Moderate Exercise Combined with Enriched Environment Enhances Learning and Memory through BDNF/TrkB Signaling Pathway in Rats

Rationale and methodology for examining the combination of aerobic exercise and cognitive rehabilitation on new learning and memory in persons with multiple sclerosis and mobility disability: Protocol for a randomized controlled trial

BACKGROUND

This paper describes the protocol for a Phase I/II, parallel-group, single-blind randomized controlled trial (RCT). The RCT investigates the combined effects of 12-weeks of aerobic exercise training (AET) integrated with virtual reality (VR) and cognitive rehabilitation (CR) on new learning and memory in 78 persons with multiple sclerosis (MS) who have mobility disability and objective impairments in learning and memory.

METHODS

Participants will undergo baseline assessments consisting of neuropsychological testing, neuroimaging, self-report questionnaires, and cardiorespiratory fitness. Participants will then be randomized into one of two conditions using concealed allocation: aerobic cycling exercise that incorporates VR combined with CR or stretching and toning (i.e., active control; S/T) combined with CR. Participants will be masked regarding the intent of the conditions. After 7-weeks of exercise alone, the 5-week Kessler Foundation modified Story Memory Technique (KF-mSMT®) will be integrated into the training. After the 12-week training period, participants will complete the same measures as at baseline administered by treatment-blinded assessors. Primary study outcomes include new learning and memory (NLM) measured by a small battery of neuropsychological assessments that assess list learning (California Verbal Learning Test-II), prose memory (Memory Assessment Scale), visuospatial memory (Brief Visuospatial Memory Test-Revised), and everyday memory (Ecological Memory Simulations). Secondary study outcomes include neuroimaging outcomes of hippocampal structure, function, and connectivity.

CONCLUSION

If successful, this trial will provide the first Class I evidence supporting the unique combination of aerobic cycling exercise with VR and CR for treating MS-related learning and memory impairments in persons with mobility disability.

The interplay between BDNF and PGC-1 alpha in maintaining brain health: role of exercise

Throughout our evolutionary history, physical activity has played a significant role in shaping our physiology. Advances in exercise science have further reinforced this concept by highlighting how exercise can change gene expression and molecular signaling to achieve various beneficial outcomes. Several studies have shown that exercise can alter neuronal functions to prevent neurodegenerative conditions like Parkinson's and Alzheimer's diseases. However, individual genotypes, phenotypes, and varying exercise protocols hinder the prescription of exercise as standard therapy. Moreover, exercise-induced molecular signaling targets can be double-edged swords, making it difficult to use exercise as the primary candidate for beneficial effects. For example, activating PGC-1 alpha and BDNF through exercise could produce several benefits in maintaining brain health, such as plasticity, neuronal survival, memory formation, cognition, and synaptic transmission. However, higher expression of BDNF might play a negative role in bipolar disorder. Therefore, further understanding of a specific mechanistic approach is required. This review focuses on how exercise-induced activation of these molecules could support brain health and discusses the potential underlying mechanisms of the effect of exercise-induced PGC-1 alpha and BDNF on brain health.

Enhancement of response learning in male rats with intrastriatal infusions of a BDNF - TrkB agonist, 7,8-dihydroxyflavone

Enhancement of learning and memory by cognitive and physical exercise may be mediated by brain-derived neurotrophic factor (BDNF) acting at tropomyosin receptor kinase B (TrkB). Upregulation of BDNF and systemic administration of a TrkB agonist, 7,8-dihydroxyflavone (7,8-DHF), enhance learning of several hippocampus-sensitive tasks in rodents. Although BDNF and 7,8-DHF enhance functions of other brain areas too, these effects have mainly targeted non-cognitive functions. One goal of the present study was to determine whether 7,8-DHF would act beyond the hippocampus to enhance cognitive functions sensitive to manipulations of the striatum. Here, we examined the effects of intrastriatal infusions of 7,8-DHF on learning a striatum-sensitive response maze and on phosphorylation of TrkB receptors in 3-month-old male Sprague Dawley rats. Most prior studies of BDNF and 7,8-DHF effects on learning and memory have administered the drugs for days to months before assessing effects on cognition. A second goal of the present study was to determine whether a single drug treatment near the time of training would effectively enhance learning. Moreover, 7,8-DHF is often tested for its ability to reverse impairments in learning and memory rather than to enhance these functions in the absence of impairments. Thus, a third goal of this experiment was to evaluate the efficacy of 7,8-DHF in enhancing learning in unimpaired rats. In untrained rats, intrastriatal infusions of 7,8-DHF resulted in phosphorylation of TrkB receptors, suggesting that 7,8-DHF acted as a TrkB agonist and BDNF mimic. The findings that a single, intra-striatal infusion of 7,8-DHF 20 min before training enhanced response learning in rats suggest that, in addition to its trophic effects, BDNF modulates learning and memory through receptor mediated cell signaling events.

Environmental enrichment changes the effects of prenatal and postnatal undernutrition on memory, anxiety traits, Bdnf and TrkB expression in the hippocampus of male adult rats

Environmental factors such as undernutrition and environmental enrichment can promote changes in the molecular and behavioural mechanisms related to cognition. Herein, we investigated the effect of enriched environment stimulation in rats that were malnourished in the pre- and postnatal periods on changes in the gene expression of brain-derived neurotrophic factor and its receptor in the hippocampus, as well as on anxiety traits and memory. Early undernutrition promoted weight reduction, increased the risk analysis, reduced permanence in the open arm of the elevated plus-maze and induced a reduction in the gene expression of brain-derived neurotrophic factor and tropomyosin receptor kinase B. However, exposure to an enriched environment from 30 to 90 days' old maintained the malnourished phenotype, leading to weight reduction in the control group. In addition, the enriched environment did not alter the risk assessment in the undernourished group, but it did increase the frequency of labyrinth entries. Sixty-day exposure to the enriched environment resulted in a reversal in the gene expression of brain-derived neurotrophic factor and tropomyosin receptor kinase B in the hippocampus of malnourished rats and favoured of long-term memory in the object recognition test in the open-field. These results suggest that an enriched environment may have a protective effect in adult life by inducing changes in long-term memory and anxiety traits in animals that were undernourished in early life. Furthermore, reversing these effects of undernutrition involves mechanisms linked to the molecular signalling of brain-derived neurotrophic factor and tropomyosin receptor kinase B in the hippocampus.

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

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

The effect of low- and moderate-intensity interval training on cognitive behaviors of male and female rats with VPA-induced autism

Introduction

This study was performed to evaluate the effects of low and moderate treadmill exercise for one month on social interaction, anxiety-like behaviors, and spatial learning and memory in male and female autistic rats.

Methods

Pregnant rats received valproic acid (VPA) (600 mg/kg/i.p) once on gestational day 12.5 to induce autism-like symptoms in the offspring. After delivery, the offspring were divided into six main groups, each with male and female subgroups: Control (CTL, prenatal normal saline), autism (prenatal VPA), low-intensity training (LIT,normal saline + low treadmill exercise), moderate -intensity training (MIT, normal saline + moderate treadmill exercise), VPA + LIT, and VPA + MIT. On the 60th day, the offspring were tested by the elevated plus maze (EPM), open field test (OFT), social interaction test (SIT), and Morris water maze (MWM).

Results

The results showed that both LIT and MIT could partly alleviate anxiety-like behaviors induced by prenatal VPA exposure in two sexes. Social impairment was observed in the autistic rats and was improved by LIT in both sexes and MIT in females. No significant change was seen in the spatial learning and memory of autistic rats by exercise.

Conclusion

The findings suggest that treadmill exercise can be helpful for improving some autism-like behaviors. Further studies are needed to investigate the involved mechanisms.

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

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

Investigation of the protective effect of long-term exercise on molecular pathways and behaviours in scopolamine induced alzheimer's disease-like condition

Despite research, the role of exercise in treatment and prevention of neurodegenerative diseases remains unclear. Our study, investigated that protective effect of treadmill exercise on molecular pathways and cognitive behaviours in a scopolamine-induced model of Alzheimer's disease. For that purpose, male Balb/c mice subjected to exercise for 12 weeks. During the last 4 weeks of exercise, mice were given an injection of scopolamine (2 mg/kg). Following injection, open field test and Morris water maze test were used to assess emotional-cognitive behaviour. Hippocampus and prefrontal cortex of mice were isolated, and levels of BDNF, TrkB, and p-GSK3ßSer389 were assessed by western blotting, and levels of APP and Aß-40 were analysed by immunohistochemistry. In our study, scopolamine administration increased anxiety-like behaviour in open field test, while negatively affecting spatial learning and memory in Morris water maze test. We found that exercise had a protective effect against cognitive and emotional decline. Scopolamine decreased levels of p-GSK3ßSer389, BDNF in hippocampus and prefrontal cortex.Whereas TrkB decreased in hippocampus and increased in prefrontal cortex. There was an increase in p-GSK3ßSer389, BDNF, TrkB in the hippocampus, and p-GSK3ßSer389, BDNF in the prefrontal cortex in the exercise + scopolamine group. Immunohistochemical analysis showed that scopolamine administration increased APP and Aß-40 in hippocampus and prefrontal cortex in neuronal and perineuronal areas whereas Aß-40 and APP were reduced in exercise + scopolamine groups. In conclusion, long-term exercise may have a protective effect against scopolamine-induced impairments in cognitive-emotional behaviour. It can be suggested that this protective effect is mediated by increased BDNF levels and GSK3ßSer389 phosphorylation.

Tenuifolin in the prevention of Alzheimer's disease-like phenotypes: Investigation of the mechanisms from the perspectives of calpain system, ferroptosis, and apoptosis

Polygala tenuifolia was documented to calm the mind and promote wisdom. However, its underlying mechanisms are still unclear. This study aimed to investigate the mechanisms underlying the effects of tenuifolin (Ten) on Alzheimer's disease (AD)-like phenotypes. We first applied bioinformatics methods to screen the mechanisms of P. tenuifolia in the treatment of AD. Thereafter, the d-galactose combined with Aβ1-42 (GCA) was applied to model AD-like behaviors and investigate the action mechanisms of Ten, one active component of P. tenuifolia. The data showed that P. tenuifolia actioned through multi-targets and multi-pathways, including regulation of synaptic plasticity, apoptosis, and calcium signaling, and so forth. Furthermore, in vitro experiments demonstrated that Ten prevented intracellular calcium overload, abnormal calpain system, and down-regulation of BDNF/TrkB signaling induced by GCA. Moreover, Ten suppressed oxidative stress and ferroptosis in HT-22 cells induced by GCA. Calpeptin and ferroptosis inhibitor prevented the decrease of cell viability induced by GCA. Interestingly, calpeptin did not interrupt GCA-induced ferroptosis in HT-22 cells but blocked the apoptosis. Animal experiments further demonstrated that Ten prevented GCA-induced memory impairment in mice and increased synaptic protein expression while reducing m-calpain expression. Ten prevents AD-like phenotypes through multiple signaling by inhibiting oxidative stress and ferroptosis, maintaining the stability of calpain system, and suppressing neuronal apoptosis.

Recent advances on the molecular mechanisms of exercise-induced improvements of cognitive dysfunction

Physical exercise is of great significance for maintaining human health. Exercise can provide varying degrees of benefits to cognitive function at all stages of life cycle. Currently, with the aging of the world's population and increase of life expectancy, cognitive dysfunction has gradually become a disease of high incidence, which is accompanied by neurodegenerative diseases in elderly individuals. Patients often exhibit memory loss, aphasia and weakening of orientation once diagnosed, and are unable to have a normal life. Cognitive dysfunction largely affects the physical and mental health, reduces the quality of life, and causes a great economic burden to the society. At present, most of the interventions are aimed to maintain the current cognitive level and delay deterioration of cognition. In contrast, exercise as a nonpharmacological therapy has great advantages in its nontoxicity, low cost and universal application. The molecular mechanisms underlying the effect of exercise on cognition are complex, and studies have been extensively centered on neural plasticity, the direct target of exercise in the brain. In addition, mitochondrial stability and energy metabolism are essential for brain status. Meanwhile, the organ-brain axis responds to exercise and induces release of cytokines related to cognition. In this review, we summarize the latest evidence on the molecular mechanisms underlying the effects of exercise on cognition, and point out directions for future research.

The Molecular Effects of Environmental Enrichment on Alzheimer's Disease

Environmental enrichment (EE) is an environmental paradigm encompassing sensory, cognitive, and physical stimulation at a heightened level. Previous studies have reported the beneficial effects of EE in the brain, particularly in the hippocampus. EE improves cognitive function as well as ameliorates depressive and anxiety-like behaviors, making it a potentially effective neuroprotective strategy against neurodegenerative diseases such as Alzheimer's disease (AD). Here, we summarize the current evidence for EE as a neuroprotective strategy as well as the potential molecular pathways that can explain the effects of EE from a biochemical perspective using animal models. The effectiveness of EE in enhancing brain activity against neurodegeneration is explored with a view to differences present in early and late life EE exposure, with its potential application in human being discussed. We discuss EE as one of the non pharmacological approaches in preventing or delaying the onset of AD for future research.

Insight Into the Mechanism of Exercise Preconditioning in Ischemic Stroke

Exercise preconditioning has attracted extensive attention to induce endogenous neuroprotection and has become the hotspot in neurotherapy. The training exercise is given multiple times before cerebral ischemia, effectively inducing ischemic tolerance and alleviating secondary brain damage post-stroke. Compared with other preconditioning methods, the main advantages of exercise include easy clinical operation and being readily accepted by patients. However, the specific mechanism behind exercise preconditioning to ameliorate brain injury is complex. It involves multi-pathway and multi-target regulation, including regulation of inflammatory response, oxidative stress, apoptosis inhibition, and neurogenesis promotion. The current review summarizes the recent studies on the mechanism of neuroprotection induced by exercise, providing the theoretical basis of applying exercise therapy to prevent and treat ischemic stroke. In addition, we highlight the various limitations and future challenges of translational medicine from fundamental study to clinical application.

Complicated Role of Exercise in Modulating Memory: A Discussion of the Mechanisms Involved

Evidence has shown the beneficial effects of exercise on learning and memory. However, many studies have reported controversial results, indicating that exercise can impair learning and memory. In this article, we aimed to review basic studies reporting inconsistent complicated effects of exercise on memory in rodents. Also, we discussed the mechanisms involved in the effects of exercise on memory processes. In addition, we tried to find scientific answers to justify the inconsistent results. In this article, the role of brain-derived neurotrophic factor (BDNF) and tropomyosin receptor kinase B (involved in synaptic plasticity and neurogenesis), and vascular endothelial growth factor, nerve growth factor, insulin-like growth factor 1, inflammatory markers, apoptotic factors, and antioxidant system was discussed in the modulation of exercise effects on memory. The role of intensity and duration of exercise, and type of memory task was also investigated. We also mentioned to the interaction of exercise with the function of neurotransmitter systems, which complicates the prediction of exercise effect via altering the level of BDNF. Eventually, we suggested that changes in the function of neurotransmitter systems following different types of exercise (depending on exercise intensity or age of onset) should be investigated in further studies. It seems that exercise-induced changes in the function of neurotransmitter systems may have a stronger role than age, type of memory task, or exercise intensity in modulating memory. Importantly, high levels of interactions between neurotransmitter systems and BDNF play a critical role in the modulation of exercise effects on memory performance.