Background: A molecular epidemiologic study provided the opportunity to characterize the biology of the biofilm–gingival interface (BGI) in 6,768 community‐dwelling subjects.
Methods: Disease ...classifications and multivariable models were developed using clinical, microbial, inflammatory, and host‐response data. The purpose was to identify new clinical categories that represented distinct biologic phenotypes based upon DNA checkerboard analyses of eight plaque bacteria, serum immunoglobulin G (IgG) titers to 17 bacteria, and the gingival crevicular fluid (GCF) levels of 16 inflammatory mediators. Five BGI clinical conditions were defined using probing depths (PDs) and bleeding on probing (BOP) scores. Subjects with all PDs ≤3 mm were grouped as BGI‐healthy (14.3% of sample) or BGI‐gingivitis (BGI‐G, 15.1%). Subjects with one or more PDs ≥4 mm deep lesion (DL) were divided into low BOP (18.0%), moderate BOP (BGI‐DL/MB, 39.7%), and severe BOP (BGI‐DL/SB, 12.9%).
Results: Subjects with BGI‐G had increased levels of Campylobacter rectus–specific serum IgG levels (P = 0.01), and those with BGI‐DL/SB had increased IgG levels to Porphyromonas gingivalis (P < 0.0003) and C. rectus (P < 0.01). BGI‐DL/SB subjects had an excessive GCF interleukin (IL)‐1β and prostaglandin E2 response and an enhanced chronic inflammatory response with significant increases in GCF IL‐6 and monocyte chemotactic peptide‐1. Within BGI‐DL/SB subjects, more severe pocketing and BOP were associated with higher levels of GCF IL‐1β, not higher microbial counts or plaque scores.
Conclusions: New BGI classifications create categories with distinct biologic phenotypes. The increased titers of C. rectus IgG among 68.5% of the BGI‐G subjects and elevated P. gingivalis titers among BGI‐DL/MB and BGI‐DL/SB subjects (63.8% and 75.7%, respectively) are strongly supportive of the microbial specificity of pathogenesis for BGI categories.
Levels of prostaglandin E2 and the prostaglandin-endoperoxide synthase-2 (PTGS2, or COX-2) increase in actively progressing periodontal lesions, but decrease in chronic disease. We hypothesized that ...chronic inflammation is associated with altered DNA methylation levels within the PTGS2 promoter, with effects on COX-2 mRNA expression. PTGS2 promoter methylation levels from periodontally inflamed gingival biopsies showed a 5.06-fold increase as compared with non-inflamed samples (p = 0.03), and the odds of methylation in a CpG site in the inflamed gingival group is 4.46 times higher than in the same site in the non-inflamed group (p = 0.016). The level of methylation at −458 bp was inversely associated with transcriptional levels of PTGS2 (RT-PCR) (p = 0.01). Analysis of the data suggests that, in chronically inflamed tissues, there is a hypermethylation pattern of the PTGS2 promoter in association with a lower level of PTGS2 transcription, consistent with a dampening of COX-2 expression in chronic periodontitis. These findings suggest that the chronic persistence of the biofilm and inflammation may be associated with epigenetic changes in local tissues at the biofilm-gingival interface.
Recent genome-wide association studies (GWAS) of chronic periodontitis (CP) offer rich data sources for the investigation of candidate genes, functional elements, and pathways. We used GWAS data of ...CP (n = 4,504) and periodontal pathogen colonization (n = 1,020) from a cohort of adult Americans of European descent participating in the Atherosclerosis Risk in Communities study and employed a MAGENTA approach (i.e., meta-analysis gene set enrichment of variant associations) to obtain gene-centric and gene set association results corrected for gene size, number of single-nucleotide polymorphisms, and local linkage disequilibrium characteristics based on the human genome build 18 (National Center for Biotechnology Information build 36). We used the Gene Ontology, Ingenuity, KEGG, Panther, Reactome, and Biocarta databases for gene set enrichment analyses. Six genes showed evidence of statistically significant association: 4 with severe CP (NIN, p = 1.6 × 10−7; ABHD12B, p = 3.6 × 10−7; WHAMM, p = 1.7 × 10−6; AP3B2, p = 2.2 × 10−6) and 2 with high periodontal pathogen colonization (red complex–KCNK1, p = 3.4 × 10−7; Porphyromonas gingivalis–DAB2IP, p = 1.0 × 10−6). Top-ranked genes for moderate CP were HGD (p = 1.4 × 10−5), ZNF675 (p = 1.5 × 10−5), TNFRSF10C (p = 2.0 × 10−5), and EMR1 (p = 2.0 × 10−5). Loci containing NIN, EMR1, KCNK1, and DAB2IP had showed suggestive evidence of association in the earlier single-nucleotide polymorphism–based analyses, whereas WHAMM and AP2B2 emerged as novel candidates. The top gene sets included severe CP (“endoplasmic reticulum membrane,” “cytochrome P450,” “microsome,” and “oxidation reduction”) and moderate CP (“regulation of gene expression,” “zinc ion binding,” “BMP signaling pathway,” and “ruffle”). Gene-centric analyses offer a promising avenue for efficient interrogation of large-scale GWAS data. These results highlight genes in previously identified loci and new candidate genes and pathways possibly associated with CP, which will need to be validated via replication and mechanistic studies.
An association between periodontitis and nonalcoholic fatty liver disease (NAFLD) has been reported by experimental animal and epidemiologic studies. This study investigated whether circulating ...levels of serum C-reactive protein (CRP) and a weighted genetic CRP score representing markers of inflammatory burden modify the association between periodontitis and NAFLD. Data came from 2,481 participants of the Study of Health in Pomerania who attended baseline examination that occurred between 1997 and 2001. Periodontitis was defined as the percentage of sites (0%, <30%, ≥30%) with probing pocket depth (PD) ≥4 mm, and NAFLD status was determined using liver ultrasound assessment. Serum CRP levels were assayed at a central laboratory, and single-nucleotide polymorphisms previously identified through genome-wide association studies as robustly associated with serum CRP were combined into a weighted genetic CRP score (wGSCRP). Logistic regression models estimated the association between periodontitis and NAFLD within strata of serum CRP and separately within strata of the wGSCRP. The prevalence of NAFLD was 26.4% (95% confidence interval CI, 24.6, 28.1) while 17.8% (95% CI, 16.0–19.6) had ≥30% of sites with PD ≥4 mm. Whereas the wGSCRP was not a modifier (Pinteraction = 0.8) on the multiplicative scale, serum CRP modified the relationship between periodontitis and NAFLD (Pinteraction = 0.01). The covariate-adjusted prevalence odds ratio of NAFLD comparing participants with ≥30% of sites with PD ≥4 mm to those with no site affected was 2.39 (95% CI, 1.32–4.31) among participants with serum CRP <1 mg/L. The corresponding estimate was 0.97 (95% CI, 0.57–1.66) for participants with serum CRP levels of 1 to 3 mg/L and 1.12 (95% CI, 0.65–1.93) for participants with serum CRP >3 mg/L. Periodontitis was positively associated with higher prevalence odds of NAFLD, and this relationship was modified by serum CRP levels.
A paucity of epidemiologic research exists regarding systemic health consequences of endodontic disease. This study evaluated whether incident radiographically evident lesions of endodontic origin ...were related to development of coronary heart disease (CHD) among 708 male participants in the VA Dental Longitudinal Study. At baseline and every three years for up to 32 years, participants (who were not VA patients) received complete medical and dental examinations, including full-mouth radiographs. Cox regression models estimated the relationship between incident lesions of endodontic origin and time to CHD diagnosis. Among those ≤ 40 years old, incident lesions of endodontic origin were significantly associated with time to CHD diagnosis (p < 0.05), after adjustment for covariates of interest, with hazard ratios decreasing as age increased. Among those > 40 years old, no statistically significant association was observed. These findings are consistent with research that suggests relationships between chronic periodontal inflammation and the development of CHD, especially among younger men.
In a previous report, we demonstrated the inverse association of high serum 8-isoprostane levels, a marker for oxidative stress, with decreased serum IgG antibodies to oral bacteria. The association ...between increased serum IgG with increased plaque and periodontitis (increased probing depths) was attenuated by high systemic oxidative stress. Other investigations have reported a role for systemic oxidative stress as a stimulus of hepatic C-reactive protein (CRP) response. These observations led us to hypothesize that the reported relationship of periodontitis to elevated serum CRP, a systemic inflammatory marker, may be modified by oxidative stress and that the levels of serum antibodies to oral bacteria might be an intermediary explanatory variable linking the association of systemic oxidative stress, periodontal disease, and levels of CRP. This hypothesis was explored as a secondary analysis of the Dental ARIC (Atherosclerosis Risk in Communities) study using serum levels of CRP, serum IgG levels to 16 oral organisms, serum levels of 8-isoprostane, and periodontal status. The findings indicate periodontitis is associated with high CRP in the presence of elevated oxidative stress that serves to suppress the IgG response. Only within the highest 8-isoprostane quartile was periodontitis (pocket depth) associated with increased serum CRP levels (P = 0.0003). Increased serum IgG antibody levels to oral bacteria were associated with lowered serum CRP levels. Thus, systemic oxidative stress, which has been demonstrated to be associated with increased levels of CRP in other studies, appears to be associated with the suppression of bacterial-specific IgG levels, which in the presence of periodontal disease can result in an enhanced systemic CRP response. Conversely, individuals with increased serum IgG antibodies to plaque bacteria exhibit lowered serum CRP levels. These 2 factors, oxidative stress and the serum IgG response, appear to function in opposing directions to modify serum levels of CRP and the association with periodontitis.
Moderate elevation of serum C-reactive protein (CRP) is a risk factor for cardiovascular disease among apparently healthy individuals, although factors that create this inflammatory response in the ...absence of systemic illness have not been clarified. This study aimed to: (1) evaluate associations among periodontal disease, established risk factors for elevated CRP, and CRP levels within the US population; and (2) determine whether total tooth loss is associated with reduced CRP. Data were obtained from the third National Health and Nutrition Examination Survey. A random sample of the US population was interviewed in their homes and examined at mobile examination centers. CRP was quantified from peripheral blood samples and analyzed as a continuous variable and as the prevalence of elevated CRP (≥ 10 mg/L). Some 12,949 people aged 18+ years who had periodontal examinations and an additional 1817 edentulous people aged 18+ years were included in the analysis. Dentate people with extensive periodontal disease (> 10% of sites with periodontal pockets 4+ mm) had an increase of approximately one-third in mean CRP and a doubling in prevalence of elevated CRP compared with periodontally healthy people. Raised CRP levels among people with extensive periodontal disease persisted in multivariate analyses (P < 0.01), with established risk factors for elevated CRP (diabetes, arthritis, emphysema, smoking, and anti-inflammatory medications) and sociodemographic factors controlled for. However, CRP levels were similarly raised in edentulous people. Furthermore, the established risk factors for elevated CRP modified relationships between oral status and CRP levels. Periodontal disease and edentulism were associated with systemic inflammatory response in the US population, most notably among people who had no established risk factors for elevated CRP.
The purpose of this study was to evaluate the microbial community (MC) composition as it relates to salivary metabolites and periodontal clinical parameters in a 21-d biofilm-overgrowth model. ...Subjects (N = 168) were enrolled equally into 5 categories of periodontal status per the biofilm-gingival interface classification. Microbial species within subgingival plaque samples were identified by human microbiome identification microarray. Whole saliva was analyzed by liquid chromatography–mass spectrometry and gas chromatography–mass spectrometry for metabolite identification. Phylum was grouped into MCs according to principal component analysis. Generalized linear and regression models were used to examine the association among MC, species, periodontal clinical parameters, and salivary metabolome. Multiple comparisons were adjusted with the false discovery rate. The study population was distributed into 8 distinct MC profiles, designated MC-1 to MC-8. MC-2 explained 14% of the variance and was dominated by Synergistetes and Spirochaetes. It was the only community structure significantly associated with high probing depth (P = 0.02) and high bleeding on probing (P = 0.008). MC-2 was correlated with traditional periodontal pathogens and several newly identified putative periodontal pathogens: Fretibacterium fastidiosum, Fretibacterium sp. OT360/OT362, Filifactor alocis, Treponema lecithinolyticum, Eubacterium saphenum, Desulfobulbus sp./OT041, and Mogibacterium timidum. Synergistetes phylum was strongly associated with 2 novel metabolites—cyclo (-leu-pro) and cyclo (-phe-pro)—at 21 d of biofilm overgrowth (P = 0.02). In subjects with severe periodontitis (P2 and P3), cyclo (-leu-pro) and cyclo (-phe-pro) were significantly associated with increased changes in probing depth at 21 d of biofilm overgrowth (P ≤ 0.05). The analysis identified a MC dominated by Synergistetes, with classic and putative newly identified pathogens/pathobionts associated with clinical disease. The metabolomic discovery of 2 novel cyclodipeptides that have been reported to serve as quorum-sensing and/or bacteriocidal/bacteriostatic molecules, in association with Synergistetes, suggests a potential role in periodontal biofilm dysbiosis and periodontal disease that warrants further investigation.
Bacterial infections are known to alter glucose metabolism within tissues via mechanisms of inflammation. We conducted this study to examine whether insulin response genes are differentially ...expressed in gingival tissues, comparing samples from experimental gingivitis and periodontitis subjects to those from healthy individuals. Total RNA was extracted from gingival biopsies from 26 participants: 8 periodontally healthy, 9 experimental gingivitis, and 9 periodontitis subjects. Gene expression patterns were evaluated with a polymerase chain reaction array panel to examine 84 candidate genes involved with glucose metabolism, insulin resistance, and obesity. Array data were evaluated with a t test adjusted by the false discover rate (P < 0.05), and ingenuity pathway analysis was performed for statistical testing of pathways. Although tissue samples were not sufficient to enable protein quantification, we confirmed the upregulation of the key gene using lipopolysaccharide-stimulated primary gingival epithelial cells by Western blot. The mRNA expression patterns of genes that are associated with insulin response and glucose metabolism are markedly different in experimental gingivitis subjects compared with healthy controls. Thirty-two genes are upregulated significantly by at least 2-fold, adjusted for false discover rate (P < 0.05). Periodontitis subjects show similar but attenuated changes in gene expression patterns, and no genes meet the significance criteria. Ingenuity pathway analysis demonstrates significant activation of the carbohydrate metabolism network in experimental gingivitis but not in periodontitis. G6PD protein increases in response to lipopolysaccharide stimulation in primary gingival epithelial cells, which is in the same direction as upregulated mRNA in tissues. Acute gingival inflammation may be associated with tissue metabolism changes, but these changes are not evident in chronic periodontitis. This study suggests that acute gingival inflammation may induce localized changes that modify tissue insulin/glucose metabolism.
Objective
To investigate racial differences in the associations between periodontitis and 10‐year self‐reported incident tooth loss in a biracial, community‐based cohort of US late middle‐aged and ...older adults.
Methods
Subjects were 3,466 dentate men and women aged 53‐74 who underwent dental examinations from 1996 to1998. In 2012‐2013, telephone interviewers asked participants about tooth loss in the preceding 10 years. Separate multivariable ordinal logistic regression models were used to calculate proportional odds ratios (OR) and 95% confidence intervals (CI) as estimates of association between periodontitis and tooth loss for Whites and African‐Americans (AAs).
Results
The majority of participants were White (85 percent) and female (57 percent) with 23 teeth on average at enrollment. Approximately half the Whites (56 percent) and AAs (49 percent) had periodontitis. At follow‐up, approximately 44 percent of AAs and 38 percent of Whites reported having lost ≥1 tooth. In multivariable models, severe periodontitis (OR = 3.03; 95% CI = 2.42‐3.80) and moderate periodontitis (OR = 1.64; 95% CI= 1.39‐1.94) were significant risk factors of incident tooth loss among Whites. For AAs, severe but not moderate periodontitis increased the odds of incident tooth loss (OR = 2.22; 95% CI = 1.37‐3.59). In the final model, education was inversely associated with incident tooth loss among AAs, while lower income was associated with greater odds of tooth loss among Whites.
Conclusions
In this population‐based cohort, there is racial heterogeneity in the association between periodontitis and tooth loss. Interventions to reduce the impact of periodontitis on tooth loss need to consider these differences.
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