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Does amyloid deposition produce a specific atrophic signature in cognitively normal subjects?

ABSTRACT: The objective of our study was to evaluate whether cognitively normal (CN) elderly participants showing elevated cortical beta-amyloid (A?) deposition have a consistent neuroanatomical signature of brain atrophy that may characterize preclinical Alzheimer's disease (AD). 115 CN participants who were A?-positive (CN +) by amyloid PET imaging; 115 CN participants who were A?-negative (CN -); and 88 A?-positive mild cognitive impairment or AD participants (MCI/AD +) were identified. Cortical thickness (FreeSurfer) and gray matter volume (SPM5) were measured for 28 regions-of-interest (ROIs) across the brain and compared across groups. ROIs that best discriminated CN - from CN + differed for FreeSurfer cortical thickness and SPM5 gray matter volume. Group-wise discrimination was poor with a high degree of uncertainty in terms of the rank ordering of ROIs. In contrast, both techniques showed strong and consistent findings comparing MCI/AD + to both CN - and CN + groups, with entorhinal cortex, middle and inferior temporal lobe, inferior parietal lobe, and hippocampus providing the best discrimination for both techniques. Concordance across techniques was higher for the CN - and CN + versus MCI/AD + comparisons, compared to the CN - versus CN + comparison. The weak and inconsistent nature of the findings across technique in this study cast doubt on the existence of a reliable neuroanatomical signature of preclinical AD in elderly PiB-positive CN participants.

SUBMITTER: Whitwell JL

PROVIDER: S-EPMC3778266 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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Does amyloid deposition produce a specific atrophic signature in cognitively normal subjects?

Whitwell Jennifer L JL Tosakulwong Nirubol N Weigand Stephen D SD Senjem Matthew L ML Lowe Val J VJ Gunter Jeffrey L JL Boeve Bradley F BF Knopman David S DS Dickerson Bradford C BC Petersen Ronald C RC Jack Clifford R CR

NeuroImage. Clinical 20130124

The objective of our study was to evaluate whether cognitively normal (CN) elderly participants showing elevated cortical beta-amyloid (Aβ) deposition have a consistent neuroanatomical signature of brain atrophy that may characterize preclinical Alzheimer's disease (AD). 115 CN participants who were Aβ-positive (CN +) by amyloid PET imaging; 115 CN participants who were Aβ-negative (CN -); and 88 Aβ-positive mild cognitive impairment or AD participants (MCI/AD +) were identified. Cortical thickn ...[more]

PMID: 24179779

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Project description:In a large multicentre sample of cognitively normal subjects, as a function of age, gender and APOE genotype, we studied the frequency of abnormal cerebrospinal fluid levels of Alzheimer's disease biomarkers including: total tau, phosphorylated tau and amyloid-β1-42. Fifteen cohorts from 12 different centres with either enzyme-linked immunosorbent assays or Luminex® measurements were selected for this study. Each centre sent nine new cerebrospinal fluid aliquots that were used to measure total tau, phosphorylated tau and amyloid-β1-42 in the Gothenburg laboratory. Seven centres showed a high correlation with the new Gothenburg measurements; therefore, 10 cohorts from these centres are included in the analyses here (1233 healthy control subjects, 40-84 years old). Amyloid-β amyloid status (negative or positive) and neurodegeneration status (negative or positive) was established based on the pathological cerebrospinal fluid Alzheimer's disease cut-off values for cerebrospinal fluid amyloid-β1-42 and total tau, respectively. While gender did not affect these biomarker values, APOE genotype modified the age-associated changes in cerebrospinal fluid biomarkers such that APOE ε4 carriers showed stronger age-related changes in cerebrospinal fluid phosphorylated tau, total tau and amyloid-β1-42 values and APOE ε2 carriers showed the opposite effect. At 40 years of age, 76% of the subjects were classified as amyloid negative, neurodegeneration negative and their frequency decreased to 32% at 85 years. The amyloid-positive neurodegeneration-negative group remained stable. The amyloid-negative neurodegeneration-positive group frequency increased slowly from 1% at 44 years to 16% at 85 years, but its frequency was not affected by APOE genotype. The amyloid-positive neurodegeneration-positive frequency increased from 1% at 53 years to 28% at 85 years. Abnormally low cerebrospinal fluid amyloid-β1-42 levels were already frequent in midlife and APOE genotype strongly affects the levels of cerebrospinal fluid amyloid-β1-42, phosphorylated tau and total tau across the lifespan without influencing the frequency of subjects with suspected non-amyloid pathology.

Project description:To improve the ability to develop treatments that prevent incipient Alzheimer disease (AD) from progressing to overt AD, it is important to understand the molecular basis of the earliest pathophysiological abnormalities and to determine how amyloid-? (A?) is involved very early in its pathogenesis.To investigate 2 specific A? oligomers, A? trimers and A?*56, in human cerebrospinal fluid (CSF); evaluate the effects of aging and AD; and obtain support for the hypothesis that they may be pathogenic by determining their relationships to CSF tau.A CSF sampling study.The University of Minnesota Medical School in Minneapolis, Minnesota, and the Salhgrenska University Hospital, Sweden.Forty-eight older adults with mild cognitive impairment or AD (impaired group); 49 age-matched cognitively intact control subjects (unimpaired group); and 10 younger, normal control subjects.Measurements of CSF A? trimers, A?*56, the 42-amino acid A? isoform (A?1-42), total tau (T-tau), and phospho-tau 181 (p-tau(181)). The hypothesis being tested was formulated after data collection. RESULTS We observed that A? trimers and A?*56 levels increased with age; within the unimpaired group, they were elevated in subjects with T-tau/A?1-42 ratios greater than a cutoff that distinguished the unimpaired group from subjects with AD. In the unimpaired group, T-tau and p-tau(181) were found to correlate strongly with A? trimers and A?*56 (r > 0.63), but not with A?1-42 (-0.10 < r < -0.01). The strong correlations were found to be attenuated in the impaired group.In cognitively intact older adults, CSF A? trimers and A?*56 were elevated in individuals at risk for AD, and they showed stronger relationships with tau than did A?1-42, a surrogate for A? fibril deposition. These findings suggest that prior to overt symptoms, 1 or both of the A? oligomers, but not fibrillar A?, is coupled to tau; however, this coupling is weakened or broken when AD advances to symptomatic stages. The uncoupling is interesting in light of the failure of experimental A? therapies to improve mild cognitive impairment/AD, which has prompted a shift in the timing of A? therapies to asymptomatic subjects. Knowing which A? species to target in asymptomatic subjects may enhance the success of future treatments for AD.

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Does amyloid deposition produce a specific atrophic signature in cognitively normal subjects?

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Does amyloid deposition produce a specific atrophic signature in cognitively normal subjects?

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