Silencing TXNIP ameliorates high uric acid-induced insulin resistance via the IRS2/AKT and Nrf2/HO-1 pathways in macrophages

Serum uric acid and mortality in metabolic dysfunction-associated steatotic liver disease: Subgroup differences

BACKGROUND AND AIMS

This study aims to investigate the association between serum uric acid (SUA) and both the risk and long-term mortality of dysfunction-associated steatotic liver disease (MASLD), and to explore differences between the pure MASLD and metabolic and alcohol related/associated liver disease (MetALD) subgroups.

METHODS AND RESULTS

We included 11,675 participants from the Third National Health and Nutrition Examination Survey, with matched mortality data up to 2019. Logistic regression and Cox proportional hazards regression evaluated the relationship between SUA and both the risk and mortality of MASLD. Non-linear correlations and threshold effects were explored using restricted cubic splines and a two-piecewise Cox proportional hazards model. We found that SUA was positively associated with the risk of MASLD [odds ratio (OR): 1.19, 95 % confidence interval (CI) 1.12-1.27]. For pure MASLD, SUA showed a positive association with all-cause mortality [<4.7 mg/dL: hazard ratio (HR): 1.34, 95 % CI 1.04-1.73; ≥4.7 mg/dL: HR: 1.08, 95 % CI 1.02-1.15] and cardiovascular mortality (HR: 1.12, 95 % CI 1.02-1.22). For MetALD, there was an inverse J-shaped relationship (threshold: 6.6 mg/dL) between SUA and all-cause mortality. Below the threshold, SUA was negatively correlated with all-cause mortality (HR: 0.42, 95 % CI 0.19-0.93), but no association was found above it (HR: 0.81, 95 % CI 0.54-1.21). Additionally, no association was observed between SUA and cardiovascular mortality.

CONCLUSIONS

SUA serves as an independent predictor of the risk and all-cause mortality of MASLD. The relationship between SUA and both all-cause and cardiovascular mortality differs between the pure MASLD and MetALD subgroups.

Discovering the anti-diabetic potential of pomegranate peel metabolites by examining molecular interplay with the thioredoxin-interacting protein

Introduction

Medicinal plants like Punica granatum (pomegranate) have traditional uses against diabetes, inflammation and other diseases. The study was initiated to get an insight into the interaction tendency of P. granatum derived compounds with diabetes associated human thioredoxin-interacting protein (TXNIP). High glucose in diabetes induces production of TXNIP resulting in β-cells apoptosis. Its inhibition might reduce the diabetes incidence.

Methods

To elucidate the therapeutic potential of P. granatum peel against diabetes through GC-MS based identification of extracted compounds followed by application of computational algorithms. P. granatum peel extracts were screened for antioxidant, anti-inflammatory, anti-diabetic, antimicrobial and wound healing properties. Phytochemical and GC-MS based analysis were performed to identify the bioactive compounds. Molecular docking analysis was performed by Auto Dock Vina to predict the binding tendency of P. granatum derived compounds with TXNIP.

Results and Discussion

The peel exhibited antioxidant, anti-inflammatory and anti-diabetic activities, which were attributed to phytochemicals like phenols, tannins and steroids. GC-MS analysis identified 3,5-octadien-2-one, 1H-pyrrole -2,5-dione, Beta-D-lyxofuranoside, 5-O-(beta-D-lyxofuranosyl)-decyl, diethyl phthalate, 9-octadecenoic acid (Z)-, methyl ester, hexadecanoic acid, methyl ester, n-hexadecanoic acid, tetradecane, 2,6,10-trimethyl, bis (2-ethylhexyl) phthalate, decane, 3,8-dimethyl, 9-octadecenoic acid (Z)-, methyl ester and bis (2-ethylhexyl) phthalate in P. granatum peel extracts. Docking analysis revealed high binding affinities of bis (2-ethylhexyl) phthalate and 9-octadecenoic acid with TXNIP i.e., -4.5 and -5.0 kcal/mol, respectively, reflecting these compounds as potent antidiabetic agents. This study validates the traditional uses of P. granatum peel and demonstrates how computational approaches can uncover pharmacologically active phytochemicals. The results suggest P. granatum peel is a promising source of novel therapeutics against diabetes, inflammation, and oxidation. Further studies on the optimization of identified ligands are warranted.

Hyperuricemia and its related diseases: mechanisms and advances in therapy

Hyperuricemia, characterized by elevated levels of serum uric acid (SUA), is linked to a spectrum of commodities such as gout, cardiovascular diseases, renal disorders, metabolic syndrome, and diabetes, etc. Significantly impairing the quality of life for those affected, the prevalence of hyperuricemia is an upward trend globally, especially in most developed countries. UA possesses a multifaceted role, such as antioxidant, pro-oxidative, pro-inflammatory, nitric oxide modulating, anti-aging, and immune effects, which are significant in both physiological and pathological contexts. The equilibrium of circulating urate levels hinges on the interplay between production and excretion, a delicate balance orchestrated by urate transporter functions across various epithelial tissues and cell types. While existing research has identified hyperuricemia involvement in numerous biological processes and signaling pathways, the precise mechanisms connecting elevated UA levels to disease etiology remain to be fully elucidated. In addition, the influence of genetic susceptibilities and environmental determinants on hyperuricemia calls for a detailed and nuanced examination. This review compiles data from global epidemiological studies and clinical practices, exploring the physiological processes and the genetic foundations of urate transporters in depth. Furthermore, we uncover the complex mechanisms by which the UA induced inflammation influences metabolic processes in individuals with hyperuricemia and the association with its relative disease, offering a foundation for innovative therapeutic approaches and advanced pharmacological strategies.

Recent advances in the effect of adipose tissue inflammation on insulin resistance

Obesity is one of the major risk factors for diabetes. Excessive accumulation of fat leads to inflammation of adipose tissue, which can increase the risk of developing diabetes. Obesity-related chronic inflammation can result in anomalies in glucose-lipid metabolism and insulin resistance, and it is a major cause of β-cell dysfunction in diabetes mellitus. Thus, a long-term tissue inflammatory response is crucial for metabolic diseases, particularly type 2 diabetes. Chronic inflammation associated with obesity increases oxidative stress, secretes inflammatory factors, modifies endocrine variables, and interferes with insulin signalling pathways, all of which contribute to insulin resistance and glucose tolerance. Insulin resistance and diabetes are ultimately caused by chronic inflammation in the stomach, pancreas, liver, muscle, and fat tissues. In this article, we systematically summarize the latest research progress on the mechanisms of adipose tissue inflammation and insulin resistance, as well as the mechanisms of cross-talk between adipose tissue inflammation and insulin resistance, with a view to providing some meaningful therapeutic strategies for the treatment of insulin resistance by controlling adipose tissue inflammation.

Associations of oxidative balance score with hyperuricemia and gout among American adults: a population-based study

Objective

The current study aimed to assess the relationships between oxidative balance score (OBS) and OBS subclasses (dietary and lifestyle OBS) with risks of hyperuricemia (HUA) and gout among American adults.

Methods

Participants in the National Health and Nutrition Examination Survey from 2007 to 2018 were initially recruited and then the final sample was restricted to adults without missing values about serum uric acid, gout, OBS, and covariates. Rao-Scott adjusted chi-square test and analysis of variance were utilized to compare the baseline characteristics in adults of different quartiles of OBS, while the weighted stepped logistic regression models were used to explore the associations of overall, dietary, and lifestyle OBS with the risks of HUA and gout. Weighted restricted cubic spline analyses were conducted to explore the nonlinear dose-response associations.

Results

The final sample consisted of 22,705 participants aged 20 years and older, which was representative of approximately 197.3 million non-institutionalized American adults. HUA and gout prevalence decreased with OBS quartiles. Compared with adults in the first quartile of OBS, those in the second (OR: 0.85, 95% CI: 0.72-0.99), third (OR: 0.71, 95% CI: 0.58-0.85), and fourth (OR: 0.48, 95% CI: 0.38-0.61) quartiles of OBS had reduced risks of hyperuricemia. Similarly, adults in the second (OR: 0.70, 95% CI: 0.51-0.97) quartile of OBS was associated with lower gout risk in comparison to adults in the lowest quartile. Regarding OBS subclasses, dietary and lifestyle OBS were both negatively correlated with the risk of HUA, and only higher lifestyle OBS was significantly associated with lower gout risk. Furthermore, the subgroup analyses and interaction effects also substantiated similar effects. Significant nonlinear dose-response relationships were observed between overall, dietary, and lifestyle OBS with HUA risk as well as that of lifestyle OBS with gout risk.

Conclusion

This study strongly suggests the significant negative associations of OBS with HUA and gout in American adults and provides a dietary and lifestyle guideline to reduce the risks.

The Role of Hyperuricemia in Cardiac Diseases: Evidence, Controversies, and Therapeutic Strategies

Hyperuricemia (HUA) may lead to myocardial cell damage, thereby promoting the occurrence and adverse outcomes of heart diseases. In this review, we discuss the latest clinical research progress, and explore the impact of HUA on myocardial damage-related diseases such as myocardial infarction, arrhythmias, and heart failure. We also combined recent findings from basic research to analyze potential mechanisms linking HUA with myocardial injury. In different pathological models (such as direct action of high uric acid on myocardial cells or combined with myocardial ischemia-reperfusion model), HUA may cause damage by activating the NOD-like receptor protein 3 inflammasome-induced inflammatory response, interfering with cardiac cell energy metabolism, affecting antioxidant defense systems, and stimulating reactive oxygen species production to enhance the oxidative stress response, ultimately resulting in decreased cardiac function. Additionally, we discuss the impact of lowering uric acid intervention therapy and potential safety issues that may arise. However, as the mechanism underlying HUA-induced myocardial injury is poorly defined, further research is warranted to aid in the development novel therapeutic strategies for HUA-related cardiovascular diseases.

The Role Played by Mitochondria in Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) refers to an endocrine disorder syndrome that are correlated with multiple organs and systems. PCOS has an effect on women at all stages of their lives, and it has an incidence nearly ranging from 6% to 20% worldwide. Mitochondrial dysfunctions (e.g., oxidative stress, dynamic imbalance, and abnormal quality control system) have been identified in patients and animal models of PCOS, and the above processes may play a certain role in the development of PCOS and its associated complications. However, their specific pathogenic roles should be investigated in depth. In this review, recent studies on the mechanisms of action of mitochondrial dysfunction in PCOS and its associated clinical manifestations are summarized from the perspective of tissues and organs, and some studies on the treatment of the disease by improving mitochondrial function are reviewed to highlight key role of mitochondrial dysfunction in this syndrome.

The dysregulation of immune cells induced by uric acid: mechanisms of inflammation associated with hyperuricemia and its complications

Changes in lifestyle induce an increase in patients with hyperuricemia (HUA), leading to gout, gouty arthritis, renal damage, and cardiovascular injury. There is a strong inflammatory response in the process of HUA, while dysregulation of immune cells, including monocytes, macrophages, and T cells, plays a crucial role in the inflammatory response. Recent studies have indicated that urate has a direct impact on immune cell populations, changes in cytokine expression, modifications in chemotaxis and differentiation, and the provocation of immune cells by intrinsic cells to cause the aforementioned conditions. Here we conducted a detailed review of the relationship among uric acid, immune response, and inflammatory status in hyperuricemia and its complications, providing new therapeutic targets and strategies.

The protective effects of uric acid against myocardial ischemia via the Nrf2 pathway

Uric acid (UA) possesses both pro- and anti-oxidative properties in ischemic heart disease, but the underlying mechanism remains unclear. We aimed to investigate UA's protective effect on myocardial ischemia by examining its effects on ECG Ischemic Alterations (EIA) and H2O2-induced oxidative stress in H9C2 myocardial cells. The incidence of EIA decreased over time and was more prevalent among women than men. A U-shaped relationship was observed between UA levels and EIA incidence, with the third quartile exhibiting a protective association. Addition of 237.9 μmol/L UA improved cellular damage and oxidative stress in H2O2-treated H9C2 cells, as determined by cell viability, LDH release, ROS levels, and total antioxidant capacity assays. UA activated the Nrf2 pathway, evidenced by increased expression of Nrf2, GCLC, and HO-1 proteins. By reversing cell cycle blockage, promoting wound healing ability, improving colony-forming capacity, and increasing angiogenesis in H2O2-treated cells, UA exhibited positive effects on cardiomyocyte growth characteristics. Additionally, use of Nrf2 inhibitor ML385 confirmed the involvement of the Nrf2 pathway by negating UA's effects on oxidatively damaged cardiomyocytes. Our findings suggest that UA induces downstream antioxidant factors to ameliorate oxidative stress by activating the Nrf2 pathway, which could be one of the targets responsible for UA's beneficial effects in myocardial ischemia.

Uric acid en route to gout

Gout and hyperuricemia (HU) have generated immense attention due to increased prevalence. Gout is a multifactorial metabolic and inflammatory disease that occurs when increased uric acid (UA) induce HU resulting in monosodium urate (MSU) crystal deposition in joints. However, gout pathogenesis does not always involve these events and HU does not always cause a gout flare. Treatment with UA-lowering therapeutics may not prevent or reduce the incidence of gout flare or gout-associated comorbidities. UA exhibits both pro- and anti-inflammation functions in gout pathogenesis. HU and gout share mechanistic and metabolic connections at a systematic level, as shown by studies on associated comorbidities. Recent studies on the interplay between UA, HU, MSU and gout as well as the development of HU and gout in association with metabolic syndromes, non-alcoholic fatty liver disease (NAFLD), and cardiovascular, renal and cerebrovascular diseases are discussed. This review examines current and potential therapeutic regimens and illuminates the journey from disrupted UA to gout.

Activation of NRF2 Signaling Pathway Delays the Progression of Hyperuricemic Nephropathy by Reducing Oxidative Stress

Hyperuricemia (HUA)-induced oxidative stress is a crucial contributor to hyperuricemic nephropathy (HN), but the molecular mechanisms underlying the disturbed redox homeostasis in kidneys remain elusive. Using RNA sequencing, together with biochemical analyses, we found that nuclear factor erythroid 2-related factor 2 (NRF2) expression and nuclear localization levels were increased in early HN progression and then gradually declined below the baseline level. We identified the impaired activity of the NRF2-activated antioxidant pathway as a driver of oxidative damage in HN progression. Through nrf2 deletion, we further confirmed aggravated kidney damage in nrf2 knockout HN mice compared with HN mice. In contrast, the pharmacological agonist of NRF2 improved kidney function and alleviated renal fibrosis in mice. Mechanistically, the activation of NRF2 signaling reduced oxidative stress by restoring mitochondrial homeostasis and reducing NADPH oxidase 4 (NOX4) expression in vivo or in vitro. Moreover, the activation of NRF2 promoted the expression levels of heme oxygenase 1 (HO-1) and quinone oxidoreductase 1 (NQO1) and enhanced the antioxidant capacity of cells. Furthermore, the activation of NRF2 ameliorated renal fibrosis in HN mice through the downregulation of the transforming growth factor-beta 1 (TGF-β1) signaling pathway and ultimately delayed the progression of HN. Collectively, these results suggested NRF2 as a key regulator in improving mitochondrial homeostasis and fibrosis in renal tubular cells by reducing oxidative stress, upregulating the antioxidant signaling pathway, and downregulating the TGF-β1 signaling pathway. The activation of NRF2 represents a promising strategy to restore redox homeostasis and combat HN.

Mechanistic insights of soluble uric acid-induced insulin resistance: Insulin signaling and beyond

Hyperuricemia is a metabolic disease caused by purine nucleotide metabolism disorder. The prevalence of hyperuricemia is increasing worldwide, with a growing trend in the younger populations. Although numerous studies have indicated that hyperuricemia may be an independent risk factor for insulin resistance, the causal relationship between the two is controversial. There are few reviews, however, focusing on the relationship between uric acid (UA) and insulin resistance from experimental studies. In this review, we summarized the experimental models related to soluble UA-induced insulin resistance in pancreas and peripheral tissues, including skeletal muscles, adipose tissue, liver, heart/cardiomyocytes, vascular endothelial cells and macrophages. In addition, we summarized the research advances about the key mechanism of UA-induced insulin resistance. Moreover, we attempt to identify novel targets for the treatment of hyperuricemia-related insulin resistance. Lastly, we hope that the present review will encourage further researches to solve the chicken-and-egg dilemma between UA and insulin resistance, and provide strategies for the pathogenesis and treatment of hyperuricemia related metabolic diseases.

Verniciflavanol A, a profisetinidin-type-4-arylflavan-3-ol from toxicodendron vernicifluum protects SH-SY5Y cells against H2O2-Induced oxidative stress

Eleven undescribed derivatives of flavan, including flavan-3,4-diols vernicinosides A-H and profisetinidin-type-4-arylflavan-3-ols verniciflavanols A-C, together with eight known compounds were purified from the heartwood of Toxicodendron vernicifluum. The chemical structures of the undescribed compounds were characterized by spectroscopic data interpretation, including NMR (¹H and ¹³C NMR HSQC and HMBC) and HRESIMS analysis. CD data analysis was conducted to assign the absolute configurations of the undescribed compounds and the active compound verniciflavanol A was also confirmed by ECD experiment. The absolute configuration of the sugar moiety was identified by GC analysis of chiral derivatives in the hydrolysate. MTT assay was applied to test these compounds against H₂O₂-induced oxidative stress in human neuroblastoma SH-SY5Y cells. Results found that verniciflavanol A demonstrated the best potential in protecting SH-SY5Y cells against H₂O₂-induced oxidative stress by inhibiting cell apoptosis and attenuate reactive oxygen species (ROS) level and mitochondrial dysfunction. And the underlying mechanism was confirmed to be associated with Nrf2-antioxidant response element signaling and IL-6 cell survival pathways.

Ganoderma lucidum polysaccharide peptide alleviates hyperuricemia by regulating adenosine deaminase and urate transporters

Hyperuricemia (HUA) affects human health and is involved in the pathogenesis of common chronic diseases. Previous studies showed that Ganoderma lucidum extract lowered HUA in animals. However, the active ingredient and pharmacological mechanism of Ganoderma lucidum extract in the improvement of HUA are unknown. The purpose of this study was to determine the anti-HUA efficacy and related mechanism of Ganoderma lucidum polysaccharide peptide (GLPP) using a potassium oxonate (PO)-induced mouse model and an adenosine-induced cell model. The experimental results showed that blood uric acid (UA) was decreased up to 40.6% by GLPP in HUA mice in a dose-dependent manner. Additionally, GLPP significantly reduced UA production by inhibiting the hepatic and blood adenosine deaminase (ADA) activity and increased UA excretion by decreasing the expression of glucose transporter 9 (GLUT9) and increasing the expression of organic anion transporter 1 (OAT1) in kidney. The adenosine-induced cell model showed that the inhibitory effect of GLPP on ADA activity may be the main reason for the alleviation of HUA by GLPP. Furthermore, PO-induced renal histopathological damage was also alleviated by GLPP in a dose-dependent manner. The experimental results in this study indicated that GLPP exerted anti-HUA effects via regulating the UA production and excretion, suggesting that GLPP could be developed into a therapeutic agent for HUA.

Thioredoxin-interacting protein deficiency protects against severe acute pancreatitis by suppressing apoptosis signal-regulating kinase 1

Acute pancreatitis is a common acute inflammatory abdominal disease. When acute pancreatitis progresses to severe acute pancreatitis (SAP), it can lead to systemic inflammation and even multiple organ failure. Thioredoxin-interacting protein (TXNIP) is an important protein involved in redox reactions of the inflammatory response. However, the specific role of TXNIP in SAP remains unclear. In this study, we investigated the role of thioredoxin interacting protein (TXNIP) in acute pancreatitis when induced by high doses of arginine. We found that pancreatic damage and the inflammatory response associated with acute pancreatitis were largely restrained in TXNIP knock-out mice but were enhanced in mice overexpressing TXNIP. Interestingly, the phosphorylation of p38, JNK, and ASK1 diminished in TXNIP-KO mice with pancreatitis in comparison with wild-type mice. The role of oxidative stress in SAP was explored in two models: TXNIP and AVV-TXNIP. TXNIP knockdown or the inhibition of ASK1 by gs-4997 abrogated the increase in p-p38, p-JNK, and p-ASK1 in AR42J cells incubated with L-Arg. The administration of gs-4997 to mice with pancreatitis largely reduced the upregulation of IL-6, IL-1β, TNF-α, and MCP-1. Systemic inflammatory reactions and injury in the lungs and kidneys were assessed in TXNIP-KO and AVV-TXNIP mice with expected outcomes. In conclusion, TXNIP is a novel mediator of SAP and exerts action by regulating inflammatory responses and oxidative stress via the ASK1-dependent activation of the JNK/p38 pathways. Thus, targeting TXNIP may represent a promising approach to protect against SAP.

A diarylheptanoid compound from Alpinia officinarum Hance ameliorates high glucose-induced insulin resistance by regulating PI3K/AKT-Nrf2-GSK3β signaling pathways in HepG2 cells

ETHNOPHARMACOLOGICAL RELEVANCE

Alpinia officinarum Hance, a perennial natural medicine-food herb, has been traditionally used to treat colds, stomachache, and diabetes for thousands of years. 1,7-Diphenyl-4E-en-3-heptanone (DPH5), a diarylheptanoid isolated from the rhizome of A. officinarum has been reported to be safe and to have antioxidant and hypoglycemic effects, suggesting its potential in the treatment of insulin resistance (IR).

AIM OF THE STUDY

Aim of to investigate the protective effect of DPH5 on IR and elucidate its underlying mechanism of action.

MATERIALS AND METHODS

HepG2 cells were used as the research objects. Glucose uptake and reactive oxygen species (ROS) levels in high glucose-induced insulin-resistant HepG2 cells were assessed using flow cytometry. Glucose consumption and the levels of malondialdehyde (MDA) and superoxide dismutase (SOD) were analyzed using the corresponding assay kits. The expression of mRNA and proteins related to insulin signaling, glucose metabolism, and antioxidant factor, including insulin receptor substrate-1 (IRS1), phosphatidylinositol 3-kinase (PI3K), protein kinase B (AKT), translocation of glucose transporter-4, glycogen synthase kinase-3β (GSK3β), glucokinase (GCK), pyruvate kinase (PK), phosphoenolpyruvate carboxykinase (PEPCK), glucose-6-phosphatase (G6Pase), nuclear factor-erythroid 2 related factor 2 (Nrf2), heme oxygenase-1 (HO-1), NADPH quinoneoxidoreductase (NQO1), and glutathione peroxidase (GSH-Px) was determined using real-time quantitative polymerase chain reaction and western blotting. Furthermore, molecular docking was performed to determine the spatial mechanism of DPH5 on the key targets PI3K, AKT, Nrf2, and GSK3β.

RESULTS

DPH5 could improve IR that manifested as increased glucose uptake and glucose consumption in insulin-resistant HepG2 cells. Moreover, DPH5 could enhance antioxidant capacity by activating Nrf2/HO-1 elements, including increasing Nrf2, HO-1, SOD, NQO1, and GSH-Px expression and reducing MDA, ROS, and JNK levels, thereby improving oxidative stress and ultimately alleviating IR. Additionally, DPH5 could promote the expression of IRS1, PI3K, AKT, GSK3β, GCK, and PK, and downregulate the expression of PEPCK and G6pase, thereby accelerating glucose utilization and enhancing insulin sensitivity. The mechanism underlying the effect of DPH5 in alleviating IR was related to the PI3K/AKT- and Nrf2/HO-1-mediated regulation of the GSK3β signaling pathway, and the results were further confirmed using the specific inhibitors LY294002 and ML385. Results from molecular docking indicated that there were different regulatory sites and interacting forces between DPH5 and PI3K, AKT, Nrf2, and GSK3β; however, the binding force was relatively strong.

CONCLUSIONS

DPH5 improved oxidative stress and glucose metabolism via modulating the PI3K/AKT-Nrf2-GSK3β pathway, thereby ameliorating IR. Overall, our findings suggest the potential of DPH5 as a natural medicine to treat type-2 diabetes mellitus.

Roles of NRF2 in Fibrotic Diseases: From Mechanisms to Therapeutic Approaches

Fibrosis is a persistent inflammatory response that causes scarring and tissue sclerosis by stimulating myofibroblasts to create significant quantities of extracellular matrix protein deposits in the tissue. Oxidative stress has also been linked to the development of fibrosis in several studies. The nuclear erythroid 2-related factor 2 (NRF2) transcription factor controls the expression of several detoxification and antioxidant genes. By binding to antioxidant response elements, NRF2 is activated by oxidative or electrophilic stress and promotes its target genes, resulting in a protective effect on cells. NRF2 is essential for cell survival under oxidative stress conditions. This review describes Kelch-like epichlorohydrin-associated protein 1 (KEAP1)/NRF2 signaling mechanisms and presents recent research advances regarding NRF2 and its involvement in primary fibrotic lesions such as pulmonary fibrosis, hepatic fibrosis, myocardial fibrosis, and renal fibrosis. The related antioxidant substances and drugs are described, along with the mechanisms by which KEAP1/NRF2 regulation positively affects the therapeutic response. Finally, the therapeutic prospects and potential value of NRF2 in fibrosis are summarized. Further studies on NRF2 may provide novel therapeutic approaches for fibrosis.

Hyperuricemia contributes to glucose intolerance of hepatic inflammatory macrophages and impairs the insulin signaling pathway via IRS2-proteasome degradation

AIM

Numerous reports have demonstrated the key importance of macrophage-elicited metabolic inflammation in insulin resistance (IR). Our previous studies confirmed that hyperuricemia or high uric acid (HUA) treatment induced an IR state in several peripheral tissues to promote the development of type 2 diabetes mellitus (T2DM). However, the effect of HUA on glucose uptake and the insulin sensitivity of macrophages and its mechanism is unclear.

METHODS

To assess systemic IR, we generated hyperuricemic mice by urate oxidase knockout (UOX-KO). Then, glucose/insulin tolerance, the tissue uptake of 18F-fluorodeoxyglucose, body composition, and energy balance were assessed. Glucose uptake of circulating infiltrated macrophages in the liver was evaluated by glucose transporter type 4 (GLUT-4) staining. Insulin sensitivity and the insulin signaling pathway of macrophages were demonstrated using the 2-NBDG kit, immunoblotting, and immunofluorescence assays. The immunoprecipitation assay and LC-MS analysis were used to determine insulin receptor substrate 2 (IRS2) levels and its interacting protein enrichment under HUA conditions.

RESULTS

Compared to WT mice (10 weeks old), serum uric acid levels were higher in UOX-KO mice (WT, 182.3 ± 5.091 μM versus KO, 421.9 ± 45.47 μM). Hyperuricemic mice with metabolic disorders and systemic IR showed inflammatory macrophage recruitment and increased levels of circulating proinflammatory cytokines. HUA inhibited the nuclear translocation of GLUT-4 in hepatic macrophages, restrained insulin-induced glucose uptake and glucose tolerance, and blocked insulin IRS2/PI3K/AKT signaling. Meanwhile, HUA mediated the IRS2 protein degradation pathway and activated AMPK/mTOR in macrophages. LC-MS analysis showed that ubiquitination degradation could be involved in IRS2 and its interacting proteins to contribute to IR under HUA conditions.

CONCLUSION

The data suggest that HUA-induced glucose intolerance in hepatic macrophages contributed to insulin resistance and impaired the insulin signaling pathway via IRS2-proteasome degradation.

Activation of p62-NRF2 Axis Protects against Doxorubicin-Induced Ferroptosis in Cardiomyocytes: A Novel Role and Molecular Mechanism of Resveratrol

Doxorubicin (DOX) is a most common anthracycline chemotherapeutic agent; however, its clinical efficacy is limited due to its severe and irreversible cardiotoxicity. Ferroptosis, characterized by iron overload and lipid peroxidation, plays a pivotal role in DOX-induced cardiotoxicity. Resveratrol (RSV) displays cardioprotective and anticancer effects, owing to its antioxidative and anti-inflammatory properties. However, the role and mechanism of RSV in DOX-mediated ferroptosis in cardiomyocytes is unclear. This study showed that DOX decreased cell viability, increased iron accumulation and lipid peroxidation in H9c2 cells; however, these effects were reversed by RSV and ferroptosis inhibitor ferrostatin-1 (Fer-1) pre-treatment. Additionally, RSV significantly increased the cell viability of H9c2 cells treated with ferroptosis inducers Erastin (Era) and RSL3. Mechanistically, RSV inhibited mitochondrial reactive oxygen species (mtROS) overproduction and upregulated the p62-NRF2/HO-1 pathway. RSV-induced NRF2 activation was partially dependent on p62, and the selective inhibition of p62 (using p62-siRNA interference) or NRF2 (using NRF2 specific inhibitor, ML385) significantly abolished the anti-ferroptosis function of RSV. Furthermore, RSV treatment protected mice against DOX-induced cardiotoxicity, including significantly improving left ventricular function, ameliorating myocardial fibrosis and suppressing ferroptosis. Consistent with in vitro results, RSV also upregulated the p62-NRF2/HO-1 expression, which was inhibited by DOX, in the myocardium. Notably, the protective effect of RSV in DOX-mediated ferroptosis was similar to that of Fer-1 in vitro and in vivo. Thus, the p62-NRF2 axis plays a critical role in regulating DOX-induced ferroptosis in cardiomyocytes. RSV as a potent p62 activator has potential as a therapeutic target in preventing DOX-induced cardiotoxicity via ferroptosis modulation.