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1.  IS LOW IRON STATUS A RISK FACTOR FOR NEURAL TUBE DEFECTS? 
Background
Folic acid supplements can protect against neural tube defects (NTDs). Low folate and low vitamin B12 status may be maternal risk factors for having an NTD affected pregnancy. However, not all NTDs are preventable by having an adequate folate/ B12 status and other potentially modifiable factors may be involved. Folate and vitamin B12 status have important links to iron metabolism. Animal studies support an association between poor iron status and NTDs but human data are scarce. We examined the relevance of low iron status in a nested NTD case-control study of women within a pregnant population-based cohort.
Methods
Pregnant women were recruited between 1986 and 1990, when vitamin or iron supplementation in early pregnancy was rare. Blood samples, taken at an average of 14 weeks gestation, were used to measure ferritin and hemoglobin in 64 women during an NTD affected pregnancy and 207 women with unaffected pregnancies.
Results
No significant differences in maternal ferritin or hemoglobin concentrations were observed between NTD affected and non-affected pregnancies (case median ferritin 16.8μg/L and hemoglobin 12.4g/dL versus 15.4μg/L and 12.3g/dL in controls). As reported previously, red cell folate and vitamin B12 concentrations were significantly lower in cases. Furthermore, there was no significant association of iron status with type of NTD lesion (anencephaly or spina bifida)
Conclusions
We conclude that low maternal iron status during early pregnancy is not an independent risk factor for NTDs. Adding iron to folic acid for periconceptional use may improve iron status but is not likely to prevent NTDs.
doi:10.1002/bdra.23223
PMCID: PMC4018583  PMID: 24535840
ferritin; iron; hemoglobin; neural tube defects
2.  Evaluation of common genetic variants in 82 candidate genes as risk factors for neural tube defects 
BMC Medical Genetics  2012;13:62.
Background
Neural tube defects (NTDs) are common birth defects (~1 in 1000 pregnancies in the US and Europe) that have complex origins, including environmental and genetic factors. A low level of maternal folate is one well-established risk factor, with maternal periconceptional folic acid supplementation reducing the occurrence of NTD pregnancies by 50-70%. Gene variants in the folate metabolic pathway (e.g., MTHFR rs1801133 (677 C > T) and MTHFD1 rs2236225 (R653Q)) have been found to increase NTD risk. We hypothesized that variants in additional folate/B12 pathway genes contribute to NTD risk.
Methods
A tagSNP approach was used to screen common variation in 82 candidate genes selected from the folate/B12 pathway and NTD mouse models. We initially genotyped polymorphisms in 320 Irish triads (NTD cases and their parents), including 301 cases and 341 Irish controls to perform case–control and family based association tests. Significantly associated polymorphisms were genotyped in a secondary set of 250 families that included 229 cases and 658 controls. The combined results for 1441 SNPs were used in a joint analysis to test for case and maternal effects.
Results
Nearly 70 SNPs in 30 genes were found to be associated with NTDs at the p < 0.01 level. The ten strongest association signals (p-value range: 0.0003–0.0023) were found in nine genes (MFTC, CDKN2A, ADA, PEMT, CUBN, GART, DNMT3A, MTHFD1 and T (Brachyury)) and included the known NTD risk factor MTHFD1 R653Q (rs2236225). The single strongest signal was observed in a new candidate, MFTC rs17803441 (OR = 1.61 [1.23-2.08], p = 0.0003 for the minor allele). Though nominally significant, these associations did not remain significant after correction for multiple hypothesis testing.
Conclusions
To our knowledge, with respect to sample size and scope of evaluation of candidate polymorphisms, this is the largest NTD genetic association study reported to date. The scale of the study and the stringency of correction are likely to have contributed to real associations failing to survive correction. We have produced a ranked list of variants with the strongest association signals. Variants in the highest rank of associations are likely to include true associations and should be high priority candidates for further study of NTD risk.
doi:10.1186/1471-2350-13-62
PMCID: PMC3458983  PMID: 22856873
Neural tube defects; Spina bifida; Folic acid; One-carbon metabolism; Candidate gene
3.  Folate and vitamin B12 in idiopathic male infertility 
Asian Journal of Andrology  2011;13(6):856-861.
Although methylenetetrahydrofolate reductase, a folate enzyme gene, has been associated with idiopathic male infertility, few studies have examined other folate-related metabolites and genes. We investigated whether idiopathic male infertility is associated with variants in folate, vitamin B12 (B12) and total homocysteine (tHcy)-related genes and measured these metabolites in blood. We conducted a case–control study that included 153 men with idiopathic infertility and 184 fertile male controls recruited at the Fertility Center and Antenatal Care Center, University Hospital, Malmö and Lund, Sweden. Serum folate, red cell folate (RCF), serum B12, plasma tHcy and semen quality were measured. Subjects were genotyped for 20 common variants in 12 genes related to folate/B12/homocysteine metabolism. Metabolite concentrations and genotype distributions were compared between cases and controls using linear and logistic regression with adjustment for covariates. The phosphatidylethanolamine N-methyltransferase (PEMT) M175V and TCblR rs173665 polymorphisms were significantly associated with infertility (P = 0.01 and P = 0.009, respectively), but not with semen quality. Among non-users of supplements, infertile men had lower serum folate concentrations than fertile men (12.89 vs. 14.73 nmol l−1; P = 0.02), but there were no significant differences in RCF, B12 or tHcy. Folate, B12 and tHcy concentrations were not correlated with any semen parameters. This study provides little support for low folate or B12 status in the pathogenesis of idiopathic male infertility. Although additional data are needed to confirm these initial findings, our results suggest that PEMT and TCblR, genes involved in choline and B12 metabolism, merit further investigation in idiopathic male infertility.
doi:10.1038/aja.2011.96
PMCID: PMC3372894  PMID: 21857689
folate; idiopathic male infertility; semen quality; vitamin B12
4.  Folate and vitamin B12 in idiopathic male infertility 
Asian Journal of Andrology  2011;13(6):856-861.
Although methylenetetrahydrofolate reductase, a folate enzyme gene, has been associated with idiopathic male infertility, few studies have examined other folate-related metabolites and genes. We investigated whether idiopathic male infertility is associated with variants in folate, vitamin B12 (B12) and total homocysteine (tHcy)-related genes and measured these metabolites in blood. We conducted a case–control study that included 153 men with idiopathic infertility and 184 fertile male controls recruited at the Fertility Center and Antenatal Care Center, University Hospital, Malmö and Lund, Sweden. Serum folate, red cell folate (RCF), serum B12, plasma tHcy and semen quality were measured. Subjects were genotyped for 20 common variants in 12 genes related to folate/B12/homocysteine metabolism. Metabolite concentrations and genotype distributions were compared between cases and controls using linear and logistic regression with adjustment for covariates. The phosphatidylethanolamine N-methyltransferase (PEMT) M175V and TCblR rs173665 polymorphisms were significantly associated with infertility (P=0.01 and P=0.009, respectively), but not with semen quality. Among non-users of supplements, infertile men had lower serum folate concentrations than fertile men (12.89 vs. 14.73 nmol l−1; P=0.02), but there were no significant differences in RCF, B12 or tHcy. Folate, B12 and tHcy concentrations were not correlated with any semen parameters. This study provides little support for low folate or B12 status in the pathogenesis of idiopathic male infertility. Although additional data are needed to confirm these initial findings, our results suggest that PEMT and TCblR, genes involved in choline and B12 metabolism, merit further investigation in idiopathic male infertility.
doi:10.1038/aja.2011.96
PMCID: PMC3372894  PMID: 21857689
folate; idiopathic male infertility; semen quality; vitamin B12
5.  Biomarkers of folate status in NHANES: a roundtable summary123456 
A roundtable to discuss the measurement of folate status biomarkers in NHANES took place in July 2010. NHANES has measured serum folate since 1974 and red blood cell (RBC) folate since 1978 with the use of several different measurement procedures. Data on serum 5-methyltetrahydrofolate (5MTHF) and folic acid (FA) concentrations in persons aged ≥60 y are available in NHANES 1999–2002. The roundtable reviewed data that showed that folate concentrations from the Bio-Rad Quantaphase II procedure (Bio-Rad Laboratories, Hercules, CA; used in NHANES 1991–1994 and NHANES 1999–2006) were, on average, 29% lower for serum and 45% lower for RBC than were those from the microbiological assay (MA), which was used in NHANES 2007–2010. Roundtable experts agreed that these differences required a data adjustment for time-trend analyses. The roundtable reviewed the possible use of an isotope-dilution liquid chromatography–tandem mass spectrometry (LC-MS/MS) measurement procedure for future NHANES and agreed that the close agreement between the MA and LC-MS/MS results for serum folate supported conversion to the LC-MS/MS procedure. However, for RBC folate, the MA gave 25% higher concentrations than did the LC-MS/MS procedure. The roundtable agreed that the use of the LC-MS/MS procedure to measure RBC folate is premature at this time. The roundtable reviewed the reference materials available or under development at the National Institute of Standards and Technology and recognized the challenges related to, and the scientific need for, these materials. They noted the need for a commutability study for the available reference materials for serum 5MTHF and FA.
doi:10.3945/ajcn.111.013011
PMCID: PMC3127517  PMID: 21593502
6.  Biomarkers of vitamin B-12 status in NHANES: a roundtable summary123456 
A roundtable to discuss the measurement of vitamin B-12 (cobalamin) status biomarkers in NHANES took place in July 2010. NHANES stopped measuring vitamin B-12–related biomarkers after 2006. The roundtable reviewed 3 biomarkers of vitamin B-12 status used in past NHANES—serum vitamin B-12, methylmalonic acid (MMA), and total homocysteine (tHcy)—and discussed the potential utility of measuring holotranscobalamin (holoTC) for future NHANES. The roundtable focused on public health considerations and the quality of the measurement procedures and reference methods and materials that past NHANES used or that are available for future NHANES. Roundtable members supported reinstating vitamin B-12 status measures in NHANES. They noted evolving concerns and uncertainties regarding whether subclinical (mild, asymptomatic) vitamin B-12 deficiency is a public health concern. They identified the need for evidence from clinical trials to address causal relations between subclinical vitamin B-12 deficiency and adverse health outcomes as well as appropriate cutoffs for interpreting vitamin B-12–related biomarkers. They agreed that problems with sensitivity and specificity of individual biomarkers underscore the need for including at least one biomarker of circulating vitamin B-12 (serum vitamin B-12 or holoTC) and one functional biomarker (MMA or tHcy) in NHANES. The inclusion of both serum vitamin B-12 and plasma MMA, which have been associated with cognitive dysfunction and anemia in NHANES and in other population-based studies, was preferable to provide continuity with past NHANES. Reliable measurement procedures are available, and National Institute of Standards and Technology reference materials are available or in development for serum vitamin B-12 and MMA.
doi:10.3945/ajcn.111.013243
PMCID: PMC3127527  PMID: 21593512
7.  A genome-wide association study of cleft lip with and without cleft palate identifies risk variants near MAFB and ABCA4 
Nature genetics  2010;42(6):525-529.
Case-parent trios were used in a genome wide association study of cleft lip with/without cleft palate (CL/P). SNPs near two genes not previously associated with CL/P [MAFB: most significant SNP rs13041247, with odds ratio per minor allele OR=0.704; 95%CI=0.635,0.778; p=2.05*10−11; and ABCA4: most significant SNP rs560426, with OR=1.432; 95%CI=1.292,1.587; p=5.70*10−12] and two previously identified regions (chr. 8q24 and IRF6) attained genome wide significance. Stratifying trios into European and Asian ancestry groups revealed differences in statistical significance, although estimated effect sizes were similar. Replication studies from several populations showed confirming evidence, with families of European ancestry giving stronger evidence for markers in 8q24 while Asian families showed stronger evidence for MAFB and ABCA4. Expression studies support a role for MAFB in palate development.
doi:10.1038/ng.580
PMCID: PMC2941216  PMID: 20436469

Results 1-8 (8)