Genome-wide analysis of dental caries and periodontitis combining clinical and self-reported data

The relationship between periodontal disease and gastric cancer: A bidirectional Mendelian randomization study

BACKGROUND

Previous observational studies have suggested a possible association between periodontal disease and gastric cancer (GC); however, a causal relationship has not yet been established. This study aimed to explore the causal relationship between the 2 through a 2-sample bidirectional Mendelian randomization (MR) study.

METHODS

Genome-wide association studies (GWAS) summary statistics were obtained from publicly available GWAS and relevant databases. Two-sample bidirectional MR analysis was conducted to investigate the causal relationship between periodontal disease and GC using the inverse-variance weighted (IVW) method selected as the primary analytical approach. Cochran Q test, MR-PRESSO, MR-pleiotropy, and leave-one-out analyses were performed to assess heterogeneity, pleiotropy, and sensitivity.

RESULTS

In European ancestry, IVW analysis revealed no causal relationship between periodontal disease and GC (OR = 1.873; 95% CI [4.788e-10, 7.323e + 09]; P = .956), or between loose teeth and GC (OR = 1.064; 95% CI [0.708, 1.598]; P = .765). In East Asian ancestry, there was no causal relationship between periodontitis and GC according to IVW (OR = 0.948; 95% CI [0.886, 1.015]; P = .126). Conversely, according to the results of the IVW analysis, there was no causal relationship between GC and periodontal disease, regardless of European or East Asian ancestry. Furthermore, there was no heterogeneity or pleiotropy in the causal relationships between these variables (all P > .05), suggesting a certain level of reliability in our results.

CONCLUSION

Within the limitations of this MR study, we found no mutual causal relationship between periodontal disease and GC. This finding can prevent overtreatment by clinical physicians and alleviate the psychological burden on patients.

Depression, stress-related disorders and risk for dental caries and periodontitis: A bidirectional and multivariable Mendelian randomization study

AIMS

Our Mendelian randomization (MR) analysis focused on investigating the bidirectional relationships between major depressive disorder (MDD), anxiety and stress-related disorder (ASRD), and dental caries as well as periodontitis.

MATERIALS AND METHODS

We used summary statistics from two studies: an MDD genome-wide association study (GWAS) including 135,458 cases with 344,901 controls and a Lundbeck Foundation Initiative for Integrative Psychiatric Research (iPSYCH) GWAS based on 12,655 ASRD individuals and 19,225 controls from Denmark. GWASs on dental caries and periodontitis were based on the Gene-Lifestyle Interactions in Dental Endpoints (GLIDE) consortium. We employed different MR approaches, such as inverse-variance weighted (IVW), MR-Egger, weighted median, and MR-PRESSO, to calculate causal effects.

RESULTS

Single-variable MR analysis revealed that ASRD was potentially significantly associated with decayed, missing, and filled tooth surfaces (DMFS) (β = 0.056; 95 % CI: 0.009, 0.103; p = 0.018). Periodontitis was suggested to be causally related to increased ASRD risk (OR = 1.143, 95 % CI: 1.008, 1.298; p = 0.038). According to the multivariable MR analysis, no significant associations were detected between MDD and ASRD and between dental caries and periodontitis, and vice versa.

CONCLUSIONS

ASRD demonstrated a potential association with DMFS, and periodontitis was found to potentially impact ASRD according to single-variable MR analysis. Nevertheless, no significant associations were identified between MDD, ASRD, dental caries, or periodontitis after adjusting for smoking status and education level. Hence, more robust genetic instruments are required to validate and reinforce our findings.

Bioinformatics for Dentistry: A secondary database for the genetics of tooth development

Genes strictly regulate the development of teeth and their surrounding oral structures. Alteration of gene regulation leads to tooth disorders and developmental anomalies in tooth, oral, and facial regions. With the advancement of gene sequencing technology, genomic data is rapidly increasing. However, the large sets of genomic and proteomic data related to tooth development and dental disorders are currently dispersed in many primary databases and literature, making it difficult for users to navigate, extract, study, or analyze. We have curated the scattered genetic data on tooth development and created a knowledgebase called 'Bioinformatics for Dentistry' (https://dentalbioinformatics.com/). This database compiles genomic and proteomic data on human tooth development and developmental anomalies and organizes them according to their roles in different stages of tooth development. The database is built by systemically curating relevant data from the National Library of Medicine (NCBI) GenBank, OMIM: Online Mendelian Inheritance in Man, AlphaFold Protein Structure Database, Reactome pathway knowledgebase, Wiki Pathways, and PubMed. The accuracy of the included data was verified from supporting primary literature. Upon data curation and validation, a simple, easy-to-navigate browser interface was created on WordPress version 6.3.2, with PHP version 8.0. The website is hosted in a cloud hosting service to provide fast and reliable data transfer rate. Plugins are used to ensure the browser's compatibility across different devices. Bioinformatics for Dentistry contains four embedded filters for complex and specific searches and free-text search options for quick and simple searching through the datasets. Bioinformatics for Dentistry is made freely available worldwide, with the hope that this knowledgebase will improve our understanding of the complex genetic regulation of tooth development and will open doors to research initiatives and discoveries. This database will be expanded in the future by incorporating resources and built-in sequence analysis tools, and it will be maintained and updated annually.

Two-sample Mendelian randomization analysis of the relationship between periodontitis and risk of upper gastrointestinal cancers

PURPOSE

The aim of the present study is to explore the possible association between periodontitis and upper gastrointestinal (UGI) cancers, including esophageal and gastric cancers, utilizing the Mendelian randomization method.

METHODS

In this research, we utilized the Mendelian randomization method to examine the causal association between periodontitis and UGI cancers. Genome-wide association studies data for periodontitis were obtained from the Gene-Lifestyle Interactions in Dental Endpoints consortium, while UGI cancers' data were accessed from FinnGen's Biobank. After rigorously screening instrumental variables for periodontitis, we analyzed them with UGI cancers primarily using the inverse variance weighted. Finally, to identify outliers, the results were subjected to a leave-one-out sensitivity analysis.

RESULTS

Inverse variance weighted (fixed effect) results revealed that periodontitis is a risk factor for gastric cancer (OR = 1.7735, 95% CI: 1.1576 to 2.7170, P = 0.0085). As for esophageal cancer, no statistically significant correlation was observed. Furthermore, no outliers were detected in any of the results.

CONCLUSION

Our two-sample Mendelian randomization study obviously demonstrates a significant positive association between periodontitis and gastric cancer, while no statistically significant correlation was found for esophageal cancer.

Quantifying variations associated with dental caries reveals disparity in effect allele frequencies across diverse populations

BACKGROUND

Dental caries (DC) is a multifaceted oral condition influenced by genetic and environmental factors. Recent advancements in genotyping and sequencing technologies, such as Genome-Wide Association Studies (GWAS) have helped researchers to identify numerous genetic variants associated with DC, but their prevalence and significance across diverse global populations remain poorly understood as most of the studies were conducted in European populations, and very few were conducted in Asians specifically in Indians.

AIM

This study aimed to evaluate the genetic affinity of effect alleles associated with DC to understand the genetic relationship between global populations with respect to the Indian context.

METHODOLOGY

This present study used an empirical approach in which variants associated with DC susceptibility were selected. These variants were identified and annotated using the GWAS summary. The genetic affinity was evaluated using Fst.

RESULTS

The effect of allele frequencies among different populations was examined, revealing variations in allele distribution. African populations exhibited higher frequencies of specific risk alleles, whereas East Asian and European populations displayed distinct profiles. South Asian populations showed a unique genetic cluster.

CONCLUSION

Our study emphasises the complex genetic landscape of DC and highlights the need for population-specific research as well as validation of GWAS-identified markers in Indians before defining them as established candidate genes.

Periodontitis and thyroid function: A bidirectional Mendelian randomization study

BACKGROUND AND OBJECTIVE

Previous studies suggest interaction between periodontitis and thyroid function, while the causality has not yet been established. We applied the Mendelian randomization (MR) method to assess bidirectional causal association between periodontitis and thyroid-related traits, including free thyroxine (FT4), thyroid stimulating hormone (TSH), hypothyroidism, hyperthyroidism and autoimmune thyroid disease (AITD).

METHODS

Genetic instruments were extracted from large-scale genome-wide association studies on normal-range FT4 (N = 49 269) and TSH (N = 54 288) levels, TSH in full range (N = 119 715); hypothyroidism (discovery/replication cohorts: N = 53 423/334 316), hyperthyroidism (discovery/replication cohorts: N = 51 823/257 552), AITD (N = 755 406) and periodontitis (N = 45 563). Here, the inverse variance weighted (IVW) method was applied as the primary analysis, and robustness of results were assessed by several pleiotropic-robust methods. Results were adjusted for Bonferroni correction thresholds with significant p < .004 (0.05/13) and suggestive p between .004 and .05.

RESULTS

The IVW analysis revealed a suggestively causal linkage between genetic predisposition to periodontitis and the increased risk of hypothyroidism (discovery cohort: odds ratio [OR] = 1.24, 95% confidence interval [CI] = 1.05-1.46, p = .012; replication cohort: OR = 1.06, 95% CI = 1.01-1.11, p = .011). No evidence was found for supporting the impact of periodontitis on hyperthyroidism and AITD risks (associated p ≥ .209), as well as thyroid-related traits on periodontitis risk (associated p ≥ .105). These findings were robust and consistent through sensitivity analysis with other MR models.

CONCLUSION

This bidirectional MR reveals periodontitis should not be attributed to variations in thyroid function but it has potential causal effect on hypothyroidism risk, which provides a better understanding of the relationship between periodontitis and thyroid function, and potential evidence for the clinical intervention of hypothyroidism. Further investigations are warranted to elucidate the nature and underlying mechanisms of this finding.

Linking periodontitis with 20 cancers, emphasis on oropharyngeal cancer: a Mendelian randomization analysis

While associations between periodontitis and an elevated risk of cancer have been suggested, the results of existing observational studies have been inconsistent, also leaving room for further investigation into the underlying mechanisms. This study was designed to delve into the possible causal link between periodontitis and 20 standard cancers while concurrently identifying potential mediators. We initiated a Mendelian randomization analysis that drew from either publicly accessible or personally obtained genome-wide association study (GWAS) datasets. The inverse variance weighting (IVW) method served as our primary tool for analysis. To ensure the strength and consistency of our results, we implemented additional strategies, including weighted median, weighted mode, MR-Egger regression, and MR pleiotropy residual sum and outlier (MR-PRESSO), bolstered by funnel plots. Our analysis unveiled an elevated risk of head and neck cancer concomitant with periodontitis (p = 0.041, OR 0.999, 95% CI 0.999-1.000), specifically a heightened risk of oropharyngeal cancer (p = 0.022, OR 0.999, 95% CI 0.999-1.000). As a result of probing into potential mediators, Fusobacterium nucleatum emerged as a likely intermediary in the promoting effect of periodontitis on oropharyngeal cancer (p = 0.021, OR 0.999, 95% CI 0.998-1.000). Inversely, basal cell carcinoma and endometrial cancer demonstrated an association with an increased incidence of periodontitis (basal cell carcinoma: p = 0.020, OR 0.987, 95% CI 0.976-0.998; endometrial cancer: p = 0.027, OR 0.984, 95% CI 0.970-0.998). However, periodontitis exerted no significant causal impact on the 19 other common cancers or the three subtypes of head and neck cancer. To conclude, our results support the theory that periodontitis contributes to an enhanced risk of head and neck cancer, particularly oropharyngeal cancer, with Fusobacterium nucleatum functioning as a potential intermediary.

Mediating and moderating effects of plasma proteomic biomarkers on the association between poor oral health problems and incident dementia: The UK Biobank study

The plasma proteome can mediate poor oral health problems (POHP)'s link to incident dementia. We screened 37,269 UK Biobank participants 50-74 years old (2006-2010) for prevalent POHP, further tested against 1463 plasma proteins and incident dementia over up to 15 years of follow-up. Total effect (TE) of POHP-dementia through plasma proteomic markers was decomposed into pure indirect effect (PIE), interaction referent (INTREF), controlled direct effect (CDE), or mediated interaction (INTMED). POHP increased the risk of all-cause dementia by 17% (P < 0.05). Growth differentiation factor 15 (GDF15) exhibited the strongest mediating effects (PIE > 0, P < 0.001), explaining 28% the total effect of POHP on dementia, as a pure indirect effect. A first principal component encompassing top 4 mediators (GDF15, IL19, MMP12, and ACVRL1), explained 11% of the POHP-dementia effect as a pure indirect effect. Pathway analysis including all mediators (k = 173 plasma proteins) revealed the involvement of the immune system, signal transduction, metabolism, disease, and gene expression, while STRING analysis indicated that top mediators within the first principal component were also represented in the two largest proteomic clusters. The dominant biological GO pathway for the GDF15 cluster was GO:0007169 labeled as "transmembrane receptor protein tyrosine kinase signaling pathway." Dementia is linked to POHP mediated by GDF15 among several proteomic markers.

Exploring the causal relationships between rheumatoid arthritis and oral phenotypes: a genetic correlation and Mendelian randomization study

Background

Rheumatoid arthritis (RA) frequently presents with oral manifestations, including gingival inflammation, loose teeth, and mouth ulcers; however, the causal connections between these conditions remain unclear. This study aims to explore the genetic correlations and causal relationships between RA and prevalent oral phenotypes.

Methods

Using summary data from genome-wide association studies of European populations, a cross-trait linkage disequilibrium score regression was conducted to estimate the genetic correlations between RA and six oral phenotypes. Subsequently, a two-sample Mendelian randomization (MR) approach was employed to assess the causal relationships, corroborated by various sensitivity analyses. Heterogeneity was addressed through the RadialMR method, while potential covariates were corrected using the multivariable MR approach.

Results

A significant negative genetic correlation was detected between RA and denture usage (rg = -0.192, p = 4.88 × 10-8). Meanwhile, a heterogenous causal relationship between RA and mouth ulcers was observed (OR = 1.027 [1.005-1.05], p = 0.016, P heterogeneity = 4.69 × 10-8), which remained robust across sensitivity analyses. After excluding outlier variants, the results demonstrated robustly consistent (OR = 1.021 [1.008-1.035], p = 1.99 × 10-3, P heterogeneity = 0.044). However, upon adjusting for covariates such as smoking, alcohol consumption, body mass index, and obesity, the significance diminished, revealing no evidence to support independent genetic associations.

Conclusion

Genetically predicted RA increases the risk of mouth ulcers, and a negative genetic correlation is identified between RA and denture use. The observed heterogeneity suggests that shared immunological mechanisms and environmental factors may play significant roles. These findings highlight the importance of targeted dental management strategies for RA patients. Further clinical guidelines are required to improve oral health among vulnerable RA patients.

No genetic causal associations between periodontitis and brain atrophy or cognitive impairment: evidence from a comprehensive bidirectional Mendelian randomization study

BACKGROUND

Observational studies have explored the relationships of periodontitis with brain atrophy and cognitive impairment, but these findings are limited by reverse causation, confounders and have reported conflicting results. Our study aimed to investigate the causal associations of periodontitis with brain atrophy and cognitive impairment through a comprehensive bidirectional Mendelian randomization (MR) research.

METHODS

We incorporated two distinct genome-wide association study (GWAS) summary datasets as an exploration cohort and a replication cohort for periodontitis. Four and eight metrics were selected for the insightful evaluation of brain atrophy and cognitive impairment, respectively. The former involved cortical thickness and surface area, left and right hippocampal volumes, with the latter covering assessments of cognitive performance, fluid intelligence scores, prospective memory, and reaction time for mild cognitive impairment to Alzheimer's disease (AD), Lewy body dementia, vascular dementia and frontotemporal dementia for severe situations. Furthermore, supplementary analyses were conducted to examine the associations between the longitudinal rates of change in brain atrophy and cognitive function metrics with periodontitis. The main analysis utilized the inverse variance weighting (IVW) method and evaluated the robustness of the results through a series of sensitivity analyses. For multiple tests, associations with p-values < 0.0021 were considered statistically significant, while p-values ≥ 0.0021 and < 0.05 were regarded as suggestive of significance.

RESULTS

In the exploration cohort, forward and reverse MR results revealed no causal associations between periodontitis and brain atrophy or cognitive impairment, and only a potential causal association was found between AD and periodontitis (IVW: OR = 0.917, 95% CI from 0.845 to 0.995, P = 0.038). Results from the replication cohort similarly corroborated the absence of a causal relationship. In the supplementary analyses, the longitudinal rates of change in brain atrophy and cognitive function were also not found to have causal relationships with periodontitis.

CONCLUSIONS

The MR analyses indicated a lack of substantial evidence for a causal connection between periodontitis and both brain atrophy and cognitive impairment.

Periodontal disease increases the severity of chronic obstructive pulmonary disease: a Mendelian randomization study

BACKGROUND

Recent research suggests that periodontitis can increase the risk of chronic obstructive pulmonary disease (COPD). In this study, we performed two-sample Mendelian randomization (MR) and investigated the causal effect of periodontitis (PD) on the genetic prediction of COPD. The study aimed to estimate how exposures affected outcomes.

METHODS

Published data from the Gene-Lifestyle Interaction in the Dental Endpoints (GLIDE) Consortium's genome-wide association studies (GWAS) for periodontitis (17,353 cases and 28,210 controls) and COPD (16,488 cases and 169,688 controls) from European ancestry were utilized. This study employed a two-sample MR analysis approach and applied several complementary methods, including weighted median, inverse variance weighted (IVW), and MR-Egger regression. Multivariable Mendelian randomization (MVMR) analysis was further conducted to mitigate the influence of smoking on COPD.

RESULTS

We chose five single-nucleotide polymorphisms (SNPs) as instrumental variables for periodontitis. A strong genetically predicted causal link between periodontitis and COPD, that is, periodontitis as an independent risk factor for COPD was detected. PD (OR = 1.102951, 95% CI: 1.005-1.211, p = 0.039) MR-Egger regression and weighted median analysis results were coincident with those of the IVW method. According to the sensitivity analysis, horizontal pleiotropy's effect on causal estimations seemed unlikely. However, reverse MR analysis revealed no significant genetic causal association between COPD and periodontitis. IVW (OR = 1.048 > 1, 95%CI: 0.973-1.128, p = 0.2082) MR Egger (OR = 0.826, 95%CI:0.658-1.037, p = 0.1104) and weighted median (OR = 1.043, 95%CI: 0.941-1.156, p = 0.4239). The results of multivariable Mendelian randomization (MVMR) analysis, after adjusting for the confounding effect of smoking, suggest a potential causal relationship between periodontitis and COPD (P = 0.035).

CONCLUSION

In this study, periodontitis was found to be independent of COPD and a significant risk factor, providing new insights into periodontitis-mediated mechanisms underlying COPD development.

No genetic causal association between periodontitis and ankylosing spondylitis: a bidirectional two-sample mendelian randomization analysis

BACKGROUND

Observational studies that reveal an association between periodontitis (PD) and ankylosing spondylitis (AS) exist. However, observational research is prone to reverse causality and confounding factors, which make it challenging to infer cause-and-effect relationships. We conducted a two-sample Mendelian randomization (MR) study to examine the causal relationship between the genetic prediction of PD and AS.

METHODS

In our study, single-nucleotide polymorphisms (SNPs) were defined as instrumental variables (IVs). The genetic association with PD came from the Gene-Lifestyle Interactions and Dental Endpoints (GLIDE) consortium, wherein 17353 cases of European ancestry and 28210 controls of European ancestry were included in this study. The genetic association with AS from the Neale Laboratory Consortium included 337,159 individuals from the United Kingdom, with 968 cases and 336,191 controls. MR analysis was mainly performed using the inverse-variance weighted (IVW) method. In addition, the robustness of the study findings was assessed using sensitivity, pleiotropy, and heterogeneity analyses.

RESULTS

Eighteen independent SNPs with P-values significantly smaller than 1 × 10- 5 were used as IV SNPs for PD, while 39 independent SNPs with P-values significantly smaller than 1 × 10- 5 were used as IV SNPs for AS. The results of the IVW method revealed no causal association between PD and AS (odds ratio = 1.00, 95% confidence interval: 0.99953 to 1.00067, P = 0.72). The MR-Egger method did not support the causal association between PD and AS. It is unlikely that horizontal pleiotropy distorts causal estimates based on sensitivity analysis. No significant heterogeneity was observed in the Q test. The ''leave-one-out'' analysis demonstrated that the robustness of our results was unaffected by eliminating any of the IVs. Likewise, no significant causative effect for AS on PD was observed in the inverse MR analysis.

CONCLUSIONS

The study results do not support shared heritability or a causal association between PD and AS.

Association between biological aging and periodontitis using NHANES 2009-2014 and mendelian randomization

Aging is a recognized risk factor for periodontitis, while biological aging could provide more accurate insights into an individual's functional status. This study aimed to investigate the potential association between biological aging and periodontitis. Epidemiological data from 9803 participants in the 2009-2014 National Health and Nutrition Examination Survey were analyzed at a cross-sectional level to assess this link. Three biological ages [Klemera-Doubal method (KDM), PhenoAge, and homeostatic dysregulation (HD)] and two measures of accelerated biological aging (BioAgeAccel and PhenoAgeAccel) were set as primary exposure and were calculated. Logistic regression and restricted cubic spline regression were employed to examine the relationship between biological aging and periodontitis. Additionally, Mendelian randomization analysis was conducted to explore the causal connection between accelerated biological aging and periodontitis. After adjusting for age, gender, race, educational level, marital status, ratio of family income, and disease conditions, this study, found a significant association between subjects with older higher biological ages, accelerated biological aging, and periodontitis. Specifically, for a per year increase in the three biological ages (HD, KDM, and PhenoAge), the risk of periodontitis increases by 15%, 3%, and 4% respectively. Individuals who had positive BioAgeAccel or PhenoAgeAccel were 20% or 37% more likely to develop periodontitis compared with those who had negative BioAgeAccel or PhenoAgeAccel. Furthermore, a significant non-linear positive relationship was observed between the three biological ages, accelerated biological aging, and periodontitis. However, the Mendelian randomization analysis indicated no causal effect of accelerated biological aging on periodontitis. Our findings suggest that biological aging may contribute to the risk of periodontitis, highlighting the potential utility of preventive strategies targeting aging-related pathways in reducing periodontitis risk among older adults.

A Polygenic Score Predicts Caries Experience in Elderly Swedish Adults

Caries is a partially heritable disease, raising the possibility that a polygenic score (PS, a summary of an individual's genetic propensity for disease) might be a useful tool for risk assessment. To date, PS for some diseases have shown clinical utility, although no PS for caries has been evaluated. The objective of the study was to test whether a PS for caries is associated with disease experience or increment in a cohort of Swedish adults. A genome-wide PS for caries was trained using the results of a published genome-wide association meta-analysis and constructed in an independent cohort of 15,460 Swedish adults. Electronic dental records from the Swedish Quality Registry for Caries and Periodontitis (SKaPa) were used to compute the decayed, missing, and filled tooth surfaces (DMFS) index and the number of remaining teeth. The performance of the PS was evaluated by testing the association between the PS and DMFS at a single dental examination, as well as between the PS and the rate of change in DMFS. Participants in the highest and lowest deciles of PS had a mean DMFS of 63.5 and 46.3, respectively. A regression analysis confirmed this association where a 1 standard deviation increase in PS was associated with approximately 4-unit higher DMFS (P < 2 × 10-16). Participants with the highest decile of PS also had greater change in DMFS during follow-up. Results were robust to sensitivity analysis, which adjusted for age, age squared, sex, and the first 20 genetic principal components. Mediation analysis suggested that tooth loss was a strong mediating factor in the association between PS and DMFS but also supported a direct genetic effect on caries. In this cohort, there are clinically meaningful differences in DMFS between participants with high and low PS for caries. The results highlight the potential role of genomic data in improving caries risk assessment.

Oral Health Education in Patients with Diabetes: A Systematic Review

Diabetes is known as a "silent epidemic" and is a public health problem that accounts for 9% of all deaths worldwide. The prevention of diabetes is a significant challenge, as its prevalence and incidence are both increasing rapidly. According to the World Health Organization (WHO), education is the cornerstone of diabetes treatment. Since the severity of oral diseases is significantly higher in diabetic patients, this systematic review aims to highlight the oral care of diabetic patients as a priority for glycemic control and the importance of education for diabetic patients' oral health. We evaluated 20 clinical studies and 15 meta-analyses from PubMed and Google Scholar over the last five years. Their main themes are the direct relationship between diabetes and oral health, especially periodontitis, and the necessity of education and behaviors that can lead to a better quality of life. Our analysis indicated that good oral health is a critical factor of glycemic control in diabetic patients and can be enhanced by targeted educational programs, backed by long-term medical and dental follow-up. Healthcare personnel should be encouraged to develop their knowledge of oral health in relation to the disease so that behaviors can be adopted to improve patients' quality of life. Telemedicine could also contribute to patient education and self-management of the disease.

Genetic evidence strengthens the bidirectional connection between oral health status and psychiatric disorders: A two-sample Mendelian randomization study

BACKGROUND

Observational studies cannot accurately infer the causal associations between oral health status and psychiatric disorders.

METHODS

We conducted univariate and multivariate Mendelian randomization (MR) analyses using single nucleotide polymorphisms (SNPs) associated with eight oral health statuses (periodontitis, DMFS, Nteeth, toothache, loose teeth, painful gums, bleeding gums, and mouth ulcers) and four psychiatric disorders (Schizophrenia, Major Depressive Disorder (MDD), anxiety and stress-related disorder (ASRD), and Bipolar Disorder (BIP)) as instrumental variables. Genetic data were sourced from the Gene-lifestyle interactions in dental endpoints (GLIDE), UK Biobank, Psychiatric Genomics Consortium (PGC), and Lundbeck Foundation Initiative for Integrative Psychiatric Research (iPSYCH). The inverse variance-weighted (IVW) approach, supported by a comprehensive sensitivity analysis, was employed.

RESULTS

Genetically predicted mouth ulcers were significantly linked to higher MDD (OR = 2.17, 95 % CI: 1.33--3.54, P< 0.01) and BIP risks (OR = 2.25, 95 % CI: 1.22-4.15, P = 0.01). BIP heightened bleeding gums risk (OR = 1.01, 95 % CI: 1.00-1.01, P < 0.01). These associations were adjusted for smoking status and alcohol consumption. Painful gums were significantly associated with MDD risk (OR = 96.48, 95 % CI: 2.66-3495.28, P = 0.01), while MDD raised periodontitis risk (OR = 2.15, 95 % CI: 1.24-3.75, P = 0.01), both confounded by smoking and alcohol. Relatively small effects between several variables, while others could not withstand correction for multiple tests.

LIMITATIONS

The sample size and limitation to European populations limits the study generalizability.

CONCLUSIONS

This study provide evidence of possible causal relationships between several oral health conditions and mental illness. Focusing on oral health and valuing mental health are important for each other and overall health.

Diet-derived circulating antioxidants, periodontitis and dental caries: A Mendelian randomization study

BACKGROUND AND OBJECTIVE

Given the potential association between oxidative stress, periodontitis and dental caries, whether dietary supplementation with antioxidants is beneficial for periodontitis and dental caries has been widely reported, but remains controversial. This study aims to clarify these relationships through two-sample Mendelian randomization (MR) analysis.

METHODS

Circulating antioxidants (copper, selenium, zinc, ascorbate, β-carotene, lycopene, retinol and vitamin E) were derived from absolute circulating antioxidants and circulating antioxidant metabolites. Summary data of periodontitis and dental caries were obtained from two separate databases, respectively. We performed inverse-variance weighted (IVW) analysis separately in different databases, followed by meta-analysis. The robustness of results was examined by sensitivity analyses, including three complementary MR methods, heterogeneity and pleiotropy tests, and PhenoScanner query.

RESULTS

IVW analysis showed that elevated levels of absolute circulating retinol reduced the risk of periodontitis (GLIDE: OR = 0.41, 95% CI = 0.18-0.95, p = .038, power = 100%; FinnGen: OR = 0.15, 95% CI = 0.04-0.54, p = .004, power = 100%). The pooled OR for periodontitis risk per unit increase of retinol is 0.30 (95% CI = 0.15-0.61, p = .001, I2 = 40.3%, power = 100%). No significant associations were noted for genetically predicted circulating antioxidants and dental caries risk. The sensitivity analyses yielded similar estimates.

CONCLUSION

This study demonstrates that a negative causality between circulating retinol and periodontitis risk, and null linkage between circulating antioxidants and dental caries risk, suggesting potential strategies for the prevention and control of periodontitis.

Association of periodontitis with gastrointestinal tract disorders: A bidirectional Mendelian randomization study

BACKGROUND

The bidirectional link of periodontitis (PD) and gastrointestinal tract (GIT) disorders has been investigated in previous epidemiological studies; however, the conclusions still remain controversial. The aim of this study was to comprehensively explore the bidirectional causal effect between PD and various GIT diseases.

METHODS

Based on summary-level data of genome-wide association studies (GWASs), a two-sample bidirectional Mendelian randomization (MR) study was undertaken. Single-nucleotide polymorphisms (SNPs) associated with PD or GIT disorders (chronic gastritis [CG], gastric ulcer [GU], duodenal ulcer [DU], gastroesophageal reflux disease [GERD], irritable bowel syndrome [IBS], and diverticular disease of the intestine [DI]) in GWASs were applied as exposure. The primary method employed was the inverse-variance weighted (IVW) method, and several sensitivity analyses were performed to investigate potential pleiotropy.

RESULTS

With regard to the investigation of the causality between PD and GIT disorders, the IVW method revealed that there is a causal impact of PD on GU (odds ratio [OR] 1.088; 95% confidence interval [CI], 1.036-1.141; adjusted p = 0.004) and DI (OR 0.938; 95% CI, 0.911-0.965; adjusted p = 0.000). However, no significant genetic liability was observed for the causal effect of PD on CG, DU, GERD, and IBS. Furthermore, the primary analysis did not demonstrate a causal effect of GIT disorders on PD.

CONCLUSION

This MR study suggests that PD may be associated with an increased risk of GU and a reduced risk of DI, with possibly limited clinical relevance. Further studies are needed to support the conclusions of this MR study.

Exploring the causal relationship between periodontitis and gut microbiome: Unveiling the oral-gut and gut-oral axes through bidirectional Mendelian randomization

AIM

This Mendelian randomization (MR) study was performed to explore the potential bidirectional causal relationship between the gut microbiome (GM) and periodontitis.

MATERIALS AND METHODS

We used genetic instruments from the genome-wide association study of European descent for periodontitis from the GeneLifestyle Interactions in Dental Endpoints (GLIDE) consortium (17,353 cases and 28,210 controls) and the FinnGen consortium (4434 cases and 259,234 controls) to investigate the causal relationship with GM (the MiBioGen consortium, 18,340 samples), and vice versa. Several MR techniques, which include inverse variance weighting (IVW), MR-Egger, weighted median, simple mode and weighted mode approaches, were employed to investigate the causal relationship between the exposures and the outcomes. Cochran's Q-test was performed to detect heterogeneity. The MR-Egger regression intercept and MR pleiotropy residual sum and outlier test (MR-PRESSO) were conducted to test potential horizontal pleiotropy. Leave-one-out sensitivity analyses were used to assess the stabilities of single nucleotide polymorphisms (SNPs). Finally, the IVW results from the two databases were analysed using meta-analysis.

RESULTS

We confirmed three potential causal relationships between GM taxa and periodontitis at the genus level. Among them, the genera Alistipes and Holdemanella were genetically associated with an increased risk of periodontitis. In reverse, periodontitis may lead to a decreased abundance of the genus Ruminococcaceae UCG014.

CONCLUSIONS

The demonstration of a causal link between GM and periodontitis provides compelling evidence, highlighting the interconnectivity and interdependence of the gut-oral and oral-gut axes.

Patients with periodontitis might increase the risk of urologic cancers: a bidirectional two-sample Mendelian randomization study

BACKGROUND

Numerous observational epidemiological studies have reported a bidirectional relationship between periodontitis and urological cancers. However, the causal link between these two phenotypes remains uncertain. This study aimed to examine the bidirectional causal association between periodontitis and four types of urological tumors, specifically kidney cancer (KC), prostate cancer (PC), bladder cancer (BC), and testis cancer (TC).

METHODS

Based on large-scale genome-wide association study (GWAS) data, we utilized the two-sample Mendelian randomization (MR) approach to evaluate causal relationships between periodontitis and urological cancers. Several MR methods covering various consistency assumptions were applied in this study, including contamination mixture and Robust Adjusted Profile Score to obtain robust results. Summary-level data of individuals with European ancestry were extracted from the UK Biobank, the Kaiser GERA cohorts, and the FinnGen consortium.

RESULTS

Our findings revealed significant positive genetic correlations between periodontitis and kidney cancer (OR 1.287; 95% CI 1.04, 1.594; P = 0.020). We did not find a significant association of periodontitis on prostate cancer, bladder cancer, and testis cancer. In reverse MR, no significant results were observed supporting the effect of urologic cancers on periodontitis (all P > 0.05).

CONCLUSION

Our study provides the evidence of a potential causal relationship between periodontitis and kidney cancer. However, large-scale studies are warranted to confirm and elucidate the underlying mechanisms of this association.

A genome-wide association study meta-analysis in a European sample of stage III/IV grade C periodontitis patients ≤35 years of age identifies new risk loci

AIM

Few genome-wide association studies (GWAS) have been conducted for severe forms of periodontitis (stage III/IV grade C), and the number of known risk genes is scarce. To identify further genetic risk variants to improve the understanding of the disease aetiology, a GWAS meta-analysis in cases with a diagnosis at ≤35 years of age was performed.

MATERIALS AND METHODS

Genotypes from German, Dutch and Spanish GWAS studies of III/IV-C periodontitis diagnosed at age ≤35 years were imputed using TopMed. After quality control, a meta-analysis was conducted on 8,666,460 variants in 1306 cases and 7817 controls with METAL. Variants were prioritized using FUMA for gene-based tests, functional annotation and a transcriptome-wide association study integrating eQTL data.

RESULTS

The study identified a novel genome-wide significant association in the FCER1G gene (p = 1.0 × 10-9 ), which was previously suggestively associated with III/IV-C periodontitis. Six additional genes showed suggestive association with p < 10-5 , including the known risk gene SIGLEC5. HMCN2 showed the second strongest association in this study (p = 6.1 × 10-8 ).

CONCLUSIONS

This study expands the set of known genetic loci for severe periodontitis with an age of onset ≤35 years. The putative functions ascribed to the associated genes highlight the significance of oral barrier tissue stability, wound healing and tissue regeneration in the aetiology of these periodontitis forms and suggest the importance of tissue regeneration in maintaining oral health.

Periodontitis and Sjogren's syndrome: a bidirectional two-sample mendelian randomization study

OBJECTIVES

Observational studies indicated a controversial relationship between periodontitis (PD) and Sjogren's syndrome (SS). To overcome restrictions in conventional observational studies, we conducted a two-sample Mendelian randomization (MR) analysis to assess the potential bidirectional relationship between PD and SS.

METHODS

We utilized the largest available genome-wide association study (GWAS) of European ancestry on both PD (17,353 cases-28,210 controls) and SS (2495 cases-365,533 controls) for MR genetic instrument selection. The random-effect inverse-variance weighted (IVW) method complemented by Causal Analysis Using Summary Effect (CAUSE), weighted median, weighted mode, simple mode, MR-Egger regression, and MR-pleiotropy residual sum and outlier (MR-PRESSO) was used for MR analysis. Subsequent pleiotropy and heterogeneity tests were conducted.

RESULTS

IVW analysis exhibited neither an effect of PD on SS (OR = 0.939, 95%CI = 0.525-1.677, P = 0.8304) nor that of SS on PD (OR = 1.007, 95%CI = 0.977-1.038, P = 0.6440). The other five complementary methods further recognized the null association with an effect size close to one. No significant pleiotropy was detected in the relationship between PD and SS (P > 0.05). Heterogeneity existed in the effect of PD on SS but not vice versa.

CONCLUSIONS

No genetic causality between PD and SS or vice versa was supported by our results under MR assumptions and limitations. The study results provided new insights into the relationship between periodontal status and sjogren's syndrome, highlighting the need for a more prudent medical intervention.

Periodontitis and osteoporosis: a two-sample Mendelian randomization analysis

The incidences of periodontitis and osteoporosis are rising worldwide. Observational studies have shown that periodontitis is associated with increased risk of osteoporosis. We performed a Mendelian randomization (MR) study to genetically investigate the causality of periodontitis on osteoporosis. We explored the causal effect of periodontitis on osteoporosis by MR analysis. A total of 9 single nucleotide polymorphisms (SNP) were related to periodontitis. The primary approach in this MR analysis was the inverse variance-weighted (IVW) method. Simple median, weighted median, and penalized weighted median were used to analyze sensitivity. The fixed-effect IVW model and random-effect IVW model showed no significant causal effect of genetically predicted periodontitis on the risk of osteoporosis (OR=1.032; 95%CI: 0.923-1.153; P=0.574; OR=1.032; 95%CI: 0.920-1.158; P=0.588, respectively). Similar results were observed in simple mode (OR=1.031; 95%CI: 0.780-1.361, P=0.835), weighted mode (OR=1.120; 95%CI: 0.944-1.328, P=0.229), simple median (OR=1.003; 95%CI: 0.839-1.197, P=0.977), weighted median (OR=1.078; 95%CI: 0.921-1.262, P=0.346), penalized weight median (OR 1.078; 95%CI: 0.919-1.264, P=0.351), and MR-Egger method (OR=1.360; 95%CI: 0.998-1.853, P=0.092). There was no heterogeneity in the IVW and MR-Egger analyses (Q=7.454, P=0.489 and Q=3.901, P=0.791, respectively). MR-Egger regression revealed no evidence of a pleiotropic influence through genetic variants (intercept: -0.004; P=0.101). The leave-one-out sensitivity analysis indicated no driven influence of any individual SNP on the association between periodontitis and osteoporosis. The Mendelian randomization analysis did not show a significant detrimental effect of periodontitis on the risk of osteoporosis.

Multi-ancestry Genome-Wide Association Study of Early Childhood Caries

Early childhood caries (ECC) is the most common non-communicable childhood disease. It is an important health problem with known environmental and social/behavioral influences that lacks evidence for specific associated genetic risk loci. To address this knowledge gap, we conducted a genome-wide association study of ECC in a multi-ancestry population of U.S. preschool-age children (n=6,103) participating in a community-based epidemiologic study of early childhood oral health. Calibrated examiners used ICDAS criteria to measure ECC with the primary trait using the dmfs index with decay classified as macroscopic enamel loss (ICDAS ≥3). We estimated heritability, concordance rates, and conducted genome-wide association analyses to estimate overall genetic effects; the effects stratified by sex, household water fluoride, and dietary sugar; and leveraged the combined gene/gene-environment effects using the 2-degree-of-freedom (2df) joint test. The common genetic variants explained 24% of the phenotypic variance (heritability) of the primary ECC trait and the concordance rate was higher with a higher degree of relatedness. We identified 21 novel non-overlapping genome-wide significant loci for ECC. Two loci, namely RP11-856F16 . 2 (rs74606067) and SLC41A3 (rs71327750) showed evidence of association with dental caries in external cohorts, namely the GLIDE consortium adult cohort (n=∼487,000) and the GLIDE pediatric cohort (n=19,000), respectively. The gene-based tests identified TAAR6 as a genome-wide significant gene. Implicated genes have relevant biological functions including roles in tooth development and taste. These novel associations expand the genomics knowledge base for this common childhood disease and underscore the importance of accounting for sex and pertinent environmental exposures in genetic investigations of oral health.

Shared genetic architecture between periodontal disease and type 2 diabetes: a large scale genome-wide cross-trait analysis

PURPOSE

To investigate the relationship between abnormal glucose metabolism, type 2 diabetes (T2D), and periodontal disease (PER) independent of Body Mass Index (BMI), we employed a genome-wide cross-trait approach to clarify the association.

METHODS

Our study utilized the most extensive genome-wide association studies conducted for populations of European ancestry, including PER, T2D, fasting glucose, fasting insulin, 2-hour glucose after an oral glucose challenge, HOMA-β, HOMA-IR (unadjusted or adjusted for BMI) and HbA1c.

RESULTS

With this approach, we were able to identify pleiotropic loci, establish expression-trait associations, and quantify global and local genetic correlations. There was a significant positive global genetic correlation between T2D (rg = 0.261, p = 2.65 × 10-13), HbA1c (rg = 0.182, p = 4.14 × 10-6) and PER, as well as for T2D independent of BMI (rg = 0.158, p = 2.34 × 10-6). A significant local genetic correlation was also observed between PER and glycemic traits or T2D. We also identified 62 independent pleiotropic loci that impact both PER and glycemic traits, including T2D. Nine significant pathways were identified between the shared genes between T2D, glycemic traits and PER. Genetically liability of HOMA-βadjBMI was causally associated with the risk of PER.

CONCLUSION

Our research has revealed a genetic link between T2D, glycemic traits, and PER that is influenced by biological pleiotropy. Notably, some of these links are not related to BMI. Our research highlights an underlying link between patients with T2D and PER, regardless of their BMI.

Sjögren's Disease and Oral Health: A Genetic Instrumental Variable Analysis

Epidemiological studies have consistently shown that Sjögren's disease (SjD) increases the risk of dental caries. Despite similar evidence indicating an elevated risk of periodontitis, SjD remains a disputed risk factor for this disease. The risk of bias in observational research is a major impediment to confirming this link. Within an instrumental variable framework, genetic variants associated with a risk factor can be used to proxy its effect on an outcome while avoiding common sources of observational study bias. In this study, we leveraged an instrumental variable approach to investigate whether SjD affects the risk of caries and periodontitis. A total of 57 genetic variants strongly associated with SjD were identified from a genome-wide association study of 2,247 European descent cases and 332,115 controls. We tested for associations of these genetic instruments with caries (measured as the number of decayed, missing, and filled surfaces in 26,792 individuals) and periodontitis (17,353 clinical periodontitis cases and 28,210 European controls). Several sensitivity analyses were used to further validate the primary inverse variance weighted (IVW) estimate. IVW analysis revealed an adverse effect of SjD on caries (β = 0.039, P = 6.3e-16) and periodontitis (odds ratio = 1.033, P = 2.3e-05). Sensitivity analyses, conducted to assess the robustness to potential violations of instrumental variable assumptions, further support these findings. Our results showed that SjD has a detrimental effect on caries and also suggest that SjD promotes periodontitis.

Self-reported oral health is associated with systemic health outcomes and all-cause mortality

BACKGROUND

Self-reported oral health questions (OHQs) are used commonly for epidemiologic surveillance of periodontal disease (PD). The authors' objective was to investigate how OHQs are associated with well-established systemic comorbidities of PD and their impact on all-cause mortality. The authors hypothesized that OHQs exhibit associations with systemic comorbidities similar to PD.

METHODS

Two independent data sets were used to achieve these objectives: the Women's Health Study, a prospective cohort of women 45 years or older with self-reported information on PD, OHQs, cardiovascular disease, diabetes, and osteoporosis in various timeframes (continuous from 1992) and the National Health and Nutrition Examination Survey (NHANES), with data on OHQs and linked mortality (1999-2018). The authors applied multivariate logistic regression models and Cox proportional hazard regression survival analyses to test their hypotheses.

RESULTS

The Women's Health Study participants who reported having PD until 2006 were more likely to later report deteriorating oral health, bone loss around their teeth, or periodontal treatment in 2018. Self-rated fair or poor oral health was independently associated with increased risk of cardiovascular disease (odds ratio, 1.39; 95% CI, 1.14 to 1.69; P < .001), diabetes (odds ratio, 1.21; 95% CI, 1.02 to 1.43; P = .028), and osteoporosis (odds ratio, 1.60; 95% CI, 1.38 to 1.84; P < .001). National Health and Nutrition Examination Survey participants who self-rated fair or poor oral health had higher risks of all-cause mortality (hazard ratio, 1.18; 95% CI, 1.02 to 1.37; P = .027).

CONCLUSIONS

Self-reported oral health had a similar magnitude of associations with systemic comorbidities as established with PD previously. Moreover, self-rated fair or poor oral health, suboptimal dental visits, or infrequent flossing were associated with increased all-cause mortality.

PRACTICAL IMPLICATIONS

These results support the use of OHQs in assessing systemic connections, especially when clinical dental access is limited. This clinical trial was registered at ClinicalTrials.gov. The registration number is NCT00000479.

Investigating the causal relationship between human blood/urine metabolites and periodontal disease using two-sample Mendelian randomization

Background and Aims

The aim is to investigate the cause-and-effect connection between metabolites found in blood/urine and the likelihood of developing periodontal disease (PD) through the utilization of a two-sample Mendelian randomization (MR) method.

Methods

Using an inverse variance weighted (IVW) method and two additional two-sample MR models, we examined the relationship between blood/urine metabolites and PD by analyzing data from a comprehensive metabolome-based genome-wide association study and the Genome-Wide Association Studies (GWAS) of PD. To assess the consistency and dependability of the findings, diversity, cross-effects, and sensitivity analyses were conducted.

Results

Out of the 35 metabolites found in blood and urine, a total of eight metabolites (C-reactive protein, Potassium in urine, Urea, Cystatin C, Non-albumin protein, Creatinine, estimated Glomerular Filtration Rate, and Phosphate) displayed a possible causal connection with the risk of dental caries/PD using the inverse variance weighted (IVW) method (p < 0.05). This includes five metabolites in the blood and three in the urine. No metabolites were statistically significant in IVW MR models (p < 3.68 × 10- 4). Even after conducting sensitivity analysis with the leave-one-out method and removing the confounding instrumental variables, the impact of these factors on dental caries/PD remained significant.

Conclusion

Based on the available evidence, it is not possible to establish a significant causal link between the 35 blood metabolites and the likelihood of developing dental caries and PD.

Association between periodontitis and endometriosis: a bidirectional Mendelian randomization study

Introduction

A potential association between periodontitis and endometriosis has been indicated in previous observational studies. Nevertheless, the causal link between these two disorders has not been clarified.

Methods

Based on publicly available genome-wide association study (GWAS) summary datasets, we conducted a bidirectional Mendelian randomization (MR) study to investigate the relationship between periodontitis and endometriosis and its subtypes. Single nucleotide polymorphisms (SNPs) strongly associated with candidate exposures at the genome-wide significance level (P < 5 × 10-8) were selected as instrumental variables (IVs). The inverse variance-weighted regression (IVW) was performed to estimate the causal effect of periodontitis on endometriosis. We further conducted two sensitivity analyses, MR-Egger and weighted median, to test the validity of our findings. The main results were replicated via data from the UK Biobank. Finally, a reverse MR analysis was performed to evaluate the possibility of reverse causality.

Results

The IVW method suggested that periodontitis was positively associated with endometriosis of the pelvic peritoneum (OR = 1.079, 95% CI = 1.016 to 1.146, P = 0.014). No causal association was indicated between periodontitis and other subtypes of endometriosis. In reversed analyses, no causal association between endometriosis or its subtypes and periodontitis was found.

Conclusions

Our study provided genetic evidence on the causal relationship between periodontitis and endometriosis of the pelvic peritoneum. More studies are necessary to explore the underlying mechanisms.

Assessing the association between tea intake and risk of dental caries and periodontitis: a two-sample Mendelian randomization study

Tea is an indispensable beverage in people's daily life. However, the relationship between tea intake and dental caries and periodontitis is controversial. We extracted datasets for tea intake and oral diseases from genome-wide association studies (GWASs) conducted by the UK Biobank and the Gene Lifestyle Interactions in Dental Endpoints consortium. We selected 38 single-nucleotide polymorphisms (SNPs) significantly associated with tea intake as instrumental variables (IVs) (P < 5.0 × 10-8). Mendelian randomization (MR) was performed to investigate the potential causality between tea intake and caries and periodontitis. Multivariable Mendelian randomization (MVMR) analyses were utilized to estimate causal effects of tea intake on risk of caries and periodontitis after adjusting for smoking, body mass index (BMI), and socioeconomic factors. The results showed that higher tea intake was suggestively associated with fewer natural teeth (β = - 0.203; 95% CI = 0.680 to 0.980; P = 0.029) and higher risk of periodontitis (OR = 1.622; 95% CI = 1.194 to 2.205; P = 0.002). After Bonferroni correction, the causality of tea intake on periodontitis remained significant. The significance of periodontitis disappeared after adjusting for the socioeconomic factors in MVMR (OR = 1.603; 95% CI = 0.964 to 2.666; P = 0.069). Tea intake had no association with risk of caries. Statistical insignificance of the heterogeneity test and pleiotropy test supported the validity of the MR study. Our results provide insight into the potential relationship between tea intake and oral diseases from a dietary lifestyle perspective, which may help prevent oral diseases.

Causal Association Analysis of Periodontitis and Inflammatory Bowel Disease: A Bidirectional Mendelian Randomization Study

BACKGROUND

Periodontitis has been reported to be associated with inflammatory bowel disease (IBD), including ulcerative colitis (UC), and Crohn's disease (CD). However, the causality of these 2 diseases remains unclear. We conducted bidirectional Mendelian randomization (MR) to investigate the causal relationship between periodontitis and IBD.

METHODS

We obtained the genome-wide association study (GWAS) summary data of European populations from FinnGen database (for IBD) and a published article (for periodontitis), from which independent single nucleotide polymorphisms were selected as instrumental variables. Inverse variance-weighted (IVW), MR-Egger, and weighted median (WM) methods were utilized for MR analysis. Heterogeneity or pleiotropy was detected through Cochran's Q test and MR-Egger intercept, respectively. Outlier was identified with MR-PRESSO (Mendelian Randomization Pleiotropy RESidual Sum and Outlier) and leave-one-out analysis. All statistical analyses were performed with R 4.2.1 and the packages of TwoSampleMR version 0.5.6.

RESULTS

Genetic prediction showed that periodontitis was the risk factor of UC (odds ratio [OR], 1.13; 95% confidence interval [CI], 1.01-1.26; P = .027), rather than of CD (OR, 0.92; 95% CI, 0.74-1.15; P = .456) and IBD (OR, 0.96; 95% CI, 0.81-1.13; P = .619). To the contrary, CD, not UC or IBD, resulted in exacerbating periodontitis in terms of the results of the IVW (OR, 1.09; 95% CI, 1.01-1.17; P = .021) and WM (OR, 1.10; 95% CI, 1.01-1.20; P = .030) methods. Heterogeneity or pleiotropy was acceptable.

CONCLUSIONS

Our results indicated that CD was the risk factor for periodontitis; conversely, periodontitis was responsible for the exacerbation of UC, enhancing the existence of mouth-gut axis. Patients with UC should pay more attention to periodontal health, while patients with periodontitis should actively pay close heed to intestinal health.

Complement C3 as a potential drug target in periodontitis: Evidence from the cis-Mendelian randomization approach

AIM

Evidence from a Phase IIa trial showed that a complement C3-targeted drug reduced gingival inflammation in patients with gingivitis. Using drug-target Mendelian randomization (MR), we investigated whether genetically proxied C3 inhibition alters the risk of periodontitis.

MATERIALS AND METHODS

We used multiple 'cis' instruments from the vicinity of the encoding loci of C3. Instrument selection was restricted to the drug target encoding loci (chromosome 19; 6,677,715-6,730,573 (GRCh37/hg19)). We selected three uncorrelated single-nucleotide polymorphisms (rs141552034, rs145406915, rs11569479) that were associated with serum C3 levels (p value <1 × 10-4 ) from a genome-wide association study (GWAS) of 5368 European descent individuals. We extracted association statistics from a GWAS of 17,353 clinical periodontitis cases and 28,210 European controls. Wald ratios were combined using inverse-variance weighted meta-analysis to estimate the odds ratio (OR) of the genetically proxied inhibition of C3 in relation to periodontitis.

RESULTS

MR analysis revealed that the inhibition of C3 reduces the odds of periodontitis (OR 0.91 per 1 standard deviation reduction in C3; 95% confidence interval 0.87-0.96, p value = .0003).

CONCLUSIONS

Findings from our MR analysis suggest a potential protective effect of C3 blockade against periodontitis.

Bioinformatics reveals the pathophysiological relationship between diabetic nephropathy and periodontitis in the context of aging

Diabetic nephropathy (DN) is one of the most common microvascular complications of diabetes mellitus. Periodontitis (PD) is a microbially-induced chronic inflammatory disease that is thought to have a bidirectional relationship with diabetes mellitus. DN and PD are recognized as models associated with accelerated aging. This study is divided into two parts, the first of which explores the bidirectional causal relationship through Mendelian randomization (MR). The second part aims to investigate the relationship between PD and DN in terms of potential crosstalk genes, aging-related genes, biological pathways, and processes using bioinformatic methods. MR analysis showed no evidence to support a causal relationship between DN and PD (P = 0.34) or PD and DN (P = 0.77). Using the GEO database, we screened 83 crosstalk genes overlapping in two diseases. Twelve paired genes identified by Pearson correlation and the four hub genes in the key cluster were jointly evaluated as key crosstalk-aging genes. Using support vector machine recursive feature elimination (SVM-RFE) and maximal clique centrality (MCC) algorithms, feature selection established five genes as the key crosstalk-aging genes. Based on five key genes, an ANN diagnostic model with reliable diagnosis of two diseases was developed. Gene enrichment analysis indicates that AGE-RAGE pathway signaling, the complement system, and multiple immune inflammatory pathways may be involved in common features of both diseases. Immune infiltration analysis reveals that most immune cells are differentially expressed in PD and DN, with dendritic cells and T cells assuming vital roles in both diseases. Overall, although there is no causal link, CSF1R, CXCL6, VCAM1, JUN and IL1B may be potential crosstalk-aging genes linking PD and DN. The common pathways and markers explored in this study could contribute to a deeper understanding of the common pathogenesis of both diseases in the context of aging and provide a theoretical basis for future research.

Association of Poor Oral Health With Neuroimaging Markers of White Matter Injury in Middle-Aged Participants in the UK Biobank

BACKGROUND AND OBJECTIVES

Poor oral health is a modifiable risk factor that is associated with clinically observed cardiovascular disease. However, the relationship between oral and brain health is not well understood. We tested the hypothesis that poor oral health is associated with worse neuroimaging brain health profiles in middle-aged persons without stroke or dementia.

METHODS

We performed a 2-stage cross-sectional neuroimaging study using UK Biobank data. First, we tested for association between self-reported poor oral health and MRI neuroimaging markers of brain health. Second, we used Mendelian randomization (MR) analyses to test for association between genetically determined poor oral health and the same neuroimaging markers. Poor oral health was defined as the presence of dentures or loose teeth. As instruments for the MR analysis, we used 116 independent DNA sequence variants linked to increased composite risk of dentures or teeth that are decayed, missing, or filled. Neuroimaging markers of brain health included white matter hyperintensity (WMH) volume and aggregate measures of fractional anisotropy (FA) and mean diffusivity (MD), 2 metrics indicative of white matter tract disintegrity obtained through diffusion tensor imaging across 48 brain regions.

RESULTS

We included 40,175 persons (mean age 55 years, female sex 53%) enrolled from 2006 to 2010, who underwent a dedicated research brain MRI between 2014 and 2016. Among participants, 5,470 (14%) had poor oral health. Poor oral health was associated with a 9% increase in WMH volume (β = 0.09, SD = 0.014, p < 0.001), 10% change in aggregate FA score (β = 0.10, SD = 0.013, p < 0.001), and 5% change in aggregate MD score (β = 0.05, SD = 0.013, p < 0.001). Genetically determined poor oral health was associated with a 30% increase in WMH volume (β = 0.30, SD = 0.06, p < 0.001), 43% change in aggregate FA score (β = 0.43, SD = 0.06, p < 0.001), and 10% change in aggregate MD score (β = 0.10, SD = 0.03, p < 0.01).

DISCUSSION

Among middle age Britons without stroke or dementia, poor oral health was associated with worse neuroimaging brain health profiles. Genetic analyses confirmed these associations, supporting a potentially causal association. Because the neuroimaging markers evaluated in this study precede and are established risk factors of stroke and dementia, our results suggest that oral health, an easily modifiable process, may be a promising target for very early interventions focused on improving brain health.

Oral Health and Brain Health: Cause, Consequence, or Confounding?

Epidemiologic studies of the association between periodontal disease and cardiovascular disease, including stroke, had mixed findings.1 Some studies have found that serum antibodies to major periodontal pathogens are associated with coronary heart disease (CHD), suggesting that periodontal infection or the host response to periodontal infection may play a causal role in CHD.1 More recently, longitudinal studies have supported an association of periodontal disease between cognitive decline and dementia.2 The motivation for these studies has been two-fold. First, periodontal disease is known to be associated with systemic inflammation,3 which, in turn, is known to be causally associated with atherosclerotic disease.4 Second, periodontal disease is potentially modifiable in the population. The limitation of all observational epidemiologic studies is the problem of confounding by incompletely measured or unmeasured variables, such as diet, health behaviors including oral hygiene, and the host response to infection. In addition, studies oral health and either cognitive decline or dementia may suffer from reverse causality; cognitive changes may lead to lessened oral hygiene and periodontal disease.

From teeth to brain: dental caries causally affects the cortical thickness of the banks of the superior temporal sulcus

OBJECTIVES

Dental caries is one of the most prevalent oral diseases and causes of tooth loss. Cross-sectional studies observed epidemiological associations between dental caries and brain degeneration disorders, while it is unknown whether dental caries causally affect the cerebral structures. This study tested whether genetically proxied DMFS (the sum of Decayed, Missing, and Filled tooth Surfaces) causally impacts the brain cortical structure using Mendelian randomization (MR).

METHODS

The summary-level GWAS meta-analysis data from the GLIDE consortium were used for DMFS, including 26,792 participants. ENIGMA (Enhancing NeuroImaging Genetics through Meta Analysis) consortium GWAS summary data of 51,665 patients were used for brain structure. This study estimated the causal effects of DMFS on the surface area (SA) and thickness (TH) of the global cortex and functional cortical regions accessed by magnetic resonance imaging (MRI). Inverse-variance weighted (IVW) was used as the primary estimate, the MR pleiotropy residual sum and outlier (MR-PRESSO), the MR-Egger intercept test, and leave-one-out analyses were used to examine the potential horizontal pleiotropy.

RESULTS

Genetically proxied DMFS decreases the TH of the banks of the superior temporal sulcus (BANSSTS) with or without global weighted (weighted, β = - 0.0277 mm, 95% CI: - 0.0470 mm to - 0.0085 mm, P = 0.0047; unweighted, β = - 0.0311 mm, 95% CI: - 0.0609 mm to - 0.0012 mm, P = 0.0412). The causal associations were robust in various sensitivity analyses.

CONCLUSIONS

Dental caries causally decrease the cerebral cortical thickness of the BANKSSTS, a cerebral cortical region crucial for language-related functions, and is the most affected brain region in Alzheimer's disease. This investigation provides the first evidence that dental caries causally affects brain structure, proving the existence of teeth-brain axes. This study also suggested that clinicians should highlight the causal effects of dental caries on brain disorders during the diagnosis and treatments, the cortical thickness of BANKSSTS is a promising diagnostic measurement for dental caries-related brain degeneration.

Denture use and risk for cardiometabolic disease: observational and Mendelian randomization analyses

AIMS

Denture use may potentially increase the risk of cardiometabolic diseases (CMDs), but the casual relevance and strength of the associations are currently unknown.

METHODS AND RESULTS

A total of 495 938 participants from the UK Biobank were included in the observational analyses. Linkage disequilibrium score (LDSC) regression and Mendelian randomization analyses were employed to estimate genetic correlation and the associations between the genetic liability for denture use with coronary artery disease, myocardial infarction, heart failure (HF), any stroke (AS), ischaemic stroke, haemorrhagic stroke, type 2 diabetes (T2D), and related clinical risk factors. In observational analysis, denture use was associated with 14-25% higher risks of various CMDs. The LDSC analysis found that denture use showed a positive genetic correlation with CMDs (rg 0.21-0.38). Genetic liability for denture use was associated with an elevated risk of HF [odds ratio: 1.49 (1.20-1.83)] and T2D [1.11 (1.01-1.24)]. By integrating genetic summary data of denture use with the sum of decayed, missing, and filled tooth surfaces (DMFS), a clinical measure of dental caries obtained from an independent source, genetically determined denture use/DMFS was also associated with an elevated risk of AS [1.21 (1.04-1.40)]. Furthermore, genetically predicted denture use/DMFS was significantly associated with established cardiometabolic risk factors, including HDL cholesterol, triglycerides, waist circumference, waist-to-hip ratio, and height.

CONCLUSION

Our study supported potential causal associations between the genetic liability for denture use and risks for HF, AS, T2D, and related clinical risk factors. These findings may inform prevention and intervention strategies targeting dental diseases and CMDs.

Development of Oral Bio-banks Past, Present and Future; Challenges and Opportunities

Biobank involves collecting, processing, storing, and organizing biosamples, along with relevant personal and health information such as medical history, family records, genetics data, and lifestyle details, for medical research and clinical care. Oral biobanking is a recently evolved field alongside the rising of precision medicine due to recent research findings in oral oncology and other oral complaints, namely caries and periodontal disease. The common samples in oral biobanks are matured and primary teeth, dental pulp cells, oral biopsies, oral rinses, saliva, and swabs from the buccal region. Moreover, biobank should not conceive of as a static collection of samples and data but as a dynamic resource for developing novel techniques that meet current scientific demands through international networking. However, the major bottlenecks associated with oral biobanks are privacy, processing of samples, normalization of data, extended durability of interest markers of banked samples, and financial sustainability of biobanks. Thus in this correspondence, we argue that an alternative approach is urgently needed to protect the interests of many stakeholders.

Visceral adipose tissue increases the risk of periodontal disease: Results from the 2011-2014 National Health and Nutrition Examination Survey and Mendelian randomization analysis

AIM

This study aimed to investigate the relationship and potential causal effect of visceral adipose tissue (VAT) on periodontal disease (PD). Despite prior research on this, there has been no definitive conclusion. Therefore, this study aimed to provide additional insight into these associations.

MATERIALS AND METHODS

This study used data from the National Health and Nutrition Examination Survey 2011-2014 to examine the association between VAT and PD in a cross-sectional study design. Various analytical methods were employed, such as multivariable logistic regression, restricted cubic spline analysis, and p-value for trend. Additionally, two-sample Mendelian randomization (MR) analysis was performed to evaluate the potential causal effect of VAT on PD risk. These methods enabled us to evaluate the association between VAT and PD and to establish whether VAT could be a causal factor in PD development.

RESULTS

The study examined a sample of 3535 participants, and the findings suggested that higher VAT levels were associated with an increased risk of PD. In addition, multivariable regression analysis conducted in six models revealed a statistically significant association between VAT and PD risk. Restricted cubic spline analysis showed an inverted U-shaped association between VAT and PD, with a turning point at 733 g of VAT. Finally, a two-sample MR analysis provided evidence for a potential causal relationship between VAT and PD risk, with an odds ratio of 1.16 (95% confidence interval: 1.02-1.33, p = .027) per kg increase in genetically predicted VAT.

CONCLUSIONS

The results of this study suggest that there is a significant association between VAT and PD and that VAT could be a potential causal factor in PD risk. Our results also suggest that although there is a potential link between VAT levels and PD risk, the effect size is modest. Therefore, interventions designed to reduce VAT levels should not be considered a primary strategy for PD risk reduction but could be one of many strategies used in a comprehensive approach to PD risk management.

Circulating Metabolites and Dental Traits: A Mendelian Randomization Study

It is of great importance to uncover causal biomarkers to gain insight into the pathogenesis of oral diseases and identify novel treatment targets for prevention and treatment thereof. This study aimed to systematically evaluate the causal effects of hundreds of metabolites on 10 dental traits using a 2-sample Mendelian randomization (MR) approach. Genetic variants from genome-wide association studies of 309 known metabolites were used as instrumental variables. We selected 10 dental traits, including clinical measures of dental diseases, from the Gene-Lifestyle Interactions in Dental Endpoints Consortium and self-reported oral health data from the UK Biobank. The causal relationships between metabolites and dental traits were inferred using the inverse variance-weighted approach and further controlled for horizontal pleiotropy using 5 additional MR methods. After correcting for multiple tests, 5 metabolites were identified as causal biomarkers. Genetically predicted increased levels of mannose were associated with lower risk of bleeding gums (odds ratio [OR] = 0.72; 95% confidence interval [CI], 0.61-0.85; P = 9.9 × 10-5). MR also indicated 4 metabolites on the causal pathway to dentures, with fructose (OR = 0.50; 95% CI, 0.36-0.70; P = 5.2 × 10-5) and 1-palmitoleoyl-glycerophosphocholine (OR = 0.67; 95% CI, 0.56-0.81; P = 4.8 × 10-5) as potential protective factors and glycine (OR = 1.22; 95% CI, 1.11-1.35; P = 5.6×10-5) and 1,5-anhydroglucitol (OR = 1.32; 95% CI, 1.14-1.52; P = 1.5 × 10-4) as risk factors. The causal associations were robust in various sensitivity analyses. We further observed some shared metabolites among different dental traits, implying similar biological mechanisms underlying the pathogenic processes. Finally, the pathway analysis revealed several significant metabolic pathways that may be involved in the development of dental disorders. Our study provides novel insights into the combination of metabolomics and genomics to reveal the pathogenesis of and therapeutic strategies for dental disorders. It highlighted 5 metabolites and several pathways as causal candidates, warranting further investigation.

Mendelian Randomisation Study on Association of Gut Microbiota and Periodontitis

OBJECTIVE

Several studies have demonstrated the possible association between gut microbiota and periodontitis. The mechanism by which gut microbiota contribute to periodontitis remains unknown.

METHODS

A 2-sample Mendelian randomisation (MR) study was conducted using publicly available Genome-Wide Association Studies (GWAS) data of European ancestry. The relationships between gut microbiota and tooth loss and periodontitis were assessed using summary-level data. Moreover, inverse variance weighted (IVW), MR-Egger, weighted median, and simple Mendelian were used. The results were further validated using sensitivity analyses.

RESULTS

A total of 211 gut microbiota were studied, including 9 phyla, 16 classes, 20 orders, 35 families, and 131 genera. The IVW method identified 16 bacterial genera related to the risk of periodontitis and tooth loss. Lactobacillaceae was associated with an increased risk of periodontitis (odds ratio [OR], 1.40, 95% confidence interval [CI], 1.03-1.91, P<.001) and tooth loss (OR, 1.12; 95% CIs, 1.02-1.24, P = .002), whereas Lachnospiraceae UCG008 was linked to a lower risk of tooth loss (P = .041). There was no heterogeneity and horizontal pleiotropy in the sensitivity analysis.

CONCLUSIONS

Several microorganisms were identified to be linked to the risk of periodontitis. Furthermore, the findings improved our understanding of gut microbiota and periodontitis pathology.

Identification of disease-associate variants of aggressive periodontitis using genome-wide association studies

Aggressive periodontitis (AgP), Stage III or IV and Grade C according to the new periodontitis classification, is characterized by the rapid destruction of periodontal tissues in the systemically healthy population and often causes premature tooth loss. The presence of familial aggregation suggests the involvement of genetic factors in the pathogenesis. However, the genes associated with the onset and progression of the disease and details of its pathogenesis have not yet been fully identified. In recent years, the genome-wide approach (GWAS), a comprehensive genome analysis method using bioinformatics, has been used to search for disease-related genes, and the results have been applied in genomic medicine for various diseases, such as cancer. In this review, we discuss GWAS in the context of AgP. First, we introduce the relationship between single-nucleotide polymorphisms (SNPs) and susceptibility to diseases and how GWAS is useful for searching disease-related SNPs. Furthermore, we summarize the recent findings of disease-related genes using GWAS on AgP inside and outside Japan and a possible mechanism of the pathogenesis of AgP based on available literature and our research findings. These findings will lead to advancements in the prevention, prognosis, and treatment of AgP.

Understanding the consequences of leisure sedentary behavior on periodontitis: A two-step, multivariate Mendelian randomization study

Background

The relationship between leisure sedentary behavior (LSB) and periodontitis risk remains unclear in terms of causality and the potential mediating effects of intermediate factors.

Materials and methods

Using the aggregate data of several large-scale genetic association studies from participants of European descent, we conducted a univariate, two-step, and multivariate Mendelian random (MR) analysis to infer the overall effect of LSB on periodontitis, and quantified the intermediary proportion of intermediary traits such as smoking.

Results

Our findings indicated that per 1-SD increase (1.87 h) in leisure screen time (LST), there was a 23 % increase in the risk of periodontitis. [odds ratios (95 % CI) = 1.23 (1.04-1.44), p = 0.013]. Smoking was found to partially mediate the overall causal effect of LST on periodontitis, with a mediation rate of 20.7 % (95 % CI: 4.9%-35.5 %). Multivariate MR analysis demonstrated that the causal effect of LST on periodontitis was weakened when adjusting for smoking, resulting in an odds ratio of 1.19 (95 % CI: 1.01-1.39, p = 0.049) for each 1 standard deviation increase in exposure.

Conclusion

The study provides evidence of a potential causal relationship between LSB characterized by LST and periodontitis, thereby further supporting the notion that reducing LSB is beneficial for health. Furthermore, it confirms the role of smoking as a mediator in this process, suggesting that inhibiting smoking behavior among individuals with long-term LSB may serve as a strategy to mitigate the risk of periodontitis.

Genetically predicted causal associations between periodontitis and psychiatric disorders

BACKGROUND

Psychiatric disorders have serious harm to individuals' lives with high disease burden. Observational studies reported inconsistent associations between periodontitis and some psychiatric disorders, and the causal correlations between them remain unknown.

OBJECTIVE

This study aims to explore the causal associations between periodontitis and psychiatric disorders.

METHODS

A series of two-sample Mendelian randomisation (MR) analyses were employed using genome-wide association study summary statistics for periodontitis in adults from Gene-Lifestyle Interactions in Dental Endpoints Consortium and 10 psychiatric disorders from Psychiatric Genomics Consortium. Causal effects were primarily estimated using the inverse-variance weighted (IVW) method. Various sensitivity analyses were also conducted to assess the robustness of our results.

FINDINGS

The MR analysis suggested that genetically determined periodontitis was not causally associated with 10 psychiatric disorders (IVW, all p>0.089). Furthermore, the reverse MR analysis revealed that 10 psychiatric disorders had no causal effect on periodontitis (IVW, all p>0.068). We discovered that all the results were consistent in the four MR analytical methods, including the IVW, MR-Egger, weighted median and weighted mode. Besides, we did not identify any heterogeneity or horizontal pleiotropy in the sensitivity analysis.

CONCLUSIONS

These results do not support bidirectional causal associations between genetically predicted periodontitis and 10 common psychiatric disorders. Potential confounders might contribute to the previously observed associations.

CLINICAL IMPLICATIONS

Our findings might alleviate the concerns of patients with periodontitis or psychiatric disorders. However, further research was warranted to delve into the intricate relationship between dental health and mental illnesses.

Investigation on the association between serum lipid levels and periodontitis: a bidirectional Mendelian randomization analysis

OBJECTIVE

Several research has considered the potential correlation between periodontitis and serum lipids. However, serum lipid profiles correlation with periodontitis remains largely unknown. The investigation objective was to examine periodontitis correlation with serum lipid levels using a bidirectional Mendelian randomization (MR) analysis.

METHODS

The study employed a bidirectional MR analysis with two samples, utilizing a freely accessible genome-wide association study (GWAS). Furthermore, the primary analysis employed the inverse variance weighted (IVW) method. To determine whether the lipid profiles were associated with periodontitis, a variety of sensitivity analyses (including MR-Egger regression, MR-PRESSO, and weighted median), as well as multivariable MR, were employed.

RESULTS

MR analysis performed by IVW did not reveal any relationship between periodontitis and low-density lipoprotein (LDL), high-density lipoprotein (HDL), triglycerides (TG), or total cholesterol (TC). It was also found that LDL, HDL, TG, and TC were not associated to periodontitis. Furthermore, the MR estimations exhibited consistency with other MR sensitivity and multivariate MR (MVMR) analyses. These results show that the correlation between serum lipid levels and periodontitis could not be established.

CONCLUSION

The finding indicates a negligible link between periodontitis and serum lipid levels were identified, despite previous observational studies reporting a link between periodontitis and serum lipid levels.

The co-occurrence of the two main oral diseases: periodontitis and dental caries

OBJECTIVES

Limited studies are available testing through multiple regression models the association between the two main oral diseases: dental caries and periodontitis. The aim of this cross-sectional population-based study was to verify whether dental caries and periodontitis co-occur in a representative sample of the South Korea population.

MATERIALS AND METHODS

A total of 23,405 subjects representative of 36.2 million of adults (KNHANES) were examined. Univariate and multiple regression analyses using 7 different models were applied, controlling for age, gender, smoking status, frequency of toothbrushing, use of interproximal toothbrushes and flossing, educational level, income, gum diseases treatment and tooth filling in the previous year, BMI, Vitamin D serum levels, alcoholism, diabetes status, stress and carbohydrates dietary intake.

RESULTS

In the fully adjusted model, participants with periodontitis had, respectively, a mean of 0.82 (95% CI: 0.41-1.23) and of 0.36 (95% CI: 0.22-0.50) more untreated decayed surfaces and teeth than participants without periodontitis, with an OR to have at least one untreated decayed surface of 1.96 (95% CI: 1.66-2.32). However, cumulative caries experience (DF scores) and periodontitis were not associated.

CONCLUSIONS

In this large nationally representative population, periodontitis and untreated dental caries co-occur. However, when considering cumulative caries experience (DF scores), the two diseases do not appear related.

CLINICAL RELEVANCE

In light of their possible co-occurrence, clinicians should implement integrative diagnostic, preventive and treatment strategies for both diseases.

Deciphering genetic causality between inflammatory bowel disease and periodontitis through bi-directional two-sample Mendelian randomization

Inflammatory bowel disease (IBD) and periodontitis are reported to be closely associated; however, whether there is a causal association between them remains unclear. To explore the existence of this causality, this study applied a bidirectional two-sample Mendelian randomization (MR). The genetic variants were obtained from the summary statistics of genome-wide association studies of IBD, including its subtypes CD and UC, and periodontitis. 175, 148, 113, and six single-nucleotide polymorphisms were selected as instrumental variables for IBD, CD, UC, and periodontitis, respectively. In MR analysis, random-effects inverse-variance weighted was used as the primary method, and weighted median and MR Egger regression were applied as the complementary method. A series of sensitivity analyses were also conducted to ensure the reliability of the results. None of these analyses found a significant effect of genetically proxied IBD and its subtypes on periodontitis, and vice versa. Subsequent sensitivity analyses did not detect any horizontal pleiotropy and heterogeneity. Caution should be exerted when it comes to clinical relevance and further studies are needed to clarify the relationship between IBD and periodontitis.

Type 1 diabetes, glycemic traits, and risk of dental caries: a Mendelian randomization study

Background: Regarding past epidemiological studies, there has been disagreement over whether type 1 diabetes (T1DM) is one of the risk factors for dental caries. The purpose of this study was to determine the causative links between genetic susceptibility to T1DM, glycemic traits, and the risk of dental caries using Mendelian randomization (MR) approaches. Methods: Summary-level data were collected on genome-wide association studies (GWAS) of T1DM, fasting glucose (FG), glycated hemoglobin (HbA1c), fasting insulin (FI), and dental caries. MR was performed using the inverse-variance weighting (IVW) method, and sensitivity analyses were conducted using the MR-Egger method, weighted median, weighted mode, replication cohort, and multivariable MR conditioning on potential mediators. Results: The risk of dental caries increased as a result of genetic susceptibility to T1DM [odds ratio (OR) = 1.044; 95% confidence interval (CI) = 1.015-1.074; p = 0.003], with consistent findings in the replication cohort. The relationship between T1DM and dental caries was stable when adjusted for BMI, smoking, alcohol intake, and type 2 diabetes (T2DM) in multivariable MR. However, no significant correlations between the risk of dental caries and FG, HbA1c, or FI were found. Conclusion: These results indicate that T1DM has causal involvement in the genesis of dental caries. Therefore, periodic reinforcement of oral hygiene instructions must be added to the management and early multidisciplinary intervention of T1DM patients, especially among adolescents and teenagers, who are more susceptible to T1DM.

Genome-wide association study identifies novel caries-associated loci showing sex-specificity-A study on the Northern Finland Birth Cohort 1966

A genome-wide association study was performed in sex-stratified groups representing three different caries phenotypes among adults. The study sample consisted of 46-year-old participants of the Northern Finland Birth Cohort 1966 study (n = 1481). The phenotypes for analyses were the dentin caries phenotype (persons having at least one tooth with dentin caries lesion), and the enamel caries phenotype (those having teeth with more than 10 enamel caries lesions), while the control group had <10 enamel caries lesions and no teeth with dentin caries, respectively. A third phenotype dubbed the caries severity phenotype had a below-average number of teeth with initial lesions and at least one extensive dentin caries lesion; their controls had an above-average number of teeth with initial caries lesions and no teeth with extensive dentin caries lesions. All analyses were performed for the whole group and for sex-stratified subgroups. In females, loci in chromosomes 2, 5, and 15 showed a statistically significant association with caries severity. In males, there was a novel association between chromosome 5 and dentin caries. The results of this study may suggest a genetic background of caries among adults. In the future, the detection of genetic predisposing variants may allow the identification of patients at risk for caries, even in the absence of behavioral and environmental risk factors.

Genome-wide Association Study Identifies Novel Risk Loci for Apical Periodontitis

INTRODUCTION

Apical periodontitis (AP) is a common consequence of root canal infection leading to periapical bone resorption. Microbial and host genetic factors and their interactions have been shown to play a role in AP development and progression. Variations in a few genes have been reported in association with AP; however, the lack of genome-wide studies has hindered progress in understanding the molecular mechanisms involved. Here, we report the first genome-wide association study of AP in a large and well-characterized population.

METHODS

Male and female adults (n = 932) presenting with deep caries and AP (cases), or deep caries without AP (controls) were included. Genotyping was performed using the Illumina Expanded Multi-Ethnic Genotyping Array (MEGA). Single-variant association testing was performed adjusting for sex and 5 principal components. Subphenotype association testing, analyses of genetically regulated gene expression, polygenic risk score, and phenome-wide association (PheWAS) analyses were also conducted.

RESULTS

Eight loci reached near genome-wide significant association with AP (P < 5 × 10-6); gene-focused analyses replicated 3 previously reported associations (P < 8.9 × 10-5). Sex-specific and subphenotype-specific analyses revealed additional significant associations with variants genome-wide. Functionally oriented gene-based analyses revealed 8 genes significantly associated with AP (P < 5 × 10-5), and PheWAS analysis revealed 33 phecodes associated with AP risk score (P < 3.08 × 10-5).

CONCLUSIONS

This study identified novel genes/loci contributing to AP and specific contributions to AP risk in men and women. Importantly, we identified additional systemic conditions significantly associated with AP risk. Our findings provide strong evidence for host-mediated effects on AP susceptibility.