Investigation of homocysteine-pathway-related variants in essential hypertension

Susceptibility to hypertension based on MTHFR rs1801133 single nucleotide polymorphism and MTHFR promoter methylation

Background

The aetio-pathologenesis of hypertension is multifactorial, encompassing genetic, epigenetic, and environmental factors. The combined effect of genetic and epigenetic changes on hypertension is not known. We evaluated the independent and interactive association of MTHFR rs1801133 single nucleotide polymorphism (SNP) and MTHFR promoter methylation with hypertension among Taiwanese adults.

Methods

We retrieved data including, MTHFR promoter methylation, MTHFR rs1801133 genotypes (CC, CT, and TT), basic demography, personal lifestyle habits, and disease history of 1,238 individuals from the Taiwan Biobank (TWB).

Results

The distributions of hypertension and MTHFR promoter methylation quartiles (β < 0.1338, 0.1338 ≤ β < 0.1385, 0.1385 ≤ β < 0.1423, and β ≥ 0.1423 corresponding to

Conclusion

Independently, rs1801133 TT was associated with a higher risk of hypertension, but methylation was not. Based on genotypes, lower methylation was dose-dependently associated with a higher risk of hypertension in individuals with the CC genotype. Our findings suggest that MTHFR rs1801133 and MTHFR promoter methylation could jointly influence hypertension susceptibility.

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Key Words

• MTHFR
• hypertension
• interaction
• promoter methylation
• rs1801133
• susceptibility

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MESH Headings Collapse

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Affiliation(s)

Ming-Huang Chiu Department of Pulmonology and Respiratory Care, Cathay General Hospital, Taipei City, Taiwan
Chia-Hsiu Chang Cardiovascular Center, Cathay General Hospital, Taipei City, Taiwan
Disline Manli Tantoh Department of Medical Imaging, Chung Shan Medical University Hospital, Taichung City, Taiwan Department of Public Health and Institute of Public Health, Chung Shan Medical University, Taichung City, Taiwan
Tsui-Wen Hsu Superintendent Office, Institute of Medicine, Cathay General Hospital, Taipei City, Taiwan
Chih-Hsuan Hsiao Department of Public Health and Institute of Public Health, Chung Shan Medical University, Taichung City, Taiwan
Ji-Han Zhong Department of Public Health and Institute of Public Health, Chung Shan Medical University, Taichung City, Taiwan
Yung-Po Liaw Department of Medical Imaging, Chung Shan Medical University Hospital, Taichung City, Taiwan Department of Public Health and Institute of Public Health, Chung Shan Medical University, Taichung City, Taiwan Institute of Medicine, Chung Shan Medical University, Taichung City, Taiwan

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Polymorphisms in the Renin-Angiotensin System and eNOS Glu298Asp Genes Are Associated with Increased Risk for Essential Hypertension in a Mexican Population

Background

Essential hypertension is the result of modifiable and genetic factors, and it is associated with increased risk for atherothrombosis. Some polymorphisms are associated with hypertensive disease. The objective was to analyze the association between eNOS Glu298Asp, MTHR C677T, AGT M235T, AGT T174M, and A1166C and ACE I/D polymorphisms with essential hypertension in the Mexican population.

Materials and Methods

In the present study, 224 patients with essential hypertension and 208 subjects without hypertension were included. The Glu298Asp, C677T, M235T, T174M, A1166C, and I/D polymorphisms were determined by the PCR-RFLP technique.

Results

We found statistical differences in age, gender, BMI, systolic and diastolic blood pressure, and total cholesterol between control and cases. However, we found no significant differences in HbA1c and triglycerides between both groups. We observed statistical significant differences in the genotype distribution of Glu298Asp (P = 0.001), I/D (P = 0.02), and M235T (P = 0.004) polymorphisms between both groups. In contrast, there were no differences related to distribution of genotypes of MTHFR C677T (P = 0.12), M174T (P = 0.46), and A1166C (P = 0.85) between cases and control groups.

Conclusions

We identified that Glu298Asp, I/D, and M234T polymorphisms represented an increased risk for essential hypertension and those genetic variants could contribute to the presence of endothelial dysfunction and vasopressor effect, hyperplasia, and hypertrophy of smooth muscle cells, which had an impact for hypertension. In contrast, we found no association between C677C, M174T, and A1166C polymorphisms and hypertensive disease. We suggested that those genetic variants could be identified in individuals with high risk to avoid hypertension and thrombotic disease.

APOE Genetic Polymorphism rs7412 T/T Genotype May Be a Risk Factor for Essential Hypertension among Hakka People in Southern China

Objective

One of the causes of hypertension is a genetic factor. The purpose of this study was to look at the relationship between apolipoprotein E (APOE) and methylenetetrahydrofolate reductase (MTHFR) polymorphisms and essential hypertension in the Hakka population.

Methods

The study included 2,850 patients with hypertension and 2,034 controls. APOE rs429358, rs7412, and MTHFR rs1801133 were genotyped by polymerase chain reaction (PCR)-microarray. The differences in these polymorphisms between the two groups were analyzed.

Results

The genotype and allele frequency of APOE and MTHFR polymorphisms did not differ significantly between hypertensive patients and controls. Patients with hypertension who were APOE rs429358C/C homozygous had higher TG, TC, LDL-C, and Apo-B levels, whereas patients with the T/T genotype had higher HDL-C levels. Patients with hypertension who were APOE rs7412T/T homozygous had higher TG and TC levels and lower LDL-C and Apo-B levels. Homocysteine (Hcy) levels in patients with MTHFR CC, CT, and TT genotypes were increased, while patients with the TT genotype and T allele had higher Hcy levels than those of patients with other genotypes and the C allele. The APOE rs7412T/T genotype in the co-dominant model (APOE rs7412T/T vs. C/C) (gender-, age-, smoking-, and drinking-adjusted OR 2.682, 95% CI, 1.072–6.710, P=0.035) was a significant risk factor for hypertension. The APOE rs429358 and MTHFR rs1801133 genotypes in co-dominant, dominant, and recessive models were not significant risk factors for hypertension.

Conclusions

It supports that APOE polymorphisms are related to hypertension in the Hakka population. Specifically, the APOE rs7412T/T genotype may be a risk factor for hypertension.

Methylenetetrahydrofolate Reductase Polymorphism (rs1801133) and the Risk of Hypertension among African Populations: A Narrative Synthesis of Literature

In this review, we have gathered and analyzed the available genetic evidence on the association between the methylenetetrahydrofolate reductase gene (MTHFR), rs1801133 and the risk of Hypertension (HTN) in African populations, which was further compared to the global data evidence. This review was reported following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol and Human Genome Epidemiology Network (HuGENet) guidelines. Literature was retrieved through major search databases, including PubMed, Scopus, Web of Science, and African Journal Online. We identified 64 potential studies, of which 4 studies were from the African continent and 60 studies were reported globally. Among the studies conducted in Africa, only two (n = 2) reported a significant association between the MTHFR (rs1801133) and the risk of developing HTN. Only one (n = 1) study population was purely composed of black Africans, while others were of other ethnicities. Among studies conducted in other continents (n = 60), forty-seven (n = 47) studies reported a positive association between MTHFR (rs1801133) and the risk of developing HTN, whereas the remaining studies (n = 14) did not show a significant association. Available literature suggests an apparent association between rs1801133 and HTN in global regions; however, such information is still scarce in Africa, especially in the black African population.

MTR, MTRR and CBS Gene Polymorphisms in Recurrent Miscarriages: A Case Control Study from North India

Background:

According to various epidemiological studies, the aetiology of recurrent miscarriages (RMs) is multifactorial. The goal of this study is to learn more about the link between genetic polymorphisms and RM.

Aim:

To evaluate the association of 5-Methytetrahydrofolate-Homocysteine Methyltransferase (MTR) A2756G, 5-Methytetrahydrofolate-Homocysteine Methyltransferase Reductase (MTRR) A66G and cystathionine beta-synthase (CBS) 844INS68 genetic polymorphisms with RM and also to understand the combined effect of the selected genotypes.

Study Setting and Design:

This was a hospital-based, case–control, observational study.

Materials and Methods:

A total of 516 participants were recruited in the present study, of which 200 RM cases and 258 controls were included in the present study. Fasting blood sample (~5ml) was drawn from all the participants and were screened for genetic polymorphisms of MTR A2756G, MTRR A66G and CBS 844INS68.

Statistical Analysis:

The frequency, odd's ratio and Hardy-Weinberg equilibrium were evaluated. SPSS (version 21.0) was used for the data analysis.

Results:

MTR A2756G genetic polymorphism was not associated with the risk of RM. The ancestral allele of MTRR A66G and the mutant allele of CBS 844INS68 was causing an increased risk of more than two folds for RM. CBS 844INS68 in combination with MTR A2756G was found to pose an increased risk of more than two folds for RM.

Conclusion:

Genetic polymorphisms particularly MTRR A66G and CBS 844INS68 seems to be elevating the risk and hence making women susceptible for RM.

Association of ALDH2 rs671 and MTHFR rs1801133 polymorphisms with hypertension among Hakka people in Southern China

Background

Genetic factors play an important role in susceptibility to hypertension. Herein, the association between acetaldehyde dehydrogenase 2 (ALDH2) and methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms and hypertension was analyzed among Hakka population in southern China.

Methods

A total of 3057 hypertensive patients and 2215 controls were enrolled. The ALDH2 rs671 and MTHFR rs1801133 genotyping were analyzed using gene chip. Relevant information and medical records of these subjects were collected.

Results

Hypertensive patients with ALDH2 rs671 G/A heterozygous had lower systolic blood pressure (SBP) than other genotypes (P < 0.001), while hypertensive patients with A allele had lower diastolic blood pressure (DBP) than patients with G allele (P < 0.001). The level of plasma homocysteine (Hcy) in patients with MTHFR CC, CT and TT genotypes showed an increasing trend (P < 0.001). The ALDH2 G/A genotype in the co-dominant model (adjusted OR 1.251, 95% CI 1.024–1.528, P = 0.028) and ALDH2 A/A genotype in the recessive model (adjusted OR 1.221, 95% CI 1.008–1.478, P = 0.041) were significant risk factors for the presence of hypertension. The MTHFR C/T genotype in the co-dominant model (adjusted OR 1.307, 95% CI 1.039–1.643, P = 0.022) and MTHFR C/T and T/T genotypes in the dominant model (adjusted OR 1.281, 95% CI 1.146–1.430, P < 0.001) were significant risk factors for the presence of hypertension. Further, logistic regression analysis showed that age, smoking, alcohol consumption, hyperhomocysteinemia, and high level of serum TG, Apo-A1, Apo-B were significant risks for hypertension.

Conclusions

In summary, ALDH2 rs671 G/A, A/A genotypes and MTHFR rs1801133 C/T, T/T genotypes may be risk factors for hypertension in this Chinese Hakka population.

Association of MTHFR Polymorphisms with H-Type Hypertension: A Systemic Review and Network Meta-Analysis of Diagnostic Test Accuracy

Purpose

An association between MTHFR polymorphisms and H-type hypertension (H-HTN) has been investigated by epidemiological studies, but results have been inconsistent. Thus, a systematic assessment of the association was performed based on a literature review and pooled analysis, to provide stronger evidence on the effects of single nucleotide polymorphisms on H-HTN risk.

Methods

Three investigators independently retrieved relevant studies in PubMed, Embase, Cochrane Library, China National Knowledge Infrastructure (CNKI), China Science and Technology Journal Database (VIP), Wanfang Database, and China Biomedical Literature Database (CBM). A fixed or random effects model was selected to calculate pooled odds ratio (OR) and 95% confidence intervals (CIs). A network meta-analysis of diagnostic test and Thakkinstian's algorithm were used to select the most appropriate genetic model, along with false-positive report probability (FPRP) for noteworthy associations. All data were processed using Stata 15.0 and Meta-Disc.

Results

A total of 14 studies involving 1759 cases and 1581 controls for MTHFR were included in our meta-analysis. In a direct meta-analysis, we found that MTHFR C667T rs1801133 significantly increased the risk of H-HTN susceptibility except for an overdominant model. However, MTHFR A1298C rs1801131 polymorphism had no significant correlation with H-HTN risk. Besides, MTHFR C667T rs1801133 is a potential diagnostic biomarker for estimating H-HTN risk. The results indicated that the dominant model was an optimal diagnosis model for excluding diseases, which could reduce a missed diagnosis rate and further improve the accuracy of disease diagnosis.

Conclusion

The present result suggests that MTHFR C667T rs1801133 polymorphism is associated with H-HTN risk and may act as a promising predictive biomarker for H-HTN risk. However, further well-designed studies are warranted to confirm these results.

Association Between MTHFR Polymorphisms and the Risk of Essential Hypertension: An Updated Meta-analysis

BACKGROUND

Since the 1990s, there have been a lot of research on single-nucleotide polymorphism (SNP) and different diseases, including many studies on 5,10-methylenetetrahydrofolate reductase (MTHFR) polymorphism and essential hypertension (EH). Nevertheless, their conclusions were controversial. So far, six previous meta-analyses discussed the internal relationship between the MTHFR polymorphism and EH, respectively. However, they did not evaluate the credibility of the positive associations. To build on previous meta-analyses, we updated the literature by including previously included papers as well as nine new articles, improved the inclusion criteria by also considering the quality of the papers, and applied new statistical techniques to assess the observed associations.

OBJECTIVES

This study aims to explore the degree of risk correlation between two MTHFR polymorphisms and EH.

METHODS

PubMed, EMBASE, the Cochrane Library, CNKI, and Wan Fang electronic databases were searched to identify relevant studies. We evaluated the relation between the MTHFR C677T (rs1801133) and A1298C (rs1801131) polymorphisms and EH by calculating the odds ratios (OR) as well as 95% confidence intervals (CI). Here we used subgroup analysis, sensitivity analysis, cumulative meta-analysis, assessment of publication bias, meta-regression meta, False-positive report probability (FPRP), Bayesian false discovery probability (BFDP), and Venice criterion.

RESULTS

Overall, harboring the variant of MTHFR C677T was associated with an increased risk of EH in the overall populations, East Asians, Southeast Asians, South Asians, Caucasians/Europeans, and Africans. After the sensitivity analysis, positive results were found only in the overall population (TT vs. CC: OR = 1.14, 95% CI: 1.00-1.30, P _h = 0.032, I ² = 39.8%; TT + TC vs. CC: OR = 1.15, 95% CI: 1.01-1.29, P _h = 0.040, I ² = 38.1%; T vs. C: OR = 1.14, 95% CI: 1.04-1.25, P _h = 0.005, I ² = 50.2%) and Asian population (TC vs. CC: OR = 1.14, 95% CI: 1.01-1.28, P _h = 0.265, I ² = 16.8%; TT + TC vs. CC: OR = 1.17, 95% CI: 1.04-1.30, P _h = 0.105, I ² = 32.9%; T vs. C: OR = 1.10, 95% CI: 1.02-1.19, P _h = 0.018, I ² = 48.6%). However, after further statistical assessment by FPRP, BFDP, and Venice criteria, the positive associations reported here could be deemed to be false-positives and present only weak evidence for a causal relationship. In addition, when we performed pooled analysis and sensitivity analysis on MTHFR A1298C; all the results were negative.

CONCLUSION

The positive relationships between MTHFR C677T and A1298C polymorphisms with the susceptibility to present with hypertension were not robust enough to withstand statistical interrogation by FPRP, BFDP, and Venice criteria. Therefore, these SNPs are probably not important in EH etiology.

Hyperhomocysteinemia: a trigger for complement-mediated TMA?

A 34-year-old man of North African descent was referred to the emergency department because of malignant hypertension (220/113 mmHg), acute visual disturbances and acute kidney failure (serum creatinine 14.0 mg/dL). Blood analysis was compatible with thrombotic microangiopathy (TMA). Kidney biopsy confirmed this diagnosis with histological changes including intimal edema, arteriolar thrombi, and severe tubulointerstitial damage. Fundoscopy showed hypertensive retinopathy stage IV. Subsequent biochemical screening revealed normal complement testing and a marked elevation in homocysteine concentration (161 µmol/L; normal value 7-15 µmol/L). Other secondary causes of TMA were excluded. Further genetic testing for cobalamin C (cblC) deficiency showed no pathogenic mutations in the MMACHC gene. However, a homozygous c.665C>T polymorphism (NM_005957.4) in the methylenetetrahydrofolate reductase (MTHFR) gene was found explaining the severe hyperhomocysteinemia due to reduced activity of MTHFR. Additional genetic testing for alternative complement pathway proteins showed mutations in the genes encoding factor H and factor B, both categorized as possibly pathogenic using mutation prediction software. This is the first described case of TMA in a patient with severe hyperhomocysteinemia caused by a genetic defect other than cblC. We postulate that endothelial damage due to hyperhomocysteinemia and hypertension could have triggered the TMA episode in this patient with two possible predisposing pathogenic mutations in the alternative complement pathway. Furthermore, our case demonstrates the need for complete full diagnostic testing in patients with TMA.

A comprehensive evaluation of association between homocysteine levels and single nucleotide polymorphisms with hypertension risk: A protocol of systematic review and network meta-analysis

BACKGROUND

According to the relevant reports that single nucleotide polymorphisms (SNPs) may contribute to change of homocysteine (HCY) levels and increase the risk of hypertension (HTN). During the inconsistent results, this meta-analysis purpose is systematically review and synthesized relevant data on HCY levels and SNPs in HTN.

METHODS

The systematic search database, from the following database to find out the association studies of SNPs and HTN publications up until March 2020 from the databases of PubMed, Embase, Web of Science, Cochrane Library, China National Knowledge Infrastructure (CNKI), the Chinese Science and Technology Periodical Database (VIP) and Wan fang databases, and Chinese Biomedical Literature Database (CBM). Network meta-analysis and Thakkinstian's algorithm were used to select the most appropriate genetic model, along with false positive report probability (FPRP) for noteworthy associations. All statistical analyses were calculated with STATA software (version 14.0; StataCorp, College Station, TX).

RESULTS

This meta-analysis will provide high-quality evidence to the effects of SNP on HTN and levels of HCY, and find between SNPs and HTN susceptibility on in all the genetic models, and choose the best one.

CONCLUSIONS

This meta-analysis will research which SNP is the most correlated with HTN risk.

REGISTRATION

INPLASY202050002.

Effects of methionine synthase and methionine synthase reductase polymorphisms on hypertension susceptibility

BACKGROUND

Polymorphisms of methylenetetrahydrofolate reductase (MTHFR) gene are strongly associated with hypertension incidence, although such association is inconsistent among ethnicities studied. However, effects of polymorphisms of other genes related to folate metabolism besides MTHFR on hypertension susceptibility are not well known yet.

OBJECTIVE

The aim of this study was to elucidate whether methionine synthase (MTR) 2756A>G and methionine synthase reductase (MTRR) 66A>G polymorphisms might be associated with risks of hypertension susceptibility in the Korean population.

METHODS

Genotyping of these two polymorphisms was performed for 232 hypertensive patients and 247 unrelated healthy controls using polymerase chain reaction-restriction fragment length polymorphism technique.

RESULTS

In the present study, mutations of MTR 2756A>G and MTRR 66A>G polymorphisms were associated with increased and decreased susceptibility to hypertension, respectively. Allele combinations from these two polymorphisms were also related to hypertension prevalence. When polymorphism data were stratified according to clinical components of hypertension, The G allele of MTR 2756A>G polymorphism was significantly associated with an increased risk of hypertension in subjects with BMI < 26.1 kg/m² (P = 0.004), WC < 87.2 in. (P = 0.021), FBG < 95.5 mg/dL (P = 0.011), triglyceride < 133.5 mg/dL (P = 0.034), and HDL-cholesterol < 52.2 mg/dL (P = 0.036). The G allele of MTRR 66A>G polymorphism was significantly associated with a decreased risk of hypertension in subjects with WC ≥ 87.2 in. (P = 0.029), FBG ≥ 95.5 mg/dL (P = 0.032) and triglyceride ≥ 133.5 mg/dL (P = 0.027).

CONCLUSION

MTR 2756A>G and MTRR 66A>G polymorphisms related to folate metabolism might be genetic markers for risk of hypertension in the Korean population.

Evidence on the causal link between homocysteine and hypertension from a meta-analysis of 40 173 individuals implementing Mendelian randomization

Numerous researchers have investigated the associations among methylenetetrahydrofolate reductase gene (MTHFR) C677T polymorphism, homocysteine (Hcy) concentration, and hypertension. However, the results are controversial. Thus, a meta-analysis implementing Mendelian randomization approach was conducted to examine the hypothesis that elevated Hcy concentration plausibly contributes to increased risk of hypertension. Based on several inclusion and exclusion criteria, eligible studies were selected to explore the correlation between MTHFR C677T and hypertension risk, MTHFR C677T and Hcy concentration in hypertension, and Hcy concentration and hypertension, and they were evaluated by odds ratios (ORs), effect size (ES), and standard mean difference with their corresponding 95% confidence intervals (95% CIs), respectively. Moreover, Mendelian randomization was implemented to evaluate the relationship between Hcy and hypertension. Consequently, 14 378 cases and 25 795 controls were involved in this study and the results showed that MTHFR C677T led to an elevated risk of hypertension (for T vs C: OR = 1.27, 95% CI = 1.17-1.37; for TT vs CC: OR = 1.53, 95% CI = 1.30-1.79). Additionally, in hypertensive subjects, the pooled Hcy concentration in individuals of TT genotype was 7.74 μmol/L (95% CI: 5.25-10.23) greater than that in individuals of CC genotype. Moreover, the pooled Hcy concentration in hypertensive was 0.69 μmol/L (95% CI: 0.50-0.87) greater than that in controls. The estimated causal OR associated with hypertension was 1.32 for 5 μmol/L Hcy increment. Via MTHFR C677T polymorphism, the findings in the present study demonstrated that there exists evidence on causal link between Hcy concentration and the risk of hypertension.

The relationship between Plasma Markers and Essential Hypertension in Middle-aged and Elderly Chinese Population: A Community Based Cross-sectional Study

Plasma markers have been continuously advocated as pointers to estimate the long-term risk of cardiovascular disease in the general population. We examined the relationship between plasma high-sensitivity C-reactive protein (hs-CRP), homocysteine (Hcy), high-sensitivity cardiac troponin T (hs-cTnT), N-terminal prohormone of brain natriuretic peptide (NT-proBNP), 25-Hydroxyvitamin D (25OHD), glycosylated hemoglobin A1c (HbA1c), and serum uric acid (SUA) levels and hypertension in middle and old aged population. A total of 2624 Chinese (62.02 ± 5.73 years old) were recruited into a population-based, cross-sectional study. Plasma hs-CRP, Hcy, HbA1c, and SUA levels were significantly higher in the hypertension group compared with control in the entire population and men (P = 0.05 for all). We observed a positive association between the highest quartiles of Hcy, NT-proBNP, HBA1c concentrations, and the prevalence of hypertension, OR (95% CI) = 1.48 (1.16–1.90), 1.62 (1.27–2.07) and 1.94 (1.49–2.52), respectively. The multivariable-adjusted OR of hypertension for the fourth versus the first quartile of homocysteine were 2.00 and 1.39 in men and women, respectively. In conclusion, our study found an independent and robust association between elevated Hcy, NT-ProBNP, and HBA1c levels and prevalence of hypertension in the middle-aged and elderly Chinese population. A follow-up study is necessary to endorse the observed association.

Associations of homocysteine status and homocysteine metabolism enzyme polymorphisms with hypertension and dyslipidemia in a Chinese hypertensive population

Background: Hypertension (HTN), dyslipidemia and hyperhomocysteinemia (HHcy) are risk factors for cardiovascular disease (CVD).Methods: Hypertensive Chinese subjects (n = 228) were enrolled. MTHFR C667T, MTHFR A1298C, MTR A2756G, and MTRR A66G genotypes were determined. Unconditional logistic regression was performed to determine the associations of serum Hcy status and genotypes with HTN and dyslipidemia.Results: The mean age of hypertensive adults was 65.53 ± 9.94 years, including 88 (38.6%) men and 140 (61.4%) women. Patients with MTHFR 667TT and MTRR GG carriers showed higher serum Hcy levels (P = 0.019 and 0.018, respectively), which is associated with higher serum triacylglycerols (TAG) and total cholesterol (TC) levels (P = 0.014 and 0.044, respectively) and a higher risk for hypertriglyceridemia (OR = 1.889, 95% CI: 1.105-3.229, P = 0.020). Compared with low Hcy and MTRR 66AA, those with high Hcy and 66AA or 66AG+GG showed higher odd\s of hypertriglyceridemia (MTRR 66AA+ high Hcy: OR: 2.692, 95% CI: 1.189-6.096, Pcombined = 0.018; MTRR 66AG/GG+ high Hcy: OR: 3.433, 95% CI: 1.517-7.772, Pcombined = 0.003, respectively). Patients with high Hcy and MTHFR 667CC, as well as those with low Hcy and 667CT+TT, showed lower odds of uncontrolled SBP (MTHFR 667CC+ high Hcy: OR: 0.338, 95% CI: 0.115-0.996, Pcombined = 0.049; MTHFR 667CT/TT+ low Hcy: OR: 0.421, 95% CI: 0.193-0.921, Pcombined = 0.030) compared to patients with low Hcy and MTHFR 667CC.Conclusions: Serum Hcy status and Hcy metabolism gene polymorphisms (MTHFR C667T and MTRR A66G) may have synergistic effects on the prevalence of HTN and dyslipidemia.

Association between plasma homocysteine and hypertension: Results from a cross-sectional and longitudinal analysis in Beijing's adult population from 2012 to 2017

Plasma homocysteine (Hcy) levels are associated with elevated blood pressure. However, the causal association between Hcy levels and the risk of hypertension remains ambiguous. Taking the study design effect into consideration, this study aimed to investigate this issue through a cross-sectional and longitudinal analysis. Data were obtained from the Beijing Health Management Cohort study, which conducted routine health check-ups from 2012 to 2017. Multivariate logistic regression was used for the cross-sectional analysis, and a quadratic inference function approach was performed for the longitudinal analysis. A total of 30 376 subjects (mean age = 50.0 years) were included in the cross-sectional analysis, and a subgroup of 3913 subjects without hypertension at baseline was included in the longitudinal analysis. After adjusting for potential confounders, the risk of hypertension increased with Hcy levels in the cross-sectional analysis using the traditional definition of hypertension (OR = 1.262, 95% CI: 1.155-1.378, Q2 vs Q1; OR = 1.458, 95% CI: 1.335-1.593, Q3 vs Q1; OR = 1.520, 95% CI: 1.388-1.664, Q4 vs Q1) and the 2017 hypertension definition (OR = 1.159, 95% CI: 1.067-1.259, Q2 vs Q1; OR = 1.328, 95% CI: 1.221-1.445, Q3 vs Q1; OR = 1.328, 95% CI: 1.217-1.449, Q4 vs Q1). The longitudinal analysis showed that hypertension risk increased in the third quartile of Hcy (OR = 1.268, 95% CI: 1.030-1.560, Q3 vs Q1). Elevated total plasma Hcy may be used as a predictive biomarker for hypertension. Attention should be paid to gender-specific mechanisms when issuing precise precautions.

A genome-wide association study of essential hypertension in an Australian population using a DNA pooling approach

Despite the success of genome-wide association studies (GWAS) in detecting genetic loci involved in complex traits, few susceptibility genes have been detected for essential hypertension (EH). We aimed to use pooled DNA GWAS approach to identify and validate novel genomic loci underlying EH susceptibility in an Australian case-control population. Blood samples and questionnaires detailing medical history, blood pressure, and prescribed medications were collected for 409 hypertensives and 409 age-, sex- and ethnicity-matched normotensive controls. Case and control DNA were pooled in quadruplicate and hybridized to Illumina 1 M-Duo arrays. Allele frequencies agreed with those reported in reference data and known EH association signals were represented in the top-ranked SNPs more frequently than expected by chance. Validation showed that pooled DNA GWAS gave reliable estimates of case and control allele frequencies. Although no markers reached Bonferroni-corrected genome-wide significance levels (5.0 × 10^-8), the top marker rs34870220 near ASGR1 approached significance (p = 4.32 × 10^-7), as did several candidate loci (p < 1 × 10^-6) on chromosomes 2, 4, 6, 9, 12, and 17. Four markers (located in or near genes NHSL1, NKFB1, GLI2, and LRRC10) from the top ten ranked SNPs were individually genotyped in pool samples and were tested for association between cases and controls using the χ ² test. Of these, rs1599961 (NFKB1) and rs12711538 (GLI2) showed significant difference between cases and controls (p < 0.01). Additionally, four top-ranking markers within NFKB1 were found to be in LD, suggesting a single strong association signal for this gene.

The relationship between MTHFR C677T gene polymorphism and essential hypertension in a sample of an Algerian population of Oran city

BACKGROUND

Many studies have investigated the role of 5,10-methylenetetrahydrofolate reductase (MTHFR) C677T gene polymorphism in essential hypertension (EH), but with conflicting results.

AIM

To determine the eventual association between 5,10-methylenetetrahydrofolate reductase (MTHFR) C677T gene polymorphism and hypertension in a sample of Algerian population from the Oran city.

METHODS

A case-control study has been performed in 154 subjects including 82 hypertensives defined as subjects with elevated systolic blood pressure SBD≥140mmHg and or sustained diastolic blood pressure DBP≥90mmHg, and 72 normotensive subjects. Polymerase chain reaction (PCR) combined with restrictive fragment length polymorphism (RFLP) was used to detect the MTHFR C677T variant.

RESULTS

We observe no significant differences between allelic and genotypic frequencies between cases and controls for C677T polymorphism (OR=1.51, 95% CI=0.89-2.56, P=0.13). Analyses adjusted for age, sex and body mass index improved the association level, though the association was still not significant (30% vs. 22%, OR=1.75, 95% CI=0.95-3.24, P=0.07).

CONCLUSION

This work showed that genetic polymorphism related to the MTHFR gene (C677T) is not associated with the risk of hypertension in this sample of Algerian population. Larger case-control samples are required to clearly assess the role of this genetic variant in EH.

Riboflavin status, MTHFR genotype and blood pressure: current evidence and implications for personalised nutrition

Clinical deficiency of the B-vitamin riboflavin (vitamin B2) is largely confined to developing countries; however accumulating evidence indicates that suboptimal riboflavin status is a widespread problem across the developed world. Few international data are available on riboflavin status as measured by the functional biomarker, erythrocyte glutathione reductase activation coefficient, considered to be the gold standard index. One important role of riboflavin in the form of flavin dinucleotide is as a co-factor for the folate-metabolising enzyme methylenetetrahydrofolate reductase (MTHFR). Homozygosity for the common C677T polymorphism in MTHFR, affecting over 10 % of the UK and Irish populations and up to 32 % of other populations worldwide, has been associated with an increased risk of CVD, and more recently with hypertension. This review will explore available studies reporting riboflavin status worldwide, the interaction of riboflavin with the MTHFR C677T polymorphism and the potential role of riboflavin in personalised nutrition. Evidence is accumulating for a novel role of riboflavin as an important modulator of blood pressure (BP) specifically in individuals with the MTHFR 677TT genotype, with results from a number of recent randomised controlled trials demonstrating that riboflavin supplementation can significantly reduce systolic BP by 5-13 mmHg in these genetically at risk adults. Studies are however required to investigate the BP-lowering effect of riboflavin in different populations and in response to doses higher than 1·6 mg/d. Furthermore, work focusing on the translation of this research to health professionals and patients is also required.

A quantitative proteomic approach for unveiling novel mechanisms associated with MeHg-induced toxicity: effects on the methylation cycle

Methylmercury (MeHg) is still a major threat for human health and the environment due to its extremely high toxicity that mainly affects the nervous system. Despite the great efforts made during the last few decades, the specific molecular mechanisms involved in MeHg-induced toxicity are still not completely unveiled. In this work we explored such mechanisms using neuroblastoma cells (Neuro-2a) and SILAC as a quantitative proteomic approach. We found that exposure of Neuro-2a cells to 2 mg L-1 MeHg for 8 h decreased the cell viability to 70% and caused significant changes in the morphology of the cells, specially regarding neurite development. Our proteomic results showed different proteins altered upon MeHg exposure that helped to identify pathways related to the toxicity exerted by MeHg. Specifically, we have found that MeHg affects the methylation cycle by inhibiting the expression of key enzymes including MTHFD1 and MTR. Moreover, we demonstrate that inhibition of MTHFD1 is not observed when exposing the cells to inorganic Hg and other heavy metals such as Pb or Cu. Thus, this work sets the stage for dissecting a specific molecular mechanism for MeHg-induced toxicity.

Association between methylenetetrahydrofolate reductase (MTHFR) C677T/A1298C polymorphisms and essential hypertension: a systematic review and meta-analysis

OBJECTIVE

Many studies have investigated the role of 5,10-methylenetetrahydrofolate reductase gene (MTHFR) C677T/A1298C polymorphisms in essential hypertension (EH), but results are inconclusive. The purpose of this meta-analysis was to clarify the effects of MTHFR C677T/A1298C polymorphisms on the risk of EH.

METHODS

Electronic databases were searched to identify relevant studies published until January 2014. Data were extracted by two independent authors. Odds ratios (ORs) with 95%confidence intervals (CIs) were used to assess the association between MTHFR C677T/A1298C polymorphisms and the risk of EH using random effect models or fixed effect models. Finally,30 studies with 5207 cases and 5383 controls were included for C677T polymorphism and 6 studies with 1009 cases and 994 controls were included for A1298C polymorphism.

RESULTS

Meta-analysis results indicated that MTHFR C677T polymorphism contributed to an increased risk of EH (for T vs. C: OR=1.30, 95%CI=1.18–1.43; for TT+CT vs. CC: OR=1.34, 95%CI=1.24–1.46; for TT vs. CC: OR=1.62, 95%CI=1.32–1.99; for TT vs. CT+CC: OR=1.41, 95%CI=1.26–1.59). However, no significant association was detected between MTHFR A1298C polymorphism and the risk of EH.

CONCLUSION

This meta-analysis supports that MTHFR C677T polymorphism plays a role in developing EH. MTHFR A1298C polymorphism may not be associated with an increased risk of EH. Further large and well-designed studies are warranted to confirm these findings.

Associations of MTHFR C677T and MTRR A66G gene polymorphisms with metabolic syndrome: a case-control study in Northern China

Prior evidence indicates that homocysteine plays a role in the development of metabolic syndrome (MetS). Methylenetetrahydrofolate reductase (MTHFR) C677T and methionine synthase reductase (MTRR) A66G polymorphisms are common genetic determinants of homocysteine levels. To investigate the associations of the MTHFR C677T and MTRR A66G polymorphisms with MetS, 692 Chinese Han subjects with MetS and 878 controls were recruited. The component traits of MetS and the MTHFR C677T and MTRR A66G genotypes were determined. A significant association was observed between the MTHFR 677T allele and increased risk of MetS, high fasting blood glucose, high waist circumference, and increasing number of MetS components. The MTRR A66G polymorphism was associated with an increased risk of MetS when combined with the MTHFR 677TT genotype, although there was no association found between MetS and MTRR A66G alone. Furthermore, the MTRR 66GG genotype was associated with high fasting blood glucose and triglycerides. Our data suggest that the MTHFR 677T allele may contribute to an increased risk of MetS in the northern Chinese Han population. The MTRR A66G polymorphism is not associated with MetS. However, it may exacerbate the effect of the MTHFR C677T variant alone. Further large prospective population-based studies are required to confirm our findings.

Homocysteine as a risk factor for hypertension: a 2-year follow-up study

Homocysteine (Hcy) is regarded as a risk factor for hypertension, but research on the causal relationship between Hcy and hypertension is limited. In the present study, we prospectively tracked the blood pressure progression of a normotensive population with different Hcy levels over a 2-year period. The incidence of hypertension with increasing Hcy quartiles produced an approximately U-shaped curve, with significance in males. Compared with the third quartile, the risk of hypertension in the first and second quartiles was increased by 1.55 (95% confidence interval [CI] 1.154–2.081) fold and 1.501 (95% CI 1.119–2.013) fold, respectively, with the increase being more significant in males. In conclusion, Hcy is related to hypertension incidence with the results approximating an U-shaped curve. Low Hcy levels might also increase the risk of hypertension.

Association between Hcy levels and the CBS844ins68 and MTHFR C677T polymorphisms with essential hypertension

The aim of the present study was to investigate the association between the homocysteine (Hcy) levels and polymorphisms of the CBS844ins68 and MTHFR C677T genes in essential hypertension (EH). The effects of the MTHFR C677T and CBS844ins68 haploid genotypes and the combined genotypes on EH and levels of Hcy were further explored. The polymorphisms of CBS844ins68 and MTHFR C677T genes in 200 EH and 200 normal tensive (NT) patients were detected using polymerase chain reaction-restriction fragment length polymorphism and analysis of the distribution of genotypes. An automated biochemical analyzer was used to measure the plasma Hcy levels and the clinical biochemistry data. The plasma Hcy levels in EH were significantly higher than those of the NT group (P<0.05). There were no significant differences (P>0.05) between males and females. Two genotypes, deletion/deletion (DD) and deletion/insertion (DI), of the CBS844ins68 polymorphism were found in two groups with no clear differences in two genotypes and allele frequency distribution (P>0.05). There were significant differences in the three genotype frequencies (χ²=6.658, χ²=4.410, P<0.05) for MTHFR C677T locus genotypes CC, CT and TT. The Hcy levels in genotypes DD and DI had no significant differences (P>0.05) and the CT and TT types were significantly higher compared to the CC genotype (P<0.05). The CC/DD combined genotype in the two groups was significantly different (P<0.05), and the odds ratio (OR), 0.569 showed that the CC/DD genotype may be a protective factor of hypertension. In the two groups, the Hcy levels for combined genotypes CC/DD, CT/DD, TT/DD and TT/DI were significantly different (P<0.05). The SHEsis software analysis linkage disequilibrium coefficient=0.216, indicates that there is probably a weak linkage for MTHFR C677T and CBS844ins68. Haplotype analysis suggested that the C-D haplotype was negatively correlated with EH (OR, 0.727) and that there was a positive correlation between T-D haplotype and EH (OR, 1.376). MTHFR C677T and CBS844ins68 polymorphisms were present in the populations studied and the CBS844ins68 homozygous mutation was not present. Therefore, there is a correlation between the polymorphisms of the MTHFR C677T gene and EH, and allele T may be one of the predisposing factors. MTHFR C677T and CBS844ins68 may exist with a certain linkage and the T-D haplotype may be a risk factor for EH.

Methylenetetrahydrofolate reductase C677T gene polymorphism and essential hypertension: A meta-analysis of 10,415 subjects

The methylenetetrahydrofolate reductase (MTHFR) C677T gene polymorphism has been suggested to be associated with the risk of essential hypertension (EH), however, results remain inconclusive. To investigate this association, the present meta-analysis of 27 studies including 5,418 cases and 4,997 controls was performed. The pooled odds ratio (OR) and its corresponding 95% confidence interval were calculated using the random-effects model. A significant association between the MTHFR C677T gene polymorphism and EH was found under the allelic (OR, 1.32; 95% CI, 1.20-1.45; P=0.000), dominant (OR, 1.39; 95% CI, 1.25-1.55; P=0.000), recessive (OR, 1.38; 95% CI, 1.18-1.62; P=0.000), homozygote (OR, 1.59; 95% CI, 1.32-1.92; P=0.000), and heterozygote (OR, 1.32; 95% CI, 1.20-1.45; P=0.000) genetic models. A strong association was also revealed in subgroups, including Asian, Caucasian and Chinese. The Japanese subgroup did not show any significant association under all models. Meta-regression analyses suggested that the study design was a potential source of heterogeneity, whereas the subgroup analysis additionally indicated that the population origin may also be an explanation. Another subgroup analysis revealed that hospital-based studies have a stronger association than population-based studies, however, the former suffered a greater heterogeneity. Funnel plot and Egger's test manifested no evidence of publication bias. In conclusion, the present study supports the evidence for the association between the MTHFR C677T gene polymorphism and EH in the whole population, as well as in subgroups, such as Asian, Caucasian and Chinese. The carriers of the 677T allele are susceptible to EH.

Correlation between cystathionine β-synthase T883C genetic polymorphism and primary hypertension

The present study aimed to investigate the correlation between cystathionine β-synthase (CBS) T833C polymorphisms and primary hypertension. A case-control study was conducted by genotyping the representative variation in 545 hypertensive individuals (aged 49.23±7.56 years) and 500 normotensive individuals (aged 49.90±10.01 years). The T833C genetic polymorphisms of the CBS enzyme were detected in all subjects by amplification refractory mutation system polymerase chain reaction (PCR) analysis. The CBS T833C polymorphism was successfully genotyped in the general population with a sample size of 1,045 (545+500) individuals. The genotypic and allelic frequency distributions of the CBS T833C polymorphism were not significantly different between the hypertensive and normotensive groups (P>0.05). The CC genotype was significantly different (P<0.05) from the CT and TT genotypes in terms of body mass index (BMI), and the levels of triglycerides (TG) and homocysteine (Hcy). Multiple logistic regression analysis revealed that BMI, total cholesterol (TC) level, smoking, plasma Hcy level and a family history of hypertension were the independent risk factors for hypertension in the population studied. The results indicate that the level of plasma Hcy was a risk factor for hypertension in the population studied. However, the mutation of the CBS T833C gene was not concluded to be an important hereditary factor for influencing the level of plasma Hcy.

Associations of MTHFR gene polymorphisms with hypertension and hypertension in pregnancy: a meta-analysis from 114 studies with 15411 cases and 21970 controls

BACKGROUND

Several epidemiological studies have investigated the associations of methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C polymorphisms with hypertension (H) or hypertension in pregnancy (HIP). However, the results were controversial. We therefore performed a comprehensive meta-analysis to provide empirical evidences on the associations.

METHODOLOGIES

The English and Chinese databases were systematically searched to identify relevant studies. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to evaluate the strength of the associations. Meta-regression, subgroup analysis, sensitivity analysis, cumulative meta-analysis and assessment of publication bias were performed in our study.

PRINCIPAL FINDINGS

A total of 114 studies with 15411 cases and 21970 controls were included, 111 studies with 15094 cases and 21633 controls for the C677T polymorphism and 21 with 2533 cases and 2976 controls for the A1298C polymorphism. Overall, the C677T polymorphism was significantly associated with H and HIP (H & HIP: OR = 1.26, 95% CI = 1.17-1.34; H: OR = 1.36, 95% CI = 1.20-1.53; HIP: OR = 1.21, 95% CI = 1.08-1.32). Stratified analysis by ethnicity revealed a significant association among East Asians and Caucasians, but not among Latinos, Black Africans, and Indians and Sri Lankans. In the stratified analyses according to source of controls, genotyping method, sample size and study quality, significant associations were observed in all the subgroups, with the exception of population based subgroup in H studies and large sample size and "others" genotyping method subgroups in HIP studies. For the A1298C polymorphism, no significant association was observed either in overall or subgroup analysis under all genetic models.

CONCLUSIONS

This meta-analysis suggests that the MTHFR C677T rather than A1298C polymorphism may be associated with H & HIP, especially among East Asians and Caucasians.

Genetic association of rs1800780 (A→G) polymorphism of the eNOS gene with susceptibility to essential hypertension in a Chinese Han population

To investigate the association of eNOS gene polymorphism with essential hypertension in the Chinese Han population, we examined polymorphisms of the rs2070744 (T→C), rs1800780 (A→G), and rs3918181 (A→G) loci. The results demonstrated that the genotypic frequency at the rs1800780 (A→G) locus was significantly different between patients with essential hypertension and the control cohorts (P < 0.05); while genotypic frequencies and allelic frequencies at rs2070744 (T→C) and rs3918181 (A→G) loci had no statistical difference between the patient group and controls (P > 0.05). In addition, haplotype analysis found a statistically significant difference for haplotype TGA, with OR (95% CI) of 1.549 (1.116-2.150) (P < 0.05). These findings suggest that polymorphism of rs1800780 (A→G) in the eNOS gene may be one of the most important genetic factors associated with essential hypertension susceptibility, and those who have haplotype TGA may be at risk to develop essential hypertension.