Irisin: An anti-inflammatory exerkine in aging and redox-mediated comorbidities

The role of irisin in exercise-induced muscle and metabolic health: a narrative review

Irisin, a myokine released during physical exercise, has emerged as a key mediator of muscle health and metabolic regulation. This review synthesizes current evidence on how aerobic exercise stimulates irisin release and its subsequent effects, including enhanced muscle mass, strength, and recovery. Additionally, irisin promotes the browning of white adipose tissue, improving fat metabolism and glucose regulation. These adaptations position irisin as a promising therapeutic target for preventing metabolic disorders and optimizing exercise protocols. By exploring human studies and mechanistic insights, this review underscores irisin's potential to address global health challenges, such as obesity and type 2 diabetes, while advancing strategies for personalized exercise interventions.

The Complex Interplay of Irisin Levels, Low Birth Weight, and Blood Pressure in Prepubescent Children

BACKGROUND

Irisin regulates various metabolic, inflammatory, and oxidative stress processes. It has been considered a promising target in the context of the development and maintenance of cardiovascular diseases. We conducted a study to evaluate the levels of plasma irisin in prepubertal children, examining its relationship with birth weight, anthropometric parameters, biochemical profile, and blood pressure levels.

METHODS

A cross-sectional study was conducted involving 136 prepubertal children aged 6 to 11 years, with 27.9% born at a low weight. Anthropometric parameters, blood pressure, and biochemical profiles were assessed.

RESULTS

Children with low birth weight had significantly lower irisin levels compared to those with normal birth weight (p < 0.001). Birth weight was negatively correlated with blood pressure levels (systolic: r = -0.213, p = 0.013; diastolic: r = -0.223, p = 0.009) and positively correlated with irisin levels (p < 0.001). Irisin levels were positively associated with systolic blood pressure, even after adjusting for birth weight, BMI, and physical activity (p < 0.001). The linear regression analysis indicated that low birth weight and high plasma levels of irisin were recognized as predictive factors of elevated blood pressure levels.

CONCLUSION

The positive correlation observed between circulating irisin and systolic blood pressure levels in children with low birth weight, despite their lower irisin levels, suggests a complex interplay between birth weight, irisin, cardiovascular regulation, and metabolic function. Understanding this relationship may require considering that irisin may play dual roles in different tissues, compensatory mechanisms, and the broader context of cardiometabolic programming in children with low birth weight.

Irisin Predicts Cardiac Contractile and Postural Dysfunction in Patients with Chronic Heart Failure

OBJECTIVE

Irisin, a myokine, has been observed to be dysregulated in various pathological conditions. However, its role in regulating chronic heart failure (CHF)-induced physical disability in older adults remains unknown. This study aimed to investigate the associations between plasma irisin levels, cardiac parameters, and physical disability in patients with CHF.

METHOD

Cardiac contractile function, handgrip strength (HGS), gait speed (GS), short physical performance battery (SPPB), plasma c-reactive protein (CRP), and irisin levels were assessed in controls (n = 56) and patients with CHF with ischemic (n = 153) and non-ischemic (n = 139) etiologies.

RESULTS

Regardless of etiologies, significantly higher plasma CRP levels and lower irisin levels were observed in patients with CHF. The irisin level was positively correlated (r2 = 0.09, p < 0.0001) with left ventricular ejection fraction (LVEF) and negatively correlated (r2 = 0.09, p < 0.0001) with CRP in patients with CHF. Moreover, the physical parameters SPPB cumulative scores were lower while the frailty scores were significantly higher. The GS and HGS were significantly lower in patients with CHF. Indicators of postural dysfunction SPPB scores (r2 = 0.41, p < 0.0001) and GS (r2 = 0.37, p < 0.0001) were positively correlated, and the frailty index score was negatively correlated with plasma irisin. The receiver operating characteristic (ROC) curve analysis revealed higher sensitivity and specificity of irisin, particularly for non-ischemic etiology.

CONCLUSIONS

Our results provide novel evidence that plasma irisin is significantly associated with systemic inflammation and cardiac and postural dysfunction in patients with CHF. These findings suggest that irisin may serve as a potential biomarker for disease severity.

Neuromuscular and biochemical responses of the hamstrings to a Flywheel Russian belt Deadlift in women and men

The purpose of the study was to analyze hamstrings muscle damage and recovery after a novel Flywheel Russian belt Deadlift (FRBD) exercise using neuromuscular tests and associated biochemical markers of structural damage. Maximal voluntary isometric contraction (MVIC) torque and rate of force development (RFD) over several time-intervals by the 90ºhip:20ºknee test (standing isometric test for the hamstrings) and range of motion (ROM) Jurdan test (combination of active knee extension test and modified Thomas test), together with serum biomarkers of muscle damage and oxidative stress, were tested at baseline and  +24h,  +48h and  +72h in healthy, untrained and physically active 15 females (age= 21.5±3.4 years) and 15 males (age= 21.4±1.9 years). FRBD-induced muscle damage was observed as a reduction in MVIC torque and RFD at all time-intervals until +72h. Also, hamstrings neuromuscular capacity reductions were associated with serum biomarkers of structural and oxidative damage. However,  only males showed ROM changes. Overall, the FRBD triggered a decrease in hamstrings neuromuscular capacities, and an upregulation of biochemical markers of structural and oxidative damage until +72h. The 90ºhip:20ºknee test provides an adequate reliability to screen hamstrings recovery in both women and men after flywheel training, through MVIC torque and both early and late RFD.

The protective effect of irisin against hemorrhagic injury is mediated by PI3K and p38 pathways in hemorrhage/resuscitation

The objective of this study was to investigate whether phosphoinositide 3-kinase (PI3K) and p38 mitogen-activated kinase contribute to the protection of irisin during hemorrhage/resuscitation. Experimental groups were divided based on the different treatments during resuscitation as follows: (1) hemorrhage: adult male CD-1 mice were subjected to hemorrhage at a mean arterial blood pressure of 35-45 mm Hg for 60 minutes, followed by resuscitation with shed blood and lactated Ringer's solution (n = 13); (2) hemorrhage + irisin: receiving irisin (5 μg/kg; n = 13); (3) hemorrhage + irisin + PI3K inhibitor: receiving both Ly294002 (1 mg/kg, i.v.) and irisin (n = 6); and (4) hemorrhage + irisin + p38 inhibitor: receiving SB202190 (1 mg/kg, i.v.) and irisin (n = 6). Compared with hemorrhage/resuscitation control, irisin improved cardiac function and the recovery of hemodynamics in association with the decreased systemic interleukin (IL)-1, IL-6, and tumor necrosis factor (TNF)-α, which were completely abrogated by PI3K or p38 inhibitions. Furthermore, the inhibition of PI3K or p38 abolished irisin-induced reduction of the inflammatory cell infiltration and terminal deoxynucleotidyl transferase-mediated digoxigenin-deoxyuridine nick-end labeling-positive apoptosis in the cardiac and skeletal muscles. Irisin reduced TNF-α and IL-6 expression in cardiac and skeletal muscles, which was abrogated by the inhibition of PI3K or p38. Irisin-treated hemorrhage increases the phosphorylation of PI3K and p38 in both cardiac and skeletal muscles, which was mitigated by the inhibition of PI3K or p38. PI3K and p38 play an important role in modulating the protective effect of irisin during the hemorrhage/resuscitation. SIGNIFICANCE STATEMENT: This study has identified a critical pathway in the regulation of trauma/hemorrhage by using a preclinical trauma model, in which irisin, as a hormone factor, stimulates PI3K and p38 pathways to induce protection against traumatic conditions. The study holds promise for developing a new therapeutic strategy to target irisin and its pathways related to PI3K and p38 to treat trauma and its comorbidities to reduce mortality for clinical implications.

Targeting AMPK with Irisin: Implications for metabolic disorders, cardiovascular health, and inflammatory conditions - A systematic review

Irisin-based interventions have gained attention for their potential to modulate the adenosine monophosphate (AMP)-activated protein kinase (AMPK) pathway in various diseases. Physiologically, irisin is a myokine released during physical exercise that exerts anti-inflammatory effects and is a metabolic and cardiometabolic enhancer. On the other hand, AMPK is crucial for maintaining energy balance and metabolic homeostasis. Therefore, individuals presenting low blood levels of irisin and AMPK dysregulation are more predisposed to metabolic disorders and cardiovascular health inflammatory conditions since regulating energy balance and metabolic homeostasis are crucial for preventing or treating these disorders. In light of those mentioned above and considering that no review has addressed the intricate relationships between irisin and AMPK regulation in the realm of metabolic disorders, cardiovascular health, and inflammatory conditions, we comprehensively reviewed studies involving irisin's effects on AMPK signaling in different models and interventions. Our systematic analysis involved in vitro studies, animal models, and their relevant clinical implications of irisin targeting AMPK due to the absence of relevant clinical trials. The outcomes and limitations of the included studies were extensively highlighted. Objectively, irisin improved metabolic disorders by enhancing β-cell function and insulin secretion in diabetes, mitigating myocardial injury in cardiovascular conditions, and reducing inflammation and oxidative stress in various injury models by targeting AMPK. However, the lack of clinical trials limits the generalizability of these findings to human subjects. Future research should focus on translating these findings into clinical applications and exploring the broader implications of irisin-based interventions in human health.

Football (soccer) match-derived hamstring muscles residual fatigue can be monitored using early rate of torque development

PURPOSE

The aim of this study was to determine whether a soccer match affects the rapid force-generating capacity of the hamstring muscles, given their key role in both horizontal ground reaction force production during sprint biomechanics, and in the deceleration of the shank during the late swing phase, where rapid force production is essential owing to time constraints. Therefore, the research objective was to determine soccer match-induced hamstrings residual fatigue and recovery through rate of torque development (RTD) and associated biochemical parameters.

METHODS

The recovery kinetics of hamstrings RTD metrics by the 90°hip:20°knee test, together with serum biomarkers (creatine kinase, mitochondrial creatine kinase, transaminases, malondialdehyde, irisin), were assessed in 19 male, regional first-division soccer players (age = 20.9 ± 2.0 years, mass = 72.6 ± 11.9 kg, height = 175.9 ± 6.9 cm [mean ± SD]), before a soccer match (MD) and post-24 h (MD+1), post-48 h (MD+2) and post-72 h (MD+3), through a repeated measures design.

RESULTS

Early RTD to 50 ms (p < 0.001, g = -1.24) and 100 ms (p < 0.001, g = -1.06) remained unrecovered on MD+3 in both hamstring muscles. However, maximal voluntary isometric contraction (MVIC) torque of the dominant and non-dominant hamstrings was unrecovered on MD+2 (p = 0.004, g = -0.91; and p = 0.002, g = -0.98, respectively) and recovered on MD+3 (p = 0.057 and p = 0.070, respectively). Further, neuromuscular deficits were coupled with myocyte structural (p = 0.002, g = 1.11) and mitochondrial damage (p = 0.004, g = 0.92) biomarkers.

CONCLUSION

Based in the findings, early RTD0-50 and RTD0-100 monitoring, through the 90°hip:20°knee IPC test, is a cost-effective method for assessing soccer match-induced hamstring muscles residual fatigue and recovery. Overall, soccer match-induced hamstring residual fatigue is not recovered within a 3-day recovery period. Practitioners can use rapid force production metrics through isometric assessments, providing a simple, non-exhaustive tool, for assessing residual fatigue status during congested competitive periods, to comprehensively balance muscle recovery with optimizing training.

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.

Current knowledge and scientific trends in myokines and exercise research in the context of obesity

The relationship between exercise and obesity has attracted increasing attention from researchers worldwide in recent years. The aim of the present study was to analyze the current knowledge and scientific trends of research into myokines and exercise in the context of obesity and provide ideas for future research strategies to prevent obesity. The study conducted a comprehensive bibliometric analysis of 300 scientific publications related to myokines, exercise, and obesity from 2004 to 2024. Applying the VOSviewer tool, the analysis revealed a significant increase over time in the number of publications on these topics, with a total of 1,142 related keywords identified. Key themes identified in the analysis included molecular processes, new organokines, skeletal muscle research, model organism studies, and human studies based on sex and age differences. The study highlighted the growing interest in the molecular mechanisms of obesity and role of myokines. Results showed a substantial increase in publications from 2014 to 2024, with a focus on new organokines (myokines, adipokines) and animal models. The analysis underscored the importance of myokines in modulating metabolic processes and their potential therapeutic implications in managing non-communicable diseases such as obesity. Furthermore, the study revealed the close relationship between exercise, myokine production, and regulation of metabolism, stress response, and inflammation. In conclusion, over the last years, increasing research interest has been focused on the molecular mechanisms of obesity and benefits of exercise, and probably will be focused on a set of myokines released during muscle contraction. A newly identified myokines has emerged as a promising marker for the prevention and control of obesity.

'Exerkines': A Comprehensive Term for the Factors Produced in Response to Exercise

Regular exercise and physical activity are now considered lifestyle factors with positive effects on human health. Physical activity reduces disease burden, protects against the onset of pathologies, and improves the clinical course of disease. Unlike pharmacological therapies, the effects mediated by exercise are not limited to a specific target organ but act in multiple biological systems simultaneously. Despite the substantial health benefits of physical training, the precise molecular signaling processes that lead to structural and functional tissue adaptation remain largely unknown. Only recently, several bioactive molecules have been discovered that are produced following physical exercise. These molecules are collectively called "exerkines". Exerkines are released from various tissues in response to exercise, and play a crucial role in mediating the beneficial effects of exercise on the body. Major discoveries involving exerkines highlight their diverse functions and health implications, particularly in metabolic regulation, neuroprotection, and muscle adaptation. These molecules, including peptides, nucleic acids, lipids, and microRNAs, act through paracrine, endocrine, and autocrine pathways to exert their effects on various organs and tissues. Exerkines represent a complex network of signaling molecules that mediate the multiple benefits of exercise. Their roles in metabolic regulation, neuroprotection, and muscle adaptation highlight the importance of physical activity in maintaining health and preventing disease.

The Application Potential of the Regulation of Tregs Function by Irisin in the Prevention and Treatment of Immune-Related Diseases

Irisin is a muscle factor induced by exercise, generated through the proteolytic cleavage of the membrane protein fibronectin type III domain-containing protein 5 (FNDC-5). Numerous studies have shown that irisin plays a significant role in regulating glucose and lipid metabolism, inhibiting oxidative stress, reducing systemic inflammatory responses, and providing neuroprotection. Additionally, irisin can exert immunomodulatory functions by regulating regulatory T cells (Tregs). Tregs are a highly differentiated subset of mature T cells that play a key role in maintaining self-immune homeostasis and are closely related to infections, inflammation, immune-related diseases, and tumors. Irisin exerts persistent positive effects on Treg cell functions through various mechanisms, including regulating Treg cell differentiation and proliferation, improving their function, modulating the balance of immune cells, increasing the production of anti-inflammatory cytokines, and enhancing metabolic functions, thereby helping to maintain immune homeostasis and prevent immune-related diseases. As an important myokine, irisin interacts with receptors on the cell membrane, activating multiple intracellular signaling pathways to regulate cell metabolism, proliferation, and function. Although the specific receptor for irisin has not been fully identified, integrins are considered potential receptors. Irisin activates various signaling pathways, including AMPK, MAPK, and PI3K/Akt, through integrin receptors, thereby exerting multiple biological effects. These research findings provide important clues for understanding the mechanisms of irisin's action and theoretical basis for its potential applications in metabolic diseases and immunomodulation. This article reviews the relationship between irisin and Tregs, as well as the research progress of irisin in immune-related diseases such as multiple sclerosis, myasthenia gravis, acquired immune deficiency syndrome, type 1 diabetes, sepsis, and rheumatoid arthritis. Studies have revealed that irisin plays an important role in immune regulation by improving the function of Tregs, suggesting its potential application value in the treatment of immune-related diseases.

The time course of irisin release after an acute exercise: relevant implications for health and future experimental designs

This study aimed to analyze the acute impact of exercise on serum irisin levels in 22 young (YA, 24.6 ± 3.5 yrs) and in 12 middle-aged male adults (MA, 54.6 ± 5.7 yrs) 15 min and 24 h after an incremental cycling exercise test to exhaustion. ELISA assay was used for serum irisin detection. Circulating irisin increased significantly from baseline (9.0 ± 2.0 ng/ml) to 15 min post-exercise (10.2 ± 2.0 ng/ml, P < 0.001), but the greatest increment was detected after 24 h (13.5 ± 2.5 ng/ml, P < 0.001) reaching more than 50% of the basal release. Levels were significantly higher in YA (9.7 ± 1.7 to 11.1 ± 1.8 to 14.5 ± 2.2 ng/ml) than MA (7.6 ± 1.6 to 8.7 ± 1.5 to 11.8± 2.2 ng/ml) for all measured time-points (P < 0.05). Nevertheless, MA showed a comparable increase in serum irisin levels when compared to YA. These findings highlight the importance of acute physical exercise as a countermeasure against age-related deterioration of skeletal muscle mass and function in both YA and MA.

Myokines: metabolic regulation in obesity and type 2 diabetes

Skeletal muscle plays a vital role in the regulation of systemic metabolism, partly through its secretion of endocrine factors which are collectively known as myokines. Altered myokine levels are associated with metabolic diseases, such as type 2 diabetes (T2D). The significance of interorgan crosstalk, particularly through myokines, has emerged as a fundamental aspect of nutrient and energy homeostasis. However, a comprehensive understanding of myokine biology in the setting of obesity and T2D remains a major challenge. In this review, we discuss the regulation and biological functions of key myokines that have been extensively studied during the past two decades, namely interleukin 6 (IL-6), irisin, myostatin (MSTN), growth differentiation factor 11 (GDF11), fibroblast growth factor 21 (FGF21), apelin, brain-derived neurotrophic factor (BDNF), meteorin-like (Metrnl), secreted protein acidic and rich in cysteine (SPARC), β-aminoisobutyric acid (BAIBA), Musclin, and Dickkopf 3 (Dkk3). Related to these, we detail the role of exercise in myokine expression and secretion together with their contributions to metabolic physiology and disease. Despite significant advancements in myokine research, many myokines remain challenging to measure accurately and investigate thoroughly. Hence, new research techniques and detection methods should be developed and rigorously tested. Therefore, developing a comprehensive perspective on myokine biology is crucial, as this will likely offer new insights into the pathophysiological mechanisms underlying obesity and T2D and may reveal novel targets for therapeutic interventions.

A Narrative Review on Adipose Tissue and Overtraining: Shedding Light on the Interplay among Adipokines, Exercise and Overtraining

Lifestyle factors, particularly physical inactivity, are closely linked to the onset of numerous metabolic diseases. Adipose tissue (AT) has been extensively studied for various metabolic diseases such as obesity, type 2 diabetes, and immune system dysregulation due to its role in energy metabolism and regulation of inflammation. Physical activity is increasingly recognized as a powerful non-pharmacological tool for the treatment of various disorders, as it helps to improve metabolic, immune, and inflammatory functions. However, chronic excessive training has been associated with increased inflammatory markers and oxidative stress, so much so that excessive training overload, combined with inadequate recovery, can lead to the development of overtraining syndrome (OTS). OTS negatively impacts an athlete's performance capabilities and significantly affects both physical health and mental well-being. However, diagnosing OTS remains challenging as the contributing factors, signs/symptoms, and underlying maladaptive mechanisms are individualized, sport-specific, and unclear. Therefore, identifying potential biomarkers that could assist in preventing and/or diagnosing OTS is an important objective. In this review, we focus on the possibility that the endocrine functions of AT may have significant implications in the etiopathogenesis of OTS. During physical exercise, AT responds dynamically, undergoing remodeling of endocrine functions that influence the production of adipokines involved in regulating major energy and inflammatory processes. In this scenario, we will discuss exercise about its effects on AT activity and metabolism and its relevance to the prevention and/or development of OTS. Furthermore, we will highlight adipokines as potential markers for diagnosing OTS.

Harmful Free Radicals in Aging: A Narrative Review of Their Detrimental Effects on Health

The production of harmful free radicals (H-FRs), especially those with oxygen or nitrogen atoms, depends on both internal and environmental causes. The negative effects of H-FRs are greatly alleviated by antioxidant protection. The harmful impact of oxidative stress, or OS, is brought on by a disparity between the defense mechanisms of the body and the creation of H-FRs. Aging is characterized by a slow decline in tissue and organ competence. Age-mediated pathologies start as an aberrant accumulation of H-FRs, which inhibit cells' capacity to divide, repair, and operate, based on the OS theorem of aging. The natural outcome of this situation is apoptosis. These conditions may include skeletal muscle dysfunction, cancer, cardiovascular, chronic hepatitis, chronic renal, and chronic pulmonary disorders. Given the substantial role that OS plays in the progression of many of these illnesses, antioxidant-based therapy may have a favorable impact on how these diseases progress. To ascertain the true efficacy of this therapy strategy, more research is necessary. The aim of this study is to provide an overview of the literature on this challenging issue that is attracting interest.

(-)-epicatechin treatment did not modify the thermogenic pathway in the gastrocnemius muscle of male rat offspring obeses by programming

The aim of this study was to analyse the expression of genes related to the regulation of energy metabolism in skeletal muscle tissue by comparing male offspring in two age groups [at 110 and 245 postnatal days (pnd)] from a mother with obesity induced by a high-fat diet and (-)-epicatechin (Epi) administration. Four groups of six male offspring from different litters were randomly selected for the control groups [C and offspring of mothers with maternal obesity (MO)] or Epi intervention groups. We evaluated the effect of Epi on gastrocnemius tissue by analysing the mRNA and protein expression levels of Fndc5/irisin, Pgc-1α, Ucp3, and Sln. Epi significantly increased the Pgc-1α protein in the MO group of offspring at 110 pnd (p < 0.036, MO vs. MO+Epi), while at 245 pnd, Epi increased Fndc5/irisin mRNA expression in the MO+Epi group versus the MO group (p = 0.006).No differences were detected in Fndc5/irisin, Ucp3 or Sln mRNA or protein levels (including Pgc-1α mRNA) in the offspring at 110 pnd or in Pgc-1α, Ucp3, or Sln mRNA or protein levels (including Fndc5/irisin protein) at 245 pnd among the experimental groups. In conclusion, (-)-epicatechin treatment increased Fndc5/irisin mRNA expression and Pgc-α protein levels in the gastrocnemius muscle of offspring at postnatal days 110 and 245. Furthermore, it is suggested that the flavonoid effect in a model of obesity and its impact on thermogenesis in skeletal muscle are regulated by a different pathway than Fndc5/irisin.

The emerging roles of irisin in vascular calcification

Vascular calcification is a common accompanying pathological change in many chronic diseases, which is caused by calcium deposition in the blood vessel wall and leads to abnormal blood vessel function. With the progress of medical technology, the diagnosis rate of vascular calcification has explosively increased. However, due to its mechanism's complexity, no effective drug can relieve or even reverse vascular calcification. Irisin is a myogenic cytokine regulating adipose tissue browning, energy metabolism, glucose metabolism, and other physiological processes. Previous studies have shown that irisin could serve as a predictor for vascular calcification, and protect against hypertension, diabetes, chronic kidney disease, and other risk factors for vascular calcification. In terms of mechanism, it improves vascular endothelial dysfunction and phenotypic transformation of vascular smooth muscle cells. All the above evidence suggests that irisin plays a predictive and protective role in vascular calcification. In this review, we summarize the association of irisin to the related risk factors for vascular calcification and mainly explore the role of irisin in vascular calcification.

Epigenetic modifications in obesity-associated diseases

The global prevalence of obesity has reached epidemic levels, significantly elevating the susceptibility to various cardiometabolic conditions and certain types of cancer. In addition to causing metabolic abnormalities such as insulin resistance (IR), elevated blood glucose and lipids, and ectopic fat deposition, obesity can also damage pancreatic islet cells, endothelial cells, and cardiomyocytes through chronic inflammation, and even promote the development of a microenvironment conducive to cancer initiation. Improper dietary habits and lack of physical exercise are important behavioral factors that increase the risk of obesity, which can affect gene expression through epigenetic modifications. Epigenetic alterations can occur in early stage of obesity, some of which are reversible, while others persist over time and lead to obesity-related complications. Therefore, the dynamic adjustability of epigenetic modifications can be leveraged to reverse the development of obesity-associated diseases through behavioral interventions, drugs, and bariatric surgery. This review provides a comprehensive summary of the impact of epigenetic regulation on the initiation and development of obesity-associated cancers, type 2 diabetes, and cardiovascular diseases, establishing a theoretical basis for prevention, diagnosis, and treatment of these conditions.

Irisin mitigates rheumatoid arthritis by suppressing mitochondrial fission via inhibiting YAP-Drp1 signaling pathway

BACKGROUND

Irisin is a hormone-like factor secreted by muscle cells and produced by cleavage of the membrane protein fibronectin type III domain protein 5 (FNDC5), which exerts anti-inflammatory and anti-proliferative effects. However, the effects and the underlying mechanisms of irisin in rheumatoid arthritis (RA) are still unclear.

METHOD

Collagen-induced arthritis (CIA) model was induced in DBA/1 mice and then treated with irisin. Arthritis index, paw thickness, weight, number of affected paws, serum inflammatory factors and related pathological tests were measured. RA fibroblast-like synoviocytes (RA-FLSs) were pretreated with IL-1β and irisin, and the migration, proliferation, invasion, oxidative stress and mitochondrial related function of RA-FLSs were detected.

RESULTS

Irisin significantly improved arthritis symptoms in CIA mice, as indicated by reduced arthritis index, alleviated paw thickness, decreased the number of affected paws and inhibited release of inflammatory factors. Irisin alleviated joint destruction, FLSs proliferation and the expression of YES-associated protein (YAP) and mitochondrial dynamic related protein 1 (Drp1) in the FLSs of CIA mice. In vitro experiment, irisin inhibited the proliferation, migration and invasion of RA-FLSs and improved oxidative stress induced by IL-1β, thereby restraining the pathogenic transformation of RA-FLSs. Mechanically, irisin suppressed the nuclear translocation of YAP, in turn, could reduce the synthesis of Drp1 protein and inhibit the mitochondrial fission of RA-FLSs, which was reversed by YAP agonists. Therefore, irisin has a protective effect on RA.

CONCLUSION

Irisin inhibits the proliferation, migration, invasion and inflammatory response of RA-FLSs by inhibiting the YAP-Drp1 signaling pathway, which implies a potential therapeutic effect on RA.

Plasma irisin and the brain-derived neurotrophic factor levels in sedentary subjects: effect of 8-weeks lifestyle intervention

Objectives. Sedentary lifestyle increasingly observed in the population contributes to the incremental incidence of obesity, cardiovascular diseases, mental disorders, type 2 diabetes, hyper-tension, dyslipidemia, and others. Physical inactivity together with an imbalance in caloric intake and expenditure leads to a loss of muscle mass, reduced insulin sensitivity, and accumulation of the visceral fat. Organokines (adipokines, myokines, hepatokines, etc.) serve in the organism for inter-organ communication. However, human studies focused on the exercise-related changes in plasma levels of certain myokines have produced contradictory results. In the present study, we verified a hypothesis that myokine irisin, which is expected to increase in response to physical activity, induces brain-derived neurotrophic factor (BDNF) production and by this way mediates the beneficial effect of exercise on several brain functions. Subjects and Methods. Women (n=27) and men (n=10) aged 44.5±12.0 years, who were sedentary and overweight/obese (men ≥25%, women ≥28% body fat), participated in the study. The effect of an 8-week intensive lifestyle intervention (150 minutes of moderate physical activity per week, diet modification, and reduction of caloric intake) on the selected organokines (irisin, BDNF) in the context of an expected improvement in cardiometabolic status was examined. Results. The 8-week lifestyle intervention resulted in a significant (p<0.05) reduction in body mass index, body fat, blood pressure, insulin resistance, lipid and liver parameters, and irisin levels (p<0.001). However, BDNF increase in the whole group did not reach statistical significance. After the improvement of cardiometabolic parameters, a significant decrease in irisin and increase in BDNF levels were also observed in the subgroup with unsatisfactory (≤5%) body weight reduction. Neither relationship between irisin and BDNF levels, nor effect of age or sex on their levels was observed. Conclusions. We cannot confirm the hypothesis that exercise-induced irisin may increase the BDNF levels, whereas, the organokine levels in the periphery may not completely reflect the processes in the brain compartments. The observed decrease in irisin levels after 8-week intensive lifestyle intervention program, which was in contrary to its supposed mechanisms of action and dynamics, suggests the presence of several yet undiscovered impacts on the secretion of irisin.

Revisiting Skeletal Muscle Dysfunction and Exercise in Chronic Obstructive Pulmonary Disease: Emerging Significance of Myokines

Skeletal muscle dysfunction (SMD) is the most significant extrapulmonary complication and an independent prognostic indicator in patients with chronic obstructive pulmonary disease (COPD). Myokines, such as interleukin (IL)-6, IL-15, myostatin, irisin, and insulin-like growth factor (IGF)-1, play important roles in skeletal muscle mitochondrial function, protein synthesis and breakdown balance, and regeneration of skeletal muscles in COPD. As the main component of pulmonary rehabilitation, exercise can improve muscle strength, muscle endurance, and exercise capacity in patients with COPD, as well as improve the prognosis of SMD and COPD by regulating the expression levels of myokines. The mechanisms by which exercise regulates myokine levels are related to microRNAs. IGF-1 expression is upregulated by decreasing the expression of miR-1 or miR-29b. Myostatin downregulation and irisin upregulation are associated with increased miR-27a expression and decreased miR-696 expression, respectively. These findings suggest that myokines are potential targets for the prevention and treatment of SMD in COPD. A comprehensive analysis of the role and regulatory mechanisms of myokines can facilitate the development of new exercise-based therapeutic approaches for patients with COPD.

Irisin, in women and men: blood pressure, heart rate, obesity and insulin resistance

Background

Irisin is a myokine that increases with leisure time physical activity (LTPA) and for which a cardiovascular protective role has been postulated. Our aim was to assess this role in the general population.

Methods

A cross-sectional analysis was performed in a large randomly selected population sample (n=2298 women and 1529 men). Apart from age and sex, we record anthropometrics (blood pressure, heart rate, obesity), lifestyle (LTPA, smoking, alcohol), and biochemical measurements (irisin, lipid profile, insulin resistance). Correlations and regression multivariate models were used to analyze the association of irisin levels with the studied factors.

Results

The variables more strongly and directly associated with irisin, adjusting the studied factors separately in women and men, were HOMA-2 (p=0.043 and p=0.001, respectively) and LTPA (p<0.001 and p=0.001, respectively). Also heart rate inversely (p=0.005 and p=0.002, respectively) and DBP directly (p<0.005 and p=0.045, respectively) were associated to irisin in both sexes. The waist/height ratio (p<0.001) was inversely associated to irisin only in women, and the alcohol drinking was directly associated (p=0.029) only in men.

Conclusion

We provide new findings for irisin, such as its association with DBP and with heart rate; furthermore, in women irisin is associated to abdominal obesity, and in men is associated to the alcohol intake. We also corroborate the association of irisin with LTPA and insulin resistance. The associations detected point towards a protective role of irisin in the maintenance of cardiometabolic health.