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  • 1
    In: Brain, Oxford University Press (OUP), ( 2024-02-07)
    Abstract: Synaptic dysfunction and degeneration is likely the key pathophysiology for the progression of cognitive decline in various dementia disorders. Synaptic status can be monitored by measurement of synaptic proteins in cerebrospinal fluid (CSF). In the current study, the aim was to investigate and compare both known and new synaptic proteins as potential biomarkers of synaptic dysfunction, especially in the context of Alzheimer’s disease (AD). Seventeen synaptic proteins were quantified in CSF using two different targeted mass spectrometry assays in the prospective Swedish BioFINDER-2 study. The study included 958 individuals, characterized as having mild cognitive impairment (MCI, n = 205), AD dementia (n = 149), and a spectrum of other neurodegenerative diseases (n = 171), as well as cognitively unimpaired (CU, n = 443). Synaptic protein levels were compared between diagnostic groups and their associations with cognitive decline and key neuroimaging measures (Aβ-PET, tau-PET, and cortical thickness) were assessed. Among the 17 synaptic proteins examined, 14 were specifically elevated in the AD continuum. SNAP-25, 14-3-3 zeta/delta, beta-synuclein, and neurogranin exhibited the highest discriminatory accuracy to differentiate AD dementia from controls (AUCs = 0.81-0.93). SNAP-25 and 14-3-3 zeta/delta also had the strongest associations with tau-PET, Aβ-PET, and cortical thickness at baseline, and were associated with longitudinal changes in these imaging biomarkers (β(SE)=-0.056(0.0006) to 0.058(0.005), p & lt; 0.0001). SNAP-25 was the strongest predictor of progression to AD dementia in non-demented individuals (Hazard ratio = 2.11). In contrast, neuronal pentraxins were decreased in all neurodegenerative diseases (except for Parkinson’s disease), and NPTX2 showed the strongest associations with subsequent cognitive decline (longitudinal MMSE; β(SE) = 0.57(0.1), p ≤ 0.0001 and mPACC; β(SE) = 0.095(0.024), p ≤ 0.001) across the AD continuum. Interestingly, utilizing a ratio of the proteins that displayed higher levels in AD, such as SNAP-25 or 14-3-3 zeta/delta, over NPTX2 improved the biomarkers’ association with cognitive decline and brain atrophy. We found that especially 14-3-3 zeta/delta and SNAP-25 are promising synaptic biomarkers of pathophysiological changes in AD. Neuronal pentraxins were identified as general indicators of neurodegeneration and associated with cognitive decline across various neurodegenerative dementias. The ratios of SNAP-25/NPTX2 and 14-3-3 zeta/delta/NPTX2 were found to best predict cognitive decline and brain atrophy.
    Type of Medium: Online Resource
    ISSN: 0006-8950 , 1460-2156
    RVK:
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2024
    detail.hit.zdb_id: 1474117-9
    SSG: 12
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  • 2
    In: Brain Communications, Oxford University Press (OUP), Vol. 4, No. 3 ( 2022-05-02)
    Abstract: A growing body of evidence suggests that astrocytes play a major role in the pathophysiology of Alzheimer’s disease. Given that APOE is primarily expressed in astrocytes, these cells might be an important link between the APOE ε4 allele and the development of Alzheimer’s disease pathology. Here, we investigate this hypothesis in vivo by measuring myo-inositol, a metabolite involved in astrocytic functions, with magnetic resonance spectroscopy. Currently, there is conflicting evidence regarding the relationship between APOE ε4 and myo-inositol concentration. Furthermore, data supporting a relationship between APOE ε4, myo-inositol and Alzheimer’s disease pathology (amyloid-beta and tau proteins) in the preclinical stage of Alzheimer’s disease are limited. A previous study revealed differences in myo-inositol levels between APOE ε4 carriers and non-carriers already in preclinical Alzheimer’s disease participants. However, other reports showed no impact of APOE genotype on the association between myo-inositol and the rate of amyloid-beta accumulation. In the present study, we determined the effect of APOE genotype on the association between myo-inositol and both amyloid-β and tau deposition quantified by PET in 428 cognitively unimpaired elderly and patients with mild cognitive impairment from the Swedish BioFINDER-2 cohort. APOE genotype impacted the associations between myo-inositol and amyloid-β pathology as revealed by an interaction effect between APOE genotype and levels of myo-inositol (P  & lt; 0.001) such that higher myo-inositol concentration was related to more amyloid-beta pathology in APOE ε4 carriers only. A similar interaction effect was also found when investigating the effect of APOE on the association between myo-inositol and tau pathology (P  & lt; 0.01). Focusing on the APOE ε4 subsample, myo-inositol partially (17%) mediated the association between amyloid-beta and tau pathology (P  & lt; 0.05). Furthermore, in a subgroup of participants with available plasma levels of glial fibrillary acidic protein, a marker of astroglial activation and astrocytosis, we found that glial fibrillary acidic protein correlated with myo-inositol only in APOE e4 carriers (APOE ε4 carriers: P  & lt; 0.01; APOE ε4 non-carriers: P  & gt; 0.8), suggesting that myo-inositol might reflect an aspect of the astrocytic involvement in Alzheimer’s pathology which is specific to the impact of APOE ε4. Therefore, we suggest that myo-inositol is a candidate in vivo marker to study the impact of APOE ε4 on the interplay between astrocytes and the pathophysiology of Alzheimer’s disease.
    Type of Medium: Online Resource
    ISSN: 2632-1297
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2022
    detail.hit.zdb_id: 3020013-1
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  • 3
    Online Resource
    Online Resource
    Oxford University Press (OUP) ; 2023
    In:  Brain Vol. 146, No. 4 ( 2023-04-19), p. 1602-1614
    In: Brain, Oxford University Press (OUP), Vol. 146, No. 4 ( 2023-04-19), p. 1602-1614
    Abstract: Markers of downstream events are a key component of clinical trials of disease-modifying therapies for Alzheimer’s disease. Morphological metrics like cortical thickness are established measures of atrophy but are not sensitive enough to detect amyloid-beta (Aβ)- related changes that occur before overt atrophy become visible. We aimed to investigate to what extent diffusion MRI can provide sensitive markers of cortical microstructural changes and to test their associations with multiple aspects of the Alzheimer’s disease pathological cascade, including both Aβ and tau accumulation, astrocytic activation and cognitive deficits. We applied the mean apparent diffusion propagator model to diffusion MRI data from 492 cognitively unimpaired elderly and patients with mild cognitive impairment from the Swedish BioFINDER-2 cohort. Participants were stratified in Aβ-negative/tau-negative, Aβ-positive/tau-negative and Aβ-positive/tau-positive based on Aβ- and tau-PET uptake. Cortical regional values of diffusion MRI metrics and cortical thickness were compared across groups. Associations between regional values of diffusion MRI metrics and both Aβ- and tau-PET uptake were also investigated along with the association with plasma level of glial fibrillary acidic protein (GFAP), a marker of astrocyte activation (available in 292 participants). Mean squared displacement revealed widespread microstructural differences already between Aβ-negative/tau-negative and Aβ-positive/tau-negative participants with a spatial distribution that closely resembled the pattern of Aβ accumulation. In contrast, differences in cortical thickness were clearly more limited. Mean squared displacement was also correlated with both Aβ- and tau-PET uptake even independently from one another and from cortical thickness. Further, the same metric exhibited significantly stronger correlations with PET uptake than cortical thickness (P & lt; 0.05). Mean squared displacement was also positively correlated with GFAP with a pattern that resembles Aβ accumulation, and GFAP partially mediated the association between Aβ accumulation and mean squared displacement. Further, impairments in executive functions were significantly more associated with mean squared displacement values extracted from a meta-region of interest encompassing regions accumulating Aβ early in the disease process, than with cortical thickness (P & lt; 0.05). Similarly, impairments in memory functions were significantly more associated with mean squared displacement values extracted from a temporal meta-region of interest than with cortical thickness (P & lt; 0.05). Metrics of cortical microstructural alteration derived from diffusion MRI are highly sensitive to multiple aspects of the Alzheimer’s disease pathological cascade. Of particular interest is the link with both Aβ-PET and GFAP, suggesting diffusion MRI might reflects microstructural changes related to the astrocytic response to Aβ aggregation. Therefore, metrics of cortical diffusion might be important outcome measures in anti-Aβ treatments clinical trials for detecting drug-induced changes in cortical microstructure.
    Type of Medium: Online Resource
    ISSN: 0006-8950 , 1460-2156
    RVK:
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2023
    detail.hit.zdb_id: 1474117-9
    SSG: 12
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  • 4
    In: Brain, Oxford University Press (OUP), Vol. 146, No. 8 ( 2023-08-01), p. 3192-3205
    Abstract: Amyloid-β (Aβ) is hypothesized to facilitate the spread of tau pathology beyond the medial temporal lobe. However, there is evidence that, independently of Aβ, age-related tau pathology might be present outside of the medial temporal lobe. We therefore aimed to study age-related Aβ-independent tau deposition outside the medial temporal lobe in two large cohorts and to investigate potential downstream effects of this on cognition and structural measures. We included 545 cognitively unimpaired adults (40–92 years) from the BioFINDER-2 study (in vivo) and 639 (64–108 years) from the Rush Alzheimer’s Disease Center cohorts (ex vivo). 18F-RO948- and 18F-flutemetamol-PET standardized uptake value ratios were calculated for regional tau and global/regional Aβ in vivo. Immunohistochemistry was used to estimate Aβ load and tangle density ex vivo. In vivo medial temporal lobe volumes (subiculum, cornu ammonis 1) and cortical thickness (entorhinal cortex, Brodmann area 35) were obtained using Automated Segmentation for Hippocampal Subfields packages. Thickness of early and late neocortical Alzheimer’s disease regions was determined using FreeSurfer. Global cognition and episodic memory were estimated to quantify cognitive functioning. In vivo age-related tau deposition was observed in the medial temporal lobe and in frontal and parietal cortical regions, which was statistically significant when adjusting for Aβ. This was also observed in individuals with low Aβ load. Tau deposition was negatively associated with cortical volumes and thickness in temporal and parietal regions independently of Aβ. The associations between age and cortical volume or thickness were partially mediated via tau in regions with early Alzheimer’s disease pathology, i.e. early tau and/or Aβ pathology (subiculum/Brodmann area 35/precuneus/posterior cingulate). Finally, the associations between age and cognition were partially mediated via tau in Brodmann area 35, even when including Aβ-PET as covariate. Results were validated in the ex vivo cohort showing age-related and Aβ-independent increases in tau aggregates in and outside the medial temporal lobe. Ex vivo age-cognition associations were mediated by medial and inferior temporal tau tangle density, while correcting for Aβ density. Taken together, our study provides support for primary age-related tauopathy even outside the medial temporal lobe in vivo and ex vivo, with downstream effects on structure and cognition. These results have implications for our understanding of the spreading of tau outside the medial temporal lobe, also in the context of Alzheimer’s disease. Moreover, this study suggests the potential utility of tau-targeting treatments in primary age-related tauopathy, likely already in preclinical stages in individuals with low Aβ pathology.
    Type of Medium: Online Resource
    ISSN: 0006-8950 , 1460-2156
    RVK:
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2023
    detail.hit.zdb_id: 1474117-9
    SSG: 12
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  • 5
    In: Brain, Oxford University Press (OUP), ( 2023-09-18)
    Abstract: Cerebrovascular pathology often co-exists with Alzheimer’s disease pathology and can contribute to Alzheimer’s disease-related clinical progression. However, the degree to which vascular burden contributes to Alzheimer’s disease pathological progression is still unclear. This study aimed to investigate interactions between vascular burden and amyloid-β pathology on both baseline tau tangle load and longitudinal tau accumulation. We included 1,229 participants from the Swedish BioFINDER-2 Study, including cognitively unimpaired and impaired participants with and without biomarker-confirmed amyloid-β pathology. All underwent baseline tau-PET ([18F]RO948) and a subset (n = 677) underwent longitudinal tau-PET after 2.5 ± 1.0 years. Tau-PET uptake was computed for a temporal meta-region-of-interest. We focused on four main vascular imaging features and risk factors: microbleeds, white matter lesion volume, stroke-related events (infarcts, lacunes and haemorrhages), and the Framingham Heart Study Cardiovascular Disease risk score. To validate our in vivo results, we examined 1,610 autopsy cases from an Arizona-based neuropathology cohort on three main vascular pathological features: cerebral amyloid angiopathy, white matter rarefaction and infarcts. For the in vivo cohort, primary analyses included age-, sex- and APOE ε4-corrected linear mixed models between tau-PET (outcome) and interactions between time, amyloid-β and each vascular feature (predictors). For the neuropathology cohort, age-, sex- and APOE ε4-corrected linear models between tau tangle density (outcome) and an interaction between plaque density and each vascular feature (predictors) were performed. In cognitively unimpaired individuals, we observed a significant interaction between microbleeds and amyloid-β pathology on greater baseline tau load (β=0.68, p  & lt; 0.001) and longitudinal tau accumulation (β=0.11, p  & lt; 0.001). For white matter lesion volume, we did not observe a significant independent interaction effect with amyloid-β on tau after accounting for microbleeds. In cognitively unimpaired individuals we further found that stroke-related events showed a significant negative interaction with amyloid-β on longitudinal tau (β=-0.08, p  & lt; 0.001). In cognitively impaired individuals, there were no significant interaction effects between cerebrovascular and amyloid-β pathology at all. In the neuropathology dataset, the in-vivo observed interaction effects between cerebral amyloid angiopathy and plaque density (β=0.38, p  & lt; 0.001) and between infarcts and plaque density (β=-0.11, p = 0.005) on tau tangle density were replicated. To conclude, we demonstrated that cerebrovascular pathology - in the presence of amyloid-β pathology - modifies tau accumulation in early stages of Alzheimer’s disease. More specifically, the co-occurrence of microbleeds and amyloid-β pathology was associated with greater accumulation of tau aggregates during early disease stages. This opens the possibility that interventions targeting microbleeds may attenuate the rate of tau accumulation in Alzheimer’s disease.
    Type of Medium: Online Resource
    ISSN: 0006-8950 , 1460-2156
    RVK:
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2023
    detail.hit.zdb_id: 1474117-9
    SSG: 12
    Library Location Call Number Volume/Issue/Year Availability
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  • 6
    Online Resource
    Online Resource
    Oxford University Press (OUP) ; 2020
    In:  Brain Vol. 143, No. 5 ( 2020-05-01), p. 1341-1349
    In: Brain, Oxford University Press (OUP), Vol. 143, No. 5 ( 2020-05-01), p. 1341-1349
    Abstract: A growing body of evidence suggests that the dysregulation of neuronal iron may play a critical role in Alzheimer’s disease. Recent MRI studies have established a relationship between iron accumulation and amyloid-β aggregation. The present study provides further insight demonstrating a relationship between iron and tau accumulation using magnetic resonance-based quantitative susceptibility mapping and tau-PET in n = 236 subjects with amyloid-β pathology (from the Swedish BioFINDER-2 study). Both voxel-wise and regional analyses showed a consistent association between differences in bulk magnetic susceptibility, which can be primarily ascribed to an increase in iron content, and tau-PET signal in regions known to be affected in Alzheimer’s disease. Subsequent analyses revealed that quantitative susceptibility specifically mediates the relationship between tau-PET and cortical atrophy measures, thus suggesting a modulatory effect of iron burden on the disease process. We also found evidence suggesting the relationship between quantitative susceptibility and tau-PET is stronger in younger participants (age ≤ 65). Together, these results provide in vivo evidence of an association between iron deposition and both tau aggregation and neurodegeneration, which help advance our understanding of the role of iron dysregulation in the Alzheimer’s disease aetiology.
    Type of Medium: Online Resource
    ISSN: 0006-8950 , 1460-2156
    RVK:
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2020
    detail.hit.zdb_id: 1474117-9
    SSG: 12
    Library Location Call Number Volume/Issue/Year Availability
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  • 7
    In: Brain Communications, Oxford University Press (OUP)
    Abstract: In Alzheimer’s disease reconfiguration and deterioration of tissue microstructure occur before substantial degeneration become evident. We explored the diffusion properties of both water, a ubiquitous marker measured by diffusion MRI, and N-acetyl-aspartate, a neuronal metabolite probed by diffusion weighted magnetic resonance spectroscopy, for investigating cortical microstructural changes downstream of Alzheimer’s disease pathology. To this aim, 50 participants from the Swedish-BioFINDER-2 study were scanned on both 7 T and 3 T MRI systems. We found that in cognitively impaired participants with evidence of both abnormal amyloid-beta (CSF amyloid-beta42/40) and tau accumulation (tau-PET) the N-acetyl-aspartate diffusion rate was significantly lower than in cognitively unimpaired participants (p & lt; 0.05). This supports the hypothesis that intraneuronal tau accumulation hinders diffusion in the neuronal cytosol. Conversely, water diffusivity was higher in cognitively impaired participants (p & lt; 0.001) and was positively associated with the concentration of myo-Inositol, a preferentially astrocytic metabolite (p & lt; 0.001), suggesting that water diffusion is sensitive to alterations in the extracellular space and in glia. In conclusion, measuring the diffusion properties of both water and N-acetyl-aspartate provides rich information on the cortical microstructure in Alzheimer’s disease, and can be used to develop new sensitive and specific markers to microstructural changes occurring during the disease course.
    Type of Medium: Online Resource
    ISSN: 2632-1297
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2024
    detail.hit.zdb_id: 3020013-1
    Library Location Call Number Volume/Issue/Year Availability
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