Folic acid-containing supplement consumption during pregnancy and risk for oral clefts: a meta-analysis

BACKGROUND: There is equivocal evidence in the published literature that folic acid supplementation during pregnancy may protect against the common congenital anomalies cleft lip with or without cleft palate (CLP) and cleft palate alone (CP). We undertook this meta-analysis to test the hypothesis that nonsyndromic oral cleft birth prevalences are different for those whose mothers took folic acid-containing supplements and for those whose mothers did not. METHODS: Human studies published in English were identified through MEDLINE, bibliography reviews, and contacting experts in the field. Within strata of prospective and case-control studies, CLP, CP, and all clefts, respectively, were analyzed using either a fixed or random effects model, as appropriate. We assessed for publication bias using Begg and Mazumdar's rank correlation and Egger's regression-based tests. RESULTS: Five prospective studies were analyzed, yielding combined relative risks of 0.51 (95% CI: 0.32, 0.95) for CLP, 1.19 (95% CI: 0.43, 3.28) for CP, and 0.55 (95% CI: 0.32, 0.95) for all clefts. Twelve case-control studies were assessed, which resulted in combined relative risks of 0.77 (95% CI: 0.65, 0.90) for CLP, 0.80 (95% CI: 0.69, 0.93) for CP, and 0.78 (95% CI: 0.71, 0.85) for all clefts. CONCLUSIONS: In aggregate, our results support the hypothesis of a protective effect of folic acid-containing supplement intake during pregnancy on the risk for oral clefts, although this conclusion is tempered by the potential for bias and uncontrolled confounding.     

Uncoupling protein 2 polymorphisms as risk factors for NTDs

BACKGROUND: Both environmental and genetic factors are involved in the etiology of NTDs. Inadequate folate intake and obesity are important environmental risk factors. Several folate‐related genetic variants have been identified as risk factors; however, little is known about how genetic variants relate to the increased risk seen in obese women. Uncoupling Protein 2 (UCP2) is an attractive candidate to screen for NTD risk because of its possible role in obesity as well as energy metabolism, type‐2 diabetes, and the regulation of reactive oxygen species. Interestingly, a previous study found that a common UCP2 compound homozygous genotype was associated with a threefold increase in NTD risk. METHODS: We evaluated three polymorphisms, ‐866G>A, A55V, and the 3′UTR 45 bp insertion/deletion, as risk factors for NTDs in Irish NTD cases (n = 169), their mothers (n = 163), their fathers (n = 167), and normal control subjects (n = 332). RESULTS: Allele and genotype frequencies were not significantly different when comparing NTD mothers, NTD fathers, or affected children to controls. Additionally, the previously reported risk genotype (combined homozygosity of 55VV and 3′UTR 45 bp deletion/deletion) was not present at a higher frequency in any NTD group when compared to controls. CONCLUSIONS: In our Irish study population, UCP2 polymorphisms did not influence NTD risk. Moreover, the prevalence of this allele in other populations was similar to the Irish prevalence but far lower than reported in the previous NTD study, suggesting that this previous finding of an association with NTDs might have been due to an unrepresentative study sample. Birth Defects Research (Part A), 2009. © 2009 Wiley‐Liss, Inc.     

Isolated oral cleft malformations: associations with maternal and infant characteristics in a California population

Data on isolated oral cleft malformations from a birth defects registry covering a large population base were examined to describe potential associations with maternal and infant characteristics. Infants with cleft palate (CP) were analyzed separately from infants with cleft lip with or without cleft palate (CLP). The prevalence of isolated CLP per 1,000 births was 0.741, approximately twice the prevalence of isolated CP, which was 0.383. Male infants were more likely to be born with CLP (OR = 1.9) but less likely to be born with CP (OR = 0.56) than were females. Women 39 years or more of age were twice as likely as 25-29 year olds to have a child with either type of cleft. Black, nonhispanic infants had a lowered risk for CLP compared to white, nonhispanics (OR = 0.40). These risks were found to be independent of each other based on multivariate analyses. Associations with either type of cleft malformation were not observed for plurality, number of previous live births, and maternal birthplace.     

Mouse genetic models of cleft lip with or without cleft palate

Nonsyndromic cleft lip and palate (CLP) is among the most common human birth defects. Transmission patterns suggest that the causes are "multifactorial" combinations of genetic and nongenetic factors, mostly distinct from those causing cleft secondary palate (CP). The major etiological factors are largely unknown, and the embryological mechanisms are not well understood. In contrast to CP or neural tube defects (NTD), CLP is uncommon in mouse mutants. Fourteen known mutants or strains express CLP, often as part of a severe syndrome, whereas nonsyndromic CLP is found in two conditional mutants and in two multifactorial models based on a hypomorphic variant with an epigenetic factor. This pattern suggests that human nonsyndromic CLP is likely caused by regulatory and hypomorphic gene variants, and may also involve epigenetics. The developmental pathogenic mechanism varies among mutants and includes deficiencies of growth of the medial, lateral or maxillary facial prominences, defects in the fusion process itself, and shifted midline position of the medial prominences. Several CLP mutants also have NTD, suggesting potential genetic overlap of the traits in humans. The mutants may reflect two interacting sets of genetic signaling pathways: Bmp4, Bmpr1a, Sp8, and Wnt9b may be in one set, and Tcfap2a and Sox11 may be in another. Combining the results of chromosomal linkage studies of unidentified human CLP genes with insights from the mouse models, the following previously unexamined genes are identified as strong candidate genes for causative roles in human nonsyndromic CLP: BMP4, BMPR1B, TFAP2A, SOX4, WNT9B, WNT3, and SP8.     

Plasma zinc concentrations of mothers and the risk of oral clefts in their children in Utah

BACKGROUND: The role of maternal zinc nutrition in human oral clefts (OCs) is unclear. We measured plasma zinc concentrations (PZn) of case and control mothers to evaluate the associations between PZn and risk of OCs with and without other malformations. METHODS: Case mothers were ascertained by the Utah Birth Defects Network and control mothers were selected from Utah birth certificates by matching for child gender and delivery month and year. Maternal blood was collected >1 year after the last pregnancy. PZn was available for 410 case mothers who were divided into four subgroups: isolated cleft lip with or without cleft palate (CL/P‐I, n = 231), isolated cleft palate (CP‐I, n = 74), CL/P with other malformations (CLP‐M, n = 42), and CP with other malformations (CP‐M, n = 63). PZn was available for 447 control mothers. The mean age of children at blood sampling was 3.7 years for all cases combined and 4.3 years for controls. RESULTS: Mean PZns of all groups were similar, and low PZn (<11.0 μmol/L) was found in 59% of cases and 62% of controls. Risk of OCs did not vary significantly across PZn quartiles for the four subgroups individually and all OC groups combined. CONCLUSIONS: We previously reported that poor maternal zinc status was a risk factor for OCs in the Philippines, where OC prevalence is high and maternal PZn is low. In Utah, however, no such association was found, suggesting that poor maternal zinc status may become a risk factor only when zinc status is highly compromised. Birth Defects Research (Part A), 2009. © 2008 Wiley‐Liss, Inc.     

Maternal periconceptional smoking and alcohol consumption and risk for select congenital anomalies

BACKGROUND: This study examined the association between maternal smoking and alcohol use (including binge drinking) during the periconceptional period (i.e., 2 months before through 2 months after conception) and the risk of orofacial clefts, NTDs, and conotruncal heart defects in offspring. METHODS: Data were drawn from a population‐based case‐control study of fetuses and live‐born infants among a cohort of California births between July 1999 and June 2003. The 1,355 cases comprised of 701 orofacial clefts, 337 NTDs, and 323 conotruncal heart defects. Information on smoking and alcohol consumption was obtained via telephone interviews with mothers of 1,355 (80% of eligibles) cases and 700 (77% of eligibles) nonmalformed, live‐born controls. RESULTS: Maternal smoking of five cigarettes or less per day was associated with reduced risks of NTDs (OR 0.7; 95% CI: 0.3, 1.4), whereas the risk associated with higher cigarette consumption was lower for conotruncal heart defects (OR 0.5; 95% CI: 0.2, 1.2). Maternal intake of alcohol less than 1 day per week was associated with a 1.6‐ to 2.1‐fold higher risk of NTDs (95% CI: 0.9, 2.6), d‐transposition of the great arteries (95% CI: 1.1, 3.2), and multiple cleft lip with or without cleft palate (CLP) (95% CI: 0.8, 4.5). Risks associated with more frequent alcohol intake were 2.1 for NTDs (95% CI: 1.1, 4.0) and 2.6 for multiple CLP (95% CI: 1.1, 6.1). CONCLUSIONS: This study observed that maternal alcohol intake increased the risk for d‐transposition of the great arteries, NTDs, and multiple CLP in infants. By contrast, smoking was associated with a lower risk of NTDs and conotruncal heart defects. Birth Defects Research (Part A), 2008. © 2008 Wiley‐Liss, Inc.     

Analysis of the SIM1 Contribution to Polygenic Obesity in the French Population

SIM1 (single‐minded 1) haploinsufficiency is responsible for obesity in both humans and mice, but the contribution of frequent DNA variation to polygenic obesity is unknown. Sequencing of all exons, exon/intron boundaries, 870 base pairs (bp) of the putative promoter, and 1,095 bp of the 3′UTR of SIM1 gene in 143 obese children and 24 control adults identified 13 common variants. After analysis of the linkage disequilibrium (LD) structure, association study of eight variants was performed in 1,275 obese children and severely obese adults, in 1,395 control subjects, and in 578 obesity‐selected pedigrees. A nominal evidence of association was found for the nonsynonymous variant P352T C/A (rs3734354) (P = 0.01, OR = 0.81 (0.70–0.95)), the +2,004 TGA ?/insT SNP (rs35180395) (P = 0.02, OR = 1.21 (1.02–1.43)), the +2,215A/G TGA SNP (rs9386126) (P = 0.002, OR = 0.81 (0.71–0.93)), and pooled childhood/adult obesity. Even though transmission disequilibrium test (TDT) further supported the association of P352T and +2,004 ?/inst T with obesity, none of these nominal associations remained significant after a multiple testing Bonferroni correction. Therefore, our study excludes a major contribution of SIM1 common variants in exons, 5′ and 3′ UTR regions in polygenic obesity susceptibility in French Europeans.     

Oxidative Stress is Associated with Genetic Polymorphisms in One-Carbon Metabolism in Coronary Artery Disease

In view of growing body of evidence favouring the association of aberrations in one-carbon metabolism and oxidative stress in the aetiology of coronary artery disease (CAD), we investigated the risk associated with polymorphisms regulating the folate uptake and transport such as the glutamate carboxypeptidase II (GCPII) C1561T, reduced folate carrier 1 (RFC1) G80A and cytosolic serine hydroxymethyltransferase (cSHMT) C1420T. We further evaluated the impact of seven putatively functional polymorphisms of this pathway on oxidative stress markers. Genotyping was performed on 288 CAD cases and 266 healthy controls along with the dietary folate assessment. GCPII C1561T polymorphism was found to be an independent risk factor (OR 2.71, 95% CI 1.47–4.98) for CAD, whereas cSHMT C1420T conferred protection (OR 0.51, 95% CI 0.37–0.70). Oxidative stress markers like the plasma levels of malondialdehyde, protein carbonyls and 8-oxo-deoxyguanosine were significantly increased and total glutathione was significantly decreased in CAD cases. Elevated oxidative stress was observed in subjects carrying GCPII 1561T and MTRR 66A-variant alleles and low oxidative stress was observed in the subjects carrying cSHMT 1420T and TYMS 5′-UTR 2R allele. GCPII C1561T, MTHFR C677T and MTRR A66G polymorphisms were observed to influence the homocysteine levels (P < 0.05). SHMT and TYMS variants were found to decrease oxidative stress by increasing the folate pool (r = 0.38, P = 0.003) and also by increasing the antioxidant status (r = 0.28, P = 0.03). Influence of dietary folate status was not observed. Overall, this study revealed elevated oxidative stress that was associated with the aberrations in one-carbon metabolism which could possibly influence the CAD risk.     

Epistatic interactions between loci of one-carbon metabolism modulate susceptibility to breast cancer

In view of growing body of evidence substantiating the role of aberrations in one-carbon metabolism in the pathophysiology of breast cancer and lack of studies on gene–gene interactions, we investigated the role of dietary micronutrients and eight functional polymorphisms of one-carbon metabolism in modulating the breast cancer risk in 244 case–control pairs of Indian women and explored possible gene–gene interactions using Multifactor dimensionality reduction analysis (MDR). Dietary micronutrient status was assessed using the validated Food Frequency Questionnaire. Genotyping was done for glutamate carboxypeptidase II (GCPII) C1561T, reduced folate carrier (RFC)1 G80A, cytosolic serine hydroxymethyltransferase (cSHMT) C1420T, thymidylate synthase (TYMS) 5′-UTR tandem repeat, TYMS 3′-UTR ins6/del6, methylenetetrahydrofolate reductase (MTHFR) C677T, methyltetrahydrofolate-homocysteine methyltransferase (MTR) A2756G, methyltetrahydrofolate-homocysteine methyltransferase reductase (MTRR) A66G polymorphisms by using the PCR-RFLP/AFLP methods. Low dietary folate intake (P < 0.001), RFC1 G80A (OR: 1.38, 95% CI 1.06–1.81) and MTHFR C677T (OR: 1.74 (1.11–2.73) were independently associated with the breast cancer risk whereas cSHMT C1420T conferred protection (OR: 0.72, 95% CI 0.55–0.94). MDR analysis demonstrated a significant tri-variate interaction among RFC1 80, MTHFR 677 and TYMS 5′-UTR loci (P _trend < 0.02) with high-risk genotype combination showing inflated risk for breast cancer (OR 4.65, 95% CI 1.77–12.24). To conclude, dietary as well as genetic factors were found to influence susceptibility to breast cancer. Further, the current study highlighted the importance of multi-loci analyses over the single-locus analysis towards establishing the epistatic interactions between loci of one-carbon metabolism modulate susceptibility to the breast cancer.     

Thymidylate synthase: a novel genetic determinant of plasma homocysteine and folate levels

The thymidylate synthase gene ( TYMS or TS) encodes a tightly regulated enzyme that catalyzes the conversion of deoxyuridylate to thymidylate, and contains a tandem repeat polymorphism that affects expression of the enzyme. We have investigated the relationship between TYMS genotype and plasma concentrations of homocysteine and folate in a cohort of 505 Chinese from Singapore. TYMS 3/3 genotype was associated with reduced plasma folate and, among individuals with low dietary folate intake, with elevated plasma homocysteine levels. These associations were independent of the well-established methylenetetrahydrofolate reductase ( MTHFR) C677T genotype effects on plasma folate and homocysteine levels. Our results suggest that TYMS and MTHFR compete for limiting supplies of folate required for the remethylation of homocysteine. These genetic determinants of plasma folate and homocysteine levels may be useful in identifying individuals at increased risk for cardiovascular disease.     

Thymidylate synthase repeat polymorphisms and risk of neural tube defects in a population from the northern United Kingdom

BACKGROUND: A 28-bp repeat polymorphism in the 5'UTR of the thymidylate synthase (TYMS) gene represents a candidate risk factor for neural tube defects (NTDs) due to involvement in folate-dependent homocysteine metabolism. Non-Hispanic, white, U.S. citizens carrying at least one 2x 28-bp repeat allele have recently been shown to be at a four-fold increased risk of spina bifida (SB). We investigated the association between this polymorphism and risk of NTD in families affected by NTDs and controls from the northern United Kingdom (UK). METHODS: PCR was performed on genomic DNA extracted from blood or mouth swabs of family members affected by NTDs (mothers, fathers, and cases), and unaffected controls (mothers and infants) to determine the number of 28-bp repeat units within the promoter region of TYMS. Case-control and TDT analyses of the influence of TYMS genotype on risk of NTD, or NTD pregnancy, were conducted. RESULTS: Odds ratio (OR) analysis indicated that individuals carrying the 2x 28-bp repeat allele either in homozygous or heterozygous form, are not at increased risk of NTDs, or of having an NTD affected pregnancy. Control population allele frequencies are seen to be markedly different between the U.S. controls and those in this study. CONCLUSIONS: TYMS polymorphism appears to be not universally associated with NTD risk across Caucasian samples. The elevated risk of spina bifida in U.S. samples appears to be driven by an unusually low risk allele (2x 28 bp) frequency in control samples. Family based (TDT) testing of U.S. samples is therefore advocated.     

The CRISPLD2 gene is involved in cleft lip and/or cleft palate in a Chinese population

BACKGROUND: Nonsyndromic cleft lip and/or cleft palate (NSCLP) are common congenital anomalies in humans, the etiologies of which are complex and associated with both genetic and environmental factors. Previous data suggested single nucleotide polymorphisms (SNPs) of rs1546124, rs4783099, and rs16974880 of the CRISPLD2 gene were associated with an increased risk of NSCLP; however, subsequent studies have yielded conflicting results. This study aims to evaluate the associations of the aforementioned polymorphisms with NSCLP in a Northwestern Chinese population. METHODS: Three CRISPLD2 SNPs were genotyped in a case‐control study (n = 907), including 444 NSCLP patients and 463 healthy individuals, using polymerase chain reaction–denaturing high‐performance liquid chromatography (PCR‐DHPLC). RESULTS: The genotype and allele frequencies of rs1546124 (odds ratio [OR], 2.30; 95% confidence interval [CI], 1.58–3.34; p = 1 × 10⁻⁵) and rs4783099 (OR, 0.73; 95% CI, 0.54–1.00; p = 0.05) were different in NSCLP patients compared with controls. Furthermore, the CC genotype at rs1546124 was associated with increased risk for cleft lip with or without cleft palate (CL/P; OR, 2.11; 95% CI, 1.41–3.15; p_correct = 1.5 × 10⁻⁴) and for cleft palate only (CPO; OR, 2.93; 95% CI, 1.69–5.07; p_correct = 5.4 × 10⁻⁴), whereas the T allele of rs4783099 was associated with decreased risk for CPO. Further gender stratification showed that the statistical association of these two loci is mainly in the male patients, and not in female patients. CONCLUSION: Our results suggest that the CRISPLD2 gene contributes to the etiology of NSCLP in the Northwestern Chinese population. SNP rs1546124 is significantly related to NSCLP, associated with both CL/P and CPO groups, and SNP rs4783099 is significantly associated with CPO. Birth Defects Research (Part A) 2011. © 2011 Wiley‐Liss, Inc.     

Cleft palate: A clinical review

Orofacial clefts, including cleft palates (CP), are one of the most common birth defects. CP have a multiplicity of effects on the individual and society in terms of economic costs, loss of productivity, psychosocial effects, and increased morbidity and mortality at all stages of life. Embryological development of the palate is well delineated, with developments in the last decade regarding the biomolecular processes involved. Etiology is complex, involving a number of genetic and environmental factors. Various techniques can be employed for the repair of CP, depending on whether the cleft is of the primary or secondary palate, the width of the cleft, whether lengthening of the palate is necessary, and with regard to concerns of disruption of midfacial growth. All surgical techniques have the goals of restoring functional speech, swallowing, and aesthetics. A multidisciplinary team is necessary for the long‐term pre‐ and postoperative care of CP patients to handle complications, associated anomalies, and to optimize function and quality of life. Birth Defects Research (Part C) 102:333–342, 2014. © 2014 Wiley Periodicals, Inc.     

Maternal multivitamin use and orofacial clefts in offspring

BACKGROUND: Cleft lip with or without cleft palate (CLP) and cleft palate alone (CP) affect approximately 1 in 1000 infants and 1 in 2,500 infants, respectively. Studies of the relation between orofacial clefts and multivitamins or folic acid have been inconsistent. METHODS: We used data from a population-based case-control study involving 309 nonsyndromic cleft-affected births (222 with CLP, 87 with CP) and 3,029 control births from 1968 to 1980 to evaluate the relation between regular multivitamin use and the birth prevalence of orofacial clefts. RESULTS: We found a 48% risk reduction for CLP (odds ratio = 0.52, 95% confidence interval = 0.34-0.80) among mothers who used multivitamins during the periconceptional period or who started multivitamin use during the first postconceptional month, after controlling for several covariates. The risk reduction for CP was less than those for CLP (odds ratio = 0.81, 95% confidence interval = 0.44-1.52); however, a small number of CP cases limited interpretation. No risk reductions for CLP or CP were found for women who began multivitamin use in the second or third month after conception. CONCLUSIONS: The magnitude of the risk reduction in our study is comparable to those of other recent studies; our study does not support the contention that only large dosages of folic acid are needed to prevent orofacial clefts. More studies are needed to test the effects of multivitamins and varying dosages of folic acid on the recurrence and/or occurrence of orofacial clefts to provide information needed to determine possible prevention strategies. Published 2001 Wiley-Liss, Inc.     

Maternal vitamin B-6 and folate status and risk of oral cleft birth defects in the Philippines

BACKGROUND: Vitamin deficiencies induce oral clefts in animal experiments, but the role of specific nutrients in human oral clefts is uncertain. METHODS: Associations between maternal vitamin B-6 and folate status and risk of nonsyndromic cleft lip, with or without cleft palate (CL/P), were examined in case-control studies at two sites in the Philippines--Negros Occidental and Davao. Cases were mothers of affected children and control mothers were those who had no children with oral clefts. RESULTS: The risk of having a CL/P-affected child increased with increasing tertile of vitamin B-6 deficiency in both Negros Occidental and Davao (odds ratios [ORs] and 95% confidence intervals [CIs] for sites combined = 1.0 [reference], OR, 2.94; 95% CI, 1.51-5.73; OR, 4.98; 95% CI, 2.56-9.67). Poor B-6 status had a stronger association with CL/P among mothers with lower versus higher plasma folate levels. Increasing tertiles of plasma folate were marginally associated with an increased risk of clefts in both sites combined (1.0 [reference]; OR, 1.58; 95% CI, 0.93-2.68; OR, 1.59; 95% CI, 0.94-2.70). Increasing tertiles of erythrocyte folate were associated with a decreased risk of CL/P in Negros Occidental (1.0 [reference]; OR, 0.34; 95% CI, 0.13-0.90; OR, 0.46; 95% CI, 0.20-1.09) and an increased risk in Davao (1.0 [reference]; OR, 1.23; 95% CI, 0.54-2.81; OR, 4.85; 95% CI, 2.24-10.50). The inconsistent associations between folate status and CL/P risk appeared to be a result of statistical interaction between folate, vitamin B-6, and case-control status that produced different results in study areas of higher versus lower prevalence of vitamin B-6 deficiency. CONCLUSIONS: Poor maternal vitamin B-6 status was consistently associated with an increased risk of CL/P at two sites in the Philippines. Folate-CL/P associations were inconsistent and may be related to the vitamin B-6 status or other characteristics of the populations under study.     

Modulatory effect of plasma folate and polymorphisms in one-carbon metabolism on catecholamine methyltransferase (COMT) H108L associated oxidative DNA damage and breast cancer risk

The present study was aimed to investigate the modulatory role of plasma folate and eight putatively functional polymorphisms of one-carbon metabolism on catecholamine methyltransferase (COMT)-mediated oxidative DNA damage and breast cancer risk. Plasma folate and 8-oxo-2'-deoxyguanosine (8-oxodG) were estimated by commercially available kits, while polymorphisms were screened by PCR-RFLP and PCR-AFLP methods. COMT H108L polymorphism showed independent association with breast cancer (OR: 1.73, 95% CI: 1.31-2.30). No significant interaction was observed between folate status and COMT genotype. Multifactor dimensionality reduction (MDR) analysis gave evidence for the significant epistatic (gene-gene) interactions (p<0.0001) of COMT H108L with reduced folate carrier 1 (RFC1) G80A, thymidylate synthase (TYMS) 5'-UTR 3R2R, TYMS 3'-UTR ins6/de16. Increased plasma 8-oxodG were observed in cases compared to controls (mean +/- SE: 5.59 +/- 0.60 vs. 3.50 +/- 0.40 ng/ml, p<0.004). Plasma folate deficiency alone was not a significant predictor of 8-oxodG elevation. The genotype combinations namely, RFC1 G80A/methionine synthase reductase (MTRR) A66G, RFC1 G80A/SHMT C1420T/TYMS 3R2R and serine hydroxymethyltransferase (SHMT) C1420T/TYMS 3R2R/methionine synthase (MTR) A2756G/COMT H108L were strong predictors of 8-oxodG elevation in the order of risk. To conclude, the current study provides substantial evidence for a cross talk between one-carbon metabolism and COMT catalysis that might influence oxidative DNA damage and breast cancer risk.     

Analysis of polymorphisms and haplotype structure of the human thymidylate synthase genetic region: a tool for pharmacogenetic studies

5-Fluorouracil (5FU), a widely used chemotherapeutic drug, inhibits the DNA replicative enzyme, thymidylate synthase (Tyms). Prior studies implicated a VNTR (variable numbers of tandem repeats) polymorphism in the 5'-untranslated region (5'-UTR) of the TYMS gene as a determinant of Tyms expression in tumors and normal tissues and proposed that these VNTR genotypes could help decide fluoropyrimidine dosing. Clinical associations between 5FU-related toxicity and the TYMS VNTR were reported, however, results were inconsistent, suggesting that additional genetic variation in the TYMS gene might influence Tyms expression. We thus conducted a detailed genetic analysis of this region, defining new polymorphisms in this gene including mononucleotide (poly A:T) repeats and novel single nucleotide polymorphisms (SNPs) flanking the VNTR in the TYMS genetic region. Our haplotype analysis of this region used data from both established and novel genetic variants and found nine SNP haplotypes accounting for more than 90% of the studied population. We observed non-exclusive relationships between the VNTR and adjacent SNP haplotypes, such that each type of VNTR commonly occurred on several haplotype backgrounds. Our results confirmed the expectation that the VNTR alleles exhibit homoplasy and lack the common ancestry required for a reliable marker of a linked adjacent locus that might govern toxicity. We propose that it may be necessary in a clinical trial to assay multiple types of genetic polymorphisms in the TYMS region to meaningfully model linkage of genetic markers to 5FU-related toxicity. The presence of multiple long (up to 26 nt), polymorphic monothymidine repeats in the promoter region of the sole human thymidylate synthetic enzyme is intriguing.     

Periconceptional multivitamin intake during early pregnancy, genetic variation of acetyl-N-transferase 1 (NAT1), and risk for orofacial clefts

BACKGROUND: Periconceptional supplementation of multivitamins that include folic acid have been shown to prevent several birth defects, including neural tube defects and orofacial clefts. We investigated whether polymorphic variants of fetal acetyl-N-transferase 1 (NAT1), an enzyme involved in the catabolism of folates, differentially interacted with maternal multivitamin use during early pregnancy to alter the risk of delivering an infant with an orofacial cleft malformation. METHODS: Using a large population-based case-control study, we genotyped 421 California infants born with an isolated cleft and 299 controls for two NAT1 polymorphisms. RESULTS: Compared to the homozygous wild-type genotypes, odds ratios for isolated cleft lip with/without cleft palate were slightly increased among infants who were homozygous for the variant alleles of NAT1 1088 and 1095. For isolated cleft palate, no similar associations with these two NAT1 variants were observed. For NAT1 1088 genotypes, we did not observe any differential risks for clefts related to maternal multivitamin intake. For NAT1 1095 genotypes, however, we found a two-fold higher risk for isolated cleft lip with/without cleft palate among infants who were homozygous for the variant allele and whose mothers did not take multivitamins during early pregnancy. CONCLUSIONS: We found evidence suggestive of an interaction between the NAT1 1095 polymorphism and lack of maternal multivitamin use that increased risks of isolated cleft lip with/without cleft palate.     

Plasma zinc concentrations of mothers and the risk of nonsyndromic oral clefts in their children: a case-control study in the Philippines

BACKGROUND: Findings from animal experiments suggest a link between poor maternal zinc status and increased risk of oral clefts in offspring; however, there are few human studies on this issue. METHODS: A case-control study was conducted using 74 case mothers of children with nonsyndromic cleft lip with or without cleft palate (CL/P, n=57) or cleft palate alone (CP, n=17), and 283 control mothers of unaffected children recruited in the Philippines in early 2003. Maternal zinc status was assessed by determining plasma zinc concentrations a mean of 5 years after delivery of the index child. Odds ratios (ORs) of estimates of the relative risk of oral clefts were calculated for quartiles of maternal plasma zinc concentrations. RESULTS: The mean plasma zinc concentration of CL/P case mothers (9.6+/-1.2, SD micromol/l) was significantly lower than that in control mothers (10.1+/-1.6 micromol/l; P<0.05). Low plasma zinc concentrations (<11.0 micromol/l) were found in 88% and 94% of CL/P and CP case mothers, respectively, and in 72% of controls (P<0.05). The ORs for CL/P and CP combined, adjusted for potential confounding factors, decreased with increasing quartile of plasma zinc as follows: 1.0 (lowest quartile reference), 0.83 (95% confidence interval 0.37-1.89), 0.70 (0.31-1.68), and 0.26 (0.10-0.70) (P trend=0.008). CONCLUSIONS: Low plasma zinc concentrations were common in Filipino women of reproductive age, and higher plasma zinc concentrations were associated with a lower risk for oral clefts in their children.     

Folate intake and MTHFR polymorphism C677T is not associated with ovarian cancer risk: evidence from the meta-analysis

Folate is essential for DNA synthesis and methylation and implicated in the process of carcinogenesis. Several studies inconclusively suggested increased folate intake may reduce ovarian cancer risk. Studies concerning the association between C677T polymorphism in methylenetetrahydrofolate reductase (MTHFR), an important enzyme in folate metabolism, and ovarian cancer risk also resulted in no agreement. The meta-analysis was conducted based on current studies to assess the association between folate intake, the MTHFR C667T polymorphism and ovarian cancer risk. 1,158 cases out of 217,309 participants from four cohort studies, 4,519 cases and 6,031 controls from four case–control studies about folate intake along with 5,617 cases and 9,808 controls from 10 publications concerning the polymorphism were pooled, respectively. We detected no significant association between total folate (RR = 1.04, 95 % confidence interval (CI) = 0.87–1.23) or dietary folate (RR = 0.88, 95 % CI = 0.75–1.05) intake and ovarian cancer risk, and also no significant relationship was found between MTHFR C677T polymorphism and ovarian cancer risk (TT vs. CC: odds ratio (OR) = 1.15, 95 % CI = 0.90–1.46; CT vs. CC: OR = 1.04, 95 % CI = 0.94–1.16). Our analysis indicated neither folate intake nor MTHFR C677T polymorphism is related to altered susceptibility of ovarian cancer.