GCN2 deficiency ameliorates cardiac dysfunction in diabetic mice by reducing lipotoxicity and oxidative stress

Cardiac energy metabolism in diabetes: emerging therapeutic targets and clinical implications

Patients with diabetes are at an increased risk for developing diabetic cardiomyopathy and other cardiovascular complications. Alterations in cardiac energy metabolism in patients with diabetes, including an increase in mitochondrial fatty acid oxidation and a decrease in glucose oxidation, are important contributing factors to this increase in cardiovascular disease. A switch from glucose oxidation to fatty acid oxidation not only decreases cardiac efficiency due to increased oxygen consumption but it can also increase reactive oxygen species production, increase lipotoxicity, and redirect glucose into other metabolic pathways that, combined, can lead to heart dysfunction. Currently, there is a lack of therapeutics available to treat diabetes-induced heart failure that specifically target cardiac energy metabolism. However, it is becoming apparent that part of the benefit of existing agents such as GLP-1 receptor agonists and sodium-glucose cotransporter 2 inhibitors may be related to their effects on cardiac energy metabolism. In addition, direct approaches aimed at inhibiting cardiac fatty acid oxidation or increasing glucose oxidation hold future promise as potential therapeutic approaches to treat diabetes-induced cardiovascular disease.

Astragalus polysaccharide alleviates oxidative stress and senescence in chondrocytes in osteoarthritis via GCN2/ATF4/TXN axis

The treatment of osteoarthritis (OA) remains challenging, with oxidative stress in the cartilage emerging as a key therapeutic target. This study investigates how Astragalus polysaccharide (APS) exerts antioxidant effects in OA using in vivo and in vitro models. In mice, APS mitigates OA progression following surgical destabilization of the medial meniscus (DMM) and protects against oxidative damage. Immunofluorescence analysis revealed decreased thioredoxin (TXN) expression in DMM cartilage, which was restored by APS. APS preserved mitochondrial function, redox balance, and matrix synthesis in chondrocytes in vitro while suppressing metalloproteinase expression. APS also reduced senescence markers (p53, p21INK4a, and p16), DNA damage, and β-galactosidase activity in tert-butyl hydroperoxide (tBHP)-treated chondrocytes. TXN knockdown significantly diminishes the protective effects of APS Further analysis showed that ATF4 overexpression supports the GCN2-ATF4 pathway's involvement in APS. GCN2 inhibition using GCN2iB reduced the regulatory impact of APS on TXN, indicating the crucial role GCN2 in APS-mediated protection. These findings demonstrated that APS protects chondrocytes from oxidative stress and senescence in OA via the GCN2/TXN pathway, suggesting its potential as a therapeutic agent for OA.

Lipotoxicity as a therapeutic target in the type 2 diabetic heart

Cardiac lipotoxicity, characterized by excessive lipid accumulation in the cardiac tissue, is a critical contributor to the pathogenesis of diabetic heart. Recent research has highlighted the key mechanisms underlying lipotoxicity, including mitochondrial dysfunction, endoplasmic reticulum stress, inflammation, and cell apoptosis, which ultimately impair the cardiac function. Various therapeutic interventions have been developed to target these pathways, mitigate lipotoxicity, and improve cardiovascular outcomes in diabetic patients. Given the global escalation in the prevalence of diabetes and the urgent demand for effective therapeutic approaches, this review focuses on how targeting cardiac lipotoxicity may be a promising avenue for treating diabetes.

Right ventricular dysfunction in preclinical models of type I and type II diabetes

Diabetic cardiomyopathy (DCM) is a growing clinical entity and major health burden characterized by comorbid diabetes mellitus and heart failure. DCM has been commonly associated with impaired function of the left ventricle (LV); however, DCM likely also occurs in the right ventricle (RV) which has distinct physiology and pathophysiology from the LV. RV dysfunction is the strongest determinant of mortality in several clinical contexts yet remains poorly studied in diabetes. We investigated RV-specific pathophysiology using two models of diabetes-a well-characterized type 2 diabetes (T2DM) model of high-fat diet and low-dose streptozotocin (STZ) in the mouse and a large animal model of type I diabetes in domestic pigs rendered diabetic with STZ. RV global and systolic function deteriorated with diabetes, alongside hypertrophic and fibrotic remodeling. We report evidence of impaired RV insulin sensitivity, dysregulated RV metabolic gene expression, and impaired mitochondrial dynamics. Importantly, while some of these outcomes were similar to those widely reported in the LV, others were not, such as unchanged antioxidant gene expression and regulators of fatty acid uptake. Importantly, these RV-specific changes occurred in both male and female T2DM mice, together emphasizing the importance of distinguishing the RV from the LV when studying DCM and begging the consideration of RV-specific therapies.

Novel insights into the GCN2 pathway and its targeting. Therapeutic value in cancer and lessons from lung fibrosis development

Defining the mechanisms that allow cells to adapt to environmental stress is critical for understanding the progression of chronic diseases and identifying relevant drug targets. Among these, activation of the pathway controlled by the eIF2-alpha kinase GCN2 is critical for translational and metabolic reprogramming of the cell in response to various metabolic, proteotoxic, and ribosomal stressors. However, its role has frequently been investigated through the lens of a stress pathway signaling via the eIF2α-activating transcription factor 4 (ATF4) downstream axis, while recent advances in the field have revealed that the GCN2 pathway is more complex than previously thought. Indeed, this kinase can be activated through a variety of mechanisms, phosphorylate substrates other than eIF2α, and regulate cell proliferation in a steady state. This review presents recent findings regarding the fundamental mechanisms underlying GCN2 signaling and function, as well as the development of drugs that modulate its activity. Furthermore, by comparing the literature on GCN2's antagonistic roles in two challenging pathologies, cancer and pulmonary diseases, the benefits, and drawbacks of GCN2 targeting, particularly inhibition, are discussed.

General control nonderepressible 2 (GCN2) as a therapeutic target in age-related diseases

The function of General Control Nonderepressible 2 (GCN2), an evolutionary-conserved component of the integrated stress response (ISR), has been well-documented across organisms from yeast to mammals. Recently GCN2 has also gained attention for its role in health and disease states. In this review, we provide a brief overview of GCN2, including its structure, activation mechanisms and interacting partners, and explore its potential significance as a therapeutic target in various age-related diseases including neurodegeneration, inflammatory disorders and cancer. Finally, we summarize the barriers to effectively targeting GCN2 for the treatment of disease and to promote a healthier aging process.

Molecular mechanisms of metabolic dysregulation in diabetic cardiomyopathy

Diabetic cardiomyopathy (DCM), one of the most serious complications of diabetes mellitus, has become recognized as a cardiometabolic disease. In normoxic conditions, the majority of the ATP production (>95%) required for heart beating comes from mitochondrial oxidative phosphorylation of fatty acids (FAs) and glucose, with the remaining portion coming from a variety of sources, including fructose, lactate, ketone bodies (KB) and branched chain amino acids (BCAA). Increased FA intake and decreased utilization of glucose and lactic acid were observed in the diabetic hearts of animal models and diabetic patients. Moreover, the polyol pathway is activated, and fructose metabolism is enhanced. The use of ketones as energy sources in human diabetic hearts also increases significantly. Furthermore, elevated BCAA levels and impaired BCAA metabolism were observed in the hearts of diabetic mice and patients. The shift in energy substrate preference in diabetic hearts results in increased oxygen consumption and impaired oxidative phosphorylation, leading to diabetic cardiomyopathy. However, the precise mechanisms by which impaired myocardial metabolic alterations result in diabetes mellitus cardiac disease are not fully understood. Therefore, this review focuses on the molecular mechanisms involved in alterations of myocardial energy metabolism. It not only adds more molecular targets for the diagnosis and treatment, but also provides an experimental foundation for screening novel therapeutic agents for diabetic cardiomyopathy.

Phytoformulation with hydroxycitric acid and capsaicin protects against high-fat-diet-induced obesity cardiomyopathy by reducing cardiac lipid deposition and ameliorating inflammation and apoptosis in the heart

BACKGROUND AND AIM

Phytoformulation therapy is a pioneering strategy for the treatment of metabolic disorders and related diseases. The aim of the present study was to investigate the protective effect of a phytoformulation consisting of hydroxycitric acid and capsaicin against obesity-related cardiomyopathy.

EXPERIMENTAL PROCEDURE

Sprague-Dawley rats were fed HFD for 21 weeks, and phytoformulation (100 mg/kg body weight) was administered orally for 45 days starting at week 16.

RESULTS AND CONCLUSION

We found that HFD supplementation resulted in significant hyperglycemia and caused an increase in cardiac lipid deposition, inflammation and apoptosis in the heart. Phytoformulation therapy not only significantly decreased blood levels of glucose, cholesterol, triglycerides, free fatty acids, and inflammatory cytokines in obese rats, but also protected cardiac tissue, as shown by histological analysis. Conversely, phytoformulation therapy decreased mRNA levels for sterol regulatory element-binding factor 1, fatty acid synthase, acetyl-CoA carboxylase, and fatty acid binding protein 1 genes involved in fatty acid synthesis and absorption in obese rats. It increased the levels of lysosomal acid lipase, hormone-sensitive lipase, and lipoprotein lipase genes involved in fatty acid degradation in the heart. In addition, the phytoformulation improved cardiac inflammation and apoptosis by downregulating the genes nuclear factor kappa-light-chain enhancer of activated B cells (NF-kB), tumour necrosis factor α, interleukin-6, toll-like receptor-4 (TLR-4), BCL2-associated X and caspase-3. In conclusion, our results show that the phytoformulation improved insulin sensitivity and attenuated myocardial lipid accumulation, inflammation, and apoptosis in the heart of HFD-induced obese rats by regulating fatty acid metabolism genes and downregulating NF-kB/TLR-4/caspase-3.

Nrf2 prevents diabetic cardiomyopathy via antioxidant effect and normalization of glucose and lipid metabolism in the heart

Metabolic disorders and oxidative stress are the main causes of diabetic cardiomyopathy. Activation of nuclear factor erythroid 2-related factor 2 (Nrf2) exerts a powerful antioxidant effect and prevents the progression of diabetic cardiomyopathy. However, the mechanism of its cardiac protection and direct action on cardiomyocytes are not well understood. Here, we investigated in a cardiomyocyte-restricted Nrf2 transgenic mice (Nrf2-TG) the direct effect of Nrf2 on cardiomyocytes in DCM and its mechanism. In this study, cardiomyocyte-restricted Nrf2 transgenic mice (Nrf2-TG) were used to directly observe whether cardiomyocyte-specific overexpression of Nrf2 can prevent diabetic cardiomyopathy and correct glucose and lipid metabolism disorders in the heart. Compared to wild-type mice, Nrf2-TG mice showed resistance to diabetic cardiomyopathy in a streptozotocin-induced type 1 diabetes mouse model. This was primarily manifested as improved echocardiography results as well as reduced myocardial fibrosis, cardiac inflammation, and oxidative stress. These results showed that Nrf2 can directly act on cardiomyocytes to exert a cardioprotective role. Mechanistically, the cardioprotective effects of Nrf2 depend on its antioxidation activity, partially through improving glucose and lipid metabolism by directly targeting lipid metabolic pathway of AMPK/Sirt1/PGC-1α activation via upstream genes of sestrin2 and LKB1, and indirectly enabling AKT/GSK-3β/HK-Ⅱ activity via AMPK mediated p70S6K inhibition.

Downregulation of nutrition sensor GCN2 in macrophages contributes to poor wound healing in diabetes

Poor skin wound healing, which is common in patients with diabetes, is related to imbalanced macrophage polarization. Here, we find that nutrition sensor GCN2 (general control nonderepressible 2) and its downstream are significantly upregulated in human skin wound tissue and mouse skin wound macrophages, but skin wound-related GCN2 expression and activity are significantly downregulated by diabetes and hyperglycemia. Using wound healing models of GCN2-deleted mice, bone marrow chimeric mice, and monocyte-transferred mice, we show that GCN2 deletion in macrophages significantly delays skin wound healing compared with wild-type mice by altering M1 and M2a/M2c polarization. Mechanistically, GCN2 inhibits M1 macrophages via OXPHOS-ROS-NF-κB pathway and promotes tissue-repairing M2a/M2c macrophages through eukaryotic translation initiation factor 2 (eIF2α)-hypoxia-inducible factor 1α (HIF1α)-glycolysis pathway. Importantly, local supplementation of GCN2 activator halofuginone efficiently restores wound healing in diabetic mice with re-balancing M1 and M2a/2c polarization. Thus, the decreased macrophage GCN2 expression and activity contribute to poor wound healing in diabetes and targeting GCN2 improves wound healing in diabetes.

Disrupted cardiac fibroblast BCAA catabolism contributes to diabetic cardiomyopathy via a periostin/NAP1L2/SIRT3 axis

BACKGROUND

Periostin is an extracellular matrix protein that plays a critical role in cell fate determination and tissue remodeling, but the underlying role and mechanism of periostin in diabetic cardiomyopathy (DCM) are far from clear. Thus, we aimed to clarify the mechanistic participation of periostin in DCM.

METHODS

The expression of periostin was examined in DCM patients, diabetic mice and high glucose (HG)-exposed cardiac fibroblasts (CF). Gain- and loss-of-function experiments assessed the potential role of periostin in DCM pathogenesis. RNA sequencing was used to investigate the underlying mechanisms of periostin in DCM.

RESULTS

A mouse cytokine antibody array showed that the protein expression of periostin was most significantly upregulated in diabetic mouse heart, and this increase was also observed in patients with DCM or HG-incubated CF. Periostin-deficient mice were protected from diabetes-induced cardiac dysfunction and myocardial damage, while overexpression of periostin held the opposite effects. Hyperglycemia stimulated the expression of periostin in a TGF-β/Smad-dependent manner. RNA sequencing results showed that periostin upregulated the expression of nucleosome assembly protein 1-like 2 (NAP1L2) which recruited SIRT3 to deacetylate H3K27ac on the promoters of the branched-chain amino acid (BCAA) catabolism-related enzymes BCAT2 and PP2Cm, resulting in BCAA catabolism impairment. Additionally, CF-derived periostin induced hypertrophy, oxidative injury and inflammation in primary cardiomyocytes. Finally, we identified that glucosyringic acid (GA) specifically targeted and inhibited periostin to ameliorate DCM.

CONCLUSION

Overall, manipulating periostin expression may function as a promising strategy in the treatment of DCM.

Shengmai injection inhibits palmitic acid-induced myocardial cell inflammatory death via regulating NLRP3 inflammasome activation

Objective

To determine the protective effect of Shengmai injection (SMI) on myocardial injury in diabetic rats and its mechanism based on NLRP3/Caspase1 signaling pathway.

Materials and methods

Rat H9c2 cardiomyocytes were cultured in vitro, and the cell survival rate of different concentrations of palmitate acid (PA) and different concentrations of SMI were detected by CCK-8. The myocardial injury cell model was induced with PA, treated with SMI, and combined with NLRP3 specific inhibitor (MCC950) to interfere with the high-fat-induced rat H9c2 myocardial cell injury model. The cell changes were observed by Hoechst/PI staining and the expression levels of MDA, SOD, and ROS in each group were detected. The protein and gene changes of the NLRP3/Caspase-1 signaling pathway were detected by Western blot and RT-qPCR, respectively.

Results

200 μmol/L of PA were selected to induce the myocardial injury cell model and 25 μL/mL of SMI was selected for intervention concentration. SMI could significantly reduce MDA expression, increase SOD level, and decrease ROS production. SMI could decrease the gene expression levels of NLRP3, ASC, Caspase-1, and GSDMD, and the protein expressions of NLRP3, ASC, Cleaved Caspase-1, GSDMD, and GSDMD-N.

Conclusion

SMI can inhibit the high-fat-induced activation of the NLRP3/Caspase-1 signaling pathway, intervene in cardiomyocyte pyroptosis, and prevent diabetic cardiomyopathy.

β-Caryophyllene, a Dietary Phytocannabinoid, Alleviates Diabetic Cardiomyopathy in Mice by Inhibiting Oxidative Stress and Inflammation Activating Cannabinoid Type-2 Receptors

Diabetes mellitus (DM) and its associated complications are considered one of the major health risks globally. Among numerous complications, diabetic cardiomyopathy (DCM) is characterized by increased accumulation of lipids and reduced glucose utilization following abnormal lipid metabolism in the myocardium along with oxidative stress, myocardial fibrosis, and inflammation that eventually result in cardiac dysfunction. The abnormal metabolism of lipids plays a fundamental role in cardiac lipotoxicity following the occurrence and development of DCM. Recently, it has been revealed that cannabinoid type-2 (CB2) receptors, an essential component of the endocannabinoid system, play a crucial role in the pathogenesis of obesity, hyperlipidemia, and DM. Provided the role of CB2R in regulating the glucolipid metabolic dysfunction and its antioxidant as well as anti-inflammatory activities, we carried out the current study to investigate the protective effects of a selective CB2R agonist, β-caryophyllene (BCP), a natural dietary cannabinoid in the murine model of DCM and elucidated the underlying pharmacological and molecular mechanisms. Mice were fed a high-fat diet for 4 weeks followed by a single intraperitoneal injection of streptozotocin (100 mg/kg) to induce the model of DCM. BCP (50 mg/kg body weight) was given orally for 12 weeks. AM630, a CB2R antagonist, was given 30 min before BCP treatment to demonstrate the CB2R-dependent mechanism of BCP. DCM mice exhibited hyperglycemia, increased serum lactate dehydrogenase, impaired cardiac function, and hypertrophy. In addition, DCM mice showed alternations in serum lipids and increased oxidative stress concomitant to reduced antioxidant defenses and enhanced cardiac lipid accumulation in the diabetic heart. DCM mice also exhibited activation of TLR4/NF-κB/MAPK signaling and triggered the production of inflammatory cytokines and inflammatory enzyme mediators. However, treatment with BCP exerted remarkable protective effects by favorable modulation of the biochemical and molecular parameters, which were altered in DCM mice. Interestingly, pretreatment with AM630 abrogated the protective effects of BCP in DCM mice. Taken together, the findings of the present study demonstrate that BCP possesses the capability to mitigate the progression of DCM by inhibition of lipotoxicity-mediated cardiac oxidative stress and inflammation and favorable modulation of TLR4/NF-κB/MAPK signaling pathways mediating the CB2R-dependent mechanism.

Different exercise training intensities prevent type 2 diabetes mellitus-induced myocardial injury in male mice

Type 2 diabetes mellitus (T2DM) usually develop myocardial injury and that exercise may have a positive effect on cardiac function. However, the effect of exercise intensity on cardiac function has not yet been fully examined. This study aimed to explore different exercise intensities on T2DM-induced myocardial injury. 18-week-old male mice were randomly divided into four groups: a control group, the T2DM, T2DM + medium-intensity continuous training (T2DM + MICT), and T2DM + high-intensity interval training (T2DM + HIIT) groups. In the experimental group, mice were given high-fat foods and streptozotocin for six weeks and then divided into two exercise training groups, in which mice were subjected to exercise five days per week for 24 consecutive weeks. Finally, metabolic characteristics, cardiac function, myocardial remodeling, myocardial fibrosis, oxidative stress, and apoptosis were analyzed. HIIT treatment improved cardiac function and improved myocardial injury. In conclusion, HIIT may be an effective means to guard against T2DM-induced myocardial injury.

Activating transcription factor 4 drives the progression of diabetic cardiac fibrosis

AIMS

Diabetic cardiomyopathy (DC) is one of serious complications of diabetic patients. This study investigated the biological function of activating transcription factor 4 (ATF4) in DC.

METHODS AND RESULTS

Streptozotocin-treated mice and high glucose (HG)-exposed HL-1 cells were used as the in vivo and in vitro models of DC. Myocardial infarction (MI) was induced by left coronary artery ligation in mice. Cardiac functional parameters were detected by echocardiography. Target molecule expression was determined by real time quantitative PCR and western blotting. Cardiac fibrosis was observed by haematoxylin and eosin and Masson's staining. Cardiac apoptosis was evaluated by terminal deoxynucleotidyl transferase dUTP nick end labelling. Activities of superoxide dismutase, glutathione peroxidase, and levels of malonic dialdehyde and reactive oxygen species were used to assess oxidative stress damage. Molecular mechanisms were evaluated by chromatin immunoprecipitation, dual luciferase assay, and co-immunoprecipitation. ATF4 was up-regulated in the DC and MI mice (P < 0.01). Down-regulation of ATF4 improved cardiac function as evidenced by changes in cardiac functional parameters (P < 0.01), inhibited myocardial collagen I (P < 0.001) and collagen III (P < 0.001) expression, apoptosis (P < 0.001), and oxidative stress (P < 0.001) in diabetic mice. Collagen I (P < 0.01) and collagen III (P < 0.01) expression was increased in MI mice, which was reversed by ATF4 silencing (P < 0.05). ATF4 depletion enhanced viability (P < 0.01), repressed apoptosis (P < 0.001), oxidative damage (P < 0.001), and collagen I (P < 0.001), and collagen III (P < 0.001) expression of HG-stimulated HL-1 cells. ATF4 transcriptionally activated Smad ubiquitin regulatory factor 2 (Smurf2, P < 0.001) to promote ubiquitination and degradation of homeodomain interacting protein kinase-2 (P < 0.001) and subsequently caused inactivation of nuclear factor erythroid 2-related factor 2/heme oxygenase 1 pathway (P < 0.001). The inhibitory effects of ATF4 silencing on HG-induced apoptosis (P < 0.01), oxidative injury (P < 0.01), collagen I (P < 0.001), and collagen III (P < 0.001) expression were reversed by Smurf2 overexpression.

CONCLUSIONS

ATF4 facilitates diabetic cardiac fibrosis and oxidative stress by promoting Smurf2-mediated ubiquitination and degradation of homeodomain interacting protein kinase-2 and then inactivation of nuclear factor erythroid 2-related factor 2/heme oxygenase 1 pathway, suggesting ATF4 as a treatment target for DC.

The protective effect of zinc, selenium, and chromium on myocardial fibrosis in the offspring of rats with gestational diabetes mellitus

The offspring of gestational diabetes mellitus (GDM) mothers are considered to be at the risk of cardiovascular diseases due to intrauterine hyperglycemia exposure. Our previous study showed that zinc, selenium, and chromium dramatically alleviated glucose intolerance in GDM rats and their offspring (P < 0.05). However, the effects of these elements on the damage of the cardiac myocytes of GDM offspring and the underlying mechanisms have not been demonstrated. Here, we investigated the beneficial effects of zinc (10 mg per kg bw), selenium (20 μg per kg bw), and chromium (20 μg per kg bw) supplementation on myocardial fibrosis in the offspring of GDM rats induced by a high-fat and sucrose (HFS) diet. The results showed that maternal GDM induced glucose intolerance, oxidative stress, cardiac inflammation and myocardial fibrosis in offspring rats during different ages (3 days, 3 weeks, and adulthood), which were ameliorated by zinc, selenium and chromium supplementation (P < 0.05). The activity of cardiac damage markers such as creatine kinase-myocardial band isoenzyme (CK-MB), lactate dehydrogenase (LDH) and aspartate aminotransferase (AST) decreased by 40-60% in element-supplemented offspring compared to that in non-supplemented offspring of GDM dams (P < 0.05). Moreover, maternal GDM-induced expression of fibrosis-related proteins and the transforming growth factor-beta 1 (TGF-β1)/small mothers against decapentaplegic homolog 3 (Smad3) signaling pathway in the heart tissue of offspring was down-regulated by zinc, selenium, and chromium supplementation (P < 0.05). In conclusion, zinc, selenium, and chromium may play a protective role in maternal GDM-induced myocardial fibrosis in offspring from birth to adulthood by inactivating the TGF-β1/Smad3 pathway.

A mitochondrial long-chain fatty acid oxidation defect leads to transfer RNA uncharging and activation of the integrated stress response in the mouse heart

AIMS

Cardiomyopathy and arrhythmias can be severe presentations in patients with inherited defects of mitochondrial long-chain fatty acid β-oxidation (FAO). The pathophysiological mechanisms that underlie these cardiac abnormalities remain largely unknown. We investigated the molecular adaptations to a FAO deficiency in the heart using the long-chain acyl-CoA dehydrogenase (LCAD) knockout (KO) mouse model.

METHODS AND RESULTS

We observed enrichment of amino acid metabolic pathways and of ATF4 target genes among the upregulated genes in the LCAD KO heart transcriptome. We also found a prominent activation of the eIF2α/ATF4 axis at the protein level that was independent of the feeding status, in addition to a reduction of cardiac protein synthesis during a short period of food withdrawal. These findings are consistent with an activation of the integrated stress response (ISR) in the LCAD KO mouse heart. Notably, charging of several transfer RNAs (tRNAs), such as tRNAGln was decreased in LCAD KO hearts, reflecting a reduced availability of cardiac amino acids, in particular, glutamine. We replicated the activation of the ISR in the hearts of mice with muscle-specific deletion of carnitine palmitoyltransferase 2.

CONCLUSIONS

Our results show that perturbations in amino acid metabolism caused by long-chain FAO deficiency impact cardiac metabolic signalling, in particular the ISR. These results may serve as a foundation for investigating the role of the ISR in the cardiac pathology associated with long-chain FAO defects.Translational Perspective: The heart relies mainly on mitochondrial fatty acid β-oxidation (FAO) for its high energy requirements. The heart disease observed in patients with a genetic defect in this pathway highlights the importance of FAO for cardiac health. We show that the consequences of a FAO defect extend beyond cardiac energy homeostasis and include amino acid metabolism and associated signalling pathways such as the integrated stress response.

Genetic and Pharmacological Inhibition of GCN2 Ameliorates Hyperglycemia and Insulin Resistance in Type 2 Diabetic Mice

It is well recognized that there is a strong and complex association between nonalcoholic fatty liver disease (NAFLD) and type 2 diabetes (T2D). We previously demonstrated that genetic knockout or pharmacological inhibition of general control nondepressible kinase 2 (GCN2), a well-known amino acid sensor, alleviated hepatic steatosis and insulin resistance in obese mice. However, whether GCN2 affects the development of T2D remains unclear. After a high-fat diet (HFD) plus low-dose streptozotocin (STZ) treatments, Gcn2−/− mice developed less hyperglycemia, insulin resistance, hepatic steatosis, and oxidative stress than wild-type (WT) mice. Inhibition of GCN2 by intraperitoneal injection of 3 mg/kg GCN2iB (a specific inhibitor of GCN2) every other day for 6 weeks also ameliorated hyperglycemia, insulin resistance, hepatic steatosis, and oxidative stress in HFD/STZ- and leptin receptor deletion (db/db)-induced T2D mice. Moreover, depletion of hepatic GCN2 in db/db mice by tail vein injection of an AAV8-shGcn2 vector resulted in similar improvement in those metabolic disorders. The protective mechanism of GCN2 inhibition in T2D mice was associated with regulation of the glucose metabolic pathway, repression of lipogenesis genes, and activation of the Nrf2 pathway. Together, our data provide evidence that strategies to inhibit hepatic GCN2 activity may be novel approaches for T2D therapy.

Inhibition of GCN2 Alleviates Cardiomyopathy in Type 2 Diabetic Mice via Attenuating Lipotoxicity and Oxidative Stress

Diabetic cardiomyopathy (DCM) is a kind of heart disease that affects diabetic patients and is one of the primary causes of death. We previously demonstrated that deletion of the general control nonderepressible 2 (GCN2) kinase ameliorates cardiac dysfunction in diabetic mice. The aim of this study was to investigate the protective effect of GCN2iB, a GCN2 inhibitor, in type 2 diabetic (T2D) mice induced by a high-fat diet (HFD) plus low-dose streptozotocin (STZ) treatments or deletion of the leptin receptor (db/db). GCN2iB (3 mg/kg/every other day) treatment for 6 weeks resulted in significant decreases in fasting blood glucose levels and body weight and increases in the left ventricular ejection fraction. GCN2iB treatment also attenuated myocardial fibrosis, lipid accumulation and oxidative stress in the hearts of T2D mice, which was associated with decreases in lipid metabolism-related genes and increases in antioxidative genes. Untargeted metabolomics and RNA sequencing analysis revealed that GCN2iB profoundly affected myocardial metabolomic profiles and gene expression profiles. In particular, GCN2iB increased myocardial phosphocreatine and taurine levels and upregulated genes involved in oxidative phosphorylation. In conclusion, the data provide evidence that GCN2iB effectively protects against cardiac dysfunction in T2D mice. Our findings suggest that GCN2iB might be a novel drug candidate for DCM therapy.

AKT/PACS2 Participates in Renal Vascular Hyperpermeability by Regulating Endothelial Fatty Acid Oxidation in Diabetic Mice

Diabetes is a chronic metabolic disorder that can cause many microvascular and macrovascular complications, including diabetic nephropathy. Endothelial cells exhibit phenotypic and metabolic diversity and are affected by metabolic disorders. Whether changes in endothelial cell metabolism affect vascular endothelial function in diabetic nephropathy remains unclear. In diabetic mice, increased renal microvascular permeability and fibrosis, as well as increased MAMs and PACS2 in renal endothelial cells, were observed. Mice lacking PACS2 improved vascular leakage and glomerulosclerosis under high fat diet. In vitro, PACS2 expression, VE-cadherin internalization, fibronectin production, and Smad-2 phosphorylation increased in HUVECs treated with high glucose and palmitic acid (HGHF). Pharmacological inhibition of AKT significantly reduced HGHF-induced upregulation of PACS2 and p-Smad2 expression. Blocking fatty acid β-oxidation (FAO) ameliorated the impaired barrier function mediated by HGHF. Further studies observed that HGHF induced decreased FAO, CPT1α expression, ATP production, and NADPH/NADP⁺ ratio in endothelial cells. However, these changes in fatty acid metabolism were rescued by silencing PACS2. In conclusion, PACS2 participates in renal vascular hyperpermeability and glomerulosclerosis by regulating the FAO of diabetic mice. Targeting PACS2 is potential new strategy for the treatment of diabetic nephropathy.

Wogonin Ameliorated Obesity-Induced Lipid Metabolism Disorders and Cardiac Injury via Suppressing Pyroptosis and Deactivating IL-17 Signaling Pathway

Obesity leads to structural and functional changes in the heart and has become a global burden of disease. Wogonin is a natural flavonoid which possesses cardioprotective, neuroprotective, and anti-cancer properties. However, the effects of wogonin on obesity-induced cardiac injury remain unclear. In this study, the high-fat diet (HFD)-induced obese mice model was successfully established. Moreover, HFD induced a fat mass and cardiac injury in mice. More importantly, wogonin treatment reduced fat mass and improved cardiac function of HFD mice. Consistently, wogonin ameliorated myocardial lipid metabolism in HFD-induced obese mice by reducing triglyceride (TC), total cholesterol (TG), and non-esterified fatty acid (NEFA) levels in serum, as well as the TG and free fatty acids (FFA) levels in heart tissues. Interestingly, wogonin treatment alleviated myocardial pyroptosis in HFD-induced obese mice. Through bioinformatic analysis, the IL-17 signaling pathway was predicted to be modulated by wogonin. Results showed that wogonin deactivated the IL-17 signaling pathway in HFD mice. These findings suggested that wogonin ameliorated obesity-induced disorders of lipid metabolism and cardiac injury via suppressing pyroptosis and deactivating the IL-17 signaling pathway, which provided a novel therapeutic strategy for HFD-induced cardiac injury.

Co-administration of hydrogen and metformin exerts cardioprotective effects by inhibiting pyroptosis and fibrosis in diabetic cardiomyopathy

Hydrogen is a novel medical gas with several properties, including anti-oxidative, anti-inflammatory, anti-apoptotic, anti-allergic, and energy metabolism stimulating properties. Hydrogen therapy has been proven effective in the treatment of myocardial ischemia, myocardial infarction, and ischemia-reperfusion injury. Diabetic cardiomyopathy (DCM) is a serious cardiovascular complication of long-term chronic diabetes that is linked to increased heart failure and arrhythmia morbidity. The effect of hydrogen on the pathogenesis of DCM is yet to be determined. Metformin is a well-known pharmacological agent for the treatment of diabetes; however, the application of large doses of the drug is limited by its side effects. Therefore, this highlights the importance of developing novel therapies against DCM. In this regard, we investigated the effect of hydrogen on DCM and the mechanisms that underlie it. Furthermore, we also assessed the efficacy of co-administration of metformin and hydrogen. In this study, we found that hydrogen improved cardiac dysfunction and abnormal morphological structure in streptozotocin-induced diabetic mice. As a mechanism, it was confirmed that hydrogen mediated its action by reducing pyroptosis via inhibition of the AMPK/mTOR/NLRP3 signaling pathway and ameliorating fibrosis via inhibition of the TGF-β1/Smad signaling pathway. Furthermore, our findings suggested that co-administration of hydrogen and metformin shows potent protective effects, as evidenced by increased survival rates, reduced fasting blood glucose, and decreased cell injury when compared to a single application of metformin. In conclusion, our study demonstrated that hydrogen inhalation attenuates DCM by reducing pyroptosis and fibrosis and that hydrogen can be combined with metformin to exhibit a more potent cardioprotective effect in DCM.

Gamma-Aminobutyrate Transaminase Protects against Lipid Overload-Triggered Cardiac Injury in Mice

Lipid overload contributes to cardiac complications of diabetes and obesity. However, the underlying mechanisms remain obscure. This study investigates the role of gamma-aminobutyrate transaminase (ABAT), the key enzyme involved in the catabolism of γ-aminobutyric acid (GABA), in lipid overload-induced cardiac injury. Microarray revealed a down-regulation of ABAT mRNA expression in high fat diet (HFD)-fed mouse hearts, which correlated with a reduction in ABAT protein level and its GABA catabolic activity. Transgenic mice with cardiomyocyte-specific ABAT over-expression (Tg-ABAT/tTA) were generated to determine the role of ABAT in lipid overload-induced cardiac injury. Feeding with a HFD to control mice for 4 months reduced ATP production and the mitochondrial DNA copy number, and induced myocardial oxidative stress, hypertrophy, fibrosis and dysfunction. Such pathological effects of HFD were mitigated by ABAT over-expression in Tg-ABAT/tTA mice. In cultured cardiomyocytes, palmitate increased mitochondrial ROS production, depleted ATP production and promoted apoptosis, all of which were attenuated by ABAT over-expression. With the inhibition of ABAT’s GABA catabolic activity, the protective effects of ABAT remained unchanged in palmitate-induced cardiomyocytes. Thus, ABAT protects the mitochondrial function in defending the heart against lipid overload-induced injury through mechanisms independent of its GABA catabolic activity, and may represent a new therapeutic target for lipid overload-induced cardiac injury.

Mesenchymal Stem Cell Therapy in Diabetic Cardiomyopathy

The incidence and prevalence of diabetes mellitus (DM) are increasing worldwide, and the resulting cardiac complications are the leading cause of death. Among these complications is diabetes-induced cardiomyopathy (DCM), which is the consequence of a pro-inflammatory condition, oxidative stress and fibrosis caused by hyperglycemia. Cardiac remodeling will lead to an imbalance in cell survival and death, which can promote cardiac dysfunction. Since the conventional treatment of DM generally does not address the prevention of cardiac remodeling, it is important to develop new alternatives for the treatment of cardiovascular complications induced by DM. Thus, therapy with mesenchymal stem cells has been shown to be a promising approach for the prevention of DCM because of their anti-apoptotic, anti-fibrotic and anti-inflammatory effects, which could improve cardiac function in patients with DM.

Intermittent Fasting Improves High-Fat Diet-Induced Obesity Cardiomyopathy via Alleviating Lipid Deposition and Apoptosis and Decreasing m6A Methylation in the Heart

Intermittent fasting (IF) plays an essential role in improving lipid metabolism disorders caused by metabolic cardiomyopathy. Growing evidence revealed that N6-methyladenosine (m6A) RNA methylation is related to obesity and lipid metabolic. Our study aimed to assess the beneficial effects of IF on lipid deposition, apoptosis, and m6A methylation in high-fat diet (HFD)-induced obesity cardiomyopathy. Male C57BL/6J mice were fed a normal diet (ND) or HFD ad libitum for 13 weeks, after which time a subgroup of HFD mice were subjected to IF for 24 h and fed HFD in the other day for 8 weeks. We found that IF intervention significantly improved cardiac functional and structural impairment and serum lipid metabolic disorder induced by HFD. Furthermore, IF intervention decreased the mRNA levels of the fatty acid uptake genes of FABP1, FATP1, and CD36 and the fatty acid synthesis genes of SREBF1, FAS, and ACCα and increased the mRNA levels of the fatty acid catabolism genes of ATGL, HSL, LAL, and LPL in cardiac tissueof HFD-induced obese mice. TUNEL-positive cells, Bax/Bcl-2 ratio, and Cleaved Caspase-3 protein expression in HFD-induced obese mice hearts was down-regulated by IF intervention. In addition, IF intervention decreased the m6A methylation levels and METTL3 expression and increased FTO expression in HFD-induced obesity cardiomyopathy. In conclusion, our findings demonstrate that IF attenuated cardiac lipid deposition and apoptosis, as well as improved cardiac functional and structural impairment in HFD-induced obesity cardiomyopathy, by a mechanism associated with decreased m6A RNA methylation levels.

Curcumin Conjugated Gold Nanoclusters as Perspective Therapeutics for Diabetic Cardiomyopathy

Accumulation of lipids in the myocardium contributes to the development of cardiac dysfunctions and various chronic diseases, such as diabetic cardiomyopathy (DCM). Curcumin (Cur) can relieve lipid accumulation problems, but its efficiency is limited by poor water solubility and biocompatibility. Herein, gold nanoclusters (AuNCs) were used to improve the efficiency of Cur, and the conjugates Curcumin-AuNCs (AuCur) were developed. In the treatment of high-fat-induced myocardial cell damage, we found that AuCur could effectively reduce intracellular lipid accumulation, the increase of reactive oxygen species (ROS), the increase of mitochondrial division, and the increase of apoptosis compared with Cur. AuCur decreased the expression of the peroxisome proliferator-activated receptors-α subtype (PPARα), and the therapeutic effect of AuCur was canceled when the expression of PPARα was enhanced. For the above reasons, AuCur treated the toxic effect of high lipid on cardiomyocytes by regulating PPARα, providing a new idea and method for the treatment of DCM.

Fibrosis of the diabetic heart: Clinical significance, molecular mechanisms, and therapeutic opportunities

In patients with diabetes, myocardial fibrosis may contribute to the pathogenesis of heart failure and arrhythmogenesis, increasing ventricular stiffness and delaying conduction. Diabetic myocardial fibrosis involves effects of hyperglycemia, lipotoxicity and insulin resistance on cardiac fibroblasts, directly resulting in increased matrix secretion, and activation of paracrine signaling in cardiomyocytes, immune and vascular cells, that release fibroblast-activating mediators. Neurohumoral pathways, cytokines, growth factors, oxidative stress, advanced glycation end-products (AGEs), and matricellular proteins have been implicated in diabetic fibrosis; however, the molecular links between the metabolic perturbations and activation of a fibrogenic program remain poorly understood. Although existing therapies using glucose- and lipid-lowering agents and neurohumoral inhibition may act in part by attenuating myocardial collagen deposition, specific therapies targeting the fibrotic response are lacking. This review manuscript discusses the clinical significance, molecular mechanisms and cell biology of diabetic cardiac fibrosis and proposes therapeutic targets that may attenuate the fibrotic response, preventing heart failure progression.

Mitochondrial Lipid Homeostasis at the Crossroads of Liver and Heart Diseases

The prevalence of NAFLD (non-alcoholic fatty liver disease) is a rapidly increasing problem, affecting a huge population around the globe. However, CVDs (cardiovascular diseases) are the most common cause of mortality in NAFLD patients. Atherogenic dyslipidemia, characterized by plasma hypertriglyceridemia, increased small dense LDL (low-density lipoprotein) particles, and decreased HDL-C (high-density lipoprotein cholesterol) levels, is often observed in NAFLD patients. In this review, we summarize recent genetic evidence, proving the diverse nature of metabolic pathways involved in NAFLD pathogenesis. Analysis of available genetic data suggests that the altered operation of fatty-acid β-oxidation in liver mitochondria is the key process, connecting NAFLD-mediated dyslipidemia and elevated CVD risk. In addition, we discuss several NAFLD-associated genes with documented anti-atherosclerotic or cardioprotective effects, and current pharmaceutical strategies focused on both NAFLD treatment and reduction of CVD risk.

GDF11 Alleviates Pathological Myocardial Remodeling in Diabetic Cardiomyopathy Through SIRT1-Dependent Regulation of Oxidative Stress and Apoptosis

Growth differentiation factor 11 (GDF11) is a member of the transforming growth factor β superfamily that alleviates cardiac hypertrophy, myocardial infarction, and vascular injury by regulating oxidative stress, inflammation, and cell survival. However, the roles and underlying mechanisms of GDF11 in diabetic cardiomyopathy (DCM) remain largely unknown. In this study, we sought to determine whether GDF11 could prevent DCM. After establishing a mouse model of diabetes by administering a high-fat diet and streptozotocin, intramyocardial injection of an adeno-associated virus was used to achieve myocardium-specific GDF11 overexpression. GDF11 remarkably improved cardiac dysfunction and interstitial fibrosis by reducing the levels of reactive oxygen species and protecting against cardiomyocyte loss. Mechanistically, decreased sirtuin 1 (SIRT1) expression and activity were observed in diabetic mice, which was significantly increased after GDF11 overexpression. To further explore how SIRT1 mediates the role of GDF11, the selective inhibitor EX527 was used to block SIRT1 signaling pathway, which abolished the protective effects of GDF11 against DCM. In vitro studies confirmed that GDF11 protected against H9c2 cell injury in high glucose and palmitate by attenuating oxidative injury and apoptosis, and these effects were eliminated by SIRT1 depletion. Our results demonstrate for the first time that GDF11 protects against DCM by regulating SIRT1 signaling pathway.

Peroxiredomin-4 ameliorates lipotoxicity-induced oxidative stress and apoptosis in diabetic cardiomyopathy

Diabetic cardiomyopathy (DCM), one severe complication in the diabetes, leads to high mortality in the diabetic patients. However, the understanding of molecular mechanisms underlying DCM is far from completion. Herein, we investigated the disease-related differences in the proteomes of DCM based on db/db mice and verified the protective roles of peroxiredoxin-4 (Prdx4) in H9c2 cardiomyocytes treated by palmitic acid (PA). Fasting blood glucose (FBG) and cardiac function was detected in the 6-month-old control and diabetic mice. The hearts were then collected and analyzed by a coupled label-free and mass spectrometry approach. In vivo investigation indicated that body weight and FBG of db/db mice markedly increased, and diabetic heart exhibited obvious cardiac hypertrophy and lipid droplet accumulation, and cardiac dysfunction as is indicated by the increases of left ventricle posterior wall thickness in systole (LVPWd) and diastole (LVPWs), and reduction of fractional shortening (FS). We used proteomic analysis and then detected a grand total of 2636 proteins. 175 differentially expressed proteins (DEPs) were markedly detected in the diabetic heart. Thereinto, Prdx4 was markedly down-regulated in the diabetic heart. In vitro experiments revealed that 250 μM PA significantly inhibited viability of H9c2 cell. PA induced much accumulation of lipid droplet in cardiomyocytes and resulted in an increase of mRNA expressions of lipogenic genes (FASN and SCD1) and cardiac hypertrophic genes. Additionally, protein level of Prdx4 evidently reduced in the PA-treated H9c2 cell. It was further found that shRNA-mediated Prdx4 knockdown exacerbated PA-induced oxidative stress and cardiomyocyte apoptosis, whereas overexpressing Prdx4 in the H9c2 cells noteworthily limited PA-induced ROS generation and cardiomyocytes apoptosis. These data collectively reveal the essential role of abnormal Prdx4 in pathological alteration of DCM, and provide potentially therapeutic target for the prevention of DCM.

Pharmacological Disruption of Phosphorylated Eukaryotic Initiation Factor-2α/Activating Transcription Factor 4/Indian Hedgehog Protects Intervertebral Disc Degeneration via Reducing the Reactive Oxygen Species and Apoptosis of Nucleus Pulposus Cells

Excessive reactive oxygen species (ROS) and apoptosis in nucleus pulposus (NP) cells accelerate the process of intervertebral disc degeneration (IDD). Here, we integrated pathological samples and in vitro and in vivo framework to investigate the impact of phosphorylation of eukaryotic initiation factor-2α (eIF2α)/activating transcription factor 4 (ATF4)/Indian hedgehog (Ihh) signaling in the IDD. From the specimen analysis of the IDD patients, we found phosphorylated eIF2α (p-eIF2α), ATF4 and Ihh protein levels were positively related while the NP tissue went degenerative. In vitro, tumor necrosis factor (TNF)-α caused the NP cell degeneration and induced a cascade of upregulation of p-eIF2α, ATF4, and Ihh. Interestingly, ATF4 could enhance Ihh expression through binding its promoter region, and silencing of ATF4 decreased Ihh and protected the NP cells from degeneration. Moreover, ISRIB inhibited the p-eIF2α, which resulted in a suppression of ATF4/Ihh, and alleviated the TNF-α-induced ROS production and apoptosis of NP cells. On the contrary, further activating p-eIF2α aggravated the NP cell degeneration, with amplification of ATF4/Ihh and a higher level of ROS and apoptosis. Additionally, applying cyclopamine (CPE) to suppress Ihh was efficient to prevent NP cell apoptosis but did not decrease the ROS level. In an instability-induced IDD model in mice, ISRIB suppressed p-eIF2α/ATF4/Ihh and prevented IDD via protecting the anti-oxidative enzymes and decreased the NP cell apoptosis. CPE prevented NP cell apoptosis but did not affect anti-oxidative enzyme expression. Taken together, p-eIF2α/ATF4/Ihh signaling involves the ROS level and apoptosis in NP cells, the pharmacological disruption of which may provide promising methods in preventing IDD.

SIRT6‑specific inhibitor OSS‑128167 exacerbates diabetic cardiomyopathy by aggravating inflammation and oxidative stress

Diabetic cardiomyopathy (DCM) is a serious complication of diabetes, which importantly contributes to the increased mortality of patients with diabetes. The development of DCM is accompanied by numerous pathological mechanisms, including oxidative stress and chronic inflammation. Accordingly, the present study aimed to determine the effects of the sirtuin 6 (SIRT6) inhibitor OSS‑128167 on DCM using a mouse model of streptozotocin (STZ)‑induced diabetes and high glucose (HG)‑treated cardiomyocytes. C57BL/6 mice were intraperitoneally injected with STZ for 5 days to simulate the diabetic cardiomyopathy model. Mice with STZ‑induced diabetes (STZ‑DM1) were orally administered OSS‑128167 (20 or 50 mg/kg) through gavage every other day. The expression of SIRT6 in myocardial tissue was detected using western blotting. Tissue staining (hematoxylin and eosin and Masson's trichrome) was used to characterize myocardial structure, TUNEL fluorescent staining was used to detect myocardial apoptosis, and immunohistochemical staining was used to detect the expression of inflammatory factors in myocardial tissue. Dihydroethidium staining and a malondialdehyde (MDA) detection kit were used to detect the oxidative stress levels in myocardial tissues. In vitro, H9c2 cells were pre‑incubated with OSS‑128167 for 1 h and then stimulated with HG (33 mM) for various durations. Expression levels of fibrosis markers, collagen‑1 and transforming growth factor (TGF)‑β, apoptosis‑related proteins, Bax, Bcl‑2 and cleaved‑poly ADP‑ribose polymerase, tumor necrosis factor‑α and the oxidative stress metabolite, 3‑nitrotyrosine were analyzed using western blotting and reverse transcription‑quantitative PCR. Commercially available kits were used to detect the activity of caspase‑3 and the content of MDA in the H9c2 cell line. The corresponding results demonstrated that OSS‑128167 aggravated diabetes‑induced cardiomyocyte apoptosis and fibrosis in mice. Mechanistically, OSS‑128167 was revealed to increase the levels of inflammatory factors and reactive oxygen species (ROS) in vitro and in vivo. In conclusion, OSS‑128167 facilitated the inflammatory response and promoted the production of ROS while aggravating DCM development. These findings indicated that SIRT6 may target two closely combined and interacting pathological processes, the inflammatory response and oxidative stress, and may serve as a potentially advantageous therapeutic target.

Cellular Protein Quality Control in Diabetic Cardiomyopathy: From Bench to Bedside

Heart failure is a serious comorbidity and the most common cause of mortality in diabetes patients. Diabetic cardiomyopathy (DCM) features impaired cellular structure and function, culminating in heart failure; however, there is a dearth of specific clinical therapy for treating DCM. Protein homeostasis is pivotal for the maintenance of cellular viability under physiological and pathological conditions, particularly in the irreplaceable cardiomyocytes; therefore, it is tightly regulated by a protein quality control (PQC) system. Three evolutionarily conserved molecular processes, the unfolded protein response (UPR), the ubiquitin-proteasome system (UPS), and autophagy, enhance protein turnover and preserve protein homeostasis by suppressing protein translation, degrading misfolded or unfolded proteins in cytosol or organelles, disposing of damaged and toxic proteins, recycling essential amino acids, and eliminating insoluble protein aggregates. In response to increased cellular protein demand under pathological insults, including the diabetic condition, a coordinated PQC system retains cardiac protein homeostasis and heart performance, on the contrary, inappropriate PQC function exaggerates cardiac proteotoxicity with subsequent heart dysfunction. Further investigation of the PQC mechanisms in diabetes propels a more comprehensive understanding of the molecular pathogenesis of DCM and opens new prospective treatment strategies for heart disease and heart failure in diabetes patients. In this review, the function and regulation of cardiac PQC machinery in diabetes mellitus, and the therapeutic potential for the diabetic heart are discussed.

Effects of Oxidative Stress on Protein Translation: Implications for Cardiovascular Diseases

Cardiovascular diseases (CVDs) are a group of disorders that affect the heart and blood vessels. Due to their multifactorial nature and wide variation, CVDs are the leading cause of death worldwide. Understanding the molecular alterations leading to the development of heart and vessel pathologies is crucial for successfully treating and preventing CVDs. One of the causative factors of CVD etiology and progression is acute oxidative stress, a toxic condition characterized by elevated intracellular levels of reactive oxygen species (ROS). Left unabated, ROS can damage virtually any cellular component and affect essential biological processes, including protein synthesis. Defective or insufficient protein translation results in production of faulty protein products and disturbances of protein homeostasis, thus promoting pathologies. The relationships between translational dysregulation, ROS, and cardiovascular disorders will be examined in this review.

Protective effects of AS-IV on diabetic cardiomyopathy by improving myocardial lipid metabolism in rat models of T2DM

Diabetic cardiomyopathy (DCM) is one of the main complications of type 2 diabetes mellitus (T2DM), and it is also one of the main causes of heart failure and death in advanced diabetes. The myocardial lipotoxic injury induced by abnormal lipid metabolism plays an important role in the occurrence and development of DCM, such as myocardial inflammation and fibrosis, ultimately leading to myocardial remodeling and cardiac insufficiency. Astragaloside IV (AS-IV) has many pharmacological effects such as anti-oxidation, anti-inflammatory, immune regulation, and anti-ischemic brain damage. This study was performed to investigate whether AS-IV could prevent T2DM-induced cardiomyopathy and regulate the abnormal myocardial lipid metabolism in diabetes. In this study, the T2DM model was induced by feeding with high-fat food and injected with low-dose STZ in rats. Then the model rats were treated with AS-IV and metformin (Met) for 8 weeks. The results showed that AS-IV improved cardiac systolic and diastolic function, and ameliorated the cardiac histopathological changes in the T2DM rats. Moreover, AS-IV significantly improved circulating TC, TG and HDL levels and cardiac lipid accumulation in T2DM rats as well as in high-fat diet (HFD) rats. Furthermore, AS-IV significantly inhibited the expressions of TNF-α, IL-6 and IL-1β and myocardial fibrosis in T2DM rats, which might be attributed to the improvement of myocardial lipid metabolism, ultimately improving cardiac function in T2DM rats. Taken together, these data suggested that AS-IV has protective effects on T2DM-induced myocardial injury in rats, and its mechanism may be related to the improvement of lipid metabolism in cardiomyocytes.

CTRP9 knockout exaggerates lipotoxicity in cardiac myocytes and high-fat diet-induced cardiac hypertrophy through inhibiting the LKB1/AMPK pathway

CTRP9 has been reported to regulate lipid metabolism and exert cardioprotective effects, yet its role in high‐fat diet (HFD)‐induced cardiac lipotoxicity and the underlying mechanisms remain unclear. In the current study, we established HFD‐induced obesity model in wild‐type (WT) or CTRP9 knockout (CTRP9‐KO) mice and palmitate‐induced lipotoxicity model in neonatal rat cardiac myocytes (NRCMs) to investigate the effects of CTRP9 on cardiac lipotoxicity. Our results demonstrated that the HFD‐fed CTRP9‐KO mice accentuated cardiac hypertrophy, fibrosis, endoplasmic reticulum (ER) stress‐initiated apoptosis and oxidative stress compared with the HFD‐fed WT mice. In vitro, CTRP9 treatment markedly alleviated palmitate‐induced oxidative stress and ER stress‐induced apoptosis in NRCMs in a dose‐dependent manner. Phosphorylated AMPK at Thr172 was reduced, and phosphorylated mammalian target of rapamycin (mTOR) was strengthened in the heart of the HFD‐fed CTRP9‐KO mice compared with the HFD‐fed control mice. In vitro, AMPK inhibitor compound C significantly abolished the effects of CTRP9 on the inhibition of the apoptotic pathway in palmitate‐treated NRCMs. In a further mechanistic study, CTRP9 enhanced expression of phosphorylated LKB1 at Ser428 and promoted LKB1 cytoplasmic localization. Besides, silencing of LKB1 gene by lentivirus significantly prohibited activation of AMPK by CTRP9 and partially eliminated the protective effect of CTRP9 on the cardiac lipotoxicity. These results indicate that CTRP9 exerted anti‐myocardial lipotoxicity properties and inhibited cardiac hypertrophy probably through the LKB1/AMPK signalling pathway.

Protective effects of dimethyl itaconate in mice acute cardiotoxicity induced by doxorubicin

Doxorubicin (DOX) is an antitumor drug widely used in hematological tumors and various solid tumors. However, the cardiotoxicity elicited by DOX severely limits its clinical treatment. Dimethyl itaconate (DI), a common form of itaconate, is found many potential targets for prevent heart injury. Here we employed wild type and Nrf2 knockout mice and induced a cardiotoxicity model by administration of DOX to clarify the effects of DI. After treatment with DI, we found that it could effectively alleviate the cardiotoxicity by analyzing morphology, LDH levels and heart weight/body weight ratio changes. Meanwhile we demonstrated that RIP3, a key protein of necrosis, was significantly decreased in DI treated group. Further we observed that treatment with DI could suppress oxidative stress by altering Nrf2/HO-1. Compared with vehicle group, DI could increase the tissue SOD and GSH, and reduce MDA levels, then DHE staining revealed that the level of ROS in DI group reduced by half. Finally, transmission electron microscope (TEM) data showed that treatment with DI obviously decreased the mitochondrial damage. While Nrf2 was ablated in mice, the protective effects of DI were vanished and SOD, GSH, MDA became unchanged related to vehicle group. This report provides the evidence for the protective effects of DI treatment in cardiotoxicity induced by DOX. On mechanisms, DI could reduce the oxidative stress by altering Nrf2/HO-1 pathway and prevent mitochondrial from damage. Taken together, these findings of this paper will afford the new therapeutic targets in DOX related cardiotoxicity.