Gene polymorphisms and periodontitis

Causal relationship between cheese intake and periodontal diseases: A two-sample Mendelian randomization study

Dietary habits have been confirmed to affect periodontal disease, but whether cheese intake is associated with periodontal disease remains unclear. This study aims to explore the causal relationship between cheese intake and periodontal disease by Mendelian randomization (MR) analysis. genome-wide association study data from the UK Biobank was utilized. In order to reveal the causal relationship between exposure (cheese intake) and outcome (periodontal disease), and to ensure the reliability of the conclusions, single nucleotide polymorphisms were rigorously selected as instrumental variables to replace the exposure. The following methods were applied for MR analysis: the inverse-variance weighted (IVW), MR-Egger, weighted median, simple mode and weighted mode methods. Sensitivity analyses included heterogeneity test, horizontal pleiotropy test and leave-one-out method. The IVW method indicated that the risk of periodontal diseases decreased as cheese intake increases (OR = 0.545, 95% CI = 0.364-0.816, P = .0032). Sensitivity analyses revealed no statistical evidence of heterogeneity or horizontal pleiotropy, confirming the robustness of the results. Increased cheese intake may reduce the risk of periodontal disease. This study provides genetic evidence supporting the inclusion of cheese in the diet for periodontal disease. Further research is needed to confirm these findings in different populations and to understand the underlying mechanisms.

Periodontal Molecular Diagnostics: State of Knowledge and Future Prospects for Clinical Application

Periodontitis leads to immunologically mediated loss of periodontium and, if untreated, can result in tooth loss. Periodontal diseases are the most prevalent in the world and have a very strong impact on patients' well-being and general health. Their treatment generates enormous costs. Given the above, precise, prompt, and predictive diagnosis of periodontal disease is of paramount importance for clinicians. The aim of the study was to summarize the state-of-the-art knowledge of molecular periodontal diagnostics and the utility of its clinical application. There is a great need to have diagnostic tests that not only describe the periodontal destruction that has occurred in the tissues but also allow clinicians to detect disease at a subclinical level before the changes occur. A test that would enable clinicians to follow the course of the disease and detect areas prone to exacerbation could be used to evaluate the effectiveness of ongoing periodontal therapies. Unfortunately, there is no such diagnostic method yet. A hopeful prospect is molecular diagnostics. There are numerous studies on biomarkers of periodontal disease. Point-of-care tests are also emerging. There are possibilities for processing large biological datasets (omics data). However, all of the above have a minor role in the overall single-patient diagnostics process. Despite advances in microbiological, molecular, and genetic research, the basis of periodontal diagnosis is still clinical examination enriched by the evaluation of radiological images.

Dual Role of IGF2BP2 in Osteoimmunomodulation during Periodontitis

Periodontitis is a complex disease characterized by distinct inflammatory stages, with a peak of inflammation in the early phase and less prominent inflammation in the advanced phase. The insulin-like growth factor 2-binding proteins 2 (IGF2BP2) has recently been identified as a new m6A reader that protects m6A-modified messenger RNAs (mRNAs) from decay, thus participating in multiple biological processes. However, its role in periodontitis remains unexplored. Here, we investigated the role of IGF2BP2 in inflammation and osteoclast differentiation using a ligature-induced periodontitis model. Our findings revealed that IGF2BP2 responded to bacterial-induced inflammatory stimuli and exhibited differential expression patterns in early and advanced periodontitis stages, suggesting its dual role in regulating this disease. Depletion of Igf2bp2 contributed to increased release of inflammatory cytokines, thereby exacerbating periodontitis after 3 d of ligature while suppressing osteoclast differentiation and ameliorating periodontitis after 14 d of ligature. Mechanistically, we demonstrated that IGF2BP2 directly interacted with Cd5l and Cd36 mRNA via RNA immunoprecipitation assay. Overexpression of CD36 or recombinant CD5L rescued the osteoclast differentiation ability of Igf2bp2-null cells upon lipopolysaccharide stimulus, and thus the downregulation of Cd36 and Cd5l effectively reversed periodontitis in the advanced stage. Altogether, this study deepens our understanding of the potential mechanistic link among the dysregulated m6A reader IGF2BP2, immunomodulation, and osteoclastogenesis during different stages of periodontitis.

Evaluation of matrix metalloproteinase-1, -2, -3, -7, and -13 gene polymorphisms in patients with chronic periodontitis and healthy controls

OBJECTIVES

The current study aimed to investigate the association of matrix metalloproteinase- (MMP-) 1, -2, -3, -7, and -13 gene polymorphisms with chronic periodontitis (CP) in an Iranian population.

MATERIALS AND METHODS

In this case-control study, 87 subjects with CP and 89 periodontally healthy subjects were allocated to case and control groups, respectively. Subjects' venous blood samples (5 cc) were collected, and DNA extraction was performed. A spectrophotometer was utilized to assess the concentration of extracted DNAs. The desired gene polymorphisms were examined using restriction fragment length polymorphism polymerase chain reaction (RFLP-PCR) followed by electrophoresis. Statistical analyses were done using the Pearson Chi-Square test, odds ratio, and t-Test using SPSS Version 28.

RESULTS

The MMP-1 (-1607 1G/2G) rs1799750, MMP-3 (-1171 5A/6A) rs3025058, and MMP-7 (-181 A/G) rs11568818 gene polymorphisms significantly differed between case and control groups (PV = 0.019, 0.007, and 0.028, respectively). In contrast, the gene polymorphisms of MMP-2 (-1306 C/T) rs243865 and MMP-13 (-77 A/G) rs2252070 did not make a significant difference. Regarding allele frequencies, the presence of the 2G allele in the MMP-1 (-1607) rs1799750 genotype increased the CP susceptibility significantly, while subjects with the 6A allele in their MMP-3 (-1171) rs3025058 genotype showed significantly lower susceptibility to CP (PV = 0.008 and < 0.001, respectively).

CONCLUSION

In the studied population, gene polymorphisms in the DNA sequences of MMP-1 (-1607 1G/2G) rs1799750, MMP-3 (-1171 5A/6A) rs3025058, and MMP-7 (-181 A/G) rs11568818 may have impacts on CP incidence.

CLINICAL RELEVANCE

Clinicians should be cautious about the association between MMP-1, MMP-3, and MMP-7 gene polymorphisms and the incidence of chronic periodontitis during periodontal treatment planning.

Analysis of the Effects of IL-6 -572 C/G, CRP -757 A/G, and CRP -717 T/C Gene Polymorphisms; IL-6 Levels; and CRP Levels on Chronic Periodontitis in Coronary Artery Disease in Indonesia

Interleukin 6 (IL-6) and C-Reactive Protein (CRP) play an important role in chronic periodontitis with coronary artery disease (CAD). Genetic factors can affect a person's risk of CAD, which affects one-third of the population. This study investigated the role of IL-6 -572 C/G, CRP -757 A/G, and CRP -717 T/C gene polymorphisms. IL-6 and CRP levels on the severity of periodontitis in CAD in Indonesia were also evaluated. This case-control study was conducted with mild and moderate-severe chronic periodontitis groups. A path analysis test was conducted with Smart PLS with a 95% confidence interval to determine the significant variable for chronic periodontitis. Our study revealed that the effects of IL-6 -572 C/G, CRP -757 A/G, and CRP -717 T/C gene polymorphisms on IL-6 levels and CRP levels were not significant. IL-6 and CRP levels were not significantly different between the two groups. We found that IL-6 levels had a significant effect on CRP levels in periodontitis patients with CAD (path coefficient 0.322, p = 0.003). IL-6 -572 C/G, CRP -757 A/G, and CRP -717 T/C gene polymorphisms had no effect on the severity of chronic periodontitis in CAD patients in the Indonesian population. We also observed no apparent effects of the influence of gene polymorphisms in IL-6 -572 C/G, CRP -757 A/G, and CRP -717 T/C genes. Although the IL-6 and CRP levels were not significantly different between the two groups, IL-6 levels affected CRP levels in periodontitis patients with CAD.

Single Nucleotide Polymorphisms in IL-1A RS1800587, IL-1B RS1143634 and Vitamin D Receptor Rs731236 in Stage III Grade B/C Periodontitis

The purpose of the study is to determine the prevalence of interleukin (IL)-1A (rs1800587), IL-1B (rs1143634) and vitamin D receptor (VDR) (TaqI, rs731236) gene polymorphisms in the Turkish population and their association with Stage III Grade B/C periodontitis. Systemically and periodontally healthy individuals (N = 100) and Stage III Grade B/C periodontitis patients (N=100) based on clinical and radiographic examination were included in this research. Clinical attachment level, probing depth, bleeding on probing, plaque and gingival indices of the subjects were measured. Genotyping of IL-1A (rs1800587), IL-1B (rs1143634) and VDR (rs731236) polymorphisms was conducted by Real Time PCR. Allelic and genotypic distributions of IL-1A (rs1800587) gene polymorphism were not associated with periodontitis (p>0.05). In IL-1B (rs1143634) gene polymorphism, the C allele was detected more frequently in healthy individuals compared with the periodontitis patients (p=0.045). CC genotype and C allele in VDR (rs731236) gene polymorphism was higher in periodontitis patients (p=0.031, p=0.034, respectively). In comparison with Grade B periodontitis patients and healthy subjects, CC genotype and C allele were observed more frequently in the Grade B periodontitis in terms of alleles (C/T) and genotypes for VDR (rs731236) polymorphism (p=0.024, p=0.008, respectively). This study presents that the VDR (rs731236) polymorphism are associated with enhanced susceptibility to Stage III periodontitis in the Turkish population. Furthermore, VDR (rs731236) polymorphism may be used as an identification criteria to discriminate Grade B and Grade C in Stage III periodontitis.

Outside the limits of bacterial viability: postbiotics in the management of periodontitis

Periodontitis is a major cause of tooth loss in adults worldwide and is caused by an unbalanced oral microbiota in a susceptible host, ultimately leading to tissue breakdown and bone loss. Traditionally, the treatment for periodontitis is scaling and root planing; however, some cases require adjuvant therapy, such as antibiotics administration or surgery. Various factors are involved in the pathogenesis and interact in an unpredictable way, increasing the complexity of the disease and making it difficult to manage. In this context, the administration of probiotics aimed at resolving bacterial dysbiosis and the associated dysregulation of the immune system has been employed in clinical trials with encouraging results. However, the use of viable microorganisms is not risk-free, and immunocompromised patients may develop adverse effects. Therefore, the use of inactivated microbial cells, cell fractions, or soluble products and metabolites of probiotics, known as postbiotics, has gained increasing attention. In this commentary, we present the current literature assessing the impact of postbiotics on the growth and metabolism of periodontal pathogens, as well as on the progression of periodontitis in rodents and humans. We also discuss the limitations of the available data and what the scientific community should consider in order to transfer this innovative therapeutic modality from the bench to the bedside.

Periodontitis as a risk factor for head and neck cancer

Background

Periodontitis may be associated with the development of head and neck cancer (HNC). A literature review was conducted to understand the possible association between them.

Material and Methods

Articles published in the PubMed database from January 1999 and May 2020 were retrieved. Limitations of the studies and biological mechanisms were discussed.

Results

A total of 4,232 articles were found. Of these, 13 were analyzed according to inclusion criteria. Most papers found some association between periodontitis and HNC, although differences in periodontal evaluation, sample size, study design and tumor sites were observed. Porphyromonas gingivalis appears to increase the chance of both diseases, and it may be one of their main potential risk factors. Genetic predisposition is increased by exposure to environmental factors which can directly induce epigenetic changes that contribute to these diseases.

Conclusions

Understanding the mechanisms related to periodontitis and HNC has increased, however, well-designed clinical studies are needed for better conclusions. Furthermore, the advent of multiple "omic" technologies will help comprehend their possible association.

Key words:Periodontitis, head and neck cancer, oral cancer, risk factors, biological factors.

MicroRNAs: Harbingers and shapers of periodontal inflammation

Periodontal disease is an inflammatory reaction of the periodontal tissues to oral pathogens. In the present review we discuss the intricate effects of a regulatory network of gene expression modulators, microRNAs (miRNAs), as they affect periodontal morphology, function and gene expression during periodontal disease. These miRNAs are small RNAs involved in RNA silencing and post-transcriptional regulation and affect all stages of periodontal disease, from the earliest signs of gingivitis to the regulation of periodontal homeostasis and immunity and to the involvement in periodontal tissue destruction. MiRNAs coordinate periodontal disease progression not only directly but also through long non-coding RNAs (lncRNAs), which have been demonstrated to act as endogenous sponges or decoys that regulate the expression and function of miRNAs, and which in turn suppress the targeting of mRNAs involved in the inflammatory response, cell proliferation, migration and differentiation. While the integrity of miRNA function is essential for periodontal health and immunity, miRNA sequence variations (genetic polymorphisms) contribute toward an enhanced risk for periodontal disease progression and severity. Several polymorphisms in miRNA genes have been linked to an increased risk of periodontitis, and among those, miR-146a, miR-196, and miR-499 polymorphisms have been identified as risk factors for periodontal disease. The role of miRNAs in periodontal disease progression is not limited to the host tissues but also extends to the viruses that reside in periodontal lesions, such as herpesviruses (human herpesvirus, HHV). In advanced periodontal lesions, HHV infections result in the release of cytokines from periodontal tissues and impair antibacterial immune mechanisms that promote bacterial overgrowth. In turn, controlling the exacerbation of periodontal disease by minimizing the effect of periodontal HHV in periodontal lesions may provide novel avenues for therapeutic intervention. In summary, this review highlights multiple levels of miRNA-mediated control of periodontal disease progression, (i) through their role in periodontal inflammation and the dysregulation of homeostasis, (ii) as a regulatory target of lncRNAs, (iii) by contributing toward periodontal disease susceptibility through miRNA polymorphism, and (iv) as periodontal microflora modulators via viral miRNAs.

Runs of homozygosity are associated with staging of periodontitis in isolated populations

Periodontitis is a common inflammatory disease characterized by a complex etiology, which is the result of a combination of genetic and environmental factors. Genetic variants linked to the periodontitis disease were already investigated, however, little was known regarding the severity of this disease. Recently, long runs of homozygosity (ROH) were associated with several multifactorial diseases. Therefore, in our work, we tried to assess the role of ROH and periodontitis status. We found an association between the excess of homozygosity owing to ROH and staging of periodontitis. More in detail, the total amount of homozygosity owing to ROH is positively associated with an increased severity of periodontitis (P = 0.0001). Regression tree analysis showed the impact of ROH burden in discriminating individuals with mild periodontitis stages I and II and periodontitis stages III and IV (P < 0.001). Furthermore, ROH mapping highlights several regions associated with a severe status of periodontitis (odds ratio > 1). Among them, we found a total of 33 genes. Interestingly, some of these genes were previously associated with granulocyte or platelet measures, both linked to the onset and the progression of periodontal disease. Our results suggest the not only single variants association test could help to risk assessment but even individual genomic features; furthermore, our ROH mapping highlighted the possible role of multiple genes in periodontal development.

Association of TNF-α-308G/A, -238G/A, -863C/A, -1031T/C, -857C/T polymorphisms with periodontitis susceptibility: Evidence from a meta-analysis of 52 studies

The association between tumor necrosis factor-alpha (TNF-α-308G/A, -238G/A, -863C/A, -1031T/C, and -857C/T) polymorphism and either chronic (CP) or aggressive (AgP) periodontitis susceptibility was conflicting. This meta-analysis aimed to quantitatively estimate the association.A total of 52 studies involving 5519 patients and 7260 controls were identified through a search of multiple electronic databases. Odds ratios (ORs) and their 95% confidence intervals using allele, homozygous, heterozygous, dominant, and recessive genetic models were computed to assess the strength of the association.The TNF-α-308G/A polymorphism was significantly associated with decreased risks of CP (GG vs AA: OR = 0.353, P < .001; GG+GA vs AA: OR = 0.480, P < .001) and AgP (G vs A: OR = 0.651, P < .001; GG vs AA: OR = 0.306, P < .001; GG+GA vs AA: OR = 0.384, P < .001) in Asians. There were no associations between TNF-α-238G/A, -863C/A, -1031T/C, -857C/T polymorphism and susceptibility to AgP. No associations were also found between CP susceptibility and TNF-α-238G/A, -857C/T polymorphism.These findings supported that TNF-α-308G/A polymorphism might be the protective factors of CP and AgP in Asians, and TNF-α-238G/A, -863C/A, -1031T/C, -857C/T polymorphism is not linked to AgP susceptibility.

Novel rare frameshift variation in aggressive periodontitis: Exomic and familial-screening analysis

BACKGROUND

Aggressive periodontitis (AgP), currently periodontitis grade C, presents early onset, rapid progression, and a poorly established genetic association. Thus, this study aimed to identify genetic variants associated with AgP via whole exome sequencing (WES) through a familial screening approach.

METHODS

WES was performed in two nuclear families, including a proband and a parent affected by AgP and an unaffected parent and sibling. Common variants among affected individuals, excluding those common to healthy people, from each family, composed the data set associated with AgP. In silico analysis evaluated the impact of each variant on protein structure and protein-protein interactions. Moreover, identified deleterious variants were validated in a populational analysis (n = 96).

RESULTS

The missense single nucleotide variations (SNVs) rs142548867 in EEFSEC (c.668C>T), rs574301770 in ZNF136 (c.466C>G), and rs72821893 in KRT25 (c.800G>A) and the frameshift indels rs37146475 in GPRC6A (c.2323-2324insT) and c.1366_1372insGGAGCAG in ELN were identified in AgP and have a predicted functional impact on proteins. In silico analysis indicated that the indel in GPRC6A generates a loss of the C-terminal tail of the Gprca protein. Furthermore, this SNV was significantly associated with AgP in a population-based investigation.

CONCLUSION

Novel frameshift variation in GPRC6A (c.2323-2324insT) was identified as a potential genetic alteration associated with AgP occurrence.

The IL18 Promoter Polymorphism, rs1946518, Is Associated with the Risk of Periodontitis in Japanese Women: The Kyushu Okinawa Maternal and Child Health Study

Interleukin-18 (IL-18) is a proinflammatory cytokine that plays an important role in periodontitis and its polymorphisms might modulate the individual susceptibility to periodontitis. Only a limited number of studies on the association between IL18 single-nucleotide polymorphisms (SNPs) and the risk of periodontitis have been realized, however. The aim of this case-control study among young post-partum Japanese women (18 to 45 years) was to determine the impact of SNPs, rs1946518 (-607 C/A) and rs187238 (-137G/C), on periodontitis. The two SNPs may be located within a transcription factor-binding element, thereby influencing transcription from the IL18 promoter. Subjects were 131 cases who had at least one tooth with a probing pocket depth of ≥ 4.0 mm and 1,017 periodontally healthy controls. Probing pocket depth measurements were performed between 1 and 12 months post-partum. In this population, the A allele of rs1946518 and the C allele of rs187238 are more common. After adjustment for age, education, smoking, and use of an interdental brush, compared with subjects with the AA or AC genotype of SNP rs1946518, those with the CC genotype had a significantly reduced risk of periodontitis (adjusted odds ratio = 0.54, 95% confidence interval = 0.29-0.97). No significant association was observed between rs187238 and the risk of periodontitis. Our study did not reveal any evidence of interaction between the IL18 polymorphisms and smoking. Our findings indicate that the IL18 promoter SNP, rs1946518, is a potential risk factor of periodontitis among young Japanese women.

Genetic Association with Subgingival Bacterial Colonization in Chronic Periodontitis

Chronic periodontitis is the most prevalent form of inflammatory destructive bone disease and has been affecting humans since antiquity. Evidence suggest that genetic factors can highly influence periodontitis risk, modulating disease elements such as the susceptibility to microbial colonization and the nature of subsequent host-microbe interaction. Several single-nucleotide polymorphisms (SNPs) have been associated with the occurrence of periodontitis, but the full range of genetic influence in periodontitis outcomes remains to be determined. In this context, this study comprises an analysis of possible correlation between periodontitis-related genetic variants with changes in the subgingival microbiological pattern performed in a Brazilian population (n = 167, comprising 76 chronic periodontitis patients and 91 healthy subjects). For the genetic characterization, 19 candidate SNPs were selected based on the top hits of previous large genome wide association studies (GWAS), while the subgingival microbiota was characterized for the presence and relative quantity of 40 bacterial species by DNA-DNA checkerboard. The case/control association test did not demonstrate a significant effect of the target SNPs with the disease phenotype. The polymorphism rs2521634 proved significantly associated with Tannerella forsythia, Actinomyces gerencseriae, Fusobacterium periodonticum, and Prevotella nigrescens; rs10010758 and rs6667202 were associated with increased counts of Porphyromonas gingivalis; and rs10043775 proved significantly associated with decreased counts of Prevotella intermedia. In conclusion, we present strong evidence supporting a direct connection between the host’s genetic profile, specifically rs2521634, rs10010758, rs6667202, and rs10043775 polymorphisms, and the occurrence of chronic periodontitis-associated bacteria.

Application of Interleukin-1 Genes and Proteins to Monitor the Status of Chronic Periodontitis

It has been widely reported that periodontitis may lead to bone tissue and teeth loss and result in failure of prosthodontics or implants. Interleukin-1 (IL-1) is a potent proinflammatory cytokine that plays an essential role during the pathogenesis of periodontitis. However, the gene polymorphisms of IL-1α, IL-1β and IL-1RN and the relationship between these protein expressions in healthy people and patients with chronic periodontitis (CP) in China have not been fully elucidated. We investigated the gene polymorphisms and protein expression of IL-1α, IL-1β and IL-1RN in healthy subjects and CP patients, and our data suggest that these gene polymorphisms are associated with CP. The frequency of the C/C genotype of IL-1α was 55% in CP patients, while in the control group it was 20% (p<0.0001). The C/C genotype of IL-1β was also higher in CP patients (51%) than in controls (21%) (p<0.0001). For the 2/2 genotype of IL-1RN, CP patients showed a 30% frequency, while in controls this was 15% (p<0.0001). Protein levels evaluated by enzyme-linked immunosorbent assay demonstrated a significant difference in secretion between patients and controls for IL-1α and IL-1β. These results indicate that genotype and protein production of IL-1α, IL-1β and IL-1RN are associated with CP in a Chinese population, and might be putative risk indicators for chronic periodontitis.

The effects of IL-10 gene polymorphism on serum, and gingival crevicular fluid levels of IL-6 and IL-10 in chronic periodontitis

OBJECTIVE

Anti-inflammatory cytokines play a crucial role in periodontitis by inhibiting synthesis of pro-inflammatory cytokines. The purpose of this study was to evaluate the effect of interleukin-10 (-597) gene polymorphism and genotype distributions on chronic periodontitis (CP) development and IL-6 and IL-10 levels in gingival crevicular fluid (GCF) and serum before and after non-surgical periodontal treatment.

MATERIAL AND METHODS

The study population consisted of 55 severe generalized CP patients as CP group and 50 healthy individuals as control group. Plaque index, gingival index, probing depth and clinical attachment level were recorded and GCF and blood samples were taken at both the baseline and the sixth week after non-surgical periodontal treatment. PCR-RFLP procedure was used for gene analyses and cytokine levels were measured via ELISA.

RESULTS

IL-10 genotype distribution was significantly different between CP and control groups (p=0.000, OR:7, 95%CI, 2.83-60.25). Clinical measurements significantly improved in the CP group after periodontal treatment (p<0.05). Periodontal treatment significantly decreased GCF IL-6 and IL-10 levels. No significant difference was found in clinical parameters between IL-10 AA and AC+CC genotypes at both the baseline and the sixth week (p>0.05). Sixth week GCF IL-10 levels were significantly lower in patients carrying IL-10 AC+CC genotype compared to the patients carrying IL-10 AA genotype (p<0.05). Serum IL-6 and IL-10 levels were lower in patients carrying the IL-10 AA genotype compared to patients with IL-10 AC+CC genotype, but the difference was not significant (p>0.05).

CONCLUSION

IL-10 AA genotype carriers had lower IL-6 and IL-6/10 levels in serum; however, GCF IL-6/10 levels were similar in both genotypes. Within the limitations of our study, a possible association between IL-10(-597) gene polymorphism and CP might be considered.

Association Study of Vitamin D Receptor (VDR) - Related Genetic Polymorphisms and their Haplotypes with Chronic Periodontitis in Colombian Population

INTRODUCTION

There is strong evidence that both genetic and environmental factors may affect the periodontal clinical status. However, epidemiological evidence on the association between Vitamin D Receptor (VDR) polymorphisms and Chronic Periodontitis (CP) has been inconsistent.

AIM

The focus of this study was to identify if a possible association between VDR Single-Nucleotide Polymorphisms (SNPs) may be implicated in the aetiopathogenesis of CP in Colombian population.

MATERIALS AND METHODS

One hundred and ten CP patients and 50 Healthy Controls (HC) were recruited. Periodontal status was assessed based on probing depth, clinical attachment level, extent, and severity of periodontal breakdown. The polymerase chain reaction-restriction fragment length polymorphism method was used to identify the VDR rs7975232, rs1544410, rs2228570, and rs731236 SNPs from saliva samples. Odds Ratios (ORs) along with their 95% Confidence Intervals (CIs) were computed to compare the distribution of genotypes/alleles between HC and CP patients, alongside with analysis of Linkage Disequilibrium (LD) and haplotype associations between SNPs. Also, an analysis of the interaction between genetic findings and those significant demographic factors was performed for all SNPs.

RESULTS

There was no association neither between the different genotypes/allele frequencies nor haplotypes and CP. Similarly, no significant differences in extent or severity amongst genotype/allele groups were observed. Even so, interaction analysis revealed significant synergistic interactions between each SNP and age associated with the disease status.

CONCLUSION

Although these results do not support that VDR SNPs could be identified as independent risk predictor variables for CP in the Colombian population, synergistic biological interactive effects of all these SNPs related to age might play a significant role in the pathogenic pathways of CP.

Evaluation of a Panel of Single-Nucleotide Polymorphisms in miR-146a and miR-196a2 Genomic Regions in Patients with Chronic Periodontitis

BACKGROUND

Periodontitis is an inflammatory disease caused by bacterial triggering of the host immune-inflammatory response, which in turn is regulated by microRNAs (miRNA). Polymorphisms in the miRNA pathways affect the expression of several target genes such as tumor necrosis factor-α and interleukins, which are associated with progression of disease.

OBJECTIVE

The objective of this study was to identify the association between the MiR-146a single nucleotide polymorphisms (SNPs) (rs2910164, rs57095329, and rs73318382), the MiR-196a2 (rs11614913) SNP and chronic periodontitis.

METHODS

Genotyping was performed for the MiR-146a (rs2910164, rs57095329, and rs73318382) and the MiR-196a2 (rs11614913) polymorphisms in 180 healthy controls and 190 cases of chronic periodontitis by the direct Sanger sequencing technique. The strength of the association between the polymorphisms and chronic periodontitis was evaluated using logistic regression analysis. Haplotype and linkage analyses among the polymorphisms was performed. Multifactorial dimensionality reduction was performed to determine epistatic interaction among the polymorphisms.

RESULTS

The MiR-196a2 polymorphism revealed a significant inverse association with chronic periodontitis. Haplotype analysis of MiR-146a and MiR-196a2 polymorphisms revealed 13 different combinations, of which 5 were found to have an inverse association with chronic periodontitis.

CONCLUSION

The present study has demonstrated a significant inverse association of MiR-196a2 polymorphism with chronic periodontitis.

Associations of Toll-Like Receptor and β-Defensin Polymorphisms with Measures of Periodontal Disease (PD) in HIV+ North American Adults: An Exploratory Study

Polymorphisms in toll-like receptor (TLR) and β-defensin (DEFB) genes have been recognized as potential genetic factors that can influence susceptibility to and severity of periodontal diseases (PD). However, data regarding associations between these polymorphisms and PD are still scarce in North American populations, and are not available in HIV+ North American populations. In this exploratory study, we analyzed samples from HIV+ adults (n = 115), who received primary HIV care at 3 local outpatient HIV clinics and were monitored for PD status. We genotyped a total of 41 single nucleotide polymorphisms (SNPs) in 8 TLR genes and copy number variation (CNV) in DEFB4/103A. We performed regression analyses for levels of 3 periodontopathogens in subgingival dental plaques (Porphyromonas gingivalis [Pg], Treponema denticola [Td], and Tannerella forsythia [Tf]) and 3 clinical measures of PD (periodontal probing depth [PPD], gingival recession [REC], and bleeding on probing [BOP]). In all subjects combined, 2 SNPs in TLR1 were significantly associated with Td, and one SNP in TLR2 was significantly associated with BOP. One of the 2 SNPs in TLR1 was significantly associated with Td in Caucasians. In addition, another SNP in TLR1 and a SNP in TLR6 were also significantly associated with Td and Pg, respectively, in Caucasians. All 3 periodontopathogen levels were significantly associated with PPD and BOP, but none was associated with REC. Instrumental variable analysis showed that 8 SNPs in 6 TLR genes were significantly associated with the 3 periodontopathogen levels. However, associations between the 3 periodontopathogen levels and PPD or BOP were not driven by associations with these identified SNPs. No association was found between DEFB4/103A CNV and any periodontopathogen level or clinical measure in all samples, Caucasians, or African Americans. Our exploratory study suggests a role of TLR polymorphisms, particularly TLR1 and TLR6 polymorphisms, in PD in HIV+ North Americans.

Periodontitis in Chronic Heart Failure

Periodontal disease has been associated with an increased risk of cardiovascular events. The purpose of our study was to investigate whether a correlation between periodontitis and chronic heart failure exists, as well as the nature of the underlying cause. We enrolled 71 patients (mean age, 54 ± 13 yr; 56 men) who had stable chronic heart failure; all underwent complete cardiologic and dental evaluations. The periodontal screening index was used to quantify the degree of periodontal disease. We compared the findings to those in the general population with use of data from the 4th German Dental Health Survey. Gingivitis, moderate periodontitis, and severe periodontitis were present in 17 (24%), 17 (24%), and 37 (52%) patients, respectively. Severe periodontitis was more prevalent among chronic heart failure patients than in the general population. In contrast, moderate periodontitis was more prevalent in the general population (P <0.00001). The severity of periodontal disease was not associated with the cause of chronic heart failure or the severity of heart failure symptoms. Six-minute walking distance was the only independent predictor of severe periodontitis. Periodontal disease is highly prevalent in chronic heart failure patients regardless of the cause of heart failure. Prospective trials are warranted to clarify the causal relationship between both diseases.

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.

GC Gene Polymorphisms and Vitamin D-Binding Protein Levels Are Related to the Risk of Generalized Aggressive Periodontitis

Objective. To explore whether GC (group-specific component) rs17467825, rs4588, and rs7041 polymorphisms are associated with generalized aggressive periodontitis. Methods. This case-control study recruited 372 patients with generalized aggressive periodontitis (group AgP) and 133 periodontal healthy subjects (group HP). GC rs17467825, rs4588, and rs7041 genotypes and plasmatic vitamin D-binding protein (DBP) were measured. Analysis of single SNP and multiple SNPs was performed and relevance between plasmatic DBP and haplotypes was analyzed. Results. GC rs17467825 GG genotype was statistically associated with lower risk for generalized aggressive periodontitis under the recessive model (OR = 0.52, 95% CI: 0.30-0.92, p = 0.028). GC rs17467825 and rs4588 had strong linkage disequilibrium with r² ≥ 0.8 and D' ≥ 0.8. Haplotype (GC rs17467825, rs4588) GC was associated with the less risk for generalized aggressive periodontitis (OR = 0.29, 95% CI: 0.09-0.96, p = 0.043). In group AgP, individuals with combined genotype (GC rs17467825, rs4588) AG+CA had significantly lower plasmatic DBP level than those with the other two combined genotypes (AG+CA versus AA+CC p = 0.007; AG+CA versus GG+AA p = 0.026). Conclusions. GC rs17467825 genotype GG and haplotype (GC rs17467825, rs4588) GC are associated with generalized aggressive periodontitis. The association may be acquired through regulating DBP levels. The functions of GC gene and DBP in inflammatory disease need to be further studied.

Role of chronic stress and depression in periodontal diseases

An extensive body of experimental and clinical evidence documents the negative impact of chronic psychological stress and depression on the immune system and health. Chronic stress and depression can result in general dysregulation of the immune system, of both cellular and humoral pathways, which may contribute to pathogenic infection and concomitant periodontal tissue destruction. In general, the evidence is consistent with the hypothesis that stress can modify the host defense and progression of periodontal infections in patients susceptible to periodontitis. However, substantial evidence also indicates that these conditions can mediate risk for disease, including periodontitis, through changes in health-related behaviors, such as oral hygiene, smoking and diet. The unequivocal interpretation of studies has also been hampered, in part, by issues related to conceptualization of stress and depression, as well as commonly associated comorbidities, such as diabetes, that can modify the onset and progression of periodontal disease. In addition, stress and depression appear to fall into a spectrum, ranging from mild to severe, involving a complex interaction of genetic background, coping strategies and environment. Differences in the conceptualization of stress and depression are probably important in assessing associations with other biologic and clinical measures. Future studies are necessary to clarify the complex interactions of chronic stress and depression in periodontal diseases.

What is the Contribution of Genetics to Periodontal Risk?

This review addresses the multicausal etiology of periodontitis, in which genetic factors play a role. The various proposed causes for periodontitis always work simultaneously, but the relative contribution of each of these varies from case to case. We are still at an early stage to identify the genes involved, in comparison with other chronic diseases. To date, the genetic variations firmly and repeatedly associated with periodontitis in some populations are found within the following genes: ANRIL, COX2, IL1, IL10, DEFB1, whereas many other proposed periodontitis candidate genes have not been firmly proven or replicated.

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.

TNF-α gene promoter polymorphisms contribute to periodontitis susceptibility: evidence from 46 studies

AIM

Tumour necrosis factor-alpha (TNF-α) plays a critical role in the pathogenesis of periodontal disease. TNF-α gene polymorphisms can influence the TNF-α production. Many studies have focused the association between TNF-α gene promoter polymorphisms and periodontitis risk, but these results are still controversial.

MATERIALS AND METHODS

A meta-analysis was performed to assess the effect of TNF-α -308G/A (rs1800629), -238G/A (rs361525) and -863C/A (rs1800630) polymorphisms on either chronic (CP) or aggressive periodontitis (AgP) risk. Odds ratios (ORs) along with their 95% confidence intervals (CIs) were calculated to assess the strength of the association. Forty-six studies involving 5186 cases and 6683 controls were retrieved and analyzed.

RESULTS

The TNF-α -308G/A AA genotype was associated with increased CP risk in Asians, non-smoking Asians and Caucasians, and this polymorphism was significantly associated with elevated risk of AgP in Asians and Caucasians. Asian individuals carrying AA genotype had a significantly increased risk for -863C/A. No significant association was identified between TNF -238G/A polymorphism and CP.

CONCLUSIONS

These findings supported that TNF-α -308G/A and -863C/A polymorphisms may contribute to the susceptibility of periodontitis.

Salivary DNA and markers of oxidative stress in patients with chronic periodontitis

OBJECTIVES

Previous observational studies have shown that periodontal status is associated with salivary markers of oxidative damage. A direct comparison of periodontitis patients and controls using a wide palette of salivary markers of oxidative stress is lacking. Characteristics of salivary DNA in periodontitis are unknown. The aim of this study was to compare the salivary markers of oxidative stress and characteristics of salivary DNA between patients with chronic periodontitis and periodontitis-free controls.

MATERIALS AND METHODS

Saliva was collected from 23 patients with chronic periodontitis and 19 periodontitis-free controls. All participants underwent a clinical periodontal examination. Markers of oxidative and carbonyl stress were measured in saliva. Human and bacterial DNA was quantified, and human DNA integrity was assessed.

RESULTS

Salivary thiobarbituric acid-reacting substances were higher in patients than in controls; at least in men, the difference was significant (p < 0.01). In women, patients had significantly lower salivary antioxidant status (p < 0.001). No quantitative differences were found regarding salivary DNA. Tendencies towards reduced DNA integrity were found in periodontitis patients.

CONCLUSIONS

The results confirmed the association of salivary thiobarbituric acid-reacting substances with periodontitis. Lipid peroxidation in periodontitis seems to be caused by increased production of reactive oxygen species in men and by decreased antioxidant status in women. Whether lower salivary DNA integrity is involved in the pathogenesis of periodontitis remains to be elucidated.

CLINICAL RELEVANCE

Salivary thiobarbituric acid-reacting substances are associated with periodontitis at least on a population level. Sex-specific causes of lipid peroxidation might point towards different pathogenic mechanisms.

The association of CSF-1 gene polymorphism with chronic periodontitis in the Han Chinese population

BACKGROUND

Chronic periodontitis (CP) is a multifactorial complex periodontal disease involving immune response, inflammation, alveolar bone resorption, and attachment loss. Colony stimulating factor-1 (CSF-1) controls the production, differentiation, and function of macrophages and plays a vital role in the innate immune response to the external microbial infections, suggesting the potential role of CSF-1 in the pathogenesis of periodontitis. The objective of this study is to determine the association of single nucleotide polymorphisms (SNPs) rs333967, rs2297706, and rs1058885 with CP in the Han Chinese population.

METHODS

Genomic DNA was isolated from buccal epithelial cells obtained from unrelated Chinese participants (440 patients with CP and 324 controls). The SNPs were genotyped by a matrix-assisted laser desorption/ionization time-of-flight mass spectrometry method.

RESULTS

Three previously identified SNPs were genotyped in Han Chinese with Shanghai origin, but none of them was statistically significantly associated with CP. However, a T-C-G haplotype in male participants showed an observed P value of 4.52(E-08), with an odds ratio of 0.092.

CONCLUSION

None of the individual SNPs among rs333967, rs2297706, and rs1058885 in CSF-1 was found statistically significantly associated with CP in the Han Chinese population with Shanghai origin, whereas a haplotype T-C-G showed an observed statistically significant association with decreased risk of CP susceptibility in males.

Genome-wide association study of periodontal health measured by probing depth in adults ages 18-49 years

The etiology of chronic periodontitis clearly includes a heritable component. Our purpose was to perform a small exploratory genome-wide association study in adults ages 18–49 years to nominate genes associated with periodontal disease−related phenotypes for future consideration. Full-mouth periodontal pocket depth probing was performed on participants (N = 673), with affected status defined as two or more sextants with probing depths of 5.5 mm or greater. Two variations of this phenotype that differed in how missing teeth were treated were used in analysis. More than 1.2 million genetic markers across the genome were genotyped or imputed and tested for genetic association. We identified ten suggestive loci (p-value ≤ 1E-5), including genes/loci that have been previously implicated in chronic periodontitis: LAMA2, HAS2, CDH2, ESR1, and the genomic region on chromosome 14q21-22 between SOS2 and NIN. Moreover, we nominated novel loci not previously implicated in chronic periodontitis or related pathways, including the regions 3p22 near OSBPL10 (a lipid receptor implicated in hyperlipidemia), 4p15 near HSP90AB2P (a heat shock pseudogene), 11p15 near GVINP1 (a GTPase pseudogene), 14q31 near SEL1L (an intracellular transporter), and 18q12 in FHOD3 (an actin cytoskeleton regulator). Replication of these results in additional samples is needed. This is one of the first research efforts to identify genetic polymorphisms associated with chronic periodontitis-related phenotypes by the genome-wide association study approach. Though small, efforts such this are needed in order to nominate novel genes and generate new hypotheses for exploration and testing in future studies.

Prioritization of candidate genes for periodontitis using multiple computational tools

BACKGROUND

Both genetic and environmental factors contribute to the development of periodontitis. Genetic studies identified a variety of candidate genes for periodontitis. The aim of the present study is to identify the most promising candidate genes for periodontitis using an integrative gene ranking method.

METHODS

Seed genes that were confirmed to be associated with periodontitis were identified using text mining. Three types of candidate genes were then extracted from different resources (expression profiles, genome-wide association studies). Combining the seed genes, four freely available bioinformatics tools (ToppGene, DIR, Endeavour, and GPEC) were integrated for prioritization of candidate genes. Candidate genes that identified with at least three programs and ranked in the top 20 by each program were considered the most promising.

RESULTS

Prioritization analysis resulted in 21 promising genes involved or potentially involved in periodontitis. Among them, IL18 (interleukin 18), CD44 (CD44 molecule), CXCL1 (chemokine [CXC motif] ligand 1), IL6ST (interleukin 6 signal transducer), MMP3 (matrix metallopeptidase 3), MMP7, CCR1 (chemokine [C-C motif] receptor 1), MMP13, and TLR9 (Toll-like receptor 9) had been associated with periodontitis. However, the roles of other genes, such as CSF3 (colony stimulating factor 3 receptor), CD40, TNFSF14 (tumor necrosis factor receptor superfamily, member 14), IFNB1 (interferon-β1), TIRAP (toll-interleukin 1 receptor domain containing adaptor protein), IL2RA (interleukin 2 receptor α), ETS1 (v-ets avian erythroblastosis virus E26 oncogene homolog 1), GADD45B (growth arrest and DNA-damage-inducible 45 β), BIRC3 (baculoviral IAP repeat containing 3), VAV1 (vav 1 guanine nucleotide exchange factor), COL5A1 (collagen, type V, α1), and C3 (complement component 3), have not been investigated thoroughly in the process of periodontitis. These genes are mainly involved in bacterial infection, immune response, and inflammatory reaction, suggesting that further characterizing their roles in periodontitis will be important.

CONCLUSIONS

A combination of computational tools will be useful in mining candidate genes for periodontitis. These theoretical results provide new clues for experimental biologists to plan targeted experiments.

Relationship between IL1 gene polymorphisms and periodontal disease in Japanese women

Epidemiological evidence on the relationship between IL1A and/or IL1B polymorphisms and periodontal disease is inconsistent. We investigated associations between three IL1 single-nucleotide polymorphisms (SNPs) in genes encoding interleukin (IL) -1α (rs1800587) and IL-1β (rs1143634 and rs16944) and the risk of periodontal disease among young Japanese women. A case-control study was performed with a total of 1150 women, including 131 subjects who had at least one tooth with a probing pocket depth of 4 mm or deeper and 1019 periodontally healthy controls. Compared with a reference group of women with the GG genotype of SNP rs16944, those with the GA genotype had a significantly reduced risk of periodontal disease, while there was no significant relationship between the AA genotype and periodontal disease. No evident relationships were observed between SNP rs1800587 or rs1143634 and periodontal disease. Our study did not reveal any evidence of interaction between the IL1 polymorphisms and smoking. The results of this study showed that the heterozygous variant genotype of the IL1 rs16944 was significantly associated with a reduced risk of periodontal disease in young Japanese women. Smoking did not significantly modify the gene-disease associations under study.

Inflammatory mediators in the pathogenesis of periodontitis

Periodontitis is a chronic inflammatory condition of the periodontium involving interactions between bacterial products, numerous cell populations and inflammatory mediators. It is generally accepted that periodontitis is initiated by complex and diverse microbial biofilms which form on the teeth, i.e. dental plaque. Substances released from this biofilm such as lipopolysaccharides, antigens and other virulence factors, gain access to the gingival tissue and initiate an inflammatory and immune response, leading to the activation of host defence cells. As a result of cellular activation, inflammatory mediators, including cytokines, chemokines, arachidonic acid metabolites and proteolytic enzymes collectively contribute to tissue destruction and bone resorption. This review summarises recent studies on the pathogenesis of periodontitis, with the main focus on inflammatory mediators and their role in periodontal disease.

Association of cytokines, high sensitive C-reactive protein, VEGF and beta-defensin-1 gene polymorphisms and their protein expressions with chronic periodontitis in the Chinese population

PURPOSES

This study aimed at investigating the association between interleukin-6 (IL-6), interleukin-12 (IL-12), C-reactive protein (CRP), vascular endothelial growth factor (VEGF) and β-defensin-1polymorphisms and the susceptibility to periodontitis in the Chinese population.

METHODS

DNA was extracted from the blood samples of 532 healthy individuals and 122 chronic periodontitis (CP) patients enrolled in the study. The genes encoding IL-6, IL-12, CRP, VEGF and β-defensin-1 were amplified using PCR and digested with restriction enzymes. The protein expression of the abovementioned genes was determined by ELISA. Differences in the allele/genotype frequencies were assessed with the chi-square test.

RESULTS

The frequencies of the C/C genotypes of IL-6, IL-12, and VEGF were higher in CP patients than healthy controls (66.3% vs 25.9%; 27.8% vs 19.9%; and 64.8% vs 52.1%, respectively). In the patients' group we also recorded frequencies of the A/A genotypes of CRP and VEGF higher than in healthy controls (63.1% vs 58.1% and 64.8% vs 35.2%, respectively). Protein production evaluated by ELISA demonstrated significant differences between CP patients and healthy controls for IL-6, IL-12, CRP, VEGF and β-defensin-1.

CONCLUSIONS

The genotypes of IL-6, IL-12, VEGF and β-defensin-1 and their protein productions were associated with CP in a Chinese population. Genotypes and serum levels of CRP were associated with CP, but alleles frequency showed no difference between CP patients and healthy controls.

Low-cost periodontal therapy

Periodontitis is a complex infectious disease that affects low-income individuals disproportionately. Periodontitis is associated with specific bacterial species and herpesviruses, and successful prevention and treatment of the disease is contingent upon effective control of these pathogens. This article presents an efficacious, highly safe, minimally invasive, practical and low-cost periodontal therapy that involves professional and patient-administered mechanical therapy and antimicrobial agents. The major components are scaling for calculus removal, periodontal pocket irrigation with potent antiseptics, and treatment with systemic antibiotics for advanced disease. Povidone-iodine and sodium hypochlorite have all the characteristics for becoming the first-choice antiseptics in the management of periodontal diseases. Both agents show excellent antibacterial and antiviral properties, are readily available throughout the world, have been safely used in periodontal therapy for decades, offer significant benefits for individuals with very limited financial resources, and are well accepted by most dental professionals and patients. Four per cent chlorhexidine applied with a toothbrush to the most posterior part to the tongue dorsum can markedly reduce or eliminate halitosis in most individuals. Systemic antibiotics are used to treat periodontopathic bacteria that are not readily reached by topical therapy, such as pathogens within gingival tissue, within furcation defects, at the base of periodontal pockets, and on the tongue, tonsils and buccal mucosae. Valuable antibiotic therapies are amoxicillin-metronidazole (250 mg of amoxicillin and 250 mg of metronidazole, three times daily for 8 days) for young and middle-aged patients, and ciprofloxacin-metronidazole (500 mg of each, twice daily for 8 days) for elderly patients and for patients in developing countries who frequently harbor enteric rods subgingivally. Scaling to remove dental calculus and the prudent use of inexpensive antimicrobial agents can significantly retard or arrest progressive periodontitis in the great majority of patients.

Exploring the genetic basis of chronic periodontitis: a genome-wide association study

Chronic periodontitis (CP) is a common oral disease that confers substantial systemic inflammatory and microbial burden and is a major cause of tooth loss. Here, we present the results of a genome-wide association study of CP that was carried out in a cohort of 4504 European Americans (EA) participating in the Atherosclerosis Risk in Communities (ARIC) Study (mean age—62 years, moderate CP—43% and severe CP—17%). We detected no genome-wide significant association signals for CP; however, we found suggestive evidence of association (P < 5 × 10⁻⁶) for six loci, including NIN, NPY, WNT5A for severe CP and NCR2, EMR1, 10p15 for moderate CP. Three of these loci had concordant effect size and direction in an independent sample of 656 adult EA participants of the Health, Aging, and Body Composition (Health ABC) Study. Meta-analysis pooled estimates were severe CP (n = 958 versus health: n = 1909)—NPY, rs2521634 [G]: odds ratio [OR = 1.49 (95% confidence interval (CI = 1.28–1.73, P = 3.5 × 10⁻⁷))]; moderate CP (n = 2293)—NCR2, rs7762544 [G]: OR = 1.40 (95% CI = 1.24–1.59, P = 7.5 × 10⁻⁸), EMR1, rs3826782 [A]: OR = 2.01 (95% CI = 1.52–2.65, P = 8.2 × 10⁻⁷). Canonical pathway analysis indicated significant enrichment of nervous system signaling, cellular immune response and cytokine signaling pathways. A significant interaction of NUAK1 (rs11112872, interaction P = 2.9 × 10⁻⁹) with smoking in ARIC was not replicated in Health ABC, although estimates of heritable variance in severe CP explained by all single nucleotide polymorphisms increased from 18 to 52% with the inclusion of a genome-wide interaction term with smoking. These genome-wide association results provide information on multiple candidate regions and pathways for interrogation in future genetic studies of CP.

IL10 -1082, IL10 -819 and IL10 -592 polymorphisms are associated with chronic periodontitis in a Macedonian population

Genetic polymorphisms in the interleukin 10 (IL10) gene have been reported to influence the host response to microbial challenge by altering levels of cytokine expression. We analyzed nucleotide polymorphisms in the promoter region of the IL10 gene and its relation with periodontal disease in a Macedonian population. The study population consisted of 111 unrelated subjects with chronic periodontitis and 299 healthy controls. DNA was isolated and IL10 genotyping performed by PCR-SSP (Heidelberg kit) for the alleles and genotypes of IL10 -1082, IL10 -819 and IL10 -592. Frequencies of IL10 haplotypes and the haplotype zygotes were also examined. Comparisons between groups were tested using the Pearson's p-value. After Bonferroni adjustment, significant associations were detected between subjects with chronic periodontitis and IL10 genotypes (IL10 -1082/A:G was negative or protective and IL10 -1082/G:G was positive or susceptible). Cytokine polymorphism on the IL10 gene appears to be associated with susceptibility to chronic periodontitis in Macedonians.