure. Embryos cultured with the zinc chelator TPEN failed to close the neural tube and showed excess apoptosis. TPEN-induced p53 protein stabilization in vivo and in neuroepithelial cell cultures and apoptosis was dependent on p53. Mechanistically, zinc deficiency resulted in disrupted interaction between p53 and the zinc-dependent E3 ubiquitin ligase Mdm2, and greatly reduced p53 ubiquitylation. Overexpression of human CHIP, a zinc-independent E3 ubiquitin ligase that targets p53, relieved TPEN-induced p53 stabilization and reduced apoptosis. Expression of p53 pro-apoptotic target genes was upregulated by zinc deficiency. Correspondingly, embryos cultured with p53 transcriptional activity inhibitor pifithrin-α could overcome TPEN-induced apoptosis and failure of neural tube closure. Our studies indicate that zinc deficiency disrupts neural tube closure through decreased p53 ubiquitylation, increased p53 stabilization and excess apoptosis.

Inositol, neural tube closure and the prevention of neural tube defects

Susceptibility to neural tube defects (NTDs), such as anencephaly and spina bifida is influenced by genetic and environmental factors including maternal nutrition. Maternal periconceptional supplementation with folic acid significantly reduces the risk of an NTD-affected pregnancy, but does not prevent all NTDs, and "folic acid non-responsive" NTDs continue to occur. Similarly, among mouse models of NTDs, some are responsive to folic acid but others are not. Among nutritional factors, inositol deficiency causes cranial NTDs in mice while supplemental inositol prevents spinal and cranial NTDs in the curly tail (Grhl3 hypomorph) mouse, rodent models of hyperglycemia or induced diabetes, and in a folate-deficiency induced NTD model. NTDs also occur in mice lacking expression of certain inositol kinases. Inositol-containing phospholipids (phosphoinositides) and soluble inositol phosphates mediate a range of functions, including intracellular signaling, interaction with cytoskeletal proteins, and regulation of membrane identity in trafficking and cell division. Myo-inositol has been trialed in humans for a range of conditions and appears safe for use in human pregnancy. In pilot studies in Italy and the United Kingdom, women took inositol together with folic acid preconceptionally, after one or more previous NTD-affected pregnancies. In nonrandomized cohorts and a randomized double-blind study in the United Kingdom, no recurrent NTDs were observed among 52 pregnancies reported to date. Larger-scale fully powered trials are needed to determine whether supplementation with inositol and folic acid would more effectively prevent NTDs than folic acid alone. Birth Defects Research 109:68-80, 2017. © 2016 The Authors Birth Defects Research Published by Wiley Periodicals, Inc.

Myoinositol: The Bridge (PONTI) to Reach a Healthy Pregnancy

The use of folic acid in the periconceptional period can prevent about 70% of neural tube defects (NTDs). In the remaining cases, no medical prevention is available, and those conditions should be defined as folate-resistant NTDs. Rodent models suggest that some folate-resistant NTDs can be prevented by inositol (myoinositol and chiroinositol) supplementation prior to pregnancy. Should folic acid be combined with myoinositol periconceptional supplementation to reduce the overall risk of NTDs even in humans? Hereafter, we discuss the results from the PONTI study that strongly support both the effectiveness and safety of myoinositol periconceptional supplementation in preventing human NTDs. We further report on the largest case series of pregnancies treated with myoinositol and folic acid. At our institution, a sequential study during 12 years involved mothers at risk of fetal NTDs, and 29 babies from 27 pregnancies were born after periconceptional combined myoinositol and folic acid supplementation. No case of NTDs was observed, despite the high recurrence risk in the mothers. Taken together, those data suggest that periconceptional folic acid plus myoinositol can reduce both the occurrence and recurrence risks of NTDs in a greater number of cases than folic acid alone.

Quantification of plasma myo-inositol using gas chromatography-mass spectrometry

BACKGROUND

Myo-inositol (MI) deficiency is associated with an increased risk for neural tube defects (NTDs), mental disorders and metabolic diseases. We developed a gas chromatography-mass spectrometry (GC-MS) method to detect MI in human plasma, which was accurate, relatively efficient and convenient for clinical application.

METHODS

An external standard method was used for determination of plasma MI. Samples were analyzed by GC-MS after derivatization. The stable-isotope labeled internal standard approach was used to validate the method's accuracy. Alpha fetal protein (AFP) was detected by chemiluminescence immunoassay.

RESULTS

The method was validated by determining the linearity, sensitivity and recovery rate. There was a good agreement between the internal standard approach and the present method. The NTD-affected pregnancies showed lower plasma MI (P=0.024) and higher AFP levels (P=0.001) than control. Maternal MI level showed a better discrimination in spina bifida subgroup, while AFP level showed a better discrimination in anencephaly subgroup after stratification analysis.

CONCLUSIONS

We developed a sensitive and reliable method for the detection of clinical plasma MI, which might be a marker for NTDs screening, and established fundamental knowledge for clinical diagnosis and prevention for the diseases related to disturbed MI metabolism.

Inositol for the prevention of neural tube defects: a pilot randomised controlled trial

Although peri-conceptional folic acid (FA) supplementation can prevent a proportion of neural tube defects (NTD), there is increasing evidence that many NTD are FA non-responsive. The vitamin-like molecule inositol may offer a novel approach to preventing FA-non-responsive NTD. Inositol prevented NTD in a genetic mouse model, and was well tolerated by women in a small study of NTD recurrence. In the present study, we report the Prevention of Neural Tube Defects by Inositol (PONTI) pilot study designed to gain further experience of inositol usage in human pregnancy as a preliminary trial to a future large-scale controlled trial to evaluate efficacy of inositol in NTD prevention. Study subjects were UK women with a previous NTD pregnancy who planned to become pregnant again. Of 117 women who made contact, ninety-nine proved eligible and forty-seven agreed to be randomised (double-blind) to peri-conceptional supplementation with inositol plus FA or placebo plus FA. In total, thirty-three randomised pregnancies produced one NTD recurrence in the placebo plus FA group (n 19) and no recurrences in the inositol plus FA group (n 14). Of fifty-two women who declined randomisation, the peri-conceptional supplementation regimen and outcomes of twenty-two further pregnancies were documented. Two NTD recurred, both in women who took only FA in their next pregnancy. No adverse pregnancy events were associated with inositol supplementation. The findings of the PONTI pilot study encourage a large-scale controlled trial of inositol for NTD prevention, but indicate the need for a careful study design in view of the unwillingness of many high-risk women to be randomised.

Maternal consumption of non-staple food in the first trimester and risk of neural tube defects in offspring

To study the associations between maternal consumption of non-staple food in the first trimester and risk of neural tube defects (NTDs) in offspring. Data collected from a hospital-based case-control study conducted between 2006 and 2008 in Shandong/Shanxi provinces including 459 mothers with NTDs-affected births and 459 mothers without NTDs-affected births. Logistic regression models were used to examine the associations between maternal consumption of non-staple food in the first trimester and risk of NTDs in offspring. The effects were evaluated by odds ratio (OR) and 95% confidence intervals (95% CIs) with SAS9.1.3.software. Maternal consumption of milk, fresh fruits and nuts in the first trimester were protective factors for total NTDs. Compared with consumption frequency of ˂1 meal/week, the ORs for milk consumption frequency of 1–2, 3–6, ≥7 meals/week were 0.50 (95% CI: 0.28–0.88), 0.56 (0.32–0.99), and 0.59 (0.38–0.90), respectively; the ORs for fresh fruits consumption frequency of 1–2, 3–6, ≥7 meals/week were 0.29 (95% CI: 0.12–0.72), 0.22 (0.09–0.53), and 0.32 (0.14–0.71), respectively; the ORs for nuts consumption frequency of 1–2, 3–6, ≥7 meals/week were 0.60 (95% CI: 0.38–0.94), 0.49 (0.31–0.79), and 0.63 (0.36–1.08), respectively. Different effects of above factors on NTDs were found for subtypes of anencephaly and spina bifida. Maternal non-staple food consumption of milk, fresh fruits and nuts in the first trimester was associated with reducing NTDs risk in offspring.

Increased trophoblast expression of NFAT5/TonEBP in pre-eclamptic placentas and hyperosmolar-treated BeWo cells

OBJECTIVES

To assess the concentrations of inositol and sorbitol, and determine the expression of related osmolyte factors [nuclear factor of activated T cells 5, also known as tonicity responsive binding protein (NFAT5/TonEBP); sodium myo-inositol transporter (SLC5A3); and aldose reductase] in placentas of pre-eclamptic (PE) patients and trophoblast BeWo cells subjected to hypertonic stress in vitro.

STUDY DESIGN

Control and PE placentas were collected. BeWo cells were cultured and subjected to a hyperosmolar solution for 4h. Western blot analysis was performed on NFAT5, SLC5A3, aldose reductase and ERK proteins. High-performance liquid chromatography was used to determine the levels of inositol and sorbitol in cell lysates.

RESULTS

Compared with control placentas, PE placentas showed higher levels of inositol and NFAT5, and lower levels of SLC5A3. Treated BeWo cells showed higher levels of inositol, sorbitol, NFAT5 total protein, SLC5A3 and aldose reductase, and increased ERK activation compared with control BeWo cells.

CONCLUSIONS

Hyperosmolar conditions increase the expression of NFAT5 in PE placentas and BeWo cells, and may account for the increased osmolyte levels. NFAT5 may accomplish this through aldose reductase and SLC5A3 in trophoblast cells.

Genetic variations in the GLUT3 gene associated with myelomeningocele

OBJECTIVE

Our objectives were to examine the extent of described sequence variation in the glucose transporter 3 (GLUT3) gene in children with myelomeningocele (MM), identify novel variations in the GLUT3 gene in these children, and determine whether these variations may confer a risk of MM.

STUDY DESIGN

We sequenced the 10 exons of GLUT3, including exon-intron boundaries, on 96 children with MM. Sequencing was performed with Sanger methods and results analyzed with deoxyribonucleic acid analysis software. Frequencies of known single-nucleotide polymorphisms were identified, and those differing from the reference sequence (GRCh37/hg19 assembly) were considered variations.

RESULTS

Six novel and 9 previously described, genetic variations were identified in our population. The novel variations included a large, 83 base pair deletion involving the core promoter region and part of exon 1 (1 of 96 children), and a 2 base pair deletion in the coding sequence of exon 4 (1 of 96 children). The remaining novel variations were located in the introns in the proximity of the splice sites. Novel mutations in GLUT3 were observed among 6.25% of our population. Additionally, the frequency of the rare allele for rs17847972 located in a splice donor site is higher (P < .001) in MM in our population than expected.

CONCLUSION

We identified previously undescribed deletions and single-nucleotide variations involving the GLUT3 gene that may be associated with increased susceptibility to MM. Of particular interest, the 2 deletions involve both an important core promoter site and a coding region predicted to have a deleterious effect. The functional significance of these findings is under investigation.

Myoinositol: a new marker of intrauterine growth restriction?

Inositol is a cyclic sugar alcohol which occurs naturally in a variety of stereoisomers, the most common of which is myo-inositol. Inositol phosphoglycan molecules have been isolated from mammalian tissues and are a major component of the intracellular mediators of insulin action. The fetus with intrauterine growth retardation (IUGR) activates a series of adaptive mechanisms to increase the chances for survival, such as a saving of glucose to ensure nutrition of the vital organs, with a consequent reduction in insulin secretion. It can be hypothesized that the reduced production of fetal insulin leads to an excretion of inositol from the intracellular to the extracellular compartment, with a consequent increase of the metabolite in plasma and urine and a decrease inside the cells. Recently, reports suggesting that the increase in extracellular myo-inositol may be a valid marker of an altered glucose metabolism during fetal development in IUGR have been published.

Changes in fetal mannose and other carbohydrates induced by a maternal insulin infusion in pregnant sheep

BACKGROUND

The importance of non-glucose carbohydrates, especially mannose and inositol, for normal development is increasingly recognized. Whether pregnancies complicated by abnormal glucose transfer to the fetus also affect the regulation of non-glucose carbohydrates is unknown. In pregnant sheep, maternal insulin infusions were used to reduce glucose supply to the fetus for both short (2-wk) and long (8-wk) durations to test the hypothesis that a maternal insulin infusion would suppress fetal mannose and inositol concentrations. We also used direct fetal insulin infusions (1-wk hyperinsulinemic-isoglycemic clamp) to determine the relative importance of fetal glucose and insulin for regulating non-glucose carbohydrates.

RESULTS

A maternal insulin infusion resulted in lower maternal (50%, P < 0.01) and fetal (35-45%, P < 0.01) mannose concentrations, which were highly correlated (r(2) = 0.69, P < 0.01). A fetal insulin infusion resulted in a 50% reduction of fetal mannose (P < 0.05). Neither maternal nor fetal plasma inositol changed with exogenous insulin infusions. Additionally, maternal insulin infusion resulted in lower fetal sorbitol and fructose (P < 0.01).

CONCLUSIONS

Chronically decreased glucose supply to the fetus as well as fetal hyperinsulinemia both reduce fetal non-glucose carbohydrates. Given the role of these carbohydrates in protein glycosylation and lipid production, more research on their metabolism in pregnancies complicated by abnormal glucose metabolism is clearly warranted.

The maternal ITPK1 gene polymorphism is associated with neural tube defects in a high-risk Chinese population

Background

Epidemiological surveys and animal studies have revealed that inositol metabolism is associated with NTDs, but the mechanisms are not clear. Inositol 1,3,4-trisphosphate 5/6-kinase (ITPK1) is a pivotal regulatory enzyme in inositol metabolic pathway. The objective was to assess the potential impact of the maternal ITPK1 genotypes on the inositol parameter and on the NTD risk in a NTD high-risk area in China.

Methodology/Results

A case-control study of pregnant women affected with NTDs (n = 200) and controls (n = 320) was carried out. 13 tag SNPs of ITPK1 were selected and genotyped by the Sequenom MassArray system. We found that 4 tag SNPs were statistically significant in spina bifida group (P<0.05). MACH was used to impute the un-genotyped SNPs in ITPK1 locus and showed that 3 meaningful SNPs in the non-coding regions were significant. We also predicted the binding capacity of transcription factors in the positive SNPs using the bioinformatics method and found that only rs3783903 was located in the conserved sequence of activator protein-1 (AP-1). To further study the association between biochemical values and genotypes, maternal plasma inositol hexakisphosphate (IP₆) levels were also assessed using LC-MS. The maternal plasma IP₆ concentrations in the spina bifida subgroup were 7.1% lower than control (136.67 vs. 147.05 ng mL⁻¹, P<0.05), and significantly lower in rs3783903 GG genotype than others (P<0.05). EMSA showed a different allelic binding capacity of AP-1 in rs3783903, which was affected by an A→G exchange. The RT-PCR suggested the ITPK1 expression was decreased significantly in mutant-type of rs3783903 compared with wild-type in the 60 healthy pregnancies (P<0.05).

Conclusions/Significance

These results suggested that the maternal rs3783903 of ITPK1 might be associated with spina bifida, and the allele G of rs3783903 might affect the binding of AP-1 and the decrease of maternal plasma IP₆ concentration in this Chinese population.

Epigenetic profiles in children with a neural tube defect; a case-control study in two populations

Folate deficiency is implicated in the causation of neural tube defects (NTDs). The preventive effect of periconceptional folic acid supplement use is partially explained by the treatment of a deranged folate-dependent one carbon metabolism, which provides methyl groups for DNA-methylation as an epigenetic mechanism. Here, we hypothesize that variations in DNA-methylation of genes implicated in the development of NTDs and embryonic growth are part of the underlying mechanism. In 48 children with a neural tube defect and 62 controls from a Dutch case-control study and 34 children with a neural tube defect and 78 controls from a Texan case-control study, we measured the DNA-methylation levels of imprinted candidate genes (IGF2-DMR, H19, KCNQ1OT1) and non-imprinted genes (the LEKR/CCNL gene region associated with birth weight, and MTHFR and VANGL1 associated with NTD). We used the MassARRAY EpiTYPER assay from Sequenom for the assessment of DNA-methylation. Linear mixed model analysis was used to estimate associations between DNA-methylation levels of the genes and a neural tube defect. In the Dutch study group, but not in the Texan study group we found a significant association between the risk of having an NTD and DNA methylation levels of MTHFR (absolute decrease in methylation of -0.33% in cases, P-value = 0.001), and LEKR/CCNL (absolute increase in methylation: 1.36% in cases, P-value = 0.048), and a borderline significant association for VANGL (absolute increase in methylation: 0.17% in cases, P-value = 0.063). Only the association between MTHFR and NTD-risk remained significant after multiple testing correction. The associations in the Dutch study were not replicated in the Texan study. We conclude that the associations between NTDs and the methylation of the MTHFR gene, and maybe VANGL and LEKKR/CNNL, are in line with previous studies showing polymorphisms in the same genes in association with NTDs and embryonic development, respectively.

Mouse as a model for multifactorial inheritance of neural tube defects

Neural tube defects (NTDs) such as spina bifida and anencephaly are some of the most common structural birth defects found in humans. These defects occur due to failures of neurulation, a process where the flat neural plate rolls into a tube. In spite of their prevalence, the causes of NTDs are poorly understood. The multifactorial threshold model best describes the pattern of inheritance of NTDs where multiple undefined gene variants interact with environmental factors to cause an NTD. To date, mouse models have implicated a multitude of genes as required for neurulation, providing a mechanistic understanding of the cellular and molecular pathways that control neurulation. However, the majority of these mouse models exhibit NTDs with a Mendelian pattern of inheritance. Still, many examples of multifactorial inheritance have been demonstrated in mouse models of NTDs. These include null and hypomorphic alleles of neurulation genes that interact in a complex fashion with other genetic mutations or environmental factors to cause NTDs. These models have implicated several genes and pathways for testing as candidates for the genetic basis of NTDs in humans, resulting in identification of putative pathogenic mutations in some patients. Mouse models also provide an experimental paradigm to gain a mechanistic understanding of the environmental factors that influence NTD occurrence, such as folic acid and maternal diabetes, and have led to the discovery of additional preventative nutritional supplements such as inositol. This review provides examples of how multifactorial inheritance of NTDs can be modeled in the mouse.

Transcriptome profiling of genes involved in neural tube closure during human embryonic development using long serial analysis of gene expression (long-SAGE)

BACKGROUND

Neural tube defects (NTDs) are common human birth defects with a complex etiology. To develop a comprehensive knowledge of the genes expressed during normal neurulation, we established transcriptomes from human neural tube fragments during and after neurulation using long Serial Analysis of Gene Expression (long-SAGE).

METHODS

Rostral and caudal neural tubes were dissected from normal human embryos aged between 26 and 32 days of gestation. Tissues from the same region and Carnegie stage were pooled (n ≥ 4) and total RNA extracted to construct four long-SAGE libraries. Tags were mapped using the UniGene Homo sapiens 17 bp tag-to-gene best mapping set. Differentially expressed genes were identified by chi-square or Fisher's exact test, and validation was performed for a subset of those transcripts using in situ hybridization. In silico analyses were performed with BinGO and EXPANDER.

RESULTS

We observed most genes to be similarly regulated in rostral and caudal regions, but expression profiles differed during and after closure. In silico analysis found similar enrichments in both regions for biologic process terms, transcription factor binding and miRNA target motifs. Twelve genes potentially expressing alternate isoforms by region or developmental stage, and the microRNAs miR-339-5p, miR-141/200a, miR-23ab, and miR-129/129-5p are among several potential candidates identified here for future research.

CONCLUSIONS

Time appears to influence gene expression in the developing central nervous system more than location. These data provide a novel complement to traditional strategies of identifying genes associated with human NTDs and offer unique insight into the genes associated with normal human neurulation.

Transplacental supply of mannose and inositol in uncomplicated pregnancies using stable isotopes

OBJECTIVE

The aim of this study was to determine relative contributions of transplacental flux vs. fetal production for inositol and mannose in normal term pregnancies.

STUDY DESIGN

Seven term uncomplicated pregnancies undergoing cesarean section were infused with (13)C- and (2)H-labeled isotopes of glucose, inositol, and mannose until a steady state was achieved. Maternal and fetal concentrations of labeled and unlabeled glucose, mannose, and inositol were measured using gas chromatography/mass spectroscopy. The fetomaternal molar percentage excess ratio was calculated for each glucose, mannose, and inositol.

RESULTS

The fetomaternal molar percentage excess ratio of mannose in the fetal artery (F(artery)/M) was 0.99 [97.5% confidence interval (CI), 0.91-1.07] and in the fetal vein (F(vein)/M), 1.02 (97.5% CI, 0.95-1.10). Both were not significantly different from 1.0, consistent with transplacental supply. The fetomaternal ratios for glucose were similar to mannose (fetal artery, 0.95; 97.5% CI, 0.84-1.15; and fetal vein, 0.96; 97.5% CI, 0.85-1.07). The fetomaternal ratio for inositol was significantly less than 1.0 (fetal artery, 0.08; 97.5% CI, 0.05-0.12; fetal vein, 0.12; 97.5% CI, 0.06-0.18), indicating little transplacental flux and significant fetal production.

CONCLUSION

In normal term pregnancies, fetal mannose and glucose concentrations are dependent upon maternal transplacental supply. Fetal inositol is not dependent upon transplacental supply.

Neural tube defects--disorders of neurulation and related embryonic processes

Neural tube defects (NTDs) are severe congenital malformations affecting 1 in every 1000 pregnancies. 'Open' NTDs result from failure of primary neurulation as seen in anencephaly, myelomeningocele (open spina bifida), and craniorachischisis. Degeneration of the persistently open neural tube in utero leads to loss of neurological function below the lesion level. 'Closed' NTDs are skin-covered disorders of spinal cord structure, ranging from asymptomatic spina bifida occulta to severe spinal cord tethering, and usually traceable to disruption of secondary neurulation. 'Herniation' NTDs are those in which meninges, with or without brain or spinal cord tissue, become exteriorized through a pathological opening in the skull or vertebral column (e.g., encephalocele and meningocele). NTDs have multifactorial etiology, with genes and environmental factors interacting to determine individual risk of malformation. While over 200 mutant genes cause open NTDs in mice, much less is known about the genetic causation of human NTDs. Recent evidence has implicated genes of the planar cell polarity signaling pathway in a proportion of cases. The embryonic development of NTDs is complex, with diverse cellular and molecular mechanisms operating at different levels of the body axis. Molecular regulatory events include the bone morphogenetic protein and Sonic hedgehog pathways which have been implicated in control of neural plate bending. Primary prevention of NTDs has been implemented clinically following the demonstration that folic acid (FA), when taken as a periconceptional supplement, can prevent many cases. Not all NTDs respond to FA, however, and adjunct therapies are required for prevention of this FA-resistant category.

Placental TonEBP/NFAT5 osmolyte regulation in an ovine model of intrauterine growth restriction

TonEBP/NFAT5 (the tonicity-responsive enhancer binding protein/nuclear factor of activated T cells) modulates cellular response to osmotic changes by accumulating inositol and sorbitol inside the cells. Our objective was to assess placental osmolytes, TonEBP/NFAT5 RNA and protein expression, and signaling molecules across gestation between control and intrauterine growth restriction (IUGR) ovine pregnancies. Pregnant sheep were placed in hyperthermic conditions to induce IUGR. Placental tissues were collected at 55, 95, and 130 days gestational age (dGA) to measure inositol, sorbitol, TonEBP/NFAT5 (NFAT5), sodium-dependent myo-inositol transporter (SMIT; official symbol SLC5A3), aldose reductase (AR), and NADPH (official symbol DE-CR1). Placental weight was reduced in IUGR compared to controls at 95 and 130 dGA. Osmolyte concentrations were similar between control and IUGR placentas, but both groups demonstrated a significant decrease in inositol concentration and an increase in sorbitol concentration with advancing gestation. Cytosolic NFAT5 protein decreased significantly from 55 to 95 dGA in both groups, and nuclear NFAT5 protein increased only at 130 dGA in the IUGR group, but no differences were seen between groups for either cytosolic or nuclear NFAT5 protein concentrations. DE-CR1 concentrations were similar between groups and increased significantly with advancing gestational age. AR was lowest at 55dGA, and SLC5A3 increased with advancing gestational age. We conclude that both placental osmolytes inositol and sorbitol (and their corresponding proteins SLC5A3 and AR) change with gestational age and are regulated, at least in part, by NFAT5 and DE-CR1 (NADPH). The inverse relationship between each osmolyte across gestation (e.g., inositol higher in early gestation and sorbitol higher in late gestation) may reflect nutritional needs that change across gestation.

Major congenital malformations in women with gestational diabetes mellitus: a systematic review and meta-analysis

BACKGROUND

The risk of major congenital malformations (MCM) is increased in women with pregestational diabetes mellitus (PGDM). Whether this risk is increased in gestational diabetes mellitus (GDM) is still debated. The aim of this study was to perform a systematic review (and meta-analysis) of major congenital malformations in women with gestational diabetes versus a reference population.

METHODS

We conducted a MEDLINE search (1 January 1995 to 31 December 2009) of original studies reporting data on major congenital malformations in women with gestational diabetes and a reference group. Information on pregestational diabetes was collected when available. Two investigators considered studies for inclusion and extracted data; discrepancies were solved by consensus. Meta-analysis tools were used to summarize results. MOOSE and PRISMA guidelines were followed.

RESULTS

Two case control and 15 cohort studies were selected out of 3488 retrieved abstracts. A higher risk of major congenital malformations was observed in offspring of women with gestational diabetes with the following relative risk (RR)/odds ratios (OR) and 95% confidence intervals (CI): RR 1.16 (1.07-1.25) in cohort studies and OR 1.4 (1.22-1.62) in case control studies. Risk of major congenital malformations was much higher in offspring of women with PGDM than in those of the reference group: RR 2.66 (2.04-3.47) in cohort studies and OR 4.7 (3.01-6.95) in the single case control study providing information.

CONCLUSION

There is a slightly higher risk of major congenital malformations in women with gestational diabetes than in the reference group. The contribution of women with overt hyperglycemia and other factors could not be ascertained. This risk, however, is much lower than in women with pregestational diabetes.

Genetic basis of susceptibility to teratogen induced birth defects

Birth defects remain the leading cause of infant death in US. The field of teratology has been focused on the causes and underlying mechanisms of birth defects for decades, yet our understanding of these critical issues remain unacceptably vague. Conclusions from years of animal and human studies made it clear that the vast majority of birth defects have multifactorial origins, with contributions from environmental and genetic factors. The environment comprises not only of the physical, biological, and chemical external environment surrounding the pregnant woman, but it also includes the internal environment of the woman's body that interact with the developing embryo in a complex fashion. The importance of maternal and embryonic genetic factors consisting of countless genetic variants/mutations that exist within every individual contribute to birth defect susceptibility is only now being more fully appreciated. This great complexity of the genome and its diversity within individuals and populations seems to be the principal reason why the same teratogenic exposure can induce severe malformation in one embryo, while fail to do so to other exposed embryos. As the interaction between genetic and environmental factors has long been recognized as the first "Principle of Teratology" by Wilson and Warkany [1965. Teratology: Principles and techniques. Chicago: University of Chicago Press], it is only recently that the appropriate investigative tools have been developed with which to fully investigate this fundamental principle. The introduction of high throughput technologies like whole genome sequencing or genome-wide association studies are promising to deliver an enormous amount of new data that will shed light on the genomic factors that contribute susceptibility to environmental teratogens. In this review, we attempt to summarize the epidemiological and experimental literature concerning birth defects whose phenotypic expression can be clearly related to the interactions between several select environmental factors and those genetic pathways in which they are most likely to have significant modifying effects. © 2011 Wiley-Liss, Inc.

Periconceptional nutrient intakes and risks of neural tube defects in California

BACKGROUND

This study investigated the association of neural tube defects (NTDs) with maternal periconceptional intake of folic acid-containing supplements and dietary nutrients, including folate, among deliveries that occurred after folic acid fortification in selected California counties.

METHODS

The population-based case-control study included fetuses and live born infants with spina bifida (189) or anencephaly (141) and 625 nonmalformed, live born controls delivered from 1999 to 2003. Mothers reported supplement use during telephone interviews, which included a 107-item food frequency questionnaire. For dietary nutrients, intakes <25th, 25th to <75th (reference), and > or =75th percentile were compared, based on control distributions.

RESULTS

After adjustment for potential confounders, any versus no supplement intake resulted in ORs of 0.8 (95% CI, 0.5-1.3) for anencephaly and 0.8 (95% CI, 0.6-1.2) for spina bifida. After stratification by maternal intake of vitamin supplements, most factors in the glycemic pathway were not associated with either NTD, with the exception of low levels of fructose and glucose that were significantly associated with anencephaly. Some nutrients that contribute to one-carbon metabolism showed lowered risks (folate, riboflavin, vitamins B(6) and B(12)); others did not (choline, methionine, zinc). Antioxidant nutrients tended to be associated with lowered risks (vitamins C, E, A, beta-carotene, lutein).

CONCLUSIONS

Mothers' intake of vitamin supplements was modestly if at all associated with a lowered risk of NTDs. Dietary intake of several nutrients contributing to one-carbon metabolism and oxidative stress were associated with reduced NTD risk.

A 10 bp deletion polymorphism and 2 new variations in the GLUT1 gene associated with meningomyelocele

We sought to examine the diversity and extent of sequence variations in GLUT1 in patients with myelomeningocele (MM) and to identify variations conferring risk of MM. Sequences of the 10 exons and exon-intron boundaries of GLUT1 for 96 patients with MM (48 Caucasians and 48 Mexican Americans) were determined by direct sequencing of DNA. Two new variants were identified. One is located within intron 7 (c.972+17t>a), 17 bases from exon 7. The other is within exon 8 (c.1016T>C) and results in an amino acid change at isoleucine 339 (p.Ile339Thr). A 10 base pair (bp) deletion within intron 9 was genotyped for 457 patients with MM and showed it to be more common in Caucasian MM patients than in Caucasian controls (P = .02). The physiologic role of the 2 newly identified variants in the GLUT1 gene and the 10 bp deletion associated with risk of MM in Caucasian patients is under investigation.

The role of inositol and the principles of labelling, extraction, and analysis of inositides in mammalian cells

Inositides have an important impact on diverse areas of cellular regulation. However, since this area has grown exponentially from the mid 1980s onwards, many workers find themselves relatively new to the field. In this chapter, we establish a broad foundation for the rest of the book by covering some important principles of inositide methodologies. The focus is especially directed to those methods or aspects of methodology not covered in detail in other chapters. This includes the often neglected influence of the inositide precursor, inositol, and important background information relating to the labelling and extraction of inositides from cells and tissues. This introductory section also gives a "birds eye" view of important methods and protocols found within this volume and hopefully acts as a touchstone to assess which of the methodologies described within this book is most appropriate for your particular study(ies) of inositides.

Genetics and development of neural tube defects

Congenital defects of neural tube closure (neural tube defects; NTDs) are among the commonest and most severe disorders of the fetus and newborn. Disturbance of any of the sequential events of embryonic neurulation produce NTDs, with the phenotype (eg anencephaly, spina bifida) varying depending on the region of neural tube that remains open. While mutation of > 200 genes is known to cause NTDs in mice, the pattern of occurrence in humans suggests a multifactorial polygenic or oligogenic aetiology. This emphasizes the importance of gene-gene and gene-environment interactions in the origins of these defects. A number of cell biological functions are essential for neural tube closure, with defects of the cytoskeleton, cell cycle and molecular regulation of cell viability prominent among the mouse NTD mutants. Many transcriptional regulators and proteins that affect chromatin structure are also required for neural tube closure, although the downstream molecular pathways regulated by these proteins is unknown. Some key signalling pathways for NTDs have been identified: over-activation of sonic hedgehog signalling and loss of function in the planar cell polarity (non-canonical Wnt) pathway are potent causes of NTD, with requirements also for retinoid and inositol signalling. Folic acid supplementation is an effective method for primary prevention of a proportion of NTDs in both humans and mice, although the embryonic mechanism of folate action remains unclear. Folic acid-resistant cases can be prevented by inositol supplementation in mice, raising the possibility that this could lead to an additional preventive strategy for human NTDs in future.

Interaction of PDGFRA promoter haplotypes and maternal environmental exposures in the risk of spina bifida

BACKGROUND

Neural tube defects are multifactorial malformations involving both environmental exposures, such as maternal nutrition, and genetic factors. Aberrant expression of the platelet-derived growth factor alpha-receptor (PDGFRA) gene has been implicated in neural-tube-defect etiology in both mice and humans.

METHODS

We investigated possible interactions between the PDGFRA promoter haplotype of mother and child, as well as maternal glucose, myo-inositol, and zinc levels, in relation to spina bifida offspring. Distributions were determined of the PDGFRA promoter haplotypes H1 and H2 in a Dutch cohort, consisting of 88 spina bifida children with 56 of their mothers, and 74 control children with 72 of their mothers, as well as maternal plasma glucose, myo-inositol, and red blood cell zinc concentrations.

RESULTS

A significantly higher frequency of H1 was observed in children with spina bifida than in controls (30.1 vs. 20.3%; OR = 1.69, 95% CI 1.02-2.83). High maternal body mass index (BMI) and glucose were significant risk factors for both H1 and H2 children, whereas low myo-inositol and zinc were risk factors for H2 but not for H1 children. Stepwise multiple logistic regression analysis showed that high maternal glucose and low myo-inositol are the main risk factors for H2 spina bifida children, whereas for H1 spina bifida children, maternal BMI was the main risk factor. Interestingly, H1 mothers (median 165.5 cm) showed a significantly lower body height than H2 mothers (median 169.1 cm; p = 0.003).

CONCLUSIONS

These data suggest that the child's PDGFRA promoter haplotype is differentially sensitive for periconceptional exposure to glucose, myo-inositol, and zinc in the risk of spina bifida.

Inositol and mannose utilization rates in term and late-preterm infants exceed nutritional intakes

Nonglucose carbohydrates such as mannose and inositol are important in early growth and development, although little is known about their metabolism. Our aim in this study was to determine the plasma appearance rates (Ra) for mannose and inositol in newborns as an index of utilization and as an improved guide to supplementation practices. We studied late-preterm (n = 9) and term (n = 5) infants (median 34 wk gestation, range 33-41 wk) using a multiple isotope infusion start time protocol to determine Ra for each carbohydrate. The plasma mannose concentration [median (range)] was 69.83 (48.60-111.75) micromol/L and the Ra was 0.59 (0.42-0.98) micromol x kg(-1) x min(-1) (854 micromol x kg(-1) x d(-1)). The plasma inositol concentration was 175.74 (59.71-300.60) micromol/L and Ra was 1.06 (0.33-1.75) micromol x kg(-1).min(-1) (1521 micromol x kg(-1) x d(-1)). The Ra for mannose and inositol are >10-fold higher than the amounts a breast-fed infant typically ingests, which are approximately 6 micromol x kg(-1) x d(-1) mannose and 150 micromol x kg(-1) x d(-1) inositol. Thus, for both mannose and inositol, the newborn infant must produce these compounds from glucose at rates sufficient to meet nutritional requirements.

Importance of gene-environment interactions in the etiology of selected birth defects

It is generally understood that both genetic and environmental factors contribute to the highly complex etiology of structural birth defects, including neural tube defects, oral clefts and congenital heart defects, by disrupting highly regulated embryonic developmental processes. The intrauterine environment of the developing embryo/fetus is determined by maternal factors such as health/disease status, lifestyle, medication, exposure to environmental teratogens, as well as the maternal genotype. Certain genetic characteristics of the embryo/fetus also predispose it to developmental abnormalities. Epidemiologic and animal studies conducted over the last few decades have suggested that the interplay between genes and environmental factors underlies the etiological heterogeneity of these defects. It is now widely believed that the study of gene-environment interactions will lead to better understanding of the biological mechanisms and pathological processes that contribute to the development of complex birth defects. It is only through such an understanding that more efficient measures will be developed to prevent these severe, costly and often deadly defects. In this review, we attempt to summarize the complex clinical and experimental literature on current hypotheses of interactions between several select environmental factors and those genetic pathways in which they are most likely to have significant modifying effects. These include maternal folate nutritional status, maternal diabetes/obesity-related conditions, and maternal exposure to selected medications and environmental contaminants. Our goal is to highlight the potential gene-environment interactions affecting early embryogenesis that deserve comprehensive study.

Risk factors for oral clefts: a population-based case-control study in Shenyang, China

Shenyang in Northern China has one of the highest reported prevalence rates of oral clefts in the world. To explore the risk factors for oral clefts in Shenyang, we carried out a population-based case-control study. A total of 360 990 births in 2000 to 2007 were screened for oral clefts; the overall prevalence was 1.76 per 1000. The ratio of cleft lip with or without cleft palate (CL +/- P) : cleft palate only (CP) was 5.60:1. The overall male : female ratio was 2.02:1. CLP and CL were more common in males than in females with a sex ratio (SR) of 2.88:1 and 1.86:1 respectively, whereas CP was more common in females with an SR of 0.71:1. Using a multivariable conditional logistic regression model, 586 oral clefts cases were compared with 1172 control mothers. Maternal factors significantly associated with increased risk for oral clefts were history of a fever or cold (adjusted OR 2.34, 95% CI 1.06, 5.60); use of analgesic and antipyretic drugs (adjusted OR 3.10, 95% CI 1.41, 6.86); poor ventilation during heating (adjusted OR 2.25, 95% CI 1.10, 4.60); and consumption of pickled vegetables >6 per week (adjusted OR 3.86, 95% CI 1.11, 13.47) during pregnancy. Factors which appeared to be protective were meat consumption >or=4 times per week (adjusted OR 0.43, 95% CI 0.28, 0.67); and legume consumption >6 times per week (adjusted OR 0.60, 95% CI 0.41, 0.89). Differences in risk were found between the two most common phenotypes, CL +/- P and CP only. Most of the environmental factors had stronger associations with risk for CL +/- P rather than CP, whereas history of oral clefts, as well as legume consumption, were more strongly associated with the risk for CP than for CL +/- P. The findings suggest that aetiological heterogeneity may exist between CL +/- P and CP.