Polymorphism of glutathione S-transferases and the potential risk of periodontitis

Objectives: Interactions of environmental and genetic factors determine the extent and severity of periodontitis. Smoking is one of the risk factors for periodontitis, and the risk may be influenced by the polymorphism of metabolizing enzymes which determine the individual's susceptibility to smoke-derived xenobiotics. Glutathione S-transferases (GSTs) is one group of these metabolizing enzymes. We therefore hypothesized that a GSTs genotype would be a risk factor for periodontitis, especially in smokers. This study is to assess the influence of the genetic polymorphisms of GSTs on periodontal status in relation to smoking in Chinese Han nationality. Methods: DNA samples were collected with buccal swabs from 112 subjects with severe chronic periodontitis and 78 periodontal healthy controls. Subjects were diagnosed as severe chronic periodontitis with the standard of mean CAL>2.5mm and 1 or more sites in 3 out of 4 quadrants with interproximal CAL measurements of >5mm and no more than 14 missing teeth. Their smoking behavior including present and past quality and quantity of smoking were recorded. The genetic polymorphisms of GSTM1 and GSTT1 were determined using MD-PCR. The distribution of GSTM1 and GSTT1 null genotypes among the groups stratified with smoking were analyzed. Results: There was no significant difference for the distribution of GSTM1 null genotype and GSTT1 null genotype between non-smoker groups of periodontitis and healthy control (For GSTM1: OR=1.06, p>0.05; For GSTT1: OR=1.46, p>0.05), but the frequencies of GSTM1 null genotype and GSTT1 null genotype were significantly higher in the smoker periodontitis group than in the smoker healthy control group (For GSTM1: OR=2.80, p<0.05; For GSTT1: OR=2.88, p<0.05). Conclusion: There is a gene-environmental interaction between smoking and the genetic polymorphisms of GSTs. Smokers bearing the GSTM1 null genotype or GSTT1 null genotype may have an increased risk of severe chronic periodontitis in Chinese Han nationality.