Habitual exercise levels are associated with cerebral amyloid load in presymptomatic autosomal dominant Alzheimer's disease

Lifetime walking and Alzheimer's pathology: A longitudinal study in older adults

IMPORTANCE

While many studies have shown that greater amounts or longer durations of walking are associated with a lower risk of Alzheimer's disease (AD) or cognitive decline in older adults, the neuropathological basis for this is not yet fully understood.

OBJECTIVE

To examine the relationship between walking intensity and duration and longitudinal changes in Alzheimer's disease (AD)-related brain pathologies, including Aβ and tau accumulation, neurodegeneration, and white matter hyperintensity (WMH).

DESIGN

Data were drawn from the Korean Brain Aging Study for the Early Diagnosis and Prediction of AD, a longitudinal cohort study (initiated in 2014).

SETTING

Community and memory clinic setting.

PARTICIPANTS

One hundred fifty-one older adults.

MAIN OUTCOME AND MEASURES

Participants underwent baseline and 4-year follow-up neuroimaging assessments. Lifetime walking, as measured using the Lifetime Total Physical Activity Questionnaire, was categorized by intensity (high vs. low) and duration (short ≤360 min/week vs. long >360 min/week), forming four combined walking groups. Aβ and tau deposition, neurodegeneration, and WMH volume were assessed via PET/MRI.

RESULTS

Long-duration or high-intensity walking was associated with significantly reduced Aβ accumulation over 4 years. The high-combined walking group showed similar benefits, while medium-combined groups did not. The effect was significant only in the early life-initiated walking subgroup. No associations were found with tau, neurodegeneration, or WMH volume.

CONCLUSIONS

Long-duration, high-intensity walking may reduce brain Aβ accumulation, potentially lowering AD risk, particularly when initiated before late life.

Treadmill exercise ameliorates hippocampal synaptic injury and recognition memory deficits by TREM2 in AD rat model

OBJECTIVE

The impairment of cognitive function has been associated with Alzheimer's disease (AD). Exercise exerts a positive modulatory effect on cognition by reducing synapse injury. However, limited in vivo evidence is available to validate the neuroprotective effect of TREM2 on synaptic function in this phenomenon. Here, we aim to explore whether physical exercise pretreatment alters Aβ-induced recognition memory impairment in structural synaptic plasticity within the hippocampus in AD rats. METHODS：: In study 1, fifty-two Sprague-Dawley (SD) rats were randomly divided into following four groups: control group (C group, n = 13), Alzheimer's disease group (AD group, n = 13), 4 weeks of physical exercise and Alzheimer's disease group (Exe+AD group, n = 13), 4 weeks of physical exercise and blank group (Exercise group, n = 13). Four weeks of treadmill exercise intervention was performed, and AD model were established by intra-cerebroventricular injection (ICV) injection of Aβ1-42 protein. After 3 weeks, we also conducted a novel object test to evaluate recognition memory in the behavior assessment. Golgi staining and transmission electron microscopy were used to evaluate the morphology and synaptic ultrastructure of neurons. Western blotting was used to measure the expression of hippocampal synaptic proteins. Extracellular neurotransmitters in the hippocampus were detected by microdialysis coupled with high-performance liquid chromatography. In study 2, 33 SD rats were randomly divided into three groups: 4 weeks of physical exercise and Alzheimer's disease group (Exe+AD group, n = 11), AAV-Control and physical exercise and Alzheimer's disease group (AAV-Control+Exe+AD group, n = 11), AAV-TREM2 and physical exercise and Alzheimer's disease group (AAV-TREM2 +Exe+AD group, n = 11). Stereotactic intracerebral injection in the bilateral hippocampus was performed to achieve microglial TREM2 down-expression by using adeno-associated virus (AAV) with CD68 promoter. After 4 weeks treadmill exercise and 3 weeks Aβ injection, all rats received behavior test and molecular experiment, which the same with experiment 2.

RESULTS

Novel recognition index in novel object recognition test significantly decreased, and western blot demonstrate that hippocampal TREM2 protein is significantly decreased (P < 0.001). But physical exercise reversed this phenomenon(P < 0.001). In addition, compared with Con group, the neuron from Exe+AD group exhibited a more complex branching pattern (P < 0.05). And impaired synaptic ultrastructure was observed in AD group. Hippocampal synaptic-related protein (SYX, SYP, GAP43, PSD95) and neurotransmitter (DA, Glu, GABA) was also significantly decreased (P < 0.01) in AD group. But the neuroprotection effect can be found in Exe+AD group, which are associated with the inhibition of synaptic injury by activate hippocampal TREM2 (P < 0.05). However, when blockade of hippocampal TREM2 reduced brain protective effect of exercise in AD rat model, including increased the damage of neuronal dendritic complexity, synaptic ultrastructure, and the decrease of hippocampal synapses-related protein, typical neurotransmitter.

CONCLUSION

Treadmill exercise facilitated recognition memory acquisition via TREM2-mediated structural synaptic plasticity of the hippocampus in an AD rat model.

Associations between moderate-to-vigorous physical activity, p-tau181, and cognition in healthy older adults with memory complaints: a secondary analysis from the MAPT

BACKGROUND

Physical activity provides benefits against cognitive decline but its associations with Alzheimer's disease pathophysiology are not fully understood. We investigated cross-sectional and longitudinal associations between moderate-to-vigorous physical activity and phosphorylated (p)-tau181 blood concentrations, and the role of p-tau181 in the associations between moderate-to-vigorous physical activity and cognition.

METHODS

In this post-hoc secondary analysis, we used data from a multicentre, randomised, placebo-controlled superiority trial (the Multidomain Alzheimer's Preventive Trial [MAPT]), in which adults aged 70 years and older were recruited from the community in 13 memory centres in France and Monaco. Individuals were eligible if they met at least one of the following criteria: spontaneous memory complaints, low gait speed (≤0·77 m/s), or limitation in at least one instrumental activity of daily living. Exclusion criteria included a dementia diagnosis, a Mini Mental State Examination score below 24, and having limitations in basic activities of daily living. For this secondary analysis, participants from MAPT were included if they had blood p-tau181 concentrations measured at baseline or at 3 years, or both timepoints. Self-reported moderate-to-vigorous physical activity (in metabolic equivalent of task min per week) and a cognitive composite score (calculated by averaging the Z scores of four cognitive tests) were assessed at baseline and at 6 months and at 1, 2, and 3 years. Mixed-effect models were used to examine the cross-sectional and longitudinal associations between moderate-to-vigorous physical activity and p-tau181 concentrations and to explore the mediating and moderating role of p-tau181 concentration on the association between moderate-to-vigorous physical activity and cognition.

FINDINGS

Between May 30, 2008, and Feb 24, 2011, 1679 individuals were enrolled in the MAPT, of whom 558 adults had measurements of p-tau181 concentrations at baseline, 3 years, or both timepoints. Higher levels of moderate-to-vigorous physical activity were associated with slower changes in p-tau181 concentrations over time. Compared with inactive individuals, those with low levels of activity (low moderate-to-vigorous physical activity × time: B = -0·109 [95% CI -0·206 to -0·012; p=0·028]) or high levels of activity (high moderate-to-vigorous physical activity × time: B=-0·114 [95% CI -0·208 to -0·020; p=0·018) had a slower increase in p-tau181 concentrations. We did not identify any association between baseline p-tau181 concentrations and baseline moderate-to-vigorous physical activity levels. The cross-sectional and longitudinal associations between moderate-to-vigorous physical activity and cognition were attenuated with increasing baseline p-tau181 concentrations. Specifically, moderate-to-vigorous physical activity was no longer favourably associated with the cognitive composite score when baseline p-tau181 concentration exceeded 9·36 pg/mL and 3·5 pg/mL for the cross-sectional association and longitudinal association, respectively.

INTERPRETATION

Our findings suggest that engaging in more moderate-to-vigorous physical activity might help to slow the age-related neurodegenerative process, although p-tau pathophysiology seems to mitigate the beneficial associations between moderate-to-vigorous physical activity and cognition in older adults. Verification of these findings in larger population samples will be needed.

FUNDING

Toulouse Gérontopôle, French Ministry of Health, and Pierre Fabre Research Institute.

Longitudinal associations between exercise and biomarkers in autosomal dominant Alzheimer's disease

INTRODUCTION

We investigated longitudinal associations between self-reported exercise and Alzheimer's disease (AD)-related biomarkers in individuals with autosomal dominant AD (ADAD) mutations.

METHODS

Participants were 308 ADAD mutation carriers aged 39.7 ± 10.8 years from the Dominantly Inherited Alzheimer's Network. Weekly exercise volume was measured via questionnaire and associations with brain volume (magnetic resonance imaging), cerebrospinal fluid biomarkers, and brain amyloid beta (Aβ) measured by positron emission tomography were investigated.

RESULTS

Greater volume of weekly exercise at baseline was associated with slower accumulation of brain Aβ at preclinical disease stages β = -0.16 [-0.23 to -0.08], and a slower decline in multiple brain regions including hippocampal volume β = 0.06 [0.03 to 0.08].

DISCUSSION

Exercise is associated with more favorable profiles of AD-related biomarkers in individuals with ADAD mutations. Exercise may have therapeutic potential for delaying the onset of AD; however, randomized controlled trials are vital to determine a causal relationship before a clinical recommendation of exercise is implemented.

HIGHLIGHTS

Greater self-reported weekly exercise predicts slower declines in brain volume in autosomal dominant Alzheimer's disease (ADAD). Greater self-reported weekly exercise predicts slower accumulation of brain amyloid beta in ADAD. Associations varied depending on closeness to estimated symptom onset.

15 Years of Longitudinal Genetic, Clinical, Cognitive, Imaging, and Biochemical Measures in DIAN

This manuscript describes and summarizes the Dominantly Inherited Alzheimer Network Observational Study (DIAN Obs), highlighting the wealth of longitudinal data, samples, and results from this human cohort study of brain aging and a rare monogenic form of Alzheimer's disease (AD). DIAN Obs is an international collaborative longitudinal study initiated in 2008 with support from the National Institute on Aging (NIA), designed to obtain comprehensive and uniform data on brain biology and function in individuals at risk for autosomal dominant AD (ADAD). ADAD gene mutations in the amyloid protein precursor (APP), presenilin 1 (PSEN1), or presenilin 2 (PSEN2) genes are deterministic causes of ADAD, with virtually full penetrance, and a predictable age at symptomatic onset. Data and specimens collected are derived from full clinical assessments, including neurologic and physical examinations, extensive cognitive batteries, structural and functional neuro-imaging, amyloid and tau pathological measures using positron emission tomography (PET), flurordeoxyglucose (FDG) PET, cerebrospinal fluid and blood collection (plasma, serum, and whole blood), extensive genetic and multi-omic analyses, and brain donation upon death. This comprehensive evaluation of the human nervous system is performed longitudinally in both mutation carriers and family non-carriers, providing one of the deepest and broadest evaluations of the human brain across decades and through AD progression. These extensive data sets and samples are available for researchers to address scientific questions on the human brain, aging, and AD.

Differences in Daily Physical Activity by Alzheimer's Risk Markers Among Older Adults

BACKGROUND

Daily physical activity patterns differ by Alzheimer's disease (AD) status and might signal cognitive risk. It is critical to understand whether patterns are disrupted early in the AD pathological process. Yet, whether established AD risk markers (β-amyloid [Aβ] or apolipoprotein E-ε4 [APOE-ε4]) are associated with differences in objectively measured activity patterns among cognitively unimpaired older adults is unclear.

METHODS

Wrist accelerometry, brain Aβ (+/-), and APOE-ε4 genotype were collected in 106 (Aβ) and 472 (APOE-ε4) participants (mean age 76 [standard deviation{SD}: 8.5) or 75 [SD: 9.2] years, 60% or 58% women) in the Baltimore Longitudinal Study of Aging. Adjusted linear and function-on-scalar regression models examined whether Aβ or APOE-ε4 status was cross-sectionally associated with activity patterns (amount, variability, or fragmentation) overall and by time of day, respectively. Differences in activity patterns by combinations of Aβ and APOE-ε4 status were descriptively examined (n = 105).

RESULTS

There were no differences in any activity pattern by Aβ or APOE-ε4 status overall. Aβ+ was associated with lower total amount and lower within-day variability of physical activity overnight and early evening, and APOE-ε4 carriers had higher total amount of activity in the evening and lower within-day variability of activity in the morning. Diurnal curves of activity were blunted among those with Aβ+ regardless of APOE-ε4 status, but only when including older adults with mild cognitive impairment/dementia.

CONCLUSIONS

Aβ+ in cognitively unimpaired older adults might manifest as lower amount and variability of daily physical activity, particularly during overnight/evening hours. Future research is needed to examine changes in activity patterns in larger samples and by other AD biomarkers.

Physical activity and amyloid beta in middle-aged and older adults: A systematic review and meta-analysis

BACKGROUND

One of the pathological hallmarks distinguishing Alzheimer's disease from other dementias is the accumulation of amyloid beta (Aβ). Higher physical activity is associated with decreased dementia risk, and one potential path could be through Aβ levels modulation. We aimed to explore the relationship between physical activity and Aβ in middle-aged and older adults.

METHODS

A systematic search of PubMed, Web of Science, PsycINFO, Cochrane Central Register of Controlled Trials, and SPORTDiscus was performed from inception to April 28, 2022. Studies were eligible if they included physical activity and Aβ data in adults aged 45 years or older. Multi-level meta-analyses of intervention and observational studies were performed to examine the role of physical activity in modulating Aβ levels.

RESULTS

In total, 37 articles were included (8 randomized controlled trials, 3 non-randomized controlled trials, 4 prospective longitudinal studies, and 22 cross-sectional studies). The overall effect size of physical activity interventions on changes in blood Aβ was medium (pooled standardized mean difference = -0.69, 95% confidence interval (95%CI): -1.41 to 0.03; I2 = 74.6%). However, these results were not statistically significant, and there were not enough studies to explore the effects of physical activity on cerebrospinal fluid (CSF) and brain Aβ. Data from observational studies were examined based on measurements of Aβ in the brain using positron emission tomography scans, CSF, and blood. Higher physical activity was positively associated with Aβ only in the CSF (Estimate r = 0.12; 95%CI: 0.05-0.18; I2 = 38.00%).

CONCLUSION

Physical activity might moderately reduce blood Aβ in middle-aged and older adults. However, results were only near statistical significance and might be interpreted with caution given the methodological limitations observed in some of the included studies. In observational studies, higher levels of physical activity were positively associated with Aβ only in CSF. Therefore, further research is needed to understand the modulating role of physical activity in the brain, CSF, and blood Aβ, as well as its implication for cognitive health.

Modifiable dementia risk factors and AT(N) biomarkers: findings from the EPAD cohort

Introduction

Modifiable risk factors account for a substantial proportion of Alzheimer's disease (AD) cases and we currently have a discrete AT(N) biomarker profile for AD biomarkers: amyloid (A), p-tau (T), and neurodegeneration (N). Here, we investigated how modifiable risk factors relate to the three hallmark AT(N) biomarkers of AD.

Methods

Participants from the European Prevention of Alzheimer's Dementia (EPAD) study underwent clinical assessments, brain magnetic resonance imaging, and cerebrospinal fluid collection and analysis. Generalized additive models (GAMs) with penalized regression splines were modeled in the AD Workbench on the NTKApp.

Results

A total of 1,434 participants were included (56% women, 39% APOE ε4+) with an average age of 65.5 (± 7.2) years. We found that modifiable risk factors of less education (t = 3.9, p < 0.001), less exercise (t = 2.1, p = 0.034), traumatic brain injury (t = -2.1, p = 0.036), and higher body mass index (t = -4.5, p < 0.001) were all significantly associated with higher AD biomarker burden.

Discussion

This cross-sectional study provides further support for modifiable risk factors displaying neuroprotective associations with the characteristic AT(N) biomarkers of AD.

Alterations in Synaptic Connectivity and Synaptic Transmission in Alzheimer's Disease with High Physical Activity

Background

Alzheimer's disease (AD) is a progressive neurodegeneration disease. Physical activity is one of the most promising modifiable lifestyles that can be effective in slowing down the progression of AD at an early stage.

Objective

Explore the molecular processes impaired in AD that were conversely preserved and enhanced by physical activity.

Methods

Integrated transcriptomic analyses were performed in datasets that contain AD patients and elders with different degrees of physical activity. The changes of the hub genes were validated through analyzing another two datasets. The expression of the hub genes was further detected in the hippocampus and cortexes of APP/PS1 transgenic mice with or without physical activity by Quantitative polymerase chain reaction (qPCR).

Results

Cross-comparison highlighted 195 DEGs displaying opposed regulation patterns between AD and high physical activity (HPA). The common DEGs were predominantly involved in synaptic vesicle recycling and synaptic transmission, largely downregulated in AD patients but upregulated in the elders with HPA. Two key modules and four hub genes that were related to synaptic vesicle turnover were obtained from the PPI network. The expression of these hub genes (SYT1, SYT4, SH3GL2, and AP2M1) was significantly decreased in AD transgenic mice and was reversed by HPA training.

Conclusions

HPA may reverse AD pathology by upregulating a range of synaptic vesicle transport related proteins which might improve the efficiency of synaptic vesicle turnover and facilitate inter-neuronal information transfer. The study provides novel insights into the mechanisms underlining the protective effects of HPA on AD.

Long-term voluntary exercise inhibited AGE/RAGE and microglial activation and reduced the loss of dendritic spines in the hippocampi of APP/PS1 transgenic mice

Alzheimer's disease (AD) is closely related to hippocampal synapse loss, which can be alleviated by running exercise. However, further studies are needed to determine whether running exercise reduces synapse loss in the hippocampus in an AD model by regulating microglia. Ten-month-old male wild-type mice and APP/PS1 mice were randomly divided into control and running groups. All mice in the running groups were subjected to voluntary running exercise for four months. After the behavioral tests, immunohistochemistry, stereological methods, immunofluorescence staining, 3D reconstruction, western blotting and RNA-Seq were performed. Running exercise improved the spatial learning and memory abilities of APP/PS1 mice and increased the total number of dendritic spines, the levels of the PSD-95 and Synapsin Ia/b proteins, the colocalization of PSD-95 and neuronal dendrites (MAP-2) and the number of PSD-95-contacting astrocytes (GFAP) in the hippocampi of APP/PS1 mice. Moreover, running exercise reduced the relative expression of CD68 and Iba-1, the number of Iba-1⁺ microglia and the colocalization of PSD-95 and Iba-1⁺ microglia in the hippocampi of APP/PS1 mice. The RNA-Seq results showed that some differentially expressed genes (DEGs) related to the complement system (Cd59b, Serping1, Cfh, A2m, and Trem2) were upregulated in the hippocampi of APP/PS1 mice, while running exercise downregulated the C3 gene. At the protein level, running exercise also reduced the expression of advanced glycation end products (AGEs), receptor for advanced glycation end products (RAGE), C1q and C3 in the hippocampus and AGEs and RAGE in hippocampal microglia in APP/PS1 mice. Furthermore, the Col6a3, Scn5a, Cxcl5, Tdg and Clec4n genes were upregulated in the hippocampi of APP/PS1 mice but downregulated after running, and these genes were associated with the C3 and RAGE genes according to protein-protein interaction (PPI) analysis. These findings indicate that long-term voluntary exercise might protect hippocampal synapses and affect the function and activation of microglia, the AGE/RAGE signaling pathway in microglia and the C1q/C3 complement system in the hippocampus in APP/PS1 mice, and these effects may be related to the Col6a3, Scn5a, Cxcl5, Tdg and Clec4n genes. The current results provide an important basis for identifying targets for the prevention and treatment of AD.

Treadmill exercise improve recognition memory by TREM2 pathway to inhibit hippocampal microglial activation and neuroinflammation in Alzheimer's disease model

Alzheimer's disease-related cognition impairment is correlated with increased neuroinflammation. Studies show that physical exercises improve cognitive function and regulate neuroinflammation. However, no sufficient studies have been performed to directly observe the mechanism of exercise-related effects on microglia and neuroinflammation, in association with memory function under Alzheimer's disease. This study aims to explore the relationship of TREM2, microglia activation and neuroinflammation in the development of Alzheimer's disease, followed by investigating why physical exercises improve cognition in the Alzheimer's disease model by means of the adeno-associated virus (AAV) injection. We found that: 1) Recognition memory impairment in Aβ-induced Alzheimer's disease model was associated with the reduction in TREM2 which induced microglial activation and neuroinflammation; 2) Exercise activated the TREM2 pathway, which was necessary for inhibiting microglial activation and neuroinflammation, leading to improved recognition memory in the Alzheimer's disease model. Together, the improvement of AD-associated recognition memory by exercises is associated with up-regulation of the TREM2 pathway which promotes the phenotypic conversion of microglia and decreases the level of neuroinflammation.

Understanding How Physical Exercise Improves Alzheimer’s Disease: Cholinergic and Monoaminergic Systems

Alzheimer’s disease (AD) is an age-related neurodegenerative disorder, characterized by the accumulation of proteinaceous aggregates and neurofibrillary lesions composed of β-amyloid (Aβ) peptide and hyperphosphorylated microtubule-associated protein tau, respectively. It has long been known that dysregulation of cholinergic and monoaminergic (i.e., dopaminergic, serotoninergic, and noradrenergic) systems is involved in the pathogenesis of AD. Abnormalities in neuronal activity, neurotransmitter signaling input, and receptor function exaggerate Aβ deposition and tau hyperphosphorylation. Maintenance of normal neurotransmission is essential to halt AD progression. Most neurotransmitters and neurotransmitter-related drugs modulate the pathology of AD and improve cognitive function through G protein-coupled receptors (GPCRs). Exercise therapies provide an important alternative or adjunctive intervention for AD. Cumulative evidence indicates that exercise can prevent multiple pathological features found in AD and improve cognitive function through delaying the degeneration of cholinergic and monoaminergic neurons; increasing levels of acetylcholine, norepinephrine, serotonin, and dopamine; and modulating the activity of certain neurotransmitter-related GPCRs. Emerging insights into the mechanistic links among exercise, the neurotransmitter system, and AD highlight the potential of this intervention as a therapeutic approach for AD.

State of Knowledge on Molecular Adaptations to Exercise in Humans: Historical Perspectives and Future Directions

For centuries, regular exercise has been acknowledged as a potent stimulus to promote, maintain, and restore healthy functioning of nearly every physiological system of the human body. With advancing understanding of the complexity of human physiology, continually evolving methodological possibilities, and an increasingly dire public health situation, the study of exercise as a preventative or therapeutic treatment has never been more interdisciplinary, or more impactful. During the early stages of the NIH Common Fund Molecular Transducers of Physical Activity Consortium (MoTrPAC) Initiative, the field is well-positioned to build substantially upon the existing understanding of the mechanisms underlying benefits associated with exercise. Thus, we present a comprehensive body of the knowledge detailing the current literature basis surrounding the molecular adaptations to exercise in humans to provide a view of the state of the field at this critical juncture, as well as a resource for scientists bringing external expertise to the field of exercise physiology. In reviewing current literature related to molecular and cellular processes underlying exercise-induced benefits and adaptations, we also draw attention to existing knowledge gaps warranting continued research effort. © 2021 American Physiological Society. Compr Physiol 12:3193-3279, 2022.

Combined effects of Aerobic exercise and 40Hz light flicker exposure on early cognitive impairments in Alzheimer's disease of 3xTg mice

Alzheimer's disease (AD) is a progressive degenerative brain disease and the primary cause of dementia. At an early stage, AD is generally characterized by short-term memory impairment, owing to dysfunctions of the cortex and hippocampus. We previously reported that a combination of exercise and 40 Hz light flickering can protect against AD-related neuroinflammation, gamma oscillations, reduction in Aβ, and cognitive decline. Therefore, we sought to extend our previous findings to the 5-month-old 3xTg-AD mouse model to examine whether the same favorable effects occur in earlier stages of cognitive dysfunction. We investigated the effects of 12 weeks of exercise combined with 40-Hz light flickering on cognitive function by analyzing neuroinflammation, mitochondrial function, and neuroplasticity in the hippocampus in a 3xTg-AD mouse model. 5-month-old 3xTg-AD mice performed 12 weeks of exercise with 40-Hz light flickering administered independently and in combination. Spatial learning and memory, long-term memory, hippocampal Aβ, tau, neuroinflammation, pro-inflammatory cytokine expression, mitochondrial function, and neuroplasticity, were analyzed. Aβ and tau proteins levels were significantly reduced in the early stage of AD, resulting in protection against cognitive decline by reducing neuroinflammation and pro-inflammatory cytokines. Furthermore, mitochondrial function improved, apoptosis was reduced, and synapse-related protein expression increased. Overall, exercise with 40-Hz light flickering was significantly more effective than exercise or 40-Hz light flickering alone, and the improvement was comparable to the levels in the non-transgenic aged-match control group. Our results indicate a synergistic effect of exercise and 40-Hz light flickering on pathological improvements in the hippocampus during early AD associated cognitive impairment.

Exercise suppresses mouse systemic AApoAII amyloidosis through enhancement of the p38 MAPK signaling pathway

Exercise interventions are beneficial for reducing the risk of age-related diseases, including amyloidosis, but the underlying molecular links remain unclear. Here, we investigated the protective role of interval exercise training in a mouse model of age-related systemic apolipoprotein A-II amyloidosis (AApoAII) and identified potential mechanisms. Mice subjected to sixteen weeks of exercise showed improved whole-body physiologic functions and exhibited substantial inhibition of amyloidosis, particularly in the liver and spleen. Exercise activated the hepatic p38 mitogen-activated protein kinase (p38 MAPK) signaling pathway and the downstream transcription factor tumor suppressor p53. This activation resulted in elevated expression and phosphorylation of heat shock protein beta-1 (HSPB1), a chaperone that defends against protein aggregation. In amyloidosis-induced mice, the hepatic p38 MAPK-related adaptive responses were additively enhanced by exercise. We observed that with exercise, greater amounts of phosphorylated HSPB1 accumulated at amyloid deposition areas, which we suspect inhibits amyloid fibril formation. Collectively, our findings demonstrate the exercise-activated specific chaperone prevention of amyloidosis, and suggest that exercise may amplify intracellular stress-related protective adaptation pathways against age-associated disorders such as amyloidosis.

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 New Frontier of Perioperative Cognitive Medicine for Alzheimer's Disease and Related Dementias

This is a review of preoperative cognitive assessment and other healthcare gaps in the care of older adults at risk for Alzheimer's disease and related dementias (ADRD) who have elected surgery with anesthesia. It summarizes concerns regarding ADRD perioperative healthcare, perioperative cognitive, and neuronal domains of vulnerability. It also offers a plan for phased preoperative cognitive screening and perioperative cognitive intervention opportunities. An argument is made for why medical professionals in the perioperative setting need fundamental training in cognitive-behavioral principles, an understanding of neurodegenerative diseases of aging, and an appreciation of the immediate and long-term medical risks for such patients undergoing anesthesia. The author's goal is to encourage readers to consider perioperative cognitive medicine as a new frontier for generating evidence-based care approaches for at-risk older adults with neurodegenerative disorders who require procedures with anesthesia.

Active Life for Brain Health: A Narrative Review of the Mechanism Underlying the Protective Effects of Physical Activity on the Brain

A growing body of evidence clearly indicates the beneficial effects of physical activity (PA) on cognition. The importance of PA is now being reevaluated due to the increase in sedentary behavior in older adults during the COVID-19 pandemic. Although many studies in humans have revealed that PA helps to preserve brain health, the underlying mechanisms have not yet been fully elucidated. In this review, which mainly focuses on studies in humans, we comprehensively summarize the mechanisms underlying the beneficial effects of PA or exercise on brain health, particularly cognition. The most intensively studied mechanisms of the beneficial effects of PA involve an increase in brain-derived neurotrophic factor (BDNF) and preservation of brain volume, especially that of the hippocampus. Nonetheless, the mutual associations between these two factors remain unclear. For example, although BDNF presumably affects brain volume by inhibiting neuronal death and/or increasing neurogenesis, human data on this issue are scarce. It also remains to be determined whether PA modulates amyloid and tau metabolism. However, recent advances in blood-based biomarkers are expected to help elucidate the beneficial effects of PA on the brain. Clinical data suggest that PA functionally modulates cognition independently of neurodegeneration, and the mechanisms involved include modulation of functional connectivity, neuronal compensation, neuronal resource allocation, and neuronal efficiency. However, these mechanisms are as yet not fully understood. A clear understanding of the mechanisms involved could help motivate inactive persons to change their behavior. More accumulation of evidence in this field is awaited.

Aging in Down Syndrome: Latest Clinical Advances and Prospects

Down syndrome (DS), or trisomy 21, is the most common genetic cause of intellectual disability [...].

Exercise-Induced Benefits for Alzheimer's Disease by Stimulating Mitophagy and Improving Mitochondrial Function

Neurons are highly specialized post-mitotic cells that are inherently dependent on mitochondria due to their higher bioenergetic demand. Mitochondrial dysfunction is closely associated with a variety of aging-related neurological disorders, such as Alzheimer’s disease (AD), and the accumulation of dysfunctional and superfluous mitochondria has been reported as an early stage that significantly facilitates the progression of AD. Mitochondrial damage causes bioenergetic deficiency, intracellular calcium imbalance and oxidative stress, thereby aggravating β-amyloid (Aβ) accumulation and Tau hyperphosphorylation, and further leading to cognitive decline and memory loss. Although there is an intricate parallel relationship between mitochondrial dysfunction and AD, their triggering factors, such as Aβ aggregation and hyperphosphorylated Tau protein and action time, are still unclear. Moreover, many studies have confirmed abnormal mitochondrial biosynthesis, dynamics and functions will present once the mitochondrial quality control is impaired, thus leading to aggravated AD pathological changes. Accumulating evidence shows beneficial effects of appropriate exercise on improved mitophagy and mitochondrial function to promote mitochondrial plasticity, reduce oxidative stress, enhance cognitive capacity and reduce the risks of cognitive impairment and dementia in later life. Therefore, stimulating mitophagy and optimizing mitochondrial function through exercise may forestall the neurodegenerative process of AD.

Mechanistic Effects of Aerobic Exercise in Alzheimer's Disease: Imaging Findings From the Pilot FIT-AD Trial

Despite strong evidence from animal models of Alzheimer's disease (AD) supporting aerobic exercise as a disease-modifying treatment for AD, human mechanistic studies are limited with mixed findings. The objective of this pilot randomized controlled trial was to examine the effects of 6-month aerobic exercise on hippocampal volume, temporal meta-regions of interest (ROI) cortical thickness, white matter hyperintensity (WMH) volume, and network failure quotient (NFQ), measured with MRI, in community-dwelling older adults with AD dementia. Additionally, the relationships between 6- and 12-month changes in MRI biomarkers and the AD Assessment Scale-Cognition (ADAS-Cog) were examined. Sixty participants were randomized, but one was excluded because baseline MRI failed quality control: 38 randomized to cycling and 21 to stretching. The intervention was moderate-intensity cycling for 20-50 mins, three times a week for 6 months. Control was low-intensity stretching. The study outcomes include hippocampal volume, temporal meta-ROI cortical thickness, WMH volume, and NFQ. Outcomes were measured at baseline, 6 months, and 12 months. The sample averaged 77.3 ± 6.3 years old with 15.6 ± 2.9 years of education and 53% men. Both groups experienced significant declines over 6 months in hippocampal volume (2.64% in cycling vs. 2.89% in stretching) and temporal meta-ROI cortical thickness (0.94 vs. 1.54%), and over 12 months in hippocampal volume (4.47 vs. 3.84%) and temporal meta-ROI cortical thickness (2.27 vs. 1.79%). These declines did not differ between groups. WMH volume increased significantly with the cycling group increasing less (10.9%) than stretching (24.5%) over 6 months (f = 4.47, p = 0.04) and over 12 months (12.1 vs. 27.6%, f = 5.88, p = 0.02). NFQ did not change significantly over time. Pairwise correlational analyses showed a significant negative correlation between 6-month changes in hippocampal volume and ADAS-Cog (r = -0.34, p < 0.05). To conclude, aerobic exercise may reduce the decline in hippocampal volume and temporal meta-ROI cortical thickness during the intervention period, but the effect sizes are likely to be very small and dose-dependent and reverse once the intervention stops. Aerobic exercise is effective on slowing down WMH progression but has no effect on NFQ. Hippocampal atrophy was associated with cognitive decline during the intervention period. Clinical Trial Registration: www.ClinicalTrials.gov, identifier: NCT01954550.

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.

Roles of physical exercise in neurodegeneration: reversal of epigenetic clock

The epigenetic clock is defined by the DNA methylation (DNAm) level and has been extensively applied to distinguish biological age from chronological age. Aging-related neurodegeneration is associated with epigenetic alteration, which determines the status of diseases. In recent years, extensive research has shown that physical exercise (PE) can affect the DNAm level, implying a reversal of the epigenetic clock in neurodegeneration. PE also regulates brain plasticity, neuroinflammation, and molecular signaling cascades associated with epigenetics. This review summarizes the effects of PE on neurodegenerative diseases via both general and disease-specific DNAm mechanisms, and discusses epigenetic modifications that alleviate the pathological symptoms of these diseases. This may lead to probing of the underpinnings of neurodegenerative disorders and provide valuable therapeutic references for cognitive and motor dysfunction.

Effectiveness of a musical fitness programme for older adults with cognitive impairment in long-term care facilities: A quasi-experimental study

OBJECTIVE

To investigate the effectiveness of a musical fitness programme (MFP) intervention in improving neuropsychiatric symptoms, depression, upper-limb muscle strength and cognition of older adults with cognitive impairment in long-term care (LTC) facilities.

BACKGROUND

Because of population ageing, the number of older adults with cognitive impairment has been increasing. The effectiveness of medications in treating cognitive impairment is limited; therefore, the global trend has been for non-pharmacological treatments. However, intervention studies of MFPs on older LTC residents with cognitive impairment are scant.

DESIGN

This study adopted a quasi-experimental design in accordance with the Transparent Reporting of Evaluations with Nonrandomized Designs (TREND) checklist. In total, 84 older adults with cognitive impairment were recruited from seven LTC facilities. The MFP was implemented from July-November 2019.

METHODS

The intervention group received the MFP, which was 50 min per session, twice a week for 12 weeks, whereas the comparison group received usual care. Neuropsychiatric inventory nursing home version, the Cornell scale for depression in dementia Chinese version, 30-s arm curl test and Mini-Mental State Examination were the outcome measures. Data were analysed using Chi-square test, t test and repeated measure analysis of variance.

RESULTS

After the intervention, the scores of neuropsychiatric inventory and the Cornell depression exhibited significant differences over time between two groups (F = 3.6, p = .029; F = 5.96, p = .003, respectively). Nevertheless, 30-s arm curl test and Mini-Mental State Examination demonstrated non-significant between-group differences.

CONCLUSION

The MFP can effectively reduce neuropsychiatric symptoms and depression in older adults with cognitive impairment in LTC facilities. To ensure a more robust evidence base, more research is warranted.

RELEVANCE TO CLINICAL PRACTICE

The MFP is a non-pharmacological treatment that can be implemented to promote psychological well-being among older adults with cognitive impairment in LTC facilities, and to indirectly reduce nursing staff burden. To assist nursing staff in providing this intervention, on-the-job training is needed.

Amyloid and Tau Pathology Associations With Personality Traits, Neuropsychiatric Symptoms, and Cognitive Lifestyle in the Preclinical Phases of Sporadic and Autosomal Dominant Alzheimer's Disease

BACKGROUND

Major prevention trials for Alzheimer's disease (AD) are now focusing on multidomain lifestyle interventions. However, the exact combination of behavioral factors related to AD pathology remains unclear. In 2 cohorts of cognitively unimpaired individuals at risk of AD, we examined which combinations of personality traits, neuropsychiatric symptoms, and cognitive lifestyle (years of education or lifetime cognitive activity) related to the pathological hallmarks of AD, amyloid-β, and tau deposits.

METHODS

A total of 115 older adults with a parental or multiple-sibling family history of sporadic AD (PREVENT-AD [PRe-symptomatic EValuation of Experimental or Novel Treatments for AD] cohort) underwent amyloid and tau positron emission tomography and answered several questionnaires related to behavioral attributes. Separately, we studied 117 mutation carriers from the DIAN (Dominant Inherited Alzheimer Network) study group cohort with amyloid positron emission tomography and behavioral data. Using partial least squares analysis, we identified latent variables relating amyloid or tau pathology with combinations of personality traits, neuropsychiatric symptoms, and cognitive lifestyle.

RESULTS

In PREVENT-AD, lower neuroticism, neuropsychiatric burden, and higher education were associated with less amyloid deposition (p = .014). Lower neuroticism and neuropsychiatric features, along with higher measures of openness and extraversion, were related to less tau deposition (p = .006). In DIAN, lower neuropsychiatric burden and higher education were also associated with less amyloid (p = .005). The combination of these factors accounted for up to 14% of AD pathology.

CONCLUSIONS

In the preclinical phase of both sporadic and autosomal dominant AD, multiple behavioral features were associated with AD pathology. These results may suggest potential pathways by which multidomain interventions might help delay AD onset or progression.

Effect of aerobic exercise on amyloid accumulation in preclinical Alzheimer's: A 1-year randomized controlled trial

BACKGROUND

Our goal was to investigate the role of physical exercise to protect brain health as we age, including the potential to mitigate Alzheimer's-related pathology. We assessed the effect of 52 weeks of a supervised aerobic exercise program on amyloid accumulation, cognitive performance, and brain volume in cognitively normal older adults with elevated and sub-threshold levels of cerebral amyloid as measured by amyloid PET imaging.

METHODS AND FINDINGS

This 52-week randomized controlled trial compared the effects of 150 minutes per week of aerobic exercise vs. education control intervention. A total of 117 underactive older adults (mean age 72.9 [7.7]) without evidence of cognitive impairment, with elevated (n = 79) or subthreshold (n = 38) levels of cerebral amyloid were randomized, and 110 participants completed the study. Exercise was conducted with supervision and monitoring by trained exercise specialists. We conducted 18F-AV45 PET imaging of cerebral amyloid and anatomical MRI for whole brain and hippocampal volume at baseline and Week 52 follow-up to index brain health. Neuropsychological tests were conducted at baseline, Week 26, and Week 52 to assess executive function, verbal memory, and visuospatial cognitive domains. Cardiorespiratory fitness testing was performed at baseline and Week 52 to assess response to exercise. The aerobic exercise group significantly improved cardiorespiratory fitness (11% vs. 1% in the control group) but there were no differences in change measures of amyloid, brain volume, or cognitive performance compared to control.

CONCLUSIONS

Aerobic exercise was not associated with reduced amyloid accumulation in cognitively normal older adults with cerebral amyloid. In spite of strong systemic cardiorespiratory effects of the intervention, the observed lack of cognitive or brain structure benefits suggests brain benefits of exercise reported in other studies are likely to be related to non-amyloid effects.

TRIAL REGISTRATION

NCT02000583; ClinicalTrials.gov.

The Protective Effect of Exercise in Neurodegenerative Diseases: The Potential Role of Extracellular Vesicles

Physical activity has systemic effects on the body, affecting almost every organ. It is important not only for general health and wellbeing, but also in the prevention of diseases. The mechanisms behind the therapeutic effects of physical activity are not completely understood; however, studies indicate these benefits are not confined to simply managing energy balance and body weight. They also include systemic factors which are released into the circulation during exercise and which appear to underlie the myriad of benefits exercise can elicit. It was shown that along with a number of classical cytokines, active tissues also engage in inter-tissue communication via extracellular vesicles (EVs), specifically exosomes and other small EVs, which are able to deliver biomolecules to cells and alter their metabolism. Thus, EVs may play a role in the acute and systemic adaptations that take place during and after physical activity, and may be therapeutically useful in the treatment of a range of diseases, including metabolic disorders such as type 2 diabetes and obesity; and the focus of this review, neurological disorders such as Alzheimer's disease.

Association of education with Aβ burden in preclinical familial and sporadic Alzheimer disease

OBJECTIVE

To determine whether years of education and the ε4 risk allele at APOE influence β-amyloid (Aβ) pathology similarly in asymptomatic individuals with a family history of sporadic Alzheimer disease (AD) and presymptomatic autosomal dominant AD mutation carriers.

METHODS

We analyzed cross-sectional data from 106 asymptomatic individuals with a parental history of sporadic AD (PREVENT-AD cohort; age 67.28 ± 4.72 years) and 117 presymptomatic autosomal dominant AD mutation carriers (DIAN cohort; age 35.04 ± 9.43 years). All participants underwent structural MRI and Aβ-PET imaging. In each cohort we investigated the influence of years of education, APOE ε4 status, and their interaction on Aβ-PET.

RESULTS

Asymptomatic individuals with a parental history of sporadic AD showed increased Aβ burden associated with APOE ε4 carriage and lower level of education, but no interaction between these. Presymptomatic mutation carriers of autosomal dominant AD showed no relation between APOE ε4 and Aβ burden, but increasing level of education was associated with reduced Aβ burden. The association between educational attainment and Aβ burden was similar in the 2 cohorts.

CONCLUSIONS

While the APOE ε4 allele confers increased tendency toward Aβ accumulation in sporadic AD only, protective environmental factors, like increased education, may promote brain resistance against Aβ pathology in both sporadic and autosomal dominant AD.

Exercise benefits on Alzheimer's disease: State-of-the-science

Although there is no unanimity, growing evidence supports the value of regular physical exercise to prevent Alzheimer's disease as well as cognitive decline in affected patients. Together with an introductory summary on epidemiological evidence, the aim of this review is to summarize the current knowledge on the potential biological mechanisms underlying exercise benefits in this condition. Regular physical exercise has proven to be beneficial for traditional cardiovascular risk factors (e.g., reduced vascular flow, diabetes) involved in the pathogenesis of Alzheimer's disease. Exercise also promotes neurogenesis via increases in exercise-induced metabolic factors (e.g., ketone bodies, lactate) and muscle-derived myokines (cathepsin-B, irisin), which in turn stimulate the production of neurotrophins such as brain-derived neurotrophic factor. Finally, regular exercise exerts anti-inflammatory effects and improves the brain redox status, thereby ameliorating the pathophysiological hallmarks of Alzheimer's disease (e.g., amyloid-β deposition). In summary, physical exercise might provide numerous benefits through different pathways that might, in turn, help prevent risk and progression of Alzheimer's disease. More evidence is needed, however, based on human studies.

Web-Based Intervention Effects on Mild Cognitive Impairment Based on Apolipoprotein E Genotype: Quasi-Experimental Study

BACKGROUND

Apolipoprotein E (APOE) ε4 allele is a major genetic risk factor for Alzheimer disease and mild cognitive impairment (MCI). Computer-based training programs can improve cognitive performance in elderly populations. However, the effects of computer-based interventions on MCI APOE ε4 carriers have never been studied before.

OBJECTIVE

The effects of different web-based interventions and the APOE isoform-specific differences in training outcomes are investigated.

METHODS

Using a quasi-experimental study design, 202 participants with MCI aged 60 years and older took part in three different intervention programs (physical and cognitive [Long-Lasting Memories, or LLM], cognitive [Active Control, or AC], or physical intervention [Physical Training Control, or PTC]) via an innovative information and communication technologies exergaming platform. Participants in each interventional group were subdivided into APOE ε4 carriers and non-APOE ε4 carriers. All participants underwent an extensive neuropsychological evaluation before and after the training, blood tests, and brain imaging.

RESULTS

All interventions resulted in multiple statistically significant cognitive benefits after the intervention. Verbal learning (California Verbal Learning Test: immediate recall test score-LLM: P=.04; AC: P<.001), working memory (digit span forward and backward test scores-AC: P=.03; PTC: P=.02 and P=.006, respectively), and long-term memory (California Verbal Learning Test: delayed recall test score-LLM: P=.02; AC: P=.002; and PTC: P=.02) were improved. There was no statistically significant difference among the intervention effects. APOE ε4 presence moderates intervention effects as the LLM intervention improved only their task-switching processing speed (Trail Making Test, Part B: P=.03) and the PTC intervention improved only the working memory (digit span backward: P=.03). No significant performance alteration was noted for the APOE ε4+ cognitive AC training group.

CONCLUSIONS

None of the applied interventions could be identified as the optimal one; it is suggested, however, that combined cognitive and physical training and physical training via exergaming may be more effective for the high-risk MCI ΑPOE ε4+ subgroup.

Twin studies on the association of physical activity with cognitive and cerebral outcomes

Regular physical activity (PA) offers positive effects on the human body. However, the effects of PA on cognition and in the brain are less clear. In this paper, we narratively review the relationship of PA with cognition and dementia, first from general perspective and then through genetically informed studies on the topic. Then we move on to imaging studies on exercise and brain anatomy first by presenting an overall picture of the topic and then discussing brain imaging studies addressing PA and brain structure in twins in more detailed way. Regarding PA and cognition or dementia, genetically informed studies are uncommon, even though the relationship between PA and cognitive ageing has been extensively studied. It is challenging to find twin pairs discordant for PA and dementia. Concerning brain imaging studies, among PA discordant young adult twin pairs, the more active co-twins showed larger gray matter volumes in striatal, prefrontal, and hippocampal regions and in electrophysiological studies automatic deviance-detection processes differed in brain regions involved with sensorimotor, visual and memory functions.

Better stress coping associated with lower tau in amyloid-positive cognitively unimpaired older adults

OBJECTIVE

Research in animals has shown that chronic stress exacerbates tau pathology. In humans, psychological stress has been associated with higher risk of Alzheimer disease clinical syndrome. The objective of this cross-sectional study was to assess the hypothesis that stress coping ability (assessed via the Brief Resilience Scale [BRS]) is associated with tau burden and to evaluate whether these associations differed by sex and amyloid status (A+/A-) in cognitively unimpaired (CU) older adults.

METHODS

We included 225 CU participants (mean age 70.4 ± 10.2 years, 48% female) enrolled in the population-based Mayo Clinic Study of Aging who completed the BRS and underwent amyloid-PET (Pittsburgh compound B-PET) and tau-PET (AV1451-PET). We fitted multiple regression and analysis of covariance models to assess the associations between BRS and tau-PET and the interaction with amyloid status and sex. We focused on entorhinal cortex (ERC) tau burden and also performed voxel-wise analyses. Age, sex, education, depression, and anxiety were considered as covariates.

RESULTS

Higher stress coping ability was associated with lower tau burden in the medial temporal lobe (including ERC) and occipito-temporal and cuneal/precuneal cortices. The association was present in both A+ and A- but weaker in A- CU older adults. There was an interaction between amyloid status and stress coping ability that was restricted to the medial temporal lobe tau such that A+ CU older adults with lower stress coping abilities showed higher tau. There were no significant interactions between stress coping and sex.

CONCLUSIONS

A faster termination of the stress response (higher coping ability) may limit the negative effects of stress on tau deposition. Conversely, lower stress coping ability may be an early sign of accumulating tau pathology. Longitudinal studies are warranted to clarify whether stress mechanisms act to exacerbate tau pathology or tau influences stress-related brain mechanisms and lowers the ability to cope with stress.

Mid- and Late-Life Leisure-Time Physical Activity and Global Brain Amyloid Burden: The Atherosclerosis Risk in Communities (ARIC)-PET Study

BACKGROUND

Physical activity (PA) may slow the development of dementia by reducing the accumulation of amyloid.

OBJECTIVE

We tested the hypothesis that higher levels of leisure-time PA in mid- or late-life were associated with lower brain amyloid burden in late-life among 326 non-demented participants from the Atherosclerosis Risk in Communities Study of brain florbetapir positron emission tomography (ARIC-PET) ancillary.

METHODS

Self-reported PA was quantified using a past-year recall, interviewer-administered questionnaire in mid-life (1987-1989, aged 45-64 years) and late-life (2011-2013, aged 67-89 years). Continuous PA estimates were classified as 1) any leisure-time PA participation (yes/no); 2) meeting the 2018 United States' PA guidelines (yes/no); and 3) per 1 standard deviation (SD) higher metabolic equivalent of task (MET) minutes per week (MET·min·wk-1). A brain magnetic resonance imaging scan with Florbetapir PET was performed in late-life. Adjusted odds ratios (OR) of elevated amyloid burden, defined as a global cortical standardized uptake value ratio (>1.2), compared to no elevated amyloid burden were estimated according to PA measures.

RESULTS

Among the 326 participants (mean age: 76 years, 42% male, 41% Black), 52% had elevated brain amyloid burden. Mid-life leisure-time PA did not show a statistically significant lower odds of elevated late-life amyloid burden (OR = 0.71, 95% CI: 0.43-1.18). A 1 SD (970 MET. min. wk-1) higher PA level in mid-life was also not significantly associated withelevated amyloid burden (OR = 0.89, 95% CI: 0.69-1.15). Similar estimates were observed for meeting versus not meeting PA guidelines in both mid- and late-life.

CONCLUSION

Self-reported higher mid- and late-life leisure-time PA were not significantly associated with lower amyloid burden. Data show a trend of an association, which is, however, imprecise, suggesting replication in larger studies.

Role of physical activity in ameliorating neuropsychiatric symptoms in Alzheimer disease: A narrative review

OBJECTIVE

Neuropsychiatric symptoms (NPs) affect almost all patients with Alzheimer disease (AD). Because of the complications associated with the pharmacological treatment, nonpharmacological treatment (such as physical activity) can be considered as an additional complementary treatment option for NPs. The aim of this review is to evaluate the impact of physical activity on NPs in patients with AD.

METHODS

We searched Pubmed and Google Scholar for potential eligible articles until March 1, 2018.

RESULTS

Although there are contradictory results showing the impact of physical exercise on NPs, most of them reported that it had a significant effect on depression and sleep disturbances in patients with AD. The beneficial effects could be explained through several mechanisms, including modulated production of neurotransmitters; increasing neurotrophins, such as brain-derived neurotrophic factor; reduction of oxidative stress and inflammation; elevation of cerebral blood flow; hypothalamic pituitary adrenal axis regulation; and support of neurogenesis and synaptogenesis. Physical activity can also improve cardiovascular risk factors, which may exaggerate NPs. There is limited evidence for other NPs such as agitation, disinhibition, apathy, hallucinations, and anxiety.

CONCLUSION

Physical activity may ameliorate depression and sleep disturbances in patients with AD. Therefore, physical activity can be a "potential" add-on treatment to drugs to reduce or prevent these symptoms onset and recurrence in patients with AD. However, further studies are needed to focus on relationship between physical activity and other NPs.

Moderate- to high-intensity exercise does not modify cortical β-amyloid in Alzheimer's disease

INTRODUCTION

Animal models of Alzheimer's disease show that exercise may modify β-amyloid (Aβ) deposition. We examined the effect of a 16-week exercise intervention on cortical Aβ in patients with mild-to-moderate Alzheimer's disease.

METHODS

Thirty-six patients with Alzheimer's disease were randomized to either one hour of aerobic exercise three times weekly for 16 weeks or usual care. Pre and post intervention, 11Carbon-Pittsburgh compound B positron emission tomography was carried out to assess cortical Aβ, and quantified using standardized uptake value rations (SUVRs).

RESULTS

The intervention showed no effect on follow-up SUVRs in a covariance analysis with group allocation, baseline intervention SUVR, age, sex, and baseline Mini-Mental State Examination as predictors. Change in SUVRs did not correlate with changes in measures of physical or aerobic fitness.

DISCUSSION

The present findings do not support an effect of exercise on Aβ. However, the relatively short intervention period may account for a lack of efficacy. Further studies should test earlier and longer interventions.

Preventing Alzheimer's: Our Most Urgent Health Care Priority

Dementia is the fastest growing epidemic in the developed nations, and if not curtailed, it will single handedly collapse our health care system. The prevalence of dementia is 1 in 10 individuals older than 65 years and increases to 50% of all individuals older than 85 years. The prevalence of Alzheimer's dementia (AD), the most common form of dementia, has been increasing rapidly and is projected to reach 16 million individuals by the year 2050. Several prevailing myths about the science of dementia are discussed, such as that AD is inevitable and that it is exclusively a genetic disease. The fact is that AD is dependent on a multitude of genetic, epigenetic, and environmental factors that interact with one another. In fact, 4 core drivers represent 90% of what determines disease progression in AD. These are (1) glucose or energy dysregulation, (2) lipid dysregulation, (3) inflammation, and (4) oxidation. Lifestyle change can significantly alter the course of AD. The authors have created an acronym-NEURO-to help lifestyle practitioners and the public remember the most important lifestyle elements in the treatment and prevention of AD based on the evidence. "N" is for Nutrition, "E" for Exercise, "U" for Unwind (stress management), "R" for Restorative Sleep, and "O" for Optimizing mental and social activity. The evidence base for each of the components is reviewed.

Exploring the relationship between physical activity, beta-amyloid and tau: A narrative review

Several prospective cohort studies have reported an association between higher levels of physical activity and decreased risk of cognitive decline and dementia, years later. To support physical activity as a preventative measure against dementia, including Alzheimer's disease (AD; the most common form of dementia), evidence regarding the underlying mechanisms is vital. Here, we review previous work examining the role of physical activity in modulating levels of AD pathological hallmarks, beta-amyloid (Aβ) and tau (in the brain, cerebrospinal fluid and blood). Robust evidence from transgenic animal studies suggests that physical activity (voluntary wheel running) and exercise (forced wheel running) are implicated in lowering levels of brain Aβ and tau. Nevertheless, evidence from human studies, utilising measurements from positron emission tomography and cerebrospinal fluid biomarkers, is less consistent. Rigorous randomised controlled trials utilising long exercise interventions are vital to further understand the relationship between physical activity and Alzheimer's disease.

Relationship between physical activity, cognition, and Alzheimer pathology in autosomal dominant Alzheimer's disease

INTRODUCTION

Little is known about effects of physical activity (PA) in genetically driven early-onset autosomal dominant Alzheimer's disease (AD).

METHODS

A total of 372 individuals participating at the Dominantly Inherited Alzheimer Network study were examined to evaluate the cross-sectional relationship of PA with cognitive performance, functional status, cognitive decline, and AD biomarkers in cerebrospinal fluid. Mutation carriers were categorized as high or low exercisers according to WHO recommendations.

RESULTS

Mutation carriers with high PA showed significantly better cognitive and functional performance and significantly less AD-like pathology in cerebrospinal fluid than individuals with low PA. Mutation carriers with high PA scored 3.4 points better on Mini Mental State Examination at expected symptom onset and fulfilled the diagnosis of very mild dementia 15.1 years later compared with low exercisers.

DISCUSSION

These results support a beneficial effect of PA on cognition and AD pathology even in individuals with genetically driven autosomal dominant AD.

Sex-Dependent Effects of Environmental Enrichment on Spatial Memory and Brain-Derived Neurotrophic Factor (BDNF) Signaling in a Developmental "Two-Hit" Mouse Model Combining BDNF Haploinsufficiency and Chronic Glucocorticoid Stimulation

Neurodevelopmental disorders are thought to be caused by a combination of adverse genetic and environmental insults. The "two-hit" hypothesis suggests that an early first "hit" primes the developing brain to be vulnerable to a second "hit" during adolescence which triggers behavioral dysfunction. We have previously modeled this scenario in mice and found that the combined effect of a genetic hapolinsuffuciency in the brain-derived neurotrophic factor (BDNF) gene (1st hit) and chronic corticosterone (CORT) treatment during adolescence (2nd hit), caused spatial memory impairments in adulthood. Environmental enrichment (EE) protocols are designed to stimulate experience-dependent plasticity and have shown therapeutic actions. This study investigated whether EE can reverse these spatial memory impairments. Wild-type (WT) and BDNF heterozygous (HET) mice were treated with corticosterone (CORT) in their drinking water (50 mg/L) from weeks 6 to 8 and exposed to EE from 7 to 9 weeks. Enriched housing included open top cages with additional toys, tunnels, housing, and platforms. Y-maze novel preference testing, to assess short-term spatial memory, was performed at 10 weeks of age. At week 16 dorsal hippocampus tissue was obtained for Western blot analysis of expression levels of BDNF, the BDNF receptor TrkB, and NMDA receptor subunits, GluNR1, 2A and 2B. As in our previous studies, spatial memory was impaired in our two-hit (BDNF HET + CORT) mice. Simultaneous EE prevented these impairments. However, EE appeared to worsen spatial memory performance in WT mice, particularly those exposed to CORT. While BDNF levels were lower in BDNF HET mice as expected, there were no further effects of CORT or EE in males but a close to significant female CORT × EE × genotype interaction which qualitatively corresponded with Y-maze performance. However, EE caused both sex- and genotype-specific effects on phosphorylated TrkB residues and GluNR expression within the dorsal hippocampus, with GluNR2B levels in males changing in parallel with spatial memory performance. In conclusion, beneficial effects of EE on spatial memory emerge only following two developmental disruptions. The mechanisms by which EE exerts its effects are likely via regulation of multiple activity-dependent pathways, including TrkB and NMDA receptor signaling.

Effects of Physical Exercise on Alzheimer's Disease Biomarkers: A Systematic Review of Intervention Studies

Physical exercise may be an important adjunct to pharmacological treatment of Alzheimer's disease (AD). Animal studies indicate that exercise may be disease modifying through several mechanisms including reduction of AD pathology. We carried out a systematic review of intervention studies of physical exercise with hippocampal volume (on MRI), amyloid-β, total tau, phosphorylated tau in cerebrospinal fluid (CSF), 18F-FDG-PET or amyloid PET as outcome measures in healthy subjects, patients with subjective memory complaints, mild cognitive impairment, or AD. We identified a total of 8 studies of which 6 investigated the effects of exercise on hippocampal volume in healthy subjects and 1 on CSF biomarkers and 1 on hippocampal volume in AD, and none investigating the remaining outcome measures or patient groups. Methodological quality of identified studies was generally low. One study found a detrimental effect on hippocampal volume and one found a positive effect, whereas the remaining studies did not find an effect of exercise on outcome measures. The present systematic study identified a relatively small number of studies, which did not support an effect of exercise on hippocampal volume. Methodological issues such small to moderate sample sizes and inadequate ramdomization procedures further limits conclusions. Our findings highlight the difficulties in conducting high quality studies of exercise and further studies are needed before definite conclusions may be reached.

Alzheimer's Disease: A Journey from Amyloid Peptides and Oxidative Stress, to Biomarker Technologies and Disease Prevention Strategies-Gains from AIBL and DIAN Cohort Studies

Worldwide there are over 46 million people living with dementia, and this number is expected to double every 20 years reaching about 131 million by 2050. The cost to the community and government health systems, as well as the stress on families and carers is incalculable. Over three decades of research into this disease have been undertaken by several research groups in Australia, including work by our original research group in Western Australia which was involved in the discovery and sequencing of the amyloid-β peptide (also known as Aβ or A4 peptide) extracted from cerebral amyloid plaques. This review discusses the journey from the discovery of the Aβ peptide in Alzheimer's disease (AD) brain to the establishment of pre-clinical AD using PET amyloid tracers, a method now serving as the gold standard for developing peripheral diagnostic approaches in the blood and the eye. The latter developments for early diagnosis have been largely achieved through the establishment of the Australian Imaging Biomarker and Lifestyle research group that has followed 1,100 Australians for 11 years. AIBL has also been instrumental in providing insight into the role of the major genetic risk factor apolipoprotein E ɛ4, as well as better understanding the role of lifestyle factors particularly diet, physical activity and sleep to cognitive decline and the accumulation of cerebral Aβ.