scholarly journals Quantitative Gradient Echo MRI Identifies Dark Matter as a New Imaging Biomarker of Neurodegeneration that Precedes Tisssue Atrophy in Early Alzheimer’s Disease

2021 ◽  
pp. 1-20
Author(s):  
Satya V.V.N. Kothapalli ◽  
Tammie L. Benzinger ◽  
Andrew J. Aschenbrenner ◽  
Richard J. Perrin ◽  
Charles F. Hildebolt ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Dark Matter ◽  
Amyloid Β ◽  
Neuronal Loss ◽  
Imaging Biomarker ◽  
Control Group ◽  
Histopathological Study ◽  
Preclinical Ad

Background: Currently, brain tissue atrophy serves as an in vivo MRI biomarker of neurodegeneration in Alzheimer’s disease (AD). However, postmortem histopathological studies show that neuronal loss in AD exceeds volumetric loss of tissue and that loss of memory in AD begins when neurons and synapses are lost. Therefore, in vivo detection of neuronal loss prior to detectable atrophy in MRI is essential for early AD diagnosis. Objective: To apply a recently developed quantitative Gradient Recalled Echo (qGRE) MRI technique for in vivo evaluation of neuronal loss in human hippocampus. Methods: Seventy participants were recruited from the Knight Alzheimer Disease Research Center, representing three groups: Healthy controls [Clinical Dementia Rating® (CDR®) = 0, amyloid β (Aβ)-negative, n = 34]; Preclinical AD (CDR = 0, Aβ-positive, n = 19); and mild AD (CDR = 0.5 or 1, Aβ-positive, n = 17). Results: In hippocampal tissue, qGRE identified two types of regions: one, practically devoid of neurons, we designate as “Dark Matter”, and the other, with relatively preserved neurons, “Viable Tissue”. Data showed a greater loss of neurons than defined by atrophy in the mild AD group compared with the healthy control group; neuronal loss ranged between 31% and 43%, while volume loss ranged only between 10% and 19%. The concept of Dark Matter was confirmed with histopathological study of one participant who underwent in vivo qGRE 14 months prior to expiration. Conclusion: In vivo qGRE method identifies neuronal loss that is associated with impaired AD-related cognition but is not recognized by MRI measurements of tissue atrophy, therefore providing new biomarkers for early AD detection.

scholarly journals Quantitative Gradient Echo MRI Identifies Dark Matter as a New Imaging Biomarker of Neurodegeneration that Precedes Tissue Atrophy in Early Alzheimer Disease

2021 ◽  
Author(s):  
Satya V.V.N. Kothapalli ◽  
Tammie L. Benzinger ◽  
Andrew. J. Aschenbrenner ◽  
Richard. J. Perrin ◽  
Charles. F. Hildebolt ◽  
...  
Keyword(s):  
Dark Matter ◽  
Alzheimer Disease ◽  
Amyloid Β ◽  
Neuronal Loss ◽  
Imaging Biomarker ◽  
Control Group ◽  
Histopathological Study ◽  
In Vivo Evaluation ◽  
Preclinical Ad

AbstractBackgroundCurrently, brain tissue atrophy serves as in vivo MRI biomarker of neurodegeneration in Alzheimer Disease (AD). However, postmortem histopathological studies show that neuronal loss in AD exceeds volumetric loss of tissue and that loss of memory in AD begins when neurons and synapses are lost. Therefore, in vivo detection of neuronal loss prior to detectable atrophy in MRI is essential for early AD diagnosis.ObjectiveTo apply a recently developed quantitative Gradient Recalled Echo (qGRE) MRI technique for in vivo evaluation of neuronal loss in human hippocampus.MethodsSeventy participants were recruited from the Knight Alzheimer Disease Research Center, representing three groups: Healthy controls [Clinical Dementia Rating® (CDR®)=0, amyloid β (Aβ)-negative), n=34]; Preclinical AD (CDR=0, Aβ-positive, n=19); and mild AD (CDR=0.5 or 1, Aβ-positive, n=17).ResultsIn hippocampal tissue, qGRE identified two types of regions: one, practically devoid of neurons, we designate as “Dark Matter”, the other, with relatively preserved neurons - “Viable Tissue”. Data showed a greater loss of neurons than defined by atrophy in the mild AD group compared with the healthy control group - neuronal loss ranged between 31% and 43% while volume loss ranged only between 10% and 19%. The concept of Dark Matter was confirmed with histopathological study of one participant who underwent in vivo qGRE 14 months prior to expiration.Conclusionin vivo qGRE method identifies neuronal loss that is associated with impaired AD-related cognition but is not recognized by MRI measurements of tissue atrophy, therefore providing new biomarkers for early AD detection.

scholarly journals Associations of AT(N) biomarkers with neuropsychiatric symptoms in preclinical Alzheimer’s disease and cognitively unimpaired individuals

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Kok Pin Ng ◽  
Hui Chiew ◽  
Pedro Rosa-Neto ◽  
Nagaendran Kandiah ◽  
Zahinoor Ismail ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Cognitive Decline ◽  
Longitudinal Studies ◽  
Neuropsychiatric Symptoms ◽  
Amyloid Β ◽  
Cross Sectional ◽  
Preclinical Ad ◽  
Cross Sectional Studies

AbstractThe development of in vivo biomarkers of Alzheimer’s disease (AD) has advanced the diagnosis of AD from a clinical syndrome to a biological construct. The preclinical stage of AD continuum is defined by the identification of AD biomarkers crossing the pathological threshold in cognitively unimpaired individuals. While neuropsychiatric symptoms (NPS) are non-cognitive symptoms that are increasingly recognized as early manifestations of AD, the associations of NPS with AD pathophysiology in preclinical AD remain unclear. Here, we review the associations between NPS and AD biomarkers amyloid-β (Aβ), tau and neurodegeneration in preclinical AD and cognitively-unimpaired individuals in 19 eligible English-language publications (8 cross-sectional studies, 10 longitudinal, 1 both cross-sectional and longitudinal). The cross-sectional studies have consistently shown that NPS, particularly depressive and anxiety symptoms, are associated with higher Aβ. The longitudinal studies have suggested that greater NPS are associated with higher Aβ and cognitive decline in cognitively unimpaired subjects over time. However, most of the studies have either cross-sectionally or longitudinally shown no association between NPS and tau pathology. For the association of NPS and neurodegeneration, two studies have shown that the cerebrospinal fluid total-tau is linked to longitudinal increase in NPS and that the NPS may predict longitudinal metabolic decline in preclinical AD, respectively. However, evidence for the association between atrophy and NPS in preclinical AD is less consistent. Therefore, future longitudinal studies with well-designed methodologies and NPS measurements are required not only to determine the relationship among AT(N) biomarkers, NPS and cognitive decline, but also to elucidate the contribution of comorbid pathology to preclinical AD.

scholarly journals A novel missense variant in ACAA1 contributes to early-onset Alzheimer’s disease, impairs lysosomal function, and facilitates amyloid-β pathology and cognitive decline

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Rongcan Luo ◽  
Yu Fan ◽  
Jing Yang ◽  
Maosen Ye ◽  
Deng-Feng Zhang ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Early Onset ◽  
Neurofibrillary Tangle ◽  
Amyloid Β ◽  
Neuronal Loss ◽  
Missense Variant ◽  
Lysosomal Function

AbstractAlzheimer’s disease (AD) is characterized by progressive synaptic dysfunction, neuronal death, and brain atrophy, with amyloid-β (Aβ) plaque deposits and hyperphosphorylated tau neurofibrillary tangle accumulation in the brain tissue, which all lead to loss of cognitive function. Pathogenic mutations in the well-known AD causal genes including APP, PSEN1, and PSEN2 impair a variety of pathways, including protein processing, axonal transport, and metabolic homeostasis. Here we identified a missense variant rs117916664 (c.896T>C, p.Asn299Ser [p.N299S]) of the acetyl-CoA acyltransferase 1 (ACAA1) gene in a Han Chinese AD family by whole-genome sequencing and validated its association with early-onset familial AD in an independent cohort. Further in vitro and in vivo evidence showed that ACAA1 p.N299S contributes to AD by disturbing its enzymatic activity, impairing lysosomal function, and aggravating the Aβ pathology and neuronal loss, which finally caused cognitive impairment in a murine model. Our findings reveal a fundamental role of peroxisome-mediated lysosomal dysfunction in AD pathogenesis.

scholarly journals Gestational Stress Augments Postpartum β-Amyloid Pathology and Cognitive Decline in a Mouse Model of Alzheimer’s Disease

2018 ◽  
Vol 29 (9) ◽  
pp. 3712-3724 ◽  
Author(s):  
Zahra Jafari ◽  
Jogender Mehla ◽  
Bryan E Kolb ◽  
Majid H Mohajerani
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Risk Factor ◽  
Cognitive Decline ◽  
Noise Exposure ◽  
Amyloid Β ◽  
Control Group ◽  
Plaque Size ◽  
Model Of Alzheimer’S Disease ◽  
Gestational Stress

Abstract Besides well-known risk factors for Alzheimer’s disease (AD), stress, and in particular noise stress (NS), is a lifestyle risk factor common today. It is known that females are at a significantly greater risk of developing AD than males, and given that stress is a common adversity in females during pregnancy, we hypothesized that gestational noise exposure could exacerbate the postpartum development of the AD-like neuropathological changes during the life span. Pregnant APPNL-G-F/NL-G-F mice were randomly assigned to either the stress condition or control group. The stress group was exposed to the NS on gestational days 12–16, which resulted in a markedly higher hypothalamic–pituitary–adrenal (HPA) axis responsivity during the postpartum stage. Higher amyloid-β (Aβ) deposition and larger Aβ plaque size in the olfactory area were the early onset impacts of the gestational stress (GS) seen at the age of 4 months. This pattern of increased Aβ aggregation and larger plaque size were observed in various brain areas involved in both AD and stress regulation, especially in limbic structures, at the age of 6 months. The GS also produced anxiety-like behavior, deficits in learning and memory, and impaired motor coordination. The findings suggest that environmental stresses during pregnancy pose a potential risk factor in accelerating postpartum cognitive decline and AD-like neuropathological changes in the dams (mothers) later in life.

scholarly journals Application of optogenetic Amyloid-β distinguishes between metabolic and physical damages in neurodegeneration

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Chu Hsien Lim ◽  
Prameet Kaur ◽  
Emelyne Teo ◽  
Vanessa Yuk Man Lam ◽  
Fangchen Zhu ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Disease Progression ◽  
Biological Effects ◽  
Amyloid Β ◽  
Tissue Loss ◽  
Amyloid Β Peptide ◽  
Physical Damage ◽  
Living Tissues

The brains of Alzheimer’s disease patients show a decrease in brain mass and a preponderance of extracellular Amyloid-β plaques. These plaques are formed by aggregation of polypeptides that are derived from the Amyloid Precursor Protein (APP). Amyloid-β plaques are thought to play either a direct or an indirect role in disease progression, however the exact role of aggregation and plaque formation in the aetiology of Alzheimer’s disease (AD) is subject to debate as the biological effects of soluble and aggregated Amyloid-β peptides are difficult to separate in vivo. To investigate the consequences of formation of Amyloid-β oligomers in living tissues, we developed a fluorescently tagged, optogenetic Amyloid-β peptide that oligomerizes rapidly in the presence of blue light. We applied this system to the crucial question of how intracellular Amyloid-β oligomers underlie the pathologies of A. We use Drosophila, C. elegans and D. rerio to show that, although both expression and induced oligomerization of Amyloid-β were detrimental to lifespan and healthspan, we were able to separate the metabolic and physical damage caused by light-induced Amyloid-β oligomerization from Amyloid-β expression alone. The physical damage caused by Amyloid-β oligomers also recapitulated the catastrophic tissue loss that is a hallmark of late AD. We show that the lifespan deficit induced by Amyloid-β oligomers was reduced with Li+ treatment. Our results present the first model to separate different aspects of disease progression.

scholarly journals Elevated Expression of MiR-17 in Microglia of Alzheimer’s Disease Patients Abrogates Autophagy-Mediated Amyloid-β Degradation

2021 ◽  
Vol 12 ◽  
Author(s):  
Shady Estfanous ◽  
Kylene P. Daily ◽  
Mostafa Eltobgy ◽  
Nicholas P. Deems ◽  
Midhun N. K. Anne ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Amyloid Β ◽  
Therapeutic Interventions ◽  
Tissue Sections ◽  
Cargo Receptor ◽  
5Xfad Mouse ◽  
Aβ Degradation

Autophagy is a proposed route of amyloid-β (Aβ) clearance by microglia that is halted in Alzheimer’s Disease (AD), though mechanisms underlying this dysfunction remain elusive. Here, primary microglia from adult AD (5xFAD) mice were utilized to demonstrate that 5xFAD microglia fail to degrade Aβ and express low levels of autophagy cargo receptor NBR1. In 5xFAD mouse brains, we show for the first time that AD microglia express elevated levels of microRNA cluster Mirc1/Mir17-92a, which is known to downregulate autophagy proteins. By in situ hybridization in post-mortem AD human tissue sections, we observed that the Mirc1/Mir17-92a cluster member miR-17 is also elevated in human AD microglia, specifically in the vicinity of Aβ deposits, compared to non-disease controls. We show that NBR1 expression is negatively correlated with expression of miR-17 in human AD microglia via immunohistopathologic staining in human AD brain tissue sections. We demonstrate in healthy microglia that autophagy cargo receptor NBR1 is required for Aβ degradation. Inhibiting elevated miR-17 in 5xFAD mouse microglia improves Aβ degradation, autophagy, and NBR1 puncta formation in vitro and improves NBR1 expression in vivo. These findings offer a mechanism behind dysfunctional autophagy in AD microglia which may be useful for therapeutic interventions aiming to improve autophagy function in AD.

Preclinical Cognitive Trajectories Differ for Alzheimer's Disease and Vascular Dementia

2012 ◽  
Vol 18 (2) ◽  
pp. 191-199 ◽  
Author(s):  
Erika J. Laukka ◽  
Stuart W.S. MacDonald ◽  
Laura Fratiglioni ◽  
Lars Bäckman
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Vascular Dementia ◽  
Early Stage ◽  
Block Design ◽  
Word Recall ◽  
Cognitive Tasks ◽  
Control Group ◽  
Age Related ◽  
Preclinical Ad

AbstractWe investigated differences between Alzheimer's disease (AD) and vascular dementia (VaD) from the appearance of the first cognitive symptoms, focusing on both time of onset and rate of accelerated decline for different cognitive functions before dementia diagnosis. Data from a longitudinal population-based study were used, including 914 participants (mean age = 82.0 years, SD = 5.0) tested with a cognitive battery (word recall and recognition, Block Design, category fluency, clock reading) on up to four occasions spanning 10 years. We fit a series of linear mixed effects models with a change point to the cognitive data, contrasting each dementia group to a control group. Significant age-related decline was observed for all five cognitive tasks. Relative to time of diagnosis, the preclinical AD persons deviated from the normal aging curve earlier (up to 9 years) compared to the preclinical VaD persons (up to 6 years). However, once the preclinical VaD persons started to decline, they deteriorated at a faster rate than the preclinical AD persons. The results have important implications for identifying the two dementia disorders at an early stage and for selecting cognitive tasks to evaluate treatment effects for persons at risk of developing AD and VaD. (JINS, 2012, 18, 191–199)

scholarly journals The relationship between cortical microstructural changes and in vivo amyloid‐β and tau in aging and preclinical Alzheimer's disease

2020 ◽  
Vol 16 (S4) ◽  
Author(s):  
Elena Rodriguez‐Vieitez ◽  
Victor Montal ◽  
Jorge Sepulcre ◽  
Cristina Lois ◽  
Bernard Hanseeuw ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Amyloid Β ◽  
Preclinical Alzheimer’S Disease ◽  
Microstructural Changes ◽  
The Relationship

scholarly journals The inhibition of cellular toxicity of amyloid-β by dissociated transthyretin

2020 ◽  
Vol 295 (41) ◽  
pp. 14015-14024 ◽  
Author(s):  
Qin Cao ◽  
Daniel H. Anderson ◽  
Wilson Y. Liang ◽  
Joshua Chou ◽  
Lorena Saelices
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Protective Effect ◽  
Amyloid Β ◽  
Inhibitory Effect ◽  
Aβ Oligomers ◽  
Cellular Toxicity ◽  
Computational Docking

The protective effect of transthyretin (TTR) on cellular toxicity of β-amyloid (Aβ) has been previously reported. TTR is a tetrameric carrier of thyroxine in blood and cerebrospinal fluid, the pathogenic aggregation of which causes systemic amyloidosis. However, studies have documented a protective effect of TTR against cellular toxicity of pathogenic Aβ, a protein associated with Alzheimer's disease. TTR binds Aβ, alters its aggregation, and inhibits its toxicity both in vitro and in vivo. In this study, we investigate whether the amyloidogenic ability of TTR and its antiamyloid inhibitory effect are associated. Using protein aggregation and cytotoxicity assays, we found that the dissociation of the TTR tetramer, required for its amyloid pathogenesis, is also necessary to prevent cellular toxicity from Aβ oligomers. These findings suggest that the Aβ-binding site of TTR may be hidden in its tetrameric form. Aided by computational docking and peptide screening, we identified a TTR segment that is capable of altering Aβ aggregation and toxicity, mimicking TTR cellular protection. EM, immune detection analysis, and assessment of aggregation and cytotoxicity revealed that the TTR segment inhibits Aβ oligomer formation and also promotes the formation of nontoxic, nonamyloid amorphous aggregates, which are more sensitive to protease digestion. Finally, this segment also inhibits seeding of Aβ catalyzed by Aβ fibrils extracted from the brain of an Alzheimer's patient. Together, these findings suggest that mimicking the inhibitory effect of TTR with peptide-based therapeutics represents an additional avenue to explore for the treatment of Alzheimer's disease.

Associations of Neprilysin Activity in CSF with Biomarkers for Alzheimer’s Disease

2019 ◽  
Vol 19 (1) ◽  
pp. 43-50 ◽  
Author(s):  
Timo Grimmer ◽  
Oliver Goldhardt ◽  
Igor Yakushev ◽  
Marion Ortner ◽  
Christian Sorg ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Fdg Pet ◽  
Amyloid Β ◽  
Neuronal Injury ◽  
Pittsburgh Compound B ◽  
Positron Emission ◽  
Amyloid Load ◽  
Alzheimer’S Pathology

Background: Neprilysin (NEP) cleaves amyloid-β 1–42 (Aβ42) in the brain. Hence, we aimed to elucidate the effect of NEP on Aβ42 in cerebrospinal fluid (CSF) and on in vivo brain amyloid load using amyloid positron emission tomography (PET) with [11C]PiB (Pittsburgh compound B). In addition, associations with the biomarkers for neuronal injury, CSF-tau and FDG-PET, were investigated. Methods: Associations were calculated using global and voxel-based (SPM8) linear regression analyses in the same cohort of 23 highly characterized Alzheimer’s disease patients. Results: CSF-NEP was significantly inversely associated with CSF-Aβ42 and positively with the extent of neuronal injury as measured by CSF-tau and FDG-PET. Conclusions: Our results on CSF-NEP are compatible with the assumption that local degradation, amongst other mechanisms of amyloid clearance, plays a role in the development of Alzheimer’s pathology. In addition, CSF-NEP is associated with the extent and the rate of neurodegeneration.

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