Exercise Training Protects Against Aging-Induced Cognitive Dysfunction via Activation of the Hippocampal PGC-1α/FNDC5/BDNF Pathway

Irisin and neuroinflammation: Challenges and opportunities

Irisin is a myokine that is cleaved from 5-domain type III fibronectin (FNDC5), and is known for its metabolic functions as it stimulates browning of white adipose tissue; similarly, effects on the central nervous system have been described, specifically in neurodevelopmental and neuroprotection processes. The purpose of this review is to describe recent information on the effects of irisin on neuroinflammation to contribute to the knowledge about the mechanisms by which irisin and exercise could generate benefits for some neurological diseases. The review conducted found several studies describing the effect of irisin on pathways such as STAT3, p38, cAMP/PKA/CREB, as well as effects on GFAP protein expression or apoptosis processes in both in vitro and in vivo models; likewise, these pathways are associated with better BDNF expression. Despite increasing information on this topic, it is still necessary to clarify the mechanisms by which irisin has effects on neuroinflammation and this could represent an opportunity to generate more treatments for diseases such as Alzheimer's, Parkinson's or Diabetes Mellitus.

Effects of Aerobic Exercise and Resistance Training on Cognitive Function: Comparative Study Based on FNDC5/Irisin/BDNF Pathway

INTRODUCTION

Exercise has been recommended to suppress or prevent cognitive decline. Aerobic exercise (AE) may suppress cognitive decline via the fibronectin type III domain-containing protein 5 (FNDC5)/irisin/brain-derived neurotrophic factor (BDNF) pathway, and resistance training (RT) has a preventive effect on cognitive decline. However, the underlying mechanism remains unclear. This study verified the differences in the effects of AE and RT in suppressing and preventing cognitive decline based on the FNDC5/irisin/BDNF pathway.

METHODS

We divided senescence-accelerated mouse-prone 8 into three groups: control (CON), AE, and RT and evaluated their memory during exercise intervention through a novel object recognition (NOR) task. We quantified FNDC5/irisin, mBDNF, and TrkB in the hippocampus using enzyme-linked immunosorbent assay and FNDC5 in skeletal muscle using Western blotting (WB).

RESULTS

Behavioral analysis using NOR showed that values for both AE and RT were significantly greater than those for CON. WB analysis showed that the peripheral FNDC5 expression in the skeletal muscle was increased in AE. The expression levels of FNDC5/irisin and mBDNF in the hippocampus were significantly increased in both AE and RT compared with that in CON but that if TrkB was increased only in AE.

CONCLUSION

No significant difference was observed between AE and RT in the inhibitory effect on age-related cognitive decline, and both groups were effective. The FNDC5/Irisin/BDNF pathway, which was the focus of this experiment, may be specific to AE. The mechanism that suppresses cognitive decline may differ depending on the type of exercise.

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.

The cerebroprotection and prospects of FNDC5/irisin in stroke

Stroke, the leading cause of disability and cognitive impairment, is also the second leading cause of death worldwide. The drugs with multi-targeted brain cytoprotective effects are increasingly being advocated for the treatment of stroke. Irisin, a newly discovered myokine produced by cleavage of fibronectin type III domain 5, has been shown to regulate glucose metabolism, mitochondrial energy, and fat browning. A large amount of evidence indicated that irisin could exert anti-inflammatory, anti-apoptotic, and antioxidant properties in a variety of diseases such as myocardial infarction, inflammatory bowel disease, lung injury, and kidney or liver disease. Studies have found that irisin is widely distributed in multiple brain regions and also plays an important regulatory role in the central nervous system. The most common cause of a stroke is a sudden blockage of an artery (ischemic stroke), and in some circumstances, a blood vessel rupture can also result in a stroke (hemorrhagic stroke). After a stroke, complicated pathophysiological processes lead to serious brain injury and neurological dysfunction. According to recent investigations, irisin may protect elements of the neurovascular unit by acting on multiple pathological processes in stroke. This review aims to outline the currently recognized effects of irisin on stroke and propose possible directions for future research.

The relationship of cognitive functions with brain damage markers, myokines and neurotrophic factors in amateur soccer players

Concussive and subconcussive head impatcs in sports have drawn more attention in recent years. Thus, the cognitive ability of soccer players and its relationship with circulating levels of irisin, brain-derived neurotrophic factor (BDNF), and neuron-specific enolase (NSE) were studied in this study. Fifteen amateur soccer players and 15 sedentary men volunteered to participate in this study. After evaluating the aerobic and anaerobic capacities of the participants, their cognitive performances were measured. Blood samples were obtained at rest, and the ELISA method was used to measure the concentrations of serum NSE, plasma BDNF, and irisin. There were no differences between groups in terms of cognitive abilities or serum NSE levels (P > 0.05). Plasma irisin (P = 0.019) and BDNF (P < 0.001) levels were higher in the soccer players than the sedentary subjects. There was a positive correlation between irisin and NSE (r = 0.461, P = 0.010) and BDNF (r = 0.405, P = 0.007) concentrations. General cognitive performance is maintained in amateur soccer players. This is accompanied by the unchanged NSE. However, elevated irisin and BDNF levels appear to be independent of cognitive performance.

Effects of Ocimum basilicum L. Extract on Hippocampal Oxidative Stress, Inflammation, and BDNF Expression in Amnesic Aged Rats

The present study was conducted to investigate the effects of Ocimum basilicum L. (OB) extract on learning and memory impairment in aged rats. Male rats were divided into the following experimental groups: Group 1 (control): including 2 months old rats, Group 2 (aged) including 2 years old rats, Groups 3-5 (aged-OB): including 2 years old rats received 50, 100, and 150 mg/kg OB for 8 weeks by oral gavage. Aging increased the delay to find the platform but, however, decreased the time spent in the target quadrant when tested by Morris water maze (MWM). Aging also reduced the latency to enter the dark chamber in the passive avoidance (PA) test compared to the control group. Moreover, interleukin-6 (IL-6) and malondialdehyde (MDA) levels were raised in the hippocampus and cortex of aged rats. In contrast, thiol levels and enzymatic activity of superoxide dismutase (SOD) and catalase (CAT) significantly reduced. In addition, aging significantly reduced BDNF expression. Finally, OB administration reversed the mentioned effects. The current research showed that OB administration improves learning/memory impairment induced by aging. It also found that this plant extract protects the brain tissues from oxidative damage and neuroinflammation.

Exercise Training Alleviates Symptoms and Cognitive Decline in a Reserpine-induced Fibromyalgia Model by Activating Hippocampal PGC-1α/FNDC5/BDNF Pathway

The purpose of this study was to assess, from a behavioral, biochemical, and molecular standpoint, how exercise training affected fibromyalgia (FM) symptoms in a reserpine-induced FM model and to look into the potential involvement of the hippocampal PGC-1α/FNDC5/BDNF pathway in this process. Reserpine (1 mg kg-1) was subcutaneously injected once daily for three consecutive days and then the rats were exercised for 21 days. Mechanical allodynia was evaluated 1, 11, and 21 days after the last injection. At the end of the exercise training protocol forced swim, open field and Morris water maze tests were performed to assess depression, locomotion and cognition, respectively. Additionally, biochemical and molecular markers related to the pathogenesis of the FM and cognitive functions were measured. Reserpine exposure was associated with a decrease in locomotion, an increase in depression, an increase in mechanical allodynia, and a decrease in spatial learning and memory (p < 0.05). These behavioral abnormalities were found to be correlated with elevated blood cytokine levels, reduced serotonin levels in the prefrontal cortex, and altered PGC-1α/FNDC5/BDNF pathway in the hippocampus (p < 0.05). Interestingly, exercise training attenuated all the neuropathological changes mentioned above (p < 0.05). These results imply that exercise training restored behavioral, biochemical, and molecular changes against reserpine-induced FM-like symptoms in rats, hence mitigating the behavioral abnormalities linked to pain, depression, and cognitive functioning.

Exercise induction at expression immediate early gene (c-Fos, ARC, EGR-1) in the hippocampus: a systematic review

The immediate early gene exhibits activation markers in the nervous system consisting of ARC, EGR-1, and c-Fos and is related to synaptic plasticity, especially in the hippocampus. Immediate early gene expression is affected by physical exercise, which induces direct ARC, EGR-1, and c-Fos expression.

Objective

To assess the impact of exercise, we conducted a literature study to determine the expression levels of immediate early genes (ARC, c-Fos, and EGR-1).

Methods

The databases accessed for online literature included PubMed-Medline, Scopus, and ScienceDirect. The original English articles were selected using the following keywords in the title: (Exercise OR physical activity) AND (c-Fos) AND (Hippocampus), (Exercise OR physical activity) AND (ARC) AND (Hippocampus), (Exercise OR physical activity) AND (EGR-1 OR zif268) AND (Hippocampus).

Results

Physical exercise can affect the expression of EGR-1, c-Fos, and ARC in the hippocampus, an important part of the brain involved in learning and memory. High-intensity physical exercise can increase c-Fos expression, indicating neural activation. Furthermore, the expression of the ARC gene also increases due to physical exercise. ARC is a gene that plays a role in synaptic plasticity and regulation of learning and memory, changes in synaptic structure and increased synaptic connections, while EGR-1 also plays a role in synaptic plasticity, a genetic change that affects learning and memory. Overall, exercise or regular physical exercise can increase the expression of ARC, c-Fos, and EGR-1 in the hippocampus. This reflects the changes in neuroplasticity and synaptic plasticity that occur in response to physical activity. These changes can improve cognitive function, learning, and memory.

Conclusion

c-Fos, EGR-1, and ARC expression increases in hippocampal neurons after exercise, enhancing synaptic plasticity and neurogenesis associated with learning and memory.

Contribution of changes in the orexin system and energy sensors in the brain in depressive disorder - a study in an animal model

BACKGROUND

Maternal elevated glucocorticoid levels during pregnancy can affect the developing fetus, permanently altering the structure and function of its brain throughout life. Excessive action of these hormones is known to contribute to psychiatric disorders, including depression.

MATERIALS

The study was performed in a rat model of depression based on prenatal administration of dexamethasone (DEX) in late pregnancy (0.1 mg/kg, days 14-21). We evaluated the effects of prenatal DEX treatment on the cognition and bioenergetic signaling pathways in the brain of adult male rats, in the frontal cortex and hippocampus, and in response to stress in adulthood, using behavioral and biochemical test batteries.

RESULTS

We revealed cognitive deficits in rats prenatally treated with DEX. At the molecular level, a decrease in the orexin A and orexin B levels and downregulation of the AMPK-SIRT1-PGC1α transduction pathway in the frontal cortex of these animals were observed. In the hippocampus, a decreased expression of orexin B was found and changes in the MR/GR ratio were demonstrated. Furthermore, an increase in HDAC5 level triggered by the prenatal DEX treatment in both brain structures and a decrease in MeCP2 level in the hippocampus were reported.

CONCLUSIONS

Our study demonstrated that prenatal DEX treatment is associated with cognitive dysfunction and alterations in various proteins leading to metabolic changes in the frontal cortex, while in the hippocampus adaptation mechanisms were activated. The presented results imply that different pathophysiological metabolic processes may be involved in depression development, which may be useful in the search for novel therapies.

A mitochondrial nexus in major depressive disorder: Integration with the psycho-immune-neuroendocrine network

Nervous system processes, including cognition and affective state, fundamentally rely on mitochondria. Impaired mitochondrial function is evident in major depressive disorder (MDD), reflecting cumulative detrimental influences of both extrinsic and intrinsic stressors, genetic predisposition, and mutation. Glucocorticoid 'stress' pathways converge on mitochondria; oxidative and nitrosative stresses in MDD are largely mitochondrial in origin; both initiate cascades promoting mitochondrial DNA (mtDNA) damage with disruptions to mitochondrial biogenesis and tryptophan catabolism. Mitochondrial dysfunction facilitates proinflammatory dysbiosis while directly triggering immuno-inflammatory activation via released mtDNA, mitochondrial lipids and mitochondria associated membranes (MAMs), further disrupting mitochondrial function and mitochondrial quality control, promoting the accumulation of abnormal mitochondria (confirmed in autopsy studies). Established and putative mechanisms highlight a mitochondrial nexus within the psycho-immune neuroendocrine (PINE) network implicated in MDD. Whether lowering neuronal resilience and thresholds for disease, or linking mechanistic nodes within the MDD pathogenic network, impaired mitochondrial function emerges as an important risk, a functional biomarker, providing a therapeutic target in MDD. Several treatment modalities have been demonstrated to reset mitochondrial function, which could benefit those with MDD.

The integrated analysis and underlying mechanisms of FNDC5 on diabetic induced cognitive deficits

OBJECTIVES

Chronic hyperglycemia is considered as an important factor to promote the neurodegenerative process of brain, and the synaptic plasticity as well as heterogeneity of hippocampal cells are thought to be associated with cognitive dysfunction in the early process of neurodegeneration. To date, fibronectin type III domain-containing protein 5 (FNDC5) has been highlighted its protective role in multiple neurodegenerative diseases. However, the potential molecular and cellular mechanisms of FNDC5 on synaptic plasticity regulation in cognitive impairment (CI) induced by diabetics are still need to known.

METHODS/DESIGN

To investigate the heterogeneity and synaptic plasticity of hippocampus in animals with CI state induced by hyperglycemia, and explore the potential role of FNDC5 involved in this process. Firstly, the single cell sequencing was performed based on the hippocampal tissue from db diabetic mice induced CI and normal health control mice by ex vivo experiments; and then the integrated analysis and observations validation using Quantitative Real-time PCR, western blot as well as other in vitro studies.

RESULTS

We observed and clarified the sub-cluster of type IC spiral ganglion neurons expressed marker genes as Trmp3 and sub-cluster of astrocytes with marker gene as Atp1a2 in hippocampal cells from diabetic animals induced CI and the effect of those on neuron-glial communication. We also found that FNDC5\BDNF-Trk axis was involved in the synaptic plasticity regulation of hippocampus. In high glucose induced brain injury model in vitro, we investigated that FNDC5 significantly regulates BDNF expression and that over-expression of FNDC5 up-regulated BDNF expression (p < 0.05) and can also significantly increase the expression of synapsin-1 (p < 0.05), which is related to synaptic plasticity, In addition, the unbalanced methylation level between H3K4 and H3K9 in Fndc5 gene promoter correlated with significantly down-regulated expression of FNDC5 (p < 0.05) in the hyperglycemia state.

CONCLUSION

The current study revealed that the synaptic plasticity of hippocampal cells in hyperglycemia might be regulated by FNDC5\BDNF-Trk axis, playing the protective role in the process of CI induced by hyperglycemia and providing a target for the early treatment of hyperglycemia induced cognitive dysfunction in clinic.

Physical Exercise as Disease-Modifying Alternative against Alzheimer's Disease: A Gut-Muscle-Brain Partnership

Alzheimer's disease (AD) is a common cause of dementia characterized by neurodegenerative dysregulations, cognitive impairments, and neuropsychiatric symptoms. Physical exercise (PE) has emerged as a powerful tool for reducing chronic inflammation, improving overall health, and preventing cognitive decline. The connection between the immune system, gut microbiota (GM), and neuroinflammation highlights the role of the gut-brain axis in maintaining brain health and preventing neurodegenerative diseases. Neglected so far, PE has beneficial effects on microbial composition and diversity, thus providing the potential to alleviate neurological symptoms. There is bidirectional communication between the gut and muscle, with GM diversity modulation and short-chain fatty acid (SCFA) production affecting muscle metabolism and preservation, and muscle activity/exercise in turn inducing significant changes in GM composition, functionality, diversity, and SCFA production. This gut-muscle and muscle-gut interplay can then modulate cognition. For instance, irisin, an exercise-induced myokine, promotes neuroplasticity and cognitive function through BDNF signaling. Irisin and muscle-generated BDNF may mediate the positive effects of physical activity against some aspects of AD pathophysiology through the interaction of exercise with the gut microbial ecosystem, neural plasticity, anti-inflammatory signaling pathways, and neurogenesis. Understanding gut-muscle-brain interconnections hold promise for developing strategies to promote brain health, fight age-associated cognitive decline, and improve muscle health and longevity.

Brain metabolism in Alzheimer's disease: biological mechanisms of exercise

Alzheimer's disease (AD) is a major subtype of neurodegenerative dementia caused by long-term interactions and accumulation of multiple adverse factors, accompanied by dysregulation of numerous intracellular signaling and molecular pathways in the brain. At the cellular and molecular levels, the neuronal cellular milieu of the AD brain exhibits metabolic abnormalities, compromised bioenergetics, impaired lipid metabolism, and reduced overall metabolic capacity, which lead to abnormal neural network activity and impaired neuroplasticity, thus accelerating the formation of extracellular senile plaques and intracellular neurofibrillary tangles. The current absence of effective pharmacological therapies for AD points to the urgent need to investigate the benefits of non-pharmacological approaches such as physical exercise. Despite the evidence that regular physical activity can improve metabolic dysfunction in the AD state, inhibit different pathophysiological molecular pathways associated with AD, influence the pathological process of AD, and exert a protective effect, there is no clear consensus on the specific biological and molecular mechanisms underlying the advantages of physical exercise. Here, we review how physical exercise improves crucial molecular pathways and biological processes associated with metabolic disorders in AD, including glucose metabolism, lipid metabolism, Aβ metabolism and transport, iron metabolism and tau pathology. How metabolic states influence brain health is also presented. A better knowledge on the neurophysiological mechanisms by which exercise improves AD metabolism can contribute to the development of novel drugs and improvement of non-pharmacological interventions.

Swimming and L-arginine loaded chitosan nanoparticles ameliorates aging-induced neuron atrophy, autophagy marker LC3, GABA and BDNF-TrkB pathway in the spinal cord of rats

Aging is associated with muscle atrophy, and erosion and destruction of neuronal pathways in the spinal cord. The study aim was to assess the effect of swimming training (Sw) and L-arginine loaded chitosan nanoparticles (LA-CNPs) on the sensory and motor neuron population, autophagy marker LC3, total oxidant status/total antioxidant capacity, behavioural test, GABA and BDNF-TrkB pathway in the spinal cord of aging rats. The rats were randomized to five groups: young (8-weeks) control (n = 7), old control (n = 7), old Sw (n = 7), old LA-CNPs (n = 7) and old Sw + LA-CNPs (n = 7). Groups under LA-CNPs supplementation received 500 mg/kg/day. Sw groups performed a swimming exercise programme 5 days per week for 6 weeks. Upon the completion of the interventions the rats were euthanized and the spinal cord was fixed and frozen for histological assessment, IHC, and gene expression analysis. The old group had more atrophy in the spinal cord with higher changes in LC3 as an indicator of autophagy in the spinal cord compared to the young group (p < 0.0001). The old Sw + LA-CNPs group increased (improved) spinal cord GABA (p = 0.0187), BDNF (p = 0.0003), TrkB (p < 0.0001) gene expression, decreased autophagy marker LC3 protein (p < 0.0001), nerve atrophy and jumping/licking latency (p < 0.0001), improved sciatic functional index score and total oxidant status/total antioxidant capacity compared to the old group (p < 0.0001). In conclusion, swimming and LA-CNPs seems to ameliorate aging-induced neuron atrophy, autophagy marker LC3, oxidant-antioxidant status, functional restoration, GABA and BDNF-TrkB pathway in the spinal cord of aging rats. Our study provides experimental evidence for a possible positive role of swimming and L-arginine loaded chitosan nanoparticles to decrease complications of aging.

NLX-101, a 5-HT1A receptor-biased agonist, improves pattern separation and stimulates neuroplasticity in aged rats

5-HT_1A serotonin receptors may play a role in cognitive function changes related to advanced age. Here, we investigated the effects of acute and repeated treatment with NLX-101 (F15599), a postsynaptic 5-HT_1A receptor-biased agonist, and F13714, a presynaptic 5-HT_1A receptor-biased agonist on spatial object pattern separation (OPS) in aged (22-24 months) rats. Neuroplasticity markers including brain-derived neurotrophic factor, PSD95, synaptophysin, and doublecortin were evaluated in the hippocampus. Unlike younger rats, aged rats were incapable of discriminating any new position of the objects in the arena, reflecting the detrimental effect of aging on pattern separation. However, aged animals treated with NLX-101 showed a significant cognitive improvement in the OPS test, accompanied by increases in hippocampal brain-derived neurotrophic factor and PSD95 protein levels. In contrast, no improvement in OPS performance was observed when aged rats received F13714. Both F13714 and NLX-101 increased the number of newborn neurons in the hippocampi of aged rats. These findings provide a rationale for targeting post-synaptic 5-HT_1A as a treatment for cognitive deficits related to aging.

Unlocking the Therapeutic Potential of Irisin: Harnessing Its Function in Degenerative Disorders and Tissue Regeneration

Physical activity is well-established as an important protective factor against degenerative conditions and a promoter of tissue growth and renewal. The discovery of Fibronectin domain-containing protein 5 (FNDC5) as the precursor of Irisin in 2012 sparked significant interest in its potential as a diagnostic biomarker and a therapeutic agent for various diseases. Clinical studies have examined the correlation between plasma Irisin levels and pathological conditions using a range of assays, but the lack of reliable measurements for endogenous Irisin has led to uncertainty about its prognostic/diagnostic potential as an exercise surrogate. Animal and tissue-engineering models have shown the protective effects of Irisin treatment in reversing functional impairment and potentially permanent damage, but dosage ambiguities remain unresolved. This review provides a comprehensive examination of the clinical and basic studies of Irisin in the context of degenerative conditions and explores its potential as a therapeutic approach in the physiological processes involved in tissue repair/regeneration.

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.

Irisin: A bridge between exercise and neurological diseases

Exercise plays a beneficial regulating role on each organ of the body through different mechanisms and is a powerful weapon to prevent disease. Irisin is released from muscle and widely distributed in the human body, participating in the physiological processes of multiple human systems and playing a protective role in multiple human organs. The protective effect of irisin on the nervous system is particularly remarkable, which can improve cognitive function, reduce the risk of ischemic stroke and improve its prognosis. Irisin also plays a guiding role in the prevention and treatment of neurodegenerative diseases and ischemic cerebrovascular diseases. Exercise is the driving factor promoting irisin secretion, and different exercise modes, intensity, frequency, and time all affect the level of serum irisin. As a result of analyzing the effects of various exercise modes on irisin secretion, we proposed an exercise program with a higher level of irisin secretion.

Musculoskeletal Deficits and Cognitive Impairment: Epidemiological Evidence and Biological Mechanisms

PURPOSE OF REVIEW

Cognitive impairment is associated with obesity, sarcopenia, and osteoporosis. However, no critical appraisal of the literature on the relationship between musculoskeletal deficits and cognitive impairment, focusing on the epidemiological evidence and biological mechanisms, has been published to date. Herein, we critically evaluate the literature published over the past 3 years, emphasizing interesting and important new findings, and provide an outline of future directions that will improve our understanding of the connections between the brain and the musculoskeletal system.

RECENT FINDINGS

Recent literature suggests that musculoskeletal deficits and cognitive impairment share pathophysiological pathways and risk factors. Cytokines and hormones affect both the brain and the musculoskeletal system; yet, lack of unified definitions and standards makes it difficult to compare studies. Interventions designed to improve musculoskeletal health are plausible means of preventing or slowing cognitive impairment. We highlight several musculoskeletal health interventions that show potential in this regard.

Apelin-13 attenuates depressive-like behaviors induced by chronic unpredictable mild stress via activating AMPK/PGC-1α/FNDC5/BDNF pathway

Chronic stress induces neuronal death and impairs hippocampal neurogenesis, thus leading to cognitive deficits and depressive-like behaviors. Our previous studies found that apelin-13, a novel neuropeptide, and its receptors can improve cognitive impairment and depressive-like behaviors in rats, but its mechanism remains unknown. The study aims to evaluate the underlying mechanism of apelin-13 on cognitive impairment and depressive-like behaviors. A 4-week chronic unpredictable mild stress (CUMS) is used to establish a rat model of depression. Apelin-13(2 ug/day) is administered daily to the rats during the last 1 week. Depressive-like behaviors, including tail suspension test (TST) and sucrose preference test (SPT), are performed. The cognitive functions are established by identify index of novel objects recognition test (NORT) and the number of crossing hidden platform in morris water maze (MWM). The neuronal death is measured by popidium iodide (PI) and flow cytometry. The activity of superoxide dismutase (SOD) and glutathione-peroxidase (GSH-PX) in the hippocampus are determined. The protein expressions of p-AMPK, AMPK, BDNF, FNDC5 and PGC-1α are examined. Golgi staining observed the spine dendritic arborization of the hippocampal cornu ammonis 1 (CA1) subregion. Results showed that apelin-13 improves cognitive impairment and ameliorates depressive-like behaviors. Moreover, apelin-13 significantly inhibits neuronal death via AMPK/PGC-1α/FNDC5/BDNF pathway. Taken together, apelin-13 could exert antidepressant effects via protecting neuron functions, which might be related to the activation of AMPK/PGC-1α/FNDC5/BDNF pathway.

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

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

Trehalose Attenuates Learning and Memory Impairments in Aged Rats via Overexpression of miR-181c

MicroRNAs have been recognized as important regulators of the aging process. Trehalose, a natural disaccharide, displays protective effects against neuronal impairment through several mechanisms. However, little is known about the interactive effects of aging and trehalose on behavioral function and underlying miRNA expression patterns in the hippocampus of young and old rats. Male Wistar rats were divided into four groups. Two groups of aged (24 months) and young (4 months) rats were administered 2% trehalose solution for 30 days. Two other groups of aged and young rats received regular tap water. At the end of treatment, rats were assessed for cognitive behavior using the Morris water maze test. The expression level of miR-181c and mir-34c was also measured by qRT-PCR. We found that trehalose treatment reduced learning and memory impairment in old rats compared to control old animals (p < 0.05). In contrast, cognitive performance was not significantly improved in trehalose-treated young rats in comparison with young controls (p > 0.05). We also showed that the expression level of miR-181c was significantly increased in trehalose-treated rats (p < 0.01). However, analysis of miR-34c expression level indicated no significant difference between trehalose-treated old rats and non-treated old animals (p > 0.05). Our results indicated that trehalose treatment improved learning and memory function in aged rats by targeting miR-181c. Therefore, trehalose administration may provide a therapeutic strategy to ameliorate age-associated cognitive impairment.

Irisin: A promising treatment for neurodegenerative diseases

The beneficial effects of exercise on human brain function have been demonstrated in previous studies. Myokines secreted by muscle have attracted increasing attention because of their bridging role between exercise and brain health. Regulated by PPARγ coactivator 1α, fibronectin type III domain-containing protein 5 releases irisin after proteolytic cleavage. Irisin, a type of myokine, is secreted during exercise, which induces white adipose tissue browning and relates to energy metabolism. Recently, irisin has been shown to exert a protective effect on the central nervous system. Irisin secretion triggers an increase in brain-derived neurotrophic factor levels in the hippocampus, contributing to the amelioration of cognition impairments. Irisin also plays an important role in the survival, differentiation, growth, and development of neurons. This review summarizes the role of irisin in neurodegenerative diseases and other neurological disorders. As a novel positive mediator of exercise in the brain, irisin may effectively prevent or decelerate the progress of neurodegenerative diseases in models and also improve cognitive functions. We place emphasis herein on the potential of irisin for prevention rather than treatment in neurodegenerative diseases. In ischemic diseases, irisin can alleviate the pathophysiological processes associated with stroke. Meanwhile, irisin has anxiolytic and antidepressant effects. The potential therapeutic effects of irisin in epilepsy and pain have been initially revealed. Due to the pleiotropic and beneficial properties of irisin, the possibility of irisin treating other neurological diseases could be gradually explored in the future.

Impact of Exercise and Aging on Mitochondrial Homeostasis in Skeletal Muscle: Roles of ROS and Epigenetics

Aging causes degenerative changes such as epigenetic changes and mitochondrial dysfunction in skeletal muscle. Exercise can upregulate muscle mitochondrial homeostasis and enhance antioxidant capacity and represents an effective treatment to prevent muscle aging. Epigenetic changes such as DNA methylation, histone posttranslational modifications, and microRNA expression are involved in the regulation of exercise-induced adaptive changes in muscle mitochondria. Reactive oxygen species (ROS) play an important role in signaling molecules in exercise-induced muscle mitochondrial health benefits, and strong evidence emphasizes that exercise-induced ROS can regulate gene expression via epigenetic mechanisms. The majority of mitochondrial proteins are imported into mitochondria from the cytosol, so mitochondrial homeostasis is regulated by nuclear epigenetic mechanisms. Exercise can reverse aging-induced changes in myokine expression by modulating epigenetic mechanisms. In this review, we provide an overview of the role of exercise-generated ROS in the regulation of mitochondrial homeostasis mediated by epigenetic mechanisms. In addition, the potential epigenetic mechanisms involved in exercise-induced myokine expression are reviewed.

Four weeks of light-intensity exercise enhances empathic behavior in mice: The possible involvement of BDNF

Empathy is one of the essential functions of mammals for maintaining relationships with others. Physical activity contributes to enhancing empathic attitude and behavior; however, it is remained to cover the effective intensity of exercise on mammal empathy. Here, we tested the effects of light-intensity exercise, which has beneficial effects on expressing neurotrophic factors in the brain, on empathic behavior. Eight-week-old male C57BL/6 mice were subjected to forced wheel running at light-intensity (7.0 m/min, 30 min/day, 5 days/week) for 4 weeks. Then, all mice were subjected to helping behavior to evaluate their empathic behavior. The insular cortex was collected for analyzing the expressions of mRNA and miRNA. Four weeks of light-intensity exercise enhanced helping behavior. Exercised mice exhibited higher Bdnf gene expressions in the insular cortex than sedentary mice. In addition, there was a significant positive correlation between mRNA levels of Fndc5 and Bdnf in the insular cortex. Based on miRNA sequencing, 26 out of 51 miRNAs were significantly upregulated, and 25 out of 51 miRNAs were significantly downregulated in the insular cortex of mice with exercise. There were significant correlations between 11 out of 51 miRNAs and helping behavior; miR-486a-3p, which relates to FNDC5 expression, was contained. These results imply that miR-486a-3p/Fndc5/Bdnf pathway in the insular cortex would be a possible target for treating empathy.

Differential effects of voluntary and forced exercise trainings on spatial learning ability and hippocampal biomarkers in aged female rats

This study aimed to compare the effects of voluntary and forced exercise trainings on cognitive functions and to evaluate their relationship with hippocampal synaptic proteins, neurotrophic factors and markers of oxidative damage in aged female rats. Aged female rats were randomly assigned to control, voluntary exercise training and forced exercise training groups. Voluntary or forced exercise trainings were performed for 12 weeks. At the end of the training period, cognitive functions of the animals were assessed with Morris water maze (MWM) test. After the behavioral test, hippocampus tissues were taken for the analysis of synaptophysin, acetylcholinesterase (AChE), brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), malondialdehyde (MDA), protein carbonyl (PC), glutathione (GSH) and superoxide dismutase (SOD). During the MWM test, the number of platform crossings was higher in the voluntary exercise group than in the control group (P < 0.05). In the hippocampus tissue, levels of the synaptophysin, BDNF, NGF and SOD were higher, but MDA levels were lower in the voluntary exercise group than in the control group (P < 0.05). Additionally, hippocampal AChE concentration was higher, but PC levels were lower in the both voluntary and forced exercise groups than in the control group (P < 0.05). In conclusion, voluntary exercise was more effective intervention to improve spatial learning ability in aging process. Increased neurotrophic factors, synaptic proteins, and improved oxidative damage may play a role in these positive effects.

The role of brain-derived neurotrophic factor and the neurotrophin receptor p75NTR in age-related brain atrophy and the transition to Alzheimer's disease

Alzheimer's disease is a neurodegenerative condition that is potentially mediated by synaptic dysfunction before the onset of cognitive impairments. The disease mostly affects elderly people and there is currently no therapeutic which halts its progression. One therapeutic strategy for Alzheimer's disease is to regenerate lost synapses by targeting mechanisms involved in synaptic plasticity. This strategy has led to promising drug candidates in clinical trials, but further progress needs to be made. An unresolved problem of Alzheimer's disease is to identify the molecular mechanisms that render the aged brain susceptible to synaptic dysfunction. Understanding this susceptibility may identify drug targets which could halt, or even reverse, the disease's progression. Brain derived neurotrophic factor is a neurotrophin expressed in the brain previously implicated in Alzheimer's disease due to its involvement in synaptic plasticity. Low levels of the protein increase susceptibility to the disease and post-mortem studies consistently show reductions in its expression. A desirable therapeutic approach for Alzheimer's disease is to stimulate the expression of brain derived neurotrophic factor and potentially regenerate lost synapses. However, synthesis and secretion of the protein are regulated by complex activity-dependent mechanisms within neurons, which makes this approach challenging. Moreover, the protein is synthesised as a precursor which exerts the opposite effect of its mature form through the neurotrophin receptor p75NTR. This review will evaluate current evidence on how age-related alterations in the synthesis, processing and signalling of brain derived neurotrophic factor may increase the risk of Alzheimer's disease.

Potential Protective Effect of Coenzyme Q10 on Doxorubicin-Induced Neurotoxicity and Behavioral Disturbances in Rats

The aim of this study was to investigate the potential neuroprotective efficacy of coenzyme Q10 (CoQ10) against doxorubicin (DOX) -induced behavioral disturbances in rats. Female rats were randomly assigned into 4 groups as control, CoQ10, DOX, and DOX plus CoQ10. The CoQ10 groups received CoQ10 (200 mg kg^-1) for 21 days, and the DOX groups received DOX (4 mg kg^-1) on days 7 and 14 of the study. The open field (OF) and elevated plus maze (EPM) tests were performed to assess locomotor activity and anxiety levels. Additionally, malondialdehyde (MDA), and protein carbonyl (PC) levels and acetylcholinesterase (AChE), and glutathione peroxidase (GPx) activities and total antioxidant capacity (TAC) were quantified in brain tissue. DOX administration caused alterations in locomotor activity, and anxiety-like behaviors. Moreover, DOX produced significant elevation in AChE activity . PC level and GPx activity tended to alter with DOX administration. Co-treatment with CoQ10 significantly attenuated DOX-induced behavioral alterations via improving AChE activity in the brain tissue of rats. CoQ10 treatment may be potential for the alleviation of DOX-induced behavioral disturbances. This improvement might be due to the inhibition of AChE activity.

Curcumin Relieves Chronic Unpredictable Mild Stress-Induced Depression-Like Behavior through the PGC-1α/FNDC5/BDNF Pathway

Methods

All rats were randomly divided into four groups, namely, control, CUMS, CUMS + CUR, and CUMS + CUR + SR18292 (PGC-1α inhibitor). Behavioral tests were conducted to assess the antidepressant-like effects of CUR. The expressions of PGC-1α, estrogen-related receptor alpha (ERRα), FNDC5, and BDNF were determined to investigate the regulatory effects of CUR on the PGC-1α/FNDC5/BDNF pathway. The PGC-1α inhibitor SR18292 was used to explore the role of PGC-1α in the induction of BDNF by CUR.

Results

Daily gavage of 100 mg/kg CUR successfully attenuated the abnormal behaviors induced by CUMS and effectively prevented CUMS-induced reduction of PGC-1α, ERRα, FNDC5, and BDNF expressions. CUR also enhanced PGC-1α and ERRα translocation from cytoplasm to nucleus. Furthermore, we found that CUR supplementation effectively promoted neurocyte proliferation and suppressed neuronal apoptosis induced by CUMS. Of note, the PGC-1α inhibitor SR18292 remarkably reversed the beneficial effects of CUR on depressed rats, indicating an important role of PGC-1α in the antidepressant-like effects of CUR.

Conclusion

Collectively, our data evaluating the neuroprotective action of CUR in the CUMS rats highlights the involvement of the PGC-1α/FNDC5/BDNF pathway in the antidepressant-like effects of CUR.

All roads lead to Rome - a review of the potential mechanisms by which exerkines exhibit neuroprotective effects in Alzheimer's disease

Age-related neurodegenerative disorders such as Alzheimer’s disease (AD) have become a critical public health issue due to the significantly extended human lifespan, leading to considerable economic and social burdens. Traditional therapies for AD such as medicine and surgery remain ineffective, impractical, and expensive. Many studies have shown that a variety of bioactive substances released by physical exercise (called “exerkines”) help to maintain and improve the normal functions of the brain in terms of cognition, emotion, and psychomotor coordination. Increasing evidence suggests that exerkines may exert beneficial effects in AD as well. This review summarizes the neuroprotective effects of exerkines in AD, focusing on the underlying molecular mechanism and the dynamic expression of exerkines after physical exercise. The findings described in this review will help direct research into novel targets for the treatment of AD and develop customized exercise therapy for individuals of different ages, genders, and health conditions.

Short-term running exercise alters DNA methylation patterns in neuronal nitric oxide synthase and brain-derived neurotrophic factor genes in the mouse hippocampus and reduces anxiety-like behaviors

Running exercise has beneficial effects on brain health. However, the effects of relatively short-term running exercise (STEx) on behavior, and its underlying signaling pathways, are poorly understood. In this study, we evaluated the possibility that the regulation by STEx of brain-derived neurotrophic factor (BDNF) and neuronal nitric oxide synthase (nNOS, encoded by NOS1), which are important molecules for anxiety regulation, might involve mechanisms of epigenetic modification, such as DNA methylation. C57BL/6J male mice were divided into sedentary (SED, n = 12) and STEx (EX, n = 15) groups; STEx was conducted with the mice for a duration of 11 days. STEx reduced anxiety-like behaviors, and STEx reduced Nos1α and increased Bdnf exon I and IV mRNA levels in the hippocampus. Interestingly, behavioral parameters were associated with Bdnf exon I and IV and Nos1α mRNA levels in the ventral, but not dorsal, hippocampal region. However, STEx had no effect on peroxisome proliferator-activated receptor-γ coactivator 1α (Pgc-1α) or fibronectin type III domain-containing 5 (Fndc5) mRNA levels, which are relatively long-term exercise-induced upstream regulators of BDNF. In parallel with gene expression changes, we found, for the first time, that STEx downregulated Bdnf promoter IV and upregulated Nos1 DNA methylation levels in the hippocampus, and these patterns were partially different between the dorsal and ventral regions. These findings suggest that the beneficial effects of running exercise on mood regulation may be controlled by alterations in epigenetic mechanisms, especially in the ventral hippocampus. These effects occur even after a relatively short-term period of exercise.

Exercise prevents the impairment of learning and memory in prenatally phthalate-exposed male rats by improving the expression of plasticity-related proteins

Regular exercise has been identified to facilitate neuroplasticity that maximize functional outcome after brain injuries. Brain-derived neurotrophic factor (BDNF) has emerged as a key facilitator of neuroplasticity after exercise. The activity-regulated cytoskeleton associated protein (Arc) is induced by BDNF and N-methyl-d-aspartic acid receptor (NMDAR), contributing to functional modification of neuroplasticity in the hippocampus. Meanwhile, early-life exposure to neuroendocrine disruptor di-(2-ethylhexyl)-phthalate (DEHP) is a risk factor for behavioral deficits, but the mechanisms responsible for DEHP-induced neurotoxicity are not well understood. The purpose of this study is to investigate whether hippocampal Arc expression is impaired by DEHP exposure and to examine the protective role of exercise in the prenatally DEHP-exposed male rats. Sprague Dawley dams were fed with vehicle or DEHP during gestation. The male offspring were trained to treadmill running for 5 weeks followed by examination of behavioral and biochemical outcomes. The results showed that DEHP-exposed rats exhibited impairment of spatial learning and memory as well as down-regulations of BDNF, NMDAR, Arc, and synaptophysin. Importantly, aerobic exercise during childhood-adolescence prevented the impairment of learning and memory by recovering the expressions of BDNF, NMDAR, Arc, and synaptophysin. These findings suggest that exercise may provide beneficial effects on ameliorating the impairment of neuroplasticity in the prenatally DEHP-exposed male rats at late adolescence.

Exercise Factors Released by the Liver, Muscle, and Bones Have Promising Therapeutic Potential for Stroke

Stroke is one of the leading causes of death and disability in the world. Stroke not only affects the patients, but also their families who serve as the primary caregivers. Discovering novel therapeutic targets for stroke is crucial both from a quality of life perspective as well as from a health economic perspective. Exercise is known to promote neuroprotection in the context of stroke. Indeed, exercise induces the release of blood-borne factors that promote positive effects on the brain. Identifying the factors that mediate the positive effects of exercise after ischemic stroke is crucial for the quest for novel therapies. This approach will yield endogenous molecules that normally cross the blood brain barrier (BBB) and that can mimic the effects of exercise. In this minireview, we will discuss the roles of exercise factors released by the liver such as beta-hydroxybutyrate (DBHB), by the muscle such as lactate and irisin and by the bones such as osteocalcin. We will also address their therapeutic potential in the context of ischemic stroke.

Hippocampal PGC-1α-mediated positive effects on parvalbumin interneurons are required for the antidepressant effects of running exercise

Running exercise was shown to have a positive effect on depressive-like symptoms in many studies, but the underlying mechanism of running exercise in the treatment of depression has not been determined. Parvalbumin-positive interneurons (PV⁺ interneurons), a main subtype of GABA neurons, were shown to be decreased in the brain during the depression. PGC-1α, a molecule that is strongly related to running exercise, was shown to regulate PV⁺ interneurons. In the present study, we found that running exercise increased the expression of PGC-1α in the hippocampus of depressed mice. Adult male mice with PGC-1α gene silencing in the hippocampus ran on a treadmill for 4 weeks. Then, depression-like behavior was evaluated by the behavioral tests, and the PV⁺ interneurons in the hippocampus were investigated. We found that running exercise could not improve depressive-like symptoms or increase the gene expression of PV because of the lack of PGC-1α in the hippocampus. Moreover, a lack of PGC-1α in the hippocampus decreased the number and activity of PV⁺ interneurons in the CA3 subfield of the hippocampus, and running exercise could not reverse the pathological changes because of the lack of PGC-1α. The present study demonstrated that running exercise regulates PV⁺ interneurons through PGC-1α in the hippocampus of mice to reverse depressive-like behaviors. These data indicated that hippocampal PGC-1α-mediated positive effects on parvalbumin interneurons are required for the antidepressant actions of running exercise. Our results will help elucidate the antidepressant mechanism of running exercise and identify new targets for antidepressant treatment.

The effectiveness of continuous and interval exercise preconditioning against chronic unpredictable stress: Involvement of hippocampal PGC-1α/FNDC5/BDNF pathway

Various exercise-training types are known to prevent depression, but mechanisms underlying their beneficial effects remain unknown. In the present study, the preconditioning effect of continuous and interval exercise on stress-induced depression was evaluated. Adult male Wistar rats in the exercise groups were made to run on a motorized treadmill, five sessions per week for six weeks. After that, to induce the depression model, the rats were exposed to chronic unpredictable stress for three weeks. Behavioral tests were assessed by open field, elevated plus maze, and forced swim tests. Hippocampal PGC-1α, FNDC5, and BDNF protein expression by Western blot and serum corticosterone by ELISA were detected. In the present results, after continuous and interval exercise periods, locomotor activity, the number of entries and time spent in the open arms were increased, and immobility time was significantly reduced. PGC-1α, FNDC5, and BDNF protein levels had a significant increase, and serum corticosterone did not change. Also, interval exercise training increased PGC-1α and FNDC5 more than continuous. Chronic unpredictable stress reduced the positive changes caused by exercise training, although, except FNDC5, exercise preconditioned groups experienced less significant adverse changes in most variables. These findings showed that both continuous and interval exercise preconditioning with increasing hippocampal PGC-1α, FNDC5, and BDNF proteins and improve the anxiety- and depression-like behaviors have a protective effect against chronic unpredictable stress.

α7 Nicotinic Acetylcholine Receptor Agonist PNU-282987 Ameliorates Cognitive Impairment Induced by Chronic Intermittent Hypoxia

PURPOSE

Cognitive impairment is an important complication of obstructive sleep apnea (OSA). Chronic intermittent hypoxia (CIH), the main pathophysiological characteristics of OSA, is closely related to cognitive dysfunction and may be mediated by alpha-7 nicotinic acetylcholine receptors (α7nAChR). This study investigated the effects and clarified the mechanisms of α7nAChR on the cognitive function of mice with CIH.

METHODS

Thirty CD-1 mice were randomly divided into room air (RA), CIH-2 weeks (CIH2W), and CIH-4 weeks (CIH4W) groups. Cognitive function was evaluated by novel object recognition (NOR) and Morris water maze (MWM) tests after exposure. Then, 104 CD-1 mice were exposed to CIH for 4 weeks and randomly divided into four groups: CIH4W (control), with dimethyl sulfoxide (DMSO) (sham), with α7nAChR-specific agonist PNU-282987 (PNU), and with α7nAChR-specific inhibitor methyllycaconitine and PNU-282987 (MLA+PNU). In addition to the evaluation of cognitive function, apoptotic bodies in the hippocampus were detected by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining, changes in p-CREB and BDNF were detected by immunohistochemistry, while those of ERK1/2, CREB, PGC-1α, FNDC5, and BDNF were detected by Western blotting in the hippocampal tissues of the mice.

RESULTS

Compared to the CIH2W and RA groups, the CIH4W group showed cognitive dysfunction in the NOR and MWM tests. The changes in cognitive dysfunction were alleviated by PNU-282987; furthermore, MLA pretreatment offset the effect. In hippocampal tissues, TUNEL assays showed decreased apoptotic cells, immunohistochemical staining showed increased expressions of p-CREB and BDNF. The expression levels of p-ERK1/2/t-ERK1/2, p-CREB/t-CREB, PGC-1α, FNDC5, and BDNF were increased after PNU-282987 injection.

CONCLUSION

Four weeks of CIH caused cognitive dysfunction in mice. Activating α7nAChR might ameliorate this dysfunction by upregulating the ERK1/2/CREB signaling pathway; enhancing PGC-1α, FNDC5, and BDNF expression levels; and reducing cell apoptosis in the hippocampal tissue of mice.

Long-Term Music Exposure Prevents Age-Related Cognitive Deficits in Rats Independently of Hippocampal Neurogenesis

Cognitive decline appears across aging. While some studies report beneficial effects of musical listening and practice on cognitive aging, the underlying neurobiological mechanisms remain unknown. This study aims to determine whether chronic (6 h/day, 3 times/week) and long-lasting (4-8 months) music exposure, initiated at middle age in rats (15 months old), can influence behavioral parameters sensitive to age effects and reduce age-related spatial memory decline in rats. Spontaneous locomotor, circadian rhythmic activity, and anxiety-like behavior as well as spatial working and reference memory were assessed in 14-month-old rats and then after 4 and 8 months of music exposure (19 and 23 months old, respectively). Spatial learning and reference memory data were followed up by considering cognitive status of animals prior to music exposure (14 months old) given by K-means clustering of individual Z-score. Hippocampal cell proliferation and brain-derived neurotrophic factor (BDNF) level in the hippocampus and frontal cortex were measured. Results show that music exposure differentially rescues age-related deficits in spatial navigation tasks according to its duration without affecting spontaneous locomotor, circadian rhythmic activity, and anxiety-like behavior. Hippocampal cell proliferation as well as hippocampal and frontal cortex BDNF levels was not affected by music across aging. Cognitive improvement by music in aging rats may require distinct neurobiological mechanisms than hippocampal cell proliferation and BDNF.

Donepezil attenuates injury following ischaemic stroke by stimulation of neurogenesis, angiogenesis, and inhibition of inflammation and apoptosis

Donepezil has proven to be an effective drug to reduce neuronal death and subsequently injury in neurodegenerative diseases. The current study evaluated the neuroprotective effects of donepezil in a rat model of ischaemic stroke and explored possible mechanisms which by this drug may reduce cell death. Temporary middle cerebral artery occlusion (tMCAO) was exerted for 45 min to induce ischaemic stroke. The animals were assigned into five groups: sham, control, and three groups treated with different doses of donepezil. Donepezil was intraperitoneally (IP) injected 4 h after reperfusion for 10 consecutive days. Infarct size was determined using TTC staining. The expression of proteins was evaluated using immunohistochemistry assays. Compared with the control group, infarct size was significantly reduced in tMCAO rats treated with different doses of donepezil. Moreover, our results showed significant decreased expression levels of apoptotic markers and pro-inflammatory mediators after treatment with different doses of donepezil for 10 days (P < 0.05). Likewise, significant increase of brain-derived neurotrophic factor (BDNF) and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) proteins were found in tMCAO rats treated with donepezil compared with the control group (P < 0.05). Collectively, our findings show the validity of donepezil as a new therapeutic agent for attenuation of injury following ischaemic stroke through attenuation of inflammation and improvement of mitochondrial function, neurogenesis, and angiogenesis.

High dose simvastatin and rosuvastatin impair cognitive abilities of healthy rats via decreasing hippocampal neurotrophins and irisin

BACKGROUND

Statins are cholesterol lowering drugs that decrease the risk of cardiovascular events, but they are related with a few unfavorable symptoms in skeletal muscle including myopathy, and mild to moderate fatigue. Additionally, there has been discrepancies about the impacts of statins on brain and cognition. This study aimed to examine the impacts of two different statins, lipophilic simvastatin and hydrophilic rosuvastatin on cognitive functions in normal healthy rats. Simultaneously, we investigated the alterations of neurotropins and irisin levels in hippocampus and myokine levels in skeletal muscle.

METHODS

The rats were dosed with 88 mg kg body weight^-1 day^-1 simvastatin (n = 8), 150 mg kg body weight^-1 day^-1 rosuvastatin (n = 8) or vehicle (n = 8) for 18 days via oral gavage. After that behavioral assessment was performed and hippocampus and skeletal muscle samples were taken for the analysis of neurotrophins and irisin levels.

RESULTS

Locomotion and learning and memory functions were lower, but anxiety levels were higher in the simvastatin and rosuvastatin groups than in the control group (P < 0.05). Hippocampal neurotrophins and irisin levels were lower, but skeletal muscle brain-derived neurotrophic factor (BDNF) and irisin levels were higher in the simvastatin and rosuvastatin groups than in the control group (P < 0.05).

CONCLUSION

These findings suggest that high dose simvastatin and rosuvastatin impair cognitive functions via decreasing BDNF, NGF and irisin levels in the hippocampus.

Interplay between hormones and exercise on hippocampal plasticity across the lifespan

The hippocampus is a brain structure known to play a central role in cognitive function (namely learning and memory) as well as mood regulation and affective behaviors due in part to its ability to undergo structural and functional changes in response to intrinsic and extrinsic stimuli. While structural changes are achieved through modulation of hippocampal neurogenesis as well as alterations in dendritic morphology and spine remodeling, functional (i.e., synaptic) changes can be noted through the strengthening (i.e., long-term potentiation) or weakening (i.e., long-term depression) of the synapses. While age, hormone homeostasis, and levels of physical activity are some of the factors known to module these forms of hippocampal plasticity, the exact mechanisms through which these factors interact with each other at a given moment in time are not completely understood. It is well known that hormonal levels vary throughout the lifespan of an individual and it is also known that physical exercise can impact hormonal homeostasis. Thus, it is reasonable to speculate that hormone modulation might be one of the various mechanisms through which physical exercise differently impacts hippocampal plasticity throughout distinct periods of an individual's life. The present review summarizes the potential relationship between physical exercise and different types of hormones (namely sex, metabolic, and stress hormones) and how this relationship may mediate the effects of physical activity during three distinct life periods, adolescence, adulthood, and senescence. Overall, the vast majority of studies support a beneficial role of exercise in maintaining hippocampal hormonal levels and consequently, hippocampal plasticity, cognition, and mood regulation.

The Combination Effects of Resveratrol and Swimming HIIT Exercise on Novel Object Recognition and Open-field Tasks in Aged Rats

INTRODUCTION

Resveratrol, a natural polyphenol abundant in grapes and red wine, has been reported to exert numerous beneficial health effects in the body. High-Intensity Interval Exercise (HIIT) is a form of interval training that provides improved athletic capacity and has a protective effect on health. The purpose of this study was to investigate the interactive effects of swimming HIIT and Resveratrol supplementation on behavioral function in Novel object recognition and open-field tests in aged rats.

METHODS

A total of 45 aged male Wistar rats with an age of 20 months were randomly assigned into five groups of control (C), swimming HIIT (SW-HIIT), swimming HIIT with Resveratrol supplementation (SW-HIIT-R), Resveratrol supplementation (R), and solvent of Resveratrol supplementation (SR). There was also another group that included young animals (2-month-old) and was used to compare with older animals. Swimming HIIT and Resveratrol supplementation groups performed the exercise and received Resveratrol (10 mg/kg/day, gavage) for six weeks. Novel object recognition and open-field tests were used for evaluating the behavioral functions in animals.

RESULTS

The results showed that HIIT and Resveratrol significantly improved recognition memory compared to old animals. Moreover, it seems that HIIT and Resveratrol partly could modulate anxiety-like behaviors compared to old animals in the open-field test.

Irisin increases the expression of anorexigenic and neurotrophic genes in mouse brain

BACKGROUND

Irisin, a newly discovered muscle-derived hormone, acts in different organs and tissues, improving energy homeostasis. In this study, we assessed, for the first time, the effects of intraperitoneal irisin injections on circulating levels of leptin and ghrelin, mRNA expression of the major hypothalamic appetite regulators and brain neurotrophic factors, as well as feeding behaviour in healthy mice.

METHODS

Twelve male 6-week-old C57BL/6 mice were randomized into two groups and intraperitoneally injected daily with irisin (0.5 μg/g body weight) or vehicle (phosphate-buffered saline [PBS]) for 14 days. On the last day of observation, leptin and ghrelin levels were measured with an enzyme-linked immunosorbent assay (ELISA). mRNA levels of genes of interest were analysed by quantitative reverse transcription polymerase chain reaction (qRT-PCR) in brain extracts.

RESULTS

Irisin administration did not change leptin or ghrelin serum concentrations. However, irisin injection increased CART, POMC, NPY, and BDNF mRNA levels, without affecting the mRNA expression of AgRP, orexin, PMCH, and UCP2. Finally, over the time frame of irisin treatment, body weight and feeding behaviour were unaltered.

CONCLUSIONS

These results suggest that intraperitoneal injection of irisin, although without effects on feeding behaviour and body weight, can increase the expression of anorexigenic and neurotrophic genes in mouse brain.

Does brain-derived neurotrophic factor mediate the effects of exercise on memory?

Objective: Brain-derived neurotrophic factor (BDNF) has been hypothesized as a potential mechanism through which exercise may subserve memory function. The present review specifically evaluates this hypothesis.Methods: Studies were identified using electronic databases, including PubMed, PsychInfo, Sports Discus and Google Scholar.Results: In total, 52 articles met the study criteria, and among these, 36 were conducted in an animal model and 16 among humans. Among the animal experiments, 100% of them demonstrated that chronic exercise improved memory function; 97% demonstrated an exercise-induced increase in BDNF; and among the eight evaluating BDNF as a mediator, 100% provided evidence that BDNF mediated the relationship between exercise and memory. The findings in the human studies were mixed. Among the human studies, 44% demonstrated that varying exercise protocols improved memory and increased BDNF levels, and among the studies evaluating BDNF as a mediator, 40% provided evidence that BDNF mediated the relationship between exercise and memory.Conclusion: In animal models, chronic exercise training robustly increases BDNF and improves memory performance, with reasonable evidence to also suggest that BDNF may mediate the exercise-memory interaction. These interrelationships, however, are less clear among humans. Future research among humans, in particular, is needed to evaluate the extent to which BDNF may mediate the relationship between exercise and memory.