Physiology and role of irisin in glucose homeostasis

Role of dysfunctional peri-organ adipose tissue in metabolic disease

Metabolic disease is a complex disorder defined by a group with interrelated factors. There is growing evidence that obesity can lead to a variety of metabolic diseases, including diabetes and cardiovascular disease. Excessive adipose tissue (AT) deposition and ectopic accumulation can lead to increased peri-organ AT thickness. Dysregulation of peri-organ (perivascular, perirenal, and epicardial) AT is strongly associated with metabolic disease and its complications. The mechanisms include secretion of cytokines, activation of immunocytes, infiltration of inflammatory cells, involvement of stromal cells, and abnormal miRNA expression. This review discusses the associations and mechanisms by which various types of peri-organ AT affect metabolic diseases while addressing it as a potential future treatment strategy.

The Role of Organokines in Obesity and Type 2 Diabetes and Their Functions as Molecular Transducers of Nutrition and Exercise

Maintaining systemic homeostasis requires the coordination of different organs and tissues in the body. Our bodies rely on complex inter-organ communications to adapt to perturbations or changes in metabolic homeostasis. Consequently, the liver, muscle, and adipose tissues produce and secrete specific organokines such as hepatokines, myokines, and adipokines in response to nutritional and environmental stimuli. Emerging evidence suggests that dysregulation of the interplay of organokines between organs is associated with the pathophysiology of obesity and type 2 diabetes (T2D). Strategies aimed at remodeling organokines may be effective therapeutic interventions. Diet modification and exercise have been established as the first-line therapeutic intervention to prevent or treat metabolic diseases. This review summarizes the current knowledge on organokines secreted by the liver, muscle, and adipose tissues in obesity and T2D. Additionally, we highlighted the effects of diet/nutrition and exercise on the remodeling of organokines in obesity and T2D. Specifically, we investigated the ameliorative effects of caloric restriction, selective nutrients including ω3 PUFAs, selenium, vitamins, and metabolites of vitamins, and acute/chronic exercise on the dysregulation of organokines in obesity and T2D. Finally, this study dissected the underlying molecular mechanisms by which nutrition and exercise regulate the expression and secretion of organokines in specific tissues.

Breathable and Stretchable Organic Electrochemical Transistors with Laminated Porous Structures for Glucose Sensing

Dynamic glucose monitoring is important to reduce the risk of metabolic diseases such as diabetes. Wearable biosensors based on organic electrochemical transistors (OECTs) have been developed due to their excellent signal amplification capabilities and biocompatibility. However, traditional wearable biosensors are fabricated on flat substrates with limited gas permeability, resulting in the inefficient evaporation of sweat, reduced wear comfort, and increased risk of inflammation. Here, we proposed breathable OECT-based glucose sensors by designing a porous structure to realize optimal breathable and stretchable properties. The gas permeability of the device and the relationship between electrical properties under different tensile strains were carefully investigated. The OECTs exhibit exceptional electrical properties (gm ~1.51 mS and Ion ~0.37 mA) and can retain up to about 44% of their initial performance even at 30% stretching. Furthermore, obvious responses to glucose have been demonstrated in a wide range of concentrations (10-7-10-4 M) even under 30% strain, where the normalized response to 10-4 M is 26% and 21% for the pristine sensor and under 30% strain, respectively. This work offers a new strategy for developing advanced breathable and wearable bioelectronics.

Low-fat dairy consumption and the risk of lung cancer: A large prospective cohort study

BACKGROUND

Despite the possible contribution of dairy products to the development or prevention of cancers, there is a lack of epidemiological evidence linking low-fat dairy consumption to the risk of developing lung cancer. This research was conducted to fill this knowledge gap.

METHODS

The data for this research were collected from the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial. The Cox proportional risk model was employed to evaluate the link between low-fat dairy consumption and the risk of developing lung cancer. Hazard ratios (HRs) and 95% confidence intervals (CIs) were measured in both unadjusted and adjusted models. A series of predefined subgroup analyses were performed to identify potential effect modifiers, and several sensitivity analyses were conducted to assess the stability of the findings.

RESULTS

The study included data from 98,459 individuals. During a total of 869,807.9 follow-up person-years, 1642 cases of lung cancer were observed, with an incidence of 0.189 cases for every 100 person-years. In the fully adjusted model, participants in the highest quartile of low-fat dairy consumption had a significantly decreased risk of lung cancer compared to the ones in the lowest quartile (HRquartile 4 vs. 1 : 0.769, 95% CI: 0.664, 0.891, ptrend  = 0.005). The restricted cubic spline plot revealed an inverse nonlinear dose-response relationship between low-fat dairy consumption and lung cancer risk (pnonlinearity  = 0.008). Subgroup analyses demonstrated that the inverse association was stronger among participants with higher daily caloric intake (pinteraction  = 0.031). Various sensitivity analyses produced consistent results.

CONCLUSION

Consuming more low-fat dairy products is significantly linked to a reduced risk of developing lung cancer, indicating that an appropriate increase in the use of low-fat dairy products may help prevent lung cancer.

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.

Association between Serum Irisin and Leptin Levels and Risk of Depressive Symptoms in the Diabetic Elderly Population

BACKGROUND

Adipokines are considered to be involved in the pathogenesis of diabetes and depression. The associations of serum levels of leptin and irisin with depressive symptoms were investigated in elderly patients with type 2 diabetes (T2DM).

METHODS

189 elderly diabetics were assessed with the 30-item Geriatric Depression Scale (GDS-30), and 57 patients with depressive symptoms and 132 controls were selected. Blood biochemical parameters, including serum irisin and leptin, were measured.

RESULTS

Serum irisin levels were decreased and leptin concentrations were significantly higher in T2DM patients with depressive symptoms compared to controls. In all subjects, the irisin level was inversely correlated with the leptin level and the GDS-30 score, whereas the leptin level was highly correlated with BMI and the GDS-30 score. Higher levels of leptin and lower concentrations of irisin are, among other factors, variables indicative of predictive capacity for depressive symptoms in elderly patients with T2DM.

CONCLUSIONS

The results indicated that irisin and leptin levels may be used as diagnostic markers of depressive symptoms in diabetic, elderly patients and as potential therapeutic targets for the treatment. Further prospective and more extensive studies are needed to clarify the role of these adipokines in the common pathogenesis of depression and diabetes.

Irisin Protects against Loss of Trabecular Bone Mass and Strength in Adult Ovariectomized Mice by Stimulating Osteoblast Activity

Irisin is a peptide secreted by skeletal muscle that plays a major role in bone metabolism. Experiments in mouse models have shown that administration of recombinant irisin prevents disuse-induced bone loss. In this study, we aimed to evaluate the effects of irisin treatment for the prevention of bone loss in the ovariectomized (Ovx) mouse, the animal model commonly used to investigate osteoporosis caused by estrogen deficiency. Micro-Ct analysis conducted on Sham mice (Sham-veh) and Ovx mice treated with vehicle (Ovx-veh) or recombinant irisin (Ovx-irisn) showed bone volume fraction (BV/TV) decreases in femurs (Ovx-veh 1.39± 0.71 vs. Sham-veh 2.84 ± 1.23; p = 0.02) and tibia at both proximal condyles (Ovx-veh 1.97 ± 0.68 vs. Sham-veh 3.48 ± 1.26; p = 0.03) and the subchondral plate (Ovx-veh 6.33 ± 0.36 vs. Sham-veh 8.18 ± 0.41; p = 0.01), which were prevented by treatment with a weekly dose of irisin for 4 weeks. Moreover, histological analysis of trabecular bone showed that irisin increased the number of active osteoblasts per bone perimeter (Ovx-irisin 32.3 ± 3.9 vs. Ovx-veh 23.5 ± 3.6; p = 0.01), while decreasing osteoclasts (Ovx-irisin 7.6 ± 2.4 vs. Ovx-veh 12.9 ± 3.04; p = 0.05). The possible mechanism by which irisin enhances osteoblast activity in Ovx mice is upregulation of the transcription factor Atf4, one of the key markers of osteoblast differentiation, and osteoprotegerin, thereby inhibiting osteoclast formation.

Irisin Ameliorates Renal Tubulointerstitial Fibrosis by Regulating the Smad4/β-Catenin Pathway in Diabetic Mice

Background

The primary pathophysiology of diabetic kidney disease (DKD) is tubulointerstitial fibrosis (TIF), and an essential contributing element is excessive extracellular matrix deposition. Irisin is a polypeptide formed by splitting fibronectin type III domain containing 5 (FNDC5), which participates in a number of physiological and pathological processes.

Methods

The purpose of this article is to examine irisin's function in DKD and analyze both its in vitro and in vivo effects. The Gene Expression Omnibus (GEO) database was used to download GSE30122, GSE104954, and GSE99325. Analysis of renal tubule samples from nondiabetic and diabetic mice identified 94 differentially expressed genes (DEGs). The transforming growth factor beta receptor 2 (TGFBR2), irisin, and TGF-β1 were utilized as DEGs to examine the impact of irisin on TIF in diabetic kidney tissue, according to the datasets retrieved from the GEO database and Nephroseq database. Additionally, the therapeutic impact of irisin was also examined using Western blot, RT-qPCR, immunofluorescence, immunohistochemistry, and kits for detecting mouse biochemical indices.

Results

In vitro, the findings demonstrated that irisin not only down-regulated the expression of Smad4 and β-catenin but also reduced the expression of proteins linked to fibrosis, the epithelial-mesenchymal transition (EMT), and mitochondrial dysfunction in HK-2 cells maintained in high glucose (HG) environment. In vivo, overexpressed FNDC5 plasmid was injected into diabetic mice to enhance its expression. Our studies found that overexpressed FNDC5 plasmid not only reversed the biochemical parameters and renal morphological characteristics of diabetic mice but also alleviated EMT and TIF by inhibiting Smad4/β-catenin signaling pathway.

Conclusion

The above experimental results revealed that irisin could reduce TIF in diabetic mice via regulating the Smad4/β-catenin pathway.

Mechanistic insights into the beneficial effects of curcumin on insulin resistance: opportunities and challenges

The past couple of decades in particular have seen a rapid increase in the prevalence of type 2 diabetes mellitus (T2DM), a debilitating metabolic disorder characterised by insulin resistance. The insufficient efficacy of current management strategies for insulin resistance calls for additional therapeutic options. The preponderance of evidence suggests potential beneficial effects of curcumin on insulin resistance, while modern science provides a scientific basis for its potential applications against the disease. Curcumin combats insulin resistance by increasing the levels of circulating irisin and adiponectin, activating PPARγ, suppressing Notch1 signalling, and regulating SREBP target genes, among others. In this review, we bring together the diverse areas pertaining to our current understanding of the potential benefits of curcumin on insulin resistance, associated mechanistic insights, and new therapeutic possibilities. Teaser: Current approaches to manage insulin resistance are not highly efficacious, which necessitates additional therapeutic options; curcumin combats insulin resistance by improving the levels of circulating irisin and adiponectin, upregulating and activating PPARγ, and suppressing Notch‑1 signalling.

Pharmacological and physiological roles of adipokines and myokines in metabolic-related dementia

Dementia is a detrimental neuropathologic condition with considerable physical, mental, social, and financial impact on patients and society. Patients with metabolic syndrome (MetS), a group of diseases that occur in tandem and increase the risk of neurologic diseases, have a higher risk of dementia. The ratio between muscle and adipose tissue is crucial in MetS, as these contain many hormones, including myokines and adipokines, which are involved in crosstalk and local paracrine/autocrine interactions. Evidence suggests that abnormal adipokine and myokine synthesis and release may be implicated in various MetS, such as atherosclerosis, diabetic mellitus (DM), and dyslipidemia, but their precise role is unclear. Here we review the literature on adipokine and myokine involvement in MetS-induced dementia via glucose and insulin homeostasis regulation, neuroinflammation, vascular dysfunction, emotional changes, and cognitive function.

Anti-inflammatory effect of Irisin on LPS-stimulated macrophages through inhibition of MAPK pathway

This study aimed to investigate the effect of irisin on LPS-induced inflammation in RAW 264.7 macrophages through inhibition of the mitogen-activated protein kinase (MAPK) pathway. A network pharmacology-based approach, combined with molecular docking and in vitro validation were performed to identify the biological activity, key targets, and potential pharmacological mechanisms of irisin against LPS-induced inflammation. By matching 100 potential genes of irisin with 1893 ulcerative colitis (UC) related genes, 51 common genes were obtained. Using protein-protein interaction networks (PPI) and component-target network analysis,10 core genes of irisin on UC were further identified. The results of gene ontology (GO) enrichment analysis showed that the molecular mechanisms of irisin on UC were mainly related to major enrichment in the categories of response to xenobiotic stimulus, response to the drug, and negative regulation of gene expression. Molecular docking results showed good binding activity for almost all core component targets. More importantly, MTT assay and flow cytometry results showed that LPS-induced cytotoxicity was reversed by irisin, after coincubation with irisin, the level of IL-12 and IL-23 decreased in LPS-stimulated RAW264.7 macrophages. Irisin pretreatment significantly inhibited the phosphorylation of ERK and AKT and increased the expression of PPAR alpha and PPAR gamma. LPS-induced enhancement of phagocytosis and cell clearance were reversed by irisin pretreatment. Irisin ameliorated LPS-induced inflammation by inhibiting cytotoxicity and apoptosis, and this protective effect may be mediated through the MAPK pathway. These findings confirmed our prediction that irisin plays an anti-inflammatory role in LPS-induced inflammation via the MAPK pathway.

Chronic voluntary wheel running exercise ameliorates metabolic dysfunction via PGC-1α expression independently of FNDC5/irisin pathway in high fat diet-induced obese mice

Exercise is an effective intervention to ameliorate metabolic diseases including obesity and insulin resistance, but the mechanisms involved in the metabolic amelioration have not yet been fully elucidated. This study aimed to determine whether AMPK-SIRT1-PGC-1α-FNDC5/Irisin-UCP1 expression is activated and whether metabolic dysfunction is ameliorated by chronic voluntary wheel running (VWR) in high-fat diet (HFD) induced obese mice. C57BL6J mice were randomly assigned into three groups at the age of 7 weeks for 10 weeks: normal chow diet (CON) group, HFD group, and HFD + VWR group. Chronic VWR ameliorates metabolic parameters and leads to increases in the expression of PGC-1α in the gastrocnemius muscle in HFD-induced obese mice. In contrast, the expression of AMPKα, SIRT1, and FNDC5, or circulating irisin levels did not lead to alteration. Improvement of metabolic health was partly mediated via PGC-1α expression by chronic VWR, but not FNDC5/Irisin pathway in HFD-induced obese mice.

Does irisin has neuroprotective effect against diabetes induced neuropathy in male rats?

We aimed to investigate the contribution of irisin in the neuroprotective process of exercise training in diabetic rats. Serum irisin levels, thermal and mechanical pain thresholds and intracellular calcium ([Ca²⁺]_i) levels in sensory neurons were measured at different time intervals during the eight weeks of exercise sessions for the control, non-exercise diabetics (3 groups) and exercise performing (low and high intensity groups) diabetic rats (n = 7-10 for all groups). Non-exercise diabetic groups were treated with irisin in different doses (1, 10 and 20 µg/kg respectively). Recovered pain thresholds at the end of the exercise sessions (p < .05), higher serum irisin levels that compared to control and diabetics (p < .05) and insignificant mean [Ca2⁺]_i peak amplitudes in sensory neurons (p > .05) obtained from experiments. Furthermore, irisin injection decreased the thermal pain threshold of diabetics only at 60th minutes (p < .05). Irisin may have a role in the neuroprotective effect of exercise training.

Effect of Irisin on Human Nucleus Pulposus Cells: New Insights into the Biological Cross-talk Between Muscle and Intervertebral Disk

STUDY DESIGN

In vitro study.

OBJECTIVE

To investigate the effect of irisin on human nucleus pulposus cells (hNPCs) in vitro.

SUMMARY OF BACKGROUND DATA

Physical exercise (PE) favours weight loss and ameliorates function in patients with low back pain. Although there is no biological evidence that the intervertebral disk (IVD) can respond to PE, recent studies have shown that running is associated with increased IVD hydration and hypertrophy. Irisin, a myokine released upon muscle contraction, has demonstrated anabolic effects on different cell types, including chondrocytes.

MATERIALS AND METHODS

hNPCs were exposed to 5, 10, and 25 ng/mL irisin. Cell proliferation, glycosaminoglycan (GAG) content, metabolic activity, gene expression of collagen type II (COL2), matrix metalloproteinase (MMP)-13, tissue inhibitor of matrix metalloproteinase (TIMP)-1 and TIMP-3, aggrecan (ACAN), interleukin (IL)-1β, a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-5 were assessed. In addition, MTT assay and ADAMTS-5, COL2, TIMP-1, and IL-1β gene expression were evaluated following incubation with irisin for 24 hours and subsequent culture with 10 ng/mL IL-1β and vice versa (incubation for 24 hours with IL-1β and subsequent culture with irisin).

RESULTS

Irisin increased hNPC proliferation, metabolic activity, and GAG content, as well as COL2, ACAN, TIMP-1 and TIMP-3 gene expression, while decreasing MMP-13 and IL-1β mRNA levels. Irisin pretreatment of hNPCs cultured in proinflammatory conditions resulted in a rescue of metabolic activity and a decrease of IL-1β levels. Similarly, incubation of hNPCs with IL-1β and subsequent exposure to irisin led to an increment of metabolic activity, COL2 gene expression, and a reduction of IL-1β and ADAMTS-5 levels.

CONCLUSIONS

Irisin increases hNPC proliferation, GAG content, metabolic activity, and promotes anabolic gene expression while reducing catabolic markers. Irisin may be one of the mediators by which PE and muscle tissues modulate IVD metabolism, suggesting the existence of a biological cross-talk between the muscle and IVD.

Myokines: Crosstalk and Consequences on Liver Physiopathology

Non-alcoholic fatty liver disease (NAFLD) is a chronic liver disease mainly characterized by the hepatic accumulation of lipid inducing a deregulation of β-oxidation. Its advanced form is non-alcoholic steatohepatitis (NASH), which, in addition to lipid accumulation, induces hepatocellular damage, oxidative stress and fibrosis that can progress to cirrhosis and to its final stage: hepatocellular carcinoma (HCC). To date, no specific therapeutic treatment exists. The implications of organ crosstalk have been highlighted in many metabolic disorders, such as diabetes, metabolic-associated liver diseases and obesity. Skeletal muscle, in addition to its role as a reservoir and consumer of energy and carbohydrate metabolism, is involved in this inter-organs’ communication through different secreted products: myokines, exosomes and enzymes, for example. Interestingly, resistance exercise has been shown to have a beneficial impact on different metabolic pathways, such as lipid oxidation in different organs through their secreted products. In this review, we will mainly focus on myokines and their effects on non-alcoholic fatty liver disease, and their complication: non-alcoholic steatohepatitis and HCC.

The Role of Adipokines in the Pathogenesis of Psoriasis

Psoriasis is a chronic and immune-mediated skin condition characterized by pro-inflammatory cytokines and keratinocyte hyperproliferation. Dendritic cells, T lymphocytes, and keratinocytes represent the main cell subtypes involved in the pathogenesis of psoriasis, while the interleukin-23 (IL-23)/IL-17 pathway enhances the disease progression. Human adipose tissue is an endocrine organ, which secretes multiple proteins, known as adipokines, such as adiponectin, leptin, visfatin, or resistin. Current evidence highlights the immunomodulatory roles of adipokines, which may contribute to the progression or suppression of psoriasis. A better understanding of the complexity of psoriasis pathophysiology linked with adipokines could result in developing novel diagnostic or therapeutic strategies. This review aims to present the pathogenesis of psoriasis and the roles of adipokines in this process.

The role of irisin and asprosin level in the pathophysiology of prediabetes

PURPOSE

We aimed to examine whether irisin and asprosin have a role in the physiopathology of prediabetes.

METHODS

Hundred people were selected between the age of 18-65 years for the study population (60 prediabetes, 40 healthy). For the follow-up study, the patients with prediabetes were offered a 3-month program for lifestyle change and then reevaluated. Our research is a single-center, prospective observational study.

RESULTS

Among the healthy group and patients with prediabetes, irisin levels were lower and asprosin levels were higher (p < 0.001) in patients. In the follow-up part, the patients' insulin levels, HOMA index scores, and asprosin levels were decreased while irisin levels were elevated (p < 0.001). Sensitivity was 98.3% and specificity was 65% for asprosin of > 56.3 ng/mL, while they were 93.3% and 65% for irisin of ≤ 120.2 pg/mL, respectively. It was found that irisin had diagnostic performance similar to insulin and the HOMA index, while asprosin performed similarly to glucose, insulin, and the HOMA index.

CONCLUSION

Both irisin and asprosin have been found to be related to the prediabetes pathway and it has been shown that these molecules may be useful in daily clinical practice with diagnostic performances similar to those of the HOMA index and insulin.

Irisin prevents hypoxic-ischemic brain damage in rats by inhibiting oxidative stress and protecting the blood-brain barrier

Hypoxic-ischemic encephalopathy (HIE) is associated with excessive inflammation, blood-brain barrier dysfunction, and oxidative stress. Irisin can reduce inflammation and ameliorate oxidative stress; however, its effects on hypoxic-ischemic brain damage in newborns are unknown. Newborn Sprague-Dawley rats were subjected to hypoxic-ischemic injury and irisin treatment. TUNEL staining assays, the albumin-Evans blue dye extravasation method, an antioxidants detection kit, quantitative reverse-transcriptase PCR, enzyme linked immunosorbent assay, Western blot analysis, immunohistochemistry, and electron microscopy were used to investigate the possible mechanisms underlying the prevention of HIE by irisin. We discovered that rats affected by HIE and administered irisin had lower levels of IL-6 (but not TNF-α or IL-1β) less oxidative stress, and enhanced blood-brain barrier integrity. Irisin can effectively attenuate brain damage by reducing oxidative stress and protecting the blood-brain barrier.

Crucial Regulatory Role of Organokines in Relation to Metabolic Changes in Non-Diabetic Obesity

Obesity is characterized by an excessive accumulation of fat leading to a plethora of medical complications, including coronary artery disease, hypertension, type 2 diabetes mellitus or impaired glucose tolerance and dyslipidemia. Formerly, several physiological roles of organokines, including adipokines, hepatokines, myokines and gut hormones have been described in obesity, especially in the regulation of glucose and lipid metabolism, insulin sensitivity, oxidative stress, and low-grade inflammation. The canonical effect of these biologically active peptides and proteins may serve as an intermediate regulatory level that connects the central nervous system and the endocrine, autocrine, and paracrine actions of organs responsible for metabolic and inflammatory processes. Better understanding of the function of this delicately tuned network may provide an explanation for the wide range of obesity phenotypes with remarkable inter-individual differences regarding comorbidities and therapeutic responses. The aim of this review is to demonstrate the role of organokines in the lipid and glucose metabolism focusing on the obese non-diabetic subgroup. We also discuss the latest findings about sarcopenic obesity, which has recently become one of the most relevant metabolic disturbances in the aging population.

The impact of sports on the normal functioning of the prostate gland: A review

This article explores the relationship of physical activity to the normal functioning of the prostate gland. The biomechanism of hormonal activity during exercise was studied, and special attention was paid to the biomechanism of an actively working muscle and the release of myokines. The analysis of the relationship between myokines and the functioning of the prostate gland was carried out. It has been established that physical activity reduces the risk of developing prostate diseases and is an important method of prevention.

Association of Plasma Irisin Levels with Circulating Endothelial Microparticles (EMPs) and Endothelial Progenitor Cells (EPCs) in Children Born Prematurely

Prematurity has been linked with endothelial dysfunction in later life. The purpose of this study was to evaluate the association between plasma irisin, an adipomyokine reported to protect the functional integrity of vascular endothelium, and circulating endothelial microparticles (EMPs) and endothelial progenitor cells (EPCs), consisting early biomarkers of endothelial dysfunction, in preterm-born children. We studied 131 prepubertal children; 61 preterm and 70 born at term (controls). Plasma irisin was determined by ELISA. Circulating CD62E(+), CD144(+) and CD31(+)/CD42b(-) EMPs, and CD34(+)/VEGFR-2(+)/CD45(-) and CD34(+)/VEGFR-2(+)/CD45dim EPCs, were determined by flow cytometry. Body mass index, waist-to-hip ratio, neck circumference, systolic and diastolic blood pressure, and biochemical parameters (glucose, lipids, insulin, HOMA-IR) were also evaluated. Plasma irisin was significantly lower (p = 0.001), whereas circulating EMPs and EPCs were higher, in children born prematurely compared to controls. Irisin was recognized as independent predictor for CD144(+) and CD31(+)/CD42b(-) EMPs, CD34(+)/VEGFR-2(+)/CD45(-) and CD34(+)/VEGFR-2(+)/CD45dim EPCs in the total study population, and for CD31(+)/CD42b(-) EMPs in the preterm group. In conclusion, plasma irisin correlates independently with circulating EMP and EPC subpopulations in prepubertal children and in preterm-born ones. Further studies in children will potentially elucidate the link between irisin and the primary stages of prematurity-related endothelial dysfunction.

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 attenuates angiotensin II-induced atrial fibrillation and atrial fibrosis via LOXL2 and TGFβ1/Smad2/3 signaling pathways

Objectives

Irisin was reported as a cardioprotective and anti-oxidative effector, while the effect on atrial fibrosis is unknown. The current research examined irisin's function in atrial fibrillation (AF); atrial fibrosis brought on by Ang II can be suppressed, thus lessening the risk of developing AF.

Materials and Methods

246 individuals were enrolled in the present case-control study. Chinese AF patients (n=126), 83 of whom were paroxysmal AF (PAF), 43 patients with persistent AF (PeAF), and 120 healthy controls. Saline or Ang II (2.0 mg/kg/day) was subcutaneously injected into healthy male C57BL/6 mice for four weeks. Once daily for four weeks, intraperitoneal injections of exogenous irisin (500 g/kg/day) were administered.

Results

In comparison to PAF patients and healthy controls (all P<0.05), PeAF patients had significantly higher rates of heart failure (HF), large left atrial size (LAD), hypertrophic protein B-type natriuretic peptide (BNP), malondialdehyde (MDA), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), C-terminal telopeptide of type I collagen (CTX-I), and transforming growth factor beta-1 (TGF-β1), while superoxide dismutase (SOD) level was low. Expression of irisin was decreased in AF patients' serum and Ang II-infused mice. Exogenous irisin dramatically reduced apoptosis, atrial fibrosis, atrial inflammation, and the susceptibility to AF caused by Ang II. In the atrial tissue, irisin inhibited Ang II-induced fibroblast transdifferentiation, LOXL2, TGF-β1, collagen production, and phosphorylation of Smad2/3.

Conclusion

The study results speculated that irisin could be a potential AF target, and it inhibited atrial fibrosis and significantly impaired increased AF susceptibility through inactivation of LOXL2 and the TGF-β/Smad pathway.

Upregulation of CCL5/RANTES Gene Expression in the Diaphragm of Mice with Cholestatic Liver Disease

Chronic liver diseases are a group of pathologies affecting the liver with high prevalence worldwide. Among them, cholestatic chronic liver diseases (CCLD) are characterized by alterations in liver function and increased plasma bile acids. Secondary to liver disease, under cholestasis, is developed sarcopenia, a skeletal muscle dysfunction with decreased muscle mass, strength, and physical function. CCL5/RANTES is a chemokine involved in the immune and inflammatory response. Indeed, CCL5 is a myokine because it is produced by skeletal muscle. Several studies show that bile acids induce CCL5/RANTES expression in liver cells. However, it is unknown if the expression of CCL5/RANTES is changed in the skeletal muscle of mice with cholestatic liver disease. We used a murine model of cholestasis-induced sarcopenia by intake of hepatotoxin 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC diet), in which we detected the mRNA levels for ccl5. We determined that mice fed the DDC diet presented high levels of serum bile acids and developed typical features of sarcopenia. Under these conditions, we detected the ccl5 gene expression in diaphragm muscle showing elevated mRNA levels compared to mice fed with a standard diet (chow diet). Our results collectively suggest an increased ccl5 gene expression in the diaphragm muscle concomitantly with elevated serum bile acids and the development of sarcopenia.

Serum Irisin level is associated with fall risk, muscle strength, and cortical porosity in postmenopausal women

BACKGROUND

Irisin plays a role in bone-muscle crosstalk, but the relationship between the serum irisin level and bone microarchitecture remains unknown.

OBJECTIVE

This study aimed to investigate the relationships between serum irisin level and fall risk, muscle strength, bone mineral density (BMD), and bone microarchitecture among Chinese postmenopausal women.

METHODS

In all 138 postmenopausal women, handgrip strength, short physical performance battery (SPPB), and the timed up-and-go test were performed to evaluate muscle strength, physical performance, and fall risk, respectively. The serum irisin was measured. High-resolution peripheral quantitative computed tomography (HR-pQCT) was performed to acquire volumetric BMD and bone microarchitecture. Bivariate analysis was used to explore relationships between serum irisin level and muscle strength and HR-pQCT parameters. Univariate and multivariate linear regression analyses were performed to determine associations between serum irisin level and vBMD and cortical porosity (Ct.Po).

RESULTS

All participants had a median serum irisin level of 3.91 μg/ml. Participants with high fall risk had significantly lower serum irisin levels than those with low fall risk (2.22 μg/ml vs. 4.16 μg/ml, p=0.024). Irisin level was positively related to handgrip strength (rs=0.185, p=0.030) and SPPB performance. In univariate linear regression, serum irisin level was positively associated with cortical volumetric BMD (Ct.vBMD, radius: standardized β=0.184, p=0.031; tibia: standardized β=0.242, p=0.004), but it had no significant associations with Ct.vBMD after multivariate adjustment. After adjusting by age, height, serum sclerostin level, and body fat ratio, only Ct.Po at the distal radius had a significantly negative association with serum irisin level (standardized β=-0.276, p=0.003).

CONCLUSION

Postmenopausal women with lower serum irisin levels have a higher fall risk, weaker muscle strength, and higher cortical porosity. Moreover, serum irisin level has a positive association with Ct.vBMD, but it is affected by factors such as age.

Changes in irisin, inflammatory cytokines and aerobic capacity in response to three weeks of supervised sprint interval training in older men

BACKGROUND

This study investigated the effects of supervised short-term sprint interval training (SIT) on circulating irisin, interleukin (IL)-6 and tumour necrosis factor (TNF)-α concentrations, and aerobic capacity and body composition values in healthy older men.

METHODS

Eleven older men (63±8 years; 178.0±5.5 cm; 82.7±8.6 kg; 22.7±3.7% body fat) underwent SIT (6 repetitions of 30 s all-out cycling bouts with 4 min active recovery after each bout) three days a week for three consecutive weeks. Body composition measured by dual-energy X-ray absorptiometry, aerobic capacity assessed by direct peak oxygen consumption (VO<inf>2peak</inf>) test and morning fasting blood samples were obtained before and after a 3-week SIT intervention.

RESULTS

Nine supervised SIT sessions moderately (effect size [ES] =0.65; P<0.05) increased irisin concentrations (from 135.40±28.73 to 154.20±47.09 ng.mL^-1) together with moderate decreases (P<0.05) in IL-6 (ES=0.89; from 1.26±0.44 to 0.87±0.44 pg.mL^-1) and TNF-α (ES=0.64; from 5.10±1.23 to 4.31±1.20 pg.mL^-1) levels in older men. In addition, increase in VO<inf>2peak</inf> was significant but small (ES=0.25; P<0.05; from 36.0±7.1 to 37.8±6.7 mL.min.^-1kg^-1), while no changes (P>0.05) in body composition variables were observed after a short-term SIT period.

CONCLUSIONS

A 3-week SIT intervention with only nine training sessions increased circulating irisin concentrations, improved inflammatory profile and aerobic capacity without changes in body composition in healthy older men. Accordingly, a short-term SIT programme is a time efficient alternative for traditional aerobic training to improve metabolic health and aerobic capacity in older adults.

Sarcopenia in Chronic Liver Disease: A Metabolic Perspective

Sarcopenia, a condition of low muscle mass, quality, and strength, is commonly found in patients with chronic liver disease (CLD) and is associated with adverse clinical outcomes including reduction in quality of life, increased mortality, and complications. A major contributor to sarcopenia in CLD is the imbalance in muscle protein turnover wherein changes in various metabolic factors such as hyperammonemia, amino acid deprivation, hormonal imbalance, gut dysbiosis, insulin resistance, chronic inflammation, etc. have important roles. In particular, hyperammonemia is a key mediator of the liver-gut axis and is known to contribute to sarcopenia by various mechanisms including increased expression of myostatin, increased phosphorylation of eukaryotic initiation factor 2a, cataplerosis of α-ketoglutarate, mitochondrial dysfunction, increased reactive oxygen species that decrease protein synthesis and increased autophagy-mediated proteolysis. Skeletal muscle is a major organ of insulin-induced glucose metabolism, and sarcopenia is closely linked to insulin resistance and metabolic syndrome. Patients with liver cirrhosis are in a hypermetabolic state that is associated with catabolism and depletion of amino acids, particularly branched-chain amino acids. Sarcopenia can have significant implications for nonalcoholic fatty liver disease, the most common form of CLD worldwide, because of the close link between metabolic syndrome and sarcopenia. This review discusses the potential metabolic derangement as a cause or effect of sarcopenia in CLD, as well as interorgan crosstalk, which that might help identifying a novel therapeutic strategies.

The Effect of Exercise Training on Irisin Secretion in Patients with Type 2 Diabetes: A Systematic Review

INTRODUCTION

Irisin is a myokine considered to be a potential mediator of exercise-induced energy metabolism and its secretion is known to promote the browning of beige fat cells in white adipose tissue. However, it is currently not known which exercise protocol is the best to enhance irisin concentration in patients with type 2 diabetes (T2D).

OBJECTIVE

The purpose of this study is to provide a review investigating the irisin response to different exercise training modalities and intensities in T2D.

METHODS

A systematic literature search was performed in May 2022.

RESULTS

After the selection process from 938 articles, six studies were included. Selected papers presented different exercise training interventions regarding intensity and modality. One study reported no significant differences in serum irisin levels after exercise training, whereas the other five showed a higher increase in serum irisin levels after exercise training with higher differences in irisin secretion after high-intensity training (HIT). No consideration was possible on exercise modalities.

CONCLUSIONS

The impact of training intensity and modality was found to be partly discordant but data seem to suggest that HIT promotes greater irisin secretion. Despite the limited evidence, HIT, both in interval and continuous modalities, could be suggested as valid exercise training to increase circulating irisin in patients with T2D.

Central Irisin Signaling Is Required for Normal Timing of Puberty in Female Mice

Timing of puberty requires exquisite coordination of genes, hormones, and brain circuitry. An increasing level of body adiposity, signaled to the brain via the fat-derived hormone leptin, is recognized as a major factor controlling puberty onset. However, it is clear that leptin is not the only metabolic cue regulating puberty, and that developmental regulation of this process also involves tissues other than adipose, with muscle development potentially playing a role in the timing of puberty. The proteolytic processing of fibronectin type 3 domain-containing protein 5 (FNDC5) releases a hormone, irisin. Irisin is primarily produced by muscle and is released into circulation, where levels increase dramatically as puberty approaches. We investigated the effects of a global deletion of the Fndc5 gene on pubertal timing. The absence of irisin induced a delay in puberty onset in female knockout mice compared with controls, without affecting body weight or gonadotropin-releasing hormone (GnRH) neuronal density. We next treated pre-pubertal wild-type male and female mice with an irisin receptor antagonist, cilengitide, for 7 days and observed a delay in first estrus occurrence compared to vehicle-treated control mice. Male puberty timing was unaffected. Next, we deleted the irisin receptor (integrin subunit alpha V) in all forebrain neurons and found a delay in the occurrence of first estrus in knockout females compared to controls. Taken together, these data suggest irisin plays a role in the timing of puberty onset in female mice via a centrally mediated mechanism.

Spinal Irisin Gene Delivery Attenuates Burn Injury-Induced Muscle Atrophy by Promoting Axonal Myelination and Innervation of Neuromuscular Junctions

Muscle loss and weakness after a burn injury are typically the consequences of neuronal dysregulation and metabolic change. Hypermetabolism has been noted to cause muscle atrophy. However, the mechanism underlying the development of burn-induced motor neuropathy and its contribution to muscle atrophy warrant elucidation. Current therapeutic interventions for burn-induced motor neuropathy demonstrate moderate efficacy and have side effects, which limit their usage. We previously used a third-degree burn injury rodent model and found that irisin-an exercise-induced myokine-exerts a protective effect against burn injury-induced sensory and motor neuropathy by attenuating neuronal damage in the spinal cord. In the current study, spinal irisin gene delivery was noted to attenuate burn injury-induced sciatic nerve demyelination and reduction of neuromuscular junction innervation. Spinal overexpression of irisin leads to myelination rehabilitation and muscular innervation through the modulation of brain-derived neurotrophic factor and glial-cell-line-derived neurotrophic factor expression along the sciatic nerve to the muscle tissues and thereby modulates the Akt/mTOR pathway and metabolic derangement and prevents muscle atrophy.

Serum vitamin D status and circulating irisin levels in older adults with sarcopenia

Background

Emerging evidence suggests sarcopenia, which is involved in the serum vitamin D deficiency and development of abnormal muscle metabolism, is predominately centered in the general older population. In the present study, we aimed to explore the relationship between the level of serum vitamin D and irisin concentrations in the older adults with sarcopenia.

Methods

A cross-sectional study was conducted which included 422 sarcopenia participants (146 males and 276 females). Sarcopenia was assessed according to the recommended diagnostic criteria of the Asia Working Group for Sarcopenia (AWGS). The levels of serum 25-hydroxyvitamin D (25(OH)D), 25-hydroxyvitamin D₂ (25(OH)D₂) and 25-hydroxyvitamin D₃ (25(OH)D₃) were determined by LC-MS/MS. Irisin levels were measured by enzyme-linked immunosorbent assay (ELISA). The relationship between serum concentration of vitamin D and irisin were determined using multiple linear regression analysis.

Results

After adjustment for potential confounding factors, a significant and positive relationship between changes in irisin across 25(OH)D, and 25(OH)D₃ was observed (standard regression coefficients of 0.150 and 0.151, respectively, P < 0.05). However, no significant relationship was observed between serum vitamin D concentrations and irisin levels in males.

Conclusions

This study demonstrated that a higher level of serum vitamin D is independently related to the increment of irisin in sarcopenia females, not in males. These investigations need to be verified in other large-scale prospective studies.

Expression analysis of irisin during different development stages of skeletal muscle in mice

BACKGROUND

As a newly discovered muscle factor secreted by skeletal muscle cells, irisin is a polypeptide fragment formed from hydrolysis of fibronectin type Ⅲ domain-containing protein 5 (FNDC5). Irisin can promote beigeing of white adipose tissue (WAT) and regulate glucose and lipid metabolisms. However, the functions of irisin in skeletal muscle development remain largely unknown. In order to characterize the expression of irisin, this study investigated the expression of irisin precursor FNDC5 in myoblasts and skeletal muscles during different developmental stages of SPF mice.

RESULTS

The Western blot, quantitative real-time PCR (qRT-PCR), and immunofluorescence assay results showed that FNDC5 was expressed in all the developmental stages of myoblasts and gastrocnemius, but its expression differed at different stages. FNDC5 protein exhibited the highest expression in gastrocnemius of sexually mature mice, followed by elderly mice and adolescent mice, and it displayed the lowest expression in pups. Additionally, FNDC5 protein was mainly expressed in cytoplasm, and it had the highest expression in primary myoblasts, followed by the myotubes with the lowest expression in C2C12 myogenic cells.

CONCLUSIONS

Overall, FNDC5 was mainly expressed in cytoplasm and extracellular matrix with different expression levels at different developmental stages of skeletal muscle cells and tissues in mice. This study will provide new strategies for promoting skeletal muscle development and treating muscle- and metabolism-related disease by using irisin.

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.

Irisin protects against obesity-related chronic kidney disease by regulating perirenal adipose tissue function in obese mice

Background

Compared with typical visceral fat deposits in obesity and metabolic syndrome, perirenal adipose tissue (PRAT) dysfunction is more closely linked to obesity-related chronic kidney disease (OB-CKD). The myokine irisin reportedly promotes positive outcomes in metabolic disease. This study investigated whether irisin could reduce urinary albumin excretion and demonstrate renoprotective effects through the regulation of PRAT function in obese mice.

Methods

C57BL/6 J mice received a high-fat diet (HFD) with or without concurrent administration of irisin. Glucose tolerance, plasma levels of free fatty acids, and urinary albumin excretion were assessed, along with renal morphology. The vascular endothelial growth factor and nitric oxide in glomeruli were also analyzed, in addition to PRAT function-associated proteins.

Results

Irisin administration significantly reduced the final body weight, fat mass, and free fatty acids, without reducing PRAT mass, in HFD mice. Furthermore, irisin decreased urinary albumin excretion and attenuated both renal fibrosis and lipid accumulation. Irisin administration led to increases in PRAT function-associated proteins, including sirtuin1, uncoupling protein-1, and heme-oxygenase-1. Ex vivo treatment of PRAT and glomeruli with irisin also restored PRAT function. Finally, irisin treatment restored the vascular endothelial growth factor–nitric oxide axis.

Conclusions

Irisin attenuated metabolic disorders and protected against OB-CKD by normalizing the PRAT–kidney axis. These results suggest that agents targeting PRAT activation might be useful for treatment of OB-CKD.

Moderate intensity continuous and interval training affect visceral fat and insulin resistance model in female rat exposed high calorie diet

Chronic high-calorie diet (HCD) combined with physical inactivity promotes obesity and insulin resistance (IR). This study aimed to analyse the comparable effect of moderate-intensity continuous training (MICT) and moderate-intensity interval training (MIIT) on visceral fat weight and IR in subjects exposed to HCD. This randomised post-test research used only a control group design with female rats (Wistar norvegicus), 8 weeks old and 100-200 g of bodyweight. They were randomly divided into four groups: standard diet group (C), HCD group (C1), HCD combined with MICT group (C2) and HCD combined with MIIT group (C3). Each group consisted of six rats. HCD consisted of ad libitum standard diet plus dextrose solution by oral gavage for 4 weeks. The MICT was conducted by swimming plus 6% load of body weight for 10 min in the first week, for 20 min in the second week and 30 min in the third and fourth week. The MIIT was conducted by swimming in a ratio between swimming and rest time at 2:1 plus 6% load of BW, performed 5×/week for 4 weeks, and increased progressively. The mean body weight pre-intervention was 152.79±13.280 g and 150.12±9.195 g post-intervention (P=0.115). The mean fasting blood glucose pre-intervention was 79±8.668 mg/dl, and post-intervention 86.29±12.142 mg/dl (P=0.142). The mean visceral fat weight between C (1.94±0.66 g), C1 (1.45±0.47 g), C2 (1.41±0.44 g), and C3 (1.22±0.59 g) was not significant (P=0.179). The mean triglyceride level for C (173.33±30.30 mg/dl), C1 (157.16±47.32 mg/dl), C2 (112.83±25.49 mg/dl), and C3 (80.33±23.47 mg/dl) was significant (P=0.000). The mean IR model for C (4.796±0.070), C1 (4.728±0.125), C2 (4.620±0.123), C3 (4.360±0.143) was significant (P=0.000). In conclusion, both MICT and MIIT have an effect to improve IR and TG. The MIIT was more effective to improve IR compared to MICT in the female rats exposed to an HCD.

Physical Activity as the Best Supportive Care in Cancer: The Clinician's and the Researcher's Perspectives

Multidisciplinary supportive care, integrating the dimensions of exercise alongside oncological treatments, is now regarded as a new paradigm to improve patient survival and quality of life. Its impact is important on the factors that control tumor development, such as the immune system, inflammation, tissue perfusion, hypoxia, insulin resistance, metabolism, glucocorticoid levels, and cachexia. An increasing amount of research has been published in the last years on the effects of physical activity within the framework of oncology, marking the appearance of a new medical field, commonly known as "exercise oncology". This emerging research field is trying to determine the biological mechanisms by which, aerobic exercise affects the incidence of cancer, the progression and/or the appearance of metastases. We propose an overview of the current state of the art physical exercise interventions in the management of cancer patients, including a pragmatic perspective with tips for routine practice. We then develop the emerging mechanistic views about physical exercise and their potential clinical applications. Moving toward a more personalized, integrated, patient-centered, and multidisciplinary management, by trying to understand the different interactions between the cancer and the host, as well as the impact of the disease and the treatments on the different organs, this seems to be the most promising method to improve the care of cancer patients.

Fndc5/irisin is regulated by myogenesis stage, irisin, muscle type and training

OBJECTIVES

Irisin, a novel myokine that responds to exercise, was initially identified as a regulator of fat tissue metabolism. We aimed to investigate fibronectin type III domain-containing protein 5 (Fndc5)/irisin, auto/para-crine role in different muscle fibers, different activities, and muscle cell differentiation.

METHODS

Using in-vitro, ex-vivo, and in-vivo muscle models, Fndc5 was studied at the physiological and molecular levels.

RESULTS

Following training, C57BL/6 mice (n=10) were subject to fast and slow-twitch muscles dissection and molecular analysis. Isolated mice (C57BL/6, n=14) slow and fast-twitch muscles were subject to electrical aerobic and anaerobic pulses stimulation (EPS). L6 muscle cells differentiation was characterized by Fndc5 differentiation-depended expression pattern parallel with significant hypertrophy, Myogenin elevation, and overlapping Peroxisome proliferator-activated receptor-gamma coactivator-1 alpha (Pgc-1α) expression pattern. Exogenous irisin significantly altered Fndc5 expression; augmented at early differentiation (3-4-fold, P<0.05) and decreased (2-fold, P<0.05) at late differentiation. Training induced a significant elevation in Fndc5/irisin and Pgc-1α expression levels in all muscle types compared to the sedentary state, where soleus muscle (slow) Fndc5 expression levels were significantly higher compared to levels in all other fast muscles (3-140-fold, P<0.001). Similarly, following EPS, Fndc5 expression levels were significantly augmented in the soleus slow muscle following both aerobic and anaerobic activity (3-3.5-fold, P<0.05) compared to extensor digitorum longus (fast) muscle.

CONCLUSIONS

Muscle cell's Fndc5 expression has a differentiation-depended pattern paralleling Pgc-1α expression and hypertrophy. Irisin autocrinally and significantly regulate Fndc5 and Pgc-1α in a differentiation-depended manner. Muscle Fndc5 expression levels are dependent on fiber type and activity type.

Irisin Promotes Osteogenesis by Modulating Oxidative Stress and Mitophagy through SIRT3 Signaling under Diabetic Conditions

Advanced glycation end products (AGEs) accumulate in the bone tissue of patients with diabetes mellitus, resulting in oxidative stress, poor bone healing, or regeneration. Irisin, a novel exercise-induced myokine, is involved in the regulation of bone metabolism. However, the effects of irisin on adipose-derived stem cell (ASC) osteogenic differentiation and bone healing under diabetic conditions remain poorly understood. ASCs were obtained from inguinal fat of Sprague-Dawley rats and treated with different concentrations of AGEs and irisin. Cell proliferation, apoptosis, and osteogenic differentiation abilities of ASCs were detected. To explore the regulatory role of sirtuin 3 (SIRT3), ASCs were transfected with lentivirus-mediated SIRT3 overexpression or knockdown vectors. Next, we investigated mitochondrial functions, mitophagy, and mitochondrial biogenesis in different groups. Moreover, SOD2 acetylation and potential signaling pathways were assessed. Additionally, a diabetic rat model was used to evaluate the effect of irisin on bone healing in calvarial critical-sized defects (CSDs) in vivo. Our results showed that irisin incubation mitigated the inhibitory effects of AGEs on ASCs by increasing cell viability and promoting osteogenesis. Moreover, irisin modulated mitochondrial membrane potential, intracellular ROS levels, mitochondrial O₂^·− status, ATP generation, complex I and IV activities, mitophagy, and mitochondrial biogenesis via a SIRT3-mediated pathway under AGEs exposure. Furthermore, in calvarial CSDs of diabetic rats, transplantation of gels encapsulating irisin-pretreated ASCs along with irisin largely enhanced bone healing. These findings suggest that irisin attenuates AGE-induced ASC dysfunction through SIRT3-mediated maintenance of oxidative stress homeostasis and regulation of mitophagy and mitochondrial biogenesis. Thus, our studies shed new light on the role of irisin in promoting the ASC osteogenesis and targeting SIRT3 as a novel therapeutic intervention strategy for bone regeneration under diabetic conditions.

Metabolomics as a Crucial Tool to Develop New Therapeutic Strategies for Neurodegenerative Diseases

Neurodegenerative diseases (NDs), such as Alzheimer’s (AD), Parkinson’s (PD), and amyotrophic lateral sclerosis (ALS), share common pathological mechanisms, including metabolism alterations. However, their specific neuronal cell types affected and molecular biomarkers suggest that there are both common and specific alterations regarding metabolite levels. In this review, we were interested in identifying metabolite alterations that have been reported in preclinical models of NDs and that have also been documented as altered in NDs patients. Such alterations could represent interesting targets for the development of targeted therapy. Importantly, the translation of such findings from preclinical to clinical studies is primordial for the study of possible therapeutic agents. We found that N-acetyl-aspartate (NAA), myo-inositol, and glutamate are commonly altered in the three NDs investigated here. We also found other metabolites commonly altered in both AD and PD. In this review, we discuss the studies reporting such alterations and the possible pathological mechanism underlying them. Finally, we discuss clinical trials that have attempted to develop treatments targeting such alterations. We conclude that the treatment combination of both common and differential alterations would increase the chances of patients having access to efficient treatments for each ND.

Irisin Is Related to Non-Alcoholic Fatty Liver Disease (NAFLD)

Irisin is a cytokine involved in many metabolic pathways occurring, among others, in muscles, adipose tissue and liver. Thus, fluctuations in irisin levels are suggested to be related to metabolic diseases. Therefore, the purpose of our study was to evaluate whether irisin may be associated with non-alcoholic fatty liver disease (NAFLD). A total of 138 patients (70/68 male/female, mean age 65.61 ± 10.44 years) were enrolled in the study. The patients were assigned to the NAFLD group (n = 72, including 46 patients with type 2 diabetes (T2DM]) and the group without NAFLD (n = 66, 31 patients with T2DM). NAFLD was diagnosed based on ultrasound examination, Hepatic Steatosis Index (HSI) and Fatty Liver Index. Baseline anthropometric, blood pressure and biochemical parameters were collected. The serum irisin level was determined using an ELISA test. We observed that NAFLD was associated with an increased concentration of irisin. Moreover, Spearman correlations and linear regression analysis revealed that irisin level correlates with some anthropometric and biochemical parameters such as body mass index, glycated hemoglobin, aspartic aminotransferase, creatinine and urea. Logistic regression analysis depicted that odds for NAFLD increase 1.17 times for each 1 μg/mL rise of irisin concentration. Finally, ROC analysis showed that the concentration of irisin possesses a discriminate capacity for NAFLD and optimal cut points concentration could be designed. The risk of NAFLD in the subgroup with irisin concentration above 3.235 μg/mL was 4.57 times higher than in patients with the lower concentration of irisin. To conclude, the obtained results suggest that irisin concentration is associated with some anthropometric and biochemical parameters and should be further investigated toward its usage as a diagnostic biomarker of NAFLD.

Relationships between Uncoupling Protein Genes UCP1, UCP2 and UCP3 and Irisin Levels in Residents of the Coldest Region of Siberia

Currently, it is known that irisin can participate in the processes of thermoregulation and browning of adipose tissue, and, therefore, it is possible that it is involved in the microevolutionary mechanisms of adaptation to a cold. The aim of this study is to investigate the relationship between the uncoupling protein genes (UCP1, UCP2, UCP3) and the irisin levels in the residents of the coldest region of Siberia. The sample consisted of 279 Yakut people (185 females, 94 males, average age 19.8 ± 2.03 years). The females plasma irisin concentration was 8.33 ± 2.74 mcg/mL and the males was 7.76 ± 1.86 mcg/mL. Comparative analysis of irisin levels with the genotypes of six studied SNP-markers in females revealed a significant association of irisin with rs1800849-UCP3. The TT genotype of rs1800849 was associated with elevated levels of irisin (p = 0.01). It was also found that this TT genotype in females was associated with reduced weight and height (p = 0.03). We searched for natural selection signals for the T-allele rs1800849-UCP3; as a result of which, it was found that this allele has a significantly high frequency of distribution in northern (45%, CI: 0.42–0.484) compared with southern Asian populations (28%, CI: 0.244–0.316) (p = 0.01). The results obtained indicate the probable involvement of irisin and the UCP3 gene in thermoregulation, and the spread of its allelic variants is probably related to adaptation to a cold climate.

Irisin Ameliorates Oxidative Stress-Induced Injury in Pancreatic Beta-Cells by Inhibiting Txnip and Inducing Stat3-Trx2 Pathway Activation

Lipotoxicity can lead to beta-cell dysfunction and apoptosis because it induces oxidative stress. Recent studies have found that Irisin prevents pancreatic beta-cell dysfunction induced by palmitic acid (PA). However, an association between the protection against oxidative stress conferred by Irisin and beta-cell dysfunction has not been fully elucidated. In this study, we observed that Irisin treatment prevented INS-1 cell apoptosis induced by PA treatment and preserved the insulin-secreting function of INS-1 cells in vitro. These effects probably resulted from the Irisin-induced decrease in intracellular ROS levels triggered by PA treatment. In addition, PA treatment induced oxidative stress partially by inhibiting the activation of thioredoxin 2 (Trx2) through its increase of thioredoxin-interacting protein (Txnip) expression. However, Irisin administration blocked the increase in Txnip expression, which reversed the PA-induced inactivation of Trx2. Irisin also increased the nuclear translocation of Stat3, and the inhibition of Stat3 by siRNAs blocked Irisin-induced Trx2 expression, indicating that both Txnip and Stat3 are involved in Irisin-induced activation of Trx2. Furthermore, blockade of Stat3 by siRNAs led to the decreased gene expression of MafA and Ins and to cessation of glucose-induced insulin secretion that had been enhanced by Irisin. In vivo, HFD treatment led to reduced glucose tolerance and an increase in the level of the oxidative marker malondialdehyde (MDA) compared to that in the control group. However, these effects were ameliorated by Irisin injection due to the inhibition of beta-cell apoptosis and the activation of Trx2, probably through Txnip inhibition and Stat3 activation. In conclusion, our results reveal a possible mechanism for Irisin-induced beta-cell protection, which is mediated through Txnip inhibition and activation of the Stat3-Trx2 pathway.

Irisin, a fascinating field in our times

Irisin is a muscle-secreted hormone that is generated by cleavage of membrane protein FNDC-5 (fibronectin type III domain-containing protein 5). Irisin is considered to be a mediator of exercise-induced metabolic improvements, such as browning of white adipose tissue, and is known to alleviate several chronic non-metabolic diseases. Thus, irisin may be an ideal therapeutic target for metabolic and non-metabolic diseases. However, several controversies regarding irisin have hindered its clinical translation. We review the generation, regulation (especially in exercise), and metabolic as well as therapeutic effects of irisin on metabolic and non-metabolic diseases. Furthermore, we discuss controversies regarding irisin and highlight potential future research directions.

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.

Metabolic properties of irisin in health and in diabetes mellitus

Irisin is a polypeptide hormone of muscle tissue (myokine), the synthesis and secretion of which increase against the background of physical exertion, which plays a significant role in the metabolism of fat, muscle and bone tissues. It is known that irisin promotes the transformation of white adipose tissue into brown adipose tissue. It has also been experimentally proven that the introduction of irisin contributed to an increase in bone mass and the prevention of osteoporosis and muscular atrophy. There are works indicating a positive effect of irisin in the functioning of bone, fat and muscle tissues in humans. Diabetes mellitus (DM) is an independent risk factor for osteoporotic fractures and the development of specific diabetic myopathy, at the cellular level similar to the aging of muscle tissue, and type 2 diabetes is also associated with the presence of obesity. Thus, it is of particular interest to study the effect of irisin on the state of bone, muscle and adipose tissues and glucose homeostasis in patients with diabetes. This literature review highlights the biological functions of irisin in healthy people and patients with DM.

Irisin enhances chondrogenic differentiation of human mesenchymal stem cells via Rap1/PI3K/AKT axis

Background

Human mesenchymal stem cells (hMSCs) have been proven to have inherent chondrogenic differentiation potential, which appears to be used in cartilage regeneration. Increasing evidence suggests that irisin enhances osteoblast differentiation of MSCs, but little is known about its potential on chondrogenic differentiation.

Methods

In the study, we investigated the effects of irisin on chondrogenic differentiation of hMSCs using a high-density pellet culture system. The cartilage pellets were evaluated by morphology, and the metabolism of cartilage matrix was detected by qPCR, western blot and immunohistochemistry. Next, RNA-seq was performed to explore the underlying mechanism. Furthermore, using the transduction of plasmid, miRNAs mimics and inhibitor, the activation of Rap1/PI3K/AKT axis, the expression level of SIPA1L2, and the functional verification of miR-125b-5p were detected on day 7 of chondrogenic differentiation of hMSCs.

Results

Compared with the controls, we found that irisin treatment could significantly enhance the chondrogenic differentiation of hMSCs, enlarge the induced-cartilage tissue and up-regulate the expression levels of cartilage markers. RNA-seq indicated that irisin activated the Rap1 and PI3K/AKT signaling pathway, and the lower expression level of SIPA1L2 and the higher expression level of miR-125b-5p were found in irisin-treated group. Further, we found that irisin treatment could up-regulate the expression level of miR-125b-5p, targeting SIPA1L2 and consequently activating the Rap1/PI3K/AKT axis on the process of chondrogenic differentiation of hMSCs.

Conclusions

Collectively, our study reveals that irisin can enhance chondrogenic differentiation of hMSCs via the Rap1/PI3K/AKT pathway, suggesting that irisin possesses prospects in cartilage regeneration.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03092-8.

The mechanism and progress of ferroptosis in pancreatic cancer

Pancreatic cancer is one of the deadliest cancers in the world, causing hundreds of thousands of deaths worldwide annually. Because of late diagnosis, rapid metastasis and drug resistance to chemotherapy, pancreatic cancer has a poor prognosis. Although the treatment of pancreatic cancer has made tremendous progress, the options for effective treatment are still limited, and new treatment methods are in crying needs to improve prognosis in clinic. Ferroptosis is an iron-dependent non-apoptotic cell death mode, which is mediated by lipid peroxidation and iron accumulation. Ferroptosis plays a momentous role in regulating different cancers in recent years, such as breast cancer, hepatocellular carcinoma, lung cancer and pancreatic cancer. In this present review, we elaborate on the regulatory mechanisms and signaling pathways of ferroptosis in pancreatic cancer, with the intention of delivering directions and new ideas for the treatment of pancreatic cancer.