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Widespread distribution of tauopathy in preclinical Alzheimer's disease.

ABSTRACT: The objective of this study was to examine the distribution and severity of tau-PET binding in cognitively normal adults with preclinical Alzheimer's disease as determined by positive beta-amyloid PET. 18F-AV-1451 tau-PET data from 109 cognitively normal older adults were processed with 34 cortical and 9 subcortical FreeSurfer regions and averaged across both hemispheres. Individuals were classified as being beta-amyloid positive (N = 25, A+) or negative (N = 84, A-) based on a 18F-AV-45 beta-amyloid-PET standardized uptake value ratio of 1.22. We compared the tau-PET binding in the 2 groups using covariate-adjusted linear regressions. The A+ cohort had higher tau-PET binding within 8 regions: precuneus, amygdala, banks of the superior temporal sulcus, entorhinal cortex, fusiform gyrus, inferior parietal cortex, inferior temporal cortex, and middle temporal cortex. These findings, consistent with preclinical involvement of the medial temporal lobe and parietal lobe and association regions by tauopathy, emphasize that therapies targeting tauopathy in Alzheimer's disease could be considered before the onset of symptoms to prevent or ameliorate cognitive decline.

SUBMITTER: Schultz SA

PROVIDER: S-EPMC6422832 | biostudies-literature | 2018 Dec

REPOSITORIES: biostudies-literature

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Widespread distribution of tauopathy in preclinical Alzheimer's disease.

Schultz Stephanie A SA Gordon Brian A BA Mishra Shruti S Su Yi Y Perrin Richard J RJ Cairns Nigel J NJ Morris John C JC Ances Beau M BM Benzinger Tammie L S TLS

Neurobiology of aging 20180901

The objective of this study was to examine the distribution and severity of tau-PET binding in cognitively normal adults with preclinical Alzheimer's disease as determined by positive beta-amyloid PET. <sup>18</sup>F-AV-1451 tau-PET data from 109 cognitively normal older adults were processed with 34 cortical and 9 subcortical FreeSurfer regions and averaged across both hemispheres. Individuals were classified as being beta-amyloid positive (N = 25, A+) or negative (N = 84, A-) based on a <sup>1 ...[more]

PMID: 30292840

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Project description:An unfortunate result of the rapid rise in geriatric populations worldwide is the increasing prevalence of age-related cognitive disorders such as Alzheimer's disease (AD). AD is a devastating neurodegenerative illness that is characterized by a profound impairment of cognitive function, marked physical disability, and an enormous economic burden on the afflicted individual, caregivers, and society in general. The rise in elderly populations is also resulting in an increase in individuals with related (potentially treatable) conditions such as "Mild Cognitive Impairment" (MCI) which is characterized by a less severe (but abnormal) level of cognitive impairment and a high-risk for developing dementia. Even in the absence of a diagnosable disorder of cognition (e.g., AD and MCI), the perception of increased forgetfulness and declining mental function is a clear source of apprehension in the elderly. This is a valid concern given that even a modest impairment of cognitive function is likely to be associated with significant disability in a rapidly evolving, technology-based society. Unfortunately, the currently available therapies designed to improve cognition (i.e., for AD and other forms of dementia) are limited by modest efficacy and adverse side effects, and their effects on cognitive function are not sustained over time. Accordingly, it is incumbent on the scientific community to develop safer and more effective therapies that improve and/or sustain cognitive function in the elderly allowing them to remain mentally active and productive for as long as possible. As diagnostic criteria for memory disorders evolve, the demand for pro-cognitive therapeutic agents is likely to surpass AD and dementia to include MCI and potentially even less severe forms of memory decline. The purpose of this review is to provide an overview of the contemporary therapeutic targets and preclinical pharmacologic approaches (with representative drug examples) designed to enhance memory function.

Project description:Alzheimer's disease (AD) is the most common form of dementia. Obesity in middle age increases AD risk and severity, which is alarming given that obesity prevalence peaks at middle age and obesity rates are accelerating worldwide. Midlife, but not late-life obesity increases AD risk, suggesting that this interaction is specific to preclinical AD. AD pathology begins in middle age, with accumulation of amyloid beta (Aβ), hyperphosphorylated tau, metabolic decline, and neuroinflammation occurring decades before cognitive symptoms appear. We used a transcriptomic discovery approach in young adult (6.5 months old) male and female TgF344-AD rats that overexpress mutant human amyloid precursor protein and presenilin-1 and wild-type (WT) controls to determine whether inducing obesity with a high-fat/high-sugar “Western” diet during preclinical AD increases brain metabolic dysfunction in dorsal hippocampus (dHC), a brain region vulnerable to the effects of obesity and early AD. Analyses of dHC gene expression data showed dysregulated mitochondrial and neurotransmission pathways, and up-regulated genes involved in cholesterol synthesis. Western diet amplified the number of genes that were different between AD and WT rats and added pathways involved in noradrenergic signaling, dysregulated inhibition of cholesterol synthesis, and decreased intracellular lipid transporters. Importantly, the Western diet impaired dHC-dependent spatial working memory in AD but not WT rats, confirming that the dietary intervention accelerated cognitive decline. To examine later consequences of early transcriptional dysregulation, we measured dHC monoamine levels in older (13 months old) AD and WT rats of both sexes after long-term chow or Western diet consumption. Norepinephrine (NE) abundance was significantly decreased in AD rats, NE turnover was increased, and the Western diet attenuated the AD-induced increases in turnover. Collectively, these findings indicate obesity during prodromal AD impairs memory, potentiates AD-induced metabolic decline likely leading to an overproduction of cholesterol, and interferes with compensatory increases in NE transmission.

Project description:BackgroundTrials of monoclonal antibodies that target various forms of amyloid at different stages of Alzheimer's disease have had mixed results.MethodsWe tested solanezumab, which targets monomeric amyloid, in a phase 3 trial involving persons with preclinical Alzheimer's disease. Persons 65 to 85 years of age with a global Clinical Dementia Rating score of 0 (range, 0 to 3, with 0 indicating no cognitive impairment and 3 severe dementia), a score on the Mini-Mental State Examination of 25 or more (range, 0 to 30, with lower scores indicating poorer cognition), and elevated brain amyloid levels on 18F-florbetapir positron-emission tomography (PET) were enrolled. Participants were randomly assigned in a 1:1 ratio to receive solanezumab at a dose of up to 1600 mg intravenously every 4 weeks or placebo. The primary end point was the change in the Preclinical Alzheimer Cognitive Composite (PACC) score (calculated as the sum of four z scores, with higher scores indicating better cognitive performance) over a period of 240 weeks.ResultsA total of 1169 persons underwent randomization: 578 were assigned to the solanezumab group and 591 to the placebo group. The mean age of the participants was 72 years, approximately 60% were women, and 75% had a family history of dementia. At 240 weeks, the mean change in PACC score was -1.43 in the solanezumab group and -1.13 in the placebo group (difference, -0.30; 95% confidence interval, -0.82 to 0.22; P = 0.26). Amyloid levels on brain PET increased by a mean of 11.6 centiloids in the solanezumab group and 19.3 centiloids in the placebo group. Amyloid-related imaging abnormalities (ARIA) with edema occurred in less than 1% of the participants in each group. ARIA with microhemorrhage or hemosiderosis occurred in 29.2% of the participants in the solanezumab group and 32.8% of those in the placebo group.ConclusionsSolanezumab, which targets monomeric amyloid in persons with elevated brain amyloid levels, did not slow cognitive decline as compared with placebo over a period of 240 weeks in persons with preclinical Alzheimer's disease. (Funded by the National Institute on Aging and others; A4 ClinicalTrials.gov number, NCT02008357.).

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Widespread distribution of tauopathy in preclinical Alzheimer's disease.

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Widespread distribution of tauopathy in preclinical Alzheimer's disease.

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