Helicobacter pylori seropositivity and its association with incident all-cause and Alzheimer's disease dementia in large national surveys

Specific and cumulative infection burden and mild cognitive impairment and dementia: A population-based study

Infection by pathogenic microbes is widely hypothesized to be a risk factor for the development of neurocognitive disorders and dementia, but evidence remains limited. We analyzed the association of seropositivity to 11 common pathogens and cumulative infection burden with neurocognitive disorder (mild cognitive impairment and dementia) in a population-based cohort of 475 older individuals (mean age = 67.6 y) followed up over 3-5 years for the risk of MCI-dementia. Specific seropositivities showed a preponderance of positive trends of association with MCI-dementia, including for Plasmodium, H. pylori, and RSV (p < 0.05), as well as Chickungunya, HSV-2, CMV and EBV (p > 0.05), while HSV-1 and HHV-6 showed equivocal or no associations, and Dengue and VZV showed negative associations (p < 0.05) with MCI-dementia. High infection burden (5 + cumulated infections) was significantly associated with an increased MCI-dementia risk in comparison with low infection burden (1-3 cumulative infections), adjusted for age, sex, and education. Intriguingly, for a majority (8 of 11) of pathogens, levels of antibody titers were significantly lower in those with MCI-dementia compared to cognitive normal individuals. Based on our observations, we postulate that individuals who are unable to mount strong immunological responses to infection by diverse microorganisms, and therefore more vulnerable to infection by greater numbers of different microbial pathogens or repeated infections to the same pathogen in the course of their lifetime are more likely to develop MCI or dementia. This hypothesis should be tested in more studies.

Smoking Impacts Alzheimer's Disease Progression Through Oral Microbiota Modulation

Alzheimer's disease (AD) is an important public health challenge with a limited understanding of its pathogenesis. Smoking is a significant modifiable risk factor for AD progression, and its specific mechanism is often interpreted from a toxicological perspective. However, microbial infections also contribute to AD, with oral microbiota playing a crucial role in its progression. Notably, smoking alters the ecological structure and pathogenicity of the oral microbiota. Currently, there is no systematic review or summary of the relationship between these three factors; thus, understanding this association can help in the development of new treatments. This review summarizes the connections between smoking, AD, and oral microbiota from existing research. It also explores how smoking affects the occurrence and development of AD through oral microbiota, and examines treatments for oral microbiota that delay the progression of AD. Furthermore, this review emphasizes the potential of the oral microbiota to act as a biomarker for AD. Finally, it considers the feasibility of probiotics and oral antibacterial therapy to expand treatment methods for AD.

Peripheral extracellular vesicles in neurodegeneration: pathogenic influencers and therapeutic vehicles

Neurodegenerative diseases (NDDs) such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis epitomize a class of insidious and relentless neurological conditions that are difficult to cure. Conventional therapeutic regimens often fail due to the late onset of symptoms, which occurs well after irreversible neurodegeneration has begun. The integrity of the blood-brain barrier (BBB) further impedes efficacious drug delivery to the central nervous system, presenting a formidable challenge in the pharmacological treatment of NDDs. Recent scientific inquiries have shifted focus toward the peripheral biological systems, investigating their influence on central neuropathology through the lens of extracellular vesicles (EVs). These vesicles, distinguished by their ability to breach the BBB, are emerging as dual operatives in the context of NDDs, both as conveyors of pathogenic entities and as prospective vectors for therapeutic agents. This review critically summarizes the burgeoning evidence on the role of extracerebral EVs, particularly those originating from bone, adipose tissue, and gut microbiota, in modulating brain pathophysiology. It underscores the duplicity potential of peripheral EVs as modulators of disease progression and suggests their potential as novel vehicles for targeted therapeutic delivery, positing a transformative impact on the future landscape of NDD treatment strategies. Search strategy A comprehensive literature search was conducted using PubMed, Web of Science, and Scopus from January 2000 to December 2023. The search combined the following terms using Boolean operators: "neurodegenerative disease" OR "Alzheimer's disease" OR "Parkinson's disease" OR "Amyotrophic lateral sclerosis" AND "extracellular vesicles" OR "exosomes" OR "outer membrane vesicles" AND "drug delivery systems" AND "blood-brain barrier". MeSH terms were employed when searching PubMed to refine the results. Studies were included if they were published in English, involved human subjects, and focused on the peripheral origins of EVs, specifically from bone, adipose tissue, and gut microbiota, and their association with related diseases such as osteoporosis, metabolic syndrome, and gut dysbiosis. Articles were excluded if they did not address the role of EVs in the context of NDDs or did not discuss therapeutic applications. The titles and abstracts of retrieved articles were screened using a dual-review process to ensure relevance and accuracy. The reference lists of selected articles were also examined to identify additional relevant studies.

Association between Helicobacter pylori infection and incident risk of dementia: The AMI cohort

BACKGROUND

Chronic infectious diseases are increasingly being considered as potential contributors to dementia risk. Among those infections, Helicobacter pylori, the main cause of chronic gastritis worldwide, has been suggested. As the prevalence of H. pylori infection has decreased, the main objective of this work was to reconsider the association between H. pylori infection and the risk of incident dementia, including Alzheimer's disease.

METHODS

Prospective cohort of 689 older (≥65 years) agricultural workers from Southwest France. Descriptive and comparative analyses were performed according to H. pylori status determined by serology at baseline. The risk of incident dementia according to H. pylori status over a 7-year follow-up was explored by survival analyses: Kaplan-Meier curve and Cox proportional hazards models.

RESULTS

Two-hundred (29.0%) participants were H. pylori-positive at baseline. Compared to H. pylori-negative participants, they showed worse cognitive performances at baseline. Eighty-five incident dementia cases were diagnosed during the follow-up period. After adjustment for age, sex, education, apolipoprotein ε4, and several cardiovascular risk factors, H. pylori remained associated with an increased risk of dementia (HR 1.70, 95% CI, 1.05-2.74). The risk was stronger for Alzheimer's disease (HR 2.85, 95% CI, 1.58-5.12).

CONCLUSIONS

Despite an observed decrease in H. pylori infection prevalence, this study provides evidence for the association between H. pylori infection and dementia. These results should encourage further research on the mechanisms underlying the contribution of infectious diseases to pathological brain aging, especially the influence of gut inflammation on the brain.

Helicobacter pylori, persistent infection burden and structural brain imaging markers

Persistent infections, whether viral, bacterial or parasitic, including Helicobacter pylori infection, have been implicated in non-communicable diseases, including dementia and other neurodegenerative diseases. In this cross-sectional study, data on 635 cognitively normal participants from the UK Biobank study (2006-21, age range: 40-70 years) were used to examine whether H. pylori seropositivity (e.g. presence of antibodies), serointensities of five H. pylori antigens and a measure of total persistent infection burden were associated with selected brain volumetric structural MRI (total, white, grey matter, frontal grey matter (left/right), white matter hyperintensity as percent intracranial volume and bi-lateral sub-cortical volumes) and diffusion-weighted MRI measures (global and tract-specific bi-lateral fractional anisotropy and mean diffusivity), after an average 9-10 years of lag time. Persistent infection burden was calculated as a cumulative score of seropositivity for over 20 different pathogens. Multivariable-adjusted linear regression analyses were conducted, whereby selected potential confounders (all measures) and intracranial volume (sub-cortical volumes) were adjusted, with stratification by Alzheimer's disease polygenic risk score tertile when exposures were H. pylori antigen serointensities. Type I error was adjusted to 0.007. We report little evidence of an association between H. pylori seropositivity and persistent infection burden with various volumetric outcomes (P > 0.007, from multivariable regression models), unlike previously reported in past research. However, H. pylori antigen serointensities, particularly immunoglobulin G against the vacuolating cytotoxin A, GroEL and outer membrane protein antigens, were associated with poorer tract-specific white matter integrity (P < 0.007), with outer membrane protein serointensity linked to worse outcomes in cognition-related tracts such as the external capsule, the anterior limb of the internal capsule and the cingulum, specifically at low Alzheimer's disease polygenic risk. Vacuolating cytotoxin A serointensity was associated with greater white matter hyperintensity volume among individuals with mid-level Alzheimer's disease polygenic risk, while among individuals with the highest Alzheimer's disease polygenic risk, the urease serointensity was consistently associated with reduced bi-lateral caudate volumes and the vacuolating cytotoxin A serointensity was linked to reduced right putamen volume (P < 0.007). Outer membrane protein and urease were associated with larger sub-cortical volumes (e.g. left putamen and right nucleus accumbens) at middle Alzheimer's disease polygenic risk levels (P < 0.007). Our results shed light on the relationship between H. pylori seropositivity, H. pylori antigen levels and persistent infection burden with brain volumetric structural measures. These data are important given the links between infectious agents and neurodegenerative diseases, including Alzheimer's disease, and can be used for the development of drugs and preventive interventions that would reduce the burden of those diseases.

Clinically apparent Helicobacter pylori infection and the risk of incident Alzheimer's disease: A population-based nested case-control study

INTRODUCTION

Our population-based study assessed whether clinically apparent Helicobacter pylori infection (CAHPI) is associated with the risk of Alzheimer's disease (AD).

METHODS

We assembled a population-based cohort of all dementia-free subjects in the United Kingdom's Clinical Practice Research Datalink (UK CPRD), aged ≥50 years (1988-2017). Using a nested case-control approach, we matched each newly developed case of AD with 40 controls. Conditional logistic regression estimated odds ratios (ORs) with 95% confidence intervals (CIs) of AD associated with CAHPI compared with no CAHPI during ≥2 years before the index date. We also used salmonellosis as a negative control exposure.

RESULTS

Among 4,262,092 dementia-free subjects, 40,455 developed AD after a mean 11 years of follow-up. CAHPI was associated with an increased risk of AD (OR, 1.11; 95% CI, 1.01-1.21) compared with no CAHPI. Salmonellosis was not associated with the risk of AD (OR, 1.03; 95% CI, 0.82-1.29).

DISCUSSION

CAHPI was associated with a moderately increased risk of AD.

HIGHLIGHTS

CAHPI was associated with an 11% increased risk of AD in subjects aged ≥50 years. The increase in the risk of AD reached a peak of 24% a decade after CAHPI onset. There was no major effect modification by age or sex. Sensitivity analyses addressing several potential biases led to consistent results.

Digestive System Diseases, Genetic Risk, and Incident Dementia: A Prospective Cohort Study

INTRODUCTION

Although digestive system disease affects gut microbiota and their metabolites associated with dementia risk, the association between digestive system diseases and incident dementia has not yet been established.

METHODS

This cohort analysis included 458,181 participants free of baseline dementia in the UK Biobank (2006-2021). The associations of 14 digestive system diseases with dementia incidence were examined in 2022 using Cox proportional hazards regression models. Analyses were performed to differentiate the associations for early-onset (age <65 years) and late-onset (age ≥65 years) dementia. Interaction and stratification analyses were performed for polygenic risk score and APOE.

RESULTS

During a median follow-up of 12.4 years, 6,415 incident dementia cases were diagnosed. Eleven digestive system diseases showed significant associations with an increased risk of dementia after controlling for covariates and multiple testing. Compared with hazard ratios for individuals without digestive system diseases, the hazard ratios of dementia increased from 1.15 (95% confidence interval=1.09, 1.23) for patients with intestinal diverticular disease to 2.31 (95% confidence interval=1.98, 2.70) for patients with cirrhosis. The associations were different between certain digestive system diseases and dementia by onset age. The associations appeared to be stronger for cirrhosis (Q=0.001), irritable bowel syndrome (Q<0.001), gastritis and duodenitis (Q=0.002), gastroesophageal reflux disease (Q<0.001), ulcerative colitis (Q=0.047), gallbladder disease (Q=0.012), and peptic ulcer (Q=0.030) with early-onset dementia. There were no interactions for polygenic risk score or APOE (p>0.05).

CONCLUSIONS

These findings suggest an increased need for dementia prevention among patients with digestive system diseases.

Peripheral inflammation is a potential etiological factor in Alzheimer's disease

Peripheral inflammation could constitute a risk factor for AD. This review summarizes the research related to peripheral inflammation that appears to have a relationship with Alzheimer's disease. We find there are significant associations between AD and peripheral infection induced by various pathogens, including herpes simplex virus type 1, cytomegalovirus, Epstein-Barr virus, human immunodeficiency virus, severe acute respiratory syndrome coronavirus 2, Porphyromonas gingivalis, Helicobacter pylori, and Toxoplasma gondii. Chronic inflammatory diseases are also reported to contribute to the pathophysiology of AD. The mechanisms by which peripheral inflammation affects the pathophysiology of AD are complex. Pathogen-derived neurotoxic molecule composition, disrupted BBB, and dysfunctional neurogenesis may all play a role in peripheral inflammation, promoting the development of AD. Anti-pathogenic medications and anti-inflammatory treatments are reported to decrease the risk of AD. Studies that could improve understanding the associations between AD and peripheral inflammation are needed. If our assumption is correct, early intervention against inflammation may be a potential method of preventing and treating AD.

Infection burden and its association with neurite orientation dispersion and density imaging markers in the UK Biobank

BACKGROUND

Infection burden (IB), although linked to neurodegeneration, including Alzheimer's Disease (AD), has not been examined against neurite orientation, dispersion, and density imaging (NODDI) measures.

METHODS

Among 38,803 UK Biobank adults (Age:40-70 years), we tested associations of total IB (IBtotal, 47.5 %) and hospital-treated IB (IBhosp, 9.7 %) with NODDI measures (5-15 years later), including volume fraction of Gaussian isotropic diffusion (ISOVF), intra-cellular volume fraction (ICVF) and orientation dispersion (OD) indices, using multiple linear regression models.

RESULTS

Total and hospital-treated infection burdens (IBtotal and IBhosp) were associated with increased ISOVF, indicating increased free-water component. IBtotal was positively associated with OD, indicating that at higher IBtotal there was greater fanning of neurites. This was more evident in the lower cardiovascular health group. IBhosp was associated with higher OD, and lower ICVF at higher AD polygenic risk. Together, these findings indicate that both total and hospital-treated infections have effects on NODDI outcomes in the direction of poor brain health. These effects were largely homogeneous across cardiovascular health and AD polygenic risk groups, with some effects shown to be stronger at poor cardiovascular health and/or higher AD risk.

CONCLUSIONS

Total and hospital-treated infections were associated with poorer white matter microstructure (higher ISOVF or OD or lower ICVF), with some heterogeneity across cardiovascular health and AD risk. Longitudinal studies with multiple repeats on neuroimaging markers in comparable samples are needed.

Hospital-treated prevalent infections, the plasma proteome and incident dementia among UK older adults

The plasma proteome can mediate the association of hospital-treated infections with dementia incidence. We screened up to 37,269 UK Biobank participants aged 50-74 years for the presence of a prevalent hospital-treated infection, subsequently tested as a predictor for ≤1,463 plasma proteins and dementia incidence. Four-way decomposition models decomposed infection-dementia total effect into pure mediation, pure interaction, neither or both through the plasma proteome. Hospital-treated infections increased dementia two-fold. The strongest mediation effect was through the growth differentiation factor 15 (GDF15) protein. Top 17 proteomic mediators explained collectively 5% of the total effect, while pathway analysis of all mediators (k = 221 plasma proteins) revealed top pathways including the immune system, signal transduction, metabolism, disease and metabolism of proteins, with the GDF15 cluster reflecting most strongly the "transmembrane receptor protein tyrosine kinase signaling pathway". The association of hospital-treated infections with dementia was partially mediated through GDF15 and other plasma proteomic markers.

Helicobacter pylori infection: a dynamic process from diagnosis to treatment

Helicobacter pylori, a gram-negative microaerophilic pathogen, causes several upper gastrointestinal diseases, such as chronic gastritis, peptic ulcer disease, and gastric cancer. For the diseases listed above, H. pylori has different pathogenic mechanisms, including colonization and virulence factor expression. It is essential to make accurate diagnoses and provide patients with effective treatment to achieve positive clinical outcomes. Detection of H. pylori can be accomplished invasively and noninvasively, with both having advantages and limitations. To enhance therapeutic outcomes, novel therapeutic regimens, as well as adjunctive therapies with probiotics and traditional Chinese medicine, have been attempted along with traditional empiric treatments, such as triple and bismuth quadruple therapies. An H. pylori infection, however, is difficult to eradicate during treatment owing to bacterial resistance, and there is no commonly available preventive vaccine. The purpose of this review is to provide an overview of our understanding of H. pylori infections and to highlight current treatment and diagnostic options.

Review of Phytochemical Potency as a Natural Anti-Helicobacter pylori and Neuroprotective Agent

Phytochemicals are plant secondary metabolites that show health benefits for humans due to their bioactivity. There is a huge variety of phytochemicals that have already been identified, and these compounds can act as antimicrobial and neuroprotection agents. Due to their anti-microbial activity and neuroprotection, several phytochemicals might have the potency to be used as natural therapeutic agents, especially for Helicobacter pylori infection and neurodegenerative disease, which have become a global health concern nowadays. According to previous research, there are some connections between H. pylori infection and neurodegenerative diseases, especially Alzheimer's disease. Hence, this comprehensive review examines different kinds of phytochemicals from natural sources as potential therapeutic agents to reduce H. pylori infection and improve neurodegenerative disease. An additional large-scale study is needed to establish the connection between H. pylori infection and neurodegenerative disease and how phytochemicals could improve this condition.

Cardiovascular health, infection burden and their interactive association with brain volumetric and white matter integrity outcomes in the UK Biobank

BACKGROUND

Cardiovascular health is associated with brain magnetic resonance imaging (MRI) markers of pathology and infections may modulate this association.

METHODS

Using data from 38,803 adults (aged 40-70 years) and followed-up for 5-15 years, we tested associations of prevalent total (47.5%) and hospital-treated infection burden (9.7%) with brain structural and diffusion-weighted MRI (i.e., sMRI and dMRI, respectively) common in dementia phenome. Poor white matter tissue integrity was operationalized with lower global and tract-specific fractional anisotropy (FA) and higher mean diffusivity (MD). Volumetric sMRI outcomes included total, gray matter (GM), white matter (WM), frontal bilateral GM, white matter hyperintensity (WMH), and selected based on previous associations with dementia. Cardiovascular health was measured with Life's Essential 8 score (LE8) converted to tertiles. Multiple linear regression models were used, adjusting for intracranial volumes (ICV) for subcortical structures, and for demographic, socio-economic, and the Alzheimer's Disease polygenic risk score for all outcomes, among potential confounders.

RESULTS

In fully adjusted models, hospital-treated infections were inversely related to GM (β ± SE: -1042 ± 379, p = 0.006) and directly related to WMH as percent of ICV (Loge transformed) (β ± SE:+0.026 ± 0.007, p < 0.001). Both total and hospital-treated infections were associated with poor WMI, while the latter was inversely related to FA within the lowest LE8 tertile (β ± SE:-0.0011 ± 0.0003, p < 0.001, PLE8×IB < 0.05), a pattern detected for GM, Right Frontal GM, left accumbens and left hippocampus volumes. Within the uppermost LE8 tertile, total infection burden was linked to smaller right amygdala while being associated with larger left frontal GM and right putamen volumes, in the overall sample. Within that uppermost tertile of LE8, caudate volumes were also positively associated with hospital-treated infections.

CONCLUSIONS

Hospital-treated infections had more consistent deleterious effects on volumetric and white matter integrity brain neuroimaging outcomes compared with total infectious burden, particularly in poorer cardiovascular health groups. Further studies are needed in comparable populations, including longitudinal studies with multiple repeats on neuroimaging markers.

Cardiovascular health, infection burden, and incident dementia in the UK Biobank

INTRODUCTION

Among older adults, total and hospitalized infection may be associated with incidence of all-cause and Alzheimer's disease (AD) dementias, with variation by cardiovascular health (CVH).

METHODS

We used Cox proportional hazards (PH) models to examine the relationships between International Classification of Diseases-10th revision (ICD-10)-specific viral and bacterial infectious agents and incident all-cause and AD dementia among 355,046 UK Biobank participants ≥50 years at baseline. Life's Essential 8 (LE8) index reflected CVH.

RESULTS

In both sexes, total infection burden (yes vs. no) was associated with all-cause dementia, with significant interactions by LE8 tertiles, whereby this relationship was significant only in the lowest LE8 tertile. Hospital-treated infection burden (yes vs no) was significantly related to all-cause and AD dementia, with no significant interaction with LE8 tertile. Age group patterns were detected.

DISCUSSION

AD and all-cause dementia were related to hospital-treated infections, while CVH modified the relationship of total infection burden with all-cause dementia. Highlights Secondary analysis on >355,000 UK Biobank participants ≥50 years at baseline. Alzheimer's disease and all-cause dementia are both related to hospital-treated infection. Cardiovascular health modifies association of infection burden with all-cause dementia.

Association between dietary zinc intake and Helicobacter pylori seropositivity in US adults: National Health and Nutrition Examination Survey

Purpose

Helicobacter pylori infection is a well-established etiological factor for gastric inflammation and a significant risk factor for the development of gastric cancer. However, the precise relationship between dietary zinc intake and seropositivity for Helicobacter pylori remains uncertain.

Methods

This cross-sectional observational study utilized data from the United States National Health and Nutrition Examination Survey conducted between 1999 and 2000. The study cohort comprised 2,884 adults aged 20 years or older who provided comprehensive 24-h dietary recall data. The presence of Helicobacter pylori infection was confirmed using serum analysis and lgG protein enzyme-linked immunosorbent assay (ELISA). Multivariable logistic regression models and generalized additive model (GAM) were employed to explore the potential association between dietary zinc intake and Helicobacter pylori seropositivity.

Results

Additionally, subgroup analysis was performed to evaluate the robustness of the primary findings. Of the 1,281 participants, 47.8% were male and the average age was 49.5 years. In the fully adjusted model, a statistically significant inverse association between dietary zinc intake and Helicobacter pylori seropositivity was observed [quartile variable, Q4 vs. Q1, odds ratio (OR): 0.72, 95% confidence interval (CI): 0.57-0.91, p = 0.007]. Furthermore, the relationship between dietary zinc intake and Helicobacter pylori seropositivity exhibited an L-shaped pattern, indicating a saturation effect. The results of sensitivity analysis remained consistent and reliable.

Conclusion

Therefore, this study suggests that higher dietary zinc intake may be associated with a lower prevalence of Helicobacter pylori seropositivity. Notably, this association follows an L-shaped pattern, with a threshold point estimated at 24.925 mg/day.

Plasmon-activated water as a therapeutic strategy in Alzheimer's disease by altering gut microbiota

Gut microbiota (GM) are involved in the pathophysiology of Alzheimer's disease (AD) and might correlate to the machinery of the gut-brain axis. Alteration of the GM profiles becomes a potential therapy strategy in AD. Here, we found that plasmon-activated water (PAW) therapy altered GM profile and reduced AD symptoms in APPswe/PS1dE9 transgenic mice (AD mice). GM profile showed the difference between AD and WT mice. PAW therapy in AD mice altered GM profile and fecal microbiota transplantation (FMT) reproduced GM profile in AD mice. PAW therapy and FMT in AD mice reduced cognitive decline and amyloid accumulation by novel object recognition (NOR) test and amyloid PET imaging. Immunofluorescent staining and western blot analysis of β-amyloid (Aβ) and phosphorylated (p)-tau in the brain of AD mice were reduced in PAW therapy and FMT. The inflammatory markers, interleukin (IL)-6, IL-1β, and tumor necrosis factor (TNF)-α and pro-inflammatory indicator of arginase-1/CD86 ratio were also reduced. Furthermore, immunohistochemistry (IHC) analysis of occludin and claudin-5 in the intestine and AXL in the brain were increased to correlate with the abundant GM in PAW therapy and FMT. Our results showed the machinery of gut-brain axis, and PAW might be a potential therapeutic strategy in AD.

Antibodies against Periodontal Microorganisms and Cognition in Older Adults

INTRODUCTION

Markers of poor oral health are associated with impaired cognition and higher risk of Alzheimer disease (AD) and thus may help predict AD.

OBJECTIVES

The aim of this study was to evaluate the cross-sectional association between empirically derived groups of 19 IgG antibodies against periodontal microorganisms and cognition in middle-aged and older adults.

METHODS

The study population consisted of participants of the third National Health and Nutrition Examination Survey (NHANES III) (1988 to 1994), who were 60 y and older, among whom cognition and IgG antibodies against 19 periodontal microorganisms were measured (N = 5,162).

RESULTS

In multivariable quantile regression analyses, the Orange-Red (Prevotella melaninogenica, Prevotella intermedia, Prevotella nigrescens, Porphyromonas gingivalis) and Yellow-Orange (Staphylococcus intermedius, Streptococcus oralis, Streptococcus mutans, Fusobacterium nucleatum, Peptostreptococcus micros, Capnocytophaga ochracea) cluster scores were negatively associated with cognition. A 1-unit higher cluster score for the Orange-Red cluster was associated on average with a lower cognitive score (β for 30th quantile = -0.2640; 95% confidence interval [CI], -0.3431 to -0.1848). Similarly, a 1-unit higher score for the Yellow-Orange cluster was associated with a lower cognitive score (β for 30th quantile = -0.2445; 95% CI, -0.3517 to -0.1372).

CONCLUSION

Groups of IgG antibodies against periodontal microorganisms were associated with lower cognition among free living adults 60 years and older, who were previously undiagnosed with cognitive impairment. Though poor oral health precedes the development of dementia and AD, oral health information is currently not used, to our knowledge, to predict dementia or AD risk. Combining our findings with current algorithms may improve risk prediction for dementia and AD.

KNOWLEDGE TRANSLATION STATEMENT

IgG antibodies against periodontal microorganisms were associated with lower cognition among adults 60 years and older previously undiagnosed with cognitive impairment. Periodontal disease may predict cognition among older adults.

Effect of polyphenol compounds on Helicobacter pylori eradication: a systematic review with meta-analysis

OBJECTIVES

Polyphenol compounds are classified as organic compounds with phenolic units exhibiting a variety of biological functions. This meta-analysis aims to assess the efficacy and safety of polyphenol compounds (curcumin, cranberry, garlic, liquorice and broccoli) in eradicating Helicobacter pylori.

DESIGN

Systematic review and meta-analysis.

METHODS

Literature searches were conducted on PubMed, Embase, The Cochrane Library, Web of Science, Medline, Chinese National Knowledge Infrastructure database, Chinese Scientific Journal Database and Wan Fang database from inception to January 2022. All randomised controlled trials comparing polyphenol compounds with the placebo or used as an adjunct treatment are included in this meta-analysis.The treatment effect for dichotomous outcomes was assessed using risk ratio (RR), while for continuous outcomes, mean differences both with 95% CIs, were used. Subgroup analyses were carried out for different treatment schemes and polyphenol compound species.

RESULTS

12 trials were included in the meta-analysis. The total eradication rate of H.pylori in the polyphenol compounds group was higher than in the group without polyphenol compounds. Statistical significance was also observed (RR 1.19, 95% CI 1.03 to 1.38, p=0.02). The most frequent adverse effects of polyphenol compounds included diarrhoea, headache and vomiting. However, there were no differences regarding side effects between the two groups (RR 1.47, 95% CI 0.83 to 2.58, p=0.18). In subgroup analyses, the H.pylori eradication rate regimens with polyphenols therapy was superior to that of regimens without polyphenols therapy in the polyphenols versus placebo subgroup (RR 4.23, 95% CI 1.38 to 12.95, p=0.01), polyphenols plus triple therapy versus triple therapy subgroup (RR 1.11, 95% CI 1.01 to 1.22, p=0.03).

CONCLUSION

Polyphenol compounds can improve H.pylori eradication rates. Polyphenol compounds plus standard triple therapy can significantly improve the eradication. However, no evidence of a higher incidence of side effects could be found.

PROSPERO REGISTRATION NUMBER

CRD42022307477.

Helicobacter pylori infection in the stomach induces neuroinflammation: the potential roles of bacterial outer membrane vesicles in an animal model of Alzheimer's disease

Helicobacter pylori (HP) is a Gram-negative bacterium that colonizes the human stomach chronically. Colonization of HP in the gastric mucosa not only causes gastrointestinal diseases, but also is associated with extra-gastric diseases, such as idiopathic thrombocytopenic purpura and neurological diseases. Among neurological diseases, epidemiological studies have shown that HP infection increases the prevalence of Alzheimer's disease (AD) and Parkinson's disease (PD). Since HP does not invade the central nervous system (CNS), it has been considered that systemic immunological changes induced by HP infection may play pathogenic roles in AD and PD. Here, we investigated the effects of HP infection on the CNS in vivo and in vitro. In the CNS, chronically HP-infected mice had microglial activation without HP colonization, although systemic immunological changes were not observed. This led us to explore the possibility that HP-derived outer membrane vesicles (HP-OMVs) could cause neuroinflammation. OMVs are small, spherical bilayer vesicles (20-500 nm) released into the extracellular space from the outer membrane of Gram-negative bacteria; OMVs contain lipopolysaccharide, proteins, peptidoglycan, DNA, and RNA. OMVs have also been shown to activate both innate and acquired immune cells in vitro, and to disrupt the tight junctions of the gastric epithelium ("leaky gut") as well as cross the blood-brain barrier in vivo. Thus, in theory, OMVs can activate immune responses in the remote organs, including the lymphoid organs and CNS, if only OMVs enter the systemic circulation. From the exosome fraction of sera from HP-infected mice, we detected HP-specific DNA, suggesting the presence of HP-OMVs. We also found that microglia incubated with HP-OMVs in vitro increased the cell proliferation, inflammatory cytokine production, and migration. On the other hand, HP-OMVs suppressed the cell proliferation of neuroblastoma in vitro. Lastly, we found that AD model mice infected with HP had amyloid plaques adjacent to activated microglia and astrocytes in vivo. Based on the literature review and our experimental data, we propose our working hypothesis that OMVs produced in chronic HP infection in the gut induce neuroinflammation in the CNS, explaining the higher prevalence of AD in HP-infected people.

Helicobacter pylori and unignorable extragastric diseases: Mechanism and implications

Considered as the most popular pathogen worldwide, Helicobacter pylori is intensively associated with diverse gastric diseases, including gastric ulcers, chronic progressive gastritis, and gastric cancer. Aside from its pathogenic effect on gastric diseases, growing evidences reveal that H. pylori may be related to numerous extragastric diseases. In this article, we reviewed recent studies and systematically elucidated that H. pylori may interfere with many biological processes outside the stomach and influence the occurrence of various extragastric diseases. Many epidemiological studies have indicated that H. pylori plays a pathogenic role in COVID-19, atherosclerosis, hyperemesis gravidarum and several other extragastric diseases, while the effect of H. pylori is currently under investigation in gastroesophageal reflux disease, asthma, and inflammatory bowel disease. Moreover, we also summarized the possible pathogenic mechanisms of H. pylori that may be related to chronic systemic inflammation and molecular mimicker. Taken together, this review provides a new perspective on the role of H. pylori in extragastric diseases and explores the possible mechanisms, which may help guide clinical treatment.

The interactions between oral-gut axis microbiota and Helicobacter pylori

In the human body, each microbial habitat exhibits a different microbial population pattern, and these distinctive microflorae are highly related to the development of diseases. The microbial interactions from host different niches are becoming crucial regulators to shape the microbiota and their physiological or pathological functions. The oral cavity and gut are the most complex and interdependent microbial habitats. Helicobacter pylori is one of the most important pathogens from digestive tract, especially the stomach, due to its direct relationships with many gastric diseases including gastric cancer. H. pylori infections can destroy the normal gastric environment and make the stomach a livable channel to enhance the microbial interactions between oral cavity and gut, thus reshaping the oral and gut microbiomes. H. pylori can be also detected in the oral and gut, while the interaction between the oral-gut axis microbiota and H. pylori plays a major role in H. pylori’s colonization, infection, and pathogenicity. Both the infection and eradication of H. pylori and its interaction with oral-gut axis microbiota can alter the balance of the microecology of the oral-gut axis, which can affect the occurrence and progress of related diseases. The shift of oral-gut axis microbiota and their interactions with H. pylori maybe potential targets for H. pylori infectious diagnosis and treatment.

An Exponential Curve Relationship Between Serum Urate and Migraine: A Cross-Section Study From NHANES

Background

Migraine is a common neurological disease and an important cause of disability worldwide. Serum urate is the end product of purine metabolism in Homo sapiens and other hominoids. Previous studies about the serum urate level in migraine were contradictory. Hence, we present a cross-section study to clarify the association between serum urate and migraine and explore the dose effect of serum urate on migraine.

Materials and Methods

The data for this cross-section study were acquired from the National Health and Nutrition Examination Survey (NHANES). A diagnosis of migraine was made through patient the self-reported and prescription medication. For data analysis, the weighted linear regression model, weighted chi-square test, logistic regression models, smooth curve fittings, and the two-piecewise linear regression model were utilized for data analysis. All data analysis was conducted on Empower software.

Results

Totally, 18,637 participants were enrolled in this study, of which 208 were migraineurs. The rest were set as control. There existed a statistically significant difference in mean age (p = 0.0389), gender (p< 0.0001), race (p< 0.0001), data release cycle (p = 0.048), drug usage, blood albumin (p< 0.0001), blood total protein (p< 0.0001), hemoglobin (p< 0.0001), serum iron (p< 0.0001), and serum urate (p< 0.0001) between the two groups. According to logistic regression models, there existed no consistent linear relationship between serum urate and migraine before (model 1: odd ratio (OR) = 0.83, p = 0.0004) or after adjusting for confounders (model 2: OR = 0.96, p = 0.5198; model 3: OR = 0.84, p = 0.0184). However, smooth curve fittings found an exponential curve relationship between serum urate and migraine. Furthermore, when serum urate was more than 7.8 mg/dl, higher serum urate was correlated with higher migraine occurrence (model 1: OR = 1.54, p = 0.0022; model 2: OR = 1.51, p = 0.0050; model 3: OR = 1.77, p = 0.0348). Besides, 8 out of the 208 migraineurs had a serum urate higher than 7.8 mg/dl.

Conclusions

In conclusion, there existed an exponential curve relationship between serum urate and migraine, with an infliction point of 7.8 mg/dl. When serum urate was more than 7.8 mg/dl, increased serum urate was correlated with higher migraine occurrence.

Helicobacter pylori Infection Acts as an Independent Risk Factor for Intracranial Atherosclerosis in Women Less Than 60 Years Old

Background: Studies show inconsistent results regarding the relationship between Helicobacter pylori (H. pylori) infection and stroke. The present study assessed a potential association between H. pylori infection and an important risk factor for stroke, intracranial atherosclerosis.

Methods: In total, 15,798 subjects with transcranial Doppler (TCD) and 13C-urea breath test (13C-UBT) were enrolled from March 2012 to March 2017. Intracranial atherosclerosis was further measured using intracranial carotid artery calcification (ICAC) on past or recent head CT, and 14,084 subjects were ultimately included in the study. Baseline demographics, atherosclerosis risk factors, and laboratory results were investigated. Since endothelial dysfunction is critical to the development of atherosclerosis, the role of H. pylori in migration, tube formation, and proliferation of human brain microvascular endothelial cells (HBMECs) was assessed in vitro.

Results: The intracranial atherosclerosis group had a higher proportion of women and a greater rate of H. pylori infection than those without intracranial atherosclerosis. H. pylori infection was significantly more common in women with intracranial atherosclerosis than males. In addition, the incidence of intracranial atherosclerosis was significantly higher in women with H. pylori infection than uninfected women (53.8 vs. 46.4%, p &lt; 0.001). In an adjusted model, H. pylori was shown to be an independent risk factor for intracranial atherosclerosis in women ≤ 60 years of age [odds ratio (OR) = 2.261, 95% CI = 1.839–2.780, p &lt; 0.001]. Serum exosomes from patients with H. pylori infection had significantly reduced brain endothelial cell migration, tube formation, and proliferation in vitro.

Conclusion:Helicobacter pylori infection may be an important independent risk factor for intracranial atherosclerosis in women ≤ 60 years of age.

Benefits of Helicobacter pylori Eradication on Extragastric Diseases

Helicobacter pylori (H. pylori) eradication can reduce the risk of gastric diseases such as gastritis, gastric ulcer, and gastric adenocarcinoma. Since H. pylori was discovered more than 30 years ago, many studies have reported associations between H. pylori infection and extragastric diseases such as immune thrombocytopenia and iron-deficiency anemia. Thus, recent guidelines recommended H. pylori eradication in patients with those diseases. In contrast, although the role of H. pylori eradication in other extragastric diseases remains controversial, there is growing evidence of its benefit on them, especially cardiovascular (ischemic heart disease and stroke), metabolic (dyslipidemia, diabetes mellitus, and non-alcoholic fatty liver disease), neurodegenerative (Parkinson’s disease and Alzheimer’s disease), autoimmune (Graves’ disease, Hashimoto’s thyroiditis, Raynaud’s syndrome, rosacea, and chronic urticaria), and other (cap polyposis, colorectal mucosa-associated lymphoid tissue lymphoma, periodontal disease, hyperemesis gravidarum, and osteoporosis) conditions. A recent prospective randomized study reported that H. pylori eradication improved insulin resistance and dyslipidemia. These findings were consistent with the results of a recent meta-analysis. Therefore, well-designed prospective interventional studies are needed to examine the effects of H. pylori eradication on various extragastric diseases.

Gram-negative bacteria and their lipopolysaccharides in Alzheimer's disease: pathologic roles and therapeutic implications

Alzheimer's disease (AD) is the most serious age-related neurodegenerative disease and causes destructive and irreversible cognitive decline. Failures in the development of therapeutics targeting amyloid-β (Aβ) and tau, principal proteins inducing pathology in AD, suggest a paradigm shift towards the development of new therapeutic targets. The gram-negative bacteria and lipopolysaccharides (LPS) are attractive new targets for AD treatment. Surprisingly, an altered distribution of gram-negative bacteria and their LPS has been reported in AD patients. Moreover, gram-negative bacteria and their LPS have been shown to affect a variety of AD-related pathologies, such as Aβ homeostasis, tau pathology, neuroinflammation, and neurodegeneration. Moreover, therapeutic approaches targeting gram-negative bacteria or gram-negative bacterial molecules have significantly alleviated AD-related pathology and cognitive dysfunction. Despite multiple evidence showing that the gram-negative bacteria and their LPS play a crucial role in AD pathogenesis, the pathogenic mechanisms of gram-negative bacteria and their LPS have not been clarified. Here, we summarize the roles and pathomechanisms of gram-negative bacteria and LPS in AD. Furthermore, we discuss the possibility of using gram-negative bacteria and gram-negative bacterial molecules as novel therapeutic targets and new pathological characteristics for AD.

Infection and Immunometabolism in the Central Nervous System: A Possible Mechanistic Link Between Metabolic Imbalance and Dementia

Metabolic syndromes are frequently associated with dementia, suggesting that the dysregulation of energy metabolism can increase the risk of neurodegeneration and cognitive impairment. In addition, growing evidence suggests the link between infections and brain disorders, including Alzheimer's disease. The immune system and energy metabolism are in an intricate relationship. Infection triggers immune responses, which are accompanied by imbalance in cellular and organismal energy metabolism, while metabolic disorders can lead to immune dysregulation and higher infection susceptibility. In the brain, the activities of brain-resident immune cells, including microglia, are associated with their metabolic signatures, which may be affected by central nervous system (CNS) infection. Conversely, metabolic dysregulation can compromise innate immunity in the brain, leading to enhanced CNS infection susceptibility. Thus, infection and metabolic imbalance can be intertwined to each other in the etiology of brain disorders, including dementia. Insulin and leptin play pivotal roles in the regulation of immunometabolism in the CNS and periphery, and dysfunction of these signaling pathways are associated with cognitive impairment. Meanwhile, infectious complications are often comorbid with diabetes and obesity, which are characterized by insulin resistance and leptin signaling deficiency. Examples include human immunodeficiency virus (HIV) infection and periodontal disease caused by an oral pathogen Porphyromonas gingivalis. This review explores potential interactions between infectious agents and insulin and leptin signaling pathways, and discuss possible mechanisms underlying the relationship between infection, metabolic dysregulation, and brain disorders, particularly focusing on the roles of insulin and leptin.

Helicobacter pylori, periodontal pathogens, and their interactive association with incident all-cause and Alzheimer's disease dementia in a large national survey

Co-infection between Helicobacter pylori (Hp) and groups of periodontal pathogens may alter the onset of Alzheimer's disease (AD) and all-cause dementia. We examined the interactive associations among Hp sero-positivity, periodontal disease (Pd), and infections with incident AD and all-cause dementia, among older adults (≥65 years at baseline). Up to 1431 participants from phase 1 of the National Health and Nutrition Survey III (1988-1991) had complete data till January 1st, 2014 on Hp sero-positivity with a mean follow-up of 10-11 years for AD and all-cause dementia incidence. Exposures consisted of 19 periodontal pathogens, constructed factors and clusters, and two Pd markers- probing depth and clinical attachment loss (CAL). Cox proportional hazards models were performed. Around 55% of the selected sample was Hp⁺. We found that Prevotella intermedia, Campylobacter Rectus, Factor 2 (Pi/Prevotella nigrescens/Prevotella melaninogenica), and the Orange-Red cluster interacted synergistically with Hp sero-positivity, particularly with respect to AD incidence. The presence of higher levels of Actinomyces Naeslundii (An) enhanced the effect of being Hp⁺ on both AD and all-cause dementia incidence. In contrast, Fusobacterim nucleatum (Fn), and Factor 1 (which included Fn), exhibited an antagonistic interaction with Hp in relation to all-cause dementia. Both probing depth and CAL had direct associations with all-cause dementia among Hp⁺ individuals, despite nonsignificant interaction. Selected periodontal pathogen titers, factors, and clusters interacted mostly synergistically, with Hp sero-positivity, to alter the risk of AD and all-cause dementia. Ultimately, a randomized controlled trial is needed, examining effects of co-eradication of Hp and select periodontal pathogens on neurodegenerative disease.

Helicobacter pylori infection and risk for developing dementia: an evidence-based meta-analysis of case-control and cohort studies

BACKGROUND

Infection with multiple pathogens may play a key role in the pathogenesis of dementia. Whether Helicobacter pylori (H. pylori) infection is associated causally with dementia is controversial.

OBJECTIVE

We conduct a meta-analysis of case-control and cohort studies on the association between H. pylori infection and the risk for all-cause and Alzheimer's disease (AD) dementia.

METHODS

Two independent reviewers searched the PubMed, Cochrane Library, and Embase databases with English language restrictions from the date of conception to September 18, 2020. The primary analysis was as follows: the exposure variable was H. pylori infection, and the outcome was incident all-cause and AD dementia. Pooled odds ratios (OR), relative risk (RR), and corresponding 95% confidence intervals (CI) were obtained using the fixed-or random-effect model. Forest plots were generated to summarize the results.

RESULTS

Ten studies involving 96,561 participants were included in the meta-analysis: 5 case-control studies and 5 cohort studies. The overall pooled cohort studies showed a significant positive association between H. pylori infection and all-cause dementia with pooled RR of 1.36 (95% CI, 1.11-1.67). There was no association between H. pylori infection and risk for developing AD: RR of 1.33 (95% CI, 0.86-2.05) in cohort studies, and OR of 1.72 (95% CI, 0.97-3.04) in case-control studies. Significant heterogeneity was showed in each comparison group.

CONCLUSION

This meta-analysis supports a positive association between H. pylori infection and the risk of all-cause dementia, but not AD dementia. Due to the interference of confounding factors, randomized controlled trials are needed to prove their causality.

Red Cell Distribution Width, Anemia, and Brain Volumetric Outcomes Among Middle-Aged Adults

BACKGROUND

Anemia and red cell distribution width (RDW) have been linked to poor cognitive performance, pending studies of underlying mechanisms.

OBJECTIVE

We examined cross-sectional relationships of initial RDW status (v1), RDW change (δ), and anemia with brain structural magnetic resonance imaging (sMRI) markers, including global and cortical brain and hippocampal and white matter lesion (WML) volumes, 5-6 years later.

METHODS

Data were used from three prospective visits within the Healthy Aging in Neighborhoods of Diversity Across the Life Span (HANDLS) study with complete v1 (2004-2009) and v2 (2009-2013) exposures and ancillary sMRI data at vscan (2011-2015, n = 213, mean v1 to vscan time: 5.7 years). Multivariable-adjusted linear regression models were conducted, overall, by sex, by race, and within non-anemics, correcting for multiple testing with q-values.

RESULTS

In minimally adjusted models (socio-demographics and follow-up time), anemiav1 and RDWv1 were consistently associated with smaller bilateral hippocampal volumes overall, and among females (q < 0.05), without significant sex differences. RDWv1 was related to smaller select regional cortical brain gray and white matter volumes in hematological measure-adjusted models; anemiav1 was associated with larger WML volumes only among whites.

CONCLUSION

In summary, baseline anemia and RDW were consistently associated with smaller bilateral hippocampal volumes, particularly among females, while anemia was linked to larger WML volume among Whites. In hematological measure-adjusted models, baseline RDW was linked to smaller regional gray and white matter volumes. Pending studies with sMRI repeats, randomized controlled trials are needed, demonstrating associations of anemia and elevated RDW with reduced brain volumes and cognitive dysfunction.

Red cell distribution width, anemia and their associations with white matter integrity among middle-aged urban adults

Anemia (blood hemoglobin [Hb] <13 g/dL among males; <12 g/dL among females) and elevated red cell distribution width (RDW) are potential risk factors for reduced brain white matter integrity (WMI), reflected by lower fractional anisotropy or increased mean diffusivity. Cross-sectional data with exposure-outcome lag time was used, whereby hematological exposures (RDW and Hb) and covariates were compiled from the Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS) study with available visit 1 (v1; 2004-2009) and/or v2 (2009-2013) data; while diffusion tensor magnetic resonance imaging (dMRI) outcome data were collected at HANDLS SCAN visit (vscan: 2011-2015, n = 214, mean follow-up from v1 ±SD: 5.6 ± 1.8 year). Multivariable-adjusted linear regression analyses were conducted, overall, stratifying by sex, and further restricting to the nonanemic for RDW exposures in part of the analyses. Among males, RDW(v1) was linked with lower global mean fractional anisotropy (standardized effect size b = -0.30, p= 0.003, q < 0.05; basic model), an association only slightly attenuated with further covariate adjustment. Anemia was not a risk factor for poor WMI, independently of RDW. Ultimately, pending further longitudinal evidence, initial RDW appears to be associated with poorer WMI among males.

Helicobacter Pylori Infection Is Associated with Neurodegeneration in Cognitively Normal Men

BACKGROUND

An association between Helicobacter pylori (H. pylori) infection and dementia was reported in previous studies; however, the evidence is inconsistent.

OBJECTIVE

In the present study, the association between H. pylori infection and brain cortical thickness as a biomarker of neurodegeneration was investigated.

METHODS

A cross-sectional study of 822 men who underwent a medical health check-up, including an esophagogastroduodenoscopy and 3.0 T magnetic resonance imaging, was performed. H. pylori infection status was assessed based on histology. Multiple linear regression analyses were conducted to evaluate the relationship between H. pylori infection and brain cortical thickness.

RESULTS

Men with H. pylori infection exhibited overall brain cortical thinning (p = 0.022), especially in the parietal (p = 0.008) and occipital lobes (p = 0.050) compared with non-infected men after adjusting for age, educational level, alcohol intake, smoking status, and intracranial volume. 3-dimentional topographical analysis showed that H. pylori infected men had cortical thinning in the bilateral lateral temporal, lateral frontal, and right occipital areas compared with non-infected men with the same adjustments (false discovery rate corrected, Q < 0.050). The association remained significant after further adjusting for inflammatory marker (C-reactive protein) and metabolic factors (obesity, dyslipidemia, fasting glucose, and blood pressure).

CONCLUSION

Our results indicate H. pylori infection is associated with neurodegenerative changes in cognitive normal men. H. pylori infection may play a pathophysiologic role in the neurodegeneration and further studies are needed to validate this association.

Associations of Infectious Agents with Alzheimer's Disease: A Systematic Review and Meta-Analysis

BACKGROUND

The role of infectious agents in the development of Alzheimer's disease (AD) has long been debated, however, uncertainties still persist.

OBJECTIVE

We aimed to illuminate the associations between infectious agents and risk of AD comprehensively.

METHODS

Studies examining the associations between AD and infectious agents were identified through a systematic search of PubMed, Embase, and Cochrane library. A random-effects meta-analysis was conducted. Publication bias was explored using funnel plot.

RESULTS

Fifty-one studies were included in the systematic review, of which forty-seven studies with 108,723 participants and 4,039 AD cases were eligible for meta-analysis. Evidence based on case control studies demonstrated that Chlamydia pneumoniae [odds ratio (OR): 4.39, 95% CI = 1.81-10.67; I2 = 68%)], Human herpes virus-6 (OR: 3.97, 95% CI = 2.04-7.75; I2 = 0%, Epstein-Barr virus (OR:1.45, 95% CI = 1.00-2.08; I2 = 0%), Herpes simplex virus-1 (OR:1.34, 95% CI = 1.02-1.75; I2 = 0%), and the Herpesviridae family (OR:1.41, 95% CI = 1.15-1.74; I2 = 12%) infection were associated with a higher risk of AD. No significant evidence of publication bias was found.

CONCLUSION

These findings strengthened the evidence that infection may play an important role in AD. Additional research is required to determine whether treatment strategies targeting infectious diseases to prevent AD are viable in the future.

Infectious Disease Burden and the Risk of Alzheimer's Disease: A Population-Based Study

BACKGROUND

Previous studies suggested a link between various infectious pathogens and the development of Alzheimer's disease (AD), posing the question whether infectious disease could present a novel modifiable risk factor.

OBJECTIVE

To assess whether infectious disease burden due to clinically apparent infections is associated with an increased risk of AD.

METHODS

We conducted a population-based nested case-control study using the United Kingdom Clinical Practice Research Datalink. We included all dementia-free subjects ≥50 years of age enrolling in the database between January 1988 and December 2017. Each case of AD identified during follow-up was matched with up to 40 controls. Conditional logistic regression estimated adjusted odds ratios (ORs) with 95% confidence intervals (CIs) of AD associated with ≥1 infection diagnosed > 2 years before the index date compared with no infection during the study period. We further stratified by time since first infection and cumulative number of infections.

RESULTS

The cohort included overall 4,262,092 individuals (mean age at cohort entry 60.4 years; 52% female). During a median follow-up of 10.5 years, 40,455 cases of AD were matched to 1,610,502 controls. Compared with having no burden of infectious disease, having a burden of infectious disease was associated with an increase in the risk of AD (OR, 1.05; 95% CI, 1.02 to 1.08). The risk increased with longer time since first infection, peaking after 12-30 years (OR, 1.11; 95% CI, 1.05-1.17). The risk did not increase with cumulative number of infections.

CONCLUSION

The overall risk of AD associated with infectious disease burden was small but increased gradually with longer time since first infection.

Relationship Between Helicobacter pylori Infection and Arteriosclerosis

It is reported that Helicobacter pylori (H. pylori) infection may be linked to non-digestive tract diseases, such as arteriosclerosis including dyslipidemia, diabetes, obesity, hypertension, and cardiovascular disease. Therefore, we reviewed recent studies available in PubMed dealing with the mechanisms of arteriosclerosis due to H. pylori infection and the effects of H. pylori eradication. Conventional studies suggested that H. pylori infection may increase the risk of arteriosclerosis. A large interventional study is required to clarify the causal relationships and the effects of bacterial eradication.

Gut flora-targeted photobiomodulation therapy improves senile dementia in an Aß-induced Alzheimer's disease animal model

BACKGROUND

Emerging evidence suggests that the gut microbiota plays an important role in the pathological progression of Alzheimer's disease (AD). Photobiomodulation (PBM) therapy is believed to have a positive regulatory effect on the imbalance of certain body functions, including inflammation, immunity, wound healing, nerve repair, and pain. Previous studies have found that the intestinal flora of patients with AD is in an unbalanced state. Therefore, we have proposed the use of gut flora-targeted PBM (gf-targeted PBM) as a method to improve AD in an Aß-induced AD mouse model.

METHODS

PBM was performed on the abdomen of the mice at the wavelengths of 630 nm, 730 nm, and 850 nm at 100 J/cm2 for 8 weeks. Morris water maze test, immunofluorescence and proteomic of hippocampus, and intestinal flora detection of fecal were used to evaluate the treatment effects of gf-targeted PBM on AD rats.

RESULTS

PBM at all three wavelengths (especially 630 nm and 730 nm) significantly improved learning retention as measured by the Morris water maze. In addition, we found reduced amyloidosis and tau phosphorylation in the hippocampus by immunofluorescence in AD mice. By using a quantitative proteomic analysis of the hippocampus, we found that gf-targeted PBM significantly altered the expression levels of 509 proteins (the same differentially expressed proteins in all three wavelengths of PBM), which involved the pathways of hormone synthesis, phagocytosis, and metabolism. The 16 s rRNA gene sequencing of fecal contents showed that PBM significantly altered the diversity and abundance of intestinal flora. Specifically, PBM treatment reversed the typical increase of Helicobacter and uncultured Bacteroidales and the decrease of Rikenella seen in AD mice.

CONCLUSIONS

Our data indicate that gf-targeted PBM regulates the diversity of intestinal flora, which may improve damage caused by AD. Gf-targeted PBM has the potential to be a noninvasive microflora regulation method for AD patients.

The role of microbial infection in the pathogenesis of Alzheimer's disease and the opportunity for protection by anti-microbial peptides

Alzheimer's disease (AD) is the most common cause of dementia. Its pathology is primarily characterized by extracellular deposits of amyloid β peptide and intracellular neurofibrillary tangles. Current rationales to explain the pathogenesis of AD include amyloid cascade, inflammation, infection defense and anti-microbial protection hypotheses. This review focuses on recent advances in the infection hypothesis, in particular on those pathogenic microbes that act systemically, via periodontal and gastro-intestinal infection routes. It is proposed that the evidence convincingly supports that pathogenic microbial infection is associated with, and is likely a causative trigger for, AD pathology. Microbes can drive AD pathology by two main pathways: either by directly infecting the brain and stimulating amyloid-mediated defence (causative trigger) or indirectly, by stimulating the pro-inflammatory effects of infection. In this context, it follows that anti-microbial/anti-infection therapies could be effective for regulating the pathology and symptoms of AD, depending on the stage of disease. As long-term administration of traditional antibiotic therapy is not recommended, alternative antibiotic agents such as anti-microbial peptides (AMPs), could be preferred for intervention and disease management of AD.

Gut microbiota in dementia. Critical review of novel findings and their potential application

There is a great deal of impetus for the comprehensive understanding of the complete pathological function, genetic information, and functional diversity of the gut microbiota that favors the development of dementia. It has been reported that patients with mild cognitive impairment and Alzheimer's disease present with several metabolic and immune-inflammatory alterations. The recently highlighted aspects of human health linked to cognitive decline include insulin-resistance, obesity, and chronic low-grade inflammation. Gut microbiota is known to produce neurotransmitters, such as GABA, acetylcholine, dopamine or serotonin, vitamins, intestinal toxins, and modulate nerve signaling - with emphasis on the vagus nerve. Additionally, gut dysbiosis results in impaired synthesis of signaling proteins affecting metabolic processes relevant to the development of Alzheimer's disease. Due to numerous links of gut microbiota to crucial metabolic and inflammatory pathways, attempts aimed at correcting the gut microflora composition may affect dementia pathology in a pleiotropic manner. Taking advantage of the metabolic effects of cold exposure on organisms by the introduction of whole-body cryostimulation in dementia patients could lead to alterations in gut microbiota and, therefore, decrease of an inflammatory response and insulin resistance, which remain one of the critical metabolic features of dementia. Further studies are needed in order to explore the potential application of recent findings and ways of achieving the desired goals.

Herpes Labialis, Chlamydophila pneumoniae, Helicobacter pylori, and Cytomegalovirus Infections and Risk of Dementia: The Framingham Heart Study

BACKGROUND

An association between chronic infectious diseases and development of dementia has been suspected for decades, based on the finding of pathogens in postmortem brain tissue and on serological evidence. However, questions remain regarding confounders, reverse causality, and how accurate, reproducible and generalizable those findings are.

OBJECTIVE

Investigate whether exposure to Herpes simplex (manifested as herpes labialis), Chlamydophila pneumoniae (C. pneumoniae), Helicobacter pylori (H. pylori), and cytomegalovirus (CMV) modifies the risk of dementia in a populational cohort.

METHODS

Questionnaires regarding incidence of herpes infections were administered to Original Framingham Study participants (n = 2,632). Serologies for C. pneumoniae, H. pylori, and CMV were obtained in Original (n = 2,351) and Offspring cohort (n = 3,687) participants. Participants are under continuous dementia surveillance. Brain MRI and neuropsychological batteries were administered to Offspring participants from 1999-2005. The association between each infection and incident dementia was tested with Cox models. Linear models were used to investigate associations between MRI or neuropsychological parameters and serologies.

RESULTS

There was no association between infection serologies and dementia incidence, total brain volume, and white matter hyperintensities. Herpes labialis was associated with reduced 10-year dementia risk (HR 0.66, CI 0.46-0.97), but not for the duration of follow-up. H. pylori antibodies were associated with worse global cognition (β -0.14, CI -0.22, -0.05).

CONCLUSION

We found no association between measures of chronic infection and incident dementia, except for a reduction in 10-year dementia risk for patients with herpes labialis. This unexpected result requires confirmation and further characterization, concerning antiviral treatment effects and capture of episodes.

The relation between Helicobacter pylori immunoglobulin G seropositivity and leukocyte telomere length in US adults from NHANES 1999-2000

BACKGROUND

Helicobacter pylori (H pylori) immunoglobulin G (IgG) seropositivity is prevalent but its relation with leukocyte telomere length (LTL), a cellular aging biomarker, is unclear.

METHODS

Among 3,472 participants from the National Health and Nutrition Examination Survey (NHANES) cycle 1999-2000, LTL was measured with the quantitative polymerase chain reaction. H pylori IgG was measured by enzyme-linked immunosorbent assays and defined as seropositivity with an immune status ratio score > 0.9. We used linear regression models to examine the relation of H pylori IgG seropositivity with continuous LTL and logistic regression for the relation with short LTL (<10th percentile of the population distribution) adjusting for potential confounders. We stratified the analyses by a priori selected variables.

RESULTS

Population prevalence of H pylori IgG seropositivity was 31.5% in the overall population with higher prevalence found in those with older age, other races than non-Hispanic whites, lower education, and being born out of the United States. Continuous LTL was non-significantly shorter in those with H Pylori IgG seropositivity versus seronegativity (mean difference = -40.3 bp, 95% CI: -112.4, 31.9). This difference was not significant after adjusting for potential confounders nor stratifying by potential effect modifiers. H Pylori IgG seropositivity was significantly associated with short LTL among the elderly (55-75 years, adjusted OR: 3.06, 95% CI: 1.17, 7.99), but not in the overall population (OR: 1.28, 95% CI: 0.81-2.02).

CONCLUSION

H Pylori IgG seropositivity was not associated with continuous LTL in the general population but may be associated with an excessively short LTL in the elderly.

Molecular Links Between Alzheimer's Disease and Gastrointestinal Microbiota: Emphasis on Helicobacter pylori Infection Involvement

Alzheimer's disease (AD) is a neurodegenerative disease and the main form of dementia, characterized by progressive cognitive decline and detrimental consequences in both personal-family and global level. Within this narrative review, we provide recent molecular aspects of Tau, a microtubule AD-associated protein, as well as amyloid beta, involved in AD pathophysiology. Moreover, we provide additional emerging data from basic research as well as clinical studies indicating an implicating role of gastrointestinal microbiota (GI-M), including Helicobacter pylori infection (Hp-I), in AD pathophysiology. Likewise, we identified through a molecular prism the current evidence of AD pathogenesis as well as its linkage with GI-M and emphasizing the role of Hp-I. All in all, additional large-scale studies are required for the further clarification of AD pathophysiology and its connection with GI-M and Hp-I, so as novel therapies on molecular basis become available.

The Microbiome as a Modifier of Neurodegenerative Disease Risk

The gut microbiome is increasingly implicated in modifying susceptibility to and progression of neurodegenerative diseases (NDs). In this review, we discuss roles for the microbiome in aging and in NDs. In particular, we summarize findings from human studies on microbiome alterations in Parkinson's disease, Alzheimer's disease, amyotrophic lateral sclerosis, and Huntington's disease. We assess animal studies of genetic and environmental models for NDs that investigate how manipulations of the microbiome causally impact the development of behavioral and neuropathological endophenotypes of disease. We additionally evaluate the likely immunological, neuronal, and metabolic mechanisms for how the gut microbiota may modulate risk for NDs. Finally, we speculate on cross-cutting features for microbial influences across multiple NDs and consider the potential for microbiome-targeted interventions for NDs.

Possible dementia risk of proton pump inhibitors and H2 receptor blockers use in the treatment of Helicobacter pylori: A meta-analysis study

INTRODUCTION

The risk of dementia when using proton-pump-inhibitors (PPIs) and H2-receptor-blockers as a treatment of Helicobacter-pylori have a lot of controversial-research with different results; however, no final recommendation was deduced from all these researches. A meta-analysis study was performed to evaluate the relationship between PPIs and H2-receptor-blockers use and dementia.

METHODS

Through a systematic literature search up to December-2019, 10-studies with 371951-subjects of them 71021Helicobacter-pylori-positive subjects using either PPIs or H2-receptor-blockers or both were identified reporting-relationships between PPIs and H2-receptor-blockers uses and dementia (10-studies contained PPIS, 4-contained H2-receptor-blockers). Odd-ratio (OR) with 95% confidence-intervals (CIs) was calculated comparing PPIs and H2-receptor-blockers users and to non-user subjects on the bases of dementia using the dichotomous-method with a random-effect-model.

RESULTS

No significant difference was found between PPIs-users or non-user (OR, 0.87; 95% CI, 0.62-1.22) or between H2-receptor blockers-users and non-users (OR, 1.21; 95% CI, 0.91-1.59) as a risk of dementia. The extent of increases in dementia with H2-receptor-blockers was higher than that with PPIs. The impact of PPIs and H2-receptor-blockers was similar in all populations.

CONCLUSIONS

Based on this meta-analysis, the contentious use of PPIs or H2-receptor-blockers may not have an independent-relationship to dementia. This suggests that using PPIs or H2-receptor-blockers is not related to dementia. However, we still have to recommend careful use of PPIs and H2-receptor-blockers when treating Helicobacter-pylori and sticking to the dose and length of treatment and not to extend it to avoid any possible risk.

Association of Intestinal Disorders with Parkinson's Disease and Alzheimer's Disease: A Systematic Review and Meta-Analysis

Parkinson's disease (PD) and Alzheimer's disease (AD) are the most common neurodegenerative disorders, with an overall global incidence of 40 million. Many studies have revealed the association of intestinal disorders and bacterial infections with PD, but few studies have found such a relationship with AD. In this meta-analysis, related articles published up to September 2018 were searched in PubMed. Of the 2121 related articles screened initially, 56 were found to be eligible. Data on the risks of PD and AD due to five intestinal disorders and infection with Helicobacter pylori, as a representative intestinal microbe, were obtained, and a fixed- or random-effects model was used to pool the odds ratios (ORs) with 95% confidence interval (CIs) from individual studies. The combined OR for all types of intestinal disorders with an increased risk of PD was 3.36 (95% CI: 2.70-4.17). The ORs for each category were as follows: constipation, 4.05 (95% CI, 3.24-5.06); inflammatory bowel disease (IBD), 1.16 (95% CI, 0.89-1.52); irritable bowel syndrome (IBS), 1.75 (95% CI, 0.55-5.56); small intestinal bacterial overgrowth, 5.15 (95% CI, 3.33-7.96); and diarrhea, 1.27 (95% CI, 0.28-5.75). The combined OR of all types of intestinal disorders with an increased risk of AD was 1.52 (95% CI, 1.09-2.13). The ORs for IBS and IBD were 1.42 (95% CI, 1.02-1.99) and 2.40 (95% CI, 1.00-5.76), respectively. The risk estimates of H. pylori infection in PD and AD patients were as follows: OR, 1.65 (95% CI, 1.43-1.91) and OR, 1.40 (95% CI, 1.12-1.76), respectively. These findings suggest that PD and AD are significantly associated with intestinal disorders. The negative roles of H. pylori in the development of PD or AD should be evaluated to shed new light on the diagnosis and treatment of PD and AD. National governments should periodically inspect the intestinal condition of residents and extend health plans to improve intestinal health to prevent potential neurological disorders.

Review: Helicobacter pylori and extragastric diseases

In the last year, many studies have demonstrated a potential role of Helicobacter pylori in the pathogenic mechanisms of different extragastric diseases. While the role of H pylori in idiopathic thrombocytopenic purpura, idiopathic iron deficiency anemia, and vitamin B12 deficiency has already been demonstrated, there is growing evidence of other related conditions, especially cardiovascular, metabolic, and neurologic disorders, including neurodegenerative diseases. A summary of the results of the most relevant studies published over the last year on this attractive topic is presented in this review.

Exploring the "Multiple-Hit Hypothesis" of Neurodegenerative Disease: Bacterial Infection Comes Up to Bat

Despite major strides in personalized genomics, it remains poorly understood why neurodegenerative diseases occur in only a fraction of individuals with a genetic predisposition and conversely, why individuals with no genetic risk of a disorder develop one. Chronic diseases like Alzheimer's, Parkinson's, and Multiple sclerosis are speculated to result from a combination of genetic and environmental factors, a concept commonly referred to as the “multiple hit hypothesis.” A number of bacterial infections have been linked to increased risk of neurodegeneration, and in some cases, clearance of bacterial pathogens has been correlated with amelioration of central nervous system (CNS) deficits. Additionally, mutations in several genes known to contribute to CNS disorders like Parkinson's Disease have repeatedly been implicated in susceptibility to intracellular bacterial infection. Recent data has begun to demonstrate roles for these genes (PARK2, PINK1, and LRRK2) in modulating innate immune outcomes, suggesting that immune dysregulation may play an even more important role in neurodegeneration than previously appreciated. This review will broadly explore the connections between bacterial infection, immune dysregulation, and CNS disorders. Understanding this interplay and how bacterial pathogenesis contributes to the “multiple-hit hypothesis” of neurodegeneration will be crucial to develop therapeutics to effectively treat both neurodegeneration and infection.