Folate supplementation increases genomic DNA methylation in the liver of elder rats

The availability of folate is implicated as a determinant of DNA methylation, a functionally important feature of DNA. Nevertheless, when this phenomenon has been examined in the rodent model, the effect has not always been observed. Several reasons have been postulated for the inconsistency between studies: the rodent is less dependent on folate as a methyl source than man; juvenile animals, which most studies use, are more resistant to folate depletion than old animals; methods to measure genomic DNA methylation might not be sensitive enough to detect differences. We therefore examined the relationship between folate and genomic DNA methylation in an elder rat model with a newly developed method that can measure genomic DNA methylation sensitively and precisely. Thirty-nine 1-year-old rats were divided into three groups and fed a diet containing 0, 4.5 or 18 mumol folate/kg (folate-deplete, -replete and -supplemented groups, respectively). Rats were killed at 8 and 20 weeks. At both time points, mean liver folate concentrations increased incrementally between the folate-deplete, -replete and -supplemented rats (P for trend <0.001) and by 20 weeks hepatic DNA methylation also increased incrementally between the folate-deplete, -replete and -supplemented rats (P for trend=0.025). At both time points folate-supplemented rats had significantly increased levels of DNA methylation compared with folate-deplete rats (P<0.05). There was a strong correlation between hepatic folate concentration and genomic DNA methylation in the liver (r 0.48, P=0.004). In the liver of this animal model, dietary folate over a wide range of intakes modulates genomic DNA methylation.     

Biochemical and molecular aberrations in the rat colon due to folate depletion are age-specific

Elder adulthood and diminished folate status are each associated with an enhanced risk of colorectal carcinogenesis. We therefore examined whether these two factors are mechanistically related. Weanling male Sprague-Dawley rats (n = 44) and 1-y-old rats (n = 44) were each divided into three groups and fed diets containing 0, 4.5 or 18 micro mol folic acid/kg (deplete, replete and supplemented groups, respectively). Rats were killed at 0, 8 and 20 wk. The folate concentrations, the distribution of the different coenzymatic forms of folate, uracil incorporation into DNA and genomic DNA methylation were measured in the colonic mucosa. Folate-deplete and folate-replete elder rats had 30-45% lower colonic folate concentrations than young rats. Furthermore, 5-methyltetrahydrofolate was uniformly depleted in colons of the elder, folate-deplete rats, whereas this depletion occurred in only a minority of the younger rats. By the end of the experiment, the folate-deplete and folate-replete elder rats had approximately 50% more uracil incorporated into their colonic DNA than the corresponding young groups (P < 0.05). In elder rats, this uracil misincorporation was incremental across the three diet groups (P-test for trend < 0.05), whereas no excess uracil incorporation was observed in young rats. Neither age nor dietary folate affected genomic DNA methylation in the colon. In conclusion, the colon of elder rats is more susceptible to biochemical and molecular consequences of folate depletion than that of young rats. However, folate supplementation is as effective at sustaining adequate colonic folate status in elder rats as it is in the young.     

Folate supplementation differently affects uracil content in DNA in the mouse colon and liver

High folate intake may increase the risk of cancer, especially in the elderly. The present study examined the effects of ageing and dietary folate on uracil misincorporation into DNA, which has a mutagenic effect, in the mouse colon and liver. Old (18 months; n 42) and young (4 months; n 42) male C57BL/6 mice were pair-fed with four different amino acid-defined diets for 20 weeks: folate deplete (0?mg/kg diet); folate replete (2?mg/kg diet); folate supplemented (8?mg/kg diet); folate deplete (0?mg/kg diet) with thymidine supplementation (1·8?g/kg diet). Thymidylate synthesis from uracil requires folate, but synthesis from thymidine is folate independent. Liver folate concentrations were determined by the Lactobacillus casei assay. Uracil misincorporation into DNA was measured by a GC/MS method. Liver folate concentrations demonstrated a stepwise increase across the spectrum of dietary folate levels in both old (P?=?0·003) and young (P?相似文献   

Genomic DNA methylation decreases in response to moderate folate depletion in elderly women

BACKGROUND: Methylation of genomic DNA is dependent on an adequate supply of folate coenzymes. Previous data support the hypothesis that abnormal DNA methylation plays an integral role in carcinogenesis. To date, no studies assessing the effect of inadequate folate status on DNA methylation in older women (aged >63 y) have been reported. OBJECTIVE: The effect of moderate folate depletion followed by folate repletion on leukocyte genomic DNA methylation was investigated in elderly women (aged 60-85 y) to evaluate whether DNA methylation could be used as a functional indicator of folate status. DESIGN: Healthy, postmenopausal women (n = 33) consumed a moderately folate-depleted diet (118 microg folate/d) for 7 wk, followed by 7 wk of folate repletion with 200 or 415 microg/d, each provided as 2 different dietary treatments for a total of 4 treatment groups (n = 30). Leukocyte DNA methylation was determined on the basis of the ability of DNA to incorporate [(3)H]methyl groups from labeled S:-adenosylmethionine in an in vitro assay. RESULTS: Incorporation of [(3)H]methyl groups increased significantly (P: = 0.0025) in response to folate depletion, suggesting undermethylation of DNA. No significant changes were detected in [(3)H]methyl incorporation in any group over the 7-wk repletion period compared with postdepletion values. CONCLUSIONS: DNA methylation status may be used as a functional indicator of moderately depleted folate status. The slow response to the repletion diets observed suggests that normalization of DNA methylation after moderate folate depletion may be delayed in older women.     

Strain differences in mice highlight the role of DNA damage in neoplasia induced by low dietary folate

In earlier work, we showed that low dietary folate induced intestinal tumors in BALB/c mice. In this study, our goal was to examine the effect of the same diets on a strain that is more resistant to tumorigenesis (C57Bl/6). We also questioned whether supplementation of the folate-deficient diet (FD) with betaine, an alternate methyl donor, would influence tumor formation. C57Bl/6 mice were fed the same diets [control diet (CD) with 2 mg folate/kg diet and FD with 0.3 mg folate/kg diet] as those in our previous study for 1 y, but they did not develop tumors. We also fed BALB/c mice the FD or FD supplemented with betaine for 1 y, but there was no change in tumor incidence. To determine the relative contributions of DNA damage and altered methylation patterns, we measured intestinal dUTP:dTTP ratios, phosphorylated histone H2AX (p-H2AX) staining, and global DNA methylation in both strains. Only BALB/c mice showed changes due to diet in dUTP:dTTP (from 2.19 +/- 0.20 in CD to 2.77 +/- 0.18 in FD; P = 0.05) and in p-H2AX staining (from 14.10 +/- 3.59% in CD to 22.40 +/- 2.65% in FD; P = 0.054). In BALB/c mice only, FD tended to have less (P = 0.06) global DNA methylation than CD. Although the FD increased plasma homocysteine and the betaine-supplemented FD lowered plasma homocysteine, the latter diet did not reduce tumor incidence. We conclude that plasma homocysteine is not likely to be associated with tumorigenesis in our model. However, DNA damage plays a critical role in initiating tumorigenesis when dietary folate is low and methylation changes may also be contributory.     

Oestrogen replacement therapy reduces total plasma homocysteine and enhances genomic DNA methylation in postmenopausal women

Although oestrogen replacement therapy (ERT), which can affect the risk of major cancers, has been known to reduce total plasma homocysteine concentrations in postmenopausal women, the mechanisms and subsequent molecular changes have not yet been defined. To investigate the effect of ERT on homocysteine metabolism, thirteen healthy postmenopausal women were enrolled in a double-blind, placebo-controlled, randomized, cross-over study consisting of two 8-week long phases, placebo and conjugated equine oestrogen (CEE; 0.625 mg/d). Concentrations of total plasma homocysteine, vitamin B6 and serum folate and vitamin B12 were measured by conventional methods. Genomic DNA methylation was measured by a new liquid chromatography/MS method and promoter methylation status of the oestrogen receptor (ER)alpha, ERbeta and p16 genes was analysed by methylation-specific PCR after bisulfite treatment. The CEE phase demonstrated a significantly decreased mean of total plasma homocysteine concentrations compared with the placebo phase (8.08 micromol/l (6.82-9.39) v. 9.29 (7.53-11.35), P < 0.05) but there was no difference in the blood concentrations of the three B vitamins. The CEE phase also showed a significantly increased genomic DNA methylation in peripheral mononuclear cells compared with the placebo phase (2.85 (SD 0.12) ng methylcytosine/microg DNA v. 2.40 +/- (SD 0.15) P < 0.05). However, there was no difference in promoter methylation in the ERalpha, ERbeta and p16 genes. This study demonstrates that decreased homocysteinaemia by CEE therapy parallels with increased genomic DNA methylation, suggesting a potential new candidate mechanism by which ERT affects the risk of cancers and a possible new candidate biomarker for the oestrogen-related carcinogenesis through folate-related one-carbon metabolism.     

Promoter methylation of E-cadherin, p16, and RAR-β(2) genes in breast tumors and dietary intake of nutrients important in one-carbon metabolism

Aberrant DNA methylation plays a critical role in carcinogenesis, and the availability of dietary factors involved in 1-carbon metabolism may contribute to aberrant DNA methylation. We investigated the association of intake of folate, vitamins B(2), B(6), B(12), and methionine with promoter methylation of E-cadherin, p16, and RAR-β(2) genes in archived tumor tissues from incident, primary breast cancer cases in a population-based case-control study. Real-time methylation-specific PCR was performed on 803 paraffin-embedded samples; usual dietary intake was queried from a food frequency questionnaire. Unconditional logistic regression was used to derive adjusted odds ratios and 95% confidence intervals for likelihood of promoter methylation for high compared to low intake of those 1-carbon nutrients. Overall, in case-case comparisons, dietary intakes of folate, vitamins B(2), B(6), B(12), and methionine were not associated with likelihood of promoter methylation of E- cadherin, p16, and RAR-β(2) for all cases combined or within strata defined by menopausal status and estrogen receptor status in this study. This finding, however, does not exclude the possibility that intake of such nutrients might have the ability to modulate promoter methylation in normal or premalignant (dysplastic) breast tissue.     

Genomic methylation of peripheral blood leukocyte DNA: influences of arsenic and folate in Bangladeshi adults

BACKGROUND: Studies in cell culture and animal models indicate that arsenic exposure induces modifications in DNA methylation, including genome-wide DNA hypomethylation. It is not known whether arsenic exposure influences genomic DNA methylation in human populations chronically exposed to arsenic-contaminated drinking water. OBJECTIVE: The objective of this study was to determine whether arsenic is associated with genomic hypomethylation of peripheral blood leukocyte (PBL) DNA in Bangladeshi adults who are chronically exposed to arsenic. We also investigated whether arsenic-induced alterations in DNA methylation may be influenced by folate nutritional status. DESIGN: PBL DNA methylation and concentrations of plasma folate, plasma arsenic, and urinary arsenic were assessed in 294 adults in Araihazar, Bangladesh. Genomic PBL DNA methylation was measured by using a [(3)H]-methyl incorporation assay. RESULTS: Urinary arsenic, plasma arsenic, and plasma folate were positively associated with the methylation of PBL DNA (P = 0.009, 0.03, and 0.03, respectively). Stratification of participants by folate nutritional status [<9 nmol/L (n = 190) or >or=9 nmol/L (n = 104)] showed that the associations between arsenic exposure and methylation of PBL DNA were restricted to persons with folate concentrations >or= 9 nmol/L. CONCLUSIONS: Contrary to our a priori hypothesis, arsenic exposure was positively associated with genomic PBL DNA methylation in a dose-dependent manner. This effect is modified by folate, which suggests that arsenic-induced increases in DNA methylation cannot occur in the absence of adequate folate. The underlying mechanisms and physiologic implications of increased genomic DNA methylation are unclear, and they warrant further study.     

Folate, DNA methylation and colo-rectal cancer

Prospective cohort and case-control studies suggest an association between low folate intake and increased risk of colo-rectal adenoma and cancer. Some, but not all, animal studies indicate that folate supplementation protects against the development of colo-rectal neoplasms, although supraphysiological folate doses have been shown to enhance tumour growth. Folate is a methyl donor for nucleotide synthesis and biological methylation reactions, including DNA methylation. A low dietary folate intake may increase the risk of colo-rectal neoplasia by inducing genomic DNA hypomethylation, which can affect the expression of proto-oncogenes and tumour suppressor genes associated with the development of cancer. Common polymorphisms in genes involved in the methylation pathway, such as methylenetetrahydrofolate reductase and methionine synthase, have been shown to influence risk of colo-rectal neoplasia, with interactions dependent on folate status and/or alcohol intake, which is known to antagonise methyl group availability. There is some evidence to show that DNA from normal-appearing colo-rectal mucosa in individuals with colo-rectal cancer is hypomethylated. In a case-control study DNA methylation in normal-appearing colo-rectal mucosa has been shown to be lower in individuals with colo-rectal cancer (P = 0.08) and colo-rectal adenoma (P = 0.009) than in controls free of colo-rectal abnormalities. Human intervention trials to date suggest that supraphysiological doses of folate can reverse DNA hypomethylation in colo-rectal mucosa of individuals with colo-rectal neoplasia. In a double-blind randomised placebo-controlled study folate supplementation at physiological doses has been shown to increase DNA methylation in leucocytes (P = 0.05) and colonic mucosa (P = 0.09). Further studies are required to confirm these findings in larger populations and to define abnormal ranges of DNA methylation.     

A lifelong exposure to a Western-style diet,but not aging,alters global DNA methylation in mouse colon

BACKGROUND/OBJECTIVESPrevious studies have indicated that when compared to young mice, old mice have lower global DNA methylation and higher p16 promoter methylation in colonic mucosa, which is a common finding in colon cancer. It is also known that a Western-style diet (WSD) high in fat and calories, and low in calcium, vitamin D, fiber, methionine and choline (based on the AIN 76A diet) is tumorigenic in colons of mice. Because DNA methylation is modifiable by diet, we investigate whether a WSD disrupts DNA methylation patterns, creating a tumorigenic environment.SUBJECTVIES/METHODSWe investigated the effects of a WSD and aging on global and p16 promoter DNA methylation in the colon. Two month old male C57BL/6 mice were fed either a WSD or a control diet (AIN76A) for 6, 12 or 17 months. Global DNA methylation, p16 promoter methylation and p16 expression were determined by LC/MS, methyl-specific PCR and real time RT-PCR, respectively.RESULTSThe WSD group demonstrated significantly decreased global DNA methylation compared with the control at 17 months (4.05 vs 4.31%, P = 0.019). While both diets did not change global DNA methylation over time, mice fed the WSD had lower global methylation relative to controls when comparing all animals (4.13 vs 4.30%, P = 0.0005). There was an increase in p16 promoter methylation from 6 to 17 months in both diet groups (P < 0.05) but no differences were observed between diet groups. Expression of p16 increased with age in both control and WSD groups.CONCLUSIONSIn this model a WSD reduces global DNA methylation, whereas aging itself has no affect. Although the epigenetic effect of aging was not strong enough to alter global DNA methylation, changes in promoter-specific methylation and gene expression occurred with aging regardless of diet, demonstrating the complexity of epigenetic patterns.     

Postweaning dietary folate deficiency provided through childhood to puberty permanently increases genomic DNA methylation in adult rat liver

Folate plays an important role in the pathogenesis of several chronic diseases by its potential ability to modulate DNA methylation. We hypothesized that the postweaning period might be a highly susceptible period to dietary folate intervention for DNA methylation patterning. We determined the effects of timing and duration of dietary folate intervention provided during the postweaning period on genomic DNA methylation in adult rat liver. In study 1, weanling rats were randomized to receive an amino acid-defined diet containing 0 (deficient), 2 (control), or 8 (supplemented) mg folic acid/kg until 8 wk of age, after which all the rats were fed the control diet until 30 wk of age. In study 2, weanling rats were fed the control diet until 8 wk of age and then randomized to receive the diet containing 0, 2, or 8 mg folic acid/kg until 30 wk of age. In study 3, weanling rats were randomized to receive these diets until 30 wk of age. Dietary folate deficiency, but not supplementation, provided during the postweaning period through childhood to puberty significantly increased genomic DNA methylation by 34-48% (P < 0.04) in rat liver that persisted into adulthood following a return to the control diet at puberty. In contrast, dietary folate deficiency or supplementation continually imposed at weaning or at puberty did not significantly affect genomic DNA methylation in adult rat liver. Our data suggest that early folate nutrition during postnatal development plays an important role in epigenetic programming that can have a permanent effect in adulthood.     

Vitamin B-12 deficiency induces anomalies of base substitution and methylation in the DNA of rat colonic epithelium

Derangements of one-carbon metabolism can directly affect the integrity of the genome by producing inappropriate uracil insertion into DNA and by altering patterns of DNA methylation. Vitamin B-12, a one-carbon nutrient, serves as a cofactor in the synthesis of precursors of biological methylation and in nucleotide synthesis. We therefore examined whether vitamin B-12 deficiency can induce these molecular anomalies in the colonic mucosa of rats. Weanling male Sprague-Dawley rats (n = 30) were divided into 2 groups and fed either a vitamin B-12-deficient diet or a similar diet containing adequate amounts of the vitamin. Rats from each group were killed at 6 and 10 wk. Uracil misincorporation into DNA was measured by GC/MS and genomic DNA methylation was measured by LC/MS. Plasma vitamin B-12 concentrations in deficient rats were below detectable limits at 6 and 10 wk; in control rats, concentrations were 0.46 +/- 0.07 and 0.42 +/- 0.10 nmol/L at those times. Although the colon total folate concentration did not differ between the groups, the proportion that was methylfolate was marginally greater in the deficient rats at 10 wk (P = 0.05) compared with control, consistent with the "methylfolate trap" that develops during vitamin B-12 deficiency. After 10 wk, the colonic DNA of the deficient rats displayed a 35% decrease in genomic methylation and a 105% increase in uracil incorporation (P < 0.05). This vitamin B-12-deficient diet, which was of insufficient severity to cause anemia or illness, created aberrations in both base substitution and methylation of colonic DNA, which might increase susceptibility to carcinogenesis.     

Promoter Methylation of E-Cadherin,p16, and RAR-β2 Genes in Breast Tumors and Dietary Intake of Nutrients Important in One-Carbon Metabolism

Aberrant DNA methylation plays a critical role in carcinogenesis, and the availability of dietary factors involved in 1-carbon metabolism may contribute to aberrant DNA methylation. We investigated the association of intake of folate, vitamins B₂, B₆, B₁₂, and methionine with promoter methylation of E-cadherin, p16, and RAR-β₂ genes in archived tumor tissues from incident, primary breast cancer cases in a population-based case-control study. Real-time methylation-specific PCR was performed on 803 paraffin-embedded samples; usual dietary intake was queried from a food frequency questionnaire. Unconditional logistic regression was used to derive adjusted odds ratios and 95% confidence intervals for likelihood of promoter methylation for high compared to low intake of those 1-carbon nutrients. Overall, in case-case comparisons, dietary intakes of folate, vitamins B₂, B₆, B₁₂, and methionine were not associated with likelihood of promoter methylation of E- cadherin, p16, and RAR-β₂ for all cases combined or within strata defined by menopausal status and estrogen receptor status in this study. This finding, however, does not exclude the possibility that intake of such nutrients might have the ability to modulate promoter methylation in normal or premalignant (dysplastic) breast tissue.     

叶酸与宫颈癌关系的病例对照研究

目的探讨膳食叶酸、血清叶酸与宫颈癌的关系以及叶酸和人乳头瘤病毒(HPV)16在宫颈癌发生中的相互作用。方法采用以医院为基础的病例对照研究方法,对111例经病理学确诊的宫颈鳞癌新发病例和111例子宫肌瘤患者进行年龄、籍贯、居住地匹配,在收集宫颈癌相关因素的同时,采用食物频数问卷(FFQ)调查膳食叶酸摄入情况,利用特异PCR检测HPV16 DNA,血清叶酸采用RIA定量测定。结果官颈癌组HPV16感染率(61．26％)显著高于对照组(28．83％),调整OR 值4．95(95％CI:2．49-9．83);病例组膳食叶酸摄入量(5．00μg/kcal±0．41 μg／kcal)和血清叶酸水平 (1．79 ng／ml±1．42 ng／ml)均低于对照组(5．14μg／kcal±0．35μg/kcal,2．59 ng／ml±2．81 ng／ml),差异有统计学意义,特别是随着血清叶酸水平的降低,患宫颈癌的危险性增加(X2=17．37,P=0．000);血清叶酸水平较低同时伴有HPV16感染患宫颈癌的危险明显高于两者单独作用之和,交互作用检验有统计学意义(G=5．56,P=0．02)。结论叶酸缺乏可增加宫颈癌发生的危险。     

Dietary selenite and azadeoxycytidine treatments affect dimethylhydrazine-induced aberrant crypt formation in rat colon and DNA methylation in HT-29 cells

Several observations implicate a role for altered DNA methylation in cancer pathogenesis. The global level of DNA methylation is generally lower; however, DNA methyltransferase (Dnmt1) activity is usually higher in tumor cells than in normal cells. The purpose of this study was to investigate whether the Dnmt1 inhibitor, 5-aza-2'-deoxycytidine (aza-dC) would alter the effect of dietary selenium on the formation of aberrant crypts. Weanling rats (n = 60) were fed three concentrations of selenium (deficient, 0.1 and 2.0 mg/kg diet) in a Torula yeast-based diet. Half of the rats were injected weekly with aza-dC (1 mg/kg, subcutaneously) and half were injected with the vehicle control (PBS). After 3.5 wk of consuming the experimental diets, the rats were given two injections of dimethylhydrazine (DMH; 25 mg/kg, intraperitoneally). Rats fed the selenium-deficient diet and injected with PBS had significantly (P < 0.006) more aberrant crypts than rats fed 0.1 or 2.0 mg selenium/kg diet (244 +/- 21 vs. 165 +/- 9 and 132 +/- 14, respectively). In contrast, when rats were injected with aza-dC, there was a significant (P < 0.0001) reduction in aberrant crypt formation and dietary selenium had no effect (62 +/- 8 vs. 77 +/- 13 vs. 54 +/- 8, in rats fed 0, 0.1 and 2.0 mg selenium/kg diet, respectively). HT-29 cells cultured in the absence of selenium had significantly hypomethylated DNA but significantly more Dnmt1 protein expression than cells cultured in the presence of 1 or 2 micromol/L selenium. These results suggest that aza-dC treatment may protect selenium-deficient rats against carcinogen-induced aberrant crypt formation.     

铀矿工GSTP1基因多态与MGMT基因和p16基因甲基化的关系

目的探讨氡职业暴露人群谷胱甘肽S-转移酶P1(GSTP1)基因多态与痰细胞6-氧-甲基嘌呤-DNA甲基转移酶(MGMT)和p16基因甲基化的关系。方法用聚合酶链反应-限制性片段长度多态性法(PCR-RFLP)确定70例氡职业暴露人群GSTP1的基因型;用聚合酶链反应-甲基化特异性法(MSP)确定痰细胞中MGMT和p16基因的甲基化与非甲基化状态。结果在70名铀矿工中,GSTP1基因A105G位点的纯合子(Ile/Ile)42例,杂合子(Ile/Val)25例和纯合子(Val/Val)3例。MGMT、p16基因甲基化率和总甲基化率分别为14.2%、8.6%和18.6%。与携带Ile/Ile人群相比,携带异常等位基因(Ile/Val与Val/Val)的人群MGMT基因甲基化和总甲基化率增加[P=0.037,OR=4.8,95%CI(1.1~21.0);P=0.016,OR=5.1,95%CI(1.4~19.6)];p16基因甲基化率差异无统计学意义[P=0.057,OR=4.6,95%CI(0.8~29.2)]。结论GSTP1(A105G)基因多态性与氡致MGMT基因甲基化和总甲基化的易感性有关。     

Thiamine, riboflavin, folate, and vitamin B12 status of low birth weight infants receiving parenteral and enteral nutrition.

Thirty infants were randomly assigned to receive either 3 mL of MVI-Pediatric supplement (PAR3 group, parenterally fed) or 2 mL (PAR2 group, parenterally fed). For the first week, 100% received total parenteral nutrition (TPN), 50% by the second, and less than 33% by the third. Eighteen control infants received enteral feeds of infant formula. Baseline (before TPN) and subsequent weekly blood samples, dietary data, and 24-hour urine collections were obtained. The adequacies of thiamine and riboflavin were assessed by the thiamine pyrophosphate effect and erythrocyte glutathione reductase activity, respectively. Urinary thiamine and riboflavin levels were measured by fluorometry. Plasma folate, red blood cell folate, urinary folate, and plasma vitamin B12 concentrations were determined by radioassay. No differences between groups were observed in thiamine pyrophosphate effect, erythrocyte glutathione reductase activity, urinary B1 or B2, or red blood cell folate levels at any time. Plasma folate differed (p less than .05) among the PAR3 group (24 +/- 7 ng/mL), and both the PAR2 (13 +/- 5 ng/mL) and enterally fed (ENT) groups (16 +/- 3 ng/mL) before the initiation of feeds, at week 1 (PAR3 = 32 +/- 15 ng/mL; PAR2 = 18 +/- 4 ng/mL; ENT = 19 +/- 9, ng/mL) and between the PAR3 (30 +/- 16 ng/mL) and PAR2 (16 +/- 4 ng/mL) infants at week 2. Plasma vitamin B12 levels differed among the ENT groups (551 +/- 287 pg/mL) and both the parenteral groups (PAR2 = 841 +/- 405 pg/mL; PAR3 = 924 +/- 424 pg/mL) at week 1 and between the ENT (530 +/- 238 pg/mL) and PAR3 (999 +/- 425 pg/mL) groups at week 2.(ABSTRACT TRUNCATED AT 250 WORDS)     

Folate status of elderly women following moderate folate depletion responds only to a higher folate intake

Dietary Reference Intakes (DRI) for folate for elderly women have been based primarily on data extrapolated from studies in younger women. This study was conducted to provide the first age-specific data in elderly women (60-85 y) from a controlled metabolic study on which to base folate intake recommendations. Subjects (n = 33) consumed a moderately folate-deplete (118 microg/d) diet for 7 wk, followed by repletion diets providing either 200 or 415 microg folate/d as diet plus folic acid (FA) or a combination of FA and orange juice (OJ) for 7 wk (n = 30). Comparisons among and within groups were made for serum folate (SF), RBC folate and plasma total homocysteine (tHcy) concentrations. SF concentrations decreased significantly (P < 0.001) during depletion (65 +/- 15%). Postrepletion, the adjusted SF concentration for subjects consuming 415 microg folate/d was significantly greater (P = 0.003) than for subjects consuming 200 microg folate/d. RBC folate concentrations decreased (P < 0.001) during depletion (21 +/- 10%) and further (P < 0.001) during repletion (5 +/- 14%). During depletion, plasma tHcy concentrations increased significantly (P < 0.001) and an inverse relationship between SF and plasma tHcy concentrations was observed in 94% of subjects (P < 0.001). Reversal of this inverse relationship was significant only for subjects consuming 415 microg folate/d (P < 0.001). Postrepletion, subjects consuming 200 microg folate/d had a significantly higher (P = 0.009) adjusted plasma tHcy concentration than subjects consuming 415 microg folate/d. These data in elderly women indicate that 415 microg/d folate, provided as a combination of diet, FA and OJ, or diet and FA, normalizes folate status more effectively than does 200 microg/d, thus providing age-specific data for future folate intake recommendations.     

Maternal methylenetetrahydrofolate reductase deficiency and low dietary folate lead to adverse reproductive outcomes and congenital heart defects in mice

BACKGROUND: Genetic or nutritional disturbances in folate metabolism may affect embryonic development because of the critical role of folate in nucleotide synthesis and methylation reactions. The possible role of a mild deficiency in methylenetetrahydrofolate reductase (MTHFR) and low dietary folate in pregnancy outcomes and heart morphogenesis requires further investigation. OBJECTIVE: We investigated the effect of mild MTHFR deficiency, low dietary folate, or both on resorption rates, on length and weight, and on the incidence of heart malformations in murine embryos. DESIGN: Female Mthfr +/+ and +/- mice were fed a control diet (CD) or a folic acid-deficient diet (FADD) before mating with male Mthfr +/- mice. On gestational day 14.5, implantation and resorption sites were recorded and viable embryos were examined for gross malformations, growth delay, and congenital heart defects. RESULTS: Plasma homocysteine in Mthfr +/- dams and in FADD-treated dams was significantly higher than that in Mthfr +/+ dams and CD-treated dams, respectively. A significantly higher rate of resorption and greater developmental delay were observed in hyperhomocysteinemic mice than in CD-treated +/+ dams. Heart defects were identified in 4 of 11, 5 of 10, and 4 of 10 litters from CD-treated +/-, FADD-treated +/+, and FADD-treated +/- dams, respectively, but not in any of those from CD-treated +/+ dams (0/11 litters). CONCLUSION: Our findings suggest that mild MTHFR deficiency, low dietary folate, or both in the dams increase the incidence of fetal loss, intrauterine growth retardation, and heart defects. These data support the benefit of folic acid supplementation in pregnant women, particularly in those with MTHFR deficiency.     

Methylation of estrogen receptor alpha and mutL homolog 1 in normal colonic mucosa: association with folate and vitamin B-12 status in subjects with and without colorectal neoplasia

BACKGROUND: Greater promoter methylation in some tumor-suppressor genes underlies most sporadic colorectal cancers and increases with age in the colon. OBJECTIVE: We tested the hypothesis that biomarkers of folate and vitamin B-12 status are associated with estrogen receptor alpha (ERalpha) and mutL homolog 1 (MLH1) promoter methylation in subjects with and without neoplasia. DESIGN: Biopsies of normal-appearing colorectal mucosa from 156 subjects with and without colorectal neoplasia (disease free, n = 76; cancer, n = 28; adenoma, n = 35; hyperplastic polyps, n = 17) were obtained at colonoscopy and used to evaluate methylation in 7 CpG sites in the ERalpha promoter and 13 CpG sites in the MLH1 promoter. Blood samples were obtained for the measurement of serum and red cell folate, serum vitamin B-12, and plasma homocysteine concentrations. Methylation indexes were generated to reflect an average methylation value across all CpG dinucleotides in both ERalpha and MLH1. RESULTS: The methylation indexes for ERalpha and MLH1 generally were significantly (P < 0.05) higher in subjects with neoplasia than in disease-free subjects. The ERalpha methylation index correlated negatively with serum vitamin B-12 (r = -0.239, P = 0.003) and positively with plasma homocysteine (r = 0.188, P = 0.021). Disease status (P < 0.005), age (P < 0.001), and serum vitamin B-12 concentrations (P = 0.006) were independent determinants of ERalpha promoter methylation. Serum and red cell folate concentrations had no influence on ERalpha promoter methylation. CONCLUSION: Serum vitamin B-12 but not folate status may be associated with ERalpha promoter methylation in normal-appearing colorectal mucosa.