Therapeutic Target For Diabetic Cardiomyopathy Research Articles

Forkhead box O1 transcription factor; a therapeutic target for diabetic cardiomyopathy.

Cardiovascular disease including diabetic cardiomyopathy (DbCM) represents the leading cause of death in people with diabetes. DbCM is defined as ventricular dysfunction in the absence of underlying vascular diseases and/or hypertension. The known molecular mediators of DbCM are multifactorial, including but not limited to insulin resistance, altered energy metabolism, lipotoxicity, endothelial dysfunction, oxidative stress, apoptosis, and autophagy. FoxO1, a prominent member of forkhead box O transcription factors, is involved in regulating various cellular processes in different tissues. Altered FoxO1 expression and activity have been associated with cardiovascular diseases in diabetic subjects. Herein we provide an overview of the role of FoxO1 in various molecular mediators related to DbCM, such as altered energy metabolism, lipotoxicity, oxidative stress, and cell death. Furthermore, we provide valuable insights into its therapeutic potential by targeting these perturbations to alleviate cardiomyopathy in settings of type 1 and type 2 diabetes.

Empagliflozin improves mitochondrial dysfunction in diabetic cardiomyopathy by modulating ketone body metabolism and oxidative stress

Ketone bodies are considered as an alternative energy source for diabetic cardiomyopathy (DCM) and can improve the energy supply of the heart muscle, suggesting that it may be an important area of research and development as a therapeutic target for DCM. Cumulative cardiovascular trials have shown that sodium-glucose cotransporter 2 (SGLT2) inhibitors reduce cardiovascular events in diabetic populations. Whether SGLT2 inhibitors improve DCM by enhancing ketone body metabolism remains and whether they help prevent oxidative damage remains to be clarified. Here, we present the combined results of nine GSE datasets for diabetic cardiomyopathy (GSE215979, GSE161931, GSE145294, GSE161052, GSE173384, GSE123975, GSE161827, GSE210612, and GSE5606). We found significant up-regulated gene 3-hydroxymethylglutaryl CoA synthetase 2 (HMGCS2) and down-regulated gene 3-hydroxybutyrate dehydrogenase (BDH1) and 3-oxoacid CoA-transferase1 (OXCT1), respectively. Based on the analysis of the constructed protein interaction network, it was found that HMGCS2 was in the core position of the interaction network. In addition, Gene ontology (GO) enrichment analysis mainly focused on redox process, acyl-CoA metabolic process, catalytic activity, redox enzyme activity and mitochondria. The activity of HMGCS2 in DCM heart was increased, while the expression of ketolysis enzymes BDH1 and OXCT1 was inhibited. In vivo, Empagliflozin (Emp) treated DCM group significantly decreased ventricular weight, myocardial cell cross-sectional area, and myocardial fibrosis. In addition, Emp further promoted the activity of BDH1 and OXCT1, increased the utilization of ketone bodies, further promoted the activity of HMGCS2 in DCM, and increased the synthesis of ketone bodies, prevented mitochondrial breakage and dysfunction, increased myocardial ATP to provide sufficient energy, inhibited oxidative stress and apoptosis of cardiac cells ex vivo, and improved the myocardial dysfunction of DCM. Emp can improve mitochondrial dysfunction in diabetic cardiomyopathy by regulating ketone body metabolism and oxidative stress. These findings provide a theoretical basis for evaluating Emp as a treatment for DCM.

ACMSD mediated de novo NAD+ biosynthetic impairment in cardiac endothelial cells as a potential therapeutic target for diabetic cardiomyopathy

Object: The highly conserved α-amino-β-carboxymuconate-ε-semialdehyde decarboxylase (ACMSD) is the key enzyme that regulates the de novo NAD+ synthesis from tryptophan. NAD+ metabolism in diabetic cardiomyopathy (DCM) was not elucidated yet. MethodsMice were assigned to non-diabetic (NDM) group, streptozocin (STZ)-induced diabetic (DM) group, and nicotinamide (NAM) treated (DM+NAM) group. ACMSD mediated NAD+ metabolism were studied both in mice and patients with diabetes. ResultsNAD+ level was significantly lower in the heart of DM mice than that of the NDM group. Supplementation with NAM could partially increased myocardial capillary density and ameliorated myocardial fibrosis by increasing NAD+ level through salvage pathway. Compared with NDM mice, the expression of ACMSD in myocardial endothelial cells of DM mice was significantly increased. It was further confirmed that in endothelial cells, high glucose promoted the expression of ACMSD. Inhibition of ACMSD could increase de novo NAD+ synthesis and improve endothelial cell function by increasing Sirt1 activity. Targeted mass spectrometry analysis indicated increased ACMSD enzyme activity in diabetic patients, higher ACMSD activity increased risk of heart diastolic dysfunction. ConclusionIn summary, increased expression of ACMSD lead to impaired de novo NAD+ synthesis in diabetic heart. Inhibition of ACMSD could potentially improve DCM.

Abstract 12317: UBC9 Alleviates Diabetic Cardiomyopathy via the Modulation of Mitophagy

Introduction: Type 2 diabetes is prevalent worldwide. Cardiovascular complications in patients with diabetes include diabetic cardiomyopathy (DCM). Ubiquitin-conjugating enzyme E2 I (UBC9) is the only SUMO-E2 enzyme that plays a key role in cardiomyocytes. Hypothesis: The present study aimed to elucidate the role and mechanism of action of UBC9 in the development of DCM. Methods: We established myocardial-specific UBC9 knockout (UBC9-CKO) and adeno-associated virus-overexpressing mouse models. Additionally, a mouse model of DCM was established using high-fat diet feeding and low-dose streptozotocin injection. This mechanism was explained by the stimulation of cultured cardiomyocytes with palmitic acid. Results: The transcript and protein levels of UBC9 were significantly decreased in the myocardium of patients with DCM. Myocardial-specific UBC9 knockout aggravated cardiac dysfunction, alleviated myocardial fibrosis and hypertrophy, and promoted mitophagy and mitochondrial damage. Meanwhile, UBC9 overexpression exhibited the opposite effects. UBC9 exerted mitochondrial protective effects independent of SUMOylation. UBC9 regulated RUNX2 degradation by directly binding to NEDD4, thus regulating PSEN2 to exert protective effects against mitophagy. Moreover, the effect of UBC9 on mitochondrial function was reversed upon PSEN2 knockdown. Conclusions: UBC9 regulates mitophagy through the NEDD4/RUNX2/PSEN2 pathway and alleviates DCM development by improving myocardial mitochondrial dysfunction. These findings offer novel perspectives on the application of UBC9 as a therapeutic target for DCM.

SIRT6: A potential therapeutic target for diabetic cardiomyopathy.

The abnormal lipid metabolism in diabetic cardiomyopathy can cause myocardial mitochondrial dysfunction, lipotoxicity, abnormal death of myocardial cells, and myocardial remodeling. Mitochondrial homeostasis and normal lipid metabolism can effectively slow down the development of diabetic cardiomyopathy. Recent studies have shown that SIRT6 may play an important role in the pathological changes of diabetic cardiomyopathy such as myocardial cell death, myocardial hypertrophy, and myocardial fibrosis by regulating mitochondrial oxidative stress and glucose and lipid metabolism. Therefore, understanding the function of SIRT6 and its role in the pathogenesis of diabetic cardiomyopathy is of great significance for exploring and developing new targets and drugs for the treatment of diabetic cardiomyopathy. This article reviews the latest findings of SIRT6 in the pathogenesis of diabetic cardiomyopathy, focusing on the regulation of mitochondria and lipid metabolism by SIRT6 to explore potential clinical treatments.

Focal adhesion kinase induces cardiac remodeling through NF-κB-mediated inflammatory responses in diabetic cardiomyopathy

BackgroundHyperglycemia-induced chronic inflammation is a crucial risk factor that causes undesirable cardiac alternations in diabetic cardiomyopathy (DCM). Focal adhesion kinase (FAK) is a non-receptor protein tyrosine kinase that primarily regulates cell adhesion and migration. Based on recent studies, FAK is involved in inflammatory signaling pathway activation in cardiovascular diseases. Here, we evaluated the possibility of FAK as a therapeutic target for DCM. MethodsA small molecular selective FAKinhibitor, PND-1186 (PND), was used to evaluate the effect of FAK on DCM in both high glucose-stimulated cardiomyocytes and streptozotocin (STZ)-induced type 1 diabetes mellitus (T1DM) mice. ResultsIncreased FAK phosphorylation was found in the hearts of STZ-induced T1DM mice. PND treatment significantly decreased the expression of inflammatory cytokines and fibrogenic markers in cardiac specimens of diabetic mice. Notably, these reductions were correlated with improved cardiac systolic function. Furthermore, PND suppressed transforming growth factor-β-activated kinase 1 (TAK1) phosphorylation and NF-κB activation in the hearts of diabetic mice. Cardiomyocytes were identified as the main contributor to FAK-mediated cardiac inflammation and the involvement of FAK in cultured primary mouse cardiomyocytes and H9c2 cells was identified. Both FAK inhibition or FAK deficiency prevented hyperglycemia-induced inflammatory and fibrotic responses in cardiomyocytes owing to the inhibition of NF-κB. Herein, FAK activation was revealed to FAK directly binding to TAK1, leading to activation of TAK1 and downstream NF-κB signaling pathway. ConclusionsFAK is a key regulator of diabetes-associated myocardial inflammatory injury by directly targeting to TAK1.

Never in mitosis gene A-related kinase-6 deficiency deteriorates diabetic cardiomyopathy via regulating heat shock protein 72.

NIMA (never in mitosis, gene A)-related kinase-6 (NEK6), a cell cycle regulatory gene, was found to regulate cardiac hypertrophy. However, its role in diabetes-induced cardiomyopathy has not been fully elucidated. This research was designed to illustrate the effect of NEK6 involved in diabetic cardiomyopathy. Here we used a streptozotocin (STZ)-induced mice diabetic cardiomyopathy model and NEK6 knockout mice to explore the role and mechanism of NEK6 in diabetic-induced cardiomyopathy. NEK6 knockout mice and wild-type littermates were subjected to STZ injection (50mg/kg/day for 5days) to induce a diabetic cardiomyopathy model. As a result, 4months after final STZ injection, DCM mice revealed cardiac hypertrophy, fibrosis, and systolic and diastolic dysfunction. NEK6 deficiency causes deteriorated cardiac hypertrophy, fibrosis, and cardiac dysfunction. Furthermore, we observed inflammation and oxidative stress in the hearts of NEK6 deficiency mice under diabetic cardiomyopathy pathology. Adenovirus was used to upregulate NEK6 in neonatal rat cardiomyocytes, and it was found that NEK6 ameliorated high glucose-induced inflammation and oxidative stress. Our findings revealed that NEK6 increased the phosphorylation of heat shock protein 72 (HSP72) and increased the protein level of PGC-1α and NRF2. Co-IP assay experiment confirmed that NEK6 interacted with HSP72. When HSP72 was silenced, the anti-inflammation and anti-oxidative stress effects of NEK6 were blurred. In summary, NEK6 may protect diabetic-induced cardiomyopathy by interacting with HSP72 and promoting the HSP72/PGC-1α/NRF2 signaling. KEY MESSAGES: NEK6 knockout deteriorated cardiac dysfunction, cardiac hypertrophy, fibrosis as well as inflammation response, and oxidative stress. NEK6 overexpression attenuated high glucose induced inflammation and oxidative stress. The underlying mechanisms of the protective role of NEK6 in the development of diabetic cardiomyopathy seem to involve the regulation of HSP72-NRF2- PGC-1α pathway. NEK6 may become a new therapeutic target for diabetic cardiomyopathy.

KLF9 Aggravates Streptozotocin-Induced Diabetic Cardiomyopathy by Inhibiting PPARγ/NRF2 Signalling.

Krüppel-like Factor 9 (KLF9) is a transcription factor that regulates multiple disease processes. Studies have focused on the role of KLF9 in the redox system. In this study, we aimed to explore the effect of KLF9 on diabetic cardiomyopathy. Cardiac-specific overexpression or silencing of KLF9 in C57BL/6 J mice was induced with an adeno-associated virus 9 (AAV9) delivery system. Mice were also subjected to streptozotocin injection to establish a diabetic cardiomyopathy model. In addition, neonatal rat cardiomyocytes were used to assess the possible role of KLF9 in vitro by incubation with KLF9 adenovirus or small interfering RNA against KLF9. To clarify the involvement of peroxisome proliferator-activated receptors (PPARγ), mice were subjected to GW9662 injection to inhibit PPARγ. KLF9 was upregulated in the hearts of mice with diabetic cardiomyopathy and in cardiomyocytes. In addition, KLF9 overexpression in the heart deteriorated cardiac function and aggravated hypertrophic fibrosis, the inflammatory response and oxidative stress in mice with diabetic cardiomyopathy. Conversely, cardiac-specific silencing of KLF9 ameliorated cardiac dysfunction and alleviated hypertrophy, fibrosis, the cardiac inflammatory response and oxidative stress. In vitro, KLF9 silencing in cardiomyocytes enhanced inflammatory cytokine release and oxidative stress; KLF9 overexpression increased these detrimental responses. Moreover, KLF9 was found to regulate the transcription of PPARγ, which suppressed the expression and nuclear translocation of nuclear Factor E2-related Factor 2 (NRF2). In mice injected with a PPARγ inhibitor, the protective effects of KLF9 knockdown on diabetic cardiomyopathy were counteracted by GW9662 injection. KLF9 aggravates cardiac dysfunction, the inflammatory response and oxidative stress in mice with diabetic cardiomyopathy. KLF9 may become a therapeutic target for diabetic cardiomyopathy.

Blockage of MyD88 in cardiomyocytes alleviates cardiac inflammation and cardiomyopathy in experimental diabetic mice

Hyperglycemia-associated inflammation contributes to diabetic cardiomyopathy. Myeloid differentiation primary-response protein 88 (MyD88) is an adapter protein of many Toll-like receptors (TLRs) and is recruited to TLRs to initiate inflammatory response in endotoxin-activated innate immunity. However, the role of MyD88 in diabetic cardiomyopathy is unknown. We examined the role and mechanism of MyD88 in inflammatory heart injuries in diabetes and identified MyD88 as a potential target for the treatment of diabetic cardiomyopathy. In this study, we first found that MyD88 expression was increased in cardiomyocytes of diabetic mouse hearts. In cultured cardiomyocytes, MyD88 inhibition either by siRNA or by small-molecular inhibitor LM8 markedly blocked TLR4-MyD88 complex formation, reduced pro-inflammatory mitogen-activated protein kinases/nuclear factor-κB (MAPKs/NF-κB) cascade activation and decreased pro-inflammatory cytokine expression under high glucose condition. Moreover, pharmacologic inhibition of MyD88 by LM8 showed significantly anti-inflammatory, anti-hypertrophic and anti-fibrotic effects in the hearts of both type 1 and type 2 diabetic mice. These beneficial effects of MyD88 inhibition were correlated to the reduced activation of TLR4-MyD88-MAPKs/NF-κB signaling pathways in the hearts. Taken together, MyD88 in cardiomyocytes mediates diabetes-induced cardiac inflammatory injuries and pharmacological inhibition of MyD88 shows significantly cardioprotective effects, indicating MyD88 as a potential therapeutic target for diabetic cardiomyopathy.

Gut microbiota: A new therapeutic target for diabetic cardiomyopathy.

Diabetic cardiomyopathy seriously affects quality of life and even threatens life safety of patients. The pathogenesis of diabetic cardiomyopathy is complex and multifactorial, and it is widely accepted that its mechanisms include oxidative stress, inflammation, insulin resistance, apoptosis, and autophagy. Some studies have shown that gut microbiota plays an important role in cardiovascular diseases. Gut microbiota and its metabolites can affect the development of diabetic cardiomyopathy by regulating oxidative stress, inflammation, insulin resistance, apoptosis, and autophagy. Here, the mechanisms of gut microbiota and its metabolites resulting in diabetic cardiomyopathy are reviewed. Gut microbiota may be a new therapeutic target for diabetic cardiomyopathy.

LncRNA-MALAT 1 regulates cardiomyocyte scorching in diabetic cardiomyopathy by targeting NLRP3.

Streptozotocin (STZ) at 35 mg/Kg was used to induce diabetes in rats. H9C2 cardiomyocytes and primary cardiomyocytes (PCM) were cultured at 5.5 and 50 mmol/L glucose, respectively. The expression levels of MALAT 1 and scorch death-related genes were detected by RT-PCR using plasmids to suppress or overexpress the related genes, respectively. Immunofluorescence, RT-PCR and Western blot were used to detect the extent of cell scorch death. MALAT 1 expression was elevated in diabetic and high glucose-induced cardiomyocytes and myocardial tissue from diabetic mice (p<0.001). Silencing of MALAT 1 alleviated cardiomyocyte scorch death by targeting NLRP3. Furthermore, silencing MALAT 1 reduced cell death and improved cardiac function and morphology. MALAT 1 is overexpressed in DCM and silencing MALAT 1 inhibits cell scorch death by affecting NLRP3 expression. We clarify for the first time that MALAT 1 may be a new therapeutic target for DCM.

Abstract 9026: Endogenous Ca2+/Calmodulin-Dependent Protein Kinase II Overactivation Exacerbates Cardiac Dysfunction and Beta-Adrenergic Desensitization in a Mouse Model With Type 2 Diabetes

Background: Emergent evidence indicates that CaMKII overactivity in diabetes (DM) plays a crucial role in the pathophysiology of diabetic cardiomyopathy (DCM) by targeting a diverse array of proteins involved in cardiac electrical, structural and functional remodeling. CaMKII has been proposed to be a therapeutic target for DCM. However, although chronic inhibition of CaMKII has been associated with cardioprotection in several cardiovascular diseases, the direct cardiac effects of CaMKII activation in type 2 (T2) DM are unclear. Moreover, whether and how DCM alters cardiac responses to CaMKII are undefined. We tested the hypothesis that in DCM, CaMKII is upregulated, which alters cardiac contractile behavior. Endogenous CaMKII activation may produce direct depressions in LV myocyte basal function and β-adrenergic reserve. Acute inactivation of CaMKII with KN93 would have a beneficial impact in DCM. Methods: LV myocyte CaMKIIδ expression and activity and myocyte functional responses were compared in 2 groups (n=9/group) of wild-type female mice: Vehicle Control (C) , animals fed chow for 14 weeks (W); T2DM, i nduced with a high-fat diet (HFD) intake for 14 W, but after fed HFD for 4 W receiving streptozotocin (STZ, 40 mg/kg/day, i.p. for 5 days). In T2DM, we further assessed myocyte contractile and [Ca 2+ ] i transient ([Ca 2+ ] iT ) responses with and without acute treatment of myocytes with KN93 (10 -6 M, 30 min). Results: Versus C, in T2DM myocytes, the CaMKIIδ protein levels (28%, 0.51 vs 0.40) and CaMKIIδ phosphorylation (79%, 0.52 vs 0.29) were significantly increased. These changes were followed by significantly reduced cell contraction (dL/dt max , 76.0 vs 137.3 μm/s), relaxation (dR/dt max , 61.7 vs 116.0 μm/s) and [Ca 2+ ] iT (0.16 vs 0.21). ISO-stimulated increases dL/dt max (39% vs 58%), dR/dt max (35% vs 54%) and [Ca 2+ ] iT (20% vs 30%) were also significantly reduced. Moreover, in T2DM myocytes, superfusion with KN93 significantly improved myocyte basal contraction (104.2 μm/s), relaxation (79.3 μm/s) and [Ca 2+ ] iT (0.21). Conclusions: In T2 diabetes-induced DCM, upregulation of CaMKIIδ has adverse functional effects. Acute endogenous CaMKII activation exacerbates LV myocyte dysfunction. The inhibition of CaMKII has a significant beneficial impact.

Reverse remodeling in diabetic cardiomyopathy: the role of extracellular matrix.

Diabetic patients are prone to suffer from cardiovascular disease, specifically from ischemic heart disease and diabetic cardiomyopathy, which have a huge impact on morbidity and mortality worldwide. Cardiac fibrosis due to alteration of the extracellular matrix (ECM) remodeling is often observed in diabetes and myocardial fibrosis is an important part of cardiac remodeling that leads to heart failure and death. At single-cell level, the ECM govern, metabolism, motility, orientation, and proliferation. However, in pathological condition such as diabetes, changes in ECM lead to fibrosis and subsequently cardiac stiffness and cardiomyocytes dysfunction. Antidiabetic drugs, particularly sodium-glucose cotransporter-2 (SGLT2) inhibitors have antifibrotic effects and may promote ECM reverse remodeling. In this review, the mechanisms, and the role of ECM remodeling and reverse remodeling as a potential therapeutic target for diabetic cardiomyopathy are discussed.

Cardiomyocyte-specific Txnip C247S mutation improves left ventricular functional reserve in streptozotocin-induced diabetic mice.

Underlying molecular mechanisms for the development of diabetic cardiomyopathy remain to be determined. Long-term exposure to hyperglycemia causes oxidative stress, which leads to cardiomyocyte dysfunction. Previous studies established the importance of thioredoxin-interacting protein (Txnip) in cellular redox homeostasis and glucose metabolism. Txnip is a highly glucose-responsive molecule that interacts with the catalytic center of reduced thioredoxin and inhibits the antioxidant function of thioredoxin. Here, we show that the molecular interaction between Txnip and thioredoxin plays a pivotal role in the regulation of redox balance in the diabetic myocardium. High glucose increased Txnip expression, decreased thioredoxin activities, and caused oxidative stress in cells. The Txnip-thioredoxin complex was detected in cells with overexpressing wild-type Txnip but not Txnip cysteine 247 to serine (C247S) mutant that disrupts the intermolecular disulfide bridge. Then, diabetes was induced in cardiomyocyte-specific Txnip C247S knock-in mice and their littermate control animals by injections of streptozotocin (STZ). Prolonged hyperglycemia upregulated myocardial Txnip expression in both genotypes. The absence of Txnip's inhibition of thioredoxin in Txnip C247S mutant hearts promoted mitochondrial antioxidative capacities in cardiomyocytes, thereby protecting the heart from oxidative damage by diabetes. Stress hemodynamic analysis uncovered that Txnip C247S knock-in hearts have a greater left ventricular contractile reserve than wild-type hearts under STZ-induced diabetic conditions. These results provide novel evidence that Txnip serves as a regulator of hyperglycemia-induced cardiomyocyte toxicities through direct inhibition of thioredoxin and identify the single cysteine residue in Txnip as a therapeutic target for diabetic injuries.NEW & NORTEWORTHY Thioredoxin-interacting protein (Txnip) has been of great interest as a molecular mechanism to mediate diabetic organ damage. Here, we provide novel evidence that a single mutation of Txnip confers a defense mechanism against myocardial oxidative stress in streptozotocin-induced diabetic mice. The results demonstrate the importance of Txnip as a cysteine-containing redox protein that regulates antioxidant thioredoxin via disulfide bond-switching mechanism and identify the cysteine in Txnip as a therapeutic target for diabetic cardiomyopathy.

Yes-Associated Protein is Involved in Myocardial Fibrosis in Rats with Diabetic Cardiomyopathy.

IntroductionRecent studies have shown that YAP is closely related to the pathological process of cardiovascular diseases. But the role of YAP in cardiac injury of diabetic cardiomyopathy (DCM) is still unclear.MethodsDiabetic cardiomyopathy rat model was established and divided into control group, DCM group, LV-SC-shRNA group and LV-YAP-shRNA group. LV-SC-shRNA group and LV-YAP-shRNA group were injected with lentivirus expressing SC-shRNA and YAP-shRNA via tail vein, respectively. Primary rat cardiac fibroblasts (CFs) were stimulated with high concentration of glucose and treated with recombinant lentivirus expressing either SC-shRNA or YAP-shRNA to observe the expression of CTGF and fibronectin, so as to observe the effect of inhibiting YAP on the pathogenesis of DCM.ResultsCompared with control group, high glucose markedly increased YAP mRNA and protein expression in DCM and CFs. Inhibition of YAP decreased myocardial fibrosis and improved cardiac function in the DCM model and decreased the expression of CTGF and fibronectin in CFs. The result suggested that YAP plays a key role in the pathological progression of DCM, and the underlying mechanisms may be associated with TEAD and CTGF.DiscussionWe found that the expression of YAP was increased both in vivo and in vitro, suggesting that YAP is closely related to DCM, and YAP knockdown can reduce myocardial fibrosis in rat model of DCM by reducing the expression of PAI-1, collagen I, collagen III, CTGF and profilin, as well as the expression of CTGF and fibronectin in CFs. This study revealed that YAP plays an important role in the pathological process of diabetic cardiomyopathy, and down-regulation of YAP expression may provide a new therapeutic target for DCM.

Novel regulation of cardiac branched-chain amino acid metabolism through AMP deaminase: a possible therapeutic target for diabetic cardiomyopathy

Abstract Background Dysregulation of branched-chain amino acid (BCAA) metabolism has been shown to be associated with type 2 diabetes mellitus (T2DM) and heart failure. BCAA reportedly protects cells from fatty acid-induced mitochondrial injury via sequestration of fatty acids in intracellular lipid droplets from mitochondria. We previously reported that up-regulation of AMP deaminase 3 (AMPD3) impairs cardiac energetics in T2DM hearts, and AMPD3 was recently shown to participate in regulation of amino acid metabolism in skeletal muscle. Purpose We hypothesized that AMPD3 regulates cardiac amino acid metabolism by interaction with branched-chain α-ketoacid dehydrogenase (BCKDH) complex and that cardioprotective effect of sodium glucose cotransporter 2 inhibitors is mediated by modification of BCAA metabolism in diabetic cardiomyocytes. Methods and results Proteomic analyses of immunoprecipitates with an anti-AMPD3 antibody in rat hearts revealed that AMPD3 interacted with the E1α component of BCKDH complex. Whereas BCKDH has been reported to localize in mitochondria matrix as a rate-limiting enzyme for BCAA catabolism, immunoblotting using subcellular fractions revealed that BCKDH E1α is present in cytosol and endoplasmic reticulum as well. AMPD3-BCKDH E1α interaction was decreased by 68% in T2DM rats (OLETF) compared to that in control rats (LETO), and significant accumulation of BCAAs was observed in OLETF hearts (317±30 vs. 213±16 nmol/g). Survival rate at 48 hours after myocardial infarction (MI) was significantly lower in OLETF than in LETO (40% vs 84%). Empagliflozin treatment (10 mg/kg/day, 14 days) before MI improved the survival rate in OLETF to 70%, increased BCAAs as the top of 92 detected metabolites (791±187 nmol/g) and significantly preserved tissue ATP in the non-MI remote region. Electron microscopy showed a significantly higher prevalence of myocardium lipid droplets in OLETF, which was further increased by empagliflozin. Conclusions Results of the present analyses support the hypotheses that conversion of BCAA-derived branched-chain α-ketoacid to branched-chain acyl-CoA is suppressed by reduced AMPD3-BCKDH interaction in the myocardium of T2DM and that empagliflozin induces compensation of the dysregulated cardiac BCAA metabolism by augmentation of BCAA influx and promotion of fatty acid sequestration in intracellular lipid droplets. Funding Acknowledgement Type of funding source: Foundation. Main funding source(s): Boehringer Ingelheim

Micro RNA-126 promoting angiogenesis in diabetic heart by VEGF/Spred-1/Raf-1 pathway: effects of high-intensity interval training.

This study aims to investigate the effect of high-intensity interval training (HIIT) on gene expression of MicroRNA-126 (miR-126) and serum concentration of vascular endothelial growth factor/ sprouty related EVH1 domain containing 1/ rapidly accelerated fibrosarcoma 1 (VEGF/Spred-1/Raf-1) proteins effective in cardiac tissue angiogenesis of diabetic rats. Forty male Wistar rats were randomly divided into four groups of healthy control (HC), diabetic control (DC), diabetic with HIIT training (DT), and healthy with HIIT training (HT). HIIT was performed 6days per week for 6weeks (with the overload). Diabetes was induced via the combination of intraperitoneal injection of streptozotocin and high-fat foods. Diabetes remarkably diminished the expressions of miR-126, VEGF and Raf-1 proteins, and augmented Spred-1 expression. Meanwhile, the implementation of HIIT gave rise to a significant enhancement in expression of miR-126 heart tissue (P < 0.01), and subsequently increased the expression of VEGF and Raf-1 proteins (P < 0.01), and declined Spred-1 expression (P < 0.01) in the training group compared to the control group. The results of this study show that HIIT increases the expression of miR-126 by activating the angiogenesis pathway of the heart tissue. Increased angiogenesis through the miR-126 pathway is vital to compensate for heart destruction induced by diabetes. Thus, the use of standard interval exercise can be introduced as a novel therapeutic target for diabetic cardiomyopathy.

Identification of key candidate genes and pathways revealing the protective effect of liraglutide on diabetic cardiac muscle by integrated bioinformatics analysis.

BackgroundDiabetes mellitus is becoming a significant health problem with the International Diabetes Federation (IDF) expecting a startling 642 million diabetes patients by 2040. Liraglutide, a glucagon-like peptide-1 (GLP-1) analog, is reported to protect against diabetic cardiomyopathy by binding to the receptor, GLP-1R. However, the underlying mechanism has yet to be clarified. This study aimed to investigate the underlying mechanisms and the effects of liraglutide on diabetic patient’s cardiac muscles.MethodsGSE102194 genetic expression profiles were extracted from the Gene Expression Omnibus (GEO) database. The gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes pathway (KEGG) enrichment analyses were carried out. Next, Cytoscape software was used to construct the protein-protein interaction (PPI) network of the differentially expressed genes (DEGs). DEGs were mapped onto a protein-protein interaction (PPI) network that comprised 249 nodes and 776 edges.ResultsA total of 520 DEGs were discovered, including 159 down-regulated genes and 361 up-regulated genes. DEGs that were upregulated were notably enriched in biological processes (BP) such as muscle system process, muscle system process, muscle structure development and anatomical structure morphogenesis while DEGs that were downregulated were rich in detection of chemical stimulus and neurological system process. KEGG pathway analysis showed the up-regulated DEGs were enriched in adrenergic signaling for cardiomyocytes, dopaminergic synapse, and circadian entrainment, while the down-regulated DEGs were enriched for factory transduction in 249 of the 520 tested samples. The modular analysis identified 4 modules that participated in some pathways associated with cardiac muscle contraction, hypertrophic cardiomyopathy (HCM), and MAPK signaling pathway.ConclusionsOur data showed that Glp-1 could decrease the protein expression of p38, JNK, ERK1/2, and MARS proteins induced by high glucose (22 mM, 72 h). This study highlights the potential physiological processes that take place in diabetic cardiac muscles exposed to liraglutide. Our findings elucidated the regulatory network in diabetic cardiomyopathy and might provide a novel diagnostic and therapeutic target for diabetic cardiomyopathy.

Exercise as A Potential Therapeutic Target for Diabetic Cardiomyopathy: Insight into the Underlying Mechanisms.

Diabetes mellitus is associated with cardiovascular, ophthalmic, and renal comorbidities. Among these, diabetic cardiomyopathy (DCM) causes the most severe symptoms and is considered to be a major health problem worldwide. Exercise is widely known as an effective strategy for the prevention and treatment of many chronic diseases. Importantly, the onset of complications arising due to diabetes can be delayed or even prevented by exercise. Regular exercise is reported to have positive effects on diabetes mellitus and the development of DCM. The protective effects of exercise include prevention of cardiac apoptosis, fibrosis, oxidative stress, and microvascular diseases, as well as improvement in cardiac mitochondrial function and calcium regulation. This review summarizes the recent scientific findings to describe the potential mechanisms by which exercise may prevent DCM and heart failure.

Current Status and Challenges of NRF2 as a Potential Therapeutic Target for Diabetic Cardiomyopathy.

Diabetic cardiomyopathy is one of the main causes of heart failure and death in patients with diabetes mellitus. Reactive oxygen species produced excessively in diabetes mellitus cause necrosis, apoptosis, ferroptosis, inflammation, and fibrosis of the myocardium as well as impair the cardiac structure and function. It is increasingly clear that oxidative stress is a principal cause of diabetic cardiomyopathy. The transcription factor nuclear factor-erythroid 2 p45-related factor 2 (NRF2) activates the transcription of more than 200 genes in the human genome. Most of the proteins translated from these genes possess anti-oxidant, anti-inflammatory, anti-apoptotic, anti-ferroptotic, and anti-fibrotic actions. There is a growing body of evidence indicating that NRF2 and its target genes are crucial in preventing high glucose-induced oxidative damage in diabetic cardiomyopathy. Recently, many natural and synthetic activators of NRF2 are shown to possess promising therapeutic effects on diabetic cardiomyopathy in animal models of diabetic cardiomyopathy. Targeting NRF2 signaling by pharmacological entities is a potential approach to ameliorating diabetic cardiomyopathy. However, the persistent high expression of NRF2 in cancer tissues also protects the growth of cancer cells. This "dark side" of NRF2 increases the challenges of using NRF2 activators to treat diabetic cardiomyopathy. In addition, some NRF2 activators were found to have off-target effects. In this review, we summarize the current status and challenges of NRF2 as a potential therapeutic target for diabetic cardiomyopathy.