ER stress and inflammation crosstalk in obesity

Reductive stress: The key pathway in metabolic disorders induced by overnutrition

BACKGROUND

The balance of redox states is crucial for maintaining physiological homeostasis. For decades, the focus has been mainly on the concept of oxidative stress, which is involved in the mechanism of almost all diseases. However, robust evidence has highlighted that reductive stress, the other side of the redox spectrum, plays a pivotal role in the development of various diseases, particularly those related to metabolism and cardiovascular health.

AIM OF REVIEW

In this review, we present an extensive array of evidence for the occurrence of reductive stress and its significant implications mainly in metabolic and cardiovascular diseases.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Reductive stress is defined as a shift in the cellular redox balance towards a more reduced state, characterized by an excess of endogenous reductants (such as NADH, NADPH, and GSH) over their oxidized counterparts (NAD+, NADP+, and GSSG). While oxidative stress has been the predominant mechanism studied in obesity, metabolic disorders, and cardiovascular diseases, growing evidence underscores the critical role of reductive stress. This review discusses how reductive stress contributes to metabolic and cardiovascular pathologies, emphasizing its effects on key cellular processes. For example, excessive NADH accumulation can disrupt mitochondrial function by impairing the electron transport chain, leading to decreased ATP production and increased production of reactive oxygen species. In the endoplasmic reticulum (ER), an excess of reductive equivalents hampers protein folding, triggering ER stress and activating the unfolded protein response, which can lead to insulin resistance and compromised cellular homeostasis. Furthermore, we explore how excessive antioxidant supplementation can exacerbate reductive stress by further shifting the redox balance, potentially undermining the beneficial effects of exercise, impairing cardiovascular health, and aggravating metabolic disorders, particularly in obese individuals. This growing body of evidence calls for a reevaluation of the role of reductive stress in disease pathogenesis and therapeutic interventions.

Daphnetin ameliorates diabetic cardiomyopathy by regulating inflammation and endoplasmic reticulum stress-induced apoptosis

Daphnetin has been demonstrated to exert beneficial effects on diabetes mellitus and renal complications. However, the role and molecular mechanism of daphnetin in diabetic cardiomyopathy (DCM) remain unclear. In this study, rats were injected with streptozotocin (STZ) to induce diabetes. The diabetic rats were then administered daphnetin (1 and 4 mg/kg) or dimethyl sulfoxide (DMSO) daily for 12 weeks. The results demonstrated that the diabetic rats exhibited elevated blood glucose levels, which were dose-dependently ameliorated by daphnetin. At 13 weeks following STZ injection, the rats exhibited typical diabetic signs, cardiac dysfunction, and evident pathological alterations in myocardial tissues. The administration of daphnetin to diabetic rats resulted in improvement in cardiac function, reductions in myocardial injury biomarkers, and the inhibition of myocardial fibrosis. Furthermore, daphnetin treatment suppressed inflammation and endoplasmic reticulum stress-induced apoptosis in a dose-dependent manner. Additionally, daphnetin exhibited partial blockade of the activation of mitogen-activated protein kinase pathways induced by diabetes. These findings indicate that daphnetin may be a promising therapeutic agent for the treatment of DCM.

Activation of protein kinase B rescues against thapsigargin-elicited cardiac dysfunction through regulation of NADPH oxidase and ferroptosis

Endoplasmic reticulum (ER) stress is a known contributor to cardiac remodeling and contractile dysfunction. Although NADPH oxidase has been implicated in ER stress-induced organ damage, its specific role in myocardial complications resulting from ER stress remains unclear. This study aimed to investigate the possible involvement of NADPH oxidase in ER stress-induced myocardial abnormalities and to evaluate the impact of Akt constitutive activation on these myocardial defects. Mice with cardiac-specific overexpression of active mutant of Akt (Myr-Akt) and their wild-type (WT) littermates were treated with ER stress instigator thapsigargin (1 mg/kg, i. p. 72 hrs) before evaluating myocardial morphology and function. Our results noted that thapsigargin significantly impaired echocardiographic parameters and cell shortening indices, including elevated LVESD, decreased ejection fraction, fractional shortening, peak shortening, electrically-stimulated intracellular Ca2+ release, and cardiomyocyte survival. These functional deteriorations were accompanied by upregulation of NADPH oxidase, O2- production, mitochondrial damage, carbonyl formation, lipid peroxidation, apoptosis, and interstitial fibrosis, with unchanged myocardial size. Constitutive Akt hyperactivation did not generate any response on myocardial morphology and function, although it greatly suppressed or nullified thapsigargin-induced myocardial remodeling and dysfunction. Thapsigargin also triggered dephosphorylation of Akt and its downstream signal GSK3β, along with development of ferroptosis, all of which were nullified by Akt hyperactivation. In vitro studies further revealed that thapsigargin provoked cardiomyocyte mechanical anomalies and lipid peroxidation, similar to in vivo results. These effects were reverted by inhibitors of NADPH oxidase and ferroptosis (apocynin and LIP1). Collectively, our data denote an important protective role for Akt hyperactivation in thapsigargin-evoked myocardial anomalies, likely through NADPH oxidase-mediated regulation of ferroptosis.

Folic Acid Prevents High-Fat Diet-Induced Postpartum Weight Retention in Rats, Which Is Associated with a Reduction in Endoplasmic Reticulum Stress-Mediated Hepatic Lipogenesis

BACKGROUND

Proactively preventing postpartum weight retention (PPWR) is one of the effective intervention strategies to reduce the occurrence of obesity in women. Population studies have shown that serum folate levels are closely related to body weight. The regulation of folic acid on lipid metabolism has been fully confirmed in both in vivo and in vitro studies. For many years, folic acid supplementation has been widely used in periconceptional women due to its role in preventing fetal neural tube defects. However, whether folic acid supplementation prior to and throughout pregnancy exerts preventive effects on PPWR remains uncertain. This study aims to investigate the preventive effect of folic acid on PPWR in rats and further explore the underlying mechanisms.

METHODS

In this study, pregnant rats were administered one of the dietary schedules: control diet (CON), high-fat diet (HF), control diet combined with folic acid (FA) and high-fat diet combined with folic acid (HF + FA).

RESULTS

We discovered that folic acid supplementation inhibited high-fat diet-induced elevations in body weight, visceral fat weight, liver weight, hepatic lipid levels and serum lipid levels at 1 week post-weaning (PW). Western blot analysis showed that folic acid supplementation inhibited the expression of endoplasmic reticulum (ER) stress-specific proteins including GRP78, PERK, eIF2α, IRE1α, XBP1 and ATF6, subsequently decreasing the expression of proteins related to lipid synthesis including SREBP-1c, ACC1 and FAS.

CONCLUSIONS

In conclusion, folic acid supplementation prior to and throughout pregnancy exerts preventive effects on high-fat diet-induced PPWR in rats, and the mechanism is associated with the inhibition of ER stress-mediated lipogenesis signaling pathways in the liver. Folic acid supplementation may serve as a potential strategy for preventing PPWR. In the future, the effectiveness of folic acid in PPWR prevention can be further verified by population studies.

Reticulophagy promotes EMT-induced fibrosis in offspring's lung tissue after maternal exposure to carbon black nanoparticles during gestation by a m5C-dependent manner

Accumulating evidence indicates that maternal exposure to carbon black nanoparticles (CBNPs) during gestation can induce multiple system abnormalities in offspring, whereas its potential mechanism in respiratory disease is still largely unknown. In order to explore the effect of maternal exposure to CBNPs on offspring's lung and latent pathogenesis, we respectively established in vivo model of pregnant rats exposed to CBNPs and ex vivo model of lung epithelial cells treated with pups' serum of pregnant rats exposed to CBNPs. After maternal exposure to CBNPs, epithelial-mesenchymal transition (EMT) and fibrosis levels increased as a result of DDRGK1-mediated reticulophagy upregulated in offspring's lung. DDRGK1 as FAM134B's cargo bound with FAM134B to mediate reticulophagy. Transcription factor "SP1" positively regulated DDRGK1 gene expression by binding to its promoter. Furthermore, the upregulation of NSUN2 elevated m5C methylation of SP1 mRNA and the protein level of SP1 subsequently increased through Ybx1 recognizing and stabilizing m5C-methylated SP1 mRNA, followed by the increased levels of reticulophagy and fibrosis in lung epithelial cells treated with offspring's serum of matrix exposed to CBNPs during gestation. In conclusion, NSUN2/Ybx1/m5C-SP1 axis promoted DDRGK1-mediated reticulophagy, which played an important role in EMT-induced fibrosis in offspring's lung tissue after maternal exposure to CBNPs during gestation.

Efficient light-induced reactive oxygen species production from a far-red ER-targeting BODIPY dye

Generation of reactive oxygen species (ROS) within the ER evokes stress leading to immunogenic cell death. A red light activated BODIPY dye capable of subcellular localization within the ER producing high quantum yields of ROS is reported. The ability of this dye to act as a photodynamic therapy (PDT) agent in breast cancer cells suggests promising organelle-targeted therapeutics.

New insights of DsbA-L in the pathogenesis of metabolic diseases

Metabolic diseases, such as obesity, diabetes mellitus, and non-alcoholic fatty liver disease (NAFLD), are abnormal conditions that result from disturbances of metabolism. With the improvement of living conditions, the morbidity and mortality rates of metabolic diseases are steadily rising, posing a significant threat to human health worldwide. Therefore, identifying novel effective targets for metabolic diseases is crucial. Accumulating evidence has indicated that disulfide bond A oxidoreductase-like protein (DsbA-L) delays the development of metabolic diseases. However, the underlying mechanisms of DsbA-L in metabolic diseases remain unclear. In this review, we will discuss the roles of DsbA-L in the pathogenesis of metabolic diseases, including obesity, diabetes mellitus, and NAFLD, and highlight the potential mechanisms. These findings suggest that DsbA-L might provide a novel therapeutic strategy for metabolic diseases.

Zhimu-Huangbai herb-pair ameliorates hepatic steatosis in mice by regulating IRE1α/XBP1s pathway to inhibit SREBP-1c

BACKGROUND

Currently, there is a lack of validated pharmacological interventions for non-alcoholic fatty liver disease (NAFLD), which is characterized by the accumulation of hepatic triglyceride. Zhimu-Huangbai (ZH) herb-pair is a traditional Chinese medicine that regulates glucose and lipid metabolism disorders. However, the precise mechanisms underlying the preventive effects of hepatic triglyceride induced by high-fat diet (HFD) remain elusive.

PURPOSE

The study aimed to examine the impact of ZH herb-pair on NAFLD in mice and explore the underlying mechanisms, particularly its effects on endoplasmic reticulum (ER) stress and lipid metabolism.

METHODS

NAFLD was induced in mice using HFD, and the treated mice were orally administered ZH, metformin (Glucophage) or lovastatin. The lipid metabolism factors, ER stress markers, and the unfolded protein response (UPR) branch factors were measured using immunohistochemistry, western blotting or qRT-PCR. Co-Immunoprecipitation (CoIP) was performed to reveal the connection between SCAP and SREBP-1c. Tunicamycin (TM) and plasmid delivery were used to induce acute ER stress or crease XBP1 gain function models. The main compounds in ZH binding to IRE1α protein were studied by molecular docking and cellular thermal shift assay (CETSA).

RESULTS

Treatment with ZH significantly ameliorated hepatic steatosis and reduced lipid synthesis process mainly inhibiting the expression of mature active form of SREBP-1c through relieving ER stress. The expression of IRE1α and XBP1s was inhibited after treatment with ZH. In addition, ZH improved the fatty liver phenotype caused by XBP1 overexpression via decreasing srebp1c transcription. In vitro experimental results suggested that the main compounds in ZH decreased cellular TG contents. Mechanistically, ZH targeted IRE1α and inhibited XBP1s mRNA expression to relieve ER stress and inhibit SREBP-1c production.

CONCLUSIONS

ZH herb-pair can protect against NAFLD by reducing the expression of SREBP-1c, in part, via regulating IRE1α/XBP1s pathway.

PTP1B inhibitor alleviates deleterious septic lung injury through Src signaling

Septic lung injury is an unmet clinical challenge due to its high mortality, and there is a lack of effective treatment. Accumulating evidence suggests that an uncontrolled pulmonary inflammatory response is important in the pathogenesis of lung injury in sepsis. Therefore, limiting excessive early inflammatory responses may be an effective strategy. We established a septic lung injury model using cecal ligation and puncture. Western blotting and immunofluorescence analyses were performed to assess the expression of PTP1B and endoplasmic reticulum (ER) stress and pyroptosis. Co-immunoprecipitation was used to analyze the binding of PTP1B and Src molecules. PTP1B is upregulated in both in vivo and in vitro models of septic lung injury. PTP1B directly binds to Src and aggravates inflammation by regulating the ER stress-pyroptosis axis. The inhibition of PTP1B alleviates inflammation and improves the prognosis of septic mice. Our study suggesting that PT1B inhibitors have clinical application value in the treatment of septic lung injury. This may provide a new strategy for the treatment of septic lung injury.

Excessive or sustained endoplasmic reticulum stress: one of the culprits of adipocyte dysfunction in obesity

As the prevalence of obesity continues to rise globally, the research on adipocytes has attracted more and more attention. In the presence of nutrient overload, adipocytes are exposed to pressures such as hypoxia, inflammation, mechanical stress, metabolite, and oxidative stress that can lead to organelle dysfunction. Endoplasmic reticulum (ER) is a vital organelle for sensing cellular pressure, and its homeostasis is essential for maintaining adipocyte function. Under conditions of excess nutrition, ER stress (ERS) will be triggered by the gathering of abnormally folded proteins in the ER lumen, resulting in the activation of a signaling response known as the unfolded protein responses (UPRs), which is a response system to relieve ERS and restore ER homeostasis. However, if the UPRs fail to rescue ER homeostasis, ERS will activate pathways to damage cells. Studies have shown a role for disturbed activation of adipocyte ERS in the pathophysiology of obesity and its complications. Prolonged or excessive ERS in adipocytes can aggravate lipolysis, insulin resistance, and apoptosis and affect the bioactive molecule production. In addition, ERS also impacts the expression of some important genes. In view of the fact that ERS influences adipocyte function through various mechanisms, targeting ERS may be a viable strategy to treat obesity. This article summarizes the effects of ERS on adipocytes during obesity.

Inhibiting endoplasmic reticulum stress alleviates perioperative neurocognitive disorders by reducing neuroinflammation mediated by NLRP3 inflammasome activation

AIM

The aim of this study is to explore the key mechanisms of perioperative neurocognitive dysfunction (PND) after anesthesia/surgery (A/S) by screening hub genes.

METHODS

Transcriptome sequencing was conducted on hippocampal samples obtained from 18-month-old C57BL/6 mice assigned to control (Ctrl) and A/S groups. The functionality of differentially expressed genes (DEGs) was investigated using Metascape. Hub genes associated with changes between the two groups were screened by combining weighted gene coexpression network analysis within CytoHubba. Reverse transcription PCR and western blotting were used to validate changes in mRNA and protein expression, respectively. NLRP3 inflammasome activation was detected by western blotting and ELISA. Tauroursodeoxycholic acid (TUDCA), an inhibitor of endoplasmic reticulum (ER) stress, was administrated preoperatively to explore its effects on the occurrence of PND. Immunofluorescence analysis was performed to evaluate the activation of astrocytes and microglia in the hippocampus, and hippocampus-dependent learning and memory were assessed using behavioral experiments.

RESULTS

In total, 521 DEGs were detected between the control and A/S groups. These DEGs were significantly enriched in biological processes related to metabolic processes and their regulation. Four hub genes (Hspa5, Igf1r, Sfpq, and Xbp1) were identified. Animal experiments have shown that mice in the A/S group exhibited cognitive impairments accompanied by increased Hspa5 and Xbp1 expression, ER stress, and activation of NLRP3 inflammasome.

CONCLUSIONS

Inhibiting ER stress alleviated cognitive impairment in A/S mice; particularly, ER stress induced by A/S results in NLRP3 inflammasome activation and neuroinflammation. Moreover, the preoperative administration of TUDCA inhibited ER stress, NLRP3 inflammasome activation, and neuroinflammation.

Association of systemic immune-inflammation index with body mass index, waist circumference and prevalence of obesity in US adults

This study aims to investigate the potential relationships between the systemic immune-inflammation index (SII) and body mass index (BMI), waist circumference, and the prevalence of obesity. A cross-sectional analysis was conducted on 7,645 individuals aged 20 and above from the NHANES 2017-2020. Multivariate linear regression analyses were conducted to evaluate the association of the logarithmically transformed SII (lgSII) with BMI and waist circumference. Additionally, multivariable logistic regression was utilized to explore the relationship between lgSII and the prevalence of obesity. Fitted smoothing curves and threshold-effect analysis were applied to elucidate nonlinear relationships. In the fully adjusted model, a positive relationship was observed between lgSII and BMI, waist circumference, and obesity prevalence (β = 3.13, 95% CI 2.10-4.16; β = 7.81, 95% CI 5.50-10.13; OR = 1.44, 95% CI 1.12-1.86). The variables of gender, age, race, education, marital status, poverty income ratio (PIR), energy intake, sleep disorder, smoking status, and alcohol use did not significantly modify the positive association between lgSII and obesity. However, physical activity appeared to influence the positive correlation between lgSII and obesity. Using a two-segment linear regression model, an inverted U-shaped relationship was observed between lgSII and both BMI and waist circumference. Furthermore, lgSII demonstrated a linear positive correlation with obesity prevalence. When stratified by physical activity, lgSII showed a non-significant negative correlation with obesity in the physically active group. Our findings underscore a robust association between the logarithmically transformed SII and BMI, waist circumference, and the prevalence of obesity.

Inhibition of ER stress using tauroursodeoxycholic acid rescues obesity-evoked cardiac remodeling and contractile anomalies through regulation of ferroptosis

Interrupted ER homeostasis contributes to the etiology of obesity cardiomyopathy although it remains elusive how ER stress evokes cardiac anomalies in obesity. Our study evaluated the impact of ER stress inhibition on cardiac anomalies in obesity. Lean and ob/ob obese mice received chemical ER chaperone tauroursodeoxycholic acid (TUDCA, 50 mg/kg/d, p.o.) for 35 days prior to evaluation of glucose sensitivity, echocardiographic, myocardial geometric, cardiomyocyte mechanical and subcellular Ca2+ property, mitochondrial integrity, oxidative stress, apoptosis, and ferroptosis. Intracellular Ca2+ governing domains including sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) were monitored by45Ca2+uptake and immunoblotting. Our results noted that TUDCA alleviated myocardial remodeling (fibrosis, hypertrophy, enlarged LVESD), echocardiographic anomalies (compromised fractional shortening and ejection fraction), cardiomyocyte contractile dysfunction (amplitude and velocity of cell shortening, relengthening time) and intracellular Ca2+ anomalies (compromised subcellular Ca2+ release, clearance and SERCA function), mitochondrial damage (collapsed membrane potential, downregulated mitochondrial elements and ultrastructural alteration), ER stress (GRP78, eIF2α and ATF4), oxidative stress, apoptosis and ferroptosis [downregulated SLC7A11, GPx4 and upregulated transferrin receptor (TFRC)] without affecting global glucose sensitivity and serum Fe2+ in obese mice. Obesity-evoked change in HSP90, phospholamban and Na+-Ca2+ exchanger was spared by the chemical ER chaperone. Moreover, in vitro results noted that TUDCA, PERK inhibitor GSK2606414, TFRC neutralizing antibody and ferroptosis inhibitor LIP1 mitigated palmitic acid-elicited changes in lipid peroxidation and mechanical function. Our findings favored a role for ferroptosis in obesity cardiomyopathy downstream of ER stress.

Obesity and lipid metabolism in the development of osteoporosis (Review)

Osteoporosis is a common bone metabolic disease that causes a heavy social burden and seriously threatens life. Improving osteogenic capacity is necessary to correct bone mass loss in the treatment of osteoporosis. Osteoblasts are derived from the differentiation of bone marrow mesenchymal stem cells, a process that opposes adipogenic differentiation. The peroxisome proliferator‑activated receptor γ and Wnt/β‑catenin signaling pathways mediate the mutual regulation of osteogenesis and adipogenesis. Lipid substances play an important role in the occurrence and development of osteoporosis. The content and proportion of lipids modulate the activity of immunocytes, mainly macrophages, and the secretion of inflammatory factors, such as IL‑1, IL‑6 and TNF‑α. These inflammatory effectors increase the activity and promote the differentiation of osteoclasts, which leads to bone imbalance and stronger bone resorption. Obesity also decreases the activity of antioxidases and leads to oxidative stress, thereby inhibiting osteogenesis. The present review starts by examining the bidirectional differentiation of BM‑MSCs, describes in detail the mechanism by which lipids affect bone metabolism, and discusses the regulatory role of inflammation and oxidative stress in this process. The review concludes that a reasonable adjustment of the content and proportion of lipids, and the alleviation of inflammatory storms and oxidative damage induced by lipid imbalances, will improve bone mass and treat osteoporosis.

Ntsr1 contributes to pulmonary hypertension by enhancing endoplasmic reticulum stress via JAK2-STAT3-Thbs1 signaling

Pulmonary hypertension (PH) is a severe clinical syndrome with pulmonary vascular remodeling and poor long-term prognosis. Neurotensin receptor 1 (Ntsr1), serve as one of the G protein-coupled receptors (GPCRs), implicates in various biological processes, but the potential effects of Ntsr1 in PH development are unclear. The Sugen/Hypoxia (SuHx) or monocrotaline (MCT) induced rat PH model was used in our study and the PH rats showed aggravated pulmonary artery remodeling and increased right ventricular systolic pressure (RVSP). Our results revealed that Ntsr1 induced endoplasmic reticulum (ER) stress response via ATF6 activation contributed to the development of PH. Moreover, RNA-sequencing (RNA-seq) and phosphoproteomics were performed and the Ntsr1-JAK2-STAT3-thrombospondin 1 (Thbs1)-ATF6 signaling was distinguished as the key pathway. In vitro, pulmonary artery smooth muscle cells (PASMCs) under hypoxia condition showed enhanced proliferation and migration properties, which could be inhibited by Ntsr1 knockdown, JAK2 inhibitor (Fedratinib) treatment, STAT3 inhibitior (Stattic) treatment, Thbs1 knockdown or ATF6 knockdown. In addition, adeno-associated virus 1 (AAV1) were used to knockdown the expression of Ntsr1, Thbs1 or ATF6 in rats and reversed the phenotype of PH. In summary, our results reveal that Ntsr1-JAK2-STAT3-Thbs1 pathway can induce enhanced ER stress via ATF6 activation and increased PASMC proliferation and migration capacities, which can be mechanism of the pulmonary artery remodeling and PH. Targeting Ntsr1 might be a novel therapeutic strategy to ameliorate PH.

The double whammy of ER-retention and dominant-negative effects in numerous autosomal dominant diseases: significance in disease mechanisms and therapy

The endoplasmic reticulum (ER) employs stringent quality control mechanisms to ensure the integrity of protein folding, allowing only properly folded, processed and assembled proteins to exit the ER and reach their functional destinations. Mutant proteins unable to attain their correct tertiary conformation or form complexes with their partners are retained in the ER and subsequently degraded through ER-associated protein degradation (ERAD) and associated mechanisms. ER retention contributes to a spectrum of monogenic diseases with diverse modes of inheritance and molecular mechanisms. In autosomal dominant diseases, when mutant proteins get retained in the ER, they can interact with their wild-type counterparts. This interaction may lead to the formation of mixed dimers or aberrant complexes, disrupting their normal trafficking and function in a dominant-negative manner. The combination of ER retention and dominant-negative effects has been frequently documented to cause a significant loss of functional proteins, thereby exacerbating disease severity. This review aims to examine existing literature and provide insights into the impact of dominant-negative effects exerted by mutant proteins retained in the ER in a range of autosomal dominant diseases including skeletal and connective tissue disorders, vascular disorders, neurological disorders, eye disorders and serpinopathies. Most crucially, we aim to emphasize the importance of this area of research, offering substantial potential for understanding the factors influencing phenotypic variability associated with genetic variants. Furthermore, we highlight current and prospective therapeutic approaches targeted at ameliorating the effects of mutations exhibiting dominant-negative effects. These approaches encompass experimental studies exploring treatments and their translation into clinical practice.

Unraveling the unfolded protein response signature: implications for tumor immune microenvironment heterogeneity and clinical prognosis in stomach cancer

BACKGROUND

Stomach cancer is a leading cause of cancer-related deaths globally due to its high grade and poor response to treatment. Understanding the molecular network driving the rapid progression of stomach cancer is crucial for improving patient outcomes.

METHODS

This study aimed to investigate the role of unfolded protein response (UPR) related genes in stomach cancer and their potential as prognostic biomarkers. RNA expression data and clinical follow-up information were obtained from the TCGA and GEO databases. An unsupervised clustering algorithm was used to identify UPR genomic subtypes in stomach cancer. Functional enrichment analysis, immune landscape analysis, and chemotherapy benefit prediction were conducted for each subtype. A prognostic model based on UPR-related genes was developed and validated using LASSO-Cox regression, and a multivariate nomogram was created. Key gene expression analyses in pan-cancer and in vitro experiments were performed to further investigate the role of the identified genes in cancer progression.

RESULTS

A total of 375 stomach cancer patients were included in this study. Analysis of 113 UPR-related genes revealed their close functional correlation and significant enrichment in protein modification, transport, and RNA degradation pathways. Unsupervised clustering identified two molecular subtypes with significant differences in prognosis and gene expression profiles. Immune landscape analysis showed that UPR may influence the composition of the tumor immune microenvironment. Chemotherapy sensitivity analysis indicated that patients in the C2 molecular subtype were more responsive to chemotherapy compared to those in the C1 molecular subtype. A prognostic signature consisting of seven UPR-related genes was constructed and validated, and an independent prognostic nomogram was developed. The gene IGFBP1, which had the highest weight coefficient in the prognostic signature, was found to promote the malignant phenotype of stomach cancer cells, suggesting its potential as a therapeutic target.

CONCLUSIONS

The study developed a UPR-related gene classifier and risk signature for predicting survival in stomach cancer, identifying IGFBP1 as a key factor promoting the disease's malignancy and a potential therapeutic target. IGFBP1's role in enhancing cancer cell adaptation to endoplasmic reticulum stress suggests its importance in stomach cancer prognosis and treatment.

Endoplasmic reticulum stress: A possible connection between intestinal inflammation and neurodegenerative disorders

BACKGROUND

Different studies have shown the key role of endoplasmic reticulum (ER) stress in autoimmune and chronic inflammatory disorders, as well as in neurodegenerative diseases. ER stress leads to the formation of misfolded proteins which affect the secretion of different cell types that are crucial for the intestinal homeostasis.

PURPOSE

In this review, we discuss the role of ER stress and its involvement in the development of inflammatory bowel diseases, chronic conditions that can cause severe damage of the gastrointestinal tract, focusing on the alteration of Paneth cells and goblet cells (the principal secretory phenotypes of the intestinal epithelial cells). ER stress is also discussed in the context of neurodegenerative diseases, in which protein misfolding represents the signature mechanism. ER stress in the bowel and consequent accumulation of misfolded proteins might represent a bridge between bowel inflammation and neurodegeneration along the gut-to-brain axis, affecting intestinal epithelial homeostasis and the equilibrium of the commensal microbiota. Targeting intestinal ER stress could foster future studies for designing new biomarkers and new therapeutic approaches for neurodegenerative disorders.

A FRET-based multifunctional fluorescence probe for the simultaneous detection of sulfite and viscosity in living cells

Viscosity and sulfur dioxide derivatives were significant indicators for the assessment of health threat and even cancers, therefore, on-site and real time detection of viscosity and sulfur dioxide derivatives has obtained considerable attentions. An FRET-based fluorescence probe JZX was designed and synthesized based on a novel energy donor of N,N-diethyl-4-(1H-phenanthro[9,10-d]imidazol-2-yl)benzamide fluorophore. JZX exhibited a large Stokes shift (230 nm), high energy transfer efficiency, wide emission channel gap (135 nm) and excellent stability and biocompatibility. JZX detected sulfur dioxide with low detection limit (55 nM), fast responding (16 min), high selectivity and sensitivity. Additionally, JZX tend to target endoplasmic reticulum of which normal metabolism will be disturbed by the abnormal levels of viscosity and sulfur dioxide derivatives. Prominently, JZX could concurrently detect viscosity and sulfur dioxide derivatives depending on different fluorescence signals in living cells for the screening of cancer cells. Hence, probe JZX will be a promising candidate for the detection of viscosity and sulfur dioxide derivatives, and even for the diagnosis of liver cancers.

D-Allulose Reduces Hypertrophy and Endoplasmic Reticulum Stress Induced by Palmitic Acid in Murine 3T3-L1 Adipocytes

Natural rare sugars are an alternative category of sweeteners with positive physiologic and metabolic effects both in in vitro and animal models. D-allulose is a D-fructose epimer that combines 70% sucrose sweetness with the advantage of an extremely low energy content. However, there are no data about the effect of D-allulose against adipose dysfunction; thus, it remains to be confirmed whether D-allulose is useful in the prevention and in treatment of adipose tissue alterations. With this aim, we evaluated D-allulose's preventive effects on lipid accumulation in 3T3-L1 murine adipocytes exposed to palmitic acid (PA), a trigger for hypertrophic adipocytes. D-allulose in place of glucose prevented adipocyte hypertrophy and the activation of adipogenic markers C/EBP-β and PPARγ induced by high PA concentrations. Additionally, D-allulose pretreatment inhibited the NF-κB pathway and endoplasmic reticulum stress caused by PA, through activation of the Nrf2 pathway. Interestingly, these effects were also observed as D-allulose post PA treatment. Although our data need to be confirmed through in vivo models, our findings suggest that incorporating D-allulose as a glucose substitute in the diet might have a protective role in adipocyte function and support a unique mechanism of action in this sugar as a preventive or therapeutic compound against PA lipotoxicity through the modulation of pathways connected to lipid transport and metabolism.

Endoplasmic reticulum stress: bridging inflammation and obesity-associated adipose tissue

Obesity presents a significant global health challenge, increasing the susceptibility to chronic conditions such as diabetes, cardiovascular disease, and hypertension. Within the context of obesity, lipid metabolism, adipose tissue formation, and inflammation are intricately linked to endoplasmic reticulum stress (ERS). ERS modulates metabolism, insulin signaling, inflammation, as well as cell proliferation and death through the unfolded protein response (UPR) pathway. Serving as a crucial nexus, ERS bridges the functionality of adipose tissue and the inflammatory response. In this review, we comprehensively elucidate the mechanisms by which ERS impacts adipose tissue function and inflammation in obesity, aiming to offer insights into targeting ERS for ameliorating metabolic dysregulation in obesity-associated chronic diseases such as hyperlipidemia, hypertension, fatty liver, and type 2 diabetes.

The effect of quercetin on adipogenesis, lipolysis, and apoptosis in 3T3-L1 adipocytes: The role of SIRT1 pathways

Background

Lipotoxicity, caused by adipocyte triglyceride over-accumulation, contributes to obesity-related comorbidities such as hypertension, type 2 diabetes, coronary heart disease, respiratory dysfunction, and osteoarthritis. This study focuses on determining how sirtuin-1 (SIRT-1) mediates quercetin's (QCT) effect on 3T3-L1 adipocytes. Key aspects of this study include preventing adipogenesis, inducing lipolysis, and stimulating adipocyte apoptosis.

Methods

3T3-L1 adipocytes underwent treatment with varying QCT doses, lipopolysaccharide (LPS), and the SIRT-1 inhibitor EX-527, followed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide [MTT] assay for cell viability assessment. Furthermore, quantitative real-time polymerase chain reaction measured mRNA expression levels of adipogenesis markers (fatty acid synthase [FASN] and peroxisome proliferator-activated receptor gamma [PPARγ]), lipolysis markers (adipose triglyceride lipase [ATGL] and hormone-sensitive lipase [HSL]), and apoptosis markers (B-cell lymphoma2 [Bcl-2], Bcl-2 Associated -X-protein [BAX] and Caspase-3).

Results

The data showed that LPS + QCT significantly reduced cell viability in a dose- and time-dependent manner, unaffected by LPS + QCT + EX-527. Treatment with LPS + QCT did not affect FASN and PPARγ expression but significantly increased ATGL and HSL mRNA expression compared with LPS alone. Interestingly, EX-527 reversed the effects of LPS + QCT on lipogenesis and lipolysis markers completely. QCT enhanced apoptosis in a SIRT-1 independent pattern.

Conclusion

The data suggest that QCT suppresses adipogenesis while increasing lipolysis via SIRT-1. However, QCT's effects on apoptosis appear to be independent of SIRT-1. These findings provide further evidence for QCT's effects on adipocytes, particularly its interaction with SIRT-1.

Quercetin declines LPS induced inflammation and augments adiponectin expression in 3T3-L1 differentiated adipocytes SIRT-1 dependently

BACKGROUND

Inflammation is an important factor contributing to obesity-induced metabolic disorders. Different investigations confirm that local inflammation in adipose issues is the primary reason for such disorder, resulting in low-grade systemic inflammation. Anti-inflammatory, antioxidant, and epigenetic modification are among the varied properties of Quercetin (QCT) as a natural flavonoid.

OBJECTIVE

The precise molecular mechanism followed by QCT to alleviate inflammation has been unclear. This study explores whether the anti-inflammatory effects of QCT in 3T3-L1 differentiated adipocytes may rely on SIRT-1.

METHODS

The authors isolated 3T3-L1 pre-adipocyte cells and exposed them to varying concentrations of QCT, lipopolysaccharide (LPS), and a selective inhibitor of silent mating type information regulation 2 homolog 1 (SIRT-1) called EX-527. After determining the optimal dosages of QCT, LPS, and EX-527, they assessed the mRNA expression levels of IL-18, IL-1, IL-6, TNF-α, SIRT-1, and adiponectin using quantitative reverse transcription-polymerase chain reaction (qRT-PCR).

RESULTS

The study showed considerable cytotoxic effects of LPS (200 ng/mL) + QCT (100 µM) + EX-527 (10 µM) on 3T3-L1 differentiated adipocytes after 48 h of incubation. QCT significantly upregulated the expression levels of adiponectin and SIRT-1 (p < 0.0001). However, introducing SIRT-1 inhibitor (p < 0.0001) reversed the impact of QCT on adiponectin expression. Additionally, QCT reduced SIRT-1-dependent pro-inflammatory cytokines in 3T3-L1 differentiated adipocytes (p < 0.0001).

CONCLUSION

This study revealed that QCT treatment reduced crucial pro-inflammatory cytokines levels and increased adiponectin levels following LPS treatment. This finding implies that SIRT-1 may be a crucial factor for the anti-inflammatory activity of QCT.

Drug targets regulate systemic metabolism and provide new horizons to treat nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH), is the advanced stage of nonalcoholic fatty liver disease (NAFLD) with rapidly rising global prevalence. It is featured with severe hepatocyte apoptosis, inflammation and hepatic lipogenesis. The drugs directly targeting the processes of steatosis, inflammation and fibrosis are currently under clinical investigation. Nevertheless, the long-term ineffectiveness and remarkable adverse effects are well documented, and new concepts are required to tackle with the root causes of NASH progression. We critically assess the recently validated drug targets that regulate the systemic metabolism to ameliorate NASH. Thermogenesis promoted by mitochondrial uncouplers restores systemic energy expenditure. Furthermore, regulation of mitochondrial proteases and proteins that are pivotal for intracellular metabolic homeostasis normalize mitochondrial function. Secreted proteins also improve systemic metabolism, and NASH is ameliorated by agonizing receptors of secreted proteins with small molecules. We analyze the drug design, the advantages and shortcomings of these novel drug candidates. Meanwhile, the structural modification of current NASH therapeutics significantly increased their selectivity, efficacy and safety. Furthermore, the arising CRISPR-Cas9 screen strategy on liver organoids has enabled the identification of new genes that mediate lipid metabolism, which may serve as promising drug targets. In summary, this article discusses the in-depth novel mechanisms and the multidisciplinary approaches, and they provide new horizons to treat NASH.

Methylparaben induces hepatic glycolipid metabolism disorder by activating the IRE1α-XBP1 signaling pathway in male mice

Methylparaben (MP), a preservative widely used in daily supplies, exists in both the environment and the human body. However, the potential health risks posed by MP remain unclear. This study aimed to unravel the mechanisms by which MP disrupts glucose and lipid homeostasis. For this, we administered MP to mice and observed changes in glucose and lipid metabolism. MP exposure led to hyperglycemia, hyperlipidemia, visceral organ injury, and hepatic lipid accumulation. RNA sequencing results from mice livers indicated a close association between MP exposure and endoplasmic reticulum (ER) stress, inflammatory response, and glucose and lipid homeostasis. Western blotting and quantitative reverse transcription-polymerase chain reaction revealed that MP activated ER stress, particularly the inositol-requiring enzyme 1 (IRE1)/X-box binding protein 1 (XBP1) pathway, which further promoted the activation of the nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) pathways. The activation of these pathways phosphorylated insulin receptor substrate-1 (IRS1) (ser 307), resulting in decreased phosphorylation of protein kinase B (Akt) (ser 473), leading to insulin resistance. Additionally, MP exposure promoted lipogenesis through ER stress. To explore potential remedies, we administered the ER stress inhibitor 4-phenylbutyric acid (4-PBA) and the IRE1α-XBP1 pathway inhibitor toyocamycin to mice, both of which protected against metabolic disorders and organ injury caused by MP. These findings suggest that MP induces disruptions in glucose and lipid metabolism through ER stress, primarily through the IRE1α-XBP1 pathway.

Adverse impacts of environmentally relevant PFOS alternatives on mice pancreatic tissues

Perfluorooctane sulfonate (PFOS) alternatives are chemicals that are used to make a range of products. Researchers have found that PFOS alternatives are probably no less toxic than PFOS, which has aroused concern. It has also revealed that the pancreas may be harmed by exposure to PFOS alternatives. However, there is insufficient evidence to demonstrate the toxicity mechanisms of PFOS alternatives. This study demonstrates the adverse effects of three PFOS alternatives on the pancreatic health of mice. After subchronic exposure to PFOS alternatives at environmentally relevant concentrations (800 μg/L perfluorohexanesulfonate, 800 μg/L perfluorobutanesulfonate, and 3 μg/L sodium ρ-perfluorous nonenoxybenzene sulfonate) via drinking water for 6 weeks, toxicity mechanisms were elucidated by examining histopathology, immunity, endoplasmic reticulum stress, 16S rRNA, and short-chain fatty acid targeted metabolomics. Sodium ρ-perfluorous nonenoxybenzene sulfonate significantly increased levels of TNF-α, IL-6, p-PERK, and ATF-4 and decreased the abundance of Akkermansia muciniphila and Lactobacillus reuteri. In addition, the three PFOS alternatives changed the composition of the gut microbiota in mice. Short-chain fatty acids, which are metabolites of the gut microbiota, also significantly decreased. Correlation analysis demonstrates that the alteration of gut microbes is related to the adverse effects on the mice pancreas. Results suggest that the murine pancreas may be toxic endpoints of PFOS alternatives. This study alerts the threats to human health and accelerates the toxicology research of an increasing number of emerging PFOS alternatives.

Bioinformatics-driven discovery of silica nanoparticles induces apoptosis and renal damage via the unfolded protein response in NRK-52E cells and rat kidney

Silica nanoparticles (SiNPs) are nanomaterials with widespread applications in drug delivery and disease diagnosis. Despite their utility, SiNPs can cause chronic kidney disease, hindering their clinical translation. The molecular mechanisms underlying SiNP-induced renal toxicity are complex and require further investigation. To address this challenge, we employed bioinformatics tools to predict the potential mechanisms underlying renal damage caused by SiNPs. We identified 1627 upregulated differentially expressed genes (DEGs) and 1334 downregulated DEGs. Functional enrichment analysis and protein-protein interaction network revealed that SiNP-induced renal damage is associated with apoptosis. Subsequently, we verified that SiNPs induced apoptosis in an in vitro model of NRK-52E cells via the unfolded protein response (UPR) in a dose-dependent manner. Furthermore, in an in vivo rat model, high-dose SiNP administration via tracheal drip caused hyalinization of the renal tubules, renal interstitial lymphocytic infiltration, and collagen fiber accumulation. Concurrently, we observed an increase in UPR-related protein levels at the onset of renal damage. Thus, our study confirmed that SiNPs induce apoptosis and renal damage through the UPR, adding to the theoretical understanding of SiNP-related kidney damage and offering a potential target for preventing and treating kidney injuries in SiNP clinical applications.

Gut microbiota-mediated IL-22 alleviates metabolic inflammation

Low-grade chronic inflammation, also known as metabolic inflammation, promotes the development of metabolic diseases. Increasing evidence suggests that changes in gut microbes and metabolites disrupt the integrity of the gut barrier and exert significant effects on the metabolism of various tissues, including the liver and adipose tissue, thereby contributing to metabolic inflammation. We observed that IL-22 is a key signaling molecule that serves as a bridge between intestinal microbes and the host, effectively alleviating metabolic inflammation by modulating the host immunomodulatory network. Here, we focused on elucidating the underlying mechanisms by which the gut microbiota and their metabolites reduce inflammation via IL-22, highlighting the favorable impact of IL-22 on metabolic inflammation. Furthermore, we discuss the potential of IL-22 as a therapeutic target for the management of metabolic inflammation and related diseases.

EDEM1 regulates the insulin mRNA level by inhibiting the endoplasmic reticulum stress-induced IRE1/JNK/c-Jun pathway

Pancreatic beta cells produce and secrete insulin as a response to rises in blood glucose. Despite the advances in understanding glucose-regulated insulin transcription and translation the mechanisms triggering the synthesis of new insulin molecules are still incompletely described. In this report, we identify EDEM1 as a new modulator of insulin synthesis and secretion. In the presence of EDEM1, INS-1E cells secrete significantly more insulin upon glucose stimulation compared to control cells. We found that overexpression of EDEM1 inhibited the IRE1/JNK/c-Jun pathway, leading to an increase in the insulin mRNA level. Similarly, EDEM1 transduced human islets secreted significantly more insulin upon stimulation. Furthermore, EDEM1 improved insulin secretion restoring normoglycemia and glucose tolerance in diabetic rats. We propose EDEM1 as a regulator of the UPR via IRE1/XBP1s and IRE1/JNK/c-Jun signaling cascades and insulin transcription in pancreatic β-cells, supporting EDEM1 as a potential target for the treatment of diabetes.

Identification of novel SCD1 inhibitor alleviates nonalcoholic fatty liver disease: critical role of liver-adipose axis

Due to the complexity and incomplete understanding of the crosstalk between liver and adipose tissue, especially the processes of hepatic lipogenesis and adipogenic differentiation, there are currently no effective drugs for the treatment of nonalcoholic fatty liver disease (NAFLD). Stearoyl-coenzyme A desaturase 1 (SCD1), which is abundantly expressed in liver and adipose tissue, may mediate the cross-talk between liver and adipose tissue. Thus, it is essential to develop specific SCD1 inhibitors that target the liver-adipose axis. Herein, we identified a novel SCD1 inhibitor, E6446, through a high-throughput virtual screen. E6646 significantly inhibited adipogenic differentiation and hepatic lipogenesis via SCD1-ATF3 signaling. The SPR results showed that E6446 had a strong interaction ability with SCD1 (KD:4.61 μM). Additionally, E6646 significantly decreased hepatic steatosis, hepatic lipid droplet accumulation and insulin resistance in high-fat diet (HFD)-fed mice. Taken together, our findings not only suggest that E6446 can serve as a new, safe and highly effective anti-NAFLD agent for future clinical use but also provide a molecular basis for the future development of SCD1 inhibitors that inhibit both adipogenic differentiation and hepatic lipogenesis. Video Abstract.

ER Stress, the Unfolded Protein Response and Osteoclastogenesis: A Review

Endoplasmic reticulum (ER) stress and its adaptive mechanism, the unfolded protein response (UPR), are triggered by the accumulation of unfolded and misfolded proteins. During osteoclastogenesis, a large number of active proteins are synthesized. When an imbalance in the protein folding process occurs, it causes osteoclasts to trigger the UPR. This close association has led to the role of the UPR in osteoclastogenesis being increasingly explored. In recent years, several studies have reported the role of ER stress and UPR in osteoclastogenesis and bone resorption. Here, we reviewed the relevant literature and discussed the UPR signaling cascade response, osteoclastogenesis-related signaling pathways, and the role of UPR in osteoclastogenesis and bone resorption in detail. It was found that the UPR signal (PERK, CHOP, and IRE1-XBP1) promoted the expression of the receptor activator of the nuclear factor-kappa B ligand (RANKL) in osteoblasts and indirectly enhanced osteoclastogenesis. IRE1 promoted osteoclastogenesis via promoting NF-κB, MAPK signaling, or the release of pro-inflammatory factors (IL-6, IL-1β, and TNFα). CREBH promoted osteoclast differentiation by promoting NFATc1 expression. The PERK signaling pathway also promoted osteoclastogenesis through NF-κB and MAPK signaling pathways, autophagy, and RANKL secretion from osteoblasts. However, salubrinal (an inhibitor of eIF2α dephosphorylation that upregulated p-eIF2α expression) directly inhibited osteoclastogenesis by suppressing NFATc1 expression and indirectly promoted osteoclastogenesis by promoting RANKL secretion from osteoblasts. Therefore, the specific effects and mechanisms of p-PERK and its downstream signaling on osteoclastogenesis still need further experiments to confirm. In addition, the exact role of ATF6 and BiP in osteoclastogenesis also required further exploration. In conclusion, our detailed and systematic review provides some references for the next step to fully elucidate the relationship between UPR and osteoclastogenesis, intending to provide new insights for the treatment of diseases caused by osteoclast over-differentiation, such as osteoporosis.

Cellular battle against endoplasmic reticulum stress and its adverse effect on health

The endoplasmic reticulum (ER) is a dynamic organelle and a reliable performer for precisely folded proteins. To maintain its function and integrity, arrays of sensory and quality control systems enhance protein folding fidelity and resolve the highest error-prone areas. Yet numerous internal and external factors disrupt its homeostasis and trigger ER stress responses. Cells try to reduce the number of misfolded proteins via the UPR mechanism, and ER-related garbage disposals systems like ER-associated degradation (ERAD), ER-lysosome-associated degradation (ERLAD), ER-Associated RNA Silencing (ERAS), extracellular chaperoning, and autophagy systems, which activates and increase the cell survival rate by degrading misfolded proteins, prevent the aggregated proteins and remove the dysfunctional organelles. Throughout life, organisms must confront environmental stress to survive and develop. Communication between the ER & other organelles, signaling events mediated by calcium, reactive oxygen species, and inflammation are linked to diverse stress signaling pathways and regulate cell survival or cell death mechanisms. Unresolved cellular damages can cross the threshold limit of their survival, resulting in cell death or driving for various diseases. The multifaceted ability of unfolded protein response facilitates the therapeutic target and a biomarker for various diseases, helping with early diagnosis and detecting the severity of diseases.

SUMOylation of ERp44 enhances Ero1α ER retention contributing to the pathogenesis of obesity and insulin resistance

OBJECTIVE

As the only E2 conjugating enzyme for the SUMO system, Ubc9-mediated SUMOylation has been recognized to regulate diverse biological processes, but its impact on adipocytes relevant to obesity and insulin resistance is yet to be elucidated.

METHODS

We established adipocyte-specific Ubc9 deficient mice to explore the effects of Ubc9 on obesity and metabolic disorders induced by high-fat diet (HFD) in adult mice. The molecular targets of SUMOylation were explored by liquid chromatography-mass spectrometry, and the regulatory mechanism of SUMOylation in T2D was analyzed.

RESULTS

Adipocyte-specific depletion of Ubc9 (AdipoQ-Cre-Ubc9^fl/fl, Ubc9^AKO) protected mice from HFD-induced obesity, insulin resistance, and hepatosteatosis. The Ubc9^AKO mice were featured by the reduced HFD-induced endoplasmic reticulum (ER) stress and inflammatory response. Mechanically, over nutrition rendered adipocytes to undergo a SUMOylation turnover characterized by the change of SUMOylation levels and substrates. ERp44 displayed the highest change in terms of SUMOylation levels of substrates involved in ER-related functions. The lack of ERp44 SUMOylation at lysine 76 (K76) located within the thioredoxin (TRX)-like domain by Ubc9 deficiency enhanced its degradation and suppressed its covalent binding to Ero1α, an oxidase that exists in the ER but lacks ER retention motif, thereby alleviating endoplasmic reticulum stress by promoting Ero1α secretion.

CONCLUSIONS

Our data suggest that modulation of ERp44 SUMOylation in adipocytes could be a feasible strategy against obesity and insulin resistance in clinical settings.

Roles of endoplasmic reticulum stress in the pathophysiology of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder among reproductive-age women, affecting up to 15% of women in this group, and the most common cause of anovulatory infertility. Although its etiology remains unclear, recent research has revealed the critical role of endoplasmic reticulum (ER) stress in the pathophysiology of PCOS. ER stress is defined as a condition in which unfolded or misfolded proteins accumulate in the ER because of an imbalance in the demand for protein folding and the protein-folding capacity of the ER. ER stress results in the activation of several signal transduction cascades, collectively termed the unfolded protein response (UPR), which regulates various cellular activities. In principle, the UPR restores homeostasis and keeps the cell alive. However, if the ER stress cannot be resolved, it induces programmed cell death. ER stress has recently been recognized to play diverse roles in both physiological and pathological conditions of the ovary. In this review, we summarize current knowledge of the roles of ER stress in the pathogenesis of PCOS. ER stress pathways are activated in the ovaries of both a mouse model of PCOS and in humans, and local hyperandrogenism in the follicular microenvironment associated with PCOS is responsible for activating these. The activation of ER stress contributes to the pathophysiology of PCOS through multiple effects in granulosa cells. Finally, we discuss the potential for ER stress to serve as a novel therapeutic target for PCOS.

Comparison between aerobic exercise training and enalapril treatment as tools to improve diet-induced metabolic-associated fatty liver disease: Effects on endoplasmic reticulum stress markers

AIMS

Endoplasmic reticulum (ER) stress poses a new pathological mechanism for metabolic-associated fatty liver disease (MAFLD). MAFLD treatment has encompassed renin-angiotensin system (RAS) blockers and aerobic exercise training, but their association with hepatic ER stress is not well known. Therefore, we aimed to compare the effects of hepatic RAS modulation by enalapril and/or aerobic exercise training over ER stress in MAFLD caused by a diet-induced obesity model.

MAIN METHODS

C57BL/6 mice were fed a standard-chow (CON, n = 10) or a high-fat (HF, n = 40) diet for 8 weeks. HF group was then randomly divided into: HF (n = 10), HF + Enalapril (EN, n = 10), HF + Aerobic exercise training (AET, n = 10), and HF + Enalapril+Aerobic exercise training (EN + AET, n = 10) for 8 more weeks. Body mass (BM) and glucose profile were evaluated. In the liver, ACE and ACE2 activity, morphology, lipid profile, and protein expression of ER stress and metabolic markers were assessed.

KEY FINDINGS

Both enalapril and aerobic exercise training provided comparable efficacy in improving diet-induced MAFLD through modulation of RAS and ER stress, but the latter was more efficient in improving ER stress, liver damage and metabolism.

SIGNIFICANCE

This is the first study to evaluate pharmacological (enalapril) and non-pharmacological (aerobic exercise training) RAS modulators associated with ER stress in a diet-induced MAFLD model.