Ethnic differences in the frequency of the C677T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene in healthy Israeli populations

The prevalence, relative risk factors and MTHFR C677T genotype of H type hypertension of the elderly hypertensives in Shanghai, China: a cross-section study : Prevalence of H type hypertension

Background

H type hypertension is defined as homocysteine (Hcy) ≥ 10 μmol/L in combination with primary hypertension. Studies demonstrated that the existence of hyperhomocysteine (HHcy) in hypertensive exacerbates the poor outcome of cardiocerebral incidents. This study was to investigate the current epidemic situation of H type hypertension and determine the risk factors in order to find intervention targets for H type hypertensives.

Methods

We conducted a cross-sectional study using cluster sampling design in Shanghai, China from July 2019 and April 2020. 23,652 patients with primary hypertension were enrolled in this study. Their medical information was recorded, and the level of Hcy concentrations and methylenetetrahydrofolate reductase (MTHFR) C677T polymorphisms were detected.

Results

In total, 22,731 of 23,652 patients were recorded. The mean age was 68.9 ± 8.6 y and 43% were men. 80.0% of the enrolled patients had H type hypertension. The frequency of allele T was 40.9%, and the proportions of the CC, CT, and TT genotypes were 36.1%, 46.0%, and 17.9%, respectively. Compared with the TT genotype, the plasma Hcy concentration levels were lower in patients with the CC/CT genotype (18.96 ± 13.48 μmol/L vs. 13.62 ± 5.20/14.28 ± 5.36, F = 75.04, p < 0.01). The risk for H type hypertension was higher in elderly people. Men had ~ 5.55-fold odds of H type hypertension compared with women. Patients with CT genotype and TT genotype had ~ 1.36- and ~ 2.76-fold odds of H type hypertension compared with those with CC genotype, respectively. Smoking and diabetes were not significantly associated with H type hypertension.

Conclusions

The prevalence of H type hypertension in patients with primary hypertension was 80.0%, which was higher than the 75% found in prior report in China. Age, gender, and MTHFR C677T polymorphisms rather than smoking and diabetes were independently associated with H type hypertension.

Distribution of MTHFR C677T Gene Polymorphism in Healthy North Indian Population and an Updated Meta-analysis

Methylenetetrahydrofolate reductase (MTHFR) is a key enzyme of folate pathway. Several polymorphisms were reported in MTHFR gene but C677T polymorphism is most studied and it has been reported to be risk factor for several diseases/disorders. The present study was designed to explore the frequency of MTHFR C677T polymorphism in North Indian healthy population. In addition to this a meta-analysis of published articles was also performed to estimate the global prevalence of MTHFR C677T polymorphism. A total of 1000 unrelated healthy subjects were selected for MTHFR C677T polymorphism analysis. Different databases were searched for eligible articles. Prevalence proportion with 95 % CI was used to determine global prevalence of T allele and TT genotype. Meta-analysis was performed by Open meta-analyst. In 1000 blood samples analyzed, the frequency of T allele and TT genotype was 11 and 1 % respectively. Results of the meta-analysis showed that the global prevalence of T allele and TT genotype were 24.0 % (95 % CI 21.7-26.5) and 7.7 % (95 % CI 6.5-8.9) respectively. In sub-group meta-analysis, the lowest frequency of T allele was found in Africans (10.3 %; 95 % CI 3.8-16.8), and highest in Europeans (34.1 %; 95 % CI 31.9-36.3). The frequency of T allele in the North India is 11 %. The results of the meta-analysis showed that the frequency of the T allele and the TT genotype of C677T is highest in the Caucasian population.

The Prevalence of Methylenetetrahydrofolate Reductase 677 C-T, Factor V 1691 G-A, and Prothrombin 20210 G-A Mutations in Healthy Populations in Sétif, Algeria

The polymorphic mutation 677 C-T in the methylenetetrahydrofolate reductase (MTHFR) gene presents a heterogeneous worldwide distribution and is associated with different disorders such as cardiovascular disease. Its frequency shows great ethnic and geographic variations. The aim of this work is to determine the frequency of MTHFR 677 C-T and coexistence of MTHFR 677 C-T with 2 other common, hereditary thrombophilia causes—namely, factor V 1691 G-A and prothrombin (PT) 20210 G-A mutation—in the Sétif region of Algeria. The study involved 147 apparently healthy participants (82 men and 65 women). Genotyping was carried out by a real-time polymerase chain reaction. The MTHFR 677T carrier frequency was found to be 54.4% (80/147); 59 individuals were heterozygous (40.1%), and 21 were homozygous (14.3%). The frequency of MTHFR 677T was found to be 34.3%. Among the 147 individuals, 3 (2.0%) had factor V Leiden, and 5 (3.4%) had PT 20210 A mutation. Of the 80 participants with MTHFR 677T mutation, 2 had heterozygote factor V 1691 G-A gene mutation, and 4 had heterozygote PT 20210 G-A gene mutation. The results showed that MTHFR 677T prevalence is quite high: an allelic frequency of 34.3% with a genotype frequency of 14.3%. Factor V 1691 G-A and PT 20210 G-A gene mutations are rare in the healthy population of the Sétif region of Algeria.

Thrombophilic polymorphisms in Israel

Three thrombophilic polymorphisms, FV G1691A, FII G20210A and MTHFR C677T were investigated in Israeli populations by FRET, (fluorescence resonance energy transfer) real-time PCR. We observe extensive variability in the frequencies of each of the polymorphisms, as has been observed in the study of other polymorphisms in these populations. Very high allele frequencies for FV G1691A (the highest 0.087 in Turkish and Greek Jews) and FII G20210A (the highest 0.061 in Georgian Jews) in some of the Israeli populations justify a clinical investigation to assess their risk for venous thrombosis. Principal Coordinates Analysis demonstrates that the Jewish populations are interspersed among the non-Jewish populations. The resemblance of some Jewish populations to certain non-Jewish populations coincides with findings based on classical markers.

Ethnic differences of coronary artery disease-associated SNPs in two Israeli healthy populations using MALDI-TOF mass spectrometry

Differences in prevalence and mortality from coronary artery disease (CAD) were observed among the different Israeli ethnic groups. The incidence of CAD in Israel is highest among Ashkenazi Jews and is much lower among Yemenite Jews. In this present study, we selected 15 single nucleotide polymorphisms (SNPs) from 14 candidate genes involved in (1) the renin-angiotensin system, (2) lipid metabolism, (3) cytokines and adhesion molecules, and (4) growth factors, and (5) the coagulation-fibrinolysis system. We analyzed the 15 SNPs in 94 Israeli healthy populations (47 Ashkenazi Jews and 47 Yemenite Jews) obtained from the National Laboratory for the Genetics of Israeli Populations. We applied chip-based MALDI-TOF mass spectrometry as a method for screening multiplexed genotyping of SNPs for ethnic difference in these healthy populations. Among the 15 candidate SNPs, significant differences in allelic frequency were observed in the 1166A>C of the AGTR1 gene, R158C of the Apo E gene, W64R of the ADRB3 gene, S101S of the TIMP 2 gene, and A222V of the MTHFR gene with respect to allele frequency. The incidence of A/C allele of the AGTR1 gene were 0.638/0.362 vs 0.765/0.235, C/T allele in the apo E gene was 0.915/0.085 vs 0.989/0.011, T/C allele of the ADRB3 gene was 0.989/0.0011 vs 0.926/0.074, G/A allele of the TIMP2 gene was 0.974/0.054 vs 0.830/0.170, and C/T allele in the MTHFR gene was 0.521/0.479 vs 0.819/0.181 for Ashkenazi Jews and Yemenite Jews, respectively. We demonstrated an ethnic difference of CAD-associated SNPs in two Israeli healthy populations using MALDI-TOF mass spectrometry. Further study is necessary to prove causal relation with CAD-associated SNPs and the prevalence of CAD.

Clinical and ethnic characteristics of stroke in an Israeli population: a study in a community hospital population

Background: Stroke mainly affects the older population, although it has also been reported in younger patients. In this study, we focused on patients 65 years of age or younger with stroke. Methods: The files of three patient populations were studied: 93 patients aged 65 years or younger with stroke (group A), 93 patients older than 65 with stroke (group B), and 604 patients without stroke representing the general population of patients admitted to our service during January 2000 (group C). We reviewed the patient files and compared patient characteristics, epidemiological features, clinical picture,imaging findings, and coagulation tests. Results: Overall, 318 patients were studied. The mean age of group A was 55 years compared to 77 years in group B and 71 years in group C. In both stroke groups (A and B), the male: female ratio was 2:1, in contrast with a balanced ratio in group C. Most of the patients in group A (63%) were of Sephardic origin compared to 39% in group B (P=0.002) and 30% in group C. The clinical picture in both stroke groups (A and B) was similar. The risk factor smoking was reported by 45% in group A and by only 29% in group B (P=0.034). Hypertension, diabetes mellitus, and hyperlipidemia were evenly prevalent in both stroke groups. The coagulation system was studied in the "young" patients (group A): hyperhomocysteinemia was found in 37%, high titers of anticardiolipin antibodies in 35%, low levels of antithrombin III in 13%, protein C deficiency in 5%, and activated protein C resistance (APCR) in 4%. Overall, 49% of the patients from group A were found to have coagulation abnormalities. Conclusions: We found in our study that the younger patient with stroke tends to be a Sephardic male with the classical risk factors as well as a history of smoking and coagulopathy. These findings suggest strict medical supervision and primary prophylaxis. This work also lays the basis for a prospective, interventional trial with younger patients.

Correlation between C677T MTHFR gene polymorphism, plasma homocysteine levels and the incidence of CAD

The lesions of coronary atherosclerosis represent the result of a complex, multicellular, inflammatory-healing response in the coronary arterial wall. In vivo and in vitro cellular and molecular studies have suggested a role for tissue homocysteine in endothelial cell injury and adverse extra-cellular matrix remodeling. Gene polymorphisms in relation with numerous risk factors might increase the incidence of coronary artery disease (CAD). In this review we have focused on the correlations between plasma homocysteine levels, the incidence of cardiovascular disease and the cytosine-to-thymidine substitution at nucleotide 677 (C677T) of the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene, coding for a key enzyme in methionine-homocysteine metabolism. The role of the C677T MTHFR gene polymorphism in the causation of CAD is controversial. We reviewed 12 recent case-control studies comprising 5370 genotyped patients with CAD and 4961 genotyped participants without CAD. There was no significant difference between those with and without CAD in the frequency of the C677T polymorphism (34.9 vs 33.6%). The frequency of homozygous C677T polymorphism in these groups was 10.9 versus 12.8%, respectively, although there were some ethnic differences in the C677T MTHFR polymorphism. In the analysis of the 12 studies, the odds ratio of CAD associated with the TT genotype (homozygous C677T polymorphism) was 1.18. Only slightly higher plasma homocysteine levels were observed in participants with the val/val (TT) genotype (14.4+/-2.9 micro mol/L in TT genotype vs 11.1+/-1.9 and 11.9+/-2 micro mol/L in CC and CT genotype, respectively). In addition, the relation between homocysteine increase after methionine loading and MTHFR genotypes is also controversial. However, hyperhomocysteinemia because of the C677T MTHFR allele may be corrected with oral folic acid therapy. Further investigations on the relationships between MTHFR genotypes and the incidence of CAD should be based on larger samples, paying attention to the differences between various ethnic populations. Individual therapeutic strategies based on single nucleotide polymorphism may become increasingly important for preventive treatment against polygenic CAD.

Differences in the frequency of the C677T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene among the Lebanese population

In view of its role in precipitating mild hyperhomocysteinemia as well as being a risk factor for vascular thrombosis, we investigated the frequency of the C677T mutation of the methylenetetrahydrofolate reductase (MTHFR) gene among 589 healthy Lebanese subjects by PCR-RFLP analysis (HinfI digestion) and compared them with those of other countries of Caucasian and non-Caucasian origin. The prevalence of the mutated homozygous (T/T) and heterozygous (C/T) C677T MTHFR genotype was 11.04% and 39.73%, respectively, giving an allele frequency of 0.309. While the prevalence of the T/T genotype was similar with respect to gender, higher prevalence was noted among Christian (13.08%) compared to Moslem (7.66%) subjects (P < 0.001), and heterogeneity in its distribution was seen in the different Lebanese provinces, and was directly related to the Christian/Moslem composition of each province. The distribution of the MTHFR C677T in Lebanon is unique with regard to its higher occurrence among Christians compared to Moslems, adding to the existing body of literature on the heterogeneity of its prevalence and distribution.

Genetic evaluation for coronary artery disease

There is substantial evidence that genetic factors contribute to coronary artery disease (CAD). Currently, family history collection and interpretation is the best method for identifying individuals with genetic susceptibility to CAD. Family history reflects not only genetic susceptibility, but also interactions between genetic, environmental, cultural, and behavioral factors. Stratification of familial risk into different risk categories (e.g., average, moderate, or high) is possible by considering the number of relatives affected with CAD and their degree of relationship, the ages of CAD onset, the occurrence of associated conditions, and the gender of affected relatives. Familial risk stratification should improve standard CAD risk assessment methods and treatment guidelines (e.g., Framingham CAD risk prediction score and Adult Treatment Panel III guidelines). Individuals with an increased familial risk for CAD should be targeted for aggressive risk factor modification. Individuals with a high familial risk might also benefit from early detection strategies and biochemical and DNA-based testing, which can further refine risk for CAD. In addition, individuals with the highest familial risk might have mendelian disorders associated with a large magnitude of risk for premature CAD. In these cases, referral for genetic evaluation should be considered, including pedigree analysis, risk assessment, genetic counseling and education, discussion of available genetic tests, and recommendations for risk-appropriate screening and preventive interventions. Research is needed to assess the feasibility, clinical validity, clinical utility, and ethical, legal, and social issues of an approach that uses familial risk stratification and genetic evaluation to enhance CAD prevention efforts.

Plasma homocysteine and parental myocardial infarction in young adults in Jerusalem

BACKGROUND

A causal role for mildly elevated plasma homocysteine (tHcy) in cardiovascular disease remains undetermined. To address the unresolved issue of the antecedent-consequent directionality of the relationship, we assessed the familial association of tHcy with parental myocardial infarction (MI) in young Israeli men and women. We also compared tHcy concentrations in Jerusalem, where rates of coronary heart disease (CHD) are high, with the United States Third National Health and Examination Survey (NHANES III).

METHODS AND RESULTS

A total of 8646 17-year-olds and 6952 parents were examined from 1976 to 1979 in Jerusalem. At ages 28 to 32 years, offspring of parents who experienced a documented MI during a 10-year follow-up (n=133 men, 62 women; 72% response) and offspring of CHD-free parents (n=389 men, 208 women; 71% response) were reexamined. tHcy levels were determined by the same laboratory for the NHANES non-Hispanic white population aged 25 to 34 years (n=379) and the Jerusalem population sample (n=858). Men from Jerusalem, but not women, had clearly higher tHcy levels than the sample from the United States (90th percentile, 23 versus 14 micromol/L). This difference was largely attributable to lower plasma vitamin B12 levels in the Israeli population. Male case offspring had higher adjusted tHcy than did controls (1.9 micromol/L, P=0.002). Logistic modeling revealed a graded increase in risk of parental MI across quintiles of offspring tHcy, with an adjusted odds ratio of 2.7 in the 5th quintile (P=0.0026 for trend).

CONCLUSIONS

The higher tHcy in young male offspring of parents with CHD suggests that elevated tHcy precedes manifestation of CHD. The elevated population tHcy in men may contribute to the high incidence of CHD in Israel.

The C677T methylenetetrahydrofolate reductase mutation is not associated with Alzheimer's disease

The methylenetetrahydrofolate reductase (MTHFR) gene has been recently considered as a candidate gene for Alzheimer's disease (AD). MTHFR is a key enzyme in the metabolism of homocysteine and elevated levels of that amino acid have been associated to Vascular Dementia and AD. A T-->C transition at codon 677 produces a thermolabile type of the enzyme. However, contrasting results on the distribution of the MTHFR C677T common polymorphism in AD have been published. We analyzed the distribution of the MTHFR and apolipoprotein E (APOE) polymorphisms in Italian patients with sporadic AD. The distribution of the C677T polymorphism did not differ in AD and controls. Our data suggest that the MTHFR polymorphism does not contribute to genetic susceptibility in Italian sporadic AD and does not mitigate the effect of ApoE epsilon4 allele on AD risk.