5,10-Methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C polymorphisms: genotype frequency and association with homocysteine and folate levels in middle-southern Italian adults

Unveiling the Therapeutic Potential of Folate-Dependent One-Carbon Metabolism in Cancer and Neurodegeneration

Cellular metabolism is crucial for various physiological processes, with folate-dependent one-carbon (1C) metabolism playing a pivotal role. Folate, a B vitamin, is a key cofactor in this pathway, supporting DNA synthesis, methylation processes, and antioxidant defenses. In dividing cells, folate facilitates nucleotide biosynthesis, ensuring genomic stability and preventing carcinogenesis. Additionally, in neurodevelopment, folate is essential for neural tube closure and central nervous system formation. Thus, dysregulation of folate metabolism can contribute to pathologies such as cancer, severe birth defects, and neurodegenerative diseases. Epidemiological evidence highlights folate's impact on disease risk and its potential as a therapeutic target. In cancer, antifolate drugs that inhibit key enzymes of folate-dependent 1C metabolism and strategies targeting folate receptors are current therapeutic options. However, folate's impact on cancer risk is complex, varying among cancer types and dietary contexts. In neurodegenerative conditions, including Alzheimer's and Parkinson's diseases, folate deficiency exacerbates cognitive decline through elevated homocysteine levels, contributing to neuronal damage. Clinical trials of folic acid supplementation show mixed outcomes, underscoring the complexities of its neuroprotective effects. This review integrates current knowledge on folate metabolism in cancer and neurodegeneration, exploring molecular mechanisms, clinical implications, and therapeutic strategies, which can provide crucial information for advancing treatments.

MTHFR and MTRR gene polymorphisms in patients with chronic hepatitis B virus infections in Zigong, Sichuan Province

BACKGROUND

Chronic hepatitis B virus (HBV) infection is a severe disease affecting the physical and economic well-being of patients. The relationship between polymorphisms in the MTHFR gene and disease progression following HBV infection remains a controversial topic.

AIM

To study MTHFR and MTRR gene polymorphisms in patients with chronic HBV infections in Zigong, Sichuan Province.

SUBJECTS AND METHODS

One hundred and ninety-one patients with chronic HBV infections were divided into three groups: the chronic hepatitis B (CHB) group (n = 71), the hepatitis B-induced liver cirrhosis (LC) group (n = 56), and the hepatitis B-related primary liver cancer (PLC) group (n = 64). The gene polymorphisms were detected using the PCR-melt curve method and analysed.

RESULTS

The distributions of MTHFR C677T (CC: 41.2% vs. 41.8%; CT: 50% vs. 45.5%; TT: 8.8% vs. 12.7%; p = 0.714), MTHFR A1298C (AA: 70.6% vs. 72.7%; AC: 26.5% vs. 25.5%; CC: 2.9% vs. 1.8%; p = 1.000), and MTRR A66G (AA: 58.1% vs. 65.5%; AG: 39.0% vs. 29.1%; 2.9% vs. 5.5%; p = 0.353) genetic polymorphisms did not vary between male and female patients from Zigong. In addition, there were no differences in the distributions of MTHFR C677T (CC: 43.4% vs. 38.8%; CT: 49.1% vs. 48.2%; TT: 7.5% vs. 12.9%; p = 0.444), MTHFR A1298C (AA: 76.4% vs. 64.7%; AC: 20.8% vs. 32.9%; CC: 2.8% vs. 2.4%; p = 0.155), and MTRR A66G (AA: 62.3% vs. 57.6%; AG: 34.0% vs. 38.8%; 3.8% vs. 3.5%; p = 0.353) genetic polymorphisms between the patients <60 and >60 years of age. The distributions of MTHFR C677T (CHB vs. LC, p = 0.888; CHB vs. PLC, p = 0.661; PLC vs. LC, p = 0.926), MTHFR A1298C (CHB vs. LC, p = 0.12; CHB vs. PLC, p = 0.263; PLC vs. LC, p = 0.550), and MTRR A66G (CHB vs. LC, p = 0.955; CHB vs. PLC, p = 0.645; PLC vs. LC, p = 0.355) gene polymorphisms were comparable between the CHB, LC, and PLC groups.

CONCLUSION

The distributions of MTHFR and MRRR genetic polymorphisms in the population with HBV infections in Zigong, Sichuan Province did not differ in age and sex. The MTHFR and MRRR genetic polymorphisms were comparable between the CHB, LC, and PLC groups.

Association between Micronutrients and Hyperhomocysteinemia: A Case-Control Study in Northeast China

Hyperhomocysteinemia (HHcy) is an independent risk factor for cardiovascular and cerebrovascular diseases where the plasma homocysteine (Hcy) concentration exceeds 15 µmol/L. HHcy is affected by vitamins B12, B6, and folic acid (fol); however, its relationship with other nutrients is not fully understood. We investigated the nutritional and genetic factors associated with HHcy and the possible dose-response relationships or threshold effects in patients in Northeast China. Genetic polymorphisms and micronutrients were tested with polymerase chain reaction and mass spectrometry, respectively. This trial was registered under trial number ChiCTR1900025136. The HHcy group had significantly more males and higher body mass index (BMI), methylenetetrahydrofolate reductase (MTHFR 677TT) polymorphism proportion, and uric acid, Zn, Fe, P, and vitamin A levels than the control group. After adjusting for age, sex, BMI, vitamin B12, fol, and MTHFR C677T, the lowest Zn quartile reduced the odds ratio of HHcy compared with the highest Zn quartile. The dose-response curves for the association between plasma Zn and HHcy were S-shaped. High plasma Zn concentrations were significantly correlated with high HHcy odds ratios, and the curve leveled off or slightly decreased. Most importantly, HHcy risk decreased with decreasing plasma Zn concentration; the threshold was 83.89 µmol/L. Conclusively, individuals residing in Northeast China, especially those with the MTHFR 677TT polymorphism, must pay attention to their plasma Zn and Hcy levels.

MTHFR SNPs (Methyl Tetrahydrofolate Reductase, Single Nucleotide Polymorphisms) C677T and A1298C Prevalence and Serum Homocysteine Levels in >2100 Hypofertile Caucasian Male Patients

Methylation is a crucially important ubiquitous biochemical process, which covalently adds methyl groups to a variety of molecular targets. It is the key regulatory process that determines the acquisition of imprinting and epigenetic marks during gametogenesis. Methylation processes are dependent upon two metabolic cycles, the folates and the one-carbon cycles. The activity of these two cycles is compromised by single nucleotide polymorphisms (SNPs) in the gene encoding the Methylenetetrahydrofolate reductase (MTHFR) enzyme. These SNPs affect spermatogenesis and oocyte maturation, creating cytologic/chromosomal anomalies. The two main MTHFR SNP variants C677T (c.6777C>T) and A1298C (c.1298A>C) together with serum homocysteine levels were tested in men with >3 years’ duration of infertility who had failed several ART attempts with the same partner. These patients are often classified as having “idiopathic infertility”. We observed that the genetic status with highest prevalence in this group is the heterozygous C677T, followed by the combined heterozygous C677T/A1298C, and then A1298C; these three variants represent 65% of our population. Only 13.1% of the patients tested are wild type (WT), C677C/A1298A). The homozygous 677TT and the combined heterozygote 677CT/1298AC groups have the highest percentage of patients with an elevated circulating homocysteine level of >15 µMolar (57.8% and 18.8%, respectively, which is highly significant for both). Elevated homocysteine is known to be detrimental to spermatogenesis, and the population with this parameter is not marginal. In conclusion, determination of these two SNPs and serum homocysteine should not be overlooked for patients with severe infertility of long duration, including those with repeated miscarriages. Patients must also be informed about pleiotropic medical implications relevant to their own health, as well as to the health of future children.

MTHFR C677T Polymorphism and Serum Homocysteine Level as Risk Factors of Coronary Heart Disease in Patients with Androgenetic Alopecia: A Case Control Study

BACKGROUND

Androgenetic alopecia (AGA) is associated with a risk of coronary heart disease (CHD), although the causes underlying this association are not clear. Serum homocysteine (SH) is a known risk factor for CHD, and methylene tetrahydrofolate reductase enzyme (MTHFR) plays a crucial role in the remethylation of homocysteine to methionine. The polymorphism C677T that affects the catalytic domain of the MTHFR protein leads to a high levels of SH. Our hypothesis was that this polymorphism and SH level are risk factors for CHD in Patients with AGA.

METHODS

A total of 106 patients with AGA and 100 well-matched healthy controls were enrolled in the study. SH levels were estimated. DNA was extracted and polymerase chain reaction amplification, followed by restriction enzyme digestion for MTHFR (C677T) gene, was conducted.

RESULTS

SH levels were significantly higher in the patient group and highest in those with the TT genotype. The mutant T allele was associated with hyperhomocysteinemia and an increased risk of CHD in patients with AGA.

CONCLUSIONS

AGA is associated with a higher risk of developing CHD due to the associated higher level of SH that, in turn, depends on and is correlated with mutant MTHFR genotypes. Cardiac evaluation and follow-up of patients with AGA is recommended for early detection and treatment of CHD to avoid an overall detrimental course.

Precision Nutrition for Alzheimer's Prevention in ApoE4 Carriers

The ApoE4 allele is the most well-studied genetic risk factor for Alzheimer’s disease, a condition that is increasing in prevalence and remains without a cure. Precision nutrition targeting metabolic pathways altered by ApoE4 provides a tool for the potential prevention of disease. However, no long-term human studies have been conducted to determine effective nutritional protocols for the prevention of Alzheimer’s disease in ApoE4 carriers. This may be because relatively little is yet known about the precise mechanisms by which the genetic variant confers an increased risk of dementia. Fortunately, recent research is beginning to shine a spotlight on these mechanisms. These new data open up the opportunity for speculation as to how carriers might ameliorate risk through lifestyle and nutrition. Herein, we review recent discoveries about how ApoE4 differentially impacts microglia and inflammatory pathways, astrocytes and lipid metabolism, pericytes and blood–brain barrier integrity, and insulin resistance and glucose metabolism. We use these data as a basis to speculate a precision nutrition approach for ApoE4 carriers, including a low-glycemic index diet with a ketogenic option, specific Mediterranean-style food choices, and a panel of seven nutritional supplements. Where possible, we integrate basic scientific mechanisms with human observational studies to create a more complete and convincing rationale for this precision nutrition approach. Until recent research discoveries can be translated into long-term human studies, a mechanism-informed practical clinical approach may be useful for clinicians and patients with ApoE4 to adopt a lifestyle and nutrition plan geared towards Alzheimer’s risk reduction.

Prevalence of thrombophilia-associated genetic risk factors in blood donors of a regional hospital in southern Brazil

Introduction

Thromboembolic events occur due to an imbalance in the hemostasis and some factors associated with this condition can be inherited. In order to evaluate the frequency of genotypes considered to be common hereditary risk factors for thrombophilia associated with venous thrombosis (g.1691G > A and g.20210G > A) and hyperhomocysteinemia (g.677C > T and g.1298A > C), samples from voluntary healthy blood donors at the Hospital de Clínicas de Porto Alegre were tested.

Methods

We examined 325 blood samples from blood donors collected from October 2017 to July 2018. Blood was collected on filter paper and the DNA was extracted for single nucleotide polymorphisms (SNPs) analysis using the qualitative real time polymerase chain reaction.

Results

The calculated frequencies of each genetic variant in heterozygosity were 4% for the FV gene (g.1691G > A), 4% for the F2 gene (g.20210G > A) and 42% and 39% for methylenetetrahydrofolate reductase (MTHFR), g.677C > T and g.1298A > C, respectively. Only the genetic variants of MTHFR were found in homozygosity, with frequencies of 14% and 6% (g.677C > T and g.1298A > C), respectively.

Discussion

Altogether, these results describe the frequencies of genetic variants associated with venous thrombosis and hyperhomocysteinemia in the analyzed group and are important to enhance our current knowledge about the genetic profiles of Brazilian blood donors.

Prevalence of methylenetetrahydrofolate reductase gene polymorphisms (C677T, and A1298C) among Saudi children receiving dental treatment

BACKGROUND

Methylenetetrahydrofolate reductase, the encoded by the MTHFR gene, plays a crucial role in converting the amino acid homocysteine to methionine. Two polymorphisms of the MTHFR gene, C677T and A1298C, reportedly reduce enzyme activity, resulting in hyperhomocysteinemia. Patients with C677T and A1298C polymorphisms may be at higher risk for developing abnormal hyperhomocysteinemia, which has been linked to catastrophic neurological including fatal outcomes.

OBJECTIVE

Determine the prevalence of the MTHFR gene variants C677T and A1298C among pediatric dental patients treated at King Abdulaziz University Hospital.

DESIGN

Cross-sectional.

SETTING

Clinics of pediatric dentistry department.

SUBJECTS AND METHODS

Healthy Saudi children 6-12 years old with no known allergies were screened for eligibility between May and December 2019. A single investigator collected saliva samples. The MTHFR C677T and A1298C polymorphisms were analyzed using polymerase chain reaction and restriction fragment length polymorphism.

MAIN OUTCOME MEASURE

The prevalence of MTHFR gene variants (C677T and A1298C) among the subjects.

SAMPLE SIZE

138.

RESULTS

MTHFR C677T polymorphism was present in 36.2% of the sample and 90.0% of children carrying this allele were heterozygotes. MTHFR A1298C polymorphism was present in 91.3% of the sample and 77.0% of the children carrying this allele were heterozygotes. No linkage disequilibrium between MTHFR C677T and MTHFR A1298C was observed within this sample.

CONCLUSIONS

Our study found a high frequency of the MTHFR A1298C genotype, which was substantially more abundant than expected based on a Hardy-Weinberg distribution. Therefore, caution is advised in using N2O in Saudi children as the increased prevalence of this MTHFR allele may increase the incidence of serious adverse effects among these children.

LIMITATIONS

Further studies are recommended with a larger sample size from randomly selected hospitals from different regions of Saudi Arabia.

CONFLICT OF INTEREST

None.

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

Background

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

Methods

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

Results

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

Conclusions

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

[Importance of the determination of MTHFR SNPs (Methylene Tetrahydrofolate Reductase Single Nucleotide Polymorphisms) in couple infertility]

OBJECTIVE

MTHFR SNPs (Methylene Tetrahydrofolate reductase Single Nucleotide polymorphisms) are biochemical modifications decreasing the capacity to form 5 MTHF 5 methyltetrahydrofolate (5MTHF). Their presence reduces the capacity of the One Carbon cycle, and so the regeneration of Homocysteine (Hcy) and in fine strongly perturbs all the methylation processes. As methylation processes are major regulators in gametogenesis and embryogenesis. We have determined the prevalence of the 2 most important SNPs A1298C and C677T in our population of patients consulting for infertility.

METHODS

Determination of the MTHFR SNPs A1298C and C677T, by hybridization using the LAMP Human MTHFR mutation KITs.

RESULTS

Only 15.8% of our patients (861) do not carry any SNP (WT wid type). Close to 20% of the patients are homozygotes for one mutation or the other. A total of 19.7% are composite heterozygous. A total of 43% of our population is considered "at risk", based on observations collected for the repeat miscarriages.

CONCLUSIONS

Determination of the 2 major MTHFR SNPs is not a "first row" choice, but it must not be neglected and should be carried out in case of repeat ART failures and repeat miscarriages. Some simple therapeutic options can be proposed: they are based on the use of 5MTHF (5MethyleneTetraHydroFolate) the compound downstream the MTHFR.

5-Methyltetrahydrofolate reduces blood homocysteine level significantly in C677T methyltetrahydrofolate reductase single-nucleotide polymorphism carriers consulting for infertility

PURPOSE

Methyltetrahydrofolate reductase (MTHFR) C677T (ala222Val) is a single-nucleotide polymorphism (SNP) that affects the formation of 5-methyltetrahydrofolate (5-MTHF), the active folate that allows the recycling of homocysteine (Hcy) to Methionine. Hcy is at the epicentre of oxidative stress and DNA methylation errors. This SNP often increases the circulating Hcy levels and consequently reduces the methylation process, which is involved in the epigenesis and imprinting of markings in gametes. This study aimed to investigate decreases in Hcy levels in MTHFR SNP carriers.

PROCEDURE

Eighty-nine couples with fertility problems for at least 3 years were included in this program. The women were systematically tested for the MTHFR C 677T isoform. If the woman tested positive, testing of the male partner was proposed. All the carriers had well-controlled blood Hcy levels before and after treatment (600μg of 5-MTHF/day, with a backup of one carbon cycle during at least 3 months).

FINDINGS

As expected, the circulating Hcy level was higher in the homozygous patients than in the heterozygous and wild-type patients. The treatments caused a significant decrease of the circulating Hcy in the SNP carriers group.

CONCLUSIONS

Couples with a long history of infertility should be analysed for MTHFR SNP and homocysteine and should be treated with physiological doses of 5-MTHF instead of high doses of folic acid.

A Case-Control Study of the Association of the Polymorphisms of MTHFR and APOE with Risk Factors and the Severity of Coronary Artery Disease

OBJECTIVES

To explore the association between single-nucleotide polymorphisms (SNPs) in MTHFR and APOE and the risk of CAD and, more importantly, the severity of CAD and the profile of serum lipids, we performed a case-control study in a Chinese Han population.

METHODS

A total of 1,207 cases of consecutive CAD-suspected inpatients were recruited, and 406 CAD cases and 231 non-CAD controls were enrolled for the final analysis after screening for exclusion criteria. All subjects had undergone coronary angiography, and the severity of CAD was evaluated by 2 cardiologists according to the Gensini scores. The genotypes of MTHFR and APOEwere detected using real-time PCR, and then verified by Sanger sequencing. Environmental risk factors, such as age, sex, smoking, alcohol consumption, hypertension, diabetes, dyslipidemia, and BMI were collected. Statistical analyses (the χ2 test, binary logistic regression analysis, and ordinal polytomous logistic regression analysis) were performed with SPSS v16.0.

RESULTS

The genotypes ofall the subjects included in the CAD and non-CAD groups in this study were successfully detected, with an agreement of 100% with Sanger sequencing. The distributions of genotypes CT and TT at MTHFR C667T were higher in CAD cases than in non-CAD controls (OR 1.99, 95% CI 1.34-2.95; OR 1.77, 95% CI 1.18-2.67; p < 0.05), whereas genotype AC at MTHFR A1298Cwas lower in CAD cases (OR 0.71, 95% CI 0.50-1.02; p < 0.05). A significant association was observed in genotypes CT and TT at MTHFR C667T and the risk of CAD (OR 1.44, 95% CI 1.27-3.67; OR 1.56, 95% CI 0.88-2.78; p < 0.05). Both genotypes and alleles of APOE were comparable in the CAD cases and non-CAD controls (p > 0.05). The genotype TT at MTHFR C667T and ε4+ at APOE were more likely to be found in the CAD subgroup with a Gensini score ≥72 (p = 0.040 and p = 0.028, respectively). Meanwhile, in the patients with genotype TT,a higher level of serum Hcy was detected, while genotype ε4+ patients possessed higher levels of serum apolipoprotein E (ApoE) and low-density lipoprotein cholesterol (LDL-C) than other genotypes.

CONCLUSION

This study revealed that the SNP site of MTHFR C667Tis associatedwith the risk of CAD in this Chinese Han population. In addition, the genotypes of TT in MTHFR C667T and ε4+in APOE may increase the severity of CAD, and higher Hcy, LDL-C, and ApoE levels may be involved in this pathogenic process.

High doses of folic acid induce a pseudo-methylenetetrahydrofolate syndrome

A 41-year-old Caucasian woman with a history of infertility dating from 2011 was identified as wild-type (no mutations) for methylenetetrahydrofolate reductase single nucleotide polymorphisms (MTHFR-SNPs). Previous treatment included three failed in vitro fertilization/intracytoplasmic sperm injection cycles as well as one failed cycle of in vitro fertilization/intracytoplasmic sperm injection with donated oocytes. Counseling for a further oocyte donation cycle included advice to take high doses of folic acid (5 mG per day). Prior to initiation of this cycle, in October 2017 she attended our unit for general gynecological assessment and was found to have a slightly increased level of homocysteine, 12.2 µmol/L. A further test in February 2018 showed an increase to 17.2 µmol/L. Folic acid was stopped, and she was treated with 5-MTHF (500 µG daily), which supports the one-carbon cycle. After 5 days of treatment, her homocysteine level dropped to a baseline level of 8.2 µmol/L. As previously described in mice, high doses of folic acid can induce a “pseudo MTHFR” syndrome in wild-type patients, leading to an elevated unmetabolized folic acid syndrome which results in increased serum levels of homocysteine.

Genetic polymorphisms of key enzymes in folate metabolism affect the efficacy of folate therapy in patients with hyperhomocysteinaemia

The aim of this study is to analyse the efficacy rate of folate for the treatment of hyperhomocysteinaemia (HHcy) and to explore how folate metabolism-related gene polymorphisms change its efficacy. This study also explored the effects of gene-gene and gene-environment interactions on the efficacy of folate. A prospective cohort study enrolling HHcy patients was performed. The subjects were treated with oral folate (5 mg/d) for 90 d. We analysed the efficacy rate of folate for the treatment of HHcy by measuring homocysteine (Hcy) levels after treatment. Unconditioned logistic regression was conducted to analyse the association between SNP and the efficacy of folic acid therapy for HHcy. The efficacy rate of folate therapy for HHcy was 56·41 %. The MTHFR rs1801133 CT genotype, TT genotype and T allele; the MTHFR rs1801131 AC genotype, CC genotype and C allele; the MTRR rs1801394 GA genotype, GG genotype and G allele; and the MTRR rs162036 AG genotype and AG+GG genotypes were associated with the efficacy of folic acid therapy for HHcy (P<0·05). No association was seen between other SNP and the efficacy of folic acid. The optimal model of gene-gene interactions was a two-factor interaction model including rs1801133 and rs1801394. The optimal model of gene-environment interaction was a three-factor interaction model including history of hypertension, history of CHD and rs1801133. Folate supplementation can effectively decrease Hcy level. However, almost half of HHcy patients failed to reach the normal range. The efficacy of folate therapy may be genetically regulated.

Investigation of potential biomarkers for thrombosis related diseases in Turkish Cypriot population

Genetic and environmental factors are involved in development of many diseases. The allelic frequencies may differ in different populations and in different ethnic groups. The aim of this study was to investigate the genotypes of MTHFR and factor VII polymorphisms and to identify biomarkers for thrombosis related diseases in Turkish Cypriot population. The lipid profiles and genotypes of MTHFR polymorphisms (rs1801133, rs1801131) and factor VII (rs6046) genes were investigated for the first time in the Turkish Cypriot population. The heterozygosity for MTHFR (rs1801133, rs1801131) and FVII (rs6046) polymorphisms is high in Turkish Cypriot population. The heterozygosity for MTHFR C677T was 38%, MTHFR A1298C was 40% and factor VII G353A was 37%, respectively. Allelic frequencies between males and females were similar. There were no correlations between the genotypes of polymorphisms and the lipid profiles. This study is the first genetic epidemiology study that investigated the allelic frequencies of MTHFR and FVII polymorphisms associated with metabolic syndromes. This study proves to be a crucial analysis in order to use these polymorphisms as a predictor of disease development in the Turkish Cypriot community.

Correlations between methylenetetrahydrofolate reductase gene polymorphisms and venous thromboembolism: A meta-analysis of 99 genetic association studies

We performed this meta-analysis to better assess the relationship between methylenetetrahydrofolate reductase gene ( MTHFR) polymorphisms and the risk of venous thromboembolism. Eligible studies were searched in PubMed, Medline, Embase, and Web of Science. Odds ratios with 95% confidence intervals were used to assess associations of MTHFR polymorphisms with venous thromboembolism. A total of 99 genetic association studies were enrolled for analyses. Although no positive results were detected in overall analyses for the rs1801131 polymorphism. Further subgroup analyses according to ethnicity of participants and type of disease revealed that the rs1801131 polymorphism was significantly correlated with the risk of pulmonary embolism. For the rs1801133 polymorphism, significant association with the risk of venous thromboembolism was found in the dominant, recessive, and allele models. Further subgroup analyses according to ethnicity of participants revealed that the rs1801133 polymorphism was significantly associated with the risk of venous thromboembolism in Caucasians, East Asians, and West Asians. When we stratified available data according to type of disease, we found that the rs1801133 polymorphism was also significantly correlated with the risk of deep vein thrombosis and pulmonary embolism. In conclusion, our findings indicate that the MTHFR rs1801133 polymorphism may serve as a potential biological marker for venous thromboembolism in Caucasians, East Asians, and West Asians. Moreover, the MTHFR rs1801133 polymorphism may be implicated in the development of deep vein thrombosis and pulmonary embolism, while the MTHFR rs1801131 polymorphism may contribute to the development of pulmonary embolism.

Prevalent genotypes of methylenetetrahydrofolate reductase (MTHFR) in recurrent miscarriage and recurrent implantation failure

OBJECTIVE

To evaluate the association of two common methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms with recurrent miscarriage (RM) and repeated implantation failure (RIF) METHODS: The study comprised of 521 patients, with a history of RM (n = 370) or RIF (n = 151). One hundred forty-four women with fallopian tube blockages who had successfully conceived after the first in vitro fertilization embryo transfer treatment served as the control group. The MTHFR alleles, genotypes, and haplotypes were assessed in different groups.

RESULTS

There was no difference in allele frequency and distribution of MTHFR polymorphisms between case and control patients. The 1298AA genotype was represented in a higher frequency, and 1298AC genotype was significantly lower in subfertile group when compared to the control group. A significant relationship was found between the 1298AC genotype and the RIF subgroup. The haplotype 677CC/1298AA was overrepresented in the RM subgroup (> 2 times) and haplotype 677CC/1298AC was underrepresented in the RIF subgroup (P < 0.05). Nevertheless, these two haplotypes were not connected to fertilization and embryo cleavage rates.

CONCLUSION

Our findings indicate that the MTHFR gene polymorphism might play a role in the etiology of patients with RM or RIF. No adverse effects of different MTHFR haplotypes on embryo development were detected. Further studies on the biological role are needed to better understand the susceptibility to pregnancy complications.

SNPs in predicting clinical efficacy and toxicity of chemotherapy: walking through the quicksand

In the "precision medicine" era, chemotherapy still remains the backbone for the treatment of many cancers, but no affordable predictors of response to the chemodrugs are available in clinical practice. Single nucleotide polymorphisms (SNPs) are gene sequence variations occurring in more than 1% of the full population, and account for approximately 80% of inter-individual genomic heterogeneity. A number of studies have investigated the predictive role of SNPs of genes enrolled in both pharmacodynamics and pharmacokinetics of chemotherapeutics, but the clinical implementation of related results has been modest so far. Among the examined germline polymorphic variants, several SNPs of dihydropyrimidine dehydrogenase (DPYD) and uridine diphosphate glucuronosyltransferases (UGT) have shown a robust role as predictors of toxicity following fluoropyrimidine- and/or irinotecan-based treatments respectively, and a few guidelines are mandatory in their detection before therapy initiation. Contrasting results, however, have been reported on the capability of variants of other genes as MTHFR, TYMS, ERCC1, XRCC1, GSTP1, CYP3A4/3A5 and ABCB1, in predicting either therapy efficacy or toxicity in patients undergoing treatment with pyrimidine antimetabolites, platinum derivatives, irinotecan and taxanes. While formal recommendations for routine testing of these SNPs cannot be drawn at this moment, therapeutic decisions may indeed benefit of germline genomic information, when available. Here, we summarize the clinical impact of germline genomic variants on the efficacy and toxicity of major chemodrugs, with the aim to facilitate the therapeutic expectance of clinicians in the odiern quicksand field of complex molecular biology concepts and controversial trial data interpretation.

Determinants of folate and vitamin B12 plasma levels in the French E3N-EPIC cohort

PURPOSE

Impaired B vitamin status has been identified as a risk factor for major chronic diseases. This study aims at examining the determinants of plasma folate and vitamin B12 concentrations, considering lifestyle factors and MTHFR polymorphisms.

METHODS

A total of 988 women aged 40-65 years from the French E3N cohort were investigated. Intakes of folate and vitamin B12 were assessed using food frequency questionnaires, and plasma concentrations were measured by microbiological assay. Dietary scores were computed to summarize folate and vitamin B12 dietary sources. MTHFR-C677T and MTHFR-A1298C were determined by Kaspar assay. Pearson's partial correlation coefficients and multivariable linear regression models were used to assess correlations between main determinants and plasma folate and vitamin B12 levels.

RESULTS

The partial correlation coefficient between dietary intakes and plasma folate was 0.19 (p value <0.001) and 0.08 (p value = 0.008) for vitamin B12. Dietary scores were the main determinant of B vitamin plasma concentrations with a percent change per unit increase of 12.64% (p value <0.001) for folate and 7.6% (p value <0.001) for vitamin B12. Homozygous (T/T) or heterozygous (C/T) women for MTHFR-C677T had lower plasma folate concentrations [C/T: -6.48% (p value = 0.038) and T/T: -15.89% (p value <0.001)] compared to women carrying the C/C genotype. Other determinants of B vitamin plasma concentration include: smoking status for folate, and age and hormone replacement therapy for vitamin B12.

CONCLUSIONS

We confirmed previous findings on the role of diet as main determinant of folate and vitamin B12 plasma concentrations. However, the impact of genetic polymorphisms and lifestyle factors on plasma B vitamin concentrations should not be neglected.

Single Nucleotide Polymorphisms in Key One-Carbon Metabolism Genes and Their Association with Blood Folate and Homocysteine Levels in a Chinese Population in Yunnan

OBJECTIVE

One-carbon metabolism (OCM) is essential for DNA synthesis and methylation. Single nucleotide polymorphisms (SNPs) within OCM genes may affect folic acid (FA) metabolism, disrupt homocysteine (Hcy) homeostasis, and increase the risk of disease. This study investigated the relationship between SNPs in key OCM genes and their association with blood FA and Hcy levels in a healthy population in Yunnan, China.

METHODS

Six SNPs within five key OCM genes (MTHFR C677T, MTHFR A1298C, MS A2756G, MTRR A66G, CBS T833C, and SHMT C1420T) were genotyped in 300 healthy volunteers (148 males and 152 females) using polymerase chain reaction/restriction fragment length polymorphism. Blood folate [serum FA (SFA) and red blood cell folate (RBC FA)] and Hcy levels were determined by chemiluminescence immunoassays and enzymatic assays.

RESULTS

Subjects with the MTHFR 677TT genotype had significantly higher Hcy levels and RBC FA concentrations compared with those harboring the MTHFR 677CC/CT genotypes (p < 0.01). Both Hcy and blood FA concentrations were also increased in subjects with MS 2756AA, as well as those within CBS 833TT, when compared with those with MS 2756AG/GG (p < 0.05) and CBS 833TC/CC (p < 0.05) genotypes, respectively. Subjects harboring the combined genotype of MTHFR 677TT and MS 2756AA had a higher Hcy concentration than those carrying other MTHFR and MS combinations (p = 0.002). Similarly, subjects harboring the combination of CBS 833TT with MTHFR 677TT had higher Hcy concentrations than those harboring other CBS and MTHFR combinations (p = 0.011).

CONCLUSIONS

The genotypes involving the MTHFR C677T, MS A2756G, and CBS T833C polymorphisms, including combinations of these genotypes, were the most important factors associated with blood FA and Hcy levels of the investigated SNPs in the OCM genes.

Methylenetetrahydrofolate Reductase Gene Polymorphism (C677T) as a Risk Factor for Arterial Thrombosis in Georgian Patients

Methylenetetrahydrofolate reductase (MTHFR) gene polymorphism (C677T)] is a well-recognized genetic risk factor for venous thrombosis; however, its association with arterial thrombosis is still under debate. Herein, we evaluated the prevalence of MTHFR C677T polymorphism in Georgian patients in comparison with healthy individuals and its association with arterial thrombosis. We enrolled 214 participants: 101 with arterial thrombosis (71.3% males; mean age: 66.3 ± 12.1 years) and 113 controls (67.3% males; mean age: 56.6 ± 11.3 years). Genomic DNA was extracted from dry blood spot on Whatman filter paper. Polymerase chain reaction was performed to determine MTHFR C677T polymorphism. Frequency of C677T allele polymorphism in controls was 21.2%, which corresponded to heterozygous and homozygous stage frequencies of 35.4% and 3.5%, respectively. In patient group, an allelic frequency of 33.2% was found, which corresponded to the presence of 48.5% of heterozygous and 8.9% of homozygous individuals. Comparing the frequency of mutated alleles between the 2 groups, a significantly high frequency of mutated alleles was found in patient group (P < .05). In conclusion, high frequency of MTHFR C677T polymorphism found in arterial thrombosis patient group suggests that this polymorphism might increase the risk of arterial thrombosis in Georgian patients.

Effect of MTHFR A1298C and MTRR A66G Genetic Mutations on Homocysteine Levels in the Chinese Population: A Systematic Review and Meta-analysis

Background and Objectives

The Chinese population typically has inadequate folate intake and no mandatory folic acid fortification. Methylenetetrahydrofolate reductase (MTHFR) and methionine synthase reductase (MTRR) are the two key regulatory enzymes in the folate/homocysteine (Hcy) metabolism. Hcy has been implicated in the pathogenesis of cardiovascular disease. We conducted a meta-analysis to assess whether the MTHFR gene A1298C and the MTRR gene A66G polymorphisms affect Hcy levels in the Chinese population.

Methods

This analysis included 13 studies with Hcy levels reported as one of the study measurements. Summary estimates of weighted mean differences and 95% confidence intervals (CIs) were obtained using random-effect models.

Results

Overall, there were no significant differences in Hcy concentrations between participants with the MTHFR 1298 CC (12 trials, n = 129), AA (n = 2166; β, -0.51 μmol/L; 95%CI: -2.14, 1.11; P = 0.53), or AC genotype (n = 958; β, 0.55 μmol/L; 95%CI: -0.72, 1.82; P = 0.40). Consistently, compared to those with the MTRR 66 GG genotype (6 trials, n = 156), similar Hcy concentrations were found in participants with the AA (n = 832; β, -0.43 μmol/L; 95%CI: -1.04, 0.17; P = 0.16) or AG (n =743; β, -0.57 μmol/L; 95%CI: -1.46, 0.31; P = 0.21) genotype. Similar results were observed for the dominant and recessive models.

Conclusions

Neither the MTHFR A1298C polymorphism nor the MTRR A66G polymorphism affects Hcy levels in the Chinese population.

Methylenetetrahydrofolate Reductase A1298C Polymorphism and Major Depressive Disorder

Major depressive disorder (MDD) is a disorder that carries significant psychosocial and economic implications. Research efforts have focused on identifying biomarkers that can aid in the prediction, diagnosis, and efficacious treatment of MDD. Most of this focus has been placed on a polymorphism of the methylenetetrahydrofolate reductase (MTHFR) gene, C677T. MTHFR C677T is screened during MDD diagnosis in many protocols. However, MTHFR C667T poses conflicting data in various ethnic groups and geographic populations calling into question its utility. Another polymorphism, MTHFR A1298C, has often taken the back-seat to MTHFR C677T in respect to research focus. MTHFR A1298C is implicated in irregular homocysteine metabolism and aberrant folate cycles and, through this, it may play a role as either a driver in the development of MDD or as a predictive or diagnostic marker, possibly in combination with C677T. The number of studies evaluating MTHFR A1298C and the power of those studies is lacking and thus larger studies are required to confirm the association between this polymorphism and MDD.

MTRR rs326119 polymorphism is associated with plasma concentrations of homocysteine and cobalamin, but not with congenital heart disease or coronary atherosclerosis in Brazilian patients

Background

Differences in the distribution of the MTRR rs326119 polymorphism (c.56 + 781 A > C) between patients with congenital heart disease (CHD) and controls have been described in Chinese individuals. The association is thought to be due to deregulation of homocysteine-cobalamin pathways. This has not been replicated in other populations. The primary objective of this study was to assess the influence of the MTRR rs326119 polymorphism on biochemical parameters of vitamin B12 metabolism, coronary lesions, and congenital heart disease in Brazilian subjects.

Methods

We selected 722 patients with CHD, 1432 patients who underwent coronary angiography, and 156 blood donors. Genotyping for the MTRR polymorphism was evaluated by high-resolution melting analysis, and biochemical tests of vitamin B12 metabolism were measured.

Results

Subjects carrying the AC or CC genotypes had higher homocysteine concentrations (9.7 ± 0.4 μmol/L and 10.1 ± 0.6 μmol/L) and lower cobalamin concentrations (260.5 ± 13.3 pmol/L and 275.6 ± 19.9 pmol/L) compared with the subjects carrying the AA genotype (8.7 ± 0.5 μmol/L and 304.8 ± 14.7 pmol/L), respectively. A multiple linear regression model also identified a significant association between the number of C variant alleles with the concentrations of homocysteine and cobalamin. Nonetheless, the allelic and genotypic distributions for MTRR rs326119 were not associated with CHD or coronary atherosclerosis in the studied samples.

Conclusion

Our findings indicate that the MTRR rs326119 variant might be a genetic marker associated with homocysteine and cobalamin concentrations, but not a strong risk factor for CHD or coronary atherosclerosis in the Brazilian population.

Folate Deficiency Was Associated with Increased Alanine Aminotransferase and Glutamyl Transpeptidase Concentrations in a Chinese Hypertensive Population: A Cross-Sectional Study

Alanine aminotransferase (ALT), aspartate transaminase (AST), and glutamyl transpeptidase (GGT) were three key enzymes in the hepatic metabolism. This study aimed to investigate the effect of homocysteine (Hcy) metabolism gene polymorphisms and serum Hcy and folate level on the hepatic functions in a Chinese hypertensive population. A representative sample with 480 subjects aged 28-75 was enrolled in 2005.9-2005.12 from six hospitals in different Chinese regions. Serum ALT, AST and GGT were measured by using an automatic biochemistry analyzer. Serum Hcy was measured by high-performance liquid chromatography, and serum folate was measured by chemiluminescent immunoassay. Known genotypes were detected by PCR-RFLP methods. The results showed that the MTHFR C677T mutation was related a decreased serum AST level (r=-0.11, p=0.026), whereas the MTHFR A1298C mutation elevated serum AST level (r=0.11, p=0.032). Furthermore, multiple regression analysis showed that folate deficiency was associated with higher serum ALT (β (SE): 0.13 (0.06), p=0.031) and GGT level (β (SE): 0.18 (0.07), p=0.011). However, serum Hcy level may not affect the hepatic functions. Our data suggested that hepatic functions were affected by MTHFR gene polymorphisms and serum folate level. Further studies are needed to confirm these correlations in a larger population.

Potential Links between Impaired One-Carbon Metabolism Due to Polymorphisms, Inadequate B-Vitamin Status, and the Development of Alzheimer's Disease

Alzheimer's disease (AD) is the major cause of dementia and no preventive or effective treatment has been established to date. The etiology of AD is poorly understood, but genetic and environmental factors seem to play a role in its onset and progression. In particular, factors affecting the one-carbon metabolism (OCM) are thought to be important and elevated homocysteine (Hcy) levels, indicating impaired OCM, have been associated with AD. We aimed at evaluating the role of polymorphisms of key OCM enzymes in the etiology of AD, particularly when intakes of relevant B-vitamins are inadequate. Our review indicates that a range of compensatory mechanisms exist to maintain a metabolic balance. However, these become overwhelmed if the activity of more than one enzyme is reduced due to genetic factors or insufficient folate, riboflavin, vitamin B6 and/or vitamin B12 levels. Consequences include increased Hcy levels and reduced capacity to synthetize, methylate and repair DNA, and/or modulated neurotransmission. This seems to favor the development of hallmarks of AD particularly when combined with increased oxidative stress e.g., in apolipoprotein E (ApoE) ε4 carriers. However, as these effects can be compensated at least partially by adequate intakes of B-vitamins, achieving optimal B-vitamin status for the general population should be a public health priority.

Determinants of hyperhomocysteinemia in healthy and hypertensive subjects: A population-based study and systematic review

AIMS

Hyperhomocysteinemia (HHcy) is known to increase the risk of many diseases. Factors influencing HHcy in healthy and hypertensive subjects remain under-researched.

METHODS

A large population-based study was conducted in 60 communities from Shenzhen, China. Responses to standardized questions on lifestyle factors and blood samples were collected from all participants after a 12-h overnight fast. Multiple linear and multivariate logistic regressions were used to explore risk factors for HHcy. Results were then compared to those from a systematic review of English-language articles listed in Pubmed, EBSCOhost, Web of Science, Embase and Cochrane libraries that investigated HHcy risk factors in healthy and hypertensive subjects.

RESULTS

A total of 1586 healthy (Male/Female = 642/944) and 5935 hypertensive subjects (Male/Female = 2928/3007) participated in our population-based study. In logistic regression analyses, age, BMI and creatinine (Cr) were risk factors, while being female, fruit intake and physical activity were protective factors for HHcy in healthy subjects. In hypertensive subjects, seven [age, smoking, salt intake, systolic blood pressure (SBP), uric acid, triglycerides (TG), and Cr] and four [female, fruit intake, total cholesterol (TC), and glucose] factors were associated with higher and lower HHcy respectively. The review of 71 studies revealed that potential risk factors for Hcy included nutritional, physiologic, lifestyle habits, ethnicity, genetics, interactions between gene-environment, gene-gene, gene-nutritional, environment-environment, nutritional-nutritional.

CONCLUSION

Our study indicates the potential importance of increasing folic acid and vitamin B supplementation, daily fruit and vegetable intake, regular exercise and refraining from tobacco smoking and alcohol consumption as preventive strategies for Hcy.

Association of MTHFR, SLC19A1 Genetic Polymorphism, Serum Folate, Vitamin B12 and Hcy Status with Cognitive Functions in Chinese Adults

Background/Aim: Studies have indicated a relationship between either gene polymorphism or in vivo B vitamins’ nutritional status with cognition in the elderly. However, the combined effects of MTHFR and SLC19A1gene polymorphism with serum folate and vitamin B₁₂ levels on cognition in Chinese adult population remain unclear. Methods: Demographic information of 426 Chinese adults aged from 55 to 90 were collected by a well designed self-administered questionnaire. The Montreal Cognitive Assessment test was utilized to evaluate the cognition status of the participants. MTHFR and SLC19A1 genotyping was analyzed using polymerase chain reaction-ligase detection reaction (PCR- LDR) method. Serum folate, vitamin B₁₂ and homocysteine (Hcy) levels were detected by commercial assay kits. Pearson’s correlation was used for data analyses and statistical significance was set at p < 0.05. Results: Serum Hcylevels demonstrated a negative correlation with serum folate (r = −0.301) and vitamin B₁₂ (r = −0.292) levels. The negative correlation found between serum Hcy levels and attention ability was observed in all 426 studied subjects (r = −0.122). Subjects with MTHFR 677 T/T and 1298 A/A genotypes demonstrated a higher serum Hcy levels (p < 0.05). Carriers of MTHFR (1298 A/C + C/C and 1793 G/A) and SLC19A1 80 G/G genotypes showed lower abstraction and delayed memory ability, respectively (p < 0.05). Subjects with MTHFR 1793 G/A genotype along with low serum folate concentration demonstrated the lowest name and orientation abilities. The effects of MTHFR 1793 G/A genotype on cognitive performance were dependent on the status of serum vitamin B₁₂. Conclusion: Cognition of adults was associated with MTHFR, SLC19A1 gene polymorphism and serum Hcy levels. This study clearly establishes a combined effect of MTHFR gene polymorphism and serum B vitamins levels on cognition in Chinese adults.

The importance of MTHFR C677T/A1298C combined polymorphisms in pulmonary embolism in Turkish population

BACKGROUND AND OBJECTIVE

Pulmonary embolism (PE) is an important cardiovascular emergency with high mortality. There are still problems related to the diagnosis of PE and genetic research may play a key role on diagnosis as well as determining risk stratification. In the present study, the aim was to evaluate MTHFR C677T and A1298C polymorphisms that play a role on folate metabolism in PE patients.

MATERIALS AND METHODS

A total of 118 PE patients and 126 controls were enrolled in the current study. Genomic DNA was isolated and genotyped using polymerase chain reaction (PCR) analyses for the MTHFR C677T and A1298C polymorphisms.

RESULTS

There was no association between clinical and demographic characteristics of PE patients and both MTHFR C677T and A1298C polymorphisms. Allele frequencies showed a significant difference between patients and controls. T allele frequency was significantly higher in the patients' group than the control group. There was an association between PE and combined MTHFR C677T and A1298C polymorphisms.

CONCLUSION

We found an association between MTHFR C677T/A1298C combined mutations and PE in the Turkish population. Future genetic studies investigating combined mutations could be very helpful to identify risk population in PE.

MTHFR: Genetic variants, expression analysis and COMT interaction in major depressive disorder

BACKGROUND

Methylenetetrahydrofolate reductase (MTHFR) genetic variations have been widely studied in major depressive disorder (MDD) and antidepressants outcome. An interaction with catechol-O-methyltransferase (COMT) has also been proved affecting depression. The aim of this study was to clarify the role of the most commonly studied single nucleotide polymorphisms (SNPs) of MTHFR gene in MDD and in treatment response mechanisms, along with the impact of the interaction with COMT.

METHODS

A total of 613 MDD patients, of whom 389 were classified as having treatment resistant depression (TRD), and 463 controls were enrolled. The A1298C, C677T and COMT Val158Met were genotyped. Genetic data were integrated with a transcriptional level analysis in peripheral blood cells (PBCs) and fibroblasts.

RESULTS

The A1298C CC homozygotes were more frequent in MDD patients compared to controls in women, increasing twice the genetic risk to develop depression. Moreover this genotype resulted in epistasis with COMT Met carriers in association with MDD. No significant effects were obtained concerning response to treatment. Transcriptional analyses highlighted a strong correlation between the mRNA levels of MTHFR in fibroblasts and COMT genotypes whereas no significant association with MDD was found. PBCs results revealed relevant influences of environmental factors.

LIMITATION

We did not measure folate and homocisteine levels.

CONCLUSION

This study showed the involvement of A1298C, Val158Met and their interaction in MDD. The transcriptional analyses supported the participation of COMT in the folate pathway, which partakes in the complex network of gene×gene and gene×environment interactions of MDD etiopathogenesis.

Evaluation of a high throughput method for the detection of mutations associated with thrombosis and hereditary hemochromatosis in Brazilian blood donors

Background

The aim of this study was to evaluate the OpenArray platform for genetic testing of blood donors and to assess the genotype frequencies of nucleotide-polymorphisms (SNPs) associated with venous thrombosis (G1691A and G20210A), hyperhomocysteinemia (C677T, A1298C), and hereditary hemochromatosis (C282Y, H63D and S65C) in blood donors from Sao Paulo, Brazil.

Methods

We examined 400 blood donor samples collected from October to November 2011. The SNPs were detected using OpenArray technology. The blood samples were also examined using a real-time PCR–FRET system to compare the results and determine the accuracy of the OpenArray method.

Results

We observed 100% agreement in all assays tested, except HFE C282Y, which showed 99.75% agreement. The HFE C282Y assay was further confirmed through direct sequencing, and the results showed that OpenArray analysis was accurate. The calculated frequencies of each SNP were FV G1691A 98.8% (G/G), 1.2% (G/A); FII G2021A 99.5% (G/G), 0.5% (G/A); MTHFR C677T 45.5% (C/C), 44.8% (C/T), 9.8% (T/T); MTHFR A1298C 60.3% (A/A), 33.6% (A/C), 6.1% (C/C); HFE C282Y 96%(G/G), 4%(G/A), HFE H63D 78.1%(C/C), 20.3% (C/G), 1.6% (G/G); and HFE S65C 98.1% (A/A), 1.9% (A/T).

Conclusion

Taken together, these results describe the frequencies of SNPs associated with diseases and are important to enhance our current knowledge of the genetic profiles of Brazilian blood donors, although a larger study is needed for a more accurate determination of the frequency of the alleles. Furthermore, the OpenArray platform showed a high concordance rate with standard FRET RT-PCR.

Effect of genetic polymorphisms involved in folate metabolism on the concentration of serum folate and plasma total homocysteine (p-tHcy) in healthy subjects after short-term folic acid supplementation: a randomized, double blind, crossover study

Data on the effect of combined genetic polymorphisms, involved in folate metabolism, on the concentration of serum folate after folic acid supplementation are scarce. Therefore, we investigated the impact of seven gene polymorphisms on the concentration of serum folate and p-tHcy in healthy subjects after short-term folic acid supplementation. In a randomized, double blind, crossover study, apparently healthy subjects were given either 0.8 mg folic acid per day (n = 46) or placebo (n = 45) for 14 days. The washout period was 14 days. Fasting blood samples were collected on day 1, 15, 30 and 45. Data on subjects on folic acid supplementation (n = 91) and on placebo (n = 45) were used for the statistical analysis. The concentration of serum folate increased higher in subjects with higher age (53.5 ± 7.0 years) than in subjects with lower age (24.3 ± 3.2 years) after folic acid supplementation (p = 0.006). The baseline concentration of serum folate in subjects with polymorphism combination, reduced folate carrier protein, RFC1-80 GA and methylenetetrahydrofolate reductase, MTHFR677 CT+TT, was lower than RFC1-80 AA and MTHFR677 CT+TT (p = 0.002). After folic acid supplementation, a higher increase in the concentration of serum folate was detected in subjects with polymorphism combination RFC1-80 GA and MTHFR677 CC than RFC1-80 GG and MTHFR CT+TT combination (p < 0.0001). The baseline concentration of plasma total homocysteine (p-tHcy) was altered by combined polymorphisms in genes associated with folate metabolism. After folic acid supplementation, in subjects with combined polymorphisms in methylenetetrahydrofolate dehydrogenase, MTHFD1-1958 and MTHFR-677 genes, the concentration of p-tHcy was changed (p = 0.002). The combination of RFC1-80 and MTHFR-677 polymorphisms had a profound affect on the concentration of serum folate in healthy subjects before and after folic acid supplementation.

Elevation in Total Homocysteine Levels in Chinese Patients With Essential Hypertension Treated With Antihypertensive Benazepril

OBJECTIVE

To investigate the effect of benazepril on plasma homocysteine (Hcy) levels and to analyze the correlation between the methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and changes in Hcy levels in response to benazepril.

METHODS

A total of 231 patients with mild to moderate essential hypertension were enrolled, and benazepril was orally administered at a dose of 10 mg/d for 2 weeks. Plasma Hcy levels were measured by high-performance liquid chromatography at baseline and after 2 weeks of treatment. Genotyping of the MTHFR C677T polymorphism was performed by TaqMan probe technique.

RESULTS

There was no significant change in Hcy level after benazepril treatment for 2 weeks (P = .97). However, stratified by baseline Hcy levels, the patients with baseline Hcy <10 μmol/L had a significant increase in plasma Hcy levels (P = .003). The results from the multivariable linear regression analysis demonstrated a significant correlation between baseline Hcy levels and the changes in Hcy levels found in both the unadjusted (P = .002) and the adjusted model (P = .004). Strikingly, we found no significant effect modification by the MTHFR C677T polymorphism on the Hcy changes after benazepril treatment. There were also no statistically significant interactions of gene and environment factors (ie, gene smoking and drinking) on the changes in Hcy levels after benazepril treatment.

CONCLUSION

Benazepril may cause an increase in plasma Hcy levels among patients with hypertension with low baseline Hcy levels, while effect modification by MTHFR C677T genotypes on the changes in Hcy levels in response to benazepril was not significant among patients with essential hypertension.

Relationship between homocysteine level and diabetic retinopathy: a systematic review and meta-analysis

Background

The relationship between homocysteine (Hcy) and diabetic retinopathy (DR) remains unclear to date. Therefore, a systematic review and meta-analysis was performed on the relationship between Hcy level and DR.

Methods

Studies were identified by searching PubMed, Embase, and Web of Science databases until 5 May, 2014.

Results

A total of 31 studies involving 6,394 participants were included in the meta-analysis. After pooling the data from each included study, the blood Hcy concentration in the DR group was observed to be higher than that in the control group [WMD = 2.55; 95% confidence interval (CI), 1.70–3.40], and diabetes mellitus (DM) patients with hyperhomocysteinemia were at a risk for DR [odds ratio (OR) = 1.93; 95% CI, 1.46–2.53]. Considering the different DM types, hyperhomocysteinemia in T1DM (OR = 1.83, 95% CI, 1.28–2.62) was associated with DR rather than in T2DM (OR = 1.59, 95% CI, 0.72–3.51). Considerable statistical heterogeneity in the overall summary estimates was partly explained by the geographical differences.

Conclusions

Results from this current meta-analysis indicate that hyperhomocysteinemia is a risk factor for DR, especially proliferative DR. Differences between geographical regions were observed in the relationship between hyperhomocysteinemia with T1DM risk. Given the heterogeneous results, the relationship between high Hcy and DR needs further investigation.

Virtual Slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/13000_2014_167

Altered protein phosphatase 2A methylation and Tau phosphorylation in the young and aged brain of methylenetetrahydrofolate reductase (MTHFR) deficient mice

Common functional polymorphisms in the methylenetetrahydrofolate reductase (MTHFR) gene, a key enzyme in folate and homocysteine metabolism, influence risk for a variety of complex disorders, including developmental, vascular, and neurological diseases. MTHFR deficiency is associated with elevation of homocysteine levels and alterations in the methylation cycle. Here, using young and aged Mthfr knockout mouse models, we show that mild MTHFR deficiency can lead to brain-region specific impairment of the methylation of Ser/Thr protein phosphatase 2A (PP2A). Relative to wild-type controls, decreased expression levels of PP2A and leucine carboxyl methyltransferase (LCMT1) were primarily observed in the hippocampus and cerebellum, and to a lesser extent in the cortex of young null Mthfr (-/-) and aged heterozygous Mthfr (+/-) mice. A marked down regulation of LCMT1 correlated with the loss of PP2A/Bα holoenzymes. Dietary folate deficiency significantly decreased LCMT1, methylated PP2A and PP2A/Bα levels in all brain regions examined from aged Mthfr (+/+) mice, and further exacerbated the regional effects of MTHFR deficiency in aged Mthfr (+/-) mice. In turn, the down regulation of PP2A/Bα was associated with enhanced phosphorylation of Tau, a neuropathological hallmark of Alzheimer's disease (AD). Our findings identify hypomethylation of PP2A enzymes, which are major CNS phosphatases, as a novel mechanism by which MTHFR deficiency and Mthfr gene-diet interactions could lead to disruption of neuronal homeostasis, and increase the risk for a variety of neuropsychiatric disorders, including age-related diseases like sporadic AD.