Zonisamide, an antiepileptic drug, alleviates diabetic cardiomyopathy by inhibiting endoplasmic reticulum stress

Nicotinamide riboside ameliorates survival time and motor dysfunction in an MPTP-Induced Parkinson's disease zebrafish model through effects on glucose metabolism and endoplasmic reticulum stress

Nicotinamide riboside (NR) is a precursor and exogenous supplement of nicotinamide adenine dinucleotide (NAD+). NR has been shown to play a beneficial role in a variety of neurodegenerative diseases. A phase 1 clinical trial identified NR as a potential neuroprotective therapy for Parkinson's disease (PD). However, the mechanism of action of NR in PD has not been fully elucidated. Therefore, the present study aimed to investigate the potential effects of NR on a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD model in zebrafish and its underlying mechanisms. The results showed that NR improved motor dysfunction, survival time, dopamine neurons, and peripheral neurons, as well as the NAD+ levels in the MPTP-affected PD zebrafish model. In addition, transcriptome sequencing analysis revealed that, after NR treatment, differentially expressed genes were significantly enriched in the glucose metabolism and protein processing pathways in the endoplasmic reticulum (ER). Quantitative PCR (qPCR) revealed that the mRNA levels of the glycoheterotrophic enzyme (involved in glucose metabolism) were significantly decreased, and the glycolytic enzyme mRNA expression levels were significantly increased. The results of the non-targeted metabolomic analysis showed that NR treatment significantly increased the levels of metabolites such as nicotinic acid ,nicotinamide, d-glucose (from the gluconeogenesis and glycolysis metabolism pathways) and some glucogenic amino acids, such as glutamine. Importantly, NR ameliorated MPTP-induced endoplasmic reticulum stress (ERS) in the PD zebrafish model through the Perk-Eif2α-Atf4-Chop pathway. These results highlight the neuroprotective effect of NR in the present PD zebrafish model through modulation of glucose metabolism and ERS via the Perk-Eif2α-Atf4-Chop pathway and provide valuable mechanistic insights into the treatment of PD.

Influence of trimetazidine on myocardial injury in mice with diabetic cardiomyopathy

INTRODUCTION

The prevalence of diabetes mellitus is increasing year by year globally, and diabetic cardiomyopathy (DCM), as the most common complication of type 2 diabetes mellitus, seriously affects the prognosis of patients. Trimetazidine (TMZ), as a drug affecting myocardial energy metabolism, mainly reduces the oxidation rate of β-oxidation by inhibiting 3-ketoacyl-CoA thiolase (3-KAT), a key enzyme in β-oxidation of free fatty acid (FFA), so that the energy metabolism substrate of cardiomyocytes preferentially selects glucose rather than fatty acids, increases the content of intracellular adenosine triphosphate (ATP), enhances the contractile function of cardiomyocytes, and improves the state of cellular ischemia and hypoxia. Previous studies have shown that TMZ is closely related to the activation and induction of apoptosis of the MAPK pathway and AMPK pathway, and plays a role in the treatment of diabetic cardiomyopathy, but the specific mechanism is still unclear.

OBJECTIVE

This study aims to investigate the impact of TMZ on myocardial damage in mice exhibiting diabetic cardiomyopathy (DCM), and to furnish a laboratory foundation for the clinical treatment of diabetic cardiomyopathy.

METHOD

Male db/db mice (6 weeks old, n = 21) and male wild-type (wt) (6 weeks old, n = 20) mice were selected for the study. The wt mice were randomly assigned to the wt group (n = 10) and wt + TMZ group (n = 10), while the remaining db/db mice were randomly allocated to the db/db group (n = 11) and db/db + TMZ group (n = 10). Following 8 weeks of feeding, the wt + TMZ group and db/db + TMZ group received TMZ via gavage, whereas the remaining groups were administered physiological saline. Periodic measurements of blood glucose, blood lipids, and myocardial enzymes were conducted in mice, with samples obtained after the 12th week for subsequent biochemical analysis, myocardial pathology assessment, immunohistochemistry, western blot analysis, and TUNEL staining (TdT-mediated dUTP Nick-End Labeling).

RESULT

GLU, TC, TG, LDL-C, and CK-MB levels were significantly higher in db/db mice compared to wt mice (GLU: M ± SD wt 5.94 ± 0.37, db/db 17.63 ± 0.89, p < 0.05, ES = 0.991; TC: M ± SD wt 3.01 ± 0.32, db/db 6.97 ± 0.36, p < 0.05, ES = 0.972; TG: M ± SD wt 0.58 ± 0.2, db/db 1.75 ± 0.14, p < 0.05, ES = 0.920; LDL-C: M ± SD wt 1.59 ± 0.12, db/db 3.87 ± 0.14, p < 0.05, ES = 0.989; CK-MB: M ± SD wt 0.12 ± 0.01, db/db 0.31 ± 0.04, p < 0.05, ES = 0.928). HDL-C levels were significantly lower in db/db mice (M ± SD wt 1.89 ± 0.08, db/db 0.64 ± 0.09, p < 0.05, ES = 0.963). Histopathological analysis confirmed myocardial damage in db/db mice. Treatment with TMZ reduced GLU, TC, TG, LDL-C, and CK-MB levels (p < 0.05, ES > 0.9) and increased HDL-C levels compared to untreated db/db mice. Additionally, TMZ treatment significantly decreased myocardial cell apoptosis (p < 0.05, ES = 0.980). These results demonstrate the efficacy of TMZ in reversing myocardial injury in DCM mice.

CONCLUSION

TMZ can mitigate myocardial damage in db/db mice by downregulating the expression of caspase-12, a protein associated with the endoplasmic reticulum stress (ERS) cell apoptosis pathway, consequently diminishing cell apoptosis. This underscores the protective efficacy of TMZ against myocardial damage in mice afflicted with DCM.

Modulating Endoplasmic Reticulum Chaperones and Mutant Protein Degradation in GABRG2(Q390X) Associated with Genetic Epilepsy with Febrile Seizures Plus and Dravet Syndrome

A significant number of patients with genetic epilepsy do not obtain seizure freedom, despite developments in new antiseizure drugs, suggesting a need for novel therapeutic approaches. Many genetic epilepsies are associated with misfolded mutant proteins, including GABRG2(Q390X)-associated Dravet syndrome, which we have previously shown to result in intracellular accumulation of mutant GABAA receptor γ2(Q390X) subunit protein. Thus, a potentially promising therapeutic approach is modulation of proteostasis, such as increasing endoplasmic reticulum (ER)-associated degradation (ERAD). To that end, we have here identified an ERAD-associated E3 ubiquitin ligase, HRD1, among other ubiquitin ligases, as a strong modulator of wildtype and mutant γ2 subunit expression. Overexpressing HRD1 or knockdown of HRD1 dose-dependently reduced the γ2(Q390X) subunit. Additionally, we show that zonisamide (ZNS)-an antiseizure drug reported to upregulate HRD1-reduces seizures in the Gabrg2+/Q390X mouse. We propose that a possible mechanism for this effect is a partial rescue of surface trafficking of GABAA receptors, which are otherwise sequestered in the ER due to the dominant-negative effect of the γ2(Q390X) subunit. Furthermore, this partial rescue was not due to changes in ER chaperones BiP and calnexin, as total expression of these chaperones was unchanged in γ2(Q390X) models. Our results here suggest that leveraging the endogenous ERAD pathway may present a potential method to degrade neurotoxic mutant proteins like the γ2(Q390X) subunit. We also demonstrate a pharmacological means of regulating proteostasis, as ZNS alters protein trafficking, providing further support for the use of proteostasis regulators for the treatment of genetic epilepsies.

Zonisamide attenuates pressure overload-induced myocardial hypertrophy in mice through proteasome inhibition

Myocardial hypertrophy is a pathological thickening of the myocardium which ultimately results in heart failure. We previously reported that zonisamide, an antiepileptic drug, attenuated pressure overload-caused myocardial hypertrophy and diabetic cardiomyopathy in murine models. In addition, we have found that the inhibition of proteasome activates glycogen synthesis kinase 3 (GSK-3) thus alleviates myocardial hypertrophy, which is an important anti-hypertrophic strategy. In this study, we investigated whether zonisamide prevented pressure overload-caused myocardial hypertrophy through suppressing proteasome. Pressure overload-caused myocardial hypertrophy was induced in mice by trans-aortic constriction (TAC) surgery. Two days after the surgery, the mice were administered zonisamide (10, 20, 40 mg·kg-1·d-1, i.g.) for four weeks. We showed that zonisamide administration significantly mitigated impaired cardiac function. Furthermore, zonisamide administration significantly inhibited proteasome activity as well as the expression levels of proteasome subunit beta types (PSMB) of the 20 S proteasome (PSMB1, PSMB2 and PSMB5) and proteasome-regulated particles (RPT) of the 19 S proteasome (RPT1, RPT4) in heart tissues of TAC mice. In primary neonatal rat cardiomyocytes (NRCMs), zonisamide (0.3 μM) prevented myocardial hypertrophy triggered by angiotensin II (Ang II), and significantly inhibited proteasome activity, proteasome subunits and proteasome-regulated particles. In Ang II-treated NRCMs, we found that 18α-glycyrrhetinic acid (18α-GA, 2 mg/ml), a proteasome inducer, eliminated the protective effects of zonisamide against myocardial hypertrophy and proteasome. Moreover, zonisamide treatment activated GSK-3 through inhibiting the phosphorylated AKT (protein kinase B, PKB) and phosphorylated liver kinase B1/AMP-activated protein kinase (LKB1/AMPKα), the upstream of GSK-3. Zonisamide treatment also inhibited GSK-3's downstream signaling proteins, including extracellular signal-regulated kinase (ERK) and GATA binding protein 4 (GATA4), both being the hypertrophic factors. Collectively, this study highlights the potential of zonisamide as a new therapeutic agent for myocardial hypertrophy, as it shows potent anti-hypertrophic potential through the suppression of proteasome.

The role of hydrogen sulfide regulation of pyroptosis in different pathological processes

Pyroptosis is one kind of programmed cell death in which the cell membrane ruptures and subsequently releases cell contents and pro-inflammatory cytokines including IL-1β and IL-18. Pyroptosis is caused by many types of pathological stimuli, such as hyperglycemia (HG), oxidative stress, and inflammation, and is mediated by gasdermin (GSDM) protein family. Increasing evidence indicates that pyroptosis plays an important role in multiple diseases, such as cancer, kidney diseases, inflammatory diseases, and cardiovascular diseases. Therefore, the regulation of pyroptosis is crucial for the occurrence, development, and treatment of many diseases. Hydrogen sulfide (H2S) is a biologically active gasotransmitter following carbon monoxide (CO) and nitrogen oxide (NO) in mammalian tissues. So far, three enzymes, including 3-mercaptopyruvate sulphurtransferase (3-MST), cystathionine γ- Lyase (CSE), and Cystine β-synthesis enzyme (CBS), have been found to catalyze the production of endogenous H2S in mammals. H2S has been reported to have multiple biological functions including anti-inflammation, anti-oxidative stress, anti-apoptosis and so on. Hence, H2S is involved in various physiological and pathological processes. In recent years, many studies have demonstrated that H2S plays a critical role by regulating pyroptosis in various pathological processes, such as ischemia-reperfusion injury, alcoholic liver disease, and diabetes cardiomyopathy. However, the relevant mechanism has not been completely understood. Therefore, elucidating the mechanism by which H2S regulates pyroptosis in diseases will help understand the pathogenesis of multiple diseases and provide important new avenues for the treatment of many diseases. Here, we reviewed the progress of H2S regulation of pyroptosis in different pathological processes, and analyzed the molecular mechanism in detail to provide a theoretical reference for future related research.

Casting Light on the Janus-Faced HMG-CoA Reductase Degradation Protein 1: A Comprehensive Review of Its Dualistic Impact on Apoptosis in Various Diseases

Nowadays, it is well recognized that apoptosis, as a highly regulated cellular process, plays a crucial role in various biological processes, such as cell differentiation. Dysregulation of apoptosis is strongly implicated in the pathophysiology of numerous disorders, making it essential to comprehend its underlying mechanisms. One key factor that has garnered significant attention in the regulation of apoptotic pathways is HMG-CoA reductase degradation protein 1, also known as HRD1. HRD1 is an E3 ubiquitin ligase located in the endoplasmic reticulum (ER) membrane. Its primary role involves maintaining the quality control of ER proteins by facilitating the ER-associated degradation (ERAD) pathway. During ER stress, HRD1 aids in the elimination of misfolded proteins that accumulate within the ER. Therefore, HRD1 plays a pivotal role in the regulation of apoptotic pathways and maintenance of ER protein quality control. By targeting specific protein substrates and affecting apoptosis-related pathways, HRD1 could be an exclusive therapeutic target in different disorders. Dysregulation of HRD1-mediated processes contributes significantly to the pathophysiology of various diseases. The purpose of this review is to assess the effect of HRD1 on the pathways related to apoptosis in various diseases from a therapeutic perspective.

Zonisamide: A Comprehensive, Updated Review for the Clinician

Purpose of Review

Zonisamide (ZNS) was first approved in the United States in 2000 for the adjunctive treatment of patients aged 16 years or older with partial (focal) seizures. Although ZNS has been proven to treat multiple seizure types, it has been largely underutilized in US clinical practice.

Recent Findings

Published literature demonstrated that antiseizure medications (ASMs) acting on Na+ and Ca2+ channels may add beneficial effects in many seizure types by reducing seizure frequency and leading to overall improvements. In addition, effects of ZNS may lead to clinical improvements in Parkinson disease, alcohol and sleep disorders, pain, and migraine. ZNS is available in multiple formulations and is a safe and effective, broad spectrum ASM.

Summary

The purpose of this review was to provide an update to what is known about the efficacy of ZNS and where it shows benefits in the treatment of patients with epilepsy and other CNS disorders through its many unique mechanisms of action.

Chinese herbal medicine and active ingredients for diabetic cardiomyopathy: molecular mechanisms regulating endoplasmic reticulum stress

Background: Diabetic cardiomyopathy (DCM) is one of the serious microvascular complications of diabetes mellitus. It is often associated with clinical manifestations such as arrhythmias and heart failure, and significantly reduces the quality of life and years of survival of patients. Endoplasmic reticulum stress (ERS) is the removal of unfolded and misfolded proteins and is an important mechanism for the maintenance of cellular homeostasis. ERS plays an important role in the pathogenesis of DCM by causing cardiomyocyte apoptosis, insulin resistance, calcium imbalance, myocardial hypertrophy and fibrosis. Targeting ERS is a new direction in the treatment of DCM. A large number of studies have shown that Chinese herbal medicine and active ingredients can significantly improve the clinical outcome of DCM patients through intervention in ERS and effects on myocardial structure and function, which has become one of the hot research directions. Purpose: The aim of this review is to elucidate and summarize the roles and mechanisms of Chinese herbal medicine and active ingredients that have the potential to modulate endoplasmic reticulum stress, thereby contributing to better management of DCM. Methods: Databases such as PubMed, Web of Science, China National Knowledge Internet, and Wanfang Data Knowledge Service Platform were used to search, analyze, and collect literature, in order to review the mechanisms by which phytochemicals inhibit the progression of DCM by targeting the ERS and its key signaling pathways. Keywords used included "diabetic cardiomyopathy" and "endoplasmic reticulum stress." Results: This review found that Chinese herbs and their active ingredients can regulate ERS through IRE1, ATF6, and PERK pathways to reduce cardiomyocyte apoptosis, ameliorate myocardial fibrosis, and attenuate myocardial hypertrophy for the treatment of DCM. Conclusion: A comprehensive source of information on potential ERS inhibitors is provided in this review. The analysis of the literature suggests that Chinese herbal medicine and its active ingredients can be used as potential drug candidates for the treatment of DCM. In short, we cannot ignore the role of traditional Chinese medicine in regulating ERS and treating DCM, and look forward to more research and new drugs to come.

Down-regulation of Hrd1 protects against myocardial ischemia-reperfusion injury by regulating PPARα to prevent oxidative stress, endoplasmic reticulum stress, and cellular apoptosis

The E3 ubiquitin ligase HMG-CoA reductase degradation protein 1 (Hrd1) is a key enzyme for ER-associated degradation of misfolded proteins. Its role in ischemic heart disease has not been fully elucidated. Here, we investigated its effect on oxidative status and cell survival in cardiac ischemia-reperfusion injury (MIRI). We found that virus-induced down-regulation of Hrd1 expression limited infarct size, decreased creatinine kinase (CK) and lactate dehydrogenase (LDH), and preserved cardiac function in mice subjected to left anterior descending coronary artery ligation and reperfusion. Silencing of the Hrd1 gene also prevented the ischemia/reperfusion (I/R)-induced (i) increase in dihydroethidium (DHE) intensity, mitochondrial production of reactive oxygen species (ROS), malondialdehyde (MDA), and nitric oxide (NO), (ii) decrease in total antioxidant capacity (T-AOC) and glutathione (GSH), (iii) disruption of mitochondrial membrane potential, and (iv) increase in the expression of glucose-regulated protein 78 (GRP78) and C/EBP homologous protein (CHOP) in ischemic heart tissue. In addition, down-regulation of Hrd1 expression prevented the abnormally increased caspase-3/caspase-9/Bax expression and decreased Bcl-2 expression in ischemic heart tissue of I/R mice. Further analysis showed that the I/R stimulus reduced peroxisome proliferation activated receptor α (PPARα) expression in ischemic heart tissue, which was partially prevented by down-regulation of Hrd1. Pharmacological inhibition of PPARα was able to abolish the preventive effect of down-regulation of Hrd1 on oxidative stress, endoplasmic reticulum stress, and cellular apoptosis in ischemic heart tissue. These data suggest that down-regulation of Hrd1 protects the heart from I/R-induced damage by suppressing oxidative stress and cellular apoptosis likely through PPARα.

Role of STIM1 in the Regulation of Cardiac Energy Substrate Preference

The heart requires a variety of energy substrates to maintain proper contractile function. Glucose and long-chain fatty acids (FA) are the major cardiac metabolic substrates under physiological conditions. Upon stress, a shift of cardiac substrate preference toward either glucose or FA is associated with cardiac diseases. For example, in pressure-overloaded hypertrophic hearts, there is a long-lasting substrate shift toward glucose, while in hearts with diabetic cardiomyopathy, the fuel is switched toward FA. Stromal interaction molecule 1 (STIM1), a well-established calcium (Ca2+) sensor of endoplasmic reticulum (ER) Ca2+ store, is increasingly recognized as a critical player in mediating both cardiac hypertrophy and diabetic cardiomyopathy. However, the cause-effect relationship between STIM1 and glucose/FA metabolism and the possible mechanisms by which STIM1 is involved in these cardiac metabolic diseases are poorly understood. In this review, we first discussed STIM1-dependent signaling in cardiomyocytes and metabolic changes in cardiac hypertrophy and diabetic cardiomyopathy. Second, we provided examples of the involvement of STIM1 in energy metabolism to discuss the emerging role of STIM1 in the regulation of energy substrate preference in metabolic cardiac diseases and speculated the corresponding underlying molecular mechanisms of the crosstalk between STIM1 and cardiac energy substrate preference. Finally, we briefly discussed and presented future perspectives on the possibility of targeting STIM1 to rescue cardiac metabolic diseases. Taken together, STIM1 emerges as a key player in regulating cardiac energy substrate preference, and revealing the underlying molecular mechanisms by which STIM1 mediates cardiac energy metabolism could be helpful to find novel targets to prevent or treat cardiac metabolic diseases.

Tanshinone IIA ameliorates experimental diabetic cardiomyopathy by inhibiting endoplasmic reticulum stress in cardiomyocytes via SIRT1

Diabetic cardiomyopathy (DCM) is a common complication in patients with diabetes, and ultimately leads to heart failure. Endoplasmic reticulum stress (ERS) induced by abnormal glycolipid metabolism is a critical factor that affects the occurrence and development of DCM. Additionally, the upregulation/activation of silent information regulation 2 homolog-1 (SIRT1) has been shown to protect against DCM. Tanshinone II A (Tan IIA), the main active component of Salviae miltiorrhizae radix et rhizome (a valuable Chinese medicine), has protective effects against cardiovascular disease and diabetes. However, its role and mechanisms in diabetes-induced cardiac dysfunction remain unclear. Therefore, we explored whether Tan IIA alleviates ERS-mediated DCM via SIRT1 and elucidated the underlying mechanism. The results suggested that Tan IIA alleviated the pathological changes in the hearts of diabetic mice, ameliorated the cytopathological morphology of cardiomyocytes, reduced the cell death rate, and inhibited the expression of ERS-related proteins and mRNA. The SIRT1 agonist inhibited the activities of glucose-regulated protein 78 (GRP78). Furthermore, the opposite results under the SIRT1 inhibitor. SIRT1 knockdown was induced by siRNA-SIRT1 transfection, and the degree of GRP78 acetylation was increased. Cumulatively, Tan IIA ameliorated DCM by inhibiting ERS and upregulating SIRT1 expression.

Diabetic cardiomyopathy: Early diagnostic biomarkers, pathogenetic mechanisms, and therapeutic interventions

Diabetic cardiomyopathy (DCM) mainly refers to myocardial metabolic dysfunction caused by high glucose, and hyperglycemia is an independent risk factor for cardiac function in the absence of coronary atherosclerosis and hypertension. DCM, which is a severe complication of diabetes, has become the leading cause of heart failure in diabetic patients. The initial symptoms are inconspicuous, and patients gradually exhibit left ventricular dysfunction and eventually develop total heart failure, which brings a great challenge to the early diagnosis of DCM. To date, the underlying pathological mechanisms of DCM are complicated and have not been fully elucidated. Although there are therapeutic strategies available for DCM, the treatment is mainly focused on controlling blood glucose and blood lipids, and there is a lack of effective drugs targeting myocardial injury. Thus, a large percentage of patients with DCM inevitably develop heart failure. Given the neglected initial symptoms, the intricate cellular and molecular mechanisms, and the lack of available drugs, it is necessary to explore early diagnostic biomarkers, further understand the signaling pathways involved in the pathogenesis of DCM, summarize the current therapeutic strategies, and develop new targeted interventions.

Molecular Mechanism Underlying Role of the XBP1s in Cardiovascular Diseases

Spliced X-box binding protein-1 (XBP1s) is a protein that belongs to the cAMP-response element-binding (CREB)/activating transcription factor (ATF) b-ZIP family with a basic-region leucine zipper (bZIP). There is mounting evidence to suggest that XBP1s performs a critical function in a range of different cardiovascular diseases (CVDs), indicating that it is necessary to gain a comprehensive knowledge of the processes involved in XBP1s in various disorders to make progress in research and clinical therapy. In this research, we provide a summary of the functions that XBP1s performs in the onset and advancement of CVDs such as atherosclerosis, hypertension, cardiac hypertrophy, and heart failure. Furthermore, we discuss XBP1s as a novel therapeutic target for CVDs.

Pretreatment with Zonisamide Mitigates Oxaliplatin-Induced Toxicity in Rat DRG Neurons and DRG Neuron–Schwann Cell Co-Cultures

Oxaliplatin (OHP) is a platinum-based agent that can cause peripheral neuropathy, an adverse effect in which the dorsal root ganglion (DRG) neurons are targeted. Zonisamide has exhibited neuroprotective activities toward adult rat DRG neurons in vitro and therefore, we aimed to assess its potential efficacy against OHP-induced neurotoxicity. Pretreatment with zonisamide (100 μM) alleviated the DRG neuronal death caused by OHP (75 μM) and the protective effects were attenuated by a co-incubation with 25 μM of the mitogen-activated protein kinase (MAPK; MEK/ERK) inhibitor, U0126, or the phosphatidyl inositol-3′-phosphate-kinase (PI3K) inhibitor, LY294002. Pretreatment with zonisamide also suppressed the OHP-induced p38 MAPK phosphorylation in lined DRG neurons, ND7/23, while the OHP-induced DRG neuronal death was alleviated by pretreatment with the p38 MAPK inhibitor, SB239063 (25 μM). Although zonisamide failed to protect the immortalized rat Schwann cells IFRS1 from OHP-induced cell death, it prevented neurite degeneration and demyelination-like changes, as well as the reduction of the serine/threonine-specific protein kinase (AKT) phosphorylation in DRG neuron–IFRS1 co-cultures exposed to OHP. Zonisamide’s neuroprotection against the OHP-induced peripheral sensory neuropathy is possibly mediated by a stimulation of the MEK/ERK and PI3K/AKT signaling pathways and suppression of the p38 MAPK pathway in DRG neurons. Future studies will allow us to solidify zonisamide as a promising remedy against the neurotoxic adverse effects of OHP.

Irisin alleviates high glucose-induced hypertrophy in H9c2 cardiomyoblasts by inhibiting endoplasmic reticulum stress

BACKGROUND

Endoplasmic reticulum stress (ERS) plays an important role in the process of myocardial hypertrophy in diabetic cardiomyopathy (DCM). Irisin, a novel cytokine, has been found to protect against cardiac diastolic dysfunction in DCM. We aimed to investigate the role of irisin in cardiac hypertrophy and to elucidate the underlying mechanisms.

METHODS

H9c2 cells were induced with 33 mM glucose to construct a cardiac hypertrophy cell model, which was then treated with irisin in the presence or absence of the ERS inducer tunicamycin (TM). The cell surface area was measured by FITC-phalloidin staining. The atrial natriuretic peptide levels were detected by an enzyme-linked immunosorbent assay. Furthermore, the expression of the ERS-related proteins, P-PERK, PERK, IRE1α and GRP78, was detected by western blotting.

RESULTS

Irisin significantly reduced myocardial hypertrophy and suppressed high glucose (HG)-induced oxidative stress. Meanwhile, the protective effect of irisin on cardiomyoblasts was reversed by the ERS inducer, TM. Additionally, we detected ERS-associated signaling pathway proteins and found that irisin significantly reduced the protein expression levels of GRP78 and p-PERK/PERK.

CONCLUSION

These results suggest that irisin ameliorates HG-induced cardiac hypertrophy by inhibiting ERS.

A Novel Compound, Tanshinol Borneol Ester, Ameliorates Pressure Overload-Induced Cardiac Hypertrophy by Inhibiting Oxidative Stress via the mTOR/β-TrCP/NRF2 Pathway

Tanshinol borneol ester (DBZ) exerts anti-atherosclerotic and anti-inflammatory effects. However, its effects on cardiac hypertrophy are not well understood. In this work, we investigated the treatment effects and potential mechanisms of DBZ on the hypertrophic heart under oxidative stress and endoplasmic reticulum (ER) stress. A hypertrophic model was established in rats using transverse-aortic constriction (TAC) surgery and in neonatal rat cardiomyocytes (NRCMs) using angiotensin II (Ang II). Our results revealed that DBZ remarkably inhibited oxidative stress and ER stress, blocked autophagy flow, and decreased apoptosis in vivo and in vitro through nuclear NRF2 accumulation, and enhanced NRF2 stability via regulating the mTOR/β-TrcP/NRF2 signal pathway. Thus, DBZ may serve as a promising therapeutic for stress-induced cardiac hypertrophy.

In vitro and in vivo studies reveal the beneficial effects of chlorogenic acid against ER stress mediated ER-phagy and associated apoptosis in the heart of diabetic rat

Endoplasmic reticulum (ER) and associated signaling pathways are involved in diabetic cardiomyopathy (DCM) however, detailed studies are not available. The present study investigated the role of ER stress and related pathways such as ER-phagy, apoptosis and their underlying mechanisms using appropriate models. Beneficial effect of chlorogenic acid was also evaluated against ER stress mediated DCM. H9c2 cells with high glucose (33 mM, in vitro model of hyperglycemia) showed significant activation of ER stress response (GRP78, PERK, IRE1α, ATF6α) and altered its regulatory proteins (PDI, ERO1α). Also, it enhanced ER-phagy through upregulation of Sec62, RTN3 and downregulation of FAM134B. High glucose caused apoptosis via increased levels of CHOP, caspase 12 and calnexin. All these proteins (PERK, IRE1α, ATF6α, RTN3, Sec62 and FAM134B) have been found to have a significant role in the functioning of heart such as excitation contraction coupling and we expect these alterations to induce cardiomyopathy during diabetes. This was confirmed in in vivo study too. High fat, high fructose diet with mild streptozotocin induced diabetic rats showed an increased expression of BNP confirming cardiac injury. We also noticed severe ER stress in the heart of diabetic animals. All these have contributed significantly into alterations in histopathology and increase of weight of the hearts. These findings clearly show that ER stress plays a vital protagonist in the progression of DCM. We also found chlorogenic acid is effective against hyperglycemia induced pathological alteration both in vitro as well as in vivo.

Zonisamide alleviates cardiac hypertrophy in rats by increasing Hrd1 expression and inhibiting endoplasmic reticulum stress

Antiepileptic drug zonisamide has been shown to be curative for Parkinson's disease (PD) through increasing HMG-CoA reductase degradation protein 1 (Hrd1) level and mitigating endoplasmic reticulum (ER) stress. Hrd1 is an ER-transmembrane E3 ubiquitin ligase, which is involved in cardiac dysfunction and cardiac hypertrophy in a mouse model of pressure overload. In this study, we investigated whether zonisamide alleviated cardiac hypertrophy in rats by increasing Hrd1 expression and inhibiting ER stress. The beneficial effects of zonisamide were assessed in two experimental models of cardiac hypertrophy: in rats subjected to abdominal aorta constriction (AAC) and treated with zonisamide (14, 28, 56 mg · kg-1 · d-1, i.g.) for 6 weeks as well as in neonatal rat cardiomyocytes (NRCMs) co-treated with Ang II (10 μM) and zonisamide (0.3 μM). Echocardiography analysis revealed that zonsiamide treatment significantly improved cardiac function in AAC rats. We found that zonsiamide treatment significantly attenuated cardiac hypertrophy and fibrosis, and suppressed apoptosis and ER stress in the hearts of AAC rats and in Ang II-treated NRCMs. Importantly, zonisamide markedly increased the expression of Hrd1 in the hearts of AAC rats and in Ang II-treated NRCMs. Furthermore, we demonstrated that zonisamide accelerated ER-associated protein degradation (ERAD) in Ang II-treated NRCMs; knockdown of Hrd1 abrogated the inhibitory effects of zonisamide on ER stress and cardiac hypertrophy. Taken together, our results demonstrate that zonisamide is effective in preserving heart structure and function in the experimental models of pathological cardiac hypertrophy. Zonisamide increases Hrd1 expression, thus preventing cardiac hypertrophy and improving the cardiac function of AAC rats.

Mitofusin-2 Enhances Mitochondrial Contact With the Endoplasmic Reticulum and Promotes Diabetic Cardiomyopathy

Diabetic cardiomyopathy has been associated with mitochondrial damage. Mitochondria–endoplasmic reticulum (ER) contact is an important determinant of mitochondrial function and ER homeostasis. We therefore investigated whether hyperglycemia can damage the mitochondria by increasing their contact with the ER in cardiomyocytes. We found that hyperglycemia induced mitochondria–ER contact in cardiomyocytes, as evidenced by the increased MMM1, MDM34, and BAP31 expressions. Interestingly, the silencing of Mfn2 reduced the cooperation between the mitochondria and the ER in cardiomyocytes. Mfn2 silencing improved cardiomyocyte viability and function under hyperglycemic conditions. Additionally, the silencing of Mfn2 markedly attenuated the release of calcium from the ER to the mitochondria, thereby preserving mitochondrial metabolism in cardiomyocytes under hyperglycemic conditions. Mfn2 silencing reduced mitochondrial reactive oxygen species production, which reduced mitochondria-dependent apoptosis in hyperglycemia-treated cardiomyocytes. Finally, Mfn2 silencing attenuated ER stress in cardiomyocytes subjected to high-glucose stress. These results demonstrate that Mfn2 promotes mitochondria–ER contact in hyperglycemia-treated cardiomyocytes. The silencing of Mfn2 sustained mitochondrial function, suppressed mitochondrial calcium overload, prevented mitochondrial apoptosis, and reduced ER stress, thereby enhancing cardiomyocyte survival under hyperglycemic conditions.

FNDC5/Irisin attenuates diabetic cardiomyopathy in a type 2 diabetes mouse model by activation of integrin αV/β5-AKT signaling and reduction of oxidative/nitrosative stress

Irisin, the cleaved form of the fibronectin type III domain containing 5 (FNDC5) protein, is involved in metabolism and inflammation. Recent findings indicated that irisin participated in cardiovascular physiology and pathology. In this study, we investigated the effects of FNDC5/irisin on diabetic cardiomyopathy (DCM) in type 2 diabetic db/db mice. Downregulation of myocardial FNDC5/irisin protein expression and plasma irisin levels was observed in db/db mice compared to db/+ controls. Moreover, echocardiography revealed that db/db mice exhibited normal cardiac systolic function and impaired diastolic function. Adverse structural remodeling, including cardiomyocyte apoptosis, myocardial fibrosis, and cardiac hypertrophy were observed in the hearts of db/db mice. Sixteen-week-old db/db mice were intramyocardially injected with adenovirus encoding FNDC5 or treated with recombinant human irisin via a peritoneal implant osmotic pump for 4 weeks. Both overexpression of myocardial FNDC5 and exogenous irisin administration attenuated diastolic dysfunction and cardiac structural remodeling in db/db mice. Results from in vitro studies revealed that FNDC5/irisin protein expression was decreased in high glucose (HG)/high fat (HF)-treated cardiomyocytes. Increased levels of inducible nitric oxide synthase (iNOS), NADPH oxidase 2 (NOX2), 3-nitrotyrosine (3-NT), reactive oxygen species (ROS), and peroxynitrite (ONOO^-) in HG/HF-treated H9C2 cells provided evidence of oxidative/nitrosative stress, which was alleviated by treatment with FNDC5/irisin. Moreover, the mitochondria membrane potential (ΔΨm) was decreased and cytochrome C was released from mitochondria with increased levels of cleaved caspase-3 in HG/HF-treated H9C2 cells, indicating the presence of mitochondria-dependent apoptosis, which was partially reversed by FNDC5/irisin treatment. Mechanistic studies showed that activation of integrin αVβ5-AKT signaling and attenuation of oxidative/nitrosative stress were responsible for the cardioprotective effects of FNDC5/irisin. Therefore, FNDC5/irisin mediates cardioprotection in DCM by inhibiting myocardial apoptosis, myocardial fibrosis, and cardiac hypertrophy. These findings implicate that FNDC5/irisin as a potential therapeutic intervention for DCM, especially in type 2 diabetes mellitus (T2DM).

Combination of Dendrobium Mixture and Metformin Curbs the Development and Progression of Diabetic Cardiomyopathy by Targeting the lncRNA NEAT1

OBJECTIVES

This study aimed to explore the efficacy of combination treatment with dendrobium mixture and metformin (Met) in diabetic cardiomyopathy (DCM) and its effects on NEAT1 and the Nrf2 signaling pathway.

METHODS

H9c2 cells were maintained in medium supplemented with either low (5.5 mmol/L) or high (50 mmol/L) glucose. Male Sprague-Dawley rats were fed a high-glucose diet and administered a single, low dose of streptozotocin (35 mg/kg) via intraperitoneal injection to induce the development of DM. After induction of DM, the rats were treated with dendrobium mixture (10 g/kg) and Met (0.18 g/kg) daily for 4 weeks. Next, quantitative reverse transcription (qRT)-PCR and western blotting were performed to evaluate the expression levels of target genes and proteins. Flow cytometry was performed to assess apoptosis, and hematoxylin and eosin staining was performed to evaluate the morphological changes in rat cardiac tissue.

RESULTS

In patients with diabetes mellitus (DM) and myocardial cells and heart tissues from rats with high glucose-induced DM, NEAT1 was downregulated, and the expression levels of Nrf2 were decreased (p<0.01, p<0.001). The combination of dendrobium mixture and Met upregulated the expression of NEAT1 which upregulated Nrf2 by targeting miR-23a-3p, resulting in reduced apoptosis and improved cardiac tissue morphology (p<0.01, p<0.001).

CONCLUSION

Dendrobium mixture and Met upregulated the expression of NEAT1 in DCM, thereby inhibiting apoptosis of myocardial cells.

PSTi8 with metformin ameliorates perimenopause induced steatohepatitis associated ER stress by regulating SIRT-1/SREBP-1c axis

Aims

Hepatic steatosis in women confronting menopause is the manifestation of substantial fructose consumption and forms a positive feedback loop to develop endoplasmic reticulum (ER) stress. Previously pancreastatin inhibitor peptide-8 (PSTi8) and Metformin (Met) combination effectively ameliorated hepatic lipid accumulation in high fructose diet (HFrD) fed diabetic mice models at reduced doses. Moreover, SIRT-1 plays a crucial role in the regulation of SREBP-1c. Hence we hypothesized that Met and PSTi8 in combination (at therapeutic lower doses) could mitigate hepatic steatosis linked ER stress by activating SIRT-1 and precluding SREBP-1c in HFrD fed 4-Vinylcyclohexenediepoxide (HVCD) induced perimenopausal rats.

Main methods

HVCD rats were fed HFrD for 12 weeks, accompanied by 14 days of treatment with Met, PSTi8, and combination. We confirmed model establishment by estrus cycle study, estradiol level, and intraperitoneal glucose tolerance test. Plasma lipid profile and liver function were determined. Also, mRNA and protein expressions were examined. Moreover, distribution of SIRT-1 and SREBP-1c was detected in HepG2 cells by immunofluorescence staining.

Key findings

HVCD group displayed augmented insulin resistance (IR), lipogenesis, and ER stress in the liver. Combination therapy improved the estrus cyclicity, estradiol, and lipid profile of HVCD rats. Met and PSTi8 combination reduced hepatic SREBP-1c and triggered SIRT-1 expression in high fructose-induced insulin-resistant HepG2 cells; consequently, combination therapy attenuated ER stress.

Significance

Succinctly, present research promotes impetus concerning the remedial impact of Met with PSTi8 at lower therapeutic doses to ameliorate hepatic IR, steatosis, and associated ER stress by revamping the SIRT-1/SREBP-1c axis in perimenopausal rats.

Heart Failure in Diabetes Mellitus: An Updated Review

Diabetes mellitus (DM) and heart failure (HF) are comorbid conditions associated with significant morbidity and mortality worldwide. Despite the availability of novel and effective therapeutic options and intensive glycaemic control strategies, mortality and hospitalisation rates continue to remain high and the incidence of HF persists. In this review, we described the impact of currently available glucose-lowering therapies in DM with a focus on HF clinical outcomes. Non-conventional modes of management and alternative pathophysiological mechanisms with the potential for therapeutic targeting are also discussed.