Passive smoking in the etiology of non-syndromic orofacial clefts:a systematic review and meta-analysis

Background Studies have found a consistent positive association between maternal smoking and nonsyndromic orofacial clefts (NSOFC). However, no comprehensive assessment of the association between NSOFC and passive smoking has been undertaken. This systematic review and meta-analysis explores the relationship between maternal passive smoking and NSOFC, and compares the associations between passive and active smoking. Methods and Findings Search strategy, inclusion / exclusion criteria, and data extraction from studies reporting maternal passive smoking and NSOFC was implemented without language restrictions. Risks of bias in the identified studies were assessed and this information was used in sensitivity analyses to explain heterogeneity. Meta-analysis and meta-regression of the extracted data were performed. Egger's test was used to test for small study effects. Fourteen eligible articles were identified. Maternal passive smoking exposure was associated with a twofold increase in risk of NSOFC (odds ratio: 2.11, 95% confidence interval: 1.54-2.89); this was apparent for both cleft lip with and without palate (OR: 2.05, 95% CI: 1.27-3.3) and cleft palate (OR: 2.11, 95% CI: 1.23-3.62). There was substantial heterogeneity between studies. In the studies that provided data enabling crude and adjusted odd ratios to be compared, adjustment for potential confounders attenuated the magnitude of association to about a 1.5-fold increase in risk. Conclusion Overall, maternal passive smoking exposure results in a 1.5 fold increase in risk of NSOFC, similar to the magnitude of risk reported for active smoking, but there is marked heterogeneity between studies. This heterogeneity is not explained by differences in the distribution of cleft types, adjustment for covariates, broad geographic region, or study bias/quality. This thorough meta-analysis provides further evidence to minimize exposure to environmental tobacco smoke in policy making fora and in health promotion initiatives.</p

Evaluating LINE-1 methylation in cleft lip tissues and its association with early pregnancy exposures

Aim: To pilot investigation of methylation of long interspersed nucleotide element-1 in lip tissues from infants with nonsyndromic cleft lip, and its association with maternal periconceptional exposures. Methods: The lateral and medial sides of the cleft lips of 23 affected infants were analyzed for long interspersed nucleotide element-1 methylation by bisulfite conversion and pyrosequencing. Results: The medial side showed 1.8% higher methylation compared with the lateral side; p = 0.031, particularly in male infants (2.7% difference; p = 0.011) or when the mothers did not take folic acid during periconceptional period (2.4% difference; p = 0.011). These results were not statistically significant when Bonferroni adjustment was used. Conclusion: The observed differences in DNA methylation, although nonsignificant after correction for multiple comparisons, suggest that differential regulation of the two sides may impact lip fusion and warrant larger-scale replication

Smoking and orofacial clefts: a United Kingdom–based case-control study

Objective: To investigate the association between smoking and orofacial clefts in the United Kingdom. Design: Case-control study in which the mother's exposure to tobacco smoke was assessed by a structured interview. Setting: Scotland and the Manchester and Merseyside regions of England. Participants: One hundred ninety children born with oral cleft between September 1, 1997, and January 31, 2000, and 248 population controls, matched with the cases on sex, date of birth, and region. Main Outcome Measure: Cleft lip with or without cleft palate and cleft palate. Results: There was a positive association between maternal smoking during the first trimester of pregnancy and both cleft lip with or without cleft palate (odds ratio 1.9, 95% confidence interval 1.1 to 3.1) and cleft palate (odds ratio 2.3, 95% confidence interval 1.3 to 4.1). There was evidence of a dose-response relationship for both types of cleft. An effect of passive smoking could not be excluded in mothers who did not smoke themselves. Conclusion: The small increased risk for cleft lip with or without cleft palate in the offspring of women who smoke during pregnancy observed in this study is in line with previous evidence. In contrast to some previous studies, an increased risk was also apparent for cleft palate. In these U.K. data, there was evidence of a dose-response effect of maternal smoking for both types of cleft. The data were compatible with a modest effect of maternal passive smoking, but the study lacked statistical power to detect or exclude such an effect with confidence. It may be useful to incorporate information on the effects of maternal smoking on oral clefts into public health campaigns on the consequences of maternal smoking

EUROCRAN WP2

A multi-centre gene-environment interaction study in orofacial clefting involving 1169 triads was carried out in 10 EU countries between 2001 and 2005. Genotyping was carried out successfully in Aberdeen, Dublin, Ferrara and Ljubljana for a range of genetic polymorphisms which included MTHFR TGFA TGFB3 SATB2 MSX1 CYP1A1 GST and NAT2. The Aberdeen centre completed a series of statistical analyses: informative case-parent triads were analysed by the transmission disequilibrium test and log-linear analysis was conducted for each of the polymorphisms, for all OFC combined, and for cleft lip and palate (CLP) and cleft palate only (CPO) separately. Among the results it was found that the MSX1 polymorphism conferred increased risk for CL(P) with maternal variant allele and a dominant effect (RR 1.34, p=0.05), but with CPO no effect was observed. All other results will be presented. In the future, additional genotyping for polymorphisms found to be significant in other populations, such as IRF6, FGFR1 and PVRL1 will be carried out

Progetto EUROCRAN: Interazione gene-ambiente nelle schisi orofacciali non-sindromiche

Le schisi orofacciali (SOF) non-sindromiche, comprendenti le labiopalatoschisi (LPS) e le palatoschisi (PS), sono malformazioni congenite la cui eziologia si ritiene sia riconducibile complessa interazione tra fattori di rischio genetici e fattori di rischio ambientali. Una ampia casistica multi-centrica, comprendente 1169 triadi composte da pazienti SOF e relativi genitori, è stata raccolta nel periodo 2001-2005 in 10 Paesi Europei nel contesto del workpackage-2 del progetto EUROCRAN, finalizzato allo studio dell’interazione gene-ambiente nelle SOF non-sindromiche. L’analisi un pannello di varianti polimorfiche in geni candidati, comprendenti MTHFR, TGFA, TGFB3, SATB2, MSX1, CYP1A1, GST e NAT2, è stata condotta applicando l’analisi-log-lineare ed il TDT (transmission disequilibrium test). Risultati preliminari evidenziano interazione gene-ambiente tra il genotipo MTHFR 677TT sia con la supplementazione in gravidanza con acido folico (FA) che con l’esposizione al fumo di tabacco. Nelle madri con supplementazione con AF il genotipo MTHFR 677TT si associa ad un effetto protettivo sia per LPS che e PS. In assenza di uso di tabacco durante la gravidanza, il genotipo materno MTHFR 677TT si accompagna a riduzione del rischio di LPS ma non di PS. Nei figli il genotipo MTHFR 677TT si associa a riduzione del rischio per SOF indipendentemente dalla supplementazione in gravidanza con AF o dalla non-esposizione al fumo di tabacco

MTHFR promoter methylation might mitigate the effect of smoking at the level of LINE-1 in cleft lip tissues: A preliminary study

Background: The medial and maxillary aspects of the upper lip originate at separate embryonic stages and therefore may experience different maternal exposure patterns which may affect methylation. Based on this hypothesis, we investigated the level of methylation of the methylene tetrahydrofolate reductase promoter gene (mMTHFR) in tissues from cleft lip, and mMTHFR levels by MTHFR c.677C &gt; T genotype. We further investigated whether mMTHFR mitigates the effect of smoking on long interspersed nuclear element (LINE-1) methylation in these tissues. Methods: DNA extracted from medial and lateral tissues of 26 infants with nonsyndromic cleft lip with or without cleft palate (nsCL/P) was bisulfite converted and mMTHFR was measured on a pyrosequenser. LINE-1 methylation and MTHFR c.677C &gt; T genotype data were obtained in our previous study. Results: There was no substantial difference in mMTHFR (p&nbsp;=.733) and LINE-1 (p&nbsp;=.148) between the two tissues. mMTHFR was not influenced by MTHFR c.677C &gt; T genotype, but there was suggestive evidence that the difference was larger among infants exposed to maternal smoking compared to nonexposed. LINE-1 methylation differences were significant (p&nbsp;=.025) in infants born to nonsmoking mothers, but this was not apparent (p&nbsp;=.872) in infants born to mothers who smoked. Our Pearson's correlation analysis suggested a weak inverse association between mMTHFR and LINE-1 (r&nbsp;=&nbsp;−.179, p&nbsp;=.381). Conclusion: Our preliminary observation of differences in patterns of mMTHFR levels in lip tissue suggests the interplay of gene and environment in the establishment of methylation in tissues at both sides of cleft lip. This requires investigation in a larger cohort, integrated with metabolic assessment