Diabetes-induced Cardiomyopathy Research Articles

Understanding diabetes-induced cardiomyopathy from the perspective of renin angiotensin aldosterone system.

Experimental and clinical evidence suggests that diabetic subjects are predisposed to a distinct cardiovascular dysfunction, known as diabetic cardiomyopathy (DCM), which could be an autonomous disease independent of concomitant micro and macrovascular disorders. DCM is one of the prominent causes of global morbidity and mortality and is on a rising trend with the increase in the prevalence of diabetes mellitus (DM). DCM is characterized by an early left ventricle diastolic dysfunction associated with the slow progression of cardiomyocyte hypertrophy leading to heart failure, which still has no effective therapy. Although the well-known "Renin Angiotensin Aldosterone System (RAAS)" inhibition is considered a gold-standard treatment in heart failure, its role in DCM is still unclear. At the cellular level of DCM, RAAS induces various secondary mechanisms, adding complications to poor prognosis and treatment of DCM. This review highlights the importance of RAAS signaling and its major secondary mechanisms involving inflammation, oxidative stress, mitochondrial dysfunction, and autophagy, their role in establishing DCM. In addition, studies lacking in the specific area of DCM are also highlighted. Therefore, understanding the complex role of RAAS in DCM may lead to the identification of better prognosis and therapeutic strategies in treating DCM.

Protective Effects of Huangqi Shengmai Yin on Type 1 Diabetes-Induced Cardiomyopathy by Improving Myocardial Lipid Metabolism.

Diabetic cardiomyopathy (DCM) is one of the many complications of diabetes. DCM leads to cardiac insufficiency and myocardial remodeling and is the main cause of death in diabetic patients. Abnormal lipid metabolism plays an important role in the occurrence and development of DCM. Huangqi Shengmai Yin (HSY) has previously been shown to alleviate signs of heart disease. Here, we investigated whether HSY could improve cardiomyopathy caused by type 1 diabetes mellitus (T1DM) and improve abnormal lipid metabolism in the diabetic heart. Streptozotocin (STZ) was used to establish the T1DM mouse model, and T1DM mice were subsequently treated with HSY for eight weeks. The changes in the cardiac conduction system, histopathology, blood myocardial injury indices, and lipid content and expression of proteins related to lipid metabolism were evaluated. Our results showed that HSY could improve electrocardiogram; decrease the serum levels of CK-MB, LDH, and BNP; alleviate histopathological changes in cardiac tissue; and decrease myocardial lipid content in T1DM mice. These results indicate that HSY has a protective effect against T1DM-induced myocardial injury in mice and that this effect may be related to the improvement in myocardial lipid metabolism.

The Potential Role of Flavonoids in Ameliorating Diabetic Cardiomyopathy via Alleviation of Cardiac Oxidative Stress, Inflammation and Apoptosis.

Diabetic cardiomyopathy is one of the major mortality risk factors among diabetic patients worldwide. It has been established that most of the cardiac structural and functional alterations in the diabetic cardiomyopathy condition resulted from the hyperglycemia-induced persistent oxidative stress in the heart, resulting in the maladaptive responses of inflammation and apoptosis. Flavonoids, the most abundant phytochemical in plants, have been reported to exhibit diverse therapeutic potential in medicine and other biological activities. Flavonoids have been widely studied for their effects in protecting the heart against diabetes-induced cardiomyopathy. The potential of flavonoids in alleviating diabetic cardiomyopathy is mainly related with their remedial actions as anti-hyperglycemic, antioxidant, anti-inflammatory, and anti-apoptotic agents. In this review, we summarize the latest findings of flavonoid treatments on diabetic cardiomyopathy as well as elucidating the mechanisms involved.

Dysregulation of circulating miRNAs promotes the pathogenesis of diabetes-induced cardiomyopathy.

Diabetic Cardiomyopathy (DCM) is characterized by myocardial dysfunction caused by diabetes mellitus. After-effects of diabetic cardiomyopathy are far more lethal than non-diabetic cardiomyopathy. More than 300 million people suffer from diabetes and cardiovascular disorder which is expected to be elevated to an alarming figure of 450 million by 2030. Recent studies suggested that miRNA plays important role in the onset of diabetic cardiomyopathy. This study was designed to identify the miRNA that is responsible for the onset of diabetic cardiomyopathy using in silico and in vitro approaches. In this study, to identify the miRNA responsible for the onset of diabetic cardiomyopathy, in silico analysis was done to predict the role of these circulating miRNAs in type 2 diabetic cardiomyopathy. Shared miRNAs that are present in both diseases were selected for further analysis. Total RNA and miRNA were extracted from blood samples taken from type 2 diabetic patients as well as healthy controls to analyze the expression of important genes like AKT, VEGF, IGF, FGF1, ANGPT2 using Real-time PCR. The expression of ANGPT2 was up-regulated and AKT, VEGF, IGF, FGF1 were down-regulated in DCM patients as compared to healthy controls. The miRNA expression of miR-17 was up-regulated and miR-24, miR-150, miR-199a, miR-214, and miR-320a were down-regulated in the DCM patients as compared to healthy controls. This shows that dysregulation of target genes and miRNA may contribute towards the pathogenesis of DCM and more studies should be conducted to elucidate the role of circulating miRNAs to use them as therapeutic and diagnostic options.

Diabetes-induced cardiomyopathy is ameliorated by heat-killed Lactobacillus reuteri GMNL-263 in diabetic rats via the repression of the toll-like receptor 4 pathway.

Diabetes mellitus (DM) leads to disorders such as cardiac hypertrophy, cardiac myocyte apoptosis, and cardiac fibrosis. Previous studies have shown that Lactobacillus reuteri GMNL-263 decreases cardiomyopathy by reducing inflammation. In this study, we investigated the potential benefit of GMNL-263 supplementation in treating diabetes-induced cardiomyocytes in rats with DM. Five-week-old male Wistar rats were randomly divided into three groups, control, DM, and rats with DM treated with different dosages of L. reuteri GMNL-263. After undergoing treatment for 4weeks, all rats were euthanized for further analysis. We observed that cardiac function and structure of rats with DM was rescued by GMNL-263. Activation of toll-like receptor 4 (TLR4)-related inflammatory, hypertrophic, and fibrotic signaling pathways in the hearts of rats with DM was reduced by treatment with GMNL-263. Our findings demonstrate that GMNL-263 inhibited diabetes-induced cardiomyocytes via the repression of the TLR4 pathway. Moreover, these findings suggest that treatment with high-dose GMNL-263 could be a precautionary therapy for reducing the diabetes-induced cardiomyopathy.

Potential of Sulforaphane as a Natural Immune System Enhancer: A Review.

Brassicaceae are an outstanding source of bioactive compounds such as ascorbic acid, polyphenols, essential minerals, isothiocyanates and their precursors, glucosinolates (GSL). Recently, GSL gained great attention because of the health promoting properties of their hydrolysis products: isothiocyanates. Among them, sulforaphane (SFN) became the most attractive one owing to its remarkable health-promoting properties. SFN may prevent different types of cancer and has the ability to improve hypertensive states, to prevent type 2 diabetes–induced cardiomyopathy, and to protect against gastric ulcer. SFN may also help in schizophrenia treatment, and recently it was proposed that SFN has potential to help those who struggle with obesity. The mechanism underlying the health-promoting effect of SFN relates to its indirect action at cellular level by inducing antioxidant and Phase II detoxifying enzymes through the activation of transcription nuclear factor (erythroid-derived 2)-like (Nrf2). The effect of SFN on immune response is generating scientific interest, because of its bioavailability, which is much higher than other phytochemicals, and its capacity to induce Nrf2 target genes. Clinical trials suggest that sulforaphane produces favorable results in cases where pharmaceutical products fail. This article provides a revision about the relationship between sulforaphane and immune response in different diseases. Special attention is given to clinical trials related with immune system disorders.

Anti-inflammatory Effects of S. cumini Seed Extract on Gelatinase-B (MMP-9) Regulation against Hyperglycemic Cardiomyocyte Stress.

Black berry (Syzygium cumini) fruit is useful in curing diabetic complications; however, its role in diabetes-induced cardiomyopathy is not yet known. In this study, we investigated the regulation of gelatinase-B (MMP-9) by S. cumini methanol seed extract (MSE) in diabetic cardiomyopathy using real-time PCR, RT-PCR, immunocytochemistry, gel diffusion assay, and substrate zymography. The regulatory effects of MSE on NF-κB, TNF-α, and IL-6 were also examined. Identification and estimation of polyphenol constituents present in S. cumini extract were carried out using reverse-phase HPLC. Further, in silico docking studies of identified polyphenols with gelatinase-B were performed to elucidate molecular level interaction in the active site of gelatinase-B. Docking studies showed strong interaction of S. cumini polyphenols with gelatinase-B. Our findings indicate that MSE significantly suppresses gelatinase-B expression and activity in high-glucose- (HG-) stimulated cardiomyopathy. Further, HG-induced activation of NF-κB, TNF-α, and IL-6 was also remarkably reduced by MSE. Our results suggest that S. cumini MSE may be useful as an effective functional food and dietary supplement to regulate HG-induced cardiac stress through gelatinase.

Ginger (Zingiber Officinale Roscoe) Extract Protects the Heart Against Inflammation and Fibrosis in Diabetic Rats

BackgroundFibrosis and inflammation in the heart of patients with diabetes mellitus alongside increased production of free radicals and collagen are together known as diabetic cardiomyopathy. Ginger rhizome has antidiabetic, antioxidant and anti-inflammatory effects. Thus, we investigated the effect of ginger extract on diabetes-induced cardiomyopathy in streptozotocin-induced diabetic rats. MethodsAnimals were divided into 7 groups: control; diabetic; diabetic treated with different doses of ginger extract of 100, 200 and 400 mg/kg; metformin (200 mg/kg); and metformin-valsartan (200 and 30 mg/kg, respectively). Serum levels of glucose, aspartate aminotransferase, lactate dehydrogenase and creatine kinase-muscle/brain were measured. Fibrosis and inflammation were determined by histologic assessment. Gene expression of transforming growth factor (TGF)-β1, TGF-β3 and angiotensin II type 1 receptor was evaluated by real-time polymerase chain reaction in heart tissue. ResultsSerum glucose level in all treated groups, except for the ginger extract 100-mg/kg group, was significantly lower than in the diabetic group. Serum levels of aspartate aminotransferase, lactate dehydrogenase and creatine kinase-muscle/brain were significantly reduced in all treated groups compared with the diabetic group. In the study of fibrosis, collagen amount in the heart tissue of all treated groups, except the ginger extract 100-mg/kg group, was significantly lower than in the diabetic group. Inflammatory cell infiltrates were decreased, and disarrangement was improved in cardiac tissues of all treated groups compared with the diabetic group. Expression of angiotensin II type 1 receptor and TGF-β1 and TGF-β3 genes in all treated groups downregulated compared with the diabetic group. ConclusionsTreatment by ginger extract reduced myocardial fibrosis and inflammation in the course of diabetic cardiomyopathy, possibly through regulation of the expression of genes involved in the SMAD/TGF-β pathway.

Mst1 knockdown alleviates cardiac lipotoxicity and inhibits the development of diabetic cardiomyopathy in db/db mice

Diabetic cardiomyopathy (DCM) accounts for increasing deaths of diabetic patients, and effective therapeutic targets are urgently needed. Myocardial lipotoxicity, which is caused by cardiac non-oxidative metabolic fatty acids and cardiotoxic fatty acid metabolites accumulation, has gained more attention to explain the increasing prevalence of DCM. However, whether mammalian Ste20-like kinase 1 (Mst1) plays a role in lipotoxicity in type 2 diabetes-induced cardiomyopathy has not yet been illustrated. Here, we found that Mst1 expression was elevated transcriptionally in the hearts of type 2 diabetes mellitus mice and palmitic acid-treated neonatal rat ventricular myocytes. Adeno-associated virus 9 (AAV9)-mediated Mst1 silencing in db/db mouse hearts significantly alleviated cardiac dysfunction and fibrosis. Notably, Mst1 knockdown in db/db mouse hearts decreased lipotoxic apoptosis and inflammatory response. Mst1 knockdown exerted protective effects through inactivation of MAPK/ERK kinase kinase 1 (MEKK1)/c-Jun N-terminal kinase (JNK) signaling pathway. Moreover, lipotoxicity induced Mst1 expression through promoting the binding of forkhead box O3 (FoxO3) and Mst1 promoter. Conclusively, we elucidated for the first time that Mst1 expression is regulated by FOXO3 under lipotoxicity stimulation and downregulation of Mst1 protects db/db mice from lipotoxic cardiac injury through MEKK1/JNK signaling inhibition, indicating that Mst1 abrogation may be a potential treatment strategy for DCM in type 2 diabetic patients.

P300 in Cardiac Development and Accelerated Cardiac Aging.

The heart is the first functional organ that develops during embryonic development. While a heartbeat indicates life, cessation of a heartbeat signals the end of life. Heart disease, due either to congenital defects or to acquired dysfunctions in adulthood, remains the leading cause of death worldwide. Epigenetics plays a key role in both embryonic heart development and heart disease in adults. Stress-induced vascular injury activates pathways involved in pathogenesis of accelerated cardiac aging that includes cellular dysfunction, pathological cardiac hypertrophy, diabetic cardiomyopathy, cardiac matrix remodeling, cardiac dysfunction and heart failure. Acetyltransferase p300 (p300), a major epigenetic regulator, plays a pivotal role in heart development during embryogenesis, as deficiency or abnormal expression of p300 leads to embryonic death at early gestation periods due to deformation of the heart and neural tube. Acetyltransferase p300 controls heart development through histone acetylation-mediated chromatin remodeling and transcriptional regulation of genes required for cardiac development. In adult hearts, p300 is differentially expressed in different chambers and epigenetically controls cardiac gene expression. Deregulation of p300, in response to prohypertrophic and profibrogenic stress signals, is associated with increased recruitment of p300 to several genes including transcription factors, increased acetylation of specific lysines in histones and transcription factors, altered chromatin organization, and increased hypertrophic and fibrogenic gene expression. Cardiac hypertrophy and myocardial fibrogenesis are common pathological manifestations of several stress-induced accelerated cardiac aging-related pathologies, including high blood pressure-induced or environmentally induced cardiac hypertrophy, myocardial infarction, diabetes-induced cardiomyopathy, and heart failure. Numerous studies using cellular and animal models clearly indicate that pharmacologic or genetic normalization of p300 activity has the potential to prevent or halt the progression of cardiac aging pathologies. Based on these preclinical studies, development of safe, non-toxic, small molecule inhibitors/epidrugs targeting p300 is an ideal approach to control accelerated cardiac aging-related deaths worldwide.

Characterising an Alternative Murine Model of Diabetic Cardiomyopathy.

The increasing burden of heart failure globally can be partly attributed to the increased prevalence of diabetes, and the subsequent development of a distinct form of heart failure known as diabetic cardiomyopathy. Despite this, effective treatment options have remained elusive, due partly to the lack of an experimental model that adequately mimics human disease. In the current study, we combined three consecutive daily injections of low-dose streptozotocin with high-fat diet, in order to recapitulate the long-term complications of diabetes, with a specific focus on the diabetic heart. At 26 weeks of diabetes, several metabolic changes were observed including elevated blood glucose, glycated haemoglobin, plasma insulin and plasma C-peptide. Further analysis of organs commonly affected by diabetes revealed diabetic nephropathy, underlined by renal functional and structural abnormalities, as well as progressive liver damage. In addition, this protocol led to robust left ventricular diastolic dysfunction at 26 weeks with preserved systolic function, a key characteristic of patients with type 2 diabetes-induced cardiomyopathy. These observations corresponded with cardiac structural changes, namely an increase in myocardial fibrosis, as well as activation of several cardiac signalling pathways previously implicated in disease progression. It is hoped that development of an appropriate model will help to understand some the pathophysiological mechanisms underlying the accelerated progression of diabetic complications, leading ultimately to more efficacious treatment options.

Protective effects of sulforaphane on type 2 diabetes-induced cardiomyopathy via AMPK-mediated activation of lipid metabolic pathways and NRF2 function

BackgroundAMP-activated protein kinase (AMPK), particularly AMPKα2 isoform, plays a critical role in maintaining cardiac homeostasis. It was reported that sulforaphane (SFN) prevented type 2 diabetes (T2D)-induced cardiomyopathy accompanied by the activation of AMPK; In this study, AMPK's pivotal role in SFN-mediated prevention against T2D-induced cardiomyopathy was tested using global deletion of AMPKα2 gene (AMPKα2-KO) mice. Methods and resultsT2D was established by feeding 3-month high-fat diet (HFD) to induce insulin resistance, followed by an intraperitoneal injection of streptozotocin (STZ) to induce mild hyperglycemia in both AMPKα2-KO and wild-type (WT) mice. Then both T2D and control mice were subsequently treated with or without SFN for 3 months while continually feeding HFD or normal diet. Upon completion of the 3-month treatment, five mice from each group were sacrificed as a 3-month time-point (3 M). The rest continued normal diet or HFD until terminating study at the sixth month (6 M) of diabetes. Cardiac function was examined with echocardiography before sacrifice at both 3 M and 6 M. SFN prevented T2D-induced progression of cardiac dysfunction, remodeling (hypertrophy and fibrosis), inflammation, and oxidative damage in wild-type diabetic mice, but not in AMPKα2-KO mice. Mechanistically, SFN prevented T2D-induced cardiomyopathy not only by improving AMPK-mediated lipid metabolic pathways, but also enhancing NRF2 activation via AMPK/AKT/GSK3β pathway. However, these improving effects of SFN were abolished in AMPKα2-KO diabetic mice. ConclusionsAMPK is indispensable for the SFN-induced prevention of cardiomyopathy in T2D, and the activation of NRF2 by SFN is mediated by AMPK/AKT/GSK3β signaling pathways.

613-P: Preventive Effect of Sulforaphane on Type 2 Diabetes-Induced Diabetic Cardiomyopathy via AMPK-Mediated Activation of Glucose/Lipid Metabolism and Nrf2 Function

Dyslipidemia has been shown to play a crucial role in the development of diabetic cardiomyopathy (DCM) in type 2 diabetes (T2D). AMP-activated protein kinase (AMPK), particularly α2 isoform can improve energy metabolism in cardiomyopathy. Sulforaphane (SFN), a natural isothiocyanate in vegetables, is important in cardiac protection from diabetes. We investigated whether SFN can protect heart from T2D damage, which is mediated by AMPKα2 via improving energy metabolism and activating Nrf2-mediated anti-oxidative pathways. AMPKα2 knockout (AMPKα2-KO) mice and their wild type (WT, C57BL/6J) mice were fed high-fat diet (HFD) for 3 months to induce insulin resistance, and then intraperitoneal injection of streptozotocin to induce hyperglycemia as T2D model. Age-matched mice were fed with normal diet (ND) without streptozotocin as control. T2D and control mice were treated with or without SFN for 3 months (3m) and then stop SFN treatment, remained feeding either ND or HFD for additional three months (6m). Echocardiography were performed before sacrifice both in 3m and 6m group. SFN treatment improved cardiac remodeling and dysfunction induced by T2D both in 3m and 6m group. The cardiac pathogenic changes induced by T2D, including fibrosis, lipotoxicity, inflammation, oxidative stress/damage along with suppression of AMPK signaling pathways was prevented by SFN in WT diabetic mice, as evidenced by down-regulating FN, TGF-β PAI-1, TNF-α, SCD-1and up-regulating CPT1-B, PPARα, Nrf2. The cardiac protection by SFN for 3 months from T2D could last till 6 months. AMPKα2-KO mice are also susceptible to T2D-induced cardiomyopathy; however, the protective effect of SFN on the heart from diabetes was lost in diabetic AMPKα2-KO mice. These results suggest that SFN treatment can attenuate cardiac damage induced by T2D both in the 3m and 6m group, and AMPKα2 plays the pivotal role in the SNF-mediated cardiac protection. Disclosure Y. Sun: None. L. Cai: None. Z. Li: None. Funding American Diabetes Association (1-18-IBS-082 to L.C.)

Trimetazidine prevents diabetic cardiomyopathy by inhibiting Nox2/TRPC3-induced oxidative stress

Diabetic cardiomyopathy (DCM) is characterized by cardiac hypertrophy, fibrosis, oxidative stress and inflammation. Trimetazidine (TMZ), a potent metabolism modulator, has been shown to be cardioprotective in experimental models of ischaemia-reperfusion and type 2 diabetes-induced cardiomyopathy. The present study examined whether TMZ inhibits cardiomyopathy induced by insulin-dependent type 1 diabetes. Wistar rats were randomly divided into control group (vehicle alone), diabetes mellitus (DM; induced by streptozocin (STZ) injection) group and DM treated with TMZ (DM/TMZ) group. Cardiac function, histology, plasma biochemistry and molecular mechanism were assessed. STZ induced diabetes in rats as indicated by hyperglycemia, increased and decreased levels of advanced glycation end products (AGEs) and insulin respectively. Diabetic rats were characterized by left ventricular dysfunction, cardiachypertrophy and fibrosis and signs of inflammation and oxidative stress in the myocardium, which were accompanied by elevated levels of NADPH oxidase 2 (Nox2) and transient receptor potential channel 3 (TRPC3) in the heart. TMZ treatment ameliorated diabetes-associated structural and functional alterations by inhibiting Nox2 and TRPC3 without having any effects on glucose, insulin and AGEs levels. These results suggest that TMZ could be used as a therapy to treat cardiomyopathy associated with type 1 induced diabetes mellitus.

Function of BRD4 in the pathogenesis of high glucose‑induced cardiac hypertrophy.

Diabetic cardiomyopathy is one of the major complications of diabetes, and due to the increasing number of patients with diabetes it is a growing concern. Diabetes-induced cardiomyopathy has a complex pathogenesis and histone deacetylase-mediated epigenetic processes are of prominent importance. The olfactory bromodomain-containing protein 4 (BRD4) is a protein that recognizes and binds acetylated lysine. It has been reported that the high expression of BRD4 is involved in the process of cardiac hypertrophy. The aim of the present study was to investigate the function of BRD4 in the process of high glucose (HG)-induced cardiac hypertrophy, and to clarify whether epigenetic regulation involving BRD4 is an important mechanism. It was revealed that BRD4 expression levels were increased in H9C2 cells following 48 h of HG stimulation. This result was also observed in a diabetic rat model. Furthermore, HG stimulation resulted in the upregulation of the myocardial hypertrophy marker, atrial natriuretic peptide, the cytoskeletal protein α-actin and fibrosis-associated genes including transforming growth factor-β, SMAD family member 3, connective tissue growth factor and collagen, type 1, α1. However, administration of the specific BRD4 inhibitor JQ1 (250 nM) for 48 h reversed this phenomenon. Furthermore, protein kinase B (AKT) phosphorylation was activated by HG stimulation and suppressed by JQ1. In conclusion, BRD4 serves an important role in the pathogenesis of HG-induced cardiomyocyte hypertrophy through the AKT pathway.

Pharmacologic Inhibition of FOXO1 Improves Cardiac Function by Enhancing Glucose Metabolism and Attenuating Apoptosis in Type‐1 Diabetic Rats

IntroductionDiabetic cardiomyopathy, which comprises structural and functional abnormalities of the myocardium, is a major etiological factor for death in diabetic patients. Altered cardiac energy metabolism and increased cardiac apoptosis may underlie the pathology of diabetic cardiomyopathy. Forkhead transcriptional factor (FOXO1) is preferably activated in the myocardium of Type2 diabetic mice and mediates excessive lipid metabolism, resulting in diabetic cardiomyopahty. However, the effect of FOXO1 in cardiac glucose oxidation and apoptosis and its contribution to cardiac function in Type 1 diabetes‐induced cardiomyopathy are largely unknown. Thus, the present study aimed to investigate whether or not pharmacological inhibition of FOXO1 by its selective inhibitor AS1842856 can attenuate diabetic cardiomyopathy in Type 1 diabetic rats and the underlying mechanisms.MethodsControl or streptozotocin (STZ, 65 mg/kg)‐induced diabetic Sprague Dawley rats (n=7 per group) received vehicle or AS1842856 (50 mg/kg) by gavage twice daily for one week starting four weeks after STZ injection. On the day of harvest, the left ventricular (LV) functions of the rats were assessed by Pressure‐volume (PV) loop analysis and the heart tissue were collected for immunofluorescence, qPCR, Western blotting, etc. The translocation of FOXO1 from cytoplasm to nucleus was performed by immunofluorescence. The mRNA expression of pyruvate dehydrogenase kinase 4 (PDK4) was measured by qPCR. The protein levels of FOXO1, phosphorylated‐FOXO1(S256), PDK4, phosphorylated pyruvate dehydrogenase (pSer293‐PDH), B‐cell lymphoma 2 (BCl2), Bcl‐2‐like protein 4 (Bax), total and cleaved‐caspase3 were detected by Western blotting analysis. TUNEL assay was performed for detection of apoptosis in the cardiac tissue.ResultsPV loop analysis indicated that heart rate (HR, bpm) was significantly reduced, and time constant of LV pressure decay (TAU, ms), slope of the end‐diastolic pressure‐volume relationship (EdPVR, mmHg/μl) were all significantly increased in Type‐1 diabeticrats as compared to non‐diabetic control rats (all P <0.05), suggesting that Type‐1 diabetic rats indicated cardiac diastolic dysfunction. These changes were associated with remarkably increased FOXO1 activity (decreased P‐FOXO1/FOXO1 ratio, increased FOXO1 nuclear translocation), reduced cardiac glucose oxidation (increased mRNA and protein expression of PDK4 and reduced expression of P‐PDH) and enhanced cardiac apoptosis (reduced Bcl2/Bax ratio, increased cleaved‐caspase3/total caspase 3 ratio and TUNEL positive cells) in Type‐1 diabetic rats (all P <0.05, vs. Control rats). However, administration of FOXO1 inhibitor AS1842856 significantly inhibited FOXO1 activity (increased P‐FOXO1/FOXO1 ratio, decreased FOXO1 nuclear translocation), increased HR, decreased TAU and EDSPVR, and reverted all the above‐mentioned diabetes‐induced biochemical changes, suggesting that pharmacological inhibition of FOXO1 may attenuate cardiomyopathy in Type‐1 diabetic rats via enhanced glucose oxidation and reduced cardiac apoptosis.ConclusionFoxO1 in mediating PDK4 expression and subsequent PDH inactivation in the heart and also activation of cardiac apoptosis may represent major mechanisms whereby inhibition of FOXO1 improves cardiac function in early stage of diabetic cardiomyopathy in Type 1 diabetic rats and may provide a promising therapeutic target to treat the disease.Support or Funding InformationThe authors' work was supported by the General Research Fund (17124614M, Research Grants Council of Hong Kong).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Fibroblast growth factor-21 prevents diabetic cardiomyopathy via AMPK-mediated antioxidation and lipid-lowering effects in the heart

Our previous studies showed that both exogenous and endogenous FGF21 inhibited cardiac apoptosis at the early stage of type 1 diabetes. Whether FGF21 induces preventive effect on type 2 diabetes-induced cardiomyopathy was investigated in the present study. High-fat-diet/streptozotocin-induced type 2 diabetes was established in both wild-type (WT) and FGF21-knockout (FGF21-KO) mice followed by treating with FGF21 for 4 months. Diabetic cardiomyopathy (DCM) was diagnosed by significant cardiac dysfunction, remodeling, and cardiac lipid accumulation associated with increased apoptosis, inflammation, and oxidative stress, which was aggravated in FGF21-KO mice. However, the cardiac damage above was prevented by administration of FGF21. Further studies demonstrated that the metabolic regulating effect of FGF21 is not enough, contributing to FGF21-induced significant cardiac protection under diabetic conditions. Therefore, other protective mechanisms must exist. The in vivo cardiac damage was mimicked in primary neonatal or adult mouse cardiomyocytes treated with HG/Pal, which was inhibited by FGF21 treatment. Knockdown of AMPKα1/2, AKT2, or NRF2 with their siRNAs revealed that FGF21 protected cardiomyocytes from HG/Pal partially via upregulating AMPK–AKT2–NRF2-mediated antioxidative pathway. Additionally, knockdown of AMPK suppressed fatty acid β-oxidation via inhibition of ACC–CPT-1 pathway. And, inhibition of fatty acid β-oxidation partially blocked FGF21-induced protection in cardiomyocytes. Further, in vitro and in vivo studies indicated that FGF21-induced cardiac protection against type 2 diabetes was mainly attributed to lipotoxicity rather than glucose toxicity. These results demonstrate that FGF21 functions physiologically and pharmacologically to prevent type 2 diabetic lipotoxicity-induced cardiomyopathy through activation of both AMPK–AKT2–NRF2-mediated antioxidative pathway and AMPK–ACC–CPT-1-mediated lipid-lowering effect in the heart.

Voltage dependence of the Ca2+ transient in endocardial and epicardial myocytes from the left ventricle of Goto-Kakizaki type 2 diabetic rats.

Diabetes mellitus is a major global health disorder and, currently, over 450million people have diabetes with 90% suffering from type 2 diabetes. Left untreated, diabetes may lead to cardiovascular diseases which are a leading cause of death in diabetic patients. Calcium is the trigger and regulator of cardiac muscle contraction and derangement in cellular Ca2+ homeostasis, which can result in heart failure and sudden cardiac death. It is of paramount importance to investigate the regional involvement of Ca2+ in diabetes-induced cardiomyopathy. Therefore, the aim of this study was to investigate the voltage dependence of the Ca2+ transients in endocardial (ENDO) and epicardial (EPI) myocytes from the left ventricle of the Goto-Kakizaki (GK) rats, an experimental model of type 2 diabetes mellitus. Simultaneous measurement of L-type Ca2+ currents and Ca2+ transients was performed by whole-cell patch clamp techniques. GK rats displayed significantly increased heart weight, heart weight/body weight ratio, and non-fasting and fasting blood glucose compared to controls (CON). Although the voltage dependence of L-type Ca2+ current was unaltered, the voltage dependence of the Ca2+ transients was reduced to similar extents in EPI-GK and ENDO-GK compared to EPI-CON and ENDO-CON myocytes. TPK L-type Ca2+ current and Ca2+ transient were unaltered. THALF decay of L-type Ca2+ current was unaltered; however, THALF decay of the Ca2+ transient was shortened in ENDO and EPI myocytes from GK compared to CON rat hearts. In conclusion, the amplitude of L-type Ca2+ current was unaltered; however, the voltage dependence of the Ca2+ transient was reduced to similar extents in EPI and ENDO myocytes from GK rats compared to their respective controls, suggesting the possibility of dysfunctional sarcoplasmic reticulum Ca2+ transport in the GK diabetic rat hearts.

Hyperglycemia-induced cardiac contractile dysfunction in the diabetic heart.

The development of a diabetic cardiomyopathy is a multifactorial process, and evidence is accumulating that defects in intracellular free calcium concentration [Ca2+]i or its homeostasis are related to impaired mechanical performance of the diabetic heart leading to a reduction in contractile dysfunction. Defects in ryanodine receptor, reduced activity of the sarcoplasmic reticulum calcium pump (SERCA) and, along with reduced activity of the sodium-calcium exchanger (NCX) and alterations in myofilament, collectively cause a calcium imbalance within the diabetic cardiomyocytes. This in turn is characterized by cytosolic calcium overloading or elevated diastolic calcium leading to heart failure. Numerous studies have been performed to identify the cellular, subcellular, and molecular derangements in diabetes-induced cardiomyopathy (DCM), but the precise mechanism(s) is still unknown. This review focuses on the mechanism behind DCM, the onset of contractile dysfunction, and the associated changes with special emphasis on hyperglycemia, mitochondrial dysfunction in the diabetic heart. Further, management strategies, including treatment and emerging therapeutic modalities, are discussed.

Tissue-engineered smooth muscle cell and endothelial progenitor cell bi-level cell sheets prevent progression of cardiac dysfunction, microvascular dysfunction, and interstitial fibrosis in a rodent model of type 1 diabetes-induced cardiomyopathy

BackgroundDiabetes mellitus is a risk factor for coronary artery disease and diabetic cardiomyopathy, and adversely impacts outcomes following coronary artery bypass grafting. Current treatments focus on macro-revascularization and neglect the microvascular disease typical of diabetes mellitus-induced cardiomyopathy (DMCM). We hypothesized that engineered smooth muscle cell (SMC)-endothelial progenitor cell (EPC) bi-level cell sheets could improve ventricular dysfunction in DMCM.MethodsPrimary mesenchymal stem cells (MSCs) and EPCs were isolated from the bone marrow of Wistar rats, and MSCs were differentiated into SMCs by culturing on a fibronectin-coated dish. SMCs topped with EPCs were detached from a temperature-responsive culture dish to create an SMC-EPC bi-level cell sheet. A DMCM model was induced by intraperitoneal streptozotocin injection. Four weeks after induction, rats were randomized into 3 groups: control (no DMCM induction), untreated DMCM, and treated DMCM (cell sheet transplant covering the anterior surface of the left ventricle).ResultsSMC-EPC cell sheet therapy preserved cardiac function and halted adverse ventricular remodeling, as demonstrated by echocardiography and cardiac magnetic resonance imaging at 8 weeks after DMCM induction. Myocardial contrast echocardiography demonstrated that myocardial perfusion and microvascular function were preserved in the treatment group compared with untreated animals. Histological analysis demonstrated decreased interstitial fibrosis and increased microvascular density in the SMC-EPC cell sheet-treated group.ConclusionsTreatment of DMCM with tissue-engineered SMC-EPC bi-level cell sheets prevented cardiac dysfunction and microvascular disease associated with DMCM. This multi-lineage cellular therapy is a novel, translatable approach to improve microvascular disease and prevent heart failure in diabetic patients.