title: Relationship between interindividual differences in nicotine metabolism and CYP2A6 genetic polymorphism in humans.
abstract: BACKGROUND
  Nicotine is mainly metabolized to cotinine by cytochrome P450 (CYP) 2A6. Previously, we found that the CYP2A6 gene was deleted homozygously in one subject who was deficient in cotinine formation from nicotine.
  
  
  OBJECTIVE
  Our objective was to clarify the relationship between interindividual differences in nicotine metabolism and CYP2A6 genetic polymorphism.
  
  
  METHODS
  Nicotine was administered to 92 healthy Japanese subjects in the form of 1 piece of nicotine gum to investigate the potency of nicotine metabolism. The cotinine-nicotine ratio of the plasma concentration 2 hours after chewing was calculated as an index of nicotine metabolism. The genotypes of CYP2A6 gene, CYP2A6*1A, CYP2A6*1B, CYP2A6*2, CYP2A6*3, CYP2A6*4, and CYP2A6*5, were determined with polymerase chain reaction-restriction fragment length polymorphism.
  
  
  RESULTS
  A large interindividual difference in nicotine metabolism was observed. Allele frequencies of CYP2A6*1A, CYP2A6*1B, and CYP2A6*4 were 42.4%, 37.5%, and 20.1%, respectively. The CYP2A6*2, CYP2A6*3, and CYP2A6*5 alleles were not found. Three subjects genotyped as CYP2A6*4/CYP2A6*4 were completely deficient in cotinine formation. The heterozygotes of the CYP2A6*4 allele tend to show lower capacities for cotinine formation. The subjects with CYP2A6*1A/CYP2A6*1B appeared to have higher capacities of cotinine formation than subjects with CYP2A6*1A/CYP2A6*1A, although the difference was not significant. The probit plot of the cotinine-nicotine ratio was not linear; this possibly indicated the existence of a novel mutation in the CYP2A6 gene genotyped as CYP2A6*1B/CYP2A6*4.
  
  
  CONCLUSIONS
  The relationship between interindividual differences in nicotine metabolism and CYP2A6 genetic polymorphism in humans was proved.
authors.affiliation: Department of Biochemistry, School of Medicine, Kanazawa University, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Nakajima
authors.forename: J T
authors.initials: JT
authors.lastname: Kwon
authors.forename: N
authors.initials: N
authors.lastname: Tanaka
authors.forename: T
authors.initials: T
authors.lastname: Zenta
authors.forename: Y
authors.initials: Y
authors.lastname: Yamamoto
authors.forename: H
authors.initials: H
authors.lastname: Yamamoto
authors.forename: H
authors.initials: H
authors.lastname: Yamazaki
authors.forename: T
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Y
authors.initials: Y
authors.lastname: Kuroiwa
authors.forename: T
authors.initials: T
authors.lastname: Yokoi
mesh_terms: D000284:Administration, Oral; D000328:Adult; D000483:Alleles; D001189:Aryl Hydrocarbon Hydroxylases; D002638:Chewing Gum; D003367:Cotinine / Q000097:blood / Q000378:metabolism; D065637:Cytochrome P-450 CYP2A6; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics* / Q000378:metabolism; D005260:Female; D005838:Genotype; D006801:Humans; D007206:Individuality; D008297:Male; D006899:Mixed Function Oxygenases / Q000235:genetics* / Q000378:metabolism; D009538:Nicotine / Q000008:administration & dosage / Q000097:blood / Q000378:metabolism*; D011110:Polymorphism, Genetic
chemical_list: D002638:Chewing Gum; D009538:Nicotine; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D001189:Aryl Hydrocarbon Hydroxylases; C585710:CYP2A6 protein, human; D065637:Cytochrome P-450 CYP2A6; D003367:Cotinine