Association of methylenetetrahydrofolate reductase gene polymorphism with carotid atherosclerosis depending on smoking status in a Japanese general population

Cross-Sectional Gene-Smoking Interaction Analysis in Relation to Subclinical Atherosclerosis-Results From the IMPROVE Study

BACKGROUND

Smoking is associated with carotid intima-media thickness (C-IMT). However, knowledge about how genetics may influence this association is limited. We aimed to perform nonhypothesis driven gene-smoking interaction analyses to identify potential genetic variants, among those included in immune and metabolic platforms, that may modify the effect of smoking on carotid intima-media thickness.

METHODS

We used baseline data from 1551 men and 1700 women, aged 55 to 79, included in a European multi-center study. Carotid intima-media thickness maximum, the maximum of values measured at different locations of the carotid tree, was dichotomized with cut point values ≥75, respectively. Genetic data were retrieved through use of the Illumina Cardio-Metabo- and Immuno- Chips. Gene-smoking interactions were evaluated through calculations of Synergy index (S). After adjustments for multiple testing, P values of <2.4×10-7 for S were considered significant. The models were adjusted for age, sex, education, physical activity, type of diet, and population stratification.

RESULTS

Our screening of 207 586 SNPs available for analysis, resulted in the identification of 47 significant gene-smoking synergistic interactions in relation to carotid intima-media thickness maximum. Among the significant SNPs, 28 were in protein coding genes, 2 in noncoding RNA and the remaining 17 in intergenic regions.

CONCLUSIONS

Through nonhypothesis-driven analyses of gene-smoking interactions, several significant results were observed. These may stimulate further research on the role of specific genes in the process that determines the effect of smoking habits on the development of carotid atherosclerosis.

Association of methylenetetrahydrofolate reductase (MTHFR) variant C677T and risk of carotid atherosclerosis: a cross-sectional analysis of 730 Chinese Han adults in Chongqing

BACKGROUND

Uncertainty still remains on the correlation of methylenetetrahydrofolate reductase (MTHFR) variant C677T with risk of carotid atherosclerosis (CAS), and there is a lack of reports on C677T/MTHFR in the Asian population. The association of C677T/MTHFR polymorphisms with CAS in the Chinese Han population in Chongqing was investigated in the present study.

METHODS

Subjects (n = 730, 214 females and 516 males, Han ethnicity) who provided an informed consent were randomly selected from the general population of Chongqing, China. Polymerase chain reaction-restriction fragment length polymorphism and Sanger sequencing genotyping assays were used to determine the MTHFR genotypes. The atherosclerosis index of the intima-media thickness (IMT) was measured by high-resolution ultrasound to evaluate the CAS. Less than 1.0 mm was considered as normal for IMT, 1.0-1.5 mm was considered as thickening, and ≥ 1.5 mm and a local bulge thickened in the lumen was considered as CAS. According to the carotid ultrasonography results, these subjects were divided into two groups: CAS-group (IMT ≥ 1.0 mm) and control group (IMT < 1.0 mm).

RESULTS

The frequency of C/T heterozygotes, T/T homozygotes genotype was significantly higher in the subjects with CAS (62% vs. 36.9%; 16.2% vs. 9.5%; 47.2% vs. 27.9%, P < 0.05), while the frequency of C/C homozygotes and C allele was significantly lower (21.8% vs. 53.7%; 52.8% vs. 72.1%, P < 0.05), when compared to the control group. The risk of CAS was higher for subjects with C/T heterozygotes and T/T homozygotes (OR = 4.06, 95% CI: 2.76-5.98, P < 0.001 and OR = 3.14, 95% CI: 1.73-5.69, P < 0.001, respectively), when compared to the subjects with the C/C genotype. In the model 1 (CT + TT versus CC), C677T/MTHFR was significantly associated with the prevalence of CAS, and the all adjusted OR values for CAS were 3.87 (95% CI, 2.67 to 5.62) in all, 17.18 (95% CI, 7.27 to 40.49) in women and 2.57 (95% CI, 1.65 to 3.99) in men after adjusting for potential confounding factors.

CONCLUSIONS

The present study suggests that a mutation in the methylenetetrahydrofolate reductase gene is a risk factor of CAS in the Chinese Han population.

Homocysteine, the methylenetetrahydrofolate reductase 677C>T polymorphism and hypertension: effect modifiers by lifestyle factors and population subgroups

Evidence linking fasting plasma total homocysteine (tHcy) and methylenetetrahydrofolate reductase (MTHFR) 677C>T genotype with hypertension is inconsistent. Differences in B vitamin status, other lifestyle factors or their consideration in analyses might explain this. We investigated these associations in the absence of mandatory fortification with folic acid and B vitamin supplement use. A cross-sectional study was conducted in 788 adults, aged 18-75 years, randomly selected from three Catalonian town population registers. Fasting plasma folate, cobalamin, tHcy, erythrocyte folate, erythrocyte glutathione reductase activation coefficient (EGRAC, functional riboflavin status indicator; increasing EGRAC indicates worsening riboflavin status), MTHFR 677C>T and solute carrier family 1 (SLC19A1) 80 G>A genotypes were determined. Medical history and lifestyle habits were recorded. Principal tHcy determinants differed between women (age, plasma folate, plasma cobalamin, cigarettes/d) and men (MTHFR 677TT genotype, plasma folate, plasma cobalamin and CT genotype). The MTHFR 677C>T polymorphism-tHcy association (β standardised regression coefficients) was stronger in male smokers (0·52, P < 0·001) compared with non-smokers (0·21, P = 0·001) and weaker in participants aged >50 years (0·19, P = 0·007) compared with ≤50 years (0·31, P < 0·001). Hypertension was more probable in the third tHcy tertile compared with other tertiles (OR 1·9; 95 % CI 1·2, 3·0), and in participants aged ≤50 years, for the MTHFR 677TT genotype compared with the CC genotype (OR 4·1; 95 % CI 1·0, 16·9). EGRAC was associated with increased probability of hypertension in participants aged >50 years (OR 6·2; 95 % CI 1·0, 38·7). In conclusion, moderately elevated tHcy and the MTHFR 677CT genotype were associated with hypertension. The MTHFR 677C>T genotype-hypertension association was confined to adults aged ≤50 years.

Single nucleotide polymorphism of MTHFR rs1801133 associated with elevated Hcy levels affects susceptibility to cerebral small vessel disease

Background

Methylenetetrahydrofolate reductase (MTHFR) is indispensable for the conversion of homocysteine (Hcy) to methionine. The single nucleotide polymorphism (SNP) of MTHFR gene (rs1801133, C667T) is correlated with decreased enzyme activity that eventually results in elevated plasma Hcy levels. Hyperhomocysteinemia has been confirmed to be involved in the pathogenesis of stroke, cerebral small vessel disease (CSVD), various metabolic disorders and so on. However, the relationship between the MTHFR gene polymorphisms, Hcy, and CSVD has not been investigated. In this study, the relationship between SNPs of MTHFR gene and CSVD was determined after adjusting for cardiovascular risk factors, and the potential mechanism based on Hcy levels was explored.

Methods

A total of 163 consecutive CSVD patients were collected as the case group. In the corresponding period, 326 healthy people were selected as the control group, who were matched to these cases according to age (±2 years) and gender at a ratio of 2:1. SNPs of MTHFR rs1801133, rs1801131, rs2274976, rs4846048, rs4846049, rs13306561 and rs3737964, were genotyped with TaqMan Pre-Designed SNP Genotyping Assays. Plasma Hcy levels were detected using Hcy reagent through enzymatic cycling assay. Multivariate analysis was used to identify the SNPs associated with CSVD susceptibility. Plasma Hcy levels were compared between different genotypes.

Results

The MTHFR rs1801133 TT and CT genotype had increased risk for CSVD, and the OR was higher in the TT genotype than in the CT genotype (2.307 vs 1.473). The plasma Hcy levels of different genotypes showed the tendency of the TT genotype > CT genotype > CC genotype (19.91 ± 8.73 pg/ml vs 17.04 ± 5.68 pg/ml vs 14.96 ± 4.85 pg/ml).

Conclusions

The SNP of MTHFR rs1801133 was correlated with CSVD, and the TT and CT genotypes had increased risk for CSVD compared to the CC genotype. The potential mechanism was associated with elevated Hcy levels.

Genetic polymorphisms of methylenetetrahydrofolate reductase C677T and risk of ischemic stroke in a southern Chinese Hakka population

Previous studies have shown that methylenetetrahydrofolate reductase (MTHFR) gene to be a genetic risk factor for the susceptibility to ischemic stroke. The aim of this case-control study was to investigate whether the polymorphisms of MTHFR C677T were associated with the susceptibility to ischemic stroke in a southern Chinese Hakka population. In this study, a total of 1967 ischemic stroke patients and 2565 controls of Chinese Hakka ethnicity were recruited. The MTHFR C677T polymorphisms were genotyped by polymerase chain reaction (PCR) amplification and microarray method. The risk of ischemic stroke was estimated by logistic regression analysis. The frequencies of CC, CT, and TT genotypes were 52.67% versus 55.63%, 40.31% versus 38.52%, and 7.02% versus 5.85% in patients with ischemic stroke versus controls, respectively. The frequency of T allele was significantly higher in ischemic stroke patients (27.17%) than in controls (25.11%) (P = .026, odds ratio [OR] 1.113, 95% confidence interval [CI] 1.013-1.223). The homozygous TT genotype in the ischemic stroke patients was associated with increased risk (P = .049, OR 1.132, 95% CI 1.001-1.281) when compared with the controls after adjustment for age and sex. The positive association was only found in dominant model without adjustment for age and sex (P = .047, OR 1.127, 95% CI 1.002-1.268). Also, the carrier status of the MTHFR T allele was identified as an independent risk factor for the development ischemic stroke even after the adjustment for conventional risk factors (P = 0.047, OR 1.109, 95% CI 0.964-1.225). Our results provide evidence that variants of MTHFR C677T gene may influence the risk of developing ischemic stroke in a southern Chinese Hakka population. Further studies are needed to confirm this association, which will promote the development of strategies for prevention and treatment of ischemic stroke in our study population.

Impact of Intima-Media Thickness Progression in the Common Carotid Arteries on the Risk of Incident Cardiovascular Disease in the Suita Study

Background

No prospective study of the relationship between intima–media thickness (IMT) progression and incident cardiovascular disease (CVD) has been performed.

Methods and Results

We studied 4724 participants (mean age: 59.7±11.9 years; without CVD at the baseline) who had carotid ultrasonographic measurement of IMT on both sides of the entire carotid artery area (ie, the entire scanned common carotid artery [CCA], carotid artery bulb, internal carotid artery, and external carotid artery areas for both sides) between April 1994 and August 2001. Carotid ultrasonographic follow‐up was performed every 2 years between April 1994 and March 2005 in 2722 of these participants, newly revealing 193 CCA plaques (maximum IMT in the CCA >1.1 mm). We followed up for incident CVD until December 2013. Statistical analyses were performed using a Cox proportional hazards regression model, evaluated using C statistics, and net reclassification improvement. During the 59 909 person‐years of follow‐up, we observed 221 strokes and 154 coronary heart disease events. CCA plaque and maximum IMT in the whole carotid artery area >1.7 mm were risk factors for CVD. CCA plaque presented an increased risk of CVD based on C statistics and the reclassification improvement of the current risk prediction model. After adding the new incident CCA plaques, during the 23 702 person‐years of follow‐up, 69 strokes and 43 coronary heart disease events occurred. The adjusted hazard ratios for incident CCA plaque were 1.95 (95% confidence interval, 1.14–3.30) in CVD and 2.01 (95% confidence interval, 1.01–3.99) in stroke.

Conclusions

Maximum IMT in the CCA contributed significantly but modestly to the predictive power of incident CVD used in calculating traditional risk factors. This study provides the first demonstration that new progression of incident CCA plaque is a CVD risk.

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.

Serum homocysteine as a risk factor for carotid intimal thickening in acute stroke: A cross sectional observational study

Introduction:

The present study aimed to analyse if there is a correlation between carotid intima medial thickening (CIMT) and Hcy in stroke patients.

Methodology:

We studied 100 consecutive cases of acute anterior circulation strokes at St. John's Medical College, Bangalore, India. Fasting serum samples for homocysteine were sent within 24 hours of admission and all patients underwent a carotid Doppler scan and carotid intima-medial thickness (CIMT) was estimated on both sides.

Results:

There was significant correlation between serum homocysteine levels and carotid intima-medial thickness (r = 0.409, p = 0.000). Also after controlling for other possible risk factors it was found that elevations in serum homocysteine levels would cause a variation of 60% in the carotid intima-medial thickening.

Conclusion:

Serum Hcy levels correlate well with CIMT and hence may predict atherothrombotic events.

Potential role of folate in pre-eclampsia

Dietary deficiencies of folate and other B vitamin cofactors involved in one-carbon metabolism, together with genetic polymorphisms in key folate-methionine metabolic pathway enzymes, are associated with increases in circulating plasma homocysteine, reduction in DNA methylation patterns, and genome instability events. All of these biomarkers have also been associated with pre-eclampsia. The aim of this review was to explore the literature and identify potential knowledge gaps in relation to the role of folate at the genomic level in either the etiology or the prevention of pre-eclampsia. A systematic search strategy was designed to identify citations in electronic databases for the following terms: folic acid supplementation AND pre-eclampsia, folic acid supplementation AND genome stability, folate AND genome stability AND pre-eclampsia, folic acid supplementation AND DNA methylation, and folate AND DNA methylation AND pre-eclampsia. Forty-three articles were selected according to predefined selection criteria. The studies included in the present review were not homogeneous, which made pooled analysis of the data very difficult. The present review highlights associations between folate deficiency and certain biomarkers observed in various tissues of women at risk of pre-eclampsia. Further investigation is required to understand the role of folate in either the etiology or the prevention of pre-eclampsia.

Association of FTO, LEPR and MTHFR gene polymorphisms with metabolic syndrome in schizophrenia patients receiving antipsychotics

AIM

The occurrence of metabolic syndrome (MS) in schizophrenia patients receiving long-term antipsychotics (APs) contributes to their high mortality rate. We aimed to determine whether genetic polymorphisms of identified candidate genes are associated with MS in our study population.

MATERIALS & METHODS

We recruited 206 schizophrenia patients receiving AP treatment for at least a year. Cross-sectional measurements of weight, height, blood pressure, waist and hip circumference, and other lipid profiles were recorded. Patient DNA was genotyped for 16 candidate gene polymorphisms.

RESULTS

Of these patients, 59.7% were found to have MS while 40.3% did not. All metabolic parameters were significantly different between the two groups. Only three of the 16 polymorphisms studied showed significant association with MS; rs9939609 of the FTO gene confers risk for MS (odds ratio [OR]: 1.73, 95% CI: 1.07-2.78, p = 0.026), while rs1137101 of the LEPR gene (OR: 0.47, 95% CI: 0.28-0.80, p = 0.005) and rs1801133 of the MTHFR gene (OR: 0.59, 95% CI: 0.35-0.99, p = 0.049) are protective against MS.

CONCLUSION

Polymorphisms of the FTO, LEPR and MTHFR genes may play a role in MS in Malaysian schizophrenia patients receiving long-term treatment with APs.

MTHFR C677T polymorphism affects normotensive diastolic blood pressure independently of blood lipids

BACKGROUND

Methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism was found to be associated with hypertension. High blood pressure (BP) is a major risk factor for cardiovascular disease, gestational hypertension, and high-risk pregnancy. BP is a complex trait strongly associated with blood lipid parameters. However, studies of the effect of MTHFR C677T polymorphism on BP levels independently of blood lipids are scarce. Our objective was to analyze and quantify the effect of MTHFR C677T polymorphism on normotensive BP independently of blood lipids.

METHODS

MTHFR C677T genotyping was done for 151 Israeli women attending the genetics clinic at Soroka Medical Center. Biochemical (blood lipids) and BP data were extracted from Soroka Medical Center records. BP was regarded as a continuous parameter using analysis of covariance and post hoc Tukey's HSD (honestly significant difference) analysis.

RESULTS

The frequencies of genotypes CC, TT, and CT were 41%, 12%, and 47%, respectively. A significant (P < 0.0001) association was found between genotype and diastolic BP (DBP) when adjusted to body mass index and age. Mean DBP was significantly lower for CC than for TT genotypes (71.2 vs. 78.7 mm Hg); however the difference between the heterozygotes (73.9 mm Hg) and the other 2 genotypes was not significant. Cholesterol, LDLcalc (LDLcalculaed), and homocysteine blood levels significantly contributed to the effect of MTHFR C677T polymorphism on the DBP trait. There was also significant association between genotype and folic acid levels.

CONCLUSIONS

MTHFR C677T polymorphism significantly affects DBP in Israeli women, independently of blood lipids. Each C to T substitution is associated with a mean 3.4-mm Hg increase in DBP.

MTHFR 677TT genotype and disease risk: is there a modulating role for B-vitamins?

Methylenetetrahydrofolate reductase (MTHFR) is a critical folate-metabolising enzyme which requires riboflavin as its co-factor. A common polymorphism (677C→T) in the MTHFR gene results in reduced MTHFR activity in vivo which in turn leads to impaired folate metabolism and elevated homocysteine concentrations. Homozygosity for this polymorphism (TT genotype) is associated with an increased risk of a number of conditions including heart disease and stroke, but there is considerable variability in the extent of excess risk in various reports. The present review will explore the evidence which supports a role for this polymorphism as a risk factor for a number of adverse health outcomes, and the potential modulating roles for B-vitamins in alleviating disease risk. The evidence is convincing in the case which links this polymorphism with hypertension and hypertensive disorders of pregnancy, particularly preeclampsia. Furthermore, elevated blood pressure was found to be highly responsive to riboflavin intervention specifically in individuals with the MTHFR 677TT genotype. Future intervention studies targeted at these genetically predisposed individuals are required to further investigate this novel gene-nutrient interaction. This polymorphism has also been associated with an increased risk of neural tube defects (NTD) and other adverse pregnancy outcomes; however, the evidence in this area has been inconsistent. Preliminary evidence has suggested that there may be a much greater need for women with the MTHFR 677TT genotype to adhere to the specific recommendation of commencing folic acid prior to conception for the prevention of NTD, but this requires further investigation.

Association of MTHFR C677T and A1298C gene polymorphisms with hypertension

OBJECTIVES

To check for the association of genetic polymorphisms related to the methylenetetrahydrofolate reductase (MTHFR) gene namely C677T and A1298C with hypertension in Saudi affected subjects from Qassim region.

SUBJECTS AND METHODS

Participants included 123 Saudi hypertensive cases (83 males and 40 females) in addition to 250 (142 males and 108 females) unrelated healthy controls from the same locality. Their age mean ±SD was 50.93 ± 15.43 years. For all subjects, DNA was extracted followed by real-time PCR amplifications for characterization of genotypes and alleles related to MTHFR C677T and A1298C gene polymorphisms

RESULTS

Total cases showed significantly higher carriage rate for the mutant allele 677T compared to controls (40.7% vs. 26%, OR=1.9, 95% CI= 1.2-3.1) with a lower frequency of the wild type 677CC genotype (59.3% vs. 74%, p=0.004). The same was observed among cases-subgroups of hypertension associated with obesity with a notably higher odds ratio (OR=2.6, 95% CI=1.3-5.01, p=0.004). Total cases showed also significantly higher frequency of mutant 1298 C allele carriage rate compared to controls (59.3% vs. 42.4%, OR=1.98, 95% CI= 1.3-3.1) with a lower frequency of the normal AA genotype (40.7% vs. 57.6%, p=0.003). The same was observed among cases-subgroups of hypertension associated with both diabetes and obesity and among cases of hypertension with obesity, also with higher odds ratio (OR=2.6 and 2.2 respectively).

CONCLUSION

This work showed that genetic polymorphisms related to the MTHFR gene are associated with the risk of hypertension particularly when accompanied with obesity and diabetes among Saudi subjects.

Association of methylenetetrahydrofolate reductase gene 677C>T polymorphism with hypertension in older women in a population of Buenos Aires City

We examined the relationship between the 677C >T polymorphism in the MTHFR gene and tHcy in normotensive (NT) and hypertensive (HT) subjects and the influence of sex and age in a cross-sectional study. Smoking habits, history of vascular disease, diabetes, and tHcy were significantly associated with T allele as hypertension risk factors. The T allele was significantly related with higher tHcy in (i) men versus women (P < .01), (ii) men and women older than 47 years versus the younger ones (P < .05 and P < .001, respectively), (iii) HT women versus NT women (P < .01), and (iv) older HT women versus older NT women (P < .01). We found an association between the 677C>T MTHFR polymorphism and tHcy with hypertension that in women is manifested with age.

Investigation of the Interaction Between the Ser447Term Polymorphism of Lipoprotein Lipase and the Stroke-Related Risk Factors in Ischemic Stroke

The present study aimed to investigate the interaction between the Ser447Term polymorphism in the lipoprotein lipase (LPL) gene and some common risk factors for stroke. A total of 704 unrelated patients with ischemic stroke were recruited for genetic analysis; they were all of Han Chinese origin. These patients were classified into subgroups based on their exposure to stroke-related risk factors, including type 2 diabetes, hypertension, smoking, and hyperlipidemia. The Ser447Term polymorphism was genotyped by PCR-based restriction fragment length polymorphism analysis. The chi-square (χ (2)) test showed that the frequency of Ser447Term G allele was significantly higher in stroke patients with a history of diabetes than in those without a history of diabetes (χ (2) = 7.25, P = 0.007, OR = 1.78, 95%CI 1.18-2.68). Allelic association was not observed in patients exposed to the other three stroke-related risk factors. The combined effect of the LPL gene polymorphisms and diabetes may contribute to the development of a subgroup of ischemic stroke.

Lack of carotid stiffening associated with MTHFR 677TT genotype in cardiorespiratory fit adults

The TT genotype of C677T polymorphism in 5,10-methylenetetrahydrofolate reductase (MTHFR) induces elevation of homocysteine level and leads to atherosclerosis and arterial stiffening. Furthermore, cardiorespiratory fitness level is also associated with arterial stiffness. In the present study, a cross-sectional investigation of 763 Japanese men and women (18-70 yr old) was performed to clarify the effects of cardiorespiratory fitness on the relationship between arterial stiffness and MTHFR C677T gene polymorphism. Arterial stiffness was assessed by carotid beta-stiffness with ultrasonography and tonometry. The study subjects were divided into high-cardiorespiratory fitness (High-Fit) and low-cardiorespiratory fitness (Low-Fit) groups based on the median value of peak oxygen uptake in each sex and decade. The plasma homocysteine level was higher in the TT genotype of MTHFR C677T polymorphism compared with CC and CT genotype individuals. MTHFR C677T polymorphism showed no effect on carotid beta-stiffness, but there was a significant interaction effect between fitness and MTHFR C677T polymorphism on carotid beta-stiffness (P = 0.0017). In the Low-Fit subjects, carotid beta-stiffness was significantly higher in individuals with the TT genotype than the CC and CT genotypes. However, there were no such differences in High-Fit subjects. In addition, beta-stiffness and plasma homocysteine levels were positively correlated in Low-Fit subjects with the TT genotype (r = 0.71, P < 0.0001), but no such correlations were observed in High-Fit subjects. In CC and CT genotype individuals, there were also no such correlations in either fitness level. These results suggest that the higher cardiorespiratory fitness may attenuate central artery stiffening associated with MTHFR C677T polymorphism.

Association of plasma B-type natriuretic peptide levels with obesity in a general urban Japanese population: the Suita Study

The inverse association between plasma B-type natriuretic peptide (BNP) levels and body mass index (BMI) has been reported in Western populations. Here we analyzed the relationship between plasma BNP and obesity in a general urban Japanese population. We recruited 1,759 subjects without atrial fibrillation or history of ischemic heart disease aged 38-95 years (mean age +/- standard deviation 64.5 +/- 10.9 years, 56.1% women, mean BMI 22.8 +/- 3.1 kg/m(2)) from the participants in the Suita Study between August 2002 and December 2003. In multivariable regression analyses adjusted for age, systolic blood pressure, pulse rate, serum creatinine, left ventricular hypertrophy in ECG, the inverse relationships between BNP levels and BMI (kg/m(2)) was found in both sexes (both p<0.001). Multivariable-adjusted mean plasma BNP levels in the group of BMI<18.5, 18.5< or =BMI< 22, 22< or =BMI<25, and 25< or =BMI were 23.4, 17.9, 14.0 and 13.0 pg/mL, respectively (trend p<0.001). The negative association of body fat (percentage and mass), skin fold thickness, or waist circumference with BNP levels was observed the negative associations in both sexes (p<0.01). Among the obesity indices, body fat mass is most tightly associated with BNP. In conclusion, plasma BNP was inversely associated with obesity related markers such as body fat mass, skinfold thickness and waist circumferences after adjusted for relevant covariates in a Japanese population.

A validated HPLC-fluorescence method with a semi-micro column for routine determination of homocysteine, cysteine and cysteamine, and the relation between the thiol derivatives in normal human plasma

A semi-micro column HPLC-fluorescence method for routine determination of thiol derivatives such as homocysteine (Hcy), cysteine (Cys) and cysteamine (CA) is described. The thiol derivatives labeled with ammonium-7-fluorobenzo-2-oxa-1,3-diazole-4-sulfonate (SBD-F) were isocratically separated within 12 min on a semi-micro ODS column (Daisopak-SP-120-5-ODS-BP) with a mixture of 25 mm acetate buffer (pH 2.00) and CH(3)CN as a mobile phase. The purity and similarity of SBD-thiols by a multi-wavelength fluorescence detector were more than 92.3 and 96.7%. The detection limits of Hcy, Cys and CA at a signal-to-noise ratio of 3 were 0.16, 0.47 and 0.03 microm, respectively. Furthermore validation parameters such as accuracy, precision and robustness of the proposed method showed satisfactory results. Almost 850 plasma sample injections (range 572-1076, n = 3) for a column could be performed without differences in retention time and peak heights of labels. As an application of the proposed method, the determination of thiol derivatives in normal human plasma (n = 103) was demonstrated. The correlation coefficients between Hcy vs Cys and Hcy vs CA were 0.38 and -0.35, respectively.

Postgraduate Symposium The MTHFR C677T polymorphism, B-vitamins and blood pressure

High blood pressure (BP) and elevated homocysteine are reported as independent risk factors for CVD and stroke in particular. The main genetic determinant of homocysteine concentrations is homozygosity (TT genotype) for the C677T polymorphism in the methylenetetrahydrofolate reductase (MTHFR) gene, typically found in approximately 10% of Western populations. The B-vitamins folate, vitamin B12and vitamin B6are the main nutritional determinants of homocysteine, with riboflavin more recently identified as a potent modulator specifically in individuals with the TT genotype. Although observational studies have reported associations between homocysteine and BP, B-vitamin intervention studies have shown little or no BP response despite decreases in homocysteine. Such studies, however, have not considered the MTHFR C677T polymorphism, which has been shown to be associated with BP. It has been shown for the first time that riboflavin is an important determinant of BP specifically in individuals with the TT genotype. Research generally suggests that 24 h ambulatory BP monitoring provides a more accurate measure of BP than casual measurements and its use in future studies may also provide important insights into the relationship between the MTHFR polymorphism and BP. Further research is also required to investigate the association between specific B-vitamins and BP in individuals with different MTHFR genotypes in order to confirm whether any genetic predisposition to hypertension is correctable by B-vitamin intervention. The present review will investigate the evidence linking the MTHFR C677T polymorphism to BP and the potential modulating role of B-vitamins.

Methylenetetrahydrofolate reductase gene polymorphism in diabetes and obesity

Methylenetetrahydrofolate reductase (MTHFR) polymorphism may play an important role in the pathophysiology of obesity and diabetes accompanied by obesity due to its influence on plasma homocysteine levels. There are significant and sometimes very strong relationship between levels of homocysteine and several multi-system diseases including CHD and CVA. To examine the association between MTHFR gene C677T polymorphism in diabetes and obesity with serum homocysteine levels. A total of 682 subjects were recruited in four groups (Normal, obese, diabetic and obese and diabetics). MTHFR gene C677T polymorphism was detected using PCR-RFLP technique. Serum homocysteine levels were measured using HPLC. There was a significant increase in the mean serum homocysteine levels in subjects carrying TT genotype (34.6 +/- 26.5) compared to subjects carrying CC (15.1 +/- 8) or CT genotype (16.4 +/- 7.8) (P < 0.000). We found no significant differences for MTHFR allele and genotype frequencies between different groups. Our data have confirmed the association between serum homocysteine levels and MTHFR C677T genotype reported in other populations.

Smoking confers a MTHFR 677C>T genotype-dependent risk for systemic atherosclerosis: results from a large number of elderly autopsy cases that died in a community-based general geriatric hospital

AIM

We attempted to explore interactions between smoking and the genetic polymorphism of 24 atherosclerosis-related candidate genes in systemic atherosclerosis.

METHODS

The study comprised 1,503 consecutive autopsy cases. The male-to-female ratio was 1.16 and the average age at death was 80.3 years. Seventy percent of men and 22% of women were current or past smokers. The degree of atherosclerosis in 10 arteries was semi-quantitatively assessed. Melting curve analysis analyzed 34 single nucleotide polymorphisms (SNPs) of 24 genes.

RESULTS

Twenty-four SNPs did not interact with smoking on atherosclerosis, while 7 SNPs interacted in one artery and 2 SNPs in two arteries. The genotypes of MTHFR 677C>T and smoking significantly interacted in four arteries, including the common carotid artery, common and external iliac arteries, and femoral artery. The odds ratios of smoking on atherosclerosis were high (3.034.63) in TT homozygotes, intermediate (1.755.24) in heterozygotes, and low (1.752.63) in CC homozygotes in systemic arteries except for cerebral and coronary arteries.

CONCLUSION

MTHFR 677 TT homozygotes are more likely to develop atherosclerosis than heterozygotes or CC homozygotes, if they smoke. Thus, smoking cessation is more important in the prevention of atherosclerosis in MTHFR 677 TT homozygotes.

Methylentetrahydrofolate reductase and nitric oxide synthase polymorphism in patients with atherosclerosis and diabetes

The development of the atherosclerosis is based on multifactorial causes. In addition to the traditional risk factors, gene polymorphisms can play a role in the disease. Therefore in this study we investigated whether the eNOS and MTHFR gene polymorphisms is associated with myocardial infarction and stroke in patients with or without diabetes. We have identified polymorphisms in the NOS 3 gene and one of these polymorphisms, Glu(298-->)Asp, was found to be a major risk factor for carotid artery disease and myocardial infarction. Our results indicate that the MTHFR G677T allele is significantly associated with MI. MTHFR 677 G/T genotyping may be of clinical importance as a prognostic and therapeutic marker, although further studies are needed to substantiate this hypothesis.

Serum total homocysteine, folate, 5,10-methylenetetrahydrofolate reductase (MTHFR) 677C-->T genotype and subclinical atherosclerosis

OBJECTIVE

To determine the relationship of serum total homocysteine (tHcy), serum folate and 5,10-methylenetetrahydrofolate reductase (MTHFR) 677C-->T genotype with ultrasonic arterial wall measurements associated with subclinical atherosclerosis.

STUDY DESIGN

Cross-sectional analysis of 767 participants in an ongoing prospective study. Intima-media thickness (IMT) of the common carotid (IMTcc), IMT of the internal carotid including plaque when present (IMT(max)) and the sum of the thickest plaques present in both carotid and both common femoral bifurcations (total plaque thickness (TPT)) were measured using ultrasound.

RESULTS

People in the upper homocysteine quartile were more likely to have clinical cardiovascular disease (CVD) than those in the lowest three quartiles. They were also more likely to have plaques. The MTHFR 677C-->T genotype was not associated with any of the measures of subclinical atherosclerosis in either men or women but was the most important determinant of total homocysteine levels in men under 60 years of age.

CONCLUSIONS

Increased homocysteine levels but not MTHFR 677C-->T genotype, are associated with subclinical atherosclerosis and the presence of plaques. Our results indicate that measurements of blood levels of homocysteine and folate in people at intermediate risk for atherosclerotic CVD before symptoms occur, might improve risk stratification and facilitate the decision to provide folate/B vitamin intervention in primary prevention.

Impact of High-Normal Blood Pressure on the Risk of Cardiovascular Disease in a Japanese Urban Cohort

Few prospective studies have examined the association between high-normal blood pressure and cardiovascular disease (CVD) in Asia. We examined the impact of high-normal blood pressure on the incidence of CVD in a general urban population cohort in Japan. We studied 5494 Japanese individuals (ages 30 to 79 years without CVD at baseline) after completing a baseline survey who received follow-up through December 2005. Blood pressure categories were defined on the basis of the ESH-ESC 2007 criteria. In 64 391 person-years of follow-up, we documented the incidence of 346 CVD events. The frequencies of high-normal blood pressure and hypertension Stage 1 and Stage ≥2 were 18.0%, 20.1%, and 10.1% for men and 15.9%, 15.6%, and 8.8% for women, respectively. Antihypertensive drug users were also classified into the baseline blood pressure categories. Compared with the optimal blood pressure group, the multivariable hazard ratios (95% confidence intervals) of CVD for normal and high-normal blood pressure and hypertension Stage 1 and Stage ≥2 were 2.04 (1.19 to 3.48), 2.46 (1.46 to 4.14), 2.62 (1.59 to 4.32), and 3.95 (2.37 to 6.58) in men and 1.12 (0.59 to 2.13), 1.54 (0.85 to 2.78), 1.35 (0.75 to 2.43), and 2.86 (1.60 to 5.12) in women, respectively. The risks of myocardial infarction and stroke for each blood pressure category were similar to those of CVD. Population-attributable fractions of high-normal blood pressure and hypertension for CVD were 12.2% and 35.3% in men and 7.1% and 23.4% in women, respectively. In conclusion, high-normal blood pressure is a risk factor for the incidence of stroke and myocardial infarction in a general urban population of Japanese men.

Measuring subclinical atherosclerosis: is homocysteine relevant?

OBJECTIVES

We systematically reviewed published studies looking at the relationship between total serum homocysteine (tHcy) and subclinical markers of atherosclerosis, such as carotid intimal-medial thickness (C-IMT), coronary artery calcium (CAC) and ankle-brachial index (ABI) in asymptomatic individuals. We analyzed these studies to examine this relationship as well as to guide future avenues of investigation by identifying studies that will help in the inclusion of tHcy levels in current guidelines on atherosclerotic disease management.

BACKGROUND

tHcy has been known to be associated with clinically evident atherosclerotic disease. However, tHcy is not incorporated in current guidelines for diagnosis of subclinical disease in high-risk asymptomatic individuals.

METHODS

We searched online databases (e.g., PUBMED, MEDLINE) for published articles assessing the relationship between tHcy and C-IMT, CAC and ABI. We limited the studies to asymptomatic populations, and excluded any study including symptomatic patients or individuals with a history of coronary, peripheral or cerebrovascular disease.

RESULTS

A systemic review of 19 articles revealed a significant association between elevated levels of tHcy and subclinical markers of atherosclerosis in asymptomatic individuals in most studies. Mean tHcy levels were consistently found to be higher in men compared to women. A total of 12 studies showed a significant association between tHcy and other risk markers of atherosclerosis, even after adjusting for age, sex and conventional risk factors. There were seven studies in unique populations that showed no significant relationship. We also observed that studies lowering baseline tHcy levels did not lead to an improvement in C-IMT, CAC or ABI scores. This might indicate that tHcy has a stronger role as a marker of atherosclerotic disease than as a risk factor for the same.

CONCLUSIONS

Based on our review, we conclude that there is a significant association between the subclinical atherosclerotic process and tHcy, and it shows potential as a cheap marker for risk stratification of asymptomatic patients. However, future studies further elucidating this association and elaborating the exact role of tHcy in the atherosclerotic disease process are required. The results of these studies suggest the incorporation of plasma tHcy levels in future risk reduction protocols for identification of individuals at higher risk of atherosclerotic events, and thus to categorize them for more aggressive treatment with established preventive and therapeutic measures.

Associations of methylenetetrahydrofolate reductase C677T polymorphism with markers of subclinical atherosclerosis: the Cardiovascular Risk in Young Finns Study

OBJECTIVE

To study whether the methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism or serum homocysteine concentration is associated with carotid artery intima media thickness (IMT), carotid artery compliance (CAC) or brachial artery flow mediated dilatation (FMD) in a healthy Finnish adult population.

METHODS

Cross-sectional data obtained in 2001 for the Cardiovascular Risk in Young Finns Study were used. Carotid artery IMT, CAC and brachial FMD were measured by ultrasound and serum homocysteine concentrations using a commercial immunoassay kit. We studied 1,440 subjects (aged 24-39 years). Genotyping was performed using the 5' nuclease TaqMan assay.

RESULTS

Homocysteine values differed between genotypes in women and men (ANOVA, p<0.001 for both sex groups): the genotype raised values in the order of CC, CT, TT. There was a significant difference in CAC values between the MTHFR genotypes in men (ANOVA, p = 0.008), and the CC genotype had the lowest values. In multivariate linear regression analysis adjusted for other major coronary risk factors (e.g. age, smoking, body mass index, systolic blood pressure, C-reactive protein), the association remained significant (R (2) = 25.8 %, beta = 0.091; p = 0.02). Homocysteine level was directly associated with CAC in the whole population (R (2) = 18.0 %, beta = 0.012; p = 0.014) and in women (R (2) = 9.3%, beta = 0.02; p = 0.013), but not in men (R (2) = 15.2 %, beta = 0.004; p = 0.444). We found no association between homocysteine level or the MTHFR polymorphism and carotid IMT or brachial artery FMD.

CONCLUSIONS

The findings suggest that the MTHFR polymorphism does not influence IMT or FMD, but that the T allele may have an effect on CAC in men.

The 677 C/T MTHFR polymorphism is associated with essential hypertension, coronary artery disease, and higher homocysteine levels

BACKGROUND

Essential hypertension (EH) and cardiovascular disease are common, multifactorial disorders likely to be influenced by multiple genes of modest effect. The C677T methylenetetrahydrofolate reductase (MTHFR) gene polymorphism is related to MTHFR enzyme activity and to plasma homocysteine (Hcy) concentration. This study was designed to investigate an association of this polymorphism with coronary artery disease (CAD), EH, and healthy subjects.

METHODS

In this study, we measured serum folate, serum vitamin B12, and plasma homocysteine and determined the MTHFR C677T genotype of 78 patients with essential hypertension, 100 patients with coronary artery disease, and 100 healthy subjects. MTHFR genotypes were assessed by real-time polymerase chain reaction.

RESULTS

CC, CT, and TT genotype frequencies were 52, 44.0, and 4.0% in patients with CAD, respectively. In patients with essential hypertension, the CC, CT, and TT genotype frequencies were 46.2, 41.0, and 12.8%, respectively. In control subjects, the CC, CT, and TT genotype frequencies were 72.0, 26.0, and 2.0%, respectively. The C allele was significantly more frequent in controls compared with patients with EH (p<0.05), and CC genotypes were more frequent in controls compared to patients with EH and CAD. Homocysteine level was higher in TT genotypes in CAD patients compared with CC and CT genotypes (p<0.01). MTHFR gene polymorphism is an independent risk factor for EH but not for CAD.

CONCLUSIONS

The TT genotype of the 677C/T MTHFR polymorphism is associated with EH and CAD. In addition, TT genotypes had higher plasma Hcy levels in CAD patients compared with CC and CT genotypes. MTHFR gene polymorphism is an independent risk factor for EH but not for CAD.

The combination of homozygous MTHFR 677T and angiotensin II type-1 receptor 1166C variants confers the risk of small-vessel-associated ischemic stroke

Previous studies have suggested that both angiotensin II type-1 receptor (AT1R) 1166C and methylenetetrahydrofolate reductase (MTHFR) 677T variants can have disadvantageous effects on the small-vessel circulation under certain conditions. The purpose of this study was to analyze the possible consequences of the simultaneous distribution of these two genetic variants in different types of ischemic stroke. The genetic and clinical data on 357 ischemic stroke patients and 263 control subjects were analyzed by using univariate and logistic statistical approaches. Neither the MTHFR 677T nor the AT1R 1166C genetic variant alone conferred the risk of any subtype of ischemic stroke. The combination of the homozygous MTHFR 677TT genotype and at least one AT1R 1166C allele occurred more frequently in the ischemic stroke patients (8.68%) than in the controls (4.56%, p < 0.05). Specific subclassification of the patients revealed an accumulation of this combination in small-vessel-associated ischemic stroke (12.2%, p < 0.01); multivariate logistic regression analysis of the data confirmed this association, with an odds ratio of 2.66 (95% confidence interval, 1.28-7.89; p < 0.05). These findings suggest that the combination of these two genetic factors can contribute to the development of small-vessel cerebral infarcts. Although the exact mechanism of action is not known, addition of the unfavourable effects on the endothelial function can be presumed.

Polymorphisms and the expression of genes encoding enzymes involved in cardiovascular diseases

BACKGROUND

Atherosclerosis, a multi-factorial disease, is the main determinant of cardiovascular disease (CVD) leading to high mortality and morbidity in westernized countries. Gene polymorphisms and gene expression related to the atherosclerosis process can be identified using a genome-wide approach or looking for candidate disease-causing genes.

METHODS

Using genome wide strategy or candidate gene approach various genes, including paraoxonase genes, which are involved in lipid metabolism, oxidation, inflammation and coagulation, have been associated to atherosclerosis.

CONCLUSION

Evaluation of gene polymorphisms, together with traditional and novel biochemical parameters, may help identify individuals at a high risk for CVD. Genetic characterization of susceptibility genes may also lead to new drugs for atherosclerosis prevention and treatment. In addition, gene expression studies can provide novel insights into the molecular mechanism of lesion development and progression.

MTHFR 677 CT/MTHFR 1298 CC genotypes are associated with increased risk of hypertension in Indians

The goals of our present study were to measure plasma homocysteine levels and determine their association with methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms (C677T and A1298C) in essential hypertensive subjects. Plasma total homocysteine and folic acid levels were measured in essential hypertensive patients (n = 153) before and after oral supplementation with either 5 mg folic acid tablet/day or 5 mg placebo/day for 4 weeks and compared with age and sex matched normotensive controls (n = 133). MTHFR gene polymorphisms (C677T and A1298C) were studied by restriction fragment length polymorphism and correlated with plasma homocysteine levels. Homocysteine levels were significantly higher in hypertensive patients as compared to controls and showed a negative correlation with plasma folate levels. Folic acid supplementation (5 mg/day) for 4 weeks resulted in a significant decrease in plasma homocysteine concentrations in these patients. Patients carrying MTHFR 677T allele (OR = 1.90; 95%CI: 1.14-3.19) or MTHFR 1298C (OR = 2.6, 95%CI: 1.55-4.40) allele were at increased risk of hypertension. The frequency of co-occurrence of MTHFR 677 CT/1298 CC genotypes was significantly higher in the patients compared to controls (P < 0.05) and was associated with increased risk of hypertension (OR = 3.54, 95%CI: 0.37-4.30). Subjects with MTHFR 1298 CC genotype had significantly higher homocysteine levels compared to those with MTHFR 1298 AA genotype (P < 0.05). Our results indicate that MTHFR 677T and 1298C alleles and co-occurrence of MTHFR 677 CT/MTHFR 1298 CC genotypes are associated with increased risk of hypertension and MTHFR 1298 CC genotype is associated with higher homocysteine levels in our subjects.

B-group vitamins, MTHFR C677T polymorphism and carotid intima-media thickness in clinically healthy subjects

OBJECTIVE

Plasma B-group vitamins and age may affect the carotid intima-media thickness (IMT) in subjects with different 677TT genotype of the methylenetetrahydrofolate reductase (MTHFR) gene.

DESIGN

A hospital-based cross-study.

SETTING

Genomic and Vascular Center, Changhua Christian Hospital, Changhua, Taiwan.

SUBJECTS

Five hundred and forty-one clinically healthy subjects.

INTERVENTION

Fasting plasma, homocysteine (Hcy), vitamin B(6), vitamin B(12), folate and B-mode carotid ultrasound.

RESULTS

MTHFR genotype, plasma concentrations of folate, vitamin B(6) and vitamin B(12) and age were significantly correlated to the plasma Hcy concentration. MTHFR 677TT carriers had higher concentrations of Hcy than did subjects with the CC and CT genotypes. Age, sex, body mass index and plasma Hcy were independent contributors to increase carotid IMT. However, with stratification by mean value of age and B-group vitamins concentrations, we found that at advanced age, lower plasma folate and vitamin B(12) were three risk factors involved in the enhancing effect of the MTHFR 677TT genotype on the increase of plasma Hcy and carotid IMT.

CONCLUSION

MTHFR 677TT-related carotid atherosclerosis was only identified in healthy elderly subjects with lower level of plasma folate and vitamin B(12).

SPONSORSHIP

Changhua Christian Hospital.

Genetic variants predisposing to cardiovascular disease

PURPOSE OF REVIEW

The goal of this review is to provide an update on the most recent and relevant findings in the area of genotype-phenotype associations as well as the relationships between genetic factors and cardiovascular disease risk markers and events. In addition, emphasis will be placed on the methodological problems associated with studying the genetics of complex disorders, specifically cardiovascular diseases.

RECENT FINDINGS

Genes associated with cardiovascular disease predisposition have been examined, including traditional cardiovascular disease candidate genes, such as ACE, AGT, eNOS, PON and MTHFR, new loci that have recently been added to the growing list of cardiovascular disease candidate genes (i.e. MEF2A, ALOX5, LTA, APOM, PDE4D), and genes that have been shown to be at the intersection of several age-related disorders through interaction with one another or with environmental factors (i.e. APOA5, APOE, PPARgamma, LPL and LIPC).

SUMMARY

During the last year, tremendous effort has been made in elucidating new genes associated with cardiovascular disease predisposition. For the most part, however, major breakthroughs have not been made, primarily due to the poor replication of results among studies, as a consequence of poor experimental design. Nevertheless, we have increased our understanding of the complexity of cardiovascular disease and the relevance of gene-environment interactions as the ultimate drivers of the individual predisposition to the disease. It is essential, therefore, that present and future genetic studies in this area take into consideration the inclusion of high-quality environmental data in the analytical process to test the clinical usefulness of a genetic marker as a risk predictor.

Polymorphism of methylenetetrahydrofolate reductase gene (C677T MTHFR) is not a confounding factor of the relationship between serum uric acid level and the prevalence of hypertension in Japanese men

BACKGROUND

The association between serum uric acid (UA) and the prevalence of hypertension, and the relationship between methylenetetrahydrofolate reductase (MTHFR) polymorphism and hypertension remains unclear. The aim of the present study was to investigate whether the C677T MTHFR mutation genotype (VV) is independently associated with the prevalence of hypertension or blood pressure (BP), and examined any interaction of MTHFR and UA with BP.

METHODS AND RESULTS

Participants were randomly selected from all residents (aged 40-69 years) in a rural county of Japan, and the data for the men (n=335) were analyzed. ;Hypertension' was defined as systolic BP >or=140 and/or diastolic BP >or=90 mmHg and/or being administered antihypertensive medication. Serum UA level was independently associated with the prevalence of hypertension (odds ratio (95% confidence interval) =2.7 (1.2-5.9), p=0.047) for the highest tertile of serum UA (>or=398.5 micromol/L (6.7 mg/dl)) vs that of the lowest tertile (<321.2 micromol/L (5.4 mg/dl)), but the MTHFR mutation was not independently associated with prevalence of hypertension or BP. No interaction of the MTHFR mutation and serum UA with BP was found.

CONCLUSIONS

The mutation of C677T MTHFR was not independently associated with the prevalence of hypertension or BP levels although serum UA was. Furthermore, the relationship between serum UA and BP was not modulated by the MTHFR mutation in Japanese men.

Association of Sixty-One Non-Synonymous Polymorphisms in Forty-One Hypertension Candidate Genes with Blood Pressure Variation and Hypertension

We previously selected a group of hypertension candidate genes by a key word search using the OMIM database of NCBI and validated 525 coding single nucleotide polymorphisms (SNPs) in 179 hypertension candidate genes by DNA sequencing in a Japanese population. In the present study, we examined the association between 61 non-synonymous SNPs and blood pressure variations and hypertension. We used DNA samples taken from 1,880 subjects in the Suita study, a population-based study using randomly selected subjects. Analyses of covariance adjusting for age, body mass index, hyperlipidemia, diabetes, smoking, drinking, and antihypertensive medication revealed that 17 polymorphisms in 16 genes (APOB, CAST, CLCNKB, CTNS, GHR, GYS1, HF1, IKBKAP, KCNJ11, LIPC, LPL, P2RY2, PON2, SLC4A1, TRH, VWF) were significantly associated with blood pressure variations. Multivariate logistic regression analysis with adjustment for the same factors revealed that 11 polymorphisms in 11 genes (CAST, CTLA4, F5, GC, GHR, LIPC, PLA2G7, SLC4A1, SLCI8A1, TRH, VWF) showed significant associations with hypertension. Five polymorphisms in five genes, CAST(calpastatin), LIPC (hepatic lipase), SLC4A1 (band 3 anion transporter), TRH (thyrotropin-releasing hormone), and VWF (von Willebrand factor), were significantly associated with both blood pressure variation and hypertension. Thus, our study suggests that these five genes were susceptibility genes for essential hypertension in this Japanese population.

Molecular Genetic Testing of Polymorphisms Associated With Venous Thrombosis

The growing knowledge of genetic polymorphisms predisposing to venous thrombosis has increased the demand for genetic testing of associated risk factors. This has prompted the need for simple, fast, reliable, and cost-effective genotyping methods for identification of those mutations. In the past decade, a large variety of DNA mutation analysis methods have been developed for detection of genetic variants associated with venous thrombosis, including PCR-based and PCR-independent technologies. Each of these technologies possesses unique advantages, but all have a common goal of simplifying and expediting mutation analysis. This review describes some of the commonly used technologies and commercially available platforms employed in clinical laboratories for genetic testing of thrombophilia. The choice of a technology for each individual laboratory would primarily depend on the specific requirements for the assay's accuracy, reliability, speed, throughput, and cost-effectiveness.

5,10-Methylenetetrahydrofolate reductase polymorphisms and the risk of pancreatic cancer

To test the hypothesis that 5,10-methylenetetrahydrofolate reductase (MTHFR) polymorphisms modify the risk of pancreatic cancer, we conducted a hospital-based, case-control study involving 347 patients with newly diagnosed pancreatic adenocarcinoma and 348 healthy controls, frequency matched by age, sex, and race. MTHFR polymorphisms were determined using the PCR-RFLP method. Association of these polymorphisms with the risk of pancreatic cancer was estimated by unconditional logistic regression analysis. We found that the C667T (but not the A1298C) polymorphism had a significant main effect on the risk of pancreatic cancer. The frequencies of the MTHFR 667CC, 667CT, and 667TT genotypes were 49.5%, 38.6%, and 11.9%, respectively, among cases compared with 48.5%, 45.0%, and 6.5%, respectively, among controls. Individuals with the 667TT genotype displayed a 2-fold increased risk for pancreatic cancer compared with those with the CC/CT genotypes [adjusted odds ratio (OR), 2.14; 95% confidence interval (95% CI), 1.14-4.01]. Multivariate analyses found that the effect of the 677TT genotype on the risk of pancreatic cancer was present among ever smokers (OR, 5.53; 95% CI, 2.0-15.3) and ever alcohol drinkers (OR, 3.16; 95% CI, 1.30-7.69) but not in never smokers (OR, 0.82; 95% CI, 0.33-2.06) and never drinkers (OR, 1.42; 95% CI, 0.56-3.62). Furthermore, a positive interaction between the MTHFR TT genotype and heavy smoking or heavy alcohol consumption was detected. The OR (95% CI) of pancreatic cancer was 6.83 (1.91-24.38) for heavy smokers among the TT carriers compared with never smokers with the CC/CT genotypes and 4.23 (0.88-20.3) for heavy drinkers with the TT genotype compared with nondrinkers with the CC/CT genotypes. These observations support a role for folate metabolism in pancreatic cancer, especially among smokers and heavy drinkers.

Low concentrations of folate, not hyperhomocysteinemia, are associated with carotid intima-media thickness

AIM

We examined whether total homocysteine, B vitamins and the 5,10-methylenetetrahydrofolate reductase (MTHFR) 677C-->T polymorphism are related to common carotid intima-media thickness, a marker of atherosclerosis, and carotid distension, a marker of arterial stiffness.

METHODS

We used cross-sectional data from 819 individuals aged 50-70 years. B-mode ultrasound of the distal common carotid arteries was performed to determine maximum carotid intima-media thickness, mean carotid intima-media thickness and distension.

RESULTS

Carotid intima-media thickness and distension did not differ across homocysteine, serum folate, vitamin B(6) and vitamin B(12) quartiles or between MTHFR C677T genotype. Erythrocyte folate was independently associated with maximum carotid intima-media thickness (mean difference first versus third quartile, 0.03 mm, 95% CI 0.004-0.06 mm; first versus fourth quartile, 0.03 mm, 95% CI -0.002 to 0.06 mm). Further adjustment for homocysteine did not affect this association. Folate deficient subjects had greater maximum carotid intima-media thickness than those with high-normal folate concentrations (serum folate: mean difference 0.05 mm, 95% CI 0.01-0.08 mm; erythrocyte folate: mean difference 0.04 mm, 95% CI -0.03 to 0.11 mm).

CONCLUSION

Low folate concentrations, independent of hyperhomocysteinemia, may promote atherogenesis. Our findings confirm the null association of homocysteine with carotid intima-media thickness observed in other population-based studies, suggesting that hyperhomocysteinemia does not perpetuate atherosclerosis or arterial stiffness.

The genetics of stroke

PURPOSE OF REVIEW

Ischaemic stroke is a heterogeneous disease caused by different pathogenic mechanisms, of which small artery and large artery stroke are the most common. The identification of the genes involved is unclear. The likely candidate genes associated with stroke are those that are associated with matrix deposition (stromelysin-1, MMP3), inflammation (IL-6), and lipid metabolism (hepatic lipase, APOE, PON1) and clotting (factor V Leiden, fibrinogen).

RECENT FINDINGS

In this review we will only discuss those genes in which there has been a significant contribution to the understanding of stroke since October 2003.

SUMMARY

The published data were reviewed to determine the robustness of these associations and to examine whether there is any evidence of risk modification by factors such as smoking habit, known to be associated with stroke.

Methylenetetrahydrofolate reductase (MTHFR) and susceptibility for (pre)neoplastic cervical disease

Methylenetetrahydrofolate reductase (MTHFR) is a critical enzyme regulating the metabolism of folate and methionine. The potential influence of MTHFR activity on DNA methylation and on the availability of uridylates and thymidylates for DNA synthesis and repair presents MTHFR as a candidate for being a cancer-predisposing gene. In the present study, we have examined a large study population to determine whether the C677T polymorphism at the MTHFR locus affects susceptibility for cervical cancer or its precursor, cervical intraepithelial neoplasia (CIN). In addition, we have investigated whether this polymorphism is causal, and not merely associated, by typing microsatellite markers in the region surrounding the MTHFR gene. A total of 311 CIN and 695 cervical cancer patients and 115 family-based and 586 unrelated controls was analysed. Association analysis showed a decreased cervical cancer risk for individuals heterozygous or homozygous for the T-allele, both for squamous cell carcinoma (heterozygous odds ration [OR] 0.66 [0.51-0.86]; homozygous OR 0.76 [0.49-1.16]) and adenocarcinoma (heterozygous OR 0.71 [0.49-1.03]; homozygous OR 0.34 [0.14-0.81]). No difference was found for high grade CIN (heterozygous OR 1.03 [0.76-1.40]; homozygous OR 0.91 [0.54-1.55]). A microsatellite haplotype containing the C allele was associated with an increased risk for cervical cancer and CIN (both among squamous cell carcinomas, adenocarcinomas and CIN II-III; OR = 2.61 [1.59-4.27]). Our study thus lends further support to the hypothesis that the MTHFR C677T polymorphism is involved in susceptibility cervical cancer but also illustrates that, despite the large sample size analysed, still larger studies are needed to establish fully the nature of this association.

Homocysteine and carotid intima-media thickness: a critical appraisal of the evidence

This review examines the relationship between hyperhomocysteinemia, a risk factor for vascular disease, and carotid intima-media thickness (CIMT), a valid marker of generalized atherosclerosis and future vascular disease risk. The relationship between two important determinants of hyperhomocysteinemia in the general population-folate status and the 677C --> T methylenetetrahydrofolate reductase (MTHFR) polymorphism-and CIMT is also covered.

METHODS

We searched literature databases for articles examining homocysteine and CIMT published before September 2003.

RESULTS

We identified 54 studies. Observational studies generally failed to demonstrate a relationship between homocysteine and CIMT in homocystinuric, uremic, hypercholesterolemic or non-insulin-dependent diabetes mellitus patients or in subjects with insulin insensitivity. Weak associations, but usually only in certain sub-populations were found in vascular disease patients and in population-based studies. B vitamins reduce the progression of CIMT in renal transplant recipients and vascular disease patients as demonstrated by two trials. The majority of studies demonstrated increased CIMT in individuals with the MTHFR 677TT genotype. Folate status showed no relation to CIMT.

DISCUSSION

In non-patient populations, hyperhomocysteinemia is weakly associated with CIMT. The association of the 677 C--> T MTHFR polymorphism with CIMT further supports this finding. Lastly, folate levels may need to reach a critically low status before an association can be found between folate and CIMT. Larger trials in various population types are needed to determine whether folate alone or in combination with Vitamins B6 and B12 will slow down or even reverse atherosclerotic progression.