Genetic modifiers of folate, vitamin B-12, and homocysteine status in a cross-sectional study of the Canadian population

GWAS of Folate Metabolism With Gene-environment Interaction Analysis Revealed the Possible Role of Lifestyles in the Control of Blood Folate Metabolites in Japanese: The J-MICC Study

BACKGROUND

The present genome-wide association study (GWAS) aimed to reveal the genetic loci associated with folate metabolites, as well as to detect related gene-environment interactions in Japanese.

METHODS

We conducted the GWAS of plasma homocysteine (Hcy), folic acid (FA), and vitamin B12 (VB12) levels in the Japan Multi-Institutional Collaborative Cohort (J-MICC) Study participants who joined from 2005 to 2012, and also estimated gene-environment interactions. In the replication phase, we used data from the Yakumo Study conducted in 2009. In the discovery phase, data of 2,263 participants from four independent study sites of the J-MICC Study were analyzed. In the replication phase, data of 573 participants from the Yakumo Study were analyzed.

RESULTS

For Hcy, MTHFR locus on chr 1, NOX4 on chr 11, CHMP1A on chr 16, and DPEP1 on chr 16 reached genome-wide significance (P < 5 × 10-8). MTHFR also associated with FA, and FUT2 on chr 19 associated with VB12. We investigated gene-environment interactions in both studies and found significant interactions between MTHFR C677T and ever drinking, current drinking, and physical activity >33% on Hcy (β = 0.039, 0.038 and -0.054, P = 0.018, 0.021 and <0.001, respectively) and the interaction of MTHFR C677T with ever drinking on FA (β = 0.033, P = 0.048).

CONCLUSION

The present GWAS revealed the folate metabolism-associated genetic loci and gene-environment interactions with drinking and physical activity in Japanese, suggesting the possibility of future personalized cardiovascular disease prevention.

Exploring Gene-Diet Interactions for Mother-Child Health: A Systematic Review of Epidemiological Studies

BACKGROUND

Maternal-child health suggests the critical impact of maternal nutrition during the pre-conception and gestational periods, with some genetic variants also playing a significant role. Our systematic review provides an overview of epidemiological studies exploring the interactions between genetic variants, maternal dietary habits, and neonatal and/or maternal pregnancy outcomes.

METHODS

From its inception until June 2023, we conducted a comprehensive literature search on PubMed, Embase, and Web of Science databases.

RESULTS

On a total of 29 epidemiological studies, 11 studies were conducted to explore the interplay between genetic variants and dietary factors, focusing on the risks associated with gestational diabetes mellitus, hypertensive disorders of pregnancy, recurrent spontaneous abortion, recurrent pregnancy loss, iron deficiency anemia, and gestational weight gain. Concerning neonatal outcomes, six studies investigated the interplay between genetic variants, dietary factors, and anthropometric measures, while eight studies delved into abnormal embryonic development, two studies focused on preterm birth, and two studies explored other neonatal outcomes.

CONCLUSIONS

Deeply understanding gene-diet interactions could be useful in developing highly personalized approaches to maternal and child nutrition, as well as in exploring the potential implications in disease prevention and the promotion of the long-term well-being of both mothers and their offspring.

Serum Vitamin B12 is a Promising Auxiliary Index for the Diagnosis of Methylmalonic Acidemia in Children: A Single Center Study in China

BACKGROUND AND AIMS

Vitamin B12 (cobalamin, VitB12) is an essential coenzyme of methylmalonyl-CoA mutase and methionine synthase. Variations in VitB12 metabolism, absorption, transport, or intake may cause changes in methylmalonic acidemia (MMA) biomarkers. We aimed to investigate whether serum Vitamin B12 levels could be used in the early detection of MMA.

MATERIALS AND METHODS

We included 241 children with MMA and 241 healthy matched controls. We measured serum VitB12 levels by an enzyme immunoassay and investigated the relationship between abnormal VitB12 levels and hematologic parameters as potential risk factors for MMA symptoms.

RESULTS

Compared with controls, the serum levels of VitB12 were increased in the MMA group (p < 0.001). Serum VitB12 distinguished patients with MMA from healthy children (p < 0.001). Serum VitB12 combined with homocysteine and ammonia identified cblC and mut type MMA, respectively (p < 0.001). Homocysteine, folate, ammonia, NLR, and red blood cells contributed to serum VitB12 in cblC type MMA (p < 0.001); homocysteine, ammonia, and red blood cells, contributed in mut type MMA (p < 0.001); and elevated VitB12 was an independent predictor of MMA clinical onset (p < 0.001).

CONCLUSION

Serum VitB12 can be used as an early diagnostic biomarker for MMA in children.

Determinants of DNMT2/TRDMT1 preference for substrates tRNA and DNA during the evolution

RNA methyltransferase DNMT2/TRDMT1 is the most conserved member of the DNMT family from bacteria to plants and mammals. In previous studies, we found some determinants for tRNA recognition of DNMT2/TRDMT1, but the preference mechanism of this enzyme for substrates tRNA and DNA remains to be explored. In the present study, CFT-containing target recognition domain (TRD) and target recognition extension domain (TRED) in DNMT2/TRDMT1 play a crucial role in the substrate DNA and RNA selection during the evolution. Moreover, the classical substrate tRNA for DNMT2/TRDMT1 had a characteristic sequence CUXXCAC in the anticodon loop. Position 35 was occupied by U, making cytosine-38 (C38) twist into the loop, whereas C, G or A was located at position 35, keeping the C38-flipping state. Hence, the substrate preference could be modulated by the easily flipped state of target cytosine in tRNA, as well as TRD and TRED. Additionally, DNMT2/TRDMT1 cancer mutant activity was collectively mediated by five enzymatic characteristics, which might impact gene expressions. Importantly, G155C, G155V and G155S mutations reduced enzymatic activities and showed significant associations with diseases using seven prediction methods. Altogether, these findings will assist in illustrating the substrate preference mechanism of DNMT2/TRDMT1 and provide a promising therapeutic strategy for cancer.

Neurovascular Correlates of Cobalamin, Folate, and Homocysteine in Dementia

BACKGROUND

Cobalamin (Cbl) and folate are common supplements clinicians prescribe as an adjuvant therapy for dementia patients, on the presumption of their neurotrophic and/or homocysteine (Hcy) lowering effect. However, the treatment efficacy has been found mixed and the effects of Cbl/folate/Hcy on the human brain remain to be elucidated.

OBJECTIVE

To explore the neurovascular correlates of Cbl/folate/Hcy in Alzheimer's disease (AD) and subcortical ischemic vascular dementia (SIVD).

METHODS

Sixty-seven AD patients and 57 SIVD patients were prospectively and consecutively recruited from an outpatient clinic. Multimodal 3-Tesla magnetic resonance imaging was performed to quantitatively evaluate cerebral blood flow (CBF) and white matter integrity. The relationship between neuroimaging metrics and the serum levels of Cbl/folate/Hcy was examined by using the Kruskal-Wallis test, partial correlation analysis, and moderation analysis, at a significance level of 0.05.

RESULTS

As a whole, CBF mainly associated with Cbl/folate while white matter hyperintensities exclusively associated with Hcy. As compared with AD, SIVD exhibited more noticeable CBF correlates (spatially widespread with Cbl and focal with folate). In SIVD, a bilateral Cbl-moderated CBF coupling was found between medial prefrontal cortex and ipsilateral basal ganglia, while in the fronto-subcortical white matter tracts, elevated Hcy was associated with imaging metrics indicative of increased injury in both axon and myelin sheath.

CONCLUSIONS

We identified the neurovascular correlates of previously reported neurotrophic effect of Cbl/folate and neurotoxic effect of Hcy in dementia. The correlates exhibited distinct patterns in AD and SIVD. The findings may help improving the formulation of supplemental Cbl/folate treatment for dementia.

Genetic Variants in Folate and Cobalamin Metabolism-Related Genes in Pregnant Women of a Homogeneous Spanish Population: The Need for Revisiting the Current Vitamin Supplementation Strategies

Polymorphisms of genes involved in the metabolism and transport of folate and cobalamin could play relevant roles in pregnancy outcomes. This study assessed the prevalence of genetic polymorphisms of folate and cobalamin metabolism-related genes such as MTHFR, MTR, CUBN, and SLC19A1 in pregnant women of a homogeneous Spanish population according to conception, pregnancy, delivery, and newborns complications. This study was conducted on 149 nulliparous women with singleton pregnancies. Sociodemographic and obstetrics variables were recorded, and all patients were genotyped in the MTHFR, MTR, CUBN, and SLC10A1 polymorphisms. The distribution of genotypes detected in this cohort was similar to the population distribution reported in Europe, highlighting that more than 50% of women were carriers of risk alleles of the studied genes. In women with the MTHFR risk allele, there was a statistically significant higher frequency of assisted fertilisation and a higher frequency of preeclampsia and preterm birth. Moreover, CUBN (rs1801222) polymorphism carriers showed a statistically significantly lower frequency of complications during delivery. In conclusion, the prevalence of genetic variants related to folic acid and vitamin B12 metabolic genes in pregnant women is related to mother and neonatal outcomes. Knowing the prevalence of these polymorphisms may lead to a personalised prescription of vitamin intake.

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.

SLC17A3 rs9379800 and Ischemic Stroke Susceptibility at the Northern Region of Malaysia

OBJECTIVES

The relationships of Paired Like Homeodomain 2 (PITX2), Ninjurin 2 (NINJ2), TWIST-Related Protein 1 (TWIST1), Ras Interacting Protein 1 (Rasip1), Solute Carrier Family 17 Member 3 (SLC17A3), Methylmalonyl Co-A Mutase (MUT) and Fer3 Like BHLH Transcription Factor (FERD3L) polymorphisms and gene expression with ischemic stroke have yet to be determined in Malaysia. Hence, this study aimed to explore the associations of single nucleotide polymorphisms (SNPs) and gene expression with ischemic stroke risk among population who resided at the Northern region of Malaysia.

MATERIALS AND METHODS

Study subjects including 216 ischemic stroke patients and 203 healthy controls were recruited upon obtaining ethical clearance. SNP genotyping was performed using polymerase chain reaction-restriction fragment length polymorphism assays. Gene expression levels were quantified by real-time polymerase chain reaction assays. Statistical and genetic analyses were conducted with SPSS version 22.2, PLINK version 1.07 and multifactor dimensionality reduction software.

RESULTS

Study subjects with G allele, CG or GG genotypes of SLC17A3 rs9379800 demonstrated increased risk of ischemic stroke with the odds ratios ranging from 1.76-fold to 3.14-fold (p<0.05). When stratified study subjects according to the ethnicity, SLC17A3 rs9379800 G allele and CG genotype contributed to 2.14- and 2.96-fold of ischemic stroke risk among Malay population significantly, in the multivariate analysis (p<0.05). However, no significant associations were observed for PITX2, NINJ2, TWIST1, Rasip1, and MUT polymorphisms with ischemic stroke risk in the multivariate analysis for the pooled cases and controls as well as when stratified them according to the ethnicity. Lower mRNA expression levels of Rasip1, SLC17A3, MUT and FERD3L were observed among cases (p<0.05). After FDR adjustment, the mRNA level of SLC17A3 remained significantly associated with ischemic stroke among Malay population (q=0.034).

CONCLUSION

In conclusion, this study suggests that SLC17A3 rs9379800 polymorphism and its gene expression contribute to significant ischemic stroke risk among Malaysian population, particularly the Malay who resided at the Northern Region of the country. Our findings can provide useful information for the future diagnosis, management and treatment of ischemic stroke patients.

Contribution of genetic ancestry and polygenic risk score in meeting vitamin B12 needs in healthy Brazilian children and adolescents

Polymorphisms in genes related to the metabolism of vitamin B12 haven’t been examined in a Brazilian population. To (a) determine the correlation between the local genetic ancestry components and vitamin B12 levels using ninety B12-related genes; (b) determine associations between these genes and their SNPs with vitamin B12 levels; (c) determine a polygenic risk score (PRS) using significant variants. This cross-sectional study included 168 children and adolescents, aged 9–13 years old. Total cobalamin was measured in plasma. Genotyping arrays and whole exome data were combined to yield ~ 7000 SNPs in 90 genes related to vitamin B12. The Efficient Local Ancestry Inference was used to estimate local ancestry for African (AFR), Native American, and European (EUR). The association between the genotypes and vitamin B12 levels were determined with generalized estimating equation. Vitamin B12 levels were driven by positive (EUR) and negative (AFR, AMR) correlations with genetic ancestry. A set of 36 variants were used to create a PRS that explained 42% of vitamin level variation. Vitamin B12 levels are influenced by genetic ancestry and a PRS explained almost 50% of the variation in plasma cobalamin in Brazilian children and adolescents.

Methylenetetrahydrofolate Reductase (MTHFR) Gene Polymorphism and Infant's Anthropometry at Birth

Identification of causal factors that influence fetal growth and anthropometry at birth is of great importance as they provide information about increased risk of disease throughout life. The association between maternal genetic polymorphism MTHFR(677)C>T and anthropometry at birth has been widely studied because of its key role in the one-carbon cycle. MTHFR(677) CT and TT genotypes have been associated with a greater risk of low birth weight, especially in case of deficient intake of folic acid during pregnancy. This study aimed to analyze the association between the maternal MTHFR(677)C>T genetic polymorphism and anthropometry at birth in a population with adequate folate consumption. We included 694 mother-newborn pairs from a prospective population-based birth cohort in Spain, in the Genetics, Early life enviroNmental Exposures and Infant Development in Andalusia (GENEIDA) project. Women were genotyped for MTHFR(677)C>T SNP by Q-PCR using TaqMan© probes. Relevant maternal and newborn information was obtained from structured questionnaires and medical records. Results showed that maternal MTHFR(677)C>T genotype was associated with newborn anthropometry. Genotypes CT or CT/TT showed statistically significant associations with increased or decreased risk of large-for-gestational-age (LGA) or small-for-gestational-age (SGA) based on weight and height, depending on the newborn's sex, as well as with SGA in premature neonates. The relationships between this maternal genotype and anthropometry at birth remained despite an adequate maternal folate intake.

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.

Bioinformatics for The Prognostic Value and Function of Cubilin (CUBN) in Colorectal Cancer

Background

Cubilin (CUBN) gene was reported to be a novel risk variant for colorectal cancer (CRC). Previous studies have shown that germline variants in known cancer driver genes are predictive of patient outcome, but no study has systematically analyzed CRC to identify CUBN that can predict patient outcome and function by using bioinformatics.

Material/Methods

The association in expression, clinicopathological parameters, and survival were analyzed by using Oncomine, UNCLA, and GEPIA, while CUBN alterations and related functional networks were identified using cBioPortal. The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes pathways (KEGG) of CUBN in CRC were explored by using LinkOmics. Gene set enrichment analysis (GSEA) examined target networks of kinases, miRNAs, and transcription factors.

Results

We found that CUBN was overexpressed in CRC. Patients who were in advanced TNM stage tended to express higher CUBN mRNA levels, while those who received radiotherapy tended to express relatively lower CUBN mRNA levels. Higher expression of CUBN was found to be associated with shorter overall survival (OS) and disease-free survival (DFS). Moreover, functional networks analysis suggested that CUBN can regulate mismatch repair, terpenoid backbone biosynthesis, base excision repair, and proteasome via vitamin digestion and absorption pathway to influence CRC occurrence.

Conclusions

These findings suggested that CUBN could serve as a prognostic and therapeutic biomarker of CRC in the future.

Association of maternal dietary intakes and CBS gene polymorphisms with congenital heart disease in offspring

BACKGROUND

Although it is generally acknowledged that genetic and environmental factors are associated with risk of congenital heart disease (CHD), the causes are not fully understood. This study aimed at assessing the association of maternal dietary intakes, genetic variants of cystathionine beta synthase (CBS) gene and their interactions with risk of CHDs in offspring.

METHOD

A hospital-based case-control study of 464 mothers with CHD infants and 504 control mothers of health infant was performed. The exposures of interest were maternal dietary intakes in early pregnancy, single nucleotide polymorphisms (SNPs) of CBS gene.

RESULTS

More frequent intake of pickled vegetables (adjusted odds ratio[aOR] = 1.81; 95% confidence interval[CI]: 1.38-2.37), smoked foods (aOR = 2.00; 95%CI: 1.53-2.60), barbecued foods (aOR = 1.63; 95%CI: 1.19-2.25) and fried foods (aOR = 1.57; 95%CI: 1.22-2.03) were associated with higher risk of CHD, while salted eggs (aOR = 0.20; 95%CI: 0.12-0.33), fish and shrimp (aOR = 0.34; 95%CI: 0.27-0.44), fresh fruits (aOR = 0.49; 95%CI: 0.37-0.66), and milk products (aOR = 0.54; 95%CI: 0.45-0.65) were associated with lower risk of CHD. The SNPs of CBS gene at rs2851391 (T/T vs C/C: aOR = 1.91, 95%CI: 1.15-3.15) and rs234714 (T/T vs C/C: aOR = 2.22, 95%CI: 1.32-3.73) significantly increased the risk of CHD. Additionally, significant interaction effects between maternal dietary intakes and CBS genetic variants on CHD risks were observed.

CONCLUSIONS

Maternal dietary factors, CBS genetic variants and their interactions were significantly associated with risk of CHD in offspring. However, it is still unclear how these factors jointly work in the development of CHD, and more studies with larger samples and prospective design are required.

Association of antenatal vitamin B complex supplementation with neonatal vitamin B12 status: evidence from a cluster randomized controlled trial

PURPOSE

Evidence about the effect of maternal vitamin B₁₂ supplementation on offspring's vitamin B₁₂ status is limited. The present interventional study sought to evaluate the association of antenatal vitamin B complex supplementation with neonatal vitamin B₁₂ status.

METHODS

In an ongoing cluster randomized controlled trial conducted in three rural counties in northwest China, pregnant women < 20 weeks of gestation were randomized to three treatment groups: blank control, iron supplements, or vitamin B complex supplements. All women were administered folic acid supplements during the periconceptional period. In a sub-study, we collected cord blood samples of 331 participants from the control or vitamin B complex groups in the Xunyi county from January 2017 to December 2017. Plasma concentrations of folate, vitamin B₁₂, and homocysteine were measured. Linear mixed models with a random intercept for cluster were used to compare biochemical indexes between groups after controlling for covariates.

RESULTS

Compared with newborns whose mothers were in the control group, newborns of the vitamin B complex-supplemented women had significantly higher cord plasma vitamin B₁₂ (P = 0.001) and lower homocysteine concentrations (P = 0.043). The association of antenatal vitamin B complex supplementation with cord blood vitamin B₁₂ concentrations appeared to be more pronounced among newborns with high folate status than those with low folate status (P_interaction = 0.060).

CONCLUSIONS

Maternal vitamin B complex supplementation during pregnancy was associated with better neonatal vitamin B₁₂ status in rural northwest China.

Personalized Nutrition for Management of Micronutrient Deficiency-Literature Review in Non-bariatric Populations and Possible Utility in Bariatric Cohort

Background

Bariatric surgery can effectively treat morbid obesity; however, micronutrient deficiencies are common despite recommendations for high-dose supplements. Genetic predisposition to deficiencies underscores necessary identification of high-risk candidates. Personalized nutrition (PN) can be a tool to manage these deficiencies.

Methods

Medline, PubMed, and Google Scholar were searched. Articles involving genetic testing, micronutrient metabolism, and bariatric surgery were included.

Results

Studies show associations between genetic variants and micronutrient metabolism. Research demonstrates genetic testing to be a predictor for outcomes among obesity and bariatric surgery populations. There is limited research in bariatric surgery and micronutrient genetic variants.

Conclusion

Genotype-based PN is becoming feasible to provide an effective treatment of micronutrient deficiencies associated with bariatric surgery. The role of genomic technology in micronutrient recommendations needs further investigation.

The Effect of Interactions between Folic Acid Supplementation and One Carbon Metabolism Gene Variants on Small-for-Gestational-Age Births in the Screening for Pregnancy Endpoints (SCOPE) Cohort Study

Small-for-gestational-age (SGA) is associated with significant perinatal morbidity and mortality. Our aim was to investigate gene-nutrient interactions between maternal one-carbon single nucleotide polymorphisms (SNPs) and folic acid supplement (FAS) use, and their association with SGA. Nulliparous New Zealand women with singleton pregnancy were recruited as part of the Screening for Pregnancy Endpoints prospective cohort study. Data on FAS use was collected via face-to-face interview at 15 weeks’ gestation; participants were followed prospectively and birth outcome data collected within 72 h of delivery. Participants were genotyped for MTHFR 677, MTHFR 1298, MTHFD1 1958, MTR 2756, MTRR 66 and TCN2 776 SNPs. Genotype data for at least one SNP was available for 1873 (93%) of eligible participants. Analysis showed a significant SNP-FAS interaction for MTHFR 1298 (p = 0.020), MTHFR 677 (p = 0.019) and TCN2 776 (p = 0.017) in relation to SGA: MTHFR 1298 CC variant non-FAS users had an increased likelihood [Odds Ratio (OR) = 2.91 (95% Confidence Interval (CI) = 1.52, 5.60] compared with wild-type (MTHFR 1298 AA) FAS users. MTHFR 677 variant allele carrier (MTHFR 677 CT + MTHFR 677 TT) non-FAS users had an increased likelihood [OR = 1.87 (95% CI = 1.21, 2.88)] compared to wild-type (MTHFR 677 CC) FAS users. TCN2 776 variant (TCN2 776 GG) non-FAS users had an increased likelihood [OR = 2.16 (95% CI = 1.26, 3.71)] compared with wild type homozygote + heterozygote (TCN2 776 CC + TCN2 776 CG) FAS users. No significant interactions were observed for MTHFD1 1958, MTR 2756 or MTRR 66 (p > 0.05). We observed an overall pattern of FAS attenuating differences in the likelihood of SGA seen between genotype groups in FAS non-users. Future research should focus on how intake of other one-carbon nutrients might mediate these gene-nutrient interactions.

Higher vitamin B12 levels in neurodevelopmental disorders than in healthy controls and schizophrenia: A comparison among participants between 2 and 53 years

Recent studies suggest that both high and low levels of vitamin B12 (vitB12) may have negative health impacts. We measured VitB12 in patients with the Neurodevelopmental disorders (ND) (n = 222), comprised of Autism Spectrum Disorders, specific Developmental disorders, and Intellectual Disability (aged 2-53 years), schizophrenia (n = 401), and healthy controls (HC) (n = 483). Age-and gender-adjusted vitB12 z-scores were calculated by comparisons with a reference population (n = 76 148). We found higher vitB12 in ND (median 420 pmol/L, mean z-score: 0.30) than in HC (316 pmol/L, z-score: 0.06, P < .01) and schizophrenia (306 pmol/L, z-score: -0.02, P < .001), which was significant after adjusting for age, gender, vitB12 supplement, folate, hemoglobin, leukocytes, liver, and kidney function (P < .02). In ND, 20% (n = 44) had vitB12 above 650 pmol/L, and 1% (n = 3) had below 150 pmol/L (common reference limits). In 6.3% (n = 14) of ND, vitB12 was above 2SD of mean in the age-and gender-adjusted reference population, which was more frequent than in HC (n = 8, 1.6%), OR: 4.0, P = .001. Low vitB12 was equally frequent as in HC, and vitB12 z-scores were equal across the age groups. To conclude, vitB12 was higher in ND than in HC and schizophrenia, suggesting a specific feature of ND, which warrants further studies to investigate the underlying mechanisms.

Fucosyltransferase Gene Polymorphisms and Lewisb-Negative Status Are Frequent in Swedish Newborns, With Implications for Infectious Disease Susceptibility and Personalized Medicine

BACKGROUND

Single-nucleotide polymorphisms (SNPs) in the fucosyltransferase genes FUT2 and FUT3 have been associated with susceptibility to various infectious and inflammatory disorders. FUT variations influence the expression of human histo-blood group antigens (HBGAs) (H-type 1 and Lewis), which are highly expressed in the gut and play an important role in microbial attachment, metabolism, colonization, and shaping of the microbiome. In particular, FUT polymorphisms confer susceptibility to specific rotavirus and norovirus genotypes, which has important global health implications.

METHODS

We designed a genotyping method using a nested polymerase chain reaction approach to determine the frequency of SNPs in FUT2 and FUT3, thereby inferring the prevalence of Lewisb-positive, Lewisb-negative, secretor, and nonsecretor phenotypes in 520 Swedish newborns.

RESULTS

There was an increased frequency of homozygotes for the minor allele for 1 SNP in FUT2 and 4 SNPs in FUT3. Overall, 37.3% of newborns were found to have Lewis b negative phenotypes (Le (a+b-) or Le (a-b-). Using our new, sensitive genotyping method, we were able to genetically define the Le (a-b-) individuals based on their secretor status and found that the frequency of Lewis b negative newborns in our cohort was 28%.

CONCLUSIONS

Given the high frequency of fucosyltransferase polymorphisms observed in our newborn cohort and the implications for disease susceptibility, FUT genotyping might play a future role in personalized health care, including recommendations for disease screening, therapy, and vaccination.

Genetic markers of One-Carbon Metabolism Disorders in Schizophrenial

The paper presents the results of the literature review and the authors’ own studies of the association of several several single-nucleotide genetic polymorphisms (SNP), which affect one-carbon metabolism, with a risk of schizophrenia and the severity of some clusters of its symptoms. Directions for further study of the role of a number of SNP of enzymes in the folate metabolism cycle and related biochemical processes in schizophrenia (in particular, their influence on the effect of personalized correction of one-carbon metabolism disorders) are determined.

GutSelf: Interindividual Variability in the Processing of Dietary Compounds by the Human Gastrointestinal Tract

Nutritional research is currently entering the field of personalized nutrition, to a large extent driven by major technological breakthroughs in analytical sciences and biocomputing. An efficient launching of the personalized approach depends on the ability of researchers to comprehensively monitor and characterize interindividual variability in the activity of the human gastrointestinal tract. This information is currently not available in such a form. This review therefore aims at identifying and discussing published data, providing evidence on interindividual variability in the processing of the major nutrients, i.e., protein, fat, carbohydrates, vitamins, and minerals, along the gastrointestinal tract, including oral processing, intestinal digestion, and absorption. Although interindividual variability is not a primary endpoint of most studies identified, a significant number of publications provides a wealth of information on this topic for each category of nutrients. This knowledge remains fragmented, however, and understanding the clinical relevance of most of the interindividual responses to food ingestion described in this review remains unclear. In that regard, this review has identified a gap and sets the base for future research addressing the issue of the interindividual variability in the response of the human organism to the ingestion of foods.

Undernutrition in childhood: Clinically based assessment tools and biological markers: Where are we and where should we go?

Despite its association with poor clinical outcomes and increased hospital costs, as of today undernutrition still goes undetected in paediatric hospitals. The reported prevalence of undernutrition in paediatric patients varies considerably. This disparity is partly due to the diversity of methods for its detection and assessment, as well as to the lack of consensus regarding its definition. Several methods, based on varied combinations of morphology characteristics, estimated nutritional intakes and medical conditions have been developed during the last 25 years. However, these tools suffer from poor sensitivity and selectivity particularly in acute conditions. Also while having their own merit, these tools mainly view malnutrition from the energy standpoint, disregarding assessment of specific micronutrients such as minerals and vitamins. In this position paper we make the point that in the era of personalized medicine, present technology offers the possibility of going beyond the traditional nutritional tools for assessing patients' status, and propose the measurement of selected micronutrients and allied metabolic markers in nutritional workup schemes adapted to each clinical condition.

The MTHFR 677C>T polymorphism is associated with unmetabolized folic acid in breast milk in a cohort of Canadian women

BACKGROUND

Maternal nutrition and genetics are determinants of breast-milk nutrient composition and, as such, are determinants of the nutritional exposure of breastfed infants.

OBJECTIVES

The aim of this study was to determine whether common maternal single nucleotide polymorphisms (SNPs) in folate-dependent enzymes are associated with breast-milk folate content in a cohort of mothers enrolled in the Maternal-Infant Research on Environmental Chemicals (MIREC) study.

METHODS

The MIREC study is a Canadian prospective pregnancy cohort study that recruited 2001 participants between 2008 and 2011. Five folate-related SNPs-MTHFR 677C>T (rs1801133), MTHFR 1298A>C (rs1801131), MTHFR 1793G>A (rs2274976), MTR 2756A>G (rs1805087), and MTRR 66A>G (rs1801394)-were genotyped. Breast milk was sampled ∼1 mo postpartum, and tetrahydrofolate (THF), 5-methyl-THF, 5-formyl-THF, 5,10-methenyl-THF, and unmetabolized folic acid (UMFA) were measured using liquid chromatography-tandem mass spectrometry in a subset of participants (n = 551). Associations were assessed using Wald's test. Associations were considered significant if P ≤ 0.01 (Bonferroni correction for multiple testing).

RESULTS

None of the SNPs were associated with total breast-milk folate. However, the MTHFR 677C>T SNP was associated with breast-milk UMFA (R2 = 0.01; unadjusted P = 0.004), explaining a small portion of total variance; this association remained significant when adjusted for other covariates, including supplemental folic acid consumption. The MTHFR 1793G>A and MTRR 66A>G SNPs tended to be associated with 5-methyl-THF (R2 = 0.008, P = 0.04) and reduced folates (THF + 5-methyl-THF + 5-formyl-THF + 5,10-methenyl-THF; R2 = 0.01, P = 0.02), respectively.

CONCLUSIONS

We found that total breast-milk folate content was not associated with any of the folate-related SNPs examined. The association between the MTHFR 677C>T SNP and breast-milk UMFA, albeit modest, highlights the need to better understand the determinants of breast-milk folate and the impact they might have on milk folate bioavailability.

Metabolic consequences of discretionary fortified beverage consumption containing excessive vitamin B levels in adolescents

Over the past decade, there has been a substantial increase in the number of beverage products containing added vitamins and minerals. Often viewed as a healthier choice by consumers, the metabolic impacts of excessive vitamin consumption are relatively unknown, especially in children. The aim of this study was to examine the effects of a widely available, vitamin fortified beverage (5h Energy Decaffeinated) on insulin sensitivity, metabolic hormones and serum metabolomic responses in adolescents. Twenty adolescents (13-19y, 10M/10F) completed two randomized trials, consuming either coloured water as placebo (PL) or a vitamin fortified, sugar free beverage (FB, 1.5ml/kg) 40min prior to a modified oral glucose tolerance test (OGTT, 1.75g/kg glucose). Samples were collected at baseline and at 30, 45, 60, 90 and 120min during the OGTT. No differences in blood glucose response were observed between the treatments. However, compared to PL, postprandial plasma C-peptide and insulin excursion was significantly greater with FB, resulting in a 28% decline in the insulin sensitivity index. This was accompanied by elevated GLP-1, glucagon and PYY responses with FB compared to PL. Serum metabolomics (¹H-NMR) analysis also revealed perturbations to vitamin B-linked one carbon metabolism flux with FB consumption that became more pronounced over time. These included a transient reduction in homocysteine flux accompanied by increases in betaine, vitamin B6, vitamin B12, choline, folate and taurine. Although these impacts are likely short-lived, results show that beverages fortified with excessive amounts of vitamins are not metabolically inert, but likely result in greater insulin secretion, differential gut hormone secretion and elevated one-carbon flux to process the excessive vitamin loads.

Biomarkers of Nutrition for Development (BOND): Vitamin B-12 Review

This report on vitamin B-12 (B12) is part of the Biomarkers of Nutrition for Development (BOND) Project, which provides state-of-the art information and advice on the selection, use, and interpretation of biomarkers of nutrient exposure, status, and function. As with the other 5 reports in this series, which focused on iodine, folate, zinc, iron, and vitamin A, this B12 report was developed with the assistance of an expert panel (BOND B12 EP) and other experts who provided information during a consultation. The experts reviewed the existing literature in depth in order to consolidate existing relevant information on the biology of B12, including known and possible effects of insufficiency, and available and potential biomarkers of status. Unlike the situation for the other 5 nutrients reviewed during the BOND project, there has been relatively little previous attention paid to B12 status and its biomarkers, so this report is a landmark in terms of the consolidation and interpretation of the available information on B12 nutrition. Historically, most focus has been on diagnosis and treatment of clinical symptoms of B12 deficiency, which result primarily from pernicious anemia or strict vegetarianism. More recently, we have become aware of the high prevalence of B12 insufficiency in populations consuming low amounts of animal-source foods, which can be detected with ≥1 serum biomarker but presents the new challenge of identifying functional consequences that may require public health interventions.

Intakes, Adequacy, and Biomarker Status of Iron, Folate, and Vitamin B12 in Māori and Non-Māori Octogenarians: Life and Living in Advanced Age: A Cohort Study in New Zealand (LiLACS NZ)

Advanced-age adults may be at risk of iron, folate, and vitamin B₁₂ deficiency due to low food intake and poor absorption. This study aimed to investigate the intake and adequacy of iron, folate, and vitamin B₁₂ and their relationship with respective biomarker status. Face-to-face interviews with 216 Māori and 362 non-Māori included a detailed dietary assessment using 2 × 24-h multiple pass recalls. Serum ferritin, serum iron, total iron binding capacity, transferrin saturation, red blood cell folate, serum folate, serum vitamin B₁₂ and hemoglobin were available at baseline. Regression techniques were used to estimate the association between dietary intake and biomarkers. The Estimated Average Requirement (EAR) was met by most participants (>88%) for dietary iron and vitamin B₁₂ (>74%) but less than half (>42%) for folate. Increased dietary folate intake was associated with increased red blood cell (RBC) folate for Māori (p = 0.001), non-Māori (p = 0.014) and serum folate for Māori (p < 0.001). Folate intake >215 µg/day was associated with reduced risk of deficiency in RBC folate for Māori (p = 0.001). Strategies are needed to optimize the intake and bioavailability of foods rich in folate. There were no significant associations between dietary iron and vitamin B₁₂ intake and their respective biomarkers, serum iron and serum vitamin B₁₂.

Identification of three novel loci of ALDH2 Gene for Serum Folate levels in a Male Chinese Population by Genome-Wide Association Study

BACKGROUND

Serum folate is important in clinical researches and DNA synthesis and methylation. Some loci and genes that are associated with folate levels had been detected by genome-wide association studies (GWAS), such as rs1801133 in MTHFR and rs1979277 in SHMT1. Nevertheless, only a small part of variants has been clearly identified for serum folate. Hence, we conducted a GWAS to discover new inherited susceptibility and gene-environment interactions on serum folate concentration.

MATERIALS AND METHODS

In a healthy Chinese population of 1999 men, genotyping was performed using Illumina HumanOmni1-Quad BeadChip. Serum folate levels were measured by enzyme-linked immunosorbent assay (ELISA), pathway enrichment analysis and statistical analysis were performed by Database for Annotation, Visualization and Integrated Discovery (DAVID) and Statistic Package for Social Science (SPSS).

RESULTS

We validated that rs1801133 in MTHFR was significantly involved in serum folate (P = 4.21 × 10^-19). Surprisingly, we discovered three novel loci rs3782886, rs671, and rs4646776 of ALDH2 gene were suggestively significantly associated with folate serum folate levels in the male population studied (P = 2.17 × 10^-7, P = 3.60 × 10^-7, P = 3.99 × 10^-7, respectively) after adjusting for population stratification, BMI and age. Men with the AA genotype had significantly higher serum folate levels compared with men with the GG/AG genotype. But we found ALDH2 gene mutation no relation to part of environmental factors on serum folate levels.

CONCLUSION

In a male Chinese population, genome-wide association study discovered that three novel SNPs rs3782886, rs671 and rs4646776 of ALDH2 gene were suggestively significantly associated with serum folate levels.

Prevention of neural tube defects in Lrp2 mutant mouse embryos by folic acid supplementation

BACKGROUND

Neural tube defects (NTDs) are among the most common structural birth defects in humans and are caused by the complex interaction of genetic and environmental factors. Periconceptional supplementation with folic acid can prevent NTDs in both mouse models and human populations. A better understanding of how genes and environmental factors interact is critical toward development of rational strategies to prevent NTDs. Low density lipoprotein-related protein 2 (Lrp2) is involved in endocytosis of the folic acid receptor among numerous other nutrients and ligands.

METHODS

We determined the effect of iron and/or folic acid supplementation on the penetrance of NTDs in the Lrp2^null mouse model. The effects of supplementation on folate and iron status were measured in embryos and dams.

RESULTS

Periconceptional dietary supplementation with folic acid did not prevent NTDs in Lrp2 mutant embryos, whereas high levels of folic acid supplementation by intraperitoneal injection reduced incidence of NTDs. Importantly, Lrp2^null/+ dams had reduced blood folate levels that improved with daily intraperitoneal injections of folate but not dietary supplementation. On the contrary, iron supplementation had no effect on the penetrance of NTDs in Lrp2 mutant embryos and negated the preventative effect of folic acid supplementation in Lrp2^null/null mutants.

CONCLUSION

Lrp2 is required for folate homeostasis in heterozygous dams and high levels of supplementation prevents NTDs. Furthermore, high levels of dietary iron supplementation interfered with folic acid supplementation negating the positive effects of supplementation in this model. Birth Defects Research 109:16-26, 2017. © 2016 The Authors Birth Defects Published by Wiley Periodicals, Inc.

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.

Meat Consumption During Pregnancy and Substance Misuse Among Adolescent Offspring: Stratification of TCN2 Genetic Variants

BACKGROUND

Reducing meat consumption is often advised; however, inadvertent nutritional deficiencies during pregnancy may result in residual neurodevelopmental harms to offspring. This study assessed possible effects of maternal diets in pregnancy on adverse substance use among adolescent offspring.

METHODS

Pregnant women and their 13-year-old offspring taking part in a prospective birth cohort study, the Avon Longitudinal Study of Parents and Children (ALSPAC), provided Food Frequency Questionnaire data from which dietary patterns were derived using principal components analysis. Multivariable logistic regression models including potential confounders evaluated adverse alcohol, cannabis, and tobacco use of the children at 15 years of age.

RESULTS

Lower maternal meat consumption was associated with greater problematic substance use among 15-year-old offspring in dose-response patterns. Comparing never to daily meat consumption after adjustment, risks were greater for all categories of problem substance use: alcohol, odds ratio OR = 1.75, 95% CI = (1.23, 2.56), p < 0.001; tobacco use OR = 1.85, 95% CI = (1.28, 2.63), p < 0.001; and cannabis OR = 2.70, 95% CI = (1.89, 4.00), p < 0.001. Given the likelihood of residual confounding, potential causality was evaluated using stratification for maternal allelic variants that impact biological activity of cobalamin (vitamin B12) and iron. Lower meat consumption disproportionally increased the risks of offspring substance misuse among mothers with optimally functional (homozygous) variants (rs1801198) of the gene transcobalamin 2 gene (TCN2) which encodes the vitamin B12 transport protein transcobalamin 2 implicating a causal role for cobalamin deficits. Functional maternal variants in iron metabolism were unrelated to the adverse substance use. Risks potentially attributable to cobalamin deficits during pregnancy include adverse adolescent alcohol, cannabis, and tobacco use (14, 37, and 23, respectively).

CONCLUSIONS

Lower prenatal meat consumption was associated with increased risks of adolescent substance misuse. Interactions between TCN2 variant status and meat intake implicate cobalamin deficiencies.

Homocysteine levels associate with subtle changes in leukocyte DNA methylation: an epigenome-wide analysis

AIM

Homocysteine (Hcy) is a sensitive marker of one-carbon metabolism. Higher Hcy levels have been associated with global DNA hypomethylation. We investigated the association between plasma Hcy and epigenome-wide DNA methylation in leukocytes.

METHODS

Methylation was measured using Illumina 450 k arrays in 2035 individuals from six cohorts. Hcy-associated differentially methylated positions and regions were identified using meta-analysis.

RESULTS

Three differentially methylated positions cg21607669 (SLC27A1), cg26382848 (AJUBA) and cg10701000 (KCNMA1) at chromosome 19, 14 and 10, respectively, were significantly associated with Hcy. In addition, we identified 68 Hcy-associated differentially methylated regions, the most significant of which was a 1.8-kb spanning domain (TNXB/ATF6B) at chromosome 6.

CONCLUSION

We identified novel epigenetic loci associated with Hcy levels, of which specific role needs to be further validated.

Associations between homocysteine metabolism related SNPs and carotid intima-media thickness: a Chinese sib pair study

Carotid intima-media thickness (CIMT) is a good surrogate for atherosclerosis. Hyperhomocysteinemia is an independent risk factor for cardiovascular diseases. We aim to investigate the relationships between homocysteine (Hcy) related biochemical indexes and CIMT, the associations between Hcy related SNPs and CIMT, as well as the potential gene–gene interactions. The present study recruited full siblings (186 eligible families with 424 individuals) with no history of cardiovascular events from a rural area of Beijing. We examined CIMT, intima-media thickness for common carotid artery (CCA-IMT) and carotid bifurcation, tested plasma levels for Hcy, vitamin B6 (VB6), vitamin B12 (VB12) and folic acid (FA), and genotyped 9 SNPs on MTHFR, MTR, MTRR, BHMT, SHMT1, CBS genes. Associations between SNPs and biochemical indexes and CIMT indexes were analyzed using family-based association test analysis. We used multi-level mixed-effects regression model to verify SNP-CIMT associations and to explore the potential gene–gene interactions. VB6, VB12 and FA were negatively correlated with CIMT indexes (p < 0.05). rs2851391 T allele was associated with decreased plasma VB12 levels (p = 0.036). In FABT, CBS rs2851391 was significantly associated with CCA-IMT (p = 0.021) and CIMT (p = 0.019). In multi-level mixed-effects regression model, CBS rs2851391 was positively significantly associated with CCA-IMT (Coef = 0.032, se = 0.009, raw p < 0.001) after Bonferoni correction (corrected α = 0.0056). Gene–gene interactions were found between CBS rs2851391 and BHMT rs10037045 for CCA-IMT (p = 0.011), as well as between CBS rs2851391 and MTR rs1805087 for CCA-IMT (p = 0.007) and CIMT (p = 0.022). Significant associations are found between Hcy metabolism related genetic polymorphisms, biochemical indexes and CIMT indexes. There are complex interactions between genetic polymorphisms for CCA-IMT and CIMT.

Intakes of Folate and Vitamin B12 and Biomarkers of Status in the Very Old: The Newcastle 85+ Study

Very old adults are at increased risk of folate and vitamin B12 deficiencies due to reduced food intake and gastrointestinal absorption. The main aim was to determine the association between folate and vitamin B12 intake from total diets and food groups, and status. Folate or vitamin B12 intakes (2 × 24 h multiple pass recalls) and red blood cell (RBC) folate or plasma vitamin B12 (chemiluminescence immunoassays) concentrations were available at baseline for 731 participants aged 85 from the Newcastle 85+ Study (North-East England). Generalized additive and binary logistic models estimated the associations between folate and vitamin B12 intakes from total diets and food groups, and RBC folate and plasma B12. Folate intake from total diets and cereal and cereal products was strongly associated with RBC folate (p < 0.001). Total vitamin B12 intake was weakly associated with plasma vitamin B12 (p = 0.054) but those with higher intakes from total diets or meat and meat products were less likely to have deficient status. Women homozygous for the FUT2 G allele had higher concentrations of plasma vitamin B12. Cereals and cereal products are a very important source of folate in the very old. Higher intakes of folate and vitamin B12 lower the risk of "inadequate" status.

Low Serum Vitamin B-12 Concentrations Are Prevalent in a Cohort of Pregnant Canadian Women

BACKGROUND

Among Canadian women of reproductive age, 5% and 20% have serum vitamin B-12 concentrations indicative of deficiency (<148 pmol/L) and marginal status (148-220 pmol/L), respectively. Given the association between suboptimal vitamin B-12 and adverse pregnancy outcomes, an understanding of vitamin B-12 status during pregnancy, and factors that influence it, is required.

OBJECTIVE

This prospective analysis from the PREFORM (PREnatal FOlic acid exposuRe on DNA Methylation in the newborn infant) study investigated 1) vitamin B-12 status in a cohort of Canadian pregnant women and their newborns, 2) the association of maternal dietary vitamin B-12 intake with maternal and cord blood concentrations of vitamin B-12 and its biomarkers, and 3) the association of fetal genetic polymorphisms with cord blood concentrations of vitamin B-12 and its biomarkers.

METHODS

In pregnant Canadian women (n = 368; mean ± SD age: 32 ± 5 y), vitamin B-12 intakes were assessed in early (0-16 wk) and mid- to late (23-37 wk) pregnancy. Serum vitamin B-12 and plasma total homocysteine (tHcy) and methylmalonic acid (MMA) in maternal blood at 12-16 wk of pregnancy and at delivery (28-42 wk) and in cord blood were measured and compared by using regression analyses. The associations of 28 fetal genetic variants in vitamin B-12 metabolism and cord blood vitamin B-12, tHcy, and MMA concentrations were assessed by using regression analysis, with adjustment for multiple testing.

RESULTS

A total of 17% and 38% of women had deficient and 35% and 43% had marginal serum vitamin B-12 concentrations at 12-16 wk of pregnancy and at delivery, respectively. Only 1.9-5.3% had elevated MMA (>271 nmol/L), and no women had elevated tHcy (>13 μmol/L). Maternal dietary vitamin B-12 intake during pregnancy was either weakly associated or not associated with maternal and cord blood vitamin B-12 (r(2) = 0.17-0.24, P < 0.0008), tHcy (P = NS) and MMA (r(2) = 0.05-0.11, P < 0.001). Fetal genetic polymorphisms were not associated with cord blood concentrations of vitamin B-12 and its biomarkers.

CONCLUSIONS

Deficient and marginal serum vitamin B-12 concentrations are prevalent in Canadian pregnant women with the use of traditional cutoffs, despite supplement use. Given the growing interest among women to adhere to a vegetarian diet that may be lower in vitamin B-12, and vitamin B-12's importance in pregnancy, the functional ramifications of these observations need to be elucidated. This trial was registered at clinicaltrials.gov as NCT02244684.

Testing and estimation in marker-set association study using semiparametric quantile regression kernel machine

We consider quantile regression for partially linear models where an outcome of interest is related to covariates and a marker set (e.g., gene or pathway). The covariate effects are modeled parametrically and the marker set effect of multiple loci is modeled using kernel machine. We propose an efficient algorithm to solve the corresponding optimization problem for estimating the effects of covariates and also introduce a powerful test for detecting the overall effect of the marker set. Our test is motivated by traditional score test, and borrows the idea of permutation test. Our estimation and testing procedures are evaluated numerically and applied to assess genetic association of change in fasting homocysteine level using the Vitamin Intervention for Stroke Prevention Trial data.

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

Dietary folate is a major source of methyl groups required for DNA methylation, an epigenetic modification that is actively maintained and remodeled during spermatogenesis. While high-dose folic acid supplementation (up to 10 times the daily recommended dose) has been shown to improve sperm parameters in infertile men, the effects of supplementation on the sperm epigenome are unknown. To assess the impact of 6 months of high-dose folic acid supplementation on the sperm epigenome, we studied 30 men with idiopathic infertility. Blood folate concentrations increased significantly after supplementation with no significant improvements in sperm parameters. Methylation levels of the differentially methylated regions of several imprinted loci (H19, DLK1/GTL2, MEST, SNRPN, PLAGL1, KCNQ1OT1) were normal both before and after supplementation. Reduced representation bisulfite sequencing (RRBS) revealed a significant global loss of methylation across different regions of the sperm genome. The most marked loss of DNA methylation was found in sperm from patients homozygous for the methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism, a common polymorphism in a key enzyme required for folate metabolism. RRBS analysis also showed that most of the differentially methylated tiles were located in DNA repeats, low CpG-density and intergenic regions. Ingenuity Pathway Analysis revealed that methylation of promoter regions was altered in several genes involved in cancer and neurobehavioral disorders including CBFA2T3, PTPN6, COL18A1, ALDH2, UBE4B, ERBB2, GABRB3, CNTNAP4 and NIPA1. Our data reveal alterations of the human sperm epigenome associated with high-dose folic acid supplementation, effects that were exacerbated by a common polymorphism in MTHFR.