Modulating fatty acid oxidation in heart failure

MRI Application and Challenges of Hyperpolarized Carbon-13 Pyruvate in Translational and Clinical Cardiovascular Studies: A Literature Review

Cardiovascular disease shows, or may even be caused by, changes in metabolism. Hyperpolarized magnetic resonance spectroscopy and imaging is a technique that could assess the role of different aspects of metabolism in heart disease, allowing real-time metabolic flux assessment in vivo. In this review, we introduce the main hyperpolarization techniques. Then, we summarize the use of dedicated radiofrequency 13C coils, and report a state of the art of 13C data acquisition. Finally, this review provides an overview of the pre-clinical and clinical studies on cardiac metabolism in the healthy and diseased heart. We furthermore show what advances have been made to translate this technique into the clinic in the near future and what technical challenges still remain, such as exploring other metabolic substrates.

Expanding the Frontiers of Guardian Antioxidant Selenoproteins in Cardiovascular Pathophysiology

Significance: Physiological levels of reactive oxygen and nitrogen species (ROS/RNS) function as fundamental messengers for many cellular and developmental processes in the cardiovascular system. ROS/RNS involved in cardiac redox-signaling originate from diverse sources, and their levels are tightly controlled by key endogenous antioxidant systems that counteract their accumulation. However, dysregulated redox-stress resulting from inefficient removal of ROS/RNS leads to inflammation, mitochondrial dysfunction, and cell death, contributing to the development and progression of cardiovascular disease (CVD). Recent Advances: Basic and clinical studies demonstrate the critical role of selenium (Se) and selenoproteins (unique proteins that incorporate Se into their active site in the form of the 21st proteinogenic amino acid selenocysteine [Sec]), including glutathione peroxidase and thioredoxin reductase, in cardiovascular redox homeostasis, representing a first-line enzymatic antioxidant defense of the heart. Increasing attention has been paid to emerging selenoproteins in the endoplasmic reticulum (ER) (i.e., a multifunctional intracellular organelle whose disruption triggers cardiac inflammation and oxidative stress, leading to multiple CVD), which are crucially involved in redox balance, antioxidant activity, and calcium and ER homeostasis. Critical Issues: This review focuses on endogenous antioxidant strategies with therapeutic potential, particularly selenoproteins, which are very promising but deserve more detailed and clinical studies. Future Directions: The importance of selective selenoproteins in embryonic development and the consequences of their mutations and inborn errors highlight the need to improve knowledge of their biological function in myocardial redox signaling. This could facilitate the development of personalized approaches for the diagnosis, prevention, and treatment of CVD. Antioxid. Redox Signal. 40, 369-432.

Cardiac Metabolism, Reprogramming, and Diseases

Cardiovascular diseases (CVD) account for the largest bulk of deaths worldwide, posing a massive burden on societies and the global healthcare system. Besides, the incidence and prevalence of these diseases are on the rise, demanding imminent action to revert this trend. Cardiovascular pathogenesis harbors a variety of molecular and cellular mechanisms among which dysregulated metabolism is of significant importance and may even proceed other mechanisms. The healthy heart metabolism primarily relies on fatty acids for the ultimate production of energy through oxidative phosphorylation in mitochondria. Other metabolites such as glucose, amino acids, and ketone bodies come next. Under pathological conditions, there is a shift in metabolic pathways and the preference of metabolites, termed metabolic remodeling or reprogramming. In this review, we aim to summarize cardiovascular metabolism and remodeling in different subsets of CVD to come up with a new paradigm for understanding and treatment of these diseases.

Energy metabolism and redox balance: How phytochemicals influence heart failure treatment

Heart Failure (HF) epitomizes a formidable global health quandary characterized by marked morbidity and mortality. It has been established that severe derangements in energy metabolism are central to the pathogenesis of HF, culminating in an inadequate cardiac energy milieu, which, in turn, precipitates cardiac pump dysfunction and systemic energy metabolic failure, thereby steering the trajectory and potential recuperation of HF. The conventional therapeutic paradigms for HF predominantly target amelioration of heart rate, and cardiac preload and afterload, proffering symptomatic palliation or decelerating the disease progression. However, the realm of therapeutics targeting the cardiac energy metabolism remains largely uncharted. This review delineates the quintessential characteristics of cardiac energy metabolism in healthy hearts, and the metabolic aberrations observed during HF, alongside the associated metabolic pathways and targets. Furthermore, we delve into the potential of phytochemicals in rectifying the redox disequilibrium and the perturbations in energy metabolism observed in HF. Through an exhaustive analysis of recent advancements, we underscore the promise of phytochemicals in modulating these pathways, thereby unfurling a novel vista on HF therapeutics. Given their potential in orchestrating cardiac energy metabolism, phytochemicals are emerging as a burgeoning frontier for HF treatment. The review accentuates the imperative for deeper exploration into how these phytochemicals specifically intervene in cardiac energy metabolism, and the subsequent translation of these findings into clinical applications, thereby broadening the horizon for HF treatment modalities.

Diastolic function in chronic kidney disease

Chronic kidney disease (CKD) is characterized by clustered age-independent concentric left ventricular (LV) geometry, geometry-independent systolic dysfunction and age and heart rate-independent diastolic dysfunction. Concentric LV geometry is always associated with echocardiographic markers of abnormal LV relaxation and increased myocardial stiffness, two hallmarks of diastolic dysfunction. Non-haemodynamic mechanisms such as metabolic and electrolyte abnormalities, activation of biological pathways and chronic exposure to cytokine cascade and the myocardial macrophage system also impact myocardial structure and impair the architecture of the myocardial scaffold, producing and increasing reactive fibrosis and altering myocardial distensibility. This review addresses the pathophysiology of diastole in CKD and its relations with cardiac mechanics, haemodynamic loading, structural conditions, non-haemodynamic factors and metabolic characteristics. The three mechanisms of diastole will be examined: elastic recoil, active relaxation and passive distensibility and filling. Based on current evidence, we briefly provide methods for quantification of diastolic function and discuss whether diastolic dysfunction represents a distinct characteristic in CKD or a proxy of the severity of the cardiovascular condition, with the potential to be predicted by the general cardiovascular phenotype. Finally, the review discusses assessment of diastolic function in the context of CKD, with special emphasis on end-stage kidney disease, to indicate whether and when in-depth measurements might be helpful for clinical decision making in this context.

Inhibition of OAT1/3 and CMPF uptake attenuates myocardial ischemia-induced chronic heart failure via decreasing fatty acid oxidation and the therapeutic effects of ruscogenin

Chronic heart failure (CHF) as a long-term disease is highly prevalent in elder people worldwide. Early diagnosis and treatments are crucial for preventing the development of CHF. Herein, we aimed to identify novel diagnostic biomarker, therapeutic target and drug for CHF. Untargeted metabolomic analysis has been used to characterize the different metabolomic profile between CHF patients and healthy people. Meanwhile, the targeted metabolomic study demonstrated the elevation of 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF) in the serum of CHF patients and coronary artery ligation-induced CHF mice. Subsequently, we firstly observed that elevation of CMPF impaired cardiac function and aggravated myocardial injury by enhancing fatty acid oxidation (FAO). Interestingly, inhibition of responsible transporters organic anion transporter 1/3 (OAT1/3) has been found to decrease the CMPF level, and suppress FAO-related key protein expressions including peroxisome proliferator-activated receptor alpha, peroxisome proliferative activated receptor-α, carnitine palmitoyl transferase 1, and malonyl CoA decarboxylase in coronary artery ligation-induced CHF mice. Meanwhile, the inhibitor of OAT1/3 presented an excellent improvement in cardiac function and histological injury. Based on the above findings, molecular docking was adopted to screen the potential therapeutic drug targeting OAT1/3, and ruscogenin (RUS) exhibited a great binding affinity with OAT1 and OAT3. Next, it was verified that RUS could remarkedly decrease the expression of OAT1/3 and CMPF levels in heart tissue of CHF mice, as well as suppress the expression of FAO-related proteins. What's more, RUS can effectively improve cardiac function, myocardial fibrosis and morphological damage. Collectively, this study provided a potential metabolic marker CMPF and novel target OAT1/3 for CHF, which were demonstrated to be involved in FAO. And RUS was identified as a potential anti-FAO drug for CHF by regulating OAT1/3.

Increased acylcarnitines in infant heart failure indicate fatty acid oxidation inhibition: towards therapeutic options?

AIMS

Heart failure in adults is characterized by reduction of long-chain fatty acid oxidation in favour of carbohydrate metabolism. This adaptive phenomenon becomes maladaptive because energy conversion decreases and lipid toxic derivatives known to impair cardiac function are accumulating. No data are available concerning metabolic modification in heart failure in children.

METHODS AND RESULTS

In order to evaluate the fatty acid oxidation in children suffering from heart failure, acylcarnitine profiles on dried blood spots were obtained from children under 16 years old with dilated cardiomyopathy and clinical heart failure (DCM-HF) and control children. Nine children were included in the DCM-HF group and eight in the control group. Acylcarnitine profiles revealed a significant 3.1-fold increase of total acylcarnitines (sum of C3 to C18 acylcarnitine species) in DCM-HF children compared with controls. This result persisted considering the sum of long-chain acylcarnitines (sum of C14 to C18 species), medium-chain acylcarnitines (sum of C8 to C12 species), and short-chain acylcarnitines (sum of C3 to C6 species), respectively, 2.0-, 2.6-, and 1.9-fold increase compared with the control group. A significant linear correlation was found between left ventricular dilatation or ejection fraction and acylcarnitines accumulation. Finally, acylcarnitine ratio C16OH/C16 and C18OH/C18 enhanced in the DCM-HF group, suggesting a diminution of the long-chain hydroxyl acyl-CoA dehydrogenase activity.

CONCLUSIONS

Our results suggest down-regulation of fatty acid oxidation in children with heart failure. Such lipidomic alteration could worsen heart function and may suggest considering a metabolic treatment of heart failure in children.

Restoration of CPT1A-mediated fatty acid oxidation in mesothelial cells protects against peritoneal fibrosis

Background: Peritoneal dialysis (PD) is limited by gradual fibrotic remodeling in the peritoneum, a process involving profibrotic response of mesothelial cells. However, the role of fatty acid oxidation (FAO) and carnitine palmitoyltransferase 1A (CPT1A) in this process remains unexplored. Methods: FAO and CPT1A expression were characterized in mesothelial cells from patients on long-term PD and from a mouse model of PD using multiple experimental methods, including single-cell sequencing, seahorse assay, real-time quantitative PCR, Western blot, and immunofluorescence staining. Overexpression of CPT1A was achieved in a human mesothelial cell line and in primary mouse mesothelial cells. Finally, genetic and pharmacological manipulations of CPT1A were performed in a mouse model of PD. Results: Herein, FAO and CPT1A expression were reduced in mesothelial cells from patients on long-term PD, which negatively correlated with expression of fibrogenic markers in these cells. This was corroborated in PD mice, as well as in mouse and human mesothelial cells incubated with transforming growth factor (TGF) β1. CPT1A overexpression in mesothelial cells, which prevented TGFβ1-induced suppression of mitochondrial respiration, restored cellular ATP levels and downregulated the expression of fibrogenic markers. Furthermore, restoration of FAO by overexpressing CPT1A in PD mice reversed profibrotic phenotype in mesothelial cells and reduced fibrotic lesions in the peritoneum. Treatment with the CPT1A activator C75 induced similar therapeutic benefit in PD mice. In contrast, inhibition of FAO with a CPT1 inhibitor caused more severe fibrosis in PD mice. Conclusions: A defective FAO is responsible for the profibrotic response of mesothelial cells and thus the peritoneal fibrogenesis. This aberrant metabolic state could be improved by modulating CPT1A in mesothelial cells, suggesting FAO enhancement in mesothelial cells is a potential treatment of peritoneal fibrosis.

The triglyceride-glucose index as a potential protective factor for hypertrophic obstructive cardiomyopathy without diabetes: evidence from a two-center study

OBJECTIVE

This study aimed to investigate the relationship between the TyG (Triglyceride-glucose index) and the prognosis of patients with HOCM (hypertrophic obstructive cardiomyopathy) without diabetes.

RESEARCH DESIGN AND METHODS

A total of 713 eligible patients with HOCM were enrolled in this study and divided into two groups based on treatment: an invasive treatment group (n = 461) and a non-invasive treatment group (n = 252). The patients in both two groups were then divided into three groups based on their TyG index levels. The primary endpoints of this study were Cardiogenic death during long-term follow-up. Kaplan-Meier analysis was used to study the cumulative survival of different groups. Restricted cubic spline was used to model nonlinear relationships between the TyG index and primary endpoints. Myocardial perfusion imaging/Myocardial metabolic imaging examinations were performed to assess glucose metabolism in the ventricular septum of the HOCM patients.

RESULTS

The follow-up time of this study was 41.47 ± 17.63 months. The results showed that patients with higher TyG index levels had better clinical outcomes (HR, 0.215; 95% CI 0.051,0.902; P = 0.036, invasive treatment group; HR, 0.179; 95% CI 0.063,0.508; P = 0.001, non-invasive treatment group). Further analysis showed that glucose metabolism in the ventricular septum was enhanced in HOCM patients.

CONCLUSIONS

The findings of this study suggest that the TyG index may serve as a potential protective factor for patients with HOCM without diabetes. The enhanced glucose metabolism in the ventricular septum of HOCM patients may provide a potential explanation for the relationship between the TyG index and HOCM prognosis.

Combining the antianginal drug perhexiline with chemotherapy induces complete pancreatic cancer regression in vivo

Pancreatic ductal adenocarcinoma (PDAC) remains one of the human cancers with the poorest prognosis. Interestingly, we found that mitochondrial respiration in primary human PDAC cells depends mainly on the fatty acid oxidation (FAO) to meet basic energy requirements. Therefore, we treated PDAC cells with perhexiline, a well-recognized FAO inhibitor used in cardiac diseases. Some PDAC cells respond efficiently to perhexiline, which acts synergistically with chemotherapy (gemcitabine) in vitro and in two xenografts in vivo. Importantly, perhexiline in combination with gemcitabine induces complete tumor regression in one PDAC xenograft. Mechanistically, this co-treatment causes energy and oxidative stress promoting apoptosis but does not exert inhibition of FAO. Yet, our molecular analysis indicates that the carnitine palmitoyltransferase 1C (CPT1C) isoform is a key player in the response to perhexiline and that patients with high CPT1C expression have better prognosis. Our study reveals that repurposing perhexiline in combination with chemotherapy is a promising approach to treat PDAC.

Redox-driven cardioprotective effects of sodium-glucose co-transporter-2 inhibitors: comparative review

Sodium-glucose co-transporter-2 inhibitors are used in the treatment of diabetes but are also emerging as cardioprotective agents in heart diseases even in the absence of type 2 diabetes. In this paper, upon providing a short overview of common pathophysiological features of diabetes, we review the clinically reported cardio- and nephroprotective potential of sodium-glucose co-transporter-2 inhibitors currently available on the market, including Dapagliflozin, Canagliflozin, and Empagliflozin. To that end, we summarize findings of clinical trials that have initially drawn attention to the drugs' organ-protective potential, before providing an overview of their proposed mechanism of action. Since we particularly expect that their antioxidative properties will broaden the application of gliflozins from therapeutic to preventive care, special emphasis was put on this aspect.

PGRMC1 Ablation Protects from Energy-Starved Heart Failure by Promoting Fatty Acid/Pyruvate Oxidation

Heart failure (HF) is an emerging epidemic with a high mortality rate. Apart from conventional treatment methods, such as surgery or use of vasodilation drugs, metabolic therapy has been suggested as a new therapeutic strategy. The heart relies on fatty acid oxidation and glucose (pyruvate) oxidation for ATP-mediated contractility; the former meets most of the energy requirement, but the latter is more efficient. Inhibition of fatty acid oxidation leads to the induction of pyruvate oxidation and provides cardioprotection to failing energy-starved hearts. One of the non-canonical types of sex hormone receptors, progesterone receptor membrane component 1 (Pgrmc1), is a non-genomic progesterone receptor associated with reproduction and fertility. Recent studies revealed that Pgrmc1 regulates glucose and fatty acid synthesis. Notably, Pgrmc1 has also been associated with diabetic cardiomyopathy, as it reduces lipid-mediated toxicity and delays cardiac injury. However, the mechanism by which Pgrmc1 influences the energy-starved failing heart remains unknown. In this study, we found that loss of Pgrmc1 inhibited glycolysis and increased fatty acid/pyruvate oxidation, which is directly associated with ATP production, in starved hearts. Loss of Pgrmc1 during starvation activated the phosphorylation of AMP-activated protein kinase, which induced cardiac ATP production. Pgrmc1 loss increased the cellular respiration of cardiomyocytes under low-glucose conditions. In isoproterenol-induced cardiac injury, Pgrmc1 knockout resulted in less fibrosis and low heart failure marker expression. In summary, our results revealed that Pgrmc1 ablation in energy-deficit conditions increases fatty acid/pyruvate oxidation to protect against cardiac damage via energy starvation. Moreover, Pgrmc1 may be a regulator of cardiac metabolism that switches the dominance of glucose-fatty acid usage according to nutritional status and nutrient availability in the heart.

PCSK9: A emerging participant in heart failure

Heart failure (HF) is a complex clinical syndrome caused by various cardiovascular diseases. Its main pathogenesis includes cardiomyocyte loss, myocardial energy metabolism disorder, and activation of cardiac inflammation. Due to the clinically unsatisfactory treatment of heart failure, different mechanisms need to be explored to provide new targets for the treatment of this disease. Proprotein convertase subtilisin/kexin type 9 (PCSK9), a gene mainly related to familial hypercholesterolemia, was discovered in 2003. Aside from regulating lipid metabolism, PCSK9 may be involved in other biological processes such as apoptosis, autophagy, pyroptosis, inflammation, and tumor immunity and related to diabetes and neurodegenerative diseases. Recently, clinical data have shown that the circulating PCSK9 level is significantly increased in patients with heart failure, and it is related to the prognosis for heart failure. Furthermore, in animal models and patients with myocardial infarction, PCSK9 in the infarct margin area was also found to be significantly increased, which further suggested that PCSK9 might be closely related to heart failure. However, the specific mechanism of how PCSK9 participates in heart failure remains to be further explored. The purpose of this review is to summarize the potential mechanism of PCSK9's involvement in heart failure, thereby providing a new treatment strategy for heart failure.

L-carnitine attenuated hyperuricemia-associated left ventricular remodeling through ameliorating cardiomyocytic lipid deposition

Hyperuricemia (HUA) is associated with left ventricular remodeling (LVR) and thereby causes the initiation and development of a large number of cardiovascular diseases. LVR is typically accompanied by cardiomyocyte energy metabolic disorder. The energy supply of cardiomyocytes is provided by glucose and fatty acid (FA) metabolism. Currently, the effect of HUA on cardiomyocytic FA metabolism is unclear. In this study, we demonstrate that UA-induced cardiomyocyte injury is associated with cytoplasmic lipid deposition, which can be ameliorated by the FA metabolism-promoting drug L-carnitine (LC). UA suppresses carnitine palmitoyl transferase 1B (CPT1B), thereby inhibiting FA transport into the mitochondrial inner matrix for elimination. LC intervention can ameliorate HUA-associated left ventricular anterior wall thickening in mice. This study showed that FA transport dysfunction plays is a critical mechanism in both cardiomyocytic injury and HUA-associated LVR and promoting cytoplasmic FA transportation through pharmacological treatment by LC is a valid strategy to attenuate HUA-associated LVR.

Impaired insulin-stimulated myocardial glucose metabolic rate is associated with reduced estimated myocardial energetic efficiency in subjects with different degrees of glucose tolerance

BACKGROUND

Alterations in myocardial mechano-energetic efficiency (MEEi), which represents the capability of the left ventricles to convert the chemical energy obtained by oxidative metabolism into mechanical work, have been associated with cardiovascular disease. Although whole-body insulin resistance has been related to impaired myocardial MEEi, it is unknown the relationship between cardiac insulin resistance and MEEi. Aim of this study was to evaluate the relationship between insulin-stimulated myocardial glucose metabolic rate (MrGlu) and myocardial MEEi in subjects having different degrees of glucose tolerance.

METHODS

We evaluated insulin-stimulated myocardial MrGlu using cardiac dynamic positron emission tomography (PET) with 18F-Fluorodeoxyglucose (18F-FDG) combined with euglycemic-hyperinsulinemic clamp, and myocardial MEEi in 57 individuals without history of coronary heart disease having different degrees of glucose tolerance. The subjects were stratified into tertiles according to their myocardial MrGlu values.

RESULTS

After adjusting for age, gender and BMI, subjects in I tertile showed a decrease in myocardial MEEi (0.31 ± 0.05 vs 0.42 ± 0.14 ml/s*g, P = 0.02), and an increase in myocardial oxygen consumption (MVO2) (10,153 ± 1375 vs 7816 ± 1229 mmHg*bpm, P < 0.0001) as compared with subjects in III tertile. Univariate correlations showed that insulin-stimulated myocardial MrGlu was positively correlated with MEEi and whole-body glucose disposal, and negatively correlated with waist circumference, fasting plasma glucose, HbA1c and MVO2. In a multivariate regression analysis running a model including several CV risk factors, the only variable that remained significantly associated with MEEi was myocardial MrGlu (β 0.346; P = 0.01).

CONCLUSIONS

These data suggest that an impairment in insulin-stimulated myocardial glucose metabolism is an independent contributor of depressed myocardial MEEi in subjects without history of CHD.

Adaptation of cardiomyogenesis to the generation and maturation of cardiomyocytes from human pluripotent stem cells

The advent of methods for efficient generation and cardiac differentiation of pluripotent stem cells opened new avenues for disease modelling, drug testing, and cell therapies of the heart. However, cardiomyocytes (CM) obtained from such cells demonstrate an immature, foetal-like phenotype that involves spontaneous contractions, irregular morphology, expression of embryonic isoforms of sarcomere components, and low level of ion channels. These and other features may affect cellular response to putative therapeutic compounds and the efficient integration into the host myocardium after in vivo delivery. Therefore, novel strategies to increase the maturity of pluripotent stem cell-derived CM are of utmost importance. Several approaches have already been developed relying on molecular changes that occur during foetal and postnatal maturation of the heart, its electromechanical activity, and the cellular composition. As a better understanding of these determinants may facilitate the generation of efficient protocols for in vitro acquisition of an adult-like phenotype by immature CM, this review summarizes the most important molecular factors that govern CM during embryonic development, postnatal changes that trigger heart maturation, as well as protocols that are currently used to generate mature pluripotent stem cell-derived cardiomyocytes.

Deficiency of Adipose Triglyceride Lipase Induces Metabolic Syndrome and Cardiomyopathy in Zebrafish

Lipid metabolism dysfunction is related to clinical disorders including obesity, cancer, liver steatosis, and cardiomyopathy. Impaired lipolytic enzymes result in altered release of free fatty acids. The dramatic change in dyslipidemia is important in lipotoxic cardiomyopathy. Adipose triglyceride lipase (ATGL) catalyzes the lipolysis of triacylglycerol to reduce intramyocardial triglyceride levels in the heart and improve myocardial function. We examined the role of ATGL in metabolic cardiomyopathy by developing an Atgl knockout (ALKO) zebrafish model of metabolic cardiomyopathy disease by continuously expressing CRISPR/Cas9 protein and atgl gene guide RNAs (gRNAs). The expressed Cas9 protein bound to four gRNAs targeting the atgl gene locus, facilitating systemic gene KO. Ablation of Atgl interfered with lipid metabolism, which induced hyperlipidemia and hyperglycemia. ALKO adults and embryos displayed hypertrophic hearts. ALKO presented a typical dilated cardiomyopathy profile with a remarkable reduction in four sarcomere genes (myosin heavy chain 7-like, actin alpha cardiac muscle 1b, myosin binding protein C3, and troponin T type 2a) and two Ca²⁺ handling regulator genes (tropomyosin 4b and ATPase sarcoplasmic/endoplasmic reticulum Ca²⁺ transporting 2b). Immune cell infiltration in cardiac tissue of ALKO provided direct evidence of advanced metabolic cardiomyopathy. The presently described model could become a powerful tool to clarify the underlying mechanism between metabolic disorders and cardiomyopathies.

Characterization of cardiac metabolism in iPSC-derived cardiomyocytes: lessons from maturation and disease modeling

Background

Induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) have emerged as a powerful tool for disease modeling, though their immature nature currently limits translation into clinical practice. Maturation strategies increasingly pay attention to cardiac metabolism because of its pivotal role in cardiomyocyte development and function. Moreover, aberrances in cardiac metabolism are central to the pathogenesis of cardiac disease. Thus, proper modeling of human cardiac disease warrants careful characterization of the metabolic properties of iPSC-CMs.

Methods

Here, we examined the effect of maturation protocols on healthy iPSC-CMs applied in 23 studies and compared fold changes in functional metabolic characteristics to assess the level of maturation. In addition, pathological metabolic remodeling was assessed in 13 iPSC-CM studies that focus on hypertrophic cardiomyopathy (HCM), which is characterized by abnormalities in metabolism.

Results

Matured iPSC-CMs were characterized by mitochondrial maturation, increased oxidative capacity and enhanced fatty acid use for energy production. HCM iPSC-CMs presented varying degrees of metabolic remodeling ranging from compensatory to energy depletion stages, likely due to the different types of mutations and clinical phenotypes modeled. HCM further displayed early onset hypertrophy, independent of the type of mutation or disease stage.

Conclusions

Maturation strategies improve the metabolic characteristics of iPSC-CMs, but not to the level of the adult heart. Therefore, a combination of maturation strategies might prove to be more effective. Due to early onset hypertrophy, HCM iPSC-CMs may be less suitable to detect early disease modifiers in HCM and might prove more useful to examine the effects of gene editing and new drugs in advanced disease stages. With this review, we provide an overview of the assays used for characterization of cardiac metabolism in iPSC-CMs and advise on which metabolic assays to include in future maturation and disease modeling studies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03021-9.

Association of Systemic Trimethyllysine With Heart Failure With Preserved Ejection Fraction and Cardiovascular Events

CONTEXT

Carnitine has been associated with cardiac energy metabolism and heart failure, but the association between its precursors-trimethyllysine (TML) and γ-butyrobetaine (GBB)-and heart failure with preserved ejection fraction (HFpEF) remains unclear.

OBJECTIVE

To evaluate the relationship between TML-related metabolites and HFpEF in an Asian population.

METHODS

The cross-sectional component of this study examined the association between plasma TML-related metabolites and HFpEF, while a prospective cohort design was applied to examine the association with incident cardiovascular events in HFpEF. Included in the study were 1000 individuals who did not have heart failure (non-HF) and 1413 patients with HFpEF. Liquid chromatography mass spectrometry was used to assess plasma carnitine, GBB, TML and trimethylamine-N-oxide (TMAO) concentrations.

RESULTS

Plasma GBB and TML were both elevated in patients with HFpEF. After adjusting for traditional risk factors and renal function, TML, but not GBB, was significantly associated with HFpEF. The odds ratio (OR) for the fourth vs first quartile of TML was 1.57 (95% CI 1.09-2.27; P-trend < .01). The OR for each SD increment of log-TML was 1.26 (95% CI 1.08-1.47). Plasma TMAO (P-interaction = 0.024) and estimated glomerular filtration rate (P-interaction = 0.024) modified the TML-HFpEF association. The addition of TML improved the diagnostic value under the multivariable model. In the prospective study of patients with HFpEF, higher plasma TML was associated with increased risk of cardiovascular events.

CONCLUSION

Plasma TML concentrations are positively associated with HFpEF, and higher plasma TML indicates increased risk of cardiovascular events.

Generation and maturation of human iPSC-derived 3D organotypic cardiac microtissues in long-term culture

Cardiovascular diseases remain the leading cause of death worldwide; hence there is an increasing focus on developing physiologically relevant in vitro cardiovascular tissue models suitable for studying personalized medicine and pre-clinical tests. Despite recent advances, models that reproduce both tissue complexity and maturation are still limited. We have established a scaffold-free protocol to generate multicellular, beating human cardiac microtissues in vitro from hiPSCs-namely human organotypic cardiac microtissues (hOCMTs)-that show some degree of self-organization and can be cultured for long term. This is achieved by the differentiation of hiPSC in 2D monolayer culture towards cardiovascular lineage, followed by further aggregation on low-attachment culture dishes in 3D. The generated hOCMTs contain multiple cell types that physiologically compose the heart and beat without external stimuli for more than 100 days. We have shown that 3D hOCMTs display improved cardiac specification, survival and metabolic maturation as compared to standard monolayer cardiac differentiation. We also confirmed the functionality of hOCMTs by their response to cardioactive drugs in long-term culture. Furthermore, we demonstrated that they could be used to study chemotherapy-induced cardiotoxicity. Due to showing a tendency for self-organization, cellular heterogeneity, and functionality in our 3D microtissues over extended culture time, we could also confirm these constructs as human cardiac organoids (hCOs). This study could help to develop more physiologically-relevant cardiac tissue models, and represent a powerful platform for future translational research in cardiovascular biology.

Regulation of the Keap1-Nrf2 Signaling Axis by Glycyrrhetinic Acid Promoted Oxidative Stress-Induced H9C2 Cell Apoptosis

Excessive reactive oxygen species (ROS) could interfere with the physiological capacities of H₉C₂ cells and cause cardiomyocyte apoptosis. Glycyrrhetinic acid (GA), one of the main medicinal component of Glycyrrhetinic Radix et Rhizoma, shows toxic and adverse side effects in the clinic setting. In particular, some studies have reported that GA exerts toxic effects on H₉C₂ cells. The purpose of this study is to assess the effect of GA-induced oxidative stress on cultured H₉C₂ cells and reveal the relevant signaling pathways. LDH assay was used to assess cell damage. Apoptosis was detected using Hoechst 33242 and a propidium iodide (PI) assay. An Annexin V-fluorescein isothiocyanate/PI double-staining assay was utilized to investigate GA-induced apoptosis in H₉C₂ cells. The expression level of specific genes/proteins was evaluated by RT-qPCR and Western blotting. Flow cytometry and DCFH-DA fluorescent testing were used to determine the ROS levels of H₉C₂ cells. The potential mechanism of GA-induced cardiomyocyte injury was also investigated. GA treatment increased ROS generation and mitochondrial membrane depolarization and triggered caspase-3/9 activation and apoptosis. GA treatment also caused the nuclear translocation of NF-E2-related factor 2 after its dissociation from Keap1. This change was accompanied by a dose-dependent decline in the expression of the downstream target gene heme oxygenase-1. The findings demonstrated that GA could regulate the Keap1-Nrf2 signaling axis and induce oxidative stress to promote the apoptosis of H₉C₂ cells.

Keeping the beat against time: Mitochondrial fitness in the aging heart

The process of aging strongly correlates with maladaptive architectural, mechanical, and biochemical alterations that contribute to the decline in cardiac function. Consequently, aging is a major risk factor for the development of heart disease, the leading cause of death in the developed world. In this review, we will summarize the classic and recently uncovered pathological changes within the aged heart with an emphasis on the mitochondria. Specifically, we describe the metabolic changes that occur in the aging heart as well as the loss of mitochondrial fitness and function and how these factors contribute to the decline in cardiomyocyte number. In addition, we highlight recent pharmacological, genetic, or behavioral therapeutic intervention advancements that may alleviate age-related cardiac decline.

The mitochondrial pyruvate carrier at the crossroads of intermediary metabolism

Pyruvate metabolism, a central nexus of carbon homeostasis, is an evolutionarily conserved process and aberrant pyruvate metabolism is associated with and contributes to numerous human metabolic disorders including diabetes, cancer, and heart disease. As a product of glycolysis, pyruvate is primarily generated in the cytosol before being transported into the mitochondrion for further metabolism. Pyruvate entry into the mitochondrial matrix is a critical step for efficient generation of reducing equivalents and ATP and for the biosynthesis of glucose, fatty acids, and amino acids from pyruvate. However, for many years, the identity of the carrier protein(s) that transported pyruvate into the mitochondrial matrix remained a mystery. In 2012, the molecular-genetic identification of the mitochondrial pyruvate carrier (MPC), a heterodimeric complex composed of protein subunits MPC1 and MPC2, enabled studies that shed light on the many metabolic and physiological processes regulated by pyruvate metabolism. A better understanding of the mechanisms regulating pyruvate transport and the processes affected by pyruvate metabolism may enable novel therapeutics to modulate mitochondrial pyruvate flux to treat a variety of disorders. Herein, we review our current knowledge of the MPC, discuss recent advances in the understanding of mitochondrial pyruvate metabolism in various tissue and cell types, and address some of the outstanding questions relevant to this field.

Serum Metabolomics Reveals Distinct Profiles during Ischemia and Reperfusion in a Porcine Model of Myocardial Ischemia-Reperfusion

Acute myocardial infarction (MI) is one of the leading causes of death worldwide. Early identification of ischemia and establishing reperfusion remain cornerstones in the treatment of MI, as mortality and morbidity can be significantly reduced by establishing reperfusion to the affected areas. The aim of the current study was to investigate the metabolomic changes in the serum in a swine model of MI induced by ischemia and reperfusion (I/R) injury, and to identify circulating metabolomic biomarkers for myocardial injury at different phases. Female Yucatan minipigs were subjected to 60 min of ischemia followed by reperfusion, and serum samples were collected at baseline, 60 min of ischemia, 4 h of reperfusion, and 24 h of reperfusion. Circulating metabolites were analyzed using an untargeted metabolomic approach. A bioinformatic approach revealed that serum metabolites show distinct profiles during ischemia and during early and late reperfusion. Some notable changes during ischemia include accumulation of metabolites that indicate impaired mitochondrial function and N-terminally modified amino acids. Changes in branched-chain amino-acid metabolites were noted during early reperfusion, while bile acid pathway derivatives and intermediates predominated in the late reperfusion phases. This indicates a potential for such an approach toward identification of the distinct phases of ischemia and reperfusion in clinical situations.

Response to triheptanoin therapy in critically ill patients with LC-FAOD: Report of patients treated through an expanded access program

Long-chain fatty acid oxidation disorders (LC-FAOD) are a group of inborn errors of metabolism wherein patients are unable to process long-chain fatty acids into useable energy in the mitochondria. LC-FAOD commonly affects organ systems with high energy demand, manifesting as hypoketotic hypoglycemia, liver dysfunction, cardiomyopathy, rhabdomyolysis, and skeletal myopathy, as well as peripheral neuropathy and retinopathy in some subtypes. Collectively, LC-FAOD have a high mortality rate, especially in cases of early onset disease, and in the presence of cardiomyopathy. Triheptanoin is a synthetic medium-odd chain triglyceride, produced using a GMP-compliant process, which was designed to replenish mitochondrial metabolic deficits and restore energy homeostasis. Prior to its approval, triheptanoin was only available through clinical trials or to seriously ill patients as part of an expanded access program (EAP) following physician request. This retrospective study examined the impact of triheptanoin on cardiovascular parameters, in critically ill patients who participated in the EAP from February 2013 to January 2018. These patients persisted in critical condition despite receiving standard treatment in highly qualified centers by expert metabolic physicians and dietitians. Physician-completed questionnaires and narrative summaries were used to evaluate the disease presentation and management prior to the trigger event leading to triheptanoin request and use, and the response to triheptanoin treatment. Following triheptanoin initiation, most patients survived the initial trigger event (e.g., severe urinary tract infection, pneumonia) and demonstrated improvements in both short-term and long-term LC-FAOD manifestations. In patients with cardiomyopathy, stabilization or improvement from pretreatment levels was reported in left ventricular ejection fraction and left ventricular mass, in particular, all infants with cardiomyopathy showed improvement in cardiac function during triheptanoin therapy. Triheptanoin therapy was generally well tolerated. The study results are consistent with the existing positive benefit/risk profile of triheptanoin and reflect the effect of triheptanoin improving cardiac function in patients experiencing severe episodes of metabolic decompensation despite standard therapy.

A New Hypothetical Concept in Metabolic Understanding of Cardiac Fibrosis: Glycolysis Combined with TGF-β and KLF5 Signaling

The accumulation of fibrosis in cardiac tissues is one of the leading causes of heart failure. The principal cellular effectors in cardiac fibrosis are activated fibroblasts and myofibroblasts, which serve as the primary source of matrix proteins. TGF-β signaling pathways play a prominent role in cardiac fibrosis. The control of TGF-β by KLF5 in cardiac fibrosis has been demonstrated for modulating cardiovascular remodeling. Since the expression of KLF5 is reduced, the accumulation of fibrosis diminishes. Because the molecular mechanism of fibrosis is still being explored, there are currently few options for effectively reducing or reversing it. Studying metabolic alterations is considered an essential process that supports the explanation of fibrosis in a variety of organs and especially the glycolysis alteration in the heart. However, the interplay among the main factors involved in fibrosis pathogenesis, namely TGF-β, KLF5, and the metabolic process in glycolysis, is still indistinct. In this review, we explain what we know about cardiac fibroblasts and how they could help with heart repair. Moreover, we hypothesize and summarize the knowledge trend on the molecular mechanism of TGF-β, KLF5, the role of the glycolysis pathway in fibrosis, and present the future therapy of cardiac fibrosis. These studies may target therapies that could become important strategies for fibrosis reduction in the future.

Heart Failure and Drug Therapies: A Metabolic Review

Cardiovascular disease is the leading cause of mortality globally with at least 26 million people worldwide living with heart failure (HF). Metabolism has been an active area of investigation in the setting of HF since the heart demands a high rate of ATP turnover to maintain homeostasis. With the advent of -omic technologies, specifically metabolomics and lipidomics, HF pathologies have been better characterized with unbiased and holistic approaches. These techniques have identified novel pathways in our understanding of progression of HF and potential points of intervention. Furthermore, sodium-glucose transport protein 2 inhibitors, a drug that has changed the dogma of HF treatment, has one of the strongest types of evidence for a potential metabolic mechanism of action. This review will highlight cardiac metabolism in both the healthy and failing heart and then discuss the metabolic effects of heart failure drugs.

Metabolic Reprogramming, Gut Dysbiosis, and Nutrition Intervention in Canine Heart Disease

This review provides a state-of-the-art overview on recent advances in systems biology in canine cardiac disease, with a focus on our current understanding of bioenergetics and amino acid metabolism in myxomatous mitral valve disease (MMVD). Cross-species comparison is drawn to highlight the similarities between human and canine heart diseases. The adult mammalian heart exhibits a remarkable metabolic flexibility and shifts its energy substrate preference according to different physiological and pathological conditions. The failing heart suffers up to 40% ATP deficit and is compared to an engine running out of fuel. Bioenergetics and metabolic readaptations are among the major research topics in cardiac research today. Myocardial energy metabolism consists of three interconnected components: substrate utilization, oxidative phosphorylation, and ATP transport and utilization. Any disruption or uncoupling of these processes can result in deranged energy metabolism leading to heart failure (HF). The review describes the changes occurring in each of the three components of energy metabolism in MMVD and HF. It also provides an overview on the changes in circulating and myocardial glutathione, taurine, carnitines, branched-chain amino acid catabolism and tryptophan metabolic pathways. In addition, the review summarizes the potential role of the gut microbiome in MMVD and HF. As our knowledge and understanding in these molecular and metabolic processes increase, it becomes possible to use nutrition to address these changes and to slow the progression of the common heart diseases in dogs.

The Remodeling Effects of High-Concentrate Diets on Microbial Composition and Function in the Hindgut of Dairy Cows

At present, research on high-concentrate (HC) diets mostly focused on the rumen, and there is a paucity of information on the hindgut microbiota of dairy cows. In the present study, a 2 × 2 crossover design with four healthy Holstein cows was used, and the metagenomics approach was adopted to reveal the remodeling effects of HC diets on hindgut microbiota and their metabolic functions. Results showed that, compared with the low-concentrate (LC) diets, HC diets have markedly decreased (p < 0.05) the abundance of cellulolytic bacteria (such as Fibrobacter, Ruminococcus, and Ruminiclostridium) and methanogens (such as Methanobrevibacter, Methanosarcina, and Methanosphaera); and correspondingly, HC diets have significantly reduced (p < 0.05) the abundance of carbohydrate-active enzymes (CAZy) related to hemicellulases (GH10, GH11, and GH54) and cellulases (GH1, GH44, and GH45) and increased the abundance of one oligosaccharide-degrading enzyme (GH32). Furthermore, 62 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways of hindgut microbiota were affected (p < 0.05) by different dietary treatments, and the major pathways altered by HC diets were “Methane metabolism” (enriched in the LC group), “Lipid metabolism” (enriched in the HC group), and several sub-pathways in “Amino acid metabolism” (such as Phenylalanine metabolism, and Phenylalanine, tyrosine, and tryptophan biosynthesis). Also, the microbial genes involved in the pathways “Methane metabolism” (except 1 gene), “Tryptophan metabolism”, and “Phenylalanine metabolism” were all decreased (p < 0.05) in the present study. These findings suggested that HC diets caused the remodeling of hindgut microbiota and its potential functions, and these results may benefit in gaining a deeper understanding of the impact of HC diets on the hindgut microbiota of dairy cows.

Letrozole Accelerates Metabolic Remodeling through Activation of Glycolysis in Cardiomyocytes: A Role beyond Hormone Regulation

Estrogen receptor-positive (ER+) breast cancer patients are recommended hormone therapy as a primary adjuvant treatment after surgery. Aromatase inhibitors (AIs) are widely administered to ER+ breast cancer patients as estrogen blockers; however, their safety remains controversial. The use of letrozole, an AI, has been reported to cause adverse cardiovascular effects. We aimed to elucidate the effects of letrozole on the cardiovascular system. Female rats exposed to letrozole for four weeks showed metabolic changes, i.e., decreased fatty acid oxidation, increased glycolysis, and hypertrophy in the left ventricle. Although lipid oxidation yields more ATP than carbohydrate metabolism, the latter predominates in the heart under pathological conditions. Reduced lipid metabolism is attributed to reduced β-oxidation due to low circulating estrogen levels. In letrozole-treated rats, glycolysis levels were found to be increased in the heart. Furthermore, the levels of glycolytic enzymes were increased (in a high glucose medium) and the glycolytic rate was increased in vitro (H9c2 cells); the same was not true in the case of estrogen treatment. Reduced lipid metabolism and increased glycolysis can lower energy supply to the heart, resulting in predisposition to heart failure. These data suggest that a letrozole-induced cardiac metabolic remodeling, i.e., a shift from β-oxidation to glycolysis, may induce cardiac structural remodeling.

Adipose Lipolysis Regulates Cardiac Glucose Uptake and Function in Mice under Cold Stress

The heart primarily uses fatty acids as energy substrates. Adipose lipolysis is a major source of fatty acids, particularly under stress conditions. In this study, we showed that mice with selective inactivation of the lipolytic coactivator comparative gene identification-58 (CGI-58) in adipose tissue (FAT-KO mice), relative to their littermate controls, had lower circulating FA levels in the fed and fasted states due to impaired adipose lipolysis. They preferentially utilized carbohydrates as energy fuels and were more insulin sensitive and glucose tolerant. Under cold stress, FAT-KO versus control mice had >10-fold increases in glucose uptake in the hearts but no increases in other tissues examined. Plasma concentrations of atrial natriuretic peptide and cardiac mRNAs for atrial and brain-type natriuretic peptides, two sensitive markers of cardiac remodeling, were also elevated. After one week of cold exposure, FAT-KO mice showed reduced cardiac expression of several mitochondrial oxidative phosphorylation proteins. After one month of cold exposure, hearts of these animals showed depressed functions, reduced SERCA2 protein, and increased proteins for MHC-β, collagen I proteins, Glut1, Glut4 and phospho-AMPK. Thus, CGI-58-dependent adipose lipolysis critically regulates cardiac metabolism and function, especially during cold adaptation. The adipose-heart axis may be targeted for the management of cardiac dysfunction.

Lactate and Myocadiac Energy Metabolism

The myocardium is capable of utilizing different energy substrates, which is referred to as “metabolic flexibility.” This process assures ATP production from fatty acids, glucose, lactate, amino acids, and ketones, in the face of varying metabolic contexts. In the normal physiological state, the oxidation of fatty acids contributes to approximately 60% of energy required, and the oxidation of other substrates provides the rest. The accumulation of lactate in ischemic and hypoxic tissues has traditionally be considered as a by-product, and of little utility. However, recent evidence suggests that lactate may represent an important fuel for the myocardium during exercise or myocadiac stress. This new paradigm drives increasing interest in understanding its role in cardiac metabolism under both physiological and pathological conditions. In recent years, blood lactate has been regarded as a signal of stress in cardiac disease, linking to prognosis in patients with myocardial ischemia or heart failure. In this review, we discuss the importance of lactate as an energy source and its relevance to the progression and management of heart diseases.

Crucial Role of Mammalian Glutaredoxin 3 in Cardiac Energy Metabolism in Diet-induced Obese Mice Revealed by Transcriptome Analysis

Obesity is often associated with metabolic dysregulation and oxidative stress with the latter serving as a possible unifying link between obesity and cardiovascular complications. Glutaredoxins (Grxs) comprise one of the major antioxidant systems in the heart. Although Grx3 has been shown to act as an endogenous negative regulator of cardiac hypertrophy and heart failure, its metabolic impact on cardiac function in diet-induced obese (DIO) mice remains largely unknown. In the present study, analysis of Grx3 expression indicated that Grx3 protein levels, but not mRNA levels, were significantly increased in the hearts of DIO mice. Cardiac-specific Grx3 deletion (Grx3 CKO) mice were viable and grew indistinguishably from their littermates after being fed a high fat diet (HFD) for one month, starting at 2 months of age. After being fed with a HFD for 8 months (starting at 2 months of age); however, Grx3 CKO DIO mice displayed left ventricular systolic dysfunction with a significant decrease in ejection fraction and fractional shortening that was associated with heart failure. ROS production was significantly increased in Grx3 CKO DIO cardiomyocytes compared to control cells. Gene expression analysis revealed a significant decline in the level of transcripts corresponding to genes associated with processes such as fatty acid uptake, mitochondrial fatty acid transport and oxidation, and citrate cycle in Grx3 CKO DIO mice compared to DIO controls. In contrast, an increase in the level of transcripts corresponding to genes associated with glucose uptake and utilization were found in Grx3 CKO DIO mice compared to DIO controls. Taken together, these findings indicate that Grx3 may play a critical role in redox balance and as a metabolic switch in cardiomyocytes contributing to the development and progression of heart failure.

Water-suppression cycling 3-T cardiac 1 H-MRS detects altered creatine and choline in patients with aortic or mitral stenosis

Cardiac proton spectroscopy (1 H-MRS) is widely used to quantify lipids. Other metabolites (e.g. creatine and choline) are clinically relevant but more challenging to quantify because of their low concentrations (approximately 10 mmol/L) and because of cardiac motion. To quantify cardiac creatine and choline, we added water-suppression cycling (WSC) to two single-voxel spectroscopy sequences (STEAM and PRESS). WSC introduces controlled residual water signals that alternate between positive and negative phases from transient to transient, enabling robust phase and frequency correction. Moreover, a particular weighted sum of transients eliminates residual water signals without baseline distortion. We compared WSC and the vendor's standard 'WET' water suppression in phantoms. Next, we tested repeatability in 10 volunteers (seven males, three females; age 29.3 ± 4.0 years; body mass index [BMI] 23.7 ± 4.1 kg/m2 ). Fat fraction, creatine concentration and choline concentration when quantified by STEAM-WET were 0.30% ± 0.11%, 29.6 ± 7.0 μmol/g and 7.9 ± 6.7 μmol/g, respectively; and when quantified by PRESS-WSC they were 0.30% ± 0.15%, 31.5 ± 3.1 μmol/g and 8.3 ± 4.4 μmol/g, respectively. Compared with STEAM-WET, PRESS-WSC gave spectra whose fitting quality expressed by Cramér-Rao lower bounds improved by 26% for creatine and 32% for choline. Repeatability of metabolite concentration measurements improved by 72% for creatine and 40% for choline. We also compared STEAM-WET and PRESS-WSC in 13 patients with severe symptomatic aortic or mitral stenosis indicated for valve replacement surgery (10 males, three females; age 75.9 ± 6.3 years; BMI 27.4 ± 4.3 kg/m2 ). Spectra were of analysable quality in eight patients for STEAM-WET, and in nine for PRESS-WSC. We observed comparable lipid concentrations with those in healthy volunteers, significantly reduced creatine concentrations, and a trend towards decreased choline concentrations. We conclude that PRESS-WSC offers improved performance and reproducibility for the quantification of cardiac lipids, creatine and choline concentrations in healthy volunteers at 3 T. It also offers improved performance compared with STEAM-WET for detecting altered creatine and choline concentrations in patients with valve disease.

Skeletal Muscle Metabolism: Origin or Prognostic Factor for Amyotrophic Lateral Sclerosis (ALS) Development?

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive and selective loss of motor neurons, amyotrophy and skeletal muscle paralysis usually leading to death due to respiratory failure. While generally considered an intrinsic motor neuron disease, data obtained in recent years, including our own, suggest that motor neuron protection is not sufficient to counter the disease. The dismantling of the neuromuscular junction is closely linked to chronic energy deficit found throughout the body. Metabolic (hypermetabolism and dyslipidemia) and mitochondrial alterations described in patients and murine models of ALS are associated with the development and progression of disease pathology and they appear long before motor neurons die. It is clear that these metabolic changes participate in the pathology of the disease. In this review, we summarize these changes seen throughout the course of the disease, and the subsequent impact of glucose–fatty acid oxidation imbalance on disease progression. We also highlight studies that show that correcting this loss of metabolic flexibility should now be considered a major goal for the treatment of ALS.

Compound Danshen Dripping Pill inhibits doxorubicin or isoproterenol-induced cardiotoxicity

Heart failure (HF) is the advanced heart disease with high morbidity and mortality. Compound DanShen Dripping Pill (CDDP) is a widely used Traditional Chinese Medicine for cardiovascular disease treatment. Herein, we investigated if CDDP can protect mice against doxorubicin (DOX) or isoprenaline (ISO)-induced HF. After 3 days feeding of normal chow containing CDDP, mice were started DOX or ISO treatment for 4 weeks or 18 days. At the end of treatment, mice were conducted electrocardiogram and echocardiographic test. Blood and heart samples were determined biochemical parameters, myocardial structure and expression of the related molecules. CDDP normalized DOX/ISO-induced heart weight changes, HF parameters and fibrogenesis. The DOX/ISO-impaired left ventricular ejection fraction and fractional shortening were restored by CDDP. Mechanistically, CDDP blocked DOX/ISO-inhibited expression of antioxidant enzymes and DOX/ISO-induced expression of pro-fibrotic molecules, inflammation and cell apoptosis. Additional DOX/ISO-impaired targets in cardiac function but protected by CDDP were identified by RNAseq, qRT-PCR and Western blot. In addition, CDDP protected cardiomyocytes against oxygen-glucose deprivation-induced injuries. Taken together, our study shows that CDDP can protect against myocardial injuries in different models, suggesting its potential application for HF treatment.

Targeting Adrenergic Receptors in Metabolic Therapies for Heart Failure

The heart has a reduced capacity to generate sufficient energy when failing, resulting in an energy-starved condition with diminished functions. Studies have identified numerous changes in metabolic pathways in the failing heart that result in reduced oxidation of both glucose and fatty acid substrates, defects in mitochondrial functions and oxidative phosphorylation, and inefficient substrate utilization for the ATP that is produced. Recent early-phase clinical studies indicate that inhibitors of fatty acid oxidation and antioxidants that target the mitochondria may improve heart function during failure by increasing compensatory glucose oxidation. Adrenergic receptors (α₁ and β) are a key sympathetic nervous system regulator that controls cardiac function. β-AR blockers are an established treatment for heart failure and α_1A-AR agonists have potential therapeutic benefit. Besides regulating inotropy and chronotropy, α₁- and β-adrenergic receptors also regulate metabolic functions in the heart that underlie many cardiac benefits. This review will highlight recent studies that describe how adrenergic receptor-mediated metabolic pathways may be able to restore cardiac energetics to non-failing levels that may offer promising therapeutic strategies.

Lactate Dehydrogenase B and Pyruvate Oxidation Pathway Associated With Carfilzomib-Related Cardiotoxicity in Multiple Myeloma Patients: Result of a Multi-Omics Integrative Analysis

Multiple myeloma (MM) is the second most frequent hematologic cancer in the United States. Carfilzomib (CFZ), an irreversible proteasome inhibitor being used to treat relapsed and refractory MM, has been associated with cardiotoxicity, including heart failure. We hypothesized that a multi-omics approach integrating data from different omics would provide insights into the mechanisms of CFZ-related cardiovascular adverse events (CVAEs). Plasma samples were collected from 13 MM patients treated with CFZ (including 7 with CVAEs and 6 with no CVAEs) at the University of Florida Health Cancer Center. These samples were evaluated in global metabolomic profiling, global proteomic profiling, and microRNA (miRNA) profiling. Integrative pathway analysis was performed to identify genes and pathways differentially expressed between patients with and without CVAEs. The proteomics analysis identified the up-regulation of lactate dehydrogenase B (LDHB) [fold change (FC) = 8.2, p = 0.01] in patients who experienced CVAEs. The metabolomics analysis identified lower plasma abundance of pyruvate (FC = 0.16, p = 0.0004) and higher abundance of lactate (FC = 2.4, p = 0.0001) in patients with CVAEs. Differential expression analysis of miRNAs profiling identified mir-146b to be up-regulatein (FC = 14, p = 0.046) in patients with CVAE. Pathway analysis suggested that the pyruvate fermentation to lactate pathway is associated with CFZ-CVAEs. In this pilot multi-omics integrative analysis, we observed the down-regulation of pyruvate and up-regulation of LDHB among patients who experienced CVAEs, suggesting the importance of the pyruvate oxidation pathway associated with mitochondrial dysfunction. Validation and further investigation in a larger independent cohort are warranted to better understand the mechanisms of CFZ-CVAEs.

Heart failure-emerging roles for the mitochondrial pyruvate carrier

The mitochondrial pyruvate carrier (MPC) is the entry point for the glycolytic end-product pyruvate to the mitochondria. MPC activity, which is controlled by its abundance and post-translational regulation, determines whether pyruvate is oxidised in the mitochondria or metabolised in the cytosol. MPC serves as a crucial metabolic branch point that determines the fate of pyruvate in the cell, enabling metabolic adaptations during health, such as exercise, or as a result of disease. Decreased MPC expression in several cancers limits the mitochondrial oxidation of pyruvate and contributes to lactate accumulation in the cytosol, highlighting its role as a contributing, causal mediator of the Warburg effect. Pyruvate is handled similarly in the failing heart where a large proportion of it is reduced to lactate in the cytosol instead of being fully oxidised in the mitochondria. Several recent studies have found that the MPC abundance was also reduced in failing human and mouse hearts that were characterised by maladaptive hypertrophic growth, emulating the anabolic scenario observed in some cancer cells. In this review we discuss the evidence implicating the MPC as an important, perhaps causal, mediator of heart failure progression.

Metabolic Interventions to Prevent Hypertrophy-Induced Alterations in Contractile Properties In Vitro

(1) Background: The exact mechanism(s) underlying pathological changes in a heart in transition to hypertrophy and failure are not yet fully understood. However, alterations in cardiac energy metabolism seem to be an important contributor. We characterized an in vitro model of adrenergic stimulation-induced cardiac hypertrophy for studying metabolic, structural, and functional changes over time. Accordingly, we investigated whether metabolic interventions prevent cardiac structural and functional changes; (2) Methods: Primary rat cardiomyocytes were treated with phenylephrine (PE) for 16 h, 24 h, or 48 h, whereafter hypertrophic marker expression, protein synthesis rate, glucose uptake, and contractile function were assessed; (3) Results: 24 h PE treatment increased expression of hypertrophic markers, phosphorylation of hypertrophy-related signaling kinases, protein synthesis, and glucose uptake. Importantly, the increased glucose uptake preceded structural and functional changes, suggesting a causal role for metabolism in the onset of PE-induced hypertrophy. Indeed, PE treatment in the presence of a PAN-Akt inhibitor or of a GLUT4 inhibitor dipyridamole prevented PE-induced increases in cellular glucose uptake and ameliorated PE-induced contractile alterations; (4) Conclusions: Pharmacological interventions, forcing substrate metabolism away from glucose utilization, improved contractile properties in PE-treated cardiomyocytes, suggesting that targeting glucose uptake, independent from protein synthesis, forms a promising strategy to prevent hypertrophy and hypertrophy-induced cardiac dysfunction.

Hypoxia-induced miR-27 and miR-195 regulate ATP consumption, viability, and metabolism of rat cardiomyocytes by targeting PPARγ and FASN expression

This study examined whether hypoxia-induced microRNA (miRNA) upregulation was related to the inhibition of chondriosome aliphatic acid oxidation in myocardial cells under anoxia. We showed that anoxia induced high expression of hypoxia-inducible factor-1-alpha, muscle carnitine palmitoyltransferase I, and vascular endothelial growth factor in cardiomyocytes. Meanwhile, miR-27 and miR-195 were also upregulated in hypoxia-induced cardiomyocytes. Furthermore, hypoxia induction led to reductions in the adenosine triphosphate (ATP) consumption rate and oxidative metabolism as well as an increase in cardiomyocyte glycolysis. Metabolic reprogramming was reduced by hypoxia, as evidenced by the downregulation of sirtuin 1, forkhead box protein O1, sterol regulatory element-binding protein 1c, ATP citrate lyase, acetyl-coenzyme A carboxylase 2, adiponutrin, adipose triglyceride lipase, and glucose transporter type 4, while miR-27 and miR-195 inhibition partially recovered the expression of these transcription factors. In addition, hypoxia induction reduced cell viability and survival by triggering apoptosis; however, miR-27 and miR-195 inhibition partially increased cell viability. Moreover, miR-27 and miR-195 targeted the 3’untranslated regions of two key lipid-associated metabolic players, peroxisome proliferator-activated receptor gamma and fatty acid synthase. In conclusion, miR-27 and miR-195 are related to hypoxia-mediated ATP levels, glycolysis, oxidation, cell survival, and a cascade of transcription factors that control metabolism in cardiomyocytes.

Role of Warburg Effect in Cardiovascular Diseases: A Potential Treatment Option

Background:

Under normal conditions, the heart obtains ATP through the oxidation of fatty acids, glucose, and ketones. While fatty acids are the main source of energy in the heart, under certain conditions, the main source of energy shifts to glucose where pyruvate converts into lactate, to meet the energy demand. The Warburg effect is the energy shift from oxidative phosphorylation to glycolysis in the presence of oxygen. This effect is observed in tumors as well as in diseases, including cardiovascular diseases. If glycolysis is more dominant than glucose oxidation, the two pathways uncouple, contributing to the severity of the heart condition. Recently, several studies have documented changes in metabolism in several cardiovascular diseases; however, the specific mechanisms remain unclear.

Methods:

This literature review was conducted by an electronic database of Pub Med, Google Scholar, and Scopus published until 2020. Relevant papers are selected based on inclusion and exclusion criteria.

Results:

A total of 162 potentially relevant articles after the title and abstract screening were screened for full-text. Finally, 135 papers were included for the review article.

Discussion:

This review discusses the effects of alterations in glucose metabolism, particularly the Warburg effect, on cardiovascular diseases, including heart failure, atrial fibrillation, and cardiac hypertrophy.

Conclusion:

Reversing the Warburg effect could become a potential treatment option for cardiovascular diseases.

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.

BIO FOr CARE: biomarkers of hypertrophic cardiomyopathy development and progression in carriers of Dutch founder truncating MYBPC3 variants-design and status

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is the most prevalent monogenic heart disease, commonly caused by truncating variants in the MYBPC3 gene. HCM is an important cause of sudden cardiac death; however, overall prognosis is good and penetrance in genotype-positive individuals is incomplete. The underlying mechanisms are poorly understood and risk stratification remains limited.

AIM

To create a nationwide cohort of carriers of truncating MYBPC3 variants for identification of predictive biomarkers for HCM development and progression.

METHODS

In the multicentre, observational BIO FOr CARe (Identification of BIOmarkers of hypertrophic cardiomyopathy development and progression in Dutch MYBPC3 FOunder variant CARriers) cohort, carriers of the c.2373dupG, c.2827C > T, c.2864_2865delCT and c.3776delA MYBPC3 variants are included and prospectively undergo longitudinal blood collection. Clinical data are collected from first presentation onwards. The primary outcome constitutes a composite endpoint of HCM progression (maximum wall thickness ≥ 20 mm, septal reduction therapy, heart failure occurrence, sustained ventricular arrhythmia and sudden cardiac death).

RESULTS

So far, 250 subjects (median age 54.9 years (interquartile range 43.3, 66.6), 54.8% male) have been included. HCM was diagnosed in 169 subjects and dilated cardiomyopathy in 4. The primary outcome was met in 115 subjects. Blood samples were collected from 131 subjects.

CONCLUSION

BIO FOr CARe is a genetically homogeneous, phenotypically heterogeneous cohort incorporating a clinical data registry and longitudinal blood collection. This provides a unique opportunity to study biomarkers for HCM development and prognosis. The established infrastructure can be extended to study other genetic variants. Other centres are invited to join our consortium.

Danhong Injection and Trimetazidine Protect Cardiomyocytes and Enhance Calcium Handling after Myocardial Infarction

Myocardial infarction (MI) is one of the leading causes of death worldwide. However, there is no effective treatment for MI. In this study, trimetazidine (TMZ) and Danhong injection (DHI), representing western medicine and traditional Chinese medicine for MI, were used as tools to identify vital processes in alleviating MI injury. Administration of DHI and TMZ obviously decreased myocardial infarct size, improved ultrasonic heart function, and reduced creatine kinase (CK), lactate dehydrogenase (LDH), and glutamic oxaloacetic transaminase (AST) levels after MI. RNA-seq results indicated calcium ion handling and negative regulation of apoptotic process were vital processes and DHI and TMZ obviously reduced the expression of CaMK II and inhibited cleaved caspase-3 and Bax. Furthermore, DHI and TMZ increased p-S16-PLB, p-S16T17-PLB, CACNA1C, p-RyR2, and p-PKA expression but did not affect SERCA2a expression. In addition to the enhancement of cardiac myocyte shortening amplitude, maximum shortening velocity, and calcium transients, DHI and TMZ increased sarcoplasmic reticulum calcium content and enhanced SERCA2a calcium uptake capability by upregulating the phosphorylation of PLB but did not affect calcium exclusion by NCX. In conclusion, DHI and TMZ protect against MI through inhibiting apoptosis by downregulating CaMKII pathway and enhancing cardiac myocyte contractile functions possibly through the PKA signaling pathway.

Mechanisms underlying the pathophysiology of heart failure with preserved ejection fraction: the tip of the iceberg

Heart failure with preserved ejection fraction (HFpEF) is a multifaceted syndrome with a complex aetiology often associated with several comorbidities, such as left ventricle pressure overload, diabetes mellitus, obesity, and kidney disease. Its pathophysiology remains obscure mainly due to the complex phenotype induced by all these associated comorbidities and to the scarcity of animal models that adequately mimic HFpEF. Increased oxidative stress, inflammation, and endothelial dysfunction are currently accepted as key players in HFpEF pathophysiology. However, we have just started to unveil HFpEF complexity and the role of calcium handling, energetic metabolism, and mitochondrial function remain to clarify. Indeed, the enlightenment of such cellular and molecular mechanisms represents an opportunity to develop novel therapeutic approaches and thus to improve HFpEF treatment options. In the last decades, the number of research groups dedicated to studying HFpEF has increased, denoting the importance and the magnitude achieved by this syndrome. In the current technological and web world, the amount of information is overwhelming, driving us not only to compile the most relevant information about the theme but also to explore beyond the tip of the iceberg. Thus, this review aims to encompass the most recent knowledge related to HFpEF or HFpEF-associated comorbidities, focusing mainly on myocardial metabolism, oxidative stress, and energetic pathways.

Targeting Fat Oxidation in Mouse Prostate Cancer Decreases Tumor Growth and Stimulates Anti-Cancer Immunity

Lipid catabolism represents an Achilles heel in prostate cancer (PCa) that can be exploited for therapy. CPT1A regulates the entry of fatty acids into the mitochondria for beta-oxidation and its inhibition has been shown to decrease PCa growth. In this study, we examined the pharmacological blockade of lipid oxidation with ranolazine in TRAMPC1 PCa models. Oral administration of ranolazine (100 mg/Kg for 21 days) resulted in decreased tumor CD8⁺ T-cells Tim3 content, increased macrophages, and decreased blood myeloid immunosuppressive monocytes. Using multispectral staining, drug treatments increased infiltration of CD8⁺ T-cells and dendritic cells compared to vehicle. Functional studies with spleen cells of drug-treated tumors co-cultured with TRAMPC1 cells showed increased ex vivo T-cell cytotoxic activity, suggesting an anti-tumoral response. Lastly, a decrease in CD4⁺ and CD8⁺ T-cells expressing PD1 was observed when exhausted spleen cells were incubated with TRAMPC1 Cpt1a-KD compared to the control cells. These data indicated that genetically blocking the ability of the tumor cells to oxidize lipid can change the activation status of the neighboring T-cells. This study provides new knowledge of the role of lipid catabolism in the intercommunication of tumor and immune cells, which can be extrapolated to other cancers with high CPT1A expression.

Predictors and prognostic role of low myocardial mechano-energetic efficiency in chronic inflammatory arthritis

OBJECTIVE

To assess the variables associated with the status of low myocardial mechano-energetic efficiency (MEE) [the ratio between myocardial left ventricular (LV) work and magnitude of myocardial oxygen consumption] and whether low-MEE is a prognosticator of adverse cardiovascular outcome in patients with chronic inflammatory arthritis.

METHODS

A total of 432 outpatients with established chronic inflammatory arthritis without overt cardiac disease were recruited from March 2014-March 2016; 216 participants were used as comparison group. Low-MEE status was a priori identified by standard echocardiography at rest as less than 0.32 ml/s per g (5th percentile of MEE calculated in 145 healthy individuals). The pre-specified primary end-point of the study was a composite of cardiovascular death/hospitalization. Follow-up ended September 2019.

RESULTS

MEE was significantly lower in chronic inflammatory arthritis patients than controls (0.35 ± 0.11 vs. 0.45 ± 0.10 ml/s per g; P < 0.001). Low-MEE was detected in 164 patients (38%). Independent predictors of low-MEE were older age, higher SBP, diabetes mellitus, LV concentric geometry and lower LV systolic function. During a follow-up of 36 (21-48) months, a primary end-point occurred in 37 patients (8.6%): 22/164 patients with low-MEE (13.4%) and 15/268 (5.6%) without low-MEE (P = 0.004). Low-MEE predicted primary end-points in multivariate Cox regression analysis [heart rate 2.23 (confidence interval 1.13-4.38), P = 0.02] together with older age, lower renal function and higher LV mass.

CONCLUSION

Low-MEE is detectable in more than one-third of patients with chronic inflammatory arthritis and is associated with traditional cardiovascular risk factors and abnormalities in LV geometry and systolic function. In these patients low-MEE is a powerful prognosticator of adverse cardiovascular events.

Atglistatin Pretreatment Preserves Remote Myocardium Function Following Myocardial Infarction

The pathological role of adipose derived fatty acids following myocardial infarction has long been hypothesized. However, most methods for reducing adipocyte lipolysis have significant non-adipose effects. Atglistatin, a direct inhibitor of the initial lipase in the lipolysis cascade, has been recently shown to inhibit adipose tissue lipolysis after oral administration. To explore the ability of Atglistatin to impact the pathophysiology of cardiac ischemia we performed prophylactic treatment of mice with Atglistatin for 2 days before 1-hour cardiac ischemia. After 7 days of reperfusion, hearts of Atglistatin treated mice showed significantly improved systolic pump function while infarct and scar size were unaffected. Strain analysis of echocardiographic data revealed an enhanced performance of the remote myocardium as cause for overall improved systolic function. The present study provides evidence that inhibition of adipocyte adipose triglyceride lipase (ATGL) using Atglistatin is able to improve cardiac function after MI by targeting the remote myocardium.