Biomarkers of vascular risk, systemic inflammation, and microvascular pathology and neuropsychiatric symptoms in Alzheimer's disease

Brain interleukins and Alzheimer's disease

The central nervous system (CNS) is immune-privileged by several immuno-modulators as interleukins (ILs). ILs are cytokines secreted by immune cells for cell-cell signaling communications and affect the functions of the CNS. ILs were reported to orchestrate different molecular and cellular mechanisms of both physiological and pathological events, through overproduction or over-expression of their receptors. They interact with numerous receptors mediating pro-inflammatory and/or anti-inflammatory actions. Interleukins have been implicated to participate in neurodegenerative diseases. They play a critical role in Alzheimer's disease (AD) pathology which is characterized by the over-production of pro-inflammatory ILs. These may aggravate neurodegeneration, in addition to their contribution to detrimental mechanisms as oxidative stress, and excitotoxicity. However, recent research on the relation between ILs and AD revealed major discrepancies. Most of the major ILs were shown to play both pro- and anti-inflammatory roles in different experimental settings and models. The interactions between different ILs through shared pathways also add to the difficulty of drawing solid conclusions. In addition, targeting the different ILs has not yielded consistent results. The repeated failures of therapeutic drugs in treating AD necessitate the search for novel agents targeting multiple mechanisms of the disease pathology. In this context, the understanding of interleukins and their roles throughout the disease progression and interaction with other systems in the brain may provide promising therapeutic targets for the prevention or treatment of AD.

Connecting the Dots: Gender, Sexuality, and Societal Influences on Cognitive Aging and Alzheimer's Disease

Alzheimer's disease (AD) has many etiologies and the impact of gender on AD changes throughout time. As a consequence of advancements in precision medical procedures and methodology, Alzheimer's disease is now better understood and treated. Several risk factors may be addressed to lower one's chances of developing Alzheimer's disease or associated dementia (ADRD). The presence of amyloid-α protein senile plaques, intracellular tau protein neurofibrillary tangles (NfTs), neurodegeneration, and neuropsychiatric symptoms (NPS) characterizes Alzheimer's disease. NPS is common in persons with Alzheimer's disease dementia, although its presentation varies widely. Gender differences might explain this clinical variability. The fundamental goal of this review is to 1) emphasize the function of old age, sex, and gender in the development of Alzheimer's disease, dementia, and ADRD, and 2) explain the importance of sexual hormones, education, and APOE (Apolipoprotein E) status. This is a narrative summary of new ideas and concepts on the differences in the chance of developing dementia or Alzheimer's disease between men and women. A more thorough examination of risk and protective variables in both men and women might hasten research into the epidemiology of neurological illnesses such as dementia and Alzheimer's disease. Similarly, future preventive efforts should target men and women separately.

Early Detection of Dementia in Populations With Type 2 Diabetes: Predictive Analytics Using Machine Learning Approach

BACKGROUND

The possible association between diabetes mellitus and dementia has raised concerns, given the observed coincidental occurrences.

OBJECTIVE

This study aimed to develop a personalized predictive model, using artificial intelligence, to assess the 5-year and 10-year dementia risk among patients with type 2 diabetes mellitus (T2DM) who are prescribed antidiabetic medications.

METHODS

This retrospective multicenter study used data from the Taipei Medical University Clinical Research Database, which comprises electronic medical records from 3 hospitals in Taiwan. This study applied 8 machine learning algorithms to develop prediction models, including logistic regression, linear discriminant analysis, gradient boosting machine, light gradient boosting machine, AdaBoost, random forest, extreme gradient boosting, and artificial neural network (ANN). These models incorporated a range of variables, encompassing patient characteristics, comorbidities, medication usage, laboratory results, and examination data.

RESULTS

This study involved a cohort of 43,068 patients diagnosed with type 2 diabetes mellitus, which accounted for a total of 1,937,692 visits. For model development and validation, 1,300,829 visits were used, while an additional 636,863 visits were reserved for external testing. The area under the curve of the prediction models range from 0.67 for the logistic regression to 0.98 for the ANNs. Based on the external test results, the model built using the ANN algorithm had the best area under the curve (0.97 for 5-year follow-up period and 0.98 for 10-year follow-up period). Based on the best model (ANN), age, gender, triglyceride, hemoglobin A1c, antidiabetic agents, stroke history, and other long-term medications were the most important predictors.

CONCLUSIONS

We have successfully developed a novel, computer-aided, dementia risk prediction model that can facilitate the clinical diagnosis and management of patients prescribed with antidiabetic medications. However, further investigation is required to assess the model's feasibility and external validity.

Associations Between Neuropsychiatric Symptoms and Inflammation in Neurodegenerative Dementia: A Systematic Review

Background

Neuropsychiatric symptoms are common in dementia and linked to adverse outcomes. Inflammation is increasingly recognized as playing a role as a driver of early disease progression in Alzheimer's disease (AD) and related dementias. Inflammation has also been linked to primary psychiatric disorders, however its association with neuropsychiatric symptoms in neurodegenerative dementias remains uncertain.

Methods

We conducted a systematic literature review investigating associations between inflammation and neuropsychiatric symptoms in neurodegenerative dementias, including AD, Lewy body, Frontotemporal, Parkinson's (PD) and Huntington's disease dementias.

Results

Ninety-nine studies met our inclusion criteria, and the majority (n = 59) investigated AD and/or mild cognitive impairment (MCI). Thirty-five studies included PD, and only 6 investigated non-AD dementias. Inflammation was measured in blood, CSF, by genotype, brain tissue and PET imaging. Overall, studies exhibited considerable heterogeneity and evidence for specific inflammatory markers was inconsistent, with lack of replication and few longitudinal studies with repeat biomarkers. Depression was the most frequently investigated symptom. In AD, some studies reported increases in peripheral IL-6, TNF-a associated with depressive symptoms. Preliminary investigations using PET measures of microglial activation found an association with agitation. In PD, studies reported positive associations between TNF-a, IL-6, CRP, MCP-1, IL-10 and depression.

Conclusion

Central and peripheral inflammation may play a role in neuropsychiatric symptoms in neurodegenerative dementias; however, the evidence is inconsistent. There is a need for multi-site longitudinal studies with detailed assessments of neuropsychiatric symptoms combined with replicable peripheral and central markers of inflammation.

APOE ε4-associated downregulation of the IL-7/IL-7R pathway in effector memory T cells: Implications for Alzheimer's disease

INTRODUCTION

The apolipoprotein E (APOE) ε4 allele exerts a significant influence on peripheral inflammation and neuroinflammation, yet the underlying mechanisms remain elusive.

METHODS

The present study enrolled 54 patients diagnosed with late-onset Alzheimer's disease (AD; including 28 APOE ε4 carriers and 26 non-carriers). Plasma inflammatory cytokine concentration was assessed, alongside bulk RNA sequencing (RNA-seq) and single-cell RNA sequencing (scRNA-seq) analysis of peripheral blood mononuclear cells (PBMCs).

RESULTS

Plasma tumor necrosis factor α, interferon γ, and interleukin (IL)-33 levels increased in the APOE ε4 carriers but IL-7 expression notably decreased. A negative correlation was observed between plasma IL-7 level and the hippocampal atrophy degree. Additionally, the expression of IL-7R and CD28 also decreased in PBMCs of APOE ε4 carriers. ScRNA-seq data results indicated that the changes were mainly related to the CD4+ Tem (effector memory) and CD8+ Tem T cells.

DISCUSSION

These findings shed light on the role of the downregulated IL-7/IL-7R pathway associated with the APOE ε4 allele in modulating neuroinflammation and hippocampal atrophy.

HIGHLIGHTS

The apolipoprotein E (APOE) ε4 allele decreases plasma interleukin (IL)-7 and aggravates hippocampal atrophy in Alzheimer's disease. Plasma IL-7 level is negatively associated with the degree of hippocampal atrophy. The expression of IL-7R signaling decreased in peripheral blood mononuclear cells of APOE ε4 carriers Dysregulation of the IL-7/IL-7R signal pathways enriches T cells.

Sex as a Determinant of Age-Related Changes in the Brain

The notion of notable anatomical, biochemical, and behavioral distinctions within male and female brains has been a contentious topic of interest within the scientific community over several decades. Advancements in neuroimaging and molecular biological techniques have increasingly elucidated common mechanisms characterizing brain aging while also revealing disparities between sexes in these processes. Variations in cognitive functions; susceptibility to and progression of neurodegenerative conditions, notably Alzheimer's and Parkinson's diseases; and notable disparities in life expectancy between sexes, underscore the significance of evaluating aging within the framework of gender differences. This comprehensive review surveys contemporary literature on the restructuring of brain structures and fundamental processes unfolding in the aging brain at cellular and molecular levels, with a focus on gender distinctions. Additionally, the review delves into age-related cognitive alterations, exploring factors influencing the acceleration or deceleration of aging, with particular attention to estrogen's hormonal support of the central nervous system.

Sex-associated microRNAs potentially implicated in sporadic Alzheimer's disease (sAD)

BACKGROUND

The onset and pathology of sporadic Alzheimer's disease (sAD) seem to be affected by both sex and genetic mechanisms. Evidence supports that the high prevalence of sAD in women, worldwide, may be attributed to an interplay among aging, sex, and lifestyle, influenced by genetics, metabolic changes, and hormones. Interestingly, epigenetic mechanisms such as microRNAs (miRNAs), known as master regulators of gene expression, may contribute to this observed sexual dimorphism in sAD.

OBJECTIVES

To investigate the potential impact of sex-associated miRNAs on processes manifesting sAD pathology, as described by the Tau-driven Adverse Outcome Pathway (AOP) leading to memory loss.

METHODS

Using publicly available human miRNA datasets, sex-biased miRNAs, defined as differentially expressed by sex in tissues possibly affected by sAD pathology, were collected. In addition, sex hormone-related miRNAs were also retrieved from the literature. The compiled sex-biased and sex hormone-related miRNAs were further plugged into the dysregulated processes of the Tau-driven AOP for memory loss.

RESULTS

Several miRNAs, previously identified as sex-associated, were implicated in dysregulated processes associated with the manifestation of sAD pathology. Importantly, the described pathology processes were not confined to a particular sex. A mechanistic-based approach utilizing miRNAs was adopted in order to elucidate the link between sex and biological processes potentially involved in the development of memory loss.

CONCLUSIONS

The identification of sex-associated miRNAs involved in the early processes manifesting memory loss may shed light to the complex molecular mechanisms underlying sAD pathogenesis in a sex-specific manner.

Association between sex and Huntington's disease: an updated review on symptomatology and prognosis of neurodegenerative disorders

Huntington's disease is a rare autosomal dominant disorder presenting with chorea, rigidity, hypo-/akinesia, cognitive decline, and psychiatric disturbances. Numerous risk factors have been defined in the onset of this disease. However, the number of CAG repeats in the genes are the most crucial factor rendering patients susceptible to the disease. Studies have shown significant differences in onset and disease presentation among the sexes, which prompts analysis of the impact of different sexes on disease etiology and progression. This article therefore discusses the evidence-based role of sex in aspects of symptomatology, pathogenesis, biomarkers, progression, and prognosis of Huntington's disease, with a secondary review of sex-linked differences in Alzheimer's and Parkinson's disease.

Alzheimer's Disease: A Review of Pathology, Current Treatments, and the Potential Therapeutic Effect of Decreasing Oxidative Stress by Combined Vitamin D and l-Cysteine Supplementation

Significance: Excess oxidative stress and neuroinflammation are risk factors in the onset and progression of Alzheimer's disease (AD) and its association with amyloid-β plaque accumulation. Oxidative stress impairs acetylcholine (ACH) and N-methyl-d-aspartate receptor signaling in brain areas that function in memory and learning. Glutathione (GSH) antioxidant depletion positively correlates with the cognitive decline in AD subjects. Treatments that upregulate GSH and ACH levels, which simultaneously decrease oxidative stress and inflammation, may be beneficial for AD. Recent Advances: Some clinical trials have shown a benefit of monotherapy with vitamin D (VD), whose deficiency is linked to AD or with l-cysteine (LC), a precursor of GSH biosynthesis, in reducing mild cognitive impairment. Animal studies have shown a simultaneous decrease in ACH esterase (AChE) and increase in GSH; combined supplementation with VD and LC results in a greater decrease in oxidative stress and inflammation, and increase in GSH levels compared with monotherapy with VD or LC. Therefore, cosupplementation with VD and LC has the potential of increasing GSH, downregulation of oxidative stress, and decreased inflammation and AChE levels. Future Directions: Clinical trials are needed to determine whether safe low-cost dietary supplements, using combined VD+LC, have the potential to alleviate elevated AChE, oxidative stress, and inflammation levels, thereby halting the onset of AD. Goal of Review: The goal of this review is to highlight the pathological hallmarks and current Food and Drug Administration-approved treatments for AD, and discuss the potential therapeutic effect that cosupplementation with VD+LC could manifest by increasing GSH levels in patients. Antioxid. Redox Signal. 40, 663-678.

Alzheimer's disease and inflammatory biomarkers positively correlate in plasma in the UK-ADRC cohort

INTRODUCTION

Protein-based plasma assays provide hope for improving accessibility and specificity of molecular diagnostics to diagnose dementia.

METHODS

Plasma was obtained from participants (N = 837) in our community-based University of Kentucky Alzheimer's Disease Research Center cohort. We evaluated six Alzheimer's disease (AD)- and neurodegeneration-related (Aβ40, Aβ42, Aβ42/40, p-tau181, total tau, and NfLight) and five inflammatory biomarkers (TNF𝛼, IL6, IL8, IL10, and GFAP) using the SIMOA-based protein assay platform. Statistics were performed to assess correlations.

RESULTS

Our large cohort reflects previous plasma biomarker findings. Relationships between biomarkers to understand AD-inflammatory biomarker correlations showed significant associations between AD and inflammatory biomarkers suggesting peripheral inflammatory interactions with increasing AD pathology. Biomarker associations parsed out by clinical diagnosis (normal, MCI, and dementia) reveal changes in strength of the correlations across the cognitive continuum.

DISCUSSION

Unique AD-inflammatory biomarker correlations in a community-based cohort reveal a new avenue for utilizing plasma-based biomarkers in the assessment of AD and related dementias.

HIGHLIGHTS

Large community cohorts studying sex, age, and APOE genotype effects on biomarkers are few. It is unknown how biomarker-biomarker associations vary through aging and dementia. Six AD (Aβ40, Aβ42, Aβ42/40, p-tau181, total tau, and NfLight) and five inflammatory biomarkers (TNFα, IL6, IL8, IL10, and GFAP) were used to examine associations between biomarkers. Plasma biomarkers suggesting increasing cerebral AD pathology corresponded to increases in peripheral inflammatory markers, both pro-inflammatory and anti-inflammatory. Strength of correlations, between pairs of classic AD and inflammatory plasma biomarker, changes throughout cognitive progression to dementia.

Neuropsychiatric Symptoms are Related to Blood-biomarkers in Major Neurocognitive Disorders

BACKGROUND

Neuropsychiatric symptoms (NPS) are highly prevalent among individuals with major neurocognitive disorders (MNCD).

OBJECTIVE

Here, we characterized blood biomarkers (metabolic, inflammatory, neurotrophic profiles and total antioxidant), body composition, physical fitness and quality of life (QoL) in individuals with MNCD according to NPS.

METHODS

The sample comprised 34 older adults (71.4% women; 74.06±6.03 yrs, with MNCD diagnosis) categorized according to 50th percentile [Low (≤12) or High (≥13)] for NPS (Neuropsychiatric Inventory Questionnaire). Sociodemographic, clinical data, body composition, anthropometric, cognitive assessment (ADAS-Cog), physical fitness (Senior Fitness Test), QoL (QoL-Alzheimer's Disease scale) were evaluated, and blood samples were collected for biochemical analysis.

RESULTS

Low compared to high NPS group showed higher levels of IL-6, IGF-1and neurotrophic zscore (composite of IGF-1, VEGF-1, BDNF). Additionally, low compared to high NPS group have higher QoL, aerobic fitness and upper body and lower body strength.

CONCLUSION

The severity of NPS seems to be related to modified neurotrophic and inflammatory outcomes, lower physical fitness, and poor QoL. Strategies to counteract NPS development may preserve the physical and mental health of individuals with MNCD.

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Therapeutic Intervention of Neuroinflammatory Alzheimer Disease Model by Inhibition of Classical Complement Pathway with the Use of Anti-C1r Loaded Exosomes

Alzheimer's disease (AD) is a complex neurodegenerative disease associated with memory decline, cognitive impairment, amyloid plaque formation and tau tangles. Neuroinflammation has been shown to be a precursor to apparent amyloid plaque accumulation and subsequent synaptic loss and cognitive decline. In this study, the ability of a novel, small molecule, T-ALZ01, to inhibit neuroinflammatory processes was analyzed. T-ALZ01, an inhibitor of complement component C1r, demonstrated a significant reduction in the levels of the inflammatory cytokines, IL-6 and TNF-α in vitro. An LPS-induced animal model, whereby animals were injected intraperitoneally with 0.5 mg/kg LPS, was used to analyze the effect of T-ALZ01 on neuroinflammation in vivo. Moreover, exosomes (nanosized, endogenous extracellular vehicles) were used as drug delivery vehicles to facilitate intranasal administration of T-ALZ01 across the blood-brain barrier. T-ALZ01 demonstrated significant reduction in degenerating neurons and the activation of resident microglia and astrocytes, as well as inflammatory markers in vivo. This study demonstrates a significant use of small molecule complement inhibitors via exosome drug delivery as a possible therapeutic in disorders characterized by neuroinflammation, such AD.

Inflammation associated with left ventricular hypertrophy in bipolar disorder: A cross-sectional study

OBJECTIVE

Inflammation has received increasing attention as a contributor to the pathophysiology of bipolar disorder (BD) and cardiac hypertrophy into heart failure (HF). Accordingly, we chose BD-related inflammatory markers to investigate their relationships with cardiac left ventricular function and structure in BD.

METHODS

Sixty physically healthy and euthymic patients with bipolar I disorder were recruited to compare with 50 healthy normal controls. The echocardiography was performed to estimate left ventricular mass index (LVMI) as a parameter of LV hypertrophy (LVH) and left ventricle ejection fraction (LVEF) as a parameter of systolic function. An LVEF above the normal range (>70%) was defined as a hyperdynamic heart. Participants' levels of inflammatory and atherosclerosis-related parameters were measured.

RESULTS

Compared with normal controls, BD group had significantly higher rates of LVH (63% vs. 42%) and hyperdynamic heart (32% vs. 2%) and higher mean values of LVMI and LVEF. After adjustment for the effects of BMI and age, multiple regression analyses of BD group showed that the peripheral level of interleukin-8 was positively associated with LVMI and the level of soluble tumor necrosis factor receptor 1 (sTNF-R1) was positively associated with LVEF.

CONCLUSIONS

Patients with BD from young adulthood are likely to have LVH with normal LV function and hyperdynamic heart associated with diastolic dysfunction. Low-grade inflammation may underlie the mechanisms of LV hypertrophy and cardiac dysfunction in BD patients.

Sex Differences in the Level of Homocysteine in Alzheimer's Disease and Parkinson's Disease Patients: A Meta-Analysis

Although recent studies suggest homocysteine (Hcy) is an independent risk factor for neurodegenerative disorders, little is known about sex differences in the levels of Hcy. In this study, we conducted a comparative meta-analysis to investigate sex differences in the levels of Hcy in both Alzheimer’s disease (AD) and Parkinson’s disease (PD) patients. Reports of Hcy stratified by sex in both AD and PD patients were obtained from electronic databases. From the initial 1595 records, 921 were assessed for eligibility, of which 16 sufficiently reported sex differences. Standardized mean difference (SMDs) using random effects together with tests of heterogeneity and quality assessment were applied in this meta-analysis. Data from 3082 diagnosed patients (1162 males and 1920 females) were included. There were statistically significant differences in the levels of Hcy between sexes in AD and PD patients, with an SMD of 0.291 [0.17, 0.41], p < 0.05, 95% CI, with higher Hcy levels detected in males. Subgroup comparisons did not find a statistically significant difference in the levels of Hcy between AD and PD patients. The overall risk of bias for the analyzed studies was low, with some moderate risk of bias across select domains. This meta-analysis determined that compared to females, males with either AD or PD have higher levels of Hcy. These findings suggest that Hcy could be a useful biomarker for predicting neurodegenerative diseases in males; however, further studies are needed to confirm the clinical utility of this suggestion.

Apathy as a Predictor of Conversion from Mild Cognitive Impairment to Alzheimer's Disease: A Texas Alzheimer's Research and Care Consortium (TARCC) Cohort-Based Analysis

BACKGROUND

Apathy is among the neuropsychiatric symptoms frequently observed in people with cognitive impairment. It has been postulated to be a potential predictor of conversion from mild cognitive impairment (MCI) to Alzheimer's disease (AD).

OBJECTIVE

To detect conversion rates from MCI to AD, and to determine the effect of apathy on the progression to AD in patients with MCI enrolled in the Texas Alzheimer's Research and Care Consortium (TARCC) cohort.

METHODS

Apathy was determined by a positive response to the respective item in the Neuropsychiatric Inventory -Questionnaire (NPI-Q) completed by family members or caregivers. The final dataset included 2,897 observations from 1,092 individuals with MCI at the baseline. Kaplan-Meier survival curves were estimated to provide indices of the probability of conversion to AD over time across all individuals as well as between those with and without apathy. Cox proportional hazards regression measured the hazard associated with apathy and several other predictors of interest.

RESULTS

Over a period of 8.21 years, 17.3% of individuals had conversion from MCI to AD (n = 190 of 1,092 total individuals) across observations. The median time-to-conversion across all participants was 6.41 years. Comparing individuals with apathy (n = 158) versus without apathy (n = 934), 36.1% and 14.2% had conversion to AD, respectively. The median time-to-conversion was 3.79 years for individuals with apathy and 6.83 years for individuals without apathy. Cox proportional hazards regression found significant effects of several predictors, including apathy, on time-to-conversion. Age and cognitive performance were found to moderate the relationship between apathy and time-to-conversion.

CONCLUSIONS

Apathy is associated with progression from MCI to AD, suggesting that it might improve risk prediction and aid targeted intervention delivery.

Blood plasma protein profiles of neuropsychiatric symptoms and related cognitive decline in older people

Neuropsychiatric symptoms (NPS) severely affect patients and their caregivers, and are associated with worse long-term outcomes. This study tested the hypothesis that altered protein levels in blood plasma could serve as biomarkers of NPS; and that altered protein levels are associated with persisting NPS and cognitive decline over time. We performed a cross-sectional and longitudinal study in older subjects with cognitive impairment and cognitively unimpaired in a memory clinic setting. NPS were recorded through the Neuropsychiatric Inventory Questionnaire (NPI-Q) while cognitive and functional impairment was assessed using the clinical dementia rating sum of boxes (CDR-SoB) score at baseline and follow-up visits. Shotgun proteomic analysis based on liquid chromatography-mass spectrometry was conducted in blood plasma samples, identifying 420 proteins. The presence of Alzheimer's Disease (AD) pathology was determined by cerebrospinal fluid biomarkers. Eighty-five subjects with a mean age of 70 (±7.4) years, 62% female and 54% with mild cognitive impairment or mild dementia were included. We found 15 plasma proteins with altered baseline levels in participants with NPS (NPI-Q score > 0). Adding those 15 proteins to a reference model based on clinical data (age, CDR-SoB) significantly improved the prediction of NPS (from receiver operating characteristic area under the curve [AUC] 0.75 to AUC 0.91, p = 0.004) with a specificity of 89% and a sensitivity of 74%. The identified proteins additionally predicted both persisting NPS and cognitive decline at follow-up visits. The observed associations were independent of the presence of AD pathology. Using proteomics, we identified a panel of specific blood proteins associated with current and future NPS, and related cognitive decline in older people. These findings show the potential of untargeted proteomics to identify blood-based biomarkers of pathological alterations relevant for NPS and related clinical disease progression.

Lithium exposure and chronic inflammation with activated macrophages and monocytes associated with atherosclerosis in bipolar disorder

BACKGROUND

Atherosclerosis accounts for cardiovascular diseases (CVDs). This study aimed to explore the association between carotid intima-media thickness (CIMT), psycho-pharmacotherapy, and inflammatory markers along with other molecules related to atherosclerosis in bipolar disorder (BD).

METHODS

The euthymic patients with bipolar I disorder (BD-I) aged over 20 years were recruited to measure CIMT through ultrasound and the blood levels of lipid profiles, soluble tumor necrosis factor receptor-1 (sTNF-R1), soluble interleukin-6 receptor (sIL-6R), monocyte chemoattractant protein-1, chitinase 3-like 1, endothelial adhesive proteins, and thrombin-antithrombin complex.

RESULTS

Participants were 103 BD-I patients with mean 44.3 years old. The ratio of lithium exposure in relation to illness chronicity and the current daily dosage of lithium therapy exhibited an inverse relationship with CIMT in the entire sample. After controlling for age and BMI, multivariate regression indicated that a higher lithium level was significantly associated with decreased CIMT in the entire sample, high-risk (those with CVDs or endocrine diseases, N = 48), middle-risk (those without CVDs and endocrine diseases, N = 55), and low-risk (those aged <45 years in the middle-risk subgroup, N = 43) subgroups. Furthermore, higher levels of sTNF-R1 in the entire sample and high-risk subgroup and sIL-6R in the middle- and low-risk subgroups were statistically associated with greater CIMT.

LIMITATION

The age range was too wide to control for the effect of age on CIMT and medication.

CONCLUSIONS

Lithium exposure may be a protective factor for atherosclerosis progression in BD-I. The chronic inflammation in BD-I with activated macrophages and monocytes may link with the atherosclerosis development over time.

Lipid Peroxidation as a Marker of Apathy and Executive Dysfunction in Patients at Risk for Vascular Cognitive Impairment

Background: The co-occurrence of apathy and executive dysfunction, a correlate of vascular cognitive impairment (VCI), is highly prevalent, yet facilitating factors are largely unknown. Objective: This study investigates the relationship between lipid peroxidation, apathy, and executive dysfunction in patients at risk for VCI. Methods: In participants with coronary artery disease, who are at a high risk of VCI, apathy (Apathy Evaluation Scale), and executive function (composite z-score based on age and education population norms from trails making test B, animal naming, and phonemic fluency tests) were assessed. Serum concentrations of an early (lipid hydroperoxide (LPH)) and late (8-isoprostane (8-ISO)) lipid peroxidation marker, were measured and the 8-ISO/LPH ratio was calculated. Results: Participants (n = 206, age±SD = 63.0±7.5, 80% men, total years of education = 15.9±3.4, AES score = 28.3±8.8, executive function = 0±1) demonstrated significantly different 8-ISO/LPH ratios between groups (F(3, 202) = 10.915, p <  0.001) with increasing levels in the following order: no apathy or executive dysfunction, only executive dysfunction (executive function composite score≤–1), only apathy (AES≥28), and both apathy and executive dysfunction. A model adjusting for demographics showed that lipid peroxidation was associated with both apathy (B(SE) = 4.63 (0.954), t = 4.852, p <  0.001) and executive function (B(SE) = –0.19 (0.079), t = –2.377, p = 0.018). However, when controlling for both demographics and vascular risk factors, lipid peroxidation was associated with only apathy (B(SE) = 3.11 (0.987), t = 3.149, p = 0.002). Conclusion: The results highlight a potentially important involvement of lipid peroxidation in the co-occurrence of apathy and executive dysfunction in those at risk for VCI.

Sex Differences in Innate Immune Response of Peripheral Blood Leukocytes of Alzheimer's Disease Patients

Neurodegenerative disorders, including Alzheimer's disease (AD), are associated with a disruption of normal immune function that could potentially impact the brain. In AD sex and gender have been noted as relevant to disease prevalence or clinical manifestation. It is suggested that disease progression could vary as a result of the different inflammation state among males and females. The objective was to investigate sex-dependent difference in innate immunity of AD patients and healthy, age-matched controls. The level of innate immunity was measured with test based on peripheral blood leukocytes (PBLs) resistance to viral infection (vesicular stomatitis virus, VSV) ex vivo. Cytokine: TNF-α, IFN-γ, IL-1β, IL-10 production by uninfected and VSV-infected PBLs ex vivo with enzyme-linked immunosorbent assay were examined. In contrast to controls, women with AD exhibit lower average level of innate immunity than AD men. The mean level of TNF-α, IL-10 and IL-1β was higher in AD men than in AD women whereas such changes were not observed among controls. The level of IFN-γ was higher in AD than in controls. PBLs from AD did not increase IFN-γ production after viral infection in contrast to controls. Leukocytes from women with AD exhibited a weaker response to viral infection and much less cytokine production compared to men with AD. It is important to consider sex as a biological variable in AD as it shows promises to advance our understanding of mechanisms of AD pathology and may be the basis for future treatment of AD.

Technical Performance Evaluation of Olink Proximity Extension Assay for Blood-Based Biomarker Discovery in Longitudinal Studies of Alzheimer's Disease

The core Alzheimer's disease (AD) cerebrospinal fluid (CSF) biomarkers; amyloid-β (Aß), total tau (t-tau), and phosphorylated tau (p-tau181), are strong indicators of the presence of AD pathology, but do not correlate well with disease progression, and can be difficult to implement in longitudinal studies where repeat biofluid sampling is required. As a result, blood-based biomarkers are increasingly being sought as alternatives. In this study, we aimed to evaluate a promising blood biomarker discovery technology, Olink Proximity Extension Assays for technical reproducibility characteristics in order to highlight the advantages and disadvantages of using this technology in biomarker discovery in AD. We evaluated the performance of five Olink Proteomic multiplex proximity extension assays (PEA) in plasma samples. Three technical control samples included on each plate allowed calculation of technical variability. Biotemporal stability was measured in three sequential annual samples from 54 individuals with and without AD. Coefficients of variation (CVs), analysis of variance (ANOVA), and variance component analyses were used to quantify technical and individual variation over time. We show that overall, Olink assays are technically robust, with the largest experimental variation stemming from biological differences between individuals for most analytes. As a powerful illustration of one of the potential pitfalls of using a multi-plexed technology for discovery, we performed power calculations using the baseline samples to demonstrate the size of study required to overcome the need for multiple test correction with this technology. We show that the power of moderate effect size proteins was strongly reduced, and as a result investigators should strongly consider pooling resources to perform larger studies using this multiplexed technique where possible.

Cerebrospinal Fluid Proteome Alterations Associated with Neuropsychiatric Symptoms in Cognitive Decline and Alzheimer's Disease

Although neuropsychiatric symptoms (NPS) are common and severely affect older people with cognitive decline, little is known about their underlying molecular mechanisms and relationships with Alzheimer’s disease (AD). The aim of this study was to identify and characterize cerebrospinal fluid (CSF) proteome alterations related to NPS. In a longitudinally followed-up cohort of subjects with normal cognition and patients with cognitive impairment (MCI and mild dementia) from a memory clinic setting, we quantified a panel of 790 proteins in CSF using an untargeted shotgun proteomic workflow. Regression models and pathway enrichment analysis were used to investigate protein alterations related to NPS, and to explore relationships with AD pathology and cognitive decline at follow-up visits. Regression analysis selected 27 CSF proteins associated with NPS. These associations were independent of the presence of cerebral AD pathology (defined as CSF p-tau181/Aβ1−42 > 0.0779, center cutoff). Gene ontology enrichment showed abundance alterations of proteins related to cell adhesion, immune response, and lipid metabolism, among others, in relation to NPS. Out of the selected proteins, three were associated with accelerated cognitive decline at follow-up visits after controlling for possible confounders. Specific CSF proteome alterations underlying NPS may both represent pathophysiological processes independent from AD and accelerate clinical disease progression.

Factors Associated with Apathy in Alzheimer’s Disease: A Cross-Sectional Analysis of the Texas Alzheimer’s Research and Care Consortium (TARCC) Study

Background: Apathy is among the most frequent neuropsychiatric syndromes in Alzheimer’s disease (AD). Objective: To determine the prevalence of apathy and the associated clinical and laboratorial parameters (focus on inflammatory biomarkers) in patients with dementia enrolled at the Texas Alzheimer’s Research and Care Consortium (TARCC) study. Methods: This is a cross-sectional analysis of TARCC baseline. Participants were evaluated through different clinical tools, including the Mini-Mental State Examination (MMSE) and the Lawton-Brody Instrumental Activities of Daily Life (IADL)/Physical Self-Maintenance Scale (PSMS). Apathy was defined by a positive response to the respective item in the Neuropsychiatric Inventory–Questionnaire applied to caregivers. Serum levels of 16 biomarkers were determined by HumanMap multiplex immunoassay. Comparisons between apathy versus non-apathy groups were carried out with non-parametric tests. Logistic regression and the least absolute shrinkage and selection operator (LASSO) were used to separately model apathy as a function of each biomarker, adjusted for the potential confounders. Results: From 1,319 patients with AD (M/F: 579/740, mean age ± SD: 75.3 ± 8.4), 373 (28.3%) exhibited apathy. When categorized according to the presence of apathy, the groups had significant differences in sex, diabetes diagnosis, and tobacco use. The apathy group also had worse cognitive performance and daily functioning than the non-apathy group as assessed, respectively, by MMSE and IADL/PSMS. Higher levels of interleukin-6, interleukin-10, and leptin were associated with higher odds of apathy. Conclusion: Apathy is associated with cognitive and functional status in AD. The association between apathy and peripheral inflammatory mediators deserves further investigation.

Gender-specific clinical risk scores incorporating blood pressure variability for predicting incident dementia

INTRODUCTION

The present study examined the gender-specific prognostic value of blood pressure (BP) and its variability in the prediction of dementia risk and developed a score system for risk stratification.

MATERIALS AND METHODS

This was a retrospective, observational population-based cohort study of patients admitted to government-funded family medicine clinics in Hong Kong between January 1, 2000 and March 31, 2002 with at least 3 blood pressure measurements. Gender-specific risk scores for dementia were developed and tested.

RESULTS

The study consisted of 74 855 patients, of whom 3550 patients (incidence rate: 4.74%) developed dementia over a median follow-up of 112 months (IQR= [59.8-168]). Nonlinear associations between diastolic/systolic BP measurements and the time to dementia presentation were identified. Gender-specific dichotomized clinical scores were developed for males (age, hypertension, diastolic and systolic BP and their measures of variability) and females (age, prior cardiovascular, respiratory, gastrointestinal diseases, diabetes mellitus, hypertension, stroke, mean corpuscular volume, monocyte, neutrophil, urea, creatinine, diastolic and systolic BP and their measures of variability). They showed high predictive strengths for both male (hazard ratio [HR]: 12.83, 95% confidence interval [CI]: 11.15-14.33, P value < .0001) and female patients (HR: 26.56, 95% CI: 14.44-32.86, P value < .0001). The constructed gender-specific scores outperformed the simplified systems without considering BP variability (C-statistic: 0.91 vs 0.82), demonstrating the importance of BP variability in dementia development.

CONCLUSION

Gender-specific clinical risk scores incorporating BP variability can accurately predict incident dementia and can be applied clinically for early disease detection and optimized patient management.

Amyloid Deposition Is Greater in Cerebral Gyri than in Cerebral Sulci with Worsening Clinical Diagnosis Across the Alzheimer's Disease Spectrum

BACKGROUND

Histopathologic studies have demonstrated differential amyloid-β (Aβ) burden between cortical sulci and gyri in Alzheimer's disease (AD), with sulci having a greater Aβ burden.

OBJECTIVE

To characterize Aβ deposition in the sulci and gyri of the cerebral cortex in vivo among subjects with normal cognition (NC), mild cognitive impairment (MCI), and AD, and to evaluate if these differences could improve discrimination between diagnostic groups.

METHODS

T1-weighted 3T MR and florbetapir (amyloid) positron emission tomography (PET) data were obtained from the Alzheimer's Disease Neuroimaging Initiative (ADNI). T1 images were segmented and the cortex was separated into sulci/gyri based on pial surface curvature measurements. T1 images were registered to PET images and regional standardized uptake value ratios (SUVr) were calculated. A linear mixed effects model was used to analyze the relationship between clinical variables and amyloid PET SUVr measurements in the sulci/gyri. Receiver operating characteristic (ROC) analysis was performed to define amyloid positivity. Logistic models were used to evaluate predictive performance of clinical diagnosis using amyloid PET SUVr measurements in sulci/gyri.

RESULTS

719 subjects were included: 272 NC, 315 MCI, and 132 AD. Gyral and sulcal Aβ increased with worsening cognition, however there was a greater increase in gyral Aβ. Females had a greater gyral and sulcal Aβ burden. Focusing on sulcal and gyral Aβ did not improve predictive power for diagnostic groups.

CONCLUSION

While there were significant differences in Aβ deposition in cerebral sulci and gyri across the AD spectrum, these differences did not translate into improved prediction of diagnosis. Females were found to have greater gyral and sulcal Aβ burden.

Peripheral inflammatory biomarkers predict the deposition and progression of amyloid-β in cognitively unimpaired older adults

INTRODUCTION

Systemic inflammation has been increasingly implicated in the pathogenesis of Alzheimer's disease (AD), yet the mechanistic and temporal specificity of this relationship is poorly understood. We aimed to characterize the cross-sectional and longitudinal associations between peripheral inflammatory biomarkers, cognition, and Aβ deposition in oldest-old cognitively unimpaired (CU) adults.

METHODS

A large sample of 139 CU older adults (mean age (range) = 85.4 (82-95)) underwent neuropsychological testing, Pittsburgh compound-B (PiB)-PET imaging and structural MRI. Hierarchical regression models examined associations between circulating inflammatory biomarkers (Interleukin-6 (IL-6), soluble Tumor Necrosis Factor receptors 1 and 2 (sTNFr1 and sTNFr2), soluble cluster of differentiation 14 (sCD14), C-reactive protein (CRP)), cognition, and global and regional Aβ deposition at baseline and over follow-up. Indices of preclinical disease, including pathologic Aβ status and hippocampal volume, were incorporated to assess conditional associations.

RESULTS

At baseline evaluation, higher concentrations of IL-6 and sTNFr2 were associated with greater global Aβ burden in those with lower hippocampal volume. In longitudinal models, IL-6 predicted subsequent conversion to MCI and both IL-6 and CRP predicted greater change in global and regional Aβ deposition specifically among participants PiB-positive at baseline. These relationships withstood adjustment for demographic factors, anti-hypertensive medication use, history of diabetes, heart disease, APOE ε4 carrier status, and white matter lesions.

DISCUSSION

In a large prospective sample of CU adults aged 80 and over, peripheral inflammatory biomarkers were associated with and predictive of the progression of Aβ deposition. This was specific to those with biomarker evidence of preclinical AD at baseline, supporting recent evidence of disease-state-dependent differences in inflammatory expression profiles. Chronic, low-level systemic inflammation may exacerbate the deposition of Aβ pathology among those with emerging disease processes, and place individuals at a higher risk of developing clinically significant cognitive impairment.

Elevated Inflammatory Markers and Arterial Stiffening Exacerbate Tau but Not Amyloid Pathology in Older Adults with Mild Cognitive Impairment

BACKGROUND

Age-related cerebrovascular and neuroinflammatory processes have been independently identified as key mechanisms of Alzheimer's disease (AD), although their interactive effects have yet to be fully examined.

OBJECTIVE

The current study examined 1) the influence of pulse pressure (PP) and inflammatory markers on AD protein levels and 2) links between protein biomarkers and cognitive function in older adults with and without mild cognitive impairment (MCI).

METHODS

This study included 218 ADNI (81 cognitively normal [CN], 137 MCI) participants who underwent lumbar punctures, apolipoprotein E (APOE) genotyping, and cognitive testing. Cerebrospinal (CSF) levels of eight pro-inflammatory markers were used to create an inflammation composite, and amyloid-beta 1-42 (Aβ42), phosphorylated tau (p-tau), and total tau (t-tau) were quantified.

RESULTS

Multiple regression analyses controlling for age, education, and APOE ɛ4 genotype revealed significant PP x inflammation interactions for t-tau (B = 0.88, p = 0.01) and p-tau (B = 0.84, p = 0.02); higher inflammation was associated with higher levels of tau within the MCI group. However, within the CN group, analyses revealed a significant PP x inflammation interaction for Aβ42 (B = -1.01, p = 0.02); greater inflammation was associated with higher levels of Aβ42 (indicative of lower cerebral amyloid burden) in those with lower PP. Finally, higher levels of tau were associated with poorer memory performance within the MCI group only (p s < 0.05).

CONCLUSION

PP and inflammation exert differential effects on AD CSF proteins and provide evidence that vascular risk is associated with greater AD pathology across our sample of CN and MCI older adults.

Dissecting Sex-Related Cognition between Alzheimer's Disease and Diabetes: From Molecular Mechanisms to Potential Therapeutic Strategies

The brain is a sexually dimorphic organ that implies different functions and structures depending on sex. Current pharmacological approaches against different neurological diseases act distinctly in male and female brains. In all neurodegenerative diseases, including Alzheimer's disease (AD), sex-related outcomes regarding pathogenesis, prevalence, and response to treatments indicate that sex differences are important for precise diagnosis and therapeutic strategy. Pathogenesis of AD includes vascular dementia, and in most cases, this is accompanied by metabolic complications with similar features as those assembled in diabetes. This review discusses how AD-associated dementia and diabetes affect cognition in relation to sex difference, as both diseases share similar pathological mechanisms. We highlight potential protective strategies to mitigate amyloid-beta (Aβ) pathogenesis, emphasizing how these drugs act in the male and female brains.

Antithrombotic therapy and the risk of new-onset dementia in elderly patients with atrial fibrillation

BACKGROUND

Atrial fibrillation (AF) is associated with an increased risk of dementia. Little is known about the relationship of antithrombotic therapy and the risk of dementia in patients with AF without clinical stroke.

METHOD

This was an observational study based on a hospital AF registry. Patients aged 65-85 years at the time of AF diagnosis were identified via the computerised database of the clinical management system. Patients with prior stroke or known cognitive dysfunction were excluded. The primary outcome was newly diagnosed dementia during the follow-up period.

RESULTS

3284 patients (mean age 76.4±5.3 years, 51.6% male) were included for analysis. The mean CHA₂DS₂-VASc score was 3.94±1.44. 18.5% patients were prescribed warfarin, 39.8% were prescribed aspirin and 41.7% were prescribed no antithrombotic therapy. After a mean follow-up of 3.6 years, 71 patients (2.2%) developed dementia, giving rise to an incidence of 0.61%/year. The incidence of dementia were 1.04%/year, 0.69%/year and 0.14%/year for patients on no therapy, aspirin and warfarin, respectively. Both univariate and multivariate analyses showed that age ≥75 years, female gender and high CHA₂DS₂-VASc score were associated with significantly higher risk of dementia; warfarin use was associated with significantly lower risk of dementia (HR: 0.14%, 95% CI 0.05 to 0.36, p<0.001). Patients on warfarin with time in therapeutic range (TTR) ≥65% had a non-significant trend towards a lower risk of dementia compared with those with TTR <65%.

CONCLUSION

In elderly AF patients, warfarin therapy was associated with a significantly lower risk of new-onset dementia compared those with no therapy or aspirin.

Strawberry Leaf Extract Treatment Alleviates Cognitive Impairment by Activating Nrf2/HO-1 Signaling in Rats With Streptozotocin-Induced Diabetes

Diabetes-associated cognitive impairment (DACI) is a common complication of diabetes mellitus (DM) that affects the central nervous system. Cognitive impairment, such as learning and memory impairment, and even dementia, is the main clinical manifestation of DACI. Unfortunately, there is no effective means by which to delay the cognitive symptoms of DM. Evidence has shown that strawberry leaf extract could alleviate cognitive decline, suppress oxidative stress, and reduce inflammatory responses in rats. In the present study, we evaluated the effect of strawberry leaf extract on cognitive function in a rat model of streptozotocin (STZ)-induced diabetes. After the continuous administration of strawberry leaf extract for 4 weeks, the Morris Water Maze (MWM) test results showed that the cognitive impairment of the rats was alleviated. Moreover, strawberry leaf extract significantly reduced the level of reactive oxygen species (ROS), decreased the level of malondialdehyde (MDA), improved the activity of superoxide dismutase (SOD) and catalase (CAT), decreased the mRNA expression of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) and decreased the protein expression of caspase-3 and caspase-9 in the hippocampus of DM rats. Also, transcription factor nuclear factor erythroid 2 (NF-E2)-related factor 2 (Nrf2)/hemeoxygenase-1(HO-1) signaling was activated by the administration of strawberry leaf extract. Our findings indicate that strawberry leaf extract may be a potential drug candidate for the treatment of DACI and may be used as a basis for further research on the development of drugs for cognitive impairment in diabetes.

Sex Differences in the Association Between Pentraxin 3 and Cognitive Decline: The Cardiovascular Health Study

BACKGROUND

The importance of systemic inflammation, measured by C-reactive protein, in cognitive decline has been demonstrated; however, the role of vascular inflammation is less understood. Pentraxin 3 (PTX3) is a novel marker of vascular inflammation.

METHODS

We followed adults 65 and older, free of cardiovascular disease (CVD) for up to 9 years (n = 1,547) in the Cardiovascular Health Study. We evaluated the relationship between PTX3 and change in cognitive function, measured using the Modified Mini-Mental State Examination (3MSE), and incident cognitive impairment (3MSE < 80). Mediation by CVD events, and effect modification by sex and apolipoprotein E ɛ4 allele (APOE4) were also examined.

RESULTS

The average decline in 3MSE was 0.77 points per year. The association between PTX3 and change in 3MSE differed between women and men (p = .02). In the adjusted model, each standard deviation higher in PTX3 was associated with a 0.20 greater decline in 3MSE score per year in women over follow-up (95% CI: -0. 37, -0.03; p = .02), compared to no change in men (β = 0.07; 95% CI: -0.08, 0.22). CVD events had a minor effect on the associations. No effect modification by APOE4 was found, although we observed the association of PTX3 and cognitive impairment in women was attenuated and nonsignificant after adjustment for APOE4. There was a paradoxical protective association between PTX3 and reduced cognitive impairment in men, even after adjustment for APOE4.

CONCLUSIONS

We found that vascular inflammation was significantly associated with cognitive decline in older women, but not men.

Association of Brain-Derived Neurotrophic Factor With Cognitive Function: An Investigation of Sex Differences in Patients With Type 2 Diabetes

OBJECTIVE

Although a reduction in brain-derived neurotrophic factor (BDNF) has been implicated as a cause of cognitive impairment in type 2 diabetes mellitus (T2DM), the role of sex in moderating this effect has not been explored.

METHODS

We compared the difference in serum BDNF and performance on the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) between 96 men and 134 women with T2DM. We compared this with the difference in serum BDNF and performance in the control group (104 men, 144 women).

RESULTS

Patients with T2DM performed worse on most RBANS indices (η = 0.372, all p < .05); within T2DM patients, men performed worse than women on the delayed memory score (74.1 (12.1) versus 79.9 (11.5), p = .002) and on the total score (71.4 (11.5) versus 76.5 (10.8), p = .025). Serum BDNF was lower in patients with T2DM versus controls (7.5 (2.7) ng/ml versus 11.5 (2.7) ng/ml, p < .001), and in men compared with women (6.9 (2.4) versus 7.9 (2.8), p = .024). Serum BDNF levels positively correlated with delayed memory score in patients with T2DM (β = 0.19, p = .007). However, this association was only observed in women, not in men (pinteraction = 0.04). Among healthy controls, no sex differences were noted in either RBANS or BDNF levels (η = 0.04, Cohen's d < 0.163, all p > .05).

CONCLUSIONS

Our results show sex differences in poorer cognitive performance, lower BDNF concentration, and their relationship in T2DM patients, suggesting that female sex may be a protective factor for cognitive decline in T2DM patients. However, the findings should be regarded as preliminary because of the cross-sectional design and chronicity of the diabetes.

Blood-based systems biology biomarkers for next-generation clinical trials in Alzheimer's disease

Alzheimer's disease (AD)-a complex disease showing multiple pathomechanistic alterations-is triggered by nonlinear dynamic interactions of genetic/epigenetic and environmental risk factors, which, ultimately, converge into a biologically heterogeneous disease. To tackle the burden of AD during early preclinical stages, accessible blood-based biomarkers are currently being developed. Specifically, next-generation clinical trials are expected to integrate positive and negative predictive blood-based biomarkers into study designs to evaluate, at the individual level, target druggability and potential drug resistance mechanisms. In this scenario, systems biology holds promise to accelerate validation and qualification for clinical trial contexts of use-including proof-of-mechanism, patient selection, assessment of treatment efficacy and safety rates, and prognostic evaluation. Albeit in their infancy, systems biology-based approaches are poised to identify relevant AD "signatures" through multifactorial and interindividual variability, allowing us to decipher disease pathophysiology and etiology. Hopefully, innovative biomarker-drug codevelopment strategies will be the road ahead towards effective disease-modifying drugs.
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A peripheral neutrophil-related inflammatory factor predicts a decline in executive function in mild Alzheimer's disease

Background

Studies suggest a role of the innate immune system, including the activity of neutrophils, in neurodegeneration related to Alzheimer’s disease (AD), but prospective cognitive data remain lacking in humans. We aimed to investigate the predictive relationship between neutrophil-associated inflammatory proteins in peripheral blood and changes in memory and executive function over 1 year in patients with AD.

Methods

Participants with AD were identified from the Alzheimer’s Disease Neuroimaging Initiative (ADNI). Neutrophil gelatinase-associated lipocalin (NGAL), myeloperoxidase (MPO), interleukin-8 (IL-8), macrophage inflammatory protein-1 beta (MIP-1β), and tumor necrosis factor (TNF) were assayed by luminex immunofluorescence multiplex assay at baseline. Confirmatory factor analysis was used to test an underlying neutrophil associated plasma inflammatory factor. Composite z-scores for memory and executive function were generated from multiple tests at baseline and at 1 year. A multiple linear regression model was used to investigate the association of the baseline inflammatory factor with changes in memory and executive function over 1 year.

Results

Among AD patients (n = 109, age = 74.8 ± 8.1, 42% women, Mini Mental State Examination [MMSE] = 23.6 ± 1.9), the neutrophil-related inflammatory proteins NGAL (λ = 0.595, p < .001), MPO (λ = 0.575, p < .001), IL-8 (λ = 0.525, p < .001), MIP-1β (λ = 0.411, p = .008), and TNF (λ = 0.475, p < .001) were found to inform an underlying factor. Over 1 year, this inflammatory factor predicted a decline in executive function (β = − 0.152, p = 0.015) but not memory (β = 0.030, p = 0.577) in models controlling for demographics, brain atrophy, white matter hyperintensities, the ApoE ε4 allele, concomitant medications, and baseline cognitive performance.

Conclusions

An inflammatory factor constructed from five neutrophil-related markers in peripheral blood predicted a decline in executive function over 1 year in people with mild AD.

Alzheimer's Disease and Neurotransmission Gene Variants: Focus on Their Effects on Psychiatric Comorbidities and Inflammatory Parameters

BACKGROUND

Alzheimer's disease (AD) is a neurodegenerative disorder accounting for 60-70% of dementia cases. Genetic origin accounts for 49-79% of disease risk. This paper aims to investigate the association of 17 polymorphisms within 7 genes involved in neurotransmission (COMT, HTR2A, PPP3CC, RORA, SIGMAR1, SIRT1, and SORBS3) and AD.

METHODS

A Greek and an Italian sample were investigated, for a total of 156 AD subjects and 301 healthy controls. Exploratory analyses on psychosis and depression comorbidities were performed, as well as on other available clinical and serological parameters.

RESULTS

AD was associated with rs4680 within the COMT gene in the total sample. Trends of association were found in the 2 subsamples. Some nominal associations were found for the depressive phenotype. rs10997871 and rs10997875 within SIRT1 were nominally associated with depression in the total sample and in the Greek subsample. rs174696 within COMT was associated with depression comorbidity in the Italian subsample.

DISCUSSION

Our data support the role of COMT, and particularly of rs4680, in the pathogenesis of AD. Furthermore, the SIRT1 gene seems to modulate depressive symptomatology in the AD population.

Lifetime surgical exposure, episodic memory, and forniceal microstructure in older adults

Introduction: Aging is associated with heterogeneous cognitive trajectories. There is considerable interest in identifying risk factors for pathological aging, with recent studies demonstrating a link between surgical procedures and proximal cognitive decline; however, the role of lifetime exposure to surgical procedures and cognitive function has been relatively unexplored. This pilot study aimed to evaluate the association between total lifetime surgical procedures and memory function in older adults. Methods: A cohort of 62 older adults underwent a neuropsychological evaluation and health history assessment. Self-reported lifetime surgical history was categorized as "cardiac" or "non-cardiac." General linear models were fit with demographics as nuisance covariates, and the total number of non-cardiac surgeries as our predictor of interest. Total scores on measures of episodic memory, language, working memory, fluency, and visuospatial function were separate outcome variables. In a secondary analysis, vascular risk factors were included as covariates. Diffusion tensor imaging was obtained for exploratory analyses of selected regions of interest. Results: The mean age of participants was 70, and 0-13 lifetime non-cardiac surgical procedures were reported. Higher numbers of lifetime non-cardiac surgical procedures were associated with worse verbal learning and memory (p = .04). The negative association between lifetime non-cardiac procedures and cognition was specific to memory. Exploratory analyses showed that higher number of lifetime non-cardiac procedures was related to lower FA in the fornix body (p = .02). Conclusions: These results of this pilot study suggest that greater lifetime exposure to surgery may be associated with worse verbal learning and memory in healthy older adults. These findings add to a growing body of literature suggesting that cumulative medical events may be risk factors for negative cognitive outcomes.

Sex and Gender Driven Modifiers of Alzheimer's: The Role for Estrogenic Control Across Age, Race, Medical, and Lifestyle Risks

Research indicates that after advanced age, the major risk factor for late-onset Alzheimer’s disease (AD) is female sex. Out of every three AD patients, two are females with postmenopausal women contributing to over 60% of all those affected. Sex- and gender-related differences in AD have been widely researched and several emerging lines of evidence point to different vulnerabilities that contribute to dementia risk. Among those being considered, it is becoming widely accepted that gonadal steroids contribute to the gender disparity in AD, as evidenced by the “estrogen hypothesis.” This posits that sex hormones, 17β-estradiol in particular, exert a neuroprotective effect by shielding females’ brains from disease development. This theory is further supported by recent findings that the onset of menopause is associated with the emergence of AD-related brain changes in women in contrast to men of the same age. In this review, we discuss genetic, medical, societal, and lifestyle risk factors known to increase AD risk differently between the genders, with a focus on the role of hormonal changes, particularly declines in 17β-estradiol during the menopause transition (MT) as key underlying mechanisms.

Effect of High-Fat Diets on Oxidative Stress, Cellular Inflammatory Response and Cognitive Function

Cognitive dysfunction is linked to chronic low-grade inflammatory stress that contributes to cell-mediated immunity in creating an oxidative environment. Food is a vitally important energy source; it affects brain function and provides direct energy. Several studies have indicated that high-fat consumption causes overproduction of circulating free fatty acids and systemic inflammation. Immune cells, free fatty acids, and circulating cytokines reach the hypothalamus and initiate local inflammation through processes such as microglial proliferation. Therefore, the role of high-fat diet (HFD) in promoting oxidative stress and neurodegeneration is worthy of further discussion. Of particular interest in this article, we highlight the associations and molecular mechanisms of HFD in the modulation of inflammation and cognitive deficits. Taken together, a better understanding of the role of oxidative stress in cognitive impairment following HFD consumption would provide a useful approach for the prevention of cognitive dysfunction.

Inflammation and cerebral small vessel disease: A systematic review

Inflammation is increasingly implicated as a risk factor for dementia, stroke, and small vessel disease (SVD). However, the underlying mechanisms and causative pathways remain unclear. We systematically reviewed the existing literature on the associations between markers of inflammation and SVD (i.e., white matter hyperintensities (WMH), lacunes, enlarged perivascular spaces (EPVS), cerebral microbleeds (CMB)) in cohorts of older people with good health, cerebrovascular disease, or cognitive impairment. Based on distinctions made in the literature, markers of inflammation were classified as systemic inflammation (e.g. C-reactive protein, interleukin-6, fibrinogen) or vascular inflammation/endothelial dysfunction (e.g. homocysteine, von Willebrand factor, Lp-PLA2). Evidence from 82 articles revealed relatively robust associations between SVD and markers of vascular inflammation, especially amongst stroke patients, suggesting that alterations to the endothelium and blood-brain barrier may be a driving force behind SVD. Conversely, cross-sectional findings on systemic inflammation were mixed, although longitudinal investigations demonstrated that elevated levels of systemic inflammatory markers at baseline predicted subsequent SVD severity and progression. Importantly, regional analysis revealed that systemic and vascular inflammation were differentially related to two distinct forms of SVD. Specifically, markers of vascular inflammation tended to be associated with SVD in areas typical of hypertensive arteriopathy (e.g., basal ganglia), while systemic inflammation appeared to be involved in CAA-related vascular damage (e.g., centrum semiovale). Nonetheless, there is insufficient data to establish whether inflammation is causal of, or secondary to, SVD. Findings have important implications on interventions, suggesting the potential utility of treatments targeting the brain endothelium and blood brain barrier to combat SVD and associated neurodegenerative diseases.

Blueberries Improve Neuroinflammation and Cognition differentially Depending on Individual Cognitive baseline Status

Daily supplementation of blueberries (BBs) reverses age-related deficits in behavior in aged rats. However, it is unknown whether BB is more beneficial to one subset of the population dependent on baseline cognitive performance and inflammatory status. To examine the effect of individual differences on the efficacy of BB, aged rats (17 months old) were assessed for cognition in the radial arm water maze (RAWM) and divided into good, average, and poor performers based on navigation errors. Half of the rats in each cognitive group were then fed a control or a 2% BB diet for 8 weeks before retesting. Serum samples were collected, pre-diet and post-diet, to assess inflammation. Latency in the radial arm water maze was significantly reduced in the BB-fed poor performers (p < .05) and preserved in the BB-fed good performers. The control-fed good performers committed more working and reference memory errors in the post-test than pretest (p < .05), whereas the BB-fed good performers showed no change. An in vitro study using the serum showed that BB supplementation attenuated lipopolysaccharide (LPS)-induced nitrite and tumor necrosis factor-alpha, and cognitive performance was associated with innate anti-inflammatory capability. Therefore, consumption of BB may reverse some age-related deficits in cognition, as well as preserve function among those with intact cognitive ability.

Exercise and the Aging Brain: Considerations for Sex Differences

Engaging in targeted exercise interventions is a promising, non-pharmacological strategy to mitigate the deleterious effects of aging and disease on brain health. However, despite its therapeutic potential, a large amount of variation exists in exercise efficacy in older adults aged 55 and older. In this review, we present the argument that biological sex may be an important moderator of the relationship between physical activity and cognition. Sex differences exist in dementia as well as in several associated risk factors, including genetics, cardiovascular factors, inflammation, hormones and social and psychological factors. Different exercise interventions, such as aerobic training and resistance training, influence cognition and brain health in older adults and these effects may be sex-dependent. The biological mechanisms underlying the beneficial effects of exercise on the brain may be different in males and females. Specifically, we examine sex differences in neuroplasticity, neurotrophic factors and physiological effects of exercise to highlight the possible mediators of sex differences in exercise efficacy on cognition. Future studies should address the potential sex difference in exercise efficacy if we are to develop effective, evidence-based exercise interventions to promote healthy brain aging for all individuals.

Abnormal levels of vascular endothelial biomarkers in schizophrenia

Schizophrenia is associated with chronic low-grade inflammation, which has been linked to increased vascular risk and rates of cardiovascular disease. Levels of vascular endothelial growth factor (VEGF), intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1) have been related to aging and neurodegeneration, but their role in schizophrenia remains uncertain. Using a cross-sectional, case-control design, this study included 99 outpatients with schizophrenia and 99 healthy comparison subjects (HCs). Sociodemographic and clinical data were collected, and plasma levels of VEGF, ICAM-1, and VCAM-1 were assayed. A "vascular endothelial index" (VEI) was computed using logistic regression to create a composite measure that maximally differed between groups. General linear models were conducted to examine the possible role of demographic, physical, and lifestyle factors. A linear combination of ICAM-1 and VCAM-1 levels best distinguished the groups, with significantly higher levels of this composite VEI in persons with schizophrenia than HCs. Group differences in the VEI persisted after adjustment for BMI and cigarette smoking. Neither age nor gender was significantly related to the VEI. Schizophrenia patients with higher VEI had earlier age of disease onset, higher systolic and diastolic blood pressure, lower high-density lipoprotein cholesterol, higher insulin resistance, lower levels of mental well-being, and higher Framingham Coronary Heart Disease Risk scores. Schizophrenia is characterized by an elevation of vascular endothelial biomarkers, specifically cell adhesion molecules poised at the intersection between inflammatory response and vascular risk. Interventions aimed at reducing vascular risk may help reduce vascular endothelial abnormalities and prevent cardiovascular morbidity and mortality in schizophrenia.

Abnormal levels of vascular endothelial biomarkers in schizophrenia

Schizophrenia is associated with chronic low-grade inflammation, which has been linked to increased vascular risk and rates of cardiovascular disease. Levels of vascular endothelial growth factor (VEGF), intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1) have been related to aging and neurodegeneration, but their role in schizophrenia remains uncertain. Using a cross-sectional, case-control design, this study included 99 outpatients with schizophrenia and 99 healthy comparison subjects (HCs). Sociodemographic and clinical data were collected, and plasma levels of VEGF, ICAM-1, and VCAM-1 were assayed. A "vascular endothelial index" (VEI) was computed using logistic regression to create a composite measure that maximally differed between groups. General linear models were conducted to examine the possible role of demographic, physical, and lifestyle factors. A linear combination of ICAM-1 and VCAM-1 levels best distinguished the groups, with significantly higher levels of this composite VEI in persons with schizophrenia than HCs. Group differences in the VEI persisted after adjustment for BMI and cigarette smoking. Neither age nor gender was significantly related to the VEI. Schizophrenia patients with higher VEI had earlier age of disease onset, higher systolic and diastolic blood pressure, lower high-density lipoprotein cholesterol, higher insulin resistance, lower levels of mental well-being, and higher Framingham Coronary Heart Disease Risk scores. Schizophrenia is characterized by an elevation of vascular endothelial biomarkers, specifically cell adhesion molecules poised at the intersection between inflammatory response and vascular risk. Interventions aimed at reducing vascular risk may help reduce vascular endothelial abnormalities and prevent cardiovascular morbidity and mortality in schizophrenia.

Amyloid beta-positive subjects exhibit longitudinal network-specific reductions in spontaneous brain activity

Amyloid beta (Aβ) deposition and cognitive decline are key features of Alzheimer's disease. The relationship between Aβ status and changes in neuronal function over time, however, remains unclear. We evaluated the effect of baseline Aβ status on reference region spontaneous brain activity (SBA-rr) using resting-state functional magnetic resonance imaging and fluorodeoxyglucose positron emission tomography in patients with mild cognitive impairment. Patients (N = 62, [43 Aβ-positive]) from the Alzheimer's Disease Neuroimaging Initiative were divided into Aβ-positive and Aβ-negative groups via prespecified cerebrospinal fluid Aβ42 or 18F-florbetapir positron emission tomography standardized uptake value ratio cutoffs measured at baseline. We analyzed interaction of biomarker-confirmed Aβ status with SBA-rr change over a 2-year period using mixed-effects modeling. SBA-rr differences between Aβ-positive and Aβ-negative subjects increased significantly over time within subsystems of the default and visual networks. Changes exhibit an interaction with memory performance over time but were independent of glucose metabolism. Results reinforce the value of resting-state functional magnetic resonance imaging in evaluating Alzheimer''s disease progression and suggest spontaneous neuronal activity changes are concomitant with cognitive decline.

DNA damage and neurodegenerative phenotypes in aged Ciz1 null mice

Cell-cycle dysfunction and faulty DNA repair are closely intertwined pathobiological processes that may contribute to several neurodegenerative disorders. CDKN1A interacting zinc finger protein 1 (CIZ1) plays a critical role in DNA replication and cell-cycle progression at the G1/S checkpoint. Germline or somatic variants in CIZ1 have been linked to several neural and extra-neural diseases. Recently, we showed that germline knockout of Ciz1 is associated with motor and hematological abnormalities in young adult mice. However, the effects of CIZ1 deficiency in much older mice may be more relevant to understanding age-related declines in cognitive and motor functioning and age-related neurologic disorders such as isolated dystonia and Alzheimer disease. Mouse embryonic fibroblasts from Ciz1^-/- mice showed abnormal sensitivity to the effects of γ-irradiation with persistent DNA breaks, aberrant cell-cycle progression, and apoptosis. Aged (18-month-old) Ciz1^-/- mice exhibited marked deficits in motor and cognitive functioning, and, in brain tissues, overt DNA damage, NF-κB upregulation, oxidative stress, vascular dysfunction, inflammation, and cell death. These findings indicate that the deleterious effects of CIZ1 deficiency become more pronounced with aging and suggest that defects of cell-cycle control and associated DNA repair pathways in postmitotic neurons could contribute to global neurologic decline in elderly human populations. Accordingly, the G1/S cell-cycle checkpoint and associated DNA repair pathways may be targets for the prevention and treatment of age-related neurodegenerative processes.

Sex differences influencing micro- and macrovascular endothelial phenotype in vitro

KEY POINTS

Endothelial dysfunction is an early hallmark of multiple disease states that also display sex differences with respect to age of onset, frequency and severity. Results of in vivo studies of basal and stimulated microvascular barrier function revealed sex differences that are difficult to ascribe to specific cells or environmental factors. The present study evaluated endothelial cells (EC) isolated from macro- and/or microvessels of reproductively mature rats under the controlled conditions of low-passage culture aiming to test the assumption that EC phenotype would be sex independent. The primary finding was that EC, regardless of where they are derived, retain a sex-bias in low-passage culture, independent of varying levels of reproductive hormones. The implications of the present study include the fallacy of expecting a universal set of mechanisms derived from study of EC from one sex and/or one vascular origin to apply uniformly to all EC under unstimulated conditions, and no less in disease.

ABSTRACT

Vascular endothelial cells (EC) are heterogeneous with respect to phenotype, reflecting at least the organ of origin, location within the vascular network and physical forces. As an independent influence on EC functions in health or aetiology, susceptibility, and progression of dysfunction in numerous disease states, sex has been largely ignored. The present study focussed on EC isolated from aorta (macrovascular) and skeletal muscle vessels (microvascular) of age-matched male and female rats under identical conditions of short-term (passage 4) culture. We tested the hypothesis that genomic sex would not influence endothelial growth, wound healing, morphology, lactate production, or messenger RNA and protein expression of key proteins (sex hormone receptors for androgen and oestrogens α and β; platelet endothelial cell adhesion molecule-1 and vascular endothelial cadherin mediating barrier function; α_v β₃ and N-cadherin influencing matrix interactions; intracellular adhesion molecule-1 and vascular cell adhesion molecule-1 mediating EC/white cell adhesion). The hypothesis was rejected because the EC origin (macro- vs. microvessel) and sex influenced multiple phenotypic characteristics. Statistical model analysis of EC growth demonstrated an hierarchy of variable importance, recapitulated for other phenotypic characteristics, with predictions assuming EC homogeneity < sex < vessel origin < sex and vessel origin. Furthermore, patterns of EC mRNA expression by vessel origin and by sex did not predict protein expression. Overall, the present study demonstrated that accurate assessment of sex-linked EC dysfunction first requires an understanding of EC function by position in the vascular tree and by sex. The results from a single EC tissue source/species/sex cannot provide universal insight into the mechanisms regulating in vivo endothelial function in health, and no less in disease.

Association between Periodontal Health Status and Cognitive Abilities. The Role of Cytokine Profile and Systemic Inflammation

Background:

Contemporary neurobiology, periodontal medicine, and immunology are now focusing on the relationship between chronic periodontitis and systemic diseases, which also include Alzheimer’s disease (AD). However a causative relationship between dementia and periodontitis has yet to be confirmed.

Objective:

The aim of the study was to determine whether periodontal health status and cognitive abilities are correlated with the relative changes in systemic measures of pro- and anti-inflammatory cytokines as a reflection of systemic inflammation. We hypothesized that poor periodontal health status may be associated with cognitive impairment and dementia via the exacerbation of systemic inflammation.

Methods:

Based on the periodontal and psychiatric examinations and the cytokine levels produced by unstimulated and LPS-stimulated PBL isolated from 128 participants, we have examined if the coexisting of these two clinically described conditions may have influence on the systemic inflammation. Mini-Mental State Examination (MMSE) and Bleeding on Probing (BoP) test results were combined into the one mathematical function U, which determines the severity of specific condition, called Cognitive and periodontal impairment state. Similarly, the levels of cytokines were combined into the one mathematical function V, whose value determines the level of Inflammatory state. The correlation between U and V was determined.

Results:

These results confirm that the presence of cognitive decline and the additional source of pro-inflammatory mediators, like periodontal health problems, aggravate the systemic inflammation.

Conclusion:

It is most likely that the comorbidity of these two disorders may deepen the cognitive impairment, and neurodegenerative lesions and advance to dementia and AD.

The technical reliability and biotemporal stability of cerebrospinal fluid biomarkers for profiling multiple pathophysiologies in Alzheimer's disease

OBJECTIVE

Alzheimer's disease (AD) is a complex neurodegenerative disease driven by multiple interacting pathophysiological processes that ultimately results in synaptic loss, neuronal death, and dementia. We implemented a fit-for-purpose modeled approach to qualify a broad selection of commercially available immunoassays and evaluate the biotemporal stability of analytes across five pathophysiological domains of interest in AD, including core amyloid-β (Aβ) and tau AD biomarkers, neurodegeneration, inflammation/immune modulation, neurovascular injury, and metabolism/oxidative stress.

METHODS

Paired baseline and eight-week CSFs from twenty participants in a clinical drug trial for mild cognitive impairment (MCI) or mild dementia due to AD were used to evaluate sensitivity, intra-assay precision, inter-assay replicability, and eight-week biotemporal stability for sixty unique analytes measured with commercially available single- and multi-plex ELISA assays. Coefficients of variation (CV) were calculated, and intraclass correlation and Wilcoxon signed rank tests were applied.

RESULTS

We identified 32 biomarker candidates with good to excellent performance characteristics according to assay technical performance and CSF analyte biotemporal stability cut-off criteria. These included: 1) the core AD biomarkers Aβ1-42, Aβ1-40, Aβ1-38, and total tau; 2) non-Aβ, non-tau neurodegeneration markers NfL and FABP3; 3) inflammation/immune modulation markers IL-6, IL-7, IL-8, IL-12/23p40, IL-15, IL-16, MCP-1, MDC, MIP-1β, and YKL-40; 4) neurovascular markers Flt-1, ICAM-1, MMP-1, MMP-2, MMP-3, MMP-10, PlGF, VCAM-1, VEGF, VEGF-C, and VEGF-D; and 5) metabolism/oxidative stress markers 24-OHC, adiponectin, leptin, soluble insulin receptor, and 8-OHdG.

CONCLUSIONS

Assays for these CSF analytes demonstrate consistent sensitivity, reliability, and biotemporally stability for use in a multiple pathophysiological CSF biomarker panel to profile AD. Their qualification enables further investigation for use in AD diagnosis, staging and progression, disease mechanism profiling, and clinical trials.

Systemic Inflammation in C57BL/6J Mice Receiving Dietary Aluminum Sulfate; Up-Regulation of the Pro-Inflammatory Cytokines IL-6 and TNFα, C-Reactive Protein (CRP) and miRNA-146a in Blood Serum

A number of experimental investigations utilizing different murine species have previously reported: (i) that standard mouse-diets supplemented with physiologically realistic amounts of neurotoxic metal salts substantially induce pro-inflammatory signaling in a number of murine tissues; (ii) that these diet-stimulated changes may contribute to a systemic inflammation (SI), a potential precursor to neurodegenerative events in both the central and the peripheral nervous system (CNS, PNS); and (iii) that these events may ultimately contribute to a chronic and progressive inflammatory neurodegeneration, such as that which is observed in Alzheimer’s disease (AD) brain. In these experiments we assayed for markers of SI in the blood serum of C57BL/6J mice after 0, 1, 3 and 5 months of exposure to a standard mouse diet that included aluminum-sulfate in the food and drinking water, compared to age-matched controls receiving magnesium-sulfate or no additions. The data indicate that the SI markers that include the pro-inflammatory cytokines interleukin-6 (IL-6) and tumor necrosis factor alpha (TNFα), the acute phase reactive protein C-reactive protein (CRP) production and a triad of pro-inflammatory microRNAs (miRNA-9, miRNA-125b and miRNA-146a) all increase in the serum after aluminum-sulfate exposure. For the first time these results suggest that ad libitum exposure to aluminum-sulfate at physiologically realistic concentrations, as would be found in the human diet over the long term, may predispose to SI and the potential development of chronic, progressive, inflammatory neurodegeneration with downstream pathogenic consequences.