The IL18 Promoter Polymorphism, rs1946518, Is Associated with the Risk of Periodontitis in Japanese Women: The Kyushu Okinawa Maternal and Child Health Study

The IL18 Promoter Polymorphism, rs1946518, Is Associated with the Risk of Periodontitis in Japanese Women: The Kyushu Okinawa Maternal and Child Health Study

KEIKO TANAKA,^1,2 YOSHIHIRO MIYAKE,^1,2 TAKASHI HANIOKA,³ SHINYA FURUKAWA,^1,2 NOBUYUKI MIYATAKE⁴ and MASASHI ARAKAWA⁵

¹Department of Epidemiology and Preventive Medicine, Ehime University Graduate School of Medicine, Toon, Ehime, Japan
²Epidemiology and Medical Statistics Unit, Translational Research Center, Ehime University Hospital, Toon, Ehime, Japan
³Department of Preventive and Public Health Dentistry, Fukuoka Dental College, Fukuoka, Fukuoka, Japan
⁴Department of Hygiene, Faculty of Medicine, Kagawa University, Kita-gun, Kagawa, Japan
⁵Health Tourism Research Fields, Graduate School of Tourism Sciences, University of the Ryukyus, Nakagami-gun, Okinawa, Japan

Interleukin-18 (IL-18) is a proinflammatory cytokine that plays an important role in periodontitis and its polymorphisms might modulate the individual susceptibility to periodontitis. Only a limited number of studies on the association between IL18 single-nucleotide polymorphisms (SNPs) and the risk of periodontitis have been realized, however. The aim of this case-control study among young post-partum Japanese women (18 to 45 years) was to determine the impact of SNPs, rs1946518 (−607 C/A) and rs187238 (−137G/C), on periodontitis. The two SNPs may be located within a transcription factor-binding element, thereby influencing transcription from the IL18 promoter. Subjects were 131 cases who had at least one tooth with a probing pocket depth of ≥ 4.0 mm and 1,017 periodontally healthy controls. Probing pocket depth measurements were performed between 1 and 12 months post-partum. In this population, the A allele of rs1946518 and the C allele of rs187238 are more common. After adjustment for age, education, smoking, and use of an interdental brush, compared with subjects with the AA or AC genotype of SNP rs1946518, those with the CC genotype had a significantly reduced risk of periodontitis (adjusted odds ratio = 0.54, 95% confidence interval = 0.29-0.97). No significant association was observed between rs187238 and the risk of periodontitis. Our study did not reveal any evidence of interaction between the IL18 polymorphisms and smoking. Our findings indicate that the IL18 promoter SNP, rs1946518, is a potential risk factor of periodontitis among young Japanese women.

keywords —— case-control study; IL18; Japan; periodontal disease; polymorphism

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Tohoku J. Exp. Med., 2017, 243, 159-164

Correspondence: Keiko Tanaka, D.D.S., Ph.D., Department of Epidemiology and Preventive Medicine, Ehime University Graduate School of Medicine, Shitsukawa, Toon, Ehime 791-0295, Japan.

e-mail: tanaka.keiko.jn@ehime-u.ac.jp