title: Influence of CYP2A6*4 genotypes on maternal serum cotinine among Chinese nonsmoking pregnant women.
abstract: BACKGROUND
  Serum cotinine is a common biomarker for smoking and secondhand smoke (SHS) exposure, but it can be affected by the activity of nicotine-metabolizing enzymes. This study investigated the influence of CYP2A6*4 genotypes on serum cotinine among nonsmoking pregnant women.
  
  
  METHODS
  We analyzed the data from 545 Chinese nonsmoking pregnant women in a case-control study on SHS exposure and birth outcomes in southern China. Participants self-reported their status and duration of SHS exposure during pregnancy right after delivery in hospital. Research staff used polymerase chain reaction to genotype CYP2A6*4 and enzyme-linked immunosorbent assay to measure cotinine levels in maternal serum samples collected before delivery. We stratified women by their self-reported SHS exposure status and CYP2A6*4 genotypes and then compared their median levels of serum cotinine.
  
  
  RESULTS
  Among women who self-reported non-SHS exposure (n = 317), the median serum cotinine levels were 2.83ng/ml for those with CYP2A6*1/*1 genotype, 1.39ng/ml for CYP2A6*1/*4, and 0.77ng/ml for CYP2A6*4/*4, respectively. Among women who self-reported SHS exposure (n = 228), the median cotinine levels were 3.32ng/ml for those with CYP2A6*1/*1 genotype, 2.38ng/ml for CYP2A6*1/*4, and 1.56ng/ml for CYP2A6*4/*4, respectively. Strikingly, self-reported SHS-exposed women with CYP2A6*1/*4 or CYP2A6*4/*4 genotype had significantly lower (rather than higher) median cotinine levels than self-reported non-SHS-exposed women with CYP2A6*1/*1 genotype (p = .012).
  
  
  CONCLUSIONS
  CYP2A6*4 genotype is associated with lower serum cotinine among Chinese nonsmoking pregnant women. Measuring CYP2A6*4 genotype may help to improve the validity of SHS exposure measurement by serum cotinine in pregnant women and possibly also in other nonpregnant populations.
authors.affiliation: Department of Biostatistics and Epidemiology, School of Public Health, Sun Yat-sen University, Guangzhou, China;
authors.forename: Chuanbo
authors.initials: C
authors.lastname: Xie
authors.forename: Xiaozhong
authors.initials: X
authors.lastname: Wen
authors.forename: Peng
authors.initials: P
authors.lastname: Ding
authors.forename: Tao
authors.initials: T
authors.lastname: Liu
authors.forename: Yanhui
authors.initials: Y
authors.lastname: He
authors.forename: Zhongzheng
authors.initials: Z
authors.lastname: Niu
authors.forename: Jianmiao
authors.initials: J
authors.lastname: Lin
authors.forename: Shixin
authors.initials: S
authors.lastname: Yuan
authors.forename: Xiaoling
authors.initials: X
authors.lastname: Guo
authors.forename: Deqin
authors.initials: D
authors.lastname: Jia
authors.forename: Weiqing
authors.initials: W
authors.lastname: Chen
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D016022:Case-Control Studies; D002681:China; D003367:Cotinine / Q000097:blood*; D003430:Cross-Sectional Studies; D065637:Cytochrome P-450 CYP2A6 / Q000235:genetics*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005838:Genotype; D006801:Humans; D011247:Pregnancy; D057566:Self Report; D012907:Smoking; D014028:Tobacco Smoke Pollution / Q000009:adverse effects*; D055815:Young Adult
chemical_list: D015415:Biomarkers; D014028:Tobacco Smoke Pollution; C585710:CYP2A6 protein, human; D065637:Cytochrome P-450 CYP2A6; D003367:Cotinine