Investigation of the haplotype in the IL8 gene association with susceptibility to chronic periodontal disease and type 2 Diabetes Mellitus

Abstract

Evidence on the relationship of cytokines, such as Interleukin 8 (IL-8), with inflammatory and / or systemic diseases is increasing. The periodontal disease (PD), which is characterized as the main cause of dental loss in adults, has a multifactorial character, influenced by the presence of periodontopathogenic microorganisms, host genetic susceptibility, immune system reaction, smoking habit and presence of diseases such as Type 2 Diabetes Mellitus (DM2). One of the most important cytokines produced by inflamed periodontal tissue is IL-8, as it acts mainly on the chemical attraction of neutrophils. In recent years, with support from FAPESP, our research group has verified that polymorphisms in the IL8 gene, such as -251(T / A), +396(T / G) and +781(C / T), forming the haplotype ATC / TTC increased susceptibility to PD by 2-fold. Such a haplotype has been shown to be functional in the transcription and translation of the IL8 gene. We currently have a larger number of patients (n = 356) with a more detailed periodontal clinical profile, which may contribute to the confirmation of these polymorphisms as genetic markers for chronic periodontitis (PC) in our population. We also intend to investigate the same polymorphisms in patients with DM2 and PD, as little is known about the association of the IL8 gene with DM2, and the aforementioned haplotype has never been investigated in this pathological context. The aim of the present study was to investigate the genetic susceptibility to chronic periodontitis associated with type 2 diabetes mellitus, given by the mentioned polymorphisms in the IL8 gene, as possible genetic markers in our population. Patients will be divided into: Group A (n = 356) patients with severe or moderate CP, Group B (n = 356) patients with mild PC and periodontally healthy and patients with DM2 and PC (DM2_PC group = 248). Patients from DM2_PC group will be compared to patients from Group A (without DM2 with severe or moderate PC, and Group B (without DM2 with mild PC or periodontally healthy). We already have the approval of the Ethics Committee, and we have extracted DNA of all patients of Groups A and B, while DM2_PC patients are being screened. Full and detailed periodontal examination of each patient is performed, and the mouthwash is collected with glucose solution to extract the DNA by salting-out method with Ammonia Acetate 8M. By the way, the fellowship candidate has been working for 2 years in the database of patients and is assisting in the extraction of DNA. Polymorphisms will be investigated by real-time PCR (Polymerase Chain Reaction -PCR) reactions utilizing TaqMan® (Thermo Fisher). The data processing from genotypes and the calculation of allele frequencies (MAF) of the polymorphisms will be performed, as well as the Hardy-Weinberg equilibrium and the degree of linkage disequilibrium between the SNPs. Multiple logistic regression analysis will be performed to adjust the results to variables such as age, gender and smoking, using program R. The statistical results will be corrected for multiple tests using the Bonferroni correction. It is hoped that this study will contribute with the understanding of the possible efficacy of these polymorphisms as genetic markers for chronic periodontitis in association with or not with DM2. (AU)