title: Cytochrome P450 2A6 Phenotyping Using Dietary Caffeine Salivary Metabolite Ratios and Genotyping Using Blood on Storage Cards in Non-smoking Japanese Volunteers.
abstract: A simple method of genotyping and phenotyping cytochrome P450 2A6 (CYP2A6) was previously reported using individual blood samples and urinary caffeine metabolite ratios of 1,7-dimethyluric acid (17U) to 1-methylxanthine (1X).
  
  
  
  Blood spotted onto storage cards and salivary caffeine metabolites were analyzed in 27 healthy non-smoking Japanese volunteers with no prior abstention from dietary caffeine intake.
  
  
  
  1,7-Dimethylxanthine (17X), 17U, 1X, and caffeine levels in spot saliva samples were determined in Japanese non-smokers by high-performance liquid chromatography under normal dietary caffeine consumption.
  
  
  
  17U/17X ratios in saliva were almost constant over time, but those of 17U/1X were variable in two subjects tested before and 1-2.5 h after caffeine treatment (a cup of black tea). In seven subjects, 17U/17X ratios in saliva were highly correlated with those in plasma (r = 0.98, p < 0.01) and well correlated with those in urine samples (r = 0.78, p < 0.05). The average 17U/17X ratios, but not 17U/1X ratios, in saliva under dietary caffeine consumption obtained from subjects with CYP2A6*1/*4 (n=11) and CYP2A6*4/*4 (whole-gene deletion, n=2) genotypes were significantly lower than those from subjects with wild-type CYP2A6*1/*1 (n=14). Genotyping was done by a multiplex real-time polymerase chain reaction method using blood spotted onto storage cards.
  
  
  
  The present results suggest that the decreased CYP2A6 function associated with the whole-gene deletion genotype (determined using blood samples) could be detected using 17U/17X ratios, but not 17U/1X ratios, in spot saliva samples under normal dietary caffeine consumption in Japanese non-smokers, just as it could be detected using urinary 17U/1X ratios.
authors.forename: Norie
authors.initials: N
authors.lastname: Murayama
authors.forename: Makiko
authors.initials: M
authors.lastname: Shimizu
authors.forename: Kenta
authors.initials: K
authors.lastname: Kobayashi
authors.forename: Izumi
authors.initials: I
authors.lastname: Kishimoto
authors.affiliation: Laboratory of Drug Metabolism and Pharmacokinetics, Showa Pharmaceutical University, 3-3165 Higashi-tamagawa Gakuen, Machida, Tokyo 194-8543. Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yamazaki
mesh_terms: D000328:Adult; D002110:Caffeine / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D065637:Cytochrome P-450 CYP2A6 / Q000097:blood / Q000235:genetics* / Q000502:physiology*; D004032:Diet; D005260:Female; D060005:Genotyping Techniques / Q000379:methods*; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D008875:Middle Aged; D060885:Multiplex Polymerase Chain Reaction; D010641:Phenotype; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods; D012463:Saliva / Q000737:chemistry*; D013048:Specimen Handling / Q000379:methods; D013662:Tea / Q000737:chemistry; D014527:Uric Acid / Q000031:analogs & derivatives / Q000652:urine; D014970:Xanthines / Q000652:urine
chemical_list: D013662:Tea; D014970:Xanthines; D014527:Uric Acid; D002110:Caffeine; C053085:1-methylxanthine; C585710:CYP2A6 protein, human; D065637:Cytochrome P-450 CYP2A6; C053084:1,7-dimethyluric acid
keywords: Blood storage card; CYP2A6; plasma; saliva; urine; whole-gene deletion