Background: Periodontitis is initiated by a dysbiosis in the subgingival microbial biofilm and can be related to host genetic factors. This study investigated association between periodontitis and single nucleotide variants (SNVs) in the IL-33 and IL1RL1 genes. Methods: This cross-sectional study involved 359 individuals from a public health service in Brazil. Structured questionnaire was used to collect health status and socioeconomic, demographic and behavioral characteristics. Periodontitis was diagnosed by clinical periodontal examination. Subgingival biofilm was collected at the deepest site of each sextant, and biofilm bacterial DNA was amplified by real time polymerase chain reaction (qPCR) to determine relative quantification of pathogens. Peripheral blood was collected for genomic DNA extraction and SNV genotyping was performed by qPCR. Logistic regression model was used to obtain association measures (95% confidence interval), by ussing the additive model. Results: The C allele variant of IL33 (rs2381416) was inversely associated with periodontitis, even after adjusting for the confounding covariates (p < 0.01 ORadjusted: 0.45; CI: 0.24-0.84), and with the presence of the Aggregatibacter actinomycetemcomitans (Aa) pathogen, adjusting for the same covariates (p < 0.01; ORadjusted: 0.46; CI: 0.27-0.76). Inverse association between this SNV and periodontitis was observed (p = 0.02; ORadjusted: 0.46; CI: 0.28-0.76) using additive genotypic model. Conclusions: Frequency of C allele variant of IL-33 (rs2381416) was lower in individuals with periodontitis and in individuals with relatively higher levels of Aa. Investigations of this variant as a potential predictor of the protective phenotype in the context of periodontitis are needed. This study will contribute to the training of health professionals involved in the treatment of periodontitis.
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