The inflammasome-mediated caspase-1 activation controls adipocyte differentiation and insulin sensitivity

Pro-inflammatory profile of visceral adipose tissue and oxidative stress in severe obese patients carrying the variant rs4612666 C of NLRP3 gene

BACKGROUND

the activation of NLRP3 inflammasome machinery has a central role in obesity-induced inflammation. Genetic studies well support the involvement of functional variants of NLRP3 and its negative regulator, CARD8, in the pathogenesis of complex diseases with an inflammatory background. We have investigated the influence of NLRP3 (rs4612666; rs10754558) and CARD8 (rs204321) genetic variants in both the inflammatory status of visceral adipose tissue (VAT) from patients with severe obesity and in the systemic oxidative stress before and after sleevegastrectomy (SLG).

METHODS

23 consecutive severe obese patients candidate to SLG were enrolled in the study. Visceral adipose tissue (VAT) biopsies, obtained during SLG, were used to evaluate the expression of NLRP3, IL-1β, IL-6, and MCP-1 by real-time RT-PCR. DNA was extracted from peripheral blood lymphocytes and genotyped by RFLP analysis. Before and 3 months after SLG, all patients underwent the assessment of oxidative stress, biochemical parameters, and body-composition as measured by bioelectrical impedance analysis (BIA).

RESULTS

Increased expression of NLRP3, IL-6, IL-1β, and MCP-1 mRNA was observed in VAT of rs4612666 C variant carriers, in which higher oxidative stress was also detected as compared to non-carrier individuals. In all patients, oxidative stress, biochemical and BIA parameters improved after SLG, regardless of genotype. No significant correlations were found with the other genetic variants.

CONCLUSIONS

Our results suggest that the NLRP3 rs4612666 C variant may promote a worse pro-inflammatory-milieu and higher oxidative stress, thus leading patients to a more severe obesity phenotype. A larger study is needed to confirm this assumption and to investigate the impact of the NLRP3 rs4612666 C variant on severe obesity.

Innate Immune Cells in the Adipose Tissue in Health and Metabolic Disease

Metabolic disorders, such as obesity, type 2 diabetes mellitus, and nonalcoholic fatty liver disease, are characterized by chronic low-grade tissue and systemic inflammation. During obesity, the adipose tissue undergoes immunometabolic and functional transformation. Adipose tissue inflammation is driven by innate and adaptive immune cells and instigates insulin resistance. Here, we discuss the role of innate immune cells, that is, macrophages, neutrophils, eosinophils, natural killer cells, innate lymphoid type 2 cells, dendritic cells, and mast cells, in the adipose tissue in the healthy (lean) and diseased (obese) state and describe how their function is shaped by the obesogenic microenvironment, and humoral, paracrine, and cellular interactions. Moreover, we particularly outline the role of hypoxia as a central regulator in adipose tissue inflammation. Finally, we discuss the long-lasting effects of adipose tissue inflammation and its potential reversibility through drugs, caloric restriction, or exercise training.

NLRP3 as a sensor of metabolism gone awry

The NLRP3 inflammasome is an important player in innate immunity and pathogenic inflammation. Numerous studies have implicated it in sensing endogenous danger signals, yet the precise mechanisms remain unknown. Here, we review the current knowledge on the organismal and cellular metabolic triggers engaging NLRP3, and the mechanisms involved in integrating the diverse signals.

Mice Deficient in the IL-1β Activation Genes Prtn3, Elane, and Casp1 Are Protected Against the Development of Obesity-Induced NAFLD

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease. Inflammatory pathways contribute to disease pathogenesis; however, regulation of the underlying mechanism is not completely understood. IL-1β, a pro-inflammatory cytokine, participates in the development and progression of NAFLD. To become bioactive, IL-1β requires enzymatic processing. Mechanisms that activate IL-1β include the classical NLRP3 inflammasome-caspase-1 and the neutrophil serine proteases, neutrophil elastase, and proteinase-3. Several studies have shown that both caspase-1 and the neutrophil serine proteases are important for NAFLD development. However, it is unknown whether these pathways interact and if they have a synergistic effect in promoting NAFLD. In the present study, we developed a novel and unique mouse model by intercrossing caspase-1/11 knockout mice with neutrophil elastase/proteinase-3 double knockout mice. Subsequently, these mice were examined regarding the development of high-fat diet–induced NAFLD. Our results show that mice deficient in caspase-1, neutrophil elastase, and proteinase-3 were protected from developing diet-induced weigh gain, liver steatosis, and adipose tissue inflammation when compared with controls. We conclude that pathways that process pro-IL-1β to bioactive IL-1β play an important role in promoting the development of NAFLD and obesity-induced inflammation. Targeting these pathways could have a therapeutic potential in patients with NAFLD.

NLRP3 Inflammasome: Potential Role in Obesity Related Low-Grade Inflammation and Insulin Resistance in Skeletal Muscle

Among multiple mechanisms, low-grade inflammation is critical for the development of insulin resistance as a feature of type 2 diabetes. The nucleotide-binding oligomerization domain-like receptor family (NOD-like) pyrin domain containing 3 (NLRP3) inflammasome has been linked to the development of insulin resistance in various tissues; however, its role in the development of insulin resistance in the skeletal muscle has not been explored in depth. Currently, there is limited evidence that supports the pathological role of NLRP3 inflammasome activation in glucose handling in the skeletal muscle of obese individuals. Here, we have centered our focus on insulin signaling in skeletal muscle, which is the main site of postprandial glucose disposal in humans. We discuss the current evidence showing that the NLRP3 inflammasome disturbs glucose homeostasis. We also review how NLRP3-associated interleukin and its gasdermin D-mediated efflux could affect insulin-dependent intracellular pathways. Finally, we address pharmacological NLRP3 inhibitors that may have a therapeutical use in obesity-related metabolic alterations.

Increased inflammasome activity in subcutaneous adipose tissue of patients with metabolic syndrome

AIMS

The metabolic syndrome (MetS) is an inflammatory disorder associated with an increased risk for diabetes and atherosclerotic cardiovascular disease (ASCVD). Studies in patients and animal models of obesity and diabetes have shown increased NOD-like receptor family pyrin domain containing 3 (NLPR3) inflammasome activity. However, there is scanty data on the activity of the NLRP3 inflammasome in patients with nascent MetS. The aim of this study was to determine the status of the inflammasome in subcutaneous adipose tissue (SAT) of patients with nascent MetS without concomitant diabetes, ASCVD and smoking.

MATERIALS AND METHODS

Patients with nascent MetS and controls were recruited from Sacramento County. Fasting blood samples were collected for biomediators of inflammation and SAT was obtained by biopsy for immunohistochemical (IHC) staining for caspase 1, IL-1β and IL-18.

RESULTS

Caspase1, a marker of inflammasome activity and its downstream mediators IL-1β and IL-18 were significantly increased in SAT of patients with MetS compared to controls. Significant positive correlations of caspase 1 were obtained with certain cardio-metabolic features, biomediators of inflammation and markers of angiogenesis and fibrosis in SAT. Both mast cell and eosinophil abundance but not macrophage density correlated with caspase1.

CONCLUSIONS

We make the novel observation that the SAT of patients with nascent MetS displays increased NLRP3 inflammasome activity manifest by increased caspase 1 in SAT and this may contribute to increased insulin resistance, inflammation and SAT fibrosis in these patients.

Identification of Common Pathogenetic Processes between Schizophrenia and Diabetes Mellitus by Systems Biology Analysis

Schizophrenia (SCZ) is a psychiatric disorder characterized by both positive symptoms (i.e., psychosis) and negative symptoms (such as apathy, anhedonia, and poverty of speech). Epidemiological data show a high likelihood of early onset of type 2 diabetes mellitus (T2DM) in SCZ patients. However, the molecular processes that could explain the epidemiological association between SCZ and T2DM have not yet been characterized. Therefore, in the present study, we aimed to identify underlying common molecular pathogenetic processes and pathways between SCZ and T2DM. To this aim, we analyzed peripheral blood mononuclear cell (PBMC) transcriptomic data from SCZ and T2DM patients, and we detected 28 differentially expressed genes (DEGs) commonly modulated between SCZ and T2DM. Inflammatory-associated processes and membrane trafficking pathways as common biological processes were found to be in common between SCZ and T2DM. Analysis of the putative transcription factors involved in the regulation of the DEGs revealed that STAT1 (Signal Transducer and Activator of Transcription 1), RELA (v-rel reticuloendotheliosis viral oncogene homolog A (avian)), NFKB1 (Nuclear Factor Kappa B Subunit 1), and ERG (ETS-related gene) are involved in the expression of common DEGs in SCZ and T2DM. In conclusion, we provide core molecular signatures and pathways that are shared between SCZ and T2DM, which may contribute to the epidemiological association between them.

Therapeutic regulation of the NLRP3 inflammasome in chronic inflammatory diseases

Inflammasomes are cytosolic pattern recognition receptors that recognize pathogen-associated molecular patterns (PAMPs) and danger-associated molecular patterns (DAMPs) derived from invading pathogens and damaged tissues, respectively. Upon activation, the inflammasome forms a complex containing a receptor protein, an adaptor, and an effector to induce the autocleavage and activation of procaspase-1 ultimately culminating in the maturation and secretion of IL-1β and IL-18 and pyroptosis. Inflammasome activation plays an important role in host immune responses to pathogen infections and tissue repair in response to cellular damage. The NLRP3 inflammasome is a well-characterized pattern recognition receptor and is well known for its critical role in the regulation of immunity and the development and progression of various inflammatory diseases. In this review, we summarize recent efforts to develop therapeutic applications targeting the NLRP3 inflammasome to cure and prevent chronic inflammatory diseases. This review extensively discusses NLRP3 inflammasome-related diseases and current development of small molecule inhibitors providing beneficial information on the design of therapeutic strategies for NLRP3 inflammasome-related diseases. Additionally, small molecule inhibitors are classified depending on direct or indirect targeting mechanism to describe the current status of the development of pharmacological inhibitors.

Vitamin D affects the neutrophil-to-lymphocyte ratio in patients with type 2 diabetes mellitus

AIMS/INTRODUCTION

Chronic inflammation is an underlying feature of type 2 diabetes mellitus. Hypovitaminosis D is associated with type 2 diabetes mellitus, but whether it contributes to chronic inflammation is unclear. We examined the effects of vitamin D on various immune markers to evaluate its contribution to systemic inflammation in type 2 diabetes mellitus.

MATERIALS AND METHODS

We retrospectively analyzed data from type 2 diabetes mellitus patients, people with prediabetes and control patients without diabetes (n = 9,746). Demographic and clinical variables were evaluated using descriptive statistics and generalized linear regression. A stratified analysis based on total serum vitamin D was also carried out.

RESULTS

Neutrophil count was a significant predictor of 1,5-anhydroglucitol and glycated hemoglobin (HbA1c) in patients with prediabetes (1,5-anhydroglucitol: β = -0.719, P < 0.001 and HbA1c: β = -0.006, P = 0.002) and patients with diabetes (1,5-anhydroglucitol: β = 0.207, P = 0.004 and HbA1c: β = -0.067, P = 0.010). Lymphocyte count was a significant predictor of HbA1c in patients without diabetes (β = 0.056, P < 0.001) and patients with prediabetes (β = 0.038, P < 0.001). The neutrophil-to-lymphocyte ratio (NLR) was a significant predictor of HbA1c in patients without diabetes (β = -0.001, P = 0.032). No immune markers differed significantly based on vitamin D level among patients without diabetes (P> 0.05 for all). Among patients with prediabetes, those who were vitamin D-deficient had the highest NLR (P = 0.040). Among patients with diabetes, those who were vitamin D-deficient had the highest neutrophil count (P = 0.001), lowest lymphocyte count (P = 0.016) and highest NLR (P < 0.001).

CONCLUSIONS

The NLR is strongly influenced by serum vitamin D level. Given the high prevalence of hypovitaminosis D and elevated NLR among chronic disease patients and the elderly, our results suggest that clinical interpretation of NLR as a predictive marker of type 2 diabetes mellitus-related inflammation should consider vitamin D level, age and pre-existing morbidity.

Lower plasma PCSK9 in normocholesterolemic subjects is associated with upregulated adipose tissue surface-expression of LDLR and CD36 and NLRP3 inflammasome

Background

LDL‐cholesterol lowering variants that upregulate receptor uptake of LDL, such as in PCSK9 and HMGCR, are associated with diabetes via unclear mechanisms. Activation of the NLRP3 inflammasome/interleukin‐1 beta (IL‐1β) pathway promotes white adipose tissue (WAT) dysfunction and type 2 diabetes (T2D) and is regulated by LDL receptors (LDLR and CD36). We hypothesized that: (a) normocholesterolemic subjects with lower plasma PCSK9, identifying those with higher WAT surface‐expression of LDLR and CD36, have higher activation of WAT NLRP3 inflammasome and T2D risk factors, and; (b) LDL upregulate adipocyte NLRP3 inflammasome and inhibit adipocyte function.

Methodology

Post hoc analysis was conducted in 27 overweight/ obese subjects with normal plasma LDL‐C and measures of disposition index (DI during Botnia clamps) and postprandial fat metabolism. WAT was assessed for surface‐expression of LDLR and CD36 (immunohistochemistry), protein expression (immunoblot), IL‐1β secretion (AlphaLISA), and function (³H‐triolein storage).

Results

Compared to subjects with higher than median plasma PCSK9, subjects with lower PCSK9 had higher WAT surface‐expression of LDLR (+81%) and CD36 (+36%), WAT IL‐1β secretion (+284%), plasma IL‐1 receptor‐antagonist (+85%), and postprandial hypertriglyceridemia, and lower WAT pro‐IL‐1β protein (−66%), WAT function (−62%), and DI (−28%), without group‐differences in body composition, energy intake or expenditure. Adjusting for WAT LDLR or CD36 eliminated group‐differences in WAT function, DI, and postprandial hypertriglyceridemia. Native LDL inhibited Simpson‐Golabi Behmel‐syndrome (SGBS) adipocyte differentiation and function and increased inflammation.

Conclusion

Normocholesterolemic subjects with lower plasma PCSK9 and higher WAT surface‐expression of LDLR and CD36 have higher WAT NLRP3 inflammasome activation and T2D risk factors. This may be due to LDL‐induced inhibition of adipocyte function.

Self-Nucleic Acid Sensing: A Novel Crucial Pathway Involved in Obesity-Mediated Metaflammation and Metabolic Syndrome

Obesity and overweight are a global health problem affecting almost one third of the world population. There are multiple complications associated with obesity including metabolic syndrome that commonly lead to development of type II diabetes and non-alcoholic fatty liver disease. The development of metabolic syndrome and severe complications associated with obesity is attributed to the chronic low-grade inflammation that occurs in metabolic tissues such as the liver and the white adipose tissue. In recent years, nucleic acids (mostly DNA), which accumulate systemically in obese individuals, were shown to aberrantly activate innate immune responses and thus to contribute to metabolic tissue inflammation. This minireview will focus on (i) the main sources and forms of nucleic acids that accumulate during obesity, (ii) the sensing pathways required for their detection, and (iii) the key cellular players involved in this process. Fully elucidating the role of nucleic acids in the induction of inflammation induced by obesity would promote the identification of new and long-awaited therapeutic approaches to limit obesity-mediated complications.

Inflamm-Aging and Brain Insulin Resistance: New Insights and Role of Life-style Strategies on Cognitive and Social Determinants in Aging and Neurodegeneration

Over the past decades, the human life span has dramatically increased, and therefore, a steady increase in diseases associated with age (such as Alzheimer's disease and Parkinson's disease) is expected. In these neurodegenerative diseases, there is a cognitive decline and memory loss, which accompany increased systemic inflammation, the inflamm-aging, and the insulin resistance. Despite numerous studies of age-related pathologies, data on the contribution of brain insulin resistance and innate immunity components to aging are insufficient. Recently, much research has been focused on the consequences of nutrients and adiposity- and nutrient-related signals in brain aging and cognitive decline. Moreover, given the role of metainflammation in neurodegeneration, lifestyle interventions such as calorie restriction may be an effective way to break the vicious cycle of metainflammation and have a role in social behavior. The various effects of calorie restriction on metainflammation, insulin resistance, and neurodegeneration have been described. Less attention has been paid to the social determinants of aging and the possible mechanism by which calorie restriction might influence social behavior. The purpose of this review is to discuss current knowledge in the interdisciplinary field of geroscience-immunosenescence, inflamm-aging, and metainflammation-which makes a significant contribution to aging. A substantial part of the review is devoted to frontiers in the brain insulin resistance in relation to neuroinflammation. In addition, we summarize new data on potential mechanisms of calorie restriction that influence as a lifestyle intervention on the social brain. This knowledge can be used to initiate successful aging and slow the onset of neurodegenerative diseases.

Role of NLRP3 Inflammasome Activation in Obesity-Mediated Metabolic Disorders

NLRP3 inflammasome is one of the multimeric protein complexes of the nucleotide-binding domain, leucine-rich repeat (NLR)-containing pyrin and HIN domain family (PYHIN). When activated, NLRP3 inflammasome triggers the release of pro-inflammatory interleukins (IL)-1β and IL-18, an essential step in innate immune response; however, defective checkpoints in inflammasome activation may lead to autoimmune, autoinflammatory, and metabolic disorders. Among the consequences of NLRP3 inflammasome activation is systemic chronic low-grade inflammation, a cardinal feature of obesity and insulin resistance. Understanding the mechanisms involved in the regulation of NLRP3 inflammasome in adipose tissue may help in the development of specific inhibitors for the treatment and prevention of obesity-mediated metabolic diseases. In this narrative review, the current understanding of NLRP3 inflammasome activation and regulation is highlighted, including its putative roles in adipose tissue dysfunction and insulin resistance. Specific inhibitors of NLRP3 inflammasome activation which can potentially be used to treat metabolic disorders are also discussed.

Adipose tissue inflammation and metabolic dysfunction in obesity

Several lines of preclinical and clinical research have confirmed that chronic low-grade inflammation of adipose tissue is mechanistically linked to metabolic disease and organ tissue complications in the overweight and obese organism. Despite this widely confirmed paradigm, numerous open questions and knowledge gaps remain to be investigated. This is mainly due to the intricately intertwined cross-talk of various pro- and anti-inflammatory signaling cascades involved in the immune response of expanding adipose depots, particularly the visceral adipose tissue. Adipose tissue inflammation is initiated and sustained over time by dysfunctional adipocytes that secrete inflammatory adipokines and by infiltration of bone marrow-derived immune cells that signal via production of cytokines and chemokines. Despite its low-grade nature, adipose tissue inflammation negatively impacts remote organ function, a phenomenon that is considered causative of the complications of obesity. The aim of this review is to broadly present an overview of adipose tissue inflammation by highlighting the most recent reports in the scientific literature and summarizing our overall understanding of the field. We also discuss key endogenous anti-inflammatory mediators and analyze their mechanistic role(s) in the pathogenesis and treatment of adipose tissue inflammation. In doing so, we hope to stimulate studies to uncover novel physiological, cellular, and molecular targets for the treatment of obesity.

White Adipose Tissue Surface Expression of LDLR and CD36 is Associated with Risk Factors for Type 2 Diabetes in Adults with Obesity

OBJECTIVE

Human conditions with upregulated receptor uptake of low-density lipoproteins (LDL) are associated with diabetes risk, the reasons for which remain unexplored. LDL induce metabolic dysfunction in murine adipocytes. Thus, it was hypothesized that white adipose tissue (WAT) surface expression of LDL receptor (LDLR) and/or CD36 is associated with WAT and systemic metabolic dysfunction. Whether WAT LDLR and CD36 expression is predicted by plasma lipoprotein-related parameters was also explored.

METHODS

This was a cross-sectional analysis of 31 nondiabetic adults (BMI > 25 kg/m² ) assessed for WAT surface expression of LDLR and CD36 (immunohistochemistry), WAT function, WAT and systemic inflammation, postprandial fat metabolism, and insulin resistance (IR; hyperinsulinemic-euglycemic clamp).

RESULTS

Fasting WAT surface expression of LDLR and CD36 was negatively associated with WAT function (³ H-triglyceride storage, r = -0.45 and -0.66, respectively) and positively associated with plasma IL-1 receptor antagonist (r = 0.64 and 0.43, respectively). Their expression was suppressed 4 hours postprandially, and reduced LDLR was further associated with IR (M/I_clamp , r = 0.61 women, r = 0.80 men). Plasma apolipoprotein B (apoB)-to-PCSK9 ratio predicted WAT surface expression of LDLR and CD36, WAT dysfunction, WAT NLRP3 inflammasome priming and disrupted cholesterol-sensing genes, and systemic IR independent of sex and body composition.

CONCLUSIONS

Higher fasting and lower postprandial WAT surface expression of LDLR and CD36 is associated with WAT dysfunction, systemic inflammation, and IR in adults with overweight/obesity, anomalies that are predicted by higher plasma apoB-to-PCSK9 ratio.

Fibroblast growth factor 2 exacerbates inflammation in adipocytes through NLRP3 inflammasome activation

Chronic inflammation in adipose tissue is the hallmark of obesity and a major risk factor for the development of obesity-induced insulin resistance. NLRP3 inflammasome regulates the maturation and secretion of pro-inflammatory cytokines, such as IL-1β and IL-18, and was recently discovered to be involved in obesity-related metabolic diseases. Fibroblast growth factors (FGFs) such as FGF1, FGF10, and FGF21 are adipokines that regulate adipocyte development and metabolism, but reports on the effect of other FGFs on adipocytes are lacking. In the present study, the novel role of FGF2 in NLRP3 inflammasome activation was elucidated. Our results showed that FGF2 levels were increased during adipocyte differentiation and in the adipose tissue of high-fat diet (HFD)-induced obese mice. Recombinant FGF2 treatment upregulated inflammasome markers such as NLRP3, which was further exaggerated by TNF-ɑ treatment. Interestingly, β-Klotho, a co-receptor of FGF21, was significantly decreased by FGF2 treatment. Results from mice confirmed the positive correlation between FGF2 and NLRP3 expression in epididymal and subcutaneous adipose tissue, while exercise training effectively reversed HFD-induced NLRP3 expression as well as FGF2 levels in both adipose depots. Our results suggest that FGF2 is an adipokine that may exacerbate the inflammatory response in adipocytes through NLRP3 inflammasome activation.

Retinol binding protein 4 primes the NLRP3 inflammasome by signaling through Toll-like receptors 2 and 4

Adipose tissue (AT) inflammation contributes to systemic insulin resistance. In obesity and type 2 diabetes (T2D), retinol binding protein 4 (RBP4), the major retinol carrier in serum, is elevated in AT and has proinflammatory effects which are mediated partially through Toll-like receptor 4 (TLR4). We now show that RBP4 primes the NLRP3 inflammasome for interleukin-1β (IL1β) release, in a glucose-dependent manner, through the TLR4/MD2 receptor complex and TLR2. This impairs insulin signaling in adipocytes. IL1β is elevated in perigonadal white AT (PGWAT) of chow-fed RBP4-overexpressing mice and in serum and PGWAT of high-fat diet-fed RBP4-overexpressing mice vs. wild-type mice. Holo- or apo-RBP4 injection in wild-type mice causes insulin resistance and elevates PGWAT inflammatory markers, including IL1β. TLR4 inhibition in RBP4-overexpressing mice reduces PGWAT inflammation, including IL1β levels and improves insulin sensitivity. Thus, the proinflammatory effects of RBP4 require NLRP3-inflammasome priming. These studies may provide approaches to reduce AT inflammation and insulin resistance in obesity and diabetes.

Low concentration IL-1β promotes islet amyloid formation by increasing hIAPP release from humanised mouse islets in vitro

AIMS/HYPOTHESIS

Aggregation of the beta cell secretory product human islet amyloid polypeptide (hIAPP) results in islet amyloid deposition, a pathological feature of type 2 diabetes. Amyloid formation is associated with increased levels of islet IL-1β as well as beta cell dysfunction and death, but the mechanisms that promote amyloid deposition in situ remain unclear. We hypothesised that physiologically relevant concentrations of IL-1β stimulate beta cell islet amyloid polypeptide (IAPP) release and promote amyloid formation.

METHODS

We used a humanised mouse model of endogenous beta cell hIAPP expression to examine whether low (pg/ml) concentrations of IL-1β promote islet amyloid formation in vitro. Amyloid-forming islets were cultured for 48 h in the presence or absence of IL-1β with or without an IL-1β neutralising antibody. Islet morphology was assessed by immunohistochemistry and islet mRNA expression, hormone content and release were also quantified. Cell-free thioflavin T assays were used to monitor hIAPP aggregation kinetics in the presence and absence of IL-1β.

RESULTS

Treatment with a low concentration of IL-1β (4 pg/ml) for 48 h increased islet amyloid prevalence (93.52 ± 3.89% vs 43.83 ± 9.67% amyloid-containing islets) and amyloid severity (4.45 ± 0.82% vs 2.16 ± 0.50% amyloid area/islet area) in hIAPP-expressing mouse islets in vitro. This effect of IL-1β was reduced when hIAPP-expressing islets were co-treated with an IL-1β neutralising antibody. Cell-free hIAPP aggregation assays showed no effect of IL-1β on hIAPP aggregation in vitro. Low concentration IL-1β did not increase markers of the unfolded protein response (Atf4, Ddit3) or alter proIAPP processing enzyme gene expression (Pcsk1, Pcsk2, Cpe) in hIAPP-expressing islets. However, release of IAPP and insulin were increased over 48 h in IL-1β-treated vs control islets (IAPP 0.409 ± 0.082 vs 0.165 ± 0.051 pmol/5 islets; insulin 87.5 ± 8.81 vs 48.3 ± 17.3 pmol/5 islets), and this effect was blocked by co-treatment with IL-1β neutralising antibody.

CONCLUSIONS/INTERPRETATION

Under amyloidogenic conditions, physiologically relevant levels of IL-1β promote islet amyloid formation by increasing beta cell release of IAPP. Neutralisation of this effect of IL-1β may decrease the deleterious effects of islet amyloid formation on beta cell function and survival.

Role of Caspase-1 in the Pathogenesis of Inflammatory-Associated Chronic Noncommunicable Diseases

Caspase-1 is the first and extensively studied inflammatory caspase that is activated through inflammasome assembly. Inflammasome is a cytosolic formation of multiprotein complex that aimed to start inflammatory response against infections or cellular damages. The process leads to an auto-activation of caspase-1 and consequent maturation of caspase-1 target molecules such as interleukin (IL)-1β and IL-18. Recently, the role of caspase-1 and inflammasome in inflammatory-induced noncommunicable diseases (NCDs) like obesity, diabetes mellitus (DM), cardiovascular diseases (CVDs), cancers and chronic respiratory diseases have widely studied. However, their reports are distinct and even they have reported contrasting role of caspase-1 in the development and progression of NCDs. A few studies have reported that caspase-1/inflammasome assembley has a protective role in the initiation and progression of these diseases through the activation of the noncanonical caspase-1 target substrates like gasdermin-D and regulation of immune cells. Conversely, others have revealed that caspase-1 has a direct/indirect effect in the development and progression of several NCDs. Therefore, in this review, we systematically summarized the role of caspase-1 in the development and progression of NCDs, especially in obesity, DM, CVDs and cancers.

Novel Function of α-Cubebenoate Derived from Schisandra chinensis as Lipogenesis Inhibitor, Lipolysis Stimulator and Inflammasome Suppressor

The efficacy of α-cubebenoate isolated from Schisandra chinensis has been previously studied in three disease areas, namely inflammation, sepsis, and allergy, and its role in other diseases is still being explored. To identify the novel function of α-cubebenoate on lipid metabolism and related inflammatory response, alterations in fat accumulation, lipogenesis, lipolysis, and inflammasome activation were measured in 3T3-L1 preadipocytes and primary adipocytes treated with α-cubebenoate. Lipid accumulation significantly decreased in MDI (3-isobutyl-1-methylxanthine, dexamethasone, and insulin)-stimulated 3T3-L1 adipocytes treated with α-cubebenoate without any significant cytotoxicity. The mRNA levels of peroxisome proliferator-activated receptor (PPAR)γ and CCAAT-enhancer binding protein (C/EBP) α for adipogenesis, as well as adipocyte fatty acid binding protein 2 (aP2) and fatty acid synthetase (FAS) for lipogenesis, were reduced after α-cubebenoate treatment, while cell cycle arrest at G2/M stage was restored in the same group. α-cubebenoate treatment induced glycerol release in primary adipocytes and enhanced expression of lipolytic proteins (HSL, perilipin, and ATGL) expression in MDI-stimulated 3T3-L1 adipocytes. Inflammasome activation and downstream cytokines expression were suppressed with α-cubebenoate treatment, but the expression of insulin receptor signaling factors was remarkably increased by α-cubebenoate treatment in MDI-stimulated 3T3-L1 adipocytes. These results indicate that α-cubebenoate may play a novel role as lipogenesis inhibitor, lipolysis stimulator, and inflammasome suppressor in MDI-stimulated 3T3-L1 adipocytes. Our results provide the possibility that α-cubebenoate can be considered as one of the candidates for obesity management.

The NLRP3 inflammasome regulates adipose tissue metabolism

Adipose tissue regulates metabolic homeostasis by participating in endocrine and immune responses in addition to storing and releasing lipids from adipocytes. Obesity skews adipose tissue adipokine responses and degrades the coordination of adipocyte lipogenesis and lipolysis. These defects in adipose tissue metabolism can promote ectopic lipid deposition and inflammation in insulin-sensitive tissues such as skeletal muscle and liver. Sustained caloric excess can expand white adipose tissue to a point of maladaptation exacerbating both local and systemic inflammation. Multiple sources, instigators and propagators of adipose tissue inflammation occur during obesity. Cross-talk between professional immune cells (i.e. macrophages) and metabolic cells (i.e. adipocytes) promote adipose tissue inflammation during metabolic stress (i.e. metaflammation). Metabolic stress and endogenous danger signals can engage pathogen recognition receptors (PRRs) of the innate immune system thereby activating pro-inflammatory and stress pathways in adipose tissue. The Nod-like receptor protein 3 (NLRP3) inflammasome can act as a metabolic danger sensor to a wide range of pathogen- and damage-associated molecular patterns (PAMPs and DAMPs). Activation of the NLRP3 inflammasome facilitates caspase-1 dependent production of the pro-inflammatory cytokines IL-1β and IL-18. Activation of the NLRP3 inflammasome can promote inflammation and pyroptotic cell death, but caspase-1 is also involved in adipogenesis. This review discusses the role of the NLRP3 inflammasome in adipose tissue immunometabolism responses relevant to metabolic disease. Understanding the potential sources of NLRP3 activation and consequences of NLRP3 effectors may reveal therapeutic opportunities to break or fine-tune the connection between metabolism and inflammation in adipose tissue during obesity.

Recent insights on modulation of inflammasomes by adipokines: a critical event for the pathogenesis of obesity and metabolism-associated diseases

Aberrant production of adipokines, a group of adipocytes-derived hormones, is considered one of the most important pathological characteristics of obesity. In individuals with obesity, beneficial adipokines, such as adiponectin are downregulated, whereas leptin and other pro-inflammatory adipokines are highly upregulated. Hence, the imbalance in levels of these adipokines is thought to promote the development of obesity-linked complications. However, the mechanisms by which adipokines contribute to the pathogenesis of various diseases have not been clearly understood. Inflammasomes represent key signaling platform that triggers the inflammatory and immune responses through the processing of the interleukin family of pro-inflammatory cytokines in a caspase-1-dependent manner. Beyond their traditional function as a component of the innate immune system, inflammasomes have been recently integrated into the pathological process of multiple metabolism- and obesity-related disorders such as cardiovascular diseases, diabetes, fatty liver disease, and cancer. Interestingly, emerging evidence also highlights the role of adipokines in the modulation of inflammasomes activation, making it a promising mechanism underlying distinct biological actions of adipokines in diseases driven by inflammation and metabolic disorders. In this review, we summarize the effects of adipokines, in particular adiponectin, leptin, visfatin and apelin, on inflammasomes activation and their implications in the pathophysiology of obesity-linked complications.

Repurposing anti-inflammasome NRTIs for improving insulin sensitivity and reducing type 2 diabetes development

Innate immune signaling through the NLRP3 inflammasome is activated by multiple diabetes-related stressors, but whether targeting the inflammasome is beneficial for diabetes is still unclear. Nucleoside reverse-transcriptase inhibitors (NRTI), drugs approved to treat HIV-1 and hepatitis B infections, also block inflammasome activation. Here, we show, by analyzing five health insurance databases, that the adjusted risk of incident diabetes is 33% lower in patients with NRTI exposure among 128,861 patients with HIV-1 or hepatitis B (adjusted hazard ratio for NRTI exposure, 0.673; 95% confidence interval, 0.638 to 0.710; P < 0.0001; 95% prediction interval, 0.618 to 0.734). Meanwhile, an NRTI, lamivudine, improves insulin sensitivity and reduces inflammasome activation in diabetic and insulin resistance-induced human cells, as well as in mice fed with high-fat chow; mechanistically, inflammasome-activating short interspersed nuclear element (SINE) transcripts are elevated, whereas SINE-catabolizing DICER1 is reduced, in diabetic cells and mice. These data suggest the possibility of repurposing an approved class of drugs for prevention of diabetes.

Adipocyte Ceramides-The Nexus of Inflammation and Metabolic Disease

Adipose depots are heterogeneous tissues that store and sense fuel levels. Through the secretion of lipids, cytokines, and protein hormones (adipokines), they communicate with other organ systems, informing them of the organism's nutritional status. The adipose tissues include diverse types of adipocytes (white, beige, and brown) distinguished by the number/size of lipid droplets, mitochondrial density, and thermogenic capacity. Moreover, they include a spectrum of immune cells that modulate metabolic activity and tissue remodeling. The unique characteristics and interplay of these cells control the production of ceramides, a class of nutrient signals derived from fat and protein metabolism that modulate adipocyte function to regulate glucose and lipid metabolism. The excessive accumulation of ceramides contributes to the adipose tissue inflammation and dysfunction that underlies cardiometabolic disease. Herein we review findings on this important class of lipid species and discuss their role at the convergence point that links overnutrition/inflammation to key features of the metabolic syndrome.

Inflammasome Deletion Promotes Anti-tumor NK Cell Function in an IL-1/IL-18 Independent Way in Murine Invasive Breast Cancer

Inflammasomes are molecular complexes that trigger an inflammatory response upon detection of pathogens or danger signals. Recent studies suggest that they are also involved in cancer progression. However, their roles during tumorigenesis remain poorly understood and controversial. Here, we investigated whether inflammasome activation supports mammary tumor growth. Using mouse models of invasive breast cancer, our results demonstrate that the absence of a functional inflammasome impairs tumor growth. Importantly, tumors implanted into inflammasome-deficient mice recruited significantly less neutrophils and more natural killer (NK) cells, and these latter cells displayed a more active phenotype. Interestingly, NK cell depletion abolished the anti-tumoral effect observed in inflammasome-deficient mice, although inflammasome-regulated cytokine neutralization had no effect. Thus, our work identifies a novel role for the inflammasome in supporting mammary tumor growth by attenuating NK cell recruitment and activity. These results suggest that inflammasome inhibition could be a putative target for treating invasive breast cancers.

NLRP3 Inflammasome in Inflammation and Metabolism: Identifying Novel Roles in Postburn Adipose Dysfunction

Inflammasomes are multiprotein complexes that respond to pathogen or host associated damage markers, leading to caspase-1 maturation and processing of pro-inflammatory cytokines. Initially, inflammasomes were implicated primarily in inflammatory and infectious conditions. However, increasing evidence demonstrates broader roles beyond inflammation, including regulation of adipose tissue metabolism after burns. Here, we conducted a search for articles on PubMed, Web of Science, Embase, Scopus, and UpToDate with applied search strategies including a combination of "burns," "trauma," "(NLRP3) inflammasome," "metabolic conditions," "white adipose tissue," "macrophages," "browning," and "lipolysis" and included papers from 2000 to 2020. We discuss unexpected roles for NLRP3, the most characterized inflammasome to date, as a key metabolic driver in a variety of conditions. In particular, we highlight the function of NLRP3 inflammasome in burn trauma, which is characterized by both hyperinflammation and hypermetabolism. We identify a critical part for NLRP3 activation in macrophage dynamics and delineate a novel role in postburn white adipose tissue remodeling, a pathological response associated with hypermetabolism and poor clinical outcomes. Mechanistically, how inflammation and inflammasome activation is linked to postburn hypermetabolism is a novel concept to contemplate, and herein we provide evidence of an immunometabolic crosstalk between adipocytes and infiltrating macrophages.

NLRP3 sparks the Greek fire in the war against lipid-related diseases

In recent years, the obesity rate worldwide has reached epidemic proportions and contributed to the growing prevalence of lipid-related diseases. A strong link between inflammation and metabolism is becoming increasingly evident. Compelling evidence has indicated the activation of the nucleotide-binding and oligomerization domain-like receptor, leucine-rich repeat and pyrin domain-containing 3 (NLRP3) inflammasome, a cytoplasmic complex containing multiple proteins, in a variety of lipid-related diseases including obesity, atherosclerosis, liver diseases, and type 2 diabetes. Recent studies have further clarified the regulatory mechanisms and the optional therapeutic agents that target NLRP3 inflammasomes. In this study, we review the recent progress in the research on NLRP3 inflammasomes and discuss their implications for a better understanding of inflammation in lipid-related disease and the prospects of targeting the NLRP3 inflammasome for therapeutic intervention.

The NLRP3 inflammasome: Mechanism of action, role in disease and therapies

NLRP3 is the best characterized cytosolic nod-like pattern recognition receptor which can detect microbial motifs, endogenous danger and stress signals. Activation of NLRP3 leads to the formation of a cytosolic multiprotein signaling complex called the inflammasome, which serves as a platform for caspase-1 activation leading to the processing of proinflammatory cytokines IL-1β, IL-18 and GSDMD mediated cell death. This form of pyroptotic cell death represents a major pathway of inflammation. Growing evidence has indicated hyperactivation of NLRP3 inflammasome is involved in a wide range of inflammatory diseases. In this review we present the recent advances in understanding the mechanism of NLRP3 activation, its role in driving inflammatory diseases, and the development of NLRP3 targeted therapies.

Suppression of GATA-3 increases adipogenesis, reduces inflammation and improves insulin sensitivity in 3T3L-1 preadipocytes

Impaired adipogenesis plays an important role in the development of obesity-associated insulin resistance and type 2 diabetes. Adipose tissue inflammation is a crucial mediator of this process. GATA-3 plays important roles in adipogenesis and inflammation. The aim of this study is to investigate the impact of GATA-3 suppression on improving adipogenesis, lowering inflammation and reversing insulin resistance. GATA-3 levels were measured in subcutaneous (SC) and omental (OM) adipose tissues obtained from insulin sensitive (IS) and insulin resistant (IR) obese individuals during weight reduction surgeries. The effect of GATA-3 suppression on adipogenesis, expression of inflammatory cytokines and insulin resistance biomarkers was performed in 3T3L-1 mouse preadipocytes via transfection with GATA-3-specific DNAzyme. GATA-3 expression was higher in OM compared to SC adipose tissues and in stromal vascular fraction-derived differentiating preadipocytes from IR obese individuals compared to their IS counterparts. Suppression of GATA-3 expression in 3T3L-1 mouse preadipocytes with GATA-3 specific inhibitor reversed 4-hydroxynonenal-induced impaired adipogenesis and triggered changes in the expression of insulin signaling-related genes. GATA-3 inhibition also modulated the expression of IL-6 and IL-10 and lowered the expression of insulin resistance biomarkers (PAI-1 and resistin) and insulin resistance phosphoproteins (p-BAD, p-PTEN and p-GSK3β). Inhibiting GATA-3 improves adipocytes differentiation, modulates the secretion of inflammatory cytokines and improves insulin sensitivity in insulin resistant cells. Suppression of GATA-3 could be a promising tool to improve adipogenesis, restore insulin sensitivity and lower obesity-associated inflammation in insulin resistant individuals.

The NLRP3 Inflammasome: Metabolic Regulation and Contribution to Inflammaging

In response to inflammatory stimuli, immune cells reconfigure their metabolism and bioenergetics to generate energy and substrates for cell survival and to launch immune effector functions. As a critical component of the innate immune system, the nucleotide-binding and oligomerization domain, leucine-rich repeat, and pyrin domain-containing 3 (NLRP3) inflammasome can be activated by various endogenous and exogenous danger signals. Activation of this cytosolic multiprotein complex triggers the release of the pro-inflammatory cytokines interleukin (IL)-1β and IL-18 and initiates pyroptosis, an inflammatory form of programmed cell death. The NLRP3 inflammasome fuels both chronic and acute inflammatory conditions and is critical in the emergence of inflammaging. Recent advances have highlighted that various metabolic pathways converge as potent regulators of the NLRP3 inflammasome. This review focuses on our current understanding of the metabolic regulation of the NLRP3 inflammasome activation, and the contribution of the NLRP3 inflammasome to inflammaging.

Recent advances in the NEK7-licensed NLRP3 inflammasome activation: Mechanisms, role in diseases and related inhibitors

The nucleotide-binding oligomerization domain (NOD)-like receptor containing pyrin domain 3 (NLRP3) inflammasome is a high-molecular-weight complex mediated by the activation of pattern-recognition receptors (PRRs) seed in innate immunity. Once NLRP3 is activated, the following recruitment of the adapter apoptosis-associated speck-like protein containing a caspase recruitment domain (CARD) (ASC) and procaspase-1 would be initiated. Cleavage of procaspase-1 into active caspase-1 then leads to the maturation of the precursor forms of interleukin (IL)-1β and IL-18 into biologically active IL-1β and IL-18. The activation of NLRP3 inflammasome is thought to be tightly associated with a regulator never in mitosis A (NIMA)-related kinase 7 (NEK7), apart from other signaling events such as K⁺ efflux and reactive oxygen species (ROS). Plus, the NLRP3 inflammasome has been linked to various metabolic disorders, chronic inflammation and other diseases. In this review, we firstly describe the cellular/molecular mechanisms of the NEK7-licensed NLRP3 inflammasome activation. Then we detail the potential inhibitors that can selectively and effectively modulate either the NEK7-NLRP3 complex itself or the related molecular/cellular events. Finally, we describe some inhibitors as promising therapeutic strategies for diverse diseases driven by NLRP3 inflammasome.

Lipids, inflammasomes, metabolism, and disease

Inflammasomes are multi-protein complexes that regulate the cleavage of cysteine protease caspase-1, secretion of inflammatory cytokines, and induction of inflammatory cell death, pyroptosis. Several members of the nod-like receptor family assemble inflammasome in response to specific ligands. An exception to this is the NLRP3 inflammasome which is activated by structurally diverse entities. Recent studies have suggested that NLRP3 might be a sensor of cellular homeostasis, and any perturbation in distinct metabolic pathways results in the activation of this inflammasome. Lipid metabolism is exceedingly important in maintaining cellular homeostasis, and it is recognized that cells and tissues undergo extensive lipid remodeling during activation and disease. Some lipids are involved in instigating chronic inflammatory diseases, and new studies have highlighted critical upstream roles for lipids, particularly cholesterol, in regulating inflammasome activation implying key functions for inflammasomes in diseases with defective lipid metabolism. The focus of this review is to highlight how lipids regulate inflammasome activation and how this leads to the progression of inflammatory diseases. The key roles of cholesterol metabolism in the activation of inflammasomes have been comprehensively discussed. Besides, the roles of oxysterols, fatty acids, phospholipids, and lipid second messengers are also summarized in the context of inflammasomes. The overriding theme is that lipid metabolism has numerous but complex functions in inflammasome activation. A detailed understanding of this area will help us develop therapeutic interventions for diseases where dysregulated lipid metabolism is the underlying cause.

Depression and Obesity: Analysis of Common Biomarkers

Depression and obesity are very common pathologies. Both cause significant problems of both morbidity and mortality and have decisive impacts not only on the health and well-being of patients, but also on socioeconomic and health expenditure aspects. Many epidemiological studies, clinical studies and meta-analyses support the association between mood disorders and obesity in relationships to different conditions such as the severity of depression, the severity of obesity, gender, socioeconomic status, genetic susceptibility, environmental influences and adverse experiences of childhood. Currently, both depression and obesity are considered pathologies with a high-inflammatory impact; it is believed that several overlapping factors, such as the activation of the cortico-adrenal axis, the exaggerated and prolonged response of the innate immune system and proinflammatory cytokines to stress factors and pathogens-as well as alterations of the intestinal microbiota which promote intestinal permeability-can favor the expression of an increasingly proinflammatory phenotype that can be considered a key and common phenomenon between these two widespread pathologies. The purpose of this literature review is to evaluate the common and interacting mechanisms between depression and obesity.

Focus on the Role of NLRP3 Inflammasome in Diseases

Inflammation is a protective reaction activated in response to detrimental stimuli, such as dead cells, irritants or pathogens, by the evolutionarily conserved immune system and is regulated by the host. The inflammasomes are recognized as innate immune system sensors and receptors that manage the activation of caspase-1 and stimulate inflammation response. They have been associated with several inflammatory disorders. The NLRP3 inflammasome is the most well characterized. It is so called because NLRP3 belongs to the family of nucleotide-binding and oligomerization domain-like receptors (NLRs). Recent evidence has greatly improved our understanding of the mechanisms by which the NLRP3 inflammasome is activated. Additionally, increasing data in animal models, supported by human studies, strongly implicate the involvement of the inflammasome in the initiation or progression of disorders with a high impact on public health, such as metabolic pathologies (obesity, type 2 diabetes, atherosclerosis), cardiovascular diseases (ischemic and non-ischemic heart disease), inflammatory issues (liver diseases, inflammatory bowel diseases, gut microbiome, rheumatoid arthritis) and neurologic disorders (Parkinson’s disease, Alzheimer’s disease, multiple sclerosis, amyotrophic lateral sclerosis and other neurological disorders), compared to other molecular platforms. This review will provide a focus on the available knowledge about the NLRP3 inflammasome role in these pathologies and describe the balance between the activation of the harmful and beneficial inflammasome so that new therapies can be created for patients with these diseases.

NLRP3 Inflammasome Activation in Adipose Tissues and Its Implications on Metabolic Diseases

Adipose tissue is an active endocrine and immune organ that controls systemic immunometabolism via multiple pathways. Diverse immune cell populations reside in adipose tissue, and their composition and immune responses vary with nutritional and environmental conditions. Adipose tissue dysfunction, characterized by sterile low-grade chronic inflammation and excessive immune cell infiltration, is a hallmark of obesity, as well as an important link to cardiometabolic diseases. Amongst the pro-inflammatory factors secreted by the dysfunctional adipose tissue, interleukin (IL)-1β, induced by the NLR family pyrin domain-containing 3 (NLRP3) inflammasome, not only impairs peripheral insulin sensitivity, but it also interferes with the endocrine and immune functions of adipose tissue in a paracrine manner. Human studies indicated that NLRP3 activity in adipose tissues positively correlates with obesity and its metabolic complications, and treatment with the IL-1β antibody improves glycaemia control in type 2 diabetic patients. In mouse models, genetic or pharmacological inhibition of NLRP3 activation pathways or IL-1β prevents adipose tissue dysfunction, including inflammation, fibrosis, defective lipid handling and adipogenesis, which in turn alleviates obesity and its related metabolic disorders. In this review, we summarize both the negative and positive regulators of NLRP3 inflammasome activation, and its pathophysiological consequences on immunometabolism. We also discuss the potential therapeutic approaches to targeting adipose tissue inflammasome for the treatment of obesity and its related metabolic disorders.

Intervention of resistant starch 3 on type 2 diabetes mellitus and its mechanism based on urine metabonomics by liquid chromatography-tandem mass spectrometry

As a severe metabolic disease, type 2 diabetes mellitus (T2DM) has aroused increasing public attentions. Resistant starch 3 (RS3), as a starch resistant to enzymatic hydrolysis owing to its special structure, has a good effect on improving insulin resistance and reducing blood sugar in T2DM patients. However, the possible mechanisms were barely interpreted yet. In our research, we aimed to evaluate the effects and the possible mechanisms of RS3 on the treatment of T2DM. ICR mice treated with high-fat diet (HFD) for eight weeks, and then injected with streptozotocin (STZ) (100 mg/kg) to establish the T2DM. We choose the mice with the fast blood glucose (FBG) more than 11 mmol/L as T2DM. After treated for 11 weeks the relevant data was analyzed. According to the results, the FBG was dramatically reduced (p < 0.05), which also downregulated triglyceride (p < 0.01) and total cholesterol (p < 0.01). Additionally, the insulin resistance indexes were significantly reduced (p < 0.01), the homeostasis model assessment-β and insulin-sensitive index were significantly improved (p < 0.01) in RS3 group. Meanwhile, the metabolic profiles of urine were analyzed and 29 potential biomarkers were screened out, including amino acids and lipids. In conclusion, we speculated that the tricarboxylic acid cycle, amino acid metabolism and lipid metabolism played roles in the therapeutic mechanisms of RS3 on T2DM.

SIRT1 Regulation in Ageing and Obesity

Ageing and obesity have common hallmarks: altered glucose and lipid metabolism, chronic inflammation and oxidative stress are some examples. The downstream effects of SIRT1 activity have been thoroughly explored, and their research is still in expanse. SIRT1 activation has been shown to regulate pathways with beneficiary effects on 1) ageing and obesity-associated metabolic disorders such as metabolic syndrome, insulin resistance and type-II diabetes with, 2) chronic inflammatory processes such as arthritis, atherosclerosis and emphysema, 3) DNA damage and oxidative stress with impact on neurodegenerative diseases, cardiovascular health and some cancers. This knowledge intensified the interest in uncovering the mechanisms regulating the expression and activity of SIRT1. This review focuses on the upstream regulatory mechanisms controlling SIRT1, and how this knowledge could potentially contribute to the development of therapeutic interventions.

Effects of oral butyrate and inulin supplementation on inflammation-induced pyroptosis pathway in type 2 diabetes: A randomized, double-blind, placebo-controlled trial

PURPOSE

Pyroptosis, a form of inflammatory programmed cell death, is activated in diabetic patients. This study was conducted to investigate the effects of daily consumption of sodium butyrate (NaBut) and high-performance (HP) inulin supplementation, individually or in combination, on the expression of pyroptosis-related genes, microRNA (miR) 146a-5p, miR-9-5p and biomarkers of oxidative stress in patients with type 2 diabetes (T2DM).

METHODS

In this study, we conducted a randomized, double-blinded, placebo-controlled clinical involving sixty patients with type 2 diabetes. Participants received 600 mg/d of NaBut (group A), 10 g/d of HP inulin (group B), 600 mg/d of NaBut + 10 g/d of HP inulin (group C) or placebo (group D) for 45 consecutive days. We assessed the pyroptosis-related genes mRNA expression in peripheral blood mononuclear cells (PBMCs), as well as the plasmatic levels of miR-146a and miR-9 before and after the intervention. Moreover, blood samples of the patients at baseline and following the intervention were tested for total antioxidant capacity (TAC), superoxide dismutase (SOD) and catalase levels using enzyme-linked immunosorbent assay (ELISA). This study was registered on the Iranian Registry of Clinical Trials website (identifier: IRCT201605262017N29; https://www.irct.ir/).

RESULTS

Following butyrate supplementation, the relative expression levels of TLR2/4, NF-κB1, Caspase-1, NLRP3, IL-1β & IL-18 were significantly downregulated (p < 0.05). Furthermore, butyrate and concomitant use of butyrate and inulin caused a significant increase in the fold change of miR-146a and miR-9 compared with the placebo group (p < 0.05). Interestingly, the changes in total antioxidant capacity (p = 0.047) and superoxide dismutase (p = 0.006) were significantly increased after butyrate and concomitant use of butyrate and inulin supplement, respectively.

CONCLUSION

In summary, the change in expression level of miR-146a-5p and miR-9-5p due to butyrate supplementation may have a pivotal role in alleviating of diabetes via inhibiting pyroptosis by targeting TLR2 and NF-κB1. These microRNAs might be considered as potential therapeutic targets in the treatment of type 2 diabetes but further researches is required to prove the link.

Maternal high-fat diet exaggerates diet-induced insulin resistance in adult offspring by enhancing inflammasome activation through noncanonical pathway of caspase-11

Objective

Maternal high-fat diet (HFD) has been shown to promote the development of insulin resistance (IR) in adult offspring; however, the underlying mechanisms remain unclear.

Methods

Eight-week-old female wild-type mice (C57BL/6) were fed either an HFD or a normal diet (ND), one week prior to mating, and the diet was continued throughout gestation and lactation. Eight-week-old male offspring of both groups were fed an HFD for 8 weeks.

Results

Offspring of HFD-fed dams (O-HFD) exhibited significantly impaired insulin sensitivity compared with the offspring of ND-fed dams (O-ND). The adipocyte size of the eWAT increased significantly in O-HFD and was accompanied by abundant crown-like structures (CLSs), as well as a higher concentration of interleukin 1β (IL-1β) in the eWAT. Treatment with an inflammasome inhibitor, MCC950, completely abrogated the enhanced IR in O-HFD. However, ex vivo caspase-1 activity in eWAT revealed no difference between the two groups. In contrast, noncanonical inflammasome activation of caspase-11 was significantly augmented in O-HFD compared with O-ND, suggesting that membrane pore formation, but not cleavage of pro-IL-1β by caspase-1, is augmented in O-HFD. To examine the membrane pore formation, we performed metabolic activation of bone marrow-derived macrophages (BMDMs). The percentage of pore formation assessed by ethidium bromide staining was significantly higher in BMDMs of O-HFD, accompanied by an enhanced active caspase-11 expression. Consistently, the concentration of IL-1β in culture supernatants was significantly higher in the BMDMs from O-HFD than those from O-ND.

Conclusions

These findings demonstrate that maternal HFD exaggerates diet-induced IR in adult offspring by enhancing noncanonical caspase-11-mediated inflammasome activation.

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Maternal HFD increases the vulnerability to HFD-induced IR in adult offspring.

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Maternal HFD augments inflammasome activation in eWAT in adult offspring.

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Treatment with an inflammasome inhibitor abrogates IR in offspring of HFD-fed dam.

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Maternal HFD augments the noncanonical inflammasome activation pathway of caspase-11.

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Maternal HFD augments IL-1β release from BMDMs by enhancing membrane pore formation.

Caspase-1 as a regulatory molecule of lipid metabolism

Caspase-1 is an evolutionarily conserved inflammatory mediated enzyme that cleaves and activates inflammatory cytokines. It can be activated through the assembly of inflammasome and its major effect is to activate the pro-inflammatory cytokines; interleukin 1β (IL-1β) and interluekine-18 (IL-18). In addition to IL-1β and IL-8, several lines of evidence showed that caspase-1 targets the substrates that are involved in different metabolic pathways, including lipid metabolism. Caspase-1 regulates lipid metabolism through cytokine dependent or cytokine independent regulation of genes that involved in lipid metabolism and its regulation. To date, there are several reports on the role of caspase-1 in lipid metabolism. Therefore, this review is aimed to summarize the role of caspase-1 in lipid metabolism and its regulation.

Globular Adiponectin Inhibits Breast Cancer Cell Growth through Modulation of Inflammasome Activation: Critical Role of Sestrin2 and AMPK Signaling

Adiponectin, an adipokine predominantly derived from adipose tissue, exhibits potent antitumor properties in breast cancer cells. However, its mechanisms of action remain elusive. Inflammasomes—intracellular multimeric protein complexes—modulate cancer cell growth in a complicated manner, as well as playing a role in the innate immune system. Herein, we examined the potential role of inflammasomes in the antitumor activity of adiponectin and found that globular adiponectin (gAcrp) significantly suppressed inflammasomes activation in breast cancer cells both in vitro and in vivo conditions, as determined by decreased expression of inflammasomes components, including NOD-like receptor pyrin domain-containing protein 3 (NLRP3) and the apoptosis-associated speck-like protein containing a CARD (ASC), and inhibition of interleukin-1β and caspase-1 activation. Treatment with pharmacological inhibitors of inflammasomes caused decrease in cell viability, apoptosis induction, and G0/G1 cell cycle arrest, suggesting that inflammasomes activation is implicated in the growth of breast cancer cells. In addition, treatment with gAcrp generated essentially similar results to those of inflammasomes inhibitors, further indicating that suppression of breast cancer cell growth by gAcrp is mediated via modulation of inflammasomes. Mechanistically, gAcrp suppressed inflammasomes activation through sestrin2 (SESN2) induction, liver kinase B1 (LKB-1)-dependent AMP-activated protein kinase (AMPK) phosphorylation, and alleviation of endoplasmic reticulum (ER) stress. Taken together, these results demonstrate that gAcrp inhibits growth of breast cancer cells by suppressing inflammasomes activation, at least in part, via SESN2 induction and AMPK activation-dependent mechanisms.

Inhibition of IL-1beta improves Glycaemia in a Mouse Model for Gestational Diabetes

Gestational diabetes mellitus (GDM) is one of the most common diseases associated with pregnancy, however, the underlying mechanisms remain unclear. Based on the well documented role of inflammation in type 2 diabetes, the aim was to investigate the role of inflammation in GDM. We established a mouse model for GDM on the basis of its two major risk factors, obesity and aging. In these GDM mice, we observed increased Interleukin-1β (IL-1β) expression in the uterus and the placenta along with elevated circulating IL-1β concentrations compared to normoglycemic pregnant mice. Treatment with an anti-IL-1β antibody improved glucose-tolerance of GDM mice without apparent deleterious effects for the fetus. Finally, IL-1β antagonism showed a tendency for reduced plasma corticosterone concentrations, possibly explaining the metabolic improvement. We conclude that IL-1β is a causal driver of impaired glucose tolerance in GDM.

Cellular Stress and General Pathological Processes

From the viewpoint of the general pathology, most of the human diseases are associated with a limited number of pathogenic processes such as inflammation, tumor growth, thrombosis, necrosis, fibrosis, atrophy, pathological hypertrophy, dysplasia and metaplasia. The phenomenon of chronic low-grade inflammation could be attributed to non-classical forms of inflammation, which include many neurodegenerative processes, pathological variants of insulin resistance, atherosclerosis, and other manifestations of the endothelial dysfunction. Individual and universal manifestations of cellular stress could be considered as a basic element of all these pathologies, which has both physiological and pathophysiological significance. The review examines the causes, main phenomena, developmental directions and outcomes of cellular stress using a phylogenetically conservative set of genes and their activation pathways, as well as tissue stress and its role in inflammatory and para-inflammatory processes. The main ways towards the realization of cellular stress and its functional blocks were outlined. The main stages of tissue stress and the classification of its typical manifestations, as well as its participation in the development of the classical and non-classical variants of the inflammatory process, were also described. The mechanisms of cellular and tissue stress are structured into the complex systems, which include networks that enable the exchange of information with multidirectional signaling pathways which together make these systems internally contradictory, and the result of their effects is often unpredictable. However, the possible solutions require new theoretical and methodological approaches, one of which includes the transition to integral criteria, which plausibly reflect the holistic image of these processes.

Chronic Adipose Tissue Inflammation Linking Obesity to Insulin Resistance and Type 2 Diabetes

Obesity is one of the major health burdens of the 21st century as it contributes to the growing prevalence of its related comorbidities, including insulin resistance and type 2 diabetes. Growing evidence suggests a critical role for overnutrition in the development of low-grade inflammation. Specifically, chronic inflammation in adipose tissue is considered a crucial risk factor for the development of insulin resistance and type 2 diabetes in obese individuals. The triggers for adipose tissue inflammation are still poorly defined. However, obesity-induced adipose tissue expansion provides a plethora of intrinsic signals (e.g., adipocyte death, hypoxia, and mechanical stress) capable of initiating the inflammatory response. Immune dysregulation in adipose tissue of obese subjects results in a chronic low-grade inflammation characterized by increased infiltration and activation of innate and adaptive immune cells. Macrophages are the most abundant innate immune cells infiltrating and accumulating into adipose tissue of obese individuals; they constitute up to 40% of all adipose tissue cells in obesity. In obesity, adipose tissue macrophages are polarized into pro-inflammatory M1 macrophages and secrete many pro-inflammatory cytokines capable of impairing insulin signaling, therefore promoting the progression of insulin resistance. Besides macrophages, many other immune cells (e.g., dendritic cells, mast cells, neutrophils, B cells, and T cells) reside in adipose tissue during obesity, playing a key role in the development of adipose tissue inflammation and insulin resistance. The association of obesity, adipose tissue inflammation, and metabolic diseases makes inflammatory pathways an appealing target for the treatment of obesity-related metabolic complications. In this review, we summarize the molecular mechanisms responsible for the obesity-induced adipose tissue inflammation and progression toward obesity-associated comorbidities and highlight the current therapeutic strategies.

The antagonism of 6-shogaol in high-glucose-activated NLRP3 inflammasome and consequent calcification of human artery smooth muscle cells

Background

Vascular calcification is the major reason for high mortality of cardiovascular complications for diabetes. Interleukin (IL)-1β has been implicated in this pathogenesis, but its precise role and clinical evidence have not been clearly identified. Hence, this study was aimed to investigate whether high concentration of glucose (HG), which mimics the hyperglycemia environment, could initiate vascular calcification through NLRP3/IL-1β inflammasome and the underlying mechanism. Recently, 6-shogaol, a major ginger derivate, has been elucidated its pharmaceutic role for various diseases. Therefore, the aims of this study also determined 6-shogaol effect in vascular calcification of HG initiation.

Result

Human artery smooth muscle cells (HASMCs) were used in this study. Glucose concentrations at 5 and 25 mM were defined as normal and HG status, respectively. The results showed that HG could increase the NLRP3, cleaved caspase 1, and pro/mature IL-1β levels to induce the expressions of bone-related matrix proteins and subsequent HASMC calcification. This process was regulated by Akt activation and reactive oxygen species (ROS) production. Moreover, 6-shogaol could inhibit the Akt/ROS signaling and NLRP3/caspase 1/IL-1β inflammasome and hence attenuated HASMC calcification.

Conclusions

This study elucidates the detailed mechanism of HG-initiated HASMC calcification through NLRP3/caspase 1/IL-1β inflammasome and indicates a potential therapeutic role of 6-shogaol in vascular calcification complication of diabetes.

The Molecular Mechanisms Underlying Mitochondria-Associated Endoplasmic Reticulum Membrane-Induced Insulin Resistance

Mitochondria and the endoplasmic reticulum (ER) are connected at multiple sites via what are known as mitochondria-associated ER membranes (MAMs). These associations are known to play an important role in maintaining cellular homeostasis. Impaired MAM signaling has wide-ranging effects in many diseases, such as obesity, diabetes, and neurodegenerative disorders. Accumulating evidence has suggested that MAMs influence insulin signaling through different pathways, including those associated with Ca²⁺ signaling, lipid metabolism, mitochondrial function, ER stress responses, and inflammation. Altered MAM signaling is a common feature of insulin resistance in different tissues, including the liver, muscle, and even the brain. In the liver, MAMs are key glucose-sensing regulators and have been proposed to be a hub for insulin signaling. Impaired MAM integrity has been reported to disrupt hepatic responses to changes in glucose availability during nutritional transition and to induce hepatic insulin resistance. Meanwhile, these effects can be rescued by the reinforcement of MAM interactions. In contrast, several studies have proposed that enhanced ER-mitochondria connections are detrimental to hepatic insulin signaling and can lead to mitochondrial dysfunction. Thus, given these contradictory results, the role played by the MAM in the regulation of hepatic insulin signaling remains elusive. Similarly, in skeletal muscle, enhanced MAM formation may be beneficial in the early stage of diabetes, whereas continuous MAM enhancement aggravates insulin resistance. Furthermore, recent studies have suggested that ER stress may be the primary pathway through which MAMs induce brain insulin resistance, especially in the hypothalamus. This review will discuss the possible mechanisms underlying MAM-associated insulin resistance as well as the therapeutic potential of targeting the MAM in the treatment of type 2 diabetes.