Characterization of the serum levels of Meteorin-like in patients with inflammatory bowel disease and its association with inflammatory cytokines

Increased serum interleukin-41 correlates with disease severity in myasthenia gravis

BACKGROUND

Myasthenia gravis (MG) is an autoimmune disease mediated by pathogenic antibodies produced by abnormally activated B cells, resulting in neuromuscular junction transmission dysfunction. Interleukin-41 (IL-41) is a novel immunomodulatory cytokine that has been implicated in various metabolic, inflammatory, and autoimmune diseases. The role of IL-41 in MG is still unclear up to now, our study aimed to investigate the level of IL-41 in MG patients and its correlation with clinical features and inflammatory indicators.

METHODS

Totally, 60 MG patients and 30 healthy controls (HC) were recruited. Baseline data and laboratory parameters were routinely recorded through electronic medical systems. IL-41 levels were measured by enzyme-linked immunosorbent assay. Proportions of T-cell and B-cell subsets and natural killer cells were analyzed by flow cytometry. The correlation between serum IL-41 and MG related parameters was investigated, and the clinical value of IL-41 in the diagnosis of MG was evaluated by receiver operator characteristic curve (ROC) analysis.

RESULTS

Serum IL-41 levels in MG patients were higher than in HC, and were higher in Myasthenia Gravis Foundation of America (MGFA) III + IV group than that in MGFA I + II group. Serum IL-41 was positively correlated with MG-specific activities of daily living scale (MG-ADL), MGFA classification, platelet to lymphocyte ratio (PLR), and proportion of CD19+ B cells, while it was negatively correlated with high-sensitive C-reactive protein (hs-CRP) and circulatory plasma cells in MG patients. Serum IL-41 levels increased in patients who were treated with efgartigimod during the first cycle of therapy. However, compared to disease initiation, serum IL-41 levels decreased when clinical features steadily improved. ROC analysis showed that IL-41 had a diagnostic value for MG.

CONCLUSION

The present findings suggested that serum IL-41 was increased in MG patients and was positively associated with the severity of the disease. IL-41 may be essential to the immunopathological mechanism of MG and a potential biomarker for MG.

Increased synthesis and intestinal expression of IL-39 in patients with inflammatory bowel disease

IL-39 (Interleukin-39) is a heterodimeric cytokine composed of IL-23p19 and EBI3 (Epstein-Barr virus-induced gene 3) subunits. Despite the evidence that correlates the role of IL-39 in regulating inflammation, its expression in the intestinal microenvironment of IBD (inflammatory bowel disease) patients is still unknown. Thus, this work was focused on characterizing relative mRNA (messenger RNA) IL-39 expression and intestinal synthesis in IBD patients. This study includes 37 patients diagnosed with ulcerative colitis (UC), 15 with Chron's disease (CD), and 22 controls. Gene expression of IL-39 subunits (IL-23p19/EBI3) was measured by RT-PCR (real time polymerase chain reaction). Intestinal synthesis was evaluated by immunohistochemistry and serum levels by ELISA. Statistical analysis was done using Prism GraphPad V6. Relative mRNA IL-39 expression was increased in patients with active UC and active CD compared to the remission UC, remission CD, and control group. High levels of relative mRNA expression of IL-39 (IL-23p19 subunit) were associated with histological activity. IHQ analysis showed increased IL-39 production in mucosa, submucosa, muscular, and serosa layer of patients with active disease. IL-39 serum production was increased in patients with UC. IL-39 gene's upregulation was found in patients with active IBD and was associated with severe histological activity in UC. This is the first report regarding the role of IL-39 in patients with IBD. The findings suggest that IL-39 might play a role as an inflammatory mediator in active IBD and could be considered a new alternative in treating this condition.

Protective role of the novel cytokine Metrnl/ interleukin-41 in host immunity defense during sepsis by promoting macrophage recruitment and modulating Treg/Th17 immune cell balance

BACKGROUND

Metrnl play an immunocytokine-like role in several diseases, which is also known as meteorin-like because it is homologous to the neurotrophic factor meteorin (Metrn). Although the expression and function of Metrnl, including neurotrophic, immunomodulatory, and insulin resistance functions in different tissues have been extensively studied, its role in sepsis has remained largely limited.

METHODS

The present work analyzed the levels of Metrnl and cytokines in the circulation, such as tumor necrosis factor (TNF-α), interleukin (IL-1)β, IL-6, IL-8, together with IL-10 among septic adult patients. Clinical information was obtained from such patients, including sofa score, procalcitonin(PCT)count, and C-reactive count (CRP) within 24 h when entering the intensive care unit (ICU). We constructed a sepsis model in Metrnl-deficient or normal wild-type mice using cecal ligation and perforation to study its functions in bacterial burden, survival, cytokine/chemokine generation, peritoneal lavage fluid neutrophils, macrophage and lymphocyte recruitment, and Treg/Th17 immune cell balance after CLP-induced sepsis.

RESULTS

The expression of Metrnl was remarkably elevated in the early phase of sepsis clinically. Its serum content in patients dying of sepsis slightly decreased relative to that in survivors. Furthermore, the concentration of Metrnl in septic cases when entering the ICU independently predicted the 28-day mortality. For septic patients who had low serum Metrnl content (≤ 274.40 pg/mL), the death risk increased by 2.3 folds relative to those who had a high serum content. It is reported that Metrnl is probably insufficient among patients dying of sepsis. Additionally, the content of Metrnl in the serum of septic patients when entering the ICU is markedly and negatively related to the levels of TNF-α, IL-1β, IL-6, IL-8, IL-17, PCT, and Sofa score. Collectively, Metrnl could be a potential therapeutic target for sepsis. A low-lethality non-severe sepsis (NSS) model was constructed, which suggested that Metrnl insufficiency elevated the death rate and reduced bacterial clearance during sepsis. For Metrnl-deficient mice, impaired sepsis immunity defense might be related to decreased macrophage recruitment and Treg/Th17 lymphocyte imbalance. Recombinant Metrnl administered to Metrnl-deficient mice abolished the immunity defense impairment following NSS while protecting the high-lethality severe sepsis (SS) model in wild-type (WT) mice. In addition, Metrnl-induced sepsis prevention was intricately associated with the increased recruitment of peritoneal macrophages and modulation of the Treg/TH17 immune cell balance. Furthermore, CCL3 exposure in Metrnl-deficient mice reduced peritoneal bacterial loads while improving survival during sepsis partially by promoting the recruitment of peritoneal macrophages. Furthermore, Metrnl regulated the polarization of M1 macrophages through the ROS signaling pathway and promoted macrophage phagocytosis, thereby killing Escherichia coli.

CONCLUSIONS

The present proof-of-concept work suggests that Metrnl-mediated recruitment of macrophages significantly affects sepsis defense in the host and modulates the Treg/Th17 immune cell balance. Findings in this work shed more light on the development of host-directed treatments that can be used to manipulate host immunity to treat sepsis.

Meteorin-like protein overexpression ameliorates fulminant hepatitis in mice by inhibiting chemokine-dependent immune cell infiltration

Myokines, which are recently identified cytokines secreted by skeletal muscle in response to stimulation, are crucial for the maintenance of liver function. Fulminant hepatitis (FH) is a life-threatening pathological condition with severe hepatic dysfunction. In this study, we investigated the role of meteorin-like (METRNL), a new myokine, in the pathogenesis of FH. We compared serum samples and liver tissues from FH patients and healthy controls and found that hepatic and serum METRNL levels were significantly increased in FH patients, and serum METRNL levels were related to disease severity in FH patients. We then established a concanavalin A-induced FH model in METRNL-overexpressing and control mice. We found that hepatic METRNL levels in FH mice were significantly increased, and METRNL in the liver was mainly derived from macrophages. In the cultured mouse macrophage line (RAW264.7 cells) and mouse primary peritoneal macrophages (PMs), METRNL overexpression significantly inhibited the release of the proinflammatory cytokines TNF and IL-1β. In METRNL-overexpressing mice, concanavalin A-induced liver injury was significantly ameliorated. Moreover, METRNL overexpression significantly reduced chemokine-dependent inflammatory cell infiltration into the liver. METRNL overexpression also suppressed liver CD4+ T cell differentiation into Th 1 cells and inhibited the secretion of Th 1 cytokines. Taken together, these data suggest that METRNL overexpression effectively ameliorates FH. Therefore, METRNL may serve as a potential biomarker and therapeutic target for FH.

Adiponectin Levels in Inflammatory Bowel Disease: A Systematic Review and Meta-Analysis

INTRODUCTION

Adipose tissue plays an important role in the pathogenesis of inflammatory conditions. The role of adipokines in inflammatory bowel disease (IBD) has been evaluated in the current literature with conflicting results. The aim of this study was to evaluate adiponectin levels in IBD patients, including Crohn's disease (CD) and ulcerative colitis (UC), compared to controls, as well as further subgroup analyses. Hence, assessing the potential role of adiponectin as a surrogate marker.

METHODS

We performed a systematic electronic search on PubMed, Embase, Scopus, and Cochrane Library, including observational or interventional studies evaluating serum or plasma adiponectin levels in IBD patients in humans. The primary summary outcome was the mean difference (MD) in serum or plasma adiponectin levels between IBD patients versus controls. Subgroup analyses were conducted involving adiponectin levels in CD and UC compared to controls, as well as CD compared to UC.

RESULTS

A total of 20 studies were included in our qualitative synthesis and 14 studies in our quantitative synthesis, with a total population sample of 2,085 subjects. No significant MD in serum adiponectin levels was observed between IBD patients versus controls {-1.331 (95% confidence interval [CI]: -3.135-0.472)}, UC patients versus controls (-0.213 [95% CI: -1.898-1.472]), and CD patients versus controls (-0.851 [95% CI: -2.263-0.561]). Nevertheless, a significant MD was found between UC patients versus CD patients (0.859 [95% CI: 0.097-1.622]).

CONCLUSIONS

Serum adiponectin levels were not able to differentiate between IBD, UC, and CD patients compared to controls. However, significantly higher serum adiponectin levels were observed in UC compared to CD patients.

Serum interleukin-38 and -41 levels as candidate biomarkers in male infertility

BACKGROUND

Interleukin (IL)-38 and IL-41 are novel cytokines, but their role in male infertility (MI) is unknown. The purpose of this study was to measure the levels of serum IL-38 and IL-41 in patients with MI and correlate these levels with semen indexes.

METHODS

Eighty-two patients with MI and 45 healthy controls (HC) were recruited for this study. Semen parameters were detected using computer-aided sperm analysis, Papanicolaou staining, ELISA, flow cytometry, peroxidase staining and enzyme methods. Serum IL-38 and IL-41 levels were determined by ELISA.

RESULTS

Serum IL-38 levels were decreased (P < 0.01) in patients with MI compared with HC. Serum IL-41 levels were significantly higher in patients with MI than in HC (P < 0.0001). In patients with MI, serum IL-38 levels were positively correlated with semen white blood cell counts (r = 0.29, P = 0.009), and there was a positive correlation between semen white blood cell counts and sperm concentration (r = 0.28, P = 0.0100) and seminal plasma elastase (r = 0.67, P < 0.0001). Receiver operating characteristic curve analysis showed that the area under the curve of IL-38 for diagnosing MI was 0.5637 (P > 0.05), and the area under the curve of IL-41 for diagnosing MI was 0.7646 (P < 0.0001).

CONCLUSIONS

Serum IL-38 levels were significantly lower, and serum IL-41 levels were higher in patients with MI. These results suggest that IL-38 and IL-41 may be novel biomarkers for the diagnosis of MI.

Pathophysiology of type 2 diabetes and the impact of altered metabolic interorgan crosstalk

Diabetes is a complex and multifactorial disease that affects millions of people worldwide, reducing the quality of life significantly, and results in grave consequences for our health care system. In type 2 diabetes (T2D), the lack of β-cell compensatory mechanisms overcoming peripherally developed insulin resistance is a paramount factor leading to disturbed blood glucose levels and lipid metabolism. Impaired β-cell functions and insulin resistance have been studied extensively resulting in a good understanding of these pathways but much less is known about interorgan crosstalk, which we define as signaling between tissues by secreted factors. Besides hormones and organokines, dysregulated blood glucose and long-lasting hyperglycemia in T2D is associated with changes in metabolism with metabolites from different tissues contributing to the development of this disease. Recent data suggest that metabolites, such as lipids including free fatty acids and amino acids, play important roles in the interorgan crosstalk during the development of T2D. In general, metabolic remodeling affects physiological homeostasis and impacts the development of T2D. Hence, we highlight the importance of metabolic interorgan crosstalk in this review to gain enhanced knowledge of the pathophysiology of T2D, which may lead to new therapeutic approaches to treat this disease.

Investigation of IL-35 and IL-39, New Members of the IL-12 Family, in Different Clinical Presentations of Brucellosis

Brucellosis is significantly influenced by the interactions between the causative Brucella bacteria and host immunity. Recently identified cytokines have been described for their immunomodulatory effects in numerous inflammatory, autoimmune and infectious diseases. Some of them are new members of cytokine superfamilies, including several members of the IL-12 superfamily (IL-35, IL-39). The major purpose of the present study was to investigate the role of these new immunomodulatory cytokines in Brucella infections. The levels of IL-35 and IL-39 in the serum of 40 acute and 40 chronic brucellosis patients and 40 healthy controls were measured by ELISA. The mRNA levels of IL-35 and IL-39 in PBMCs were detected by RT-qPCR. Both IL-35 and IL-39 serum concentrations were significantly higher in healthy control subjects than in brucellosis patients, and IL-35 and IL-39 serum levels of chronic brucellosis patients were higher than those of acute cases. It was also found that the expression of Ebi3/IL-12A (IL-35 genes) and Ebi3/IL-23A (IL-39 genes) was upregulated in chronic brucellosis patients compared to healthy controls. Moreover, the expression of the Ebi3/IL-12A and Ebi3/IL-23A genes was lower in patients with acute brucellosis than in patients with chronic brucellosis. Overall, this study showed that IL-35 and IL-39 are positively correlated in brucellosis and significantly decreased during the disease. Significantly lower levels of IL-35 and IL-39 in acute brucellosis than in chronic brucellosis and healthy controls suggest that these cytokines may play a key role in suppressing the immune response to brucellosis and its progression to chronicity.

Meteorin-like/Metrnl, a novel secreted protein implicated in inflammation, immunology, and metabolism: A comprehensive review of preclinical and clinical studies

Meteorin-like, also known as Metrnl, Meteorin-β, Subfatin, and Cometin, is a novel secreted protein exerting pleiotropic effects on inflammation, immunology, and metabolism. Earlier research on this hormone focused on regulating energy expenditure and glucose homeostasis. Consequently, several studies attempted to characterize the molecule mechanism of Metrnl in glucose metabolism and obesity-related disorders but reported contradictory clinical results. Recent studies gradually noticed its multiple protective functions in inflammatory immune regulations and cardiometabolic diseases, such as inducing macrophage activation, angiogenesis, tissue remodeling, bone formation, and preventing dyslipidemias. A comprehensive understanding of this novel protein is essential to identify its significance as a potential therapeutic drug or a biomarker of certain diseases. In this review, we present the current knowledge on the physiology of Metrnl and its roles in inflammation, immunology, and metabolism, including animal/cell interventional preclinical studies and human clinical studies. We also describe controversies regarding the data of circulation Metrnl in different disease states to determine its clinical application better.

Elevated levels of Metrnl in rheumatoid arthritis: Association with disease activity

BACKGROUND

Meteorin-like (Metrnl) is a novel adipokine that is highly expressed in white adipose tissues. Whether Metrnl plays a role in rheumatoid arthritis (RA) remains unclear. In this study, sera from 159 RA patients, 28 osteoarthritis (OA) patients, and 50 healthy individuals were included. The serum levels of Metrnl were measured using an enzyme-linked immunosorbent assay. Clinical parameters, including disease activity score 28 (DAS28), C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), rheumatoid factor (RF), antibodies to cyclic citrulline peptide (anti-CCP), inflammatory cytokines, and blood biochemical indices were collected.

RESULTS

Metrnl levels were higher in RA patients compared to OA patients and controls. In the RA group, serum Metrnl levels were positively correlated with DAS28, RF, and CRP levels. However, in the RA group, serum Metrnl levels were not correlated with ESR, anti-CCP, immunoglobulins, and blood biochemical indices.

CONCLUSION

This study showed that Metrnl is involved in the pathogenesis of RA. Increase in serum Metrnl levels is closely related to RA activity.

Decreased serum interleukin-41/Metrnl levels in patients with Graves' disease

Background

Interleukin (IL)‐41, also known as Metrnl, is a novel immunomodulatory cytokine, which is involved in the pathogenesis of many inflammatory and metabolic diseases, but its role in thyroid autoimmune diseases is not clear. The aim of this study was to evaluate the serum IL‐41 levels in patients with Graves' disease (GD) and its relationship with GD.

Methods

This study included a total of 49 GD patients and 47 age‐ and sex‐matched healthy individuals. All baseline data were obtained by physical examination. Free triiodothyronine 3 (FT3), free triiodothyronine 4 (FT4), thyroid‐stimulating hormone (TSH), anti‐thyroglobulin antibodies (TgAb), thyroid peroxidase antibody (TPOAb), and thyrotropin receptor antibody (TRAb) levels in plasma of GD patients were measured by chemiluminescence. The high‐sensitivity C‐reactive protein (CRP) and white blood cell count (WBC) were detected using automated biochemical analyzer. Serum IL‐41 levels were measured by enzyme‐linked immunosorbent assay.

Results

Serum IL‐41 levels in patients with GD were significantly lower than those in healthy controls (201.0 vs. 260.8 pg/mL, p < 0.05). There was a significant positive correlation between IL‐41 level and CRP (r = 0.2947, p = 0.0385) and WBC (r = 0.4104, p = 0.0034) in GD patients. CRP was positively correlated with TRAb (r = 0.2874, p = 0.0452) and TSH (r = 0.3651, p = 0.0099) levels in GD patients.

Conclusions

This study demonstrates that GD patients have decreased serum IL‐41 levels, and IL‐41 plays a potential role in abnormal immune response of GD patients.

Anti-inflammatory Effect of a Novel Pectin Polysaccharide From Rubus chingii Hu on Colitis Mice

Rubus chingii Hu has been used as a functional food for a long time. A novel pectin polysaccharide named RCHP-S from R. chingii Hu was structurally identified and explored its anti-inflammatory effect on colitis mice. RCHP-S was composed of mannose, rhamnose, glucuronic acid, galacturonic acid, glucose, galactose, and arabinose. NMR spectroscopy and methylation analysis showed that RCHP-S was mainly composed of HG-type pectin domains but also contains a small amount of RG-I. The anti-inflammatory tests indicated that the mouse macrophage RAW 264.7 cells pretreated with RCHP-S could show a significant inhibitory effect on the mRNA level of iNOS, IL-1β, IL-6, and TNF-α in vitro. Polysaccharide RCHP-S reduced the enteritis symptoms in dextran sulfate sodium (DSS)-induced colitis mice by inhibiting released inflammatory factors. These results indicated that the R. chingii Hu polysaccharide can be used as food additives for the treatment of intestinal inflammation.

The Therapeutic Efficacy of Adipose Tissue-Derived Mesenchymal Stem Cell Conditioned Medium on Experimental Colitis Was Improved by the Serum From Colitis Rats

Adipose derived mesenchymal stem cells (AD-MSCs) have shown therapeutic potential in treatments of inflammatory bowel disease (IBD). Due to the harsh host environment and poor survival of the cells, controversy concerning the homing, proliferation and differentiation of MSCs in lesion tissue still remains. It has been reported that conditioned media from MSCs could improve the colitis, whereas the therapeutic efficiency could be significantly elevated by the stimulation of pro-cytokines. In this study, we pre-treated the adipose derived MSCs with the serum from colitis rats and then the activated conditioned media (CM-AcMSC) were collected. To compare the therapeutic effects of CM-MSC and CM-AcMSC on IBD, we constructed dextran sodium sulphate (DSS)-induced colitis rat models. The colitis was induced in rats by administrating 5% DSS in drinking water for 10 days, and the disease symptoms were recorded daily. The colon histopathological changes were observed by different staining methods (H&E and PAS). The expression levels of MUC2 and tight junctions (TJs) were determined by RT-qPCR. The levels of inflammatory cytokines were analyzed by ELISA and western blot analysis. Our findings suggested that CM-AcMSC was more effective in ameliorating the clinical features and histological damage scores. Treatment with CM-AcMSC significantly increased the expression of MUC2 and TJs and suppressed the production of pro-inflammatory cytokines in colonic tissues of colitis rats. The inhibitory effects of CM-AcMSC on inflammatory responses of colitis rats were mediated by NF-κB signaling pathway. These results suggested that pre-activation of MSCs with serum from colitis rats could promote the production of paracrine factors and improve the therapeutic effects of conditioned medium on colitis rats.

Role of Adipose Tissue in Inflammatory Bowel Disease

Inflammatory bowel diseases (IBDs), chronic inflammatory disorders affecting the gastrointestinal tract, include Crohn's disease and ulcerative colitis. There are increasing clinical and experimental data showing that obesity, especially visceral adiposity, plays a substantial role in the pathogenesis of IBD. Obesity seems to be an important risk factor also for IBD disease severity and clinical outcomes. Visceral adipose tissue is an active multifunctional metabolic organ involved in lipid storage and immunological and endocrine activity. Bowel inflammation penetrates the surrounding adipose tissue along the mesentery. Mesenteric fat serves as a barrier to inflammation and controls immune responses to the translocation of gut bacteria. At the same time, mesenteric adipose tissue may be the principal source of cytokines and adipokines responsible for inflammatory processes associated with IBD. This review is particularly focusing on the potential role of adipokines in IBD pathogenesis and their possible use as promising therapeutic targets.

Adipokines, Myokines, and Hepatokines: Crosstalk and Metabolic Repercussions

Adipose, skeletal, and hepatic muscle tissues are the main endocrine organs that produce adipokines, myokines, and hepatokines. These biomarkers can be harmful or beneficial to an organism and still perform crosstalk, acting through the endocrine, paracrine, and autocrine pathways. This study aims to review the crosstalk between adipokines, myokines, and hepatokines. Far beyond understanding the actions of each biomarker alone, it is important to underline that these cytokines act together in the body, resulting in a complex network of actions in different tissues, which may have beneficial or non-beneficial effects on the genesis of various physiological disorders and their respective outcomes, such as type 2 diabetes mellitus (DM2), obesity, metabolic syndrome, and cardiovascular diseases (CVD). Overweight individuals secrete more pro-inflammatory adipokines than those of a healthy weight, leading to an impaired immune response and greater susceptibility to inflammatory and infectious diseases. Myostatin is elevated in pro-inflammatory environments, sharing space with pro-inflammatory organokines, such as tumor necrosis factor-alpha (TNF-α), interleukin-1 (IL-1), resistin, and chemerin. Fibroblast growth factor FGF21 acts as a beta-oxidation regulator and decreases lipogenesis in the liver. The crosstalk mentioned above can interfere with homeostatic disorders and can play a role as a potential therapeutic target that can assist in the methods of diagnosing metabolic syndrome and CVD.

Myokine-mediated exercise effects: the role of myokine meteorin-like hormone (Metrnl)

Meterorin-like hormone (Metrnl), as a novel secreted factor, has been shown to be involved in physiological and pathophysiological processes. The behaviour of Metrnl in metabolic conditions like type 2 diabetes is conflicting. Metrnl-mediated (treatment with Metrnl) auto/paracrine actions in skeletal muscle are glucose uptake, fat oxidation and muscle regeneration. Exercise-induced Metrnl actions are increased fat oxidation in both skeletal muscle and adipose tissue, the control of inflammation in adipose tissue (metainflammation), and the regulation of muscle regeneration. Based on the current knowledge, Metrnl as a myokine can establish the muscle-fat crosstalk; however, the ability of Metrnl as a myokine to create other crosstalks remains unclear yet. Additionally, given the considerable anti-inflammatory roles of Metrnl in muscle regeneration, it could be a potential therapeutic candidate for muscle-related inflammatory diseases and ageing skeletal muscle which need to be addressed in the future studies.