Lifestyle and genetic determinants of folate and vitamin B 12 levels in a general adult population

Serum folate mediates the associations of MTHFR rs1801133 polymorphism with blood glucose levels and gestational diabetes mellitus in Chinese Han pregnant women

This study aimed to explore the mediation effects of one-carbon metabolism (OCM) related nutrients on the association between MTHFR rs1801133 polymorphism and gestational diabetes mellitus (GDM). Folate, vitamin B12 and homocysteine (Hcy) were measured in the serum of 1254 pregnant women. Linear and logistic regressions were used to estimate the associations of OCM nutrients and MTHFR rs1801133 polymorphism with blood glucose levels and GDM risk. Mediation analysis was applied to test the mediation effects of folate, vitamin B12 and Hcy on the association of MTHFR rs1801133 polymorphism with blood glucose concentrations and GDM. Pregnant women with MTHFR rs1801133 CC genotype had higher serum folate (10·75 v. 8·90 and 9·40 ng/ml) and lower serum Hcy (4·84 v. 4·93 and 5·20 μmol/l) than those with CT and TT genotypes. Folate concentrations were positively associated with fasting plasma glucose (FPG), 1-h plasma glucose (1-h PG), 2-h plasma glucose (2-h PG) and GDM risk. Vitamin B12 levels were negatively correlated with FPG and GDM. Although no direct association was found between MTHFR rs1801133 genotypes and GDM, there were significant indirect effects of MTHFR rs1801133 CC genotype on FPG (β: 0·005; 95 % CI: 0·001, 0·013), 1-h PG (β: 0·006; 95 % CI: 0·001, 0·014), 2-h PG (β: 0·007; 95 % CI: 0·001, 0·015) and GDM (β: 0·006; 95 % CI: 0·001, 0·014) via folate. In conclusion, serum folate mediates the effect of MTHFR rs1801133 on blood glucose levels and GDM. Our findings potentially provide a feasible GDM prevention strategy via individualised folate supplementation according to the MTHFR genotypes.

Folate Deficiency Enhanced Inflammation and Exacerbated Renal Fibrosis in High-Fat High-Fructose Diet-Fed Mice

The prevalence of obesity and chronic kidney disease (CKD) is increasing simultaneously and rapidly worldwide. Our previous study showed that folate deficiency increased lipid accumulation and leptin production of adipocytes. Whether folate plays a role in CKD, particularly obesity-related nephropathy remains unclear. To investigate the effects of folate deficiency on CKD in diet-induced obese mice, four groups of male C57BL/6 mice were fed either a normal-fat diet (NF) with folate (NF+f); NF without folate (NF-f); high-fat high-fructose diet (HFF) with folate (HFF+f); or HFF without folate (HFF-f) for 12 months during the study. The results showed that HFF increased not only body weight, fasting blood glucose, total cholesterol (TC), low-density lipoprotein (LDL)-cholesterol, and blood pressure, but also cytokines levels, such as interleukin (IL)-2, interferon (IFN)-γ, IL-17A/F, IL-6, monocyte chemoattractant protein (MCP)-1, and transforming growth factor (TGF)-β1. The indicators of kidney failure including urinary protein, neutrophil gelatinase-associated lipocalin (NGAL), renal type I and IV collagen deposits and leptin content, and serum creatinine were also increased by HFF. Folate-deficient diets further elevated serum TC, LDL-cholesterol, IL-6, tumor necrosis factor (TNF)-α, MCP-1, TGF-β1, and leptin, but decreased IL-10 level, and thus exacerbated renal fibrosis. To investigate the possible mechanisms of folate deficiency on renal injury, phosphorylation of pro-fibrosis signaling molecules, including signal transducer and activator of transcription (STAT)3 and small mothers against decapentaplegic (Smad)2/3, were assayed. Both HFF and folate deficiency significantly increased the phosphorylation of STAT3 and Smad2/3, suggesting synergistic effects of HFF-f on chronic renal inflammation and fibrosis. In conclusion, the results demonstrated that folate deficiency might aggravate inflammatory status and enhance renal fibrosis.

Folate Status as a Nutritional Indicator among People with Substance Use Disorder; A Prospective Cohort Study in Norway

Substance use disorder (SUD) is associated with poor nutrition. Vitamin B9, or folate, is an important micronutrient for health. The aim of this prospective longitudinal cohort study was to assess serum folate levels among people with SUD and to investigate the impact of factors related to substance use severity on folate status. Participants were recruited from outpatient clinics for opioid agonist therapy (OAT) and municipal health-care clinics for SUD in Western Norway. They were assessed annually, including blood sampling for determination of micronutrient status. Overall, 663 participants with a total of 2236 serum folate measurements were included. A linear mixed model was applied, and measures are presented as β-coefficients with 95% confidence interval (CI). Forty-eight percent (CI: 44−51) of the population had low serum folate levels (s-folate < 10 nmol/L), and 23% (CI: 20−26) were deficient (s-folate < 6.8 nmol/L) at baseline. Sixty percent (CI: 53−65) sustained their poor folate status in at least one subsequent assessment. Except for weekly use of cannabis (mean difference in serum folate [nmol/L]: −1.8, CI: −3.3, −0.25) and alcohol (1.9, CI: 0.15, 3.6), weekly use of no other substance class was associated with baseline differences in serum folate when compared to less frequent or no use. Injecting substances was associated with a reduction in serum folate over time (−1.2, CI: −2.3, −0.14), as was higher dosages of OAT medication (−1.1, CI: −2.2, −0.024). Our findings emphasize the need of addressing nutrition among people with severe SUD.

Folate Deficiency Increased Lipid Accumulation and Leptin Production of Adipocytes

Imbalanced dietary habits are closely associated with poor micronutrients status and the development of obesity. Previous studies have shown that serum folate level is decreased in obese individuals. However, whether folate deficiency could result in adiposity is still unclear. The aim of this study was to investigate the effects of dietary folate on lipid accumulation and leptin production using both in vivo and in vitro studies. Male C57BL/6 mice were fed with a diet with (f1) or without (f0) folate in a high-fat (HF) diet containing high-sucrose (HFS-f1, HFS-f0) for 4.5-5 months in Experiment 1, or an HF diet (HF-f1, HF-f0) for 12 months in Experiment 2, or an HF diet containing high-fructose (HFF-f1, HFF-f0) for 12 months in Experiment 3, compared with the normal-fat (NF-f1, NF-f0) diet, respectively. The serum levels of folate and leptin, white adipose tissue (WAT), size of adipocytes, hepatic contents of triglyceride (TG), and cholesterol were measured. In vitro study, TG contents, proinflammatory cytokines, leptin, and expressions of hypoxia-inducible factor (HIF)-1α and lipogenesis-related genes of 3T3-L1 adipocytes cultured with (f1) or without (f0) folate were assayed. The results showed that folate deficiency together with a high-fat diet (HFS-f0, HF-f0, HFF-f0) had higher WAT mass, adipocyte size, serum leptin level, and hepatic TG compared to those of the folate-sufficient groups (HFS-f1, HF-f1, and HFF-f1). Folate deficiency with a high-fat high -sucrose or -fructose diet (HFS-f0, HFF-f0) significantly increased the body weight of the mice. Increased intracellular TG, leptin, monocyte chemotactic protein (MCP)-1 and interleukin (IL)-6 levels, and the expression of Hif1α and lipogenesis-related genes Cebpα, Cebpβ, Acc1, Fasn, and Fabp4 were also detected in folate-deficient 3T3-L1 adipocytes. Our results suggested that folate deficiency increased lipid accumulation and leptin production of adipocytes, and thus, inadequate folate status might be one of the risk factors for adiposity.

Associations between Genetic Variants and Blood Biomarkers of One-Carbon Metabolism in Postmenopausal Women from the Women's Health Initiative Observational Study

BACKGROUND

Genetic variation in one-carbon metabolism may affect nutrient concentrations and biological functions. However, data on genetic variants associated with blood biomarkers of one-carbon metabolism in US postmenopausal women are limited, and whether these associations were affected by the nationwide folic acid (FA) fortification program is unclear.

OBJECTIVES

We investigated associations between genetic variants and biomarkers of one-carbon metabolism using data from the Women's Health Initiative Observational Study.

METHODS

In 1573 non-Hispanic White (NHW) and 282 Black/African American, American Indian/Alaska Native, Asian/Pacific Islander, and Hispanic/Latino women aged 50-79 y, 288 nonsynonymous and tagging single-nucleotide variants (SNVs) were genotyped. RBC folate, plasma folate, pyridoxal-5'-phosphate (PLP), vitamin B-12, homocysteine, and cysteine concentrations were determined in 12-h fasting blood. Multivariable linear regression tested associations per variant allele and for an aggregated genetic risk score. Effect modifications before, during, and after nationwide FA fortification were examined.

RESULTS

After correction for multiple comparisons, among NHW women, 5,10-methylenetetrahydrofolate reductase (MTHFR) rs1801133 (677C→T) variant T was associated with lower plasma folate (-13.0%; 95% CI: -17.3%, -8.6%) and higher plasma homocysteine (3.5%; 95% CI: 1.7%, 5.3%) concentrations. Other associations for nonsynonymous SNVs included DNMT3A rs11695471 (T→A) with plasma PLP; EHMT2 rs535586 (G→A), TCN2 rs1131603 (L349S A→G), and TCN2 rs35838082 (R188W G→A) with plasma vitamin B-12; CBS rs2851391 (G→A) with plasma homocysteine; and MTHFD1 rs2236224 (G→A) and rs2236225 (R653Q G→A) with plasma cysteine. The influence of FA fortification on the associations was limited. Highest compared with lowest quartiles of aggregated genetic risk scores from SNVs in MTHFR and MTRR were associated with 14.8% to 18.9% lower RBC folate concentrations. Gene-biomarker associations were similar in women of other races/ethnicities.

CONCLUSIONS

Our findings on genetic variants associated with several one-carbon metabolism biomarkers may help elucidate mechanisms of maintaining B vitamin status in postmenopausal women.

B vitamin blood concentrations and one-carbon metabolism polymorphisms in a sample of Italian women and men attending a unit of transfusion medicine: a cross-sectional study

PURPOSE

To define blood status of folate, vitamin B12, vitamin B6, homocysteine, and major one-carbon metabolism-related polymorphisms in healthy, males and females blood donors, aged 18-65 years were evaluated. General characteristics and lifestyle factors were also investigated.

METHODS

An explorative cross-sectional study design was used to evaluate a sample of blood donors attending the Unit of Transfusion Medicine of the Verona University Hospital, Italy. From April 2016 to May 2018, 499 subjects were enrolled (255 men, 244 women of whom 155 of childbearing age). Major clinical characteristics including lifestyle and dietary habits, B vitamins and homocysteine were analyzed. The MTHFR 677 C>T, cSHMT 1420 C>T, DHFR 19 bp ins/del, RFC1 80 G>A polymorphisms were also determined.

RESULTS

Mean plasma concentrations of folate, vitamin B12, vitamin B6 and homocysteine were 14.2 nmol/L (95% CI 13.7-14.8), 271.9 pmol/L (95% CI 262.6-281.5), 51.0 nmol/L (95% CI 48.7-53.4) and 13.5 µmol/L (95% CI 13.1-14.0), respectively. Plasma folate, was adequate (> 15 nmol/L) in 44.7% of all subjects, 39.0% of males and 42.5% of women < 45 years. Similarly, vitamin B12 was adequate (> 350 pmol/L) in 25.1% of all subjects and in 20.3% of men ≥ 45 years. The rare allele frequencies were 0.21 for MTHFR 677TT, 0.11 for cSHMT 1420TT, 0.18 for DHFR 19 bp del/del, 0.20 for RFC1 80AA, and a gene-nutrient interaction was confirmed for folate concentrations according to MTHFR 677C>T and DHFR 19 bp del/del.

CONCLUSION

An Italian sample of healthy blood donors shows that an adequate concentration of plasma folate and vitamin B12 is reached only in a limited percentage of subjects, thus encouraging consideration for specific public health strategies.

Prevention of Neural Tube Defects in Europe: A Public Health Failure

Objective: Thirty years ago it was demonstrated that folic acid taken before pregnancy and in early pregnancy reduced the risk of a neural tube defect (NTD). Despite Public Health Initiatives across Europe recommending that women take 0.4 mg folic acid before becoming pregnant and during the first trimester, the prevalence of NTD pregnancies has not materially decreased in the EU since 1998, in contrast to the dramatic fall observed in the USA. This study aimed to estimate the number of NTD pregnancies that would have been prevented if flour had been fortified with folic acid in Europe from 1998 as it had been in the USA. Design and Setting: The number of NTD pregnancies from 1998 to 2017 that would have been prevented if folic acid fortification had been implemented in the 28 countries who were members of the European Union in 2019 was predicted was predicted using data on NTD prevalence from 35 EUROCAT congenital anomaly registries and literature searches for population serum folate levels and folic acid supplementation. Results: From 1998 to 2017 an estimated 95,213 NTD pregnancies occurred amongst 104 million births in the 28 countries in the EU, a prevalence of 0.92 per 1,000 births. The median serum folate level in Europe over this time period was estimated to be 14.1 μg/L. There is a lack of information about women taking folic acid supplements before becoming pregnant and during the first trimester of pregnancy, with one meta-analysis indicating that around 25% of women did so. An estimated 14,600 NTD pregnancies may have been prevented if the European countries had implemented fortification at the level adopted by the USA in 1998 and 25% of women took folic acid supplements. An estimated 19,500 NTD pregnancies would have been prevented if no women took folic acid supplements. Conclusions: This study suggests that failure to implement mandatory folic acid fortification in the 28 European countries has caused, and continues to cause, neural tube defects to occur in almost 1,000 pregnancies every year.

Genetic Variants Shaping Inter-individual Differences in Response to Dietary Intakes-A Narrative Review of the Case of Vitamins

Recent advances in the field of nutrigenetics have provided evidence on how genetic variations can impact the individuals' response to dietary intakes. An objective and reliable assessment of dietary exposures should rely on combinations of methodologies including frequency questionnaires, short-term recalls or records, together with biological samples to evaluate markers of intake or status and to identify genetic susceptibilities. In an attempt to present current knowledge on how genetic fingerprints contribute to an individual's nutritional status, we present a review of current literature describing associations between genetic variants and levels of well-established biomarkers of vitamin status in free-living and generally healthy individuals. Based on the outcomes of candidate gene, genome-wide-association studies and meta-analyses thereof, we have identified several single nucleotide polymorphisms (SNPs) involved in the vitamins' metabolic pathways. Polymorphisms in genes encoding proteins involved in vitamin metabolism and transport are reported to have an impact on vitamin D status; while genetic variants of vitamin D receptor were most frequently associated with health outcomes. Genetic variations that can influence vitamin E status include SNPs involved in its uptake and transport, such as in SCAR-B1 gene, and in lipoprotein metabolism. Variants of the genes encoding the sodium-dependent vitamin C transport proteins are greatly associated with the body's status on vitamin C. Regarding the vitamins of the B-complex, special reference is made to the widely studied variant in the MTHFR gene. Methodological attributes of genetic studies that may limit the comparability and interpretability of the findings are also discussed. Our understanding of how genes affect our responses to nutritional triggers will enhance our capacity to evaluate dietary exposure and design personalized nutrition programs to sustain health and prevent disease.

One Carbon Metabolism and Mammalian Pregnancy Outcomes

One-carbon metabolism is involved in varieties of physiological processes in mammals, including nucleic acid synthesis, amino acid homeostasis, epigenetic regulation, redox balance and neurodevelopment. The current evidence linking levels of one-carbon nutrients during pregnancy to the development of oocytes, embryos, and placentas, as well as maternal and offspring health, is reviewed. The sources of mammalian one-carbon units, the pathways active in mammalian one-carbon metabolism, the maternal and fetal needs for one-carbon units and their functions during pregnancy are described. The demand for one-carbon metabolism is highest during pregnancy compared to the entire lifetime of a mammal. The primary types of one-carbon metabolism in mammals are the folate cycle, methionine cycle and transsulfuration pathway, which varies at different pregnancy stages (e.g., methylation programming of embryo, neural development of fetus, fetal growth and placenta development). Therefore, an overall consideration of one-carbon metabolism requirements for different pregnancy stages, is called for, specifically, the balance of all nutrients involved, not just one single nutrient in one-carbon metabolism. Moreover, the establishment of an ideal one-carbon metabolism requirement model is suggested according to the requirements for different pregnancy stages to support optimal pregnancy outcomes and maternal and offspring health.

Relationship between intake and plasma concentrations of vitamin B12 and folate in 873 adults with a physically active lifestyle: a cross-sectional study

BACKGROUND

Vitamin B12 and folate function as co-factors in pathways used during physical activity. Physical activity may therefore increase vitamin requirements, leading to a risk of deficient plasma concentrations. We aimed to investigate the relationship between intake and plasma concentrations of vitamin B12 and folate in physically active adults, as well as identify other determinants of vitamin B12 and folate plasma concentrations.

METHODS

The study population consisted of 873 adults (528 men and 345 women), aged 19-78 years, who participated in a 4-day walking event. The relationship between intake and plasma concentrations of vitamin B12 and folate was assessed using correlation and linear regression analyses. In addition, potential other determinants (sex, age, body mass index, energy intake and physical activity) of vitamin plasma concentrations were investigated.

RESULTS

Significant positive correlations were observed between intake and plasma concentrations of vitamin B12 [Pearson's correlation coefficient = 0.15; 95% confidence interval (CI) = 0.08-0.21] and folate (Pearson's correlation coefficient = 0.18; 95% CI = 0.12-0.25). In addition to vitamin intake, sex, age and energy intake were also determinants of both vitamin B12 and folate plasma concentrations in multivariable regression models.

CONCLUSIONS

The results suggest a positive association between intake and plasma concentrations for both vitamin B12 and folate in physically active people. By contrast to our hypothesis, physical activity was not a determinant of vitamin B12 and folate plasma concentrations. However, sex, age and energy intake were found to be determinants. Thus, when studying the relationship between intake and plasma concentrations of vitamin B12 or folate, these factors should be taken into account.

Environmental UVR Levels and Skin Pigmentation Gene Variants Associated with Folate and Homocysteine Levels in an Elderly Cohort

Ultraviolet radiation (UVR) is a ubiquitous exposure which may contribute to decreased folate levels. Skin pigmentation mediates the biological effect of UVR exposure, but its relationship to folate levels is unexamined. Interactions may exist between UVR and pigmentation genes in determining folate status, which may, in turn, impact homocysteine levels, a potential risk factor for multiple chronic diseases. Therefore, independent and interactive influences of environmental UVR and genetic variants related to skin pigmentation (MC1R-rs1805007, IRF4-rs12203592 and HERC2-rs12913832) on folate (red blood cell (RBC) and serum) and homocysteine levels were examined in an elderly Australian cohort (n = 599). Genotypes were assessed by RT/RFLP-PCR, and UVR exposures were assessed as the accumulated erythemal dose rate accumulated over 4 months (4M-EDR). Multivariate analysis found significant negative associations between 4M-EDR and RBC folate (p < 0.001, β = −0.19), serum folate (p = 0.045, β = −0.08) and homocysteine levels (p < 0.001, β = −0.28). Significant associations between MC1R-rs1805007 and serum folate levels (p = 0.020), and IRF4-rs12203592 and homocysteine levels (p = 0.026) occurred but did not remain significant following corrections with confounders. No interactions between 4M-EDR and pigmentation variants in predicting folate/homocysteine levels were found. UVR levels and skin pigmentation-related variants are potential determinants of folate and homocysteine status, although, associations are mixed and complex, with further studies warranted.

Genome-wide association study of circulating folate one-carbon metabolites

Experimental, observational, and clinical trials support a critical role of folate one-carbon metabolism (FOCM) in colorectal cancer (CRC) development. In this report, we focus on understanding the relationship between common genetic variants and metabolites of FOCM. We conducted a genome-wide association study of FOCM biomarkers among 1,788 unaffected (without CRC) individuals of European ancestry from the Colon Cancer Family Registry. Twelve metabolites, including 5-methyltetrahydrofolate, vitamin B₂ (flavin mononucleotide and riboflavin), vitamin B₆ (4-pyridoxic acid, pyridoxal, and pyridoxamine), total homocysteine, methionine, S-adenosylmethionine, S-adenosylhomocysteine, cystathionine, and creatinine were measured from plasma using liquid chromatography-mass spectrometry (LC-MS) or LC-MS/MS. For each individual biomarker, we estimated genotype array-specific associations followed by a fixed-effect meta-analysis. We identified the variant rs35976024 (at 2p11.2 and intronic of ATOH8) associated with total homocysteine (p = 4.9 × 10^-8 ). We found a group of six highly correlated variants on chromosome 15q14 associated with cystathionine (all p < 5 × 10^-8 ), with the most significant variant rs28391580 (p = 2.8 × 10^-8 ). Two variants (rs139435405 and rs149119426) on chromosome 14q13 showed significant (p < 5 × 10^-8 ) associations with S-adenosylhomocysteine. These three biomarkers with significant associations are closely involved in homocysteine metabolism. Furthermore, when assessing the principal components (PCs) derived from seven individual biomarkers, we identified the variant rs12665366 (at 6p25.3 and intronic of EXOC2) associated with the first PC (p = 2.3 × 10^-8 ). Our data suggest that common genetic variants may play an important role in FOCM, particularly in homocysteine metabolism.

Evaluation of Vitamin B12, Folate and Ferritin Serum Levels in Jordanian Population

Vitamin B12, folate, and ferritin are vital for the development of the nervous system, blood formation, and diverse metabolic functions. The aim of the current study is to evaluate the status of vitamin B12, folate and ferritin in the Jordanian population across distinct geographical locations. In this retrospective study, the cohort population included 2,880 Jordanian individuals with an average age of 47 y for males and 34 y for females (January 2014-December 2016). Vitamin B12, folate, and ferritin were measured in the blood samples by immunoassay on an automated instrument. Prevalence of low levels of vitamin B12 among males and females was similar across the four regions (24%). Equivalently high levels of folate were reported in males (24.4%) and females (23.4%). Additionally, 37.4% of males and 20.4% of females showed low levels of ferritin. Pearson's correlations did not show any association between age, vitamin B12, folate, and ferritin levels in both sexes. Univariate odd ratio (OR) and age-adjusted OR in males showed a significant decrease in low vitamin B12 risk in the region of Tafela when compared to Irbid. In conclusion, our results showed a significant difference in vitamin B12 levels between populations according to their geographical locations. Ferritin levels were low in almost a quarter of the Jordanian population with a high prevalence in males and females in Irbid and Maan, respectively. These differences might be associated with the genetic, dietary and lifestyle situation which requires further studies to elucidate the risk factors for vitamin B12 and ferritin deficiency.

The Cigarette Smoking, Coffee and Supplements Intake at Students of Sarajevo University

Introduction:

The dietary supplements are defined as vitamins and minerals or herbal products and are typically given in the form of a capsule or tablet. The nonsmokers are more attempted to use dietary supplements than individuals who smoke.

Aim:

In our investigation, we examined associations between vitamin B, folic acid, multivitamin or mineral intake among the student population and their correlation with smoking prevalence and drinking coffee.

Materials and methods:

We used a questionnaire to examine the general characteristics of the subjects, age, sex, their lifestyle, cigarette smoking, coffee intake and their use of dietary supplements. Data were collected from participants of the University of Sarajevo and a longitudinal study of 960 men and women aged 18-24 years from 2017 to 2018 was conducted.

Results:

The results showed that 32% of students took vitamin B supplements and 10% folic acid. In opposite, more than half of students took multivitamins (59.5%) and minerals (60.4%) less than one year. About a quarter or less took multivitamins (23.9%) and minerals (24.3%) for years. Less than 20% of students took multivitamins and minerals within a period of one year. In student population smoking prevalence was estimated at 21.2% and coffee intake in 71.2%. The smoking and use of vitamin B supplements were independent of each other, p = 0.201. The use of folic acid did not depend on smoking p = 0.501. There were no observed correlations between multivitamin and mineral supplement consumption compared to smoking status or drinking coffee.

Conclusion:

Deficient dietary intake of folic acid and B vitamins from food and supplemental sources appear to be one of the atherosclerosis incidences. Further studies should examine associations between dietary supplements intake and lifestyle of students, as well as smoking status and coffee intake.

Serum folate concentrations at diagnosis are associated with hepatocellular carcinoma survival in the Guangdong Liver Cancer Cohort study

Existing data on folate status and hepatocellular carcinoma (HCC) prognosis are scarce. We prospectively examined whether serum folate concentrations at diagnosis were associated with liver cancer-specific survival (LCSS) and overall survival (OS) among 982 patients with newly diagnosed, previously untreated HCC, who were enrolled in the Guangdong Liver Cancer Cohort (GLCC) study between September 2013 and February 2017. Serum folate concentrations were measured using chemiluminescent microparticle immunoassay. Cox proportional hazards models were performed to estimate hazard ratios (HR) and 95 % CI by sex-specific quartile of serum folate. Compared with patients in the third quartile of serum folate, patients in the lowest quartile had significantly inferior LCSS (HR = 1·48; 95 % CI 1·05, 2·09) and OS (HR = 1·43; 95 % CI 1·03, 1·99) after adjustment for non-clinical and clinical prognostic factors. The associations were not significantly modified by sex, age at diagnosis, alcohol drinking status and Barcelona Clinic Liver Cancer (BCLC) stage. However, there were statistically significant interactions on both multiplicative and additive scale between serum folate and C-reactive protein (CRP) levels or smoking status and the associations of lower serum folate with worse LCSS and OS were only evident among patients with CRP > 3·0 mg/l or current smokers. An inverse association with LCSS were also observed among patients with liver damage score ≥3. These results suggest that lower serum folate concentrations at diagnosis are independently associated with worse HCC survival, most prominently among patients with systemic inflammation and current smokers. A future trial of folate supplementation seems to be promising in HCC patients with lower folate status.

Analysis of genetic polymorphism of methylenetetrahydrofolate reductase in a large ethnic Hakka population in southern China

Methylenetetrahydrofolate reductase (MTHFR) catalyzes conversion of methylene tetrahydrofolate to methylte trahydrofolate. MTHFR C677T polymorphism has been regarded as a risk factor for various vascular diseases. Our study aimed to investigate the distribution frequencies of this polymorphism among Hakka population living in southern China. We retrospectively recruited 5102 unrelated Chinese Hakka subjects. MTHFR C677T polymorphism was tested using the polymerase chain reaction (PCR) and DNA sequencing. A total of 2358 males and 2744 females (aged from 10 years to 101 years) were included in this study. In total, 2835 (55.63%) subjects were homozygous for the C allele (CC), 1939 (38.00%) subjects were heterozygous (CT), and 325 (6.37%) subjects were homozygous for the T allele (TT). The allelic frequency of mutant T was 25.37% with 325 individual homozygous for this defective allele resulting in a frequency of about 6.37% for the TT genotype. According to the study results, the overall frequency of MTHFR C677T genotypes did not differ significantly among the gender and age groups. Our study showed the prevalence of MTHFR C677T polymorphism in a large ethnic Hakka population living in southern China. It would be important implications for the primary prevention of various vascular diseases.

Determinants of folate and vitamin B12 plasma levels in the French E3N-EPIC cohort

PURPOSE

Impaired B vitamin status has been identified as a risk factor for major chronic diseases. This study aims at examining the determinants of plasma folate and vitamin B12 concentrations, considering lifestyle factors and MTHFR polymorphisms.

METHODS

A total of 988 women aged 40-65 years from the French E3N cohort were investigated. Intakes of folate and vitamin B12 were assessed using food frequency questionnaires, and plasma concentrations were measured by microbiological assay. Dietary scores were computed to summarize folate and vitamin B12 dietary sources. MTHFR-C677T and MTHFR-A1298C were determined by Kaspar assay. Pearson's partial correlation coefficients and multivariable linear regression models were used to assess correlations between main determinants and plasma folate and vitamin B12 levels.

RESULTS

The partial correlation coefficient between dietary intakes and plasma folate was 0.19 (p value <0.001) and 0.08 (p value = 0.008) for vitamin B12. Dietary scores were the main determinant of B vitamin plasma concentrations with a percent change per unit increase of 12.64% (p value <0.001) for folate and 7.6% (p value <0.001) for vitamin B12. Homozygous (T/T) or heterozygous (C/T) women for MTHFR-C677T had lower plasma folate concentrations [C/T: -6.48% (p value = 0.038) and T/T: -15.89% (p value <0.001)] compared to women carrying the C/C genotype. Other determinants of B vitamin plasma concentration include: smoking status for folate, and age and hormone replacement therapy for vitamin B12.

CONCLUSIONS

We confirmed previous findings on the role of diet as main determinant of folate and vitamin B12 plasma concentrations. However, the impact of genetic polymorphisms and lifestyle factors on plasma B vitamin concentrations should not be neglected.

An update on vitamin B12-related gene polymorphisms and B12 status

Background

Vitamin B12 is an essential micronutrient in humans needed for health maintenance. Deficiency of vitamin B12 has been linked to dietary, environmental and genetic factors. Evidence for the genetic basis of vitamin B12 status is poorly understood. However, advancements in genomic techniques have increased the knowledge-base of the genetics of vitamin B12 status. Based on the candidate gene and genome-wide association (GWA) studies, associations between genetic loci in several genes involved in vitamin B12 metabolism have been identified.

Objective

The objective of this literature review was to identify and discuss reports of associations between single-nucleotide polymorphisms (SNPs) in vitamin B12 pathway genes and their influence on the circulating levels of vitamin B12.

Methods

Relevant articles were obtained through a literature search on PubMed through to May 2017. An article was included if it examined an association of a SNP with serum or plasma vitamin B12 concentration. Beta coefficients and odds ratios were used to describe the strength of an association, and a P < 0.05 was considered as statistically significant. Two reviewers independently evaluated the eligibility for the inclusion criteria and extracted the data.

Results

From 23 studies which fulfilled the selection criteria, 16 studies identified SNPs that showed statistically significant associations with vitamin B12 concentrations. Fifty-nine vitamin B12-related gene polymorphisms associated with vitamin B12 status were identified in total, from the following populations: African American, Brazilian, Canadian, Chinese, Danish, English, European ancestry, Icelandic, Indian, Italian, Latino, Northern Irish, Portuguese and residents of the USA.

Conclusion

Overall, the data analyzed suggests that ethnic-specific associations are involved in the genetic determination of vitamin B12 concentrations. However, despite recent success in genetic studies, the majority of identified genes that could explain variation in vitamin B12 concentrations were from Caucasian populations. Further research utilizing larger sample sizes of non-Caucasian populations is necessary in order to better understand these ethnic-specific associations.

Methylene-tetrahydrofolate reductase contributes to allergic airway disease

Rationale

Environmental exposures strongly influence the development and progression of asthma. We have previously demonstrated that mice exposed to a diet enriched with methyl donors during vulnerable periods of fetal development can enhance the heritable risk of allergic airway disease through epigenetic changes. There is conflicting evidence on the role of folate (one of the primary methyl donors) in modifying allergic airway disease.

Objectives

We hypothesized that blocking folate metabolism through the loss of methylene-tetrahydrofolate reductase (Mthfr) activity would reduce the allergic airway disease phenotype through epigenetic mechanisms.

Methods

Allergic airway disease was induced in C57BL/6 and C57BL/6^Mthfr-/- mice through house dust mite (HDM) exposure. Airway inflammation and airway hyperresponsiveness (AHR) were measured between the two groups. Gene expression and methylation profiles were generated for whole lung tissue. Disease and molecular outcomes were evaluated in C57BL/6 and C57BL/6^Mthfr-/- mice supplemented with betaine.

Measurements and main results

Loss of Mthfr alters single carbon metabolite levels in the lung and serum including elevated homocysteine and cystathionine and reduced methionine. HDM-treated C57BL/6^Mthfr-/- mice demonstrated significantly less airway hyperreactivity (AHR) compared to HDM-treated C57BL/6 mice. Furthermore, HDM-treated C57BL/6^Mthfr-/- mice compared to HDM-treated C57BL/6 mice have reduced whole lung lavage (WLL) cellularity, eosinophilia, and Il-4/Il-5 cytokine concentrations. Betaine supplementation reversed parts of the HDM-induced allergic airway disease that are modified by Mthfr loss. 737 genes are differentially expressed and 146 regions are differentially methylated in lung tissue from HDM-treated C57BL/6^Mthfr-/- mice and HDM-treated C57BL/6 mice. Additionally, analysis of methylation/expression relationships identified 503 significant correlations.

Conclusion

Collectively, these findings indicate that the loss of folate as a methyl donor is a modifier of allergic airway disease, and that epigenetic and expression changes correlate with this modification. Further investigation into the mechanisms that drive this observation is warranted.

Associations of genetic determinants of serum vitamin B12 and folate concentrations with hay fever and asthma: a Mendelian randomization meta-analysis

BACKGROUND/OBJECTIVES

Studies of the effect of vitamin B12 and folate on the risk of asthma and hay fever have shown inconsistent results that may be biased by reverse causation and confounding. We used a Mendelian randomization approach to examine a potential causal effect of vitamin B12 and folate on hay fever, asthma, and selected biomarkers of allergy by using 11 vitamin B12-associated single-nucleotide polymorphisms (SNPs) and 2 folate-associated SNPs as unconfounded markers.

SUBJECTS/METHODS

We included 162,736 participants from 9 population-based studies including the UK Biobank. Results were combined in instrumental variable and meta-analyses and effects expressed as odds ratios (ORs) or estimates with 95% confidence interval (CI).

RESULTS

Using genetic proxies for B12 and folate, instrumental variable analyses did not show evidence for associations between serum B12 and hay fever: OR = 1.02 (95% CI: 0.98, 1.05), asthma: OR = 0.99 (95% CI: 0.95, 1.04), allergic sensitization: OR = 1.02 (95% CI: 0.74, 1.40), or change in serum IgE: 10.0% (95% CI: -9.6%, 29.6%) per 100 pg/ml B12. Similarly, there was no evidence for association between serum folate and hay fever: OR = 0.74 (95% CI: 0.45, 1.21), asthma: OR = 0.80 (95% CI: 0.43, 1.49), or allergic sensitization: OR = 1.92 (95% CI: 0.11, 33.45), but there was a statistically significant association with change in serum IgE: 2.0% (95% CI: 0.43%, 3.58%) per 0.1 ng/ml serum folate.

CONCLUSIONS

Our results did not support the hypothesis that levels of vitamin B12 and folate are causally related to hay fever, asthma, or biomarkers of allergy, but we found evidence of a positive association between serum folate and serum total IgE.

Folate status in women of childbearing age with obesity: a review

Several studies have described a positive association between elevated BMI and birth defects risk. Data on plasma concentration of folate in pregnant women with obesity have shown values far below those recommended, regardless of diet, while folate levels should increase before pregnancy to reduce neural tube defects. We report a descriptive review of the most recent studies (from 2005 to 2015) to evaluate folate status through a population of women of childbearing age affected by obesity. The literature contains few studies, which present conflicting results regarding folate status in non-pregnant women of childbearing age affected by obesity, and it appears that there is a modification in folate metabolism, with a reduction in plasma folate levels and an increase in erythrocyte folate uptake. In conclusion, the folate status in women of childbearing age should be assessed by both plasma and erythrocyte levels to start a personalised and more adequate supplementation before conception. Further studies need to be conducted in a larger population, which take into account variables that can affect folate metabolism, such as dietary intake, lifestyle and genetic factors, oral contraceptives or other drug use, previous weight-loss programmes, or a history of bariatric surgery.

Vitamin B12 deficiency

Vitamin B₁₂ (B12; also known as cobalamin) is a B vitamin that has an important role in cellular metabolism, especially in DNA synthesis, methylation and mitochondrial metabolism. Clinical B12 deficiency with classic haematological and neurological manifestations is relatively uncommon. However, subclinical deficiency affects between 2.5% and 26% of the general population depending on the definition used, although the clinical relevance is unclear. B12 deficiency can affect individuals at all ages, but most particularly elderly individuals. Infants, children, adolescents and women of reproductive age are also at high risk of deficiency in populations where dietary intake of B12-containing animal-derived foods is restricted. Deficiency is caused by either inadequate intake, inadequate bioavailability or malabsorption. Disruption of B12 transport in the blood, or impaired cellular uptake or metabolism causes an intracellular deficiency. Diagnostic biomarkers for B12 status include decreased levels of circulating total B12 and transcobalamin-bound B12, and abnormally increased levels of homocysteine and methylmalonic acid. However, the exact cut-offs to classify clinical and subclinical deficiency remain debated. Management depends on B12 supplementation, either via high-dose oral routes or via parenteral administration. This Primer describes the current knowledge surrounding B12 deficiency, and highlights improvements in diagnostic methods as well as shifting concepts about the prevalence, causes and manifestations of B12 deficiency.

South Asian Ethnicity Is Related to the Highest Risk of Vitamin B12 Deficiency in Pregnant Canadian Women

Vitamin B12 (B12) adequacy during pregnancy is crucial for maternal health and optimal fetal development; however, suboptimal B12 status has been reported in pregnant Canadian women. Methylmalonic acid (MMA) is a sensitive indicator of B12 status. Since few studies have measured MMA during pregnancy in Canadian women, the objective of this study was to evaluate B12 status in pregnant women living in Metro Vancouver, using both plasma total B12 and MMA. We recruited a convenience sample of 320 pregnant women between 20 and 35 gestational weeks from local healthcare facilities. Plasma total B12 concentrations indicative of deficiency (<148 pmol/L) and suboptimal B12 status (148–220 pmol/L) were found in 18% and 33% of the women, respectively. Normal plasma MMA concentration (<210 nmol/L) was observed in 82% of all women. Gestational age was a strong predictor of plasma total B12 and MMA concentration, and South Asian ethnicity of B-12 deficiency and MMA concentrations. Overall, there was a high discrepancy between the prevalence of B12 inadequacy depending on the biomarker used. Independently, however, South Asian women were at particular risk for B12 deficiency, likely due to lower animal source food intake. Further study of this vulnerable group and performance testing of B12 biomarkers is warranted.

Genetic determinants of serum vitamin B12 and their relation to body mass index

Lower serum vitamin B12 levels have been related to adverse metabolic health profiles, including adiposity. We used a Mendelian randomization design to test whether this relation might be causal. We included two Danish population-based studies (ntotal = 9311). Linear regression was used to test for associations between (1) serum vitamin B12 levels and body mass index (BMI), (2) genetic variants and serum vitamin B12 levels, and (3) genetic variants and BMI. The effect of a genetically determined decrease in serum vitamin B12 on BMI was estimated by instrumental variable regression. Decreased serum vitamin B12 associated with increased BMI (P < 1 × 10-4). A genetic risk score based on eight vitamin B12 associated variants associated strongly with serum vitamin B12 (P < 2 × 10-43), but not with BMI (P = 0.91). Instrumental variable regression showed that a 20% decrease in serum vitamin B12 was associated with a 0.09 kg/m2 (95% CI 0.05; 0.13) increase in BMI (P = 3 × 10-5), whereas a genetically induced 20% decrease in serum vitamin B12 had no effect on BMI [-0.03 (95% CI -0.22; 0.16) kg/m2] (P = 0.74). Nevertheless, the strongest serum vitamin B12 variant, FUT2 rs602662, which was excluded from the B12 genetic risk score due to potential pleiotropic effects, showed a per allele effect of 0.15 kg/m2 (95% CI 0.01; 0.32) on BMI (P = 0.03). This association was accentuated including two German cohorts (ntotal = 5050), with a combined effect of 0.19 kg/m2 (95% CI 0.08; 0.30) (P = 4 × 10-4). We found no support for a causal role of decreased serum vitamin B12 levels in obesity. However, our study suggests that FUT2, through its regulation of the cross-talk between gut microbes and the human host, might explain a part of the observational association between serum vitamin B12 and BMI.

Folate deficiency affects dendritic cell function and subsequent T helper cell differentiation

Insufficient folate status may be related to the increasing prevalence of immune- or inflammation-related chronic diseases. To investigate the effects of folate on immune regulation, we examined the impact of folate deficiency (FD) on dendritic cell (DC) maturation and function and, thus, T helper (Th) cells differentiation. First, bone marrow-derived DCs (BMDCs) were generated from BALB/c mice bone marrow cells cultured in folate-containing (F-BMDCs) or folate-deficient (FD-BMDCs) medium. FD-BMDC displayed more immature phenotype including reduced levels of major histocompatibility complex class II (MHC II), co-stimulatory molecules and characteristic of higher endocytic activity. FD-BMDC produced less IL-12p70 and proinflammatory cytokines in response to lipopolysaccharide. This aberrant DC maturation due to FD resulted in reduced BMDC-induced Th cell activity and lower IL-2, IFNγ, IL-13 and IL-10 productions. Further in vivo study confirmed significantly lower IFNγ and IL-10 productions by T cells and showed higher splenic naïve Th and lower memory T, effector T and regulatory T cell (Treg) percentages in mice fed with the FD diet for 13 weeks. To investigate the role of DCs on T cell activity, splenic DCs (spDC) from FD mice were cocultured with Th cells. The FD spDC had lower MHC II and CD80 expressions and subsequently impaired DC-induced Th differentiation, shown as decreased cytokine productions. This study demonstrated that folate deficiency impaired DC functions and, thus, Th differentiation and responses, suggesting that folate plays a crucial role in maintaining Th cells homeostasis.

Genetic and environmental factors associated with vitamin B12status in Amazonian children

Objective

To evaluate the prevalence of vitamin B12deficiency and factors associated with vitamin B12status in Amazonian children.

Design

Genetic risk score (GRS), socio-economic and nutritional status, and morbidity data were the independent variables used in multiple linear regression models to evaluate factors associated with vitamin B12status in a population-based cross-sectional study. GRS was created by summing a number of known risk alleles for low serum vitamin B12.

Setting

Acrelândia, western Brazilian Amazon.

Subjects

Children (n988) aged <10 years.

Results

Overall prevalence of vitamin B12deficiency (<150 pmol/l) was 4·2 (95 % CI 3·0, 5·6) % and was highest in children aged <24 months: 13·6 (95 % CI % 8·8, 19·7) %. For children <24 months, wealth index (β=0·017,P=0·030) and animal protein intake(β=0·219,P=0·003) were positively associated with vitamin B12status. GRS (β=−0·114,P<0·001) and serum homocysteine (β=–0·049,P<0·001) were negatively associated. Among children aged ≥24 months, vitamin B12status was positively associated with wealth index (β=0·012,P<0·001), height-for-ageZ-score (β=0·024, P=0·033) and serum vitamin A (β=0·089,P<0·001). Age≥60 months(β=–0·118,P<0·001), GRS (β=–0·048, P<0·001), maternal schooling <5 years (β=–0·083,P<0·001), low intake of animal-derived foods (β=–0·050,P=0·030), serum homocysteine (β=–0·053,P<0·001), serum folate ≥23·6 nmol/l (β=–0·055,P=0·012) and geohelminth infection (β=–0·141,P=0·017) were negatively associated with vitamin B12status.

Conclusions

GRS, poverty, low intake of animal-derived foods, geohelminth infection, vitamin A and folate status were important factors associated with vitamin B12status of children in our study.

MTHFR C677T genotype and cardiovascular risk in a general population without mandatory folic acid fortification

PURPOSE

Meta-analyses have suggested an effect of MTHFR C677T genotype (rs1801133), a proxy for blood total homocysteine, on cardiovascular disease (CVD) in populations with low population dietary folate. The aim was to examine the association and effect modification by serum folate and vitamin B12 levels between MTHFR and CVD-related outcomes in a general population with no mandatory folic acid fortification policy.

METHODS

The study population included 13,748 adults retrieved from pooling of four population-based studies conducted in Denmark. MTHFR genotype, serum folate (measured in approximately 9,356 individuals), and serum vitamin B12 (9,215 individuals), hypertension, and dyslipidemia were measured at baseline, and participants were followed for a mean of 10.5-11.7 years in central registries for diagnoses of stroke (623 incidents), ischaemic heart disease (IHD) (835 incidents), and all-cause mortality (1,272 incidents).

RESULTS

The MTHFR genotype (TT vs. CC/CT) was not associated with hypertension [OR (95% CI) 1.09 (0.95-1.25)], dyslipidemia [OR (95% CI) 0.97 (0.84-1.11)], stroke [HR (95% CI) 0.92 (0.69-1.23)], and all-cause mortality [HR (95% CI) 0.94 (0.77-1.14)], either overall, or in participants with low serum folate or B12 status (P values for interactions 0.15-0.94). Individuals with the MTHFR TT genotype had a higher risk of IHD (HR (95% CI) 1.38 (1.11-1.71)), but this association was not modified by folate status (P value for interaction 0.45).

CONCLUSIONS

Our results do not support a causal relationship between homocysteine and CVD. However, we cannot exclude a direct causal effect of MTHFR C677T genotype on IHD.

Should we monitor vitamin B12 and folate levels in Crohn's disease patients?

OBJECTIVE

Crohn's disease commonly involves the small intestine, which is the site of vitamin B12 and folate absorption. Our aim was to define the prevalence of vitamin B12 and folate deficiency in patients with Crohn's disease and to identify predictive factors associated with such abnormalities.

METHODS

Two years prospective study of 180 consecutive Crohn's disease patients. Vitamin B12 and folate deficiency was defined as serum levels below 200 pg/ml and 3 ng/ml, respectively. We analysed prevalence of these deficiencies and possible predictive factors including small intestine resection, disease location, activity and duration of disease. Controls were ulcerative colitis patients (n = 70).

RESULTS

The prevalence of B12 deficiency in Crohn's disease was 15.6% (95%CI 9.7-20%) compared with 2.8% (95%CI 0.8-9.8%) in ulcerative colitis (p = 0.007). With regard to folate deficiency, the prevalence in patients with Crohn's disease was 22.2% (95%CI 16-28%) compared with 4.3% (95%CI 1.4-12%) in ulcerative colitis (p = 0.001); 7.8% of Crohn's disease patients had macrocytic anemia. Ileal resection was found to be a risk factor for B12 deficiency (OR 2.7; 1.2-6.7; p = 0.02), and disease activity a risk factor for folate deficiency (OR 2.4; 1.2-5.1; p = 0.01).

CONCLUSION

A significant proportion of patients with Crohn's disease suffer from vitamin B12 and/or folate deficiency, suggesting that regular screening should be performed, with closer monitoring in patients with ileal resection or active disease.

MTHFR polymorphisms and capecitabine-induced toxicity in patients with metastatic colorectal cancer

OBJECTIVE

The availability of current chemotherapeutic options for metastatic colorectal cancer (mCRC) has increased survival, but it is also accompanied by considerable morbidity. Fluoropyrimidines are the mainstay of systemic therapy. Germline pharmacogenetic markers involved in 5-fluorouracil pharmacodynamics could provide individualized pretreatment tools for predicting toxicity. Research on methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms and fluoropyrimidine treatment outcome has focused on intravenous 5-fluorouracil and has yielded inconclusive results. The literature on pharmacogenetics in capecitabine-based chemotherapy is scarce. Therefore, we analysed the association of MTHFR gene polymorphisms and the occurrence of serious toxicity of first-line capecitabine monotherapy and combination therapy.

METHODS

One hundred and twenty-seven patients treated with first-line monotherapy capecitabine and 141 patients on capecitabine-irinotecan combination therapy were recruited from the CAIRO trial, an open-label phase III randomized trial, comparing sequential versus combination chemotherapy with capecitabine, irinotecan and oxaliplatin in mCRC. All patients were genotyped for MTHFR 1298A>C and 677C>T polymorphisms and analysed in both cohorts separately for the association between the MTHFR genotype and incidence of grade 3-4 overall toxicity and specific adverse events, as well as efficacy parameters.

RESULTS

MTHFR 1298A>C and 677C>T genotypes were not associated with grade 3-4 overall toxicity, febrile neutropenia or hand-foot syndrome. MTHFR 1298CC homozygotes showed a borderline significantly higher incidence of grade 3-4 diarrhoea compared with MTHFR 1298AC or AA individuals (25 vs. 5%, P=0.041) in the monotherapy cohort. No significant association was found between the MTHFR genotypes and efficacy parameters in either treatment cohort.

CONCLUSION

MTHFR polymorphisms are not associated with toxicity or efficacy in mCRC patients treated with capecitabine-based chemotherapy.

Genetic architecture of vitamin B12 and folate levels uncovered applying deeply sequenced large datasets

Genome-wide association studies have mainly relied on common HapMap sequence variations. Recently, sequencing approaches have allowed analysis of low frequency and rare variants in conjunction with common variants, thereby improving the search for functional variants and thus the understanding of the underlying biology of human traits and diseases. Here, we used a large Icelandic whole genome sequence dataset combined with Danish exome sequence data to gain insight into the genetic architecture of serum levels of vitamin B₁₂ (B₁₂) and folate. Up to 22.9 million sequence variants were analyzed in combined samples of 45,576 and 37,341 individuals with serum B₁₂ and folate measurements, respectively. We found six novel loci associating with serum B₁₂ (CD320, TCN2, ABCD4, MMAA, MMACHC) or folate levels (FOLR3) and confirmed seven loci for these traits (TCN1, FUT6, FUT2, CUBN, CLYBL, MUT, MTHFR). Conditional analyses established that four loci contain additional independent signals. Interestingly, 13 of the 18 identified variants were coding and 11 of the 13 target genes have known functions related to B₁₂ and folate pathways. Contrary to epidemiological studies we did not find consistent association of the variants with cardiovascular diseases, cancers or Alzheimer's disease although some variants demonstrated pleiotropic effects. Although to some degree impeded by low statistical power for some of these conditions, these data suggest that sequence variants that contribute to the population diversity in serum B₁₂ or folate levels do not modify the risk of developing these conditions. Yet, the study demonstrates the value of combining whole genome and exome sequencing approaches to ascertain the genetic and molecular architectures underlying quantitative trait associations.

Genome-wide association studies have in recent years revealed a wealth of common variants associated with common diseases and phenotypes. We took advantage of the advances in sequencing technologies to study the association of low frequency and rare variants in conjunction with common variants with serum levels of vitamin B₁₂ (B₁₂) and folate in Icelanders and Danes. We found 18 independent signals in 13 loci associated with serum B₁₂ or folate levels. Interestingly, 13 of the 18 identified variants are coding and 11 of the 13 target genes have known functions related to B₁₂ and folate pathways. These data indicate that the target genes at all of the loci have been identified. Epidemiological studies have shown a relationship between serum B₁₂ and folate levels and the risk of cardiovascular diseases, cancers, and Alzheimer's disease. We investigated association between the identified variants and these diseases but did not find consistent association.

Intake and blood concentrations of folate and their association with health-related behaviors in Korean college students

The purpose of this study is to assess folate intake, and serum and red blood cell (RBC) folate concentrations, and investigate the association between folate status and health-related behaviors among Korean college students. A total of 169 students, aged between 18 and 27 years, participated in this study. Dietary intake data were collected by trained interviewers using a 24-hour recall method for three non-consecutive days in 2009. Information on health-related behaviors was obtained by a self-administered questionnaire. Serum and RBC folate concentrations were measured by microbiological assay. The average intakes of folate were 456 µgDFE and 347 µgDFE in male and female students, respectively. While the average serum folate concentration was significantly lower in male students (8.9 ng/mL) compared to female students (12.5 ng/mL), RBC concentrations were not significantly different between male (398.6 ng/mL) and female students (405.3 ng/mL). In male students, low serum folate concentrations were associated with total folate intake less than the Estimated Average Requirement, non-use of folic acid supplements, smoking, alcohol drinking at least once a week and low physical activity. In female students, low serum folate concentrations were associated with smoking and alcohol drinking at least two drinks at a time and BMI ≥ 25. Alcohol drinking and low physical activity were also associated with low RBC folate concentrations in both male and female students. In order to improve folate nutritional status of college students, the practice of desirable health-related behaviors, such as non-smoking, moderate alcohol drinking, regular physical activity, and maintenance of healthy BMI should be encouraged along with consumption of folate-rich foods and supplements.

Maternal folate status in early pregnancy and child emotional and behavioral problems: the Generation R Study

BACKGROUND

Maternal prenatal folate status has been linked to neurodevelopmental disorders, but the association with child emotional and behavioral problems is unclear.

OBJECTIVES

We assessed the association of maternal folate status during pregnancy with child emotional and behavioral problems. Also, we examined whether any association between folate status and child problems is a consequence of maternal folic acid supplement use or variation in maternal MTHFR genotype.

DESIGN

Within a population-based cohort, we measured maternal plasma folate concentrations in early pregnancy and assessed folic acid supplement use by questionnaire. Mothers of European descent were genotyped for the MTHFR 677 C→T polymorphism. Child emotional and behavioral problems were assessed with the Child Behavior Checklist at 3 y in 3209 children.

RESULTS

Children of mothers with prenatal folate deficiency were at higher risk of emotional problems (OR: 1.57; 95% CI: 1.03, 2.38) but not behavioral problems (OR: 1.00; 95% CI: 0.64, 1.56) after adjustment for confounders. A higher risk of emotional problems was also found in children whose mothers started using folic acid supplements late or did not use supplements at all (OR: 1.45; 95% CI: 1.14, 1.84) than in children whose mothers started periconceptionally. However, low plasma folate concentrations only partly explained this association (OR: 1.38; 95% CI: 1.08, 1.78). Although related to plasma folate concentrations, maternal MTHFR genotype did not explain the association of folate status with offspring emotional problems.

CONCLUSION

Low maternal folate status during early pregnancy is associated with a higher risk of emotional problems in the offspring.

High circulating folate and vitamin B-12 concentrations in women during pregnancy are associated with increased prevalence of atopic dermatitis in their offspring

Recent studies suggest that in utero exposure of methyl donors influences programming of the fetal immune system in favor of development of allergic disease. The aim of this study was to assess whether the MTHFR C677T polymorphism, folic acid supplementation, and circulating folate and vitamin B-12 concentrations during pregnancy were associated with wheezing, shortness of breath, and atopic dermatitis in offspring. The study was a population-based birth cohort from fetal life until 48 mo (n = 8742). The use of folic acid supplementation during pregnancy was assessed by questionnaire. Plasma folate and serum vitamin B-12 concentrations and the MTHFR C677T polymorphism were available from blood collected in early pregnancy. Atopic dermatitis, wheezing, and shortness of breath in the offspring were assessed by parental-derived questionnaires at 12, 24, 36, and 48 mo. Maternal folate >16.2 nmol/L and vitamin B-12 >178 pmol/L were positively associated with the development of atopic dermatitis [adjusted OR: 1.18 (95% CI: 1.05-1.33) and adjusted OR: 1.30 (95% CI: 1.06-1.60) for the highest quartiles of folate and vitamin B-12 concentrations, respectively] but not with wheezing and shortness of breath. Maternal MTHFR C677T polymorphism and folic acid supplementation were not associated with wheezing, shortness of breath, and atopic dermatitis. No interactions were found by age, family history of atopy, folic acid supplementation, MTHFR C677T polymorphism, or maternal smoking (P-interaction > 0.10). High folate and vitamin B-12 levels during pregnancy are associated with increased prevalence of atopic dermatitis in the offspring. Potential risks of high folate and vitamin B-12 concentrations on allergic outcomes should be evaluated when discussing mandatory fortification programs.

Healthcare-related characteristics of low vs normal folate levels among women of child-bearing age

OBJECTIVE

Despite the institution of mandatory folic acid fortification in the US, folate deficiencies still occur and are associated with an increased risk of several conditions. Since little is known regarding the relationship between folate status and other clinical, demographic, and healthcare-related characteristics, the objective of the study was to compare healthcare-related characteristics among US child-bearing age women with low vs normal red blood cell (RBC) folate levels.

RESEARCH DESIGN AND METHODS

Data from the 2003-2006 National Health and Nutrition Examination Survey (NHANES) were used to conduct a retrospective cohort study. Women (aged 18-45 when surveyed) were categorized in two cohorts for comparison: normal RBC folate level (≥ 140 ng/ml, NFL) and low RBC folate level (<140 ng/ml, LFL).

RESULTS

Of the 2816 subjects, 5.9% were assigned to the LFL cohort and were significantly younger (28 vs 30 years, p=0.01); a greater proportion were 18-25 years old (55.7% vs 39.9%, p<0.001) or African-American (55.1% vs 22.3%, p<0.01). A lower proportion of LFL women were insured (67.3% vs 75.5%, p=0.01) with low rates of private insurance (39.5% vs 53.1%, p<0.01), while Medicaid/SCHIP coverage was similar (16.8% vs 15.1%, p=0.56). Predictors of low folate levels included aged 36-45 years (OR: 2.14 [95% CI: 1.04, 4.39]) and never being married (2.65 [1.34, 5.24]), while a household income ≥ $75,000 reduced the likelihood of having low folate levels (0.20 [0.06, 0.73]).

LIMITATIONS

The proportion of women with low folate levels was small, with the sample size limiting the ability to adjust for other factors during analysis. Medical histories were based on patient interviews and are subject to recall bias.

CONCLUSION

LFL women are younger and have low rates of private insurance coverage compared to women with normal folate levels. Differences in age, marital status, and household income are associated with folate status.

Vitamin B-12, folate, iron, and vitamin A concentrations in rural Indian children are associated with continued breastfeeding, complementary diet, and maternal nutrition

BACKGROUND

Determinants of vitamin B-12, folate, iron, and vitamin A concentrations in young children in rural south Asia are poorly understood. These micronutrients are crucial for the production of hemoglobin and have other important physiologic functions.

OBJECTIVE

We sought to develop explanatory models for concentrations of vitamin B-12, folate, ferritin, and retinol binding protein (RBP) in children aged between 1 and 2 y in rural Karnataka, India.

DESIGN

We performed a cross-sectional study in 12-23-mo-old toddlers who lived in 2 rural districts of Karnataka, India. For each child, data concerning dietary, food-security, and sociodemographic and maternal factors were obtained, and serum vitamin B-12, folate, ferritin, and RBP were measured. Multiple regression and structural equation modeling were applied to determine associations with micronutrient concentrations.

RESULTS

Of 396 sampled children, 254 children (65.6%) had at least one micronutrient deficiency. With the use of multiple regression, continued breastfeeding was independently associated with the concentration of each micronutrient [(log) vitamin B-12: standardized coefficient of -0.30 (P < 0.001); folate: standardized coefficient of +0.20 (P < 0.001); (log) ferritin: standardized coefficient of -0.18 (P = 0.004); (log) RBP: standardized coefficient of-0.21 (P < 0.001)]. Children who continued to breastfeed received less nutrition from complementary foods and belonged to poorer families with higher food insecurity. A structural equation model for children's vitamin B-12 concentrations was developed that highlighted the interrelation between wealth, continued breastfeeding, complementary diet, and vitamin B-12 concentrations in children.

CONCLUSIONS

Micronutrient deficiencies are common in this population. Rural Indian children between 1 and 2 y of age who continue to breastfeed should be especially targeted during micronutrient-supplementation programs. This trial was registered in the Australian and New Zealand Clinical Trials Registry as ACTRN12611000596909.

Genetic and lifestyle variables associated with homocysteine concentrations and the distribution of folate derivatives in healthy premenopausal women

BACKGROUND

Low folate and high homocysteine (Hcy) concentrations are associated with pregnancy-related pathologies such as spina bifida. Polymorphisms in folate/Hcy metabolic enzymes may contribute to this potentially pathogenic biochemical phenotype.

METHODS

The study comprised 26 Caucasian and 23 African-American premenopausal women. Subjects gave fasting blood samples for biochemical phenotyping and genotyping. Total Hcy (tHcy) and both plasma and red blood cell (RBC) folate derivatives (i.e. tetrahydrofolate [THF], 5-methylTHF [5-MTHF], and 5,10-methenylTHF [5,10-MTHF]) were measured using stable isotope dilution liquid chromatography, multiple reaction monitoring, and mass spectrometry. Eleven polymorphisms from nine folate/Hcy pathway genes were genotyped. Tests of association between genetic, lifestyle, and biochemical variables were applied.

RESULTS

In African American women, tHcy concentrations were associated (p < 0.05) with total RBC folate, RBC 5-MTHF, B(12), and polymorphisms in methionine synthase (MTR) and thymidylate synthase (TYMS). In Caucasian women, tHcy concentrations were not associated with total folate levels, but were associated (p < 0.05) with RBC THF, ratios of RBC 5-MTHF:THF, and polymorphisms in 5,10-methylenetetrahydrofolate reductase (MTHFR) and MTR. In African Americans, folate derivative levels were associated with smoking, B(12), and polymorphisms in MTR, TYMS, methionine synthase reductase (MTRR), and reduced folate carrier1 (RFC1). In Caucasians, folate derivative levels were associated with vitamin use, B(12), and polymorphisms in MTHFR, TYMS, and RFC1.

CONCLUSIONS

Polymorphisms in the folate/Hcy pathway are associated with tHcy and folate derivative levels. In African American and Caucasian women, different factors are associated with folate/Hcy phenotypes and may contribute to race-specific differences in the risks of a range of pregnancy-related pathologies.

Atopy, asthma, and lung function in relation to folate and vitamin B(12) in adults

BACKGROUND

Recent studies suggested low serum folate and impaired folate metabolism as potential risk factors for development of asthma and atopic disease, but the results are inconsistent. The aim of this study was to investigate the relations of markers of folate and vitamin B₁₂ (B₁₂) deficiency with different phenotypes of asthma and atopy.

METHODS

A random sample of 6784 persons from a general population aged 30-60 years participated in a health examination in 1999-2001, and 4516 (66.6%) of those also participated in a follow-up examination 5 years later. The examinations included spirometry, measurements of serum folate and B₁₂, specific IgE to inhalant allergens, total IgE, and genotyping of the MTHFR-C677T polymorphism - a genetic marker of impaired folate metabolism. Information about dietary intake of folate and B₁₂, asthma diagnosis, and airway symptoms was obtained by questionnaires.

RESULTS

Low serum folate levels and the TT genotype of the MTHFR-C677T polymorphism were associated with increased prevalence of self-reported doctor-diagnosed asthma [odds ratio (OR) 1.37, 95% confidence interval (CI) 1.05-1.79 and OR 1.52; 95% CI 1.12-2.06, respectively] and attacks of shortness of breath (OR 1.43, 95% CI 1.14-1.79 and OR 1.47; 95% CI: 1.14-1.91, respectively). We found no significant associations with lung function or atopic outcomes. Serum levels of B₁₂ and dietary intake of folate and B₁₂ were not associated with asthma or atopy.

CONCLUSIONS

We found that two objective markers of folate deficiency were associated with self-reported doctor-diagnosed asthma and attacks of shortness of breath, but not with lung function or atopy.