Mitophagy in Diabetic Cardiomyopathy: Roles and Mechanisms

WIPI1-mediated mitophagy dysfunction in ventricular remodeling associated with long-term diabetes mellitus

BACKGROUND

WIPI1 is a member of the WD-repeat protein family that interacts with phosphoinositides and plays a crucial role in autophagy. This study investigated how WIPI1-mediated mitophagy dysfunction contributes to ventricular remodeling in rat and mouse models of diabetes mellitus.

METHODS

The study utilized a 32-weeks diabetic animal model to simulate long-term diabetic conditions. AAV9-cTNT-WIPI1 vectors were employed to overexpress WIPI1 in the myocardium. Cardiac function was assessed by echocardiography. Mitochondrial membrane potential was assessed using JC-1 dye. Oxygen consumption rates were quantified using an Oxygraph-O2K high-resolution respirometry.

RESULTS

Long-term diabetes led to decreased ejection fraction and fractional shortening associated with a marked increase in ventricular fibrosis and elevated expression of fibrotic markers such as collagen type I and periostin. Expression of autophagy markers such as LC3b-II and SQSTM1 was reduced, and colocalization with mitochondria was disrupted, suggesting failures in autophagosome formation and maturation. This impairment was further supported by decreased levels of mitophagy-related proteins (PINK and Parkin), indicating impaired mitophagy. WIPI1 knockdown led to mitochondrial dysfunction, characterized by loss of membrane potential and reduced respiratory capacity.

CONCLUSION

WIPI1 is essential for proper mitophagy function. Its downregulation produces ventricular remodeling and dysfunction. These findings suggest that targeting WIPI1-mediated pathways could be a potential therapeutic strategy for treating diabetic cardiomyopathy by improving mitochondrial health and mitophagic processes.

Semaglutide administration protects cardiomyocytes in db/db mice via energetic improvement and mitochondrial quality control

Diabetic cardiomyopathy causes end-stage heart failure, resulting in high morbidity and mortality in type 2 diabetes mellitus (T2DM) patients. Long-term treatment targeting metabolism is an emerging field in the treatment of diabetic cardiomyopathy. Semaglutide, an agonist of the glucagon-like peptide 1 receptor, is clinically approved for the treatment of T2DM and provides cardiac benefits in patients. However, the cardioprotective mechanism of semaglutide, especially its direct effects on cardiomyocytes (CMs), is not fully understood. Here, we used 8-week diabetic and obese db/db mice treated with semaglutide (200 μg·kg·d-1, i.p.) to study its direct effect on CMs and the underlying mechanisms. Our results revealed that the consecutive application of semaglutide improved cardiac function. Increased AMPK and ULK1 phosphorylation levels were detected, accompanied by elevated [Ca2+]mito. Seahorse analysis revealed that semaglutide increases ATP production via elevated basal and maximum respiration rates as well as spare respiration capacity in CMs. Transmission electron microscopy revealed improved mitochondrial morphology in the cardiomyocytes of db/db mice. On the other hand, Western blot analysis revealed increased Parkin and LC3 protein expression, indicating mitophagy in CMs. Collectively, our findings demonstrate that semaglutide directly protects CMs from high-glucose damage by promoting AMPK-dependent ATP production as well as ULK1-mediated mitophagy in db/db mice.

Dysregulation of Mitochondrial in Pulmonary Hypertension-Related Right Ventricular Remodeling: Pathophysiological Features and Targeting Drugs

Pulmonary hypertension (PH) is a life-threatening condition characterized by right ventricular (RV) remodeling, which is a major determinant of patient survival. The progression of right ventricular remodeling is significantly influenced by mitochondrial dysfunction, providing profound insights into vascular health and cardiovascular risk. In this review, we discuss the molecular targets, pathophysiological characteristics, and potential mechanisms underlying mitochondrial dysfunction in PH, encompassing disturbances in mitochondrial dynamics, inflammation, and dysregulation of mitochondrial energy metabolism. Finally, we review the primary therapeutic targets currently utilized to address cardiac dysfunction resulting from mitochondrial damage. Hopefully, this might inspire novel approaches to the management of cardiovascular disorders.

Critical Appraisal of Pharmaceutical Therapy in Diabetic Cardiomyopathy-Challenges and Prospectives

Diabetes mellitus (DM) is a multifaceted disorder with a pandemic spread and a remarkable burden of cardiovascular mortality and morbidity. Diabetic cardiomyopathy (DBCM) has been increasingly recognized as the development of cardiac dysfunction, which is accompanied by heart failure (HF) symptoms in the absence of obvious reasons like ischemic heart disease, hypertension, or valvulopathies. Several pathophysiological mechanisms have been proposed, including metabolic disorders (e.g., glycation products), oxidative stress, low-grade inflammation, mitochondrial dysfunction, etc., which should guide the development of new therapeutic strategies. Up to now, HF treatment has not differed between patients with and without diabetes, which limits the expected benefits despite the high cardiovascular risk in the former group. However, DBCM patients may require different management, which prioritize anti-diabetic medications or testing other novel therapies. This review aims to appraise the challenges and prospectives of the individualized pharmaceutical therapy for DBCM.

A reliable strategy for establishment of an animal model of diabetic cardiomyopathy: Induction by a high-fat diet combined with single or multiple injections of low-dose streptozotocin

BACKGROUND

Diabetic cardiomyopathy (DCM) is one of the leading causes of death in patients with diabetes mellitus (DM). This study aimed to identify a reliable method for establishing an animal model of DCM for investigation of new targets and treatments.

METHODS

Eighty-four 4-week-old male Sprague-Dawley rats were randomly allocated to receive a normal diet or a high-fat diet (HFD) in an approximate ratio of 1:3. At 9 weeks of age, rats in the HFD group received streptozotocin (STZ) 30 mg/kg by intraperitoneal injection and rats in the control group received the same volume of buffer solution. The rodent model of DM was deemed to be successfully established when a random blood glucose measurement was >16.7 mmol/L on three consecutive occasions. If necessary, STZ was readministered.

RESULTS

Three of the 64 rats in the HFD group died after a second STZ injection. DM was induced in 14, 39, and 8 rats after one, two, and three injections, respectively, with cumulative success rates of 21.9 %, 82.8 %, and 95.3 %. Three months later, the rats with DM showed persistent hyperglycemia and insulin resistance and developed histopathological changes indicating cardiac hypertrophy, myocardial fibrosis, and diastolic dysfunction. The metabolic and cardiac histopathological changes were consistent regardless of whether DM was induced by one, two, or three injections of STZ.

CONCLUSION

An HFD combined with one or more intraperitoneal injections of low-dose STZ is a straightforward and reliable method for inducing DCM in rats. When a single dose of STZ fails to induce DM, repeated injections can be considered.

ZIP7 contributes to the pathogenesis of diabetic cardiomyopathy by suppressing mitophagy in mouse hearts

BACKGROUND

Although the exact role of mitophagy in the pathogenesis of diabetic cardiomyopathy (DCM) caused by type 2 diabetes mellitus (T2DM) remains controversial, recent studies revealed inhibition of mitophagy exacerbates cardiac injury in DCM. The zinc transporter ZIP7 has been reported to be upregulated by high glucose in cardiomyocytes and ZIP7 upregulation leads to inhibition of mitophagy in mouse hearts in the setting of ischemia/reperfusion. Nevertheless, little is known about the role of ZIP7 and its relationship with mitophagy in DCM caused by T2DM.

METHODS

T2DM was induced with high-fat diet (HFD) and streptozotocin. The cardiac-specific ZIP7 conditional knockout (ZIP7 cKO) mice were generated by adopting CRISPR/Cas9 system. Cardiac function was evaluated with echocardiography. Mitophagy was assessed by detecting mito-LC3II, mitoKeima, and mitoQC. Reactive oxygen species (ROS) were detected with DHE and mitoB.

RESULTS

ZIP7 was upregulated by T2DM in mouse hearts and ZIP7 cKO reduced mitochondrial ROS generation in mouse hearts with T2DM. Mitophagy was suppressed by T2DM in mouse hearts, which was prevented by ZIP7 cKO. T2DM inhibited PINK1 and Parkin accumulation in cardiac mitochondria, an effect that was prevented by ZIP7 cKO, pointing to that ZIP7 upregulation mediates T2DM-induced suppression of mitophagy by inhibiting the PINK1/Parkin pathway. T2DM induced mitochondrial hyperpolarization and decrease of mitochondrial Zn2+ and this was blocked by ZIP7 cKO, indicating that upregulation of ZIP7 leads to mitochondrial hyperpolarization by reducing Zn2+ within mitochondria. Finally, ZIP7 cKO prevented cardiac dysfunction and fibrosis caused by T2DM.

CONCLUSIONS

ZIP7 upregulation mediates the inhibition of mitophagy by T2DM in mouse hearts by suppressing the PINK1/Parkin pathway. Reduction of mitochondrial Zn2+ due to upregulation of ZIP7 accounts for the inhibition of the PINK1/Parkin pathway. Prevention of ZIP7 upregulation is essential for the treatment of T2DM-induced cardiomyopathy.

Exendin-4 exhibits cardioprotective effects against high glucose-induced mitochondrial abnormalities: Potential role of GLP-1 receptor and mTOR signaling

Mitochondrial dysfunction is associated with hyperglycemic conditions and insulin resistance leading to cellular damage and apoptosis of cardiomyocytes in diabetic cardiomyopathy. The dysregulation of glucagon-like peptide-1 (GLP-1) receptor and mammalian target of rapamycin (mTOR) is linked to cardiomyopathies and myocardial dysfunctions mediated by hyperglycemia. However, the involvements of mTOR for GLP-1 receptor-mediated cardioprotection against high glucose (HG)-induced mitochondrial disturbances are not clearly identified. The present study demonstrated that HG-induced cellular stress and mitochondrial damage resulted in impaired ATP production and oxidative defense markers such as catalase and SOD2, along with a reduction in survival markers such as Bcl-2 and p-Akt, while an increased expression of pro-apoptotic marker Bax was observed in H9c2 cardiomyoblasts. In addition, the autophagic marker LC3-II was considerably reduced, together with the disruption of autophagy regulators (p-mTOR and p-AMPKα) under the hyperglycemic state. Furthermore, there was a dysregulated expression of several indicators related to mitochondrial homeostasis, including MFN2, p-DRP1, FIS1, MCU, UCP3, and Parkin. Remarkably, treatment with either exendin-4 (GLP-1 receptor agonist) or rapamycin (mTOR inhibitor) significantly inhibited HG-induced mitochondrial damage while co-treatment of exendin-4 and rapamycin completely reversed all mitochondrial abnormalities. Antagonism of GLP-1 receptors using exendin-(9-39) abolished these cardioprotective effects of exendin-4 and rapamycin under HG conditions. In addition, exendin-4 attenuated HG-induced phosphorylation of mTOR, and this inhibitory effect was antagonized by exendin-(9-39), indicating the regulation of mTOR by GLP-1 receptor. Therefore, improvement of mitochondrial dysfunction by stimulating the GLP-1 receptor/AMPK/Akt pathway and inhibiting mTOR signaling could ameliorate cardiac abnormalities caused by hyperglycemic conditions.

MiR-21-3p inhibitor exerts myocardial protective effects by altering macrophage polarization state and reducing excessive mitophagy

Chronic heart failure (CHF) is closely associated with inflammation and mitochondrial dysfunction in cardiomyocytes. This study attempts to investigate the effects of microRNA-21-3p (miR-21-3p) on macrophage polarization and mitophagy in CHF. Here we found miR-21-3p was upregulated in CHF and negatively correlated with carnitine palmitoyl transferase 1A (CPT1A). L-palmitoyl carnitine (L-PC) exacerbated isoproterenol (ISO)-induced myocardial structural disruption and fibrosis in rats, which was exacerbated by miR-21-3p. Mechanistically, miR-21-3p accelerated M1 macrophage polarization. Both miR-21-3p inhibitor and CPT1A overexpression suppressed mitophagy. The inhibition of CPT1A on mitophagy was reversed by miR-21-3p. MiR-21-3p targeted CPT1A mRNA and co-localized with CPT1A protein in cardiomyocytes. In the co-culture system of M1 macrophages and H9c2 cells, miR-21-3p mimics in H9c2 cells promoted M1 polarization, whereas miR-21-3p inhibitor reduced M1 phenotype. M1 macrophages exacerbated H9c2 cell damage. These findings support the potential therapeutic targeting of miR-21-3p to regulate inflammation and mitophagy by inducing CPT1A in CHF.

High glucose- or AGE-induced oxidative stress inhibits hippocampal neuronal mitophagy through the Keap1-Nrf2-PHB2 pathway in diabetic encephalopathy

Diabetic encephalopathy (DE) is a severe complication of diabetes, but its pathogenesis remains unclear. This study aimed to investigate the roles and underlying mechanisms of high glucose (HG)- and advanced glycosylation end product (AGE)-induced oxidative stress (OS) in the cognitive decline in DE. The DE mouse model was established using a high-fat diet and streptozotocin, and its cognitive functions were evaluated using the Morris Water Maze, novel object recognition, and Y-maze test. The results revealed increased reactive oxygen species (ROS) generation, mitophagy inhibition, and decreased prohibitin 2 (PHB2) expression in the hippocampal neurons of DE mice and HG- or AGE-treated HT-22 cells. However, overexpression of PHB2 reduced ROS generation, reversed mitophagy inhibition, and improved mitochondrial function in the HG- or AGE-treated HT-22 cells and ameliorated cognitive decline, improved mitochondrial structural damage, and reversed mitophagy inhibition of hippocampal neurons in DE mice. Further analysis revealed that the Kelch-like ECH-associated protein 1 (Keap1)-nuclear factor erythroid 2-related factor 2 (Nrf2) pathway was involved in the HG- or AGE-mediated downregulation of PHB2 in HT-22 cells. These results demonstrate that HG- or AGE-induced OS inhibits the mitophagy of hippocampal neurons via the Keap1-Nrf2-PHB2 pathway, thereby contributing to the cognitive decline in DE.

Prevalence and associations of asymptomatic left ventricular systolic dysfunction in Lebanese patients with type 2 diabetes mellitus

BACKGROUND

Diabetes Mellitus is a prevalent disease with a growing impact on individuals worldwide. Evaluating the prevalence of subclinical left ventricular dysfunction and understanding its associations with microvascular complications, uncontrolled glycemia, diabetes duration, and patient age is crucial. Our aim is to determine the utility of screening for this condition.

METHODS

We conducted a retrospective cohort study involving 159 asymptomatic individuals with type 2 diabetes. Bivariate analysis was employed to assess potential factors and their associations with subclinical left ventricular dysfunction. Patients with a history of cardiac disease or interventions were excluded.

RESULTS

The average age of our sample was 61.5 years. Almost half of the patients exhibited an HbA1c exceeding 7% (50.3%), and approximately half had an ejection fraction (EF) of less than 55% (50.9%). In the bivariate analysis, a notable difference in microvascular diabetic complications was observed among different EF groups. Specifically, nephropathy (62%), neuropathy (57.5%), and retinopathy (74.4%) were significantly more prevalent among patients with an EF < 55%. We also identified a significant age difference between groups, with a higher mean diabetes duration (14.1 ± 7.7 years) in the lower EF group. Notably, 63.7% of patients with an HbA1c exceeding 7% exhibited an EF < 55%. Older patients were associated with a lower EF, with an adjusted odds ratio (aOR) of 0.94. An HbA1c of 7% or less was linked to a higher likelihood of an EF > 55%.

CONCLUSION

We established a correlation between subclinical left ventricular systolic dysfunction and microvascular complications. However, further extensive prospective research is necessary to deepen our understanding of these associations and their clinical implications.

Mitochondrial Dysfunction in Glycogen Storage Disorders (GSDs)

Glycogen storage disorders (GSDs) are a group of inherited metabolic disorders characterized by defects in enzymes involved in glycogen metabolism. Deficiencies in enzymes responsible for glycogen breakdown and synthesis can impair mitochondrial function. For instance, in GSD type II (Pompe disease), acid alpha-glucosidase deficiency leads to lysosomal glycogen accumulation, which secondarily impacts mitochondrial function through dysfunctional mitophagy, which disrupts mitochondrial quality control, generating oxidative stress. In GSD type III (Cori disease), the lack of the debranching enzyme causes glycogen accumulation and affects mitochondrial dynamics and biogenesis by disrupting the integrity of muscle fibers. Malfunctional glycogen metabolism can disrupt various cascades, thus causing mitochondrial and cell metabolic dysfunction through various mechanisms. These dysfunctions include altered mitochondrial morphology, impaired oxidative phosphorylation, increased production of reactive oxygen species (ROS), and defective mitophagy. The oxidative burden typical of GSDs compromises mitochondrial integrity and exacerbates the metabolic derangements observed in GSDs. The intertwining of mitochondrial dysfunction and GSDs underscores the complexity of these disorders and has significant clinical implications. GSD patients often present with multisystem manifestations, including hepatomegaly, hypoglycemia, and muscle weakness, which can be exacerbated by mitochondrial impairment. Moreover, mitochondrial dysfunction may contribute to the progression of GSD-related complications, such as cardiomyopathy and neurocognitive deficits. Targeting mitochondrial dysfunction thus represents a promising therapeutic avenue in GSDs. Potential strategies include antioxidants to mitigate oxidative stress, compounds that enhance mitochondrial biogenesis, and gene therapy to correct the underlying mitochondrial enzyme deficiencies. Mitochondrial dysfunction plays a critical role in the pathophysiology of GSDs. Recognizing and addressing this aspect can lead to more comprehensive and effective treatments, improving the quality of life of GSD patients. This review aims to elaborate on the intricate relationship between mitochondrial dysfunction and various types of GSDs. The review presents challenges and treatment options for several GSDs.

GSK-3α-BNIP3 axis promotes mitophagy in human cardiomyocytes under hypoxia

Dysregulated autophagy/mitophagy is one of the major causes of cardiac injury in ischemic conditions. Glycogen synthase kinase-3alpha (GSK-3α) has been shown to play a crucial role in the pathophysiology of cardiac diseases. However, the precise role of GSK-3α in cardiac mitophagy remains unknown. Herein, we investigated the role of GSK-3α in cardiac mitophagy by employing AC16 human cardiomyocytes under the condition of acute hypoxia. We observed that the gain-of-GSK-3α function profoundly induced mitophagy in the AC16 cardiomyocytes post-hypoxia. Moreover, GSK-3α overexpression led to increased ROS generation and mitochondrial dysfunction in cardiomyocytes, accompanied by enhanced mitophagy displayed by increased mt-mKeima intensity under hypoxia. Mechanistically, we identified that GSK-3α promotes mitophagy through upregulation of BNIP3, caused by GSK-3α-mediated increase in expression of HIF-1α and FOXO3a in cardiomyocytes post-hypoxia. Moreover, GSK-3α displayed a physical interaction with BNIP3 and, inhibited PINK1 and Parkin recruitment to mitochondria was observed specifically under hypoxia. Taken together, we identified a novel mechanism of mitophagy in human cardiomyocytes. GSK-3α promotes mitochondrial dysfunction and regulates FOXO3a -mediated BNIP3 overexpression in cardiomyocytes to facilitate mitophagy following hypoxia. An interaction between GSK-3α and BNIP3 suggests a role of GSK-3α in BNIP3 recruitment to the mitochondrial membrane where it enhances mitophagy in stressed cardiomyocytes independent of the PINK1/Parkin.

Mitophagy and cGAS-STING crosstalk in neuroinflammation

Mitophagy, essential for mitochondrial health, selectively degrades damaged mitochondria. It is intricately linked to the cGAS-STING pathway, which is crucial for innate immunity. This pathway responds to mitochondrial DNA and is associated with cellular stress response. Our review explores the molecular details and regulatory mechanisms of mitophagy and the cGAS-STING pathway. We critically evaluate the literature demonstrating how dysfunctional mitophagy leads to neuroinflammatory conditions, primarily through the accumulation of damaged mitochondria, which activates the cGAS-STING pathway. This activation prompts the production of pro-inflammatory cytokines, exacerbating neuroinflammation. This review emphasizes the interaction between mitophagy and the cGAS-STING pathways. Effective mitophagy may suppress the cGAS-STING pathway, offering protection against neuroinflammation. Conversely, impaired mitophagy may activate the cGAS-STING pathway, leading to chronic neuroinflammation. Additionally, we explored how this interaction influences neurodegenerative disorders, suggesting a common mechanism underlying these diseases. In conclusion, there is a need for additional targeted research to unravel the complexities of mitophagy-cGAS-STING interactions and their role in neurodegeneration. This review highlights potential therapies targeting these pathways, potentially leading to new treatments for neuroinflammatory and neurodegenerative conditions. This synthesis enhances our understanding of the cellular and molecular foundations of neuroinflammation and opens new therapeutic avenues for neurodegenerative disease research.

Methionine sulfoxide reductase B2 protects against cardiac complications in diabetes mellitus

Diabetes mellitus (DM) is a progressive, chronic metabolic disorder characterized by high oxidative stress, which can lead to cardiac damage. Methionine sulfoxylation (MetO) of proteins by excessive reactive oxygen species (ROS) can impair the basic functionality of essential cellular proteins, contributing to heart failure. Methionine sulfoxide reductase B2 (MsrB2) can reverse oxidation induced MetO in mitochondrial proteins, so we investigated its role in diabetic cardiomyopathy. We observed that DM-induced heart damage in diabetic mice model is characterized by increased ROS, increased protein MetO with mitochondria structural pathology, and cardiac fibrosis. In addition, MsrB2 was significantly increased in mouse DM cardiomyocytes, supporting the induction of a protective process. Further, MsrB2 directly induces Parkin and LC3 activation (mitophagy markers) in cardiomyocytes. In MsrB2, knockout mice displayed abnormal electrophysiological function, as determined by ECG analysis. Histological analysis confirmed increased cardiac fibrosis and disrupted cardiac tissue in MsrB2 knockout DM mice. We then corroborated our findings in human DM heart samples. Our study demonstrates that increased MsrB2 expression in the heart protects against diabetic cardiomyopathy.

Association between METS-IR and heart failure: a cross-sectional study

Background

Prior research has indicated the importance of insulin resistance in the development of heart failure (HF). The metabolic score for insulin resistance (METS-IR), a novel measure for assessing insulin resistance, has been found to be associated with cardiovascular disease (CVD). Nevertheless, the relationship between METS-IR and heart failure remains uncertain.

Methods

This cross-sectional study collected data from the 2007-2018 National Health and Nutrition Examination Survey (NHANES). Multivariable logistic regression analysis and smoothing curve fitting were performed to explore the relationship between METS-IR and the risk of heart failure. Subgroup analysis and receiver operating characteristic (ROC) curve analysis were also conducted.

Results

A total of 14772 patients were included, of whom 485 (3.28%) had heart failure. We observed a significant positive association between METS-IR and the risk of heart failure in a fully adjusted model (per 1-unit increment in METS-IR: OR: 2.44; 95% CI: 1.38, 4.32). Subgroup analysis and interaction tests revealed no significant influence on this relationship. A saturation effect and nonlinear relationship between METS-IR and heart failure risk were found using a smoothing curve fitting analysis. The relationship was represented by a J-shaped curve with an inflection point at 40.966.

Conclusions

The results of our study indicated a J-shaped association between METS-IR and HF in adults in the United States. METS-IR may be a promising novel index for predicting the risk of heart failure. More longitudinal studies are needed to further verify causal relationships and validate the results in different classifications of heart failure populations.

Autophagy and mitophagy as potential therapeutic targets in diabetic heart condition: Harnessing the power of nanotheranostics

Autophagy and mitophagy pose unresolved challenges in understanding the pathology of diabetic heart condition (DHC), which encompasses a complex range of cardiovascular issues linked to diabetes and associated cardiomyopathies. Despite significant progress in reducing mortality rates from cardiovascular diseases (CVDs), heart failure remains a major cause of increased morbidity among diabetic patients. These cellular processes are essential for maintaining cellular balance and removing damaged or dysfunctional components, and their involvement in the development of diabetic heart disease makes them attractive targets for diagnosis and treatment. While a variety of conventional diagnostic and therapeutic strategies are available, DHC continues to present a significant challenge. Point-of-care diagnostics, supported by nanobiosensing techniques, offer a promising alternative for these complex scenarios. Although conventional medications have been widely used in DHC patients, they raise several concerns regarding various physiological aspects. Modern medicine places great emphasis on the application of nanotechnology to target autophagy and mitophagy in DHC, offering a promising approach to deliver drugs beyond the limitations of traditional therapies. This article aims to explore the potential connections between autophagy, mitophagy and DHC, while also discussing the promise of nanotechnology-based theranostic interventions that specifically target these molecular pathways.

Pathophysiology and Advances in the Therapy of Cardiomyopathy in Patients with Diabetes Mellitus

Diabetes mellitus (DM) is known as the first non-communicable global epidemic. It is estimated that 537 million people have DM, but the condition has been properly diagnosed in less than half of these patients. Despite numerous preventive measures, the number of DM cases is steadily increasing. The state of chronic hyperglycaemia in the body leads to numerous complications, including diabetic cardiomyopathy (DCM). A number of pathophysiological mechanisms are behind the development and progression of cardiomyopathy, including increased oxidative stress, chronic inflammation, increased synthesis of advanced glycation products and overexpression of the biosynthetic pathway of certain compounds, such as hexosamine. There is extensive research on the treatment of DCM, and there are a number of therapies that can stop the development of this complication. Among the compounds used to treat DCM are antiglycaemic drugs, hypoglycaemic drugs and drugs used to treat myocardial failure. An important element in combating DCM that should be kept in mind is a healthy lifestyle-a well-balanced diet and physical activity. There is also a group of compounds-including coenzyme Q10, antioxidants and modulators of signalling pathways and inflammatory processes, among others-that are being researched continuously, and their introduction into routine therapies is likely to result in greater control and more effective treatment of DM in the future. This paper summarises the latest recommendations for lifestyle and pharmacological treatment of cardiomyopathy in patients with DM.

Interleukin-1β polarization in M1 macrophage mediates myocardial fibrosis in diabetes

BACKGROUND

Diabetes is a global health problem whose common complication is diabetic cardiomyopathy, characterized by chronic inflammation of the heart muscle. Macrophages are the main white blood cells found in the resting heart. Therefore, we investigated the underling mechanism of macrophage on myocardial fibrosis in diabetes.

METHODS

Here, echocardiography was utilized to evaluate cardiac function, and the degree of myocardial fibrosis was assessed using Masson's trichrome staining, followed by single-cell RNA sequencing (scRNA-seq) to analyze the phenotype, function, developmental trajectory, and interactions between immune cells, endothelial cells (ECs), and fibroblasts (FBs) in the hearts of db/db mice at different stages of diabetes. Macrophages and cardiac fibroblasts were also co-cultured in order to study the signaling between macrophages and fibroblasts.

RESULTS

We found that with the development of diabetes mellitus, myocardial hypertrophy and fibrosis occurred that was accompanied by cardiac dysfunction. A significant proportion of immune cells, endothelial cells, and fibroblasts were identified by RNA sequencing. The most significant changes observed were in macrophages, which undergo M1 polarization and are critical for oxidative stress and extracellular matrix (ECM) formation. We further found that M1 macrophages secreted interleukin-1β (IL-1β), which interacted with the receptor on the surface of fibroblasts, to cause myocardial fibrosis. In addition, crosstalk between M1 macrophages and endothelial cells also plays a key role in fibrosis and immune response regulation through IL-1β and corresponding receptors.

CONCLUSIONS

M1 macrophages mediate diabetic myocardial fibrosis through interleukin-1β interaction with fibroblasts.

Hyperglycemia triggers RyR2-dependent alterations of mitochondrial calcium homeostasis in response to cardiac ischemia-reperfusion: Key role of DRP1 activation

Hyperglycemia increases the heart sensitivity to ischemia-reperfusion (IR), but the underlying cellular mechanisms remain unclear. Mitochondrial dynamics (the processes that govern mitochondrial morphology and their interactions with other organelles, such as the reticulum), has emerged as a key factor in the heart vulnerability to IR. However, it is unknown whether mitochondrial dynamics contributes to hyperglycemia deleterious effect during IR. We hypothesized that (i) the higher heart vulnerability to IR in hyperglycemic conditions could be explained by hyperglycemia effect on the complex interplay between mitochondrial dynamics, Ca2+ homeostasis, and reactive oxygen species (ROS) production; and (ii) the activation of DRP1, a key regulator of mitochondrial dynamics, could play a central role. Using transmission electron microscopy and proteomic analysis, we showed that the interactions between sarcoplasmic reticulum and mitochondria and mitochondrial fission were increased during IR in isolated rat hearts perfused with a hyperglycemic buffer compared with hearts perfused with a normoglycemic buffer. In isolated mitochondria and cardiomyocytes, hyperglycemia increased mitochondrial ROS production and Ca2+ uptake. This was associated with higher RyR2 instability. These results could contribute to explain the early mPTP activation in mitochondria from isolated hearts perfused with a hyperglycemic buffer and in hearts from streptozotocin-treated rats (to increase the blood glucose). DRP1 inhibition by Mdivi-1 during the hyperglycemic phase and before IR induction, normalized Ca2+ homeostasis, ROS production, mPTP activation, and reduced the heart sensitivity to IR in streptozotocin-treated rats. In conclusion, hyperglycemia-dependent DRP1 activation results in higher reticulum-mitochondria calcium exchange that contribute to the higher heart vulnerability to IR.

Construction and analysis of a network of exercise-induced mitochondria-related non-coding RNA in the regulation of diabetic cardiomyopathy

Diabetic cardiomyopathy (DCM) is a major factor in the development of heart failure. Mitochondria play a crucial role in regulating insulin resistance, oxidative stress, and inflammation, which affect the progression of DCM. Regular exercise can induce altered non-coding RNA (ncRNA) expression, which subsequently affects gene expression and protein function. The mechanism of exercise-induced mitochondrial-related non-coding RNA network in the regulation of DCM remains unclear. This study seeks to construct an innovative exercise-induced mitochondrial-related ncRNA network. Bioinformatic analysis of RNA sequencing data from an exercise rat model identified 144 differentially expressed long non-coding RNA (lncRNA) with cutoff criteria of p< 0.05 and fold change ≥1.0. GSE6880 and GSE4745 were the differentially expressed mRNAs from the left ventricle of DCM rat that downloaded from the GEO database. Combined with the differentially expressed mRNA and MitoCarta 3.0 dataset, the mitochondrial located gene Pdk4 was identified as a target gene. The miRNA prediction analysis using miRanda and TargetScan confirmed that 5 miRNAs have potential to interact with the 144 lncRNA. The novel lncRNA-miRNA-Pdk4 network was constructed for the first time. According to the functional protein association network, the newly created exercise-induced ncRNA network may serve as a promising diagnostic marker and therapeutic target, providing a fresh perspective to understand the molecular mechanism of different exercise types for the prevention and treatment of diabetic cardiomyopathy.

Secreted frizzled-related protein 2 ameliorates diabetic cardiomyopathy by activating mitophagy

OBJECTIVES

Secreted frizzled-related protein 2 (SFRP2), a novel adipokine that used to be considered an inhibitor of the canonical Wnt pathway, may play a protective role in metabolic disorders. However, its effect on diabetic cardiomyopathy was still unclear. Accumulating evidence indicates that mitophagy can protect cardiac function in the diabetic heart. The present study aimed to explore the roles of SFRP2 on diabetic cardiomyopathy, focusing on the effects and mechanisms for regulating mitophagy.

METHODS

Wild-type H9c2 cells, Sfrp2 overexpression and knockdown H9c2 cells were exposed to a glucolipotoxic milieu. Reactive oxygen species (ROS) production, cell viability, apoptosis, mitophagy and lysosomal activity were detected. The interaction of SFRP2 with frizzled 5 (FZD5), and its effect on expression and intracellular localization of transcription factor EB (TFEB) and β-catenin were also explored. Diabetic rats and Sfrp2 overexpression diabetic rats were constructed to further document the findings from the in vitro study.

RESULTS

The expression of SFRP2 was low and mitophagy was inhibited in H9c2 cells in a glucolipotoxic milieu. Sfrp2 overexpression activated mitophagy and reduced H9c2 cells injury, whereas Sfrp2 deficiency inhibited mitophagy and worsened this injury. Consistent with the in vitro findings, Sfrp2 overexpression ameliorated the impairment in cardiac function of diabetic rats by activating mitophagy. Sfrp2 overexpression upregulated the expression of calcineurin and TFEB, but did not affect β-catenin in vitro and in vivo. The calcineurin inhibitor tacrolimus can inhibit mitophagy and worsen cell injury in Sfrp2 overexpression H9c2 cells. Furthermore, we found that FZD5 is required for the SFRP2-induced activation of the calcineurin/TFEB pathway and interacts with SFRP2 in H9c2 cells. Transfection with small interfering RNA targeting FZD5 opposed the effects of Sfrp2 overexpression on mitophagy and cell survival in a glucolipotoxic environment.

CONCLUSIONS

SFRP2 can protect the diabetic heart by interacting with FZD5 and activating the calcineurin/TFEB pathway to upregulate mitophagy in H9c2 cells.

The essential role of glutamine metabolism in diabetic cardiomyopathy: A review

Diabetic cardiomyopathy (DCM) is a pathophysiological condition caused by diabetes mellitus and is the leading cause of diabetes mellitus-related mortality. The pathophysiology of DCM involves various processes, such as oxidative stress, inflammation, ferroptosis, and abnormal protein modification. New evidence indicates that dysfunction of glutamine (Gln) metabolism contributes to the pathogenesis of DCM by regulating these pathophysiological mechanisms. Gln is a conditionally essential amino acid in the human body, playing a vital role in maintaining cell function. Although the precise molecular mechanisms of Gln in DCM have yet to be fully elucidated, recent studies have shown that supplementing with Gln improves cardiac function in diabetic hearts. However, excessive Gln may worsen myocardial injury in DCM by generating a large amount of glutamates or increasing O-GlcNacylation. To highlight the potential therapeutic method targeting Gln metabolism and its downstream pathophysiological mechanisms, this article aims to review the regulatory function of Gln in the pathophysiological mechanisms of DCM.

Roles of mitochondrial dynamics and mitophagy in diabetic myocardial microvascular injury

Myocardial microvessels are composed of a monolayer of endothelial cells, which play a crucial role in maintaining vascular barrier function, luminal latency, vascular tone, and myocardial perfusion. Endothelial dysfunction is a key factor in the development of cardiac microvascular injury and diabetic cardiomyopathy. In addition to their role in glucose oxidation and energy metabolism, mitochondria also participate in non-metabolic processes such as apoptosis, intracellular ion handling, and redox balancing. Mitochondrial dynamics and mitophagy are responsible for regulating the quality and quantity of mitochondria in response to hyperglycemia. However, these endogenous homeostatic mechanisms can both preserve and/or disrupt non-metabolic mitochondrial functions during diabetic endothelial damage and cardiac microvascular injury. This review provides an overview of the molecular features and regulatory mechanisms of mitochondrial dynamics and mitophagy. Furthermore, we summarize findings from various investigations that suggest abnormal mitochondrial dynamics and defective mitophagy contribute to the development of diabetic endothelial dysfunction and myocardial microvascular injury. Finally, we discuss different therapeutic strategies aimed at improving endothelial homeostasis and cardiac microvascular function through the enhancement of mitochondrial dynamics and mitophagy.

Transcription factor EB: A potential integrated network regulator in metabolic-associated cardiac injury

With the worldwide pandemic of metabolic diseases, such as obesity, diabetes, and non-alcoholic fatty liver disease (NAFLD), cardiometabolic disease (CMD) has become a significant cause of death in humans. However, the pathophysiology of metabolic-associated cardiac injury is complex and not completely clear, and it is important to explore new strategies and targets for the treatment of CMD. A series of pathophysiological disturbances caused by metabolic disorders, such as insulin resistance (IR), hyperglycemia, hyperlipidemia, mitochondrial dysfunction, oxidative stress, inflammation, endoplasmic reticulum stress (ERS), autophagy dysfunction, calcium homeostasis imbalance, and endothelial dysfunction, may be related to the incidence and development of CMD. Transcription Factor EB (TFEB), as a transcription factor, has been extensively studied for its role in regulating lysosomal biogenesis and autophagy. Recently, the regulatory role of TFEB in other biological processes, including the regulation of glucose homeostasis, lipid metabolism, etc. has been gradually revealed. In this review, we will focus on the relationship between TFEB and IR, lipid metabolism, endothelial dysfunction, oxidative stress, inflammation, ERS, calcium homeostasis, autophagy, and mitochondrial quality control (MQC) and the potential regulatory mechanisms among them, to provide a comprehensive summary for TFEB as a potential new therapeutic target for CMD.

Glucose fluctuation promotes mitochondrial dysfunctions in the cardiomyocyte cell line HL-1

AIMS

Glycemic variability has been suggested as a risk factor for diabetes complications but the precise deleterious mechanisms remain poorly understood. Since mitochondria are the main source of energy in heart and cardiovascular diseases remain the first cause of death in patients with diabetes, the aim of the study was to evaluate the impact of glucose swings on mitochondrial functions in the cardiomyocyte cell line HL-1.

METHODS

HL-1 cells were exposed to low (LG, 2.8 mmol/l), normal (NG, 5.5 mmol/l), high (HG, 25 mmol/l) or intermittent high glucose (IHG, swing between low and high) every 2h during 12h (short-time treatment) or every 12h during 72h (long-time treatment). Anaerobic catabolism of glucose was evaluated by measuring glucose consumption and lactate production, oxidative phosphorylation was evaluated by polarography and ATP measurement, mitochondrial superoxide anions and the mitochondrial membrane potential (MMP) were analysed using fluorescent probes, and the protein oxidation was measured by oxyblot.

RESULTS

IHG and HG increased glucose consumption and lactate production compared to LG and NG but without any difference between short- and long-time treatments. After 72h and unlike to LG, NG and HG, we didn't observe any increase of the mitochondrial respiration in the presence of succinate upon IHG treatment. IHG, and to a lesser extent HG, promoted a time-dependent decrease of the mitochondrial membrane potential compared to LG and NG treatments. HG and IHG also increased superoxide anion production compared to LG and NG both at 12 and 72h but with a higher increase for IHG at 72h. At last, both HG and IHG stimulated protein oxidation at 72h compared to LG and NG treatments.

CONCLUSIONS

Our results demonstrated that exposure of HL-1 cells to glucose swings promoted time-dependent mitochondrial dysfunctions suggesting a deleterious effect of such condition in patients with diabetes that could contribute to diabetic cardiomyopathy.

Effects of non-coding RNAs and RNA-binding proteins on mitochondrial dysfunction in diabetic cardiomyopathy

Vascular complications are the main cause of diabetes mellitus-associated morbidity and mortality. Oxidative stress and metabolic dysfunction underly injury to the vascular endothelium and myocardium, resulting in diabetic angiopathy and cardiomyopathy. Mitochondrial dysfunction has been shown to play an important role in cardiomyopathic disruptions of key cellular functions, including energy metabolism and oxidative balance. Both non-coding RNAs and RNA-binding proteins are implicated in diabetic cardiomyopathy, however, their impact on mitochondrial dysfunction in the context of this disease is largely unknown. Elucidating the effects of non-coding RNAs and RNA-binding proteins on mitochondrial pathways in diabetic cardiomyopathy would allow further insights into the pathophysiological mechanisms underlying diabetic vascular complications and could facilitate the development of new therapeutic strategies. Stem cell-based models can facilitate the study of non-coding RNAs and RNA-binding proteins and their unique characteristics make them a promising tool to improve our understanding of mitochondrial dysfunction and vascular complications in diabetes.

Metrnl ameliorates diabetic cardiomyopathy via inactivation of cGAS/STING signaling dependent on LKB1/AMPK/ULK1-mediated autophagy

INTRODUCTION

Meteorin-like hormone (Metrnl) is ubiquitously expressed in skeletal muscle, heart, and adipose with beneficial roles in obesity, insulin resistance, and inflammation. Metrnl is found to protect against cardiac hypertrophy and doxorubicin-induced cardiotoxicity. However, its role in diabetic cardiomyopathy (DCM) is undefined.

OBJECTIVES

We aimed to elucidate the potential roles of Metrnl in DCM.

METHODS

Gain- andloss-of-function experimentswere utilized to determine the roles of Metrnl in the pathological processes of DCM.

RESULTS

We found that plasma Metrnl levels, myocardial Metrnl protein and mRNA expressions were significantly downregulated in both streptozotocin (STZ)-induced (T1D) mice and leptin receptor deficiency (db/db) (T2D) mice. Cardiac-specific overexpression (OE) of Metrnl markedly ameliorated cardiac injury and dysfunction in both T1D and T2D mice. In sharp contrast, specific deletion of Metrnl in the heart had the opposite phenotypes. In parallel, Metrnl OE ameliorated, whereas Metrnl downregulation exacerbated high glucose (HG)-elicited hypertrophy, apoptosis and oxidative damage in primary neonatal rat cardiomyocytes. Antibody-induced blockade of Metrnl eliminated the effects of benefits of Metrnl in vitro and in vivo. Mechanistically, Metrnl activated the autophagy pathway and inhibited the cGAS/STING signaling in a LKB1/AMPK/ULK1-dependent mechanism in cardiomyocytes. Besides, Metrnl-induced ULK1 phosphorylation facilitated the dephosphorylation and mitochondrial translocation of STING where it interacted with tumor necrosis factor receptor-associated factor 2 (TRAF2), a scaffold protein and E3 ubiquitin ligase that was responsible for ubiquitination and degradation of STING, rendering cardiomyocytes sensitive to autophagy activation.

CONCLUSION

Thus, Metrnl may be an attractive therapeutic target or regimen for treating DCM.

Distinct Roles of DRP1 in Conventional and Alternative Mitophagy in Obesity Cardiomyopathy

BACKGROUND

Obesity induces cardiomyopathy characterized by hypertrophy and diastolic dysfunction. Whereas mitophagy mediated through an Atg7 (autophagy related 7)-dependent mechanism serves as an essential mechanism to maintain mitochondrial quality during the initial development of obesity cardiomyopathy, Rab9 (Ras-related protein Rab-9A)-dependent alternative mitophagy takes over the role during the chronic phase. Although it has been postulated that DRP1 (dynamin-related protein 1)-mediated mitochondrial fission and consequent separation of the damaged portions of mitochondria are essential for mitophagy, the involvement of DRP1 in mitophagy remains controversial. We investigated whether endogenous DRP1 is essential in mediating the 2 forms of mitophagy during high-fat diet (HFD)-induced obesity cardiomyopathy and, if so, what the underlying mechanisms are.

METHODS

Mice were fed either a normal diet or an HFD (60 kcal %fat). Mitophagy was evaluated using cardiac-specific Mito-Keima mice. The role of DRP1 was evaluated using tamoxifen-inducible cardiac-specific Drp1knockout (Drp1 MCM) mice.

RESULTS

Mitophagy was increased after 3 weeks of HFD consumption. The induction of mitophagy by HFD consumption was completely abolished in Drp1 MCM mouse hearts, in which both diastolic and systolic dysfunction were exacerbated. The increase in LC3 (microtubule-associated protein 1 light chain 3)-dependent general autophagy and colocalization between LC3 and mitochondrial proteins was abolished in Drp1 MCM mice. Activation of alternative mitophagy was also completely abolished in Drp1 MCM mice during the chronic phase of HFD consumption. DRP1 was phosphorylated at Ser616, localized at the mitochondria-associated membranes, and associated with Rab9 and Fis1 (fission protein 1) only during the chronic, but not acute, phase of HFD consumption.

CONCLUSIONS

DRP1 is an essential factor in mitochondrial quality control during obesity cardiomyopathy that controls multiple forms of mitophagy. Although DRP1 regulates conventional mitophagy through a mitochondria-associated membrane-independent mechanism during the acute phase, it acts as a component of the mitophagy machinery at the mitochondria-associated membranes in alternative mitophagy during the chronic phase of HFD consumption.

The role of circadian clock-controlled mitochondrial dynamics in diabetic cardiomyopathy

Diabetes mellitus is a metabolic disease with a high prevalence worldwide, and cardiovascular complications are the leading cause of mortality in patients with diabetes. Diabetic cardiomyopathy (DCM), which is prone to heart failure with preserved ejection fraction, is defined as a cardiac dysfunction without conventional cardiac risk factors such as coronary heart disease and hypertension. Mitochondria are the centers of energy metabolism that are very important for maintaining the function of the heart. They are highly dynamic in response to environmental changes through mitochondrial dynamics. The disruption of mitochondrial dynamics is closely related to the occurrence and development of DCM. Mitochondrial dynamics are controlled by circadian clock and show oscillation rhythm. This rhythm enables mitochondria to respond to changing energy demands in different environments, but it is disordered in diabetes. In this review, we summarize the significant role of circadian clock-controlled mitochondrial dynamics in the etiology of DCM and hope to play a certain enlightening role in the treatment of DCM.

Insights into SGLT2 inhibitor treatment of diabetic cardiomyopathy: focus on the mechanisms

Among the complications of diabetes, cardiovascular events and cardiac insufficiency are considered two of the most important causes of death. Experimental and clinical evidence supports the effectiveness of SGLT2i for improving cardiac dysfunction. SGLT2i treatment benefits metabolism, microcirculation, mitochondrial function, fibrosis, oxidative stress, endoplasmic reticulum stress, programmed cell death, autophagy, and the intestinal flora, which are involved in diabetic cardiomyopathy. This review summarizes the current knowledge of the mechanisms of SGLT2i for the treatment of diabetic cardiomyopathy.

Metformin Collaborates with PINK1/Mfn2 Overexpression to Prevent Cardiac Injury by Improving Mitochondrial Function

Both mitochondrial quality control and energy metabolism are critical in maintaining the physiological function of cardiomyocytes. When damaged mitochondria fail to be repaired, cardiomyocytes initiate a process referred to as mitophagy to clear defective mitochondria, and studies have shown that PTEN-induced putative kinase 1 (PINK1) plays an important role in this process. In addition, previous studies indicated that peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α) is a transcriptional coactivator that promotes mitochondrial energy metabolism, and mitofusin 2 (Mfn2) promotes mitochondrial fusion, which is beneficial for cardiomyocytes. Thus, an integration strategy involving mitochondrial biogenesis and mitophagy might contribute to improved cardiomyocyte function. We studied the function of PINK1 in mitophagy in isoproterenol (Iso)-induced cardiomyocyte injury and transverse aortic constriction (TAC)-induced myocardial hypertrophy. Adenovirus vectors were used to induce PINK1/Mfn2 protein overexpression. Cardiomyocytes treated with isoproterenol (Iso) expressed high levels of PINK1 and low levels of Mfn2, and the changes were time dependent. PINK1 overexpression promoted mitophagy, attenuated the Iso-induced reduction in MMP, and reduced ROS production and the apoptotic rate. Cardiac-specific overexpression of PINK1 improved cardiac function, attenuated pressure overload-induced cardiac hypertrophy and fibrosis, and facilitated myocardial mitophagy in TAC mice. Moreover, metformin treatment and PINK1/Mfn2 overexpression reduced mitochondrial dysfunction by inhibiting ROS generation leading to an increase in both ATP production and mitochondrial membrane potential in Iso-induced cardiomyocyte injury. Our findings indicate that a combination strategy may help ameliorate myocardial injury by improving mitochondrial quality.

The Role of Alternative Mitophagy in Heart Disease

Autophagy is essential for maintaining cellular homeostasis through bulk degradation of subcellular constituents, including misfolded proteins and dysfunctional organelles. It is generally governed by the proteins Atg5 and Atg7, which are critical regulators of the conventional autophagy pathway. However, recent studies have identified an alternative Atg5/Atg7-independent pathway, i.e., Ulk1- and Rab9-mediated alternative autophagy. More intensive studies have identified its essential role in stress-induced mitochondrial autophagy, also known as mitophagy. Alternative mitophagy plays pathophysiological roles in heart diseases such as myocardial ischemia and pressure overload. Here, this review discusses the established and emerging mechanisms of alternative autophagy/mitophagy that can be applied in therapeutic interventions for heart disorders.

Parkin-mediated mitophagy is negatively regulated by FOXO3A, which inhibits Plk3-mediated mitochondrial ROS generation in STZ diabetic stress-treated pancreatic β cells

Diabetes mellitus (DM) is one of the most researched metabolic diseases worldwide. It leads to extensive complications such as cardiovascular disease, nephropathy, retinopathy, and peripheral and central nervous system through an inability to produce or respond to insulin. Although oxidative stress-mediated mitophagy has been reported to play an important role in the pathogenesis of DM, specific studies are still lacking as well as remain highly controversial. Here, we found that Parkin-mediated mitophagy in pancreatic β cells under streptozotocin (STZ)-diabetic stress was induced by Polo-like kinase 3 (Plk3) and inhibited by the transcription factor Forkhead Box O3A (FOXO3A). STZ stress induces mitochondrial recruitment of Parkin through Plk3-mediated mitochondrial reactive oxygen species (ROS) generation, which causes pancreatic cell damage. Conversely, FOXO3A acts as negative feedback to prevent diabetic stress by inhibiting Plk3. Meanwhile, antioxidants including N-acetylcysteine (NAC) and natural COA water scientifically block these mitochondrial ROS and mitochondrial recruitment of Parkin by inhibiting Plk3. Through a 3D organoid ex vivo model, we confirmed that not only ROS inhibitors but also mitophagy inhibitory factors such as 3-MA or Parkin deletion can compensate for pancreatic cell growth and insulin secretion under STZ diabetic stress. These findings suggest that the Plk3-mtROS-PINK1-Parkin axis is a novel mitophagy process that inhibits pancreatic β-cell growth and insulin secretion and FOXO3A and antioxidants may provide new alternatives for effective diabetes treatment strategies in the future.

Glucagon-Like Peptide-1 Receptor Agonist Protects Against Diabetic Cardiomyopathy by Modulating microRNA-29b-3p/SLMAP

Purpose

Our aims were to investigate the pathogenesis of diabetic cardiomyopathy (DCM) and to explore the protective effect of glucagon-like peptide-1 receptor agonist (GLP-1RA) on DCM.

Methods

After 12 weeks of treatment with exenatide-loaded microspheres, a long-acting GLP-1RA, in DCM mice, cardiac structure and function were evaluated by plasma B-type natriuretic peptide (BNP), echocardiography, H&E, oil red and Sirius staining. The expression of glucagon-like peptide-1 receptor in mouse heart tissue was determined by immunofluorescence staining. The label-free proteomic analysis of cardiac proteins was conducted among control, DCM and DM+GLP-1RA groups. Then, quantitative real-time PCR, Western blotting and dual-luciferase reporter assay were performed to verify the regulation of target protein by the upstream microRNA (miRNA).

Results

GLP-1RA treatment obviously improved serum BNP, myocardial fibrosis, lipid deposition of the myocardium and echocardiography parameters in DCM mice. Sarcolemmal membrane-associated protein (SLMAP) was one of 61 differentially expressed cardiac proteins found in three groups by proteomic analysis. Up-regulation of microRNA-29b-3p (miR-29b-3p) and down-regulation of SLMAP were found in the ventricular myocardium of GLP-1RA-treated DCM mice. SLMAP was a target of miR-29b-3p, while GLP-1RA regulated SLMAP expression through miR-29b-3p. Furthermore, inhibition of glucagon-like peptide-1 receptor (GLP-1R) in cardiomyocytes reversed the effects of GLP-1RA on miR-29b/SLMAP.

Conclusion

SLMAP may play roles in the pathogenesis of DCM and may be a target of GLP-1RA in protecting against DCM. After binding to myocardial GLP-1R, GLP-1RA can regulate the expression of myocardial SLMAP through miR-29b-3p.

Current understanding on pathogenesis and effective treatment of glycogen storage disease type Ib with empagliflozin: new insights coming from diabetes for its potential implications in other metabolic disorders

Glycogen storage type Ib (GSDIb) is a rare inborn error of metabolism caused by glucose-6-phosphate transporter (G6PT, SLC37A4) deficiency. G6PT defect results in excessive accumulation of glycogen and fat in the liver, kidney, and intestinal mucosa and into both glycogenolysis and gluconeogenesis impairment. Clinical features include hepatomegaly, hypoglycemia, lactic acidemia, hyperuricemia, hyperlipidemia, and growth retardation. Long-term complications are liver adenoma, hepatocarcinoma, nephropathy and osteoporosis. The hallmark of GSDIb is neutropenia, with impaired neutrophil function, recurrent infections and inflammatory bowel disease. Alongside classical nutritional therapy with carbohydrates supplementation and immunological therapy with granulocyte colony-stimulating factor, the emerging role of 1,5-anhydroglucitol in the pathogenesis of neutrophil dysfunction led to repurpose empagliflozin, an inhibitor of the renal glucose transporter SGLT2: the current literature of its off-label use in GSDIb patients reports beneficial effects on neutrophil dysfunction and its clinical consequences. Surprisingly, this glucose-lowering drug ameliorated the glycemic and metabolic control in GSDIb patients. Furthermore, numerous studies from big cohorts of type 2 diabetes patients showed the efficacy of empagliflozin in reducing the cardiovascular risk, the progression of kidney disease, the NAFLD and the metabolic syndrome. Beneficial effects have also been described on peripheral neuropathy in a prediabetic rat model. Increasing evidences highlight the role of empagliflozin in regulating the cellular energy sensors SIRT1/AMPK and Akt/mTOR, which leads to improvement of mitochondrial structure and function, stimulation of autophagy, decrease of oxidative stress and suppression of inflammation. Modulation of these pathways shift the oxidative metabolism from carbohydrates to lipids oxidation and results crucial in reducing insulin levels, insulin resistance, glucotoxicity and lipotoxicity. For its pleiotropic effects, empagliflozin appears to be a good candidate for drug repurposing also in other metabolic diseases presenting with hypoglycemia, organ damage, mitochondrial dysfunction and defective autophagy.

Low-Intensity Pulsed Ultrasound Counteracts Advanced Glycation End Products-Induced Corpus Cavernosal Endothelial Cell Dysfunction via Activating Mitophagy

Injury to corpus cavernosal endothelial cells (CCECs) is an important pathological basis of diabetes mellitus-induced erectile dysfunction (DMED), while low-intensity pulsed ultrasound (LIPUS) has been shown to improve erectile function in DMED. To further understand its therapeutic mechanism of action, in this study, we first demonstrated increased apoptosis and shedding in the CCECs of DMED patients, accompanied by significant mitochondrial injury by immunohistochemistry and electron microscopy of corpus cavernosum tissue. Next, we used advanced glycation end products (AGEs) to simulate the diabetic environment in vitro and found that AGES damaged mitochondria and inhibited angiogenesis in CCECs in a dose-dependent manner, while LIPUS treatment significantly reversed its effects. Mechanistic studies based on transcriptome sequencing showed that LIPUS significantly up-regulated LC3 and PARKIN protein levels in mitochondria, promoted mitophagy, and affected mitochondrial dynamics and reactive oxygen species (ROS) production. In addition, the protective effects of LIPUS were abrogated when mitophagy was inhibited by 3-methyladenine. In summary, LIPUS exerted potent inhibitory effects on AGES-induced CCEC failure via mitophagy, providing a theoretical basis for DMED treatment that encompasses the protection of endothelial structure and function.

SUMOylation targeting mitophagy in cardiovascular diseases

Small ubiquitin-like modifier (SUMO) plays a key regulatory role in cardiovascular diseases, such as cardiac hypertrophy, hypertension, atherosclerosis, and cardiac ischemia-reperfusion injury. As a multifunctional posttranslational modification molecule in eukaryotic cells, SUMOylation is essentially associated with the regulation of mitochondrial dynamics, especially mitophagy, which is involved in the progression and development of cardiovascular diseases. SUMOylation targeting mitochondrial-associated proteins is admittedly considered to regulate mitophagy activation and mitochondrial functions and dynamics, including mitochondrial fusion and fission. SUMOylation triggers mitochondrial fusion to promote mitochondrial dysfunction by modifying Fis1, OPA1, MFN1/2, and DRP1. The interaction between SUMO and DRP1 induces SUMOylation and inhibits lysosomal degradation of DRP1, which is further involved in the regulation of mitochondrial fission. Both SUMOylation and deSUMOylation contribute to the initiation and activation of mitophagy by regulating the conjugation of MFN1/2 SERCA2a, HIF1α, and PINK1. SUMOylation mediated by the SUMO molecule has attracted much attention due to its dual roles in the development of cardiovascular diseases. In this review, we systemically summarize the current understanding underlying the expression, regulation, and structure of SUMO molecules; explore the biochemical functions of SUMOylation in the initiation and activation of mitophagy; discuss the biological roles and mechanisms of SUMOylation in cardiovascular diseases; and further provide a wider explanation of SUMOylation and deSUMOylation research to provide a possible therapeutic strategy for cardiovascular diseases. Considering the precise functions and exact mechanisms of SUMOylation in mitochondrial dysfunction and mitophagy will provide evidence for future experimental research and may serve as an effective approach in the development of novel therapeutic strategies for cardiovascular diseases. Regulation and effect of SUMOylation in cardiovascular diseases via mitophagy. SUMOylation is involved in multiple cardiovascular diseases, including cardiac hypertrophy, hypertension, atherosclerosis, and cardiac ischemia-reperfusion injury. Since it is expressed in multiple cells associated with cardiovascular disease, SUMOylation can be regulated by numerous ligases, including the SENP family proteins PIAS1, PIASy/4, UBC9, and MAPL. SUMOylation regulates the activation and degradation of PINK1, SERCA2a, PPARγ, ERK5, and DRP1 to mediate mitochondrial dynamics, especially mitophagy activation. Mitophagy activation regulated by SUMOylation further promotes or inhibits ventricular diastolic dysfunction, perfusion injury, ventricular remodelling and ventricular noncompaction, which contribute to the development of cardiovascular diseases.

Multi-omics insights into potential mechanism of SGLT2 inhibitors cardiovascular benefit in diabetic cardiomyopathy

Background

Metabolic and energy disorders are considered central to the etiology of diabetic cardiomyopathy (DCM). Sodium-glucose cotransporter-2 inhibitors (SGLT2i) can effectively reduce the risk of cardiovascular death and heart failure in patients with DCM. However, the underlying mechanism has not been elucidated.

Methods

We established a DCM rat model followed by treatment with empagliflozin (EMPA) for 12 weeks. Echocardiography, blood tests, histopathology, and transmission electron microscopy (TEM) were used to evaluate the phenotypic characteristics of the rats. The proteomics and metabolomics of the myocardium in the rat model were performed to identify the potential targets and signaling pathways associated with the cardiovascular benefit of SGLT2i.

Results

The diabetic rat showed pronounced DCM characterized by mitochondrial pleomorphic, impaired lipid metabolism, myocardial fibrosis, and associated diastolic and systolic functional impairments in the heart. To some extent, these changes were ameliorated after treatment with EMPA. A total of 43 proteins and 34 metabolites were identified as targets in the myocardium of diabetic rats treated with EMPA. The KEGG analysis showed that arachidonic acid is associated with the maximum number of related pathways and may be a potential target of EMPA treatment. Fatty acid (FA) metabolism was enhanced in diabetic hearts, and the perturbation of biosynthesis of unsaturated FAs and arachidonic acid metabolism was a potential enabler for the cardiovascular benefit of EMPA.

Conclusion

SGLT2i ameliorated lipid accumulation and mitochondrial damage in the myocardium of diabetic rats. The metabolomic and proteomic data revealed the potential targets and signaling pathways associated with the cardiovascular benefit of SGLT2i, which provides a valuable resource for the mechanism of SGLT2i.

Research progress on ncRNAs regulation of mitochondrial dynamics in diabetes

Diabetes mellitus and its complications are major health concerns worldwide that should be routinely monitored for evaluating disease progression. And there is currently much evidence to suggest a critical role for mitochondria in the common pathogenesis of diabetes and its complications. Mitochondrial dynamics are involved in the development of diabetes through mediating insulin signaling and insulin resistance, and in the development of diabetes and its complications through mediating endothelial impairment and other closely related pathophysiological mechanisms of diabetic cardiomyopathy (DCM). noncoding RNAs (ncRNAs) are closely linked to mitochondrial dynamics by regulating the expression of mitochondrial dynamic-associated proteins, or by regulating key proteins in related signaling pathways. Therefore, this review summarizes the research progress on the regulation of Mitochondrial Dynamics by ncRNAs in diabetes and its complications, which is a promising area for future antibodies or targeted drug development.

Potential diabetic cardiomyopathy therapies targeting pyroptosis: A mini review

Pyroptosis is primarily considered a pro-inflammatory class of caspase-1- and gasdermin D (GSDMD)-dependent programmed cell death. Inflammasome activation promotes the maturation and release of interleukin (IL)-1β and IL-18, cleavage of GSDMD, and development of pyroptosis. Recent studies have reported that NLRP3 inflammasome activation-mediated pyroptosis aggravates the formation and development of diabetes cardiomyopathy (DCM). These studies provide theoretical mechanisms for exploring a novel approach to treat DCM-associated cardiac dysfunction. Accordingly, this review aims to summarize studies that investigated possible DCM therapies targeting pyroptosis and elucidate the molecular mechanisms underlying NLRP3 inflammasome-mediated pyroptosis, and its potential association with the pathogenesis of DCM. This review may serve as a basis for the development of potential pharmacological agents as novel and effective treatments for managing and treating DCM.

Mitochondrial quality control in diabetic cardiomyopathy: from molecular mechanisms to therapeutic strategies

In diabetic cardiomyopathy (DCM), a major diabetic complication, the myocardium is structurally and functionally altered without evidence of coronary artery disease, hypertension or valvular disease. Although numerous anti-diabetic drugs have been applied clinically, specific medicines to prevent DCM progression are unavailable, so the prognosis of DCM remains poor. Mitochondrial ATP production maintains the energetic requirements of cardiomyocytes, whereas mitochondrial dysfunction can induce or aggravate DCM by promoting oxidative stress, dysregulated calcium homeostasis, metabolic reprogramming, abnormal intracellular signaling and mitochondrial apoptosis in cardiomyocytes. In response to mitochondrial dysfunction, the mitochondrial quality control (MQC) system (including mitochondrial fission, fusion, and mitophagy) is activated to repair damaged mitochondria. Physiological mitochondrial fission fragments the network to isolate damaged mitochondria. Mitophagy then allows dysfunctional mitochondria to be engulfed by autophagosomes and degraded in lysosomes. However, abnormal MQC results in excessive mitochondrial fission, impaired mitochondrial fusion and delayed mitophagy, causing fragmented mitochondria to accumulate in cardiomyocytes. In this review, we summarize the molecular mechanisms of MQC and discuss how pathological MQC contributes to DCM development. We then present promising therapeutic approaches to improve MQC and prevent DCM progression.

Perspectives for Forkhead box transcription factors in diabetic cardiomyopathy: Their therapeutic potential and possible effects of salvianolic acids

Diabetic cardiomyopathy (DCM) is the primary cause of morbidity and mortality in diabetic cardiovascular complications, which initially manifests as cardiac hypertrophy, myocardial fibrosis, dysfunctional remodeling, and diastolic dysfunction, followed by systolic dysfunction, and eventually end with acute heart failure. Molecular mechanisms underlying these pathological changes in diabetic hearts are complicated and multifactorial, including but not limited to insulin resistance, oxidative stress, lipotoxicity, cardiomyocytes apoptosis or autophagy, inflammatory response, and myocardial metabolic dysfunction. With the development of molecular biology technology, accumulating evidence illustrates that members of the class O of Forkhead box (FoxO) transcription factors are vital for maintaining cardiomyocyte metabolism and cell survival, and the functions of the FoxO family proteins can be modulated by a wide variety of post-translational modifications including phosphorylation, acetylation, ubiquitination, arginine methylation, and O-glycosylation. In this review, we highlight and summarize the most recent advances in two members of the FoxO family (predominately FoxO1 and FoxO3a) that are abundantly expressed in cardiac tissue and whose levels of gene and protein expressions change as DCM progresses, with the goal of providing valuable insights into the pathogenesis of diabetic cardiovascular complications and discussing their therapeutic potential and possible effects of salvianolic acids, a natural product.

Biomarkers of Oxidative Stress Tethered to Cardiovascular Diseases

Cardiovascular disease (CVD) is a broad term that incorporated a group of conditions that affect the blood vessels and the heart. CVD is a foremost cause of fatalities around the world. Multiple pathophysiological mechanisms are involved in CVD; however, oxidative stress plays a vital role in generating reactive oxygen species (ROS). Oxidative stress occurs when the concentration of oxidants exceeds the potency of antioxidants within the body while producing reactive nitrogen species (RNS). ROS generated by oxidative stress disrupts cell signaling, DNA damage, lipids, and proteins, thereby resulting in inflammation and apoptosis. Mitochondria is the primary source of ROS production within cells. Increased ROS production reduces nitric oxide (NO) bioavailability, which elevates vasoconstriction within the arteries and contributes to the development of hypertension. ROS production has also been linked to the development of atherosclerotic plaque. Antioxidants can decrease oxidative stress in the body; however, various therapeutic drugs have been designed to treat oxidative stress damage due to CVD. The present review provides a detailed narrative of the oxidative stress and ROS generation with a primary focus on the oxidative stress biomarker and its association with CVD. We have also discussed the complex relationship between inflammation and endothelial dysfunction in CVD as well as oxidative stress-induced obesity in CVD. Finally, we discussed the role of antioxidants in reducing oxidative stress in CVD.

Mitochondrial Dynamics and Mitophagy in Cardiometabolic Disease

Mitochondria play a key role in cellular metabolism. Mitochondrial dynamics (fusion and fission) and mitophagy, are critical to mitochondrial function. Fusion allows organelles to share metabolites, proteins, and mitochondrial DNA, promoting complementarity between damaged mitochondria. Fission increases the number of mitochondria to ensure that they are passed on to their offspring during mitosis. Mitophagy is a process of selective removal of excess or damaged mitochondria that helps improve energy metabolism. Cardiometabolic disease is characterized by mitochondrial dysfunction, high production of reactive oxygen species, increased inflammatory response, and low levels of ATP. Cardiometabolic disease is closely related to mitochondrial dynamics and mitophagy. This paper reviewed the mechanisms of mitochondrial dynamics and mitophagy (focus on MFN1, MFN2, OPA1, DRP1, and PINK1 proteins) and their roles in diabetic cardiomyopathy, myocardial infarction, cardiac hypertrophy, heart failure, atherosclerosis, and obesity.

The Beneficial Effects of Chinese Herbal Monomers on Ameliorating Diabetic Cardiomyopathy via Nrf2 Signaling

Diabetic cardiomyopathy (DCM) is the main factor responsible for poor prognosis and survival in patients with diabetes. The highly complex pathogenesis of DCM involves multiple signaling pathways, including nuclear factor-κB (NF-κB) signaling pathway, adenosine monophosphate-activated protein kinase (AMPK) signaling pathway, phosphatidylinositol 3-kinase-protein kinase B (Akt) signaling pathway, mitogen-activated protein kinase (MAPK) signaling pathway, and transforming growth factor-β (TGF-β) signaling pathway. Nuclear factor erythroid-2-related factor 2 (Nrf2) seems essential to the amelioration of the progression of DCM, not only through counterbalancing oxidative stress, but also through interacting with other signaling pathways to combat inflammation, the disorder in energy homeostasis and insulin signaling, and fibrosis. It has been evidenced that Chinese herbal monomers could attenuate DCM through the crosstalk of Nrf2 with other signaling pathways. This article has summarized the pathogenesis of DCM (especially in oxidative stress), the beneficial effects of ameliorating DCM via the Nrf2 signaling pathway and its crosstalk, and examples of Chinese herbal monomers. It will facilitate pharmacological research and development to promote the utilization of traditional Chinese medicine in DCM.

Pathophysiology and Treatment of Diabetic Cardiomyopathy and Heart Failure in Patients with Diabetes Mellitus

There is a close relationship between diabetes mellitus and heart failure, and diabetes is an independent risk factor for heart failure. Diabetes and heart failure are linked by not only the complication of ischemic heart disease, but also by metabolic disorders such as glucose toxicity and lipotoxicity based on insulin resistance. Cardiac dysfunction in the absence of coronary artery disease, hypertension, and valvular disease is called diabetic cardiomyopathy. Diabetes-induced hyperglycemia and hyperinsulinemia lead to capillary damage, myocardial fibrosis, and myocardial hypertrophy with mitochondrial dysfunction. Lipotoxicity with extensive fat deposits or lipid droplets is observed on cardiomyocytes. Furthermore, increased oxidative stress and inflammation cause cardiac fibrosis and hypertrophy. Treatment with a sodium glucose cotransporter 2 (SGLT2) inhibitor is currently one of the most effective treatments for heart failure associated with diabetes. However, an effective treatment for lipotoxicity of the myocardium has not yet been established, and the establishment of an effective treatment is needed in the future. This review provides an overview of heart failure in diabetic patients for the clinical practice of clinicians.

miR-340-5p Mediates Cardiomyocyte Oxidative Stress in Diabetes-Induced Cardiac Dysfunction by Targeting Mcl-1

Diabetic cardiomyopathy (DCM) is initially characterized by early diastolic dysfunction, left ventricular remodeling, hypertrophy, and myocardial fibrosis, and it is eventually characterized by clinical heart failure. MicroRNAs (miRNAs), endogenous small noncoding RNAs, play significant roles in diabetes mellitus (DM). However, it is still largely unknown about the mechanism that links miRNAs and the development of DCM. Here, we aimed to elucidate the mechanism underlying the potential role of microRNA-340-5p in DCM in db/db mouse, which is a commonly used model of type 2 DM and diabetic complications that lead to heart failure. We first demonstrated that miR-340-5p expression was dramatically increased in heart tissues of mice and cardiomyocytes under diabetic conditions. Overexpression of miR-340-5p exacerbated DCM, which was reflected by extensive myocardial fibrosis and more serious dysfunction in db/db mice as represented by increased apoptotic cardiomyocytes, elevated ROS production, and impaired mitochondrial function. Inhibition of miR-340-5p by a tough decoy (TUD) vector was beneficial for preventing ROS production and apoptosis, thus rescuing diabetic cardiomyopathy. We identified myeloid cell leukemia 1 (Mcl-1) as a major target gene for miR-340-5p and showed that the inhibition of Mcl-1 was responsible for increased functional loss of mitochondria, oxidative stress, and cardiomyocyte apoptosis, thereby caused cardiac dysfunction in diabetic mice. In conclusion, our results showed that miR-340-5p plays a crucial role in the development of DCM and can be targeted for therapeutic intervention.

Notoginsenoside R1 Protects Against High Glucose-Induced Cell Injury Through AMPK/Nrf2 and Downstream HO-1 Signaling

Notoginsenoside R1 (NGR1), the primary bioactive compound found in Panax notoginseng, is believed to have antihypertrophic and antiapoptotic properties, and has long been used to prevent and treat cardiovascular diseases. However, its potential role in prevention of diabetic cardiomyopathy remains unclear. The present study aimed to investigate the mechanism of NGR1 action in high glucose-induced cell injury. H9c2 cardiomyocytes were cultured in a high-glucose medium as an in-vitro model, and apoptotic cells were visualized using TUNEL staining. Expression of Nrf2 and HO-1 was measured using Western blotting or reverse transcription-quantitative PCR (RT-qPCR). The Nrf2 small interfering (si) RNA was transfected into cardiomyocytes using Opti-MEM containing Lipofectamine^® RNAiMAX. NGR1 protected H9c2 cardiomyocytes from cell death, apoptosis and hypertrophy induced by high glucose concentration. Expression of auricular natriuretic peptide and brain natriuretic peptide was remarkably reduced in NGR1-treated H9C2 cells. Western blot analysis showed that high glucose concentration markedly inhibited AMPK, Nrf2 and HO-1, and this could be reversed by NGR1 treatment. However, the cardioprotective effect of NGR1 was attenuated by compound C, which reverses Nrf2 and HO-1 expression levels, suggesting that AMPK upregulates Nrf2 and HO-1 gene expression, protein synthesis and secretion. Transfection of H9C2 cells with Nrf2 siRNA markedly reduced the cardioprotective effect of NGR1 via reduced expression of HO-1. These results indicated that NGR1 attenuated high glucose-induced cell injury via AMPK/Nrf2 signaling and its downstream target, the HO-1 pathway. We conclude that the cardioprotective effects of NGR1 result from upregulation of AMPK/Nrf2 signaling and HO-1 expression in cardiomyocytes. Our findings suggest that NGR1 treatment might provide a novel therapy for diabetic cardiomyopathy.