Oral Health as a Risk Factor for Alzheimer Disease

Detection of Amyloid-β Peptides in Gingival Crevicular Fluid and Its Effect on Oral Pathogens

Periodontitis is the most common oral inflammatory disease, contributing to the onset and progression of Alzheimer's disease. However, a full investigation has not been performed on the expression level of amyloid-β (Aβ) peptides in gingival crevicular fluid (GCF) and its effects on oral pathogens. This study aimed to analyze the expression level of Aβ peptides in GCF of patients with periodontitis and the effects of Aβ peptides against common oral pathogens. GCF samples were collected from patients with periodontitis (n = 15) and periodontally healthy people (n = 10). The antimicrobial effects of Aβ peptides were evaluated on four common oral pathogenic strains using an MTT assay, crystal violet staining, fluorescence microscope, and transmission electron microscope. The protein levels of Aβ40 and Aβ42 were upregulated in the GCF of periodontitis group compared with the healthy group. Both Aβ40 and Aβ42 exhibited antimicrobial effects on Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, and Lactobacillus acidophilus in both planktonic and biofilm conditions. Further, only Aβ40 showed an antimicrobial effect on the Fusobacterium nucleatum. The results of this study demonstrate that Aβ peptides in GCF may be a relevant indicator of periodontitis status. Besides, the antimicrobial peptides derived from Aβ peptides have great potential in periodontal therapy.

Comparison of light gradient boosting and logistic regression for interactomic hub genes in Porphyromonas gingivalis and Fusobacterium nucleatum-induced periodontitis with Alzheimer's disease

Introduction

Porphyromonas gingivalis and Treponema species have been found to invade the central nervous system through virulence factors, causing inflammation and influencing the host immune response. P. gingivalis interacts with astrocytes, microglia, and neurons, leading to neuroinflammation. Aggregatibacter actinomycetemcomitans and Fusobacterium nucleatum may also play a role in the development of Alzheimer's disease. Interactomic hub genes, central to protein-protein interaction networks, are vulnerable to perturbations, leading to diseases such as cancer, neurodegenerative disorders, and cardiovascular diseases. Machine learning can identify differentially expressed hub genes in specific conditions or diseases, providing insights into disease mechanisms and developing new therapeutic approaches. This study compares the performance of light gradient boosting and logistic regression in identifying interactomic hub genes in P. gingivalis and F. nucleatum-induced periodontitis with those in Alzheimer's disease.

Methods

Using the GSE222136 dataset, we analyzed differential gene expression in periodontitis and Alzheimer's disease. The GEO2R tool was used to identify differentially expressed genes under different conditions, providing insights into molecular mechanisms. Bioinformatics tools such as Cytoscape and CytoHubba were employed to create gene expression networks to identify hub genes. Logistic regression and light gradient boosting were used to predict interactomic hub genes, with outliers removed and machine learning algorithms applied.

Results

The data were cross-validated and divided into training and testing segments. The top hub genes identified were TNFRSF9, LZIC, TNFRSF8, SLC45A1, GPR157, and SLC25A33, which are induced by P. gingivalis and F. nucleatum and are responsible for endothelial dysfunction in brain cells. The accuracy of logistic regression and light gradient boosting was 67% and 60%, respectively.

Discussion

The logistic regression model demonstrated superior accuracy and balance compared to the light gradient boosting model, indicating its potential for future improvements in predicting hub genes in periodontal and Alzheimer's diseases.

Oral Health Status and Factors Associated with Oral Health in Patients with Alzheimer's Disease: A Matched Case-Control Observational Study

Background: Alzheimer's disease (AD) is a chronic neurodegenerative disease, ranking as the seventh leading cause of death in both sexes. There is increasing awareness of the role of chronic periodontal disease and severe tooth loss as a modifiable risk factor for developing AD. The aim of the present observational study was to assess AD patients with non-affected healthy controls in the context of their dental and periodontal health outcomes; additionally, the potential impact of anamnestic factors and lifestyle habits on oral health outcomes was also studied. Methods: A total of n = 41 AD patients receiving treatment at the Department of Psychiatry, University of Szeged, were compared with n = 41 age- and gender-matched controls from individuals seeking dental treatment and from retirement homes (mean age was 83.32 ± 7.82 years). Dental and periodontal status indices were assessed according to World Health Organization (WHO) criteria. Results: Overall, 51.2%, 68.3%, and 87.8% of AD patients received mood stabilizers, drugs for their non-cognitive symptoms and cognitive symptoms, respectively. Severe tooth loss was observed in 43.9% of AD patients and 56.1% of controls, respectively. There were no significant differences among AD patients and controls regarding the dental status indices studied (p > 0.05 for all indicators). AD patients had significantly higher plaque indices (%) (59.06 ± 15.45 vs. 41.35 ± 7.97; p < 0.001), bleeding on probing (BOP%) (62.65 ± 12.00 vs. 40.12 ± 10.86; p < 0.001), pocket depth [PD] (2.63 ± 0.56 vs. 2.29 ± 0.13; p = 0.002) and attachment loss [AL] (2.85 ± 0.79 vs. 2.39 ± 0.41; p = 0.026) values, compared to controls. Smoking (vs. non-smokers; 56.28 ± 12.36 vs. 51.40 ± 13.23, p = 0.038) and consumption of alcohol (vs. non-drinkers; 58.68 ± 9.86 vs. 54.78 ± 14.86, p = 0.040) were associated with higher plaque indices [%], while no similar effects were shown for dental status parameters (p > 0.05). In contrast, coffee intake and vitamin supplement use had no significant effect on dental or periodontal status parameters (p > 0.05 in all cases). Conclusions: The results of our study underscore the substantial treatment needs of AD patients, calling for heightened awareness among dental healthcare professionals.

Microbial Trojan Horses: Virulence Factors as Key Players in Neurodegenerative Diseases

Changes in population demographics indicate that the elderly population will reach 2.1 billion worldwide by 2050. In parallel, there will be an increase in neurodegenerative diseases such as Alzheimer's and Parkinson's. This review explores dysbiosis occurring in these pathologies and how virulence factors contribute to the worsening or development of clinical conditions, and it summarizes existing and potential ways to combat microorganisms related to these diseases. Microbiota imbalances can contribute to the progression of neurodegenerative diseases by increasing intestinal permeability, exchanging information through innervation, and even acting as a Trojan horse affecting immune cells. The microorganisms of the microbiota produce virulence factors to protect themselves from host defenses, many of which contribute to neurodegenerative diseases. These virulence factors are expressed according to the genetic composition of each microorganism, leading to a wide range of factors to be considered. Among the main virulence factors are LPS, urease, curli proteins, amyloidogenic proteins, VacA, and CagA. These factors can also be packed into bacterial outer membrane vesicles, which transport proteins, RNA, and DNA, enabling distal communication that impacts various diseases, including Alzheimer's and Parkinson's.

Loss of dental pulp potentially increased the risk of Alzheimer's dementia

Background/purpose

Chronic periodontitis and tooth loss contribute to cognitive decline. Since many biological processes are shared by loss of teeth and loss of pulps, this study investigated the potential association between loss of pulp and the development of dementia.

Materials and methods

A retrospective cohort analysis was conducted to investigate the association between dental treatment and the development of dementia. The records of dental treatment during the 10 years prior to the first diagnosis of dementia were extracted from the Elderly Cohort Database of the National Health Information Sharing Service of Korea. The independence of dementia compared to the number of pulps or teeth removed was evaluated using the chi-squared test. The subjects were grouped by the number of teeth or pulps treated, and their odds ratio for dementia was calculated.

Results

Analysis of 591,592 sessions for pulpectomy and 710,722 sessions for tooth extraction from 558,147 individuals revealed a significant association with Alzheimer's dementia, but not with vascular or unspecified dementia. The number of dementia patients based on the number of pulps or teeth extracted were significantly different across age groups. The odds ratios demonstrated a tendency to increase with the number of dental treatments and decrease with age at the time of diagnosis of dementia. The number of pulps removed to achieve a notable impact on Alzheimer's dementia was found to be lower than the number of teeth extracted.

Conclusion

The loss of pulp increased incidence of Alzheimer's dementia, with the impact being more pronounced in younger geriatric groups.

Oral Health and Its Associated Factors Among the Elderly in the Emergency Department: A Latent Class Analysis

Purpose

The objective of this study was to investigate latent classes of oral health and the factors associated with them in acutely admitted elderly inpatients.

Patients and Methods

A cross-sectional study was conducted using purposive sampling to survey Chinese older-adult acutely inpatients. Data was collected utilizing several instruments, including a general information questionnaire, Brief Oral Health Status Examination (BOHSE), Oral Frailty Index-8 (OFI-8), Mini-Nutritional Assessment Short Form (MNA-SF), and Frailty Screening Questionnaire (FSQ). Latent class analysis was applied to identify distinct categories of oral health among elderly inpatients, and multinomial logistic regression was employed to analyze the factors associated with different oral health categories.

Results

In this study, a total of 504 elderly patients were ultimately included, leading to the identification of three latent classes of oral health: "oral health-low level group (41.27%)", "oral health-moderate level group (25.4%)", and "oral health-high level group (33.33%)". The findings revealed that patients with advanced age, elevated neutrophil percentage, and higher C-reactive protein (CRP) values were more likely to be classified in the low oral health group. Additionally, individuals experiencing malnutrition and frailty had a higher risk of falling into the low oral health category. Those with comorbidities and oral frailty were more prevalent in the moderate oral health group. At the same time, elderly patients with higher BMI (22.95±3.043) ratios were more likely to be categorized in the high oral health group.

Conclusion

This study sheds light on three distinct latent classes of oral health among acutely admitted elderly inpatients. These findings underscore the importance of healthcare professionals focusing on the assessment and health education of elderly patients' oral health. Furthermore, personalized interventions should be developed to promote healthy aging, with particularly attention to enhancing oral health outcomes in this population.

Update on modifiable risk factors for Alzheimer's disease and related dementias

PURPOSE OF REVIEW

All human beings undergo a lifelong cumulative exposure to potentially preventable adverse factors such as toxins, infections, traumatisms, and cardiovascular risk factors, collectively termed exposome. The interplay between the individual's genetics and exposome is thought to have a large impact in health outcomes such as cancer and cardiovascular disease. Likewise, a growing body of evidence is supporting the idea that preventable factors explain a sizable proportion of Alzheimer's disease and related dementia (ADRD) cases.

RECENT FINDINGS

Here, we will review the most recent epidemiological, experimental preclinical, and interventional clinical studies examining some of these potentially modifiable risk factors for ADRD. We will focus on new evidence regarding cardiovascular risk factors, air pollution, viral and other infectious agents, traumatic brain injury, and hearing loss.

SUMMARY

While greater and higher quality epidemiological and experimental evidence is needed to unequivocally confirm their causal link with ADRD and/or unravel the underlying mechanisms, these modifiable risk factors may represent a window of opportunity to reduce ADRD incidence and prevalence at the population level via health screenings, and education and health policies.

The "Hit and Run" Hypothesis for Alzheimer's Disease Pathogenesis

Alzheimer's disease (AD) is a devastating neurodegenerative disorder affecting millions worldwide. Emerging research has challenged the conventional notion of a direct correlation between amyloid deposition and neurodegeneration in AD. Recent studies have suggested that amyloid and Tau deposition act as a central nervous system (CNS) innate immune driver event, inducing chronic microglial activation that increases the susceptibility of the AD brain to the neurotoxicity of infectious insults. Although modifiable risk factors account for up to 50% of AD risk, the mechanisms by which they interact with the core process of misfolded protein deposition and neuroinflammation in AD are unclear and require further investigation. This update introduces a novel perspective, suggesting that modifiable risk factors act as external insults that, akin to infectious agents, cause neurodegeneration by inducing recurrent acute neurotoxic microglial activation. This pathological damage occurs in AD pathology-primed regions, creating a "hit and run" mechanism that leaves no discernible pathological trace of the external insult. This model, highlighting microglia as a pivotal player in risk factor-mediated neurodegeneration, offers a new point of view on the complex associations of modifiable risk factors and proteinopathy in AD pathogenesis, which may act in parallel to the thoroughly studied amyloid-driven Tau pathology, and strengthens the therapeutic rationale of combining immune modulation with tight control of risk factor-driven insults.