Metabolic cardiomyopathies

Class I and II Histone Deacetylase Inhibitors as Therapeutic Modulators of Dilated Cardiac Tissue-Derived Mesenchymal Stem/Stromal Cells

The prevalence of dilated cardiomyopathy (DCM) is increasing globally, highlighting the need for innovative therapeutic approaches to prevent its onset. In this study, we examined the energetic and epigenetic distinctions between dilated and non-dilated human myocardium-derived mesenchymal stem/stromal cells (hmMSCs) and assessed the effects of class I and II HDAC inhibitors (HDACi) on these cells and their cardiomyogenic differentiation. Cells were isolated from myocardium biopsies using explant outgrowth methods. Mitochondrial and histone deacetylase activities, ATP levels, cardiac transcription factors, and structural proteins were assessed using flow cytometry, PCR, chemiluminescence, Western blotting, and immunohistochemistry. The data suggest that the tested HDAC inhibitors improved acetylation and enhanced the energetic status of both types of cells, with significant effects observed in dilated myocardium-derived hmMSCs. Additionally, the HDAC inhibitors activated the cardiac transcription factors Nkx2-5, HOPX, GATA4, and Mef2C, and upregulated structural proteins such as cardiac troponin T and alpha cardiac actin at both the protein and gene levels. In conclusion, our findings suggest that HDACi may serve as potential modulators of the energetic status and cardiomyogenic differentiation of human heart hmMSCs. This avenue of exploration could broaden the search for novel therapeutic interventions for dilated cardiomyopathy, ultimately leading to improvements in heart function.

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.

A Meta-Analysis Approach to Gene Regulatory Network Inference Identifies Key Regulators of Cardiovascular Diseases

Cardiovascular diseases (CVDs) represent a major concern for global health, whose mechanistic understanding is complicated by a complex interplay between genetic predisposition and environmental factors. Specifically, heart failure (HF), encompassing dilated cardiomyopathy (DC), ischemic cardiomyopathy (ICM), and hypertrophic cardiomyopathy (HCM), is a topic of substantial interest in basic and clinical research. Here, we used a Partial Correlation Coefficient-based algorithm (PCC) within the context of a meta-analysis framework to construct a Gene Regulatory Network (GRN) that identifies key regulators whose activity is perturbed in Heart Failure. By integrating data from multiple independent studies, our approach unveiled crucial regulatory associations between transcription factors (TFs) and structural genes, emphasizing their pivotal roles in regulating metabolic pathways, such as fatty acid metabolism, oxidative stress response, epithelial-to-mesenchymal transition, and coagulation. In addition to known associations, our analysis also identified novel regulators, including the identification of TFs FPM315 and OVOL2, which are implicated in dilated cardiomyopathies, and TEAD1 and TEAD2 in both dilated and ischemic cardiomyopathies. Moreover, we uncovered alterations in adipogenesis and oxidative phosphorylation pathways in hypertrophic cardiomyopathy and discovered a role for IL2 STAT5 signaling in heart failure. Our findings underscore the importance of TF activity in the initiation and progression of cardiac disease, highlighting their potential as pharmacological targets.

Ferroptosis and cuproptposis in kidney Diseases: dysfunction of cell metabolism

Metal ions play an important role in living organisms and are involved in essential physiological activities. However, the overload state of ions can cause excess free radicals, cell damage, and even cell death. Ferroptosis and cuproptosis are specific forms of cell death that are distinct from apoptosis, necroptosis, and other regulated cell death. These unique modalities of cell death, dependent on iron and copper, are regulated by multiple cellular metabolic pathways, including steady-state metal redox treatment mitochondrial activity of lipid, amino acid and glucose metabolism, and various signaling pathways associated with disease. Although the mechanisms of ferroptosis and cuproptosis are not yet fully understood, there is no doubt that ion overload plays a crucial act in these metal-dependent cell deaths. In this review, we discussed the core roles of ion overload in ferroptosis and cuproptosis, the association between metabolism imbalance and ferroptosis and cuproptosis, the extract the diseases caused by ion overload and current treatment modalities.

The Structure of the Cardiac Mitochondria Respirasome Is Adapted for the β-Oxidation of Fatty Acids

It is well known that in the heart and kidney mitochondria, more than 95% of ATP production is supported by the β-oxidation of long-chain fatty acids. However, the β-oxidation of fatty acids by mitochondria has been studied much less than the substrates formed during the catabolism of carbohydrates and amino acids. In the last few decades, several discoveries have been made that are directly related to fatty acid oxidation. In this review, we made an attempt to re-evaluate the β-oxidation of long-chain fatty acids from the perspectives of new discoveries. The single set of electron transporters of the cardiac mitochondrial respiratory chain is organized into three supercomplexes. Two of them contain complex I, a dimer of complex III, and two dimers of complex IV. The third, smaller supercomplex contains a dimer of complex III and two dimers of complex IV. We also considered other important discoveries. First, the enzymes of the β-oxidation of fatty acids are physically associated with the respirasome. Second, the β-oxidation of fatty acids creates the highest level of QH2 and reverses the flow of electrons from QH2 through complex II, reducing fumarate to succinate. Third, β-oxidation is greatly stimulated in the presence of succinate. We argue that the respirasome is uniquely adapted for the β-oxidation of fatty acids. The acyl-CoA dehydrogenase complex reduces the membrane's pool of ubiquinone to QH2, which is instantly oxidized by the smaller supercomplex, generating a high energization of mitochondria and reversing the electron flow through complex II, which reverses the electron flow through complex I, increasing the NADH/NAD+ ratio in the matrix. The mitochondrial nicotinamide nucleotide transhydrogenase catalyzes a hydride (H-, a proton plus two electrons) transfer across the inner mitochondrial membrane, reducing the cytosolic pool of NADP(H), thus providing the heart with ATP for muscle contraction and energy and reducing equivalents for the housekeeping processes.

Comparative assessment of erythrocyte sphingolipid levels as potential cardiovascular health markers in women from Libya and Serbia: a small-scale study

Aim: Cardiovascular diseases (CVDs) represent the major cause of morbidity and mortality worldwide including Libya, where they account for 43% of all deaths. Sphingolipids are involved in the pathology of numerous diseases including cardiovascular diseases and are proposed as potential biomarkers of cardiovascular health that could be more effective compared to traditional clinical biomarkers. The aim of this study was to determine the sphingolipid content in the erythrocyte membrane of Libyan migrant and Serbian resident women. In addition, to examine if sphingolipid levels could be used as a novel indicator of cardiovascular risk, we evaluated possible correlations with some well-established biomarkers of cardiovascular health.Materials and Methods: A total of 13 Libyan and 15 Serbian healthy women participated in the study. The high-performance version thin-layer chromatography (HPTLC) using the image analysis tool JustTLC was applied for quantification of erythrocytes' sphingolipids.Results: Lower mean values of erythrocytes' sphingolipids and cholesterol concentrations were found in the group of Libyan emigrants compared to Serbian resident women. Besides, in this group of apparently healthy women (n = 28), the sphingolipid content of erythrocytes was inversely related to the Omega-3 index (r =-0.492, p = 0.008) and directly linked to vitamin D status (r = 0.433, p = 0.021) and membrane cholesterol levels (r = 0.474, p = 0.011).Conclusion: The erythrocytes' sphingolipid levels should be measured/assessed as an additional biomarker of CV health, by applying a simple and routine method. Still, further investigation in a larger population-specific context is warranted.

Role of Lymphangiogenesis in Cardiac Repair and Regeneration

This article highlights the importance of the structure and function of cardiac lymphatics in cardiovascular diseases and the therapeutic potential of cardiac lymphangiogenesis. Specifically, we explore the innate lymphangiogenic response to damaged cardiac tissue or cardiac injury, derive key findings from regenerative models demonstrating how robust lymphangiogenic responses can be supported to improve cardiac function, and introduce an approach to imaging the structure and function of cardiac lymphatics.

Sterile inflammation and the NLRP3 inflammasome in cardiometabolic disease

Inflammation plays an important role in the pathophysiology of cardiometabolic diseases. Sterile inflammation, a non-infectious and damage-associated molecular pattern (DAMP)-induced innate response, is now well-established to be closely associated with development and progression of cardiometabolic diseases. The NOD-like receptor (NLR) family pyrin domain-containing 3 (NLRP3) inflammasome is well-established as a major player in sterile inflammatory responses. It is a multimeric cytosolic protein complex which regulates the activation of caspase-1 and subsequently promotes cleavage and release of interleukin (IL)-1 family cytokines, which have a deleterious impact on the development of cardiometabolic diseases. Therefore, targeting NLRP3 itself or the downstream consequences of NLRP3 activation represent excellent potential therapeutic targets in inflammatory cardiometabolic diseases. Here, we review our current understanding of the role which NLRP3 inflammasome regulation plays in cardiometabolic diseases such as obesity, diabetes, non-alcoholic steatohepatitis (NASH), atherosclerosis, ischemic heart disease and cardiomyopathy. Finally, we highlight the potential of targeting NLPR3 or related signaling molecules as a therapeutic approach.

Obesity phenotypes and cardiovascular risk: From pathophysiology to clinical management

Obesity epidemic reached the dimensions of a real global health crisis with more than one billion people worldwide living with obesity. Multiple obesity-related mechanisms cause structural, functional, humoral, and hemodynamic alterations with cardiovascular (CV) deleterious effects. A correct assessment of the cardiovascular risk in people with obesity is critical for reducing mortality and preserving quality of life. The correct identification of the obesity status remains difficult as recent evidence suggest that different phenotypes of obesity exist, each one associated with different degrees of CV risk. Diagnosis of obesity cannot depend only on anthropometric parameters but should include a precise assessment of the metabolic status. Recently, the World Heart Federation and World Obesity Federation provided an action plan for management of obesity-related CV risk and mortality, stressing for the instauration of comprehensive structured programs encompassing multidisciplinary teams. In this review we aim at providing an updated summary regarding the different obesity phenotypes, their specific effects on CV risk and differences in clinical management.

Bacterial toxins and heart function: heat-labile Escherichia coli enterotoxin B promotes changes in cardiac function with possible relevance for sudden cardiac death

Bacterial toxins can cause cardiomyopathy, though it is not its most common cause. Some bacterial toxins can form pores in the membrane of cardiomyocytes, while others can bind to membrane receptors. Enterotoxigenic E. coli can secrete enterotoxins, including heat-resistant (ST) or labile (LT) enterotoxins. LT is an AB5-type toxin that can bind to specific cell receptors and disrupt essential host functions, causing several common conditions, such as certain diarrhea. The pentameric B subunit of LT, without A subunit (LTB), binds specifically to certain plasma membrane ganglioside receptors, found in lipid rafts of cardiomyocytes. Isolated guinea pig hearts and cardiomyocytes were exposed to different concentrations of purified LTB. In isolated hearts, mechanical and electrical alternans and an increment of heart rate variability, with an IC50 of ~0.2 μg/ml LTB, were observed. In isolated cardiomyocytes, LTB promoted significant decreases in the amplitude and the duration of action potentials. Na+ currents were inhibited whereas L-type Ca2+ currents were augmented at their peak and their fast inactivation was promoted. Delayed rectifier K+ currents decreased. Measurements of basal Ca2+ or Ca2+ release events in cells exposed to LTB suggest that LTB impairs Ca2+ homeostasis. Impaired calcium homeostasis is linked to sudden cardiac death. The results are consistent with the recent view that the B subunit is not merely a carrier of the A subunit, having a role explaining sudden cardiac death in children (SIDS) infected with enterotoxigenic E. coli, explaining several epidemiological findings that establish a strong relationship between SIDS and ETEC E. coli.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12551-023-01100-6.

Phenotype and pathology of the dilated cardiomyopathy with ataxia syndrome in children

The dilated cardiomyopathy with ataxia syndrome (DCMA) is an autosomal recessive mitochondrial disease caused by mutations in the DnaJ heat shock protein family (Hsp40) member C19 (DNAJC19) gene. DCMA or 3-methylglutaconic aciduria type V is globally rare, but the largest number of patients in the world is found in the Hutterite population of southern Alberta in Canada. We provide an update on phenotypic findings, natural history, pathological findings, and our clinical experience. We analyzed all available records for 43 patients diagnosed with DCMA between 2005 and 2015 at the Alberta Children's Hospital. All patients studied were Hutterite and homozygous for the causative DNAJC19 variant (c.130-1G>C, IVS3-1G>C) and had elevated levels of 3-methyglutaconic acid. We calculated a birth prevalence of 1.54 cases per 1000 total births in the Hutterite community. Children were small for gestational age at birth and frequently required supplemental nutrition (63%) or surgical placement of a gastrostomy tube (35%). Early mortality in this cohort was high (40%) at a median age of 13 months (range 4-294 months). Congenital anomalies were common as was dilated cardiomyopathy (50%), QT interval prolongation (83%), and developmental delay (95%). Tissue pathology was analyzed in a limited number of patients and demonstrated subendocardial fibrosis in the heart, macrovesicular steatosis and fibrosis in the liver, and structural abnormalities in mitochondria. This report provides clinical details for a cohort of children with DCMA and the first presentation of tissue pathology for this disorder. Despite sharing common genetic etiology and environment, the disease is highly heterogeneous for reasons that are not understood. DCMA is a clinically heterogeneous systemic mitochondrial disease with significant morbidity and mortality that is common in the Hutterite population of southern Alberta.

The Emerging Role of FUNDC1-Mediated Mitophagy in Cardiovascular Diseases

Mitochondria are highly dynamic organelles and play essential role in ATP synthase, ROS production, innate immunity, and apoptosis. Mitochondria quality control is critical for maintaining the cellular function in response to cellular stress, growth, and differentiation Signals. Damaged or unwanted mitochondria are selectively removed by mitophagy, which is a crucial determinant of cell viability. Mitochondria-associated Endoplasmic Reticulum Membranes (MAMs) are the cellular structures that connect the ER and mitochondria and are involved in calcium signaling, lipid transfer, mitochondrial dynamic, and mitophagy. Abnormal mitochondrial quality induced by mitophagy impairment and MAMs dysfunction is associated with many diseases, including cardiovascular diseases (CVDs), metabolic syndrome, and neurodegenerative diseases. As a mitophagy receptor, FUNDC1 plays pivotal role in mitochondrial quality control through regulation of mitophagy and MAMs and is closely related to the occurrence of several types of CVDs. This review covers the regulation mechanism of FUNDC1-mediated mitophagy and MAMs formation, with a particular focus on its role in CVDs.

Effect of different alcohol consumption levels on the left atrial size: A cross-sectional study in rural China

OBJECTIVE

Previous studies have investigated the relationship between alcohol and ventricular structure; however, few studies have evaluated the relation between alcohol consumption and the atrium size. In this study, we aimed to test the association between alcohol consumption and left atrium (LA) size in the general population.

METHODS

A population-based sample of 10,211 subjects aged ≥35 years and free from hypertension at baseline were followed from January 2012 to August 2013. Left atrial enlargement (LAE) was defined as the ratio of LA diameter to body surface area exceeding 2.4 cm/m2 in both the sexes. Independent factors for LAE were estimated by multiple logistic regression analyses.

RESULTS

The study included 10,211 participants (4,751 men and 5,460 women). Left atrial diameter/body surface area (LAD/BSA) was higher in the moderate and heavy alcohol consumption groups than in the non-drinker group (non-drinker, 20.5±0.03 cm/m2; moderate, 20.8±0.09 cm/m2; and heavy, 20.6±0.06 cm/m2; p<0.001). Both the groups of moderate and heavy drinkers had a higher incidence of LAE than the non-drinker group (6.9% of non-drinkers, 9.9% of moderate drinkers, and 8.4% of heavy drinkers; p<0.001). After adjusting for related risk factors, multiple logistic regression analyses showed that moderate drinkers had an approximately 1.4-fold higher risk of LAE [odds ratio (OR): 1.387, 95% confidence interval (CI) 1.056-1.822, p=0.019] compared with the non-drinkers, and the heavy drinkers had an approximately 1.2-fold higher risk of LAE (OR: 1.229, 95% CI: 1.002-1.508, p=0.047) compared with that of the non-drinkers.

CONCLUSION

Both heavy and moderate drinkers had increased odds for LAE compared with participants with no alcohol consumption in the general population.

Imaging techniques for the assessment of adverse cardiac remodeling in metabolic syndrome

Metabolic syndrome (MetS) includes different metabolic conditions (i.e. abdominal obesity, impaired glucose tolerance, hypertriglyceridemia, decreased HDL cholesterol, and/or hypertension) that concour in the development of cardiovascular disease and diabetes. MetS individuals often show adverse cardiac remodeling and myocardial dysfunction even in the absence of overt coronary artery disease or valvular affliction. Diastolic impairment and hypertrophy are hallmarks of MetS-related cardiac remodeling and represent the leading cause of heart failure with preserved ejection fraction (HFpEF). Altered cardiomyocyte function, increased neurohormonal tone, interstitial fibrosis, coronary microvascular dysfunction, and a myriad of metabolic abnormalities have all been implicated in the development and progression of adverse cardiac remodeling related to MetS. However, despite the enormous amount of literature produced on this argument, HF remains a leading cause of morbidity and mortality in such population. The early detection of initial adverse cardiac remodeling would enable the optimal implementation of effective therapies aiming at preventing the progression of the disease to the symptomatic phase. Beyond conventional imaging techniques, such as echocardiography, cardiac tomography, and magnetic resonance, novel post-processing tools and techniques provide information on the biological processes that underlie metabolic heart disease. In this review, we summarize the pathophysiology of MetS-related cardiac remodeling and illustrate the relevance of state-of-the-art multimodality cardiac imaging to identify and quantify the degree of myocardial involvement, prognosticate long-term clinical outcome, and potentially guide therapeutic strategies.

The utilization of positron emission tomography in the evaluation of renal health and disease

Purpose

Positron emission tomography (PET) is a nuclear imaging technique that uses radiotracers to visualize metabolic processes of interest across different organs, to diagnose and manage diseases, and monitor therapeutic response. This systematic review aimed to characterize the value of PET for the assessment of renal metabolism and function in subjects with non-oncological metabolic disorders.

Methods

This review was conducted and reported in accordance with the PRISMA statement. Research articles reporting “kidney” or “renal” metabolism evaluated with PET imaging between 1980 and 2021 were systematically searched in Medline/PubMed, Science Direct, and the Cochrane Library. Search results were exported and stored in RefWorks, the duplicates were removed, and eligible studies were identified, evaluated, and summarized.

Results

Thirty reports met the inclusion criteria. The majority of the studies were prospective (73.33%, n = 22) in nature. The most utilized PET radiotracers were 15O-labeled radio water (H215O, n = 14) and 18F-fluorodeoxyglucose (18F-FDG, n = 8). Other radiotracers used in at least one study were 14(R,S)-(18)F-fluoro-6-thia-heptadecanoic acid (18F-FTHA), 18F-Sodium Fluoride (18F-NaF), 11C-acetate, 68-Gallium (68Ga), 13N-ammonia (13N-NH3), Rubidium-82 (82Rb), radiolabeled cationic ferritin (RadioCF), 11C‐para-aminobenzoic acid (11C-PABA), Gallium-68 pentixafor (68Ga-Pentixafor), 2-deoxy-2-F-fluoro-d-sorbitol (F-FDS) and 55Co-ethylene diamine tetra acetic acid (55Co-EDTA).

Conclusion

PET imaging provides an effective modality for evaluating a range of metabolic functions including glucose and fatty acid uptake, oxygen consumption and renal perfusion. Multiple positron emitting radiolabeled racers can be used for renal imaging in clinical settings. PET imaging thus holds the potential to improve the diagnosis of renal disorders, and to monitor disease progression and treatment response.

Cardiometabolism as an Interlocking Puzzle between the Healthy and Diseased Heart: New Frontiers in Therapeutic Applications

Cardiac metabolism represents a crucial and essential connecting bridge between the healthy and diseased heart. The cardiac muscle, which may be considered an omnivore organ with regard to the energy substrate utilization, under physiological conditions mainly draws energy by fatty acids oxidation. Within cardiomyocytes and their mitochondria, through well-concerted enzymatic reactions, substrates converge on the production of ATP, the basic chemical energy that cardiac muscle converts into mechanical energy, i.e., contraction. When a perturbation of homeostasis occurs, such as an ischemic event, the heart is forced to switch its fatty acid-based metabolism to the carbohydrate utilization as a protective mechanism that allows the maintenance of its key role within the whole organism. Consequently, the flexibility of the cardiac metabolic networks deeply influences the ability of the heart to respond, by adapting to pathophysiological changes. The aim of the present review is to summarize the main metabolic changes detectable in the heart under acute and chronic cardiac pathologies, analyzing possible therapeutic targets to be used. On this basis, cardiometabolism can be described as a crucial mechanism in keeping the physiological structure and function of the heart; furthermore, it can be considered a promising goal for future pharmacological agents able to appropriately modulate the rate-limiting steps of heart metabolic pathways.

Mitochondrial Function and Dysfunction in Dilated Cardiomyopathy

Cardiac tissue requires a persistent production of energy in order to exert its pumping function. Therefore, the maintenance of this function relies on mitochondria that represent the “powerhouse” of all cardiac activities. Mitochondria being one of the key players for the proper functioning of the mammalian heart suggests continual regulation and organization. Mitochondria adapt to cellular energy demands via fusion-fission events and, as a proof-reading ability, undergo mitophagy in cases of abnormalities. Ca²⁺ fluxes play a pivotal role in regulating all mitochondrial functions, including ATP production, metabolism, oxidative stress balance and apoptosis. Communication between mitochondria and others organelles, especially the sarcoplasmic reticulum is required for optimal function. Consequently, abnormal mitochondrial activity results in decreased energy production leading to pathological conditions. In this review, we will describe how mitochondrial function or dysfunction impacts cardiac activities and the development of dilated cardiomyopathy.

Mitochondrial Dysfunction and Heart Disease: Critical Appraisal of an Overlooked Association

The myocardium is among the most energy-consuming tissues in the body, burning from 6 to 30 kg of ATP per day within the mitochondria, the so-called powerhouse of the cardiomyocyte. Although mitochondrial genetic disorders account for a small portion of cardiomyopathies, mitochondrial dysfunction is commonly involved in a broad spectrum of heart diseases, and it has been implicated in the development of heart failure via maladaptive circuits producing and perpetuating mitochondrial stress and energy starvation. In this bench-to-bedside review, we aimed to (i) describe the key functions of the mitochondria within the myocardium, including their role in ischemia/reperfusion injury and intracellular calcium homeostasis; (ii) examine the contribution of mitochondrial dysfunction to multiple cardiac disease phenotypes and their transition to heart failure; and (iii) discuss the rationale and current evidence for targeting mitochondrial function for the treatment of heart failure, including via sodium-glucose cotransporter 2 inhibitors.

Beta 1 adrenoceptor blockade promotes angiogenesis in hypertrophied myocardium of transverse aortic constricted mice

Left ventricular hypertrophy (LVH) is an adaptive structural remodelling consequent to uncontrolled blood pressure. Impaired angiogenesis plays a vital role in transiting LVH into cardiac failure. Catecholamines modulate myocardial function through beta adrenoceptors, and their blockers (β-AR) reduce cardiovascular morbidity and mortality by decelerating the LVH progression. Nonetheless, the effect of β-AR blockers on myocardial vascular bed remains largely obscure. Hence, this study is focussed on analysing the possible outcomes of β-AR blockers on myocardial vascular remodelling using a surgically induced LVH mice model. Transverse aortic constricted mice and sham-operated mice were administered with metoprolol at a dose of 30 mg/kg/d for 60 days and myocardial vascular endothelial growth factor (VEGF) alpha levels, GSH/GSSG ratio, myocardial protein carbonyl content, hypertrophy index and global myocardial function, trans-aortic fluid dynamics and expression pattern of angiopoietin-1 and VEGF alpha were assessed. These findings were further confirmed by histochemical analysis for myocardial capillary density, perivascular fibrosis ratio and intimal thickening. Sub- chronic β-AR blockade reduced the oxidative stress, hypertrophic index, intimal thickening and perivascular fibrosis ratio. A marked increase in myocardial VEGF, angiopoietin 1, global myocardial function and myocardial capillary density was also observed. There was a reduction in the LVH and upregulation of myocardial angiogenesis concluding that β-AR blockers prevent adverse vascular remodelling which might underlie its concealed mechanism of action.

Fatal COVID-19 infection in a patient with long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency: A case report

Long-chain fatty-acyl CoA dehydrogenase deficiency (LCHADD) is an inborn error of long chain fatty acid oxidation with various features including hypoketotic hypoglycemia, recurrent rhabdomyolysis, pigmentary retinopathy, peripheral neuropathy, cardiomyopathy, and arrhythmias. Various stresses trigger metabolic decompensation. Coronavirus disease 2019 (COVID-19) is a pandemic caused by the RNA virus SARS-CoV-2 with diverse presentations ranging from respiratory symptoms to myocarditis. We report a case of a patient with LCHADD who initially presented with typical metabolic decompensation symptoms including nausea, vomiting, and rhabdomyolysis in addition to mild cough, and was found to have COVID-19. She developed acute respiratory failure and refractory hypotension from severe cardiomyopathy which progressed to multiple organ failure and death. Our case illustrates the need for close monitoring of cardiac function in patients with a long-chain fatty acid oxidation disorder.

Drug Development and the Use of Induced Pluripotent Stem Cell-Derived Cardiomyocytes for Disease Modeling and Drug Toxicity Screening

: Over the years, numerous groups have employed human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) as a superb human-compatible model for investigating the function and dysfunction of cardiomyocytes, drug screening and toxicity, disease modeling and for the development of novel drugs for heart diseases. In this review, we discuss the broad use of iPSC-CMs for drug development and disease modeling, in two related themes. In the first theme-drug development, adverse drug reactions, mechanisms of cardiotoxicity and the need for efficient drug screening protocols-we discuss the critical need to screen old and new drugs, the process of drug development, marketing and Adverse Drug reactions (ADRs), drug-induced cardiotoxicity, safety screening during drug development, drug development and patient-specific effect and different mechanisms of ADRs. In the second theme-using iPSC-CMs for disease modeling and developing novel drugs for heart diseases-we discuss the rationale for using iPSC-CMs and modeling acquired and inherited heart diseases with iPSC-CMs.

Histone Deacetylase Inhibitor Suberoylanilide Hydroxamic Acid Improves Energetic Status and Cardiomyogenic Differentiation of Human Dilated Myocardium-Derived Primary Mesenchymal Cells

Background. In this study the effect of histone deacetylase (HDAC) inhibitor suberoylanilide hydroxamic acid (SAHA) on the energetic status and cardiomyogenic differentiation of human healthy and dilated myocardium-derived mesenchymal stromal cells (hmMSC) have been investigated. Methods. The hmMSC were isolated from the healthy and dilated post-operation heart biopsies by explant outgrowth method. Cell proliferation, HDAC activity, mitochondrial membrane potential, and level of adenosine triphosphate (ATP) were evaluated. The effect of SAHA on mitochondrial parameters has been investigated also by Seahorse XF analyzer and cardiomyogenic differentiation was confirmed by the expression of transcription factor NK2 Homeobox 5 (Nkx2.5), cardiac troponin T and alpha cardiac actin at gene and protein levels. Results. Dilated myocardium-derived hmMSC had almost 1.5 folds higher HDAC activity compared to the healthy cells and significantly lower mitochondrial membrane potential and ATP level. HDAC class I and II inhibitor SAHA improved energetic status of mitochondria in dilated myocardium-isolated hmMSC and increased expression of cardiac specific proteins during 14 days of exposure of cells to SAHA. Conclusions. HDAC inhibitor SAHA can be a promising therapeutic for dilated cardiomyopathy (DCM). Dilated hmMSC exposed to SAHA improved energetic status and, subsequently, cardiomyogenic differentiation. Data suggest that human dilated myocardium-derived MSC still have cardio tissue regenerative potential, which might be stimulated by HDAC inhibitors.

Exercise enhances cardiac function by improving mitochondrial dysfunction and maintaining energy homoeostasis in the development of diabetic cardiomyopathy

Diabetic cardiomyopathy (DCM) is a major cause of morbidity and mortality in diabetic patients. Reactive oxygen species (ROS) produced by oxidative stress play an important role in the development of DCM. DCM involves abnormal energy metabolism, thereby reducing energy production. Exercise has been reported to be effective in protecting the heart against ROS accumulation during the development of DCM. We hypothesize that the AMPK/PGC-1α axis may play a crucial role in exercise-induced bioenergetic metabolism and aerobic respiration on oxidative stress parameters in the development of diabetic cardiomyopathy. Using a streptozotocin/high-fat diet mouse to generate a diabetic model, our aim was to evaluate the effects of exercise on the cardiac function, mitochondrial oxidative capacity, mitochondrial function, and cardiac expression of PGC-1α. Mice fed a high-fat diet were given MO-siPGC-1α or treated with AMPK inhibitor. Mitochondrial structure and effects of switching between the Warburg effect and aerobic respiration were analysed. Exercise improved blood pressure and systolic dysfunction in diabetic mouse hearts. The beneficial effects of exercise were also observed in a mitochondrial function study, as reflected by an enhanced oxidative phosphorylation level, increased membrane potential, and decreased ROS level and oxygen consumption. On the other hand, depletion of PGC-1α attenuated the effects of exercise on the enhancement of mitochondrial function. In addition, PGC-1α may be responsible for reversing the Warburg effect to aerobic respiration, thus enhancing mitochondrial metabolism and energy homoeostasis. In this study, we demonstrate the protective effects of exercise on shifting energy metabolism from fatty acid oxidation to glucose oxidation in an established diabetic stage. These data suggest that exercise is effective at ameliorating diabetic cardiomyopathy by improving mitochondrial function and reducing metabolic disturbances.

Intracellular calcium mishandling leads to cardiac dysfunction and ventricular arrhythmias in a mouse model of propionic acidemia

Propionic acidemia (PA) is a rare metabolic disease associated with mutations in genes encoding the α and β subunits of the enzyme propionyl-CoA carboxylase. The accumulation of toxic metabolites results in mitochondrial dysfunction, increased reactive oxygen species production and oxidative damage, which have been associated with the disease pathophysiology. Clinical symptoms are heterogeneous and include cardiac complications, mainly cardiac dysfunction and arrhythmias, which are recognized as one of the major life-threatening manifestations in patients. We aimed to investigate the molecular mechanisms underlying the cardiac phenotype using a hypomorphic mouse model (Pcca^-/-(A138T)) that recapitulates some biochemical and clinical characteristics of PA. We demonstrate that Pcca^-/-(A138T) mice present with depressed cardiac function along with impaired cell contractility when compared to the wild-type mice. Cardiac dysfunction in Pcca^-/-(A138T) mice was associated with lower systolic Ca²⁺ release ([Ca²⁺]_i transients), impairment in the sarcoplasmic reticulum (SR) Ca²⁺ load and decreased Ca²⁺ re-uptake by SR-Ca²⁺ ATPase (SERCA2a). These functional changes correlated well with the depressed activity of SERCA2a, the elevated ROS levels and SERCA2a oxidation rate in cardiomyocytes isolated from Pcca^-/-(A138T) mice. In addition, decreased SR-Ca²⁺ load in Pcca^-/-(A138T) cardiomyocytes was associated with increased diastolic Ca²⁺ release. The increase in Ca²⁺ sparks, Ca²⁺ waves and spontaneous [Ca²⁺]_i transients in Pcca^-/-(A138T) cardiomyocytes could be responsible for the induction of ventricular arrhythmias detected in these mice. Overall, our results uncover the role of impaired Ca²⁺ handling in arrhythmias and cardiac dysfunction in PA, and identify new targets for the development of therapeutic approaches for this devastating metabolic disease.

Re-balancing cellular energy substrate metabolism to mend the failing heart

Fatty acids and glucose are the main substrates for myocardial energy provision. Under physiologic conditions, there is a distinct and finely tuned balance between the utilization of these substrates. Using the non-ischemic heart as an example, we discuss that upon stress this substrate balance is upset resulting in an over-reliance on either fatty acids or glucose, and that chronic fuel shifts towards a single type of substrate appear to be linked with cardiac dysfunction. These observations suggest that interventions aimed at re-balancing a tilted substrate preference towards an appropriate mix of substrates may result in restoration of cardiac contractile performance. Examples of manipulating cellular substrate uptake as a means to re-balance fuel supply, being associated with mended cardiac function underscore this concept. We also address the molecular mechanisms underlying the apparent need for a fatty acid-glucose fuel balance. We propose that re-balancing cellular fuel supply, in particular with respect to fatty acids and glucose, may be an effective strategy to treat the failing heart.

Cardiomyopathy in Children: Classification and Diagnosis: A Scientific Statement From the American Heart Association

In this scientific statement from the American Heart Association, experts in the field of cardiomyopathy (heart muscle disease) in children address 2 issues: the most current understanding of the causes of cardiomyopathy in children and the optimal approaches to diagnosis cardiomyopathy in children. Cardiomyopathies result in some of the worst pediatric cardiology outcomes; nearly 40% of children who present with symptomatic cardiomyopathy undergo a heart transplantation or die within the first 2 years after diagnosis. The percentage of children with cardiomyopathy who underwent a heart transplantation has not declined over the past 10 years, and cardiomyopathy remains the leading cause of transplantation for children >1 year of age. Studies from the National Heart, Lung, and Blood Institute-funded Pediatric Cardiomyopathy Registry have shown that causes are established in very few children with cardiomyopathy, yet genetic causes are likely to be present in most. The incidence of pediatric cardiomyopathy is ≈1 per 100 000 children. This is comparable to the incidence of such childhood cancers as lymphoma, Wilms tumor, and neuroblastoma. However, the published research and scientific conferences focused on pediatric cardiomyopathy are sparcer than for those cancers. The aim of the statement is to focus on the diagnosis and classification of cardiomyopathy. We anticipate that this report will help shape the future research priorities in this set of diseases to achieve earlier diagnosis, improved clinical outcomes, and better quality of life for these children and their families.

Effects of gene therapy on cardiovascular symptoms of lysosomal storage diseases

Lysosomal storage diseases (LSDs) are inherited conditions caused by impaired lysosomal function and consequent substrate storage, leading to a range of clinical manifestations, including cardiovascular disease. This may lead to significant symptoms and even cardiac failure, which is an important cause of death among patients. Currently available treatments do not completely correct cardiac involvement in the LSDs. Gene therapy has been tested as a therapeutic alternative with promising results for the heart disease. In this review, we present the results of different approaches of gene therapy for LSDs, mainly in animal models, and its effects in the heart, focusing on protocols with cardiac functional analysis.

[The role of sphingolipids in cardiovascular pathologies]

Cardiovascular diseases (CVD) remain the leading cause of death in industrialized countries. One of the most significant risk factors for atherosclerosis is hypercholesterolemia. Its diagnostics is based on routine lipid profile analysis, including the determination of total cholesterol, low and high density lipoprotein cholesterol, and triglycerides. However in recent years, much attention has been paid to the crosstalk between the metabolic pathways of the cholesterol and sphingolipids biosynthesis. Sphingolipids are a group of lipids, containing a molecule of aliphatic alcohol sphingosine. These include sphingomyelins, cerebrosides, gangliosides and ceramides, sphingosines, and sphingosine-1-phosphate (S-1-P). It has been found that catabolism of sphingolipids is associated with catabolism of cholesterol. However, the exact mechanism of this interaction is still unknown. Particular attention as CVD inducer attracts ceramide (Cer). Lipoprotein aggregates isolated from atherosclerotic pluques are enriched with Cer. The level of Cer and sphingosine increases after ischemia reperfusion of the heart, in the infarction zone and in the blood, and also in hypertension. S-1-P exhibits pronounced cardioprotective properties. Its content sharply decreases with ischemia and myocardial infarction. S-1-P presents predominantly in HDL, and influences their multiple functions. Increased levels of Cer and sphingosine and decreased levels of S-1-P formed in the course of coronary heart disease can be an important factor in the development of atherosclerosis. It is proposed to use determination of sphingolipids in blood plasma as markers for early diagnosis of cardiac ischemia and for hypertension in humans. There are intensive studies aimed at correction of metabolism S-1-P. The most successful drugs are those that use S-1-P receptors as a targets, since all of its actions are receptor-mediated.

Semantic Multi-Classifier Systems Identify Predictive Processes in Heart Failure Models across Species

Genetic model organisms have the potential of removing blind spots from the underlying gene regulatory networks of human diseases. Allowing analyses under experimental conditions they complement the insights gained from observational data. An inevitable requirement for a successful trans-species transfer is an abstract but precise high-level characterization of experimental findings. In this work, we provide a large-scale analysis of seven weak contractility/heart failure genotypes of the model organism zebrafish which all share a weak contractility phenotype. In supervised classification experiments, we screen for discriminative patterns that distinguish between observable phenotypes (homozygous mutant individuals) as well as wild-type (homozygous wild-types) and carriers (heterozygous individuals). As the method of choice we use semantic multi-classifier systems, a knowledge-based approach which constructs hypotheses from a predefined vocabulary of high-level terms (e.g., Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways or Gene Ontology (GO) terms). Evaluating these models leads to a compact description of the underlying processes and guides the screening for new molecular markers of heart failure. Furthermore, we were able to independently corroborate the identified processes in Wistar rats.

Metabolic Effects of Metformin in the Failing Heart

Accumulating evidence shows that metformin is an insulin-sensitizing antidiabetic drug widely used in the treatment of type 2 diabetes mellitus (T2DM), which can exert favorable effects on cardiovascular risk and may be safely used in patients with heart failure (HF), and even able to reduce the incidence of HF and to reduce HF mortality. In failing hearts, metformin improves myocardial energy metabolic status through the activation of AMP (adenosine monophosphate)-activated protein kinase (AMPK) and the regulation of lipid and glucose metabolism. By increasing nitric oxide (NO) bioavailability, limiting interstitial fibrosis, reducing the deposition of advanced glycation end-products (AGEs), and inhibiting myocardial cell apoptosis metformin reduces cardiac remodeling and hypertrophy, and thereby preserves left ventricular systolic and diastolic functions. While a lot of preclinical and clinical studies showed the cardiovascular safety of metformin therapy in diabetic patients and HF, to confirm observed benefits, the specific large-scale trials configured for HF development in diabetic patients as a primary endpoints are necessary.

Mitochondrial G8292A and C8794T mutations in patients with Niemann-Pick disease type C

Niemann-Pick disease type C (NP-C) is a neurovisceral lipid storage disorder. At the cellular level, the disorder is characterized by accumulation of unesterified cholesterol and glycolipids in the lysosomal/late endosomal system. NP-C is transmitted in an autosomal recessive manner and is caused by mutations in either the NPC1 (95% of families) or NPC2 gene. The estimated disease incidence is 1 in 120,000 live births, but this likely represents an underestimate, as the disease may be under-diagnosed due to its highly heterogeneous presentation. Variants of adenosine triphosphatase (ATPase) subunit 6 and ATPase subunit 8 (ATPase6/8) in mitochondrial DNA (mtDNA) have been reported in different types of genetic diseases including NP-C. In the present study, the blood samples of 22 Iranian patients with NP-C and 150 healthy subjects as a control group were analyzed. The DNA of the blood samples was extracted by the salting out method and analyzed for ATPase6/8 mutations using polymerase chain reaction sequencing. Sequence variations in mitochondrial genome samples were determined via the Mitomap database. Analysis of sequencing data confirmed the existence of 11 different single nucleotide polymorphisms (SNPs) in patients with NP-C1. One of the most prevalent polymorphisms was the A8860G variant, which was observed in both affected and non-affected groups and determined to have no significant association with NP-C incidence. Amongst the 11 polymorphisms, only one was identified in the ATPase8 gene, while 9 including A8860G were observed in the ATPase6 gene. Furthermore, two SNPs, G8292A and C8792A, located in the non-coding region of mtDNA and the ATPase6 gene, respectively, exhibited significantly higher prevalence rates in NP-C1 patients compared with the control group (P<0.01). The present study suggests that there may be an association between mitochondrial ATPase6/8 mutations and the incidence of NP-C disease. In addition, the mitochondrial SNPs identified maybe pathogenic mutations involved in the development and prevalence of NP-C. Furthermore, these results suggest a higher occurrence of mutations in ATPase6 than in ATPase8 in NP-C patients.

From cell to heart: the impact of the cell organelles dysfunction on heart disease

: Cellular morphology reflects biologic behavior and activity of the tissue and of the organ also reflects the genetic and molecular biology of the cells themselves. This intermediary position places examination of the cell in a key role to our understanding of the innumerable processes that affect this closely knit chain, from molecules to host. A large volume of the cell is occupied by organelles that come in a variety of shapes and sizes. Organelles are dynamic to maintain homeostasis and adjust to the various functions of the cell. The cardiovascular system is metabolically very active and is therefore particularly vulnerable to defects of the cellular substructures, such as the mitochondrial respiratory chain. Given the functional complexity of the cardiovascular system, it is not surprising that defects in cell organelles produce diverse clinical manifestations. Organelle dysfunction is being recognized as the basis of a wide variety of heart diseases. In this review, the authors discuss the relationship between organelle structure and function in myocardial cells and how these organelles have been linked to the cardiovascular diseases.

Ordinary differential equations and Boolean networks in application to modelling of 6-mercaptopurine metabolism

We consider two approaches to modelling the cell metabolism of 6-mercaptopurine, one of the important chemotherapy drugs used for treating acute lymphocytic leukaemia: kinetic ordinary differential equations, and Boolean networks supplied with one controlling node, which takes continual values. We analyse their interplay with respect to taking into account ATP concentration as a key parameter of switching between different pathways. It is shown that the Boolean networks, which allow avoiding the complexity of general kinetic modelling, preserve the possibility of reproducing the principal switching mechanism.

Barth Syndrome: Connecting Cardiolipin to Cardiomyopathy

The Barth syndrome (BTHS) is caused by an inborn error of metabolism that manifests characteristic phenotypic features including altered mitochondrial membrane phospholipids, lactic acidosis, organic acid-uria, skeletal muscle weakness and cardiomyopathy. The underlying cause of BTHS has been definitively traced to mutations in the tafazzin (TAZ) gene locus on chromosome X. TAZ encodes a phospholipid transacylase that promotes cardiolipin acyl chain remodeling. Absence of tafazzin activity results in cardiolipin molecular species heterogeneity, increased levels of monolysocardiolipin and lower cardiolipin abundance. In skeletal muscle and cardiac tissue mitochondria these alterations in cardiolipin perturb the inner membrane, compromising electron transport chain function and aerobic respiration. Decreased electron flow from fuel metabolism via NADH ubiquinone oxidoreductase activity leads to a buildup of NADH in the matrix space and product inhibition of key TCA cycle enzymes. As TCA cycle activity slows pyruvate generated by glycolysis is diverted to lactic acid. In turn, Cori cycle activity increases to supply muscle with glucose for continued ATP production. Acetyl CoA that is unable to enter the TCA cycle is diverted to organic acid waste products that are excreted in urine. Overall, reduced ATP production efficiency in BTHS is exacerbated under conditions of increased energy demand. Prolonged deficiency in ATP production capacity underlies cell and tissue pathology that ultimately is manifest as dilated cardiomyopathy.

Triheptanoin treatment in patients with pediatric cardiomyopathy associated with long chain-fatty acid oxidation disorders

Long-chain fatty acid oxidation disorders (LC-FAOD) can cause cardiac hypertrophy and cardiomyopathy, often presenting in infancy, typically leading to death or heart transplant despite ongoing treatment. Previous data on triheptanoin treatment of cardiomyopathy in LC-FAOD suggested a clinical benefit on heart function during acute failure. An additional series of LC-FAOD patients with critical emergencies associated with cardiomyopathy was treated with triheptanoin under emergency treatment or compassionate use protocols. Case reports from 10 patients (8 infants) with moderate or severe cardiomyopathy associated with LC-FAOD are summarized. The majority of these patients were detected by newborn screening, with follow up confirmatory testing, including mutation analysis; all patients were managed with standard treatment, including medium chain triglyceride (MCT) oil. While on this regimen, they presented with acute heart failure requiring hospitalization and cardiac support (ventilation, ECMO, vasopressors) and, in some cases, resuscitation. The patients discontinued MCT oil and began treatment with triheptanoin, an investigational drug. Triheptanoin is expected to provide anaplerotic metabolites, to replace deficient TCA cycle intermediates and improve effective energy metabolism. Cardiac function was measured by echocardiography and ejection fraction (EF) was assessed. EF was moderately to severely impaired prior to triheptanoin treatment, ranging from 12-45%. Improvements in EF began between 2 and 21days following initiation of triheptanoin, and peaked at 33-71%, with 9 of 10 patients achieving EF in the normal range. Continued treatment was associated with longer-term stabilization of clinical signs of cardiomyopathy. The most common adverse event observed was gastrointestinal distress. Of the 10 patients, 7 have continued on treatment, 1 elected to discontinue due to tolerability issues, and 2 patients died from other causes. Two of the case histories illustrate that cardiomyopathy may also develop later in childhood and/or persist into adulthood. Overall, the presented cases suggest a therapeutic effect of triheptanoin in the management of acute cardiomyopathy associated with LC-FAOD.

Role of proteases in the pathophysiology of cardiac disease

Cardiovascular disease is a major cause of death and thus a great deal of effort has been made in salvaging the diseased myocardium. Although various factors have been identified as possible causes of different cardiac diseases such as heart failure and ischemic heart disease, there is a real need to elucidate their role for the better understanding of the cardiac disease pathology and formulation of strategies for developing newer therapeutic interventions. In view of the intimate involvement of different types of proteases in maintaining cellular structure, the role of proteases in various cardiac diseases has become the focus of recent research. Proteases are present in the cytosol as well as are localized in a number of subcellular organelles in the cell. These are known to use extracellular matrix, cytoskeletal, sarcolemmal, sarcoplasmic reticular, mitochondrial and myofibrillar proteins as substrates. Work from different laboratories using a wide variety of techniques has shown that the activation of proteases causes alterations of a number of specific proteins leading to subcellular remodeling and cardiac dysfunction. Inhibition of protease action by different drugs and agents, therefore, has a clinical relevance and is expected to form a part of new treatment paradigm for improving heart function. This review examines the biochemistry and localization of some of the proteases in the cardiac tissue in addition to identification of the sites of action of some protease inhibitors. (Mol Cell Biochem 263: 241-256, 2004).

Metabolomics-assisted proteomics identifies succinylation and SIRT5 as important regulators of cardiac function

Cellular metabolites, such as acyl-CoA, can modify proteins, leading to protein posttranslational modifications (PTMs). One such PTM is lysine succinylation, which is regulated by sirtuin 5 (SIRT5). Although numerous proteins are modified by lysine succinylation, the physiological significance of lysine succinylation and SIRT5 remains elusive. Here, by profiling acyl-CoA molecules in various mouse tissues, we have discovered that different tissues have different acyl-CoA profiles and that succinyl-CoA is the most abundant acyl-CoA molecule in the heart. This interesting observation has prompted us to examine protein lysine succinylation in different mouse tissues in the presence and absence of SIRT5. Protein lysine succinylation predominantly accumulates in the heart whenSirt5is deleted. Using proteomic studies, we have identified many cardiac proteins regulated by SIRT5. Our data suggest that ECHA, a protein involved in fatty acid oxidation, is a major enzyme that is regulated by SIRT5 and affects heart function.Sirt5knockout (KO) mice have lower ECHA activity, increased long-chain acyl-CoAs, and decreased ATP in the heart under fasting conditions.Sirt5KO mice develop hypertrophic cardiomyopathy, as evident from the increased heart weight relative to body weight, as well as reduced shortening and ejection fractions. These findings establish that regulating heart metabolism and function is a major physiological function of lysine succinylation and SIRT5.

Metabolic remodeling in early development and cardiomyocyte maturation

Aberrations in metabolism contribute to a large number of diseases, such as diabetes, obesity, cancer, and cardiovascular diseases, that have a substantial impact on the mortality rates and quality of life worldwide. However, the mechanisms leading to these changes in metabolic state--and whether they are conserved between diseases--is not well understood. Changes in metabolism similar to those seen in pathological conditions are observed during normal development in a number of different cell types. This provides hope that understanding the mechanism of these metabolic switches in normal development may provide useful insight in correcting them in pathological cases. Here, we focus on the metabolic remodeling observed both in early stage embryonic stem cells and during the maturation of cardiomyocytes.

Glutamine and glutamate limit the shortening of action potential duration in anoxia-challenged rabbit hearts

In clinical conditions, amino acid supplementation is applied to improve contractile function, minimize ischemia/reperfusion injury, and facilitate postoperative recovery. It has been shown that glutamine enhances myocardial ATP/APD (action potential duration) and glutathione/oxidized glutathione ratios, and can increase hexosamine biosynthesis pathway flux, which is believed to play a role in cardioprotection. Here, we studied the effect of glutamine and glutamate on electrical activity in Langendorff-perfused rabbit hearts. The hearts were supplied by Tyrode's media with or without 2.5 mmol/L glutamine and 150 μmol/L glutamate, and exposed to two 6-min anoxias with 20-min recovery in between. Change in APD was detected using a monophasic action potential probe. A nonlinear mixed-effects regression technique was used to evaluate the effect of amino acids on APD over the experiment. Typically, the dynamic of APD change encompasses three phases: short transient increase (more prominent in the first episode), slow decrease, and fast increase (starting with the beginning of recovery). The effect of both anoxic challenge and glutamine/glutamate was cumulative, being more pronounced in the second anoxia. The amino acids' protective effect became largest by the end of anoxia – 20.0% (18.9, 95% CI: [2.6 ms, 35.1 ms]), during the first anoxia and 36.6% (27.1, 95% CI: [7.7 ms, 46.6 ms]), during the second. Following the second anoxia, APD difference between control and supplemented hearts progressively increased, attaining 10.8% (13.6, 95% CI: [4.1 ms, 23.1 ms]) at the experiments' end. Our data reveal APD stabilizing and suggest an antiarrhythmic capacity of amino acid supplementation in anoxic/ischemic conditions.

Sphingolipids in cardiovascular diseases and metabolic disorders

Many investigations suggest the pivotal role of sphingolipids in the pathogenesis of lifestyle diseases such as myocardial infarction, hypertension, stroke, diabetes mellitus type 2 and obesity. Some studies suggest that sphingolipids are important factors in cellular signal transduction. They serve as biologically active components of cell membrane and are involved in many processes such as proliferation, maturation and apoptosis. Recently, ceramide and sphingosine-1-phosphate have become the target of many investigations. Ceramide is generated in three metabolic pathways and many factors induce its production as a cellular stress response. Ceramide has proapoptotic properties and acts as a precursor for many other sphingolipids. Sphingosine-1-phosphate is a ceramide derivative, acting antiapoptotically and mitogenically and it is importantly involved in cardioprotection. Further research on the involvement of sphingolipids in cellular pathophysiology may improve the prevention and therapy of lifestyle diseases.

Neurological and cardiac responses after treatment with miglustat and a ketogenic diet in a patient with Sandhoff disease

Sandhoff disease is a progressive neurodegenerative disorder characterized by accumulation of GM2 gangliosides. We describe a 6-year-old male with coarse facial features, developmental delay, refractory seizures, hypertrophic cardiomyopathy, who was later found to have Sandhoff disease. Previous studies have revealed that caloric restriction in combination with miglustat increased survival and motor behavior in mouse model of Sandhoff disease. These findings suggest that combination therapy may result in improved outcomes for patients with Sandhoff. Initiation of treatment with miglustat and a ketogenic diet was followed by improvement of the patient's seizure control and cardiac function. Further clinical investigation is required to better determine the benefit of management in late-onset forms of Sandhoff disease.

Advantages of early replacement therapy for mucopolysaccharidosis type VI: echocardiographic follow-up of siblings

Mucopolysaccharidosis type VI (Marateaux-Lamy syndrome) is an autosomal recessive disorder caused by deficient activity of the enzyme N-acetylgalactosamine-4-sulphatase (arylsulphatase B). Cytoplasmic vacuoles full of dermatan sulphate are observed in endothelial cells, myocyte, and fibroblasts, compromising the function of cardiovascular structures and contributing significantly towards morbidity and mortality. The primary objective of this study was to assess the advantages of early replacement therapy with recombinant human arylsulphatase B through the echocardiographic follow-up of sisters who started treatment at quite different ages: one at 9 years and the other at 1 year and 7 months. The older sibling showed striking mitral and aortic valve compromise when she was only 2 years old and finally needed cardiac surgery at the age of 8, even before starting enzyme replacement. Differently, the younger one has developed only mild mitral and aortic lesions throughout the follow-up period of 3 years. The two siblings had left ventricle cardiomyopathy, but partial reverse remodelling was induced by enzyme replacement therapy in both cases. The younger sibling has never received any cardiovascular drugs, whereas the older one has been using β-blockers and diuretics in addition to enzyme therapy to cope with heart failure. Comparing the outcomes of these two sisters with a very aggressive phenotype of mucopolysaccharidosis type VI, the conclusion was that early onset of therapy may slow down the disease progression and prevent severe cardiac lesions to be established. Moreover, patients' compliance is essential for the success of treatment, as sequential echocardiographic evaluation demonstrated worsening of some cardiac lesions whenever infusions were missed.

Desialylation of surface receptors as a new dimension in cell signaling

Terminal sialic acid residues are found in abundance in glycan chains of glycoproteins and glycolipids on the surface of all live cells forming an outer layer of the cell originally known as glycocalyx. Their presence affects the molecular properties and structure of glycoconjugates, modifying their function and interactions with other molecules. Consequently, the sialylation state of glycoproteins and glycolipids has been recognized as a critical factor modulating molecular recognitions inside the cell, between the cells, between the cells and the extracellular matrix, and between the cells and certain exogenous pathogens. Until recently sialyltransferases that catalyze transfer of sialic acid residues to the glycan chains in the process of their biosynthesis were thought to be mainly responsible for the creation and maintenance of a temporal and spatial diversity of sialylated moieties. However, the growing evidence suggests that in mammalian cells, at least equally important roles belong to sialidases/neuraminidases, which are located on the cell surface and in intracellular compartments, and may either initiate the catabolism of sialoglycoconjugates or just cleave their sialic acid residues, and thereby contribute to temporal changes in their structure and functions. The current review summarizes emerging data demonstrating that mammalian neuraminidase 1, well known for its lysosomal catabolic function, is also targeted to the cell surface and assumes the previously unrecognized role as a structural and functional modulator of cellular receptors.

Dynamic reorganization of the AC16 cardiomyocyte transcriptome in response to TNFα signaling revealed by integrated genomic analyses

BACKGROUND

Defining cell type-specific transcriptomes in mammals can be challenging, especially for unannotated regions of the genome. We have developed an analytical pipeline called groHMM for annotating primary transcripts using global nuclear run-on sequencing (GRO-seq) data. Herein, we use this pipeline to characterize the transcriptome of an immortalized adult human ventricular cardiomyocyte cell line (AC16) in response to signaling by tumor necrosis factor alpha (TNFα), which is controlled in part by NF-κB, a key transcriptional regulator of inflammation. A unique aspect of this work is the use of the RNA polymerase II (Pol II) inhibitor α-amanitin, which we used to define a set of RNA polymerase I and III (Pol I and Pol III) transcripts.

RESULTS

Using groHMM, we identified ~30,000 coding and non-coding transcribed regions in AC16 cells, which includes a set of unique Pol I and Pol III primary transcripts. Many of these transcripts have not been annotated previously, including enhancer RNAs originating from NF-κB binding sites. In addition, we observed that AC16 cells rapidly and dynamically reorganize their transcriptomes in response to TNFα stimulation in an NF-κB-dependent manner, switching from a basal state to a proinflammatory state affecting a spectrum of cardiac-associated protein-coding and non-coding genes. Moreover, we observed distinct Pol II dynamics for up- and downregulated genes, with a rapid release of Pol II into productive elongation for TNFα-stimulated genes. As expected, the TNFα-induced changes in the AC16 transcriptome resulted in corresponding changes in cognate mRNA and protein levels in a similar manner, but with delayed kinetics.

CONCLUSIONS

Our studies illustrate how computational genomics can be used to characterize the signal-regulated transcriptome in biologically relevant cell types, providing new information about how the human genome is organized, transcribed and regulated. In addition, they show how α-amanitin can be used to reveal the Pol I and Pol III transcriptome. Furthermore, they shed new light on the regulation of the cardiomyocyte transcriptome in response to a proinflammatory signal and help to clarify the link between inflammation and cardiomyocyte function at the transcriptional level.