Metabolic syndrome: is Nlrp3 inflammasome a trigger or a target of insulin resistance?

Neuropathological links between T2DM and LOAD: systematic review and meta-analysis

Recent decades have described parallel neuropathological mechanisms increasing the risk for developing late-onset Alzheimer's dementia (LOAD) in type 2 diabetes mellitus (T2DM); however, still little is known of the role of diabetic encephalopathy and brain atrophy in LOAD. The aim of this systematic review is to provide a comprehensive view on diabetic encephalopathy/cerebral atrophy, taking into account neuroimaging data, neuropathology, metabolic and endocrine mechanisms, amyloid formation, brain perfusion impairments, neuroimmunology, and inflammasome activation. Key switches were identified, to further meta-analyze genomic candidate loci and epigenetic modifications. For the qualitative meta-analysis of genomic bases extracted, human linkage studies were examined; for epigenetic mechanisms, data from both human and animal studies are described. For the systematic review of pathophysiological mechanisms, 1,259 publications were evaluated and 93 gene loci extracted for candidate risk linkages. Sixty-six publications were evaluated for genomic association and descriptions of epigenomic modifications. Overall accumulated results highlight the insulin signaling system, vascular markers, inflammation and inflammasome pathways, amylin interactions, and glycosylation mechanisms. The protocol was registered with PROSPERO (ID: CRD42023440535).

Molecular mechanisms linking type 2 diabetes mellitus and late-onset Alzheimer's disease: A systematic review and qualitative meta-analysis

Research evidence indicating common metabolic mechanisms through which type 2 diabetes mellitus (T2DM) increases risk of late-onset Alzheimer's dementia (LOAD) has accumulated over recent decades. The aim of this systematic review is to provide a comprehensive review of common mechanisms, which have hitherto been discussed in separate perspectives, and to assemble and evaluate candidate loci and epigenetic modifications contributing to polygenic risk linkages between T2DM and LOAD. For the systematic review on pathophysiological mechanisms, both human and animal studies up to December 2023 are included. For the qualitative meta-analysis of genomic bases, human association studies were examined; for epigenetic mechanisms, data from human studies and animal models were accepted. Papers describing pathophysiological studies were identified in databases, and further literature gathered from cited work. For genomic and epigenomic studies, literature mining was conducted by formalised search codes using Boolean operators in search engines, and augmented by GeneRif citations in Entrez Gene, and other sources (WikiGenes, etc.). For the systematic review of pathophysiological mechanisms, 923 publications were evaluated, and 138 gene loci extracted for testing candidate risk linkages. 3 57 publications were evaluated for genomic association and descriptions of epigenomic modifications. Overall accumulated results highlight insulin signalling, inflammation and inflammasome pathways, proteolysis, gluconeogenesis and glycolysis, glycosylation, lipoprotein metabolism and oxidation, cell cycle regulation or survival, autophagic-lysosomal pathways, and energy. Documented findings suggest interplay between brain insulin resistance, neuroinflammation, insult compensatory mechanisms, and peripheral metabolic dysregulation in T2DM and LOAD linkage. The results allow for more streamlined longitudinal studies of T2DM-LOAD risk linkages.

SMPDL3B is palmitoylated and stabilized by ZDHHC5, and its silencing aggravates diabetic retinopathy of db/db mice: Activation of NLRP3/NF-κB pathway

Abnormal inflammation of vascular endothelial cells occurs frequently in diabetic retinopathy (DR). Sphingomyelin phosphodiesterase acid-like 3B (SMPDL3B) is a lipid raft enzyme and plays an anti-inflammatory role in various diseases but its function in DR-related vascular endothelial dysfunction remains unknown. We first found that SMPDL3B expression was upregulated from week 10 to 18 in the retinal tissues of db/db mice. Particularly, the high expression of SMPDL3B was mainly observed in retinal vascular endothelium of DR mice. To interfere retinal SMPDL3B expression, adeno-associated viruses 2 (AAV-2) containing SMPDL3B specific shRNA (1233-1253 bp) were injected into the vitreous cavity of db/db mice. SMPDL3B silencing exacerbated the spontaneous DR by further activating the NF-κB/NLRP3 pro-inflammatory pathway. In vitro, human retinal microvascular endothelial cells (HRVECs) were infected with SMPDL3B-shRNA lentiviruses and then stimulated with 30 mM glucose (HG) for 24 h. SMPDL3B-silenced HRVECs secreted more interleukin-1β and had enhanced nuclear p65 translocation. Notably, HG treatment induced the palmitoylation of SMPDL3B. Zinc finger DHHC-type palmitoyltransferase 5 (ZDHHC5) is a palmitoyltransferase that catalyzes the palmitoylation of its substrates, HG exposure increased the interaction between ZDHHC5 and SMPDL3B in HRVECs. 2-BP, a palmitoylation inhibitor, accelerated the protein degradation of SMPDL3B, whereas palmostatin B, a depalmitoylation inhibitor, decreased its turnover rate in HRVECs. Collectively, the present study suggests a compensatory increase of SMPDL3B in HG-treated HRVECs and the retinal tissues of DR mice, indicating that SMPDL3B may be a potential target for DR treatment.

Berberine inhibits NLRP3 inflammasome activation by regulating mTOR/mtROS axis to alleviate diabetic cardiomyopathy

Diabetes cardiomyopathy (DCM) refers to myocardial dysfunction and disorganization resulting from diabetes. In this study, we investigated the effects of berberine on cardiac function in male db/db mice with metformin as a positive control. After treatment for 8 weeks, significant improvements in cardiac function and a reduction in collagen deposition were observed in db/db mice. Furthermore, inflammation and pyroptosis were seen to decrease in these mice, as evidenced by decreased expressions of p-mTOR, NOD-like receptor thermal protein domain associated protein 3 (NLRP3), IL-1β, IL-18, caspase-1, and gasdermin D (GSDMD). In vitro experiments on H9C2 cells showed that glucose exposure at 33 mmol/L induced pyroptosis, whereas berberine treatment reduced the expression of p-mTOR and NLRP3 inflammasome components. Moreover, berberine treatment was seen to inhibit the generation of mitochondrial reactive oxygen species (mtROS) and effectively improve cell damage in high glucose-induced H9C2 cells. The mTOR inhibitor, Torin-1, showed a therapeutic effect similar to that of berberine, by reducing the expression of NLRP3 inflammasome components and inhibiting mtROS generation. However, the activation of mTOR by MHY1485 partially nullified berberine's protective effects during high glucose stress. Collectively, our study reveals the mechanism that berberine regulates the mTOR/mtROS axis to inhibit pyroptosis induced by NLRP3 inflammasome activation, thereby alleviating DCM.

TXNIP inhibition in the treatment of type 2 diabetes mellitus: design, synthesis, and biological evaluation of quinazoline derivatives

Thioredoxin interacting protein (TXNIP) is a potential drug target for type 2 diabetes mellitus (T2DM) treatment. A series of quinazoline derivatives were designed, synthesised, and evaluated to inhibit TXNIP expression and protect from palmitate (PA)-induced β cell injury. In vitro cell viability assay showed that compounds D-2 and C-1 could effectively protect β cell from PA-induced apoptosis, and subsequent results showed that these two compounds decreased TXNIP expression by accelerating its protein degradation. Mechanistically, compounds D-2 and C-1 reduced intracellular reactive oxygen species (ROS) production and modulated TXNIP-NLRP3 inflammasome signalling, and thus alleviating oxidative stress injury and inflammatory response under PA insult. Besides, these two compounds were predicted to possess better drug-likeness properties using SwissADME. The present study showed that compounds D-2 and C-1, especially compound D-2, were potent pancreatic β cell protective agents to inhibit TXNIP expression and might serve as promising lead candidates for the treatment of T2DM.

Protective role of vitamin D against oxidative stress in diabetic retinopathy

Diabetic retinopathy (DR) is a microvascular complication of diabetes mellitus. There is much evidence showing that a high level of mitochondrial overproduction of reactive oxygen species in the diabetic retina contributes in modifying cellular signalling and leads to retinal cell damage and finally to the development of DR pathogenesis. In the last few decades, it has been reported that vitamin D is involved in DR pathogenesis. Vitamin D, traditionally known as an essential nutrient crucial in bone metabolism, has also been proven to be a very effective antioxidant. It has been demonstrated that it modulates the production of advanced glycosylated end products, as well as several pathways including protein kinase C, the polyol pathway leading to the reduction of free radical formation. It prevents the translocation of nuclear factor kappa B, preventing the inflammatory response, acting as an immunomodulator, and modulates autophagy and apoptosis. In this review, we explore the molecular mechanisms by which vitamin D protects the eye from oxidative stress, in order to evaluate whether vitamin D supplementation may be useful to mitigate the deleterious effects of free radicals in DR.

Dioscorea zingiberensis ameliorates diabetic nephropathy by inhibiting NLRP3 inflammasome and curbing the expression of p66Shc in high-fat diet/streptozotocin-induced diabetic mice

OBJECTIVES

Diabetic nephropathy (DN) is a severe diabetic complication. Dioscorea zingiberensis (DZ) possesses excellent pharmacological properties with lower toxicity. The purpose of this study was to investigate the efficacy and mechanism of DZ in DN.

METHODS

DN was established by the high-fat diet combining intraperitoneal injection of streptozotocin in mice. The DZ (125 and 250 mg/kg/day) were intragastrical administered for 8 consecutive weeks. After treatment, blood, urine and kidney tissue were collected for biological detection, renal morphology, fibrosis and molecular mechanism research, respectively.

KEY FINDINGS

This study has shown that DZ significantly ameliorated kidney hypertrophy, renal structural damage and abnormal function of the kidney indicators (creatinine, urinary protein and blood urea nitrogen). Further molecular mechanism data suggested that the NLRP3/Cleaved-caspase-1 signal pathway was remarkably activated in DN, and DZ treatment reversed these changes, which indicated that it effectively attenuated inflammatory response caused by hyperglycaemia. In addition, DN inhibits hyperglycaemia-induced activation of oxidative stress by suppressing the expression of p66Shc proteins.

CONCLUSIONS

DZ could efficiently suppress oxidative stress and inflammatory responses to postpone the development of DN, and its mechanism might be related to inhibition of NLRP3 and p66Shc activities. Thus, DZ could be developed into a new therapeutic agent for DN.

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.

Associations between ketone bodies and fasting plasma glucose in individuals with post-pancreatitis prediabetes

Context: Levels of ketone bodies are altered in both acute pancreatitis and type 1 and type 2 diabetes. However, the role of ketone bodies in the pathogenesis of abnormal glucose metabolism after pancreatitis is largely unknown.Objective: To investigate the associations between ketone bodies and glucose homeostasis in individuals with post-pancreatitis prediabetes (PPP) versus normoglycaemia after pancreatitis (NAP).Methods: Fasting blood samples were analysed for acetoacetate, β-hydroxybutyrate, and markers of glucose metabolism at a median of 26 months after acute pancreatitis. A series of linear regression analyses were conducted adjusting for patient- and pancreatitis-related characteristics.Results: The study included 27 individuals with PPP and 52 with NAP. β-hydroxybutyrate was significantly associated with fasting plasma glucose (p = .002) and explained 26.2% of its variance in PPP, but not in NAP (p = .814; 0%). Acetoacetate was not significantly associated with fasting plasma glucose in both PPP (p = .681) or NAP (p = .661).Conclusions: An inverse association between β-hydroxybutyrate and fasting plasma glucose characterises PPP and this may have translational implications.

Metabolically Healthy Obesity-Heterogeneity in Definitions and Unconventional Factors

The concept of heterogeneity among obese individuals in their risk for developing metabolic dysfunction and associated complications has been recognized for decades. At the origin of the heterogeneity idea is the acknowledgement that individuals with central obesity are more prone to developing type 2 diabetes and cardiovascular disease than those with peripheral obesity. There have been attempts to categorize subjects according to their metabolic health and degree of obesity giving rise to different obese and non-obese phenotypes that include metabolically unhealthy normal-weight (MUHNW), metabolically healthy obese (MHO), and metabolically unhealthy obese (MUO). Individuals belonging to the MHO phenotype are obese according to their body mass index although exhibiting fewer or none metabolic anomalies such as type 2 diabetes, dyslipidemia, hypertension, and/or unfavorable inflammatory and fribinolytic profiles. However, some authors claim that MHO is only transient in nature. Additionally, the phenotype categorization is controversial as it lacks standardized definitions possibly blurring the distinction between obesity phenotypes and confounding the associations with health outcomes. To add to the discussion, the factors underlying the origin or protection from metabolic deterioration and cardiometabolic risk for these subclasses are being intensely investigated and several hypotheses have been put forward. In the present review, we compare the different definitions of obesity phenotypes and present several possible factors underlying them (adipose tissue distribution and cellularity, contaminant accumulation on the adipose tissue, dysbiosis and metabolic endotoxemia imposing on to the endocannabinoid tone and inflammasome, and nutrient intake and dietary patterns) having inflammatory activation at the center.

The Effects of Acute and Chronic Aerobic Activity on the Signaling Pathway of the Inflammasome NLRP3 Complex in Young Men

Background and Objectives: The results of the studies show that the intensity and volume of aerobic exercise activity produce different responses of the immune system. This study aims to show how the signaling pathway of the inflammatory NLRP3 complex is influenced by the acute and chronic effects of moderate and high-intensity aerobic exercises in young men. Materials and Methods: Accordingly, 60 healthy (BMI = 23.56 ± 2.67) young (24.4 ± 0.4) students volunteered to participate in the study that was randomly divided into two experimental (n = 20) groups and one control (n = 20) group. The training protocol started with two intensity levels of 50% for a moderate group and 70% of maximum heart rate for high group for 30 min and then continued until reaching 70% (moderate group) and 90% (high group) of the maximum heart rate, respectively. Using Real Time-PCR method, the expression of NLRP3 gene and ELISA- were measured by IL-1β, IL-18. Results: The results showed that acute aerobic exercise with moderate intensity had no significant effect on the expression of NLRP3 gene and serum levels of IL-1β and IL-18 cytokines (p > 0.05) when acute exercise, with high intensity, begins an initiation of the activity of the inflammatory complex with elevated serum levels of IL-1β, IL-18, and NLRP3 gene expression (p < 0.05). In addition, chronic exercise with moderate intensity significantly reduced the expression of NLRP3 gene and serum levels of IL-1β, IL-18 cytokines (p < 0.05). In the case of chronic exercise with high intensity, a significant increase in expression of gene, NLRP3 and serum levels of IL-1β, IL-18 cytokines were observed (p < 0.05). Conclusions: Generally, it can be concluded that chronic exercise with moderate intensity is effective in decreasing the expression of the inflammasome and inflammation.

Evaluation on the effect of hydrogen sulfide on the NLRP3 signaling pathway and its involvement in the pathogenesis of atherosclerosis

BACKGROUND

As a common disease, the incidence of atherosclerosis (AS) in the world is high. Therefore, we aimed to evaluate the involvement of hydrogen sulfide (H ₂ S)/cystathionine γ-lyase (CSE) in the pathogenesis of AS as well as their possible signaling pathways.

METHODS

Enzyme-linked immunosorbent assay, real-time polymerase chain reaction, and Western blot analysis were used to detect the effect of CSE on the expression of inflammatory cytokines, ie, H ₂ S, thioredoxin-interacting protein (TXNIP), NLRP3, apoptosis-associated speck-like protein (ASC), caspase-1, and interleukin (IL)-1β. In addition, immunohistochemistry and Western blot analysis were performed to detect the levels of TXNIP, NLRP3, ASC, caspase-1, IL-1β, and IL-18 among different groups.

RESULT

Knockdown of CSE by the transfection of CSE small interfering RNA upregulated the levels of two inflammatory cytokines, ie, IL-1β and IL-18. In addition, the downregulation of CSE promoted the expression of TXNIP, NLRP3, ASC, caspase-1, and IL-1β in THP-1 cells. Meanwhile, treating the cells with sodium hydrosulfide (NaHS) inhibited the productions of IL-1β and IL-18. Furthermore, upregulation of H ₂ S synthesis by treating the cells with NaHS also reduced the protein levels of TXNIP, NLRP3, ASC, caspase-1, and IL-1β. Finally, the protein levels of TXNIP and NLRP3 in the AS group were much higher than those in the AS + H ₂ S group, which in turn was higher than the sham group. In addition, the AS group displayed the highest protein levels of TXNIP, NLRP3, ASC, caspase-1, IL-1β, and IL-18, while the levels of these proteins in the AS + H ₂ S group were higher than those in the sham group.

CONCLUSION

In summary, the present finding suggested a possible linkage between H ₂ S metabolism and AS through the H ₂ S/CSE-TXNIP-NLRP3-IL-18/IL-1β-nitric oxide (NO) signaling pathway.

Anti-inflammatory effect of Resolvin D1 on LPS-treated MG-63 cells

Inflammation reaction plays an important role in the pathogenesis of ankle fracture. The aim of the present study was to investigate the effect of RvD1 on the inflammatory response and underlying molecular mechanisms in MG-63 cells. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and ELISA were used to determine the mRNA and protein expression of cytokines extracted from peripheral blood in children with or without ankle fracture, respectively. MG-63 cells were pre-treated with/without RvD1 and stimulated with 1 µg/ml LPS. The cell viability was detected by MTT assay. The production of cytokines from MG-63 cells was assessed by RT-qPCR and western blot, respectively. The expression of p-p38, NF-κB (p50) and cyclooxygenase-2 (COX-2) mRNA and protein were detected by western blot and/or RT-qPCR. The levels of NLRP3, associated recruitment domain (ASC), cleaved caspase1, caspase-1 were measured by RT-qPCR and/or western blot. The levels of interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF-α) mRNA and protein were up-regulated in children with ankle fracture compared with healthy children. RvD1 treatment did not induce cytotoxicity in MG-63 cells, but it can inhibit LPS induced MG-63 cell proliferation inhibition. RvD1 was able to dose-dependently reverse LPS induced up-regulation of TNF-α, IL-1β, IL-6 mRNA and protein expression. Furthermore, the LPS induced up-regulation of p-p38, NF-κB (p50), and NLRP3, ASC, cleaved caspase-1/caspase-1, and COX-2 was dose-dependently reversed by RvD1. In conclusion, The present study demonstrated that RvD1 inhibited inflammation though inhibiting MAPKp38/NF-κB pathway and NLRP3 inflammasome expression in MG-63 cells, indicating that it may be an effective drug for the treatment of ankle fracture.

Age and Age-Related Diseases: Role of Inflammation Triggers and Cytokines

Cytokine dysregulation is believed to play a key role in the remodeling of the immune system at older age, with evidence pointing to an inability to fine-control systemic inflammation, which seems to be a marker of unsuccessful aging. This reshaping of cytokine expression pattern, with a progressive tendency toward a pro-inflammatory phenotype has been called "inflamm-aging." Despite research there is no clear understanding about the causes of "inflamm-aging" that underpin most major age-related diseases, including atherosclerosis, diabetes, Alzheimer's disease, rheumatoid arthritis, cancer, and aging itself. While inflammation is part of the normal repair response for healing, and essential in keeping us safe from bacterial and viral infections and noxious environmental agents, not all inflammation is good. When inflammation becomes prolonged and persists, it can become damaging and destructive. Several common molecular pathways have been identified that are associated with both aging and low-grade inflammation. The age-related change in redox balance, the increase in age-related senescent cells, the senescence-associated secretory phenotype (SASP) and the decline in effective autophagy that can trigger the inflammasome, suggest that it may be possible to delay age-related diseases and aging itself by suppressing pro-inflammatory molecular mechanisms or improving the timely resolution of inflammation. Conversely there may be learning from molecular or genetic pathways from long-lived cohorts who exemplify good quality aging. Here, we will discuss some of the current ideas and highlight molecular pathways that appear to contribute to the immune imbalance and the cytokine dysregulation, which is associated with "inflammageing" or parainflammation. Evidence of these findings will be drawn from research in cardiovascular disease, cancer, neurological inflammation and rheumatoid arthritis.

TXNIP in Metabolic Regulation: Physiological Role and Therapeutic Outlook

Background & Objective:

Thioredoxin-interacting protein (TXNIP) also known as thioredoxin binding protein-2 is a ubiquitously expressed protein that interacts and negatively regulates expression and function of Thioredoxin (TXN). Over the last few years, TXNIP has attracted considerable attention due to its wide-ranging functions impacting several aspects of energy metabolism. TXNIP acts as an important regulator of glucose and lipid metabolism through pleiotropic actions including regulation of β-cell function, hepatic glucose production, peripheral glucose uptake, adipogenesis, and substrate utilization. Overexpression of TXNIP in animal models has been shown to induce apoptosis of pancreatic β-cells, reduce insulin sensitivity in peripheral tissues like skeletal muscle and adipose, and decrease energy expenditure. On the contrary, TXNIP deficient animals are protected from diet induced insulin resistance and type 2 diabetes.

Summary:

Consequently, targeting TXNIP is thought to offer novel therapeutic opportunity and TXNIP inhibitors have the potential to become a powerful therapeutic tool for the treatment of diabetes mellitus. Here we summarize the current state of our understanding of TXNIP biology, highlight its role in metabolic regulation and raise critical questions that could help future research to exploit TXNIP as a therapeutic target.

Shortcuts to a functional adipose tissue: The role of small non-coding RNAs

Metabolic diseases such as type 2 diabetes are a major public health issue worldwide. These diseases are often linked to a dysfunctional adipose tissue. Fat is a large, heterogenic, pleiotropic and rather complex tissue. It is found in virtually all cavities of the human body, shows unique plasticity among tissues, and harbors many cell types in addition to its main functional unit - the adipocyte. Adipose tissue function varies depending on the localization of the fat depot, the cell composition of the tissue and the energy status of the organism. While the white adipose tissue (WAT) serves as the main site for triglyceride storage and acts as an important endocrine organ, the brown adipose tissue (BAT) is responsible for thermogenesis. Beige adipocytes can also appear in WAT depots to sustain heat production upon certain conditions, and it is becoming clear that adipose tissue depots can switch phenotypes depending on cell autonomous and non-autonomous stimuli. To maintain such degree of plasticity and respond adequately to changes in the energy balance, three basic processes need to be properly functioning in the adipose tissue: i) adipogenesis and adipocyte turnover, ii) metabolism, and iii) signaling. Here we review the fundamental role of small non-coding RNAs (sncRNAs) in these processes, with focus on microRNAs, and demonstrate their importance in adipose tissue function and whole body metabolic control in mammals.

Effect of betaine on hepatic insulin resistance through FOXO1-induced NLRP3 inflammasome

In the present study, we attempted to elucidate whether molecular modulation of inflammation by betaine through the forkhead box O1 (FOXO1)-induced NLRP3 inflammasome improves insulin resistance. Betaine is a major water-soluble component of Lycium chinense. It mainly functions as an oxidative metabolite of choline by suppressing superoxide-induced free radicals by donating methyl groups. The FOXO1 transcription factor regulates various genes involved in cellular metabolic processes related to cell death as well as oxidative stress responses through binding to the thioredoxin-interacting protein (TXNIP). Betaine is known to inhibit FOXO1 phosphorylation through phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) in liver cells exposed to insulin. To elucidate the molecular mechanism of inactivation of insulin-induced FOXO1 by the antioxidant betaine, we used HepG2 cells and the liver of db/db mice treated with betaine at a dose of 50 mg/kg/day for 3 weeks. We found that the activation of NLRP3 inflammasome genes was reduced by betaine, which resulted in the suppression of reactive species (RS) production in liver cells. In addition, betaine inhibited insulin-induced PI3K/AKT and FOXO1 activation. Therefore, betaine suppressed the cytokine interleukin-1β production by inhibiting the activation of the NLRP3 inflammasome via interaction of FOXO1 and TXNIP. Our results suggest that betaine inhibits the FOXO1 binding to TXNIP, leading to the suppression of RS-induced NLRP3 inflammasome activation in a diabetic liver.

Resolvin D1 inhibits inflammatory response in STZ-induced diabetic retinopathy rats: Possible involvement of NLRP3 inflammasome and NF-κB signaling pathway

PURPOSE

To investigate the effect of resolvin D1 (RvD1) on the Nod-like receptor family pyrin domain-containing (NLRP3) inflammasome and the nuclear factor-kappa beta (NF-κB) pathway in streptozotocin (STZ)-induced diabetic retinopathy in rats.

METHODS

Ninety-six male rats were divided into four groups: control, STZ, RvD1, and vehicle. The rats with diabetic retinopathy induced by STZ in the RvD1 and vehicle groups were given an intravitreal injection of RvD1 (1,000 ng/kg) or the same dosage of vehicle, respectively. All rats were euthanized 7 days following treatment. Hematoxylin and eosin staining was used to observe the pathological changes in the retinal tissues. The location and expression of the NLRP3 inflammasome components, including NLRP3, caspase-associated recruitment domain (ASC), and caspase-1, in the retinas were detected using immunohistochemistry, real-time PCR, and western blot, respectively. Retinal homogenate of rats were collected for the detection of the downstream molecules interleukin 1 beta (IL-1β) and IL-18 of the NLRP3 inflammasome with enzyme-linked immunosorbent assay kits.

RESULTS

The levels of NLRP3, ASC, cleaved caspase-1, IL-1β, and IL-18 were upregulated in the retinas of the STZ-induced diabetic rats; however, these changes were partially inhibited by the RvD1 treatment. Furthermore, the administration of RvD1 suppressed activation of NF-kB, which was upregulated in STZ-induced diabetic retinopathy.

CONCLUSIONS

RvD1 plays a protective role in STZ-induced diabetic retinopathy by inhibiting the level of activation of the NLRP3 inflammasome and associated cytokine production, suggesting targeting of this pathway might be an effective strategy in treatment of diabetic retinopathy.

NLRP3 Inflammasome Expression and Signaling in Human Diabetic Wounds and in High Glucose Induced Macrophages

Introduction. To investigate the contribution and mechanism of NLRP3 inflammasome expression in human wounds in diabetes mellitus and in high glucose induced macrophages. Methods. In the present study, we compared the expression of NLRP3 inflammasome in debridement wound tissue from diabetic and nondiabetic patients. We also examined whether high glucose induces NLRP3 inflammasome expression in cultures THP-1-derived macrophages and the influence on IL-1β expression. Results. The expressions of NLRP3, caspase1, and IL-1β, at both the mRNA and protein level, were significantly higher in wounds of diabetic patients compared with nondiabetic wounds (P < 0.05). High glucose induced a significant increase in NLRP3 inflammasome and IL-1β expression in THP-1-derived macrophages. M1 macrophage surface marker with CCR7 was significantly upregulated after high glucose stimulation. SiRNA-mediated silencing of NLRP3 expression downregulates the expression of IL-1β. Conclusion. The higher expression of NLRP3, caspase1, and secretion of IL-1β, signaling, and activation might contribute to the hyperinflammation in the human diabetic wound and in high glucose induced macrophages. It may be a novel target to treat the DM patients with chronic wound.

Pulmonary transcriptional response to ozone in healthy and cardiovascular compromised rat models

The genetic cardiovascular disease (CVD) and associated metabolic impairments can influence the lung injury from inhaled pollutants. We hypothesized that comparative assessment of global pulmonary expression profile of healthy and CVD-prone rat models will provide mechanistic insights into susceptibility differences to ozone. The lung expression profiles of healthy Wistar Kyoto (WKY) and CVD-compromised spontaneously hypertensive (SH), stroke-prone SH (SHSP), obese SH heart failure (SHHF) and obese, atherosclerosis-prone JCR rats were analyzed using Affymetrix platform immediately after 4-h air or 1 ppm ozone exposure. At baseline, the JCR exhibited the largest difference in the number of genes among all strains when compared with WKY. Interestingly, the number of genes affected by ozone was inversely correlated with genes different at baseline relative to WKY. A cluster of NFkB target genes involved in cell-adhesion, antioxidant response, inflammation and apoptosis was induced in all strains, albeit at different levels (JCR < WKY < SHHF < SH < SHSP). The lung metabolic syndrome gene cluster indicated expressions in opposite directions for SHHF and JCR suggesting different mechanisms for common disease phenotype and perhaps obesity-independent contribution to exacerbated lung disease. The differences in expression of adrenergic receptors and ion-channel genes suggested distinct mechanisms by which ozone might induce protein leakage in CVD models, especially SHHF and JCR. Thus, the pulmonary response to ozone in CVD strains was likely linked to the defining gene expression profiles. Differential transcriptional patterns between healthy and CVD rat strains at baseline, and after ozone suggests that lung inflammation and injury might be influenced by multiple biological pathways affecting inflammation gene signatures.

Loss of Nlrp3 Does Not Protect Mice from Western Diet-Induced Adipose Tissue Inflammation and Glucose Intolerance

We tested the hypothesis that loss of Nlrp3 would protect mice from Western diet-induced adipose tissue (AT) inflammation and associated glucose intolerance and cardiovascular complications. Five-week old C57BL6J wild-type (WT) and Nlrp3 knockout (Nlrp3-/-) mice were randomized to either a control diet (10% kcal from fat) or Western diet (45% kcal from fat and 1% cholesterol) for 24 weeks (n = 8/group). Contrary to our hypothesis that obesity-mediated white AT inflammation is Nlrp3-dependent, we found that Western diet-induced expression of AT inflammatory markers (i.e., Cd68, Cd11c, Emr1, Itgam, Lgals, Il18, Mcp1, Tnf, Ccr2, Ccl5 mRNAs, and Mac-2 protein) were not accompanied by increased caspase-1 cleavage, a hallmark feature of NLRP3 inflammasome activation. Furthermore, Nlrp3 null mice were not protected from Western diet-induced white or brown AT inflammation. Although Western diet promoted glucose intolerance in both WT and Nlrp3-/- mice, Nlrp3-/- mice were protected from Western diet-induced aortic stiffening. Additionally, Nlrp3-/- mice exhibited smaller cardiomyocytes and reduced cardiac fibrosis, independent of diet. Collectively, these findings suggest that presence of the Nlrp3 gene is not required for Western diet-induced AT inflammation and/or glucose intolerance; yet Nlrp3 appears to play a role in potentiating arterial stiffening, cardiac hypertrophy and fibrosis.

Crosstalk between the heart and peripheral organs in heart failure

Mediators from peripheral tissues can influence the development and progression of heart failure (HF). For example, in obesity, an altered profile of adipokines secreted from adipose tissue increases the incidence of myocardial infarction (MI). Less appreciated is that heart remodeling releases cardiokines, which can strongly impact various peripheral tissues. Inflammation, and, in particular, activation of the nucleotide-binding oligomerization domain-like receptors with pyrin domain (NLRP3) inflammasome are likely to have a central role in cardiac remodeling and mediating crosstalk with other organs. Activation of the NLRP3 inflammasome in response to cardiac injury induces the production and secretion of the inflammatory cytokines interleukin (IL)-1β and IL-18. In addition to having local effects in the myocardium, these pro-inflammatory cytokines are released into circulation and cause remodeling in the spleen, kidney, skeletal muscle and adipose tissue. The collective effects of various cardiokines on peripheral organs depend on the degree and duration of myocardial injury, with systematic inflammation and peripheral tissue damage observed as HF progresses. In this article, we review mechanisms regulating myocardial inflammation in HF and the role of factors secreted by the heart in communication with peripheral tissues.

High Glucose and Lipopolysaccharide Prime NLRP3 Inflammasome via ROS/TXNIP Pathway in Mesangial Cells

While inflammation is considered a central component in the development in diabetic nephropathy, the mechanism remains unclear. The NLRP3 inflammasome acts as both a sensor and a regulator of the inflammatory response. The NLRP3 inflammasome responds to exogenous and endogenous danger signals, resulting in cleavage of procaspase-1 and activation of cytokines IL-1β, IL-18, and IL-33, ultimately triggering an inflammatory cascade reaction. This study observed the expression of NLRP3 inflammasome signaling stimulated by high glucose, lipopolysaccharide, and reactive oxygen species (ROS) inhibitor N-acetyl-L-cysteine in glomerular mesangial cells, aiming to elucidate the mechanism by which the NLRP3 inflammasome signaling pathway may contribute to diabetic nephropathy. We found that the expression of thioredoxin-interacting protein (TXNIP), NLRP3, and IL-1β was observed by immunohistochemistry in vivo. Simultaneously, the mRNA and protein levels of TXNIP, NLRP3, procaspase-1, and IL-1β were significantly induced by high glucose concentration and lipopolysaccharide in a dose-dependent and time-dependent manner in vitro. This induction by both high glucose and lipopolysaccharide was significantly inhibited by N-acetyl-L-cysteine. Our results firstly reveal that high glucose and lipopolysaccharide activate ROS/TXNIP/ NLRP3/IL-1β inflammasome signaling in glomerular mesangial cells, suggesting a mechanism by which inflammation may contribute to the development of diabetic nephropathy.

The protective effects of curculigoside A on adjuvant-induced arthritis by inhibiting NF-кB/NLRP3 activation in rats

The purpose of this study was to investigate the protective effects of curculigoside A (CA) on adjuvant arthritis (AA) rats and explore its possible mechanisms. AA was induced by intradermal injection of Freund's complete adjuvant (FCA). Male SD rats were treated with CA(10 and 20mg/kg) from days 18 to 24 after immunization. The levels of interleukin (IL)-6, IL-1β, tumor necrosis factor-α (TNF-α) and prostaglandin E2 (PGE2) in serum were determined by ELISA. Moreover, the levels of super oxide dismutase (SOD) and malondialdehyde (MDA) were determined using commercial kits. In particular, NLRP3 inflammasome and NF-кB pathway were detected by Western blot. As expected, CA at 10 and 20mg/kg significantly relieved the hind paw swelling and arthritis index, reduced the levels of IL-6 IL-1β, PGE2, TNF-α, MDA and increased SOD activity in serum. In addition, CA effectively down-regulated the expression of NF-кB/NLRP3 pathway. These findings showed that CA exerted beneficial effects on rheumatoid arthritis in rats.

Leukocyte infiltration and activation of the NLRP3 inflammasome in white adipose tissue following thermal injury

OBJECTIVES

Severe thermal injury is associated with extreme and prolonged inflammatory and hypermetabolic responses, resulting in significant catabolism that delays recovery or even leads to multiple organ failure and death. Burned patients exhibit many symptoms of stress-induced diabetes, including hyperglycemia, hyperinsulinemia, and hyperlipidemia. Recently, the nucleotide-binding domain, leucine-rich family (NLR), pyrin-containing 3 (NLRP3) inflammasome has received much attention as the sensor of endogenous "danger signals" and mediator of "sterile inflammation" in type II diabetes. Therefore, we investigated whether the NLRP3 inflammasome is activated in the adipose tissue of burned patients, as we hypothesize that, similar to the scenario observed in chronic diabetes, the cytokines produced by the inflammasome mediate insulin resistance and metabolic dysfunction.

DESIGN

Prospective cohort study.

SETTING

Ross Tilley Burn Centre & Sunnybrook Research Institute.

PATIENTS

We enrolled 76 patients with burn sizes ranging from 1% to 70% total body surface area. All severely burned patients exhibited burn-induced insulin resistance and hyperglycemia.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We examined the adipose tissue of control and burned patients and found, via flow cytometry and gene expression studies, increased infiltration of leukocytes-especially macrophages-and evidence of inflammasome priming and activation. Furthermore, we observed increased levels of interleukin-1β in the plasma of burned patients when compared to controls.

CONCLUSIONS

In summary, our study is the first to show activation of the inflammasome in burned humans, and our results provide impetus for further investigation of the role of the inflammasome in burn-induced hypermetabolism and, potentially, developing novel therapies targeting this protein complex for the treatment of stress-induced diabetes.