Maternal one-carbon nutrient intake and cancer risk in offspring

Folate Intake and Risk of Urothelial Carcinoma: A Systematic Review and Meta-Analysis of Epidemiological Studies

We aimed to investigate the association between folate intake and the risk of urothelial carcinoma (UC). A systematic literature search using Pubmed and EMBASE databases was performed to find prospective cohort studies, population-based case-control study or hospital-based case-control study investigating the association of folate intake and the risk of UC. A total of 19 studies involving 11,175 cases and 656,161 individuals were included. High intake of folate was associated with a decreased risk of UC, with a pooled OR of 0.78 (95% CI: 0.66-0.93, P = 0.006) for the highest category of intake vs. the lowest. The data suggested that folate may contribute to the prevention of urothelial cancer. However, the association was observed only in case-control studies (OR = 0.56, 95% CI: 0.39-0.79, P = 0.001), but not in cohort studies (RR = 0.97, 95% CI: 0.87-1.09, P = 0.638). Dose-response meta-analysis showed that an increment of folate intake (100 μg/day) corresponded to an 8% deceased risk of invasive UC (RR = 0.92, 95% CI: 0.87-0.98, P = 0.004). High folate intake might be inversely associated with risk of UC particularly invasive UC, which needs to be confirmed.

Folate pathways mediating the effects of ethanol in tumorigenesis

Folate and alcohol are dietary factors affecting the risk of cancer development in humans. The interaction between folate status and alcohol consumption in carcinogenesis involves multiple mechanisms. Alcoholism is typically associated with folate deficiency due to reduced dietary folate intake. Heavy alcohol consumption also decreases folate absorption, enhances urinary folate excretion and inhibits enzymes pivotal for one-carbon metabolism. While folate metabolism is involved in several key biochemical pathways, aberrant DNA methylation, due to the deficiency of methyl donors, is considered as a common downstream target of the folate-mediated effects of ethanol. The negative effects of low intakes of nutrients that provide dietary methyl groups, with high intakes of alcohol are additive in general. For example, low methionine, low-folate diets coupled with alcohol consumption could increase the risk for colorectal cancer in men. To counteract the negative effects of alcohol consumption, increased intake of nutrients, such as folate, providing dietary methyl groups is generally recommended. Here mechanisms involving dietary folate and folate metabolism in cancer disease, as well as links between these mechanisms and alcohol effects, are discussed. These mechanisms include direct effects on folate pathways and indirect mediation by oxidative stress, hypoxia, and microRNAs.

Association Between One-carbon Metabolism-related Vitamins and Risk of Breast Cancer: A Systematic Review and Meta-analysis of Prospective Studies

Epidemiologic studies focusing on the association between 1-carbon metabolism-related vitamins (ie, folate, vitamin B₆, vitamin B₂, vitamin B₁₂) and breast cancer risk have reported inconsistent findings. We conducted a systematic search of the reported data and performed a meta-analysis of prospective case-control and cohort studies to derive a more precise evaluation. The PubMed and EMBASE databases were searched to identify eligible studies. A total of 27 studies involving 49,707 cases and 1,274,060 individuals were included in the meta-analysis. The results indicated that a high intake of folate, vitamin B₆, and vitamin B₂ might decrease the risk of breast cancer. The corresponding pooled relative risks (RRs) for the highest intake compared with the lowest were 0.93 (95% confidence interval [CI], 0.88-0.99; P = .018), 0.94 (95% CI, 0.89-1.00; P = .037) and 0.90 (95% CI, 0.82-0.99; P = .026). No significant association between vitamin B₁₂ and breast cancer risk was found (RR, 0.99; 95% CI, 0.94-1.04; P = .604). Further study showed that folate and vitamin B₆ might decrease the risk of estrogen receptor-negative (ER^-)/progesterone receptor-negative (PR^-) breast cancer but not ER⁺/PR⁺ breast cancer. The dose-response meta-analysis indicated a significant linearity relationship between folate intake and a reduced risk of ER^-/PR^- breast cancer. An increment of folate intake (100 μg/d) corresponded to a 7% deceased risk of ER^-/PR^- breast cancer (RR, 0.93; 95% CI, 0.89-0.98; P = .007). In conclusion, a high intake of 1-carbon metabolism-related vitamins might contribute to the prevention of breast cancer, especially ER^-/PR^- breast cancer.

Periconceptional intake of folic acid among low-risk women in Canada: summary of a workshop aiming to align prenatal folic acid supplement composition with current expert guidelines

The Government of Canada and the Society of Obstetricians and Gynaecologists of Canada both recommend a daily multivitamin supplement containing 400 µg folic acid (FA) for the primary prevention of neural tube defects among low-risk women from before conception and throughout lactation. Prenatal supplements marketed and prescribed in Canada typically exceed the recommended dose, usually providing ≥1000 µg FA/d. This high daily dose, coupled with staple-food FA fortification, has resulted in the observation of very high blood folate concentrations among reproductive-aged women consuming FA-containing supplements. The long-term consequences of high folate status on fetal development are unknown; however, evidence from animal studies and some human epidemiologic data suggest potential adverse consequences. To address this issue, a workshop was convened with the overall goal to identify challenges and solutions to aligning supplemental FA intakes with current evidence-based recommendations. Thirty-eight stakeholders from academia, industry, government, and health professional groups participated. Group discussions facilitated the identification and prioritization of 5 key challenges for which solutions and implementation strategies were proposed. The 5 themes encompassed clarity and harmonization of evidence-based guidelines, reformulation or relabeling of FA-containing supplements, access to FA for all women, knowledge dissemination strategies and education of the public and health care professionals, and attitude change to overcome the perception of "more is better." A combination of the proposed implementation strategies involving all key stakeholders and directed to health care professionals and the public may enable a sustainable change to align FA intake during the periconceptional period with evidence-based recommendations.

Maternal western-style diet enhances the effects of chemically-induced mammary tumors in female rat offspring through transcriptome changes

Previous studies have shown that early life intake of high-fat diet or western-style diet (WD) enhances the development of mammary tumors in adult female rats. Thus, we hypothesized that maternal WD throughout pregnancy and the lactation period could speed up the development of MNU-induced mammary tumors and alter their gene expression. For this, the present study investigated the gene expression profile of chemically-induced mammary tumors in female rat offspring from dams fed a WD or a control diet. Pregnant female Sprague-Dawley rats received a WD (high-fat, low-fiber and oligoelements) or a control diet from gestational day 12 until post-natal day (PND) 21. At PND 21, female offspring received a single dose of N-Methyl-N-Nitrosourea (MNU, 50 mg/kg body weight) and were fed a control diet for 13 weeks. Tumor incidence, multiplicity, and latency were recorded and mammary gland samples were collected for histopathology and gene expression analysis. Tumor multiplicity and histological grade were significantly higher and tumor latency was lower in WD offspring compared to control offspring. Transcriptome profiling identified 57 differentially expressed genes in tumors from WD offspring as compared to control offspring. There was also an increase in mRNA expression of genes such as Emp3, Ccl7, Ets1, Abcc5, and Cyr61, indicative of more aggressive disease detected in tumors from WD offspring. Thus, maternal WD diet increased MNU-induced mammary carcinogenesis in adult female offspring through transcriptome changes that resulted in a more aggressive disease.

Intake of Dietary One-Carbon Metabolism-Related B Vitamins and the Risk of Esophageal Cancer: A Dose-Response Meta-Analysis

Several B vitamins are essential in the one-carbon metabolism pathway, which is central to DNA methylation, synthesis, and repair. Moreover, an imbalance in this pathway has been linked to certain types of cancers. Here, we performed a meta-analysis in order to investigate the relationship between the intake of four dietary one-carbon metabolism-related B vitamins (B2, B6, folate, and B12) and the risk of esophageal cancer (EC). We searched PubMed, Web of Science, and Embase for relevant studies published through 1 March 2018. The odds ratio (OR) with 95% confidence interval (CI) for the highest versus the lowest level of each dietary B vitamin was then calculated. From 21 articles reporting 26 studies including 6404 EC cases and 504,550 controls, we found an inverse correlation between the consumption of vitamin B6 and folate and the risk of EC; this association was specific to the US, Europe, and Australia, but was not found in Asia. A dose-response analysis revealed that each 100 μg/day increase in folate intake reduced the risk of EC by 12%. Moreover, each 1 mg/day increase in vitamin B6 intake decreased the risk of EC by 16%. Surprisingly, we found that each 1 μg/day increase in vitamin B12 intake increased the risk of esophageal adenocarcinoma by 2%, particularly in the US and Europe, suggesting both geographic and histological differences. Together, our results suggest that an increased intake of one-carbon metabolism-related B vitamins may protect against EC, with the exception of vitamin B12, which should be consumed in moderation.

Dietary Associations with a Breast Cancer Risk Biomarker Depend on Menopause Status

We investigated how timing influences the role of diet in breast cancer risk with a cross-sectional study of pre-malignant change in breast tissue. Women with an elevated risk of developing breast cancer (33 premenopausal and 32 postmenopausal) completed the National Cancer Institute's food frequency questionnaire and underwent random periareolar fine-needle aspiration for evaluation of cytologic atypia, an established risk biomarker. Fatty acid composition of breast adipose was measured in 32 (49%) subjects. We found that premenopausal and postmenopausal women had similar diets, but the associations between atypia and intake of total n-3 polyunsaturated fatty acids (PUFA) and soy differed by menopause status (both P interaction < 0.001). Total n-3 PUFA intake was inversely associated with atypia among premenopausal women (P < 0.0001), but not among postmenopausal women (P = 0.91); associations were similar for soy (P = 0.0003 and P = 0.48, respectively). This pattern of dietary interaction with menopause was mirrored in tissue fatty acids (P interaction < 0.05), wherein 1) higher levels of linolelaidic acid (an industrially-produced trans fat) and 2) lower levels of docosahexaenoic acid (the predominant long-chain n-3 PUFA) in breast adipose were associated with atypia in premenopausal (both P < 0.05) but not postmenopausal women (both P > 0.37). Dietary associations with breast cancer risk are stronger prior to menopause.

Epigenetic modulators, modifiers and mediators in cancer aetiology and progression

This year is the tenth anniversary of the publication in this journal of a model suggesting the existence of 'tumour progenitor genes'. These genes are epigenetically disrupted at the earliest stages of malignancies, even before mutations, and thus cause altered differentiation throughout tumour evolution. The past decade of discovery in cancer epigenetics has revealed a number of similarities between cancer genes and stem cell reprogramming genes, widespread mutations in epigenetic regulators, and the part played by chromatin structure in cellular plasticity in both development and cancer. In the light of these discoveries, we suggest here a framework for cancer epigenetics involving three types of genes: 'epigenetic mediators', corresponding to the tumour progenitor genes suggested earlier; 'epigenetic modifiers' of the mediators, which are frequently mutated in cancer; and 'epigenetic modulators' upstream of the modifiers, which are responsive to changes in the cellular environment and often linked to the nuclear architecture. We suggest that this classification is helpful in framing new diagnostic and therapeutic approaches to cancer.

Methylating micronutrient supplementation during pregnancy influences foetal hepatic gene expression and IGF signalling and increases foetal weight

PURPOSE

Maternal diet during pregnancy impacts foetal growth and development. In particular, dietary levels of methylating micronutrients (methionine, folate, choline, vitamins B6, and B12) interfere with the availability and allocation of methyl groups for methylation reactions, thereby influencing normal transcription. However, the currently recommended methylating micronutrient supplementation regimen is haphazard and arbitrary at best.

METHODS

To investigate the effects of a methylating micronutrient-rich maternal diet, pregnant Pietrain sows were fed either a standard diet (CON) or a diet supplemented with methionine, folate, choline, B6, B12, and zinc (MET). Foetal liver and muscle (M. longissimus dorsi) tissues were collected at 35, 63, and 91 days post-conception. Transcriptional responses to diet were assessed in foetal liver. Altered insulin-like growth factor (IGF) signalling in transcriptome analyses prompted investigation of IGF-2 and insulin-like growth factor binding proteins (IGFBPs) levels in muscle and liver.

RESULTS

Maternal diet enriched with methylating micronutrients was associated with increased foetal weight in late gestation. Hepatic transcriptional patterns also revealed differences in vitamin B6 and folate metabolism between the two diets, suggesting that supplementation was effective. Additionally, shifts in growth-supporting metabolic routes of the lipid and energy metabolism, including IGF signalling, and of cell cycle-related pathways were found to occur in liver tissue in supplemented individuals. Weight differences and modulated IGF pathways were also reflected in the muscle content of IGF-2 (increased in MET) and IGFBP-2 (decreased in MET).

CONCLUSIONS

Maternal dietary challenges provoke stage-dependent and tissue-specific transcriptomic modulations in the liver pointing to molecular routes contributing to the organismal adaptation. Subtle effects on late foetal growth are associated with changes in the IGF signalling mainly in skeletal muscle tissue that is less resilient to dietary stimuli than liver.

Maternal western style diet increases susceptibility to chemically-induced mammary carcinogenesis in female rats offspring

The present study investigated whether maternal exposure to western style diet (WD) increases susceptibility to mammary carcinogenesis induced by N-methyl-N-nitrosourea (MNU) in female offspring. Pregnant female Sprague-Dawley rats received WD diet or control diet from gestational day 12 until postnatal day (PND) 21. At PND 21, female offspring received a single dose of MNU (50 mg/kg body weight) and were fed chow diet until PND 110. Mammary gland structures were assessed on whole-mount preparations in the offspring at PND 21, and tumor morphology was examined at PND 110. Immunohistochemical analysis for cell proliferation (PCNA), apoptosis (cleaved caspase-3) and estrogen receptor alpha (ER-α) was performed in mammary terminal end buds (TEBs) at PND 21, and PCNA, ER-α, and p63 analysis in mammary tumors at PND 110. Maternal WD intake induced a significant increase in the number of TEBs (P = 0.024) and in PCNA labeling index (P < 0.020) in the mammary glands at PND 21. Tumor multiplicity, tumor weight, and PCNA labeling indexes were significantly higher in the WD offspring than that of the control offspring (P < 0.05). These findings indicate that maternal western style diet potentially enhanced the development of mammary tumors induced by MNU in female offspring, possibly by affecting the mammary gland differentiation.

Folate deficiency-induced oxidative stress contributes to neuropathy in young and aged zebrafish--implication in neural tube defects and Alzheimer's diseases

Folate is a nutrient essential for the development, function and regeneration of nervous systems. Folate deficiency has been linked to many neurological disorders including neural tube defects in fetus and Alzheimer's diseases in the elderly. However, the etiology underlying these folate deficiency-associated diseases is not completely understood. In this study, zebrafish transgenic lines with timing and duration-controllable folate deficiency were developed by ectopically overexpressing a recombinant EGFP-γ-glutamyl hydrolase (γGH). Impeded neural crest cell migration was observed in the transgenic embryos when folate deficiency was induced in early stages, leading to defective neural tube closure and hematopoiesis. Adding reduced folate or N-acetylcysteine reversed the phenotypic anomalies, supporting the causal link between the increased oxidative stress and the folate deficiency-induced abnormalities. When folate deficiency was induced in aged fish accumulation of beta-amyloid and phosphorylated Tau protein were found in the fish brain cryo-sections. Increased autophagy and accumulation of acidic autolysosome were apparent in folate deficient neuroblastoma cells, which were reversed by reduced folate or N-acetylcysteine supplementation. Decreased expression of cathepsin B, a lysosomal protease, was also observed in cells and tissue with folate deficiency. We concluded that folate deficiency-induced oxidative stress contributed to the folate deficiency-associated neuropathogenesis in both early and late stages of life.

Vitamin B12: one carbon metabolism, fetal growth and programming for chronic disease

This review brings together human and animal studies and reviews that examine the possible role of maternal vitamin B12 (B12) on fetal growth and its programming for susceptibility to chronic disease. A selective literature review was undertaken to identify studies and reviews that investigate these issues, particularly in the context of a vegetarian diet that may be low in B12 and protein and high in carbohydrate. Evidence is accumulating that maternal B12 status influences fetal growth and development. Low maternal vitamin B12 status and protein intake are associated with increased risk of neural tube defect, low lean mass and excess adiposity, increased insulin resistance, impaired neurodevelopment and altered risk of cancer in the offspring. Vitamin B12 is a key nutrient associated with one carbon metabolic pathways related to substrate metabolism, synthesis and stability of nucleic acids and methylation of DNA which regulates gene expression. Understanding of factors regulating maternal-fetal one carbon metabolism and its role in fetal programming of non communicable diseases could help design effective interventions, starting with maternal nutrition before conception.

Methotrexate-induced decrease in embryonic 5-methyl-tetrahydrofolate is irreversible with leucovorin supplementation

Folate is a nutrient crucial for rapidly growing tissues, including developing embryos and cancer cells. Folate participates in the biosynthesis of nucleic acids, proteins, amino acids, S-adenosylmethionine, many neurotransmitters, and some vitamins. The intracellular folate pool consists of different folate adducts, which carry one-carbon units at three different oxidative states and participate in distinct biochemical reactions. Therefore, the content and dynamics of folate adducts will affect the homeostasis of the metabolites generated in these folate-mediated reactions. Currently, the knowledge on the level of each individual folate adduct in developing embryos is limited. With an improved high-performance liquid chromatography protocol, we found that tetrahydrofolate (THF), the backbone of one-carbon carrier, gradually increased and became dominant in developing zebrafish embryos. 5-methyl-tetrahydrofolate (5-CH3-THF) was abundant in unfertilized eggs but decreased rapidly when embryos started to proliferate and differentiate. 10-formyltetrahydrofolate at first increased after fertilization, and then dropped dramatically before reaching a sustained level at later stages. Dihydrofolate (DHF) slightly decreased initially and remained low throughout embryogenesis. Exposure to methotrexate significantly decreased 5-CH3-THF levels and increased DHF pools, besides causing brain ventricle anomaly. Rescuing with leucovorin partly reversed the abnormal phenotype. Unexpectedly, the level of 5-CH3-THF remained low even when leucovorin was added for rescue. Our results show that different folate adducts fluctuated significantly and differentially in concert with the physiological requirement specific for the corresponding developmental stages. Furthermore, methotrexate lowered the level of 5-CH3-THF in developing embryos, which could not be reversed with folate supplementation and might be more substantial to cellular methylation potential and epigenetic control than to nucleotide synthesis.

Folate and fetal programming: a play in epigenomics?

Folate plays a key role in the interactions between nutrition, fetal programming, and epigenomics. Maternal folate status influences DNA methylation, inheritance of the agouti phenotype, expression of imprinting genes, and the effects of mycotoxin FB1 on heterochromatin assembly in rodent offspring. Deficiency in folate and other methyl donors increases birth defects and produces visceral manifestations of fetal programming, including liver and heart steatosis, through imbalanced methylation and acetylation of PGC1-α and decreased SIRT1 expression, and produces persistent cognitive and learning disabilities through impaired plasticity and hippocampal atrophy. Maternal folate supplementation also produces long-term epigenomic effects in offspring, some beneficial and others negative. Deciphering these mechanisms will help understanding the discordances between experimental models and population studies of folate deficiency and supplementation.

Prognostic significance of promoter DNA methylation in patients with childhood neuroblastoma

PURPOSE

To characterize the clinical significance of promoter methylation in a cohort of primary neuroblastoma tumors and investigate the association between DNA methylation and clinical outcome.

EXPERIMENTAL DESIGN

A customized Illumina GoldenGate methylation assay was used to assess methylation status of 96 CpG sites within 48 candidate genes in primary neuroblastoma tumors obtained from 131 children diagnosed in Australia. Genes were selected on the basis of previous reports of altered DNA methylation in embryonal cancers. Levels of DNA methylation were validated in a subset of 48 patient samples using combined bisulfite restriction analysis (CoBRA) and bisulfite sequencing. A Cox proportional hazards model was used to investigate the association between promoter hypermethylation and the risk of relapse/death within 5 years of diagnosis, while adjusting for known prognostic factors including MYCN amplification, age, and stage at diagnosis.

RESULTS

Levels of promoter methylation of DNAJC15, neurotrophic tyrosine kinase receptor 1 or TrkA (NTRK1), and tumor necrosis factor receptor superfamily, member 10D (TNFRSF10D), were higher in older patients at diagnosis (P < 0.01), whereas higher levels of methylation of DNAJC15, NTRK1, and PYCARD were observed in patients with MYCN amplification (P < 0.001). In multivariate analysis, hypermethylation of folate hydrolase (FOLH1), myogenic differentiation-1 (MYOD1), and thrombospondin-1 (THBS1) remained significant independent predictors of poorer clinical outcome after adjusting for known prognostic factors (P ≤ 0.017). Moreover, more than 30% of patients displayed hypermethylation in 2 genes or more and were at least 2 times more likely to relapse or die (HR = 2.72, 95% confidence interval = 1.55-4.78, P = 0.001), independent of MYCN status, age, and stage at diagnosis.

CONCLUSIONS

Our findings highlight the potential use of methylation profiling to identify additional prognostic markers and detect new therapeutic targets for selected patient subsets.

A candidate gene study of one-carbon metabolism pathway genes and colorectal cancer risk

The risk of colorectal cancer (CRC) may be influenced by aberrant DNA methylation and altered nucleotide synthesis and repair, possibly caused by impaired dietary folate intake as well as by polymorphic variants in one-carbon metabolism genes. A case-control study using seventy-one CRC patients and eighty unrelated healthy controls was carried out to assess the genetic association of fifteen SNP and one insertion in nine genes belonging to the folate pathway. Polymorphism selection was based on literature data, and included those which have a known or suspected functional impact on cancer and missense polymorphisms that are most likely to alter protein function. Genotyping was performed by real-time PCR and PCR followed by restriction analysis. The likelihood ratio statistic indicated that most of the polymorphisms were not associated with the risk of CRC. However, an increased risk of CRC was observed for two variant alleles of SNP mapping on the transcobalamin 2 gene (TCN2): C776G (rs1801198) and c.1026-394T>G (rs7286680). Considering the crucial biological function played by one-carbon metabolism genes, further investigations with larger cohorts of CRC patients are needed in order to confirm our preliminary results. These preliminary results indicate that TCN2 polymorphisms can be a susceptibility factor for CRC.

Environmental epigenetics: prospects for studying epigenetic mediation of exposure-response relationships

Changes in epigenetic marks such as DNA methylation and histone acetylation are associated with a broad range of disease traits, including cancer, asthma, metabolic disorders, and various reproductive conditions. It seems plausible that changes in epigenetic state may be induced by environmental exposures such as malnutrition, tobacco smoke, air pollutants, metals, organic chemicals, other sources of oxidative stress, and the microbiome, particularly if the exposure occurs during key periods of development. Thus, epigenetic changes could represent an important pathway by which environmental factors influence disease risks, both within individuals and across generations. We discuss some of the challenges in studying epigenetic mediation of pathogenesis and describe some unique opportunities for exploring these phenomena.