Treadmill Exercise Ameliorates Spatial Learning and Memory Deficits Through Improving the Clearance of Peripheral and Central Amyloid-Beta Levels

Targeting necroptosis in Alzheimer's disease: can exercise modulate neuronal death?

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by cognitive decline and neuronal degeneration. Emerging evidence implicates necroptosis in AD pathogenesis, driven by the RIPK1-RIPK3-MLKL pathway, which promotes neuronal damage, inflammation, and disease progression. Exercise, as a non-pharmacological intervention, can modulate key inflammatory mediators such as TNF-α, HMGB1, and IL-1β, thereby inhibiting necroptotic signaling. Additionally, exercise enhances O-GlcNAc glycosylation, preventing Tau hyperphosphorylation and stabilizing neuronal integrity. This review explores how exercise mitigates necroptosis and neuroinflammation, offering novel therapeutic perspectives for AD prevention and management.

Effects of Pretreatment With Coenzyme Q10 (CoQ10) and High-Intensity Interval Training (HIIT) on FNDC5, Irisin, and BDNF Levels, and Amyloid-Beta (Aβ) Plaque Formation in the Hippocampus of Aβ-Induced Alzheimer's Disease Rats

AIMS

Physical exercise has been shown to protect against cognitive decline in Alzheimer's disease (AD), likely through the upregulation of brain-derived neurotrophic factor (BDNF). Recent studies have reported that exercise activates the FNDC5/irisin pathway in the hippocampus of mice, triggering a neuroprotective gene program that includes BDNF. This study aimed to investigate the effects of 8 weeks of pretreatment with coenzyme Q10 (CoQ10) and high-intensity interval training (HIIT), both individually and in combination, on FNDC5, irisin, BDNF, and amyloid-beta (Aβ) plaque formation in the hippocampus of Aβ-related AD rats.

METHODS

In this study, 72 male Wistar rats were randomly assigned to one of the following groups: control, sham, HIIT (low intensity: 3 min running at 50%-60% VO2max; high intensity: 4 min running at 85%-90% VO2max), Q10 (50 mg/kg, orally administered), Q10 + HIIT, AD, AD + HIIT, AD + Q10, and AD + Q10 + HIIT.

RESULTS

Aβ injection resulted in a trend toward decreased levels of FNDC5, irisin, and BDNF, alongside increased Aβ plaque formation in the hippocampus of Aβ-induced AD rats. However, pretreatment with CoQ10, HIIT, or their combination significantly restored hippocampal levels of FNDC5, irisin, and BDNF, while also inhibiting Aβ plaque accumulation in these rats.

CONCLUSION

Pretreatment with CoQ10 and HIIT improved the Aβ-induced reduction in BDNF levels probably through the FNDC5/irisin pathway and preventing Aβ plaque formation.

The effect of the APOE4 genotype on physiological and cognitive health in randomised controlled trials with an exercise intervention: a systematic review and meta-analysis

BACKGROUND

Alzheimer's disease is caused by modifiable and non-modifiable risk factors. Randomised controlled trials have investigated whether the strongest genetic risk factor for Alzheimer's disease, APOE4, impacts the effectiveness of exercise on health. Systematic reviews are yet to evaluate the effect of exercise on physical and cognitive outcomes in APOE genotyped participants. A quality assessment of these randomised controlled trials is needed to understand the impact genotype has on the potential success of intervention. This systematic review aimed to determine if the APOE4 genotype influences the effectiveness of exercise-based randomised controlled trials.

METHOD

Searches on MEDLINE, EMBASE, and PsycINFO identified eligible exercise based randomised controlled trials incorporating participants with varied cognitive abilities. Quality assessments were conducted.

RESULTS

Nineteen studies met the inclusion criteria for systematic review, and 3 for the meta-analysis. Very low to moderate quality evidence showed that APOE4 carriers benefitted more than APOE4 non-carriers on cognitive (e.g. executive function, learning) and physical (e.g. relative telomere length) outcomes after exercise; and that APOE4 non-carriers benefited over carriers for physical (serum BDNF, gait speed) and cognitive (global cognition, verbal memory) markers. Very low quality evidence indicated that there was no evidence of difference between APOE4 carriers and non-carriers on physical function outcomes in meta-analysis. Several areas of study design and reporting, including maintenance of relative exercise intensity and complete statistical reporting, were identified as needing improvement.

DISCUSSION

This systematic review found very limited evidence to suggest that exercise interventions can benefit APOE4 carriers and non-carriers equally, though conclusions were limited by evidence quality. Further randomised controlled trials, stratifying participants by APOE status are required to better understand the relationship between APOE genotype and the effect of exercise on health-related outcomes.

TRIAL REGISTRATION

This review was registered with PROSPERO (CRD42023436842). Registered on June 16, 2023.

Understanding the Molecular Impact of Physical Exercise on Alzheimer's Disease

Alzheimer's disease is one of the most common neurodegenerative diseases, characterized by a wide range of neurological symptoms that begin with personality changes and psychiatric symptoms, progress to mild cognitive impairment, and eventually lead to dementia. Physical exercise is part of the non-pharmacological treatments used in Alzheimer's disease, as it has been shown to delay the neurodegenerative process by improving the redox state in brain tissue, providing anti-inflammatory effects or stimulating the release of the brain-derived neurotrophic factor that enhances the brain structure and cognitive performance. Here, we reviewed the results obtained from studies conducted in both animal models and human subjects to comprehend how physical exercise interventions can exert changes in the molecular mechanisms underlying the pathophysiological processes in Alzheimer's disease: amyloid β-peptide pathology, tau pathology, neuroglial changes, mitochondrial dysfunction, and oxidative stress. Physical exercise seems to have a protective effect against Alzheimer's disease, since it has been shown to induce positive changes in some of the biomarkers related to the pathophysiological processes of the disease. However, additional studies in humans are necessary to address the current lack of conclusive evidence.

A meta-analysis of the efficacy of physical exercise interventions on activities of daily living in patients with Alzheimer's disease

Objective

This study aimed to systematically review published randomized controlled trials on the effects of physical exercise on activities of daily living (ADL) in Alzheimer's patients through meta-analysis, thereby synthesizing existing evidence to provide scientific intervention recommendations for exercise prescriptions in Alzheimer's patients.

Methods

Based on strict literature inclusion and exclusion criteria, a systematic search was conducted in databases including PubMed and Web of Science from their inception to July 1, 2024. The Cochrane risk assessment tool was used to evaluate the design of randomized controlled trials. Studies reporting on physical exercise interventions for ADL in Alzheimer's patients were systematically identified. Subgroup analyses and meta-regression were performed to explore sources of heterogeneity.

Results

Nineteen articles, for analysis, providing 27 randomized controlled trials (RCTs). A random-effects model was used to calculate the effect size and 95% confidence interval for each independent study, and meta-analysis was performed using Stata 16.0 and RevMan 5.4 software. The results showed that physical exercise might significantly improve ADL in Alzheimer's patients (SMD = 0.33, 95% CI: 0.12-0.54, I 2 = 81.7%). Sensitivity analysis confirmed the robustness of the results (p > 0.05). Egger's test did not reveal significant publication bias (p = 0.145). Samples were divided into different subgroups based on intervention content, duration, frequency, and session length. Subgroup analysis based on intervention characteristics showed that resistance training or aerobic exercise (SMD = 0.83, 95% CI: 0.60-1.05), long-term interventions (>6 months, SMD = 0.31, 95% CI: 0.13-0.49), medium-frequency interventions (4-5 times per week, SMD=0.39, 95% CI: 0.23-0.55), and short-duration training ( ≤ 30 min, SMD = 0.96, 95% CI: 0.71-1.21) might be most effective in enhancing ADL in Alzheimer's patients. These improvements were not only statistically significant but also had substantial impact in clinical practice.

Conclusion

Resistance training or aerobic exercise lasting more than 6 months, 4-5 times per week, and lasting no more than 30 min per session may be most effective in improving ADLs in patients with Alzheimer's disease.

Physical Exercise and Mechanism Related to Alzheimer's Disease: Is Gut-Brain Axis Involved?

BACKGROUND

Alzheimer's disease is a progressive neurodegenerative disease characterized by structural changes in the brain, including hippocampal atrophy, cortical thinning, amyloid plaques, and tau tangles. Due to the aging of the global population, the burden of Alzheimer's disease is expected to increase, making the exploration of non-pharmacological interventions, such as physical exercise, an urgent priority.

RESULTS

There is emerging evidence that regular physical exercise may mitigate the structural and functional declines associated with Alzheimer's disease. The underlying mechanisms, however, remain poorly understood. Gut-brain axis research is a promising area for further investigation. This system involves bidirectional communication between the gut microbiome and the brain. According to recent studies, the gut microbiome may influence brain health through modulating neuroinflammation, producing neuroactive compounds, and altering metabolic processes. Exercise has been shown to alter the composition of the gut microbiome, potentially impacting brain structure and function. In this review, we aim to synthesize current research on the relationship between physical exercise, structural brain changes in Alzheimer's disease, and the gut-brain axis.

CONCLUSIONS

In this study, we will investigate whether changes in the gut microbiome induced by physical exercise can mediate its neuroprotective effects, offering new insights into the prevention and treatment of Alzheimer's disease. By integrating findings from neuroimaging studies, clinical trials, and microbiome research, this review will highlight potential mechanisms. It will also identify key gaps in the literature. This will pave the way for future research directions.

8-weeks aerobic exercise ameliorates cognitive deficit and mitigates ferroptosis triggered by iron overload in the prefrontal cortex of APP Swe/PSEN 1dE9 mice through Xc-/GPx4 pathway

Background

Alzheimer's disease (AD) is a degenerative disorder of the central nervous system characterized by notable pathological features such as neurofibrillary tangles and amyloid beta deposition. Additionally, the significant iron accumulation in the brain is another important pathological hallmark of AD. Exercise can play a positive role in ameliorating AD, but the mechanism is unclear. The purpose of the study is to explore the effect of regular aerobic exercise iron homeostasis and lipid antioxidant pathway regarding ferroptosis in the prefrontal cortex (PFC) of APP Swe/PSEN 1dE9 (APP/PS1) mice.

Methods

Eighty 6-month-old C57BL/6 J and APP/PS1 mice were divided equally into 8-weeks aerobic exercise groups and sedentary groups. Subsequently, Y-maze, Morris water maze test, iron ion detection by probe, Western Blot, ELISA, RT-qPCR, HE, Nissle, Prussian Blue, IHC, IF, and FJ-C staining experiments were conducted to quantitatively assess the behavioral performance, iron levels, iron-metabolism-related proteins, lipid antioxidant-related proteins and morphology in each group of mice.

Results

In APP/PS1 mice, the increase in heme input proteins and heme oxygenase lead to the elevated levels of free iron in the PFC. The decrease in ferritin content by ferritin autophagy fails to meet the storage needs for excess free iron within the nerve cells. Ultimately, the increase of free ferrous iron triggers the Fenton reaction, may lead to ferroptosis and resulting in cognitive impairment in APP/PS1 mice. However, 8-weeks aerobic exercise induce upregulation of the Xc-/GPx4 pathway, which can reverse the lipid peroxidation process, thereby inhibiting ferroptosis in APP/PS1 mice.

Conclusion

8 weeks aerobic exercise can improve learning and memory abilities in AD, upregulate GPx4/Xc- pathway in PFC to reduce ferroptosis induced by AD.

Moderate aerobic training enhances the effectiveness of insulin therapy through hypothalamic IGF1 signaling in rat model of Alzheimer's disease

Alzheimer's disease (AD) is a neurological condition that is connected with a decline in a person's memory as well as their cognitive ability. One of the key topics of AD research has been the exploration of metabolic causes. We investigated the effects of treadmill exercise and intranasal insulin on learning and memory impairment and the expression of IGF1, BDNF, and GLUT4 in hypothalamus. The animals were put into 9 groups at random. In this study, we examined the impact of insulin on spatial memory in male Wistar rats and analyzed the effects of a 4-week pretreatment of moderate treadmill exercise and insulin on the mechanisms of improved hypothalamic glucose metabolism through changes in gene and protein expression of IGF1, BDNF, and GLUT4. We discovered that rat given Aβ25-35 had impaired spatial learning and memory, which was accompanied by higher levels of Aβ plaque burden in the hippocampus and lower levels of IGF1, BDNF, and GLUT4 mRNA and protein expression in the hypothalamus. Additionally, the administration of exercise training and intranasal insulin results in the enhancement of spatial learning and memory impairments, the reduction of plaque burden in the hippocampus, and the enhancement of the expression of IGF1, BDNF, and GLUT4 in the hypothalamus of rats that were treated with Aβ25-35. Our results show that the improvement of learning and spatial memory due to the improvement of metabolism and upregulation of the IGF1, BDNF, and GLUT4 pathways can be affected by pretreatment exercise and intranasal insulin.

GluN2A or GluN2B subunits of the NMDA receptor contribute to changes in neuronal excitability and impairments in LTP in the hippocampus of aging mice but do not mediate detrimental effects of oligomeric Aβ (1-42)

Studies in rodent models have revealed that oligomeric beta-amyloid protein [Aβ (1-42)] plays an important role in the pathogenesis of Alzheimer's disease. Early elevations in hippocampal neuronal excitability caused by Aβ (1-42) have been proposed to be mediated via enhanced activation of GluN2B-containing N-methyl-D-aspartate receptors (NMDAR). To what extent GluN2A or GluN2B-containing NMDAR contribute to Aβ (1-42)-mediated impairments of hippocampal function in advanced rodent age is unclear. Here, we assessed hippocampal long-term potentiation (LTP) and neuronal responses 4-5 weeks after bilateral intracerebral inoculation of 8-15 month old GluN2A+/- or GluN2B+/- transgenic mice with oligomeric Aβ (1-42), or control peptide. Whole-cell patch-clamp recordings in CA1 pyramidal neurons revealed a more positive resting membrane potential and increased total spike time in GluN2A+/-, but not GluN2B+/--hippocampi following treatment with Aβ (1-42) compared to controls. Action potential 20%-width was increased, and the descending slope was reduced, in Aβ-treated GluN2A+/-, but not GluN2B+/- hippocampi. Sag ratio was increased in Aβ-treated GluN2B+/--mice. Firing frequency was unchanged in wt, GluN2A+/-, and GluN2B+/-hippocampi after Aβ-treatment. Effects were not significantly different from responses detected under the same conditions in wt littermates, however. LTP that lasted for over 2 h in wt hippocampal slices was significantly reduced in GluN2A+/- and was impaired for 15 min in GluN2B+/--hippocampi compared to wt littermates. Furthermore, LTP (>2 h) was significantly impaired in Aβ-treated hippocampi of wt littermates compared to wt treated with control peptide. LTP induced in Aβ-treated GluN2A+/- and GluN2B+/--hippocampi was equivalent to LTP in control peptide-treated transgenic and Aβ-treated wt animals. Taken together, our data indicate that knockdown of GluN2A subunits subtly alters membrane properties of hippocampal neurons and reduces the magnitude of LTP. GluN2B knockdown reduces the early phase of LTP but leaves later phases intact. Aβ (1-42)-treatment slightly exacerbates changes in action potential properties in GluN2A+/--mice. However, the vulnerability of the aging hippocampus to Aβ-mediated impairments of LTP is not mediated by GluN2A or GluN2B-containing NMDAR.

Intranasal insulin intake and exercise improve memory function in amyloid-β induced Alzheimer's-like disease in rats: Involvement of hippocampal BDNF-TrkB receptor

The most prevalent type of dementia, Alzheimer's disease (AD), is a compelling illustration of the link between cognitive deficits and neurophysiological anomalies. We investigated the possible protective effect of intranasal insulin intake with exercise on amyloid-β (Aβ)-induced neuronal damage. The level of hippocampal brain-derived neurotrophic factor (BDNF) and tropomyosin-related kinase B (TrkB) were analyzed to understand the involvement of BDNF-TrkB pathway in this modulation. In this study, we induced AD-like pathology by amyloid-β (Aβ) administration. Then, we examined the impact of a 4-week pretreatment of moderate treadmill exercise and intranasal intake of insulin on working and spatial memory in male Wistar rats. We also analyzed the mechanisms of improved memory and anxiety through changes in the protein level of BDNF and TrkB. Results showed that animals received Aβ had impaired working memory, increased anxiety which were accompanied by lower protein levels of BDNF and TrkB in the hippocampus. The exercise training and intranasal insulin improved working memory deficits, decreased anxiety, and increased BDNF, and TrkB levels in the hippocampus of animals received Aβ. Our finding of improved memory performance after intranasal intake of insulin and exercise may be of significance for the treatment of memory impairments and anxiety-like behavior in AD.

Environmental enrichment improves cognitive function, learning, memory and anxiety-related behaviours in rodent models of dementia: Implications for future study

Environmental enrichment (EE) is a process of brain stimulation by modifying the surroundings, for example, by changing the sensory, social, or physical conditions. Rodents have been used in such experimental strategies through exposure to diverse physical, social, and exploration conditions. The present study conducted an extensive analysis of the existing literature surrounding the impact of EE on dementia rodent models. The review emphasised the two principal aspects that are very closely related to dementia: cognitive function (learning and memory) as well as psychological factors (anxiety-related behaviours such as phobias and unrealistic worries). Also highlighted were the mechanisms involved in the rodent models of dementia showing EE effects. Two search engines, PubMed and Science Direct, were used for data collection using the following keywords: environmental enrichment, dementia, rodent model, cognitive performance, and anxiety-related behaviour. Fifty-five articles were chosen depending on the criteria for inclusion and exclusion. The rodent models with dementia demonstrated improved learning and memory in the form of hampered inflammatory responses, enhanced neuronal plasticity, and sustained neuronal activity. EE housing also prevented memory impairment through the prevention of amyloid beta (Aβ) seeding formation, an early stage of Aβ plaque formation. The rodents subjected to EE were observed to present increased exploratory activity and exert less anxiety-related behaviour, compared to those in standard housing. However, some studies have proposed that EE intervention through exercise would be too mild to counteract the anxiety-related behaviour and risk assessment behaviour deficits in the Alzheimer's disease rodent model. Future studies should be conducted on old-aged rodents and the duration of EE exposure that would elicit the greatest benefits since the existing studies have been conducted on a range of ages and EE durations. In summary, EE had a considerable effect on dementia rodent models, with the most evident being improved cognitive function.

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.

Adiponectin receptor 1 could explain the sex differences in molecular basis of cognitive improvements induced by exercise training in type 2 diabetic rats

Adipokines dysregulation, the main reason for cognitive impairments (CI) induced by diabetes, shows a sex-dependent pattern inherently and in response to exercise. This study aimed to compare the attenuating effect of 8-week high intensity-interval training (HIIT) on type 2 diabetes (T2D)-induced CI between male and female rats with a special focus on adiponectin and leptin. 28 male & 28 female Wistar rats with an average age of 8 weeks were randomly assigned into four groups: control (Con), exercise (EX), Diabetes (T2D), and Type 2 diabetes + exercise (T2D + Ex). Rats in EX and T2D + EX groups performed HIIT for eight weeks (80-100% Vmax, 4-10 intervals). T2D was induced by 2 months of a high-fat diet and a single dose of STZ (35 mg/kg) administration. Leptin and adiponectin levels in serum were measured along with hippocampal expression of leptin and adiponectin receptors, AMP-activated protein kinase (AMPK), dephosphorylated glycogen synthase kinase-3 beta (Dep-GSK3β), Tau, and beta-amyloid (Aβ). Homeostasis model assessments (HOMAs) and quantitative insulin-sensitivity check index (QUICKI) indices were calculated. Our results showed that following T2D, serum levels of APN, and hippocampal levels of adiponectin receptor 1 (APNR1) were higher and HOMA-IR was lower in female than male rats (P < 0.05). However, after 8 weeks of HIIT, hippocampal levels of APNR1 and AMPK as well as QUICKI were lower and hippocampal levels of GSK, Tau, and Aβ were higher in females compared to male rats (P < 0.05). While the risk of CI following T2D was more in male than female rats HIIT showed a more ameliorating effect in male animals with APN1 as the main player.

Modulation of microRNAs through Lifestyle Changes in Alzheimer's Disease

Lifestyle factors, including diet and physical activity (PA), are known beneficial strategies to prevent and delay Alzheimer's disease (AD) development. Recently, microRNAs have emerged as potential biomarkers in multiple diseases, including AD. The aim of this review was to analyze the available information on the modulatory effect of lifestyle on microRNA expression in AD. Few studies have addressed this question, leaving important gaps and limitations: (1) in human studies, only circulating microRNAs were analyzed; (2) in mice studies, microRNA expression was only analyzed in brain tissue; (3) a limited number of microRNAs was analyzed; (4) no human nutritional intervention studies were conducted; and (5) PA interventions in humans and mice were poorly detailed and only included aerobic training. Despite this, some conclusions could be drawn. Circulating levels of let-7g-5p, miR-107, and miR-144-3p were associated with overall diet quality in mild cognitive impairment patients. In silico analysis showed that these microRNAs are implicated in synapse formation, microglia activation, amyloid beta accumulation, and pro-inflammatory pathways, the latter also being targeted by miR-129-5p and miR-192-5p, whose circulating levels are modified by PA in AD patients. PA also modifies miR-132, miR-15b-5p, miR-148b-3p, and miR-130a-5p expression in mice brains, which targets are related to the regulation of neuronal activity, ageing, and pro-inflammatory pathways. This supports the need to further explore lifestyle-related miRNA changes in AD, both as biomarkers and therapeutic targets.

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.

Protective effects of sleep duration and physical activity on cognitive performance are influenced by β-amyloid and brain volume but not tau burden among cognitively unimpaired older adults

BACKGROUND AND OBJECTIVES

Sleep and physical activity have gained traction as modifiable risk factors for Alzheimer's disease. Sleep duration is linked to amyloid-β clearance while physical activity is associated with brain volume maintenance. We investigate how sleep duration and physical activity are associated with cognition by testing if the associations between sleep duration or physical activity to cognition are explained by amyloid-β burden and brain volume, respectively. Additionally, we explore the mediating role of tau deposition in sleep duration-cognition and physical activity-cognition relationships.

METHODS

This cross-sectional study obtained data from participants in the Anti-Amyloid Treatment in Asymptomatic Alzheimer's Disease (A4) study, a randomized clinical trial. In trial screening, cognitively unimpaired participants (age 65-85 years) underwent amyloid PET and brain MRI; APOE genotype and lifestyle questionnaire data were obtained. Cognitive performance was assessed using the Preclinical Alzheimer Cognitive Composite (PACC). Self-reported nightly sleep duration and weekly physical activity were the primary predictors. Regional Aβ and tau pathologies and volumes were the proposed variables influencing relationships between sleep duration or physical activity and cognition.

RESULTS

Aβ data were obtained from 4322 participants (1208 with MRI, 59% female, 29% amyloid positive). Sleep duration was associated with a Aβ composite score (β = -0.005, CI: (-0.01, -0.001)) and Aβ burden in the anterior cingulate (ACC) (β = -0.012, CI: (-0.017, -0.006)) and medial orbitofrontal cortices (MOC) (β = -0.009, CI: (-0.014, -0.005)). Composite (β = -1.54, 95% CI:(-1.93, -1.15)), ACC (β = -1.22, CI:(-1.54, -0.90)) and MOC (β = -1.44, CI:(-1.86, -1.02)) Aβ deposition was associated with PACC. Sleep duration-PACC association was explained by Aβ burden in path analyses. Physical activity was associated with hippocampal (β = 10.57, CI: (1.06, 20.08)), parahippocampal (β = 9.3, CI: (1.69, 16.91)), entorhinal (β = 14.68, CI: (1.75, 27.61), and fusiform gyral (β = 38.38, CI: (5.57, 71.18)) volumes, which were positively associated with PACC (p < 0.02 for hippocampus, entorhinal cortex and fusiform gyrus). Physical activity-cognition relationship was explained by regional volumes. PET tau imaging was available for 443 participants. No direct sleep duration-tau burden, physical activity by tau burden, or mediation by regional tau was observed in sleep duration-cognition or physical activity-cognition relationships.

DISCUSSION

Sleep duration and physical activity are associated with cognition through independent paths of brain Aβ and brain volume, respectively. These findings implicate neural and pathological mechanisms for the relationships between sleep duration and physical activity on cognition. Dementia risk reduction approaches that emphasize the adequate sleep duration and a physically active lifestyle may benefit those with risk for Alzheimer's disease.

Minocycline effects on memory and learning impairment in the beta-amyloid-induced Alzheimer's disease model in male rats using behavioral, biochemical, and histological methods

Alzheimer's disease (AD), as an advanced neurodegenerative disease, is characterized by the everlasting impairment of memory, which is determined by hyperphosphorylation of intracellular Tau protein and accumulation of beta-amyloid (Aβ) in the extracellular space. Minocycline is an antioxidant with neuroprotective effects that can freely cross the blood-brain barrier (BBB). This study investigated the effect of minocycline on the changes in learning and memory functions, activities of blood serum antioxidant enzymes, neuronal loss, and the number of Aβ plaques after AD induced by Aβ in male rats. Healthy adult male Wistar rats (200-220g) were divided randomly into 11 groups (n = 10). The rats received minocycline (50 and 100 mg/kg/day; per os (P.O.)) before, after, and before/after AD induction for 30 days. At the end of the treatment course, behavioral performance was measured by standardized behavioral paradigms. Subsequently, brain samples and blood serum were collected for histological and biochemical analysis. The results indicated that Aβ injection impaired learning and memory performances in the Morris water maze test, reduced exploratory/locomotor activities in the open field test, and enhanced anxiety-like behavior in the elevated plus maze. The behavioral deficits were accompanied by hippocampal oxidative stress (decreased glutathione (GSH) peroxidase enzyme activity and increased malondialdehyde (MDA) levels in the brain (hippocampus) tissue), increased number of Aβ plaques, and neuronal loss in the hippocampus evidenced by Thioflavin S and H&E staining, respectively. Minocycline improved anxiety-like behavior, recovered Aβ-induced learning and memory deficits, increased GSH and decreased MDA levels, and prevented neuronal loss and the accumulation of Aβ plaques. Our results demonstrated that minocycline has neuroprotective effects and can reduce memory dysfunction, which are due to its antioxidant and anti-apoptotic effects.

Leveraging the glymphatic and meningeal lymphatic systems as therapeutic strategies in Alzheimer's disease: an updated overview of nonpharmacological therapies

Understanding and treating Alzheimer's disease (AD) has been a remarkable challenge for both scientists and physicians. Although the amyloid-beta and tau protein hypothesis have largely explained the key pathological features of the disease, the mechanisms by which such proteins accumulate and lead to disease progression are still unknown. Such lack of understanding disrupts the development of disease-modifying interventions, leaving a therapeutic gap that remains unsolved. Nonetheless, the recent discoveries of the glymphatic pathway and the meningeal lymphatic system as key components driving central solute clearance revealed another mechanism underlying AD pathogenesis. In this regard, this narrative review integrates the glymphatic and meningeal lymphatic systems as essential components involved in AD pathogenesis. Moreover, it discusses the emerging evidence suggesting that nutritional supplementation, non-invasive brain stimulation, and traditional Chinese medicine can improve the pathophysiology of the disease by increasing glymphatic and/or meningeal lymphatic function. Given that physical exercise is a well-regarded preventive and pro-cognitive intervention for dementia, we summarize the evidence suggesting the glymphatic system as a mediating mechanism of the physical exercise therapeutic effects in AD. Targeting these central solute clearance systems holds the promise of more effective treatment strategies.

Effects of enriched environment on the expression of β-amyloid and transport-related proteins LRP1 and RAGE in chronic sleep-deprived mice

Sleep plays an important role in the learning process and memory consolidation, and sleep deprivation (SD) leads to inadequate memory consolidation and plays an important role in brain development and plasticity. SD increases β-amyloid levels while impairing cognitive function. We explored the effect of enriched environment (EE) on β-amyloid and transporter protein LRP1 and receptor for advanced glycosylation end-products (RAGE) expression in chronic sleep deprived mice. We randomly divided mice into four groups (n = 10), the standard environment group (Ctrl group), the sleep deprivation group (SD group), the enriched environment intervention group (EE group), and the sleep deprivation plus environmental enrichment intervention group (SD + EE group). A modified multi-platform SD model was used to sleep deprive the mice for 19 h per day. Five hours of EE intervention was performed daily in the EE group and the SD + EE group, respectively. The behavioral measurements of mice were performed by Y-maze method and new object recognition; the expression levels of Aβ1-42, LRP1, and RAGE in prefrontal cortex and hippocampus of mice were measured by immunofluorescence; the expression levels of LRP1 and RAGE in prefrontal cortex and hippocampus were detected by Western blot. The results showed that EE could effectively ameliorate the effects of SD on cognitive impairment, reduce SD induced Aβ deposition, and decrease the expression of RAGE, while increase the expression of LRP1.

The effect of chronic stress and its preconditioning on spatial memory as well as hippocampal LRP1 and RAGE expression in a streptozotocin-induced rat model of Alzheimer's disease

According to available evidence, prolonged or chronic exposure to stress is detrimental to various brain structures, including the hippocampus. The current study examined the expression of two critical blood-brain barrier receptors required for amyloid-beta clearance to understand better the mechanism by which chronic stress impairs learning and memory in patients with Alzheimer's disease (AD). Rats were randomly assigned to one of two groups in this study: experiment 1 and experiment 2. Each main group was then divided into four subgroups. Rats were bilaterally injected with streptozotocin (STZ, 3 mg/kg, twice) using the intracerebroventricular (ICV) technique to induce the Alzheimer's model. Additionally, they were subjected to foot shock (1 mA, 1 Hz) for 10 s every 60 s (1 h/day) for ten consecutive days prior to and following STZ injection. The Morris Water Maze (MWM) test was used to assess spatial learning and memory. Real-time PCR was used to determine Low-density lipoprotein receptor-related protein-1 (LRP1) and receptor for advanced glycation end-products (RAGE) mRNA levels in the hippocampus. Moreover, the animals' body weights were determined as physiological parameters in all groups. The results indicated that 10-day chronic electric foot shock stress reduced body weight, impaired spatial learning and memory, decreased hippocampal LRP1 mRNA expression, and increased hippocampal RAGE mRNA expression in a rat AD model. It can be concluded that chronic stress in conjunction with AD alters the expression of LRP1 and RAGE in the hippocampus. The findings pave the way for scientists to develop novel treatment strategies for AD.

Targeting Alzheimer's Disease: The Critical Crosstalk between the Liver and Brain

Alzheimer's disease (AD), an age-related neurodegenerative disorder, is currently incurable. Imbalanced amyloid-beta (Aβ) generation and clearance are thought to play a pivotal role in the pathogenesis of AD. Historically, strategies targeting Aβ clearance have typically focused on central clearance, but with limited clinical success. Recently, the contribution of peripheral systems, particularly the liver, to Aβ clearance has sparked an increased interest. In addition, AD presents pathological features similar to those of metabolic syndrome, and the critical involvement of brain energy metabolic disturbances in this disease has been recognized. More importantly, the liver may be a key regulator in these abnormalities, far beyond our past understanding. Here, we review recent animal and clinical findings indicating that liver dysfunction represents an early event in AD pathophysiology. We further propose that compromised peripheral Aβ clearance by the liver and aberrant hepatic physiological processes may contribute to AD neurodegeneration. The role of a hepatic synthesis product, fibroblast growth factor 21 (FGF21), in the management of AD is also discussed. A deeper understanding of the communication between the liver and brain may lead to new opportunities for the early diagnosis and treatment of AD.

Treadmill exercise promotes E3 ubiquitin ligase to remove amyloid β and P-tau and improve cognitive ability in APP/PS1 transgenic mice

Background

Moderate physical exercise is conducive to the brains of healthy humans and AD patients. Previous reports have suggested that treadmill exercise plays an anti-AD role and improves cognitive ability by promoting amyloid clearance, inhibiting neuronal apoptosis, reducing oxidative stress level, alleviating brain inflammation, and promoting autophagy–lysosome pathway in AD mice. However, few studies have explored the relationships between the ubiquitin–proteasome system and proper exercise in AD. The current study was intended to investigate the mechanism by which the exercise-regulated E3 ubiquitin ligase improves AD.

Methods

Both wild type and APP/PS1 transgenic mice were divided into sedentary (WTC and ADC) and exercise (WTE and ADE) groups (n = 12 for each group). WTE and ADE mice were subjected to treadmill exercise of 12 weeks in order to assess the effect of treadmill running on learning and memory ability, Aβ plaque burden, hyperphosphorylated Tau protein and E3 ubiquitin ligase.

Results

The results indicated that exercise restored learning and memory ability, reduced Aβ plaque areas, inhibited the hyperphosphorylation of Tau protein activated PI3K/Akt/Hsp70 signaling pathway, and improved the function of the ubiquitin–proteasome system (increased UCHL-1 and CHIP levels, decreased BACE1 levels) in APP/PS1 transgenic mice.

Conclusions

These findings suggest that exercise may promote the E3 ubiquitin ligase to clear β-amyloid and hyperphosphorylated Tau by activating the PI3K/Akt signaling pathway in the hippocampus of AD mice, which is efficient in ameliorating pathological phenotypes and improving learning and memory ability.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02607-7.

Aerobic Exercise Regulates Apoptosis through the PI3K/Akt/GSK-3β Signaling Pathway to Improve Cognitive Impairment in Alzheimer’s Disease Mice

Neuronal apoptosis is an important factor in the etiology of Alzheimer's disease (AD). Aerobic exercise (AE) enhances learning and memory, improves cognitive impairment, increases telomere binding protein expression, and decreases apoptosis regulators, but it remains unclear whether it can improve cognitive impairment caused by neuronal apoptosis in AD. Therefore, this study investigated whether an 8-week running table exercise intervention could reduce apoptosis and improve cognitive function in the hippocampal neurons of AD model mice. After the exercise intervention, we evaluated the learning memory ability (positioning, navigation, and spatial search) of mice using a Morris water labyrinth, Nissl staining, immunohistochemistry, and protein application to detect hippocampal PI3K/Akt/GSK-3β signaling pathway protein and hippocampal neuronal cell apoptosis protein B cell lymphoma 2 (Bcl-2) and apoptosis-promoting protein bcl-2-related X (Bax) protein expression. The results showed that aerobic exercise improved the location and spatial exploration ability of mice, increased the number of PI3K- and p-Akt-positive cells, increased the expression of PI3K, p-Akt, and bcl-2 proteins, decreased the expression of GSK-3β and Bax proteins, and increased the bcl-2/Bax ratio of mice. The results suggest that aerobic exercise can reduce apoptosis and improve cognitive function in AD mice. The molecular mechanism may involve activation of the PI3K/Akt/GSK-3β signaling pathway.

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.

Long-term running exercise alleviates cognitive dysfunction in APP/PSEN1 transgenic mice via enhancing brain lysosomal function

Amyloid-β peptide (Aβ) aggregation is the hallmark of Alzheimer's disease (AD). The imbalance between the production and clearance of Aβ results in the accumulation and aggregation of Aβ in the brain. Thus far, few drugs are available for AD treatment, but exercise has been recognized for its cognition-enhancing properties in AD patients. The underlying mechanisms remain unclear. Our recent study showed that long-term running exercise could activate the lysosomal function in the brains of mice. In this study, we investigated whether exercise could reduce Aβ accumulation by activating lysosomal function in APP/PSEN1 transgenic mice. Started at the age of 5 months, the mice were trained with a running wheel at the speed of 18 r/min, 40 min/d, 6 d/week for 5 months, and were killed at the end of the 10th month, then brain tissue was collected for biochemical analyses. The cognitive ability was assessed in the 9th month. We showed that long-term exercise significantly mitigated cognitive dysfunction in AD mice, accompanied by the enhanced lysosomal function and the clearance of Aβ in the brain. Exercise significantly promoted the nuclear translocation of transcription factor EB (TFEB), and increased the interaction between nuclear TFEB with AMPK-mediated acetyl-CoA synthetase 2, thus enhancing transcription of the genes associated with the biogenesis of lysosomes. Exercise also raised the levels of mature cathepsin D and cathepsin L, suggesting that more Aβ peptides could be degraded in the activated lysosomes. This study demonstrates that exercise may improve the cognitive dysfunction of AD by enhancing lysosomal function.

The Association Between Alzheimer's Disease-Related Markers and Physical Activity in Cognitively Normal Older Adults

Previous studies have indicated that physical activity may be beneficial in reducing the risk for Alzheimer's disease (AD), although the underlying mechanisms are not fully understood. The goal of this study was to evaluate the relationship between habitual physical activity levels and brain amyloid deposition and AD-related blood biomarkers (i.e., measured using a novel high-performance mass spectrometry-based assay), in apolipoprotein E (APOE) ε4 carriers and noncarriers. We evaluated 143 cognitively normal older adults, all of whom had brain amyloid deposition assessed using positron emission tomography and had their physical activity levels measured using the International Physical Activity Questionnaire (IPAQ). We observed an inverse correlation between brain amyloidosis and plasma beta-amyloid (Aβ)₁₋₄₂ but found no association between brain amyloid and plasma Aβ₁₋₄₀ and amyloid precursor protein (APP)_669−711. Additionally, higher levels of physical activity were associated with lower plasma Aβ₁₋₄₀, Aβ₁₋₄₂, and APP_669−711 levels in APOE ε4 noncarriers. The ratios of Aβ₁₋₄₀/Aβ₁₋₄₂ and APP_669−711/Aβ₁₋₄₂, which have been associated with higher brain amyloidosis in previous studies, differed between APOE ε4 carriers and non-carriers. Taken together, these data indicate a complex relationship between physical activity and brain amyloid deposition and potential blood-based AD biomarkers in cognitively normal older adults. In addition, the role of APOE ε4 is still unclear, and more studies are necessary to bring further clarification.

The APOE ε3/ε4 Genotype Drives Distinct Gene Signatures in the Cortex of Young Mice

Introduction

Restrictions on existing APOE mouse models have impacted research toward understanding the strongest genetic risk factor contributing to Alzheimer's disease (AD) and dementia, APOEε4 , by hindering observation of a key, common genotype in humans - APOEε3/ε4 . Human studies are typically underpowered to address APOEε4 allele risk as the APOEε4/ε4 genotype is rare, which leaves human and mouse research unsupported to evaluate the APOEε3/ε4 genotype on molecular and pathological risk for AD and dementia.

Methods

As a part of MODEL-AD, we created and validated new versions of humanized APOEε3/ε3 and APOEε4/ε4 mouse strains that, due to unrestricted breeding, allow for the evaluation of the APOEε3/ε4 genotype. As biometric measures are often translatable between mouse and human, we profiled circulating lipid concentrations. We also performed transcriptional profiling of the cerebral cortex at 2 and 4 months (mos), comparing APOEε3/ε4 and APOEε4/ε4 to the reference APOEε3/ε3 using linear modeling and WGCNA. Further, APOE mice were exercised and compared to litter-matched sedentary controls, to evaluate the interaction between APOEε4 and exercise at a young age.

Results

Expression of human APOE isoforms were confirmed in APOEε3/ε3, APOEε3/ε4 and APOEε4/ε4 mouse brains. At two mos, cholesterol composition was influenced by sex, but not APOE genotype. Results show that the APOEε3/ε4 and APOEε4/ε4 genotype exert differential effects on cortical gene expression. APOEε3/ε4 uniquely impacts 'hormone regulation' and 'insulin signaling,' terms absent in APOEε4/ε4 data. At four mos, cholesterol and triglyceride levels were affected by sex and activity, with only triglyceride levels influenced by APOE genotype. Linear modeling revealed APOEε3/ε4 , but not APOEε4/ε4 , affected 'extracellular matrix' and 'blood coagulation' related terms. We confirmed these results using WGCNA, indicating robust, yet subtle, transcriptional patterns. While there was little evidence of APOE genotype by exercise interaction on the cortical transcriptome at this young age, running was predicted to affect myelination and gliogenesis, independent of APOE genotype with few APOE genotype-specific affects identified.

Discussion

APOEε4 allele dosage-specific effects were observed in circulating lipid levels and cortical transcriptional profiles. Future studies are needed to establish how these data may contribute to therapeutic development in APOEε3/ε4 and APOEε4/ε4 dementia patients.

Effects of involuntary treadmill running in combination with swimming on adult neurogenesis in an Alzheimer's mouse model

Physical exercise plays a role on the prevention and treatment of Alzheimer's disease (AD), but the exercise mode and the mechanism for these positive effects is still ambiguous. Here, we investigated the effect of an aerobic interval exercise, running in combination with swimming, on behavioral dysfunction and associated adult neurogenesis in a mouse model of AD. We demonstrate that 4 weeks of the exercise could ameliorate Aβ₄₂ oligomer-induced cognitive impairment in mice utilizing Morris water maze tests. Additionally, the exercised Aβ₄₂ oligomer-induced mice exhibited a significant reduction of anxiety- and depression-like behaviors compared to the sedentary Aβ₄₂ oligomer-induced mice utilizing an Elevated zero maze and a Tail suspension test. Moreover, by utilizing 5'-bromodeoxyuridine (BrdU) as an exogenous cell tracer, we found that the exercised Aβ₄₂ oligomer-induced mice displayed a significant increase in newborn cells (BrdU⁺ cells), which differentiated into a majority of neurons (BrdU⁺ DCX⁺ cells or BrdU⁺NeuN⁺ cells) and a few of astrocytes (BrdU⁺GFAP⁺ cells). Likewise, the exercised Aβ₄₂ oligomer-induced mice also displayed the higher levels of NeuN, PSD95, synaptophysin, Bcl-2 and lower level of GFAP protein. Furthermore, alteration of serum metabolites in transgenic AD mice between the exercised and sedentary group were significantly associated with lipid metabolism, amino acid metabolism, and neurotransmitters. These findings suggest that combined aerobic interval exercise-mediated metabolites and proteins contributed to improving adult neurogenesis and behavioral performance after AD pathology, which might provide a promising therapeutic strategy for AD.

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.

Recent Neurotherapeutic Strategies to Promote Healthy Brain Aging: Are we there yet?

Owing to the global exponential increase in population ageing, there is an urgent unmet need to develop reliable strategies to slow down and delay the ageing process. Age-related neurodegenerative diseases are among the main causes of morbidity and mortality in our contemporary society and represent a major socio-economic burden. There are several controversial factors that are thought to play a causal role in brain ageing which are continuously being examined in experimental models. Among them are oxidative stress and brain inflammation which are empirical to brain ageing. Although some candidate drugs have been developed which reduce the ageing phenotype, their clinical translation is limited. There are several strategies currently in development to improve brain ageing. These include strategies such as caloric restriction, ketogenic diet, promotion of cellular nicotinamide adenine dinucleotide (NAD+) levels, removal of senescent cells, 'young blood' transfusions, enhancement of adult neurogenesis, stem cell therapy, vascular risk reduction, and non-pharmacological lifestyle strategies. Several studies have shown that these strategies can not only improve brain ageing by attenuating age-related neurodegenerative disease mechanisms, but also maintain cognitive function in a variety of pre-clinical experimental murine models. However, clinical evidence is limited and many of these strategies are awaiting findings from large-scale clinical trials which are nascent in the current literature. Further studies are needed to determine their long-term efficacy and lack of adverse effects in various tissues and organs to gain a greater understanding of their potential beneficial effects on brain ageing and health span in humans.

Cognitive Aging and the Promise of Physical Activity

Is the field of cognitive aging irretrievably concerned with decline and deficits, or is it shifting to emphasize the hope of preservation and enhancement of cognitive function in late life? A fragment of an answer comes from research attempting to understand the reasons for individual variability in the extent and rate of cognitive decline. This body of work has created a sense of optimism based on evidence that there are some health behaviors that amplify cognitive performance or mitigate the rate of age-related cognitive decline. In this context, we discuss the role of physical activity on neurocognitive function in late adulthood and summarize how it can be conceptualized as a constructive approach both for the maintenance of cognitive function and as a therapeutic for enhancing or optimizing cognitive function in late life. In this way, physical activity research can be used to shape perceptions of cognitive aging. Expected final online publication date for the Annual Review of Clinical Psychology, Volume 18 is May 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

The beneficial effect of exercise against Alzheimer's disease may result from improved brain glucose metabolism

The potential of physical exercise as an intervention for Alzheimer's disease (AD) has been extensively reported. In fact, a number of studies have highlighted improvements in β-amyloid (Aβ) peptide and hyperphosphorylated tau (p-tau) as critical mechanisms in exercise-induced beneficial neurological outcomes. However, no therapeutic management have been proven to be effective in humans. Recent evidence has shown that AD may be a metabolic disease related to glucose metabolic dysfunction in the brain. In this regard, some of the mechanisms responsible for the beneficial effects of physical exercise in the pathology of AD appear to be related to alterations in glucose metabolism. Therefore, we propose that the neuroprotective effect of physical exercise against AD through synergetic improvement in brain glucose metabolism and its pathophysiology. The novel perspective presented here partly explains the failure of Aβ/tau-based therapeutic approaches and provides evidence for brain glucose metabolism as a potential therapeutic target in AD.

The Beneficial Role of Exercise on Treating Alzheimer's Disease by Inhibiting β-Amyloid Peptide

Alzheimer's disease (AD) is associated with a very large burden on global healthcare systems. Thus, it is imperative to find effective treatments of the disease. One feature of AD is the accumulation of neurotoxic β-amyloid peptide (Aβ). Aβ induces multiple pathological processes that are deleterious to nerve cells. Despite the development of medications that target the reduction of Aβ to treat AD, none has proven to be effective to date. Non-pharmacological interventions, such as physical exercise, are also being studied. The benefits of exercise on AD are widely recognized. Experimental and clinical studies have been performed to verify the role that exercise plays in reducing Aβ deposition to alleviate AD. This paper reviewed the various mechanisms involved in the exercise-induced reduction of Aβ, including the regulation of amyloid precursor protein cleaved proteases, the glymphatic system, brain-blood transport proteins, degrading enzymes and autophagy, which is beneficial to promote exercise therapy as a means of prevention and treatment of AD and indicates that exercise may provide new therapeutic targets for the treatment of AD.

Effect of involuntary chronic physical exercise on beta-amyloid protein in experimental models of Alzheimer's disease: Systematic review and meta-analysis

The excessive deposition of β-amyloid proteins (Aβ) is directly correlated with the establishment and development of Alzheimer's Disease (AD). Current treatments for AD only reduce symptoms instead of acting on Aβ, the primary etiological agent. Hence, the anti-amyloid effect of regular exercise has been widely investigated as an alternative therapy. This systematic review and meta-analysis examined the anti-amyloid effect of regular physical exercise in animal models of AD. The search was conducted on the electronic databases Pubmed, Embase, Scopus and Web of Science without data limitation and using the following describers: "amyloid beta" (OR senile plaque OR amyloid plaque) and "exercise" (OR physical activity OR training). The risk of bias was evaluated using the SYRCLE's tool. Meta-analyses were conducted using models of random continuous effects. A total of 36 studies were selected and most used: transgenic mice (n = 29), treadmill training, duration of 12 weeks (interval of 4 to 28 weeks), rate of 60 min/day (interval of 30 min and up until free access) and speed of 12 m/min (interval of 3.2 to 32 m/min). The hippocampus and cortex were the most frequently investigated regions. Meta-analysis demonstrated a decrease in Aβ with greater effect in unspecified isoforms Meta-analysis demonstrated a decrease in Aβ with greater effect in unspecified isoforms (N = 4; SMD = -2.71, IC 95%: -3.59, -1.84, p < 0.00001, Q2 = 3.38, I2 = 11%) and Aβ_1-42 (N = 21; SMD = -1.94, IC 95%: -2.37, -1.51, p < 0.00001, Q2 = 33,37, I2 = 40%). Concerning training, greater effect was found with: 1) swimming (N = 4; SMD = -1.98, IC 95%: -3,28 - -0,68, p = 0.003, Q2 = 9.74, I2 = 69%), 2) moderate intensity (N = 4; SMD = -2.03, IC 95%: -3.31 - -0.75, p < 0.005, Q² = 12.68, I² = 76%); 3) duration up to six weeks (N = 6; N = 6; SMD = -2.35, IC 95%: -3.15 - -1.55, p < 0.00001, Q² = 8.38, I² = 40%); 4) young animals (SMD = -2.00, IC 95%: -2.59 - -1.42, p < 0.00001, Q² = 24.90, I² = 52%); 5) in the amygdala region (N = 1; SMD = -8.56, IC 95%: -12.88 - -4.23, p = 0.0001) and females (N = 4; SMD = -2.14, IC 95%: -3.48 - -0.79, p = 0.002, Q² = 10.31, I² = 71%). However, the reduction of Aβ was associated with decrease of amyloidogenic pathway and increase of non-amyloidogenic. Hence, regular physical exercise demonstrated anti-amyloid effect in experimental models of AD through positive alterations in APP processing through different signaling pathways.

Untypical Metabolic Adaptations in Spontaneously Hypertensive Rats to Free Running Wheel Activity Includes Uncoupling Protein-3 (UCP-3) and Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9) Expression

Obesity and hypertension are common risk factors for cardiovascular disease whereas an active lifestyle is considered as protective. However, the interaction between high physical activity and hypertension is less clear. Therefore, this study investigates the impact of high physical activity on the muscular and hepatic expression of glucose transporters (Glut), uncoupling proteins (UCPs), and proprotein convertase subtilisin/kexin type 9 (PCSK9) in spontaneously hypertensive rats (SHRs). Twenty-four female rats (12 normotensive rats and 12 SHRs) were divided into a sedentary control and an exercising group that had free access to running wheels at night for 10 months. Blood samples were taken and blood pressure was determined. The amount of visceral fat was semi-quantitatively analyzed and Musculus gastrocnemius, Musculus soleus, and the liver were excised. Acute effects of free running wheel activity were analyzed in 15 female SHRs that were sacrificed after 2 days of free running wheel activity. M. gastrocnemius and M. soleus differed in their mRNA expression of UCP-2, UCP-3, GLUT-4, and PCSK9. Hypertension was associated with lower levels of UCP-2 and PCSK9 mRNA in the M. gastrocnemius, but increased expression of GLUT-1 and GLUT-4 in the M. soleus. Exercise down-regulated UCP-3 in the M. soleus in both strains, in the M. gastrocnemius only in normotensives. In SHRs exercise downregulated the expression of UCP-2 in the M. soleus. Exercise increased the expression of GLUT-1 in the M. gastrocnemius in both strains, and that of GLUT-4 protein in the M. soleus, whereas it increased the muscle-specific expression of PCSK9 only in normotensive rats. Effects of exercise on the hepatic expression of cholesterol transporters were seen only in SHRs. As an acute response to exercise increased expressions of the myokine IL-6 and that of GLUT-1 were found in the muscles. This study, based on transcriptional adaptations in striated muscles and livers, shows that rats perform long-term metabolic adaptations when kept with increased physical activity. These adaptations are at least in part required to stabilize normal protein expression as protein turnover seems to be modified by exercise. However, normotensive and hypertensive rats differed in their responsiveness. Based on these results, a direct translation from normotensive to hypertensive rats is not possible. As genetic differences between normotensive humans and patients with essential hypertension are likely to be present as well, we would expect similar differences in humans that may impact recommendations for non-pharmacological interventions.

Neuroprotective mechanisms of chronic physical exercise via reduction of β-amyloid protein in experimental models of Alzheimer's disease: A systematic review

AIMS

Alzheimer's disease (AD) is the most common irreversible chronic neurodegenerative disease. It is characterized by the abnormal accumulation of β-amyloid protein (Aβ), which triggers homeostatic breakage in several physiological systems. However, the effect of chronic exercise on the formation of Aβ as an alternative therapy has been investigated. This systematic review examines the antiamyloid effect of different types and intensities of exercise, seeking to elucidate its neuroprotective mechanisms.

MAIN METHODS

The research was conducted in the electronic databases Pubmed, Embase, Scopus and Web of Science, using the following descriptors: "amyloid beta" (OR senile plaque OR amyloid plaque) and "exercise" (OR physical activity OR training). The risk of bias was evaluated through SYRCLE's Risk of Bias for experimental studies.

KEY FINDINGS

2268 articles were found, being 36 included in the study. A higher frequency of use of mice with genetic alterations was identified for the Alzheimer's disease (AD) model (n = 29). It was used as chronic training: treadmill running (n = 24), voluntary running wheel (n = 7), swimming (n = 4) and climbing (n = 2). The hippocampus and the cortex were the most investigated regions. However, physiological changes accompanied by the reduction of Aβ and associated with AD progression were verified. It is concluded that exercise reduces the production of Aβ in models of animals with AD.

SIGNIFICANCE

Nevertheless, this effect contributes to the improvement of several physiological aspects related to Aβ and that contribute to neurological impairment in AD.

Working memory and hippocampal expression of BDNF, ARC, and P-STAT3 in rats: effects of diet and exercise

OBJECTIVES

Mounting evidence suggests diet and exercise influence learning and memory (LM). We compared a high-fat, high-sucrose Western diet (WD) to a plant-based, amylose/amylopectin blend, lower-fat diet known as the Daniel Fast (DF) in rats with and without regular aerobic exercise on a task of spatial working memory (WM).

METHODS

Rats were randomly assigned to the WD or DF at 6 weeks of age. Exercised rats (WD-E, DF-E) ran on a treadmill 3 times/week for 30 min while the sedentary rats did not (WD-S, DF-S). Rats adhered to these assignments for 12 weeks, inclusive of ab libitum food intake, after which mild food restriction was implemented to encourage responding during WM testing. For nine months, WM performance was assessed once daily, six days per week, after which hippocampal sections were collected for subsequent analysis of brain-derived neurotrophic factor (BDNF), activity-regulated cytoskeletal protein (ARC), and signal transducer and activator of transcription 3 (P-STAT3, Tyr705).

RESULTS

DF-E rats exhibited the best DSA performance. Surprisingly, the WD-S group outperformed the WD-E group, but had significantly lower BDNF and ARC relative to the DF-S group, with a similar trend from the WD-E group. P-STAT3 expression was also significantly elevated in the WD-S group compared to both the DF-S and WD-E groups.

DISCUSSION

These results support previous research demonstrating negative effects of the WD on spatial LM, demonstrate the plant-based DF regimen combined with chronic aerobic exercise produces measurable WM and neuroprotective benefits, and suggest the need to carefully design exercise prescriptions to avoid over-stressing individuals making concurrent dietary changes.

Moderate treadmill exercise improves spatial learning and memory deficits possibly via changing PDE-5, IL-1 β and pCREB expression

Alzheimer's is a progressive disorder of the nervous system. Prior studies suggested that physical activity contributes to the improvement of cognitive impairment and slows down pathogenesis of AD; however, the exact mechanisms for this have not been fully understood. Therefore, in this study, we examined the effect of aerobic training before and after induction of Alzheimer's on spatial learning and memory, expression of interleukin-1 beta (IL-1β), cAMP-responsive element-binding protein (pCREB), and Phosphodiesterase-5 (PDE-5) in the hippocampus of male rats Wistar. Aβ was microinjected into the CA1 area of the hippocampus animals. The moderate treadmill exercise protocols for pre and post induction of Alzheimer's were the same (5 days/week, for 4 weeks with a customized regime). The Morris Water Maze (MWM) method has been to assess spatial learning and memory. The real time-PCR method was used to measure gene expression. Our results showed that intra-hippocampal injection of Aβ1-42 impaired spatial learning and memory which was accompanied by reduced pCREB activity and elevated IL-1β and PDE-5 in the hippocampus of rats. In contrast, moderate treadmill exercise ameliorated the Aβ1-42-induced spatial learning and memory deficit, which was accompanied by restored pCREB activity and decreasing IL-1β and PDE-5 levels. In conclusion, our finding suggests that exercise before and after Alzheimer's induction leads to an increase in pCREB and an alleviation of inflammation which likely involved in ameliorating spatial learning and memory deficits in an animal model of AD.

Meta-analysis: Resistance Training Improves Cognition in Mild Cognitive Impairment

This study investigated the benefits of resistance training on cognition in patients with mild cognitive impairment. We searched the PubMed, Embase and Cochrane Library databases, and seven randomized controlled trials were reviewed. We evaluated the risk of bias using the Cochrane Collaboration’s bias assessment tool. Standard mean differences with 95% confidence intervals were calculated for statistical analysis. This meta-analysis assessed three variables: general cognitive function, executive function and working memory. The results indicate that general cognitive function improved significantly (standardized mean difference: 0.53, P=0.04), and further subgroup analyses on frequency and duration per session showed that the subgroups ‘twice a week’ (P=0.01) and ‘duration per session >60 min’ (P=0.0006) exhibited better performance than the subgroups ‘three time a week’ (P=0.47) and ‘duration per session <60 min’ (P=0.53). Additionally, a moderate effect size was found in executive function (standardized mean difference: 0.50, P=0.0003), and there was non-significant effect in working memory (P=0.14). In summary, resistance training may mitigate mild cognitive impairment by improving cognition. Larger-scale studies are recommended to demonstrate the relationship between resistance training and cognition in mild cognitive impairment.

Treadmill Exercise Attenuates Aβ-Induced Mitochondrial Dysfunction and Enhances Mitophagy Activity in APP/PS1 Transgenic Mice

Mitochondrial dysfunction is a hallmark of Alzheimer's disease (AD), which may be related to mitophagy failure. Previous reports suggest that treadmill exercise protects against mitochondrial dysfunction in AD. However, few studies have investigated the relationship between mitophagy and mitochondrial adaptation caused by treadmill exercise in AD. The current study aimed to investigate whether exercise-ameliorated AD is associated with changes in mitophagy activity. Both Wild-type and APP/PS1 transgenic mice were divided into sedentary (WTC and ADC) and exercise (WTE and ADE) groups (n = 9 for each group). WTE and ADE mice were subjected to treadmill exercise for 12 weeks, followed by evaluating the effect of treadmill exercise on learning and memory ability, Aβ plaques, mitochondrial Aβ peptide level, synaptic activity and mitochondrial function. Meanwhile, mitophagy-related proteins PINK1, Parkin, LC3II and P62 were measured in the hippocampal mitochondrial fractions. The results indicated that exercise not only restored learning and memory ability, but also reduced Aβ plaque area, mitochondrial Aβ peptide level, and increased levels of synaptic markers SYN and GAP43, as well as reversed mitochondrial dysfunction (defective mitochondrial ultrastructure, decreased PGC-1α, TFAM and ATP levels) in APP/PS1 transgenic mice. Moreover, exercise increased mitophagy activity as evidenced by a significant decrease in levels of P62 and PINK1 as well as an increase in levels of LC3II and Parkin in ADE mice. These findings suggest that treadmill exercise can enhance mitophagy activity in the hippocampus, which is efficient in ameliorating pathological phenotypes of APP/PS1 transgenic mice.

The effects of stress on cardiovascular disease and Alzheimer's disease: Physical exercise as a counteract measure

AD is a complicated multi-systemic neurological disorder that involves different biological pathways. Several risk factors have been identified, including chronic stress. Chronic stress produces an alteration in the activity of the hypothalamic pituitary adrenal (HPA) system, and the autonomic nervous system (ANS), which over time increase the risk of AD and also the incidence of cardiovascular disease (CVD) and risk factors, such as hypertension, obesity and type 2 diabetes, associated with cognitive impairment and AD. Considering the multi-factorial etiology of AD, understanding the complex interrelationships between different risk factors is of potential interest for designing adequate strategies for preventing, delaying the onset or slowing down the progression of this devastating disease. Thus, in this review we will explore the general mechanisms and evidence linking stress, cardiovascular disease and AD, and discuss the potential benefits of physical activity for AD by counteracting the negative effects of chronic stress, CVD and risk factors.

Strength exercise suppresses STZ-induced spatial memory impairment and modulates BDNF/ERK-CAMKII/CREB signalling pathway in the hippocampus of mice

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that has generated scientific interest because of its prevalence in the population. Studies indicate that physical exercise promotes neuroplasticity and improves cognitive function in animal models and in human beings. The aim of the present study was to investigate the effects of strength exercise on the hippocampal protein contents and memory performance in mice subjected to a model of sporadic AD induced by streptozotocin (STZ). Swiss mice received two injections of STZ (3 mg/kg, intracerebroventricular). After 21 days, they began physical training using a ladde. Mice performed this protocol for 4 weeks. After the last exercise training session, mice performed the Morris Water Maze test. The samples of hippocampus were excised and used to determine protein contents of brain-derived neurotrophic factor (BDNF), extracellular signal-regulated kinase-Ca²⁺ (ERK), calmodulin-dependent protein kinase (CAMKII) and cAMP-response element-binding protein (CREB) signalling pathway. Strength exercise was effective against the decrease in the time spent and distance travelled in the target quadrant by STZ-injected mice. Strength exercise was also effective against the reduction of mature BDNF, tropomyosin receptor kinase B and neuronal nuclear antigen (NeuN) hippocampal protein levels in STZ mice. The decrease in the hippocampal ratio of pERK/ERK, pCAMKII/CAMKII and pCREB/CREB induced by STZ was reversed by strength exercise. Strength exercise decreased Bax/Bcl2 ratio in the hippocampus of STZ-injected mice. The present study demonstrates that strength exercise modulated the hippocampal BDNF/ERK-CAMKII/CREB signalling pathway and suppressed STZ-induced spatial memory impairment in mice.

Transcriptional profiling predicts running promotes cerebrovascular remodeling in young but not midlife mice

Background

The incidence of dementia and cognitive decline is increasing with no therapy or cure. One of the reasons treatment remains elusive is because there are various pathologies that contribute to age-related cognitive decline. Specifically, with Alzheimer’s disease, targeting to reduce amyloid beta plaques and phosphorylated tau aggregates in clinical trials has not yielded results to slow symptomology, suggesting a new approach is needed. Interestingly, exercise has been proposed as a potential therapeutic intervention to improve brain health and reduce the risk for dementia, however the benefits throughout aging are not well understood.

Results

To better understand the effects of exercise, we preformed transcriptional profiling on young (1–2 months) and midlife (12 months) C57BL/6 J (B6) male mice after 12 weeks of voluntary running. Data was compared to age-matched sedentary controls. Interestingly, the midlife running group naturally broke into two cohorts based on distance ran - either running a lot and more intensely (high runners) or running less and less intensely (low runners). Midlife high runners had lower LDL cholesterol as well as lower adiposity (%fat) compared to sedentary, than midlife low runners compared to sedentary suggesting more intense running lowered systemic markers of risk for age-related diseases including dementias. Differential gene analysis of transcriptional profiles generated from the cortex and hippocampus showed thousands of differentially expressed (DE) genes when comparing young runners to sedentary controls. However, only a few hundred genes were DE comparing either midlife high runners or midlife low runners to midlife sedentary controls. This indicates that, in our study, the effects of running are reduced through aging. Gene set enrichment analyses identified enrichment of genes involved in extracellular matrix (ECM), vascular remodeling and angiogenesis in young runners but not midlife runners. These genes are known to be expressed in multiple vascular-related cell types including astrocytes, endothelial cells, pericytes and smooth muscle cells.

Conclusions

Taken together these results suggest running may best serve as a preventative measure to reduce risk for cerebrovascular decline. Ultimately, this work shows that exercise may be more effective to prevent dementia if introduced at younger ages.

Pioglitazone Reduces β Amyloid Levels via Inhibition of PPARγ Phosphorylation in a Neuronal Model of Alzheimer's Disease

It has been demonstrated that peroxisome proliferator-activated receptor γ (PPARγ) can regulate the transcription of its target gene, insulin-degrading enzyme (IDE), and thus enhance the expression of the IDE protein. The protein can degrade β amyloid (Aβ), a core pathological product of Alzheimer’s disease (AD). PPARγ can also regulate the transcription of other target gene, β-amyloid cleavage enzyme 1 (BACE1), and thus inhibit the expression of the BACE1 protein. BACE1 can hydrolyze amyloid precursor protein (APP), the precursor of Aβ. In adipose tissue, PPARγ agonists can inhibit the phosphorylation of PPARγ by inhibiting cyclin-dependent kinase 5 (CDK5), which in turn affects the expression of target genes regulated by PPARγ. PPARγ agonists may also exert inhibitory effects on the phosphorylation of PPARγ in the brain, thereby affecting the expression of the aforementioned PPARγ target genes and reducing Aβ levels. The present study confirmed this hypothesis by showing that PPARγ agonist pioglitazone attenuated the neuronal apoptosis of primary rat hippocampal neurons induced by Aβ_1–42, downregulated CDK5 expression, weakened the binding of CDK5 to PPARγ, reduced PPARγ phosphorylation, increased the expression of PPARγ and IDE, decreased the expression of BACE1, reduced APP production, and downregulated intraneuronal Aβ_1–42 levels. These effects were inhibited by the PPARγ antagonist GW9662. After CDK5 silencing with CDK5 shRNA, the above effect of pioglitazone was not observed, except when upregulating the expression of PPARγ in Aβ_1–42 treated neurons. In conclusion, this study demonstrated that pioglitazone could inhibit the phosphorylation of PPARγ in vitro by inhibiting CDK5 expression, which in turn affected the expression of PPARγ target genes Ide and Bace1, thereby promoting Aβ degradation and reducing Aβ production. This reduced Aβ levels in the brain, thereby exerting neuroprotective effects in an AD model.