Interactions between genetic variants involved in the folate metabolic pathway and serum lipid, homocysteine levels on the risk of recurrent spontaneous abortion

MTHFR gene polymorphisms in diabetes mellitus

The methylenetetrahydrofolate reductase (MTHFR), methionine synthase (MTR), and methionine synthase reductase (MTRR) are three regulatory enzymes in the folic acid (FA) cycle play a critical role in the balance of methionine and homocysteine. MTHFR and MTRR gene polymorphisms affect the biochemical activities of enzymes, impairing the remethylation of homocysteine to methionine. In 1972, severe MTHFR deficiency resulting in homocystinuria was first reported, suggesting MTHFR involvement in the disease. MTHFR C677T polymorphism can independently increase the risk of high homocysteine (HHcy) in plasma. Elevation of homocysteine levels could increase the risk of microvascular damage, thrombosis, heart disease, etc. Vascular complications were regarded as a leading major cause of diabetes mortality, and disability increases individual health and economic burden. Diabetes mellitus (DM) is a chronic inflammatory disease, and conventional medications do not provide a complete cure for diabetes. It was essential to identify other risk factors for the intervention and prevention of diabetes. MTHFR gene polymorphism is an emerging risk factor in diabetes. Recent studies have shown that polymorphisms of the MTHFR gene play a significant role in the pathophysiology of diabetes, including inflammation and insulin resistance. This review summarizes the association between MTHER gene polymorphism and diabetes.

Docosahexaenoic acid, eicosapentaenoic acid, arachidonic acid, and neural tube defects in Tunisian population

OBJECTIVE

To determine the effect of maternal status in (plasma and red blood cell) folate, vitamin B12, homocysteine, and vitamin D, as well as their interaction with MTHFR (C677T and A1298C) and MTRR A66G polymorphisms, on maternal plasma docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and arachidonic acid (ARA) levels and the risk of neural tube defects (NTDs).

METHODS

ARA, EPA, and DHA composition was assessed using capillary gas chromatography.

RESULTS

ARA and DHA levels were higher in controls than in case mothers for low plasma folate status. For low red blood cell folate status, DHA levels were higher in controls than in case mothers. For high homocysteine levels, ARA and DHA levels were higher in controls than in case mothers. NTD mothers had lower EPA and DHA levels for low vitamin B12 levels. NTD mothers had lower DHA levels for low vitamin D levels. For low plasma folate status, DHA levels in the MTHFR C677T gene and ARA and EPA levels in MTHFR A1298C gene were different among the three genotypes in case mothers. DHA levels in the MTHFR C677T gene were different among the three genotypes in case mothers for both low and high homocysteine levels. For low vitamin B12 levels, ARA and DHA levels were different among the three genotypes of the MTHFR C677T gene in case mothers. In the MTHFR C677T gene, ARA and DHA levels were different among the three genotypes in case mothers for low vitamin D levels.

CONCLUSIONS

More advanced research is required to verify a suitable biochemical parameter status in relation to the genotypes in pregnant women.

Association of MTHFR (C677T, A1298C) and MTRR A66G polymorphisms with fatty acids profile and risk of neural tube defects

OBJECTIVE

This study aims to determine if 5,10-methylenetetrahydrofolate reductase (MTHFR C677T and A1298C) and methionine synthase reductase (MTRR A66G) gene polymorphisms were associated with fatty acid (FA) levels in mothers of fetuses with neural tube defects (NTDs) and whether these associations were modified by environmental factors.

METHODS

Plasma FA composition was assessed using capillary gas chromatography. Concentrations of studied FA were compared between 42 mothers of NTDs fetuses and 30 controls as a function of each polymorphism by the Kruskal-Wallis nonparametric test.

RESULTS

In MTHFR gene C677T polymorphism, cases with (CT + TT) genotype had lower monounsaturated FAs (MUFA) and omega-3 polyunsaturated FA (n-3 PUFA) levels, but higher omega-6 polyunsaturated FAs (n-6 PUFA) and omega-6 polyunsaturated FAs: omega-3 polyunsaturated FAs (n-6:n-3) ratio levels. In MTRR gene A66G polymorphism, cases with (AG + GG) genotype had lower MUFA levels, but higher PUFA and n-6 PUFA levels. Controls with (AG + GG) genotype had lower n-6 PUFA levels. In MTHFR gene C677T polymorphism, cases with smoking spouses and (CT + TT) genotype had lower MUFA and n-3 PUFA levels, but higher PUFA, n-6 PUFA, and n-6:n-3 ratio levels. Cases with (CT + TT) genotype and who used sauna during pregnancy had lower n-3 PUFA levels. In MTRR gene A66G polymorphism, cases with (AG + GG) genotype and who used sauna during pregnancy had higher PUFA and n-6 PUFA levels.

CONCLUSIONS

Further research is required to clarify the association of FA metabolism and (MTHFR, MTRR) polymorphisms with NTDs.

HNRNPC mediated m6A methylation of 5-methyltetrahydrofolate-homocysteine methyltransferase and involved in the occurrence of RSA

N6-methyladenosine methylated modification has been shown to play roles in recurrent spontaneous abortion. We aimed to explore role of heterogeneous nuclear ribonucleoprotein C in the occurrence of recurrent spontaneous abortion. We collected embryonic villous tissues from 3 patients with recurrent spontaneous abortion (RSA group) and 3 normal control pregnancy patients. Methylated RNA immunoprecipitation sequencing, RNA sequencing, methylated RNA immunoprecipitation quantitative PCR were conducted to detect the differentially expressed m6A methylation modification gene and regulatory gene in patients with recurrent spontaneous abortion. Methylated RNA immunoprecipitation sequencing and RNA sequencing results showed that the mRNA expression level of heterogeneous nuclear ribonucleoprotein C significantly decreased in RSA group and mRNA expression level of 5-methyltetrahydrofolate-homocysteine methyltransferase increased. Real-time quantitative PCR confirmed the differential expression of heterogeneous nuclear ribonucleoprotein C and 5-methyltetrahydrofolate-homocysteine methyltransferase. Methylated RNA immunoprecipitation quantitative PCR result showed that mRNA m6A modification level of 5-methyltetrahydrofolate-homocysteine methyltransferase decreased in RSA group. The results of western blotting, real-time quantitative PCR, immunofluorescence, matrigel invasion and wound healing assays indicated that heterogeneous nuclear ribonucleoprotein C might regulate the expression of 5-methyltetrahydrofolate-homocysteine methyltransferase by mediating m6A modification, thereby reducing the proliferation and migration of trophoblast cell line, ultimately leading to the occurrence of recurrent spontaneous abortion.

Thrombophilic gene polymorphisms and recurrent pregnancy loss: a systematic review and meta-analysis

PURPOSE

Recurrent pregnancy loss (RPL) is affecting 1-4% of women who conceive approximately, and no cause could be found in more than 50% of women suffering from RPL. Inherited thrombophilias have got increasing attention in women with unexplained RPL, so we aim to explore the relationship among these most common thrombophilic polymorphisms and RPL through a literature review and meta-analysis.

METHODS

Observational studies from PubMed, Embase, Cochrane, and Web of Science from 1997 to 7 April 2022 were searched. For each genetic variant, a fixed or random-effect model was used according to the heterogeneity test to calculate pooled ORs and 95% CIs for both dominant and recessive genetic models. Egger's line regression test was used to assess publication bias. The quality of the included articles was assessed by the Newcastle Ottawa scale.

RESULTS

A total of 124 articles comprising 17,278 RPL patients and 16,021 controls were included. Results showed that hyperhomocysteinemia (MTHFR) C677T (dominant model: OR, 1.43; 95% CI, 1.25-1.64; recessive model: OR, 1.60; 95% CI, 1.36-1.87), MTHFR A1298C (dominant model: OR, 1.66; 95% CI, 1.26-2.18; recessive model: OR, 1.79; 95% CI, 1.42-2.26), PAI-1 4G/5G (dominant model: OR, 1.67; 95% CI, 1.36-2.06; recessive model: OR, 1.80; 95% CI, 1.39-2.32), angiotensin-converting enzyme I/D (OR, 1.23; 95% CI, 1.00-1.53), Factor XIII V34L (OR, 1.38; 95% CI, 1.02-1.87), and β-fibrinogen-455G/A (OR, 1.60; 95% CI, 1.02-2.51) were significantly associated with RPL.

CONCLUSION

This study provides potentially useful clinical markers to evaluate the risk of RPL or to help unexplained RPL patients identify possible causes, which may allow for targeted treatment.

Insulin resistance in women with recurrent miscarriage: a systematic review and meta-analysis

PURPOSE

This review aimed to investigate the association of insulin resistance (IR) in women with recurrent pregnancy loss compared to women with normal pregnancy history.

METHODS

PubMed, EMBASE, the Web of Science and Google Scholar databases were accessed to collect published observational studies that compared IR of recurrent pregnancy loss women with healthy women until the 6^th of October 2022. Outcomes assessed in this review and meta-analysis included fasting blood glucose, fasting plasma insulin, homeostasis model assessment for IR, glucose to insulin ratio. Mean differences, odds ratios with 95% confidence interval were pooled using the fixed or random effect models. Sensitivity analyses were performed to validate the robustness of the results. Review Manager version 5.4.1 and Stata version 8.0 were used.

RESULTS

A total of nineteen studies involving 4453 individuals were included. Recurrent pregnancy loss patients presented significantly higher fasting blood glucose, fasting plasma insulin, homeostasis model assessment for IR, and lower glucose to insulin ratios. Additionally, recurrent pregnancy loss patients had higher rates of IR as defined by abnormal fasting plasma insulin, homeostasis model assessment for IR, and glucose to insulin ratio. Sensitivity analyses validated the robustness of the results.

CONCLUSION

In the current review, we show that recurrent pregnancy loss is associated with a higher degree of IR and highlight the importance of screening and treatment of IR.

Associations of Two Common Polymorphisms in MTHFR Gene with Blood Lipids and Therapeutic Efficacy of Simvastatin

BACKGROUND AND PURPOSE

Cardio-cerebrovascular disease is an important public health challenge worldwide, and its complex etiology has not been elucidated fully. The study was to investigate the relationship between two common polymorphisms C677T and A1298C in the methylenetetrahydrofolate reductase (MTHFR) gene, baseline lipids and the lipid-lowering efficacy of simvastatin in a Chinese hyperlipidemic population.

METHODS

All participants were recruited from Anhui, China. By the extreme sampling method, we selected subjects with low response (n=108) and high response (n=106) based on their adjusted lipid-lowering response to simvastatin administrated for 8 consecutive weeks. Both MTHFR C677T and A1298C loci were genotyped by MALDI-TOF MS platform. Serum triglyceride (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) levels were measured at baseline and after 8 weeks of oral 20 mg/d tablet of simvastatin.

RESULTS

Patients with the 677TT genotype had significantly higher baseline TC, HDL-C, and change in HDL-C (ΔHDL-C) levels after treatment than those with 677CC+CT genotypes (β = 0.207, P = 0.045; β = 0.182, P = 0.026; and β = 0.16, P = 0.002, respectively). Patients with 1298AC+CC genotypes had significantly higher baseline LDL-C and change in LDL-C (ΔLDL-C) levels (β = 0.276, P =0.043; β = 0.359, P = 0.025, respectively) than those with 1298AA genotype. We found statistical interactions between the two SNPs in association with baseline HDL-C (P for interaction = 0.034), TC (P for interaction = 0.069), and TG (P for interaction = 0.034). Baseline TC (P = 0.027) and HDL-C (P = 0.046) and change in HDL-C (P = 0.019) were different among those with the MTHFR A-T haplotype compared with A-C.

CONCLUSIONS

Our major findings suggest that both MTHFR C677T and A1298C polymorphisms could be important genetic determinants of lipid traits and drug efficacy of simvastatin. This will contribute to a better understanding of strategies for personalized medication in Chinese patients with dyslipidemia.

Hyperhomocysteinemia and low vitamin B12 are associated with the risk of early pregnancy loss: A clinical study and meta-analyses

One-carbon metabolism is crucial for the maintenance of healthy pregnancy and alterations in this pathway have been associated with various pregnancy-related complications. Therefore, the present study was conducted to test the hypothesis that the altered folic acid, vitamin B12 and homocysteine levels are associated with the risk of early pregnancy loss (EPL). Plasma folic acid, vitamin B12 and homocysteine levels were analyzed in 83 females with EPL and 70 healthy pregnant females in their first trimester. Further, meta-analyses of folic acid, vitamin B12 and homocysteine were also performed involving various eligible studies. Results from our case-control study and meta-analysis showed that folic acid deficiency is not associated with the risk of EPL. On the other hand, low vitamin B12 and hyperhomocysteinemia were individually found to be significant risk factors for EPL in the present study (P < .01, P < .05, respectively) and meta-analysis as well (P < .001, P < .05, respectively). Vitamin B12 deficiency in combination with hyperhomocysteinemia was a more serious risk factor for EPL (Odds Ratio = 4.98, P = 0.002). Therefore, we conclude that vitamin B12 deficiency and elevated homocysteine levels are independent risk factors for EPL, and of higher risk when combined. The assessment of vitamin B12 and homocysteine levels may serve as a good screening marker for EPL risk.

A Novel Review of Homocysteine and Pregnancy Complications

Homocysteine (Hct) is a substance produced in the metabolism of methionine. It is an essential type of amino acid gained from the daily diet. Methylenetetrahydrofolate reductase (MTHFR) gene mutation is related to elevated total homocysteine (tHct) expressions, in particular, among women with low folate intake. Hyperhomocysteinemia (HHct) is caused by numerous factors, such as genetic defects, lack of folic acid, vitamin B₆ and B₁₂ deficiency, hypothyroidism, drugs, aging, and renal dysfunction. Increased Hct in peripheral blood may lead to vascular illnesses, coronary artery dysfunction, atherosclerotic changes, and embolic diseases. Compared to nonpregnant women, the Hct level is lower in normal pregnancies. Recent studies have reported that HHct was associated with numerous pregnancy complications, including recurrent pregnancy loss (RPL), preeclampsia (PE), preterm delivery, placental abruption, fetal growth restriction (FGR), and gestational diabetes mellitus (GDM). Besides, it was discovered that neonatal birth weight and maternal Hct levels were negatively correlated. However, a number of these findings lack consistency. In this review, we summarized the metabolic process of Hct in the human body, the levels of Hct in different stages of normal pregnancy reported in previous studies, and the relationship between Hct and pregnancy complications. The work done is helpful for obstetricians to improve the likelihood of a positive outcome during pregnancy complications. Reducing the Hct level with a high dosage of folic acid supplements during the next pregnancy could be helpful for females who have suffered pregnancy complications due to HHct.

The association between 5, 10 - methylenetetrahydrofolate reductase and the risk of unexplained recurrent pregnancy loss in China: A Meta-analysis

BACKGROUD

To analyze the correlation between gene polymorphisms of 5,10- methylenetetrahydrofolate reductase (MTHFR) and risk of unexplained recurrent pregnancy loss (URPL) in Chinese women.

METHODS

Eligible studies were searched in Pubmed, Embase, Web of Science, Wanfang, and China National Knowledge Infrastructure (CNKI) databases. Established inclusion criteria were used to screening articles, subsequently evaluate the quality of the included studies, Stata 16.0 PM and RevMan 5.3 software were conducted for meta-analysis. The pooled odds ratio (OR) with 95% confidence interval (CI) was determined to assess the relationship between MTHFR and risk of URPL in Chinese women.

RESULTS

For MTHFR C677T, fifty studies were included, involving 6677 URPL cases and 8111 controls. The overall results showed that MTHFR C677T was significantly correlated with URPL risk, especially in the homozygous model (TT vs CC; OR 3.06; 95% CI 2.56-3.66). For MTHFR A1298C, twenty-first studies were included, involving 3439 URPL cases and 3155 controls. The results showed that MTHFR A1298C was also significantly correlated with URPL risk in recessive (CC vs AC + AA; OR 1.55; 95% CI 1.25-1.93) and homozygous (CC vs AA; OR 1.53; 95% CI 1.22-1.91) models. In addition, sub-group results showed that no significant difference between north and south China populations in the MTHFR gene polymorphisms and URPL risk. Of note, the patients carrying MTHFR C677T and MTHFR A1298C joint mutants had no synergistic effect (OR 2.71; 95% CI 0.84-8.70) on the occurrence of URPL compared with the wild-type homozygous genotype (MTHFR 677CC/ MTHFR 1298AA).

CONCLUSION

Studies included in this meta-analysis suggested that MTHFR 677T allele and 677TT genotype and MTHFR 1298CC genotype were both associated with URPL; testing MTHFR C677T gene polymorphism was a more appropriate target compared with other mutations in the prediction of URPL.

Hypermethylation of dihydrofolate reductase promoter increases the risk of hypertension in Chinese

Background:

DNA methylation was considered to play an important role in hypertension. However, the direct association between dihydrofolate reductase (DHFR) promoter methylation and hypertension remains unclear. We thus aimed to investigate the relationship between DNA methylation of DHFR promoter and hypertension.

Materials and Methods:

A total of 371 hypertensive patients (diastolic blood pressure ≥90 mmHg and/or systolic blood pressure ≥140 mmHg or a history of antihypertensive treatment) and 320 age- and sex-matched healthy controls from the Hypertension Management Information System in Nanshan Community Health Service Centers were included in this case–control study. Quantitative methylation-specific polymerase chain reaction was used to measure the level of DHFR promoter methylation, which was presented as the percentage of methylated reference (PMR). A multivariate logistic regression model was used to explore the risk of DHFR promoter methylation.

Results:

Our results indicated that the level of DHFR promoter methylation was higher in hypertensive patients (median PMR, 34.32%; interquartile range, 11.34–119.60) than in healthy controls (median PMR, 18.45%; interquartile range, 8.16–35.40) (P < 0.001). Multivariable analysis showed that the risk of DHFR promoter hypermethylation was significantly higher in hypertensive patients than in healthy controls (odds ratio = 3.94, 95% confidence interval = 2.56–6.02, P < 0.001). Furthermore, hypermethylation was positively associated with sex, high blood homocysteine levels, and alcohol drinking. In particular, the area under the receiver operating characteristic curve was 0.688 (0.585–0.668) for the male hypertensive patients, suggesting the potential diagnostic value of DHFR promoter methylation in male hypertension.

Conclusion:

Our results demonstrated that DHFR promoter hypermethylation is positively associated with the risk of hypertension in Chinese.

Systemic risk factors correlated with hyperhomocysteinemia for specific MTHFR C677T genotypes and sex in the Chinese population

Background

Methyltetrahydrofolate reductase (MTHFR) is a main regulatory enzyme in homocysteine (Hcy) metabolism. A common C677T mutation in the MTHFR gene results in decreased enzyme activity, which contributes to hyperhomocysteinemia (HHcy). Previous studies have shown that HHcy was correlated with various systemic diseases, such as cardiovascular disease, stroke, cancer, renal failure and so on. However, we hypothesized that HHcy in different genotype and sex groups may have different risk factors, which would lead to various pathologic states. Therefore, the aim of this study was to explore systemic information that are correlated with HHcy for specific MTHFR C677T genotypes and sex, which might be useful for predicting and preventing systemic diseases.

Methods

This cross-sectional study was performed through November 2017 to July 2019. A total of 4,534 adults aged 20–75 y were selected for this study. All the participants underwent a physical examination, blood tests and MTHFRC677T genotyping. Multivariable linear regression was performed to explore the risk factors for HHcy for each sex and genotype.

Results

The average of Hcy level is higher in the TT genotype than CC and CT genotypes (P=0.000). Multiple linear regression analysis identified the common protective factors (folate and Vit B12) and risk factor (Cr) for HHcy. Besides that, each group has its specific risk factors—female-CT (age, SBP, and Hb), female-TT (SBP and AST); male-CC (age, AST and Hb), male-CT (age and AST) and male-TT (SBP, AST, and Hb).

Conclusions

HHcy was associated with different risk factors for each specific sex and genotype. These risk factors might be useful for predicting and preventing systemic diseases.