The Role of PGC-1α/UCP2 Signaling in the Beneficial Effects of Physical Exercise on the Brain

GDF5 as a rejuvenating treatment for age-related neuromuscular failure

Sarcopenia involves a progressive loss of skeletal muscle force, quality and mass during ageing, which results in increased inability and death; however, no cure has been established thus far. Growth differentiation factor 5 (GDF5) has been described to modulate muscle mass maintenance in various contexts. For our proof of concept, we overexpressed GDF5 by AAV vector injection in tibialis anterior muscle of adult aged (20 months) mice and performed molecular and functional analysis of skeletal muscle. We analysed human vastus lateralis muscle biopsies from adult young (21-42 years) and aged (77-80 years) donors, quantifying the molecular markers modified by GDF5 overexpression in mouse muscle. We validated the major effects of GDF5 overexpression using human immortalized myotubes and Schwann cells. We established a preclinical study by treating chronically (for 4 months) aged mice using recombinant GDF5 protein (rGDF5) in systemic administration and evaluated the long-term effect of this treatment on muscle mass and function. Here, we demonstrated that GDF5 overexpression in the old tibialis anterior muscle promoted an increase of 16.5% of muscle weight (P = 0.0471) associated with a higher percentage of 5000-6000 µm2 large fibres (P = 0.0211), without the induction of muscle regeneration. Muscle mass gain was associated with an amelioration of 26.8% of rate of force generation (P = 0.0330) and better neuromuscular connectivity (P = 0.0098). Moreover, GDF5 overexpression preserved neuromuscular junction morphology (38.5% of nerve terminal area increase, P < 0.0001) and stimulated the expression of reinnervation-related genes, in particular markers of Schwann cells (fold-change 3.19 for S100b gene expression, P = 0.0101). To characterize the molecular events induced by GDF5 overexpression during ageing, we performed a genome-wide transcriptomic analysis of treated muscles and showed that this factor leads to a 'rejuvenating' transcriptomic signature in aged mice, as 42% of the transcripts dysregulated by ageing reverted to youthful expression levels upon GDF5 overexpression (P < 0.05). Towards a preclinical approach, we performed a long-term systemic treatment using rGDF5 and showed its effectiveness in counteracting age-related muscle wasting, improving muscle function (17.8% of absolute maximal force increase, P = 0.0079), ensuring neuromuscular connectivity and preventing neuromuscular junction degeneration (7.96% of AchR area increase, P = 0.0125). In addition, in human muscle biopsies, we found the same age-related alterations than those observed in mice and improved by GDF5 and reproduced its major effects on human cells, suggesting this treatment as efficient in humans. Overall, these data provide a foundation to examine the curative potential of GDF5 drug in clinical trials for sarcopenia and, eventually, other neuromuscular diseases.

Irisin in Reproduction: Its Roles and Therapeutic Potential in Male and Female Fertility Disorders

The current study focused on identifying the potential of irisin in mammalian reproduction. The established role of irisin, a proteolytic product of FNDC5, in adipose tissue browning, energy metabolism, and thermogenesis suggests its role in reproductive health, often disturbed by metabolic imbalances. Various studies on mice demonstrated irisin's role in improving spermatogenesis, sperm count, and testosterone levels by influencing the hypothalamus-pituitary-gonadal axis. Moreover, in females, there is a fluctuation in levels of irisin during critical reproductive stages, including menstrual cycles, puberty, and pregnancy. Conditions like pregnancy complications, precocious puberty, and polycystic ovary syndrome (PCOS) are found to have an association with abnormal irisin levels. The potential role of irisin in endometrial receptivity and preventing endometritis is also discussed in this review. Overall, the influence of irisin on female and male reproduction is evident from various studies. However, further research is needed to elucidate irisin mechanism in reproduction and its potential as a therapeutic or diagnostic tool for reproductive dysfunctions and infertility.

Mitochondrial biogenesis disorder and oxidative damage promote refractory apical periodontitis in rat and human

AIM

To elucidate whether mitochondrial biogenesis disorder and damage from oxidative stress promote refractory apical periodontitis (RAP) in rat and human.

METHODOLOGY

Twenty Enterococcus faecalis-induced RAPs were established in the maxillary first molars of male Wistar rats. Concurrently, 12 periapical lesion specimens from patients presenting with RAP were obtained by apicoectomy. Radiographic examination and histologic analysis were conducted to evaluate periapical bone tissue destruction and morphological changes. The expression of key regulators of mitochondrial biogenesis, PGC-1α and Nrf2, were detected by immunohistochemistry and double immunofluorescence staining, Western blot and real-time PCR were also assayed. Mitochondrial ROS (mtROS) was identified by MitoSOX staining. Mitochondrial function was detected by the quantification of ATP production, mitochondrial DNA (mtDNA) copy number and activities of mitochondrial respiratory chain complexes. Furthermore, mitochondrial oxidative stress was evaluated by the determination of 3-nitrotyrosine (3-NT), 4-hydroxy-2-nonenal (4-HNE) and 8-hydroxy-deoxyguanosine (8-OHdG) expression levels, as well as malondialdehyde (MDA) expression and antioxidant capacity. Student's t-test was performed to determine significance between the groups; p < .05 was considered significant.

RESULTS

In the maxilla, significantly more bone resorption, greater number of periapical apoptotic cells and Tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells were observed in the RAP group compared with the control group (p < .01). PGC-1α and Nrf2 were significantly reduced in rat and human RAP lesions compared to the control group (p < .01) at both the mRNA and protein levels. Double immunofluorescence analysis of PGC-1α or Nrf2 with TOMM20 also indicated that mitochondrial biogenesis was impaired in RAP group (p < .01). Additionally, mitochondrial dysfunction was observed in RAP group, as reflected by increased mtROS, decreased ATP production, reduced mtDNA copy number and complexes of the mitochondrial respiratory chain. Finally, the expression levels of mitochondrial oxidative stress markers, 3-NT, 4-HNE and 8-OHdG, were significantly increased in the RAP group (p < .01). Consistent with this, systemic oxidative damage was also present in the progression of RAP, including increased MDA expression and decreased antioxidant activity (p < .01).

CONCLUSIONS

Mitochondrial biogenesis disorder and damage from oxidative stress contribute to the development of RAP.

The activation of AMPK/PGC-1α/GLUT4 signaling pathway through early exercise improves mitochondrial function and mitigates ischemic brain damage

Mitochondria play a crucial role in maintaining cellular energy supply and serve as a source of energy for repairing nerve damage following a stroke. Given that exercise has the potential to enhance energy metabolism, investigating the impact of exercise on mitochondrial function provides a plausible mechanism for stroke treatment. In our study, we established the middle cerebral artery occlusion (MCAO) model in Sprague-Dawley rats and implemented early exercise intervention. Neurological severity scores, beam-walking test score, and weight were used to evaluate neurological function. The volume of cerebral infarction was measured by MRI. Nerve cell apoptosis was detected by TUNEL staining. Mitochondrial morphology and structure were detected by mitochondrial electron microscopy. Mitochondrial function was assessed using membrane potential and ATP measurements. Western blotting was used to detect the protein expression of AMPK/PGC-1α/GLUT4. Through the above experiments, we found that early exercise improved neurological function in rats after MCAO, reduced cerebral infarction volume and neuronal apoptosis, promoted the recovery of mitochondrial morphology and function. We further examined the protein expression of AMPK/PGC-1α/GLUT4 signaling pathway and confirmed that early exercise was able to increase its expression. Therefore, we suggest that early exercise initiated the AMPK/PGC-1α/GLUT4 signaling pathway, restoring mitochondrial function and augmenting energy supply. This, in turn, effectively improved both nerve and body function in rats following ischemic stroke.

Shaping down syndrome brain cognitive and molecular changes due to aging using adult animals from the Ts66Yah murine model

Down syndrome (DS) is the most common condition with intellectual disability and is caused by trisomy of Homo sapiens chromosome 21 (HSA21). The increased dosage of genes on HSA21 is associated with early neurodevelopmental changes and subsequently at adult age with the development of Alzheimer-like cognitive decline. However, the molecular mechanisms promoting brain pathology along aging are still missing. The novel Ts66Yah model represents an evolution of the Ts65Dn, used in characterizing the progression of brain degeneration, and it manifest phenotypes closer to human DS condition. In this study we performed a longitudinal analysis (3-9 months) of adult Ts66Yah mice. Our data support the behavioural alterations occurring in Ts66Yah mice at older age with improvement in the detection of spatial memory defects and also a new anxiety-related phenotype. The evaluation of hippocampal molecular pathways in Ts66Yah mice, as effect of age, demonstrate the aberrant regulation of redox balance, proteostasis, stress response, metabolic pathways, programmed cell death and synaptic plasticity. Intriguingly, the genotype-driven changes observed in those pathways occur early promoting altered brain development and the onset of a condition of premature aging. In turn, aging may account for the subsequent hippocampal deterioration that fall in characteristic neuropathological features. Besides, the analysis of sex influence in the alteration of hippocampal mechanisms demonstrate only a mild effect. Overall, data collected in Ts66Yah provide novel and consolidated insights, concerning trisomy-driven processes that contribute to brain pathology in conjunction with aging. This, in turn, aids in bridging the existing gap in comprehending the intricate nature of DS phenotypes.

Energy expenditure related biomarkers following bariatric surgery: a prospective six-month cohort study

BACKGROUND

Mitochondria dysfunction is one of the major causes of insulin resistance, and other countless complications of obesity. PGC-1α, and UCP-2 play key roles in energy expenditure regulation in the mitochondrial thermogenesis. However, the effects of bariatric surgery on the level of PGC-1α and UCP-2 and their relationships are unclear.

OBJECTIVE

This study aimed to investigate the effect of bariatric surgery on key pathways in energy, and to assess the potential predictive role of body composition and metabolic parameters in this regard.

SETTINGS

Hazrat-e Rasool General Hospital, Center of Excellence of International Federation for Surgery of Obesity.

METHODS

This prospective cohort study was carried out on 45 patients with morbid obesity who underwent Roux-en-Y gastric bypass surgery. The patients have evaluated three-time points at baseline, three, and six months after the surgery. Body composition components, the levels of PGC-1α, UCP-2, and metabolic parameters were measured three times during this study.

RESULTS

Significant changes in TWL%, EBMIL%, and metabolic lab tests were observed at three- and six months post-surgery (P < 0.001). The PGC-1α and UCP-2 had a significant increase three and then six-month post-operation compared with the baseline (P < 0.001). Moreover, multivariate linear regression analysis identified that the changing trend of PGC-1α was associated with insulin, uric Acid, HOMA-IR, fat mass and trunk fat mass. UCP-2 was associated with TSH, AST, fat mass and FFM.

CONCLUSIONS

Bariatric surgery has been shown to have a positive effect on UCP-2 and PGC-1α levels, as well as body composition and metabolic parameters. As a result, it is believed that bariatric surgery could improve thermogenesis and energy expenditure by enhancing mitochondrial biogenesis and function. However, further studies are needed to fully understand the precise mechanisms and possible causal relationship.

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.

FNDC5/Irisin protects neurons through Caspase3 and Bax pathways

Irisin is a glycosylated protein formed from the hydrolysis of fibronectin type III domain-containing protein 5 (FNDC5). Recent studies have demonstrated that FNDC5/Irisin is involved in the regulation of glucose and lipid metabolism, it can inhibit inflammation and have neuroprotective effects. However, the effect and mechanism of FNDC5/Irisin on motor neuron-like cell lines (NSC-34) have not been reported. In this study, we used lipopolysaccharide to construct cellular oxidative stress injury models and investigated the potential roles of FNDC5/Irisin on neurons by different cellular and molecular pathways. Taken together, our findings showed that FNDC5/Irisin can protect neurons, and this effect might be associated with Caspase3 and Bax pathways. These results laid the foundation for neuronal protection and clinical translation of FNDC5/Irisin therapy.

Plausible Role of Mitochondrial DNA Copy Number in Neurodegeneration-a Need for Therapeutic Approach in Parkinson's Disease (PD)

Parkinson's disease (PD) is an advancing age-associated progressive brain disorder which has various diverse factors, among them mitochondrial dysfunction involves in dopaminergic (DA) degeneration. Aging causes a rise in mitochondrial abnormalities which leads to structural and functional modifications in neuronal activity and cell death in PD. This ends in deterioration of mitochondrial function, mitochondrial alterations, mitochondrial DNA copy number (mtDNA CN) and oxidative phosphorylation (OXPHOS) capacity. mtDNA levels or mtDNA CN in PD have reported that mtDNA depletion would be a predisposing factor in PD pathogenesis. To maintain the mtDNA levels, therapeutic approaches have been focused on mitochondrial biogenesis in PD. The depletion of mtDNA levels in PD can be influenced by autophagic dysregulation, apoptosis, neuroinflammation, oxidative stress, sirtuins, and calcium homeostasis. The current review describes the regulation of mtDNA levels and discusses the plausible molecular pathways in mtDNA CN depletion in PD pathogenesis. We conclude by suggesting further research on mtDNA depletion which might show a promising effect in predicting and diagnosing PD.

Irisin, adropin, and preptin as biomarkers of energy dysregulation in depressive disorder

OBJECTIVE

Lack of energy, fatigue, debility are often seen in depression and hardly respond to treatment. Finding some biomarkers for these symptoms may be important for diagnosis and treatment. We aimed to investigate the possible relationship between depression and energy-related molecules irisin, adropin and preptin.

METHODS

There were 117 patients with depression and 59 healthy volunteers included in the study. Sociodemographic characteristics and clinical features of groups were evaluated, and depressed patients were divided into subtypes, then irisin, adropin, preptin levels were compared between depressive patients and healthy controls and between subtypes. Depression severity, quality of life, functionality and the relations with irisin, adropin and preptin levels and associations between depression subtypes were evaluated.

RESULTS

Irisin, adropin, and preptin levels were lower in depression, positively correlated with quality of life, and negatively correlated with depression severity and functional impairment. Depression subtypes showed no difference in irisin, adropin and preptin levels.

CONCLUSIONS

We found decreased serum irisin, adropin and preptin levels in depression. Our results may support investigation of irisin, adropin and preptin as biomarkers for depression but it might be more meaningful to evaluate these biomarkers in a long-term follow-up.

Mechanism of PGC-1α-mediated mitochondrial biogenesis in cerebral ischemia-reperfusion injury

Cerebral ischemia-reperfusion injury (CIRI) is a series of cascade reactions that occur after blood flow recanalization in the ischemic zone in patients with cerebral infarction, causing an imbalance in intracellular homeostasis through multiple pathologies such as increased oxygen free radicals, inflammatory response, calcium overload, and impaired energy metabolism, leading to mitochondrial dysfunction and ultimately apoptosis. Rescue of reversibly damaged neurons in the ischemic hemispheric zone is the key to saving brain infarction and reducing neurological deficits. Complex and active neurological functions are highly dependent on an adequate energy supply from mitochondria. Mitochondrial biogenesis (MB), a process that generates new functional mitochondria and restores normal mitochondrial function by replacing damaged mitochondria, is a major mechanism for maintaining intra-mitochondrial homeostasis and is involved in mitochondrial quality control to ameliorate mitochondrial dysfunction and thus protects against CIRI. The main regulator of MB is peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α), which improves mitochondrial function to protect against CIRI by activating its downstream nuclear respiratory factor 1 (NRF1) and mitochondrial transcription factor A (TFAM) to promote mitochondrial genome replication and transcription. This paper provides a theoretical reference for the treatment of neurological impairment caused by CIRI by discussing the mechanisms of mitochondrial biogenesis during cerebral ischemia-reperfusion injury.

Mitochondrial dysfunction in aging

Aging is a complex process that features a functional decline in many organelles. Although mitochondrial dysfunction is suggested as one of the determining factors of aging, the role of mitochondrial quality control (MQC) in aging is still poorly understood. A growing body of evidence points out that reactive oxygen species (ROS) stimulates mitochondrial dynamic changes and accelerates the accumulation of oxidized by-products through mitochondrial proteases and mitochondrial unfolded protein response (UPRmt). Mitochondrial-derived vesicles (MDVs) are the frontline of MQC to dispose of oxidized derivatives. Besides, mitophagy helps remove partially damaged mitochondria to ensure that mitochondria are healthy and functional. Although abundant interventions on MQC have been explored, over-activation or inhibition of any type of MQC may even accelerate abnormal energy metabolism and mitochondrial dysfunction-induced senescence. This review summarizes mechanisms essential for maintaining mitochondrial homeostasis and emphasizes that imbalanced MQC may accelerate cellular senescence and aging. Thus, appropriate interventions on MQC may delay the aging process and extend lifespan.

The Role of PGC-1α-Mediated Mitochondrial Biogenesis in Neurons

Neurons are highly dependent on mitochondrial ATP production and Ca²⁺ buffering. Neurons have unique compartmentalized anatomy and energy requirements, and each compartment requires continuously renewed mitochondria to maintain neuronal survival and activity. Peroxisome proliferator-activated receptor-gamma coactivator-1α (PGC-1α) is a key factor in the regulation of mitochondrial biogenesis. It is widely accepted that mitochondria are synthesized in the cell body and transported via axons to the distal end. However, axonal mitochondrial biogenesis is necessary to maintain axonal bioenergy supply and mitochondrial density due to limitations in mitochondrial axonal transport rate and mitochondrial protein lifespan. In addition, impaired mitochondrial biogenesis leading to inadequate energy supply and neuronal damage has been observed in neurological disorders. In this review, we focus on the sites where mitochondrial biogenesis occurs in neurons and the mechanisms by which it maintains axonal mitochondrial density. Finally, we summarize several neurological disorders in which mitochondrial biogenesis is affected.

The health benefit of physical exercise on COVID-19 pandemic: Evidence from mainland China

Objectives

Our study aims to investigate the health benefit of regular physical exercise participation on a series of COVID-19 outcomes including COVID-19 morbidity, mortality, and cure rate.

Methods

Prefecture-level panel data related to physical exercise and the COVID-19 pandemic in China were collected from January 1 to March 17, 2020, (N = 21379). Multiple linear regression was conducted, and the ordinary least squares technique was used to estimate the coefficient.

Results

It was shown that regular sports participation significantly negatively affected COVID-19 morbidity (estimate = -1.1061, p<0.01) and mortality (estimate = -0.3836, p<0.01), and positively affected cure rate (estimate = 0.0448, p<0.01), implying that engaging in physical exercise regularly does have a significant positive effect on COVID-19 outcomes. Then, we explored the heterogeneity of the effect of physical exercise on areas with different risk levels and it was revealed that the effect of physical exercise was more pronounced in high-risk areas in terms of morbidity (estimate = -1.8776, p<0.01 in high-risk areas; estimate = -0.0037, p<0.01 in low-risk areas), mortality (estimate = -0.3982, p<0.01 in high-risk areas; estimate = -0.3492, p<0.01 in low-risk areas), and cure rate (estimate = 0.0807, p<0.01 in high-risk areas; 0.0193 = -0.0037, p<0.05 in low-risk areas).

Conclusions

Our results suggest that regularly engaging in physical exercise before the pandemic has positive health effects, especially in the case of a more severe epidemic. Therefore, we urge readers to actively engage in physical exercise so that we can reduce the risks in the event of a pandemic.

Recent Neurotherapeutic Strategies to Promote Healthy Brain Aging: Are we there yet?

Owing to the global exponential increase in population ageing, there is an urgent unmet need to develop reliable strategies to slow down and delay the ageing process. Age-related neurodegenerative diseases are among the main causes of morbidity and mortality in our contemporary society and represent a major socio-economic burden. There are several controversial factors that are thought to play a causal role in brain ageing which are continuously being examined in experimental models. Among them are oxidative stress and brain inflammation which are empirical to brain ageing. Although some candidate drugs have been developed which reduce the ageing phenotype, their clinical translation is limited. There are several strategies currently in development to improve brain ageing. These include strategies such as caloric restriction, ketogenic diet, promotion of cellular nicotinamide adenine dinucleotide (NAD+) levels, removal of senescent cells, 'young blood' transfusions, enhancement of adult neurogenesis, stem cell therapy, vascular risk reduction, and non-pharmacological lifestyle strategies. Several studies have shown that these strategies can not only improve brain ageing by attenuating age-related neurodegenerative disease mechanisms, but also maintain cognitive function in a variety of pre-clinical experimental murine models. However, clinical evidence is limited and many of these strategies are awaiting findings from large-scale clinical trials which are nascent in the current literature. Further studies are needed to determine their long-term efficacy and lack of adverse effects in various tissues and organs to gain a greater understanding of their potential beneficial effects on brain ageing and health span in humans.

Toward the Decipherment of Molecular Interactions in the Diabetic Brain

Diabetes mellitus (DM) has been associated with cognitive complications in the brain resulting from acute and chronic metabolic disturbances happening peripherally and centrally. Numerous studies have reported on the morphological, electrophysiological, biochemical, and cognitive changes in the brains of diabetic individuals. The detailed pathophysiological mechanisms implicated in the development of the diabetic cognitive phenotype remain unclear due to intricate molecular changes evolving over time and space. This review provides an insight into recent advances in understanding molecular events in the diabetic brain, focusing on cerebral glucose and insulin uptake, insulin action in the brain, and the role of the brain in the regulation of glucose homeostasis. Fully competent mitochondria are essential for energy metabolism and proper brain function; hence, the potential contribution of mitochondria to the DM-induced impairment of the brain is also discussed.

Anti-inflammatory effects of exercise training. A systematic review

Introduction: The diseases number with a known inflammatory etiology is constantly increasing. Cardiovascular and neurodegenerative diseases, osteoporosis, cancer, asthma, atherosclerosis, type 2 diabetes and obesity are associated with chronic low-grade inflammation. There is evidence that individuals who engage in intense physical activity or who exercise regularly, shows changes in biomarkers associated with chronic inflammation. Physical exercise is useful in preventing many diseases, due to improved cardiorespiratory, metabolic, musculoskeletal function. All these improve the immunity and antioxidant capacity, thus reducing the incidence of acute and chronic inflammatory diseases. Materials and Methods: In this study were included 90 bibliographic sources, of which the title contains the following keywords: exercise - 23, inflammation - 27, anti-inflammatory - 6, IL-6 - 13, IL-10 - 4, myokine - 3, IL-15 - 3, irisin - 6, obesity - 11, chronic inflammation - 7. This study discussed aspects of exercise, pro- and anti-inflammatory cytokines, immunological mechanisms, the dual role of IL-6 cytokine, and the anti-inflammatory effects of physical exercise. Results: Physical exercise is an efficient clinical tool, that limits chronic inflammation activating the immune system that will increase the level of anti-inflammatory IL-6 myokine. There is a direct relationship between the volume and intensity of exercise and the amount of IL-6 myokine in the blood stream. Conclusions: These studies contribute significantly to the understanding of the mechanisms of the anti-inflammatory effect of exercise. More studies on chronic low-grade inflammatory diseases are needed to understand their pathophysiology, and that will inspire the specialists improve long-term treatment strategies. Keywords: physical exercise, chronic low-grade inflammation, anti-inflammatory, IL-6, myokine,

Connection Lost, MAM: Errors in ER-Mitochondria Connections in Neurodegenerative Diseases

Mitochondria associated membranes (MAMs), as the name suggests, are the membranes that physically and biochemically connect mitochondria with endoplasmic reticulum. MAMs not only structurally but also functionally connect these two important organelles within the cell which were previously thought to exist independently. There are multiple points of communication between ER-mitochondria and MAMs play an important role in both ER and mitochondria functions such as Ca²⁺ homeostasis, proteostasis, mitochondrial bioenergetics, movement, and mitophagy. The number of disease-related proteins and genes being associated with MAMs has been continually on the rise since its discovery. There is an overwhelming overlap between the biochemical functions of MAMs and processes affected in neurodegenerative disorders such as Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and Huntington's disease (HD). Thus, MAMs have received well-deserving and much delayed attention as modulators for ER-mitochondria communication and function. This review briefly discusses the recent progress made in this now fast developing field full of promise for very exciting future therapeutic discoveries.

Neuroprotective Effects of Exogenous Irisin in Kainic Acid-Induced Status Epilepticus

Elevated reactive oxygen species (ROS) level is considered a crucial causative factor for neuronal damage in epilepsy. Irisin has been reported to ameliorate mitochondrial dysfunction and to reduce ROS levels; therefore, in this study, the effect of exogenous irisin on neuronal injury was evaluated in rats with kainic acid (KA)-induced status epilepticus (SE). Our results showed that exogenous irisin treatment significantly increased the expression of brain-derived neurotrophic factor (BDNF) and uncoupling protein 2 (UCP2), and reduced the levels of neuronal injury and mitochondrial oxidative stress. Additionally, an inhibitor of UCP2 (genipin) was administered to investigate the underlying mechanism of irisin-induced neuroprotection; in rats treated with genipin, the neuroprotective effects of irisin on KA-induced SE were found to be partially reversed. Our findings confirmed the neuroprotective effects of exogenous irisin and provide evidence that these effects may be mediated via the BDNF/UCP2 pathway, thus providing valuable insights that may aid the development of exogenous irisin treatment as a potential therapeutic strategy against neuronal injury in epilepsy.

From Exercise to Cognitive Performance: Role of Irisin

The beneficial effects of exercise on the brain are well known. In general, exercise offers an effective way to improve cognitive function in all ages, particularly in the elderly, who are considered the most vulnerable to neurodegenerative disorders. In this regard, myokines, hormones secreted by muscle in response to exercise, have recently gained attention as beneficial mediators. Irisin is a novel exercise-induced myokine, that modulates several bodily processes, such as glucose homeostasis, and reduces systemic inflammation. Irisin is cleaved from fibronectin type III domain containing 5 (FNDC5), a transmembrane precursor protein expressed in muscle under the control of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α). The FNDC5/irisin system is also expressed in the hippocampus, where it stimulates the expression of the neurotrophin brain-derived neurotrophic factor in this area that is associated with learning and memory. In this review, we aimed to discuss the role of irisin as a key mediator of the beneficial effects of exercise on synaptic plasticity and memory in the elderly, suggesting its roles within the main promoters of the beneficial effects of exercise on the brain.

Exercise training mitigates ER stress and UCP2 deficiency-associated coronary vascular dysfunction in atherosclerosis

Endoplasmic reticulum (ER) stress and uncoupling protein-2 (UCP2) activation are opposing modulators of endothelial dysfunction in atherosclerosis. Exercise reduces atherosclerosis plaques and enhances endothelial function. Our aim was to understand how exercise affects ER stress and UCP2 activation, and how that relates to endothelial dysfunction in an atherosclerotic murine model. Wild type (C57BL/6, WT) and apolipoprotein-E-knockout (ApoE^tm1Unc, ApoE KO) mice underwent treadmill exercise training (EX) or remained sedentary for 12 weeks. Acetylcholine (ACh)-induced endothelium-dependent vasodilation was determined in the presence of an eNOS inhibitor (L-NAME), UCP2 inhibitor (genipin), and ER stress inducer (tunicamycin). UCP2, ER stress markers and NLRP3 inflammasome signaling were quantified by western blotting. p67^phox and superoxide were visualized using immunofluorescence and DHE staining. Nitric oxide (NO) was measured by nitrate/nitrite assay. ACh-induced vasodilation was attenuated in coronary arterioles of ApoE KO mice but improved in ApoE KO-EX mice. Treatment of coronary arterioles with L-NAME, tunicamycin, and genipin significantly attenuated ACh-induced vasodilation in all mice except for ApoE KO mice. Exercise reduced expression of ER stress proteins, TXNIP/NLRP3 inflammasome signaling cascades, and Bax expression in the heart of ApoE KO-EX mice. Further, exercise diminished superoxide production and NADPH oxidase p67^phox expression in coronary arterioles while simultaneously increasing UCP2 expression and nitric oxide (NO) production in the heart of ApoE KO-EX mice. Routine exercise alleviates endothelial dysfunction in atherosclerotic coronary arterioles in an eNOS, UCP2, and ER stress signaling specific manner, and resulting in reduced TXNIP/NLRP3 inflammasome activity and oxidative stress.

Peroxisome Proliferator-Activated Receptor-Gamma (PPAR-ɣ): Molecular Effects and Its Importance as a Novel Therapeutic Target for Cerebral Ischemic Injury

Cerebral ischemic injury is a leading cause of death and long-term disability throughout the world. Peroxisome proliferator-activated receptor gamma (PPAR-ɣ) is a ligand-activated nuclear transcription factor that is a member of the PPAR family. PPAR-ɣ has been shown in several in vitro and in vivo models to prevent post-ischemic inflammation and neuronal damage by negatively controlling the expression of genes modulated by cerebral ischemic injury, indicating a neuroprotective effect during cerebral ischemic injury. A extensive literature review of PubMed, Medline, Bentham, Scopus, and EMBASE (Elsevier) databases was carried out to understand the nature of the extensive work done on the mechanistic role of Peroxisome proliferator activated receptor gamma and its modulation in Cerebral ischemic injury. PPAR-ɣ can interact with specific DNA response elements to control gene transcription and expression when triggered by its ligand. It regulates lipid metabolism, improves insulin sensitivity, modulates antitumor mechanisms, reduces oxidative stress, and inhibits inflammation. This review article provides insights on the current state of research into the neuroprotective effects of PPAR-ɣ in cerebral ischemic injury, as well as the cellular and molecular mechanisms by which these effects are modulated, such as inhibition of inflammation, reduction of oxidative stress, suppression of pro-apoptotic production, modulation of transcription factors, and restoration of injured tissue through neurogenesis and angiogenesis.

An Inhibitor of NF-κB and an Agonist of AMPK: Network Prediction and Multi-Omics Integration to Derive Signaling Pathways for Acteoside Against Alzheimer's Disease

Alzheimer’s disease (AD) is the most frequent type of dementia. Acteoside (ACT) is a compound isolated from Cistanche tubulosa, which possesses excellent neuroprotective properties. However, the underlying mechanism of ACT in regulating microglia polarization remains ill-defined. Therefore, a computational network model was established to identify the driving targets of ACT and predict its mechanism by integrating multiple available databases. The AlCl₃-induced AD model in zebrafish larvae was successfully constituted to demonstrate the therapeutic efficacy of ACT. Subsequently, LPS-induced BV-2 cells uncovered the positive role of ACT in M1/M2 polarization. The NF-κB and AMPK pathways were further confirmed by transcriptomic analysis, metabolomics analysis, molecular biology techniques, and molecular docking. The research provided an infusive mechanism of ACT and revealed the connection between metabolism and microglia polarization from the perspective of mitochondrial function. More importantly, it provided a systematic and comprehensive approach for the discovery of drug targets, including the changes in genes, metabolites, and proteins.

MiR-193b deregulation is associated with Parkinson's disease

PGC-1α/FNDC5/BDNF has found to be a critical pathway in neurodegeneration. MicroRNAs (miR(NA)s) are non-coding regulatory RNAs whose dysregulation has been observed in multiple neurological disorders, and miRNA-mediated gene deregulation plays a decisive role in PD. Here, candidate miRNA was chosen based on the literature survey and in silico studies. Chronic and acute models of PD were created using MPP+-treated SH-SY5Y cells. Twenty PD patients and 20 healthy volunteers were recruited. RT-qPCR was performed to assess the expression of miRNA and genes. Severe mitochondrial dysfunction induced by acute MPP+ treatment instigated compensatory mechanisms through enhancing expression of PGC-1α/FNDC5/BDNF pathway genes, while chronic MPP+ toxicity led to down-regulated levels of the genes in SH-SY5Y cells. PD peripheral blood mononuclear cells (PBMCs) also showed decreased expression of target genes. There were significant changes in the level of miR-193b in both models, as well as PD PBMCs. Moreover, miR-193b overexpression significantly affected PGC-1α, FNDC5 and TFAM levels. Interestingly, down-regulations of PGC-1α, FNDC5, BDNF and TFAM were inversely correlated with miR-193b up-regulation in PD PBMCs. This study showed the deregulation of PGC-1α/FNDC5/BDNF pathway in PD models and PBMCs, verifying its importance in neurodegeneration. Our findings also revealed that miR-193b functions in PD development, possibly through regulating PGC-1α/FNDC5/BDNF pathway, suggesting miR-193b as a potential biomarker for PD diagnosis.

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.

Physical Exercise and Alzheimer's Disease: Effects on Pathophysiological Molecular Pathways of the Disease

Alzheimer’s disease (AD), the most common form of neurodegenerative dementia in adults worldwide, is a multifactorial and heterogeneous disorder characterized by the interaction of genetic and epigenetic factors and the dysregulation of numerous intracellular signaling and cellular/molecular pathways. The introduction of the systems biology framework is revolutionizing the study of complex diseases by allowing the identification and integration of cellular/molecular pathways and networks of interaction. Here, we reviewed the relationship between physical activity and the next pathophysiological processes involved in the risk of developing AD, based on some crucial molecular pathways and biological process dysregulated in AD: (1) Immune system and inflammation; (2) Endothelial function and cerebrovascular insufficiency; (3) Apoptosis and cell death; (4) Intercellular communication; (5) Metabolism, oxidative stress and neurotoxicity; (6) DNA damage and repair; (7) Cytoskeleton and membrane proteins; (8) Synaptic plasticity. Moreover, we highlighted the increasingly relevant role played by advanced neuroimaging technologies, including structural/functional magnetic resonance imaging, diffusion tensor imaging, and arterial spin labelling, in exploring the link between AD and physical exercise. Regular physical exercise seems to have a protective effect against AD by inhibiting different pathophysiological molecular pathways implicated in AD.

PPARγ/PGC1α signaling as a potential therapeutic target for mitochondrial biogenesis in neurodegenerative disorders

Neurodegenerative diseases represent some of the most devastating neurological disorders, characterized by progressive loss of the structure and function of neurons. Current therapy for neurodegenerative disorders is limited to symptomatic treatment rather than disease modifying interventions, emphasizing the desperate need for improved approaches. Abundant evidence indicates that impaired mitochondrial function plays a crucial role in pathogenesis of many neurodegenerative diseases and so biochemical factors in mitochondria are considered promising targets for pharmacological-based therapies. Peroxisome proliferator-activated receptors-γ (PPARγ) are ligand-inducible transcription factors involved in regulating various genes including peroxisome proliferator-activated receptor gamma co-activator-1 alpha (PGC1α). This review summarizes the evidence supporting the ability of PPARγ-PGC1α to coordinately up-regulate the expression of genes required for mitochondrial biogenesis in neurons and provide directions for future work to explore the potential benefit of targeting mitochondrial biogenesis in neurodegenerative disorders. We have highlighted key roles of NRF2, uncoupling protein-2 (UCP2), and paraoxonase-2 (PON2) signaling in mediating PGC1α-induced mitochondrial biogenesis. In addition, the status of PPARγ modulators being used in clinical trials for Parkinson's disease (PD), Alzheimer's disease (AD) and Huntington's disease (HD) has been compiled. The overall purpose of this review is to update and critique our understanding of the role of PPARγ-PGC1α-NRF2 in the induction of mitochondrial biogenesis together with suggestions for strategies to target PPARγ-PGC1α-NRF2 signaling in order to combat mitochondrial dysfunction in neurodegenerative disorders.

Circulating Extracellular Vesicles: The Missing Link between Physical Exercise and Depression Management?

Depression is associated with an increased risk of aging-related diseases. It is also seemingly a common psychological reaction to pandemic outbreaks with forced quarantines and lockdowns. Thus, depression represents, now more than ever, a major global health burden with therapeutic management challenges. Clinical data highlights that physical exercise is gaining momentum as a non-pharmacological intervention in depressive disorders. Although it may contribute to the reduction of systemic inflammation associated with depression, the mechanisms underlying the beneficial physical exercise effects in emotional behavior remain to be elucidated. Current investigations indicate that a rapid release of extracellular vesicles into the circulation might be the signaling mediators of systemic adaptations to physical exercise. These biological entities are now well-established intercellular communicators, playing a major role in relevant physiological and pathophysiological functions, including brain cell-cell communication. We also reviewed emerging evidence correlating depression with modified circulating extracellular vesicle surfaces and cargo signatures (e.g., microRNAs and proteins), envisioned as potential biomarkers for diagnosis, efficient disease stratification and appropriate therapeutic management. Accordingly, the clinical data summarized in the present review prompted us to hypothesize that physical exercise-related circulating extracellular vesicles contribute to its antidepressant effects, particularly through the modulation of inflammation. This review sheds light on the triad "physical exercise-extracellular vesicles-depression" and suggests new avenues in this novel emerging field.

Mitochondria in Sex Hormone-Induced Disorder of Energy Metabolism in Males and Females

Androgens have a complex role in the regulation of insulin sensitivity in the pathogenesis of type 2 diabetes. In male subjects, a reduction in androgens increases the risk for insulin resistance, which is improved by androgen injections. However, in female subjects with polycystic ovary syndrome (PCOS), androgen excess becomes a risk factor for insulin resistance. The exact mechanism underlying the complex activities of androgens remains unknown. In this review, a hormone synergy-based view is proposed for understanding this complexity. Mitochondrial overactivation by substrate influx is a mechanism of insulin resistance in obesity. This concept may apply to the androgen-induced insulin resistance in PCOS. Androgens and estrogens both exhibit activities in the induction of mitochondrial oxidative phosphorylation. The two hormones may synergize in mitochondria to induce overproduction of ATP. ATP surplus in the pancreatic β-cells and α-cells causes excess secretion of insulin and glucagon, respectively, leading to peripheral insulin resistance in the early phase of type 2 diabetes. In the skeletal muscle and liver, the ATP surplus contributes to insulin resistance through suppression of AMPK and activation of mTOR. Consistent ATP surplus leads to mitochondrial dysfunction as a consequence of mitophagy inhibition, which provides a potential mechanism for mitochondrial dysfunction in β-cells and brown adipocytes in PCOS. The hormone synergy-based view provides a basis for the overactivation and dysfunction of mitochondria in PCOS-associated type 2 diabetes. The molecular mechanism for the synergy is discussed in this review with a focus on transcriptional regulation. This view suggests a unifying mechanism for the distinct metabolic roles of androgens in the control of insulin action in men with hypogonadism and women with PCOS.

Irisin: linking metabolism with heart failure

The heart is an organ with extremely high energy expenditure, and cardiac performance is consistent with its metabolic level. Under pathological situations, the heart adjusts its metabolic pattern through mitochondrial regulation and substrate selection to maintain energy homeostasis. Heart failure is associated with impaired cardiac energy production, transduction or utilization. Reduced exercise tolerance, skeletal muscle dystrophy and even cardiac cachexia are commonly found in patients with advanced heart failure. Irisin is a newly identified myokine and is mainly secreted by skeletal muscles after exercise. Irisin regulates metabolism and plays essential roles in the development of metabolic diseases. The heart is another abundant source of irisin synthesis and secretion other than skeletal muscle. However, the functions of irisin in the heart have not been completely elucidated. This review introduces the current understanding of the physiological role of irisin, alteration of irisin levels in heart failure, possible mechanisms of irisin in metabolic remodeling and cardiac hypertrophy, and perspectives of irisin serving as a novel target in the management of heart failure.

Irisin and Autophagy: First Update

Aging and sedentary life style are considered independent risk factors for many disorders. Under these conditions, accumulation of dysfunctional and damaged cellular proteins and organelles occurs, resulting in a cellular degeneration and cell death. Autophagy is a conserved recycling pathway responsible for the degradation, then turnover of cellular proteins and organelles. This process is a part of the molecular underpinnings by which exercise promotes healthy aging and mitigate age-related pathologies. Irisin is a myokine released during physical activity and acts as a link between muscles and other tissues and organs. Its main beneficial function is the change of subcutaneous and visceral adipose tissue into brown adipose tissue, with a consequential increase in thermogenesis. Irisin modulates metabolic processes, acting on glucose homeostasis, reduces systemic inflammation, maintains the balance between resorption and bone formation, and regulates the functioning of the nervous system. Recently, some of its pleiotropic and favorable properties have been attributed to autophagy induction, posing irisin as an important regulator of autophagy by exercise. This review article proposes to bring together for the first time the "state of the art" knowledge regarding the effects of irisin and autophagy. Furthermore, treatments on relation between exercise/myokines and autophagy have been also achieved.

Cold Exposure After Exercise Impedes the Neuroprotective Effects of Exercise on Thermoregulation and UCP4 Expression in an MPTP-Induced Parkinsonian Mouse Model

Moderate exercise and mild hypothermia have protective effects against brain injury and neurodegeneration. Running in a cold environment alters exercise-induced hyperthermia and outcomes; however, evaluations of post-exercise cold exposure related to exercise benefits for the brain are relatively rare. We investigated the effects of 4°C cold exposure after exercise on exercise-induced thermal responses and neuroprotection in an MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine)-induced Parkinsonian mouse model. Male C57BL/6J mice were pretreated with MPTP for five consecutive days and follow-up treadmill exercise for 4 weeks. After 1-h running at a 22°C temperature, the mice were exposed to a 4°C environment for 2 h. An MPTP injection induced a transient drop in body and brain temperatures, while mild brain hypothermia was found to last for 4 weeks after MPTP treatment. Preventing brain hypothermia by exercise or 4°C exposure was associated with an improvement in MPTP-induced striatal uncoupling protein 4 (UCP4) downregulation and nigrostriatal dopaminergic neurodegeneration. However, 4°C exposure after exercise abrogated the exercise-induced beneficial effects and thermal responses in MPTP-treated mice, including a low amplitude of exercise-induced brain hyperthermia and body temperature while at rest after exercise. Our findings elucidate that post-exercise thermoregulation and UCP4 expression are important in the neuroprotective effects of exercise against MPTP toxicity.

Exercise-induced immune system response: Anti-inflammatory status on peripheral and central organs

A wide array of molecular pathways has been investigated during the past decade in order to understand the mechanisms by which the practice of physical exercise promotes neuroprotection and reduces the risk of developing communicable and non-communicable chronic diseases. While a single session of physical exercise may represent a challenge for cell homeostasis, repeated physical exercise sessions will improve immunosurveillance and immunocompetence. Additionally, immune cells from the central nervous system will acquire an anti-inflammatory phenotype, protecting central functions from age-induced cognitive decline. This review highlights the exercise-induced anti-inflammatory effect on the prevention or treatment of common chronic clinical and experimental settings. It also suggests the use of pterins in biological fluids as sensitive biomarkers to follow the anti-inflammatory effect of physical exercise.

Effects of Recombinant Spidroin rS1/9 on Brain Neural Progenitors After Photothrombosis-Induced Ischemia

The existence of niches of stem cells residence in the ventricular-subventricular zone and the subgranular zone in the adult brain is well-known. These zones are the sites of restoration of brain function after injury. Bioengineered scaffolds introduced in the damaged loci were shown to support neurogenesis to the injury area, thus representing a strategy to treat acute neurodegeneration. In this study, we explored the neuroprotective activity of the recombinant analog of Nephila clavipes spidroin 1 rS1/9 after its introduction into the ischemia-damaged brain. We used nestin-green fluorescent protein (GFP) transgenic reporter mouse line, in which neural stem/progenitor cells are easily visualized and quantified by the expression of GFP, to determine the alterations in the dentate gyrus (DG) after focal ischemia in the prefrontal cortex. Changes in the proliferation of neural stem/progenitor cells during the first weeks following photothrombosis-induced brain ischemia and in vitro effects of spidroin rS1/9 in rat primary neuronal cultures were the subject of the study. The introduction of microparticles of the recombinant protein rS1/9 into the area of ischemic damage to the prefrontal cortex leads to a higher proliferation rate and increased survival of progenitor cells in the DG of the hippocampus which functions as a niche of brain stem cells located at a distance from the injury zone. rS1/9 also increased the levels of a mitochondrial probe in DG cells, which may report on either an increased number of mitochondria and/or of the mitochondrial membrane potential in progenitor cells. Apparently, the stimulation of progenitor cells was caused by formed biologically active products stemming from rS1/9 biodegradation which can also have an effect upon the growth of primary cortical neurons, their adhesion, neurite growth, and the formation of a neuronal network. The high biological activity of rS1/9 suggests it as an excellent material for therapeutic usage aimed at enhancing brain plasticity by interacting with stem cell niches. Substances formed from rS1/9 can also be used to enhance primary neuroprotection resulting in reduced cell death in the injury area.

Evaluation of COMT (rs4680), CNR2 (rs2501432), CNR2 (rs2229579), UCP2 (rs659366), and IL-17 (rs763780) gene variants in synthetic cannabinoid use disorder patients

Synthetic cannabinoids (SC) are psychoactive drugs that generally produce more severe clinical outcomes compared to Δ9-tetrahydrocannabinol. This study aimed to evaluate the relationship between clinical features of synthetic cannabinoid use disorder (SCUD) and COMT (rs4680), CNR2 (rs2501432), CNR2 (rs2229579), UCP2 (rs659366), and IL-17 (rs763780) gene variants in SCUD patients by comparing the genotype distributions of gene variants between patients and healthy controls. Based on the DSM-5 criteria, 94 patients with SCUD, confirmed with a positive urine test, and 95 healthy volunteers were included in the study. Self-mutilation, suicidal behavior, psychotic symptoms, drug-induced psychosis, tobacco use disorder (TUD) or alcohol use disorder (AUD) comorbidity, and family history of TUD or AUD were evaluated in all patients. PCR-RFLP was used to identify gene variants from DNA material. The distributions of CNR2 (rs2229579) and UCP2 (rs659366) variants were significantly different in patients diagnosed with SCUD compared to the control group. SC-related psychotic symptoms were associated with the IL-17 (rs763780) variant in SCUD patients who had an onset of SC usage under 18 years of age. While the COMT Val108Met gene variant was related to self-mutilation, the COMT Val158Met variant was associated with attempted suicide. In addition, in SCUD patients, the UCP2 (rs659366) variant was associated with a family history of AUD or TUD. In summary, CNR2 (rs2229579) and UCP2 (rs659366) variants were associated with SCUD. While SC-related psychotic symptoms were related to the IL-17 (rs763780) variant, the COMT variants were associated with self-mutilation or attempted suicide in SCUD patients.

Neuroprotective and neuro-survival properties of safinamide against methamphetamine-induced neurodegeneration: Hypothetic possible role of BDNF/TrkB/PGC-1α signaling pathway and mitochondrial uncoupling protein -2(UCP-2)

Methamphetamine is a behavioral psychostimulant that has a high potential for misuse and induction of neurotoxicity. Safinamide is a novel inhibitor of monoamine oxidase B (MAOB) with neuroprotective properties. Methamphetamine abuse causes dysfunction in the respiratory chain of the mitochondria, but the specific signaling mechanism and role of the uncoupling protein-2(UCP-2) remain unclear. As we know, some indirect evidence indicates that neurodegeneration can be caused by inhibition of the brain-derived neurotrophic factor (BDNF) receptor, TrkB and its downstream signaling pathway, such as the PGC-1α protein. Neuroprotective strategies and approaches to the management, treatment or prevention of methamphetamine-induced neurodegeneration by modulating BDNF / TrkB / PGC-1α-UCP-2 can be considered as novel therapeutic approaches to these psychostimulant neurochemical and neurobehavioral approaches. Previous studies have shown that safinamide, a monoamine oxidase-B (MAOB) inhibitor, can function as a neuroprotective agent and inhibit the neurodegenerative process especially in Parkinson's disease but its impact on other neurodegenerative processes and drug-induced neurotoxicity remain unclear. Although there is some evidence that BDNF / TrkB / PGC-1α-UCP-2 signaling pathway and mitochondrial UCP-2 mediated safinamide induced neuroprotection but it's exact and precise mechanism of action and neuroprotective effects in neurodegenerative disorder and the protective properties against methamphetamine induced neurodegeneration and the role of BDNF / TrkB / PGC-1α signaling pathway and role of mitochondrial UCP-2 in this process have not yet been clarified. Therefore, in subjects addicted to methamphetamine, we hypothesized that safinamide will provide neuroprotection against methamphetamine-prompted neurodegeneration, and it appears that BDNF / TrkB / PGC-1α signaling pathway and mitochondrial UCP-2 are likely to play a critical role.

Involvement of GPX4 in irisin's protection against ischemia reperfusion-induced acute kidney injury

Ischemia reperfusion (I/R)-induced acute kidney injury (AKI) is a common and serious condition. Irisin, an exercise-induced hormone, improves mitochondrial function and reduces reactive oxygen species (ROS) production. Glutathione peroxidase 4 (GPX4) is a key regulator of ferroptosis and its inactivation aggravates renal I/R injury by inducing ROS production. However, the effect of irisin on GPX4 and I/R-induced AKI is still unknown. To study this, male adult mice were subjected to renal I/R by occluding bilateral renal hilum for 30 min, which was followed by 24 hr reperfusion. Our results showed serum irisin levels were decreased in renal I/R mice. Irisin (250 μg/kg) treatment alleviated renal injury, downregulated inflammatory response, improved mitochondrial function, and reduced ER stress and oxidative stress after renal I/R, which were associated with upregulation of GPX4. Treated with RSL3 (a GPX4 inhibitor) abolished irisin's protective effect. Thus, irisin attenuates I/R-induced AKI through upregulating GPX4.

Targeting sirtuin activity with nicotinamide riboside reduces neuroinflammation in a GWI mouse model

Gulf War Illness (GWI) affects 30% of veterans from the 1991 Gulf War (GW), who suffer from symptoms that reflect ongoing mitochondria dysfunction. Brain mitochondria bioenergetics dysfunction in GWI animal models corresponds with astroglia activation and neuroinflammation. In a pilot study of GW veterans (n = 43), we observed that blood nicotinamide adenine dinucleotide (NAD) and sirtuin 1 (Sirt1) protein levels were decreased in the blood of veterans with GWI compared to healthy GW veterans. Since nicotinamide riboside (NR)-mediated targeting of Sirt1 is shown to improve mitochondria function, we tested whether NR can restore brain bioenergetics and reduce neuroinflammation in a GWI mouse model. We administered a mouse diet supplemented with NR at 100μg/kg daily for 2-months to GWI and control mice (n = 27). During treatment, mice were assessed for fatigue-type behavior using the Forced Swim Test (FST), followed by euthanasia for biochemistry and immunohistochemistry analyses. Fatigue-type behavior was elevated in GWI mice compared to control mice and lower in GWI mice treated with NR compared to untreated GWI mice. Levels of plasma NAD and brain Sirt1 were low in untreated GWI mice, while GWI mice treated with NR had higher levels, similar to those of control mice. Deacetylation of the nuclear-factor κB (NFκB) p65 subunit and peroxisome proliferator-activated receptor gamma coactivator 1-α (PGC-1α) was an increase in the brains of NR-treated GWI mice. This corresponded with a decrease in pro-inflammatory cytokines and lipid peroxidation and an increase in markers of mitochondrial bioenergetics in the brains of GWI mice. These findings suggest that targeting NR mediated Sirt1 activation restores brain bioenergetics and reduces inflammation in GWI mice. Further evaluation of NR in GWI is warranted to determine its potential efficacy in treating GWI.

BST Stimulation Induces Atrophy and Changes in Aerobic Energy Metabolism in Rat Skeletal Muscles-The Biphasic Action of Endogenous Glucocorticoids

(1) The primary involvement in stress-induced disturbances in skeletal muscles is assigned to the release of glucocorticoids (GCs). The current study aims to investigate the impact of the biphasic action of the chronic stress response (CSR) induced by the electrical stimulation of the bed nucleus of the stria terminalis (BST) effects on muscle atrophy and aerobic energy metabolism in soleus (SOL) and extensor digitorum longus (EDL) muscles. (2) Male Wistar rats (n = 17) were used. The rats were divided randomly into three groups: the BST two weeks (ST2), four weeks (ST4), and the sham (SHM) electrically stimulated group. The plasma corticosterone (CORT) and irisin concentration were measured. Glucocorticoid and mineralocorticoid receptors (GR and MR), 11β-hydroxysteroid dehydrogenase type 1 and 2 (HSD11B1 and HSD11B2), atrogin-1, and insulin-like growth factor-1 (IGF-1) level were determined in SOL and EDL muscles. Citrate synthase (CS) activity was measured in both muscles. (3) We found elevated plasma concentration of CORT and irisin, raised the level of GR in SOL muscle, and the higher level of MR in both muscles in the ST4 group. The level of HSD11B1 was also higher in the ST4 group compared to the SHM group. Moreover, we observed increased activity of CS in SOL. (4) We suggest that biphasic action of the glucocorticoid induced by the CSR occurs and causes dysregulation of proteins involved in muscle atrophy and aerobic energy metabolism. Our findings potentially contribute to a better understanding of the mechanisms by which GCs and the CSR may regulate muscle atrophy and energy preservation of the red muscle.

New insights into the cellular activities of Fndc5/Irisin and its signaling pathways

Fndc5, a well-defined myokine and also identified as an adipokine, has a critical role in modulation of metabolism and protection against obesity. These important functions are mediated by irisin, a secretory peptide produced from proteolytic processing of Fndc5. The other beneficial physiological effects of irisin are alleviation of oxidative stress, neuroprotective effects, and anti-inflammatory properties and associated anti-metastatic effects. Fndc5/irisin exerts its biological effects through several intracellular signaling pathways. The major signaling pathway is thought to be MAPK signaling pathways which are involved in neural differentiation, browning of white adipocytes, as well as osteoblast proliferation and differentiation. Other essential functions of Fndc5/irisin are mediated through additional pathways including AMPK pathway, PI3K/AKT, and STAT3/Snail. Thorough understanding of the mechanisms of irisin actions are essential in order to develop Fndc5/irisin for therapeutic purposes. In the present review, we focus on the current knowledge of the signaling pathways that elicit irisin actions.

Exercise, redox system and neurodegenerative diseases

Regular exercise induces a wide range of redox system-associated molecular adaptive responses to the nervous system. The intermittent induction of reactive oxygen species (ROS) during acute exercise sessions and the related upregulation of antioxidant/repair and housekeeping systems are associated with improved physiological function. Exercise-induced proliferation and differentiation of neuronal stem cells are ROS dependent processes. The increased production of brain derived neurotrophic factor (BDNF) and the regulation by regular exercise are dependent upon redox sensitive pathways. ROS are causative and associative factors of neurodegenerative diseases and regular exercise provides significant neuroprotective effects against Alzheimer's disease, Parkinson's disease, and hypoxia/reperfusion related disorders. Regular exercise regulates redox homeostasis in the brain with complex multi-level molecular pathways.

Identification of irisin as a therapeutic agent that inhibits oxidative stress and fibrosis in a murine model of chronic pancreatitis

BACKGROUND

Abnormal activation of pancreatic stellate cells (PSCs) plays a crucial role in the pathogenesis of chronic pancreatitis (CP). Irisin, an exercise-induced hormone, has been shown to mitigate liver fibrosis by inhibiting the activation of hepatic stellate cells. However, the effect of irisin in CP has not been evaluated.

METHODS

This study aimed to determine whether irisin is protective in CP. CP was induced by 6 IP injections of cerulein (50 μg/kg/body weight). HPSCs were treated with 5 ng/ml TGF-β1 as in vitro experiment.

RESULTS

Our results showed that repeated cerulein injection induced severe pancreatic injury and fibrosis in mice and the serum irisin level in cerulein-treated mice decreased as in CP patients. Excessive oxidative and ER stress was also present in the pancreas of cerulein-treated mice. Irisin treatment significantly alleviated pancreatic injury and fibrosis, which was associated with reduced oxidative and ER stress. In cultured PSCs, irisin directly inhibited TGF-β-induced α-SMA and collagen I expression. This effect appears to be mediated through downregulation of kindlin-2 and inhibition of the SMAD2/3 pathway.

CONCLUSIONS

Irisin alleviated pancreatic injury and fibrosis, which was associated with reduced oxidative and ER stress. Thus, irisin may offer therapeutic potential for patients with CP.

Irisin Exerts Inhibitory Effect on Adipogenesis Through Regulation of Wnt Signaling

Irisin is an exercise-induced myokine known to induce adipocyte browning through induction of uncoupling protein 1. Recent studies have reported that irisin is also an adipokine. However, there is limiting evidence on the role of endogenous irisin from adipocytes. In this study we aim to elucidate the expression and secretion pattern of irisin during adipocyte differentiation and the role of endogenous and exogenous irisin on the adipogenic process. As such, recombinant irisin, plasmid expressing FNDC5 and small interfering RNA were utilized. Our results show that the gene expression of irisin precursor FNDC5 and irisin secretion increases at the early stage of adipogenesis. Both recombinant irisin treated cells and FNDC5-overexpressed cells resulted in inhibition of adipogenesis evidenced by downregulated C/EBPα, PPARγ, and FABP4 expression and reduced lipid accumulation. Further data showed that the inhibitory effect of irisin on adipogenesis is mediated though potentiation of Wnt expression, which is known to determine the fate of mesenchymal stem cells and regulate adipogenesis. Conversely, FNDC5 knockdown cells showed downregulated Wnt expression, but failed to further induce adipogenesis. This study suggests that both exogenous and endogenous irisin is able to inhibit adipogenesis and that activation of Wnt and subsequent repression of transcription factors is partly involved in this process. This provides a novel insight on the local effect of irisin on adipocytes and additional benefit to protect against obesity-related metabolic disorders.

Irisin as a Multifunctional Protein: Implications for Health and Certain Diseases

Sedentary life style is considered to be an independent risk factor for many disorders, including development of type 2 diabetes, obesity, immune dysfunction, asthma, and neurological or coronary heart disease. Irisin is released from myocytes during physical activity, and acts as a link between muscles and other tissues and organs. This myokine is produced as a result of proteolytic cleavage of FNDC5 protein present in the membrane of myocytes. Secretion of irisin is regulated by N-linked oligosaccharides attached to the protein molecule. The two N-glycan molecules, which constitute a significant part of the irisin glycoprotein, regulate the browning of adipocytes, which is the most important function of irisin. A receptor specific for irisin has still not been discovered. In some tissues irisin probably acts via integrins, which are widely expressed transmembrane receptors. Many studies have confirmed the multifunctional role of irisin and the beneficial effects of this molecule on body homeostasis. Irisin reduces systemic inflammation, maintains the balance between resorption and bone formation, and modulates metabolic processes and the functioning of the nervous system. It suppresses the expression and release of pro-inflammatory cytokines in obese individuals and attenuates inflammation in adipose tissue. The impact of irisin on cancer cell proliferation, migration, and invasion has also been demonstrated in numerous studies, which proves its role in carcinogenesis. Owing to these pleiotropic and beneficial properties, irisin may be a potential option to prevent and treat civilization-related diseases which are, nowadays, considered to be the major health problems in Western societies.