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APOE and A?PP gene variation in cortical and cerebrovascular amyloid-? pathology and Alzheimer's disease: a population-based analysis.

ABSTRACT: Cortical and cerebrovascular amyloid-? (A?) deposition is a hallmark of Alzheimer's disease (AD), but also occurs in elderly people not affected by dementia. The apolipoprotein E (APOE) ?4 is a major genetic modulator of A? deposition and AD risk. Variants of the amyloid-? protein precursor (A?PP) gene have been reported to contribute to AD and cerebral amyloid angiopathy (CAA). We analyzed the role of APOE and A?PP variants in cortical and cerebrovascular A? deposition, and neuropathologically verified AD (based on modified NIA-RI criteria) in a population-based autopsy sample of Finns aged ? 85 years (Vantaa85 + Study; n = 282). Our updated analysis of APOE showed strong associations of the ?4 allele with cortical (p = 4.91 × 10-17) and cerebrovascular (p = 9.87 × 10-11) A? deposition as well as with NIA-RI AD (p = 1.62 × 10-8). We also analyzed 60 single nucleotide polymorphisms (SNPs) at the A?PP locus. In single SNP or haplotype analyses there were no statistically significant A?PP locus associations with cortical or cerebrovascular A? deposition or with NIA-RI AD. We sequenced the promoter of the A?PP gene in 40 subjects with very high A? deposition, but none of these subjects had any of the previously reported or novel AD-associated mutations. These results suggest that cortical and cerebrovascular A? depositions are useful quantitative traits for genetic studies, as highlighted by the strong associations with the APOE ?4 variant. Promoter mutations or common allelic variation in the A?PP gene do not have a major contribution to cortical or cerebrovascular A? deposition, or very late-onset AD in this Finnish population based study.

SUBMITTER: Peuralinna T

PROVIDER: S-EPMC3516850 | biostudies-literature | 2011

REPOSITORIES: biostudies-literature

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APOE and AβPP gene variation in cortical and cerebrovascular amyloid-β pathology and Alzheimer's disease: a population-based analysis.

Peuralinna Terhi T Tanskanen Maarit M Mäkelä Mira M Polvikoski Tuomo T Paetau Anders A Kalimo Hannu H Sulkava Raimo R Hardy John J Lai Shiao-Lin SL Arepalli Sampath S Hernandez Dena D Traynor Bryan J BJ Singleton Andrew A Tienari Pentti J PJ Myllykangas Liisa L

Journal of Alzheimer's disease : JAD 20110101 2

Cortical and cerebrovascular amyloid-β (Aβ) deposition is a hallmark of Alzheimer's disease (AD), but also occurs in elderly people not affected by dementia. The apolipoprotein E (APOE) ε4 is a major genetic modulator of Aβ deposition and AD risk. Variants of the amyloid-β protein precursor (AβPP) gene have been reported to contribute to AD and cerebral amyloid angiopathy (CAA). We analyzed the role of APOE and AβPP variants in cortical and cerebrovascular Aβ deposition, and neuropathologically ...[more]

PMID: 21654062

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Project description: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.

Project description:ImportanceThe effect of β-amyloid (Aβ) accumulation on regional structural brain changes in early stages of Alzheimer disease (AD) is not well understood.ObjectiveTo test the hypothesis that the development of Aβ pathology is related to increased regional atrophy in the brains of cognitively normal (CN) persons.Design, setting, and participantsLongitudinal clinicobiomarker cohort study involving 47 CN control subjects and 15 patients with AD dementia. All participants underwent repeated cerebrospinal fluid Aβ42 and structural magnetic resonance imaging measurements for up to 4 years. Cognitively normal controls were classified using the longitudinal cerebrospinal fluid Aβ42 data and included 13 stable Aβ negative (normal baseline Aβ42 levels, with less than the median reduction over time), 13 declining Aβ negative (normal baseline Aβ42 levels, with greater than the median reduction over time), and 21 Aβ positive (pathologic baseline Aβ42 levels). All 15 patients with AD dementia were Aβ positive.Main outcomes and measuresGroup effects on regional gray matter volumes at baseline and over time, tested by linear mixed-effects models.ResultsBaseline gray matter volumes were similar among the CN Aβ groups, but atrophy rates were increased in frontoparietal regions in the declining Aβ-negative and Aβ-positive groups and in amygdala and temporal regions in the Aβ-positive group. Aβ-positive patients with AD dementia had further increased atrophy rates in hippocampus and temporal and cingulate regions.Conclusions and relevanceEmerging Aβ pathology is coupled to increased frontoparietal (but not temporal) atrophy rates. Atrophy rates peak early in frontoparietal regions but accelerate in hippocampus, temporal, and cingulate regions as the disease progresses to dementia. Early-stage Aβ pathology may have mild effects on local frontoparietal cortical integrity while effects in temporal regions appear later and accelerate, leading to the atrophy pattern typically seen in AD.

Dataset Information

APOE and A?PP gene variation in cortical and cerebrovascular amyloid-? pathology and Alzheimer's disease: a population-based analysis.

Publications

APOE and AβPP gene variation in cortical and cerebrovascular amyloid-β pathology and Alzheimer's disease: a population-based analysis.

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