The effect of physical exercise on cerebral blood flow in Alzheimer's disease

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.

Effects of home-based and telerehabilitation exercise on mental and physical health, and disease cost in people with Alzheimer's disease: A meta-analysis

BACKGROUND

Alzheimer's disease (AD) is a very disabling long-term disease that requires continuous regular care. A cost-effective and sustainable means of such care may be physical activity or exercise delivered at home or through telerehabilitation. The aim of this study is to determine the effects of home-based or telerehabilitation exercise in people with AD.

METHOD

PubMED, Embase, Web of Science (WoS), PEDro, and CENTRAL were searched for randomized controlled trials until January 2024. The data extracted include the characteristics of the participants, the interventions used for both experimental and the control groups, the baseline, post-intervention and follow-up mean and standard deviation values on the outcomes assessed and the findings of the included studies. Cochrane risks of bias assessment tool and PEDro scale were used to assess the risks of bias and methodological quality of the studies. The results were analyzed using narrative and quantitative syntheses.

RESULT

Eleven articles from nine studies (n=550) were included in the study. The results showed that, only global cognitive function (SMD = 0.72, 95% CI = 0.19-1.25, p=0.007), neuropsychiatric symptom (MD = -5.28, 95% CI =-6.22 to -4.34, p<0.0001) and ADL (SMD =3.12, 95% CI =0.11-6.13, p=0.04) improved significantly higher in the experimental group post-intervention. At follow-up, the significant difference was maintained only in neuropsychiatric symptoms (MD =-6.20, 95% CI =-7.17 to -5.23, p<0.0001).

CONCLUSION

There is a low evidence on the effects of home-based physical activity or exercise on global cognitive function, neuropsychiatric symptoms and ADL.

Understanding the mechanisms of disease modifying effects of aerobic exercise in people with Alzheimer's disease

Alzheimer's disease (AD) is a very disabling disease. Pathologically, it is characterized by the presence of amyloid plaques and neurofibrillary tangles in the brain that results in neurodegeneration. Its clinical manifestations include progressive memory impairment, language decline and difficulty in carrying out activities of daily living (ADL). The disease is managed using interventions such as pharmacological interventions and aerobic exercise. Use of aerobic exercise has shown some promises in reducing the risk of developing AD, and improving cognitive function and the ability to carry out both basic and instrumental ADL. Although, the mechanisms through which aerobic exercise improves AD are poorly understood, improvement in vascular function, brain glucose metabolism and cardiorespiratory fitness, increase in antioxidant capacity and haemoglobin level, amelioration of immune-related and inflammatory responses, modulation of concentration of circulating Neurotrophins and peptides and decrease in concentration of tau protein and cortisol level among others seem to be the possible mechanisms. Therefore, understanding these mechanisms is important to help characterize the dose and the nature of the aerobic exercise to be given. In addition, they may also help in finding ways to optimize other interventions such as the pharmacological interventions. However, more quality studies are needed to verify the mechanisms.

Prevention of Alzheimer's disease through diet: An exploratory review

Introduction

This exploratory review article describes about the genetic factors behind Alzheimer's disease (AD), their association with foods, and their relationships with cognitive impairment. It explores the dietary patterns and economic challenges in AD prevention.

Methods

Scopus, PubMed and Google Scholar were searched for articles that examined the relationships between Diets, Alzheimer's Disease (AD), and Socioeconomic conditions in preventative Alzheimer's disease studies. Graphs and Network analysis data were taken from Scopus under the MeSH search method, including words, Alzheimer's, APoE4, Tau protein, APP, Amyloid precursor protein, Beta-Amyloid, Aβ, Mediterranean Diet, MD, DASH diet, MIND diet, SES, Socioeconomic, Developed country, Underdeveloped country, Preventions. The network analysis was done through VOS viewer.

Results

Mediterranean diet (MD) accurately lowers AD (Alzheimer's Disease) risk to 53% and 35% for people who follow it moderately. MIND scores had a statistically significant reduction in AD rate compared to those in the lowest tertial (53% and 35% reduction, respectively). Subjects with the highest adherence to the MD and DASH had a 54% and 39% lower risk of developing AD, respectively, compared to those in the lowest tertial. Omega-6, PUFA, found in nuts and fish, can play most roles in the clearance of Aβ. Vitamin D inhibits induced fibrillar Aβ apoptosis. However, the high cost of these diet components rise doubt about the effectiveness of AD prevention through healthy diets.

Conclusion

The finding of this study revealed an association between diet and the effects of the chemical components of foods on AD biomarkers. More research is required to see if nutrition is a risk or a protective factor for Alzheimer's disease to encourage research to be translated into therapeutic practice and to clarify nutritional advice.

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.

Advancing Alzheimer's Therapeutics: Exploring the Impact of Physical Exercise in Animal Models and Patients

Alzheimer's disease (AD) is the main neurodegenerative disorder characterized by several pathophysiological features, including the misfolding of the tau protein and the amyloid beta (Aβ) peptide, neuroinflammation, oxidative stress, synaptic dysfunction, metabolic alterations, and cognitive impairment. These mechanisms collectively contribute to neurodegeneration, necessitating the exploration of therapeutic approaches with multiple targets. Physical exercise has emerged as a promising non-pharmacological intervention for AD, with demonstrated effects on promoting neurogenesis, activating neurotrophic factors, reducing Aβ aggregates, minimizing the formation of neurofibrillary tangles (NFTs), dampening inflammatory processes, mitigating oxidative stress, and improving the functionality of the neurovascular unit (NVU). Overall, the neuroprotective effects of exercise are not singular, but are multi-targets. Numerous studies have investigated physical exercise's potential in both AD patients and animal models, employing various exercise protocols to elucidate the underlying neurobiological mechanisms and effects. The objective of this review is to analyze the neurological therapeutic effects of these exercise protocols in animal models and compare them with studies conducted in AD patients. By translating findings from different approaches, this review aims to identify opportune, specific, and personalized therapeutic windows, thus advancing research on the use of physical exercise with AD patients.

Addressing depression in older adults with Alzheimer's through cognitive behavioral therapy: systematic review and meta-analysis

Objectives

This systematic review and meta-analysis was conducted to provide an analysis of the published data about the effects of cognitive behavioral therapies on the depression of older adults with a diagnosis of Alzheimer's disease.

Methods

This study was performed following the PRISMA 2020 guidelines. The search was performed between March and April 2023, using four electronic databases: PubMed, Web of Science, Cinhal and Scopus. Different keywords combined with Boolean operators were utilized. Only 11 articles were included out of the initial 212.

Results

Cognitive behavioral therapy was found to reduce depression in individuals with Alzheimer's, including treatments with low frequency but a longer intervention time.

Conclusion

This systematic review and meta-analysis found that the psychosocial therapy cognitive behavioral therapy is effective in improving depression in individuals with a diagnosis of Alzheimer's. However, results are inconclusive due to the disparity of the findings and the heterogeneity of the applied protocols, so more studies are needed on this topic.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=416396, CRD42023416396.

Associations between everyday activities and arterial spin labeling-derived cerebral blood flow: A longitudinal study in community-dwelling elderly volunteers

Cerebral blood flow (CBF) is critical for brain metabolism and function. Age-related changes in CBF are associated with increased risk of neurocognitive disorders and vascular events such as stroke. Identifying correlates and positive modifiers of age-related changes in CBF before the emergence of incipient clinical decline may inform public health advice and clinical practice. Former research has been inconclusive regarding the association between regular physical activity and CBF, and there is a lack of studies on the association between level of everyday activities and CBF, in older adults. To investigate these relationships, 118 healthy community-dwelling adults (65-89 years) underwent pseudo-continuous arterial spin labeling (ASL) MRI, neurocognitive, physical, and activity assessments at baseline. Eighty-six participants completed a follow-up ASL MRI, on average 506 (SD = 113) days after the baseline scan. Cross-sectional analysis revealed credible evidence for positive associations between time spent on low intensity physical activity and CBF in multiple cortical and subcortical regions, time spent on moderate to vigorous intensity physical activity and accumbens CBF, participation in social activity and CBF in multiple cortical regions, and between reading and thalamic CBF, indicating higher regional CBF in more active adults. Longitudinal analysis revealed anecdotal evidence for an interaction between time and baseline level of gardening on occipital and parietal CBF, and baseline reading on pallidum CBF, indicating more change in CBF in adults with lower level of activity. The findings support that malleable lifestyle factors contribute to healthy brain aging, with relevance for public health guidelines.

Preventive Strategies for Cognitive Decline and Dementia: Benefits of Aerobic Physical Activity, Especially Open-Skill Exercise

As there is no curative treatment for dementia, including Alzheimer's disease (AD), it is important to establish an optimal nonpharmaceutical preventive intervention. Physical inactivity is a representative modifiable risk factor for dementia, especially for AD in later life (>65 years). As physical activity and exercise are inexpensive and easy to initiate, they may represent an effective nonpharmaceutical intervention for the maintenance of cognitive function. Several studies have reported that physical activity and exercise interventions are effective in preventing cognitive decline and dementia. This review outlines the effects of physical activity and exercise-associated interventions in older adults with and without cognitive impairment and subsequently summarizes their possible mechanisms. Furthermore, this review describes the differences between two types of physical exercise-open-skill exercise (OSE) and closed-skill exercise (CSE)-in terms of their effects on cognitive function. Aerobic physical activity and exercise interventions are particularly useful in preventing cognitive decline and dementia, with OSE exerting a stronger protective effect on cognitive functions than CSE. Therefore, the need to actively promote physical activity and exercise interventions worldwide is emphasized.

A Review on Phyto-Therapeutic Approaches in Alzheimer's Disease

Neurodegenerative diseases occur due to progressive and sometimes irreversible loss of function and death of nerve cells. A great deal of effort is being made to understand the pathogenesis of neurodegenerative diseases. In particular, the prevalence of Alzheimer's disease (AD) is quite high, and only symptomatic therapy is available due to the absence of radical treatment. The aim of this review is to try to elucidate the general pathogenesis of AD, to provide information about the limit points of symptomatic treatment approaches, and to emphasize the potential neurologic effects of phytocompounds as new tools as therapeutic agents for disease prevention, retardation, and therapy. This survey also covers the notable properties of herbal compounds such as their effects on the inhibition of an enzyme called acetylcholinesterase, which has significant value in the treatment of AD. It has been proven that phytopharmaceuticals have long-term effects that could protect nervous system health, eliminate inflammatory responses, improve cognitive damage, provide anti-aging effects in the natural aging process, and alleviate dementia sequelae. Herbal-based therapeutic agents can afford many advantages and can be used as potentially as new-generation therapeutics or complementary agents with high compliance, fewer adverse effects, and lower cost in comparison to the traditional pharmaceutical agents in the fight against AD.

Effects of Physical Exercise Training on Cerebral Blood Flow Measurements: A Systematic Review of Human Intervention Studies

The aim of this systematic review was to examine the effects of physical exercise training on cerebral blood flow (CBF), which is a physiological marker of cerebrovascular function. Relationships between training-induced effects on CBF with changes in cognitive performance were also discussed. A systematic search was performed up to July 2022. Forty-five intervention studies with experimental, quasi-experimental, or pre-post designs were included. Sixteen studies (median duration: 14 weeks) investigated effects of physical exercise training on CBF markers using magnetic resonance imaging, 20 studies (median duration: 14 weeks) used transcranial Doppler ultrasound, and eight studies (median duration: 8 weeks) used near-infrared spectroscopy. Studies using magnetic resonance imaging observed consistent increases in CBF in the anterior cingulate cortex and hippocampus, but not in whole-brain CBF. Effects on resting CBF-measured with transcranial Doppler ultrasound and near-infrared spectroscopy-were variable, while middle cerebral artery blood flow velocity increased in some studies following exercise or hypercapnic stimuli. Interestingly, concomitant changes in physical fitness and regional CBF were observed, while a relation between training-induced effects on CBF and cognitive performance was evident. In conclusion, exercise training improved cerebrovascular function because regional CBF was changed. Studies are however still needed to establish whether exercise-induced improvements in CBF are sustained over longer periods of time and underlie the observed beneficial effects on cognitive performance.

Exosomal miR-532-5p induced by long-term exercise rescues blood-brain barrier function in 5XFAD mice via downregulation of EPHA4

The breakdown of the blood-brain barrier, which develops early in Alzheimer's disease (AD), contributes to cognitive impairment. Exercise not only reduces the risk factors for AD but also confers direct protection against cognitive decline. However, the exact molecular mechanisms remain elusive, particularly whether exercise can liberate the function of the blood-brain barrier. Here, we demonstrate that long-term exercise promotes the clearance of brain amyloid-β by improving the function of the blood-brain barrier in 5XFAD mice. Significantly, treating primary brain pericytes or endothelial cells with exosomes isolated from the brain of exercised 5XFAD mice improves cell proliferation and upregulates PDGFRβ, ZO-1, and claudin-5. Moreover, exosomes isolated from exercised mice exhibit significant changes in miR-532-5p. Administration or transfection of miR-532-5p to sedentary mice or primary brain pericytes and endothelial cells reproduces the improvement of blood-brain barrier function. Exosomal miR-532-5p targets EPHA4, and accordingly, expression of EphA4 is decreased in exercised mice and miR-532-5p overexpressed mice. A specific siRNA targeting EPHA4 recapitulates the effects on blood-brain barrier-associated cells observed in exercised 5XFAD mice. Overall, our findings suggest that exosomes released by the brain contain a specific miRNA that is altered by exercise and has an impact on blood-brain barrier function in AD.

Normal pace walking is beneficial to young participants’ executive abilities

Background

Exercise can improve cognitive function. The impact of acute exercise on cognition is related to exercise intensity. This study aimed to explore whether normal walking had a beneficial effect on cognition.

Methods

Compared with standing still, thirty healthy young men walked on a treadmill at a normal pace, and completed the Stroop test. Near-infrared spectroscopy was used to monitor the hemodynamic changes of the prefrontal cortex during the entire experiment.

Results

Studies showed that normal walking did not stimulate higher average cerebral oxygen in the PFC, but the peak cerebral oxygen in cognitive tests during walking was higher (Stroop Word: 2.56 ± 0.43 and 3.80 ± 0.50, P < 0.01, Stroop Color: 2.50 ± 0.37 and 3.66 ± 0.59, P < 0.05, Stroop Color-Word: 4.13 ± 0.55 and 5.25 ± 0.66, P < 0.01, respectively), and better results were achieved in the Stroop Color-Word test, which was reflected in faster reaction times (49.18 ± 1.68 s, 56.92 ± 2.29 s, respectively, P < 0.001) and higher accuracies (46.19 ± 0.69, 44.15 ± 0.91, respectively, P = 0.018).

Conclusion

For healthy young people, even a normal walk is therefore good for cognition.

Therapeutic non-invasive brain treatments in Alzheimer's disease: recent advances and challenges

Alzheimer's disease (AD) is one of the major neurodegenerative diseases and the most common form of dementia. Characterized by the loss of learning, memory, problem-solving, language, and other thinking abilities, AD exerts a detrimental effect on both patients' and families' quality of life. Although there have been significant advances in understanding the mechanism underlying the pathogenesis and progression of AD, there is no cure for AD. The failure of numerous molecular targeted pharmacologic clinical trials leads to an emerging research shift toward non-invasive therapies, especially multiple targeted non-invasive treatments. In this paper, we reviewed the advances of the most widely studied non-invasive therapies, including photobiomodulation (PBM), transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS), and exercise therapy. Firstly, we reviewed the pathological changes of AD and the challenges for AD studies. We then introduced these non-invasive therapies and discussed the factors that may affect the effects of these therapies. Additionally, we review the effects of these therapies and the possible mechanisms underlying these effects. Finally, we summarized the challenges of the non-invasive treatments in future AD studies and clinical applications. We concluded that it would be critical to understand the exact underlying mechanisms and find the optimal treatment parameters to improve the translational value of these non-invasive therapies. Moreover, the combined use of non-invasive treatments is also a promising research direction for future studies and sheds light on the future treatment or prevention of AD.

The Differential Effect of Schooling and Physical Activity on Dementia in Older Women and Men from Brazil: Implications for Policymaking

Background: Modifiable risk factors exert crucial impact on dementia. Objective: We sought to answer the question: do two modifiable risk factors, schooling level and physical activity (PA), affect cognitive function similarly in each sex? Methods: This cross-sectional study was conducted in 2019 and 2021, and the survey was applied to the residents of the metropolitan area of Santos, a seashore of Sao Paulo State. Four hundred and twenty-two participants (women = 254 and men = 168) were eligible. Baecke questionnaire for the elderly was applied for the classification as physically inactive (PI) or active (PA). Cognitive function was assessed by the Mini-Mental State Examination (MMSE) and the Clinical Dementia Rating (CDR). Participants were also stratified by schooling status for both sexes. Results: Higher education had a sex-independent positive influence on MMSE and CDR (p <  0.001). PA influences positively MMSE in older women (PI: 25±5 and PA: 27±3, p <  0.03), but has no effect in older men (26±5 and 25±5, p >  0.05). Concordantly, older women who were PA (1.7 and 0 %) showed a lower prevalence of dementia compared with PI (6.2 and 2.1%), for mild and moderate respectively. Active older women had higher odds of improving the MMSE score (OR: 1.093; 95% CI: 1.008–1.186) than men (OR: 0.97 (95% CI: 0.896–1.051). Conclusion: Education affects cognitive function equally in Brazilian elderly whereas older women are more responsive to the beneficial effects of PA for dementia than men.

Effects of a multicomponent day-care program on cerebral blood flow in patients with mild cognitive impairment

BACKGROUND

Mild cognitive impairment (MCI) is a prodromal phase of dementia and is considered an important period for intervention to prevent conversion to dementia. It has been well established that multicomponent day-care programs including exercise training, cognitive intervention and music therapy have beneficial effects on cognition, but the effects on cerebral blood flow (CBF) in MCI remain unknown. This study examined whether a multicomponent day-care program would have beneficial effects on the longitudinal changes of CBF in MCI patients.

METHODS

Participants were 24 patients with MCI attending a day-care program; they underwent two ⁹⁹ mTc-ethyl cysteinate dimer single photon emission computed tomography scans during the study period. We evaluated the association between the changes of regional cerebral blood flow and the attendance rate.

RESULTS

There was a significant negative correlation between the reduction of regional CBF in the right parietal region and the attendance rate. We found no significant relation between the baseline CBF images and the attendance rate.

CONCLUSIONS

Our results suggest that continuous participation in a multicomponent day-care program might prevent reduction in brain activity in patients with MCI.

Effects of interventions on cerebral perfusion in the Alzheimer's disease spectrum: A systematic review

Cerebral perfusion dysfunctions are seen in the early stages of Alzheimer's disease (AD). We systematically reviewed the literature to investigate the effect of pharmacological and non-pharmacological interventions on cerebral hemodynamics in randomized controlled trials involving AD patients or Mild Cognitive Impairment (MCI) due to AD. Studies involving other dementia types were excluded. Data was searched in April 2021 on MEDLINE, Embase, and Web of Science. Risk of bias was assessed using Cochrane Risk of Bias Tool. A meta-synthesis was performed separating results from MCI and AD studies. 31 studies were included and involved 310 MCI and 792 CE patients. The MCI studies (n = 8) included physical, cognitive, dietary, and pharmacological interventions. The AD studies (n = 23) included pharmacological, physical interventions, and phytotherapy. Cerebral perfusion was assessed with PET, ASL, Doppler, fNIRS, DSC-MRI, Xe-CT, and SPECT. Randomization and allocation concealment methods and subject characteristics such as AD-onset, education, and ethnicity were missing in several papers. Positive effects on hemodynamics were seen in 75 % of the MCI studies, and 52 % of the AD studies. Inserting cerebral perfusion outcome measures, together with established AD biomarkers, is fundamental to target all disease mechanisms and understand the role of cerebral perfusion in AD.

Effect of exercise on cognitive impairment in patients undergoing haemodialyses: A systematic review and meta-analysis of randomised controlled trials

BACKGROUND

The influence of exercise on cognition in patients undergoing haemodialysis has been examined. However, evidence elucidating the effects in this patient group is scarce.

OBJECTIVE

To examine the effect of exercise on cognitive impairment in patients undergoing haemodialysis and provide insight into the effects of various characteristics of exercise on cognitive impairment in this population.

DESIGN

A systematic review and meta-analysis, following the guidance of PRISMA was undertaken.

PARTICIPANTS

Adult patients undergoing haemodialysis.

RESULTS

This review found that exercise significantly improved cognitive impairment in patients undergoing haemodialysis (SMD = 0.37, 95% CI: 0.13, 0.60, p = 0.002). Subgroup analyses demonstrated that both intradialytic exercise (SMD = 0.82, 95% CI: 0.37, 1.26, p < 0.001) and interdialytic exercise (SMD = 0.24, 95% CI: 0.01, 0.47, p = 0.038), exercise for 16 weeks or over (SMD = 0.33, 95% CI: 0.07, 0.58, p = 0.012), and lasting for more than 30 minutes (SMD = 0.52, 95% CI: 0.17, 0.86, p = 0.004) significantly alleviated cognitive impairment. The effect of exercise on cognitive impairment in patients less than 65 years of age (SMD = 0.39, 95% CI: 0.10, 0.68, p = 0.009) was significantly better than those over 65.

CONCLUSION

Exercise significantly improves cognitive impairment in patients undergoing haemodialysis. Both Intradialytic and interdialytic exercise of at least 30 minutes duration, 3 times weekly, and at least for 16 weeks may play a significant role in alleviating cognitive impairment in patients under 65 years of age.

The Comparative Effectiveness of Traditional Chinese Medicine Exercise Therapies in Elderly People With Mild Cognitive Impairment: A Systematic Review and Network Meta-Analysis

Background

Mild cognitive impairment (MCI) in the elderly is a health problem worldwide. Studies have confirmed that traditional Chinese medicine (TCM) exercise therapies can improve MCI. However, which therapy is the best and their impacts on brain function remain controversial and uncertain. This study aims to compare and rank TCM exercise therapies for MCI in the elderly, and analyze their effects on brain function, in order to find an optimal intervention and provide a basis for clinical treatments decision-making.

Methods

The Web of Science, PubMed, EMBASE, Cochrane Central Register of Controlled Trials, Clinical Trials, China National Knowledge Infrastructure (CNKI), Wangfang database, China Science and Technology Journal Database, and Chinese Biomedical Medicine (CBM) were searched through October 28, 2021. Two researchers reviewed all the studies and extracted the data. The ADDIS software version 1.16.8 and the Bayesian hierarchical model were used for pair-wise meta-analysis and network meta-analysis, and the STATA software version 14.0 was used to draw the network evidence plots and funnel plots.

Results

A total of 23 studies on 2282 participants were included in this study. In the pair-wise meta-analysis, TCM exercise therapies (Baduanjin exercise, Tai Chi, Liuzijue exercise and finger exercise) were superior to non-TCM exercise therapies (stretching and toning exercise, usual care, health education and routine daily activities) in terms of MMSE, MoCA and ADL outcomes. In the network meta-analysis, the MMSE outcome ranked Baduanjin exercise (78%) as the best intervention and Tai Chi (36%) as the second. The MoCA outcome ranked Baduanjin exercise (62%) as the best intervention. For the ADL outcome, Baduanjin exercise (60%) ranked the best, and followed by finger exercise (43%).

Conclusion

TCM exercise therapies may improve the cognitive function in elderly patients with MCI. Among the four therapies included, the Baduanjin exercise may be the preferred therapy for MCI in the elderly, and its mechanism may be related to the regulation of cognitive-related brain function and structure.

Systematic Review Registration

https://inplasy.com, identifier: INPLASY202070006.

Pre-stroke Physical Activity and Cerebral Collateral Circulation in Ischemic Stroke: A Potential Therapeutic Relationship?

Favorable cerebral collateral circulation contributes to hindering penumbral tissue from progressing to infarction and is associated with positive clinical outcomes after stroke. Given its clinical importance, improving cerebral collateral circulation is considered a therapeutic target to reduce burden after stroke. We provide a hypothesis-generating discussion on the potential association between pre-stroke physical activity and cerebral collateral circulation in ischemic stroke. The recruitment of cerebral collaterals in acute ischemic stroke may depend on anatomical variations, capacity of collateral vessels to vasodilate, and individual risk factors. Physical activity is associated with improved cerebral endothelial and vascular function related to vasodilation and angiogenic adaptations, and risk reduction in individual risk factors. More research is needed to understand association between cerebral collateral circulation and physical activity. A presentation of different methodological considerations for measuring cerebral collateral circulation and pre-stroke physical activity in the context of acute ischemic stroke is included. Opportunities for future research into cerebral collateral circulation, physical activity, and stroke recovery is presented.

Sixteen weeks of aerobic exercise does not alter resting-state connectivity of the precuneus in patients with Alzheimer's disease

INTRODUCTION

In healthy elderly persons and patients with mild cognitive impairment, physical exercise can increase functional brain connectivity in the default mode network (DMN) measured by restingstate functional magnetic resonance imaging (rs-fMRI). However, no studies have so far investigated the effect of physical exercise on functional resting-state connectivity in the DMN in patients with Alzheimer's disease (AD).

OBJECTIVE

In a single-blinded randomized controlled trial, we assessed the effects of an aerobic exercise intervention of 16 weeks of physical exercise on DMN connectivity using rs-fMRI in patients with AD.

METHODS

Forty-five patients were randomly assigned to either a control or exercise group. The exercise group performed 60-min of aerobic exercise three times per week for 16 weeks. All the patients underwent whole-brain rs-fMRI at 3 T, at baseline, and after 16 weeks. Since the posterior cingulate cortex (PCC) and adjacent precuneus constitute a central hub of the DMN, this parietal region was defined as region-ofinterest and used as the seed region for functional connectivity analysis of the rs-fMRI data treating age and gender as covariates.

RESULTS

Neither seed-based analysis, seeded in the PCC/precuneus region nor ICA-based analyses, focusing on components of the DMN network, showed any exercise-induced changes in functional resting-state connectivity from baseline to follow-up.

CONCLUSION

16 weeks of aerobic exercise does not modify functional connectivity of the PCC/precuneus region in patients with AD. A longer intervention may be needed to show the effect of exercise on brain connectivity.

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.

Exercise-Mediated Alteration of miR-192-5p Is Associated with Cognitive Improvement in Alzheimer's Disease

INTRODUCTION

Physical exercise is an important component of managing Alzheimer's disease (AD). miRNAs can be modulated by exercise intervention.

OBJECTIVE

The study explored the involvement and potential mechanism of miR-192-5p in the protective effect of physical exercise on AD.

METHODS

Ninety AD patients were enrolled, in which 45 cases accepted cycling training for continuous 3 months. The expression changes of miR-192-5p before and after exercise were analyzed by reverse transcription-quantitative PCR. 8-month-old APP/PS1 double Tg mice were used as the AD animal model. Mice in the voluntary exercise (VE) group received VE for 4 weeks. Morris water maze (MWM) test was used to evaluate the learning and memory function. Enzyme-linked immunosorbent assay was used to calculate the level of IL-1β, IL-6, and TNF-α.

RESULTS

AD patients showed elevated MMSE scores, decreased ADAS-cog and NPI-Q scores after 3 months of exercise. miR-192-5p was downregulated in the serum of AD patients and correlated with the levels of MMSE score, ADAS-cog, and NPI-Q score. A positive association was detected between serum miR-192-5p with TNF-α, IL-6, and IL-1β levels. MiR-192-5p is downregulated in the hippocampus tissues of mice after VE. Overexpression of miR-192-5p reversed the neuroprotective effect of exercise on AD in mice and promoted the inflammatory response of AD mice.

CONCLUSION

MiR-192-5p can be modulated by the exercise intervention and involved in the protective effect of exercise on AD.

Exercise interventions in Alzheimer's disease: A systematic review and meta-analysis of randomized controlled trials

AIMS

To assess the potential multi-domain benefits of exercise interventions on patients with Alzheimer's disease (AD), as well as to determine the specific effects of different exercise modalities (aerobic, strength, or combined training).

METHODS

A systematic search was conducted in PubMed and Web of Science until March 2021 for randomized controlled trials assessing the effect of exercise interventions (compared with no exercise) on patients with AD. Outcomes included cognitive function (mini-mental state examination [MMSE] test), physical function (e.g., 6-minute walking test [6MWT]), functional independence (Barthel index), and neuropsychiatric symptoms (Neuropsychiatric Inventory [NPI]). A random-effects meta-analysis was conducted.

RESULTS

28 studies (total n = 1337 participants, average age 79-90 years) were included in the systematic review, of which 21 could be meta-analyzed. Although considerable heterogeneity was found, exercise interventions induced several significant benefits, including in Barthel index (n = 147 patients, mean difference [MD]=8.36 points, 95% confidence interval [CI]=0.63-16.09), 6MWT (n = 369, MD=84 m, 95% CI=44-133)), and NPI (n = 263, MD=-4.4 points, 95% CI=-8.42 to -0.38). Benefits were also found in the MMSE test, albeit significance was only reached for aerobic exercise (n = 187, MD=2.31 points, 95% CI 0.45-4.27).

CONCLUSIONS

Exercise interventions appear to exert multi-domain benefits in patients with AD.

Cerebral blood flow in mild cognitive impairment and Alzheimer's disease: A systematic review and meta-analysis

BACKGROUND

Reduced cerebral blood flow (CBF) contributes to the pathophysiology of Alzheimer's disease (AD). However, it is unclear whether there is a spatial-temporal-specific pattern of changed CBF in AD progression.

METHODS

We systematically screened literature databases for cross-sectional and longitudinal studies reporting resting CBF or CBF velocity (CBFv) among patients with AD, mild cognitive impairment (MCI), and healthy controls (HCs). Standardised mean differences (SMDs) for CBF and mean differences (MDs) for CBFv were calculated. Quality assessments, meta-analysis, subgroup analysis, and meta-regression were subsequently performed (PROSPERO: CRD42020207548).

RESULTS

Overall, 244 studies comprising 13,644 participants and 60 regions were included. Compared with HCs, AD subjects had decreased resting CBF throughout the brain (SMD range: -1.87 to -0.32), especially within the posterior cingulate and temporal-parietal regions. However, MCI subjects presented decreased CBF in ten regions with modest effects (SMD range: -0.86 to -0.25), especially in the precuneus. We identified the decreased CBF in the temporal, parietal, and hippocampal regions was associated with the lower AD Mini-Mental State Examination scores.

CONCLUSIONS

Our findings suggest that the spatial-temporal pattern of CBF decreased from the precuneus, posterior cingulate and temporal-parietal regions to broader areas with progression from HC to MCI to AD, supporting the incorporation of CBF into the AD research framework.

Xueshuantong Improves Functions of Lymphatic Ducts and Modulates Inflammatory Responses in Alzheimer's Disease Mice

Recent studies have revealed significant contributions of lymphatic vessels (LVs) to vital functions of the brain, especially related to clearance of waste from the brain and immune responses in the brain. These studies collectively indicate that enhancing the functions of LVs may improve brain functions during brain aging and in Alzheimer’s disease (AD) where LV functions are impaired. However, it is currently unknown whether this enhancement can be achieved using small molecules. We have previously shown that a widely used Chinese herbal medicine Xueshuantong (XST) significantly improves functions and reduces pathology in AD transgenic mice associated with elevated cerebral blood flow (CBF). Here, we show that XST partially rescues deficits in lymphatic structures, improves clearance of amyloid-β (Aβ) from the brain, and reduces the inflammatory responses in the serum and brains of transgenic AD mice. In addition, we showed that this improvement in the lymphatic system occurs independently of elevated CBF, suggesting independent modulation and limited interaction between blood circulation and lymphatic systems. Moreover, XST treatment leads to a significant increase in GLT-1 level and a significantly lower level of MMP-9 and restores AQP4 polarity in APP/PS1 mice. These results provide the basis for further exploration of XST to enhance or restore LV functions, which may be beneficial to treat neurodegenerative diseases or promote healthy aging.

Relationship between objectively measured physical activity on neuropathology and cognitive outcomes in older adults: Resistance versus resilience?

INTRODUCTION

Physical activity (PA) is associated with better cognitive and brain health. However, it remains unclear whether PA relates to accumulation of disease pathology ("resistance") or indirectly moderates adverse effects of pathology on cognition ("cognitive resilience").

METHODS

Five hundred thirteen Rush Memory and Aging Project (MAP) decedents completed longitudinal actigraphy monitoring, cognitive testing, and neuropathological examination. Cross-sectional models tested the relationship between average PA and pathology, and the moderating effect of baseline PA on the association between pathology and cognition. Longitudinal models examined whether changes in PA moderated associations between pathology and cognition.

RESULTS

PA was negatively associated with Lewy body disease (LBD), but positively associated with Alzheimer's disease (AD) burdens. Baseline PA attenuated the association between cerebrovascular pathology and cognition, whereas longitudinal change in PA attenuated associations between AD, cerebral amyloid angiopathy, TAR DNA-binding protein 43, and atherosclerosis on cognitive decline.

DISCUSSION

Whereas PA relates to "cognitive resilience" against cerebrovascular disease, AD, and other neuropathologies, "resistance" effects were limited.

Effects of Exercise in the Treatment of Alzheimer's Disease: An Umbrella Review of Systematic Reviews and Meta-Analyses

The authors aimed to provide an overview of the evidence on the effects of exercise in people with Alzheimer's disease through a comprehensive review of the existing systematic reviews and meta-analyses. A literature search was performed in CINAHL, Cochrane Library, EMBASE, PubMed, SPORTDiscus, Scopus, and Web of Science databases according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The AMSTAR-2-Tool was used for the quality assessment. Twenty-three reviews fulfilled the criteria. Most of the reviews investigated the effects of aerobic exercise on Alzheimer's disease symptoms. The largest effects of exercise were seen in terms of improved cognition by multiple exercises. The majority of the reviews were rated as being of moderate quality and none were classified as having high quality. Exercise is an effective way to treat Alzheimer's disease symptoms and has a low incidence of related adverse events. As most reviews were evaluated as low-moderate quality, caution is needed in the interpretation of the results.

Exercise, Arterial Stiffness, and Cerebral Vascular Function: Potential Impact on Brain Health

Exercise is associated with higher cognitive function and is a promising intervention to reduce the risk of dementia. With advancing age, there are changes in the vasculature that have important clinical implications for brain health and cognition. Primary aging and vascular risk factors are associated with increases in arterial stiffness and pulse pressure, and reductions in peripheral vascular function.

OBJECTIVE

The purpose is to discuss the epidemiological, observational, and mechanistic evidence regarding the link between age-related changes in vascular health and brain health.

METHODS

We performed a literature review and integrated with our published data.

RESULTS

Epidemiological evidence suggests a link between age-related increases in arterial stiffness and lower cognitive function, which may be mediated by cerebral vascular function, including cerebral vasoreactivity and cerebral pulsatility. Age-associated impairments in central arterial stiffness and peripheral vascular function have been attenuated or reversed through lifestyle behaviors such as exercise. Greater volumes of habitual exercise and higher cardiorespiratory fitness are associated with beneficial effects on both peripheral vascular health and cognition. Yet, the extent to which exercise directly influences cerebral vascular function and brain health, as well as the associated mechanisms remains unclear.

CONCLUSION

Although there is evidence that exercise positively impacts cerebral vascular function, more research is necessary in humans to optimize experimental protocols and address methodological limitations and physiological considerations. Understanding the impact of exercise on cerebral vascular function is important for understanding the association between exercise and brain health and may inform future intervention studies that seek to improve cognition.

How does physical activity benefit people living with dementia? A systematic review to identify the potential mechanisms of action

Purpose

One limitation of research that assesses the effectiveness of physical activity interventions for people with dementia is that most do not describe the intervention in sufficient detail to ascertain a theoretical basis or mechanism of action that determines the effective components. This paper aims to identify studies which evaluate the mechanisms of action of physical activity interventions for people with dementia, to further inform effective intervention development.

Design/methodology/approach

Papers were screened for evidence of evaluation of specific forms of physical activity, using pre-defined inclusion criteria. Analysis was conducted to ascertain if mechanisms of action were corroborated by data within and between studies.

Findings

The authors identified 26 studies with a measured mechanism of action; these related to the effects of physical activity on either neurological structure or endocrinal markers, including hormones. Physical activity had potential to reduce hippocampal atrophy, increase neural recruitment, activate the noradrenergic system and improve anti-inflammatory responses. While individual studies were hampered by small sample sizes, the body of evidence indicated that physical activity may have potential to delay cognitive decline.

Practical implications

Mechanisms of action in relation to dementia and physical activity are likely to be multifaceted, and physical activity may be protective against progression in the early stages of cognitive decline. Physical activity may be of greatest benefit if incorporated into on-going lifestyle, rather than engaged in for short periods, and combined with social interaction.

Originality/value

This paper is unique in its focus on the mechanisms of action of physical activity interventions for people with dementia.

Lactate as Potential Mediators for Exercise-Induced Positive Effects on Neuroplasticity and Cerebrovascular Plasticity

The accumulated evidence from animal and human studies supports that exercise is beneficial to physical health. Exercise can upregulate various neurotrophic factors, activate neuroplasticity, and play a positive role in improving and enhancing cerebrovascular function. Due to its economy, convenience, and ability to prevent or ameliorate various aging-related diseases, exercise, a healthy lifestyle, is increasingly popularized by people. However, the mechanism by which exercise performs this function and how it is transmitted from muscles to the brain remains incompletely understood. Here, we review the beneficial effects of exercise with different intensities on the brain with a focus on the positive effects of lactate on neuroplasticity and cerebrovascular plasticity. Based on these recent studies, we propose that lactate, a waste previously misunderstood as a by-product of glycolysis in the past, may be a key signal molecule that regulates the beneficial adaptation of the brain caused by exercise. Importantly, we speculate that a central protective mechanism may underlie the cognitive benefits induced by exercise.

Effects of far infrared light on Alzheimer's disease-transgenic mice

Far infrared light has been used in many medical procedures. However, the detailed biological mechanisms of infrared light’s effects have not yet been elucidated. Many researchers have pointed out the thermal effects of treatments such as infrared saunas, which are known to increase blood flow. Alzheimer’s disease (AD) is associated with gradual decreases in brain blood flow and resulting dementia. In this study, we attempted to clarify the beneficial effects of far infrared light using the 5xFAD mouse, a transgenic model of AD. We exposed 5xFAD mice to far infrared light for 5 months. Among the far infrared-exposed AD mice, body weights were significantly decreased, and the levels of nerve growth factor and brain-derived neurotrophic factor protein were significantly increased in selected brain areas (compared to those in non-irradiated AD mice). However, cognition and motor function (as assessed by Morris water maze and Rota Rod tests, respectively) did not differ significantly between the irradiated and non-irradiated AD mouse groups. These results indicated that exposure to far infrared light may have beneficial biological effects in AD mice. However, the experimental schedule and methods may need to be modified to obtain clearer results.

Effects of cardiorespiratory fitness and exercise training on cerebrovascular blood flow and reactivity: a systematic review with meta-analyses

We address two aims: Aim 1 (Fitness Review) compares the effect of higher cardiorespiratory fitness (CRF) (e.g., endurance athletes) with lower CRF (e.g., sedentary adults) on cerebrovascular outcomes, including middle cerebral artery velocity (MCAv), cerebrovascular reactivity and resistance, and global cerebral blood flow, as assessed by transcranial Doppler (TCD) or magnetic resonance imaging (MRI). Aim 2 (Exercise Training Review) determines the effect of exercise training on cerebrovascular outcomes. Systematic review of studies with meta-analyses where appropriate. Certainty of evidence was assessed by the Grading of Recommendations Assessment, Development, and Evaluation (GRADE). Twenty studies (18 using TCD) met the eligibility criteria for Aim 1, and 14 studies (8 by TCD) were included for Aim 2. There was a significant effect of higher CRF compared with lower CRF on cerebrovascular resistance (effect size = -0.54, 95% confidence interval = -0.91 to -0.16) and cerebrovascular reactivity (0.98, 0.41-1.55). Studies including males only demonstrated a greater effect of higher CRF on cerebrovascular resistance than mixed or female studies (male only: -0.69, -1.06 to -0.32; mixed and female studies: 0.10, -0.28 to 0.49). Exercise training did not increase MCAv (0.05, -0.21 to 0.31) but showed a small nonsignificant improvement in cerebrovascular reactivity (0.60, -0.08 to 1.28; P = 0.09). Exercise training showed heterogeneous effects on regional but little effect on global cerebral blood flow as measured by MRI. High CRF positively effects cerebrovascular function, including decreased cerebrovascular resistance and increased cerebrovascular reactivity; however, global cerebral blood flow and MCAv are primarily unchanged following an exercise intervention in healthy and clinical populations.NEW & NOTEWORTHY Higher cardiorespiratory fitness is associated with lower cerebrovascular resistance and elevated cerebrovascular reactivity at rest. Only adults with a true-high fitness based on normative data exhibited elevated middle cerebral artery velocity. The positive effect of higher compared with lower cardiorespiratory fitness on resting cerebrovascular resistance was more evident in male-only studies when compared with mixed or female-only studies. A period of exercise training resulted in negligible changes in middle cerebral artery velocity and global cerebral blood flow, with potential for improvements in cerebrovascular reactivity.

Physical Exercise Training Improves Judgment and Problem-Solving and Modulates Serum Biomarkers in Patients with Alzheimer's Disease

Alzheimer's disease (AD) is characterized by progressive impairment of memory, with an etiology involving oxidative stress and inflammation. Exercise training is a safe, efficacious, and economic approach to manage neurodegenerative diseases. In AD, the biomarkers of oxidative damage to lipids, proteins, and DNA are elevated. In the present study, we aimed to evaluate whether exercise is effective in patients with AD by assessing the serum biomarkers associated with the redox status, neurotrophin levels, and inflammatory system. This nonrandomized clinical study (n = 15) involved 22 training sessions performed twice a week (60 min/session) in patients diagnosed with AD. The cognitive and self-awareness tests were performed 48 h before and after the physical training session. In patients with AD, physical training significantly improved the judgment and problem-solving domains of the memory score; however, general mental health, memory, orientation, and home/hobby domains were improved slightly, and the neurotrophin levels remained unaltered. Significantly, the markers of protein integrity also increased following exercise. Furthermore, catalase activity and ROS levels decreased, nitrite levels increased, and interleukin-4 level increased following physical training in patients with AD. Although proinflammatory cytokines remained unaltered, the levels of neuron-specific enolase, a marker of neuronal damage, decreased following exercise training in these patients. In conclusion, physical exercise training could be a safe and effective method for blocking the AD progression and improving the antioxidant capacity and anti-inflammatory system, whereas certain assessed biomarkers could be utilized to monitor AD therapy.

Personalized treatment interventions: nonpharmacological and natural treatment strategies in Alzheimer's disease

Introduction: Alzheimer's disease (AD) is a slow, irreversible, progressive, complex, and fatal neurodegenerative disorder. Available pharmacological treatment, known for almost two decades, does not cure the disease, but only alleviates the symptoms, with various efficacy and different side effects. Therefore, there is an unmet need to find other person-centered or personalized approaches to treat AD.Areas covered: This article describes the application of precision medicine-like approaches utilizing nonpharmacological treatment strategies and the use of natural products in personalized care for patients with AD.Expert opinion: Due to the heterogeneity of disease symptoms, somatic conditions, and patient preferences, there is definitely no "one size fits all" intervention. Therefore, individualized treatment choice is based on dementia stage, medical and psychiatric comorbidity, leading symptoms, patient preferences, and remaining capacity of the patient. In the absence of disease-modifying agents, a patient-centered, multidisciplinary team approach appears to be the best option to alleviate the heavy symptomatic burden in this unfortunate population. Hence, appropriate interventions can be offered along the AD continuum, while a better understanding of personal characteristics might help in establishing optimal individualized treatment, as well as its duration and intensity, to deliver interventions in the most effective ways.

Physical Exercise and Alzheimer's Disease: Effects on Pathophysiological Molecular Pathways of the Disease

Alzheimer’s disease (AD), the most common form of neurodegenerative dementia in adults worldwide, is a multifactorial and heterogeneous disorder characterized by the interaction of genetic and epigenetic factors and the dysregulation of numerous intracellular signaling and cellular/molecular pathways. The introduction of the systems biology framework is revolutionizing the study of complex diseases by allowing the identification and integration of cellular/molecular pathways and networks of interaction. Here, we reviewed the relationship between physical activity and the next pathophysiological processes involved in the risk of developing AD, based on some crucial molecular pathways and biological process dysregulated in AD: (1) Immune system and inflammation; (2) Endothelial function and cerebrovascular insufficiency; (3) Apoptosis and cell death; (4) Intercellular communication; (5) Metabolism, oxidative stress and neurotoxicity; (6) DNA damage and repair; (7) Cytoskeleton and membrane proteins; (8) Synaptic plasticity. Moreover, we highlighted the increasingly relevant role played by advanced neuroimaging technologies, including structural/functional magnetic resonance imaging, diffusion tensor imaging, and arterial spin labelling, in exploring the link between AD and physical exercise. Regular physical exercise seems to have a protective effect against AD by inhibiting different pathophysiological molecular pathways implicated in AD.

Physical exercise promotes brain remodeling by regulating epigenetics, neuroplasticity and neurotrophins

Exercise has been shown to have beneficial effects on brain functions in humans and animals. Exercise can improve memory and learning in age-related neurodegenerative diseases. In animal models, physical exercise regulates epigenetics, promotes synaptic plasticity and hippocampal neurogenesis, regulates the expression levels of neurotrophic factors, and improves cognitive function. Therefore, exercise is very important for brain rehabilitation and remodeling. The purpose of this review is to explore the mechanisms by which exercise exerts positive effects on brain function. This knowledge implies that physical exercise can be used as a non-drug therapy for neurological diseases.

Effects of physical activities on dementia-related biomarkers: A systematic review of randomized controlled trials

INTRODUCTION

Physical activities (PA) may lead to improved cognition in mild cognitive impairment (MCI), Alzheimer's disease (AD), and dementia. The mechanisms mediating potential PA effects are unknown. Assessment of PA effects on relevant biomarkers may provide insights into mechanisms underlying potential PA effects on cognition.

METHODS

We systematically reviewed randomized controlled trials (RCTs) that studied PA effects on biomarkers in MCI, AD, and dementia populations. We examined whether biological mechanisms were hypothesized to explain associations among PA, biomarkers, and cognitive functions. We used the PubMed database and searched for RCTs with PA until October 31, 2019.

RESULTS

Of 653 studies examining changes in biomarkers in PA trials, 18 studies met inclusion criteria for the present review. Some studies found favorable effects of PA on neurotrophic and inflammatory biomarkers. AD pathological markers were rarely investigated, with inconclusive results. Most studies were relatively small in sample size, of limited duration, and not all studies compared the changes in biomarkers between the control and experimental groups.

DISCUSSION

There is only limited use of potentially informative biomarkers in PA trials for MCI, AD, and dementia. Most studies did not examine the role of biomarkers to study associations between PA and cognitive functions in their analyses. Several potential biomarkers remain uninvestigated. Careful use of biomarkers may clarify mechanisms underlying PA effects on cognition. Our review serves as a useful resource for developing future PA RCTs aimed at improving cognitive functions in MCI, AD, and dementias.

Exercise as Potential Therapeutic Target to Modulate Alzheimer's Disease Pathology in APOE ε4 Carriers: A Systematic Review

Alzheimer's disease (AD) is a progressive neurodegenerative disease for which no effective treatment exists at present. Previous research has found that exercise reduces the risk of AD. Since the apolipoprotein E (APOE) ε4 allele increases the risk of AD and is associated with faster disease progression than the other isoforms, we aimed to highlight the impact of exercise on AD pathology in APOE ε4 carriers. This review focuses on the effect of exercise on cognitive function, dementia risk, amyloid-β (Aβ) metabolism, lipid metabolism, neuroinflammation, neurotrophic factors and vascularization in APOE ε4 carriers. We searched the literature in the PubMed electronic database using the following search terms: physical activity, exercise, aerobic fitness, training, sport, APOE4, Alzheimer's disease, AD and dementia. By cross-referencing, additional publications were identified. Selected studies required older adults to take part in an exercise intervention or to make use of self-reported physical activity questionnaires. All included studies were written and published in English between 2000 and 2020. From these studies, we conclude that exercise is a non-pharmacological treatment option for high-risk APOE ε4 carriers to ameliorate the AD pathological processes including reducing Aβ load, protecting against hippocampal atrophy, improving cognitive function, stabilizing cholesterol levels and lowering pro-inflammatory signals. Variation in study design related to age, cognitive outcomes and the type of intervention explained the differences in study outcomes. However, exercise seems to be effective in delaying the onset of AD and may improve the quality of life of AD patients.

A Randomized Controlled Trial on the Effects of a 12-Week High- vs. Low-Intensity Exercise Intervention on Hippocampal Structure and Function in Healthy, Young Adults

Physical exercise affects hippocampal structure and function, but the underlying neural mechanisms and the effects of exercise intensity remain incompletely understood. Therefore, we undertook a comprehensive, multi-modal 3T and 7T MRI randomized controlled trial (Netherlands Trial Register - NL5847) in which we randomized 52 young, non-athletic volunteers to a 12-week low- or high-intensity exercise program. Using state-of-the-art methods, we investigated changes in hippocampal volume, as well as changes in vasculature, neuro-metabolites, and peripheral growth factors as potential underpinnings. Cardiorespiratory fitness improved over time (p < 0.001), but no interaction with exercise intensity was found (p = 0.48). Accordingly, we did not observe significant interactions between exercise condition and time on MRI measures (all p > 0.06). However, we found a significant decrease in right hippocampal volume (p < 0.01), an increase in left hippocampal glutathione (p < 0.01), and a decrease of left hippocampal cerebral blood volume (p = 0.01) over time, regardless of exercise condition. Additional exploratory analyses showed that changes in brain-derived neurotrophic factor (p = 0.01), insulin-like growth-factor (p = 0.03), and dorsal anterior cingulate cortex N-acetyl-aspartate levels (p = 0.01) were positively associated with cardiorespiratory fitness changes. Furthermore, a trend toward a positive association of fitness and gray-matter cerebral blood flow (p = 0.06) was found. Our results do not provide evidence for differential effects between high-intensity (aerobic) and low-intensity (toning) exercise on hippocampal structure and function in young adults. However, we show small but significant effects of exercise on hippocampal volume, neurometabolism and vasculature across exercise conditions. Moreover, our exploratory results suggest that exercise might not specifically only benefit hippocampal structure and function, but rather has a more widespread effect. These findings suggest that, in agreement with previous MRI studies demonstrating moderate to strong effects in elderly and diseased populations, but none to only mild effects in young healthy cohorts, the benefits of exercise on the studied brain measures may be age-dependent and restorative rather than stimulatory. Our study highlights the importance of a multi-modal, whole-brain approach to assess macroscopic and microscopic changes underlying exercise-induced brain changes, to better understand the role of exercise as a potential non-pharmacological intervention.

Mechanisms of neuroplasticity and brain degeneration: strategies for protection during the aging process

Aging is a dynamic and progressive process that begins at conception and continues until death. This process leads to a decrease in homeostasis and morphological, biochemical and psychological changes, increasing the individual’s vulnerability to various diseases. The growth in the number of aging populations has increased the prevalence of chronic degenerative diseases, impairment of the central nervous system and dementias, such as Alzheimer’s disease, whose main risk factor is age, leading to an increase of the number of individuals who need daily support for life activities. Some theories about aging suggest it is caused by an increase of cellular senescence and reactive oxygen species, which leads to inflammation, oxidation, cell membrane damage and consequently neuronal death. Also, mitochondrial mutations, which are generated throughout the aging process, can lead to changes in energy production, deficiencies in electron transport and apoptosis induction that can result in decreased function. Additionally, increasing cellular senescence and the release of proinflammatory cytokines can cause irreversible damage to neuronal cells. Recent reports point to the importance of changing lifestyle by increasing physical exercise, improving nutrition and environmental enrichment to activate neuroprotective defense mechanisms. Therefore, this review aims to address the latest information about the different mechanisms related to neuroplasticity and neuronal death and to provide strategies that can improve neuroprotection and decrease the neurodegeneration caused by aging and environmental stressors.

Interaction between physical exercise and APOE gene polymorphism on cognitive function in older people

We aimed to present an overview of the literature regarding the interaction between physical exercise and APOE gene polymorphism on cognitive function, particularly in patients with Alzheimer's disease (AD). Firstly, this review focused on the effect of the physical exercise on cognitive function, regardless of APOE gene polymorphism. Some studies have shown that a high level of cardiorespiratory fitness is associated with less neuronal damage with an improvement in memory score tests whereas other studies failed to detect any association between physical exercise and cognitive improvement either in healthy individuals or patients with AD. Taken together, standardized protocols and more longitudinal studies are required to provide a better insight into the effects of physical exercise on cognitive function. Although there is no agreement in the literature regarding the effects of physical exercise on cognitive function, it is well established that it improves social interaction and the feeling of well-being, thereby positively contributing to the quality of life of the elderly. Regarding the influence of physical exercise on cognitive function in APOE ε4 allele carriers, the data trend shows that the carriers of allele ε4 for APOE gene were more responsive to the beneficial effects of physical exercise on cognitive function compared with non-carriers. Nevertheless, studies with larger sample sizes will provide more accuracy about this relationship.

Protective Factors Modulate the Risk of Beta Amyloid in Alzheimer's Disease

Aim

To identify the factors protecting Abeta-positive subjects with normal cognition (NC) or mild cognitive impairment (MCI) from conversion to Alzheimer's disease (AD).

Methods

Subjects with MCI in the Alzheimer's Disease Neuroimaging Initiative (ADNI) database, with baseline data for neuropsychological tests, brain beta amyloid (Abeta), magnetic resonance imaging (MRI), APOE genotyping, and 18F-FDG-PET (FDG), were included for analysis.

Results

Elevated brain amyloid was associated with a higher risk of conversion from MCI to AD (41.5%) relative to Abeta levels of <1.231 (5.5%) but was not associated with conversion from NC to AD (0.0 vs. 1.4%). In the multivariate Cox regression analyses, elevated Abeta increased the risk of AD, while higher whole-brain cerebral glucose metabolism (CGM) assessed by FDG decreased the risk of AD in subjects with the same amount of Abeta. Even in the patients with heavily elevated brain amyloid, those with FDG > 5.946 had a lower risk of AD. ApoE4 carrier status did not influence the protective effect.

Conclusion

Higher average CGM based on FDG modified the progression to AD, indicating a protective function. The results suggest that the inclusion of this CGM measured by FDG would enrich clinical trial design and that increasing CGM along with the use of anti-Abeta agents might be a potential prevention strategy for AD.

Immediate effects of a single session of physical exercise on cognition and cerebral blood flow: A randomized controlled study of older adults

BACKGROUND

Regular physical activity is beneficial for cognitive performance in older age. A single bout of aerobic physical exercise can transiently improve cognitive performance. Researchers have advanced improvements in cerebral circulation as a mediator of long-term effects of aerobic physical exercise on cognition, but the immediate effects of exercise on cognition and cerebral perfusion are not well characterized and the effects in older adults are largely unknown.

METHODS

Forty-nine older adults were randomized to a 30-min aerobic exercise at moderate intensity or relaxation. Groups were matched on age and cardiovascular fitness (VO2 max). Average Grey Matter Blood Flow (GMBF), measured by a pulsed arterial-spin labeling (pASL) magnetic resonance imaging (MRI) acquisition, and working memory performance, measured by figurative n-back tasks with increasing loads were assessed before and 7 min after exercising/resting.

RESULTS

Accuracy on the n-back task increased from before to after exercising/resting regardless of the type of activity. GMBF decreased after exercise, relative to the control (resting) group. In the exercise group, higher n-back performance after exercise was associated with lower GMBF in the right hippocampus, left medial frontal cortex and right orbitofrontal cortex, and higher cardiovascular fitness was associated with lower GMBF.

CONCLUSION

The decrease of GMBF reported in younger adults shortly after exercise also occurs in older adults and relates to cardiovascular fitness, potentially supporting the link between cardiovascular fitness and cerebrovascular reactivity in older age.

Myokines mediate the cross talk between skeletal muscle and other organs

Myokines are muscle-derived cytokines and chemokines that act extensively on organs and exert beneficial metabolic functions in the whole-body through specific signal networks. Myokines as mediators provide the conceptual basis for a whole new paradigm useful for understanding how skeletal muscle communicates with other organs. In this review, we summarize and discuss classes of myokines and their physiological functions in mediating the regulatory roles of skeletal muscle on other organs and the regulation of the whole-body energy metabolism. We review the mechanisms involved in the interaction between skeletal muscle and nonmuscle organs through myokines. Moreover, we clarify the connection between exercise, myokines and disease development, which may contribute to the understanding of a potential mechanism by which physical inactivity affects the process of metabolic diseases via myokines. Based on the current findings, myokines are important factors that mediate the effect of skeletal muscle on other organ functions and whole-body metabolism.

Physical exercise in the prevention and treatment of Alzheimer's disease

Dementia is one of the greatest global challenges for health and social care in the 21st century. Alzheimer's disease (AD), the most common type of dementia, is by no means an inevitable consequence of growing old. Several lifestyle factors may increase, or reduce, an individual's risk of developing AD. Much has been written over the ages about the benefits of exercise and physical activity. Among the risk factors associated with AD is a low level of physical activity. The relationship between physical and mental health was established several years ago. In this review, we discuss the role of exercise (aerobic and resistance) training as a therapeutic strategy for the treatment and prevention of AD. Older adults who exercise are more likely to maintain cognition. We address the main protective mechanism on brain function modulated by physical exercise by examining both human and animal studies. We will pay especial attention to the potential role of exercise in the modulation of amyloid β turnover, inflammation, synthesis and release of neurotrophins, and improvements in cerebral blood flow. Promoting changes in lifestyle in presymptomatic and predementia disease stages may have the potential for delaying one-third of dementias worldwide. Multimodal interventions that include the adoption of an active lifestyle should be recommended for older populations.

A pilot study investigating the effects of voluntary exercise on capillary stalling and cerebral blood flow in the APP/PS1 mouse model of Alzheimer's disease

Exercise exerts a beneficial effect on the major pathological and clinical symptoms associated with Alzheimer’s disease in humans and mouse models of the disease. While numerous mechanisms for such benefits from exercise have been proposed, a clear understanding of the causal links remains elusive. Recent studies also suggest that cerebral blood flow in the brain of both Alzheimer’s patients and mouse models of the disease is decreased and that the cognitive symptoms can be improved when blood flow is restored. We therefore hypothesized that the mitigating effect of exercise on the development and progression of Alzheimer’s disease may be mediated through an increase in the otherwise reduced brain blood flow. To test this idea, we performed a pilot study to examine the impact of three months of voluntary wheel running in a small cohort of ~1-year-old APP/PS1 mice on short-term memory function, brain inflammation, amyloid deposition, and baseline cerebral blood flow. Our findings that exercise led to a trend toward improved spatial short-term memory, reduced brain inflammation, markedly increased neurogenesis in the dentate gyrus, and a reduction in hippocampal amyloid-beta deposits are consistent with other reports on the impact of exercise on the progression of Alzheimer’s related symptoms in mouse models. Notably, we did not observe any impact of wheel running on overall baseline blood flow nor on the incidence of non-flowing capillaries, a mechanism we recently identified as one contributing factor to cerebral blood flow deficits in mouse models of Alzheimer’s disease. Overall, our findings add to the emerging picture of differential effects of exercise on cognition and blood flow in Alzheimer’s disease pathology by showing that capillary stalling is not decreased following exercise.

Effects of Moderate Intensity Exercise on the Cortical Thickness and Subcortical Volumes of Preclinical Alzheimer's Disease Patients: A Pilot Study

OBJECTIVE

We aimed to explore the impact of moderate intensity exercise on the cortical thickness and subcortical volumes of preclinical Alzheimer's disease (AD) patients.

METHODS

Sixty-three preclinical AD patients with magnetic resonance imaging (MRI) and 18-florbetaben positron emission tomography (PET) data were enrolled in the study. Information on demographic characteristics, cognitive battery scores, self-reported exercise habits were attained. Structural magnetic resonance images were analyzed and processed using Freesurfer v6.0.

RESULTS

Compared to Exercise group, Non-Exercise group demonstrated reduced cortical thickness in left parstriangularis, rostral middle frontal, entorhinal, superior frontal, lingual, superior parietal, lateral occipital, inferior parietal gyrus, temporal pole, precuneus, insula, fusiform gyrus, right precuneus, superiorparietal, lateral orbitofrontal, rostral middle frontal, medial orbitofrontal, superior frontal, lingual, middle temporal gyrus, insula, supramarginal, parahippocampal, paracentral gyrus. Volumes of right thalamus, caudate, putamen, pallidum, hippocampus, amygdala were also reduced in Non-Exercise group.

CONCLUSION

Moderate intensity exercise affects cortical and subcortical structures in preclinical AD patients. Thus, physical exercise has a potential to be an effective intervention to prevent future cognitive decline in those at high risk of AD.

Exercise training ameliorates cerebrovascular dysfunction in a murine model of Alzheimer's disease: role of the P2Y2 receptor and endoplasmic reticulum stress

Cerebrovascular dysfunction is a critical risk factor for the pathogenesis of Alzheimer's disease (AD). The purinergic P2Y2 receptor and endoplasmic reticulum (ER) stress are tightly associated with vascular dysfunction and the pathogenesis of AD. However, the protective effects of exercise training on P2Y2 receptor- and ER stress-associated cerebrovascular dysfunction in AD are mostly unknown. Control (C57BL/6, CON) and AD (APP/PS1dE9, AD) mice underwent treadmill exercise training (EX). 2-MeS-ATP-induced dose-dependent vasoreactivity was determined by using a pressurized posterior cerebral artery (PCA) from 10-12-mo-old mice. Human brain microvascular endothelial cells (HBMECs) were exposed to laminar shear stress (LSS) at 20 dyn/cm² for 30 min, 2 h, and 24 h. The expression of P2Y2 receptors, endothelial nitric oxide synthase (eNOS), and ER stress signaling were quantified by Western blot analysis. Notably, exercise converted ATP-induced vasoconstriction in the PCA from AD mice to vasodilation in AD+EX mice to a degree commensurate to the vascular reactivity observed in CON mice. Exercise reduced the expression of amyloid peptide precursor (APP) and increased the P2Y2 receptor and Akt/eNOS expression in AD mice brain. Mechanistically, LSS increased the expression of both P2Y2 receptor and eNOS protein in HBMECs, but these increases were blunted by a P2Y2 receptor antagonist in HBMECs. Exercise also reduced the expression of aberrant ER stress markers p-IRE1, p/t-eIF2α, and CHOP, as well as Bax/Bcl-2, in AD mice brain. Collectively, our results demonstrate for the first time that exercise mitigates cerebrovascular dysfunction in AD through modulating P2Y2 receptor- and ER stress-dependent endothelial dysfunction.NEW & NOTEWORTHY A limited study has investigated whether exercise training can improve cerebrovascular function in Alzheimer's disease. The novel findings of the study are that exercise training improves cerebrovascular dysfunction through enhancing P2Y2 receptor-mediated eNOS signaling and reducing ER stress-associated pathways in AD. These data suggest that exercise training, which regulates P2Y2 receptor and ER stress in AD brain, is a potential therapeutic strategy for Alzheimer's disease.