Translating the biology of aging into novel therapeutics for Alzheimer disease

Amyloid precursor protein and presenilin-1 knock-in immunodeficient mice exhibit intraneuronal Aβ pathology, microgliosis, and extensive neuronal loss

INTRODUCTION

Transgenic mice overexpressing familial Alzheimer's disease (AD) mutations (FAD) show non-physiological traits, and their immunocompetent backgrounds limit their use in AD immunotherapy research. Preclinical models that reflect human immune responses in AD are needed.

METHODS

Using CRISPR-Cas9, we developed single (NA) and double (NAPS) knock-in (KI) amyloid precursor protein (APP)KM670,671NL (Swedish) and presenilin 1 (PS 1)M146VFAD mutations on an immunodeficient NOG (NOD.Cg-PrkdcscidIl2rgtm1Sug/JicTac) background. The models were confirmed by Sanger sequencing and evaluated for AD-like pathology.

RESULTS

Both NA and NAPS mice developed pathology without overexpression artifacts. Mutation-induced upregulation of APP-CTF-β led to intraneuronal human amyloid beta (Aβ) (6E10) deposits and amyloid-associated microgliosis as early as 3 months, which increased with age. The addition of the PS 1M146V mutation doubled the amyloid load. The models displayed broad neuronal loss, resulting in brain atrophy in older mice.

DISCUSSION

These models replicate intraneuronal amyloid pathology and, with human immune reconstitution potential, enable novel studies of human immune responses in AD.

HIGHLIGHTS

A novel Alzheimer's disease (AD) knock-in (KI) mouse was developed and characterized on an immunodeficient NOG background. The model provides a platform for human immune studies and the evaluation of immunotherapies for AD. The KI mice demonstrate intraneuronal Aβ deposits and amyloid-associated microglial reactions. KI mice demonstrate extensive neuronal loss. Human immune reconstitution enables studies of infectious AD co-morbidities, such as the human immunodeficiency and herpes simplex viruses.

Examining the effects of extremely low-frequency magnetic fields on cognitive functions and functional brain markers in aged mice

Extremely low-frequency magnetic fields (ELF-MFs) are ubiquitously present in various environments of everyday life. While surveys from the World Health Organization (WHO) have not demonstrated the existence of ELF-MF-induced harmful consequences in healthy subjects, whether older adults are more vulnerable to the effects of residential and occupational ELF-MF exposure, and therefore may be at risk, remains unsettled. Here, we explored this potential health issue by investigating, in aged mice, the effects of chronic exposure to ELF-MFs (50 Hz ELF-MF at 1 mT for 8 h/day, 5 days/week for 12 consecutive weeks) on cognitive functions and expression profile of brain markers typically associated with aggravated aging or the development of Alzheimer`s disease (AD). Sham-exposed mice showed a significant age-related decline in spatial memory functions compared to young adult mice. However, this expected pattern was neither exacerbated nor counteracted by chronic exposure to ELF-MFs. No difference in hippocampal expression of APP-695, Aβ(1-42), S100b and GFAP proteins or in the pTau/Tau ratio was observed between sham- and ELF-MF-exposed aged mice, suggesting that chronic exposure to ELF-MFs does not aggravate aging and associated neuroinflammation, or promote pathological pathways involved in the initiation of AD. Because care should be taken in extrapolating these results to older adults with various comorbidities, applying current exposure limits to existing or new sensitive ELF-MF locations is recommended.

Inhibition of amyloid β aggregation and BACE1, and protective effect on SH-SY5Y cells, by p-terphenyl compounds from mushroom Thelephora aurantiotincta

The number of patients with Alzheimer's disease (AD) is expected to increase as the population ages. The amyloid cascade hypothesis is proposed as the pathogenic mechanism of AD. We report the isolation and structural determination of three new p-terphenyl compounds, thelephantin P (1), thelephantin Q (2), and thelephantin R (3), with four known compounds (4-7), from the fruiting bodies of Thelephora aurantiotincta Corner. We evaluated Aβ aggregation and BACE1 inhibitory activities and neuroprotective activities of these isolated compounds. Compound 1 was shown to be multi-inhibitors for AD. Compound 1 had an IC50 = 12.9 μM (Aβ), 6.3 μM (BACE1), and EC50 = 8.0 μM (neuroprotection), respectively. Therefore, these compounds are potential therapeutic agents for AD.

L-arginine mitigates choroid plexus changes in Alzheimer's disease rat model via oxidative/inflammatory burden and behavioral modulation

Aging is a risk factor for Alzheimer's disease (AD), leading to choroid plexus (CP) alterations. This study aimed to explore the possible therapeutic mechanisms of ARG on AD-induced CP changes. Sprague-Dawley rats were divided into 6 groups (n = 7 per group): adult, adult+ARG, aged, aged+ARG, aged+AD, and aged+AD+ARG groups. Evaluations were for Y-maze test, serum levels of oxidative/inflammatory markers, and serum and cerebrospinal fluid (CSF) markers of AD, histopathology, immunohistochemistry, and histomorphometry. The aged+AD group demonstrated a significant decline in maze test parameters, total antioxidant capacity (TAC), brain-derived neurotrophic factor (BDNF) levels, and vascular endothelial growth factor (VEGF) immunoexpression, while tumour necrosis factor-α (TNF-α), interleukin-1 beta (IL-1β), beta-amyloid (Aβ) levels and amyloid protein precursor (APP), and heat shock protein90 (HSP90) immunoexpressions were significantly increased. Sections of this group showed flat epitheliocytes, congested capillaries, connective tissue expansion, and degenerated endothelium. These parameters were modulated by ARG administration, via increased levels of TAC (1.37 vs 2.17 mmol/L), (p = 0.018) BDNF (serum: 48.50 vs 78.41; CSF: 4.07 vs 7.11 pg/ml) (p< 0.001), and VEGF (0.07 vs 0.26 OD) (p< 0.001), in addition to decreased levels of TNF-α (86.63 vs 41.39 pg/ml) (p< 0.001), IL-1β (96.04 vs 39.57 pg/ml) (p< 0.001), Aβ (serum: 67.40 vs 47.30; CSF: 189.26 vs 169.84 pg/ml) (p< 0.001), and HSP90 (0.54 vs 0.13 OD) (p< 0.001). In conclusion, ARG ameliorates the AD-associated CP changes, including histopathological, oxidative/inflammatory, and AD markers, and VEGF and HSP90 immunohistochemical alterations. Dietary ARG consumption is recommended to avoid AD progression in the elderly.

From Fundamentals to Innovation in Alzheimer's Disease: Molecular Findings and Revolutionary Therapies

Alzheimer's disease (AD) is a global health concern and the leading cause of dementia in the elderly. The prevalence of this neurodegenerative condition is projected to increase concomitantly with increased life expectancy, resulting in a significant economic burden. With very few FDA-approved disease-modifying drugs available for AD, there is an urgent need to develop new compounds capable of impeding the progression of the disease. Given the unclear etiopathogenesis of AD, this review emphasizes the underlying mechanisms of this condition. It explores not only well-studied aspects, such as the accumulation of Aβ plaques and neurofibrillary tangles, but also novel areas, including glymphatic and lymphatic pathways, microbiota and the gut-brain axis, serotoninergic and autophagy alterations, vascular dysfunction, the metal hypothesis, the olfactory pathway, and oral health. Furthermore, the potential molecular targets arising from all these mechanisms have been reviewed, along with novel promising approaches such as nanoparticle-based therapy, neural stem cell transplantation, vaccines, and CRISPR-Cas9-mediated genome editing techniques. Taking into account the overlap of these various mechanisms, individual and combination therapies emerge as the future direction in the AD strategy.

The Combined Effect of Green Tea, Saffron, Resveratrol, and Citicoline against Neurodegeneration Induced by Oxidative Stress in an In Vitro Model of Cognitive Decline

During ageing, the brain is vulnerable to a growing imbalance of the antioxidant defence system, resulting in increased oxidative stress. This condition may be mainly responsible for cognitive decline, resulting in synaptic transmission disruptions and the onset of neuronal dysfunction. In this context, developing efficient preventive and therapeutic strategies against increased oxidative stress and decreased antioxidant defence mechanisms should be considered a public health priority to promote healthy ageing. Therefore, the current study explored the benefits of a novel combination of green tea, saffron, trans-Reveratrol, and citicoline, called MIX, on improving intracellular processes to ameliorate the mechanisms linked to cognitive decline under oxidative stress conditions. First, the ability of MIX to cross the blood-brain barrier (BBB) was evaluated in an in vitro model, analysing TEER value and the specific tight junctions; second, the CCF-STTG1 cell line was pretreated with 200 µM H2O2 for 30 min to explore the effects of the single active compounds and their combination under oxidative stress conditions. Our results demonstrated for the first time the synergistic effects of the new combination to improve the absorption rate of individual agents through the BBB and maintain its integrity. Subsequently, further research was done to assess the positive role of the combination to counteract oxidative damage; as expected, MIX restored the neurodegenerative state activated by 200 µM H2O2, reducing mitochondrial damage, and improving survival pathways. Additionally, MIX acted as a regulator of both cellular energy metabolism and apoptosis, reducing the inflammatory state activated by oxidative stress. Finally, MIX can balance neurotrophin production to prevent mitochondrial disruption. In conclusion, MIX counteracted the adverse effects of brain oxidative stress, suggesting that this new proposed formulation prevents the molecular mechanisms underlying the onset of cognitive decline, even in support of conventional therapy.

Coupling of Alzheimer's Disease Genetic Risk Factors with Viral Susceptibility and Inflammation

Alzheimer's disease (AD) is a neurodegenerative disease characterized by persistent cognitive decline. Amyloid plaque deposition and neurofibrillary tangles are the main pathological features of AD brain, though mechanisms leading to the formation of lesions remain to be understood. Genetic efforts through genome-wide association studies (GWAS) have identified dozens of risk genes influencing the pathogenesis and progression of AD, some of which have been revealed in close association with increased viral susceptibilities and abnormal inflammatory responses in AD patients. In the present study, we try to present a list of AD candidate genes that have been shown to affect viral infection and inflammatory responses. Understanding of how AD susceptibility genes interact with the viral life cycle and potential inflammatory pathways would provide possible therapeutic targets for both AD and infectious diseases.

Exploring the effect of gut microbiome on Alzheimer's disease

Alzheimer's disease (AD) is the most widespread and irreversible form of dementia and accounts for more than half of dementia cases. The most significant risk factors for AD are aging-related exacerbations, degradation of anatomical pathways, environmental variables and mitochondrial dysfunction. Finding a decisive therapeutic solution is a major current issue. Nuanced interactions between major neuropathological mechanisms in AD in patients and microbiome have recently gained rising attention. The presence of bacterial amyloid in the gut triggers the immune system, resulting in increased immune feedbacks and endogenous neuronal amyloid within the CNS. Also, early clinical research revealed that changing the microbiome with beneficial bacteria or probiotics could affect brain function in AD. New approaches focus on the possible neuroprotective action of disease-modifying medications in AD. In the present review, we discuss the impact of the gut microbiota on the brain and review emerging research that suggests a disruption in the microbiota-brain axis can affect AD by mediating neuroinflammation. Such novel methods could help the development of novel therapeutics for AD.

Pyrogallol intermediates elicit beta-amyloid secretion via radical formation and alterations in intracellular trafficking, distinct from pyrogallol-generated superoxide

This study unveils a novel role of pyrogallol (PG), a recognized superoxide generator, in inducing beta-amyloid (Aβ) secretion in an Alzheimer's disease (AD) cellular model. Contrary to expectations, the analysis of dihydroethidium fluorescence and UV-VIS spectrum scanning reveals that Aβ secretion arises from PG reaction intermediates rather than superoxide or other by-products. Investigation into Aβ secretion mechanisms identifies dynasore-dependent endocytosis and BFA-dependent exocytosis as independent pathways, regulated by tiron, tempol, and superoxide dismutase. Cell-type specificity is observed, with 293sw cells showing both pathways, while H4sw cells and primary astrocytes from an AD animal model exclusively exhibit the Aβ exocytosis pathway. This exploration contributes to understanding PG's chemical reactions and provides insights into the interplay between environmental factors, free radicals, and AD, linking occupational PG exposure to AD risk as reported in the literature.

Agmatine as a novel intervention for Alzheimer's disease: Pathological insights and cognitive benefits

Alzheimer's disease (AD) is a devastating neurodegenerative disorder characterized by progressive cognitive decline and a significant societal burden. Despite extensive research and efforts of the multidisciplinary scientific community, to date, there is no cure for this debilitating disease. Moreover, the existing pharmacotherapy for AD only provides symptomatic support and does not modify the course of the illness or halt the disease progression. This is a significant limitation as the underlying pathology of the disease continues to progress leading to the deterioration of cognitive functions over time. In this milieu, there is a growing need for the development of new and more efficacious treatments for AD. Agmatine, a naturally occurring molecule derived from L-arginine, has emerged as a potential therapeutic agent for AD. Besides this, agmatine has been shown to modulate amyloid beta (Aβ) production, aggregation, and clearance, key processes implicated in AD pathogenesis. It also exerts neuroprotective effects, modulates neurotransmitter systems, enhances synaptic plasticity, and stimulates neurogenesis. Furthermore, preclinical and clinical studies have provided evidence supporting the cognition-enhancing effects of agmatine in AD. Therefore, this review article explores the promising role of agmatine in AD pathology and cognitive function. However, several limitations and challenges exist, including the need for large-scale clinical trials, optimal dosing, and treatment duration. Future research should focus on mechanistic investigations, biomarker studies, and personalized medicine approaches to fully understand and optimize the therapeutic potential of agmatine. Augmenting the use of agmatine may offer a novel approach to address the unmet medical need in AD and provide cognitive enhancement and disease modification for individuals affected by this disease.

A multimodal precision-prevention approach combining lifestyle intervention with metformin repurposing to prevent cognitive impairment and disability: the MET-FINGER randomised controlled trial protocol

BACKGROUND

Combining multimodal lifestyle interventions and disease-modifying drugs (novel or repurposed) could provide novel precision approaches to prevent cognitive impairment. Metformin is a promising candidate in view of the well-established link between type 2 diabetes (T2D) and Alzheimer's Disease and emerging evidence of its potential neuro-protective effects (e.g. vascular, metabolic, anti-senescence). MET-FINGER aims to test a FINGER 2.0 multimodal intervention, combining an updated FINGER multidomain lifestyle intervention with metformin, where appropriate, in an APOE ε4-enriched population of older adults (60-79 years) at increased risk of dementia.

METHODS

MET-FINGER is an international randomised, controlled, parallel-group, phase-IIb proof-of-concept clinical trial, where metformin is included through a trial-within-trial design. 600 participants will be recruited at three sites (UK, Finland, Sweden). Participants at increased risk of dementia based on vascular risk factors and cognitive screening, will be first randomised to the FINGER 2.0 intervention (lifestyle + metformin if eligible; active arm) or to receive regular health advice (control arm). Participants allocated to the FINGER 2.0 intervention group at risk indicators of T2D will be additionally randomised to receive metformin (2000 mg/day or 1000 mg/day) or placebo. The study duration is 2 years. The changes in global cognition (primary outcome, using a Neuropsychological Test Battery), memory, executive function, and processing speed cognitive domains; functional status; lifestyle, vascular, metabolic, and other dementia-related risk factors (secondary outcomes), will be compared between the FINGER 2.0 intervention and the control arm. The feasibility, potential interaction (between-groups differences in healthy lifestyle changes), and disease-modifying effects of the lifestyle-metformin combination will be exploratory outcomes. The lifestyle intervention is adapted from the original FINGER trial (diet, physical activity, cognitive training, monitoring of cardiovascular/metabolic risk factors, social interaction) to be consistently delivered in three countries. Metformin is administered as Glucophage®XR/SR 500, (500 mg oral tablets). The metformin/placebo treatment will be double blinded.

CONCLUSION

MET-FINGER is the first trial combining a multimodal lifestyle intervention with a putative repurposed disease-modifying drug for cognitive impairment prevention. Although preliminary, its findings will provide crucial information for innovative precision prevention strategies and form the basis for a larger phase-III trial design and future research in this field.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT05109169).

Mitochondrial Complex I and β-Amyloid Peptide Interplay in Alzheimer's Disease: A Critical Review of New and Old Little Regarded Findings

Alzheimer's disease (AD) is the most common neurodegenerative disorder and the main cause of dementia which is characterized by a progressive cognitive decline that severely interferes with daily activities of personal life. At a pathological level, it is characterized by the accumulation of abnormal protein structures in the brain-β-amyloid (Aβ) plaques and Tau tangles-which interfere with communication between neurons and lead to their dysfunction and death. In recent years, research on AD has highlighted the critical involvement of mitochondria-the primary energy suppliers for our cells-in the onset and progression of the disease, since mitochondrial bioenergetic deficits precede the beginning of the disease and mitochondria are very sensitive to Aβ toxicity. On the other hand, if it is true that the accumulation of Aβ in the mitochondria leads to mitochondrial malfunctions, it is otherwise proven that mitochondrial dysfunction, through the generation of reactive oxygen species, causes an increase in Aβ production, by initiating a vicious cycle: there is therefore a bidirectional relationship between Aβ aggregation and mitochondrial dysfunction. Here, we focus on the latest news-but also on neglected evidence from the past-concerning the interplay between dysfunctional mitochondrial complex I, oxidative stress, and Aβ, in order to understand how their interplay is implicated in the pathogenesis of the disease.

Reverse Electron Transport at Mitochondrial Complex I in Ischemic Stroke, Aging, and Age-Related Diseases

Stroke is one of the leading causes of morbidity and mortality worldwide. A main cause of brain damage by stroke is ischemia-reperfusion (IR) injury due to the increased production of reactive oxygen species (ROS) and energy failure caused by changes in mitochondrial metabolism. Ischemia causes a build-up of succinate in tissues and changes in the mitochondrial NADH: ubiquinone oxidoreductase (complex I) activity that promote reverse electron transfer (RET), in which a portion of the electrons derived from succinate are redirected from ubiquinol along complex I to reach the NADH dehydrogenase module of complex I, where matrix NAD+ is converted to NADH and excessive ROS is produced. RET has been shown to play a role in macrophage activation in response to bacterial infection, electron transport chain reorganization in response to changes in the energy supply, and carotid body adaptation to changes in the oxygen levels. In addition to stroke, deregulated RET and RET-generated ROS (RET-ROS) have been implicated in tissue damage during organ transplantation, whereas an RET-induced NAD+/NADH ratio decrease has been implicated in aging, age-related neurodegeneration, and cancer. In this review, we provide a historical account of the roles of ROS and oxidative damage in the pathogenesis of ischemic stroke, summarize the latest developments in our understanding of RET biology and RET-associated pathological conditions, and discuss new ways to target ischemic stroke, cancer, aging, and age-related neurodegenerative diseases by modulating RET.

Sex-specific declines in cholinergic-targeting tRNA fragments in the nucleus accumbens in Alzheimer's disease

Introduction

Females with Alzheimer's disease (AD) suffer accelerated dementia and loss of cholinergic neurons compared to males, but the underlying mechanisms are unknown. Seeking causal contributors to both these phenomena, we pursued changes in tRNA fragments (tRFs) targeting cholinergic transcripts (CholinotRFs).

Methods

We analyzed small RNA-sequencing data from the nucleus accumbens (NAc) brain region which is enriched in cholinergic neurons, compared to hypothalamic or cortical tissues from AD brains; and explored small RNA expression in neuronal cell lines undergoing cholinergic differentiation.

Results

NAc CholinotRFs of mitochondrial genome origin showed reduced levels that correlated with elevations in their predicted cholinergic-associated mRNA targets. Single cell RNA seq from AD temporal cortices showed altered sex-specific levels of cholinergic transcripts in diverse cell types; inversely, human-originated neuroblastoma cells under cholinergic differentiation presented sex-specific CholinotRF elevations.

Discussion

Our findings support CholinotRFs contributions to cholinergic regulation, predicting their involvement in AD sex-specific cholinergic loss and dementia.

Prelimbic Cortical Stimulation with L-methionine Enhances Cognition through Hippocampal DNA Methylation and Neuroplasticity Mechanisms

Declining global DNA methylation and cognitive impairment are reported to occur in the normal aging process. It is not known if DNA methylation plays a role in the efficacy of memory-enhancing therapies. In this study, aged animals were administered prelimbic cortical deep brain stimulation (PrL DBS) and/or L-methionine (MET) treatment. We found that PrL DBS and MET (MET-PrL DBS) co-administration resulted in hippocampal-dependent spatial memory enhancements in aged animals. Molecular data suggested MET-PrL DBS induced DNA methyltransferase DNMT3a-dependent methylation, robust synergistic upregulation of neuroplasticity-related genes, and simultaneous inhibition of the memory-suppressing gene calcineurin in the hippocampus. We further found that MET-PrL DBS also activated the PKA-CaMKIIα-BDNF pathway, increased hippocampal neurogenesis, and enhanced dopaminergic and serotonergic neurotransmission. We next inhibited the activity of DNA methyltransferase (DNMT) by RG108 infusion in the hippocampus of young animals to establish a causal relationship between DNMT activity and the effects of PrL DBS. Hippocampal DNMT inhibition in young animals was sufficient to recapitulate the behavioral deficits observed in aged animals and abolished the memory-enhancing and molecular effects of PrL DBS. Our findings implicate hippocampal DNMT as a therapeutic target for PrL DBS and pave way for the potential use of non-invasive neuromodulation modalities against dementia.

miRNAs and Alzheimer's Disease: Exploring the Role of Inflammation and Vitamin E in an Old-Age Population

Alzheimer's disease (AD) is the most frequent cause of dementia worldwide and represents one of the leading factors for severe disability in older persons. Although its etiology is not fully known yet, AD may develop due to multiple factors, including inflammation and oxidative stress, conditions where microRNAs (miRNAs) seem to play a pivotal role as a molecular switch. All these aspects may be modulated by nutritional factors. Among them, vitamin E has been widely studied in AD, given the plausibility of its various biological functions in influencing neurodegeneration. From a cohort of old-aged people, we measured eight vitamin E forms (tocopherols and tocotrienols), thirty cytokines/chemokines, and thirteen exosome-extracted miRNAs in plasma of subjects suffering from subjects affected by AD and age-matched healthy controls (HC). The sample population included 80 subjects (40 AD and 40 HC) with a mean age of 77.6 ± 3.8 years, mostly women (45; 56.2%). Of the vitamin E forms, only α-tocopherol differed between groups, with significantly lower levels in AD. Regarding the examined inflammatory molecules, G-CSF, GM-CSF, INF-α2, IL-3, and IL-8 were significantly higher and IL-17 lower in AD than HC. Among all miRNAs examined, AD showed downregulation of miR-9, miR-21, miR29-b, miR-122, and miR-132 compared to controls. MiR-122 positively and significantly correlated with some inflammatory molecules (GM-CSF, INF-α2, IL-1α, IL-8, and MIP-1β) as well as with α-tocopherol even after correction for age and gender. A final binary logistic regression analysis showed that α-tocopherol serum levels were associated with a higher AD probability and partially mediated by miR-122. Our results suggest an interplay between α-tocopherol, inflammatory molecules, and microRNAs in AD, where miR-122 may be a good candidate as modulating factor.

Progranulin mutations in clinical and neuropathological Alzheimer's disease

INTRODUCTION

Progranulin (GRN) mutations occur in frontotemporal lobar degeneration (FTLD) and in Alzheimer's disease (AD), often with TDP-43 pathology.

METHODS

We determined the frequency of rs5848 and rare, pathogenic GRN mutations in two autopsy and one family cohort. We compared Braak stage, β-amyloid load, hyperphosphorylated tau (PHFtau) tangle density and TDP-43 pathology in GRN carriers and non-carriers.

RESULTS

Pathogenic GRN mutations were more frequent in all cohorts compared to the Genome Aggregation Database (gnomAD), but there was no evidence for association with AD. Pathogenic GRN carriers had significantly higher PHFtau tangle density adjusting for age, sex and APOE ε4 genotype. AD patients with rs5848 had higher frequencies of hippocampal sclerosis and TDP-43 deposits. Twenty-two rare, pathogenic GRN variants were observed in the family cohort.

DISCUSSION

GRN mutations in clinical and neuropathological AD increase the burden of tau-related brain pathology but show no specific association with β-amyloid load or AD.

Focal-type, but not Diffuse-type, Amyloid Beta Plaques are Correlated with Alzheimer's Neuropathology, Cognitive Dysfunction, and Neuroinflammation in the Human Hippocampus

Amyloid beta (Aβ) plaques are one of the hallmarks of Alzheimer’s disease (AD). However, currently available anti-amyloid therapies fail to show effectiveness in the treatment of AD in humans. It has been found that there are different types of Aβ plaque (diffuse and focal types) in the postmortem human brain. In this study, we aimed to investigate the correlations among different types of Aβ plaque and AD-related neuropathological and cognitive changes based on a postmortem human brain bank in China. The results indicated that focal plaques, but not diffuse plaques, significantly increased with age in the human hippocampus. We also found that the number of focal plaques was positively correlated with the severity of AD-related neuropathological changes (measured by the “ABC” scoring system) and cognitive decline (measured by the Everyday Cognitive Insider Questionnaire). Furthermore, most of the focal plaques were co-localized with neuritic plaques (identified by Bielschowsky silver staining) and accompanied by microglial and other inflammatory cells. Our findings suggest the potential of using focal-type but not general Aβ plaques as biomarkers for the neuropathological evaluation of AD.

Arc Regulates Transcription of Genes for Plasticity, Excitability and Alzheimer’s Disease

The immediate early gene Arc is a master regulator of synaptic function and a critical determinant of memory consolidation. Here, we show that Arc interacts with dynamic chromatin and closely associates with histone markers for active enhancers and transcription in cultured rat hippocampal neurons. Both these histone modifications, H3K27Ac and H3K9Ac, have recently been shown to be upregulated in late-onset Alzheimer’s disease (AD). When Arc induction by pharmacological network activation was prevented using a short hairpin RNA, the expression profile was altered for over 1900 genes, which included genes associated with synaptic function, neuronal plasticity, intrinsic excitability, and signalling pathways. Interestingly, about 100 Arc-dependent genes are associated with the pathophysiology of AD. When endogenous Arc expression was induced in HEK293T cells, the transcription of many neuronal genes was increased, suggesting that Arc can control expression in the absence of activated signalling pathways. Taken together, these data establish Arc as a master regulator of neuronal activity-dependent gene expression and suggest that it plays a significant role in the pathophysiology of AD.

Novel effective small-molecule inhibitors of protein kinases related to tau pathology in Alzheimer's disease

Background: Alzheimer's disease (AD) drugs in therapy are limited to acetylcholine esterase inhibitors and memantine. Newly developed drugs against a single target structure have an insufficient effect on symptomatic AD patients. Results: Novel aromatically anellated pyridofuranes have been evaluated for inhibition of AD-relevant protein kinases cdk1, cdk2, gsk-3b and Fyn. Best activities have been found for naphthopyridofuranes with a hydroxyl function as part of the 5-substituent and a hydrogen or halogen substituent in the 8-position. Best results in nanomolar ranges were found for benzopyridofuranes with a 6-hydroxy and a 3-alkoxy substitution or an exclusive 6-alkoxy substituent. Conclusion: First lead compounds were identified inhibiting two to three kinases in nanomolar ranges to be qualified as an innovative approach for AD multitargeting.

Update on new trend and progress of the mechanism of polysaccharides in the intervention of Alzheimer's disease, based on the new understanding of relevant theories: A review

Alzheimer's disease (AD), a neurodegenerative disease with insidious onset and progressive progression, is the main type of dementia. Currently, there is no specific cure for the disease. At the same time, a series of drug developments based on the classic theory, the Aβ cascade hypothesis, have not completed phase III clinical trials, challenging the hypothesis. Polysaccharides obtained from natural products can be used in the treatment of AD, which has attracted academic attention due to its advantages of multi-target, multi-channel, no or modest side effects. The TCM syndrome type of AD is mainly "qi and blood deficiency, kidney essence deficiency", and the medicine is mainly used to replenish qi and blood, kidney and bone marrow. Thus, there has been extensive and in-depth research on polysaccharides obtained from tonic Chinese herbal medicine in China. Based on this background, this paper evaluated the effects and mechanisms of natural polysaccharides on AD by combing and screening English and related literature in recent 5 years and summarized the extraction process and structure-activity relationship of polysaccharides.

Manganese-enhanced magnetic resonance imaging method detects age-related impairments in axonal transport in mice and attenuation of the impairments by a microtubule-stabilizing compound

In this study a manganese-enhanced magnetic resonance imaging (MEMRI) method was developed for mice for measuring axonal transport (AXT) rates in real time in olfactory receptor neurons, which project from the olfactory epithelium to the olfactory neuronal layer of the olfactory bulb. Using this MEMRI method, two major experiments were conducted: 1) an evaluation of the effects of age on AXT rates and 2) an evaluation of the brain-penetrant, microtubule-stabilizing agent, Epothilone D for effect on AXT rates in aged mice. In these studies, we improved upon previous MEMRI approaches to develop a method where real-time measurements (32 time points) of AXT rates in mice can be determined over a single (approximately 100 min) scanning session. In the age comparisons, AXT rates were significantly higher in young (mean age ∼4.0 months old) versus aged (mean age ∼24.5 months old) mice. Moreover, in aged mice, eight weeks of treatment with Epothilone D, (0.3 and 1.0 mg/kg) was associated with statistically significant increases in AXT rates compared to vehicle-treated subjects. These experiments conducted in a living mammalian model (i.e., wild type, C57BL/6 mice), using a new modified MEMRI method, thus provide further evidence that the process of aging leads to decreases in AXT rates in the brain and they further support the argument that microtubule-based therapeutic strategies designed to improve AXT rates have potential for age-related neurological disorders.

Inhibitory Effects of Macelignan on Tau Phosphorylation and Aβ Aggregation in the Cell Model of Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder mainly affecting old population. In this study, two Tau overexpressing cell lines (SH-SY5Y/Tau and HEK293/Tau), N2a/SweAPP cell line, and 3× Transgene (APPswe/PS1M146V/TauP301L) mouse primary nerve cell lines were used as AD models to study the activity and molecular mechanism of macelignan, a natural compound extracted from Myristica fragrans, against AD. Our study showed that macelignan could reduce the phosphorylation of Tau at Thr 231 site, Ser 396 site, and Ser 404 site in two overexpressing Tau cell lines. It also could decrease the phosphorylation of Tau at Ser 404 site in mouse primary neural cells. Further investigation of its mechanism found that macelignan could reduce the phosphorylation of Tau by increasing the level of autophagy and enhancing PP2A activity in Tau overexpressing cells. Additionally, macelignan could activate the PERK/eIF2α signaling pathway to reduce BACE1 translation, which further inhibits the cleavage of APP and ultimately suppresses Aβ deposition in N2a/SweAPP cells. Taken together, our results indicate that macelignan has the potential to be developed as a treatment for AD.

Biological aging processes underlying cognitive decline and neurodegenerative disease

Alzheimer's disease and related dementias (ADRD) are among the top contributors to disability and mortality in later life. As with many chronic conditions, aging is the single most influential factor in the development of ADRD. Even among older adults who remain free of dementia throughout their lives, cognitive decline and neurodegenerative changes are appreciable with advancing age, suggesting shared pathophysiological mechanisms. In this Review, we provide an overview of changes in cognition, brain morphology, and neuropathological protein accumulation across the lifespan in humans, with complementary and mechanistic evidence from animal models. Next, we highlight selected aging processes that are differentially regulated in neurodegenerative disease, including aberrant autophagy, mitochondrial dysfunction, cellular senescence, epigenetic changes, cerebrovascular dysfunction, inflammation, and lipid dysregulation. We summarize research across clinical and translational studies to link biological aging processes to underlying ADRD pathogenesis. Targeting fundamental processes underlying biological aging may represent a yet relatively unexplored avenue to attenuate both age-related cognitive decline and ADRD. Collaboration across the fields of geroscience and neuroscience, coupled with the development of new translational animal models that more closely align with human disease processes, is necessary to advance novel therapeutic discovery in this realm.

Mechanisms of Mitochondrial Malfunction in Alzheimer’s Disease: New Therapeutic Hope

Mitochondria play a critical role in neuron viability or death as it regulates energy metabolism and cell death pathways. They are essential for cellular energy metabolism, reactive oxygen species production, apoptosis, Ca⁺⁺ homeostasis, aging, and regeneration. Mitophagy and mitochondrial dynamics are thus essential processes in the quality control of mitochondria. Improvements in several fundamental features of mitochondrial biology in susceptible neurons of AD brains and the putative underlying mechanisms of such changes have made significant progress. AD's etiology has been reported by mitochondrial malfunction and oxidative damage. According to several recent articles, a continual fusion and fission balance of mitochondria is vital in their normal function maintenance. As a result, the shape and function of mitochondria are inextricably linked. This study examines evidence suggesting that mitochondrial dysfunction plays a significant early impact on AD pathology. Furthermore, the dynamics and roles of mitochondria are discussed with the link between mitochondrial malfunction and autophagy in AD has also been explored. In addition, recent research on mitochondrial dynamics and mitophagy in AD is also discussed in this review. It also goes into how these flaws affect mitochondrial quality control. Furthermore, advanced therapy techniques and lifestyle adjustments that lead to improved management of the dynamics have been demonstrated, hence improving the conditions that contribute to mitochondrial dysfunction in AD.

Short term treatment with a cocktail of rapamycin, acarbose and phenylbutyrate delays aging phenotypes in mice

Pharmaceutical intervention of aging requires targeting multiple pathways, thus there is rationale to test combinations of drugs targeting different but overlapping processes. In order to determine if combining drugs shown to extend lifespan and healthy aging in mice would have greater impact than any individual drug, a cocktail diet containing 14 ppm rapamycin, 1000 ppm acarbose, and 1000 ppm phenylbutyrate was fed to 20-month-old C57BL/6 and HET3 4-way cross mice of both sexes for three months. Mice treated with the cocktail showed a sex and strain-dependent phenotype consistent with healthy aging including decreased body fat, improved cognition, increased strength and endurance, and decreased age-related pathology compared to mice treated with individual drugs or control. The severity of age-related lesions in heart, lungs, liver, and kidney was consistently decreased in mice treated with the cocktail compared to mice treated with individual drugs or control, suggesting an interactive advantage of the three drugs. This study shows that a combination of three drugs, each previously shown to enhance lifespan and health span in mice, is able to delay aging phenotypes in middle-aged mice more effectively than any individual drug in the cocktail over a 3-month treatment period.

Blood biomarkers for cognitive decline and clinical progression in a Mexican American cohort

Introduction: The clinical translation of biofluid markers for dementia requires validation in diverse cohorts. The study goal was to evaluate if blood biomarkers reflecting diverse pathophysiological processes predict disease progression in Mexican American adults. Methods: Mexican American adults (n = 745), 50 years of age and older, completed annual assessments over a mean of 4 years. Serum collected at baseline was assayed for total tau, neurofilament light (NFL), ubiquitin carboxyl-terminal hydrolase LI, glial fibrillary acidic protein (GFAP), soluble cluster of differentiation 14 (sCD14), and chitinase-3-like protein 1 (YKL-40). Results: Higher GFAP and NFL were associated with global cognitive decline. Only GFAP was associated with increased incident dementia risk (hazard ratio: 1.611 (95% confidence interval: 1.204-2.155)) and inclusion of additional biomarkers did not improve model fit. Discussion: Among a panel of six blood biomarkers previously associated with neurodegenerative disease, only GFAP predicted incident dementia in our cohort. The findings suggest that blood GFAP levels may aid dementia-risk prediction among Mexican American adults.

Cannabinol inhibits oxytosis/ferroptosis by directly targeting mitochondria independently of cannabinoid receptors

The oxytosis/ferroptosis regulated cell death pathway recapitulates many features of mitochondrial dysfunction associated with the aging brain and has emerged as a potential key mediator of neurodegeneration. It has thus been proposed that the oxytosis/ferroptosis pathway can be used to identify novel drug candidates for the treatment of age-associated neurodegenerative diseases that act by preserving mitochondrial function. Previously, we identified cannabinol (CBN) as a potent neuroprotector. Here, we demonstrate that not only does CBN protect nerve cells from oxytosis/ferroptosis in a manner that is dependent on mitochondria and it does so independently of cannabinoid receptors. Specifically, CBN directly targets mitochondria and preserves key mitochondrial functions including redox regulation, calcium uptake, membrane potential, bioenergetics, biogenesis, and modulation of fusion/fission dynamics that are disrupted following induction of oxytosis/ferroptosis. These protective effects of CBN are at least partly mediated by the promotion of endogenous antioxidant defenses and the activation of AMP-activated protein kinase (AMPK) signaling. Together, our data highlight the potential of mitochondrially-targeted compounds such as CBN as novel oxytotic/ferroptotic inhibitors to rescue mitochondrial dysfunction as well as opportunities for the discovery and development of future neurotherapeutics.

Alcohol-Induced Neuroinflammatory Response and Mitochondrial Dysfunction on Aging and Alzheimer's Disease

Mitochondria are essential organelles central to various cellular functions such as energy production, metabolic pathways, signaling transduction, lipid biogenesis, and apoptosis. In the central nervous system, neurons depend on mitochondria for energy homeostasis to maintain optimal synaptic transmission and integrity. Deficiencies in mitochondrial function, including perturbations in energy homeostasis and mitochondrial dynamics, contribute to aging, and Alzheimer's disease. Chronic and heavy alcohol use is associated with accelerated brain aging, and increased risk for dementia, especially Alzheimer's disease. Furthermore, through neuroimmune responses, including pro-inflammatory cytokines, excessive alcohol use induces mitochondrial dysfunction. The direct and indirect alcohol-induced neuroimmune responses, including pro-inflammatory cytokines, are critical for the relationship between alcohol-induced mitochondrial dysfunction. In the brain, alcohol activates microglia and increases inflammatory mediators that can impair mitochondrial energy production, dynamics, and initiate cell death pathways. Also, alcohol-induced cytokines in the peripheral organs indirectly, but synergistically exacerbate alcohol's effects on brain function. This review will provide recent and advanced findings focusing on how alcohol alters the aging process and aggravates Alzheimer's disease with a focus on mitochondrial function. Finally, we will contextualize these findings to inform clinical and therapeutic approaches towards Alzheimer's disease.

The adaptive aging brain

The aging brain is shaped by many structural and functional alterations. Recent cross-disciplinary efforts have uncovered powerful and integrated adaptive mechanisms that promote brain health and prevent functional decline during aging. Here, we review some of the most robust adaptive mechanisms and how they can be engaged to protect, and restore the aging brain.

An App knock-in rat model for Alzheimer's disease exhibiting Aβ and tau pathologies, neuronal death and cognitive impairments

A major obstacle in Alzheimer's disease (AD) research is the lack of predictive and translatable animal models that reflect disease progression and drug efficacy. Transgenic mice overexpressing amyloid precursor protein (App) gene manifest non-physiological and ectopic expression of APP and its fragments in the brain, which is not observed in AD patients. The App knock-in mice circumvented some of these problems, but they do not exhibit tau pathology and neuronal death. We have generated a rat model, with three familiar App mutations and humanized Aβ sequence knocked into the rat App gene. Without altering the levels of full-length APP and other APP fragments, this model exhibits pathologies and disease progression resembling those in human patients: deposit of Aβ plaques in relevant brain regions, microglia activation and gliosis, progressive synaptic degeneration and AD-relevant cognitive deficits. Interestingly, we have observed tau pathology, neuronal apoptosis and necroptosis and brain atrophy, phenotypes rarely seen in other APP models. This App knock-in rat model may serve as a useful tool for AD research, identifying new drug targets and biomarkers, and testing therapeutics.

Extending human healthspan and longevity: a symposium report

For many years, it was believed that the aging process was inevitable and that age-related diseases could not be prevented or reversed. The geroscience hypothesis, however, posits that aging is, in fact, malleable and, by targeting the hallmarks of biological aging, it is indeed possible to alleviate age-related diseases and dysfunction and extend longevity. This field of geroscience thus aims to prevent the development of multiple disorders with age, thereby extending healthspan, with the reduction of morbidity toward the end of life. Experts in the field have made remarkable advancements in understanding the mechanisms underlying biological aging and identified ways to target aging pathways using both novel agents and repurposed therapies. While geroscience researchers currently face significant barriers in bringing therapies through clinical development, proof-of-concept studies, as well as early-stage clinical trials, are underway to assess the feasibility of drug evaluation and lay a regulatory foundation for future FDA approvals in the future.

Predictors of Healthcare Utilization Among Older Adults with Moderate to Severe Cognitive Limitations in Ghana: A Cross-Sectional Analysis of the WHO Study on Global Ageing and Adult Health (SAGE) Wave 1

BACKGROUND

As the number of older adults in Ghana keeps increasing, so does the prevalence of aging-related diseases and conditions that tend to lead to cognitive decline. However, knowledge on the predicting factors of healthcare utilization among older adults with cognitive limitations is still scarce.

OBJECTIVE

This study examines the predictive factors of healthcare-seeking behavior among older adults with moderate-to-severe cognitive limitations in Ghana.

METHODS

Based on Andersen's behavioral model of health service utilization, the study analyzed data from 3106 older adults with moderate to severe cognitive limitations in Ghana aged 50+ using Bivariate Probit Regression and the Heckman Selection Model.

RESULTS

Results showed that individuals who were aged 75+, living in urban settlements, educated, higher income levels and parents who had some level of education, pension benefits, and both mandatory and voluntary health insurance were more likely to seek inpatient care. Enabling resources such as the national health insurance scheme and other types of medical insurance, household income, pension benefits, and predisposition factors like education influenced outpatient and inpatient healthcare consumption for older adults with moderate to severe cognitive limitations but had little influence on the choice of healthcare facility except for health insurance.

CONCLUSION

Since the healthcare-seeking behavior of older adults with moderate-to-severe cognitive limitations is driven by an amalgamation of several internal and external factors, there is a need for policy change to understand and cautiously incorporate these factors into the decision to improve equitable access to healthcare services for these individuals, as not all sizes fit all in providing quality care for them.

iPSC-derived cortical neurons to study sporadic Alzheimer disease: A transcriptome comparison with post-mortem brain samples

Alzheimer's disease (AD) is the most common cause of dementia, characterized by the progressive impairment of cognition and memory loss. Sporadic AD (sAD) represents approximately 95 % of the AD cases and is induced by a complex interplay between genetic and environmental factors called "Alzheimerogens". Heavy metals (e.g. copper) and pesticides (e.g. fipronil) can affect many AD-related processes, including neuroinflammation (considered as AD-inducing factor). Research would benefit from in vitro models to investigate effects of Alzheimerogens. We compared transcriptomics changes in sAD induced pluripotent stem cell (iPSC) derived cortical neurons to differentially expressed genes (DEGs) identified in post-mortem AD brain tissue. These analyses showed that many AD-related processes could be identified in the sAD iPSC-derived neurons, and furthermore, could even identify more DEGs functioning in these processes than post-mortem AD-brain tissue. Thereafter, we exposed the iPSCs to AD-inducing factors (copper(II)chloride, fipronil sulfone and an inflammatory cytokine cocktail). Cytokine exposure induced expression of immune related genes while copper-exposure affected genes involved in lipid and cholesterol metabolism, which are known AD-related processes. Fipronil-exposure did not result in significant transcriptomic changes, although prolonged exposures or higher doses may be necessary. Overall, we show that iPSC-derived cortical neurons can be beneficial in vitro models to identify Alzheimerogens and AD-related molecular mechanisms.

Autophagy in Alzheimer's disease pathogenesis: Therapeutic potential and future perspectives

Alzheimer's disease (AD) is a complex neurodegenerative disease in the elderly and the most common cause of human dementia. AD is characterized by accumulation of abnormal protein aggregates including amyloid plaques (composed of beta-amyloid (Aβ) peptides) and neurofibrillary tangles (formed by hyper-phosphorylated tau protein). Synaptic plasticity, neuroinflammation, calcium signaling etc. also show dysfunction in AD patients. Autophagy is an evolutionarily conserved lysosome-dependent cellular event in eukaryotes. It is closely linked to modulation of protein metabolism, through which damaged organelles and mis-folded proteins are degraded and then recycled to maintain protein homeostasis. Accumulating evidence has shown that impaired autophagy also contributes to AD pathogenesis. In the present review, we highlight the role of autophagy, including bulk and selective autophagy, in regulating metabolic circuits in AD pathogenesis. We also discuss the potential and future perspectives of autophagy-inducing strategies in AD therapeutics.

The Potential Effect of Insulin on AChE and Its Interactions with Rivastigmine In Vitro

There is no definite cure for Alzheimer’s disease (AD) due to its multifactorial origin. Drugs that inhibit acetylcholinesterase (AChE), such as rivastigmine, are promising symptomatic treatments for AD. Emerging evidence suggests that insulin therapy can hinder several aspects of AD pathology. Insulin has been shown to modify the activity of AChE, but it is still unknown how insulin and AChE interact. Combination therapy, which targets several features of the disease based on existing medications, can provide a worthy therapy option for AD management. However, to date, no studies have examined the potential interaction of insulin with AChE and/or rivastigmine in vitro. In the present study, we employed the Response Surface Methodology (RSM) as an in vitro assessment to investigate the effect of insulin on both AChE activity and rivastigmine inhibitory action using a common spectrophotometric assay for cholinesterase activity, Ellman’s method. Our results showed that insulin, even at high concentrations, has an insignificant effect on both the activity of AChE and rivastigmine’s inhibitory action. The variance of our data is near zero, which means that the dispersion is negligible. However, to improve our understanding of the possible interaction of insulin and rivastigmine, or its target AChE, more in silico modelling and in vivo studies are needed.

Dynamic-Inspired Perspective on the Molecular Inhibitor of Tau Aggregation by Glucose Gallates Based on Human Neurons

A molecular inhibitor of tau protein aggregation offers an attractive therapeutic possibility as disease-modifying treatment of Alzheimer's disease. However, the ineffectiveness as well as adjoint toxicity due to superficial understanding of the inhibition mechanism has hindered drug development. Conventional approaches for screening drug ligands rely on compatible docking with the well-defined structure of a protein receptor. Therefore, the design of tau aggregation inhibitors has been inevitably hindered by the unstructured, highly dynamic nature of the tau protein. This paper suggested a new strategy for reducing tau aggregation through a dynamic process of conformational isomerization. A group of glucose gallate derivatives were selected as tau aggregation inhibitors. These star-shaped molecules have a biocompatible glucose core surrounded by several gallic acid polyphenol arms, which can bind to peptide chains at different sites, probably through hydrogen bonds and π-π stacking. Theoretically, by elevating the saddle point on the potential energy surfaces (PES) of proteins, the barrier in the dynamic pathway of peptide isomerization, glucose gallates effectively inhibit tau aggregation through a dynamic mechanism. A tau cell model based on human neurons was constructed. For the first time, we confirmed that the moderate thermodynamic binding of the molecular ligand to the tau peptide chain can not only prevent the isomerization of the peptide chain leading to aggregation but also avoid toxicity resulting from the dissociation of tau from microtubules.

A multitude of signaling pathways associated with Alzheimer's disease and their roles in AD pathogenesis and therapy

The exact molecular mechanisms associated with Alzheimer's disease (AD) pathology continue to represent a mystery. In the past decades, comprehensive data were generated on the involvement of different signaling pathways in the AD pathogenesis. However, the utilization of signaling pathways as potential targets for the development of drugs against AD is rather limited due to the immense complexity of the brain and intricate molecular links between these pathways. Therefore, finding a correlation and cross-talk between these signaling pathways and establishing different therapeutic targets within and between those pathways are needed for better understanding of the biological events responsible for the AD-related neurodegeneration. For example, autophagy is a conservative cellular process that shows link with many other AD-related pathways and is crucial for maintenance of the correct cellular balance by degrading AD-associated pathogenic proteins. Considering the central role of autophagy in AD and its interplay with many other pathways, the finest therapeutic strategy to fight against AD is the use of autophagy as a target. As an essential step in this direction, this comprehensive review represents recent findings on the individual AD-related signaling pathways, describes key features of these pathways and their cross-talk with autophagy, represents current drug development, and introduces some of the multitarget beneficial approaches and strategies for the therapeutic intervention of AD.

Decreased Levels of Insulin-Like Growth Factor-1 Are Associated with Alzheimer's Disease: A Meta-Analysis

BACKGROUND

Alterations in levels of peripheral insulin-like growth factor-1 (IGF-1) in Alzheimer's disease (AD) have been reported in several studies, and results are inconsistent.

OBJECTIVE

We conducted a meta-analysis to investigate the relationship between peripheral and cerebrospinal fluid IGF-1 levels and AD or mild cognitive impairment (MCI).

METHODS

A systematic search in PubMed, Medline, Web of Science, Embase, and Cochrane Library was conducted and 18 studies were included.

RESULTS

Results of random-effects meta-analysis showed that there was no significant difference between AD patients and healthy control (17 studies; standard mean difference [SMD], -0.01; 95%CI, -0.35 to 0.32) and between MCI patients and healthy control (6 studies; SMD, -0.20; 95%CI, -0.52 to 0.13) in peripheral IGF-1 levels. Meta-regression analyses identified age difference might explain the heterogeneity (p = 0.017). However, peripheral IGF-1 levels were significantly decreased in AD subjects (9 studies; SMD, -0.44; 95%CI, -0.81 to -0.07) and MCI subjects exhibited a decreasing trend (4 studies; SMD, -0.31; 95%CI, -0.72 to 0.11) in studies with sample size≥80. Cerebrospinal fluid IGF-1 levels also significantly decreased in AD subjects (3 studies; SMD, -2.40; 95%CI, -4.36 to -0.43).

CONCLUSION

These findings suggest that decreased peripheral and cerebrospinal fluid IGF-1 levels might be a potential marker for the cognitive decline and progression of AD.

Delineating the Role of Mitophagy Inducers for Alzheimer Disease Patients

Alzheimer’s disease (AD) is the most common cause of dementia in elderly that serves to be a formidable socio-economic and healthcare challenge in the 21^st century. Mitochondrial dysfunction and impairment of mitochondrial-specific autophagy, namely mitophagy, have emerged as important components of the cellular processes contributing to the development of AD pathologies, namely amyloid-β plaques (Aβ) and neurofibrillary tangles (NFT). Here, we highlight the recent advances in the association between impaired mitophagy and AD, as well as delineate the potential underlying mechanisms. Furthermore, we conduct a systematic review the current status of mitophagy modulators and analyzed their relevant mechanisms, evaluating on their advantages, limitations and current applications in clinical trials for AD patients. Finally, we describe how deep learning may be a promising method to rapid and efficient discovery of mitophagy inducers as well as general guidance for the workflow of the process.

How can dementia and disability be prevented in older adults: where are we today and where are we going?

Ageing of the population, together with population growth, has brought along an ample increase in the number of older individuals living with dementia and disabilities. Dementia is the main cause of disability in old age, and promoting healthy brain ageing is considered as a key element in diminishing the burden of age-related disabilities. The World Health Organization recently launched the first risk reduction guidelines for cognitive impairment and dementia. According to recent estimates, approximately 40% of dementia cases worldwide could be attributable to 12 modifiable risk factors: low education; midlife hypertension and obesity; diabetes, smoking, excessive alcohol use, physical inactivity, depression, low social contact, hearing loss, traumatic brain injury and air pollution indicating clear prevention potential. Dementia and physical disability are closely linked with shared risk factors and possible shared underlying mechanisms supporting the possibility of integrated preventive interventions. FINGER trial was the first large randomized controlled trial indicating that multidomain lifestyle-based intervention can prevent cognitive and functional decline amongst at-risk older adults from the general population. Within the World-Wide FINGERS network, the multidomain FINGER concept is now tested and adapted worldwide proving evidence and tools for effective and easily implementable preventive strategies. Close collaboration between researchers, policymakers and healthcare practitioners, involvement of older adults and utilization of new technologies to support self-management is needed to facilitate the implementation of the research findings. In this scoping review, we present the current scientific evidence in the field of dementia and disability prevention and discuss future directions in the field.

Alzheimer and Purinergic Signaling: Just a Matter of Inflammation?

Alzheimer's disease (AD) is a widespread neurodegenerative pathology responsible for about 70% of all cases of dementia. Adenosine is an endogenous nucleoside that affects neurodegeneration by activating four membrane G protein-coupled receptor subtypes, namely P1 receptors. One of them, the A_2A subtype, is particularly expressed in the brain at the striatal and hippocampal levels and appears as the most promising target to counteract neurological damage and adenosine-dependent neuroinflammation. Extracellular nucleotides (ATP, ADP, UTP, UDP, etc.) are also released from the cell or are synthesized extracellularly. They activate P2X and P2Y membrane receptors, eliciting a variety of physiological but also pathological responses. Among the latter, the chronic inflammation underlying AD is mainly caused by the P2X7 receptor subtype. In this review we offer an overview of the scientific evidence linking P1 and P2 mediated purinergic signaling to AD development. We will also discuss potential strategies to exploit this knowledge for drug development.

Genipin Attenuates Tau Phosphorylation and Aβ Levels in Cellular Models of Alzheimer's Disease

Alzheimer's disease (AD) is a devastating brain disorder characterized by neurofibrillary tangles and amyloid plaques. Inhibiting Tau protein and amyloid-beta (Aβ) production or removing these molecules is considered potential therapeutic strategies for AD. Genipin is an aglycone and is isolated from the extract of Gardenia jasminoides Ellis fruit. In this study, the effect and molecular mechanisms of genipin on the inhibition of Tau aggregation and Aβ generation were investigated. The results showed that genipin bound to Tau and protected against heparin-induced Tau fibril formation. Moreover, genipin suppressed Tau phosphorylation probably by downregulating the expression of CDK5 and GSK-3β, and activated mTOR-dependent autophagy via the SIRT1/LKB1/AMPK signaling pathway in Tau-overexpressing cells. In addition, genipin decreased Aβ production by inhibiting BACE1 expression through the PERK/eIF2α signaling pathway in N2a/SweAPP cells. These data indicated that genipin could effectively lead to a significant reduction of phosphorylated Tau level and Aβ generation in vitro, suggesting that genipin might be developed into an effective therapeutic complement or a potential nutraceutical for preventing AD.

The emerging role of the sigma-1 receptor in autophagy: hand-in-hand targets for the treatment of Alzheimer's

INTRODUCTION

Autophagy is a cellular catabolic mechanism that helps clear damaged cellular components and is essential for normal cellular and tissue function. The sigma-1 receptor (σ-1R) is a chaperone protein involved in signal transduction, neurite outgrowth, and plasticity, improving memory, and neuroprotection. Recent evidence shows that σ-1R can promote autophagy. Autophagy activation by the σ-1Rs along with other neuroprotective effects makes it an interesting target for the treatment of Alzheimer's disease. AF710B, T-817 MA, and ANAVEX2-73 are some of the σ-1R agonists which have shown promising results and have entered clinical trials. These molecules have also been found to induce autophagy and show cytoprotective effects in cellular models.

AREAS COVERED

This review provides insight into the current understanding of σ-1R functions related to autophagy and their role in alleviating AD.

EXPERT OPINION

We propose a mechanism through which the activation of σ-1R and autophagy could alter amyloid precursor protein processing to inhibit amyloid-β production by reconstituting cholesterol and gangliosides in the lipid raft to offer neuroprotection against AD. Future AD treatment could involve the combined targeting of the σ-1R and autophagy activation. We suggest that future studies investigate the link between autophagy the σ-1R and AD.

Aged rhesus monkeys: Cognitive performance categorizations and preclinical drug testing

Rodent models have facilitated major discoveries in neurobiology, however, the low success rate of novel medications in clinical trials have led to questions about their translational value in neuropsychiatric drug development research. For age-related disorders of cognition such as Alzheimer' disease (AD) there is interest in moving beyond transgenic amyloid-β and/or tau-expressing rodent models and focusing more on natural aging and dissociating "healthy" from "pathological" aging to identify new therapeutic targets and treatments. In complex disorders such as AD, it can also be argued that animals with closer neurobiology to humans (e.g., nonhuman primates) should be employed more often particularly in the later phases of drug development. The purpose of the work described here was to evaluate the cognitive capabilities of rhesus monkeys across a wide range of ages in different delayed response tasks, a computerized delayed match to sample (DMTS) task and a manual delayed match to position (DMTP) task. Based on specific performance criteria and comparisons to younger subjects, the older subjects were generally less proficient, however, some performed as well as young subjects, while other aged subjects were markedly impaired. Accordingly, the older subjects could be categorized as aged "cognitively-unimpaired" or aged "cognitively-impaired" with a third group (aged-other) falling in between. Finally, as a proof of principle, we demonstrated using the DMTP task that aged cognitively-impaired monkeys are sensitive to the pro-cognitive effects of a nicotinic acetylcholine receptor (nAChR) partial agonist, encenicline, suggesting that nAChR ligands remain viable as potential treatments for age-related disorders of cognition.

Gene- and age-informed screening for preclinical Alzheimer's disease trials

INTRODUCTION

Elevated β-amyloid is used to enroll individuals into preclinical Alzheimer's disease trials, but the screening process is inefficient and expensive. Novel enrichment methods are needed to improve efficiency of enrollment.

METHODS

Alzheimer's disease incidence rates and a polygenic hazard score were used to create a gene- and age-defined ADAge. An ADAge cutpoint was chosen to optimally predict β-amyloid positivity among clinically normal Alzheimer's Disease Neuroimaging Initiative participants and applied to an independent Alzheimer's Disease Research Center validation cohort. The impact of ADAge enrichment on screening costs was evaluated in the Anti-Amyloid Treatment in Asymptomatic Alzheimer's Disease trial data.

RESULTS

In the validation cohort, the ADAge-enriched sample had a higher proportion of individuals with elevated β-amyloid (difference [95% CI] 0.19[0.07 to 0.33]) than the unenriched sample. ADAge enrichment lowered screening costs by $4.41 million (31.00%) in the real-world clinical trial scenario.

DISCUSSION

ADAge enrichment provides for a more efficient and cost-effective means to enroll clinically normal individuals with elevated β-amyloid in clinical trials.

Differential Diagnosis of Cognitive Decline in Elderly Individuals With Multiple Sclerosis

Due to increasingly improved disability outcomes, and the resultant significantly improved life span, of the multiple sclerosis (MS) population, questions regarding cognitive aging and the prevalence of comorbid Alzheimer disease (AD) have emerged. We describe neuropsychological and MRI-based changes that occurred in an 84-year-old MS patient with comorbid amnestic mild cognitive impairment (a precursor to AD) and cerebrovascular pathology. The neuropsychological examination demonstrated impairment in cognitive processing speed as well as in verbal and visual memory-domains that are potentially affected by any, or all, of the three co-existing diseases. Amyloid-based PET imaging showed increased focal uptake within the gray matter of the occipital lobe. We highlight how these clinical and radiologic observations can inform future research that could elucidate interactions between MS, a probable AD diagnosis, and cerebrovascular pathology in elderly individuals with MS. A comprehensive neuropsychological examination of multiple cognitive domains of individuals with MS may aid in the differential diagnosis of late-in-life cognitive decline.