Physical exercise alleviates ER stress in obese humans through reduction in the expression and release of GRP78 chaperone

Skeletal muscle disorders as risk factors for type 2 diabetes

The incidence and prevalence of muscular disorders and of type 2 diabetes (T2D) is increasing and both represent highly significant healthcare problems, both economically and compromising quality of life. Interestingly, skeletal muscle dysfunction and T2D share some commonalities including dysregulated glucose homeostasis, increased oxidative stress, dyslipidemia, and cytokine alterations. Several lines of evidence have hinted to a relationship between skeletal muscle dysfunction and T2D. For instance, T2D affects skeletal muscle morphology, functionality, and overall health through altered protein metabolism, impaired mitochondrial function, and ultimately cell viability. Conversely, humans suffering from myopathies and their experimental models demonstrated increased incidence of T2D through altered muscle glucose disposal function due to abnormal calcium homeostasis, compromised mitochondrial function, dyslipidemia, increased inflammatory cytokines and fiber size alterations and disproportions. Lifestyle modifications are essential for improving and maintaining mobility and metabolic health in individuals suffering from myopathies along with T2D. In this review, we updated current literature evidence on clinical incidence of T2D in inflammatory, mitochondrial, metabolic myopathies, and muscular dystrophies and further discussed the molecular basis of these skeletal muscle disorders leading to T2D.

Aging and voluntary exercise's effects on Aβ1-42 levels, endoplasmic reticulum stress factors, and apoptosis in the hippocampus of old male rats

Within the aging cortex, amyloid beta peptide (Aβ) is a crucial element of the senile plaques, a hallmark feature often observed in cases of Alzheimer's disease (AD). The UPR (unfolded protein response), a cellular mechanism for protein folding, is switched on by Aβ accumulation. Endoplasmic reticulum (ER) stress has been identified as playing a role in aging and the development of neurodegenerative diseases. The exact molecular pathways leading to perishing of cells from Aβ-induced ER stress, as well as the impact of voluntary exercise on these mechanisms, are still subjects awaiting a definitive answer yet. In the current study, 18 male Wistar rats were included: 6 young rats (3 months old; 200-250 g) in the Young Control group, and 12 old rats (18 months old; 400-430 g) randomly allocated to the Old Control and Old Exercise groups. The rat cages had running wheels for them to voluntarily run on for 8 weeks. This was followed by Western blotting, immunohistochemical staining, biochemical as well as morphological analyses. Voluntary exercise reduced Aβ1-42 deposition (P < 0.001) and inhibited the activation of caspase-8 (P < 0.001) and caspase-12 (P < 0.01), and on top of that down-regulated the expression of ATF6 (P < 0.001), CHOP (P < 0.01), and p-PERK (P < 0.05) proteins in the hippocampus of old male rats. Exercise amplified the population of Bcl-2-expressing cells and decreased the population of Bax-expressing cells in the hippocampus of the Old Exercise group (P < 0.001). Voluntary exercise inhibited the apoptotic pathways and suppressed the activation of UPR signaling pathways. Hence, voluntary exercise may be a therapeutic strategy and a promising approach to prevent AD through modulation of Aβ-induced ER stress.

Upregulation of GRP78 is accompanied by decreased antioxidant response and mitophagy promotion in streptozotocin-induced type 1 diabetes in rats

Endoplasmic reticulum stress, oxidative stress, and mitochondrial dysfunction are interconnected processes involved in the pathogenesis of diabetes mellitus (DM). In the present study, we demonstrate a distinct unfolded protein response (UPR) signaling pathways in two mammalian models of DM: β-TC-6 cell line and streptozotocin-induced type 1 diabetes model in rats. However, a feature common to both systems was the upregulation of the GRP78 protein. Moreover, in vivo studies showed the disruption of the antioxidant system and an escalation of mitophagy against the background of a depletion of the level of ATP in pancreatic cells. In conclusion, we suggest that glucotoxic conditions induced GRP78 upregulation, and next cause depletion of the antioxidant pool and disruption of the functioning of antioxidant defense enzymes and in consequence promote mitophagy in pancreatic cells. Therefore, GRP78 may be considered as a potential therapeutic factor in patients with diabetes.

Understanding the impact of ER stress on lung physiology

Human lungs consist of a distinctive array of cell types, which are subjected to persistent challenges from chemical, mechanical, biological, immunological, and xenobiotic stress throughout life. The disruption of endoplasmic reticulum (ER) homeostatic function, triggered by various factors, can induce ER stress. To overcome the elevated ER stress, an adaptive mechanism known as the unfolded protein response (UPR) is activated in cells. However, persistent ER stress and maladaptive UPR can lead to defects in proteostasis at the cellular level and are typical features of the lung aging. The aging lung and associated lung diseases exhibit signs of ER stress-related disruption in cellular homeostasis. Dysfunction resulting from ER stress and maladaptive UPR can compromise various cellular and molecular processes associated with aging. Hence, comprehending the mechanisms of ER stress and UPR components implicated in aging and associated lung diseases could enable to develop appropriate therapeutic strategies for the vulnerable population.

Predictive utility of nomogram based on serum glucose-regulated protein 78 and kidney function for long-term kidney graft survival

The estimated glomerular filtration rate (eGFR) at 1 year post-transplantation is a well-established predictor of long-term graft survival; however, its predictive accuracy needs improvement. We retrospectively analyzed data from 51 kidney transplant recipients at Kanazawa Medical University Hospital (January 2001-February 2015). Cox regression was used to identify risk factors for death-censored graft loss and create a nomogram to predict graft survival at 15 years post-transplantation. The predictive factors ultimately included in the nomogram included eGFR and serum glucose-regulated protein 78 (GRP78) at 1 year post-transplantation. In terms of discrimination, assessed by area under the receiver operating characteristic curve (AUC-ROC), no significant difference was noted between the eGFR model (AUC 0.84 [0.67-1.00]) and nomogram (AUC 0.92 [0.82-1.00]) (p = 0.38). However, calibration, evaluated by the calibration plot, indicated superiority of the nomogram over the eGFR model, confirmed in the internal validation cohort using the Bootstrap method. Regarding clinical value evaluated by decision curve analysis, the nomogram showed a greater net benefit than the eGFR model, especially at wider diagnostic thresholds (particularly important lower thresholds). Our findings suggest the added predictive value of serum GRP78 at 1 year post-transplantation for long-term graft survival prediction.

Adipose tissue in older individuals: a contributing factor to sarcopenia

Sarcopenia is a geriatric syndrome characterized by a functional decline in muscle. The prevalence of sarcopenia increases with natural aging, becoming a serious health problem among elderly individuals. Therefore, understanding the pathology of sarcopenia is critical for inhibiting age-related alterations and promoting health and longevity in elderly individuals. The development of sarcopenia may be influenced by interactions between visceral and subcutaneous adipose tissue and skeletal muscle, particularly under conditions of chronic low-grade inflammation and metabolic dysfunction. This hypothesis is supported by the following observations: (i) accumulation of senescent cells in both adipose tissue and skeletal muscle with age; (ii) gut dysbiosis, characterized by an imbalance in gut microbial communities as the main trigger for inflammation, sarcopenia, and aged adipose tissue; and (iii) microbial dysbiosis, which could impact the onset or progression of a senescent state. Moreover, adipose tissue acts as an endocrine organ, releasing molecules that participate in intricate communication networks between organs. Our discussion focuses on novel adipokines and their role in regulating adipose tissue and muscle, particularly those influenced by aging and obesity, emphasizing their contributions to disease development. On the basis of these findings, we propose that age-related adipose tissue and sarcopenia are disorders characterized by chronic inflammation and metabolic dysregulation. Finally, we explore new potential therapeutic strategies involving specialized proresolving mediator (SPM) G protein-coupled receptor (GPCR) agonists, non-SPM GPCR agonists, transient receptor potential (TRP) channels, antidiabetic drugs in conjunction with probiotics and prebiotics, and compounds designed to target senescent cells and mitigate their pro-inflammatory activity.

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.

Endoplasmic reticulum stress mechanisms and exercise intervention in type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a metabolic disease primarily characterized by insulin resistance (IR) and insufficient insulin secretion. The unfolded protein response (UPR) overactivation induced by endoplasmic reticulum stress (ERS) appears to play a key role in this process, although the exact pathogenesis of T2DM is not fully understood. Studies have demonstrated that appropriate exercise can regulate ERS in the heart, liver, pancreas, skeletal muscle, and other body tissues leading to an improvement in diabetes and its complications. However, the exact mechanism remains unclear. By analyzing the relationship between ERS, T2DM pathology, and exercise intervention, this review concludes that exercise can increase insulin sensitivity, inhibit IR, promote insulin secretion and alleviate T2DM by regulating ERS. This paper specifically reviews the signaling pathways by which ERS induces diabetes, the mechanisms of exercise regulation of ERS in diabetes, and the varying effects of different types of exercise on diabetes improvement through ERS mechanisms. Physical exercise is an effective non-pharmacological intervention for T2DM. Thus, further exploration of how exercise regulates ERS in diabetes could refine "precision exercise medicine" for diabetes and identify new drug targets.

Inflammation-mediated metabolic regulation in adipose tissue

Chronic inflammation of adipose tissue is a prominent characteristic of many metabolic diseases. Lipid metabolism in adipose tissue is consistently dysregulated during inflammation, which is characterized by substantial infiltration by proinflammatory cells and high cytokine concentrations. Adipose tissue inflammation is caused by a variety of endogenous factors, such as mitochondrial dysfunction, reactive oxygen species (ROS) production, endoplasmic reticulum (ER) stress, cellular senescence, ceramides biosynthesis and mediators of lipopolysaccharides (LPS) signaling. Additionally, the gut microbiota also plays a crucial role in regulating adipose tissue inflammation. Essentially, adipose tissue inflammation arises from an imbalance in adipocyte metabolism and the regulation of immune cells. Specific inflammatory signals, including nuclear factor-κB (NF-κB) signaling, inflammasome signaling and inflammation-mediated autophagy, have been shown to be involved in the metabolic regulation. The pathogenesis of metabolic diseases characterized by chronic inflammation (obesity, insulin resistance, atherosclerosis and nonalcoholic fatty liver disease [NAFLD]) and recent research regarding potential therapeutic targets for these conditions are also discussed in this review.

Intestinal heat shock proteins in metabolic syndrome: Novel mediators of obesity and its comorbidities resolution after metabolic surgery

Over the past 40 years, the prevalence of obesity has risen dramatically, reaching epidemic proportions. Metabolic surgery has proven to be highly effective in treating obesity, leading to significant improvements or complete resolution of obesity-related comorbidities. Research conducted in both animals and humans suggests that the metabolic benefits achieved through metabolic surgery cannot be solely attributed to weight loss. Indeed, there has been an increasing recognition of intestinal inflammation as a novel factor influencing obesity. The gastrointestinal tract is continuously exposed to dietary components, particularly diets rich in saturated fats, which are known to contribute to obesity. It is now widely accepted that heat shock proteins can be released from various cells including intestinal epithelial cells and act as proinflammatory signals. Several studies have shown that circulating levels of glucose-regulated protein 78 (GRP78) are increased in subjects with obesity and correlate with the severity of the disease. Moreover, mice with a partial knockout of GRP78 are protected from diet-induced obesity. In this review, we discuss the role of GRP78 in the development of obesity. Several evidence suggests that GRP78 can influence adipogenesis, lipid droplets stabilization, insulin resistance, and liver steatosis. We also provide an update on GRP78 regulation following metabolic surgery, focusing on the bypass of the small intestine as a key factor for GRP78 secretion. Finally, we discuss the potential role of monoclonal antibodies against GRP78 as a treatment for obesity.

DNAJB3 attenuates ER stress through direct interaction with AKT

Metabolic stress involved in several dysregulation disorders such as type 2 diabetes mellitus (T2DM) results in down regulation of several heat shock proteins (HSPs) including DNAJB3. This down regulation of HSPs is associated with insulin resistance (IR) and interventions which induce the heat shock response (HSR) help to increase the insulin sensitivity. Metabolic stress leads to changes in signaling pathways through increased activation of both c-jun N-terminal kinase-1 (JNK1) and the inhibitor of κB inflammatory kinase (IKKβ) which in turn leads to inactivation of insulin receptor substrates 1 and 2 (IRS-1 and IRS-2). DNAJB3 interacts with both JNK1 and IKKβ kinases to mitigate metabolic stress. In addition DNAJB3 also activates the PI3K-PKB/AKT pathway through increased phosphorylation of AKT1 and its substrate AS160, a Rab GTPase-activating protein, which results in mobilization of GLUT4 transporter protein and improved glucose uptake. We show through pull down that AK T1 is an interacting partner of DNAJB3, further confirmed by isothermal titration calorimetry (ITC) which quantified the avidity of AKT1 for DNAJB3. The binding interface was identified by combining protein modelling with docking of the AKT1-DNAJB3 complex. DNAJB3 is localized in the cytoplasm and ER, where it interacts directly with AKT1 and mobilizes AS160 for glucose transport. Inhibition of AKT1 resulted in loss of GLUT4 translocation activity mediated by DNAJB3 and also abolished the protective effect of DNAJB3 on tunicamycin-induced ER stress. Taken together, our findings provide evidence for a direct protein-protein interaction between DNAJB3 and AKT1 upon which DNAJB3 alleviates ER stress and promotes GLUT4 translocation.

ER stress and inflammation crosstalk in obesity

The endoplasmic reticulum (ER) governs the proper folding of polypeptides and proteins through various chaperones and enzymes residing within the ER organelle. Perturbation in the ER folding process ensues when overwhelmed protein folding exceeds the ER handling capacity, leading to the accumulation of misfolded/unfolded proteins in the ER lumen-a state being referred to as ER stress. In turn, ER stress induces a gamut of signaling cascades, termed as the "unfolded protein response" (UPR) that reinstates the ER homeostasis through a panel of gene expression modulation. This type of UPR is usually deemed "adaptive UPR." However, persistent or unresolved ER stress hyperactivates UPR response, which ultimately, triggers cell death and inflammatory pathways, termed as "maladaptive/terminal UPR." A plethora of evidence indicates that crosstalks between ER stress (maladaptive UPR) and inflammation precipitate obesity pathogenesis. In this regard, the acquisition of the mechanisms linking ER stress to inflammation in obesity might unveil potential remedies to tackle this pathological condition. Herein, we aim to elucidate key mechanisms of ER stress-induced inflammation in the context of obesity and summarize potential therapeutic strategies in the management of obesity through maneuvering ER stress and ER stress-associated inflammation.

Exercise sustains the hallmarks of health

Exercise has long been known for its active role in improving physical fitness and sustaining health. Regular moderate-intensity exercise improves all aspects of human health and is widely accepted as a preventative and therapeutic strategy for various diseases. It is well-documented that exercise maintains and restores homeostasis at the organismal, tissue, cellular, and molecular levels to stimulate positive physiological adaptations that consequently protect against various pathological conditions. Here we mainly summarize how moderate-intensity exercise affects the major hallmarks of health, including the integrity of barriers, containment of local perturbations, recycling and turnover, integration of circuitries, rhythmic oscillations, homeostatic resilience, hormetic regulation, as well as repair and regeneration. Furthermore, we summarize the current understanding of the mechanisms responsible for beneficial adaptations in response to exercise. This review aimed at providing a comprehensive summary of the vital biological mechanisms through which moderate-intensity exercise maintains health and opens a window for its application in other health interventions. We hope that continuing investigation in this field will further increase our understanding of the processes involved in the positive role of moderate-intensity exercise and thus get us closer to the identification of new therapeutics that improve quality of life.

GRP78 Activity Moderation as a Therapeutic Treatment against Obesity

Glucose-regulated protein 78 (GRP78), a molecular chaperone, is overexpressed in patients suffering from obesity, fatty liver, hyperlipidemia and diabetes. GRP78, therefore, can be not only a biomarker to predict the progression and prognosis of obesity and metabolic diseases but also a potential therapeutic target for anti-obesity treatment. In this paper, GRP78 inhibitors targeting its ATPase domain have been reviewed. Small molecules and proteins that directly bind GRP78 have been described. Putative mechanisms of GRP78 in regulating lipid metabolism were also summarized so as to investigate the role of GRP78 in obesity and other related diseases and provide a theoretical basis for the development and design of anti-obesity drugs targeting GRP78.

Endoplasmic Reticulum Stress: A New Research Direction for Polycystic Ovary Syndrome?

Polycystic ovary syndrome (PCOS) is one of the most common gynecological endocrine disorders, with sporadic ovulation, excessive androgens, and polycystic ovarian changes as the main clinical manifestations. Due to the high heterogeneity of its clinical manifestations, the discussion on its pathogenesis has not been unified. Current research has found that genetic factors, hyperandrogenism, chronic inflammation and oxidative stress, insulin resistance, and obesity are strongly associated with PCOS. Recently, when studying the specific mechanisms of the abovementioned factors in PCOS, the biological response process of endoplasmic reticulum stress (ERS) has gradually come to researchers' attention, and several studies have confirmed the involvement of ERS in the pathogenesis of PCOS and the improvement of a series of pathological manifestations of PCOS after the application of ERS inhibitors, which may be a new entry point for the treatment of PCOS. In this article, we review the relationship between ERS and various pathogenic factors of PCOS.

Circulating TRB3 and GRP78 levels in type 2 diabetes patients: crosstalk between glucose homeostasis and endoplasmic reticulum stress

PURPOSE

Endoplasmic reticulum (ER) stress is implicated in the development of type 2 diabetes mellitus (T2DM) and insulin resistance. Tribbles homolog 3 (TRB3) is a pseudokinase upregulated by ER stress and hyperglycemia. Glucose-regulated protein 78 (GRP78) is an ER stress protein that is overexpressed under ER stress conditions. The current study aimed to investigate serum levels of TRB3 and GRP78, as an ER stress marker, in T2DM patients and their correlations with the metabolic profile.

METHODS

Fifty-seven patients with type 2 diabetes and 23 healthy control subjects were evaluated for serum concentrations of TRB3, GRP78, and AGEs by enzyme-linked immunosorbent assay (ELISA). Fasting plasma glucose (FPG), HbA1c, lipid profile, TNF-α and insulin were also measured, and insulin resistance was calculated using a homeostasis model assessment of insulin resistance (HOMA-IR).

RESULTS

Serum concentrations of TRB3, GRP78, AGEs, and TNF-α were significantly higher in T2DM patients compared to the healthy controls. Moreover, a statistically significant positive correlation was observed between plasma concentrations of TRB3 and FPG, HbA1c, HOMA-IR, and AGE. GRP78 levels were positively correlated with HbA1c and AGEs. There was also a positive correlation between GRP78 and TRB3. AGEs levels were positively correlated with the levels of FPG, HbA1c, HOMA-IR, and TNF-α.

CONCLUSION

The current findings suggest that TRB3 and GRP78 may contribute to the pathogenesis of T2DM and might be considered as a therapeutic targets for the treatment of this disease.

ER stress in obesity pathogenesis and management

Given the unprecedented global pandemic of obesity, a better understanding of the etiology of adiposity will be necessary to ensure effective management of obesity and related complications. Among the various potential factors contributing to obesity, endoplasmic reticulum (ER) stress refers to a state of excessive protein unfolding or misfolding that is commonly found in metabolic diseases including diabetes mellitus, insulin resistance (IR), and non-alcoholic fatty liver disease, although its role in obesogenesis remains controversial. ER stress is thought to drive adiposity by dampening energy expenditure, making ER stress a likely therapeutic target for the management of obesity. We summarize the role of ER stress and the ER stress response in the onset and development of obesity, and discuss the underlying mechanisms involved with a view to identifying novel therapeutic strategies for obesity prevention and management.

Urocortin 3 overexpression reduces ER stress and heat shock response in 3T3-L1 adipocytes

The neuropeptide urocortin 3 (UCN3) has a beneficial effect on metabolic disorders, such as obesity, diabetes, and cardiovascular disease. It has been reported that UCN3 regulates insulin secretion and is dysregulated with increasing severity of obesity and diabetes. However, its function in the adipose tissue is unclear. We investigated the overexpression of UCN3 in 3T3-L1 preadipocytes and differentiated adipocytes and its effects on heat shock response, ER stress, inflammatory markers, and glucose uptake in the presence of stress-inducing concentrations of palmitic acid (PA). UCN3 overexpression significantly downregulated heat shock proteins (HSP60, HSP72 and HSP90) and ER stress response markers (GRP78, PERK, ATF6, and IRE1α) and attenuated inflammation (TNFα) and apoptosis (CHOP). Moreover, enhanced glucose uptake was observed in both preadipocytes and mature adipocytes, which is associated with upregulated phosphorylation of AKT and ERK but reduced p-JNK. Moderate effects of UCN3 overexpression were also observed in the presence of 400 μM of PA, and macrophage conditioned medium dramatically decreased the UCN3 mRNA levels in differentiated 3T3-L1 cells. In conclusion, the beneficial effects of UCN3 in adipocytes are reflected, at least partially, by the improvement in cellular stress response and glucose uptake and attenuation of inflammation and apoptosis.

The Effect of Resistance Training and Berberine Chloride on the Apoptosis-related Unfolded Protein Response Signaling Pathway in the Hippocampus of Diazinon-poisoned Rats

INTRODUCTION

Diazinon is one of the most widely-used organophosphate pesticides in the world. This toxin enters the body in various ways and induces oxidative stress in various tissues. It has been proved that activation of Unfolded Protein Response (UPR) under oxidative stress is a steady mechanism for maintaining cell function and survival. Therefore, the present study aimed to review the effect of Resistance Training (RT) and Berberine Chloride (BC) on the apoptosis-related UPR signaling pathway in the hippocampus of diazinon-poisoned rats.

METHODS

In this experimental study, 40 male Wistar rats weighing 250 ±50 g were randomly divided into eight groups of five rats of 1) diazinon + 2 mg/kg BC + RT, 2) diazinon + 15 mg/kg BC + RT, 3) diazinon, 4) diazinon + RT, 5) diazinon + 2 mg/kg BC, 6) diazinon + 15 mg/kg BC, 7) healthy control, and 8) sham. The groups were treated for 5 weeks. At the end of the fifth week, ATF-4, ATF-6, and CHOP gene expression in hippocampus tissue were measured by quantitative real-time RT-PCR.

RESULTS

Diazinon significantly increased the expression of ATF-4, ATF-6, and CHOP in the hippocampus tissue of rats. Administrating 15 mg/kg BC with RT significantly decreased these genes, indicating a decrease in the rate of apoptosis in the hippocampus.

CONCLUSION

This study showed that RT and BC have a protective effect against diazinon-induced toxicity in the hippocampus.

Resistance exercise training improves glucose homeostasis by enhancing insulin secretion in C57BL/6 mice

Resistance exercise exerts beneficial effects on glycemic control, which could be mediated by exercise-induced humoral factors released in the bloodstream. Here, we used C57Bl/6 healthy mice, submitted to resistance exercise training for 10 weeks. Trained mice presented higher muscle weight and maximum voluntary carrying capacity, combined with reduced body weight gain and fat deposition. Resistance training improved glucose tolerance and reduced glycemia, with no alterations in insulin sensitivity. In addition, trained mice displayed higher insulinemia in fed state, associated with increased glucose-stimulated insulin secretion. Islets from trained mice showed reduced expression of genes related to endoplasmic reticulum (ER) stress, associated with increased expression of Ins2. INS-1E beta-cells incubated with serum from trained mice displayed similar pattern of insulin secretion and gene expression than isolated islets from trained mice. When exposed to CPA (an ER stress inducer), the serum from trained mice partially preserved the secretory function of INS-1E cells, and prevented CPA-induced apoptosis. These data suggest that resistance training, in healthy mice, improves glucose homeostasis by enhancing insulin secretion, which could be driven, at least in part, by humoral factors.

A Weak Response to Endoplasmic Reticulum Stress Is Associated With Postoperative Organ Failure in Patients Undergoing Cardiac Surgery With Cardiopulmonary Bypass

Introduction: Endoplasmic reticulum stress (ERS) is involved in inflammatory organ failure. Our objective was to describe ERS, its unfolded protein response (UPR) expression/kinetics during cardiac surgery with cardiopulmonary bypass (CPB) and its association with postoperative organ failure (OF). Methods: Prospective study conducted on patients undergoing cardiac surgery with CPB. Blood samples were taken before (Pre-CPB), 2 h (H2-CPB) and 24 h (H24-CPB) after CPB. Plasma levels of 78 kDa Glucose- Regulated Protein (GRP78, final effector of UPR) were evaluated by ELISA. The expression of genes coding for key elements of UPR (ATF6, ATF4, sXBP1, CHOP) was evaluated by quantitative PCR performed on total blood. OF was defined as invasive mechanical ventilation and/or acute kidney injury and/or hemodynamic failure requiring catecholamines. Results: We included 46 patients, GRP78 was decreased at H2-CPB [1,328 (878-1,730) ng/ml vs. 2,348 (1,655-3,730) ng/ml Pre-CPB; p < 0.001] but returned to basal levels at H24-CPB [2,068 (1,436-3,005) ng/ml]. The genes involved in UPR had increased expression at H2 and H24. GRP78 plasma levels in patients with OF at H24-CPB (n = 10) remained below Pre-CPB levels [-27.6 (-51.5; -24.2)%] compared to patients without OF (n = 36) in whom GRP78 levels returned to basal levels [0.6 (-28.1; 26.6)%; p < 0.01]. H24-CPB ATF6 and CHOP expressions were lower in patients with OF than in patients without OF [2.3 (1.3-3.1) vs. 3.0 (2.7-3.7), p < 0.05 and 1.3 (0.9-2.0) vs. 2.2 (1.7-2.9), p < 0.05, respectively]. Conclusions: Low relative levels of GRP78 and weak UPR gene expression appeared associated with postoperative OF. Further studies are needed to understand ERS implication during acute organ failure in humans.

ER-Mitochondria Contacts and Insulin Resistance Modulation through Exercise Intervention

The endoplasmic reticulum (ER) makes physical contacts with mitochondria at specific sites, and the hubs between the two organelles are called mitochondria-associated ER membranes (MAMs). MAMs are known to play key roles in biological processes, such as intracellular Ca²⁺ regulation, lipid trafficking, and metabolism, as well as cell death, etc. Studies demonstrated that dysregulation of MAMs significantly contributed to insulin resistance. Alterations of MAMs’ juxtaposition and integrity, impaired expressions of insulin signaling molecules, disruption of Ca²⁺ homeostasis, and compromised metabolic flexibility are all actively involved in the above processes. In addition, exercise training is considered as an effective stimulus to ameliorate insulin resistance. Although the underlying mechanisms for exercise-induced improvement in insulin resistance are not fully understood, MAMs may be critical for the beneficial effects of exercise.

Up-regulation of Thioredoxin 1 by aerobic exercise training attenuates endoplasmic reticulum stress and cardiomyocyte apoptosis following myocardial infarction

Exercise training (ET) has been reported to reduce oxidative stress and endoplasmic reticulum (ER) stress in the heart following myocardial infarction (MI). Thioredoxin 1 (Trx1) plays a protective role in the infarcted heart. However, whether Trx1 regulates ER stress of the infarcted heart and participates in ET-induced cardiac protective effects are still not well known. In this work, H9c2 cells were treated with hydrogen peroxide (H₂O₂) and recombinant human Trx1 protein (TXN), meanwhile, adult male C57B6L mice were used to establish the MI model, and subjected to a six-week aerobic exercise training (AET) with or without the injection of Trx1 inhibitor, PX-12. Results showed that H₂O₂ significantly increased reactive oxygen species (ROS) level and the expression of TXNIP, CHOP and cleaved caspase12, induced cell apoptosis; TXN intervention reduced ROS level and the expression of CHOP and cleaved caspase12, and inhibited cell apoptosis in H₂O₂-treated H9c2 cells. Furthermore, AET up-regulated endogenous Trx1 protein expression and down-regulated TXNIP expression, restored ROS level and the expression of ER stress-related proteins, inhibited cell apoptosis as well as improved cardiac fibrosis and heart function in mice after MI. PX-12 partly inhibited the AET-induced beneficial effects in the infarcted heart. This study demonstrates that Trx1 attenuates ER stress-induced cell apoptosis, and AET reduces MI-induced ROS overproduction, ER stress and cell apoptosis partly through up-regulating of Trx1 expression in mice with MI.

Understanding the Role of Exercise in Nonalcoholic Fatty Liver Disease: ERS-Linked Molecular Pathways

Nonalcoholic fatty liver disease (NAFLD) is globally prevalent and characterized by abnormal lipid accumulation in the liver, frequently accompanied by insulin resistance (IR), enhanced hepatic inflammation, and apoptosis. Recent studies showed that endoplasmic reticulum stress (ERS) at the subcellular level underlies these featured pathologies in the development of NAFLD. As an effective treatment, exercise significantly reduces hepatic lipid accumulation and thus alleviates NAFLD. Confusingly, these benefits of exercise are associated with increased or decreased ERS in the liver. Further, the interaction between diet, medication, exercise types, and intensity in ERS regulation is more confusing, though most studies have confirmed the benefits of exercise. In this review, we focus on understanding the role of exercise-modulated ERS in NAFLD and ERS-linked molecular pathways. Moderate ERS is an essential signaling for hepatic lipid homeostasis. Higher ERS may lead to increased inflammation and apoptosis in the liver, while lower ERS may lead to the accumulation of misfolded proteins. Therefore, exercise acts like an igniter or extinguisher to keep ERS at an appropriate level by turning it up or down, which depends on diet, medications, exercise intensity, etc. Exercise not only enhances hepatic tolerance to ERS but also prevents the malignant development of steatosis due to excessive ERS.

Soluble Epoxide Hydrolase 2 Expression Is Elevated in Obese Humans and Decreased by Physical Activity

Epoxide hydrolase 2 (EPHX2) is an emerging therapeutic target in several immunometabolic disorders. EPHX2 metabolizes anti-inflammatory epoxyeicosatrienoic acids into pro-inflammatory diols. The contribution of EPHX2 activity to human obesity remains unexplored. We compared the expression of EPHX2 between lean and obese humans (n = 20 each) in subcutaneous adipose tissue (SAT) and peripheral blood mononuclear cells (PBMCs) using RT-PCR, Western Blot analysis, immunohistochemistry, and confocal microscopy before and after a 3-month physical activity regimen. We also assessed EPHX2 levels during preadipocyte differentiation in humans and mice. EPHX2 mRNA and protein expression were significantly elevated in obese subjects, with concomitant elevated endoplasmic reticulum (ER) stress components (the 78-kDa glucose-regulated protein; GRP78, and the Activating transcription factor 6; ATF6) and inflammatory markers (Tumor necrosis factor-α; TNFα, and Interleukin 6; IL6) as compared to controls (p < 0.05). EPHX2 mRNA levels strongly correlated with adiposity markers. In obese individuals, physical activity attenuated EPHX2 expression levels in both the SAT and PBMCs, with a parallel decrease in ER stress and inflammation markers. EPHX2 expression was also elevated during differentiation of both human primary and 3T3-L1 mouse preadipocytes. Mediators of cellular stress (palmitate, homocysteine, and macrophage culture medium) also increased EPHX2 expression in 3T3-L1 preadipocytes. Our findings suggest that EPHX2 upregulation is linked to ER stress in adiposity and that physical activity may attenuate metabolic stress by reducing EPHX2 expression.

Exercise Training Promotes Cardiac Hydrogen Sulfide Biosynthesis and Mitigates Pyroptosis to Prevent High-Fat Diet-Induced Diabetic Cardiomyopathy

Obesity increases the risk of developing diabetes and subsequently, diabetic cardiomyopathy (DMCM). Reduced cardioprotective antioxidant hydrogen sulfide (H₂S) and increased inflammatory cell death via pyroptosis contribute to adverse cardiac remodeling and DMCM. Although exercise training (EX) has cardioprotective effects, it is unclear whether EX mitigates obesity-induced DMCM by increasing H₂S biosynthesis and mitigating pyroptosis in the heart. C57BL6 mice were fed a high-fat diet (HFD) while undergoing treadmill EX for 20 weeks. HFD mice developed obesity, hyperglycemia, and insulin resistance, which were reduced by EX. Left ventricle pressure-volume measurement revealed that obese mice developed reduced diastolic function with preserved ejection fraction, which was improved by EX. Cardiac dysfunction was accompanied by increased cardiac pyroptosis signaling, structural remodeling, and metabolic remodeling, indicated by accumulation of lipid droplets in the heart. Notably, EX increased cardiac H₂S concentration and expression of H₂S biosynthesis enzymes. HFD-induced obesity led to features of type 2 diabetes (T2DM), and subsequently DMCM. EX during the HFD regimen prevented the development of DMCM, possibly by promoting H₂S-mediated cardioprotection and alleviating pyroptosis. This is the first report of EX modulating H₂S and pyroptotic signaling in the heart.

The Circulating GRP78/BiP Is a Marker of Metabolic Diseases and Atherosclerosis: Bringing Endoplasmic Reticulum Stress into the Clinical Scenario

BACKGROUND

Glucose-regulated protein 78/Binding immunoglobulin protein (GRP78/BiP) is a protein associated with endoplasmic reticulum stress and is upregulated by metabolic alterations at the tissue-level, such as hypoxia or glucose deprivation, and it is hyper-expressed in fat tissue of obese individuals.

OBJECTIVE

To investigate the role of the GRP78/BiP level as a metabolic and vascular disease biomarker in patients with type 2 diabetes (DM), obesity and metabolic syndrome (MS).

METHODS

Four hundred and five patients were recruited, of whom 52.5% were obese, 72.8% had DM, and 78.6% had MS. The intimae media thickness (cIMT) was assessed by ultrasonography. The plasma GRP78/BiP concentration was determined, and its association with metabolic and vascular parameters was assessed. Circulating GRP78/BiP was also prospectively measured in 30 DM patients before and after fenofibrate/niacin treatment and 30 healthy controls.

RESULTS

In the cross-sectional study, the GRP78/BiP level was significantly higher in the patients with obesity, DM, and MS. Age-, gender- and BMI-adjusted GRP78/BiP was directly associated with LDL-cholesterol, non-HDL-cholesterol, triglycerides, apoB, and cIMT. GRP78/BiP was positively associated to carotid plaque presence in the adjusted model, irrespective of obesity, DM and MS. In the prospective study, nicotinic acid treatment produced a significant reduction in the GRP78/BiP levels that was not observed with fenofibrate.

CONCLUSIONS

GRP78/BiP plasma concentrations are increased in patients with both metabolic derangements and subclinical atherosclerosis. GRP78/BiP could be a useful marker of metabolic and cardiovascular risk.

GRP78 Level Is Altered in the Brain, but Not in Plasma or Cerebrospinal Fluid in Parkinson's Disease Patients

Accumulation of misfolded proteins results in cellular stress, and is detected by specific sensors in the endoplasmic reticulum, collectively known as the unfolded protein response (UPR). It has been prominently proposed that the UPR is involved in the pathophysiology of Parkinson's disease (PD). In the present study, the levels of the UPR proteins and mRNA transcripts were quantified in post mortem brain tissue from PD patients and matched controls. The level of a key mediator of the UPR pathway, glucose-regulated protein 78 (GRP78), was significantly decreased in temporal cortex and cingulate gyrus, whereas there were no significant changes in the caudate nucleus, prefrontal, or parietal cortex regions. On the other hand, GRP78 mRNA level was significantly increased in caudate nucleus, cingulate gyrus, prefrontal, and parietal cortex regions. GRP78 protein level was also measured in plasma and cerebrospinal fluid, but there were no differences in these levels between PD patients and control subjects. Furthermore, immunofluorescence labeling of the CD4⁺ T cells from PD patients showed that GRP78 protein is found in the cytoplasm. However, GRP78 level in PD patients was not significantly different from control subjects. Unlike the previous Lewy body dementia study, the present investigation reports reduced cortical protein, but increased transcript levels of GPR78 in PD. In summary, these data provide further evidence that GRP78 regulation is dysfunctional in the brains of PD patients.

Naringenin ameliorates insulin resistance by modulating endoplasmic reticulum stress in hepatitis C virus-infected liver

Hepatitis C virus (HCV) infection may lead to hepatic insulin resistance (IR), and endoplasmic reticulum (ER) stress has been found to induce IR. In our previous study, naringenin (NGEN) had an insulin sensitization effect on the HCV core protein (HCVCP) infected mouse livers. In the present study, we examined the effects of NGEN on HCVCP infection-induced ER stress and investigated the insulin sensitization mechanism involved. We found that XBP1s was up-regulated in the livers of HCV-infected patients, in hepatocytes with HCV infection, and in HCVCP-infected mice. HCVCP induces ER stress in the mouse liver and hepatocytes by increasing XBP1s and downstream gene expression. Pre-treatment with NGEN inhibited the ER stress and downstream gene expression both in vivo and in vitro. Similar to the HCVCP infection results, NGEN also inhibited the ER stress in tunicamycin-treated Huh-7.5.1 cells. In addition, the role of IRE1α in HCVCP-induced IR was detected, and knockdown of IRE1α abolished HCVCP-stimulated IR. Overexpression induced IR but could be abolished by NGEN. NGEN also blocked the HCVCP-induced IRE1α expression levels that were up-regulated in vivo. Our data reveal that ER stress may be associated with HCV-induced IR, and NGEN treatment inhibited ER stress activity and increased insulin sensitivity by decreasing the expression of IRE1α.

DNAJB3 attenuates metabolic stress and promotes glucose uptake by eliciting Glut4 translocation

Failure of the heat shock response is a key event that leads to insulin resistance and type 2 diabetes. We recently showed that DNAJB3 co-chaperone is downregulated in obese and diabetic patients and that physical exercise restores its normal expression with a significant improvement of the clinical outcomes. In 3T3-L1 adipocytes, DNAJB3 has a role in improving the sensitivity to insulin and glucose uptake. In co-immunoprecipitation assays, DNAJB3 interacts with both JNK1 and IKKβ kinases. However, the functional impact of such interaction on their activities has not been investigated. Here, we assessed the effect of DNAJB3 on the respective activity of JNK1 and IKKβ in cell-based assays. Using JNK1- and IKKβ-dependent luciferase reporters, we show a marked decrease in luciferase activity by DNAJB3 in response to PMA and TNF-α that was consistent with a decrease in the translocation of p65/NF-κB to the nucleus in response to LPS. Furthermore, TNF-α-mediated IL-6 promoter activation and endogenous mRNA expression are significantly abrogated by DNAJB3 both in 3T3-L1 and C2C12 cells. The ability of DNAJB3 to mitigate ER stress and oxidative stress was also investigated and our data show a significant improvement of both forms of stress. Finally, we examined the effect of overexpressing and knocking down the expression of DNAJB3 on glucose uptake in C2C12 as well as the molecular determinants. Accordingly, we provide evidence for a role of DNAJB3 in promoting both basal and insulin-stimulated glucose uptake. Our finding reveals also a novel role of DNAJB3 in eliciting Glut4 translocation to the plasma membrane. These results suggest a physiological role of DNAJB3 in mitigating metabolic stress and improving glucose homeostasis and could therefore represent a novel therapeutic target for type 2 diabetes.

Vaspin promotes insulin sensitivity of elderly muscle and is upregulated in obesity

Adipokines have emerged as central mediators of insulin sensitivity and metabolism, in part due to the known association of obesity with metabolic syndrome disorders such as type 2 diabetes. Recent studies in rodents have identified the novel adipokine vaspin, as playing a protective role in inflammatory metabolic diseases by functioning to promote insulin sensitivity during metabolic stress. However, at present the skeletal muscle and adipose tissue expression of vaspin in humans is poorly characterised. Furthermore, the functional role of vaspin in skeletal muscle insulin sensitivity has not been studied. Since skeletal muscle is the major tissue for insulin-stimulated glucose uptake understanding the functional role of vaspin in human muscle insulin signalling is critical in determining its role in glucose homeostasis. The objective of this study was to profile the skeletal muscle and subcutaneous adipose tissue expression of vaspin in humans of varying adiposity and to determine the functional role of vaspin in mediating insulin signalling and glucose uptake in human skeletal muscle. Our data shows that vaspin is secreted from both human subcutaneous adipose tissue and skeletal muscle, and is more highly expressed in obese older individuals compared to lean older individuals. Furthermore, we demonstrate that vaspin induces activation of the PI3K/AKT axis, independent of insulin receptor activation, promotes GLUT4 expression and translocation and sensitises older obese human skeletal muscle to insulin-mediated glucose uptake.

Role of Dietary Lipids in Modulating Inflammation through the Gut Microbiota

Inflammation and its resolution is a tenuous balance that is under constant contest. Though several regulatory mechanisms are employed to maintain homeostasis, disruptions in the regulation of inflammation can lead to detrimental effects for the host. Of note, the gut and microbial dysbiosis are implicated in the pathology of systemic chronic low-grade inflammation which has been linked to several metabolic diseases. What remains to be described is the extent to which dietary fat and concomitant changes in the gut microbiota contribute to, or arise from, the onset of metabolic disorders. The present review will highlight the role of microorganisms in host energy regulation and several mechanisms that contribute to inflammatory pathways. This review will also discuss the immunomodulatory effects of the endocannabinoid system and its link with the gut microbiota. Finally, a brief discussion arguing for improved taxonomic resolution (at the species and strain level) is needed to deepen our current knowledge of the microbiota and host inflammatory state.

Impaired Adipogenesis and Dysfunctional Adipose Tissue in Human Hypertrophic Obesity

The subcutaneous adipose tissue (SAT) is the largest and best storage site for excess lipids. However, it has a limited ability to expand by recruiting and/or differentiating available precursor cells. When inadequate, this leads to a hypertrophic expansion of the cells with increased inflammation, insulin resistance, and a dysfunctional prolipolytic tissue. Epi-/genetic factors regulate SAT adipogenesis and genetic predisposition for type 2 diabetes is associated with markers of an impaired SAT adipogenesis and development of hypertrophic obesity also in nonobese individuals. We here review mechanisms for the adipose precursor cells to enter adipogenesis, emphasizing the role of bone morphogenetic protein-4 (BMP-4) and its endogenous antagonist gremlin-1, which is increased in hypertrophic SAT in humans. Gremlin-1 is a secreted and a likely important mechanism for the impaired SAT adipogenesis in hypertrophic obesity. Transiently increasing BMP-4 enhances adipogenic commitment of the precursor cells while maintained BMP-4 signaling during differentiation induces a beige/brown oxidative phenotype in both human and murine adipose cells. Adipose tissue growth and development also requires increased angiogenesis, and BMP-4, as a proangiogenic molecule, may also be an important feedback regulator of this. Hypertrophic obesity is also associated with increased lipolysis. Reduced lipid storage and increased release of FFA by hypertrophic SAT are important mechanisms for the accumulation of ectopic fat in the liver and other places promoting insulin resistance. Taken together, the limited expansion and storage capacity of SAT is a major driver of the obesity-associated metabolic complications.

Urocortin 3 Levels Are Impaired in Overweight Humans With and Without Type 2 Diabetes and Modulated by Exercise

Urocortin3 (UCN3) regulates metabolic functions and is involved in cellular stress response. Although UCN3 is expressed in human adipose tissue, the association of UCN3 with obesity and diabetes remains unclear. This study investigated the effects of Type 2 diabetes (T2D) and increased body weight on the circulatory and subcutaneous adipose tissue (SAT) levels of UCN3 and assessed UCN3 modulation by a regular physical exercise. Normal-weight (n = 37) and overweight adults with and without T2D (n = 98 and n = 107, respectively) were enrolled in the study. A subset of the overweight subjects (n = 39 for each group) underwent a supervised 3-month exercise program combining both moderate intensity aerobic exercise and resistance training with treadmill. UCN3 levels in SAT were measured by immunofluorescence and RT-PCR. Circulatory UCN3 in plasma was assessed by ELISA and was correlated with various clinical and metabolic markers. Our data revealed that plasma UCN3 levels decreased in overweight subjects without T2D compared with normal-weight controls [median; 11.99 (0.78-86.07) and 6.27 (0.64-77.04), respectively; p < 0.001], whereas plasma UCN3 levels increased with concomitant T2D [median; 9.03 (0.77-104.92) p < 0.001]. UCN3 plasma levels were independently associated with glycemic index; fasting plasma glucose and hemoglobin A1c (r = 0.16 and r = 0.20, p < 0.05, respectively) and were significantly different between both overweight, with and without T2D, and normal-weight individuals (OR = 2.11 [1.84-4.11, 95% CI] and OR = 2.12 [1.59-3.10, 95% CI], p < 0.01, respectively). Conversely, the UCN3 patterns observed in SAT were opposite to those in circulation; UCN3 levels were significantly increased with body weight and decreased with T2D. After a 3-month supervised exercise protocol, UCN3 expression showed a significant reduction in SAT of both overweight groups (2.3 and 1.6-fold change; p < 0.01, respectively). In conclusion, UCN levels are differentially dysregulated in obesity in a tissue-dependent manner and can be mitigated by regular moderate physical exercise.

Endoplasmic Reticulum Unfolded Protein Response, Aging and Exercise: An Update

The endoplasmic reticulum (ER) is a dynamic and multifunctional organelle responsible for protein biosynthesis, folding, assembly and modifications. Loss of protein folding regulation, which leads to unfolded or misfolded proteins accumulation inside the ER lumen, drives ER stress (ERS) and unfolded protein response (UPR) activation. During aging, there is a decline in the ability of the cell to handle protein folding, accumulation and aggregation, and the function of UPR is compromised. There is a progressive failure of the chaperoning systems and a decline in many of its components, so that the UPR activation cannot rescue the ERS. Physical activity has been proposed as a powerful tool against aged-related diseases, which are linked to ERS. Interventional studies have demonstrated that regular exercise is able to decrease oxidative stress and inflammation and reverse mitochondrial and ER dysfunctions. Exercise-induced metabolic stress could activate the UPR since muscle contraction is directly involved in its activation, mediating exercise-induced adaptation responses. In fact, regular moderate-intensity exercise-induced ERS acts as a protective mechanism against current and future stressors. However, biological responses vary according to exercise intensity and therefore induce different degrees of ERS and UPR activation. This article reviews the effects of aging and exercise on ERS and UPR, also analyzing possible changes induced by different types of exercise in elderly subjects.

Glucose-regulated protein 78 in the aqueous humor in diabetic macular edema patients

In this study, we explored the presence and elevation of glucose-regulated protein 78 (GRP78) in aqueous humor of patients with diabetic macular edema (DME).After comparing DME patients with the controls, we analyzed GRP78 and vascular endothelial growth factor (VEGF) levels in DME patients. We examined factors associated with GRP78 levels in DME patients.GRP78 was detected in aqueous humor with elevated levels in DME patients. Stepwise backward regression analysis showed that GRP78 levels were associated with the VEGF levels and the duration of diabetes (P < .001 and P = .002, respectively). However, no statistical significance was observed between GRP78 levels and the decrease in CST following 3 monthly anti-VEGF treatments in univariate regression analysis (P = .695).We showed that GRP78 is elevated in DME patients. In addition, there is a correlation between GRP78 and VEGF levels in aqueous humor. However, GRP78 levels were not associated with the responsiveness of anti-VEGF in DME patients.

Heat Shock Proteins as a Potential Therapeutic Target in the Treatment of Gestational Diabetes Mellitus: What We Know so Far

Gestational diabetes mellitus (GDM) is a complex condition that involves a variety of pathological mechanisms, including pancreatic β-cell failure, insulin resistance, and inflammation. There is an increasing body of literature suggesting that these interrelated phenomena may arise from the common mechanism of endoplasmic reticulum (ER) stress. Both obesity-associated nutrient excess and hyperglycemia disturb ER function in protein folding and transport. This results in the accumulation of polypeptides in the ER lumen and impairs insulin secretion and signaling. Exercise elicits metabolic adaptive responses, which may help to restore normal chaperone expression in insulin-resistant tissues. Pharmacological induction of chaperones, mimicking the metabolic effect of exercise, is a promising therapeutic tool for preventing GDM by maintaining the body's natural stress response. Metformin, a commonly used diabetes medication, has recently been identified as a modulator of ER-stress-associated inflammation. The results of recent studies suggest the potential use of chemical ER chaperones and antioxidant vitamins as therapeutic interventions that can prevent glucose-induced ER stress in GDM placentas. In this review, we discuss whether chaperones may significantly contribute to the pathogenesis of GDM, as well as whether they can be a potential therapeutic target in GDM treatment.

Protein translation associated to PERK arm is a new target for regulation of metainflammation: A connection with hepatocyte cholesterol

Endoplasmic reticulum stress is a cellular phenomenon that has been associated with metabolic disorders, contributing to the development of obesity, fatty liver disease, and dyslipidemias. Under metabolic overload conditions, in cells with a high protein-secretory activity, such as hepatocytes and Langerhans β cells, the unfolded protein response (UPR) is critical in to maintain protein homeostasis (proteostasis). UPR integrated by a tripartite signaling system, through activating transcription factor 6, protein kinase R-like endoplasmic reticulum kinase (PERK), and inositol-requiring enzyme 1, regulates gene transcription and translation to resolve stress and conserve proteostasis. In the current study, we demonstrated in hepatocytes under metabolic overload by saturated palmitic and stearic fatty acids, through activation of PERK signaling and CCAAT-enhancer-binding protein homologous protein (CHOP) transcription factor, an association with the expression of cyclooxygenase 2. More important, isolated exosomes from supernatants of macrophages exposed to lipopolysaccharides can also induce a metainflammation phenomenon, and when treated on hepatocytes, induced a rearrangement in cholesterol metabolism through sterol regulatory element-binding protein 2 (SREBP2), low-density lipoprotein receptor (LDLR), apolipoprotein A-I, and ABCA1. Moreover, we demonstrate the cellular effect of terpene-derived molecules, such as cryptotanshinone, isolated of plant Salvia brandegeei, regulating metainflammatory conditions through PERK pathway in both hepatocytes and β cells. Our data suggest the presence of a modulatory mechanism on specific protein translation process. This effect could be mediated by eukaryotic initiation factor-4A, evaluating salubrinal as a control molecule. Likewise, the protective mechanisms of unsaturated fatty acids, such as oleic and palmitoleic acid were confirmed. Therefore, modulation of metainflammation suggests a new target through PERK signaling in cells with a high secretory activity, and possibly the regulation of cholesterol in hepatocytes is promoted via exosomes.

Hypothalamic endoplasmic reticulum stress as a key mediator of obesity-induced leptin resistance

Obesity is an epidemic disease that is increasing worldwide and is a major risk factor for many metabolic diseases. However, effective agents for the prevention or treatment of obesity remain limited. Therefore, it is urgent to clarify the pathophysiological mechanisms underlying the development and progression of obesity and exploit potential agents to cure and prevent this disease. According to a recent study series, obesity is associated with the development of endoplasmic reticulum stress and the activation of its stress responses (unfolded protein response) in metabolically active tissues, which contribute to the development of obesity-related insulin and leptin resistance, inflammation and energy imbalance. Hypothalamic endoplasmic reticulum stress is the central mechanism underlying the development of obesity-associated leptin resistance and disruption of energy homeostasis; thus, targeting endoplasmic reticulum stress offers a promising therapeutic strategy for improving leptin sensitivity, increasing energy expenditure and ultimately combating obesity. In this review, we highlight the relationship between and mechanism underlying hypothalamic endoplasmic reticulum stress and obesity-associated leptin resistance and energy imbalance and provide new insight regarding strategies for the treatment of obesity.

Physical Exercise Enhanced Heat Shock Protein 60 Expression and Attenuated Inflammation in the Adipose Tissue of Human Diabetic Obese

Heat shock protein 60 (HSP60) is a key protein in the crosstalk between cellular stress and inflammation. However, the status of HSP60 in diabetes and obesity is unclear. In the present study, we investigated the hypothesis that HSP60 expression levels in the adipose tissue of human obese adults with and without diabetes are different and physical exercise might affect these levels. Subcutaneous adipose tissue (SAT) and blood samples were collected from obese adults with and without diabetes (n = 138 and n = 92, respectively, at baseline; n = 43 for both groups after 3 months of physical exercise). Conventional RT-PCR, immunohistochemistry, immunofluorescence, and ELISA were used to assess the expression and secretion of HSP60. Compared with obese adults without diabetes, HSP60 mRNA and protein levels were decreased in SAT in diabetic obese together with increased inflammatory marker expression and glycemic levels but lower VO2 Max. More interestingly, a 3-month physical exercise differentially affected HSP60 expression and the heat shock response but attenuated inflammation in both groups, as reflected by decreased endogenous levels of IL-6 and TNF-α. Indeed, HSP60 expression levels in SAT were significantly increased by exercise in the diabetes group, whereas they were decreased in the non-diabetes group. These results were further confirmed using immunofluorescence microscopy and anti-HSP60 antibody in SAT. Exercise had only marginal effects on HSP60 secretion and HSP60 autoantibody levels in plasma in both obese with and without diabetes. Physical exercise differentially alleviates cellular stress in obese adults with and without diabetes despite concomitant attenuation of the inflammatory response.

Modulation of mitochondrial dysfunction and endoplasmic reticulum stress are key mechanisms for the wide-ranging actions of epoxy fatty acids and soluble epoxide hydrolase inhibitors

The arachidonic acid cascade is arguably the most widely known biologic regulatory pathway. Decades after the seminal discoveries involving its cyclooxygenase and lipoxygenase branches, studies of this cascade remain an active area of research. The third and less widely known branch, the cytochrome P450 pathway leads to highly active oxygenated lipid mediators, epoxy fatty acids (EpFAs) and hydroxyeicosatetraenoic acids (HETEs), which are of similar potency to prostanoids and leukotrienes. Unlike the COX and LOX branches, no pharmaceuticals currently are marketed targeting the P450 branch. However, data support therapeutic benefits from modulating these regulatory lipid mediators. This is being approached by stabilizing or mimicking the EpFAs or even by altering the diet. These approaches lead to predominantly beneficial effects on a wide range of apparently unrelated states resulting in an enigma of how this small group of natural chemical mediators can have such diverse effects. EpFAs are degraded by soluble epoxide hydrolase (sEH) and stabilized by inhibiting this enzyme. In this review, we focus on interconnected aspects of reported mechanisms of action of EpFAs and inhibitors of soluble epoxide hydrolase (sEHI). The sEHI and EpFAs are commonly reported to maintain homeostasis under pathological conditions while remaining neutral under normal physiological conditions. Here we provide a conceptual framework for the unique and broad range of biological activities ascribed to epoxy fatty acids. We argue that their mechanism of action pivots on their ability to prevent mitochondrial dysfunction, to reduce subsequent ROS formation and to block resulting cellular signaling cascades, primarily the endoplasmic reticulum stress. By stabilizing the mitochondrial - ROS - ER stress axis, the range of activity of EpFAs and sEHI display an overlap with the disease conditions including diabetes, fibrosis, chronic pain, cardiovascular and neurodegenerative diseases, for which the above outlined mechanisms play key roles.

The Role of Endoplasmic Reticulum Stress in Cardiovascular Disease and Exercise

Endoplasmic reticulum (ER) stress, which is highly associated with cardiovascular disease, is triggered by a disturbance in ER function because of protein misfolding or an increase in protein secretion. Prolonged disruption of ER causes ER stress and activation of the unfolded protein response (UPR) and leads to various diseases. Eukaryotic cells respond to ER stress via three major sensors that are bound to the ER membrane: activating transcription factor 6 (ATF6), inositol-requiring protein 1α (IRE1α), and protein kinase RNA-like ER kinase (PERK). Chronic activation of ER stress causes damage in endothelial cells (EC) via apoptosis, inflammation, and oxidative stress signaling pathways. The alleviation of ER stress has recently been accepted as a potential therapeutic target to treat cardiovascular diseases such as heart failure, hypertension, and atherosclerosis. Exercise training is an effective nonpharmacological approach for preventing and alleviating cardiovascular disease. We here review the recent viewing of ER stress-mediated apoptosis and inflammation signaling pathways in cardiovascular disease and the role of exercise in ER stress-associated diseases.

Metabolic syndrome enhances endoplasmic reticulum, oxidative stress and leukocyte-endothelium interactions in PCOS

OBJECTIVE

Polycystic ovary syndrome (PCOS) is associated with insulin resistance, which can lead to metabolic syndrome (MetS). Oxidative stress and leukocyte-endothelium interactions are related to PCOS. Our aim was to evaluate whether the presence of MetS in PCOS patients can influence endoplasmic reticulum (ER) and oxidative stress and leukocyte-endothelium interactions.

MATERIAL AND METHODS

This was a prospective controlled study conducted in an academic medical center. The study population consisted of 148 PCOS women (116 without/32 with MetS) and 112 control subjects (87 without / 25 with MetS). Metabolic parameters, reactive oxygen species (ROS) production, ER stress markers (GRP78, sXBP1, ATF6), leukocyte-endothelium interactions, adhesion molecules (VCAM-1, ICAM-1, E-Selectin), TNF-α and IL-6 were determined.

RESULTS

Total ROS, inflammatory parameters and adhesion molecules were enhanced in the presence of MetS (p<0.05), and the PCOS+MetS group showed higher levels of IL-6 and ICAM-1 than controls (p<0.05). Increased adhesion and leukocyte rolling flux were observed in PCOS and PCOS+MetS groups vs their respective controls (p<0.05). GRP78 protein expression was higher in the PCOS groups (p<0.05 vs controls) and sXBP1 was associated with the presence of MetS (p<0.05 vs controls without MetS). Furthermore, PCOS+MetS patients exhibited higher GRP78 and ATF6 levels than controls and PCOS patients without MetS (p<0.05). In PCOS women, HOMA-IR was positively correlated with ICAM-1 (r=0.501; p<0.01), ROS (r=0.604; p<0.01), rolling flux (r=0.455;p<0.05) and GRP78 (r=0.574; p<0.001).

CONCLUSION

Our findings support the hypothesis of an association between altered metabolic status, increased ROS production, ER stress and leukocyte-endothelium interactions in PCOS, all of which are related to vascular complications.