Emerging Actors in Diabetic Cardiomyopathy: Heartbreaker Biomarkers or Therapeutic Targets?

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.

MiR-144 protects the heart from hyperglycemia-induced injury by regulating mitochondrial biogenesis and cardiomyocyte apoptosis

Several lines of evidence have revealed the potential of microRNAs (miRNAs, miRs) as biomarkers for detecting diabetic cardiomyopathy, although their functions in hyperglycemic cardiac dysfunction are still lacking. In this study, mitochondrial biogenesis was markedly impaired induced by high glucose (HG), as evidenced by dysregulated mitochondrial structure, reduced mitochondrial DNA contents, and biogenesis-related mRNA levels, accompanied by increased cell apoptosis. MiR-144 was identified to be decreased in HG-induced cardiomyocytes and in streptozotocin (STZ)-challenged heart samples. Forced miR-144 expression enhanced mitochondrial biogenesis and suppressed cell apoptosis, while miR-144 inhibition exhibited the opposite results. Rac-1 was identified as a target gene of miR-144. Decreased Rac-1 levels activated AMPK phosphorylation and PGC-1α deacetylation, leading to increased mitochondrial biogenesis and reduced cell apoptosis. Importantly, the systemic neutralization of miR-144 attenuated mitochondrial disorder and ventricular dysfunction following STZ treatment. Additionally, plasma miR-144 decreased markedly in diabetic patients with cardiac dysfunction. The receiver-operator characteristic curve showed that plasma miR-144 could specifically predict diabetic patients developing cardiac dysfunction. In conclusion, this study provides strong evidence suggesting that miR-144 protects heart from hyperglycemia-induced injury by improving mitochondrial biogenesis and decreasing cell apoptosis via targeting Rac-1. Forced miR-144 expression might, thus, be a protective strategy for treating hyperglycemia-induced cardiac dysfunction.

Up-regulation of microRNA-203 inhibits myocardial fibrosis and oxidative stress in mice with diabetic cardiomyopathy through the inhibition of PI3K/Akt signaling pathway via PIK3CA

Diabetic cardiomyopathy (DCM) refers to the myocardial dysfunction in the absence of coronary artery disease and hypertension. Recently, the role of microRNAs (miRs) in gene expression regulation has attracted much more attention. Studies have shown that the PI3K/Akt signaling pathway is involved in the growth, metabolism and apoptosis of myocardial cells. Therefore, this study aimed to explore the regulatory role of miR-203 in myocardial fibrosis in mice with DCM via involvement of the PI3K/Akt signaling pathway. Firstly, mouse model of diabetes mellitus (DM) was established and injected with agomir, antagomir or IGF-1 (PI3K/Akt signaling pathway activator) for investigating the role of miR-203 in PIK3CA and the PI3K/Akt signaling pathway. PIK3CA was identified as a target gene of miR-203, and overexpressed miR-203 inhibited the activation of PI3K/Akt signaling pathway. The obtained results indicated that up-regulation of miR-203 reduced myocardial hypertrophy, myocardial fibrosis, myocardial apoptosis, and levels of PIK3CA, PI3K, Akt, CoI I, CoI III, ANP, MDA and ROS in the myocardial tissues, by which DM-induced cardiac dysfunction and pathological changes could be ameliorated. Collectively, our present study highlighted that overexpression of miR-203 may function as a cardioprotective regulator in DCM by targeting PIK3CA via inactivation of PI3K/Akt signaling pathway.

Hydrogen sulfide-mediated regulation of cell death signaling ameliorates adverse cardiac remodeling and diabetic cardiomyopathy

The death of cardiomyocytes is a precursor for the cascade of hypertrophic and fibrotic remodeling that leads to cardiomyopathy. In diabetes mellitus (DM), the metabolic environment of hyperglycemia, hyperlipidemia, and oxidative stress causes cardiomyocyte cell death, leading to diabetic cardiomyopathy (DMCM), an independent cause of heart failure. Understanding the roles of the cell death signaling pathways involved in the development of cardiomyopathies is crucial to the discovery of novel targeted therapeutics and biomarkers for DMCM. Recent evidence suggests that hydrogen sulfide (H2S), an endogenous gaseous molecule, has cardioprotective effects against cell death. However, very little is known about signaling by which H2S and its downstream targets regulate myocardial cell death in the DM heart. This review focuses on H2S in the signaling of apoptotic, autophagic, necroptotic, and pyroptotic cell death in DMCM and other cardiomyopathies, abnormalities in H2S synthesis in DM, and potential H2S-based therapeutic strategies to mitigate myocardial cell death to ameliorate DMCM.

Tetrahydrocurcumin Ameliorates Diabetic Cardiomyopathy by Attenuating High Glucose-Induced Oxidative Stress and Fibrosis via Activating the SIRT1 Pathway

Hyperglycemia-induced oxidative stress and fibrosis play a crucial role in the development of diabetic cardiomyopathy (DCM). Tetrahydrocurcumin (THC), a major bioactive metabolite of natural antioxidant curcumin, is reported to exert even more effective antioxidative and superior antifibrotic properties as well as anti-inflammatory and antidiabetic abilities. This study was designed to investigate the potential protective effects of THC on experimental DCM and its underlying mechanisms, pointing to the role of high glucose-induced oxidative stress and interrelated fibrosis. In STZ-induced diabetic mice, oral administration of THC (120 mg/kg/d) for 12 weeks significantly improved the cardiac function and ameliorated myocardial fibrosis and cardiac hypertrophy, accompanied by reduced reactive oxygen species (ROS) generation. Mechanically, THC administration remarkably increased the expression of the SIRT1 signaling pathway both in vitro and in vivo, further evidenced by decreased downstream molecule Ac-SOD2 and enhanced deacetylated production SOD2, which finally strengthened antioxidative stress capacity proven by repaired activities of SOD and GSH-Px and reduced MDA production. Additionally, THC treatment accomplished its antifibrotic effect by depressing the ROS-induced TGFβ1/Smad3 signaling pathway followed by reduced expression of cardiac fibrotic markers α-SMA, collagen I, and collagen III. Collectively, these finds demonstrated the therapeutic potential of THC treatment to alleviate DCM mainly by attenuating hyperglycemia-induced oxidative stress and fibrosis via activating the SIRT1 pathway.

(Pro)renin receptor-mediated myocardial injury, apoptosis, and inflammatory response in rats with diabetic cardiomyopathy

Excessive activation of the renin-angiotensin system (RAS) in diabetic cardiomyopathy (DCM) provokes a series of structural and functional abnormalities, and causes ventricular remodeling and heart failure in diabetes. (Pro)renin receptor (PRR) is a component of the RAS and has been reported to be up-regulated in some cardiovascular diseases. Furthermore, PRR blockade in some cardiovascular diseases, such as myocardial infarction and hypertension, has been demonstrated to reverse their pathogenesis. However, there have been few studies about the function of PRR in the pathogenesis of DCM. In this study, we hypothesized that PRR is involved in the pathogenesis of DCM and mediates myocardial injury in DCM. To explore the role of PRR in DCM, we evaluated the effects of PRR overexpression and knockdown on the DCM phenotype in vivo and in vitro The results show that PRR overexpression exacerbates myocardial injury and the inflammatory response in rats with DCM. Conversely, PRR knockdown alleviates myocardial fibrosis, apoptosis, and the inflammatory response, reversing the cardiac dysfunction in rats with DCM. In cell experiments, PRR overexpression also up-regulated the protein expression of collagen I and fibronectin, aggravated the inflammatory response, and increased the production of reactive oxygen species, whereas PRR knockdown had the opposite effect. Thus, PRR mediates myocardial injury, apoptosis, and the inflammatory response, likely through a PRR/extracellular signal-regulated kinase/reactive oxygen species pathway.

Diabetic Cardiomyopathy: Five Major Questions with Simple Answers

Diabetes is a major risk factor for heart disease. Diabetic cardiomyopathy is a long-lasting process that affects the myocardium in patients who have no other cardiac conditions. The condition has a complex physiopathology which can be subdivided into processes that cause diastolic and/or systolic dysfunction. It is believed to be more common than reported, but this has not been confirmed by a large study. Diagnosis can involve imaging; biomarkers cannot be used to identify diabetic cardiomyopathy at an early stage. In people with diabetes, there should be a focus on prevention and, if diabetic cardiomyopathy develops, the objective is to delay disease progression. Further studies into identifying and managing diabetic cardiomyopathy are essential to reduce the risk of heart failure in people with diabetes.

Activating Cannabinoid Receptor 2 Protects Against Diabetic Cardiomyopathy Through Autophagy Induction

Cannabinoid receptor 2 (CB₂) has been reported to produce a cardio-protective effect in cardiovascular diseases such as myocardial infarction. Here in this study, we investigated the role of CB₂ in diabetic cardiomyopathy (DCM) and its underlying mechanisms. HU308 was used for the selective activation of CB₂. Bafilomycin A1 was used for the blockade of autophagy and compound C was used to inhibit AMPK signaling. An streptozotocin (STZ)-induced mice model and high glucose (HG)-challenged cardiomyocytes were applied for study. Cardiac function was detected by echocardiography and Western blot for the detection of autophagy-related and its signaling-related proteins. Transmission electron microscopy was used for the analysis of autophagosome number. Cell viability was detected by Cell Counting Kit-8 (CCK-8) and lactate dehydrogenase (LDH) release assays. We found that activating CB₂ by HU308 improved cardiac function in DCM as well as cell viability in cardiomyocytes under HG challenge, while the administration of bafilomycin A1 attenuated the protective effects. HU308 enhanced the level of autophagy in the heart tissues from DCM mice as well as cardiomyocytes under HG challenge. HU308 triggered the AMPK-mTOR-p70S6K signaling pathway, while the administration of compound C attenuated the cardio-protective effect of HU308 in cardiomyocytes under HG challenge. In conclusion, we initially demonstrated that activating CB₂ produced a cardio-protective effect in DCM as well as cardiomyocytes under HG challenge through inducing the AMPK-mTOR-p70S6K signaling-mediated autophagy.

Long noncoding RNAs: A new player in the prevention and treatment of diabetic cardiomyopathy?

Diabetic cardiomyopathy (DCM) can cause extensive necrosis of the heart muscle by metabolic disorders and microangiopathy, with subclinical cardiac dysfunction, and eventually progress to heart failure, arrhythmia, and cardiogenic shock; severe patients may even die suddenly. Long noncoding RNAs (lncRNAs) are a class of nonprotein-coding RNAs longer than 200 nucleotides. They have critical roles in various biological processes, including gene expression regulation, genomic imprinting, nuclear-cytoplasmic trafficking, RNA splicing, and translational control. Recent studies indicated that lncRNAs extensively participate in the development of diverse cardiac diseases, such as cardiac ischaemia, hypertrophy, and heart failure. Little is known about lncRNA in DCM. In this review, we summarize the current literature on lncRNAs in DCM studies, aiming to provide new methods for DCM's future prevention and treatment strategies.

Diabetic Cardiomyopathy: Current and Future Therapies. Beyond Glycemic Control

Diabetes mellitus and the associated complications represent a global burden on human health and economics. Cardiovascular diseases are the leading cause of death in diabetic patients, who have a 2–5 times higher risk of developing heart failure than age-matched non-diabetic patients, independent of other comorbidities. Diabetic cardiomyopathy is defined as the presence of abnormal cardiac structure and performance in the absence of other cardiac risk factors, such coronary artery disease, hypertension, and significant valvular disease. Hyperglycemia, hyperinsulinemia, and insulin resistance mediate the pathological remodeling of the heart, characterized by left ventricle concentric hypertrophy and perivascular and interstitial fibrosis leading to diastolic dysfunction. A change in the metabolic status, impaired calcium homeostasis and energy production, increased inflammation and oxidative stress, as well as an accumulation of advanced glycation end products are among the mechanisms implicated in the pathogenesis of diabetic cardiomyopathy. Despite a growing interest in the pathophysiology of diabetic cardiomyopathy, there are no specific guidelines for diagnosing patients or structuring a treatment strategy in clinical practice. Anti-hyperglycemic drugs are crucial in the management of diabetes by effectively reducing microvascular complications, preventing renal failure, retinopathy, and nerve damage. Interestingly, several drugs currently in use can improve cardiac health beyond their ability to control glycemia. GLP-1 receptor agonists and sodium-glucose co-transporter 2 inhibitors have been shown to have a beneficial effect on the cardiovascular system through a direct effect on myocardium, beyond their ability to lower blood glucose levels. In recent years, great improvements have been made toward the possibility of modulating the expression of specific cardiac genes or non-coding RNAs in vivo for therapeutic purpose, opening up the possibility to regulate the expression of key players in the development/progression of diabetic cardiomyopathy. This review summarizes the pathogenesis of diabetic cardiomyopathy, with particular focus on structural and molecular abnormalities occurring during its progression, as well as both current and potential future therapies.

MiR-873 inhibition enhances gefitinib resistance in non-small cell lung cancer cells by targeting glioma-associated oncogene homolog 1

BACKGROUND

The five-year survival rate of non-small cell lung cancer (NSCLC) patients is very low. MiR-873 is involved in the growth, metastasis, and differentiation of tumors. Herein, we determined the target gene and influence of miR-873 in NSCLC.

METHODS

MiRanda and Targetscan websites were used to predict the target gene of miR-873 in NSCLC. Luciferase activity was examined using a dual luciferase reporter gene assay kit. The viability, tube formation, and proliferation of cells were analyzed by cell counting kit-8, angiogenic analysis, and flow cytometry, respectively. The levels of miR-873 and GLI1 were evaluated using quantitative real-time PCR and Western blot assays.

RESULTS

Low levels of GLI1 and high levels of miR-873 were observed in an NSCLC cell line (PC9) highly sensitive to EGFR-tyrosine kinase inhibitors. There was a negative correlation between miR-873 and GLI1 expression in PC9 and PC9/GR cells. The inhibition of miR-873 enhanced GLI1 levels. MiR-873 expression was inhibited by gefitinib. Gefitinib markedly reduced the viability, tube formation, and cell number in PC9 cells. However, suppression of miR-873 enhanced the resistance and knockdown of GLI1 enhanced the sensitivity of PC9 cells to gefitinib.

CONCLUSIONS

GLI1 is a target gene of miR-873 in NSCLC. The inhibition of miR-873 increased gefitinib resistance of NSCLC cells via the upregulation of GLI1. These results indicate that miR-873-GLI1 signaling is involved in gefitinib resistance in NSCLC.