Alzheimer's Disease Phenotype Research Articles

Patterns of Early Neocortical Amyloid-β Accumulation: A PET Population-Based Study.

The widespread deposition of amyloid-β (Aβ) plaques in late-stage Alzheimer disease is well defined and confirmed by invivo PET. However, there are discrepancies between which regions contribute to the earliest topographic Aβ deposition within the neocortex. Methods: This study investigated Aβ signals in the perithreshold SUV ratio range using Pittsburgh compound B (PiB) PET in a population-based study cross-sectionally and longitudinally. PiB PET scans from 1,088 participants determined the early patterns of PiB loading in the neocortex. Results: Early-stage Aβ loading is seen first in the temporal, cingulate, and occipital regions. Regional early deposition patterns are similar in both apolipoprotein ε4 carriers and noncarriers. Clustering analysis shows groups with different patterns of early amyloid deposition. Conclusion: These findings of initial Aβ deposition patterns may be of significance for diagnostics and understanding the development of Alzheimer disease phenotypes.

Assessment of neurovascular uncoupling: APOE status is a key driver of early metabolic and vascular dysfunction.

Alzheimer's disease (AD) is the most common cause of dementia worldwide, with apolipoprotein Eε4 (APOEε4) being the strongest genetic risk factor. Current clinical diagnostic imaging focuses on amyloid and tau; however, new methods are needed for earlier detection. PET imaging was used to assess metabolism-perfusion in both sexes of aging C57BL/6J, and hAPOE mice, and were verified by transcriptomics, and immunopathology. All hAPOE strains showed AD phenotype progression by 8months, with females exhibiting the regional changes, which correlated with GO-term enrichments for glucose metabolism, perfusion, and immunity. Uncoupling analysis revealed APOEε4/ε4 exhibited significant Type-1 uncoupling (↓ glucose uptake, ↑ perfusion) at 8 and 12months, while APOEε3/ε4 demonstrated Type-2 uncoupling (↑ glucose uptake, ↓ perfusion), while immunopathology confirmed cell specific contributions. This work highlights APOEε4 status in AD progression manifests as neurovascular uncoupling driven by immunological activation, and may serve as an early diagnostic biomarker. We developed a novel analytical method to analyze PET imaging of 18F-FDG and 64Cu-PTSM data in both sexes of aging C57BL/6J, and hAPOEε3/ε3, hAPOEε4/ε4, and hAPOEε3/ε4 mice to assess metabolism-perfusion profiles termed neurovascular uncoupling. This analysis revealed APOEε4/ε4 exhibited significant Type-1 uncoupling (decreased glucose uptake, increased perfusion) at 8 and 12 months, while APOEε3/ε4 demonstrated significant Type-2 uncoupling (increased glucose uptake, decreased perfusion) by 8 months which aligns with immunopathology and transcriptomic signatures. This work highlights that there may be different mechanisms underlying age related changes in APOEε4/ε4 compared with APOEε3/ε4. We predict that these changes may be driven by immunological activation and response, and may serve as an early diagnostic biomarker.

Amyloid-β neuropathology induces bone loss in male mice by suppressing bone formation and enhancing bone resorption

Alzheimer's disease (AD) and osteoporosis often coexist in the elderly. Although observational studies suggest an association between these two diseases, the pathophysiologic link between AD and skeletal health has been poorly defined. We examined the skeletal phenotype of 5xFAD mice, an AD model with accelerated neuron-specific amyloid-β accumulation causing full-blown AD phenotype by the age of 8 months. Micro-computed tomography indicated significantly lower trabecular and cortical bone parameters in 8-month-old male, but not female, 5xFAD mice than sex-matched wild-type littermates. Dynamic histomorphometry revealed reduced bone formation and increased bone resorption, and quantitative RT-PCR showed elevated skeletal RANKL gene expression in 5xFAD males. These mice also had diminished body fat percentage with unaltered lean mass, as determined by dual-energy X-ray absorptiometry (DXA), and elevated Ucp1 mRNA levels in brown adipose tissue, consistent with increased sympathetic tone, which may contribute to the osteopenia observed in 5xFAD males. Nevertheless, no significant changes could be detected between male 5xFAD and wild-type littermates regarding the serum and skeletal concentrations of norepinephrine. Thus, brain-specific amyloid-β pathology is associated with osteopenia and appears to affect both bone formation and bone resorption. Our findings shed new light on the pathophysiologic link between Alzheimer's disease and osteoporosis.

Sarcopenia as a Risk Factor for Alzheimer's Disease: Genetic and Epigenetic Perspectives.

Sarcopenia, defined as the age-associated loss of muscle mass and increased fragility with age, is increasing worldwide. The condition often precedes the development of Alzheimer's disease, thereby decreasing the levels of mobility and physical activity in those affected. Indeed, the loss of muscle mass has, in some studies, been associated with an increased risk of Alzheimer's disease and other dementias. However, a detailed understanding of the interplay between both conditions is not available and needs to be thoroughly addressed. In the following review, we focus on several genes, specifically APOE, BDNF, ACE, FTO, and FNDC5, that have been associated with both conditions. We also discuss the epigenetic regulation of each of these genes along with non-coding RNAs (ncRNAs) that may have a role in the development of both the sarcopenic and Alzheimer's disease phenotypes. Finally, we assert that the application of systems biology will unravel the relationship between sarcopenia and Alzheimer's disease and believe that the prevention of muscle loss in older age will reduce the incidence of debilitating cognitive decline.

Symptom-based staging for logopenic variant primary progressive aphasia.

Logopenic variant primary progressive aphasia (lvPPA) is a major variant presentation of Alzheimer's disease (AD) that signals the importance of communication dysfunction across AD phenotypes. A clinical staging system is lacking for the evolution of AD-associated communication difficulties that could guide diagnosis and care planning. Our aim was to create a symptom-based staging scheme for lvPPA, identifying functional milestones relevant to the broader AD spectrum. An international lvPPA caregiver cohort was surveyed on symptom development under an 'exploratory' survey (34 UK caregivers). Feedback from this survey informed the development of a 'consolidation' survey (27 UK, 10 Australian caregivers) in which caregivers were presented with six provisional clinical stages and feedback was analysed using a mixed-methods approach. Six clinical stages were endorsed. Early symptoms included word-finding difficulty, with loss of message comprehension and speech intelligibility signalling later-stage progression. Additionally, problems with hearing in noise, memory and route-finding were prominent early non-verbal symptoms. 'Milestone' symptoms were identified that anticipate daily-life functional transitions and care needs. This work introduces a new symptom-based staging scheme for lvPPA, and highlights milestone symptoms that could inform future clinical scales for anticipating and managing communication dysfunction across the AD spectrum.

Divergent Age-Dependent Conformational Rearrangement within Aβ Amyloid Deposits in APP23, APPPS1, and AppNL-F Mice.

Amyloid plaques composed of fibrils of misfolded Aβ peptides are pathological hallmarks of Alzheimer's disease (AD). Aβ fibrils are polymorphic in their tertiary and quaternary molecular structures. This structural polymorphism may carry different pathologic potencies and can putatively contribute to clinical phenotypes of AD. Therefore, mapping of structural polymorphism of Aβ fibrils and structural evolution over time is valuable to understanding disease mechanisms. Here, we investigated how Aβ fibril structures in situ differ in Aβ plaque of different mouse models expressing familial mutations in the AβPP gene. We imaged frozen brains with a combination of conformation-sensitive luminescent conjugated oligothiophene (LCO) ligands and Aβ-specific antibodies. LCO fluorescence mapping revealed that mouse models APP23, APPPS1, and AppNL-F have different fibril structures within Aβ-amyloid plaques depending on the AβPP-processing genotype. Co-staining with Aβ-specific antibodies showed that individual plaques from APP23 mice expressing AβPP Swedish mutation have two distinct fibril polymorph regions of core and corona. The plaque core is predominantly composed of compact Aβ40 fibrils, and the corona region is dominated by diffusely packed Aβ40 fibrils. Conversely, the AβPP knock-in mouse AppNL-F, expressing the AβPP Iberian mutation along with Swedish mutation has tiny, cored plaques consisting mainly of compact Aβ42 fibrils, vastly different from APP23 even at elevated age up to 21 months. Age-dependent polymorph rearrangement of plaque cores observed for APP23 and APPPS1 mice >12 months, appears strongly promoted by Aβ40 and was hence minuscule in AppNL-F. These structural studies of amyloid plaques in situ can map disease-relevant fibril polymorph distributions to guide the design of diagnostic and therapeutic molecules.

Brain Organoids, the Path Forward?

Brain Organoids, the Path Forward?

Oral Administration of Euonymus alatus Leaf Extract Ameliorates Alzheimer's Disease Phenotypes in 5xFAD Transgenic Mice.

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease and is frequently characterized by progressive and irreversible impairment of cognitive functions. However, its etiology remains poorly understood, limiting therapeutic interventions. Our previous study showed that the ethanol extract of Euonymus alatus leaves (EA) positively affected scopolamine-induced hypomnesia in the normal mouse model by promoting nuclear factor E2-related factor 2 (Nrf2) activation. Herein, we examined whether EA administration could ameliorate major AD phenotypes that are manifested in 5xFAD transgenic mice. Two-month-old mice were orally administered with EA at a dose of 50, 100, or 150 mg/kg body weight/day thrice a week for 14 weeks. We observed that EA administration improved behavioral deficits as assessed by the passive avoidance, Morris water maze, and Y-maze tasks; decreased the plasma levels of pro-inflammatory cytokines, including TNFα and IL-1β; decreased the protein expression levels of inflammatory mediators in the hippocampus; and attenuated histological damage and amyloid beta plaques in the hippocampal region of 5xFAD mouse brain. Interestingly, our data demonstrated that the effectiveness was partially attributed to quercetin, which was noted to be a component of EA. Hence, these findings suggest that a long-term administration of EA could alleviate AD symptoms and delay its progression.

Sex-Dependent Effects of Chronic Circadian Disruption in AβPP/PS1 Mice.

Chronic disruption of the circadian timing system, often reflected as a loss of restful sleep, also includes myriad other pathophysiological effects. The current study examined how chronic circadian disruption (CD) could contribute to pathology and rate of progression in the AβPP/PS1 mouse model of Alzheimer's disease (AD). A chronic CD was imposed until animals reached 6 or 12 months of age in AβPP/PS1 and C57BL/6J control mice. Home cage activity was monitored for a period of 3-4 weeks prior to the endpoint along with a single timepoint measure of glucose sensitivity. To assess long term effects of CD on the AD phenotype, animals were re-entrained to a no disruption (ND) schedule just prior to the endpoint, after which a Morris water maze (MWM) was used to assess spatial learning and memory. Dampening of nighttime activity levels occurred in disrupted animals, and female animals demonstrated a greater adaptability to CD. Diminished arginine vasopressin (AVP) and vasoactive intestinal peptide (VIP) levels in the suprachiasmatic nucleus (SCN) of 12-month male AβPP/PS1 exposed to the CD paradigm were observed, potentially accounting for the diminished re-entrainment response. Similarly, CD worsened performance in the MWM in 12-month male AβPP/PS1 animals, whereas no effect was seen in females. Collectively, these findings show that exposure to chronic CD impairs circadian behavioral patterns and cognitive phenotypes of AβPP/PS1 mouse model in a sex-dependent manner.

The Carnitine Palmitoyl-Transferase 2 Cascade Hypothesis for Alzheimer's Disease.

Despite decades of intense research, the precise etiology of Alzheimer's disease (AD) remains unclear. In this hypothesis, we present a new perspective on this matter by identifying carnitine palmitoyl transferase-2 (CPT2) as a central target in AD. CPT2 is an enzyme situated within the inner mitochondrial membrane, playing a crucial role in beta-oxidation of fatty acids. It exhibits high sensitivity to hydrogen peroxide. This sensitivity holds relevance for the etiology of AD, as all major risk factors for the disease share a commonality in producing an excess of hydrogen peroxide right at this very mitochondrial membrane. We will explain the high sensitivity of CPT2 to hydrogen peroxide and elucidate how the resulting inhibition of CPT2 can lead to the characteristic phenotype of AD, thus clarifying its central role in the disease's etiology. This insight holds promise for the development of therapies for AD which can be implemented immediately.

Comprehensive Analysis of Metabolites in Postmortem Brains of Patients with Alzheimer's Disease.

Disturbed metabolism has been proposed as being involved in the pathogenesis of Alzheimer's disease (AD), and more evidence from human AD brains is required. In this study, we attempted to identify or confirm modulations in the levels of metabolites associated with AD in postmortem AD brains. We performed metabolomics analyses using a gas chromatography mass spectrometry system in postmortem brains of patients with confirmed AD, patients with CERAD score B, and control subjects. Impaired phosphorylation of glucose and elevation of several tricarboxylic acid (TCA) metabolites, except citrate, were observed and the degree of impaired phosphorylation and elevation in the levels of the TCA cycle metabolites were negatively and positively correlated, respectively, with the clinical phenotypes of AD. The levels of uronic acid pathway metabolites were modulated in AD and correlated positively with the amyloid-β content. The associations of nucleic acid synthesis and amino acid metabolites with AD depended on the kinds of metabolites; in particular, the contents of ribose 5-phosphate, serine and glycine were negatively correlated, while those of ureidosuccinic acid and indole-3-acetic acid were positively modulated in AD. Comprehensive statistical analyses suggested that alterations in the inositol pathway were most closely associated with AD. The present study revealed many novel associations between metabolites and AD, suggesting that some of these might serve as novel potential therapeutic targets for AD.

APOE ε4 allele status modulates the spatial patterns of progressive atrophy in the temporal lobes after mild traumatic brain injury.

We evaluated how the apolipoprotein E (APOE) ε4 allele modulated the spatial patterns of longitudinal atrophy in the Alzheimer's disease-vulnerable brain areas of patients with mild traumatic brain injury (mTBI) from the acute to chronic phase post injury. Fifty-nine adult patients with acute mTBI and 48 healthy controls with APOE ε4 allele testing underwent T1-weighted magnetic resonance imaging and neuropsychological assessments with 6 to 12 months of follow-up. Progressive brain volume loss was compared voxel-wise in the temporal lobes. Patients with the APOE ε4 allele presented significant longitudinal atrophy in the left superior and middle temporal gyri, where the progressive gray matter volume loss predicted longitudinal impairment in language fluency, whereas mTBI APOE ε4 allele noncarriers showed mainly significant longitudinal atrophy in the medial temporal lobes, without significant neuropsychological relevance. The atrophy progression observed in mTBI patients with the APOE ε4 allele may increase the possibility of developing a specific phenotype of Alzheimer's disease with language dysfunction. The apolipoprotein E (APOE) ε4 allele and mild traumatic brain injury (mTBI) are risk factors for Alzheimer's disease (AD) progression.It is unclear how the interaction of mTBI with the APOE ε4 allele impacts the progressive atrophy topography in AD-vulnerable brain regions.In this study, patients with the APOE ε4 allele showed progressive atrophy patterns similar to the early stage of logopenic variant of primary progressive aphasia (lvPPA) phenotype of AD. APOE ε4 allele carriers with mTBI history may be at the risk of developing a given AD phenotype with language dysfunction.

Impact of apolipoprotein E isoforms on sporadic Alzheimer's disease: beyond the role of amyloid beta.

The impact of apolipoprotein E (ApoE) isoforms on sporadic Alzheimer's disease has long been studied; however, the influences of apolipoprotein E gene (APOE) on healthy and pathological human brains are not fully understood. ApoE exists as three common isoforms (ApoE2, ApoE3, and ApoE4), which differ in two amino acid residues. Traditionally, ApoE binds cholesterol and phospholipids and ApoE isoforms display different affinities for their receptors, lipids transport and distribution in the brain and periphery. The role of ApoE in the human depends on ApoE isoforms, brain regions, aging, and neural injury. APOE ε4 is the strongest genetic risk factor for sporadic Alzheimer's disease, considering its role in influencing amyloid-beta metabolism. The exact mechanisms by which APOE gene variants may increase or decrease Alzheimer's disease risk are not fully understood, but APOE was also known to affect directly and indirectly tau-mediated neurodegeneration, lipids metabolism, neurovascular unit, and microglial function. Consistent with the biological function of ApoE, ApoE4 isoform significantly altered signaling pathways associated with cholesterol homeostasis, transport, and myelination. Also, the rare protective APOE variants confirm that ApoE plays an important role in Alzheimer's disease pathogenesis. The objectives of the present mini-review were to describe classical and new roles of various ApoE isoforms in Alzheimer's disease pathophysiology beyond the deposition of amyloid-beta and to establish a functional link between APOE, brain function, and memory, from a molecular to a clinical level. APOE genotype also exerted a heterogeneous effect on clinical Alzheimer's disease phenotype and its outcomes. Not only in learning and memory but also in neuropsychiatric symptoms that occur in a premorbid condition. Clarifying the relationships between Alzheimer's disease-related pathology with neuropsychiatric symptoms, particularly suicidal ideation in Alzheimer's disease patients, may be useful for elucidating also the underlying pathophysiological process and its prognosis. Also, the effects of anti-amyloid-beta drugs, recently approved for the treatment of Alzheimer's disease, could be influenced by the APOE genotype.

Presenilin Gene Mutation-associated Psychosis: Phenotypic Characteristics and Clinical Implications.

Although psychotic symptoms have been described in association with rare presenilin ( PSEN ) gene mutations underlying early-onset Alzheimer disease (AD), no contemporary reviews on this topic exist. The purpose of this review is to characterize the psychiatric phenotype (specifically with respect to psychosis) of PSEN1 and PSEN2 variant-associated AD. A PubMed search was completed in July 2023. Only articles that described individuals harboring a PSEN1 or PSEN2 mutation who experienced symptoms of psychosis were included in the review. Thirty-three articles describing 52 individuals were included in the review, as well as one other study that provided limited information pertaining to an additional 21 cases. While visual hallucinations were the most common psychotic symptom, followed by persecutory delusions, auditory hallucinations occurred in ~17% of individuals. In ~33% of the reviewed cases psychotic symptoms were present at or near disease onset, and 9 of these individuals experienced auditory hallucinations and/or delusions in the absence of visual hallucinations (~17% of all cases). In many cases, symptoms developed at a relatively young age. As presenilin gene variant-associated psychosis may resemble a primary psychotic disorder, clinicians should be vigilant with respect to screening for signs/symptoms suggestive of neurodegeneration in first-episode psychosis.

Elevated Amyloid-β PET Scan and Cognitive and Functional Decline in Mild Cognitive Impairment and Dementia of Uncertain Etiology.

Elevated amyloid-β (Aβ) on positron emission tomography (PET) scan is used to aid diagnosis of Alzheimer's disease (AD), but many prior studies have focused on patients with a typical AD phenotype such as amnestic mild cognitive impairment (MCI). Little is known about whether elevated Aβ on PET scan predicts rate of cognitive and functional decline among those with MCI or dementia that is clinically less typical of early AD, thus leading to etiologic uncertainty. We aimed to investigate whether elevated Aβ on PET scan predicts cognitive and functional decline over an 18-month period in those with MCI or dementia of uncertain etiology. In 1,028 individuals with MCI or dementia of uncertain etiology, we evaluated the association between elevated Aβ on PET scan and change on a telephone cognitive status measure administered to the participant and change in everyday function as reported by their care partner. Individuals with either MCI or dementia and elevated Aβ (66.6% of the sample) showed greater cognitive decline compared to those without elevated Aβ on PET scan, whose cognition was relatively stable over 18 months. Those with either MCI or dementia and elevated Aβ were also reported to have greater functional decline compared to those without elevated Aβ, even though the latter group showed significant care partner-reported functional decline over time. Elevated Aβ on PET scan can be helpful in predicting rates of both cognitive and functional decline, even among cognitively impaired individuals with atypical presentations of AD.

Novel Pathogenic Mechanism of Late-onset Alzheimer's Disease by Deficiency of NMDA Receptor Subunit GluN3A

Late-onset Alzheimer’s disease (AD) and related dementia (ADRD) are serious neurodegenerative disorders among aging populations. The progress of AD/ADRD cultivates over years to decades in humans and several months in animal models. Ca<sup>2+</sup> homeostasis is a core function of neurons where the N-methyl-D-aspartate (NMDA) receptor plays a major role in excitatory neuronal activities. The Ca<sup>2+</sup> hypothesis of AD proposes that even slight but sustained Ca<sup>2+</sup> dyshomeostasis in the brain is a critical pathophysiology or pathogenesis of AD. However, instigating factors like the trigger and time/duration of the Ca<sup>2+</sup> dysregulation in AD progression have been largely obscure, while β-amyloid (Aβ) peptides are often indicated as the trigger. Hyperactivities of excitatory neurons and NMDARs have been implicated in AD as a main mediating mechanism caused by AD pathologies such as Aβ deposition. NMDAR overactivation is restrained by the unique regulatory GluN3 subunits (GluN3A and GluN3B; previously known as NR3A and NR3B). Expression of GluN3A in the receptor complex reduces NMDAR currents and Ca<sup>2+</sup> influx, while deletion of GluN3A causes larger NMDA currents and elevated intracellular Ca<sup>2+</sup>. Significant GluN3A levels are detected in both rodent and human adult/aging brains. We hypothesized that the “gatekeeper” role of GluN3A is constantly required for Ca<sup>2+</sup> homeostasis and normal aging; its deficiency can lead to slowly evolved “degenerative excitotoxicity”. Our in vitro, ex vivo, and in vivo studies using GluN3A knockout (KO) mice of young and older ages revealed neuronal hyperactivity, moderate but sustained elevation of cytosolic Ca<sup>2+</sup>, chronic inflammation, neuronal loss/apoptosis, synaptic impairments and progressive cognitive deficits. The AD hallmarks of Aβ and tau pathology were identified after, but not before, cognition decline. In the “gain of function” experiment, expression of GluN3A in the GluN3A KO brain prevented AD progression. Specific regional knockdown of GluN3A in the cortex and hippocampus of wild-type mice at the adult age (3 months old) resulted in similar AD/ADRD phenotypic alterations in the following 3-6 months. The NMDAR antagonist memantine (MEM) is approved by FDA as a symptomatic treatment for moderate-severe AD patients. According to the chronic neurohyperactivity in AD progression and the modified Ca<sup>2+</sup> hypothesis that Ca<sup>2+</sup> dysregulation is an early and “life-long” pathogenesis, the maintenance of NMDAR normal activity by MEM or other safe NMDAR antagonists could be a disease-modifying early treatment in preclinical/prodromal stages. This prediction is endorsed by clinical trials using MEM and other NMDAR antagonists in mild cognitive impairment (MCI) and early AD patients, showing beneficial effects of maintaining cognitive functions. Consistently, we showed that, in GluN3A KO mice and 5xFAD mice, early and chronic MEM treatment (started at 3-month of age and lasted for 3-6 months) prevented or attenuated AD phenotypes. Meanwhile, the chronic MEM therapy in mice showed preconditioning effect of neuroprotection against ischemic stroke that strikes over 50% AD patients. Large clinical trials of long-term and more systematic examinations on AD/ADRD progression and the comorbidity of stroke are warranted for this innovative therapy. Our results support the modification of Ca<sup>2+</sup> hypothesis of AD with the novel amyloid-independent mechanism. Specifically, the deficiency of GluN3A alone causes lifelong Ca<sup>2+</sup>-related progression of AD pathophysiology and amyloid pathology. The long-term GluN3A modulation of NMDARs signifies new therapeutic targets and possible preventive interventions for late-onset AD/ ADRD.

Potentially Pathogenic SORL1 Mutations Observed in Autosomal-Dominant Cases of Alzheimer's Disease Do Not Modulate APP Physiopathological Processing.

The SORL1 gene encodes LR11/SorLA, a protein that binds β-amyloid precursor protein (APP) and drives its intracellular trafficking. SORL1 mutations, occurring frequently in a subset of familial cases of Alzheimer's disease (AD), have been documented, but their pathogenic potential is not yet clear and questions remain concerning their putative influence on the physiopathological processing of APP. We have assessed the influence of two SORL1 mutations that were described as likely disease-causing and that were associated with either benign (SorLA924) or severe (SorLA511) AD phenotypes. We examined the influence of wild-type and mutants SorLA in transiently transfected HEK293 cells expressing either wild-type or Swedish mutated APP on APP expression, secreted Aβ and sAPPα levels, intracellular Aβ 40 and Aβ42 peptides, APP-CTFs (C99 and C83) expressions, α-, β- and γ-secretases expressions and activities as well as Aβ and CTFs-degrading enzymes. These paradigms were studied in control conditions or after pharmacological proteasomal modulation. We also established stably transfected CHO cells expressing wild-type SorLA and established the colocalization of APP and either wild-type or mutant SorLA. SorLA mutations partially disrupt co-localization of wild-type sorLA with APP. Overall, although we mostly confirmed previous data concerning the influence of wild-type SorLA on APP processing, we were unable to evidence significant alterations triggered by our set of SorLA mutants, whatever the cells or pharmacological conditions examined. Our study , however, does not rule out the possibility that other AD-linked SORL1 mutations could indeed affect APP processing, and that pathogenic mutations examined in the present study could interfere with other cellular pathways/triggers in AD.

Tetrahydroalstonine possesses protective potentials on palmitic acid stimulated SK-N-MC cells by suppression of Aβ1-42 and tau through regulation of PI3K/Akt signaling pathway

Alzheimer's disease (AD) is the most common neurodegenerative disease. The morbidity of Alzheimer's disease is currently on the rise worldwide, but no effective treatment is available. Cornus officinalis is an herb and edible plant used in traditional Chinese medicine, whose extract has neuroprotective properties. In this investigation, we endeavored to refine a systems pharmacology strategy combining bioinformatics analysis, drug prediction, network pharmacology, and molecular docking to screen tetrahydroalstonine (THA) from Cornus officinalis as a therapeutic component for AD. Subsequent in vitro experiments were validated using MTT assay, Annexin V-PI flow cytometry, Western blotting, and immunofluorescence analysis. In Palmitate acid-induced SK-N-MC cells, THA restored the impaired PI3K/AKT signaling pathway, regulated insulin resistance, and attenuated BACE1 and GSK3β activity. In addition, THA significantly reduced cell apoptosis rate, down-regulated relative levels of p-JNK/JNK, Bax/Bcl-2, cytochrome C, active caspase-3 and caspase-3, and attenuated Palmitate acid-induced Aβ1-42 and Tau generation. THA may regulate the phenotype of AD and reduce cell apoptosis by modulating the PI3K/AKT signaling pathway. This systematic analysis provides new ramifications concerning the therapeutic utility of tetrahydroalstonine for AD.

Clinical Phenotypes of Alzheimer’s Disease: Pathological Correlates of Regional Cortical Volume

AbstractBackgroundRecent studies highlight distinct patterns of cortical atrophy in amnestic (typical) and non‐amnestic (atypical – behavioural, dysexecutive and visuospatial) clinical phenotypes of Alzheimer’s disease (AD). The current study aimed to assess regional phenotypic MRI patterns of cortical atrophy, and their association with Amyloid‐beta (Aβ), phosphorylated Tau (pTau), and axonal degeneration (NfL).MethodPostmortem In‐situ 3DT1 3T‐MRI data were collected for 28 AD (14 typical, 14 atypical) and 10 control brain donors. Images were segmented using QyScore® and regional volumes according to the AAL3 atlas were obtained. At subsequent autopsy, Eight brain regions from the right hemisphere were selected and immunostained for Aβ (4G8), pTau (AT8), and Neurofilament light (NfL), and quantified for area% load. Group comparisons and MRI volume‐pathology associations were analyzed using linear models with covariates age, gender, postmortem delay, and intracranial volume when applicable.ResultsWhen assessing regional cortical volumes, compared to controls, typical AD showed a more parietal‐temporal, while atypical AD showed a more a frontal‐temporal atrophy pattern (fig1).Typical and atypical phenotypes showed different pathological load across all selected regions in both Aβ and NFL (p = 0.032,p = 0.0007, respectively). Subsequent explorative assessment indicates a difference in regional pTau distribution between behavioural, dysexecutive and visuospatial subtypes, specifically in the occipital region (fig2).Addressing MRI‐pathology associations across all selected regions, we observed a positive association between cortical volume and Aβ in typical AD (β = 1.98,p = 0.026), while both pTau and NFL showed a negative association (β = ‐0.26,p = 0.004; β = ‐2.00,p = 0.001, respectively). In atypical AD, only NFL showed a significant negative association (β = ‐2.27,p<0.001) with cortical volume. Regionally (fig3), only NfL associated with MRI volume; with the precuneus in both typical and atypical AD (β = ‐2.81,p = 0.044; β = ‐3.81,p = 0.011, respectively), and with posterior cingulate cortex volume in atypical AD (β = ‐3.24,p = 0.045).ConclusionThis study found varying atrophy patterns in AD phenotypes when compared to controls. Across all selected regions, typical AD showed volume‐pathology associations with Aβ, pTau and axonal damage, while atypical AD only showed associations with axonal damage, indicating a possible difference in volume‐pathology associations between phenotypes. Regionally, cortical volume was predominantly associated with axonal damage, rather than Aβ or pTau protein accumulation, in parietal regions.

Relationships between polymorphisms in keratin genes and Alzheimer’s disease phenotypes.

AbstractBackgroundKeratins are genetically polymorphic and are the largest subset of intermediate filaments. Keratins are also implicated in signaling pathways, inflammation, and disease states. Keratin 9 (KRT9) protein has been identified to have high diagnostic accuracy for Alzheimer’s disease (AD) (PMID:22045497); it was detected in cerebrospinal fluid (CSF) of AD patients but not healthy controls (PMID:24959311). Plasma keratin 9 concentrations also positively correlated with AD‐associated proteins (e.g., apolipoprotein E and tau) in AD patients (PMID:26973255). Post‐translational modification of keratin 83 (KRT83) protein has been associated with serum asymmetric dimethylarginine levels (PMID:34181092), a vascular risk factor implicated in AD. However, our understanding of the role of genetic variation in AD risk is incomplete. Here, we investigate associations between single nucleotide polymorphisms (SNPs) in KRT9, KRT83, and KRT2 (Keratin 2, couples with keratin 9) and AD biomarker phenotypes.MethodIndividuals with mild cognitive impairment (MCI) or AD, and clinically normal controls were selected among ADNI participants. Participants underwent genome‐wide genotyping. Keratin gene variants were identified from the genome‐wide data using dbSNP variant IDs and genotypes were coded additively. Linkage‐disequilibrium‐based clumping on minor allele frequency (MAF) was applied to prioritize more common SNPs. CSF‐Aβ42, ‐tau, and phosphorylated‐tau (p‐tau) levels were quantified via Roche Elecsys immunoassays. Brain‐Aβ deposition was evaluated via normalized PET‐18F‐AV‐45 cortical summary measures (SUVR). White matter hyperintensities (WMH) were obtained from MRI 3D‐T1 and FLAIR sequences via an automated atlas‐based segmentation pipeline. Linear regression models controlling for age, sex, Mini‐Mental State Exam, APOE‐ε4 status, and head size were used to assess association and interaction effects between SNPs and the AD phenotypes in R.ResultAmong included participants (n = 907, 73±7.2 years, 44% female), SNPs in KRT2 (e.g. 3’UTR‐variant rs117041267‐G/A; MAF = 1.4%) and KRT83 (e.g. upstream‐variant KRT83‐rs17119838‐C/T; MAF = 15.6%) were associated with higher CSF‐Aβ42 concentrations (F(2,905) = 4.26,p = 0.014; and F(2,905) = 6.61,p = 0.0014, respectively). Upstream‐variant KRT83‐rs182354391‐C/G (MAF = 1%) showed an association with lower CSF‐tau (F(1,904) = 5.44,p = 0.020). Multiple KRT9 and KRT2 SNPs also showed association with WMH, while KRT2 and KRT83 intron variants showed associations with PET‐Aβ.ConclusionThese candidate gene analyses suggest involvement of multiple keratin family genes in AD, as indicated by differences in amyloid and tau biomarkers, and white matter disease.