| 11. |
- Santillo, Alexander F, et al.
(författare)
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Divergent functional connectivity changes associated with white matter hyperintensities
- 2024
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Ingår i: NeuroImage. - 1095-9572. ; 296
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Tidskriftsartikel (refereegranskat)abstract
- Age-related white matter hyperintensities are a common feature and are known to be negatively associated with structural integrity, functional connectivity, and cognitive performance. However, this has yet to be fully understood mechanistically. We analyzed multiple MRI modalities acquired in 465 non-demented individuals from the Swedish BioFINDER study including 334 cognitively normal and 131 participants with mild cognitive impairment. White matter hyperintensities were automatically quantified using fluid-attenuated inversion recovery MRI and parameters from diffusion tensor imaging were estimated in major white matter fibre tracts. We calculated fMRI resting state-derived functional connectivity within and between predefined cortical regions structurally linked by the white matter tracts. How change in functional connectivity is affected by white matter lesions and related to cognition (in the form of executive function and processing speed) was explored. We examined the functional changes using a measure of sample entropy. As expected hyperintensities were associated with disrupted structural white matter integrity and were linked to reduced functional interregional lobar connectivity, which was related to decreased processing speed and executive function. Simultaneously, hyperintensities were also associated with increased intraregional functional connectivity, but only within the frontal lobe. This phenomenon was also associated with reduced cognitive performance. The increased connectivity was linked to increased entropy (reduced predictability and increased complexity) of the involved voxels' blood oxygenation level-dependent signal. Our findings expand our previous understanding of the impact of white matter hyperintensities on cognition by indicating novel mechanisms that may be important beyond this particular type of brain lesions.
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| 12. |
- Spotorno, Nicola, et al.
(författare)
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Astrocytic function is associated with both amyloid-β and tau pathology in non-demented APOE 4 carriers
- 2022
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Ingår i: Brain Communications. - : Oxford University Press (OUP). - 2632-1297. ; 4:3
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Tidskriftsartikel (refereegranskat)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 < 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 < 0.01). Focusing on the APOE ϵ4 subsample, myo-inositol partially (17%) mediated the association between amyloid-beta and tau pathology (P < 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 < 0.01; APOE ϵ4 non-carriers: P > 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.
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| 13. |
- Spotorno, Nicola, et al.
(författare)
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Diffusion MRI tracks cortical microstructural changes during the early stages of Alzheimer’s disease
- 2024
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Ingår i: Brain. - 0006-8950. ; 147:3, s. 961-969
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Tidskriftsartikel (refereegranskat)abstract
- There is increased interest in developing markers reflecting microstructural changes that could serve as outcome measures in clinical trials. This is especially important after unexpected results in trials evaluating disease-modifying therapies targeting amyloid-β (Aβ), where morphological metrics from MRI showed increased volume loss despite promising clinical treatment effects. In this study, changes over time in cortical mean diffusivity, derived using diffusion tensor imaging, were investigated in a large cohort (n = 424) of non-demented participants from the Swedish BioFINDER study. Participants were stratified following the Aβ/tau (AT) framework. The results revealed a widespread increase in mean diffusivity over time, including both temporal and parietal cortical regions, in Aβ-positive but still tau-negative individuals. These increases were steeper in Aβ-positive and tau-positive individuals and robust to the inclusion of cortical thickness in the model. A steeper increase in mean diffusivity was also associated with both changes over time in fluid markers reflecting astrocytic activity (i.e. plasma level of glial fibrillary acidic protein and CSF levels of YKL-40) and worsening of cognitive performance (all P < 0.01). By tracking cortical microstructural changes over time and possibly reflecting variations related to the astrocytic response, cortical mean diffusivity emerges as a promising marker for tracking treatments-induced microstructural changes in clinical trials.
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| 14. |
- Spotorno, Nicola, et al.
(författare)
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Diffusion tensor MRI to distinguish progressive supranuclear palsy from a-synucleinopathies
- 2019
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Ingår i: Radiology. - : Radiological Society of North America (RSNA). - 0033-8419 .- 1527-1315. ; 293:3, s. 646-653
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Tidskriftsartikel (refereegranskat)abstract
- Background: The differential diagnosis of progressive supranuclear palsy (PSP) and Lewy body disorders, which include Parkinson disease and dementia with Lewy bodies, is often challenging due to the overlapping symptoms. Purpose: To develop a diagnostic tool based on diffusion tensor imaging (DTI) to distinguish between PSP and Lewy body disorders at the individual-subject level. Materials and Methods: In this retrospective study, skeletonized DTI metrics were extracted from two independent data sets: the discovery cohort from the Swedish BioFINDER study and the validation cohort from the Penn Frontotemporal Degeneration Center (data collected between 2010 and 2018). Based on previous neuroimaging studies and neuropathologic evidence, a combination of regions hypothesized to be sensitive to pathologic features of PSP were identified (ie, the superior cerebellar peduncle and frontal white matter) and fractional anisotropy (FA) was used to compute an FA score for each individual. Classification performances were assessed by using logistic regression and receiver operating characteristic analysis. Results: In the discovery cohort, 16 patients with PSP (mean age 6 standard deviation, 73 years 6 5; eight women, eight men), 34 patients with Lewy body disorders (mean age, 71 years 6 6; 14 women, 20 men), and 44 healthy control participants (mean age, 66 years 6 8; 26 women, 18 men) were evaluated. The FA score distinguished between clinical PSP and Lewy body disorders with an area under the curve of 0.97 6 0.04, a specificity of 91% (31 of 34), and a sensitivity of 94% (15 of 16). In the validation cohort, 34 patients with PSP (69 years 6 7; 22 women, 12 men), 25 patients with Lewy body disorders (70 years 6 7; nine women, 16 men), and 32 healthy control participants (64 years 6 7; 22 women, 10 men) were evaluated. The accuracy of the FA score was confirmed (area under the curve, 0.96 6 0.04; specificity, 96% [24 of 25]; and sensitivity, 85% [29 of 34]). Conclusion: These cross-validated findings lay the foundation for a clinical test to distinguish progressive supranuclear palsy from Lewy body disorders.
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| 15. |
- Spotorno, Nicola, et al.
(författare)
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Diffusion weighted magnetic resonance spectroscopy revealed neuronal specific microstructural alterations in Alzheimer’s disease
- 2024
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Ingår i: Brain Communications. - 2632-1297. ; 6:1
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Tidskriftsartikel (refereegranskat)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 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 < 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 < 0.001) and was positively associated with the concentration of myo-inositol, a preferentially astrocytic metabolite (P < 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.
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| 16. |
- Spotorno, Nicola, et al.
(författare)
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Measures of cortical microstructure are linked to amyloid pathology in Alzheimer's disease
- 2023
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Ingår i: Brain. - : Oxford University Press (OUP). - 0006-8950 .- 1460-2156. ; 146:4, s. 1602-1614
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Tidskriftsartikel (refereegranskat)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 < 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 < 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 < 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.
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| 17. |
- Spotorno, Nicola, et al.
(författare)
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Plasma neurofilament light protein correlates with diffusion tensor imaging metrics in frontotemporal dementia
- 2020
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Ingår i: Plos One. - : Public Library of Science (PLoS). - 1932-6203. ; 15:10
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Tidskriftsartikel (refereegranskat)abstract
- Neurofilaments are structural components of neurons and are particularly abundant in highly myelinated axons. The levels of neurofilament light chain (NfL) in both cerebrospinal fluid (CSF) and plasma have been related to degeneration in several neurodegenerative conditions including frontotemporal dementia (FTD) and NfL is currently considered as the most promising diagnostic and prognostic fluid biomarker in FTD. Although the location and function of filaments in the healthy nervous system suggests a link between increased NfL and white matter degeneration, such a claim has not been fully elucidated in vivo, especially in the context of FTD. The present study provides evidence of an association between the plasma levels of NfL and white matter involvement in behavioral variant FTD (bvFTD) by relating plasma concentration of NfL to diffusion tensor imaging (DTI) metrics in a group of 20 bvFTD patients. The results of both voxel-wise and tract specific analysis showed that increased plasma NfL concentration is associated with a reduction in fractional anisotropy (FA) in a widespread set of white matter tracts including the superior longitudinal fasciculus, the fronto-occipital fasciculus the anterior thalamic radiation and the dorsal cingulum bundle. Plasma NfL concentration also correlated with cortical thinning in a portion of the right medial prefrontal cortex and of the right lateral orbitofrontal cortex. These results support the hypothesis that blood NfL levels reflect the global level of neurodegeneration in bvFTD and help to advance our understanding of the association between this blood biomarker for FTD and the disease process.
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| 18. |
- Spotorno, Nicola, et al.
(författare)
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Relationship between cortical iron and tau aggregation in Alzheimer's disease
- 2020
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Ingår i: Brain : a journal of neurology. - : Oxford University Press (OUP). - 1460-2156. ; 143:5, s. 1341-1349
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Tidskriftsartikel (refereegranskat)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.
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| 19. |
- Spotorno, Nicola, et al.
(författare)
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The mean diffusion propagator model revealed cortical microstructural changes associated with both amyloid-β and tau pathology and astroglial activation
- 2022
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Ingår i: Alzheimer's and Dementia. - : Wiley. - 1552-5260 .- 1552-5279. ; 18:S1
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Tidskriftsartikel (refereegranskat)abstract
- Background: Markers of downstream events are a key component of clinical trials of disease-modifying therapies for Alzheimer’s disease (AD). Morphometric metrics like cortical thickness are established measures of atrophy but are not sensitive enough to detect 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 that could complement morphometric macrostructural measures. Method: We applied the mean apparent diffusion propagator model (MAP-MRI) to diffusion MRI data from 492 cognitively unimpaired elderly and patients with mild cognitive impairment from the Swedish BioFINDER-2 cohort. MAP-MRI extends diffusion tensor imaging and provides metrics sensitive to subtle changes in the cortex. 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 both MAP-MRI metrics and CT were compared across groups. Associations between regional values of MAP-MRI metrics and both Aβ- and tau-PET uptake were also investigated as well as the association between MAP-MRI metrics and plasma level of GFAP, a marker of astroglial activation (available in 292 participants). Result: Mean square displacement (MSD) from MAP-MRI 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 appeared to be more limited (figure 1). MSD was also highly correlated with both Aβ- and tau-PET uptake even independently from one another (figure 2). Regional MSD values were associated with GFAP with a pattern that resemble Aβ accumulation, and GFAP partially mediated the association between Aβ and MSD. A sensitivity analysis controlling for cortical thickness revealed that the associations between MSD and Aβ-PET, tau-PET and GFAP were largely independent from macrostructural changes (figures 2-3). Conclusion: Metrics of cortical microstructural alteration derived from MAP-MRI are highly sensitive to multiple aspects of the AD pathological cascade. Of particular interest is the link between MSD, Aβ-PET and GFAP which suggests MSD might reflects microstructural changes related to the astrocytic response to Aβ aggregation. Therefore, MSD could help monitoring the response to anti-Aβ treatments in clinical trials.
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| 20. |
- Wuestefeld, Anika, et al.
(författare)
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Age-related and amyloid-beta-independent tau deposition and its downstream effects
- 2023
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Ingår i: Brain : a journal of neurology. - 1460-2156. ; 146:8, s. 3192-3205
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Tidskriftsartikel (refereegranskat)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.
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