Pathophysiological association between periodontal disease and Alzheimer's disease: Importance of periodontal health in the elderly

Increased IgA-mediated responses to the gut paracellular pathway and blood-brain barrier proteins predict delirium due to hip fracture in older adults

Introduction

Delirium is accompanied by immune response system activation, which may, in theory, cause a breakdown of the gut barrier and blood-brain barrier (BBB). Some results suggest that the BBB is compromised in delirium, but there is no data regarding the gut barrier. This study investigates whether delirium is associated with impaired BBB and gut barriers in elderly adults undergoing hip fracture surgery.

Methods

We recruited 59 older adults and measured peak Delirium Rating Scale (DRS) scores 2-3 days after surgery, and assessed plasma IgG/IgA levels (using ELISA techniques) for zonulin, occludin, claudin-6, β-catenin, actin (indicating damage to the gut paracellular pathway), claudin-5 and S100B (reflecting BBB damage), bacterial cytolethal distending toxin (CDT), LPS-binding protein (LBP), lipopolysaccharides (LPS), Porphyromonas gingivalis, and Helicobacter pylori.

Results

Results from univariate analyses showed that delirium is linked to increased IgA responses to all the self-epitopes and antigens listed above, except for LPS. Part of the variance (between 45-48.3%) in the peak DRS score measured 2-3 days post-surgery was explained by independent effects of IgA directed to LPS and LBP (or bacterial CDT), baseline DRS scores, and previous mild stroke. Increased IgA reactivity to the paracellular pathway and BBB proteins and bacterial antigens is significantly associated with the activation of M1 macrophage, T helper-1, and 17 cytokine profiles.

Conclusion

Heightened bacterial translocation, disruption of the tight and adherens junctions of the gut and BBB barriers, elevated CDT and LPS load in the bloodstream, and aberrations in cell-cell interactions may be risk factors for delirium.

Advances in the Study of the Pathology and Treatment of Alzheimer's Disease and Its Association with Periodontitis

Alzheimer's disease (AD) has become one of the leading causes of health problems in the elderly, and studying its causes and treatments remains a serious challenge for researchers worldwide. The two main pathological features of Alzheimer's disease are the extracellular deposition of β-amyloid (Aβ) to form senile plaques and the intracellular aggregation of hyperphosphorylated Tau protein to form neurofibrillary tangles (NFTs). Researchers have proposed several hypotheses to elucidate the pathogenesis of AD, but due to the complexity of the pathophysiologic factors involved in the development of AD, no effective drugs have been found to stop the progression of the disease. Currently, the mainstay drugs used to treat AD can only alleviate the patient's symptoms and do not have a therapeutic effect. As researchers explore interactions among diseases, much evidence suggests that there is a close link between periodontitis and AD, and that periodontal pathogenic bacteria can exacerbate Aβ deposition and Tau protein hyperphosphorylation through neuroinflammatory mechanisms, thereby advancing the pathogenesis of AD. This article reviews recent advances in the pathogenesis of AD, available therapeutic agents, the relevance of periodontitis to AD, and mechanisms of action.

Association of tooth count with cognitive decline and dementia in the Finnish adult population

AIM

To evaluate whether tooth loss is associated with cognitive decline and incident dementia.

MATERIALS AND METHODS

We analysed data from the Finnish population-based Health 2000 and follow-up Health 2011 surveys (participants aged ≥30 years and without dementia at baseline; N = 5506 at baseline and 3426 at 11-year follow-up). Dementia diagnoses until 2015 were ascertained from national registers (N = 5542). Tooth count was dichotomized as adequate (≥20) versus tooth loss (<20). Tooth loss was further stratified into 10-19 teeth, 1-9 teeth and edentulism. Upper and lower jaws were also considered separately. Baseline cognitive test scores were dichotomized by median as high versus low, and 11-year change as decline versus no decline.

RESULTS

Tooth loss (<20) was associated with lower baseline overall cognition (odds ratio [OR] = 1.21, 95% confidence interval [CI] = 1.03-1.43), 11-year cognitive decline (OR = 1.30, 95% CI = 1.05-1.70) and higher 15-year dementia risk (hazard ratio = 1.52, 95% CI = 1.15-2.02) after adjusting for multiple confounders. After adjustment for dentures, associations became non-significant, except for 10-19 teeth remaining and dementia. Results were similar after considering reverse causality bias; however, 10-19 teeth remaining was significantly associated with 11-year cognitive decline even after adjustment for dentures. No jaw-specific differences were observed.

CONCLUSIONS

Tooth loss adversely impacts the risk of cognitive decline and dementia. The role of dentures should be further explored.

Interdisciplinary Approaches to Deal with Alzheimer's Disease-From Bench to Bedside: What Feasible Options Do Already Exist Today?

Alzheimer's disease is one of the most common neurodegenerative diseases in the western population. The incidence of this disease increases with age. Rising life expectancy and the resulting increase in the ratio of elderly in the population are likely to exacerbate socioeconomic problems. Alzheimer's disease is a multifactorial disease. In addition to amyloidogenic processing leading to plaques, and tau pathology, but also other molecular causes such as oxidative stress or inflammation play a crucial role. We summarize the molecular mechanisms leading to Alzheimer's disease and which potential interventions are known to interfere with these mechanisms, focusing on nutritional approaches and physical activity but also the beneficial effects of cognition-oriented treatments with a focus on language and communication. Interestingly, recent findings also suggest a causal link between oral conditions, such as periodontitis or edentulism, and Alzheimer's disease, raising the question of whether dental intervention in Alzheimer's patients can be beneficial as well. Unfortunately, all previous single-domain interventions have been shown to have limited benefit to patients. However, the latest studies indicate that combining these efforts into multidomain approaches may have increased preventive or therapeutic potential. Therefore, as another emphasis in this review, we provide an overview of current literature dealing with studies combining the above-mentioned approaches and discuss potential advantages compared to monotherapies. Considering current literature and intervention options, we also propose a multidomain interdisciplinary approach for the treatment of Alzheimer's disease patients that synergistically links the individual approaches. In conclusion, this review highlights the need to combine different approaches in an interdisciplinary manner, to address the future challenges of Alzheimer's disease.

Periodontal health, cognitive decline, and dementia: A systematic review and meta-analysis of longitudinal studies

BACKGROUND

Emerging evidence indicates that poor periodontal health adversely impacts cognition. This review examined the available longitudinal evidence concerning the effect of poor periodontal health on cognitive decline and dementia.

METHODS

Comprehensive literature search was conducted on five electronic databases for relevant studies published until April 2022. Longitudinal studies having periodontal health as exposure and cognitive decline and/or dementia as outcomes were considered. Random effects pooled estimates and 95% confidence intervals were generated (pooled odds ratio for cognitive decline and hazards ratio for dementia) to assess whether poor periodontal health increases the risk of cognitive decline and dementia. Heterogeneity between studies was estimated by I2 and the quality of available evidence was assessed through quality assessment criteria.

RESULTS

Adopted search strategy produced 2132 studies for cognitive decline and 2023 for dementia, from which 47 studies (24 for cognitive decline and 23 for dementia) were included in this review. Poor periodontal health (reflected by having periodontitis, tooth loss, deep periodontal pockets, or alveolar bone loss) was associated with both cognitive decline (OR = 1.23; 1.05-1.44) and dementia (HR = 1.21; 1.07-1.38). Further analysis, based on measures of periodontal assessment, found tooth loss to independently increase the risk of both cognitive decline (OR = 1.23; 1.09-1.39) and dementia (HR = 1.13; 1.04-1.23). Stratified analysis based on the extent of tooth loss indicated partial tooth loss to be important for cognitive decline (OR = 1.50; 1.02-2.23) and complete tooth loss for dementia (HR = 1.23; 1.05-1.45). However, the overall quality of evidence was low, and associations were at least partly due to reverse causality.

CONCLUSIONS

Poor periodontal health and tooth loss appear to increase the risk of both cognitive decline and dementia. However, the available evidence is limited (e.g., highly heterogenous, lacking robust methodology) to draw firm conclusions. Further well-designed studies involving standardized periodontal and cognitive health assessment and addressing reverse causality are highly warranted.

Dental follicle cells derived small extracellular vesicles inhibit pathogenicity of Porphyromonas gingivalis

OBJECTIVE

It aims to explore the effect of dental follicle cells derived small extracellular vesicles (D-sEV) with or without lipopolysaccharides (LPS) pretreating on the pathogenicity of Porphyromonas gingivalis (P. gingivalis).

METHODS

The antibacterial effects of D-sEV were evaluated by measuring the growth, biofilm formation, gingipains and type IX secretion system (T9SS) expression of P. gingivalis. And the influence of D-sEV on P. gingivalis adhesion, invasion, cytotoxicity, and host immune response was examined in gingival epithelial cells (GECs). Then P. gingivalis treated with D-sEV was applied to investigate the pathogenicity in experimental periodontitis of mice.

RESULTS

It showed that both D-sEV and P. gingivalis LPS pretreated D-sEV (L-D-sEV) could target P. gingivalis, inhibit their growth and biofilm formation, and hinder the attachment and invasion in GECs, therefore remarkably decreasing P. gingivalis cytotoxicity and the expression of IL-1β and IL-6 in GECs. In addition, they significantly reduced the expression of P. gingivalis virulence factors (gingipains and T9SS). In vivo, it showed that the bacteria in the gingiva were significantly decreased after sEV treatment. Meanwhile, less bone loss and fewer inflammatory cells infiltration and osteoclast formation in D-sEV and L-D-sEV groups.

CONCLUSION

Both D-sEV and L-D-sEV were proven to inhibit the pathogenicity of P.gingivalis and thus prevented the development of periodontitis.

Oral biosciences: The annual review 2021

BACKGROUND

The Journal of Oral Biosciences is devoted to advancing and disseminating fundamental knowledge concerning every aspect of oral biosciences.

HIGHLIGHT

This review features review articles in the fields of "Extracellular Vesicles," "Propolis," "Odontogenic Tumors," "Periodontitis," "Periodontium," "Flavonoids," "Lactoferrin," "Dental Plaque," "Anatomy," "Induced Pluripotent Stem Cells," "Bone Cell Biology," "Dysgeusia," "Dental Caries," and "Dental Pulp Cavity," in addition to the review article by the winners of the "Lion Award" ("Sox9 function in salivary gland development") presented by the Japanese Association for Oral Biology.

CONCLUSION

These reviews in the Journal of Oral Biosciences have inspired its readers to broaden their knowledge regarding various aspects of oral biosciences. The current editorial review introduces these exciting review articles.