Pharmacological Strategies to Improve Dendritic Spines in Alzheimer’s Disease

2020 ◽  
pp. 1-17
Author(s):  
Miren Ettcheto ◽  
Oriol Busquets ◽  
Amanda Cano ◽  
Elena Sánchez-Lopez ◽  
Patricia R. Manzine ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Gut Microbiota ◽  
Dendritic Spines ◽  
Late Onset ◽  
Metabolic Stress ◽  
Environmental Stressors ◽  
Impact Pathways ◽  
Neurotrophic Factor Signaling ◽  
The Brain

To deeply understand late onset Alzheimer’s disease (LOAD), it may be necessary to change the concept that it is a disease exclusively driven by aging processes. The onset of LOAD could be associated with a previous peripheral stress at the level of the gut (changes in the gut microbiota), obesity (metabolic stress), and infections, among other systemic/environmental stressors. The onset of LOAD, then, may result from the generation of mild peripheral inflammatory processes involving cytokine production associated with peripheral stressors that in a second step enter the brain and spread out the process causing a neuroinflammatory brain disease. This hypothesis could explain the potential efficacy of Sodium Oligomannate (GV–971), a mixture of acidic linear oligosaccharides that have shown to remodel gut microbiota and slowdown LOAD. However, regardless of the origin of the disease, the end goal of LOAD–related preventative or disease modifying therapies is to preserve dendritic spines and synaptic plasticity that underlay and support healthy cognition. Here we discuss how systemic/environmental stressors impact pathways associated with the regulation of spine morphogenesis and synaptic maintenance, including insulin receptor and the brain derived neurotrophic factor signaling. Spine structure remodeling is a plausible mechanism to maintain synapses and provide cognitive resilience in LOAD patients. Importantly, we also propose a combination of drugs targeting such stressors that may be able to modify the course of LOAD by acting on preventing dendritic spines and synapsis loss.

scholarly journals Gut Microbiota and Dysbiosis in Alzheimer’s Disease: Implications for Pathogenesis and Treatment

2020 ◽  
Vol 57 (12) ◽  
pp. 5026-5043 ◽  
Author(s):  
Shan Liu ◽  
Jiguo Gao ◽  
Mingqin Zhu ◽  
Kangding Liu ◽  
Hong-Liang Zhang
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Gut Microbiota ◽  
Gut Dysbiosis ◽  
Bidirectional Communication ◽  
Significant Research ◽  
Novel Therapeutic Strategies ◽  
The Brain ◽  
Brain Homeostasis ◽  
Gut Microbiota Composition

Abstract Understanding how gut flora influences gut-brain communications has been the subject of significant research over the past decade. The broadening of the term “microbiota-gut-brain axis” from “gut-brain axis” underscores a bidirectional communication system between the gut and the brain. The microbiota-gut-brain axis involves metabolic, endocrine, neural, and immune pathways which are crucial for the maintenance of brain homeostasis. Alterations in the composition of gut microbiota are associated with multiple neuropsychiatric disorders. Although a causal relationship between gut dysbiosis and neural dysfunction remains elusive, emerging evidence indicates that gut dysbiosis may promote amyloid-beta aggregation, neuroinflammation, oxidative stress, and insulin resistance in the pathogenesis of Alzheimer’s disease (AD). Illustration of the mechanisms underlying the regulation by gut microbiota may pave the way for developing novel therapeutic strategies for AD. In this narrative review, we provide an overview of gut microbiota and their dysregulation in the pathogenesis of AD. Novel insights into the modification of gut microbiota composition as a preventive or therapeutic approach for AD are highlighted.

scholarly journals Neuronal heparan sulfates promote amyloid pathology by modulating brain amyloid-β clearance and aggregation in Alzheimer’s disease

2016 ◽  
Vol 8 (332) ◽  
pp. 332ra44-332ra44 ◽  
Author(s):  
Chia-Chen Liu ◽  
Na Zhao ◽  
Yu Yamaguchi ◽  
John R. Cirrito ◽  
Takahisa Kanekiyo ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Late Onset ◽  
Amyloid Β ◽  
Amyloid Plaques ◽  
Therapeutic Interventions ◽  
Postmortem Human Brain ◽  
Aβ Clearance ◽  
Heparan Sulfates ◽  
The Brain

Accumulation of amyloid-β (Aβ) peptide in the brain is the first critical step in the pathogenesis of Alzheimer’s disease (AD). Studies in humans suggest that Aβ clearance from the brain is frequently impaired in late-onset AD. Aβ accumulation leads to the formation of Aβ aggregates, which injure synapses and contribute to eventual neurodegeneration. Cell surface heparan sulfates (HSs), expressed on all cell types including neurons, have been implicated in several features in the pathogenesis of AD including its colocalization with amyloid plaques and modulatory role in Aβ aggregation. We show that removal of neuronal HS by conditional deletion of the Ext1 gene, which encodes an essential glycosyltransferase for HS biosynthesis, in postnatal neurons of amyloid model APP/PS1 mice led to a reduction in both Aβ oligomerization and the deposition of amyloid plaques. In vivo microdialysis experiments also detected an accelerated rate of Aβ clearance in the brain interstitial fluid, suggesting that neuronal HS either inhibited or represented an inefficient pathway for Aβ clearance. We found that the amounts of various HS proteoglycans (HSPGs) were increased in postmortem human brain tissues from AD patients, suggesting that this pathway may contribute directly to amyloid pathogenesis. Our findings have implications for AD pathogenesis and provide insight into therapeutic interventions targeting Aβ-HSPG interactions.

scholarly journals The Implication of the Brain Insulin Receptor in Late Onset Alzheimer’s Disease Dementia

2018 ◽  
Vol 11 (1) ◽  
pp. 11 ◽  
Author(s):  
Jaume Folch ◽  
Miren Ettcheto ◽  
Oriol Busquets ◽  
Elena Sánchez-López ◽  
Rubén Castro-Torres ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Insulin Receptor ◽  
Late Onset ◽  
Brain Insulin ◽  
The Brain ◽  
Alzheimer’S Disease Dementia

scholarly journals Mechanisms of Brain Aging Regulation by Insulin: Implications for Neurodegeneration in Late-Onset Alzheimer's Disease

2011 ◽  
Vol 2011 ◽  
pp. 1-9 ◽  
Author(s):  
Artur F. Schuh ◽  
Carlos M. Rieder ◽  
Liara Rizzi ◽  
Márcia Chaves ◽  
Matheus Roriz-Cruz
Keyword(s):  
Alzheimer’S Disease ◽  
Insulin Resistance ◽  
Alzheimer's Disease ◽  
Brain Aging ◽  
Late Onset ◽  
Energy Deficit ◽  
Insulin Degrading Enzyme ◽  
Microvascular Endothelium ◽  
Chronic Hyperglycemia ◽  
The Brain

Insulin and IGF seem to be important players in modulating brain aging. Neurons share more similarities with islet cells than any other human cell type. Insulin and insulin receptors are diffusely found in the brain, especially so in the hippocampus. Caloric restriction decreases insulin resistance, and it is the only proven mechanism to expand lifespan. Conversely, insulin resistance increases with age, obesity, and sedentarism, all of which have been shown to be risk factors for late-onset Alzheimer's disease (AD). Hyperphagia and obesity potentiate the production of oxidative reactive species (ROS), and chronic hyperglycemia accelerates the formation of advanced glucose end products (AGEs) in (pre)diabetes—both mechanisms favoring a neurodegenerative milieu. Prolonged high cerebral insulin concentrations cause microvascular endothelium proliferation, chronic hypoperfusion, and energy deficit, triggering β-amyloid oligomerization and tau hyperphosphorylation. Insulin-degrading enzyme (IDE) seems to be the main mechanism in clearing β-amyloid from the brain. Hyperinsulinemic states may deviate IDE utilization towards insulin processing, decreasing β-amyloid degradation.

scholarly journals A lipid-invasion model for Alzheimer’s Disease

2019 ◽  
Author(s):  
Jonathan D Rudge
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Late Onset ◽  
Principal Role ◽  
Lipid Droplet Formation ◽  
Invasion Model ◽  
Β Amyloid ◽  
Mass Influx ◽  
The Brain

This paper describes a potential new explanation for Alzheimer’s disease (AD), referred to here as the lipid-invasion model. It proposes that AD is primarily caused by the influx of lipids following the breakdown of the blood brain barrier (BBB). The model argues that a principal role of the BBB is to protect the brain from external lipid access. When the BBB is damaged, it allows a mass influx of (mainly albumin-bound) free fatty acids (FFAs) and lipid-rich lipoproteins to the brain, which in turn causes neurodegeneration, amyloidosis, tau tangles and other AD characteristics. The model also argues that, whilst β-amyloid causes neurodegeneration, as is widely argued, its principal role in the disease lies in damaging the BBB. It is the external lipids, entering as a consequence, that are the primary drivers of neurodegeneration in AD., especially FFAs, which induce oxidative stress, stimulate microglia-driven neuroinflammation, and inhibit neurogenesis. Simultaneously, the larger, more lipid-laden lipoproteins, characteristic of the external plasma but not the CNS, cause endosomal-lysosomal abnormalities, amyloidosis and the formation of tau tangles, all characteristic of AD. In most cases (certainly in late-onset, noninherited forms of the disease) amyloidosis and tau tangle formation are consequences of this external lipid invasion, and in many ways more symptomatic of the disease than causative. In support of this, it is argued that the pattern of damage caused by the influx of FFAs into the brain is likely to resemble the neurodegeneration seen in alcohol-related brain damage (ARBD), a disease that shows many similarities to AD, including the areas of the brain it affects. The fact that neurodegeneration is far more pronounced in AD than in ARBD, and characterised by other features, such as amyloidosis and tau tangles, most likely results from the greater heterogeneity of the lipid assault in AD compared with ethanol alone. The lipid-invasion model, described here, arguably provides the first cohesive, multi-factorial explanation of AD that accounts for all currently known major risk factors, and explains all AD-associated pathologies, including those, such as endosomal-lysosomal dysfunction and excessive lipid droplet formation, that are not well-accounted for in other explanation of this disease.

scholarly journals A lipid-invasion model for Alzheimer’s Disease

2019 ◽  
Author(s):  
Jonathan D Rudge
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Late Onset ◽  
Principal Role ◽  
Lipid Droplet Formation ◽  
Invasion Model ◽  
Β Amyloid ◽  
Mass Influx ◽  
The Brain

This paper describes a potential new explanation for Alzheimer’s disease (AD), referred to here as the lipid-invasion model. It proposes that AD is primarily caused by the influx of lipids following the breakdown of the blood brain barrier (BBB). The model argues that a principal role of the BBB is to protect the brain from external lipid access. When the BBB is damaged, it allows a mass influx of (mainly albumin-bound) free fatty acids (FFAs) and lipid-rich lipoproteins to the brain, which in turn causes neurodegeneration, amyloidosis, tau tangles and other AD characteristics. The model also argues that, whilst β-amyloid causes neurodegeneration, as is widely argued, its principal role in the disease lies in damaging the BBB. It is the external lipids, entering as a consequence, that are the primary drivers of neurodegeneration in AD., especially FFAs, which induce oxidative stress, stimulate microglia-driven neuroinflammation, and inhibit neurogenesis. Simultaneously, the larger, more lipid-laden lipoproteins, characteristic of the external plasma but not the CNS, cause endosomal-lysosomal abnormalities, amyloidosis and the formation of tau tangles, all characteristic of AD. In most cases (certainly in late-onset, noninherited forms of the disease) amyloidosis and tau tangle formation are consequences of this external lipid invasion, and in many ways more symptomatic of the disease than causative. In support of this, it is argued that the pattern of damage caused by the influx of FFAs into the brain is likely to resemble the neurodegeneration seen in alcohol-related brain damage (ARBD), a disease that shows many similarities to AD, including the areas of the brain it affects. The fact that neurodegeneration is far more pronounced in AD than in ARBD, and characterised by other features, such as amyloidosis and tau tangles, most likely results from the greater heterogeneity of the lipid assault in AD compared with ethanol alone. The lipid-invasion model, described here, arguably provides the first cohesive, multi-factorial explanation of AD that accounts for all currently known major risk factors, and explains all AD-associated pathologies, including those, such as endosomal-lysosomal dysfunction and excessive lipid droplet formation, that are not well-accounted for in other explanation of this disease.

Retinoic Acid and the Gut Microbiota in Alzheimer’s Disease: Fighting Back-to-Back?

2019 ◽  
Vol 16 (5) ◽  
pp. 405-417 ◽  
Author(s):  
Kristina Endres
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Retinoic Acid ◽  
Gut Microbiota ◽  
Disease Risk ◽  
Current Knowledge ◽  
Retinoid Signaling ◽  
Retinoid Metabolism ◽  
Organ Systems ◽  
The Brain

Background: There is growing evidence that the gut microbiota may play an important role in neurodegenerative diseases such as Alzheimer’s disease. However, how these commensals influence disease risk and progression still has to be deciphered. Objective: The objective of this review was to summarize current knowledge on the interplay between gut microbiota and retinoic acid. The latter one represents one of the important micronutrients, which have been correlated to Alzheimer’s disease and are used in initial therapeutic intervention studies. Methods: A selective overview of the literature is given with the focus on the function of retinoic acid in the healthy and diseased brain, its metabolism in the gut, and the potential influence that the bioactive ligand may have on microbiota, gut physiology and, Alzheimer’s disease. Results: Retinoic acid can influence neuronal functionality by means of plasticity but also by neurogenesis and modulating proteostasis. Impaired retinoid-signaling, therefore, might contribute to the development of diseases in the brain. Despite its rather direct impact, retinoic acid also influences other organ systems such as gut by regulating the residing immune cells but also factors such as permeability or commensal microbiota. These in turn can also interfere with retinoid-metabolism and via the gutbrain- axis furthermore with Alzheimer’s disease pathology within the brain. Conclusion: Potentially, it is yet too early to conclude from the few reports on changed microbiota in Alzheimer’s disease to a dysfunctional role in retinoid-signaling. However, there are several routes how microbial commensals might affect and might be affected by vitamin A and its derivatives.

scholarly journals PLCG2 as a Risk Factor for Alzheimer's Disease

2020 ◽  
Author(s):  
Andy Po-Yi Tsai ◽  
Chuanpeng Dong ◽  
Christoph Preuss ◽  
Miguel Moutinho ◽  
Peter Bor-Chian Lin ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Late Onset ◽  
Missense Variant ◽  
Parahippocampal Gyrus ◽  
Carrier Status ◽  
Eqtl Analysis ◽  
Expression Levels ◽  
Amyloid Pathology ◽  
The Brain

Abstract Background Alzheimer's disease (AD) is characterized by robust microgliosis and phenotypic changes that accompany disease pathogenesis. Indeed, genetic variants in microglial genes are linked to risk for late-onset AD (LOAD). Phospholipase C 𝛾 2 (PLCG2) participates in the transduction of signals emanating from immune cell-surface receptors that regulate the inflammatory response and is selectively expressed by microglia in the brain. A rare variant in PLCG2 (P522R) was previously found to be protective against LOAD. Here, we performed association analysis to identify a new genetic variation in PLCG2 that is associated with elevated risk for LOAD.Methods Using whole genome sequencing (N=1,894) and RNA-Seq (N=1,077) data from the AMP-AD cohort, we investigated whether a missense variant in PLCG2 (M28L) was associated with risk for LOAD. We have examined the homology model and space-filling model of PLCG2 generated with PyMOL to investigate the protein structure of PLCG2 with substitutions of LOAD risk and protective variants in PLCG2 . Gene expression analysis and expression quantitative trait loci (eQTL) of PLCG2 were conducted. We also evaluated the relationship between PLCG2 expression levels and amyloid plaque density and expression levels of microglia specific markers ( AIF1 and TMEM119 ). Age, sex, and APOE ε4 carrier status were used as covariates. Finally, we investigated the longitudinal changes PLCG2 expression in the 5XFAD mouse model of AD and it relationship to amyloid pathology progression.Results A rare missense variant in PLCG2 (M28L) confers increased AD risk ( p =0.047; OR=1.164 [95% CI=1.002-1.351]). PLCG2 is highly expressed in the brain and was significantly up-regulated in the parahippocampal gyrus, superior temporal gyrus, and inferior temporal gyrus in LOAD. Higher PLCG2 expression levels were associated with increased brain amyloid deposition. The findings were validated in 5xFAD mice, showing a disease progression-dependent increase in Plcg2 expression with amyloid pathology. Furthermore, eQTL analysis identified several variants as associated with increased PLCG2 expression levels in the brain and other organs.Conclusions Our results provide further evidence that PLCG2 and the M28L variant confers increase risk for LOAD and may play an important role in AD pathophysiology.

Mitochondrial Dysfunction as a Causative Factor in Alzheimer’s Disease-Spectrum Disorders: Lymphocytes as a Window to the Brain

2021 ◽  
Vol 18 ◽  
Author(s):  
Marko Jörg ◽  
Johanna E. Plehn ◽  
Kristina Friedland ◽  
Walter E. Müller
Keyword(s):  
Oxidative Stress ◽  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Mitochondrial Dysfunction ◽  
Late Onset ◽  
Causative Factor ◽  
Disease Spectrum ◽  
The Brain ◽  
Peripheral Markers

: Alzheimer's disease (AD) is the most common progressive neurodegenerative disease. Today, AD affects millions of people worldwide and the number of AD cases will further increase with longer life expectancy. The AD brain is marked by severe neurodegeneration, such as the loss of synapses and neurons, atrophy and depletion of neurotransmitter systems, especially in the hip- pocampus and cerebral cortex. Recent findings highlight the important role of mitochondrial dys- function and increased oxidative stress in the pathophysiology of late-onset Alzheimer’s disease (LOAD). These alterations are not only observed in the brain of AD patients but also in the periph- ery. In this review, we discuss the potential role of elevated apoptosis, increased oxidative stress and mitochondrial dysfunction as peripheral markers for the detection of AD in blood cells e.g. lymphocytes. We evaluate recent findings regarding impaired mitochondrial function comprising mitochondrial respiration, reduced complex activities of the respiratory chain and altered Mitochon- drial Membrane Potential (MMP) in lymphocytes as well as in neurons. Finally, we will question whether these mitochondrial parameters might be suitable as an early peripheral marker for the de- tection of LOAD but also for the transitional stage between normal aging and Dementia, “Mild Cognitive Impairment” (MCI).

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