Aβ Concentrations Research Articles

Misfolding and Aggregation of Amyloid Proteins at Physiologically Relevant Concentrations at the Liquid-Membrane Interface

The aggregation of amyloid beta (Aβ) is a self-assembly process that results in the production of fibrillar structures along with neurotoxic aggregates. However, in the vast majority studies in vitro the required Aβ concentrations is several orders higher of the physiological relevant concentrations of Aβ; no aggregation is observed at physiological low nanomolar range of Aβ. This suggests that the assembly of Aβ in aggregates in vivo utilizes pathways different from those used in experiments in vitro.

Cerebrospinal fluid biomarkers of glial and axonal injury in cervical spondylotic myelopathy.

Degenerative cervical spondylotic myelopathy (CSM) is a major cause of spinal cord dysfunction with an unpredictable prognosis. Βiomarkers reflecting pathophysiological processes in CSM have been insufficiently investigated. It was hypothesized that preoperative cerebrospinal fluid (CSF) biomarker levels are altered in patients with CSM and correlate with neurological status and outcome. CSF biomarkers from patients with CSM and controls were analyzed with immunoassays. Spinal cord changes were evaluated with MRI. The American Spinal Cord Injury Association Impairment Scale, the Japanese Orthopaedic Association Cervical Myelopathy Evaluation Questionnaire (JOACMEQ), and the EQ-5D questionnaire were applied prior to and 3 months after surgery. A p value < 0.05 was considered statistically significant. Twenty consecutive CSM patients with a mean age of 67.7 ± 13 years and 63 controls with a mean age of 65.2 ± 14.5 years (p > 0.05) were included in the study. In the CSM subjects, CSF neurofilament light subunit (NF-L) and glial fibrillary acidic protein (GFAP) concentrations were higher (p < 0.05), whereas fatty acid-binding protein 3 (FABP3), soluble amyloid precursor proteins (sAPPα and sAPPβ), and amyloid β (Aβ) peptide (Aβ38, Aβ40, and Aβ42) concentrations were lower than in controls (p < 0.05). Aβ peptide levels correlated positively with symptom duration. Preoperative JOACMEQ lower extremity function and CSF NF-L levels correlated positively, and the JOACMEQ bladder function correlated negatively with sAPPα and sAPPβ (p < 0.05). CSF NF-L and FABP3 levels were higher in patients with improved outcome (EQ-5D visual analog scale difference > 20). CSF biomarkers of glial and axonal damage, inflammation, and synaptic changes are altered in symptomatic CSM patients, indicating that axonal injury, astroglial activation, and Aβ dysmetabolism may be present in these individuals. These findings reflect CSM pathophysiology and may aid in prognostication. However, future studies including larger patient cohorts, postoperative biomarker data and imaging, and longer follow-up times are required to validate the present findings.

Cholesterol in Membranes Facilitates Aggregation of Amyloid β Protein at Physiologically Relevant Concentrations.

The formation of amyloid β (1-42) (Aβ42) oligomers is considered to be a critical step in the development of Alzheimer's disease (AD). However, the mechanism underlying this process at physiologically low concentrations of Aβ42 remains unclear. We have previously shown that oligomers assemble at such low Aβ42 monomer concentrations in vitro on phospholipid membranes. We hypothesized that membrane composition is the factor controlling the aggregation process. Accumulation of cholesterol in membranes is associated with AD development, suggesting that insertion of cholesterol into membranes may initiate the Aβ42 aggregation, regardless of a low monomer concentration. We used atomic force microscopy (AFM) to test the hypothesis and directly visualize the aggregation process of Aβ42 on the surface of a lipid bilayer depending on the cholesterol presence. Time-lapse AFM imaging unambiguously demonstrates that cholesterol in the lipid bilayer significantly enhances the aggregation process of Aβ42 at nanomolar monomer concentration. Quantitative analysis of the AFM data shows that both the number of Aβ42 oligomers and their sizes grow when cholesterol is present. Importantly, the aggregation process is dynamic, so the aggregates assembled on the membrane can dissociate from the bilayer surface into the bulk solution. Computational modeling demonstrated that the lipid bilayer containing cholesterol had an elevated affinity to Aβ42. Moreover, monomers adopted the aggregation-prone conformations present in amyloid fibrils. The results lead to the model for the on-surface aggregation process in which the self-assembly of Aβ oligomers is controlled by the lipid composition of cellular membranes.

Quantification of Amyloid-β in Plasma by Simple and Highly Sensitive Immunoaffinity Enrichment and LC-MS/MS Assay.

Numerous immunoassays have been developed to quantify amyloid β1-40 (Aβ40) and amyloid β1-42 (Aβ42). Nevertheless, given the low concentration of Aβ and the high levels of interfering factors in plasma, quantification of plasma Aβ is still challenging. To overcome the problems related to the specificity of Aβ immunoassays, this study aimed to develop an immunoaffinity enrichment and LC-MS/MS (IA-MS) assay. We developed an IA-MS assay using antibody-labeled magnetic beads for purification and LC-MS/MS for Aβ quantification. To avoid the loss of Aβ due to aggregation in acidic buffer, we used alkaline elution buffer for immunoaffinity enrichment. The concentrations of the Aβs in plasma samples were measured, and the correlation between the plasma and cerebrospinal fluid (CSF) Aβ42/Aβ40 ratio was also evaluated. The intensities of the Aβ mass peaks were significantly higher with the alkaline elution buffer than with the acidic elution buffer (Aβ40: 3.6-fold, Aβ42: 5.4-fold). This assay exhibited high reproducibility (intra-assay and inter-assay precision, %CV <15), and the working ranges of Aβ40 and Aβ42 were determined to be 21.7 to 692.8 pg/mL and 5.6 to 180.6 pg/mL, respectively. The concentrations of Aβ40 and Aβ42 in plasma were measured by IA-MS, and the plasma Aβ42/Aβ40 ratio was correlated with the CSF Aβ42/Aβ40 ratio (rs = 0.439, P < 0.01). The IA-MS assay has sufficient analytic performance for measuring endogenous Aβ40 and Aβ42 in plasma. This assay can lead to new lines of clinical discovery related to amyloid pathology.

Ex Vivo Investigation of Bexarotene and Nicotinamide Function as a Protectıve Agent on Rat Synaptosomes Treated with Aβ(1-42).

In this study, we were aimed to investigate the neuroprotective effects of bexarotene and nicotinamide in synaptosomes incubated with amyloid-beta (Aβ). Our study consists of 2 parts, in vivo and in vitro. In the in vivo section, twenty-four Wistar albino male rats were divided into 4 groups (control, dimethyl sulfoxide (DMSO), nicotinamide and bexarotene) with six animals in each group. DMSO(1%), nicotinamide(100mg/kg) and bexarotene(0.1mg/kg) were administered intraperitoneally to animals in the experimental groups for seven days. In the in vitro part of our study, three different isolation methods were used to obtain the synaptosomes from the brain tissue. Total antioxidant capacity(TAS), total oxidant capacity(TOS), cleaved caspase 3(CASP3), cytochrome c(Cyt c), sirtuin 1(SIRT1), peroxisome proliferator-activated receptor gamma(PPARγ) and poly(ADP-ribose) polymerase-1(PARP-1) levels in the synaptosomes incubated with a concentration of 10µM Aβ(1-42) were measured by enzyme-linked immunosorbent assay method. Biochemical analysis and histopathological examinations in serum and brain samples showed that DMSO, nicotinamide and bexarotene treatments did not cause any damage to the rat brain tissue. We found that in vitro Aβ(1-42) administration decreased TAS, SIRT1 and PPARγ levels in synaptosomes while increasing TOS, CASP3, Cyt c, and PARP1 levels. Nicotinamide treatment suppressed oxidative stress and apoptosis by supporting antioxidant capacity and increased PPARγ through SIRT1 activation, causing PARP1 to decrease. On the other hand, bexarotene caused a moderate increase in SIRT1 levels with PPARγ activation. Consequently, we found that nicotinamide can be more effective than bexarotene in AD pathogenesis by regulating mitochondrial functions in synaptosomes.

Serum Aβ Levels are Associated with Age-related Cataract.

To investigate the levels and clinical relevance of serum β-amyloid (Aβ) in age-related cataract (ARC) patients. In the present study, an overall of 402 ARC patients and 450 normal controls were recruited between June 2018 and December 2019. Serum Aβ1-40 and Aβ1-42 concentrations were assessed by Elisa. The ARC patients were further grouped into several subgroups according to gender, age, types of ARC, and degree of lens opacity. The association of Aβ levels with ARC was determined using logistic regression models. ARC patients had significantly higher serum Aβ1-40 and Aβ1-42 levels than normal control. A similar finding was observed in subjects aged over 60years. Serum Aβ concentrations were significant correlated with the degrees of lens opacity in C-ARC and N-ARC subjects. Logistic regression analyses revealed that serum Aβ1-40 (ORs=1.202, 95% CI 1.077 to 1.341) and Aβ1-42 (ORs=1.686, 95% CI 1.351 to 2.103) levels were potential risk factors for ARC. ARC patients have higher serum Aβ1-40, as well as Aβ1-42 levels, which may reflect an association between Aβ and ARC pathogenesis. Serum Aβ1-42 and Aβ1-40 levels are potential risk factors for ARC.

Comparative Study between Croton tiglium Seeds and Moringa oleifera Leaves Extracts, after Incorporating Silver Nanoparticles, on Murine Brains

Croton tiglium seeds and Moringa oleifera leaves extracts are rich in phytoconstituents with the antioxidant efficiency which can be enhanced by incorporating silver nanoparticles (Ag-NPs). The present study was designed to compare the effect of C. tiglium seeds and M. oleifera leaves nano-extracts on brain tissues of murine models. During the current study, acetylcholine esterase (ACHE), β-amyloid (Aβ) content and inflammatory markers were measured in brain tissues. Moreover, native protein, lipoprotein and isoenzymes patterns were electrophoretically detected. Also, the interferon-gamma (INF-γ) receptor protein was studied by molecular dynamic simulation to evaluate the significant alterations on brain tissues. It was found that ACHE, Aβ contents and inflammatory markers increased in the C. tiglium nano-extract treated group at a dose of 6.5 ml/kg. Furthermore, it caused qualitative electrophoretic abnormalities represented by lowering similarity index (SI) values. Also, the resides range 119~127 represent the most reactive and flexible site in INF-γ receptor protein. On the other hand, it was shown that no significant differences were induced by silver M. oleifera nano-extract.

Addition of Aβ42 to Total Cerebral Small Vessel Disease Score Improves the Prediction for Cognitive Impairment in Cerebral Small Vessel Disease Patients.

PurposeTo investigate the associations between concentrations of Aβ40 and Aβ42 and vascular cognitive impairment (VCI) in cerebral small vessel disease (CSVD) patients and evaluate the value of combination of levels of Aβ40 or Aβ42 and the total CSVD score in predicting VCI.Patients and MethodsA total of 199 CSVD patients were divided into VCI group and non-VCI group according to the criteria of VCI. Demographic data, MRI markers of CSVD, blood pressure, vascular risk factors, laboratory markers, and serum Aβ40 and Aβ42 concentration were collected. Univariate analysis was performed with the Student’s t-test, Mann–Whitney U-test or Chi-square test. Variables with P<0.10 in univariate analysis were then included in multivariate analysis that used a backward stepwise logistic regression model. The predictive values were assessed with receiver operating characteristic (ROC) curve.ResultsVCI was determined in 112 CSVD patients (56.3%). Hyperlipidemia (OR: 1.618, 95% CI: 1.265–3.049), the total CSVD score (OR: 1.414, 95% CI: 1.213–2.278) and serum Aβ42 concentration (OR: 1.401, 95% CI: 1.212–1.946) were independent risk factors for VCI in CSVD patients with adjustment for age, education years, diabetes and fasting blood-glucose (FBG). The area under curves (AUCs) were 0.640 (SE: 0.040, 95% CI: 0.563–0.718), 0.733 (SE: 0.035, 95% CI: 0.664–0.802) and 0.827 (SE: 0.030, 95% CI: 0.768–0.887), respectively, for the total CSVD score, serum Aβ42 concentration and their combination applied in predicting VCI in CSVD patients. Z test demonstrated that the AUC of combination prediction was significantly higher than individual prediction (0.827 vs 0.640, Z=3.740, P<0.001; 0.827 vs 0.733, Z=2.039, P=0.021).ConclusionCombination of Aβ42 and total CSVD score could significantly elevate the predictive value of cognitive impairment in CSVD patients.

Association and Interaction of &lt;i&gt;TOMM40&lt;/i&gt; and &lt;i&gt;PVRL2&lt;/i&gt; with Plasma Amyloid-Β and Alzheimer's Disease Among Chinese Older Adults: A Population-Based Study

Background: Despite genetic studies have identified Alzheimer’s disease (AD)-associated SNPs in TOMM40 and PVRL2 genes, the underlying mechanisms have not yet been elucidated. We examined their associations and interactions with AD risk and plasma AD biomarkers among Chinese older adults. Methods: This population-based study included 4876 participants (age ≥65 years, 57.2% women) from the MIND-China study. TOMM40(rs2075650) and PVRL2(rs6859) polymorphisms were detected using multiple-polymerase chain reaction amplification. Plasma Aβ40, Aβ42, and t-tau concentrations were measured using SIMOA in a subsample (n=1257). Data was analyzed using multiple logistic and general linear regression models. Findings: AD was diagnosed in 182 participants. The multi-adjusted odds ratio of AD was 6.24(95%CI 1.73-22.48) for TOMM40GG (vs. AA), 1.47(0.89-2.42) for PVRL2AA (vs. GG), and 12.87(3.97-41.73) for having both risk alleles (P interaction =0.0003). In the plasma biomarker subsample, TOMM40GG was significantly associated with lower plasma Aβ42 and the Aβ42-to-Aβ40 ratio (p<0.05). Interpretation: TOMM40 and PVRL2 genes could interact to substantially increase the likelihood of AD, possibly through influencing Aβ metabolism. Funding Statement: MIND-China was supported from the National Key R&D Program of China (2017YFC1310100), the National Nature Science (81861138008, 82011530139), the Academic Promotion Program of Shandong First Medical University (2019QL020), and the Taishan Scholar Program of Shandong Province, China. C Qiu received grants from the Swedish Research Council (2017-00740, 2017-05819, and 2020-01574), the Swedish Foundation for International Cooperation in Research and Higher Education (STINT) (CH2019-8320) for the Joint China-Sweden Mobility program, and the Karolinska Institutet, Stockholm, Sweden. Declaration of Interests: All authors have declared that they have no competing interests. Ethics Approval Statement: The MIND-China project was approved by the Ethics Committee of Shandong Provincial Hospital affiliated to Shandong University, Jinan, Shandong. All participants provided written informed consent for both study enrollment and blood sample collection, or in case of persons with severe cognitive impairment, their informants provided informed consent. Trial Registration: MIND-China was registered in the Chinese Clinical Trial Registry (registration no.: ChiCTR1800017758).

Apolipoprotein E Polymorphism and Oxidative Stress in Human Peripheral Blood Cells: Can Physical Activity Reactivate the Proteasome System through Epigenetic Mechanisms?

Alzheimer's disease (AD) is characterized by proteasome activity impairment, oxidative stress, and epigenetic changes, resulting in β-amyloid (Aβ) production/degradation imbalance. Apolipoprotein E (ApoE) is implicated in Aβ clearance, and particularly, the ApoE ε4 isoform predisposes to AD development. Regular physical activity is known to reduce AD progression. However, the impact of ApoE polymorphism and physical exercise on Aβ production and proteasome system activity has never been investigated in human peripheral blood cells, particularly in erythrocytes, an emerging peripheral model used to study biochemical alteration. Therefore, the influence of ApoE polymorphism on the antioxidant defences, amyloid accumulation, and proteasome activity was here evaluated in human peripheral blood cells depending on physical activity, to assess putative peripheral biomarkers for AD and candidate targets that could be modulated by lifestyle. Healthy subjects were enrolled and classified based on the ApoE polymorphism (by the restriction fragment length polymorphism technique) and physical activity level (Borg scale) and grouped into ApoE ε4/non-ε4 carriers and active/non-active subjects. The plasma antioxidant capability (AOC), the erythrocyte Aβ production/accumulation, and the nuclear factor erythroid 2-related factor 2 (Nrf2) mediated proteasome functionality were evaluated in all groups by the chromatographic and immunoenzymatic assay, respectively. Moreover, epigenetic mechanisms were investigated considering the expression of histone deacetylase 6, employing a competitive ELISA, and the modulation of two key miRNAs (miR-153-3p and miR-195-5p), through the miRNeasy Serum/Plasma Mini Kit. ApoE ε4 subjects showed a reduction in plasma AOC and an increase in the Nrf2 blocker, miR-153-3p, contributing to an enhancement of the erythrocyte concentration of Aβ. Physical exercise increased plasma AOC and reduced the amount of Aβ and its precursor, involving a reduced miR-153-3p expression and a miR-195-5p enhancement. Our data highlight the impact of the ApoE genotype on the amyloidogenic pathway and the proteasome system, suggesting the positive impact of physical exercise, also through epigenetic mechanisms.

Schisandrin Inhibits NLRP1 Inflammasome-Mediated Neuronal Pyroptosis in Mouse Models of Alzheimer's Disease.

BackgroundIn recent years, schisandrin (SCH) was proved to improve Alzheimer's Disease (AD). The aim of our study is to explore the effect of SCH on neuronal pyroptosis in the disease.MethodsA Morris water maze test was performed to evaluate the spatial learning and memory retention of AD mouse. ELISA was fulfilled to examine the concentration of Aβ, IL-1β, and IL-18. Western blot was performed to detect the expression of apoptosis- and pyroptosis-related proteins. Besides, the neuronal apoptosis rate was examined using TUNEL assay. Immunohistochemistry was utilized to detect the activation of NLRP1 inflammasome.ResultsHere, AD mice have serious cognitive impairment. Meantime, Aβ was highly expressed in the brains of AD mice. SCH could effectively rescue the cognitive impairment in AD mice and impede the production of Aβ. Subsequently, we further demonstrated that SCH repressed neuronal apoptosis, pyroptosis-related proteins expression, and the activation of NLRP1 inflammasome in the hippocampus of AD mice. We also proved that Aβ induced neuronal apoptosis and pyroptosis in vitro. However, the effects of Aβ on neuronal apoptosis and pyroptosis were partly reversed by SCH treatment.ConclusionOverall, our data indicated that SCH improved cognitive impairment in AD mice through inhibition of NLRP1 inflammasome-mediated neuronal pyroptosis and neuronal apoptosis. Our works provided new evidence to support SCH acting as a potential treatment method in AD.

The association of circulating amylin with β-amyloid in familial Alzheimer's disease.

IntroductionThis study assessed the hypothesis that circulating human amylin (amyloid‐forming) cross‐seeds with amyloid beta (Aβ) in early Alzheimer's disease (AD).MethodsEvidence of amylin‐AD pathology interaction was tested in brains of 31 familial AD mutation carriers and 20 cognitively unaffected individuals, in cerebrospinal fluid (CSF) (98 diseased and 117 control samples) and in genetic databases. For functional testing, we genetically manipulated amylin secretion in APP/PS1 and non‐APP/PS1 rats.ResultsAmylin‐Aβ cross‐seeding was identified in AD brains. High CSF amylin levels were associated with decreased CSF Aβ42 concentrations. AD risk and amylin gene are not correlated. Suppressed amylin secretion protected APP/PS1 rats against AD‐associated effects. In contrast, hypersecretion or intravenous injection of human amylin in APP/PS1 rats exacerbated AD‐like pathology through disruption of CSF‐brain Aβ exchange and amylin‐Aβ cross‐seeding.DiscussionThese findings strengthened the hypothesis of circulating amylin‐AD interaction and suggest that modulation of blood amylin levels may alter Aβ‐related pathology/symptoms.

Machine Learning-Supported Analyses Improve Quantitative Histological Assessments of Amyloid-β Deposits and Activated Microglia.

Background:Detailed pathology analysis and morphological quantification is tedious and prone to errors. Automatic image analysis can help to increase objectivity and reduce time. Here, we present the evaluation of the DeePathology STUDIO™ for automatic analysis of histological whole-slide images using machine learning/artificial intelligence.Objective:To evaluate and validate the use of DeePathology STUDIO for the analysis of histological slides at high resolution.Methods:We compared the DeePathology STUDIO and our current standard method using macros in AxioVision for the analysis of amyloid-β (Aβ) plaques and microglia in APP-transgenic mice at different ages. We analyzed density variables and total time invested with each approach. In addition, we correlated Aβ concentration in brain tissue measured by ELISA with the results of Aβ staining analysis.Results:DeePathology STUDIO showed a significant decrease of the time for establishing new analyses and the total analysis time by up to 90%. On the other hand, both approaches showed similar quantitative results in plaque and activated microglia density in the different experimental groups. DeePathology STUDIO showed higher sensitivity and accuracy for small-sized plaques. In addition, DeePathology STUDIO allowed the classification of plaques in diffuse- and dense-packed, which was not possible with our traditional analysis.Conclusion:DeePathology STUDIO substantially reduced the effort needed for a new analysis showing comparable quantitative results to the traditional approach. In addition, it allowed including different objects (categories) or cell types in a single analysis, which is not possible with conventional methods.

Plasma Biomarkers Ascertained With Immunomagnetic Reduction Diagnosing Early-Stage Alzheimer's Disease: A Systematic Review

ABSTRACT Introduction Alzheimer's disease (AD) will become a prominent public health issue in the future given its cognitively debilitating nature. As the advent of global ageing society is expected, AD may bring tremendous socioeconomical costs if current diagnosis methods stay put. In this article, we performed a systematic review of a recent (less than 10 years) ultrasensitive technology, the immunomagnetic reduction (IMR), which shows promising potential of early diagnosis of AD. Methods We searched the Pubmed and Embase databases for studies that included keywords “early-stage Alzheimer's disease” and “immunomagnetic signal reduction.” Results After full-text review, a total of 7 studies were included for final analysis. Most included studies have reported on Aβ40, Aβ42, t-tau, and levels of these biomarkers in the plasma of early AD patients comparing those in the healthy population. The ranges of the mean Aβ40 levels are as follows: 59.2 to 60.9 for control groups and 36.9 to 39.5 pg/mL for AD. Aβ42 and t-tau concentrations are both markedly lower than Aβ40, Aβ42 at 15.5 to 16.1 for control groups and 17.9 to 19 pg/mL for AD; t-tau levels were 13.5 to 14.3 for control groups and 39.4 to 46.7 pg/mL for AD. There is a significant increasing level of plasma Aβ42 by IMR assays in early AD patients across nearly all the included studies. There is a possible relationship between plasma levels of IMR AD biomarkers and (1) degree of hippocampal atrophy using magnetic resonance imaging, and (2) amount of brain amyloid accumulation using positron emission tomography. Conclusion IMR assay is an ultrasensitivity technique that is useful for detection of early AD, which can provide benefits on understanding the disease progression of AD and encourage early medical invention for AD patients.

Liver Growth Factor "LGF" as a Therapeutic Agent for Alzheimer's Disease.

Alzheimer’s disease (AD) is a progressive degenerative disorder and the most common cause of dementia in aging populations. Although the pathological hallmarks of AD are well defined, currently no effective therapy exists. Liver growth factor (LGF) is a hepatic albumin–bilirubin complex with activity as a tissue regenerating factor in several neurodegenerative disorders such as Parkinson’s disease and Friedreich’s ataxia. Our aim here was to analyze the potential therapeutic effect of LGF on the APPswe mouse model of AD. Twenty-month-old mice received intraperitoneal (i.p.) injections of 1.6 µg LGF or saline, twice a week during three weeks. Mice were sacrificed one week later, and the hippocampus and dorsal cortex were prepared for immunohistochemical and biochemical studies. LGF treatment reduced amyloid-β (Aβ) content, phospho-Tau/Tau ratio and the number of Aβ plaques with diameter larger than 25 µm. LGF administration also modulated protein ubiquitination and HSP70 protein levels, reduced glial reactivity and inflammation, and the expression of the pro-apoptotic protein Bax. Because the administration of this factor also restored cognitive damage in APPswe mice, we propose LGF as a novel therapeutic tool that may be useful for the treatment of AD.

Impact of APOE‐ε4 on cerebral amyloid deposition in participants with abnormal soluble amyloid levels

AbstractBackgroundAmyloid pathology can be detected using cerebrospinal fluid (CSF) biomarkers and positron emission tomography (PET) imaging, even though they measure two distinct beta‐amyloid (Aβ) pools. While CSF Aβ concentrations reflect the clearance of soluble amyloid species from the brain, PET imaging informs on the presence of insoluble fibrillary plaques in the brain tissue. Many studies have shown the concordance between the two measures in individuals along the Alzheimer’s continuum. Here, we assessed whether APOE‐ε4, the major genetic risk factor for Alzheimer’s disease (AD), affects the pattern of cerebral Aβ load as a function of CSF Aβ levels.MethodThe first consecutive 276 cognitively unimpaired (CDR = 0) individuals of the ALFA+ study, aged between 48 and 74, with valid structural MRI and [18F]flutemetamol (FTM) PET, APOE genotyping and CSF samples were included. Aβ40 and Aβ42 concentrations were determined with the Roche NeuroToolKit (Roche Diagnostics) and parametric standardized uptake value ratio images (SUVr) were calculated with the whole cerebellum as reference region. A voxel‐wise regression was performed to predict FTM uptake, with the following independent variables: age, sex, APOE‐ε4, and CSF Aβ42/40 ratio. Statistical threshold was set to p &lt; 0.001 with a cluster extent correction of 100 voxels.ResultAs expected, CSF Aβ42/40 ratio was negatively associated with cerebral FTM uptake (Figure 1a‐1b). Age and APOE‐ε4 gene dose mapped onto distinct spatial patterns of FTM‐binding across the whole sample (Figure 2b‐2c). Importantly, we found a significant interaction between CSF Aβ42/40 and APOE‐ε4 indicating that carriers had a negative association between fluid and imaging Aβ measures in the bilateral hippocampus, as well as the bilateral middle temporal and temporo‐parietal junction (Figure 3).ConclusionCompared to non‐carriers, APOE‐ε4 carriers showed higher cerebral Ab load for any given level of CSF Aβ42/40 in areas that are not typically vulnerable to Aβ deposition yet undergoing neurodegeneration early in the Alzheimer’s continuum, such as the hippocampus. This suggests that APOE‐ε4 may influence the biological mechanisms regulating the equilibrium between soluble and deposited amyloid, which may transcend the hindering effect caused by Aβ fibrillary plaques and render medial temporal lobe structures particularly vulnerable when Aβ metabolism becomes deficient.

In‐vivo characterization of progressive amnestic syndrome due to suspected neurodegenerative non‐Alzheimer’s disease

AbstractBackgroundNeuropathological bases of suspected non‐Alzheimer’s disease pathophysiology (SNAP) have recently been identified as frequent causes of progressive isolated amnestic non Alzheimer’s disease (AD) neurodegenerative diseases1,2. Nonetheless, their in‐vivo profiles have so far been only poorly characterized. The goal of this study is to specify their clinical, neuroimaging profile and evolution, compared to patients with amnestic AD and cognitively normal subjects.MethodsWe retrospectively selected patients with progressive amnestic syndrome of hippocampal type3, signs of neurodegeneration (elevated CSF t‐ tau concentration and/or brain hypometabolism and/or atrophy) and normal CSF Amyloid values (Aβ42 concentration ; Aβ40/42 ratio if available) from 3 tertiary memory centers (amnestic SNAP). They were compared to patients with prodromal typical (amnestic) AD (without impairment of instrumental functions, MMSE &gt;20, elevated CSF p‐tau and abnormal CSF Amyloid values) and cognitively normal controls with normal CSF Amyloid values. We compared clinical data and neuropsychological tests between amnestic SNAP and the two other groups.Results25 patients with amnestic SNAP (median age=74.7), 24 amnestic AD (median age=71) and 35 controls (median age=75) were included. At baseline, controls had better global cognitive performances (MMSE=29 vs. 27 vs. 25 respectively, p&lt;0.001) as well as verbal fluency performances than amnestic SNAP and amnestic AD but no significant difference were found between amnestic SNAP and AD (p=0.096). Executive functioning was significantly different between controls, amnestic SNAP and AD (FAB=17, 16 and 14 respectively, p&lt;0.001) and there was a significant difference between amnestic SNAP and AD (p=0.034). We found no other significant difference between amnestic SNAP and AD: neither regarding memory performances (FCSRT) nor other cognitive functions (language, visuo‐spatial abilities).ConclusionPatients with amnestic SNAP show a weaker impairment in executive functions than patients with prodromal amnestic AD, highlighting a specific identifiable baseline neuropsychological pattern. This work will be completed by the analysis of clinical evolution, and the pattern of brain atrophy and brain metabolism that will be available at the time of AAIC.

Retention Period of Amyloid β1-42 in the Brain Extracellular Fluid as the Toxicological Determinant in Freely Moving Rats.

The pathological significance of amyloid-β1-42 (Aβ1-42) dynamics is poorly understood in the brain extracellular compartment. Here we test which of the concentration or the retention is critical for Aβ1-42 toxicity after injection of equal dose into dentate granule cell layer of freely moving rats. The toxicity of Aβ1-42 (25 µM) was compared between injections at the rate of 0.25 µL/min for 4 min (fast injection) and 0.025 µL/min for 40 min (slow injection). Dentate gyrus long-term potentiation (LTP) was affected 1 and 2 h after the fast injection, but not 4 h. In contrast, LTP was affected even 72 h after the slow injection. Aβ1-42 staining 5 min after finish of the slow injection was more intense in the dentate granule cell layer than of the fast injection. The present study indicates that the retention of Aβ1-42 in the extracellular fluid is correlated with neuronal Aβ1-42 uptake and plays a key role in Aβ1-42 neurotoxicity. In the extracellular fluid of the dentate gyrus, the retention period of Aβ1-42 is much more critical for Aβ1-42 toxicity than Aβ1-42 concentration. It is likely that Aβ1-42 toxicity is accelerated by the disturbance of Aβ1-42 metabolism in the dentate gyrus.

Plasma amyloid‐β dynamics are regulated by the sleep‐wake cycle

AbstractBackgroundIt has been reported that sleep is an important physiological process and conducive to the elimination of brain metabolites and the recovery of brain function. Growing evidence suggested that sleep disorders were related to increased risk of AD and Aβ accumulation in the brain. Although peripheral Aβ clearance is associated with brain Aβ deposition, but the relationship between sleep‐wake cycle and plasma Aβ levels is unclear.MethodThirty cognitively normal healthy adults (aged 29.07 ± 8.12), sixteen males (53.33%), were recruited. Participants underwent normal sleep and peripheral blood samples were collected every three hours between 20:00 and 8:00 the next day. Plasma Aβ40, Aβ42, total tau, phosphorylated tau 181 (P‐tau), soluble low‐density lipoprotein receptor‐related protein (sLRP1) and soluble receptors for advanced glycation end products (sRAGE) levels were measured using ELISA kits.ResultPlasma Aβ40 concentration at 5:00 decreased significantly compared with plasma level at 23:00 (p=0.041), and there is a dynamic tendency of decreasing after sleep onset and increasing after awake, which is in accordance with the sleep‐wake cycle. Furthermore, Aβ40 and Aβ42 levels were positively correlated with plasma sLRP1 (Aβ40: r=0.1791, p=0.0283; Aβ42: r=0.1780, p=0.0293). However, there was no significant dynamic change in Aβ42, Tau, P‐tau, Tau, sLRP1 and sRAGE levels in twelve hours.ConclusionPlasma Aβ40 dynamics are regulated by the sleep‐wake cycle, and it may play a positive feedback regulating role in sLRP1 level.

Small molecule inhibitors of apolipoprotein E4‐catalyzed amyloid‐β fibrillization as novel therapeutics for Alzheimer’s disease

AbstractBackgroundAlzheimer’s disease (AD) is a progressive neurodegenerative illness initiated by fibrillization of the amyloid‐beta (Aβ) peptide in the brain. Genetic factors can increase the risk for developing AD, especially in individuals who carry the ε4 allele of the apolipoprotein E (APOE) gene. Having one copy of APOE4 doubles the risk for AD, whereas being homozygous for APOE4 increases the risk by greater than ten‐fold. ApoE4 acts as a catalyst to accelerate the polymerization rate of Aβ into neurotoxic oligomers and filaments; thus, inhibiting this enzymatic process is a promising therapeutic approach to preventing AD. We therefore developed an ApoE4‐Aβ fibrillization assay for high‐throughput drug screening of small molecule compounds.MethodA design of experiments (DOE) approach was employed to optimize the ApoE4‐Aβ fibrillization assay. A series of fractional factorial and surface response designs were used to determine the concentrations of Aβ, ApoE4, and thioflavin T that yielded the greatest rate and amount of Aβ fibrillization. The optimized assay was then used to screen two small molecule libraries representing more than 3,000 compounds, most of which are drugs or natural compounds that have already been tested in humans for other indications. Hit compounds were next evaluated for cytotoxicity and inhibition of Aβ neuropathology in primary mouse neurons expressing human Aβ and exposed to human ApoE4 over nine days in culture.ResultA primary screen of two small molecule libraries identified 31 hit compounds that significantly inhibited ApoE4‐catalyzed Aβ fibrillization in a dose‐dependent manner. Primary hit compounds were then tested in primary mouse neurons, where six compounds were validated as non‐cytotoxic and were effective at inhibiting Aβ neuropathology. One of the six lead compounds (epigallocatechin gallate) had been studied previously as a potential therapy for neurodegenerative disease, thus validating the overall screening approach.ConclusionSix small molecule compounds were identified as novel inhibitors of ApoE4‐catalyzed Aβ fibrillization in high‐throughput screens. Three are FDA‐approved drugs for indications unrelated to AD. We are currently performing preclinical evaluations of these compounds in AD rodent models to determine their therapeutic potential for the treatment of AD.