Search

Blood-based diagnostics and prognostics in sporadic Alzheimer's disease (AD) are important for identifying at-risk individuals for therapeutic interventions.In three stages, a total of 34 leukocyte antigens were examined by flow cytometry immunophenotyping. Data were analyzed by logistic regression and receiver operating characteristic (ROC) analyses.We identified leukocyte markers differentially expressed in the patients with AD. Pathway analysis revealed a complex network involving upregulation of complement inhibition and downregulation of cargo receptor activity and Aβ clearance. A proposed panel including four leukocyte markers - CD11c, CD59, CD91, and CD163 - predicts patients' PET Aβ status with an area under the curve (AUC) of 0.93 (0.88 to 0.97). CD163 was the top performer in preclinical models. These findings have been validated in two independent cohorts.Our finding of changes on peripheral leukocyte surface antigens in AD implicates the deficit in innate immunity. Leukocyte-based biomarkers prove to be both sensitive and practical for AD screening and diagnosis.

An unresolved question for the understanding of Alzheimer’s disease (AD) pathophysiology is why a significant percentage of amyloid β (Aβ)-positive cognitively unimpaired (CU) individuals do not develop detectable downstream tau pathology and, consequently, clinical deterioration. In vitro evidence suggests that reactive astrocytes are key to unleashing Aβ effects in pathological tau phosphorylation. In a large study (n=1,016) across three cohorts, we tested whether astrocyte reactivity modulates the association of Aβ with plasma tau phosphorylation in CU people. We found that Aβ pathology was associated with increased plasma phosphorylated tau levels only in individuals positive for astrocyte reactivity (Ast+). Cross-sectional and longitudinal tau-PET analysis revealed that tau tangles accumulated as a function of Aβ burden only in CU Ast+ individuals with a topographic distribution compatible with early AD. Our findings suggest that increased astrocyte reactivity is an important upstream event linking Aβ burden with initial tau pathology which might have implications for the biological definition of preclinical AD and for selecting individuals for early preventive clinical trials.

The mechanisms by which the apolipoprotein E ε4 (APOEε4) allele influences Alzheimer’s disease (AD) pathophysiological progression are poorly understood. Here, we tested the association of APOEε4 carriership and amyloid-β (Aβ) burden with longitudinal tau pathology progression. We studied 104 individuals across the aging and AD spectrum who underwent clinical assessments, APOE genotyping, magnetic resonance imaging, positron emission tomography (PET) for Aβ ([18F]AZD4694) and tau ([18F]MK-6240) at baseline, as well as a follow-up tau-PET scan (mean follow-up, 2.4 years). We further assessed longitudinal changes in tau phosphorylation (plasma phosphorylated tau at threonine 217 [p-tau217+]), brain atrophy (gray matter density), and clinical function (clinical dementia rating scale sum of boxes). We found that APOEε4 carriership potentiates Aβ effects on longitudinal tau tangle accumulation over two years. The APOEε4-potentiated Aβ effects on tangles were mediated by longitudinal plasma p-tau217+ increase. This longitudinal tau accumulation as measured by PET was accompanied by brain atrophy and clinical decline. Our results support a model in which the APOEε4 allele plays a key role in Aβ downstream effects on the aggregation of phosphorylated tau in the form of neurofibrillary tangles in the living human brain.

Cerebral microbleeds (CMB) are associated with cognitive impairment and hypertensive or cerebral amyloid angiopathy. The pathophysiology and clinical significance of CMB in dementia with Lewy bodies (DLB) are not well understood. Our study aimed to investigate the prevalence of CMB in DLB and to estimate the magnitudes of their clinical associations.Twenty participants with DLB (mean age 74 ± 5 years) were included in this cross-sectional study. All participants underwent 3 T magnetic resonance imaging. CMB number and location were assessed on susceptibility-weighted imaging or quantitative susceptibility mapping. Amyloid-beta (Aβ) positron emission tomography (PET) scans were also performed. Between-group comparisons were estimated using risk ratios (RR) for categorical variables, and mean differences or median regression coefficients for continuous variables.CMB were present in 30% of the DLB participants, with a lobar predominance observed. DLB with CMB were more likely to be on antithrombotic therapy (100%), compared to those without CMB (43%; RR 2.33 [95% CI 1.27, 4.27]). Those with CMB were also more likely to report a history of hypertension (100%) compared to those without (70%; RR 1.75 [95% CI 1.11, 2.75]). DLB core clinical features, cognition and functional status did not differ between the two groups. There was no association found between the presence of CMB and cortical Aβ deposition on PET imaging.CMB are not uncommon in DLB and may be associated with hypertensive small vessel disease. Further studies into the pathophysiology and clinical implications of CMB in DLB are needed.

Purpose Early after [18F]PI-2620 PET tracer administration, perfusion imaging has potential for regional assessment of neuronal injury in neurodegenerative diseases. This is while standard late-phase [18F]PI-2620 tau-PET is able to discriminate 4-repeat tauopathies (4RTs) from disease controls and healthy controls. Here, we investigated whether early-phase [18F]PI-2620 PET has an additive value for biomarker based evaluation of 4RTs. Methods Seventy-eight patients with 4RTs (71±7y, 39 female), 79 patients with other neurodegenerative diseases (67±12y, 35 female) and twelve age-matched controls (69±8y, 8 female) underwent dynamic (0-60 min) [18F]PI-2620 PET imaging. Regional perfusion (0.5-2.5 min p.i.) and tau load (20-40 min p.i.) were measured in 246 predefined brain regions [standardized-uptake-value-ratios (SUVr), cerebellar reference]. Regional SUVr were compared between 4RTs and controls by an ANOVA including false-discovery-rate (FDR, p18F]PI-2620 perfusion imaging mirrors known topology of regional hypoperfusion in 4RTs. Single region hypoperfusion is not specific for 4RTs, but perfusion pattern expression provides an additive value for the discrimination of 4RTs from other neurodegenerative diseases and correlates closer with clinical severity than tau pattern expression.

Early after [Seventy-eight patients with 4RTs (71 ± 7 years, 39 female), 79 patients with other neurodegenerative diseases (67 ± 12 years, 35 female) and twelve age-matched controls (69 ± 8 years, 8 female) underwent dynamic (0-60 min) [Patients with 4RTs had significant hypoperfusion in 21/246 brain regions, most dominant in thalamus, caudate nucleus, and anterior cingulate cortex, fitting to the topology of the 4RT disease spectrum. However, single region hypoperfusion was not specific regarding the discrimination of patients with 4RTs against patients with other neurodegenerative diseases. In contrast, perfusion pattern expression showed promise for discrimination of patients with 4RTs from other neurodegenerative diseases (AUC: 0.850). Discrimination by the combined perfusion-tau pattern expression (AUC: 0.903) exceeded that of the sole tau pattern expression (AUC: 0.864) and the discriminatory power of the combined perfusion-tau pattern expression was replicated in the external dataset (AUC: 0.917). Perfusion but not tau pattern expression was associated with PSP rating scale (R = 0.402; p = 0.0012) and activities of daily living (R = - 0.431; p = 0.0005).[

To date, 3 18F-labeled PET tracers have been approved for assessing cerebral amyloid plaque pathology in the diagnostic workup of suspected Alzheimer disease (AD). Although scanning protocols are relatively similar across tracers, U.S. Food and Drug Administration- and the European Medicines Agency-approved visual rating protocols differ among the 3 tracers. This proof-of-concept study assessed the comparability of the 3 approved visual rating protocols to classify a scan as amyloid-positive or -negative, when applied by groups of experts and nonexperts to all 3 amyloid tracers. Methods: In an international multicenter approach, both expert (n = 4) and nonexpert raters (n = 3) rated scans acquired with 18F-florbetaben, 18F-florbetapir and 18F-flutemetamol. Scans obtained with each tracer were presented for reading according to all 3 approved visual rating protocols. In a randomized order, every single scan was rated by each reader according to all 3 protocols. Raters were blinded for the amyloid tracer used and asked to rate each scan as positive or negative, giving a confidence judgment after each response. Percentage of visual reader agreement, interrater reliability, and agreement of each visual read with binary quantitative measures (fixed SUV ratio threshold for positive or negative scans) were computed. These metrics were analyzed separately for expert and nonexpert groups. Results: No significant differences in using the different approved visual rating protocols were observed across the different metrics of agreement in the group of experts. Nominal differences suggested that the 18F-florbetaben visual rating protocol achieved the highest interrater reliability and accuracy especially under low confidence conditions. For the group of nonexpert raters, significant differences between the different visual rating protocols were observed with overall moderate-to-fair accuracy and with the highest reliability for the 18F-florbetapir visual rating protocol. Conclusion: We observed high interrater agreement despite applying different visual rating protocols for all 18F-labeled amyloid tracers. This implies that the results of the visual interpretation of amyloid imaging can be well standardized and do not depend on the rating protocol in experts. Consequently, the creation of a universal visual assessment protocol for all amyloid imaging tracers appears feasible, which could benefit especially the less-experienced readers. ispartof: JOURNAL OF NUCLEAR MEDICINE vol:62 issue:7 pages:999-1005 ispartof: location:United States status: published

To date, 3

This case report presents in-vivo findings on the spatial and temporal relationship between focal Ab-amyloid deposition, cerebral micro-haemorrhages and superficial siderosis. A 65-year-old woman underwent 11C-PiB PET scans that revealed an atypical focal and asymmetrical pattern of Ab-amyloid deposition and MRI scans that revealed cerebral micro-haemorrhages and superficial siderosis. Almost all micro-haemorrhages were associated with focal Ab-amyloid deposition. Follow-up 11C-PiB PET and MRI scans showed progression of the disease. We speculate that Abamyloid deposition affects the structural integrity of arterioles, thereby predisposing them to micro haemorrhages. In support of this hypothesis, progression of MRI lesions was observed only in areas associated with Ab-amyloid deposition.

Background: The Australian Imaging, Biomarkers and Lifestyle (AIBL) flagship study of aging aimed to recruit 1000 individuals aged over 60 to assist with prospective research into Alzheimer's disease (AD). This paper describes the recruitment of the cohort and gives information about the study methodology, baseline demography, diagnoses, medical comorbidities, medication use, and cognitive function of the participants.Methods: Volunteers underwent a screening interview, had comprehensive cognitive testing, gave 80 ml of blood, and completed health and lifestyle questionnaires. One quarter of the sample also underwent amyloid PET brain imaging with Pittsburgh compound B (PiB PET) and MRI brain imaging, and a subgroup of 10% had ActiGraph activity monitoring and body composition scanning.Results: A total of 1166 volunteers were recruited, 54 of whom were excluded from further study due to comorbid disorders which could affect cognition or because of withdrawal of consent. Participants with AD (211) had neuropsychological profiles which were consistent with AD, and were more impaired than participants with mild cognitive impairment (133) or healthy controls (768), who performed within expected norms for age on neuropsychological testing. PiB PET scans were performed on 287 participants, 100 had DEXA scans and 91 participated in ActiGraph monitoring.Conclusion: The participants comprising the AIBL cohort represent a group of highly motivated and well-characterized individuals who represent a unique resource for the study of AD. They will be reassessed at 18-month intervals in order to determine the predictive utility of various biomarkers, cognitive parameters and lifestyle factors as indicators of AD, and as predictors of future cognitive decline.

Increased rates of brain atrophy measured from serial magnetic resonance imaging precede symptom onset in Alzheimer's disease and may be useful outcome measures for prodromal clinical trials. Appropriate trial design requires a detailed understanding of the relationships between β-amyloid load and accumulation, and rate of brain change at this stage of the disease. Fifty-two healthy individuals (72.3 ± 6.9 years) from Australian Imaging, Biomarkers and Lifestyle Study of Aging had serial (0, 18 m, 36 m) magnetic resonance imaging, (0, 18 m) Pittsburgh compound B positron emission tomography, and clinical assessments. We calculated rates of whole brain and hippocampal atrophy, ventricular enlargement, amyloid accumulation, and cognitive decline. Over 3 years, rates of whole brain atrophy (p0.001), left and right hippocampal atrophy (p = 0.001, p = 0.023), and ventricular expansion (p0.001) were associated with baseline β-amyloid load. Whole brain atrophy rates were also independently associated with β-amyloid accumulation over the first 18 months (p = 0.003). Acceleration of left hippocampal atrophy rate was associated with baseline β-amyloid load across the cohort (p0.02). We provide evidence that rates of atrophy are associated with both baseline β-amyloid load and accumulation, and that there is presymptomatic, amyloid-mediated acceleration of hippocampal atrophy. Clinical trials using rate of hippocampal atrophy as an outcome measure should not assume linear decline in the presymptomatic phase.

factors influence the proportion of dementia subtypes. Dementia in India is expected to reach epidemic proportions in the next two decades but studies on dementia are few. We studied patients attending a memory clinic in a private hospital in South India to describe the clinical profile and compare the socio-cultural factors influencing diagnosis and dementia care in this population with studies from developed countries. Methods: Consecutive patients attending the memory clinic at Manipal hospital, Bangalore over three years were included. Socio-demographic information including income, education and linguistic background was collected. All patients underwent detailed neurological evaluation, cognitive testing, blood tests and neuroimaging. The diagnosis of MCI, dementia and the different subtypes was based on standard criteria. Results: The mean age at presentation was 65.8(9.0) years, range 4087 years. There were 127 men and 93 women. Of the total 220 patients, MCI was diagnosed in 57 (25.9%), Alzheimer’s disease (AD) in 62 (28.1%), vascular dementia (VaD) in 38 (17.3%), and mixed dementia in four patients. 37 (16.8%) patients were diagnosed as frontotemporal lobar degeneration (FTD) and its variants. Other degenerative dementias were seen in 13 and miscellaneous causes in 8 patients. One patient did not appear to have any cognitive impairment. Majority of the patients (80.4%) were bilingual or multilingual and 10 (4.9%) patients were illiterate. VaD was more common in men (3:1) and AD in women (1.5:1). Majority of the MCI patients had depression (54.4%) and seven patients developed AD during follow-up. All the patients were cared for at home by relatives except for one patient who had an appointed caretaker. Conclusions: Alzheimer’s disease was more common than vascular dementia in this study from an urban hospital in South India, in spite of the high prevalence of vascular risk factors in this population. Depression was a common cause of mild cognitive impairment. In this study of a relatively young (mean age) dementia cohort, all patients had home based care in contrast to studies from developed countries. P1-146 PREDICTORS OF COGNITIVE DECLINE AT 18 MONTH FOLLOW UPAMONG 1112 PARTICIPANTS IN THE AUSTRALIAN IMAGING, BIOMARKERS AND LIFESTYLE FLAGSHIP STUDY OFAGEING (AIBL) Kathryn A. Ellis, Christopher Rowe, ColinMasters, Cassandra Szoeke, Kevin Taddei, Ralph Martins, Victor Villemagne, Michael Fahey, David Ames, PaulMaruff, Ping Zhang, Greg Savage, AIBLResearch Group, Lance Macaulay, University of Melbourne, Kew; Austin Health, University of Melbourne, Heidelberg, Melbourne; University of Melbourne, Melbourne, VIC; CSIRO, Melbourne; Edith Cowan University, Perth; Edith Cowan University, Perth; Austin Health, Melbourne; Division of Mathematics, Informatics and Statistics, CSIRO, Parkville, VIC; National Ageing Research Institute, Parkville; CogState, Melbourne; CSIRO, Parkville; Macquarie Centre for Cognitive Science, Macquarie University, Sydney, NSW; Mental Health Research Institute, Perth; CSIRO, Parkville.