Endothelial cell-cardiomyocyte crosstalk in diabetic cardiomyopathy

Mitochondrial dysfunction in the pathogenesis of endothelial dysfunction

Cardiovascular diseases (CVDs) are a matter of concern worldwide, and mitochondrial dysfunction is one of the major contributing factors. Vascular endothelial dysfunction has a major role in the development of atherosclerosis because of the abnormal chemokine secretion, inflammatory mediators, enhancement of LDL oxidation, cytokine elevation, and smooth muscle cell proliferation. Endothelial cells transfer oxygen from the pulmonary circulatory system to the tissue surrounding the blood vessels, and a majority of oxygen is transferred to the myocardium by endothelial cells, which utilise a small amount of oxygen to generate ATP. Free radicals of oxide are produced by mitochondria, which are responsible for cellular oxygen uptake. Increased mitochondrial ROS generation and reduction in agonist-stimulated eNOS activation and nitric oxide bioavailability were directly linked to the observed change in mitochondrial dynamics, resulting in various CVDs and endothelial dysfunction. Presently, the manuscript mainly focuses on endothelial dysfunction, providing a deep understanding of the various features of mitochondrial mechanisms that are used to modulate endothelial dysfunction. We talk about recent findings and approaches that may make it possible to detect mitochondrial dysfunction as a potential biomarker for risk assessment and diagnosis of endothelial dysfunction. In the end, we cover several targets that may reduce mitochondrial dysfunction through both direct and indirect processes and assess the impact of several different classes of drugs in the context of endothelial dysfunction.

Heparanase Stimulation of Physiologic Cardiac Hypertrophy Is Suppressed After Chronic Diabetes, Resulting in Cardiac Remodeling and Dysfunction

In addition to controlling smooth muscle tone in coronary vessels, endothelial cells also influence subjacent cardiomyocyte growth. Because heparanase, with exclusive expression in endothelial cells, enables extracellular matrix remodeling, angiogenesis, metabolic reprogramming, and cell survival, it is conceivable that it could also encourage development of cardiac hypertrophy. Global heparanase overexpression resulted in physiologic cardiac hypertrophy, likely an outcome of HSPG clustering and activation of hypertrophic signaling. The heparanase autocrine effect of releasing neuregulin-1 could have also contributed to this overexpression. Hyperglycemia induced by streptozotocin-induced diabetes sensitized the heart to flow-induced release of heparanase and neuregulin-1. Despite this excess secretion, progression of diabetes caused significant gene expression changes related to mitochondrial metabolism and cell death that led to development of pathologic hypertrophy and heart dysfunction. Physiologic cardiac hypertrophy was also observed in rats with cardiomyocyte-specific vascular endothelial growth factor B overexpression. When perfused, hearts from these animals released significantly higher amounts of both heparanase and neuregulin-1. However, subjecting these animals to diabetes triggered robust transcriptome changes related to metabolism and a transition to pathologic hypertrophy. Our data suggest that in the absence of mechanisms that support cardiac energy generation and prevention of cell death, as seen after diabetes, there is a transition from physiologic to pathologic cardiac hypertrophy and a decline in cardiac function.

ARTICLE HIGHLIGHTS

Lipoprotein lipase as a target for obesity/diabetes related cardiovascular disease

Worldwide, the prevalence of obesity and diabetes have increased, with heart disease being their leading cause of death. Traditionally, the management of obesity and diabetes has focused mainly on weight reduction and controlling high blood glucose. Unfortunately, despite these efforts, poor medication management predisposes these patients to heart failure. One instigator for the development of heart failure is how cardiac tissue utilizes different sources of fuel for energy. In this regard, the heart switches from using various substrates, to predominantly using fatty acids (FA). This transformation to using FA as an exclusive source of energy is helpful in the initial stages of the disease. However, over the progression of diabetes this has grave end results. This is because toxic by-products are produced by overuse of FA, which weaken heart function (heart disease). Lipoprotein lipase (LPL) is responsible for regulating FA delivery to the heart, and its function during diabetes has not been completely revealed. In this review, the mechanisms by which LPL regulates fuel utilization by the heart in control conditions and following diabetes will be discussed in an attempt to identify new targets for therapeutic intervention. Currently, as treatment options to directly target diabetic heart disease are scarce, research on LPL may assist in drug development that exclusively targets fuel utilization by the heart and lipid accumulation in macrophages to help delay, prevent, or treat cardiac failure, and provide long-term management of this condition during diabetes.

Endothelial dysfunction in vascular complications of diabetes: a comprehensive review of mechanisms and implications

Diabetic vascular complications are prevalent and severe among diabetic patients, profoundly affecting both their quality of life and long-term prospects. These complications can be classified into macrovascular and microvascular complications. Under the impact of risk factors such as elevated blood glucose, blood pressure, and cholesterol lipids, the vascular endothelium undergoes endothelial dysfunction, characterized by increased inflammation and oxidative stress, decreased NO biosynthesis, endothelial-mesenchymal transition, senescence, and even cell death. These processes will ultimately lead to macrovascular and microvascular diseases, with macrovascular diseases mainly characterized by atherosclerosis (AS) and microvascular diseases mainly characterized by thickening of the basement membrane. It further indicates a primary contributor to the elevated morbidity and mortality observed in individuals with diabetes. In this review, we will delve into the intricate mechanisms that drive endothelial dysfunction during diabetes progression and its associated vascular complications. Furthermore, we will outline various pharmacotherapies targeting diabetic endothelial dysfunction in the hope of accelerating effective therapeutic drug discovery for early control of diabetes and its vascular complications.

Urine-derived stem cell therapy for diabetes mellitus and its complications: progress and challenges

Diabetes mellitus (DM) is a chronic and relentlessly progressive metabolic disease characterized by a relative or absolute deficiency of insulin in the body, leading to increased production of advanced glycosylation end products that further enhance oxidative and nitrosative stresses, often leading to multiple macrovascular (cardiovascular disease) and microvascular (e.g., diabetic nephropathy, diabetic retinopathy, and neuropathy) complications, representing the ninth leading cause of death worldwide. Existing medical treatments do not provide a complete cure for DM; thus, stem cell transplantation therapy has become the focus of research on DM and its complications. Urine-derived stem cells (USCs), which are isolated from fresh urine and have biological properties similar to those of mesenchymal stem cells (MSCs), were demonstrated to exert antiapoptotic, antifibrotic, anti-inflammatory, and proangiogenic effects through direct differentiation or paracrine mechanisms and potentially treat patients with DM. USCs also have the advantages of simple noninvasive sample collection procedures, minimal ethical issues, low cost, and easy cell isolation methods and thus have received more attention in regenerative therapies in recent years. This review outlines the biological properties of USCs and the research progress and current limitations of their role in DM and related complications. In summary, USCs have shown good versatility in treating hyperglycemia-impaired target organs in preclinical models, and many challenges remain in translating USC therapies to the clinic.

Reduction in Insulin Uncovers a Novel Effect of VEGFB on Cardiac Substrate Utilization

BACKGROUND

The heart relies heavily on external fatty acid (FA) for energy production. VEGFB (vascular endothelial growth factor B) has been shown to promote endothelial FA uptake by upregulating FA transporters. However, its impact on LPL (lipoprotein lipase)-mediated lipolysis of lipoproteins, a major source of FA for cardiac use, is unknown.

METHODS

VEGFB transgenic (Tg) rats were generated by using the α-myosin heavy chain promoter to drive cardiomyocyte-specific overexpression. To measure coronary LPL activity, Langendorff hearts were perfused with heparin. In vivo positron emission tomography imaging with [18F]-triglyceride-fluoro-6-thia-heptadecanoic acid and [11C]-palmitate was used to determine cardiac FA uptake. Mitochondrial FA oxidation was evaluated by high-resolution respirometry. Streptozotocin was used to induce diabetes, and cardiac function was monitored using echocardiography.

RESULTS

In Tg hearts, the vectorial transfer of LPL to the vascular lumen is obstructed, resulting in LPL buildup within cardiomyocytes, an effect likely due to coronary vascular development with its associated augmentation of insulin action. With insulin insufficiency following fasting, VEGFB acted unimpeded to facilitate LPL movement and increase its activity at the coronary lumen. In vivo PET imaging following fasting confirmed that VEGFB induced a greater FA uptake to the heart from circulating lipoproteins as compared with plasma-free FAs. As this was associated with augmented mitochondrial oxidation, lipid accumulation in the heart was prevented. We further examined whether this property of VEGFB on cardiac metabolism could be useful following diabetes and its associated cardiac dysfunction, with attendant loss of metabolic flexibility. In Tg hearts, diabetes inhibited myocyte VEGFB gene expression and protein secretion together with its downstream receptor signaling, effects that could explain its lack of cardioprotection.

CONCLUSIONS

Our study highlights the novel role of VEGFB in LPL-derived FA supply and utilization. In diabetes, loss of VEGFB action may contribute toward metabolic inflexibility, lipotoxicity, and development of diabetic cardiomyopathy.

Fetoplacental endothelial dysfunction in gestational diabetes mellitus and maternal obesity: A potential threat for programming cardiovascular disease

Gestational diabetes mellitus (GDM) and maternal obesity (MO) increase the risk of adverse fetal outcomes, and the incidence of cardiovascular disease later in life. Extensive research has been conducted to elucidate the underlying mechanisms by which GDM and MO program the offspring to disease. This review focuses on the role of fetoplacental endothelial dysfunction in programming the offspring for cardiovascular disease in GDM and MO pregnancies. We discuss how pre-existing maternal health conditions can lead to vascular dysfunction in the fetoplacental unit and the fetus. We also examine the role of fetoplacental endothelial dysfunction in impairing fetal cardiovascular system development and the involvement of nitric oxide and hydrogen sulfide in mediating fetoplacental vascular dysfunction. Furthermore, we suggest that the L-Arginine-Nitric Oxide and the Adenosine-L-Arginine-Nitric Oxide (ALANO) signaling pathways are pertinent targets for research. Despite significant progress in this area, there are still knowledge gaps that need to be addressed in future research.

Unraveling the Intricate Roles of Exosomes in Cardiovascular Diseases: A Comprehensive Review of Physiological Significance and Pathological Implications

Exosomes, as potent intercellular communication tools, have garnered significant attention due to their unique cargo-carrying capabilities, which enable them to influence diverse physiological and pathological functions. Extensive research has illuminated the biogenesis, secretion, and functions of exosomes. These vesicles are secreted by cells in different states, exerting either protective or harmful biological functions. Emerging evidence highlights their role in cardiovascular disease (CVD) by mediating comprehensive interactions among diverse cell types. This review delves into the significant impacts of exosomes on CVD under stress and disease conditions, including coronary artery disease (CAD), myocardial infarction, heart failure, and other cardiomyopathies. Focusing on the cellular signaling and mechanisms, we explore how exosomes mediate multifaceted interactions, particularly contributing to endothelial dysfunction, oxidative stress, and apoptosis in CVD pathogenesis. Additionally, exosomes show great promise as biomarkers, reflecting differential expressions of NcRNAs (miRNAs, lncRNAs, and circRNAs), and as therapeutic carriers for targeted CVD treatment. However, the specific regulatory mechanisms governing exosomes in CVD remain incomplete, necessitating further exploration of their characteristics and roles in various CVD-related contexts. This comprehensive review aims to provide novel insights into the biological implications of exosomes in CVD and offer innovative perspectives on the diagnosis and treatment of CVD.

Heparanase-A single protein with multiple enzymatic and nonenzymatic functions

Heparanase (Hpa1) is expressed by tumor cells and cells of the tumor microenvironment and functions extracellularly to remodel the extracellular matrix (ECM) and regulate the bioavailability of ECM-bound factors, augmenting, among other effects, gene transcription, autophagy, exosome formation, and heparan sulfate (HS) turnover. Much of the impact of heparanase on tumor progression is related to its function in mediating tumor-host crosstalk, priming the tumor microenvironment to better support tumor growth, metastasis, and chemoresistance. The enzyme appears to fulfill some normal functions associated, for example, with vesicular traffic, lysosomal-based secretion, autophagy, HS turnover, and gene transcription. It activates cells of the innate immune system, promotes the formation of exosomes and autophagosomes, and stimulates signal transduction pathways via enzymatic and nonenzymatic activities. These effects dynamically impact multiple regulatory pathways that together drive tumor growth, dissemination, and drug resistance as well as inflammatory responses. The emerging premise is that heparanase expressed by tumor cells, immune cells, endothelial cells, and other cells of the tumor microenvironment is a key regulator of the aggressive phenotype of cancer, an important contributor to the poor outcome of cancer patients and a valid target for therapy. So far, however, antiheparanase-based therapy has not been implemented in the clinic. Unlike heparanase, heparanase-2 (Hpa2), a close homolog of heparanase (Hpa1), does not undergo proteolytic processing and hence lacks intrinsic HS-degrading activity, the hallmark of heparanase. Hpa2 retains the capacity to bind heparin/HS and exhibits an even higher affinity towards HS than heparanase, thus competing for HS binding and inhibiting heparanase enzymatic activity. It appears that Hpa2 functions as a natural inhibitor of Hpa1 regulates the expression of selected genes that maintain tissue hemostasis and normal function, and plays a protective role against cancer and inflammation, together emphasizing the significance of maintaining a proper balance between Hpa1 and Hpa2.

Role of vascular endothelial growth factor B in nonalcoholic fatty liver disease and its potential value

Nonalcoholic fatty liver disease (NAFLD) refers to fatty liver disease caused by liver injury factors other than alcohol. The disease is characterized by diffuse fat infiltration, including simple steatosis (no inflammatory fat deposition), nonalcoholic fatty hepatitis, liver fibrosis, and so on, which may cause liver cirrhosis, liver failure, and even liver cancer in the later stage of disease progression. At present, the pathogenesis of NAFLD is still being studied. The "two-hit" theory, represented by lipid metabolism disorder and inflammatory reactions, is gradually enriched by the "multiple-hit" theory, which includes multiple factors, such as insulin resistance and adipocyte dysfunction. In recent years, vascular endothelial growth factor B (VEGFB) has been reported to have the potential to regulate lipid metabolism and is expected to become a novel target for ameliorating metabolic diseases, such as obesity and type 2 diabetes. This review summarizes the regulatory role of VEGFB in the onset and development of NAFLD and illustrates its underlying molecular mechanism. In conclusion, the signaling pathway mediated by VEGFB in the liver may provide an innovative approach to the diagnosis and treatment of NAFLD.

The role of the microcirculation and integrative cardiovascular physiology in the pathogenesis of ICU-acquired weakness

Skeletal muscle dysfunction after critical illness, defined as ICU-acquired weakness (ICU-AW), is a complex and multifactorial syndrome that contributes significantly to long-term morbidity and reduced quality of life for ICU survivors and caregivers. Historically, research in this field has focused on pathological changes within the muscle itself, without much consideration for their in vivo physiological environment. Skeletal muscle has the widest range of oxygen metabolism of any organ, and regulation of oxygen supply with tissue demand is a fundamental requirement for locomotion and muscle function. During exercise, this process is exquisitely controlled and coordinated by the cardiovascular, respiratory, and autonomic systems, and also within the skeletal muscle microcirculation and mitochondria as the terminal site of oxygen exchange and utilization. This review highlights the potential contribution of the microcirculation and integrative cardiovascular physiology to the pathogenesis of ICU-AW. An overview of skeletal muscle microvascular structure and function is provided, as well as our understanding of microvascular dysfunction during the acute phase of critical illness; whether microvascular dysfunction persists after ICU discharge is currently not known. Molecular mechanisms that regulate crosstalk between endothelial cells and myocytes are discussed, including the role of the microcirculation in skeletal muscle atrophy, oxidative stress, and satellite cell biology. The concept of integrated control of oxygen delivery and utilization during exercise is introduced, with evidence of physiological dysfunction throughout the oxygen delivery pathway - from mouth to mitochondria - causing reduced exercise capacity in patients with chronic disease (e.g., heart failure, COPD). We suggest that objective and perceived weakness after critical illness represents a physiological failure of oxygen supply-demand matching - both globally throughout the body and locally within skeletal muscle. Lastly, we highlight the value of standardized cardiopulmonary exercise testing protocols for evaluating fitness in ICU survivors, and the application of near-infrared spectroscopy for directly measuring skeletal muscle oxygenation, representing potential advancements in ICU-AW research and rehabilitation.

The role of histone deacetylases in cardiac energy metabolism in heart diseases

Heart diseases are associated with substantial morbidity and mortality worldwide. The underlying mechanisms and pathological changes associated with cardiac diseases are exceptionally complex. Highly active cardiomyocytes require sufficient energy metabolism to maintain their function. Under physiological conditions, the choice of fuel is a delicate process that depends on the whole body and organs to support the normal function of heart tissues. However, disordered cardiac metabolism has been discovered to play a key role in many forms of heart diseases, including ischemic heart disease, cardiac hypertrophy, heart failure, and cardiac injury induced by diabetes or sepsis. Regulation of cardiac metabolism has recently emerged as a novel approach to treat heart diseases. However, little is known about cardiac energy metabolic regulators. Histone deacetylases (HDACs), a class of epigenetic regulatory enzymes, are involved in the pathogenesis of heart diseases, as reported in previous studies. Notably, the effects of HDACs on cardiac energy metabolism are gradually being explored. Our knowledge in this respect would facilitate the development of novel therapeutic strategies for heart diseases. The present review is based on the synthesis of our current knowledge concerning the role of HDAC regulation in cardiac energy metabolism in heart diseases. In addition, the role of HDACs in different models is discussed through the examples of myocardial ischemia, ischemia/reperfusion, cardiac hypertrophy, heart failure, diabetic cardiomyopathy, and diabetes- or sepsis-induced cardiac injury. Finally, we discuss the application of HDAC inhibitors in heart diseases and further prospects, thus providing insights into new treatment possibilities for different heart diseases.

FGF21/FGFR1-β-KL cascade in cardiomyocytes modulates angiogenesis and inflammation under metabolic stress

Diabetes is a metabolic disorder with an increased risk of developing heart failure. Inflammation and damaged vasculature are the cardinal features of diabetes-induced cardiac damage. Moreover, systemic metabolic stress triggers discordant intercellular communication, thus culminating in cardiac dysfunction. Fibroblast growth factor 21 (FGF21) is a pleiotropic hormone transducing cellular signals via fibroblast growth factor receptor 1 (FGFR1) and its co-receptor beta-klotho (β-KL). This study first demonstrated a decreased expression or activity of FGFR1 and β-KL in both human and mouse diabetic hearts. Reinforcing cardiac FGFR1 and β-KL expression can alleviate pro-inflammatory response and endothelial dysfunction upon diabetic stress. Using proteomics, novel cardiomyocyte-derived anti-inflammatory and proangiogenic factors regulated by FGFR1-β-KL signaling were identified. Although not exhaustive, this study provides a unique insight into the protective topology of the cardiac FGFR1-β-KL signaling-mediated intercellular reactions in the heart in response to metabolic stress.

COVID-19 mRNA Vaccines: The Molecular Basis of Some Adverse Events

Each injection of any known vaccine results in a strong expression of pro-inflammatory cytokines. This is the result of the innate immune system activation, without which no adaptive response to the injection of vaccines is possible. Unfortunately, the degree of inflammation produced by COVID-19 mRNA vaccines is variable, probably depending on genetic background and previous immune experiences, which through epigenetic modifications could have made the innate immune system of each individual tolerant or reactive to subsequent immune stimulations.We hypothesize that we can move from a limited pro-inflammatory condition to conditions of increasing expression of pro-inflammatory cytokines that can culminate in multisystem hyperinflammatory syndromes following COVID-19 mRNA vaccines (MIS-V). We have graphically represented this idea in a hypothetical inflammatory pyramid (IP) and we have correlated the time factor to the degree of inflammation produced after the injection of vaccines. Furthermore, we have placed the clinical manifestations within this hypothetical IP, correlating them to the degree of inflammation produced. Surprisingly, excluding the possible presence of an early MIS-V, the time factor and the complexity of clinical manifestations are correlated to the increasing degree of inflammation: symptoms, heart disease and syndromes (MIS-V).

Deciphering endothelial heterogeneity in health and disease at single-cell resolution: progress and perspectives

Endothelial cells (ECs) constitute the inner lining of vascular beds in mammals and are crucial for homeostatic regulation of blood vessel physiology, but also play a key role in pathogenesis of many diseases, thereby representing realistic therapeutic targets. However, it has become evident that ECs are heterogeneous, encompassing several subtypes with distinct functions, which makes EC targeting and modulation in diseases challenging. The rise of the new single-cell era has led to an emergence of studies aimed at interrogating transcriptome diversity along the vascular tree, and has revolutionized our understanding of EC heterogeneity from both a physiological and pathophysiological context. Here, we discuss recent landmark studies aimed at teasing apart the heterogeneous nature of ECs. We cover driving (epi)genetic, transcriptomic, and metabolic forces underlying EC heterogeneity in health and disease, as well as current strategies used to combat disease-enriched EC phenotypes, and propose strategies to transcend largely descriptive heterogeneity towards prioritization and functional validation of therapeutically targetable drivers of EC diversity. Lastly, we provide an overview of the most recent advances and hurdles in single EC OMICs.

The regulation of cardiac intermediary metabolism by NADPH oxidases

NADPH oxidases (NOXs), enzymes whose primary function is to generate reactive oxygen species, are important regulators of the heart's physiological function and response to pathological insults. The role of NOX-driven redox signalling in pathophysiological myocardial remodelling, including processes such as interstitial fibrosis, contractile dysfunction, cellular hypertrophy, and cell survival, is well recognized. While the NOX2 isoform promotes many detrimental effects, the NOX4 isoform has attracted considerable attention as a driver of adaptive stress responses both during pathology and under physiological states such as exercise. Recent studies have begun to define some of the NOX4-modulated mechanisms that may underlie these adaptive responses. In particular, novel functions of NOX4 in driving cellular metabolic changes have emerged. Alterations in cellular metabolism are a recognized hallmark of the heart's response to physiological and pathological stresses. In this review, we highlight the emerging roles of NOX enzymes as important modulators of cellular intermediary metabolism in the heart, linking stress responses not only to myocardial energetics but also other functions. The novel interplay of NOX-modulated redox signalling pathways and intermediary metabolism in the heart is unravelling a new aspect of the fascinating biology of these enzymes which will inform a better understanding of how they drive adaptive responses. We also discuss the implications of these new findings for therapeutic approaches that target metabolism in cardiac disease.

Flow-Induced Secretion of Endothelial Heparanase Regulates Cardiac Lipoprotein Lipase and Changes Following Diabetes

Background Lipoprotein lipase (LPL)-derived fatty acid is a major source of energy for cardiac contraction. Synthesized in cardiomyocytes, LPL requires translocation to the vascular lumen for hydrolysis of lipoprotein triglyceride, an action mediated by endothelial cell (EC) release of heparanase. We determined whether flow-mediated biophysical forces can cause ECs to secrete heparanase and thus regulate cardiac metabolism. Methods and Results Isolated hearts were retrogradely perfused. Confluent rat aortic ECs were exposed to laminar flow using an orbital shaker. Cathepsin L activity was determined using gelatin-zymography. Diabetes was induced in rats with streptozotocin. Despite the abundance of enzymatically active heparanase in the heart, it was the enzymatically inactive, latent heparanase that was exceptionally responsive to flow-induced release. EC exposed to orbital rotation exhibited a similar pattern of heparanase secretion, an effect that was reproduced by activation of the mechanosensor, Piezo1. The laminar flow-mediated release of heparanase from EC required activation of both the purinergic receptor and protein kinase D, a kinase that assists in vesicular transport of proteins. Heparanase influenced cardiac metabolism by increasing cardiomyocyte LPL displacement along with subsequent replenishment. The flow-induced heparanase secretion was augmented following diabetes and could explain the increased heparin-releasable pool of LPL at the coronary lumen in these diabetic hearts. Conclusions ECs sense fluid shear-stress and communicate this information to subjacent cardiomyocytes with the help of heparanase. This flow-induced mechanosensing and its dynamic control of cardiac metabolism to generate ATP, using LPL-derived fatty acid, is exquisitely adapted to respond to disease conditions, like diabetes.

Neuregulin-1, a potential therapeutic target for cardiac repair

NRG1 (Neuregulin-1) is an effective cardiomyocyte proliferator, secreted and released by endothelial vascular cells, and affects the cardiovascular system. It plays a major role in heart growth, proliferation, differentiation, apoptosis, and other cardiovascular processes. Numerous experiments have shown that NRG1 can repair the heart in the pathophysiology of atherosclerosis, myocardial infarction, ischemia reperfusion, heart failure, cardiomyopathy and other cardiovascular diseases. NRG1 can connect related signaling pathways through the NRG1/ErbB pathway, which form signal cascades to improve the myocardial microenvironment, such as regulating cardiac inflammation, oxidative stress, necrotic apoptosis. Here, we summarize recent research advances on the molecular mechanisms of NRG1, elucidate the contribution of NRG1 to cardiovascular disease, discuss therapeutic approaches targeting NRG1 associated with cardiovascular disease, and highlight areas for future research.

The heart-brain axis: A proteomics study of meditation on the cardiovascular system of Tibetan Monks

Background

There have been mixed reports on the beneficial effects of meditation in cardiovascular disease (CVD), which is widely considered the leading cause of death worldwide.

Methods

To clarify the role of meditation in modulating the heart-brain axis, we implemented an extreme phenotype strategy, i.e., Tibetan monks (BMI > 30) who practised 19.20 ± 7.82 years of meditation on average and their strictly matched non-meditative Tibetan controls. Hypothesis-free advanced proteomics strategies (Data Independent Acquisition and Targeted Parallel Reaction Monitoring) were jointly applied to systematically investigate and target the plasma proteome underlying meditation. Total cholesterol, low-density lipoprotein cholesterol  (LDL-C), apolipoprotein B (Apo B) and lipoprotein (a) [Lp(a)] as the potential cardiovascular risk factors were evaluated. Heart rate variability (HRV) was assessed by electrocardiogram.

Findings

Obesity, hypertension, and reduced HRV is offset by long-term meditation. Notably, meditative monks have blood pressure and HRV comparable to their matched Tibetan controls. Meditative monks have a protective plasma proteome, related to decreased atherosclerosis, enhanced glycolysis, and oxygen release, that confers resilience to the development of CVD. In addition, clinical risk factors in plasma were significantly decreased in monks compared with controls, including total cholesterol, LDL-C, Apo B, and Lp(a).

Interpretation

To our knowledge, this work is the first well-controlled proteomics investigation of long-term meditation, which opens up a window for individuals characterized by a sedentary lifestyle to improve their cardiovascular health with an accessible method practised for more than two millennia.

Funding

See the Acknowledgements section.

Cellular interplay between cardiomyocytes and non-myocytes in diabetic cardiomyopathy

Patients with Type 2 diabetes mellitus (T2DM) frequently exhibit a distinctive cardiac phenotype known as diabetic cardiomyopathy. Cardiac complications associated with T2DM include cardiac inflammation, hypertrophy, fibrosis and diastolic dysfunction in the early stages of the disease, which can progress to systolic dysfunction and heart failure. Effective therapeutic options for diabetic cardiomyopathy are limited and often have conflicting results. The lack of effective treatments for diabetic cardiomyopathy is due in part, to our poor understanding of the disease development and progression, as well as a lack of robust and valid preclinical human models that can accurately recapitulate the pathophysiology of the human heart. In addition to cardiomyocytes, the heart contains a heterogeneous population of non-myocytes including fibroblasts, vascular cells, autonomic neurons and immune cells. These cardiac non-myocytes play important roles in cardiac homeostasis and disease, yet the effect of hyperglycaemia and hyperlipidaemia on these cell types are often overlooked in preclinical models of diabetic cardiomyopathy. The advent of human induced pluripotent stem cells provides a new paradigm in which to model diabetic cardiomyopathy as they can be differentiated into all cell types in the human heart. This review will discuss the roles of cardiac non-myocytes and their dynamic intercellular interactions in the pathogenesis of diabetic cardiomyopathy. We will also discuss the use of sodium-glucose cotransporter 2 inhibitors as a therapy for diabetic cardiomyopathy and their known impacts on non-myocytes. These developments will no doubt facilitate the discovery of novel treatment targets for preventing the onset and progression of diabetic cardiomyopathy.

Reactive Oxygen Species-Mediated Diabetic Heart Disease: Mechanisms and Therapies

Significance: Diabetic heart disease (DHD) is the primary cause of mortality in people with diabetes. A significant contributor to the development of DHD is the disruption of redox balance due to reactive oxygen species (ROS) overproduction resulting from sustained high glucose levels. Therapies specifically focusing on the suppression of ROS will hugely benefit patients with DHD. Recent Advances: In addition to the gold standard pharmacological therapies, the recent development of gene therapy provides an exciting avenue for developing new therapeutics to treat ROS-mediated DHD. In particular, microRNAs (miRNAs) are gaining interest due to their crucial role in several physiological and pathological processes, including DHD. Critical Issues: miRNAs have many targets and differential function depending on the environment. Therefore, a proper understanding of the function of miRNAs in specific cell types and cell states is required for the successful application of this technology. In the present review, we first provide an overview of the role of ROS in contributing to DHD and the currently available treatments. We then discuss the newer gene therapies with a specific focus on the role of miRNAs as the causative factors and therapeutic targets to combat ROS-mediated DHD. Future Directions: The future of miRNA therapeutics in tackling ROS-mediated DHD is dependent on a complete understanding of how miRNAs behave in different cells and environments. Future research should also aim to develop conditional miRNA therapeutic platforms capable of switching on and off in response to disruptions in the redox state. Antioxid. Redox Signal. 36, 608-630.

Does optimal HbA1c in diabetes differ according to drug treatment? An evaluation of national electronic database in Malta

BACKGROUND AND AIMS

A J-shaped relationship between HbA_1c and mortality has been reported in subjects with type 2 diabetes. The postulated mechanism linking low HbA_1c with increased mortality is increased hypoglycaemia risk. We tested this hypothesis by comparing the relationship between low HbA_1c to mortality in patients on therapies with different hypoglycaemia risk.

METHODS

We selected patients on any type of treatment for diabetes from a national electronic database (n = 25,743) and linked to other databases, including laboratory database and the national mortality register.

RESULTS

We observed a J-shaped or U-shaped association between HbA_1c and all-cause mortality in the whole type 2 diabetes patient cohort as well as in patients on metformin monotherapy and in those on metformin-sulphonylurea combination therapy, but not in subjects on sulphonylurea monotherapy or in those on insulin.

CONCLUSIONS

Our data confirm the J-shaped relationship between HbA_1c and mortality in type 2 diabetes, but suggest that a low HbA_1c is deleterious even in absence of hypoglycaemia and that subjects with type 2 diabetes might require a slightly elevated blood glucose for optimal outcome. Our data also suggest that the increased mortality associated with sulphonylureas cannot be mediated solely through increased hypoglycaemia risk.

MiR-30 promotes fatty acid beta-oxidation and endothelial cell dysfunction and is a circulating biomarker of coronary microvascular dysfunction in pre-clinical models of diabetes

Background

Type 2 diabetes (T2D) is associated with coronary microvascular dysfunction, which is thought to contribute to compromised diastolic function, ultimately culminating in heart failure with preserved ejection fraction (HFpEF). The molecular mechanisms remain incompletely understood, and no early diagnostics are available. We sought to gain insight into biomarkers and potential mechanisms of microvascular dysfunction in obese mouse (db/db) and lean rat (Goto-Kakizaki) pre-clinical models of T2D-associated diastolic dysfunction.

Methods

The microRNA (miRNA) content of circulating extracellular vesicles (EVs) was assessed in T2D models to identify biomarkers of coronary microvascular dysfunction/rarefaction. The potential source of circulating EV-encapsulated miRNAs was determined, and the mechanisms of induction and the function of candidate miRNAs were assessed in endothelial cells (ECs).

Results

We found an increase in miR-30d-5p and miR-30e-5p in circulating EVs that coincided with indices of coronary microvascular EC dysfunction (i.e., markers of oxidative stress, DNA damage/senescence) and rarefaction, and preceded echocardiographic evidence of diastolic dysfunction. These miRNAs may serve as biomarkers of coronary microvascular dysfunction as they are upregulated in ECs of the left ventricle of the heart, but not other organs, in db/db mice. Furthermore, the miR-30 family is secreted in EVs from senescent ECs in culture, and ECs with senescent-like characteristics are present in the db/db heart. Assessment of miR-30 target pathways revealed a network of genes involved in fatty acid biosynthesis and metabolism. Over-expression of miR-30e in cultured ECs increased fatty acid β-oxidation and the production of reactive oxygen species and lipid peroxidation, while inhibiting the miR-30 family decreased fatty acid β-oxidation. Additionally, miR-30e over-expression synergized with fatty acid exposure to down-regulate the expression of eNOS, a key regulator of microvascular and cardiomyocyte function. Finally, knock-down of the miR-30 family in db/db mice decreased markers of oxidative stress and DNA damage/senescence in the microvascular endothelium.

Conclusions

MiR-30d/e represent early biomarkers and potential therapeutic targets that are indicative of the development of diastolic dysfunction and may reflect altered EC fatty acid metabolism and microvascular dysfunction in the diabetic heart.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-022-01458-z.

MiR-30 promotes fatty acid beta-oxidation and endothelial cell dysfunction and is a circulating biomarker of coronary microvascular dysfunction in pre-clinical models of diabetes

BACKGROUND

Type 2 diabetes (T2D) is associated with coronary microvascular dysfunction, which is thought to contribute to compromised diastolic function, ultimately culminating in heart failure with preserved ejection fraction (HFpEF). The molecular mechanisms remain incompletely understood, and no early diagnostics are available. We sought to gain insight into biomarkers and potential mechanisms of microvascular dysfunction in obese mouse (db/db) and lean rat (Goto-Kakizaki) pre-clinical models of T2D-associated diastolic dysfunction.

METHODS

The microRNA (miRNA) content of circulating extracellular vesicles (EVs) was assessed in T2D models to identify biomarkers of coronary microvascular dysfunction/rarefaction. The potential source of circulating EV-encapsulated miRNAs was determined, and the mechanisms of induction and the function of candidate miRNAs were assessed in endothelial cells (ECs).

RESULTS

We found an increase in miR-30d-5p and miR-30e-5p in circulating EVs that coincided with indices of coronary microvascular EC dysfunction (i.e., markers of oxidative stress, DNA damage/senescence) and rarefaction, and preceded echocardiographic evidence of diastolic dysfunction. These miRNAs may serve as biomarkers of coronary microvascular dysfunction as they are upregulated in ECs of the left ventricle of the heart, but not other organs, in db/db mice. Furthermore, the miR-30 family is secreted in EVs from senescent ECs in culture, and ECs with senescent-like characteristics are present in the db/db heart. Assessment of miR-30 target pathways revealed a network of genes involved in fatty acid biosynthesis and metabolism. Over-expression of miR-30e in cultured ECs increased fatty acid β-oxidation and the production of reactive oxygen species and lipid peroxidation, while inhibiting the miR-30 family decreased fatty acid β-oxidation. Additionally, miR-30e over-expression synergized with fatty acid exposure to down-regulate the expression of eNOS, a key regulator of microvascular and cardiomyocyte function. Finally, knock-down of the miR-30 family in db/db mice decreased markers of oxidative stress and DNA damage/senescence in the microvascular endothelium.

CONCLUSIONS

MiR-30d/e represent early biomarkers and potential therapeutic targets that are indicative of the development of diastolic dysfunction and may reflect altered EC fatty acid metabolism and microvascular dysfunction in the diabetic heart.

Human-induced pluripotent stem cells in cardiovascular research: current approaches in cardiac differentiation, maturation strategies, and scalable production

Manifestations of cardiovascular diseases (CVDs) in a patient or a population differ based on inherent biological makeup, lifestyle, and exposure to environmental risk factors. These variables mean that therapeutic interventions may not provide the same benefit to every patient. In the context of CVDs, human-induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) offer an opportunity to model CVDs in a patient-specific manner. From a pharmacological perspective, iPSC-CM models can serve as go/no-go tests to evaluate drug safety. To develop personalized therapies for early diagnosis and treatment, human-relevant disease models are essential. Hence, to implement and leverage the utility of iPSC-CMs for large-scale treatment or drug discovery, it is critical to (i) carefully evaluate the relevant limitations of iPSC-CM differentiations, (ii) establish quality standards for defining the state of cell maturity, and (iii) employ techniques that allow scalability and throughput with minimal batch-to-batch variability. In this review, we briefly describe progress made with iPSC-CMs in disease modelling and pharmacological testing, as well as current iPSC-CM maturation techniques. Finally, we discuss current platforms for large-scale manufacturing of iPSC-CMs that will enable high-throughput drug screening applications.

Cardiac-specific VEGFB overexpression reduces lipoprotein lipase activity and improves insulin action in rat heart

Cardiac muscle uses multiple sources of energy including glucose and fatty acid (FA). The heart cannot synthesize FA and relies on obtaining it from other sources, with lipoprotein lipase (LPL) breakdown of lipoproteins suggested to be a key source of FA for cardiac use. Recent work has indicated that cardiac vascular endothelial growth factor B (VEGFB) overexpression expands the coronary vasculature and facilitates metabolic reprogramming that favors glucose utilization. We wanted to explore whether this influence of VEGFB on cardiac metabolism involves regulation of LPL activity with consequent effects on lipotoxicity and insulin signaling. The transcriptomes of rats with and without cardiomyocyte-specific overexpression of human VEGFB were compared by using RNA sequencing. Isolated perfused hearts or cardiomyocytes incubated with heparin were used to enable measurement of LPL activity. Untargeted metabolomic analysis was performed for quantification of cardiac lipid metabolites. Cardiac insulin sensitivity was evaluated using fast-acting insulin. Isolated heart and cardiomyocytes were used to determine transgene-encoded VEGFB isoform secretion patterns and mitochondrial oxidative capacity using high-resolution respirometry and extracellular flux analysis. In vitro, transgenic cardiomyocytes incubated overnight and thus exposed to abundantly secreted VEGFB isoforms, in the absence of any in vivo confounding regulators of cardiac metabolism, demonstrated higher basal oxygen consumption. In the whole heart, VEGFB overexpression induced an angiogenic response that was accompanied by limited cardiac LPL activity through multiple mechanisms. This was associated with a lowered accumulation of lipid intermediates, diacylglycerols and lysophosphatidylcholine, that are known to influence insulin action. In response to exogenous insulin, transgenic hearts demonstrated increased insulin sensitivity. In conclusion, the interrogation of VEGFB function on cardiac metabolism uncovered an intriguing and previously unappreciated effect to lower LPL activity and prevent lipid metabolite accumulation to improve insulin action. VEGFB could be a potential cardioprotective therapy to treat metabolic disorders, for example, diabetes.NEW & NOTEWORTHY In hearts overexpressing vascular endothelial growth factor B (VEGFB), besides its known angiogenic response, multiple regulatory mechanisms lowered coronary LPL. This was accompanied by limited cardiac lipid metabolite accumulation with an augmentation of cardiac insulin action. Our data for the first time links VEGFB to coronary LPL in regulation of cardiac metabolism. VEGFB may be cardioprotective in metabolic disorders like diabetes.

Regulatory role of TIGAR on endothelial metabolism and angiogenesis

Endothelial glycolytic metabolism plays an important role in the process of angiogenesis. TP53-induced glycolysis and apoptosis regulator (TIGAR) is a significant mediator of cellular energy homeostasis. However, the role of TIGAR in endothelial metabolism, angiogenesis, and coronary flow reserve (CFR) has not been studied. The present study investigated whether knockout (KO) of TIGAR improves endothelial glycolytic function and angiogenesis. In vitro, aortic endothelial cells (ECs) from TIGAR KO mice exhibited increased expression of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase isoform-3 (PFKFB3) and increased glycolytic function. These were accompanied by increased mitochondrial basal/maximal respiration and ATP production. Furthermore, knockout of TIGAR in ECs enhanced endothelial proliferation, migration, and tube formation. Knockout of TIGAR also significantly increased aortic sprouting ex vivo. In vivo, knockout of TIGAR increased the expression of proangiogenic factor, angiopoietin-1 (Ang-1) in mouse hearts. Knockout of TIGAR also significantly increased coronary capillary density with enhanced CFR in these hearts. Furthermore, TIGAR KO mice subjected to pressure overload (PO), a common model to study angiogenesis and cardiac hypertrophy, exhibited elevated expression of Ang-1, VEGF, and PFKFB3 than that of the wild-type (WT) mice. WT mice subjected to PO exhibited a significant reduction of coronary capillary density and impaired CFR, but TIGAR KO mice did not. In addition, knockout of TIGAR blunted TAC-induced cardiac hypertrophy and dysfunction seen in the WT mice. In conclusion, knockout of TIGAR improves endothelial angiogenetic capabilities by enhancing the endothelial glycolytic function, mitochondrial respiration, and proangiogenic signaling, which leads to increased coronary capillary density and vascular function and protects against chronic stress.

S-Propargyl-Cysteine Attenuates Diabetic Cardiomyopathy in db/db Mice Through Activation of Cardiac Insulin Receptor Signaling

Background: Endogenous hydrogen sulfide (H₂S) is emerging as a key signal molecule in the development of diabetic cardiomyopathy. The aim of this study was to explore the effect and underlying mechanism of S-propargyl-cysteine (SPRC), a novel modulator of endogenous H₂S, on diabetic cardiomyopathy in db/db diabetic mice.

Methods and Results: Vehicle or SPRC were orally administered to 8-month-old male db/db mice and their wild type littermate for 12 weeks. SPRC treatment ameliorated myocardial hypertrophy, fibrosis, and cardiac systolic dysfunction assessed by histopathological examinations and echocardiography. The functional improvement by SPRC was accompanied by a reduction in myocardial lipid accumulation and ameliorated plasma lipid profiles. SPRC treatment improved glucose tolerance in db/db mice, with fasting blood glucose and peripheral insulin resistance remaining unchanged. Furthermore, insulin receptor signaling involving the phosphorylation of protein kinase B (Akt/PKB) and glycogen synthase kinase 3β (GSK3β) were elevated and activated by SPRC treatment. Primary neonatal mice cardiomyocytes were cultured to explore the mechanisms of SPRC on diabetic cardiomyopathy in vitro. Consistent with the results in vivo, SPRC not only up-regulated insulin receptor signaling pathway in cardiomyocytes in dose-dependent manner in the basal state, but also relieved the suppression of insulin receptor signaling induced by high concentrations of glucose and insulin. Furthermore, SPRC also enhanced the expression of glucose transporter 4 (GLUT4) and ³H glucose uptake in cardiomyocytes.

Conclusions: In this study, we found a novel beneficial effect of SPRC on diabetic cardiomyopathy, which was associated with activation of insulin receptor signaling. SPRC may be a promising medication for diabetic cardiomyopathy in type 2 diabetes mellitus patients.

Emergence of SGLT2 Inhibitors as Powerful Antioxidants in Human Diseases

Sodium-glucose cotransporter 2 (SGLT2) inhibitors are a new class of oral glucose-lowering agents. Apart from their glucose-lowering effects, large clinical trials assessing certain SGLT2 inhibitors have revealed cardiac and renal protective effects in non-diabetic patients. These excellent outcomes motivated scientists and clinical professionals to revisit their underlying mechanisms. In addition to the heart and kidney, redox homeostasis is crucial in several human diseases, including liver diseases, neural disorders, and cancers, with accumulating preclinical studies demonstrating the therapeutic benefits of SGLT2 inhibitors. In the present review, we aimed to update recent advances in the antioxidant roles of SGLT2 inhibitors in common but debilitating human diseases. We anticipate that this review will guide new research directions and novel therapeutic strategies for diabetes, cardiovascular diseases, nephropathies, liver diseases, neural disorders, and cancers in the era of SGLT2 inhibitors.

Lipoprotein Lipase and Its Delivery of Fatty Acids to the Heart

Ninety percent of plasma fatty acids (FAs) are contained within lipoprotein-triglyceride, and lipoprotein lipase (LPL) is robustly expressed in the heart. Hence, LPL-mediated lipolysis of lipoproteins is suggested to be a key source of FAs for cardiac use. Lipoprotein clearance by LPL occurs at the apical surface of the endothelial cell lining of the coronary lumen. In the heart, the majority of LPL is produced in cardiomyocytes and subsequently is translocated to the apical luminal surface. Here, vascular LPL hydrolyzes lipoprotein-triglyceride to provide the heart with FAs for ATP generation. This article presents an overview of cardiac LPL, explains how the enzyme works, describes key molecules that regulate its activity and outlines how changes in LPL are brought about by physiological and pathological states such as fasting and diabetes, respectively.

Cancer therapy-related cardiac dysfunction: is endothelial dysfunction at the heart of the matter?

Significant improvements in cancer survival have brought to light unintended long-term adverse cardiovascular effects associated with cancer treatment. Although capable of manifesting a broad range of cardiovascular complications, cancer therapy-related cardiac dysfunction (CTRCD) remains particularly common among the mainstay anthracycline-based and human epidermal growth factor receptor-targeted therapies. Unfortunately, the early asymptomatic stages of CTRCD are difficult to detect by cardiac imaging alone, and the initiating mechanisms remain incompletely understood. More recently, circulating inflammatory markers, cardiac biomarkers, microRNAs, and extracellular vesicles (EVs) have been considered as early markers of cardiovascular injury. Concomitantly, the role of the endothelium in regulating cardiac function in the context of CTRCD is starting to be understood. In this review, we highlight the impact of breast cancer therapies on the cardiovascular system with a focus on the endothelium, and examine the status of circulating biomarkers, including inflammatory markers, cardiac biomarkers, microRNAs, and endothelial cell-derived EVs. Investigation of these emerging biomarkers may uncover mechanisms of injury, detect early stages of cardiovascular damage, and elucidate novel therapeutic approaches.

Therapeutic potential of targeting oxidative stress in diabetic cardiomyopathy

Even in the absence of coronary artery disease and hypertension, diabetes mellitus (DM) may increase the risk for heart failure development. This risk evolves from functional and structural alterations induced by diabetes in the heart, a cardiac entity termed diabetic cardiomyopathy (DbCM). Oxidative stress, defined as the imbalance of reactive oxygen species (ROS) has been increasingly proposed to contribute to the development of DbCM. There are several sources of ROS production including the mitochondria, NAD(P)H oxidase, xanthine oxidase, and uncoupled nitric oxide synthase. Overproduction of ROS in DbCM is thought to be counterbalanced by elevated antioxidant defense enzymes such as catalase and superoxide dismutase. Excess ROS in the cardiomyocyte results in further ROS production, mitochondrial DNA damage, lipid peroxidation, post-translational modifications of proteins and ultimately cell death and cardiac dysfunction. Furthermore, ROS modulates transcription factors responsible for expression of antioxidant enzymes. Lastly, evidence exists that several pharmacological agents may convey cardiovascular benefit by antioxidant mechanisms. As such, increasing our understanding of the pathways that lead to increased ROS production and impaired antioxidant defense may enable the development of therapeutic strategies against the progression of DbCM. Herein, we review the current knowledge about causes and consequences of ROS in DbCM, as well as the therapeutic potential and strategies of targeting oxidative stress in the diabetic heart.

CircRNAs in diabetic cardiomyopathy

Diabetic cardiomyopathy is an important irreversible chronic cardiovascular complication in diabetic patients. This condition is described as early diastolic dysfunction, myocardial fibrosis, cardiac hypertrophy, systolic dysfunction and other complex pathophysiological events, which ultimately lead to heart failure. Despite these characteristics, the underlying mechanisms resulting in diabetic cardiomyopathy are still unknown. With the developments in molecular biotechnology, increasing evidence shows that circRNAs play critical roles in the pathogenesis of diabetic cardiomyopathy. The purpose of this review is to summarize recent studies on the role of circRNAs in the pathophysiological process to provide novel prevention and treatment strategies for diabetic cardiomyopathy, oxidative stress, inflammation, endothelial dysfunction, myocardial fibrosis and cell death in diabetic cardiomyopathy.

Application of Animal Models in Diabetic Cardiomyopathy

Diabetic heart disease is a growing and important public health risk. Apart from the risk of coronary artery disease or hypertension, diabetes mellitus (DM) is a well-known risk factor for heart failure in the form of diabetic cardiomyopathy (DiaCM). Currently, DiaCM is defined as myocardial dysfunction in patients with DM in the absence of coronary artery disease and hypertension. The underlying pathomechanism of DiaCM is partially understood, but accumulating evidence suggests that metabolic derangements, oxidative stress, increased myocardial fibrosis and hypertrophy, inflammation, enhanced apoptosis, impaired intracellular calcium handling, activation of the renin-angiotensin-aldosterone system, mitochondrial dysfunction, and dysregulation of microRNAs, among other factors, are involved. Numerous animal models have been used to investigate the pathomechanisms of DiaCM. Despite some limitations, animal models for DiaCM have greatly advanced our understanding of pathomechanisms and have helped in the development of successful disease management strategies. In this review, we summarize the current pathomechanisms of DiaCM and provide animal models for DiaCM according to its pathomechanisms, which may contribute to broadening our understanding of the underlying mechanisms and facilitating the identification of possible new therapeutic targets.

Diabetes changes gene expression but not DNA methylation in cardiac cells

BACKGROUND

Diabetes mellitus is a worldwide epidemic that causes high mortality due to cardiovascular complications, in particular heart failure. Diabetes is associated with profound pathophysiological changes in the heart. The aim of this study was to investigate the impact of diabetes on gene expression and DNA methylation in cardiac cells.

METHODS AND RESULTS

Transcriptome analysis of heart tissue from mice with streptozotocin-induced diabetes revealed only 39 genes regulated, whereas cell type-specific analysis of the diabetic heart was more sensitive and more specific than heart tissue analysis and revealed a total of 3205 differentially regulated genes in five cell types. Whole genome DNA methylation analysis with basepair resolution of distinct cardiac cell types identified highly specific DNA methylation signatures of genic and regulatory regions. Interestingly, despite marked changes in gene expression, DNA methylation remained stable in streptozotocin-induced diabetes. Integrated analysis of cell type-specific gene expression enabled us to assign the particular contribution of single cell types to the pathophysiology of the diabetic heart. Finally, analysis of gene regulation revealed ligand-receptor pairs as potential mediators of heterocellular interaction in the diabetic heart, with fibroblasts and monocytes showing the highest degree of interaction.

CONCLUSION

In summary, cell type-specific analysis reveals differentially regulated gene programs that are associated with distinct biological processes in diabetes. Interestingly, despite these changes in gene expression, cell type-specific DNA methylation signatures of genic and regulatory regions remain stable in diabetes. Analysis of heterocellular interactions in the diabetic heart suggest that the interplay between fibroblasts and monocytes is of pivotal importance.

Label-free and noninvasive method for assessing the metabolic status in type 2 diabetic rats with myocardium diastolic dysfunction

This study assesses the metabolic status of rat diabetic cardiomyopathy (DCM) models. Echocardiography is used to detect the diastolic dysfunction in type 2 diabetic rats, and a lower threshold for inducible atrial fibrillation is found in type 2 diabetic rats with diastolic dysfunction compared to the control. Metabolic abnormalities are detected by status changes of reduced nicotinamide adenine dinucleotide (phosphate) (NAD(P)H), which is an essential coenzyme in cells or tissues. Fluorescence lifetime imaging microscopy (FLIM) is used to monitor changes in NAD(P)H in both myocardial tissues and blood. FLIM reveals that the protein-bound proportion of NAD(P)H in rat myocardium in the DCM group is smaller than the control group, which indicates the oxidative phosphorylation rate of the DCM group decreased. Similar results are found for blood plasma of DCM rats by the FLIM study. FLIM exhibits high potential for screening DCM as a label-free, sensitive, and noninvasive method.

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

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

A novel oral glucagon-like peptide 1 receptor agonist protects against diabetic cardiomyopathy via alleviating cardiac lipotoxicity induced mitochondria dysfunction

Diabetic cardiomyopathy is one of the major cardiovascular complications of diabetes mellitus associated with left ventricular diastolic dysfunction. There are still no specific therapeutic guidelines for the disease. In recent years, glucagon-like peptide 1 receptor agonists were proved to exert cardioprotective effects in comprehensive studies. Therefore, we examined whether a novel oral availably glucagon-like peptide 1 receptor agonist, oral hypoglycemic peptide 2 (OHP2), could protect against diabetic cardiomyopathy in high-fat diets and continuous streptozocin injection induced rat models. After treatment for eight weeks, heart function was evaluated by echocardiography. As expected, OHP2 improved cardiac structure and function beyond glycemic control. Both hyperlipidemia and myocardium lipid accumulation were decreased by OHP2 treatment. In addition, OHP2 reversed oxidative stress and mitochondrial dysfunction in diabetic hearts. In vitro study suggested that OHP2 prevented palmitic acid-induced oxidative stress and mitochondrial dysfunction via suppressing intercellular lipid accumulation. Hence, our present findings pointed out that OHP2 is a promising oral glucagon-like peptide 1 receptor agonist for preventing diabetic cardiomyopathy.

Forensic interrogation of diabetic endothelitis in cardiovascular diseases and clinical translation in heart failure

Diabetic heart disease (DHD) can be classified as a primary consequence from several pathophysiological manifestation of diabetes mellitus (DM) on cardiac tissues or secondarily in extracardiac tissues and is encountered as either primary or secondary complications of DM. Endothelitis is inflammation of the vascular endothelium and is likely to be seen in the majority of patients who start to manifest an end organ complication of DM in this case DHD. Diabetes is a leading cause for many cardiovascular syndromes and diseases including congestive heart failure (CHF) however much remains unknown about the transition from diagnosed DM to clinical state and the contribution of the various mechanical and counterregulatory systems in the manifested complaint. Diastolic heart failure or heart failure with preserved ejection fraction (DHF/HFpEF), accounts for half of all CHF presentations, has DM as a major contributor, however, there remain large gaps in clinical and pathophysiological understanding. This review aims to explore the microscopic aspects in diabetic endothelitis and provide a clinical link to with context to HFpEF.

Low-Level Nanog Expression in the Regulation of Quiescent Endothelium

Supplemental Digital Content is available in the text.

Nanog is expressed in adult endothelial cells (ECs) at a low-level, however, its functional significance is not known. The goal of our study was to elucidate the role of Nanog in adult ECs using a genetically engineered mouse model system.

Endothelial Sirtuin 3 Dictates Glucose Transport to Cardiomyocyte and Sensitizes Pressure Overload-Induced Heart Failure

Background

Alterations of energetic metabolism are suggested to be an important contributor to pressure overload (PO)‐induced heart failure. Our previous study reveals that knockout of endothelial Sirtuin 3 (SIRT3) alters glycolysis and impairs diastolic function. We hypothesize that endothelial SIRT3 regulates glucose utilization of cardiomyocytes and sensitizes PO‐induced heart failure.

Methods and Results

SIRT3 endothelial cell knockout mice and their control SIRT3 LoxP mice were subjected to PO by transverse aortic constriction for 7 weeks. The ratio of heart weight to tibia length was increased in both strains of mice, in which SIRT3 endothelial cell knockout mice+transverse aortic constriction exhibited more severe cardiac hypertrophy. Coronary blood flow and systolic function were significantly decreased in SIRT3 endothelial cell knockout mice+transverse aortic constriction compared with SIRT3 LoxP mice+transverse aortic constriction, as evidenced by lower systolic/diastolic ratio, ejection fraction, and fractional shortening. PO‐induced upregulation of apelin and glucose transporter 4 were significantly reduced in the hearts of SIRT3 endothelial cell knockout mice. In vitro, levels of hypoxia‐inducible factor‐1α and glucose transporter 1 and glucose uptake were significantly reduced in SIRT3 knockout endothelial cells. Furthermore, hypoxia‐induced apelin expression was abolished together with reduced apelin‐mediated glucose uptake in SIRT3 knockout endothelial cells. Exposure of cardiomyocyte with apelin increased expression of glucose transporter 1 and glucose transporter 4. This was accompanied by a significant increase in glycolysis. Supplement of apelin in SIRT3 knockout hypoxic endothelial cell media increased glycolysis in the cardiomyocytes.

Conclusions

Knockout of SIRT3 disrupts glucose transport from endothelial cells to cardiomyocytes, reduces cardiomyocyte glucose utilization via apelin in a paracrine manner, and sensitizes PO‐induced heart failure. Endothelial SIRT3 may regulate cardiomyocyte glucose availability and govern the function of the heart.

Involvement of Heparanase in Endothelial Cell-Cardiomyocyte Crosstalk

Traditionally, the management of diabetes has focused mainly on controlling high blood glucose levels. Unfortunately, despite valiant efforts to normalize this blood glucose, poor medication management predisposes these patients to heart failure. Following diabetes, how the heart utilizes different sources of fuel for energy is key to the development of heart failure. The diabetic heart switches from using both glucose and fats, to predominately using fats as an energy resource for maintaining its activities. This transformation to using fats as an exclusive source of energy is helpful in the initial stages of the disease and is tightly controlled. However, over the progression of diabetes, there is a loss of this controlled supply and use of fats, which ultimately has terrible consequences since the uncontrolled use of fats produces toxic by-products which weaken heart function and cause heart disease. Heparanase is a key player that directs how much fats are provided to the heart and does so in association with several partners like LPL and VEGFs. Together, they regulate the amount of fats supplied, and their subsequent breakdown to provide energy. Following diabetes, there is a disruption in this network resulting in fat oversupply and cell death. Understanding how the heparanase-LPL-VEGFs "ensemble" cooperates, and its dysfunction in the diabetic heart would be useful in restoring metabolic equilibrium and limiting diabetes-related cardiac damage.

Forty Years of Basic and Translational Heparanase Research

This review summarizes key developments in the heparanase field obtained 20 years prior to cloning of the HPSE gene and nearly 20 years after its cloning. Of the numerous publications and review articles focusing on heparanase, we have selected those that best reflect the progression in the field as well as those we regard important accomplishments with preference to studies performed by scientists and groups that contributed to this book. Apart from a general 'introduction' and 'concluding remarks', the abstracts of these studies are presented essentially as published along the years. We apologize for not being objective and not being able to include some of the most relevant abstracts and references, due to space limitation. Heparanase research can be divided into two eras. The first, initiated around 1975, dealt with identifying the enzyme, establishing the relevant assay systems and investigating its biological activities and significance in cancer and other pathologies. Studies performed during the first area are briefly introduced in a layman style followed by the relevant abstracts presented chronologically, essentially as appears in PubMed. The second era started in 1999 when the heparanase gene was independently cloned by 4 research groups [1-4]. As expected, cloning of the heparanase gene boosted heparanase research by virtue of the readily available recombinant enzyme, molecular probes, and anti-heparanase antibodies. Studies performed during the second area are briefly introduced followed by selected abstracts of key findings, arranged according to specific topics.

The pivotal role of nuclear factor erythroid 2-related factor 2 in diabetes-induced endothelial dysfunction

Endothelial dysfunction (ED) is a key event in the onset and progression of vascular complications associated with diabetes. Regulation of endothelial function and the underlying signaling mechanisms in the progression of diabetes-induced vascular complications have been well established. Recent studies indicate that increased oxidative stress is an important determinant of endothelial injury and patients with hypertension display ED mediated by impaired Nitric Oxide (NO) availability. Further, oxidative stress is known to be associated with inflammation and ED in vascular remodeling and diabetes-associated hypertension. Numerous strategies have been developed to improve the function of endothelial cells and increasing number of evidences highlight the indispensable role of antioxidants in modulation of endothelium-dependent vasodilation responses. Nuclear factor Erythroid 2-related factor 2 (Nrf2), is the principal transcriptional regulator, that is central in mediating oxidative stress signal response. Having unequivocally established the relationship between type 2 diabetes mellitus (T2DM) and oxidative stress, the pivotal role of Nrf2/Keap1/ARE network, has taken the center stage as target for developing therapies towards maintaining the cellular redox environment. Several activators of Nrf2 are known to combat diabetes-induced ED and few are currently in clinical trials. Focusing on their therapeutic value in diabetes-induced ED, this review highlights some natural and synthetic molecules that are involved in the modulation of the Nrf2/Keap1/ARE network and its underlying molecular mechanisms in the regulation of ED. Further emphasis is also laid on the therapeutic benefits of directly up-regulating Nrf2-mediated antioxidant defences in regulating endothelial redox homeostasis for countering diabetes-induced ED.

Diabetes Mellitus Severity and a Switch From Using Lipoprotein Lipase to Adipose-Derived Fatty Acid Results in a Cardiac Metabolic Signature That Embraces Cell Death

Background

Fatty acid (FA) provision to the heart is from cardiomyocyte and adipose depots, plus lipoprotein lipase action. We tested how a graded reduction in insulin impacts the source of FA used by cardiomyocytes and the cardiac adaptations required to process these FA.

Methods and Results

Rats injected with 55 (D55) or 100 (D100) mg/kg streptozotocin were terminated after 4 days. Although D55 and D100 were equally hyperglycemic, D100 showed markedly lower pancreatic and plasma insulin and loss of lipoprotein lipase, which in D55 hearts had expanded. There was minimal change in plasma FA in D55. However, D100 exhibited a 2‐ to 3‐fold increase in various saturated, monounsaturated, and polyunsaturated FA in the plasma. D100 demonstrated dramatic cardiac transcriptomic changes with 1574 genes differentially expressed compared with only 49 in D55. Augmented mitochondrial and peroxisomal β‐oxidation in D100 was not matched by elevated tricarboxylic acid or oxidative phosphorylation. With increasing FA, although control myocytes responded by augmenting basal respiration, this was minimized in D55 and reversed in D100. Metabolomic profiling identified significant lipid accumulation in D100 hearts, which also exhibited sizeable change in genes related to apoptosis and terminal deoxynucleotidyl transferase dUTP nick‐end labeling–positive cells.

Conclusions

With increasing severity of diabetes mellitus, when the diabetic heart is unable to control its own FA supply using lipoprotein lipase, it undergoes dramatic reprogramming that is linked to handling of excess FA that arise from adipose tissue. This transition results in a cardiac metabolic signature that embraces mitochondrial FA overload, oxidative stress, triglyceride storage, and cell death.

Cardiomyopathy Associated with Diabetes: The Central Role of the Cardiomyocyte

The term diabetic cardiomyopathy (DCM) labels an abnormal cardiac structure and performance due to intrinsic heart muscle malfunction, independently of other vascular co-morbidity. DCM, accounting for 50%–80% of deaths in diabetic patients, represents a worldwide problem for human health and related economics. Optimal glycemic control is not sufficient to prevent DCM, which derives from heart remodeling and geometrical changes, with both consequences of critical events initially occurring at the cardiomyocyte level. Cardiac cells, under hyperglycemia, very early undergo metabolic abnormalities and contribute to T helper (Th)-driven inflammatory perturbation, behaving as immunoactive units capable of releasing critical biomediators, such as cytokines and chemokines. This paper aims to focus onto the role of cardiomyocytes, no longer considered as “passive” targets but as “active” units participating in the inflammatory dialogue between local and systemic counterparts underlying DCM development and maintenance. Some of the main biomolecular/metabolic/inflammatory processes triggered within cardiac cells by high glucose are overviewed; particular attention is addressed to early inflammatory cytokines and chemokines, representing potential therapeutic targets for a prompt early intervention when no signs or symptoms of DCM are manifesting yet. DCM clinical management still represents a challenge and further translational investigations, including studies at female/male cell level, are warranted.

Ginseng for the treatment of diabetes and diabetes-related cardiovascular complications: a discussion of the evidence 1

Diabetes mellitus (DM) is a chronic metabolic disorder associated with elevated blood glucose levels due either to insufficient insulin production (type 1 DM) or to insulin resistance (type 2 DM). The incidence of DM around the world continues to rise dramatically with more than 400 million cases reported today. Among the most serious consequences of chronic DM are cardiovascular complications that can have deleterious effects. Although numerous treatment options are available, including both pharmacological and nonpharmacological, there is substantial emerging interest in the use of traditional medicines for the treatment of this condition and its complications. Among these is ginseng, a medicinal herb that belongs to the genus Panax and has been used for thousands of years as a medicinal agent especially in Asian cultures. There is emerging evidence from both animal and clinical studies that ginseng, ginseng constituents including ginsenosides, and ginseng-containing formulations can produce beneficial effects in terms of normalization of blood glucose levels and attenuation of cardiovascular complications through a multiplicity of mechanisms. Although more research is required, ginseng may offer a useful therapy for the treatment of diabetes as well as its complications.