Increased expression of the interleukin-1 receptor-associated kinase (IRAK)-1 is associated with adipose tissue inflammatory state in obesity

Interleukin-1 receptor-associated kinase 2 promotes inflammatory reactions by activating the nuclear factor kappa-B signaling pathway in diabetic nephropathy

Diabetic nephropathy (DN) is a major complication of diabetes. Interleukin-1 receptor-associated kinase 2 (IRAK2) has been implicated in various diseases. This study aimed to investigate the role of IRAK2 in DN progression and its association with inflammation and the nuclear factor-kappa B (NF-κB) signaling pathway. DN model mice were generated by intraperitoneal injection of streptozotocin. IRAK2 expression was upregulated in the DN model mice. IRAK2 knockdown increased weight and reduced blood glucose levels in DN model mice. In addition, IRAK2 downregulation improved glomerular morphology in DN mice. IRAK2 knockdown reduced the levels of kidney damage biomarkers (24-h urinary protein, urine albumin-creatinine ratio, and plasma creatinine) and inflammatory cytokines (IL-6, tumor necrosis factor [TNF]-α, TNF-1R, and TNF-2R). Moreover, IRAK2 activated the NF-κB signaling pathway in DN model mice. Overexpression of NF-κB exacerbated DN progression, and IRAK2 knockdown reversed these effects. IRAK2 promoted DN progression and inflammation by activating the NF-κB signaling pathway. These findings suggest that IRAK2 is a potential therapeutic target for DN treatment.

Modulation of IRAK enzymes as a therapeutic strategy against SARS-CoV-2 induced cytokine storm

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the cause of the current pandemic coronavirus disease 2019 (COVID-19). Dysregulated and excessive production of cytokines and chemokines, known as cytokine storm, is frequently seen in patients with severe COVID-19 disease and it can provoke a severe systematic inflammation in the patients. The IL-1R/TLRs/IRAKs signaling network is a key pathway in immune cells that plays a central role in regulating innate immunity and inflammatory responses via stimulating the expression and production of various proinflammatory molecules including cytokines. Modulation of IRAKs activity has been proposed to be a promising strategy in the treatment of inflammatory disorders. In this review, we highlight the biochemical properties of IRAKs and their role in regulating inflammatory molecular signaling pathways and discuss the potential targeting of IRAKs to suppress the SARS-CoV-2-induced cytokine storm in COVID-19 patients.

Adipose Tissue Caveolin-1 Upregulation in Obesity Involves TNF-α/NF-κB Mediated Signaling

Obesity is characterized by chronic low-grade inflammation. Obese people have higher levels of caveolin-1 (CAV1), a structural and functional protein present in adipose tissues (ATs). We aimed to define the inflammatory mediators that influence CAV1 gene regulation and the associated mechanisms in obesity. Using subcutaneous AT from 27 (7 lean and 20 obese) normoglycemic individuals, in vitro human adipocyte models, and in vivo mice models, we found elevated CAV1 expression in obese AT and a positive correlation between the gene expression of CAV1, tumor necrosis factor-alpha (TNF-α), and the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). CAV1 gene expression was associated with proinflammatory cytokines and chemokines and their cognate receptors (r ≥ 0.447, p ≤ 0.030), but not with anti-inflammatory markers. CAV1 expression was correlated with CD163, indicating a prospective role for CAV1 in the adipose inflammatory microenvironment. Unlike wild-type animals, mice lacking TNF-α exhibited reduced levels of CAV1 mRNA/proteins, which were elevated by administering exogenous TNF-α. Mechanistically, TNF-α induces CAV1 gene transcription by mediating NF-κB binding to its two regulatory elements located in the CAV1 proximal regulatory region. The interplay between CAV1 and the TNF-α signaling pathway is intriguing and has potential as a target for therapeutic interventions in obesity and metabolic syndromes.

Genipin Attenuates Diabetic Cognitive Impairment by Reducing Lipid Accumulation and Promoting Mitochondrial Fusion via FABP4/Mfn1 Signaling in Microglia

The present study was conducted to evaluate the effect of genipin (GEN) on the microglia of diabetic cognitive impairment and explore its potential mechanism. Diabetic mice were induced by STZ/HFD, while GEN was intragastrically and intraventricularly treated. The human microglia cell HMC3 was induced by LPS/HG/PA. As a result, GEN attenuated diabetic symptoms and diabetic cognitive impairment-related behavior in novel object recognition, Morris water maze and passive avoidance tests. GEN inhibited M1 microglia polarization, lipid accumulation, oxidative stress and promoted mitochondrial fusion via FABP4/Mfn1. FABP4 overexpression, Mfn1 overexpression, selective FABP4 inhibitor BMS, and Mfn1 SiRNA were employed for investigating the mechanism. The inhibitory effect of GEN on ROS may be associated with NOX2 signaling and the translocation of p47phox/p67phox to the cell membrane. With the ROS scavenger NAC, it was proved that ROS participated in GEN-mediated inflammation and lipid accumulation. GEN inhibited the phosphorylation and nucleus translocation of NF-κB. GEN inhibited the ubiquitination of Mfn1, which was mediated by the E3 ligase Hrd1. GEN also enhanced microglia phagocytosis. Molecular docking predicted that GEN may interact with FABP4 by hydrogen bond at the S53 and R78 residues. In conclusion, GEN attenuated diabetic cognitive impairment by inhibiting inflammation, lipid accumulation and promoting mitochondrial fusion via FABP4/Mfn1 signaling.

Expression of Steroid Receptor RNA Activator 1 (SRA1) in the Adipose Tissue Is Associated with TLRs and IRFs in Diabesity

Steroid receptor RNA activator gene (SRA1) emerges as a player in pathophysiological responses of adipose tissue (AT) in metabolic disorders such as obesity and type 2 diabetes (T2D). We previously showed association of the AT SRA1 expression with inflammatory cytokines/chemokines involved in metabolic derangement. However, the relationship between altered adipose expression of SRA1 and the innate immune Toll-like receptors (TLRs) as players in nutrient sensing and metabolic inflammation as well as their downstream signaling partners, including interferon regulatory factors (IRFs), remains elusive. Herein, we investigated the association of AT SRA1 expression with TLRs, IRFs, and other TLR-downstream signaling mediators in a cohort of 108 individuals, classified based on their body mass index (BMI) as persons with normal-weight (N = 12), overweight (N = 32), and obesity (N = 64), including 55 with and 53 without T2D. The gene expression of SRA1, TLRs-2,3,4,7,8,9,10 and their downstream signaling mediators including IRFs-3,4,5, myeloid differentiation factor 88 (MyD88), interleukin-1 receptor-associated kinase 1 (IRAK1), and nuclear factor-κB (NF-κB) were determined using qRT-PCR and SRA1 protein expression was determined by immunohistochemistry. AT SRA1 transcripts' expression was significantly correlated with TLRs-3,4,7, MyD88, NF-κB, and IRF5 expression in individuals with T2D, while it associated with TLR9 and TRAF6 expression in all individuals, with/without T2D. SRA1 expression associated with TLR2, IRAK1, and IRF3 expression only in individuals with obesity, regardless of diabetes status. Furthermore, TLR3/TLR7/IRAK1 and TLR3/TLR9 were identified as independent predictors of AT SRA1 expression in individuals with obesity and T2D, respectively. Overall, our data demonstrate a direct association between the AT SRA1 expression and the TLRs together with their downstream signaling partners and IRFs in individuals with obesity and/or T2D.

Dectin-1 as a Potential Inflammatory Biomarker for Metabolic Inflammation in Adipose Tissue of Individuals with Obesity

In obesity, macrophage activation and infiltration in adipose tissue (AT) underlie chronic low-grade inflammation-induced insulin resistance. Although dectin-1 is primarily a pathogen recognition receptor and innate immune response modulator, its role in metabolic syndromes remains to be clarified. This study aimed to investigate the dectin-1 gene expression in subcutaneous AT in the context of obesity and associated inflammatory markers. Subcutaneous AT biopsies were collected from 59 nondiabetic (lean/overweight/obese) individuals. AT gene expression levels of dectin-1 and inflammatory markers were determined via real-time reverse transcriptase-quantitative polymerase chain reaction. Dectin-1 protein expression was assessed using immunohistochemistry. Plasma lipid profiles were measured by ELISA. AT dectin-1 transcripts and proteins were significantly elevated in obese as compared to lean individuals. AT dectin-1 transcripts correlated positively with body mass index and fat percentage (r ≥ 0.340, p ≤ 0.017). AT dectin-1 RNA levels correlated positively with clinical parameters, including plasma C-reactive protein and CCL5/RANTES, but negatively with that of adiponectin. The expression of dectin-1 transcripts was associated with that of various proinflammatory cytokines, chemokines, and their cognate receptors (r ≥ 0.300, p ≤ 0.05), but not with anti-inflammatory markers. Dectin-1 and members of the TLR signaling cascade were found to be significantly associated, suggesting an interplay between the two pathways. Dectin-1 expression was correlated with monocyte/macrophage markers, including CD16, CD68, CD86, and CD163, suggesting its monocytes/macrophage association in an adipose inflammatory microenvironment. Dectin-1 expression was independently predicted by CCR5, CCL20, TLR2, and MyD88. In conclusion, dectin-1 may be regarded as an AT biomarker of metabolic inflammation in obesity.

1,4-Naphthoquinone Is a Potent Inhibitor of IRAK1 Kinases and the Production of Inflammatory Cytokines in THP-1 Differentiated Macrophages

Quinones are a class of cyclic organic compounds that are widely distributed in nature and have been shown to exhibit anti-inflammatory, antioxidant, and anticancerous activities. However, the molecular mechanisms/signaling by which these molecules exert their effect are still not fully understood. In this study, a group of quinone-derived compounds were examined for their potential inhibitory effect against human IRAK1 and IRAK4 kinases in vitro. We have identified five compounds: 1,4-naphthoquinone, emodin, shikonin, plumbagin, and menadione (vitamin K3) as active and selective inhibitors of human IRAK1 enzyme in vitro. The biochemical binding and molecular interactions between the active compounds and IRAK1's catalytic site were demonstrated in silico using structural-based docking and dynamic simulation analysis. Also, 1,4-naphthoquinone was found to effectively inhibit the growth of cancer cell lines overexpressing IRAK1. Furthermore, 1,4-naphthoquinone potently suppressed the production and secretion of key proinflammatory cytokine proteins IL-8, IL-1β, IL-10, TNF-α, and IL-6 in LPS-stimulated PMA-induced human THP-1 macrophages. In conclusion, 1,4-naphthoquinone is an effective inhibitor of IRAK1 kinases and their mediated inflammatory cytokines production in LPS-stimulated PMA-induced human THP-1 macrophages.

Adipose Tissue Steroid Receptor RNA Activator 1 (SRA1) Expression Is Associated with Obesity, Insulin Resistance, and Inflammation

Steroid receptor RNA activator 1 (SRA1) is involved in pathophysiological responses of adipose tissue (AT) in obesity. In vitro and animal studies have elucidated its role in meta-inflammation. Since SRA1 AT expression in obesity/type 2 diabetes (T2D) and the relationship with immune-metabolic signatures remains unclear, we assessed AT SRA1 expression and its association with immune–metabolic markers in individuals with obesity/T2D. For this, 55 non-diabetic and 53 T2D individuals classified as normal weight (NW; lean), overweight, and obese were recruited and fasting blood and subcutaneous fat biopsy samples were collected. Plasma metabolic markers were assessed using commercial kits and AT expression of SRA1 and selected immune markers using RT-qPCR. SRA1 expression was significantly higher in non-diabetic obese compared with NW individuals. SRA1 expression associated with BMI, PBF, serum insulin, and HOMA-IR in the total study population and people without diabetes. SRA1 associated with waist circumference in people without diabetes and NW participants, whereas it associated inversely with HbA1c in overweight participants. In most study subgroups AT SRA1 expression associated directly with CXCL9, CXCL10, CXCL11, TNF-α, TGF-β, IL2RA, and IL18, but inversely with CCL19 and CCR2. TGF-β/IL18 independently predicted the SRA1 expression in people without diabetes and in the total study population, while TNF-α/IL-2RA predicted SRA1 only in people with diabetes. TNF-α also predicted SRA1 in both NW and obese people regardless of the diabetes status. In conclusion, AT SRA1 expression is elevated in people with obesity which associates with typical immunometabolic markers of obesity/T2D, implying that SRA1 may have potential as a biomarker of metabolic derangements.

Identification of Key Pathways and Genes in Obesity Using Bioinformatics Analysis and Molecular Docking Studies

Obesity is an excess accumulation of body fat. Its progression rate has remained high in recent years. Therefore, the aim of this study was to diagnose important differentially expressed genes (DEGs) associated in its development, which may be used as novel biomarkers or potential therapeutic targets for obesity. The gene expression profile of E-MTAB-6728 was downloaded from the database. After screening DEGs in each ArrayExpress dataset, we further used the robust rank aggregation method to diagnose 876 significant DEGs including 438 up regulated and 438 down regulated genes. Functional enrichment analysis was performed. These DEGs were shown to be significantly enriched in different obesity related pathways and GO functions. Then protein-protein interaction network, target genes - miRNA regulatory network and target genes - TF regulatory network were constructed and analyzed. The module analysis was performed based on the whole PPI network. We finally filtered out STAT3, CORO1C, SERPINH1, MVP, ITGB5, PCM1, SIRT1, EEF1G, PTEN and RPS2 hub genes. Hub genes were validated by ICH analysis, receiver operating curve (ROC) analysis and RT-PCR. Finally a molecular docking study was performed to find small drug molecules. The robust DEGs linked with the development of obesity were screened through the expression profile, and integrated bioinformatics analysis was conducted. Our study provides reliable molecular biomarkers for screening and diagnosis, prognosis as well as novel therapeutic targets for obesity.

IRAK inhibitor can improve insulin sensitivity in insulin-resistant mice fed with a high-fat diet

Background

Obesity and the inflammation associated with it, play a key role in the development of insulin resistance through the release of inflammatory cytokines and free fatty acids and the stimulation of toll-like receptors (TLR). Interleukin-1 receptor-associated kinase (IRAK), which mediates the activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway, is an important molecule in TLR signaling. The NF-κB pathway can reduce insulin efficacy by increasing the expression of proinflammatory cytokines. There is no safe inhibitor for the NF-κB pathway, and for this reason, the upper mediator of this pathway was selected for investigation.

Objectives

To determine the effects of an IRAK inhibitor on insulin resistance and serum biochemical factors in high-fat-fed insulin-resistant mice.

Methods

Insulin resistance was developed in C57BL/6J mice by 12 weeks of a high-fat diet. Subsequently, the IRAK 1/4 inhibitor 1-(2-(4-morpholinyl)ethyl)-2-(3-nitrobenzoylamino)benzimidazole (IRAKi)/or pioglitazone, or both, were administered for a further 2 weeks. After 12 h fasting, blood and tissue samples were collected, insulin and glucose levels were assayed, and the homeostatic model assessment was used to quantify insulin resistance (HOMA-IR).

Results

The IRAKi decreased blood glucose levels significantly (253 ± 14.3 mg/dL vs 390.1 ± 16.6 mg/dL) and increased insulin sensitivity compared with untreated controls. However, we did not find a synergistic effect of IRAKi with pioglitazone in increasing insulin sensitivity.

Conclusion

IRAKis can increase insulin sensitivity and their efficacy is comparable to pioglitazone. However, combined administration of pioglitazone and IRAKi had no synergistic effect compared with monotherapy.

Elevated adipose tissue associated IL-2 expression in obesity correlates with metabolic inflammation and insulin resistance

Adipose tissue (AT) associated cytokines are involved in the development of chronic low-grade inflammation in obese individuals. IL-2, a pleiotropic cytokine, contributes to immune alterations during inflammation. However, the interaction between AT-IL-2 and other inflammatory biomolecules in obesity remains elusive. We investigated whether AT-IL-2 expression was associated with markers of inflammation and insulin resistance in overweight/obese individuals. Subcutaneous fat tissues were collected from 56 individuals (lean/overweight/obese) for RNA extraction. IL-2 and inflammatory mediators were quantified by qRT-PCR and immunohistochemistry. CRP was measured by ELISA. AT-IL-2 expression was higher in obese compared with lean individuals (P < 0.021) and correlated with BMI. IL-2 correlated with interleukins IL-8 and IL-12A (r = 0.333–0.481; p = 0.0001–0.029); as well as with chemokines and their receptors including CCL5, CCL19, CCR2 and CCR5 (r = 0.538–0.677; p < 0.0001). Moreover, IL-2 correlated with toll-like receptors (TLR2, TLR8, TLR10), interferon regulatory factor 5 (IRF5) and cluster of differentiation CD11c (r = 0.282–0.357; p < 0.039). Notably, IL-2 was associated positively with fasting blood glucose (FBG), HbA1c, TGL and CRP (r ≥ 0.423;P ≤ 0.007). In multiple regression analysis, IL-2 is an independent predictor of IL-8, IL-12A, TLR10, TGL and HbA1c. Overall, our data demonstrate that increased expression of the AT-IL-2, in obesity, may represent a novel biomarker for progression of metabolic inflammation and insulin-resistance.

Cytokines and the immune response in obesity-related disorders

The increasing prevalence of obesity and the associated morbidity and mortality are important public health problems globally. There is an important relationship between an unhealthy lifestyle and increased serum inflammatory cytokines. Adipocytes secrete several pro-inflammatory cytokines involved in the recruitment and activation of macrophages resulting in chronic low-grade inflammation. Increased cytokines in obese individual are related to the progression of several disorders including cardiovascular disease, hypertension, and insulin resistance. In present review we have summarized the crucial roles of cytokines and their inflammatory functions in obesity-related immune disorders.

Correlation Profile of Suppression of Tumorigenicity 2 and/or Interleukin-33 with Biomarkers in the Adipose Tissue of Individuals with Different Metabolic States

PURPOSE

The suppression of tumorigenicity 2 (ST2) has two main splice variants including a membrane bound (ST2) form, which activates the myeloid differentiation primary response 88 (MyD88)/nuclear factor-kappa B (NF-κB) signaling pathway, and a secreted soluble form (sST2), which acts as a decoy receptor for ST2 ligand, interleukin (IL)-33. The IL-33/ST2 axis is protective against obesity, insulin resistance, and type 2 diabetes (T2D). In humans, adipose tissue IL-33 displays distinct correlation profiles with glycated hemoglobin, ST2, and other immunometabolic mediators, depending on the glycemic health of the individuals. We determined whether adipose tissue ST2 displays distinct correlation profiles with immunometabolic mediators and whether ST2 and/or IL-33 are correlated with intracellular signaling molecules.

PATIENTS AND METHODS

A total of 91 adults with normal glycemia, prediabetes, and T2D were included. After measuring their anthropometric and biochemical parameters, subcutaneous adipose tissues were isolated and mRNA expression of biomarkers was measured.

RESULTS

In individuals with normal glycemia, adipose tissue ST2 was directly correlated with chemokine (C-C motif) ligand (CCL)-2, CCL5, IL-12, fibrinogen-like protein 2 (FGL2) and interferon regulatory factor (IRF)-4, but inversely correlated with cytochrome C oxidase subunit 7A1. IL-33 and ST2 were directly correlated with tumor necrosis factor receptor-associated factor 6 (TRAF6), NF-κB, and nuclear factor of activated T-cells 5 (NFAT5). In individuals with prediabetes, ST2 was inversely correlated with IL-5, whereas IL-33 but not ST2 was directly correlated with MyD88 and NF-κB. In individuals with T2D, ST2 was directly correlated with CCL2, IL-1β, and IRF5. IL-33 and ST2 were directly correlated with MyD88, TRAF6, and NF-κB.

CONCLUSION

Adipose tissue ST2 and IL-33 show different correlation profiles with various immunometabolic biomarkers depending on the metabolic state of the individuals. Therefore, targeting the IL-33/ST2 axis might form the basis for novel therapies to combat metabolic disorders.

Adipose tissue gene expression of CXCL10 and CXCL11 modulates inflammatory markers in obesity: implications for metabolic inflammation and insulin resistance

BACKGROUND

The CXCL subfamily of chemokines (CXCL9, CXCL10, and CXCL11; angiostatic chemokines) plays a key role in many inflammatory diseases. However, the expression of CXCLs in adipose tissue (AT) during obesity and association of these CXCLs with inflammatory markers and insulin resistance are poorly understood. Therefore, this study aimed to investigate the effects of CXCL gene expression on subcutaneous AT inflammatory markers and insulin resistance.

METHODS

Subcutaneous-fat biopsies were collected from 59 nondiabetic (lean/overweight/obese) individuals for RNA isolation. Expression levels of AT CXCL and inflammatory markers were determined by quantitative reverse transcriptase polymerase chain reaction (RT-qPCR). Biomedical parameters in the plasma were measured by enzyme-linked immunosorbent assay (ELISA). Insulin resistance was estimated using homeostatic model assessment (HOMA-IR).

RESULTS

AT CXCL expression was higher in obese compared with lean individuals (p < 0.05) and positively correlated with body mass index (BMI; r ⩾ 0.269, p < 0.05). Expression of CXCL9, CXCL10, and CXCL11 correlated significantly with various pro-inflammatory markers, including family members of interleukins, chemokines, and their prospective receptors (r ⩾ 0.339, p ⩽ 0.009), but not anti-inflammatory markers. CXCL11 expression correlated specifically with the expression of CCL5, CCL18, TLR3, TLR4, TLR8, IRF5, and NF-κB (r ⩾ 0.279, p ⩽ 0.039). Notably, CXCL11 was correlated with C-reactive protein (CRP), fasting blood glucose (FBG), and HOMA-IR. In multiple regression analysis, CXCL11 was identified as an independent predictor of CCL19, CCL5, IL-6, and TLR3.

CONCLUSION

These data suggest that the CXCL family members, specifically CXCL10 and CXCL11, are potential biomarkers for the onset of AT inflammation during obesity.

The Exercise Training Modulatory Effects on the Obesity-Induced Immunometabolic Dysfunctions

Reduced physical activity rate in people's lifestyle is a global concern associated with the prevalence of health disorders such as obesity and metabolic disturbance. Ample evidence has indicated a critical role of the immune system in the aggravation of obesity. The type, duration, and production of adipose tissue-released mediators may change subsequent inactive lifestyle-induced obesity, leading to the chronic systematic inflammation and monocyte/macrophage (MON/MФ) phenotype polarization. Preliminary adipose tissue expansion can be inhibited by changing the lifestyle. In this context, exercise training is widely recommended due to a definite improvement of energy balance and the potential impacts on the inflammatory signaling cascades. How exercise training affects the immune system has not yet been fully elucidated, because its anti-inflammatory, pro-inflammatory, or even immunosuppressive impacts have been indicated in the literature. A thorough understanding of the mechanisms triggered by exercise can suggest a new approach to combat meta-inflammation-induced metabolic diseases. In this review, we summarized the obesity-induced inflammatory pathways, the roles of MON/MФ polarization in adipose tissue and systemic inflammation, and the underlying inflammatory mechanisms triggered by exercise during obesity.

Molecular characterization and expressional modulation of IRAK1 as downstream signaling adaptor molecule of TLR-signaling pathways in Labeo rohita following PAMPs stimulation and bacterial infections

Interleukin-1 receptor associated kinase (IRAK1) is one of the crucial signal transduction mediators in TLR/IL-1R signaling pathways in host immune system. To investigate about it in rohu (Labeo rohita), one of the economically important freshwater fish species in the Indian subcontinent, we cloned, characterized and analyzed its expression following bacterial infection and pathogens associated molecular patterns (PAMPs) stimulation. The full-length cDNA of rohu IRAK1 (LrIRAK1) consisted of 2765 nucleotide (nt) having an ORF of 2115 nt encoding a polypeptide of 704 amino acids (aa) with a molecular mass of 70.4 kDa. Structurally, LrIRAK1 consisted of twenty-nine helix, twelve strands and forty one coils making one N-terminal death domain (19-94 aa) and a central serine threonine kinase catalytic domain (or kinase domain) (188-489aa). In addition to these two prominent domains, LrIRAK1 also contained highly conserved amino acids viz., lysine ²¹⁵ and aspartic acid ³¹⁴ and threonine ^{185, 361} which were reported to be important for kinase and phosphorylation activity respectively in other animals. Similar to higher vertebrates, LrIRAK1 also consisted of CDK1 (cyclin-dependent kinase1) at 338-352 aa; NEK2 (NIMA-related kinase 2) at 47-61 aa; NEK6 (NIMA-related kinase 6) at 581-595 aa and AMPK (AMP- activated protein kinase) motif at 518-538 aa. Phylogenetically, LrIRAK1 is closely related to cave fish, common carp exhibiting high similarity (~95%) and identity (~90%). In the uninfected fish, the LrIRAK1 expression was highest in liver (~11.5 fold) and lowest in blood. In response to Aeromonas hydrophila, Edwardsiella tarda and Bacillus subtilis infection and various TLR and NLR-ligands stimulation, the expression of LrIRAK1 was markedly enhanced at various time points in almost all the tested tissues. These results together suggest the key role of LrIRAK1 in pattern recognition receptors (PRRs)-mediated host defense against pathogenic insults.

Increased Adipose Tissue Expression of Interferon Regulatory Factor (IRF)-5 in Obesity: Association with Metabolic Inflammation

Interferon regulatory factor (IRF)-5 is known to be involved in M1 macrophage polarization, however, changes in the adipose expression of IRF5 in obesity and their relationship with the local expression of proinflammatory cytokines/chemokines are unknown. Therefore, IRF5 gene expression was determined in the subcutaneous adipose tissue samples from 53 non-diabetic individuals (6 lean, 18 overweight, and 29 obese), using real-time RT-PCR. IRF5 protein expression was also assessed using immunohistochemistry and/or confocal microscopy. Adipose gene expression of signature immune metabolic markers was also determined and compared with adipose IRF5 gene expression. Systemic levels of C-reactive protein and adiponectin were measured by ELISA. The data show that adipose IRF5 gene (P = 0.008) and protein (P = 0.004) expression was upregulated in obese compared with lean individuals. IRF5 expression changes correlated positively with body mass index (BMI; r = 0.37/P = 0.008) and body fat percentage (r = 0.51/P = 0.0004). In obese, IRF5 changes associated positively with HbA1c (r = 0.41/P = 0.02). A good agreement was found between gene and protein expression of IRF5 in obese subjects (r = 0.65/P = 0.001). IRF5 gene expression associated positively with adipose inflammatory signatures including local expression of TNF-α, IL-6, CXCL8, CCL-2/5, IL-1β, IL-18, CXCL-9/10, CCL7, CCR-1/2/5, TLR-2/7/8/9, IRF3, MyD88, IRAK-1, and inflammatory macrophage markers (P < 0.05). Interestingly, IRF5 gene expression correlated positively with CRP (r = 0.37, P = 0.03) and negatively with adiponectin levels (r = −0.43, P = 0.009). In conclusion, elevated adipose IRF5 expression in obesity concurs with the typical inflammatory signatures, locally and systemically. Hence, the IRF5 upregulation may represent a novel adipose tissue marker for metabolic inflammation.

Association between Adipose Tissue Interleukin-33 and Immunometabolic Markers in Individuals with Varying Degrees of Glycemia

Introduction

Interleukin-33 (IL-33), the ligand for the receptor ST2, is abundant in adipose tissue, including preadipocytes, adipocytes, and endothelial cells. The IL-33/ST2 axis is protective against obesity, insulin resistance, and type 2 diabetes (T2D) in animal models. We determined whether adipose tissue IL-33 was associated with glycated hemoglobin (HbA1c), as well as mediators of inflammation and immune regulation and beiging of adipose tissue, among individuals with varying degrees of glycemia.

Materials and Methods

A total of 91 adults with normoglycemia, prediabetes, and T2D were included. After measuring their anthropometric and biochemical parameters, subcutaneous adipose tissue samples were isolated and mRNA expression of cytokines, chemokines, chemokine receptors, pattern recognition receptors, and mediators involved in beiging of adipose tissue were measured.

Results

Adipose tissue IL-33 was inversely associated with HbA1c in individuals with normoglycemia and T2D but not in those with prediabetes and was inversely correlated with fasting plasma glucose in individuals with T2D and with a better glycemic control. IL-33-to-ST2 ratio was inversely correlated with HbA1c in individuals with normoglycemia but not in those with prediabetes or T2D. IL-33 was directly associated with ST2, CD302, fibrinogen-like protein 2 (FGL2), and PR domain containing 16 (PRDM16) but inversely correlated with chemokine (C-C motif) ligand (CCL) 7 and CCL8 in individuals with normoglycemia. Similarly, IL-33 was directly associated with ST2, CD302, FGL2, PRDM16, and, additionally, toll-like receptor (TLR) 3 and IL-12A in individuals with T2D. However, IL-33 was not associated with any of these mediators but was directly and strongly associated with TLR9 in individuals with prediabetes.

Conclusions

IL-33 and/or IL-33/ST2 dynamics and biological functions may play a role in overall glycemia among humans and may represent a novel target by which glucose-lowering managements confer their beneficial effects.

The changes in immune cell concentration during the progression of pre-diabetes to type 2 diabetes in a high-fat high-carbohydrate diet-induced pre-diabetic rat model

Pre-diabetes is a long-lasting condition that precedes type 2 diabetes (T2D). T2D has been shown to suppress the immune response. However, it remains unclear if immune activation occurs before the onset of T2D during the progression of the pre-diabetic state. This study sought to characterize the changes in general immunity occurring during the progression from pre-diabetes to T2D. Male rats were fed a high-fat high-carbohydrate diet for 20 weeks (pre-diabetes induction period) and kept on the same diet being monitored for a further 12 weeks (experimental period). Blood was collected for haemocytometer analysis on week 0, 4, 8, and 12 of the experimental period after which the animals were sacrificed. Plasma was collected from centrifuged blood for ELISA (TNF-α, CRP, P-selectin, CD40 L, fibrinogen, and IL-6). Blood neutrophils percentage significantly decreased at week 12 possibly due to recruited neutrophils migrating to an inflamed area such as visceral adipose tissue as further observed. Due to hyperglycaemia, there was significant increase in blood lymphocytes percentage at week 12. Blood monocytes percentage significantly increased at week 12. Monocytes recruited and circulated in blood due to hyperglycaemia for glucose uptake to decrease it from circulation. Blood eosinophils percentage significantly decreased at week 12. Eosinophils migrated to inflamed areas such as visceral adipose tissue as further observed. Blood basophils percentage significantly increased due to their recruitment and activation. TNF-α, CRP, and IL-6 increased significantly after 12 weeks. There was also upregulation of fibrinogen, P-selectin, and CD40L. The results of this study show that there are changes in immune cells concentration and that immune cells such as neutrophils and eosinophils migrate to inflamed areas such as adipose tissue. There is also upregulation of various inflammatory cytokines. Based on these findings, immune activation begins during the pre-diabetic state as there is upregulation of inflammatory markers.

Innate Immune Signaling and Its Role in Metabolic and Cardiovascular Diseases

The innate immune system is an evolutionarily conserved system that senses and defends against infection and irritation. Innate immune signaling is a complex cascade that quickly recognizes infectious threats through multiple germline-encoded cell surface or cytoplasmic receptors and transmits signals for the deployment of proper countermeasures through adaptors, kinases, and transcription factors, resulting in the production of cytokines. As the first response of the innate immune system to pathogenic signals, inflammatory responses must be rapid and specific to establish a physical barrier against the spread of infection and must subsequently be terminated once the pathogens have been cleared. Long-lasting and low-grade chronic inflammation is a distinguishing feature of type 2 diabetes and cardiovascular diseases, which are currently major public health problems. Cardiometabolic stress-induced inflammatory responses activate innate immune signaling, which directly contributes to the development of cardiometabolic diseases. Additionally, although the innate immune elements are highly conserved in higher-order jawed vertebrates, lower-grade jawless vertebrates lack several transcription factors and inflammatory cytokine genes downstream of the Toll-like receptors (TLRs) and retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs) pathways, suggesting that innate immune signaling components may additionally function in an immune-independent way. Notably, recent studies from our group and others have revealed that innate immune signaling can function as a vital regulator of cardiometabolic homeostasis independent of its immune function. Therefore, further investigation of innate immune signaling in cardiometabolic systems may facilitate the discovery of new strategies to manage the initiation and progression of cardiometabolic disorders, leading to better treatments for these diseases. In this review, we summarize the current progress in innate immune signaling studies and the regulatory function of innate immunity in cardiometabolic diseases. Notably, we highlight the immune-independent effects of innate immune signaling components on the development of cardiometabolic disorders.

Adipose tissue expression of CCL19 chemokine is positively associated with insulin resistance

BACKGROUND

Chemokines produced by adipose tissue (AT) are involved in the development of chronic low-grade inflammation in obese humans and rodents. AT CCL19 expression in obesity and its association with metabolic inflammation and insulin resistance are poorly understood. This study aimed to investigate the effects of CCL19 gene expression on inflammatory markers in subcutaneous AT and insulin resistance.

METHODS

Subcutaneous adipose samples were collected from 56 non-diabetic (26-obese, 21-overweight, and 9-lean) individuals. Expression of CCL19 and inflammatory markers was determined using real-time RT-PCR. Plasma C-reactive protein (CRP) and adiponectin were measured by ELISA. Insulin sensitivity was assessed using homeostasis model assessment index (HOMA).

RESULTS

CCL19 expression was significantly higher in obese compared with lean individuals (P < 0.034). The elevated expression of CCL19 associated positively with body mass index (r = 0.253; P = 0.049). CCL19 expression correlated positively with IL-8 (r = 0.39; P = 0.006), IL-12 (r = 0.43; P = 0.003), IP-10 (r = 0.25; P = 0.07), CCL5 (r = 0.37; P = 0.011), CCR2 (r = 0.44; P = 0.001), and CCR5 (r = 0.35; P = 0.009). Additionally, CCL19 was positively correlated with triglycerides (TG: r = 0.41; P = 0.001), fasting blood glucose (FBG: r = 0.49; P < 0.0001), glycated haemoglobin (HbA1c: r = 0.396; P = 0.001), and CRP (r = 0.387; P = 0.019) whereas it had negative association with HDL cholesterol (r = -0.282; P = 0.035) and adiponectin (-0.393; P = 0.019). Notably, HOMA-IR correlated positively with CCL19 (r = 0.38; P = 0.01). In multiple regression analysis, CCL19 is an independent predictor of IL-8 and IL-12.

CONCLUSIONS

These data demonstrate that increased AT expression of CCL19 in obesity may represent a molecular link between metabolic inflammation and insulin resistance.

Identification, characterisation and preliminary functional analysis of IRAK-M in grass carp (Ctenopharyngodon idella)

Interleukin-1 receptor-associated kinase (IRAK) family members play important roles in myeloid differentiation primary response 88 (MyD88)-dependent toll-like receptor (TLR) signaling, the crucial innate immune pathway in vertebrates. In the present study, the IRAK family gene IRAK-M (also called IRAK3) from grass carp (Ctenopharyngodon idella) was cloned and characterised. IRAK-M was mainly enriched in the spleen, and the significantly altered expression was observed after grass carp reovirus (GCRV) infection. Subcellular localisation showed that IRAK-M protein distributed uniformly in the entire cell and co-localised with MyD88 in the cytoplasm of transfected cells. Additionally, the interaction between IRAK-M and MyD88 was confirmed by bimolecular fluorescence complementation (BiFC) system. Moreover, deficient of IRAK-M in C. idella kidney cell line (CIK) with small interference RNA (siRNA) upregulated polyinosinic:polycytidylic acid (poly(I:C))-induced inflammatory cytokines production, including interleukin 8 (IL-8), IL-6, and tumour necrosis factor α (TNF-α), which reveals that IRAK-M functions as a negative regulator of inflammatory cytokines. Taken together, our results demonstrate that IRAK-M gene plays an important role in innate immune regulation and provide new insights into understanding the functional characteristics of the IRAK-M in teleosts.

Inhibition of interleukin-1 receptor-associated kinase 1 (IRAK1) as a therapeutic strategy

Interleukin-1 receptor-associated kinases (IRAK1, IRAK2, IRAK3 [IRAK-M], and IRAK4) are serine-threonine kinases involved in toll-like receptor and interleukin-1 signaling pathways, through which they regulate innate immunity and inflammation. Evidence exists that IRAKs play key roles in the pathophysiologies of cancers, and metabolic and inflammatory diseases, and that IRAK inhibition has potential therapeutic benefits. Molecules capable of selectively interfering with IRAK function and expression have been reported, paving the way for the clinical evaluation of IRAK inhibition. Herein, we focus on IRAK1, review its structure and physiological roles, and summarize emerging data for IRAK1 inhibitors in preclinical and clinical studies.

Inhibition of Interleukin-1 Receptor-Associated Kinases 1/4, Increases Gene Expression and Serum Level of Adiponectin in Mouse Model of Insulin Resistance

Insulin resistance is a feature of most patients with type 2 diabetes mellitus. Epidemiological evidence suggest a correlation between inflammation and insulin resistant states such as obesity, but the underlying mechanisms are largely unknown. Interleukin-1 receptor-associated kinases (IRAK) play a central role in inflammatory responses by regulating the expression of various inflammatory genes in immune cells. This study was aimed to investigate the effect of IRAK inhibitor on gene transcription and serum concentration of adiponectin in insulin-resistant mice. Experimental mice were randomly divided into 6 groups: the healthy control group was fed a regular chow diet while other groups were fed with a high-fat diet for 12 weeks. After this period, the animals were treated with IRAK inhibitor, pioglitazone, both IRAK and pioglitazone, and DMSO, for two weeks. Adiponectin gene expression level was analyzed by real-time PCR. Additionally, serum adiponectin levels were measured by ELISA. Homeostasis model assessment-adiponectin (HOMA-AD) as an insulin sensitivity index was calculated. IRAK inhibitor and pioglitazone increased significantly the expression of adiponectin gene. Also, adiponectin concentration in the control group (9.67±1.1 μg/ml) increased to 25.34±2.04 μg/ml in pioglitazone treatment group. IRAK inhibitor also increased adiponectin concentration (18.24±1.53 μg/ml) but did not show a synergistic effect with pioglitazone when administered simultaneously (26.66±2.5 μg/ml). HOMA-AD was 0.33±0.04 in pioglitazone treated group, 0.6±0.13 in IRAK inhibitor group, and 0.31±0.03 in animals that received IRAKi and pioglitazone. Our findings suggest that increased adiponectin secretion from adipose tissue mediated by IRAK inhibitor may increase the insulin sensitivity in an animal model of insulin resistance.

Pro-atherogenic and pro-oxidant crosstalk between adipocytes and macrophages

PURPOSE

Obesity, which is characterized by triglyceride accumulation mainly in adipocytes but also in arterial wall cells such as macrophages, is a major risk factor for developing atherosclerosis. We aimed to identify the crosstalk related to lipid metabolism and oxidation status between adipocytes and macrophages.

METHODS

We used a co-culture model system with J477A.1 cultured macrophages and 3T3L1 cultured adipocytes. For an in-vivo co-culture system, we used C57BL/6 mouse peritoneal macrophages and visceral or subcutaneous adipose tissue.

RESULTS

Adipocytes significantly increased reactive oxygen species generation, up to twofold, and decreased cholesterol content by 22% in the co-cultured macrophages. Macrophages significantly increased triglyceride-biosynthesis rate by twofold and decreased triglyceride-degradation rate by 30%, resulting in increased triglyceride accumulation in the co-cultured adipocytes by up to 72%. In the in-vivo mouse model, visceral adipose tissue crosstalk with macrophages resulted in a significant pro-atherogenic phenotype with respect to cellular cholesterol metabolism. In contrast, the interaction between subcutaneous adipose tissue and macrophages mostly affected cellular triglyceride metabolism. There were no significant effects on mitochondrial respiration capacity in the macrophages. Upon oxidative-stress reduction in the co-cultured cells using the polyphenol-rich antioxidant, pomegranate juice, the expression of genes related to cellular lipid accumulation was significantly reduced.

CONCLUSIONS

We reveal, for the first time, that paracrine interactions between adipocytes and macrophages result in oxidative stress and lipids metabolic alterations in both cells, toward increased atherogenicity which can be reversed by phenolic antioxidants.

Pilot study of the antifibrotic effects of the multikinase inhibitor pacritinib in a mouse model of liver fibrosis

Background

Fibrotic diseases result from an exuberant response to chronic inflammation. Myelofibrosis is the end result of inflammation in bone, caused by an inflammatory process triggered by production of abnormal myeloid cells driven by mutations affecting the JAK-STAT pathway. Inflammatory cytokine overproduction leads to increased mesenchymal cell proliferation, culminating in fibrosis. Although JAK2 inhibitors, such as the JAK1/2 inhibitor ruxolitinib and the JAK2/FLT3/CSF1R/IRAK1 inhibitor pacritinib suppress abnormal clone expansion in myelofibrosis, ruxolitinib does not appear to prevent or reverse bone-marrow fibrosis in most patients. In two Phase III clinical trials, pacritinib, however, demonstrated improvements in platelet counts and hemoglobin and reductions in transfusion burden in some patients with baseline cytopenias, suggesting it may improve bone-marrow function. Unlike ruxolitinib, pacritinib suppresses signaling through IRAK1, a key control point for inflammatory and fibrotic signaling.

Purpose

To investigate potential antifibrotic effects of pacritinib in an animal model of liver fibrosis relevant to the observed course of human disease.

Methods

Pacritinib, negative control (vehicle), and positive control (the angiotensin 2-receptor antagonist and PPARγ partial agonist telmisartan) were assessed in the murine Stelic animal model, which mimics the clinically observed progression from hepatic steatosis to nonalcoholic steatohepatitis, liver fibrosis, and hepatocellular carcinoma. Histopathological analysis used hematoxylin and eosin staining. Body and liver weight changes, nonalcoholic fatty-liver disease activity scores, and plasma cytokeratin 18 fragment levels (a biomarker of hepatic necrosis) were measured.

Results

Pacritinib-treated mice had significantly (P<0.01) reduced fibrotic areas in liver compared to vehicle control and significantly (P<0.05) lower levels of CK18. The antifibrotic effect of pacritinib was comparable to that of telmisartan, but without significant effects on fat accumulation.

Conclusion

These results, the first to demonstrate hepatic antifibrotic effects for pacritinib in an animal model of liver disease, provide preliminary support for potential clinical applications of pacritinib in fibrotic diseases other than myelofibrosis.

Increased adipose tissue expression of IL-18R and its ligand IL-18 associates with inflammation and insulin resistance in obesity

INTRODUCTION

The proinflammatory cytokine IL-18 is involved in the pathogenesis of metabolic syndrome. While the changes in IL-18 are known, IL-18R expression and relationship with IL-18 and other inflammatory markers in the adipose tissue in obesity/type-2 diabetes (T2D) remain unclear.

METHODS

We, therefore, determined the adipose tissue expression of IL-18R and IL-18 mRNA/protein in lean, overweight, and obese individuals with and without T2D, 15 each, using qRT-PCR, immunohistochemistry, and confocal microscopy. Data (mean ± SEM) were analyzed using unpaired t-test and Pearson's correlation (r); all P values ≤0.05 were considered statistically significant.

RESULTS

We found the upregulated gene/protein expression of IL-18R and IL-18 in non-diabetic obese/overweight as compared with lean individuals (P < 0.05). BMI correlated positively (P < 0.05) with the adipose tissue expression of IL-18R (mRNA: r = 0.90 protein: r = 0.84) and IL-18 (mRNA: r = 0.84 protein: r = 0.80). Similarly, in T2D individuals, gene and protein expression of IL-18R/IL-18 was significantly higher in obese as compared with overweight/lean individuals. The BMI was associated with the changes in both IL-18R (mRNA: r = 0.55 protein: r = 0.50) and IL-18 (mRNA: r = 0.53 protein: r = 0.57) expression. IL-18R/IL-18 gene expression in the adipose tissue was positively associated (P < 0.05) with local gene expression of other inflammatory markers including CD11c, CD86, CD68, CD163, TNF-α, and CCL5. Homeostatic model assessment of insulin resistance (HOMA-IR) was higher in diabetic/non-diabetic obese and it correlated with BMI (P < 0.05). IL-18R and IL-18 mRNA/protein expression in obesity was associated with HOMA-IR only in non-diabetics.

CONCLUSIONS

The adipose tissue IL-18R/IL-18 expression is enhanced in obesity which associates with proinflammatory gene signature and insulin resistance in these individuals.

Deficiency in IRAK4 activity attenuates manifestations of murine Lupus

Interleukin-1 receptor-associated kinase (IRAK) 4 mediates host defense against infections. As an active kinase, IRAK4 elicits full spectra of myeloid differentiation primary response protein (MyD) 88-dependent responses, while kinase-inactive IRAK4 induces a subset of cytokines and negative regulators whose expression is not regulated by mRNA stability. IRAK4 kinase activity is critical for resistance against Streptococcus pneumoniae, but its involvement in autoimmunity is incompletely understood. In this study, we determined the role of IRAK4 kinase activity in murine lupus. Lupus development in BXSB mice expressing the Y chromosome autoimmunity accelerator (Yaa) increased basal and Toll-like receptor (TLR) 4/7-induced phosphorylation of mitogen-activated protein kinases, p65 nuclear factor-κB (NF-κB), enhanced tumor necrosis factor (TNF)-α and C-C motif chemokine ligand (CCL) 5 gene expression in splenic macrophages, but decreased levels of Toll-interacting protein and IRAK-M, without affecting IRAK4 or IRAK1 expression. Mice harboring kinase-inactive IRAK4 on the lupus-prone Yaa background manifested blunted TLR signaling in macrophages and reduced glomerulonephritis, splenomegaly, serum anti-nuclear antibodies, numbers of splenic macrophages, total and TNF-α⁺ dendritic cells, activated T- and B-lymphocytes, and lower TNF-α expression in macrophages compared with lupus-prone mice with functional IRAK4. Thus, IRAK4 kinase activity contributes to murine lupus and could represent a new therapeutic target.

Characterization, expression, and functional study of IRAK-1 from grouper, Epinephelus coioides

As crucial components of the toll-like receptor (TLR) and interleukin-1 (IL-1) receptor (IL-1R) signaling pathways, interleukin-1 receptor associated kinase (IRAK) family members play essential roles in an animal's immune response. In this study, an IRAK family member, designated EcIRAK-1, was identified in the orange-spotted grouper Epinephelus coioides, and its role in signal transduction investigated. The full-length EcIRAK-1 gene is 2822 bp, encoding a 760-amino-acid protein that has the typical characteristics of mammalian IRAK-1, including an N-terminal death domain, a ProST domain, a central kinase domain, and C-terminal C1 and C2 domains. EcIRAK-1 shares 42%-79% sequence identity with other fish IRAK-1 proteins, and the death and kinase domains are more conserved than the other domains. Several important amino acids and motifs of mammalian IRAK-1 are also conserved in the grouper and other piscine IRAK-1s. In healthy grouper, EcIRAK-1 was broadly expressed in all the tissues tested, with the highest expression in the gill and skin. After infection with Cryptocaryon irritans, EcIRAK-1 expression increased in the gill and spleen. After its exogenous expression in HEK293T cells, EcIRAK-1 significantly activated nuclear factor kappaB (NF-κB). The death domain, ProST domain, and some conserved amino acids, such as T58, T207, K237, and T387, in EcIRAK-1 are required for its signaling function. These data demonstrate that piscine IRAK-1 has the same structural characteristics as its mammalian counterpart and that its function is conserved among vertebrates.