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.

IL-13 -1112 polymorphism and periodontitis susceptibility: a meta-analysis

Background

Several studies have examined the association between the IL-13 -1112C/T polymorphism and the risk of periodontitis. However, these studies have reached different conclusions. The aim of the current study was to investigate the link between this IL-13 -1112 polymorphism and susceptibility to periodontitis.

Methods

We utilized electronic databases, including the CNKI (China National Knowledge Infrastructure), Wanfang, PubMed, Embase, and Cochrane Library databases, to manually search for relevant research published through November 30, 2016. The Chinese and English terms used to search the literature included “periodontitis”, “periodontal disease”, “IL 13”, “IL-13”, and “interleukin-13”. In accordance with our inclusion criteria, we selected studies that involved case-control trials. All of these case-control trials described their objectives, design and specific statistical methods. For all included studies, odds ratios (ORs) and 95% confidence intervals (95% CIs) were provided or could be calculated from the study data. The quality of the included literature was evaluated using the Newcastle-Ottawa scale (NOS). STATA 12.0 was used to calculate the sizes of the combined effects and conduct a sensitivity analysis of the results.

Results

Our meta-analysis included 4 articles representing 5 case-control studies with a total of 710 cases and 671 control subjects. The meta-analysis results indicated that the CC vs TT model, CT vs TT model and TT vs CT + CC model (CC VS TT: OR = 0.615, 95% CI = 0.395–0.957; CT vs TT: OR = 0.518, 95% CI = 0.323–0.830; and TT vs CT + CC: OR = 1.739, 95% CI = 1.130–2.676) were significant in five IL-13 -1112 gene polymorphism and periodontitis susceptibility models. Subgroup analysis indicated that the CC vs TT, CT vs TT and TT vs CT + CC models were significant in the chronic periodontitis (CP) group, whereas no significant differences were found in the five aggressive periodontitis (AgP) group models. The sensitivity analysis showed that dropping any single study did not affect the pooled analysis results.

Conclusion

The IL-13 -1112 polymorphism may be associated with susceptibility to periodontitis. The IL-13 -1112 gene polymorphism may be associated with susceptibility to CP but not to AgP. Thus, large-scale, multi-ethnic case-control trials are still warranted.

Interleukin polymorphisms in aggressive periodontitis: A literature review

Aggressive periodontitis (AgP), occurs in a younger age group (≤35 years) and is associated with the rapid destruction of periodontal attachment and supporting bone. Genetic polymorphisms are allelic variants that occur in at least 1% of the population that could potentially alter the function of the proteins that they encode. Interleukins are a group of cytokines that have complex immunological functions including proliferation, migration, growth and differentiation of cells and play a key role in the immunopathogenesis of periodontal disease. The aim of this review was to summarize the findings of studies that reported associations or potential associations of polymorphisms in the interleukin family of cytokines, specifically with AgP.

Toll-like receptor 2 gene polymorphisms associated with aggressive periodontitis in Japanese

BACKGROUND AND OBJECTIVE

Aggressive periodontitis is a rare and very severe periodontal disease of early onset, which is closely associated with Porphyromonas.gingivalis (P.g.) infection in the Japanese population. TLR2 encodes Toll-like receptor 2, which plays an important role in the protective response to P.g. infection. We investigated a possible association between TLR2 and aggressive periodontitis.

MATERIAL AND METHODS

Of 2,460 Japanese patients with periodontitis, 38 patients with aggressive periodontitis were enrolled in this study. These 38 aggressive periodontitis patients and 190 Japanese healthy controls were examined for an insertion/deletion (Ins/Del) polymorphism in exon 1, a polymorphism in intron 1 (rs7696323), and a synonymous polymorphism in exon 3 (rs3804100) in TLR2.

RESULTS

We found significant associations of resistance to aggressive periodontitis with the Ins allele (allele frequency in the patients versus controls, 0.540 vs. 0.676, OR=0.56, 95% confidence interval (CI); 0.34-0.92, p=0.022) and the T allele of rs3804100 (0.579 vs. 0.716, OR=0.55, 95% CI; 0.33-0.91, p=0.018), although the C allele of rs7696323 showed no significant association (0.733 vs. 0.829, OR=0.58). A permutation test of Ins/Del-rs7696323-rs3804100 haplotype revealed a significant association between Ins-C-T haplotype (0.252 vs. 0.479, p=0.0003) and resistance to aggressive periodontitis.

CONCLUSIONS

The TLR2 polymorphisms were suggested to confer protection against aggressive periodontitis in a Japanese population. The association should be replicated in other cohorts to further identify the responsible TLR polymorphism(s) involved in the pathogenesis of aggressive periodontitis.

Analysis of polymorphisms in the lactotransferrin gene promoter and dental caries

Regarding host aspects, there has been strong evidence for a genetic component in the etiology of caries. The salivary protein lactotransferrin (LTF) exhibits antibacterial activity, but there is no study investigating the association of polymorphisms in the promoter region of LTF gene with caries. The objective of this study was firstly to search the promoter region of the human LTF gene for variations and, if existent, to investigate the association of the identified polymorphisms with dental caries in 12-year-old students. From 687 unrelated, 12-year-old, both sex students, 50 individuals were selected and divided into two groups of extreme phenotypes according to caries experience: 25 students without (DMFT = 0) and 25 with caries experience (DMFT ≥ 4). The selection of individuals with extreme phenotypes augments the chances to find gene variations which could be associated with such phenotypes. LTF gene-putative promoter region (+39 to −1143) of the selected 50 individuals was analyzed by high-resolution melting technique. Fifteen students, 8 without (DMFT = 0) and 7 with caries experience (mean DMFT = 6.28), presented deviations of the pattern curve suggestive of gene variations and were sequenced. However, no polymorphisms were identified in the putative promoter region of the LTF gene.

The genetic impact of the Q551R interleukin-4 receptor alpha polymorphism for aggressive or chronic periodontitis and the occurrence of periodontopathic bacteria

OBJECTIVE

The Q551R polymorphism of the gene encoded for the α chain of the interleukin-4 receptor (IL-4RA) could influence both IL-4 and IL-13 signalling. Since both cytokines could be important in the pathogenesis of periodontitis the aim of this study was to evaluate putative associations of the Q551R polymorphism to generalized aggressive or chronic periodontitis and five periodontopathogens.

DESIGN

154 patients with severe generalized periodontitis (chronic: n=68, mean age=48.7 ± 9.4 years; aggressive: n=86, mean age=40.4 ± 9.8 years) and controls without periodontitis (n=89, mean age=46.2 ± 10.8 years) were included. The Q551R polymorphism was analysed by PCR-SSP CTS-Kit, Heidelberg, Germany. Subgingival bacteria were determined molecular biologically using micro-Ident test (HainLifescience, Nehren, Germany). Distributions of single alleles and genotypes were calculated by Chi(2)-test with Yates correction or Fisher's exact test. Adjusted odds ratios were generated by logistic regression with respect to established cofactors for periodontitis.

RESULTS

The mutant allele R551 (p(Y)=0.013) and the genotypes QR+RR (p(B)=0.024) occurred more frequently amongst patients with chronic periodontitis vs. controls. Carriers of the Q551R polymorphism had an increased adjusted odds ratio for chronic periodontitis (OR=3.2, 95%CI 1.5-6.5, p=0.002) and severe periodontitis (chronic+aggressive) in general (OR=2.0, 95%CI 1.1-3.6, p=0.003). Moreover, in the total study cohort the Q551R polymorphism was associated with the presence of Tannerella forsythia (90.3% vs. 78.0%, p(Y)=0.01).

CONCLUSIONS

The Q551R IL-4RA polymorphism is a putative risk indicator for severe chronic periodontitis, but was not significant associated to AP.