Association between smoking habits and tryptophan hydroxylase gene C218A polymorphism among the Japanese population.
BACKGROUND
Genetic polymorphisms have proposed a new insight in smoking behavior. Genes in serotonin system are one of the candidates because of serotonin's role in mood regulation. A polymorphism C218A in intron 7 of the tryptophan hydroxylase (TPH) gene has been hypothesized in relation to smoking predisposition.


METHODS
We examined the association on two Japanese populations: one was from the first-visit outpatients of Aichi Cancer Center Hospital during 3-month period between April and June, 2001 (N=591), and the second was from the examinees who attended a health checkup program supported by the Nagoya municipal government in 2000 (N=446). Written documents on informed consent were obtained and lifestyle questionnaires were recorded. TPH C218A genotypes were determined by the polymerase chain reaction with confronting two-pair primers (PCR-CTPP) method.


RESULTS
The frequencies of the C- and A-allele were 52% and 48%, respectively, which was in Hardy-Weinberg equilibrium. As for current smoking status, no associations were statistically observed. It was, however, indicated that smokers with A/A genotype started smoking earlier in their life. Among male health examinees, mean ages at starting smoking were 18.7 (A/A), 19.9 (C/A), and 22.4 years (C/C), (P<0.01). Also, on the Aichi Cancer Center Hospital subjects aged 60 and older, mean ages were 19.0 (A/A), 20.2 (C/A), and 20.3 years (C/C) for males and 22.3 (A/A), 31.0 (C/A), and 33.0 years (C/C) for females (P<0.05).


CONCLUSIONS
The present study demonstrated that the TPH C218A polymorphism in intron 7 had no association with current smoking status in Japanese population. The hypothesis of early smoking initiation of A/A genotype was partially in agreement.
Mizuno
Shoichi
S
Group of Epidemiology and Health Promotion, Tokyo Metropolitan Institute of Gerontology, Japan.
Ito
Hidemi
H
Hamajima
Nobuyuki
N
Tamakoshi
Akiko
A
Hirose
Kaoru
K
Tajima
Kazuo
K
D000293:Adolescent; D000328:Adult; D000483:Alleles; D005260:Female; D005787:Gene Frequency; D005838:Genotype; D015438:Health Behavior; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008297:Male; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D012309:Risk-Taking; D012907:Smoking / Q000453:epidemiology / Q000235:genetics*; D011795:Surveys and Questionnaires; D014365:Tryptophan Hydroxylase / Q000235:genetics*
D014365:Tryptophan Hydroxylase