Mechanisms Of Diabetic Cardiomyopathy Research Articles

Phloridzin prevents diabetic cardiomyopathy by reducing inflammation and oxidative stress

Oxidative stress and inflammation significantly contribute to the pathogenesis of diabetic cardiomyopathy (DCM). Persistent inflammatory stimuli drive the progression of myocardial fibrosis and impaired cardiac function. Phloridzin (Phl), a natural compound, demonstrates both anti-inflammatory and antioxidant properties. Nevertheless, its therapeutic potential and underlying mechanisms in DCM remain unclear. This study aimed to elucidate the mechanisms through which Phl inhibited myocardial fibrosis and exerted its antioxidative effects. The impact of Phl on DCM was evaluated using a high-fat/high-sugar diet combined with streptozotocin to induce an animal model and an in vitro H9C2 cell model stimulated by high glucose (HG). Untargeted metabolomics identified potential mechanisms underlying myocardial fibrosis. Phl treatment significantly enhanced left ventricular ejection fraction (EF%) and shortening fraction (FS%), while reducing myocardial injury markers, such as lactate dehydrogenase and creatine phosphokinase-MB, and suppressing myocardial collagen fiber accumulation. Simultaneously, Phl attenuated myocardial inflammation via inhibition of MyD88/NF-κB signaling, modulated the Nrf2/GPX4 axis to counter oxidative stress, and mitigated ferroptosis. In vitro, Phl inhibited high glucose-induced myocardial hypertrophy and fibrosis in H9C2 cells, while also repressing NF-κB activation in cardiomyocytes. Metabolomic profiling revealed that Phl ameliorated DCM through modulation of glycerophospholipid metabolic pathways, linking these metabolic shifts to enhanced antioxidant capacity, thereby reflecting its ability to reduce oxidative stress in the myocardium. Collectively, Phl provides cardioprotective effects by alleviating inflammation and oxidative damage.

PiR112710 attenuates diabetic cardiomyopathy through inhibiting Txnip/NLRP3-mediated pyroptosis in db/db mice

PIWI-interacting RNAs (piRNAs) are involved in the regulation of hypertrophic cardiomyopathy, heart failure and myocardial methylation. However, their functions and the underlying molecular mechanisms in diabetic cardiomyopathy (DCM) have yet to be fully elucidated. In the present study, a pyroptosis-associated piRNA (piR112710) was identified that ameliorates cardiac remodeling through targeting the activation of inflammasomes and mitochondrial dysfunction that are mediated via the thioredoxin-interacting protein (Txnip)/NLRP3 signaling axis. Subsequently, the cardioprotective effects of piR112710 on both the myocardium from db/db mice and cardiomyocytes from neonatal mice that were incubated with a high concentration of glucose combined with palmitate were examined. piR112710 was found to significantly improve cardiac dysfunction in db/db mice, characterized by improved echocardiography, lower levels of fibrosis, attenuated expression levels of inflammatory factors and pyroptosis-associated proteins (namely, Txnip, ASC, NLRP3, caspase-1 and GSDMD-N), and enhanced myocardial mitochondrial respiratory functions. In cultured neonatal mice cardiomyocytes, piR112710 deficiency and high glucose along with palmitate treatment led to significantly upregulated expression levels of pyroptosis associated proteins and collagens, oxidative stress, mitochondrial dysfunction and increased levels of inflammatory factors. Supplementation with piR112710, however, led to a reversal of the aforementioned changes induced by high glucose and palmitate. Mechanistically, the cardioprotective effect of piR112710 appears to be dependent upon effective elimination of reactive oxygen species and inactivation of the Txnip/NLRP3 signaling axis. Taken together, the findings of the present study have revealed that the piRNA-mediated inhibitory mechanism involving the Txnip/NLRP3 axis may participate in the regulation of pyroptosis, which protects against DCM both in vivo and in vitro. piR112710 may therefore be a potential therapeutic target for the reduction of myocardial injury caused by cardiomyocyte pyroptosis in DCM.

Protein PDK4 Interacts with HMGCS2 to Facilitate High Glucoseinduced Myocardial Injuries.

As a distinct type of cardiomyopathy, diabetic cardiomyopathy (DCM) is featured as diastolic or systolic cardiac dysfunction in diabetic patients. In order to broaden the understanding of molecular mechanisms in DCM, we intended to explore the mechanism of the interaction between PDK4 protein and Hmgcs2 in high glucose (HG)-induced myocardial damage. PDK4 and Hmgcs2 expression in the myocardium of diabetes mellitus (DM) model rats and HG-incubated cardiomyocyte line H9C2 was analyzed by western blot analysis. Echocardiography and TUNEL assay were utilized for respective assessment of cardiac structure and function and cardiomyocyte apoptosis in DM rats after silencing PDK4 or/and Hmgcs2. In vitro, the impact of PDK4 and Hmgcs2 on HG-induced cardiomyocyte injuries was identified with cell counting kit-8 and flow cytometry assays, along with detection of LDH release, caspase-3/7 activities, and reactive oxygen species (ROS) and malondialdehyde (MDA) levels. Moreover, a coimmunoprecipitation assay was utilized to test the interaction between PDK4 and Hmgcs2. Both PDK4 and Hmgcs2 were highly expressed in the myocardial tissues of DM rats. Mechanistically, PDK4 interacted with Hmgcs2 to upregulate Hmgcs2 expression in HG-induced H9C2 cells. Silencing PDK4 improved cardiac function and reduced cardiomyocyte apoptosis in DM rats. In HG-induced H9C2 cells, PDK4 or Hmgcs2 silencing enhanced cell viability and reduced LDH release, caspase-3/7 activities, cell apoptosis, and ROS and MDA levels, and these trends were further promoted by the simultaneous silencing of PDK4 and Hmgcs2. In summary, the silencing of PDK4 and Hmgcs2 alleviated HG-induced myocardial injuries through their interaction.

Ferroptosis: roles and molecular mechanisms in diabetic cardiomyopathy.

Diabetic cardiomyopathy (DCM) is a serious complication of type 1 and type 2 diabetes, which leads to the aggravation of myocardial fibrosis, disorders involving systolic and diastolic functions, and increased mortality of patients with diabetes through mechanisms such as glycolipid toxicity, inflammatory response, and oxidative stress. Ferroptosis is a form of iron-dependent regulatory cell death that is attributed to the accumulation of lipid peroxides and an imbalance in redox regulation. Increased production of lipid reactive oxygen species (ROS) during ferroptosis promotes oxidative stress and damages myocardial cells, leading to myocardial systolic and diastolic dysfunction. Overproduction of ROS is an important bridge between ferroptosis and DCM, and ferroptosis inhibitors may provide new targets for the treatment of patients with DCM.

MicroRNA-494 regulates high glucose-induced cardiomyocyte apoptosis and autophagy by PI3K/AKT/mTOR signalling pathway.

Diabetic cardiomyopathy (DCM) is one of the major cardiovascular complications of diabetes. However, the mechanism of DCM is not fully understood. Studies have confirmed that certain microRNAs (miRNAs/miRs) are key regulators of DCM. The aim of this study was to investigate the role and mechanism of microRNA (miR)-494 in cardiomyocyte apoptosis and autophagy induced by high glucose (HG). By establishing a rat DCM model and an HG-treated H9c2 cells injury model, cardiac function was detected by echocardiography, myocardial tissue was stained by immunohistochemistry, and Cell Counting Kit-8 assay and lactate dehydrogenase assay were used to detect the cardiomyocyte injury. Cell apoptosis was detected by terminal deoxynucleotidyl transferase dUTP nick end labelling staining, and western blotting was used to detect death and autophagy. The results showed that the expression level of miR-494 was higher in the myocardial tissue of DCM rats and the myocardial cells of H9c2 treated with HG. Compared with the corresponding negative control groups, miR-494 mimics enhanced HG-induced apoptosis and autophagy, whereas miR-494 inhibitors showed the opposite effect, corresponding PI3K, AKT, and mTOR phosphorylation level has changed. These findings identify that miR-494 could regulate cell apoptosis and autophagy through PI3K/AKT/mTOR signalling pathway, participating in the regulation of cardiomyocyte cell damage after HG. These findings provide new insights for the further study of the molecular mechanism and treatment of DCM.

Role of cannabinoids and the endocannabinoid system in modulation of diabetic cardiomyopathy

Diabetic complications, chiefly seen in long-term situations, are persistently deleterious to a large extent, requiring multi-factorial risk reduction strategies beyond glycemic control. Diabetic cardiomyopathy is one of the most common deleterious diabetic complications, being the leading cause of mortality among diabetic patients. The mechanisms of diabetic cardiomyopathy are multi-factorial, involving increased oxidative stress, accumulation of advanced glycation end products (AGEs), activation of various pro-inflammatory and cell death signaling pathways, and changes in the composition of extracellular matrix with enhanced cardiac fibrosis. The novel lipid signaling system, the endocannabinoid system, has been implicated in the pathogenesis of diabetes and its complications through its two main receptors: Cannabinoid receptor type 1 and cannabinoid receptor type 2, alongside other components. However, the role of the endocannabinoid system in diabetic cardiomyopathy has not been fully investigated. This review aims to elucidate the possible mechanisms through which cannabinoids and the endocannabinoid system could interact with the pathogenesis and the development of diabetic cardiomyopathy. These mechanisms include oxidative/ nitrative stress, inflammation, accumulation of AGEs, cardiac remodeling, and autophagy. A better understanding of the role of cannabinoids and the endocannabinoid system in diabetic cardiomyopathy may provide novel strategies to manipulate such a serious diabetic complication.

Mechanisms of cardiac dysfunction in diabetic cardiomyopathy: molecular abnormalities and phenotypical variants.

Diabetic cardiomyopathy (DCM) is a diabetes mellitus-induced pathophysiological condition characterized by cardiac structural, functional, and metabolic changes that can result in heart failure (HF), in the absence of coronary artery disease, hypertension, and valvular heart disease. Metabolic alterations such as hyperglycemia, insulin resistance, hyperinsulinemia, and increased metabolism of free fatty acids result in oxidative stress, inflammation, advanced glycation end products formation, abnormalities in calcium homeostasis, and apoptosis that are responsible for structural remodeling. Cardiac stiffness, hypertrophy, and fibrosis eventually lead to dysfunction and HF with preserved ejection fraction and/or HF with reduced ejection fraction. In this review, we analyzed in detail the cellular and molecular mechanisms and the metabolic pathways involved in the pathophysiology of DCM. Different phenotypes are observed in DCM, and it is not clear yet if the restrictive and the dilated phenotypes are distinct or represent an evolution of the same disease. Phenotypic differences can be observed between T1DM and T2DM DCM, possibly explained by the different myocardial insulin action. Further studies are needed in order to better understand the underlying mechanisms of DCM and to identify appropriate therapeutic targets and novel strategies to prevent and reverse the progression toward heart failure in diabetic patients.

Changes in microRNA Expression Profiles in Diabetic Cardiomyopathy Rats Following H3 Relaxin Treatment.

MicroRNAs (miRNAs) are noncoding RNAs that play an important role in the mechanisms of diabetic cardiomyopathy (DCM); however, whether human recombinant relaxin-3 (H3 relaxin) inhibits myocardial injury in DCM rats and the underlying mechanisms involving miRNAs remain unknown. miRNA expression profiles were detected using miRNA microarray and bioinformatics analyses of myocardial tissues from control, DCM, and H3 relaxin-administered DCM groups, and the regulatory mechanisms of the miRNAs were investigated. A total of 5 miRNAs were downregulated in the myocardial tissues of DCM rats and upregulated in H3 relaxin-treated DCM rats, and 1 miRNA (miRNA let-7d-3p) was increased in the myocardial tissue of DCM rats and decreased in H3 relaxin-treated DCM rats as revealed by miRNA microarray and validated by real-time polymerase chain reaction. Important signaling pathways were found to be triggered by the differentially expressed miRNAs, including metabolism, cancer, Rap1, PI3K-Akt, and MAPK signaling pathways. The study revealed that H3 relaxin improved glucose uptake in DCM rats, potentially via the regulation of miRNA let-7d-3p.

The characteristics of heart failure in patients with diabetes mellitus in Sanglah Hospital Denpasar

Background: The prevalence of heart failure (HF) is 4 times higher in patients with diabetes mellitus (DM) than general population. Coronary heart disease (CHD), hypertension, DM, obesity, smoking and atrial fibrillation are risk factors for HF. However, many observational studies have shown that DM is an independent risk factor for HF through the mechanism of diabetic cardiomyopathy. Objective: This study aimed to determine the characteristic heart failure in patients with DM. Methods: This study used a cross sectional descriptive design and the secondary data originating from medical records of patient in the intermediate ward and intensive care coronary care unit, Sanglah Hospital on March 2020 - March 2021. The inclusion criteria were DM patients with acute or chronic HF, while the exclusions criteria were DM patients with anemia, pregnancy and incomplete medical record data. Result: A total of 65 subjects were male (43%), aged > 60 years (52.3%), had a history of smoking (50.8%), experienced obesity grade I (35.4), with duration of DM > 5 years (67.7%) and had poor glycemic control (55.4%). The majority of DM complications were CHD (86.2%). Based on echocardiography results, the subjects had heart failure with reduced ejection fraction (43.1%), left atrial dilatation (58.5%), left ventricular hypertrophy (80%), heart valve abnormalities (66.2%) and left ventricular diastolic dysfunction (73.8%). Conclusion: There were no subjects who only suffered from DM type 2 without other comorbid diseases such as CHD, hypertension or heart valve disease.

Mechanisms of diabetic cardiomyopathy and potential therapeutic strategies: preclinical and clinical evidence.

The pathogenesis and clinical features of diabetic cardiomyopathy have been well-studied in the past decade, but effective approaches to prevent and treat this disease are limited. Diabetic cardiomyopathy occurs as a result of the dysregulated glucose and lipid metabolism associated with diabetes mellitus, which leads to increased oxidative stress and the activation of multiple inflammatory pathways that mediate cellular and extracellular injury, pathological cardiac remodelling, and diastolic and systolic dysfunction. Preclinical studies in animal models of diabetes have identified multiple intracellular pathways involved in the pathogenesis of diabetic cardiomyopathy and potential cardioprotective strategies to prevent and treat the disease, including antifibrotic agents, anti-inflammatory agents and antioxidants. Some of these interventions have been tested in clinical trials and have shown favourable initial results. In this Review, we discuss the mechanisms underlying the development of diabetic cardiomyopathy and heart failure in type 1 and type 2 diabetes mellitus, and we summarize the evidence from preclinical and clinical studies that might provide guidance for the development of targeted strategies. We also highlight some of the novel pharmacological therapeutic strategies for the treatment and prevention of diabetic cardiomyopathy.

Mitochondrial Mechanisms in Diabetic Cardiomyopathy.

Mitochondrial medicine is increasingly discussed as a promising therapeutic approach, given that mitochondrial defects are thought to contribute to many prevalent diseases and their complications. In individuals with diabetes mellitus (DM), defects in mitochondrial structure and function occur in many organs throughout the body, contributing both to the pathogenesis of DM and complications of DM. Diabetic cardiomyopathy (DbCM) is increasingly recognized as an underlying cause of increased heart failure in DM, and several mitochondrial mechanisms have been proposed to contribute to the development of DbCM. Well established mechanisms include myocardial energy depletion due to impaired adenosine triphosphate (ATP) synthesis and mitochondrial uncoupling, and increased mitochondrial oxidative stress. A variety of upstream mechanisms of impaired ATP regeneration and increased mitochondrial reactive oxygen species have been proposed, and recent studies now also suggest alterations in mitochondrial dynamics and autophagy, impaired mitochondrial Ca2+ uptake, decreased cardiac adiponectin action, increased O-GlcNAcylation, and impaired activity of sirtuins to contribute to mitochondrial defects in DbCM, among others. In the current review, we present and discuss the evidence that underlies both established and recently proposed mechanisms that are thought to contribute to mitochondrial dysfunction in DbCM.

Role of Cytochrome p450 and Soluble Epoxide Hydrolase Enzymes and Their Associated Metabolites in the Pathogenesis of Diabetic Cardiomyopathy.

A plethora of studies have demonstrated that cardiomyopathy represents a serious source of morbidity and mortality in patients with diabetes. Yet, the underlying mechanisms of diabetic cardiomyopathy are still poorly understood. Of interest, cytochrome P450 2J (CYP2J) and soluble epoxide hydrolase (sEH) are known to control the maintenance of cardiovascular health through the regulation of cardioprotective epoxyeicosatrienoic acids (EETs) and its less active products, dihydroxyeicosatrienoic acids (DHETs). Therefore, we examined the role of the aforementioned pathway in the development of diabetic cardiomyopathy. Our diabetic model initiated cardiomyopathy as indexed by the increase in the expression of hypertrophic markers such as NPPA. Furthermore, diabetic cardiomyopathy was associated with a low level of cardiac EETs and an increase of the DHETs/EETs ratio both in vivo and in cardiac cells. The modulation in EETs and DHETs was attributed to the increase of sEH and the decrease of CYP2J. Interestingly, the reduction of sEH attenuates cardiotoxicity mediated by high glucose in cardiac cells. Mechanistically, the beneficial effect of sEH reduction might be due to the decrease of phosphorylated ERK1/2 and p38. Overall, the present work provides evidence that diabetes initiates cardiomyopathy through the increase in sEH, the reduction of CYP2J, and the decrease of cardioprotective EETs.

PI3Ks in diabetic cardiomyopathy

Diabetic cardiomyopathy refers to the heart disease without coronary artery disease and hypertension, diabetic patients with ventricular dysfunction. The molecular mechanism of diabetic cardiomyopathy remains unclear. Protein and lipid kinase phosphoinositol 3-kinase (PI3Ks) are thought to regulate cardiac damage in diabetes mellitus. This article reviews the role of PI3K subtypes and downstream signal transduction in the pathogenesis of diabetic cardiomyopathy, including cardiac metabolic regulation, contractility, hypertrophy, cardiomyocyte death and inflammation. Key words: 1-phosphatidylinositol 3-kinase; Diabetes complications; Cardiomyopathies/ET; Review

Identification of Core Gene Biomarkers in Patients with Diabetic Cardiomyopathy.

Diabetic cardiomyopathy (DCM) is a disorder of the myocardium in diabetic patients, which is one of the critical complications of diabetes giving rise to an increased mortality. However, the underlying mechanisms of DCM remain incompletely understood presently. This study was designed to screen the potential molecules and pathways implicated with DCM. GSE26887 involving 5 control individuals and 7 DCM patients was selected from the GEO database to identify the differentially expressed genes (DEGs). DAVID was applied to perform gene ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses. A protein-protein interaction (PPI) network was also constructed to visualize the interactions among these DEGs. To further validate significant genes and pathways, quantitative real-time PCR (qPCR) and Western blot were performed. A total of 236 DEGs were captured, including 134 upregulated and 102 downregulated genes. GO, KEGG, and the PPI network disclosed that inflammation, immune disorders, metabolic disturbance, and mitochondrial dysfunction were significantly enriched in the development of DCM. Notably, IL6 was an upregulated hub gene with the highest connectivity degree, suggesting that it may interact with a great many molecules and pathways. Meanwhile, SOCS3 was also one of the top 15 hub genes in the PPI network. Herein, we detected the protein level of STAT3 and SOCS3 in a mouse model with DCM. Western blot results showed that the protein level of SOCS3 was significantly lower while phosphorylated-STAT3 (P-STAT3) was activated in mice with DCM. In vitro results also uncovered the similar alterations of SOCS3 and P-STAT3 in cardiomyocytes and cardiac fibroblasts induced by high glucose (HG). However, overexpression of SOCS3 could significantly reverse HG-induced cardiomyocyte hypertrophy and collagen synthesis of cardiac fibroblasts. Taken together, our analysis unveiled potential biomarkers and molecular mechanisms in DCM, which could be helpful to the diagnosis and treatment of DCM.

Gene expression profiles of rat MMECs with different glucose levels and fgl2 gene silencing.

Cardiac microvascular endothelial cells (MMECs) is one of the key factors in the process of diabetic cardiomyopathy, a common chronic complication of diabetes. Fibrinogen-like protein 2 (FGL2) is linked to apoptosis, angiogenesis, and inflammatory response, all of which also occur in diabetes. Thus, we investigate the role of FGL 2 and other genes in the pathology of diabetic cardiomyopathy. In the present study, we used high-throughput microarray to profile gene expression in rat myocardial MMECs with or without silencing the fgl2 gene and in different glucose environments. We use volcanic maps to isolate genes with significantly different expression levels between conditions, using the standard statistical criteria of fold changes ≥1.5 and P-values ≤0.05. From this list, we identified genes with the most signicant changes in RNA levels and confirmed their protein-level changes with Western blot. Furthermore, bioinformatic analysis predicts possible pathophysiology and clinical relevance of these proteins in diabetic cardiomyopathy. We identified 17 upregulated and 15 downregulated genes caused by silencing fgl2 gene. Most of them are involved in metabolism, ion transport, cell membrane surface recognition signal modification, inflammatory response, and immune response. Using Western blot, we were able to confirm protein-level expression changes of three genes. Specifically, in both normal and high glucose conditions, silencing fgl2 significantly decreased the expression levels of CCL3 and PLAGL1 while increasing the expression level of CTSC. Significantly, bioinformatic analyses show that CCL3 is related to type 1 diabetes, PLAGL1 to cardiomyocytes, and CTSC to albuminuria in type 2 diabetes. Our study provides clues for further studies on the mechanism of diabetic cardiomyopathy as well as function of FGL2 in this process, potentially offering new therapeutic strategies for treating diabetic cardiomyopathy.

Diabetic cardiomyopathy: a hyperglycaemia- and insulin-resistance-induced heart disease.

Diabetic cardiomyopathy is characterised in its early stages by diastolic relaxation abnormalities and later by clinical heart failure in the absence of dyslipidaemia, hypertension and coronary artery disease. Insulin resistance, hyperinsulinaemia and hyperglycaemia are each independent risk factors for the development of diabetic cardiomyopathy. The pathophysiological factors in diabetes that drive the development of cardiomyopathy include systemic metabolic disorders, inappropriate activation of the renin-angiotensin-aldosterone system, subcellular component abnormalities, oxidative stress, inflammation and dysfunctional immune modulation. These abnormalities collectively promote cardiac tissue interstitial fibrosis, cardiac stiffness/diastolic dysfunction and, later, systolic dysfunction, precipitating the syndrome of clinical heart failure. Recent evidence has revealed that dysregulation of coronary endothelial cells and exosomes also contributes to the pathology behind diabetic cardiomyopathy. Herein, we review the relationships among insulin resistance/hyperinsulinaemia, hyperglycaemia and the development of cardiac dysfunction. We summarise the current understanding of the pathophysiological mechanisms in diabetic cardiomyopathy and explore potential preventative and therapeutic strategies.

Abstract 13412: Differential Insulin-dependent Signaling Pathways Modulated by Hydrogen Peroxide in Cardiac Myocytes

Hydrogen peroxide (H 2 O 2 ) has long been implicated in insulin signal transduction, yet the mechanisms whereby insulin regulates intracellular H 2 O 2 to modulate physiological responses remain obscure. Here we explore the roles of H 2 O 2 in regulation of insulin pathways in cardiac myocytes. We found that insulin inhibits cardiac myocyte beta adrenergic physiological and biochemical responses. We found that catalase (which degrades H 2 O 2 ) completely blocks the ability of insulin to activate the insulin-responsive kinases Akt/mTOR and also to attenuate beta adrenergic receptor-mediated increases in myocyte contractility. These insulin responses are abrogated in a mouse model of type 2 diabetes, establishing a key role for H 2 O 2 -dependent pathways in the diabetic heart. To directly probe intracellular H 2 O 2 responses to insulin in cardiac myocytes, we constructed a novel recombinant AAV9 vector expressing the fluorescent H 2 O 2 biosensor HyPer, which we used to infect mice in vivo . We isolated cardiac myocytes from mice infected with this biosensor and performed quantitative imaging studies. This approach revealed robust insulin-dependent increases in cardiac myocyte H 2 O 2 in response to insulin in wild-type mice. Attenuated H 2 O 2 responses were observed in myocytes isolated from mouse lines deficient in the NADPH oxidase isoforms Nox2 or Nox4 that had been infected with HyPer-AAV9. In Nox2 knockout myocytes, we found that insulin-promoted phosphorylation of kinases Akt and mTor is markedly attenuated, while insulin-dependent inhibition of beta adrenergic contractility is unaffected. In contrast, in cardiac myocytes isolated from the Nox4 knockout mouse, insulin-dependent Akt/mTor phosphorylation responses are unaffected, while the ability of insulin to attenuate the beta adrenergic increase in myocyte contractility was lost. These studies represent an important advance in our understanding of insulin action in the heart by identifying a proximal point of bifurcation in insulin signaling via the differential activation of two NADPH oxidase isoforms. The work also provides insight into mechanisms of diabetic cardiomyopathy, and suggest that insulin resistance in the diabetic heart may unmask potentially deleterious beta adrenergic responses.

107 - Experimental Model of Type 2 Diabetic Cardiomyopathy: A State of cGMP Deficiency

Introduction: Patients with type 2 diabetes mellitus (DM) are predisposed to long term cardiovascular complications, including development of myocardial dysfunction and heart failure. Despite the high prevalence of diabetic cardiomyopathy, characterized by diastolic dysfunction independent of coronary artery disease and thought to be related to metabolic derangements and protein alterations, not much is known regarding the genesis and treatment of this condition. The development of an experimental type 2 diabetes mellitus animal model can help to better understand pathophysiology and mechanisms of diabetic cardiomyopathy. Methods: Genetically designated Zucker diabetic ZDFO rats and Zucker lean non-diabetic ZDFL rats (ten each) were maintained on Purina 5008 diet from 13 to 32 weeks of age. Echocardiography with strain imaging was performed, and vital signs and blood work were obtained from the rats at the beginning and end of the study. Echocardiography was used to assess left ventricular (LV) structure and function. At the end of 32 weeks, rats were anesthetized and arterial blood was collected from carotid artery. Cardiac tissues were harvested for histological analysis and sections stained with Picrosirius Red to assess for fibrosis. Results: The development of diabetes was confirmed by HbA1c measurements (diabetic rats 12.7 ± 0.2 vs nondiabetic rats 5.1 ± 0.1%, P < .01). There was no difference in LV ejection fraction between the diabetic rats as compared to nondiabetic controls (78.1 ± 0.6 vs 78.0 ± 0.7%, P = .87). However, there was evidence of diastolic dysfunction with longitudinal strain imaging. Early diastolic strain demonstrated a trend for difference in the diabetic group from 13 to 32 weeks (−10.9 ± 0.6 to −9.6 ± 0.7, P = .16) that is not seen in the nondiabetic group (−11.1 ± 0.5 to −11.6 ± 0.9, P = .98). The diabetic vs nondiabetic rats had increased mean arterial pressures at 32 weeks (106 ± 4 vs 95 ± 2 mmHg, P = .01). LV mass indexed to rat body weight was increased in the diabetic vs nondiabetic rats (2.34 ± 0.36 vs 2.06 ± 0.03 mg/g, P < .01). Upon tissue histological examination, there was greater LV interstitial (21.6 ± 3 vs 10.8 ± 1%, P = .01) and perivascular (25.8 ± 3 vs 14.8 ± 1%, P < .01) fibrosis. The diabetic vs nondiabetic rats had decreased plasma cGMP at 32 weeks (2.8 ± 0.7 vs 8.9 ± 1.7 pmol/ml, P = .01) and no difference in plasma BNP (24.6 ± 5.5 vs 18.4 ± 2.6 pg/ml, P = .76). Conclusion: In this genetically designated Zucker type 2 diabetes mellitus rat model, we demonstrated that there is development of cardiac hypertrophy, fibrosis and diastolic dysfunction, along with a cGMP deficiency state. Future studies using these diabetic animal models can help better elucidate the pathophysiology of diabetic cardiomyopathy and development of novel therapeutic options.

Abstract 439: Modeling Diabetic Cardiomyopathy Model Using Human Induced Pluripotent Stem Cell-derived Cardiomyocytes

Background: Diabetic cardiomyopathy (DCM) is one of the major cardiac complications in diabetic patients. However, the underlying mechanisms and pathogenesis of diabetic cardiomyopathy are only partially understood and the specific therapeutic target remains unknown. Here, we developed an in vitro diabetic cardiomyopathy model through simple metabolic manipulation using human induced pluripotent stem cell (iPSC)-derived cardiomyocytes (iPSC-CMs). Methods: After 30 days from initial differentiation, iPSC-CMs were cultured with maturation medium (containing fatty acid but no glucose) for 3 days to obtain matured cardiomyocyte properties. Maturation extent of iPSC-CMs was analyzed using patch-clamp to analyze electrophysiological properties and RT-PCR to analyze cardiomyocyte-specific structure proteins and ion channel expression. Matured iPSC-CMs were then treated with 11 mM glucose for 2 days. 11 mM glucose represents mild glucose conditions in diabetic patients. Cardiomyopathy phenotype of iPSC-CMs was evaluated by analyzing brain natriuretic peptide (BNP) secretion from iPSC-CMs using ELISA. Result: Differentiated iPSCs-CMs were immature. Following 3 day culture in maturation medium, iPSC-CMs exhibited the cardiomyocyte maturation characteristics: 1) an increase of contractility with diminished automaticity, suggesting progressive maturation toward adult cardiomyocytes, 2) the lower maximal diastolic potential and increased amplitude, indicating functional maturation, and 3) an upregulation of the following gene expression: sarcomeric proteins (e.g., TNNI3, MYL2 and MYL3) and potassium channel α-subunit genes (KCNJ12 and KCNJ4). Matured iPSC-CMs treated with 11 mM glucose showed increase in cell size and BNP secretion (17-fold increase vs. control cells without glucose, p&lt;0.01). These results suggested that cardiomyocytes exposure to the maturation medium followed by diabetic milieu of glucose recapitulate DCM in vitro . Conclusion: We conclude that the phenotype of DCM can be modeled using cultured iPSC-derived cardiomyocytes through diabetic extracellular milieu. This clinically relevant stem cell model would be a powerful platform to study novel mechanisms of DCM and the specific therapeutic targets.

GW26-e1025 Fenofibrate Prevention of Diabetic Cardiomyopathy Is Mediated by FGF21 Via Sirt1-Dependent Autophagy Modulation

Diabetes mellitus (DM) is one of the greatest public health threats in modern societies. And among all the diabetic complications, diabetic cardiomyopathy (DCM) has been recognized as the leading cause of morbidity and mortality. Thus, the elucidation of pathological mechanisms in DCM is urgently