Irisin: a new molecular marker and target in metabolic disorder

Association between coffee intake and skeletal muscle mass among U.S. adults: a population-based study

Background

A limited number of studies have reported that the possible effects of coffee intake on skeletal muscle mass, but the results have been inconsistently conclusive and there are no large sample studies concerning the U.S. population. Therefore, the purpose of our study was to explore the connection between coffee consumption and skeletal muscle mass in U.S. adults.

Methods

The population for this cross-sectional study was drawn from the National Health and Nutrition Examination Survey (NHANES) from 2011 to 2018. Appendicular lean mass was accurately obtained from DXA, and skeletal muscle mass was assessed using appendicular skeletal muscle mass adjusted for body mass index (ASMBMI). Coffee and caffeine consumptions were obtained on a 24-h dietary recall questionnaire. Furthermore, the associations between coffee and caffeine intake and skeletal muscle mass were evaluated using three multiple linear regression models and smoothed curve fitting. Subgroup analyses based on age, gender, ethnicity and body mass index (BMI) were performed to assess the robustness of these relationships.

Results

This cross-sectional survey included a total of 8,333 participants. After adjusting for all covariates, higher intake of coffee, caffeinated coffee, and caffeine was associated with elevated ASMBMI (coffee: β = 0.01, 95% CI: 0.01, 0.02, P-value < 0.001; caffeinated coffee: β = 0.01, 95% CI: 0.01, 0.02, P-value < 0.001; caffeine: β = 0.02, 95% CI: 0.01, 0.04, P-value < 0.001). Meanwhile, smoothed curve fitting showed that coffee, caffeinated coffee, and caffeine intake were linearly and positively associated with ASMBMI. After further stratification by sex, age, and ethnicity, the positive relationships between coffee (especially caffeinated coffee) and caffeine intake and ASMBMI were not modified (P for interaction > 0.05). However, these relationships disappeared when the BMI over 30 kg/m2.

Conclusions

In general, consumption of coffee and caffeine is positively associated with skeletal muscle mass. Therefore, an appropriate increase in coffee and caffeine intake may be advocated in populations at high risk for low skeletal muscle mass.

A comparison of brown fat tissue related hormone levels in metabolically healthy and unhealthy individuals with obesity

PURPOSE

One of the key functions of brown adipose tissue is its positive impact on metabolism. This study aimed to examine the potential involvement of brown fat-related hormones in the development of metabolically healthy obesity. Specifically, we sought to compare the levels of NRG4, FGF21, and irisin between metabolically healthy and unhealthy individuals with obesity.

METHODS

Patients with BMI ≥ 30 kg/m2 and aged between 20 and 50 years were included in the study. Among these patients, those who did not have any metabolic syndrome criteria except for increased waist circumference were defined as metabolically healthy obese. Age, gender, BMI, body fat, and muscle mass, matched metabolically healthy and unhealthy obese groups were compared in terms of FGF21, irisin, and NRG4 levels.

RESULTS

Metabolically healthy and unhealthy obese groups were similar in terms of age and gender. There was no difference between the two groups in terms of BMI, weight, total body fat, muscle, fat-free mass, distribution of body fat and muscle mass. No statistically significant difference was found between irisin, NRG4, and FGF21 levels between metabolically healthy and unhealthy individuals with obesity. It was found that irisin had a significant inverse correlation with BMI and body fat percentage.

CONCLUSION

The present study showed no difference between metabolically healthy and unhealthy obese individuals in terms of irisin, FGF21, and NRG4 levels. The weak association between irisin and BMI and body fat percentage may suggest a potential link between irisin with metabolic health.

Skeletal Muscle-Derived Irisin Enhances Gemcitabine Sensitivity and Suppresses Migration Ability in Pancreatic Ductal Adenocarcinoma

BACKGROUND

High skeletal muscle mass might be a prognostic factor for patients with pancreatic ductal adenocarcinoma (PDAC); however, the underlying reason is unclear. We hypothesized that myokines, which are cytokines secreted by the skeletal muscle, function as suppressors of PDAC. We specifically examined irisin, a myokine, which plays a critical role in the modulation of metabolism, to clarify the anticancer mechanisms.

METHODS

First, the effect of the conditioned medium (CM) from skeletal muscle cells and from irisin-knockdown skeletal muscle cells on PDAC cell lines was evaluated. We then investigated the effects and anticancer mechanism of irisin in PDAC cells, and evaluated the anticancer effect of recombinant irisin in a PDAC xenograft mouse model. Finally, patients undergoing pancreatic resection for PDAC were divided into two groups based on their serum irisin level, and the long-term outcomes were evaluated.

RESULTS

The CM enhanced gemcitabine sensitivity by inducing apoptosis and decreasing cell migration by inhibiting epithelial-mesenchymal transition (EMT) in PDAC cell lines. The CM derived from irisin-knockdown skeletal muscle cells did not affect the PDAC cell lines. The addition of recombinant irisin to PDAC cell lines facilitated sensitivity to gemcitabine by inhibiting the mitogen-activated protein kinase (MAPK) pathway, and decreased migration by inhibiting EMT via the transforming growth factor-β/SMAD pathway. Xenografts injected with gemcitabine and recombinant irisin grew slower than the xenografts injected with gemcitabine alone. The overall survival was prolonged in the high-irisin group compared with that in the low-irisin group.

CONCLUSIONS

Skeletal muscle-derived irisin may affect PDAC by enhancing its sensitivity to gemcitabine and suppressing EMT.

Increased Circulating Irisin Levels in Kidney Transplant Patients: Is There a Connection with Glycaemic Control?

Irisin is a myokine with potential effects on glucose metabolism and the development of diabetes in humans. We analysed irisin serum levels (ISL) in 47 patients without diabetes before and 1, 2, 3, 4 and 5 weeks after kidney transplantation (KTx). All measurements of irisin before KTx levels were lower than 25 ng/mL (median 8.4 ng/mL). We found an outstanding increase in ISL measured after KTx, reaching more than 1000 times in 44% of patients (HIL-high irisin level group). The increase appeared at the first measurement (one week after KTx). Factors connected to the large growth of ISL were, i.e., BMI > 30 (p = 0.04) and subsequent KTx-second and third (p < 0.001). The global mean blood glucose level during the first two weeks after KTx was significantly lower in the HIL group (p = 0.002), the same as the day-by-day analysed mean fasting and postprandial serum glucose in the first days after KTx. In 12 months of observation, diabetes requiring insulin therapy occurred in the HIL group at a rate of 19%, while in the rest of the patients, the rate was 27%, p = 0.526. Irisin levels increase significantly in some patients after kidney transplantation, accompanied by lower blood glucose levels in the early post-transplant period. Whether an increase in irisin levels results in better glycaemic control remains questionable and requires further research, as well as the relationship between irisin levels and the occurrence of PTDM.

Physical exercise for a healthy pregnancy: the role of placentokines and exerkines

Complications such as diabetes and preeclampsia can occur during pregnancy. Moderate-intensity exercise can prevent such complications by releasing placentokines and exerkines, such as apelin, adiponectin, leptin, irisin, and chemerin. Exercise and apelin increase thermogenesis and glucose uptake in pregnancy by activating AMPK, PI3K, PGC-1α, AKT1, UCP3, and sarcolipin. Exercise increases apelin levels to reduce preeclampsia symptoms by increasing eNOS, NO, placental growth factor (PlGF), and VEGF and decreasing levels of fms-like tyrosine kinase 1 (sFlt-1), soluble endoglin (sEng), and oxidative stress. A negative relationship has been reported between plasma leptin and VO2peak/kg and VO2peak in women with gestational diabetes. In active women, decreases in leptin levels reduce the risk of preeclampsia by ~ 40%. Higher adiponectin levels are associated with greater physical activity and lead to increased insulin sensitivity. Increased adiponectin levels in preeclampsia and exercise counteract inflammatory and atherogenic activities while also having vascular protective effects. Exercise increases irisin levels that correlate negatively with fasting glucose, insulin concentration, and glycosylated hemoglobin levels. Irisin augments mRNA expression levels of UCP1 and cell death-inducing DNA fragmentation factor-like effector A (cidea) to cause browning of adipose tissue, increased thermogenesis, and increased energy consumption. Irisin concentrations in mothers with preeclampsia in the third trimester negatively correlate with systolic and diastolic blood pressure. Expression levels of chemerin, IL-6, and TNF-α are increased in gestational diabetes, and the increases in chemerin in late pregnancy positively correlate with the ratio of sFlt-1 to PlGF as a marker of preeclampsia. The effects of physical exercise on placentokines and exerkines in women at various stages of pregnancy remain poorly understood.

Irisin and Cardiometabolic Disorders in Obesity: A Systematic Review

Background

Overweight and obesity are global health issues, impacting a significant portion of young adults. Obesity is a complex condition influenced by genetics and environmental factors, leading to increased susceptibility to cardiovascular diseases (CVDs), hypertension, dyslipidemia, and insulin resistance. Irisin, a protein derived from the cleavage of fibronectin type III domain-containing protein 5, may have relationship with these cardiometabolic diseases.

Objective

This systematic review aims to examine the relationship between serum irisin levels and obesity, particularly in individuals predisposed to cardiovascular risk factors.

Methods

A thorough literature search was conducted in multiple databases, including "Science Direct," "Scopus," "PubMed," and "Lilacs," from July 2020. Inclusion criteria encompassed subjects with metabolic disorders (with or without obesity, BMI ≥30 kg/m2), clinical trials, and observational studies published between 2010 and June 2020. Exclusion criteria were animal studies, meta-analyses, systematic reviews, studies evaluating only healthy subjects, and those investigating disorders beyond cardiometabolic diseases.

Results

Out of 151 identified articles, 30 met the inclusion criteria. These studies, published between 2013 and 2020, assessed adults (≥21 years) and included 26 observational studies and 4 clinical trials (n = 7585 subjects). All studies examined irisin's role in obesity and CVDs, often including associated diseases such as type 2 diabetes and hypertension. Despite varying sample sizes, the samples within the articles were homogeneous. Observational studies exhibited a low risk of bias in at least 60% of the evaluated domains. Clinical trials demonstrated a low risk of bias in at least 50% of the domains. Limitations. Although the systematic review provides valuable insights, it is limited by the available literature and the varying methodologies used across studies.

Conclusion

The review suggests that irisin plays a significant role as both a preventive measure and a biomarker for comorbidities linked to obesity and cardiometabolic disorders. Future research should focus on standardized irisin measurement methods and diverse populations to further elucidate its mechanisms of action.

Circulating and/or cutaneous irisin resistance: A novel link among androgenetic alopecia, comorbid metabolic syndrome and cardiovascular risks

BACKGROUND

Androgenetic alopecia (AGA) is a common cause of hair loss in both genders that may be associated with disturbed systemic metabolism. Irisin is a hormone-like myokine that greatly influences systemic metabolism and is linked to cardiovascular diseases.

AIM

To detect irisin role in AGA and its associated metabolic syndrome (MetS) and cardiovascular risk.

PATIENTS/METHODS

This case-control study included 44 AGA patients of both genders and 22 healthy individuals. Serum irisin level was measured using ELISA and scalp biopsy was taken to detect irisin immunohistochemically. Carotid Doppler ultrasonography was performed to measure carotid intima media thickness (CIMT).

RESULTS

Higher serum irisin was significantly detected in AGA patients (p ˂ 0.001), and in males (p = 0.01) particularly severe cases (p ˂ 0.001). It was significantly higher in AGA patients presenting with MetS and those suffering from dyslipidemia (p ˂ 0.001 for both). Multivariate regression analysis proved BMI (p = 0.01) and serum irisin (p = 0.02) as independent predictors of CIMT abnormality among AGA patients. Regarding cutaneous irisin expression, the epidermal H-score was significantly higher in AGA patients with MetS compared to those without (p = 0.04). Epidermal H-score ˃100 was significantly associated with male gender (p = 0.05), severe AGA (p = 0.02), MetS (p = 0.03), dyslipidemia (p = 0.03), and abnormal CIMT (p = 0.03).

CONCLUSION

High serum irisin and upregulated epidermal irisin expression are associated with the incidence of MetS, dyslipidemia, and CIMT abnormality among AGA patients. This may indicate resistance to irisin, which hinders its favorable cardiometabolic actions. Further studies are warranted to investigate the concept of irisin resistance in AGA patients, which was uniquely discussed in the present study.

Metformin Protects Rat Skeletal Muscle from Physical Exercise-Induced Injury

Metformin (Met) is a drug commonly prescribed in type 2 diabetes mellitus. Its efficacy is due to the suppression of hepatic gluconeogenesis, enhancement of peripheral glucose uptake and lower glucose absorption by the intestine. Recent studies have reported Met efficacy in other clinical applications, such as age-related diseases. Despite the wide clinical use of Met, its mechanism of action on muscle and its effect on muscle performance are unclear. We investigated the effects of Met combined with training on physical performance (PP) in healthy rats receiving Met for 8 weeks while undergoing daily moderate exercise. We evaluated the following: PP through graded endurance exercise test performed before the beginning of the training protocol and 48 h before the end of the training period; blood ALT, AST, LDH and CK-MB levels in order to address muscle damage; and several blood and muscle myokines and the expression of factors believed to be involved in muscle adaptation to exercise. Our data demonstrate that Met does not improve the positive effects of exercise on performance, although it protects myocytes from exercise-induced damage. Moreover, given that Met positively affects exercise-induced muscle adaptation, our data support the idea of the therapeutic application of Met when muscle function and structure are compromised.

Irisin as a Novel Biomarker of Subclinical Atherosclerosis in Severe Obesity

Severe obesity (SO) can accelerate atherosclerosis and the onset of acute cardiovascular events. The diagnosis of atherosclerosis in the context of a high body mass index (BMI) can be challenging, making the identification of biomarkers clinically relevant. We aimed to assess the usefulness of irisin as a biomarker for subclinical atherosclerosis in participants with SO. This prospective observational study included 61 participants undergoing bariatric surgery for SO, defined as a BMI >40 kg/m² or >35 kg/m² with at least one comorbidity. Atherosclerotic plaques were detected by ultrasound. Plasma samples were obtained 1 month before and at 6 and 12 months after bariatric surgery to measure irisin by ELISA. Additionally, subcutaneous samples of adipose tissue were taken and genotyped to identify irisin polymorphism rs3480. Irisin levels were positively correlated with BMI (r = 0.23, p = 0.0064), negatively correlated with atheroma-related parameters (e.g., carotid intima-media thickness), and lower in subjects with atheroma (p < 0.0002). Irisin also showed good overall accuracy for discriminating plaque presence (AUC, 0.81; 95% CI, 0.6956-0.9156). However, the rs3480 polymorphism correlated with neither the irisin levels nor the presence of atheromas. Iirisin could identify subclinical atherosclerosis in SO and might facilitate clinical diagnosis.

Proteomic Analysis of Skeletal Muscle and White Adipose Tissue after Aerobic Exercise Training in High Fat Diet Induced Obese Mice

Obesity is associated with excessive fat accumulation in adipose tissue and other organs, such as skeletal muscle, whereas aerobic exercise (AE) plays an important role in managing obesity through profound protein regulation. Our study aimed to investigate the impact of AE on proteomic changes in both the skeletal muscle and the epididymal fat pad (EFP) of high-fat-diet-induced obese mice. Bioinformatic analyses were performed on differentially regulated proteins using gene ontology enrichment analysis and ingenuity pathway analysis. Eight weeks of AE significantly reduced body weight, increased the serum FNDC5 level, and improved the homeostatic model assessment of insulin resistance. A high-fat diet caused alterations in a subset of proteins involved in the sirtuin signaling pathway and the production of reactive oxygen species in both skeletal muscle and EFP, leading to insulin resistance, mitochondrial dysfunction, and inflammation. On the other hand, AE upregulated skeletal muscle proteins (NDUFB5, NDUFS2, NDUFS7, ETFD, FRDA, and MKNK1) that enhance mitochondrial function and insulin sensitivity. Additionally, the upregulation of LDHC and PRKACA and the downregulation of CTBP1 in EFP can promote the browning of white adipose tissue with the involvement of FNDC5/irisin in the canonical pathway. Our study provides insights into AE-induced molecular responses and may help further develop exercise-mimicking therapeutic targets.

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.

Molecular Basis of Irisin Regulating the Effects of Exercise on Insulin Resistance

Insulin resistance is recognized as one major feature of metabolic syndrome, and frequently emerges as a difficult problem encountered during long-term pharmacological treatment of diabetes. Insulin resistance often causes organs or tissues, such as skeletal muscle, adipose, and liver, to become less responsive or resistant to insulin. Exercise can promote the physiological function of those organs and tissues and benefits insulin action via increasing insulin receptor sensitivity, glucose uptake, and mitochondrial function. This is done by decreasing adipose tissue deposition, inflammatory cytokines, and oxidative stress. However, understanding the mechanism that regulates the interaction between exercise and insulin function becomes a challenging task. As a novel myokine, irisin is activated by exercise, released from the muscle, and affects multi-organ functions. Recent evidence indicates that it can promote glucose uptake, improve mitochondrial function, alleviate obesity, and decrease inflammation, as a result leading to the improvement of insulin action. We here will review the current evidence concerning the signaling pathways by which irisin regulates the effect of exercise on the up-regulation of insulin action in humans and animals.

The role of a recently discovered peptide—irisin—in physiological and pathological processes

Irisin, a cleaved fragment of fibronectin type III domain-containing protein 5 (FNDC5), was originally described as a factor stimulating browning of white adipose tissue, produced during physical exercise by skeletal muscles. However, irisin is not only a new and promising biomarker of metabolism; its expression has been found in a wide variety of tissues and organs such as the peripheral nerves, stomach, pancreas, and skin, and recent data also indicate its role in cancer. Numerous studies focus on the protective role of this protein, which could become an important factor in predicting disease risk, disease prognosis, or possible metastases in cancer patients. Possible use of irisin in therapy is also worth considering. The aim of this paper is to systematize knowledge on the role of irisin in patients and to draw attention to its role in skin diseases including acne vulgaris, psoriasis vulgaris, and hidradenitis suppurativa.

Irisin Acts via the PGC-1α and BDNF Pathway to Improve Depression-like Behavior

Depression is the most prevalent psychiatric disorder experienced by the world's population. Mechanisms associated with depression-like behavior have not been fully investigated. Among the therapeutic solution for depression, exercise is considered an important regulator attenuating depressive neuropathology. Exercise has been reported to boost the secretion of myokines such as irisin and myostatin in skeletal muscles. Myokines secreted during exercise are involved in various cellular responses including the endocrine and autocrine systems. Especially, irisin as a cleaved version of fibronectin domain-containing protein 5 has multiple functions such as white fat-browning, energy expenditure increase, anti-inflammatory effects, and mitochondrial function improvement in both systemic circulation and central nervous system. Furthermore, irisin activates energy metabolism-related signaling peroxisome proliferator-activated receptor-gamma coactivator-1 alpha and memory formation-related signaling brain-derived neurotrophic factor involved in depression. However, the role and mechanism of irisin in depression disorder is not obvious until now. Here, we review recent evidences regarding the therapeutic effect of irisin in depression disorder. We suggest that irisin is a key molecule that suppresses several neuropathological mechanisms involved in depression.

Effects of GLP-1 receptor agonists on myokine levels and pro-inflammatory cytokines in patients with type 2 diabetes mellitus

BACKGROUND AND AIMS

To evaluate the change in circulating serum irisin and interleukin-6 (IL-6), in patients with type 2 diabetes mellitus (T2DM) after 6 and 12 months of GLP-1 treatment.

METHODS AND RESULTS

Eighty-five patients with T2DM inadequately controlled with insulin or other hypoglycaemic drugs were added to dulaglutide (N° = 44) and liraglutide (N° = 41) treatment. After 6 months of GLP-1 analogues a significant decrease in BMI (p < 0.001), waist circumference (WC) (p < 0.001), fasting blood glucose (p < 0.001), HbA1c (p < 0.001), total cholesterol (p < 0.001), LDL-cholesterol (p = 0.003), triglycerides (p = 0.017), IL-6 (p = 0.045) and a significant increase in serum irisin (p < 0.001) were observed compared to baseline. After 12 months of treatment no significant differences were found compared to the levels at 6 months. The change in irisin from baseline (Δ_irisin) was significantly related to the changes in total-cholesterol (Δ_total-cholesterol) (r = -0.293; p = 0.020), while the change in IL-6 (Δ_IL-6) was significantly related to the changes in WC (Δ_WC) (r = 0.347; p = 0.006).

CONCLUSIONS

Additive treatment with GLP1-analogues results in an increase in serum circulating irisin levels and a decrease in IL-6. The post-treatment change in irisin was correlated with a decrease in total cholesterol, while the change in IL-6 was correlated with a decrease in WC.

MAP/Microtubule Affinity Regulating Kinase 4 Inhibitory Potential of Irisin: A New Therapeutic Strategy to Combat Cancer and Alzheimer's Disease

Irisin is a clinically significant protein playing a valuable role in regulating various diseases. Irisin attenuates synaptic and memory dysfunction, highlighting its importance in Alzheimer's disease. On the other hand, Microtubule Affinity Regulating Kinase 4 (MARK4) is associated with various cancer types, uncontrolled neuronal migrations, and disrupted microtubule dynamics. In addition, MARK4 has been explored as a potential drug target for cancer and Alzheimer's disease therapy. Here, we studied the binding and subsequent inhibition of MARK4 by irisin. Irisin binds to MARK4 with an admirable affinity (K = 0.8 × 107 M-1), subsequently inhibiting its activity (IC50 = 2.71 µm). In vitro studies were further validated by docking and simulations. Molecular docking revealed several hydrogen bonds between irisin and MARK4, including critical residues, Lys38, Val40, and Ser134. Furthermore, the molecular dynamic simulation showed that the binding of irisin resulted in enhanced stability of MARK4. This study provides a rationale to use irisin as a therapeutic agent to treat MARK4-associated diseases.

Circulating IRAPe, Irisin, and IL-34 in Relation to Insulin Resistance in Patients With Type 2 Diabetes

PURPOSE

This study aimed to evaluate the role of the extracellular part of insulin-regulated aminopeptidase (IRAPe), interleukin (IL)-34, irisin, and visfatin in the development of insulin resistance (IR) in patients with type 2 diabetes mellitus (T2DM).

METHODS

This observational parallel-group study was conducted in 60 subjects without T2DM who served as a control group and 60 patients with newly diagnosed T2DM. The 2 groups were matched for age, sex ratio, and body mass index. Anthropometric parameters; fasting blood glucose; fasting plasma insulin; Homeostatic Model Assessment for IR (HOMA-IR) index; glycated hemoglobin (HbA_1c); and circulating levels of IL-34, visfatin, irisin, and IRAPe were assessed.

RESULTS

The group with T2DM showed significantly higher IL-34 and visfatin levels and significantly lower irisin and IRAPe levels as compared to the healthy control group. IL-34 and visfatin were significantly positively correlated with fasting blood glucose, fasting plasma insulin, HOMA-IR, and HbA_1c. On the other hand, irisin and IRAPe were significantly negatively correlated with fasting blood glucose, fasting plasma insulin, HOMA-IR, and HbA_1c. IL-34 was positively associated with visfatin, while negatively associated with both irisin and IRAPe.

IMPLICATIONS

IL-34, visfatin, irisin, and IRAPe may play a vital role in T2DM and in diabetes-associated IR. Additionally, IRAPe may represent a useful and direct marker for use in the detection of IR in the diabetic population. ClinicalTrials.gov identifier: NCT04107259.

Effect of Irisin on LIF and integrin αvβ3 in rats of implantation failure

OBJECTIVE

The aim of this study is to investigate the effect of irisin on leukemia inhibitory factor (LIF) and integrin αvβ3 in implantation failure uterus.

METHODS

Early pregnant rats were randomly divided into normal group (N), mifepristone treated group (M), irisin group (I) and progestin group (P). The implantation failure model was established using mifepristone. Second, we evaluated the average number of embryos and detected the expression of LIF and integrin αvβ3 protein and mRNA in endometrium.

RESULTS

Compared with group M, the average number of embryos was significantly higher in group N, P and I, the expression of LIF and integrin αvβ3 in endometrium was significantly higher in group N, P and I.

CONCLUSION

Irisin could improve the poor receptive state of endometrium by promoting LIF and integrin αvβ3 secretion to improve blastocyst implantation in rats of implantation failure.

Serum Irisin Levels in Central Precocious Puberty and Its Variants

AIM

The exact mechanisms that trigger the onset of puberty are not well known. Adipomyokines are postulated to stimulate the central neural network. In the present study, we investigated irisin levels in girls with central precocious puberty (CPP), slowly progressing precocious puberty (SPPP), or premature thelarche (PT); we also studied prepubertal girls and to determine if this adipomyokine could be used as a marker in this context.

METHODS

A total of 94 girls including 33 with CPP, 31 with precocious puberty (PP) variants (SPPP or PT), and 30 healthy controls were enrolled to the study. The mean irisin levels were compared between groups. The bivariate correlations of irisin levels with clinical and laboratory parameters were assessed. Multivariate linear regression analysis was performed to determine independent predictive factors of irisin levels.

RESULTS

Irisin levels were higher in the CPP group compared with the other groups (CPP group: 723.25 ± 62.35 ng/mL; PP variants group: 529.60 ± 39.66 ng/mL; and control group: 325.03 ± 27.53 ng/mL) (P < 0.001). Irisin levels were positively correlated with body mass index standard deviation scores (BMI-SDS), height-SDS, weight-SDS, bone age, uterus long axis, ovary size, baseline FSH and LH, and peak LH levels. Multivariate linear regression analysis revealed that irisin levels had the strongest correlation with peak LH. The other independent predictive factor of irisin levels was BMI-SDS.

CONCLUSIONS

The mean irisin levels were higher in patients with CPP compared with other groups. The results of this study imply that increased irisin levels may be used as a marker of CPP provided that these findings are confirmed in larger prospective studies.

Irisin in Liver Cirrhosis

Background: Sarcopenia is a prevalent muscle abnormality characterized by progressive and generalized loss of skeletal muscle mass and strength, common among patients with decompensated advanced chronic liver disease (dACLD). Irisin is a recently identified myokine, which is mainly expressed and secreted by skeletal muscle. Pointing to the essential role of irisin in metabolic regulation and energy expenditure we hypothesize that it plays an important role in cirrhosis development and progression. Aim: To assess irisin serum levels in patients with dACLD, with different cirrhosis stage and etiology. To analyze relationship between sarcopenia and irisin serum levels. Methods: Serum irisin concentrations were measured with commercially available ELISA kits in 88 cirrhotic patients. Recorded parameters of muscle mass were hand-grip strength (HGS), mid-arm muscle circumference (MAC), and transversal psoas muscle index (TPMI). Results: There was no difference in serum irisin levels between cirrhotic patients with different Child-Pugh (CTP) and model of end-stage liver disease (MELD) score, and those with and without ascites. The Liver Frailty Index (LFI) was significantly higher in patients with more advanced liver disease according to CTP and MELD. There was no association between serum irisin level with MAC (r = 0.04, p = 0.74) nor with TPMI (r = 0.20, p = 0.06). We observed significant negative correlation between serum irisin level and age (r = −0.35, p < 0.001). Conclusions: Serum irisin levels did not correlate with sarcopenia. There was no difference in serum irisin levels between cirrhotic patients with and without diabetes. There was no difference in serum irisin levels among patients with more severe dACLD, although we observed significant LFI increase among patients with more advanced liver disease.

The Potential Role of Irisin in Vascular Function and Atherosclerosis: A Review

Exercise is an effective intervention for both the prevention and the treatment of obesity and insulin resistance because skeletal muscle secretes many bioactive proteins that contribute to the beneficial effect of exercise. It has been revealed that irisin plays an important role in metabolic homeostasis and both acute and chronic exercises increase circulating irisin in experimental animal models and in humans. Although previous studies have reported that the irisin-related signaling mechanism may play a beneficial role in the treatment of metabolic diseases including obesity, metabolic syndrome, insulin resistance, and diabetes mellitus, studies on whether irisin plays a key role in vascular function and vascular complications are still insufficient. Therefore, the current review aims to summarize the accumulating evidence showing the potential role of irisin, especially in vascular reactivity and vascular abnormalities such as atherosclerosis.

Serum irisin levels in metabolically healthy versus metabolically unhealthy obesity: A case-control study

Background: Metabolically healthy obese (MHO) individuals appear to be protected or more resistant to the progression of obesity-related metabolic disorders. Hormonal regulation associated with adipose or muscular tissues such as irisin and leptin may facilitate the healthy metabolic profile of MHO cases. In this case-control study, the differences between serum level of irisin was investigated in metabolically unhealthy obese (MUO) and metabolically healthy obese (MHO) individuals.

Methods: The study participants included obese individuals with metabolic syndrome (MetS) (n=51) and 2 control groups that included weight matched cases without MetS (n=51) and normal weight cases without MetS (n=51). Diagnosis of MetS was made based on the Adult Treatment Panel III (ATPIII) criteria. Serum levels of leptin and irisin were determined by enzyme-linked immune-sorbent assay (ELISA) kit. Receiver Operator Characteristic (ROC) curve, multiple linear regression, and one-way ANOVA analysis were used in SPSS 16 software. Significant level was set at 0.05.

Results: Based on the statistical analysis, serum levels of irisin were 2.91±1.6, 3.14±1.4, and 4.47±3.23 (ng/mL) in MUO, MHO, and nonobese metabolically healthy participants, respectively (P = 0.001). Also, serum levels of leptin were 14.06±12.4, 11.2±9.3, and 7.09±7.1 (ng/mL) in MUO, MHO, and nonobese metabolically healthy cases, respectively (p=0.002). After adjusting for demographic variables, a significant association was found between irisin and study groups (β = 0.77, P = 0.001), weight (β=-0.03, p=0.014), BMI (β=-0.11, p=0.006), TG (β=-0.003, p=0.025), fat mass (β=-0.04, p=0.046), and fat free mass (β=0.08, p=0.014).

Conclusion: Obese patients with/without MetS had lower level of irisin than normal weight participants.

Association between plasma irisin and glucose metabolism in pregnant women is modified by dietary n-3 polyunsaturated fatty acid intake

AIMS/INTRODUCTION

The role of irisin in maternal glucose metabolism and how it would respond to dietary n-3 polyunsaturated fatty acid (n-3 PUFA) intake remains unclear. This study aimed to explore whether maternal plasma irisin is associated with glucose metabolism and whether this association is modified by dietary n-3 PUFA.

MATERIALS AND METHODS

A total of 932 pregnant women (20-28 weeks' gestation) aged 20-45 years were recruited. Dietary n-3 PUFA was estimated using a validated quantitative food frequency questionnaire. Plasma irisin and insulin were tested by enzyme-linked immunosorbent assay, and insulin resistance (IR) was estimated using the homeostatic model assessment (HOMA). Gestational diabetes mellitus was diagnosed with a 75-g oral glucose tolerance test. Adjusted multivariable linear regression and logistic regression were carried out to examine the associations between plasma irisin and glucose metabolism. The moderating effect of dietary n-3 PUFA intake was determined by fully multiplicative models by including the interaction term.

RESULTS

Maternal plasma irisin was negatively associated with HOMA-IR and oral glucose tolerance test 0 h glucose level (β -0.250, -0.067; corrected P-value for false discovery rate = 0.012, 0.018, respectively), positively associated with HOMA of insulin sensitivity (β 0.028; corrected P-value for false discovery rate = 0.012), but not associated with postprandial glucose or the risk of gestational diabetes mellitus. Furthermore, we found a moderating effect of dietary n-3 PUFA on the relationships of plasma irisin with HOMA-IR and HOMA of insulin sensitivity; these associations were strengthened with increased n-3 PUFA intake (β -0.037, 0.004; P = 0.014, 0.041, respectively).

CONCLUSIONS

Plasma irisin was negatively associated with HOMA-IR and fasting glucose, whereas it was positively associated with HOMA of insulin sensitivity in pregnant women. We first showed that these associations were modified by dietary n-3 PUFA intake.

Effect of Long-Term Moderate Physical Exercise on Irisin between Normal Weight and Obese Men

BACKGROUND

Irisin is a myokine that has a beneficial effect on obesity and glucose metabolism by increasing energy expenditure. This study aims to investigate the effect of long-term moderate physical exercise on irisin levels and its correlations with body mass index (BMI), waist circumferences (WC), and metabolic parameters in normal weight and obese males. Material and method. A follow-up case-control study of sixty male participants, comprised of thirty normal weight and thirty obese, who had undergone supervised long-term moderate physical exercises for six months. Serum irisin levels, fasting blood glucose, serum insulin, homeostatic model assessment of the insulin resistance index (HOMA-IR), and β-cell function (HOMA-B2) were assessed.

RESULTS

Long-term moderate exercise induced elevation of the irisin level significantly (P < 0.0001) with significant reduction of the BMI, WC, fasting blood glucose, insulin, HOMA-IR, and HOMA-B2 levels (P < 0.0001) in comparison between obese and normal weight groups. There are significant differences for each parameter in each obese and normal weight group before and after physical exercise with exception of the BMI and WC in the normal group. Significant negative correlations were shown between irisin and blood glucose and insulin and HOMA-IR levels in the obese group and normal weight group.

CONCLUSION

Irisin improves glucose homeostasis after long-term moderate physical exercises, suggesting that irisin could have regulatory effect on glucose, insulin resistance, and obesity and it could be used as a potential therapy for obesity and insulin resistance.

Physical Activity-Dependent Regulation of Parathyroid Hormone and Calcium-Phosphorous Metabolism

Exercise perturbs homeostasis, alters the levels of circulating mediators and hormones, and increases the demand by skeletal muscles and other vital organs for energy substrates. Exercise also affects bone and mineral metabolism, particularly calcium and phosphate, both of which are essential for muscle contraction, neuromuscular signaling, biosynthesis of adenosine triphosphate (ATP), and other energy substrates. Parathyroid hormone (PTH) is involved in the regulation of calcium and phosphate homeostasis. Understanding the effects of exercise on PTH secretion is fundamental for appreciating how the body adapts to exercise. Altered PTH metabolism underlies hyperparathyroidism and hypoparathyroidism, the complications of which affect the organs involved in calcium and phosphorous metabolism (bone and kidney) and other body systems as well. Exercise affects PTH expression and secretion by altering the circulating levels of calcium and phosphate. In turn, PTH responds directly to exercise and exercise-induced myokines. Here, we review the main concepts of the regulation of PTH expression and secretion under physiological conditions, in acute and chronic exercise, and in relation to PTH-related disorders.

A pilot study on the relation between irisin single-nucleotide polymorphism and risk of myocardial infarction

BACKGROUND

Myocardial infarction (MI) is the major cause of death and disability worldwide. Many recent studies revealed the relationship between circulating irisin levels, endothelial dysfunctions and subclinical atherosclerosis in adult patients.

OBJECTIVES

The aim of this study was to investigate the distribution of Irisin gene single nucleotide polymorphism in patients with MI and its association with other clinical and laboratory variables in these patients.

PATIENTS AND METHODS

This study was carried out in 100 patients with MI, and 100 healthy subjects served as controls. All studied subjects underwent laboratory investigations, including measurement of total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-c) high-density lipoprotein cholesterol (HDL-c), creatinine kinase-MB (CK-MB), troponin I (TnI) and genotyping of rs 3480 and rs726344 of Irisin genes using the TaqMan Allelic Discrimination assay technique.

RESULTS

There was a significant difference of Irisin genotypes in patients when compared to controls. By estimating odd ratio (OR) an association was found between G allele of rs 3480 and A allele of rs726344with increase the risk of developing myocardial infarction by 4.03 and 3.47 fold respectively. GG of rs 3480 carriers had significantly increased Troponin I and triglyceride levels, while GA carriers of rs726344 had significantly increased CKMB, Total cholesterol, LDLc, HDLc, troponin I and triglyceride levels compared with other genotypes.

CONCLUSION

G allele of rs 3480 and A allele of rs726344can considered as genetic risk factors for MI; these findings could have an impact on preventive strategy for myocardial infarction.

Exercise-Induced Circulating Irisin Level Is Correlated with Improved Cardiac Function in Rats

Irisin, a recently identified myokine, plays an important physiological role in modulating energy homeostasis. However, the role of irisin in cardiac function during exercise has not been evaluated. In this study, we investigated the effect of exercise on irisin, pro-inflammatory cytokines, and cardiac function during 12 weeks of exercise in rats. Eight-week-old Sprague-Dawley male rats were randomly divided into two groups (n = 9 per group): sedentary control (CON) and exercise (EXE) groups. The EXE group was trained on a motorized treadmill at 20 m/min, for 60 min/day, five times/week for 12 weeks. The EXE group showed a decrease in abdominal visceral fat (p < 0.05), epididymal fat (p < 0.01), and total cholesterol (TC) (p < 0.05) and an increase in irisin levels (p < 0.01). Irisin negatively correlated with abdominal visceral (p < 0.05) and epididymal fat (p < 0.05) and positively correlated with the ejection fraction (p < 0.05), fractional shortening (p < 0.05), and cardiac output (p < 0.05). In conclusion, exercise decreases the abdominal visceral and epididymal fat and TC levels, possibly caused by elevated irisin levels, thus improving the cardiac function. This suggests that exercise-induced circulating irisin levels correlate with improved cardiac function in rats.

Vitamin D supplementation improves SIRT1, Irisin, and glucose indices in overweight or obese type 2 diabetic patients: a double-blind randomized placebo-controlled clinical trial

BACKGROUND

Vitamin D (VD) may increase sirtuin 1 (SIRT1) and subsequently PPAR-γ coactivator 1α (PGC-1α) and irisin levels and these improvements may reduce insulin resistance (IR). The aim was to assess the effects of vitamin D supplementation on SIRT1, irisin, and IR in overweight/obese type 2 diabetes (T2D) patients.

METHODS

Ninety T2D males and females were recruited as a clinical trial study (mean of age and body mass index (BMI) of intervention and placebo groups were 50.05 ± 10.17 and 50.36 ± 10.2 yrs. and 31.37 ± 3.4 and 30.43 ± 3.2 kg/m², respectively). The inclusion criteria were T2D, VD deficient, BMI > 25 kg/m², and serum HbA1c < 8.5%. The exclusion criteria were using vitamin and mineral supplements, having any acute disease, recent modifying dose or type of drugs. The supplementation was 50,000 IU/week VD or placebo for 8 weeks. The demographic characteristics, anthropometrics, dietary intakes and physical activity status, sun exposure status, fasting blood sugar (FBS) and insulin, glycosylated hemoglobin (HbA1c), irisin, SIRT1, 25-hydroxy D3 (25(OH)VD), homeostasis model assessment of insulin resistance (HOMA-IR), and quantitative insulin sensitivity check index (QUICKI) were determined. The significant P-value was ≤0.05.

RESULTS

The increase of serum VD, SIRT1, and irisin in the intervention group was significant (p < 0.001). HbA1c was decreased significantly by 1%. The changes in the other glucose indices (FBS, insulin, and IR) were non-significant.

CONCLUSIONS

VD supplementation may improve T2D by decreasing HbA1c and increasing SIRT1 and irisin in VD deficient T2D patients. Further trials are suggested.

TRIAL REGISTRATION

Iranian Registry of Clinical Trials, IRCT201604202365N11. Registered 21/08/2016, http://en.irct.ir/trial/2019.

Relationship of Vitamin D-Deficient Diet and Irisin, and Their Impact on Energy Homeostasis in Rats

Background and Objective

Previous studies have identified the role of irisin and vitamin D in energy homeostasis. However, the effect of irisin and vitamin D on energy regulation has not been thoroughly investigated. Therefore, in this study, the effects of a vitamin D-deficient diet and irisin on total energy expenditure (TEE), food intake, and blood metabolites were investigated in rats.

Methods

Sixteen healthy weaned male albino rats were randomly divided into two groups: a group fed a normal balanced growth diet (group A: n = 8) and a group fed a normocalcemic diet that is vitamin D deficient with limited ultraviolet (UV) light exposure (group B, n = 8). After 6 weeks, the volumes of respiratory gases were measured by open-circuit indirect calorimetry. Serum irisin, 25-OHVD₃, calcium, insulin, and glucose levels were measured using ELISA. The respiratory quotient (RQ), energy expenditure, and Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) were calculated.

Results

Rats with hypovitaminosis D were hypoirisinemic. Food intake, RQ (to the range of using endogenous fat), and glucose levels reduced significantly, while insulin levels increased. Body weight and TEE were non-significant changed. Additionally, irisin was strongly and positively correlated with body weight under normal conditions (r = 0.905, p < 0.01), and a moderate negative correlation in group B (r = −0.429, p < 0.05). TEE and irisin showed no significant correlation.

Conclusion

This study demonstrated that the early changes in energy homeostasis and irisin levels during states of hypovitaminosis D are affected by long-term consumption of a vitamin D-deficient diet with limited UV exposure.

Serum Irisin: Pathogenesis and Clinical Research in Cardiovascular Diseases

Recently, muscular function/dysfunction has gained importance in the maintenance of metabolic homeostasis in cardiovascular diseases. Skeletal muscle plays a vital role in coordinating the activity and metabolism of endocrine organs by secreting many myokines, especially irisin. Irisin is a polypeptide hormone consisting of 112 amino acids secreted into the blood from muscle and adipose tissues. Serum irisin levels are associated with cardiometabolic risk factors such as obesity and insulin resistance as defined by homeostatic model assessment. Irisin reduces endothelial damage by inhibiting inflammation and oxidative stress, thus playing a key role in maintaining endothelial cell function. Unsurprisingly, low irisin levels cause endothelial dysfunction and increase the incidence of atherosclerosis. We aimed to summarize the studies on this issue since we have not found any review in the literature on the role of serum irisin levels in the process of atherosclerosis and other cardiovascular events in cardiovascular diseases.

Beta-Aminoisobutyric Acid Inhibits Hypothalamic Inflammation by Reversing Microglia Activation

Beta-aminoisobutyric acid (BAIBA), a natural thymine catabolite, is involved in the beneficial effects of exercise on metabolic disorders. In particular, it has been reported to reverse the inflammatory processes observed in the peripheral organs of animal models of obesity. Therefore, this study aimed to investigate whether BAIBA improves hypothalamic inflammation, which is also tightly coupled with the development of obesity. We observed that treatment with BAIBA effectively reversed palmitic acid-induced hypothalamic inflammation and microglial activation in vivo. Consistent with these findings, we confirmed that BAIBA reversed body weight gain and increased adiposity observed in mice fed with a high-fat diet. Collectively, the current findings evidence the beneficial impacts of BAIBA on the imbalance of energy metabolism linked to hypothalamic inflammation.

The diagnostic and prognostic roles of serum irisin in bladder cancer

BACKGROUND

Egypt is among the countries with the highest incidence of bladder cancer (BC). Adipokines involved in BC development. This study aimed to examine the diagnostic and prognostic roles of irisin in BC through its function as an adipokine.

PATIENTS AND METHODS

This study included 150 subjects; 75 patients newly diagnosed as BC and 75 apparently healthy subjects. Serum irisin levels were quantified by enzyme-linked immunosorbent assay.

RESULTS

Serum irisin levels exhibited significantly lower levels in BC patients compared to controls (1.07 [0.51-1.96] and 1.8 [0.5-2.44] µg/mL), respectively (P < 0.001). Serum irisin was positively correlated with BMI (r = 0.386, P = 0.001) and negatively correlated with serum cholesterol (r = -0.58, P < 0.0001). Irisin had 74.7% sensitivity and 90.7% specificity at a cutoff point of ≤1.2 µg/mL. Serum irisin levels reduction can predict the BC stages, when adjusted for BMI and serum cholesterol level, serum irisin had an adjusted odds ratio of 14 (P = 0.001). Low serum irisin patients had a higher mortality rate when compared to those with high levels (38.2% vs 5%).

CONCLUSION

BC patients had significantly lower levels of serum irisin. Serum irisin showed acceptable performance criteria in BC diagnosis. It had a limited role in BC grading but showed a decreasing trend in different BC stages. Serum irisin seems to be an excellent diagnostic and prognostic marker for BC.

Antroquinonol Attenuated Abdominal and Hepatic Fat Accumulation in Rats Fed an Obesogenic Diet

An imbalance of energy intake and expenditure leads to fat accumulation and metabolic disorders. The aim of the study was to investigate the effects of antroquinonol on diet-induced obesity. Thirty-two rats were divided into a control group (C), an obesogenic group (OB), and two experimental groups consuming 25 (OB-AQ25) and 50 mg/kg (OB-AQ50) antroquinonol (n = 8). After a 12-week experimental period, we collected blood, liver, abdominal fat, and gastrocnemius muscle tissue for analysis. The obesogenic diet induced greater weight gain and fat accumulation, and increased hepatic lipids, and tumor necrosis factor-α and interleukin-1β concentrations in rats. Antroquinonol consumption reduced epididymal and hepatic lipids and inflammatory cytokines. We found that antroquinonol upregulated hepatic adenosine monophosphate-activated protein kinase and downregulated sterol regulatory element-binding protein-1 protein expressions and downregulated fatty acid synthase mRNA expression. In addition, gastrocnemius fibronectin type III domain containing 5 protein expression was also higher in the B group. In conclusion, our results suggested that consuming antroquinonol may ameliorate diet-induced abdominal and hepatic fat accumulation. PRACTICAL APPLICATION: Antroquinonol is a bioactive compound derived from Antrodia camphorate which is traditionally used in Chinese medicinal cuisine, and is used for developing functional foods in Taiwan. This is the first study investigating the possible effects of antroquinonol on obesity and we found that antroquinonol can ameliorate diet-induced obesity, and therefore may be used in further studies and functional food development.

Association of irisin and oxidative stress with biochemical parameters in patients with metabolic syndrome

Background Irisin, a hormone-like myokine, is suspected to have a role in metabolic syndrome (MetS) through regulating energy homeostasis and mediating physical activity. In this regard, the role of irisin and malondialdehyde (MDA) along with some other biochemical parameters in the prediction of MetS was examined in the present investigation. Materials and methods In the present case-control study, 36 subjects diagnosed with MetS according to International Diabetes Federation were considered as cases and were matched in age and gender with 31 healthy participants. The difference of biochemical indicators between cases and controls were determined whether by independent t-test or the Mann-Whitney U-test. The predictors of MetS and insulin resistance (IR) were examined through logistic and linear regressions analysis models, respectively. Results Irisin and MDA were not found to be predictors for MetS in logistic regression; p = 0.258 and p = 0.694, respectively. The IR was found to be the only direct predictor of MetS (p = 0.010). Similarly, in linear regression, irisin and MDA were not identified to be predictors for IR; p = 0.801 and p = 0.781, respectively. Conclusions The study did not show that irisin and MDA, directly and indirectly, were predictors of MetS disorder. The IR was only predictor of MetS.

Potential exerkines for physical exercise-elicited pro-cognitive effects: Insight from clinical and animal research

A sedentary lifestyle is now known as a critical risk factor for accelerated aging-related neurodegenerative disorders. In contract, having regular physical exercise has opposite effects. Clinical findings have suggested that physical exercise can promote brain plasticity, particularly the hippocampus and the prefrontal cortex, that are important for learning and memory and mood regulations. However, the underlying mechanisms are still unclear. Animal studies reveal that the effects of physical exercise on promoting neuroplasticity could be mediated by different exerkines derived from the peripheral system and the brain itself. This book chapter summarizes the recent evidence from clinical and pre-clinical studies showing the emerging mediators for exercise-promoted brain health, including myokines secreted from skeletal muscles, adipokines from adipose tissues, and other factors secreted from the bone and liver.

Association between Circulating Irisin and C-Reactive Protein Levels: A Systematic Review and Meta-Analysis

BACKGROUND

Although previous studies have demonstrated that irisin plays an anti-inflammatory role in the body, conflicting results have been reported regarding the correlation between serum levels of irisin and C-reactive protein (CRP). The present meta-analysis was conducted to further investigate the correlation between irisin and CRP levels.

METHODS

We systematically searched PubMed, the Cochrane Library, Web of Science, Embase, SCOPUS, and Ovid to retrieve studies assessing the correlation between irisin and CRP levels. Meta-analyses were performed using a random-effects model, and the I² index was used to evaluate heterogeneity.

RESULTS

Of the 428 studies that were initially found, 14 studies with 2,530 participants met the inclusion criteria for the meta-analysis. The pooled effect size was calculated as 0.052 (95% confidence interval, -0.047 to 0.152; P=0.302). Subgroup analyses identified s ignificant, positive, but weak correlations between CRP and irisin levels in cohort studies, studies conducted among healthy participants, studies in which the male-to-female ratio was less than 1, in overweight or obese subjects, and in studies with a sample size of at least 100 participants.

CONCLUSION

The present meta-analysis found no overall significant correlation between irisin and CRP levels, although a significant positive correlation was found in overweight or obese subjects. Well-designed studies are needed to verify the results of the present meta-analysis.

Green cardamom supplementation improves serum irisin, glucose indices, and lipid profiles in overweight or obese non-alcoholic fatty liver disease patients: a double-blind randomized placebo-controlled clinical trial

Background

Despite the reported health effects of cardamom on dyslipidemia, hepatomegaly, and fasting hyperglycemia, no human research has studied its potency in non-alcoholic fatty liver disease (NAFLD) as the hepatic part of metabolic syndrome. Our aim was determining the effects of green cardamom (GC) on serum glucose indices, lipids, and irisin level among overweight or obese NAFLD patients.

Methods

The place of participant recruitment was the polyclinic of the National Iranian Oil Company (NIOC) central hospital in Tehran. Based on the ultrasonography and eligibility criteria, 87 participants were randomly divided into two groups as cardamom (n = 43) or placebo (n = 44). The supplementation was two 500 mg capsules 3 times/day with meals for 3 months. Serum irisin, fasting blood sugar (FBS), insulin (FBI), total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-c), and high-density lipoprotein cholesterol (HDL-c) were measured. Quantitative insulin sensitivity check index (QUICKI) and homeostasis model assessment-insulin resistance (HOMA-IR) were also calculated.

Results

In comparison with placebo, GC significantly increased irisin, HDL-c, and QUICKI and decreased FBI, TG, LDL-c, HOMA-IR, and the grade of fatty liver (P < 0.05). After adjustment for confounders, the changes were similar (P < 0.05) with an exception for LDL-c which had a trend (P = 0.07). The differences in FBS, TC, and body mass index (BMI) were not significant (P > 0.05).

Conclusion

GC supplement improved the grade of fatty liver, serum glucose indices, lipids, and irisin level among overweight or obese NAFLD patients. The changes in these biomarkers may yield beneficial effects on NAFLD. Further trials on the efficacy of GC for clinical practice are suggested.

Trial registration

Iranian Registry of Clinical Trials, IRCT2015121317254N4. Registered 27/12/2015,

Electronic supplementary material

The online version of this article (10.1186/s12906-019-2465-0) contains supplementary material, which is available to authorized users.

The association between serum irisin levels and cardiovascular disease in diabetic patients

BACKGROUND

Cardiovascular disease is the most common cause of mortality and morbidity in diabetic patients. Insulin resistance has been shown to be reduced by the secretion of irisin from muscle and adipose tissues. This study was aimed at determining the relationship between serum irisin levels and angiographically defined coronary artery disease (CAD) in type II diabetic patients.

METHODS

In this case-control study, 30 diabetic subjects with angiographically defined CAD were compared with 30 age- and sex-matched diabetic subjects without CAD in terms of clinical and laboratory parameters including serum irisin levels.

RESULTS

Serum levels of Irisin were significantly higher in the diabetic group without CAD compared with the group with CAD (P = 0.048). Serum irisin levels showed a significant positive correlation with BMI (r = 0.374, P = 0.004) and fasting insulin (r = 0.303, P = 0.021), and a significant negative correlation with diabetes duration (r = -0.384, P = 0.002). Based on the results of the binary logistic regression model, circulating levels of irisin were associated with the presence of CAD in diabetes (p = 0.038) after adjusting for potential confounders.

CONCLUSION

Serum irisin levels were lower in the diabetic patients with cardiovascular complication compared with the uncomplicated diabetic patients. Therefore, additional larger scale studies are needed to determine the role of irisin in monitoring CAD in diabetic patients.

IRISIN AND CHEMERIN LEVELS IN PATIENTS WITH TYPE 2 DIABETES MELLITUS

Context

Changes in the secretion of signaling molecules that originates from adipose tissue and inflammation draw attention in the pathogenesis of type 2 DM. Chemerin, one of the signaling molecules of adipose origin, and irisin, defined as the Renaissance of the metabolism, are among these molecules.

Objectives

This cross-sectional study was planned in order to compare the values of serum irisin and chemerin levels in patients newly diagnosed with T2DM and in healthy subjects.

Subjects and Methods

The study included 41 patients newly diagnosed with T2DM and 49 healthy individuals. The chemistry parameters were analyzed with a biochemistry autoanalyzer, and hormonal parameters were analyzed with an immunoassay analyzer. Plasma irisin and chemerin levels were measured using the enzyme-linked immunosorbent assay method.

Results

There was a significant difference between the groups in terms of glucose, HbA1C, Insulin, HOMA-IR and lipid panel results. Irisin levels in the group of patients newly diagnosed with T2DM were lower than in the control group. Chemerin levels in the group of patients newly diagnosed with T2DM were higher than in the control group.

Conclusion

Consequently, diabetes-dependent changes in chemerin and irisin concentrations suggest that these two hormones have a role in the pathophysiology of DM. Further studies are required to understand the complex structure of the signaling pathways of chemerin and irisin molecules as well as the physiological importance of these molecules as metabolism regulators especially in humans.

Effects of running a marathon on irisin concentration in men aged over 50

Our aim was to verify whether running a marathon is associated with changes in irisin concentration in healthy, endurance-trained men. In an observational study, we assessed baseline biochemical and fitness parameters of 28 middle-aged runners (mean ± SD age, BMI, VO2max: 58 ± 8 years; 24.5 ± 3 kg/m2; 51.1 ± 1.7 ml/kg/min). We evaluated irisin before, immediately after, and 7 days after the marathon. Irisin concentration decreased from a baseline value of 639 ± 427 to 461 ± 255 ng/ml immediately after the marathon (p < 0.05). After 7 days, it was still significantly lower than before the race, at 432 ± 146 ng/ml (p < 0.05). We found no correlations between irisin concentration and the training history of the studied subjects. We conclude that a long-distance run may have a negative impact on irisin release in men. This effect was not correlated with the training history of runners.

The Role of Irisin in Alzheimer's Disease

Alzheimer’s disease (AD) is characterized by progressive memory dysfunction, oxidative stress, and presence of senile plaques formed by amyloid beta (Aβ) accumulation in the brain. AD is one of the most important causes of morbidity and mortality worldwide. AD has a variety of risk factors, including environmental factors, metabolic dysfunction, and genetic background. Recent research has highlighted the relationship between AD and systemic metabolic changes such as glucose and lipid imbalance and insulin resistance. Irisin, a myokine closely linked to exercise, has been associated with glucose metabolism, insulin sensitivity, and fat browning. Recent studies have suggested that irisin is involved in the process in central nervous system (CNS) such as neurogenesis and has reported the effects of irisin on AD as one of the neurodegenerative disease. Here, we review the roles of irisin with respect to AD and suggest that irisin highlight therapeutic important roles in AD. Thus, we propose that irisin could be a potential future target for ameliorating AD pathology and preventing AD onset.

Irisin as a Novel Marker for Insulin Resistance in Iraqi Women with Polycystic Ovary Syndrome Before and After Metformin Therapy

Background

Polycystic ovarian syndrome affects 5-10% of women; it represents the most common cause of hyperinsulinemia with anovulation. Many biomarkers are used to assess insulin resistance. Irisin is a newly discovered myokine associated with insulin resistance and other metabolic syndromes.

Objective

To measure the serum level of irisin in polycystic ovary syndrome patients and assess the effect of metformin treatment on its level.

Method

This study was a prospective interventional study conducted in a private clinic and Al-Yarmouk Teaching Hospital in Baghdad City from January 1, 2017, till April 1, 2018. A hundred women were enrolled in the study. Fifty of them suffered from PCOS and other fifty were normal. They were randomly selected according to computer-based randomization and assigned as a control group. Hormonal, biochemical and oral glucose tolerance tests were performed on all patients, including Irisin. The results have been compared for both groups. Twenty-nine women of PCOS patients received metformin for a course period of 4 months as the changes in their biochemical results were evaluated.

Result

Serum irisin level was higher in patients group compared to control group (312 ± 134.3 and 188.4 ± 53.8 μg/l, respectively), and the difference was statistically significant as the p value < 0.001. After 4 months treatment with metformin for twenty-nine polycystic patients, there was a significant reduction in irisin level by (165.8 ± 55.6 μg/l) and the p value was significant.

Conclusion

Irisin might be used as a simple test for the prediction of insulin resistance in PCOS patients.

The bone anabolic effects of irisin are through preferential stimulation of aerobic glycolysis

Irisin, a recently identified hormone secreted by skeletal muscle in response to exercise, exhibits anabolic effects on the skeleton primarily through the stimulation of bone formation. However, the mechanism underlying the irisin-stimulated anabolic response remains largely unknown. To uncover the underlying mechanism, we biosynthesized recombinant irisin (r-irisin) using an Escherichia coli expression system and used it to treat several osteoblast cell types. Our synthesized r-irisin could promote proliferation and differentiation of osteoblasts as evidenced by enhanced expression of osteoblast-specific transcriptional factors, including Runt-related transcription factor-2 (Runx2), Oster (Osx), as well as early osteoblastic differentiation markers such as alkaline phosphatase (Alp) and collagen type I alpha 1 (Col1a1). Furthermore, we showed that the promotion of r-irisin on the proliferation and differentiation of osteoblast lineage cells are preferentially through aerobic glycolysis, as indicated by the enhanced abundance of representative enzymes such as lactate dehydrogenase A (LDHA) and pyruvate dehydrogenase kinase 1 (PDK1), together with increased lactate levels. Suppression of r-irisin-mediated aerobic glycolysis with Dichloroacetate blunted its anabolic effects. The favorite of the aerobic glycolysis after r-irisin treatment was then confirmed in primary calvarial cells by metabolic analysis using gas chromatography-mass spectrometry. Thus, our results suggest that the anabolic actions of r-irisin on the regulation of osteoblast lineage cells are preferentially through aerobic glycolysis, which may help to develop new irisin-based bone anabolic agents.

Does iris(in) bring bad news or good news?

Irisin, a novel myokine produced in response to physical activity, promotes white-to-brown fat transdifferentiation. The name irisin referred to the ancient Greek goddess Iris, the messenger who delivered (bad) news from the gods. In mice, it has been demonstrated that irisin plays a key role in metabolic regulation, energy expenditure and glucose homeostasis. New findings from various studies carried out in both animals and humans suggest that irisin might also have other favorable effects, such as increasing bone cortical mass, preventing hepatic lipid accumulation, and improving cognitive functions, thus mediating many exercise-induced health benefits. However, data on the role and function of irisin in humans have prompted controversy, due mostly to the only recent confirmation of the presence of irisin in humans. Another strong limitation to the understanding of irisin mechanisms of action is the lack of knowledge about its receptor, which until now remains unidentified in humans and in animals. This review presents an overall analysis of the history of irisin, its expression, and its involvement in health, especially in humans. Level of Evidence Level V, review.

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.

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

Molecular dynamics simulation and steered molecular dynamics simulation on irisin dimers

Irisin is found closely associated with promoting the browning of beige fat cells in white adipose tissue. The crystal structure reveals that irisin forms a continuous inter-subunit β-sheet dimer. Here, molecular dynamics (MD) simulation and steered molecular dynamics (SMD) simulation were performed to investigate the dissociation process and the intricate interactions between the two irisin monomers. In the process of MD, the interactions between the monomers were roughly analyzed through the average numbers of both hydrophobic contacts and H-bonds. Then, SMD was performed to investigate the accurate interaction energy between the monomers. By the analysis of dissociation energy, the van der Waals (vdW) force was identified as the major energy to maintain the dimer structure, which also verified the results of MD simulation. Meanwhile, 11 essential residues were discovered by the magnitude of rupture force during dissociation. Among them, residues Arg75, Glu79, Ile77, Ala88, and Trp90 were reported in a previous study using the method of mutagenesis and size exclusion chromatography, and several new important residues (Arg72, Leu74, Phe76, Gln78, Val80, and Asp91) were also identified. Interestingly, the new important residues that we discovered and the important residues that were reported are located in the opposite side of the β-sheet of the dimer.