The methylenetetrahydrofolate reductase C677T mutation induces cell-specific changes in genomic DNA methylation and uracil misincorporation: a possible molecular basis for the site-specific cancer risk modification

Relationship between MTHFR gene polymorphism and risk of thrombosis in postoperative patients with colorectal cancer

An association between the methylenetetrahydrofolate reductase (MTHFR) C667T genotype and the risk of colorectal cancer, as well as a link between MTHFR gene polymorphism and thrombosis, have been revealed. However, the connection between MTHFR gene polymorphism and the risk of thrombosis in patients with colorectal cancer has remained to be fully elucidated. The present study investigated the link between MTHFR gene polymorphism and basic clinical data, postoperative D-dimer (DDi), postoperative thromboelastogram and postoperative thrombosis in 591 patients who underwent surgery for colorectal cancer. Postoperative DDi, thromboelastogram and postoperative thrombosis were not significantly different among patients with colorectal cancer and different MTHFR genotypes. While the results were 'negative', the present study may help physicians understand that it is not necessary to detect MTHFR polymorphism for therapeutic purposes. Regarding the danger of venous thrombosis, more focus should be placed on the standardized procedural enforcement system for deep vein thrombosis prevention for patients undergoing pelvic and abdominal surgery.

The evolution of human skin pigmentation: A changing medley of vitamins, genetic variability, and UV radiation during human expansion

This review examines putative, yet likely critical evolutionary pressures contributing to human skin pigmentation and subsequently, depigmentation phenotypes. To achieve this, it provides a synthesis of ideas that frame contemporary thinking, without limiting the narrative to pigmentation genes alone. It examines how geography and hence the quality and quantity of UV exposure, pigmentation genes, diet-related genes, vitamins, anti-oxidant nutrients, and cultural practices intersect and interact to facilitate the evolution of human skin color. The article has a strong focus on the vitamin D-folate evolutionary model, with updates on the latest biophysical research findings to support this paradigm. This model is examined within a broad canvas that takes human expansion out of Africa and genetic architecture into account. A thorough discourse on the biology of melanization is provided (includes relationship to BH4 and DNA damage repair), with the relevance of this to the UV sensitivity of folate and UV photosynthesis of vitamin D explained in detail, including the relevance of these vitamins to reproductive success. It explores whether we might be able to predict vitamin-related gene polymorphisms that pivot metabolism to the prevailing UVR exposome within the vitamin D-folate evolutionary hypothesis context. This is discussed in terms of a primary adaptive phenotype (pigmentation/depigmentation), a secondary adaptive phenotype (flexible metabolic phenotype based on vitamin-related gene polymorphism profile), and a tertiary adaptive strategy (dietary anti-oxidants to support the secondary adaptive phenotype). Finally, alternative evolutionary models for pigmentation are discussed, as are challenges to future research in this area.

Methodological and Biological Factors Influencing Global DNA Methylation Results Measured by LINE-1 Pyrosequencing Assay in Colorectal Tissue and Liquid Biopsy Samples

Long interspersed nuclear element 1 (LINE-1) bisulfite pyrosequencing is a widely used technique for genome-wide methylation analyses. We aimed to investigate the effects of experimental and biological factors on its results to improve the comparability. LINE-1 bisulfite pyrosequencing was performed on colorectal tissue (n = 222), buffy coat (n = 39), and plasma samples (n = 9) of healthy individuals and patients with colorectal tumors. Significantly altered methylation was observed between investigated LINE-1 CpG positions of non-tumorous tissues (p ≤ 0.01). Formalin-fixed, paraffin-embedded biopsies (73.0 ± 5.3%) resulted in lower methylation than fresh frozen samples (76.1 ± 2.8%) (p ≤ 0.01). DNA specimens after long-term storage showed higher methylation levels (+3.2%, p ≤ 0.01). In blood collection tubes with preservatives, cfDNA and buffy coat methylation significantly changed compared to K3EDTA tubes (p ≤ 0.05). Lower methylation was detected in older (>40 years, 76.8 ± 1.7%) vs. younger (78.1 ± 1.0%) female patients (p ≤ 0.05), and also in adenomatous tissues with MTHFR 677CT, or 1298AC mutations vs. wild-type (p ≤ 0.05) comparisons. Based on our findings, it is highly recommended to consider the application of standard DNA samples in the case of a possible clinical screening approach, as well as in experimental research studies.

MTHFR Knockdown Assists Cell Defense against Folate Depletion Induced Chromosome Segregation and Uracil Misincorporation in DNA

Folate depletion causes chromosomal instability by increasing DNA strand breakage, uracil misincorporation, and defective repair. Folate mediated one-carbon metabolism has been suggested to play a key role in the carcinogenesis and progression of hepatocellular carcinoma (HCC) through influencing DNA integrity. Methylenetetrahydrofolate reductase (MTHFR) is the enzyme catalyzing the irreversible conversion of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate that can control folate cofactor distributions and modulate the partitioning of intracellular one-carbon moieties. The association between MTHFR polymorphisms and HCC risk is inconsistent and remains controversial in populational studies. We aimed to establish an in vitro cell model of liver origin to elucidate the interactions between MTHFR function, folate status, and chromosome stability. In the present study, we (1) examined MTHFR expression in HCC patients; (2) established cell models of liver origin with stabilized inhibition of MTHFR using small hairpin RNA delivered by a lentiviral vector, and (3) investigated the impacts of reduced MTHFR and folate status on cell cycle, methyl group homeostasis, nucleotide biosynthesis, and DNA stability, all of which are pathways involved in DNA integrity and repair and are critical in human tumorigenesis. By analyzing the TCGA/GTEx datasets available within GEPIA2, we discovered that HCC cancer patients with higher MTHFR had a worse survival rate. The shRNA of MTHFR (shMTHFR) resulted in decreased MTHFR gene expression, MTHFR protein, and enzymatic activity in human hepatoma cell HepG2. shMTHFR tended to decrease intracellular S-adenosylmethionine (SAM) contents but folate depletion similarly decreased SAM in wildtype (WT), negative control (Neg), and shMTHFR cells, indicating that in cells of liver origin, shMTHFR does not exacerbate the methyl group supply in folate depletion. shMTHFR caused cell accumulations in the G2/M, and cell population in the G2/M was inversely correlated with MTHFR gene level (r = −0.81, p < 0.0001), MTHFR protein expression (r = −0.8; p = 0.01), and MTHFR enzyme activity (r = −0.842; p = 0.005). Folate depletion resulted in G2/M cell cycle arrest in WT and Neg but not in shMTHFR cells, indicating that shMTHFR does not exacerbate folate depletion-induced G2/M cell cycle arrest. In addition, shMTHFR promoted the expression and translocation of nuclei thymidine synthetic enzyme complex SHMT1/DHFR/TYMS and assisted folate-dependent de novo nucleotide biosynthesis under folate restriction. Finally, shMTHFR promoted nuclear MLH1/p53 expression under folate deficiency and further reduced micronuclei formation and DNA uracil misincorporation under folate deficiency. In conclusion, shMTHFR in HepG2 induces cell cycle arrest in G2/M that may promote nucleotide supply and assist cell defense against folate depletion-induced chromosome segregation and uracil misincorporation in the DNA. This study provided insight into the significant impact of MTHFR function on chromosome stability of hepatic tissues. Data from the present study may shed light on the potential regulatory mechanism by which MTHFR modulates the risk for hepatic malignancies.

Biophysical evidence to support and extend the vitamin D-folate hypothesis as a paradigm for the evolution of human skin pigmentation

OBJECTIVE

To test the "vitamin D-folate hypothesis for the evolution of human skin pigmentation."

METHODS

Total ozone mapping spectrometer (TOMS) satellite data were used to examine surface UV-irradiance in a large (n = 649) Australian cross-sectional study population. Genetic analysis was used to score vitamin D- and folate-related gene polymorphisms (n = 22), along with two pigmentation gene variants (IRF4-rs12203592/HERC2-rs12913832). Red cell folate and vitamin D₃ were measured by immunoassay and HPLC, respectively.

RESULTS

Ultraviolet radiation (UVR) and pigmentation genes interact to modify blood vitamin levels; Light skin IRF4-TT genotype has greatest folate loss while light skin HERC2-GG genotype has greatest vitamin D₃ synthesis (reflected in both TOMS and seasonal data). UV-wavelength exhibits a dose-response relationship in folate loss within light skin IRF4-TT genotype (305 > 310 > 324 > 380 nm). Significant vitamin D₃ photosynthesis only occurs within light skin HERC2-GG genotype, and is maximal at 305 nm. Three dietary antioxidants (vitamins C, E, and β-carotene) interact with UVR and pigmentation genes preventing oxidative loss of labile reduced folate vitamers, with greatest benefit in light skin IRF4-TT subjects. The putative photosensitiser, riboflavin, did not sensitize red cell folate to UVR and actually afforded protection. Four genes (5xSNPs) influenced blood vitamin levels when stratified by pigmentation genotype; MTHFR-rs1801133/rs1801131, TS-rs34489327, CYP24A-rs17216707, and VDR-ApaI-rs7975232. Lightest IRF4-TT/darkest HERC2-AA genotype combination (greatest folate loss/lowest vitamin D₃ synthesis) has 0% occurrence. The opposing, commonest (39%) compound genotype (darkest IRF4-CC/lightest HERC2-GG) permits least folate loss and greatest synthesis of vitamin D₃ .

CONCLUSION

New biophysical evidence supports the vitamin D-folate hypothesis for evolution of skin pigmentation.

Vitamin-related phenotypic adaptation to exposomal factors: The folate-vitamin D-exposome triad

The biological role of two key vitamins, folic acid and vitamin D is so fundamental to life processes, it follows that their UV sensitivity, dietary abundance (both key exposomal factors) and variability in dependent genes will modify their functional efficacy, particularly in the context of maintaining the integrity and function of genome and epigenome. This article therefore examines folate and vitamin D-related phenotypic adaptation to environmental factors which vary across the human life cycle as well as over an evolutionary time-scale. Molecular mechanisms, key nutrigenomic factors, phenotypic maladaptation and evolutionary models are discussed.

Folinate Supplementation Ameliorates Methotrexate Induced Mitochondrial Formate Depletion In Vitro and In Vivo

(1) Background: Antifolate methotrexate (MTX) is the most common disease-modifying antirheumatic drug (DMARD) for treating human rheumatoid arthritis (RA). The mitochondrial-produced formate is essential for folate-mediated one carbon (1C) metabolism. The impacts of MTX on formate homeostasis in unknown, and rigorously controlled kinetic studies can greatly help in this regard. (2) Methods: Combining animal model (8-week old female C57BL/6JNarl mice, n = 18), cell models, stable isotopic tracer studies with gas chromatography/mass spectrometry (GC/MS) platforms, we systematically investigated how MTX interferes with the partitioning of mitochondrial and cytosolic formate metabolism. (3) Results: MTX significantly reduced de novo deoxythymidylate (dTMP) and methionine biosyntheses from mitochondrial-derived formate in cells, mouse liver, and bone marrow, supporting our postulation that MTX depletes mitochondrial 1C supply. Furthermore, MTX inhibited formate generation from mitochondria glycine cleavage system (GCS) both in vitro and in vivo. Folinate selectively rescued 1C metabolic pathways in a tissue-, cellular compartment-, and pathway-specific manner: folinate effectively reversed the inhibition of mitochondrial formate-dependent 1C metabolism in mouse bone marrow (dTMP, methionine, and GCS) and cells (dTMP and GCS) but not methionine synthesis in liver/liver-derived cells. Folinate failed to fully recover hepatic mitochondrial-formate utilization for methionine synthesis, suggesting that the efficacy of clinical folinate rescue in MTX therapy on hepatic methionine metabolism is poor. (4) Conclusion: Conducting studies in mouse and cell models, we demonstrate novel findings that MTX specifically depletes mitochondrial 1C supply that can be ameliorated by folinate supplementation except for hepatic transmethylation. These results imply that clinical use of low-dose MTX may particularly impede 1C metabolism via depletion of mitochondrial formate. The MTX induced systematic and tissue-specific formate depletion needs to be addressed more carefully, and the efficacy of folinate with respect to protecting against such depletion deserves to be evaluated in medical practice.

Tracing Metabolic Fate of Mitochondrial Glycine Cleavage System Derived Formate In Vitro and In Vivo

Folate-mediated one-carbon (1C) metabolism is a major target of many therapies in human diseases. Studies have focused on the metabolism of serine 3-carbon as it serves as a major source for 1C units. The serine 3-carbon enters the mitochondria transferred by folate cofactors and eventually converted to formate and serves as a major building block for cytosolic 1C metabolism. Abnormal glycine metabolism has been reported in many human pathological conditions. The mitochondrial glycine cleavage system (GCS) catalyzes glycine degradation to CO₂ and ammonium, while tetrahydrofolate (THF) is converted into 5,10-methylene-THF. GCS accounts for a substantial proportion of whole-body glycine flux in humans, yet the particular metabolic route of glycine 2-carbon recycled from GCS during mitochondria glycine decarboxylation in hepatic or bone marrow 1C metabolism is not fully investigated, due to the limited accessibility of human tissues. Labeled glycine at 2-carbon was given to humans and primary cells in previous studies for investigating its incorporations into purines, its interconversion with serine, or the CO₂ production in the mitochondria. Less is known on the metabolic fate of the glycine 2-carbon recycled from the GCS; hence, a model system tracing its metabolic fate would help in this regard. We took the direct approach of isotopic labeling to further explore the in vitro and in vivo metabolic fate of the 2-carbon from [2-¹³C]glycine and [2-¹³C]serine. As the 2-carbon of glycine and serine is decarboxylated and catabolized via the GCS, the original 13C-labeled 2-carbon is transferred to THF and yield methyleneTHF in the mitochondria. In human hepatoma cell-lines, 2-carbon from glycine was found to be incorporated into deoxythymidine (dTMP, dT + 1), M + 3 species of purines (deoxyadenine, dA and deoxyguanine, dG), and methionine (Met + 1). In healthy mice, incorporation of GCS-derived formate from glycine 2-carbon was found in serine (Ser + 2 via cytosolic serine hydroxy methyl transferase), methionine, dTMP, and methylcytosine (mC + 1) in bone marrow DNA. In these experiments, labeled glycine 2-carbon directly incorporates into Ser + 1, A + 2, and G + 2 (at C2 and C8 of purine) in the cytosol. It is noteworthy that since the serine 3-carbon is unlabeled in these experiments, the isotopic enrichments in dT + 1, Ser + 2, dA + 3, dG + 3, and Met + 1 solely come from the 2-carbon of glycine/serine recycled from GCS, re-enters the cytosolic 1C metabolism as formate, and then being used for cytosolic syntheses of serine, dTMP, purine (M + 3) and methionine. Taken together, we established model systems and successfully traced the metabolic fate of mitochondrial GCS-derived formate from glycine 2-carbon in vitro and in vivo. Nutritional supply significantly alters formate generation from GCS. More GCS-derived formate was used in hepatic serine and methionine syntheses, whereas more GCS-derived formate was used in dTMP synthesis in the bone marrow, indicating that the utilization and partitioning of GCS-derived 1C unit are tissue-specific. These approaches enable better understanding concerning the utilization of 1C moiety generated from mitochondrial GCS that can help to further elucidate the role of GCS in human disease development and progression in future applications. More studies on GCS using these approaches are underway.

Stability and refolding of Dihydrofolate reductase enhances with nano-conjugation

The nano-conjugation of proteins is an active area of research due to potential biomedical and nanotechnological applications. Many protein-nanoconjugates were designed for various applications, such as drug delivery, molecular imaging, and liquid biopsy etc. However, the challenges remain to ensure protein stability and to retain the conformational state of the protein intact upon nano-conjugation. In this communication we have reported the status of stability and refolding ability of Au-NP conjugated zDHFR protein. The effect of nano-conjugation of zDHFR on the thermal stability and it's refolding from thermally denatured state have been extensively studied. Zebrafish Dihydrofolate reductase (zDHFR) is an essential enzyme which acts as a crucial part in synthesis of purine, thymidylate and various amino acids in cells. We have nano-conjugated zDHFR protein with Au-nanoparticles and studies were conducted for thermally denatured Au-NP conjugated zDHFR and compared with the non-conjugated protein. Refolding experiment of heat denatured Au-NP conjugated zDHFR was carried out to check the status of refolding and the result was compared with the non-conjugated protein. Our observation reveals that nano-conjugation stabilises the zDHFR protein against thermal denaturation. Furthermore, the nano-conjugation promotes refolding process of thermally unfolded DHFR such that the yield of refolding substantially increases.

Metabolism as a central regulator of β-cell chromatin state

Pancreatic β-cells are critical mediators of glucose homeostasis in the body, and proper cellular nutrient metabolism is critical to β-cell function. Several interacting signaling networks that uniquely control β-cell metabolism produce essential substrates and co-factors for catalytic reactions, including reactions that modify chromatin. Chromatin modifications, in turn, regulate gene expression. The reactions that modify chromatin are therefore well-positioned to adjust gene expression programs according to nutrient availability. It follows that dysregulation of nutrient metabolism in β-cells may impact chromatin state and gene expression through altering the availability of these substrates and co-factors. Metabolic disorders such as type 2 diabetes (T2D) can significantly alter metabolite levels in cells. This suggests that a driver of β-cell dysfunction during T2D may be the altered availability of substrates or co-factors necessary to maintain β-cell chromatin state. Induced changes in the β-cell chromatin modifications may then lead to dysregulation of gene expression, in turn contributing to the downward cascade of events that leads to the loss of functional β-cell mass, and loss of glucose homeostasis, that occurs in T2D.

Investigating the methylation status of DACT2 gene and its association with MTHFR C677T polymorphism in patients with colorectal cancer

Colorectal cancer (CRC) is one of the common causes of cancer death in Iranian population. Both genetic and epigenetic changes have been implicated in CRC pathogenesis. DACT2 gene as one of the WNT signaling pathway inhibitor was shown to display tumor suppressor activity in many cancers. The aim of present study was to investigate the methylation status of DACT2 gene and its association with methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism in CRC patients. Fifty formalin-fixed paraffin-embedded cancerous and adjacent healthy tissues obtained from CRC patient were investigated. Genomic DNA was isolated using a FFPE commercial DNA extraction kit. The methylation status was evaluated by methylation specific PCR. Genotyping of MTHFR C677T polymorphism was performed using PCR-RFLP technique. Statistical analysis was done by GraphPad Prism 8. Results indicated that the frequency of methylated DACT2 gene was significantly higher in cancerous tissue relative to adjacent healthy tissue (P<0.001). DACT2 gene methylation was significantly more common among carriers of MTHFR 677CC genotype (P=0.035) and significantly less common among carriers of MTHFR 677T allele (P value =0.006). In conclusion the present study identified DACT2 gene methylation as a significant risk factor for CRC development. Moreover, the low frequency of DACT2 gene methylation among carriers of MTHFR 677T allele may confer a protective role for this common polymorphism against CRC risk.

MTHFR C677T polymorphism increases MTX sensitivity via the inhibition of S-adenosylmethionine and de novo purine synthesis

Objective: Currently, no guidelines are established for pharmacogenomic testing involving folate metabolic genes in long-term disease-modifying antirheumatic drugs' (DMARD) therapies. We carefully investigated how common genetic variations in methylenetetrahydrofolate reductase (MTHFR) influence cellular metabolic kinetics in response to methotrexate (MTX). Designs: Two distinct cell models: HepG2 with stabilized MTHFR inhibition using shRNA delivered by a Lentiviral vector; and Epstein-Barr virus transformed human lymphoblasts expressing MTHFR polymorphic allele 677C and 677T were used. Disease activity and DMARD use were compared between MTHFR-677CC, CT and TT rheumatoid arthritis (RA) patients in a cross-sectional study (n=120). Results: Compared with MTHFR-CC, MTHFR-TT carriers had lower mean weakly MTX dose (9.8 ± 3.3 compared with 12.1 ± 3.5, P<0.05). More MTHFR-TT carriers (8/11, 73%) reported MTX-related side effects compared with MTHFR-677CC (32/57, 56%) and MTHFR-677CT (30/51, 59%). No genotypic difference was found in other DMARDs. At the same dose of MTX, lymphoblasts were more sensitive in cell survival, protein and thymidine syntheses whereas HepG2 models were more susceptible to the inhibition of S-adenosylmethionine (adoMet) synthesis. MTHFR-C677T altered protein turnover and folate mediated 1-carbon metabolic fluxes in lymphoblasts with and without MTX. MTHFR function significantly affected transmethylation fluxes and adoMet homeostasis but not nucleotide biosyntheses in MTX-treated HepG2 cell-lines. Conclusion: Combining cell models, kinetic studies, and genetic tests in humans, the present study gives insight on how MTHFR effects hepatic transmethylation homeostasis during MTX therapy. We provide platforms that help predict the genetic impact on antifolate drugs, and further delineate tissue-specific target pathway in DMARD therapies. We suggest that genetic factors should be taken into account in clinical practice.

Association of Single Nucleotide Polymorphisms (SNPs) in Genes Encoding for Folate Metabolising Enzymes with Glioma and Meningioma in Indian Population

Background:

The association of primary brain tumors with Single Nucleotide polymorphisms (SNPs) in genes of folate metabolising enzymes have been reported to vary among different ethnic population. Here, we have studied the association of SNPs of folate metabolizing genes with the primary brain tumors (glioma and meningioma) in North Indian population.

Methods:

SNPs of genes coding for folate metabolizing enzymes was carried out in 288 study population from North India [Glioma (n=108), Meningioma (n=76) and healthy-control (n=104)]. The allele-specific polymerase chain reaction (ARMS-PCR) was used to analyse the SNP A1298C of the MTHFR (Methylenetetrahydrofolate-reductase) and the SNP A66G of the methionine synthase reductase (MTRR) genes. The PCR-RLFP (Restriction Fragment Length Polymorphism) was used to analyse the SNP C677T of the Methylene tetrahydrofolate-reductase and the SNP A2756G of the methionine-synthase (MTR) genes. Serum homocysteine, vitamin B₁₂ and folate levels were evaluated in controls/patients serum using Chemiluminescence immunoassay and the levels were correlated with SNPs genotype.

Results:

The CC genotype of MTHFR A1298C was observed to have reduced risk of having meningioma than AA genotype (odd ratio=0.62, 95%CI 0.32-0.97, p=0.03). Similarly, the AG genotype of MTRR A66G showed reduced risk of glioma than AA genotype (odd ratio=0.56, 95%CI 0.32-0.97, p=0.039). Furthermore, in patients with AA genotype of MTR A2756G and CT genotype of MTHFR C677T showed higher serum homocysteine level than GG genotype (8.6 µmol/L, p=0.048) and CC genotype (11.2µmol/L, p=0.039) respectively.

Conclusion:

Our findings provide an insight into the risk association of SNPs in MTHFR A1298C and MTRR A66G genes with glioma/meningioma patients. Further studies are needed to evaluate their clinical implications.

The MTHFR polymorphism affect the susceptibility of HCC and the prognosis of HCC liver transplantation

BACKGROUND

Methylenetetrahyfrofolate reductase (MTHFR) is the key enzyme for one carbon and folate metabolism. Previous studies have drawn different conclusions about the relationship between the mutation of MTHFR and hepatocellular carcinoma (HCC) occurrence. MTHFR polymorphisms' influence on liver transplantation for HCC recurrence has yet not been reported. Aim of this study was to clarify the impact of MTHFR polymorphism on hepatocarcinogenesis and the prognosis of liver transplant recipient with HCC.

METHODS

This study enrolled 244 HCC patients and 487 healthy individuals in Chinese Han population to analyze the influence of MTHFR polymorphism on HCC susceptibility first. Furthermore, this research choose another 100 donors' and 104 recipients' specimens to detect the association between polymorphism of MTHFR and post-transplant HCC recurrence.

RESULT

rs1801131 polymorphism A to C was associated with the occurrence of HCC in Chinese Han population (p < 0.05), especially in age exceeding 50 years (p < 0.01). No association was observed with rs1801133 polymorphism and HCC occurrence. The mean tumor-free survival for recipients with donor liver graft rs1801133 C to T variants was shorter than CC type (12.63 ± 3.84 vs 22.43 ± 4.74 months, p < 0.05). Multivariate analysis revealed that Donor rs1801133 and Hangzhou criteria were two independent prognostic factors for tumor-free survival (p < 0.05). Neither donor rs1801131 polymorphism nor recipients' MTHFR polymorphisms was associated with HCC recurrence.

CONCLUSION

This study demonstrated that MTHFR polymorphism was associated with HCC occurrence and post-transplant HCC recurrence. rs1801131 mutation A to C is a valuable molecular biomarker for predicting HCC occurrence in Chinese Han population. Donor MTHFR rs1801133 C to T polymorphism could present as a promising prognostic biomarkers for HCC recurrence in liver transplant recipients.

MTHFR gene variants and non-MALT lymphoma development in primary Sjogren's syndrome

Primary Sjogren’s syndrome (pSS) confers increased risk for non-Hodgkin lymphoma (NHL) development. Two common polymorphisms, the c. 677C > T and c. 1298A > C, of the methylene-tetrahydrofolate reductase (MTHFR) gene, an enzyme essential in DNA synthesis and methylation, have been associated with susceptibility to NHL. Herein, we tested the hypothesis that MTHFR variants contribute to pSS-related lymphomagenesis. 356 pSS patients, of whom 75 had MALT and 19 non-MALT NHL and 600 healthy controls were genotyped for the detection of MTHFR polymorphisms. DNA methylation levels were assessed by pyrosequencing of the LINE-1 retroelement promoter in DNA from 55 salivary gland tissues from pSS patients. DNA double-strand breaks were determined in peripheral blood mononuclear cells from 13 pSS patients, using comet assay. Αnalysis according to lymphoma subtype revealed increased frequency of c. 677C > T TT genotype and T allele, as well as reduced prevalence of the c. 1298A > C C allele in the pSS non-MALT group compared to controls and patients without NHL. MTHFR c. 677C > T TT genotype was associated with reduced DNA methylation levels, while MTHFR c. 1298A > C AC genotype with reduced DNA double-strand breaks levels. MTHFR variants may be involved in SS non-MALT NHL development, through contribution to defective DNA methylation and genomic instability.

Epigenetics, nutrition and mental health. Is there a relationship?

Many aspects of human development and disease are influenced by the interaction between genetic and environmental factors. Understanding how our genes respond to the environment is central to managing health and disease, and is one of the major contemporary challenges in human genetics. Various epigenetic processes affect chromosome structure and accessibility of deoxyribonucleic acid (DNA) to the enzymatic machinery that leads to expression of genes. One important epigenetic mechanism that appears to underlie the interaction between environmental factors, including diet, and our genome, is chemical modification of the DNA. The best understood of these modifications is methylation of cytosine residues in DNA. It is now recognized that the pattern of methylated cytosines throughout our genomes (the 'methylome') can change during development and in response to environmental cues, often with profound effects on gene expression. Many dietary constituents may indirectly influence genomic pathways that methylate DNA, and there is evidence for biochemical links between nutritional quality and mental health. Deficiency of both macro- and micronutrients has been associated with increased behavioural problems, and nutritional supplementation has proven efficacious in treatment of certain neuropsychiatric disorders. In this review we examine evidence from the fields of nutrition, developmental biology, and mental health that supports dietary impacts on epigenetic processes, particularly DNA methylation. We then consider whether such processes could underlie the demonstrated efficacy of dietary supplementation in treatment of mental disorders, and whether targeted manipulation of DNA methylation patterns using controlled dietary supplementation may be of wider clinical value.

The MTHFR C677T mutation is not a risk factor recognized for HBV-related HCC in a population with a high prevalence of this genetic marker

BACKGROUND

Polymorphism of the methylenetetrahydrofolate reductase (MTHFR) gene can affect disease progression in HBV infection. However, the results from different reports are inconsistent. The aim of this study was to investigate the association between the MTHFR C677T polymorphism and the outcome of HBV infection in a Tianjin Han population.

METHODS

TaqMan SNP genotyping was employed to determine the alleles and genotypes of MTHFR C677T in 2511 subjects from various stages of HBV infection and 549 healthy controls.

RESULTS

Of the 3060 subjects, the genotypic frequencies were CT 48.9%, TT 29.3% and CC 21.8%; the allelic frequencies were T 53.8% and C 46.2%. There was no significant difference in genotypic or allelic distribution among the different disease groups. When either healthy subjects or self-limited subjects were used as controls, the TT genotype and the T allele conferred protective effects against hepatocellular carcinoma (HCC) (HCC vs healthy subjects: OR=0.588, 95% CI=0.413-0.836, P=0.003; OR=0.768, 95% CI=0.645-0.915, P=0.003, respectively. HCC vs self-limited subjects: OR=0.598, 95% CI=0.404-0.886, P=0.010; OR=0.772, 95% CI=0.635-0.940, P=0.010, respectively). After sub-stratification by gender, the prevalence of the TT genotype or T allele was the lowest in the male HCC group (TT 23.5%, T 49.8%). The protective effects of the TT genotype and the T allele were observed in male HCC and cirrhotic subjects (HCC vs self-limited subjects: OR=0.470, 95% CI=0.288-0.766, P=0.002; OR=0.681, 95% CI=0.535-0.866, P=0.002, respectively. Liver cirrhosis vs self-limited subjects: OR=0.624, 95% CI=0.392-0.992, P=0.046; OR=0.791, 95% CI=0.627-0.998, P=0.048, respectively), but not in female. When the subjects were stratified according to the clinical features, no statistically significant difference in the genotypic distribution was observed (P>0.05).

CONCLUSIONS

The TT genotype and T allele of MTHFR C677T may confer a protective effect on disease progression to HCC in HBV-infected individuals, especially among male patients, in a population with a high prevalence of this genetic marker.

Association between Methylenetetrahydrofolate Reductase (MTHFR) Gene Polymorphisms and Susceptibility to Childhood Acute Lymphoblastic Leukemia in an Iranian Population

BACKGROUND

The present study was aimed to examine the possible association between methylene tetrahydrofolate reductase (MTHFR) gene polymorphisms and childhood acute lymphoblastic leukemia (ALL) in a sample of Iranian population.

SUBJECTS AND METHODS

A total of 220 subjects including 100 children diagnosed with ALL and 120 healthy children participated in the case-control study. The single nucleotide polymorphisms (SNPs) of MTHFR were determined by ARMS-PCR or PCR-RFLP method.

RESULTS

Our investigation revealed that rs13306561 both TC and TC + CC genotypes decreased the risk of ALL compared to TT genotype (OR=0.32, 95%CI=0.15-0.68, p=0.002 and OR=0.35, 95%CI=0.17-0.70, p=0.003, respectively). In addition, the rs13306561 C allele decreased the risk of ALL in comparison with T allele (OR=0.42, 95% CI=0.22-0.78, P=0.005). MTHFR rs1801131 (A1298C) polymorphism showed that the AC heterozygous genotype decreased the risk of ALL in comparison with AA homozygous genotype (OR=0.43, 95%CI=0.21-0.90, p=0.037). Neither the overall Chi-square comparison of cases and control subjects (𝜒2=5.54, p=0.063) nor the logistic regression analysis showed significant association between C677T polymorphism and ALL (OR=1.25, 95% CI=0.69-2.23, p=0.552; CT vs. CC).

CONCLUSION

The current investigation findings showed that MTHFR rs1801131 and rs13306561 polymorphisms decreased the risk of ALL in the population which has been studied. Further studies with larger sample sizes and different ethnicities are required to validate our findings.

Polymorphisms in methylenetetrahydrofolate reductase and cystathionine beta-synthase in oral cancer - a case-control study in southeastern Brazilians

Introduction

Oral squamous cell carcinoma (OSCC) is a serious public health problem, due to its high mortality rate and worldwide rising incidence. OSCC susceptibility is mediated by interactions between genetic and environmental factors. Studies suggest that genetic variants encoding enzymes involved in folate metabolism may modulate OSCC risk by altering DNA synthesis/repair and methylation process.

Objective

The goals of this study were to evaluate the association of three genotypic polymorphism (MTHFR C677T, MTHFR A1298C and CBS 844ins68) and oral cancer risk in southeastern Brazilians and evaluate the interactions between polymorphisms and clinical histopathological parameters.

Methods

This case–control study included 101 cases and 102 controls in the state of Espírito Santo, Brazil. MTHFR genotyping was done by PCR-RFLP (polymerase chain reaction – restriction fragment length polymorphism) and CBS genotyping by PCR (polymerase chain reaction) analysis.

Results

MTHFR C677T polymorphism was associated with lymph node involvement. Genotype CT + TT acted as a protective factor. MTHFR A1298C AC + CC genotype was associated with tumor differentiation, and possibly with a better prognosis. In risk analysis, no correlation was observed between genotypes and OSCC.

Conclusion

We concluded that MTHFR C677T, MTHFR A1298C and CBS 844ins68 polymorphisms were not associated with OSCC risk in southeastern Brazilians; however, we suggest a prognosis effect associated with MTHFR C677T and A1298C polymorphisms in OSCC.

The association between RFC1 G80A polymorphism and cancer susceptibility: Evidence from 33 studies

Aberrant folate metabolism is closely related to tumorigenesis. Genetic variations in the Reduced folate carrier 1 (RFC1) may alter the progress of folate metabolism, and thereby cause the initiation and progress of the cancer. Considerable studies have performed to investigate the association between RFC1 G80A (rs1051266) polymorphism and cancer susceptibility, but the conclusions were conflicting. Therefore, we conducted a meta-analysis to reevaluate the association of RFC1 G80A polymorphism with cancer risk. PubMed and EMBASE were searched for eligible studies. The association of RFC1 G80A polymorphism and cancer risk was evaluated by the pooled odds ratios (ORs) and corresponding 95% confidence intervals (CIs). The significant association was found between RFC1 G80A polymorphism and hematological malignance susceptibility (A vs. G: OR=1.11, 95%CI=1.003-1.23, P=0.045; GA vs. GG: OR=1.18, 95%CI=1.06-1.31, P=0.002; AA+GA vs. GG: OR=1.18, 95%CI=1.07-1.29, P=0.001). Stratified analysis by ethnicity indicated that the association became more prominent among Caucasians (GA vs. GG: OR=1.28, 95%CI=1.12-1.45, P<0.001; AA+GA vs. GG: OR=1.21, 95%CI=1.08-1.36, P=0.001). In term of the cancer type, this polymorphism significantly increased the risk of acute lymphoblast leukemia (GA vs. GG: OR=1.13, 95%CI=1.001-1.28, P=0.048; AA+GA vs. GG: OR=1.28, 95%CI=1.13-1.46, P<0.001) and acute myeloid leukemia (GA vs. GG: OR=2.57, 95%CI=1.37-4.85, P=0.003). No significant association between RFC1 G80A polymorphism and overall solid cancer risk was observed, but a protective association with digestive cancer risk was found (GA vs. GG: OR=0.89, 95%CI= 0.81-0.99, P=0.030). The comprehensive meta-analysis encouraged the notion that RFC1 G80A polymorphism may play an important role in hematopoietic system malignance. These findings need further validation in the large multicenter investigations.

Mthfr as a modifier of the retinal phenotype of Crb1(rd8/rd8) mice

Mutations in crumb homologue 1 (CRB1) in humans are associated with Leber's congenital amaurosis (LCA) and retinitis pigmentosa (RP). There is no clear genotype-phenotype correlation for human CRB1 mutations in RP and LCA. The high variability in clinical features observed in CRB1 mutations suggests that environmental factors or genetic modifiers influence severity of CRB1 related retinopathies. Retinal degeneration 8 (rd8) is a spontaneous mutation in the Crb1 gene (Crb1(rdr/rd8)). Crb1(rdr/rd8) mice present with focal disruption in the outer retina manifesting as white spots on fundus examination. Mild retinal dysfunction with decreased b-wave amplitude has been reported in Crb1(rdr/rd8) mice at 18 months. Methylene tetrahydrofolate reductase (MTHFR) is a crucial enzyme of homocysteine metabolism. MTHFR mutations are prevalent in humans and are linked to a broad spectrum of disorders including cardiovascular and neurodegenerative diseases. We recently reported the retinal phenotype in Mthfr-deficient (Mthfr(+/-)) heterozygous mice. At 24 weeks the mice showed decreased RGC function, thinner nerve fiber layer, focal areas of vascular leakage and 20% fewer cells in the ganglion cell layer (GCL). Considering the variability in CRB1-related retinopathies and the high occurrence of human MTHFR mutations we evaluated whether Mthfr deficiency influences rd8 retinal phenotype. Mthfr heterozygous mice with rd8 mutations (Mthfr(+/-)(rd8/rd8)) and Crb(rd8/rd8) mice (Mthfr(+/+rd8/rd8)) mice were subjected to comprehensive retinal evaluation using ERG, fundoscopy, fluorescein angiography (FA), morphometric and retinal flat mount immunostaining analyses of isolectin-B4 at 8-54 wks. Assessment of retinal function revealed a significant decrease in the a-, b- and c-wave amplitudes in Mthfr(+/-)(rd8/rd8) mice at 52 wks. Fundoscopic evaluation demonstrated the presence of signature rd8 spots in Mthfr(+/+rd8/rd8) mice and an increase in the extent of these rd8 spots in Mthfr(+/-)(rd8/rd8) mice at 24 weeks and beyond. FA revealed marked vascular leakage, ischemia and vascular tortuosity in Mthfr(+/-)(rd8/rd8) mice at 24 and 52 weeks. Retinal dysplasia was observed in ∼14-33% Mthfr(+/-)(rd8/rd8) mice by morphometric analysis. This was accompanied by a ∼20% reduction in cells of the GCL of Mthfr(+/-)(rd8/rd8) mice at 24 and 52 weeks. Retinal flat mount immunostaining with isolectin-B4 showed neovascularization and loss of blood vessel integrity in Mthfr(+/-)(rd8/rd8) mice in contrast to mild vasculopathy in Mthfr(+/+rd8/rd8) mice. Taken together, our data support an earlier onset and worsened retinal phenotype when Mthfr and rd8 mutations coexist. Our study sets the stage for future studies to investigate the role of MTHFR deficiency in human CRB1 retinopathies.

Methylenetetrahydrofolate reductase gene C677T polymorphism and breast cancer risk: Evidence for genetic susceptibility

There are several evidences supporting the role of 5–10 methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms in breast cancer (BC). Case control association studies on breast cancer have been repeatedly performed over the last two decades, but results are inconsistent. We performed a meta-analysis to confirm the association between MTHFR C677T polymorphism and BC risk.

The articles were retrieved by searching the PubMed, Google Scholar, and Springer Link databases. Crude odds ratios (OR) with 95% confidence intervals (CIs) was used to assess the strength of association between C677T polymorphism and BC. Publication bias was assessed by Egger's and Begg-Mazumdar tests. Meta-analysis was performed with Open Meta Analyst.

Total 75 studies with 31,315 cases and 35, 608 controls were found suitable for the inclusion in the present meta-analysis. The results of meta-analysis suggested that there were moderate significant association between C677T polymorphism and BC risk using overall comparisons in five genetic models (T vs. C: OR = 1.08, 95% CI = 1.03–1.13, p = < 0.001; TT + CT vs. CC: OR = 1.06, 95% CI = 1.02–1.09, p = < 0.001; TT vs. CC: OR = 1.17, 95% CI = 1.06–1.28, p = 0.001; CT vs. CC OR = 1.05, 95% CI = 1.01–1.08, p = 0.005; TT vs. CT + CC: OR = 1.12, 95% CI = 1.03–1.22, p = 0.005). In conclusion, results of present meta-analysis showed modest association between MTHFR C677T polymorphism with breast cancer in total studies. However, sub-group analysis results based on ethnicity showed strong significant association between TT genotype and breast cancer (TT vs. CC; OR°=°1.26; 95% CI: 1.06–1.51; p = 0.009) in Asian population but in Caucasian population such association was not observed (TT vs. CC; OR°=°1.08; 95% CI: 0.99–1.14; p = 0.05).

Germline and somatic genetic predictors of pathological response in neoadjuvant settings of rectal and esophageal cancers: systematic review and meta-analysis

Oncologists have pointed out an urgent need for biomarkers that can be useful for clinical application to predict the susceptibility of patients to preoperative therapy. This review collects, evaluates and combines data on the influence of reported somatic and germline genetic variations on histological tumor regression in neoadjuvant settings of rectal and esophageal cancers. Five hundred and twenty-seven articles were identified, 204 retrieved and 61 studies included. Among 24 and 14 genetic markers reported for rectal and esophageal cancers, respectively, significant associations in meta-analyses were demonstrated for the following markers. In rectal cancer, major response was more frequent in carriers of the TYMS genotype 2 R/2 R-2 R/3 R (rs34743033), MTHFR genotype 677C/C (rs1801133), wild-type TP53 and KRAS genes. In esophageal cancer, successful therapy appeared to correlate with wild-type TP53. These results may be useful for future research directions to translate reported data into practical clinical use.

MTHFR 677C>T polymorphism and the risk of breast cancer: evidence from an original study and pooled data for 28031 cases and 31880 controls

BACKGROUND

Methylenetetrahydrofolate reductase (MTHFR) acts at an important metabolic point in the regulation of cellular methylation reaction. It assists in the conversion of 5, 10-methylenetetrahydrofolate to 5-methyltetrahydrofolate. The latter aids in remethylation of homocysteine to de novo methionine that is required for DNA synthesis. The objective of this study was to examine the effect of MTHFR 677 C>T polymorphism on the risk of breast cancer in the Indian sub-continent.

METHODS AND RESULTS

We genotyped 677 C>T locus in 1096 individuals that were classified into cases (N=588) and controls (N=508). Genotype data were analyzed using chi-square test. No significant difference was observed in the distribution of genotypes between cases and controls in north Indian (P = 0.932), south Indian (P = 0.865), and pooled data (P = 0.680). To develop a consensus regarding the impact of 677C>T polymorphism on breast cancer risk, we also conducted a meta-analysis on 28031 cases and 31880 controls that were pooled from sixty one studies. The overall summary estimate upon meta-analysis suggested no significant correlation between the 677C>T substitution and breast cancer in the dominant model (Fixed effect model: OR = 0.97, P=0.072, Random effects model: OR = 0.96, P = 0.084) or the recessive model (Fixed effect model: OR = 1.05, P = 0.089; Random effects model: OR= 1.08, P= 0.067).

CONCLUSION

677 C>T substitution does not affect breast cancer risk in the Indo-European and Dravidian populations of India. Analysis on pooled data further ruled out association between the 677 C>T polymorphism and breast cancer. Therefore, 677 C>T substitution does not appear to influence the risk of breast cancer.

Single nucleotide polymorphisms of one-carbon metabolism and cancers of the esophagus, stomach, and liver in a Chinese population

One-carbon metabolism (folate metabolism) is considered important in carcinogenesis because of its involvement in DNA synthesis and biological methylation reactions. We investigated the associations of single nucleotide polymorphisms (SNPs) in folate metabolic pathway and the risk of three GI cancers in a population-based case-control study in Taixing City, China, with 218 esophageal cancer cases, 206 stomach cancer cases, 204 liver cancer cases, and 415 healthy population controls. Study participants were interviewed with a standardized questionnaire, and blood samples were collected after the interviews. We genotyped SNPs of the MTHFR, MTR, MTRR, DNMT1, and ALDH2 genes, using PCR-RFLP, SNPlex, or TaqMan assays. To account for multiple comparisons and reduce the chances of false reports, we employed semi-Bayes (SB) shrinkage analysis. After shrinkage and adjusting for potential confounding factors, we found positive associations between MTHFR rs1801133 and stomach cancer (any T versus C/C, SB odds-ratio [SBOR]: 1.79, 95% posterior limits: 1.18, 2.71) and liver cancer (SBOR: 1.51, 95% posterior limits: 0.98, 2.32). There was an inverse association between DNMT1 rs2228612 and esophageal cancer (any G versus A/A, SBOR: 0.60, 95% posterior limits: 0.39, 0.94). In addition, we detected potential heterogeneity across alcohol drinking status for ORs relating MTRR rs1801394 to esophageal (posterior homogeneity P = 0.005) and stomach cancer (posterior homogeneity P = 0.004), and ORs relating MTR rs1805087 to liver cancer (posterior homogeneity P = 0.021). Among non-alcohol drinkers, the variant allele (allele G) of these two SNPs was inversely associated with the risk of these cancers; while a positive association was observed among ever-alcohol drinkers. Our results suggest that genetic polymorphisms related to one-carbon metabolism may be associated with cancers of the esophagus, stomach, and liver. Heterogeneity across alcohol consumption status of the associations between MTR/MTRR polymorphisms and these cancers indicates potential interactions between alcohol drinking and one-carbon metabolic pathway.

Lower serum folate is associated with development and invasiveness of gastric cancer

AIM: To evaluate the associations of serum folate level with development, invasiveness and patient survival of gastric cancer.

METHODS: In this nested case-control study, patients with newly diagnosed gastric cancer undergoing gastrectomy were enrolled, and patients receiving chemotherapy prior to surgery, with other concurrent malignancy, or of the aboriginal and alien populations were excluded. In total, 155 gastric cancer patients and 149 healthy controls were enrolled for determination of serum folate levels and their correlation with gastric cancer. Using the median value of serum folate computed among the overall population as the cutoff value, the associations between serum folate and gastric cancer in all cases and different age and gender subgroups were analyzed by multivariate logistic regression analysis. In the patient cohort of gastric cancer, receiver-operating characteristic analyses were performed to calculate the best cutoff values of serum folate, and the associations between serum folate levels and clinicopathological features were further analyzed by multivariate regression analysis. Survival analyses were conducted using the Cox proportional hazards model.

RESULTS: The mean serum folate level was significantly lower in gastric cancer patients than that in controls (3.71 ± 0.30 ng/mL vs 8.00 ± 0.54 ng/mL, P < 0.01), and folate levels were consistently lower in gastric cancer patients regardless of age and gender (all P < 0.01). Using the median serum folate value as the cutoff value, low serum folate was significantly associated with gastric cancer risk in the whole population (OR = 19.77, 95%CI: 10.54-37.06, P < 0.001) and all strata (age < 60 years OR = 17.39, 95%CI: 7.28-41.54, age ≥ 60 years (OR = 21.67, 95%CI: 8.27-56.80), males (OR = 17.95, 95%CI: 7.93-40.62), and females (OR = 20.95, 95%CI: 7.66-57.31); all P < 0.001. In the patient cohort of gastric cancer, the respective cutoff values showed that low serum folate levels were significantly associated with serosal invasion (OR = 2.54, 95%CI: 1.23-5.23), lymphatic invasion (OR = 2.23, 95%CI: 1.17-4.26), and liver metastasis (OR = 6.67, 95%CI: 1.28-34.91) of gastric cancer (all P < 0.05). Serum folate level below 1.90 ng/mL was associated with poor patient survival (HR = 1.84, 95%CI: 1.04-3.27, P < 0.05) in univariate analysis.

CONCLUSION: Lower serum folate levels were significantly associated with gastric cancer development and invasive phenotypes. The role of folate depletion in gastric cancer invasion warrants further study.

MTHFR C677T polymorphism, folate status and colon cancer risk in acromegalic patients

BACKGROUND

Acromegalic patients have a higher risk of developing colorectal tumours (CRT). The common C677T polymorphism in methylenetetrahydrofolate reductase (MTHFR) gene is a well-documented CRT risk factor in the general population, but its role in acromegaly has never been examined.

PURPOSE

We investigated the influence of MTHFR C677T polymorphism, folate status and other lifestyle, nutritional and disease-specific variables on CRT risk in acromegaly.

METHODS

Clinical data were collected from 115 acromegalic patients (25 with active disease) who underwent a complete colonoscopy. C677T MTHFR genotype, homocysteine, vitamin B12, insulin growth factor and insulin levels, as well as metabolic variables were evaluated.

RESULTS

Colorectal tumours were identified in 51 patients (3 adenocarcinomas). MTHFR C677T distribution was in the Hardy-Weinberg equilibrium and similar in patients with or without CRT. There was a correlation between patients with TT genotype and CRT occurrence (Spearman's test: P = 0.03), with an Odds Ratio (OR) of 1.32 (95% CI 0.522-3.362, P NS). A folate-MTHFR genotype interaction on CRT risk was found (P = 0.037): in the lower folate subgroup, TT patients showed a 2.4 higher OR for CRT (95% CI 0.484-11.891; P NS) than C-allele carriers. Smoking (P = 0.007), increased HbA1c levels (P = 0.021), dyslipidaemia (P = 0.049), acromegaly control (P = 0.057), and folate-MTHFR genotype interaction (P = 0.088) were associated with CRT at multivariate analysis.

CONCLUSIONS

In this cohort of acromegalic patients, CRT risk is increased in 677TT MTHFR patients with low plasma folate levels. Smoking, high HbA1c levels, dyslipidaemia and disease activity were also associated with increased CRT risk.

Vitamin D, folate, and potential early lifecycle environmental origin of significant adult phenotypes

Solar radiation early in pregnancy interacts with light sensitive vitamins to influence an embryo's genetic profile. This influences both adult disease risk and may play a role in the evolution of skin colour.

Background and objectives: Vitamin D and folate are highly UV sensitive, and critical for maintaining health throughout the lifecycle. This study examines whether solar irradiance during the first trimester of pregnancy influences vitamin D receptor (VDR) and nuclear folate gene variant occurrence, and whether affected genes influence late-life biochemical/clinical phenotypes.

Methodology: 228 subjects were examined for periconceptional exposure to solar irradiance, variation in vitamin D/folate genes (polymerase chain reaction (PCR)), dietary intake (food frequency questionnaire (FFQ)) and important adult biochemical/clinical phenotypes.

Results: Periconceptional solar irradiance was associated with VDR-BsmI (P = 0.0008^wk7), TaqI (P = 0.0014^wk7) and EcoRV (P = 0.0030^wk6) variant occurrence between post-conceptional weeks 6–8, a period when ossification begins. Similar effects were detected for other VDR gene polymorphisms. Periconceptional solar irradiance was also associated with 19 bp del-DHFR (P = 0.0025^wk6), and to a lesser extent C1420T-SHMT (P = 0.0249^wk6), a folate-critical time during embryogenesis. These same genes were associated with several late-life phenotypes: VDR-BsmI, TaqI and ApaI determined the relationship between dietary vitamin D and both insulin (P < 0.0001/BB, 0.0007/tt and 0.0173/AA, respectively) and systolic blood pressure (P = 0.0290/Bb, 0.0299/Tt and 0.0412/AA, respectively), making them important early and late in the lifecycle. While these and other phenotype associations were found for the VDR variants, folate polymorphism associations in later-life were limited to C1420T-SHMT (P = 0.0037 and 0.0297 for fasting blood glucose and HbA1c levels, respectively). We additionally report nutrient–gene relationships with body mass index, thiol/folate metabolome, cognition, depression and hypertension. Furthermore, photoperiod at conception influenced occurrence of VDR-Tru9I and 2R3R-TS genotypes (P = 0.0120 and 0.0360, respectively).

Conclusions and implications: Findings identify environmental and nutritional agents that may interact to modify gene–phenotype relationships across the lifecycle, offering new insight into human ecology. This includes factors related to both disease aetiology and the evolution of skin pigmentation.

Female breast cancer and alcohol consumption: a review of the literature

CONTEXT

Consumption of alcoholic beverages is one of the single most important known and modifiable risk factor for human cancer. Among women, breast cancer is the most common cancer worldwide and the leading cause of cancer-related mortality. Consumption of alcoholic beverages is causally associated with female breast cancer and the association shows a linear dose-response relationship. The role of heavy drinking has been long recognized and even a moderate intake is associated with an increased risk for breast cancer. The present review is an update of the current evidence on the association between alcohol consumption and breast cancer risk. The aim is to gain further insight into this association and to improve our current understanding of the effects of the major modifying factors.

EVIDENCE ACQUISITION

Epidemiologic and experimental studies published since the most recent International Agency for Research on Cancer (IARC) Monograph on alcoholic beverages were identified in PubMed using a combination of keywords such as alcohol, breast cancer, polymorphisms, menopausal status.

EVIDENCE SYNTHESIS

Cumulative lifetime consumption, drinking frequency, drinking patterns and timing of exposure each modulate the association between alcohol consumption and breast cancer. Hormonal status, genetic polymorphisms, and nutritional factors may interact with ethanol metabolism and further influence breast cancer risk.

CONCLUSIONS

Better standardization among experimental and epidemiologic designs in assessing alcohol intake and timing of exposure may improve our understanding of the heterogeneity observed across studies, possibly allowing the quantification of the effects of occasional heavy drinking and the identification of a window of higher susceptibility to breast cancer development.

Nutrition in early life and the programming of adult disease: a review

Foetal development and infancy are life stages that are characterised by rapid growth, development and maturation of organs and systems. Variation in the quality or quantity of nutrients consumed by mothers during pregnancy, or infants during the first year of life, can exert permanent and powerful effects upon developing tissues. These effects are termed 'programming' and represent an important risk factor for noncommunicable diseases of adulthood, including the metabolic syndrome and coronary heart disease. This narrative review provides an overview of the evidence-base showing that indicators of nutritional deficit in pregnancy are associated with a greater risk of type-2 diabetes and cardiovascular mortality. There is also a limited evidence-base that suggests some relationship between breastfeeding and the timing and type of foods used in weaning, and disease in later life. Many of the associations reported between indicators of early growth and adult disease appear to interact with specific genotypes. This supports the idea that programming is one of several cumulative influences upon health and disease acting across the lifespan. Experimental studies have provided important clues to the mechanisms that link nutritional challenges in early life to disease in adulthood. It is suggested that nutritional programming is a product of the altered expression of genes that regulate the cell cycle, resulting in effective remodelling of tissue structure and functionality. The observation that traits programmed by nutritional exposures in foetal life can be transmitted to further generations adds weight the argument that heritable epigenetic modifications play a critical role in nutritional programming.

Polymorphisms in genes involved in folate metabolism modify the association of dietary and circulating folate and vitamin B-6 with cervical neoplasia

High folate intake has been suggested as an important factor in cancer prevention; however, previous studies on the relation among folate intake, serum folate, and plasma homocysteine (hcy) are controversial. We conducted a hospital-based, case-control study in Brazil investigating associations between dietary and circulating vitamins B-6 and B-12 and folate, hcy, genotypes of folate-metabolizing enzyme methylenetetrahydrofolate reductase (MTHFR C677T, A1298C), 5-methyltetrahydrofolate-homocysteine methyltransferase (MTR A2756G), methionine synthase reductase (MTRR A66G), and reduced folate carrier (RFC1 G80A) and risk of cervical intraepithelial neoplasia (CIN) grades 1 (CIN1), 2 (CIN2), and 3 (CIN3). The study was composed by 453 controls, 140 CIN1, 126 CIN2, and 231 CIN3. We investigated the joint effects of genetic variants of folate-related genes using genetic risk scores (GRSs) by summing the number of risk alleles for CIN1 and CIN2+ (CIN2 and CIN3 cases). The OR (95% CI) for CIN1 and CIN2+ per each risk allele were 1.29 (1.01, 1.65) and 1.22 (1.01, 1.46), respectively. An association between folate intake and CIN2+ was observed only after stratification according to GRS: crude OR (95% CI) for lower folate intake and GRS ≥ 4 was 1.67 (0.92, 3.04) (P-trend < 0.001) compared with higher folate intake (above the median) and GRS ≤ 3. The CIN2+ risk of lower serum vitamin B-6 and GRS ≥ 4 was 2.14 (0.92, 5.02) (P-trend = 0.05) and lower serum folate (below the median) and GRS ≥ 4 was 0.49 (0.20, 1.17) (P-trend = 0.05) after adjustment for confounding variables and human papillomavirus infection. Our data suggest that polymorphisms in genes related to folate metabolism modify the association of dietary and circulating folate and vitamin B-6 with cervical neoplasia.

A novel role of the tumor suppressor GNMT in cellular defense against DNA damage

Glycine N-methyltransferase (GNMT) is a folate binding protein commonly diminished in human hepatoma yet its role in tumor development remains to be established. GNMT binds to methylfolate but is also inhibited by it; how such interactions affect human carcinogenesis is unclear. We postulated that GNMT plays a role in folate-dependent methyl group homeostasis and helps maintain genome integrity by promoting nucleotide biosynthesis and DNA repair. To test the hypothesis, GNMT was over-expressed in GNMT-null cell lines cultured in conditions of folate abundance or restriction. The partitioning of folate dependent 1-carbon groups was investigated using stable isotopic tracers and GC/MS. DNA damage was assessed as uracil content in cell models, as well as in Gnmt wildtype (Gnmt(+/+)), heterozygote (Gnmt(+/-)) and knockout (Gnmt(-/-)) mice under folate deplete, replete, or supplementation conditions. Our study demonstrated that GMMT 1) supports methylene-folate dependent pyrimidine synthesis; 2) supports formylfolate dependent purine syntheses; 3) minimizes uracil incorporation into DNA when cells and animals were exposed to folate depletion; 4) translocates into nuclei during prolonged folate depletion. In conclusion, loss of GNMT impairs nucleotide biosynthesis. Over-expression of GNMT enhances nucleotide biosynthesis and improves DNA integrity by reducing uracil misincorporation in DNA both in vitro and in vivo. To our best knowledge, the role of GNMT in folate dependent 1-carbon transfer in nucleotide biosynthesis has never been investigated. The present study gives new insights into the underlying mechanism by which GNMT can participate in tumor prevention/suppression in humans.

Interrelationships among genetic C677T polymorphism of 5,10-methylenetetrahydrofolate reductase, biochemical folate status, and lymphocytic p53 oxidative damage in association with tumor malignancy and survivals of patients with hepatocellular carcinoma

SCOPE

Metabolic genotypes of 5,10-methylenetetrahydrofolate reductase (MTHFR) and folate status on oxidative DNA lesions in hepatocellular carcinoma (HCC) has not been elucidated. The aims of the study were to investigate the folate-polymorphic interactions on genetic oxidative damage in association with advanced HCC malignancy and prognosis.

METHODS AND RESULTS

The study included 232 HCC patients with folate nutrition, MTHFR C677T polymorphic, p53 genetic and tumour pathological data collected and analyzed for their survivals after a 7.8-years following up. By adjustment for oxidative risk factors of HCC, the compound CT and TT genotypes in relative to the CC wild-type were associated with 83% reduced lymphocytic p53 oxidative lesions of HCC patients with RBC folate lower than 688 ng/mL (OR: 0.17, 95%CI: 0.07-0.43). Such genetic protective effects by the CT/TT genotypes were 2-fold enhanced among those with high RBC folate (OR: 0.08, 95% CI: 0.03-0.21, P for interaction < 0.001). For those with non-folate-deficient status, the compound CT and TT vs. CC genotypes were associated with 80% reduced risks of advanced HCC stages (III&IV) (OR: 0.2, 95%CI: 0.08-0.56). Such protection was negated either by adjustment of lymphocytic p53 oxidative lesions or by 3-fold increased risks among those with high RBC status (OR: 0.6, 95%CI; 0.31-1.41, P for interaction = 0.009). Multivariate Cox proportional hazards analysis showed that the CT/TT genotypes vs. CC wild-type were the independent predictable factor for better survival outcome of HCC patients (HR: 0.48, CI = 0.30-0.79). For CC homozygote, the second vs. the bottom tertile levels of RBC status were associated with 2-fold increased mortality rate of HCC patients (HR: 2.05, CI = 1.0-4.1).

CONCLUSION

Our data demonstrated that reduced MTHFR activities associated with the MTHFR T allele may interact with RBC folate as the risk modifiers of lymphocytic p53 oxidative lesions of HCC patients. The CT/TT genotypes correlated with lower risks of late-stage HCC and a favorable survival of HCC patients, depending on p53 oxidative lesions or RBC folate status.

Folate and B12 in prostate cancer

Mechanisms postulated to link folate and B12 metabolism with cancer, including genome-wide hypomethylation, gene-specific promoter hypermethylation, and DNA uracil misincorporation, have been observed in prostate tumor cells. However, epidemiological studies of prostate cancer risk, based on dietary intakes and blood levels of folate and vitamin B12 and on folate-pathway gene variants, have generated contradictory findings. In a meta-analysis, circulating concentrations of B12 (seven studies, OR = 1.10; 95% CI 1.01, 1.19; P = 0.002) and (in cohort studies) folate (five studies, OR = 1.18; 95% CI 1.00, 1.40; P = 0.02) were positively associated with an increased risk of prostate cancer. Homocysteine was not associated with risk of prostate cancer (four studies, OR = 0.91; 95% CI 0.69, 1.19; P = 0.5). In a meta-analysis of folate-pathway polymorphisms, MTR 2756A > G (eight studies, OR = 1.06; 95% CI 1.00, 1.12; P = 0.06) and SHMT1 1420C > T (two studies, OR = 1.11; 95% CI 1.00, 1.22; P = 0.05) were positively associated with prostate cancer risk. There were no effects due to any other polymorphisms, including MTHFR 677C > T (12 studies, OR = 1.04; 95% CI 0.97, 1.12; P = 0.3). The positive association of circulating B12 with an increased risk of prostate cancer could be explained by reverse causality. However, given current controversies over mandatory B12 fortification, further research to eliminate a causal role of B12 in prostate cancer initiation and/or progression is required. Meta-analysis does not entirely rule out a positive association of circulating folate with increased prostate cancer risk. As with B12, even a weak positive association would be a significant public health issue, given the high prevalence of prostate cancer and concerns about the potential harms versus benefits of mandatory folic acid fortification.

Methyl nutrients, DNA methylation, and cardiovascular disease

Diet plays an important role in the development and prevention of cardiovascular disease (CVD), but the molecular mechanisms are not fully understood. DNA methylation has been implicated as an underlying molecular mechanism that may account for the effect of dietary factors on the development and prevention of CVD. DNA methylation is an epigenetic process that provides "marks" in the genome by which genes are set to be transcriptionally activated or silenced. Epigenomic marks are heritable but are also responsive to environmental shifts, such as changes in nutritional status, and are especially vulnerable during development. S-adenosylmethionine is the methyl group donor for DNA methylation and several nutrients are required for the production of S-adenosylmethionine. These methyl nutrients include vitamins (folate, riboflavin, vitamin B12, vitamin B6, choline) and amino acids (methionine, cysteine, serine, glycine). As such, imbalances in the metabolism of these nutrients have the potential to affect DNA methylation. The focus of this review is to provide an overview on the current understanding of the relationship between methyl nutrient status and DNA methylation patterns and the potential role of this interaction in CVD pathology.

Association between polymorphisms in genes encoding methylenetetrahydrofolate reductase and the risk of Ménière's disease

Folate metabolism is essential for cellular functioning. Despite extensive research on the roles of folate-metabolism-related gene polymorphisms in the pathophysiology of many diseases, such as cardiovascular disease, cancers, and sudden sensorineural hearing loss, little is known about their association with Ménière's disease (MD). The aim of this study was to investigate the effect of methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms (C677T and A1298C) on the risk of MD in a Japanese population. We examined the C677T and A1298C (rs1801133 and rs1801131) polymorphisms in the MTHFR gene and compared them between 1946 adults (986 men and 960 women) participating in the National Institute for Longevity Sciences Longitudinal Study of Aging and 86 cases of MD. A multiple logistic regression was performed to obtain odds ratios (ORs) for the risk of MD regarding the MTHFR polymorphisms before (model 1) and after (model 2) adjustment for age and sex factors. The OR of MTHFR C677T for the risk of MD was 0.669 (95% confidence interval [CI], 0.479-0.934) in model 1 and 0.680 (95% CI, 0.484-0.954) in model 2. In contrast, the OR of MTHFR A1298C for the risk of MD was 1.503 (95% CI, 1.064-2.123) in model 1 and 1.505 (95% CI, 1.045-2.167) in model 2. Our results imply that the MTHFR C677T and A1298C polymorphisms are associated with the risk of MD.

Folate-genetics and colorectal neoplasia: what we know and need to know next

SCOPE

The metabolism of folate involves a complex network of polymorphic enzymes that may explain a proportion of the risk associated with colorectal neoplasia. Over 60 observational studies primarily in non-Hispanic White populations have been conducted on selected genetic variants in specific genes, MTHFR, MTR, MTRR, CBS, TCNII, RFC, GCPII, SHMT, TYMS, and MTHFD1, including five meta-analyses on MTHFR 677C>T (rs1801133) and MTHFR 1298C>T (rs1801131); two meta-analyses on MTR-2756A>C (rs1805087); and one for MTRR 66A>G (rs1801394).

METHODS AND RESULTS

This systematic review synthesizes these data, highlighting the consistent inverse association between MTHFR 677TT genotype and risk of colorectal cancer (CRC) and its null association with adenoma risk. Results for other variants varied across individual studies; in our meta-analyses we observed some evidence for SHMT 1420C>T (rs1979277) ((odds ratio) OR = 0.85; 95% confidence interval (CI) = 0.73-1.00 for TT v. CC) and TYMS 5' 28 bp repeat (rs34743033) and CRC risk (OR = 0.84; 95% CI = 0.75-0.94 for 2R/3R v. 3R/3R and OR = 0.82; 95% CI = 0.69-0.98 for 2R/2R v. 3R/3R).

CONCLUSION

To gain further insight into the role of folate variants in colorectal neoplasia will require incorporating measures of the metabolites, including B-vitamin cofactors, homocysteine and S-adenosylmethionine, and innovative statistical methods to better approximate the folate one-carbon metabolism pathway.

Global DNA hypomethylation in peripheral blood mononuclear cells as a biomarker of cancer risk

BACKGROUND

Global DNA hypomethylation is an early molecular event in carcinogenesis. Whether methylation measured in peripheral blood mononuclear cells (PBMCs) DNA is a clinically reliable biomarker for early detection or cancer risk assessment is to be established.

METHODS

From an original sample-set of 753 male and female adults (ages 64.8 ± 7.3 years), PBMCs DNA methylation was measured in 68 subjects with history of cancer at time of enrollment and 62 who developed cancer during follow-up. Age- and sex-matched controls for prevalent and incident cancer cases (n = 68 and 58, respectively) were also selected. Global DNA methylation was assessed by liquid chromatography/mass spectrometry (LC/MS). Methylenetetrahydrofolate reductase (MTHFR) 677C>T genotype and plasma folate concentrations were also determined for the known gene-nutrient interaction affecting DNA methylation.

RESULTS

Cancer subjects had significantly lower PBMCs-DNA methylation than controls [4.39 (95% confidence intervals (CI), 4.25-4.53) vs. 5.13 (95% CI, 5.03-5.21) %mCyt/(mCyt+Cyt); P < 0.0001]. A DNA methylation threshold of 4.74% clearly categorized patients with cancer from controls so that those with DNA methylation less than 4.74% showed an increased prevalence of cancer than those with higher levels (91.5% vs. 19%; P < 0.001). Subjects with cancer at follow-up had, already at enrollment, reduced DNA methylation as compared with controls [4.34 (95% CI, 4.24-4.51) vs. 5.08 (95% CI, 5.05-5.22) %mCyt/(mCyt+Cyt); P < 0.0001]. Moreover, MTHFR677C>T genotype and folate interact for determining DNA methylation, so that MTHFR677TT carriers with low folate had the lowest DNA methylation and concordantly showed a higher prevalence of cancer history (OR, 7.04; 95% CI, 1.52-32.63; P = 0.013).

CONCLUSIONS

Genomic PBMCs-DNA methylation may be a useful epigenetic biomarker for early detection and cancer risk estimation.

IMPACT

This study identifies a threshold for PBMCs-DNA methylation to detect cancer-affected from cancer-free subjects and an at-risk condition for cancer based on genomic DNA methylation and MTHFR677C>T-folate status.

Homocysteinylated protein levels in internal mammary artery (IMA) fragments and its genotype-dependence. S-homocysteine-induced methylation modifications in IMA and aortic fragments

The resistance of internal mammary artery (IMA) toward atherosclerosis is not well understood. In plasma, homocysteine (Hcy) occurs in reduced, oxidized, homocysteine thiolactone and a component of proteins as a result of N- or S-homocysteinylation. We evaluated S/N-homocysteinylated protein levels in IMA fragments of patients undergoing coronary artery bypass grafting, and whether they were affected by genetic common variants. We tested whether tHcy, Hcy-S-protein levels, genotypes or Hcy-induced methylation modifications were related to differences in iNOS, Ddah2, and eNOS gene expression between territories. A small percentage of Hcy-S-proteins were found in IMA fragments. The Mthfr C677T (rs1801133) and Pon-1 Leu55Met (rs854560) variants were associated with Hcy-S-proteins. We observed a gradual difference according to Hcy-S-protein levels in the methylation degree of the Ddah2 gene promoter in aortic, but not in IMA, fragments. No correlation between the degree of methylation and the Ddah2 gene expression levels was found in both types of analyzed fragments. Total Hcy but not Hcy-S-proteins correlated with iNOS promoter methylation. Analyzed variants seem to contribute to the in vivo Hcy binding properties to IMA. The contribution of the Hcy-derived methylation modifications to Ddah2 and eNOS gene expression seems to be tissue-specific and independent of the Ddah2/ADMA/eNOS pathway. Hcy-derived methylation modifications to the iNOS gene promoter contribute to a lesser extent to iNOS gene expression.

Low-dose methotrexate inhibits methionine S-adenosyltransferase in vitro and in vivo

Methionine S-adenosyltransferase (MAT) catalyzes the only reaction that produces the major methyl donor in mammals. Low-dose methotrexate is the most commonly used disease-modifying antirheumatic drug in human rheumatic conditions. The present study was conducted to test the hypothesis that methotrexate inhibits MAT expression and activity in vitro and in vivo. HepG2 cells were cultured under folate restriction or in low-dose methotrexate with and without folate or methionine supplementation. Male C57BL/6J mice received methotrexate regimens that reflected low-dose clinical use in humans. S-adenosylmethionine and MAT genes, proteins and enzyme activity levels were determined. We found that methionine or folate supplementation greatly improved S-adenosylmethionine in folate-depleted cells but not in cells preexposed to methotrexate. Methotrexate but not folate depletion suppressed MAT genes, proteins and activity in vitro. Low-dose methotrexate inhibited MAT1A and MAT2A genes, MATI/II/III proteins and MAT enzyme activities in mouse tissues. Concurrent folinate supplementation with methotrexate ameliorated MAT2A reduction and restored S-adenosylmethionine in HepG2 cells. However, posttreatment folinate rescue failed to restore MAT2A reduction or S-adenosylmethionine level in cells preexposed to methotrexate. Our results provide both in vitro and in vivo evidence that low-dose methotrexate inhibits MAT genes, proteins, and enzyme activity independent of folate depletion. Because polyglutamated methotrexate stays in the hepatocytes, if methotrexate inhibits MAT in the liver, then the efficacy of clinical folinate rescue with respect to maintaining hepatic S-adenosylmethionine synthesis and normalizing the methylation reactions would be limited. These findings raise concerns on perturbed methylation reactions in humans on low-dose methotrexate. Future studies on the clinical physiological consequences of MAT inhibition by methotrexate and the potential benefits of S-adenosylmethionine supplementation on methyl group homeostasis in clinical methotrexate therapies are warranted.

Genetic and non-genetic influences during pregnancy on infant global and site specific DNA methylation: role for folate gene variants and vitamin B12

Inter-individual variation in patterns of DNA methylation at birth can be explained by the influence of environmental, genetic and stochastic factors. This study investigates the genetic and non-genetic determinants of variation in DNA methylation in human infants. Given its central role in provision of methyl groups for DNA methylation, this study focuses on aspects of folate metabolism. Global (LUMA) and gene specific (IGF2, ZNT5, IGFBP3) DNA methylation were quantified in 430 infants by Pyrosequencing®. Seven polymorphisms in 6 genes (MTHFR, MTRR, FOLH1, CβS, RFC1, SHMT) involved in folate absorption and metabolism were analysed in DNA from both infants and mothers. Red blood cell folate and serum vitamin B₁₂ concentrations were measured as indices of vitamin status. Relationships between DNA methylation patterns and several covariates viz. sex, gestation length, maternal and infant red cell folate, maternal and infant serum vitamin B₁₂, maternal age, smoking and genotype were tested. Length of gestation correlated positively with IGF2 methylation (rho = 0.11, p = 0.032) and inversely with ZNT5 methylation (rho = −0.13, p = 0.017). Methylation of the IGFBP3 locus correlated inversely with infant vitamin B₁₂ concentration (rho = −0.16, p = 0.007), whilst global DNA methylation correlated inversely with maternal vitamin B₁₂ concentrations (rho = 0.18, p = 0.044). Analysis of common genetic variants in folate pathway genes highlighted several associations including infant MTRR 66G>A genotype with DNA methylation (χ² = 8.82, p = 0.003) and maternal MTHFR 677C>T genotype with IGF2 methylation (χ² = 2.77, p = 0.006). These data support the hypothesis that both environmental and genetic factors involved in one-carbon metabolism influence DNA methylation in infants. Specifically, the findings highlight the importance of vitamin B₁₂ status, infant MTRR genotype and maternal MTHFR genotype, all of which may influence the supply of methyl groups for DNA methylation. In addition, gestational length appears to be an important determinant of infant DNA methylation patterns.

DNA methylation in peripheral blood measured by LUMA is associated with breast cancer in a population-based study

Our purpose was to identify epigenetic markers of breast cancer risk, which can be reliably measured in peripheral blood and are amenable for large population screening. We used 2 independent assays, luminometric methylation assay (LUMA) and long interspersed elements-1 (LINE-1) to measure "global methylation content" in peripheral blood DNA from a well-characterized population-based case-control study. We examined associations between methylation levels and breast cancer risk among 1055 cases and 1101 controls and potential influences of 1-carbon metabolism on global methylation. Compared with women in the lowest quintile of LUMA methylation, those in the highest quintile had a 2.41-fold increased risk of breast cancer (95% confidence interval: 1.83-3.16; P, trend<0.0001). The association did not vary by other key tumor characteristics and lifestyle risk factors. Consistent with LUMA findings, genome-wide methylation profiling of a subset of samples revealed greater promoter hypermethylation in breast cancer case participants (P=0.04); higher LUMA was associated with higher promoter methylation in the controls (P=0.05). LUMA levels were also associated with functional sodium nitroprusside in key 1-carbon metabolizing genes, MTHFR C677T (P=0.001) and MTRR A66G (P=0.018). LINE-1 methylation was associated with neither breast cancer risk nor 1-carbon metabolism. Our results show that global promoter hypermethylation measured in peripheral blood was associated with breast cancer risk.

Cardiometabolic risk and the MTHFR C677T variant in children treated with second-generation antipsychotics

Second-generation antipsychotics (SGAs) are increasingly being used to treat children with a variety of psychiatric illnesses. Metabolic syndrome (MetS), a risk factor for cardiovascular disease, is a side-effect of SGA-treatment. We conducted a cross-sectional study and assessed the association of the methylenetetrahydrofolate reductase (MTHFR) C677T variant with features of MetS in SGA-treated (n=105) and SGA-naïve (n=112) children. We targeted the MTHFR C677T variant, because it is associated with risk for cardiovascular disease, and features of MetS in adults without psychiatric illness. MetS in children is based on the presence of any three of the following: waist circumference ≥ 90th percentile for age and sex; plasma triglyceride ≥ 1.24 mmol l(-1); plasma high-density lipoprotein-cholesterol ≤ 1.03 mmol l(-1); systolic or diastolic blood pressure ≥ 90th percentile for age, sex, and height; and fasting glucose ≥ 5.6 mmol l(-1). We found that 15% of SGA-treated children had MetS compared with 2% of SGA-naïve children (OR 8.113, P<0.05). No effect of the MTHFR C677T variant on psychiatric diagnosis was observed. The MTHFR 677T allele was associated (P<0.05) with MetS (OR 5.75, 95% CI= 1.18-28.12) in SGA-treated children. Models adjusted for duration of SGA treatment, ethnicity, sex, age and use of other medications revealed a positive relationship between the MTHFR 677T allele and diastolic blood pressure Z-scores (P=0.001) and fasting plasma glucose (P<0.05) in SGA-treated children. These findings illustrate the high prevalence of MetS in SGA-treated children and suggest metabolic alterations associated with the MTHFR C677T variant may have a role in the development of MetS features in SGA-treated children.

Nutrigenomics: implications for breast and colon cancer prevention

Nutrigenomics refers to the interaction between one's diet and his/her genes. These interactions can markedly influence digestion, absorption, and the elimination of bioactive food components, as well as influence their site of actions/molecular targets. Nutrigenomics comprises nutrigenetics, epigenetics, and transcriptomics, coupled with other "omic," such as proteomics and metabolomics, that apparently account for the wide variability in cancer risk among individuals with similar dietary habits. Multiple food components including essential nutrients, phytochemical, zoochemicals, fungochemical, and bacterochemicals have been implicated in cancer risk and tumor behavior, admittedly with mixed results. Such findings suggest that not all individuals respond identically to a diet. This chapter highlights the influence of single-nucleotide polymorphism, copy number, epigenetic events, and transcriptomic homeostasis as factors influencing the response to food components and ultimately health, including cancer risk. Both breast and colorectal cancers are reviewed as examples about how nutrigenomics may influence the response to dietary intakes. As the concept that "one size fits all" comes to an end and personalized approaches surface, additional research data will be required to identify those who will benefit most from dietary change and any who might be placed at risk because of an adjustment.