Plasma irisin levels progressively increase in response to increasing exercise workloads in young, healthy, active subjects

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

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

Exercise training mode effects on myokine expression in healthy adults: A systematic review with meta-analysis

BACKGROUND

The benefits of exercise are well known; however, many of the underlying molecular mechanisms are not fully understood. Skeletal muscle secretes myokines, which mediate muscle-organ crosstalk. Myokines regulate satellite-cell proliferation and migration, inflammatory cascade, insulin secretion, angiogenesis, fatty oxidation, and cancer suppression. To date, the effects of different exercise modes (namely, aerobic and resistance exercise) on myokine response remain to be elucidated. This is crucial considering the clinical implementation of exercise to enhance general health and wellbeing and as a medical treatment.

METHODS

A systematic search was undertaken in PubMed, MEDLINE, CINAHL, Embase, SPORTDiscus, and Web of Science in April 2023. Eligible studies examining the effects of a single bout of exercise on interleukin15 (IL-15), irisin, secreted protein acidic and rich in cysteine (SPARC), oncostatin M (OSM), and decorin were included. A random-effects meta-analysis was also undertaken to quantify the magnitude of change.

RESULTS

Sixty-two studies were included (n = 1193). Overall, exercise appeared to induce small to large increases in myokine expression, with effects observed immediately after to 60 min post-exercise, although these were mostly not statistically significant. Both aerobic and resistance exercise resulted in changes in myokine levels, without any significant difference between training modes, and with the magnitude of change differing across myokines. Myokine levels returned to baseline levels within 180 min to 24 h post-exercise. However, owing to potential sources of heterogeneity, most changes were not statistically significant, indicating that precise conclusions cannot be drawn.

CONCLUSION

Knowledge is limited but expanding with respect to the impact of overall and specific effects of exercise on myokine expression at different time points in the systemic circulation. Further research is required to investigate the effects of different exercise modes at multiple time points on myokine response.

Research trends and hotspot evolution of exercise-regulated myokines: a bibliometric analysis from 2003 to 2023

Background

The lack of physical activity is a common issue in modern society and is considered a major risk factor for various chronic non-communicable diseases. Bioactive factors secreted by skeletal muscle during exercise play a crucial role in inter-organ interactions. Since the concept of "myokines" was proposed in 2004, hundreds of regulatory myokines have been identified. Visual analysis of research on exercise-regulated myokines is significant to explore research hotspots and frontiers in this field.

Methods

Research literature on exercise-regulated myokines from 2003 to 2023 in the "Web of Science" database was used as the data source. Knowledge maps were drawn using "VOS Viewer, CiteSpace, and R-bibliometrix" software.

Results

A total of 1,405 papers were included, showing a fluctuating yet slow growth in annual publications. The United States and China led in the number of publications and collaboration networks. Harvard University ranked first with 120 publications. CIBER (centrality 0.16) and the University of California System (centrality 0.16) were pivotal in advancing this field. PEDERSEN BK led author rankings with 41 publications and 1,952 citations. FRONTIERS IN PHYSIOLOGY ranked first among journals with 64 publications and the highest g-index (39), while PLoS One had the highest h-index (25) and most citations (2,599). Key co-cited reference clusters included #1 skeletal muscle dysfunction, #2 obesity, #6 ASCs, and #7 adaptive immunocytes. Pontus Boström's paper had a notable citation burst intensity of 77.37. High-frequency keywords were "exercise" (509), "skeletal muscle" (452), and "expression" (293), with long-term keywords such as #0 irisin, #2 insulin resistance, #3 transcription, and #6 physical activity. Recently, keywords like "physical exercise," "resistance exercise," "aerobic exercise," "insulin," and "oxidative stress" have emerged.

Conclusion

Research in the field of exercise-regulated myokines shows an overall upward trend. The focus areas include myokines mediated by different types of exercise, the interaction of irisin-mediated muscle with other organs, and the important role of myokine-mediated oxidative stress in exercise simulation.

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.

Association between modifiable lifestyle factors and telomere length: a univariable and multivariable Mendelian randomization study

BACKGROUND

Telomere length has long been recognized as a valuable biomarker of aging and is inversely correlated with chronological age. Various lifestyle factors have been implicated in telomere shortening or preservation; however, the association between lifestyle factors and telomere length remains controversial. To address this issue, we conducted a Mendelian randomization (MR) analysis to investigate the potential causal associations between multiple lifestyle factors and telomere length.

METHODS

Independent genetic variants strongly associated with lifestyle factors (tobacco smoking, sleep duration, insomnia, and physical activity) were selected as instrumental variables from corresponding genome-wide association studies (GWASs). Summary-level data for telomere length was obtained from a GWAS comprising 472,174 European ancestries. Univariable and multivariable MR analyses were performed to assess the relationships.

RESULTS

The genetic liability to lifetime smoking was robustly associated with shorter telomere length (odd ratio [OR]: 0.882; 95% confidence interval [CI]: 0.847-0.918). Genetically predicted insomnia was also linked to shorter telomere length (OR: 0.972; 95% CI: 0.959-0.985), while no significant association was observed between sleep duration and telomere length. Furthermore, a suggestive association was found between moderate-to-vigorous physical activity and longer telomere length (OR: 1.680; 95% CI: 1.115-2.531). In multivariable MR analyses, adjusting for potential mediators such as body mass index, type 2 diabetes, alcohol consumption, and alcohol use disorder, the associations of lifetime smoking and insomnia with telomere length remained robust.

CONCLUSION

Our findings suggest that smoking and insomnia may contribute to telomere shortening, while physical activity may play a role in telomere length maintenance. These findings underscore the importance of managing positive risk factors and adopting a healthy lifestyle to promote telomere health.

Sex Differences in Bone, Muscle, and Inflammatory Markers and Their Associations with Muscle Performance Variables

The importance of various markers such as Sclerostin, Dickkopf-1 (DKK-1), Irisin, receptor activator of NF-kB ligand (RANKL), and Vitamin D have been well studied in bone metabolism. Additionally, inflammatory cytokines such as tumor necrosis factor-alpha (TNF-α) and Interleukin 6 (IL-6) have been shown to hinder muscle protein synthesis, leading to the loss of muscle and strength. However, a research gap exists in understanding their role in muscle function and physical activity. Therefore, this study aims to explore the serum levels of Sclerostin, DKK-1, Irisin, IL-6, RANKL, Vitamin D, and TNF-α and assess their relationships with upper- and lower-body strength in young adults. In this study, 38 college-aged students (18-23 years), males and females, participated and completed the protocols. The participants' lower and upper body strength were assessed by the vertical jump test (Just Jump, Probotic, AL) with a Tendo FitroDyne (Tendo Sports Machines, Trencin, Slovak Republic) and handgrip (HG) dynamometry (Takei Scientific Instruments, Yashiroda, Japan), respectively. Fasting morning blood samples were analyzed for serum levels of biomarkers by ELISA. The results indicate significant sex differences in Sclerostin, DKK-1, Irisin, and Vitamin D levels (p < 0.05). Furthermore, a positive association was observed between Sclerostin, DKK-1, and Vitamin D, with lower body muscle performance variables (p < 0.05). Conversely, a significant negative correlation was observed between TNF-α and lower-body muscle performance variables (p < 0.05). The results suggest that these markers may have a distinct effect on muscle performance, underscoring the need for further investigation to elucidate the concept of muscle-bone crosstalk.

Time Spent Jogging/Running and Biological Aging in 4458 U.S. Adults: An NHANES Investigation

Telomere length is a good index of cellular aging. Longer telomeres are predictive of longer life, and healthy lifestyles are associated with longer telomeres. This study explored the relationship between time spent jogging or running each week and leukocyte telomere length (LTL) in 4458 randomly selected U.S. adults. The association was studied using data collected by the National Health and Nutrition Examination Survey (NHANES), and a cross-sectional design. Total weekly jog/run time was calculated from survey responses. From the minute totals, three categories were formed: <10 min/week, 10-74 min/week, and ≥75 min/week. Adults in the third category met the U.S. guidelines. Data were analyzed using one-way ANOVA. Partial correlation was used to adjust for differences in potential mediating factors, including demographic and lifestyle/medical factors. In the total sample, after adjusting for all the potential covariates, mean LTL significantly differed across the three jog/run categories (F = 4.1, p = 0.0272). Specifically, adults who met the guidelines via jogging and/or running had significantly longer telomeres than adults who performed no jogging/running. Adults in the middle category did not differ from the other two categories. A minimum of 75 min of jogging/running weekly is predictive of longer telomeres when compared to adults who do not jog or run regularly.

Highlighting the idea of exerkines in the management of cancer patients with cachexia: novel insights and a critical review

BACKGROUND

Exerkines are all peptides, metabolites, and nucleic acids released into the bloodstream during and after physical exercise. Exerkines liberated from skeletal muscle (myokines), the heart (cardiokines), liver (hepatokines), white adipose tissue (adipokines), brown adipose tissue (batokines), and neurons (neurokines) may benefit health and wellbeing. Cancer-related cachexia is a highly prevalent disorder characterized by weight loss with specific skeletal muscle and adipose tissue loss. Many studies have sought to provide exercise strategies for managing cachexia, focusing on musculoskeletal tissue changes. Therefore, understanding the responses of musculoskeletal and other tissue exerkines to acute and chronic exercise may provide novel insight and recommendations for physical training to counteract cancer-related cachexia.

METHODS

For the purpose of conducting this study review, we made efforts to gather relevant studies and thoroughly discuss them to create a comprehensive overview. To achieve this, we conducted searches using appropriate keywords in various databases. Studies that were deemed irrelevant to the current research, not available in English, or lacking full-text access were excluded. Nevertheless, it is important to acknowledge the limited amount of research conducted in this specific field.

RESULTS

In order to obtain a comprehensive understanding of the findings, we prioritized human studies in order to obtain results that closely align with the scope of the present study. However, in instances where human studies were limited or additional analysis was required to draw more robust conclusions, we also incorporated animal studies. Finally, 295 studies, discussed in this review.

CONCLUSION

Our understanding of the underlying physiological mechanisms related to the significance of investigating exerkines in cancer cachexia is currently quite basic. Nonetheless, this demonstrated that resistance and aerobic exercise can contribute to the reduction and control of the disease in individuals with cancer cachexia, as well as in survivors, by inducing changes in exerkines.

Contribution of High-Intensity Interval Exercise in the Fasted State to Fat Browning: Potential Roles of Lactate and β-Hydroxybutyrate

PURPOSE

Fat browning contributes to energy consumption and may have metabolic benefits against obesity; however, the potential roles of lactate and β-hydroxybutyrate (β-HB) in fat browning remain unclear. We investigated the roles of a single bout of aerobic exercise that increases lactate and β-HB levels in the fasted state on the regulation of fat browning in rats and humans.

METHODS

Male Sprague-Dawley rats were exposed to 24-h fasting and/or a single bout moderate-intensity aerobic exercise (40 min): sedentary (CON), exercise (ND-EX), fasting (FAST), and exercise + fasting (F-EX). Adult men ( n = 13) were randomly assigned into control with food intake (CON), exercise with intensity at onset of blood lactate accumulation in the fasted state (F-OBLA), and high-intensity interval exercise in the fasted state (F-HIIE) until each participant expended 350 kcal of energy. For evaluating the effects of exercise intensity in rats, we conducted another set of animal experiment, including groups of sedentary fed control, fasting control, and exercise with moderate-intensity or HIIE for 40 min after a 24-h fasting.

RESULTS

Regardless of fasting, single bout of exercise increases the concentration of lactate and β-HB in rats, but the exercise in the fasted state increases the β-HB level more significantly in rats and humans. F-EX-activated fat browning (AMPK-SirT1-PGC1α pathway and PRDM16) and thermogenic factor (UCP1) in white fat of rats. In rats and humans, exercise in the fasted state increased the blood levels of fat browning-related adipomyokines. In particular, compared with F-OBLA, F-HIIE more efficiently increases free fatty acid as well as blood levels of fat browning adipomyokines in humans, which was correlated with blood levels of lactate and β-HB. In rats that performed exercise with different intensity, the higher plasma lactate and β-HB levels, and higher expression of p-AMPK, UCP1, and PRDM16 in white adipose tissue of HIIE group than those of moderate-intensity group, were observed.

CONCLUSIONS

A single bout of aerobic exercise in the fasted state significantly induced fat browning-related pathways, free fatty acid, and adipomyokines, particularly F-HIIE in human. Although further evidence for supporting our results is required in humans, aerobic exercise in the fasted state with high intensity that increase lactate and β-HB may be a modality of fat browning.

The Positive Effect of Four-Week Combined Aerobic-Resistance Training on Body Composition and Adipokine Levels in Obese Females

Obesity is a metabolic disease that is caused by a lack of physical activity and is associated with an increased risk of chronic inflammation. A total of 40 obese adolescent females with an average age of 21.93 ± 1.35 years and average body mass index (BMI) of 30.81 ± 3.54 kg/m² were enrolled in this study, randomized, and divided into four groups, i.e., control (CTL; n = 10), moderate intensity aerobic training (MAT; n = 10), moderate intensity resistance training (MRT; n = 10), and moderate intensity combined aerobic-resistance training (MCT; n = 10). The enzyme-linked immunosorbent assay (ELISA) kits method was used to analyze the adiponectin and leptin levels between pre-intervention and post-intervention. Statistical analysis was conducted using a paired sample t-test, while correlation analysis between variables used the Pearson product-moment correlation test. Research data showed that MAT, MRT, and MCT significantly increased adiponectin levels and decreased leptin levels compared to the CTL (p ≤ 0.05). The results of the correlation analysis of delta (∆) data showed that an increase in adiponectin levels was significantly negatively correlated with a decrease in body weight (BW) (r = -0.671, p ≤ 0.001), BMI (r = -0.665, p ≤ 0.001), and fat mass (FM) (r = -0.694, p ≤ 0.001) and positively correlated with an increase in skeletal muscle mass (SMM) (r = 0.693, p ≤ 0.001). Whereas, a decrease in leptin levels was significantly positively correlated with a decrease in BW (r = 0.744, p ≤ 0.001), BMI (r = 0.744, p ≤ 0.001), and FM (r = 0.718, p ≤ 0.001) and negatively correlated with an increase in SMM (r = -0.743, p ≤ 0.001). In summary, it can be concluded that our data show that adiponectin levels increased and leptin levels decreased after the intervention of aerobic, resistance, and combined aerobic-resistance training.

Effect of Exercise Interventions on Irisin and Interleukin-6 Concentrations and Indicators of Carbohydrate Metabolism in Males with Metabolic Syndrome

Irisin (IR) is a biomarker that is associated with metabolic syndrome (MetS). However, the available evidence on the association of IR, physical activity, and MetS status are contradictory. Therefore, the present study aimed to investigate the effect of exercise intervention on IR and interleukin-6 (IL-6) levels and indicators of carbohydrate metabolism in males with MetS. The study included 62 males with MetS (age 36.6 ± 6.9 years, BMI 33.6 ± 4.4 kg/m²) randomly assigned to: examined group 1 (EG1, n = 21) with aerobic exercise intervention, examined group 2 (EG2, n = 21) with combined aerobic and resistance exercise intervention, both for 12 weeks, and the control group (CG, n = 20) without intervention. Anthropometric measurements, body composition (body fat [BF], fat free mass [FFM]) as well as a biochemical blood analysis (irisin [IR], interleukin-6 [IL-6], insulin [INS] and glucose [GL]) were performed at baseline, 6 and 12 weeks of intervention, and 4 weeks after ending the intervention (follow-up). Intergroup and intragroup comparisons were performed. In EG1, an increase in IR level was observed as well as decreases in IL-6, BF, and GL levels in relation to the initial measurement. In EG2, decreases in IL-6, BF, and INS levels were observed as well as an increase in FFM level. In CG, no changes were found. Aerobic-resistance exercise led to a greater reduction in the concentrations of IL-6 and INS and more favorable changes in body composition (BF and FFM) than the use of aerobic training alone in males with MetS.

Irisin: A bridge between exercise and neurological diseases

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

The serum irisin response to prolonged physical activity in temperate and hot environments in older men with hypertension or type 2 diabetes

Current labor demographics are changing, with the number of older adults increasingly engaged in physically demanding occupations expected to continually rise, which are often performed in the heat. Given an age-related decline in whole-body heat loss, older adults are at an elevated risk of developing heat injuries that may be exacerbated by hypertension (HTN) and type 2 diabetes (T2D). Elevated irisin production may play a role in mitigating the excess oxidative stress and acute inflammation associated with physically demanding work in the heat. However, the effects of HTN and T2D on this response remain unclear. Therefore, we evaluated serum irisin before and after 3-h of moderate intensity exercise (metabolic rate: 200 W/m²) and at the end of 60-min of post-exercise recovery in a temperate (wet-bulb globe temperature (WBGT) 16 °C) and high-heat stress (WBGT 32 °C) environment in 12 healthy older men (mean ± SD; 59 ± 4 years), 10 men with HTN (60 ± 4 years), and 9 men with T2D (60 ± 5 years). Core temperature (T_co) was measured continuously. In the heat, total exercise duration was significantly lower in older men with HTN and T2D (both, p ≤ 0.049). Despite T_co not being different between groups, T_co was higher in the hot compared to the temperate condition for all groups (p < 0.001). Similarly, serum irisin concentrations did not differ between groups under either condition but were elevated relative to the temperate condition during post-exercise and end-recovery in the heat (+93.9 pg/mL SEM 26 and + 70.5 pg/mL SEM 38 respectively; both p ≤ 0.014). Thus, our findings indicate similar irisin responses in HTN and T2D compared to healthy, age-matched controls, despite reduced exercise tolerance during prolonged exercise in the heat. Therefore, older workers with HTN and T2D may exhibit greater cellular stress during prolonged exercise in the heat, underlying greater vulnerability to heat-induced cellular injury.

Systematic Review and Meta-Analysis of Circulating Irisin Levels Following Endurance Training: Results of Continuous and Interval Training

Background

Irisin has been suggested as a helpful hormone for adverse metabolic conditions. However, the interaction between acute endurance exercises and irisin is still unclear. The purpose of this systematic review and meta-analysis was to determine the acute effect of endurance training, either continuous or interval training, on circulating irisin in healthy adults.

Methods

Literature search was conducted in Web of Science, PubMed, Scopus and CINAHL until September 2022. Clinical trials measuring irisin levels following a single session of interval or continuous endurance training in healthy adults were eligible. Cohen’s d effect size (95% confidence level), subgroup analyses and univariate meta-regression were calculated using a random-effects model. The procedures described by PRISMA were followed and the protocol was prospectively registered with PROSPERO (CRD 42021240971).

Results

Data of the 16 included studies comprising 412 individuals showed a significant increase following one session of continuous endurance training (d = 0.33, 95% CI: 0.20 to 0.46 , p < 0.001), while interval training did not change circulating irisin (d = 0.16, 95% CI: −0.12 to 0.44 , p = 0.202). Both subgroup and univariate meta-regression analyses showed non-significant differences in the change of circulating irisin comparing blood measurement, exercise mode or previous level of physical activity of the participants and circulating irisin at baseline, duration, or intensity of the exercise, respectively.

Conclusion

Continuous method for endurance training increases circulating irisin in healthy adults, while studies measuring circulating irisin following interval training in healthy adults are still limited to be conclusive.

Comparison irisin peptide serum level in pregnant women with and without gestational diabetes mellitus: A case-control study

INTRODUCTION

Gestational diabetes mellitus (GDM) is a metabolic disease that affects mother and foetus during pregnancy, causing acute and chronic adverse effects. Irisin is proposed as a novel marker to predict GDM. The aim of this study was to assess the role of irisin peptide serum levels in gestational diabetes and compare with healthy pregnant women.

METHODS

This case-control study was conducted on women at 24 to 34 weeks of gestation in Ghaem Hospital affiliated with Mashhad University of Medical Sciences between May 2016 and June 2019. In two study groups, GDM and non-GDM women, an association between maternal serum irisin levels and clinical and biochemical parameters were evaluated. Maternal serum irisin levels were measured by an enzyme immunoassay method. Body mass index, serum levels of glucose, oral glucose tolerance test (OGTT), insulin, haemoglobin A1C, homeostatic model assessment of insulin resistance (HOMA IR) and irisin were evaluated.

RESULTS

Totally, 56 participants (30 non-GDM women and 26 women with GDM) were enrolled. Not statistically significant was observed in serum irisin levels between GDM and non-GDM women. (p = .814) Irisin levels were not significantly associated with maternal age, systolic and diastolic blood pressure, the number of pregnancies, gestational age, fasting blood sugar, insulin, HOMA IR, one-hour and two-hour serum glucose and body mass index.

CONCLUSIONS

There is no significant difference between GDM and non-GDM groups in the case of irisin value and later, no association of irisin with metabolic and anthropometric parameters. These findings need to be assessed in future experiments.

Irisin, an Effective Treatment for Cardiovascular Diseases?

Irisin, as one of the myokines induced by exercise, has attracted much attention due to its important physiological functions such as white fat browning, the improvement in metabolism, and the alleviation of inflammation. Despite the positive role that irisin has been proven to play in the prevention and treatment of cardiovascular diseases, whether it can become a biomarker and potential target for predicting and treating cardiovascular diseases remains controversial, given the unreliability of its detection methods, the uncertainty of its receptors, and the species differences between animals and humans. This paper was intended to review the role of irisin in the diagnosis and treatment of cardiovascular diseases, the potential molecular mechanism, and the urgent problems to be solved in hopes of advancing our understanding of irisin as well as providing data for the development of new and promising intervention strategies by discussing the causes of contradictory results.

The effects of different types of exercise on circulating irisin levels in healthy individuals and in people with overweight, metabolic syndrome and type 2 diabetes

Irisin is a myokine secreted during exercise. It has drawn the attention of researchers as it regulates several effects of exercise that are considered beneficial. It has also been proposed as a therapeutic tool to treat metabolic disorders. In recent years, the effect of different types of training on circulating irisin has been studied in large populations. An overall beneficial result has been shown, however, the outcome of the investigations has raised some controversy. Herein we evaluated the existing literature on the effects of different types of training on the circulating irisin levels in healthy subjects and in those displaying different metabolic condition. We conducted queries in the PubMed and Web of Science databases for literature published between January 2010 and January 2021. Thirty-seven original articles were retrieved and they were included in this review. Any letter to the editor, meta-analyses, reviews, and systematic review articles were excluded. From these 37 articles, 19 of them reported increased levels of circulating irisin. The interventions encompassed aerobic, resistance, combined, circuit, and interval training types. Such increase of circulating irisin was reported for healthy subjects and for those displaying different metabolic condition. A training that is steadily kept with a moderate to high intensity, including that characterized by brief highly intense intervals, were distinguishable from the rest. Nevertheless, the training effectiveness as evaluated by the increased circulating irisin levels depends on the subject’s metabolic condition and age.

Dysregulated myokines and signaling pathways in skeletal muscle dysfunction in a cigarette smoke–induced model of chronic obstructive pulmonary disease

Skeletal muscle dysfunction is an important extrapulmonary comorbidity of chronic obstructive pulmonary disease (COPD). Muscle-derived cytokines (myokines) play important roles in skeletal muscle growth and function, but their contributions to skeletal muscle dysfunction in COPD have not been fully understood. In the current study, by using a well-established mouse model of COPD with skeletal muscle dysfunction, we found that the expressions of Fndc5 (fibronectin type III domain-containing protein 5, the precursor of irisin) and peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α) were decreased, while myostatin (Mstn), phosphorylated extracellular regulated kinase (p-Erk1/2), and p-Smad3 expressions were upregulated in skeletal muscles from cigarette smoke-exposed mice and in cigarette smoke extract (CSE)-stimulated C2C12 myotubes. Treatment with Smad3 or Erk1/2 inhibitors partially restored the expression of Fndc5 in CSE-stimulated C2C12 myotubes. Taken together, CSE exposure, by upregulation of p-Erk1/2, promoted the expression of Mstn, which further inhibited Fndc5 expression by the p-Smad3/PGC-1α pathway, revealing a novel regulating mechanism of myokines in the pathogenesis of skeletal muscle comorbidities of COPD.

Exerkines and long-term synaptic potentiation: Mechanisms of exercise-induced neuroplasticity

Physical exercise may improve cognitive function by modulating molecular and cellular mechanisms within the brain. We propose that the facilitation of long-term synaptic potentiation (LTP)-related pathways, by products induced by physical exercise (i.e., exerkines), is a crucial aspect of the exercise-effect on the brain. This review summarizes synaptic pathways that are activated by exerkines and may potentiate LTP. For a total of 16 exerkines, we indicated how blood and brain exerkine levels are altered depending on the type of physical exercise (i.e., cardiovascular or resistance exercise) and how they respond to a single bout (i.e., acute exercise) or multiple bouts of physical exercise (i.e., chronic exercise). This information may be used for designing individualized physical exercise programs. Finally, this review may serve to direct future research towards fundamental gaps in our current knowledge regarding the biophysical interactions between muscle activity and the brain at both cellular and system levels.

Moderate-intensity exercise decreases the circulating level of betatrophin and its correlation among markers of obesity in women

OBJECTIVES

Positive energy homeostasis due to overnutrition and a sedentary lifestyle triggers obesity. Obesity has a close relationship with elevated levels of betatrophin and may increase the risk of developing metabolic syndrome. Therefore, lifestyle modification through a nonpharmacological approach based on physical exercise is the right strategy in lowering betatrophin levels. This study aimed to analyze the effect of moderate-intensity interval and continuous exercises on decreased betatrophin levels and the association between betatrophin levels and obesity markers in women.

METHODS

A total of 30 women aged 20-24 years old were randomly divided into three groups. Measurement of betatrophin levels using Enzyme-Linked Immunosorbent Assay (ELISA). Data analysis techniques used were one-way ANOVA and parametric linear correlation.

RESULTS

The results showed that the average levels of betatrophin pre-exercise were 200.40 ± 11.03 pg/mL at CON, 203.07 ± 42.48 pg/mL at MIE, 196.62 ± 21.29 pg/mL at MCE, and p=0.978. Average levels of betatrophin post-exercise were 226.65 ± 18.96 pg/mL at CON, 109.31 ± 11.23 pg/mL at MIE, 52.38 ± 8.18 pg/mL at MCE, and p=0.000. Pre-exercise betatrophin levels were positively correlated with age, BMI, FM, WHR, FBG, and PBF (p≤0.001).

CONCLUSIONS

Our study showed that betatrophin levels are decreased by 10 min post-MIE and post-MCE. However, moderate-intensity continuous exercise is more effective in lowering betatrophin levels than moderate-intensity interval exercise. In addition, pre-exercise betatrophin levels also have a positive correlation with obesity markers.

Biological Response of Irisin Induced by Different Types of Exercise in Obese Subjects: A Non-Inferiority Controlled Randomized Study

Simple Summary

Among healthy male and female obese individuals undergoing a 12-week aerobic exercise program with either moderate intensity endurance or high-intensity interval training for losing weight, a reduction of circulating irisin was observed. Irisin is an important adipo-myokine implicated in the regulation of energy metabolism and cardiovascular health. Sex differences in the circulating levels of this biomarker have been previously reported and are likely related to the different anthropometric features between the sexes. A sex-specific modulation of circulating irisin levels should be further explored to tailor sex-specific training approaches for improving the cardiovascular health of obese subjects.

Abstract

Background: Weight loss through physical exercise is warranted among obese individuals. Recently, a greater benefit in cardiorespiratory fitness was achievable with high-intensity interval training (HIIT) as compared with moderate intensity continuous training. The beneficial effect of training on CV health might be related to a specific modulation of circulating irisin, an adypo-myokine implicated in the regulation of energy expenditure. Methods: The present study investigates the circulating plasma levels of irisin at baseline and in response to 12-week of training program either with HIIT or moderate-intensity continuous training (MICT) among young female and male obese subjects. Clinical, anthropometric, and training characteristics for each participant were available. A sex-disaggregated data for circulating plasma levels of irisin pre- and post-training are provided as well as an adjusted multivariate linear regression model to identify the determinants of post-training irisin levels. Results: Data from a total of 32 obese healthy individuals (47% female, mean age 38.7 years, mean BMI 35.6 kg/m²), randomized in a 1:1 manner to HIIT or MICT were analyzed. Circulating plasma levels of irisin similarly and significantly decreased in both MICT and HIIT interventional groups. Females had higher post-exercise irisin levels than males (6.32 [5.51–6.75] vs. 4.97 [4.57–5.72] μg/mL, p = 0.001). When stratified by an interventional group, a statistically significant difference was observed only for the MICT group (male, 4.76 [4.20–5.45] μg/mL vs. female 6.48 [4.88–6.84] μg/mL p = 0.03). The circulating post-training level of irisin was independently associated with post-training fat-free mass (β −0.34, 95% confidence interval, CI −0.062, −0.006, p = 0.019) in a model adjusted confounders. When female sex was added into the adjusted model, it was retained as the only factor independently associated with irisin levels (β 1.22, 95% CI, 0.50, 1.93, p = 0.002). Conclusions: In obese healthy subjects, circulating irisin levels were reduced in response to 12-weeks of exercise involving either HIIT or MICT. A sex-specific differences in circulating irisin levels at baseline and as biological response to chronic exercise was described. Sex-specific biological response of irisin to exercise should be further explored to tailor sex-specific training approaches for improving the cardiovascular health of obese healthy subjects.

Irisin response to acute moderate intensity exercise and high intensity interval training in youth of different obesity statuses: A randomized crossover trial

Limited data exist regarding the impact of an acute bout of exercise with varying intensities on irisin levels in the youth of different obesity statuses. The objectives were to (1) compare an acute bout of moderate continuous intensity (MCI) exercise and an acute bout of high‐intensity interval training (HIIT) on irisin response in youth with different obesity statuses and, (2) investigate whether changes in irisin levels are correlated with exploratory outcomes. A randomized crossover design study was conducted on 25 youth aged 12–18 years old. Participants were classified as either healthy weight (BMI percentile <85; n = 14) or overweight/obese (BMI percentile ≥85; n = 11). Participants performed an MCI exercise session at 50% of heart rate reserve for 35 min and a HIIT exercise session for 35 min, with intervals every 5 min increasing from 50% heart rate reserve to 85–90% for 2 min. Irisin was measured using an enzyme‐linked immunoabsorbent assay from plasma sampling obtained throughout the exercise (at times 0, 7, 14, 21, 28, and 35 min). A time effect was observed throughout the HIIT session [F(1,5) = 6.478, p < 0.001]. Bonferonni post‐hoc analysis revealed significant differences in irisin levels post‐exercise (35 min) compared to times 7, 14, 21, and 28 min. Irisin increased during HIIT (81.0% ± 71.3; p = 0.012) in youth with a healthy weight. No differences were observed for youth living as overweight or with obesity. Overall, HIIT elicits a higher peak irisin response compared to MCI exercise training in youth.

Serum irisin level is independent of sarcopenia and related muscle parameters in older adults

BACKGROUND

Accumulating evidence indicates that irisin, a myokine consisting of 112 amino acids, protects against muscle wasting in an autocrine manner; however, its impact on human muscle metabolism is still inconclusive. In this cross-sectional study, we aimed to investigate whether circulating irisin could be a potential biomarker reflecting muscle health in older adults.

METHODS

Comprehensive assessment of muscle mass; muscle function, including grip strength, gait speed, chair stand test, and short physical performance battery (SPPB); and muscle quality was performed in 143 older adults who visited outpatient geriatrics and endocrinology clinics. Sarcopenia was defined using the Asian-specific cutoff value. Blood samples were also collected to determine serum irisin concentration which was measured using enzyme immunoassay.

RESULTS

The serum irisin level was not significantly different according to the status of sarcopenia, low muscle mass, weak muscle strength, poor physical performance, and poor muscle quality, before or after adjustment for age, sex, appendicular skeletal muscle (ASM), and body mass index. Consistently, the association of circulating irisin level with sarcopenia-related parameters (skeletal muscle index, grip strength, gait speed, chair stand test, SPPB, and grip strength/body weight or ASM) was not evident in any adjustment models.

CONCLUSIONS

Despite the clear implication of irisin's involvement in muscle metabolism based on experimental research, we did not observe a definite association between its serum level and clinical muscle parameters in humans. These results suggest that the blood irisin level may not accurately predict the risk of sarcopenia in older adults.

Irisin ameliorates male sexual dysfunction in paroxetine-treated male rats

Sexual dysfunction is a common clinical condition due to different causes including the use of selective serotonin reuptake inhibitors (SSRI). Especially, SSRI paroxetine is known to cause numerous types of sexual dysfunction in men. There is growing interest in exercise as a non-pharmacological approach for the treatment of SSRI-induced sexual dysfunction. With these in mind, we investigated the effects of irisin, which is a recently detected exercise-linked hormone, on paroxetine-induced sexual dysfunction in male rats. Our findings showed that circulating irisin levels were lower in paroxetine-induced sexual dysfunction in male rats (20 mg/kg/day for 8 weeks by oral gavage than in vehicle-treated rats). In addition, results from sexual behavioral tests revealed that subcutaneous irisin perfusion (100 ng/kg/day via mini-osmotic pumps for 28 days) ameliorated sexual motivation and copulatory performance in sexually impaired male rats treated with paroxetine. The significantly reduced serum testosterone levels and α1-adrenoceptors (ADRA1A) and tyrosine hydroxylase gene (TH) expression levels in the nucleus accumbens (NAc) in paroxetine-induced sexually dysfunctioning male rats were markedly increased following irisin exposure. Similarly, the expression levels of ADRA1A and TH in the medial preoptic area (mPOA) significantly increased in male rats co-administered with paroxetine and irisin compared to the vehicle-treated male rats. These results demonstrate that irisin may be a therapeutic modality that mimics/supports the beneficial effects of exercise for improving SSRI-associated sexual dysfunction in men through increase in serum testosterone levels and increased expression of α1-adrenoceptors and TH in the NAc and mPOA associated with sexual motivation and copulatory behaviors.

Factors mediating exercise-induced organ crosstalk

Exercise activates a plethora of metabolic and signalling pathways in skeletal muscle and other organs causing numerous systemic beneficial metabolic effects. Thus, regular exercise may ameliorate and prevent the development of several chronic metabolic diseases. Skeletal muscle is recognized as an important endocrine organ regulating systemic adaptations to exercise. Skeletal muscle may mediate crosstalk with other organs through the release of exercise-induced cytokines, peptides and proteins, termed myokines, into the circulation. Importantly, other tissues such as the liver and adipose tissue may also release cytokines and peptides in response to exercise. Hence, exercise-released molecules are collectively called exerkines. Moreover, extracellular vesicles (EVs), in the form of exosomes or microvesicles, may carry some of the signals involved in tissue crosstalk. This review focuses on the role of factors potentially mediating crosstalk between muscle and other tissues in response to exercise.

Inflammatory markers in response to interval and continuous exercise in obese women

Obesity is strongly associated with the degree of inflammation characterised by proinflammatory cytokines, such as tumour necrosis factor-α (TNF-α). Lifestyle modification with exercise is the right strategy because it can stimulate interleukin 6 (IL-6) secretion which acts as an anti-inflammatory. This study aimed to analyse the response of interval and continuous exercise to inflammatory markers in obese women. Twenty-four women participated in this study and were randomly divided into 3 groups: CONG (n=8, control group without any intervention): MCEG (n=8, continuous exercise group) and MIEG (n=8, interval exercise group). ELISA was used to measure the levels of IL-6 and TNF-α, pre-exercise and post-exercise. The data were analysed using the paired sample t-test. The mean levels of TNF-α, pre-exercise and post-exercise, were 19.35±2.73 vs 19.36±2.23 pg/ml (P=0.989) in CONG, 19.42±2.79 vs 16.63±0.82 pg/ml (P=0.017) in MCEG, and 19.46±3.08 vs 16.96±2.11 pg/ml (P=0.079) in MIEG. Mean levels of IL-6, pre-exercise and post-exercise, were 7.56±2.88 vs 7.66±4.12 pg/ml (P=0.957) for CONG, 7.68±3.41 vs 13.97±2.38 pg/ml (P=0.001) for MCEG, and 7.78±1.99 vs 13.66±3.55 pg/ml (P=0.001) for MIEG. We concluded that interval and continuous exercise decreased pro-inflammatory and increased anti-inflammatory cytokines.

Multifactorial Mechanism of Sarcopenia and Sarcopenic Obesity. Role of Physical Exercise, Microbiota and Myokines

Obesity and ageing place a tremendous strain on the global healthcare system. Age-related sarcopenia is characterized by decreased muscular strength, decreased muscle quantity, quality, and decreased functional performance. Sarcopenic obesity (SO) is a condition that combines sarcopenia and obesity and has a substantial influence on the older adults’ health. Because of the complicated pathophysiology, there are disagreements and challenges in identifying and diagnosing SO. Recently, it has become clear that dysbiosis may play a role in the onset and progression of sarcopenia and SO. Skeletal muscle secretes myokines during contraction, which play an important role in controlling muscle growth, function, and metabolic balance. Myokine dysfunction can cause and aggravate obesity, sarcopenia, and SO. The only ways to prevent and slow the progression of sarcopenia, particularly sarcopenic obesity, are physical activity and correct nutritional support. While exercise cannot completely prevent sarcopenia and age-related loss in muscular function, it can certainly delay development and slow down the rate of sarcopenia. The purpose of this review was to discuss potential pathways to muscle deterioration in obese individuals. We also want to present the current understanding of the role of various factors, including microbiota and myokines, in the process of sarcopenia and SO.

The exercise-instrumental music program and irisin levels in younger non-professional athletes

A passive lifestyle and lack of exercise are triggering factors in increasing metabolic syndrome, whereas metabolic syndrome is associated with increased morbidity and mortality. This study aimed to analyse an exercise-based non-pharmacological approach combined with instrumental music to the plasma levels of irisin. The study employed a randomised pretest-posttest-only group design recruiting 30 male participants. The individuals aged between 19-21 years, body mass index (BMI) 18.5-24.9 kg/m2, normal blood pressure, normal resting heart rate (RHR), VO2max 40-50 ml/kg bodyweight/min, normal haemoglobin (Hb). The subjects were randomly divided into three groups, MIE (n=10, moderate-intensity exercise), MIEM (n=10, moderate-intensity exercise + instrumental music), and HIE (n=10, high-intensity exercise). Blood sampling was collected from pre- and 5 min post-exercise treatment. ELISA method was used to measure the circulating irisin levels. The non-parametric Kruskal-Wallis test, Mann Whitney test and Spearman correlation were chosen to analyse the data. The results showed that there is no significant difference in pre-exercise irisin levels (ng/ml) in MIE (1.58±0.89), MIEM (1.77±3.12), and HIE (1.65±0.88) with a P-value of 0.098. Importantly, the alteration of irisin levels post-exercise program revealed that the level of this peptide (ng/ml) is higher in HIE (7.28±5.11) compared to MIE (1.95±1.85) and MIEM (4.16±3.40) with a P-value of 0.019. The plasma levels of irisin significantly correlate to energy expenditure (r=0.353, P≤0.01), plasma peroxisome proliferator-activated receptor gamma coactivator-1α (r=0.597, P≤0.001), and high-density lipoprotein (r=0.513, P≤0.01). In summary, increased irisin secretion may directly contribute to the gradual alteration of energy expenditure and correlate to physical exercise intensity-related musical treatment.

High-Intense Interval Training Prevents Cognitive Impairment and Increases the Expression of Muscle Genes FNDC5 and PPARGC1A in a Rat Model of Alzheimer's Disease

BACKGROUND

Alzheimer's disease is the most common neurodegenerative disease in the world, characterized by the progressive loss of neuronal structure and function, whose main histopathological landmark is the accumulation of β-amyloid in the brain.

OBJECTIVE

It is well known that exercise is a neuroprotective factor and that muscles produce and release myokines that exert endocrine effects in inflammation and metabolic dysfunction. Thus, this work intends to establish the relationship between the benefits of exercise through the chronic training of HIIT on cognitive damage induced by the Alzheimer's model by the injection of β amyloid1-42.

METHODS

For this purpose, forty-eight male Wistar rats were divided into four groups: Sedentary Sham (SS), Trained Sham (ST), Sedentary Alzheimer's (AS), and Trained Alzheimer's (AT). Animals were submitted to stereotactic surgery and received a hippocampal injection of Aβ1-42 or a saline solution. Seven days after surgery, twelve days of treadmill adaptation followed by five maximal running tests (MRT) and fifty-five days of HIIT, rats underwent the Morris water maze test. The animals were then euthanized, and their gastrocnemius muscle tissue was extracted to analyze the Fibronectin type III domain containing 5 (FNDC5), PPARG Coactivator 1 Alpha (PPARGC1A), and Integrin subunit beta 5 (ITGB5-R) expression by qRT-PCR in addition to cross-sectional areas.

RESULTS

The HIIT prevents the cognitive deficit induced by the infusion of amyloid β1-42 (p < 0.0001), causes adaptation of muscle fibers (p < 0.0001), modulates the gene expression of FNDC5 (p < 0.01), ITGB5 (p < 0.01) and PPARGC1A (p < 0.01), and induces an increase in peripheral protein expression of FNDC5 (p < 0.005).

CONCLUSION

Thus, we conclude that HIIT can prevent cognitive damage induced by the infusion of Aβ1-42, constituting a non-pharmacological tool that modulates important genetic and protein pathways.

Effects of In Vitro Muscle Contraction on Thermogenic Protein Levels in Co-Cultured Adipocytes

The crosstalk between the exercising muscle and the adipose tissue, mediated by myokines and metabolites, derived from both tissues during exercise has created a controversy between animal and human studies with respect to the impact of exercise on the browning process. The aim of this study was to investigate whether co-culturing of C2C12 myotubes and 3T3-L1 adipocytes under the stimuli of electrical pulse stimulation (EPS) mimicking muscle contraction can impact the expression of UCP1, PGC-1a, and IL-6 in adipocytes, therefore providing evidence on the direct crosstalk between adipocytes and stimulated muscle cells. In the co-cultured C2C12 cells, EPS increased the expression of PGC-1a (p = 0.129; d = 0.73) and IL-6 (p = 0.09; d = 1.13) protein levels. When EPS was applied, we found that co-culturing led to increases in UCP1 (p = 0.044; d = 1.29) and IL-6 (p = 0.097; d = 1.13) protein expression in the 3T3-L1 adipocytes. The expression of PGC-1a increased by EPS but was not significantly elevated after co-culturing (p = 0.448; d = 0.08). In vitro co-culturing of C2C12 myotubes and 3T3-L1 adipocytes under the stimuli of EPS leads to increased expression of thermogenic proteins. These findings indicate changes in the expression pattern of proteins related to browning of adipose tissue, supporting the use of this in vitro model to study the crosstalk between adipocytes and contracting muscle.

Irisin injection mimics exercise effects on the brain proteome

Physical inactivity can endanger human health and increase the incidence of neurodegenerative disease. Exercise has tremendous beneficial effects on brain health and cognitive function, especially in older adults. It also improves brain-related outcomes in depression, epilepsy and neurodegenerative disorders, such as Parkinson's disease and Alzheimer's disease. Irisin is a mediator of the beneficial effects of exercise. This study aimed to assess the proteome alterations in adult male National Maritime Research Institute (NMRI) mice brain tissue upon three different conditions including endurance exercise, resistance exercise and irisin injection. Quantification of irisin levels in blood was performed using irisin-ELISA Kit. Quantification and identification of proteins via two-dimensional gel electrophoresis and matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry (MS)/MS showed the alteration of at least 21 proteins due to different treatments. Cellular pathway analysis revealed common beneficial effects of sole irisin treatment and different exercise procedures suggesting the capability of irisin injection to substitute the exercise when physical activity is not possible.

Irisin serum increasing pattern is higher at moderate-intensity continuous exercise than at moderate-intensity interval exercise in obese females

Lifestyle, unhealthy eating patterns, and low physical activity become trigger factors of obesity. Therefore, lifestyle modification with an exercise-based nonpharmacological approach is one of the strategies for combat obesity. This study aims to analyse the response of moderate-intensity interval and continuous exercise to irisin level increasing pattern on the obese female. A total of 21 obese females were enrolled in this study and given moderate-intensity interval exercise (MIIE) and moderate-intensity continuous exercise (MICE). ELISA was used to quantify the serum level of irisin in all samples. Statistical analysis was performed using one way-ANOVA and Tukey’s honestly significant difference (HSD) post hoc test. Mean irisin levels of pre-exercise at control (CON), MIIE, and MICE were 3.26±1.28l, 3.44±0.56 and 3.89±1.08 ng/ml, respectively (P=0.519). The mean irisin level of 10 min post-exercise was 2.99±0.86 ng/ml at CON, 4.82±1.01 ng/ml at MIIE, and 5.99±1.27 ng/ml at MICE (P=0.000). The mean irisin levels of 6 h post-exercise were 3.04±0.60, 4.56±0.87, and 5.73±1.02 ng/ml at CON, MIIE, and MICE, respectively (P=0.000). The mean irisin level of 24 h post-exercise was 3.04±0.91 ng/ml at CON, 4.64±0.69 ng/ml at MIIE, and 5.69±1.53 ng/ml at MICE (P=0.002). We conclude that the post-exercise serum irisin level increased in both MICE and MIIE subjects, and the post-exercise serum irisin level maintained higher in the MICE than in the MIIE in the obese female subjects.

Combined Physical Training Increases Plasma Brain-Derived Neurotropic Factor Levels, But Not Irisin in People Living with HIV/AIDS

This study evaluated plasma levels of brain-derived neurotropic factor (BDNF), irisin, and lactate in people living with HIV/AIDS who completed a combined physical training program. Nineteen HIV+ participants (age: 39.60 ± 10.96 years; carrier time: 7.75 ± 7.88 years; time of ART: 6.41 ± 5.93 years) performed strength/aerobic training (combined physical training) in the same session for 8 weeks and levels of BDNF, irisin, and lactate were assessed. BDNF (pg/mL) was higher post-CPT (Pre: 1258.73 ± 372.30; Post: 1504.17 ± 322.30; p < 0.001). Irisin (ng/mL) showed no change (Pre: 115.61 ± 72.41; Post: 125.87 ± 81.14; p = 0.973). There was positive correlation between irisin and lactate (mmol/L) pre (r = 0.55, p = 0.04), and lactate values were higher in the group with the highest value of irisin (3.65 ± 0.69 × 2.82 ± 0.59, p = 0.02). Combined physical training results in increased basal BDNF in people living with HIV/AIDS, this finding suggests that increased concentration of BDNF may be associated with decreased chances of developing cognitive disorders or HIV-associated dementia. Further studies involving molecular mechanisms on this subject are necessary.

Acute effects of high-intensity interval training and moderate-intensity continuous exercise on BDNF and irisin levels and neurocognitive performance in late middle-aged and older adults

The purposes of the present study were (1) to explore and compare the acute effects of high-intensity interval training (HIIT) and moderate-intensity continuous exercise (MICE) on neurocognitive performance and molecular biomarkers in late middle-aged and older adults, and (2) to examine the relationships of HIIT/MICE exercise-induced neurocognitive changes with changes in circulating irisin and BDNF levels elicited by different acute exercise modes. Using a within-subject design, twenty-one participants completed an acute bout of 30 min of HIIT, MICE, or a non-exercise-intervention (REST) session in a counterbalanced order. The neuropsychological [i.e., accuracy rate (AR) and reaction time (RT)] and neurophysiological [i.e., event-related potential (ERP) P3 latency and amplitude] indices were simultaneously measured when the participants performed a working memory task at baseline and after an intervention mode. Blood samples were also taken before and after the intervention mode. The results showed that, although ARs were significantly increased only via the MICE intervention mode, the acute HIIT and MICE interventions improved RT performance and increased ERP P3 amplitudes in the late middle-aged and older adults under consideration. Serum BDNF levels were significantly increased with the acute HIIT and MICE interventions, and significant irisin level increases were only observed following the HIIT intervention. However, changes in the levels of Irisin and BDNF pre- and post-intervention were not correlated with changes in neurocognitive performance, with the exception of the correlation between the changes in irisin levels and RTs with acute exercise in the MICE intervention mode. The present findings suggested similar beneficial effects on neurocognitive performance (i.e., RTs and ERP P3 amplitudes) and peripheral BDNF levels following MICE and HIIT interventions in the middle-aged and older adults. In terms of ARs and irisin, the two acute exercise modes appear to induce divergent effects. Irisin may play a potential facilitating role in the neuropsychological (e.g., RT) performance of working memory in such a group. However, the mechanisms remain to be determined.

Effects of Padel Competition on Brain Health-Related Myokines

Padel is becoming one of the most widespread racket sports that may have potential health benefits. Considering that several myokines mediate the cross-talk between skeletal muscles and the brain, exerting positive effects on brain health status, this study was designed to evaluate the responses of brain-derived neurotrophic factor (BDNF), leukemia inhibitory factor (LIF), and irisin (IR) to padel competition in trained players and to determine whether these responses were sex-dependent. Twenty-four trained padel players (14 women and 10 men with a mean age of 27.8 ± 6.3 years) participated voluntarily in this study. Circulating levels of BDNF, LIF, and IR were assessed before and after simulated padel competition (real playing time, 27.8 ± 8.49 min; relative intensity, 75.2 ± 7.9% maximum heart rate). Except for BDNF responses observed in female players (increasing from 1531.12 ± 269.09 to 1768.56 ± 410.75 ng/mL), no significant changes in LIF and IR concentrations were reported after padel competition. In addition, no sex-related differences were found. Moreover, significant associations between IR and BDNF were established at both pre- and post-competition. Our results suggest that while competitive padel practice stimulates BDNF response in female players, padel competition failed to boost the release of LIF and IR. Future studies are needed to further explore the role of these exercise-induced myokines in the regulation of brain functions and to identify the field sports that can contribute to myokine-mediated muscle–brain crosstalk.

Irisin, Fibroplast Growth Factor-21, and Follistatin Responses to Endurance Rowing Training Session in Female Rowers

Purpose: This study examined selected myokine responses to an endurance rowing training session, and whether metabolic demands of the acute aerobic rowing exercise together with training volume, aerobic capacity, and body composition variables affect potential exercise-induced changes in the myokine levels in female rowers. Methods: Fifteen national level female rowers [18.3 ± 1.6 years; 172.0 ± 5.0 cm, 67.5 ± 8.8 kg; maximal oxygen consumption (VO₂max): 47.2 ± 7.9 ml.min.^-1 kg^-1] performed a 1-h rowing ergometer exercise at the intensity of 70% of VO₂max [distance: 12.1 ± 1.1 km; energy expenditure (EE): 639 ± 69 kcal; heart rate (HR): 151 ± 7 beats.min^-1] followed by a 30-min recovery period. Venous blood samples were collected before and after exercise, and analyzed for irisin, fibroplast growth factor-21 (FGF-21), and follistatin conentrations. Results: Plasma irisin and FGF-21 concentrations were increased (by 8%; p = 0.013 and by 13%; p < 0.0001, respectively) immediately after the aerobic rowing exercise. Follistatin was significantly increased (by 11%; p = 0.001) only after the first 30 min of recovery. Exercise metabolic demand variables such as distance covered and total EE were correlated with the pre-to-post-exercise increases in FGF-21 concentrations (r = 0.52; p = 0.047 and r = 0.68; p = 0.005, respectively). Exercise-induced increases in irisin levels were related to aerobic capacity as measured by VO₂max (r = 0.53; p = 0.041) and training stress as measured by weekly training volume (r = 0.54; p = 0.039) in female rowers. Conclusion: Acute negative energy balance induced by a single endurance rowing training session elicited significant increases in irisin, FGF-21, and follistatin levels in national level female rowers. While exercise-induced increases in FGF-21 levels were associated with exercise metabolic demand measures, exercise-induced increases in irisin concentrations were related to aerobic capacity and training stress measures in female rowers.

A Single Bout of High-intensity Interval Exercise Increases Corticospinal Excitability, Brain-derived Neurotrophic Factor, and Uncarboxylated Osteolcalcin in Sedentary, Healthy Males

Exercise induces neuroplasticity in descending motor pathways facilitating motor learning, and as such it could be utilized as an intervention in neurorehabilitation, for example when re-learning motor skills after stroke. To date, however, the neurophysiological and molecular mechanisms underlying exercise-induced neuroplasticity remain largely unknown impeding the potential utilization of exercise protocols as 'motor learning boosters' in clinical and non-clinical settings. Here, we assessed corticospinal excitability, intracortical facilitation (ICF) and short-interval intracortical inhibition (SICI) using transcranial magnetic stimulation (TMS) and serum biochemical markers including brain-derived neurotrophic factor (BDNF), total and precursor cathepsin B (tCTSB, proCTSB), uncarboxylated and carboxylated osteocalcin (unOCN, cOCN) and irisin using ELISA. Measurements were carried out in sedentary, healthy males before and after a single session of high-intensity interval exercise (HIIE) or in individuals who rested and did not perform exercise (No Exercise). We found that HIIE increased corticospinal excitability, BDNF and unOCN, and decreased cOCN. We also determined that greater increases in BDNF were associated with increases in unOCN and irisin and decreases in cOCN only in participants who underwent HIIE, suggesting that unOCN and irisin may contribute to exercise-induced BDNF increases. Conversely, no changes other than a decrease in serum unOCN/tOCN were found in No Exercise participants. The present findings show that a single session of HIIE is sufficient to modulate corticospinal excitability and to increase BDNF and unOCN in sedentary, healthy males.

Relative energy deficiency in sports (RED-S): elucidation of endocrine changes affecting the health of males and females

The purpose of this review is to present a different perspective of the relative energy deficiency syndrome, to improve understanding of associated endocrine alterations, and to highlight the need for further research in this area. The term "female athlete triad" was coined over 25 years ago to describe three interrelated components: disordered eating, menstrual dysfunction, and low bone mass. The syndrome's etiology is attributed to energy intake deficiency relative to energy expenditure required for health, function, and daily living. Recently, it became clear that there was a need to broaden the term, as the disorder is not an issue of only three interrelated problems but of a whole spectrum of insults resulting from low energy availability (LEA; i.e., insufficient energy availability to cover basic physiological demands) that can potentially affect any exerciser, irrespective of gender. The new model, termed relative energy deficiency in sport (RED-S), has received greater scrutiny in sports medicine due to its effects on both health and performance in athletes of both sexes. RED-S results from low-energy diets (intentional or unintentional) and/or excessive exercise. Energy deficiency reduces hypothalamic pulsatile release of gonadotropin-releasing hormone, this impairing anterior pituitary release of gonadotropins. In women, reduced FSH and LH pulsatility produces hypoestrogenism, causing functional hypothalamic amenorrhea and decreased bone mass. In men, it reduces testosterone and negatively affects bone health. Moreover, LEA alters other hormonal pathways, causing physiological consequences, such as alteration of the thyroid hormone signaling pathways, leptin levels, carbohydrate metabolism, the growth hormone/insulin-like growth factor-1 axis, and sympathetic/parasympathetic tone. This review explains and clarifies the effects of RED-S in both sexes.

Comparison of Irisin Serum Healthy Untrained Males on Treadmill Exercises by Increasing Gradually Speed Vs Inclination

Aerobic exercise can improve cardiorespiratory fitness in young people. Irises released into the bloodstream function to execute regulation of energy metabolism, triggering browning white adipose, which is useful in mitochondrial biogenesis. The American College of Sport Medicine (ACSM) recommends moderate intensity cardiorespiratory fitness training with a frequency of 3-5 times a week, duration of 20-60 minutes, using a treadmill. Study subjects (n = 20) were divided randomly into 2 groups, namely the moderate intensity Treadmill training group with gradual speed improvement and gradual inclination increase. Serum slices are measured on the first and last day of exercise. There was an increasing of irisin serum  in the moderate intensity Treadmill training group by increasing gradually speed after 2 weeks of exercise, both 30 minutes pre-exercise (p = 0.02) and 1 hour post exercise (p = 0.01). Medium intensity Treadmill training with 2 weeks gradual speed increase with frequency 3 times a week can increase serum slice in men, healthy untrained young men.

Muscle-Bone Crosstalk in Chronic Obstructive Pulmonary Disease

Sarcopenia and osteoporosis are common musculoskeletal comorbidities of chronic obstructive pulmonary disease (COPD) that seriously affect the quality of life and prognosis of the patient. In addition to spatially mechanical interactions, muscle and bone can also serve as endocrine organs by producing myokines and osteokines to regulate muscle and bone functions, respectively. As positive and negative regulators of skeletal muscles, the myokines irisin and myostatin not only promote/inhibit the differentiation and growth of skeletal muscles, but also regulate bone metabolism. Both irisin and myostatin have been shown to be dysregulated and associated with exercise and skeletal muscle dysfunction in COPD. During exercise, skeletal muscles produce a large amount of IL-6 which acts as a myokine, exerting at least two different conflicting functions depending on physiological or pathological conditions. Remarkably, IL-6 is highly expressed in COPD, and considered to be a biomarker of systemic inflammation, which is associated with both sarcopenia and bone loss. For osteokines, receptor activator of nuclear factor kappa-B ligand (RANKL), a classical regulator of bone metabolism, was recently found to play a critical role in skeletal muscle atrophy induced by chronic cigarette smoke (CS) exposure. In this focused review, we described evidence for myokines and osteokines in the pathogenesis of skeletal muscle dysfunction/sarcopenia and osteoporosis in COPD, and proposed muscle-bone crosstalk as an important mechanism underlying the coexistence of muscle and bone diseases in COPD.

Plasma irisin and its associations with oxidative stress in athletes suffering from overtraining syndrome

Irisin is a novel exercise-induced myokine that may be involved in regulating energy metabolism. We determined whether overtraining syndrome (OTS) and its biochemical markers are associated with plasma irisin levels in athletes. Seven severely overtrained athletes (OA) and 10 healthy control athletes (CA) were recruited and examined at the time of diagnosis (baseline) and after 6- and 12-months follow-up. Training volume and intensity were initially restricted but progressively increased in OA as OTS symptoms alleviated; CA continued their normal training routine. A maximal cycle ergometer test was performed with irisin analyzed before and after the test. Before the exercise test, irisin levels tended to be lower in OA than in CA at baseline (154.5 ± 28.5 vs. 171.7 ± 58.7 ng/mL). In both groups, at rest irisin levels changed only marginally during follow-up and were not affected by maximal exercise, nor were they associated with physical performance or body fat percentage. Irisin concentration at rest correlated positively with an oxidative stress marker, malondialdehyde (MDA) and negatively with an antioxidant protection marker, oxygen radical absorbance capacity (ORAC) in response to the exercise test in OA at baseline. Our findings help to clarify the possible contribution of irisin and its association with oxidative stress in the pathophysiology of OTS.

The "irisin system": From biological roles to pharmacological and nutraceutical perspectives

The scientific interest in irisin, a myokine discovered in 2012, has grown exponentially in recent years. Irisin, which is mainly produced in skeletal muscle, influences the browning process of adipose tissue and lipid and energy metabolism. Recent discoveries highlight that the potential of this hormone may have been underestimated. In the first part of this review, reports on irisin structure and molecules involved in its metabolic pathway are shown. Furthermore, data related to unclear aspects are also reported: distribution, different gene expression of its precursors in different tissues, physiological levels of circulating irisin, and pharmacokinetic and pharmacodynamic profile. The second part of this work focuses on exogenous stimuli and pharmacological agents which regulate the metabolic pathway of irisin and its serum concentration. In addition to physical exercise and exposure to low temperatures, which were early recognized as exogenous stimuli able to promote the production of this myokine, preclinical and clinical evidence demonstrates the ability of natural and synthetic molecules to interfere with this metabolic pathway. Current experimental data on irisin cannot dissolve all doubts related to this interesting molecule, but they certainly underline its potential for therapeutic purposes. Thus, identification of new pharmacological tools able to act on the irisin pathway is a challenging issue for biomedical research.

Effects of a One-week Vacation with Various Activity Programs on Metabolism and Adipokines

This study was conducted as part of a larger study of East Tyrolean health tourism, and investigates the effects of an active seven-day vacation on metabolic parameters and adipokines. Fifty-two healthy vacationers participated in two types of vacation activities (golf vs. Nordic walking or e-biking [nw&eb]). In the former group, 30 subjects played golf for a mean duration of 33.5 h per week; in the NW&EB group, 22 persons performed Nordic walking or e-biking for a mean duration of 14.2 h per week. Metabolic parameters and adipokines, such as leptin, adiponectin, GF-21, irisin, omentin-1, betatrophin, and resistin, were measured one day before and one day after the stay. After one week, only the NW&EB group experienced a significant decrease of 1.0 kg in body weight. Significant changes in HDL-C, FGF-21, irisin, and omentin-1 were seen in the golf group; and in triglycerides, HbA1c, leptin and adiponectin in the NW&EB group. No significant changes in betatrophin or resistin were registered in either group. A seven-day vacation with an activity program for several hours per week causes favorable changes in metabolic parameters and adipokines known to be involved in the pathophysiology of the metabolic syndrome. The changes differed in their magnitude and significance, depending on the type of activity.

Changes in Inflammatory Cytokines and Irisin in Response to High Intensity Swimming in Adolescent versus Adult Male Swimmers

Swimming is a popular youth sport that is considered beneficial for cardiovascular fitness. However, the potential inflammatory outcomes of high intensity swimming in younger swimmers are unclear, as is the response of irisin, a myokine released during exercise with anti-inflammatory properties. This study compared the plasma concentrations of interleukins 1-beta (IL-1β), 6 (IL-6), 10 (IL-10), tumor necrosis factor alpha (TNF-α) and irisin in response to intense swimming between adolescent and adult male swimmers. Thirty-two swimmers (16 adolescents, 14 ± 1 years; 16 adults, 21.5 ± 3.1 years) completed a high intensity interval swimming trial. At rest, only TNF-α was higher (33%, p < 0.05) in adolescents compared with adults. There was an overall significant increase in IL-1β from pre- to post-swimming (3% in adolescents, 24% in adults), but no significant interaction. IL-10 significantly increased in both groups (+34% in adolescents, +56% in adults). IL-6 and TNF-α increased significantly (+32% and +26%, respectively) in adults, but not in adolescents (+2% and -9%, respectively). Adults showed a small, but significant decrease in irisin (-5%), with no change in adolescents. The lack of an IL-6, TNF-α and irisin response to intense swimming in adolescent swimmers may suggest a blunted inflammatory and myokine response following high intensity exercise in trained youth.