Early-onset Alzheimer's Disease Research Articles

The effects of mosaicism on biological and clinical markers of Alzheimer's disease in adults with Down syndrome

Individuals with Down syndrome (DS) are at high risk of early-onset Alzheimer's disease (AD); yet, some 20 percent do not develop any signs of dementia until after 65 years or in their lifetime. Mosaicism could contribute to this phenotypic variation, where some disomic cells could lead to lower levels of gene products from chromosome21. We examined longitudinal neuropsychological and biomarker data from two large studies of DS: the Alzheimer Biomarker Consortium-Down syndrome study (ABC-DS) (n=357); and a legacy study (n=468). We assessed mosaicism using karyotyping or GWAS data. Participants had data on plasma AD biomarkers (Aβ40, Aβ42, tau, and NfL) and longitudinal cognitive measures. A subset had cerebrospinal fluid biomarkers (Aβ40, Aβ42, tau, ptau181, and NfL) and amyloid and tau PET data. For both cohorts, the prevalence of mosaicism was <10% (ABC-DS: 7.3%; Legacy: 9.6%), and those with mosaicism had lower plasma Aβ40 and Aβ42 concentrations. For the older legacy cohort, when compared to those with full trisomy, those with mosaicism had significantly smaller decline in total and annualized neurocognitive scores, and lower incidence and prevalence of dementia. Mosaicism in DS was associated with lower concentrations of plasma Aβ peptides, possibly leading to lower AD risk. However, its clinical impact was less clear in the younger ABC-DC cohort, and a follow-up study is warranted. National Institutes of Health (R01AG014673, P01HD035897, R56AG061837), NIA (U01AG051412, U19AG068054), NICHD, ADRC programs, the Eunice Kennedy Shriver Intellectual and Developmental Disabilities Research Centers Program, and NCATS (UL1TR001873).

CRISPR/Cas9 Gene Editing: A Novel Approach Towards Alzheimer's Disease Treatment.

In defiance of the vast amount of information regarding Alzheimer's disease (AD) that has been learned over the past thirty years, progress toward developing an effective therapy has been difficult. A neurological ailment that progresses and cannot be reversed is Alzheimer's disease, which shows neurofibrillary tangles, beta-amyloid plaque, and a lack of cognitive processes that is created by tau protein clumps with hyperphosphorylation that finally advances to neuronal damage without a recognized treatment, which has stimulated research into new therapeutic strategies. The protein CAS9 is linked to CRISPR, which is a clustered Regularly Interspaced Short Palindromic Repeat that inactivates or corrects a gene by recognizing a gene sequence that produces a doublestranded break has enchanted a whole amount of interest towards its potency to cure gene sequences in AD. The novel CRISPR-Cas9 applications for developing in vitro and in vivo models to the benefit of AD investigation and therapies are thoroughly analyzed in this work. The discussion will also touch on the creation of delivery methods, which is a significant obstacle to the therapeutic use of CRISPR/Cas9 technology. By concentrating on specific genes, such as those that are significant early- onset AD risk factors and late-onset AD risk factors, like the apolipoprotein E4 (APOE4) gene, this study aims to evaluate the potential application of CRISPR/Cas9 as a possible treatment for AD.

Distinct tau pathologies in the nucleus basalis of Meynert between early-onset and late-onset Alzheimer's disease patients revealed by positron emission tomography.

Tau accumulation in the nucleus basalis of Meynert (nbM) has been documented in Alzheimer's disease (AD), but its relationship to neuropathological changes in other brain regions and cognitive deficits remains unclear, particularly between early-onset AD (EOAD) and late-onset AD (LOAD). To evaluate tau accumulation patterns in the nbM and other brain regions in EOAD and LOAD using 18F-florzolotau PET and examine correlations with cognitive function. Thirty-eight amyloid-positive AD patients (15 EOAD, 23 LOAD) and 46 healthy controls underwent 18F-florzolotau PET. Tau levels were quantified in the nbM and Braak-staging regions. Postmortem brain samples were examined to assess 18F-florzolotau binding to tau deposits. EOAD showed a higher overall tau burden, including in the nbM, compared with LOAD. However, nbM tau levels correlated more strongly with cognitive decline in LOAD than EOAD. The relationship between nbM tau and neocortical tau differed between EOAD and LOAD. Histopathology revealed abundant 18F-florzolotau labeling of neurofibrillary tangles (NFTs) and ghost tangles in AD nbM samples. This study provides the first in vivo PET evidence of differential nbM tau pathology between EOAD and LOAD, with higher accumulation but weaker correlation to cognition in EOAD. The distinct relationships between nbM and cortical tau in EOAD and LOAD suggest divergent pathological trajectories. 18F-florzolotau PET successfully visualized NFTs and extracellular ghost tangles in the nbM across AD stages. These findings highlight the importance of considering age of onset when evaluating tau pathology and its clinical correlates in AD.

Targeting the cholinergic anti-inflammatory pathway for type 2 diabetes prevention: A retrospective cohort study.

Chronic inflammation is a key factor in type 2 diabetes mellitus (T2DM) development. The cholinergic anti-inflammatory pathway (CAP) reduces inflammation by activating α7 nicotinic acetylcholine receptors (α7nAChRs) on macrophages, suppressing proinflammatory cytokines. Acetylcholinesterase inhibitors (AChEis), primarily used for Alzheimer's disease (AD), may exert anti-inflammatory effects through the CAP. One AChEi, galantamine, also directly agonizes α7nAChRs, potentially enhancing its anti-inflammatory properties. This study aimed to investigate the association between AChEi use, particularly galantamine, and T2DM risk in AD patients. We conducted a retrospective analysis of Veterans Health Administration (VA) data, examining early- and late-onset AD patients receiving galantamine or other AD medications. Propensity score matching was used to balance groups and minimize confounding. Cox proportional hazard models assessed T2DM risk for galantamine, other AChEis and memantine. A total of 40 065 AD patients were included in the study. Among early-onset AD patients, galantamine use significantly reduced T2DM risk (hazard ratio [HR] = 0.80, 95% confidence interval [CI]: 0.66-0.98). Memantine also showed a protective effect (HR = 0.82, 95% CI: 0.69-1) in this group. Neither galantamine nor memantine influenced T2DM risk in late-onset AD. Other AD medications showed no association with T2DM risk. Galantamine use was associated with a lower risk of T2DM in early-onset AD patients, potentially due to enhanced anti-inflammatory effects through both AChE inhibition and direct α7nAChR agonism. Memantine also demonstrated a protective effect. These findings suggest potential new applications for existing AD medications in T2DM prevention, particularly in early-onset AD patients. Further research, including randomized controlled trials with diverse populations, is needed to confirm these results and the underlying mechanisms.

Amyloid beta-induced signalling in leptomeningeal cells and its impact on astrocyte response.

The pathological signature of Alzheimer's disease (AD) includes the accumulation of toxic protein aggregates, mainly consisting of amyloid beta (Aβ). Recent strides in fundamental research underscore the pivotal role of waste clearance mechanisms in the brain suggesting it may be an early indication of early onset AD. This study delves into the involvement of leptomeningeal cells (LMCs), crucial components forming integral barriers within the clearance system, in the context of AD. We examined the inflammatory cytokine responses of LMCs in the presence of Aβ, alongside assessments of LMC growth response, viability, oxidative stress, and changes in vimentin expression. The LMCs showed no changes in growth, viability, oxidative stress, or vimentin expression in the presence of Aβ, indicating that LMCs are less susceptible to Aβ damage compared to other CNS cells. However, LMCs exhibited a unique pro-inflammatory response to Aβ when compared to an LPS inflammatory control, showing an mRNA expression of pro-inflammatory cytokines such IL-6, IL-10 and IL-33 but no changes in IL-1α and IL-1β. Furthermore, LMCs influenced the astrocyte response to Aβ, as conditioned media from Aβ-treated LMCs was observed to downregulate somatic S100β in astrocytes. We also investigated whether the JAK/STAT3 pathway was involved in the Aβ response of the LMCs, as this pathway has been shown to be activated in astrocytes and neurons in the presence of Aβ. JAK/STAT3 activation was assessed through phosphorylated STAT3, revealing that JAK/STAT3 was not active in the cells when in the presence of Aβ. However, when JAK1 and JAK2 were inhibited, cytokine protein levels of IL7, IL10, IL15 and IL33 levels, which had shown alteration when LMCs were treated with Aβ, returned to base levels. This indicates that although JAK1/STAT3 and JAK2/STAT3 are not the direct pathway for Aβ response in LMCs, JAK1 and JAK2 may still play a role in regulating cytokine levels, potentially through indirect means or crosstalk. Overall, our findings reveal that LMCs are resilient to Aβ toxicity and suggest that JAK1/STAT3 and JAK2/STAT3 does not play a central role in the inflammatory response, providing new insights into the cellular mechanisms underlying AD.

Comprehensive mapping of synaptic vesicle protein 2A (SV2A) in health and neurodegenerative diseases: a comparative analysis with synaptophysin and ground truth for PET-imaging interpretation.

Synaptic dysfunction and loss are central to neurodegenerative diseases and correlate with cognitive decline. Synaptic Vesicle Protein 2A (SV2A) is a promising PET-imaging target for assessing synaptic density in vivo, but comprehensive mapping in the human brain is needed to validate its biomarker potential. This study used quantitative immunohistochemistry and Western blotting to map SV2A and synaptophysin (SYP) densities across six cortical regions in healthy controls and patients with early-onset Alzheimer's disease (EOAD), late-onset Alzheimer's disease (LOAD), progressive supranuclear palsy (PSP), and frontotemporal lobar degeneration with TDP-43 inclusions (FTLD-GRN). We identified region in SV2A density among controls and observed disease- and region-specific reductions, with the most severe in FTLD-GRN (up to 59.5%) and EOAD. EOAD showed a 49% reduction in the middle frontal gyrus (MFG), while LOAD had over 30% declines in the inferior frontal gyrus (IFG) and hippocampus (CA1). In PSP, smaller but significant reductions were noted in the hippocampal formation, with the inferior temporal gyrus (ITG) relatively unaffected. A strong positive correlation between SV2A and SYP densities confirmed SV2A's reliability as a synaptic integrity marker. This study supports the use of SV2A PET imaging for early diagnosis and monitoring of neurodegenerative diseases, providing essential data for interpreting in vivo PET results. Further research should explore SV2A as a therapeutic target and validate these findings in larger, longitudinal studies.

On the Therapeutic Use of Monoclonal Antibodies Against Amyloid Plaques in Older Adults with Down Syndrome: A Narrative Review and Perspective

Down syndrome (DS) is a genetic disorder caused by an extra copy of chromosome 21 (trisomy 21 or T21) and is associated with an increased risk of early-onset Alzheimer’s disease (AD), also known as DS-associated AD (DSAD). Individuals with DS typically develop amyloid neuropathology in their late-thirties to early-forties and the mean age of onset of clinical dementia is approximately 55 years. Recent advances in AD clinical research have focused on monoclonal antibodies (mAbs) targeting amyloid-β (Aβ) plaques as a potential therapeutic approach. Therefore, there has been guarded enthusiasm about using anti-amyloid mAbs in the prevention/treatment of DSAD. This narrative review and perspective explores the current understanding of amyloid pathology in AD and DSAD, the rationale for using anti-amyloid mAbs in the treatment of DSAD, and the challenges and opportunities for research toward the application of this therapeutic strategy to older adults with DS.

Identification of nitric oxide-mediated necroptosis as the predominant death route in Parkinson’s disease

Parkinson's disease (PD) involves multiple forms of neuronal cell death, but the dominant pathway involved in disease progression remains unclear. This study employed RNA sequencing (RNA-seq) of brain tissue to explore gene expression patterns across different stages of PD. Using the Scaden deep learning algorithm, we predicted neurocyte subtypes and modelled dynamic interactions for five classic cell death pathways to identify the predominant routes of neuronal death during PD progression. Our cell type-specific analysis revealed an increasing shift towards necroptosis, which was strongly correlated with nitric oxide synthase (NOS) expression across most neuronal subtypes. In vitro experiments confirmed that nitric oxide (NO) is a key mediator of necroptosis, leading to nuclear shrinkage and decreased mitochondrial membrane potential via phosphorylation of the PIP1/PIP3/MLKL signalling cascade. Importantly, specific necroptosis inhibitors significantly mitigated neuronal damage in both in vitro and in vivo PD models. Further analysis revealed that NO-mediated necroptosis is prevalent in early-onset Alzheimer's disease (AD) and amyotrophic lateral sclerosis (ALS) and across multiple brain regions but not in brain tumours. Our findings suggest that NO-mediated necroptosis is a critical pathway in PD and other neurodegenerative disorders, providing potential targets for therapeutic intervention.

Early detection of dementia through retinal imaging and trustworthy AI

Alzheimer’s disease (AD) is a global healthcare challenge lacking a simple and affordable detection method. We propose a novel deep learning framework, Eye-AD, to detect Early-onset Alzheimer’s Disease (EOAD) and Mild Cognitive Impairment (MCI) using OCTA images of retinal microvasculature and choriocapillaris. Eye-AD employs a multilevel graph representation to analyze intra- and inter-instance relationships in retinal layers. Using 5751 OCTA images from 1671 participants in a multi-center study, our model demonstrated superior performance in EOAD (internal data: AUC = 0.9355, external data: AUC = 0.9007) and MCI detection (internal data: AUC = 0.8630, external data: AUC = 0.8037). Furthermore, we explored the associations between retinal structural biomarkers in OCTA images and EOAD/MCI, and the results align well with the conclusions drawn from our deep learning interpretability analysis. Our findings provide further evidence that retinal OCTA imaging, coupled with artificial intelligence, will serve as a rapid, noninvasive, and affordable dementia detection.

Systematic evaluation of multifactorial causal associations for Alzheimer's disease and an interactive platform MRAD developed based on Mendelian randomization analysis.

Alzheimer's disease (AD) is a complex degenerative disease of the central nervous system, and elucidating its pathogenesis remains challenging. In this study, we used the inverse-variance weighted (IVW) model as the major analysis method to perform hypothesis-free Mendelian randomization (MR) analysis on the data from MRC IEU OpenGWAS (18,097 exposure traits and 16 AD outcome traits), and conducted sensitivity analysis with six models, to assess the robustness of the IVW results, to identify various classes of risk or protective factors for AD, early-onset AD, and late-onset AD. We generated 400,274 data entries in total, among which the major analysis method of the IVW model consists of 73,129 records with 4840 exposure traits, which fall into 10 categories: Disease, Medical laboratory science, Imaging, Anthropometric, Treatment, Molecular trait, Gut microbiota, Past history, Family history, and Lifestyle trait. More importantly, a freely accessed online platform called MRAD (https://gwasmrad.com/mrad/) has been developed using the Shiny package with MR analysis results. Additionally, novel potential AD therapeutic targets (CD33, TBCA, VPS29, GNAI3, PSME1) are identified, among which CD33 was positively associated with the main outcome traits of AD, as well as with both EOAD and LOAD. TBCA and VPS29 were negatively associated with the main outcome traits of AD, as well as with both EOAD and LOAD. GNAI3 and PSME1 were negatively associated with the main outcome traits of AD, as well as with LOAD, but had no significant causal association with EOAD. The findings of our research advance our understanding of the etiology of AD.

Systematic evaluation of multifactorial causal associations for Alzheimer’s disease and an interactive platform MRAD developed based on Mendelian randomization analysis

Alzheimer’s disease (AD) is a complex degenerative disease of the central nervous system, and elucidating its pathogenesis remains challenging. In this study, we used the inverse-variance weighted (IVW) model as the major analysis method to perform hypothesis-free Mendelian randomization (MR) analysis on the data from MRC IEU OpenGWAS (18,097 exposure traits and 16 AD outcome traits), and conducted sensitivity analysis with six models, to assess the robustness of the IVW results, to identify various classes of risk or protective factors for AD, early-onset AD, and late-onset AD. We generated 400,274 data entries in total, among which the major analysis method of the IVW model consists of 73,129 records with 4840 exposure traits, which fall into 10 categories: Disease, Medical laboratory science, Imaging, Anthropometric, Treatment, Molecular trait, Gut microbiota, Past history, Family history, and Lifestyle trait. More importantly, a freely accessed online platform called MRAD (https://gwasmrad.com/mrad/) has been developed using the Shiny package with MR analysis results. Additionally, novel potential AD therapeutic targets (CD33, TBCA, VPS29, GNAI3, PSME1) are identified, among which CD33 was positively associated with the main outcome traits of AD, as well as with both EOAD and LOAD. TBCA and VPS29 were negatively associated with the main outcome traits of AD, as well as with both EOAD and LOAD. GNAI3 and PSME1 were negatively associated with the main outcome traits of AD, as well as with LOAD, but had no significant causal association with EOAD. The findings of our research advance our understanding of the etiology of AD.

Francisco Lopera obituary: neurologist who traced genetic origin of early-onset Alzheimer's.

Francisco Lopera obituary: neurologist who traced genetic origin of early-onset Alzheimer's.

Understanding Down Syndrome: A Systematic Review of Genetic, Clinical, and Cognitive Implications

Down syndrome (DS) is the most common chromosomal disorder, primarily caused by trisomy 21, and is associated with a range of genetic, clinical, and cognitive challenges. This systematic review aims to provide a comprehensive understanding of these aspects by synthesizing recent research on the genetic mechanisms underlying DS, its common clinical manifestations, and the cognitive impairments often observed in affected individuals. Genetic studies highlight the complexity of trisomy 21 and its impact on phenotypic variability. Clinically, DS is associated with distinct physical features, congenital heart defects, and a predisposition to conditions such as thyroid disorders and leukemia. Cognitive impairments, including intellectual disability and early-onset Alzheimer's disease, present significant challenges for individuals with DS, often requiring early intervention and lifelong support. Recent advancements in medical care, therapeutic interventions, and educational strategies have improved quality of life and life expectancy for individuals with DS. This review identifies gaps in the current literature, such as the need for more personalized therapeutic approaches based on genetic variability, and highlights areas for future research to further improve outcomes for individuals with Down syndrome.

Identification of key proteins in early-onset Alzheimer's disease based on WGCNA.

Early-onset Alzheimer's disease (EOAD) is sporadic, highly heterogeneous, and its underlying pathogenic mechanisms remain largely elusive. Proteomics research aims to uncover the biological processes and key proteins involved in disease progression. However, no proteomic studies to date have specifically focused on EOAD brain tissue. We integrated proteomic data from brain tissues of two Alzheimer's disease (AD) cohorts and constructed a protein co-expression network using weighted gene co-expression network analysis (WGCNA). We identified modules associated with EOAD, conducted functional enrichment analysis to understand the biological processes involved in EOAD, and pinpointed potential key proteins within the core modules most closely linked to AD pathology. In this study, we identified a total of 2,749 proteins associated with EOAD. Through protein co-expression network analysis, we discovered 41 distinct co-expression modules. Notably, the proteins within the core module most closely linked to AD pathology were significantly enriched in neutrophil degranulation. Additionally, we identified two potential key proteins within this core module that have not been previously reported in AD and validated their expression levels in 5xFAD mice. In summary, through a protein co-expression network analysis, we identified EOAD-related biological processes and molecular pathways, and screened and validated two key proteins, ERBB2IP and LSP1. These proteins may play an important role in the progression of EOAD, suggesting they could serve as potential therapeutic targets for the disease.

Alzheimer's disease induced neurons bearing PSEN1 mutations exhibit reduced excitability.

Alzheimer's disease (AD) is a devastating neurodegenerative condition that affects memory and cognition, characterized by neuronal loss and currently lacking a cure. Mutations in PSEN1 (Presenilin 1) are among the most common causes of early-onset familial AD (fAD). While changes in neuronal excitability are believed to be early indicators of AD progression, the link between PSEN1 mutations and neuronal excitability remains to be fully elucidated. This study examined iPSC-derived neurons (iNs) from fAD patients with PSEN1 mutations S290C or A246E, alongside CRISPR-corrected isogenic cell lines, to investigate early changes in excitability. Electrophysiological profiling revealed reduced excitability in both PSEN1 mutant iNs compared to their isogenic controls. Neurons bearing S290C and A246E mutations exhibited divergent passive membrane properties compared to isogenic controls, suggesting distinct effects of PSEN1 mutations on neuronal excitability. Additionally, both PSEN1 backgrounds exhibited higher current density of voltage-gated potassium (Kv) channels relative to their isogenic iNs, while displaying comparable voltage-gated sodium (Nav) channel current density. This suggests that the Nav/Kv imbalance contributes to impaired neuronal firing in fAD iNs. Deciphering these early cellular and molecular changes in AD is crucial for understanding disease pathogenesis.

Alzheimer's dementia in people with Down syndrome : Results of guideline-assisted expert interviews on healthcare deficits in the diagnostics and treatment as well as solution approaches

People with Down syndrome have agenetically increased risk of developing early onset Alzheimer's dementia. An interview study with healthcare providers, patient representatives and employees in residential and work facilities was conducted to identify deficits in the healthcare process and approaches to overcoming them. In this study 14 semi-structured interviews were conducted and analyzed using qualitative content analysis. Alack of knowledge and experience on the part of medical service providers in dealing with and providing medical care for people with Down syndrome was identified as akey challenge. In addition, the diagnosis of dementia in people with Down syndrome is difficult for various reasons (including lack of appropriate diagnostic tools in standard care and lack of time or financial resources). Doubts were expressed about the efficacy of antidementia medications and the reasons for the increased use of sedatives were discussed. Attentive observation of behavior and involvement of caregivers, regular review and reduction of polypharmacy and the use of alternative behavior modification techniques were mentioned as possible solutions. The identified deficits in the medical care of the target population and the approaches to solving them will be incorporated into the development of health policy recommendations in order to optimize the care situation of those affected in the long term.

Genotyping Apolipoprotein E (APOE) Isoforms with Sequence-Specific-Primer (SSP)-PCR in Early‑Onset Alzheimer’s Disease Patients: A Rapid and Revised Methodology

Alzheimer's disease (AD) is a neurodegenerative disorder that causes progressive damage to brain cells, leading to impairment in cognitive functions. The Apolipoprotein E (APOE) variants play a significant role in the genetic basis of AD, especially late-onset AD (LOAD), and increase the disease risk at an earlier age. Although controversial, some studies reveal the association between APOE genotype and early-onset AD (EOAD) regardless of family history. Therefore, diagnostic laboratories widely perform routine tests to determine the APOE genotype. In the present study, we implemented a revised methodology for the Sequence-Specific-Primer-PCR (SSP-PCR) test for rapid APOE genotyping in 67 EOAD patients. Then, the findings were validated using automatic sequencing with newly designed primers for the related region of the APOE. We state clearly that the applicability of the SSP-PCR method was improved when the primer concentrations of control genes were increased 2-fold, as we reported. All data obtained from SSP-PCR were consistent with Sanger sequencing confirmations. Based on the genotyping results, the four different APOE genotypes were detected: E2/E4, E3/E3, E3/E4, and E4/E4. The frequencies were 1.5% (n=1) for E2/E4, 76.1% (n=51) for E3/E3, 16.4% (n=11) for E3/E4, and 6% (n=4) for E4/E4. In the study group, 23.9% (n=16) of the patients had homozygous or heterozygous APOE E4. However, we detected no significant association between the clinical features and the APOE genotype. As a result, this method is reliable, cost-effective, and rapid for performing genotyping analysis of the APOE for routine tests and research studies with larger EOAD cohorts.

MRI-Based Multi-Class Relevance Vector Machine Classification of Neurodegenerative Diseases.

Machine learning algorithms are a promising automated candidate that can help mitigate the growing need for dementia experts. Despite the substantial development in MRI-based machine learning analyses, case misclassification is a universal finding, yet the reasons behind misclassification are poorly understood. We implemented a multi-class classification approach that uses relevance vector machine and logistic classification to classify research participants based on their whole-brain T1-weighted MRI scans. A total of 468 participants from seven diagnostic classes were included: 144 healthy controls, 84 Alzheimer's disease, 108 behavioral variant frontotemporal dementia (bvFTD), 30 semantic variant primary progressive aphasia (svPPA), 30 non-fluent variant primary progressive aphasia (nfvPPA), 30 corticobasal syndrome (CBS), and 42 progressive supranuclear palsy syndrome (PSPS). We compared the algorithm's diagnostic accuracy against the clinical, pathological, genetic, and quantitative imaging data. The exact neurodegenerative syndrome was predicted in 71% of the cases, the neurodegenerative disease spectrum was predicted in 80% of the cases, and the algorithm distinguished controls from any dementia in 85% of the cases. The algorithm showed high performance in diagnosing healthy controls, moderate performance in diagnosing AD, bvFTD, and svPPA, and low performance in diagnosing CBS, nfvPPA, and PSPS. Based on the quantitative imaging data, most of the misclassified neurodegenerative cases had minimal atrophy and brain volumes comparable to healthy controls. In AD, early-onset AD cases with minimal brain atrophy represented most of the misclassified cases. In bvFTD, FTD genetic mutation carriers (predominantly C9orf72 repeat expansion), FTD phenocopy, patients meeting only possible bvFTD criteria represented most misclassified cases. Case misclassification in machine learning studies in neurodegenerative diseases results from neurodegenerative disease heterogeneity and the limitations of structural MRI's ability to capture the whole gamut of biological changes. Larger and more inclusive datasets that are representative of population biologic heterogeneity are needed to train better machine learning techniques, and a margin of error is expected and should be acceptable, like the uncertainty of a clinical diagnosis by a dementia expert.

MTHFR Polymorphisms and Plasma Homocysteine in Early-Onset Alzheimer's Disease: A Case-Control Study

Background: Early-onset Alzheimer's disease (EOAD) constitutes 1-2% of all Alzheimer's cases, presenting with poorer prognosis, progressive symptoms, and reduced life expectancy compared to late-onset Alzheimer’s, thereby increasing socioeconomic burden. Elevated plasma homocysteine levels due to MTHFR gene polymorphisms are implicated in Alzheimer's etiology. The present study aims to explore the association between MTHFR gene polymorphisms in Sudanese population. Methods: Seventy-three EOAD patients were assessed for MTHFR C677T and A1298C polymorphisms, alongside plasma homocysteine levels. Results: Significant associations were observed between CT and TT alleles, elevated plasma homocysteine levels, and EOAD. Conclusion: MTHFR C677T polymorphism was associated in EOAD in Sudanese population. Elevated plasma homocysteine levels might frame this association and potentially contribute to the disease onset before the age of 65.

Medial temporal lobe atrophy patterns in early-versus late-onset amnestic Alzheimer’s disease

BackgroundThe medial temporal lobe (MTL) is hypothesized to be relatively spared in early-onset Alzheimer’s disease (EOAD). Yet, detailed examination of MTL subfields and drivers of atrophy in amnestic EOAD is lacking.MethodsBioFINDER-2 participants with memory impairment, abnormal amyloid-β and tau-PET were included. Forty-one amnestic EOAD individuals ≤65 years and, as comparison, late-onset AD (aLOAD, ≥70 years, n = 154) and amyloid-β-negative cognitively unimpaired controls were included. MTL subregions and biomarkers of (co-)pathologies were measured.ResultsAD groups showed smaller MTL subregions compared to controls. Atrophy patterns were similar across AD groups: aLOAD showed thinner entorhinal cortices than aEOAD; aEOAD showed thinner parietal regions than aLOAD. aEOAD showed lower white matter hyperintensities than aLOAD. No differences in MTL tau-PET or transactive response DNA binding protein 43-proxy positivity were found.ConclusionsWe found evidence for MTL atrophy in amnestic EOAD and overall similar levels to aLOAD of MTL tau pathology and co-pathologies.