A prospective study on blood Aβ levels and the cognitive function of patients with hemodialysis: a potential therapeutic strategy for Alzheimer’s disease

The impact of hemodiafiltration on cognitive function in patients with end-stage renal disease

Background

Patients with end-stage renal disease are more likely to suffer cognitive impairment. Cognitive impairment may lead to long-term severe adverse consequences.

Purpose

To explore the impact of different blood purification therapy on cerebral blood flow and cognitive functions in end-stage renal disease.

Materials and methods

This prospective study evaluated patients with end-stage renal disease undergoing blood purification from January to March 2021. Matched healthy controls were also included. Participants performed neurocognitive measurements, including a mini-mental state examination, logical memory test-20-minutes delayed, verbal fluency test, digit span test, clock drawing test, and stroop color and word test C. In addition, we tested plasma amyloid-β protein levels, serum Fe and hemoglobin levels in blood samples. Cerebral blood flow was measured using pulsed pseudocontinuous arterial spin labeling. We analyzed and compared the correlation between cognitive function, biomarkers, and cerebral blood flow between patients and healthy subjects, as well as between patients with different treatments.

Results

A total of 44 patients with end-stage renal disease (mean age, 57.39 years ± 8.63) and 46 healthy controls (mean age, 56.15 years ± 6.40) were recruited. Patients receive hemodialysis three times a week, and 27 of them have been replaced hemodialysis for hemodiafiltration twice a month. The cognitive function of patients was worse than healthy controls (P < 0.05). The patients showed higher plasma concentrations of amyloid-β40, amyloid-β42, Tau, and pTau181 than healthy controls (P < 0.05). The group receiving both hemodialysis and hemodiafiltration had higher cerebral blood flow signal values in the left caudate nucleus (chuster-level P < 0.05, voxel-level P < 0.001). They also exhibited better verbal fluency function than the hemodialysis-only group (P < 0.05).

Conclusion

Patients with the end-stage renal disease showed widespread cognitive declines. Cerebral blood flow generally decreased in the cerebral cortex and increased in subcortical regions. The hemodiafiltration may protect verbal function by increasing cerebral blood flow in the left caudate.

New, Fully Implantable Device for Selective Clearance of CSF-Target Molecules: Proof of Concept in a Murine Model of Alzheimer’s Disease

We have previously proposed a radical change in the current strategy to clear pathogenic proteins from the central nervous system (CNS) based on the cerebrospinal fluid (CSF)-sink therapeutic strategy, whereby pathogenic proteins can be removed directly from the CNS via CSF. To this aim, we designed and manufactured an implantable device for selective and continuous apheresis of CSF enabling, in combination with anti-amyloid-beta (Aβ) monoclonal antibodies (mAb), the clearance of Aβ from the CSF. Here, we provide the first proof of concept in the APP/PS1 mouse model of Alzheimer’s disease (AD). Devices were implanted in twenty-four mice (seventeen APP/PS1 and seven Wt) with low rates of complications. We confirmed that the apheresis module is permeable to the Aβ peptide and impermeable to mAb. Moreover, our results showed that continuous clearance of soluble Aβ from the CSF for a few weeks decreases cortical Aβ plaques. Thus, we conclude that this intervention is feasible and may provide important advantages in terms of safety and efficacy.

A Profile of Nanoparticle-Based Plasma Neurodegenerative Biomarkers for Cognitive Function Among Patients Undergoing Hemodialysis

Purpose

This study aimed to compare the plasma levels of nanoparticle-based neurodegenerative biomarkers between hemodialysis (HD) participants with grossly normal cognitive function and healthy controls.

Patients and Methods

A cohort of participants undergoing maintenance HD and healthy controls were enrolled for comparison between July and October 2021. The immunomagnetic reduction method was used to measure plasma neurodegenerative biomarkers Aβ_1-40, Aβ_1-42, tau protein, and neurofilament light chain (NfL). The clinical dementia rating (CDR) was used to evaluate cognitive function. A receiver operating characteristic curve was used to discriminate between HD participants and healthy controls.

Results

There were 52 and 18 participants in the HD and healthy control groups, respectively. The mean age of the HD participants was 62 years, and that of the healthy controls was 57 years. The mean HD vintage in the HD cohort was 11.8 years. HD participants demonstrated significantly higher plasma levels of Aβ_1-42, tau protein, Aβ_1-42 × tau, and NfL and Aβ_1-42/Aβ_1-40 ratio and significantly lower plasma Aβ_1-40 levels than healthy controls. The measured plasma biomarkers could not discriminate between CDR0 and CDR0.5 HD participants. The area under the curve of the study biomarkers to discriminate HD participants from healthy controls ranged from 0.987 (Aβ_1-42 × tau) to 0.889 (NfL).

Conclusion

The plasma levels of nanoparticle-based neurodegenerative biomarkers were higher in HD participants with grossly normal cognitive function than in healthy controls. These findings imply that neurodegenerative changes appear in HD participants. A profile of plasma neurodegenerative biomarkers could be considered a potential surrogate for evaluating long-term cognitive function in HD participants.

Effects of heparan sulfate from porcine mucosa on Aβ1-42-induced neurotoxicity in vitro and in vivo

Amyloid-β (Aβ) deposition and neurotoxicity play an important role in Alzheimer's disease (AD). Notably, the nonnegligible role of endogenous heparan sulfate (HS) in the release, uptake and misfolding of Aβ sheds light on the discovery of HS as an effective drug for AD. In this work, the effects of HS from porcine mucosa (PMHS) on Aβ_1-42-induced neurotoxicity were investigated both in vitro and in vivo. The in vitro AD model was established in SH-SY5Y via treatment with oligomeric Aβ_1-42, and the in vivo AD model was established by intracerebroventricular injection of Aβ_1-42 to KM mice. The results showed that in vitro, PMHS could ameliorate the inflammation and apoptosis response of SH-SY5Y cells induced by Aβ_1-42; in vivo, PMHS could not only improve the cognitive impairment induced by Aβ_1-42 but also inhibit neuroinflammation and apoptosis in the brain. Furthermore, PMHS lowered the levels of Aβ_1-42 in the peripheral circulation and brain by improving the phagocytosis function of neutrophils. This is the first report that PMHS enhances the phagocytosis function of neutrophils to alleviate Aβ-induced neurotoxicity. Moreover, our work verified the feasibility of peripheral Aβ clearance for improving neurotoxicity. Conclusively, we believe that PMHS could be developed into neuroprotective drugs for AD.

First-in-human study of blood amyloid β removal from early Alzheimer's disease patients with normal kidney function

INTRODUCTION

Amyloid β (Aβ) is a brain protein that causes Alzheimer's disease (AD). This study aimed to verify whether hemadsorption using a hexadecyl-alkylated cellulose bead (HexDC) column removes blood Aβ and brain Aβ accumulation in mild cognitive impairment/mild AD cases with normal kidney function.

METHODS

Two patients with positive Aβ on brain imaging underwent HexDC hemadsorption weekly for 6 months.

RESULTS

The Aβ removal efficiency of HexDC was 87-99%. Aβ_1-40 /Aβ_1-42 influx into the blood in one session was 596/56 ng and 489/48 ng for Case A and Case B, respectively. Although brain Aβ accumulation did not clearly change after six months of hemadsorption, cognitive functions measured by the two tests were maintained or slightly improved.

CONCLUSION

Blood Aβ removal was performed in two early AD patients with normal kidney function without adverse events, and it slightly improved or maintained cognitive function. This article is protected by copyright. All rights reserved.

Cerebrospinal Fluid (CSF) Exchange Therapy with Artificial CSF Enriched with Mesenchymal Stem Cell Secretions Ameliorates Cognitive Deficits and Brain Pathology in Alzheimer's Disease Mice

BACKGROUND

The high complexity of neurodegenerative diseases, including Alzheimer's disease (AD), and the lack of effective treatments point to the need for a broader therapeutic approach to target multiple components involved in the disease pathogenesis.

OBJECTIVE

To test the efficacy of 'cerebrospinal fluid (CSF) exchange therapy' in AD-mice. This novel therapeutic approach we recently proposed is based on the exchange of the endogenous pathogenic CSF with a new and healthy one by drainage of the endogenous CSF and its continuous replacement with artificial CSF (aCSF) enriched with secretions from human mesenchymal stem cells (MSCs).

METHODS

We treated AD-mice (amyloid-beta injected) with MSC secretions-enriched-aCSF using an intracerebroventricular CSF exchange procedure. Cognitive and histological analysis were performed.

RESULTS

We show that the MSC secretions enriched CSF exchange therapy improved cognitive performance, paralleled with increased neuronal counts (NeuN positive cells), reduced astrocytic burden (GFAP positive cells), and increased cell proliferation and neurogenesis (Ki67 positive cells and DCX positive cells) in the hippocampus. This beneficial effect was noted on days 5-10 following 3-consecutive daily exchange treatments (3 hours a day). A stronger effect was noted using a more prolonged CSF exchange protocol (3-consecutive daily exchange treatments with 3 additional treatments twice weekly), with cognitive follow-up performed as early as 2-3 days after treatment. Some increase in hippocampal cell proliferation, but no change in the other histological parameters, was noticed when performing CSF exchange therapy using unenriched aCSF relative to untreated AD-mice, yet smaller than with the enriched aCSF treatment.

CONCLUSION

These findings point to the therapeutic potential of the CSF exchange therapy using MSC secretions-enriched aCSF in AD, and might be applied to other neurodegenerative and dementia diseases.

Aβ Influx into the Blood Evoked by Different Blood Aβ Removal Systems: A Potential Therapy for Alzheimer's Disease

PURPOSE

Amyloid-β (Aβ) is a brain protein that causes Alzheimer's disease. We have revealed that extracorporeal blood Aβ-removal systems evoked a large Aβ influx into the blood. This study investigated the system that is more effective in evoking Aβ influx.

METHODS

Aβ removal activities were compared between hexadecyl-alkylated cellulose beads (HexDC) and fragments of polysulfone hollow fibers (PSf-HFs) in mini-columns to eliminate the filtration effect. Then, adsorptive filtration systems were adapted for PSf hemodialyzers to enhance Aβ adsorption on micropores in the wall of hollow fibers. Plasma Aβ concentrations of patients with renal failure were analyzed during treatment with PSf hemodialyzers alone for 8 h or tandemly connected HexDC and PSf hemodialyzers for 4 h.

RESULTS

In the in vitro study, Aβ removal efficiency for HexDC was approximately 100% during the 60 min treatment, whereas the removal efficiency for PSf-HF fragments gradually decreased. However, PSf hemodialyzer in adsorptive filtration systems removed Aβs comparably or more than HexDC. Aβ influx into the blood increases time-dependently. Concomitant use of HexDC and PSf hemodialyzer evoked a larger Aβ_1-40 influx than that of PSf hemodialyzer alone. However, Aβ_1-42 influx by PSf hemodialyzer alone was similar to or a little larger than influx by the combined system. Both systems evoked almost doubled Aβ influx than estimated Aβs existing in the normal brain during the 4 h treatment.

CONCLUSION

PSf hemodialyzer alone for a longer period and concomitant use of HexDC and PSf hemodialyzer for a shorter time effectively evoked a larger Aβ influx. To evoke Aβ_1-42 influx, PSf hemodialyzer alone was effective enough. These findings of devices and treatment time may lead to optimal clinical settings for therapy and prevention of Alzheimer's disease.

The Alzheimer's Disease Amyloid-Beta Hypothesis in Cardiovascular Aging and Disease: JACC Focus Seminar

Aging-related cellular and molecular processes including low-grade inflammation are major players in the pathogenesis of cardiovascular disease (CVD) and Alzheimer's disease (AD). Epidemiological studies report an independent interaction between the development of dementia and the incidence of CVD in several populations, suggesting the presence of overlapping molecular mechanisms. Accumulating experimental and clinical evidence suggests that amyloid-beta (Aβ) peptides may function as a link among aging, CVD, and AD. Aging-related vascular and cardiac deposition of Αβ induces tissue inflammation and organ dysfunction, both important components of the Alzheimer's disease amyloid hypothesis. In this review, the authors describe the determinants of Aβ metabolism, summarize the effects of Aβ on atherothrombosis and cardiac dysfunction, discuss the clinical value of Αβ1-40 in CVD prognosis and patient risk stratification, and present the therapeutic interventions that may alter Aβ metabolism in humans.

Influx of Tau and Amyloid-β Proteins into the Blood During Hemodialysis as a Therapeutic Extracorporeal Blood Amyloid-β Removal System for Alzheimer's Disease

The accumulation of amyloid-β protein (Aβ) and tau in the brain is a major pathological change related to Alzheimer's disease. We have continued to develop Extracorporeal Blood Aβ Removal Systems (E-BARS) as a method for enhancing Aβ clearance from the brain. Our previous report revealed that dialyzers effectively remove blood Aβ and evoke large Aβ influxes into the blood, resulting in a decrease in brain Aβ accumulation after initiating hemodialysis, and that patients who underwent hemodialysis had lower brain Aβ accumulation than those who did not. Here, plasma total tau concentrations from 30 patients undergoing hemodialysis were measured using an ultrasensitive immunoassay and compared to those from 11 age-matched controls. Plasma total tau concentrations were higher in patients with renal failure regardless of whether they underwent hemodialysis, suggesting the involvement of the kidneys in tau degradation and excretion. Hemodialyzers effectively removed blood Aβ but not extracorporeal blood tau. The influx of tau into the blood was observed at around the 1 h period during hemodialysis sessions. However, the influx amount of tau was far smaller than that of Aβ. Furthermore, histopathological analysis revealed similar, not significantly less, cerebral cortex phosphorylated tau accumulation between the 17 patients who underwent hemodialysis and the 16 age-matched subjects who did not, although both groups showed sparse accumulation. These findings suggest that hemodialysis may induce both tau and Aβ migration into the blood. However, as a therapeutic strategy for Alzheimer's disease, it may only be effective for removing Aβ from the brain.

Renal Contributions in the Pathophysiology and Neuropathological Substrates Shared by Chronic Kidney Disease and Alzheimer's Disease

Chronic kidney disease and Alzheimer’s disease are chronic conditions highly prevalent in elderly communities and societies, and a diagnosis of them is devastating and life changing. Demanding therapies and changes, such as non-compliance, cognitive impairment, and non-cognitive anomalies, may lead to supplementary symptoms and subsequent worsening of well-being and quality of life, impacting the socio-economic status of both patient and family. In recent decades, additional hypotheses have attempted to clarify the connection between these two diseases, multifactorial in their nature, but even so, the mechanisms behind this link are still elusive. In this paper, we sought to highlight the current understanding of the mechanisms for cognitive decline in patients with these concurrent pathologies and provide insight into the relationship between markers related to these disease entities and whether the potential biomarkers for renal function may be used for the diagnosis of Alzheimer’s disease. Exploring detailed knowledge of etiologies, heterogeneity of risk factors, and neuropathological processes associated with these conditions opens opportunities for the development of new therapies and biomarkers to delay or slow their progression and validation of whether the setting of chronic kidney disease could be a potential determinant for cognitive damage in Alzheimer’s disease.

Alzheimer's disease; a review of the pathophysiological basis and therapeutic interventions

Alzheimer's disease (AD) is a neurodegenerative disorder and is identified as the most common cause for dementia. Despite huge global economic burden and the impact on the close family of the patients, there is no definitive cure and thus, improved treatment methods are of need. While memory and cognition are severely affected in AD, exact etiology is yet unknown. The β-Amyloid plaque formation and aggregation hypothesis is among the well-known hypotheses used to explain disease pathogenesis. Currently there are five Food and Drug Administration (FDA) approved drugs as treatment options. All these drugs are used for symptomatic treatment of AD. Thus, disease modifying therapies which can directly address the pathological changes in AD, are needed. Such therapies could be designed based on inhibiting key steps of pathogenesis. Currently there are novel AD drug candidates with various therapeutic mechanisms, undergoing different stages of drug development. Extensive research is being done globally to broaden understanding of the exact mechanisms involved in AD and to develop therapeutic agents that can successfully hinder the occurrence and progression of the disease. In this review, a comprehensive approach to understanding AD and suggestions to be considered in the development of therapeutics for it are presented.

Removal of Aβ Oligomers from the Blood: A Potential Therapeutic System for Alzheimer's Disease

PURPOSE

Amyloid-β protein (Aβ) is one of the causative proteins of Alzheimer's disease. We have been developing extracorporeal blood Aβ-removal systems as a method for enhancing Aβ clearance from the brain. We reported previously that medical adsorbents and hemodialyzers removed Aβ monomers from peripheral blood, which was associated with influx of Aβ monomers from the brain into the bloodstream. Our intent here was to develop a method to promote clearance of Aβ oligomers and to provide an estimate of the molecular size of intact Aβ oligomers in plasma.

METHODS

Two hollow-fiber devices with different pore sizes (Membranes A and B) were evaluated as removers of Aβ oligomers with human plasma in vitro. The concomitant removal of Aβ oligomers and monomers was investigated by using Membrane B and hexadecyl alkylated cellulose beads or polysulfone hemodialyzers. Double-filtration plasmapheresis with Membrane A was investigated as an approach for the removal of plasma Aβ oligomers in humans.

RESULTS

Aβ oligomers were effectively removed by both Membranes A and B. The increase of Aβ oligomers in plasma was observed just after the removal of plasma Aβ oligomers in humans. The intact molecular size of major Aβ oligomers in the plasma was estimated to be larger than albumin at approximately 60 kDa or more. Additionally, the concomitant removal of Aβ monomers and oligomers evoked dissociation of larger Aβ oligomers into smaller ones and monomers.

CONCLUSION

Aβ oligomers were cleared from plasma both in vitro and in human subjects by using hollow-fiber membranes with large pores, indicating that their intact sizes were mostly larger than 60 kDa. Aβ oligomers in peripheral circulation were increased after some clearances in human. Further investigation will determine whether the Aβ oligomers detected in circulation after clearance were via influx from the brain.

Relationship of amyloid-β1-42 in blood and brain amyloid: Ginkgo Evaluation of Memory Study

A blood test that predicts the extent of amyloid plaques in the brain and risk of Alzheimer's disease would have important benefits for the early identification of higher risk of dementia and Alzheimer's disease and the evaluation of new preventative therapies. The goal of this study was to determine whether plasma levels of amyloid-β1-42, 1-40 and the amyloid-β1-42/1-40 ratio among participants in the Pittsburgh centre of the Ginkgo Evaluation of Memory Study were related to the extent of brain fibrillar amyloid plaques measured in 2009 using Pittsburgh compound-B PET imaging, hippocampal volume, cortical thickness in the temporal lobe and white matter lesions. There were 194 participants who had Pittsburgh compound-B measurements in 2009 with the mean age of 85 years; 96% were white and 60% men. Pittsburgh compound-B positivity was defined as a standardized uptake value ratio of ≥1.57. Amyloid-β in blood was measured using a sandwich enzyme-linked immunosorbent assay developed by Eli Lilly and modified at the University of Vermont. All participants were nondemented as of 2008 at the time of study close out. The study sample included 160 with blood samples drawn in 2000-02 and 133 from 2009 and also had brain amyloid measured in 2009. All blood samples were analysed at the same time in 2009. Plasma amyloid-β1-42 was inversely related to the percent Pittsburgh compound-B positive (standardized uptake value ratio ≥1.57), β -0.04, P = 0.005. Practically all participants who were apolipoprotein-E4 positive at older ages were also Pittsburgh compound-B positive for fibrillar amyloid. Among apolipoprotein-E4-negative participants, quartiles of amyloid-β1-42 were inversely related to Pittsburgh compound-B positivity. In multiple regression models, plasma amyloid-β1-42 measured in 2000-02 or 2009 were significantly and inversely related to Pittsburgh compound-B positivity as was the amyloid-β1-42/1-40 ratio. There was a 4-fold increase in the odds ratio for the presence of Pittsburgh compound-B positivity in the brain in 2009 for the first quartile of amyloid-β1-42 as compared with the fourth quartile in the multiple logistic model. This is one of the first longitudinal studies to evaluate the relationship between amyloid-β1-42 in the blood and the extent of brain amyloid deposition measured by PET imaging using Pittsburgh compound-B. Our findings showed that remote and recent low plasma amyloid-β1-42 levels were inversely associated with brain amyloid deposition in cognitively normal individuals. However, changes in plasma amyloid-β1-42 over time (8 years) were small and not related to the amount of Pittsburgh compound-B.

Albumin Exchange in Alzheimer's Disease: Might CSF Be an Alternative Route to Plasma?

Amyloid β (Aβ) in brain parenchyma is thought to play a central role in the pathogenesis of Alzheimer's disease (AD). Aβ is transported from the brain to the plasma via complex transport mechanisms at the blood-brain barrier (BBB). About 90–95% of plasma Aβ may be bound to albumin. Replacement of serum albumin in plasma has been proposed as a promising therapy for AD. However, the efficacy of this approach may be compromised by altered BBB Aβ receptors in AD, as well as multiple pools of Aβ from other organs in exchange with plasma Aβ, competing for albumin binding sites. The flow of interstitial fluid (ISF) into cerebrospinal fluid (CSF) is another major route of Aβ clearance. Though the concentration of albumin in CSF is much lower than in plasma, the mixing of CSF with ISF is not impeded by a highly selective barrier and, hence, Aβ in the two pools is in more direct exchange. Furthermore, unlike in plasma, Aβ in CSF is not in direct exchange with multiple organ sources of Aβ. Here we consider albumin replacement in CSF as an alternative method for therapeutic brain Aβ removal and describe the possible advantages and rationale supporting this hypothesis.

Blood amyloid levels and risk of dementia in the Ginkgo Evaluation of Memory Study (GEMS): A longitudinal analysis

INTRODUCTION

Both high or low plasma amyloid levels have been associated with risk of dementia in nondemented subjects.

METHODS

We examined baseline plasma β-amyloid (Aβ) levels in relationship to incident dementia during a period of 8.5 years in 2840 subjects age >75 years; 2381 were cognitively normal (CN) and 450 mild cognitive impairment.

RESULTS

Increased plasma Aβ1-40 and Aβ1-42 levels were associated with gender (women), age, low education, creatinine levels, history of stroke, and hypertension. CN participants who developed dementia had lower levels of Aβ1-42 and Aβ1-42/Aβ1-40 ratio compared with those who did not. Aβ levels did not predict dementia in mild cognitive impairment participants.

DISCUSSION

There was an inverse association between Aβ1-42 and Aβ1-42/Aβ1-40 ratio to risk of dementia in CN participants. Cerebral and cardiovascular disease and renal function are important determinants of increased Aβ levels and must be considered in evaluations of relationship of plasma Aβ and subsequent risk of dementia.

Mild cognitive impairment in maintenance hemodialysis patients: a cross-sectional survey and cohort study

Introduction

Few studies focused on mild cognitive impairment (MCI) in maintenance hemodialysis (MHD) patients. This study was conducted to survey the prevalence, the potent risk factors of MCI in MHD patients, and further observe the progress of MCI in a period of 6 months.

Methodology

Mini-Mental State Examination, and Montreal Cognitive Assessment were used to assess cognitive condition. MHD patients were enrolled from The First Affiliated Hospital of Nanjing Medical University, who had a stable hemodialysis history for more than 3 months.

Results

Sixty-four MHD patients and 54 general subjects were finally included. The average age of both groups was more than 60 years. The prevalence of MCI in the MHD group was significantly higher than that in general population (60.9% vs 29.6%, P<0.05). Spearman correlation analysis indicated that MCI was related to age, comorbidities, education years, uric acid, serum albumin, and blood pressure. The prevalence and severity of MCI in the MHD group remained unchanged during the 6 months (prevalence: 59.5%–66.6%, MoCA scores: 22.9–22.5).

Conclusion

MHD patients sustain a fairly high prevalence of MCI. Multiple risk factors influence the incidence and progression of MCI in MHD patients. More attention should be paid to this special population.

Correlates of cognitive impairment in patients with chronic kidney failure on haemodialysis: Systematic review and meta-analysis

AIM

To review and identify correlates of cognitive impairment in patients with chronic kidney failure (CKF) on haemodialysis.

BACKGROUND

The literature is consistent with regard to the high prevalence of cognitive impairment among patients with CKF on haemodialysis and its dependence on multidimensional risk factors.

DESIGN

Systematic review and meta-analysis based on Cochrane Handbook and PRISMA.

DATA SOURCES

Electronic searches of the MEDLINE, EMBASE, Cochrane Library databases and major Korean databases were used. Only original research that assessed correlates of cognitive impairment in patients with CKF on haemodialysis and published between 2004-2016 in English or Korean were included.

REVIEW METHODS

Studies were selected according to the PICOS: Population (chronic kidney failure patients with cognitive impairment on haemodialysis); Intervention (not applicable); Comparison (healthy controls or patients with chronic kidney failure on haemodialysis without cognitive impairment); Outcome (cognitive impairment); and Study design (primarily nonexperimental correlational studies and studies with experimental, quasi-experimental, or pre-post cohort designs). Q-test and I² index were used to examine study homogeneity.

RESULTS

A total of 39 studies were finally included. Age, gender, stroke history, difficulties in activities of daily life, haemoglobin levels, pain, sleep difficulties, and depression were found to be significant correlates of cognitive impairment.

CONCLUSIONS

Nurses should be aware that the risk of cognitive impairment in patients with CKF on haemodialysis can be significantly higher for elders, women and in patients with a stroke, greater difficulties in activities of daily living, lower haemoglobin concentrations, higher pain levels, sleep difficulties, or depression.

Estimated Glomerular Filtration Rate is not Associated with Alzheimer's Disease in a Northern Ireland Cohort

BACKGROUND

Alzheimer's disease (AD) prevalence is increasing globally and typically progresses for several years prior to clinical presentation of dementia. Renal dysfunction and vascular disease have been reported in association with dementia in several cross-sectional and longitudinal studies, and may contribute to AD risk. Experimental and observational studies suggest amyloid-β (Aβ) clearance may be impaired in chronic kidney disease (CKD) indicating a mechanism for increased AD risk.

OBJECTIVE

The objective of this study was to compare estimated glomerular filtration rate (eGFR) between individuals with AD and cognitively intact controls, controlling for potential confounding factors.

METHODS

A cross-sectional, case-control study was carried out in 317 cognitively normal participants and 253 cases with a clinical diagnosis of AD in a UK tertiary care dementia clinic. Associations were considered using logistic regression adjusting for confounding variables (age, APOEɛ4 genotype, systolic blood pressure, education (left school at 14), and smoking status).

RESULTS

AD cases were older than cognitively intact controls, had lower MMSE scores, were more likely to have at least one APOEɛ4 allele, had higher rates of smoking, were more likely to be taking aspirin and/or clopidogrel, and had lower blood pressure. We found no significant association between eGFR and AD both before and following adjustment for appropriate confounders.

CONCLUSION

This study failed to find an association between eGFR and AD in a cross-sectional sample study of elderly white individuals.

Targeting Beta-Amyloid at the CSF: A New Therapeutic Strategy in Alzheimer's Disease

Although immunotherapies against the amyloid-β (Aβ) peptide tried so date failed to prove sufficient clinical benefit, Aβ still remains the main target in Alzheimer’s disease (AD). This article aims to show the rationale of a new therapeutic strategy: clearing Aβ from the CSF continuously (the “CSF-sink” therapeutic strategy). First, we describe the physiologic mechanisms of Aβ clearance and the resulting AD pathology when these mechanisms are altered. Then, we review the experiences with peripheral Aβ-immunotherapy and discuss the related hypothesis of the mechanism of action of “peripheral sink.” We also present Aβ-immunotherapies acting on the CNS directly. Finally, we introduce alternative methods of removing Aβ including the “CSF-sink” therapeutic strategy. As soluble peptides are in constant equilibrium between the ISF and the CSF, altering the levels of Aβ oligomers in the CSF would also alter the levels of such proteins in the brain parenchyma. We conclude that interventions based in a “CSF-sink” of Aβ will probably produce a steady clearance of Aβ in the ISF and therefore it may represent a new therapeutic strategy in AD.

Removal of blood amyloid-β with hemodialysis reduced brain amyloid-β, confirmed by brain imaging: a case report

The accumulation of amyloid-β protein (Aβ) in the brain signifies a major pathological change of Alzheimer's disease (AD). Extracorporeal blood Aβ removal system (E-BARS) has been under development as a tool for enhancing the clearance of Aβ from the brain. Previously, we revealed that dialyzers remove blood Aβs effectively, evoking substantial Aβ influx into the blood during hemodialysis sessions as one form of blood Aβ removal by E-BARS, and that postmortem brains of hemodialysis patients exhibited lower Aβ accumulation. Here, we present a case report of a 77-year-old male patient with end-stage renal failure whose Aβ accumulation in the brain declined by initiating and continuing hemodialysis for 6 months. This report suggests that blood Aβ removal by E-BARS could be an effective therapeutic method for AD.

Adsorptive filtration systems for effective removal of blood amyloid β: a potential therapy for Alzheimer's disease

Accumulation of amyloid-β protein (Aβ) in the brain causes cognitive impairment in Alzheimer's disease. We hypothesized that an extracorporeal system that rapidly removed Aβ from the blood may accelerate Aβ drainage from the brain. We previously reported that dialyzers remove blood Aβs effectively, mainly by adsorption on the inner surfaces of the hollow fibers, resulting in lower Aβ accumulation in the brains of patients undergoing hemodialysis than the controls without hemodialysis. The aim of the present study was to create a more convenient and effective blood Aβ removal system using adsorptive filtration, in which the filtrate returned to the body. Filtration from inside to outside of the fibers may enhance the adsorption of plasma Aβs on the surface of micropores inside the hollow fiber walls. Hence, pool solutions of 4 ng/mL synthetic Aβ_1-40 and Aβ_1-42 peptides (300 mL) or human plasma (1000 mL of 250-346 pg/mL Aβ_1-40 and 30-48 pg/mL Aβ_1-42) were circulated through polysulfone dialyzers at a flow rate of 50 mL/min to evaluate an adsorptive filtration system. The rates of Aβ reduction from the pool solutions significantly increased along with the filtration rates. A filtration rate of > 1 mL/min, preferably 5-10 mL/min resulted in an 80-100% reduction of Aβs within 30 min of circulation. The rates of Aβs passing through the membrane walls were maintained around 0% for plasma Aβs during circulation. Thus, our adsorptive filtration systems may be useful for removing blood Aβs for patients with Alzheimer's disease.

Peritoneal dialysis reduces amyloid-beta plasma levels in humans and attenuates Alzheimer-associated phenotypes in an APP/PS1 mouse model

Clearance of amyloid-beta (Aβ) from the brain is an important therapeutic strategy for Alzheimer's disease (AD). Current studies mainly focus on the central approach of Aβ clearance by introducing therapeutic agents into the brain. In a previous study, we found that peripheral tissues and organs play important roles in clearing brain-derived Aβ, suggesting that the peripheral approach of removing Aβ from the blood may also be effective for AD therapy. Here, we investigated whether peritoneal dialysis, a clinically available therapeutic method for chronic kidney disease (CKD), reduces brain Aβ burden and attenuates AD-type pathologies and cognitive impairments. Thirty patients with newly diagnosed CKD were enrolled. The plasma Aβ concentrations of the patients were measured before and after peritoneal dialysis. APP/PS1 mice were subjected to peritoneal dialysis once a day for 1 month from 6 months of age (prevention study) or 9 months of age (treatment study). The Aβ in the interstitial fluid (ISF) was collected using microdialysis. Behavioural performance, long-term potentiation (LTP), Aβ burden and other AD-type pathologies were measured after 1 month of peritoneal dialysis. Peritoneal dialysis significantly reduced plasma Aβ levels in both CKD patients and APP/PS1 mice. Aβ levels in the brain ISF of APP/PS1 mice immediately decreased after reduction of Aβ in the blood during peritoneal dialysis. In both prevention and treatment studies, peritoneal dialysis substantially reduced Aβ deposition, attenuated other AD-type pathologies, including Tau hyperphosphorylation, glial activation, neuroinflammation, neuronal loss, and synaptic dysfunction, and rescued the behavioural deficits of APPswe/PS1 mice. Importantly, the Aβ phagocytosis function of microglia was enhanced in APP/PS1 mice after peritoneal dialysis. Our study suggests that peritoneal dialysis is a promising therapeutic method for AD, and Aβ clearance using a peripheral approach could be a desirable therapeutic strategy for AD.

Patients that have Undergone Hemodialysis Exhibit Lower Amyloid Deposition in the Brain: Evidence Supporting a Therapeutic Strategy for Alzheimer's Disease by Removal of Blood Amyloid

As a proof of concept that removal of blood amyloid-β (Aβ) can reduce Aβ deposition in the brains of patients with Alzheimer's disease, cortices of patients who had undergone hemodialysis (HD), which removes Aβ from the blood, were histochemically analyzed; postmortem brain sections were stained with anti-Aβ antibodies. Brains from patients who had undergone HD had significantly fewer senile plaques than those of patient who had not undergone HD. This significant difference was also confirmed by silver staining. Our findings suggest that removal of blood Aβ by hemodialysis results in lower accumulation of Aβ in the brain.

Toward the treatment for Alzheimer's disease: adsorption is primary mechanism of removing amyloid β protein with hollow-fiber dialyzers of the suitable materials, polysulfone and polymethyl methacrylate

The accumulation of amyloid β protein (Aβ) in the brain reflects cognitive impairment in Alzheimer's disease. We hypothesized that the rapid removal of Aβ from the blood by an extracorporeal system may act as a peripheral Aβ sink from the brain. The present study aimed to determine the optimal materials and modality for Aβ removal by hemodialyzers. In a batch analysis, hollow-fiber fragments of polysulfone (PSf) and polymethyl methacrylate (PMMA) showed greater removal efficiency of Aβ than did other materials, such as cellulose-triacetates and ethylene-vinyl alcohol copolymer (PSf:PMMA at 30 min, 98.6 ± 2.4 %:97.8 ± 0.4 % for Aβ1-40 and 96.6 ± 0.3 %:99.0 ± 1.0 % for Aβ1-42). In a modality study, the Aβ solution was applied to PSf dialyzers and circulated in the dialysis and Air-filled adsorption-mode (i.e., the outer space of the hollow fibers was filled with air) or phosphate-buffered saline (PBS)-filled adsorption modes. The Aβ1-40 removal efficiency of the pre/post dialyzer in the Air-filled adsorption-mode was the highest (62.4 ± 12.6 %, p = 0.007). In a flow rate study in the Air-filled adsorption-mode, 200 mL/min showed the highest Aβ1-40 reduction rate of pool solution (97.3 ± 0.8 % at 15 min) compared with 20 mL/min (p = 0.00001) and 50 mL/min (p = 0.00382). PMMA dialyzers showed similar high reduction rates. Thus, the optimal modality for Aβ removal was the adsorption-mode with PSf or PMMA hollow fibers at around 50 mL/min flow rate, which seems to be suitable for clinical use.