Irisin and leptin concentrations in relation to obesity, and developing type 2 diabetes: A cross sectional and a prospective case-control study nested in the Normative Aging Study

Irisin: muscle's novel player in endoplasmic reticulum stress and disease

Irisin, an exercise-induced myokine, exhibits elevated levels during physical activity, yet its role in modulating the unfolded protein response (UPR) remains poorly understood. This comprehensive review pioneers an in-depth examination of irisin-mediated endoplasmic reticulum (ER) stress mitigation across various diseases. We provide a nuanced characterization of irisin's molecular profile, biological activity, and significance as a skeletal muscle-derived cytokine analogue. Our discussion elucidates the complex interplay between exercise, irisin signalling, and metabolic outcomes, highlighting key molecular interactions driving salutary effects. Moreover, we delineate the UPR's role as a critical ER stress countermeasure and underscore irisin's pivotal function in alleviating this stress, revealing potential therapeutic avenues for disease management. Exercise-induced release of irisin ameliorates ER stress through AMPK phosphorylation during various diseases (Icon image source: www.flaticon.com ).

Role and Functions of Irisin: A Perspective on Recent Developments and Neurodegenerative Diseases

Irisin is a peptide derived from fibronectin type III domain-containing protein 5 (FNDC5) and is primarily produced by muscle fibers under the regulation of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) during exercise. Irisin has been the subject of extensive research due to its potential as a metabolic regulator and its antioxidant properties. Notably, it has been associated with protective actions within the brain. Despite growing interest, many questions remain regarding the molecular mechanisms underlying its effects. This review summarizes recent findings on irisin, highlighting its pleiotropic functions and the biological processes and molecular cascades involved in its action, with a particular focus on the central nervous system. Irisin plays a crucial role in neuron survival, differentiation, growth, and development, while also promoting mitochondrial homeostasis, regulating apoptosis, and facilitating autophagy-processes essential for normal neuronal function. Emerging evidence suggests that irisin may improve conditions associated with non-communicable neurological diseases, including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, frontotemporal dementia, and multiple sclerosis. Given its diverse benefits, irisin holds promise as a novel therapeutic agent for preventing and treating neurological diseases.

Understanding the Role of Irisin in Longevity and Aging: A Narrative Review

Irisin is a protein resulting from a proteolytic cleavage of fibronectin type III domain-containing protein 5 (FND5). The ability of irisin to modulate adipocyte and control glucose metabolism in human metabolic diseases gave rise to the hypothesis that irisin could have a pivotal role in aging-related diseases. Although in animal models, increased levels of irisin have been positively associated with better health outcomes, in humans, its role remains controversial. To provide an overview of the main finding on irisin in older adults, a comprehensive search was performed through the MEDLINE-PubMed, Web of Science, Scopus, and Cochrane databases for studies conducted in older adults (≥60 years) published since 2012. After grouping and analyzing the articles based on diseases associated with older adults, the main conclusion of this narrative review is that the included studies did not yield consistent evidence regarding the association between irisin and health or disease in older adults. Further studies are necessary to clarify the effective role of this protein in promoting health and longevity.

Relationship of serum irisin levels, physical activity, and metabolic syndrome biomarkers in obese individuals with low-calorie intake and non-obese individuals with high-calorie intake

BACKGROUND

Despite all the advances in our knowledge regarding obesity, our understanding of its etiology is still far from complete. This study aimed to evaluate the association of serum irisin levels with physical activity and some of the metabolic syndrome-related biomarkers among obese people with low-calorie intake and non-obese people with high-calorie intake.

METHODS

Obese and non-obese healthy individuals with respectively low and high-calorie intakes were recruited. Irisin and other biomarkers were measured using standard biochemical methods. Participants' physical activity was evaluated by administering the International Physical Activity Questionnaire (IPAQ). To analyze the body composition of the participants, a standard body composition device (ioi 353) was applied. Logistic regression was used to calculate the odds ratio (OR) and to examine the effect of confounders such as age, sex, genetics, and activity.

RESULTS

Data from the seventy-seven participants were included in the final analysis. The mean age of the participants in the obese and non-obese groups was 38.33 ± 14.88 and 30.24 ± 13.37 years, respectively. Participants in the obese group had lower physical activity compared to the non-obese group (3395.38 ± 2801 MET-min/week vs. 6015.18 ± 3178 MET-min/week; p < 0.001). The Irisin concentration in the obese and non-obese groups was 7.84 ± 2.49 ng/ml and 8.06 ± 1.89 ng/ml, respectively, which wasn't significantly different (p = 0.66). We observed a noteworthy and favorable association between irisin concentration and total body water (TBW), lean body mass (LBM), and soft lean mass (SLM) in the non-obese group.

CONCLUSIONS

These data indicated that although obese participants were relatively inactive compared to non-obese individuals, circulating irisin level wasn't significantly different between the two groups.

Influence of rosiridin on streptozotocin-induced diabetes in rodents through endogenous antioxidants-inflammatory cytokines pathway and molecular docking study

The research was undertaken to assess the antidiabetic activity of rosiridin in the streptozotocin (STZ)-induced diabetic model. Type 2 diabetes mellitus was elicited chemically in experimental animals using STZ (60 mg/kg, i.p.). Experimental rats were arbitrarily allocated to normal control, rosiridin perse, diabetic control, and STZ + rosiridin groups. After the confirmation of diabetes, rosiridin (10 mg/kg) was given orally to the experimental animals for 30 days. Various anti-diabetic (blood glucose, insulin), hypolipidemic, anti-inflammatory (Nuclear factor kappa B, tumour necrosis factor-α, interleukin beta (IL-1β), and IL-6), antioxidant (and malondialdehyde level, hepatic function and others markers (ALT, AST, adiponectin, and FNDC5) and histopathological indices of injury were evaluated. In addition, the rosinidin was docked into the active site of NF-Kβ (1SVC), FNDC5 (4LSD) and adiponectin (5LXG) proteins with AutoDock tools. MD simulations were carried out for the complexes of rosiridin with NF-Kβ, myokine and human adiponectin receptor 1. Rosiridin treatment restored the biochemical parameters and preserved the histopathological building of the pancreas as compared to the diabetic rats. Histopathological analysis of the pancreas confirmed that rosiridin antidiabetic efficacy in the STZ-induced diabetes mellitus model. The 5LXG_rosinidin showed favourable affinity with the best binding energies at -7.534 kcal/mol. MD simulations were carried out for the complexes of rosiridin with NF-Kβ, myokine and human adiponectin receptor 1, the complex of myokine and rosiridin exhibited the most stable complex. Rosiridin may exhibit considerable anti-diabetic activity in the STZ-induced diabetes mellitus model.Communicated by Ramaswamy H. Sarma.

Alterations in Biomarkers Associated with Cardiovascular Health and Obesity with Short-Term Lifestyle Changes in Overweight Women: The Role of Exercise and Diet

Background and Objectives: In this study, the effects of an eight-week exercise and nutrition program on blood lipids, glucose, insulin, insulin resistance (HOMA-IR), leptin, ghrelin, irisin, malondialdehyde (MDA), and Growth Differentiation Factor 15 (GDF15) in overweight women were investigated. Materials and Methods: A total of 48 women volunteers participated in this study. The participants were randomly divided into four groups: control (C), exercise (E), nutrition (N), exercise + nutrition (E + N). While no intervention was applied to group C, the other groups participated in the predetermined programs for 8 weeks. At the beginning and end of this study, body composition was measured and blood samples were taken. Results: It was determined that the body composition components, lipid profile indicators, insulin, glucose, insulin resistance, leptin, ghrelin, irisin, and MDA parameters examined in this study showed positive changes in the intervention groups. Group E had a greater effect on body muscle percentage, MDA, and irisin levels, while group N had a greater effect on blood lipids and ghrelin levels. Conclusions: As a result, it is thought that lifestyle changes are important to improve cardiovascular health and combat obesity, and that maintaining a healthy diet together with exercise may be more effective.

Irisin preserves mitochondrial integrity and function in tubular epithelial cells after ischemia-reperfusion-induced acute kidney injury

AIMS

A myokine secreted by skeletal muscles during exercise called irisin mitigates ischemia-reperfusion (I/R) injury in epithelial cells of various organs by limiting damage to mitochondria. We test whether irisin may preserve the mitochondrial integrity and function in renal tubular epithelial cells and protect against ischemia-reperfusion-induced acute kidney injury (AKI).

METHODS

We correlated serum irisin levels with serum creatinine and BUN levels from both AKI patients and healthy individuals. In mice with irisin administration, various renal injury markers such as serum creatinine, BUN, kidney injury molecule-1 (Kim-1), and neutrophil gelatinase-associated lipocalin (NGAL), and renal histopathology were assessed after I/R. To identify the potential mechanisms of the protective of irisin's protective effect, we perfused proximal tubules under confocal microscopy and analyzed kidney tissues by qPCR, western blot, and immunohistochemistry.

RESULTS

Serum irisin correlated inversely with serum creatinine and BUN levels were significantly lower in AKI patients than in healthy subjects. Administering irisin to mice after I/R decreased biomarker levels for AKI including serum creatinine, BUN, Kim-1, NAGL and lessened histological changes. In kidney tissues of mice, irisin upregulated the mitochondrial autophagy marker protein microtubule-associated protein 1 light chain 3 (LC3), the mitochondrial autophagy pathway-related proteins PTEN-induced putative kinase 1 (PINK1) and Parkinson's disease 2 parkin (PARK2) and downregulated the reactive substrate protein sequestosome 1 (P62) and mitochondrial membrane proteins translocase of outer mitochondrial membrane 20 (TOM20) and translocase of inner mitochondrial membrane 23 (TIM23).

CONCLUSION

Irisin protects against renal I/R injury, which may involve the preservation of mitochondrial integrity and function.

Unlocking liver health: Can tackling myosteatosis spark remission in metabolic dysfunction-associated steatotic liver disease?

Myosteatosis is highly prevalent in metabolic dysfunction-associated steatotic liver disease (MASLD) and could reciprocally impact liver function. Decreasing muscle fat could be indirectly hepatoprotective in MASLD. We conducted a review to identify interventions reducing myosteatosis and their impact on liver function. Non-pharmacological interventions included diet (caloric restriction or lipid enrichment), bariatric surgery and physical activity. Caloric restriction in humans achieving a mean weight loss of 3% only reduces muscle fat. Lipid-enriched diet increases liver fat in human with no impact on muscle fat, except sphingomyelin-enriched diet which reduces both lipid contents exclusively in pre-clinical studies. Bariatric surgery, hybrid training (resistance exercise and electric stimulation) or whole-body vibration in human decrease both liver and muscle fat. Physical activity impacts both phenotypes by reducing local and systemic inflammation, enhancing insulin sensitivity and modulating the expression of key mediators of the muscle-liver-adipose tissue axis. The combination of diet and physical activity acts synergistically in liver, muscle and white adipose tissue, and further decrease muscle and liver fat. Several pharmacological interventions (patchouli alcohol, KBP-089, 2,4-dinitrophenol methyl ether, adipoRon and atglistatin) and food supplementation (vitamin D or resveratrol) improve liver and muscle phenotypes in pre-clinical studies by increasing fatty acid oxidation and anti-inflammatory properties. These interventions are effective in reducing myosteatosis in MASLD while addressing the liver disease itself. This review supports that disturbances in inter-organ crosstalk are key pathophysiological mechanisms involved in MASLD and myosteatosis pathogenesis. Focusing on the skeletal muscle might offer new therapeutic strategies to treat MASLD by modulating the interactions between liver and muscles.

Evidence That Peripheral Leptin Resistance in Omental Adipose Tissue and Liver Correlates with MASLD in Humans

Leptin regulates lipid metabolism, maximizing insulin sensitivity; however, peripheral leptin resistance is not fully understood, and its contribution to metabolic dysfunction-associated steatotic liver disease (MASLD) is unclear. This study evaluated the contribution of the leptin axis to MASLD in humans. Forty-three participants, mostly female (86.04%), who underwent cholecystectomy were biopsied. Of the participants, 24 were healthy controls, 8 had MASLD, and 11 had metabolic dysfunction-associated steatohepatitis (MASH). Clinical and biochemical data and the gene expression of leptin, leptin receptor (LEPR), suppressor of cytokine signaling 3 (SOCS3), sterol regulatory element-binding transcription factor 1 (SREBF1), stearoyl-CoA desaturase-1 (SCD1), and patatin-like phospholipase domain-containing protein 2 (PNPLA2), were determined from liver and adipose tissue. Higher serum leptin and LEPR levels in the omental adipose tissue (OAT) and liver with MASH were found. In the liver, LEPR was positively correlated with leptin expression in adipose tissue, and SOCS3 was correlated with SREBF1-SCD1. In OAT, SOCS3 was correlated with insulin resistance and transaminase enzymes (p < 0.05 for all. In conclusion, we evidenced the correlation between the peripheral leptin resistance axis in OAT-liver crosstalk and the complications of MASLD in humans.

Diabetes Mellitus Should Be Considered While Analysing Sarcopenia-Related Biomarkers

Sarcopenia is a chronic, progressive skeletal muscle disease characterised by low muscle strength and quantity or quality, leading to low physical performance. Patients with type 2 diabetes mellitus (T2DM) are more at risk of sarcopenia than euglycemic individuals. Because of several shared pathways between the two diseases, sarcopenia is also a risk factor for developing T2DM in older patients. Various biomarkers are under investigation as potentially valuable for sarcopenia diagnosis and treatment monitoring. Biomarkers related to sarcopenia can be divided into markers evaluating musculoskeletal status (biomarkers specific to muscle mass, markers of the neuromuscular junction, or myokines) and markers assuming causal factors (adipokines, hormones, and inflammatory markers). This paper reviews the current knowledge about how diabetes and T2DM complications affect potential sarcopenia biomarker concentrations. This review includes markers recently proposed by the expert group of the European Society for the Clinical and Economic Aspects of Osteoporosis, Osteoarthritis and Musculoskeletal Diseases (ESCEO) as those that may currently be useful in phase II and III clinical trials of sarcopenia: myostatin (MSTN); follistatin (FST); irisin; brain-derived neurotrophic factor (BDNF); procollagen type III N-terminal peptide (PIIINP; P3NP); sarcopenia index (serum creatinine to serum cystatin C ratio); adiponectin; leptin; insulin-like growth factor-1 (IGF-1); dehydroepiandrosterone sulphate (DHEAS); C-reactive protein (CRP); interleukin-6 (IL-6), and tumor necrosis factor α (TNF-α). A better understanding of factors influencing these biomarkers' levels, including diabetes and diabetic complications, may lead to designing future studies and implementing results in clinical practice.

Adiponectin Resistance in Obesity: Adiponectin Leptin/Insulin Interaction

The adiponectin (APN) levels in obesity are negatively correlated with chronic subclinical inflammation markers. The hypertrophic adipocytes cause obesity-linked insulin resistance and metabolic syndrome. Furthermore, macrophage polarization is a key determinant regulating adiponectin receptor (AdipoR1/R2) expression and differential adiponectin-mediated macrophage inflammatory responses in obese individuals. In addition to decrease in adiponectin concentrations, the decline in AdipoR1/R2 messenger ribonucleic acid (mRNA) expression leads to a decrement in adiponectin binding to cell membrane, and this turns into attenuation in the adiponectin effects. This is defined as APN resistance, and it is linked with insulin resistance in high-fat diet-fed subjects. The insulin-resistant group has a significantly higher leptin-to-APN ratio. The leptin-to-APN ratio is more than twofold higher in obese individuals. An increase in expression of AdipoRs restores insulin sensitivity and β-oxidation of fatty acids via triggering intracellular signal cascades. The ratio of high molecular weight to total APN is defined as the APN sensitivity index (ASI). This index is correlated to insulin sensitivity. Homeostasis model of assessment (HOMA)-APN and HOMA-estimated insulin resistance (HOMA-IR) are the most suitable methods to estimate the metabolic risk in metabolic syndrome. While morbidly obese patients display a significantly higher plasma leptin and soluble (s)E-selectin concentrations, leptin-to-APN ratio, there is a significant negative correlation between leptin-to-APN ratio and sP-selectin in obese patients. When comparing the metabolic dysregulated obese group with the metabolically healthy obese group, postprandial triglyceride clearance, insulin resistance, and leptin resistance are significantly delayed following the oral fat tolerance test in the first group. A neuropeptide, Spexin (SPX), is positively correlated with the quantitative insulin sensitivity check index (QUICKI) and APN. APN resistance together with insulin resistance forms a vicious cycle. Despite normal or high APN levels, an impaired post-receptor signaling due to adaptor protein-containing pleckstrin homology domain, phosphotyrosine-binding domain, and leucine zipper motif 1 (APPL1)/APPL2 may alter APN efficiency and activity. However, APPL2 blocks adiponectin signaling through AdipoR1 and AdipoR2 because of the competitive inhibition of APPL1. APPL1, the intracellular binding partner of AdipoRs, is also an important mediator of adiponectin-dependent insulin sensitization. The elevated adiponectin levels with adiponectin resistance are compensatory responses in the condition of an unusual discordance between insulin resistance and APN unresponsiveness. Hypothalamic recombinant adeno-associated virus (rAAV)-leptin (Lep) gene therapy reduces serum APN levels, and it is a more efficient strategy for long-term weight maintenance.

Adiponectin-leptin ratio for the early detection of lean non-alcoholic fatty liver disease independent of insulin resistance

BACKGROUND

Lean Non-alcoholic Fatty Liver Disease (NAFLD) shares a similar disease burden to those of their overweight counterparts and should be detected early. We hypothesized that the adiponectin-leptin ratio (AL ratio) could be a good marker for early detection of lean NAFLD independent of insulin resistance.

MATERIALS AND METHODS

A total of 575 adults without diabetes were enrolled in a community-based study. The subjects were stratified into the lean controls, lean NAFLD, simple overweight/obesity and overweight/obesity NAFLD groups according to body mass index (BMI) and ultrasonographic fatty liver indicators. Serum adiponectin and leptin levels were measured by enzyme-linked immunosorbent assay. Multivariate logistic regression analyses were performed to estimate the odds ratio of having NAFLD in relation to the tertiles of serum AL concentration after adjustment. Receiver operating characteristic (ROC) analyses were applied to evaluate the diagnostic performance of the AL ratio for NAFLD.

RESULTS

The mean age of the participants was 42.8 ± 11.5 years. Comparing with the lean controls, the odds of having lean NAFLD for the highest versus the lowest tertile of AL ratio was 0.28(95%CI: 0.12-0.69) after adjustment. Putting AL ratio, BMI, triglyceride, AST/ALT ratio to the diagnosis performance of NAFLD, the ROC was 0.85 (95% CI: 0.82-0.88), 0.83 (95% CI 0.78-0.87) and 0.86 (95% CI 081-0.91) for all NAFLD, NAFLD in women and NAFLD in men, respectively. (p < .001).

CONCLUSIONS

The study revealed that the AL ratio could be a good biomarker to early distinguish lean NAFLD patients from lean controls independent of insulin resistance. [AQ3]Key messagesThe prevalence of non-alcoholic fatty liver disease (NAFLD) increases globally and is related to liver diseases and metabolic dysfunctions. Lean subset of NAFLD shares a similar disease burden to those of their overweight counterparts and should be detected early.Adiponectin-leptin ratio were associated with the severity of steatosis and was a predictor of obese NAFLD better than each single adipokine. To date, there is no investigation that explores specifically for the relationship between lean NAFLD and AL ratio.Our study found that adiponectin-leptin ratio is a sole independent marker regardless of insulin resistance in lean NAFLD. Having lean NAFLD for the highest versus the lowest tertile of adiponectin-leptin ratio was 0.28(95%CI: 0.12-0.69) after adjustment of age, sex, current smoking, exercise habits, HOMA-IR and AST/ALT. ROC for the NAFLD performance is good for the early detection (0.85; 95% CI: 0.82-0.88). Further rigorous investigation is necessary and should be promptly performed.

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.

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.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Obesity and diabetes

Obesity, which has currently reached pandemic dimensions, is usually accompanied by diabetes mellitus type 2 (T2DM). These two conditions share common pathophysiological mechanisms. Adipose tissue secretes cytokines which are involved in inflammation and various endocrine functions. As for T2DM, it is characterized also by inflammation, mitochondrial dysfunction, and hyperinsulinemia. These conditions occur also in other diseases related to obesity and T2DM, like cardiovascular disease (CVD) and nonalcoholic fatty liver disease (NAFLD). Thus, management of obesity-related complications with lifestyle modification, anti-obesity drugs, and bariatric surgery, all contribute to improvement in any of these conditions. This review provides an overview of the literature addressing the association between obesity and T2DM, briefly discussing the pathophysiological mechanisms linking these conditions and outlining the management approach at the overlap of obesity and T2DM.

Metformin induces pyroptosis in leptin receptor-defective hepatocytes via overactivation of the AMPK axis

Metformin is the biguanide of hepatic insulin sensitizer for patients with non-alcohol fatty liver disease (NAFLD). Findings regarding its efficacy in restoring blood lipids and liver histology have been contradictory. In this study, we explore metformin's preventive effects on NAFLD in leptin-insensitive individuals. We used liver tissue, serum exosomes and isolated hepatocytes from high-fat diet (HFD)-induced Zucker diabetic fatty (ZDF) rats and leptin receptor (Lepr) knockout rats to investigate the correlation between hepatic Lepr defective and liver damage caused by metformin. Through immunostaining, RT-PCR and glucose uptake monitoring, we showed that metformin treatment activates adenosine monophosphate (AMP)-activated protein kinase (AMPK) and its downstream cytochrome C oxidase (CCO). This leads to overactivation of glucose catabolism-related genes, excessive energy repertoire consumption, and subsequent hepatocyte pyroptosis. Single-cell RNA sequencing further confirmed the hyper-activation of glucose catabolism after metformin treatment. Altogether, we showed that functional Lepr is necessary for metformin treatment to be effective, and that long-term metformin treatment might promote NAFLD progression in leptin-insensitive individuals. This provides important insight into the clinical application of metformin.

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

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

Aerobic Versus Resistance Training: Leptin and Metabolic Parameters Improvement in Type 2 Diabetes Obese Men

Purpose: The purpose of the research was to determine the changes in metabolic parameters, leptin, and irisin levels after aerobic and resistance training in type-2 diabetes obese men. Methods: Forty-five participants in the age range of 17-25 years were randomized into three groups: aerobic training (AT), resistance training (RT), and control (CO). All training sessions were fulfilled 4 days per week for two months. The aerobic training began with intensity of 65% of the maximum aerobic power and finished with 90%. The resistance program started with 50% of one-repetition maximum and reached 70% in the 8th week. Results: Factorial analysis of variance and Bonferroni post-hoc test revealed significant decreases in leptin (p = .043), fasting blood sugar (FBS) (p = .023), insulin (p = .001), homeostasis model assessment for insulin resistance (HOMA-IR) (p = .022) in AT compared with CO and insulin (p = .006) in AT compared with RT. The change of percent body fat (PBF) was positively correlated only with change of HOMA-IR in AT group (p = .032) at p < .05. Conclusion: The result suggests that, compared to resistance training, aerobic training can control metabolic situations such as insulin resistance through the leptin hormone function, and not irisin in type-2 diabetes obese men.

Evaluating the effects of Juglans regia L. extract on hyperglycaemia and insulin sensitivity in experimental type 2 diabetes in rat

OBJECTIVE

The present study aimed to investigate the effects of Juglans regia (JR) extract on hyperglycaemia and insulin sensitivity.

METHODS

Forty rats were divided into 4 groups: Control (C), Diabetes Control (DC), Diabetes + Juglans regia (D + JR) and Diabetes + Metformin (D + M).

RESULTS

In the D + JR group, Fasting blood glucose (FBG) levels decreased from day 14 onwards. There was a significant decrease in plasma levels of Fibronectin Type III Domain Containing 5 (FNDC5) and adiponectin (ADP) in the DC group compared to the C group (p < .01, p < .001 respectively). In the D + JR group, there was a significant increase in plasma FNDC5 and ADP (p < .05), while the plasma Tumour necrosis factor-alpha (TNF-α) levels were decreased compared to the DC group (p < .001).

CONCLUSIONS

In conclusion, the present study found that JR and its bioactive components alleviated insulin resistance by increasing ADP and FNDC5 and decreasing FBG in a rat model of streptozotocin (STZ) + nicotinamide (NAD)-induced type 2 diabetes (T2D).HighlightsJuglans regia extract increased insulin sensitivity.Juglans regia extract significantly reduced the level of fasting blood glucose.Juglans regia extract reduced TNF-α levels in rats with type 2 diabetes.Juglans regia extract prevent weight loss in type 2 diabetes.

Irisin Protects Cerebral Neurons from Hypoxia/Reoxygenation via Suppression of Apoptosis and Expression of Pro-Inflammatory Cytokines

BACKGROUND

Ischemic stroke is a major health issue that causes high incidents of morbidity and mortality worldwide. Irisin is an excise-induced protein that has exhibited pleiotropic properties. Accumulating evidence reveals its critical roles in the regulation of various cellular functions, including nervous system functions. This study aims to disclose the effect of irisin on rat cerebral neurons suffering from hypoxia/reoxygenation (H/R) treatment and to explore the potential underlying molecular mechanisms.

METHODS

The percentage of rat cerebral neuron cell death was determined by flow cytometry analysis and MTT assay. The expression levels of target genes were measured by western blotting and real-time quantitative reverse transcription PCR assay.

RESULTS

Our results demonstrated that irisin treatment substantially reduced H/R-induced apoptosis of rat cerebral neurons. Further investigation revealed that irisin treatment markedly decreased mitogen-activated protein kinase (MAPK) signaling pathway activation and suppressed pro-informatory cytokine expression in cerebral neurons with H/R challenge. Finally, we showed that the neuroprotective effect and anti-inflammatory effect of irisin were comparable with three MAPK signaling inhibitors.

CONCLUSION

Irisin exerts profound neuroprotective and anti-inflammatory effects on H/R-stimulated cerebral neurons by inhibiting the MAPK signaling activation. Therefore, irisin may serve as a potential drug for the treatment of patients with ischemic stroke.

Circulating Ism1 Reduces the Risk of Type 2 Diabetes but not Diabetes-Associated NAFLD

PURPOSE

To examine the association of serum Ism1, a new adipokine that can regulate glucose uptake, with type 2 diabetes (T2D) in a Chinese population. Considering high prevalence of Nonalcoholic Fatty Liver Disease in patients with type 2 diabetes and the regulating role of Ism1 on glucose uptake of peripheral tissues, we further explored the association between Ism1 and diabetes-associated nonalcoholic fatty liver disease.

METHODS

A total of 120 newly diagnosed T2D patients and 60 control subjects with normal glucose were recruited in the case-control study. Serum Ism1 concentrations were determined by ELISA. Multivariate logistic regression analysis was used to evaluate the independent association of serum Ism1 concentration with the risk of T2D. The 120 newly diagnosed T2D patients were divided into uncomplicated T2D group and diabetes-associated NAFLD group according to the FLI score.

RESULTS

The Ism1 level of normoglycemic controls was higher than that of T2D patients (3.91 ± 0.24 ng/ml vs 3.01 ± 0.16 ng/ml, P=0.001). Based on quartile analysis of Ism1 level, the proportion of high circulating Ism1 levels in the control group increased while T2D group decreased, and the distribution difference was statistically significant (P=0.015). Logistic regression analysis indicated that the serum Ism1 level was an independent protective factor of type 2 diabetes (OR=0.69, 95%CI: 0.54-0.89). The decrease of Ism1 level did not increase the risk of non-alcoholic fatty liver disease in diabetic patients by Binary logistic regression analysis (OR=1.08, 95% CI: 0.69-1.69).

CONCLUSIONS

The increase of serum Ism1 was associated with a decreased risk of diabetes, and it did not reduce the risk of non-alcoholic fatty liver disease in diabetic patients.

The Associations Between Serum Concentrations of Irisin and Glucose-dependent Insulinotropic Polypeptide with Body Mass Index Among Women with and Without Polycystic Ovary Syndrome

BACKGROUND

The actions of adipocytokines may be a connective factor between obesity and polycystic ovary syndrome (PCOS). It is suggested that irisin, as recently described cytokine secreted by skeletal muscles and glucose-dependent insulinotropic polypeptide (GIP) as an incretin hormone that induces cytokine expression, may play key roles in favoring obesity in these women.

OBJECTIVES

We aimed to evaluate the association between body mass index (BMI) and serum concentrations of irisin/GIP in women with and without PCOS in the linear and non-linear models.

METHODS

This cross-sectional study was conducted among 159 PCOS and 82 healthy eumenorrheic non-hirsute women aged 20 - 50 years. The fractional-polynomial model was used to develop a model of continuous risk factors, which evaluates non-linear associations between irisin/GIP and BMI among women with and without PCOS.

RESULTS

Women with PCOS were significantly younger (28.2 ± 5.8 vs. 33.0 ± 7.8 years, P < 0.001) and had a greater BMI (26.6 ± 5.2 vs. 25.2 ± 4.8 kg/m², P = 0.04) than the healthy counterparts. There were no significant linear and non-linear associations between serum concentration of irisin/GIP and BMI in both groups. The analysis of pair-wise age and BMI matching of women with PCOS and controls confirmed these findings.

CONCLUSIONS

This study showed that irisin and GIP have no association with BMI in women with or without PCOS. This finding could help to better understand the underlying pathophysiological status of PCOS, insulin resistance, and obesity-related disorders. Further large cohort studies are needed to confirm these findings.

Dietary Intervention, When Not Associated With Exercise, Upregulates Irisin/FNDC5 While Reducing Visceral Adiposity Markers in Obese Rats

Obesity is an epidemic disease and the expansion of adipose tissue, especially visceral fat, promotes the secretion of factors that lead to comorbidities such as diabetes and cardiovascular diseases. Thus, diet and exercise have been proposed as an intervention to reverse these complications. An adipocytokine, known as irisin, mediates the beneficial effects of exercise. It has been proposed as a therapeutic potential in controlling obesity. In view of the above, this paper attempts to determine the modulation of irisin, visceral adiposity and biochemical markers in response to dietary intervention and aerobic exercise. To do this, 52 diet-induced obese male Wistar rats were divided into the following four groups: high-fat diet and exercise (HFD-Ex); HFD-Sedentary (HFD-Sed); chow-diet and exercise (CD-Exercise); and CD-Sed. The exercise-trained group performed a treadmill protocol for 60 min/day, 3 days/week for 8 weeks. Body mass (BM), body fat (BF), fat mass (FM), and fat-free mass (FFM) were analyzed. Mesenteric (MES), epididymal (EPI), and retroperitoneal (RET) adipose tissue was collected and histological analysis was performed. Biochemical irisin, triglycerides, glucose, insulin and inflammatory markers were determined and, FNDC5 protein expression was analyzed. In this study, the diet was the most important factor in reducing visceral adiposity in the short and long term. Exercise was an important factor in preserving muscle mass and reducing visceral depots after a long term. Moreover, the combination of diet and exercise can enhance these effects. Diet and exercise exclusively were the factors capable of increasing the values of irisin/FNDC5, however it did not bring cumulative effects of both interventions. Prescriptions to enhance the obesity treatments should involve reducing visceral adiposity by reducing the fat content in the diet associated with aerobic exercise.

A study of leptin and its gene 2548 G/A Rs7799039 single-nucleotide polymorphisms in Egyptian children: A single-center experience

BACKGROUND/OBJECTIVES

The pathophysiology of obesity is multifactorial, including genetic and environmental factors. Previous studies had highlighted the association of the leptin gene/receptor with obesity. We aimed to study the leptin gene rs7799039 single nucleotide polymorphism (SNP) in children, and its association with the children's characteristics.

METHODS

A cross-sectional analytic study that included 143 children with obesity (cases) and a comparable group of 86 lean children as controls. The anthropometric measures, blood pressure, and biochemical testing were done for all participants. The real-time polymerase chain reaction was used to detect rs7799039 SNP variant alleles and ELISA for leptin level assessment.

RESULTS

The distribution of rs7799039 SNPs genotypes GG/GA/AA was comparable between both groups. Testing children regardless of their body mass index showed that the abnormalities in blood pressure, lipids values, insulin resistance, and hepatic insulin sensitivity were significantly associated with increased leptin levels. Among cases, the abnormal metabolic status was associated with higher leptin levels.

CONCLUSIONS

The genotype' distribution of leptin gene rs7799039 SNP was similar in both children with obesity and those with normal-weight. The high blood pressure, abnormal lipid profile, and metabolic disturbances, were significantly associated with higher leptin levels and not with leptin gene rs7799039 SNP.

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 Leptin in Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD), which affects about a quarter of the global population, poses a substantial health and economic burden in all countries, yet there is no approved pharmacotherapy to treat this entity, nor well-established strategies for its diagnosis. Its prevalence has been rapidly driven by increased physical inactivity, in addition to excessive calorie intake compared to energy expenditure, affecting both adults and children. The increase in the number of cases, together with the higher morbimortality that this disease entails with respect to the general population, makes NAFLD a serious public health problem. Closely related to the development of this disease, there is a hormone derived from adipocytes, leptin, which is involved in energy homeostasis and lipid metabolism. Numerous studies have verified the relationship between persistent hyperleptinemia and the development of steatosis, fibrinogenesis and liver carcinogenesis. Therefore, further studies of the role of leptin in the NAFLD spectrum could represent an advance in the management of this set of diseases.

Increased FNDC5/IRISIN protein expression in breast cancer tissue is associated with obesity in postmenopausal women

AIM

To analyse the fibronectin type III domain containing 5 (FNDC5)/irisin expression in tumour tissue of postmenopausal women presenting breast cancer and different body mass indexes (BMIs), proposing that obesity deregulates the expression of FNDC5/irisin at the breast tumour level. In addition, we investigated if different breast cancer cell lines are capable to synthesise this protein.

METHODS

A total of 150 postmenopausal women (50 with a normal BMI, 50 presenting overweight and 50 having obesity) diagnosed with operable breast cancer were included. FNDC5/irisin expression was determined by immunohistochemistry or by immunocytochemistry. Qualitative analysis of protein expression was performed by the H-Score method, through ImageJ's IHC Profiler software. Statistical analyses were carried out using STATA V.14.0 (Texas, USA); p value<0.05 was accepted as statistically significant. Statistical power of the study was >80% with a p<0.05.

RESULTS

FNDC5/irisin expression in breast cancer tissue of postmenopausal women with obesity was significantly increased when compared with FNDC5/irisin expression in women with a normal BMI (p=0.001). Furthermore, three breast cancer cell lines studied were capable to synthesise and express FNDC5/irisin, being the BT-474 cell line the one that exhibited the highest intensity of expression.

CONCLUSIONS

Our results confirm that women with breast cancer and obesity exhibit an increased irisin expression in their tumorous tissue compared with women with breast cancer and normal BMI. Likewise, in vitro breast cancer cell lines have the capacity to synthesise and express FNDC5/irisin, without any extracellular stimuli, however the microenvironment surrounding these cells in vivo participates in its regulation.

Crossing the Antarctica: Exploring the Effects of Appetite-Regulating Hormones and Indicators of Nutrition Status during a 93-Day Solo-Expedition

Future deep space astronauts must maintain adequate nutrition despite highly stressful, isolated, confined and dangerous environments. The present case-study investigated appetite regulating hormones, nutrition status, and physical and emotional stress in a space analog condition: an explorer conducting a 93-day unsupported solo crossing of Antarctica. Using the dried blood spot (DBS) method, the subject drew samples of his blood on a regular basis during the expedition. The DBSs were later analyzed for the appetite regulating hormones leptin and adiponectin. Energy intake and nutritional status were monitored by analysis of albumin and globulin (including their ratio). Interleukin-6 (IL-6) was also analyzed and used as an energy sensor. The results showed a marked reduction in levels of the appetite-reducing hormone, leptin, and the appetite stimulating hormone, adiponectin, during both extreme physical and psychological strain. Nutrition status showed a variation over the expedition, with below-normal levels during extreme psychological strain and levels abutting the lower bounds of the normal range during a phase dominated by extreme physical hardship. The IL-6 levels varied substantially, with levels above the normal range except during the recovery phase. It was concluded that a daily intake of 5058 to 5931 calories seemed to allow recovery of both appetite and nutritional status between extreme physical and psychological hardship during a long Arctic expedition. Furthermore, IL-6 may be a sensor in the muscle-liver, muscle-fat and muscle-brain crosstalk. These results may help guide nutrition planning for future astronaut crews, mountaineers and others involved in highly demanding missions.

Irisin plays an important role in the outcomes of newly diagnosed prediabetes in adults in Guiyang, China

AIMS/INTRODUCTION

To explore the potential role of irisin in the outcomes of newly diagnosed prediabetes.

MATERIALS AND METHODS

Data were obtained from the Guiyang subcenter of the Risk Evaluation of cAncers in Chinese diabeTic Individuals: a lONgitudinal (REACTION) study. A total of 2,530 participants had newly diagnosed prediabetes at baseline and completed follow up. The nested 1:1 case-control study included 161 participants who developed diabetes mellitus at follow up, and 161 age- and sex-matched controls. The follow-up study included 86 matched case-control pairs. Fasting serum irisin levels were measured using enzyme-linked immunosorbent assay.

RESULTS

Baseline serum irisin levels were higher in the cases than in the controls (P = 0.002); high baseline serum irisin levels were an independent risk factor for the development of diabetes (odds ratio 1.235, 95% confidence interval 1.025-1.488). After adjustment for age, sex, body mass index, glycated hemoglobin (HbA1c), smoking, exercise, and family history of diabetes, subjects in the highest quartile of irisin levels had a higher risk of diabetes than those in the lowest quartile (odds ratio 3.065, 95% confidence interval 1.511-6.218). The extent of decrease in irisin levels during follow-up was greater in the cases than in the controls (P < 0.001). Baseline serum irisin levels were positively correlated with the extent of decrease in irisin during follow-up (r = 0.773, P < 0.001). After adjustment for confounding factors, subjects with a decrease of irisin above the median had much higher risk for diabetes (odds ratio 5.077, 95% confidence interval 2.112-12.206).

CONCLUSIONS

Irisin might play an important role in the outcomes of newly diagnosed prediabetes in adults in Guiyang, and can predict the risk for developing diabetes in these individuals.

Irisin supports integrin-mediated cell adhesion of lymphocytes

Irisin, a myokine released from skeletal muscle, has recently been found to act as a ligand for the integrins αVβ5, αVβ1, and α5β1 expressed on mesenchymal cells, thereby playing an important role in the metabolic remodeling of the bone, skeletal muscle and adipose tissues. Although the immune-modulatory effects of irisin in chronic inflammation have been documented, its interactions with lymphocytic integrins have yet to be elucidated. Here, we show that irisin supports the cell adhesion of human and mouse lymphocytes. Cell adhesion assays using a panel of inhibitory antibodies to integrins have shown that irisin-mediated lymphocyte adhesion involves multiple integrins including not only α4β1 and α5β1, but also leukocyte-specific αLβ2 and α4β7. Importantly, mouse lymphocytic TK-1 cells that lack the expression of β1 integrins have exhibited αLβ2- and α4β7-mediated cell adhesion to irisin. Irisin has also been demonstrated to bind to purified recombinant integrin αLβ2 and α4β7 proteins. Thus, irisin represents a novel ligand for integrin αLβ2 and α4β7, capable of supporting lymphocyte cell adhesion independently of β1 integrins. These results suggest that irisin may play an important role in regulating lymphocyte adhesion and migration in the inflamed vasculature.

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Irisin, a myokine released from skeletal muscle, binds to integrins αLβ2 and α4β7 in addition to integrins α4β1 and α5β1.

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Irisin acts as an integrin ligand capable of supporting cell adhesion of human and mouse lymphocytes.

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The results of this study significantly expand upon the role of irisin as a contributor to metabolic regulation.

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Irisin deposited on the inflamed vasculature may participate in the metabolic regulation of lymphocyte migration.

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

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

Integrin-Ligand Interactions in Inflammation, Cancer, and Metabolic Disease: Insights Into the Multifaceted Roles of an Emerging Ligand Irisin

Integrins are transmembrane proteins that mediate cellular adhesion and migration to neighboring cells or the extracellular matrix, which is essential for cells to undertake diverse physiological and pathological pathways. For integrin activation and ligand binding, bidirectional signaling across the cell membrane is needed. Integrins aberrantly activated under pathologic conditions facilitate cellular infiltration into tissues, thereby causing inflammatory or tumorigenic progressions. Thus, integrins have emerged to the forefront as promising targets for developing therapeutics to treat autoimmune and cancer diseases. In contrast, it remains a fact that integrin-ligand interactions are beneficial for improving the health status of different tissues. Among these ligands, irisin, a myokine produced mainly by skeletal muscles in an exercise-dependent manner, has been shown to bind to integrin αVβ5, alleviating symptoms under unfavorable conditions. These findings may provide insights into some of the underlying mechanisms by which exercise improves quality of life. This review will discuss the current understanding of integrin-ligand interactions in both health and disease. Likewise, we not only explain how diverse ligands play different roles in mediating cellular functions under both conditions via their interactions with integrins, but also specifically highlight the potential roles of the emerging ligand irisin in inflammation, cancer, and metabolic disease.

A Randomized Controlled Trial on the Effects of 12 Weeks of Aerobic, Resistance, and Combined Exercises Training on the Serum Levels of Nesfatin-1, Irisin-1 and HOMA-IR

Background/objective: This study aimed to investigate the impacts of a 12-week training of the aerobic exercise (AE), resistance exercise (RE), and combined exercise (CE) on the serum levels of nesfatin-1, irisin-1 and some other metabolic and anthropometric indices in overweight women with metabolic syndrome. Methods: Sixty overweight women with metabolic syndrome were assigned equally into four groups: aerobic exercise (AE, n = 15), resistance exercise (RE, n = 15), combined exercise (CE, n = 15), and control (n = 15). All groups underwent 12 weeks of intervention. The study variables were measured before and 24 h after the intervention period. Results: Twelve weeks of training resulted in an increase of irisin-1 in the AE and CE groups and nesfatin-1 in all the intervention groups. As expected, all the trained groups exhibited a positive alteration in anthropometric indices and lipid profile in comparison with the control group. Besides, compared with the control group, insulin resistance (based on the homeostatic model assessment) in AE (p = 0.022), RE (p = 0.032), and CE (p < 0.001) groups were reduced significantly. According to the observed changes in the measured indices, serum irisin-1 was significantly correlated with body weight, BMI, body fat percentage, fasting insulin, and HOMA-IR. However, with regard to nesfatin-1, only a negative correlation was observed with body fat percentage and LDL-cholesterol. Conclusions: The 12-week systematic training program changed circulating irisin-1 and nesfatin-1. Also, change in the serum irisin-1 and nesfatin-1 were correlated with the change in glycemic and anthropometric indices in addition to LDL-cholesterol. Also, exercise training significantly reduced fasting insulin and HOMA-IR in all the intervention groups. RCT Registration Code: IRCT20180806040721N2.

Irisin and Autophagy: First Update

Aging and sedentary life style are considered independent risk factors for many disorders. Under these conditions, accumulation of dysfunctional and damaged cellular proteins and organelles occurs, resulting in a cellular degeneration and cell death. Autophagy is a conserved recycling pathway responsible for the degradation, then turnover of cellular proteins and organelles. This process is a part of the molecular underpinnings by which exercise promotes healthy aging and mitigate age-related pathologies. Irisin is a myokine released during physical activity and acts as a link between muscles and other tissues and organs. Its main beneficial function is the change of subcutaneous and visceral adipose tissue into brown adipose tissue, with a consequential increase in thermogenesis. Irisin modulates metabolic processes, acting on glucose homeostasis, reduces systemic inflammation, maintains the balance between resorption and bone formation, and regulates the functioning of the nervous system. Recently, some of its pleiotropic and favorable properties have been attributed to autophagy induction, posing irisin as an important regulator of autophagy by exercise. This review article proposes to bring together for the first time the "state of the art" knowledge regarding the effects of irisin and autophagy. Furthermore, treatments on relation between exercise/myokines and autophagy have been also achieved.

Aerobic exercise training-induced irisin secretion is associated with the reduction of arterial stiffness via nitric oxide production in adults with obesity

This study aimed to clarify whether muscle-derived irisin secretion induced by aerobic exercise training is involved in reduction of arterial stiffness via arterial nitric oxide (NO) productivity in obesity. In animal study, 16 Otsuka Long-Evans Tokushima Fatty (OLETF) rats with obesity were randomly divided into 2 groups: sedentary control (OLETF-CON) and 8-week aerobic treadmill training (OLETF-EX) groups. In human study, 15 subjects with obesity completed 8-week aerobic exercise training for 45 min at 60%-70% peak oxygen uptake intensity for 3 days/week. As a result of animal study, carotid-femoral pulse wave velocity (cfPWV) was decreased, and arterial phosphorylation levels of AMP-activated protein kinase (AMPK), protein kinase B (Akt), and endothelial NO synthase (eNOS), circulating levels of nitrite/nitrate (NOx) and irisin, and muscle messenger RNA expression of fibronectin type III domain containing 5 (Fndc5) were increased in the OLETF-EX group compared with OLETF-CON group. In a human study, regular aerobic exercise reduced cfPWV and elevated circulating levels of NOx and irisin. Furthermore, change in circulating irisin levels by regular exercise was positively correlated with circulating NOx levels and was negatively correlated with cfPWV. Thus, aerobic exercise training-induced increase in irisin secretion may be related to reduction of arterial stiffness achieved by NO production via activated arterial AMPK-Akt-eNOS signaling pathway in obesity. Novelty Aerobic exercise training promoted irisin secretion with upregulation of muscle Fndc5 gene expression in rats with obesity. Irisin affected the activation of arterial AMPK-Akt-eNOS signaling by aerobic exercise training. Increased serum irisin level by aerobic exercise training was associated with reduction of arterial stiffness in obese adults.

The effects of aerobic, resistance, and combined exercises on the plasma irisin levels, HOMA-IR, and lipid profiles in women with metabolic syndrome: A randomized controlled trial

Background/objective

Irisin is suggested to be an exercise beneficial effects mediator. This study aimed to examine the effects of the aerobic exercise (AE), resistance exercise (RE), and combined exercise (CE) on the plasma levels of irisin and some metabolic and anthropometric indices.

Methods

Sixty overweight women with metabolic syndrome were assigned equally into four groups: AE, RE, CE, and control. The study variables were measured before and 24 h after the intervention period.

Results

None of the study groups showed statistically significant changes in the serum irisin. However, muscle mass significantly increased in the RE and CE groups. Also, a significant decrease was observed in the body fat percentage in all groups. In addition, compared with the control group, the homeostatic model assessment of insulin resistance in the AE (p = 0.021), RE (p = 0.039), and in the CE (p = 0.003) groups reduced significantly. According to the analysis of indices’ changes, serum irisin was significantly correlated with the body fat percentage (r = 0.532) and HOMA-IR (r = 0.424).

Conclusions

The systematic exercise program for 8-weeks did not change circulating irisin and no statistically significant difference was observed between the exercise methods. Also, serum irisin seemed to be associated with the glycemic status, body fat and weight independent of exercise activity.

RCT registration code

IRCT20180806040721N2.

Registry name

Iranian Registry of Clinical Trials.

Gene polymorphisms of Patatin-like phospholipase domain containing 3 (PNPLA3), adiponectin, leptin in diabetic obese patients

Obesity leads a crucial importance in metabolic disorders, as well as type 2 diabetes mellitus. Our present study was designed to assess the potential role of irisin, adiponectin, leptin and gene polymorphism of PNPLA3, leptin and adiponectin as predictive markers of diabetes associated with obesity. One hundred eighty subjects were distributed to three groups including; healthy non-diabetic non obese volunteers as a control group, diabetic non obese group, and diabetic obese group (n = 60 for each group). Fasting blood samples of all groups were collected to determine fasting blood glucose, insulin levels, insulin resistance, total cholesterol, high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), triacylglycerol, irisin, adiponectin, leptin; as well as, polymorphism of PNPLA3, adiponectin and leptin. The results showed that glucose, insulin resistance, total cholesterol, irisin, leptin, LDL-C, triacylglycerol concentrations were significantly increased, however, insulin, HDL-C, adiponectin were significantly decreased in diabetic obese patients in relation to diabetic non-obese patients as well as in healthy volunteers. The polymorphism of PNPLA3 rs738409 was linearly related to irisin and leptin but was not related with circulating concentrations of adiponectin. We concluded that increased irisin and leptin levels can predict the insulin resistance in obese patients. Moreover, patients who have mutant genotype of PNPLA3 I148 gene (rs738409) C>G, ADIPOQ gene (rs266729) G>C and LEP gene (rs2167270) G>A showed a significant higher susceptibility rate for DM in obese people than those with wild type. This could be considered as an adjustable retort to counter the impact of obesity on glucose homeostasis.

Serum Irisin, Adropin, and Preptin in Obese Patients 6 Months After Bariatric Surgery

BACKGROUND/OBJECTIVES

The reduction of body mass after bariatric surgery affects energy metabolism and may involve changes in irisin, preptin, and adropin production.

SUBJECTS AND METHODS

Fifty-five morbidly obese patients with a mean body mass index (BMI) of 45.7 ± 5.8 kg/m² were treated with either laparoscopic sleeve gastrectomy(n = 30) or laparoscopic adjustable gastric banding (n = 25). Forty-six (83.6%) were followed-up 6 months after surgery. The control group included 15 healthy non-obese participants. Anthropometric measurements, lipid profiles, HbA1c, and serum irisin, preptin, and adropin were assessed at baseline and on follow-up.

RESULTS

The serum concentrations of all three peptides were higher at 6 months than at baseline but only irisin (p = 0.02) and adropin (p = 0.000001) were significantly higher. The increase in preptin was borderline significant (p = 0.051). Changes of serum concentrations of all three peptides were bidirectional.

CONCLUSION

Body mass reduction resulting from bariatric procedures may change the production of energy regulating peptides, but not always in a favorable manner.

Effect of BMI on blood value of patients on HCG day with IUI treatment

BACKGROUND

This study aims to analyze the effect of the body mass index (BMI) on E₂, P and LH values in females who received intrauterine insemination (IUI) treatment on human chorionic gonadotropin (HCG) day.

METHODS

A total of 2319 cycles of IUI-assisted pregnancy treatment were selected in our hospital. Based on the BMI, female infertility patients are divided into three groups: normal weight group, overweight and obese group.

RESULTS

For patients with natural cycles and ≤ 35 years old, there were 440, 178 and 197 cases in the three groups, respectively. For patients with natural cycles and > 35 years old, there were 90, 83 and 81 cycles in the three groups, respectively. For patients with induced ovulation cycle and ≤ 35 years old, there were 425, 203 and 516 cases in the three groups, respectively. For patients with induced ovulation cycle and > 35 years old, there were 26, 26 and 54 cases in the three groups, respectively.

CONCLUSION

When a patient is ≤35 years old, the BMI affects the E₂, LH and P values on the day of artificial insemination. However, the BMI is negatively correlated with E₂, LH and P in IUI on HCG day. After controlling for age and assisted pregnancy, the correlation analysis revealed that the BMI is negatively correlated with hormone E₂ and LH. The higher the BMI was, the lower the levels of hormones E₂, LH and P became. However, in the present study, the BMI did not significantly improve the clinical pregnancy rate of patients who received IUI.

Irisin and markers of metabolic derangement in non-diabetic Caucasian subjects with stage I-II obesity during early aging

Irisin concentrations are decreased in subjects with overt diabetes and upregulated in those with obesity or impaired fasting glucose. However, gender-balanced data in older populations, in whom risk factors commonly culminate in overt cardiovascular disease, are scarce. We assessed in non-diabetic Caucasian subjects with stage I-II obesity in the early aging range (50 to 70 years), the relationship between irisin, body composition and markers of metabolic derangement by gender. In 60 (31 women, 29 men) non-diabetics with a body mass index ≥30 - ≤40 kg/m², we measured anthropometrics and body composition (Air Displacement Plethysmography). We assayed lipid and glucose profile by routine methods, plasma irisin by ELISA and measured insulin resistance by the HOMA index. Irisin levels were higher in women than in men (161 [105–198]) vs 83 [33–115] ng/ml, P<0.001), and correlated directly with HOMA index in both (rho 0.735, P<0.001 M, rho 0.452, P = 0.011 F). Sex differences were maintained across insulin resistance severity stages. In men, irisin concentrations correlated directly with body mass index (rho 0.755, P<0.001), waist circumference (rho 0.623, P<0.001), fat mass index (rho 0.762, P<0.001), glucose (rho 0.408, P = 0.028), the fatty liver index (rho 0.705, P<0.001) and FINDRISC score (rho 0.536, P = 0.003). Among non-diabetic Caucasian subjects with obesity in the early stages of aging, irisin levels reflect the amount of body fat and insulin resistance severity, independently of between-gender differences in the adipomyokine concentrations and are associated with markers of visceral adiposity in men but not in women.

DOCK5 regulates energy balance and hepatic insulin sensitivity by targeting mTORC1 signaling

The dedicator of cytokinesis 5 (DOCK5) is associated with obesity. However, the mechanism by which DOCK5 contributes to obesity remains completely unknown. Here, we show that hepatic DOCK5 expression significantly decreases at a state of insulin resistance (IR). Deletion of DOCK5 in mice reduces energy expenditure, promotes obesity, augments IR, dysregulates glucose metabolism, and activates the mTOR (Raptor)/S6K1 pathway under a high-fat diet (HFD). The overexpression of DOCK5 in hepatocytes inhibits gluconeogenic gene expression and increases the level of insulin receptor (InsR) and Akt phosphorylation. DOCK5 overexpression also inhibits mTOR/S6K1 phosphorylation and decreases the level of raptor protein expression. The opposite effects were observed in DOCK5-deficient hepatocytes. Importantly, in liver-specific Raptor knockout mice and associated hepatocytes, the effects of an adeno-associated virus (AAV8)- or adenovirus-mediated DOCK5 knockdown on glucose metabolism and insulin signaling are largely eliminated. Additionally, DOCK5-Raptor interaction is indispensable for the DOCK5-mediated regulation of hepatic glucose production (HGP). Therefore, DOCK5 acts as a regulator of Raptor to control hepatic insulin activity and glucose homeostasis.

Association of Circulating Irisin Levels with Adiposity and Glucose Metabolic Profiles in a Middle-Aged Chinese Population: A Cross-Sectional Study

OBJECTIVE

The myokine irisin has been proposed to affect obesity and metabolism disorders. However, data about the association of irisin with obesity and glucose metabolic status in humans remains controversial, and limited data are available concerning the Chinese population. This study aimed to evaluate the association between serum irisin concentrations and obesity, as well as glucose metabolic and cardiovascular factors in the middle-aged physical activity-matched Chinese Han race population.

METHODS

A total of 740 participants were included in this cross-sectional study, who were divided into a normal weight (NW) group, overweight/obese (OB) group, normal weight type 2 diabetes (DM-NW) group and overweight/obese diabetes (DM-OB) group, and physical activity was evaluated and matched for the four groups. Circulating irisin levels were analyzed and compared among the groups with different adiposity and glucose status. Linear regression analysis was performed to test the relationship between serum irisin and adiposity indices, glucose metabolic and other cardiovascular risk factors.

RESULTS

Circulating irisin levels were significantly correlated with higher levels of direct and indirect adiposity markers, including BMI, waist circumference and fat mass, and other cardiovascular risk factors, such as plasma triglyceride and low-density lipoprotein cholesterol level (p < 0.01). Diabetes patients had lower irisin levels compared to non-diabetes participants, in either normal weight and obese group, resulting in a correlation of irisin with HbA1c, HOMA-IR and HOMA-IS (p < 0.01). Linear regression analysis demonstrated that irisin serum concentrations were independently associated with sex, BMI, HbA1c, HOMA-IR and HOMA-IS (R² = 0.465).

CONCLUSION

These data indicated that circulating irisin was affected by adiposity and glucose metabolism condition in the middle-aged Chinese population. The increase of irisin under conditions of obesity may indicate its physiological function to improve glucose tolerance which is often impaired in obese subjects, but this compensatory secretion of irisin seems likely to be progressing to a secretion failure once diabetes developed.

Irisin reverses intestinal epithelial barrier dysfunction during intestinal injury via binding to the integrin αVβ5 receptor

Disruption of the gut barrier results in severe clinical outcomes with no specific treatment. Metabolic disorders and destruction of enterocytes play key roles in gut barrier dysfunction. Irisin is a newly identified exercise hormone that regulates energy metabolism. However, the effect of irisin on gut barrier function remains unknown. The therapeutic effect of irisin on gut barrier dysfunction was evaluated in gut ischemia reperfusion (IR). The direct effect of irisin on gut barrier function was studied in Caco-2 cells. Here, we discovered that serum and gut irisin levels were decreased during gut IR and that treatment with exogenous irisin restored gut barrier function after gut IR in mice. Meanwhile, irisin decreased oxidative stress, calcium influx and endoplasmic reticulum (ER) stress after gut IR. Moreover, irisin protected mitochondrial function and reduced enterocyte apoptosis. The neutralizing antibody against irisin significantly aggravated gut injury, oxidative stress and enterocyte apoptosis after gut IR. Further studies revealed that irisin activated the AMPK-UCP 2 pathway via binding to the integrin αVβ5 receptor. Inhibition of integrin αVβ5, AMPK or UCP 2 abolished the protective role of irisin in gut barrier function. In conclusion, exogenous irisin restores gut barrier function after gut IR via the integrin αVβ5-AMPK-UCP 2 pathway.

Superiority of the Non-Glycosylated Form Over the Glycosylated Form of Irisin in the Attenuation of Adipocytic Meta-Inflammation: A Potential Factor in the Fight Against Insulin Resistance

Irisin is an adipomyokine that promotes the browning of white adipose tissue and exhibits protective potential against the development of insulin resistance and type 2 diabetes. In our bodies, it occurs in its glycosylated form (G-IR): its activity is still poorly understood, because the majority of studies have used its non-glycosylated counterpart (nG-IR). Glycosylation can affect protein function: therefore, the present study attempted to compare the actions of both forms of irisin toward inflammatory activation of the main component of adipose tissue. The study was carried out in a coculture of 3T3 adipocytes and RAW 264.7 macrophages maintained in the presence of nG-IR or G-IR. The impact on vitality and the expression and release of key inflammatory mediators important for insulin resistance and diabetes development were assessed. The studies showed that both forms effectively inhibited the expression and release of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, macrophage chemotactic protein (MCP)-1, high-mobility group box (HMGB1), leptin, and adiponectin. However, in the case of TNF-α, IL-1β, MCP-1, and HMGB1, the inhibition exerted by nG-IR was more prominent than that by G-IR. In addition, only nG-IR significantly inhibited macrophage migration. Here, nG-IR seemed to be the stronger inhibitor of the development of obesity-related inflammation; however, G-IR also had anti-inflammatory potential.