Blood pressure and Alzheimer's disease: A review of meta-analysis

Exercise-induced modulation of miRNAs and gut microbiome: a holistic approach to neuroprotection in Alzheimer's disease

Alzheimer's disease (AD), a progressive neurodegenerative disorder, is marked by cognitive decline, neuroinflammation, and neuronal loss. MicroRNAs (miRNAs) have emerged as critical regulators of gene expression, influencing key pathways involved in neuroinflammation and neurodegeneration in AD. This review delves into the multifaceted role of exercise in modulating miRNA expression and its interplay with the gut microbiome, proposing a comprehensive framework for neuroprotection in AD. By synthesizing current research, we elucidate how exercise-induced changes in miRNA profiles can mitigate inflammatory responses, promote neurogenesis, and reduce amyloid-beta and tau pathologies. Additionally, we explore the gut-brain axis, highlighting how exercise-driven alterations in gut microbiota composition can further influence miRNA expression, thereby enhancing cognitive function and reducing neuroinflammatory markers. This holistic approach underscores the potential of targeting exercise-regulated miRNAs and gut microbiome interactions as a novel, noninvasive therapeutic strategy to decelerate AD progression and improve quality of life for patients. This approach aims to decelerate disease progression and improve patient outcomes, offering a promising avenue for enhancing the effectiveness of AD management.

The association between pulse wave velocity and cerebrospinal fluid biomarkers for Alzheimer's disease

We examined the association between arterial stiffness using non-invasive pulse wave velocity (PWV) and cerebrospinal fluid (CSF) Alzheimer's disease (AD) biomarkers. We conducted a cross-sectional multivariate logistic regression analysis using established cut-off values for PWV and CSF biomarkers. Of the 739 participants, 69% were female, 84% were White, 12% were Black, and the mean age was 62. After adjustment for potential confounders, participants with high PWV had 94% (OR = 1.94, 95% CI 1.20-3.20) greater odds of AD biomarker positivity for tTau/Aβ42 and 108% (OR = 2.08, 95% Cl, 1.27-3.46) for pTau181/Aβ42. Our results suggest that higher arterial stiffness is associated with AD CSF biomarker positivity.

Visual screening of butyrylcholinesterase inhibitors by a cellulose membrane biosensor with amide-bonded immobilization of butyrylcholinesterase in a solid-phase enzyme-catalyzed reaction

The rapid discovery of highly active butyrylcholinesterase (BChE) inhibitors is key to the treatment of the late stages of Alzheimer's disease. Herein, a colorimetric cellulose membrane (CM)-based biosensor was developed. The CM was employed as a carrier, which can be immobilized with the BChE and 5,5'-dithio-(2-nitrobenzoic acid) (DTNB) to prepare the biosensor for the solid-phase enzyme-catalyzed reaction. Specifically, the CM was oxidized to the oxidized cellulose membrane (OCM), which can further covalently bind the BChE to prepare the BChE-immobilized cellulose membrane (BCM). Then, the DTNB was adsorbed to the BCM to prepare the BDCM biosensor. The BDCM biosensor can visually detect S-butyrylthiocholine iodide at the yellow light signal with several characters, including sensitivity (LOD 1.56 μM), affinity (Km = 140.48 ± 5.42 μM), stability (over 1 month), via the BChE-catalyzed solid-phase reaction. Furthermore, the BDCM biosensor was applied to screen and determine the specific commercial BChE inhibitors tacrine and rivastigmine, with the IC50 values of 30.99 ± 12.20 nM and 2.02 ± 0.13 μM, respectively, from 13 different commercial inhibitors. This work provided a new method of visual BChE inhibitor screening and a useful strategy for the design of enzyme-based immobilization technology cellulose membrane biosensors.

Relationship between diastolic blood pressure and Alzheimer disease: A 2-sample Mendelian randomization study based on an automated screening method for exposure factors and empirical validation

This study investigates the causal relationship between diastolic blood pressure (DBP) and Alzheimer disease (AD) using 2-sample Mendelian randomization (MR) analysis with publicly available genome-wide association study (GWAS) data and empirical validation. Automated screening identified DBP as a factor related to AD. Two-sample MR analyses were conducted using inverse variance weighting (IVW), MR-Egger regression, weighted median, simple mode, and weighted mode methods. Tests for pleiotropy, heterogeneity, and stability of genetic variants were performed. Data included DBP from Europeans (n = 422,713) and AD cases (n = 753) and controls (n = 736) of European ancestry. An empirical sample of 125 patients with cardiovascular disease in Chinese was used to verify the possibility of the above relationship by restricted cubic spline method. Thirty-seven genome-wide significant nucleotide polymorphisms from DBP GWAS were used as instrumental variables. IVW showed a causal relationship between DBP and AD (β = -1.594, SE = 0.580, P = .006). MR-Egger regression indicated minimal pleiotropy (intercept = 0.037; P = .736) and confirmed the causal relationship (β = -3.110, SE = 1.376, P = .030). The weighted median method also supported this relationship (β = -1.868, SE = 0.856, P = .029). The simple and weighted mode methods did not find significant relationships (P > .1). No heterogeneity or asymmetry was detected by Cochran Q test or the funnel plot, and the leave-one-out method showed stable results. The validation results indicate that the aforementioned findings are stable within the normal range of DBP. MR analysis supports a potential causal link between higher DBP and a lower risk of AD. The screening exposure method used could enhance MR study efficiency.

Association of Hypertension with Different Cognitive Disorders

This literature review explores the association between hypertension and major neurocognitive disorders, including delirium, Alzheimer's disease, vascular dementia, Lewy body dementia, and frontotemporal dementia, which contribute significantly to global mortality and morbidity. Hypertension is a potentially modifiable risk factor for cognitive decline, as it contributes to the progression of neurodegenerative pathologies via vascular damage, inflammation, and the disruption of the blood-brain barrier. Despite this, the effectiveness of antihypertensive treatments in preventing or alleviating cognitive decline remains contentious. While some research highlights the potential benefits of angiotensin-converting enzyme inhibitors and angiotensin receptor blockers, other studies show inconsistent results, complicated by variations in hypertension definitions, diagnostic criteria for cognitive disorders, and confounding factors like medication adherence. Furthermore, the complex bidirectional relationship between hypertension and major neurocognitive disorders warrants more investigation, as cognitive decline can exacerbate cardiovascular risks through heightened inflammatory responses and compromised autonomic regulation. This review underscores the need for prospective, long-term studies to elucidate the relationships between hypertension and cognitive disorders and to evaluate the potential therapeutic benefits of antihypertensive treatments.

Development and validation of the Florey Dementia Risk Score web-based tool to screen for Alzheimer's disease in primary care

Background

It is estimated that ∼60% of people with Alzheimer's disease (AD) are undetected or undiagnosed, with higher rates of underdiagnosis in low-to middle-income areas with limited medical resources. To promote health equity, we have developed a web-based tool that utilizes easy-to-collect clinical data to enhance AD detection rate in primary care settings.

Methods

This study was leveraged on the data collected from participants of the Australian Imaging, Biomarker & Lifestyle (AIBL) study and the Religious Orders Study and Memory and Aging Project (ROSMAP). The study included three phases: (1) constructing and evaluating a model on retrospective cohort data (1407 AIBL participants), (2) performing simulated trials to assess model accuracy (30 AIBL participants) and missing data tolerability (30 AIBL participants), and (3) external evaluation using a non-Australian dataset (500 ROSMAP participants). The auto-score machine learning algorithm was employed to develop the Florey Dementia Risk Score (FDRS). All the simulated trials and evaluation were performed using a web-based FDRS tool.

Findings

FDRS achieved an area under the curve (AUC) of approximately 0.82 [95% CI, 0.75-0.88], with a sensitivity of 0.74 [0.60-0.86] and a specificity of 0.73 [0.70-0.79]. The accuracy of the simulated pilot trial for 30 AIBL participants with complete record was 87% (26/30 correct), while it only slightly decreased (80.0-83.3%, depending on imputation methods) for another 30 AIBL participants with one or two missing data. FDRS achieved an AUC of 0.82 [0.77-0.86] of 500 ROSMAP participants.

Interpretation

The FDRS tool offers a potential low-cost solution to AD screening in primary care. The present study warrants future trials of FDRS for optimization and to confirm its generalizability across a more diverse population, especially people in low-income countries.

Funding

National Health and Medical Research Council, Australia (GNT2007912) and Alzheimer's Association, USA (23AARF-1020292).

MicroRNAs: pioneering regulators in Alzheimer's disease pathogenesis, diagnosis, and therapy

This article delves into Alzheimer's disease (AD), a prevalent neurodegenerative condition primarily affecting the elderly. It is characterized by progressive memory and cognitive impairments, severely disrupting daily life. Recent research highlights the potential involvement of microRNAs in the pathogenesis of AD. MicroRNAs (MiRNAs), short non-coding RNAs comprising 20-24 nucleotides, significantly influence gene regulation by hindering translation or promoting degradation of target genes. This review explores the role of specific miRNAs in AD progression, focusing on their impact on β-amyloid (Aβ) peptide accumulation, intracellular aggregation of hyperphosphorylated tau proteins, mitochondrial dysfunction, neuroinflammation, oxidative stress, and the expression of the APOE4 gene. Our insights contribute to understanding AD's pathology, offering new avenues for identifying diagnostic markers and developing novel therapeutic targets.

Comparative Study of Risk Factors Associated with Normal Cognition and Cognitive Impairment in Rural West Elderly Texans

Background

Alzheimer's disease (AD) is related to one or more chronic illnesses, which may develop cognitive decline and dementia. Cognitive impairment is increasing, and public health officials must address risk factors for AD to improve the health of rural West Texas communities.

Objective

The purpose of this study was to explore the sociodemographic and chronic disease risk factors related to cognitive impairment among elderly adults living in Cochran, Parmer, and Bailey counties in rural West Texas.

Methods

Statistical methods such as Pearson's chi-squared, proportion tests, univariate binary logistic regression, and a multivariable logistic regression were utilized to analyze data. SPSS software was used to detect the significant relationship between cognitive impairment and risk factors.

Results

Summary statistics were obtained for sociodemographic and chronic diseases by using cross-tabulation analysis and comparing the county respondents with proportion tests. A univariate binary logistic regression method was utilized and found that age group 60-69, anxiety, depression, diabetes, hypertension, and cardiovascular disease were significantly associated with cognitive impairment. Using a multivariable logistic regression approach, it was found that Bailey County (age group 60-69) had a higher likelihood (p = 0.002) of cognitive impairment than Parmer (p = 0.067) and Cochran counties (p = 0.064). The risk of females (p = 0.033) in Parmer County was 78.3% lower compared to males in developing AD.

Conclusions

Identifying significant risk factors for cognitive impairment are important in addressing issues of geographic variations and integrating such factors may guide relevant policy interventions to reduce cognitive impairment incidence in rural communities within West Texas.

Age-Related Effects of AT1 Receptor Antagonist Losartan on Cognitive Decline in Spontaneously Hypertensive Rats

Both hypertension and aging are known to increase the vulnerability of the brain to neurovascular damage, resulting in cognitive impairment. The present study investigated the efficacy of the antihypertensive drug losartan on age- and hypertension-associated cognitive decline and the possible mechanism underlying its effect in spontaneously hypertensive rats (SHRs). Losartan was administered (10 mg/kg, i.p. for 19 days) to 3- and 14-month-old SHRs. Age-matched Wistar rats were used as controls. Working memory, short-term object recognition, and spatial memory were assessed using the Y-maze, object recognition test (ORT) and radial arm maze (RAM) test. The expression of markers associated with aging, oxidative stress, and memory-related signaling was assessed in the frontal cortex (FC) and hippocampus. Motor activity measured over 24 h was not different between groups. Middle-aged vehicle-treated SHRs showed poorer performance in spontaneous alternation behavior (SAB) and activity in the first Y-maze test than their younger counterparts, suggesting age-related reduced "decision making" and reactivity in a novel environment. Losartan improved the age- and hypertension-induced decline in short-term recognition and spatial memory measured in the ORT and the second Y-maze test, particularly in the middle-aged rats, but was ineffective in the young adult rats. Changes in memory and age-related markers such as cAMP response element-binding protein (CREB) and amyloid-β1-42 (Aβ1-42) and increased oxidative stress were observed in the hippocampus but not in the FC between young adult and middle-aged vehicle-treated SHRs. Losartan increased CREB expression while reducing Aβ1-42 levels and concomitant oxidative stress in middle-aged SHRs compared with vehicle-treated SHRs. In conclusion, our study highlights the complex interplay between hypertension, aging, and cognitive impairment. It suggests that there is a critical time window for therapeutic intervention with angiotensin II type 1 receptor blockers.

Dementia and depression: Biological connections with amyloid β protein

Dementia is an umbrella term for a broad group of age-associated neurodegenerative diseases. It is estimated that dementia affects 50 million people worldwide and that Alzheimer's disease (AD) is responsible for up to 75% of cases. Small extracellular senile plaques composed of filamentous aggregates of amyloid β (Aβ) protein tend to bind to neuronal receptors, affecting cholinergic, serotonergic, dopaminergic and noradrenergic neurotransmission, leading to neuroinflammation, among other pathophysiologic processes and subsequent neuronal death, followed by dementia. The amyloid cascade hypothesis points to a pathological process in the cleavage of the amyloid precursor protein (APP), resulting in pathological Aβ. There is a close relationship between the pathologies that lead to dementia and depression. It is estimated that depression is prevalent in up to 90% of individuals diagnosed with Parkinson's disease, with varying severity, and in 20 to 30% of cases of Alzheimer's disease. The hypothalamic pituitary adrenal (HPA) axis is the great intermediary between the pathophysiological mechanisms in neurodegenerative diseases and depression. This review discusses the role of Aβ protein in the pathophysiological mechanisms of dementia and depression, considering the HPA axis, neuroinflammation, oxidative stress, signalling pathways and neurotransmission.

Using Focus Groups to Explore Older Black Men's Perception of Dietary Interventions

Older Black men are underrepresented in research despite being disproportionately affected by Alzheimer's disease (AD) and cardiovascular (CV) risk factors related to AD compared with non-Hispanic Whites. Although dietary interventions have shown promise to reduce modifiable CV risk factors related to AD, Black Americans have lower adherence likely due to lack of cultural considerations. Using a noninterventional convergent parallel mixed-methods approach, this study examined the cultural contexts that inform perceptions of dietary interventions among older Midwestern Black men. All participants completed an online demographic and dietary habit survey prior to focus group discussions. Two focus group discussion sessions were conducted with a total of 10 cognitively normal Black men aged 55 years and older. Survey data were analyzed using a frequency analysis and qualitative data were analyzed using a six-step thematic analysis process. Most men indicated having hypertension (N = 7, 77.8%) and currently not following a dietary eating pattern (N = 8, 88.9%). Emerging themes identified included (1) knowledge of dementia, (2) perceptions of dietary interventions, (3) barriers impacting participation in dietary interventions, and (4) overcoming barriers to engage Black men in dietary interventions. Findings from this study should inform the design of future dietary interventions for AD prevention to enhance participation among older Black men.

Alzheimer's disease: The role of proteins in formation, mechanisms, and new therapeutic approaches

Alzheimer's disease (AD) is a progressive neurological disorder that affects the central nervous system (CNS), leading to memory and cognitive decline. In AD, the brain experiences three main structural changes: a significant decrease in the quantity of neurons, the development of neurofibrillary tangles (NFT) composed of hyperphosphorylated tau protein, and the formation of amyloid beta (Aβ) or senile plaques, which are protein deposits found outside cells and surrounded by dystrophic neurites. Genetic studies have identified four genes associated with autosomal dominant or familial early-onset AD (FAD): amyloid precursor protein (APP), presenilin 1 (PS1), presenilin 2 (PS2), and apolipoprotein E (ApoE). The formation of plaques primarily involves the accumulation of Aβ, which can be influenced by mutations in APP, PS1, PS2, or ApoE genes. Mutations in the APP and presenilin (PS) proteins can cause an increased amyloid β peptides production, especially the further form of amyloidogenic known as Aβ42. Apart from genetic factors, environmental factors such as cytokines and neurotoxins may also have a significant impact on the development and progression of AD by influencing the formation of amyloid plaques and intracellular tangles. Exploring the causes and implications of protein aggregation in the brain could lead to innovative therapeutic approaches. Some promising therapy strategies that have reached the clinical stage include using acetylcholinesterase inhibitors, estrogen, nonsteroidal anti-inflammatory drugs (NSAIDs), antioxidants, and antiapoptotic agents. The most hopeful therapeutic strategies involve inhibiting activity of secretase and preventing the β-amyloid oligomers and fibrils formation, which are associated with the β-amyloid fibrils accumulation in AD. Additionally, immunotherapy development holds promise as a progressive therapeutic approach for treatment of AD. Recently, the two primary categories of brain stimulation techniques that have been studied for the treatment of AD are invasive brain stimulation (IBS) and non-invasive brain stimulation (NIBS). In this article, the amyloid proteins that play a significant role in the AD formation, the mechanism of disease formation as well as new drugs utilized to treat of AD will be reviewed.