Exercise and BDNF reduce Aβ production by enhancing α-secretase processing of APP

Efficacy of exercise rehabilitation for managing patients with Alzheimer's disease

Alzheimer's disease (AD) is a progressive and degenerative neurological disease characterized by the deterioration of cognitive functions. While a definitive cure and optimal medication to impede disease progression are currently unavailable, a plethora of studies have highlighted the potential advantages of exercise rehabilitation for managing this condition. Those studies show that exercise rehabilitation can enhance cognitive function and improve the quality of life for individuals affected by AD. Therefore, exercise rehabilitation has been regarded as one of the most important strategies for managing patients with AD. Herein, we provide a comprehensive analysis of the currently available findings on exercise rehabilitation in patients with AD, with a focus on the exercise types which have shown efficacy when implemented alone or combined with other treatment methods, as well as the potential mechanisms underlying these positive effects. Specifically, we explain how exercise may improve the brain microenvironment and neuronal plasticity. In conclusion, exercise is a cost-effective intervention to enhance cognitive performance and improve quality of life in patients with mild to moderate cognitive dysfunction. Therefore, it can potentially become both a physical activity and a tailored intervention. This review may aid the development of more effective and individualized treatment strategies to address the challenges imposed by this debilitating disease, especially in low- and middle-income countries.

Walking time and genetic predisposition for Alzheimer's disease: Results from the HELIAD study

Objective: Our study aimed to explore whether physical condition might affect the association between genetic predisposition for Alzheimer's Disease (AD) and AD incidence. Methods: The sample of participants consisted of 561 community-dwelling adults over 64 years old, without baseline dementia (508 cognitively normal and 53 with mild cognitive impairment), deriving from the HELIAD, an ongoing longitudinal study with follow-up evaluations every 3 years. Physical condition was assessed at baseline through walking time (WT), while a Polygenic Risk Score for late onset AD (PRS-AD) was used to estimate genetic predisposition. The association between WT and PRS-AD with AD incidence was evaluated with Cox proportional hazard models adjusted for age, sex, education years, global cognition score and APOE ε-4 genotype. Then, the association between WT and AD incidence was investigated after stratifying participants by low and high PRS-AD. Finally, we examined the association between PRS-AD and AD incidence after stratifying participants by WT. Results: Both WT and PRS-AD were connected with increased AD incidence (p < 0.05), after adjustments. In stratified analyses, in the slow WT group participants with a greater genetic risk had a 2.5-fold higher risk of developing AD compared to participants with lower genetic risk (p = 0.047). No association was observed in the fast WT group or when participants were stratified based on PRS-AD. Conclusions: Genetic predisposition for AD is more closely related to AD incidence in the group of older adults with slow WT. Hence, physical condition might be a modifier in the relationship of genetic predisposition with AD incidence.

New Advances in the Pharmacology and Toxicology of Lithium: A Neurobiologically Oriented Overview

Over the last six decades, lithium has been considered the gold standard treatment for the long-term management of bipolar disorder due to its efficacy in preventing both manic and depressive episodes as well as suicidal behaviors. Nevertheless, despite numerous observed effects on various cellular pathways and biologic systems, the precise mechanism through which lithium stabilizes mood remains elusive. Furthermore, there is recent support for the therapeutic potential of lithium in other brain diseases. This review offers a comprehensive examination of contemporary understanding and predominant theories concerning the diverse mechanisms underlying lithium's effects. These findings are based on investigations utilizing cellular and animal models of neurodegenerative and psychiatric disorders. Recent studies have provided additional support for the significance of glycogen synthase kinase-3 (GSK3) inhibition as a crucial mechanism. Furthermore, research has shed more light on the interconnections between GSK3-mediated neuroprotective, antioxidant, and neuroplasticity processes. Moreover, recent advancements in animal and human models have provided valuable insights into how lithium-induced modifications at the homeostatic synaptic plasticity level may play a pivotal role in its clinical effectiveness. We focused on findings from translational studies suggesting that lithium may interface with microRNA expression. Finally, we are exploring the repurposing potential of lithium beyond bipolar disorder. These recent findings on the therapeutic mechanisms of lithium have provided important clues toward developing predictive models of response to lithium treatment and identifying new biologic targets. SIGNIFICANCE STATEMENT: Lithium is the drug of choice for the treatment of bipolar disorder, but its mechanism of action in stabilizing mood remains elusive. This review presents the latest evidence on lithium's various mechanisms of action. Recent evidence has strengthened glycogen synthase kinase-3 (GSK3) inhibition, changes at the level of homeostatic synaptic plasticity, and regulation of microRNA expression as key mechanisms, providing an intriguing perspective that may help bridge the mechanistic gap between molecular functions and its clinical efficacy as a mood stabilizer.

Potential Alzheimer's disease drug targets identified through microglial biology research

INTRODUCTION

Microglia, the primary immune cells in the brain, play multifaceted roles in Alzheimer's disease (AD). Microglia can potentially mitigate the pathological progression of AD by clearing amyloid beta (Aβ) deposits in the brain and through neurotrophic support. In contrast, disproportionate activation of microglial pro-inflammatory pathways, as well as excessive elimination of healthy synapses, can exacerbate neurodegeneration in AD. The challenge, therefore, lies in discerning the precise regulation of the contrasting microglial properties to harness their therapeutic potential in AD.

AREAS COVERED

This review examines the evidence relevant to the disease-modifying effects of microglial manipulators in AD preclinical models. The deleterious pro-inflammatory effects of microglia in AD can be ameliorated via direct suppression or indirectly through metabolic manipulation, epigenetic targeting, and modulation of the gut-brain axis. Furthermore, microglial clearance of Aβ deposits in AD can be enhanced via strategically targeting microglial membrane receptors, lysosomal functions, and metabolism.

EXPERT OPINION

Given the intricate and diverse nature of microglial responses throughout the course of AD, therapeutic interventions directed at microglia warrant a tactical approach. This could entail employing therapeutic regimens, which concomitantly suppress pro-inflammatory microglial responses while selectively enhancing Aβ phagocytosis.

Exercise Improves Cerebral Blood Flow and Functional Outcomes in an Experimental Mouse Model of Vascular Cognitive Impairment and Dementia (VCID)

Vascular cognitive impairment and dementia (VCID) are a growing threat to public health without any known treatment. The bilateral common carotid artery stenosis (BCAS) mouse model is valid for VCID. Previously, we have reported that remote ischemic postconditioning (RIPostC) during chronic cerebral hypoperfusion (CCH) induced by BCAS increases cerebral blood flow (CBF), improves cognitive function, and reduces white matter damage. We hypothesized that physical exercise (EXR) would augment CBF during CCH and prevent cognitive impairment in the BCAS model. BCAS was performed in C57/B6 mice of both sexes to establish CCH. One week after the BCAS surgery, mice were randomized to treadmill exercise once daily or no EXR for four weeks. CBF was monitored with an LSCI pre-, post, and 4 weeks post-BCAS. Cognitive testing was performed for post-BCAS after exercise training, and brain tissue was harvested for histopathology and biochemical test. BCAS led to chronic hypoperfusion resulting in impaired cognitive function and other functional outcomes. Histological examination revealed that BCAS caused changes in neuronal morphology and cell death in the cortex and hippocampus. Immunoblotting showed that BCAS was associated with a significant downregulate of AMPK and pAMPK and NOS3 and pNOS3. BCAS also decreased red blood cell (RBC) deformability. EXR therapy increased and sustained improved CBF and cognitive function, muscular strength, reduced cell death, and loss of white matter. EXR is effective in the BCAS model, improving CBF and cognitive function, reducing white matter damage, improving RBC deformability, and increasing RBC NOS3 and AMPK. The mechanisms by which EXR improves CBF and attenuates tissue damage need further investigation.

Polysaccharide from Polygala tenuifolia alleviates cognitive decline in Alzheimer's disease mice by alleviating Aβ damage and targeting the ERK pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Polygala tenuifolia is used in a variety of Chinese medicine prescriptions for the classic dementia treatment, and polysaccharide is an important active component in the herb.

AIM OF THE STUDY

This study investigated the in vivo anti-Alzheimer's disease (AD) activity of the polysaccharide PTPS from Polygala tenuifolia using the senescence-accelerated mouse/prone8 (SAMP8) model and explored its molecular mechanism to lay the foundation for the development of polysaccharide-based anti-AD drugs.

MATERIALS AND METHODS

The Morris water maze test (MWM)was used to detect changes in the spatial cognitive ability of mice, and Nissl staining was applied to observe the state of neurons in the classic hippocampus. The levels of acetylcholine (ACh) and acetylcholinesterase (AChE) were measured by ELISA. Immunofluorescence was used to reflect β-amyloid (Aβ) levels in brain tissue. Apoptosis was evaluated by TdT-mediated dUTP Nick-End Labeling (TUNEL) method. The status of dendritic branches and spines was observed by Golgi staining. Meanwhile, the expression levels of recombinant human insulin-degrading enzyme (IDE), brain-derived neurotrophic factor (BDNF), tyrosine kinase receptor B (TrkB), extracellular regulated protein kinases (ERK), and cAMP-response element binding protein (CREB) proteins were determined by Western blotting.

RESULTS

PTPS improves spatial cognitive deficits in AD mice, reduces cellular damage in the CA3 region of the hippocampus, maintains the balance of the cholinergic system, and exerts an anti-AD effect in vivo. The molecular mechanism of its action may be related to the reduction of Aβ deposition as well as the activation of ERK pathway-related proteins with enhanced synaptic plasticity.

CONCLUSIONS

PTPS is able to exert anti-AD activity in vivo by mitigating Aβ damage and targeting the ERK pathway.

Exercise mimetics: a novel strategy to combat neuroinflammation and Alzheimer's disease

Neuroinflammation is a pathological hallmark of Alzheimer's disease (AD), characterized by the stimulation of resident immune cells of the brain and the penetration of peripheral immune cells. These inflammatory processes facilitate the deposition of amyloid-beta (Aβ) plaques and the abnormal hyperphosphorylation of tau protein. Managing neuroinflammation to restore immune homeostasis and decrease neuronal damage is a therapeutic approach for AD. One way to achieve this is through exercise, which can improve brain function and protect against neuroinflammation, oxidative stress, and synaptic dysfunction in AD models. The neuroprotective impact of exercise is regulated by various molecular factors that can be activated in the same way as exercise by the administration of their mimetics. Recent evidence has proven some exercise mimetics effective in alleviating neuroinflammation and AD, and, additionally, they are a helpful alternative option for patients who are unable to perform regular physical exercise to manage neurodegenerative disorders. This review focuses on the current state of knowledge on exercise mimetics, including their efficacy, regulatory mechanisms, progress, challenges, limitations, and future guidance for their application in AD therapy.

Bridging neurotrophic factors and bioactive peptides to Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder. As the demographic shifting towards an aging population, AD has emerged as a prominent public health concern. The pathogenesis of AD is complex, and there are no effective treatment methods for AD until now. In recent years, neurotrophic factors and bioactive peptides including brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF), irisin, melatonin, have been discovered to exert neuroprotective functions for AD. Bioactive peptides can be divided into two categories based on their sources: endogenous and exogenous. This review briefly elaborates on the pathogenesis of AD and analyzes the regulatory effects of endogenous and exogenous peptides on the pathogenesis of AD, thereby providing new therapeutic targets for AD and a theoretical basis for the application of bioactive peptides as adjunctive therapies for AD.

Physical activity and brain amyloid beta: A longitudinal analysis of cognitively unimpaired older adults

INTRODUCTION

The current study evaluated the relationship between habitual physical activity (PA) levels and brain amyloid beta (Aβ) over 15 years in a cohort of cognitively unimpaired older adults.

METHODS

PA and Aβ measures were collected over multiple timepoints from 731 cognitively unimpaired older adults participating in the Australian Imaging, Biomarkers and Lifestyle (AIBL) Study of Aging. Regression modeling examined cross-sectional and longitudinal relationships between PA and brain Aβ. Moderation analyses examined apolipoprotein E (APOE) ε4 carriage impact on the PA-Aβ relationship.

RESULTS

PA was not associated with brain Aβ at baseline (β = -0.001, p = 0.72) or over time (β = -0.26, p = 0.24). APOE ε4 status did not moderate the PA-Aβ relationship over time (β = 0.12, p = 0.73). Brain Aβ levels did not predict PA trajectory (β = -54.26, p = 0.59).

DISCUSSION

Our study did not identify a relationship between habitual PA and brain Aβ levels.

HIGHLIGHTS

Physical activity levels did not predict brain amyloid beta (Aβ) levels over time in cognitively unimpaired older adults (≥60 years of age). Apolipoprotein E (APOE) ε4 carrier status did not moderate the physical activity-brain Aβ relationship over time. Physical activity trajectories were not impacted by brain Aβ levels.

Converged avenues: depression and Alzheimer's disease- shared pathophysiology and novel therapeutics

Depression, a highly prevalent disorder affecting over 280 million people worldwide, is comorbid with many neurological disorders, particularly Alzheimer's disease (AD). Depression and AD share overlapping pathophysiology, and the search for accountable biological substrates made it an essential and intriguing field of research. The paper outlines the neurobiological pathways coinciding with depression and AD, including neurotrophin signalling, the hypothalamic-pituitary-adrenal axis (HPA), cellular apoptosis, neuroinflammation, and other aetiological factors. Understanding overlapping pathways is crucial in identifying common pathophysiological substrates that can be targeted for effective management of disease state. Antidepressants, particularly monoaminergic drugs (first-line therapy), are shown to have modest or no clinical benefits. Regardless of the ineffectiveness of conventional antidepressants, these drugs remain the mainstay for treating depressive symptoms in AD. To overcome the ineffectiveness of traditional pharmacological agents in treating comorbid conditions, a novel therapeutic class has been discussed in the paper. This includes neurotransmitter modulators, glutamatergic system modulators, mitochondrial modulators, antioxidant agents, HPA axis targeted therapy, inflammatory system targeted therapy, neurogenesis targeted therapy, repurposed anti-diabetic agents, and others. The primary clinical challenge is the development of therapeutic agents and the effective diagnosis of the comorbid condition for which no specific diagnosable scale is present. Hence, introducing Artificial Intelligence (AI) into the healthcare system is revolutionary. AI implemented with interdisciplinary strategies (neuroimaging, EEG, molecular biomarkers) bound to have accurate clinical interpretation of symptoms. Moreover, AI has the potential to forecast neurodegenerative and psychiatric illness much in advance before visible/observable clinical symptoms get precipitated.

An Interaction between Brain-Derived Neurotrophic Factor and Stress-Related Glucocorticoids in the Pathophysiology of Alzheimer's Disease

Both the brain-derived neurotrophic factor (BDNF) and glucocorticoids (GCs) play multiple roles in various aspects of neurons, including cell survival and synaptic function. BDNF and its receptor TrkB are extensively expressed in neurons of the central nervous system (CNS), and the contribution of the BDNF/TrkB system to neuronal function is evident; thus, its downregulation has been considered to be involved in the pathogenesis of Alzheimer's disease (AD). GCs, stress-related molecules, and glucocorticoid receptors (GRs) are also considered to be associated with AD in addition to mental disorders such as depression. Importantly, a growing body of evidence suggests a close relationship between BDNF/TrkB-mediated signaling and the GCs/GR system in the CNS. Here, we introduce the current studies on the interaction between the neurotrophic system and stress in CNS neurons and discuss their involvement in the pathophysiology of AD.

Inhibition of CX3CL1 by treadmill training prevents osteoclast-induced fibrocartilage complex resorption during TBI healing

Introduction

The healing of tendon-bone injuries is very difficult, often resulting in poor biomechanical performance and unsatisfactory functional recovery. The tendon-bone insertion has a complex four distinct layers structure, and previous studies have often focused on promoting the regeneration of the fibrocartilage layer, neglecting the role of its bone end repair in tendon-bone healing. This study focuses on the role of treadmill training in promoting bone regeneration at the tendon-bone insertion and its related mechanisms.

Methods

After establishing the tendon-bone insertion injury model, the effect of treadmill training on tendon-bone healing was verified by Micro CT and HE staining; then the effect of CX3CL1 on osteoclast differentiation was verified by TRAP staining and cell culture; and finally the functional recovery of the mice was verified by biomechanical testing and behavioral test.

Results

Treadmill training suppresses the secretion of CX3CL1 and inhibits the differentiation of local osteoclasts after tendon-bone injury, ultimately reducing osteolysis and promoting tendon bone healing.

Discussion

Our research has found the interaction between treadmill training and the CX3CL1-C3CR1 axis, providing a certain theoretical basis for rehabilitation training.

Histone acetylation in an Alzheimer's disease cell model promotes homeostatic amyloid-reducing pathways

Alzheimer's Disease (AD) is a disorder characterized by cognitive decline, neurodegeneration, and accumulation of amyloid plaques and tau neurofibrillary tangles in the brain. Dysregulation of epigenetic histone modifications may lead to expression of transcriptional programs that play a role either in protecting against disease genesis or in worsening of disease pathology. One such histone modification, acetylation of histone H3 lysine residue 27 (H3K27ac), is primarily localized to genomic enhancer regions and promotes active gene transcription. We previously discovered H3K27ac to be more abundant in AD patient brain tissue compared to the brains of age-matched non-demented controls. In this study, we use iPSC-neurons derived from familial AD patients with an amyloid precursor protein (APP) duplication (APPDup neurons) as a model to study the functional effect of lowering CBP/P300 enzymes that catalyze H3K27ac. We found that homeostatic amyloid-reducing genes were upregulated in the APPDup neurons compared to non-demented controls. We lowered CBP/P300 to reduce H3K27ac, which led to decreased expression of numerous of these homeostatic amyloid-reducing genes, along with increased extracellular secretion of a toxic amyloid-β species, Aβ(1-42). Our findings suggest that epigenomic histone acetylation, including H3K27ac, drives expression of compensatory genetic programs in response to AD-associated insults, specifically those resulting from APP duplication, and thus may play a role in mitigating AD pathology in neurons.

Harnessing Passive Pulsatile Shear Stress for Alzheimer's Disease Prevention and Intervention

 Alzheimer's disease (AD) affects more than 40 million people worldwide and is the leading cause of dementia. This disease is a challenge for both patients and caregivers and puts a significant strain on the global healthcare system. To address this issue, the Lancet Commission recommends focusing on reducing modifiable lifestyle risk factors such as hypertension, diabetes, and physical inactivity. Passive pulsatile shear stress (PPSS) interventions, which use devices like whole-body periodic acceleration, periodic acceleration along the Z-axis (pGz), and the Jogging Device, have shown significant systemic and cellular effects in preclinical and clinical models which address these modifiable risks factors. Based on this, we propose that PPSS could be a potential non-pharmacological and non-invasive preventive or therapeutic strategy for AD. We perform a comprehensive review of the biological basis based on all publications of PPSS using these devices and demonstrate their effects on the various aspects of AD. We draw from this comprehensive analysis to support our hypothesis. We then delve into the possible application of PPSS as an innovative intervention. We discuss how PPSS holds promise in ameliorating hypertension and diabetes while mitigating physical inactivity, potentially offering a holistic approach to AD prevention and management.

Aniracetam: An Evidence-Based Model for Preventing the Accumulation of Amyloid-β Plaques in Alzheimer's Disease

 Alzheimer's disease is the leading cause of dementia in the world. It affects 6 million people in the United States and 50 million people worldwide. Alzheimer's disease is characterized by the accumulation of amyloid-β plaques (Aβ), an increase in tau protein neurofibrillary tangles, and a loss of synapses. Since the 1990s, removing and reducing Aβ has been the focus of Alzheimer's treatment and prevention research. The accumulation of Aβ can lead to oxidative stress, inflammation, neurotoxicity, and eventually apoptosis. These insults impair signaling systems in the brain, potentially leading to memory loss and cognitive decline. Aniracetam is a safe, effective, cognitive-enhancing drug that improves memory in both human and animal studies. Aniracetam may prevent the production and accumulation of Aβ by increasing α-secretase activity through two distinct pathways: 1) increasing brain derived neurotrophic factor expression and 2) positively modulating metabotropic glutamate receptors. This is the first paper to propose an evidence-based model for aniracetam reducing the accumulation and production of Aβ.

Exercise Intervention for Alzheimer's Disease: Unraveling Neurobiological Mechanisms and Assessing Effects

Alzheimer's disease (AD) is a progressive neurodegenerative disease and a major cause of age-related dementia, characterized by cognitive dysfunction and memory impairment. The underlying causes include the accumulation of beta-amyloid protein (Aβ) in the brain, abnormal phosphorylation, and aggregation of tau protein within nerve cells, as well as neuronal damage and death. Currently, there is no cure for AD with drug therapy. Non-pharmacological interventions such as exercise have been widely used to treat AD, but the specific molecular and biological mechanisms are not well understood. In this narrative review, we integrate the biology of AD and summarize the knowledge of the molecular, neural, and physiological mechanisms underlying exercise-induced improvements in AD progression. We discuss various exercise interventions used in AD and show that exercise directly or indirectly affects the brain by regulating crosstalk mechanisms between peripheral organs and the brain, including "bone-brain crosstalk", "muscle-brain crosstalk", and "gut-brain crosstalk". We also summarize the potential role of artificial intelligence and neuroimaging technologies in exercise interventions for AD. We emphasize that moderate-intensity, regular, long-term exercise may improve the progression of Alzheimer's disease through various molecular and biological pathways, with multimodal exercise providing greater benefits. Through in-depth exploration of the molecular and biological mechanisms and effects of exercise interventions in improving AD progression, this review aims to contribute to the existing knowledge base and provide insights into new therapeutic strategies for managing AD.

Irisin reduces amyloid-β by inducing the release of neprilysin from astrocytes following downregulation of ERK-STAT3 signaling

A pathological hallmark of Alzheimer's disease (AD) is the deposition of amyloid-β (Aβ) protein in the brain. Physical exercise has been shown to reduce Aβ burden in various AD mouse models, but the underlying mechanisms have not been elucidated. Irisin, an exercise-induced hormone, is the secreted form of fibronectin type-III-domain-containing 5 (FNDC5). Here, using a three-dimensional (3D) cell culture model of AD, we show that irisin significantly reduces Aβ pathology by increasing astrocytic release of the Aβ-degrading enzyme neprilysin (NEP). This is mediated by downregulation of ERK-STAT3 signaling. Finally, we show that integrin αV/β5 acts as the irisin receptor on astrocytes required for irisin-induced release of astrocytic NEP, leading to clearance of Aβ. Our findings reveal for the first time a cellular and molecular mechanism by which exercise-induced irisin attenuates Aβ pathology, suggesting a new target pathway for therapies aimed at the prevention and treatment of AD.

Diverse signaling mechanisms and heterogeneity of astrocyte reactivity in Alzheimer's disease

Alzheimer's disease (AD) affects various brain cell types, including astrocytes, which are the most abundant cell types in the central nervous system (CNS). Astrocytes not only provide homeostatic support to neurons but also actively regulate synaptic signaling and functions and become reactive in response to CNS insults through diverse signaling pathways including the JAK/STAT, NF-κB, and GPCR-elicited pathways. The advent of new technology for transcriptomic profiling at the single-cell level has led to increasing recognition of the highly versatile nature of reactive astrocytes and the context-dependent specificity of astrocyte reactivity. In AD, reactive astrocytes have long been observed in senile plaques and have recently been suggested to play a role in AD pathogenesis and progression. However, the precise contributions of reactive astrocytes to AD remain elusive, and targeting this complex cell population for AD treatment poses significant challenges. In this review, we summarize the current understanding of astrocyte reactivity and its role in AD, with a particular focus on the signaling pathways that promote astrocyte reactivity and the heterogeneity of reactive astrocytes. Furthermore, we explore potential implications for the development of therapeutics for AD. Our objective is to shed light on the complex involvement of astrocytes in AD and offer insights into potential therapeutic targets and strategies for treating and managing this devastating neurodegenerative disorder.

Mechanisms of the Beneficial Effects of Exercise on Brain-Derived Neurotrophic Factor Expression in Alzheimer's Disease

Brain-derived neurotrophic factor (BDNF) is a key molecule in promoting neurogenesis, dendritic and synaptic health, neuronal survival, plasticity, and excitability, all of which are disrupted in neurological and cognitive disorders such as Alzheimer's disease (AD). Extracellular aggregates of amyloid-β (Aβ) in the form of plaques and intracellular aggregates of hyperphosphorylated tau protein have been identified as major pathological insults in the AD brain, along with immune dysfunction, oxidative stress, and other toxic stressors. Although aggregated Aβ and tau lead to decreased brain BDNF expression, early losses in BDNF prior to plaque and tangle formation may be due to other insults such as oxidative stress and contribute to early synaptic dysfunction. Physical exercise, on the other hand, protects synaptic and neuronal structure and function, with increased BDNF as a major mediator of exercise-induced enhancements in cognitive function. Here, we review recent literature on the mechanisms behind exercise-induced BDNF upregulation and its effects on improving learning and memory and on Alzheimer's disease pathology. Exercise releases into the circulation a host of hormones and factors from a variety of peripheral tissues. Mechanisms of BDNF induction discussed here are osteocalcin, FNDC5/irisin, and lactate. The fundamental mechanisms of how exercise impacts BDNF and cognition are not yet fully understood but are a prerequisite to developing new biomarkers and therapies to delay or prevent cognitive decline.

The benefits of rehabilitation exercise in improving chronic traumatic encephalopathy: recent advances and future perspectives

Traumatic encephalopathy syndrome (TES) is used to describe the clinical manifestations of chronic traumatic encephalopathy (CTE). However, effective treatment and prevention strategies are lacking. Increasing evidence has shown that rehabilitation training could prevent cognitive decline, enhance brain plasticity, and effectively improve neurological function in neurodegenerative diseases. Therefore, the mechanisms involved in the effects of rehabilitation exercise therapy on the prognosis of CTE are worth exploring. The aim of this article is to review the pathogenesis of CTE and provide a potential clinical intervention strategy for CTE.

Involvement of brain-derived neurotrophic factor signaling in the pathogenesis of stress-related brain diseases

Neurotrophins including brain-derived neurotrophic factor, BDNF, have critical roles in neuronal differentiation, cell survival, and synaptic function in the peripheral and central nervous system. It is well known that a variety of intracellular signaling stimulated by TrkB, a high-affinity receptor for BDNF, is involved in the physiological and pathological neuronal aspects via affecting cell viability, synaptic function, neurogenesis, and cognitive function. As expected, an alteration of the BDNF/TrkB system is suspected to be one of the molecular mechanisms underlying cognitive decline in cognitive diseases and mental disorders. Recent evidence has also highlighted a possible link between the alteration of TrkB signaling and chronic stress. Furthermore, it has been demonstrated that downregulation of the BDNF/TrkB system and chronic stress have a role in the pathogenesis of Alzheimer's disease (AD) and mental disorders. In this review, we introduce current evidence showing a close relationship between the BDNF/TrkB system and the development of cognition impairment in stress-related disorders, and the possible contribution of the upregulation of the BDNF/TrkB system in a therapeutic approach against these brain diseases.

Effect of exercise on the hypothalamic-pituitary-gonadal axis in a rat model of Alzheimer's disease

Hypothalamic-pituitary-gonadal (HPG) axis dysregulation was suggested to play a crucial role in Alzheimer's disease (AD). This study investigated the effects of exercise on HPG hormones in an AD rat model, as a possible mechanism underlying the favorable effect of exercise on AD. Forty male Wistar albino rats 2-3 months old were subdivided randomly into two groups (n = 20 each): AD group (injected intraperitoneally with aluminum chloride (70 mg/kg/day) for 6 weeks) and Control group. Each group was subdivided into exercised or non-exercised group (n = 10 each). Exercised groups were subjected to a swimming protocol (60 min/day, 5 days/week, 4 weeks). Serum HPG hormones, hippocampal β-amyloid levels and Morris water-maze cognition were assessed. Results demonstrated higher levels of β-amyloid, gonadotropin releasing hormone (GnRH), luteinizing hormone (LH) and follicle stimulating hormone (FSH) together with lower testosterone levels and cognitive impairment in the AD rats compared to controls. Β-amyloid levels negatively correlated with testosterone levels and positively correlated with GnRH, LH and FSH among the AD rats. Higher testosterone and lower GnRH, LH, FSH and β-amyloid levels, as well as cognitive improvement, were observed in the exercised compared to non-exercised AD rats, suggesting a modulatory role of exercise training on AD-associated HPG axis dysregulation.

Effects of Voluntary Physical Exercise on the Neurovascular Unit in a Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is the most common neurodegenerative disorder worldwide. Histopathologically, AD presents two pathognomonic hallmarks: (1) neurofibrillary tangles, characterized by intracellular deposits of hyperphosphorylated tau protein, and (2) extracellular amyloid deposits (amyloid plaques) in the brain vasculature (cerebral amyloid angiopathy; CAA). It has been proposed that vascular amyloid deposits could trigger neurovascular unit (NVU) dysfunction in AD. The NVU is composed primarily of astrocytic feet, endothelial cells, pericytes, and basement membrane. Although physical exercise is hypothesized to have beneficial effects against AD, it is unknown whether its positive effects extend to ameliorating CAA and improving the physiology of the NVU. We used the triple transgenic animal model for AD (3xTg-AD) at 13 months old and analyzed through behavioral and histological assays, the effect of voluntary physical exercise on cognitive functions, amyloid angiopathy, and the NVU. Our results show that 3xTg-AD mice develop vascular amyloid deposits which correlate with cognitive deficits and NVU alteration. Interestingly, the physical exercise regimen decreases amyloid angiopathy and correlates with an improvement in cognitive function as well as in the underlying integrity of the NVU components. Physical exercise could represent a key therapeutic approach in cerebral amyloid angiopathy and NVU stability in AD patients.

Brain metabolism in Alzheimer's disease: biological mechanisms of exercise

Alzheimer's disease (AD) is a major subtype of neurodegenerative dementia caused by long-term interactions and accumulation of multiple adverse factors, accompanied by dysregulation of numerous intracellular signaling and molecular pathways in the brain. At the cellular and molecular levels, the neuronal cellular milieu of the AD brain exhibits metabolic abnormalities, compromised bioenergetics, impaired lipid metabolism, and reduced overall metabolic capacity, which lead to abnormal neural network activity and impaired neuroplasticity, thus accelerating the formation of extracellular senile plaques and intracellular neurofibrillary tangles. The current absence of effective pharmacological therapies for AD points to the urgent need to investigate the benefits of non-pharmacological approaches such as physical exercise. Despite the evidence that regular physical activity can improve metabolic dysfunction in the AD state, inhibit different pathophysiological molecular pathways associated with AD, influence the pathological process of AD, and exert a protective effect, there is no clear consensus on the specific biological and molecular mechanisms underlying the advantages of physical exercise. Here, we review how physical exercise improves crucial molecular pathways and biological processes associated with metabolic disorders in AD, including glucose metabolism, lipid metabolism, Aβ metabolism and transport, iron metabolism and tau pathology. How metabolic states influence brain health is also presented. A better knowledge on the neurophysiological mechanisms by which exercise improves AD metabolism can contribute to the development of novel drugs and improvement of non-pharmacological interventions.

Neuroprotective effects of the PPARβ/δ antagonist GSK0660 in in vitro and in vivo Parkinson's disease models

BACKGROUND

The underlying mechanism of Parkinson's disease are still unidentified, but excitotoxicity, oxidative stress, and neuroinflammation are considered key actors. Proliferator activated receptors (PPARs) are transcription factors involved in the control of numerous pathways. Specifically, PPARβ/δ is recognized as an oxidative stress sensor, and we have previously reported that it plays a detrimental role in neurodegeneration.

METHODS

Basing on this concept, in this work, we tested the potential effects of a specific PPARβ/δ antagonist (GSK0660) in an in vitro model of Parkinson's disease. Specifically, live-cell imaging, gene expression, Western blot, proteasome analyses, mitochondrial and bioenergetic studies were performed. Since we obtained promising results, we tested this antagonist in a 6-hydroxydopamine hemilesioned mouse model. In the animal model, behavioral tests, histological analysis, immunofluorescence and western blot of substantia nigra and striatum upon GSK0660 were assayed.

RESULTS

Our findings suggested that PPARβ/δ antagonist has neuroprotective potential due to neurotrophic support, anti-apoptotic and anti-oxidative effects paralleled to an amelioration of mitochondria and proteasome activity. These findings are strongly supported also by the siRNA results demonstrating that by silencing PPARβ/δ a significative rescue of the dopaminergic neurons was obtained, thus indicating an involvement of PPARβ/δ in PD's pathogenesis. Interestingly, in the animal model, GSK0660 treatment confirmed neuroprotective effects observed in the in vitro studies. Neuroprotective effects were highlighted by the behavioural performance and apomorphine rotation tests amelioration and the reduction of dopaminergic neuronal loss. These data were also confirmed by imaging and western blotting, indeed, the tested compound decreased astrogliosis and activated microglia, concomitant with an upregulation of neuroprotective pathways.

CONCLUSIONS

In summary, PPARβ/δ antagonist displayed neuroprotective activities against 6-hydroxydopamine detrimental effects both in vitro and in vivo models of Parkinson's disease, suggesting that it may represent a novel therapeutic approach for this disorder.

Molecular and neural roles of sodium-glucose cotransporter 2 inhibitors in alleviating neurocognitive impairment in diabetic mice

Diabetes causes a variety of molecular changes in the brain, making it a real risk factor for the development of cognitive dysfunction. Complex pathogenesis and clinical heterogeneity of cognitive impairment makes the efficacy of current drugs limited. Sodium-glucose cotransporter 2 inhibitors (SGLT2i) gained our attention as drugs with potential beneficial effects on the CNS. In the present study, these drugs ameliorated the cognitive impairment associated with diabetes. Moreover, we verified whether SGLT2i can mediate the degradation of amyloid precursor protein (APP) and modulation of gene expression (Bdnf, Snca, App) involved in the control of neuronal proliferation and memory. The results of our research proved the participation of SGLT2i in the multifactorial process of neuroprotection. SGLT2i attenuate the neurocognitive impairment through the restoration of neurotrophin levels, modulation of neuroinflammatory signaling, and gene expression of Snca, Bdnf, and App in the brain of diabetic mice. The targeting of the above-mentioned genes is currently seen as one of the most promising and developed therapeutic strategies for diseases associated with cognitive dysfunction. The results of this work could form the basis of a future administration of SGLT2i in diabetics with neurocognitive impairment.

High-Intensity Interval Training Ameliorates Molecular Changes in the Hippocampus of Male Rats with the Diabetic Brain: the Role of Adiponectin

Alzheimer's disease (AD) is closely related to type 2 diabetes (T2D). This study investigated the impact of high-intensity interval training (HIIT) on diabetes-induced disturbances in AD-related factors (including AMP-activated protein kinase (AMPK), glycogen synthase kinase-3β (GSK3β), and tau protein) in the hippocampus, with the main focus on adiponectin signaling.In total, 28 male Wistar rats at the age of 8 weeks were randomly assigned to four groups (n = 7 in each group): control (Con), type 2 diabetes (T2D), HIIT (Ex), and type 2 diabetes + HIIT (T2D + Ex). T2D was induced by a high-fat diet plus a single dose of streptozotocin (STZ). Rats in Ex and T2D + Ex groups performed 8 weeks of HIIT (running at 8-95% of V_max, 4-10 intervals). Insulin and adiponectin levels in serum and hippocampus were measured along with hippocampal expression of insulin and adiponectin receptors, phosphorylated AMPK, dephosphorylated GSK3β, and phosphorylated tau. Homeostasis model assessment for insulin resistance (HOMA-IR), homeostasis model assessment for insulin resistance beta (HOMA-β), and quantitative insulin sensitivity check index (QUICKI) were calculated to assess insulin resistance and sensitivity. T2D decreased insulin and adiponectin levels in serum and hippocampus, as well as the hippocampal levels of insulin and adiponectin receptors and AMPK, but increased GSK3β and tau in the hippocampus. HIIT reversed diabetes-induced impairments and consequently decreased tau accumulation in the hippocampus of diabetic rats. HOMA-IR, HOMA-β, and QUICKI were improved in Ex and T2D + Ex groups. Overall, our results confirmed that T2D has undesirable effects on the levels of some Alzheimer's-related factors in the hippocampus, and HIIT could ameliorate these impairments in the hippocampus.

Chronic seizures induce sex-specific cognitive deficits with loss of presenilin 2 function

Patients with early-onset Alzheimer's disease (EOAD) are at elevated risk for seizures, including patients with presenilin 2 (PSEN2) variants. Like people with epilepsy, uncontrolled seizures may worsen cognitive function in AD. While the relationship between seizures and amyloid beta accumulation has been more thoroughly investigated, the role of other drivers of seizure susceptibility in EOAD remain relatively understudied. We therefore sought to define the impact of loss of normal PSEN2 function and chronic seizures on cognitive function in the aged brain. Male and female PSEN2 KO and age- and sex-matched wild-type (WT) mice were sham or corneal kindled beginning at 6-months-old. Kindled and sham-kindled mice were then challenged up to 6 weeks later in a battery of cognitive tests: non-habituated open field (OF), T-maze spontaneous alternation (TM), and Barnes maze (BM), followed by immunohistochemistry for markers of neuroinflammation and neuroplasticity. PSEN2 KO mice required significantly more stimulations to kindle (males: p < 0.02; females: p < 0.02) versus WT. Across a range of behavioral tests, the cognitive performance of kindled female PSEN2 KO mice was most significantly impaired versus age-matched WT females. Male BM performance was generally worsened by seizures (p = 0.038), but loss of PSEN2 function did not itself worsen cognitive performance. Conversely, kindled PSEN2 KO females made the most BM errors (p = 0.007). Chronic seizures also significantly altered expression of hippocampal neuroinflammation and neuroplasticity markers in a sex-specific manner. Chronic seizures may thus significantly worsen hippocampus-dependent cognitive deficits in aged female, but not male, PSEN2 KO mice. Our work suggests that untreated focal seizures may worsen cognitive burden with loss of normal PSEN2 function in a sex-related manner.

Circulating micro-RNAs Differentially Expressed in Korean Alzheimer's Patients With Brain Aβ Accumulation Activate Amyloidogenesis

BACKGROUND

Roles for extracellular vesicles (EVs) enriched with micro-RNAs (miRNAs) have been proposed in Alzheimer's disease (AD) pathogenesis, leading to the discovery of blood miRNAs as AD biomarkers. However, the diagnostic utility of specific miRNAs is not consistent. This study aimed to discover blood miRNAs that are differentially expressed in Korean AD patients, evaluate their clinical performance, and investigate their role in amyloidogenesis.

METHODS

We discovered miRNAs differentially expressed in AD (N = 8) from cognitively normal participants (CN, N = 7) or Parkinson's disease (PD) patients (N = 8). We evaluated the clinical performance of these miRNAs in plasma of subgroup (N = 99) and in plasma EVs isolated from the total cohort (N = 251). The effects of miRNAs on amyloidogenesis and on the regulation of their target genes were investigated in vitro.

RESULTS

Among 17 upregulated and one downregulated miRNAs in AD (>twofold), miR-122-5p, miR-210-3p, and miR-590-5p were differentially expressed compared with CN or PD. However, the diagnostic performance of the selected plasma or EV miRNAs in total participants were limited (area under the curve < 0.8). Nevertheless, levels of 3 miRNAs in plasma or plasma EVs of participants who were amyloid positron emission tomography (Aβ-PET) positive were significantly higher than those from the Aβ-PET negative participants (p < .05). The selected miRNAs induced Aβ production (p < .05) through activation of β-cleavage of amyloid precursor protein (CTF-β; p < .01), and downregulated their target genes (ADAM metallopeptidase domain 10, Brain-derived neurotrophic factor, and Jagged canonical notch ligand 1; p < .05), which was further supported by pathway enrichment analysis of target genes of the miRNAs.

CONCLUSION

In conclusion, despite of the limited diagnostic utility of selected miRNAs as plasma or plasma EV biomarkers, the discovered miRNAs may play a role in amyloidogenesis during AD onset and progression.

Exploring the Causality Between Plasma Brain-Derived Neurotrophic Factor and Neurological Diseases: A Mendelian Randomization Study

BACKGROUND

Brain-derived neurotrophic factor (BDNF) is a protein synthesized in the brain and widely expressed in the nervous system. Previous studies have demonstrated a controversial role of BDNF in neurological diseases.

OBJECTIVE

In this study, we aimed to assess the association between BDNF levels and the risk of neurological diseases by Mendelian randomization analysis.

METHODS

From a genome-wide association analysis of plasma proteins comprising 3,301 European participants, we isolated 25 genetic variations as instrumental variables for BDNF levels. Summary statistics data on six common neurological diseases as outcome variables. Two-sample Mendelian randomization (MR) analysis was used to assess whether plasma BDNF is causally related to neurological diseases. We also performed sensitivity analysis to ensure the robustness of the results and reverse MR to exclude potential reverse causality.

RESULTS

We confirmed the significant causal relationship between BDNF levels and the risk of Alzheimer's disease (AD) (OR, 0.92; 95% CI, 0.85, 0.98; p = 0.013). Other methods have also shown similar results. We infer that BDNF also reduces the risk of epilepsy (OR, 0.94; 95% CI, 0.90, 0.98; p = 0.004). In reverse MR analysis, we also found that AD can affect the level of BDNF.

CONCLUSIONS

Our study suggests higher plasma BDNF was associated with the reduced risk of AD. Moreover, higher plasma BDNF is a protective factor on AD and focal epilepsy. The results provide credence to the idea that BDNF may play a significant role in the development of focal epilepsy and AD.

Alternative Pharmacological Strategies for the Treatment of Alzheimer's Disease: Focus on Neuromodulator Function

Alzheimer's disease (AD) is a neurodegenerative disorder, comprising 70% of dementia diagnoses worldwide and affecting 1 in 9 people over the age of 65. However, the majority of its treatments, which predominantly target the cholinergic system, remain insufficient at reversing pathology and act simply to slow the inevitable progression of the disease. The most recent neurotransmitter-targeting drug for AD was approved in 2003, strongly suggesting that targeting neurotransmitter systems alone is unlikely to be sufficient, and that research into alternate treatment avenues is urgently required. Neuromodulators are substances released by neurons which influence neurotransmitter release and signal transmission across synapses. Neuromodulators including neuropeptides, hormones, neurotrophins, ATP and metal ions display altered function in AD, which underlies aberrant neuronal activity and pathology. However, research into how the manipulation of neuromodulators may be useful in the treatment of AD is relatively understudied. Combining neuromodulator targeting with more novel methods of drug delivery, such as the use of multi-targeted directed ligands, combinatorial drugs and encapsulated nanoparticle delivery systems, may help to overcome limitations of conventional treatments. These include difficulty crossing the blood-brain-barrier and the exertion of effects on a single target only. This review aims to highlight the ways in which neuromodulator functions are altered in AD and investigate how future therapies targeting such substances, which act upstream to classical neurotransmitter systems, may be of potential therapeutic benefit in the sustained search for more effective treatments.

Regulation of the Soluble Amyloid Precursor Protein α (sAPPα) Levels by Acetylcholinesterase and Brain-Derived Neurotrophic Factor in Lung Cancer Cell Media

In comparing two human lung cancer cells, we previously found lower levels of acetylcholinesterase (AChE) and intact amyloid-β40/42 (Aβ), and higher levels of mature brain-derived neurotrophic factor (mBDNF) in the media of H1299 cells as compared to A549 cell media. In this study, we hypothesized that the levels of soluble amyloid precursor protein α (sAPPα) are regulated by AChE and mBDNF in A549 and H1299 cell media. The levels of sAPPα were higher in the media of H1299 cells. Knockdown of AChE led to increased sAPPα and mBDNF levels and correlated with decreased levels of intact Aβ40/42 in A549 cell media. AChE and mBDNF had opposite effects on the levels of Aβ and sAPPα and were found to operate through a mechanism involving α-secretase activity. Treatment with AChE decreased sAPPα levels and simultaneously increased the levels of intact Aβ40/42 suggesting a role of the protein in shifting APP processing away from the non-amyloidogenic pathway and toward the amyloidogenic pathway, whereas treatment with mBDNF led to opposite effects on those levels. We also show that the levels of sAPPα are regulated by protein kinase C (PKC), extracellular signal-regulated kinase (ERK)1/2, phosphoinositide 3 Kinase (PI3K), but not by protein kinase A (PKA).

Plasma Amyloid-β dynamics in late-life major depression: a longitudinal study

Depressed individuals are twice as likely to develop Alzheimer's disease (AD) as compared to controls. Brain amyloid-β (Aβ) deposition is believed to have a major role in AD pathogenesis but studies also suggest associations of Aβ dynamics and depression. The aim of this study was to test if plasma Aβ levels are longitudinally associated to late-life depression. We measured plasma levels of amyloid-β_1-40 (Aβ40) and amyloid-β_1-42 (Aβ42) peptides longitudinally for three consecutive years in 48 cognitively intact elderly subjects with late-life major depressive disorder (LLMD) and 45 age-matched cognitively healthy controls. We found that the Aβ42/Aβ40 plasma ratio was significantly and steadily lower in depressed subjects compared to controls (p < 0.001). At screening, Aβ42/Aβ40 plasma did not correlate with depression severity (as measured with Hamilton Depression Scale) or cognitive performance (as measured with Mini-Mental State Examination) but was associated to depression severity at 3 years after adjustment for age, education, cognitive performance, and antidepressants use. This study showed that reduced plasma Aβ42/Aβ40 ratio is consistently associated with LLMD diagnosis and that increased severity of depression at baseline predicted low Aβ42/Aβ40 ratio at 3 years. Future studies are needed to confirm these findings and examine if the consistently lower plasma Aβ42/Aβ40 ratio in LLMD reflects increased brain amyloid deposition, as observed in AD subjects, and an increased risk for progressive cognitive decline and AD.

Effects of an Exercise Program Combining Aerobic and Resistance Training on Protein Expressions of Neurotrophic Factors in Obese Rats Injected with Beta-Amyloid

In this study, the effects of a 12-week exercise program combining aerobic and resistance training on high-fat diet-induced obese Sprague Dawley (SD) rats after the injection of beta-amyloid into the cerebral ventricle were investigated. Changes in physical fitness, cognitive function, blood levels of beta-amyloid and metabolic factors, and protein expressions of neurotrophic factors related to brain function such as BDNF (brain-derived neurotrophic factor) in the quadriceps femoris, hippocampus, and cerebral cortex were analyzed. The subjects were thirty-two 10-week-old SD rats (DBL Co., Ltd., Seoul, Korea). The rats were randomized into four groups: β-Non-Ex group (n = 8) with induced obesity and βA25-35 injection into the cerebral ventricle through stereotactic biopsy; β-Ex group (n = 8) with induced obesity, βA25-35 injection, and exercise; S-Non-Ex group (n = 8) with an injection of saline in lieu of βA25-35 as the control; and S-Ex group (n = 8) with saline injection and exercise. The 12-week exercise program combined aerobic training and resistance training. As for protein expressions of the factors related to brain function, the combined exercise program was shown to have a clear effect on activating the following factors: PGC-1α (peroxisome proliferator-activated receptor gamma coactivator 1-alpha), FNDC5 (fibronectin type III domain-containing protein 5), and BDNF in the quadriceps femoris; TrkB (Tropomyosin receptor kinase B), FNDC5, and BDNF in the hippocampus; PGC-1α, FNDC5, and BDNF in the cerebral cortex. The protein expression of β-amyloid in the cerebral cortex was significantly lower in the β-Ex group than in the β-Non-Ex group (p < 0.05). The 12-week intervention with the combined exercise program of aerobic and resistance training was shown to improve cardiopulmonary function, muscular endurance, and short-term memory. The results demonstrate a set of positive effects of the combined exercise program, which were presumed to have arisen mainly due to its alleviating effect on β-amyloid plaques, the main cause of reduced brain function, as well as the promotion of protein expressions of PGC-1α, FNDC5, and BDNF in the quadriceps femoris, hippocampus, and cerebral cortex.

APP Processing: A Biochemical Competition Influenced by Exercise-Induced Signaling Mediators?

Neurodegenerative diseases, such as Alzheimer's disease (AD), are becoming more common in aging our society. One specific neuropathological hallmark of this disease is excessive accumulation of amyloid-β (Aβ) peptides, which can aggregate to form the plaques commonly associated with this disease. These plaques are often observed well before clinical diagnosis of AD. At the cellular level, both production and aggregation of Aβ peptides in the brain is detrimental to neuronal cell production, survival, and function, as well as often resulting in neuronal dysfunction and death. Exercise and physical activity have been shown to improve overall health, including brain health, and in the last several years there has been evidence to support that exercise may be able to regulate Aβ peptide production in the brain. Exercise promotes the release of a wide array of signaling mediators from various metabolically active tissues and organs in the body. These exercise-induced signaling mediators could be the driving force behind some of the beneficial effects observed in brain with exercise. This review will aim to discuss potential exercise-induced signaling mediators with the capacity to influence various proteins involved in the formation of Aβ peptide production in the brain.

Protective Effects of Dendrobium nobile Lindl. Alkaloids on Alzheimer's Disease-like Symptoms Induced by High-methionine Diet

BACKGROUND

High methionine-diet (HMD) causes Alzheimer's disease (AD)-like symptoms. Previous studies have shown that Dendrobium nobile Lindle. alkaloids (DNLA) have potential benefits for AD Object: The objective of this study has been to explore whether DNLA can improve AD-like symptoms induced by HMD.

METHODS

Mice were fed with 2% HMD diet for 11 weeks; the DNLA20 control group (20 mg/kg), DNLA10 group (10 mg/kg), and DNLA20 group (20 mg/kg) were administered DNLA for 3 months. Morris water maze test was used to detect learning and memory ability. Neuron damage was evaluated by HE and Nissl staining. Levels of homocysteine (Hcy), beta-amyloid 1-42 (Aβ_1-42), S-adenosine methionine (SAM) and S-adenosine homocysteine (SAH) were detected by ELISA. Immunofluorescence and western blotting (WB) were used to determine the expression of proteins. CPG island methylation levels were accessed by Methylation-specific PCR (MSP) and MethylTarget methylation detection.

RESULTS

Morris water maze test revealed that DNLA improved learning and memory dysfunction. HE, Nissl, and immunofluorescence staining showed that DNLA alleviated neuron damage and reduced the 5-methylcytosine (5-mC), Aβ_1-40) and Aβ_1-42) levels. DNLA also decreased the levels of Hcy and Aβ_1-42) in the serum, along with decreasing SAM/SAH level in the liver tissue. WB results showed that DNLA down-regulated the expression of amyloid-precursor protein (APP), presenilin-1 (PS1), beta-secretase-1 (BACE1), DNA methyltransferase1 (DNMT1), Aβ_1-40) and Aβ_1-42) proteins. DNLA also up-regulated the proteins expression of insulin-degrading enzyme (IDE), neprilysin (NEP), DNMT3a and DNMT3b. Meanwhile, DNLA increased CPG island methylation levels of APP and BACE1 genes.

CONCLUSION

DNLA alleviated AD-like symptoms induced by HMD via the DNA methylation pathway.

Functionalized nanoparticles for brain targeted BDNF gene therapy to rescue Alzheimer's disease pathology in transgenic mouse model

Brain-derived neurotrophic factor (BDNF) is actively produced and utilized in cortical circuits throughout life to sustain neuronal function and synaptic plasticity. In animal models of Alzheimer's Disease (AD), highly invasive BDNF gene therapy using viral vectors has successfully shown enhanced synaptic protein expression, proliferation of neurons and attenuation of amyloidogenic processes. However, to eliminate virus-related safety issues and invasive procedures, our present study has explored brain-targeted lipid-based nanoparticles that can deliver plasmid encoding BDNF to brain in a safe and efficient manner. Efficacy of these nanoparticles was tested in early (6-months) and advanced stage (9-months) transgenic APP/PS1 AD mice. Liposomes were surface-functionalized with brain targeting ligand, mannose, and cell-penetrating peptides (rabies virus-derived peptide or penetratin). These bifunctionalized nanoparticles enhanced BDNF expression by ~2 times and resulted in >40% (p < 0.05) reduction in toxic amyloid-beta peptides in 6- and 9-months old APP/PS1 mice brains compared to their age-matched untreated controls. Plaque load was reduced ~7 and ~3 times (p < 0.05), respectively, whereas synaptic proteins, synaptophysin and PSD-95, were found to be increased >90% (p < 0.05) in both age groups of transgenic mice treated with bifunctionalized nanoparticles. No untoward adverse effects were observed throughout treatment, suggesting a safe and effective strategy to rescue AD pathology.

Comorbidity of osteoporosis and Alzheimer's disease: Is `AKT `-ing on cellular glucose uptake the missing link?

Osteoporosis and Alzheimer's disease (AD) are both degenerative diseases. Osteoporosis often proceeds cognitive deficits, and multiple studies have revealed common triggers that lead to energy deficits in brain and bone. Risk factors for osteoporosis and AD, such as obesity, type 2 diabetes, aging, chemotherapy, vitamin deficiency, alcohol abuse, and apolipoprotein Eε4 and/or Il-6 gene variants, reduce cellular glucose uptake, and protective factors, such as estrogen, insulin, exercise, mammalian target of rapamycin inhibitors, hydrogen sulfide, and most phytochemicals, increase uptake. Glucose uptake is a fine-tuned process that depends on an abundance of glucose transporters (Gluts) on the cell surface. Gluts are stored in vesicles under the plasma membrane, and protective factors cause these vesicles to fuse with the membrane, resulting in presentation of Gluts on the cell surface. This translocation depends mainly on AKT kinase signaling and can be affected by a range of factors. Reduced AKT kinase signaling results in intracellular glucose deprivation, which causes endoplasmic reticulum stress and iron depletion, leading to activation of HIF-1α, the transcription factor necessary for higher Glut expression. The link between diseases and aging is a topic of growing interest. Here, we show that diseases that affect the same biochemical pathways tend to co-occur, which may explain why osteoporosis and/or diabetes are often associated with AD.

Gender influence on clinical manifestations, depressive symptoms and brain-derived neurotrophic factor (BDNF) serum levels in patients affected by fibromyalgia

INTRODUCTION

OBJECTIVES: Fibromyalgia (FM) is a common rheumatic disorder characterized by chronic, widespread pain associated with several not painful symptoms. The contribution of gender to the manifestation of the disease may influence the higher prevalence of FM among women. In spite of this, how patients' gender influences the clinical manifestation of FM is still not well understood. The frequent association with neuropsychiatric symptoms raised the attention on the role of neurotrophins, including the brain-derived neurotrophic factor (BDNF) as potential biomarkers of the condition. Aims of the study were to evaluate the influence of gender on clinical manifestations and to investigate BDNF serum levels as a potential biomarker of FM.

METHODS

We consecutively enrolled 201 adult patients of both sexes diagnosed with FM. For each patient, we collected clinical and clinimetric data and, in a subgroup of 40 patients, we measured serum BDNF levels. BDNF levels have been measured also in 40 matched healthy controls (HC).

RESULTS

Several symptoms were significantly higher in women compared with men, including pain, fatigue, memory problems, tenderness, balance problems and sensitivity to environmental stimuli. On the contrary, men reported a significant higher frequency of coexisting depressive symptoms. BDNF levels were significantly lower in FM patients compared with HC, discriminating with good accuracy the condition.

CONCLUSION

Gender influences FM clinical manifestations, with a higher prevalence of pain, fatigue and other common FM symptoms among women while higher frequency of neuropsychiatric symptoms among men. BDNF offers promises as a potential biomarker of the disease. Key Points • Gender-related differences in the clinical manifestations of FM may contribute to the higher prevalence of FM among females. Indeed, women show higher levels of pain and symptoms traditionally associated to FM, which are evaluated to establish the diagnosis according to the clinical criteria. • The new insights into the pathogenesis of the disease raised the attention on the role of brain mediators in FM. Among these, BNDF shows potential as a diagnostic biomarker.

Physical Exercise, a Potential Non-Pharmacological Intervention for Attenuating Neuroinflammation and Cognitive Decline in Alzheimer's Disease Patients

This narrative review summarises the evidence for considering physical exercise (PE) as a non-pharmacological intervention for delaying cognitive decline in patients with Alzheimer’s disease (AD) not only by improving cardiovascular fitness but also by attenuating neuroinflammation. Ageing is the most important risk factor for AD. A hallmark of the ageing process is a systemic low-grade chronic inflammation that also contributes to neuroinflammation. Neuroinflammation is associated with AD, Parkinson’s disease, late-onset epilepsy, amyotrophic lateral sclerosis and anxiety disorders. Pharmacological treatment of AD is currently limited to mitigating the symptoms and attenuating progression of the disease. AD animal model studies and human studies on patients with a clinical diagnosis of different stages of AD have concluded that PE attenuates cognitive decline not only by improving cardiovascular fitness but possibly also by attenuating neuroinflammation. Therefore, low-grade chronic inflammation and neuroinflammation should be considered potential modifiable risk factors for AD that can be attenuated by PE. This opens the possibility for personalised attenuation of neuroinflammation that could also have important health benefits for patients with other inflammation associated brain disorders (i.e., Parkinson’s disease, late-onset epilepsy, amyotrophic lateral sclerosis and anxiety disorders). In summary, life-long, regular, structured PE should be considered as a supplemental intervention for attenuating the progression of AD in human. Further studies in human are necessary to develop optimal, personalised protocols, adapted to the progression of AD and the individual’s mental and physical limitations, to take full advantage of the beneficial effects of PE that include improved cardiovascular fitness, attenuated systemic inflammation and neuroinflammation, stimulated brain Aβ peptides brain catabolism and brain clearance.

Can exercise training teach us how to treat Alzheimer's disease?

Alzheimer's disease (AD) is the most common cause of dementia and there is currently no cure. Novel approaches to treat AD and curb the rapidly increasing worldwide prevalence and costs of dementia are needed. Physical inactivity is a significant modifiable risk factor for AD, estimated to contribute to 12.7% of AD cases worldwide. Exercise interventions in humans and animals have shown beneficial effects of exercise on brain plasticity and cognitive functions. In animal studies, exercise also improved AD pathology. The mechanisms underlying these effects of exercise seem to be associated mainly with exercise performance or cardiorespiratory fitness. In addition, exercise-induced molecules of peripheral origin seem to play an important role. Since exercise affects the whole body, there likely is no single therapeutic target that could mimic all the benefits of exercise. However, systemic strategies may be a viable means to convey broad therapeutic effects in AD patients. Here, we review the potential of physical activity and exercise training in AD prevention and treatment, shining light on recently discovered underlying mechanisms and concluding with a view on future development of exercise-free treatment strategies for AD.

Post-Exercise Serum from Humans Influences the Biological Tug of War of APP Processing in Human Neuronal Cells

Neurodegenerative diseases such as Alzheimer's disease (AD) are becoming more prevalent in our aging society. One specific neuropathological hallmark of this disease is the accumulation of amyloid-β (Aβ) peptides, which aggregate to form extra-neuronal plaques. Increased Aβ peptides are often observed well before symptoms of AD develop, highlighting the importance of targeting Aβ producing pathways early on in disease progression. Evidence indicates that exercise has the capacity to reduce Aβ peptide production in the brain however the mechanisms remain unknown. Exercise-induced signaling mediators could be the driving force behind some of the beneficial effects observed in the brain with exercise. The purpose of this study was to examine if post-exercise serum and the factors it contains can alter neuronal APP processing. Human SH-SY5Y neuronal cells were differentiated with retinoic acid for 5 days and treated with 10% pre- or post-exercise serum from humans for 30 minutes. Cells were collected for analysis of acute (30 minutes; n=6) or adaptive (24 hours post-treatment; n=6) responses. There were no statistical differences in ADAM10 and BACE1 mRNA or protein expression with post-exercise serum treatment at either time point. However, there was an increase in the ratio of sAPPa to sAPPβ protein content (p=0.05) after 30 minutes of post-exercise serum treatment. Additionally, 30 minutes of post-exercise serum treatment increased ADAM10 (p=0.01) and BACE1 (p=0.02) activity. These findings suggest that post-exercise serum modulates important enzymes involved in APP processing, pushing the cascade towards the non-amyloidogenic arm.

Brain-derived neurotrophic factor in Alzheimer's disease and its pharmaceutical potential

Synaptic abnormalities are a cardinal feature of Alzheimer's disease (AD) that are known to arise as the disease progresses. A growing body of evidence suggests that pathological alterations to neuronal circuits and synapses may provide a mechanistic link between amyloid β (Aβ) and tau pathology and thus may serve as an obligatory relay of the cognitive impairment in AD. Brain-derived neurotrophic factors (BDNFs) play an important role in maintaining synaptic plasticity in learning and memory. Considering AD as a synaptic disorder, BDNF has attracted increasing attention as a potential diagnostic biomarker and a therapeutical molecule for AD. Although depletion of BDNF has been linked with Aβ accumulation, tau phosphorylation, neuroinflammation and neuronal apoptosis, the exact mechanisms underlying the effect of impaired BDNF signaling on AD are still unknown. Here, we present an overview of how BDNF genomic structure is connected to factors that regulate BDNF signaling. We then discuss the role of BDNF in AD and the potential of BDNF-targeting therapeutics for AD.

Brothers in arms: proBDNF/BDNF and sAPPα/Aβ-signaling and their common interplay with ADAM10, TrkB, p75NTR, sortilin, and sorLA in the progression of Alzheimer's disease

Brain-derived neurotrophic factor (BDNF) is an important modulator for a variety of functions in the central nervous system (CNS). A wealth of evidence, such as reduced mRNA and protein level in the brain, cerebrospinal fluid (CSF), and blood samples of Alzheimer's disease (AD) patients implicates a crucial role of BDNF in the progression of this disease. Especially, processing and subcellular localization of BDNF and its receptors TrkB and p75 are critical determinants for survival and death in neuronal cells. Similarly, the amyloid precursor protein (APP), a key player in Alzheimer's disease, and its cleavage fragments sAPPα and Aβ are known for their respective roles in neuroprotection and neuronal death. Common features of APP- and BDNF-signaling indicate a causal relationship in their mode of action. However, the interconnections of APP- and BDNF-signaling are not well understood. Therefore, we here discuss dimerization properties, localization, processing by α- and γ-secretase, relevance of the common interaction partners TrkB, p75, sorLA, and sortilin as well as shared signaling pathways of BDNF and sAPPα.

Effect of soluble amyloid precursor protein-alpha on adult hippocampal neurogenesis in a mouse model of Alzheimer's disease

Soluble amyloid precursor protein-alpha (sAPPα) is a regulator of neuronal and memory mechanisms, while also having neurogenic and neuroprotective effects in the brain. As adult hippocampal neurogenesis is impaired in Alzheimer’s disease, we tested the hypothesis that sAPPα delivery would rescue adult hippocampal neurogenesis in an APP/PS1 mouse model of Alzheimer’s disease. An adeno-associated virus-9 (AAV9) encoding murine sAPPα was injected into the hippocampus of 8-month-old wild-type and APP/PS1 mice, and later two different thymidine analogues (XdU) were systemically injected to label adult-born cells at different time points after viral transduction. The proliferation of adult-born cells, cell survival after eight weeks, and cell differentiation into either neurons or astrocytes was studied. Proliferation was impaired in APP/PS1 mice but was restored to wild-type levels by viral expression of sAPPα. In contrast, sAPPα overexpression failed to rescue the survival of XdU⁺-labelled cells that was impaired in APP/PS1 mice, although it did cause a significant increase in the area density of astrocytes in the granule cell layer across both genotypes. Finally, viral expression of sAPPα reduced amyloid-beta plaque load in APP/PS1 mice in the dentate gyrus and somatosensory cortex. These data add further evidence that increased levels of sAPPα could be therapeutic for the cognitive decline in AD, in part through restoration of the proliferation of neural progenitor cells in adults.

The Gut Microbiota-Brain Axis: A New Frontier on Neuropsychiatric Disorders

Alzheimer's disease (AD) is a progressive and incurable neurodegenerative disorder of integrative areas of the brain, characterized by cognitive decline and disability resulting in negative impacts on the family of the patients and the health care services worldwide. AD involves oxidative stress, neuroinflammation and accelerated apoptosis, accompanied by deposition of amyloid-β peptide plaques and tau protein-based neurofibrillary tangles in the central nervous system. Among the multiple factors that contribute to the onset and evolution of this disease, aging stands out. That is why the prevalence of this disease has increased due to the constant increase in life expectancy. In the hope of finding new, more effective methods to slow the progression of this disease, over the last two decades, researchers have promoted "omics"-based approaches that include the gut microbiota and their reciprocal interactions with different targets in the body. This scientific advance has also led to a better understanding of brain compartments and the mechanisms that affect the integrity of the blood-brain barrier. This review aims to discuss recent advances related to the gut-brain-microbiota axis in AD. Furthermore, considering that AD involves psychiatric symptoms, this review also focuses on the psychiatric factors that interact with this axis (an issue that has not yet been sufficiently addressed in the literature).

APOE ε4 and exercise interact in a sex‐specific manner to modulate dementia risk factors

Introduction

Apolipoprotein E (APOE) ε4 is the strongest genetic risk factor for Alzheimer's disease and related dementias (ADRDs), affecting many different pathways that lead to cognitive decline. Exercise is one of the most widely proposed prevention and intervention strategies to mitigate risk and symptomology of ADRDs. Importantly, exercise and APOE ε4 affect similar processes in the body and brain. While both APOE ε4 and exercise have been studied extensively, their interactive effects are not well understood.

Methods

To address this, male and female APOE ε3/ε3, APOE ε3/ε4, and APOE ε4/ε4 mice ran voluntarily from wean (1 month) to midlife (12 months). Longitudinal and cross‐sectional phenotyping were performed on the periphery and the brain, assessing markers of risk for dementia such as weight, body composition, circulating cholesterol composition, murine daily activities, energy expenditure, and cortical and hippocampal transcriptional profiling.

Results

Data revealed chronic running decreased age‐dependent weight gain, lean and fat mass, and serum low‐density lipoprotein concentration dependent on APOE genotype. Additionally, murine daily activities and energy expenditure were significantly influenced by an interaction between APOE genotype and running in both sexes. Transcriptional profiling of the cortex and hippocampus predicted that APOE genotype and running interact to affect numerous biological processes including vascular integrity, synaptic/neuronal health, cell motility, and mitochondrial metabolism, in a sex‐specific manner.

Discussion

These data in humanized mouse models provide compelling evidence that APOE genotype should be considered for population‐based strategies that incorporate exercise to prevent ADRDs and other APOE‐relevant diseases.

Voluntary wheel running alters markers of amyloid-beta precursor protein processing in an ovarian hormone depleted model

INTRODUCTION

Aberrant cleavage of the transmembrane protein, amyloid-beta precursor protein (ABPP), results in the overproduction of amyloid-beta (AB) peptides which can form senile plaques in the brain. These plaques can get lodged within synapses and disrupt neuronal communication ultimately leading to rampant neuron death. The rate-limiting enzyme in AB production is beta-site ABPP cleaving enzyme 1 (BACE1). In females, estrogen loss is associated with increases in AB and BACE1 content and activity. Exercise is known to have anti-amyloidogenic effects and may be able to alter BACE1 in cases of ovarian hormone depletion. This study aimed to examine the effects of physical activity on BACE1 in intact and ovariectomized female mice.

METHODS

Female C57BL/6 mice (24 weeks old) underwent bilateral ovariectomy (OVX; n=20) or SHAM surgery (SHAM; n=20). Mice were assigned to one of four groups (n=10/group) for 8 weeks: (1) sham (SHAM), (2) sham with a wheel (SHAM VWR), (3) ovariectomized (OVX), or (4) ovariectomized with a wheel (OVX VWR).

RESULTS

Novel object recognition testing demonstrated that OVX mice had a lower percentage of novel object investigation time compared to SHAM. OVX mice also had higher prefrontal cortex BACE1 activity compared to SHAM (p<0.0001), while the OVX+VWR activity was not different from SHAM.

DISCUSSIONS

Our results demonstrate that voluntary wheel running in an ovariectomized model prevented increases in BACE1 activity, maintained memory recall, and may provide a method of slowing the progression of Alzheimer's disease.

Psychedelic-inspired approaches for treating neurodegenerative disorders

Psychedelics are increasingly being recognized for their potential to treat a wide range of brain disorders including depression, post-traumatic stress disorder (PTSD), and substance use disorder. Their broad therapeutic potential might result from an ability to rescue cortical atrophy common to many neuropsychiatric and neurodegenerative diseases by impacting neurotrophic factor gene expression, activating neuronal growth and survival mechanisms, and modulating the immune system. While the therapeutic potential of psychedelics has not yet been extended to neurodegenerative disorders, we provide evidence suggesting that approaches based on psychedelic science might prove useful for treating these diseases. The primary target of psychedelics, the 5-HT_2A receptor, plays key roles in cortical neuron health and is dysregulated in Alzheimer's disease. Moreover, evidence suggests that psychedelics and related compounds could prove useful for treating the behavioral and psychological symptoms of dementia (BPSD). While more research is needed to probe the effects of psychedelics in models of neurodegenerative diseases, the robust effects of these compounds on structural and functional neuroplasticity and inflammation clearly warrant further investigation.