Grinberg, Lea

Abstract Frontotemporal lobar degeneration (FTLD) and Alzheimer’s disease (AD) differ in their clinical features and genetic etiologies but share progressive cognitive decline. Emerging evidence implicates lipid dysregulation in neurodegeneration, but its extent across FTLD subtypes and how it compares to AD are unclear. Here, we performed integrated lipidomic and proteomic analyses of matched frontal (disease-vulnerable) and occipital (relatively spared) post-mortem cortices from individuals with genetic and sporadic FTLD-TDP, FTLD-tau (Pick’s disease, PiD), AD, and controls. FTLD and AD exhibited convergent lipid alterations, including reduced levels of cardiolipins and phosphatidylethanolamines, alongside increased gangliosides, diacylglycerols, cholesterol esters, acylcarnitines, and coenzyme Q, with generally greater changes in FTLD frontal cortex. FTLD displayed additional alterations, including reductions in bis(monoacylglycerol)phosphate, ceramides, phosphatidylserines, phosphatidylinositols, and sulfatides. These lipid changes were accompanied by proteomic alterations involving lysosomal proteins, phospholipases, phospholipid remodeling enzymes, and fatty acid oxidation pathways. Although lipidomic and proteomic signatures were broadly shared across FTLD subtypes, GRN associated FTLD-TDP and PiD showed the most extensive alterations. Triglycerides were selectively reduced in PiD in association with decreased DGAT1 expression, whereas cholesterol esters were elevated across all subtypes except C9orf72 associated FTLD-TDP. These findings identify shared disruptions in lipid homeostasis and lysosomal lipid metabolism across FTLD and AD, highlighting convergent metabolic pathways underlying neurodegeneration.

Abstract INTRODUCTION Similarities between frontotemporal lobar degeneration with transactive response DNA‐binding protein of 43 kDa (TDP‐43) (FTLD‐TDP) and limbic‐predominant age‐related TDP‐43 encephalopathy neuropathologic change (LATE‐NC) raise questions about whether they represent distinct entities or a single disease spectrum. The literature mostly examined series with disproportionate numbers of LATE‐NC over FTLD‐TDP. METHODS Leveraging a clinicopathological collection of FTLD‐TDP ( N = 148) from the University of California, San Francisco, we compared demographic, clinical, genetic, and neuropathological features of FTLD‐TDP, particularly FTLD‐TDP type A ( N = 39), and LATE‐NC ( N = 42). RESULTS FTLD‐TDP type A cases were younger at onset and death, had shorter disease duration, and frequent genetic causes ( GRN , C9ORF72 ) compared to LATE‐NC, which were mostly sporadic and older. Blinded evaluation of middle frontal gyrus (MFG) TDP‐43 immunostaining alone proved insufficient to reliably differentiate FTLD‐TDP type A from LATE‐NC stage 3. However, factoring in all neuropathologic features, FTLD type A and LATE‐NC could be differentiated with >95% confidence. DISCUSSION These overall findings support distinct diagnostic entities for FTLD‐TDP and LATE‐NC.

Abstract INTRODUCTION Clinicopathological studies offer crucial interpretations of 18 F‐flortaucipir (FTP) tau positron emission tomography (PET) signal but are limited by methods. We leveraged whole‐brain, quantitative immunohistochemical (IHC) Alzheimer's Disease (AD) tau density maps to comprehensively evaluate the FTP tracer. METHODS We generated IHC maps for three AD‐tau antibodies—AT8, AT100, and MC1—using two human brains histologically staged at Braak IV and VI. FTP‐PET scans were acquired 6 and 10 weeks prior to death. Using region‐wise and voxelwise methods, we correlated FTP‐PET with IHC signals. RESULTS Only AT8 (p‐tau Ser202/Thr205; neuronal and neuritic tau pathology) showed a notable correlation with FTP standardized uptake value ratios (SUVRs) in the Braak VI case (Spearman's rank correlation coefficient [r s ] = 0.461, p < 0.001). FTP SUVRs failed to capture medial temporal lobe (MTL) tau burden, whereas neocortical regions showed lower IHC burden but more variability in FTP uptake. DISCUSSION Although FTP signals correlate well with AT8‐positive tau in the more advanced case, they underestimate the severity of MTL burden, potentially confounding assessments of tau‐targeted therapies.

BACKGROUND: Cerebrovascular disease is prevalent in older adults and is associated with cognitive impairment. Although the association between brain infarcts and cognition has been widely investigated, the contribution of vascular disease to cognitive impairment has been less studied, particularly in non-White populations. We investigated the epidemiological and clinical characteristics of vascular disease phenotypes and their association with cognitive abilities in a diverse population. METHODS: In a Brazilian population–based clinicopathological study (recruitment between 2004 and 2024), inclusion criteria were age at death ≥18 years and the availability of an informant. Clinical information and cognitive abilities were assessed through informant interviews. Hyaline arteriolosclerosis (HA) was evaluated in 13 brain areas and categorized as absent, mild, moderate, or severe. Moderate/severe HA defined microvascular disease (Micro[+]). Intracranial atherosclerosis in the circle of Willis was similarly classified, with moderate/severe cases defining macrovascular disease (Macro[+]). Four vascular profiles were compared: Micro[+]/Macro[+], Micro[−]/Macro[+], Micro[+]/Macro[−], and Micro[−]/Macro[−]. Linear regression models adjusted for sociodemographic, clinical, and cerebrovascular/neurodegenerative lesions evaluated the association of cognition with vascular profiles, and microvascular and macrovascular diseases separately. RESULTS: Of 2418 participants, 834 with missing data were excluded, yielding a final sample of 1584 individuals (mean age, 74.3±13.4 years; 776 [49%] women; 982 [62%] White). Microvascular disease was slightly more frequent (31%) than macrovascular (29%). Regarding vascular profiles, 788 (50%) participants were Micro[−]/Macro[−], 334 (21%) Micro[+]/Macro[−], 301 (19%) Micro[−]/Macro[+], and 161 (10%) Micro[+]/Macro[+]. Micro[+] participants were older and more frequently women, and had worse cognitive abilities. Vascular groups were similar regarding most clinical comorbidities. HA (β, 0.81 [95% CI, 0.25–1.36]; P =0.004) and Micro[+]/Macro[+] phenotype (β, 1.25 [95% CI, 0.38–2.12]; P =0.005) were associated with worse cognitive abilities compared with HA-negative and Micro[−]/Macro[−] participants, respectively. CONCLUSIONS: HA was as frequent as intracranial atherosclerosis. HA and the vascular phenotype with both microvascular and macrovascular diseases were associated with worse cognition.

Abstract Chronic traumatic encephalopathy (CTE) is a progressive neurodegenerative disease linked to repetitive traumatic brain injury, but its prevalence and risk factors in the general population remain poorly defined. We investigated CTE neuropathological changes (CTE-NC) in an admixed, population-based clinicopathological cohort. Neuropathological evaluation was conducted on brain samples from 1151 individuals in the University of São Paulo Biobank for Aging Studies collected from 2004 to 2022. CTE-NC and aging-related tau astrogliopathy (ARTAG) were assessed across 14 963 histological slides using p-tau immunostaining. Clinical, cognitive, and neuropsychiatric data were obtained via informant interviews; information on sports exposure and traumatic brain injury history was limited. Seven cases (0.6%) met criteria for CTE-NC, mean age at death 73.4 ± 12.5 years; 1 was female. Dementia was present in 43% of CTE-NC cases; 57% exhibited neuropsychiatric symptoms. Most common co-pathologies were Alzheimer disease-type changes, ARTAG, and argyrophilic grain disease. Comprehensive exposure histories were unavailable for most cases; 2 had documented soccer involvement. These findings indicate that CTE-NC is rare in this population-based Brazilian cohort and predominantly affects males with frequent coexisting neuropathologies. Findings align with reports from high-income countries and support prioritizing primary prevention by reducing exposure to repetitive head impacts in sport and other settings.

Abstract The link between regional tau load and clinical manifestation of Alzheimer’s disease (AD) highlights the importance of characterizing spatial tau distribution across disease variants. In typical (memory-predominant) AD, the spatial progression of tau pathology mirrors the functional connections from temporal lobe epicentres. However, given the limited spatial heterogeneity of tau in typical AD, atypical (non-amnestic-predominant) AD variants with distinct tau patterns provide a key opportunity to investigate the universality of connectivity as a scaffold for tau progression. In this large-scale, multicentre study across 14 international sites, we included cross-sectional tau-PET data from 320 individuals with atypical AD (n = 139 posterior cortical atrophy/PCA-AD; n = 103 logopenic variant primary progressive aphasia/lvPPA-AD; n = 35 behavioural variant AD/bvAD; n = 43 corticobasal syndrome/CBS-AD), with a subset of individuals (n = 78) having longitudinal tau-PET data. Additionally, as an independent sample, we included regional post-mortem tau stainings from 93 atypical AD patients from two sites (n = 19 PCA-AD, n = 32 lvPPA-AD, n = 23 bvAD, n = 19 CBS-AD). Gaussian mixture modelling was used to harmonize different tau-PET tracers by transforming tau-PET standardized uptake value ratios to tau positivity probabilities (a uniform scale ranging from 0% to 100%). Using linear regression, we assessed whether brain regions with stronger resting-state functional MRI-based functional connectivity, derived from healthy elderly controls in the Alzheimer’s Disease Neuroimaging Initiative (ADNI), showed greater covariance in cross-sectional and longitudinal tau-PET and post-mortem tau pathology. Furthermore, we examined whether functional connectivity of tau-PET epicentres (i.e. the top 5% of regions with the highest baseline tau load) and tau-PET accumulation epicentres (i.e. the top 5% of regions with the highest tau accumulation rates) was associated with cross-sectional and longitudinal tau patterns. Our findings show that tau-PET epicentres aligned with clinical variants, e.g. a visual network predominant pattern in PCA-AD (‘visual AD’) and left-hemispheric temporal predominance, particularly within the language network, in lvPPA-AD (‘language AD’). Moreover, more strongly functionally connected regions showed correlated concurrent tau-PET levels (confirmed with post-mortem data) and tau-PET accumulation rates. The functional connectivity profile of tau-PET epicentres and accumulation epicentres corresponded to tau-PET progression patterns, with higher tau-PET levels and accumulation rates in functionally close regions, and lower tau-PET levels and accumulation rates in functionally distant regions. Our data are consistent with the hypothesis that tau propagation occurs along functional connections originating from local epicentres, across all AD clinical variants. Since tau proteinopathy is a major driver of neurodegeneration and cognitive decline, this finding may advance personalized medicine and participant-specific end points in clinical trials.

AbstractINTRODUCTIONPlasma amyloid beta42/amyloid beta40 (Aβ42/Aβ40) and phosphorylated tau217 (p‐tau217) identify individuals with primary Alzheimer's disease (AD). They may detect AD co‐pathology in the setting of other primary neurodegenerative diseases, but this has not been systematically studied.METHODSWe compared the clinical, neuroimaging, and neuropathological associations of plasma Aβ42/Aβ40 (mass spectrometry), p‐tau217 (electrochemiluminescence), and neurofilament light ([NfL], single molecule array [Simoa]), as markers of AD co‐pathology, in a sporadic frontotemporal dementia (FTD) cohort (n = 620).RESULTSAβ42/Aβ40 showed no clinicopathological associations. High p‐tau217 was present in amnestic dementia (AmD) presumed to be due to FTD, logopenic primary progressive aphasia (lvPPA), and APOEε4 carriers, and correlated with worse baseline and longitudinal clinical scores, lower hippocampal volumes, and more severe AD co‐pathology (Braak Stage). NfL was elevated in all FTD phenotypes, and correlated with clinical scores and frontotemporal brain volumes.DISCUSSIONPlasma p‐tau217 has clinical, neuroimaging, and neuropathological correlates in sporadic FTD and may identify FTD cases with AD co‐pathology.Highlights Alzheimer's disease (AD) features could be identified with plasma phosphorylated tau217 (p‐tau217) in frontotemporal lobar degeneration (FTLD). Plasma p‐tau217 is a better discriminator of AD co‐pathology and AD‐associated features in FTLD than plasma amyloid beta42/amyloid beta40 (Aβ42/Aβ40) and neurofilament light (NfL). In FTLD, plasma p‐tau217, but not Aβ42/Aβ40 or neurofilament light, has phenotypical, neurocognitive, and neuroimaging correlates suggestive of AD co‐pathology.