Do multivitamin or folic acid supplements reduce the risk for congenital heart defects? Evidence and gaps

Understanding the Genetic and Non-genetic Interconnections in the Aetiology of Isolated Congenital Heart Disease: An Updated Review: Part 1

PURPOSE OF REVIEW

Congenital heart disease (CHD) is the most frequently occurring birth defect. Majority of the earlier reviews focussed on the association of genetic factors with CHD. A few epidemiological studies provide convincing evidence for environmental factors in the causation of CHD. Although the multifactorial theory of gene-environment interaction is the prevailing explanation, explicit understanding of the biological mechanism(s) involved, remains obscure. Nonetheless, integration of all the information into one platform would enable us to better understand the collective risk implicated in CHD development.

RECENT FINDINGS

Great strides in novel genomic technologies namely, massive parallel sequencing, whole exome sequencing, multiomics studies supported by system-biology have greatly improved our understanding of the aetiology of CHD. Molecular genetic studies reveal that cardiac specific gene variants in transcription factors or signalling molecules, or structural proteins could cause CHD. Additionally, non-hereditary contributors such as exposure to teratogens, maternal nutrition, parental age and lifestyle factors also contribute to induce CHD. Moreover, DNA methylation and non-coding RNA are also correlated with CHD. Here, we inform that a complex combination of genetic, environmental and epigenetic factors interact to interfere with morphogenetic processes of cardiac development leading to CHD. It is important, not only to identify individual genetic and non-inherited risk factors but also to recognize which factors interact mutually, causing cardiac defects.

Gestational palmitic acid suppresses embryonic GATA-binding protein 4 signaling and causes congenital heart disease

Dysregulated maternal fatty acid metabolism increases the risk of congenital heart disease (CHD) in offspring with an unknown mechanism, and the effect of folic acid fortification in preventing CHD is controversial. Using gas chromatography coupled to either a flame ionization detector or mass spectrometer (GC-FID/MS) analysis, we find that the palmitic acid (PA) concentration increases significantly in serum samples of pregnant women bearing children with CHD. Feeding pregnant mice with PA increased CHD risk in offspring and cannot be rescued by folic acid supplementation. We further find that PA promotes methionyl-tRNA synthetase (MARS) expression and protein lysine homocysteinylation (K-Hcy) of GATA4 and results in GATA4 inhibition and abnormal heart development. Targeting K-Hcy modification by either genetic ablation of Mars or using N-acetyl-L-cysteine (NAC) decreases CHD onset in high-PA-diet-fed mice. In summary, our work links maternal malnutrition and MARS/K-Hcy with the onset of CHD and provides a potential strategy in preventing CHD by targeting K-Hcy other than folic acid supplementation.

Multivitamin intake and the risk of congenital heart defects: A cohort study

OBJECTIVE

Congenital heart disease (CHD) is the most common type of congenital birth defect, but little is known about possible modifiable behavioral risk factors. The study aimed to assess whether intake of periconceptional or postconceptional multivitamin was associated with a decreased risk of CHD in the offspring.

STUDY DESIGN

The study population comprised 15,567 women from the Copenhagen Pregnancy Cohort with complete data on multivitamin intake before and during pregnancy, who gave birth to live-born singletons from October 2012 to October 2016. Main outcome measure was CHD defined according to the International Classification of Diseases (ICD), 10th revision. Cases of CHD were classified into five subgroups based on the clinical phenotype: 1) Conotruncal defects, 2) Left ventricular outflow tract obstruction, 3) Right ventricular outflow tract obstruction, 4) Septal defects, and 5) Other CHD. Multivariate logistic regression analyses were performed with adjustment for maternal age, chronic disease, assisted reproductive technology, smoking status, and alcohol consumption.

RESULTS

Of the 15,567 included women, 31.9 % reported a daily multivitamin intake in the periconceptional period, 53.7 % in the postconceptional period, and 14.4 % women did not report a daily multivitamin intake. The prevalence of CHD in the population was 0.7 % (n = 112). Periconceptional and postconceptional multivitamin intake was not associated with risk of overall CHD in offspring: Adjusted OR was 0.64 (95 % CI 0.36-1.13) and 0.77 (95 % CI 0.47-1.30), respectively.

CONCLUSION

The current large cohort study did not show a preventive effect of multivitamin intake in the periconceptional or postconceptional period on the risk of CHD in the offspring.

Gestational Leucylation Suppresses Embryonic T-Box Transcription Factor 5 Signal and Causes Congenital Heart Disease

Dysregulated maternal nutrition, such as vitamin deficiencies and excessive levels of glucose and fatty acids, increases the risk for congenital heart disease (CHD) in the offspring. However, the association between maternal amino-acid levels and CHD is unclear. Here, it is shown that increased leucine levels in maternal plasma during the first trimester are associated with elevated CHD risk in the offspring. High levels of maternal leucine increase embryonic lysine-leucylation (K-Leu), which is catalyzed by leucyl-tRNA synthetase (LARS). LARS preferentially binds to and catalyzes K-Leu modification of lysine 339 within T-box transcription factor TBX5, whereas SIRT3 removes K-Leu from TBX5. Reversible leucylation retains TBX5 in the cytoplasm and inhibits its transcriptional activity. Increasing embryonic K-Leu levels in high-leucine-diet fed or Sirt3 knockout mice causes CHD in the offspring. Targeting K-Leu using the leucine analogue leucinol can inhibit LARS activity, reverse TBX5 K-Leu modification, and decrease the occurrence of CHD in high-leucine-diet fed mice. This study reveals that increased maternal leucine levels increases CHD risk in the offspring through inhibition of embryonic TBX5 signaling, indicating that leucylation exerts teratogenic effects during heart development and may be an intervening target of CHD.

Deleterious Rare Mutations of GLI1 Dysregulate Sonic Hedgehog Signaling in Human Congenital Heart Disease

The Glioma-associated oncogene (Gli) family members of zinc finger DNA-binding proteins are core effectors of Sonic hedgehog (SHH) signaling pathway. Studies in model organisms have identified that the Gli genes play critical roles during organ development, including the heart, brain, kidneys, etc. Deleterious mutations in GLI genes have previously been revealed in several human developmental disorders, but few in congenital heart disease (CHD). In this study, the mutations in GLI1-3 genes were captured by next generation sequencing in human cohorts composed of 412 individuals with CHD and 213 ethnically matched normal controls. A total of 20 patient-specific nonsynonymous rare mutations in coding regions of human GLI1-3 genes were identified. Functional analyses showed that GLI1 c.820G> T (p.G274C) is a gain-of-function mutation, while GLI1 c.878G>A (p.R293H) and c.1442T>A (p.L481X) are loss-of-function mutations. Our findings suggested that deleterious rare mutations in GLI1 gene broke the balance of the SHH signaling pathway regulation and may constitute a great contribution to human CHD, which shed new light on understanding genetic mechanism of embryo cardiogenesis regulated by SHH signaling.

Maternal Folic Acid Intake and Methylation Status of Genes Associated with Ventricular Septal Defects in Children: Case-Control Study

Background: DNA methylation is the best epigenetic mechanism for explaining the interactions between nutrients and genes involved in intrauterine growth and development programming. A possible contributor of methylation abnormalities to congenital heart disease is the folate methylation regulatory pathway; however, the mechanisms and methylation patterns of VSD-associated genes are not fully understood. Objective: To determine if maternal dietary intake of folic acid (FA) is related to the methylation status (MS) of VSD-associated genes (AXIN1, MTHFR, TBX1, and TBX20). Methods: Prospective case–control study; 48 mothers and their children were evaluated. The mothers’ dietary variables were collected through a food frequency questionnaire focusing on FA and the consumption of supplements with FA. The MS of promoters of genes was determined in the children. Results: The intake of FA supplements was significantly higher in the control mothers. In terms of maternal folic acid consumption, significant differences were found in the first trimester of pregnancy. Significant differences were observed in the MS of MTHFR and AXIN1 genes in VSD and control children. A correlation between maternal FA supplementation and MS of AXIN1 and TBX20 genes was found in control and VSD children, respectively. Conclusions: A lower MS of AXIN1 genes and a higher MS of TBX20 genes is associated with FA maternal supplementation.

Paternal genetic variants and risk of obstructive heart defects: A parent-of-origin approach

Previous research on risk factors for obstructive heart defects (OHDs) focused on maternal and infant genetic variants, prenatal environmental exposures, and their potential interaction effects. Less is known about the role of paternal genetic variants or environmental exposures and risk of OHDs. We examined parent-of-origin effects in transmission of alleles in the folate, homocysteine, or transsulfuration pathway genes on OHD occurrence in offspring. We used data on 569 families of liveborn infants with OHDs born between October 1997 and August 2008 from the National Birth Defects Prevention Study to conduct a family-based case-only study. Maternal, paternal, and infant DNA were genotyped using an Illumina Golden Gate custom single nucleotide polymorphism (SNP) panel. Relative risks (RR), 95% confidence interval (CI), and likelihood ratio tests from log-linear models were used to estimate the parent-of-origin effect of 877 SNPs in 60 candidate genes in the folate, homocysteine, and transsulfuration pathways on the risk of OHDs. Bonferroni correction was applied for multiple testing. We identified 3 SNPs in the transsulfuration pathway and 1 SNP in the folate pathway that were statistically significant after Bonferroni correction. Among infants who inherited paternally-derived copies of the G allele for rs6812588 in the RFC1 gene, the G allele for rs1762430 in the MGMT gene, and the A allele for rs9296695 and rs4712023 in the GSTA3 gene, RRs for OHD were 0.11 (95% CI: 0.04, 0.29, P = 9.16x10^-7), 0.30 (95% CI: 0.17, 0.53, P = 9.80x10^-6), 0.34 (95% CI: 0.20, 0.57, P = 2.28x10^-5), and 0.34 (95% CI: 0.20, 0.58, P = 3.77x10^-5), respectively, compared to infants who inherited maternally-derived copies of the same alleles. We observed statistically significant decreased risk of OHDs among infants who inherited paternal gene variants involved in folate and transsulfuration pathways.

Obstructive heart defects are birth defects that cause obstruction to the blood flow of the developing heart. Common OHDs include coarctation of the aorta, aortic stenosis and pulmonary stenosis. While there is a fair amount of literature indicating an association between maternal genetic variants and OHDs, less is known about the role of paternal genetic variants in the etiology of OHDs. We used a genotype clustering algorithm, SNPMClust, that was developed in-house at the Arkansas Center for Birth Defects Research and Prevention to study the role of paternal genetic variants in the folate, homocysteine and transsulfuration pathways. Maternal, paternal, and infant DNA specimens were collected from participants of the National Birth Defects Prevention Study, a large population-based case-control study in the United States, and were genotyped using an Illumina Golden Gate custom single nucleotide polymorphism (SNP) panel. We identified 4 SNPs in the folate and transsulfuration pathways, rs6812588, rs1762430, rs9296695, and rs4712023, that were associated with a statistically significant decreased risk of OHDs for infants who inherited a paternally-derived copy of the variant allele compared to infants who inherited a maternal copy of the variant allele. In conclusion, we observed a significantly decreased risk and less epigenetic influence of paternal genetic variants on OHDs compared to maternally-derived variants.

Analysis of MTR and MTRR Gene Polymorphisms in Chinese Patients With Ventricular Septal Defect

Background:

Congenital heart defects (CHDs) are the most common birth defects and ventricular septal defects (VSDs) are one of the most common types of CHDs. Genes involved in homocysteine/folate metabolism may play important roles in CHDs. Methionine synthase and methionine synthase reductase (MTRR) are key regulatory enzymes involved in the metabolic pathway of homocysteine.

Methods:

We investigated whether a polymorphism (A2756G) of the methionine synthase and 2 polymorphisms (A66G and C524T) of the MTRR gene are associated with VSDs. A total of 183 children with VSDs and 201 healthy children were studied.

Results:

The polymorphisms were detected by polymerase chain reaction amplification and sequencing of the amplified product. Significant differences in the distributions of the A66G and C524T alleles were observed between VSD cases and controls, and a slightly increased risk of VSDs was associated with either of the 66AG, 524CT, and 524TT genotypes [odds ratios (OR)=1.796, 1.909, and 2.088, respectively]. The genotype frequency of 66AG in VSDs patients was significantly different from those of controls (ORs=3.147). In addition, the combined 66AG/524CT and 66GG/524TT in VSDs had ORs 2.937 and 5.344, respectively.

Conclusions:

MTRR A66G and C524T polymorphisms are associated with increased risk of VSDs.

Modulation of ADAR mRNA expression in patients with congenital heart defects

Adenosine (A) to inosine (I) RNA editing is a hydrolytic deamination reaction catalyzed by the adenosine deaminase (ADAR) enzyme acting on double-stranded RNA. This posttranscriptional process diversifies a plethora of transcripts, including coding and noncoding RNAs. Interestingly, few studies have been carried out to determine the role of RNA editing in vascular disease. The aim of this study was to determine the potential role of ADARs in congenital heart disease. Strong downregulation of ADAR2 and increase in ADAR1 expression was observed in blood samples from congenital heart disease (CHD) patients. The decrease in expression of ADAR2 was in line with its downregulation in ventricular tissues of dilated cardiomyopathy patients. To further decipher the plausible regulatory pathway of ADAR2 with respect to heart physiology, miRNA profiling of ADAR2 was performed on tissues from ADAR2-/- mouse hearts. Downregulation of miRNAs (miR-29b, miR-405, and miR-19) associated with cardiomyopathy and cardiac fibrosis was observed. Moreover, the upregulation of miR-29b targets COL1A2 and IGF1, indicated that ADAR2 might be involved in cardiac myopathy. The ADAR2 target vascular development associated protein-coding gene filamin B (FLNB) was selected. The editing levels of FLNB were dramatically reduced in ADAR2^-/- mice; however, no observable changes in FLNB expression were noted in ADAR2^-/- mice compared to wild-type mice. This study proposes that sufficient ADAR2 enzyme activity might play a vital role in preventing cardiovascular defects.

Maternal LINE-1 DNA Methylation and Congenital Heart Defects in Down Syndrome

Background: Down syndrome (DS) is one of the most common chromosomal abnormalities associated with congenital heart defects (CHD), with approximately 40 to 60% of cases showing cardiac defects. This study assessed (i) the association between maternal LINE-1 methylation and the occurrence of CHDs in children with DS and (ii) the impact of endogenous maternal factors (MTHFR C677T polymorphism and maternal age) and exogenous maternal factors (cigarette smoking, alcohol intake, medication use, body mass index and dietary habits such as folate intake) on maternal LINE-1 methylation and on the occurrence of CHD in children with DS.

Patients and Methods: The study included 90 mothers of children with DS of maternal origin (49% DS-CHD⁺ mothers/51% DS-CHD⁻ mothers). LINE-1 DNA methylation was analyzed in peripheral blood lymphocytes by quantification of LINE-1 methylation using the MethyLight method. MTHFR C677T polymorphism genotyping was performed using PCR-RFLP.

Results: LINE-1 methylation was not significantly different between DS-CHD⁺ and DS-CHD⁻ mothers (P = 0.997). Combination of MTHFR C677T genotype/diet and BMI were significant independent predictors of LINE-1 DNA methylation in DS-CHD⁺ mothers (β −0.40, P = 0.01 and β −0.32, P = 0.03, respectively). In the analyzed multivariate model (model P = 0.028), these two factors explained around 72% of the variance in LINE-1 DNA methylation in mothers of children with DS and CHD. The group with the highest BMI (≥30 kg/m2) had significantly lower LINE-1 methylation than the group with normal BMI (Bonferroni post hoc P = 0.03) and the overweight group (Bonferroni post hoc P = 0.04). The lowest LINE-1 DNA methylation values were found in DS-CHD⁺ mothers with the CT+TT genotype and a low-folate diet; the values were significantly lower than the values in mothers with the CC genotype and a folate-rich diet (Bonferroni post hoc P = 0.04).

Conclusion: Association between maternal LINE-1 methylation and CHD in children with DS was not found. Study showed that the MTHFR genotype/diet combination and BMI were significantly associated with LINE-1 methylation in mothers of children with DS-CHD⁺. These results highlight the need for a multifactorial approach to assess the roles of endogenous and exogenous maternal factors in maternal LINE-1 DNA methylation and the consequent pathologies in children. More extensive studies in a larger sample may help elucidate these relationships.

The Role of Oxidative Stress in the Pathomechanism of Congenital Malformations

Congenital anomalies are significant causes of mortality and morbidity in infancy and childhood. Embryogenesis requires specific signaling pathways to regulate cell proliferation and differentiation. These signaling pathways are sensitive to endogenous and exogenous agents able to produce several structural changes of the developing fetus. Oxidative stress, due to an imbalance between the production of reactive oxygen species and antioxidant defenses, disrupts signaling pathways with a causative role in birth defects. This review provides a basis for understanding the role of oxidative stress in the pathomechanism of congenital malformations, discussing the mechanisms related to some congenital malformations. New insights in the knowledge of pathomechanism of oxidative stress-related congenital malformations, according to experimental and human studies, represent the basis of possible clinical applications in screening, prevention, and therapies.

Risk Factors for Ventricular Septal Defects in Murmansk County, Russia: A Registry-Based Study

Cardiovascular malformations are one of the most common birth defects among newborns and constitute a leading cause of perinatal and infant mortality. Although some risk factors are recognized, the causes of cardiovascular malformations (CVMs) remain largely unknown. In this study, we aim to identify risk factors for ventricular septal defects (VSDs) in Northwest Russia. The study population included singleton births registered in the Murmansk County Birth Registry (MCBR) between 1 January 2006 and 31 December 2011. Infants with a diagnosis of VSD in the MCBR and/or in the Murmansk Regional Congenital Defects Registry (up to two years post-delivery) constituted the study sample. Among the 52,253 infants born during the study period there were 744 cases of septal heart defects (SHDs), which corresponds to a prevalence of 14.2 [95% confidence interval (CI) of 13.2–15.3] per 1000 infants. Logistic regression analyses were carried out to identify VSD risk factors. Increased risk of VSDs was observed among infants born to mothers who abused alcohol [OR = 4.83; 95% CI 1.88–12.41], or smoked during pregnancy [OR = 1.35; 95% CI 1.02–1.80]. Maternal diabetes mellitus was also a significant risk factor [OR = 8.72; 95% CI 3.16–24.07], while maternal age, body mass index, folic acid and multivitamin intake were not associated with increased risk. Overall risks of VSDs for male babies were lower [OR = 0.67; 95% CI 0.52–0.88].

A parent-of-origin analysis of paternal genetic variants and increased risk of conotruncal heart defects

The association between conotruncal heart defects (CTHDs) and maternal genetic and environmental exposures is well studied. However, little is known about paternal genetic or environmental exposures and risk of CTHDs. We assessed the effect of paternal genetic variants in the folate, homocysteine, and transsulfuration pathways on risk of CTHDs in offspring. We utilized National Birth Defects Prevention Study data to conduct a family-based case only study using 616 live-born infants with CTHDs, born October 1997-August 2008. Maternal, paternal and infant DNA was genotyped using an Illumina® Golden Gate custom single nucleotide polymorphism (SNP) panel. Relative risks (RR) and 95% confidence intervals (CI) from log-linear models determined parent of origin effects for 921 SNPs in 60 candidate genes involved in the folate, homocysteine, and transsulfuration pathways on risk of CTHDs. The risk of CTHD among children who inherited a paternally derived copy of the A allele on GLRX (rs17085159) or the T allele of GLRX (rs12109442) was 0.23 (95%CI: 0.12, 0.42; p = 1.09 × 10^-6 ) and 0.27 (95%CI: 0.14, 0.50; p = 2.06 × 10^-5 ) times the risk among children who inherited a maternal copy of the same allele. The paternally inherited copy of the GSR (rs7818511) A allele had a 0.31 (95%CI: 0.18, 0.53; p = 9.94 × 10^-6 ] risk of CTHD compared to children with the maternal copy of the same allele. The risk of CTHD is less influenced by variants in paternal genes involved in the folate, homocysteine, or transsulfuration pathways than variants in maternal genes in those pathways.

A genetic variant in a homocysteine metabolic gene that increases the risk of congenital cardiac septal defects in Han Chinese populations

Elevated homocysteine levels are known to be a risk factor for congenital cardiac septal defects (CCSDs), but the mechanism underlying this effect is unknown. The genetic variants that were significantly associated with circulating homocysteine concentrations have been systematically identified through the genome-wide association studies of one-carbon core metabolites. To examine the role of the genome-wide significant homocysteine related variants in the occurrence of CCSDs, we investigated the association between these variants and CCSDs in Han Chinese populations. Five variants of the genome-wide significant homocysteine-related genes were selected for analysis in two stages of case-controlled studies with a total of 904 CCSD patients and 997 controls. SYT9 expression was detected in human cardiovascular tissue using qRT-PCR. The intronic variant rs11041321 of the SYT9 gene was associated with an increased risk of developing CCSDs in both the separate and combined case-controlled studies. Combined samples from the two stage cohorts had a significant elevation in CCSD risk for the T allele (OR = 1.43, P = 2.6 × 10^-6 ), CT genotype and TT genotype (CT: OR = 1.30, TT: OR = 2.21; P = 1 × 10^-4 ) compared with the wild-type C allele and CC genotype, respectively. The risky T allele carriers exhibited decreased SYT9 mRNA expression, compared with wild-type C allele carriers. The intronic SYT9 variant rs11041321, which exhibits a significant genome-wide association with circulating homocysteine, was associated with the occurrence of CCSDs. This finding helps to characterize the unexpected role of SYT9 in homocysteine metabolism and the development of CCSDs, which further highlighted the interplay of diet, genetics, and human birth defects. © 2017 IUBMB Life, 69(9):700-705, 2017.

Lower Circulating Folate Induced by a Fidgetin Intronic Variant Is Associated With Reduced Congenital Heart Disease Susceptibility

BACKGROUND

Folate deficiency is an independent risk factor for congenital heart disease (CHD); however, the maternal plasma folate level is paradoxically not a good diagnostic marker. Genome-wide surveys have identified variants of nonfolate metabolic genes associated with the plasma folate level, suggesting that these genetic polymorphisms are potential risk factors for CHD.

METHODS

To examine the effects of folate concentration-related variations on CHD risk in the Han Chinese population, we performed 3 independent case-control studies including a total of 1489 patients with CHD and 1745 control subjects. The expression of the Fidgetin (FIGN) was detected in human cardiovascular and decidua tissue specimens with quantitative real-time polymerase chain reaction and Western blotting. The molecular mechanisms were investigated by luciferase reporter assays, surface plasmon resonance, and chromatin immunoprecipitation. FIGN-interacting proteins were confirmed by tandem affinity purification and coimmunoprecipitation. Proteasome activity and metabolite concentrations in the folate pathway were quantified with a commercial proteasome activity assay and immunoassays, respectively.

RESULTS

The +94762G>C (rs2119289) variant in intron 4 of the FIGN gene was associated with significant reduction in CHD susceptibility (P=5.1×10^-14 for the allele, P=8.5×10^--13 for the genotype). Analysis of combined samples indicated that CHD risks in individuals carrying heterozygous (GC) or homozygous (CC) genotypes were reduced by 44% (odds ratio [OR]=0.56; 95% confidence interval [CI]=0.47-0.67) and 66% (OR=0.34; 95% CI=0.23-0.50), respectively, compared with those with the major GG genotype. Minor C allele carriers who had decreased plasma folate levels exhibited significantly increased FIGN expression because the transcription suppressor CREB1 did not bind the alternative promoter of FIGN isoform X3. Mechanistically, increased FIGN expression led to the accumulation of both reduced folate carrier 1 and dihydrofolate reductase via inhibition of their proteasomal degradation, which promoted folate absorption and metabolism.

CONCLUSIONS

We report a previously undocumented finding that decreased circulating folate levels induced by increased folate transmembrane transport and utilization, as determined by the FIGN intronic variant, serves as a protective mechanism against CHD. Our results may explain why circulating folate levels do not have a good diagnostic value.

Maternal and infant genetic variants, maternal periconceptional use of selective serotonin reuptake inhibitors, and risk of congenital heart defects in offspring: population based study

Objective To evaluate whether the association between maternal periconceptional use of selective serotonin reuptake inhibitors (SSRIs) and increased risk of congenital heart defects in offspring is modified by maternal or infant genetic variants in folate, homocysteine, or transsulfuration pathways.Design Population based study. DNA from mothers, fathers, and infants was genotyped with an Illumina GoldenGate custom single nucleotide polymorphism panel. A hybrid design based on a log linear model was used to calculate relative risks and Bayesian false discovery probabilities (BFDP) to identify polymorphisms associated with congenital heart defects modified by SSRI use.Data sources Data from the US National Birth Defects Prevention Study on 1180 liveborn infants with congenital heart defects and 1644 controls, born 1997-2008.Main outcome measures Cases included infants with selected congenital heart defects and control infants had no major defects. SSRI use was obtained from telephone interviews with mothers.Results For women who reported taking SSRIs periconceptionally, maternal SHMT1 (rs9909104) GG and AGgenotypes were associated with a 5.9 and 2.4 increased risk of select congenital heart defects in offspring, respectively, versus the AA genotype (BFDP=0.69). Compared with the AA genotype, BHMT (rs492842 and rs542852) GG and AG genotypes were associated with twice the riskof congenital heart defects (BFDP=0.74 and 0.79, respectively). MGST1 (rs2075237) CC and ACgenotypes were associated with an increased risk compared with the GG genotype (8.0 and 2.8, respectively; BFDP=0.79). Single nucleotide polymorphism in infant genes in the folate (MTHFS rs12438477), homocysteine (TRDMT1 rs6602178 and GNMT rs11752813) and transsulfuration (GSTP1 rs7941395 and MGST1 rs7294985) pathways were also associated with an increased risk of congenital heart defects.Conclusions Common maternal or infant genetic variants in folate, homocysteine, or transsulfuration pathways are associated with an increased risk of certain congenital heart defects among children of women taking SSRIs during cardiogenesis.

Study on Environmental Causes and SNPs of MTHFR, MS and CBS Genes Related to Congenital Heart Disease

PURPOSE

Congenital heart diseases (CHD) are among the most common birth defects in China. Environmental causes and folate metabolism changes may alter susceptibility to CHD. The aim of this study is to evaluate the relevant risk-factors of children with CHD and their mothers.

METHODS

138 children with CHD and 207 normal children for controls were recruited. Their mothers were also enlisted in this study and interviewed following a questionnaire about their pregnant history and early pregnancy situation. Five single nucleotide polymorphisms (SNPs) in methylenetetrahydrofolate reductase (MTHFR), methionine synthase (MS) and cystathionine β-synthase (CBS) of mothers and children were genotyped.

RESULTS

There were significant differences in the gender of children, occupation of mothers, family history with CHD, history of abortion, history of adverse pregnancy, early pregnancy health, fetus during pregnancy, pesticide exposure and drug exposure in CHD group and control group ( P < 0.05). Logistic regression analyses showed that after adjustment for above factors, MTHFR rs1801131 were significantly associated with their offspring CHD risk in mothers. Compared with the mothers whose MTHFR were rs1801131 AA and AC genotypes, the mothers who got a mutation of MTHFR rs1801131 CC genotypes had a 267% increase in risk of given birth of a CHD children (OR = 3.67,95%CI = 1.12-12.05). Meanwhile, MTHFR rs1801131 were significantly associated with CHD susceptibility in children (OR = 1.42, 95% CI = 1.00-2.44 in additive model).

CONCLUSIONS

Besides mothers' social and fertility characteristics, our results suggested that the genetic variants in folate metabolism pathway might be one of the most related risk-factors of CHD. MTHFR rs1801131 were identified as loci in Chinese population that were involved in CHD.

Obstructive heart defects associated with candidate genes, maternal obesity, and folic acid supplementation

Right-sided and left-sided obstructive heart defects (OHDs) are subtypes of congenital heart defects, in which the heart valves, arteries, or veins are abnormally narrow or blocked. Previous studies have suggested that the development of OHDs involved a complex interplay between genetic variants and maternal factors. Using the data from 569 OHD case families and 1,644 control families enrolled in the National Birth Defects Prevention Study (NBDPS) between 1997 and 2008, we conducted an analysis to investigate the genetic effects of 877 single nucleotide polymorphisms (SNPs) in 60 candidate genes for association with the risk of OHDs, and their interactions with maternal use of folic acid supplements, and pre-pregnancy obesity. Applying log-linear models based on the hybrid design, we identified a SNP in methylenetetrahydrofolate reductase (MTHFR) gene (C677T polymorphism) with a main genetic effect on the occurrence of OHDs. In addition, multiple SNPs in betaine-homocysteine methyltransferase (BHMT and BHMT2) were also identified to be associated with the occurrence of OHDs through significant main infant genetic effects and interaction effects with maternal use of folic acid supplements. We also identified multiple SNPs in glutamate-cysteine ligase, catalytic subunit (GCLC) and DNA (cytosine-5-)-methyltransferase 3 beta (DNMT3B) that were associated with elevated risk of OHDs among obese women. Our findings suggested that the risk of OHDs was closely related to a combined effect of variations in genes in the folate, homocysteine, or glutathione/transsulfuration pathways, maternal use of folic acid supplements and pre-pregnancy obesity.

Preconceptual Folic Acid Use and Recurrence Risk Counseling for Congenital Heart Disease

OBJECTIVE

Recurrence risk of congenital heart disease (CHD) in families with an affected first-degree relative is increased as compared with the general population. Advances in genetic testing and evidence that preconceptual folic acid supplementation may decrease risk of CHD warrant preventative counseling for at-risk families. Our goal was to document patterns of preconceptual folic acid supplementation and recurrence risk counseling in at-risk families in order to identify opportunities for improved preventative care.

DESIGN

Mothers referred for a fetal echocardiogram were prospectively enrolled. Cases were defined as mothers deemed to be at higher risk of having an affected fetus with CHD given an affected parent or affected previous pregnancy with CHD. Controls were defined as mothers with no prenatal risk factors. Mothers completed a validated questionnaire assessing use of folic acid supplementation and receipt of recurrence risk counseling. Chi-square analyses were performed to analyze questionnaire responses and demographic data.

RESULTS

A total of 314 subjects participated (controls = 216, cases = 98). Cases took preconceptual folic acid supplementation more often than controls (P < .001), but only 55% started preconceptually. Maternal advanced education and counseling (P < .001) were associated with preconceptual supplementation, whereas complexity of CHD in the relative was not. While 70% of cases received some recurrence risk counseling, those with advanced education and complex CHD in the affected relative were more likely to receive counseling. Few at-risk cases interacted with genetic services (19%).

CONCLUSIONS

At-risk mothers with lower education are less likely to take preconceptual folic acid supplementation or receive recurrence risk counseling. Health care providers should proactively provide this information to all at-risk patients and develop collaborations with genetic services.

Genetic basis of congenital cardiovascular malformations

Cardiovascular malformations are a singularly important class of birth defects and due to dramatic improvements in medical and surgical care, there are now large numbers of adult survivors. The etiologies are complex, but there is strong evidence that genetic factors play a crucial role. Over the last 15 years there has been enormous progress in the discovery of causative genes for syndromic heart malformations and in rare families with Mendelian forms. The rapid characterization of genomic disorders as major contributors to congenital heart defects is also notable. The genes identified encode many transcription factors, chromatin regulators, growth factors and signal transduction proteins- all unified by their required roles in normal cardiac development. Genome-wide sequencing of the coding regions promises to elucidate genetic causation in several disorders affecting cardiac development. Such comprehensive studies evaluating both common and rare variants would be essential in characterizing gene-gene interactions, as well as in understanding the gene-environment interactions that increase susceptibility to congenital heart defects.

Methylene tetrahydrofolate reductase polymorphisms and homocysteine level in heart defects

BACKGROUND

While several single nucleotide polymorphisms are known to influence the metabolism of folate, the methylene tetrahydrofolate reductase (MTHFR) gene has been the most extensively studied. The aim of this study was to investigate the relationship between the MTHFR polymorphisms 1298A>C and 677C>T and congenital heart disease. In addition, the relationship between these gene polymorphisms and homocysteine level was determined in Turkish subjects.

METHODS

Patients with non-syndromic congenital heart defects who were admitted to the Pediatric Cardiology Unit at Hacettepe University Ihsan Dogramaci Children's Hospital, Ankara, Turkey between June 2002 and June 2003 were recruited for the study. A total of 163 children with congenital heart defects (mean age, 7.63 ± 6.03 years; M/F, 93/70) and 93 healthy controls were analyzed.

RESULTS

When evaluated either separately or together, there were no differences in the frequency of MTHFR 677C>T or 1298A>C polymorphisms between the children with congenital heart defects and the control group. The results were the same when considering only conotruncal defects. Those with the 677C>T polymorphism had significantly lower homocysteine level (P = 0.004), but the 1298A>C polymorphism was not related to homocysteine level.

CONCLUSION

No relationship was found between congenital heart defects and 1298A>C or 677C>T polymorphisms. The 677C>T polymorphism was related to low homocysteine level. Because there is often much heterogeneity between populations, this study should be conducted in different populations and with larger numbers of participants.

A genetic variant in vitamin B12 metabolic genes that reduces the risk of congenital heart disease in Han Chinese populations

BACKGROUND

Genome-wide association studies on components of the one-carbon metabolic pathway revealed that human vitamin B12 levels could be significantly influenced by variations in the fucosyltransferase 2 (FUT2), cubilin (CUBN), and transcobalamin-I (TCN1) genes. An altered vitamin B12 level is an important factor that disturbs the homeostasis of the folate metabolism pathway, which in turn can potentially lead to the development of congenital heart disease (CHD). Therefore, we investigated the association between the variants of vitamin B12-related genes and CHD in Han Chinese populations.

METHODS AND RESULTS

Six variants of the vitamin B12-related genes were selected for analysis in two independent case-control studies, with a total of 868 CHD patients and 931 controls. The variant rs11254363 of the CUBN gene was associated with a decreased risk of developing CHD in both the separate and combined case-control studies. Combined samples from the two cohorts had a significant decrease in CHD risk for the G allele (OR = 0.48, P = 1.7×10⁻⁵) and AG+GG genotypes (OR = 0.49, P = 4×10⁻⁵), compared with the wild-type A allele and AA genotype, respectively.

CONCLUSIONS

Considering the G allele of variant rs11254363 of the CUBN gene was associated with an increased level of circulating vitamin B12. This result suggested that the carriers of the G allele would benefit from the protection offered by the high vitamin B12 concentration during critical heart development stages. This finding shed light on the unexpected role of CUBN in CHD development and highlighted the interplay of diet, genetics, and human birth defects.

Folate deficiency and folic acid supplementation: the prevention of neural-tube defects and congenital heart defects

Diet, particularly vitamin deficiency, is associated with the risk of birth defects. The aim of this review paper is to show the characteristics of common and severe neural-tube defects together with congenital heart defects (CHD) as vitamin deficiencies play a role in their origin. The findings of the Hungarian intervention (randomized double-blind and cohort controlled) trials indicated that periconceptional folic acid (FA)-containing multivitamin supplementation prevented the major proportion (about 90%) of neural-tube defects (NTD) as well as a certain proportion (about 40%) of congenital heart defects. Finally the benefits and drawbacks of three main practical applications of folic acid/multivitamin treatment such as (i) dietary intake; (ii) periconceptional supplementation; and (iii) flour fortification are discussed. The conclusion arrived at is indeed confirmation of Benjamin Franklin's statement: "An ounce of prevention is better than a pound of care".

Risk and protective factors in the origin of conotruncal defects of heart--a population-based case-control study

Congenital heart defect (CHD) cases have been evaluated together as a group in some previous epidemiological studies. However, different CHD entities have different etiologies, and the underlying causes are unclear in the vast majority of patients. Thus the aim of this study was to analyze the possible association of different maternal diseases with the risk of four types of conotruncal defects (CTD), that is, truncus arteriosus, d-transposition of the great arteries, tetralogy of Fallot, and double-outlet right ventricle based on autopsy or surgical report diagnosis. Acute and chronic diseases with related drug treatments and peri-conceptual folic acid or multivitamin supplementations were compared in mothers of 598 CTD cases, of 902 matched controls, and 38,151 population controls without any defects, and with 20,896 malformed controls with other isolated non-cardiac defects in the population-based large dataset of the Hungarian Case-Control Surveillance of Congenital Abnormalities. Mothers who had medically recorded influenza and the common cold with secondary complications in the prenatal maternity logbook during the second and/or third gestational months were associated with a higher risk of CTD (OR with 95% CI: 2.22, 1.19-3.88). The common denominator of these maternal diseases may be high fever, which could be prevented by antifever therapies. On the other hand, high doses of medically recorded folic acid in early pregnancy were able to reduce the birth prevalence of CTD (OR with 95% CI: 0.54, 0.39-0.73), and this reduction was significant in transposition of the great arteries (0.46, 0.29-0.71) as well. In conclusion, high fever related maternal diseases may have a role in the origin of CTD, while high doses of folic acid in early pregnancy were able to reduce of CTD, particularly transposition of great vessels.

Elevated dimethylglycine in blood of children with congenital heart defects and their mothers

OBJECTIVE

Congenital Heart Defects (CHD) may be related to nutritional deficiencies affecting the methylation cycle. We aimed to study the metabolic markers of the betaine homocysteine methyl transferase (BHMT) pathway in children with CHD and their mothers compared to children without CHD and their mothers.

MATERIALS AND METHODS

Children with CHD (n=105, age < 3 years) and mothers of 80 of the affected children were studied. The controls were non-CHDs children of comparable age as the CHD group (n=52) and their mothers (n=50). We measured serum or plasma concentrations of the metabolites of the methylation cycle homocysteine (HCY), methylmalonic acid (MMA), cystathionine, S-adenosylmethionine (SAM), S-adenosylhomocysteine (SAH), betaine, choline, and dimethylglycine (DMG).

RESULTS

Children with CHD had higher plasma SAM (131 vs. 100 nmol/L) and DMG (8.7 vs. 6.0 μmol/L) and lower betaine/DMG ratio (7.5 vs. 10.2) compared to the controls. Mothers of CHD children showed also higher DMG (6.1 vs. 4.1 µmol/L) and lower betaine/DMG ratio compared with the mothers of the controls. Higher SAM levels were related to higher cystathionine, MMA, betaine, choline, and DMG. MMA elevation in the patients was related to higher HCY, SAM, betaine and DMG.

CONCLUSIONS

Elevated DMG in CHD children and their mothers compared to the controls can indicate upregulation of the BHMT pathway in this disease group. Nutritional factors are related to metabolic imbalance during pregnancy that may be related to worse birth outcome.

Increased maternal cytokine production and congenital heart defects

Congenital heart defects (CHDs) are a major cause of infant mortality. Most CHDs are thought to result from genetic, lifestyle, and environmental factors that include maternal obesity, diabetes, toxicant exposure, and alterations in anti-oxidant capacity. Since these well-documented risk factors are also associated with immune dysregulation, we sought to compare the maternal immune response in mothers carrying a fetus with a CHD with those mothers whose pregnancies were not affected by any birth defect. We conducted a case-control study to examine the maternal cytokine profile using multiplex technology in pregnant mothers (subject mean=26 weeks' gestation). This investigation revealed that whole blood cultures derived from case mothers produced higher levels of certain cytokines and chemokines compared with cultures from control subjects when activated with mitogen. Cultures from case subjects produced higher levels of IL-10, IL-13, IL-4, IL-5, IL-17, and IL-6, when stimulated with mitogen compared with control subjects. Plasma levels of chemokine MIP-1α were higher in cases compared with controls. In contrast, C-reactive protein levels were not statistically different. These results demonstrate the need to further examine the maternal cytokine signature in CHD-affected pregnancies. This information could pave the way toward maternal immunotherapeutic intervention to prevent CHDs, and novel biomarker discovery to improve pre-natal diagnosis.

Associations between maternal genotypes and metabolites implicated in congenital heart defects

BACKGROUND

The development of non-syndromic congenital heart defects (CHDs) involves a complex interplay of genetics, metabolism, and lifestyle. Previous studies have implicated maternal single nucleotide polymorphisms (SNPs) and altered metabolism in folate-related pathways as CHD risk factors.

OBJECTIVE

We sought to discover associations between maternal SNPs and metabolites involved in the homocysteine, folate, and transsulfuration pathways, and determine if these associations differ between CHD cases and controls.

DESIGN

Genetic, metabolic, demographic, and lifestyle information was available for 335 mothers with CHD-affected pregnancies and 263 mothers with unaffected pregnancies. Analysis was conducted on 1160 SNPs, 13 plasma metabolites, and 2 metabolite ratios. A two-stage multiple linear regression was fitted to each combination of SNP and metabolite/ratio.

RESULTS

We identified 4 SNPs in the methionine adenosyltransferase II alpha (MAT2A) gene that were associated with methionine levels. Three SNPs in tRNA aspartic acid methyltransferase 1 (TRDMT1) gene were associated with total plasma folate levels. Glutamylcysteine (GluCys) levels were associated with multiple SNPs within the glutathione peroxidase 6 (GPX6) and O-6-methylguanine-DNA methyltransferase (MGMT) genes. The regression model revealed interactions between genotype and case-control status in the association of total plasma folate, total glutathione (GSH), and free GSH, to SNPs within the MGMT, 5,10-methenyltetrahydrofolate synthetase (MTHFS), and catalase (CAT) genes, respectively.

CONCLUSIONS

Our study provides further evidence that genetic variation within folate-related pathways accounts for inter-individual variability in key metabolites. We identified specific SNP-metabolite relationships that differed in mothers with CHD-affected pregnancies, compared to controls. Our results underscore the importance of multifactorial studies to define maternal CHD risk.

A functional variant in the cystathionine β-synthase gene promoter significantly reduces congenital heart disease susceptibility in a Han Chinese population

Homocysteine is an independent risk factor for various cardiovascular diseases. There are two ways to remove homocysteine from embryonic cardiac cells: remethylation to form methionine or transsulfuration to form cysteine. Cystathionine β-synthase (CBS) catalyzes the first step of homocysteine transsulfuration as a rate-limiting enzyme. In this study, we identified a functional variant -4673C>G (rs2850144) in the CBS gene promoter region that significantly reduces the susceptibility to congenital heart disease (CHD) in a Han Chinese population consisting of 2 340 CHD patients and 2 270 controls. Individuals carrying the heterozygous CG and homozygous GG genotypes had a 15% (odds ratio (OR) = 0.85, 95% confidence interval (CI) = 0.75-0.96, P = 0.011) and 40% (OR = 0.60, 95% CI = 0.49-0.73, P = 1.78 × 10(-7)) reduced risk to develop CHD than the wild-type CC genotype carriers in the combined samples, respectively. Additional stratified analyses demonstrated that CBS -4673C>G is significantly related to septation defects and conotruncal defects. In vivo detection of CBS mRNA levels in human cardiac tissues and in vitro luciferase assays consistently showed that the minor G allele significantly increased CBS transcription. A functional analysis revealed that both the attenuated transcription suppressor SP1 binding affinity and the CBS promoter hypomethylation specifically linked with the minor G allele contributed to the remarkably upregulated CBS expression. Consequently, the carriers with genetically increased CBS expression would benefit from the protection due to the low homocysteine levels maintained by CBS in certain cells during the critical heart development stages. These results shed light on unexpected role of CBS and highlight the importance of homocysteine removal in cardiac development.Cell Research advance online publication 18 September 2012; doi:10.1038/cr.2012.135.

Association between maternal occupational exposure to organic solvents and congenital heart defects, National Birth Defects Prevention Study, 1997-2002

OBJECTIVE

To examine the relation between congenital heart defects (CHDs) in offspring and estimated maternal occupational exposure to chlorinated solvents, aromatic solvents and Stoddard solvent during the period from 1 month before conception through the first trimester.

METHODS

The study population included mothers of infants with simple isolated CHDs and mothers of control infants who delivered from 1997 through 2002 and participated in the National Birth Defects Prevention Study. Two methods to assess occupational solvent exposure were employed: an expert consensus-based approach and a literature-based approach. Multiple logistic regression was used to calculate adjusted ORs and 95% CIs for the association between solvent classes and CHDs.

RESULTS

2951 control mothers and 2047 CHD case mothers were included. Using the consensus-based approach, associations were observed for exposure to any solvent and any chlorinated solvent with perimembranous ventricular septal defects (OR 1.6, 95% CI 1.0 to 2.6 and OR 1.7, 95% CI 1.0 to 2.8, respectively). Using the literature-based approach, associations were observed for: any solvent exposure with aortic stenosis (OR 2.1, 95% CI 1.1 to 4.1) and Stoddard solvent exposure with d-transposition of the great arteries (OR 2.0, 95% CI 1.0 to 4.2), right ventricular outflow tract obstruction defects (OR 1.9, 95% CI 1.1 to 3.3) and pulmonary valve stenosis (OR 2.1, 95% CI 1.1 to 3.8).

CONCLUSIONS

The authors found evidence of associations between occupational exposure to solvents and several types of CHDs. These results should be interpreted in light of the potential for misclassification of exposure.

A derangement of the maternal lipid profile is associated with an elevated risk of congenital heart disease in the offspring

BACKGROUND AND AIMS

Maternal hyperglycaemia and hyperhomocysteinaemia are risk factors for congenital heart disease (CHD). These metabolic derangements and deranged lipid levels are associated with adult cardiovascular disease. We examined whether maternal lipid levels are associated with the risk of CHD offspring.

METHODS AND RESULTS

From 2003 onwards, a case-control study was conducted. Participants were mothers of children with (n = 261) and without (n = 325) CHD. At around 16 months after the index-pregnancy, maternal lipid levels were determined. Maternal characteristics and lipid levels were compared by Student's t-test. In a multivariable logistic regression model, risk estimates were calculated for associations between CHD and lipid levels. Adjustments were made for maternal age, diabetes, ethnicity, body mass index (BMI), parity, periconception folic acid use and total homocysteine levels. Outcome measures are presented in (geometric) means (p5-p95) and odds ratios (ORs) with 95% confidence intervals (CIs). Case mothers showed higher cholesterol (4.9 vs. 4.7 mmol l(-1), P < 0.05), low-density lipoprotein (LDL)-cholesterol (3.2 vs. 3.0 mmol l(-1), P < 0.05), apolipoprotein B (84.0 vs. 80.0 mg dl(-1), P < 0.01) and homocysteine (10.8 vs. 10.2 μmol l(-1), P < 0.05) than controls. LDL-cholesterol above 3.3 mmol l(-1) (OR 1.6 (95%CI, 1.1-2.3)) and apolipoprotein B above 85.0 mg dl(-1) were associated with an almost twofold increased CHD risk (OR 1.8 (95%CI, 1.2-2.6)). This was supported by elevated CHD risks per unit standard deviation increase in cholesterol (OR 1.2 (95% CI 1.03-1.5)), LDL-cholesterol (OR 1.3 (95%CI, 1.1-1.6) and apolipoprotein B (OR 1.3 (95% CI 1.1-1.6)). Apolipoprotein B was most strongly associated with CHD risk.

CONCLUSION

A mildly deranged maternal lipid profile is associated with an increased risk of CHD offspring.

Homocysteine exposure affects early hemodynamic parameters of embryonic chicken heart function

Maternal hyperhomocysteinemia has been associated with an increased risk of newborns with a congenital heart defect. This has been substantiated in the chicken embryo, as congenital heart defects have been induced after homocysteine treatment. Comparable heart defects are observed in venous clipping studies, a model of altered embryonic blood flow. Because of this overlap in heart defects, our aim was to test the hypothesis that homocysteine would cause alterations in embryonic heart function that precede the structural malformations previously described. Therefore, Doppler flow velocity waveforms were recorded in both primitive ventricles and the outflow tract of the embryonic heart of homocysteine treated and control chicken embryos at embryonic day 3.5. Homocysteine treatment consisted of 50 μL 0.05 M L-homocysteine thiolactone at 24, 48, and 72 hr. Homocysteine-treated embryos displayed significantly lower mean heart rates of 134 (SD 22) bpm, compared to 150 (14) bpm in control embryos. Homocysteine treatment caused an inhibiting effect on hemodynamic parameters, and altered heart function was presented by a shift in the proportions of the different wave times in percentage of total cycle time. Homocysteine induces changes in hemodynamic parameters of early embryonic chicken heart function. These changes may precede morphological changes and contribute to the development of CHD defects through alterations in shear stress and shear stress related genes, as seen before in venous clipping studies.

Gene variants in the folate-mediated one-carbon metabolism (FOCM) pathway as risk factors for conotruncal heart defects

We evaluated 35 variants among four folate-mediated one-carbon metabolism pathway genes, MTHFD1, SHMT1, MTHFR, and DHFR as risk factors for conotruncal heart defects. Cases with a diagnosis of single gene disorders or chromosomal aneusomies were excluded. Controls were randomly selected from area hospitals in proportion to their contribution to the total population of live-born infants. Odds ratios (OR) and the 95% confidence intervals (CI) were computed for each genotype (homozygous variant or heterozygote, vs. homozygous wildtype) and for increase of each less common allele (log-additive model). Interactions between each variant and three folate intake variables (maternal multivitamin use, maternal dietary folate intake, and combined maternal folate intake) were also evaluated under the log-additive model. In general, we did not identify notable associations. The A allele of MTHFD1 rs11627387 was associated with a 1.7-fold increase in conotruncal defects risk in both Hispanic mothers (OR = 1.7, 95% CI = 1.1-2.5) and Hispanic infants (OR = 1.7, 95% CI = 1.2-2.3). The T allele of MTHFR rs1801133 was associated with a 2.8-fold increase of risk among Hispanic women whose dietary folate intake was ≤ 25th centile. The C allele of MTHFR rs1801131 was associated with a two-fold increase of risk (OR = 2.0, 95% CI = 1.0-3.9) only among those whose dietary folate intake was >25th centile. Our study suggested that MTHFD1 rs11627387 may be associated with risk of conotruncal defects through both maternal and offspring genotype effect among the Hispanics. Maternal functional variants in MTHFR gene may interact with dietary folate intake and modify the conotruncal defects risk in the offspring.

Genetic polymorphisms of the TYMS gene are not associated with congenital cardiac septal defects in a Han Chinese population

BACKGROUND

Clinical research indicates that periconceptional administration of folic acid can reduce the occurrence of congenital cardiac septal defects (CCSDs). The vital roles of folate exhibits in three ways: the unique methyl donor for DNA expression regulation, the de novo biosynthesis of purine and pyrimidine for DNA construction, and the serum homocysteine removal. Thymidylate synthase (TYMS) is the solo catalysis enzyme for the de novo synthesis of dTMP, which is the essential precursor of DNA biosynthesis and repair process. To examine the role of TYMS in Congenital Cardiac Septal Defects (CCSDs) risk, we investigated whether genetic polymorphisms in the TYMS gene associated with the CCSDs in a Han Chinese population.

METHOD

Polymorphisms in the noncoding region of TYMS were identified via direct sequencing in 32 unrelated individuals composed of half CCSDs and half control subjects. Nine SNPs and two insertion/deletion polymorphisms were genotyped from two independent case-control studies involving a total of 529 CCSDs patients and 876 healthy control participants. The associations were examined by both single polymorphism and haplotype tests using logistic regression.

RESULT

We found that TYMS polymorphisms were not related to the altered CCSDs risk, and even to the changed risk of VSDs subgroup, when tested in both studied groups separately or in combination. In the haplotype analysis, there were no haplotypes significantly associated with risks for CCSDs either.

CONCLUSION

Our results show no association between common genetic polymorphisms of the regulatory region of the TYMS gene and CCSDs in the Han Chinese population.

Meta analysis of the association between MTHFR C677T polymorphism and the risk of congenital heart defects

Methylenetetrahydrofolate reductase (MTHFR) polymorphism C667T has been associated with congenital malformation; this common missense mutation in the MTHFR gene may reduce enzymatic action, and may be involved in the etiology of congenital heart defects (CHD). The aim of this study was to investigate the relationship of the MTHFR C677T polymorphism with the risk of CHD in children with CHD and their parents by meta-analysis. Studies were identified by searching electronic literature for papers before 2011, focusing on MTHFR C667T and the risk of CHD. All data were analyzed using the fixed effects model in Cochrane Review Manager 5.1.1. Twenty eligible case-control and family-based studies were included. Overall analysis yielded pooled odds ratios (OR) of 1.55 (95%CI 1.25-1.93), 1.84 (95%CI 1.23-2.74) and 1.20 (95%CI 0.94-1.54) for fetal, paternal and maternal MTHFR TT genotypes in case-control studies, respectively, but yielded a summarized OR of 0.9 (95%CI 0.97-1.12) in family-based studies. Our results suggested that the fetal and paternal MTHFR C667T gene may be associated with an increased occurrence of CHD. Further larger studies should be performed to investigate the interaction between maternal genetic polymorphism, folic acid intake and hyperhomocysteinemia, and the development of CHD.

Functional variant in methionine synthase reductase intron-1 significantly increases the risk of congenital heart disease in the Han Chinese population

BACKGROUND

Homocysteine is known to be an independent risk factor for congenital heart disease (CHD). Methionine synthase reductase (MTRR) is essential for the adequate remethylation of homocysteine, which is the dominant pathway for homocysteine removal during early embryonic development.

METHODS AND RESULTS

Here, we report that the c.56+781 A>C (rs326119) variant of intron-1 of MTRR significantly increases the risk of CHD in the Han Chinese population. In 3 independent case-control studies involving a total of 2340 CHD patients and 2270 healthy control participants from different geographic areas, we observed that patients carrying the heterozygous AC and homozygous CC genotype had a 1.40-fold (odds ratio=1.40; P=2.32×10(-7)) and 1.84-fold (odds ratio=1.84; P=2.3×10(-11)) increased risk, respectively, of developing CHD than those carrying the wild-type AA genotype. Both in vivo quantitative real-time polymerase chain reaction analysis of MTRR mRNA in cardiac tissue samples from CHD patients and in vitro luciferase assays in transfected cells demonstrated that the c.56+781 C allele profoundly decreased MTRR transcription. Further analysis demonstrated that the c.56+781 C allele manifested reduced CCAAT/enhancer binding protein-α binding affinity. In addition, healthy individuals with the homozygous CC genotype had significantly elevated levels of plasma homocysteine compared with the wild-type AA carriers.

CONCLUSIONS

We have demonstrated that the MTRR c.56+781 A>C variant is an important genetic marker for increased CHD risk because this variant results in functionally reduced MTRR expression at the transcriptional level. Our results accentuate the significance of functional single-nucleotide polymorphisms in noncoding regions of the homocysteine/folate metabolism pathway core genes for their potential contributions to the origin of CHD.

A66G and C524T polymorphisms of the methionine synthase reductase gene are associated with congenital heart defects in the Chinese Han population

Congenital heart defects (CHDs) are the most common birth defects; genes involved in homocysteine/folate metabolism may play important roles in CHDs. Methionine synthase reductase (MTRR) is one of the key regulatory enzymes involved in the metabolic pathway of homocysteine. We investigated whether two polymorphisms (A66G and C524T) of the MTRR gene are associated with CHDs. A total of 599 children with CHDs and 672 healthy children were included; the polymorphisms were detected by PCR and RFLP analysis. Significant differences in the distributions of A66G and C524T alleles were observed between CHD cases and controls, and slightly increased risks of CHD were associated with 66GG and 524CT genotypes (odds ratios = 1.545 and 1.419, respectively). The genotype frequencies of 524CT in the VSD subgroup, 66GG and 524CT in the PDA subgroup were significantly different from those of controls. In addition, the combined 66AA/524CT, 66AG/524CT and 66GG/524CT in CHDs had odds ratios = 1.589, 1.422 and 1.934, respectively. Increased risks were also observed in 66AA/524CT and 66GG/524CT for ASD, 66AG/524CT for VSD, as well as 66GG/524CT for PDA. In conclusion, MTRR A66G and C524T polymorphisms are associated with increased risk of CHDs.

Socioeconomic status and prevalence of congenital heart defects: does universal access to health care system eliminate the gap?

BACKGROUND

A twofold increase in the prevalence of congenital heart defects (CHDs) has been reported since the early 1970s with higher rates among children from low socioeconomic status (SES). This increase and the observed SES gap are postulated to be reflective of higher ascertainment, especially increased use of ultrasound and echography. The purpose of this study was to examine if trends over time in the prevalence of CHD were the same for high and low SES groups.

METHODS

Using the child's health number as a unique identifier and through record linkage, children born in Ontario between 1994 and 2007 were followed for the diagnosis of CHD. Using postal codes and census information, SES quintiles were assigned to each child. We used adjusted rates and used multivariate models to compare trends in the prevalence rate among children born in different SES groups.

RESULTS

Children born in low SES areas (23% of all births) had significantly higher rates of CHDs (rate ratio = 1.20; 95% confidence interval [CI] = 1.15-1.24). While prevalence of nonsevere CHDs declined in all SES groups since 2000, severe CHDs, especially atrial septal defects were on the rise during the study period.

DISCUSSION

It is assumed that increased ascertainment is responsible for observed increase in the prevalence of CHD, especially minor defects. While the trend and pattern over time changed for severe and nonsevere CHDs, the SES gap remained consistent during the study period. Our results indicate that even free and universal access to a health care system does not eliminate the SES gap observed in the prevalence of CHD.

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.

MTHFR 677C->T genotype is associated with folate and homocysteine concentrations in a large, population-based, double-blind trial of folic acid supplementation

BACKGROUND

The methylenetetrahydrofolate reductase (MTHFR) genotype is associated with modification of disease and risk of neural tube defects. Plasma and red blood cell (RBC) folate and plasma homocysteine concentrations change in response to daily intakes of folic acid supplements, but no large-scale or population-based randomized trials have examined whether the MTHFR genotype modifies the observed response.

OBJECTIVE

We sought to determine whether the MTHFR 677C→T genotype modifies the response to folic acid supplementation during and 3 mo after discontinuation of supplementation.

DESIGN

Northern Chinese women of childbearing age were enrolled in a 6-mo supplementation trial of different folic acid doses: 100, 400, and 4000 μg/d and 4000 μg/wk. Plasma and RBC folate and plasma homocysteine concentrations were measured at baseline; after 1, 3, and 6 mo of supplementation; and 3 mo after discontinuation of supplementation. MTHFR genotyping was performed to identify a C→T mutation at position 677 (n = 932).

RESULTS

Plasma and RBC folate and homocysteine concentrations were associated with MTHFR genotype throughout the supplementation trial, regardless of folic acid dose. MTHFR TT was associated with lower folate concentrations, and the trend of TT < CC was maintained at even the highest doses. Folic acid doses of 100 μg/d or 4000 μg/wk did not reduce high homocysteine concentrations in those with the MTHFR TT genotype.

CONCLUSION

MTHFR genotype was an independent predictor of plasma and RBC folate and plasma homocysteine concentrations and did not have a significant interaction with folic acid dose during supplementation. This trial was registered at clinicaltrials.gov as NCT00207558.

A maternal dietary pattern characterised by fish and seafood in association with the risk of congenital heart defects in the offspring

OBJECTIVE

To identify maternal dietary patterns related to biomarkers of methylation and to investigate associations between these dietary patterns and the risk of congenital heart defects (CHDs) in the offspring.

DESIGN

Case-control study.

SETTING

Western part of the Netherlands, 2003-08.

POPULATION

One hundred and seventy-nine mothers of children with CHD and 231 mothers of children without a congenital malformation.

METHODS

Food intake was obtained by food frequency questionnaires. The reduced rank regression method was used to identify dietary patterns related to the biomarker concentrations of methylation in blood.

MAIN OUTCOME MEASURES

Dietary patterns, vitamin B and homocysteine concentrations, biomarkers of methylation (S-adenosylmethionine [SAM] and S-adenosylhomocysteine [SAH]) and the risk of CHD estimated by odds ratios and 95% confidence intervals.

RESULTS

The one-carbon-poor dietary pattern, comprising a high intake of snacks, sugar-rich products and beverages, was associated with SAH (β = 0.92, P < 0.001). The one-carbon-rich dietary pattern with high fish and seafood intake was associated with SAM (β = 0.44, P < 0.001) and inversely with SAH (β =-0.08, P < 0.001). Strong adherence to this dietary pattern resulted in higher serum (P <0.05) and red blood cell (P < 0.01) folate and a reduced risk of CHD in offspring: odds ratio, 0.3 (95% confidence interval, 0.2-0.6).

CONCLUSIONS

The one-carbon-rich dietary pattern, characterised by the high intake of fish and seafood, is associated with a reduced risk of CHD. This finding warrants further investigation in a randomised intervention trial.

Association between selected folate pathway polymorphisms and nonsyndromic limb reduction defects: a case-parental analysis

Inadequate folate status resulting from either genetic variation or nutritional deficiencies has been associated with an increased risk of congenital malformations including orofacial clefting, limb, cardiac and neural tube defects. Few epidemiological studies have examined the association between limb reduction defects (LRDs) and folate-related genetic polymorphisms other than MTHFR 677C→T. We conducted a case-parental analysis of 148 families who participated in the National Birth Defects Prevention Study to examine the association between nonsyndromic transverse and longitudinal LRDs with five single nucleotide polymorphisms (SNPs) in genes encoding enzymes in folate and methionine pathways. Log-linear Poisson regression, adapted for analysis of case-parental data assuming an additive genetic model, was used to estimate genetic relative risks and 95% confidence intervals for the association between LRDs and each SNP. Among women who did not take multivitamin supplements, the MTHFR 677T variant acts via the offspring's genome to increase the risk of LRDs. No association between LRDs and any fetal SNP was found among women who used multivitamin supplements. These results suggest the possibility that initiating folic acid supplementation prior to pregnancy may reduce the risk of having a LRD-affected pregnancy, especially in women whose offspring inherit one or two copies of the MTHFR 677T variant.

General maternal medication use, folic acid, the MDR1 C3435T polymorphism, and the risk of a child with a congenital heart defect

OBJECTIVE

We sought to investigate maternal and child functional MDR1 C3435T polymorphism, periconception medication, folic acid use, and the risk of a congenital heart defect (CHD) in the offspring.

STUDY DESIGN

MDR1 3435C>T genotyping was performed in 283 case triads (mother, father, child) and 308 control triads. Information on periconception medication and folic acid use was obtained through questionnaires.

RESULTS

Mothers with MDR1 3435CT/TT genotype and using medication showed a significant association with the risk of a child with CHD (odds ratio [OR], 2.4; 95% confidence interval [CI], 1.3-4.3) compared to mothers with MDR1 3435CC genotype not using medication. This risk increased without folic acid use (OR, 2.8; 95% CI, 1.2-6.4), and decreased in folic acid users (OR, 1.7; 95% CI, 0.8-3.7). Children carrying the MDR1 3435CT/TT genotype and periconceptionally exposed to medication without folic acid did not show significant risks.

CONCLUSION

Mothers carrying the MDR1 3435T allele, using medication without folic acid, are at nearly 3-fold increased risk for CHD in the offspring.

Congenital heart defects and biomarkers of methylation in children: a case-control study

BACKGROUND

Derangements in the maternal methylation pathway, expressed by global hypomethylation and hyperhomocysteinemia, are associated with the risk of having a child with a congenital heart defect (CHD). It is not known whether periconception exposure to these metabolic derangements contributes to chromosome segregation and metabolic programming of this pathway in the foetus.

DESIGN

In a Dutch population-based case-control study of 143 children with CHD and 186 healthy children, we investigated S-adenosylmethionine (SAM), S-adenosylhomocysteine (SAH), total homocysteine (tHcy), the vitamins folate and B12 and the functional single nucleotide polymorphisms in the folate gene MTHFR 677C>T and 1298A>C. Comparisons were made between cases and controls adjusting for age, medication, vitamin use and CHD family history.

RESULTS

In the overall CHD group, the median concentrations of SAM (P = 0·011), folate in serum (P = 0·021) and RBC (P = 0·030) were significantly higher than in the controls. Subgroup analysis showed that this was mainly attributable to complex CHD with higher SAM (P < 0·001), SAH (P = 0·012) and serum folate (P = 0·010) independent of carriership of MTHFR polymorphisms. Highest concentrations of SAM, SAH and folate RBC were observed in complex syndromic CHD. The subgroup of children with Down syndrome, however, showed significantly higher SAH (P = 0·037) and significantly lower SAM:SAH ratio (P = 0·034) compared with other complex CHD, suggesting a state of global hypomethylation.

CONCLUSION

High concentrations of methylation biomarkers in very young children are associated with complex CHD. Down syndrome and CHD may be associated with a global hypomethylation status, which has to be confirmed in tissues and global DNA methylation in future studies.

Variation in folate pathway genes contributes to risk of congenital heart defects among individuals with Down syndrome

Cardiac abnormalities are one of the most common congenital defects observed in individuals with Down syndrome. Considerable research has implicated both folate deficiency and genetic variation in folate pathway genes with birth defects, including both congenital heart defects (CHD) and Down syndrome (DS). Here, we test variation in folate pathway genes for a role in the major DS-associated CHD atrioventricular septal defect (AVSD). In a group of 121 case families (mother, father, and proband with DS and AVSD) and 122 control families (mother, father, and proband with DS and no CHD), tag SNPs were genotyped in and around five folate pathway genes: 5,10-methylenetetrahyrdofolate reductase (MTHFR), methionine synthase (MTR), methionine synthase reductase (MTRR), cystathionine beta-synthase (CBS), and the reduced folate carrier (SLC19A1, RFC1). SLC19A1 was found to be associated with AVSD using a multilocus allele-sharing test. Individual SNP tests also showed nominally significant associations with odds ratios of between 1.34 and 3.78, depending on the SNP and genetic model. Interestingly, all marginally significant SNPs in SLC19A1 are in strong linkage disequilibrium (r(2)> or = 0.8) with the nonsynonymous coding SNP rs1051266 (c.80A>G), which has previously been associated with nonsyndromic cases of CHD. In addition to SLC19A1, the known functional polymorphism MTHFR c.1298A was over-transmitted to cases with AVSD (P=0.05) and under-transmitted to controls (P=0.02). We conclude, therefore, that disruption of the folate pathway contributes to the incidence of AVSD among individuals with DS.