Sex differences in genetic susceptibility to maternal mercury and head circumference at birth = Sex differences in genetic susceptibility to maternal mercury and head circumference at birth

다국어 초록 (Multilingual Abstract)

Introduction
Some studies have reported effects of prenatal mercury (Hg) on reduced head circmiiference at birth; however, modifying effects of maternal glutathione S-transferase Ml (GSTM1) or glutathione S-transferase T1 (GSTT1) genotype and infant sex remain unexplored. Our aim was to examine interactions among blood Hg, sex, and GSTM1/GSTT1 polymorphisms in reducing head circumference at birth.
Methods
This study used data from Mothers and Children’ s Environmental Health study (2006-2011) that included total Hg concentration in maternal and cord blood from 515 women and newborns. Information on head circumference (HC) was obtained from medical records and head circumference-to-length ratio (HCLR) was calculated. We defined the threshold level for Hg effects at the 90^th percentile. Linearregressions were adjusted for pre pregnancy weight, age, education, parity, weight gain during pregnancy, gestationalage, and urinarycotinine levels, and effect modification was examined instratified analysis and by fitting interaction terms.
Results
Hg level in early pregnancy that exceeded the
90thpercentile(5.79/g/L)wassignificantlyassociatedwithsmallerHCinmalesofmothershavingnullalleleforGSTM1(β=-0.86;95%confidenceinterval:-1.63,-0.09)(HgxsexxGSTMlnullPinteraction=0.02).ResultsweresimilarforHCLRmodels(Pinteraction=0.04).However, theineteractionofHglevelduringpregnancyorincordblood,sex,andGSTTlnullwasnotsignificant.FurtheranalysesstratifiedbysexandGSTMlgenotyperevealedsignificantinteractionsbetweenHglevelinearlypregnancyandsexonlyininfantsborntomothershavingGSTMlnull(Hgxsex,Pinteraction=0.01)butnotinGSTMlpresentgenotype(Pinteraction=0.37).
Conclusions
Small HC at birth is related to behavioural symptoms later in life; therefore, the most evident effects of Hg on the reduced HC in males born to mothers with GSTM1 null genotype need further investigations to validate our findings.