Role In Alzheimer's Disease Pathology Research Articles

New plasma LC-MS/MS assays for the quantitation of beta-amyloid peptides and identification of apolipoprotein E proteoforms for Alzheimer's disease risk assessment.

Early detection of Alzheimer's disease (AD) represents an unmet clinical need. Beta-amyloid (Aβ) plays an important role in AD pathology, and the Aβ42/40 peptide ratio is a good indicator for amyloid deposition. In addition, variants of the apolipoprotein E (APOE) gene are associated with variable AD risk. Here, we describe the development and validation of high-throughput liquid chromatography-tandem mass spectrometry (LC-MS/MS) assays for plasma Aβ40 and Aβ42 quantitation, as well as apolipoprotein E (ApoE) proteotype determination as a surrogate for APOE genotype. Aβ40 and Aβ42 were simultaneously immunoprecipitated from plasma, proteolytically digested, and quantitated by LC-MS/MS. ApoE proteotype status was qualitatively assessed by targeting tryptic peptides from the ApoE2, ApoE3, and ApoE4 proteoforms. Both assays were validated according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. Within-run precision was 1.8%-4.2% (Aβ40), 1.9%-7.2% (Aβ42), and 2.6%-8.3% (Aβ42/40 ratio). Between-run precision was 3.5%-5.9% (Aβ40), 3.8%-8.0% (Aβ42), and 3.3%-8.7% (Aβ42/40 ratio). Both Aβ40 and Aβ42 were linear from 10 to 2500 pg/mL. Identified ApoE proteotypes had 100% concordance with APOE genotypes. We have developed a precise, accurate, and sensitive high-throughput LC-MS/MS assay for plasma Aβ40, Aβ42, and proteoforms of ApoE.

Downregulation of peripheral luteinizing hormone rescues ovariectomy-associated cognitive deficits in APP/PS1 mice

Alzheimer's disease (AD) is more prevalent in women than men, supposing due to the decline of estrogens in menopause, accompanied by increased gonadotropins such as luteinizing hormone (LH). We and others found that the transcription factor early growth response-1 (EGR1) regulates cholinergic function including the expression of acetylcholinesterase (AChE) and plays a significant role in cognitive decline of AD. Here we investigated in APP/PS1 mice by ovariectomy (OVX) and estradiol (E2) supplementation or inhibition of LH the effect on hippocampus-related cognition and related molecular changes. We found that OVX-associated cognitive impairment was accompanied by increased dorsal hippocampal EGR1 expression, which was rescued by downregulating peripheral LH rather than by supplementing E2. We also found in postmortem AD brains a higher expression of pituitary LH-mRNA and higher EGR1 expression in the posterior hippocampus. Both, in human and mice, there was a significant positive correlation between respectively posterior/dorsal hippocampal EGR1 and peripheral LH expression. We conclude that peripheral increased LH and increased posterior hippocampal EGR1 plays a significant role in AD pathology.

Amyloid Precursor Protein and Alzheimer's Disease.

Alzheimer's disease (AD) is one of the most common neurodegenerative disorders associated with age or inherited mutations. It is characterized by severe dementia in the late stages that affect memory, cognitive functions, and daily life overall. AD progression is linked to the accumulation of cytotoxic amyloid beta (Aβ) and hyperphosphorylated tau protein combined with other pathological features such as synaptic loss, defective energy metabolism, imbalances in protein, and metal homeostasis. Several treatment options for AD are under investigation, including antibody-based therapy and stem cell transplantation. Amyloid precursor protein (APP) is a membrane protein considered to play a main role in AD pathology. It is known that APP in physiological conditions follows a non-amyloidogenic pathway; however, it can proceed to an amyloidogenic scenario, which leads to the generation of extracellular deleterious Aβ plaques. Not all steps of APP biogenesis are clear so far, and these questions should be addressed in future studies. AD is a complex chronic disease with many factors that contribute to disease progression.

Mechanistic insights into MARK4 inhibition by galantamine toward therapeutic targeting of Alzheimer's disease.

Introduction: Hyperphosphorylation of tau is an important event in Alzheimer's disease (AD) pathogenesis, leading to the generation of "neurofibrillary tangles," a histopathological hallmark associated with the onset of AD and related tauopathies. Microtubule-affinity regulating kinase 4 (MARK4) is an evolutionarily conserved Ser-Thr (S/T) kinase that phosphorylates tau and microtubule-associated proteins, thus playing a critical role in AD pathology. The uncontrolled neuronal migration is attributed to overexpressed MARK4, leading to disruption in microtubule dynamics. Inhibiting MARK4 is an attractive strategy in AD therapeutics. Methods: Molecular docking was performed to see the interactions between MARK4 and galantamine (GLT). Furthermore, 250 ns molecular dynamic studies were performed to investigate the stability and conformational dynamics of the MARK4-GLT complex. We performed fluorescence binding and isothermal titration calorimetry studies to measure the binding affinity between GLT and MARK4. Finally, an enzyme inhibition assay was performed to measure the MARK4 activity in the presence and absence of GLT. Results: We showed that GLT, an acetylcholinesterase inhibitor, binds to the active site cavity of MARK4 with an appreciable binding affinity. Molecular dynamic simulation for 250ns demonstrated the stability and conformational dynamics of the MARK4-GLT complex. Fluorescence binding and isothermal titration calorimetry studies suggested a strong binding affinity. We further show that GLT inhibits the kinase activity of MARK4 significantly (IC50 = 5.87µM). Conclusion: These results suggest that GLT is a potential inhibitor of MARK4 and could be a promising therapeutic target for AD. GLT's inhibition of MARK4 provides newer insights into the mechanism of GLT's action, which is already used to improve cognition in AD patients.

Hepatic soluble epoxide hydrolase activity regulates cerebral Aβ metabolism and the pathogenesis of Alzheimer’s disease in mice

Alzheimer's disease (AD) is caused by a complex interaction between genetic and environmental factors. However, how the role of peripheral organ changes in response to environmental stimuli during aging in AD pathogenesis remains unknown. Hepatic soluble epoxide hydrolase (sEH) activity increases with age. Hepatic sEH manipulation bidirectionally attenuates brain amyloid-β (Aβ) burden, tauopathy, and cognitive deficits in AD mouse models. Moreover, hepatic sEH manipulation bidirectionally regulates the plasma level of 14,15-epoxyeicosatrienoic acid (-EET), which rapidly crosses the blood-brain barrier and modulates brain Aβ metabolism through multiple pathways. A balance between the brain levels of 14,15-EET and Aβ is essential for preventing Aβ deposition. In AD models, 14,15-EET infusion mimicked the neuroprotective effects of hepaticsEH ablation at biological and behavioral levels. These results highlight the liver's key role in AD pathology,and targeting the liver-brain axis in response to environmental stimuli may constitute a promising therapeutic approach for AD prevention.

RNA Hypomethylation and Unchanged DNA Methylation Levels in the Cortex of ApoE4 Carriers and Alzheimer's Disease Subjects.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder, and ApoE4 variants are significant risk factors for AD. Epigenetic modifications are involved in AD pathology. However, it is unclear whether DNA/RNA methylation plays a role in AD pathology, and dysregulation of DNA/RNA methylation occurs in ApoE4 carriers. The present study aimed to determine whether dysregulation of DNA/RNA methylation is present in the brains of ApoE4 carriers and AD patients. In this study, postmortem brain tissues from carriers of ApoE4 and ApoE3, from AD and non- AD controls, were used in the analysis of DNA/RNA methylation, methyltransferases, and their demethylases. Immunofluorescence staining indicates that RNA methylation is suppressed in ApoE4 carriers. Further analysis shows that the expression of RNA methyltransferases and an RNA methylation reader is suppressed in ApoE4 carriers, whereas RNA demethylase expression is increased. RNA hypomethylation occurs in NeuN+ neurons in ApoE4 carriers and AD patients. Furthermore, in ApoE4 carriers, both DNA methyltransferases and demethylases are downregulated, and overall DNA methylation levels are unchanged. Our finding indicates that RNA methylation decreased in ApoE4 carriers before AD pathology and AD individuals. The expression of RNA methyltransferases and RNA methylation reader is inhibited, and RNA demethylase is upregulated in ApoE4 carriers, which leads to suppression of RNA methylation, and the suppression precedes the AD pathogenesis and persists through AD pathology.

Aging induces abnormal accumulation of Aβ in extracellular vesicle and/or intraluminal membrane vesicle-rich fractions in nonhuman primate brain

Aβ metabolism in the brain is mediated by endocytosis, one part of the intracellular membrane trafficking system. We previously showed that aging attenuates the interaction of dynein with dynactin, which disrupts the endosomal/lysosomal trafficking pathway involved in Aβ metabolism, resulting in intracellular accumulation of Aβ. Several studies have shown that in Alzheimer's disease (AD), intraneuronal accumulation of Aβ precedes extracellular Aβ depositions. However, it is unclear what accounts for this transition from intracellular to extracellular depositions. Accumulating evidence suggest that autophagy has an important role in AD pathology, and we observed that autophagy-related protein levels began to decrease before amyloid plaque formation in cynomolgus monkey brains. Surprisingly, experimental induction of autophagosome formation in Neuro2a cells significantly increased intracellular Aβ and decreased extracellular release of Aβ, accompanied by the prominent reduction of extracellular vesicle (EV) secretion. RNAi study confirmed that EV secretion affected intracellular and extracellular Aβ levels, and siRNA-induced downregulation of autophagosome formation enhanced EV secretion to ameliorate intracellular Aβ accumulation induced by dynein knockdown. In aged cynomolgus monkeys, Aβ levels in EV/intraluminal membrane vesicle (ILV)-rich fractions isolated from temporal lobe parenchyma were drastically increased. Moreover, EV/ILV marker proteins overlapped spatially with amyloid plaques. These findings suggest that EV would be an important carrier of Aβ in brain and abnormal accumulation of Aβ in EVs/ILVs may be involved in the transition of age-dependent Aβ pathology.

Glucose transporters in Alzheimer's disease

BackgroundPhysiological brain function depends on tight glucose regulation, including transport and phosphorylation, the first step in its metabolism. Impaired glucose regulation is increasingly implicated in the pathophysiology of Alzheimer's disease (AD). Glucose hypometabolism in AD may be at least partly due to impaired glucose transport at the blood-brain barrier (BBB). Glucose transporters (GLUTs) are an integral component of the BBB. There is evidence of a significant reduction in vascular and non-vascular forms of GLUT1 and GLUT3 in AD brains compared to age-matched controls. Glucose transport, as well as phosphorylation, appears to be a rate limiting step for glucose metabolism in the brain. We have reviewed the literature on glucose transport abnormalities in AD and the effect such abnormalities have on the brain.MethodPublished literature between 1st January 1946 and 1st November 2019 was identified using EMBASE and MEDLINE databases and titles and abstracts were scanned. Human studies (autopsy and imaging) and data from animal models were included while reviews, letters and cellular or molecular studies were excluded from the search.ResultAutopsy studies in AD patients show significant reductions in GLUT3 in areas of the brain closely associated with AD pathology. Patients with AD and diabetes showed greater reductions of GLUT1 and GLUT3. A longitudinal study showed significant reductions in GLUT3 levels which correlated with greater amyloid-β (Aβ) and neurofibrillary tangle pathological burden in participants with AD pathology at post-mortem but without evidence of cognitive dysfunction in their lifetime. Some studies showed increased GLUT1, with others showing reduced GLUT1, levels in AD brain. A newly recognised GLUT12 appears to be increased in AD. Animal studies showed similar results with GLUT1 and GLUT3 knockout animal models exhibiting AD pathology, while overexpression of GLUT1 or treatment with metformin decreased Aβ toxicity in a Drosophila model of AD. GLUT2 levels were increased in both human AD brain and in an animal model of AD. Imaging studies using fluorodeoxyglucose [18F]FDG with positron emission tomography (FDG-PET) in AD subjects show reductions in glucose transport and glucose metabolism in areas most affected in AD. A small randomised control trial showed anti-diabetic medications improved the glucose transport in AD subjects.ConclusionGLUTs play a significant role in AD pathology with evidence suggesting that GLUT3 reductions may precede the onset of clinical symptoms, while GLUT2 and GLUT12 may have a compensatory role. Repurposing anti-diabetic drugs shows promising results in both animal and human studies of AD.

Hypermethylation of Mitochondrial Cytochrome b and Cytochrome c Oxidase II Genes with Decreased Mitochondrial DNA Copy Numbers in the APP/PS1 Transgenic Mouse Model of Alzheimer's Disease.

Alzheimer's disease (AD) is the most common cause of dementia. Increasing evidence shows that mitochondrial DNA (mtDNA) methylation plays an essential role in many diseases related to mitochondrial dysfunction. Since mitochondrial impairment is a key feature of AD, mtDNA methylation may also contribute to AD, but few studies have addressed this issue. Methylation changes of the mitochondrial cytochrome b (CYTB) and cytochrome c oxidase II (COX II) genes in AD have not been reported. We analyzed mtDNA methylation changes of the CYTB and COX II genes in an APP/PS1 transgenic mouse model of AD using pyrosequencing. We examined mtDNA copy numbers and the levels of expression by quantitative real-time PCR. Average methylation levels of different CpG sites were ≤ 4.0%. Methylated mtDNA accounted for only a small part of the total mtDNA. We also observed hypermethylation of mitochondrial CYTB and COX II genes with decreased mtDNA copy numbers and expression in the hippocampi of APP/PS1 transgenic mice. mtDNA methylation may play an important role in AD pathology, which may open a new window for AD therapy.

Analysis the alteration of systemic inflammation in old and young APP/PS1 mouse.

The impairment of cognitive function was considered as a major clinic feature in Alzheimer's disease (AD) patients. Thus, a number of researches related to AD were focused on the changes in brain. However, as a neurodegenerative disorder with systemic inflammation, the periphery organs may also play a key role in AD pathology. Here, we pose the hypothesis that histopathology and inflammatory response of periphery organs may alter with aging in APP/PS1 mouse model. Therefore, we performed immunohistochemical staining technology to double label Aβ plaques and microglia cells in brain. The H&E staining was performed in periphery tissues and the mRNA expression of inflammatory factors IL-6, IL-10 and TNF-α were also determined. Next, the index of oxidative stress was measured. Consequently, the level of inflammatory factors was significantly increased in 24months APP/PS1 mice. Furthermore, the enzyme activity of SOD, CAT and GSH were significantly decreased in colon and other organs. Our results demonstrated the increased inflammation response and declined antioxidative capacity of periphery organs in aged APP/PS1 mice, which suggesting that a more comprehensive perspective to study AD were necessary.

Novel therapeutic strategies for Alzheimer's disease targeting brain cholesterol homeostasis.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder and the most common cause of dementia. Aβ plaques and tauopathy are two major concerns associated with AD. Moreover, excessive Aβ accumulation can lead to other nonspecific metabolic brain abnormalities. There are various genetic, environmental, and other risk factors associated with AD. Identification of risk factors and its mechanisms by which these factors impart role in AD pathology would be helpful for the prevention of AD progression. Altered cholesterol homeostasis could be considered as a risk factor for AD progression. Brain cholesterol dysmetabolism is recognized as one of the crucial attributes for AD that affect major hallmarks of AD including neurodegeneration. To fill the gap between altered cholesterol levels in the brain and AD, the researchers started focusing on statins as re-purposing drugs for AD treatment. The various other hypothesis has been suggested due to a lack of beneficial results of statins in clinical trials, such as reduced brain cholesterol could underlie poor cognition. Unfortunately, it is still unclear, whether an increase or decrease in brain cholesterol levels responsible for Alzheimer's disease or not. Presently, scientists believed that managing the level of cholesterol in the brain may help as an alternative treatment strategy for AD. In this review, we focused on the therapeutic strategies for AD by targeting brain cholesterol levels.

Alzheimer's disease in the gut-Major changes in the gut of 5xFAD model mice with ApoA1 as potential key player.

Alzheimer's disease (AD) affects around 33 million people worldwide, which makes it the most prominent form of dementia. The main focus of AD research has been on the central nervous system (CNS) for long, but in recent years, the gut gained more attention. The intestinal tract is innervated by the enteric nervous system (ENS), built of numerous different types of neurons showing great similarity to neurons of the CNS. It already has been demonstrated that the amyloid precursor protein, which plays a major role in AD pathology, is also expressed in these cells. We analyzed gut tissue of AD model mice (5xFAD) and the respective wild-type littermates at different pathological stages: pre-pathological, early pathological and late pathological. Our results show significant difference in function of the intestine of 5xFAD mice as compared to wild-type mice. Using a pathway array detecting 84 AD-related gene products, we found ApoA1 expression significantly altered in colon tissue of 5xFAD mice. Furthermore, we unveil ApoA1's beneficial impact on cell viability and calcium homeostasis of cultured enteric neurons of 5xFAD animals. With this study, we demonstrate that the intestine is altered in AD-like pathology and that ApoA1 might be one key player within the gut.

Potential Novel Role of COVID-19 in Alzheimer's Disease and Preventative Mitigation Strategies.

There are a number of potential implications for the field of Alzheimer's disease (AD) stemming from the global spread of SARS-CoV-2. Neuroinflammation is known to be a prominent feature of neurodegeneration and plays a major role in AD pathology. Immune response and excessive inflammation in COVID-19 may also accelerate the progression of brain inflammatory neurodegeneration, and elderly individuals are more susceptible to severe outcomes after SARS-CoV-2 infection. Individuals with type 2 diabetes (T2D) are at an increased risk for AD as well as severe outcomes after SARS-CoV-2 infection. Genetic and socioeconomic factors influencing the rates of T2D, AD, and COVID-19 severity may create an exceptionally high-risk profile for certain demographics such as African Americans and Hispanic Americans. Type I interferon response plays an important role in both host response to viral infection, as well as AD pathology and may be a sensible therapeutic target in both AD and COVID-19.

Alzheimer's and Hyperglycemia: Role of the Insulin Signaling Pathway and GSK-3 Inhibition in Paving a Path to Dementia.

In this project, we are trying to review the articles that discuss the relationship between insulin signaling and Alzheimer's disease (AD). Another focus of this project is to find the best treatment regimen that can reduce the progression of AD in patients with impaired glucose metabolism. We used Pubmed database to collect our data and used the following keywords: Alzheimer’s disease, insulin signaling pathway, type 3 diabetes, type 2 diabetes, insulin, and insulin resistance in our revision; we included free articles that were published in the last 10 years and excluded articles that were written in any language other than English. We reviewed 68 articles. Forty-nine out of 68 articles were containing materials that are relevant for this project. We found that there is a relation between AD and the insulin signaling pathway. Insulin signaling pathway impairment leads to hyperphosphorylation of Tau protein, which plays a vital role in AD pathology. The effect of insulin on cognition is bidirectional; the intranasal route of insulin showed to have a promising effect on cognition improvement. Subcutaneous and intravenous insulin can increase the risk of dementia. Further studies are encouraged to use a specific anti-diabetic medication that can reduce the progression of AD.

MiR-409-5p as a Regulator of Neurite Growth Is Down Regulated in APP/PS1 Murine Model of Alzheimer’s Disease

Alzheimer’s disease (AD) is a heterogeneous neurodegenerative disease. Recent studies suggest that miRNA expression changes are associated with the development of AD. Our previous study showed that the expression level of miR-409-5p was stably downregulated in the early stage of APP/PS1 double transgenic mice model of AD. We now report that miR-409-5p impairs neurite outgrowth, decreases neuronal viability, and accelerates the progression of Aβ1–42-induced pathologies. In this study, we found that Aβ1–42 peptide significantly decreased the expression of miR-409-5p, which was consistent with the expression profile of miR-409-5p in the APP/PS1 mice cortexes. Plek was confirmed to be a potential regulatory target of miR-409-5p by luciferase assay and Western blotting. Overexpression of miR-409-5p has an obvious neurotoxicity in neuronal cell viability and differentiation, whereas Plek overexpression could partially rescue neurite outgrowth from this toxicity. Some cytoskeleton regulatory proteins have been found to be related to AD pathogenesis. Our data show some clues that cytoskeletal reorganization may play roles in AD pathology. The early downregulation of miR-409-5p in AD progression might be a self-protective reaction to alleviate the synaptic damage induced by Aβ, which may be used as a potential early biomarker of AD.

ApoE4 Alters ABCA1 Membrane Trafficking in Astrocytes.

The APOE ε4 allele is the strongest genetic risk factor for late-onset Alzheimer's disease (AD). ApoE protein aggregation plays a central role in AD pathology, including the accumulation of β-amyloid (Aβ). Lipid-poor ApoE4 protein is prone to aggregate and lipidating ApoE4 protects it from aggregation. The mechanisms regulating ApoE4 aggregation in vivo are surprisingly not known. ApoE lipidation is controlled by the activity of the ATP binding cassette A1 (ABCA1). ABCA1 recycling and degradation is regulated by ADP-ribosylation factor 6 (ARF6). We found that ApoE4 promoted greater expression of ARF6 compared with ApoE3, trapping ABCA1 in late-endosomes and impairing its recycling to the cell membrane. This was associated with lower ABCA1-mediated cholesterol efflux activity, a greater percentage of lipid-free ApoE particles, and lower Aβ degradation capacity. Human CSF from APOE ε4/ε4 carriers showed a lower ability to induce ABCA1-mediated cholesterol efflux activity and greater percentage of aggregated ApoE protein compared with CSF from APOE ε3/ε3 carriers. Enhancing ABCA1 activity rescued impaired Aβ degradation in ApoE4-treated cells and reduced both ApoE and ABCA1 aggregation in the hippocampus of male ApoE4-targeted replacement mice. Together, our data demonstrate that aggregated and lipid-poor ApoE4 increases ABCA1 aggregation and decreases ABCA1 cell membrane recycling. Enhancing ABCA1 activity to reduce ApoE and ABCA1 aggregation is a potential therapeutic strategy for the prevention of ApoE4 aggregation-driven pathology.SIGNIFICANCE STATEMENT ApoE protein plays a key role in the formation of amyloid plaques, a hallmark of Alzheimer's disease (AD). ApoE4 is more aggregated and hypolipidated compared with ApoE3, but whether enhancing ApoE lipidation in vivo can reverse ApoE aggregation is not known. ApoE lipidation is controlled by the activity of the ATP binding cassette A1 (ABCA1). In this study, we demonstrated that the greater propensity of lipid-poor ApoE4 to aggregate decreased ABCA1 membrane recycling and its ability to lipidate ApoE. Importantly, enhancing ABCA1 activity to lipidate ApoE reduced ApoE and ABCA1 aggregation. This work provides critical insights into the interactions among ABCA1, ApoE lipidation and aggregation, and underscores the promise of stabilizing ABCA1 activity to prevent ApoE-driven aggregation pathology.

TRANSCRIPTOMIC PROFILING OF MICROGLIA FROM AN ALZHEIMER'S DISEASE MOUSE MODEL AND FROM HUMAN INDUCED PLURIPOTENT STEM CELLS REVEALS EFFECTS OF THE APOE4 GENOTYPE

A number of risk factors for sporadic Alzheimer's disease (AD) have been identified, with the strongest genetic factor being the E4 allele of apolipoprotein E (APOE4). There are a several pathways through which APOE4 can act to increase AD risk, including via its actions on neuroinflammation and glial function. Microglia, one of the major immune cell types of the brain, are known to have a role in AD pathology and have previously been shown to have altered phenotypes in the context of APOE4. Several recent reports have demonstrated that microglia display unique transcriptional profiles in the context of AD and other neurodegenerative conditions. However, whether and how APOE4 may alter microglial transcriptomic signatures has thus far not been examined. We assessed the effects of APOE4 on microglial transcription profiles using both mouse models of AD and human induced pluripotent stem cells (iPSCs). CD11b+ microglia were isolated from EFAD mice, which carry either human APOE3 or APOE4 and the 5xFAD transgenes, and were analyzed by RNAseq. Additionally, iPSCs from APOE3 and APOE4 carriers were differentiated into microglia and their transcriptional profiles were assessed by RNAseq, both at baseline and after inflammatory insults. APOE4 is associated with transcriptional changes in a number of microglial genes, including an up-regulation of a number of inflammatory pathways and altered macrophage-associated networks. Determining how APOE4 affects microglial transcription will be critical in understanding how this AD risk factor alters the function of microglia and contributes to disease. We have identified microglial networks that are altered in the context of APOE4, enabling us to examine how these pathways may be impacting AD risk and progression.

Novel Blood Biomarkers that Correlate with Cognitive Performance and Hippocampal Volumetry: Potential for Early Diagnosis of Alzheimer's Disease.

Differential diagnosis of people presenting with mild cognitive impairment (MCI) that will progress to Alzheimer's disease (AD) remains clinically challenging. Current criteria used to define AD include a series of neuropsychological assessments together with relevant imaging analysis such as magnetic resonance imaging (MRI). The clinical sensitivity and specificity of these assessments would be improved by the concomitant use of novel serum biomarkers. The branched chain aminotransferase proteins (BCAT) are potential candidates as they are significantly elevated in AD brain, correlate with Braak Stage, and may have a role in AD pathology. In this hypothesis-driven project, we aimed to establish if serum BCAT and its metabolites are significantly altered in AD participants and assess their role as markers of disease pathology. Serum amino acids were measured using a triple quadrupole mass spectrometer for tandem mass spectroscopy together with BCAT levels using western blot analysis, coupled with neuropsychological assessments and MRI. We present data supporting a substantive mutually correlated system between BCAT and glutamate, neuropsychological tests, and MRI for the diagnosis of AD. These three domains, individually, and in combination, show good utility in discriminating between groups. Our model indicates that BCAT and glutamate accurately distinguish between control and AD participants and in combination with the neuropsychological assessment, MoCA, improved the overall sensitivity to 1.00 and specificity to 0.978. These findings indicate that BCAT and glutamate have potential to improve the clinical utility and predictive power of existing methods of AD assessment and hold promise as early indicators of disease pathology.

Reassembly of native components with donepezil to execute dual-missions in Alzheimer's disease therapy

Alzheimer's disease (AD) is a multifaceted and progressive neurodegenerative disease characterized by accumulation of amyloid-beta (Aβ) and deficits of acetylcholine. Accordingly, the intra−/extra-cerebral level of high density lipoprotein (HDL) is crucial on the pathogenesis of AD; and most of all, various HDL-protein subtypes play a double-edged role in AD pathology, of which apolipoprotein A-I (apoA-I) gives protective outcomes. Inspired from “HDL bionics”, we proposed biologically reassembled nanodrugs, donepezil-loaded apolipoprotein A-I-reconstituted HDL (rHDL/Do) that concurrently executed dual-missions of Aβ-targeting clearance and acetylcholinesterase (AChE) inhibition in AD therapy. Once prepared, rHDL/Do nanodrug achieved high drug encapsulation efficiency of 90.47%, and mimicked the configurations and properties of natural lipoproteins aiming to significantly enhance BBB penetration and modulate Aβ-induced neuronal damage both in vitro and in vivo. Surface plasmon resonance (SPR) analysis confirmed that rHDL/Do facilitated microglial-mediated Aβ intake and degradation, demonstrating low KD value with Aβ affinity (2.45 × 10−8 of Aβ monomer and 2.78 × 10−8 of Aβ oligomer). In AD animal models, daily treatment of rHDL/Do efficiently inhibited AChE activity, ameliorated neurologic variation, promoted Aβ clearance, and rescued memory loss at a safe level. The collective findings indicated that the biological nanodrug was provided with the capacities of BBB penetration, Aβ capture and degradation via microglial cells, and cholinergic dysfunction amelioration after controlled donepezil release. In summary, rHDL/Do nanodrugs could offer a promising strategy to synergize both symptom control and disease modification in AD therapy.

The role of myelin damage in Alzheimer's disease pathology.

Although Alois Alzheimer described myelin disruption in Alzheimer’s disease (AD) as early as in 1911, his observation has escaped the attention of researchers since that time. Alzheimer’s disease has been mainly considered as a grey matter disorder; nevertheless, recent evidence suggests that myelin impairment may play an important role in AD pathology. Classical neuropathological changes in AD, e.g. the accumulation of aggregated Aβ 42 and the presence of neurofibrillary tangles, are responsible for neuronal loss, but they may also induce death of oligodendrocytes and myelin damage. There is also evidence that myelin pathology may even precede Aβ and tau pathologies in AD. The state of the art does not allow us to determine whether myelin damage is a primary or a secondary injury in AD subjects. The article presents an overview of current knowledge on the role of myelin in AD pathology and its interactions with Aβ and tau pathologies.