Prevalence of methylenetetrahydrofolate reductase C677T and its association with arterial and venous thrombosis in the Chinese population

Cerebral Venous Sinus Thrombosis: Current Updates in the Asian Context

BACKGROUND

Cerebral venous sinus thrombosis (CVT) is a life-threatening cause of stroke in Asian countries. South Asia, comprising of India, Pakistan, and Bangladesh, contributed to 40% of strokes in women. Major CVT registries are from the Western nations, which differs from the Asian countries with respect to epidemiology, gender biases, and risk factors. This review focuses on the various aspects of relevance in evaluation and management of patients with CVT in the Asian context.

SUMMARY

The incidence of CVT is higher in Asia than in Western nations. Young age, female gender, especially in pregnancy and puerperal period, and dehydration appear to be the critical risk factors. Tropical infections like malaria, scrub typhus, and flaviviral encephalitis predispose to CVT. There is a higher prevalence of inherited thrombophilia in the Asian cohorts, contributing to prothrombotic states. Anticoagulation and supportive management offer excellent outcomes. Newer anticoagulants are safe and efficacious. In medically refractory cases, endovascular treatment offers modest benefits. Decompressive hemicraniectomy, when done early, offers mortality benefits in patients with large hemorrhagic venous infarctions.

KEY MESSAGES

CVT is an important cause of stroke with a high burden in South Asian countries. Establishment of robust registries is the need of the hour to study the natural history, course, and outcomes and to develop management algorithms tailored to the available resources.

Association of methylenetetrahydrofolate reductase (MTHFR) rs1801133 (677C>T) gene polymorphism with ischemic stroke risk in different populations: An updated meta-analysis

Background: Recently, increasing evidence has implicated methylenetetrahydrofolate reductase (MTHFR) gene mutation as a risk factor for ischemic stroke (IS) in the general population. However, studies have been inconclusive and lack evidence on specific populations. We aim to determine whether the rs1801133 (NC_000001.11 (MTHFR):g. 677C>T (p.Ala222Val) variant, we termed as MTHFR rs1801133 (677 C>T), is linked to an increased risk of IS in different age groups and ancestry groups. Methods: The literature relevant to our study was found by searching the PubMed, Cochrane Library, Web of Science, EMBASE, and CNKI databases. A random effect model analysis was used to calculate the pooled odds ratio (OR) and 95% confidence interval (CI) to evaluate any possible association. We conducted a subgroup analysis based on the age and ancestry groups of the included populations. Results: As of March 2022, 1,925 citations had been identified in electronic databases, of which 96 studies involving 34,814 subjects met our eligibility criteria. A strong link was found between IS and the MTHFR gene rs1801133 (677C>T) polymorphism in all genetic models [dominant genetic model (OR = 1.47; 95%CI = 1.33-1.61; p < 0.001), recessive genetic model (OR = 1.52; 95%CI = 1.36-1.71; p < 0.001), heterozygous model (OR = 1.36; 95%CI = 1.24-1.48; p < 0.001), homozygous model (OR = 1.82; 95%CI = 1.58-2.11; p < 0.001), and T allelic genetic model (OR = 1.37; 95%CI = 1.27-1.48; p < 0.001)]. Further subgroup analyses indicated that the MTHFR rs1801133 (677C>T) variant may increase the risk of IS in Asian, Hispanic, or Latin population, middle-aged, and elderly populations (p < 0.001). Conclusion: Our results implied that mutation of the T allele of MTHFR rs1801133 (677C>T) could be a risk factor for IS. A significant association was found among Asian, Hispanic, or Latin population, middle-aged, and elderly people.

Relationship of Methylenetetrahydrofolate Reductase (MTHFR) C677T Variation With Susceptibility of Patients With Ischemic Stroke: A Meta-Analysis

Discovery and validation of genetic factors for multifactorial and polygenic disorders like stroke are needed to make progress in precision medicine. Although some traditional risk factors for stroke have been identified, they do not fully explain the pathophysiological mechanism of ischemic stroke. The research of genetic risk factors is becoming increasingly relevant in the understanding of stroke mechanisms and the finding of population-specific therapeutic targets. The methylenetetrahydrofolate reductase (MTHFR) gene is involved in homocysteine metabolism, and a high homocysteine level is a risk factor for stroke. Using a meta-analysis technique, we investigated the link between the MTHFR C677T gene polymorphism and the risk of ischemic stroke.

We used the electronic databases PubMed, Medline, Embase, and Google Scholar to find articles in the Journal of Stroke. If heterogeneity was more than 50%, pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated using a random-effects model; otherwise, a fixed-effects model was used.

A total of 67 case-control studies with 17,704 cases and 21,981 controls met our inclusion criteria. The Asian population was represented by 41 studies, whereas the Caucasian population was represented by 26. Under the recessive model, a gene polymorphism at the 677 location of the MTHFR gene is related to an elevated risk of ischemic stroke (OR: 1.29, 95% CI: 1.22-1.37, P < 0.001).

People who have the MTHFR C677T gene polymorphism have a greater risk of stroke than people who do not.

A systematic review and meta-analysis expounding the relationship between methylene tetrahydrofolate reductase gene polymorphism and the risk of intracerebral hemorrhage among populations

Background: The relationship between methylenetetrahydrofolate reductase (MTHFR) gene C677T and A1298C polymorphism with the risk of intracerebral hemorrhage (ICH) has remained to be controversial in recent years. This meta-analysis is aimed to confirm the association of these.

Methods: Systematically searching the related studies from the PubMed, Embase, Cochrane Library, China national knowledge internet database from 1 January 1990 to 1 June 2022. The odd ratio (ORs) and 95% confidence interval (CIs) of gene-disease correlation in various gene models were calculated by fixed or random effect model of meta-analysis. We included 20 case-control studies in this meta-analysis with a total of 1,989 ICH patients and 4,032 health controls originated from Asian, Caucasian, and African populations.

Results: The statistical analysis demonstrated the association of MTHFR C677T gene polymorphism with ICH in allele model [OR_{T VS. C} = 1.20 (95%CI: 1.06–1.36)]; homozygote model [OR _{TT VS. CC} = 1.50 (95%CI: 1.20–1.88)]; dominant model [OR _{CT+ TT VS. CC} = 1.23 (95%CI: 1.03–1.48)] and recessive model [OR_{TT VS. CT+CC} = 1.37 (95%CI: 1.17–1.60)]. Besides, we also found the relationship of MTHFR C677T gene polymorphism with Asian in four comparison model (OR_{T VS. C} = 1.19.95%CI:1.09–1.37, OR_{TT VS. CC} = 1.46.95%CI: 1.15–1.85, OR _{CT+ TT VS. CC} = 1.25.95%CI: 1.01–1.54, OR_{TT VS. CT+CC} = 1.34.95%CI: 1.54–1.17) and Caucasian in four comparison model (OR_{T VS. C} = 1.90.95%CI: 1.22–2.97, OR_{TT VS. CC} = 2.67.95%CI: 1.42–5.00, OR _{CT+ TT VS. CC} = 1.56.95%CI: 1.05–2.32, OR_{TT VS. CT+CC} = 2.25.95%CI: 1.46–4.00). But no statistically significant correlation between A1298C polymorphism and the occurrence of ICH was detected in four studies.

Conclusion: MTHFR C677T gene polymorphism increases the risk of ICH in Asian and Caucasian populations but has no impact on the incidence in African communities. More importantly, the risk of ICH increases in TT genotype individuals in comparison to CT and CC genotype individuals in Asian and Caucasian populations.

Association between MTHFR C677T polymorphism and risk of coronary artery disease in the Chinese population: meta-analysis

BACKGROUND

Previous studies have investigated the close association between the MTHFR C677T polymorphism and the risk of coronary heart disease (CAD) in the Chinese population. However, the results remain inconclusive. Therefore, this meta-analysis was performed to derive a more precise estimate of these associations.

METHODS

Odds ratios (OR) with 95% confidence intervals (CI) were used to assess the relationship between the MTHFR C677T polymorphism and the risk of CAD. Studies were identified by searching the literature for articles published before 2017.

RESULTS

A total of 39 studies comprising 12,101 individuals (6117 cases and 5984 controls) were included. For the allelic model T vs. C, the pooled OR was 1.43 (95% CI: 1.30-1.57, p < 0.0001); for the recessive model TT vs. CC + TC, the pooled OR was 1.48 (95% CI: 1.29-1.70, p < 0.0001); for the dominant model TT + TC vs. CC, the pooled OR was 1.65 (95% CI: 1.43-1.89, p < 0.0001).

CONCLUSION

In the subgroup analysis of high-quality studies, an obvious association was observed between the MTHFR C677T polymorphism and CAD risk in the Chinese population.

Meta-analysis of the relationship between methylenetetrahydrofolate reductase C677T and A1298C polymorphism and venous thromboembolism in the Caucasian and Asian

Recent years, it is a highly debated topic that whether methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and A1298C polymorphism could increase susceptibility to venous thromboembolism (VTE) in the Asian and Caucasian. Therefore, we expect to settle that controversy evidentially. Basic methods: Electronic databases (Pubmed, embase, Cochrane library, scopus, OvidSP, Wiley Online library, Springer link, EBSCO, Elsevier Science Direct, Google scholar) without date limitation were searched. Crude odds ratio (OR) along with 95% confidence interval (95% CI) was calculated to assess the association quantitatively. Finally, a total of 37 eligible studies were included, containing 31 for MTHFR C677T polymorphism and 6 for MTHFR A1298C polymorphism. The pooled results suggested that MTHFR C677T mutation may increase susceptibility to VTE in reverse recessive model (CC+CT vs TT): OR = 0.68 (0.56, 0.83), reverse dominant model (CC vs CT +TT): OR = 0.82 (0.72, 0.94), heterozygote model (CT vs TT): OR = 0.65 (0.52, 0.81), homozygote model (CC vs TT): OR = 0.73 (0.60, 0.89) and allele model (C vs T): OR = 0.80 (0.71, 0.90). Subgroup analysis about Asian also support that results, but Caucasian group not. In addition, MTHFR A1298C polymorphism may be not related to VTE in all genetic model. The results of meta-analysis indicated that MTHFR C677T polymorphism might increase the risk of VTE, especially in Asian population.

Methylenetetrahydrofolate reductase polymorphism in healthy volunteers and its correlation with homocysteine levels in patients with thrombosis

OBJECTIVE:

To determine prevalence of methylenetetrahydrofolate reductase (MTHFR) mutations in apparently healthy individuals residing in Mumbai and patients with deep vein thrombosis (DVT) and coronary artery disease (CAD) and to correlate these polymorphisms with homocysteine (Hcy) levels.

MATERIALS AND METHODS:

This case–control study was initiated after receiving ethical approval and following the participant's written consent. One hundred and twenty unmatched healthy volunteers and 240 patients with arterial and venous thrombosis were enrolled. The prevalence of C677T and A1298C MTHFR mutations was detected using polymerase chain reaction-restriction fragment length polymorphism technique. Serum Hcy concentration and lipid levels were determined using biochemical kits.

RESULTS:

Allele frequency of 677T was 7%, 15%, and 14% in healthy controls, DVT, and CAD patients, respectively, while for 1298C allele, it was 31%, 33%, and 29%, respectively. The lipid markers in CAD patients were significantly low in comparison to the controls while the Hcy level in patients with thrombosis was higher in comparison with the controls. Highest Hcy levels were observed in participants with TT genotype followed by CT genotype and CC genotype in all the three groups. A higher risk of raised Hcy levels was seen in the variants (CT + TT) as compared to CC genotype in DVT (odds ratio [OR] = 3.39, 95% confidence interval [CI] = 1.39–8.2,P < 0.01) and CAD (OR = 21.67, 95%CI = 4.87–96.47,P < 0.0001). The risk observed for A1298C was 2.28 and 2.12 times higher in variants (AC + CC) of both DVT and CAD (OR = 2.28, 95%CI = 1.09–4.75 and OR = 2.12, 95%CI = 1.02–4.40, respectively).

CONCLUSIONS:

The prevalence of variants was more in thrombosis patients as compared to unmatched controls. Our study highlights the fact that MTHFR C677T polymorphism as compared to A1298C significantly affects Hcy levels in patients with thrombosis indicating that patients with mutant variants are at higher risk of rapid progression of their disease condition.

Targeted gene expression study using TaqMan low density array to gain insights into venous thrombo-embolism (VTE) pathogenesis at high altitude

Venous thrombo-embolism (VTE) is multi-factorial disease involving several genetic and acquired risk factors responsible for its onset. It may occur spontaneously upon climbing at High Altitude (HA). Several studies demonstrated that hypoxic conditions prevailing at HA pose an independent risk factor for VTE; however, molecular mechanism remains unknown. Present study aims to identify genes associated with HA-induced VTE pathophysiology using real time TaqMan Low-Density Array (TLDA) of known candidate genes. Gene expression of total 93 genes were studied and analyzed in patients of VTE from HA (HA-VTE) and from sea level (SL-VTE) in comparison to respective controls. Both HA-VTE and SL-VTE patients showed up-regulation of 37 genes involved in blood coagulation cascade, clot formation, platelet formation, endothelial response, angiogenesis, cell adhesion and calcium channel activity. Seven genes including ACE, EREG, C8A, DLG2, USF1, F2 and PCDHA7 were up-regulated in both HA-controls and VTE patients (both HA-VTE and SL-VTE) indicating their role during VTE event and also upon HA exposure. Ten genes; CDH18, FGA, EDNBR, GATA2, MAPK9, BCAR1, FRK, F11, PCDHA1 and ST8SIA4 were uniquely up-regulated in HA-VTE. The differentially expressed genes from the present study could be determining factors for HA-VTE susceptibility and provide insights into VTE occurrence at HA.

TIPSS for variceal bleeding in patients with idiopathic non-cirrhotic portal hypertension: comparison with patients who have cirrhosis

BACKGROUND

In patients with idiopathic non-cirrhotic portal hypertension (INCPH), the usual recommended strategy for management of variceal bleeding is the same as that in cirrhosis. However, this policy has been challenged by the different natural history between INCPH and cirrhosis.

AIM

To compare outcomes after transjugular intrahepatic portosystemic shunt (TIPSS) between INCPH and cirrhotic patients admitted for variceal bleeding.

METHODS

Between March 2001 and September 2015, 76 consecutive patients with biopsy-proven INCPH undergoing TIPSS for variceal bleeding in a tertiary-care centre were included. 76 patients with cirrhotic portal hypertension receiving TIPSS for variceal bleeding, and matched for age, sex, Child-Pugh class, stent type and index year of TIPSS creation served as controls.

RESULTS

Patients with INCPH, compared to those with cirrhosis, had significantly lower mortality (11% vs 36% at 5 years, adjusted HR, 0.37; 95% CI 0.15-0.87, P = 0.022), overt hepatic encephalopathy (16% vs 33% at 5 years, adjusted HR, 0.35; 95% CI 0.16-0.75, P = 0.007) and hepatic impairment, despite similar rates of further bleeding (33% vs 32% at 5 years, adjusted HR, 0.72; 95% CI 0.36-1.44, P = 0.358), and shunt dysfunction (35% vs 36% at 5 years, adjusted HR, 0.84; 95% CI 0.41-1.72, P = 0.627). These findings were consistent across different relevant subgroups.

CONCLUSIONS

Patients with INCPH treated with TIPSS for variceal bleeding had similar progression of portal hypertension (further bleeding and shunt dysfunction) but fewer complications of liver disease (overt hepatic encephalopathy and hepatic insufficiency) and lower mortality rate compared with cirrhotic patients with comparable liver function.

High-throughput blood sample preparation for single nucleotide polymorphism genotyping in less than 25 min

Straightforward, rapid and high-throughput pretreatment for single nucleotide polymorphisms (SNP) genotyping is critically needed in clinical practice. However, all existing SNP genotyping methods require DNA purification step, which is labor-intensive and time-consuming. We develop a protocol for SNP genotyping by combining whole blood lysis (WBL) with qPCR and justify the practicality of our method in blood samples from 140 donors, including 40 samples from healthy donors, and 100 samples from donors with either low white blood cell counts, high level of serum uric acid or triglyceride. When compared with Sanger sequencing, the gold standard for SNP genotyping, our method exhibits a 100% consistency in the aspect of sensitivity and specificity. In addition, our method can obtain amplifiable DNA within 25 mins (which is the fastest to the best of our knowledge) from 48 samples. The blood samples, even with low white blood cell counts, high level of serum uric acid or triglyceride could not affect the sensitivity and specificity of our method. Our study demonstrates that the combination of WBL and qPCR genotyping can serve as a high-throughput and robust approach for routine clinical SNP genotyping.

High prevalence of factor V Leiden and prothrombin G20101A mutations in Kashmiri patients with venous thromboembolism

AIM

The genetic variants of the factor V (G1691A), prothrombin (G20210A) and MTHFR (C677T) genes have been widely implicated as inherited risk factors for developing venous thrombosis. This study was undertaken to reveal the frequency of these mutations in Kashmiri patients with venous thromboembolism.

METHODOLOGY

A case-control study was designed with 250 VTE patients and 250 healthy controls. The mutations were analysed using ARMS-PCR and PCR-RFLP approach.

RESULT

The factor V Leiden G1691A mutation was found in 17/250 (6.8%) VTE patients and prothrombin G20210A mutation was found in 7/250 (2.8%) VTE patients while no mutation was found in any of the healthy controls. Both the mutations were found to be significantly associated with the increased risk of VTE (p = 0.0001 and 0.0150 respectively) while no association of VTE risk with MTHFR C677T polymorphism was found (p = 0.53).

CONCLUSION

The increased frequency of factor V Leiden G1691A and prothrombin G20210A mutation in VTE patients indicates a significant role of these mutations in the development of VTE in our population. We therefore suggest the routine screening of these two mutations as thrombophilic markers in Kashmiri patients with venous thromboembolism.

Vascular Genetic Variants and Ischemic Stroke Susceptibility in Albanians from the Republic of Macedonia

BACKGROUND

Acute first-ever ischemic stroke (FIS) is a heterogeneous, polygenic disorder. The contribution of vascular genetic variants as inherited causes of ischemic stroke has remained controversial.

AIM

To examine the association of genetic variants in vascular factors with the occurrence of FIS.

MATERIAL AND METHODS

The current research was performed in a group of 39 patients with FIS (study group) and 102 healthy volunteers (control group). We analyzed the prevalence of vascular genetic variants in following genes: factor V, prothrombin, methylenetetrahydrofolate reductase (MTHFR), factor XIII, plasminogen activator 1, endothelial protein C receptor (EPCR), apolipoprotein B, apolipoprotein E, β-fibrinogen, human platelet antigen 1, angiotensin-converting enzyme (ACE), endothelial nitric oxide synthase (eNOS) and lymphotoxin alpha.

RESULTS

It was found that heterozygous LTA 804C>A and FXIII V34L Leu/Leu were significantly more frequent in patients with FIS than in control group (p = 0.036 and p = 0.017, respectively). The frequency of FXIII V34L Val/Val was significantly lower in patients with FIS than in control group (p = 0.020). Other frequencies of vascular gene variants in patients with FIS and in control group were not significantly different.

CONCLUSIONS

This is the first comprehensive study to present data indicating that polymorphism of vascular genes in the prevalence of acute FIS exists in the Albanian population from the Republic of Macedonia. Variations in these genes have been detected in patients with acute FIS, suggesting that their combination might act in a susceptible or protective manner in this Albanian population.

The MTHFR C677T Polymorphism and Risk of Intracerebral Hemorrhage in a Chinese Han Population

BACKGROUND

Methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism has been speculated to be and extensively investigated as a risk factor for various vascular diseases, including intracerebral hemorrhage (ICH). However, results from published studies regarding the role of C677T polymorphism in ICH risk in Chinese populations were contradictory rather than conclusive.

MATERIAL/METHODS

In this study, a total of 180 ICH patients and 180 matched controls of Chinese Han ethnicity were enrolled. The MTHFR C677T polymorphism was genotyped by polymerase chain reaction-ligation detection reaction (PCR-LDR). A meta-analysis was conducted by combining our data with previous relevant studies in Chinese populations.

RESULTS

In our case-control study, similar allele frequency (p=0.492) and genotype distribution (p=0.748) of MTHFR C677T polymorphism were detected between ICH patients and controls. Further analysis based on hematoma location did not show a significant association. When combined with previous studies, however, C677T polymorphism was found to be significantly associated with an increased risk for ICH in Chinese populations (recessive model: OR=1.57, 95%CI=1.29-1.91). When focusing on the Han ethnicity, carriers of the TT genotype had an increased risk of ICH (recessive model: OR=1.36, 95%CI=1.05-1.75).

CONCLUSIONS

In this case-control study we did not observe that the MTHFR C677T polymorphism was associated with ICH risk in people of Chinese Han ethnicity. However, when combined with previous published studies, a significant association of C677T polymorphism with an increased risk of ICH was detected in Chinese populations, and also in the subgroup analysis focusing on Han ethnicity.

Association between 5,10-Methylenetetrahydrofolate Reductase C677T Gene Polymorphism and Risk of Ischemic Stroke: A Meta-analysis

BACKGROUND

Hyperhomocysteinemia, a condition that is strongly determined by dietary intake of B vitamins, has been suggested to be an independent risk factor for ischemic stroke (IS). To test this hypothesis, we performed a meta-analysis to investigate the associations between 5,10-methylenetetrahydrofolate reductase (MTHFR) C677T gene polymorphism, which plays a critical role in modulating plasma homocysteine concentrations, and IS risk.

MATERIALS AND METHODS

We searched case-control studies on the association between MTHFR C677T genetic polymorphism and susceptibility to IS through PubMed, Embase, and Medline databases from January 2000 up to October 2014. The random-effects model was employed because moderate heterogeneity across studies was observed, as assessed by I(2) statistic. Publication bias was estimated using funnel plot and Egger's regression test.

RESULTS

A total of 22 case-control studies were included in the current meta-analysis. Significant associations between MTHFR C677T genetic polymorphism and IS were found under the dominant model (pooled odds ratio [OR] = 1.40, 95% confidence interval [CI]: 1.24-1.57), the recessive model (pooled OR = 1.37, 95% CI: 1.16-1.61), and the allele model (pooled OR = 1.29, 95% CI: 1.18-1.42).

CONCLUSIONS

The meta-analysis suggests that MTHFR C677T genetic polymorphism is significantly associated with susceptibility to IS, which provides evidence supporting hyperhomocysteinemia as a risk factor for stroke.

Factor V Leiden, factor V Cambridge, factor II GA20210, and methylenetetrahydrofolate reductase in cerebral venous and sinus thrombosis: A case-control study

Background:

Factor V G1691A (FV Leiden), FII GA20210, and methylenetetrahydrofolate reductase (MTHFR) C677T mutations are the most common genetic risk factors for thromboembolism in the Western countries. However, there is rare data in Iran about cerebral venous and sinus thrombosis (CVST) patients. The aim of this study was to evaluate the frequency of common genetic thrombophilic factors in CVST patients.

Materials and Methods:

Forty consequently CVST patients from two University Hospital in Isfahan University of Medical Sciences aged more than 15 years from January 2009 to January 2011 were recruited. In parallel, 51 healthy subjects with the same age and race from similar population selected as controls. FV Leiden, FII GA20210, MTHFR C677T, and FV Cambridge gene mutations by polymerase chain reaction technique were evaluated in case and control groups.

Results:

FV Leiden, FII GA20210, and FV Cambridge gene mutations had very low prevalence in both case (5%, 2%, 0%) and control (2.5%, 0%, 0%) and were not found any significant difference between groups. MTHFR C677T mutations was in 22 (55%) of patients in case group and 18 (35.5%) of control group (P = 0.09).

Conclusion:

This study showed that the prevalence of FV Leiden, FII GA20210, and FV Cambridge were low. Laboratory investigations of these mutations as a routine test for all patients with CVST may not be cost benefit.

Association between MTHFR C677T polymorphism and venous thromboembolism risk in the Chinese population: a meta-analysis of 24 case-controlled studies

The association between methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms and venous thromboembolism (VTE) risk in the Chinese population has been widely reported, but results were inconsistent and underpowered. To elucidate the variable results, a meta-analysis and systematic review were performed from all case-controlled studies relating MTHFR C677T polymorphism by pooling data on them. We estimated the pooled odds ratio with its 95% confidence intervals to assess this possible association. Finally, a total of 24 studies with 2339 cases and 4048 controls were included in the current meta-analysis. Significant association was found with VTE risk for all genetic models. Subgroup analyses by type of VTE further identified the above-mentioned association in deep vein thrombosis/pulmonary embolism and splanchnic vein thrombosis. The findings from our meta-analysis support the associations of MTHFR C677T polymorphism with VTE risk in the Chinese population.

Quantitative assessment of association between rs1801133 polymorphism and susceptibility to stroke

Methylenetetrahydrofolate reductase (MTHFR) is an important enzyme involved in folate metabolism, which is essential for DNA synthesis and methylation. Genetic variations in the MTHFR gene seem to contribute to a decreased activity of MTHFR, ultimately confer increased susceptibility to stroke. To assess the association between this polymorphism and stroke risk, we conducted a comprehensive meta-analysis based on 73 eligible studies. A total of 73 studies, including 10,225 cases and 13,800 controls identified between 1999 and 2012, were selected through researching the PubMed, MEDLINE, EMBASE, Cochrane Library, Web of Science, and Chinese Biomedical Chinese National Knowledge Infrastructure and Literature database databases. Odds ratios (ORs) with corresponding 95% confidence intervals (CIs) were used to assess the association. Overall, a significant elevated risk of stroke risk was associated with the rs1801133 polymorphism in all genetic models (homozygote model: OR 1.296, 95% CI 1.109-1.514; dominant model: OR 1.179, 95% CI 1.058-1.315; recessive model: OR 1.209, 95% CI 1.063-1.375; allele comparison model: OR 1.154, 95% CI 1.061-1.256). In the stratified analyses, significantly increased stroke risks were indicated among Asians in all genetic models (homozygote model: OR 1.726, 95% CI 1.314-2.267; dominant model: OR 1.535, 95% CI 1.282-1.838; recessive model: OR 1.452, 95% CI 1.160-1.818; allele comparison model: OR 1.403, 95% CI 1.211-1.626).The present meta-analysis suggests that rs1801133 polymorphism contributes to the risk of stroke, of note, in Asian populations.

Methylenetetrahydrofolate reductase (C677T and A1298C) polymorphisms, hyperhomocysteinemia, and ischemic stroke in Tunisian patients

OBJECTIVE

The present study evaluated the role of the methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C gene polymorphisms and correlated these results with plasma homocysteine (Hcy) levels in Tunisian ischemic stroke (IS) patients.

METHODS

Overall, 84 patients with IS were included and compared with 100 healthy controls. The most common stroke risk factors were investigated. Fasting plasma Hcy levels were measured. Genotyping of the MTHFR C677T and A1298 polymorphisms was studied by polymerase chain reaction.

RESULTS

Aside from tobacco and alcohol use, the other studied factors were significant risk factors for IS. Mean plasma Hcy levels were significantly higher in IS patients than in controls (16.1 ± 8.28 μmol/L versus 8.76 ± 3.48 μmol/L, P < 10(-3)). Significant associations were found with both the MTHFR 677(CT + TT) and 1298 (AC + CC) genotypes in comparison with controls (P < 10(-3)). A significant synergistic interaction was also found with the double heterozygote MTHFR 677CT/1298AC (P < 10(-3)). Homocysteine levels were significantly higher in IS patients with the MTHFR C677T variant (CT and TT genotypes) (P < 10(-3)); however, the difference was not significant with the MTHFR A1298C variant (AC and CC genotypes) (P = .31).

CONCLUSION

The MTHFR C677T and A1298 polymorphisms (individually or in concert) and hyperhomocysteinemia represent important risk factors for IS. Elevated Hcy levels were found to be associated with the MTHFR C677T variant; however, no significant association was found with the MTHFR A1298C variant.

Quantitative assessment of the association between MTHFR C677T polymorphism and hemorrhagic stroke risk

Many studies have investigated the association between methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and hemorrhagic stroke, but the impact of MTHFR C677T on hemorrhagic stroke is unclear owing to the obvious inconsistence among those studies. This study aimed to quantify the strength of the association between MTHFR C677T polymorphism and hemorrhagic stroke risk. We searched Pubmed, Emabse and Wangfang databases for studies investigating the association between MTHFR C677T polymorphism and hemorrhagic stroke risk. We estimated the pooled odds ratio (OR) with its 95 % confidence intervals (95 % CI) to assess this possible association. Meta-analysis of included studies suggested that TT genotype was obviously associated with increased risk of hemorrhagic stroke (OR (TT versus CC) = 1.84, 95 % CI 1.45-2.34; OR (TT versus CT) = 1.53, 95 % CI 1.23-1.90; OR (TT versus CT/CC) = 1.64, 95 % CI 1.24-2.00) compared with CC or CT genotypes of MTHFR C677T polymorphism. Subgroup analyses by ethnicity further identified the association above in both Asians and Caucasians. No evidence of publication bias was observed. Thus, meta-analyses of available data suggest an obvious association between MTHFR C677T polymorphism and hemorrhagic stroke risk, and TT genotype contributes to increased risk of hemorrhagic stroke.

Cervical cancer with polymorphism in MTHFR C677T gene: a systematic review and meta-analysis

To perform a meta-analysis investigating the association of MTHFR C677T polymorphism and susceptibility of cervical cancer. All case-control studies published in English and Chinese with estimates of the relationship between MTHFR C677T polymorphism and risk of cervical cancer were analyzed using odds ratio (OR) with 95 % confidence interval (CI). A total of 10 studies (2,023 cases and 2,570 controls) were included in the meta-analysis. No significant association was observed between T allele and C allele (OR = 0.90; 95 %CI = 0.70-1.17; P = 0.43), and for genotype TT versus CC (OR = 1.09; 95 %CI = 0.74-1.61; P = 0.67), CT versus CC (OR = 0.95; 95 %CI = 0.75-1.20; P = 0.65), CT + TT versus CC (OR = 0.91; 95 %CI = 0.66-1.24; P = 0.55). The current meta-analysis results suggest that the MTHFR C677T polymorphism may not be associated with cervical cancer.

Association of MTHFR 677T variant allele with risk of intracerebral haemorrhage: a meta-analysis

BACKGROUND

Previous studies concerning the association between methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and risk of intracerebral haemorrhage (ICH) reported conflicting results. A meta-analysis of published studies was performed to allow a more reliable estimate of this association.

METHODS

Relevant studies concerning the association between MTHFR C677T polymorphism and risk of ICH were included into this meta-analysis. Odds ratios (OR) and 95% confidence intervals (CI) were determined for this gene-disease association using fixed or random effect models.

RESULTS

Finally, 16 studies with a total of 1828 cases and 4067 controls were included. Meta-analyses of a total of 16 studies showed that there was an obvious association of MTHFR 677T allele with risk of ICH under all four comparison models (OR(T vs. C)=1.38, 95% CI 1.17-1.62, P<0.001; OR(TT vs. CC)=1.90 95% CI 1.42-2.55, P<0.001; OR(TT vs. TC/CC)=1.38 95% CI 1.20-1.59, P<0.001; OR(TT/TC vs. CC)=1.41 95% CI 1.12-1.78, P=0.003). Besides, both subgroup analyses and sensitivity analysis further identified the association above.

CONCLUSION

The MTHFR 677T allele is associated with risk of ICH, and individuals with TT genotype have an obviously higher risk of ICH than those with the CC genotype.

Thrombophilia among Chinese women with venous thromboembolism during pregnancy

AIMS

To assess the prevalence of thrombophilia among Chinese women with venous thromboembolism (VTE) developed during pregnancy.

METHODS

Based on information from a tertiary teaching unit, all recorded cases of deep vein thrombosis (DVT) and pulmonary embolism (PE) during pregnancy diagnosed between 1997 and 2005, were assessed for prevalence of thrombophilia. Fifty-five healthy women, who had at least one normal pregnancy but without any previous history of VTE, were recruited as controls.

RESULTS

A total of 44 subjects completed thrombophilia screening, of whom 5 (11%) were confirmed to have thrombophilia [protein C (PC) deficiency (2), protein S (PS) deficiency (1), combined PC & PS deficiency (1) and antithrombin III deficiency (1)]. Homozygous 5,10-methylenetetrahydrofolate reductase (C677T) gene mutation was found in 6 (14%) subjects but not in the controls. There was no antiphospholipid syndrome, activated PC resistance, factor V Leiden or prothrombin gene mutations.

CONCLUSION

In the Chinese population, PS and PC deficiencies are common thrombophilia for VTE during pregnancy and thrombophilia screening should be recommended in all pregnant women who suffer from VTE.

The 677C>T Mutation of the MTHFR Gene Increases the Risk of Venous Thromboembolism in Koreans and a Meta-Analysis From Asian Population

The frequency of methylenetetrahydrofolate reductase (MTHFR) mutations varies between racial and ethnic groups, and there are also conflicting data regarding MTHFR gene mutations in Asian patients with venous thromboembolism (VTE). The aim of this study was to examine the association between common MTHFR gene mutations (677C>T and 1298A>C) and risk of VTE in Koreans. This study was a retrospective case–control study. We enrolled 203 patients with VTE and 403 controls. For the 677C>T polymorphism, there was no difference in the frequency of the CT genotype and TT genotype between the patients with VTE and the controls. However, in the recessive analysis (CC + CT vs TT), the frequency of the TT genotype was significantly higher in VTE than in controls (odds ratio = 1.700; 95% confidence interval = 1.108-2.607, P = .015). In conclusion, the TT genotype of MTHFR 677C>T increases the risk of VTE in Koreans. This finding was supported by meta-analysis of previous Asian studies.

MTHFR C677T polymorphism and its relationship to myocardial infarction in the Eastern Black Sea region of Turkey

BACKGROUND AND AIMS

An association of homozygous MTHFR 677T genotypes with elevated plasma homocysteine level has been documented, but results are still controversial. We aimed to investigate prevalence of the C677T polymorphism in patients with acute myocardial infarction (MI) in the Eastern Black Sea region of Turkey.

METHODS

We studied genomic DNA of 231 unrelated patients (aged 59 ± 13 years; 175 male, 56 female) with first anterior acute MI and 242 healthy controls (aged 54 ± 19 years; 182 male, 60 female) using real-time polymerase chain reaction kits for the MTHFR C677T mutation.

RESULTS

Prevalence of MTHFR C677T mutant genotype was 49.1% (CT: 45.8%, TT: 3.3%) in controls and 48.45% (CT: 38.5%, TT: 9.95%) in patients with acute MI. The TT mutation was more frequent in patients with acute MI than in controls (9.95 vs. 3.3%) (OR; 3.23, 95% CI; [1.34-8.05], p = 0.003).

CONCLUSIONS

The MTHFR gene homozygote TT mutation is a risk factor for patients with MI in the eastern Black Sea Turkish Population.

Is thrombophilia a major risk factor for deep vein thrombosis of the lower extremities among Lebanese patients?

Aim

Factor V Leiden (R506Q) mutation is the most commonly observed inherited genetic abnormality related to vein thrombosis. Lebanon has one of the highest frequencies of this mutation in the world with a prevalence of 14.4% in the general population. The aim of this study is to define risk factors including inherited genetic abnormalities among Lebanese patients with lower extremity deep vein thrombosis. We report the clinical outcome of patients with thrombophilia.

Methods

From January 1998 to January 2008, 162 patients (61 males and 101 females) were diagnosed with lower extremity deep vein thrombosis. Mean age was 61 years (range: 21 to 95 years).

Results

The most frequent risk factors for vein thrombosis were surgery, advanced age, obesity, and cancer. Twenty-five patients had thrombophilia, 16 patients had factor V Leiden (R506Q) mutation, and seven patients had MTHFR C677T mutation. Ninety-two percent of patients screened for thrombophilia were positive. Screening was requested in young patients (16), patients with recurrent (11), spontaneous (8), and extensive (5) venous thrombosis, familial history (5), pregnancy (4), estroprogestative treatment (3), and air travel (1). Nine patients had one, 11 patients had two, and five had three of these conditions. Follow-up (6 to 120 months) of these 25 patients treated with antivitamin K did not reveal recurrences or complications related to venous thromboembolism.

Conclusion

Factor V Leiden mutation followed by MTHFR mutation are the most commonly observed genetic abnormalities in these series. Defining risk factors and screening for thrombophilia when indicated reduce recurrence rate and complications. Recommendations for thrombophilia screening will be proposed.

Severe skin necrosis after breast reconstruction with a transverse rectus abdominis musculocutaneous flap in methylenetetrahydrofolate reductase deficiency

We report a case of unexpected severe skin necrosis after autologous transverse rectus abdominis musculocutaneous flap breast reconstruction in a patient with homozygosis for the 5,10- methylenetetrahydrofolate reductase (MTHFR) gene. This genetic deficiency is hypothesised as the cause of this exceptional skin necrosis. A 46-year-old woman underwent a radical mastectomy and immediate rectus abdominis musculocutaneous flap breast reconstruction. At the end of surgery, the blood supply to the flap and the abdominal wall was excellent. On the 5th postoperative day, the patient developed an extensive abdominal skin necrosis and a partial flap necrosis on the reconstructed breast. The rectus abdominis musculocutaneous flap breast reconstruction can be proposed to patients without any haemostatic defect in order to avoid life-threatening complications and unaesthetic results. This procedure requires careful patient selection, detailed preoperative planning, and complete laboratory investigations: However, mutation of the 5,10- methylenetetrahydrofolate reductase gene is too exceptional to form part of the routine preoperative investigation and can be looked for in these cases of extensive necrosis.

Genetics of ischaemic stroke among persons of non-European descent: a meta-analysis of eight genes involving approximately 32,500 individuals

BACKGROUND

Ischaemic stroke in persons of European descent has a genetic basis, but whether the stroke-susceptibility alleles, the strength of any association, and the extent of their attributable risks are the same in persons of non-European descent remains unanswered. Whether ethnicity itself has a relevant or substantial contribution on those effect estimates is controversial. Comparative analyses between the ethnic groups may allow general conclusions to be drawn about polygenic disorders.

METHODS AND FINDINGS

We performed a literature-based systematic review of genetic association studies in stroke in persons of non-European descent. Odds ratios (ORs) and 95% confidence intervals (CIs) were determined for each gene-disease association using fixed and random effect models. We further performed a comparative genetic analysis across the different ethnic groups (including persons of European descent derived from our previous meta-analysis) to determine if genetic risks varied by ethnicity. Following a review of 500 manuscripts, eight candidate gene variants were analysed among 32,431 individuals (12,883 cases and 19,548 controls), comprising mainly Chinese, Japanese, and Korean individuals. Of the eight candidate genes studied, three were associated with ischaemic stroke: the angiotensin I converting enzyme (ACE) insertion/deletion (I/D) polymorphism with a mean OR of 1.90 (95% CI 1.23-2.93) in the Chinese and 1.74 (95% CI 0.88-3.42) in the Japanese; the summary OR for the C677T variant of 5,10-methylenetetrahydrofolate reductase (MTHFR) was 1.18 (95% CI 0.90-1.56) in Chinese and 1.34 (95% CI 0.87-2.06) in Koreans; and the pooled OR for the apolipoprotein E (APOE) gene was 2.18 (95% CI 1.52-3.13) in Chinese and 1.51 (95% CI 0.93-2.45) in Japanese. Comparing the commonly investigated stroke genes among the Asian groups against studies in persons of European descent, we found an absence of any substantial qualitative or quantitative interaction for ORs by ethnicity. However, the number of individuals recruited per study in the studies of persons of non-European descent was significantly smaller compared to studies of persons of European descent, despite a similar number of studies conducted per gene.

CONCLUSIONS

These data suggest that genetic associations studied to date for ischaemic stroke among persons of non-European descent are similar to those for persons of European descent. Claims of differences in genetic effects among different ethnic populations for complex disorders such as stroke may be overstated. However, due to the limited number of gene variants evaluated, the relatively smaller number of individuals included in the meta-analyses of persons of non-European descent in stroke, and the possibility of publication bias, the existence of allele variants with differential effects by ethnicity cannot be excluded.

Lack of association of methylenetetrahydrofolate reductase 677C>T mutation with coronary artery disease in a Pakistani population

Pakistanis belong to the South Asian population which has the highest known rate of coronary artery disease. Folic acid deficiency also appears to be highly prevalent in this population. Methylenetetrahydrofolate reductase (MTHFR) 677C>T polymorphism decreases the activity of this enzyme and can be associated with mild to moderate hyperhomocysteinemia in homozygotes, particularly when there is folic acid deficiency, as well as with coronary artery disease. To assess the value of genotyping the MTHFR 677C>T dimorphism, we carried out a case-control study of dimorphism 677C>T for putative association with myocardial infarction (MI) among Pakistani nationals. We investigated a sample population of 622 Pakistanis consisting of 225 controls and 397 patients with clinical diagnosis of acute MI (AMI). MTHFR C677T alleles were determined by assays based on polymerase chain reaction and restriction endonuclease analysis. Frequencies of C alleles were 0.87 among controls and 0.86 among AMI patients. The MTHFR 677C>T dimorphism showed no association with MI (χ² = 0.25, 1df, P=0.62), serum levels of folate and vitamin B12 and plasma level of vitamin B6. A significant association, however, was found between homozygous 677T genotype and plasma levels of homocysteine. Multivariate analysis of the data showed that in case of log homocysteine, age and MTHFR genotypes were significantly different (P<0.001). In case of B12, smoking and age were found to be statistically significant (P<0.001), while in case of serum folate only smoking was found to be significant (P<0.001). The results indicate that MTHFR 677C>T polymorphism, though associated with homocysteine levels, confers no significant risk of coronary artery disease in the Pakistani population investigated here. We suggest that the higher incidence of AMI in South Asia occurs through mechanisms other than the MTHFR related pathways.

Dose-Related Association of MTHFR 677T Allele With Risk of Ischemic Stroke

Background— Data are conflicting concerning ischemic stroke risk associated with a common polymorphism in the gene encoding 5,10-methylenetetrahydrofolate reductase ( MTHFR 677C→T), which predisposes to hyperhomocystinemia in vivo.

Methods— We performed a systematic review and meta-analysis of published relevant literature. We included cohort, case-control, or cross-sectional studies reporting the frequencies of heterozygous (CT) and homozygous (TT) genotypes in (a) all stroke/TIA (overall group) and (b) imaging-proven ischemic stroke (best-phenotyped group).

Results— Among 14 870 subjects, the pooled estimated risk of stroke/TIA associated with the 677T allele increased in a dose-dependent manner (T allele pooled OR 1.17, 95%CI 1.09 to 1.26, TT genotype pooled OR 1.37, 95%CI 1.15 to 1.64). An almost-identical relationship was observed when the analysis was restricted to imaging-proven ischemic stroke (T allele pooled OR 1.18, 95%CI 1.09 to 1.29, TT genotype pooled OR 1.48, 95%CI 1.22 to 1.8).

Conclusion— A graded increase in ischemic stroke risk with increasing MTHFR 677T allele dose was observed, suggesting an influence of this polymorphism as a genetic stroke risk factor and supporting other evidence indicating a causal relationship between elevated homocysteine and stroke.

Idiopathic intracranial hypertension, polycystic-ovary syndrome, and thrombophilia

We studied thrombophilia, hypofibrinolysis, and polycystic-ovary syndrome (PCOS) in 65 women consecutively referred because of idiopathic intracranial hypertension (IIH) as a means of better understanding the origin of IIH, with the ultimate goal of developing novel medical therapies for IIH. Our hypothesis: IIH results in part from inadequate drainage of cerebrospinal fluid (CSF) resulting from thrombotic obstruction to CSF resorption-outflow, favored by thrombophilia-hypofibrinolysis. We conducted the polymerase chain reaction (PCR) and assessed serologic coagulation measures in 65 women (64 of them white) with IIH, PCR in 102 healthy white female controls (72 children, 30 age-matched adults), and serologic measures in the 30 adults. Of the 65 patients, 37 (57%) were found to have PCOS; 16 (43%) were obese (BMI > or = 30 to < 40), and 19 (51%) were extremely obese (BMI > or = 40). Of the 65 women with IIH, 25 (38%) were homozygous for the thrombophilic C677T MTHFR mutation, compared with 14% of controls (14/102) ( P = .0002). Thrombophilic high concentrations of factor VIII (>150%) were present in 9 of 65 (14%) IIH cases, compared with 0 of 30 controls (0%) (Fisher's p [p f ] = .053). An increased concentration of lipoprotein A (> or = 35 mg/dL), associated with hypofibrinolysis, was present in 19 of 65 IIH cases (29%), compared with 3 of 30 controls (10%) (p f = .039). IIH occurred in 18 of 65 IIH patients taking estrogen-progestin contraceptives (28%), in 6 patients taking hormone-replacement therapy (9%), and in 5 pregnant subjects (8%). We speculate that PCOS, associated with obesity and extreme obesity, is a treatable promoter of IIH. We also speculate that if thrombophilia-hypofibrinolysis and subsequent thrombosis are associated with reduced CSF resorption in the arachnoid villi of the brain, thrombophilia and hypofibrinolysis-often exacerbated by thrombophilic exogenous estrogens, pregnancy, or the paradoxical hyperestrogenemia of PCOS-are treatable promoters of IIH.

Homocysteine, MTHFR and risk of venous thrombosis: a meta-analysis of published epidemiological studies

CONTEXT

It has been suggested that elevated total plasma homocysteine levels are associated with the risk of venous thrombosis.

OBJECTIVE

To assess the relationship of homocysteine and the MTHFR 677TT genotype and the risk of venous thrombosis by conducting a meta-analysis of all relevant studies.

DATA SOURCES AND SELECTION

Studies (case-control or nested case-control) were identified by searches of electronic literature for relevant reports published before July 2003 on homocysteine and the MTHFR 677TT genotype and venous thrombosis as an end-point, by hand-searching reference lists of original articles (including meta-analyses) on this topic and by contact with investigators in the field.

DATA EXTRACTION

A meta-analysis of 24 retrospective (n = 3289 cases) and three prospective studies (n = 476 cases) was carried out to examine the association of homocysteine with venous thrombosis. A meta-analysis of 53 studies (n = 8364 cases) of the MTHFR 677TT genotype (that increases homocysteine) was carried out to assess if this association is causal.

DATA SYNTHESIS

A 5 micromol L(-1) higher measured homocysteine level was associated with a 27% (95% CI: 1-59) higher risk of venous thrombosis in prospective studies and a 60% (95% CI: 10-134) higher risk in retrospective studies. The 677TT genotype was associated with a 20% (95% CI: 8-32) higher risk of venous thrombosis compared with the 677CC genotype. In contrast with non-American studies, the 677TT genotype had no effect on venous thrombosis in North America, due probably to the higher intake of folate and riboflavin in North America.

CONCLUSION

This meta-analysis of prospective and retrospective studies demonstrates a modest association of homocysteine with venous thrombosis. The elevated risk associated with the MTHFR 677TT genotype provides some support for causality.

MTHFR C677T polymorphism and its relation to ischemic stroke in the Black Sea Turkish population

The MTHFR C677T mutation has been shown to be associated with venous thrombosis. The role of this mutation in ischemic stroke is unclear. We investigated whether the MTHFR mutation is a risk factor for patients with ischemic stroke in the Black Sea Turkish population or not. We analyzed 30 patients (19 male, 11 female) [median age: 50 years (range: 28-78)] with ischemic stroke who had no known predisposition factors for stroke and 242 (182 male, 60 female) healthy controls [median age: 42 years (range: 18-65)]. Detection of the MTHFR C677T mutation was performed by using commercially available allele-specific PCR-ELISA kits. Prevalence of the MTHFR C677T genotype was 49.1% (CT, 45.8%; TT, 3.3%) in controls and 50% (CT, 43.3%; TT, 6.6%) in patients [OR: 1.03, 95% CI (0.45-2.35]). The prevalence of homozygous gene mutation for MTHFR was higher among patients with stroke than control subjects, but this difference was not statistically significant. The MTHFR gene mutation is not a risk factor for ischemic stroke formation in patients from the Black Sea region in Turkey.

Warfarin skin necrosis associated with protein S deficiency and a mutation in the methylenetetrahydrofolate reductase gene

The use of warfarin is rarely complicated by skin necrosis. We describe a 50-year-old woman who presented with a left leg deep venous thrombosis and subsequent pulmonary embolism. She was initially anticoagulated with low-molecular weight heparin and subsequently warfarin. Within 4 days abdominal skin necrosis developed. Investigations revealed the presence of protein S deficiency and in addition, a mutation in the methylenetetrahydrofolate reductase gene (MTHFR). We present, to our best knowledge, the first case of warfarin skin necrosis associated with a methylenetetrahydrofolate reductase mutation.

Large volume donor plasmapheresis in inherited thrombophilia implicated in arterial thrombosis

BACKGROUND

Life-threatening complications following apheresis are rare, and include venous thrombosis. Arterial thrombosis following apheresis has not been reported.

CASE REPORT

A 48 year old donor had cerebral infarction following large volume plasma donation. The outcome was fatal. He was found to be heterozygous for both methylene tetrahydrofolate reductase (MTHFR) 677C-T mutation and Prothrombin 20210G-A allele.

CONCLUSION

This case suggests that large volume plasma donation may trigger arterial thrombotic events in inherited thrombophilia. Therefore, the effects of plasmapheresis on coagulation system should be studied thoroughly.

Serum homocysteine, thermolabile variant of methylene tetrahydrofolate reductase (MTHFR), and venous thromboembolism: Longitudinal Investigation of Thromboembolism Etiology (LITE)

We sought to examine prospectively the association of serum homocysteine and the methylene tetrahydrofolate reductase (MTHFR) C677T gene polymorphism with risk of venous thromboembolism (VTE). We studied these relationships in a nested case-control study of 303 VTE cases and 635 matched controls from a population-based cohort of 21,680 adults from six U.S. communities. The highest quintile of serum homocysteine carried a non-statistically significant adjusted odds ratio of 1.55 (95% CI, 0.93-2.58) compared to the lowest quintile in the overall cohort but a significant association among adults aged 45-64 years (OR = 2.05, 95% CI, 1.10-3.83) and an inverse association in those > or = 65 years of age. Carriers of the MTHFR C677T polymorphism were not at higher risk for VTE than those with normal genotype (OR = 0.74, 95% CI = 0.56-0.98). Our prospective data showed, at most, a weak relationship between homocysteine and VTE risk, with associations larger among younger participants. MTHFR C677T was not a risk factor for VTE.

Hyperhomocysteinemia and thrombosis

Homocysteine remains an enigmatic marker for vascular disease. Studies have shown hyperhomocysteinemia is a risk factor for VTE, cerebrovascular disease, and coronary artery disease. This relationship, however, has not been consistently corroborated by studies of patients with genetic polymorphisms that alter homocysteine metabolism. Studies at the molecular level reveal interactions between homocysteine, the endothelium, and the clotting system. Further investigation at the basic science level is needed to determine whether homocysteine is a marker of vascular injury and thrombotic potential or whether it plays a pathogenic role. Preliminary trials with vitamins clearly show that safe, inexpensive treatment can lower homocysteine levels. The clinical impact on decreasing vascular disease, however, has yet to be shown. Until there is evidence that treatment improves outcomes, testing for homocysteine and treating hyperhomocysteinemia will be a debatable issue. A series of vitamin intervention trials begun in 1997 will enroll tens of thousands of patients (Table 1) and will, it is hoped, provide the necessary information for developing evidence-based guidelines.

Prevalence of the 20210 G-->A prothrombin variant and its association with coronary artery disease in a Middle Eastern Arab population

BACKGROUND

No reports are available on the distribution of the 20210 G-->A prothrombin variant among Middle Eastern Arabs. Additionally, to date, studies that attempt to establish this polymorphism as an independent risk factor or as a predictor for coronary artery disease (CAD) have yielded conflicting results.

OBJECTIVE

To determine the prevalence of the 20210 G-->A prothrombin variant among Middle Eastern Arabs and to evaluate the potential relevance of this variant to Arab patients with angiographically documented CAD.

METHODS AND RESULTS

We used the polymerase chain reaction and restriction enzyme digestion to determine the prevalence of this polymorphism in 613 individuals from Arabic ethnic origin with CAD and from 593 healthy blood donors (BDs) from an identical ethnic background. Within the BD group (n = 593), 10 individuals (1.7%) were heterozygous, 583 individuals (98.3%) were normal, and none were homozygous for the 20210 G-->A prothrombin variant. Within the CAD group (n = 613), 13 individuals (2.1%) were heterozygous, 600 individuals (97.9%) were normal, and none were homozygous for the 20210 G-->A prothrombin variant. A chi(2) analysis was used to evaluate any significance in the distribution of genotypes. A value of 1.23 was obtained. Values less than 3.84 indicate no statistically significant difference between the heterozygous carriers of the 20210A allele in both study groups.

CONCLUSIONS

In our population of Middle Eastern Arabs, the presence of the 20210 G-->A prothrombin variant is not associated with patients with angiographically documented CAD. Therefore, this variant cannot be considered as an independent risk factor or as a predictor for CAD in this population.

Lack of association between methylenetetrahydrofolate reductase (MTHFR) C677T and ischaemic heart disease (IHD): family-based association study in a Spanish population

The effect of the C677T polymorphism in the methylenetetrahydrofolate reductase (MTHFR) gene, traditionally associated with ischaemic heart disease (IHD), was assessed in a Spanish population. The transmission disequilibrium test (TDT) was used to determine a possible association in a sample of 101 trios of IHD patients. The distribution of MTHFR genotypes was similar in the IHD subjects and the parental group; the TT genotype was present in 14.9% of IHD patients, as compared to 15.2% in the parents. The frequency of the T allele was also similar in IHD cases and parents (39.6% vs. 42.4%; p = 0.649). The TDT confirmed that the observed transmission of the T allele did not deviate significantly from the expected one (chi2 = 0.743; p > 0.4). Our TDT analysis clearly demonstrates a lack of association between the T allele of the C677T mutation in MTHFR and cardiovascular artery disease, both for the general group and for different risk subgroups (smokers, hypertension, male sex, overweight and type A behaviour pattern) in the Spanish population.

Age, sex and vitamin status affect plasma level of homocysteine, but hyperhomocysteinaemia is possibly not an important risk factor for venous thrombophilia in Taiwanese Chinese

The biological effects of age, sex and vitamin status on plasma total homocysteine (tHcy), and association of hyperhomocysteinaemia with venous thromboembolism in Taiwanese Chinese individuals, were investigated. Eighty patients (16-85 years) with venous thrombophilia and 123 healthy subjects (15-85 years) without history of vascular thrombosis were studied for plasma levels of tHcy, folate and vitamin B12. A multivariate analysis in healthy subjects revealed that plasma tHcy levels tended to increase with age (P < 0.001) and with decreasing plasma levels of folate (P=0.001) or vitamin B12 (P < 0.029); men tended to have higher plasma tHcy levels than women (P=0.006). Thrombotic risk assessment in a case-control study demonstrated that neither plasma level of tHcy [odds ratio (OR), 1.07; 95% confidence interval (CI), 0.96-1.18; P=0.210] nor hyperhomocysteinaemia (OR, 1.65; 95% CI, 0.50-5.49; P=0.415) was significantly associated with venous thrombophilia. The relationship between hyperhomocysteinaemia and recurrence of episode remained insignificant (P=0.560). We conclude that age, sex and vitamin status affect plasma tHcy but hyperhomocysteinaemia is possibly not an important risk factor for venous thrombophilia in Taiwanese Chinese.

A low prevalence of the C677T mutation in the methylenetetrahydrofolate reductase gene in Asian Indians

The prevalence of the C677T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene in Asian Indians from India was determined and the association of the mutant allele with coronary artery disease (CAD) was evaluated in a case-control study. The case group consisted of 251 patients with CAD; 195 male and 56 female aged from 29 to 82 years (mean age +/- SD, 57.5 +/- 10.6 years). The control group consisted of 216 apparently healthy individuals without evidence of CAD; 161 male and 55 female aged from 30 to 83 years (mean age +/- SD, 54.9 +/- 10.4 years). All the patients were assessed by coronary angiography. While 33 patients had normal coronaries, 23, 25 and 39 patients had single-vessel, two-vessel and triple-vessel disease, respectively. Eighty-three patients (33%) had suffered myocardial infarction less than a year to five years earlier. The C677T polymorphism in the MTHFR gene was assessed. While 31% of the controls and 38% of the patients had the heterozygous genotype, 2% of the control group and none of the patients had the mutant homozygous genotype. The overall 'T' allelic frequencies were comparable in control and patient groups (0.18 and 0.19, respectively), but the association of the sum of heterozygous and homozygous genotypes with CAD (1, 2 or 3-vessel disease) was statistically significant for females only [Odds ratio (95% confidence intervals), 2.8 (1.1-6.9), p = 0.023]. No association was found between genotype distribution and previous myocardial infarction or severity of atherosclerosis.