Regular exercise prevents non-cognitive disturbances in a rat model of Alzheimer's disease

Effects of the combination of high-intensity interval training and Ecdysterone on learning and memory abilities, antioxidant enzyme activities, and neuronal population in an Amyloid-beta-induced rat model of Alzheimer's disease

AIMS

Oxidative stress and neuronal death are the primary reasons for the progression of amyloid-beta (Aβ) deposition and cognitive deficits in Alzheimer's disease (AD). Ecdysterone (ecdy), a common derivative of ecdysteroids, possesses free radical scavenging and cognitive-improving effects. High-intensity interval training (HIIT) can be a therapeutic strategy for improving cognitive decline and oxidative stress. The present study was aimed to evaluate the effect of HIIT exercise and ecdy consumption synergistically on the changes in learning and memory functions, activities of hippocampal antioxidant enzymes, and neuronal population after AD induced by Aβ in male rats.

MATERIALS AND METHODS

Following ten days of Aβ injection, HIIT exercise and ecdy treatment (10 mg/kg/day; P.O.) were initiated and continued for eight consecutive weeks in rats. At the end of the treatment period, the rat's learning and memory functions were assessed using Morris water maze and passive avoidance tests. The activity of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GRx), and changes in neuronal population were evaluated in rats' brains.

RESULTS

The results indicated that Aβ injection disrupted spatial/passive avoidance learning and memory in both tests, accompanied by a decrease in the SOD and CAT (as endogenous antioxidants) in rats' hippocampus. Additionally, Aβ injection resulted in neuronal loss in the cerebral cortex and hippocampus. Although the consumption of ecdy separately improved spatial/passive avoidance learning and memory impairments, recovered hippocampal activity of SOD, CAT, GRx, and prevented the hippocampal neuronal loss, its combination along with HIIT resulted in a more powerful and effective amelioration in all the above-mentioned Aβ-neuropathological changes.

CONCLUSION

Our results confirm that a combination of HIIT and ecdy treatment could be a promising potential therapeutic option against AD-associated cognitive decline, owing to their free radical scavenging and neuroprotective properties.

Therapeutic Effects of High-Intensity Interval Training Exercise Alone and Its Combination with Ecdysterone Against Amyloid Beta-Induced Rat Model of Alzheimer's Disease: A Behavioral, Biochemical, and Histological Study

Hippocampal oxidative stress has a vital role in the pathophysiology of Alzheimer's disease (AD)-associated behavioral deficits. Ecdysterone (Ecdy), a natural product and primary steroid hormone, exhibits anti-oxidative and neuroprotective effects. High-intensity interval training (HIIT) has emerged as an effective method for improving physiological brain functions. The present study was designed to investigate the comparative effects of separate and combined HIIT and Ecdy treatment on behavioral functions, hippocampal oxidative status, histological changes in an amyloid-beta (Aβ)-induced rat model of AD. Adult male rats were treated simultaneously with HIIT exercise and Ecdy (10 mg/kg/day; P.O.), starting ten days after Aβ-injection, and they continued for eight consecutive weeks. At the end of the treatment course, the behavioral functions of the rats were assessed by commonly-used behavioral paradigms. Subsequently, brain samples were collected for histological analysis and hippocampus samples were collected for biochemical analysis. Results illustrated that Aβ injection impaired learning and memory performances in both novel object recognition and Barnes maze tests, reduced exploratory/locomotor activities in open field test, enhanced anxiety-like behavior in elevated plus-maze (P < 0.05). These behavioral deficits accompanied hippocampal oxidative stress (decreased total antioxidant capacity content and glutathione peroxidase enzyme activity, increased total oxidant status and malondialdehyde level) and neuronal loss in the cerebral cortex and hippocampus in H&E staining (P < 0.05). HIIT and Ecdy improved anxiety-like behavior, attenuated total oxidant status and malondialdehyde, and prevented the neuronal loss (P < 0.05). However, their combination resulted in a more complete and powerful improvement in all the above-mentioned Aβ-related deficits (P < 0.05). Overall, these data provide evidence that a combination of HIIT and Ecdy treatment improves Aβ-induced behavioral deficits, possibly through ameliorating hippocampal oxidative status and preventing neuronal loss.

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

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

The effect of exercise on early sensorimotor performance alterations in the 3xTg-AD model of Alzheimer's disease

Alzheimer's disease (AD) is characterized by a progressive decline in cognitive function; however, recent evidence suggests that non-cognitive sensorimotor and psychomotor symptoms accompany early stages of the disease in humans and AD models. Although exercise is emerging as an important therapeutic to combat AD progression, little is known about the effect of exercise on sensorimotor domain functions. The purpose of this study was to determine if early sensorimotor symptoms accompany deficits in Morris water maze (MWM) performance in the 3xTg-AD model, and investigate if exercise could protect against early behavioral decline. 3xTg-AD and wild-type (WT) control mice were subjected to 12 weeks of moderate intensity wheel running or remained sedentary. At 6 months of age, animals underwent a series of sensorimotor and MWM testing. 3xTg-AD mice displayed deficits in sensorimotor function (beam traversal, spontaneous activity, and adhesive removal) and MWM performance. Interestingly, 3xTg-AD animals exhibited increased freezing and unusual shaking/tremoring behaviors not displayed by WT controls. Exercise improved beam traversal, adhesive removal, and reduced the unusual motor-related behaviors in 3xTg-AD mice. Our study shows that sensorimotor symptoms coincide with deficits in MWM performance, and suggest that exercise may mitigate deficits associated with early disease in 3xTg-AD mice.

Harnessing Neuroplasticity to Promote Brain Health in Aging Adults: Protocol for the MOVE-Cog Intervention Study

Background

Extensive evidence supports a link between aerobic exercise and cognitive improvements in aging adults. A major limitation with existing research is the high variability in cognitive response to exercise. Our incomplete understanding of the mechanisms that influence this variability and the low adherence to exercise are critical knowledge gaps and major barriers for the systematic implementation of exercise for promoting cognitive health in aging.

Objective

We aimed to provide an in-person and remotely delivered intervention study protocol with the main goal of informing the knowledge gap on the mechanistic action of exercise on the brain by characterizing important mechanisms of neuroplasticity, cardiorespiratory fitness response, and genetics proposed to underlie cognitive response to exercise.

Methods

This is an open-label, 2-month, interventional study protocol in neurologically healthy sedentary adults. This study was delivered fully in-person and in remote options. Participants underwent a total of 30 sessions, including the screening session, 3 pretest (baseline) assessments, 24 moderate-to-vigorous aerobic exercise sessions, and 3 posttest assessments. We recruited participants aged 55 years and above, sedentary, and cognitively healthy. Primary outcomes were neuroplasticity, cognitive function, and cardiorespiratory fitness. Secondary outcomes included genetic factors, endothelium function, functional mobility and postural control, exercise questionnaires, depression, and sleep. We also explored study feasibility, exercise adherence, technology adaptability, and compliance of both in-person and remote protocols.

Results

The recruitment phase and data collection of this study have concluded. Results are expected to be published by the end of 2021 or in early 2022.

Conclusions

The data generated in these studies will introduce tangible parameters to guide the development of personalized exercise prescription models for maximal cognitive benefit in aging adults. Successful completion of the specific aims will enable researchers to acquire the appropriate expertise to design and conduct studies by testing personalized exercise interventions in person and remotely delivered, likely to be more effective at promoting cognitive health in aging adults.

Trial Registration

ClinicalTrials.gov NCT03804528; http://clinicaltrials.gov/ct2/show/NCT03804528

International Registered Report Identifier (IRRID)

RR1-10.2196/33589

Multicomponent Training Prevents Memory Deficit Related to Amyloid-β Protein-Induced Neurotoxicity

BACKGROUND

Alzheimer's disease (AD) is characterized by the accumulation of the amyloid-β peptide in the brain, leading to early oxidative stress and neurotoxicity. It has been suggested that physical exercise could be beneficial in preventing AD, but studies with multicomponent training are scanty.

OBJECTIVE

Verify the effects of multicomponent exercise training to prevent deficits in recognition memory related to Aβ neurotoxicity.

METHODS

We subjected Wistar rats to multicomponent training (including aerobic and anaerobic physical exercise and cognitive exercise) and then infused amyloid-β peptide into their hippocampus.

RESULTS

We show that long-term multicomponent training prevents the amyloid-β-associated neurotoxicity in the hippocampus. It reduces hippocampal lipid peroxidation, restores antioxidant capacity, and increases glutathione levels, finally preventing recognition memory deficits.

CONCLUSION

Multicomponent training avoids memory deficits related to amyloid-β neurotoxicity on an animal model.

Exposure to footshock stress downregulates antioxidant genes and increases neuronal apoptosis in an Aβ(1-42) rat model of Alzheimer's disease

Post-traumatic stress disorder (PTSD) is a neuropsychiatric disorder that develops from exposure to trauma, mostly when normal psychological mechanisms fail. Studies have shown that people who have PTSD are susceptible to developing dementia, mostly Alzheimer's disease (AD), suggesting common underlying risk factors in the comorbidity. However, data elucidating links between these conditions is scarce. Here we show that footshock stress exacerbates AD-like pathology. To induce a trauma-like condition, the rats were exposed to multiple intense footshocks followed by a single reminder. This was followed by bilateral intrahippocampal lesions with amyloid-beta (Aβ) (1-42), to model AD-like pathology. We found that footshocks increased anxiety behavior and impaired fear memory extinction in Aβ(1-42) lesioned rats. We also found a reduced expression of nuclear factor erythroid 2-related factor 2 (Nrf2), NAD (P) H: quinone oxidoreductase 1 (NQO1), heme oxygenase-1 (HO-1), and an increased expression of Kelch-like ECH-associated protein 1 (Keap1) in the amygdala and hippocampus. Furthermore, oxidative stress level was sustained, which was associated with increased apoptosis in the amygdala and hippocampus. Our finding suggests that AD-like pathology can induce oxidative changes in the amygdala and hippocampus, which can be exaggerated by footshock stress.

The Reversal of Memory Deficits in an Alzheimer's Disease Model Using Physical and Cognitive Exercise

Alzheimer’s disease (AD) is the leading cause of dementia in the world, accounting for 50–75% of cases. Currently, there is limited treatment for AD. The current pharmacological therapy minimizes symptom progression but does not reverse brain damage. Studies focused on nonpharmacological treatment for AD have been developed to act on brain plasticity and minimize the neurotoxicity caused by the amyloid-beta (Aβ) peptide. Using a neurotoxicity model induced by Aβ in rats, the present study shows that physical (PE) and cognitive exercise (CE) reverse recognition memory deficits (with a prominent effect of long-term object recognition memory), decrease hippocampal lipid peroxidation, restore the acetylcholinesterase activity altered by Aβ neurotoxicity, and seems to reverse, at least partially, hippocampal tissue disorganization.

One physical exercise session promotes recognition learning in rats with cognitive deficits related to amyloid beta neurotoxicity

Alzheimer's disease is a progressive neurodegenerative pathological process that causes memory loss and cognitive impairment. One of the pathological characteristics of Alzheimer's disease is the amyloid-β protein aggregation on the brain. The regular practice of physical exercise is a consolidated strategy on the prevention of cognitive deficits; however, little is known about the effects of acute exercise on memory. We hypothesize that one physical exercise session could act as a modulator of learning. Here we investigated the effects of one single session of running (aerobic) or strength (anaerobic) exercise on memory deficits related to neurotoxicity induced by amyloid-β. Male Wistar rats were submitted to stereotaxic surgery to intrahippocampal infusion of amyloid-β protein or saline (control). Ten days after the surgery the rats were submitted to the object recognition (OR) memory task. Immediately after the OR learning session, some rats were submitted to one treadmill running or strength exercise session. Then, the animals were submitted to memory tests 24 h, 7, and 14 days after the OR learning. We demonstrated that one physical exercise session, both aerobic as anaerobic, performed after learning improves learning and memory, promoting memory persistence in control rats and memory consolidation in rats submitted to amyloid-β neurotoxicity model. Notably, the effects of the aerobic exercise session seem to be more prominent, since they also reflect in an improvement of object discrimination index for 7 days in control animals. We verified that the mechanisms involved in the effects of aerobic exercise include the dopaminergic system activation. The mechanisms involved in the anaerobic exercise effects seem to be others since no alterations on hippocampal dopamine or noradrenaline levels were detected.

Exercise for Brain Health: An Investigation into the Underlying Mechanisms Guided by Dose

There is a strong link between the practice of regular physical exercise and maintenance of cognitive brain health. Animal and human studies have shown that exercise exerts positive effects on cognition through a variety of mechanisms, such as changes in brain volume and connectivity, cerebral perfusion, synaptic plasticity, neurogenesis, and regulation of trophic factors. However, much of this data has been conducted in young humans and animals, raising questions regarding the generalizability of these findings to aging adults. Furthermore, it is not clear at which doses these effects might take place, and if effects would differ with varying exercise modes (such as aerobic, resistance training, combinations, or other). The purpose of this review is to summarize the evidence on the effects of exercise interventions on various mechanisms believed to support cognitive improvements: cerebral perfusion, synaptic neuroplasticity, brain volume and connectivity, neurogenesis, and regulation of trophic factors. We synthesized the findings according to exposure to exercise (short- [1 day-16 weeks], medium- [24-40 weeks], and long-term exercise [52 weeks and beyond]) and have limited our discussion of dose effects to studies in aging adults and aged animals (when human data was not available).

Moderate treadmill exercise ameliorates amyloid-β-induced learning and memory impairment, possibly via increasing AMPK activity and up-regulation of the PGC-1α/FNDC5/BDNF pathway

Alzheimer's disease (AD) is a neurodegenerative disorder associated with loss of memory and cognitive abilities. Previous evidence suggested that exercise ameliorates learning and memory deficits by increasing brain derived neurotrophic factor (BDNF) and activating downstream pathways in AD animal models. However, upstream pathways related to increase BDNF induced by exercise in AD animal models are not well known. We investigated the effects of moderate treadmill exercise on Aβ-induced learning and memory impairment as well as the upstream pathway responsible for increasing hippocampal BDNF in an animal model of AD. Animals were divided into five groups: Intact, Sham, Aβ_1-42, Sham-exercise (Sham-exe) and Aβ_1-42-exercise (Aβ-exe). Aβ was microinjected into the CA1 area of the hippocampus and then animals in the exercise groups were subjected to moderate treadmill exercise (for 4 weeks with 5 sessions per week) 7 days after microinjection. In the present study the Morris water maze (MWM) test was used to assess spatial learning and memory. Hippocampal mRNA levels of BDNF, peroxisome proliferator-activated receptor gamma co-activator 1 alpha (PGC-1α), fibronectin type III domain-containing 5 (FNDC5) as well as protein levels of AMPK-activated protein kinase (AMPK), PGC-1α, BDNF, phosphorylation of AMPK were measured. Our results showed that intra-hippocampal injection of Aβ_1-42 impaired spatial learning and memory which was accompanied by reduced AMPK activity (p-AMPK/total-AMPK ratio) and suppression of the PGC-1α/FNDC5/BDNF pathway in the hippocampus of rats. In contrast, moderate treadmill exercise ameliorated the Aβ_1-42-induced spatial learning and memory deficit, which was accompanied by restored AMPK activity and PGC-1α/FNDC5/BDNF levels. Our results suggest that the increased AMPK activity and up-regulation of the PGC-1α/FNDC5/BDNF pathway by exercise are likely involved in mediating the beneficial effects of exercise on Aβ-induced learning and memory impairment.

The relationship between stress and Alzheimer's disease

Stress is critically involved in the development and progression of disease. From the stress of undergoing treatments to facing your own mortality, the physiological processes that stress drives have a serious detrimental effect on the ability to heal, cope and maintain a positive quality of life. This is becoming increasingly clear in the case of neurodegenerative diseases. Neurodegenerative diseases involve the devastating loss of cognitive and motor function which is stressful in itself, but can also disrupt neural circuits that mediate stress responses. Disrupting these circuits produces aberrant emotional and aggressive behavior that causes long-term care to be especially difficult. In addition, added stress drives progression of the disease and can exacerbate symptoms. In this review, I describe how neural and endocrine pathways activated by stress interact with ongoing neurodegenerative disease from both a clinical and experimental perspective.

Exercise decreases BACE and APP levels in the hippocampus of a rat model of Alzheimer's disease

We investigated the effect of treadmill exercise training on the levels of Alzheimer's disease (AD)-related protein molecules in the DG and CA1 areas of a rat model of AD, i.c.v. infusion of Aβ1-42 peptide, 2weeks (250pmol/day). Aβ infusion markedly increased protein levels of amyloid precursor protein (APP), the secretase beta-site APP cleaving enzyme-1 (BACE-1) and Aβ in the CA1 and DG areas. The results also revealed that 4weeks of treadmill exercise prevented the increase in the levels of APP, BACE-1 and Aβ proteins in both hippocampal areas. Exercise, however, did not affect the levels of these proteins in normal rats. We suggest that exercise might be changing the equilibrium of APP processing pathway towards the nonpathogenic pathway most probably via increasing BDNF levels in the brain of AD model.

Exercise as a Positive Modulator of Brain Function

Various forms of exercise have been shown to prevent, restore, or ameliorate a variety of brain disorders including dementias, Parkinson's disease, chronic stress, thyroid disorders, and sleep deprivation, some of which are discussed here. In this review, the effects on brain function of various forms of exercise and exercise mimetics in humans and animal experiments are compared and discussed. Possible mechanisms of the beneficial effects of exercise including the role of neurotrophic factors and others are also discussed.

Treadmill exercise ameliorates Alzheimer disease-associated memory loss through the Wnt signaling pathway in the streptozotocin-induced diabetic rats

Diabetes mellitus is considered as a risk factor for Alzheimer disease. The aim of the present study was to evaluate the possibility whether treadmill exercise ameliorates Alzheimer disease-associated memory loss in the diabetes mellitus. For this study, the effects of treadmill exercise on short-term memory and spatial learning ability in relation with Wnt signaling pathway were evaluated using the streptozotocin (STZ)-induced diabetic rats. Diabetes was induced by intraperitoneal injection of STZ. Step-down avoidance task and 8-arm radial maze test were performed for the memory function. Immunohistochemistry for 5-bro-mo-2′-deoxyridine (BrdU) and doublecortin (DCX) and Western blot for Wnt3 and glycogen synthase kinase-3β (GSK-3β) were conducted. The rats in the exercise groups were made to run on the treadmill for 30 min per one day, 5 times a week, during 12 weeks. In the present results, short-term memory and spatial learning ability were deteriorated by induction of diabetes. Treadmill exercise improved short-term memory and spatial learning ability in the diabetic rats. The numbers of BrdU-positive and DCX-positive cells in the hippocampal dentate gyrus were decreased by induction of diabetes. Treadmill exercise increased these numbers in the diabetic rats. Wnt3 expression in the hippocampus was decreased and GSK-3β expression in the hippocampus was increased by induction of diabetes. Treadmill exercise increased Wnt3 expression and suppressed GSK-3β expression in the diabetic rats. The present study suggests that treadmill exercise alleviates Alzheimer disease-associated memory loss by increasing neurogenesis through activating Wnt signaling pathway in the diabetic rats.

Comparison of the Effect of Exercise on Late-Phase LTP of the Dentate Gyrus and CA1 of Alzheimer's Disease Model

We investigated the neuroprotective effect of regular treadmill exercise training on long-term memory and its correlate: the late-phase long-term potentiation (L-LTP) and plasticity- and memory-related signaling molecules in the DG and CA1 areas of a rat model of Alzheimer's disease (AD) (i.c.v. infusion of Aβ_1-42 peptides, 2 weeks, 250 pmol/day). Testing in the radial arm water maze revealed severe impairment of spatial long-term memory in Aβ-infused sedentary rats but not in exercised Aβ-infused rats. The L-LTP, measured as changes in the field (f)EPSP and in the amplitude of population spike (pspike), was induced by multiple high-frequency stimulation in the CA1 and DG areas of anesthetized rats. The L-LTP of fEPSP in both areas was severely impaired in the sedentary Aβ rats but not in exercised Aβ rats. However, L-LTP of the pspike was severely suppressed in the CA1 area but not in the DG of sedentary Aβ rats. Immunoblot analysis revealed no increase in the levels of phosphorylated (p)-CREB, CaMKIV, and brain-derived neurotrophic factor (BDNF) in both CA1 and DG areas of sedentary Aβ rats during L-LTP, whereas the levels of these molecules were robustly increased in exercised Aβ rats. Impairment of synaptic function may be due to deleterious changes in the molecular signaling cascades that mediate synaptic structural and functional changes. The protective effect of regular exercise can be a promising therapeutic measure for countering or delaying the AD-like pathology.

Long-term moderate treadmill exercise promotes stress-coping strategies in male and female rats

Recent evidence has revealed the impact of exercise in alleviating anxiety and mood disorders; however, the exercise protocol that exerts such benefit is far from known. The current study was aimed to assess the effects of long-term moderate exercise on behavioural coping strategies (active vs. passive) and Hypothalamic-Pituitary-Adrenal response in rats. Sprague-Dawley male and female rats were exposed to 32-weeks of treadmill exercise and then tested for two-way active avoidance learning (shuttle-box). Two groups were used as controls: a non-handled sedentary group, receiving no manipulation, and a control group exposed to a stationary treadmill. Female rats displayed shorter escape responses and higher number of avoidance responses, reaching criterion for performance earlier than male rats. In both sexes, exercise shortened escape latencies, increased the total number of avoidances and diminished the number of trials needed to reach criterion for performance. Those effects were greater during acquisition in female rats, but remained over the shuttle-box sessions in treadmill trained male rats. In females, exercise did not change ACTH and corticosterone levels after shuttle-box acquisition. Collectively, treadmill exercise improved active coping strategies in a sex-dependent manner. In a broader context, moderate exercise could serve as a therapeutic intervention for anxiety and mood disorders.

Long-term treadmill exercise attenuates tau pathology in P301S tau transgenic mice

Background

Recent epidemiological evidence suggests that modifying lifestyle by increasing physical activity could be a non-pharmacological approach to improving symptoms and slowing disease progression in Alzheimer’s disease and other tauopathies. Previous studies have shown that exercise reduces tau hyperphosphorylation, however, it is not known whether exercise reduces the accumulation of soluble or insoluble tau aggregates and neurofibrillary tangles, which are both neuropathological hallmarks of neurodegenerative tauopathy. In this study, 7-month old P301S tau transgenic mice were subjected to 12-weeks of forced treadmill exercise and evaluated for effects on motor function and tau pathology at 10 months of age.

Results

Exercise improved general locomotor and exploratory activity and resulted in significant reductions in full-length and hyperphosphorylated tau in the spinal cord and hippocampus as well as a reduction in sarkosyl-insoluble AT8-tau in the spinal cord. Exercise did not attenuate significant neuron loss in the hippocampus or cortex. Key proteins involved in autophagy—microtubule-associated protein 1A/1B light chain 3 and p62/sequestosome 1 —were also measured to assess whether autophagy is implicated in the exercised-induced reduction of aggregated tau protein. There were no significant effects of forced treadmill exercise on autophagy protein levels in P301S mice.

Conclusions

Our results suggest that forced treadmill exercise differently affects the brain and spinal cord of aged P301S tau mice, with greater benefits observed in the spinal cord versus the brain. Our work adds to the growing body of evidence that exercise is beneficial in tauopathy, however these benefits may be more limited at later stages of disease.

Moderate Treadmill Exercise Protects Synaptic Plasticity of the Dentate Gyrus and Related Signaling Cascade in a Rat Model of Alzheimer's Disease

The dentate gyrus (DG) of the hippocampus is known to be more resistant to the effects of various external factors than other hippocampal areas. This study investigated the neuroprotective effects of moderate treadmill exercise on early-phase long-term potentiation (E-LTP) and its molecular signaling pathways in the DG of amyloid β rat model of sporadic Alzheimer's disease (AD). Animals were preconditioned to run on treadmill for 4 weeks and concurrently received ICV infusion of Aβ₁₋₄₂ peptides (250 pmol/day) during the third and fourth weeks of exercise training. We utilized in vivo electrophysiological recordings to assess the effect of exercise and/or AD pathology on basal synaptic transmission and E-LTP magnitude of the perforant pathway synapses in urethane-anesthetized rats. Immunoblotting analysis was used to quantify changes in the levels of learning and memory-related key signaling molecules. The AD-impaired basal synaptic transmission and suppression of E-LTP in the DG were prevented by prior moderate treadmill exercise. In addition, exercise normalized the basal levels of memory and E-LTP-related signaling molecules including Ca(2+)/calmodulin-dependent protein kinase II (CaMKII), calcineurin (PP2B), and brain-derived neurotrophic factor (BDNF). Exercise also prevented the reduction of phosphorylated CaMKII and aberrant increase of PP2B seen after E-LTP induction in amyloid-infused rats. Our data suggests that by restoring the balance of kinase-phosphatase, 4 weeks of moderate treadmill exercise prevents DG synaptic deficits and deleterious alterations in signaling pathways associated with AD.