A Systematic Review and Meta-Analysis on Multiple Cytokine Gene Polymorphisms in the Pathogenesis of Periodontitis

Aim

Periodontitis is an inflammatory disease that destroys both soft and hard periodontal tissues. However, a complex periodontal cytokine network remains unclear. This systematic review explored multiple cytokine gene polymorphisms in the pathogenesis of periodontitis.

Material and Methods

A systematic search was performed using the databases from previous publications, which indicated the association between cytokine polymorphisms and periodontitis pathogenesis. Meta-analysis was conducted using fixed or randomized models to calculate the significance of multiple cytokine polymorphisms. A total of 147 articles were analyzed with polymorphisms in 12 interleukins [Th1 (IL-2, IFN-γ, and TNF-α), Th2 (IL-4 and IL-13), Th17 (IL-1α, IL-1β, IL-6, and IL-17), and Treg cytokines (IL-10 and TGF-β)]. Doi plot was used to probe the occurrence of publication bias.

Results

The polymorphisms of IL-2 and TNF-α of Th1 cytokine family may be associated with the pathogenesis or the prevention of periodontitis risk, while the polymorphism of IFN-γ is not related to periodontitis risk. The polymorphisms for IL-4 and IL-13 of Th2 cytokine family are not found to be associated with the pathogenesis of periodontitis. For the polymorphisms of the members of Th17 cytokine family, different IL-1α polymorphisms may have inverse actions in the pathogenesis of periodontitis. IL-1β is a noteworthy cytokine biomarker in periodontitis development and progression. IL-6 may have a protective function in the inflammatory responses of periodontitis, and IL-17 has a weak relationship the inflammatory responses. The polymorphisms for the members of Treg cell cytokines may have a protective function against periodontitis risk. LFK indexes show the major asymmetry due to publication bias.

Conclusion

IL-1β is a notable cytokine biomarker in periodontitis risk. Treg cytokines favor an anti-inflammatory and protective environment. Further data are needed to confirm the present conclusion due to publication bias.

Interleukin-6-174G/C Polymorphism Contributes to Periodontitis Susceptibility: An Updated Meta-Analysis of 21 Case-Control Studies

Introduction. Chronic Periodontitis (CP) is suggested to be related to gene variations. Present study aims to quantitatively estimate the association between interleukin-6- (IL-6-) 174G/C polymorphism and CP susceptibility. Materials and Methods. Pubmed, Embase, and Web of Science were searched up to May 2016. The meta-analyses were performed using STATA 12.0. Results. 21 studies were yielded. Significant associations were found under heterozygote comparison and dominant model in studies fulfilling HWE (GC versus GG: OR = 0.690, 95% CI = 0.560–0.849, P = 0.000; CC + GC versus GG: OR = 0.690, 95% CI = 0.568–0.838, P < 0.001); significant associations were found under heterozygote comparison and dominant model in Caucasian studies fulfilling HWE (GC versus GG: OR = 0.752, 95% CI = 0.577–0.980, P = 0.035; CC + GC versus GG: OR = 0.737, 95% CI = 0.576–0.944, P = 0.016); significant associations were found under allele comparison, heterozygote comparison, and dominant model in Brazilian population (C versus G: OR = 0.648, 95% CI = 0.497–0.845, P = 0.001; GC versus GG: OR = 0.621, 95% CI = 0.441–0.876, P = 0.007; CC + GC versus GG: OR = 0.649, 95% CI = 0.470–0.896, P = 0.009). Conclusion. IL-6 174 polymorphism is associated with CP susceptibility. In Brazilian and Caucasian population, IL-6 174 GG genotype plays as a risk factor to CP.

Association among interleukin-6 gene polymorphisms, type 2 diabetes mellitus, and chronic periodontitis: a pilot study

AIM

The purpose of this pilot study was to determine the association between single nucleotide polymorphisms (-174 G>C) in the interleukin-6 (IL-6) gene with chronic periodontitis (CP) and type 2 diabetes mellitus (T2DM) in south Indian population.

METHODS

Genomic DNA was obtained from the white blood cells of 30 patients with T2DM, 30 patients with CP, 30 patients with T2DM with CP, and 30 controls. DNA was amplified using polymerase chain reaction with specific primers flanking the locus -174 of the IL-6 gene and further genotyped using the restriction fragment length polymorphism method. The genotype distribution and allele frequencies between the study groups were determined using χ² -test. The relative risk was estimated with a 95% confidence interval.

RESULTS

The CP group (26.7%) displayed a greater percentage of GC genotype (P = 0.026) when compared to the control group (3.3%). A statistically-significant difference in the allele frequencies was found between the control and CP group with the C-allele frequency being greater (0.13) in the CP group than normal controls (0.02).

CONCLUSION

The GC genotype was found to be the risk genotype and the C allele was found to be the risk allele for the development of CP.

Correlation of the interleukin-29 levels in crevicular fluid and plasma with the genetic polymorphism in chronic and aggressive periodontitis patients

OBJECTIVE

To assess the effect of single nucleotide polymorphism (SNP) on the Interleukin (IL-29) quantity in gingival crevicular fluid (GCF) and plasma of chronic and aggressive periodontitis patients.

DESIGN

Patients with periodontal health (n=30), chronic generalized periodontitis (n=30) and generalized aggressive periodontitis (n=30) were subjected to IL-29 quantity estimation in GCF and plasma using enzyme linked immunosorbent assay and was correlated with IL-29 SNP (rs30461) using polymerase chain reaction.

RESULTS

IL-29 concentration in GCF and plasma was highest in aggressive periodontitis patients (114.17 ± 95.07pg/ml and 149.69 ± 109.90pg/ml respectively). The least concentration was found in subjects with healthy periodontium (47.50 ± 37.75pg/ml and 54.52 ± 37.53pg/ml) and in chronic periodontitis it was found to be 65.01 ± 41.26pg/ml and 81.17 ± 46.23pg/ml. The difference in the quantity of IL-29 in GCF and plasma among different groups was statistically significant (p<0.001 and p<0.001 respectively). rs30461 polymorphism of IL-29 analysis revealed that difference in the prevalence of A/A, A/G and G/G genotype among three groups was not statistically significant (p=0.097).

CONCLUSION

Increased quantity of IL-29 in GCF and plasma of subjects with periodontitis suggests a role in pathogenesis of periodontitis and the SNP (rs30461) is not related to susceptibility to periodontitis in this population of Indian individuals.

Interleukin-6 c.-174G>C Polymorphism and Periodontitis in a Brazilian Population

Aim. Periodontitis is an inflammatory disease that affects the teeth supporting structures, triggered by periodontal pathogens, and is influenced by environmental and genetic factors. Genes encoding molecules related to the immune response, such as cytokine, are the main candidates for polymorphisms analysis and may be possibly associated with this pathology. A G/C promoter polymorphism on the IL6 gene has been shown to affect basal IL-6 levels. The aim of this study was to investigate the association between the IL6 c.-174G>C polymorphism and periodontitis in individuals from Vitória da Conquista, Bahia, Brazil. Material and Methods. Three hundred and thirty individuals (134 cases, 196 controls) were genotyped for the IL6 c.-174G>C by MS-PCR technique. Concentrations of salivary IL-6 were determined by ELISA method. Results. The IL6 c.-174G>C polymorphism was associated with periodontitis when comparing the distribution of genotypes between patients with periodontitis and control subjects. The GC genotype appeared as a protective factor for periodontitis. Results showed increased levels of salivary IL-6 in periodontitis patients. Nevertheless, there was no relationship between the concentrations of IL-6 and genotypes when comparing the case and control groups. Conclusions. Our data indicate an association between IL6 c.-174G>C polymorphism and periodontitis and showed that IL-6 may be considered an important marker for periodontitis.

Association between COX-2 rs 6681231 genotype and interleukin-6 in periodontal connective tissue. A pilot study

OBJECTIVES

The aim of this pilot study was to investigate associations between IL-6 and COX-2 expression in gingival biopsies and both clinical diagnosis and genotypes in the IL-6 and COX-2 genes.

DESIGN

A case-control study included 41 gingival biopsies obtained from Caucasian patients grouped according to clinical diagnosis of gingival health (n = 10), gingivitis (n = 15) or chronic periodontitis (n = 16). Immunohistochemistry analyses were performed to determine COX-2 expression in lamina propria, IL-6 expression in lamina propria and gingival epithelium and level of inflammatory cell infiltrate. Individual DNA was extracted and genotyped by real-time PCR for IL6 SNPs rs 2069827 and rs 2069825 and for COX-2 rs 6681231.

RESULTS

The percentage of cellular COX-2 expression was associated with the extent of periodontal disease (Arbes index p = 0.026) and inflammatory infiltrate (p<0.0001). No association was observed between IL6 haplotypes and cells positive to IL-6 or COX-2 in gingival tissues. The COX-2 rs 6681231 was associated with cells positive to IL-6 in the connective tissue (p = 0.032).

CONCLUSIONS

COX-2 expression in gingival tissues may be a marker of periodontal disease severity. COX-2 rs 6681231 may be associated with IL-6 local production in gingival tissues.

An interleukin-6 gene promoter polymorphism is associated with polycystic ovary syndrome in South Indian women

PURPOSE

Polycystic ovary syndrome (PCOS) is a most common endocrine disorder of reproductive age women. Interleukin-6 is involved in the pathophysiological characteristics associated with polycystic ovary syndrome (PCOS). The-174 G/C IL-6 gene promoter region single nucleotide polymorphism (SNP) may influence or modulate gene function and/or transcriptional efficiency. The current study was aimed to evaluate the association between IL-6 gene -174 G/C promoter polymorphism and Polycystic Ovary Syndrome in South Indian women.

METHODS

In the present study, we examined the genotypic and allele distribution among the PCOS patients (n = 104) and controls (n = 156). The genotypes of IL-6 -174 G/C SNP were analyzed by polymerase chain reaction (PCR) and sequencing analysis. The allele frequency and genotype distributions of cases and controls were analyzed using Fisher's exact test.

RESULTS

The genotype frequencies observed among the 104 cases and 156 controls were G/G 66.3 % and 49.4 %, G/C 29.8 % and 46.8 %, and C/C 3.8 % and 3.8 % (OR: 1.6226, CI: 1.0574-2.4899). The G and C allele frequencies were 81.25 % and 72.8 %, and 18.75 % and 27.2 %, respectively. The genotype and allele distribution revealed significant differences between PCOS patients and controls (all P values < 0.05).

CONCLUSION

Our findings showed a significant statistical association between IL-6 -174 G/C SNP and PCOS risk in South Indian women. The 'G' allele frequency influences significantly higher in PCOS patients than controls. However, the exact mechanism by which 'G' allele frequency influence PCOS patients is yet to be determined.

Variations in inflammatory genes are associated with periodontitis

BACKGROUND

Periodontitis is a multi-factorial disease and several risk-factors such as infections, inflammatory responses, oral hygiene, smoke, aging and individual predisposition are involved in the disease. Pathogens trigger chronic inflammation with cytokines release which in turn leads to the destruction of the connective and the teeth supporting bone. The identification of genetic factors controlling oral inflammation may increase our understanding of genetic predisposition to periodontitis.Single nucleotide polymorphisms in the promoter region of Vascular Endothelial Growth Factor, Alpha-1-Antichymotripsin, hydroxy-methyl-glutaryl CoA reductase, Interferon alpha, Interleukin-1 Beta, Interleukin 10, Interleukin 6 and Tumor Necrosis Factor- alpha genes from a case/control study were investigated.

RESULTS

The C allele of Vascular Endothelial Growth Factor, A allele of Interleukin 10 and GG genotype of Tumor Necrosis Factor-α were individually associated with chronic periodontitis. However, the concomitant presence of the three genetic markers in the same subjects appeared to play a synergistic role and increased several folds the risk of the disease.

CONCLUSIONS

Our findings offer new tools to implement the screening of unaffected subjects with an increased susceptibility of periodontitis and increase our understanding regarding the genetic inflammatory background related to familiarity of the disease.