The Role of Glial Cells and Synapse Loss in Mouse Models of Alzheimer's Disease

Complement 3a induces the synapse loss via C3aR in mitochondria-dependent NLRP3 activating mechanisms during the development and progression of Alzheimer's disease

As a central molecule in complement system (CS), complement (C) 3 is upregulated in the patients and animal models of Alzheimer's disease (AD). C3 will metabolize to iC3b and C3a. iC3b is responsible for clearing β-amyloid protein (Aβ). In this scenario, C3 exerts neuroprotective effects against the disease via iC3b. However, C3a will inhibit microglia to clear the Aβ, leading to the deposition of Aβ and impair the functions of synapses. To their effects on AD, activation of C3a and C3a receptor (C3aR) will impair the mitochondria, leading to the release of reactive oxygen species (ROS), which activates the NOD-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasomes. The overloading of NLRP3 inflammasomes activate microglia, leading to the formation of inflammatory environment. The inflammatory environment will facilitate the deposition of Aβ and abnormal synapse pruning, which results in the progression of AD. Therefore, the current review will decipher the mechanisms of C3a inducing the synapse loss via C3aR in mitochondria-dependent NLRP3 activating mechanisms, which facilitates the understanding the AD.

Research progress in the mechanism of acupuncture regulating microglia in the treatment of Alzheimer's disease

Alzheimer's disease (AD) is the most common neurodegenerative disease in the central nervous system, characterized by memory and cognitive dysfunction. Acupuncture is an effective means to alleviate the symptoms of AD. Recent studies have shown that microglia play an important role in the occurrence and development of AD. Acupuncture can regulate the activity of microglia, inhibit neuroinflammation, regulate phagocytosis, and clear Aβ Pathological products such as plaque can protect nerve cells and improve cognitive function in AD patients. This article summarizes the relationship between microglia and AD, as well as the research progress in the mechanism of acupuncture regulating microglia in the treatment of AD. The mechanism of acupuncture regulating microglia in the treatment of AD is mainly reviewed from two aspects: inhibiting neuroinflammatory activity and regulating phagocytic function.

Retinal ganglion cell type-specific expression of synuclein family members revealed by scRNA-sequencing

Synuclein family members (Snca, Sncb, and Scng) are expressed in the retina, but their precise locations and roles are poorly understood. We performed an extensive analysis of the single-cell transcriptome in healthy and injured retinas to investigate their expression patterns and roles. We observed the expression of all synuclein family members in retinal ganglion cells (RGCs), which remained consistent across species (human, mouse, and chicken). We unveiled differential expression of Snca across distinct clusters (highly expressed in most), while Sncb and Sncg displayed uniform expression across all clusters. Further, we observed a decreased expression in RGCs following traumatic axonal injury. However, the proportion of α-Syn-positive RGCs in all RGCs and α-Syn-positive intrinsically photosensitive retinal ganglion cells (ipRGCs) in all ipRGCs remained unaltered. Lastly, we identified changes in communication patterns preceding cell death, with particular significance in the pleiotrophin-nucleolin (Ptn-Ncl) and neural cell adhesion molecule signaling pathways, where communication differences were pronounced between cells with varying expression levels of Snca. Our study employs an innovative approach using scRNA-seq to characterize synuclein expression in health retinal cells, specifically focusing on RGC subtypes, advances our knowledge of retinal physiology and pathology.

Histaminergic neurotransmission in aging and Alzheimer's disease: A review of therapeutic opportunities and gaps

Introduction

Alzheimer's disease (AD) is a progressive neurodegenerative disorderfeaturing a brain accumulation of extracellular β-amyloidplaques (Aβ) and intracellular neurofibrillary tautangles (NFTs). Although cognitive decline is a disease-defining symptom of AD, sleep dysfunction, a common symptom often preceding cognitive decline, hasrecently gained more attention as a core AD symptom. Polysomnography and othersleep measures show sleep fragmentation with shortening of N3 sleep togetherwith excessive daytime sleepiness (EDS) and sundowning as the main findings in AD patients. The latter reflects dysfunction of the wake-promoting neurons (WPNs), including histaminergic neurons (HAN) located in thetuberomammillary nucleus (TMN) of the posterior hypothalamus, which projectunmyelinated axons to various parts of the brain. Histamine's role in cognitionand arousal is broadly recognized. Selective targeting of histaminergic subtype-3 and 4 receptors show therapeutic potential in rodent models of AD andaging.

Method

Based on PubMed, Scopus, and google scholar databases search, this review summarizes the current knowledge on the histaminergic system in AD and aging, its therapeutic potential in AD, and highlight areas where moreresearch is needed.

Results

Animal studies have demonstrated that pharmacological manipulation of histaminergic receptors or histamine supplementation improves cognition in AD models. However, measurements of HA or HA metabolite levels in the human brainand CSF present contradictory reports due to either lack of power or controls for known confounders.

Discussion

Systemic studies including broad age, sex, neuropathological diagnosis, and disease stage are warranted to fill the gap in our current understanding of the histaminergic neurotransmitter/neuromodulator system in humans, especially age-related changes, and therapeuticpotential of histamine in AD-related dysfunction.

The interactions of amyloid β aggregates with phospholipid membranes and the implications for neurodegeneration

Misfolding, aggregation and accumulation of Amyloid-β peptides (Aβ) in neuronal tissue and extracellular matrix are hallmark features of Alzheimer's disease (AD) pathology. Soluble Aβ oligomers are involved in neuronal toxicity by interacting with the lipid membrane, compromising its integrity, and affecting the function of receptors. These facts indicate that the interaction between Aβ oligomers and cell membranes may be one of the central molecular level factors responsible for the onset of neurodegeneration. The present review provides a structural understanding of Aβ neurotoxicity via membrane interactions and contributes to understanding early events in Alzheimer's disease.

Royal jelly improves learning and memory deficits in an amyloid β-induced model of Alzheimer's disease in male rats: Involvement of oxidative stress

Alzheimer's disease (AD) as the commonest type of dementia is associated with the cognitive function failure. Oxidative stress performs an essential role in the progression of AD. Royal jelly (RJ) is a natural product of bees with antioxidant and anti-inflammatory properties. The present research aimed to investigate the possible protective effect of RJ on learning and memory in a rat model of Aβ-induced AD. Forty male adult Wistar rats were equally distributed into five groups: control, sham-operated, Aβ (receiving intracerebroventricular (ICV) injection of amyloid beta (Aβ1-40)), Aβ + RJ 50 mg/kg, and Aβ + RJ 100 mg/kg. RJ was administered daily post-surgery by oral gavage for four weeks. Behavioral learning and memory were examined using the novel object recognition (NOR) and passive avoidance learning (PAL) tests. Also, oxidative stress markers, such as malondialdehyde (MDA), total oxidant status (TOS) and total antioxidant capacity (TAC), were assessed in the hippocampus. Aβ reduced step-through latency (STLr) and increased time spent in the dark compartment (TDC) in the PAL task and also decreased discrimination index in the NOR test. Administration of RJ ameliorated the Aβ-related memory impairment in both NOR and PAL tasks. Aβ decreased TAC and increased MDA and TOS levels in the hippocampus, whereas RJ administration reversed these Aβ-induced alterations. Our results indicated that RJ has the potential to ameliorate learning and memory impairment in the Aβ model of AD via attenuating oxidative stress.

New Insights into Microglial Mechanisms of Memory Impairment in Alzheimer's Disease

Alzheimer's disease (AD) is the most common progressive and irreversible neurodegeneration characterized by the impairment of memory and cognition. Despite years of studies, no effective treatment and prevention strategies are available yet. Identifying new AD therapeutic targets is crucial for better elucidating the pathogenesis and establishing a valid treatment of AD. Growing evidence suggests that microglia play a critical role in AD. Microglia are resident macrophages in the central nervous system (CNS), and their core properties supporting main biological functions include surveillance, phagocytosis, and the release of soluble factors. Activated microglia not only directly mediate the central immune response, but also participate in the pathological changes of AD, including amyloid-beta (Aβ) aggregation, tau protein phosphorylation, synaptic dissection, neuron loss, memory function decline, etc. Based on these recent findings, we provide a new framework to summarize the role of microglia in AD memory impairment. This evidence suggests that microglia have the potential to become new targets for AD therapy.

Amyloid beta induces Fmr1 ‐dependent translational suppression and hyposynchrony of neural activity via phosphorylation of eIF2α and eEF2

Alzheimer's disease (AD) is the most common cause of dementia, with the accumulation of amyloid beta peptide (Aβ) being one of the main causes of the disease. Fragile X mental retardation protein (FMRP), encoded by fragile X mental retardation 1 (Fmr1), is an RNA‐binding protein that represses translation of its bound mRNAs or exerts other indirect mechanisms that result in translational suppression. Because the accumulation of Aβ has been shown to cause translational suppression resulting from the elevated cellular stress response, in this study we asked whether and how Fmr1 is involved in Aβ‐induced translational regulation. Our data first showed that the application of synthetic Aβ peptide induces the expression of Fmr1 in cultured primary neurons. We followed by showing that Fmr1 is required for Aβ‐induced translational suppression, hyposynchrony of neuronal firing activity, and loss of excitatory synapses. Mechanistically, we revealed that Fmr1 functions to repress the expression of phosphatases including protein phosphatase 2A (PP2A) and protein phosphatase 1 (PP1), leading to elevated phosphorylation of eukaryotic initiation factor 2‐α (eIF2α) and eukaryotic elongation factor 2 (eEF2), and subsequent translational suppression. Finally, our data suggest that such translational suppression is critical to Aβ‐induced hyposynchrony of firing activity, but not the loss of synapses. Altogether, our study uncovers a novel mechanism by which Aβ triggers translational suppression and we reveal the participation of Fmr1 in altered neural plasticity associated with Aβ pathology. Our study may also provide information for a better understanding of Aβ‐induced cellular stress responses in AD.

NHE6 depletion corrects ApoE4-mediated synaptic impairments and reduces amyloid plaque load

Apolipoprotein E4 (ApoE4) is the most important and prevalent risk factor for late-onset Alzheimer’s disease (AD). The isoelectric point of ApoE4 matches the pH of the early endosome (EE), causing its delayed dissociation from ApoE receptors and hence impaired endolysosomal trafficking, disruption of synaptic homeostasis, and reduced amyloid clearance. We have shown that enhancing endosomal acidification by inhibiting the EE-specific sodium-hydrogen exchanger 6 (NHE6) restores vesicular trafficking and normalizes synaptic homeostasis. Remarkably and unexpectedly, loss of NHE6 (encoded by the gene Slc9a6) in mice effectively suppressed amyloid deposition even in the absence of ApoE4, suggesting that accelerated acidification of EEs caused by the absence of NHE6 occludes the effect of ApoE on amyloid plaque formation. NHE6 suppression or inhibition may thus be a universal, ApoE-independent approach to prevent amyloid buildup in the brain. These findings suggest a novel therapeutic approach for the prevention of AD by which partial NHE6 inhibition reverses the ApoE4-induced endolysosomal trafficking defect and reduces plaque load.

Metabolic Regulation of Glia and Their Neuroinflammatory Role in Alzheimer's Disease

Alzheimer's disease (AD) is an aging-related neurodegenerative disorder. It is characterized clinically by progressive memory loss and impaired cognitive function. Its progression occurs from neuronal synapse loss to amyloid pathology and Tau deposit which eventually leads to the compromised neuronal function. Neurons in central nervous tissue work in a composite and intricate network with the glia and vascular cells. Microglia and astrocytes are becoming the prime focus due to their involvement in various aspects of neurophysiology, such as trophic support to neurons, synaptic modulation, and brain surveillance. AD is also often considered as the sequela of prolonged metabolic dyshomeostasis. The neuron and glia have different metabolic profiles as cytosolic glycolysis and mitochondrial-dependent oxidative phosphorylation (OXPHOS), especially under dyshomeostasis or with aging pertaining to their unique genetic built-up. Various efforts are being put in to decipher the role of mitochondrial dynamics regarding their trafficking, fission/fusion imbalance, and mitophagy spanning over both neurons and glia to improve aging-related brain health. The mitochondrial dysfunction may lead to activation in various signaling mechanisms causing metabolic reprogramming in glia cells, further accelerating AD-related pathogenic events. The glycolytic-dominant astrocytes switch to the neurotoxic phenotype, i.e., disease-associated astrocyte under metabolic stress. The microglia also transform from resting to reactive phenotype, i.e., disease-associated microglia. It may also exist in otherwise a misconception an M1, glycolytic, or M2, an OXPHOS-dependent phenotype. Further, glial transformation plays a vital role in regulating hallmarks of AD pathologies like synapse maintenance, amyloid, and Tau clearance. In this updated review, we have tried to emphasize the metabolic regulation of glial reactivity, mitochondrial quality control mechanisms, and their neuroinflammatory response in Alzheimer's progression.

Age-related changes in brain phospholipids and bioactive lipids in the APP knock-in mouse model of Alzheimer's disease

Sustained brain chronic inflammation in Alzheimer’s disease (AD) includes glial cell activation, an increase in cytokines and chemokines, and lipid mediators (LMs), concomitant with decreased pro-homeostatic mediators. The inflammatory response at the onset of pathology engages activation of pro-resolving, pro-homeostatic LMs followed by a gradual decrease. We used an APP knock-in (App KI) AD mouse that accumulates β-amyloid (Aβ) and presents cognitive deficits (at 2 and 6 months of age, respectively) to investigate LMs, their precursors, biosynthetic enzymes and receptors, glial activation, and inflammatory proteins in the cerebral cortex and hippocampus at 2-, 4-, 8- and 18-month-old in comparison with wild-type (WT) mice. We used LC-mass-spectrometry and MALDI molecular imaging to analyze LMs and phospholipids, and immunochemistry for proteins. Our results revealed an age-specific lipid and cytokine profile, and glial activation in the App KI mice. Despite an early onset of Aβ pathology, pro-inflammatory and pro-resolving LMs were prominently increased only in the oldest age group. Furthermore, the LM biosynthetic enzymes increased, and their receptor expression decreased in the aged App KI mice. Arachidonic acid (AA)-containing phospholipid molecular species were elevated, correlating with decreased cPLA2 activity. MALDI molecular imaging depicted differential distribution of phospholipids according to genotype in hippocampal layers. Brain histology disclosed increased microglia proliferation starting from young age in the App KI mice, while astrocyte numbers were enhanced in older ages. Our results demonstrate that the brain lipidome is modified preferentially during aging as compared to amyloid pathology in the model studied here. However, alterations in phospholipids signal early pathological changes in membrane composition.

Detection of Synaptic Proteins in Microglia by Flow Cytometry

A growing body of evidence indicates that microglia actively remove synapses in vivo, thereby playing a key role in synaptic refinement and modulation of brain connectivity. This phenomenon was mainly investigated in immunofluorescence staining and confocal microscopy. However, a quantification of synaptic material in microglia using these techniques is extremely time-consuming and labor-intensive. To address this issue, we aimed to quantify synaptic proteins in microglia using flow cytometry. With this approach, we first showed that microglia from the healthy adult mouse brain contain a detectable level of VGLUT1 protein. Next, we found more than two-fold increased VGLUT1 immunoreactivity in microglia from the developing brain (P15) as compared to adult microglia. These data indicate that microglia-mediated synaptic pruning mostly occurs during the brain developmental period. We then quantified the VGLUT1 staining in microglia in two transgenic models characterized by pathological microglia-mediated synaptic pruning. In the 5xFAD mouse model of Alzheimer's disease (AD) microglia exhibited a significant increase in VGLUT1 immunoreactivity before the onset of amyloid pathology. Moreover, conditional deletion of TDP-43 in microglia, which causes a hyper-phagocytic phenotype associated with synaptic loss, also resulted in increased VGLUT1 immunoreactivity within microglia. This work provides a quantitative assessment of synaptic proteins in microglia, under homeostasis, and in mouse models of disease.

Both Amyloid-β Peptide and Tau Protein Are Affected by an Anti-Amyloid-β Antibody Fragment in Elderly 3xTg-AD Mice

Alzheimer's disease (AD) is the most common dementia worldwide. According to the amyloid hypothesis, the early accumulation of the Aβ-peptide triggers tau phosphorylation, synaptic dysfunction, and eventually neuronal death leading to cognitive impairment, as well as behavioral and psychological symptoms of dementia. ScFv-h3D6 is a single-chain variable fragment that has already shown its ability to diminish the amyloid burden in 5-month-old 3xTg-AD mice. However, tau pathology is not evident at this early stage of the disease in this mouse model. In this study, the effects of scFv-h3D6 on Aβ and tau pathologies have been assessed in 22-month-old 3xTg-AD mice. Briefly, 3xTg-AD female mice were treated for 2 weeks with scFv-h3D6 and compared with 3xTg-AD and non-transgenic (NTg) mice treated with PBS. The treatment with scFv-h3D6 was unequivocally effective in reducing the area of Aβ staining. Furthermore, a tendency for a reduction in tau levels was also observed after treatment that points to the interplay between Aβ and tau pathologies. The pro-inflammatory state observed in the 3xTg-AD mice did not progress after scFv-h3D6 treatment. In addition, the treatment did not alter the levels of apolipoprotein E or apolipoprotein J. Thus, a 2-week treatment with scFv-h3D6 was able to reduce AD-like pathology in elderly 3xTg-AD female mice.

Melatonin regulates mitochondrial dynamics and alleviates neuron damage in prion diseases

Prion diseases are neurodegenerative diseases associated with neuron damage and behavioral disorders in animals and humans. Melatonin is a potent antioxidant and is used to treat a variety of diseases. We investigated the neuroprotective effect of melatonin on prion-induced damage in N2a cells. N2a cells were pretreated with 10 μM melatonin for 1 hour followed by incubation with 100 μM PrP^106-126 for 24 hours. Melatonin markedly alleviated PrP^106-126-induced apoptosis of N2a cells, and inhibited PrP^106-126-induced mitochondrial abnormality and dysfunction, including mitochondrial fragmentation and overproduction of reactive oxygen species (ROS), suppression of ATP, reduced mitochondrial membrane potential (MMP), and altered mitochondrial dynamic proteins dynamin-related protein 1 (DRP1) and optic atrophy protein 1 (OPA1). Our findings identify that pretreatment with melatonin prevents the deleterious effects of PrPSc on mitochondrial function and dynamics, protects synapses and alleviates neuron damage. Melatonin could be a novel and effective medication in the therapy of prion diseases.

Cornel iridoid glycoside ameliorates cognitive deficits in APP/PS1/tau triple transgenic mice by attenuating amyloid-beta, tau hyperphosphorylation and neurotrophic dysfunction

Background

Targeted proteinopathy is involved in creating pharmacological agents that protect against Alzheimer disease (AD). Cornel iridoid glycoside (CIG) is an effective component derived from Cornus officinalis. The present study aimed to determine the effects of CIG on β-amyloid (Aβ) and tau pathology and the underlying mechanisms in APP/PS1/tau triple transgenic (3×Tg) model mice.

Methods

We intragastrically administered 16-month-old 3×Tg mice with CIG (100 and 200 mg/kg) daily for two months. Learning and memory abilities were determined using the Morris water maze (MWM) and object recognition tests (ORT). Amyloid plaques and Aβ40/42 and the expression of related proteins in the cerebral cortex and hippocampus of mice was determined by western blotting

Results

CIG improved learning and memory impairment in 3×Tg model mice, decreased amyloid plaque deposition, Aβ40/42 and the expression of full-length amyloid precursor protein, and increased levels of ADAM-10 (α-secretase), neprilysin (NEP), and insulin degrading enzyme (IDE) in the brains of the model mice. CIG also reduced tau hyperphosphorylation, and elevated phosphorylation level of GSK-3β at Ser9 and methylation of PP2A catalytic subunit C in the model mice. Moreover, CIG increased the expression of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and phosphorylated cAMP-responsive element binding protein (p-CREB) in the brain of 3×Tg mice.

Conclusions

CIG ameliorated learning and memory deficit via reducing Aβ content and, tau hyperphosphorylation and increasing neurotrophic factors in the brain of 3×Tg mice. These results suggest that CIG may be beneficial for AD therapy.

Safranal, an active ingredient of saffron, attenuates cognitive deficits in amyloid β-induced rat model of Alzheimer's disease: underlying mechanisms

Alzheimer's disease (AD) is the most prevalent neurodegenerative amyloid disorder with progressive deterioration of cognitive and memory skills. Despite many efforts, no decisive therapy yet exists for AD. Safranal is the active constituent of saffron essential oil with antioxidant, anti-inflammatory, and anti-apoptotic properties. In this study, the possible beneficial effect of safranal on cognitive deficits was evaluated in a rat model of AD induced by intrahippocampal amyloid beta (Aβ_1-40). Safranal was daily given p.o. (0.025, 0.1, and 0.2 ml/kg) post-surgery for 1 week and finally learning and memory were evaluated in addition to assessment of the involvement of oxidative stress, inflammation, and apoptosis. Findings showed that safranal treatment of amyloid β-microinjected rats dose-dependently improved cognition in Y-maze, novel-object discrimination, passive avoidance, and 8-arm radial arm maze tasks. Besides, safranal attenuated hippocampal level of malondialdehyde (MDA), reactive oxygen species (ROS), protein carbonyl, interleukin 1β (IL-1β), interleukin 6 (IL-6), tumor necrosis factor α (TNFα), nuclear factor-kappa B (NF-kB), apoptotic biomarkers including caspase 3 and DNA fragmentation, glial fibrillary acidic protein (GFAP), myeloperoxidase (MPO), and acetylcholinesterase (AChE) activity and improved superoxide dismutase (SOD) activity and mitochondrial membrane potential (MMP) with no significant effect on nitrite, catalase activity, and glutathione (GSH). Furthermore, safranal prevented CA1 neuronal loss due to amyloid β_1-40. In summary, safranal treatment of intrahippocampal amyloid beta_1-40-microinjected rats could prevent learning and memory decline via neuronal protection and at a molecular level through amelioration of apoptosis, oxidative stress, inflammation, cholinesterase activity, neutrophil infiltration, and also by preservation of mitochondrial integrity.

Suppression of the Peripheral Immune System Limits the Central Immune Response Following Cuprizone-Feeding: Relevance to Modelling Multiple Sclerosis

Cuprizone (CPZ) preferentially affects oligodendrocytes (OLG), resulting in demyelination. To investigate whether central oligodendrocytosis and gliosis triggered an adaptive immune response, the impact of combining a standard (0.2%) or low (0.1%) dose of ingested CPZ with disruption of the blood brain barrier (BBB), using pertussis toxin (PT), was assessed in mice. 0.2% CPZ(±PT) for 5 weeks produced oligodendrocytosis, demyelination and gliosis plus marked splenic atrophy (37%) and reduced levels of CD4 (44%) and CD8 (61%). Conversely, 0.1% CPZ(±PT) produced a similar oligodendrocytosis, demyelination and gliosis but a smaller reduction in splenic CD4 (11%) and CD8 (14%) levels and no splenic atrophy. Long-term feeding of 0.1% CPZ(±PT) for 12 weeks produced similar reductions in CD4 (27%) and CD8 (43%), as well as splenic atrophy (33%), as seen with 0.2% CPZ(±PT) for 5 weeks. Collectively, these results suggest that 0.1% CPZ for 5 weeks may be a more promising model to study the ‘inside-out’ theory of Multiple Sclerosis (MS). However, neither CD4 nor CD8 were detected in the brain in CPZ±PT groups, indicating that CPZ-mediated suppression of peripheral immune organs is a major impediment to studying the ‘inside-out’ role of the adaptive immune system in this model over long time periods. Notably, CPZ(±PT)-feeding induced changes in the brain proteome related to the suppression of immune function, cellular metabolism, synaptic function and cellular structure/organization, indicating that demyelinating conditions, such as MS, can be initiated in the absence of adaptive immune system involvement.

Liver Dysfunction as a Novel Player in Alzheimer's Progression: Looking Outside the Brain

Alzheimer's disease (AD) afflicts an estimated 20 million people worldwide and is the fourth-leading cause of death in the developed world. The most common cause of dementia in older individuals, AD is characterized by neuropathologies including synaptic and neuronal degeneration, amyloid plaques, and neurofibrillary tangles (NTFs). Amyloid plaques are primarily composed of amyloid-beta peptide (Aβ), which accumulates in the brains of patients with AD. Further, small aggregates termed Aβ oligomers are implicated in the synaptic loss and neuronal degeneration underlying early cognitive impairments. Whether Aβ accumulates in part because of dysregulated clearance from the brain remains unclear. The flow of substances (e.g., nutrients, drugs, toxins) in and out of the brain is mediated by the blood-brain-barrier (BBB). The BBB exhibits impairment in AD patients and animal models. The effect of BBB impairment on Aβ, and whether BBB function is affected by non-neurological pathologies that impair peripheral clearance requires further investigation. In particular, impaired peripheral clearance is a feature of nonalcoholic fatty liver disease (NAFLD), a spectrum of liver disorders characterized by accumulation of fat in the liver accompanied by varying degrees of inflammation and hepatocyte injury. NAFLD has reached epidemic proportions, with an estimated prevalence between 20% and 30% of the general population. This chronic condition may influence AD pathogenesis. This review article summarizes the current state of the literature linking NAFLD and AD, highlighting the role of the major Aβ efflux and clearance protein, the LRP-1 receptor, which is abundantly expressed in liver, brain, and vasculature.

miRNAs Identify Shared Pathways in Alzheimer's and Parkinson's Diseases

Despite the identification of several dozens of common genetic variants associated with Alzheimer's disease (AD) and Parkinson's disease (PD), most of the genetic risk remains uncharacterised. Therefore, it is important to understand the role of regulatory elements, such as miRNAs. Dysregulated miRNAs are implicated in AD and PD, with potential value in dissecting the shared pathophysiology between the two disorders. miRNAs relevant to both neurodegenerative diseases are related to axonal guidance, apoptosis, and inflammation, therefore, AD and PD likely arise from similar underlying biological pathway defects. Furthermore, pathways regulated by APP, L1CAM, and genes of the caspase family may represent promising therapeutic miRNA targets in AD and PD since they are targeted by dysregulated miRNAs in both disorders.