Differences in peripheral oxidative stress markers in Alzheimer's disease, vascular dementia and mixed dementia patients

Statins for vascular dementia: A hype or hope

Vascular dementia (VaD) is a second most common type of dementia subsequent to Alzheimer disease (AD). VaD is characterized by cognitive impairment and memory loss that may progress due to the development of cerebral amyloid angiopathy (CAA) a hallmark of AD. CAA triggers the progression of ischemic and hemorrhagic strokes with the subsequent the development of VaD and mixed dementia. Early diagnosis of patients with appropriate use of anti-inflammatory can prevent CAA-related inflammation and VaD development. Currently, there are no effective drugs in the management of VaD. Of note, cholesterol-lowering agent statins which are commonly used in patients with vascular diseases and dyslipidemia may affect the progression of VaD. Many previous studies highlighted the potential therapeutic efficacy of statins in treating VaD. Though, the underlying mechanisms of statins in prevention and treatment of VaD are not fully clarified. Consequently, this review aims to discuss the mechanistic role of statins in the management of VaD, and how statins may adversely affect the cognitive function in VaD patients.

Assessing Association Between Circulating Bilirubin Levels and the Risk of Frailty: An Observational and Mendelian Randomization Study

BACKGROUND

Bilirubin is a by-product of haemoglobin breakdown and has been reported to be a potent antioxidant recently. While elevated levels of bilirubin have been linked to a reduced risk of various diseases, their role remains unknown in frailty. This study aims to explore the relationship between serum bilirubin levels and the risk of frailty.

METHODS

This cohort study included 442 223 White British participants (aged 39 to 73 years) with an available frailty index at baseline (2006 to 2010) from the UK Biobank. The associations of total/direct bilirubin levels with the continuous frailty index were analysed by multivariable linear regression, and multivariable logistic regression was used after classifying frailty outcomes into non-frailty, pre-frailty and frailty. A Mendelian randomization (MR) analysis was applied to evaluate the association of genetically predicted bilirubin levels with frailty risk.

RESULTS

The prevalence rates of both pre-frailty and frailty were 46.17% and 12.49%, respectively, with higher rates observed in women than in men (pre-frailty: 47.33% vs. 44.79%, frailty: 13.64% vs. 11.13%, respectively). There was a non-linear negative association between total bilirubin levels and frailty indexes (p < 0.0001). Mildly elevated total bilirubin levels had protective effects against pre-frailty (OR = 0.863, 95% CI: 0.849 to 0.879, p < 0.001) and frailty (OR = 0.660, 95% CI: 0.641 to 0.679, p < 0.001). Increased total bilirubin levels were more beneficial for women with frailty risk (percent changes per SD μmol/L = -0.37%, 95% CI: -0.40% to -0.34%). The MR analysis revealed a negative association between genetically predicted total/direct bilirubin levels and frailty risk (both p < 0.0001).

CONCLUSIONS

Circulating total/direct bilirubin levels were negatively associated with frailty risk in White British individuals. Mildly elevated total bilirubin levels were more beneficial for women subpopulation.

Liver function and Alzheimer's brain pathologies: A longitudinal study: Liver and Alzheimer's pathologies

IMPORTANCE

The neuropathological links underlying the association between changes in liver function and AD have not yet been clearly elucidated.

OBJECTIVE

We aimed to examine the relationship between liver function markers and longitudinal changes in Alzheimer's disease (AD) core pathologies.

DESIGN

Data from the Korean Brain Aging Study for the Early Diagnosis and Prediction of Alzheimer's Disease, a longitudinal cohort study initiated in 2014, were utilized.

SETTING

Community and memory clinic setting.

PARTICIPANTS

Three hundred forty-seven older adults.

MAIN OUTCOME AND MEASURES

Participants underwent baseline and 2-year follow-up evaluations, including liver function assessments and various brain imaging techniques, such as amyloid and tau PET, FDG-PET, and MRI). Liver function indicators [alanine aminotransferase (ALT), aspartate aminotransferase (AST), and total bilirubin] were examined as exposure variables.

RESULTS

Higher baseline ALT levels were associated with a greater increase in beta-amyloid deposition over 2 years [β = 0.166, Bonferroni-corrected P (PB) = 0.012], while lower total bilirubin levels were associated with a greater increase in tau deposition over the same period (β = -0.570, PB < 0.001). In contrast, AST alone showed no significant association with changes of AD pathologies.

CONCLUSIONS AND RELEVANCE

The findings suggest a possible link between lower liver function and the accumulation of core AD pathologies in the brain. These results also support the possibility that the liver-brain axis could be a potential target for therapeutic or preventive strategies against AD.

Accelerated cognitive aging in chronically infected HIV-1 positive individuals despite effective long-term antiretroviral therapy

People living with HIV (PLHIV) are known to be at a higher risk of developing an array of aging-related diseases despite well-adhered combined antiretroviral therapy (cART). The present study aimed to investigate the impact of chronic HIV infection on neurocognitive function in virally suppressed PLHIV. We enrolled HIV-positive individuals randomly from an ART Center in Chennai, South India. A similar number of HIV-uninfected individuals matched for age and gender with the HIV-infected individuals served as controls. All individuals provided a detailed clinical history and underwent neuropsychological assessment using the International HIV Dementia Scale (IHDS). Plasma proteome analysis was performed using the Proximity extension assay (PEA) with the Olink® neuroexploratory panel, and untargeted metabolomics was performed using Ultra-High-Performance Liquid Chromatography/Mass Spectrometry/Mass Spectrometry. Despite a median duration of 9 years on first-line cART and suppressed viremia, a significant proportion of PLHIV registered significant levels of asymptomatic neurocognitive impairment, with 71% of these individuals scoring ≤ 10 in the IHDS test. We also observed significant alterations in a number of proteins and metabolites that are known to be associated with neuroinflammation, neurodegeneration, cognitive impairment, and gastrointestinal cancers, in the PLHIV group. Thus the study provides clinical as well as laboratory evidence to substantiate the presence of asymptomatic neurocognitive impairment in a large proportion of PLHIV, despite adequate cART and undetectable viremia, thereby supporting the view that HIV infection potentiates the risk for accelerated and accentuated neurological aging. This observation highlights the need to devise and implement appropriate intervention strategies for better long term management of HIV-infected persons.

Associations of apolipoprotein E ε4 allele, regional cerebral blood flow, and serum liver function markers in patients with cognitive impairment

Introduction

The ε4 allele of the apolipoprotein E gene (APOE4) is expressed abundantly in both the brain and peripheral circulation as a genetic risk factor for Alzheimer's disease (AD). Cerebral blood flow (CBF) dysfunction is an essential feature of AD, and the liver plays an important role in the pathogenesis of dementia. However, the associations of APOE4 with CBF and liver function markers in patients with cognitive impairment remains unclear. We aimed to evaluate the associations of APOE4 with CBF measured by arterial spin labeling (ASL) magnetic resonance imaging (MRI) and serum liver function markers in participants who were diagnosed with cognitive impairment.

Methods

Fourteen participants with AD and sixteen with amnestic mild cognitive impairment (MCI) were recruited. In addition to providing comprehensive clinical information, all patients underwent laboratory tests and MRI. All participants were divided into carriers and noncarriers of the ε4 allele, and T-tests and Mann-Whitney U tests were used to observe the differences between APOE4 carriers and noncarriers in CBF and liver function markers.

Results

Regarding regional cerebral blood flow (rCBF), APOE4 carriers showed hyperperfusion in the bilateral occipital cortex, bilateral thalamus, and left precuneus and hypoperfusion in the right lateral temporal cortex when compared with noncarriers. Regarding serum liver function markers, bilirubin levels (including total, direct, and indirect) were lower in APOE4 carriers than in noncarriers.

Conclusion

APOE4 exerts a strong effect on CBF dysfunction by inheritance, representing a risk factor for AD. APOE4 may be related to bilirubin metabolism, potentially providing specific neural targets for the diagnosis and treatment of AD.

Effect of woohwangchungsimwon and donepezil co-treatment on cognitive function and serum metabolic profiles in a scopolamine-induced model of Alzheimer's disease

ETHNOPHARMACOLOGICAL RELEVANCE

Woohwangchungsimwon (WCW) is a traditional medicine used in East Asian countries to treat central nervous system disorders. Reported pharmacological properties include antioxidant effects, enhanced learning and memory, and protection against ischemic neuronal cell death, supporting its use in treating neurodegenerative diseases like Alzheimer's disease (AD).

AIM OF THE STUDY

The study aims to assess the effects of co-treatment with WCW and donepezil on cognitive functions and serum metabolic profiles in a scopolamine-induced AD model.

MATERIALS AND METHODS

Cell viability and reactive oxygen species (ROS) levels were measured in amyloid β-peptide25-35 (Aβ25-35)-induced SH-SY5Y cells. An AD model was established in ICR mice by intraperitoneal scopolamine administration. Animals underwent the step-through passive avoidance test (PAT) and Morris water maze (MWM) test. Hippocampal tissues were collected to examine specific protein expression. Serum metabolic profiles were analyzed using nuclear magnetic resonance (NMR) spectroscopy.

RESULTS

Co-treatment with WCW and donepezil increased cell viability and reduced ROS production in Aβ25-35-induced SH-SY5Y cells compared to that with donepezil treatment alone. Co-treatment improved cognitive functions and was comparable to donepezil treatment alone in the PAT and MWM tests. Pathways related to tyrosine, phenylalanine, and tryptophan biosynthesis, phenylalanine metabolism, and cysteine and methionine metabolism were altered by co-treatment. Levels of tyrosine and methionine, major serum metabolites in these pathways, were significantly reduced after co-treatment.

CONCLUSIONS

Co-treatment with WCW and donepezil shows promise as a therapeutic strategy for AD and is comparable to donepezil alone in improving cognitive function. Reduced tyrosine and methionine levels after co-treatment may enhance cognitive function by mitigating hypertyrosinemia and hyperhomocysteinemia, known risk factors for AD. The serum metabolic profiles obtained in this study can serve as a foundation for developing other bioactive compounds using a scopolamine-induced mouse model.

Uric acid levels and their association with vascular dementia and Parkinson's disease dementia: a meta-analysis

OBJECTIVES

To explore the association between uric acid (UA) levels and vascular dementia (VaD) and Parkinson's disease dementia (PDD), a meta-analysis was conducted.

METHODS

The relevant studies were identified by searching PubMed, Embase, Web of Science, and Cochrane Collaboration Database up to May 2022. Pooled analysis, sensitivity analysis, and publication bias examination were all conducted. All analyses were performed by using STATA 16.

RESULTS

Twelve studies with a total of 2097 subjects were included. The pooled analysis showed that UA levels were not associated with VaD (WMD =  - 10.99 μmol/L, 95% CI (- 48.05, 26.07), P = 0.561) but were associated with PDD (WMD =  - 25.22 μmol/L, 95% CI (- 43.47, - 6.97), P = 0.007). The statistical stability and reliability were evaluated using sensitivity analysis and publication bias outcomes.

CONCLUSION

UA levels are associated with PDD but not with VaD. This study will help to strengthen our knowledge of the pathophysiologies of VaD and PDD, and promote the development of prevention and treatment strategies.

Imperatorin exerts antioxidant effects in vascular dementia via the Nrf2 signaling pathway

Imperatorin, an active ingredient extracted from Angelica and Qianghuo, has anti-inflammatory, anti-oxidative stress damage, blocking calcium channels, and other properties. Our preliminary findings revealed the protective role of imperatorin in the treatment of vascular dementia, we further explored the underlying mechanisms concerning the neuroprotection function of imperatorin in vascular dementia. The cobalt chloride (C_OCl2)-induced chemical hypoxia and hypoglycemia of hippocampal neuronal cells was applied as in vitro vascular dementia model. Primary neuronal cells was isolated from the hippocampal tissue of SD suckling rats within 24 h of birth. Hippocampal neurons were identified by immunofluorescence staining of microtubule-associated protein 2. Silencing or overexpression of Nrf2 was conducted by transfection of corresponding plasmids in hippocampal neuronal cells. Cell viability was detected by MTT assay to determine the optimal modeling concentration of CoCl2. Mitochondrial membrane potential, intracellular reactive oxygen species and apoptosis rate was measured by flow cytometry. The expression of anti-oxidative proteins was detected by quantitative real-time PCR and western blot, including Nrf2, NQO-1 and HO-1. Nrf2 nuclear translocation was detected using laser confocal microscopy. The modeling concentration of CoCl2 was 150umol/l, and the best interventional concentration of imperatorin was 7.5umol/l. Significantly, imperatorin facilitated the nuclear localization of Nrf2, promoted the expressions of Nrf2, NQO-1, and HO-1 relative to the model-control group. Moreover, imperatorin reduced the mitochondrial membrane potential and ameliorated CoCl2-induced hypoxic apoptosis in hippocampal neurons. On the contrary, silencing Nrf2 completely abrogated the protective effects of imperatorin. Imperatorin might be an effective drug for preventing and treating vascular dementia.

Association between serum total bilirubin and Alzheimer's disease: A bidirectional Mendelian randomization study

Oxidative stress plays an important role in the pathogenesis of Alzheimer's disease (AD). As a potent antioxidant, serum bilirubin is decreased in AD and may be related to its pathogenesis, but the causal association between serum bilirubin and AD has not been reported. This was investigated in the present study by bidirectional two-sample Mendelian randomization (MR) analysis. Genetic instruments at the genome-wide significance level (P < 5 × 10-8) were selected from the United Kingdom Biobank (n = 342,829). Summary-level AD data were obtained from a large-scale genome-wide association study (n = 63,926). Causal estimates were evaluated using the inverse variance weighted (IVW) approach and other five complementary methods. MR-Egger, IVW and MR pleiotropy residual sum and outlier (MR-PRESSO) methods were used for sensitivity analyses. The results showed that there was no significant association between serum total bilirubin and AD (odds ratio=1.003, 95% confidence interval: 0.967-1.041, P = 0.865). Inverse MR revealed that serum total bilirubin was increased in AD (beta = 0.009, SE = 0.003, P = 0.010). These results indicate that serum total bilirubin is not causally associated with AD and cannot be used for screening or diagnosis, but can potentially serve as a biomarker of disease severity, and it needs further clinical studies.

Circulating serum metabolites as predictors of dementia: a machine learning approach in a 21-year follow-up of the Whitehall II cohort study

BACKGROUND

Age is the strongest risk factor for dementia and there is considerable interest in identifying scalable, blood-based biomarkers in predicting dementia. We examined the role of midlife serum metabolites using a machine learning approach and determined whether the selected metabolites improved prediction accuracy beyond the effect of age.

METHODS

Five thousand three hundred seventy-four participants from the Whitehall II study, mean age 55.8 (standard deviation (SD) 6.0) years in 1997-1999 when 233 metabolites were quantified using nuclear magnetic resonance metabolomics. Participants were followed for a median 21.0 (IQR 20.4, 21.7) years for clinically-diagnosed dementia (N=329). Elastic net penalized Cox regression with 100 repetitions of nested cross-validation was used to select models that improved prediction accuracy for incident dementia compared to an age-only model. Risk scores reflecting the frequency with which predictors appeared in the selected models were constructed, and their predictive accuracy was examined using Royston's R², Akaike's information criterion, sensitivity, specificity, C-statistic and calibration.

RESULTS

Sixteen of the 100 models had a better c-statistic compared to an age-only model and 15 metabolites were selected at least once in all 16 models with glucose present in all models. Five risk scores, reflecting the frequency of selection of metabolites, and a 1-SD increment in all five risk scores was associated with higher dementia risk (HR between 3.13 and 3.26). Three of these, constituted of 4, 5 and 15 metabolites, had better prediction accuracy (c-statistic from 0.788 to 0.796) compared to an age-only model (c-statistic 0.780), all p<0.05.

CONCLUSIONS

Although there was robust evidence for the role of glucose in dementia, metabolites measured in midlife made only a modest contribution to dementia prediction once age was taken into account.

Structural characterization of polysaccharide purified from Amanita caesarea and its pharmacological basis for application in Alzheimer's disease: endoplasmic reticulum stress

Alzheimer's disease (AD) leads to progressive declines in memory and learning. This disease may arise from endoplasmic reticulum stress due to protein misfolding, which promotes inflammatory pathway activation and induces neuronal cell apoptosis. Polysaccharide is one of the main active components of the mushroom Amanita caesarea (A. caesarea) and has been proven to act as an antioxidant, immune regulatory and anti-inflammatory agent with neurodevelopmental effects. In this study, polysaccharide isolated from A. caesarea (ACPS2) was subjected to analysis to determine the main components, homogeneity and molecular weight and characterize the structure. Furthermore, APP/PS1 mice were orally treated with ACPS2 for 6 weeks. Structural characterization of ACPS2 revealed a mass average molar mass of 16.6 kDa and a structure containing a main chain and branching. In vivo, treatment with ACPS2 for 6 weeks significantly improved cognition and anxious behavior in APP/PS1 mice using Morris water maze and open-field test. Alleviation of brain injury, amyloid-β deposition and tau hyperphosphorylation were observed in ACPS2-treated AD mice. No changes in other tissues were observed. ACPS2 appeared to alleviate inflammation in vivo, as determined by decreases in the serum concentrations of tumor necrosis factor-α and interleukin-1β relative to those in non-treated mice. ACPS2 improved cholinergic system function and stabilized oxidative stress in APP/PS1 mice. Proteomics and bioinformatics analyses showed that the therapeutic effect of ACPS2 is achieved through regulation of oxidative stress-mediated endoplasmic reticulum stress. Furthermore, ACPS2 exerted anti-AD effects by regulating nuclear factor-E2-related factor 2 (Nrf2) signaling, thereby inhibiting endoplasmic reticulum stress and nuclear factor-kappa B (NF-κB) activation.

A Tau-Driven Adverse Outcome Pathway Blueprint Toward Memory Loss in Sporadic (Late-Onset) Alzheimer's Disease with Plausible Molecular Initiating Event Plug-Ins for Environmental Neurotoxicants

The worldwide prevalence of sporadic (late-onset) Alzheimer's disease (sAD) is dramatically increasing. Aging and genetics are important risk factors, but systemic and environmental factors contribute to this risk in a still poorly understood way. Within the frame of BioMed21, the Adverse Outcome Pathway (AOP) concept for toxicology was recommended as a tool for enhancing human disease research and accelerating translation of data into human applications. Its potential to capture biological knowledge and to increase mechanistic understanding about human diseases has been substantiated since. In pursuit of the tau-cascade hypothesis, a tau-driven AOP blueprint toward the adverse outcome of memory loss is proposed. Sequences of key events and plausible key event relationships, triggered by the bidirectional relationship between brain cholesterol and glucose dysmetabolism, and contributing to memory loss are captured. To portray how environmental factors may contribute to sAD progression, information on chemicals and drugs, that experimentally or epidemiologically associate with the risk of AD and mechanistically link to sAD progression, are mapped on this AOP. The evidence suggests that chemicals may accelerate disease progression by plugging into sAD relevant processes. The proposed AOP is a simplified framework of key events and plausible key event relationships representing one specific aspect of sAD pathology, and an attempt to portray chemical interference. Other sAD-related AOPs (e.g., Aβ-driven AOP) and a better understanding of the impact of aging and genetic polymorphism are needed to further expand our mechanistic understanding of early AD pathology and the potential impact of environmental and systemic risk factors.

The Influence of Serum Uric Acid Level on Alzheimer's Disease: A Narrative Review

As a powerful antioxidant in the human body, uric acid (UA) has been the subject of increasing research that focused on its influence on Alzheimer's disease (AD) in recent years. The latest literature was gathered to describe the influence of serum uric acid (SUA) level on the onset and progression of AD and to analyze the possibility that SUA is a biomarker of Alzheimer's disease. A large number of existing studies suggested that the SUA level was lower or tended to decrease in patients with AD, and increased SUA level may have a protective effect in AD, which could reduce the risk of onset and slowing the course of the disease. However, some Mendelian randomization analyses suggested that genetically determined uric acid was not associated with AD risk. Existing research results are contradictory due to the high inconsistency of the studies, the selection of subjects, and other factors. UA also showed a strong association with cognitive function, and there appeared to be a gender-selective neuroprotective action. Due to its potent antioxidant properties, the low uric acid level may contribute to oxidative stress to accelerate disease progression. But some preclinical data showed a possibility that in some special cases, UA had a prooxidant properties. The possibility was raised in the discussion of the underlying mechanism that both the low uric acid level and the rapidly progressive course of the disease were the consequence of malnutrition. This paper reviews recent advances in the study of SUA and AD which offers the possibility of new biomarker, new prevention, and treatment strategies for Alzheimer's disease.

Serum Uric Acid and the Risk of Dementia: A Systematic Review and Meta-Analysis

Background: This meta-analysis aimed to evaluate the relationship between serum uric acid (UA) and the risk of dementia and its subtypes.

Methods: Embase, PubMed, and Web of Science were searched from inception to July 2020. Random-effect models were employed to analyze the standard mean difference (SMD) with the corresponding 95% confidence intervals (CI).

Results: Twenty-three eligible studies involving 5,575 participants were identified. The overall results showed lower levels of UA in dementia relative to non-dementia controls [SMD = −0.32 (−0.64; −0.01) p = 0.04]. The subgroup analysis of the type of dementia demonstrated a significant association of UA with Alzheimer's disease (AD) [SMD = −0.58 (−1.02; −0.15) p = 0.009] and Parkinson's disease with dementia (PDD) [SMD = −0.33 (−0.52; −0.14) p = 0.001] but not with vascular dementia (VaD). The stratification analysis of the concentrations of UA revealed that the UA quartile 1–2 was negatively correlated with dementia and neurodegenerative subtypes (p < 0.05), whereas a positive correlation of UA quartile 4 with dementia was noted (p = 0.028). Additionally, the meta-regression analysis on confounders showed that not age, body mass index, diabetes mellitus, hypertension, or smoking but education (p = 0.003) exerted an influence of the UA in the risk estimate of dementia.

Conclusions: Low concentrations of UA (< 292 μmol/L or 4.91 mg/dL) is a potential risk factor for AD and PDD but not for VaD. The mechanism of different concentrations of the UA in dementia needs to be confirmed through further investigation.

Abnormal Serum Bilirubin/Albumin Concentrations in Dementia Patients With Aβ Deposition and the Benefit of Intravenous Albumin Infusion for Alzheimer's Disease Treatment

Background

Our previous study in animal models revealed that bilirubin could induce Aβ formation and deposition. Bilirubin may be important in neurodegenerative dementia with Aβ deposition. Hence, lowering the concentration of the free bilirubin capable of crossing the blood brain-barrier may benefit the treatment of Alzheimer's disease (AD).

Objectives

The objectives of this study were to examine the change in the serum bilirubin and albumin concentrations of dementia patients with Aβ deposition, and to determine the effects of intravenous administration of albumin in the treatment of AD.

Methods

Bilirubin and albumin concentrations in dementia patients with Aβ deposition were examined. Cell viability and apoptosis were determined in dopaminergic neuron-like cells MN9D treated with bilirubin in the presence of diverse concentrations of serum. Human albumin at a dose of 10 g every 2 weeks for 24 weeks was administered intravenously to AD patients to examine the effect of albumin on AD symptoms.

Results

Significantly higher indirect bilirubin (IBIL) concentrations, lower albumin concentrations, and higher ratio of IBIL to albumin (IBIL/ALB) were observed in dementia patients with Aβ deposition, including AD, dementia with Lewy bodies, and general paresis of insane. In vitro assays showed that bilirubin-induced injury in cultured dopaminergic neuron-like cells negatively depends on the concentration of serum in the culture medium. General linear model with repeated measures analysis indicated a main effect of group on the change in albumin concentrations and Alzheimer's Disease Cooperative Study Activities of Daily Living Inventory scale (ADCS-ADL) scores, and the main effect of time and group, and group-by-time interaction on the change of Clinical Dementia Rating Scale-Sum of Boxes (CDR-SB) scores. Analysis of the combined data of the entire 28 weeks of assessment period using the area under curve convincingly showed significantly improvements in the change of albumin concentrations, ADCS-ADL scores, and CDR-SB scores.

Conclusion

IBIL and the IBIL/ALB ratio are significantly higher in dementia patients with Aβ deposition, and intravenous administration of albumin is beneficial to AD treatment.

Trial Registration

The intervention study was registered at http://www.chictr.org.cn (ChiCTR-IOR-17011539). Date of registration: June 1, 2017.

Redox modifications in synaptic components as biomarkers of cognitive status, in brain aging and disease

Aging is a natural process that includes several changes that gradually make organisms degenerate and die. Harman's theory proposes that aging is a consequence of the progressive accumulation of oxidative modifications mediated by reactive oxygen/nitrogen species, which plays an essential role in the development and progression of many neurodegenerative diseases. This review will focus on how abnormal redox modifications induced by age impair the functionality of neuronal redox-sensitive proteins involved in axonal elongation and guidance, synaptic plasticity, and intercellular communication. We will discuss post-transcriptional regulation of gene expression by microRNAs as a mechanism that controls the neuronal redox state. Finally, we will discuss how some brain-permeant antioxidants from the diet have a beneficial effect on cognition. Taken together, the evidence revised here indicates that oxidative-driven modifications of specific proteins and changes in microRNA expression may be useful biomarkers for aging and neurodegenerative diseases. Also, some specific antioxidant therapies have undoubtedly beneficial neuroprotective effects when administered in the correct doses, in the ideal formulation combination, and during the appropriate therapeutic window. The use of some antioxidants is, therefore, still poorly explored for the treatment of neurodegenerative diseases such as Alzheimer's disease.

The Relationship Between Serum VCAM-1 and Alzheimer's Disease in Patients with Type 2 Diabetes Mellitus

BACKGROUND

Previous studies have reported that diabetes mellitus (DM) is a risk factor for Alzheimer's disease (AD). Vascular cell adhesion molecule-1 (VCAM-1) plays an important role in the pathological process of atherosclerosis. The aim was to elucidate the relationship between serum VCAM-1 and early AD in DM patients.

METHODS

Serum samples for VCAM-1 were tested in 208 DM patients. All included DM patients were followed up for a median of 36 months prospectively. The prognostic value of serum VCAM-1 for predicting AD events was analyzed by using Cox proportional hazard.

RESULTS

Serum VCAM-1 was independently associated with AD history after adjusting for related confounding factors in patients with DM at baseline by using the logistic regression analysis (OR=1.861; 95% CI, 1.435-2.539; P _trend=0.020). The Cox proportional hazard model suggested that VCAM-1 was a prognostic factor for AD events in the DM patients (HR=2.728; 95% CI, 1.785-5.439; P _trend<0.001). Stratified analysis showed that the significant association between AD event and serum VCAM-1 in DM patients was not affective by CVD history.

CONCLUSION

Our results showed that higher VCAM-1 levels were significantly related to a higher risk of AD events in DM patients. The serum biomarker might be beneficial to predict AD early. Serum VCAM-1 might be a good biochemical parameter for predicting AD in DM.

Oxidative Stress Indexes for Diagnosis of Health or Disease in Humans

Oxidative stress (OS) is the imbalance between oxidant and antioxidant molecules, in favor of oxidants, that causes aging and disease. Many studies have been published that demonstrate the relationship between OS and human health and disease; however, the following questions arise: (i) how are we sure that the OS is present in a biological process? (ii) Is the OS reported in the different investigations equivalent? (iii) What are the best oxidant and antioxidant markers for OS diagnosis? (iv) Can we establish the types and the intensity of the OS? (v) Does OS index could be useful for research and/or application in clinical medicine? In this regard, several indexes have been proposed to measure OS in humans relative to the state of health and disease, among which the following can be highlighted: Oxidative Stress Index (OSI), Tiol Ratios (-SH/TT, -SS/-SH, and-SS/TT), Glutathione Ratio (GSSG/GSH), Oxidative Stress Score (OSS), and OXY-index. Therefore, the aim of this review is to present the state of the art of knowledge about OS indexes for diagnosis of health or disease in humans. We searched for articles in English or Spanish in the PubMed/MEDLINE and Scopus electronic databases published up until May 2019. The keywords used were “oxidative stress,” “index,” and “oxidative stress index.” It was identified 11479 records in both databases, and 490 articles were analyzed. Our review suggests that all indexes analyzed allow diagnose and differentiate the OS related to human health and disease. Also, the studies on OSI, Oxy-score, and OSS indexes have proven to be reliable, practical, and with clinical utility. However, it is necessary to continue with longitudinal studies, especially assess the usefulness of the indexes in the clinical prognosis, and make comparative studies between the different indexes.

Oxidative Stress in Elderly with Different Cognitive Status: My Mind Project

BACKGROUND

Biomarkers of oxidative stress have been associated with cognitive status in humans and have been proposed to guide prognosis/treatment in Alzheimer's disease (AD) and mild cognitive impairment (MCI).

OBJECTIVE

The aim of this study was to compare oxidative stress status in the plasma of mild-moderate AD, MCI, and healthy elderly with normal cognition (HE) undergoing a non-pharmacological intervention including multi-modal cognitive training ("My Mind Project").

METHODS

A prospective randomized trial involving 321 elderly people enrolled in Marche Region, Italy. Each subject was randomly assigned to an experimental (cognitive training) or to a control group. Cognitive performances and biomarkers have been analyzed before intervention (baseline), immediately after termination (follow-up 1), after 6 months (follow-up 2), and after 2 years (follow-up 3). The biological antioxidant potential (BAP) to Diacron reactive oxygen metabolites (d-ROM) ratio has been used as an indicator of oxidative stress status and as outcome variable.

RESULTS

We have found no differences in the oxidative status among AD, MCI, and HE. Neither did we find a significant effect of the intervention within experimental groups. Gender was the sole factor with a strong significant effect on BAP/d-ROM.

CONCLUSIONS

Based on these results, the utility of biomarkers of oxidative stress to guide prognosis/treatment in AD or MCI seems to be limited by lack of specificity, large interindividual variability, and gender bias.

Emerging Biomarkers in Vascular Cognitive Impairment and Dementia: From Pathophysiological Pathways to Clinical Application

Vascular pathology is the second most common neuropathology of dementia after Alzheimer’s disease (AD), with small vessels disease (SVD) being considered the major cause of vascular cognitive impairment and dementia (VCID). This review aims to evaluate pathophysiological pathways underlying a diagnosis of VCID. Firstly, we will discuss the role of endothelial dysfunction, blood-brain barrier disruption and neuroinflammation in its pathogenesis. Then, we will analyse different biomarkers including the ones of inflammatory responses to central nervous system tissue injuries, of coagulation and thrombosis and of circulating microRNA. Evidences on peripheral biomarkers for VCID are still poor and large-scale, prospectively designed studies are needed to translate these findings into clinical practice, in order to set different combinations of biomarkers to use for differential diagnosis among types of dementia.

Plasma Antioxidant Status in Patients with Alzheimer's Disease and Cognitively Intact Elderly: A Meta-Analysis of Case-Control Studies

Serum antioxidants may afford neuroprotection against Alzheimer's disease (AD) via correction of the pro-oxidative imbalance but findings reported have been inconsistent. We compared the pooled mean difference in serum levels of ten dietary antioxidants between patients with AD and cognitively intact controls from 52 studies in meta-analyses using random-effects models. Patients with AD had significantly lower plasma levels of α-carotene, β-carotene, lycopene, lutein, vitamin A, C, and E, and uric acid. No significant difference was observed for plasma levels of β-cryptoxanthin and zeaxanthin. Considerable heterogeneity was detected across studies. The lower serum levels of dietary antioxidants from the carotene and vitamin subclasses observed in individuals with AD suggest reduced systemic availability of these subclasses in this prevalent form of dementia. To our knowledge, these are the first meta-analyses to demonstrate lower serum lycopene and to evaluate β-cryptoxanthin, lutein, and zeaxanthin levels in AD. In light of the significant heterogeneity detected across studies, caution should be exercised in the interpretation of the data and therapeutic intervention approaches considered through supplementation measures. Our data may better inform interventions to improve antioxidant status in a condition of major public health importance.

Uric acid and incident dementia over 12 years of follow-up: a population-based cohort study

OBJECTIVES

In patients with gout, maintaining too low serum uric acid (SUA) level with urate-lowering therapy is a concern because uric acid is thought to be neuroprotective. However, the relation between SUA and dementia remains debated. This study aimed to investigate the impact of SUA level on the incidence of dementia.

METHODS

We assessed the longitudinal association between SUA level and incident dementia (Diagnostic and Statistical Manual of Mental Disorders Version IV (DSM-IV) criteria) in a large cohort of healthy older people from the community (Three-City Dijon cohort). Additionally, we investigated the relation between SUA level and MRI markers of brain ageing (white matter hyperintensity volume (WMHV), lacunes and hippocampal volume).

RESULTS

The study sample comprised 1598 people (mean (SD) age 72.4(4.1) years, 38.3% male). During the 13,357 person-years of follow-up (median duration: 10.1 years), dementia developed in 110 participants (crude incidence rate: 8.2/1000 person-years). After multiple adjustments, the multivariate HR with the highest (≥75th percentile) versus lowest SUA level was 1.79 (95% CI 1.17 to 2.73; p=0.007). The association was stronger with vascular or mixed dementia (HR=3.66 (95% CI 1.29 to 10.41), p=0.015) than Alzheimer's disease (HR=1.55 (95% CI 0.92 to 2.61), p=0.10). There was a non-significant trend towards an association between high SUA level and extensive WMHV (p=0.10), a biomarker of small vessel disease, but not hippocampal volume (p=0.94) or lacunes (p=0.86). The association between SUA level and vascular or mixed dementia might be affected by interim strokes.

CONCLUSIONS

Risk of dementia, especially vascular or mixed dementia, may be increased with high SUA levels in elderly people.

Redox theory of aging: implications for health and disease

Genetics ultimately defines an individual, yet the phenotype of an adult is extensively determined by the sequence of lifelong exposures, termed the exposome. The redox theory of aging recognizes that animals evolved within an oxygen-rich environment, which created a critical redox interface between an organism and its environment. Advances in redox biology show that redox elements are present throughout metabolic and structural systems and operate as functional networks to support the genome in adaptation to environmental resources and challenges during lifespan. These principles emphasize that physical and functional phenotypes of an adult are determined by gene-environment interactions from early life onward. The principles highlight the critical nature of cumulative exposure memories in defining changes in resilience progressively during life. Both plasma glutathione and cysteine systems become oxidized with aging, and the recent finding that cystine to glutathione ratio in human plasma predicts death in coronary artery disease (CAD) patients suggests this could provide a way to measure resilience of redox networks in aging and disease. The emerging concepts of cumulative gene-environment interactions warrant focused efforts to elucidate central mechanisms by which exposure memory governs health and etiology, onset and progression of disease.

Targeting Free Radicals in Oxidative Stress-Related Human Diseases

Cancer and Alzheimer's disease (AD) are characterized by (i) opposing biological mechanisms, (ii) an inverse correlation between their incidences, and (iii) oxidative stress being a common denominator of both diseases. Increased formation of reactive oxygen species (ROS) in cancer cells from oncogenic signaling and/or metabolic disturbances leads to upregulation of cellular antioxidant capacity to maintain ROS levels below a toxic threshold. Combining drugs that induce high levels of ROS with compounds that suppress cellular antioxidant capacity by depleting antioxidant systems [glutathione (GSH), superoxide dismutase (SOD), and thioredoxin (TRX)] and/or targeting glucose metabolism represents a potential anticancer strategy. In AD, free metals and/or Aβ:metal complexes may cause damage to biomolecules in the brain (via Fenton reaction), including DNA. Metal chelation, based on the application of selective metal chelators or metal delivery, may induce neuroprotective signaling and represents a promising therapeutic strategy. This review examines therapeutic strategies based on the modulation of oxidative stress in cancer and AD.

The levels of 7,8-dihydrodeoxyguanosine (8-oxoG) and 8-oxoguanine DNA glycosylase 1 (OGG1) - A potential diagnostic biomarkers of Alzheimer's disease

Evidence indicates that oxidative stress contributes to neuronal cell death in Alzheimer's disease (AD). Increased oxidative DNA damage l, as measured with 8-oxoguanine (8-oxoG), and reduced capacity of proteins responsible for removing of DNA damage, including 8-oxoguanine DNA glycosylase 1 (OGG1), were detected in brains of AD patients. In the present study we assessed peripheral blood biomarkers of oxidative DNA damage, i.e. 8- oxoG and OGG1, in AD diagnosis, by comparing their levels between the patients and the controls. Our study was performed on DNA and serum isolated from peripheral blood taken from 100 AD patients and 110 controls. For 8-oxoG ELISA was employed. The OGG1 level was determined using ELISA and Western blot technique. Levels of 8-oxoG were significantly higher in DNA of AD patients. Both ELISA and Western blot showed decreased levels of OGG1 in serum of AD patients. Our results show that oxidative DNA damage biomarkers detected in peripheral tissue could reflect the changes occurring in the brain of patients with AD. These results also suggest that peripheral blood samples may be useful to measure oxidative stress biomarkers in AD.