Oxidative balance, homocysteine, and uric acid levels in older patients with Late Onset Alzheimer's Disease or Vascular Dementia

High plasma homocysteine levels predict the progression from mild cognitive impairment to dementia

High levels of blood homocysteine (HCy), a well-known cardiovascular risk factor and promoter of oxidative stress, have been associated with the incidence of cognitive impairment and dementia. Nonetheless, contrasting data are still present on its involvement in the progression from Mild Cognitive Impairment (MCI) to overt dementia. In this study we aimed to observe whether blood HCy level are associated with the evolution from MCI, divided into amnestic MCI (aMCI) and non-amnestic MCI (naMCI), to dementia. Blood HCy was measured in 311 MCI subjects (aMCI: 64%, naMCI: 36%) followed-up for a median of 33 months (range 10-155 months). At follow-up, 137 individuals converted to dementia (naMCI, n = 34; aMCI, n = 103). Based on HCy distribution, subjects in the highest tertile had a greater risk to convert to dementia compared to tertile I (Hazard Ratio (95% confidence interval): 2.25 (1.05-4.86); p = 0.04). aMCI subjects did not show increased risk to convert to dementia with increasing HCy concentration, but was significant in naMCI (p = 0.04). We observed a non-significant increase in the risk of progression to dementia from naMCI/low HCy (reference group, HCy cutoff value = 16 μmol/L) to naMCI/high HCy, but it was significant from aMCI/low HCy (HR: 2.73; 95%CI: 1.06-7.0; p:0.03), to aMCI/high HCy (HR: 3.24; 95%CI: 1.17-8.47; p:0.02). Our results suggest that HCy levels are associated with the progression from MCI to dementia. This association seems significant only for the naMCI group, indirectly supporting the notion that hyperhomocysteinemia damages the nervous system through its role as a vascular risk factor.

The effect of acupuncture on oxidative stress in animal models of vascular dementia: a systematic review and meta-analysis

BACKGROUND

Growing evidence showed that acupuncture may improve cognitive function by reducing oxidative stress, key to the pathogenesis in vascular dementia (VaD), but this is yet to be systematically analysed. This study aimed to summarize and evaluate the effect of acupuncture on oxidative stress in animal models of VaD.

METHOD

Eight databases including PubMed, Embase, Web of Science, Cochrane library, CNKI, Wan Fang, CBM, and VIP were searched since their establishment until April 2023, for studies that reported the effect of acupuncture on oxidative stress in VaD animal models. Relevant literature was screened, and information was extracted by two reviewers. The primary outcomes were the levels of oxidative stress indicators. The methodological quality was assessed via the SYRCLE Risk of Bias Tool. Statistical analyses were performed using the RevMan and Stata software.

RESULTS

In total, 22 studies with 747 animals were included. The methodology of most studies had flaws or uncertainties. The meta-analysis indicated that, overall, acupuncture significantly reduced the expression of pro-oxidants including reactive oxygen species (standardized mean differences [SMDs] = -4.29, 95% confidence interval [CI]: -6.26, -2.31), malondialdehyde (SMD = -2.27, 95% CI: -3.07, -1.47), nitric oxide (SMD = -0.85, 95% CI: -1.50, -0.20), and nitric oxide synthase (SMD = -1.01, 95% CI: -1.69, -0.34) and enhanced the levels of anti-oxidants including super oxide dismutase (SMD = 2.80, 95% CI: 1.98, 3.61), glutathione peroxidase (SMD = 1.32, 95% CI: -0.11, 2.76), and catalase (SMD = 1.31, 95% CI: 0.05, 2.58) in VaD animal models. In subgroup analyses, acupuncture showed significant effects on most variables. Only partial modelling methods and treatment duration could interpret the heterogeneity of some outcomes.

CONCLUSION

Acupuncture may inhibit oxidative stress to improve cognitive deficits in animal models of VaD. Nevertheless, the methodological quality is unsatisfactory. More high-quality research with a rigorous design and further experimental researches and clinical trials are needed to confirm these findings.

SYSTEMATIC REVIEW REGISTRATION

This study was registered in PROSPERO (CRD42023411720).

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.

Dapagliflozin Ameliorates Cognitive Impairment in Aluminum-Chloride-Induced Alzheimer's Disease via Modulation of AMPK/mTOR, Oxidative Stress and Glucose Metabolism

Alzheimer's disease (AD) is a progressive neurological illness characterized by memory loss and cognitive deterioration. Dapagliflozin was suggested to attenuate the memory impairment associated with AD; however, its mechanisms were not fully elucidated. This study aims to examine the possible mechanisms of the neuroprotective effects of dapagliflozin against aluminum chloride (AlCl₃)-induced AD. Rats were distributed into four groups: group 1 received saline, group 2 received AlCl₃ (70 mg/kg) daily for 9 weeks, and groups 3 and 4 were administered AlCl₃ (70 mg/kg) daily for 5 weeks. Dapagliflozin (1 mg/kg) and dapagliflozin (5 mg/kg) were then given daily with AlCl₃ for another 4 weeks. Two behavioral experiments were performed: the Morris Water Maze (MWM) and the Y-maze spontaneous alternation (Y-maze) task. Histopathological alterations in the brain, as well as changes in acetylcholinesterase (AChE) and amyloid β (Aβ) peptide activities and oxidative stress (OS) markers, were all evaluated. A western blot analysis was used for the detection of phosphorylated 5' AMP-activated protein kinase (p-AMPK), phosphorylated mammalian target of Rapamycin (p-mTOR) and heme oxygenase-1 (HO-1). Tissue samples were collected for the isolation of glucose transporters (GLUTs) and glycolytic enzymes using PCR analysis, and brain glucose levels were also measured. The current data demonstrate that dapagliflozin represents a possible approach to combat AlCl₃-induced AD in rats through inhibiting oxidative stress, enhancing glucose metabolism and activating AMPK signaling.

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.

PI3K-Akt signaling pathway based on network pharmacology for the anti-Alzheimer's disease effect of licorice stem flavonoids

Active ingredients were screened by TCMSP and swissADME, meanwhile, PharmMapper combined with UniProt database was used to predict the active ingredient target information, GeneCard database was employed to obtain Alzheimer's disease (AD)-related genes, Cytoscapes 3.7.2 software was utilized to map the active ingredient-target effect. Besides, Cytoscapes 3.7.2 software Bisogenet and Cyto NCA plug-in combined with STRING platform were utilized to map the protein-protein interaction (PPI) network, DAVID was employed for GO annotation, while KEGG plug-in was used for KEGG pathway enrichment. Mice were tested for inflammatory damage induced by intracerebral injection of lipopolysaccharide (LPS), as well as learning memory and anxiety by water maze and open field tests. In addition, the expression of Caspase-3 and Caspase-9, together with inflammatory factors TNF-α, IL-6, and IL-1β was analyzed in serum. The expression levels of proteins related to PI3K-Akt signaling pathway in the brain were detected by Western blot (WB) assay. According to the results of network pharmacology, there were 35 active ingredients of licorice stem and leaf flavonoids screened, which exerted the anti-Alzheimer's disease (AD) effects via 67 targets and activated 41 signaling pathways including the PI3K-Akt pathway. Furthermore, Behavioural results revealed that Licorice stem and leaf flavonoids improved the learning and memory abilities of model mice and significantly improved the anxiety caused by inflammatory brain damage. Moreover, as suggested by HE staining and TUNEL staining of brain sections, Glycyrrhiza glabra stem and leaf flavonoids alleviated morphological lesions and cell nuclear damage in brain tissue. Results: of brain homogenate supernatant assay demonstrated that Glycyrrhiza glabra stem and leaf flavonoids had a significant effect on the levels of oxidative indicators superoxide dismutase (SOD), catalase (CAT), malonaldehyde (MDA), acetylcholine (Ach), acetylcholinesterase (AchE), Caspase-3, Caspase-9 and serum inflammatory factors TNF-α, IL-6 and IL-1β. Additionally, WB assay results indicated that the PI3K-Akt signaling pathway was activated.

Current Drug Targets in Alzheimer's Associated Memory Impairment: A Comprehensive Review

Alzheimer's disease (AD) is the most prevalent form of dementia among geriatrics. It is a progressive, degenerative neurologic disorder that causes memory and cognition loss. The accumulation of amyloid fibrils and neurofibrillary tangles in the brain of AD patients is a distinguishing feature of the disease. Therefore, most of the current therapeutic goals are targeting inhibition of beta-amyloid synthesis and aggregation as well as tau phosphorylation and aggregation. There is also a loss of the cholinergic neurons in the basal forebrain, and first-generation therapeutic agents were primarily focused on compensating for this loss of neurons. However, cholinesterase inhibitors can only alleviate cognitive symptoms of AD and cannot reduce the progression of the disease. Understanding the molecular and cellular changes associated with AD pathology has advanced significantly in recent decades. The etiology of AD is complex, with a substantial portion of sporadic AD emerging from unknown reasons and a lesser proportion of early-onset familial AD (FAD) caused by a mutation in several genes, such as the amyloid precursor protein (APP), presenilin 1 (PS1), and presenilin 2 (PS2) genes. Hence, efforts are being made to discover novel strategies for these targets for AD therapy. A new generation of AChE and BChE inhibitors is currently being explored and evaluated in human clinical trials for AD symptomatic treatment. Other approaches for slowing the progression of AD include serotonergic modulation, H3 receptor antagonism, phosphodiesterase, COX-2, and MAO-B inhibition. The present review provides an insight into the possible therapeutic strategies and their molecular mechanisms, enlightening the perception of classical and future treatment approaches.

Comparative Investigation of Raw and Processed Radix Polygoni Multiflori on the Treatment of Vascular Dementia by Liquid Chromatograph-Mass Spectrometry Based Metabolomic Approach

Radix Polygoni Multiflori (PM) is a well-known nootropic used in traditional Chinese medicine (TCM). Considering the efficacy and application discrepancy between raw (RPM) and processed PM (PPM), the similarities and differences between them in the treatment of vascular dementia (VaD) is intriguing. In this study, a VaD rat model was constructed by 2-vessel occlusion (2-VO). During 28 days of treatment, plasma was collected on days 7, 14, 21, and 28 after the start of dosing and the metabolic profile was analyzed by HPLC-MS/MS-based metabolomics. The Morris Water Maze Test, hematoxylin-eosin and Nissl staining, and biochemical analysis were used to assess cognitive function, pathogenic alterations and oxidative stress, respectively. RPM and PPM effectivelyreducedthe 2VO-induced cognitive impairment and mitigated histological alterations in hippocampus tissue. The 2-VO model significantly elevated MDA level and decreased SOD activity and GSH level, indicating severe oxidative stress, which could also be attenuated by RPM and PPM treatment. RPM outperformed PPM in decreasing MDA levels while PPM outperformed RPM in increasing GSH levels. Differential metabolites were subjected to Metabolite Set Enrichment Analysis (MSEA) and genes corresponding to proteins having interactions with metabolites were further annotated with Gene Ontology (GO). Both RPM and PPM ameliorated VaD-relevant vitamin B6 metabolism, pentose phosphate pathways, and taurine and hypotaurine metabolism. In addition, the metabolism of cysteine and methionine was regulated only by RPM, and riboflavin metabolism was modulated only by PPM. The results suggested that raw and processed PM had comparable efficacy in the treatment of VaD but also with some mechanistic differenece.

Blood levels of circulating methionine components in Alzheimer’s disease and mild cognitive impairment: A systematic review and meta-analysis

Background

Circulating methionine components have been reported to be associated with Alzheimer’s disease (AD) and mild cognitive impairment (MCI), although outcomes are not always consistent.

Materials and methods

Database searching was conducted using PubMed, Embase, Cochrane Library, and Web of Science from inception to 26 December 2021. In this study, two reviewers independently identified eligible articles and extracted the data. We used Joanna Briggs Institute (JBI) Critical Appraisal tools to assess the overall quality of the included studies. STATA software was employed to perform meta-analysis evaluating the standardized mean difference (SMD) with its 95% confidence intervals (CIs) using random-effects models. Evidence quality was assessed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) criteria.

Results

Totally, 30 observational studies were eligible for inclusion. Compared with cognitively normal controls, patients with AD had increased homocysteine (Hcy) levels in the blood [standardized mean difference (SMD) = 0.59, 95% confidence interval [CI]: 0.36–0.82, P = 0.000], plasma (SMD = 0.39, 95% CI: 0.23–0.55, P = 0.000), and serum (SMD = 1.56, 95% CI: 0.59–2.95, P = 0.002). Patients with MCI were not significantly different from controls (SMD = 0.26, 95% CI: –0.07–0.58, P = 0.127). Patients with AD or MCI did not significantly differ from controls of blood vitamin B12 levels, AD (SMD = –0.05, 95% CI: –0.19–0.08, P = 0.440), or MCI (SMD = 0.01, 95% CI: –0.16–0.17, P = 0.94). Some cohort studies have suggested that higher Hcy, methionine, and S-adenosylmethionine levels may accelerate cognitive decline in patients with MCI or AD, and vitamin B12 deficiency is a risk factor for the disease; however, the results of other studies were inconsistent. According to the GRADE system, all these outcomes scored very low to low quality, and no high-quality evidence was found.

Conclusion

Only Hcy levels in the plasma and serum were found to be inversely related to the risk of AD. However, due to the low quality of supporting these results, high-quality studies are needed to verify these findings.

Systematic Review Registration

http://www.crd.york.ac.uk/PROSPERO/, identifier CRD42022308961.

The association of serum uric acid with cognitive impairment and ATN biomarkers

Background

Cognitive impairment (CI) has become a worldwide health problem. The relationship between CI and uric acid (UA) is contradictory.

Objective

We included participants with a full spectrum of CI, from cognitively unimpaired (CU) to dementia, from the Chongqing Ageing & Dementia Study (CADS).

Methods

First, we identified the relationships between serum UA (sUA) and cognitive function in different stages of CI. Second, we analyzed these relationships among different stages and types of CI. Finally, we explored the association between sUA and amyloid/tangle/neurodegeneration (ATN) biomarkers.

Results

We recruited 427 participants from the CADS, including 382 participants with mini-mental state examination (MMSE) evaluation. The levels of sUA were positively correlated with MMSE scores (p < 0.001), and the correlation was prominent in the course of dementia and in the type of Alzheimer’s disease (AD). The levels of UA had a positive correlation with plasma amyloid-β 42 (Aβ42) (p = 0.004). Higher levels of sUA weakened the correlation of MMSE scores with CSF ATN biomarkers and the correlation of CSF Aβ42 with tau.

Conclusion

UA is positively correlated with cognitive function, especially in the advanced stage of AD. The probable neuroprotective effects of sUA mainly act on Aβ42 and the downstream pathological cascade.

Potential Value of Serum Uric Acid in the Identification of Postoperative Delirium in Geriatric Patients Undergoing Knee Replacement

Objectives

The relationship between preoperative serum uric acid (SUA) and cerebrospinal fluid (CSF) Alzheimer-related biomarkers were investigated to determine whether high SUA is a potential risk factor for postoperative delirium (POD) and to evaluate its predictive efficacy.

Methods

The participants were selected from the Perioperative Neurocognitive Disorder Risk Factor and Prognosis (PNDRFAP) study and the Perioperative Neurocognitive Disorder and Biomarker Lifestyle (PNDABLE) study. The logistic regression equation was used to analyze the risk factors and protective factors of POD. The interaction term (SUA × Sex) was introduced into the linear model to explore the potential modification effects of sex on the identified correlations. We analyzed the mediating effects of Alzheimer-related biomarkers. Finally, we constructed the receiver operating characteristic (ROC) curve and the nomogram model to evaluate the efficacy of SUA and Alzheimer-related biomarkers in predicting POD.

Results

Patients with POD had elevated SUA level (PNDRFAP: p = 0.002, PNDABLE: p < 0.001). Preoperative SUA level was positively correlated with CSF phosphorylated tau (P-tau) (p = 0.027) and β-amyloid42 (Aβ₄₂)/P-tau (p = 0.023). Interaction analysis did not find any modification effect of sex. The relationship between SUA and POD was partially mediated by CSF P-tau (15.3%). ROC curve showed that the model combining SUA and Alzheimer-related biomarkers had better performance in predicting POD [area under the curve (AUC) = 0.880; p < 0.001], and the predictive model is accurate.

Conclusions

High SUA may enhance CSF P-tau level, thus increasing the risk of POD, and the model combining SUA and Alzheimer-related biomarkers can accurately predict the occurrence of POD.

Oxidative stress and antioxidant defenses in mild cognitive impairment: A systematic review and meta-analysis

This study aims to systematically review and meta-analyze the nitro-oxidative stress (O&NS)/antioxidant (ANTIOX) ratio in the peripheral blood of people with mild cognitive impairment (MCI). We searched PubMed, Scopus, Google Scholar, and Web of Science for articles published from inception until July 31, 2021. Forty-six studies on 3.798 MCI individuals and 6.063 healthy controls were included. The O&NS/ANTIOX ratio was significantly higher in MCI than in controls with a Standardized Mean Difference (SMD)= 0.378 (95% CI: 0.250; 0.506). MCI individuals showed increased lipid peroxidation (SMD=0.774, 95%CI: 4.416; 1.132) and O&NS-associated toxicity (SMD=0.621, CI: 0.377; 0.865) and reduced glutathione (GSH) defenses (SMD=0.725, 95%CI: 0.269; 1.182) as compared with controls. MCI was also accompanied by significantly increased homocysteine (SMD=0.320, CI: 0.059; 0.581), but not protein oxidation, and lowered non-vitamin (SMD=0.347, CI: 0.168; 0.527) and vitamin (SMD=0.564, CI: 0.129; 0.999) antioxidant defenses. The results show that MCI is at least in part due to increased neuro-oxidative toxicity and suggest that treatments targeting lipid peroxidation and the GSH system may be used to treat or prevent MCI.

Metabolomics Deciphering the Potential Biomarkers of Hengqing I Prescription against Vascular Dementia

With the aging of population, vascular dementia (VaD) seriously threatens people's health and quality of life. It is of great significance to explore biomarkers of VaD from the perspective of metabolomics and traditional Chinese medicine (TCM). Therefore, VaD was divided into kidney deficiency and blood stasis syndrome (KDBS) and non-KDBS according to TCM. Then, some patients received the treatment of Hengqing I (HQI) prescription. The urine of six groups (VaD group, normal group, KDBS group, non-KDBS group, HQI group, and control group) was detected on LC-MS/MS. Multivariate statistical analysis showed that the metabolic profiles of the three comparisons were significantly different. The top analysis-ready molecules of downregulated histamine and upregulated biotin, methionine, pantothenic acid, SAH, histidine, and kaempferol may be the most related metabolites. These putative biomarkers play an important role in the regulation of key metabolic processes linked to VaD. Additionally, pathway analysis showed aminoacyl-tRNA biosynthesis, and amino acids metabolic pathways were highly correlated with the occurrence of VaD. In this present paper, vitamins, amino acids, and their derivatives were selected as the basis for VaD diagnosis and treatment monitoring, and the significance of TCM classification and Hengqing I prescription in the treatment of VaD was discussed.

Cognitive Impairment in End Stage Renal Disease Patients Undergoing Hemodialysis: Markers and Risk Factors

(1) Background: Cognitive impairment (CI) is common in chronic kidney disease (CKD) and patients treated with hemodialysis. (2) Methods: The systematic review was prepared following the PRISMA statement (2013). The biomedical electronic databases MEDLINE and SCOPUS were searched. (3) Results: out of 1093 studies, only 30, which met problem and population criteria, were included in this review. The risk factors for CI can be divided into three groups: traditional risk factors (present in the general population), factors related to dialysis sessions, and nontraditional risk factors occurring more frequently in the HD group. (4) Conclusions: the methods of counteracting CI effective in the general population should also be effective in HD patients. However, there is a need to develop unique anti-CI approaches targeting specific HD risk factors, i.e., modified hemodialysis parameters stabilizing cerebral saturation and blood flow.

The Correlations Between Serum Hcy Level and Seizures and Cognitive Function in Patients After Stroke

BACKGROUNDS

Post-stroke cognitive dysfunction (PSCI), a set of illnesses ranging from moderate cognitive impairment to dementia, which is one of the most prevalent consequences following a stroke. Homocysteine (Hcy) has been related to a number of neurological and systemic diseases. It's also a known risk factor for cardiovascular disease and systemic atherosclerosis (CVD). The link between Hcy and PSCI, on the other hand, is unknown.

METHODS

Our hospital evaluated 325 patients with acute cerebral infarction between January 1, 2018 and December 1, 2021. There are biological markers and baseline data available. Patients were divided into two groups based on the results of the Montreal Cognitive Assessment (MoCA). The researchers performed logistic regression analysis to find variables that may be linked to PSCI.

RESULTS

HCY levels were significantly higher in PSCI patients than in non-PSCI patients. Age, education, seizure manifestation, and income level were all shown to be independent risk variables for PSCI in a multivariate logistic analysis. Hcy levels in PSCI patients differed considerably between the high and low groups. The high and low Hcy levels groups had significantly varied hypertension histories and urine levels. Hcy levels in PSCI patients differed considerably between the high and low groups. The high and low Hcy levels groups had significantly varied hypertension histories and urine levels.

CONCLUSION

Serum Hcy levels have been linked to PSCI in post-stroke patients, and researchers believe that serum Hcy levels will diminish PSCI.

B vitamins and prevention of cognitive decline and incident dementia: a systematic review and meta-analysis

CONTEXT

Elevation of homocysteine (Hcy) levels is well-established as a risk factor for dementia, yet controversy exists regarding whether B-vitamin-mediated reduction of homocysteine levels can benefit cognitive function.

OBJECTIVE

To investigate whether B vitamin supplementation can reduce the risk of cognitive decline and incident dementia.

DATA SOURCES

The PubMed, EMBASE, Cochrane Library, and Web of Science were systematically searched for articles published from the inception dates to March 1, 2020. Randomized controlled trials (RCT) were included if B vitamins were supplied to investigate their effect on the rate of cognitive decline. Cohort studies investigating dietary intake of B vitamins and the risk of incident dementia were eligible. Cross-sectional studies comparing differences in levels of B vitamins and Hcy were included.

DATA EXTRACTION

Two reviewers independently performed data extraction and assessed the study quality.

DATA ANALYSIS

Random-effect or fixed-effect models, depending on the degree of heterogeneity, were performed to calculate mean differences (MDs), hazard ratios (HRs), and odds ratios (ORs).

RESULTS

A total of 95 studies with 46175 participants (25 RCTs, 20 cohort studies, and 50 cross-sectional studies) were included in this meta-analysis. This meta-analysis supports that B vitamins can benefit cognitive function as measured by Mini-Mental State Examination score changes (6155 participants; MD, 0.14, 95%CI 0.04 to 0.23), and this result was also significant in studies where placebo groups developed cognitive decline (4211 participants; MD, 0.16, 95%CI 0.05 to 0.26), suggesting that B vitamins slow cognitive decline. For the > 12 months interventional period stratum, B vitamin supplementation decreased cognitive decline (3814 participants; MD, 0.15, 95%CI 0.05 to 0.26) compared to placebo; no such outcome was detected for the shorter interventional stratum (806 participants; MD, 0.18, 95%CI -0.25 to 0.61). In the non-dementia population, B vitamin supplementation slowed cognitive decline (3431 participants; MD, 0.15, 95%CI 0.04 to 0.25) compared to placebo; this outcome was not found for the dementia population (642 participants; MD, 0.20, 95%CI -0.35 to 0.75). Lower folate levels (but not B12 or B6 deficiency) and higher Hcy levels were significantly associated with higher risks of dementia (folate: 6654 participants; OR, 1.76, 95%CI 1.24 to 2.50; Hcy: 12665 participants; OR, 2.09, 95%CI 1.60 to 2.74) and cognitive decline (folate: 4336 participants; OR, 1.26, 95%CI 1.02 to 1.55; Hcy: 6149 participants; OR, 1.19, 95%CI 1.05 to 1.34). Among the population without dementia aged 50 years and above, the risk of incident dementia was significantly decreased among individuals with higher intake of folate (13529 participants; HR, 0.61, 95%CI 0.47 to 0.78), whereas higher intake of B12 or B6 was not associated with lower dementia risk.

CONCLUSIONS

This meta-analysis suggests that B vitamin supplementation is associated with slowing of cognitive decline, especially in populations who received early intervention and intervention of long duration; the study also indicates that higher intake of dietary folate, but not B12 or B6, is associated with a reduced risk of incident dementia in non-dementia aged population. Given the prevalence of dementia cases in many countries with aging populations, public health policies should be introduced to ensure that subgroups of the population at risk have an adequate B vitamin status.

Serum oxidized low density lipoprotein serves as a mediator for the inverse relationship between serum d-ribose and cognitive performance in type 2 diabetic patients

Chronic hyperglycemia, proinflammatory state, and oxidative stress are implicated in the etiology of mild cognitive impairment (MCI) in type 2 diabetes mellitus (T2DM) patients. However, roles and mechanisms of the diabetes-related dys-regulation of serum d-ribose in the pathogenesis remain unclear. This study was to assess: 1) changes of serum d-ribose in T2DM patients with or without MCI compared with healthy controls; and 2) associations of serum d-ribose with key biomarkers of ribosylation [advanced glycation end products (AGEs) and receptor for advanced glycation end products (RAGE)], inflammation (IL-6 and NF-κB) and oxidative stress [oxidized low density lipoproteins (ox-LDL), advanced oxidation protein products (AOPP), total thiol, and non-protein thiol)]. A cross-sectional study was conducted with 1564 initial participants including 362 T2DM patients. Based on their fasting blood glucose concentrations and Montreal cognitive assessment (MoCA) scores, we selected 89 participants and divided them into three groups: 27 healthy controls, 26 T2DM patients with normal cognition, 36 T2DM patients with MCI. All participants were gone through standard anthropometric tests and biochemical examinations of serum clinical profiles and concentrations of d-ribose, AGE, RAGE, IL-6, NF-κB, ox-LDL, AOPP, total thiol, and non-protein thiol. Serum concentrations of d-ribose, ox-LDL, and AOPP were greater (P < 0.05) in the T2DM-MCI patients than that in the T2DM or controls. Serum d-ribose exhibited a positive correlation (P < 0.05) with serum AGEs, RAGE, ox-LDL, and fasting blood glucose, but a negative correlation (P < 0.05) with MoCA score. This negative relationship remained (P < 0.05) after adjusting various covariates, and was found to be mediated (P < 0.05) by serum ox-LDL. In conclusion, our results reveal serum ox-LDL as a potential mediator for the inverse relationship between the elevation of serum d-ribose concentration and the decline of cognitive performance in the T2DM-MCI patients.

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.

Homocysteine and Folic Acid: Risk Factors for Alzheimer's Disease-An Updated Meta-Analysis

Background: Recent studies have reported that homocysteine (Hcy) may play a vital role in the pathogenesis of vascular dementia (VaD) and Alzheimer's disease (AD). Our study explored the relationship between the plasma Hcy and folate levels and the risk of dementia.

Methods: We searched Embase, PubMed, and Web of Science for published literature, including case-control studies and prospective cohort studies, and performed a systematic analysis.

Results: The results of our meta-analysis, consisting of case-control studies, showed higher levels of Hcy and lower levels of folate in dementia, AD, and VaD patients than those in non-demented controls (for dementia: SMD = 0.812, 95% CI [0.689, 0.936], p = 0.000 for Hcy; SMD = −0.677, 95% CI [−0.828, −0.525], p = 0.000 for folate). AD patients showed significantly lower plasma Hcy levels compared to VaD patients (SMD = −0.278, 95% CI [−0.466, −0.09], p = 0.000). Subgroup analysis revealed that ethnicity, average age, and dementia type had no significant effect on this association. Furthermore, from the analysis of prospective cohort studies, we identified that elevated plasma Hcy levels were associated with an increased risk of dementia, AD, and VaD (RR_dementia = 1.22, 95% CI [1.08, 1.36]; RR_AD = 1.07, 95% CI [1.04, 1.11]; RR_VaD = 1.13, 95% CI [1.04, 1.23]). In addition, every 5 μmol/L increase in the plasma Hcy level was associated with a 9% increased risk of dementia and a 12% increased risk of AD.

Conclusion: Hcy and folic acid are potential predictors of the occurrence and development of AD. A better understanding of their function in dementia could provide evidence for clinicians to rationalize clinical intervention strategies.

Study on Mechanism of Ginkgo biloba L. Leaves for the Treatment of Neurodegenerative Diseases Based on Network Pharmacology

Ginkgo biloba L. leaves (GBLs), as widely used plant extract sources, significantly improve cognitive, learning and memory function in patients with dementia. However, few studies have been conducted on the specific mechanism of Neurodegenerative diseases (NDs). In this study, network pharmacology was employed to elucidate potential mechanism of GBLs in the treatment of NDs. Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP) was used to obtain the chemical components in accordance with the screening principles of oral availability and drug-like property. Potential targets of GBLs were integrated with disease targets, and intersection targets were exactly the potential action targets of GBLs for treating NDs; these key targets were enriched and analyzed by the protein protein interaction (PPI) analysis and molecular docking verification. Key genes were ultimately used to find the biological pathway and explain the therapeutic mechanism by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. Twenty-seven active components of GBLs may affect biological processes such as oxidative reactions and activate transcription factor activities. These components may also affect 120 metabolic pathways, such as the PI3K/AKT pathway, by regulating 147 targets, including AKT1, ALB, HSP90AA1, PTGS2, MMP9, EGFR and APP. By using the software iGEMDOCK, the main target proteins were found to bind well to the main active components of GBLs. GBLs have the characteristics of multi-component and multi-target synergistic effect on the treatment of NDs, which preliminarily predicted its possible molecular mechanism of action, and provided the basis for the follow-up study.

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.

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.

Uric Acid in Metabolic and Cerebrovascular Disorders: A Review

BACKGROUND

Several studies showed a close link between metabolic syndrome (MetS), type 2 diabetes (T2DM) and cerebrovascular diseases. There is considerable debate regarding the role of uric acid (UA) as a risk factor in these conditions.

OBJECTIVE

The aim of this narrative review is to discuss the links between UA, MetS, T2DM and cerebrovascular disease.

METHODS

An extensive review has been conducted based on the scientific literature published in English, and indexed in MEDLINE (through PubMed), EMBASE, the Cochrane Library, the Agency for Healthcare Research and Quality, and Google Scholar from January to May 2019. Additional relevant studies published after the initial review were also considered during the period of June 2019-October 2019, during which, this manuscript was written. The Mesh Terms considered were: uric acid, antioxidant, oxidant, metabolic syndrome, diabetes, cerebrovascular diseases, stroke, haemorrhagic stroke, neurocognitive disorders, and their combinations.

RESULTS

The literature review shows a dose-dependent inflammatory action of UA, which occurs with serum concentrations >4 mg/dl (>0.24 mmol/l), representing one of the contributors to the chronic inflammatory process that underlies metabolic and cerebrovascular diseases.

CONCLUSION

UA, which is associated with arterial hypertension and cardiovascular diseases, represents one of the indicators of oxidative homeostasis. Increasing concentrations represent a status of active inflammation which is observed with metabolic and cerebrovascular diseases.

Activation of arginase II by asymmetric dimethylarginine and homocysteine in hypertensive rats induced by hypoxia: a new model of nitric oxide synthesis regulation in hypertensive processes?

In recent years, the increase in blood pressure at high altitudes has become an interesting topic among high-altitude researchers. In our animal studies using Wistar rats, we observed the existence of two rat populations that exhibit differential physiological responses during hypoxic exposure. These rats were classified as hypoxia-induced hypertensive rats and nonhypertensive rats. A decrease in nitric oxide levels was reported in different hypertension models associated with increased concentrations of asymmetric dimethylarginine (ADMA) and homocysteine, and we recently described an increase in arginase type II expression under hypoxia. ADMA and homocysteine decrease nitric oxide (NO) bioavailability; however, whether ADMA and homocysteine have a regulatory effect on arginase activity and therefore regulate another NO synthesis pathway is unknown. Therefore, the aim of this study was to measure basal ADMA and homocysteine levels in hypoxia-induced hypertensive rats and evaluate their effect on arginase II activity. Our results indicate that hypoxia-induced hypertensive rats presented lower nitric oxide concentrations than nonhypertensive rats, associated with higher concentrations of homocysteine and ADMA. Hypoxia-induced hypertensive rats also presented lower dimethylarginine dimethylaminohydrolase-2 and cystathionine β-synthase levels, which could explain the high ADMA and homocysteine levels. In addition, we observed that both homocysteine and ADMA had a significant effect on arginase II activation in the hypertensive rats. Therefore, we suggest that ADMA and homocysteine have dual regulatory effects on NO synthesis. The former has an inhibitory effect on eNOS, and the latter has a secondary activating effect on arginase II. We propose that arginase II is activated by AMDA and homocysteine in hypoxia-induced hypertensive rats.

Shared perturbations in the metallome and metabolome of Alzheimer's, Parkinson's, Huntington's, and dementia with Lewy bodies: A systematic review

Despite differences in presentation, age-related dementing diseases such as Alzheimer's (AD), Parkinson's (PD), and Huntington's diseases (HD), and dementia with Lewy bodies (DLB) may share pathogenic processes. This review aims to systematically assemble and compare findings in various biochemical pathways across these four dementias. PubMed and Google Scholar were screened for articles reporting on brain and biofluid measurements of metals and/or metabolites in AD, PD, HD, or DLB. Articles were assessed using specific a priori-defined inclusion and exclusion criteria. Of 284 papers identified, 198 met criteria for inclusion. Although varying coverage levels of metals and metabolites across diseases and tissues made comparison of many analytes impossible, several common findings were identified: elevated glucose in both brain tissue and biofluids of AD, PD, and HD cases; increased iron and decreased copper in AD, PD and HD brain tissue; and decreased uric acid in biofluids of AD and PD cases. Other analytes were found to differ between diseases or were otherwise not covered across all conditions. These findings indicate that disturbances in glucose and purine pathways may be common to AD, PD, and HD. However, standardisation of methodologies and better coverage in some areas - notably of DLB - are necessary to validate and extend these findings.

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.

Methylenetetrahydrofolate reductase C667T polymorphism and susceptibility to late-onset Alzheimer's disease in the Italian population

INTRODUCTION

This study is a meta-analysis of the published studies on the relationship between methylenetetrahydrofolate reductase (MTHFR) C667T polymorphism and the risk of late- onset Alzheimer 's disease (LOAD) in Italian cohorts.

EVIDENCE ACQUISITION

We conducted a search on the electronic databases PubMed/Medline, Web of Science and Scopus. All cohort and case-control studies investigating the association between MTHFR 677T polymorphism and LOAD in Italian population published any time to May 8, 2020 were included in the analysis.

EVIDENCE SYNTHESIS

From an initial screening of 136 articles, 4 were included into the systemic review. The pooled analysis based on the co-dominant model revealed that the MTHFR C677T polymorphism was associated with a significant risk of LOAD among Italian cohorts (TC vs. CC: OR=1.20, 95% CI=1.06-1.36, P=0.004, I²=0%). Conversely, the pooled analysis based on the allelic model demonstrated a non-significant relationship between the MTHFR C677T polymorphism and susceptibility to LOAD in Italians (OR: 1.25, 95% CI: 0.99-1.59, P=0.060, I²=14.6%). Moreover, Italian subjects with MTHFR 677TT genotype resulted to have a significantly increased susceptibility to LOAD (OR=1.75, 95% CI=1.23-2.50, P=0.002, I²=0%).

CONCLUSIONS

The present meta-analysis showed only trend of association between MTHFR C677T polymorphism and LOAD in Italian population; however, it also demonstrated an increased susceptibility of LOAD in patients having MTHFR 677TT genotype. Further studies are needed to establish whether MTHFR polymorphisms can be used as non-invasive biomarker for LOAD.

The importance of BDNF and RAGE in diabetes-induced dementia

Diabetes-induced dementia is an emerging neurodisorder all over the world. The prevalence rates of dementia and diabetes have been gradually increasing worldwide. Diabetes has been known to lead to oxidative stress, inflammation aggravation, and hyperglycemia conditions in the brain. Various diabetic implications cause the lower secretion of brain-derived neurotrophic factor (BDNF) and the increase of receptor for advanced glycation end products (RAGE), ultimately leading to both cerebrovascular dysfunction and cognitive decline. Here, we summarized the significant evidences highlighting the specific mechanisms between BDNF and RAGE and cerebrovascular dysfunction and memory function and how these relate to diabetes-induced dementia. Especially, we review that the association between BDFN and RAGE in neuroinflammation, the reduction of long-term potentiation, and the vascular implications in brain.

Edaravone protects from memory impairment induced by chronic L-methionine administration

Hyperhomocysteinemia is a well-known cause of cognitive impairment and neurodegeneration. Increased oxidative stress in the brain has a major possible role in hyperhomocysteinemia-induced pathogenesis. Edaravone is a potent free radical scavenger that has a neuroprotective effect against memory impairment in several experimental models. The current study investigated the possible protective effect of edaravone in L-methionine-induced vascular dementia in a rat model. L-methionine was given (1.7 mg/kg/day) through oral gavage, while edaravone was given (6 mg/kg/day) intraperitoneally. The administration of methionine and edaravone started concomitantly and continued for a total of 9 weeks. Spatial learning and memory were assessed using the radial arm water maze (RAWM). Changes in the oxidative stress-related biomarkers in the hippocampus were assessed using enzymatic assays. Chronic L-methionine administration resulted in short-term and long-term memory impairment, whereas edaravone prevented such effect. Furthermore, edaravone ameliorated L-methionine induced decrease in the activity of the antioxidant enzymes catalase and glutathione peroxidase as well as the ratio of reduced glutathione to oxidized glutathione (GSH/GSSG ratio). Edaravone also prevented increase in the oxidized glutathione (GSSG) secondary to chronic L-methionine administration. In conclusion, the current study suggests that memory impairment and oxidative stress secondary to chronic L-methionine administration can be prevented by edaravone, probably via enhancing antioxidant mechanisms in the hippocampus.

Arylesterase Activity of Paraoxonase-1 in Serum and Cerebrospinal Fluid of Patients with Alzheimer's Disease and Vascular Dementia

BACKGROUND

It has been suggested that circulating Paraoxonase-1 (PON1) and apolipoprotein A1 (APOA1), which closely interacts with the antioxidant enzyme, could be implicated in Alzheimer's disease (AD) and vascular dementia (VaD) development. This study aimed to evaluate PON1 changes in serum and cerebrospinal fluid (CSF) as evidence for its association with AD or VaD.

METHODS

Serum PON-arylesterase activity was measured in patients with AD, VaD, and CONTROLS distributed in two cohorts: Ferrara cohort (FC: n = 503, age = 74 years) and Amsterdam Dementia cohort (ADC: n = 71, age = 65 years). In the last cohort, CSF PON-arylesterase, CSF β-amyloid1-42, p-tau and t-tau, and imaging biomarkers were also measured.

RESULTS

AD and VaD patients of FC showed significantly lower levels of serum PON-arylesterase compared to CONTROLS, but this outcome was driven by older subjects (>71 years, p < 0.0001). In the younger ADC, a similar decreasing (but not significant) trend was observed in serum and CSF. Intriguingly, PON-arylesterase per APOA1 correlated with t-tau in AD group (r = -0.485, p = 0.002).

CONCLUSION

These results suggest that decreased peripheral PON-arylesterase might be a specific feature of older AD/VaD patients. Moreover, we showed that PON-arylesterase/APOA1 is inversely related to neurodegeneration in AD patients, suggesting a prognostic usefulness of this composite parameter.

Update on the Neurobiology of Vascular Cognitive Impairment: From Lab to Clinic

In the last years, there has been a significant growth in the literature exploring the pathophysiology of vascular cognitive impairment (VCI). As an "umbrella term" encompassing any degree of vascular-related cognitive decline, VCI is deemed to be the most common cognitive disorder in the elderly, with a significant impact on social and healthcare expenses. Interestingly, some of the molecular, biochemical, and electrophysiological abnormalities detected in VCI seem to correlate with disease process and progression, eventually promoting an adaptive plasticity in some patients and a maladaptive, dysfunctional response in others. However, the exact relationships between vascular lesion, cognition, and neuroplasticity are not completely understood. Recent findings point out also the possibility to identify a panel of markers able to predict cognitive deterioration in the so-called "brain at risk" for vascular or mixed dementia. This will be of pivotal importance when designing trials of disease-modifying drugs or non-pharmacological approaches, including non-invasive neuromodulatory techniques. Taken together, these advances could make VCI a potentially preventable cause of both vascular and degenerative dementia in late life. This review provides a timely update on the recent serological, cerebrospinal fluid, histopathological, imaging, and neurophysiological studies on this "cutting-edge" topic, including the limitations, future perspectives and translational implications in the diagnosis and management of VCI patients.

Update on the Neurobiology of Vascular Cognitive Impairment: From Lab to Clinic

In the last years, there has been a significant growth in the literature exploring the pathophysiology of vascular cognitive impairment (VCI). As an "umbrella term" encompassing any degree of vascular-related cognitive decline, VCI is deemed to be the most common cognitive disorder in the elderly, with a significant impact on social and healthcare expenses. Interestingly, some of the molecular, biochemical, and electrophysiological abnormalities detected in VCI seem to correlate with disease process and progression, eventually promoting an adaptive plasticity in some patients and a maladaptive, dysfunctional response in others. However, the exact relationships between vascular lesion, cognition, and neuroplasticity are not completely understood. Recent findings point out also the possibility to identify a panel of markers able to predict cognitive deterioration in the so-called "brain at risk" for vascular or mixed dementia. This will be of pivotal importance when designing trials of disease-modifying drugs or non-pharmacological approaches, including non-invasive neuromodulatory techniques. Taken together, these advances could make VCI a potentially preventable cause of both vascular and degenerative dementia in late life. This review provides a timely update on the recent serological, cerebrospinal fluid, histopathological, imaging, and neurophysiological studies on this "cutting-edge" topic, including the limitations, future perspectives and translational implications in the diagnosis and management of VCI patients.

Uric acid is associated with cognitive impairment in the elderly patients receiving maintenance hemodialysis-A two-center study

BACKGROUND

Elevated serum uric acid (SUA) has been associated with vascular cognitive impairment (CI) in the elderly. However, its relationship with cognitive function in the elderly patients receiving maintenance hemodialysis (MHD) has not yet been elucidated.

OBJECTIVE

The cognitive impairment is prevalent in MHD patients. Various insults may contribute to cognitive impairment in patients with MHD. The aim of this study was to investigate the relationship between SUA and CI in the elderly patients receiving MHD.

METHODS

A total of 180 elderly MHD subjects from two hospitals were enrolled in our study. Cognitive function domains were evaluated by MMSE at the beginning of the trial. Demographic and clinical characteristics were collected and recorded.

RESULTS

The subjects were stratified into quartiles according to SUA level. Demographic and clinical characteristics such as age, gender, smoking habit, education year, blood pressure (BP), hemoglobin, albumin, blood glucose (BG), total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL), low-density lipoprotein cholesterol (LDL), blood urea nitrogen (BUN), and serum creatinine (Scr) did not differ dramatically among groups (p > .05). The Q1 group showed the highest MMSE scores, and the Q4 group showed the lowest MMSE sores (p < .05). There was a negative correlation between SUA and MMSE scores (r = -.307, p = .014), and this correlation was independent of demographic and clinical characteristics.

CONCLUSIONS

Elevated SUA maybe contributes to CI in the elderly MHD patients. SUA level is independent risk for the CI in the elderly MHD patients.

Changes in Adipose Tissue Distribution and Association between Uric Acid and Bone Health during Menopause Transition

Despite convincing experimental evidence, epidemiological studies on the effects of serum uric acid (SUA) on bone health are still conflicting since factors influencing SUA bioavailability have not been adequately considered. To shed some light on this issue, we investigated the impact of adiposity and menopause status on the relationship between SUA and bone health. We examined SUA in relation to bone mineral density (BMD) at different skeletal sites and with markers of bone metabolism in 124 pre-menopausal and 234 post-menopausal women and assessed whether adiposity, evaluated by anthropometry and dual x-ray absorptiometry (DXA), might have a discriminant role. After conservative adjustment (covariates: age, hormones treatment, smoking and time since menopause), SUA showed a significant and positive association with total hip BMD (β = 0.220, p < 0.01) among postmenopausal women, maintained also after adjustment for legs adiposity. Notably, stratification for waist circumference quartiles revealed that the correlation between SUA and total hip BMD was significant (r = 0.444, p = 0.001) in the highest quartile (91–100 cm). Our results suggest that SUA might be beneficial for bone health in postmenopausal women being characterized by a more android fat distribution, ascribing to SUA a discriminant role during menopause transition, potentially relevant also for men.

Serum beta-secretase 1 (BACE1) activity as candidate biomarker for late-onset Alzheimer's disease

Beta-secretase (BACE1) is a key enzyme in the formation of amyloid-β; its activity/concentration is increased in brain and cerebrospinal fluid of patients with late-onset Alzheimer's disease (LOAD). Since BACE1 was found also in blood, we evaluated its potential as peripheral biomarker. To this aim, serum BACE1 activity was assessed in 115 subjects with LOAD and 151 controls. We found that BACE1 changed across groups (p < 0.001) with a 25% increase in LOAD versus controls. High levels of BACE1 (IV quartile) were independently associated with the diagnosis of LOAD (OR 2.8; 1.4-5.7). Diagnostic accuracy was 76% for LOAD. Our data suggest that increased BACE1 activity in serum may represent a potential biomarker for LOAD. Additional studies are needed to confirm the usefulness of BACE1, alone or in combination with other markers, in discriminating patients and predicting LOAD onset and progression.

Rehmannioside A attenuates cognitive deficits in rats with vascular dementia (VD) through suppressing oxidative stress, inflammation and apoptosis

Vascular dementia (VD) is a degenerative cerebrovascular disorder, leading to progressive decline of cognitive abilities and memory. Rehmannioside A (ReA) is isolated from Rehmanniae Radix, which exhibits protective role against various diseases. The present study was performed to calculate the possible neuroprotective effects of ReA on VD. Here, the morris water maze (MWM) test and electrophysiological recordings indicated that ReA reduced cognitive deficits. Additionally, through hematoxylin and eosin (H&E) and Nissl staining, ReA attenuated the histological alterations of hippocampus in rats with VD. ReA group significantly reduced oxidative stress, inflammatory response and apoptosis in the hippocampus of rats with VD, which was linked to the activation of nuclear erythroid related factor-2 (Nrf2), while the inactivation of nuclear factor-κB (NF-κB) and Caspase-3. Further, the anti-oxidative, anti-inflammatory and anti-apoptosis abilities of ReA were confirmed in cells stimulated by hydrogen peroxide. Overall, the results above demonstrated the protective effects of ReA against cognitive deficits and indicated the potential value of ReA in the therapy of VD in future.

Association of homocysteine, folate, and white matter hyperintensities in Parkinson's patients with different motor phenotypes

OBJECTIVE

To investigate the association of homocysteine (Hcy), folate, and white matter hyperintensities in Parkinson's disease (PD) with different motor phenotypes.

METHODS

Of the PD patients, 176 were included. Based on the Unified Parkinson's Disease Rating Scale, the PD patients were classified into postural instability gait disorder (PIGD) and non-PIGD phenotypes. According to the Fazekas score, patients were divided into the none/mild white matter hyperintensity (WMH) group and the moderate/severe WMH group. The relationship of Hcy, folate, and white matter hyperintensities (WMHs), and the motor phenotype of PD were analyzed.

RESULTS

PD-PIGD patients had higher proportion of moderate/severe WMHs, Hcy levels, and lower folate levels than PD-non-PIGD patients (p all ≤ 0.001). In the subgroup analysis, patients with both PD-PIGD and moderate/severe WMHs had the highest Hcy and lowest folate levels compared with others. Binary logistic regression analysis showed that age, folate, and Hcy were independent risk factors for WMHs. In an a priori-determined stratified analysis, after adjustment for confounding factors, the odds ratio of WMHs was 8.01 (95% CI 2.700-23.767, p trend = 0.001) in the patients with Hcy levels in the highest quintile compared with the lowest quintile and 16.81 (95% CI 4.74-59.65, p trend < 0.001) in the patients with folate levels in the lowest quintile compared with the highest quintile.

CONCLUSIONS

Our data showed a close association between WMHs and Hcy, folate especially in PD-PIGD patients. It can be speculated that higher Hcy and lower folate probably played important roles in the development of WMHs and motor heterogeneity in PD.

Neuroprotective effects of zafirlukast, piracetam and their combination on L-Methionine-induced vascular dementia in rats

Vascular dementia is considered a vascular cognitive impairment disease caused by neuronal degeneration in the brain. Several studies have supported the hypothesis that oxidative stress and endothelial dysfunction are the main pathogenic factors in vascular dementia. This current study aims to determine the possible neuroprotective effects of zafirlukast, piracetam and the combination of piracetam and zafirlukast on L-methionine-induced vascular dementia in rats. Male Wistar albino rats were divided into five groups. Group I was the normal control, and group II received L-methionine (1700 mg/kg, P.O.) for 32 days. The remaining groups received zafirlukast (20 mg/kg, P.O.), piracetam (600 mg/kg, P.O.) or their combination (zafirlukast 20 mg/kg + piracetam 600 mg/kg, P.O.) for 32 days after L-methionine administration. Afterwards, the cognitive and memory performances of the rats were investigated using the novel object recognition (NOR) test; rats were then sacrificed for histopathological and biochemical analyses. L-methionine-induced vascular dementia altered rats' behaviours and the brain contents of different neurotransmitters and acetylcholinesterase activity while increasing levels of oxidative stress and causing notable histopathological alterations in brain tissues. The treatment of vascular dementia with zafirlukast and the combination improved neurochemical, behavioural and histological alterations to a comparable level to those of piracetam. Thus, zafirlukast, piracetam and the combination of both drugs can be considered as potential therapeutic strategies for the treatment of vascular dementia induced by L-methionine. To the best of our knowledge, this study is the first to explore the neuroprotective effects of zafirlukast and piracetam on L-methionine-induced vascular 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.

Evaluating the link between Paraoxonase-1 levels and Alzheimer's disease development

At present, the etiopathogenesis of Alzheimer's disease (AD), the most common form of dementia, remains far to be fully deciphered. In the recent years, also the centrality of amyloid-β peptide in the pathogenesis of the neurodegenerative disease has been questioned and other hypotheses have been advanced. Notably, a common denominator of many of these theoretical models is represented by oxidative stress, which is widely proposed to play a role in the disease initiation and/or progression. Paraoxonase 1 (PON1) is a high-density lipoprotein (HDL)-associated enzyme that endows its carrier with multiple biological functions, including the ability to contrast oxidative damage to lipid components of lipoproteins and cells and protect from toxicity of specific organophosphorus pesticides. The peculiar multi-functionality nature of PON1 might be the key for explaining the vast epidemiological data showing a close association between low serum PON1 activity and risk of several diseases, including cardiovascular and neurodegenerative diseases, in particular AD. In this review, we discuss the possible link between PON1 with AD pathogenesis and we hypothesize eventual mechanistic pathways that could account from epidemiological observations. We also highlight the methodological issue limitation in PON1 studies that still impede to give a definitive and certain picture of its effective biological impact on human health including AD.

Testing a Combination of Markers of Systemic Redox Status as a Possible Tool for the Diagnosis of Late Onset Alzheimer's Disease

Background

Blood-based parameters reflecting systemic abnormalities associated with typical brain physiopathological hallmarks could be a satisfactory answer to the need of less costly/intrusive and widely available biomarkers for late onset Alzheimer's disease (LOAD). Cumulating evidence from ourselves and others suggests that systemic oxidative stress (OxS) is precociously associated with LOAD. On this basis, we aimed to identify a combination of markers of redox status that could aid the diagnosis of LOAD.

Methods

We reexamined and crossed previous data on 9 serum markers of OxS obtained in a cohort including n = 84 controls and n = 90 LOAD patients by multivariate logistic regression analyses.

Results

A multimarker panel was identified that included significantly increased (hydroperoxides and uric acid) and decreased (thiols, residual antioxidant power, and arylesterase activity) markers. The multivariate model yielded an area under receiver-operating characteristic curve (AUC) of 0.808 for the discrimination between controls and LOAD patients, with specificity and sensitivity of 64% and 79%, respectively.

Conclusions

This study identified a panel of serum markers that distinguish individuals with LOAD from cognitively healthy control subjects. Replication studies on a larger independent cohort are required to confirm and extend our data.

Ling-Yang-Gou-Teng-decoction prevents vascular dementia through inhibiting oxidative stress induced neurovascular coupling dysfunction

ETHNOPHARMACOLOGICAL RELEVANCE

Vascular dementia (VaD) is the common cognitive disorder derived mainly from lacunar stroke (LS). The oxidative stress induced neurovascular coupling (NVC) dysfunction involves in the pathogenesis of VaD. Currently, there is no specific drug for VaD. Ling-Yang-Gou-Teng -Decoction (LG), a well-known traditional Chinese formula, has been used for preventing VaD in clinic.

AIM OF THE STUDY

In this study, we aimed to investigate the underlying mechanism of LG on VaD in rats.

MATERIALS AND METHOD

VaD was replicated with autologous micro-thrombi against the background of hypercholesterolemia induced with high fatty diet. PTX (68.90 mg/kg/day), LG with three dosages (2.58, 8.14, 25.80 g/kg/day) was orally administrated to VaD rats, respectively. The NVC sensitivity was defined as the ratio of the microcirculative cerebral blood velocity (CBV) to the electroencephalograph (EEG) before and after penicillin stimulation. Behavioral performance, pathological changes of brain and oxidation related molecules were detected to assess the effects of LG on VaD.

RESULTS

LG exhibited beneficial effects on the VaD, which was demonstrated as improved exploratory, learning and memory abilities, relieved vascular or neural pathological changes in cerebral cortex or hippocampus. LG maintained NVC sensitivity, which was confirmed as significantly increased ΔCBV and the elevated ratio of ΔCBV/ΔqEEG. The underlying mechanisms of LG was associated with antioxidant effects, which was confirmed as significantly decreased nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2) expression, and increased superoxide dismutase 3 (SOD3) expression. LG also reduced iNOS, increased nNOS and eNOS expression to restore NO bioavailability.

CONCLUSIONS

The results suggested that LG prevented VaD may associate with inhibiting oxidative stress, protecting NO bioavailability, and then maintaining NVC sensitivity.

OxInflammation: From Subclinical Condition to Pathological Biomarker

Inflammation is a complex systemic response evolved to cope with cellular injury, either due to infectious agents or, in general, with sporadic events challenging tissue integrity and function. Researchers involved in different fields have the tendency to look at the inflammatory response with different angles, according to their specific interest. Established its complexity, one of the most evident features of the inflammatory response is the generation of a pro-oxidative environment due to the production of high fluxes of pro-oxidant species. This production begins locally, close to the sites of tissue damage or infection, but eventually becomes a chronic challenge for the organism, if the inflammatory response is not properly controlled. In this review, we focus on this specific aspect of chronic, low-level sub-clinical inflammatory response. We propose the term "OxInflammation" as a novel operative term describing a permanent pro-oxidative feature that interact, in a positive feed-back manner, to a not yet clinically detectable inflammatory process, leading in a long run (chronically) to a systemic/local damage, as a consequence of the cross talk between inflammatory, and oxidative stress mediators. Therefore, it could be useful to analyze inflammatory markers in pathologies where there is an alteration of the redox homeostasis, although an inflammatory status is not clinically evident.

Sex-Dependent Associations of Serum Uric Acid with Brain Function During Aging

Serum uric acid (SUA) is an abundant natural antioxidant capable of reducing cellular oxidation, a major cause of neurodegenerative disease. In line with this, SUA levels are lower in Alzheimer's disease; however, the association between SUA and cognition remains unclear. Results from studies examining the effects of SUA on cognition may be difficult to interpret in the context of normal versus pathological aging. This study examined sex-specific associations of baseline SUA with cognition during aging. Data from dementia-free participants initially aged 26-99 (N = 1,451) recruited for the Baltimore Longitudinal Study of Aging (BLSA), were used in the current analyses. SUA was assessed using blood samples collected during research visits. Cognition was measured using five composite scores (verbal memory, attention, executive function, language, and visuospatial ability). At the first study visit, compared with women, men were older, more likely to be White, had more years of education, higher baseline SUA levels, and higher cardiovascular risk scores. Higher baseline SUA was associated with attenuated declines in attention (β= 0.006; p = 0.03) and visuospatial abilities (β= 0.007; p = 0.01) in men. There was a trend to suggest higher baseline SUA in men was associated with attenuated declines in language, but this finding did not reach statistical significance (p = 0.09). There were no significant findings with SUA and cognition in women. In this sample of cognitively healthy, community-dwelling adults, we found that higher SUA levels at baseline were associated with attenuated declines in attention and visuospatial abilities in men. SUA was not associated with cognition or change in cognition over time in women.

Low-grade systemic inflammation is associated with functional disability in elderly people affected by dementia

The decline in basic and instrumental activities of daily living (BADLs and IADLs, respectively) is a well-established clinical hallmark of dementia. Growing evidence has shown that systemic subclinical inflammation may be related to functional impairment. We evaluated the possible association between low-grade systemic inflammation and functional disability in older individuals affected by dementia. We explored the association between high-sensitivity C-reactive protein (hs-CRP) levels and BADLs/IADLs in older individuals affected by late onset Alzheimer's disease (LOAD; n 110), "mixed" dementia (n 135), or mild cognitive impairment (MCI; n 258), and compared them with 75 normal Controls. Independent of age, gender, comorbidity, and other potential confounders, higher hs-CRP was significantly associated with poorer BADLs (loss ≥ 1 function) in people with LOAD (odds ratio [OR] 3.14, 95% confidence interval [CI], 1.33-7.33) and mixed dementia (OR 2.48, 95%CI 1.12-5.55), but not in those with MCI (OR 1.38, 95%CI 0.83-2.45) or Controls (OR 2.98, 95%CI 0.54-10.10). No association emerged between hs-CRP and IADLs in any of the sub-group. Our data suggest that systemic low-grade inflammation may contribute to functional disability in older patients with dementia.

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.

Serum Uric Acid and Its Association with Longitudinal Cognitive Change Among Urban Adults

Uric acid, a waste metabolite among humans, was linked to various cognitive outcomes. We describe sex and age-group specific associations of baseline serum uric acid (SUAbase) and significant change in SUA (ΔSUA: 1 versus 0 = decrease versus no change; 2 versus 0 = increase versus no change) with longitudinal annual rate of cognitive change among a large sample of urban adults. Data from the Healthy Aging in Neighborhoods of Diversity across the Life Span study, 2004-2009 (visit 1) and 2009-2013 (visit 2) were used. Of 3,720 adults selected at baseline (age range: 30-64 y), complete data were available for N = 1,487-1,602 with a mean repeat of 1.5-1.7 visits/participant. Cognitive test domains spanned attention, processing speed, learning/memory, executive function, visuo-spatial/visuo-construction ability, language/verbal, and global cognitive function. SUA was measured at both visits. Multiple mixed-effects regression analyses were conducted. In the total population, a higher SUAbase was associated with a faster annual rate of decline on a measure of visual memory/visuo-construction ability (the Benton Visual Retention Test) by γ= 0.07 with a standard error of 0.02, p < 0.001. Among older men, a significant increase in SUA was associated with slower decline on a test of attention/processing speed, namely Trailmaking test, Part A, measured in seconds to completion (γ= -6.91 ± 1.73, p < 0.001). In sum, a higher SUAbase was associated with faster cognitive decline over-time in a visual memory/visuo-construction ability test. ΔSUA had particular beneficial effects of an increasing ΔSUA on the domain of attention/processing speed among older men. More longitudinal studies are needed to examine cognitive domain-specific effects of over-time change in SUA within sex and age groups.

Relationship between Serum Uric Acid and Vascular Function and Structure Markers and Gender Difference in a Real-World Population of China-From Beijing Vascular Disease Patients Evaluation Study (BEST) Study

AIM

The study was done to establish the relationship between serum uric acid (UA) and vascular function and structure parameters including carotid femoral pulse wave velocity (CF-PWV), carotid radial pulse wave velocity (CR-PWV), cardio ankle vascular index (CAVI), ankle brachial index (ABI), and carotid intima-media thickness (CIMT), and the gender difference in a real-world population from China.

METHODS

A total of 979 subjects were enrolled (aged 60.86±11.03 years, male 416 and female 563). Value of UA was divided by 100 (UA/100) for analysis.

RESULTS

Body mass index (BMI), diastolic blood pressure (DBP), fasting plasma glucose (FPG), UA, and UA/100 were significantly higher in males compared with females (all p＜0.05); pulse pressure (PP), total cholesterol (TC), high density lipoprotein cholesterol (HDL-C), and low density lipoprotein cholesterol (LDL-C) were lower in males than females (all p＜0.05). All vascular parameters including CF-PWV, CR-PWV, CAVI, ABI, and CIMT were higher in males than females (all p＜0.05). Multiple linear regression analysis showed that UA/100 was independently positively linearly correlated with CAVI (B=0.143, p=0.001) and negatively correlated with ABI in the male population (B=－0.012, p=0.020). In people with higher UA, the risk of higher CF-PWV was 1.593 (p＜0.05).

CONCLUSIONS

1. All vascular parameters were higher in males than females. There was no gender difference in the relationship between UA and vascular markers except in ABI. 2. UA was independently linearly correlated with CAVI. 3. In people with higher UA level, the risk of higher CF-PWV increased. Therefore, higher UA may influence the vascular function mainly instead of vascular structure.

Presence of Anticardiolipin Antibodies in Patients with Dementia: A Systematic Review and Meta-Analysis

Growing evidences are supporting towards the involvement of antiphospholipid antibodies [aPLs e.g., lupus anticoagulant (LA), anticardiolipin (aCL) and anti-β2-glycoprotein I (anti-β2-GPI) antibodies] in various neurological manifestations including migraine, epilepsy and dementia in the presence or absence of autoimmune diseases such as antiphospholipid syndrome or systemic lupus erythematosus. The aim of this systematic review and meta-analysis was to assess the presence of aPLs in dementia patients without a diagnosis of any autoimmune disease. Electronic databases (e.g., PubMed, Web of Science, Scopus, ScienceDirect and Google Scholar) were searched without any year or language restrictions and based on the inclusion criteria, nine prospective case-control studies assessing only aCL were included involving 372 dementia patients and 337 healthy controls. No studies were found to assess the presence of both LA or anti-β2-GPI. The study-specific odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using random-effects model. We observed the prevalence of aCL in dementia was higher (32.80%) than that of controls (9.50%) e.g., 3.45 times higher risk of presenting with dementia than the controls, and significant presence of aCL antibodies was detected in dementia patients compared to controls (OR: 4.94, 95% CI: 2.66 - 9.16, p < 0.00001; I² = 32%, p = 0.16). Publication bias was not observed from Egger's (p = 0.081) and Begg's tests (p = 0.180). Based on the study quality assessment using modified Newcastle-Ottawa Scale for case-control studies, seven of nine studies were of high methodological quality scoring ≥ 7 (median value). In summary, aCL antibodies were significantly present in dementia patients suggesting that aCL antibodies are generated due to the autoimmune-derived effects of dementia or there might be a potential causative role of this autoantibody in dementia pathogenesis.

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.