Unknown,Transcriptomics,Genomics,Proteomics

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High-dose folic acid supplementation alters the human sperm methylome and is influenced by the MTHFR C677T polymorphism

ABSTRACT: Dietary folate is a major source of methyl groups required for DNA methylation, an epigenetic modification that is actively maintained and remodelled during spermatogenesis. While high dose folic acid supplementation (up to ten times the daily recommended dose) has been shown to improve sperm parameters in infertile men, the effects of supplementation on the sperm epigenome are unknown. To assess the impact of six months of high dose folic acid supplementation on the sperm epigenome, we studied 30 men with idiopathic infertility. Blood folate concentrations increased significantly after supplementation with no significant improvements in sperm parameters. Methylation levels of the differentially methylated regions of several imprinted loci (H19, DLK1/GTL2, MEST, SNRPN, PLAGL1, KCNQ1OT1) were normal both before and after supplementation. Reduced representation bisulfite sequencing (RRBS) revealed a significant global loss of methylation across different regions of the sperm genome. The most marked loss of DNA methylation was found in sperm from patients homozygous for the methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism, a common polymorphism in a key enzyme required for folate metabolism. RRBS analysis also showed that most of the differentially methylated tiles were located in DNA repeats, low CpG density and intergenic regions. Ingenuity Pathway Analysis revealed that methylation of promoter regions was altered in several genes involved in cancer and neurobehavioral disorders including CBFA2T3, PTPN6, COL18A1, ALDH2, UBE4B, ERBB2, GABRB3, CNTNAP4 and NIPA1. Our data reveal alterations of the human sperm epigenome associated with high dose folic acid supplementation, effects that were exacerbated by a common polymorphism in MTHFR. Reduced representation bisulfite sequencing of 28 human sperm samples before and after 6 month of high dose folic acid supplementation.

ORGANISM(S): Homo sapiens

SUBMITTER: Mahmoud Aarabi

PROVIDER: E-GEOD-72606 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Study question: Do short-term and long-term exposures to low dose folic acid supplementation alter DNA methylation in sperm? Summary answer: No alterations in sperm DNA methylation patterns were found following the administration of low dose folic acid supplements of 400 μg/day for 90 days (short-term exposure) or when pre-fortification of food with folic acid and post-fortification sperm samples (long-term exposure) were compared. What is known already: Excess dietary folate may be detrimental to health and DNA methylation profiles due to folate’s role in one carbon metabolism and the formation of S-adenosyl methionine, the universal methyl donor. DNA methylation patterns are established in developing male germ cells and have been suggested to be affected by high dose (5 mg/day) folic acid supplementation. Participants/materials, setting, methods: Blood and seminal plasma folate levels were measured in participants before and following the 90-day treatment with placebo or supplement. Sperm DNA methylation was assessed using the whole genome and genome-wide techniques, MassArray epityper, restriction landmark genomic scanning, methyl-CpG immunoprecipitation and Illumina HumanMethylation450 Bead Array. Main results and the role of chance: Following treatment, supplemented individuals had significantly higher levels of blood and seminal plasma folates compared to placebo. Initial first generation genome-wide analyses of sperm DNA methylation showed little evidence of changes when comparing pre- and post-treatment samples. With Illumina HumanMethylation450 BeadChip arrays, no significant changes were observed in individual probes following low-level supplementation; when compared with those of the post-fortification cohort, there were also few differences in methylation despite exposure to years of fortified foods. Limitations, reasons for caution: This study was limited to the number of participants available in each cohort, in particular those who were not exposed to early (pre-1998) fortification of food with folic acid. While genome-wide DNA methylation was assessed with several techniques that targeted genic and CpG rich regions, intergenic regions were less well interrogated. Wider implications of the findings: Overall, our findings provide evidence that short term exposure to low dose folic acid supplements of 400 μg/day, over a period of 3 months, a duration of time that might occur during infertility treatments, has no major impact on the sperm DNA methylome.

Project description:Background: We tested the hypothesis that short-term supplementation with a physiological dose of folate can alter global gene expression in the colon of subjects with colorectal adenoma using a randomised double blind placebo controlled trial design. Materials and Methods: Fourteen subjects with histologically confirmed colorectal adenoma, randomised to receive folic acid (400M-BM-5g/d, n=6) or placebo (n=8) for 10 weeks, had blood samples and colonic tissue biopsies collected before and after the intervention. Blood samples were used to determine serum and red cell folate, plasma homocysteine, and genetic polymorphisms in methylenetetrahydrofolate reductase (MTHFR C677T) and methionine synthase (MS A2756G). RNA extracted from normal-appearing colonic tissue samples was used to determine global gene expression in the colon using AffymetrixM-oM-^CM-^R Microarray GeneChips. Microarray results were confirmed by quantitative real time RT-PCR. Two methods were used to analyse the microarray data: (1) differences between pre- and post-intervention gene expression values in the folic acid and placebo groups separately using paired-sample t tests; (2) differences between the folic acid and placebo groups in the ratio of post-intervention to pre-intervention gene expression values using independent sample t-tests. Results: (1) Following intervention, sixty seven genes were up-regulated and 13 genes were down-regulated in the folic acid group, while 21 genes were up-regulated and none were down-regulated in the placebo group (P<0.05, adjusted for multiple testing). (2) Thirty six genes were up-regulated and 18 genes were down-regulated in the folic acid group when compared with placebo, but none of these were statistically significant after adjustment for multiple testing. These genes are involved in multiple pathways, including cell cycle, signal transduction, cell differentiation, transport, cell division, cell motility, protein transport and immune response. There were no genes involved in 1-carbon metabolism that were altered in expression, although several genes involved in neoplasia were up-regulated. Conclusions: These results indicate that while folic acid can modify gene expression, it is difficult to separate its effects from the natural variability in gene expression in the colon. Fourteen patients with colorectal adenoma were treated with either folate supplementation (6 subjects) or a placebo (8 subjects) for 10 weeks in a randomised double-blind trial. Colonic biopsies of normal tissue were taken before and after the intervention, and analysed for gene expression.

Project description:STUDY QUESTION: Could clinically-relevant moderate and/or high dose maternal folic acid supplementation prevent aberrant developmental and epigenetic outcomes associated with assisted reproductive technologies (ART)? SUMMARY ANSWER: Our results demonstrate dose-dependent and sex-specific effects of folic acid supplementation in ART and provide evidence that moderate dose supplements may be optimal for both sexes. WHAT IS KNOWN ALREADY: Children conceived using ART are at an increased risk for growth and genomic imprinting disorders, often associated with DNA methylation defects. Folic acid supplementation is recommended during pregnancy to prevent adverse offspring outcomes; however, the effects of folic acid supplementation in ART remain unclear. STUDY DESIGN, SIZE, DURATION: Outbred female mice were fed 3 folic-acid supplemented diets, control (rodent daily recommended intake or DRI; CD), moderate (4-fold DRI; 4FASD) or high (10-fold DRI; 10FASD) dose, for six weeks prior to ART and throughout gestation. Mouse ART involved a combination of superovulation, in vitro fertilization, embryo culture and embryo transfer. PARTICIPANTS/MATERIALS, SETTING, METHODS: Upon collection of midgestation embryos and placentas (n=74-99 embryos/group), all embryos were assessed for developmental delay and gross morphological abnormalities. Embryos and placentas were also examined at the epigenetic level. We assessed methylation at four imprinted genes (Snrpn, Kcnq1ot1, Peg1, and H19) in matched midgestation embryos and placentas (n=31-32/group) using bisulfite pyrosequencing. In addition, we examined genome-wide DNA methylation patterns in midgestation placentas (n=6 normal placentas per sex/group) and embryos (n=6 normal female embryos/group; n=3 delayed female embryos/group) using reduced representation bisulfite sequencing. MAIN RESULTS AND THE ROLE OF CHANCE: Moderate, but not high dose supplementation, was associated with a decrease in the proportion of developmentally delayed embryos. Although moderate dose folic acid supplementation reduced DNA methylation variance at certain imprinted genes in embryonic and placental tissues, high dose supplementation exacerbated the negative effects of ART at imprinted loci. Furthermore, folic acid supplements resolved female-biased aberrant imprinted gene methylation. Supplementation was more effective at correcting ART-induced genome-wide methylation defects in male versus female placentas; however, folic acid supplementation also led to additional methylation perturbations which were far more pronounced in males. LIMITATIONS, REASONS FOR CAUTION: Although the combination of mouse ARTs utilized in this study consisted of techniques commonly used in human fertility clinics, there may be species differences. Therefore, human studies, designed to determine the optimal levels of folic acid supplementation for ART pregnancies, and taking into account fetal sex, are warranted. WIDER IMPLICATIONS OF THE FINDINGS: Taken together, our findings support moderation in the dose of folic acid supplements taken during ART.

Project description:Defects in homocysteine and folate metabolism are associated with increased risks for neural tube and congenital heart defects, cardiovascular disease and stroke, cancers, and neurodegeneration. In many but not all cases, dietary supplementation with folate significantly reduces the severity and incidence of these conditions. Common polymorphisms modulate these metabolic pathways and disease risks, but do not fully account for the particular birth defects and adult diseases that occur in at-risk individuals. To test whether other pathways contribute to disease pathogenesis, we analyzed global and pathway-specific changes in gene expression and levels of selected metabolites after depletion and repletion of dietary folate in two genetically distinct inbred strains of mice. Compared to the C57BL/6J strain, A/J showed greater homeostatic response to folate perturbation by retaining a higher serum folate level and minimizing global gene expression changes. Remarkably, folate perturbation led to systematic strain-specific differences only in the expression profile of the cholesterol biosynthesis pathway and translated to changes in levels of serum and liver total cholesterol. By genetically increasing serum and liver total cholesterol levels in APOE deficient mice, we modestly but significantly improved folate retention during folate depletion, suggesting an interplay between homocysteine and folate metabolism and cholesterol metabolism. Absence of measurable changes in global methylation patterns or amelioration of effects with supplementation with an alternative methyl donor suggest that dietary folate perturbations do not act through large-scale or general changes in methylation. These results suggest that homeostatic responses in cholesterol metabolism contribute to the beneficial effects of dietary folate supplementation. Keywords: time course, stress response, diet, genetic, homeostasis Six-week old female A/J and C57BL/6J mice were purchased from the Jackson Laboratory. All mice were raised on a control diet containing four ppm folic acid (Basal Diet 5755, TestDiet) for one week before the start of studies. Selected mice were then placed on folic acid deficient diet (58C3, TestDiet) containing 1% succinylsulfathiazole, a non-absorbable antibiotic commonly used to suppress folate production by bacteria in the intestine. We had nine different treatment plans per strain with eight replicate mice per treatment. There were four folic acid depletion treatment in which mice were placed on folic acid deficient diet for 1, 2, 7, or 14 days. There were two folic acid repletion treatment in which mice were placed on folic acid deficient diet for 14 days followed by 1 day on control diet and another set of mice on 14 days of folic acid deficient diet followed by 7 days of control diet. There were three control time points in which mice were placed on the control diet for 0, 9, or 22 days. Eight biological replicate liver tissue from each treatment was pooled and total RNA from each pool and total RNA from Universal Mouse Reference RNA (Stratagene) were aminoallyl labeled with Cy3 and Cy5 in duplicate, with reversing of dyes.

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High-dose folic acid supplementation alters the human sperm methylome and is influenced by the MTHFR C677T polymorphism

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