Genetic variations of MTHFR gene and their association with preterm birth in Korean women

Congenital septal defects in Karachi, Pakistan: an update of mutational screening by high-resolution melting (HRM) analysis of MTHFR C677T

BACKGROUND

Congenital heart defects (CHDs) are the heart structural malformations present at birth. Septal defects account for 40% of CHD, including atrial, ventricular and atrioventricular septal defects. In Pakistan, the prevalence of CHD is 3.4 in 1000, and a study estimated that 60,000 babies are born with CHD annually. Methylenetetrahydrofolate reductase (MTHFR), a chief enzyme, involved in the folate metabolism. The missense mutation, C677T (rs1801133), exists in MTHFR gene, results in a MTHFR thermolabile variant having low enzymatic activity. The study is aim to identify the MTHFR C677T variant association with septal defects.

METHODS

Samples of 194 CHD patients (age [Formula: see text]= 5.8 ± 5.1) and 50 normal echo controls (age [Formula: see text]= 6.0 ± 4.9), confirmed by pediatric consultant, were collected. Extracted DNA, quantified by agarose gel electrophoresis and nanodrop, was screened for SNP by high-resolution melting (HRM). Further, HRM results were confirmed using restriction analysis and sequencing. HRM was simply and precisely genotyped the samples within 3 h at low cost.

RESULTS

Genotypic data suggested that heterozygous mutant (CT) was frequent in congenital septal defect patients (0.26) which was higher than controls (0.143), p > 0.05. Mutant (TT) genotype was not found in this study.

CONCLUSIONS

rs1801133 has lack of significant association with congenital septal defects. The absence of TT genotype in this study suggesting the role of natural selection in targeted population. HRM is an easy, fast and next generation of PCR, which may be used for applied genomics.

The Role of Genetics in Preterm Birth

Preterm birth (PTB), defined as the birth of a child before 37 completed weeks gestation, affects approximately 11% of live births and is the leading cause of death in children under 5 years. PTB is a complex disease with multiple risk factors including genetic variation. Much research has aimed to establish the biological mechanisms underlying PTB often through identification of genetic markers for PTB risk. The objective of this review is to present a comprehensive and updated summary of the published data relating to the field of PTB genetics. A literature search in PubMed was conducted and English studies related to PTB genetics were included. Genetic studies have identified genes within inflammatory, immunological, tissue remodeling, endocrine, metabolic, and vascular pathways that may be involved in PTB. However, a substantial proportion of published data have been largely inconclusive and multiple studies had limited power to detect associations. On the contrary, a few large hypothesis-free approaches have identified and replicated multiple novel variants associated with PTB in different cohorts. Overall, attempts to predict PTB using single "-omics" datasets including genomic, transcriptomic, and epigenomic biomarkers have been mostly unsuccessful and have failed to translate to the clinical setting. Integration of data from multiple "-omics" datasets has yielded the most promising results.

Emerging role of toll-like receptors signaling and its regulators in preterm birth: a narrative review

INTRODUCTION

Despite intensive research, preterm birth (PTB) rates have not decreased significantly in recent years due to a lack of understanding of the underlying causes and insufficient treatment options for PTB. We are committed to finding promising biomarkers for the treatment of PTB.

METHODS

An extensive search of the literature was conducted with MEDLINE/PubMed, and in total, 151 studies were included and summarized in the present review.

RESULTS

Substantial evidence supports that the infection and/or inflammatory cascade associated with infection is an early event in PTB. Toll-like receptor (TLR) is a prominent pattern recognition receptor (PRR) found on both immune and non-immune cells, including fetal membrane cells. The activation of TLR downstream molecules, followed by TLR binding to its ligand, is critical for infection and inflammation, leading to the involvement of the TLR signaling pathway in PTB. TLR ligands are derived from microbial components and molecules released by damaged and dead cells. Particularly, TLR4 is an essential TLR because of its ability to recognize lipopolysaccharide (LPS). In this comprehensive overview, we discuss the role of TLR signaling in PTB, focus on numerous host-derived genetic and epigenetic regulators of the TLR signaling pathway, and cover ongoing research and prospective therapeutic options for treating PTB by inhibiting TLR signaling.

CONCLUSION

This is a critical topic because TLR-related molecules and mechanisms may enable obstetricians to better understand the physiological changes in PTB and develop new treatment and prevention strategies.

Association of MTHFR C677T polymorphism with risk of preterm birth in Indian mothers: a case–control study

Background

Since MTHFR is the key enzyme in folate metabolism, its reduction can lead to hyperhomocysteinemia, which can have a negative impact on pregnancy outcome. Moreover, MTHFR polymorphism has also been linked with oxidative stress and genotoxicity. Identifying its ethnicity-specific association can help to reduce the incidence of preterm birth (PTB). Material and methods: Age-matched preterm birth mothers (< 37 weeks) and full-term mothers (> 37 weeks) were carefully selected for the study. The polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) method was adopted to analyse MTHFR C677T polymorphism. Oxidative stress (OS) analysis was performed by measuring the levels of antioxidants (superoxide dismutase (SOD) and catalase (CAT)) and OS damage markers (lipid peroxidation (LPO), total protein). Genotoxicity was confirmed by the cytokinesis-block micronucleus cytome (CBMN-Cyt) assay. The statistical analysis was performed by Student’s t test, chi-square test, and one-way ANOVA. The relevant risk of premature delivery was represented by odds ratios (ORs) with 95% confidence intervals (95% CIs).

Results

The MTHFR polymorphism showed statistical significance for PTB outcome with CT and TT genotype frequencies at p < 0.01 and p < 0.05, respectively, between cases and controls. Within the PTB categories (extreme-, very-, moderate-PTB), TT genotype showed statistical significance at (p < 0.05), while CT genotype remained insignificant. Also, statistically high oxidative stress and DNA damage were observed in cases compared to controls for all genotypes. Furthermore, the T allele of the MTHFR gene was found to be linked with significantly increased OS and DNA damage on comparison within the groups.

Conclusions

This study confirms the MTHFR C677T polymorphism, oxidative stress, and genotoxicity biomarkers are associated with the PTB outcome. Analysis of these biomarkers during pregnancy can be of clinical significance.

Association of methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms with vitamin B12 deficiency and adverse perinatal outcomes among pregnant women of rural South India - a cross sectional longitudinal study

OBJECTIVES

To determine the occurrence of MTHFR gene polymorphisms and to study their association with vitamin B12 deficiency and adverse perinatal outcomes among a cohort of pregnant women from Kaniyambadi block, Tamil Nadu.

METHODS

120 consecutive pregnant women who were ≤20 weeks of gestational age from the 82 villages of Kaniyambadi block were recruited. Genomic DNA was isolated from the peripheral blood. PCR amplification was done followed by Sangers sequencing. Maternal and neonatal outcomes were extracted. Data was entered and analysed.

RESULTS

Our study found the occurrence of c.1298A>C variant in homozygous state in 14.2% and c.677C>T heterozygous state in 15%. Sanger sequencing of exon 7 identified another pathogenic variant c.1262G>T in heterozygous state in two of them. Both the mothers who harboured that variant had preterm delivery and one of them gave birth to a low-birth-weight neonate. In the entire cohort, 5% of the mothers had abortion, 4.2% of them had preterm delivery and 8.8% of the neonates had low birth weight. Presence of c.1298A>C or c.677C>T variants were associated with vitamin B12 deficiency [Pearson Chi squared value (χ²)=7.9 and 7.6 respectively; p=0.02]. Heterozygous pathogenic variant c.1262G>T was associated with both adverse maternal [χ²=11.5; p=0.001] and neonatal [χ²=18.3; p=0.009] outcomes.

CONCLUSIONS

MTHFR gene polymorphisms could be associated with several adverse perinatal outcomes and vitamin B12 deficiency. Further larger studies are needed to prove the pathogenicity of c.1262G>T variant on pregnancy.

Association of MTHFR 677C>T polymorphism with pregnancy outcomes in IVF/ICSI-ET recipients with adequate synthetic folic acid supplementation

Methylenetetrahydrofolate reductase (MTHFR) genetic polymorphism rs1801133 (677C>T) will decrease the utilization of folate. Folate deficiency and its resulting homocysteine (HCY) accumulation can impair female fertility. Folic acid (FA) supplementation is necessary in pregnant women who are undergoing in-vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) - embryo transfer (ET), and especially in women with MTHFR rs1801133 C-to-T mutations. At present, affordable and accessible synthetic FA is mainly used. However, some studies have suggested that 5-methylenetetrahydrofolate (5-MTHF), a type of active FA, may be more suitable for women with the MTHFR 677C>T polymorphism, since it is safer and more effective. This retrospective study aimed to evaluate whether the MTHFR rs1801133 gene polymorphism is related to the pregnancy outcomes of IVF/ICSI-ET recipients after sufficient supplementation with FA instead of 5-MTHF. Data on 692 women undergoing IVF/ICSI-ET and taking adequate FA were collected. Participant characteristics were compared using the Kruskal-Wallis test and Pearson chi-square test. Logistic regressions were used to calculate the odds ratio (OR) and 95% confidence interval (95% CI), after adjusting for age, BMI, method of fertilization, method of embryo transfer and number of embryos transferred. An additive model (T/T vs. C/C), dominant model (C/T + T/T vs. C/C), and recessive model (T/T vs. C/T + C/C) were evaluated. Analysis revealed that MTHFR rs1801133 in IVF/ICSI-ET women with adequate FA supplementation was not associated with the pregnancy rate but with age (OR = 0.91, 95% CI = 0.88, 0.94, P < 0.001) and BMI (OR = 0.95, 95% CI = 0.90, 0.997, P = 0.037). In 349 clinically pregnant women, no association of the MTHFR 677C>T with pregnancy outcomes was found in the additive model, dominant model, or recessive model. Of the 273 women with positive pregnancy outcomes, 34 had a preterm delivery. MTHFR 677C>T was not associated with a preterm delivery after adjusting for age and BMI. The current results indicated that MTHFR polymorphism rs1801133 was not related to the pregnancy rate or pregnancy outcomes of women undergoing IVF/ICSI-ET with adequate synthetic FA supplementation, suggesting that simple supplementation with less expensive and readily available FA, rather than expensive 5-MTHF, appeared to be appropriate.

Relationships between Maternal Gene Polymorphisms in One Carbon Metabolism and Adverse Pregnancy Outcomes: A Prospective Mother and Child Cohort Study in China

Background: To investigate relationships between five single nucleotide polymorphisms (SNP) in four maternal genes involved in one carbon metabolism and adverse pregnancy outcomes, including preterm birth (PTB), low birth weight (LBW), and small-for-gestational-age (SGA). Methods: This was a prospective mother and child cohort study in Wuqiang, China. Pregnant women (n = 939) were recruited from Jun 2016 to Oct 2018. Pregnancy outcomes (PTB, LBW, and SGA) were extracted from medical records and other information including age at childbearing, maternal education level, gravidity, parity, pre-pregnancy weight and height was collected by using a structured questionnaire. The maternal serum folate concentration was measured by using Abbott Architect i2000SR chemiluminescence analyzer in the first prenatal care visit. DNA genotyping of methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C, methionine synthase reductase (MTRR) A66G, methionine synthase (MTR) A2756G, and thymidylate synthetase (TYMS) rs3819102 was processed by Sequenom MassARRAY iPLEX Platform. Univariate and multivariate logistics regression analysis were used to test the relationships between 5 SNPs and PTB, LBW, SGA. Results: Totally, 849 dyads of women and infants were included in the analysis. The prevalence of PTD, LBW, and SGA were 3.76%, 1.58%, and 5.31% respectively. The homozygote frequencies of MTHFR C677T, MTHFR A1298C, MTRR A66G, MTR A2756G, and TYMS rs3819102 were 44.2%, 1.4%, 6.7%, 1.3%, and 3.2%, and the alt allele frequencies were 66.1%, 10.8%, 24.9%, 10.5%, and 20.5% respectively. The average serum folate concentration was 11.95 ng/mL and the folate deficiency rate was 0.47%. There were no significant associations between MTHFR C677T, MTHFR A1298C, MTRR A66G, MTR A2756G, TYMS rs3819102 alleles and PTD, LBW, SGA (p > 0.05). Conclusions: In the population with adequate folate status and low prevalence of adverse pregnancy outcomes, MTHFR C677T, MTHFR A1298C, MTRR A66G, MTR A2756G, TYMS rs3819102 alleles may not be related to PTD, LBW, and SGA.