Interleukin-38 increases the insulin sensitivity in children with the type 2 diabetes

Impact of chronic hyperglycaemia on the coronary microcirculation - benefits of targeting IL-36 and diet reversal

Following myocardial infarction (MI), patients with type 2 diabetes mellitus (T2DM) have poorer prognosis which may be linked to increased susceptibility of coronary microvessels to injury. Interleukin-36 (IL-36) may mediate this injury but its role in the microcirculation of the chronically hyperglycaemic injured heart is unknown. Intravital and laser speckle imaging of the anaesthetised mouse beating heart evaluated the impact of a 16-week high fat diet (HFD)-induced hyperglycaemia ± myocardial ischaemia-reperfusion injury (IR) injury on coronary microvessels. Neutrophil/platelet recruitment, neutrophil extracellular trap formation, cellular necrosis, vascular leakage, vascular tonal changes, functional capillary density, overall ventricular perfusion and levels of circulating inflammatory cytokines were assessed alongside the vasculoprotective ability of an IL-36 receptor antagonist (IL-36Ra). Whether heightened microvessel damage in injured HFD mice was permanent or reversible was investigated after normalising hyperglycaemia through diet reversal (DR). Microcirculatory events assessed were perturbed basally in HFD mice and further after injury. IL-36Ra mitigated these effects and improved infarct size. DR was also beneficial, decreasing neutrophil recruitment to levels below those seen in untreated mice. Mechanistically, benefits of both IL-36Ra and DR could be explained by decreased endothelial oxidative stress and VCAM-1 expression and possibly by raised levels of IL-4/IL-13. Basal changes in chronically hyperglycaemic coronary microvessels that are heightened in the aftermath of reperfusion may explain the poorer outcomes in MI patients with T2DM. These findings are the first to highlight the specific benefits of IL-36 inhibition and reversing hyperglycaemia through dietary modification on the coronary microcirculation in a preclinical model of T2DM.

The role of IL-1 family cytokines in diabetic cardiomyopathy

Diabetic cardiomyopathy (DCM) is the primary cause of heart failure in patients with diabetes and is characterised by contractile dysfunction and left ventricular hypertrophy. The complex pathological and physiological mechanisms underlying DCM have contributed to a limited number of available treatment options. A substantial body of evidence has established that DCM is a low-grade inflammatory cardiovascular disorder, with the interleukin-1 (IL-1) family of cytokines playing crucial roles in initiating inflammatory responses and shaping innate and adaptive immunity. In this review, we aim to provide an overview of the underlying mechanisms of the IL-1 family and their relevance in DCM of various aetiologies. Furthermore, we highlighted potential therapeutic targets within the IL-1 family for the management of DCM.

Evaluation of Salivary Il-38 Levels in Periodontitis: A Cross-Sectional Study

The goal of the current study was to assess levels of salivary interleukin (IL)-38, IL-1β, and IL-10 in various periodontal clinical conditions. In total, 60 (20 healthy, 20 gingivitis, and 20 stage II-III, grade A-B periodontitis) subjects were included in the study. Demographic and clinical periodontal parameters were recorded. Samples were examined for IL-38, IL-1β, and IL-10 levels by means of enzyme-linked immunosorbent assay. Results demonstrated that the periodontitis group had significantly lower salivary IL-38 levels (P < 0.05) than the healthy group. Salivary IL-10 levels did not differ significantly between the groups (P > 0.05). The salivary IL-1β levels of gingivitis (P < 0.001) and periodontitis groups (P < 0.01) were significantly higher than those of the healthy group. The present study indicated that IL-38 level is decreased in periodontal disease. The results suggested a possible role of IL-38 in the periodontal inflammation process. Clarifying the mechanisms of IL-38 in the inflammatory process may contribute to the development of novel treatment strategies in periodontal diseases.

Interleukin-38 in atherosclerosis

Chronic inflammation caused by immune cells and their mediators is a characteristic of atherosclerosis. Interleukin-38 (IL-38), a member of the IL-1 family, exerts multiple anti-inflammatory effects via specific ligand-receptor interactions. Upon recognizing a specific receptor, IL-38 restrains mitogen-activated protein kinase (MAPK), nuclear factor kappa B (NK-κB), or other inflammation-related signaling pathways in inflammatory disease. Further research has shown that IL-38 also displays anti-atherosclerotic effects and reduces the occurrence and risk of cardiovascular events. On the one hand, IL-38 can regulate innate and adaptive immunity to inhibit inflammation, reduce pathological neovascularization, and inhibit apoptosis. On the other hand, it can curb obesity, reduce hyperlipidemia, and restrain insulin resistance to reduce cardiovascular disease risk. Therefore, this article expounds on the vital function of IL-38 in the development of atherosclerosis to provide a theoretical basis for further in-depth studies of IL-38 and insights on the prophylaxis and treatment of atherosclerosis.

Clinical relevance and therapeutic potential of IL-38 in immune and non-immune-related disorders

Interleukin-38 (IL-38) is the most recent member of the IL-1 family that acts as a natural inflammatory inhibitor by binding to cognate receptors, particularly the IL-36 receptor. In vitro, animal and human studies on autoimmune, metabolic, cardiovascular and allergic diseases, as well sepsis and respiratory viral infections, have shown that IL-38 exerts an anti-inflammatory activity by modulating the generation and function of inflammatory cytokines (e.g. IL-6, IL-8, IL-17 and IL-36) and regulating dendritic cells, M2 macrophages and regulatory T cells (Tregs). Accordingly, IL-38 may possess therapeutic potential for these types of diseases. IL-38 down-regulates CCR3+ eosinophil cells, CRTH2+ Th2 cells, Th17 cells, and innate lymphoid type 2 cells (ILC2), but up-regulates Tregs, and this has influenced the design of immunotherapeutic strategies based on regulatory cells/cytokines for allergic asthma in future studies. In auto-inflammatory diseases, IL-38 alleviates skin inflammation by regulating γδ T cells and limiting the production of IL-17. Due to its ability to suppress IL-1β, IL-6 and IL-36, this cytokine could reduce COVID-19 severity, and might be employed as a therapeutic tool. IL-38 may also influence host immunity and/or the components of the cancer microenvironment, and has been shown to improve the outcome of colorectal cancer, and may participate in tumour progression in lung cancer possibly by modulating CD8 tumour infiltrating T cells and PD-L1 expression. In this review, we first briefly present the biological and immunological functions of IL-38, and then discuss the important roles of IL-38 in various types of diseases, and finally highlight its use in therapeutic strategies.

Serum interleukin-38 levels correlated with insulin resistance, liver injury and lipids in non-alcoholic fatty liver disease

Background

Insulin resistance, liver injury and dyslipidemia are reported in non-alcoholic fat liver disease (NAFLD) patients. Interleukin (IL)-38 may take part in the pathophysiology of insulin resistance. Nevertheless, the function of IL-38 in NAFLD is unknown. Herein, we determined whether serum IL-38 level might be utilised as a biochemical marker for diagnosing NAFLD.

Methods

NAFLD patients and healthy participants (n = 91 each) were enrolled. Circulating serum IL-38 levels were detected using enzyme-linked immunosorbent assay. Other metabolic and inflammatory indices related to NAFLD were also assessed.

Results

Patients with NAFLD had higher serum IL-38 levels than healthy individuals. Significantly higher serum IL-38 levels were found in patients with severe and moderate NAFLD than in patients with mild NAFLD. IL-38 showed a significant correlation with parameters of insulin resistance, inflammation, and liver enzyme in NAFLD cases. Anthropometric, insulin resistance, inflammatory parameters, lipids and frequency of NAFLD showed significant differences among the serum IL-38 level tertiles. Participants in the 2nd and 3rd tertiles of serum IL-38 levels had a greater risk of NAFLD than those in the 1st tertile. Furthermore, IL-38 ROC curve showed a high area under ROC with 0.861.

Conclusions

It is possible for serum IL-38 to be a biomarker for NAFLD.

Interleukin-38 promotes skin tumorigenesis in an IL-1Rrp2-dependent manner

Interleukin-38 (IL-38) is strongly associated with chronic inflammatory diseases; however, its role in tumorigenesis is poorly understood. We demonstrated that expression of IL-38, which exhibits high expression in the skin, is downregulated in human cutaneous squamous cell carcinoma and 7,12-dimethylbenzanthracene/12-O-tetradecanoyl phorbol-13-acetate-induced mouse skin tumorigenesis. IL-38 keratinocyte-specific knockout mice displayed suppressed skin tumor formation and malignant progression. Keratinocyte-specific deletion of IL-38 was associated with reduced expression of inflammatory cytokines, leading to reduced myeloid cell infiltration into the local tumor microenvironment. IL-38 is dispensable for epidermal mutagenesis, but IL-38 keratinocyte-specific deletion reduces proliferative gene expression along with epidermal cell proliferation and hyperplasia. Mechanistically, we first demonstrated that IL-38 activates the c-Jun N-terminal kinase (JNK)/activator protein 1 signal transduction pathway to promote the expression of cancer-related inflammatory cytokines and proliferation and migration of tumor cells in an IL-1 receptor-related protein 2 (IL-1Rrp2)-dependent manner. Our findings highlight the role of IL-38 in the regulation of epidermal cell hyperplasia and pro-tumorigenic microenvironment through IL-1Rrp2/JNK and suggest IL-38/IL-1Rrp2 as a preventive and potential therapeutic target in skin cancer.

Serum levels of novel anti-inflammatory cytokine Interleukin-38 in diabetes patients infected with latent tuberculosis (DM-LTB-3)

IL-38 is a recently discovered, novel anti-inflammatory cytokine, which belongs to the IL-1β family. The role played by this cytokine in diabetes-tuberculosis nexus is not known. Serum levels of IL-38, TNF-α, IL-6, and IL-1β in Normal Glucose Tolerance (NGT) and chronic Diabetes (DM) subjects, both with and without latent tuberculosis (LTB) (n = 256) were quantified by ELISA. While, serum levels of IL-38 were significantly reduced, the levels of TNF-α, IL-6, and IL-1β were not altered, in LTB infected diabetes patients. While no significant secretion of IL-38 was detected in the quantiferon supernatant, secretion of TNF-α, IL-6, and IL-1β was significantly reduced in LTB infected diabetes patients. The decreased systemic levels of IL-38 and reduced in vitro secretion of other pro-inflammatory cytokines might represent a crucial pathway associated with diabetes-tuberculosis nexus.

The emerging roles of IL-36, IL-37, and IL-38 in diabetes mellitus and its complications

Diabetes mellitus is a metabolic disease caused by a combination of genetics and environmental factors. The importance of the inflammatory response occurring in the pancreas and adipose tissue in the occurrence and progression of diabetes has been gradually accepted. Excess blood glucose and free fatty acids produce large amounts of inflammatory cytokines and chemokines through oxidative stress and endoplasmic reticulum stress. There is sufficient evidence that proinflammatory mediators, such as interleukin (IL)-1β, IL-6, macrophage chemotactic protein-1, and tumor necrosis factor-α, are engaged in the insulin resistance in peripheral adipose tissue and the apoptosis of pancreatic β-cells. IL-36, IL-37, and IL-38, as new members of the IL-1 family, play an indispensable effect in the regulation of immune system homeostasis and are involved in the pathogenesis of inflammatory and autoimmune diseases. Recently, the abnormal expression of IL-36, IL-37, and IL-38 in diabetes has been reported. In this review, we discuss the emerging functions, potential mechanisms, and future research directions on the role of IL-36, IL-37, and IL-38 in diabetes mellitus and its complications.

Immunobiological Properties and Clinical Applications of Interleukin-38 for Immune-Mediated Disorders: A Systematic Review Study

Exponential growth in the usage of "cytokines" (as seroimmunobiomarkers) has facilitated more accurate prognosis, early diagnosis, novel, and efficient immunotherapeutics. Numerous studies have reported immunopathophysiological and immunopathological processes of interleukin-38 (IL-38). Therefore, in this systematic review article, the authors aimed to present an updated comprehensive overview on the immunobiological mechanisms, diagnostic, and immune gene-based therapeutic potentials of IL-38. According to our inclusion and exclusion criteria, a total of 216 articles were collected from several search engines and databases from the January 2012 to July 2021 time interval by using six main keywords. Physiologic or pathologic microenvironments, optimal dosage, and involved receptors affect the functionalities of IL-38. Alterations in serum levels of IL-38 play a major role in the immunopathogenesis of a wide array of immune-mediated disorders. IL-38 shows anti-inflammatory activities by reduction or inhibition of pro-inflammatory cytokines, supporting the therapeutic aspects of IL-38 in inflammatory autoimmune diseases. According to the importance of pre-clinical studies, it seems that manipulation of the immune system by immunomodulatory properties of IL-38 can increase the accuracy of diagnosis, and decipher optimal clinical outcomes. To promote our knowledge, more collaboration is highly recommended among laboratory scientists, internal/infectious diseases specialists, oncologists, immunologists, diseases-specific biomarkers scientists, and basic medical researchers.

Biology of interleukin-38 and its role in chronic inflammatory diseases

Interleukin (IL)-38 is the tenth member of the IL-1 cytokine family. IL-38 shares high similarity with IL-36Ra and IL-1Ra and can bind to their receptors, thus exerting an anti-inflammatory effect. Despite the lack of a signal peptide, IL-38 can be released from several cell types, but its maturation process remains obscure. The role of IL-38 in numerous inflammatory diseases, especially in autoimmune diseases, has been extensively studied. In this review, we discuss the characteristics, biological functions and pathways of IL-38, as well as its role in several chronic inflammatory diseases. Better understanding the role of IL-38 will pave the way for clinical treatments in the near future.

Plasma levels of interleukin-38 in healthy aging and in type 2 diabetes

Plasma levels of interleukin (IL)-38 were evaluated in patients with type 2 diabetes (T2DM) and healthy controls. Plasma IL-38 was higher in T2DM patients and positively related to waist/hip ratio, HbA1c, uric acid, liver function tests, triglycerides and total proteins. Patients suffering from diabetic nephropathy had the highest IL-38 levels.

Interleukin-38 inhibits adipogenesis and inflammatory cytokine production in 3T3-L1 preadipocytes

Interleukin-38 (IL-38) is a novel member of the IL-1 cytokine family with anti-inflammatory activity. However, its effect on adipogenesis and inflammatory cytokines secretion of adipocytes in vitro has not been reported. To address whether IL-38 inhibits adipogenesis and inflammation in vitro, adipose precursor 3T3-L1 cells were cultured with or without IL-38. The morphology and size of lipid droplets in 3T3-L1 cells were measured by Oil red O staining. The mRNA expression levels of GATA-binding protein-3 (GATA-3), glucose transporter type 4 (GLUT4), peroxisome proliferator-associated receptor γ2, IL-1β, IL-6, and monocyte chemoattractant protein-1 (MCP-1) in 3T3-L1 cells were detected by real-time PCR, The contents of IL-6, IL-1β, and MCP-1 in 3T3-L1 cell medium supernatants were determined by enzyme-linked immunosorbent assay. IL-38 significantly decreased the number of lipid droplets in 3T3-L1 cells. IL-38 also increased GATA-3 and GLUT4 mRNA expression and inhibited IL-1β, IL-6, and MCP-1 secretion by 3T3-L1 cells. It is concluded that IL-38 can inhibit the differentiation of human adipocytes and inflammatory cytokine production by 3T3-L1 cells.