FNDC5/irisin is not only a myokine but also an adipokine

Irisin in thyroid diseases

Irisin, a hormone-like adipo-myokine, has garnered considerable attention in recent years for its potential impact in metabolic diseases. Its physiological effects are similar to those of thyroid hormones, prompting numerous investigations into potential correlations and interactions between irisin and thyroid function through various in vitro and animal experiments. However, existing studies suggest that the relationship between irisin and thyroid diseases is highly complex and multifaceted. In this paper, we have summarized the research results on serum irisin and thyroid function, providing an overview of advancements and constraints in current research on irisin and thyroid hormones. The aim is to offer insights and directions for future clinical trials in this field.

Mechanisms by which obesity regulates inflammation and anti-tumor immunity in cancer

Obesity is associated with an increased risk for 13 different cancers. The increased risk for cancer in obesity is mediated by obesity-associated changes in the immune system. Obesity has distinct effects on different types of inflammation that are tied to tumorigenesis. For example, obesity promotes chronic inflammation in adipose tissue that is tumor-promoting in peripheral tissues. Conversely, obesity inhibits acute inflammation that rejects tumors. Obesity therefore promotes cancer by differentially regulating chronic versus acute inflammation. Given that obesity is chronic, the initial inflammation in adipose tissue will lead to systemic inflammation that could induce compensatory anti-inflammatory reactions in peripheral tissues to suppress chronic inflammation. The overall effect of obesity in peripheral tissues is therefore dependent on the duration and severity of obesity. Adipose tissue is a complex tissue that is composed of many cell types in addition to adipocytes. Further, adipose tissue cellularity is different at different anatomical sites throughout the body. Consequently, the sensitivity of adipose tissue to obesity is dependent on the anatomical location of the adipose depot. For example, obesity induces more inflammation in visceral than subcutaneous adipose tissue. Based on these studies, the mechanisms by which obesity promotes tumorigenesis are multifactorial and immune cell type-specific. The objective of our paper is to discuss the cellular mechanisms by which obesity promotes tumorigenesis by regulating distinct types of inflammation in adipose tissue and the tumor microenvironment.

Irisin's emerging role in Parkinson's disease research: A review from molecular mechanisms to therapeutic prospects

Parkinson's disease (PD), a neurodegenerative disorder characterized by impaired motor function, is typically treated with medications and surgery. However, recent studies have validated physical exercise as an effective adjunct therapy, significantly improving both motor and non-motor symptoms in PD patients. Irisin, a myokine, has garnered increasing attention for its beneficial effects on the nervous system. Research has shown that irisin plays a crucial role in regulating metabolic balance, optimizing autophagy, maintaining mitochondrial quality, alleviating oxidative stress and neuroinflammation, and regulating cell death-all processes intricately linked to the pathogenesis of PD. This review examines the mechanisms through which irisin may counteract PD, provides insights into its biological effects, and considers its potential as a target for therapeutic strategies.

Assessment of brain-derived neurotrophic factor and irisin concentration in children with chronic kidney disease: a pilot study

Patients suffering from chronic kidney disease (CKD) are particularly placed at risk of multiorgan complications. One of them is malnutrition, which adds up to a higher mortality factor among them. This study was designed to determine the usefulness of brain-derived neurotrophic factor (BDNF) and irisin assays in the assessment of CKD development. The study group included 28 children with CKD at stages 2-5 treated conservatively. The outcome of our study revealed decreased serum BDNF and irisin levels in CKD patients, whereas urine concentrations were increased for BDNF and decreased for irisin, comparing to healthy controls. There was a positive correlation between anthropometric measures and urine BDNF concentration, as well as anthropometric measures and both serum and urine irisin levels in the study group, however no dependence of the tested markers on the stage of CKD was observed. In recent years, a role of myokines was described as vital for maintaining metabolic homeostasis therefore we suspect a potential role of these multifaceted markers in detecting malnutrition in CKD children.

Differential mitochondrial adaptation and FNDC5 production in brown and white adipose tissue in response to cold and obesity

OBJECTIVE

Fibronectin type III domain-containing protein 5 (FNDC5) modulates adipocyte metabolism by increasing white and brown adipose tissue (WAT and BAT) browning and activity, respectively. We investigated whether FNDC5 can regulate visceral WAT and BAT adaptive thermogenesis by improving mitochondrial homeostasis in response to cold and obesity.

METHODS

Adipose tissue expression of FNDC5 and factors involved in mitochondrial homeostasis were determined in patients with normal weight and obesity (n = 159) and in rats with diet-induced obesity after 1 week of cold exposure (n = 61). The effect of different FNDC5 concentrations on mitochondrial biogenesis, dynamics, and mitophagy was evaluated in vitro in human adipocytes.

RESULTS

In human visceral adipocytes, FNDC5/irisin triggered mitochondrial biogenesis (TFAM) and fusion (MFN1, MFN2, and OPA1) while inhibiting peripheral fission (DNM1L and FIS1) and mitophagy (PINK1 and PRKN). Circulating and visceral WAT expression of FNDC5 was decreased in patients and experimental animals with obesity, whereas its receptor, integrin αV, was upregulated. Obesity increased mitochondrial fusion while decreasing mitophagy in visceral WAT from patients and rats. By contrast, in rat BAT, an upregulation of Fndc5 and genes involved in mitochondrial biogenesis and fission was observed. Cold exposure promoted mitochondrial biogenesis and healthy peripheral fission while repressing Fndc5 expression and mitophagy in BAT from rats.

CONCLUSIONS

Depot differences in FNDC5 production and mitochondrial adaptations in response to obesity and cold might indicate a self-regulatory mechanism to control thermogenesis in response to energy needs.

Exerkines: Benign adaptation for exercise and benefits for non-alcoholic fatty liver disease

Exercise has multiple beneficial effects on human metabolic health and is regarded as a "polypill" for various diseases. At present, the lack of physical activity usually causes an epidemic of chronic metabolic syndromes, including obesity, cardiovascular diseases, and non-alcoholic fatty liver disease (NAFLD). Remarkably, NAFLD is emerging as a serious public health issue and is associated with the development of cirrhosis and hepatocellular carcinoma. Unfortunately, specific drug therapies for NAFLD and its more severe form, non-alcoholic steatohepatitis (NASH), are currently unavailable. Lifestyle modification is the foundation of treatment recommendations for NAFLD and NASH, especially for exercise. There are under-appreciated organs that crosstalk to the liver during exercise such as muscle-liver crosstalk. Previous studies have reported that certain exerkines, such as FGF21, GDF15, irisin, and adiponectin, are beneficial for liver metabolism and have the potential to be targeted for NAFLD treatment. In addition, some of exerkines can be modified for the new proteins and get enhanced functions, like IL-6/IC7Fc. Another importance of exercise is the physiological adaptation that combats metabolic diseases. Thus, this review aims to summarize the known exerkines and utilize a multi-omics mining tool to identify more exerkines for the future research. Overall, understanding the mechanisms by which exercise-induced exerkines exert their beneficial effects on metabolic health holds promise for the development of novel therapeutic strategies for NAFLD and related diseases.

Irisin Protects Musculoskeletal Homeostasis via a Mitochondrial Quality Control Mechanism

Irisin, a myokine derived from fibronectin type III domain-containing 5 (FNDC5), is increasingly recognized for its protective role in musculoskeletal health through the modulation of mitochondrial quality control. This review synthesizes the current understanding of irisin's impact on mitochondrial biogenesis, dynamics, and autophagy in skeletal muscle, elucidating its capacity to bolster muscle strength, endurance, and resilience against oxidative-stress-induced muscle atrophy. The multifunctional nature of irisin extends to bone metabolism, where it promotes osteoblast proliferation and differentiation, offering a potential intervention for osteoporosis and other musculoskeletal disorders. Mitochondrial quality control is vital for cellular metabolism, particularly in energy-demanding tissues. Irisin's influence on this process is highlighted, suggesting its integral role in maintaining cellular homeostasis. The review also touches upon the regulatory mechanisms of irisin secretion, predominantly induced by exercise, and its systemic effects as an endocrine factor. While the therapeutic potential of irisin is promising, the need for standardized measurement techniques and further elucidation of its mechanisms in humans is acknowledged. The collective findings underscore the burgeoning interest in irisin as a keystone in musculoskeletal health and a candidate for future therapeutic strategies.

Short- and long-term effects of concurrent aerobic and resistance training on circulating irisin levels in overweight or obese individuals: a systematic review and meta-analysis of randomized controlled trials

Background

Concurrent training (CT) is emerging as a practical and effective approach to enhance body composition, cardiovascular function, and muscle mass, thereby elevating overall individual health. This study aims to systematically investigate the effects of short- and long-term concurrent aerobic and resistance training on circulating irisin levels in overweight or obese individuals.

Methodology

The electronic databases, including China National Knowledge Infrastructure, PubMed, Embase, Wan Fang Database, and Web of Science, were systematically searched for articles on "concurrent training" and "irisin" published from their inception to 30 November 2023. The pooled effect size was determined using standardized mean difference (SMD) and corresponding 95% confidence intervals (CIs). The study protocol received registration with the International Prospective Register of Systematic Reviews (CRD42023494163).

Results

All nine studies, encompassing a total of 264 participants, were randomized controlled trials and met the eligibility criteria. Results indicate that short- and long-term concurrent training moderately increased circulating irisin levels compared to the control group (SMD = 0.56, 95% CI [0.33-0.80], p = 0.00; I 2 = 36.6%, heterogeneity p = 0.106). Subgroup analyses revealed that both equal to or less than 10 weeks (SMD = 0.78, 95% CI [0.18-1.37], p = 0.01; I 2 = 62.3%, heterogeneity p = 0.03) and more than 10 weeks (SMD = 0.45, 95% CI [0.14-0.76], p = 0.00; I 2 = 0%, heterogeneity p = 0.54) of concurrent training significantly increased circulating irisin levels in overweight or obese individuals. There were no significant between-group differences (I 2 = 0%, p = 0.34). Additionally, concurrent training significantly increased irisin levels in overweight or obese participants (SMD = 1.06, 95% CI [0.34-1.78], p = 0.00; I 2 = 50.6%, heterogeneity p = 0.13) and in type 2 diabetes patients (SMD = 0.70, 95% CI [0.30-1.10], p = 0.00; I 2 = 0%, heterogeneity p = 0.99). However, no significant effect was observed in patients with metabolic syndrome (SMD = 0.21, 95% CI [-0.25-0.68], p = 0.37; I 2 = 38.7%, heterogeneity p = 0.18). There were significant between-group differences (I 2 = 53.9%, p = 0.11). Lastly, concurrent training significantly increased circulating irisin levels in overweight or obese individuals aged 45-60 years (SMD = 0.56, 95% CI [0.25-0.86], p = 0.00; I 2 = 6.5%, heterogeneity p = 0.38), and a significant increase in irisin levels was observed 12 h post-intervention (SMD = 0.70, 95% CI [0.35-1.05], p = 0.00; I 2 = 0%, heterogeneity p = 0.74). However, none of the above categorical variables showed significant between-group differences.

Conclusions

Short- and long-term concurrent training can effectively improve circulating irisin levels in overweight or obese individuals. However, the effects of short- and long-term concurrent training should consider the participants' health status, age, and the timing of post-exercise measurements to maximize health benefits.

Ketogenic diet with aerobic exercise can induce fat browning: potential roles of β-hydroxybutyrate

Introduction

Despite evidence suggesting that metabolic intermediates like β-HB influence white adipose tissue (WAT) metabolism, the precise molecular mechanisms remain unclear. The aim of this study was to investigate the impact of beta-hydroxybutyrate (β-HB) on the fat browning program and to explore the underlying molecular mechanisms using both in vitro and in vivo models. We assessed the effects of β-HB on fat browning in adipocytes using 3T3-L1 cells and rat models.

Methods

We evaluated the effects of β-HB on fat browning, thermogenesis, lipid accumulation, adipokine expression, and mitochondrial biogenesis by treating mature 3T3-L1 adipocytes with sodium β-HB for 24 h or by continuously exposing preadipocytes to β-HB during the 8-day differentiation process. Male Sprague Dawley rats were divided into control, exercise only (EX), ketogenic diet only (KD), and combined exercise and ketogenic diet (KE) groups for an 8-week intervention involving diet and/or exercise. After intervention, we evaluated WAT histology, plasma lipids and adipokines, and the expression of markers related to fat browning, thermogenesis and mitochondrial biogenesis in WAT of rats.

Results

In our adipocyte culture experiments, β-HB reduced intracellular lipid accumulation by enhancing lipolysis and stimulated the expression of thermogenic and fat browning genes like uncoupling protein 1 (UCP1), PR domain containing 16 (PRDM16), and adipokines such as fibroblast growth factor 21 (FGF21) and Fibronectin type III domain-containing protein 5 (FDNC5). Additionally, β-HB activated the AMPK-SIRT1-PGC-1α pathway, with UCP1 and PRDM16 upregulation mediated by β-HB intracellular action and SIRT1 activity. In animal experiments, KE group raised β-HB levels, decreasing body weight and blood lipids. KD with EX promoted WAT browning possibly via AMPK-SIRT1-PGC-1α, augmenting PRDM16, UCP1, FGF21, and FNDC5 expression.

Conclusion

β-HB induction via KD and/or EX shows potential in promoting WAT browning by activating mitochondrial biogenesis, lipolysis, and thermogenesis, suggesting that dietary and physical intervention inducing β-HB may benefit metabolic health.

The cerebroprotection and prospects of FNDC5/irisin in stroke

Stroke, the leading cause of disability and cognitive impairment, is also the second leading cause of death worldwide. The drugs with multi-targeted brain cytoprotective effects are increasingly being advocated for the treatment of stroke. Irisin, a newly discovered myokine produced by cleavage of fibronectin type III domain 5, has been shown to regulate glucose metabolism, mitochondrial energy, and fat browning. A large amount of evidence indicated that irisin could exert anti-inflammatory, anti-apoptotic, and antioxidant properties in a variety of diseases such as myocardial infarction, inflammatory bowel disease, lung injury, and kidney or liver disease. Studies have found that irisin is widely distributed in multiple brain regions and also plays an important regulatory role in the central nervous system. The most common cause of a stroke is a sudden blockage of an artery (ischemic stroke), and in some circumstances, a blood vessel rupture can also result in a stroke (hemorrhagic stroke). After a stroke, complicated pathophysiological processes lead to serious brain injury and neurological dysfunction. According to recent investigations, irisin may protect elements of the neurovascular unit by acting on multiple pathological processes in stroke. This review aims to outline the currently recognized effects of irisin on stroke and propose possible directions for future research.

Weighing in on the role of brown adipose tissue for treatment of obesity

Brown adipose tissue (BAT) activation is an emerging target for obesity treatments due to its thermogenic properties stemming from its ability to shuttle energy through uncoupling protein 1 (Ucp1). Recent rodent studies show how BAT and white adipose tissue (WAT) activity can be modulated to increase the expression of thermogenic proteins. Consequently, these alterations enable organisms to endure cold-temperatures and elevate energy expenditure, thereby promoting weight loss. In humans, BAT is less abundant in obese subjects and impacts of thermogenesis are less pronounced, bringing into question whether energy expending properties of BAT seen in rodents can be translated to human models. Our review will discuss pharmacological, hormonal, bioactive, sex-specific and environmental activators and inhibitors of BAT to determine the potential for BAT to act as a therapeutic strategy. We aim to address the feasibility of utilizing BAT modulators for weight reduction in obese individuals, as recent studies suggest that BAT's contributions to energy expenditure along with Ucp1-dependent and -independent pathways may or may not rectify energy imbalance characteristic of obesity.

Associations between total, free and bioavailable 25-hydroxyvitamin D forms with adiponectin and irisin in maternal-neonatal pairs at birth from Greece

Background

Apart from the well-established skeletal effects, vitamin D has been explored as a secretagogue influencing various adipokines, including adiponectin and irisin. Recent evidence suggests that specific forms of 25-Hydroxyvitamin D (25(OHD), such as free and bioavailable 25(OH)D, may provide more accurate measurements of vitamin D status. The relationship between vitamin D status and serum irisin and adiponectin concentrations remains largely unexplored, particularly during pregnancy.

Methods

We analyzed data from 67 healthy maternal-neonatal pairs from Northern Greece at birth. Biochemical and hormonal tests were conducted on each maternal-neonatal pair. The vitamin D forms were estimated using validated mathematical models. Subsequently, regression analyses were conducted to determine the association between the vitamin D forms and adipokine levels.

Results

Bioavailable maternal 25(OH)D was inversely associated with neonatal irisin concentrations [β=-73.46 (-140.573 to -6.341), p=0.034]. No other associations were observed between maternal vitamin D status and neonatal adipokine concentrations.

Conclusion

In conclusion, maternal bioavailable vitamin D concentrations are inversely associated with neonatal serum irisin concentrations, warranting further studies to evaluate the underlying mechanisms for this finding.

Liraglutide promotes UCP1 expression and lipolysis of adipocytes by promoting the secretion of irisin from skeletal muscle cells

Although Liraglutide (Lira) increases serum irisin levels in type 2 diabetes mellitus (T2DM), it is unclear whether it induces expression of uncoupling protein 1 (UCP1) of adipocytes via promoting irisin secretion from skeletal muscle. Male T2DM rats were treated with 0.4 mg/kg/d Lira twice a day for 8 weeks, and the protein expression of phosphorylated AMP kinase (p-AMPK), phosphorylated acetyl-CoA carboxylase 1 (p-ACC1) and UCP1 in white adipose tissues were detected. Differentiated C2C12 cells were treated with palmitic acid (PA) and Lira to detect the secretion of irisin. Differentiated 3T3-L1 cells were treated with irisin, supernatant from Lira-treated C2C12 cells, Compound C or siAMPKα1, the triglyceride (TG) content and the related gene expression were measured. The transcriptome in irisin-treated differentiated 3T3-L1 cells was analyzed. Lira elevated serum irisin levels, decreased the adipocyte size and increased the protein expression of UCP1, p-AMPK and p-ACC1 in WAT. Moreover, it promoted the expression of PGC1α and FNDC5, the secretion of irisin in PA-treated differentiated C2C12 cells. The irisin and supernatant decreased TG synthesis and promoted the expression of browning- and lipolysis-related genes in differentiated 3T3-L1 cells. While Compound C and siAMPKα1 blocked AMPK activities and expression, irisin partly reversed the pathway. Finally, the transcriptome analysis indicated that differently expressed genes are mainly involved in browning and lipid metabolism. Overall, our findings showed that Lira modulated muscle-to-adipose signaling pathways in diabetes via irisin-mediated AMPKα/ACC1/UCP1/PPARα pathway. Our results suggest a new mechanism for the treatment of T2DM by Lira.

Alpha-Lipoic Acid Induces Adipose Tissue Browning through AMP-Activated Protein Kinase Signaling in Vivo and in Vitro

Background

AMP-activated protein kinase (AMPK) is a key enzyme for cellular energy homeostasis and improves metabolic disorders. Brown and beige adipose tissues exert thermogenesis capacities to dissipate energy in the form of heat. Here, we investigated the beneficial effects of the antioxidant alpha-lipoic acid (ALA) in menopausal obesity and the underlying mechanisms.

Methods

Female Wistar rats (8 weeks old) were subjected to bilateral ovariectomy (Ovx) and divided into four groups: Sham (n=8), Ovx (n=11), Ovx+ALA2 (n=10), and Ovx+ALA3 (n=6) (ALA 200 and 300 mg/kg/day, respectively; gavage) for 8 weeks. 3T3-L1 cells were used for in vitro study.

Results

Rats receiving ALA2 and ALA3 treatment showed significantly lower levels of body weight and white adipose tissue (WAT) mass than those of the Ovx group. ALA improved plasma lipid profiles including triglycerides, total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol. Hematoxylin & eosin staining of inguinal WAT showed that ALA treatment reduced Ovx-induced adipocyte size and enhanced uncoupling protein 1 (UCP1) expression. Moreover, plasma levels of irisin were markedly increased in ALA-treated Ovx rats. Protein expression of brown fat-specific markers including UCP1, PRDM16, and CIDEA was downregulated by Ovx but markedly increased by ALA. Phosphorylation of AMPK, its downstream acetyl-CoA carboxylase, and its upstream LKB1 were all significantly increased by ALA treatment. In 3T3-L1 cells, administration of ALA (100 and 250 μM) reduced lipid accumulation and enhanced oxygen consumption and UCP1 protein expression, while inhibition of AMPK by dorsomorphin (5 μM) significantly reversed these effects.

Conclusion

ALA improves estrogen deficiency-induced obesity via browning of WAT through AMPK signaling.

Effects of aquatic versus land-based exercise on irisin and fibroblast growth factor 21 expression and triiodothyronine and free fatty acid levels in elderly women

BACKGROUND

This study investigated the impacts of exercise on irisin and fibroblast growth factor 21 (FGF-21) expression, as well as triiodothyronine (T3 ) and free fatty acid (FFA) levels in elderly women.

METHODS

Thirty women aged 65 to 70 years (10 per group) were randomly assigned to aquatic exercise, land exercise, and control groups. The aquatic and land groups engaged in 3 exercise sessions per week (60 min/session) for 16 weeks. The intensity was progressively increased every 4 weeks.

RESULTS

Irisin and FGF-21 levels significantly increased in the aquatic exercise group. In the posttest, the aquatic exercise group had the highest irisin levels. Significant findings were observed for irisin and FGF-21 for the main effect between aquatic and band exercise groups (p<0.05 for both), the main effect between measurement times (p<0.01 and p<0.001, respectively), and the interaction effect (p<0.05 and p<0.001, respectively). The irisin level was significantly higher in the aquatic than in the land group 30 minutes after the last session (p<0.05). In both exercise groups, T3 levels were significantly higher 30 minutes after the final session (p<0.05) than before the program. The FFA level was significantly higher in the aquatic exercise group than the others. In the aquatic group, FFA levels were significantly higher 30 minutes after both the first (p<0.01) and the last (p<0.001) session compared to pre-program values.

CONCLUSION

Differences in exercise type and environment can promote fat metabolism by stimulating hormonal changes that induce brown fat activity and browning.

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

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

Molecular insights of exercise therapy in disease prevention and treatment

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

Irisin influences the in vitro differentiation of human mesenchymal stromal cells, promoting a tendency toward beiging adipogenesis

Mammals exhibit two distinct types of adipose depots: white adipose tissue (WAT) and brown adipose tissue (BAT). While WAT primarily functions as a site for energy storage, BAT serves as a thermogenic tissue that utilizes energy and glucose consumption to regulate core body temperature. Under specific stimuli such as exercise, cold exposure, and drug treatment, white adipocytes possess a remarkable ability to undergo transdifferentiation into brown-like cells known as beige adipocytes. This transformation process, known as the "browning of WAT," leads to the acquisition of new morphological and physiological characteristics by white adipocytes. We investigated the potential role of Irisin, a 12 kDa myokine that is secreted in mice and humans by skeletal muscle after physical activity, in inducing the browning process in mesenchymal stromal cells (MSCs). A subset of the MSCs possesses the remarkable capability to differentiate into different cell types such as adipocytes, osteocytes, and chondrocytes. Consequently, comprehending the effects of Irisin on MSC biology becomes a crucial factor in investigating antiobesity medications. In our study, the primary objective is to evaluate the impact of Irisin on various cell types engaged in distinct stages of the differentiation process, including stem cells, committed precursors, and preadipocytes. By analyzing the effects of Irisin on these specific cell populations, our aim is to gain a comprehensive understanding of its influence throughout the entire differentiation process, rather than solely concentrating on the final differentiated cells. This approach enables us to obtain insights into the broader effects of Irisin on the cellular dynamics and mechanisms involved in adipogenesis.

Whole-body deletion of Endospanin 1 protects from obesity-associated deleterious metabolic alterations

The importance of the proper localization of most receptors at the cell surface is often underestimated, although this feature is essential for optimal receptor response. Endospanin 1 (Endo1) (also known as OBRGRP or LEPROT) is a protein generated from the same gene as the human leptin receptor and regulates the trafficking of proteins to the surface, including the leptin receptor. The systemic role of Endo1 on whole-body metabolism has not been studied so far. Here, we report that general Endo1-KO mice fed a high-fat diet develop metabolically healthy obesity with lipid repartitioning in organs and preferential accumulation of fat in adipose tissue, limited systematic inflammation, and better controlled glucose homeostasis. Mechanistically, Endo1 interacts with the lipid translocase CD36, thus regulating its surface abundance and lipid uptake in adipocytes. In humans, the level of Endo1 transcripts is increased in the adipose tissue of patients with obesity, but low levels rather correlate with a profile of metabolically healthy obesity. We suggest here that Endo1, most likely by controlling CD36 cell surface abundance and lipid uptake in adipocytes, dissociates obesity from diabetes and that its absence participates in metabolically healthy obesity.

Exercise in Diabetic Nephropathy: Protective Effects and Molecular Mechanism

Diabetic nephropathy (DN) is a serious complication of diabetes, and its progression is influenced by factors like oxidative stress, inflammation, cell death, and fibrosis. Compared to drug treatment, exercise offers a cost-effective and low-risk approach to slowing down DN progression. Through multiple ways and mechanisms, exercise helps to control blood sugar and blood pressure and reduce serum creatinine and albuminuria, thereby alleviating kidney damage. This review explores the beneficial effects of exercise on DN improvement and highlights its potential mechanisms for ameliorating DN. In-depth understanding of the role and mechanism of exercise in improving DN would pave the way for formulating safe and effective exercise programs for the treatment and prevention of DN.

Differences in the Impact of Various Types of Exercise on Irisin Levels: A Systematic Review and Meta-Analysis

Background

Irisin, a myokine that is responsive to exercise, induces significant changes in subcutaneous adipose tissue. By promoting the browning of white fat tissue, it enhances energy expenditure, thereby addressing overweight and obesity. This systematic review and meta-analysis aimed to compare the effects of different types of physical exercises on irisin levels in overweight and obese adults.

Methods

Specifically, the review focused on studies involving obese or overweight individuals who participated in exercise training for a minimum of 8 weeks, with measured and reported changes in serum irisin levels compared to a control group. Data were collected from four databases (Google Scholar, ISI Web of Science Core Collection, PubMed, and Scopus). The risk of bias was assessed using the Begg and Egger tests, and the results were synthesized.

Results

Initial searches identified 560 titles, out of which only seven met the criteria for inclusion in the systematic review. Statistical analysis demonstrated a significant increase in serum irisin concentration (SMD = 0.957, P = 0.005) among obese and overweight individuals who engaged in exercise, compared to the passive control group. High-intensity interval training (HIIT) (SMD = 1.229, P < 0.001) had a more pronounced effect on increasing serum irisin levels than other exercise protocols. Furthermore, the effectiveness of exercise varied based on the participants' weight status (significant changes for overweight individuals; P < 0.001 and insignificant changes for obese individuals; P = 0.1), age (significant changes for those under 40 years old; P < 0.001 and insignificant changes for those over 40 years old; P = 0.322), and gender (significant changes for men; P < 0.001 and insignificant changes for women; P = 0.285).

Conclusions

Consequently, exercise can elevate serum irisin levels, leading to alterations in adipose tissue phenotype and thermogenesis, ultimately contributing to weight reduction in obese and overweight individuals.

Myokines Produced by Cultured Bovine Satellite Cells Harvested from 3- and 11-Month-Old Angus Steers

The myokines interleukin 6 (IL-6), interleukin 15 (IL-15), myonectin (CTRP15), fibronectin type III domain containing protein 5/irisin (FNDC5), and brain-derived neurotrophic factor (BDNF) are associated with skeletal muscle cell proliferation, differentiation, and muscle hypertrophy in biomedical model species. This study evaluated whether these myokines are produced by cultured bovine satellite cells (BSCs) harvested from 3- and 11-month-old commercial black Angus steers and if the expression and secretion of these targets change across 0, 12, 24, and 48 h in vitro. IL-6, IL-15, FNDC5, and BDNF expression were greater (p ≤ 0.05) in the differentiated vs. undifferentiated BSCs at 0, 12, 24, and 48 h. CTRP15 expression was greater (p ≤ 0.03) in the undifferentiated vs. differentiated BSCs at 24 and 48 h. IL-6 and CTRP15 protein from culture media were greater (p ≤ 0.04) in undifferentiated vs. differentiated BSCs at 0, 12, 24, and 48 h. BDNF protein was greater in the media of differentiated vs. undifferentiated BSCs at 0, 12, 24, and 48 h. IL-6, 1L-15, FNDC5, and BDNF are expressed in association with BSC differentiation, and CTRP15 appears to be expressed in association with BSC proliferation. This study also confirms IL-6, IL-15, CTRP15, and BDNF proteins present in media collected from primary cultures of BSCs.

Examining the effects of coronary artery disease- and mitochondrial biogenesis-related genes' and microRNAs' expression levels on metabolic disorders in epicardial adipose tissue

BACKGROUND AND AIMS

Epicardial adipose tissue (EAT) surrounds the heart and coronary arteries and is important for comprehending the pathogenesis of coronary artery disease (CAD). We aimed to evaluate the expressions of mitochondrial biogenesis- and CAD-related genes and miRNAs in EAT by comparing them to visceral adipose tissue (VAT) in CAD, diabetes, and obesity subgroups.

METHODS

In this study, a total of 93 individuals were recruited, and EAT samples (63 CAD; 30 non-CAD) and VAT samples from 65 individuals (46 CAD; 19 non-CAD) were collected. For further analysis, the study population was divided according to obesity and diabetes status. PRKAA1, PPARGC1A, SIRT1, RELA, TNFA, and miR-155-5p, let-7g-5p, miR-1247-5p, miR-326 expression levels were examined.

RESULTS

PRKAA1 and let-7g-5p were differentially expressed in EAT compared to VAT. TNFA expression was upregulated significantly in both tissues of CAD patients. In EAT, PRKAA1, PPARGC1A, and SIRT1 were downregulated with diabetes. Moreover, PPARGC1A expression is decreased under the condition of obesity in both tissues. EAT expressions of miR-1247-5p and miR-326 were downregulated with obesity, while miR-155-5p is decreased only in the VAT of obese. Also, miRNAs and genes were correlated with biochemical parameters and each other in EAT and VAT (p < 0.050).

CONCLUSIONS

The findings demonstrating distinct let-7g-5p and AMPKα1 mRNA expression between EAT and VAT underscores the importance of tissue-specific regulation in different clinical outcomes. In addition, the differential expressions of investigated genes and miRNAs highlight their responsiveness to obesity, DM, and CAD in adipose tissues.

The Role of FNDC5/Irisin in Cardiovascular Disease

Disorders of cardiomyocyte metabolism play a crucial role in many cardiovascular diseases, such as myocardial infarction, heart failure and ischemia-reperfusion injury. In myocardial infarction, cardiomyocyte metabolism is regulated by mitochondrial changes and biogenesis, which allows energy homeostasis. There are many proteins in cells that regulate and control metabolic processes. One of them is irisin (Ir), which is released from the transmembrane protein FNDC5. Initial studies indicated that Ir is a myokine secreted mainly by skeletal muscles. Further studies showed that Ir was also present in various tissues. However, its highest levels were observed in cardiomyocytes. Ir is responsible for many processes, including the conversion of white adipose tissue (WAT) to brown adipose tissue (BAT) by increasing the expression of thermogenin (UCP1). In addition, Ir affects mitochondrial biogenesis. Therefore, the levels of FNDC5/Ir in the blood and myocardium may be important in cardiovascular disease. This review discusses the current knowledge about the role of FNDC5/Ir in cardiovascular disease.

The role of irisin in kidney diseases

Irisin is a hormone that is produced mainly by skeletal muscles in response to exercise. It has been found to have a close correlation with obesity and diabetes mellitus for its energy expenditure and metabolic properties. Recent research has revealed that irisin also possesses anti-inflammatory, anti-oxidative and anti-apoptotic properties, which make it associated with major chronic diseases, such as chronic kidney disease (CKD), liver diseases, osteoporosis, atherosclerosis and Alzheimer s disease. The identification of irisin has not only opened up new possibilities for monitoring metabolic and non-metabolic diseases but also presents a promising therapeutic target due to its multiple biological functions. Studies have shown that circulating irisin levels are lower in CKD patients than in non-CKD patients and decrease with increasing CKD stage. Furthermore, irisin also plays a role in many CKD-related complications like protein energy wasting (PEW), cardiovascular disease (CVD) and chronic kidney disease-mineral and bone disorder (CKD-MBD). In this review, we present the current knowledge on the role of irisin in kidney diseases and their complications.

The association of serum irisin with anthropometric, metabolic, and bone parameters in obese children and adolescents

Background

Irisin is an adipomyokine secreted by muscle and adipose cells, and it plays a role in glucose, fat, and bone metabolism. This study aimed to determine the correlation of serum irisin levels with anthropometric, metabolic, and bone parameters in obese children and adolescents.

Methods

This single-center study included 103 Korean children and adolescents: 54 (52.4%) obese participants with a body mass index (BMI) ≥95th percentile and 49 (47.6%) healthy controls with BMI within the 15th to 85th percentile. Various parameters were measured, including fasting blood glucose, fasting insulin, homeostasis model assessment of insulin resistance (HOMA-IR), triglyceride and glucose (TyG) index, lipid profile, alkaline phosphatase (ALP), osteocalcin, and 25(OH)-Vitamin D levels. Bone mineral density (BMD) was measured using dual-energy X-ray absorptiometry (DEXA) in 33 healthy subjects.

Results

Serum irisin was significantly higher in the obese group than in the control group (mean 18.1 ± 3.5 vs. 16.2 ± 2.0 ng/mL; p = 0.001). Serum irisin level was positively correlated with chronological age (r = 0.28; p = 0.004), height SDS (r = 0.24; p = 0.02), BMI SDS (r = 0.37; p < 0. 001), fasting glucose (r = 0.27; p = 0.007), fasting insulin (r = 0.23; p = 0.03), HOMA-IR (r = 0.21; p = 0.04), osteocalcin (r = 0.27; p = 0.006) and negatively correlated with HDL cholesterol (r = -0.29; p = 0.005). All these correlations were evident in obese subjects but not in healthy subjects. ALP and 25(OH)-Vitamin D were unrelated to irisin levels. Among 33 healthy subjects, total body-less head (TBLH) BMD Z-score was positively correlated with serum irisin (r = 0.39; p = 0.03), osteocalcin (r = 0.40; p = 0.02), fasting insulin (r = 0.39; p = 0.04), and HOMA-IR (r = 0.38; p = 0.047).

Conclusion

This study demonstrated an association between irisin levels and glucose, lipid, and bone parameters in children and adolescents. Our findings suggest that irisin has a potential role in metabolic disorders and bone health in obese children and adolescents.

Cardioprotective Effects of Exercise: The Role of Irisin and Exosome

Exercise is an effective measure for preventing and treating cardiovascular diseases, although the exact molecular mechanism remains unknown. Previous studies have shown that both irisin and exosomes can improve the course of cardiovascular disease independently. Therefore, it is speculated that the cardiovascular protective effect of exercise is also related to its ability to regulate the concentrations of irisin and exosomes in the circulatory system. In this review, the potential synergistic interactions between irisin and exosomes are examined, as well as the underlying mechanisms including the AMPK/PI3K/AKT pathway, the TGFβ1/Smad2/3 pathway, the PI3K/AKT/VEGF pathway, and the PTEN/PINK1/Parkin pathway are examined. This paper provides evidence to propose that exercise promotes the release of exosomes enriched with irisin, miR-486-5p and miR-342-5p from skeletal muscles, which results in the activation protective networks in the cardiovascular system. Moreover, the potential synergistic effect in exosomal cargo can provide new ideas for clinical research of exercise mimics.

Irisin/BDNF signaling in the muscle-brain axis and circadian system: A review

In mammals, the timing of physiological, biochemical and behavioral processes over a 24-h period is controlled by circadian rhythms. To entrain the master clock located in the suprachiasmatic nucleus of the hypothalamus to a precise 24-h rhythm, environmental zeitgebers are used by the circadian system. This is done primarily by signals from the retina via the retinohypothalamic tract, but other cues like exercise, feeding, temperature, anxiety, and social events have also been shown to act as non-photic zeitgebers. The recently identified myokine irisin is proposed to serve as an entraining non-photic signal of exercise. Irisin is a product of cleavage and modification from its precursor membrane fibronectin type Ⅲ domain-containing protein 5 (FNDC5) in response to exercise. Apart from well-known peripheral effects, such as inducing the "browning" of white adipocytes, irisin can penetrate the blood-brain barrier and display the effects on the brain. Experimental data suggest that FNDC5/irisin mediates the positive effects of physical activity on brain functions. In several brain areas, irisin induces the production of brain-derived neurotrophic factor (BDNF). In the master clock, a significant role in gating photic stimuli in the retinohypothalamic synapse for BDNF is suggested. However, the brain receptor for irisin remains unknown. In the current review, the interactions of physical activity and the irisin/BDNF axis with the circadian system are reconceptualized.

The Role of Irisin throughout Women's Life Span

Since its discovery, much attention has been drawn to irisin's potential role in metabolic and reproductive diseases. This narrative review summarizes and updates the possible role played by this fascinating molecule in different physiological (puberty and menopause) and pathological (polycystic ovary syndrome (PCOS), functional hypothalamic amenorrhea (FHA), endometriosis, and gestational diabetes) conditions that can affect women throughout their entire lives. Irisin appears to be an important factor for the hypothalamic-pituitary-gonadal axis activation, and appears to play a role in the timing of puberty onset. Serum irisin levels have been proposed as a biomarker for predicting the future development of gestational diabetes (GDM). Its role in PCOS is still controversial, although an "irisin resistance" mechanism has been hypothesized. In addition to its impact on metabolism, irisin also appears to influence bone health. Irisin levels are inversely correlated with the prevalence of fractures in postmenopausal women. Similar mechanisms have also been postulated in young women with FHA. In clinical settings, further controlled, prospective and randomized clinical trials are needed to investigate the casual relationship between irisin levels and the conditions described and, in turn, to establish the role of irisin as a prognostic/diagnostic biomarker or a therapeutic target.

Inhibition of integrin alpha v/beta 5 mitigates the protective effect induced by irisin in hemorrhage

INTRODUCTION

Irisin plays an important role in regulating tissue stress, cardiac function, and inflammation. Integrin αvβ5 was recently identified as a receptor for irisin to elicit its physiologic function. It remains unknown whether integrin αvβ5 is required for irisin's function in modulating the physiologic response to hemorrhage. The objective of this study is to examine if integrin αvβ5 contributes to the effects of irisin during the hemorrhagic response.

METHODS

Hemorrhage was induced in mice by achieving a mean arterial blood pressure of 35-45 mmHg for one hour, followed by two hours of resuscitation. Irisin (0.5  μg/kg) was administrated to assess its pharmacologic effects in hemorrhage. Cilengitide, a cyclic Arg-Gly-Asp peptide (cRGDyK) which is an inhibitor of integrin αvβ5, or control RGDS (1 mg/kg) was administered with irisin. In another cohort of mice, the irisin-induced protective effect was examined after knocking down integrin β5 with nanoparticle delivery of integrin β5 sgRNA using CRSIPR/Cas-9 gene editing. Cardiac function and hemodynamics were measured using echocardiography and femoral artery catheterization, respectively. Systemic cytokine releases were measured using Enzyme-linked immunosorbent assay (ELISA). Histological analyses were used to determine tissue damage in myocardium, skeletal muscles, and lung tissues. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) was carried out to assess apoptosis in tissues.

RESULTS

Hemorrhage induced reduction of integrin αvβ5 in skeletal muscles and repressed recovery of cardiac performance and hemodynamics. Irisin treatment led to significantly improved cardiac function, which was abrogated by treatment with Cilengitide or knockdown of integrin β5. Furthermore, irisin resulted in a marked suppression of tumor necrosis factor-α (TNF-α) and interleukin-1 (IL-1), muscle edema, and inflammatory cells infiltration in myocardium and skeletal muscles, which was attenuated by Cilengitide or knockdown of integrin β5. Irisin-induced reduction of apoptosis in the myocardium, skeletal muscles, and lung, which were attenuated by either the inhibition of integrin αvβ5, or knockdown of integrin β5.

CONCLUSION

Integrin αvβ5 plays an important role for irisin in modulating the protective effect during hemorrhage.

Childhood Obesity, Diabetes. and Cardiovascular Disease Risk

This mini-review aims to briefly summarize the pathophysiology of childhood obesity, type 2 diabetes mellitus (T2DM), and cardiovascular disease (CVD) risk in children and adolescents. Recent data on efficacy of lifestyle interventions, medications, and metabolic surgery for obesity, T2DM, and CVD risk factors are also reviewed. We conducted a PubMed search of English-language original and review articles relevant to childhood obesity, T2DM, and CVD risk factors, and biomarkers in children with an emphasis on recent publications. Childhood obesity arises from an intricate interaction between genetic, physiologic, environmental, and socioeconomic factors. The rise in the prevalence of childhood obesity is associated with the development of comorbidities including T2DM and CVD at an early age. A multipronged approach is central to the detection, monitoring, and management of childhood obesity and associated adverse metabolic consequences.

RS3480 Polymorphism of FNDC5/Irisin Is Associated with Type 2 Diabetes Mellitus in Maya-Mestizo Women

Objective: To investigate the possible association between rs3480 and rs16835198 of the fibronectin type III domain containing 5 (FNDC5)/Irisin and their haplotypes with the presence of type 2 diabetes mellitus (T2DM) in Maya-Mestizo women. Methods: We studied 547 postmenopausal women of Maya-Mestizo origin. The diagnosis of T2DM was based on the criteria of the American Diabetes Association. DNA was obtained from blood leukocytes. rs3480 and rs16835198 of FNDC5/Irisin were studied using real-time polymerase chain reaction allelic discrimination. Deviations from Hardy-Weinberg equilibrium and alleles differences, as well as genotype frequencies between groups, were assessed by χ2 tests. Using logistic regression analysis, the odds ratio and 95% confidence intervals were calculated to estimate the association between both polymorphisms of FNDC5/Irisin and the presence of T2DM. Pairwise linkage disequilibrium between polymorphisms was calculated by direct correlation r2, and haplotype analysis was conducted. Results: We found that the G-allele of rs3480, as well as under a dominant model, this polymorphism was significantly associated with T2DM (P = 0.028 and P = 0.003, respectively). Besides, one haplotype was associated with T2DM (P = 0.035). Conclusions: Our results suggest that the FNDC5/Irisin rs3480, and one haplotype formed by rs3480 and rs16835198 were associated with the risk of presenting T2DM in Maya-Mestizo women.

Cytokines and exosomal miRNAs in skeletal muscle-adipose crosstalk

Skeletal muscle and adipose tissues (ATs) are secretory organs that release secretory factors including cytokines and exosomes. These factors mediate muscle-adipose crosstalk to regulate systemic metabolism via paracrine and endocrine pathways. Myokines and adipokines are cytokines secreted by skeletal muscle and ATs, respectively. Exosomes loaded with nucleic acids, proteins, lipid droplets, and organelles can fuse with the cytoplasm of target cells to perform regulatory functions. A major regulatory component of exosomes is miRNA. In addition, numerous novel myokines and adipokines have been identified through technological innovations. These discoveries have identified new biomarkers and sparked new insights into the molecular regulation of skeletal muscle growth and adipose deposition. The knowledge may contribute to potential diagnostic and therapeutic targets in metabolic disease.

The Effect of Bariatric Surgery on Irisin Level: a Systematic Review and Meta-analysis

This systematic analysis and meta-analysis aimed to assess changes in the plasma levels of irisin after bariatric surgery. Search strategy, study screening, and data gathering were all conducted using a checklist and the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA). Two researchers independently extracted the data, and a third person was included to resolve disagreements. The results illustrated no statistical difference between before and after surgery irisin plasma levels (P = 0.216, 95% CI = -1.812-0.410, SMD = -0.701, I-squared = 94.9%). BMI exhibited a meaningful decline after surgery compared to preoperative values (SMD = -3.09, 95% CI = -4.59--1.59, I-squared = 95.5%, P<0.05). According to our analysis, it can be concluded that irisin plasma levels are not significantly influenced by bariatric surgery.

Irisin deficiency exacerbates diet-induced insulin resistance and cardiac dysfunction in type II diabetes in mice

Irisin is involved in the regulation of a variety of physiological conditions, metabolism, and survival. We and others have demonstrated that irisin contributes critically to modulation of insulin resistance and the improvement of cardiac function. However, whether the deletion of irisin will regulate cardiac function and insulin sensitivity in type II diabetes remains unclear. We utilized the CRISPR/Cas-9 genome-editing system to delete irisin globally in mice and high-fat diet (HFD)-induced type II diabetes model. We found that irisin deficiency did not result in developmental abnormality during the adult stage, which illustrates normal cardiac function and insulin sensitivity assessed by glucose tolerance test in the absence of stress. The ultrastructural analysis of the transmission electronic microscope (TEM) indicated that deletion of irisin did not change the morphology of mitochondria in myocardium. Gene expression profiling showed that several key signaling pathways related to integrin signaling, extracellular matrix, and insulin-like growth factors signaling were coordinately downregulated by deletion of irisin. However, when mice were fed a high-fat diet and chow food for 16 wk, ablation of irisin in mice exposed to HFD resulted in much more severe insulin resistance, metabolic derangements, profound cardiac dysfunction, and hypertrophic response and remodeling as compared with wild-type control mice. Taken together, our results indicate that the loss of irisin exacerbates insulin resistance, metabolic disorders, and cardiac dysfunction in response to HFD and promotes myocardial remodeling and hypertrophic response. This evidence reveals the molecular evidence and the critical role of irisin in modulating insulin resistance and cardiac function in type II diabetes.NEW & NOTEWORTHY By utilizing the CRISPR/Cas-9 genome-editing system and high-fat diet (HFD)-induced type II diabetes model, our results provide direct evidence showing that the loss of irisin exacerbates cardiac dysfunction and insulin resistance while promoting myocardial remodeling and a hypertrophic response in HFD-induced diabetes. This study provides new insight into understanding the molecular evidence and the critical role of irisin in modulating insulin resistance and cardiac function in type II diabetes.

The relationship of circulating neuregulin 4 and irisin, and traditional and novel cardiometabolic risk factors with the risk and severity of coronary artery disease

BACKGROUND AND AIMS

Neuregulin 4 (NRG4) and irisin are adipokines that have been suggested to be associated with cardiometabolic risk factors and coronary artery disease (CAD), but the data are inconclusive. This study aimed to investigate the relationship between circulating NRG4 and irisin and cardiometabolic risk factors with CAD risk and severity.

METHODS AND RESULTS

In this cross-sectional study, the presence of CAD and the severity of stenosis (gensini score) were documented based on coronary angiography in 166 adults. Circulating NRG4 and irisin, glucose homeostasis markers, hs-CRP, lipid profiles, blood pressure, and anthropometric measurements were assessed as well. Age (p = 0.005), sex (p = 0.008), SBP (p = 0.033), DBP (p = 0.04), MAP (p = 0.018), FBG (p = 0.012), insulin (p = 0.039) and HOMA-IR (p = 0.01) were significantly associated with odds of having CAD. The final logistic regression model showed that age, sex, HOMA-IR, and MAP were the most important determinants of having CAD. There were no significant associations between circulating irisin and NRG4 with odds of having CAD. The final general linear model showed that being men (β = 17.303, 95% CI: 7.086-27.52, P = 0.001), age (Aβ = 0.712, 95% CI: 0.21-1.214, P = 0.006), HOMA-IR (Aβ = 2.168, 95% CI: 0.256 to 4.079, P = 0.027), and NRG4 level (β = 1.836, 95% CI: 0.119-3.553, P = 0.036) were directly associated with higher gensini score. Participants with the three-vessel disease had a mean increase of about 5 units in circulating irisin compared to those with no clinical CAD (β = 5.221, 95% CI: 0.454-9.987, p = 0.032).

CONCLUSIONS

This study showed that the adipokines NRG4 and Irisin might be associated with the severity of coronary stenosis.

Significance of Plasma Irisin, Adiponectin, and Retinol Binding Protein-4 Levels as Biomarkers for Obstructive Sleep Apnea Syndrome Severity

OBJECTIVE

Obstructive sleep apnea syndrome (OSAS) is a common sleep disorder that is caused by the reduction or cessation of airflow in the upper airway. Irisin, retinol-binding protein-4 (RBP-4), and adiponectin are the three significant factors in the metabolic process of the human body. The objective of this study was to investigate whether plasma irisin, RBP-4, and adiponectin levels are associated with the severity of OSAS.

METHODS

According to inclusion and exclusion criteria, 125 patients with OSAS and 46 healthy, gender-matched controls were included in this study. The patients were classified according to the apnea hypopnea index (AHI) as 14 mild cases (5 < AHI < 15), 23 moderate OSAS cases (15 < AHI < 30), and 88 severe OSAS cases (AHI > 30). The plasma irisin, RBP-4, and adiponectin levels were measured and compared between groups.

RESULTS

RBP-4 levels were higher in severe OSAS compared to other groups, and irisin levels were significantly lower in severe OSAS compared to other groups. There was a negative correlation between irisin and RBP-4 (r = -0.421; p < 0.001), and irisin and AHI (r = -0.834; p < 0.001), and a positive correlation between irisin and adiponectin (r = 0.240; p = 0.002). There was a negative correlation between RBP-4 and adiponectin (r = -0.507; p < 0.001) and a positive correlation between RBP-4 and AHI (r = 0.473; p < 0.001). As a predictor of OSAS, adiponectin showed the highest specificity (84.8%) and RBP-4 the highest sensitivity (92.0%).

CONCLUSION

Circulating adiponectin, irisin, and RBP-4 may be new biomarkers in OSAS patients in addition to risk factors such as diabetes, obesity, and hypertension. When polysomnography is not available, these parameters and clinical data can be used to diagnose the disease. As a result, patients with an AHI score greater than thirty should be closely monitored for metabolic abnormalities.

Nordic Walking training in BungyPump form improves cognitive functions and physical performance and induces changes in amino acids and kynurenine profiles in older adults

Introduction

Although impacts of physical activity on cognitive functions have been intensively investigated, they are still far from being completely understood. The aim of this study was to evaluate the effect of 12 weeks of the Nordic Walking training with BungyPump resistance poles (NW-RSA) on the amino acid and kynurenine profiles as well as selected myokine/exerkine concentrations, which may modify the interface between physical and cognitive functions.

Methods

A group of 32 older adults participated in the study. Before and after the intervention, body composition, cognitive functions, and physical performance were assessed. Blood samples were taken before and 1 h after the first and last sessions of the NW-RSA training, to determine circulating levels of exercise-induced proteins, i.e., brain-derived neurotrophic factor (BDNF), irisin, kynurenine (KYN), metabolites, and amino acids.

Results

The NW-RSA training induced a significant improvement in cognitive functions and physical performance as well as a reduction in fat mass (p = 0.05). Changes were accompanied by a decline in resting serum BDNF (p = 0.02) and a slight reduction in irisin concentration (p = 0.08). Still, changes in irisin concentration immediately after the NW-RSA intervention depended on shifts in kynurenine-irisin dropped as kynurenine increased. The kynurenine-to-tryptophan and phenylalanine-to-tyrosine ratios decreased significantly, suggesting their possible involvement in the amelioration of cognitive functions. No changes of glucose homeostasis or lipid profile were found. Shifts in the concentrations of selected amino acids might have covered the increased energy demand in response to the NW-RSA training and contributed to an improvement of physical performance.

Conclusion

Regular Nordic Walking training with additional resistance (BungyPump) improved cognitive functions and physical performance. These positive effects were associated with a reduced BDNF concentration and kynurenine-to-tryptophan ratio as well as changes in the amino acid profile.

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.

Adipokines in atherosclerosis: unraveling complex roles

Adipokines are biologically active factors secreted by adipose tissue that act on local and distant tissues through autocrine, paracrine, and endocrine mechanisms. However, adipokines are believed to be involved in an increased risk of atherosclerosis. Classical adipokines include leptin, adiponectin, and ceramide, while newly identified adipokines include visceral adipose tissue-derived serpin, omentin, and asprosin. New evidence suggests that adipokines can play an essential role in atherosclerosis progression and regression. Here, we summarize the complex roles of various adipokines in atherosclerosis lesions. Representative protective adipokines include adiponectin and neuregulin 4; deteriorating adipokines include leptin, resistin, thrombospondin-1, and C1q/tumor necrosis factor-related protein 5; and adipokines with dual protective and deteriorating effects include C1q/tumor necrosis factor-related protein 1 and C1q/tumor necrosis factor-related protein 3; and adipose tissue-derived bioactive materials include sphingosine-1-phosphate, ceramide, and adipose tissue-derived exosomes. However, the role of a newly discovered adipokine, asprosin, in atherosclerosis remains unclear. This article reviews progress in the research on the effects of adipokines in atherosclerosis and how they may be regulated to halt its progression.

The Developmental Implications of Muscle-Targeted Magnetic Mitohormesis: A Human Health and Longevity Perspective

Muscle function reflects muscular mitochondrial status, which, in turn, is an adaptive response to physical activity, representing improvements in energy production for de novo biosynthesis or metabolic efficiency. Differences in muscle performance are manifestations of the expression of distinct contractile-protein isoforms and of mitochondrial-energy substrate utilization. Powerful contractures require immediate energy production from carbohydrates outside the mitochondria that exhaust rapidly. Sustained muscle contractions require aerobic energy production from fatty acids by the mitochondria that is slower and produces less force. These two patterns of muscle force generation are broadly classified as glycolytic or oxidative, respectively, and require disparate levels of increased contractile or mitochondrial protein production, respectively, to be effectively executed. Glycolytic muscle, hence, tends towards fibre hypertrophy, whereas oxidative fibres are more disposed towards increased mitochondrial content and efficiency, rather than hypertrophy. Although developmentally predetermined muscle classes exist, a degree of functional plasticity persists across all muscles post-birth that can be modulated by exercise and generally results in an increase in the oxidative character of muscle. Oxidative muscle is most strongly correlated with organismal metabolic balance and longevity because of the propensity of oxidative muscle for fatty-acid oxidation and associated anti-inflammatory ramifications which occur at the expense of glycolytic-muscle development and hypertrophy. This muscle-class size disparity is often at odds with common expectations that muscle mass should scale positively with improved health and longevity. Brief magnetic-field activation of the muscle mitochondrial pool has been shown to recapitulate key aspects of the oxidative-muscle phenotype with similar metabolic hallmarks. This review discusses the common genetic cascades invoked by endurance exercise and magnetic-field therapy and the potential physiological differences with regards to human health and longevity. Future human studies examining the physiological consequences of magnetic-field therapy are warranted.

Move Your Body toward Healthy Aging: Potential Neuroprotective Mechanisms of Irisin in Alzheimer's Disease

Alzheimer's disease (AD) is the leading cause of dementia in older adults, having a significant global burden and increasing prevalence. Current treatments for AD only provide symptomatic relief and do not cure the disease. Physical activity has been extensively studied as a potential preventive measure against cognitive decline and AD. Recent research has identified a hormone called irisin, which is produced during exercise, that has shown promising effects on cognitive function. Irisin acts on the brain by promoting neuroprotection by enhancing the growth and survival of neurons. It also plays a role in metabolism, energy regulation, and glucose homeostasis. Furthermore, irisin has been found to modulate autophagy, which is a cellular process involved in the clearance of protein aggregates, which are a hallmark of AD. Additionally, irisin has been shown to protect against cell death, apoptosis, oxidative stress, and neuroinflammation, all of which are implicated in AD pathogenesis. However, further research is needed to fully understand the mechanisms and therapeutic potential of irisin in AD. Despite the current gaps in knowledge, irisin holds promise as a potential therapeutic target for slowing cognitive decline and improving quality of life in AD patients.

Role of irisin in bone diseases

Bone diseases are common among middle-aged and elderly people, and harm to activities of daily living (ADL) and quality of life (QOL) for patients. It is crucial to search for key regulatory factors associated with the development of bone diseases and explore potential therapeutic targets for bone diseases. Irisin is a novel myokine that has been discovered in recent years. Accumulating evidence indicates that irisin has beneficial effects in the treatment of various diseases such as metabolic, cardiovascular and neurological disorders, especially bone-related diseases. Recent studies had shown that irisin plays the role in various bone diseases such as osteoarthritis, osteoporosis and other bone diseases, suggesting that irisin may be a potential molecule for the prevention and treatment of bone diseases. Therefore, in this review, by consulting the related domestic and international literature of irisin and bone diseases, we summarized the specific regulatory mechanisms of irisin in various bone diseases, and provided a systematic theoretical basis for its application in the diagnosis and treatment of the bone diseases.

Exercise-regulated white adipocyte differentitation: An insight into its role and mechanism

White adipocytes play a key role in the regulation of fat mass amount and energy balance. An appropriate level of white adipocyte differentiation is important for maintaining metabolic homeostasis. Exercise, an important way to improve metabolic health, can regulate white adipocyte differentiation. In this review, the effect of exercise on the differentiation of white adipocytes is summarized. Exercise could regulate adipocyte differentiation in multiple ways, such as exerkines, metabolites, microRNAs, and so on. The potential mechanism underlying the role of exercise in adipocyte differentiation is also reviewed and discussed. In-depth investigation of the role and mechanism of exercise in white adipocyte differentiation would provide new insights into exercise-mediated improvement of metabolism and facilitate the application of exercise-based strategy against obesity.

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.

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.

Differential remodeling of subcutaneous white and interscapular brown adipose tissue by long-term exercise training in aged obese female mice

Obesity exacerbates aging-induced adipose tissue dysfunction. This study aimed to investigate the effects of long-term exercise on inguinal white adipose tissue (iWAT) and interscapular brown adipose tissue (iBAT) of aged obese mice. Two-month-old female mice received a high-fat diet for 4 months. Then, six-month-old diet-induced obese animals were allocated to sedentarism (DIO) or to a long-term treadmill training (DIOEX) up to 18 months of age. In exercised mice, iWAT depot revealed more adaptability, with an increase in the expression of fatty acid oxidation genes (Cpt1a, Acox1), and an amelioration of the inflammatory status, with a favorable modulation of pro/antiinflammatory genes and lower macrophage infiltration. Additionally, iWAT of trained animals showed an increment in the expression of mitochondrial biogenesis (Pgc1a, Tfam, Nrf1), thermogenesis (Ucp1), and beige adipocytes genes (Cd137, Tbx1). In contrast, iBAT of aged obese mice was less responsive to exercise. Indeed, although an increase in functional brown adipocytes genes and proteins (Pgc1a, Prdm16 and UCP1) was observed, few changes were found on inflammation-related and fatty acid metabolism genes. The remodeling of iWAT and iBAT depots occurred along with an improvement in the HOMA index for insulin resistance and in glucose tolerance. In conclusion, long-term exercise effectively prevented the loss of iWAT and iBAT thermogenic properties during aging and obesity. In iWAT, the long-term exercise program also reduced the inflammatory status and stimulated a fat-oxidative gene profile. These exercise-induced adipose tissue adaptations could contribute to the beneficial effects on glucose homeostasis in aged obese mice.

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.

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.

The Association of Serum Irisin with Impaired Glucose Before and After Laparoscopic Sleeve Gastrectomy in Obesity

BACKGROUND

To demonstrate the association of irisin levels with impaired glucose before and after laparoscopic sleeve gastrectomy (LSG) in patients with obesity.

METHODS

Thirty-six patients with obesity undergoing LSG were included. We tested the irisin levels before and after LSG and conducted an evaluation of baseline irisin levels with elevated glucose as well as irisin changes with weight loss and its association with glucose control after LSG.

RESULTS

Anthropometric measurements, body fat index, and metabolic parameters were significantly improved in 3 months following LSG (all p < 0.05). Baseline irisin levels were significantly higher in obesity with elevated fasting glucose than that with normal glucose (2.98 [2.37, 3.63] vs. 3.72 [3.06, 5.32], p = 0.031). After adjustment for sex, gender, and body mass index (BMI), obesity with higher irisin levels was prone to have impaired fasting glucose (OR = 2.499, 95% CI = 1.047-5.964). According to receiver operating characteristic curve analysis, the diagnostic accuracy and sensitivity of baseline irisin levels on impaired fasting glucose were 75% and 77.8%. Irisin levels decreased from 3.29 (2.67, 4.43) to 2.82 (2.41, 3.25) ng/mL (p = 0.009) after LSG. The decreases of weight, BMI, and FFA were more in irisin changes group (△irisin ≥ 0.5) than in no irisin changes group (△irisin < 0.5). And △irisin was negatively associated with postprandial glucose (PG) at 3 months after LSG (0.5 h-PG, r =  - 0.478, p = 0.029; 2 h-PG, r =  - 0.406, p = 0.017).

CONCLUSIONS

Elevated baseline irisin levels indicated the impaired glucose in obesity. The decrease of irisin with weight loss provided more evidence for the contribution of serum irisin secretion by fat mass in obesity.