Plasma antioxidant status, immunoglobulin g oxidation and lipid peroxidation in demented patients: relevance to Alzheimer disease and vascular dementia

Molecular biomarkers for vascular cognitive impairment and dementia

As disease-specific interventions for dementia are being developed, the ability to identify the underlying pathology and dementia subtypes is increasingly important. Vascular cognitive impairment and dementia (VCID) is the second most common cause of dementia after Alzheimer disease, but progress in identifying molecular biomarkers for accurate diagnosis of VCID has been relatively limited. In this Review, we examine the roles of large and small vessel disease in VCID, considering the underlying pathophysiological processes that lead to vascular brain injury, including atherosclerosis, arteriolosclerosis, ischaemic injury, haemorrhage, hypoperfusion, endothelial dysfunction, blood-brain barrier breakdown, inflammation, oxidative stress, hypoxia, and neuronal and glial degeneration. We consider the key molecules in these processes, including proteins and peptides, metabolites, lipids and circulating RNA, and consider their potential as molecular biomarkers alone and in combination. We also discuss the challenges in translating the promise of these biomarkers into clinical application.

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.

Low blood carotenoid status in dementia and mild cognitive impairment: A systematic review and meta-analysis

BACKGROUND

Given their potent antioxidation properties, carotenoids play a role in delaying and preventing dementia and mild cognitive impairment (MCI). However, observational studies have found inconsistent results regarding the associations between blood carotenoid levels and the risk of dementia and MCI. We conducted this systematic review and meta-analysis to investigate the relationship between blood carotenoid levels and the risk of dementia and MCI.

METHODS

A systematic search was performed in the Web of Science, PubMed, Embase, and Cochrane Library electronic databases to retrieve relevant English articles published from their inception until February 23, 2023. Study quality was assessed by the Newcastle-Ottawa scale. Standardized mean differences (SMDs) and 95% confidence intervals (CIs) were pooled using random-effect meta-analyses. Ultimately, 23 studies (n = 6610) involving 1422 patients with dementia, 435 patients with MCI, and 4753 controls were included.

RESULTS

Our meta-analysis showed that patients with dementia had lower blood lycopene (SMD: -0.521; 95%CI: -0.741, -0.301), α-carotene (SMD: -0.489; 95%CI: -0.697, -0.281), β-carotene (SMD: -0.476; 95%CI: -0.784, -0.168), lutein (SMD: -0.516; 95%CI: -0.753, -0.279), zeaxanthin (SMD: -0.571; 95%CI: -0.910, -0.232) and β-cryptoxanthin (SMD: -0.617; 95%CI: -0.953, -0.281) than the controls. Our results indicated that blood carotenoid levels were significantly lower in patients with dementia than in controls, despite high heterogeneity across the studies. Owing to insufficient data, we did not observe a similar and stable relationship between blood carotenoid levels and MCI.

CONCLUSIONS

Our meta-analysis indicated that lower blood carotenoid levels may be a risk factor for dementia and MCI.

Dityrosine cross-linking and its potential roles in Alzheimer's disease

Oxidative stress is a significant source of damage that accumulates during aging and contributes to Alzheimer's disease (AD) pathogenesis. Oxidation of proteins can give rise to covalent links between adjacent tyrosines known as dityrosine (DiY) cross-linking, amongst other modifications, and this observation suggests that DiY could serve as a biomarker of accumulated oxidative stress over the lifespan. Many studies have focused on understanding the contribution of DiY to AD pathogenesis and have revealed that DiY crosslinks can be found in both Aβ and tau deposits - the two key proteins involved in the formation of amyloid plaques and tau tangles, respectively. However, there is no consensus yet in the field on the impact of DiY on Aβ and tau function, aggregation, and toxicity. Here we review the current understanding of the role of DiY on Aβ and tau gathered over the last 20 years since the first observation, and discuss the effect of this modification for Aβ and tau aggregation, and its potential as a biomarker for AD.

Lycopene: Sojourn from kitchen to an effective therapy in Alzheimer's disease

Reports on a significant positive correlation between consumption of carotenoid-rich food and prevention of Alzheimer's disease (AD) led to the investigation of carotenoids for the treatment and prevention of AD. More than 1100 types of carotenoids are found naturally, out of which only around 50 are absorbed and metabolized in human body. Lycopene is one of the most commonly ingested members of fat-soluble carotenoid family that gives vegetables and fruits their red, yellow, or orange color. Lycopene has established itself as a promising therapy for AD owing to its neuroprotective activities, including antioxidant, anti-inflammatory, and antiamyloidogenic properties. In this review, we highlight the various in vitro and preclinical studies demonstrating the neuroprotective effect of lycopene. Also, some epidemiological and interventional studies investigating the protective effect of lycopene in AD have been discussed. Diving deeper, we also discuss various significant mechanisms, through which lycopene exerts its remissive effects in AD. Finally, to overcome the issue of poor chemical stability and bioavailability of lycopene, some of the novel delivery systems developed for lycopene have also been briefly highlighted.

A quantitative meta-analysis of vitamin C in the pathophysiology of Alzheimer’s disease

Purpose

Alzheimer’s disease (AD) is a multifaceted neurodegenerative disorder with many complex pathways feeding into its pathogenesis and progression. Vitamin C, an essential dietary antioxidant, is vital for proper neurological development and maintenance. This meta-analysis and systematic review attempted to define the relationship between vitamin C plasma levels and AD while highlighting the importance and involvement of vitamin C in the pathogenesis of AD.

Materials and methods

PRISMA guidelines were used to obtain studies quantifying the plasma levels of vitamin C in AD and control subjects. The literature was searched in the online databases PubMed, Google Scholar, and Web of Science. A total of 12 studies were included (n = 1,100) and analyzed using Comprehensive Meta-Analysis 3.0.

Results

The results show that there is a significant decrease in the plasma vitamin C levels of AD patients as compared to healthy controls (pooled SMD with random-effect model: −1.164, with 95%CI: −1.720 to −0.608, Z = −4.102, p = 0.00) with significant heterogeneity (I² = 93.218). The sensitivity analysis showed directionally similar results. Egger’s regression test (p = 0.11) and visual inspection of the funnel plot showed no publication bias.

Conclusion

Based on these studies, it can be deduced that the deficiency of vitamin C is involved in disease progression and supplementation is a plausible preventive and treatment strategy. However, clinical studies are warranted to elucidate its exact mechanistic role in AD pathophysiology and prevention.

Low Plasma Ergothioneine Predicts Cognitive and Functional Decline in an Elderly Cohort Attending Memory Clinics

Low blood concentrations of the diet-derived compound ergothioneine (ET) have been associated with cognitive impairment and cerebrovascular disease (CeVD) in cross-sectional studies, but it is unclear whether ET levels can predict subsequent cognitive and functional decline. Here, we examined the temporal relationships between plasma ET status and cognition in a cohort of 470 elderly subjects attending memory clinics in Singapore. All participants underwent baseline plasma ET measurements as well as neuroimaging for CeVD and brain atrophy. Neuropsychological tests of cognition and function were assessed at baseline and follow-up visits for up to five years. Lower plasma ET levels were associated with poorer baseline cognitive performance and faster rates of decline in function as well as in multiple cognitive domains including memory, executive function, attention, visuomotor speed, and language. In subgroup analyses, the longitudinal associations were found only in non-demented individuals. Mediation analyses showed that the effects of ET on cognition seemed to be largely explainable by severity of concomitant CeVD, specifically white matter hyperintensities, and brain atrophy. Our findings support further assessment of plasma ET as a prognostic biomarker for accelerated cognitive and functional decline in pre-dementia and suggest possible therapeutic and preventative measures.

Vascular Dementia and Crosstalk Between the Complement and Coagulation Systems

Vascular Dementia (VaD) is a neurocognitive disorder caused by reduced blood flow to the brain tissue, resulting in infarction, and is the second most common type of dementia. The complement and coagulation systems are evolutionary host defence mechanisms activated by acute tissue injury to induce inflammation, clot formation and lysis; recent studies have revealed that these systems are closely interlinked. Overactivation of these systems has been recognised to play a key role in the pathogenesis of neurological disorders such as Alzheimer's disease and multiple sclerosis, however their role in VaD has not yet been extensively reviewed. This review aims to bridge the gap in knowledge by collating current understanding of VaD to enable identification of complement and coagulation components involved in the pathogenesis of this disorder that may have their effects amplified or supressed by crosstalk. Exploration of these mechanisms may unveil novel therapeutic targets or biomarkers that would improve current treatment strategies for VaD.

The Associations of Plasma/Serum Carotenoids with Alzheimer's Disease: A Systematic Review and Meta-Analysis

BACKGROUND

Multiple lines of evidence indicate protective effects of carotenoids in Alzheimer's disease (AD). However, previous epidemiological studies reported inconsistent results regarding the associations between carotenoids levels and the risk of AD.

OBJECTIVE

Our study aims to evaluate the associations of six major members of carotenoids with the occurrence of AD by conducting a systematic review and meta-analysis.

METHODS

Following PRISMA guidelines, a comprehensive literature search of PubMed, Web of Science, Ebsco, and PsycINFO databases was conducted, and the quality of each included studies was evaluated by a validated scoring systems. Standardized mean differences (SMD) with 95% confidence intervals (CI) were determined by using a random effects model. Heterogeneity was evaluated by I2 statistics. Publication bias was detected using funnel plots and Egger's test.

RESULTS

Sixteen studies, with 10,633 participants were included. Pooled analysis showed significantly lower plasma/serum levels of lutein (SMD = -0.86, 95% CI: -1.67 to -0.05, p = 0.04) and zeaxanthin (SMD = -0.59; 95% CI: -1.12 to -0.06, p = 0.03) in patients with AD versus cognitively intact controls, while α-carotene (SMD = 0.21, 95% CI: -0.68 to 0.26, p = 0.39), β-carotene (SMD = 0.04, 95% CI: -0.57 to 0.65, p = 0.9), lycopene (SMD = -0.12, 95% CI: -0.96 to 0.72, p = 0.78), and β-cryptoxanthin (SMD = -0.09, 95% CI: -0.83 to 0.65, p = 0.81) did not achieve significant differences.

CONCLUSION

Of six major members of carotenoids, only lutein and zeaxanthin concentrations in plasma/serum were inversely related to the risk of AD. More high-quality longitudinal studies are needed to verify these findings.

Emerging insights into the role of albumin with plasma exchange in Alzheimer's disease management

Alzheimer's disease (AD) is a neurodegenerative process that inexorably leads to progressive deterioration of cognition function and, ultimately, death. Central pathophysiologic features of AD include the accumulation of extracellular plaques comprised of amyloid-β peptide (Aβ) and the presence of intraneuronal neurofibrillary tangles. However, a large body of evidence suggests that oxidative stress and inflammation are major contributors to the pathogenesis and progression of AD. To date, available pharmacologic treatments are only symptomatic. Clinical trials focused on amyloid and non-amyloid-targeted treatments with small molecule pharmacotherapy and immunotherapies have accumulated a long list of failures. Considering that around 90 % of the circulating Aβ is bound to albumin, and that a dynamic equilibrium exists between peripheral and central Aβ, plasma exchange with albumin replacement has emerged as a new approach in a multitargeted AD therapeutic strategy (AMBAR Program). In plasma exchange, a patient's plasma is removed by plasmapheresis to eliminate toxic endogenous substances, including Aβ and functionally impaired albumin. The fluid replacement used is therapeutic albumin, which acts not only as a plasma volume expander but also has numerous pleiotropic functions (e.g., circulating Aβ- binding capacity, transporter, detoxifier, antioxidant) that are clinically relevant for the treatment of AD. Positive results from the AMBAR Program (phase 1, 2, an 2b/3 trials), i.e., slower decline or stabilization of disease symptoms in the most relevant clinical efficacy and safety endpoints, offer a glimmer of hope to both AD patients and caregivers.

Nutritional cognitive neuroscience of aging: Focus on carotenoids and cognitive frailty

The term „nutritional cognitive neuroscience” was recently established to define a research field focusing on the impact of nutrition on cognition and brain health across the life span. In this overview, we summarize the robust evidence on the role of carotenoids as micronutrients with different biological properties in persons with cognitive (pre)frailty. As neurodegenerative processes during aging occur in a continuum from brain aging to dementia, we propose the name „nutritional cognitive neuroscience of aging“ to define research on the role of nutrition and micronutrients in cognitive frailty. Further studies are warranted which integrate carotenoid interventions in multidomain, personalized lifestyle strategies.

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Cognitive integrity is an essential element of healthy and active ageing.

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Oxidative distress is strongly linked to neurodegeneration.

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Consumption and levels of carotenoids are linked to cognitive frailty.

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There is conflict of evidence for intervention trials with carotenoids in dementia.

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Future studies with carotenoids should be within personalized and multidomain strategies.

Vascular Risk Factors and Alzheimer's Disease: Blood-Brain Barrier Disruption, Metabolic Syndromes, and Molecular Links

Alzheimer's disease (AD) is a neurodegenerative disorder, marked by cortical and hippocampal deposition of amyloid-β (Aβ) plaques and neurofibrillary tangles and cognitive impairment. Studies indicate a prominent link between cerebrovascular abnormalities and the onset and progression of AD, where blood-brain barrier (BBB) dysfunction and metabolic disorders play key risk factors. Pericyte degeneration, endothelial cell damage, astrocyte depolarization, diminished tight junction integrity, and basement membrane disarray trigger BBB damage. Subsequently, the altered expression of low-density lipoprotein receptor-related protein 1 and receptor for advanced glycation end products at the microvascular endothelial cells dysregulate Aβ transport across the BBB. White matter lesions and microhemorrhages, dyslipidemia, altered brain insulin signaling, and insulin resistance contribute to tau and Aβ pathogenesis, and oxidative stress, mitochondrial damage, inflammation, and hypoperfusion serve as mechanistic links between pathophysiological features of AD and ischemia. Deregulated calcium homeostasis, voltage gated calcium channel functioning, and protein kinase C signaling are also common mechanisms for both AD pathogenesis and cerebrovascular abnormalities. Additionally, APOE polymorphic alleles that characterize impaired cerebrovascular integrity function as primary genetic determinants of AD. Overall, the current review enlightens key vascular risk factors for AD and underscores pathophysiologic relationship between AD and vascular dysfunction.

Association Between Serum Uric Acid Levels and Cognitive Function in Patients with Ischemic Stroke and Transient Ischemic Attack (TIA): A 3-Month Follow-Up Study

PURPOSE

Cognitive impairment is a common complication after stroke and transient ischemic attack (TIA). The relationship between serum uric acid (SUA) and post-stroke cognitive impairment (PSCI) is controversial. This study evaluated the association of different SUA levels in the normal range and PSCI at 3 months.

PATIENTS AND METHODS

A total of 1523 patients with ischemic stroke/TIA were recruited from the Impairment of Cognition and Sleep (ICONS) subgroup of the China National Stroke Registry-3 (CNSR-3). SUA concentration was assessed at baseline. Global cognitive status was evaluated using the Montreal Cognitive Assessment (MoCA). The main clinical outcome was the incidence of PSCI assessed at 3 months after stroke/TIA. The association between SUA status and the risk of PSCI was assessed with multiple regression models adjusted for potential covariates.

RESULTS

Among the 1523 patients (1391 (91.33%) stroke patients and 132 (8.67%) TIA patients), 747 (49.05%) patients had PSCI at 3 months. Compared to the reference group, there was an increased risk of PSCI in males with SUA levels in the first (OR=1.76) and fourth quartiles (OR=1.47). A U-shaped association between SUA levels and the incidence of PSCI with an inflection point of 297 mmol/L was also found in males. However, there was no association between SUA levels and PSCI in females.

CONCLUSION

The association between SUA and PSCI differed between males and females. In males, both low and high SUA levels were associated with relatively higher incidences of PSCI, supporting a U-shaped association between SUA levels and PSCI.

The relationship between serum uric acid and cognitive function in patients with chronic heart failure

BACKGROUND

Evidence has shown that serum uric acid (UA) is associated with cognitive function, but this finding remains debatable. Serum UA is commonly elevated in patients with chronic heart failure (CHF), especially in men. However, the relationship between serum UA and cognitive function in CHF populations and stratified by sex are unclear. We aimed to examine whether serum UA was independently associated with cognitive function in CHF populations after controlling for demographic, medical and psychological variables and whether there was a sex difference in the association between serum UA and cognitive function among male and female CHF patients.

METHODS

One hundred ninety-two hospitalized patients with CHF underwent an assessment of cognitive function using the Montreal Cognitive Assessment (MoCA) and the determination of serum UA. Hyperuricemia was defined as serum UA ≥7 mg/dl in men and ≥ 6 mg/dl in women. Multiple linear hierarchical regression analyses were conducted to examine the independent association between serum UA and cognitive function in CHF populations and stratified by sex.

RESULTS

The mean serum UA concentration of participants was 7.3 ± 2.6 mg/dL. The prevalence of hyperuricemia was 54.7% (105 of 192) in CHF patients, 52.9% (64 of 121) in men, and 57.7% (41 of 71) in women. In the total sample, higher serum UA was associated with poorer cognitive function independent of demographic, medical and psychological variables (β = - 0.130, ΔR² = 0.014, p = 0.015). In sex-stratified groups, elevated serum UA was independently associated with worse cognitive function in men (β = - 0.247, ΔR² = 0.049, p = 0.001) but not in women (β = - 0.005, ΔR² = 0.000, p = 0.955).

CONCLUSIONS

Higher serum UA is independently associated with poorer cognitive function in CHF populations after adjusting for confounding variables. Furthermore, elevated serum UA is independently related to worse performance on cognitive function in men but not in women. More longitudinal studies are needed to examine the association between serum UA and cognitive function in CHF populations and stratified by sex.

Early Detection and Prevention of Alzheimer's Disease: Role of Oxidative Markers and Natural Antioxidants

Oxidative stress (OS) contributes to Alzheimer’s disease (AD) pathology. OS can be a result of increased reactive oxygen/nitrogen species, reduced antioxidants, oxidatively damaged molecules, and/or a combination of these factors. Scientific literature is scarce for the markers of OS-specific for detecting AD at an early stage. The first aim of the current review is to provide an overview of the potential OS markers in the brain, cerebrospinal fluid (CSF), blood and/or urine that can be used for early diagnosis of human AD. The reason for exploring OS markers is that the proposed antioxidant therapies against AD appear to start too late to be effective. The second aim is to evaluate the evidence for natural antioxidants currently proposed to prevent or treat AD symptoms. To address these two aims, we critically evaluated the studies on humans in which various OS markers for detecting AD at an early stage were presented. Non-invasive OS markers that can detect mild cognitive impairment (MCI) and AD at an early stage in humans with greater specificity and sensitivity are primarily related to lipid peroxidation. However, a combination of OS markers, family history, and other biochemical tests are needed to detect the disease early on. We also report that the long-term use of vitamins (vitamin E as in almonds) and polyphenol-rich foods (curcumin/curcuminoids of turmeric, ginkgo biloba, epigallocatechin-3-gallate in green tea) seem justified for ameliorating AD symptoms. Future research on humans is warranted to justify the use of natural antioxidants.

Clinical Utility of Plasma Lipid Peroxidation Biomarkers in Alzheimer's Disease Differential Diagnosis

BACKGROUND

Differential diagnosis of Alzheimer's disease (AD) is a complex task due to the clinical similarity among neurodegenerative diseases. Previous studies showed the role of lipid peroxidation in early AD development. However, the clinical validation of potential specific biomarkers in minimally invasive samples constitutes a great challenge in early AD diagnosis.

METHODS

Plasma samples from participants classified into AD (n = 138), non-AD (including MCI and other dementias not due to AD) (n = 70) and healthy (n = 50) were analysed. Lipid peroxidation compounds (isoprostanes, isofurans, neuroprostanes, neurofurans) were determined by ultra-performance liquid chromatography coupled with tandem mass spectrometry. Statistical analysis for biomarkers' clinical validation was based on Elastic Net.

RESULTS

A two-step diagnosis model was developed from plasma lipid peroxidation products to diagnose early AD specifically, and a bootstrap validated AUC of 0.74 was obtained.

CONCLUSION

A promising AD differential diagnosis model was developed. It was clinically validated as a screening test. However, further external validation is required before clinical application.

Inflammation, Lipid (Per)oxidation, and Redox Regulation

Significance: Inflammation increases during the aging process. It is linked to mitochondrial dysfunction and increased reactive oxygen species (ROS) production. Mitochondrial macromolecules are critical targets of oxidative damage; they contribute to respiratory uncoupling with increased ROS production, redox stress, and a cycle of senescence, cytokine production, and impaired oxidative phosphorylation. Targeting the formation or accumulation of oxidized biomolecules, particularly oxidized lipids, in immune cells and mitochondria could be beneficial for age-related inflammation and comorbidities. Recent Advances: Inflammation is central to age-related decline in health and exhibits a complex relationship with mitochondrial redox state and metabolic function. Improvements in mass spectrometric methods have led to the identification of families of oxidized phospholipids (OxPLs), cholesterols, and fatty acids that increase during inflammation and which modulate nuclear factor erythroid 2-related factor 2 (Nrf2), peroxisome proliferator-activated receptor gamma (PPARγ), activator protein 1 (AP1), and NF-κB redox-sensitive transcription factor activity. Critical Issues: The kinetic and spatial resolution of the modified lipidome has profound and sometimes opposing effects on inflammation, promoting initiation at high concentration and resolution at low concentration of OxPLs. Future Directions: There is an emerging opportunity to prevent or delay age-related inflammation and vascular comorbidity through a resolving (oxy)lipidome that is dependent on improving mitochondrial quality control and restoring redox homeostasis.

Usefulness of routine blood test-driven clusters for predicting acute exacerbation in patients with asthma

AIM

Acute exacerbation (AE) is a significant burden in the management of asthma. In this study we aimed to investigate whether routine blood test results predicted AE in asthmatics.

METHODS

We applied k-means cluster to routine blood test results which included eosinophil counts, total calcium, phosphorus, uric acid (UA), total cholesterol, total protein, albumin, total bilirubin, alkaline phosphatase, aspartate transaminase (AST), alanine transferase (ALT), gamma-glutamyltransferase, blood urea nitrogen, creatinine, and high-sensitive C-reactive protein (hsCRP) obtained from 590 asthmatics. AEs collected over the prospective follow-up of one-year were used to evaluate clinical trajectories of these clusters.

RESULTS

Three blood clusters were identified. The essential features of each cluster can be characterized as follows: (i) high eosinophil count, UA, total cholesterol, AST, ALT, and hsCRP levels (Cluster 1); (ii) intermediate features (Cluster 2); (iii) low UA, total cholesterol and total bilirubin levels (Cluster 3). Kaplan-Meier analysis confirmed that clusters were strongly predictive of time to the first AE (log-rank P = 0.001). Hazard ratio for each group was as follows: Cluster 2 = 1, Cluster 1 = 2.67 (1 vs. 2, P = 4.68 × 10^-4), and Cluster 3 = 1.69 (2 vs. 3, P = 0.021).

CONCLUSIONS

We defined three blood clusters in asthmatics. These blood clusters are easily identifiable from routine test results and may help clinicians to predict the future risk of AE in asthmatics.

Berberine for prevention of dementia associated with diabetes and its comorbidities: A systematic review

BACKGROUND

A growing number of epidemiological studies indicate that metabolic syndrome (MetS) and its associated features play a key role in the development of certain degenerative brain disorders, including Alzheimer's disease and vascular dementia. Produced by several different medicinal plants, berberine is a bioactive alkaloid with a wide range of pharmacological effects, including antidiabetic effects. However, it is not clear whether berberine could prevent the development of dementia in association with diabetes.

OBJECTIVE

To give an overview of the therapeutic potential of berberine as a treatment for dementia associated with diabetes.

SEARCH STRATEGY

Database searches A and B were conducted using PubMed and ScienceDirect. In search A, studies on berberine's antidementia activities were identified using "berberine" and "dementia" as search terms. In search B, recent studies on berberine's effects on diabetes were surveyed using "berberine" and "diabetes" as search terms.

INCLUSION CRITERIA

Clinical and preclinical studies that investigated berberine's effects associated with MetS and cognitive dysfunction were included.

DATA EXTRACTION AND ANALYSIS

Data from studies were extracted by one author, and checked by a second; quality assessments were performed independently by two authors.

RESULTS

In search A, 61 articles were identified, and 22 original research articles were selected. In search B, 458 articles were identified, of which 101 were deemed relevant and selected. Three duplicates were removed, and a total of 120 articles were reviewed for this study. The results demonstrate that berberine exerts beneficial effects directly in the brain: enhancing cholinergic neurotransmission, improving cerebral blood flow, protecting neurons from inflammation, limiting hyperphosphorylation of tau and facilitating β-amyloid peptide clearance. In addition, evidence is growing that berberine is effective against diabetes and associated disorders, such as atherosclerosis, cardiomyopathy, hypertension, hepatic steatosis, diabetic nephropathy, gut dysbiosis, retinopathy and neuropathy, suggesting indirect benefits for the prevention of dementia.

CONCLUSION

Berberine could impede the development of dementia via multiple mechanisms: preventing brain damages and enhancing cognition directly in the brain, and indirectly through alleviating risk factors such as metabolic dysfunction, and cardiovascular, kidney and liver diseases. This study provided evidence to support the value of berberine in the prevention of dementia associated with MetS.

miRNA 933 Expression by Endothelial Cells is Increased by 27-Hydroxycholesterol and is More Prevalent in Plasma from Dementia Patients

Alzheimer’s disease (AD) etiology is complex; gene and environmental risk factors may interact to predispose to disease. From single nucleotide polymorphism analyses and genome-wide association studies, a number of candidate risk genes for the onset of AD have been identified and cluster around lipid metabolism and inflammation. We hypothesized that endothelial cells which line the blood-brain barrier are likely to be critical mediators of systemic metabolism within the brain. Therefore, we have studied the effect of 27 hydroxycholesterol (27-OHC) on microvascular endothelial cell (HMVEC) redox state, inflammatory cytokine secretion, and microRNA (miR) expression. Using a transwell method, we have studied directional secretion profiles for the proinflammatory cytokines TNFα and IL-6 and confirmed that 27-OHC induces discrete and directional inflammatory molecular signatures from HMVEC. The lipids caused depletion of cellular glutathione and cytokine secretion is HMVEC-redox state-dependent. Discovery miR expression change in HMVEC with and without 27-OHC treatment was undertaken. We selected three genes for further analysis by qPCR; miR-144 and 146 expression, which are anti-inflammatory and redox regulating modulators, were not affected significantly by 27-OHC. However, increased expression of a putative neurotrophic regulatory factor miR933 in HMVEC with 27-OHC was confirmed by qPCR. In plasma from patients with dementia, all three miR were found at significantly elevated levels compared to healthy older adults. These data highlight that 27-OHC has an important regulatory effect on endothelial microvascular cells to increase expression of a miR (–933) and secretion of inflammatory cytokines that are elevated in plasma from dementia patients.

Emerging molecular mechanisms of vascular dementia

PURPOSE OF REVIEW

Microvascular ischemic disease of the brain is a common cause of cognitive impairment and dementia, particularly in the context of preexisting cardiovascular risk factors and aging. This review summarizes our current understanding of the emerging molecular themes that underlie progressive and irreparable vascular disease leading to neuronal tissue injury and dementia.

RECENT FINDINGS

Cardiometabolic risk factors including diabetes and hypertension are known to contribute to vascular disease. Currently, the impact of these risk factors on the integrity and function of the brain vasculature has been target of intense investigation. Molecularly, the consequences associated with these risk factors indicate that reactive oxygen species are strong contributors to cerebrovascular dysfunction and injury. In addition, genetic linkage analyses have identified penetrant monogenic causes of vascular dementia. Finally, recent reports begun to uncover a large number of polymorphisms associated with a higher risk for cerebrovascular disease.

SUMMARY

A comprehensive picture of key risk factors and genetic predispositions that contribute to brain microvascular disease and result in vascular dementia is starting to emerge. Understanding their relationships and cross-interactions will significantly aid in the development of preventive and intervention strategies for this devastating condition.

Beneficial effects and potential risks of tomato consumption for human health: An overview

Tomato and its derived products have a very interesting nutritional value in addition to prominent antioxidant, anti-inflammatory, and anticancer activities. Tomatoes are generally quite safe to eat. However, overall consumption varies from individual to individual. Indeed, either beneficial or harmful effects of plants or their derived products are closely related to quality, including the presence of biologically active compounds. On the other hand, the synthesis and accumulation of these bioactive molecules depends on many other factors, such as environmental conditions. In this sense, this review briefly highlights the relationship between the chemistry of tomato and its derived products and their beneficial or harmful effects on human health, such as gastroesophageal reflux disease or heartburn, allergies, kidney and cardiovascular disorders, prostate cancer, irritable bowel syndrome, lycopenodermia, body aches, arthritis, and urinary problems.

Cognition, Olfaction and Uric Acid in Early de novo Parkinson's Disease

Objective

Cognitive impairment is one of the nonmotor symptoms in Parkinson’s disease (PD), and olfactory dysfunction is used as a marker to detect premotor stages of PD. Serum uric acid (sUA) levels have been found to be a risk factor for PD. Our objective in this study was to examine whether sUA levels are associated with cognitive changes and olfactory dysfunction in early de novo PD patients.

Methods

The study participants included 196 de novo PD patients. We assessed cognitive function by the Korean versions of the Mini-Mental State Examination and the Montreal Cognitive Assessment and assessed olfactory function by the Korean version of the Sniffin’ Sticks test.

Results

The mean sUA level was 4.7 mg/dL and was significantly lower in women than in men. Cognitive scores were lower in women, suggesting that sUA levels were related to cognitive function. The olfactory functions were not related to sUA level but were clearly associated with cognitive scores. Olfactory threshold, odor discrimination, and odor identification were all significantly related to cognitive scores.

Conclusion

We conclude that lower sUA levels were associated with cognitive impairment, not olfactory dysfunction, in de novo PD patients. This finding suggests that UA is neuroprotective as an antioxidant in the cognitive function of PD patients.

A Novel scFv Anti-Aβ Antibody Reduces Pathological Impairments in APP/PS1 Transgenic Mice via Modulation of Inflammatory Cytokines and Aβ-related Enzymes

Immunotherapy for Alzheimer's disease (AD) remains promising in the improvement of cognition and memory via the clearing of amyloid-β protein (Aβ) in the AD brain, despite some side effects. Our previous studies demonstrated that the 31-35 sequence of the Aβ molecule was the shortest active center and that polyclonal anti-Aβ31-35 antibody reduced neuronal apoptosis and cognitive impairments induced with acute Aβ application. The present study designed a novel single-chain variable fragment (scFv) monoclonal anti-Aβ31-35 antibody (scFv17) that specifically recognized extracellular Aβ and observed protective effects of scFv17 on pathological impairments in APP/PS1 transgenic mice. We also investigated its cellular and molecular mechanisms and found that scFv17 and 6E10 (a positive control) exhibited similar Aβ-clearing ability and that scFv17 produced a stronger effect in clearing Aβ oligomers than 6E10. scFv17, but not 6E10, enhanced anti-inflammatory responses with significant increases in IL-10 and TGF-β. 6E10 decreased BACE1 levels, and scFv17 significantly increased the level of secreted amyloid precursor protein-α (sAPPα), which is an important physiological neurotrophin from APP generated by α-secretase. 6E10 and scFv17, especially the latter, dramatically down-regulated the expression of neprilysin, which is an enzyme expressed in proportion to Aβ concentration. Therefore, the present study demonstrated that the novel monoclonal anti-Aβ31-35 antibody scFv17 effectively reduced pathological impairments in APP/PS1 transgenic mice via modulation of inflammatory cytokines and Aβ-related enzymes, which supports scFv17 as a new alternative in the current immunotherapy of AD.

Simvastatin reduces circulating oxysterol levels in men with hypercholesterolaemia

Oxysterols (OHC) are biologically active cholesterol metabolites circulating in plasma that may be formed enzymatically (e.g. 24S-OHC, 25-OHC and 27-OHC) or by autoxidative mechanisms (e.g. 7-ketocholesterol, 7β-OHC and 25-OHC). Oxysterols are more soluble than cholesterol and are reported to exert inflammatory, cytoprotective and apoptotic effects according to concentration and species. Esterified oxysterols have been analysed in people with dementia and cardiovascular diseases although there is no consistent relationship between oxysterol esters and disease. However, oxysterol esters are held in lipoprotein core and may not relate to the concentration and activity of plasma free oxysterols. Methodological limitations have challenged the analysis of free oxysterols to date. We have developed a fast, sensitive and specific quantitative LC-MS/MS, multiple reaction monitoring (MRM) method to target five oxysterols in human plasma with analyte recoveries between 72% and 82% and sensitivities between 5 and 135 pg/ml. A novel method was used to investigate the hypothesis that simvastatin may reduce the concentrations of specific plasma free oxysterols in hypercholesterolaemia. Twenty healthy male volunteers were recruited (aged 41-63 years); ten were asymptomatic with high plasma cholesterol > 6.5 mM and ten were healthy with normal plasma cholesterol (< 6.5 mM). Simvastatin (40 mg/day) was prescribed to those with hypercholesterolaemia. Plasma samples were taken from both groups at baseline and after three months. Simvastatin reduced plasma cholesterol by ~35% (p < 0.05) at the end of three months. Oxysterols generated by autoxidation (but not enzymatically) were elevated up to 45 fold in hypercholesterolaemic midlife men. Plasma oxysterols were restored to those of healthy controls after simvastatin intervention suggesting that autoxidation is either prevented by simvastatin directly or that autoxidation is less prevalent when plasma cholesterol concentrations are within the normal range.

Do low-serum vitamin E levels increase the risk of Alzheimer disease in older people? Evidence from a meta-analysis of case-control studies

OBJECTIVE

Whether low-serum vitamin E increases the risk of Alzheimer disease (AD) in older people remains inconclusive. This meta-analysis aims to synthesize evidence-based case-control studies to evaluate the association between serum vitamin E and the risk of AD.

METHODS

Potentially relevant studies were selected through PubMed, Embase, Wanfang, Chongqing VIP, and China National Knowledge Infrastructure databases by using the core terms Vitamin E/alpha-tocopherol and Alzheime's disease/senile dementia/AD in the titles, abstracts, and keywords of the articles. The association between serum vitamin E levels and AD was estimated by using the weighted mean difference (WMD) and 95% confidence interval by adopting a random effects model. Heterogeneity was assessed by using Cochran Q test and I² statistic. Forest plot was used to present the results graphically from meta-analysis. Publication bias was evaluated by using funnel plots and Egger test.

RESULTS

We identified 17 studies that met the eligibility criteria. The studies included 2057 subjects with 904 AD patients and 1153 controls. The results indicated that AD patients had a lower concentration of serum vitamin E compared with healthy controls among older people (WMD = -6.811 μmol/L, 95% confidence interval -8.998 to -4.625; Z = -6.105, P < .001). Publication bias was not detected and sensitivity analysis performed by omitting each study, and calculating the pooled WMD again for the remaining studies indicated the results stable.

CONCLUSIONS

Alzheimer disease is associated with a low concentration of serum vitamin E in older people. However, necessary prospective cohort studies should be conducted to determine the risk of serum vitamin E for AD in the future.

A Long Journey into Aging, Brain Aging, and Alzheimer's Disease Following the Oxidative Stress Tracks

The Editors of the Journal of Alzheimer's Disease invited Professor Patrizia Mecocci to contribute a review article focused on the importance and implications of her research on aging, brain aging, and senile dementias over the last years. This invitation was based on an assessment that she was one of the journal's top authors and a strong supporter of the concept that oxidative stress is a major contributor to several alterations observed in age-related conditions (sarcopenia, osteoporosis) and, more significantly, in brain aging suggesting a pivotal role in the pathogenesis and progression of one of the most dramatic age-related diseases, Alzheimer's disease (AD). Her first pioneering research was on the discovery of high level of 8-hydroxy-2'-deoxyguanosine (OH8dG), a marker of oxidation in nucleic acids, in mitochondrial DNA isolated from cerebral cortex. This molecule increases progressively with aging and more in AD brain, supporting the hypothesis that oxidative stress, a condition of unbalance between the production of reactive oxygen species and antioxidants, gives a strong contribution to the high incidence of AD in old age subjects. OH8dG also increases in peripheral lymphocyte from AD subjects, suggesting that AD is not only a cerebral but also a systemic disease. The role of antioxidants, particularly vitamin E and zinc, were also studied in longevity and in cognitive decline and dementia. This review shows the main findings from Mecocci's laboratory related to oxidative stress in aging, brain aging, and AD and discusses the importance and implications of some of the major achievements in this field of research.

A Mini-Review of the NADPH oxidases in Vascular Dementia: Correlation with NOXs and Risk Factors for VaD

Oxidative stress (OS) is one of the factors that cause dementia conditions such as Alzheimer’s disease and vascular dementia (VaD). In the pathogenesis of VaD, OS is associated with risk factors that include increased age, hypertension, and stroke. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOXs) are a molecular source of reactive oxygen species (ROS). According to recent studies, inhibition of NOX activity can reduce cognitive impairment in animal models of VaD. In this article, we review the evidence linking cognitive impairment with NOX-dependent OS, including the vascular NOX and non-vascular NOX systems, in VaD.

Vitamin C Status and Cognitive Function: A Systematic Review

Vitamin C plays a role in neuronal differentiation, maturation, myelin formation and modulation of the cholinergic, catecholinergic, and glutaminergic systems. This review evaluates the link between vitamin C status and cognitive performance, in both cognitively intact and impaired individuals. We searched the PUBMED, SCOPUS, SciSearch and the Cochrane Library from 1980 to January 2017, finding 50 studies, with randomised controlled trials (RCTs, n = 5), prospective (n = 24), cross-sectional (n = 17) and case-control (n = 4) studies. Of these, 36 studies were conducted in healthy participants and 14 on cognitively impaired individuals (including Alzheimer’s and dementia). Vitamin C status was measured using food frequency questionnaires or plasma vitamin C. Cognition was assessed using a variety of tests, mostly the Mini-Mental-State-Examination (MMSE). In summary, studies demonstrated higher mean vitamin C concentrations in the cognitively intact groups of participants compared to cognitively impaired groups. No correlation between vitamin C concentrations and MMSE cognitive function was apparent in the cognitively impaired individuals. The MMSE was not suitable to detect a variance in cognition in the healthy group. Analysis of the studies that used a variety of cognitive assessments in the cognitively intact was beyond the scope of this review; however, qualitative assessment revealed a potential association between plasma vitamin C concentrations and cognition. Due to a number of limitations in these studies, further research is needed, utilizing plasma vitamin C concentrations and sensitive cognitive assessments that are suitable for cognitively intact adults.

Peripheral Vitamin C Levels in Alzheimer's Disease: A Cross-Sectional Study

We previously reported lower lymphocyte vitamin C levels in individuals with type 2 diabetes mellitus and in individuals with severe Parkinson's disease. Oxidative stress has been proposed to play a key role in the progression of Alzheimer's disease. Thus, the objective of this study was to investigate the association between peripheral levels of vitamin C and the progression of cognitive dysfunction in Alzheimer's disease. Fifty individuals with Alzheimer's disease being treated at Shizuoka General Hospital were consecutively enrolled in this study from December 2009 to March 2015 (76.0±9.7 y of age [mean±SD]; 32 men and 18 women; Mini-Mental State Examination Japanese version (MMSE-J) score range, 8-27). Plasma and lymphocyte vitamin C levels in fasting blood samples were measured. The association between the MMSE-J scores and vitamin C levels was estimated using Spearman's rank correlation coefficient (ρ) and the criteria defined by Swinscow. Spearman's ρ for the relationship between peripheral vitamin C levels and the MMSE-J score was ρ=0.17 for plasma vitamin C and ρ=0.26 for lymphocyte vitamin C. Thus, the associations were relatively weak based on the criteria. In contrast with type 2 diabetes mellitus and Parkinson's disease, lymphocyte vitamin C levels in the peripheral blood may not directly reflect the progression of cognitive dysfunction in Alzheimer's disease. Additional longitudinal studies are needed to evaluate the clinical importance of changes of peripheral vitamin C status in Alzheimer's disease.

A double blind placebo controlled randomized trial of the effect of acute uric acid changes on inflammatory markers in humans: A pilot study

Uric acid has been linked with increased risk of chronic disease such as cardiovascular disease and this association has been attributed to a pro-inflammatory effect. Indeed, observational studies have shown that high uric acid is associated with high level of pro-inflammatory cytokines in the blood. However, whether high uric acid directly affects inflammation or rather represents a parallel defensive antioxidant mechanism in response to pathology that causes inflammation is unknown. To determine whether acute increase or decrease uric acid levels affects inflammation in healthy individuals, a randomized, placebo-controlled, double blind clinical study of uric acid or rasburicase with 20 healthy volunteers in each treatment-placebo group was conducted at the National Institute on Aging (NIA) Clinical Research Unit (CRU) at Harbor Hospital in Baltimore, MD. Change in inflammatory response was assessed by administering an oral lipid tolerance before and after the treatment of uric acid, rasburicase and placebo. Following uric acid administration, there was an accentuated increase in IL-6 during the oral lipid tolerance test (P<0.001). No significant differences were observed after lowering of uric acid with rasburicase. No side effects were reported throughout the trial. In health individuals, acute increase in uric acid results in an increased IL-6 response when challenged with lipid load. Such effect of amplification of inflammatory response may explain the higher risk of chronic diseases observed in subclinical hyperuricemia in observational studies.

Trial Registration: ClinicalTrials.gov NCT01323335

Phospholipid oxidation and carotenoid supplementation in Alzheimer's disease patients

Alzheimer's disease (AD) is a progressive, neurodegenerative disease, characterised by decline of memory, cognitive function and changes in behaviour. Generic markers of lipid peroxidation are increased in AD and reactive oxygen species have been suggested to be involved in the aetiology of cognitive decline. Carotenoids are depleted in AD serum, therefore we have compared serum lipid oxidation between AD and age-matched control subjects before and after carotenoid supplementation. The novel oxidised phospholipid biomarker 1-palmitoyl-2-(5'-oxo-valeroyl)-sn-glycero-3-phosphocholine (POVPC) was analysed using electrospray ionisation tandem mass spectrometry (MS) with multiple reaction monitoring (MRM), 8-isoprostane (IsoP) was measured by ELISA and ferric reducing antioxidant potential (FRAP) was measured by a colorimetric assay. AD patients (n=21) and healthy age-matched control subjects (n=16) were supplemented with either Macushield™ (10mg meso-zeaxanthin, 10mg lutein, 2mg zeaxanthin) or placebo (sunflower oil) for six months. The MRM-MS method determined serum POVPC sensitively (from 10µl serum) and reproducibly (CV=7.9%). At baseline, AD subjects had higher serum POVPC compared to age-matched controls, (p=0.017) and cognitive function was correlated inversely with POVPC (r=-0.37; p=0.04). After six months of carotenoid intervention, serum POVPC was not different in AD patients compared to healthy controls. However, POVPC was significantly higher in control subjects after six months of carotenoid intervention compared to their baseline (p=0.03). Serum IsoP concentration was unrelated to disease or supplementation. Serum FRAP was significantly lower in AD than healthy controls but was unchanged by carotenoid intervention (p=0.003). In conclusion, serum POVPC is higher in AD patients compared to control subjects, is not reduced by carotenoid supplementation and correlates with cognitive function.

Hypercholesterolaemia and vascular dementia

Vascular dementia (VaD) is the second commonest cause of dementia. Stroke is the leading cause of disability in adults in developed countries, the second major cause of dementia and the third commonest cause of death. Traditional vascular risk factors-diabetes, hypercholesterolaemia, hypertension and smoking-are implicated as risk factors for VaD. The associations between cholesterol and small vessel disease (SVD), stroke, cognitive impairment and subsequent dementia are complex and as yet not fully understood. Similarly, the effects of lipids and lipid-lowering therapy on preventing or treating dementia remain unclear; the few trials that have assessed lipid-lowering therapy for preventing (two trials) or treating (four trials) dementia found no evidence to support the use of lipid-lowering therapy for these indications. It is appropriate to treat those patients with vascular risk factors that meet criteria for lipid-lowering therapy for the primary and secondary prevention of cardiovascular and cerebrovascular events, and in line with current guidelines. Managing the individual patient in a holistic manner according to his or her own vascular risk profile is recommended. Although the paucity of randomized controlled evidence makes for challenging clinical decision making, it provides multiple opportunities for on-going and future research, as discussed here.

Does Vitamin C Influence Neurodegenerative Diseases and Psychiatric Disorders?

Vitamin C (Vit C) is considered to be a vital antioxidant molecule in the brain. Intracellular Vit C helps maintain integrity and function of several processes in the central nervous system (CNS), including neuronal maturation and differentiation, myelin formation, synthesis of catecholamine, modulation of neurotransmission and antioxidant protection. The importance of Vit C for CNS function has been proven by the fact that targeted deletion of the sodium-vitamin C co-transporter in mice results in widespread cerebral hemorrhage and death on post-natal day one. Since neurological diseases are characterized by increased free radical generation and the highest concentrations of Vit C in the body are found in the brain and neuroendocrine tissues, it is suggested that Vit C may change the course of neurological diseases and display potential therapeutic roles. The aim of this review is to update the current state of knowledge of the role of vitamin C on neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, Huntington's disease, multiple sclerosis and amyotrophic sclerosis, as well as psychiatric disorders including depression, anxiety and schizophrenia. The particular attention is attributed to understanding of the mechanisms underlying possible therapeutic properties of ascorbic acid in the presented disorders.

Targeting urate to reduce oxidative stress in Parkinson disease

Oxidative stress has been implicated as a core contributor to the initiation and progression of multiple neurological diseases. Genetic and environmental factors can produce oxidative stress through mitochondrial dysfunction leading to the degeneration of dopaminergic and other neurons underlying Parkinson disease (PD). Although clinical trials of antioxidants have thus far failed to demonstrate slowed progression of PD, oxidative stress remains a compelling target. Rather than prompting abandonment of antioxidant strategies, these failures have raised the bar for justifying drug and dosing selections and for improving study designs to test for disease modification by antioxidants. Urate, the main antioxidant found in plasma as well as the end product of purine metabolism in humans, has emerged as a promising potential neuroprotectant with advantages that distinguish it from previously tested antioxidant agents. Uniquely, higher urate levels in plasma or cerebrospinal fluid (CSF) have been linked to both a lower risk of developing PD and to a slower rate of its subsequent progression in numerous large prospective epidemiological and clinical cohorts. Laboratory evidence that urate confers neuroprotection in cellular and animal models of PD, possibly via the Nrf2 antioxidant response pathway, further strengthened its candidacy for rapid clinical translation. An early phase trial of the urate precursor inosine demonstrated its capacity to safely produce well tolerated, long-term elevation of plasma and CSF urate in early PD, supporting a phase 3 trial now underway to determine whether oral inosine dosed to elevate urate to concentrations predictive of favorable prognosis in PD slows clinical decline in people with recently diagnosed, dopamine transporter-deficient PD.

The protective role of plant biophenols in mechanisms of Alzheimer's disease

Self-assembly of amyloid beta peptide (Aβ) into the neurotoxic oligomers followed by fibrillar aggregates is a defining characteristic of Alzheimer's disease (AD). Several lines of proposed hypotheses have suggested the mechanism of AD pathology, though the exact pathophysiological mechanism is not yet elucidated. The poor understanding of AD and multitude of adverse responses reported from the current synthetic drugs are the leading cause of failure in the drug development to treat or halt the progression of AD and mandate the search for safer and more efficient alternatives. A number of natural compounds have shown the ability to prevent the formation of the toxic oligomers and disrupt the aggregates, thus attracted much attention. Referable to the abundancy and multitude of pharmacological activities of the plant active constituents, biophenols that distinguish them from the other phytochemicals as a natural weapon against the neurodegenerative disorders. This review provides a critical assessment of the current literature on in vitro and in vivo mechanistic activities of biophenols associated with the prevention and treatment of AD. We have contended the need for more comprehensive approaches to evaluate the anti-AD activity of biophenols at various pathologic levels and to assess the current evidences. Consequently, we highlighted the various problems and challenges confronting the AD research, and offer recommendations for future research.

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

AIMS

We determined whether the possible roles of oxidative stress differ in the pathophysiology and cognitive decline of Alzheimer's disease (AD), vascular dementia (VaD) and mixed Alzheimer's/vascular dementia (MD).

METHODS

We measured the levels of diacron reactive oxygen metabolite (dROM), reflecting the amount of organic hydroperoxides, and biological anti-oxidant potential (BAP), measuring the ferric reducing ability of blood plasma, in 72 patients with AD, 27 with VaD, 24 with MD and 53 non-demented outpatients (control group). In addition, endogenous plasma anti-oxidants, such as albumin, total bilirubin and uric acid, were compared among the groups. All participants with VaD and MD showed extensive white matter hyperintensity, in addition to multiple lacunes.

RESULTS

The dROM levels were significantly higher in the AD and MD groups than in the control group. The BAP levels were significantly lower in the MD group than in the control, AD and VaD groups. The AD group showed significantly lower levels of bilirubin and uric acid than the control group. The MD group showed a significantly lower level of albumin than the control and AD groups, and a significantly lower level of bilirubin than the control group. The Mini-Mental State examination scores correlated significantly with dROM levels and BAP/dROM ratios in the AD group.

CONCLUSIONS

An imbalance in pro-oxidant and anti-oxidant defenses is apparently involved in the pathophysiology of the AD and MD groups. The extent of oxidative stress damage might differ in subtypes of dementia by being greater in the MD group than in other types of dementia. Synergic effects of the degenerative element of AD and white matter lesions might be associated with oxidative stress damage in the MD group.

The Oxygen Paradox, oxidative stress, and ageing

Professor Helmut Sies is being lauded in this special issue of Archives of Biochemistry & Biophysics, on the occasion of his retirement as Editor-in-Chief. There is no doubt that Helmut has exerted an enormously positive influence on this journal, the fields of Biochemistry & Biophysics in general, and the areas of free radical and redox biology & medicine in particular. Helmut Sies' many discoveries about peroxide metabolism, glutathione, glutathione peroxidases, singlet oxygen, carotenoids in general and lycopene in particular, and flavonoids, fill the pages of his more than 600 publications. In addition, he will forever be remembered for coining the term 'oxidative stress' that is so widely used (and sometimes abused) by most of his colleagues.

Redox Proteomic Profiling of Specifically Carbonylated Proteins in the Serum of Triple Transgenic Alzheimer's Disease Mice

Oxidative stress is a key event in the onset and progression of neurodegenerative diseases, including Alzheimer’s disease (AD). To investigate the role of oxidative stress in AD and to search for potential biomarkers in peripheral blood, serums were collected in this study from the 3-, 6-, and 12-month-old triple transgenic AD mice (3×Tg-AD mice) and the age- and sex-matched non-transgenic (non-Tg) littermates. The serum oxidized proteins were quantified by slot-blot analysis and enzyme-linked immunosorbent assay (ELISA) to investigate the total levels of serum protein carbonyl groups. Western blotting, in conjunction with two-dimensional gel electrophoresis (2D-Oxyblot), was employed to identify and quantify the specifically-carbonylated proteins in the serum of 3×Tg-AD mice. The results showed that the levels of serum protein carbonyls were increased in the three month old 3×Tg-AD mice compared with the non-Tg control mice, whereas no significant differences were observed in the six and 12 months old AD mice, suggesting that oxidative stress is an early event in AD progression. With the application of 2D-Oxyblot analysis, (immunoglobin) Ig gamma-2B chain C region (IGH-3), Ig lambda-2 chain C region (IGLC2), Ig kappa chain C region (IGKC), and Ig kappa chain V-V region HP R16.7 were identified as significantly oxidized proteins compared with the control. Among them IGH-3 and IGKC were validated via immunoprecipitation and Western blot analysis. Identification of oxidized proteins in the serums of 3×Tg-AD mice can not only reveal potential roles of those proteins in the pathogenesis of AD but also provide potential biomarkers of AD at the early stage.

Serum uric acid level and association with cognitive impairment and dementia: systematic review and meta-analysis

Serum uric acid (sUA) level may be associated with cognitive impairment/dementia. It is possible this relationship varies with dementia subtype, particularly between vascular dementias (VaD) and Alzheimer's (AD) or Parkinson's disease (PDD)-related dementia. We aimed to present a synthesis of all published data on sUA and relationship with dementia/cognition through systematic review and meta-analysis. We included studies that assessed the association between sUA and any measure of cognitive function or a clinical diagnosis of dementia. We pre-defined subgroup analyses for patients with AD, VaD, PDD, mild cognitive impairment (MCI), and mixed or undifferentiated. We assessed risk of bias/generalizability, and where data allowed, we performed meta-analysis to describe pooled measures of association across studies. From 4811 titles, 46 papers (n = 16,688 participants) met our selection criteria. Compared to controls, sUA was lower in dementia (SDM -0.33 (95%CI)). There were differences in association by dementia type with apparent association for AD (SDM -0.33 (95%CI)) and PDD (SDM -0.67 (95%CI)) but not in cases of mixed dementia (SDM 0.19 (95%CI)) or VaD (SDM -0.05 (95%CI)). There was no correlation between scores on Mini-Mental State Examination and sUA level (summary r 0.08, p = 0.27), except in patients with PDD (r 0.16, p = 0.003). Our conclusions are limited by clinical heterogeneity and risk of bias in studies. Accepting this caveat, the relationship between sUA and dementia/cognitive impairment is not consistent across all dementia groups and in particular may differ in patients with VaD compared to other dementia subtypes.

LDL-lipids from patients with hypercholesterolaemia and Alzheimer's disease are inflammatory to microvascular endothelial cells: mitigation by statin intervention

Elevated low-density lipoprotein (LDL) concentration in mid-life increases the risk of developing Alzheimer's disease (AD) in later life. Increased oxidized LDL (oxLDL) modification and nitration is observed during dementia and hypercholesterolaemia. We investigated the hypothesis that statin intervention in mid-life mitigates the inflammatory effects of oxLDL on the microvasculature. Human microvascular endothelial cells (HMVECs) were maintained in transwells to mimic the microvasculature and exposed to patient and control LDL. Blood was obtained from statin-naive, normo- and hyper-lipidaemic subjects, AD with vascular dementia (AD-plus) and AD subjects (n=10/group) at baseline. Only hyperlipidaemic subjects with normal cognitive function received 40 mg of simvastatin intervention/day for 3 months. Blood was re-analysed from normo- and hyper-lipidaemic subjects after 3 months. LDL isolated from statin-naive hyperlipidaemic, AD and AD-plus subjects was more oxidized (agarose gel electrophoretic mobility, protein carbonyl content and 8-isoprostane F2α) compared with control subjects. Statin intervention decreased protein carbonyls (2.5±0.4 compared with 3.95±0.2 nmol/mg; P<0.001) and 8-isoprostane F2α (30.4±4.0 pg/ml compared with 43.5±8.42 pg/ml; P<0.05). HMVEC treatment with LDL-lipids (LDL-L) from hyperlipidaemic, AD and AD-plus subjects impaired endothelial tight junction expression and decreased total glutathione levels (AD; 18.61±1.3, AD-plus; 16.5±0.7 nmol/mg of protein) compared with untreated cells (23.8±1.2 compared with nmol/mg of protein). Basolateral interleukin (IL)-6 secretion was increased by LDL-L from hyperlipidaemic (78.4±1.9 pg/ml), AD (63.2±5.9 pg/ml) and AD-plus (80.8±0.9 pg/ml) groups compared with healthy subject lipids (18.6±3.6 pg/ml). LDL-L isolated after statin intervention did not affect endothelial function. In summary, LDL-L from hypercholesterolaemic, AD and AD-plus patients are inflammatory to HMVECs. In vivo intervention with statins reduces the damaging effects of LDL-L on HMVECs.

Inverse Association Between Serum Uric Acid Levels and Alzheimer's Disease Risk

The association between Alzheimer's disease and uric acid levels had gained great interest in recent years, but there was still lack of definite evidence. A systematic review and meta-analysis of relevant studies was performed to comprehensively estimate the association. Relevant studies published before October 26, 2014, were searched in PubMed, Embase, and China Biology Medicine (CBM) databases. Study-specific data were combined using random-effects or fixed-effects models of meta-analysis according to between-study heterogeneity. Twenty-four studies (21 case-control and 3 cohort studies) were finally included into the meta-analysis. Those 21 case-control studies included a total of 1128 cases of Alzheimer's disease and 2498 controls without Alzheimer's disease. Those 3 cohort studies included a total of 7327 participants. Meta-analysis showed that patients with Alzheimer's disease had lower levels of uric acid than healthy controls (weighted mean difference (WMD) = -0.77 mg/dl, 95% CI -2.28 to -0.36, P = 0.0002). High serum uric acid levels were significantly associated with decreased risk of Alzheimer's disease (risk ratio (RR) = 0.66, 95% CI 0.52-0.85, P = 0.001). There was low risk of publication bias in the meta-analysis. There is an inverse association between serum uric acid levels and Alzheimer's disease. High serum uric acid level is a protective factor of Alzheimer's disease.

The role of antioxidants in the chemistry of oxidative stress: A review

This Review Article is focused on the action of the reactive oxygenated species in inducing oxidative injury of the lipid membrane components, as well as on the ability of antioxidants (of different structures and sources, and following different mechanisms of action) in fighting against oxidative stress. Oxidative stress is defined as an excessive production of reactive oxygenated species that cannot be counteracted by the action of antioxidants, but also as a perturbation of cell redox balance. Reactive oxygenated/nitrogenated species are represented by superoxide anion radical, hydroxyl, alkoxyl and lipid peroxyl radicals, nitric oxide and peroxynitrite. Oxidative stress determines structure modifications and function modulation in nucleic acids, lipids and proteins. Oxidative degradation of lipids yields malondialdehyde and 4-hydroxynonenal, but also isoprostanes, from unsaturated fatty acids. Protein damage may occur with thiol oxidation, carbonylation, side-chain oxidation, fragmentation, unfolding and misfolding, resulting activity loss. 8-hydroxydeoxyguanosine is an index of DNA damage. The involvement of the reactive oxygenated/nitrogenated species in disease occurrence is described. The unbalance between the oxidant species and the antioxidant defense system may trigger specific factors responsible for oxidative damage in the cell: over-expression of oncogene genes, generation of mutagen compounds, promotion of atherogenic activity, senile plaque occurrence or inflammation. This leads to cancer, neurodegeneration, cardiovascular diseases, diabetes, kidney diseases. The concept of antioxidant is defined, along with a discussion of the existent classification criteria: enzymatic and non-enzymatic, preventative or repair-systems, endogenous and exogenous, primary and secondary, hydrosoluble and liposoluble, natural or synthetic. Primary antioxidants are mainly chain breakers, able to scavenge radical species by hydrogen donation. Secondary antioxidants are singlet oxygen quenchers, peroxide decomposers, metal chelators, oxidative enzyme inhibitors or UV radiation absorbers. The specific mechanism of action of the most important representatives of each antioxidant class (endogenous and exogenous) in preventing or inhibiting particular factors leading to oxidative injury in the cell, is then reviewed. Mutual influences, including synergistic effects are presented and discussed. Prooxidative influences likely to occur, as for instance in the presence of transition metal ions, are also reminded.

Biomarkers of lipid peroxidation in Alzheimer disease (AD): an update

Increasing evidence suggests that free radical-mediated oxidation of biological substrates is a key feature of Alzheimer's disease (AD) pathogenesis. While it has long been established that biomarkers of lipid peroxidation (LPO) are elevated in AD brain as well as ventricular CSF postmortem, more recent studies have demonstrated increased LPO biomarkers in postmortem brain from subjects with mild cognitive impairment, the earliest clinically detectable phase of dementia and preclinical AD, the earliest detectable pathological phase. Furthermore, multiple LPO biomarkers are elevated in readily accessible biological fluids throughout disease progression. Collectively, these studies demonstrate that LPO is an early feature during disease progression and may be considered a key pathway for targeted therapeutics as well as an enhancer of diagnostic accuracy for early detection of subjects during the prodromal phase.

Serum uric acid and impaired cognitive function in a cohort of healthy young elderly: data from the Brisighella Study

Contrasting evidence shows a possible association between serum uric acid (SUA) and cognitive function in elderly subjects. We aimed at evaluating the impact of circulating SUA levels on cognitive function in a cohort of pharmacologically untreated young elderly subjects. For this study, we selected 288 healthy young elderly participants from the historical cohort of the Brisighella Heart Study (M: 108, F: 180; mean age: 69 ± 6 years old). Exclusion criteria were limitation of activities of daily living, depression, chronic pharmacological treatment, patients in secondary prevention for cardiovascular disease, known neurodegenerative disorders, confirmed diabetes or gout, and ultrasonic evaluated carotid atherosclerosis. Cognitive functions were assessed by scholarship-adjusted mini-mental state examination (MMSE). A stepwise multiple regression analysis was carried out including a large set of clinical and laboratory parameters, carotid intima-media thickness, and the Beck Depression scale score. The analysis was then repeated by gender. In the multiple regression analysis, the only factors associated with the MMSE score were: age (B = -0.058, 95% CI -0.108, -0.009, p = 0.022), LDL-C (B = -0.639, 95% CI -0.912, -0.411, p = 0.034) and SUA (B = -0.527, 95% CI -0.709, -0.344, p = 0.022). Repeating the analysis by low or high SUA level (based on the gender specific SUA distribution 50th percentile), it appears that in subjects with a low SUA, cognitive decline is only associated with age, while in those with high SUA it is associated with LDL-C (OR 1.18, 95% CI 1.07-1.33, p = 0.019) and SBP (OR 1.02, 95% CI 1.001-1.048, p = 0.039). Our data demonstrate a positive association between circulating levels of uric acid and cognitive dysfunction in a sample of pharmacologically untreated young elderly subjects.

Plasma levels of HDL and carotenoids are lower in dementia patients with vascular comorbidities

Elevated serum cholesterol concentrations in mid-life increase risk for Alzheimer's disease (AD) in later life. However, lower concentrations of cholesterol-carrying high density lipoprotein (HDL) and its principal apolipoprotein A1 (ApoA1) correlate with increased risk for AD. As HDL transports oxocarotenoids, which are scavengers of peroxynitrite, we have investigated the hypothesis that lower HDL and oxocarotenoid concentrations during AD may render HDL susceptible to nitration and oxidation and in turn reduce the efficiency of reverse cholesterol transport (RCT) from lipid-laden cells. Fasting blood samples were obtained from subjects with (1) AD without cardiovascular comorbidities and risk factors (AD); (2) AD with cardiovascular comorbidities and risk factors (AD Plus); (3) normal cognitive function; for carotenoid determination by HPLC, analysis of HDL nitration and oxidation by ELISA, and 3H-cholesterol export to isolated HDL. HDL concentration in the plasma from AD Plus patients was significantly lower compared to AD or control subject HDL levels. Similarly, lutein, lycopene, and zeaxanthin concentrations were significantly lower in AD Plus patients compared to those in control subjects or AD patients, and oxocarotenoid concentrations correlated with Mini-Mental State Examination scores. At equivalent concentrations of ApoA1, HDL isolated from all subjects irrespective of diagnosis was equally effective at mediating RCT. HDL concentration is lower in AD Plus patients' plasma and thus capacity for RCT is compromised. In contrast, HDL from patients with AD-only was not different in concentration, modifications, or function from HDL of healthy age-matched donors. The relative importance of elevating HDL alone compared with elevating carotenoids alone or elevating both to reduce risk for dementia should be investigated in patients with early signs of dementia.

The management of hyperuricemia with urate deposition

Recent epidemiological data suggest a progressive increase of serum levels of uric acid worldwide. This rise in the prevalence of hyperuricemia may be related to the epidemic diffusion of overweight and obesity as well as the shifts in diet with increased consumption of foods rich in purines, alcoholic consumption, and soft drinks sweetened with fructose. The rise in serum uric acid levels worldwide may be regarded as leading an increased risk for gout and other systemic diseases, especially in the cardio-renal system. Therefore, careful management of hyperuricemia with urate deposition is crucial to prevent or even treat those systemic diseases. Despite this, hyperuricemia and gout often remain untreated. This paper reviews current evidence on the management of hyperuricemia with urate deposition, with a focus on its most controversial aspects. This review is based on a PubMed/Embase database search for articles on hyperuricemia and its impact on cardiovascular and renal function.