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

Effects of exercise on brain-derived neurotrophic factor in Alzheimer's disease models: A systematic review and meta-analysis

A growing body of research examining effects of exercise on brain-derived neurotrophic factor (BDNF) in Alzheimer's disease (AD) models, while due to differences in gender, age, disease severity, brain regions examined, and type of exercise intervention, findings of available studies were conflicting. In this study, we aimed to evaluate current evidence regarding effects of exercise on BDNF in AD models. Searches were performed in PubMed, Web of Science, Cochrane, and EBSCO electronic databases, through July 20, 2023. We included studies that satisfied the following criteria: eligible studies should (1) report evidence on experimental work with AD models; (2) include an exercise group and a control group (sedentary); (3) use BDNF as the outcome indicator; and (4) be randomized controlled trials (RCTs). From 1196 search records initially identified, 36 studies met the inclusion criteria. There was a significant effect of exercise on increasing BDNF levels in AD models [standardized mean differences (SMD) = 0.98, P < 0.00001]. Subgroup analysis showed that treadmill exercise (SMD = 0.92, P< 0.0001), swimming (SMD = 1.79, P< 0.0001), and voluntary wheel running (SMD = 0.51, P= 0.04) were all effective in increasing BDNF levels in AD models. In addition, exercise significantly increased BDNF levels in the hippocampus (SMD = 0.92, P< 0.00001) and cortex (SMD = 1.56, P= 0.02) of AD models. Exercise, especially treadmill exercise, swimming, and voluntary wheel running, significantly increased BDNF levels in hippocampus and cortex of AD models, with swimming being the most effective intervention type.

Electroacupuncture activates AMPKα1 to improve learning and memory in the APP/PS1 mouse model of early Alzheimer's disease by regulating hippocampal mitochondrial dynamics

OBJECTIVE

Studies have shown that electroacupuncture (EA) can alleviate cognitive impairments from Alzheimer's disease (AD) by regulating the expression of adenosine monophosphate-activated protein kinase (AMPK), but the specific mechanism involved remains to be elucidated. Therefore, this study explores the potential mechanism by which EA improves cognitive function from the perspective of mitochondrial dynamics.

METHODS

The four-month-old transgenic mice with amyloid precursor protein (APP)/presenilin 1 (PS1) and AMPKα1-subunit conditional knockout (AMPKα1-cKO) were used for experiments. To evaluate the effects of EA treatment on cognitive function, the T-maze and Morris water maze were used. In addition, chemical exchange saturation transfer, thioflavin staining, transmission electron microscopy, mitochondrial membrane potential, and Western blotting were used to examine the potential mechanisms underlying the effects of EA on APP/PS1 mice.

RESULTS

Both APP/PS1 mice and AMPKα1-cKO mice exhibited dysfunction in mitochondrial dynamics accompanied by learning and memory impairment. Inactivation of the AMPK/peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) pathway increased pathological amyloid-β (Aβ) deposition and aggravated the dysfunction in mitochondrial dynamics. In addition, EA rescued learning and memory deficits in APP/PS1 mice by activating the AMPK/PGC-1α pathway, specifically by reducing pathological Aβ deposition, normalizing energy metabolism, protecting the structure and function of mitochondria, increasing the levels of mitochondrial fusion proteins, and downregulating the expression of fission proteins. However, the therapeutic effect of EA on cognition in APP/PS1 mice was hindered by AMPKα1 knockout.

CONCLUSION

The regulation of hippocampal mitochondrial dynamics and reduction in Aβ deposition via the AMPK/PGC-1α pathway are critical for the ability of EA to ameliorate cognitive impairment in APP/PS1 mice. Please cite this article as: Jia WW, Lin HW, Yang MG, Dai YL, Ding YY, Xu WS, Wang SN, Cao YJ, Liang SX, Wang ZF, Chen C, Liu WL. Electroacupuncture activates AMPKα1 to improve learning and memory in the APP/PS1 mouse model of early Alzheimer's disease by regulating hippocampal mitochondrial dynamics. J Integr Med. 2024; Epub ahead of print.

The protective effect of biotin supplementation and swimming training on cognitive impairment and mental symptoms in a rat model of Alzheimer's disease: A behavioral, biochemical, and histological study

Vitamin B (Vit B) plays a regulatory role in cognitive memory and learning. We examined the biochemical and behavioral effects of biotin supplementation (BS) and swimming training (ST) on Alzheimer's disease (AD), the most common type of dementia, in male rats. Sixty rats were randomly assigned to six groups: control, sham (receiving phosphate-buffered saline), AD (receiving a single injection of Aβ into the lateral ventricle), ST (for 28 days and before Aβ injection), and BS (receiving BS through oral gavage for 28 days before Aβ injection). The treatments were continued until the end of the behavioral tests. Learning and memory functions were investigated through the Morris water maze (MWM) and depression and anxiety-like behaviors were tested by elevated plus-maze (EPM) and forced swimming tests. In addition, oxidative stress biomarkers, such as total thiol groups (TTG) and malondialdehyde (MDA) in serum were assessed and histological studies were performed using brain tissues. In the AD group, Aβ increased the distance traveled and escape latency in the MWM, but co-administration of BS and ST attenuated the results of the MWM, EPM, and FST tests. Furthermore, BS decreased the litigious biochemical effects of Aβ by enhancing the levels of TTG, in addition to reducing serum MDA levels. The use of BS as a potent antioxidant improved Aβ-induced memory impairment. It attenuated oxidative stress biomarkers in the brain (number of Aβ plaques) and serum of AD rats. We provide evidence for the use of BS in neurodegenerative disorders, such as AD, to elucidate the possible mechanisms.

Moderate aerobic training enhances the effectiveness of insulin therapy through hypothalamic IGF1 signaling in rat model of Alzheimer's disease

Alzheimer's disease (AD) is a neurological condition that is connected with a decline in a person's memory as well as their cognitive ability. One of the key topics of AD research has been the exploration of metabolic causes. We investigated the effects of treadmill exercise and intranasal insulin on learning and memory impairment and the expression of IGF1, BDNF, and GLUT4 in hypothalamus. The animals were put into 9 groups at random. In this study, we examined the impact of insulin on spatial memory in male Wistar rats and analyzed the effects of a 4-week pretreatment of moderate treadmill exercise and insulin on the mechanisms of improved hypothalamic glucose metabolism through changes in gene and protein expression of IGF1, BDNF, and GLUT4. We discovered that rat given Aβ25-35 had impaired spatial learning and memory, which was accompanied by higher levels of Aβ plaque burden in the hippocampus and lower levels of IGF1, BDNF, and GLUT4 mRNA and protein expression in the hypothalamus. Additionally, the administration of exercise training and intranasal insulin results in the enhancement of spatial learning and memory impairments, the reduction of plaque burden in the hippocampus, and the enhancement of the expression of IGF1, BDNF, and GLUT4 in the hypothalamus of rats that were treated with Aβ25-35. Our results show that the improvement of learning and spatial memory due to the improvement of metabolism and upregulation of the IGF1, BDNF, and GLUT4 pathways can be affected by pretreatment exercise and intranasal insulin.

Irisin Levels in Cerebrospinal Fluid Correlate with Biomarkers and Clinical Dementia Scores in Alzheimer Disease

OBJECTIVE

Irisin, released by muscles during exercise, was recently identified as a neuroprotective factor in mouse models of Alzheimer disease (AD). In a cohort of AD patients, we studied cerebrospinal fluid (CSF) and plasma irisin levels, sex interactions, and correlations with disease biomarkers.

METHODS

Correlations between CSF and plasma irisin levels and AD biomarkers (amyloid β 1-42, hyperphosphorylated tau, and total tau [t-tau]) and Clinical Dementia Rating Scale Sum of Boxes (CDR-SOB) were analyzed in a cohort of patients with Alzheimer dementia (n = 82), mild cognitive impairment (n = 44), and subjective memory complaint (n = 20) biologically characterized according to the recent amyloid/tau/neurodegeneration classification.

RESULTS

CSF irisin was reduced in Alzheimer dementia patients (p < 0.0001), with lower levels in female patients. Moreover, CSF irisin correlated positively with Aβ42 in both female (r = 0.379, p < 0.001) and male (r = 0.262, p < 0.05) patients, and negatively with CDR-SOB (r = -0.234, p < 0.05) only in female patients. A negative trend was also observed between CSF irisin and t-tau levels in all patients (r = -0.144, p = 0.082) and in the female subgroup (r = -0.189, p = 0.084).

INTERPRETATION

The results highlight the relationship between irisin and biomarkers of AD pathology, especially in females. Our findings also offer perspectives toward the use of irisin as a marker of the AD continuum. ANN NEUROL 2024;96:61-73.

The Effects of Appropriate Perioperative Exercise on Perioperative Neurocognitive Disorders: a Narrative Review

Perioperative neurocognitive disorders (PNDs) are now considered the most common neurological complication in older adult patients undergoing surgical procedures. A significant increase exists in the incidence of post-operative disability and mortality in patients with PNDs. However, no specific treatment is still available for PNDs. Recent studies have shown that exercise may improve cognitive dysfunction-related disorders, including PNDs. Neuroinflammation is a key mechanism underlying exercise-induced neuroprotection in PNDs; others include the regulation of gut microbiota and mitochondrial and synaptic function. Maintaining optimal skeletal muscle mass through preoperative exercise is important to prevent the occurrence of PNDs. This review summarizes current clinical and preclinical evidence and proposes potential molecular mechanisms by which perioperative exercise improves PNDs, providing a new direction for exploring exercise-mediated neuroprotective effects on PNDs. In addition, it intends to provide new strategies for the prevention and treatment of PNDs.

Effects of moderate intensity training and lithium on spatial learning and memory in a rat model: The role of SIRT3 and PGC1-α expression levels and brain-derived neurotropic factor

In this study we investigated the potential synergistic effects of moderate interval training (MIT) and lithium on spatial learning and memory. Forty-two male Wistar males were classified into six groups including I: Control, II: 10 mg/kg/day IP lithium (Li10), III: MIT, IV: Li10 + MIT, V: 40 mg/kg/day IP lithium (Li40), and VI: Li40 + MIT. Then, the rats underwent Morris Water Maze (MWM) test to assess their spatial memory and learning ability. Brain-derived neurotrophic factor (BDNF) density was measured by enzyme-linked immunosorbent assay (ELISA), and the expression of PGC1 and SIRT3 were assessed via qRT-PCR. The results show that MIT improves both memory and spatial learning; but lithium alone, does not cause this. Additionally, those exposed to a combination of exercise and lithium also had improved spatial learning and memory. Finally, we observed a positive role of BDNF protein, and PGC1 gene on the effects of exercise and lithium.

The potential anti-Alzheimer's activity of Oxalis corniculata Linn. Methanolic extract in experimental rats: Role of APOE4/LRP1, TLR4/NF-κβ/NLRP3, Wnt 3/β-catenin/GSK-3β, autophagy and apoptotic cues

ETHNOPHARMACOLOGICAL RELEVANCE

Oxalis corniculata (O. corniculata) is a member of Oxalidaceae family, widely distributed in Asia, Europe, America, and Africa, used extensively as food and its traditional folkloric uses include management of epilepsy, gastric disorders, and neurodegenerative diseases, together with its use in enhancing health. Numerous pharmacological benefits of O. corniculata are linked to its anti-inflammatory and antioxidant abilities. One of the most prevalent neurodegenerative disorders is Alzheimer's disease (AD) in which neuroinflammation and oxidative stress are its main pathogenic processes.

AIM OF THE STUDY

Our research aimed to study the neuroprotective effect of the methanolic extract of Oxalis corniculata Linn. (O. corniculata ME), compared to selenium (Se) against AlCl3-induced AD.

MATERIALS AND METHODS

Forty male albino rats were allocated into four groups (Gps). Gp I a control group, the rest of the animals received AlCl3 (Gp II-Gp IV). Rats in Gp III and IV were treated with Se and O. corniculata ME, respectively.

RESULTS

The chemical profile of O. corniculata ME was studied using ultraperformance liquid chromatography-electrospray ionization-quadrupole time-of-flight mass spectrometry, allowing the tentative identification of sixty-six compounds, including organic acids, phenolics and others, cinnamic acid and its derivatives, fatty acids, and flavonoids. AlCl3 showed deterioration in short-term memory and brain histological pictures. Our findings showed that O. corniculata ME and selenium helped to combat oxidative stress produced by accumulation of AlCl3 in the brain and in prophylaxis against AD. Thus, Selenium (Se) and O. corniculata ME restored antioxidant defense, via enhancing Nrf2/HO-1 hub, hampered neuroinflammation, via TLR4/NF-κβ/NLRP3, along with dampening apoptosis, Aβ generation, tau hyperphosphorylation, BACE1, ApoE4 and LRP1 levels. Treatments also promoted autophagy and modulated Wnt 3/β-catenin/GSK3β cue.

CONCLUSIONS

It was noted that O. corniculata ME showed a notable ameliorative effect compared to Se on Nrf2/HO-1, TLR4/NF-κβ/NLRP3, APOE4/LRP1, Wnt 3/β-catenin/GSK-3β and PERK axes.

Brain and Blood Transcriptome-Wide Association Studies Identify Five Novel Genes Associated with Alzheimer's Disease

INTRODUCTION

Transcriptome-wide Association Studies (TWAS) extend genome-wide association studies (GWAS) by integrating genetically-regulated gene expression models. We performed the most powerful AD-TWAS to date, using summary statistics from cis -eQTL meta-analyses and the largest clinically-adjudicated Alzheimer's Disease (AD) GWAS.

METHODS

We implemented the OTTERS TWAS pipeline, leveraging cis -eQTL data from cortical brain tissue (MetaBrain; N=2,683) and blood (eQTLGen; N=31,684) to predict gene expression, then applied these models to AD-GWAS data (Cases=21,982; Controls=44,944).

RESULTS

We identified and validated five novel gene associations in cortical brain tissue ( PRKAG1 , C3orf62 , LYSMD4 , ZNF439 , SLC11A2 ) and six genes proximal to known AD-related GWAS loci (Blood: MYBPC3 ; Brain: MTCH2 , CYB561 , MADD , PSMA5 , ANXA11 ). Further, using causal eQTL fine-mapping, we generated sparse models that retained the strength of the AD-TWAS association for MTCH2 , MADD , ZNF439 , CYB561 , and MYBPC3 .

DISCUSSION

Our comprehensive AD-TWAS discovered new gene associations and provided insights into the functional relevance of previously associated variants.

Unveiling the interplay of AMPK/SIRT1/PGC-1α axis in brain health: Promising targets against aging and NDDs

The escalating prevalence of neurodegenerative diseases (NDDs) within an aging global population presents a pressing challenge. The multifaceted pathophysiological mechanisms underlying these disorders, including oxidative stress, mitochondrial dysfunction, and neuroinflammation, remain complex and elusive. Among these, the AMPK/SIRT1/PGC-1α pathway emerges as a pivotal network implicated in neuroprotection against these destructive processes. This review sheds light on the potential therapeutic implications of targeting this axis, specifically emphasizing the promising role of flavonoids in mitigating NDD-related complications. Expanding beyond conventional pharmacological approaches, the exploration of non-pharmacological interventions such as exercise and calorie restriction (CR), coupled with the investigation of natural compounds, offers a beacon of hope. By strategically elucidating the intricate connections within these pathways, this review aims to pave the ways for novel multi-target agents and interventions, fostering a renewed optimism in the quest to combat and manage the debilitating impacts of NDDs on global health and well-being.

Intranasal insulin intake and exercise improve memory function in amyloid-β induced Alzheimer's-like disease in rats: Involvement of hippocampal BDNF-TrkB receptor

The most prevalent type of dementia, Alzheimer's disease (AD), is a compelling illustration of the link between cognitive deficits and neurophysiological anomalies. We investigated the possible protective effect of intranasal insulin intake with exercise on amyloid-β (Aβ)-induced neuronal damage. The level of hippocampal brain-derived neurotrophic factor (BDNF) and tropomyosin-related kinase B (TrkB) were analyzed to understand the involvement of BDNF-TrkB pathway in this modulation. In this study, we induced AD-like pathology by amyloid-β (Aβ) administration. Then, we examined the impact of a 4-week pretreatment of moderate treadmill exercise and intranasal intake of insulin on working and spatial memory in male Wistar rats. We also analyzed the mechanisms of improved memory and anxiety through changes in the protein level of BDNF and TrkB. Results showed that animals received Aβ had impaired working memory, increased anxiety which were accompanied by lower protein levels of BDNF and TrkB in the hippocampus. The exercise training and intranasal insulin improved working memory deficits, decreased anxiety, and increased BDNF, and TrkB levels in the hippocampus of animals received Aβ. Our finding of improved memory performance after intranasal intake of insulin and exercise may be of significance for the treatment of memory impairments and anxiety-like behavior in AD.

Exercise mimetics: a novel strategy to combat neuroinflammation and Alzheimer's disease

Neuroinflammation is a pathological hallmark of Alzheimer's disease (AD), characterized by the stimulation of resident immune cells of the brain and the penetration of peripheral immune cells. These inflammatory processes facilitate the deposition of amyloid-beta (Aβ) plaques and the abnormal hyperphosphorylation of tau protein. Managing neuroinflammation to restore immune homeostasis and decrease neuronal damage is a therapeutic approach for AD. One way to achieve this is through exercise, which can improve brain function and protect against neuroinflammation, oxidative stress, and synaptic dysfunction in AD models. The neuroprotective impact of exercise is regulated by various molecular factors that can be activated in the same way as exercise by the administration of their mimetics. Recent evidence has proven some exercise mimetics effective in alleviating neuroinflammation and AD, and, additionally, they are a helpful alternative option for patients who are unable to perform regular physical exercise to manage neurodegenerative disorders. This review focuses on the current state of knowledge on exercise mimetics, including their efficacy, regulatory mechanisms, progress, challenges, limitations, and future guidance for their application in AD therapy.

Effect of berberine on cognitive function and β-amyloid precursor protein in Alzheimer's disease models: a systematic review and meta-analysis

Introduction: Berberine is an isoquinoline alkaloid extracted from Berberis vulgaris, which possesses a variety of pharmacological activities. Alzheimer's disease (AD) is a complex disease with multiple pathologic factors, with cognitive decline being the main manifestation of AD. The neuroprotective effects of berberine in animal models of Alzheimer's disease (AD) have been widely reported, exhibiting protective effects against risk factors associated with AD. In this study, we summarize and evaluate the effects of berberine on cognitive function and β-amyloid precursor protein in animal models of AD. Material and methods: Eligible studies were retrieved from PubMed, MEDLINE, EMBASE, Web of Science, and Cochrane Library databases up to 1 June 2023. Risk of bias was assessed by the Systematic Review Center for Laboratory Animal Experiments (SYRCLE). Statistical analyses were performed using STATA 14.0 and Review Manger 5.4 software to calculate weighted standardized mean difference (SMD) and 95% confidence intervals (CI), Morris water maze (MWM) test and β-amyloid precursor protein as outcome measures. Heterogeneity was tested using the I2 test. Sensitivity analysis and publication bias were also assessed. Results: 19 studies involving 360 animals met the inclusion criteria, and the results of the meta-analysis showed that berberine decreased escape latency (SMD = -2.19, 95% CI: (-2.50, -1.88), p < 0.00001), increased the number of platform crossings (SMD = 4.27, 95% CI (3.38, 5.17), p < 0.00001), time in the target quadrant (SMD = 5.92, 95% CI (4.43, 7.41), p < 0.00001) and APP expression (SMD = 0.73, 95% CI: (0.25, 1.21), p = 0.003). Conclusion: Berberine can regulate APP expression and improve cognitive function in animal models of AD, and the mechanism may be related to the involvement of berberine in APP processing and influence the expression of its related factors. Systematic review registration: PROSPERO, CRD42023437445.

1,5-anhydro-D-fructose induces anti-aging effects on aging-associated brain diseases by increasing 5'-adenosine monophosphate-activated protein kinase activity via the peroxisome proliferator-activated receptor-γ co-activator-1α/brain-derived neurotrophic factor pathway

5'-Adenosine monophosphate-activated protein kinase (AMPK) is a metabolic sensor that serves as a cellular housekeeper; it also controls energy homeostasis and stress resistance. Thus, correct regulation of this factor can enhance health and survival. AMPK signaling may have a critical role in aging-associated brain diseases. Some in vitro studies have shown that 1,5-anhydro-D-fructose (1,5-AF) induces AMPK activation. In the present study, we experimentally evaluated the effects of 1,5-AF on aging-associated brain diseases in vivo using an animal model of acute ischemic stroke (AIS), stroke-prone spontaneously hypertensive rats (SHRSPs), and the spontaneous senescence-accelerated mouse-prone 8 (SAMP8) model. In the AIS model, intraperitoneal injection of 1,5-AF reduced cerebral infarct volume, neurological deficits, and mortality. In SHRSPs, oral administration of 1,5-AF reduced blood pressure and prolonged survival. In the SAMP8 model, oral administration of 1,5-AF alleviated aging-related decline in motor cognitive function. Although aging reduced the expression levels of peroxisome proliferator-activated receptor-γ co-activator-1α (PGC-1α) and brain-derived neurotrophic factor (BDNF), we found that 1,5-AF activated AMPK, which led to upregulation of the PGC-1α/BDNF pathway. Our results suggest that 1,5-AF can induce endogenous neurovascular protection, potentially preventing aging-associated brain diseases. Clinical studies are needed to determine whether 1,5-AF can prevent aging-associated brain diseases.

The benefits of rehabilitation exercise in improving chronic traumatic encephalopathy: recent advances and future perspectives

Traumatic encephalopathy syndrome (TES) is used to describe the clinical manifestations of chronic traumatic encephalopathy (CTE). However, effective treatment and prevention strategies are lacking. Increasing evidence has shown that rehabilitation training could prevent cognitive decline, enhance brain plasticity, and effectively improve neurological function in neurodegenerative diseases. Therefore, the mechanisms involved in the effects of rehabilitation exercise therapy on the prognosis of CTE are worth exploring. The aim of this article is to review the pathogenesis of CTE and provide a potential clinical intervention strategy for CTE.

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.

Precious but convenient means of prevention and treatment: physiological molecular mechanisms of interaction between exercise and motor factors and Alzheimer's disease

Disproportionate to the severity of Alzheimer's disease (AD) and the huge number of patients, the exact treatment and prevention of AD is still being explored. With increasing ageing, the search for means to prevent and treat AD has become a high priority. In the search for AD, it has been suggested that exercise may be one of the more effective and less costly means of preventing and treating AD, and therefore a large part of current research is aimed at exploring the effectiveness of exercise in the prevention and treatment of AD. However, due to the complexity of the specific pathogenesis of AD, there are multiple hypotheses and potential mechanisms for exercise interventions in AD that need to be explored. This review therefore specifically summarises the hypotheses of the interaction between exercise and AD from a molecular perspective, based on the available evidence from animal models or human experiments, and explores them categorised according to the pathologies associated with AD: exercise can activate a number of signalling pathways inhibited by AD (e.g., Wnt and PI3K/Akt signalling pathways) and reactivate the effects of downstream factors regulated by these signalling pathways, thus acting to alleviate autophagic dysfunction, relieve neuroinflammation and mitigate Aβ deposition. In addition, this paper introduces a new approach to regulate the blood-brain barrier, i.e., to restore the stability of the blood-brain barrier, reduce abnormal phosphorylation of tau proteins and reduce neuronal apoptosis. In addition, this paper introduces a new concept." Motor factors" or "Exerkines", which act on AD through autocrine, paracrine or endocrine stimulation in response to movement. In this process, we believe there may be great potential for research in three areas: (1) the alleviation of AD through movement in the brain-gut axis (2) the prevention and treatment of AD by movement combined with polyphenols (3) the continued exploration of movement-mediated activation of the Wnt signalling pathway and AD.

BDNF Augmentation Using Riluzole Reverses Doxorubicin-Induced Decline in Cognitive Function and Neurogenesis

Cancer-related cognitive impairment (CRCI) considerably affects the quality of life of millions of cancer survivors. Brain-derived neurotrophic factor (BDNF) has been shown to promote survival, differentiation, and maintenance of in vivo dentate neurogenesis, and chemotherapy induces a plethora of physiological and cellular alterations, including a decline in neurogenesis and increased neuroinflammation linked with cognitive impairments. In our clinical studies, breast cancer patients treated with doxorubicin (Adriamycin®, ADR) experienced a significant reduction in the blood levels of BDNF that was associated with a higher risk of CRCI. Our past rodent studies in CRCI have also shown a significant reduction in dentate neurogenesis accompanied by cognitive impairment. In this study, using a female mouse model of ADR-induced cognitive decline, we tested the impact of riluzole (RZ), an orally active BDNF-enhancing medication that is FDA-approved for amyotrophic lateral sclerosis. ADR-treated mice receiving RZ in the drinking water for 1 month showed significant improvements in hippocampal-dependent learning and memory function (spatial recognition), fear extinction memory consolidation, and reduced anxiety-like behavior. RZ prevented chemotherapy-induced reductions of BDNF levels in the hippocampus. Importantly, RZ mitigated chemotherapy-induced loss of newly born, immature neurons, dentate neurogenesis, and neuroinflammation. In conclusion, this data provides pre-clinical evidence for a translationally feasible approach to enhance the neuroprotective effects of RZ treatment to prevent CRCI.

Exercise modulates APOE expression in brain cortex of female APOE3 and APOE4 targeted replacement mice

Apolipoprotein E (ApoE) is the main cholesterol carrier of the brain and the ε4 gene variant (APOE4) is the most prevalent genetic risk factor for Alzheimer's disease (AD), increasing risk up to 15-fold. Several studies indicate that APOE4 modulates critical factors for neuronal function, including brain-derived neurotrophic factor (BDNF) and peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α). Both proteins show exercise-induced upregulation, which is presumed to mediate many of the beneficial effects of physical activity including improved cognition; however, there is variability in results between individuals potentially in-part due to genetic variations including APOE isoform. This study aimed to determine if the two most prevalent human APOE isoforms influence adaptive responses to exercise-training. Targeted replacement mice, homozygous for either APOE3 or APOE4 were randomized into exercised and sedentary groups. Baseline locomotor function and voluntary wheel-running behavior was reduced in APOE4 mice. Exercised groups were subjected to daily treadmill running for 8 weeks. ApoE protein in brain cortex was significantly increased by exercise in both genotypes. PGC-1α mRNA levels in brain cortex were significantly lower in APOE4 mice, and only tended to increase with exercise in both genotypes. Hippocampal BDNF protein were similar between genotypes and was not significantly modulated by treadmill running. Behavioral and biochemical variations between APOE3 and APOE4 mice likely contribute to the differential risk for neurological and vascular diseases and the exercise-induced increase in ApoE levels suggests an added feature of the potential efficacy of physical activity as a preventative and therapeutic strategy for neurogenerative processes in both genotypes.

Cordyceps militaris acidic polysaccharides improve learning and memory impairment in mice with exercise fatigue through the PI3K/NRF2/HO-1 signalling pathway

Excessive exercise leads to body fatigue and destroys the balance of the oxidation/oxidation resistance system in the body, thus damaging the central nervous system and reducing learning and memory ability. Nrf2 is an important transcription factor that regulates the cell oxidative stress response. Therefore, the research and development of natural antioxidants with the effect of regulating Nrf2-related signalling pathways to improve central fatigue caused by body fatigue has application value. Methods and results: Cordyceps militaris polysaccharides were extracted, isolated and purified via DEAE-cellulose 52 and Sepharose CL-6B columns to obtain two saccharides, Cordyceps militaris acidic polysaccharides (CMPB) and CMPB-b. The results of behavioural tests showed that compared with the model group, the learning and memory abilities of the CMPB-H group (800 mg/kg) mice were remarkably improved in the dark avoidance and Morris water maze tasks (p < 0.01), and the levels of fatigue metabolites and oxidative stress in the body were obviously decreased (p < 0.01). The expression level of BDNF, PI3K, Nrf2 and HO-1 proteins in the hippocampus were significantly increased (p < 0.01). In vitro experiments, compared with the PC12 oxidative stress model group, CMPB-b high-dose group (100 μg/mL) had remarkably improved oxidative stress. CMPB-b also obviously promoted the phosphorylation of PI3K and AKT proteins (p < 0.01) and the nuclear translocation of Nrf2 (p < 0.01), and significantly increased the expression of HO-1 (p < 0.01). Conclusion: CMPB can alleviate the fatigue state of high-intensity swimming mice and improve the learning and memory impairment of exercise-fatigue mice by regulating the Nrf2-related signalling pathway. Its antioxidant active component CMPB-b exerts in vitro antioxidative neurological damage by the same mechanism. Our systematic studies provide strong supporting evidence for the future use of Cordyceps militaris acidic polysaccharides in health products to improve resistance to fatigue.

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 Alleviates Abnormal Autophagy in Brain Cells of APP/PS1 Mice by Upregulating AdipoR1 Levels

Abnormalities in autophagy are associated with Alzheimer’s disease (AD)-like lesions. Studies have shown that exercise can significantly improve AD autophagy abnormalities, but the mechanism underlying this phenomenon remains unclear. APN not only has an important regulatory effect on AD autophagy abnormalities, but also is affected by exercise. Therefore, this study aims to reveal the pathway by which exercise regulates abnormal autophagy in AD using the APN–AdipoR1 signaling pathway as an entry point. The results of the study showed that APP/PS1 double transgenic AD model mice (24 weeks) showed decreased AdipoR1 levels in the brain, abnormal autophagy, increased Aβ deposition, and increased cell apoptosis, and dendritic spines and cognitive function were reduced. Twelve weeks of aerobic exercise enhanced lysosomes and alleviated abnormal autophagy by activating the AdipoR1/AMPK/TFEB signaling pathway in the brains of AD mice, thereby alleviating Aβ deposition and its associated AD-like abnormalities. These findings suggest that the AdipoR1 plays an important role in aerobic exercise’s alleviation of abnormal autophagy in AD brain cells and alleviation of AD-like lesions.

The roles, mechanism, and mobilization strategy of endogenous neural stem cells in brain injury

Brain injury poses a heavy disease burden in the world, resulting in chronic deficits. Therapies for brain injuries have been focused on pharmacologic, small molecule, endocrine and cell-based therapies. Endogenous neural stem cells (eNSCs) are a group of stem cells which can be activated in vivo by damage, neurotrophic factors, physical factor stimulation, and physical exercise. The activated eNSCs can proliferate, migrate and differentiate into neuron, oligodendrocyte and astrocyte, and play an important role in brain injury repair and neural plasticity. The roles of eNSCs in the repair of brain injury include but are not limited to ameliorating cognitive function, improving learning and memory function, and promoting functional gait behaviors. The activation and mobilization of eNSCs is important to the repair of injured brain. In this review we describe the current knowledge of the common character of brain injury, the roles and mechanism of eNSCs in brain injury. And then we discuss the current mobilization strategy of eNSCs following brain injury. We hope that a comprehensive awareness of the roles and mobilization strategy of eNSCs in the repair of cerebral ischemia may help to find some new therapeutic targets and strategy for treatment of stroke.

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.

Hypothalamus-Muscle Parallel Induction of Metabolic Pathways Following Physical Exercise

The modern lifestyle requires less physical activity and skills during our daily routine, leading to multiple pathologies related to physical disabilities and energy accessibility. Thus, exploring the mechanisms underlying the metabolic regulation of exercise is crucial. Here, we characterized the effect of forced and voluntary endurance exercises on three key metabolic signaling pathways, sirtuins, AMPK, and mTOR, across several metabolic tissues in mice: brain, muscles, and liver. Both voluntary and forced exercises induced AMPK with higher intensity in the first. The comparison between those metabolic tissues revealed that the hypothalamus and the hippocampus, two brain parts, showed different metabolic signaling activities. Strikingly, despite the major differences in the physiology of muscles and hypothalamic tissues, the hypothalamus replicates the metabolic response of the muscle in response to physical exercise. Specifically, muscles and hypothalamic tissues showed an increase and a decrease in AMPK and mTOR signaling, respectively. Overall, this study reveals new insight into the relation between the hypothalamus and muscles, which enhances the coordination within the muscle-brain axis and potentially improves the systemic response to physical activity performance and delaying health inactivity disorders.

Neurogenic effects of rotarod walking exercise in subventricular zone, subgranular zone, and substantia nigra in MPTP-induced Parkinson's disease mice

Parkinson's disease (PD) is the second most common neurodegenerative disease after Alzheimer's disease, and its incidence is predicted to increase worldwide. Striatal dopamine depletion caused by substantia nigra (SN) degeneration is a pathological hallmark of PD and is strongly associated with cardinal motor and non-motor symptoms. Previous studies have reported that exercise increases neuroplasticity and promotes neurorestoration by increasing neurotrophic factors and synaptic strength and stimulating neurogenesis in PD. In the present study, we found that rotarod walking exercise, a modality of motor skill learning training, improved locomotor disturbances and reduced nigrostriatal degeneration in the subacute 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD. In addition, our exercise regimen improved MPTP-induced perturbation of adult neurogenesis in some areas of the brain, including the subventricular zone, subgranular zone, SN, and striatum. Moreover, rotarod walking activated the phosphorylation of adenosine monophosphate-activated protein kinase (AMPK) and induced brain-derived neurotrophic factor (BDNF) expression in these regions. The results suggest that motor skill learning training using rotarod walking improves adult neurogenesis and restores motor performance by modulating the AMPK/BDNF pathway. Therefore, our findings provide evidence for neuroprotective effects and improved neuroplasticity in PD through motor skill learning training.

Treat more than heat-New therapeutic implications of Cimicifuga racemosa through AMPK-dependent metabolic effects

BACKGROUND

Cimicifuga racemosa extracts (CRE) have obtained a "well-established use status" in the treatment of postmenopausal (i.e., climacteric) complaints, which predominantly include vasomotor symptoms such as hot flushes and sweating, as well as nervousness, irritability, and metabolic changes. Although characteristic postmenopausal complaints are known for a very long time and the beneficial effects of CRE on climacteric symptoms are well accepted, both the pathophysiology of postmenopausal symptoms and the mechanism of action of CREs are not yet fully understood. In particular, current hypotheses suggest that changes in the α-adrenergic and serotonergic signaling pathways secondary to estrogen depletion are responsible for the development of hot flushes.

PURPOSE

Some of the symptoms associated with menopause cannot be explained by these hypotheses. Therefore, we attempted to extend our classic understanding of menopause by integrating of partly age-related metabolic impairments.

METHODS

A comprehensive literature survey was performed using the PubMed database for articles published through September 2021. The following search terms were used: (cimicifuga OR AMPK) AND (hot flush* OR hot flash* OR menopaus* OR osteoporos* OR cancer OR antioxida* OR cardiovasc*). No limits were set with respect to language, and the references cited in the articles retrieved were used to identify additional publications.

RESULTS

We found that menopause is a manifestation of the general aging process, with specific metabolic changes that aggravate menopausal symptoms, which are accelerated by estrogen depletion and associated neurotransmitter dysregulation. Cimicifuga extracts with their metabolic effects mitigate climacteric symptoms but may also modulate the aging process itself. Central to these effects are effects of CRE on the metabolic key regulator, the AMP-activated protein kinase (AMPK).

CONCLUSIONS

As an extension of this effect dimension, other off-label indications may appear attractive in the sense of repurposing of this herbal treatment.

Biochanin A alleviates cognitive impairment and hippocampal mitochondrial damage in ovariectomized APP/PS1 mice

BACKGROUND

Estrogen deficiency leads to mitochondrial defects that precede Alzheimer's disease (AD)-associated pathological changes in a postmenopausal mouse model. Biochanin A (BCA) is a phytoestrogen isolated from Trifolium pratense L. used to relieve postmenopausal problems in women. In previous work, we observed that oral BCA treatment led to neuroprotection in an ovariectomized rat model. The objective of this study was to investigate whether and how BCA protects against hippocampal mitochondrial damage in a postmenopausal model of AD.

METHOD

APP/PS1 mice underwent bilateral ovariectomy and then, seven days later, received oral BCA at 20 or 40 mg/kg, or oral estradiol at 0.5 mg/kg, daily for 90 days. Sham animals were not ovariectomized and received no additional treatments. Cognitive function was examined using the passive avoidance task, novel object recognition test, and Morris water maze test. The level of circulating estrogen in vivo was assessed indirectly by measuring the wet weight of the uterus. We detected Aβ deposition and PGC-1α in brain by immunohistochemistry; p62, by immunofluorescence; and ERα, ERβ, PGC-1α, NRF1, mtTFA, Drp1, OPA1, Mfn2, Beclin1, LC3B, Pink1, and Parkin by immunoblotting.

RESULTS

BCA treatment rescued cognitive decline and reduced Aβ deposition and BACE1 expression in the hippocampus of ovariectomized APP/PS1 mice. BCA reversed the imbalance of mitochondrial dynamics caused by ovariectomy by increasing the expression of phospho-Drp1 (ser637), OPA1, and Mfn2. BCA reversed abnormal mitophagy induced by ovariectomy by increasing the expression of Beclin1, LC3B, Pink1, and Parkin, as well as by reducing the expression of p62.

CONCLUSIONS

BCA treatment enhances learning and memory abilities and alleviates AD symptoms in a postmenopausal model of AD. A possible mechanism is that BCA rescues the reduction of mitochondrial biogenesis, imbalance of mitochondrial dynamics, and abnormal mitophagy caused by ovariectomy. This study supports further research on BCA to develop treatments for postmenopausal women with AD.

AMPK and the Adaptation to Exercise

Noncommunicable diseases are chronic diseases that contribute to death worldwide, but these diseases can be prevented and mitigated with regular exercise. Exercise activates signaling molecules and the transcriptional network to promote physiological adaptations, such as fiber type transformation, angiogenesis, and mitochondrial biogenesis. AMP-activated protein kinase (AMPK) is a master regulator that senses the energy state, promotes metabolism for glucose and fatty acid utilization, and mediates beneficial cellular adaptations in many vital tissues and organs. This review focuses on the current, integrative understanding of the role of exercise-induced activation of AMPK in the regulation of system metabolism and promotion of health benefits.

Swimming exercise versus L-carnosine supplementation for Alzheimer's dementia in rats: implication of circulating and hippocampal FNDC5/irisin

Recent studies have suggested that irisin may act as a potential neurokine. Exercise and L-carnosine supplementation showed neuroprotective effects in Alzheimer's disease (AD)-like conditions. However, the regulation of irisin in the hippocampus of streptozotocin (STZ)-induced memory impairment and its relation to insulin signalling remain to be investigated. This study was designed to compare the effect of swimming exercise and L-carnosine intake on serum, CSF and hippocampal irisin in rats received intracerebroventricular (ICV) injection of STZ. Rats were recruited in swimming paradigm, received oral carnosine (100 mg/kg/day) or vehicle treated. After 5 weeks, rats were sacrificed after neurobehavioural testing. CSF and serum irisin were determined. Hippocampal tissues were used to assess expression of FNDC5/irisin, BDNF and proteins related to insulin signalling, in addition to β-amyloid peptide and phosphorylated tau protein levels. We observed decreased hippocampal, but not CSF or serum, irisin in ICV-STZ-injected rats. Exercise and carnosine intake almost normalized hippocampal FNDC5/irisin expression which was associated with reduced soluble β-amyloid peptide and phosphorylated tau protein, improved BDNF and insulin signalling proteins, with corresponding mitigated cognitive impairments. However, hippocampal FNDC5/irisin was not correlated with serum or CSF irisin levels. Histologically, both interventions ameliorated the hippocampal damage in STZ-injected rats. The current study reveals that carnosine is equivalent to exercise in reversing cognitive decline and Alzheimer's biomarkers. In both interventions, enhancement of hippocampal FNDC5/irisin and insulin signalling may be involved in mediating these neuroprotective effects.

Brothers in arms: proBDNF/BDNF and sAPPα/Aβ-signaling and their common interplay with ADAM10, TrkB, p75NTR, sortilin, and sorLA in the progression of Alzheimer's disease

Brain-derived neurotrophic factor (BDNF) is an important modulator for a variety of functions in the central nervous system (CNS). A wealth of evidence, such as reduced mRNA and protein level in the brain, cerebrospinal fluid (CSF), and blood samples of Alzheimer's disease (AD) patients implicates a crucial role of BDNF in the progression of this disease. Especially, processing and subcellular localization of BDNF and its receptors TrkB and p75 are critical determinants for survival and death in neuronal cells. Similarly, the amyloid precursor protein (APP), a key player in Alzheimer's disease, and its cleavage fragments sAPPα and Aβ are known for their respective roles in neuroprotection and neuronal death. Common features of APP- and BDNF-signaling indicate a causal relationship in their mode of action. However, the interconnections of APP- and BDNF-signaling are not well understood. Therefore, we here discuss dimerization properties, localization, processing by α- and γ-secretase, relevance of the common interaction partners TrkB, p75, sorLA, and sortilin as well as shared signaling pathways of BDNF and sAPPα.

Treadmill Exercise Prevents Decline in Spatial Learning and Memory in 3×Tg-AD Mice through Enhancement of Structural Synaptic Plasticity of the Hippocampus and Prefrontal Cortex

Alzheimer’s disease (AD) is characterized by deficits in learning and memory. A pathological feature of AD is the alterations in the number and size of synapses, axon length, dendritic complexity, and dendritic spine numbers in the hippocampus and prefrontal cortex. Treadmill exercise can enhance synaptic plasticity in mouse or rat models of stroke, ischemia, and dementia. The aim of this study was to examine the effects of treadmill exercise on learning and memory, and structural synaptic plasticity in 3×Tg-AD mice, a mouse model of AD. Here, we show that 12 weeks treadmill exercise beginning in three-month-old mice improves spatial working memory in six-month-old 3×Tg-AD mice, while non-exercise six-month-old 3×Tg-AD mice exhibited impaired spatial working memory. To investigate potential mechanisms for the treadmill exercise-induced improvement of spatial learning and memory, we examined structural synaptic plasticity in the hippocampus and prefrontal cortex of six-month-old 3×Tg-AD mice that had undergone 12 weeks of treadmill exercise. We found that treadmill exercise led to increases in synapse numbers, synaptic structural parameters, the expression of synaptophysin (Syn, a presynaptic marker), the axon length, dendritic complexity, and the number of dendritic spines in 3×Tg-AD mice and restored these parameters to similar levels of non-Tg control mice without treadmill exercise. In addition, treadmill exercise also improved these parameters in non-Tg control mice. Strengthening structural synaptic plasticity may represent a potential mechanism by which treadmill exercise prevents decline in spatial learning and memory and synapse loss in 3×Tg-AD mice.

Irisin Serum Levels and Skeletal Muscle Assessment in a Cohort of Charcot-Marie-Tooth Patients

BACKGROUND

Charcot-Marie-Tooth (CMT) indicates a group of inherited polyneuropathies whose clinical phenotypes primarily include progressive distal weakness and muscle atrophy. Compelling evidence showed that the exercise-mimetic myokine irisin protects against muscle wasting in an autocrine manner, thus possibly preventing the onset of musculoskeletal atrophy. Therefore, we sought to determine if irisin serum levels correlate with biochemical and muscle parameters in a cohort of CMT patients.

METHODS

This cohort study included individuals (N=20) diagnosed with CMT disease. Irisin and biochemical markers were quantified in sera. Skeletal muscle mass (SMM) was evaluated by bioelectric impedance analysis, muscle strength by handgrip, and muscle quality was derived from muscle strength and muscle mass ratio.

RESULTS

CMT patients (m/f, 12/8) had lower irisin levels than age and sex matched healthy subjects (N=20) (6.51 ± 2.26 vs 9.34 ± 3.23 μg/ml; p=0.003). SMM in CMT patients was always lower compared to SMM reference values reported in healthy Caucasian population matched for age and sex. Almost the totality of CMT patients (19/20) showed low muscle quality and therefore patients were evaluated on the basis of muscle strength. Irisin was lower in presence of pathological compared to normal muscle strength (5.56 ± 1.26 vs 7.67 ± 2.72 μg/ml; p=0.03), and directly correlated with the marker of bone formation P1PN (r= 0.669; 95%CI 0.295 to 0.865; p=0.002), but inversely correlated with Vitamin D (r=-0.526; 95%CI -0,791 to -0,095; p=0.017). Surprisingly, in women, irisin levels were higher than in men (7.31 ± 2.53 vs 5.31 ± 1.02 μg/ml, p=0.05), and correlated with both muscle strength (r=0.759; 95%CI 0.329 to 0.929; p=0.004) and muscle quality (r=0.797; 95%CI 0.337 to 0.950; p=0.006).

CONCLUSION

Our data demonstrate lower irisin levels in CMT patients compared to healthy subjects. Moreover, among patients, we observed, significantly higher irisin levels in women than in men, despite the higher SMM in the latter. Future studies are necessary to establish whether, in this clinical contest, irisin could represent a marker of the loss of muscle mass and strength and/or bone loss.

Exercise training ameliorates cognitive dysfunction in amyloid beta-injected rat model: possible mechanisms of Angiostatin/VEGF signaling

Vascular endothelial growth factor (VEGF) regulates angio/neurogenesis and also tightly links to the pathogenesis of Alzheimer's disease (AD). Although exercise has a beneficial effect on neurovascular function and cognitive function, the direct effect of exercise on VEGF-related signaling and cognitive deficit in AD is incompletely understood. Therefore, the purpose of this study was to investigate the protective effect of exercise on angiostatin/VEGF cascade and cognitive function in AD model rats. Wistar male rats were randomly divided into five groups: control (CON), injection of DMSO (Sham-CON), CON-exercise (sham-EX), intrahippocampal injection of Aβ (Aβ), and Aβ-exercise (Aβ-EX). Rats in EX groups underwent treadmill exercise for 4 weeks, then the cognitive function was measured by the Morris Water Maze (MWM) test. mRNA levels of hypoxia-induced factor-1α (HIF-1α), vascular endothelial growth factor (VEGF), vascular endothelial growth factor receptor 2 (VEGFR2), and angiostatin were determined in hippocampus by RT-PCR. We found that spatial learning and memory were impaired in Aβ-injected rats, but exercise training improved it. Moreover, exercise training increased the reduced mRNA expression level of VEGF signaling, including HIF1α, VEGF, and VEGFR2 in the hippocampus from Aβ-injected rats. Also, the mRNA expression level of angiostatin was elevated in the hippocampus from Aβ-injected rats, and exercise training abrogated its expression. Our findings suggest that exercise training improves cognitive function in Aβ-injected rats, possibly through enhancing VEGF signaling and reducing angiostatin.

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.

Toxic Substance-induced Hippocampal Neurodegeneration in Rodents as Model of Alzheimer’s Dementia

BACKGROUND: Alzheimer’s Dementia (AD) cases are increasing with the global elderly population. To study the part of the brain affected by AD, animal models for hippocampal degeneration are still necessary to better understand AD pathogenesis and develop treatment and prevention measures. AIM: This study was a systematic review of toxic substance-induced animal models of AD using the Morris Water Maze method in determining hippocampal-related memory impairment. Our aim was reviewing the methods of AD induction using toxic substances in laboratory rodents and evaluating the report of the AD biomarkers reported in the models. METHODS: Data were obtained from articles in the PubMed database, then compiled, categorized, and analyzed. Eighty studies published in the past 5 years were included for analysis. RESULTS AND DISCUSSION: The most widely used method was intracerebroventricular injection of amyloid-β _substances. However, some less technically challenging techniques using oral or intraperitoneal administration of other toxic substances also produce successful models. Instead of hippocampal neurodegeneration, many studies detected biomarkers of the AD pathological process while some reported inflammation, oxidative stress, neurotrophic factors, and changes of cholinergic activity. Female animals were underrepresented despite a high incidence of AD in women. CONCLUSION: Toxic substances may be used to develop AD animal models characterized with appropriate AD pathological markers. Characterization of methods with the most easy-handling techniques and more studies in female animal models should be encouraged.

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

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

The beneficial effect of exercise against Alzheimer's disease may result from improved brain glucose metabolism

The potential of physical exercise as an intervention for Alzheimer's disease (AD) has been extensively reported. In fact, a number of studies have highlighted improvements in β-amyloid (Aβ) peptide and hyperphosphorylated tau (p-tau) as critical mechanisms in exercise-induced beneficial neurological outcomes. However, no therapeutic management have been proven to be effective in humans. Recent evidence has shown that AD may be a metabolic disease related to glucose metabolic dysfunction in the brain. In this regard, some of the mechanisms responsible for the beneficial effects of physical exercise in the pathology of AD appear to be related to alterations in glucose metabolism. Therefore, we propose that the neuroprotective effect of physical exercise against AD through synergetic improvement in brain glucose metabolism and its pathophysiology. The novel perspective presented here partly explains the failure of Aβ/tau-based therapeutic approaches and provides evidence for brain glucose metabolism as a potential therapeutic target in AD.

Exercise-Induced Lactate Release Mediates Mitochondrial Biogenesis in the Hippocampus of Mice via Monocarboxylate Transporters

Regular exercise training induces mitochondrial biogenesis in the brain via activation of peroxisome proliferator-activated receptor gamma-coactivator 1α (PGC-1α). However, it remains unclear whether a single bout of exercise would increase mitochondrial biogenesis in the brain. Therefore, we first investigated whether mitochondrial biogenesis in the hippocampus is affected by a single bout of exercise in mice. A single bout of high-intensity exercise, but not low- or moderate-intensity, increased hippocampal PGC-1α mRNA and mitochondrial DNA (mtDNA) copy number at 12 and 48h. These results depended on exercise intensity, and blood lactate levels observed immediately after exercise. As lactate induces mitochondrial biogenesis in the brain, we examined the effects of acute lactate administration on blood and hippocampal extracellular lactate concentration by in vivo microdialysis. Intraperitoneal (I.P.) lactate injection increased hippocampal extracellular lactate concentration to the same as blood lactate level, promoting PGC-1α mRNA expression in the hippocampus. However, this was suppressed by administering UK5099, a lactate transporter inhibitor, before lactate injection. I.P. UK5099 administration did not affect running performance and blood lactate concentration immediately after exercise but attenuated exercise-induced hippocampal PGC-1α mRNA and mtDNA copy number. In addition, hippocampal monocarboxylate transporters (MCT)1, MCT2, and brain-derived neurotrophic factor (BDNF) mRNA expression, except MCT4, also increased after high-intensity exercise, which was abolished by UK5099 administration. Further, injection of 1,4-dideoxy-1,4-imino-D-arabinitol (glycogen phosphorylase inhibitor) into the hippocampus before high-intensity exercise suppressed glycogen consumption during exercise, but hippocampal lactate, PGC-1α, MCT1, and MCT2 mRNA concentrations were not altered after exercise. These results indicate that the increased blood lactate released from skeletal muscle may induce hippocampal mitochondrial biogenesis and BDNF expression by inducing MCT expression in mice, especially during short-term high-intensity exercise. Thus, a single bout of exercise above the lactate threshold could provide an effective strategy for increasing mitochondrial biogenesis in the hippocampus.

The Beneficial Role of Exercise on Treating Alzheimer's Disease by Inhibiting β-Amyloid Peptide

Alzheimer's disease (AD) is associated with a very large burden on global healthcare systems. Thus, it is imperative to find effective treatments of the disease. One feature of AD is the accumulation of neurotoxic β-amyloid peptide (Aβ). Aβ induces multiple pathological processes that are deleterious to nerve cells. Despite the development of medications that target the reduction of Aβ to treat AD, none has proven to be effective to date. Non-pharmacological interventions, such as physical exercise, are also being studied. The benefits of exercise on AD are widely recognized. Experimental and clinical studies have been performed to verify the role that exercise plays in reducing Aβ deposition to alleviate AD. This paper reviewed the various mechanisms involved in the exercise-induced reduction of Aβ, including the regulation of amyloid precursor protein cleaved proteases, the glymphatic system, brain-blood transport proteins, degrading enzymes and autophagy, which is beneficial to promote exercise therapy as a means of prevention and treatment of AD and indicates that exercise may provide new therapeutic targets for the treatment of AD.

miR-31-5p Promotes Oxidative Stress and Vascular Smooth Muscle Cell Migration in Spontaneously Hypertensive Rats via Inhibiting FNDC5 Expression

Oxidative stress and the migration of vascular smooth muscle cells (VSMCs) are important for vascular remodeling in a variety of vascular diseases. miR-31-5p promotes cell migration in colorectal cancer cells but inhibits cell migration in renal cell carcinoma. However, whether miR-31-5p is involved in oxidative stress and VSMC migration remains unknown. This study shows the crucial roles of miR-31-5p in oxidative stress and VSMC migration, as well as underlying mechanisms. Experiments were carried out in primary VSMCs from aortic media of Wistar–Kyoto rats (WKY) and spontaneously hypertensive rats (SHR), as well as the A7r5 cell line. Oxidative stress was assessed by NADPH oxidase (NOX) expression, NOX activity, and reactive oxygen species (ROS) production. Cell migration was evaluated with a Boyden chamber assay and a wound healing assay. The miR-31-5p mimic and inhibitor promoted and attenuated oxidative stress and cell migration in the VSMCs of SHR, respectively. A dual-luciferase reporter assay indicated that miR-31-5p targeted the 3’UTR domain of FNDC5. The miR-31-5p level was raised and FNDC5 expression was reduced in the VSMCs of SHR compared with those of WKY. The miR-31-5p mimic reduced FNDC5 expression in the A7r5 cells and the VSMCs of both WKY and SHR, while the miR-31-5p inhibitor only increased FNDC5 expression in the VSMCs of SHR. Exogenous FNDC5 attenuated not only the oxidative stress and VSMC migration in SHR but also the roles of the miR-31-5p mimic in inducing oxidative stress and VSMC migration. These results indicate that miR-31-5p promotes oxidative stress and VSMC migration in SHR via inhibiting FNDC5 expression. The increased miR-31-5p and reduced FNDC5 in the VSMCs of SHR contribute to enhanced oxidative stress and cell migration.

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.

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

This study aimed to investigate the effects and potential mechanisms of exercise combined with an enriched environment on learning and memory in rats. Forty healthy male Wistar rats (7 weeks old) were randomly assigned into 4 groups (N = 10 in each group): control (C) group, treadmill exercise (TE) group, enriched environment (EE) group and the TE + EE group. The Morris water maze (MWM) test was used to evaluate the learning and memory ability in all rats after eight weeks of exposure in the different conditions. Moreover, we employed enzyme-linked immunosorbent assay (ELISA) to determine the expression of brain-derived neurotrophic factor (BDNF) and receptor tyrosine kinase B (TrkB) in the rats. The data showed that the escape latency and the number of platform crossings were significantly better in the TE + EE group compared to the TE, EE or C groups (p < 0.05). In addition, there was upregulation of BDNF and TrkB in rats in the TE + EE group compared to those in the TE, EE or C groups (p < 0.05). Taken together, the data robustly demonstrate that the combination of TE + EE enhances learning and memory ability and upregulates the expression of both BDNF and TrkB in rats. Thus, the BDNF/TrkB signaling pathway might be modulating the effect of exercise and enriched environment in improving learning and memory ability in rats.

l-Theanine Ameliorates d-Galactose-Induced Brain Damage in Rats via Inhibiting AGE Formation and Regulating Sirtuin1 and BDNF Signaling Pathways

The maintenance of homeostasis is essential for mitigating stress and delaying degenerative diseases such as Alzheimer's disease (AD). AD is generally defined as the abnormal production of β-amyloid (Aβ) and advanced glycation end products (AGEs). The effects of l-theanine on Aβ and AGE generation were investigated in this study. Decreased AGEs and Aβ_1-42 levels were reflected by increased acetylcholine (ACh) concentration and acetylcholinesterase (AChE) activity inhibition compared to model rats. l-Theanine also inhibited nuclear factor-κB (p65) protein expression by activating sirtuin1 (SIRT1), reducing inflammatory factor expression, and downregulating the mRNA and protein expression of AGE receptors (RAGE). Superoxide dismutase 2 and catalase protein expressions were markedly upregulated by l-theanine, whereas oxidative stress-related injury was alleviated. The expression of peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α) was also found to be increased. H&E staining showed that the apoptosis of hippocampal neurons was mitigated by decreased Bax and cleaved-caspase-3 protein expression and the increase of Bcl-2 protein expression. Moreover, l-theanine increased the gene and protein expression of brain-derived neurotrophic factor (BDNF). These findings suggest that the potential preventive effects of l-theanine against AD may be attributed to its regulation of SIRT1 and BDNF proteins and its mitigation of AGEs/RAGE signaling pathways in the brain tissue of AD model rats.

Multiple Roles in Neuroprotection for the Exercise Derived Myokine Irisin

Exercise has multiple beneficial effects on health including decreasing the risk of neurodegenerative diseases. Such effects are thought to be mediated (at least in part) by myokines, a collection of cytokines and other small proteins released from skeletal muscles. As an endocrine organ, skeletal muscle synthesizes and secretes a wide range of myokines which contribute to different functions in different organs, including the brain. One such myokine is the recently discovered protein Irisin, which is secreted into circulation from skeletal muscle during exercise from its membrane bound precursor Fibronectin type III domain-containing protein 5 (FNDC5). Irisin contributes to metabolic processes such as glucose homeostasis and browning of white adipose tissue. Irisin also crosses the blood brain barrier and initiates a neuroprotective genetic program in the hippocampus that culminates with increased expression of brain derived neurotrophic factor (BDNF). Furthermore, exercise and FNDC5/Irisin have been shown to have several neuroprotective effects against injuries in ischemia and neurodegenerative disease models, including Alzheimer's disease. In addition, Irisin has anxiolytic and antidepressant effects. In this review we present and summarize recent findings on the multiple effects of Irisin on neural function, including signaling pathways and mechanisms involved. We also discuss how exercise can positively influence brain function and mental health via the "skeletal muscle-brain axis." While there are still many unanswered questions, we put forward the idea that Irisin is a potentially essential mediator of the skeletal muscle-brain crosstalk.

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.

Adenosine monophosphate activated protein kinase (AMPK) is essential for the memory improving effect of adiponectin

Adiponectin (APN) plays a major role in the regulation of insulin sensitivity and glucose homeostasis. Insulin and APN have a positive effect on memory. In this study, we examined whether the inhibition of AMPK could block the memory improving effect of APN or affect the IRS1 expression. Animal model of AD was developed by intracerebroventricular (icv) injection of 3 mg/kg streptozotocin (STZ), in 12 weeks old Wistar rats, on days 1 and 3 after cannulation. Dorsomorphin (DM) and APN (600 nM) were injected 30 and 20 min before the acquisition phase, respectively. DM was applied in 3 different doses (0.2, 2 and 20 μM). All behavioral tests were performed on days 15 and 16; the Preference Index (PI) was calculated for novel object recognition (NOR) test, while the step through latency (STL) and total time in dark compartment (TDC) were recorded and analyzed for the passive avoidance task. Relative expression of insulin receptor substrate-1 (IRS-1) protein in the hippocampus was measured by western blotting. In early retrieval test, STZ + APN treatment increased STL (P < 0.0001) and decreased TDC (P < 0.05) in comparison to STZ group, while STZ + APN + DM (2μM) caused a decrease in STL (P < 0.05) and increase in TDC (0.2μM and 2μM DM; P < 0.05). Icv injection of DM (0.2μM and 2μM) before APN decreased the PI significantly (P < 0.05) in comparison to STZ + APN group. APN treatment raised the IRS-1 expression and DM reversed this increment, significantly (P < 0.0001). It is concluded that the memory improving effect of APN is mediated, at least in part, by the AMPK pathway. APN is also able to boost insulin signaling by overexpression of IRS-1 in the hippocampus.