Search

Objective: To describe the collection methods for perilymph fluid biopsy during cochlear implantation, detect levels of amyloid β 42 and 40 (Aβ42 and Aβ40), and total tau (tTau) analytes with a high‐precision assay, to compare these levels with patient age and Montreal Cognitive Assessment (MoCA) scores, and explore potential mechanisms and relationships with otic pathology. Study Design: Prospective study. Setting: Tertiary referral center. Methods: Perilymph was collected from 25 patients using polyimide tubing to avoid amyloid adherence to glass, and analyzed with a single‐molecule array advanced digital enzyme‐linked immunosorbent assay platform for Aβ40, Aβ42, and tTau. Cognition was assessed by MoCA. Results: Perilymph volumes ranged from ∼1 to 13 µL, with analyte concentrations spanning 2.67 to 1088.26 pg/mL. All samples had detectable levels of tTau, Aβ40, and Aβ42, with a significant positive correlation between Aβ42 and Aβ40 levels. Levels of Aβ42, Aβ40, and tTau were positively correlated with age, while MoCA scores were inversely correlated with age. tTau and Aβ42/Aβ40‐ratios were significantly correlated with MoCA scores. Conclusion: Alzheimer's disease‐associated peptides Aβ42, Aβ40, and tau analytes are detectable in human perilymph at levels approximately 10‐fold lower than those found in cerebrospinal fluid (CSF). These species increase with age and correlate with cognitive impairment indicators, suggesting their potential utility as biomarkers for cognitive impairment in patients undergoing cochlear implantation. Future research should investigate the origin of these analytes in the perilymph and their potential links to inner ear pathologies and hearing loss, as well as their relationships to CSF and plasma levels in individuals. [ABSTRACT FROM AUTHOR]

BackgroundPlasma biomarker has the potential to be the reliable and propagable approach in the early stage diagnosis of Alzheimer’s disease (AD). However, conventional methods appear powerless in the detection of these biomarkers at low concentrations in plasma. Here, we determined plasma biomarker concentrations of patients across the AD spectrum by an improved digital enzyme-linked immunosorbent assay (ELISA) technique. Confirms the predictive and diagnostic value of this method for AD patients and study the relationships between these biomarkers and cognitive status.MethodsPlasma concentrations of amyloid-beta 40 (Aβ40), amyloid-beta 42 (Aβ42) and plasma phosphorylated tau at threonine 181 (p-tau181) were determined in 43 AD patients, 33 mild cognitive impairment (MCI) patients and 40 normal cognition (NC) subjects as healthy controls using the improved digital ELISA technique. In addition, all subjects were required to receive neuropsychological assessments.ResultsPlasma p-tau181 level showed certain discrepancies between NC and MCI (p < 0.05), AD (p < 0.01) groups. The level of plasma Aβ42 (p < 0.05) and Aβ40 (p < 0.01) was significantly different between AD and NC group. The p-tau181 level was able to distinguish AD (AUC = 0.8768) and MCI (AUC = 0.7932) from NC with higher accuracy than Aβ42/Aβ40 ratio (AUC = 0.8343, AUC = 0.6569). Both p-tau181 (CDR: r = 0.388 p

Abstract Background Large-scale cohort and epidemiological studies suggest that PTSD confers risk for dementia in later life but the biological mechanisms underlying this association remain unknown. This study examined this question by assessing the influences of PTSD, APOE ε4 genotypes, DNA methylation, and other variables on the age- and dementia-associated biomarkers Aβ40, Aβ42, GFAP, NfL, and pTau-181 measured in plasma. Our primary hypothesis was that PTSD would be associated with elevated levels of these markers. Methods Analyses were based on data from a PTSD-enriched cohort of 849 individuals. We began by performing factor analyses of the biomarkers, the results of which identified a two-factor solution. Drawing from the ATN research framework, we termed the first factor, defined by Aβ40 and Aβ42, “Factor A” and the second factor, defined by GFAP, NfL and pTau-181, “Factor TN.” Next, we performed epigenome-wide association analyses (EWAS) of the two-factor scores. Finally, using structural equation modeling (SEM), we evaluated (a) the influence of PTSD, age, APOE ε4 genotype and other covariates on levels of the ATN factors, and (b) tested the mediating influence of the EWAS-significant DNAm loci on these associations. Results The Factor A EWAS identified one significant locus, cg13053408, in FANCD2OS. The Factor TN analysis identified 3 EWAS-significant associations: cg26033520 near ASCC1, cg23156469 in FAM20B, and cg15356923 in FAM19A4. The SEM showed age to be related to both factors, more so with Factor TN (β = 0.581, p

Background: Large-scale cohort and epidemiological studies suggest that PTSD confers risk for dementia in later life but the biological mechanisms underlying this association remain unknown. This study examined this question by assessing the influences of PTSD, APOE ε4 genotypes, DNA methylation, and other variables on the age- and dementia-associated biomarkers Aβ40, Aβ42, GFAP, NfL, and pTau-181 measured in plasma. Our primary hypothesis was that PTSD would be associated with elevated levels of these markers. Methods: Analyses were based on data from a PTSD-enriched cohort of 849 individuals. We began by performing factor analyses of the biomarkers, the results of which identified a two-factor solution. Drawing from the ATN research framework, we termed the first factor, defined by Aβ40 and Aβ42, "Factor A" and the second factor, defined by GFAP, NfL and pTau-181, "Factor TN." Next, we performed epigenome-wide association analyses (EWAS) of the two-factor scores. Finally, using structural equation modeling (SEM), we evaluated (a) the influence of PTSD, age, APOE ε4 genotype and other covariates on levels of the ATN factors, and (b) tested the mediating influence of the EWAS-significant DNAm loci on these associations. Results: The Factor A EWAS identified one significant locus, cg13053408, in FANCD2OS. The Factor TN analysis identified 3 EWAS-significant associations: cg26033520 near ASCC1, cg23156469 in FAM20B, and cg15356923 in FAM19A4. The SEM showed age to be related to both factors, more so with Factor TN (β = 0.581, p < 0.001) than Factor A (β = 0.330, p < 0.001). Genotype-determined African ancestry was associated with lower Factor A (β = 0.196, p < 0.001). Contrary to our primary hypothesis, we found a modest negative bivariate correlation between PTSD and the TN factor scores (r = − 0.133, p < 0.001) attributable primarily to reduced levels of GFAP (r = − 0.128, p < 0.001). Conclusions: This study identified novel epigenetic associations with ATN biomarkers and demonstrated robust age and ancestral associations that will be essential to consider in future efforts to develop the clinical applications of these tests. The association between PTSD and reduced GFAP, which has been reported previously, warrants further investigation. [ABSTRACT FROM AUTHOR]

INTRODUCTION: Despite their increased application, the heritability of Alzheimer's disease (AD)–related blood‐based biomarkers remains unexplored. METHODS: Plasma amyloid beta 40 (Aβ40), Aβ42, the Aβ42/40 ratio, total tau (t‐tau), and neurofilament light (NfL) data came from 1035 men 60 to 73 years of age (μ = 67.0, SD = 2.6). Twin models were used to calculate heritability and the genetic and environmental correlations between them. RESULTS: Additive genetics explained 44% to 52% of Aβ42, Aβ40, t‐tau, and NfL. The Aβ42/40 ratio was not heritable. Aβ40 and Aβ42 were genetically near identical (rg = 0.94). Both Aβ40 and Aβ42 were genetically correlated with NfL (rg = 0.35 to 0.38), but genetically unrelated to t‐tau. DISCUSSION: Except for Aβ42/40, plasma biomarkers are heritable. Aβ40 and Aβ42 share mostly the same genetic influences, whereas genetic influences on plasma t‐tau and NfL are largely unique in early old‐age men. The absence of genetic associations between the Aβs and t‐tau is not consistent with the amyloid cascade hypothesis. [ABSTRACT FROM AUTHOR]

Introduction: Alzheimer's disease (AD) is characterized by decreased cerebrospinal fluid (CSF) Aβ42 and Aβ42/Aβ40 ratio. Aβ peptides can now be measured also in plasma and are promising peripheral biomarkers for AD. We evaluated the relationships of plasma Aβ species with their CSF counterparts, kidney function, and serum/CSF albumin ratio (Q-Alb) in AD patients. Materials and methods: We measured plasma Aβ42 and Aβ40, as well as CSF AD biomarkers, with the fully automated Lumipulse platform in a cohort of N = 30 patients with clinical and neurochemical diagnosis of AD. Results: The two plasma Aβ peptides correlated strongly with each other (r = 0.7449), as did the corresponding CSF biomarkers (r = 0.7670). On the contrary, the positive correlations of plasma Aβ42, Aβ40, and Aβ42/Aβ40 ratio with their CSF counterparts and the negative correlation of plasma Aβ42/Aβ40 ratio with CSF P-tau181 were not statistically significant. Plasma levels of both Aβ species negatively correlated with estimated glomerular filtration rate (eGFR) (Aβ42: r = -0.4138; Aβ40: r = -0.6015), but plasma Aβ42/Aβ40 ratio did not. Q-Alb did not correlate with any plasma Aβ parameter. Discussion: Plasma Aβ42 and Aβ40 are critically influenced by kidney function; however, their ratio is advantageously spared from this effect. The lack of significant correlations between plasma Aβ species and their CSF counterparts is probably mainly due to small sample size and inclusion of only Aβ + individuals. Q-Alb is not a major determinant of plasma Aβ concentrations, highlighting the uncertainties about mechanisms of Aβ transfer between CNS and periphery. [ABSTRACT FROM AUTHOR]

Introduction: Human herpes simplex virus 1 (HSV1) is discussed to induce amyloid‐β (Aβ) accumulation and neurofibrillary tangles of hyperphosphorylated tau (pTau) in Alzheimer's disease (AD) in cell culture and animal models. Aβ appears to be virostatic. We investigated the association between intrathecal antibodies against HSV or cytomegalovirus (CMV) and cerebrospinal fluid (CSF) AD biomarkers. Methods: Aβ42/Aβ40 ratio, pTau, and tTau were measured in CSF of 117 patients with early AD positive for amyloid pathology (A+) and 30 healthy controls (A‐). CSF‐to‐serum anti‐HSV1/2‐IgG antibody indices (AI‐IgGHSV1/2) and CMV (AI‐IgGCMV) were determined by enzyme‐linked immunosorbent assay (ELISA). Results: Exclusively in HSV1‐seropositive AD, pTau was positively and significantly predicted by AI‐IgGHSV1/2 and negatively by the Aβ42/Aβ40 ratio in both univariate and multivariate regression analyses. Furthermore, a significant and negative interaction between the AI‐IgGHSV1/2 and Aβ42/Aβ40 ratio on pTau was found. Discussion: The results support the hypothesis that HSV infection contributes to AD. Highlights: HSV antibody index is positively associated with tau pathology in patients with AD.HSV antibody index is negatively associated with cerebral FDG metabolism.Amyloid modulates the association of HSV antibody index with CSF‐pTau.HSV in AD offers a pathophysiological model connecting tau and amyloid. [ABSTRACT FROM AUTHOR]

Generation of amyloid-β peptides (Aβs) by proteolytic cleavage of the amyloid-β protein precursor (AβPP), especially increased production of Aβ42/Aβ43 over Aβ40, and their aggregation as oligomers and plaques, represent a characteristic feature of Alzheimer's disease (AD). In familial AD (FAD), altered Aβ production originates from specific mutations of AβPP or presenilins 1/2 (PS1/PS2), the catalytic subunits of γ-secretase. In sporadic AD, the origin of altered production of Aβs remains unknown. We hypothesize that the 'human chemical exposome' contains products able to favor the production of Aβ42/Aβ43 over Aβ40 and shorter Aβs. To detect such products, we screened a library of 3500 + compounds in a cell-based assay for enhanced Aβ42/Aβ43 production. Nine pyrazole insecticides were found to induce a β- and γ-secretase-dependent, 3-10-fold increase in the production of extracellular Aβ42 in various cell lines and neurons differentiated from induced pluripotent stem cells derived from healthy and FAD patients. Immunoprecipitation/mass spectrometry analyses showed increased production of Aβs cleaved at positions 42/43, and reduced production of peptides cleaved at positions 38 and shorter. Strongly supporting a direct effect on γ-secretase activity, pyrazoles shifted the cleavage pattern of another γ-secretase substrate, alcadeinα, and shifted the cleavage of AβPP by highly purified γ-secretase toward Aβ42/Aβ43. Focusing on fipronil, we showed that some of its metabolites, in particular the persistent fipronil sulfone, also favor the production of Aβ42/Aβ43 in both cell-based and cell-free systems. Fipronil administered orally to mice and rats is known to be metabolized rapidly, mostly to fipronil sulfone, which stably accumulates in adipose tissue and brain. In conclusion, several widely used pyrazole insecticides enhance the production of toxic, aggregation prone Aβ42/Aβ43 peptides, suggesting the possible existence of environmental "Alzheimerogens" which may contribute to the initiation and propagation of the amyloidogenic process in sporadic AD.

Aggregation of amyloid-β (Aβ) protein plays a central role in Alzheimer's disease. Because protein aggregation is a concentration-dependent process, rigorous investigations require accurate concentration measurements. Owing to the high aggregation propensity of Aβ protein, working solutions of Aβ are typically in the low micromolar range. Therefore, an ideal Aβ quantification method requires high sensitivity without sacrificing speed and accuracy. Absorbance at 280 nm is frequently used to measure Aβ concentration, but the sensitivity is low with only one tyrosine and no tryptophan residues in the Aβ sequence. Here we present a fluorescence method for Aβ quantification using fluorescamine, which gives high fluorescence upon reaction with primary amines. We show that, using hen egg white lysozyme as a standard, fluorescence correlates linearly with primary amine concentration across a wide range of fluorescamine concentrations, from 62.5 to 1000 µM. The maximal sensitivity of detection is achieved at a fluorescamine concentration of 250 µM or higher. The fluorescamine method is compatible with the presence of dimethyl sulfoxide, which is commonly used in the preparation of Aβ oligomers, and limits the use of absorbance at 280 nm due to its high background reading. Using aggregation kinetics, we show that the fluorescamine method gives accurate concentration measurements at low micromolar range and leads to highly consistent aggregation data. We recommend the fluorescamine assay to be used for routine and on-the-fly concentration determination in Aβ oligomerization and fibrillization experiments.

β-Amyloid (Aβ) peptide fibrillation, one of the characteristic hallmarks of Alzheimer's disease, is determined by many interfacial physical-chemical factors, e.g., charge, hydrophobicity, etc. Despite extensive research, chiral effect in different-scales on the fibrillation process of Aβ remains unclear. Herein, molecular-scale, sub-nanoscale, and nanoscale chiral-structures were constructed to investigate their chiral effect on the fibrillation of Aβ40 peptides. Chiral structures from molecular-scale to nanoscale were obtained from the different periods of the chemosynthesis process of chiral ZnS quantum-dots (QDs), confirmed by real-time monitoring of circular dichroism spectra. For molecular-scale, both L-penicillamine (L-P) and D-P ligands accelerated the fibrillation of Aβ40, and the speed-up effect of D-P was slightly stronger than L-P. For sub-nanoscale, both two chiral Zn-complexes (L-Zn and D-Zn) induced the agglomeration of Aβ40 without chirality discrimination. For nanoscale, both L-ZnS and D-ZnS QDs inhibited the fibrillation of Aβ40, and the inhibition effect of L-ZnS was notably better than that of D-ZnS. In-situ kinetics experiments of Aβ40 co-incubated with two chiral QDs demonstrated that L-ZnS completely prevents the misfolding of Aβ40 from unfolded to β-sheet, while D-ZnS cannot achieve this. Further site-replacement experiments and simulation results revealed the underlying molecular mechanisms of the different inhibition efficiency of chiral ZnS QDs on Aβ40 fibrillation, which mainly attribute to the stereoselectivity interaction between the chiral ligands of ZnS QDs and electro-positive amino acid residues (R5, K16, and K28) of Aβ40. This work offers a microscopic insight of chiral effect on Aβ fibrillation exerted by structures in different-scales, and provides a guidance in precise regulation of protein fibrillation via manipulating chiral structures in different-scales. [ABSTRACT FROM AUTHOR]

Jianping Liu,1 Weihua Zhao,2 Qinghong Gui,1 Ying Zhang,1 Zaiyu Guo,2 Wei Liu3 1Department of Neurology, Tianjin TEDA Hospital, Tianjin 300457, People’s Republic of China; 2Department of Neurosurgery, Tianjin TEDA Hospital, Tianjin 300457, People’s Republic of China; 3Department of Neurology, Tianjin Medical University General Hospital, Tianjin 300052, People’s Republic of ChinaCorrespondence: Zaiyu GuoDepartment of Neurosurgery, Tianjin TEDA Hospital, No. 65, The Third Avenue, Tianjin Economy Development Area, Tianjin 300457, People’s Republic of ChinaTel +86-15302100230Email guozaiyu_teda@163.comWei LiuDepartment of Neurology, Tianjin Medical University General Hospital, No. 154, An Shan Road, Heping District, Tianjin 300052, People’s Republic of ChinaTel +86-2260362255Email liuweithird@126.comPurpose: To 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 Methods: A 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.Results: VCI 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).Conclusion: Combination of Aβ42 and total CSVD score could significantly elevate the predictive value of cognitive impairment in CSVD patients.Keywords: Aβ40, Aβ42, vascular cognitive impairment, cerebral small vessel disease, total cerebral small vessel disease score

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.

Background: There is no consensus regarding the diagnostic value of cerebrospinal fluid (CSF) Alzheimer's disease (AD) biomarkers in cerebral amyloid angiopathy (CAA).Objective: To describe the CSF levels of Aβ42, Aβ40, total protein Tau, and phosphorylated-Tau (p-Tau) in a large series of probable CAA patients and to compare with AD patients in order to identify a specific pattern in CAA but also to look for correlations with the neuroimaging profile.Methods: We retrospectively included from 2 French centers probable CAA patients according to modified Boston criteria who underwent lumbar puncture (LP) with CSF AD biomarker quantifications. Two neurologists independently analyzed all MRI sequences. A logistic regression and Spearman's correlation coefficient were used to identify correlation between MRI and CSF biomarkers in CAA.Results: We included 63 probable CAA and 27 AD patients. Among CAA 50.8% presented with decreased Aβ42 level associated with elevated p-Tau and/or Tau, 34.9% with isolated decreased Aβ42 level and 14.3% patients with normal Aβ42 level. Compared to AD, CAA showed lower levels of Tau (p = 0.008), p-Tau (p = 0.004), and Aβ40 (p = 0.001) but similar Aβ42 level (p = 0.07). No correlation between Aβ42 or Aβ40 levels and neuroimaging was found.Conclusion: CSF biomarkers may improve the accuracy of the modified Boston criteria with altered profile in 85% of the patients fulfilling revised Boston criteria for probable CAA. Aβ40 appears as an interesting selective biomarker in differential diagnosis. [ABSTRACT FROM AUTHOR]

Amyloid-β 40 peptides [Aβ1-40 (Aβ40)] are present within amyloid plaques in the brains of patients with Alzheimer's disease (AD). Even though Aβ peptides are considered neurotoxic, they can mediate many biological processes, both in adult brains and throughout brain development. However, the physiological function of these Aβ peptides remains poorly understood, and the existing data are sometimes controversial. Here, we analyze and compare the effects of monomeric Aβ40 on the biology of differentiating human neural stem cells (human NSCs). For that purpose, we used a model of human NSCs called hNS1. Our data demonstrated that Aβ40 at high concentrations provokes apoptotic cellular death and the damage of DNA in human NSCs while also increasing the proliferation and favors neurogenesis by raising the percentage of proliferating neuronal precursors. These effects can be mediated, at least in part, by β-catenin. These results provide evidence of how Aβ modulate/regulate human NSC proliferation and differentiation, suggesting Aβ40 may be a pro-neurogenic factor. Our data could contribute to a better understanding of the molecular mechanisms involved in AD pathology and to the development of human NSC-based therapies for AD treatment, since these results could then be used in diagnosing the disease at early stages and be applied to the development of new treatment options. [ABSTRACT FROM AUTHOR]

Purpose: The development of blood biomarkers that reflect Alzheimer's disease (AD) pathophysiology (phosphorylated tau and amyloid-β) has offered potential as scalable tests for dementia differential diagnosis and early detection. In 2019, the Geneva AD Biomarker Roadmap Initiative included blood biomarkers in the systematic validation of AD biomarkers. Methods: A panel of experts convened in November 2019 at a two-day workshop in Geneva. The level of maturity (fully achieved, partly achieved, preliminary evidence, not achieved, unsuccessful) of blood biomarkers was assessed based on the Biomarker Roadmap methodology and discussed fully during the workshop which also evaluated cerebrospinal fluid (CSF) and positron emission tomography (PET) biomarkers. Results: Plasma p-tau has shown analytical validity (phase 2 primary aim 1) and first evidence of clinical validity (phase 3 primary aim 1), whereas the maturity level for Aβ remains to be partially achieved. Full and partial achievement has been assigned to p-tau and Aβ, respectively, in their associations to ante-mortem measures (phase 2 secondary aim 2). However, only preliminary evidence exists for the influence of covariates, assay comparison and cut-off criteria. Conclusions: Despite the relative infancy of blood biomarkers, in comparison to CSF biomarkers, much has already been achieved for phases 1 through 3 – with p-tau having greater success in detecting AD and predicting disease progression. However, sufficient data about the effect of covariates on the biomarker measurement is lacking. No phase 4 (real-world performance) or phase 5 (assessment of impact/cost) aim has been tested, thus not achieved. [ABSTRACT FROM AUTHOR]

A-type EGCG dimer is a new proanthocyanidins dimer from persimmon fruits. In the present study, we firstly examined the effects of EGCG and A-type EGCG dimer on Aβ40-fibrillization, and then the detailed mechanisms behind the inhibitory effects of polyphenols on Aβ40 amyloid fibrils formation were investigated by PICUP assay, ESI-MS, NMR and molecular docking. Our results confirmed that A-type EGCG dimer exhibited stronger inhibitory effect on the formation of Aβ40 amyloid fibrils. We found that A-type EGCG dimer possessed more binding sites on Aβ40 peptide than EGCG. Notably, compared with EGCG, A-type EGCG dimer could interact with more amino acid residues which possessed obvious aggregation-propensity. And our results also suggested that the hydrophobic interaction was the principal driving force to inhibit the formation of Aβ40 amyloid fibrils by A-type EGCG dimer. We believed that our study could provide useful insights for the design of low-molecular weight inhibitors of Aβ aggregation.

Purpose: To 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 Methods: A 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. Results: VCI 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). Conclusion: Combination of Aβ42 and total CSVD score could significantly elevate the predictive value of cognitive impairment in CSVD patients. [ABSTRACT FROM AUTHOR]

Aquaporin-4 (AQP4) is located mainly in the astrocytic end-feet around cerebral blood vessels and regulates ion and water homeostasis in the brain. While deletion of AQP4 is shown to reduce amyloid-β (Aβ) clearance and exacerbate Aβ peptide accumulation in plaques and vessels of Alzheimer's disease mouse models, the mechanism and clearing pathways involved are debated. Here, we investigated how inhibiting the function of AQP4 in healthy male C57BL/6 J mice impacts clearance of Aβ40, the more soluble Aβ isoform. Using two-photon in vivo imaging and visualizing vessels with Sulfurodamine 101 (SR101), we first showed that Aβ40 injected as a ≤ 0.5-μl volume in the cerebral cortex diffused rapidly in parenchyma and accumulated around blood vessels. In animals treated with the AQP4 inhibitor TGN-020, the perivascular Aβ40 accumulation was significantly (P < 0.001) intensified by involving four times more vessels, thus suggesting a generalized clearance defect associated with vessels. Increasing the injecting volume to ≥ 0.5 ≤ 1 μl decreased the difference of Aβ40-positive vessels observed in non-treated and AQP4 inhibitor-treated animals, although the difference was still significant (P = 0.001), suggesting that larger injection volumes could overwhelm intramural vascular clearance mechanisms. While both small and large vessels accumulated Aβ40, for the ≤ 0.5-μl volume group, the average diameter of the Aβ40-positive vessels tended to be larger in control animals compared with TGN-020-treated animals, although the difference was non-significant (P = 0.066). Using histopathology and ultrastructural microscopy, no vascular structural change was observed after a single massive dose of TGN-020. These data suggest that AQP4 deficiency is directly involved in impaired Aβ brain clearance via the peri-/para-vascular routes, and AQP4-mediated vascular clearance might counteract blood-brain barrier abnormalities and age-related vascular amyloidopathy. [ABSTRACT FROM AUTHOR]

Amyloid‐beta (Aβ) protein is related to Alzheimer disease (AD), and various experiments have shown that oligomers as small as dimers are cytotoxic. Recent studies have concluded that interactions of Aβ with neuronal cell membranes lead to disruption of membrane integrity and toxicity and they play a key role in the development of AD. Molecular dynamics (MD) simulations have been used to investigate Aβ in aqueous solution and membranes. We have previously studied monomeric Aβ40 embedded in dipalmitoylphosphatidylcholine (DPPC) membrane using MD simulations. Here, we explore interactions of two Aβ40 peptides in DPPC bilayer and its consequences on dimer distribution in a lipid bilayer and on the secondary structure of the peptides. We explored that N‐terminals played an important role in dimeric Aβ peptide aggregations and Aβ‐bilayer interactions, while C‐terminals bound peptides to bilayer like anchors. We did not observe exiting of peptides in our simulations although we observed insertion of peptides into the core of bilayer in some of our simulations. So it seems that the presence of Aβ on membrane surface increases its aggregation rate, and as diffusion occurs in two dimensions, it can increase the probability of interpeptide interactions. We found that dimeric Aβ, like monomeric one, had the ability to cause structural destabilization of DPPC membrane, which in turn might ultimately lead to cell death in an in vivo system. This information could have important implications for understanding the affinity of Aβ oligomers (here dimer) for membranes and the mechanism of Aβ oligomer toxicity in AD. [ABSTRACT FROM AUTHOR]

Herpes zoster is associated with an increased dementia and neovascular macular degeneration risk and a decline in glycemic control in diabetes mellitus. Because amyloid is present and pathogenic in these diseases, we quantified amyloid, Aβ40, Aβ42, and amylin in 14 zoster and 10 control plasmas. Compared with controls, zoster plasma had significantly elevated amyloid that correlated with Aβ42 and amylin levels and increased amyloid aggregation with addition of exogenous Aβ42 or amylin. These results suggest that zoster plasma contains factor(s) that promotes aggregation of amyloidogenic peptides, potentially contributing to the toxic amyloid burden and explaining accelerated disease progression following zoster. [ABSTRACT FROM AUTHOR]

Amyloidogenesis, with its multifaceted nature spanning from peptide self-assembly to membrane-mediated structural transitions, presents a significant challenge for the interdisciplinary scientific community. Here, we emphasize on how Singular Value Decomposition (SVD) can be employed to reveal hidden patterns and dominant modes of interaction that govern the complex process of amyloidogenesis. We first utilize SVD analysis on Circular Dichroism (CD) spectral datasets to identify the intermediate structural species emerging during peptide-membrane interactions and to determine binding constants more precisely than conventional methods. We investigate the monomer loss kinetics associated with peptide self-assembly using Nuclear Magnetic Resonance (NMR) dataset and determine the global kinetic parameters through SVD. Furthermore, we explore the seeded growth of amyloid fibrils by analyzing a time-dependent NMR dataset, shedding light on the kinetic intricacies of this process. Our analysis uncovers two distinct states in the aggregation of Aβ40 and pinpoints key residues responsible for this seeded growth. To strengthen our findings and enhance their robustness, we validate those using simulated data, thereby highlighting the physical interpretations derived from SVD. Overall, SVD analysis offers a model-free, global kinetic perspective, enabling the selection of optimal kinetic models. This study not only contributes valuable insights into the dynamics but also highlights the versatility of SVD in unravelling complex processes of amyloidogenesis. [Display omitted] • Singular Value Decomposition (SVD) was employed to unreveal hidden patterns. • Three different systems were utilized in this study. • SVD provided precise outcomes compared to standard methods. • SVD acts as an intermediate filter of the data matrix to provide a rigorous and model-free outcome. [ABSTRACT FROM AUTHOR]

Prakash Chandra Bhatt,1 Amita Verma,2 Fahad A Al-Abbasi,3 Firoz Anwar,3 Vikas Kumar,4 Bibhu Prasad Panda1 1Microbial and Pharmaceutical Biotechnology Laboratory, Centre for Advanced Research in Pharmaceutical Science, Faculty of Pharmacy, Jamia Hamdard, New Delhi, India; 2Bioorganic & Medicinal Chemistry Research Laboratory, Department of Pharmaceutical Sciences, Faculty of Health Sciences, Sam Higginbottom University of Agriculture, Technology and Sciences, Allahabad, Uttar Pradesh, India; 3Department of Biochemistry, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia; 4Natural Product Drug Discovery Laboratory, Department of Pharmaceutical Sciences, Faculty of Health Sciences, Sam Higginbottom University of Agriculture, Technology and Sciences, Allahabad, Uttar Pradesh, India Abstract: According to the World Health Organization, globally there are around 18 million patients suffering from Alzheimer’s disease (AD), and this number is expected to double by 2025. The pathophysiology of AD includes selective deposition of Aβ peptide in the mitochondria of cells, which inhibits uptake of glucose by neurons and key enzyme functions. Current drug treatments for AD are unable to rectify the underlying pathology of the disease; they only provide short-term symptomatic relief, so there is a need for the development of newer treatment regimes. The antiamyloid activity, antifibrinolytic activity, and antithrombotic activity of nattokinase holds potential for the treatment of AD. As nattokinase is a protein, its stability restricts its usage to a greater extent, but this limitation can be overcome by nanoencapsulation. In this work, we successfully synthesized polymeric nanoparticles of nattokinase and characterized its use by different techniques: transmission electron microscopy, scanning electron microscopy, DTS Nano, differential scanning calorimetry, Fourier-transform infrared spectroscopy, thioflavin T-binding assay, in vitro drug release, antifibrinolytic activity, and in vivo antiamyloid activity. As brain targeting of hydrophilic drugs is complicated due to the stringent nature of blood–brain barrier, in the current experimental study, we conjugated poly(lactic-co-glycolic acid) (PLGA)-encapsulated nattokinase with Tet1 peptide, which exhibits retrograde transportation properties because of its affinity to neurons. Our study suggests that PLGA-encapsulated nattokinase polymeric nanoparticles are able to downregulate amyloid aggregation and exhibit antifibrinolytic activity. The encapsulation of nattokinase in PLGA did not affect its enzyme activity, so the prepared nanoformulation containing nattokinase can be used as an effective drug treatment against AD. Keywords: nattokinase, PLGA, Aβ40, Alzheimer’s disease, surface modification, TEM, Tet1 peptide

Introduction: Despite their increased application, the heritability of Alzheimer's disease (AD)-related blood-based biomarkers remains unexplored., Methods: Plasma amyloid beta 40 (Aβ40), Aβ42, the Aβ42/40 ratio, total tau (t-tau), and neurofilament light (NfL) data came from 1035 men 60 to 73 years of age (μ = 67.0, SD = 2.6). Twin models were used to calculate heritability and the genetic and environmental correlations between them., Results: Additive genetics explained 44% to 52% of Aβ42, Aβ40, t-tau, and NfL. The Aβ42/40 ratio was not heritable. Aβ40 and Aβ42 were genetically near identical (r g  = 0.94). Both Aβ40 and Aβ42 were genetically correlated with NfL (r g  = 0.35 to 0.38), but genetically unrelated to t-tau., Discussion: Except for Aβ42/40, plasma biomarkers are heritable. Aβ40 and Aβ42 share mostly the same genetic influences, whereas genetic influences on plasma t-tau and NfL are largely unique in early old-age men. The absence of genetic associations between the Aβs and t-tau is not consistent with the amyloid cascade hypothesis., (© 2023 The Authors. Alzheimer's & Dementia published by Wiley Periodicals LLC on behalf of Alzheimer's Association.)

Cerebrospinal fluid (CSF) amyloid-β (Aβ)42 and tau are biomarkers for Alzheimer's disease (AD); however, the effects of other neurodegenerative processes on these biomarkers remain unclear. We measured Aβ40, Aβ42, total tau, phosphorylated-tau, and α-synuclein in CSF and plasma using matched samples from various neurodegenerative diseases to expand our basic knowledge on these biomarkers and their practical applications. A total of 213 CSF and 183 plasma samples were analyzed from cognitively unimpaired subjects, and patients with Alzheimer's disease dementia (ADD), mild cognitive impairment (MCI), non-AD dementias, and other neurological diseases. The CSF/plasma ratios of Aβ40 and Aβ42 were approximately 25:1. Aβ40/42 ratios in CSF and plasma were both 10:1. The CSF total tau/P181tau ratio was 6:1. The CSF/plasma α-synuclein ratio was 1:65. Significantly decreased Aβ42 levels and an increased Aβ40/42 ratio in CSF in ADD/MCI suggested that these relationships were specifically altered in AD. Increased total tau levels in ADD/MCI, encephalopathy, and multiple system atrophy, and increased P181tau in ADD/MCI indicated that these biomarkers corresponded to neurodegeneration and tauopathy, respectively. Although CSF α-synuclein levels were increased in ADD/MCI, there was no merit in measuring α-synuclein in CSF or plasma as a biomarker. The combination of biomarkers by the Aβ40/42 ratio×p181tau reflected specific changes due to the AD pathology in ADD/MCI. Thus, CSF Aβ40, Aβ42, p181tau, and tau were identified as biomarkers for aggregated Aβ associated state (A), aggregated tau associated state (T), and neurodegeneration state (N) pathologies in AD based on the NIA-AA criteria. Overlaps in these biomarkers need to be considered in clinical practice for differential diagnoses of neurodegenerative diseases. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A-type EGCG dimer was a potent inhibitor of Aβ 40 peptide aggregation. • A-type EGCG dimer prominently inhibited the oligomerization of Aβ 40. • A-type EGCG dimer predominantly interacted with Aβ 40 peptide with 1:2. • A-type EGCG dimer interacted with amino acids possessed high aggregation-propensity. Abstract A-type EGCG dimer is a new proanthocyanidins dimer from persimmon fruits. In the present study, we firstly examined the effects of EGCG and A-type EGCG dimer on Aβ 40 -fibrillization, and then the detailed mechanisms behind the inhibitory effects of polyphenols on Aβ 40 amyloid fibrils formation were investigated by PICUP assay, ESI-MS, NMR and molecular docking. Our results confirmed that A-type EGCG dimer exhibited stronger inhibitory effect on the formation of Aβ 40 amyloid fibrils. We found that A-type EGCG dimer possessed more binding sites on Aβ 40 peptide than EGCG. Notably, compared with EGCG, A-type EGCG dimer could interact with more amino acid residues which possessed obvious aggregation-propensity. And our results also suggested that the hydrophobic interaction was the principal driving force to inhibit the formation of Aβ 40 amyloid fibrils by A-type EGCG dimer. We believed that our study could provide useful insights for the design of low-molecular weight inhibitors of Aβ aggregation. [ABSTRACT FROM AUTHOR]

The present study evaluated the effects of s-nitrosoglutathione (GSNO), a nitrosothiol and sustained NO releaser, on experimental model of sporadic Alzheimer`s disease (sAD) in rats. Levels of Aβ40, Aβ42 and BDNF were assessed in brain hippocampal homogenates for correlative purposes. Intracerebroventricular-Streptozotocin (icv-STZ) induced increased escape latencies (acquisition) and reduced time in target quadrant (probe trial) in Morris Water Maze (MWM) test at 3 months post icv-STZ administration. These behavioural changes were associated with increased Aβ depositions and lowered BDNF levels in brain hippocampal homogenates. Pre-treatment with GSNO (50 μg/kg/day), reduced the icv-STZ induced cognitive deficits in acquisition and probe trials in the MWM. The icv-STZ induced elevations in Aβ40 and Aβ42 and reduced levels of BDNF in hippocampal homogenates were also attenuated after GSNO treatment in these rats. The NO-precursor, l -arginine (100 mg/kg) induced similar effects on behavioural and biochemical parameters tested but was marginally less consistent as compared to those seen with GSNO. The results suggest that GSNO ameliorates the cognitive deficits and associated brain biochemical changes in this experimental model of sporadic AD, and NO-BDNF interactions could play crucial role in these effects. [ABSTRACT FROM AUTHOR]

Agonists of M1 muscarinic acetylcholine receptors are promising therapeutic agents for the treatment of Alzheimer's disease (AD). An example of one of these agents is xanomeline, which has been a leading candidate, however induces various unwanted adverse effects. 3‑[3‑(3‑florophenyl‑2‑propyn‑1‑ylthio)‑1,2,5‑ thiadiazol‑4‑yl]‑1,2,5,6‑tetrahydro‑1‑methylpyridine oxalate (EUK1001), a fluorinated derivative of xanomeline, has been demonstrated to attenuate AD‑like neurodegenerative pathology in presenilin‑deficient mice, which has no β‑amyloid (Aβ) pathology. The present study assessed the effect of EUK1001 on the behavioral performance of the 3xTg‑AD model of AD. EUK1001 treatment decreased cognitive deficits in male and female AD mice in the Morris water maze test and novel object recognition tasks. EUK1001 also decreased Aβ42, however not Aβ40 in the cortex and hippocampus of AD mice. EUK1001 may also alter amyloid precursor protein processing to a nonamyloidgenic pathway in vitro. These results demonstrate that EUK1001 may ameliorate the cognitive dysfunction of AD mice, possibly by reducing Aβ production. Therefore, EUK1001 may be an effective treatment for AD. [ABSTRACT FROM AUTHOR]

The abnormal deposition of amyloid- β (A β) peptides in the brain is the main neuropathological hallmark of Alzheimer's disease (AD). Amyloid deposits are formed by a heterogeneous mixture of A β peptides, among which the most studied are A β40 and A β42. A β40 is abundantly produced in the human brain, but the level of A β42 is remarkably increased in the brain of AD patients. Aside from A β40 and A β42, recent data have raised the possibility that A β43 peptides may be instrumental in AD pathogenesis. Besides its length, whether the A β aggregated form accounts for the neurotoxicity is also particularly controversial. A β fibrils are generally considered as key pathogenic substances in AD pathogenesis. Nevertheless, recent data implicated soluble A β oligomers as the main cause of synaptic dysfunction and memory loss in AD. To further address this uncertainty, we analyzed the neurotoxicity of different A β species and A β forms at the cellular level. The results showed that A β42 could form oligomers significantly faster than A β40 and A β43 and A β42 oligomers showed the greatest level of neurotoxicity. Regardless of the length of A β peptides, A β oligomers induced significantly higher cytotoxicity compared with the other two A β forms. Surprisingly, the neurotoxicity of fibrils in PC12 cells was only marginally but not significantly stronger than monomers, contrary to previous reports. Altogether, our findings demonstrate the high pathogenicity of A β42 among the three A β species and support the idea that A β42 oligomers contribute to the pathological events leading to neurodegeneration in AD. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Aggregation of amyloid-β (Aβ) protein plays a central role in Alzheimer's disease. Because protein aggregation is a concentration-dependent process, rigorous investigations require accurate concentration measurements. Owing to the high aggregation propensity of Aβ protein, working solutions of Aβ are typically in the low micromolar range. Therefore, an ideal Aβ quantification method requires high sensitivity without sacrificing speed and accuracy. Absorbance at 280 nm is frequently used to measure Aβ concentration, but the sensitivity is low with only one tyrosine and no tryptophan residues in the Aβ sequence. Here we present a fluorescence method for Aβ quantification using fluorescamine, which gives high fluorescence upon reaction with primary amines. We show that, using hen egg white lysozyme as a standard, fluorescence correlates linearly with primary amine concentration across a wide range of fluorescamine concentrations, from 62.5 to 1000 µM. The maximal sensitivity of detection is achieved at a fluorescamine concentration of 250 µM or higher. The fluorescamine method is compatible with the presence of dimethyl sulfoxide, which is commonly used in the preparation of Aβ oligomers, and limits the use of absorbance at 280 nm due to its high background reading. Using aggregation kinetics, we show that the fluorescamine method gives accurate concentration measurements at low micromolar range and leads to highly consistent aggregation data. We recommend the fluorescamine assay to be used for routine and on-the-fly concentration determination in Aβ oligomerization and fibrillization experiments.

The combination of decreased amyloid β42 (Aβ42) and increased total tau proteins (T-Tau) and phosphorylated tau (P-Tau) in cerebrospinal fluid (CSF) has recently been considered as a biological diagnostic criterion of Alzheimer’s disease (AD). Previous studies showed significant heterogeneity in CSF Aβ42 levels to discriminate AD from non-AD patients. It was also suggested that the CSF amyloid peptide β42/β40 ratio has better diagnostic performance than Aβ42 alone. The objective of the present study was to investigate the potential added value of determining CSF amyloid β40 peptide (Aβ40) for biological diagnosis of AD when CSF Aβ42 levels failed.CSF AD biomarkers were run in 2,171 samples from 1,499 AD and 672 non-AD patients. The following pathologic thresholds were used to define an AD-positive CSF biomarker profile: T-Tau ≥ 400 ng/L, P-Tau181 ≥ 60 ng/L and Aβ42 ≤ 700 ng/L. CSF Aβ40 was assayed in AD patients with CSF Aβ42 levels above 700 ng/L and non-AD patients with CSF Aβ42 levels below 700 ng/L. CSF Aβ40 levels were higher in AD than non-AD patients. The ROC curves of CSF Aβ40 and the Aβ42/Aβ40 ratio defined AD cut off values at 12,644 ng/L and 0.06 respectively. In AD patients with non-pathological CSF Aβ42, CSF Aβ40 concentration was able to correct 76.2% of cases when expressed as CSF Aβ42/Aβ40 ratio and 94.7% of cases when used alone. Using CSF Aβ42 and then CSF Aβ40, the percentage of misinterpreted AD patients fell to 1.0%.CSF Aβ40 concentration improved interpretation of Aβ42 level for the diagnosis of Alzheimer’s disease. CSF Aβ40 alone showed better diagnostic performance than the amyloid peptide Aβ42/Aβ40 ratio. The added value of determining CSF Aβ40 in AD diagnosis now needs confirming in a cohort of definite AD patients and to be completed with novel amyloid cascade biomarkers.

Alzheimer’s disease (AD) is the only one among top ten diseases in USA that cannot be cured, prevented or slowed down. At molecular level the mechanism of onset has been closely associated with mis-folding of Aβ40 and Aβ42 and is well supported by the genetic data for AD. Extensive research efforts have led to identification of factors and metal ions that could manipulate Aβ equilibrium, especially Ca 2+ . Previously, we reported selectively acceleration of Aβ42 fibril formation by Ca 2+ in vitro within physiological concentrations (BBA (2009) 1794:1536) . Aβ40 on the other hand did not appear to be significantly affected by Ca 2+ addition. In an effort to understand the distinctive behavior of Aβ40, we monitored changes of Aβ40 aggregation by intrinsic tyrosine fluorescence and CD and took different approaches for data processing. Our analysis of CD data indicates a complex effect induced by the addition of 2 mM Ca 2+ resulting in an increase in the rate of transformation from monomer to β-sheet rich fibrilar or intermediate species formation in Aβ40. Surprisingly, the kinetics observed by intrinsic fluorescence studies in this article and ThT, SEC or EM studies in our previous report were not able to unravel the existence of this effect in Aβ40. [ABSTRACT FROM AUTHOR]

Recent epidemiological and clinical data suggest that elevated serum homocysteine levels may increase the risk of developing Alzheimer's disease (AD), but the underlying mechanisms are unknown. We tested the hypothesis that high serum homocysteine concentration may increase amyloid beta-peptide (Aβ) levels in the brain and could therefore accelerate AD neuropathology. For this purpose, we mated a hyperhomocysteinemic CBStm1Unc mouse carrying a heterozygous dominant mutation in cystathionine-beta-synthase (CBS*) with the APP*/PS1* mouse model of brain amyloidosis. The APP*/PS1*/CBS* mice showed significant elevations of serum homocysteine levels compared to the double transgenic APP*/PS1* model of amyloidosis. Results showed that female (but not male) APP*/PS1*/CBS* mice exhibited significant elevations of Aβ40 and Aβ42 levels in the brain. Correlations between homocysteine levels in serum and brain Aβ levels were statistically significant. No increases in beta secretase activity or evidence of neuronal cell loss in the hyperhomocysteinemic mice were found.The causes of neuronal dysfunction and degeneration in AD are not fully understood, but increased production of Aβ seems to be of major importance. By unveiling a link between homocysteine and Aβ levels, these findings advance our understanding on the mechanisms involved in hyperhomocysteinemia as a risk factor for AD.

Aims: Previous studies have suggested that insulin‐like growth factor‐I (IGF‐I) deficiency may lead to cognitive deficits in neurodegenerative diseases such as Alzheimer's disease. The present study aimed to investigate the possible relationship between cognitive function and concentration of IGF‐I or amyloid beta protein (Aβ) in serum in Alzheimer's patients. Methods: A total of 81 Japanese patients were enrolled in this study. Concentrations of IGF‐I, Aβ42, and Aβ40 in serum were measured. Two neuropsychological tests, Mini‐Mental State Examination and Hasegawa's Dementia Scale‐Revised (HDS‐R), were also performed. Linear correlations among the age, serum IGF‐I, serum Aβ42 or Aβ40, Aβ42/Aβ40 ratio, Mini‐Mental State Examination or HDS‐R total score, and the scores for six HDS‐R subscales were analyzed by regression analysis. Results: IGF‐I showed a significant negative correlation with age (β = −0.357, P = 0.002) and a positive correlation with Aβ42/Aβ40 ratio (β = 0.318, P = 0.007). Serum IGF‐I and both the Mini‐Mental State Examination and the HDS‐R total score also correlated (β = 0.505, β = 0.524, P < 0.01). Among the HDS‐R subscales, ‘Recall’ (ρ = 0.379, P < 0.01), ‘Verbal fluency’ (ρ = 0.360, P < 0.01), and ‘Attention and calculation’ (ρ = 0.389, P < 0.01) showed significant positive correlations with serum IGF‐I. Conclusion: The results, specifically that lower serum IGF‐I was associated with cognitive impairment, suggest that metabolism of IGF‐I may be involved in the pathogenesis of cognitive deficits in Alzheimer's disease. [ABSTRACT FROM AUTHOR]

Background: Dementia with Lewy bodies (DLB) symptoms are close to those of Alzheimer's disease (AD), and the differential diagnosis is difficult especially early in the disease. Unfortunately, AD biomarkers in cerebrospinal fluid (CSF), and more particularly Aβ1 - 42, appear to be altered in dementia with Lewy bodies (DLB). However, the level of these biomarkers has never been studied in the prodromal stage of the disease.Objective: To compare these biomarkers between DLB and AD, with a particular focus on the prodromal stage.Methods: A total of 166 CSF samples were collected at the memory clinic of Strasbourg. They were obtained from prodromal DLB (pro-DLB), DLB dementia, prodromal AD (pro-AD), and AD dementia patients, and elderly controls. Phospho-Tau181, total-Tau, Aβ42, and Aβ40 were measured in the CSF.Results: At the prodromal stage, contrary to AD patients, DLB patients' biomarker levels in the CSF were not altered. At the demented stage of DLB, Aβ42 levels were reduced as well as Aβ40 levels. Thus, the Aβ42/Aβ40 ratio remained unchanged between the prodromal and demented stages, contrary to what was observed in AD. Tau and Phospho-Tau181 levels were unaltered in DLB patients.Conclusions: We have shown that at the prodromal stage the DLB patients had no pathological profile. Consequently, CSF AD biomarkers are extremely useful for differentiating AD from DLB patients particularly at this stage when the clinical diagnosis is difficult. Thus, these results open up new perspectives on the interpretation of AD biomarkers in DLB. [ABSTRACT FROM AUTHOR]

The combination of decreased amyloid β42 (Aβ42) and increased total tau proteins (T-Tau) and phosphorylated tau (P-Tau) in cerebrospinal fluid (CSF) has recently been considered as a biological diagnostic criterion of Alzheimer's disease (AD). Previous studies showed significant heterogeneity in CSF Aβ42 levels to discriminate AD from non-AD patients. It was also suggested that the CSF amyloid peptide β42/β40 ratio has better diagnostic performance than Aβ42 alone. The objective of the present study was to investigate the potential added value of determining CSF amyloid β40 peptide (Aβ40) for biological diagnosis of AD when CSF Aβ42 levels failed. CSF AD biomarkers were run in 2,171 samples from 1,499 AD and 672 non-AD patients. The following pathologic thresholds were used to define an AD-positive CSF biomarker profile: T-Tau = 400 ng/L, P-Tau181 ≥ 60 ng/L, and Aβ42 ≤ 700 ng/L. CSF Aβ40 was assayed in AD patients with CSF Aβ42 levels above 700 ng/L and non-AD patients with CSF Aβ42 levels below 700 ng/L. CSF Aβ40 levels were higher in AD than non-AD patients. The receiver operator characteristic curves of CSF Aβ40 and the Aβ42/Aβ40 ratio defined AD cut-off values at 12,644 ng/L and 0.06, respectively. In AD patients with non-pathological CSF Aβ42, CSF Aβ40 concentration was able to correct 76.2% of cases when expressed as CSF Aβ42/Aβ40 ratio and 94.7% of cases when used alone. Using CSF Aβ42 and then CSF Aβ40, the percentage of misinterpreted AD patients fell to 1.0%. CSF Aβ40 concentration improved interpretation of Aβ42 level for the diagnosis of AD. CSF Aβ40 alone showed better diagnostic performance than the amyloid peptide Aβ42/Aβ40 ratio. The added value of determining CSF Aβ40 in AD diagnosis now needs confirming in a cohort of definite AD patients and to be completed with novel amyloid cascade biomarkers. [ABSTRACT FROM AUTHOR]

The abnormal accumulation of amyloid- β (A β) peptide in the brain is one of the most important hallmarks of Alzheimer's disease. A β is an aggregation-prone and toxic polypeptide with 39-43 residues, derived from the amyloid precursor protein proteolysis process. According to the amyloid hypothesis, abnormal accumulation of A β in the brain is the primary influence driving Alzheimer's disease pathologies. Among all kinds of A β isoforms, A β40 and A β42 are believed to be the most important ones. Although these two kinds of A β differ only in two amino acid residues, recent studies show that they differ significantly in their metabolism, physiological functions, toxicities, and aggregation mechanism. In this review, we mainly summarize the similarities and differences between A β42 and A β40, recent studies on selective inhibitors as well as probes will also be mentioned. Copyright © 2015 European Peptide Society and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Purpose: To determine whether Aβ40 levels in the follicular fluid (FF) of infertile women undergoing IVF demonstrate a relationship with IVF cycle parameters and outcome. Methods: FF Aβ40 levels were compared between patients achieving ongoing pregnancy and those with unsuccessful cycles. Clinical data such as ongoing pregnancy rate, implantation rate, number of oocytes retrieved, number of 8 cells embryos with ≤5 % fragmants, ratio of 8 cells embryos with ≤5 % fragmants to total embryos per patient and cleavage rate were compared among three percentile groups of Aβ40. CCK-8 method was used to measure the effect of Aβ40 on rat granulosa cells proliferation in vitro. RT-PCR was used to detect the mRNA expression levels of steroidogenesis related genes. Results: Patients achieving ongoing pregnancy ( n = 26; 50.98 %) demonstrated significantly higher FF Aβ40 levels compared to those with unsuccessful cycles ( n = 25; 49.02 %; P = 0.024). No significant differences were observed in APP (amyloid precursor protein) and its other proteolysis products including sAPPα, sAPPβand Aβ 42 between the two groups. Statistically significant differences between the three percentile groups of Aβ 40 were observed only in the implantation rates and ongoing pregnancy rates. There were no statistically significant differences between the three percentile groups in the age, No. oocytes retrieved, No. 2 pronucleus, No. embryos transferred, No. 8 cells embryos with ≤5 % fragmants and cleavage rate. Significantly negative correlation exists between APP and AFC (antral follicle count) (R =−0.360, P = 0.005) and oocytes retrieved (R =−0.378, P = 0.004). There were also significantly positive correlations between Aβ40 and Aβ42 (R = 0.407, P = 0.000), between AFC and oocytes retrieved (R = 0.476, P = 0.000). Rat granulosa cells treated with Aβ40 of different concentrations have improved their proliferative ability. Cells treated with 200 pg/ml Aβ40 have the strongest ability of proliferation. 200 pg/ml Aβ40 enhanced the expression of key molecules during steroidogenesis such as IGF-1,IGF-1receptor (IGF-1R),FSH receptor (FSHR),P450 aromatase (P450arom),steroidogenic acute regulatory protein (StAR) and cholesterol side-chain cleavage cytochromes P450(P450scc). Conclusions: Aβ40 levels in follicle fluid may be associated with ongoing pregnancy and the moderate expression level of Aβ40 is important for oocytes and embryos development. [ABSTRACT FROM AUTHOR]

In addition to their neurotoxic role in Alzheimer's disease (AD), β-amyloid peptides (Aβs) are also known to play physiological roles. Here, we show that recombinant Aβ40 significantly increased the outward current of the GABAA receptor containing (GABAAα6) in rat cerebellar granule neurons (CGNs). The Aβ40-mediated increase in GABAAα6 current was mediated by an increase in GABAAα6 protein expression at the translational rather than the transcriptional level. The exposure of CGNs to Aβ40 markedly induced the phosphorylation of ERK ( pERK) and mammalian target of rapamycin (pmTOR). The increase in GABAAα6 current and expression was attenuated by specific inhibitors of ERK or mTOR, suggesting that the ERK and mTOR signaling pathways are required for the effect of Aβ40 on GABAAα6 current and expression in CGNs. A pharmacological blockade of the p75 neurotrophin receptor (p75NTR), but not the insulin or α7- nAChR receptors, abrogated the effect of Aβ40 on GABAAα6 protein expression and current. Furthermore, the expression of GABAAα6 was lower in CGNs from APP−/− mice than in CGNs from wild-type mice. Moreover, the internal granule layer (IGL) in APP−/− mice was thinner than the IGL in wild-type mice. The injection of Aβ40 into the cerebellum reversed this effect, and the application of p75NTR blocking antibody abolished the effects of Aβ40 on cerebellum morphology in APP−/− mice. Our results suggest that low concentrations of Aβ40 play a role in regulating CGN maturation through p75NTR. [ABSTRACT FROM AUTHOR]

Cerebral amyloid angiopathy (CAA) is a critical factor in the pathogenesis of Alzheimer's disease (AD). In the clinical setting, nearly 98% AD patients have CAA, and 75% of these patients are rated as severe CAA. It is characterized by the deposition of the β-amyloid peptide (mainly Aβ40) in the walls of cerebral vessels, which induces the degeneration of vessel wall components, reduces cerebral blood flow, and aggravates cognitive decline. Platelets are anuclear cell fragments from bone marrow megakaryocytes and their function in hemostasis and thrombosis has long been recognized. Recently, increasing evidence suggests that platelet activation can also mediate the onset and development of CAA. First, platelet activation and adhesion to a vessel wall is the initial step of vascular injury. Activated platelets contribute to more than 90% circulating Aβ (mainly Aβ1-40), which in turn activates platelets and results in the vicious cycle of Aβ overproduction in damaged vessel. Second, the uncontrolled activation of platelets leads to a chronic inflammatory reaction by secretion of chemokines (eg, platelet factor 4 [PF4], regulated upon activation normal T-cell expressed and presumably secreted [RANTES], and macrophage inflammatory protein [MIP-1α]), interleukins (IL-1β, IL-7, and IL-8), prostaglandins, and CD40 ligand (CD40L). The interaction of these biological response modulators with platelets, endothelial cells, and leukocytes establishes a localized inflammatory response that contributes to CAA formation. Finally, activated platelets are the upholder of fibrin clots, which are structurally abnormal and resistant to degradation in the presence of Aβ42. Thus, opinion has emerged that targeting blood platelets may provide a new avenue for anti-AD therapy. [ABSTRACT FROM AUTHOR]

According to the modified Boston criteria, cerebral amyloid angiopathy (CAA) can present with lobar hematoma (LH) or superficial siderosis (SS). Recently, decreased CSF β-amyloid peptide 40 and 42 (Aβ40; Aβ42) and increased total and phosphorylated tau (t-tau; p-tau) concentrations have been described in CAA presenting with LH. Our aim was to analyze CSF biomarkers as a diagnostic tool for CAA according to the modified Boston criteria. We prospectively included patients with possible or probable CAA according to the modified Boston criteria. CSF was analyzed for t-tau, p-tau, Aβ42, and Aβ40. Data were compared with AD patients ( n = 42) and controls ( n = 14). Thirteen CAA patients were included, nine presenting with LH and four with SS. T-tau and p-tau levels in CAA were higher than controls, but lower than in AD. Differences in t-tau and p-tau levels between CAA versus controls and AD were all significant apart of the CAA p-tau levels comparison with controls. Aβ42 levels in CAA were significantly lower than in controls, and slightly higher than in AD, though non-significantly. Aβ40 levels in CAA were non-significantly lower than in controls, and significantly lower than in AD. Combining the findings of our study and the earlier report, we confirm that patients with suspected CAA have significantly different values for t-tau, Aβ42, Aβ42/t-tau, and Aβ40. Especially Aβ40 levels seem to be of clinical interest to differentiate CAA from AD. CSF biomarkers have to be analyzed in a larger number of CAA patients, and compared to patients with other disorders causing LH or SS. [ABSTRACT FROM AUTHOR]

Abstract: Alzheimer''s disease, the most common cause of dementia in the elderly and characterized by the deposition and accumulation of plaques, is composed in part of β-amyloid (Aβ) peptides, loss of neurons, and the accumulation of neurofibrillary tangles. Here, we describe ponezumab, a humanized monoclonal antibody, and show how it binds specifically to the carboxyl (C)-terminus of Aβ40. Ponezumab can label Aβ that is deposited in brain parenchyma found in sections from Alzheimer''s disease casualties and in transgenic mouse models that overexpress Aβ. Importantly, ponezumab does not label full-length, non-cleaved amyloid precursor protein on the cell surface. The C-terminal epitope of the soluble Aβ present in the circulation appears to be available for ponezumab binding because systemic administration of ponezumab greatly elevates plasma Aβ40 levels in a dose-dependent fashion after administration to a mouse model that overexpress human Aβ. Administration of ponezumab to transgenic mice also led to a dose-dependent reduction in hippocampal amyloid load. To further explore the nature of ponezumab binding to Aβ40, we determined the X-ray crystal structure of ponezumab in complex with Aβ40 and found that the Aβ40 carboxyl moiety makes extensive contacts with ponezumab. Furthermore, the structure–function analysis supported this critical requirement for carboxy group of AβV40 in the Aβ–ponezumab interaction. These findings provide novel structural insights into the in vivo conformation of the C-terminus of Aβ40 and the brain Aβ-lowering efficacy that we observed following administration of ponezumab in transgenic mouse models. [Copyright &y& Elsevier]

In Alzheimer’s disease (AD), Purkinje neurons in the cerebellum are spared, while, for instance, pyramidal neurons in the hippocampus are neuropathologically affected. Several lines of evidence suggest that the pathogenesis could be induced by the concentration-dependent polymerization of the amyloid β-peptide (Aβ) into extracellular oligomers. The role of intracellular Aβ is not fully investigated, but recent data indicate that also this pool could be of importance. Here, we use laser capture microdissection microscopy for isolation of Purkinje neurons from AD cases and controls, and quantify the low levels of intracellular Aβ using a novel and highly sensitive ELISA. Similar to Cornu Ammonis 1 pyramidal neurons, the intracellular levels of the most toxic variant, Aβ42, as well as the Aβ42/Aβ40 ratio, were increased in Purkinje neurons from sporadic AD cases as compared to controls. However, the levels of Aβ42 as well as Aβ40 were clearly lower in Purkinje neurons than in pyramidal neurons. Based on the volume of the captured Purkinje neurons, the intraneuronal concentrations of Aβ42 were calculated to be 200 nM in sporadic AD cases and 90 nM in controls. The corresponding concentrations in pyramidal neurons from hippocampus were 3 μM and 660 nM, respectively. The Aβ40 concentration was not significantly altered in AD cases compared to controls. However, we found ten times higher concentration of Aβ40 in pyramidal neurons (10 μM) compared to Purkinje neurons (1 μM). Finally, we suggest that high concentration of intracellular Aβ42 correlates with vulnerability to AD neuropathology. [ABSTRACT FROM AUTHOR]

Several studies have shown that reduced amyloid-β 1-42 (Aβ {42}) and increased tau levels in cerebrospinal fluid (CSF) reflect increased Alzheimer's disease (AD) pathology in the brain. β-site APP cleaving enzyme (BACE1) is thought to be the major β-secretase involved in Aβ production in the brain, and therefore we investigated the relation between BACE1 activity and CSF markers Aβ {40}, Aβ_{42}, total tau (t-tau), and tau phosphorylated at threonine 181 (p-tau) in CSF of control (n=12), mild cognitive impairment (n=18), and AD (n=17) subjects. Patients were classified according to their Aβ {42}, t-tau, and p-tau CSF biomarker levels, with either an AD-like biomarker profile (two or three biomarkers abnormal: Aβ {42} 495 pg/ml in combination with t-tau > 356 pg/ml, and/or p-tau > 54 pg/ml) or a normal biomarker profile (&les; one biomarker abnormal). This resulted in 19 subjects with an AD-like biomarker profile (66 ± 6 years, 53% female, and Mini-Mental Status Examination (MMSE) score: 23 ± 5) and 28 subjects with a normal biomarker profile (62 ± 11 years, 43% female, and MMSE score: 27 ± 4). Subjects with an AD-like biomarker profile had higher CSF BACE1 activity levels, compared to patients with a normal biomarker profile (20 pg/ml and 16 pg/ml respectively; p=0.01), when controlled for age and gender. In the whole sample, BACE1 activity correlated with CSF levels of Aβ{40}, t-tau, and p-tau (r=0.38, r=0.63, and r=0.65; all p< 0.05), but not with Aβ {42}. These data suggest that increased BACE1 activity in CSF relates to AD pathology in the brain. [ABSTRACT FROM AUTHOR]