Irisin attenuates intestinal injury, oxidative and endoplasmic reticulum stress in mice with L-arginine-induced acute pancreatitis

Rutin protects the pancreas from inflammatory injury and oncogene-driven tumorigenesis by inhibiting acinar to ductal metaplasia

Rutin is a valuable traditional Chinese medicine known for its anti-inflammatory and anticancer effects. It has been shown to be effective in treating various inflammation-associated diseases. Here, we investigated the influence of rutin on acute pancreatitis and tumorigenesis. Using C57BL/6J mice and Kras mutant transgenic mice, we induced pancreatitis and acinar regeneration models. Pancreatic malondialdehyde (MDA), superoxide dismutase (SOD) activity and reduced glutathione (GSH) contents were measured for oxidative stress. Histological staining and a pancreatic acinar 3D culture model were used to clarify the influence of rutin on ADM in vivo and in vitro. Western blotting was adopted to detect ADM markers amylase and CK19. We found that rutin ameliorated inflammatory injury to the pancreas in both caerulein- and arginine-induced AP. Then, we revealed that the anti-damage effect of rutin may be due to its inhibition of oxidative stress. In addition, an acinar 3D culture model showed that rutin inhibited the formation of ADM by activating AMPK in acinar cells. Finally, the activation of AMPK is believed to be a potential mechanism by which rutin exerts inhibitory effects on Kras-driven tumorigenesis. Rutin inhibited AP-induced pancreatic injury and oncogenic Kras-driven tumorigenesis by inhibiting ADM.

Endoplasmic reticulum stress in acute pancreatitis: Exploring the molecular mechanisms and therapeutic targets

Acute pancreatitis (AP) is associated with multiple cellular mechanisms that trigger and or are triggered by the inflammatory injury and death of the acinar cells. One of the key mechanisms is the endoplasmic reticulum (ER) stress, which manifests as an accumulation of misfolded proteins within ER, an event that has proinflammatory and proapoptotic consequences. Hence, the degree of cell insult during AP could considerably depend on the signaling pathways that are upregulated during ER stress and its resulting dyshomeostasis such as C/EBP homologous protein (CHOP), cJUN NH2-terminal kinase (JNK), nuclear factor kappa B (NF-κB), and NOD-like receptor protein 3 (NLRP3) inflammasome. Exploring these molecular pathways is an interesting area for translational medicine as it may lead to identifying new therapeutic targets in AP. This review of the literature aims to shed light on the different roles of ER stress in the etiopathogenesis and pathogenesis of AP. Then, it specifically focuses on the therapeutic implications of ER stress in this context.

CIRP contributes to multiple organ damage in acute pancreatitis by increasing endothelial permeability

Acute pancreatitis can lead to systemic inflammation and multiple organ damage. Increased endothelial permeability is a hallmark of systemic inflammation. Several studies have demonstrated that cold-inducible RNA-binding protein (CIRP) functions as a proinflammatory factor in various diseases. However, its role in endothelial barrier dysfunction during acute pancreatitis remains unknown. To study this, acute pancreatitis was induced by two hourly intraperitoneal injections of 4.0 g/kg L-arginine in wild-type (WT) or CIRP knockout mice. Our results showed that CIRP levels in the pancreas, small intestine, lung, and liver were upregulated at 72 h after the induction of acute pancreatitis in WT mice. CIRP deficiency significantly attenuated tissue injury, edema, and extravasation of Evans blue in the pancreas, small intestine, lung, and liver at 72 h after L-arginine injection. Administration of C23, a specific antagonist of CIRP, at 2 h after the last injection of L-arginine also produced similar protective effects as CIRP knockout in mice. In vitro studies showed that recombinant CIRP caused a significant reduction in transcellular electric resistance in HUVEC monolayers. Immunocytochemical analysis of endothelial cells exposed to CIRP revealed an increased formation of actin stress fibers. VE-cadherin and β-catenin staining showed intercellular gaps were formed in CIRP-stimulated cells. Western blot analysis showed that CIRP induced SRC phosphorylation at TYR416. Exposure to the SRC inhibitor PP2 reduced CIRP-induced endothelial barrier dysfunction in HUVEC monolayers. In conclusion, blocking CIRP mitigates acute pancreatitis-induced multiple organ damage by alleviating endothelial hyperpermeability. Targeting CIRP may be a potential therapeutic option for acute pancreatitis.

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 ).

Irisin-mediated KEAP1 degradation alleviates oxidative stress and ameliorates pancreatitis

Oxidative stress (OS) injury is pivotal in acute pancreatitis (AP) pathogenesis, contributing to inflammatory cascades. Irisin, a ubiquitous cytokine, exhibits antioxidant properties. However, the role of irisin in AP remains inconclusive. Our study aims to elucidate irisin expression in AP patients and investigate its mechanism of action to propose a novel treatment strategy for AP. Serum irisin levels in 65 AP patients were quantified using an enzyme-linked immunosorbent assay and correlated with disease severity scores. Core genes implicated in AP-related oxidative stress were identified and screened via bioinformatics analysis. The therapeutic efficacy of irisin in AP was confirmed using a murine cerulein-induced AP model. The intrinsic mechanism of irisin's antioxidative stress action was investigated and verified in pancreatic AR42J cells (Supplementary Fig. 1). Common targets shared by irisin and AP were further validated using a molecular docking model which was constructed for virtual docking analysis. This study investigated alterations in redox status in AP and found a significant reduction in serum irisin levels, correlating inversely with AP severity. In a murine AP model, we showed that irisin triggers an antioxidative stress program via the KEAP1 gene; this process helps reestablish redox balance by decreasing the buildup of reactive oxygen species (ROS) and suppressing the secretion of inflammatory mediators within pancreatic tissues Notably, increased KEAP1 expression counteracted the antioxidative effects of irisin. Our findings unveil a novel therapeutic mechanism for AP, wherein irisin inhibits KEAP1 to alleviate OS. Increasing irisin levels in vivo presents a promising strategy for AP treatment.

Nanotherapeutics-mediated restoration of pancreatic homeostasis and intestinal barrier for the treatment of severe acute pancreatitis

Severe acute pancreatitis (SAP) is an inflammatory disease of the pancreas accompanied with intestinal injury, and effective therapeutic modalities are still highly lacking. Herein, a facile and effective nanotherapeutics (pHA@IBNCs) is developed to alleviate pancreatic inflammation and restore intestinal barrier for SAP treatment. Epigallocatechin gallate (EGCG, an anti-oxidant), interleukin-22 (IL-22, an anti-inflammatory and epithelial barrier-protecting cytokine), and bovine serum albumin (a framework protein), are assembled via non-covalent interactions to form nanocomplexes (IBNCs). Then, phenylboronic acid-modified hyaluronic acid (pHA) is synthesized and coated onto IBNCs via formation of the reversible boronate ester bonds to obtain pHA@IBNCs. Upon intravenous injection, pHA@IBNCs could efficiently accumulate at the lesion sites of sodium taurocholate (STC)-induced SAP mice, based on their prolonged blood circulation time and pHA-mediated targeting of activated intestinal epithelial cells and macrophages. Inside the inflammatory microenvironment, over-produced reactive oxygen species (ROS) trigger the shedding of the pHA layer and release of the drug payloads. Thereby, EGCG cooperates with IL-22 to attenuate pancreatitis and restore the intestinal barrier by scavenging ROS, suppressing pro-inflammatory cytokines secretion, and promoting the repair of intestinal epithelia. Such a nano-therapeutic approach targeting multiple pathological events may serve as a promising paradigm for the effective management of SAP.

Irisin: A Multifaceted Hormone Bridging Exercise and Disease Pathophysiology

The fibronectin domain-containing protein 5 (FNDC5), or irisin, is an adipo-myokine hormone produced during exercise, which shows therapeutic potential for conditions like metabolic disorders, osteoporosis, sarcopenia, obesity, type 2 diabetes, and neurodegenerative diseases, including Alzheimer's disease (AD). This review explores its potential across various pathophysiological processes that are often considered independent. Elevated in healthy states but reduced in diseases, irisin improves muscle-adipose communication, insulin sensitivity, and metabolic balance by enhancing mitochondrial function and reducing oxidative stress. It promotes osteogenesis and mitigates bone loss in osteoporosis and sarcopenia. Irisin exhibits anti-inflammatory effects by inhibiting NF-κB signaling and countering insulin resistance. In the brain, it reduces amyloid-β toxicity, inflammation, and oxidative stress, enhancing brain-derived neurotrophic factor (BDNF) signaling, which improves cognition and synaptic health in AD models. It also regulates dopamine pathways, potentially alleviating neuropsychiatric symptoms like depression and apathy. By linking physical activity to systemic health, irisin emphasizes its role in the muscle-bone-brain axis. Its multifaceted benefits highlight its potential as a therapeutic target for AD and related disorders, with applications in prevention, in treatment, and as a complement to exercise strategies.

Biomimetic mesenchymal stem cell membrane-coated nanoparticle delivery of MKP5 inhibits hepatic fibrosis through the IRE/XBP1 pathway

Hepatic fibrosis is a common disease with high morbidity and mortality rates. The complex and poorly understood mechanisms underlying hepatic fibrosis represent a significant challenge for the development of more effective therapeutic strategies. MKP5 is a potential regulator of multiple fibrotic diseases. However, its precise role and mechanism of action in hepatic fibrosis remains unclear. This study identified a reduction in MKP5 expression in fibrotic liver tissues of mice treated with CCl4 and observed that MKP5 knockout mice exhibited a more pronounced development of hepatic fibrosis. In addition, RNA-seq data indicated activation of protein processing in the endoplasmic reticulum signalling pathway in fibrotic liver tissues of mice lacking MKP5. Mechanistically, MKP5 inhibits the activation of hepatic stellate cells (HSCs) and hepatocyte apoptosis through the regulation of the IRE/XBP1 pathway. Based on these findings, we developed PLGA-MKP5 nanoparticles coated with a mesenchymal stem cell membrane (MSCM). Our results demonstrated that MSCM-PLGA-MKP5 was most effective in attenuating hepatic inflammation and fibrosis in murine models by modulating the IRE/XBP1 axis. This study contributes to the current understanding of the pathogenesis of hepatic fibrosis, suggesting that the targeted delivery of MKP5 via a nano-delivery system may represent a promising therapeutic approach to treat hepatic fibrosis.

The Role of the Myokine Irisin in the Protection and Carcinogenesis of the Gastrointestinal Tract

Recently discovered irisin, a member of the myokines family, is a potential mediator of exercise-induced energy metabolism and a factor promoting browning of the white adipose tissue. Recent evidence indicates that this myokine, released from contracting muscles, can mediate the beneficial effects of exercise on health. Irisin may be a potential therapeutic agent against obesity and has been shown to play an important role in the protection of various cells, tissues, and organs due to its anti-inflammatory, antioxidative, and anti-cancer properties. Our aim was to review the recent experimental and clinical studies on irisin and its expression, release into the bloodstream, tissue targets, and potential contribution to the protective effects of exercise in the gastrointestinal tract. Particular emphasis was placed on inflammatory bowel disease, intestinal ischemia/reperfusion injury, periodontitis, and other digestive tract disorders, including carcinogenesis. Overall, irisin holds significant potential as a novel target molecule, offering a safe and therapeutic approach to treating various gastrointestinal diseases.

Milk fat globule epidermal growth factor 8 alleviates liver injury in severe acute pancreatitis by restoring autophagy flux and inhibiting ferroptosis in hepatocytes

BACKGROUND

Liver injury is common in severe acute pancreatitis (SAP). Excessive autophagy often leads to an imbalance of homeostasis in hepatocytes, which induces lipid peroxidation and mitochondrial iron deposition and ultimately leads to ferroptosis. Our previous study found that milk fat globule epidermal growth factor 8 (MFG-E8) alleviates acinar cell damage during SAP via binding to αvβ3/5 integrins. MFG-E8 also seems to mitigate pancreatic fibrosis via inhibiting chaperone-mediated autophagy.

AIM

To speculate whether MFG-E8 could also alleviate SAP induced liver injury by restoring the abnormal autophagy flux.

METHODS

SAP was induced in mice by 2 hly intraperitoneal injections of 4.0 g/kg L-arginine or 7 hly injections of 50 μg/kg cerulein plus lipopolysaccharide. mfge8-knockout mice were used to study the effect of MFG-E8 deficiency on SAP-induced liver injury. Cilengitide, a specific αvβ3/5 integrin inhibitor, was used to investigate the possible mechanism of MFG-E8.

RESULTS

The results showed that MFG-E8 deficiency aggravated SAP-induced liver injury in mice, enhanced autophagy flux in hepatocyte, and worsened the degree of ferroptosis. Exogenous MFG-E8 reduced SAP-induced liver injury in a dose-dependent manner. Mechanistically, MFG-E8 mitigated excessive autophagy and inhibited ferroptosis in liver cells. Cilengitide abolished MFG-E8's beneficial effects in SAP-induced liver injury.

CONCLUSION

MFG-E8 acts as an endogenous protective mediator in SAP-induced liver injury. MFG-E8 alleviates the excessive autophagy and inhibits ferroptosis in hepatocytes by binding to integrin αVβ3/5.

Investigation of new inflammatory biomarkers in patients with brucella

BACKGROUND

Delayed diagnosis and inadequate treatment of infectious and inflammatory diseases, such as Brucella, lead to high rates of mortality and morbidity. The aim of our study was to investigate the association between serum levels of apelin, presepsin, and irisin with inflammation, laboratory parameters, and blood culture in patients with brucella.

PATIENTS AND METHODS

This prospective case-control study involves 30 patients with brucellosis and 30 healthy, matched control subjects. Thirty patients who were diagnosed with brucellosis were aged ≥ 18 years. Blood samples were taken from the patients on the first day they were diagnosed with brucellosis. The values of irisin, presepsin, and apelin were studied. In addition, blood samples were also taken from 30 healthy individuals for the control group. Irisin, presepsin, and apelin values that were measured in the patients on the first day were compared with those values measured in the control group.

RESULTS

The sex and age statuses of the subjects are matched among the groups. The levels of irisin were significantly higher in patients with brucellosis compared to the control group (p<0.045). There was no significant difference between the two groups in terms of apelin and presepsin levels (p values 0.087 and 0.162, respectively). There was a positive correlation between irisin levels and elevated ALT levels, as well as positive blood cultures.

CONCLUSIONS

It appears that the measurement of irisin levels may be beneficial in patients with brucellosis. Irisin can be used as a diagnostic marker for brucella infection and may greatly clinicians to predict the severity disease and treatment response.

Adipo-myokine Irisin, a Promising Antioxidant against Nicotine Induced Oxidative Stress in BALB/c mice

Objectives

To determine the role of r-irisin in attenuating nicotine-induced oxidative stress by estimating serum oxidative stress markers and antioxidant enzymes in BALB/c mice.

Method

This 18 month experimental study was carried out at Foundation University Islamabad and National Institute of Health starting in 2020. Thirty healthy BALB/c mice were divided into three groups. Group-I (control group) received normal saline 1ml/kg body weight intra-peritoneally daily for 28 days. Experimental group, Group-II received nicotine 2mg/kg body weight intra-peritoneally, for 28 days to induce oxidative stress. Experimental Group-III was given r-irisin 0.5 μg/g body weight/day via tail vein injection, for the last 14 days in addition to intraperitoneal nicotine for 28 days. On 29th day, intra-cardiac blood samples were taken for estimation of serum antioxidant enzymes [Superoxide dismutase (SOD), Reduced Glutathione (GSH) and Catalases (CAT)], and Thiobarbituric Acid-Reactive Substances (TBARS) levels as lipid peroxidation marker using ELISA. SPSS version 24 was used for statistical analysis. Significant difference in parameters across groups was calculated using one way ANOVA. P-value of < 0.05 was considered significant.

Results

Group-II showed statistically significant increase in serum lipid peroxidation marker (TBARS) levels (p<0.001) and reduction in serum anti-oxidative enzymes (SOD, CAT, GSH) levels (p< 0.001) as compared to Group-I. In Group-III, with co administration of r-irisin, significant improvement in antioxidant enzymes levels and reduction in TBARS levels was observed (p< 0.001) as compared to Group-II.

Conclusion

Irisin ameliorates nicotine induced oxidative stress by improving serum anti-oxidant enzyme levels and reducing serum lipid peroxidation marker.

Potential role of irisin in digestive system diseases

Digestive system diseases (DSD) are very complex conditions that severely threaten human health. Therefore, there is an urgent need to develop new pharmacological treatment strategies. Irisin, a myokine discovered in 2012, is produced by fibronectin type III domain-containing protein 5 (FNDC5), which is a transmembrane protein. Irisin is involved in promoting the browning of white adipose tissue, the regulation of energy metabolism, and the improvement of insulin resistance. Irisin is also an essential mediator of the inflammatory response, oxidative stress, and cell apoptosis. Recent studies have proved that irisin concentration is altered in DSD and exerts pivotal effects on the initiation, progression, and prognosis of these diseases through various mechanisms. Therefore, studying the expression and function of irisin may have great significance for the diagnosis and treatment of DSD. Here, we focus on irisin and explore the multiple molecular pathways targeted by irisin therapy. This review indicates that irisin can serve as a diagnostic marker or potential therapeutic agent for DSD. DATA AVAILABILITY: Not applicable.

Physical Exercise as Disease-Modifying Alternative against Alzheimer's Disease: A Gut-Muscle-Brain Partnership

Alzheimer's disease (AD) is a common cause of dementia characterized by neurodegenerative dysregulations, cognitive impairments, and neuropsychiatric symptoms. Physical exercise (PE) has emerged as a powerful tool for reducing chronic inflammation, improving overall health, and preventing cognitive decline. The connection between the immune system, gut microbiota (GM), and neuroinflammation highlights the role of the gut-brain axis in maintaining brain health and preventing neurodegenerative diseases. Neglected so far, PE has beneficial effects on microbial composition and diversity, thus providing the potential to alleviate neurological symptoms. There is bidirectional communication between the gut and muscle, with GM diversity modulation and short-chain fatty acid (SCFA) production affecting muscle metabolism and preservation, and muscle activity/exercise in turn inducing significant changes in GM composition, functionality, diversity, and SCFA production. This gut-muscle and muscle-gut interplay can then modulate cognition. For instance, irisin, an exercise-induced myokine, promotes neuroplasticity and cognitive function through BDNF signaling. Irisin and muscle-generated BDNF may mediate the positive effects of physical activity against some aspects of AD pathophysiology through the interaction of exercise with the gut microbial ecosystem, neural plasticity, anti-inflammatory signaling pathways, and neurogenesis. Understanding gut-muscle-brain interconnections hold promise for developing strategies to promote brain health, fight age-associated cognitive decline, and improve muscle health and longevity.

Irisin ameliorates myocardial ischemia-reperfusion injury by modulating gut microbiota and intestinal permeability in rats

Recently, myocardial ischemia-reperfusion (I/R) injury was suggested associated with intestinal flora. However, irisin has demonstrated beneficial effects on myocardial I/R injury, thus increasing interest in exploring its mechanism. Therefore, whether irisin interferes in gut microbiota and gut mucosal barrier during myocardial I/R injury was investigated in the present study. Irisin was found to reduce the infiltration of inflammatory cells and fracture in myocardial tissue, myocardial enzyme levels, and the myocardial infarction (MI) area. In addition, the data showed that irisin reverses I/R-induced gut dysbiosis as indicated by the decreased abundance of Actinobacteriota and the increased abundance of Firmicutes, and maintains intestinal barrier integrity, reduces metabolic endotoxemia, and inhibits the production of proinflammatory cytokines interleukin 1β (IL-1β), interleukin 6 (IL-6), and tumor necrosis factor α (TNF-α). Based on the results, irisin could be a good candidate for ameliorating myocardial I/R injury and associated diseases by alleviating gut dysbiosis, endothelial dysfunction and anti-inflammatory properties.

Targeting extracellular CIRP with an X-aptamer shows therapeutic potential in acute pancreatitis

Severe acute pancreatitis (AP) is associated with a high mortality rate. Cold-inducible RNA binding protein (CIRP) can be released from cells in inflammatory conditions and extracellular CIRP acts as a damage-associated molecular pattern. This study aims to explore the role of CIRP in the pathogenesis of AP and evaluate the therapeutic potential of targeting extracellular CIRP with X-aptamers. Our results showed that serum CIRP concentrations were significantly increased in AP mice. Recombinant CIRP triggered mitochondrial injury and ER stress in pancreatic acinar cells. CIRP^-/- mice suffered less severe pancreatic injury and inflammatory responses. Using a bead-based X-aptamer library, we identified an X-aptamer that specifically binds to CIRP (XA-CIRP). Structurally, XA-CIRP blocked the interaction between CIRP and TLR4. Functionally, it reduced CIRP-induced pancreatic acinar cell injury in vitro and L-arginine-induced pancreatic injury and inflammation in vivo. Thus, targeting extracellular CIRP with X-aptamers may be a promising strategy to treat AP.

Irisin inhibits neutrophil extracellular traps formation and protects against acute pancreatitis in mice

INTRODUCTION

Irisin is a newly discovered myokine which links exercise to inflammation and inflammation-related diseases through macrophage regulation. However, the effect of irisin on the activity of inflammation related immune cells (such as neutrophils) has not been clearly described.

OBJECTIVES

The objective of our study was to explore the effect of irisin on the neutrophil extracellular traps (NETs) formation.

METHODS

Phorbol-12-myristate-13-acetate (PMA) was used to construct a classic neutrophil inflammation model that was used to observe the formation of NETs in vitro. We studied the effect of irisin on NETs formation and its regulation mechanism. Subsequently, acute pancreatitis (AP) was used to verify the protective effect of irisin in vivo, which was an acute aseptic inflammatory response disease model closely related to NETs.

RESULTS

Our study found that addition of irisin significantly reduced the formation of NETs via regulation of the P38/MAPK pathway through integrin αVβ5, which might be the one of key pathways in NETs formation, and which could theoretically offset the immunoregulatory effect of irisin. Systemic treatment with irisin reduced the severity of tissue damage common in the disease and inhibited the formation of NETs in pancreatic necrotic tissue of two classical AP mouse models.

CONCLUSION

The findings confirmed for the first time that irisin could inhibit NETs formation and protect mice from pancreatic injury, which further elucidated the protective effect of exercise on acute inflammatory injury.

Skeletal Muscle Myokine Expression in Critical Illness, Association With Outcome and Impact of Therapeutic Interventions

Context

Muscle expresses and secretes several myokines that bring about benefits in distant organs.

Objective

We investigated the impact of critical illness on muscular expression of irisin, kynurenine aminotransferases, and amylase; association with clinical outcome; and impact of interventions that attenuate muscle wasting/weakness.

Methods

We studied critically ill patients who participated in 2 randomized controlled trials (EPaNIC/NESCI) and documented time profiles in critically ill mice. Included in the study were 174 intensive care unit (ICU) patients (day 8 ± 1) vs 19 matched controls, and 60 mice subjected to surgery/sepsis vs 60 pair-fed healthy mice. Interventions studied included 7-day neuromuscular electrical stimulation (NMES), and withholding parenteral nutrition (PN) in the first ICU week (late PN) vs early PN. The main outcome measures were FNDC5 (irisin- precursor), KYAT1, KYAT3, and amylase mRNA expression in skeletal muscle.

Results

Critically ill patients showed 34% to 80% lower mRNA expression of FNDC5, KYAT1, and amylases than controls (P < .0001). Critically ill mice showed time-dependent reductions in all mRNAs compared with healthy mice (P ≤ .04). The lower FNDC5 expression in patients was independently associated with a higher ICU mortality (P = .015) and ICU-acquired weakness (P = .012), whereas the lower amylase expression in ICU survivors was independently associated with a longer ICU stay (P = .0060). Lower amylase expression was independently associated with a lower risk of death (P = .048), and lower KYAT1 expression with a lower risk of weakness (P = .022). NMES increased FNDC5 expression compared with unstimulated muscle (P = .016), and late PN patients had a higher KYAT1 expression than early PN patients (P = .022).

Conclusion

Expression of the studied myokines was affected by critical illness and associated with clinical outcomes, with limited effects of interventions that attenuate muscle wasting or weakness.

Paeonol protects against acute pancreatitis by Nrf2 and NF-κB pathways in mice

OBJECTIVES

Paeonol (PAE) is an active ingredient with anti-inflammatory and antioxidant properties. This study was designed to investigate the effect of PAE on acute pancreatitis (AP).

METHODS

AP was induced by the intraperitoneal injection of 20% l-arginine (4 g/kg) for 6 h. Mice were pretreated with PAE (25, 50 or 100 mg/kg) intragastrically for 5 days. The histological damage and alterations of biochemical indicators, inflammatory cytokines and oxidative stress factors in AP mice were detected. The Nrf2 and NF-κB pathways were examined to illustrate the potential mechanism.

KEY FINDINGS

In AP model, we found that PAE attenuated histological injury of pancreatic tissues, reduced the serum levels of α-amylase and increased Ca2+ contents in a dose-dependent manner. The white blood cell content, and IL-1β, IL-6 and TNF-α levels in the serum of AP mice were reduced by PAE. Furthermore, PAE caused a reduction of MPO and MDA levels, accompanied by an increase in SOD activity in the pancreas of AP mice. We also demonstrated that the alterations of Nrf2 and NF-κB pathways in AP mice were reversed by PAE.

CONCLUSIONS

PAE attenuates inflammation and oxidative stress in the development of AP by the regulation of Nrf2 and NF-κB pathways.

The potential role of FNDC5/irisin in various liver diseases: awakening the sleeping beauties

Fibronectin type III domain-containing protein 5 (FNDC5) is a transmembrane protein and the precursor of irisin, which serves as a systemic exerkine/myokine with multiple origins. Since its discovery in 2012, this hormone-like polypeptide has rapidly evolved to a component significantly involved in a gamut of metabolic dysregulations and various liver diseases. After a decade of extensive investigation on FNDC5/irisin, we are still surrounded by lots of open questions regarding its diagnostic and therapeutic values. In this review, we first concentrated on the structure-function relationship of FNDC5/irisin. Next, we comprehensively summarised the current knowledge and research findings regarding pathogenic roles/therapeutic applications of FNDC5/irisin in the context of non-alcoholic fatty liver disease, fibrosis, liver injury due to multiple detrimental insults, hepatic malignancy and intrahepatic cholestasis of pregnancy. Moreover, the prominent molecules involved in the underlying mechanisms and signalling pathways were highlighted. As a result, emerging evidence reveals FNDC5/irisin may act as a proxy for diagnosing liver disease pathology, a sensitive biomarker for assessing damage severity, a predisposing factor for surveilling illness progression and a treatment option with protective/preventive impact, all of which are highly dependent on disease grading and contextually pathological features.

Antioxidant Effects of Irisin in Liver Diseases: Mechanistic Insights

Oxidative stress is a crucial factor in the development of various liver diseases. Irisin, a metabolic hormone discovered in 2012, is mainly produced by proteolytic cleavage of fibronectin type III domain containing 5 (FNDC5) in skeletal muscles. Irisin is induced by physical exercise, and a rapidly growing body of literature suggests that irisin is, at least partially, responsible for the beneficial effects of regular exercise. The major biological function of irisin is believed to be involved in the maintenance of metabolic homeostasis. However, recent studies have suggested the therapeutic potential of irisin against a variety of liver diseases involving its antioxidative function. In this review, we aim to summarize the accumulating evidence demonstrating the antioxidative effects of irisin in liver diseases, with an emphasis on the current understanding of the potential molecular mechanisms.

MFG-E8 Maintains Cellular Homeostasis by Suppressing Endoplasmic Reticulum Stress in Pancreatic Exocrine Acinar Cells

Excessive endoplasmic reticulum (ER) stress contributes significantly to the pathogenesis of exocrine acinar damage in acute pancreatitis. Our previous study found that milk fat globule EGF factor 8 (MFG-E8), a lipophilic glycoprotein, alleviates acinar cell damage during AP via binding to αvβ3/5 integrins. Ligand-dependent integrin-FAK activation of STAT3 was reported to be of great importance for maintaining cellular homeostasis. However, MFG-E8's role in ER stress in pancreatic exocrine acinar cells has not been evaluated. To study this, thapsigargin, brefeldin A, tunicamycin and cerulein + LPS were used to induce ER stress in rat pancreatic acinar cells in vitro. L-arginine- and cerulein + LPS-induced acute pancreatitis in mice were used to study ER stress in vivo. The results showed that MFG-E8 dose-dependently inhibited ER stress under both in vitro and in vivo conditions. MFG-E8 knockout mice suffered more severe ER stress and greater inflammatory response after L-arginine administration. Mechanistically, MFG-E8 increased phosphorylation of FAK and STAT3 in cerulein + LPS-treated pancreatic acinar cells. The presence of specific inhibitors of αvβ3/5 integrin, FAK or STAT3 abolished MFG-E8's effect on cerulein + LPS-induced ER stress in pancreatic acinar cells. In conclusion, MFG-E8 maintains cellular homeostasis by alleviating ER stress in pancreatic exocrine acinar cells.

Neuroprotective Effects of Exogenous Irisin in Kainic Acid-Induced Status Epilepticus

Elevated reactive oxygen species (ROS) level is considered a crucial causative factor for neuronal damage in epilepsy. Irisin has been reported to ameliorate mitochondrial dysfunction and to reduce ROS levels; therefore, in this study, the effect of exogenous irisin on neuronal injury was evaluated in rats with kainic acid (KA)-induced status epilepticus (SE). Our results showed that exogenous irisin treatment significantly increased the expression of brain-derived neurotrophic factor (BDNF) and uncoupling protein 2 (UCP2), and reduced the levels of neuronal injury and mitochondrial oxidative stress. Additionally, an inhibitor of UCP2 (genipin) was administered to investigate the underlying mechanism of irisin-induced neuroprotection; in rats treated with genipin, the neuroprotective effects of irisin on KA-induced SE were found to be partially reversed. Our findings confirmed the neuroprotective effects of exogenous irisin and provide evidence that these effects may be mediated via the BDNF/UCP2 pathway, thus providing valuable insights that may aid the development of exogenous irisin treatment as a potential therapeutic strategy against neuronal injury in epilepsy.

Irisin alleviates obesity-related spermatogenesis dysfunction via the regulation of the AMPKα signalling pathway

BACKGROUND

Infertility is a common complication in obese men. Oxidative stress and testicular apoptosis play critical roles in obesity-induced spermatogenesis dysfunction. It has been reported that irisin, an exercise-induced myokine, may attenuate oxidative damage and testicular apoptosis in several diseases; however, its role in obesity-induced spermatogenesis dysfunction remains unclear. The purpose of this study was to investigate the role and underlying mechanism of irisin in obesity-induced dysfunction of spermatogenesis.

METHODS

Male mice were fed a high-fat diet (HFD) for 24 weeks to establish a model of obesity-induced spermatogenesis dysfunction. To explore the effects of irisin, mice were subcutaneously infused with recombinant irisin for 8 weeks beginning at 16 weeks after starting a HFD. To confirm the role of AMP-activated protein kinase α (AMPKα), AMPKα-deficient mice were used.

RESULTS

The data showed decreased serum irisin levels in obese patients, which was negatively correlated with sperm count and progressive motility. Irisin was downregulated in the plasma and testes of obese mice. Supplementation with irisin protected against HFD-induced spermatogenesis dysfunction and increased testosterone levels in mice. HFD-induced oxidative stress, endoplasmic reticulum (ER) stress and testicular apoptosis were largely attenuated by irisin treatment. Mechanistically, we identified that irisin activated the AMPKα signalling pathway. With AMPKα depletion, we found that the protective effects of irisin on spermatogenesis dysfunction were abolished in vivo and in vitro.

CONCLUSIONS

In conclusion, we found that irisin alleviated obesity-related spermatogenesis dysfunction via activation of the AMPKα signalling pathway. Based on these findings, we hypothesized that irisin is a potential therapeutic agent against obesity-related spermatogenesis dysfunction.

Irisin protects female mice with LPS-induced endometritis through the AMPK/NF-κB pathway

OBJECTIVES

This research was designed to determine the role of irisin in lipopolysaccharide (LPS)-induced endometritis in female mice.

MATERIALS AND METHODS

Animals were randomly assigned into sham, sham + irisin, LPS, LPS + irisin (0.1, 1, 10 μg/kg), and LPS + irisin + compound C groups. Histological features and expression of AMPK, NF-κB, inflammatory mediators, and oxidative stress markers were compared among different groups.

RESULTS

The results showed that LPS resulted in obvious uterus damage, meanwhile, the inflammatory mediators (COX-2, iNOS, IL-1β, IL-6, and TNF-α), as well as NF-κB in the uterine tissue, were significantly increased and the level of adenosine monophosphate-activated protein kinase (AMPK) was reduced. Nevertheless, pretreatment with irisin reversed the phenomena caused by LPS. Interestingly, compound C (AMPK inhibitor) abolished irisin's effects on the uterus, which suggested that irisin's beneficial function was achieved through regulating the AMPK-NF-κB pathway. Moreover, LPS-induced alterations of oxidative factors (MnSOD, GSH, and MDA) were reversed significantly by pretreatment with irisin. This data indicated irisin's beneficial function was also related to antioxidation besides anti-inflammation.

CONCLUSION

Our study implies that irisin is a potential therapeutic agent for endometritis.

Milk Fat Globule-EGF Factor 8 Alleviates Pancreatic Fibrosis by Inhibiting ER Stress-Induced Chaperone-Mediated Autophagy in Mice

Pancreatic fibrosis is an important pathophysiological feature of chronic pancreatitis (CP). Our recent study has shown that milk fat globule-EGF factor 8 (MFG-E8) is beneficial in acute pancreatitis. However, its role in CP remained unknown. To study this, CP was induced in male adult Mfge8-knockout (Mfge8-KO) mice and wild type (WT) mice by six intraperitoneal injections of cerulein (50 μg/kg/body weight) twice a week for 10 weeks. The results showed that knockout of mfge8 gene aggravated pancreatic fibrosis after repeated cerulein injection. In WT mice, pancreatic levels of MFG-E8 were reduced after induction of CP and administration of recombinant MFG-E8 alleviated cerulein-induced pancreatic fibrosis. The protective effect of MFG-E8 in CP was associated with reduced autophagy and oxidative stress. In human pancreatic stellate cells (PSCs), MFG-E8 inhibited TGF-β1-induced ER stress and autophagy. MFG-E8 downregulated the expression of lysosomal associated membrane protein 2A (LAMP2A), a key factor in ER stress-induced chaperone-mediated autophagy (CMA). QX77, an activator of CMA, eliminated the effects of MFG-E8 on TGF-β1-induced PSC activation. In conclusion, MFG-E8 appears to mitigate pancreatic fibrosis via inhibiting ER stress-induced chaperone-mediated autophagy. Recombinant MFG-E8 may be developed as a novel treatment for pancreatic fibrosis in CP.

Protective effects of baicalin on caerulein-induced AR42J pancreatic acinar cells by attenuating oxidative stress through miR-136-5p downregulation

Baicalin, the main active component of Scutellaria baicalensis, has antioxidant and anti-apoptotic effects and is used to treat acute pancreatitis; however, its specific mechanism is unclear. This study aims to determine the protective effect and underlying mechanism of baicalin on AR42J pancreatic acinar cell injury. AR42J acinar cells (caerulein, 10 nmol/L) were induced in vitro to establish a cell model for acute pancreatitis. Cell relative survival was measured by thiazolyl blue tetrazolium bromide, and cell apoptosis and death were examined by flow cytometry. The expression levels of superoxide dismutase1 (SOD1), Bax, survivin, Bcl-2, caspase-3, and caspase-7 proteins were analyzed by Western blot, and those of SOD1 mRNA and miR-136-5p were determined by RT-PCR. The activities of GSH, SOD1, ROS, and MDA were also investigated. Compared with those of the caerulein group, the relative survival rate and activity of AR42J pancreatic acinar cells with different baicalin concentrations were significantly increased (p < 0.05), and the supernatant amylase level was markedly decreased (p < 0.05). In addition, the ROS and MDA activities and mir-136-5p expression were significantly decreased, and the GSH activities and SOD1 gene and protein expression levels were markedly increased (p < 0.05). These results suggest that baicalin reduced the caerulein-induced death of AR42J acinar cells and alleviated the caerulein-induced injury in pancreatic acinar cells by inhibiting oxidative stress. The mechanism may be related to the decreased expression of Mir-136-5p and the increased expression of SOD1 gene and protein.

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.

Irisin Protects Against Motor Dysfunction of Rats with Spinal Cord Injury via Adenosine 5'-Monophosphate (AMP)-Activated Protein Kinase-Nuclear Factor Kappa-B Pathway

The aim of the present research was to investigate the effects of irisin, a skeletal muscle-derived myokine, on spinal cord injury (SCI) in rats and explore the possible mechanisms. SCI model was constructed in male SD rats. The effects of irisin on SCI rats were assessed via behavior tests including Basso, Beattie, and Bresnahan (BBB) scoring method and inclined plane test, followed by histomorphology tests including HE staining, Nissl staining, and transmission electron microscope examination. Biochemical analyses including PCR, Western blots and ELISA were employed to further evaluate the changes at molecular level of SCI rats. In addition, lipopolysaccharide (LPS)-induced cell damage model was established in PC12 cells to verify the mechanism of irisin's effect on nerve cells in vitro. Results showed that the BBB score and the angle of incline significantly decreased after SCI surgery, however, chronic irisin treatment improved SCI-induced motor dysfunction. HE and Nissl staining assays showed that SCI surgery induced histological injury of spinal cord, which could be reversed by irisin treatment. Morphological abnormality of nerve cells caused by SCI also could be alleviated by irisin. Further biochemical analyses showed that irisin inhibited SCI-induced overexpression of Interleukin-1β (IL-1β), Interleukin- 6 (IL-6), tumor necrosis factor alpha (TNF-α), inducible nitricoxidesynthase (iNOS) and Cyclooxygenase-2 (COX-2)], as well as nuclear factor kappa-B (NF-κB)p65 in rats, and the positive function of irisin could be reversed by Compound C treatment. In our in vitro study, LPS-induced declines of cell viability and neurite length of PC12 cell were inhibited by irisin treatment, and irisin inhibited LPS-induced overexpression of NF-κBp65, IL-1β, IL-6, TNF-α, iNOS and COX-2. These changes could be reversed by activated protein kinase (AMPK) siRNA pre-treatment. Taken together, irisin could protect the rats from SCI, and its protection is associated with the regulation of adenosine 5'-monophosphate-activated protein kinase (AMPK)- NF-κB signaling pathway.