Serum Irisin Level Can Predict the Severity of Coronary Artery Disease in Patients with Stable Angina

Irisin protects against cardiac injury by inhibiting NLRP3 inflammasome-mediated pyroptosis during remodeling after infarction

This study aimed to explore the cardioprotective mechanism of irisin in the context of cardiac injury. Utilizing a myocardial infarction (MI) mouse model, we investigated the therapeutic potential of recombinant human irisin (rhIrisin) administered for 28 days post-infarction. The efficacy of irisin treatment was evaluated through echocardiographic assessment of cardiac function and serum analysis of myocardial injury markers. Our research provided novel insights into the impacts of irisin on the NLR Family Pyrin Domain Containing 3 (NLRP3) inflammasome activation and pyroptosis, assessed both in vivo in MI mice and in vitro in hypoxia/reoxygenation-treated H9C2 cells. Remarkably, irisin treatment significantly reduced levels of lactate dehydrogenase (LDH), creatine kinase-MB (CK-MB), and troponin I, indicating reduced myocardial injury. Echocardiography highlighted substantial improvements in left ventricular ejection fraction (LVEF), left ventricular fractional shortening (LVFS), and dimensions (LVIDd and LVIDs) in irisin-treated mice, underscoring enhanced cardiac function. Moreover, irisin was shown to significantly suppress the mRNA and protein expressions of key components involved in NLRP3 inflammasome pathway (NLRP3, ASC, caspase-1 (p20), and interleukin-18 (IL-18)) both in MI-induced mice and hypoxia/reoxygenation-treated cells. This study firstly reveals that the cardioprotective effect of irisin is mediated through the attenuation of NLRP3 inflammasome activation and pyroptosis, positioning irisin as a promising therapeutic agent for cardiac injury.

Inflammation Is a Histological Characteristic of Skeletal Muscle in Chronic Limb Threatening Ischemia

BACKGROUND

The loss of skeletal muscle is a prognostic factor in several diseases including in patients with chronic limb threatening ischemia (CLTI). Patients with CLTI also have a lower skeletal mass and area when compared to those with claudication. However, there are no currently available data regarding the histological characteristics of core muscles in patients with CLTI. This study aims to determine the differences in core skeletal muscles between patients with claudication and those with CLTI. The second aim is to evaluate the differences in myokines, which are molecules secreted by skeletal muscle, between patients with claudication and those with CLTI.

METHODS

An observational, prospective study was conducted from January 2018 to July 2022 involving consecutive patients with peripheral arterial disease (PAD). The clinical characteristics were registered. In PAD patients with surgical indication for common femoral artery approach, samples of sartorius skeletal muscle (and not from the limb muscles directly involved in the ischemic process) were collected. The samples were submitted to histological characterization on hematoxylin-eosin and to immunohistochemical analysis to detect CD45+ leukocytes and CD163+ macrophages. The extent of the inflammatory cells (leukocytes and macrophages) was semiquantitatively assessed using a 0-to-4 grade scale as follows: absent (0†), mild (†), moderate (††), severe (†††), and very severe (††††). Serum levels of myokines: irisin, myostatin, IL-8, and lL-6 were determined with multiplex bead-based immunoassay.

RESULTS

119 patients (mean age: 67.58 ± 9.60 years old, 79.80% males) 64 with claudication and 54 with CLTI were enrolled in the study. No differences were registered between patients with claudication and those with CLTI on age, gender, cardiovascular risk factors, and medication, except on smoking habits. There was a significantly higher prevalence of smokers and a higher smoking load in the claudication group. Samples of sartorius skeletal muscle from 40 patients (14 with claudication and 26 with CLTI) were submitted to histological analysis. No differences were found in skeletal muscle fibers preservation, trauma, or hemorrhage (on hematoxylin-eosin staining). However, in the immunohistochemistry study, we found more inflammatory cells CD45+ leukocytes in patients with CLTI when compared to those with claudication [CD45+ ≥ moderate (††): claudication (n = 14): 4; 28.57%; CLTI (n = 25): 16; 64.00%; P = 0.034]. Patients with CLTI also had higher tissue levels of CD163+ macrophages, but this difference was not significant [CD163+ ≥ moderate (††): claudication (n = 13): 7; 53.85%; CLTI (n = 27): 21; 77.78%; P = 0.122]. The serum levels of the myokines, irisin, and myostatin were below the lower limit of detection, in the majority of patients, so no valid results were obtained. However, patients with CLTI had a higher serum level of Interleukin (IL)-6 and IL-8.

CONCLUSIONS

CLTI patients exhibit increased quantities of leukocytes in their sartorius muscle, as well as elevated serum levels of myokines IL-8 and IL-6. Inflamed skeletal muscle can contribute to the loss of muscle mass and account for the lower density of skeletal muscle observed in CLTI. Additionally, inflamed skeletal muscle may contribute to the development of systemic inflammation through the secretion of pro-inflammatory cytokines into the systemic circulation. Halting the inflammatory process could eventually improve the prognosis of CLTI patients.

Irisin: A Potentially Fresh Insight into the Molecular Mechanisms Underlying Vascular Aging

Aging is a natural process that affects all living organisms, including humans. Aging is a complex process that involves the gradual deterioration of various biological processes and systems, including the cardiovascular system. Vascular aging refers to age-related changes in blood vessels. These changes can increase the risk of developing cardiovascular diseases, such as hypertension, atherosclerosis, and stroke. Recently, an exercise-induced muscle factor, irisin, was found to directly improve metabolism and regulate the balance of glucolipid metabolism, thereby counteracting obesity and insulin resistance. Based on a growing body of evidence, irisin modulates vascular aging. Adenosine monophosphate-activated protein kinase (AMPK) serves as a pivotal cellular energy sensor and metabolic modulator, acting as a central signaling cascade to coordinate various cellular processes necessary for maintaining vascular homeostasis. The vascular regulatory effects of irisin are closely intertwined with its interaction with the AMPK pathway. In conclusion, understanding the molecular processes used by irisin to regulate changes in vascular diseases caused by aging may inspire the development of techniques that promote healthy vascular aging. This review sought to describe the impact of irisin on the molecular mechanisms of vascular aging, including inflammation, oxidative stress, and epigenetics, from the perspective of endothelial cell function and vascular macroregulation, and summarize the multiple signaling pathways used by irisin to regulate vascular aging.

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.

Serum Irisin Levels Are Inversely Correlated With the Severity of Coronary Artery Disease Confirmed by Coronary Angiography: A Comparative Cross-Sectional Study

Introduction Irisin, a newly discovered myokine, has been reported for its role in coronary artery disease (CAD), which is a major cause of mortality worldwide. Atherosclerosis is the primary cause of CAD. Irisin has been reported to reduce atherosclerosis by improving endothelial function and inhibiting inflammation via iNOS/NF-κB pathways. We sought to investigate the relationship between serum irisin levels and the severity of CAD that is confirmed with coronary angiography. Methods A comparative cross-sectional study was designed between the Chemical Pathology and Cardiology departments at KEMU/Mayo Hospital in Lahore, Pakistan. Patients were divided into group A with mild CAD (<50% stenosis) and group B with moderate-severe CAD (>50% stenosis). Serum was collected from venous blood, and irisin levels were analyzed by ELISA. Inclusion criteria: patients with stable CAD. Exclusion criteria: History of coronary artery bypass grafting (CABG), acute coronary syndrome (ACS), active or chronic infection, hepatic or renal dysfunction. Results The mean + SD age (years) of patients in group B (57.0±9.5) was significantly higher than group A (50.0±13.7). Irisin levels (μg/ml) were significantly higher in group A (15.3±4.6) than in group B (9.3±2.4). Irisin levels were significantly negatively correlated with the severity of CAD (% stenosis). Conclusion Serum irisin levels are low in patients with moderate to severe CAD, and they are negatively correlated with the severity of CAD (% stenosis).

Irisin Is Target of Sphingosine-1-Phosphate/Sphingosine-1-Phosphate Receptor-Mediated Signaling in Skeletal Muscle Cells

Irisin is a hormone-like myokine produced in abundance by skeletal muscle (SkM) in response to exercise. This myokine, identical in humans and mice, is involved in many signaling pathways related to metabolic processes. Despite much evidence on the regulators of irisin and the relevance of sphingolipids for SkM cell biology, the contribution of these latter bioactive lipids to the modulation of the myokine in SkM is missing. In particular, we have examined the potential involvement in irisin formation/release of sphingosine-1-phosphate (S1P), an interesting bioactive molecule able to act as an intracellular lipid mediator as well as a ligand of specific G-protein-coupled receptors (S1PR). We demonstrate the existence of distinct intracellular pools of S1P able to affect the expression of the irisin precursor FNDC. In addition, we establish the crucial role of the S1P/S1PR axis in irisin formation/release as well as the autocrine/paracrine effects of irisin on myoblast proliferation and myogenic differentiation. Altogether, these findings provide the first evidence for a functional crosstalk between the S1P/S1PR axis and irisin signaling, which may open new windows for potential therapeutic treatment of SkM dysfunctions.

Tissue and Serum Biomarkers in Degenerative Aortic Stenosis-Insights into Pathogenesis, Prevention and Therapy

Background and Aim. Degenerative Aortic Stenosis (DAS) is a common disease that causes substantial morbidity and mortality worldwide, especially in the older population. Our aim was to further investigate novel serum and tissue biomarkers to elucidate biological processes involved in this entity. Material and Methods. We evaluated the expression of six biomarkers significantly involved in cardiovascular pathology, i.e., irisin, periostin, osteoglycin, interleukin 18, high mobility group box 1 and proprotein convertase subtilisin/kexin type 9 in the serum at the protein level, and in the tissue at both the protein and mRNA levels of patients with AS (N = 60). Five normal valves obtained after transplantation from hearts of patients with idiopathic dilated cardiomyopathy were also studied. Serum measurements were also performed in 22 individuals without valvular disease who served as controls (C). Results. Higher levels of all factors were found in DAS patients’ serum than in normal C. IHC and PCR mRNA tissue analysis showed the presence of all biomarkers in the aortic valve cusps with DAS, but no trace of PCR mRNA was found in the five transplantation valves. Moreover, periostin serum levels correlated significantly with IHC and mRNA tissue levels in AS patients. Conclusion. We showed that six widely prevalent biomarkers affecting the atherosclerotic process were also involved in DAS, suggesting a strong osteogenic and pro-inflammatory profile, indicating that aortic valve calcification is a multifactorial biological process.

Irisin expression and FNDC5 (rs3480) gene polymorphism in type 2 diabetic patients with and without CAD

BACKGROUND

Irisin was found to correlate with coronary artery disease (CAD) in diabetic patients. This study investigated the association of irisin and FNDC5 (SNP rs3480) with the presence and severity of CAD in T2DM.

METHODS

This cross-sectional study included 100 patients with T2DM divided into two groups, DM group (n = 50), including patients without CAD and CAD group (n = 50), including those confirmed to have CAD by coronary angiography. Irisin was measured. SNP rs3480 genotyping of FNDC5 was done.

RESULTS

Irisin levels were significantly lower in the CAD group (p < 0.001). The CAD group had significantly higher HbA1c and lower HDL (p < 0.001). Patients with controlled DM had significantly higher irisin levels (p < 0.001). single nucleotide polymorphism (SNP) rs3480 was not associated with irisin levels, and the FNDC5 rs3480 AA reference allele was significantly associated with significant CAD.

CONCLUSION

Irisin appears to be protective against developing CAD in diabetic patients. Irisin level was an independent predictor of significant CAD in diabetic patients combined with the FNDC5 rs3480 genotype.

CLINICAL TRIAL REGISTRATION NUMBER

NCT04957823.

Association Between Serum Irisin Levels and ST-Segment Elevation Myocardial Infarction

Background

An acute ST-elevation myocardial infarction (STEMI) is a serious cardiovascular condition with a high risk of morbidity and mortality. Irisin is adipomyokine that is associated with various health conditions. In post-STEMI, elevated serum irisin levels are associated with more adverse cardiovascular events.

Objective

The purpose of this study was to investigate associations between the serum irisin levels and acute MI (AMI) and whether irisin may be a useful biomarker for severity of AMI in patients with STEMI. Possible correlations between serum irisin and cardiac troponin-I (cTi) levels were investigated.

Methods

A total of 90 subjects (46 control subjects and 44 STEMI patients) were included in the study. Besides demographic data, presence of diabetes mellitus and hypertension, electrocardiography (ECG) findings, blood biochemistry, cardiac biomarkers (cTi) and serum irisin levels were examined.

Results

Significantly lower heart rate (HR) and significantly higher ST-elevation and QTc interval were detected in ECG recordings in STEMI patients (p < 0.05). Serum irisin levels were significantly lower in STEMI patients compared to the control subjects (p < 0.001). The decrease in the serum irisin levels was significantly correlated with the increase in cTi levels, as well as increased QTc (p < 0.05). The sensitivity and specificity of irisin were found to be 93% and 78%, respectively.

Conclusion

Decreased irisin levels were found to be highly predictive in STEMI. In patients with STEMI, the serum irisin levels were associated with cTi levels and QTc, suggesting that irisin is a promising biomarker for AMI cases.

Irisin, an Effective Treatment for Cardiovascular Diseases?

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

Irisin as a Novel Biomarker of Subclinical Atherosclerosis, Cardiovascular Risk and Severe Disease in Axial Spondyloarthritis

Introduction

Patients with axial spondyloarthritis (axSpA) have a high disease burden mainly due to the rheumatic disease itself, and also exhibit accelerated atherosclerosis, that leads to a higher incidence of cardiovascular (CV) disease. Accordingly, the identification of biomarkers of CV risk and inflammation in axSpA patients is clinically relevant. In this sense, given the beneficial functions exerted by the adipomyokine irisin in processes related to CV disease and inflammation, our aim was to assess, for the first time, the role of irisin as a genetic and serological biomarker of subclinical atherosclerosis, CV risk and disease severity in axSpA patients.

Methods

A large cohort of 725 Spanish patients with axSpA was included. Subclinical atherosclerosis (presence of plaques and abnormal carotid intima-media thickness values) was evaluated by carotid ultrasound. Four irisin polymorphisms (rs16835198 G/T, rs3480 A/G, rs726344 G/A, and rs1570569 G/T) were genotyped by TaqMan probes. Additionally, serum irisin levels were determined by ELISA.

Results

Low irisin levels were linked to the presence of plaques (p=0.002) and atherogenic index values ≥4 (p=0.01). Serum irisin were positively correlated with C-peptide levels (p<0.001) and negatively correlated with visual analogue scale and Bath Ankylosing Spondylitis Metrology Index (p<0.05 in all the cases). Moreover, lower irisin levels were observed in patients with sacroiliitis and in those with a negative HLA-B27 status (p<0.001 and p=0.006, respectively), as well as in those treated with non-steroidal anti-inflammatory drugs and conventional disease-modifying antirheumatic drugs (p<0.001 and p=0.002, respectively). Interestingly, the TT genotype and the T allele of rs16835198 were less frequent in axSpA patients with ASDAS >2.1 (Odds Ratio (OR): 0.48 [0.28-0.83] and OR: 0.73 [0.57-0.92], respectively, p=0.01 in both cases). Additionally, the frequency of rs1570569 T allele was higher in these patients (OR: 1.46 [1.08-1.97], p=0.01). Furthermore, the GGGT haplotype was more frequent in patients with ASDAS values >2.1 (OR: 1.73 [1.13-2.66], p=0.01).

Conclusions

Our results indicate that low serum irisin levels could be indicators of the presence of subclinical atherosclerosis, high CV risk and more severe disease in axSpA patients. In addition, irisin may also constitute a genetic biomarker of disease activity in axSpA.

Association of lower serum irisin levels with diabetes mellitus: Irrespective of coronary collateral circulation, and syntax score

Objective:

Irisin is a myokine thought to be involved in the pathophysiological process of atherosclerosis with its’ cardiovascular protective effects. Patients with diabetes mellitus (DM) have lower levels of irisin. Therefore, we investigated whether there is a connection between irisin, DM, coronary collateral circulation (CCC), and SYNTAX scores representing coronary artery disease (CAD) severity.

Methods:

This study evaluated 86 patients who have at least one epicardial coronary artery with chronic total occlusion. We included Rentrop 0–1 into the poor CCC group (n=45) and Rentrop 2–3 into the good CCC group (n=41) and measured serum irisin levels.

Results:

Irisin levels did not differ (17585 [882–37741] pg/ml and (17504 [813–47683] pg/ml, p=0.772) between the two groups. Irisin levels were lower in patients with diabetes (n=41; 14485 [813–29398] pg/ml) than those without diabetes (n=45; 19724 [865–47683] pg/ml (p=0.002). Irisin was not correlated with SYNTAX scores. In multivariate analysis, DM (OR=0.463; CI: 0.184–0.783; p=0.012) was a negative predictor of good CCC development

Conclusion:

Although its level is decreased in patients with diabetes, serum irisin levels have no role in the pathophysiology of collateral development and CAD severity.

Irisin Promotes Cardiac Homing of Intravenously Delivered MSCs and Protects against Ischemic Heart Injury

Few intravenously administered mesenchymal stromal cells (MSCs) engraft to the injured myocardium, thereby limiting their therapeutic efficacy for the treatment of ischemic heart injury. Here, it is found that irisin pretreatment increases the cardiac homing of adipose tissue-derived MSCs (ADSCs) administered by single and multiple intravenous injections to mice with MI/R by more than fivefold, which subsequently increases their antiapoptotic, proangiogenic, and antifibrotic effects in rats and mice that underwent MI/R. RNA sequencing, Kyoto Encyclopedia of Genes and Genomes (KEGG) signaling pathway analysis, and loss-of-function studies identified CSF2RB as a cytokine receptor that facilitates the chemotaxis of irisin-treated ADSCs in the presence of CSF2, a chemokine that is significantly upregulated in the ischemic heart. Cardiac-specific CSF2 knockdown blocked the cardiac homing and cardioprotection abilities of intravenously injected irisin-treated ADSCs in mice subjected to MI/R. Moreover, irisin pretreatment reduced the apoptosis of hydrogen peroxide-induced ADSCs and increased the paracrine proangiogenic effect of ADSCs. ERK1/2-SOD2, and ERK1/2-ANGPTL4 are responsible for the antiapoptotic and paracrine angiogenic effects of irisin-treated ADSCs, respectively. Integrin αV/β5 is identified as the irisin receptor in ADSCs. These results provide compelling evidence that irisin pretreatment can be an effective means to optimize intravenously delivered MSCs as therapy for ischemic heart injury.

Irisin: A Promising Target for Ischemia-Reperfusion Injury Therapy

Ischemia-reperfusion injury (IRI) is defined as the total combined damage that occurs during a period of ischemia and following the recovery of blood flow. Oxidative stress, mitochondrial dysfunction, and an inflammatory response are factors contributing to IRI-related damage that can each result in cell death. Irisin is a polypeptide that is proteolytically cleaved from the extracellular domain of fibronectin type III domain-containing protein 5 (FNDC5). Irisin acts as a myokine that potentially mediates beneficial effects of exercise by reducing oxidative stress, improving mitochondrial fitness, and suppressing inflammation. The existing literature also suggests a possible link between irisin and IRI, involving mechanisms similar to those associated with exercise. This article will review the pathogenesis of IRI and the potential benefits and current limitations of irisin as a therapeutic strategy for IRI, while highlighting the mechanistic correlations between irisin and IRI.

Roles and Mechanisms of Irisin in Attenuating Pathological Features of Osteoarthritis

To investigate the effects and mechanisms of irisin, a newly discovered myokine, in cartilage development, osteoarthritis (OA) pathophysiology and its therapeutic potential for treating OA we applied the following five strategical analyses using (1) murine joint tissues at different developmental stages; (2) human normal and OA pathological tissue samples; (3) experimental OA mouse model; (4) irisin gene knockout (KO) and knock in (KI) mouse lines and their cartilage cells; (5) in vitro mechanistic experiments. We found that Irisin was involved in all stages of cartilage development. Both human and mouse OA tissues showed a decreased expression of irisin. Intra-articular injection of irisin attenuated ACLT-induced OA progression. Irisin knockout mice developed severe OA while irisin overexpression in both irisin KI mice and intraarticular injection of irisin protein attenuated OA progression. Irisin inhibited inflammation and promoted anabolism in chondrogenic ADTC5 cells. Proliferative potential of primary chondrocytes from KI mice was found to be enhanced, while KO mice showed an inhibition under normal or inflammatory conditions. The primary chondrocytes from irisin KI mice showed reduced expression of inflammatory factors and the chondrocytes isolated from KO mice showed an opposite pattern. In conclusion, it is the first time to show that irisin is involved in cartilage development and OA pathogenesis. Irisin has the potential to ameliorate OA progression by decreasing cartilage degradation and inhibiting inflammation, which could lead to the development of a novel therapeutic target for treating bone and cartilage disorders including osteoarthritis.

Irisin in atherosclerosis

Irisin, a novel exercise-induced myokine, has been shown to play important roles in increasing white adipose tissue browning, regulating energy metabolism and improving insulin resistance. Growing evidence suggests a direct role for irisin in preventing atherosclerosis (AS) by inhibiting oxidative stress, improving dyslipidemia, facilitating anti-inflammation, reducing cellular damage and recovering endothelial function. In addition, some studies have noted that serum irisin levels play an essential role in cardiovascular diseases (CVDs) risk prediction, highlighting that irisin has the potential to be a useful predictive marker and therapeutic target of AS, especially in monitoring therapeutic efficacy. This review summarizes the understanding of irisin-mediated regulation in essential biological pathways and functions in atherosclerosis and prompts further exploitation of the biological properties of irisin in the pathogenesis of atherosclerosis.

Role of Irisin in Myocardial Infarction, Heart Failure, and Cardiac Hypertrophy

Irisin is a myokine derived from the cleavage of fibronectin type III domain-containing 5. Irisin regulates mitochondrial energy, glucose metabolism, fatty acid oxidation, and fat browning. Skeletal muscle and cardiomyocytes produce irisin and affect various cardiovascular functions. In the early phase of acute myocardial infarction, an increasing irisin level can reduce endothelial damage by inhibiting inflammation and oxidative stress. By contrast, higher levels of irisin in the later phase of myocardial infarction are associated with more cardiovascular events. During different stages of heart failure, irisin has various influences on mitochondrial dysfunction, oxidative stress, metabolic imbalance, energy expenditure, and heart failure prognosis. Irisin affects blood pressure and controls hypertension through modulating vasodilatation. Moreover, irisin can enhance vasoconstriction via the hypothalamus. Because of these dual effects of irisin on cardiovascular physiology, irisin can be a critical therapeutic target in cardiovascular diseases. This review focuses on the complex functions of irisin in myocardial ischemia, heart failure, and cardiac hypertrophy.

Common single nucleotide polymorphisms in the FNDC5 gene and serum irisin levels in acute myocardial infarction

OBJECTIVE

Acute myocardial infarction (AMI) is the most common type of coronary artery disease. The irisin hormone encoded by the fibronectin type III domain-containing protein-5 (FNDC5) gene is synthesized in muscle, heart, and fat tissues. The present study aims to investigate serum irisin concentrations and FNDC5 genetic variants in patients with AMI through comparison with controls.

METHODS

This study included 225 patients with AMI and 225 healthy subjects. Blood samples were obtained from patients during the first 1-24 hours after AMI. Serum irisin concentration was measured with enzyme-linked immunosorbent assay (ELISA). The variants of rs16835198, rs3480, and rs726344 in the FNDC5 gene were genotyped with real time polymerase chain reaction (RT-PCR).

RESULTS

Compared with control serum irisin concentrations were significantly lower in patients with AMI. Serum irisin concentrations of patients with AMI showed a significant and gradual decrease from 6 hours up to 24 hours (p<0.05). There were no significant differences between the patient and control groups based on genotype and allele frequencies of rs16835198, rs3480, and rs726344 in the FNDC5 gene (p>0.05). However, the frequency of the TT genotype in male patients with AMI (6.4%) was significantly lower compared with control male subjects (16.2%). In addition, the GGT haplotype was identified as the protective haplotype against the risk of AMI (p<0.001; odds ratio=0.107).

CONCLUSIONS

The findings of the study suggest that serum irisin concentration could serve as a novel biological marker for the early diagnosis of AMI.

Serum Irisin May Predict Cardiovascular Events in Elderly Patients With Chronic Kidney Disease Stage 3-5

OBJECTIVE

Irisin is a circulating myokine released from skeletal muscles after physical exercise. Irisin production decreases during the course of chronic kidney disease (CKD) as a potential consequence of sarcopenia and physical inactivity.

METHODS

This observational study explored the relationship of serum irisin with cardiovascular outcome in 79 patients with stage 3-5 CKD.

RESULTS

Serum irisin was significantly higher in healthy subjects (n = 20) than that in CKD patients (7 ± 2 vs. 3.1 ± 0.9 μg/mL; P = .0001) and was higher in patients with CKD stage 3 (3.2 ± 1 μg/mL) than in patients at stage 4 and 5 taken together (n = 36, 2.8 ± 0.7 μg/mL, P = .05). Patients in the lowest serum irisin tertile had lower serum 1,25(OH)₂D levels (21 ± 11 pg/mL) than patients in the middle (30 ± 13 pg/mL; P = .005) and the highest tertile (27 ± 14 pg/mL; P = .047). Patients in the highest tertile had lower Kauppila score (10.6 ± 6.9) than patients in the middle (11.8 ± 5.5; P = .007) and the lowest tertile (6.9 ± 6.8; P = .043). Twenty patients suffered from cardiovascular events during a 3-year follow-up. A Cox regression model using age, body weight, presence of diabetes mellitus, gender, Kauppila calcification score, serum values of FGF23 (as logarithm), phosphate, sclerostin, albumin and cholesterol, estimated glomerular filtration rate, and serum irisin tertiles as covariates showed that patients in the highest tertile of serum irisin had a lower cardiovascular risk than patients in the middle tertile (B, 2.38; odds ratio, 10.8; 95% confidence interval, 1.65-58.13; P = .013) or in the lowest tertile (B, 1.61; odds ratio, 5; 95% confidence interval, 1.09-22.83; P = .038).

CONCLUSIONS

These findings suggest that serum irisin may be a marker of cardiovascular outcome in patients with CKD.

Irisin-Associated Neuroprotective and Rehabilitative Strategies for Stroke

Irisin, a newly discovered protein hormone that is secreted in response to low frequency whole body vibration (LFV), could be a promising post-stroke rehabilitation therapy for patients who are frail and cannot comply with regular rehabilitation therapy. Irisin is generated from a membrane-bound precursor protein fibronectin type III domain-containing protein 5 (FNDC5). Aside from being highly expressed in muscle, FNDC5 is highly expressed in the brain. The cleaved form of FNDC5 was found in the cerebrospinal fluid as well as in various regions of the brain. Numerous studies suggest that irisin plays a key role in brain metabolism and inflammation regulation. Both the metabolism and inflammation govern stroke outcome, and in a published study, we demonstrated that LFV therapy following middle cerebral artery occlusion significantly reduced innate immune response, improved motor function and infarct volume in reproductively senescent female rats. The observed effect of LFV therapy could be working via irisin, therefore, the current review focuses to understand various aspects of irisin including its mechanism of action on the brain.

Association of Circulating Irisin Levels and the Characteristics and Prognosis of Coronary Artery Disease

BACKGROUND

Irisin is a new muscle factor discovered in recent years that shows a strong association with metabolic diseases. However, its role in coronary artery disease (CAD) is still controversial. We performed this study to determine the relationship of serum irisin with the characteristics and prognosis of CAD.

MATERIALS AND METHODS

Patients with acute coronary syndrome (ACS) (n = 355), stable coronary artery disease (SCAD) (n = 162), nonobstructive coronary artery disease (NO-CAD) (n = 126) and normal coronary arteries (n = 109) were enrolled. An enzyme-linked immunosorbent assay kit was used to measure serum irisin concentrations. Major adverse cardiovascular events (MACEs) of patients with SCAD (n = 132) and ACS (n = 331) after percutaneous coronary intervention (PCI) were recorded during a 12-month follow-up. Receiver-operator characteristic (ROC) curve analysis was used to explore predictors of CAD. Kaplan-Meier survival analysis and the Cox proportional hazards regression model were used to explore the association between serum irisin levels and MACEs.

RESULTS

Serum irisin levels in patients with ACS, SCAD, NO-CAD and normal coronary arteries were 196.62±72.05 ng/ml, 216.81±79.69 ng/ml, 245.26±77.92 ng/ml and 300.17±76.74 ng/ml, respectively (p<0.001). ROC curve analysis indicated that serum irisin concentrations were a valuable biomarker of coronary lesions (AUC=0.799), CAD (AUC=0.734) and ACS (AUC=0.681). Survival analysis demonstrated that patients with high irisin levels exhibited a higher event-free survival rate in both the SCAD and ACS groups after successful PCI.

CONCLUSIONS

Serum irisin levels were significantly decreased in patients with CAD. Patients with ACS exhibited the lowest serum irisin levels. Furthermore, serum irisin levels were interrelated with prognosis in patients with CAD after PCI.

Irisin: A New Code Uncover the Relationship of Skeletal Muscle and Cardiovascular Health During Exercise

Exercise not only produces beneficial effects on muscle itself via various molecular pathways, but also mediates the interaction between muscles and other organs in an autocrine/paracrine manner through myokines, which plays a positive role in maintaining overall health. Irisin, an exercise-derived myokine, has been found involved in the regulation of some cardiovascular diseases. However, the relationship between irisin and cardiovascular health is not fully elucidated and there are some divergences on the regulation of irisin by exercise. In this review, we present the current knowledge on the origin and physiology of irisin, describe the regulation of irisin by acute and chronic exercises, and discuss the divergences of the related research results. Importantly, we discuss the role of irisin as a biomarker in the diagnosis of cardiovascular diseases and describe its treatment and molecular mechanism in some cardiovascular diseases. It is expected that irisin will be used as a therapeutic agent to combat cardiovascular diseases or other disorders caused by inactivity in the near future.

Lower Serum Irisin Levels Are Associated with Increased Abdominal Aortic Calcification in Peritoneal Dialysis Patients

Introduction

Vascular calcification (VC), with the mechanisms remaining unclear, is closely related with dialysis patients' cardiovascular mortality and all-cause mortality. Irisin is a newly identified myokine. This study aims to evaluate the serum irisin levels of peritoneal dialysis (PD) patients and their relationship with VC.

Methods

This cross-sectional study enrolled stable PD patients in Peking University Third Hospital who were followed for >6 months. We used plain X-ray films of abdomen to quantitatively evaluate VC of abdominal aorta. VC was evaluated by abdominal aortic calcification (AAC) scores, and PD patients were divided into the high AAC score group (AAC score ≥4) and the low AAC score group (AAC score <4). Demographic data and laboratory indexes were collected. Serum irisin concentrations were measured by enzyme-linked immunosorbent assay.

Results

A total of 102 PD patients were enrolled in this study, and 52 patients (51.0%) were found to have a high AAC score of ≥4. Age, diabetic mellitus proportion, pulse pressure, hypercalcemia (corrected calcium >2.54 mmol/L) rate, serum ultrasensitive C reactive protein, and AAC scores were significantly higher in the high AAC score group than those of the low AAC score group (p < 0.05). The high AAC score group had lower diastolic blood pressure, serum albumin, and serum carbon dioxide combining power compared with the low AAC score group (p < 0.05). Serum irisin levels of PD patients with a high AAC score were significantly lower than those of PD patients with a low AAC score (109.7 ± 13.1 ng/mL vs. 115.9 ± 10.1 ng/mL, p = 0.010). The multivariate logistic regression analyses showed that serum irisin, diabetic mellitus, serum ultrasensitive C reactive protein, and age were independent factors influencing the occurrence of VC in PD patients.

Conclusion

Our results are the first to provide a clinical evidence of the association between serum irisin and abdominal aortic calcification in PD patients. Lower irisin levels, diabetic mellitus, higher serum ultrasensitive C reactive protein, and older age could be potential predictive factors for VC in PD patients.

Myokines and Heart Failure: Challenging Role in Adverse Cardiac Remodeling, Myopathy, and Clinical Outcomes

Heart failure (HF) is a global medical problem that characterizes poor prognosis and high economic burden for the health system and family of the HF patients. Although modern treatment approaches have significantly decreased a risk of the occurrence of HF among patients having predominant coronary artery disease, hypertension, and myocarditis, the mortality of known HF continues to be unacceptably high. One of the most important symptoms of HF that negatively influences tolerance to physical exercise, well-being, social adaptation, and quality of life is deep fatigue due to HF-related myopathy. Myopathy in HF is associated with weakness of the skeletal muscles, loss of myofibers, and the development of fibrosis due to microvascular inflammation, metabolic disorders, and mitochondrial dysfunction. The pivotal role in the regulation of myocardial and skeletal muscle rejuvenation, attenuation of muscle metabolic homeostasis, and protection against ischemia injury and apoptosis belongs to myokines. Myokines are defined as a wide spectrum of active molecules that are directly synthesized and released by both cardiac and skeletal muscle myocytes and regulate energy homeostasis in autocrine/paracrine manner. In addition, myokines have a large spectrum of pleiotropic capabilities that are involved in the pathogenesis of HF including cardiac remodeling, muscle atrophy, and cardiac cachexia. The aim of the narrative review is to summarize the knowledge with respect to the role of myokines in adverse cardiac remodeling, myopathy, and clinical outcomes among HF patients. Some myokines, such as myostatin, irisin, brain-derived neurotrophic factor, interleukin-15, fibroblast growth factor-21, and growth differential factor-11, being engaged in the regulation of the pathogenesis of HF-related myopathy, can be detected in peripheral blood, and the evaluation of their circulating levels can provide new insights to the course of HF and stratify patients at higher risk of poor outcomes prior to sarcopenic stage.

The Controversial Role of Irisin in Clinical Management of Coronary Heart Disease

Irisin, a PGC1α-dependent myokine, was once believed to have beneficial effects induced by exercise. Since its first discovery of adipose browning in 2012, multiple studies have been trying to explore the metabolic functions of irisin, such as glucose and lipid metabolism. However, recently many studies with irisin concentration measuring were doubt for methodological problems, which may account for the continuous inconsistencies. New tools like recombinant irisin and gene-knockout mice are required to reconfirm the questioned functions of irisin. In this paper, we make a critical introduction to the latest researches concerning the relationship between irisin and coronary heart disease, which includes atherosclerosis, stable angina pectoris and acute coronary syndromes. These studies provided various controversial evidence of short and long-term monitoring and therapeutic effect from molecular cellular mechanisms, in vivo experiments and epidemiological investigation. But with ambiguities, irisin still has a long way to go to identify its functions in the clinical management.

The Impact of an Optimism Training Intervention on Biological Measures Associated With Cardiovascular Health: Data From a Randomized Controlled Trial

OBJECTIVE

Positive psychological constructs, such as optimism, are associated with cardiovascular health, and changes in biological measures associated with heart health have been proposed as potential mediators of these relationships. In this analysis of data from a randomized controlled trial, we examined the impact of an optimism training intervention on biological measures associated with cardiac health in patients with coronary artery disease.

METHODS

We analyzed data from an 8-week, randomized, controlled trial of a group-based optimism training intervention in 61 patients with coronary artery disease. High-sensitivity C-reactive protein (hs-CRP), interleukin 6, irisin, and fibrinogen were measured at baseline, 8 weeks, and 16 weeks. Mixed-effects regression analyses were performed to examine the effects of the intervention on changes in biological measures at 8 and 16 weeks.

RESULTS

At 8 weeks, the intervention led to significantly greater reductions in hs-CRP (B = -0.851 [standard error {SE} = 0.273, p = .002) and fibrinogen (B = -0.148 [SE = 0.062], p = .016), and a greater increase in irisin (B = 0.252 [SE = 0.114], p = .027) compared with the control condition. These changes persisted at 16 weeks (hs-CRP: B = -1.078 [SE = 0.276], p < .001; fibrinogen: B = -0.270 [SE = 0.062], p < .001; irisin: B = 0.525 [SE = 0.116], p < .001), and interleukin 6 additionally was impacted at this time point (B = -0.214 [SE = 0.064], p = .001). Exploratory mediation analyses failed to identify significant psychological or health behavior mediators of these relationships.

CONCLUSIONS

A group-based optimism training intervention resulted in significant, robust, and sustained changes in biological measures associated with cardiac health. Further studies are needed to confirm these findings in a larger sample and identify potential mediating variables.

TRIAL REGISTRATION

Iran Registry of Clinical Trials No. 2016070328769 N1.

Variations in Irisin, Bone Mineral Density, Bone Mineral Content, and Body Composition After Laparoscopic Bariatric Procedures in Obese Adults

INTRODUCTION

This study was aimed to assess irisin levels in obesity (OB) and T2DM individuals and investigate the dynamic changes of irisin, bone mineral density (BMD), bone mineral content, and body composition in 19 OB patients after laparoscopic bariatric procedures, and also to evaluate the correlation of irisin, with BMD and body composition.

METHODS

Forty-five OB, 20 T2DM, and 20 healthy adults had been recruited. Levels of irisin were measured in all subjects. Metabolic characteristics were obtained from OB and T2DM patients. Nineteen patients were randomly assigned to be received Roux-en-Y gastric bypass (LRYGB) or laparoscopic sleeve gastrectomy (LSG) procedure and to be completed 6-month follow-up. Irisin, BMD, bone mineral content, and body composition were measured at each visit.

RESULTS

Significantly higher circulating irisin levels were measured in the OB group compared with T2DM and control groups. FINS, C-P, HOMA-IR, FBCI, HBCI, ALT, AST, and UA levels of OB were significantly higher than those of T2DM patients. While FBG and HbA1c of the OB were significantly lower than T2DM group. There were significant differences among circulating irisin, BMD, and body composition after laparoscopic bariatric surgery. Levels of irisin were decreased after operations including both LRYGB and LSG surgery compared with preoperation. At each time point (1, 3, and 6 months) of postoperation, there was no significant difference in percentage of total weight loss between LSG and LRYGB group. The positive correlation of irisin levels with total BMD, muscle, and fat masses were found during 6-month follow-up after surgery.

CONCLUSIONS

The levels of irisin were higher in OB patients. There were positive correlations of irisin levels with total BMD, muscle, and fat masses during 6-month follow-up after surgery. Irisin may be involved in the occurrence and development of obese and it is related to BMD and body composition. Both LRYGB and LSG operations could decrease the circulating levels of irisin.

Alterations of irisin, adropin, preptin and BDNF concentrations in coronary heart disease patients comorbid with depression

Background

Depression is a well-known co-morbidity of coronary heart disease (CHD) and these two diseases share common risk mechanisms. Here, the aim of this study was to investigate the possible link between energy homeostasis regulation and CHD patients comorbid with depression.

Methods

Two hundred and nine CHD patients and 101 matched healthy individuals were included. Demographic, clinical data were collected, serum irisin, adropin, preptin and brain-derived neurotrophic factor (BDNF) levels were determined by a double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA), and the depression was scored by Patient Health Questionnaire-9 (PHQ-9). Correlation analysis as well as multiple linear regression was used to assess the relationship between the three peptides, BDNF serum levels and PHQ-9 scores.

Results

Irisin serum level was significantly lower in CHD patients without depression as compared with healthy controls (P=0.002), as well as adropin (P=0.000), preptin (P=0.000) and BDNF (P=0.000). Furthermore, similar trends were observed in CHD patients with depression in terms of irisin, adropin and BDNF as compared with CHD patients without depression (P=0.006; P=0.003; P=0.002; respectively). Multiple logistic regression results confirmed the contribution of irisin and BDNF to the occurrence of depression in CHD. Interestingly, correlations analysis revealed significant negative correlations between PHQ-9 scores and irisin, adropin, BDNF level (r=-0.43, P<0.01; r=-0.29, P<0.05; r=-0.45, P<0.001 respectively), and irisin serum level was positively correlated with BDNF (r=0.38, P<0.01).

Conclusions

Our study firstly identified the role of energy homeostasis in the susceptibility to depression in CHD patients, and the interaction between irisin and BDNF could trigger the imbalance of energy homeostasis that occurs in depression of CHD patients.

Decreased Concentration of Irisin Is Associated with Poor Functional Outcome in Ischemic Stroke

Irisin was discovered as a PGC-1a-activated messenger of myocytes that links sedentary lifestyle, obesity, and diabetes. In this study, we investigated the short-term prognostic value of early measurement of irisin concentration in 1530 Han Chinese patients with acute ischemic stroke (AIS) from three stroke centers. The subjects were the first-ever AIS patients who were hospitalized at three stroke centers during the period from January 2015 to December 2016. Clinical information and stroke severity were collected at admission. Neurological evaluations were conducted at the 6-month follow-up. Serum levels of irisin, National Institutes of Health Stroke Scale (NIHSS), and conventional risk factors were evaluated to determine their value to predict functional outcome and mortality within 6 months. Multivariate analyses were performed using logistic regression models. During follow-up, a poor functional outcome was found in 588 patients (38.4%; 95% confidence interval (CI), 36.0-40.9%), and 325 patients died (21.2%; 95% CI, 19.2-23.3%). The stroke patients included in the study were divided into four groups according to irisin quartiles (first is the lowest level). Poor outcome across the irisin quartiles ranged from 54.5% (first quartile) to 21.7% (fourth quartile), and mortality rate ranged from 39.3% (first quartile) to 6.3% (fourth quartile). In a multivariate model using the first quartile (Q1) of irisin vs. Q2-Q4 together with the clinical variables, the marker displayed prognostic information and increased odds ratios of poor outcome by 58% (OR for Q1, 1.58 [95% CI, 1.12-2.43]) and mortality by 185% (OR for Q1, 2.85 [95% CI, 1.79-4.02]). In addition, a model containing known risk factors plus irisin compared with a model containing known risk factors without irisin showed a greater discriminatory ability to predict poor outcome (the area under the curve (AUC) with an increase from 0.73 to 0.75 [95% CI, 0.70-0.81]) and mortality (the AUC increased from 0.80 to 0.83 [95% CI, 0.78-0.87]). Irisin is a novel, independent prognostic marker improving currently used risk stratification of stroke patients. Further studies are needed to confirm this association, which may pave the way to new therapeutic options. Trial registration: ChiCTR-OPC- 17013501.

Novel adipokines vaspin and irisin as risk biomarkers for cardiovascular diseases in type 2 diabetes mellitus

AIMS

Vaspin and irisin are novel cytokines proposed as potential new biomarkers of insulin resistance and endothelial dysfunction. This work is to investigate circulating levels of vaspin and irisin in patients with type 2 diabetes mellitus (T2DM) with and without cardiovascular disease (CVD) to study potential association with disease risk.

MATERIALS AND METHODS

Circulating levels of vaspin and irisin were assayed in serum from 135 T2DM patients (with and without CVD) and 70 control subjects by ELISA.

RESULTS

Vaspin levels were significantly higher in T2DM patients than in control subjects (6798 ± 3540 pg/ml vs. 3215 ± 3209 pg/ml, p = 0.001) and in CVD patients than in non-CVD patients (7417.3 ± 3507.6 pg/ml vs. 6017.3 ± 3606.4 pg/ml, p = 0.001), with significant positive correlations with BMI, FPG, serum insulin and HOMA-IR. Irisin levels were significantly lower in T2DM patients than in controls (71.15 ± 67.57 ng/ml vs.127 ± 71.57 ng/ml, p = 0.004), and in CVD patients than in non-CVD patients (55.77 ± 54.82 ng/ml vs. 115.5 ± 67 ng/ml, p = 0.003), with significant correlations with HbA1c, HOMA-IR and BMI in diabetic patients, and with HbA1c and TG in CVD patients. Elevated levels of vaspin was associated with 1.7 times increased CVD risk (p = 0.001, OR = 1.7, 95%CI = 1.21-2.39), while lower levels of irisin associated with 1.6 times increased CVD risk (p = 0.007, OR = 1.6, 95%CI = 1.45-2.28). ROC analysis indicated serum vaspin and irisin as independent CVD risk biomarkers with sensitivity, 94% and 73.7%, and specificity, 74% and 74.1%; respectively.

CONCLUSION

Our results indicate that circulating vaspin and irisin are potential new independent CVD risk biomarkers in T2DM.

An update on the role of irisin in the regulation of endocrine and metabolic functions

Irisin is a novel myokine and adipokine that has gained much attention recently due to its mechanisms of action. Irisin is secreted following proteolytic cleavage of its precursor fibronectin type III domain containing 5 (FNDC5). Following its release, irisin exerts its major action by increasing the expression of mitochondrial uncoupling protein 1 (UCP 1), which facilitates the conversion of white adipose tissue (WAT) into beige adipose tissue. Irisin is distributed in various body tissues and several actions have been attributed to its presence in those tissues. It has been suggested that it plays a role in metabolic diseases, ageing, inflammation and neurogenesis. However, the circulating levels of irisin are modulated by several factors such as diet, obesity, exercise, pharmacological agents and different pathological conditions. In this review, we have discussed the mechanisms by which irisin influences the functions of different body systems and how external factors in turn affect the circulating level of irisin. In conclusion, modification of circulating irisin level may help in the management of a variety of endocrine and metabolic disorders.

Relationship of serum irisin levels to prevalence and progression of coronary artery calcification: A prospective, population-based study

BACKGROUND

The mechanisms by which exercise reduces the risk of coronary heart disease remain poorly understood. Irisin, an exercise-induced polypeptide secreted from skeletal muscles, is proposed to potentially mediate beneficial effects of exercise, especially in metabolic regulation and development of atherosclerosis. We examined whether higher serum irisin levels are associated with lower prevalence and progression of coronary atherosclerosis.

METHODS AND RESULTS

We performed a prospective, population-based study of Japanese men aged 40-79 years without known coronary heart disease. We measured baseline serum irisin levels using an enzyme-linked immunosorbent assay and quantified coronary artery calcification (CAC) from serial computed tomography scans. Of 1038 participants (mean age, 63.9 years) at baseline, 670 (64.6%) had prevalent CAC. Of 810 participants at follow-up (median, 5.1 years), 407 (50.3%) experienced CAC progression. In Poisson regression with robust error variance adjusted for age and behavioral factors, serum irisin levels were inversely associated with CAC prevalence (relative risk [RR] of 4th versus 1st quartiles [95% confidence interval], 0.88 [0.78-0.99]; trend P = 0.016) and CAC progression (RR, 0.76 [0.63-0.91]; trend P = 0.002). After further adjustment for cardiometabolic risk factors, the inverse association with CAC prevalence disappeared (RR, 0.95 [0.84-1.08]; trend P = 0.319), but that with CAC progression persisted (RR, 0.77 [0.64-0.93]; trend P = 0.003). These associations were consistent when we applied ordinal logistic regression and across subgroups by cardiometabolic risk factor status.

CONCLUSIONS

Higher serum irisin levels were associated with less burden of coronary atherosclerosis. This association would be mediated through and beyond traditional cardiometabolic pathways.

Decreased level of irisin, a skeletal muscle cell-derived myokine, is associated with post-stroke depression in the ischemic stroke population

Background

Depression is a frequent mood disorder in stroke patient. Our aim was to determine irisin levels in serum and investigate their associations with post-stroke depression (PSD) in a 6-month follow-up study in Chinese patients with first-ever acute ischemic stroke (AIS).

Methods

The subjects were first-ever AIS patients who were hospitalized at three stroke centers during the period from January 2015 to December 2016. Neurological and neuropsychological evaluations were conducted at the 6-month follow-up. Serum irisin concentrations were measured by enzyme-linked immunosorbent assay (ELISA).

Results

During the study period, 1205 patients were included in the analysis. There were 370 patients (30.7%) classified as depression. The depression distribution across the irisin quartiles ranged between 49.8% (first quartile) and 9.9% (fourth quartile). In the patients with depression, serum irisin levels were lower compared with those in patients without depression (P < 0.001). In a multivariate model using the first (Q1) quartile of irisin vs. Q2–4 together with the clinical variables, the marker displayed predictive information and increased risk of PSD by 75% (odds ratio [OR] for Q1, 1.75 [95% confidence interval [CI], 1.15–2.65]). In addition, a model containing known risk factors plus irisin compared with a model containing known risk factors without irisin showed a greater discriminatory ability; the area under the curve (AUC) increased from 0.77 to 0.81 (95% CI, 0.76–0.86).

Conclusions

The data suggested that reduced serum levels of irisin were powerful biological markers of risk of developing PSD even after adjustment by variables. Further studies are necessary to confirm this association, which may open the way to the proposal of new therapeutic options.

Trial registration

ChiCTR-OPC-17013501. Retrospectively registered 23 September 2017

Serum levels of irisin predict short-term outcomes in ischemic stroke

OBJECTIVE

Irisin is a 112-amino acid peptide found in rat and human skeletal muscle after exercise. Previous studies had suggested that higher circulating irisin levels were associated with an increased risk of vascular atherosclerosis and cardiovascular diseases. In this study, we determined irisin levels in serum, and investigated their associations with functional outcomes in a 3-month follow-up study in Chinese patients with first-ever acute ischemic stroke (AIS).

METHODS

From September 2015 to December 2016, consecutive first-ever AIS patients admitted to the Department of Emergency of our hospital were identified. Serum irisin levels were measured at admission. Functional impairment was evaluated at discharge using the modified Rankin scale. The levels of irisin were expressed as median and interquartile ranges [IQR].

RESULTS

The irisin level was obtained in 324 patients (97.6%) with a median value of 291.2 ng/ml (IQR: 214.1-404.2 ng/ml). There were significantly negative correlations between levels of irisin and NHISS (r = -0.272; P < 0.001) and BMI (r = -0.193; P = 0.003). A poor functional outcome was found in 99 patients (30.6%; 95%CI: 25.5-35.6%). The poor functional outcome distribution across the irisin quartiles ranged between 51.9% (first quartile: Q1) to 12.4% (fourth quartile: Q4). In a multivariate model using the Q1 of irisin vs. Q2-4 together with the clinical variables, the marker displayed prognostic information and increased risk of poor outcomes by 94% (OR for Q1, 1.94 [95% CI, 1.19-3.42]; P = 0.018) and mortality 66% (OR for Q1, 1.66 [95% CI, 1.11-3.07]; P = 0.009). In addition, a model containing known risk factors plus irisin compared with a model containing known risk factors without irisin showed a greater discriminatory ability to predict poor outcomes (P = 0.01) and mortality (P = 0.02).

CONCLUSIONS

A low serum irisin level is a predictor of poor early functional outcome in ischemic stroke patients. The underlying mechanisms of these associations remain to be investigated.

Association of Markers of Proinflammatory Phenotype and Beige Adipogenesis with Metabolic Syndrome in Chinese Centrally Obese Adults

BACKGROUND

Visceral adiposity is associated with higher productions of C-reactive protein (CRP) and interleukin-6 (IL-6). Inflammation of obese adipose tissues could contribute to systemic metabolic dysregulation, especially thermogenic activity of white adipose tissues, namely, beige adipogenesis, characterized by altered irisin expression. Thus, we investigated the roles of inflammation and adipocyte beiging in Chinese centrally obese (CO) adults with metabolic syndrome (MetS).

METHODS

This cross-sectional study was conducted on 54 CO and 58 non-CO subjects drawn from 1492 Chinese people with age and sex matched during November 2010 and August 2013. Twenty (37.0%) of the CO subjects fulfilled the IDF worldwide definition of MetS. Serum CRP, IL-6, and irisin levels were examined.

RESULTS

Higher CRP and IL-6, but lower irisin, levels were manifested in MetS versus non-MetS subjects with or without CO. Multiple linear regression identified high-density lipoprotein cholesterol level as the only independent risk factor for irisin level. Categorized by median of CRP and IL-6 levels, a lower irisin level was only observed in high CRP group.

CONCLUSION

Under the condition of central obesity, chronic inflammation and impaired beige adipogenesis are associated with MetS in Chinese adults.

Plasma irisin is elevated in type 2 diabetes and is associated with increased E-selectin levels

Background

Irisin is a hormone released mainly from skeletal muscle after exercise which increases adipose tissue energy expenditure. Adipocytes can also release irisin after exercise, acting as a local adipokine to induce white adipose tissue to take on a brown adipose tissue-like phenotype, suggesting that irisin and its receptor may represent a novel molecular target for the treatment of obesity and obesity-related diabetes. Previous reports provide conflicting evidence regarding circulating irisin levels in patients with type 2 diabetes (T2DM).

Methods

This study investigated plasma irisin concentrations in 79 T2DM individuals, assessing potential associations with measures of segmental body composition, markers of endothelial dysfunction and peripheral blood mononuclear cell telomere length (TL).

Results

Resting, overnight-fasted plasma irisin levels were significantly higher in this group of T2DM patients compared with levels we previously reported in healthy volunteers (p < 0.001). Moreover, plasma irisin displayed a positive correlation with body mass index (p = 0.04), body fat percentage (p = 0.03), HbA1c (p = 0.03) and soluble E-selectin (p < 0.001). A significant negative association was observed between plasma irisin and visceral adiposity (p = 0.006) in T2DM patients. Multiple regression analysis revealed that circulating soluble E-selectin levels could be predicted by plasma irisin (p = 0.004). Additionally, cultured human umbilical vein endothelial cells (HUVEC) exposed to 200 ng/ml irisin for 4 h showed a significant fourfold increase in E-selectin and 2.5-fold increase in ICAM-1 gene expression (p = 0.001 and p = 0.015 respectively), and there was a 1.8-fold increase in soluble E-selectin in conditioned media (p < 0.05).

Conclusion

These data suggest that elevated plasma irisin in T2DM is associated with indices of adiposity, and that irisin may be involved in pro-atherogenic endothelial disturbances that accompany obesity and T2DM. Accordingly, irisin may constitute a potentially novel therapeutic opportunity in the field of obesity and cardiovascular diabetology.