Molecular mechanisms underlying the potentially adverse effects of folate

Regulatory mechanisms of one-carbon metabolism enzymes

One-carbon metabolism is a central metabolic pathway critical for the biosynthesis of several amino acids, methyl group donors, and nucleotides. The pathway mostly relies on the transfer of a carbon unit from the amino acid serine, through the cofactor folate (in its several forms), and to the ultimate carbon acceptors that include nucleotides and methyl groups used for methylation of proteins, RNA, and DNA. Nucleotides are required for DNA replication, DNA repair, gene expression, and protein translation, through ribosomal RNA. Therefore, the one-carbon metabolism pathway is essential for cell growth and function in all cells, but is specifically important for rapidly proliferating cells. The regulation of one-carbon metabolism is a critical aspect of the normal and pathological function of the pathway, such as in cancer, where hijacking these regulatory mechanisms feeds an increased need for nucleotides. One-carbon metabolism is regulated at several levels: via gene expression, posttranslational modification, subcellular compartmentalization, allosteric inhibition, and feedback regulation. In this review, we aim to inform the readers of relevant one-carbon metabolism regulation mechanisms and to bring forward the need to further study this aspect of one-carbon metabolism. The review aims to integrate two major aspects of cancer metabolism-signaling downstream of nutrient sensing and one-carbon metabolism, because while each of these is critical for the proliferation of cancerous cells, their integration is critical for comprehensive understating of cellular metabolism in transformed cells and can lead to clinically relevant insights.

Probing Folate-Responsive and Stage-Sensitive Metabolomics and Transcriptional Co-Expression Network Markers to Predict Prognosis of Non-Small Cell Lung Cancer Patients

Tumour metabolomics and transcriptomics co-expression network as related to biological folate alteration and cancer malignancy remains unexplored in human non-small cell lung cancers (NSCLC). To probe the diagnostic biomarkers, tumour and pair lung tissue samples (n = 56) from 97 NSCLC patients were profiled for ultra-performance liquid chromatography tandem mass spectrometry (UPLC/MS/MS)-analysed metabolomics, targeted transcriptionomics, and clinical folate traits. Weighted Gene Co-expression Network Analysis (WGCNA) was performed. Tumour lactate was identified as the top VIP marker to predict advance NSCLC (AUC = 0.765, Sig = 0.017, CI 0.58-0.95). Low folate (LF)-tumours vs. adjacent lungs displayed higher glycolytic index of lactate and glutamine-associated amino acids in enriched biological pathways of amino sugar and glutathione metabolism specific to advance NSCLCs. WGCNA classified the green module for hub serine-navigated glutamine metabolites inversely associated with tumour and RBC folate, which module metabolites co-expressed with a predominant up-regulation of LF-responsive metabolic genes in glucose transport (GLUT1), de no serine synthesis (PHGDH, PSPH, and PSAT1), folate cycle (SHMT1/2 and PCFR), and down-regulation in glutaminolysis (SLC1A5, SLC7A5, GLS, and GLUD1). The LF-responsive WGCNA markers predicted poor survival rates in lung cancer patients, which could aid in optimizing folate intervention for better prognosis of NSCLCs susceptible to folate malnutrition.

Exploratory Metabolomics Underscores the Folate Enzyme ALDH1L1 as a Regulator of Glycine and Methylation Reactions

Folate (vitamin B9) is involved in one-carbon transfer reactions and plays a significant role in nucleic acid synthesis and control of cellular proliferation, among other key cellular processes. It is now recognized that the role of folates in different stages of carcinogenesis is complex, and more research is needed to understand how folate reactions become dysregulated in cancers and the metabolic consequences that occur as a result. ALDH1L1 (cytosolic 10-formyltetrahydrofolate dehydrogenase), an enzyme of folate metabolism expressed in many tissues, is ubiquitously downregulated in cancers and is not expressed in cancer cell lines. The RT4 cell line (derived from papillary bladder cancer) which expresses high levels of ALDH1L1 represents an exception, providing an opportunity to explore the metabolic consequences of the loss of this enzyme. We have downregulated this protein in RT4 cells (shRNA driven knockdown or CRISPR driven knockout) and compared metabolomes of ALDH1L1-expressing and -deficient cells to determine if metabolic changes linked to the loss of this enzyme might provide proliferative and/or survival advantages for cancer cells. In this study, cell extracts were analyzed using Ultra High Performance Liquid Chromatography High Resolution Mass Spectrometry (UHPLC-HR-MS). A total of 13,339 signals were identified or annotated using an in-house library and public databases. Supervised and unsupervised multivariate analysis revealed metabolic differences between RT4 cells and ALDH1L1-deficient clones. Glycine (8-fold decrease) and metabolites derived from S-adenosylmethionine utilizing pathways were significantly decreased in the ALDH1L1-deficient clones, compared with RT4 cells. Other changes linked to ALDH1L1 downregulation include decreased levels of amino acids, Krebs cycle intermediates, and ribose-5-phosphate, and increased nicotinic acid. While the ALDH1L1-catalyzed reaction is directly linked to glycine biosynthesis and methyl group flux, its overall effect on cellular metabolism extends beyond immediate metabolic pathways controlled by this enzyme.

Dietary habits, nutrition and esophageal cancer: A case-control study on Kazakhs in Xinjiang

OBJECTIVE

To explore associations between dietary habits and esophageal epithelial cell carcinoma (ESCC) and provide a potential direction for exploring how different dietary habits and nutrient intake might affect ESCC development.

METHODS

198 ESCC cases and 200 controls on Kazakhs were recruited in Xinjiang from 2010 to 2019 for a group-matched case-control study. The case group were recruited from the First Affiliated Hospital of Xinjiang Medical University and Affiliated Cancer Hospital of Xinjiang Medical University. The control population were recruited from two parts: hospital-based control and population-based control. The diagnosis was confirmed by histological examination. The food frequency questionnaire was used to investigate the dietary nutrients intake. Folic acid, vitamin B12, and DNA-methyltransferase 1(DNMT1) levels were measured in serum samples obtained from cases and controls.

RESULTS

The cholesterol intake of ESCC group was significantly higher than that of the control group while the intakes of protein, thiamin, riboflavin, folic acid, vitamin A, B6, C and E were significantly lower than the control group. Factors including lacking fresh vegetables and fruits, low educational level, low income, alcohol drinking, eating solid and dry food and smoked meat, dieting irregularly, salty taste preference, low serum folic acid level and high serum DNMT1 level were associated with increased risk of ESCC in Kazakhs.

CONCLUSION

Dietary habits and nutrient intake were associated with increased risk of ESCC in Kazakhs that may provide a potential direction for further studies.

Absorption and Tissue Distribution of Folate Forms in Rats: Indications for Specific Folate Form Supplementation during Pregnancy

Food fortification and folic acid supplementation during pregnancy have been implemented as strategies to prevent fetal malformations during pregnancy. However, with the emergence of conditions where folate metabolism and transport are disrupted, such as folate receptor alpha autoantibody (FRαAb)-induced folate deficiency, it is critical to find a folate form that is effective and safe for pharmacologic dosing for prolonged periods. Therefore, in this study, we explored the absorption and tissue distribution of folic acid (PGA), 5-methyl-tetrahydrofolate (MTHF), l-folinic acid (levofolinate), and d,l-folinic acid (Leucovorin) in adult rats. During absorption, all forms are converted to MTHF while some unconverted folate form is transported into the blood, especially PGA. The study confirms the rapid distribution of absorbed folate to the placenta and fetus. FRαAb administered, also accumulates rapidly in the placenta and blocks folate transport to the fetus and high folate concentrations are needed to circumvent or overcome the blocking of FRα. In the presence of FRαAb, both Leucovorin and levofolinate are absorbed and distributed to tissues better than the other forms. However, only 50% of the leucovorin is metabolically active whereas levofolinate is fully active and generates higher tetrahydrofolate (THF). Because levofolinate can readily incorporate into the folate cycle without needing methylenetetrahydrofolate reductase (MTHFR) and methionine synthase (MS) in the first pass and is relatively stable, it should be the folate form of choice during pregnancy, other disorders where large daily doses of folate are needed, and food fortification.

Sex-Specific Metabolic Effects of Dietary Folate Withdrawal in Wild-Type and Aldh1l1 Knockout Mice

ALDH1L1 (10-formyltetrahydrofolate dehydrogenase), an enzyme of folate metabolism, is highly expressed in the liver. It regulates the overall flux of folate-bound one-carbon groups by converting 10-formyltetrahydrofolate to tetrahydrofolate and CO2 in a NADP+-dependent reaction. Our previous study revealed that Aldh1l1 knockout (KO) mice have an altered liver metabotype with metabolic symptoms of folate deficiency when fed a standard chow diet containing 2 ppm folic acid. Here we performed untargeted metabolomic analysis of liver and plasma of KO and wild-type (WT) male and female mice fed for 16 weeks either standard or folate-deficient diet. OPLS-DA, a supervised multivariate technique that was applied to 6595 and 10,678 features for the liver and plasma datasets, respectively, indicated that genotype and diet, alone or in combination, gave distinct metabolic profiles in both types of biospecimens. A more detailed analysis of affected metabolic pathways based on most confidently identified metabolites in the liver and plasma (OL1 and OL2a ontology level) indicated that the dietary folate restriction itself does not fully recapitulate the metabolic effect of the KO. Of note, dietary folate withdrawal enhanced the metabolic perturbations linked to the ALDH1L1 loss only for a subset of metabolites. Importantly, both the ALDH1L1 loss and dietary folate deficiency produced sex-specific metabolic effects.

The potential use of folate and its derivatives in treating psychiatric disorders: A systematic review

OBJECTIVES

To examine the strengths and limitations of existing data to provide guidance for the use of folate supplements as treatment, with or without other psychotropic medications, in various psychiatric disorders. To identify area for further research in terms of the biosynthesis of mechanism of folate and genetic variants in metabolic pathway in human.

METHODS

A systematic review of published literature following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, to assess whether folate supplements are beneficial in certain psychiatric disorders (depression, bipolar disorder, schizophrenia, autism spectrum disorder, and attention deficit hyperactivity disorder). Methodology of this review is registered with Prospero (Registration number CRD 42021266605).

DATA SOURCES

Eligible studies were identified using a systematic search of four electronic databases: Embase, Pubmed, PsycINFO, and Cochrane. The search strategy covered the time period from 1974 to August 16th, 2021. Therefore, this review examines randomized control trials or open-label trials completed during this period.

RESULTS

We identified 23 studies of folate supplements in various psychiatric disorders for critical review. Of these, 9 studies investigated the efficacy of folate supplements in major depressive disorders, 5 studies in schizophrenia, 6 studies in autism spectrum disorder, 2 studies in bipolar affective disorder and 1 study in attention deficit hyperactive disorder. The most consistent finding association of oral levomefolic acid or 5-methylfolate with improvement in clinical outcomes in mental health conditions as mentioned above, especially in major depressive disorder (including postpartum and post-menopausal depression), schizophrenia, autism spectrum disorder, attention deficit hyperactivity disorder and bipolar affective disorder. Folate supplements were well tolerated.

LIMITATION

Our results are not representative of all types of studies such as case reports or case series studies, nor are they representative of the studies conducted in languages that are not in English or not translated in English.

CONCLUSION

Increasing evidence from clinical trials consistently demonstrate folate supplements, especially levomefolic acid or 5-methylfolate, may improve clinical outcomes for certain psychiatric diseases, especially as an adjunct pharmacotherapy with minimal side effects.

Dietary Folic Acid Alters Metabolism of Multiple Vitamins in a CerS6- and Sex-Dependent Manner

Folic acid, an oxidized synthetic pro-vitamin B₉, is widely used in vitamin supplement formulations and food fortification to maintain optimal folate status in humans. Studies on folic acid (FA) efficiency in improving folate status and correcting folate deficiency pathologies are abundant, but precise knowledge of FA effects on human and animal tissues is not available. In our recent study, 10-week-old wild-type and CerS6 knockout (KO) mice were placed on FA-deficient, control, or FA over-supplemented diet for 4 weeks. Untargeted metabolomics characterization of mouse liver, brain, and testes tissues after the dietary treatment revealed profound effects of FA on the liver metabolome. Here, we present the analysis of dietary FA effects on tissue concentrations of other vitamins in mice. Despite the expectation that identical dietary supply of the vitamins (excluding FA) to each group should support similar tissue vitamins concentrations, metabolomics data demonstrate significant alterations of tissue concentrations of multiple vitamins by different levels of FA supplementation that were sex- and genotype-dependent. Moreover, we found significant differences in the liver concentration of retinol, thiamin diphosphate, pantetheine, pyridoxal, and pyridoxamine between males and females. While the liver had more changes in vitamins and vitamin derivative levels, the brain tissue and testes also showed changes linked to FA supplementation. Over-supplementation with FA had negative effects on concentrations of vitamins A, B₁, B₂, and B₆, or their metabolites in the liver, but increased intermediates in coenzyme A (CoA) biosynthesis, as well as gamma/beta-tocopherol and phosphorylated forms of B₆ in the CerS6 KO brain. Overall, our data demonstrate that dietary FA supplementation significantly affects the metabolism of other vitamins, and that these effects depend on the CerS6 status and sex of the animal. Further research is required to determine whether the observed effects are specific to FA, and the mechanisms that are involved.

Computational algorithmic and molecular dynamics study of functional and structural impacts of non-synonymous single nucleotide polymorphisms in human DHFR gene

Human dihydrofolate reductase (DHFR) is a conserved enzyme that is central to folate metabolism and is widely targeted in pathogenic diseases as well as cancers. Although studies have reported the fact that genetic mutations in DHFR leads to a rare autosomal recessive inborn error of folate metabolism and drug resistance, there is a lack of an extensive study on how the deleterious non-synonymous SNPs (nsSNPs) disrupt its phenotypic effects. In this study, we aim at discovering the structural and functional consequences of nsSNPs in DHFR by employing a combined computational approach consisting of ten recently developed in silico tools for identification of damaging nsSNPs and molecular dynamics (MD) simulation for getting deeper insights into the magnitudes of damaging effects. Our study revealed the presence of 12 most deleterious nsSNPs affecting the native phenotypic effects, with three (R71T, G118D, Y122D) identified in the co-factor and ligand binding active sites. MD simulations also suggested that these three SNPs particularly Y122D, alter the overall structural flexibility and dynamics of the native DHFR protein which can provide more understandings into the crucial roles of these mutants in influencing the loss of DHFR function.

A Retrospective Cross-Sectional Cohort Trial Assessing the Prevalence of MTHFR Polymorphisms and the Influence of Diet on Platinum Resistance in Ovarian Cancer Patients

Ovarian cancer has the lowest survival rate in gynaecologic malignancies with a 5-year survival rate of 43%. Platinum resistance is one of the main drivers of ovarian cancer mortality, of which aberrant methylation has been cited as a significant contributor. Understanding the essential role of the methylenetetrahydrofolate reductase enzyme (MTHFR) on DNA synthesis and repair, and how nutrient status can vastly affect its performance, led to the investigation of MTHFR status and dietary influence on platinum response in epithelial ovarian cancer (EOC) patients. Twenty-five adult female patients who completed first-line platinum-based chemotherapy for primary ovarian cancer were selected from Icon Cancer Centres in Australia. Participants were grouped based on platinum response. A full medical and family history, food frequency questionnaire and single blood test were completed, testing for MTHFR polymorphisms, serum folate, serum and active B12 and homocysteine levels. Nineteen of twenty-five participants had an MTHFR polymorphism. Of those, 20% were compound heterozygous, 12% were heterozygous C677T (CT), 4% homozygous C677T, 12% homozygous A1298C and 28% were heterozygous A1298C (AC). Statistically significant associations were found between dietary zinc (p = 0.0086; 0.0030; 0.0189) and B12 intakes in CT genotypes (p = 0.0157; 0.0030; 0.0068) indicating that zinc or vitamin B12 intakes below RDI were associated with this genotype. There were strong associations of vitamin B6 intakes in AC genotypes (p = 0.0597; 0.0547; 0.0610), and dietary folate in compound heterozygotes with sensitive and partially sensitive disease (p = 0.0627; 0.0510). There were also significant associations between serum folate (p = 0.0478) and dietary B12 (p = 0.0350) intakes above RDI and platinum sensitivity in wild-types as well as strong associations with homocysteine levels (p = 0.0886) and zinc intake (p = 0.0514). Associations with dietary B12 (p = 0.0514) and zinc intakes (p = 0.0731) were also strong in resistant wild types. Results indicate that dietary zinc, B12 and B6 intakes may be associated with platinum sensitivity dependent on MTHFR genotype. These results require further research to clarify the dosages necessary to elicit a response; however, they provide a novel foundation for acknowledging the role of diet on treatment response in EOC.

Ceramide synthase 6 mediates sex-specific metabolic response to dietary folic acid in mice

Folic acid-fortified foods and multi-vitamin supplements containing folic acid (FA) are widely used around the world, but the exact mechanisms/metabolic effects of FA are not precisely identified. We have demonstrated that Ceramide Synthase 6 (CerS6) and C_16:0-ceramide mediate response to folate stress in cultured cells. Here we investigated the dietary FA effects on mouse liver metabolome, with a specific focus on sphingolipids, CerS6 and C_16:0-ceramide. Wild-type and CerS6^-/- mice were fed FA-deficient, control, or FA over-supplemented diets for 4 weeks. After dietary treatment, liver concentrations of ceramides, sphingomyelins and hexosylceramides were measured by LC-MS/MS and complemented by untargeted metabolomic characterization of mouse livers. Our study shows that alterations in dietary FA elicit multiple sphingolipid responses mediated by CerS6 in mouse livers. Folic acid-deficient diet elevated C_14:0-, C_18:0- and C_20:0- but not C_16:0-ceramide in WT male and female mice. Additionally, FA over-supplementation increased multiple sphingomyelin species, including total sphingomyelins, in both sexes. Of note, concentrations of C_14:0- and C_16:0-ceramides and hexosylceramides were significantly higher in female livers than in male. The latter were increased by FD diet, with no difference between sexes in total pools of these sphingolipid classes. Untargeted liver metabolomic analysis concurred with the targeted measurements and showed broad effects of dietary FA and CerS6 status on multiple lipid classes including sex-specific effects on phosphatidylethanolamines and diacylglycerols. Our study demonstrates that both dietary FA and CerS6 status exhibit pleiotropic and sex-dependent effects on liver metabolism, including hepatic sphingolipids, diacylglycerols, long chain fatty acids, and phospholipids.

Properties and reactivity of the folic acid and folate photoproduct 6-formylpterin

Folates (vitamin B9) are essential components of our diet and our gut microbiota. They are omnipresent in our cells and blood. Folates are necessary for DNA synthesis, methylation, and other vital bioprocesses. Folic acid (FA), as the synthetic form of folates, is largely found in supplements and fortified foods. FA and folate drugs are also extensively used as therapeutics. Therefore, we are continuously exposed to the pterin derivatives, and their photo-degradation products, such as 6-formylpterin (6-FPT) and pterin-6-carboxylic acid. During ultraviolet radiation, these two photolytic products generate reactive oxygen species (ROS) responsible for the cellular oxidative stress. 6-FPT can exhibit variable pro/anti-oxidative roles depending on the cell type and its environment (acting as a cell protector in normal cells, or as an enhancer of drug-induced cell death in cancer cells). The ROS-modulating capacity of 6-FPT is well-known, whereas its intrinsic reactivity has been much less investigated. Here, we have reviewed the properties of 6-FPT and highlighted its capacity to form covalent adducts with the ROS-scavenging drug edaravone (used to treat stroke and amyotrophic lateral sclerosis) as well as its implication in immune surveillance. 6-FPT and its analogue acetyl-6-FPT function as small molecule antigens, recognized by the major histocompatibility complex-related class I-like molecule, MR1, for presentation to mucosal-associated invariant T (MAIT) cells. As modulators of the MR1/MAIT machinery, 6-FPT derivatives could play a significant immuno-regulatory role in different diseases. This brief review shed light on the multiple properties and cellular activities of 6-FPT, well beyond its primary ROS-generating activity.

The Incoherent Fluctuation of Folate Pools and Differential Regulation of Folate Enzymes Prioritize Nucleotide Supply in the Zebrafish Model Displaying Folate Deficiency-Induced Microphthalmia and Visual Defects

Objective

Congenital eye diseases are multi-factorial and usually cannot be cured. Therefore, proper preventive strategy and understanding the pathomechanism underlying these diseases become important. Deficiency in folate, a water-soluble vitamin B, has been associated with microphthalmia, a congenital eye disease characterized by abnormally small and malformed eyes. However, the causal-link and the underlying mechanism between folate and microphthalmia remain incompletely understood.

Methods

We examined the eye size, optomotor response, intracellular folate distribution, and the expression of folate-requiring enzymes in zebrafish larvae displaying folate deficiency (FD) and ocular defects.

Results

FD caused microphthalmia and impeded visual ability in zebrafish larvae, which were rescued by folate and dNTP supplementation. Cell cycle analysis revealed cell accumulation at S-phase and sub-G1 phase. Decreased cell proliferation and increased apoptosis were found in FD larvae during embryogenesis in a developmental timing-specific manner. Lowered methylenetetrahydrofolate reductase (mthfr) expression and up-regulated methylenetetrahydrofolate dehydrogenase (NADP⁺-dependent)-1-like (mthfd1L) expression were found in FD larvae. Knocking-down mthfd1L expression worsened FD-induced ocular anomalies; whereas increasing mthfd1L expression provided a protective effect. 5-CH₃-THF is the most sensitive folate pool, whose levels were the most significantly reduced in response to FD; whereas 10-CHO-THF levels were less affected. 5-CHO-THF is the most effective folate adduct for rescuing FD-induced microphthalmia and defective visual ability.

Conclusion

FD impeded nucleotides formation, impaired cell proliferation and differentiation, caused apoptosis and interfered active vitamin A production, contributing to ocular defects. The developmental timing-specific and incoherent fluctuation among folate adducts and increased expression of mthfd1L in response to FD reflect the context-dependent regulation of folate-mediated one-carbon metabolism, endowing the larvae to prioritize the essential biochemical pathways for supporting the continuous growth in response to folate depletion.

Knockout of Putative Tumor Suppressor Aldh1l1 in Mice Reprograms Metabolism to Accelerate Growth of Tumors in a Diethylnitrosamine (DEN) Model of Liver Carcinogenesis

Simple Summary

Cancers often loose the enzyme of folate metabolism ALDH1L1. We proposed that such loss is advantageous for the malignant tumor growth and tested this hypothesis in mice proficient or deficient (gene knockout) in ALDH1L1 expression. Liver cancer in both groups was induced by injection of chemical carcinogen diethylnitrosamine. While the number of tumors observed in ALDH1L1 proficient and deficient mice was similar, tumors grew faster and to a larger size in the knockout mice. We conclude that the ALDH1L1 loss promotes liver tumor growth without affecting tumor initiation or multiplicity. Accelerated growth of tumors lacking the enzyme was linked to several metabolic pathways, which are beneficial for rapid proliferation.

Abstract

Cytosolic 10-formyltetrahydrofolate dehydrogenase (ALDH1L1) is commonly downregulated in human cancers through promoter methylation. We proposed that ALDH1L1 loss promotes malignant tumor growth. Here, we investigated the effect of the Aldh1l1 mouse knockout (Aldh1l1^−/−) on hepatocellular carcinoma using a chemical carcinogenesis model. Fifteen-day-old male Aldh1l1 knockout mice and their wild-type littermate controls (Aldh1l1^+/+) were injected intraperitoneally with 20 μg/g body weight of DEN (diethylnitrosamine). Mice were sacrificed 10, 20, 28, and 36 weeks post-DEN injection, and livers were examined for tumor multiplicity and size. We observed that while tumor multiplicity did not differ between Aldh1l1^−/− and Aldh1l1^+/+ animals, larger tumors grew in Aldh1l1^−/− compared to Aldh1l1^+/+ mice at 28 and 36 weeks. Profound differences between Aldh1l1^−/− and Aldh1l1^+/+ mice in the expression of inflammation-related genes were seen at 10 and 20 weeks. Of note, large tumors from wild-type mice showed a strong decrease of ALDH1L1 protein at 36 weeks. Metabolomic analysis of liver tissues at 20 weeks showed stronger differences in Aldh1l1^+/+ versus Aldh1l1^−/− metabotypes than at 10 weeks, which underscores metabolic pathways that respond to DEN in an ALDH1L1-dependent manner. Our study indicates that Aldh1l1 knockout promoted liver tumor growth without affecting tumor initiation or multiplicity.

Metabolic Response of Triple-Negative Breast Cancer to Folate Restriction

Background: Triple-negative breast cancers (TNBCs), accounting for approximately 15% of breast cancers, lack targeted therapy. A hallmark of cancer is metabolic reprogramming, with one-carbon metabolism essential to many processes altered in tumor cells, including nucleotide biosynthesis and antioxidant defenses. We reported that folate deficiency via folic acid (FA) withdrawal in several TNBC cell lines results in heterogenous effects on cell growth, metabolic reprogramming, and mitochondrial impairment. To elucidate underlying drivers of TNBC sensitivity to folate stress, we characterized in vivo and in vitro responses to FA restriction in two TNBC models differing in metastatic potential and innate mitochondrial dysfunction. Methods: Metastatic MDA-MB-231 cells (high mitochondrial dysfunction) and nonmetastatic M-Wnt cells (low mitochondrial dysfunction) were orthotopically injected into mice fed diets with either 2 ppm FA (control), 0 ppm FA, or 12 ppm FA (supplementation; in MDA-MB-231 only). Tumor growth, metabolomics, and metabolic gene expression were assessed. MDA-MB-231 and M-Wnt cells were also grown in media with 0 or 2.2 µM FA; metabolic alterations were assessed by extracellular flux analysis, flow cytometry, and qPCR. Results: Relative to control, dietary FA restriction decreased MDA-MB-231 tumor weight and volume, while FA supplementation minimally increased MDA-MB-231 tumor weight. Metabolic studies in vivo and in vitro using MDA-MB-231 cells showed FA restriction remodeled one-carbon metabolism, nucleotide biosynthesis, and glucose metabolism. In contrast to findings in the MDA-MB-231 model, FA restriction in the M-Wnt model, relative to control, led to accelerated tumor growth, minimal metabolic changes, and modest mitochondrial dysfunction. Increased mitochondrial dysfunction in M-Wnt cells, induced via chloramphenicol, significantly enhanced responsiveness to the cytotoxic effects of FA restriction. Conclusions: Given the lack of targeted treatment options for TNBC, uncovering metabolic vulnerabilities that can be exploited as therapeutic targets is an important goal. Our findings suggest that a major driver of TNBC sensitivity to folate restriction is a high innate level of mitochondrial dysfunction, which can increase dependence on one-carbon metabolism. Thus, folate deprivation or antifolate therapy for TNBCs with metabolic inflexibility due to their elevated levels of mitochondrial dysfunction may represent a novel precision-medicine strategy.

DNA Methylation Patterning and the Regulation of Beta Cell Homeostasis

Pancreatic beta cells play a central role in regulating glucose homeostasis by secreting the hormone insulin. Failure of beta cells due to reduced function and mass and the resulting insulin insufficiency can drive the dysregulation of glycemic control, causing diabetes. Epigenetic regulation by DNA methylation is central to shaping the gene expression patterns that define the fully functional beta cell phenotype and regulate beta cell growth. Establishment of stage-specific DNA methylation guides beta cell differentiation during fetal development, while faithful restoration of these signatures during DNA replication ensures the maintenance of beta cell identity and function in postnatal life. Lineage-specific transcription factor networks interact with methylated DNA at specific genomic regions to enhance the regulatory specificity and ensure the stability of gene expression patterns. Recent genome-wide DNA methylation profiling studies comparing islets from diabetic and non-diabetic human subjects demonstrate the perturbation of beta cell DNA methylation patterns, corresponding to the dysregulation of gene expression associated with mature beta cell state in diabetes. This article will discuss the molecular underpinnings of shaping the islet DNA methylation landscape, its mechanistic role in the specification and maintenance of the functional beta cell phenotype, and its dysregulation in diabetes. We will also review recent advances in utilizing beta cell specific DNA methylation patterns for the development of biomarkers for diabetes, and targeting DNA methylation to develop translational approaches for supplementing the functional beta cell mass deficit in diabetes.

Prevotella histicola Protects From Arthritis by Expansion of Allobaculum and Augmenting Butyrate Production in Humanized Mice

Bacterial therapeutics are the emergent alternatives in treating autoimmune diseases such as Rheumatoid Arthritis [RA]. P. histicola MCI 001 is one such therapeutic bacterium that has been proven to treat autoimmune diseases such as RA and multiple sclerosis [MS] in animal models. The present study characterized P. histicola MCI 001 isolated from a human duodenal biopsy, and evaluated its impact on the gut microbial and metabolic profile in a longitudinal study using the collagen-induced arthritis model in HLA-DQ8.AEo transgenic mice. P. histicola MCI 001 though closely related to the type strain of P. histicola, DSM 19854, differed in utilizing glycerol. In culture, P. histicola MCI 001 produced vitamins such as biotin and folate, and was involved in digesting complex carbohydrates and production of acetate. Colonization study showed that duodenum was the predominant niche for the gavaged MCI 001. A longitudinal follow-up of gut microbial profile in arthritic mice treated with MCI 001 suggested that dysbiosis caused due to arthritis was partially restored to the profile of naïve mice after treatment. A taxon-level analysis suggested an expansion of intestinal genus Allobaculum in MCI001 treated arthritic mice. Eubiosis achieved post treatment with P. histicola MCI 001 was also reflected in the increased production of short-chain fatty acids [SCFAs]. Present study suggests that the treatment with P. histicola MCI 001 leads to an expansion of Allobaculum by increasing the availability of simple carbohydrates and acetate. Restoration of microbial profile and metabolites like butyrate induce immune and gut homeostasis.

Prognostic Significance of Plasma Folate and Cobalamin Concentrations in Non-Muscle-Invasive Bladder Cancer: A Prospective Cohort Study

This cohort study aimed to investigate prognostic significance of plasma folate and cobalamin in non-muscle-invasive bladder cancer (NMIBC). A total of 177 NMIBC patients were followed over a period extending to 6 years. Cox regression models were applied to estimate risks for recurrence and progression according to plasma vitamins tertiles. Compared to first tertile, third tertile of plasma folate [HR (95% CI), 10.5 (1.32-83.4); p = 0.026] was associated, and of plasma cobalamin [2.12 (0.63-7.25); p = 0.116] tended to be associated with higher risk for progression. NIMBC patients with high folate/cobalamin statuses should make the physician more alert for a likely poor outcome.

Moderately high folate level may offset the effects of aberrant DNA methylation of P16 and P53 genes in esophageal squamous cell carcinoma and precancerous lesions

BACKGROUND

This study evaluated gene-nutrition interactions between folate and the aberrant DNA methylation of tumor suppressor genes in different stages of carcinogenesis of esophageal squamous cell carcinoma (ESCC).

METHODS

Two hundred ESCC cases, 200 esophageal precancerous lesion (EPL) cases, and 200 controls matched by age (± 2 years) and gender were used for this study. Baseline data and dietary intake information was collected via questionnaire. The serum folate levels and methylation status of promoter regions of p16 and p53 were detected.

RESULTS

The interactions of increased serum folate level with unmethylated p16 and p53 promoter regions were significantly associated with a reduced risk of both EPL and ESCC (p for interaction < 0.05). The interactions of the lowest quartile of serum folate level with p16 or p53 methylation was significantly associated with an increased risk of ESCC (OR = 2.96, 95% CI, 1.45-6.05; OR = 2.34, 95% CI, 1.15-4.75). An increased serum folate level was also related to a decreasing trend of EPL and ESCC risks when p16 or p53 methylation occurred. The interaction of spinach, Chinese cabbage, liver and bean intake with unmethylated p16 and p53 was significantly associated with a reduced risk of EPL or ESCC (p for interaction < 0.05).

CONCLUSIONS

The interactions between a high folate level and unmethylated p16 and p53 promoter regions may have a strong preventive effect on esophageal carcinogenesis. Additionally, a high folate level may offset the tumor-promoting effects of aberrant DNA methylation of the genes, but it is also noteworthy that a very high level of folate may not have a protective effect on EPL in some cases.

Low folate intake and serum levels are associated with higher body mass index and abdominal fat accumulation: a case control study

BACKGROUND

The link between folate metabolism and obesity has recently been underlined, suggesting that folate deficiency may lead to body weight gain and adiposity. We thus wished to determine whether the inefficiency in folate metabolism caused by genetic variation in the MTHFR and DHFR genes in folate metabolism, or inadequate folate intake, is associated with obesity.

METHODS

A case-control study including 421 healthy participants (aged 20-40) was performed in Poznań, Poland. The cases were 213 subjects with BMI > 25 kg/m2, while the controls were 208 subjects with BMI < 25 kg/m2. Genotyping of rs70991108 (DHFR) and rs1801133 (MTHFR) was performed using TaqMan probes. Serum folate concentrations were measured using an enzyme-linked immunosorbent assay and homocysteine was assessed with high performance liquid chromatography.

RESULTS

Subjects with overweight and obesity had 12% lower folate intake (p < 0.05) and 8.5% lower folate serum concentrations (p < 0.01) than the controls. Serum folate concentrations and folate intake were inversely associated with body fat percentage (p < 0.05) and waist circumference (p < 0.05 and p < 0.001, respectively). Serum folate concentration, though not folate intake, was negatively associated with WHR and BMI (p < 0.05, for both associations).

CONCLUSIONS

Lower folate intake and serum levels are weakly, but independently, associated with greater body weight and central adiposity in people aged 20-40. MTHFR and DHFR polymorphism seems not to have significant impact on body weight.

Promoter Hypermethylation of Wnt/β-catenin Signaling Pathway Inhibitor WIF-1 Gene and its Association with MTHFR C677T Polymorphism in Patients with Colorectal Cancer

OBJECTIVES

Colorectal cancer (CRC) is a common malignancy with a high rate of mortality. The dysregulation of genes involved in the Wnt/β-catenin signaling pathway is a common finding in cancers. Wnt-inhibitory factor-1 (WIF-1) suppresses the Wnt/β-catenin signaling pathway and its inactivation by genetics and epigenetic changes may cause cancer. We investigated the DNA methylation status of the WIF-1 gene in patients with CRC and its interaction with MTHFR C677T polymorphism, a known modifier of methylation reaction.

METHODS

We investigated 50 cancerous tissues and the adjacent non-cancerous tissue. Genomic DNA was extracted using a commercial kit and was treated by sodium bisulfite. Methylation-specific PCR was used for methylation analysis, and restriction fragment length polymorphism PCR to analyze the C677T polymorphism of the MTHFR gene.

RESULTS

The frequency of WIF1 promoter DNA methylation was significantly higher in cancerous tissue than adjacent non-cancerous tissue (52.0% vs. 8.0%; p < 0.001). WIF1 promoter DNA methylation status showed a significant association only with tumor location (p = 0.009). Carriers of TT genotype and T allele of MTHFR C677T polymorphism had a significantly higher frequency of unmethylated WIF1 gene than methylated WIF-1 gene in cancerous tissue (p = 0.025 and p = 0.001, respectively).

CONCLUSIONS

Promoter DNA hypermethylation of the WIF-1 gene is a significant risk factor for CRC development, which was significantly associated with tumor location only. The significant association of TT genotype and T allele of MTHFR C677T polymorphism with unmethylated WIF-1 gene suggests a protective role for this common polymorphism against methylation-induced development of CRC.

Effects of folic acid withdrawal on transcriptomic profiles in murine triple-negative breast cancer cell lines

We have previously shown that withdrawal of folic acid led to metabolic reprogramming and a less aggressive phenotype in a mouse cell model of triple-negative breast cancer (TNBC). Herein, we evaluate the effects of folic acid withdrawal on transcriptomic profiles in these cells. Murine cell lines were originally derived from a pool of spontaneous mammary tumors grown in MMTV-Wnt1 transgenic mice. Based on their differential molecular characteristics and metastatic potential, these cell lines were previously characterized as non-metastatic epithelial (E-Wnt), non-metastatic mesenchymal (M-Wnt) and metastatic mesenchymal (metM-Wnt^liver) cells. Using custom two-color 180K Agilent microarrays, we have determined gene expression profiles for three biological replicates of each subtype kept on standard medium (2.2 μM folic acid) or folic acid-free medium for 72 h. The analyses revealed that more genes were differentially expressed upon folic acid withdrawal in M-Wnt cells (1884 genes; Benjamini-Hochberg-adjusted P-value <0.05) compared to E-Wnt and metM-Wnt^liver cells (108 and 222 genes, respectively). Pathway analysis has identified that type I interferon signaling was strongly affected by folic acid withdrawal, with interferon-responsive genes consistently being upregulated upon folic acid withdrawal in M-Wnt cells. Of note, repressed interferon signaling has been established as one of the characteristics of aggressive human TNBC, and hence reactivation of this pathway may be a promising therapeutic approach. Overall, while our study indicates that the response to folic acid withdrawal varies by molecular subtype and cellular phenotype, it also underscores the necessity to further investigate one-carbon metabolism as a potential therapeutic means in the treatment of advanced TNBC.

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.

Untargeted adductomics of newborn dried blood spots identifies modifications to human serum albumin associated with childhood leukemia

The developing fetus is exposed to chemicals, which are metabolized to electrophiles that form adducts with nucleophilic Cys34 of human serum albumin (HSA). By measuring these adducts in neonatal blood spots (NBS), we obtain information regarding fetal exposures during the last month of gestation. To discover potential risk factors for childhood leukemia resulting from in utero exposures, we used untargeted adductomics to measure HSA-Cys34 adducts in 782 archived NBS, collected from incident cases of childhood acute lymphoblastic leukemia (ALL) or acute myeloid leukemia (AML) and matched population-based controls. Among a total of 28 Cys34 modifications that were measured, we found no differences in adduct abundances between childhood leukemia cases and controls overall. However, cases of T-cell ALL had higher abundances of adducts of reactive carbonyl species and a Cys34 disulfide of homocysteine was present at lower levels in AML cases. These results suggest that oxidative stress and lipid peroxidation may be etiologic factors of T-cell ALL, and alterations in one-carbon metabolism and epigenetic changes may be predictors of AML. Future replication of the results with larger sample sizes is necessary.

Supplementation with 5-formyltetrahydrofolate alleviates ultraviolet B-inflicted oxidative damage in folate-deficient zebrafish

Ultraviolet (UV) is an omnipresent environmental carcinogen transmitted by sunlight. Excessive UV irradiation has been correlated to an increased risk of skin cancers. UVB, the most mutagenic component among the three UV constituents, causes damage mainly through inducing DNA damage and oxidative stress. Therefore, strategies or nutrients that strengthen an individual's resistance to UV-inflicted harmful effects shall be beneficial. Folate is a water-soluble B vitamin essential for nucleotides biosynthesis, and also a strong biological antioxidant, hence a micronutrient with potential of modulating individual's vulnerability to UV exposure. In this study, we investigated the impact of folate status on UV sensitivity and the protective activity of folate supplementation using a zebrafish model. Elevated reactive oxygen species (ROS) level and morphological injury were observed in the larvae exposed to UVB, which were readily rescued by supplementing with folic acid, 5-formyltetrahydrofolate (5-CHO-THF) and N-acetyl-L-cysteine (NAC). The UVB-inflicted abnormalities and mortality were worsened in Tg(hsp:EGFP-γGH) larvae displaying folate deficiency. Intriguingly, only supplementation with 5-CHO-THF, as opposed to folic acid, offered significant and consistent protection against UVB-inflicted oxidative damage in the folate-deficient larvae. We concluded that the intrinsic folate status correlates with the vulnerability to UVB-induced damage in zebrafish larvae. In addition, 5-CHO-THF surpassed both folic acid and NAC in preventing UVB-inflicted oxidative stress and injury in our current experimental zebrafish model.

The Role of Single-Nucleotide Polymorphisms in the Function of Candidate Tumor Suppressor ALDH1L1

Folate (vitamin B9) is a common name for a group of coenzymes that function as carriers of chemical moieties called one-carbon groups in numerous biochemical reactions. The combination of these folate-dependent reactions constitutes one-carbon metabolism, the name synonymous to folate metabolism. Folate coenzymes and associated metabolic pathways are vital for cellular homeostasis due to their key roles in nucleic acid biosynthesis, DNA repair, methylation processes, amino acid biogenesis, and energy balance. Folate is an essential nutrient because humans are unable to synthesize this coenzyme and must obtain it from the diet. Insufficient folate intake can ultimately increase risk of certain diseases, most notably neural tube defects. More than 20 enzymes are known to participate in folate metabolism. Single-nucleotide polymorphisms (SNPs) in genes encoding for folate enzymes are associated with altered metabolism, changes in DNA methylation and modified risk for the development of human pathologies including cardiovascular diseases, birth defects, and cancer. ALDH1L1, one of the folate-metabolizing enzymes, serves a regulatory function in folate metabolism restricting the flux of one-carbon groups through biosynthetic processes. Numerous studies have established that ALDH1L1 is often silenced or strongly down-regulated in cancers. The loss of ALDH1L1 protein positively correlates with the occurrence of malignant tumors and tumor aggressiveness, hence the enzyme is viewed as a candidate tumor suppressor. ALDH1L1 has much higher frequency of non-synonymous exonic SNPs than most other genes for folate enzymes. Common SNPs at the polymorphic loci rs3796191, rs2886059, rs9282691, rs2276724, rs1127717, and rs4646750 in ALDH1L1 exons characterize more than 97% of Europeans while additional common variants are found in other ethnic populations. The effects of these SNPs on the enzyme is not clear but studies indicate that some coding and non-coding ALDH1L1 SNPs are associated with altered risk of certain cancer types and it is also likely that specific haplotypes define the metabolic response to dietary folate. This review discusses the role of ALDH1L1 in folate metabolism and etiology of diseases with the focus on non-synonymous coding ALDH1L1 SNPs and their effects on the enzyme structure/function, metabolic role and association with cancer.

Changes in intracellular folate metabolism during high-dose methotrexate and Leucovorin rescue therapy in children with acute lymphoblastic leukemia

Background

Methotrexate (MTX) is an important anti-folate agent in pediatric acute lymphoblastic leukemia (ALL) treatment. Folinic acid rescue therapy (Leucovorin) is administered after MTX to reduce toxicity. Previous studies hypothesized that Leucovorin could ‘rescue’ both normal healthy cells and leukemic blasts from cell death. We assessed whether Leucovorin is able to restore red blood cell folate levels after MTX.

Methods

We prospectively determined erythrocyte folate levels (5-methyltetrahydrofolate (THF) and non-methyl THF) and serum folate levels in 67 children with ALL before start (T0) and after stop (T1) of HD-MTX and Leucovorin courses.

Results

Erythrocyte folate levels increased between T0 and T1 (mean ± SD: 416.7 ± 145.5 nmol/L and 641.2 ± 196.3 nmol/L respectively, p<0.001). This was due to an increase in 5-methyl THF levels (mean increase: 217.7 ± 209.5 nmol/L, p<0.001), whereas non-methyl THF levels did not change (median increase: 0.6 nmol/L [-9.9–11.1], p = 0.676). Serum folate levels increased between T0 and T1 (median increase: 29.2 nmol/L [32.9–74.0], p<0.001). Results were not significantly affected by age, sex, ALL immunophenotype and MTHFR c.677C>T genotype.

Conclusion

Intracellular folate levels accumulate after HD-MTX and Leucovorin therapy in children with ALL, suggesting that Leucovorin restores the intracellular folate pool. Future studies are necessary to assess concomitant lower uptake of MTX.

Circulating Micronutrient Biomarkers Are Associated With 3 Measures of Frailty: Evidence From the Irish Longitudinal Study on Ageing

OBJECTIVES

To examine the associations between 3 frailty instruments and circulating micronutrients in a large representative sample of older adults.

DESIGN

Cross-sectional data from a nationally representative cohort study conducted between October 2009 and July 2011.

PARTICIPANTS AND SETTING

Adults age ≥50 years (n = 4068) living in the community in Ireland.

MEASUREMENTS

Circulating micronutrients (lutein, zeaxanthin, folate, vitamin B-12, and vitamin D) were measured, transformed, and standardized. Frailty was assessed using the Frailty Phenotype, the Frailty Index, and the FRAIL Scale (fatigue, resistance, ambulation, illnesses, and loss of weight), instruments. Multinomial logistic regression determined associations between micronutrients and prefrailty or frailty. Models were adjusted for sociodemographic, lifestyle, health, and seasonal factors.

RESULTS

Adjusting for age, sex, and educational attainment, all 3 measures of frailty were associated with lower levels of lutein [relative risk ratios (RRRs): 0.43‒0.63], zeaxanthin (RRRs: 0.49‒0.63), and vitamin D (RRRs: 0.51‒0.75), and with the accumulation of micronutrient insufficiencies (RRRs: 1.42‒1.90). Attenuated but significant associations were also observed with all measures of prefrailty for lutein, vitamin D, and number of micronutrient insufficiencies. The associations with frailty persisted following additional adjustment for social, lifestyle, and health and seasonal factors, and following multiple test correction.

CONCLUSIONS AND IMPLICATIONS

We have presented the most consistent evidence in the largest study to date that micronutrient concentrations are associated with prefrailty and frailty in older adults. Our data suggest that low micronutrient status has potential as an easily modifiable marker and intervention target for frailty and supports further investigation into micronutrient supplementation and fortification to prevent frailty and disability among older adults.

Loss of ALDH1L1 folate enzyme confers a selective metabolic advantage for tumor progression

ALDH1L1 (cytosolic 10-formyltetrahydrofolate dehydrogenase) is the enzyme in folate metabolism commonly downregulated in human cancers. One of the mechanisms of the enzyme downregulation is methylation of the promoter of the ALDH1L1 gene. Recent studies underscored ALDH1L1 as a candidate tumor suppressor and potential marker of aggressive cancers. In agreement with the ALDH1L1 loss in cancer, its re-expression leads to inhibition of proliferation and to apoptosis, but also affects migration and invasion of cancer cells through a specific folate-dependent mechanism involved in invasive phenotype. A growing body of literature evaluated the prognostic value of ALDH1L1 expression for cancer disease, the regulatory role of the enzyme in cellular proliferation, and associated metabolic and signaling cellular responses. Overall, there is a strong indication that the ALDH1L1 silencing provides metabolic advantage for tumor progression at a later stage when unlimited proliferation and enhanced motility become critical processes for the tumor expansion. Whether the ALDH1L1 loss is involved in tumor initiation is still an open question.

Toward a better understanding of folate metabolism in health and disease

Folate metabolism is crucial for many biochemical processes, including purine and thymidine monophosphate (dTMP) biosynthesis, mitochondrial protein translation, and methionine regeneration. These biochemical processes in turn support critical cellular functions such as cell proliferation, mitochondrial respiration, and epigenetic regulation. Not surprisingly, abnormal folate metabolism has been causally linked with a myriad of diseases. In this review, we provide a historical perspective, delve into folate chemistry that is often overlooked, and point out various missing links and underdeveloped areas in folate metabolism for future exploration.

Plasma B-vitamin and one-carbon metabolites and risk of breast cancer before and after folic acid fortification in the United States

Prior epidemiologic findings for plasma folate and B-vitamins and breast cancer risk are inconsistent and have not assessed the influence of folic acid fortification. Therefore, we examined the associations of plasma folate, B₁₂ , pyridoxal 5'-phosphate (PLP), homocysteine, cysteine and cysteinylglycine with breast cancer risk, before and after fortification. We conducted a nested case-control study within the prospective Nurses' Health Study. In 1989-1990 (pre-fortification), 32,826 women donated a blood sample and 18,743 donated an additional blood sample in 2000-2001 (post-fortification). Between the first blood collection and 2006, 1874 incident breast cancer cases with at least one blood sample and 367 with two were 1:1 matched to controls. Conditional logistic regression was used to estimate relative risks (RR) and 95% confidence intervals (CI) adjusting for breast cancer risk factors. Overall, higher plasma folate, B₁₂ , PLP, homocysteine, cysteine and cysteinylglycine levels were not associated with breast cancer risk. Associations did not vary by in situ/invasive, hormone receptor status, or tumor molecular subtype. Additionally, associations were null before and after fortification. For example, the RR (95% CI) for the highest versus lowest tertile of 1990 (pre-fortification) plasma folate with 1990-2000 follow-up was 0.93 (0.75-1.16) and for the 2000 plasma folate (post-fortification) with 2000-2006 follow-up the RR (95% CI) was 1.17 (0.79-1.74). Plasma folate, B₁₂ , PLP, homocysteine, cysteine and cysteinylglycine were not significantly associated with breast cancer overall, before and after fortification, or with specific tumor molecular subtypes. However, long term associations (>8 years) after the implementation of fortification could not be examined.

Modulation of dietary folate with age confers selective hepatocellular epigenetic imprints through DNA methylation

The present study has been designed to determine the effect of folate modulation (deficiency/supplementation) with aging on the promoter methylation of tumor suppressor and proto-oncogenes to understand the underlying mechanism of epigenetic alterations. Folate deficiency was induced for 3 and 5 months in weanling, young and adult groups, and after 3 months of folate deficiency, they were repleted with physiological folate (2 mg/kg diet) and folate oversupplementation (8 mg/kg diet) for another 2 months. The methylation facet in the present study revealed that the combined effect of folate deficiency and aging decreased the methylation index. Folate deficiency with age resulted in the up-regulation of proto-oncogenes (C-MYC and C-JUN) and cell cycle regulator gene Cyclin E as a result of promoter hypomethylation. However, in case of tumor suppressor genes (p53, p15ink4b and p16ink4a), the expression levels were found to be decreased at transcriptional level due to promoter hypermethylation. Upon repletion with physiological folate and folate oversupplementation, we found down-regulation of proto-oncogenes and up-regulation of tumor suppressor genes as a result of promoter hypermethylation and hypomethylation, respectively. Deregulation of these important genes due to folate deficiency may contribute toward the pathogenesis at cellular level.

Combinatorial Treatment Effects in a Cell Culture Model of Alzheimer's Disease

BACKGROUND

Alzheimer's disease (AD) is the leading cause of dementia, and as its prevalence increases, so does its detrimental impact on society. The currently available therapies have limited efficacy, leaving AD patients on an irrevocably fatal path of this disease.

OBJECTIVE

The purpose of this study was to test efficacy of a novel combinatorial treatment approach to alleviate AD-like pathology.

METHODS

We selected four naturally occurring compounds and used them in different combinations to test their effect on AD-like pathology. Employing a well-established cell culture AD model system, we evaluated levels of several diverse biomarkers associated with a number of cellular pathways associated with AD. The readouts included: amyloid-β peptides, anti-inflammatory and anti-apoptotic proteins, oxidative enzymes, and reactive oxygen species.

RESULTS

Using this approach, we demonstrated that the compounds delivered in combination had higher efficacy than individual treatments. Specifically, we observed significant reduction in levels of the amyloid-β peptides, as well as pro-inflammatory proteins and reactive oxygen species. Similarly, delivery of compounds in combination resulted in an increased expression of anti-apoptotic proteins and anti-oxidative enzymes. Collectively, these modifications in AD pathology biomarkers reflect a promising therapeutic and preventive strategy to combat this disease.

CONCLUSION

The above findings support a novel therapeutic approach to address a currently unmet medical need, which would benefit not only AD patients and their caregivers, but also society as a whole.

ALDH1L1 and ALDH1L2 Folate Regulatory Enzymes in Cancer

Epidemiological studies implicate excess ethanol ingestion as a risk factor for several cancers and support the concept of a synergistic effect of chronic alcohol consumption and folate deficiency on carcinogenesis. Alcohol consumption affects folate-related genes and enzymes including two major folate-metabolizing enzymes, ALDH1L1 and ALDH1L2. ALDH1L1 (cytosolic 10-formyltetrahydrofolate dehydrogenase) is a regulatory enzyme in folate metabolism that controls the overall flux of one-carbon groups in folate-dependent biosynthetic pathways. It is strongly and ubiquitously down-regulated in malignant tumors via promoter methylation, and recent studies underscored this enzyme as a candidate tumor suppressor and potential marker of aggressive cancers. A related enzyme, ALDH1L2, is the mitochondrial homolog of ALDH1L1 encoded by a separate gene. In contrast to its cytosolic counterpart, ALDH1L2 is expressed in malignant tumors and cancer cell lines and was implicated in metastasis regulation. This review discusses the link between folate and cancer, modifying effects of alcohol consumption on folate-associated carcinogenesis, and putative roles of ALDH1L1 and ALDH1L2 in this process.

One crisis, diverse impacts-Tissue-specificity of folate deficiency-induced circulation defects in zebrafish larvae

Folate (vitamin B9) is an essential nutrient required for cell survival, proliferation, differentiation and therefore embryogenesis. Folate deficiency has been associated with many diseases, including congenital heart diseases and megaloblastic anemia, yet the mechanisms underlying these remains elusive. Here, we examine the impact of folate deficiency on the development of the circulation system using a zebrafish transgenic line which displays inducible folate deficiency. Impaired hematopoiesis includes decreased hemoglobin levels, decreased erythrocyte number, increased erythrocyte size and aberrant c-myb expression pattern were observed in folate deficient embryos. Cardiac defects, including smaller chamber size, aberrant cardiac function and cmlc2 expression pattern, were also apparent in folate deficient embryos. Characterization of intracellular folate content in folate deficiency revealed a differential fluctuation among the different folate derivatives that carry a single carbon group at different oxidation levels. Rescue attempts by folic acid and nucleotides resulted in differential responses among affected tissues, suggesting that different pathomechanisms are involved in folate deficiency-induced anomalies in a tissue-specific manner. The results of the current study provide an explanation for the inconsistent outcome observed clinically in patients suffering from folate deficiency and/or receiving folate supplementation. This study also supports the use of this model for further research on the defective cardiogenesis and hematopoiesis caused by folate deficiency.

Polyamines, folic acid supplementation and cancerogenesis

Clinical practice and experimental studies have shown the necessity of sufficient quantities of folic acid intake for normal embryogenesis and fetal development in the prevention of neural tube defects (NTDs) and neurological malformations. So, women of childbearing age must be sure to have an adequate folate intake periconceptionally, prior to and during pregnancy. Folic acid fortification of all enriched cereal grain product flour has been implemented in many countries. Thus, hundreds of thousands of people have been exposed to an increased intake of folic acid. Folate plays an essential role in the biosynthesis of methionine. Methionine is the principal aminopropyl donor required for polyamine biosynthesis, which is up-regulated in actively growing cells, including cancer cells. Folates are important in RNA and DNA synthesis, DNA stability and integrity. Clinical and epidemiological evidence links folate deficiency to DNA damage and cancer. On the other hand, long-term folate oversupplementation leads to adverse toxic effects, resulting in the appearance of malignancy. Considering the relationship of polyamines and rapidly proliferating tissues (especially cancers), there is a need for better investigation of the relationship between the ingestion of high amounts of folic acid in food supplementation and polyamine metabolism, related to malignant processes in the human body.

Metabolic Reprogramming by Folate Restriction Leads to a Less Aggressive Cancer Phenotype

Folate coenzymes are involved in biochemical reactions of one-carbon transfer, and deficiency of this vitamin impairs cellular proliferation, migration, and survival in many cell types. Here, the effect of folate restriction on mammary cancer was evaluated using three distinct breast cancer subtypes differing in their aggressiveness and metastatic potential: noninvasive basal-like (E-Wnt), invasive but minimally metastatic claudin-low (M-Wnt), and highly metastatic claudin-low (metM-Wnt^liver) cell lines, each derived from the same pool of MMTV-Wnt-1 transgenic mouse mammary tumors. NMR-based metabolomics was used to quantitate 41 major metabolites in cells grown in folate-free medium versus standard medium. Each cell line demonstrated metabolic reprogramming when grown in folate-free medium. In E-Wnt, M-Wnt, and metM-Wnt^liver cells, 12, 29, and 25 metabolites, respectively, were significantly different (P < 0.05 and at least 1.5-fold change). The levels of eight metabolites (aspartate, ATP, creatine, creatine phosphate, formate, serine, taurine and β-alanine) were changed in each folate-restricted cell line. Increased glucose, decreased lactate, and inhibition of glycolysis, cellular proliferation, migration, and invasion occurred in M-Wnt and metM-Wnt^liver cells (but not E-Wnt cells) grown in folate-free versus standard medium. These effects were accompanied by altered levels of several folate-metabolizing enzymes, indicating that the observed metabolic reprogramming may result from both decreased folate availability and altered folate metabolism. These findings reveal that folate restriction results in metabolic and bioenergetic changes and a less aggressive cancer cell phenotype.

IMPLICATIONS

Metabolic reprogramming driven by folate restriction represents a therapeutic target for reducing the burden of breast cancer. Mol Cancer Res; 15(2); 189-200. ©2016 AACR.

Rising rates of colorectal cancer among younger Iranians: is diet to blame?

BACKGROUND

Colorectal cancer (crc) is one of the most prevalent cancers in the world. Although the incidence of crc is currently very low in the older Iranian population compared with Western populations, young Iranians show a rising trend of crc-that is, the age-adjusted rate is close in the young Iranian population compared with the U.S. population, and the rate in older Iranians is much lower.

METHODS

To assess a putative relationship between diet and a rising rate of crc in younger Iranians, a combined text word and mesh heading search strategy identified relevant studies through Google Scholar and medline.

RESULTS

A critical look at diet among Iranians shows major issues that might be raising the risk for crc. There are also scenarios other than diet for the rise, such as the young age structure of the country. However, the actual scenario is more complex.

CONCLUSIONS

In Iran, crc is one of the most common incident cancers and a common cause of cancer death. Primary and secondary prevention-with attention to a healthy lifestyle, physical activity, and screening-should be enhanced in the general population.

High folic acid diet enhances tumour growth in PyMT-induced breast cancer

Background:

The B-vitamin folate is among the most studied bioactive food compound, and a dietary intake meeting the daily requirements has been found to reduce the risk of cancer and cardiovascular diseases as well as preventing neural tube defects during fetal development. Several countries have therefore introduced dietary fortification with folic acid. However, clinical and animal studies suggest that folic acid has a dual role in cancer development.

Methods:

During the period of initial tumour progression, MMTV-PyMT (MMTV-polyoma virus middle T) transgenic mice were fed with normal diet and high folic acid diet.

Results:

We found that PyMT-induced breast tumours highly express the cancer-specific folate receptor (FR), a feature they share with several human epithelial cancers in which expression of FRα correlates with tumour grade. Mice receiving a high folic acid diet displayed a significantly increased tumour volume compared with mice receiving normal diet. In the largest tumours, only found in mice on high folic acid diet, STAT3 was activated. In primary cells from PyMT tumours, STAT3 was activated upon treatment with folic acid in culture.

Conclusions:

Our results offer a novel molecular explanation for folic acid-induced growth of existing tumours.

Folate deficiency-triggered redox pathways confer drug resistance in hepatocellular carcinoma

Patients with hepatocellular carcinoma (HCC) are prone to folate deficiency (FD). Here we showed that, in cell line-specific manner, FD caused resistance to FD-induced oxidative stress and multi-drug resistance (MDR). This resistance was due to upregulation of glucose-regulated protein 78 (GRP78) and Survivin. Using siRNA and Epigallocatechin gallate (EGCG), we found that GRP78 and Survivin cooperatively conferred MDR by decreasing FD-induced ROS generation. Our data showed that FD increases GRP78 and Survivin, which serve as ROS inhibitors, causing MDR in HCC. We suggest that folate supplementation may enhance the efficacy of chemotherapy.

Perspectives on the design and methodology of periconceptional nutrient supplementation trials

Periconceptional supplementation could extend the period over which maternal and fetal nutrition is improved, but there are many challenges facing early-life intervention studies. Periconceptional trials differ from pregnancy supplementation trials, not only because of the very early or pre-gestational timing of nutrient exposure but also because they generate subsidiary information on participants who remain non-pregnant. The methodological challenges are more complex although, if well designed, they provide opportunities to evaluate concurrent hypotheses related to the health of non-pregnant women, especially nulliparous adolescents. This review examines the framework of published and ongoing randomised trial designs. Four cohorts typically arise from the periconceptional trial design--two of which are non-pregnant and two are pregnant--and this structure provides assessment options related to pre-pregnant, maternal, pregnancy and fetal outcomes. Conceptually the initial decision for single or micronutrient intervention is central--as is the choice of dosage and content--in order to establish a comparative framework across trials, improve standardisation, and facilitate interpretation of mechanistic hypotheses. Other trial features considered in the review include: measurement options for baseline and outcome assessments; adherence to long-term supplementation; sample size considerations in relation to duration of nutrient supplementation; cohort size for non-pregnant and pregnant cohorts as the latter is influenced by parity selection; integrating qualitative studies and data management issues. Emphasis is given to low resource settings where high infection rates and the possibility of nutrient-infection interactions may require appropriate safety monitoring. The focus is on pragmatic issues that may help investigators planning a periconceptional trial.

Effect of methotrexate exposure at late gestation on development of telencephalon in rat fetal brain

Pregnant rats were treated with 30 mg/kg of methotrexate (MTX) on gestation day (GD) 16, and fetal brains were examined time-dependently. On GD 20, the appearance of the telencephalon in the MTX group was different from that in the control group, and the major axis of the telencephalon of the MTX group was shortened, compared to that of the control group. In the sagittal section of the telencephalon in the MTX group on GD 20, histopathological findings of deformation and narrowing of the cerebral ventricle, the disturbance of the arrangement of the marginal cell layer of subventricular zone (SVZ) and thickening of telencephalic wall, cortical plate and ventricular zone (VZ)/SVZ were possibly attributable to neuronal migration disorders by MTX. Through all the experimental period, few pyknotic cells or TUNEL-positive cells were observed in the VZ/SVZ of the telencephalic wall and striatum in the control group. On the other hand, in the VZ/SVZ of the telencephalic wall and striatum in the MTX group, pyknotic cells or TUNEL-positive cells were observed on GD 17, and they increased significantly on GD18 and then decreased to the control levels from GD 19 onward. The phospho-Histone H3-positive rate decreased remarkedly in the VZ/SVZ of the telencephalic wall and striatum of the MTX group on GDs 17 and 18, compared to the control group, but they recovered on and after GD 19. These results suggested that there was a high possibility that development of the telencephalon in this period required strong folic acid.

Prospective association between dietary folate intake and skin cancer risk: results from the Supplémentation en Vitamines et Minéraux Antioxydants cohort

BACKGROUND

The role of folate in skin carcinogenesis is unclear, with experimental data suggesting potentially protective but also deleterious effects.

OBJECTIVE

Our main objective was to investigate the prospective association between dietary folate intake and risks of skin cancer (overall), nonmelanoma skin cancer (NMSC), and basal cell carcinoma (BCC). As an exploratory analysis, we also investigated the prospective association between erythrocyte folate concentration and skin cancer risk.

DESIGN

In this study, we included 5880 participants in the Supplémentation en Vitamines et Minéraux Antioxydants (SU.VI.MAX) cohort (follow-up: 1994-2007) who completed at least six 24-h dietary records during the first 2 y of the study. Associations between sex-specific tertiles of dietary and erythrocyte folate and skin cancer risk were assessed by using multivariate Cox proportional hazards models.

RESULTS

After a median follow-up of 12.6 y, 144 incident skin cancers were diagnosed. Dietary folate intake was associated with increased risk of overall skin cancer [HR for tertile 3 compared with tertile 1 (HR(T3vs.T1)): 1.79; 95% CI: 1.07, 2.99; P-trend = 0.03], NMSC (HR(T3vs.T1): 1.85; 95% CI: 1.06, 3.23; P-trend = 0.03), and BCC (HR(T3vs.T1): 1.78; 0.98, 3.24; P-trend = 0.05). This association was observed in women (corresponding P-trend = 0.007, 0.009, and 0.009, respectively) but not in men (P-trend = 0.8, 0.8, and 0.9, respectively). P-interaction values between tertiles of dietary folate intake and sex were 0.04, 0.02, and 0.02 for overall skin cancer, NMSC, and BCC, respectively. Erythrocyte folate concentration was directly associated with increased risk of overall skin cancer (HR(T3vs.T1): 2.54; 95% CI: 0.95, 6.81; P-trend = 0.03), NMSC (HR(T3vs.T1): 3.49; 95% CI: 1.11, 11.0; P-trend = 0.01), and BCC (HR(T3vs.T1): 7.44; 95% CI: 1.57, 35.3; P-trend = 0.004) (men and women combined).

CONCLUSIONS

This prospective study suggests an association between dietary folate intake and erythrocyte folate concentration and increased risk of overall skin cancer, NMSC, and BCC. Although several mechanistic hypotheses and 2 previous large prospective studies on BCC are in line with these results, epidemiologic literature is limited, and future research is needed to better elucidate the potential role of folate in the cause of skin cancers.

Folate ameliorates dexamethasone-induced fetal and placental growth restriction potentially via improvement of trophoblast migration

Overexposure to prenatal dexamethasone (Dex) leads to small placental and fetal size and the alteration of fetal programming. Folate plays important roles in processes associated with successful pregnancy, including angiogenesis and trophoblast invasion. Placental folate transport is altered with prenatal Dex administration. The purpose of this study was to investigate the protective role of maternal folate administration in placentas exposed to Dex. In vitro, four groups of C57BL/6J pregnant mice were utilized: 1) normal drinking water+Saline injection group (NN); 2) normal drinking water+Dex injection group (ND); 3) drinking water with folate+Saline injection group (FN); and 4) drinking water with folate+Dex injection group (FD). In vivo, four treatment groups of the human extravillous trophoblast HTR-8/SVneo cells were classified: 1) control (NN); 2) Dex treatment (ND); 3) folate treatment (FN); and 4) folate and Dex treatment (FD). The results showed the maternal folate increases the placental size, birth weight, and expression of matrix metalloproteinases 9 (MMP9) in a mice model of Dex overexposure. In human extravillous trophoblast HTR8/SVneo, folate ameliorated the Dex-induced supress of cell migration and improved the expression/activity of MMP2 and MMP9. In conclusion, folate might be a potential therapy intervention to reduce the adverse effects of prenatal Dex exposure partially via improved trophoblast migration.

Aldehyde dehydrogenase homologous folate enzymes: Evolutionary switch between cytoplasmic and mitochondrial localization

Cytosolic and mitochondrial 10-formyltetrahydrofolate dehydrogenases are products of separate genes in vertebrates but only one such gene is present in invertebrates. There is a significant degree of sequence similarity between the two enzymes due to an apparent origin of the gene for the mitochondrial enzyme (ALDH1L2) from the duplication of the gene for the cytosolic enzyme (ALDH1L1). The primordial ALDH1L gene originated from a natural fusion of three unrelated genes, one of which was an aldehyde dehydrogenase. Such structural organization defined the catalytic mechanism of these enzymes, which is similar to that of aldehyde dehydrogenases. Here we report the analysis of ALDH1L1 and ALDH1L2 genes from different species and their phylogeny and evolution. We also performed sequence and structure comparison of ALDH1L enzymes possessing aldehyde dehydrogenase catalysis to those lacking this feature in an attempt to explain mechanistic differences between cytoplasmic ALDH1L1 and mitochondrial ALDH1L2 enzymes and to better understand their functional roles.

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.

Mechanism of drug-induced gingival overgrowth revisited: a unifying hypothesis

Drug-induced gingival overgrowth (DIGO) is a disfiguring side effect of anti-convulsants, calcineurin inhibitors, and calcium channel blocking agents. A unifying hypothesis has been constructed which begins with cation flux inhibition induced by all three of these drug categories. Decreased cation influx of folic acid active transport within gingival fibroblasts leads to decreased cellular folate uptake, which in turn leads to changes in matrix metalloproteinases metabolism and the failure to activate collagenase. Decreased availability of activated collagenase results in decreased degradation of accumulated connective tissue which presents as DIGO. Studies supporting this hypothesis are discussed.

Rho GTPases RhoA and Rac1 mediate effects of dietary folate on metastatic potential of A549 cancer cells through the control of cofilin phosphorylation

Folate, an important nutrient in the human diet, has been implicated in cancer, but its role in metastasis is not established. We have shown previously that the withdrawal of medium folate leads to the inhibition of migration and invasion of A549 lung carcinoma cells. Here we have demonstrated that medium folate regulates the function of Rho GTPases by enabling their carboxyl methylation and translocation to plasma membrane. Conversely, the lack of folate leads to the retention of these proteins in endoplasmic reticulum. Folate also promoted the switch from inactive (GDP-bound) to active (GTP-bound) GTPases, resulting in the activation of downstream kinases p21-activated kinase and LIM kinase and phosphorylation of the actin-depolymerizing factor cofilin. We have further demonstrated that in A549 cells two GTPases, RhoA and Rac1, but not Cdc42, are immediate sensors of folate status: the siRNA silencing of RhoA or Rac1 blocked effects of folate on cofilin phosphorylation and cellular migration and invasion. The finding that folate modulates metastatic potential of cancer cells was confirmed in an animal model of lung cancer using tail vein injection of A549 cells in SCID mice. A folate-rich diet enhanced lung colonization and distant metastasis to lymph nodes and decreased overall survival (35 versus 63 days for mice on a folate-restricted diet). High folate also promoted epithelial-mesenchymal transition in cancer cells and experimental mouse tumors. Our study provides experimental evidence for a mechanism of metastasis promotion by dietary folate and highlights the interaction between nutrients and metastasis-related signaling.