Exercise induces hippocampal BDNF through a PGC-1α/FNDC5 pathway

Therapeutic potential of exercise-hormone irisin in Alzheimer's disease

Irisin is a myokine that is generated by cleavage of the membrane protein fibronectin type III domain-containing protein 5 (FNDC5) in response to physical exercise. Studies reveal that irisin/FNDC5 has neuroprotective functions against Alzheimer's disease, the most common form of dementia in the elderly, by improving cognitive function and reducing amyloid-β and tau pathologies as well as neuroinflammation in cell culture or animal models of Alzheimer's disease. Although current and ongoing studies on irisin/FNDC5 show promising results, further mechanistic studies are required to clarify its potential as a meaningful therapeutic target for alleviating Alzheimer's disease. We recently found that irisin treatment reduces amyloid-β pathology by increasing the activity/levels of amyloid-β-degrading enzyme neprilysin secreted from astrocytes. Herein, we present an overview of irisin/FNDC5's protective roles and mechanisms against Alzheimer's disease.

Efficacy of exercise rehabilitation for managing patients with Alzheimer's disease

Alzheimer's disease (AD) is a progressive and degenerative neurological disease characterized by the deterioration of cognitive functions. While a definitive cure and optimal medication to impede disease progression are currently unavailable, a plethora of studies have highlighted the potential advantages of exercise rehabilitation for managing this condition. Those studies show that exercise rehabilitation can enhance cognitive function and improve the quality of life for individuals affected by AD. Therefore, exercise rehabilitation has been regarded as one of the most important strategies for managing patients with AD. Herein, we provide a comprehensive analysis of the currently available findings on exercise rehabilitation in patients with AD, with a focus on the exercise types which have shown efficacy when implemented alone or combined with other treatment methods, as well as the potential mechanisms underlying these positive effects. Specifically, we explain how exercise may improve the brain microenvironment and neuronal plasticity. In conclusion, exercise is a cost-effective intervention to enhance cognitive performance and improve quality of life in patients with mild to moderate cognitive dysfunction. Therefore, it can potentially become both a physical activity and a tailored intervention. This review may aid the development of more effective and individualized treatment strategies to address the challenges imposed by this debilitating disease, especially in low- and middle-income countries.

Adolescent treadmill exercise enhances hippocampal brain-derived neurotrophic factor (BDNF) expression and improves cognition in autism-modeled rats

Autism spectrum disorder (ASD) is a prevalent neurodevelopmental disorder characterized by repetitive behaviors and altered communication abilities. Exercise is a low-cost intervention that could improve cognitive function and improve brain plasticity mechanisms. Here, the valproic acid (VPA) model was utilized to induce ASD-like phenotypes in rodents. Animals were exercised on a treadmill and performance was evaluated on a cognitive flexibility task. Biomarkers related to exercise and plasticity regulation were quantified from the prefrontal cortex, hippocampus, and skeletal muscle. Exercised VPA animals had higher levels of hippocampal BDNF compared to sedentary VPA animals and upregulated antioxidant enzyme expression in skeletal muscle. Cognitive improvements were demonstrated in both sexes, but in different domains of cognitive flexibility. This research demonstrates the benefits of exercise and provides evidence that molecular responses to exercise occur in both the central nervous system and in the periphery. These results suggest that improving regulation of BDNF via exercise, even at low intensity, could provide better synaptic regulation and cognitive benefits for individuals with ASD.

Peripheral to brain and hippocampus crosstalk induced by exercise mediates cognitive and structural hippocampal adaptations

Endurance exercise leads to robust increases in memory and learning. Several exercise adaptations occur to mediate these improvements, including in both the hippocampus and in peripheral organs. Organ crosstalk has been becoming increasingly more present in exercise biology, and studies have shown that peripheral organs can communicate to the hippocampus and mediate hippocampal changes. Both learning and memory as well as other hippocampal functional-related changes such as neurogenesis, cell proliferation, dendrite morphology and synaptic plasticity are controlled by these exercise responsive peripheral proteins. These peripheral factors, also called exerkines, are produced by several organs including skeletal muscle, liver, adipose tissue, kidneys, adrenal glands and circulatory cells. Previous reviews have explored some of these exerkines including muscle-derived irisin and cathepsin B (CTSB), but a full picture of peripheral to hippocampus crosstalk with novel exerkines such as selenoprotein 1 (SEPP1) and platelet factor 4 (PF4), or old overlooked ones such as lactate and insulin-like growth factor 1 (IGF-1) is still missing. We provide 29 different studies of 14 different exerkines that crosstalk with the hippocampus. Thus, the purpose of this review is to explore peripheral exerkines that have shown to exert hippocampal function following exercise, demonstrating their particular effects and molecular mechanisms in which they could be inducing adaptations.

Plasma irisin associations with executive function among children in a prospective cohort

OBJECTIVE

To examine the longitudinal associations between irisin and executive function among children, as well as the sex difference in this correlation.

METHODS

The study involving 330 children aged 6-10 years conducted in Guangzhou, China. Baseline surveys and fasting blood samples were collected in 2017. Plasma irisin concentration was measured using Enzyme-Linked Immunosorbent Assay (ELISA). Executive function was assessed by the Behavior Rating Inventory of Executive Function (BRIEF) scale in 2017 and followed up after 2 years. Multivariable linear regression was used for association analysis.

RESULTS

The plasma irisin concentration was 9.04±2.18 ng/mL. There was no statistical difference in plasma irisin and change values of BRIEF T-scores between boys and girls. No significant associations were found between plasma irisin and change values of BRIEF T-scores (P > 0.05) in the overall sample. Further subgroup analyses according to sex revealed that plasma irisin was negatively associated with change values of behavior regulation index (BRI, β=-0.521, 95 %CI: -1.036 ∼ -0.006), emotional control (β=-0.649, 95 %CI: -1.249 ∼ -0.049), working memory T-scores (β=-0.774, 95 %CI: -1.350 ∼ -0.199) in girls. Moreover, we firstly identified a sex effect modification in the association of plasma irisin with change values of working memory T-score (Pinterference=0.012).

CONCLUSIONS

Higher irisin concentration was associated with better executive function performance in girls. Further studies that included populations in other regions or countries are needed to confirm these findings.

Neurophysiological effects of acute aerobic exercise in young adults: a systematic review and meta-analysis

Evidence continues to accumulate that acute aerobic exercise (AAE) impacts neurophysiological excitability as measured by transcranial magnetic stimulation (TMS). Yet, uncertainty exists about which TMS measures are modulated after AAE in young adults. The influence of AAE intensity and duration of effects are also uncertain. This pre-registered meta-analysis (CRD42017065673) addressed these uncertainties by synthesizing data from 23 studies (including 474 participants) published until February 2024. Meta-analysis was run using a random-effects model and Hedge's g used as effect size. Our results demonstrated a decrease in short-interval intracortical inhibition (SICI) following AAE (g = 0.27; 95 % CI [0.16-0.38]; p <.0001), particularly for moderate (g = 0.18; 95 % CI [0.05-0.31]; p <.01) and high (g = 0.49; 95 % CI [0.27-0.71]; p <.0001) AAE intensities. These effects remained for 30 minutes after AAE. Additionally, increased corticospinal excitability was only observed for high intensity AAE (g = 0.28; 95 % CI, [0.07-0.48]; p <.01). Our results suggest potential mechanisms for inducing a more susceptible neuroplastic environment following AAE.

Exercise-produced irisin effects on brain-related pathological conditions

Exercise increases peroxisome proliferator-activated receptor-gamma coactivator 1-alpha (PGC-1α) expression, which in turn causes the fibronectin type III domain containing 5 (FNDC5) protein to be produced. This protein is then cleaved, primarily in skeletal muscle fibers, to produce irisin. When the mature FNDC5 is cleaved by proteases, Irisin - which is the fibronectin III domain without the signal sequence - is released. Resistance, aerobic, and high-intensity interval training (HIIT) are recognized as forms of physical exercise that raise irisin levels, and insulin receptor phosphorylation in tyrosine residues, favoring an increase in the activity of the insulin-dependent pathway (PI3K pathway) and assisting in the fight against insulin resistance, inflammation, and cognitive decline. Irisin may represent a promising option for the therapeutic targeting in several brain-related pathological conditions, like Alzheimer's disease (AD), Parkinson's disease (PD), epilepsy, type 2 diabetes, and obesity. Exercise protocols are healthy and inexpensive interventions that can help find cellular and molecular changes in several brain-related pathological conditions. Here, it was reviewed what is known about exercise-produced irisin studies involving AD, PD, epilepsy, type 2 diabetes, and obesity.

Hypocretin-1/Hypocretin Receptor 1 Regulates Neuroplasticity and Cognitive Function through Hippocampal Lactate Homeostasis in Depressed Model

Cognitive dysfunction is not only a common symptom of major depressive disorder, but also a more common residual symptom after antidepressant treatment and a risk factor for chronic and recurrent disease. The disruption of hypocretin regulation is known to be associated with depression, however, their exact correlation is remains to be elucidated. Hypocretin-1 levels are increased in the plasma and hypothalamus from chronic unpredictable mild stress (CUMS) model mice. Excessive hypocretin-1 conducted with hypocretin receptor 1 (HCRTR1) reduced lactate production and brain-derived neurotrophic factor (BDNF) expression by hypoxia-inducible factor-1α (HIF-1α), thus impairing adult hippocampal neuroplasticity, and cognitive impairment in CUMS model. Subsequently, it is found that HCRTR1 antagonists can reverse these changes. The direct effect of hypocretin-1 on hippocampal lactate production and cognitive behavior is further confirmed by intraventricular injection of hypocretin-1 and microPET-CT in rats. In addition, these mechanisms are further validated in astrocytes and neurons in vitro. Moreover, these phenotypes and changes in molecules of lactate transport pathway can be duplicated by specifically knockdown of HCRTR1 in hippocampal astrocytes. In summary, the results provide molecular and functional insights for involvement of hypocretin-1-HCRTR1 in altered cognitive function in depression.

Intracerebroventricular administration of the exercise hormone irisin or acute strenuous exercise alleviates epileptic seizure-induced neuroinflammation and improves memory dysfunction in rats

BACKGROUND

Status epilepticus is a common and potentially life-threatening neurological emergency with a high risk for cognitive and neurobiological impairment. Our aim was to evaluate the neuroprotective effects of centrally administered irisin and acute exhausting exercise against oxidative brain injury and memory dysfunction due to a pentylenetetrazole (PTZ)-induced single seizure. Male Sprague Dawley rats with intracerebroventricular (icv) cannulas were randomly divided into intraperitoneally (ip) saline-injected control and PTZ-injected (45 mg/kg) seizure groups. Both the control and PTZ groups were then treated with irisin (7.5 µg/kg, 2 µl, icv), saline (2 µl, icv) or were forced to an acute bout of strenuous exercise before the ip injection of saline (control) or PTZ. Seizures were evaluated using the Racine score. To evaluate memory performance, a passive avoidance test was performed before and after PTZ injection. Following euthanasia at the 24th hour of seizure induction, brain tissues were removed for histopathological examination and for evaluating oxidative damage, antioxidant capacity, and neurotransmitter levels.

RESULTS

Glutamate/GABA imbalance observed in PTZ rats was corrected by irisin administration (p < 0.001/p < 0.01), while irisin prevented the generation of reactive oxygen species and lipid peroxidation (p < 0.05 - 0.001) and replenished the antioxidant catalase and glutathione levels (p < 0.01-0.01) in the cerebral tissue, and reduced the histologically evident neuronal injury due to a single seizure (p < 0.05 - 0.01). Irisin also delayed the onset of seizures (p < 0.05) and improved memory dysfunction (p < 0.05), but did not affect the severity of seizures. The acute exhaustive swimming exercise completed before PTZ-seizure depressed glutamate level (p < 0.001), maintained the oxidant/antioxidant balance, alleviated neuronal injury (p < 0.05 - 0.01) and upregulated cerebral BDNF expression (p < 0.05).

CONCLUSION

In conclusion, acute high-intensity exercise or exogenously administered irisin provides neuroprotection by maintaining the balance of excitatory/inhibitory neurotransmitters and oxidant/antioxidant systems.

Aerobic exercise improves cognitive flexibility and modulates regional volume changes in a rat model of autism

Gestational exposure to valproic acid (VPA) is a risk factor for autism spectrum disorder (ASD). Rodents exposed to VPA in utero display common features of ASD, including volumetric dysregulation in higher-order cognitive regions like the medial prefrontal cortex (mPFC), the anterior cingulate cortex (ACC), and the hippocampus. Exercise has been shown in elderly populations to boost cognition and to buffer against brain volume losses with age. This study employed an adolescent treadmill exercise intervention to facilitate cognitive flexibility and regional brain volume regulation in rats exposed to VPA during gestation. It was found that exercise improved performance on extra-dimensional shifts of attention on a set-shifting task, which is indicative of improved cognitive flexibility. Exercise decreased frontal cortex volume in females, whereas in males exercise increased the ventral hippocampus. These findings suggest that aerobic exercise may be an effective intervention to counteract the altered development of prefrontal and hippocampal regions often observed in ASD.

Does the liver facilitate aging-related cognitive impairment: Conversation between liver and brain during exercise?

Liver, an important regulator of metabolic homeostasis, is critical for healthy brain function. In particular, age-related neurodegenerative diseases seriously reduce the quality of life for the elderly. As population aging progresses rapidly, unraveling the mechanisms that effectively delay aging has become critical. Appropriate exercise is reported to improve aging-related cognitive impairment. Whereas current studies focused on exploring the effect of exercise on the aging brain itself, ignoring the persistent effects of peripheral organs on the brain through the blood circulation. The aim of this paper is to summarize the communication and aging processes of the liver and brain and to emphasize the metabolic mechanisms of the liver-brain axis about exercise ameliorating aging-related neurodegenerative diseases. A comprehensive understanding of the potential mechanisms about exercise ameliorating aging is critical for improving adaptation to age-related brain changes and formulating effective interventions against age-related cognitive decline.

Exercise epigenetics is fueled by cell bioenergetics: Supporting role on brain plasticity and cognition

Exercise has the unique aptitude to benefit overall health of body and brain. Evidence indicates that the effects of exercise can be saved in the epigenome for considerable time to elevate the threshold for various diseases. The action of exercise on epigenetic regulation seems central to building an "epigenetic memory" to influence long-term brain function and behavior. As an intrinsic bioenergetic process, exercise engages the function of the mitochondria and redox pathways to impinge upon molecular mechanisms that regulate synaptic plasticity and learning and memory. We discuss how the action of exercise uses mechanisms of bioenergetics to support a "epigenetic memory" with long-term implications for neural and behavioral plasticity. This information is crucial for directing the power of exercise to reduce the burden of neurological and psychiatric disorders.

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 relevance of BDNF for neuroprotection and neuroplasticity in multiple sclerosis

Background

Neuroplasticity as a mechanism to overcome central nervous system injury resulting from different neurological diseases has gained increasing attention in recent years. However, deficiency of these repair mechanisms leads to the accumulation of neuronal damage and therefore long-term disability. To date, the mechanisms by which remyelination occurs and why the extent of remyelination differs interindividually between multiple sclerosis patients regardless of the disease course are unclear. A member of the neurotrophins family, the brain-derived neurotrophic factor (BDNF) has received particular attention in this context as it is thought to play a central role in remyelination and thus neuroplasticity, neuroprotection, and memory.

Objective

To analyse the current literature regarding BDNF in different areas of multiple sclerosis and to provide an overview of the current state of knowledge in this field.

Conclusion

To date, studies assessing the role of BDNF in patients with multiple sclerosis remain inconclusive. However, there is emerging evidence for a beneficial effect of BDNF in multiple sclerosis, as studies reporting positive effects on clinical as well as MRI characteristics outweighed studies assuming detrimental effects of BDNF. Furthermore, studies regarding the Val66Met polymorphism have not conclusively determined whether this is a protective or harmful factor in multiple sclerosis, but again most studies hypothesized a protective effect through modulation of BDNF secretion and anti-inflammatory effects with different effects in healthy controls and patients with multiple sclerosis, possibly due to the pro-inflammatory milieu in patients with multiple sclerosis. Further studies with larger cohorts and longitudinal follow-ups are needed to improve our understanding of the effects of BDNF in the central nervous system, especially in the context of multiple sclerosis.

Factors associated with perceived cognitive function in breast cancer patients treated with chemotherapy: A multicenter cross-sectional study

PURPOSE

This study aimed to investigate the factors associated with perceived cognitive function among breast cancer patients treated with chemotherapy in China.

METHODS

The study was a multicenter cross-sectional design. Data were collected from 10 public hospitals in China between April 2022 and February 2023. A total of 741 participants completed questionnaires assessing sociodemographic and medical characteristics, perceived cognitive function, sleep quality, fatigue, anxiety, and depression. Hierarchical multiple regression analysis was used to assess the determinants of cognitive function.

RESULTS

The hierarchical multiple regression model accounted for 31.5% of variation in perceived cognitive function (sociodemographic 4.5%; medical 6.6%; exercise frequency 6.6%; sleep quality 2.1%; fatigue 2.8%; anxiety combined with depression 9.0%). Education level, chemotherapy type, number of chemotherapy cycles, and cyclophosphamide drug use were significant predisposing factors of perceived cognitive function (p < 0.001). Exercising ≥3 times/week (p < 0.001) was a significant factor positively influencing perceived cognitive function, meanwhile, anxiety (p < 0.001) and depression (p < 0 0.001) were negative factors.

CONCLUSION

Our findings suggest that patients with low education levels, postoperative chemotherapy, cyclophosphamide treatment, and a greater number of chemotherapy cycles need more assessment. Sedentary patients, those who have never exercised, and those with anxiety or depression all showed greater cognitive decline. By identifying susceptible populations, encouraging regular exercise, and addressing anxiety and depression, healthcare professionals can contribute significantly to prevent patients' cognitive decline throughout chemotherapy.

The effects of whole-body vibration therapy on immune and brain functioning: current insights in the underlying cellular and molecular mechanisms

Whole-body vibration (WBV) therapy is a way of passive exercise in which subjects are exposed to mild and well-controlled mechanical vibrations through a vibrating platform. For a long time, studies have focused on the effects and applications of WBV to enhance musculoskeletal performance in athletes and patients suffering from musculoskeletal disorders. Recent evidence points toward the positive effect of WBV on the brain and its therapeutic potential in brain disorders. Research being done in the field gradually reveals cellular and molecular mechanisms underlying WBV affecting the body and brain. Particularly, the influence of WBV on immune and brain function is a growing field that warrants an up-to-date and integrated review. Immune function is closely intertwined with brain functioning and plays a significant role in various brain disorders. Dysregulation of the immune response is linked to conditions such as neuroinflammation, neurodegenerative diseases, and mood disorders, highlighting the crucial connection between the immune system and the brain. This review aims to explore the impact of WBV on the cellular and molecular pathways involved in immune and brain functions. Understanding the effects of WBV at a cellular and molecular level will aid in optimizing WBV protocols to improve its therapeutic potential for brain disorders.

Integrating analysis of mRNA expression profiles indicates Sgk1 as a key mediator in muscle-brain crosstalk during resistance exercise

Abundant evidence has shown the protective effect of aerobic exercise on central neuronal system, however, research about resistance exercise remains limited. To evaluate the effect and potential molecular mechanisms of resistance exercise in improving cognition and mental health, three-month-old male C57BL/6J mice underwent resistance training for five weeks. Body parameters, cognitive performance and synaptic plasticity were then assessed. In both groups, total RNA from the frontal cortex, hippocampus and gastrocnemius was isolated and sequenced, GO term and KEGG analysis were performed to identify molecular mechanisms. The results from RNA sequencing were then verified by RT-PCR. Our data found that mice in training group showed reduced anxiety-like behavior and better spatial memory. Accordingly, resistance exercise specifically increased the number of thin spines without affecting the number of other kind of spines. mRNA sequence analysis showed that resistance exercise induced differential expression of hundreds of genes in the above three tissues. KEGG analysis indicated the FoxO signaling pathway the most significant changed pathway throughout the brain and muscle. GO terms analysis showed that Sgk1 was enriched in the three key cognition related BP, including long-term memory, learning or memory and memory, and the expression level of Sgk1 was positive related with cognitive performance in the water maze. In conclusion, resistance exercise improved the mental health, cognition and synaptic plasticity of mice. Integrating analysis of mRNA expression profiles in frontal cortex, hippocampus and muscle reveals Sgk1 as the key mediator in brain-muscle crosstalk.

Effects of Intermittent Hypoxia Protocols on Cognitive Performance and Brain Health in Older Adults Across Cognitive States: A Systematic Literature Review

Background

The rise in the aging population highlights the need to address cognitive decline and neurodegenerative diseases. Intermittent hypoxia (IH) protocols show promise in enhancing cognitive abilities and brain health.

Objective

This review evaluates IH protocols' benefits on cognition and brain health in older adults, regardless of cognitive status.

Methods

A systematic search following PRISMA guidelines was conducted across four databases (PubMed, Scopus, Web of Science, and Cochrane Library) and two registers, covering records from inception to May 2024 (PROSPERO: CRD42023462177). Inclusion criteria were: 1) original research with quantitative details; 2) studies involving older adults, with or without cognitive impairment; 3) studies including IH protocols; 4) articles analyzing cognition and brain health in older adults.

Results

Seven studies and five registered trials met the criteria. Findings indicate that Intermittent Hypoxia Training (IHT) and Intermittent Hypoxia-Hyperoxia Training (IHHT) improved cognitive functions and brain health. Intermittent Hypoxic Exposure (IHE) improved cerebral tissue oxygen saturation, middle cerebral arterial flow velocity, and cerebral vascular conductance, particularly in cognitively impaired populations. IHT and IHHT had no significant effect on BDNF levels. There is a lack of studies on IHHE in older adults with and without cognitive impairment.

Conclusions

IH protocols may benefit cognition regardless of cognitive status. IHT and IHE positively affect cerebral outcomes, with all protocols having limited effects on BDNF levels. Future research should standardize IH protocols, investigate long-term cognitive effects, and explore neuroprotective biomarkers. Combining these protocols with physical exercise across diverse populations could refine interventions and guide targeted therapeutic strategies.

Can exercise benefits be harnessed with drugs? A new way to combat neurodegenerative diseases by boosting neurogenesis

Adult hippocampal neurogenesis (AHN) is affected by multiple factors, such as enriched environment, exercise, ageing, and neurodegenerative disorders. Neurodegenerative disorders can impair AHN, leading to progressive neuronal loss and cognitive decline. Compelling evidence suggests that individuals engaged in regular exercise exhibit higher production of proteins that are essential for AHN and memory. Interestingly, specific molecules that mediate the effects of exercise have shown effectiveness in promoting AHN and cognition in different transgenic animal models. Despite these advancements, the precise mechanisms by which exercise mimetics induce AHN remain partially understood. Recently, some novel exercise molecules have been tested and the underlying mechanisms have been proposed, involving intercommunications between multiple organs such as muscle-brain crosstalk, liver-brain crosstalk, and gut-brain crosstalk. In this review, we will discuss the current evidence regarding the effects and potential mechanisms of exercise mimetics on AHN and cognition in various neurological disorders. Opportunities, challenges, and future directions in this research field are also discussed.

Acute Effects of High-Intensity Resistance Exercise on Recognition of Relational Memory, Lactate, and Serum and Plasma Brain-Derived Neurotrophic Factor

ABSTRACT

Baumgartner, NW, Belbis, MD, Kargl, C, Holmes, MJ, Gavin, TP, Hirai, DM, and Kao, S-C. Acute effects of high-intensity resistance exercise on recognition of relational memory, lactate, and serum and plasma brain-derived neurotrophic factor. J Strength Cond Res XX(X): 000-000, 2024-Acute aerobic exercise improves memory, but this phenomenon is understudied in response to resistance exercise (RE) despite evidence that RE-induced increases in lactate and brain-derived neurotrophic factor (BDNF) play mechanistic roles in memory performance. To determine the acute effect of RE on lactate, BDNF, and their associations with object and relational memory, blood lactate, and serum and plasma BDNF were taken from 36 adults (average age 23.64 ± 3.89 years; 18 woman) before and immediately after 42 minutes of high-intensity RE and a rest condition on counterbalanced days. Subjects then immediately studied a series of paired objects and completed object and relational recognition tasks. Results revealed a condition by trial interaction, previously studied objects were remembered less accurately following RE (d = 0.66) but recognition occurred faster (d = 0.28), indicating a speed-accuracy tradeoff following RE. There was no effect of either intervention on relational recognition performance. Lactate (d = 3.68) and serum BDNF (d = 0.74) increased following RE, whereas there was no time-related change in lactate and serum BDNF following rest. However, changes in lactate and BDNF did not predict any measures of object (rs < 0.25, ps > 0.16) or relation recognition (rs < 0.28, ps > 0.13). Collectively, these findings suggest that acute high-intensity RE selectively improves the processing speed of recognizing objects at the cost of less accurate recognition of previously studied objects. Furthermore, changes in object and relational memory performance are unlikely driven by acute increases in lactate or BDNF following high-intensity RE.

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.

FNDC5/Irisin in dementia and cognitive impairment: update and novel perspective

Epidemiological surveys show that the incidence of age-related dementia and cognitive impairment is increasing and it has been a heavy burden for society, families, and healthcare systems, making the preservation of cognitive function in an increasingly aging population a major challenge. Exercise is beneficial for brain health, and FDNC5/irisin, a new exercise-induced myokine, is thought to be a beneficial mediator to cognitive function and plays an important role in the crosstalk between skeletal muscle and brain. This review provides a critical assessment of the recent progress in both fundamental and clinical research of FDNC5/irisin in dementia and cognitive impairment-related disorders. Furthermore, we present a novel perspective on the therapeutic effectiveness of FDNC5/irisin in alleviating these conditions.

The therapeutic potential of irisin to mitigate the risk of metabolic syndrome in postmenopausal women

Oestradiol withdrawal at menopause predisposes women to metabolic syndrome, a cluster of interrelated conditions including obesity, insulin resistance, dyslipidaemia and hypertension that together confer an increased risk of developing type 2 diabetes mellitus and cardiovascular disease. Hormone replacement therapies are commonly used to treat acute symptoms of the perimenopausal period, and whilst they have been associated with metabolic improvements in many studies, long-term use is considered unviable. Novel approaches are required to mitigate the risk of postmenopausal metabolic syndrome. In 2012, the exercise-inducible myokine irisin was isolated from the skeletal muscle of mice and identified to have anti-obesity and antidiabetic effects in vivo. Irisin is now recognised to exert pleiotropic action on cognitive, bone and metabolic health. There is accumulating evidence from in vitro and in vivo rodent studies that irisin can mitigate each component condition of metabolic syndrome. In postmenopausal women, independent associations have been observed between (a) exercise and plasma irisin concentration and (b) plasma irisin concentration and reduced incidence of metabolic syndrome. To date, however, no study has considered the mechanistic basis by which irisin, whether exercise-induced or exogenously administered, could reduce the incidence or severity of metabolic syndrome in postmenopausal women. This review aims to analyse the literature concerning the metabolic actions of irisin, with a focus on its therapeutic potential for metabolic syndrome driven by a state of oestradiol depletion. It evaluates the practicality of exercise as a therapy and discusses other irisin-based therapeutic strategies that may alleviate postmenopausal metabolic syndrome. Finally, it highlights areas where future research is required to advance knowledge of irisin's biological action such that it could be considered a viable candidate for clinical application.

Dose-response effects of physical exercise standardized volume on peripheral biomarkers, clinical response, and brain connectivity in Parkinson's disease: a prospective, observational, cohort study

Background

Exercise has been proposed as the "Universal Prescription for Parkinson's Disease"; however, the specificity of exercise dose in terms of frequency, intensity, duration, and type to be prescribed remains to be elucidated. The 2018 US updated guidelines and WHO Guidelines on Physical Activity and Sedentary Behavior recommend older adults (> 65+ years) to achieve weekly minimal activity levels, indicating the intensity of aerobic exercise as the metabolic equivalent of task and duration as minutes/week (150-300 min/week at a moderate intensity of 3-5.9 MET- or 75-150 min/week of a vigorous intensity of ≥6 MET). Translating these recommendations to PD patients, the study aimed to assess the dose-response effects of standardized volume of structured exercise, measured as METs-minutes/week (weekly energy expenditure) of two different rehabilitation settings to quantify the change in neurotrophic factors. The exercise-induced benefits between the two rehabilitation settings will be evaluated based on motor and non-motor symptoms, kinematic parameters of gait, cognitive function, quality of life, and cortical activity and brain connectivity.

Methods

METEX-PD is a pilot, prospective, observational, cohort study. The study will enroll consecutively thirty (N = 30) participants with mild-to-moderate Parkinson's disease diagnosis to be assigned to a non-intensive or intensive rehabilitation group. The non-intensive rehabilitation group will achieve a range of 180-270 METs-min/week (90 min/week of low-intensity aerobic exercise, 2-3 METs), while the intensive rehabilitation group will exercise at 1350-1980 METs-min/week (225 min/week of high-intensity aerobic exercise, 6-8.8 METs). The METEX-PD trial will last 12 weeks, including 4 weeks of aerobic training program and two follow-ups. Assessments will be performed at baseline (T0), at the end of the exercise program (T1-end of the program), and 4- and 8 weeks after the end of the training program (FU-1 and FU-2). The primary outcome is the change from baseline in peripheral blood BDNF levels. Secondary outcomes are differences in peripheral biomarkers, functional-motor assessments, clinical-functional evaluations, and brain imaging.

Conclusion

METEX-PD trial will enable us to estimate the change in BDNF levels and other peripheral biomarkers under precise exercise-induced energy expenditure. The primary results of the METEX-PD study will allow the development of a larger multicenter randomized controlled trial to investigate the molecular pathways inducing the change in selected neurotrophic factors, such as BDNF, IGF-1, or irisin, and the downstream mechanisms of neuroplasticity in PD patients.

Skeletal muscle: molecular structure, myogenesis, biological functions, and diseases

Skeletal muscle is an important motor organ with multinucleated myofibers as its smallest cellular units. Myofibers are formed after undergoing cell differentiation, cell-cell fusion, myonuclei migration, and myofibril crosslinking among other processes and undergo morphological and functional changes or lesions after being stimulated by internal or external factors. The above processes are collectively referred to as myogenesis. After myofibers mature, the function and behavior of skeletal muscle are closely related to the voluntary movement of the body. In this review, we systematically and comprehensively discuss the physiological and pathological processes associated with skeletal muscles from five perspectives: molecule basis, myogenesis, biological function, adaptive changes, and myopathy. In the molecular structure and myogenesis sections, we gave a brief overview, focusing on skeletal muscle-specific fusogens and nuclei-related behaviors including cell-cell fusion and myonuclei localization. Subsequently, we discussed the three biological functions of skeletal muscle (muscle contraction, thermogenesis, and myokines secretion) and its response to stimulation (atrophy, hypertrophy, and regeneration), and finally settled on myopathy. In general, the integration of these contents provides a holistic perspective, which helps to further elucidate the structure, characteristics, and functions of skeletal muscle.

Protective effects of treadmill exercise on apoptotic neuronal damage and astrocyte activation in ovariectomized and/or diabetic rat prefrontal cortex: molecular and histological aspects

OBJECTIVE

Both estrogen deprivation and diabetes mellitus are known as risk factors for neuronal damage. Using an animal model of ovariectomized and/or streptozotocin (STZ)-induced diabetes mellitus, we examined expression of apoptosis-related proteins, neuronal damage, and astrocyte activation in prefrontal cortex of rats with/without treadmill exercise.

METHODS

Adult female Wistar rats were divided into control, ovariectomized (Ovx, bilateral ovariectomy), diabetic (Dia, STZ 60 mg/kg; i.p.), and ovariectomized diabetic (Ovx + Dia) groups. Next, animals in each group were randomly subdivided into non-exercise and exercise subgroups. Animals in the exercise groups underwent moderate treadmill running for 4 weeks (5 days/week). Thereafter, expression of Bax, Bcl-2, and caspase-3, as apoptosis-related proteins, number of neurons, and number of glial fibrillary acidic protein (GFAP)-positive cells in prefrontal cortex were measured using immunoblotting, cresyl violet staining, and immunohistochemistry, respectively.

RESULTS

In both Dia and Ovx + Dia groups, Bax and caspase-3 protein levels and number of GFAP-positive cells were higher than those in the control group, while Bcl-2 protein level and number of neurons compared were lower than the control group. Beneficial effects of exercise to prevent apoptosis-mediated neuronal damage and astrocyte activation were also observed in the Dia group.

CONCLUSION

Based on our results, physical exercise could be beneficial to attenuate diabetes-induced neuronal damage in the prefrontal cortex via inhibition of apoptosis.

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.

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.

Molecular mechanisms linking type 2 diabetes mellitus and late-onset Alzheimer's disease: A systematic review and qualitative meta-analysis

Research evidence indicating common metabolic mechanisms through which type 2 diabetes mellitus (T2DM) increases risk of late-onset Alzheimer's dementia (LOAD) has accumulated over recent decades. The aim of this systematic review is to provide a comprehensive review of common mechanisms, which have hitherto been discussed in separate perspectives, and to assemble and evaluate candidate loci and epigenetic modifications contributing to polygenic risk linkages between T2DM and LOAD. For the systematic review on pathophysiological mechanisms, both human and animal studies up to December 2023 are included. For the qualitative meta-analysis of genomic bases, human association studies were examined; for epigenetic mechanisms, data from human studies and animal models were accepted. Papers describing pathophysiological studies were identified in databases, and further literature gathered from cited work. For genomic and epigenomic studies, literature mining was conducted by formalised search codes using Boolean operators in search engines, and augmented by GeneRif citations in Entrez Gene, and other sources (WikiGenes, etc.). For the systematic review of pathophysiological mechanisms, 923 publications were evaluated, and 138 gene loci extracted for testing candidate risk linkages. 3 57 publications were evaluated for genomic association and descriptions of epigenomic modifications. Overall accumulated results highlight insulin signalling, inflammation and inflammasome pathways, proteolysis, gluconeogenesis and glycolysis, glycosylation, lipoprotein metabolism and oxidation, cell cycle regulation or survival, autophagic-lysosomal pathways, and energy. Documented findings suggest interplay between brain insulin resistance, neuroinflammation, insult compensatory mechanisms, and peripheral metabolic dysregulation in T2DM and LOAD linkage. The results allow for more streamlined longitudinal studies of T2DM-LOAD risk linkages.

Applied physiology: gut microbiota and antimicrobial therapy

The gut microbiota plays an important role in maintaining human health and in the pathogenesis of several diseases. Antibiotics are among the most commonly prescribed drugs and have a significant impact on the structure and function of the gut microbiota. The understanding that a healthy gut microbiota prevents the development of many diseases has also led to its consideration as a potential therapeutic target. At the same time, any factor that alters the gut microbiota becomes important in this approach. Exercise and antibacterial therapy have a direct effect on the microbiota. The review reflects the current state of publications on the mechanisms of intestinal bacterial involvement in the pathogenesis of cardiovascular, metabolic, and neurodegenerative diseases. The physiological mechanisms of the influence of physical activity on the composition of the gut microbiota are considered. The mechanisms of the common interface between exercise and antibacterial therapy will be considered using the example of several socially important diseases. The aim of the study is to show the physiological relationship between the effects of exercise and antibiotics on the gut microbiota.

Physical exercise, cognition, and brain health in aging

Exercise training is an important strategy to counteract cognitive and brain health decline during aging. Evidence from systematic reviews and meta-analyses supports the notion of beneficial effects of exercise in cognitively unimpaired and impaired older individuals. However, the effects are often modest, and likely influenced by moderators such as exercise training parameters, sample characteristics, outcome assessments, and control conditions. Here, we discuss evidence on the impact of exercise on cognitive and brain health outcomes in healthy aging and in individuals with or at risk for cognitive impairment and neurodegeneration. We also review neuroplastic adaptations in response to exercise and their potential neurobiological mechanisms. We conclude by highlighting goals for future studies, including addressing unexplored neurobiological mechanisms and the inclusion of under-represented populations.

The mitochondrial quality control system: a new target for exercise therapeutic intervention in the treatment of brain insulin resistance-induced neurodegeneration in obesity

Obesity is a major global health concern because of its strong association with metabolic and neurodegenerative diseases such as diabetes, dementia, and Alzheimer's disease. Unfortunately, brain insulin resistance in obesity is likely to lead to neuroplasticity deficits. Since the evidence shows that insulin resistance in brain regions abundant in insulin receptors significantly alters mitochondrial efficiency and function, strategies targeting the mitochondrial quality control system may be of therapeutic and practical value in obesity-induced cognitive decline. Exercise is considered as a powerful stimulant of mitochondria that improves insulin sensitivity and enhances neuroplasticity. It has great potential as a non-pharmacological intervention against the onset and progression of obesity associated neurodegeneration. Here, we integrate the current knowledge of the mechanisms of neurodegenration in obesity and focus on brain insulin resistance to explain the relationship between the impairment of neuronal plasticity and mitochondrial dysfunction. This knowledge was synthesised to explore the exercise paradigm as a feasible intervention for obese neurodegenration in terms of improving brain insulin signals and regulating the mitochondrial quality control system.

A prognostic neural epigenetic signature in high-grade glioma

Neural-tumor interactions drive glioma growth as evidenced in preclinical models, but clinical validation is limited. We present an epigenetically defined neural signature of glioblastoma that independently predicts patients' survival. We use reference signatures of neural cells to deconvolve tumor DNA and classify samples into low- or high-neural tumors. High-neural glioblastomas exhibit hypomethylated CpG sites and upregulation of genes associated with synaptic integration. Single-cell transcriptomic analysis reveals a high abundance of malignant stemcell-like cells in high-neural glioblastoma, primarily of the neural lineage. These cells are further classified as neural-progenitor-cell-like, astrocyte-like and oligodendrocyte-progenitor-like, alongside oligodendrocytes and excitatory neurons. In line with these findings, high-neural glioblastoma cells engender neuron-to-glioma synapse formation in vitro and in vivo and show an unfavorable survival after xenografting. In patients, a high-neural signature is associated with decreased overall and progression-free survival. High-neural tumors also exhibit increased functional connectivity in magnetencephalography and resting-state magnet resonance imaging and can be detected via DNA analytes and brain-derived neurotrophic factor in patients' plasma. The prognostic importance of the neural signature was further validated in patients diagnosed with diffuse midline glioma. Our study presents an epigenetically defined malignant neural signature in high-grade gliomas that is prognostically relevant. High-neural gliomas likely require a maximized surgical resection approach for improved outcomes.

Impact of menopause-associated frailty on traumatic brain injury

Navigating menopause involves traversing a complex terrain of hormonal changes that extend far beyond reproductive consequences. Menopausal transition is characterized by a decrease in estradiol-17β (E2), and the impact of menopause resonates not only in the reproductive system but also through the central nervous system, musculoskeletal, and gastrointestinal domains. As women undergo menopausal transition, they become more susceptible to frailty, amplifying the risk and severity of injuries, including traumatic brain injury (TBI). Menopause triggers a cascade of changes leading to a decline in muscle mass, accompanied by diminished tone and excitability, thereby restricting the availability of irisin, a crucial hormone derived from muscles. Concurrently, bone mass undergoes reduction, culminating in the onset of osteoporosis and altering the dynamics of osteocalcin, a hormone originating from bones. The diminishing levels of E2 during menopause extend their influence on the gut microbiota, resulting in a reduction in the availability of tyrosine, tryptophan, and serotonin metabolites, affecting neurotransmitter synthesis and function. Understanding the interplay between menopause, frailty, E2 decline, and the intricate metabolisms of bone, gut, and muscle is imperative when unraveling the nuances of TBI after menopause. The current review underscores the significance of accounting for menopause-associated frailty in the incidence and consequences of TBI. The review also explores potential mechanisms to enhance gut, bone, and muscle health in menopausal women, aiming to mitigate frailty and improve TBI outcomes.

Can irisin be developed as the molecular evolutionary clock based on the origin and functions?

Irisin, a myokine identified in 2012, has garnered research interest for its capacity to induce browning of adipocytes and improve metabolic parameters. As such, the potential therapeutic applications of this exercise-induced peptide continue to be explored. Though present across diverse animal species, sequence analysis has revealed subtle variation in the irisin protein. In this review, we consider the effects of irisin on disease states in light of its molecular evolution. We summarize current evidence for irisin's influence on pathologies and discuss how sequence changes may inform development of irisin-based therapies. Furthermore, we propose that the phylogenetic variations in irisin could potentially be leveraged as a molecular clock to elucidate evolutionary relationships.

Molecular insights of exercise therapy in disease prevention and treatment

Despite substantial evidence emphasizing the pleiotropic benefits of exercise for the prevention and treatment of various diseases, the underlying biological mechanisms have not been fully elucidated. Several exercise benefits have been attributed to signaling molecules that are released in response to exercise by different tissues such as skeletal muscle, cardiac muscle, adipose, and liver tissue. These signaling molecules, which are collectively termed exerkines, form a heterogenous group of bioactive substances, mediating inter-organ crosstalk as well as structural and functional tissue adaption. Numerous scientific endeavors have focused on identifying and characterizing new biological mediators with such properties. Additionally, some investigations have focused on the molecular targets of exerkines and the cellular signaling cascades that trigger adaption processes. A detailed understanding of the tissue-specific downstream effects of exerkines is crucial to harness the health-related benefits mediated by exercise and improve targeted exercise programs in health and disease. Herein, we review the current in vivo evidence on exerkine-induced signal transduction across multiple target tissues and highlight the preventive and therapeutic value of exerkine signaling in various diseases. By emphasizing different aspects of exerkine research, we provide a comprehensive overview of (i) the molecular underpinnings of exerkine secretion, (ii) the receptor-dependent and receptor-independent signaling cascades mediating tissue adaption, and (iii) the clinical implications of these mechanisms in disease prevention and treatment.

Exercise derived myokine irisin as mediator of cardiorespiratory, metabolic and thermal adjustments during central and peripheral chemoreflex activation

Exercise elicits physiological adaptations, including hyperpnea. However, the mechanisms underlying exercise-induced hyperpnea remain unresolved. Skeletal muscle acts as a secretory organ, releasing irisin (IR) during exercise. Irisin can cross the blood-brain barrier, influencing muscle and tissue metabolism, as well as signaling in the central nervous system (CNS). We evaluated the effect of intracerebroventricular or intraperitoneal injection of IR in adult male rats on the cardiorespiratory and metabolic function during sleep-wake cycle under room air, hypercapnia and hypoxia. Central IR injection caused an inhibition on ventilation (VE) during wakefulness under normoxia, while peripheral IR reduced VE during sleep. Additionally, central IR exacerbates hypercapnic hyperventilation by increasing VE and reducing oxygen consumption. As to cardiovascular regulation, central IR caused an increase in heart rate (HR) across all conditions, while no change was observed following peripheral administration. Finally, central IR attenuated the hypoxia-induced regulated hypothermia and increase sleep episodes, while peripheral IR augmented CO2-induced hypothermia, during wakefulness. Overall, our results suggest that IR act mostly on CNS exerting an inhibitory effect on breathing under resting conditions, while stimulating the hypercapnic ventilatory response and increasing HR. Therefore, IR seems not to be responsible for the exercise-induced hyperpnea, but contributes to the increase in HR.

Photobiomodulation in experimental models of Alzheimer's disease: state-of-the-art and translational perspectives

Alzheimer's disease (AD) poses a significant public health problem, affecting millions of people across the world. Despite decades of research into therapeutic strategies for AD, effective prevention or treatment for this devastating disorder remains elusive. In this review, we discuss the potential of photobiomodulation (PBM) for preventing and alleviating AD-associated pathologies, with a focus on the biological mechanisms underlying this therapy. Future research directions and guidance for clinical practice for this non-invasive and non-pharmacological therapy are also highlighted. The available evidence indicates that different treatment paradigms, including transcranial and systemic PBM, along with the recently proposed remote PBM, all could be promising for AD. PBM exerts diverse biological effects, such as enhancing mitochondrial function, mitigating the neuroinflammation caused by activated glial cells, increasing cerebral perfusion, improving glymphatic drainage, regulating the gut microbiome, boosting myokine production, and modulating the immune system. We suggest that PBM may serve as a powerful therapeutic intervention for AD.

Irisin inhibits microglial senescence via TFAM-mediated mitochondrial metabolism in a mouse model of tauopathy

BACKGROUND

The accumulation of senescent microglia has been highlighted as a critical contributor to the progression of tauopathies. Irisin, a muscle-derived hormone produced by the proteolytic cleavage of Fibronectin-domain III containing 5 (FNDC5), mediates the pleiotropic effects of exercise on the physical body. Herein, we investigate the potential role of irisin in microglial senescence in tauopathies.

METHODS

To model tauopathies both in vivo and in vitro, we utilized P301S tau transgenic mice and tau K18 fibril-treated microglia BV2 cells, respectively. We first examined the expression of the irisin expression and senescence phenotypes of microglia in tauopathies. Subsequently, we investigated the impact of irisin on microglial senescence and its underlying molecular mechanisms.

RESULT

We observed a reduction in irisin levels and an onset of premature microglial senescence both in vivo and in vitro. Irisin administration was found to counteract microglial senescence and ameliorate cognitive decline in P301S mice. Mechanistically, irisin effectively inhibited microglial senescence by stimulating the expression of mitochondrial transcription factor A (TFAM), a master regulator of mitochondrial respiratory chain biogenesis, thereby enhancing mitochondrial oxidative phosphorylation (OXPHOS). Silencing TFAM eliminated the inhibitory effect of irisin on microglial senescence as well as the restorative effect of irisin on mitochondrial OXPHOS. Furthermore, the SIRT1/PGC1α signaling pathway appeared to be implicated in irisin-mediated upregulation of TFAM.

CONCLUSION

Taken together, our study revealed that irisin mitigated microglial senescence via TFAM-driven mitochondrial biogenesis, suggesting a promising new avenue for therapeutic strategies targeting tauopathies.

Neuronal innervation regulates the secretion of neurotrophic myokines and exosomes from skeletal muscle

Myokines and exosomes, originating from skeletal muscle, are shown to play a significant role in maintaining brain homeostasis. While exercise has been reported to promote muscle secretion, little is known about the effects of neuronal innervation and activity on the yield and molecular composition of biologically active molecules from muscle. As neuromuscular diseases and disabilities associated with denervation impact muscle metabolism, we hypothesize that neuronal innervation and firing may play a pivotal role in regulating secretion activities of skeletal muscles. We examined this hypothesis using an engineered neuromuscular tissue model consisting of skeletal muscles innervated by motor neurons. The innervated muscles displayed elevated expression of mRNAs encoding neurotrophic myokines, such as interleukin-6, brain-derived neurotrophic factor, and FDNC5, as well as the mRNA of peroxisome-proliferator-activated receptor γ coactivator 1α, a key regulator of muscle metabolism. Upon glutamate stimulation, the innervated muscles secreted higher levels of irisin and exosomes containing more diverse neurotrophic microRNAs than neuron-free muscles. Consequently, biological factors secreted by innervated muscles enhanced branching, axonal transport, and, ultimately, spontaneous network activities of primary hippocampal neurons in vitro. Overall, these results reveal the importance of neuronal innervation in modulating muscle-derived factors that promote neuronal function and suggest that the engineered neuromuscular tissue model holds significant promise as a platform for producing neurotrophic molecules.

Exploring the Effect of Acute and Regular Physical Exercise on Circulating Brain-Derived Neurotrophic Factor Levels in Individuals with Obesity: A Comprehensive Systematic Review and Meta-Analysis

Obesity is a major global health concern linked to cognitive impairment and neurological disorders. Circulating brain-derived neurotrophic factor (BDNF), a protein crucial for neuronal growth and survival, plays a vital role in brain function and plasticity. Notably, obese individuals tend to exhibit lower BDNF levels, potentially contributing to cognitive decline. Physical exercise offers health benefits, including improved circulating BDNF levels and cognitive function, but the specific impacts of acute versus regular exercise on circulating BDNF levels in obesity are unclear. Understanding this can guide interventions to enhance brain health and counter potential cognitive decline in obese individuals. Therefore, this study aimed to explore the impact of acute and regular physical exercise on circulating BDNF in individuals with obesity. The target population comprised individuals classified as overweight or obese, encompassing both acute and chronic protocols involving all training methods. A comprehensive search was conducted across computerized databases, including PubMed, Academic Search Complete, and Web of Science, in August 2022, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Initially, 98 studies were identified, from which 16 studies, comprising 23 trials, met the selection criteria. Substantial heterogeneity was observed for both acute (I2 = 80.4%) and long-term effects (I2 = 88.7%), but low risk of bias for the included studies. A single session of exercise increased circulating BDNF levels among obese patients compared to the control group (ES = 1.25, 95% CI = 0.19 to 2.30, p = 0.021). However, with extended periods of physical exercise, there was no significant increase in circulating BDNF levels when compared to the control group (ES = 0.49, 95% CI = -0.08 to 1.06, p = 0.089). These findings highlight the need to consider exercise duration and type when studying neurobiological responses in obesity and exercise research. The study's results have implications for exercise prescription in obesity management and highlight the need for tailored interventions to optimize neurotrophic responses. Future research should focus on elucidating the adaptive mechanisms and exploring novel strategies to enhance BDNF modulation through exercise in this population. However, further research is needed considering limitations such as the potential age-related confounding effects due to diverse participant ages, lack of sex-specific analyses, and insufficient exploration of how specific exercise parameters (e.g., duration, intensity, type) impact circulating BDNF.

FNDC5/irisin mediates the protective effects of Innovative theta-shaking exercise on mouse memory

As a passive motion and non-invasive treatment, theta-shaking exercise is considered an alternative to traditional active exercise for slowing down brain ageing. Here, we studied the influence of theta-shaking exercise on fibronectin type III domain containing 5/irisin (FNDC5/irisin) in the anterior nucleus of the thalamus, hippocampus, and medial prefrontal cortex (ATN-HPC-MPFC). Further, we assessed memory in senescence-accelerated prone mice (SAMP-10 mice) using a behavioural test to confirm the protective effect of theta-shaking exercise against age-related memory decline. SAMP-10 mice were subjected to theta-shaking exercise for 9-30 weeks. Mice then performed the T-maze test and passive avoidance task. Immunohistochemical analysis and ELISA were used to assess FNDC5/irisin, nerve growth factor (NGF), and neurotrophin 4/5 (NT4/5) expression in the ATN-HPC-MPFC. In the shaking group, FNDC5 was locally upregulated within the hippocampus and MPFC area rather than exhibiting even distribution throughout brain tissue. Irisin levels were generally higher in the control group. Meanwhile, hippocampal NGF levels were significantly higher in the shaking group, with no differences noted in neurotrophin levels. Theta-shaking preserved normal neurons in certain sub-regions. However, no beneficial changes in neuronal density were noted in the ATN. Theta-shaking exercise positively affects memory function in SAMP-10 mice. FNDC5 upregulation and higher levels of NGF, along with the potential involvement of irisin, may have contributed to the preservation of normal neuronal density in the hippocampus and MPFC subregions.

Deletion of FNDC5/irisin modifies murine osteocyte function in a sex-specific manner

Irisin, released from exercised muscle, has been shown to have beneficial effects on numerous tissues but its effects on bone are unclear. We found significant sex and genotype differences in bone from wildtype (WT) mice compared to mice lacking Fndc5 (knockout [KO]), with and without calcium deficiency. Despite their bone being indistinguishable from WT females, KO female mice were partially protected from osteocytic osteolysis and osteoclastic bone resorption when allowed to lactate or when placed on a low-calcium diet. Male KO mice have more but weaker bone compared to WT males, and when challenged with a low-calcium diet lost more bone than WT males. To begin to understand responsible molecular mechanisms, osteocyte transcriptomics was performed. Osteocytes from WT females had greater expression of genes associated with osteocytic osteolysis and osteoclastic bone resorption compared to WT males which had greater expression of genes associated with steroid and fatty acid metabolism. Few differences were observed between female KO and WT osteocytes, but with a low-calcium diet, the KO females had lower expression of genes responsible for osteocytic osteolysis and osteoclastic resorption than the WT females. Male KO osteocytes had lower expression of genes associated with steroid and fatty acid metabolism, but higher expression of genes associated with bone resorption compared to male WT. In conclusion, irisin plays a critical role in the development of the male but not the female skeleton and protects male but not female bone from calcium deficiency. We propose irisin ensures the survival of offspring by targeting the osteocyte to provide calcium in lactating females, a novel function for this myokine.

Exercise mitigates a gut microbiota-mediated reduction in adult hippocampal neurogenesis and associated behaviours in rats

Lifestyle factors, especially exercise, impact the manifestation and progression of psychiatric and neurodegenerative disorders such as depression and Alzheimer's disease, mediated by changes in hippocampal neuroplasticity. The beneficial effects of exercise may be due to its promotion of adult hippocampal neurogenesis (AHN). Gut microbiota has also been showed to be altered in a variety of brain disorders, and disturbances of the microbiota have resulted in alterations in brain and behaviour. However, whether exercise can counteract the negative effects of altered gut microbiota on brain function remains under explored. To this end, chronic disruption of the gut microbiota was achieved using an antibiotic cocktail in rats that were sedentary or allowed voluntary access to running wheels. Sedentary rats with disrupted microbiota displayed impaired performance in hippocampal neurogenesis-dependent tasks: the modified spontaneous location recognition task and the novelty suppressed feeding test. Performance in the elevated plus maze was also impaired due to antibiotics treatment. These behaviours, and an antibiotics-induced reduction in AHN were attenuated by voluntary exercise. The effects were independent of changes in the hippocampal metabolome but were paralleled by caecal metabolomic changes. Taken together these data highlight the importance of the gut microbiota in AHN-dependent behaviours and demonstrate the power of lifestyle factors such as voluntary exercise to attenuate these changes.

A potential research target for cardiac rehabilitation: brain-derived neurotrophic factor

Cardiovascular diseases pose a major threat to human life, functional activity, and quality of life. Once the disease is present, patients can experience varying degrees of problems or limitations on three levels: physical, psychological, and social. Patients with cardiovascular disease are always at risk for adverse cardiac events, decreased physical activity, psychoemotional disturbances, and limited social participation due to their varying pathologies. Therefore, personalized cardiac rehabilitation is of great significance in improving patients' physical and mental functions, controlling disease progression, and preventing deterioration. There is a consensus on the benefits of cardiac rehabilitation in improving patients' quality of life, enhancing functional activity, and reducing mortality. As an important part of cardiac rehabilitation, Exercise plays an irreplaceable role. Aerobic exercise, resistance training, flexibility training, and other forms of exercise are recommended by many experts. Improvements in exercise tolerance, lipid metabolism, cardiac function, and psychological aspects of the patients were evident with appropriate exercise interventions based on a comprehensive assessment. Further studies have found that brain-derived neurotrophic factor may be an important mediator of exercise's ability to improve cardiovascular health. Brain-derived neurotrophic factor exerts multiple biological effects on the cardiovascular system. This article provides another perspective on the cardiac effects of exercise and further looks at the prospects for the use of brain-derived neurotrophic factor in cardiac rehabilitation. Meanwhile, the new idea that brain-derived neurotrophic factor is a key mediator connecting the brain-cardiac axis is proposed in light of the current research progress, to provide new ideas for clinical rehabilitation and scientific research.

Effects of Gestational Exercise on Nociception, BDNF, and Irisin Levels in an Animal Model of ADHD

Abnormal cognitive and sensorial properties have been reported in patients with psychiatric and neurodevelopmental conditions, such as attention deficit hyperactivity disorder (ADHD). ADHD patients exhibit impaired dopaminergic signaling and plasticity in brain areas related to cognitive and sensory processing. The spontaneous hypertensive rat (SHR), in comparison to the Wistar Kyoto rat (WKY), is the most used genetic animal model to study ADHD. Brain neurotrophic factor (BDNF), critical for midbrain and hippocampal dopaminergic neuron survival and differentiation, is reduced in both ADHD subjects and SHR. Physical exercise (e.g. swimming) promotes neuroplasticity and improves cognition by increasing BDNF and irisin. Here we investigate the effects of gestational swimming on sensorial and behavioral phenotypes, striatal dopaminergic parameters, and hippocampal FNDC5/irisin and BDNF levels observed in WKY and SHR. Gestational swimming improved nociception in SHR rats (p = 0.006) and increased hippocampal BDNF levels (p = 0.02) in a sex-dependent manner in adolescent offspring. Sex differences were observed in hippocampal FNDC5/irisin levels (p = 0.002), with females presenting lower levels than males. Our results contribute to the notion that swimming during pregnancy is a promising alternative to improve ADHD phenotypes in the offspring.

Association between hypothalamic Alzheimer's disease pathology and body mass index: The Hisayama study

The hypothalamus is the region of the brain that integrates the neuroendocrine system and whole-body metabolism. Patients with Alzheimer's disease (AD) have been reported to exhibit pathological changes in the hypothalamus, such as neurofibrillary tangles (NFTs) and amyloid plaques (APs). However, few studies have investigated whether hypothalamic AD pathology is associated with clinical factors. We investigated the association between AD-related pathological changes in the hypothalamus and clinical pictures using autopsied brain samples obtained from deceased residents of a Japanese community. A total of 85 autopsied brain samples were semi-quantitatively analyzed for AD pathology, including NFTs and APs. Our histopathological studies showed that several hypothalamic nuclei, such as the tuberomammillary nucleus (TBM) and lateral hypothalamic area (LHA), are vulnerable to AD pathologies. NFTs are observed in various neuropathological states, including normal cognitive cases, whereas APs are predominantly observed in AD. Regarding the association between hypothalamic AD pathologies and clinical factors, the degree of APs in the TBM and LHA was associated with a lower body mass index while alive, after adjusting for sex and age at death. However, we found no significant association between hypothalamic AD pathology and the prevalence of hypertension, diabetes, or dyslipidemia. Our study showed that a lower BMI, which is a poor prognostic factor of AD, might be associated with hypothalamic AP pathology and highlighted new insights regarding the disruption of the brain-whole body axis in AD.

Dietary fasting and time-restricted eating in Huntington's disease: therapeutic potential and underlying mechanisms

Huntington's disease (HD) is a devastating neurodegenerative disorder caused by aggregation of the mutant huntingtin (mHTT) protein, resulting from a CAG repeat expansion in the huntingtin gene HTT. HD is characterized by a variety of debilitating symptoms including involuntary movements, cognitive impairment, and psychiatric disturbances. Despite considerable efforts, effective disease-modifying treatments for HD remain elusive, necessitating exploration of novel therapeutic approaches, including lifestyle modifications that could delay symptom onset and disease progression. Recent studies suggest that time-restricted eating (TRE), a form of intermittent fasting involving daily caloric intake within a limited time window, may hold promise in the treatment of neurodegenerative diseases, including HD. TRE has been shown to improve mitochondrial function, upregulate autophagy, reduce oxidative stress, regulate the sleep-wake cycle, and enhance cognitive function. In this review, we explore the potential therapeutic role of TRE in HD, focusing on its underlying physiological mechanisms. We discuss how TRE might enhance the clearance of mHTT, recover striatal brain-derived neurotrophic factor levels, improve mitochondrial function and stress-response pathways, and synchronize circadian rhythm activity. Understanding these mechanisms is critical for the development of targeted lifestyle interventions to mitigate HD pathology and improve patient outcomes. While the potential benefits of TRE in HD animal models are encouraging, future comprehensive clinical trials will be necessary to evaluate its safety, feasibility, and efficacy in persons with HD.

Irisin/PGC-1α/FNDC5 pathway in Parkinson's disease: truth under the throes

Parkinson's disease (PD) is considered one of the most common neurodegenerative brain diseases which involves the deposition of α-synuclein. Irisin hormone, a newly discovered adipokine, has a valuable role in diverse neurodegenerative diseases. Therefore, this review aims to elucidate the possible role of the irisin hormone in PD neuropathology. Irisin hormone has a neuroprotective effect against the development and progression of various neurodegenerative disorders by increasing the expression of brain-derived neurotrophic factor (BDNF). Irisin hormone has anti-inflammatory, anti-apoptotic, and anti-oxidative impacts, thereby reducing the expression of the pro-inflammatory cytokines and the progression of neuroinflammation. Irisin-induced PGC-1α could potentially prevent α-synuclein-induced dopaminergic injury, neuroinflammation, and neurotoxicity in PD. Inhibition of NF-κB by irisin improves PGC-1α and FNDC5 signaling pathway with subsequent attenuation of PD neuropathology. Therefore, the irisin/PGC-1α/FNDC5 pathway could prevent dopaminergic neuronal injury. In conclusion, the irisin hormone has a neuroprotective effect through its anti-inflammatory and antioxidant impacts with the amelioration of brain BDNF levels. Further preclinical and clinical studies are recommended in this regard.