Demographic, Physiologic, and Lifestyle Characteristics Observed with Serum Total Folate Differ Among Folate Forms: Cross-Sectional Data from Fasting Samples in the NHANES 2011-2016.

BACKGROUND: Serum folate forms were measured in the US population during recent NHANES to assess folate status. OBJECTIVE: We describe post-folic acid-fortification concentrations of serum folate forms in the fasting US population ≥1 y from the NHANES 2011-2016. METHODS: We measured 5 biologically active folates and 1 oxidation product (MeFox) of 5-methyltetrahydrofolate (5-methyl-THF). We calculated geometric means of 5-methyl-THF, unmetabolized folic acid (UMFA), nonmethyl folate (sum of tetrahydrofolate, 5-formyltetrahydrofolate, and 5,10-methenyltetrahydrofolate), total folate (sum of above biomarkers), and MeFox by demographic, physiologic, and lifestyle variables; estimated the magnitude of variables on biomarker concentrations after covariate adjustment; and determined the prevalence of UMFA >2 nmol/L. RESULTS: After demographic adjustment, age, sex, and race-Hispanic origin were significantly associated with most folate forms. MeFox increased with age, while 5-methyl-THF, UMFA, and nonmethyl folate displayed U-shaped age patterns. Compared with non-Hispanic whites, non-Hispanic blacks had 23% lower predicted 5-methyl-THF but comparable UMFA; non-Hispanic Asians had comparable 5-methyl-THF but 28% lower UMFA; Hispanics, non-Hispanic Asians, and non-Hispanic blacks had ∼20% lower MeFox. After additional physiologic and lifestyle adjustment, predicted UMFA and MeFox concentrations were 43% and 112% higher, respectively, in adults with chronic kidney disease and 17% and 15% lower, respectively, in adults consuming daily 1-<2 alcoholic beverages; 5-methyl-THF concentrations were 20% lower in adult smokers. The prevalence of UMFA >2 nmol/L was highest in persons aged ≥70 y (9.01%) and lowest in those aged 12-19 y (1.14%). During 2011-2014, the prevalence was 10.6% in users and 2.22% in nonusers of folic acid-containing supplements. CONCLUSIONS: In fasting persons ≥1 y, the demographic, physiologic, and lifestyle characteristics observed with serum total folate differed among folate forms, suggesting biological and/or genetic influences on folate metabolism. High UMFA was mostly observed in supplement users and older persons.

Daily supplementation with 5 mg of folic acid in Brazilian patients with hereditary spherocytosis.

Patients with hereditary spherocytosis (HS) have increased rates of erythropoiesis and higher folate requirements. In a case-control study of patients with HS, we evaluated the associations between the use of 5 mg folic acid (FA) daily and serum concentrations of folate, unmetabolized folic acid (UMFA), interleukin (IL)-6, IL-8, IL-10, interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α); and mRNA expression of dihydrofolate reductase (DHFR), methylene tetrahydrofolate reductase (MTHFR), IL8, IFNG and TNFA genes. Total serum folate and folate forms were measured in 27 patients with HS (21 users [HS-U] and 6 non-users [HS-NU] of supplemental FA) and 54 healthy controls not consuming 5 mg/day supplemental FA. Each patient was matched to two controls based on age, sex and body mass index. The mononuclear leucocyte mRNA expression of relevant genes and their products were determined. Serum folate, UMFA, 5-methyl-tetrahydrofolate (5-methyl-THF) and tetrahydrofolate (THF) concentrations were significantly higher in HS-U compared with matched healthy controls (p<0.001, n=42). HS-NU had lower serum folate concentrations than matched healthy controls (p=0.044, n=12). HS-U and HS-NU presented similar hematological and biochemical markers profiles. No differences were found between HS-U and HS-NU for cytokine serum concentrations and mRNA expression genes. DHFR mRNA expression was higher in HS-U than in HS-NU. The use of high daily doses of FA for treatment of patients with HS may be excessive and is associated with elevated serum UMFA and elevated DHFR mRNA expression. It is not known whether long-term high-dose FA use by patients with HS might have adverse health effects.

A Daily Dose of 5 mg Folic Acid for 90 Days Is Associated with Increased Serum Unmetabolized Folic Acid and Reduced Natural Killer Cell Cytotoxicity in Healthy Brazilian Adults.

Background: The effects of high-dose folic acid (FA) supplementation in healthy individuals on blood folate concentrations and immune response are unknown.Objective: The aim of the study was to evaluate the effects of daily consumption of a tablet containing 5 mg FA on serum folate; number and cytotoxicity of natural killer (NK) cells; mRNA expression of dihydrofolate reductase (DHFR), methylenetetrahydrofolate reductase (MTHFR), interferon γ (IFNG), tumor necrosis factor α (TNFA), and interleukin 8 (IL8) genes; and concentrations of serum inflammatory markers.Methods: This prospective clinical trial was conducted in 30 healthy Brazilian adults (15 women), aged 27.7 y (95% CI: 26.4, 29.1 y), with a body mass index (in kg/m2) of 23.1 (95% CI: 22.0, 24.3). Blood was collected at baseline and after 45 and 90 d of the intervention. Serum folate concentrations were measured by microbiological assay and HPLC-tandem mass spectrometry [folate forms, including unmetabolized folic acid (UMFA)]. We used real-time polymerase chain reaction to assess mononuclear leukocyte mRNA expression and flow cytometry to measure the number and cytotoxicity of NK cells.Results: Serum folate concentrations increased by ∼5-fold after the intervention (P < 0.001), and UMFA concentrations increased by 11.9- and 5.9-fold at 45 and 90 d, respectively, when compared with baseline (P < 0.001). UMFA concentrations increased (>1.12 nmol/L) in 29 (96.6%) participants at day 45 and in 26 (86.7%) participants at day 90. We observed significant reductions in the number (P < 0.001) and cytotoxicity (P = 0.003) of NK cells after 45 and 90 d. Compared with baseline, DHFR mRNA expression was higher at 90 d (P = 0.006) and IL8 and TNFA mRNA expressions were higher at 45 and 90 d (P = 0.001 for both).Conclusion: This noncontrolled intervention showed that healthy adults responded to a high-dose FA supplement with increased UMFA concentrations, changes in cytokine mRNA expression, and reduced number and cytotoxicity of NK cells. This trial was registered at www.ensaiosclinicos.gov.br as RBR-2pr7zp.

Folate status and concentrations of serum folate forms in the US population: National Health and Nutrition Examination Survey 2011-2.

Serum and erythrocyte (RBC) total folate are indicators of folate status. No nationally representative population data exist for folate forms. We measured the serum folate forms (5-methyltetrahydrofolate (5-methylTHF), unmetabolised folic acid (UMFA), non-methyl folate (sum of tetrahydrofolate (THF), 5-formyltetrahydrofolate (5-formylTHF), 5,10-methenyltetrahydrofolate (5,10-methenylTHF)) and MeFox (5-methylTHF oxidation product)) by HPLC-MS/MS and RBC total folate by microbiologic assay in US population ≥ 1 year (n approximately 7500) participating in the National Health and Nutrition Examination Survey 2011-2. Data analysis for serum total folate was conducted including and excluding MeFox. Concentrations (geometric mean; detection rate) of 5-methylTHF (37·5 nmol/l; 100 %), UMFA (1·21 nmol/l; 99·9 %), MeFox (1·53 nmol/l; 98·8 %), and THF (1·01 nmol/l; 85·2 %) were mostly detectable. 5-FormylTHF (3·6 %) and 5,10-methenylTHF (4·4 %) were rarely detected. The biggest contributor to serum total folate was 5-methylTHF (86·7 %); UMFA (4·0 %), non-methyl folate (4·7 %) and MeFox (4·5 %) contributed smaller amounts. Age was positively related to MeFox, but showed a U-shaped pattern for other folates. We generally noted sex and race/ethnic biomarker differences and weak (Spearman's r< 0·4) but significant (P< 0·05) correlations with physiological and lifestyle variables. Fasting, kidney function, smoking and alcohol intake showed negative associations. BMI and body surface area showed positive associations with MeFox but negative associations with other folates. All biomarkers showed significantly higher concentrations with recent folic acid-containing dietary supplement use. These first-time population data for serum folate forms generally show similar associations with demographic, physiological and lifestyle variables as serum total folate. Patterns observed for MeFox may suggest altered folate metabolism dependent on biological characteristics.

The association between circulating total folate and folate vitamers with overall survival after postmenopausal breast cancer diagnosis.

We studied the relationship between plasma total folate and folate vitamer concentrations [5-methyltetrahydrofolic acid, pteroylglutamic acid (folic acid) and tetrahydrofolic acid] with overall survival after breast cancer diagnosis. A secondary aim was to assess the relationship between folic acid supplement use with circulating total folate and folate vitamer concentrations. Participants were postmenopausal women diagnosed with breast cancer (n = 498) with an average follow-up of 6.7 yr. Plasma total folate and folate vitamers were measured by isotope-dilution LC-MS/MS in samples collected at or postdiagnosis. Cox proportional multivariate hazards models (controlled for stage, age at diagnosis, body mass index, parity, hormone replacement therapy use, treatment, alcohol use, folic acid use, and energy intake), were used to assess overall survival after breast cancer diagnosis. We found that the relative risk of dying for women with plasma total folate concentrations in the highest quartile was 59% lower (hazard ratio: 0.41, 95% confidence interval: 0.19-0.90) compared with the lowest quartile. Data on supplement use showed that women taking folic acid supplements had significantly higher circulating total folate and folate vitamer concentrations (P < 0.0001), suggesting that increased folate consumption through diet and/or supplementation may improve prognosis after breast cancer diagnosis.

Folate is absorbed across the human colon: evidence by using enteric-coated caplets containing 13C-labeled [6S]-5-formyltetrahydrofolate.

BACKGROUND: Folate intakes that do not meet or greatly exceed requirements may be associated with negative health outcomes. A better understanding of contributors that influence the input side will help establish dietary guidance that ensures health benefits without associated risks. Colonic microbiota produce large quantities of folate, and [(13)C5]5-formyltetrahydrofolate infused during colonoscopy is absorbed. However, it is unclear if significant quantities of folate are absorbed in an intact microbiome. OBJECTIVE: We determined whether and how much of a physiologic dose of [(13)C5]5-formyltetrahydrofolate delivered in a pH-sensitive enteric caplet to an intact colonic microbiome is absorbed. DESIGN: Healthy adults ingested a specially designed pH-sensitive acrylic copolymer-coated barium sulfate caplet that contained 855 nmol (400 µg) [(13)C5]5-formyltetrahydrofolate. After a washout period ≥ 4 wk, subjects received an intravenous injection of the same compound (214 nmol). Serially collected blood samples before and after each test dose were analyzed by using a microbiological assay and liquid chromatography-tandem mass spectrometry. RESULTS: Caplet disintegration in the colon was observed by fluoroscopic imaging for 6 subjects with a mean (± SD) complete disintegration time of 284 ± 155 min. The mean (± SEM) rate of appearance of [(13)C5]5-methyltetrahydrofolate in plasma was 0.33 ± 0.09 (caplet) and 5.8 ± 1.2 (intravenous) nmol/h. Likely because of the significant time in the colon, the mean apparent absorption across the colon was 46%. CONCLUSIONS: Folate is absorbed across the colon in humans with an undisturbed microbiome. This finding and previous observations of the size of the colonic depot of folate and its potential for manipulation by diet (eg, dietary fiber, oligosaccharides, and probiotics) suggest that an individual's dietary folate requirement may differ depending on the consumption of dietary constituents that affect the size and composition of their gastrointestinal microbiota. In addition, a systematic investigation of the role of colonic folate on gastrointestinal development and the prevention of colorectal cancer is warranted. This trial was registered at clinicaltrials.gov as NCT00941174.

Serum cotinine and whole blood folate concentrations in pregnancy.

PURPOSE: Prenatal tobacco smoke exposure may be associated with low maternal folate levels that increase the risk of adverse infant and child health outcomes by reducing folate availability during fetal development. METHODS: Using data from the Health Outcomes and Measures of the Environment Study, we examined the relationship between secondhand or active tobacco smoke exposure and whole blood folate concentrations in pregnant women from Cincinnati, Ohio (n = 362) at approximately 16-week gestation. We used multivariable linear regression to examine the association between continuous or categorical serum cotinine levels and whole blood folate levels, adjusting for sociodemographic, dietary, and perinatal variables. RESULTS: After adjustment for potential confounders, an interquartile range increases in serum cotinine concentration (0.012-0.224 ng/mL) was suggestively associated with decreased whole blood folate levels (ß, -23 nmol/L; 95% confidence interval (CI), -49, 3; P value = .08). Compared with unexposed women, reductions in mean whole blood folate were observed among active smokers (ß, -94, 95% CI, 195, 6 nmol/L; P value = .40); smaller reductions were observed among women with secondhand exposure (ß, 26; CI, 84, 32 nmol/L; P value = .07). CONCLUSIONS: Consistent with prior studies, active smoking was associated with reduced whole blood folate levels among these pregnant women. Secondhand tobacco smoke exposures were associated with small and imprecise reductions in whole blood folate levels.

Folate is absorbed across the colon of adults: evidence from cecal infusion of (13)C-labeled [6S]-5-formyltetrahydrofolic acid.

BACKGROUND: Folate deficiency increases the risk of several human diseases. Likewise, high intakes of folate, particularly synthetic folic acid intake, may be associated with adverse health outcomes in humans. A more comprehensive understanding of the "input side" of folate nutrition may help to set dietary recommendations that strike the right balance between health benefits and risks. It is well known that the microflora in the colon produce large quantities of folate that approach or exceed recommended dietary intakes; however, there is no direct evidence of the bioavailability of this pool in humans. OBJECTIVE: The objective was to determine whether, and to what extent, the natural folate vitamer 5-formyltetrahydrofolic acid is absorbed across the intact colon of humans. DESIGN: During screening colonoscopy, 684 nmol (320 microg) [(13)C]glutamyl-5-formyltetrahydrofolic acid was infused directly into the cecum of 6 healthy adults. Three or more weeks later, each subject received an intravenous injection of the same compound (172 nmol). Blood samples were collected before and after each treatment. The ratio of labeled to unlabeled folates was determined in plasma by tandem mass spectrometry. RESULTS: The apparent rate of folate absorption across the colon of a bolus dose of [(13)C]5-formyltetrahydrofolic acid infused into the cecum was 0.6 +/- 0.2 nmol/h, as determined by the appearance of [(13)C(5)]5-methyltetrahydrofolic acid in plasma. In comparison, the rate of appearance of [(13)C(5)]5-methyltetrahydrofolic acid after an intravenous injection of [(13)C(5)]5-formyltetrahydrofolate was 7 +/- 1.2 nmol/h. CONCLUSION: Physiologic doses of natural folate are absorbed across the intact colon in humans.

Disabled-2 heterozygous mice are predisposed to endometrial and ovarian tumorigenesis and exhibit sex-biased embryonic lethality in a p53-null background.

Disabled-2 (Dab2) is a phosphoprotein involved in cellular signal transduction and endocytic trafficking. The expression of Dab2 is frequently lost or suppressed in several epithelial tumors, and studies of its cellular function and growth suppressive activity when re-expressed in cancer cells led to the suggestion that Dab2 is a tumor suppressor. A role for Dab2 in epithelial cell positioning organization was derived from study of knockout mice: homozygous deletion of dab2 results in early embryonic lethality due to the disorganization of the primitive endoderm, the first epithelium in early embryos. We now report that dab2 heterozygous mice develop uterine hyperplasia and ovarian preneoplastic morphological changes at a high frequency. Crossing into a p53(-/-) background unexpectedly produced few female dab2(+/-):p53(-/-) mice, while the male dab2(+/-):p53(-/-) were born at the expected Mendelian frequency. The tumor-prone phenotype of dab2(+/-) mice provides additional support for a role of human Dab2 as a tumor suppressor, and the sex-biased embryonic lethality suggests a genetic interaction between p53 and dab2 genes in female mice.