Overexpression of the amyloid precursor protein (APP) gene on chromosome 21 in Down syndrome (DS) has been linked to increased brain amyloid levels and early-onset Alzheimer's disease (AD). An ...elderly man with phenotypic DS and partial trisomy of chromosome 21 (PT21) lacked triplication of APP affording an opportunity to study the role of this gene in the pathogenesis of dementia. Multidisciplinary studies between ages 66-72 years comprised neuropsychological testing, independent neurological exams, amyloid PET imaging with 11C-Pittsburgh compound-B (PiB), plasma amyloid-β (Aβ) measurements, and a brain autopsy examination. The clinical phenotype was typical for DS and his intellectual disability was mild in severity. His serial neuropsychological test scores showed less than a 3% decline as compared to high functioning individuals with DS who developed dementia wherein the scores declined 17-28% per year. No dementia was detected on neurological examinations. On PiB-PET scans, the patient with PT21 had lower PiB standard uptake values than controls with typical DS or sporadic AD. Plasma Aβ42 was lower than values for demented or non-demented adults with DS. Neuropathological findings showed only a single neuritic plaque and neurofibrillary degeneration consistent with normal aging but not AD. Taken together the findings in this rare patient with PT21 confirm the obligatory role of APP in the clinical, biochemical, and neuropathological findings of AD in DS.
Abstract Introduction Individuals with Down syndrome (DS) exhibit Alzheimer's disease (AD) neuropathology and dementia early in life. Blood biomarkers of AD neuropathology would be valuable, as ...non-AD intellectual disabilities of DS and AD dementia overlap clinically. We hypothesized that elevations of amyloid-β (Aβ) peptides and phosphorylated-tau in neuronal exosomes may document preclinical AD. Methods AD neuropathogenic proteins Aβ1–42 , P-T181-tau, and P-S396-tau were quantified by enzyme-linked immunosorbent assays in extracts of neuronal exosomes purified from blood of individuals with DS and age-matched controls. Results Neuronal exosome levels of Aβ1–42 , P-T181-tau, and P-S396-tau were significantly elevated in individuals with DS compared with age-matched controls at all ages beginning in childhood. No significant gender differences were observed. Discussion These early increases in Aβ1–42 , P-T181-tau, and P-S396-tau in individuals with DS may provide a basis for early intervention as targeted treatments become available.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Individuals with Down syndrome (DS) are increasingly eligible for clinical trial intervention, particularly for the treatment or prevention of Alzheimer disease (AD). Yet, little is known about ...research attitudes that may contribute to decisions regarding clinical trial enrollment for people with DS, a gap which is addressed in the current study.
The Research Attitudes Questionnaire (RAQ) is a brief validated instrument that measures cultural and social factors which influence clinical trial enrollment decisions in the general population. Applied herein to a cohort of 1002 families who have an individual with DS, this survey was carried out through a national registry (DS-Connect). In addition to the RAQ, demographic data were collected.
The response rate to the survey was 49.9%. Respondents were asked to complete demographic information and to respond to the 7 question RAQ. The scores were stratified by a cut point assigned a priori into those more favorable toward research participation vs. those less favorably inclined. Within this sample, nearly 95% self-identified as the primary caretaker for the individual with DS. The RAQ score analyses generally indicated favorable respondent views toward research with particularly high favorability ratings from respondents who had previously participated in research and from those who were older (P = .01 to .001).
This is one of the first formal studies to evaluate research attitudes among relatives of individuals with DS and shows the feasibility of using this approach to answer important questions that will guide trialists developing treatments for AD in DS. Future research will require broadening the racial and ethnic mix of respondents and the role that a standardized assessment of research attitudes will have for clinical trial participation.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
People with Down syndrome (DS) are at high risk for developing Alzheimer disease (AD) with age. Typically, by age 40 years, most people with DS have sufficient neuropathology for an AD diagnosis. ...Interestingly, atherosclerosis and hypertension are atypical in DS with age, suggesting the lack of these vascular risk factors may be associated with reduced cerebrovascular pathology. However, because the extra copy of APP leads to increased beta-amyloid peptide (Aβ) accumulation in DS, we hypothesized that there would be more extensive and widespread cerebral amyloid angiopathy (CAA) with age in DS relative to sporadic AD. To test this hypothesis CAA, atherosclerosis and arteriolosclerosis were used as measures of cerebrovascular pathology and compared in post mortem tissue from individuals with DS (n = 32), sporadic AD (n = 80) and controls (n = 37). CAA was observed with significantly higher frequencies in brains of individuals with DS compared to sporadic AD and controls. Atherosclerosis and arteriolosclerosis were rare in the cases with DS. CAA in DS may be a target for future interventional clinical trials.
Early markers are needed for more effective prevention of Alzheimer's disease. We previously showed that individuals with Alzheimer's disease have decreased plasma DYRK1A levels compared to controls. ...We assessed DYRK1A in the plasma of cognitively healthy elderly volunteers, individuals with either Alzheimer's disease (AD), tauopathies or Down syndrome (DS), and in lymphoblastoids from individuals with DS. DYRK1A levels were inversely correlated with brain amyloid β burden in asymptomatic elderly individuals and AD patients. Low DYRK1A levels were also detected in patients with tauopathies. Individuals with DS had higher DYRK1A levels than controls, although levels were lower in individuals with DS and with dementia. These data suggest that plasma DYRK1A levels could be used for early detection of at risk individuals of AD and for early detection of AD. We hypothesize that lack of increase of DYRK1A at middle age (40-50 years) could be a warning before the cognitive decline, reflecting increased risk for AD.
Introduction
Microglial cells play an important role in the development of Alzheimer's disease (AD). People with Down syndrome (DS) inevitably develop AD neuropathology (DSAD) by 40 years of age. We ...characterized the distribution of different microglial phenotypes in the brains of people with DS and DSAD.
Methods
Autopsy tissue from the posterior cingulate cortex (PCC) from people with DS, DSAD, and neurotypical controls was immunostained with the microglial marker Iba1 to assess five microglia morphological types.
Results
Individuals with DS have more hypertrophic microglial cells in their white matter. In the gray matter, individuals with DSAD had significantly fewer ramified microglia and more dystrophic microglia than controls and the younger individuals with DS. The DSAD group also exhibited more rod‐shaped and amoeboid cells than the AD group.
Discussion
Individuals with DS and DSAD show a microglial phenotype that distinguishes them from non‐DS controls.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Introduction
Virtually all individuals with Down syndrome (DS) will develop Alzheimer's disease (AD) pathology by age 40. Cerebrospinal fluid (CSF) biomarkers have characterized AD pathology in ...cohorts of late‐onset AD (LOAD) and autosomal‐dominant AD (ADAD). Few studies have evaluated such biomarkers in adults with DS.
Methods
CSF concentrations of amyloid beta (Aβ)40, Aβ42, tau, phospho‐tau181 (p‐tau), neurofilament light chain (NfL), soluble triggering receptor expressed on myeloid cells 2 (sTREM2), chitinase‐3‐like protein 1 (YKL‐40), alpha synuclein (αSyn), neurogranin (Ng), synaptosomal‐associated protein 25 (SNAP‐25), and visinin‐like protein 1 (VILIP‐1) were assessed in CSF from 44 adults with DS from the Alzheimer's Biomarker Consortium–Down Syndrome study. Biomarker levels were evaluated by cognitive status, age, and apolipoprotein E gene (APOE) ε4 carrier status.
Results
Biomarker abnormalities indicative of amyloid deposition, tauopathy, neurodegeneration, synaptic dysfunction, and neuroinflammation were associated with increased cognitive impairment. Age and APOE ε4 status influenced some biomarkers.
Discussion
The profile of many established and emerging CSF biomarkers of AD in a cohort of adults with DS was similar to that reported in LOAD and ADAD, while some differences were observed.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Down syndrome (DS) provides a model for studying important aspects of Alzheimer disease (AD). Chromosome 21 contains several genes that have been implicated in neurodegenerative mechanisms. These ...include Cu/Zn superoxide dismutase (SOD-1), Ets-2 transcription factors, Down Syndrome Critical Region 1 (DSCR1) stress-inducible factor, and the amyloid precursor protein (APP). The accumulation of Abeta plaques is progressive across the lifespan in DS. Overexpression of APP in the obligate region for DS is associated with abundant Abeta plaques and tangles consistent with Braak stage V-VI. Intraneuronal Abeta in DS appears to trigger a pathological cascade leading to oxidative stress and a neurodegeneration typical of AD. There are suggestions that an increase in subcellular processing of APP and factors related to membrane APP cleavage favor the secretion of Abeta with age in DS. A misbalance between SOD-1 and glutathione perioxidase activity in DS has been linked to free radical generation. Ets-2 and DSCR1 overexpression in DS has been linked to cell degeneration. Age-related accumulation of somatic DNA mutations in both DS and AD contribute to oxidative stress that exacerbates the imbalance in gene expression. This leads to enhanced Abeta deposition and further neuronal vulnerability. The consequence of these factors and their temporal relationships is likely to be the subject of future research. Since the pathological processes leading to AD are seen across the lifespan in DS, an opportunity is afforded for early pharmacological intervention in the disorder.
INTRODUCTION
Virtually all people with Down syndrome (DS) develop neuropathology associated with Alzheimer's disease (AD). Atrophy of the hippocampus and entorhinal cortex (EC), as well as elevated ...plasma concentrations of neurofilament light chain (NfL) protein, are markers of neurodegeneration associated with late‐onset AD. We hypothesized that hippocampus and EC gray matter loss and increased plasma NfL concentrations are associated with memory in adults with DS.
METHODS
T1‐weighted structural magnetic resonance imaging (MRI) data were collected from 101 participants with DS. Hippocampus and EC volume, as well as EC subregional cortical thickness, were derived. In a subset of participants, plasma NfL concentrations and modified Cued Recall Test scores were obtained. Partial correlation and mediation were used to test relationships between medial temporal lobe (MTL) atrophy, plasma NfL, and episodic memory.
RESULTS
Hippocampus volume, left anterolateral EC (alEC) thickness, and plasma NfL were correlated with each other and were associated with memory. Plasma NfL mediated the relationship between left alEC thickness and memory as well as hippocampus volume and memory.
DISCUSSION
The relationship between MTL gray matter and memory is mediated by plasma NfL levels, suggesting a link between neurodegenerative processes underlying axonal injury and frank gray matter loss in key structures supporting episodic memory in people with DS.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
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