Targeting mitochondrial oxidative metabolism as an approach to treat heart failure

The ketogenic diet does not improve cardiac function and blunts glucose oxidation in ischaemic heart failure

AIMS

Cardiac energy metabolism is perturbed in ischaemic heart failure and is characterized by a shift from mitochondrial oxidative metabolism to glycolysis. Notably, the failing heart relies more on ketones for energy than a healthy heart, an adaptive mechanism that improves the energy-starved status of the failing heart. However, whether this can be implemented therapeutically remains unknown. Therefore, our aim was to determine if increasing ketone delivery to the heart via a ketogenic diet can improve the outcomes of heart failure.

METHODS AND RESULTS

C57BL/6J male mice underwent either a sham surgery or permanent left anterior descending coronary artery ligation surgery to induce heart failure. After 2 weeks, mice were then treated with either a control diet or a ketogenic diet for 3 weeks. Transthoracic echocardiography was then carried out to assess in vivo cardiac function and structure. Finally, isolated working hearts from these mice were perfused with appropriately 3H or 14C labelled glucose (5 mM), palmitate (0.8 mM), and β-hydroxybutyrate (β-OHB) (0.6 mM) to assess mitochondrial oxidative metabolism and glycolysis. Mice with heart failure exhibited a 56% drop in ejection fraction, which was not improved with a ketogenic diet feeding. Interestingly, mice fed a ketogenic diet had marked decreases in cardiac glucose oxidation rates. Despite increasing blood ketone levels, cardiac ketone oxidation rates did not increase, probably due to a decreased expression of key ketone oxidation enzymes. Furthermore, in mice on the ketogenic diet, no increase in overall cardiac energy production was observed, and instead, there was a shift to an increased reliance on fatty acid oxidation as a source of cardiac energy production. This resulted in a decrease in cardiac efficiency in heart failure mice fed a ketogenic diet.

CONCLUSION

We conclude that the ketogenic diet does not improve heart function in failing hearts, due to ketogenic diet-induced excessive fatty acid oxidation in the ischaemic heart and a decrease in insulin-stimulated glucose oxidation.

Reduced mitochondrial pyruvate carrier expression in hearts with heart failure and reduced ejection fraction patients: ischemic vs. non-ischemic origin

Introduction and objectives

Mitochondrial pyruvate carrier (MPC) mediates the entry of pyruvate into mitochondria, determining whether pyruvate is incorporated into the Krebs cycle or metabolized in the cytosol. In heart failure (HF), a large amount of pyruvate is metabolized to lactate in the cytosol rather than being oxidized inside the mitochondria. Thus, MPC activity or expression might play a key role in the fate of pyruvate during HF. The purpose of this work was to study the levels of the two subunits of this carrier, named MPC1 and MPC2, in human hearts with HF of different etiologies.

Methods

Protein and mRNA expression analyses were conducted in cardiac tissues from three donor groups: patients with HF with reduced ejection fraction (HFrEF) with ischemic cardiomyopathy (ICM) or idiopathic dilated cardiomyopathy (IDC), and donors without cardiac pathology (Control). MPC2 plasma levels were determined by ELISA.

Results

Significant reductions in the levels of MPC1, MPC2, and Sirtuin 3 (SIRT3) were observed in ICM patients compared with the levels in the Control group. However, no statistically significant differences were revealed in the analysis of MPC1 and MPC2 gene expression among the groups. Interestingly, Pyruvate dehydrogenase complex (PDH) subunits expression were increased in the ICM patients. In the case of IDC patients, a significant decrease in MPC1 was observed only when compared with the Control group. Notably, plasma MPC2 levels were found to be elevated in both disease groups compared with that in the Control group.

Conclusion

Decreases in MPC1 and/or MPC2 levels were detected in the cardiac tissues of HFrEF patients, with ischemic or idiopatic origen, indicating a potential reduction in mitochondrial pyruvate uptake in the heart, which could be linked to unfavorable clinical features.

From Beats to Metabolism: the Heart at the Core of Interorgan Metabolic Cross Talk

The heart, once considered a mere blood pump, is now recognized as a multifunctional metabolic and endocrine organ. Its function is tightly regulated by various metabolic processes, at the same time it serves as an endocrine organ, secreting bioactive molecules that impact systemic metabolism. In recent years, research has shed light on the intricate interplay between the heart and other metabolic organs, such as adipose tissue, liver, and skeletal muscle. The metabolic flexibility of the heart and its ability to switch between different energy substrates play a crucial role in maintaining cardiac function and overall metabolic homeostasis. Gaining a comprehensive understanding of how metabolic disorders disrupt cardiac metabolism is crucial, as it plays a pivotal role in the development and progression of cardiac diseases. The emerging understanding of the heart as a metabolic and endocrine organ highlights its essential contribution to whole body metabolic regulation and offers new insights into the pathogenesis of metabolic diseases, such as obesity, diabetes, and cardiovascular disorders. In this review, we provide an in-depth exploration of the heart's metabolic and endocrine functions, emphasizing its role in systemic metabolism and the interplay between the heart and other metabolic organs. Furthermore, emerging evidence suggests a correlation between heart disease and other conditions such as aging and cancer, indicating that the metabolic dysfunction observed in these conditions may share common underlying mechanisms. By unraveling the complex mechanisms underlying cardiac metabolism, we aim to contribute to the development of novel therapeutic strategies for metabolic diseases and improve overall cardiovascular health.

Advances in Metabolic Remodeling and Intervention Strategies in Heart Failure

The heart is the most energy-demanding organ throughout the whole body. Perturbations or failure in energy metabolism contributes to heart failure (HF), which represents the advanced stage of various heart diseases. The poor prognosis and huge economic burden associated with HF underscore the high unmet need to explore novel therapies targeting metabolic modulators beyond conventional approaches focused on neurohormonal and hemodynamic regulators. Emerging evidence suggests that alterations in metabolic substrate reliance, metabolic pathways, metabolic by-products, and energy production collectively regulate the occurrence and progression of HF. In this review, we provide an overview of cardiac metabolic remodeling, encompassing the utilization of free fatty acids, glucose metabolism, ketone bodies, and branched-chain amino acids both in the physiological condition and heart failure. Most importantly, the latest advances in pharmacological interventions are discussed as a promising therapeutic approach to restore cardiac function, drawing insights from recent basic research, preclinical and clinical studies.

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.

Mitochondrial transplantation: the advance to therapeutic application and molecular modulation

Mitochondrial transplantation provides a novel methodology for rescue of cell viability and cell function following ischemia-reperfusion injury and applications for other pathologies are expanding. In this review we present our methods and acquired data and evidence accumulated to support the use of mitochondrial transplantation.

Real-time resolution studies of the regulation of pyruvate-dependent lactate metabolism by hexokinases in single cells

Lactate is a mitochondrial substrate for many tissues including neuron, muscle, skeletal and cardiac, as well as many cancer cells, however little is known about the processes that regulate its utilization in mitochondria. Based on the close association of Hexokinases (HK) with mitochondria, and the known cardio-protective role of HK in cardiac muscle, we have investigated the regulation of lactate and pyruvate metabolism by hexokinases (HKs), utilizing wild-type HEK293 cells and HEK293 cells in which the endogenous HKI and/or HKII have been knocked down to enable overexpression of wild type and mutant HKs. To assess the real-time changes in intracellular lactate levels the cells were transfected with a lactate specific FRET probe. In the HKI/HKII double knockdown cells, addition of extracellular pyruvate caused a large and sustained decrease in lactate. This decrease was rapidly reversed upon inhibition of the malate aspartate shuttle by aminooxyacetate, or inhibition of mitochondrial oxidative respiration by NaCN. These results suggest that in the absence of HKs, pyruvate-dependent activation of the TCA cycle together with the malate aspartate shuttle facilitates lactate transformation into pyruvate and its utilization by mitochondria. With replacement by overexpression of HKI or HKII the cellular response to pyruvate and NaCN was modified. With either hexokinase present, both the decrease in lactate due to the addition of pyruvate and the increase following addition of NaCN were either transient or suppressed altogether. Blockage of the pentose phosphate pathway with the inhibitor 6-aminonicotinamide (6-AN), abolished the effects of HK replacement. These results suggest that blocking of the malate aspartate shuttle by HK may involve activation of the pentose phosphate pathway and increased NADPH production.

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.

Multitargeting in cardioprotection: An example of biaromatic compounds

A multitarget drug design approach is actively developing in modern medicinal chemistry and pharmacology, especially with regard to multifactorial diseases such as cardiovascular diseases, cancer, and neurodegenerative diseases. A detailed study of many well-known drugs developed within the single-target approach also often reveals additional mechanisms of their real pharmacological action. One of the multitarget drug design approaches can be the identification of the basic pharmacophore models corresponding to a wide range of the required target ligands. Among such models in the group of cardioprotectors is the linked biaromatic system. This review develops the concept of a "basic pharmacophore" using the biaromatic pharmacophore of cardioprotectors as an example. It presents an analysis of possible biological targets for compounds corresponding to the biaromatic pharmacophore and an analysis of the spectrum of biological targets for the five most known and most studied cardioprotective drugs corresponding to this model, and their involvement in the biological effects of these drugs.

Comparative Metabolomics in Single Ventricle Patients after Fontan Palliation: A Strong Case for a Targeted Metabolic Therapy

Most studies on single ventricle (SV) circulation take a physiological or anatomical approach. Although there is a tight coupling between cardiac contractility and metabolism, the metabolic perspective on this patient population is very recent. Early findings point to major metabolic disturbances, with both impaired glucose and fatty acid oxidation in the cardiomyocytes. Additionally, Fontan patients have systemic metabolic derangements such as abnormal glucose metabolism and hypocholesterolemia. Our literature review compares the metabolism of patients with a SV circulation after Fontan palliation with that of patients with a healthy biventricular (BV) heart, or different subtypes of a failing BV heart, by Pubmed review of the literature on cardiac metabolism, Fontan failure, heart failure (HF), ketosis, metabolism published in English from 1939 to 2023. Early evidence demonstrates that SV circulation is not only a hemodynamic burden requiring staged palliation, but also a metabolic issue with alterations similar to what is known for HF in a BV circulation. Alterations of fatty acid and glucose oxidation were found, resulting in metabolic instability and impaired energy production. As reported for patients with BV HF, stimulating ketone oxidation may be an effective treatment strategy for HF in these patients. Few but promising clinical trials have been conducted thus far to evaluate therapeutic ketosis with HF using a variety of instruments, including ketogenic diet, ketone esters, and sodium-glucose co-transporter-2 (SGLT2) inhibitors. An initial trial on a small cohort demonstrated favorable outcomes for Fontan patients treated with SGLT2 inhibitors. Therapeutic ketosis is worth considering in the treatment of Fontan patients, as ketones positively affect not only the myocardial energy metabolism, but also the global Fontan physiopathology. Induced ketosis seems promising as a concerted therapeutic strategy.

High-Density Lipoprotein Lipidomics in Chronic Kidney Disease

BACKGROUND

Patients with chronic kidney disease (CKD) have dysfunctional high-density lipoprotein (HDL) particles as compared with the general population. Understanding the lipid composition of HDL may provide mechanistic insight. We tested associations of estimated glomerular filtration rate (eGFR) and albuminuria with relative HDL abundance of ceramides, sphingomyelins, and phosphatidylcholines in participants with CKD.

METHODS

We studied 490 participants with CKD from the Seattle Kidney Study. HDL was isolated from plasma; targeted lipidomics was used to quantify the relative abundance of ceramides, sphingomyelins, and phosphatidylcholines per 10 µg of total HDL protein. We evaluated the associations of eGFR and albuminuria with levels of individual lipids and lipid classes (including 7 ceramides, 6 sphingomyelins, and 24 phosphatidylcholines) using multivariable linear regression, controlling for multiple comparisons via the false discovery rate.

RESULTS

The mean (SD) eGFR was 45 (24) mL/min/1.73 m2; the median (IQR[interquartile range]) albuminuria was 108 (16, 686) mg/g (12.2 [1.8, 77.6] mg/mmol) urine creatinine. After adjusting for demographics, past medical history, laboratory values, and medication use, eGFR was not associated with higher relative abundance of any class of lipids or individual lipids. Greater albuminuria was significantly associated with a higher relative abundance of total ceramides and moderate-long R-chain sphingomyelins, ceramides 22:0 and 24:1, hexosylceramide 16:0, sphingomyelin 16:0, and phosphatidylcholines 29:0, 30:1, and 38:2; the strongest association was for hexosylceramide 16:0 (increase per doubling of urine albumin to creatinine ratio 0.022 (95% CI, 0.012-0.032).

CONCLUSIONS

Greater albuminuria was significantly associated with specific alterations in the lipid composition of HDL in participants with CKD.

KDM8 epigenetically controls cardiac metabolism to prevent initiation of dilated cardiomyopathy

Cardiac metabolism is deranged in heart failure, but underlying mechanisms remain unclear. Here, we show that lysine demethylase 8 (Kdm8) maintains an active mitochondrial gene network by repressing Tbx15, thus preventing dilated cardiomyopathy leading to lethal heart failure. Deletion of Kdm8 in mouse cardiomyocytes increased H3K36me2 with activation of Tbx15 and repression of target genes in the NAD+ pathway before dilated cardiomyopathy initiated. NAD+ supplementation prevented dilated cardiomyopathy in Kdm8 mutant mice, and TBX15 overexpression blunted NAD+-activated cardiomyocyte respiration. Furthermore, KDM8 was downregulated in human hearts affected by dilated cardiomyopathy, and higher TBX15 expression defines a subgroup of affected hearts with the strongest downregulation of genes encoding mitochondrial proteins. Thus, KDM8 represses TBX15 to maintain cardiac metabolism. Our results suggest that epigenetic dysregulation of metabolic gene networks initiates myocardium deterioration toward heart failure and could underlie heterogeneity of dilated cardiomyopathy.

Acquired disorders of mitochondrial metabolism and dynamics in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is an orphan disease of the cardiopulmonary unit that reflects an obstructive pulmonary vasculopathy and presents with hypertrophy, inflammation, fibrosis, and ultimately failure of the right ventricle (RVF). Despite treatment using pulmonary hypertension (PH)-targeted therapies, persistent functional impairment reduces the quality of life for people with PAH and death from RVF occurs in approximately 40% of patients within 5 years of diagnosis. PH-targeted therapeutics are primarily vasodilators and none, alone or in combination, are curative. This highlights a need to therapeutically explore molecular targets in other pathways that are involved in the pathogenesis of PAH. Several candidate pathways in PAH involve acquired mitochondrial dysfunction. These mitochondrial disorders include: 1) a shift in metabolism related to increased expression of pyruvate dehydrogenase kinase and pyruvate kinase, which together increase uncoupled glycolysis (Warburg metabolism); 2) disruption of oxygen-sensing related to increased expression of hypoxia-inducible factor 1α, resulting in a state of pseudohypoxia; 3) altered mitochondrial calcium homeostasis related to impaired function of the mitochondrial calcium uniporter complex, which elevates cytosolic calcium and reduces intramitochondrial calcium; and 4) abnormal mitochondrial dynamics related to increased expression of dynamin-related protein 1 and its binding partners, such as mitochondrial dynamics proteins of 49 kDa and 51 kDa, and depressed expression of mitofusin 2, resulting in increased mitotic fission. These acquired mitochondrial abnormalities increase proliferation and impair apoptosis in most pulmonary vascular cells (including endothelial cells, smooth muscle cells and fibroblasts). In the RV, Warburg metabolism and induction of glutaminolysis impairs bioenergetics and promotes hypokinesis, hypertrophy, and fibrosis. This review will explore our current knowledge of the causes and consequences of disordered mitochondrial function in PAH.

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.

Major ginsenosides from Panax ginseng promote aerobic cellular respiration and SIRT1-mediated mitochondrial biosynthesis in cardiomyocytes and neurons

Background

Aerobic cellular respiration provides chemical energy, adenosine triphosphate (ATP), to maintain multiple cellular functions. Sirtuin 1 (SIRT1) can deacetylate peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α) to promote mitochondrial biosynthesis. Targeting energy metabolism is a potential strategy for the prevention and treatment of various diseases, such as cardiac and neurological disorders. Ginsenosides, one of the major bioactive constituents of Panax ginseng, have been extensively used due to their diverse beneficial effects on healthy subjects and patients with different diseases. However, the underlying molecular mechanisms of total ginsenosides (GS) on energy metabolism remain unclear.

Methods

In this study, oxygen consumption rate, ATP production, mitochondrial biosynthesis, glucose metabolism, and SIRT1-PGC-1α pathways in untreated and GS-treated different cells, fly, and mouse models were investigated.

Results

GS pretreatment enhanced mitochondrial respiration capacity and ATP production in aerobic respiration-dominated cardiomyocytes and neurons, and promoted tricarboxylic acid metabolism in cardiomyocytes. Moreover, GS clearly enhanced NAD⁺-dependent SIRT1 activation to increase mitochondrial biosynthesis in cardiomyocytes and neurons, which was completely abrogated by nicotinamide. Importantly, ginsenoside monomers, such as Rg1, Re, Rf, Rb1, Rc, Rh1, Rb2, and Rb3, were found to activate SIRT1 and promote energy metabolism.

Conclusion

This study may provide new insights into the extensive application of ginseng for cardiac and neurological protection in healthy subjects and patients.

Sodium-Glucose Co-Transporter 2 Inhibition With Empagliflozin Improves Cardiac Function After Cardiac Arrest in Rats by Enhancing Mitochondrial Energy Metabolism

Empagliflozin is a newly developed antidiabetic drug to reduce hyperglycaemia by highly selective inhibition of sodium–glucose co-transporter 2. Hyperglycaemia is commonly seen in patients after cardiac arrest (CA) and is associated with worse outcomes. In this study, we examined the effects of empagliflozin on cardiac function in rats with myocardial dysfunction after CA. Non-diabetic male Sprague–Dawley rats underwent ventricular fibrillation to induce CA, or sham surgery. Rats received 10 mg/kg of empagliflozin or vehicle at 10 min after return of spontaneous circulation by intraperitoneal injection. Cardiac function was assessed by echocardiography, histological analysis, molecular markers of myocardial injury, oxidative stress, mitochondrial ultrastructural integrity and metabolism. We found that empagliflozin did not influence heart rate and blood pressure, but left ventricular function and survival time were significantly higher in the empagliflozin treated group compared to the group treated with vehicle. Empagliflozin also reduced myocardial fibrosis, serum cardiac troponin I levels and myocardial oxidative stress after CA. Moreover, empagliflozin maintained the structural integrity of myocardial mitochondria and increased mitochondrial activity after CA. In addition, empagliflozin increased circulating and myocardial ketone levels as well as heart β-hydroxy butyrate dehydrogenase 1 protein expression. Together, these metabolic changes were associated with an increase in cardiac energy metabolism. Therefore, empagliflozin favorably affected cardiac function in non-diabetic rats with acute myocardial dysfunction after CA, associated with reducing glucose levels and increasing ketone body oxidized metabolism. Our data suggest that empagliflozin might benefit patients with myocardial dysfunction after CA.

Cardiomyocyte-specific miR-100 overexpression preserves heart function under pressure overload in mice and diminishes fatty acid uptake as well as ROS production by direct suppression of Nox4 and CD36

MicroRNAs are key regulators of the cardiac response to injury. MiR-100 has recently been suggested to be involved in different forms of heart failure, but functional studies are lacking. In the present study, we examined the impact of transgenic miR-100 overexpression on cardiac structure and function during physiological aging and pathological pressure-overload-induced heart failure in mice after transverse aortic constriction surgery. MiR-100 was moderately upregulated after induction of pressure overload in mice. While in our transgenic model the cardiomyocyte-specific overexpression of miR-100 did not result in an obvious cardiac phenotype in unchallenged mice, the transgenic mouse strain exhibited less left ventricular dilatation and a higher ejection fraction than wildtype animals, demonstrating an attenuation of maladaptive cardiac remodeling by miR-100. Cardiac transcriptome analysis identified a repression of several regulatory genes related to cardiac metabolism, lipid peroxidation, and production of reactive oxygen species (ROS) by miR-100 overexpression, possibly mediating the observed functional effects. While the modulation of ROS-production seemed to be indirectly affected by miR-100 via Alox5-and Nox4-downregulation, we demonstrated that miR-100 induced a direct repression of the scavenger protein CD36 in murine hearts resulting in a decreased uptake of long-chain fatty acids and an alteration of mitochondrial respiratory function with an enhanced glycolytic state. In summary, we identified miR-100 as a modulator of cardiac metabolism and ROS production without an apparent cardiac phenotype at baseline but a protective effect under conditions of pressure-overload-induced cardiac stress, providing new insight into the mechanisms of heart failure.

Ketone Ester D-β-Hydroxybutyrate-(R)-1,3 Butanediol Prevents Decline in Cardiac Function in Type 2 Diabetic Mice

Background

Heart failure is responsible for approximately 65% of deaths in patients with type 2 diabetes mellitus. However, existing therapeutics for type 2 diabetes mellitus have limited success on the prevention of diabetic cardiomyopathy. The aim of this study was to determine whether moderate elevation in D‐β‐hydroxybutyrate improves cardiac function in animals with type 2 diabetes mellitus.

Methods and Results

Type 2 diabetic (db/db) and their corresponding wild‐type mice were fed a control diet or a diet where carbohydrates were equicalorically replaced by D‐β‐hydroxybutyrate‐(R)‐1,3 butanediol monoester (ketone ester [KE]). After 4 weeks, echocardiography demonstrated that a KE diet improved systolic and diastolic function in db/db mice. A KE diet increased expression of mitochondrial succinyl‐CoA:3‐oxoacid‐CoA transferase and restored decreased expression of mitochondrial β‐hydroxybutyrate dehydrogenase, key enzymes in cardiac ketone metabolism. A KE diet significantly enhanced both basal and ADP‐mediated oxygen consumption in cardiac mitochondria from both wild‐type and db/db animals; however, it did not result in the increased mitochondrial respiratory control ratio. Additionally, db/db mice on a KE diet had increased resistance to oxidative and redox stress, with evidence of restoration of decreased expression of thioredoxin and glutathione peroxidase 4 and less permeability transition pore activity in mitochondria. Mitochondrial biogenesis, quality control, and elimination of dysfunctional mitochondria via mitophagy were significantly increased in cardiomyocytes from db/db mice on a KE diet. The increase in mitophagy was correlated with restoration of mitofusin 2 expression, which contributed to improved coupling between cytosolic E3 ubiquitin ligase translocation into mitochondria and microtubule‐associated protein 1 light chain 3–mediated autophagosome formation.

Conclusions

Moderate elevation in circulating D‐β‐hydroxybutyrate levels via KE supplementation enhances mitochondrial biogenesis, quality control, and oxygen consumption and increases resistance to oxidative/redox stress and mPTP opening, thus resulting in improvement of cardiac function in animals with type 2 diabetes mellitus.

Post-translational Acetylation Control of Cardiac Energy Metabolism

Perturbations in myocardial energy substrate metabolism are key contributors to the pathogenesis of heart diseases. However, the underlying causes of these metabolic alterations remain poorly understood. Recently, post-translational acetylation-mediated modification of metabolic enzymes has emerged as one of the important regulatory mechanisms for these metabolic changes. Nevertheless, despite the growing reports of a large number of acetylated cardiac mitochondrial proteins involved in energy metabolism, the functional consequences of these acetylation changes and how they correlate to metabolic alterations and myocardial dysfunction are not clearly defined. This review summarizes the evidence for a role of cardiac mitochondrial protein acetylation in altering the function of major metabolic enzymes and myocardial energy metabolism in various cardiovascular disease conditions.

Thyroid hormones and the potential for regulating glucose metabolism in cardiomyocytes during insulin resistance and T2DM

In order for the heart to maintain its continuous mechanical work and provide the systolic movement to uphold coronary blood flow, substantial synthesis of adenosine triphosphate (ATP) is required. Under normal conditions cardiac tissue utilizes roughly 70% fatty acids (FA), and 30% glucose for the production of ATP; however, during impaired metabolic conditions like insulin resistance and diabetes glucose metabolism is dysregulated and FA account for 99% of energy production. One of the major consequences of a shift in FA metabolism in cardiac tissue is an increase in reactive oxygen species (ROS) and lipotoxicity, which ultimately lead to mitochondrial dysfunction. Thyroid hormones (TH) have direct effects on cardiac function and glucose metabolism during impaired metabolic conditions suggesting that TH may improve glucose metabolism in an insulin resistant condition. None-classical TH signaling in the heart has shown to phosphorylate protein kinase B (Akt) and increase activity of phosphoinositide-3-kinase (PI3K), which are critical mediators in the insulin-stimulated glucose uptake pathway. Studies on peripheral tissues such as skeletal muscle and adipocytes have demonstrated TH treatment improved glucose intolerance in a diabetic model and increased insulin-regulated glucose transporter (GLUT4) mRNA levels. GLUT4 is a downstream target of thyroid response element (TRE), which demonstrates that THs regulate glucose via GLUT4. Elevated 3,5,3'-triiodothyronine (T3) increased glucose oxidation rate and decreased the glycolytic intermediate, fructose 6-phosphate (F6P) in cardiomyocytes, in addition to increasing mitochondrial biogenesis and pyruvate transport across the mitochondrial membrane. These findings along with a few other studies on T3 treatment in cardiac tissue suggest TH may improve glucose metabolism in an insulin resistant model and ameliorate the effects of diabetes and metabolic syndrome. This review highlights the potential benefits of exogenous TH on ameliorating metabolic dysfunction in the heart.

Interplay Between Reactive Oxygen/Reactive Nitrogen Species and Metabolism in Vascular Biology and Disease

Reactive oxygen species (ROS; e.g., superoxide [O₂^•-] and hydrogen peroxide [H₂O₂]) and reactive nitrogen species (RNS; e.g., nitric oxide [NO^•]) at the physiological level function as signaling molecules that mediate many biological responses, including cell proliferation, migration, differentiation, and gene expression. By contrast, excess ROS/RNS, a consequence of dysregulated redox homeostasis, is a hallmark of cardiovascular disease. Accumulating evidence suggests that both ROS and RNS regulate various metabolic pathways and enzymes. Recent studies indicate that cells have mechanisms that fine-tune ROS/RNS levels by tight regulation of metabolic pathways, such as glycolysis and oxidative phosphorylation. The ROS/RNS-mediated inhibition of glycolytic pathways promotes metabolic reprogramming away from glycolytic flux toward the oxidative pentose phosphate pathway to generate nicotinamide adenine dinucleotide phosphate (NADPH) for antioxidant defense. This review summarizes our current knowledge of the mechanisms by which ROS/RNS regulate metabolic enzymes and cellular metabolism and how cellular metabolism influences redox homeostasis and the pathogenesis of disease. A full understanding of these mechanisms will be important for the development of new therapeutic strategies to treat diseases associated with dysregulated redox homeostasis and metabolism. Antioxid. Redox Signal. 34, 1319-1354.

Cellular and molecular pathobiology of heart failure with preserved ejection fraction

Heart failure with preserved ejection fraction (HFpEF) affects half of all patients with heart failure worldwide, is increasing in prevalence, confers substantial morbidity and mortality, and has very few effective treatments. HFpEF is arguably the greatest unmet medical need in cardiovascular disease. Although HFpEF was initially considered to be a haemodynamic disorder characterized by hypertension, cardiac hypertrophy and diastolic dysfunction, the pandemics of obesity and diabetes mellitus have modified the HFpEF syndrome, which is now recognized to be a multisystem disorder involving the heart, lungs, kidneys, skeletal muscle, adipose tissue, vascular system, and immune and inflammatory signalling. This multiorgan involvement makes HFpEF difficult to model in experimental animals because the condition is not simply cardiac hypertrophy and hypertension with abnormal myocardial relaxation. However, new animal models involving both haemodynamic and metabolic disease, and increasing efforts to examine human pathophysiology, are revealing new signalling pathways and potential therapeutic targets. In this Review, we discuss the cellular and molecular pathobiology of HFpEF, with the major focus being on mechanisms relevant to the heart, because most research has focused on this organ. We also highlight the involvement of other important organ systems, including the lungs, kidneys and skeletal muscle, efforts to characterize patients with the use of systemic biomarkers, and ongoing therapeutic efforts. Our objective is to provide a roadmap of the signalling pathways and mechanisms of HFpEF that are being characterized and which might lead to more patient-specific therapies and improved clinical outcomes.

Short-term administration of C. aronia stimulates insulin signaling, suppresses fatty acids metabolism, and increases glucose uptake and utilization in the hearts of healthy rats

This study evaluated the effect of Crataegus aronia (C. aronia) aqueous extract on cardiac substrate utilization and insulin signaling in adult male healthy Wistar rats. Rats (n = 18/group) were either administered normal saline (vehicle) or treated with C. aronia aqueous extract (200 mg/kg) for 7 days, daily. Fasting plasma glucose and insulin levels were not significantly changed in C. aronia-treated rats but were significantly reduced after both the intraperitoneal glucose or insulin tolerance tests. Besides, C. aronia significantly increased the left ventricular (LV) activities of phosphofructokinase (PFK) and pyruvate dehydrogenase (PDH), two markers of glycolysis and glucose oxidation, respectively, and suppressed the levels of pyruvate dehydrogenase kinase 4 (PDK4), an inhibitor of PDH. Concomitantly, it significantly reduced the LV levels of carnitine palmitoyltransferase 1 (CPT1) and PPARα, two markers of fatty acid (FAs) oxidations. Under basal and insulin stimulation, C. aronia aqueous extract boosted insulin signaling in the LV of rats by increasing the protein levels of p-IRS (Tyr⁶¹²) and p-Akt (Ser⁴⁷³) and suppressing protein levels of p-mTOR (Ser 2448) and p-IRS (Ser³⁰⁷). In parallel, C. aronia also increased the protein levels of GLUT-4 in the membrane fraction of the treated LVs. All these effects were also associated with a significant increase in AMPK activity (phosphorylation at Thr¹⁷²), a major energy modulator that stimulates glucose utilization. In conclusion, short-term administration of C. aronia aqueous extract shifts the cardiac metabolism toward glucose utilization, thus making this plant a potential therapeutic medication in cardiac disorders with impaired metabolism.

Ketone Therapy for Heart Failure: Current Evidence for Clinical Use

During conditions that result in depleted circulating glucose levels, ketone bodies synthesized in the liver are necessary fuel substrates for the brain. In other organs such as the heart, the reliance on ketones for generating energy is less life threatening as the heart can utilize alternative fuel sources such as fatty acids. However, during pathophysiological conditions such as heart failure, cardiac defects in metabolic processes that normally allow for sufficient energy production from fatty acids and carbohydrates contribute to a decline in contractile function. As such, it has been proposed that the failing heart relies more on ketone bodies as an energy source than previously appreciated. Furthermore, it has been suggested that ketone bodies may function as signaling molecules that can suppress systemic and cardiac inflammation. Thus, it is possible that intentionally elevating circulating ketones may be beneficial as an adjunct treatment for heart failure. Although many approaches can be used for 'ketone therapy', each of these has their own advantages and disadvantages in the treatment of heart failure. Thus, we summarize current preclinical and clinical studies involving various types of ketone therapy in cardiac disease and discuss the advantages and disadvantages of each modality as possible treatments for heart failure.

Testosterone activates glucose metabolism through AMPK and androgen signaling in cardiomyocyte hypertrophy

Background

Testosterone regulates nutrient and energy balance to maintain protein synthesis and metabolism in cardiomyocytes, but supraphysiological concentrations induce cardiac hypertrophy. Previously, we determined that testosterone increased glucose uptake—via AMP-activated protein kinase (AMPK)—after acute treatment in cardiomyocytes. However, whether elevated glucose uptake is involved in long-term changes of glucose metabolism or is required during cardiomyocyte growth remained unknown. In this study, we hypothesized that glucose uptake and glycolysis increase in testosterone-treated cardiomyocytes through AMPK and androgen receptor (AR).

Methods

Cultured cardiomyocytes were stimulated with 100 nM testosterone for 24 h, and hypertrophy was verified by increased cell size and mRNA levels of β-myosin heavy chain (β-mhc). Glucose uptake was assessed by 2-NBDG. Glycolysis and glycolytic capacity were determined by measuring extracellular acidification rate (ECAR).

Results

Testosterone induced cardiomyocyte hypertrophy that was accompanied by increased glucose uptake, glycolysis enhancement and upregulated mRNA expression of hexokinase 2. In addition, testosterone increased AMPK phosphorylation (Thr172), while inhibition of both AMPK and AR blocked glycolysis and cardiomyocyte hypertrophy induced by testosterone. Moreover, testosterone supplementation in adult male rats by 5 weeks induced cardiac hypertrophy and upregulated β-mhc, Hk2 and Pfk2 mRNA levels.

Conclusion

These results indicate that testosterone stimulates glucose metabolism by activation of AMPK and AR signaling which are critical to induce cardiomyocyte hypertrophy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40659-021-00328-4.

Trimetazidine in Heart Failure

Heart failure is a systemic syndrome caused by multiple pathological factors. Current treatments do not have satisfactory outcomes. Several basic studies have revealed the protective effect of trimetazidine on the heart, not only by metabolism modulation but also by relieving myocardial apoptosis, fibrosis, autophagy, and inflammation. Clinical studies have consistently indicated that trimetazidine acts as an adjunct to conventional treatments and improves the symptoms of heart failure. This review summarizes the basic pathological changes in the myocardium, with an emphasis on the alteration of cardiac metabolism in the development of heart failure. The clinical application of trimetazidine in heart failure and the mechanism of its protective effects on the myocardium are carefully discussed, as well as its main adverse effects. The intention of this review is to highlight this treatment as an effective alternative against heart failure and provide additional perspectives for future studies.

Metabolomics coupled with integrated approaches reveal the therapeutic effects of higenamine combined with [6]-gingerol on doxorubicin-induced chronic heart failure in rats

Background

This study was aimed to investigate the therapeutic effects and potential mechanism of higenamine combined with [6]-gingerol (HG/[6]-GR) against doxorubicin (DOX)—induced chronic heart failure (CHF) in rats.

Materials and methods

Therapeutic effects of HG/[6]-GR on hemodynamics indices, serum biochemical indicators, histopathology and TUNEL staining of rats were assessed. Moreover, a UHPLC-Q-TOF/MS-based serum metabolic approach was performed to identify the metabolites and possible pathways of HG/[6]-GR on DOX-induced CHF.

Results

HG/[6]-GR had effects on regulating hemodynamic indices, alleviating serum biochemical indicators, improving the pathological characteristics of heart tissue and reducing the apoptosis of myocardial cells. Serum metabolisms analyses indicated that the therapeutic effects of HG and [6]-GR were mainly associated with the regulation of eight metabolites, including acetylphosphate, 3-Carboxy-1-hydroxypropylthiamine diphosphate, coenzyme A, palmitic acid, PE(O-18:1(1Z)/20:4(5Z,8Z,11Z,14Z)), oleic acid, lysoPC(18:1(9Z)), and PC(16:0/16:0). Pathway analysis showed that HG/[6]-GR on CHF treatment was related to twelve pathways, including glycerophospholipid metabolism, fatty acid metabolism, pantothenate and CoA biosynthesis, citrate cycle (TCA cycle), pyruvate metabolism, and arachidonic acid metabolism. Serum metabolites and metabolic pathways regulated by HG/[6]-GR appear to be related to energy metabolism.

Conclusion

Multivariate statistical analysis has provided new insights for understanding CHF and investigating the therapeutic effects and mechanisms of HG/[6]-GR, which influencing the metabolites and pathways related to energy metabolism pathway.

The evolving systemic biomarker milieu in obese ZSF1 rat model of human cardiometabolic syndrome: Characterization of the model and cardioprotective effect of GDF15

Cardiometabolic syndrome has become a global health issue. Heart failure is a common comorbidity of cardiometabolic syndrome. Successful drug development to prevent cardiometabolic syndrome and associated comorbidities requires preclinical models predictive of human conditions. To characterize the heart failure component of cardiometabolic syndrome, cardiometabolic, metabolic, and renal biomarkers were evaluated in lean and obese ZSF1 19- to 32-week-old male rats. Histopathological assessment of kidneys and hearts was performed. Cardiac function, exercise capacity, and left ventricular gene expression were also analyzed. Obese ZSF1 rats exhibited multiple features of human cardiometabolic syndrome by pathological changes in systemic renal, metabolic, and cardiovascular disease circulating biomarkers. Hemodynamic assessment, echocardiography, and decreased exercise capacity confirmed heart failure with preserved ejection fraction. RNA-seq results demonstrated changes in left ventricular gene expression associated with fatty acid and branched chain amino acid metabolism, cardiomyopathy, cardiac hypertrophy, and heart failure. Twelve weeks of growth differentiation factor 15 (GDF15) treatment significantly decreased body weight, food intake, blood glucose, and triglycerides and improved exercise capacity in obese ZSF1 males. Systemic cardiovascular injury markers were significantly lower in GDF15-treated obese ZSF1 rats. Obese ZSF1 male rats represent a preclinical model for human cardiometabolic syndrome with established heart failure with preserved ejection fraction. GDF15 treatment mediated dietary response and demonstrated a cardioprotective effect in obese ZSF1 rats.

Evolution of altered tubular metabolism and mitochondrial function in sepsis-associated acute kidney injury

Sepsis-associated acute kidney injury (s-AKI) has a staggering impact in patients and lacks any treatment. Incomplete understanding of the pathogenesis of s-AKI is a major barrier to the development of effective therapies. We address the gaps in knowledge regarding renal oxygenation, tubular metabolism, and mitochondrial function in the pathogenesis of s-AKI using the cecal ligation and puncture (CLP) model in mice. At 24 h after CLP, renal oxygen delivery was reduced; however, fractional oxygen extraction was unchanged, suggesting inefficient renal oxygen utilization despite decreased glomerular filtration rate and filtered load. To investigate the underlying mechanisms, we examined temporal changes in mitochondrial function and metabolism at 4 and 24 h after CLP. At 4 h after CLP, markers of mitochondrial content and biogenesis were increased in CLP kidneys, but mitochondrial oxygen consumption rates were suppressed in proximal tubules. Interestingly, at 24 h, proximal tubular mitochondria displayed high respiratory capacity, but with decreased mitochondrial content, biogenesis, fusion, and ATP levels in CLP kidneys, suggesting decreased ATP synthesis efficiency. We further investigated metabolic reprogramming after CLP and observed reduced expression of fatty acid oxidation enzymes but increased expression of glycolytic enzymes at 24 h. However, assessment of functional glycolysis revealed lower glycolytic capacity, glycolytic reserve, and compensatory glycolysis in CLP proximal tubules, which may explain their susceptibility to injury. In conclusion, we demonstrated significant alterations in renal oxygenation, tubular mitochondrial function, and metabolic reprogramming in s-AKI, which may play an important role in the progression of injury and recovery from AKI in sepsis.

Snail augments fatty acid oxidation by suppression of mitochondrial ACC2 during cancer progression

This study reports a mechanism of mitochondrial ATP generation whereby EMT-inducer Snail controls ACC2 abundance and subsequent fatty acid oxidation to support cancer survival under starvation conditions.

Despite the importance of mitochondrial fatty acid oxidation (FAO) in cancer metabolism, the biological mechanisms responsible for the FAO in cancer and therapeutic intervention based on catabolic metabolism are not well defined. In this study, we observe that Snail (SNAI1), a key transcriptional repressor of epithelial–mesenchymal transition, enhances catabolic FAO, allowing pro-survival of breast cancer cells in a starved environment. Mechanistically, Snail suppresses mitochondrial ACC2 (ACACB) by binding to a series of E-boxes located in its proximal promoter, resulting in decreased malonyl-CoA level. Malonyl-CoA being a well-known endogenous inhibitor of fatty acid transporter carnitine palmitoyltransferase 1 (CPT1), the suppression of ACC2 by Snail activates CPT1-dependent FAO, generating ATP and decreasing NADPH consumption. Importantly, combinatorial pharmacologic inhibition of pentose phosphate pathway and FAO with clinically available drugs efficiently reverts Snail-mediated metabolic reprogramming and suppresses in vivo metastatic progression of breast cancer cells. Our observations provide not only a mechanistic link between epithelial–mesenchymal transition and catabolic rewiring but also a novel catabolism-based therapeutic approach for inhibition of cancer progression.

A procedure to extract functional isolated mitochondria from small-sized human atrial samples. Application to obesity with a partial characterisation of the organelles

Evaluating the activity of cardiac mitochondria is probably the best way to estimate early cellular damage in chronic pathology. Early diagnosis allows rapid therapeutic intervention thus increasing patient survival rate in a number of diseases. However, data on human cardiac mitochondria are scarce in the international literature. Here, we describe a method to extract and study functional mitochondria from the small-sized right atrial aliquots (minimum of 400 mg) obtained during extracorporeal circulation and usually considered as surgical waste products. The mitochondria were purified through several mechanical processes (fine myocardial cutting, tissue grinding and potter Elvehjem homogenising), an enzymatic proteolytic action (subtilisin) and differential centrifugations. In chronic pathologies, including obesity, early disturbances of mitochondrial function can occur. The effects of obesity on the rate of mitochondrial oxygen consumption and H₂O₂ release were thus determined with three different substrates (glutamate/malate, succinate/rotenone and palmitoylcarnitine/malate). The human atrial mitochondria were of high quality from a functional viewpoint, compared to rat ventricle organelles, but the extraction yield of the human mitochondria was twice lower than that of rat mitochondria. Tests showed that glutamate/malate-related ADP-stimulated respiration was strongly increased in obese subjects, although the oxidation of the other two substrates was unaffected. Reactive oxygen species (ROS) production by the isolated mitochondria was low in comparison with that of the lean subjects. These results confirm those found in one of our previous studies in the ventricles of rats fed a high-fat diet. In conclusion, the described method is simple, reliable and sensitive. It allows for the description of the impact of obesity on the function of atrial mitochondria while using only a small patient sampling (n = 5 in both the lean and the obese groups).

FOXO1 contributes to diabetic cardiomyopathy via inducing imbalanced oxidative metabolism in type 1 diabetes

Forkhead box protein O1 (FOXO1), a nuclear transcription factor, is preferably activated in the myocardium of diabetic mice. However, its role and mechanism in the development of diabetic cardiomyopathy in non-obese insulin-deficient diabetes are unclear. We hypothesized that cardiac FOXO1 over-activation was attributable to the imbalanced myocardial oxidative metabolism and mitochondrial and cardiac dysfunction in type 1 diabetes. FOXO1-selective inhibitor AS1842856 was administered to streptozotocin-induced diabetic (D) rats, and cardiac functions, mitochondrial enzymes PDK4 and CPT1 and mitochondrial function were assessed. Primary cardiomyocytes isolated from non-diabetic control (C) and D rats were treated with or without 1 µM AS1842856 and underwent Seahorse experiment to determine the effects of glucose, palmitate and pyruvate on cardiomyocyte bioenergetics. The results showed diabetic hearts displayed elevated FOXO1 nuclear translocation, concomitant with cardiac and mitochondrial dysfunction (manifested as elevated mtROS level and reduced mitochondrial membrane potential) and increased cell apoptosis (all P < .05, D vs C). Diabetic myocardium showed impaired glycolysis, glucose oxidation and elevated fatty acid oxidation and enhanced PDK4 and CPT1 expression. AS1842856 attenuated or prevented all these changes except for glycolysis. We concluded that FOXO1 activation, through stimulating PDK4 and CPT1, shifts substrate selection from glucose to fatty acid and causes mitochondrial and cardiac dysfunction.

Metabolic remodeling of substrate utilization during heart failure progression

Heart failure (HF) is a clinical syndrome caused by a decline in cardiac systolic or diastolic function, which leaves the heart unable to pump enough blood to meet the normal physiological requirements of the human body. It is a serious disease burden worldwide affecting nearly 23 million patients. The concept that heart failure is "an engine out of fuel" has been generally accepted and metabolic remodeling has been recognized as an important aspect of this condition; it is characterized by defects in energy production and changes in metabolic pathways involved in the regulation of essential cellular functions such as the process of substrate utilization, the tricarboxylic acid cycle, oxidative phosphorylation, and high-energy phosphate metabolism. Advances in second-generation sequencing, proteomics, and metabolomics have made it possible to perform comprehensive tests on genes and metabolites that are crucial in the process of HF, thereby providing a clearer and comprehensive understanding of metabolic remodeling during HF. In recent years, new metabolic changes such as ketone bodies and branched-chain amino acids were demonstrated as alternative substrates in end-stage HF. This systematic review focuses on changes in metabolic substrate utilization during the progression of HF and the underlying regulatory mechanisms. Accordingly, the conventional concepts of metabolic remodeling characteristics are reviewed, and the latest developments, particularly multi-omics studies, are compiled.

Danqi Pill Protects Against Heart Failure Post-Acute Myocardial Infarction via HIF-1α/PGC-1α Mediated Glucose Metabolism Pathway

AIM

Heart failure (HF) post-acute myocardial infarction (AMI) leads to a large number of hospitalizations and deaths worldwide. Danqi pill (DQP) is included in the 2015 national pharmacopoeia and widely applied in the treatment of HF in clinics in China. We examined whether DQP acted on glucose metabolism to protect against HF post-AMI via hypoxia inducible factor-1 alpha (HIF-1α)/peroxisome proliferator-activated receptor α co-activator (PGC-1α) pathway.

METHODS AND RESULTS

In this study, left anterior descending (LAD) artery ligation induced HF post-AMI rats and oxygen-glucose deprivation-reperfusion (OGD/R)-induced H9C2 cell model were structured to explore the efficacy and mechanism of DQP. Here we showed that DQP protected the heart against ischemic damage as evidenced by improved cardiac functions and attenuated inflammatory infiltration. The expressions of critical proteins involved in glucose intake and transportation such as GLUT4 and PKM2 were up-regulated, while negative regulatory proteins involved in oxidative phosphorylation were attenuated in the treatment of DQP. Moreover, DQP up-regulated NRF1 and TFAM, promoted mitochondrial biogenesis and increased myocardial adenosine triphosphate (ATP) level. The protection effects of DQP were significantly compromised by HIF-1α siRNA, suggesting that HIF-1α signaling pathway was the potential target of DQP on HF post-AMI.

CONCLUSIONS

DQP exhibits the efficacy to improve myocardial glucose metabolism, mitochondrial oxidative phosphorylation and biogenesis by regulating HIF-1α/PGC-1α signaling pathway in HF post-AMI rats.

Titin truncations lead to impaired cardiomyocyte autophagy and mitochondrial function in vivo

Titin-truncating variants (TTNtv) are the most common genetic cause of dilated cardiomyopathy. TTNtv occur in ~1% of the general population and causes subclinical cardiac remodeling in asymptomatic carriers. In rat models with either proximal or distal TTNtv, we previously showed altered cardiac metabolism at baseline and impaired cardiac function in response to stress. However, the molecular mechanism(s) underlying these effects remains unknown. In the current study, we used rat models of TTNtv to investigate the effect of TTNtv on autophagy and mitochondrial function, which are essential for maintaining cellular metabolic homeostasis and cardiac function. In both the proximal and distal TTNtv rat models, we found increased levels of LC3B-II and p62 proteins, indicative of diminished autophagic degradation. The accumulation of autophagosomes and p62 protein in cardiomyocytes was also demonstrated by electron microscopy and immunochemistry, respectively. Impaired autophagy in the TTNtv heart was associated with increased phosphorylation of mTOR and decreased protein levels of the lysosomal protease, cathepsin B. In addition, TTNtv hearts showed mitochondrial dysfunction, as evidenced by decreased oxygen consumption rate in cardiomyocytes, increased levels of reactive oxygen species and mitochondrial protein ubiquitination. We also observed increased acetylation of mitochondrial proteins associated with decreased NAD+/NADH ratio in the TTNtv hearts. mTORC1 inhibitor, rapamycin, was able to rescue the impaired autophagy in TTNtv hearts. In summary, TTNtv leads to impaired autophagy and mitochondrial function in the heart. These changes not only provide molecular mechanisms that underlie TTNtv-associated ventricular remodeling but also offer potential targets for its intervention.

Dichloroacetate Ameliorates Cardiac Dysfunction Caused by Ischemic Insults Through AMPK Signal Pathway-Not Only Shifts Metabolism

Dichloroacetate (DCA), an inhibitor of pyruvate dehydrogenase kinase (PDK), regulates substrate metabolism in the heart. AMP-activated protein kinase (AMPK) is an age-related energy sensor that protects the heart from ischemic injury. This study aims to investigate whether DCA can protect the heart from ischemic injury through the AMPK signaling pathway. Young (3-4 months) and aged (20-24 months) male C57BL/6J mice were subjected to ligation of the left anterior descending coronary artery (LAD) for an in vivo ischemic model. The systolic function of the hearts was significantly decreased in both young and aged mice after 45 min of ischemia and 24 h of reperfusion. DCA treatment significantly improved cardiac function in both young and aged mice. The myocardial infarction analysis demonstrated that DCA treatment significantly reduced the infarction size caused by ischemia/reperfusion (I/R) in both young and aged mice. The isolated-cardiomyocyte experiments showed that DCA treatment ameliorated contractile dysfunction and improved the intracellular calcium signal of cardiomyocytes under hypoxia/reoxygenation (H/R) conditions. These cardioprotective functions of DCA can be attenuated by inhibiting AMPK activation. Furthermore, the metabolic measurements with an ex vivo working heart system demonstrated that the effects of DCA treatment on modulating the metabolic shift response to ischemia and reperfusion stress can be attenuated by inhibiting AMPK activity. The immunoblotting results showed that DCA treatment triggered cardiac AMPK signaling pathway by increasing the phosphorylation of AMPK's upstream kinase liver kinase B1 (LKB1) under both sham operations and I/R conditions. Thus, except from modulating metabolism in hearts, the cardioprotective function of DCA during I/R was mediated by the LKB1-AMPK pathway.

Mitochondrial function in the heart: the insight into mechanisms and therapeutic potentials

Mitochondrial dysfunction is considered as a crucial contributory factor in cardiac pathology. This has highlighted the therapeutic potential of targeting mitochondria to prevent or treat cardiac disease. Mitochondrial dysfunction is associated with aberrant electron transport chain activity, reduced ATP production, an abnormal shift in metabolic substrates, ROS overproduction and impaired mitochondrial dynamics. This review will cover the mitochondrial functions and how they are altered in various disease conditions. Furthermore, the mechanisms that lead to mitochondrial defects and the protective mechanisms that prevent mitochondrial damage will be discussed. Finally, potential mitochondrial targets for novel therapeutic intervention will be explored. We will highlight the development of small molecules that target mitochondria from different perspectives and their current progress in clinical trials. LINKED ARTICLES: This article is part of a themed section on Mitochondrial Pharmacology: Featured Mechanisms and Approaches for Therapy Translation. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.22/issuetoc.

Metabolomic Perspectives in Antiblastic Cardiotoxicity and Cardioprotection

Despite advances in supportive and protective therapy for myocardial function, cardiovascular diseases due to antineoplastic therapy-primarily cardiomyopathy associated with contractile dysfunction-remain a major cause of morbidity and mortality. Because of the limitations associated with current therapies, investigators are searching for alternative strategies that can timely recognise cardiovascular damage-thus permitting a quick therapeutic approach-or prevent the development of the disease. Damage to the heart can result from both traditional chemotherapeutic agents, such as anthracyclines, and new targeted therapies, such as tyrosine kinase inhibitors. In recent years, metabolomics has proved to be a practical tool to highlight fundamental changes in the metabolic state in several pathological conditions. In this article, we present the state-of-the-art technology with regard to the metabolic mechanisms underlying cardiotoxicity and cardioprotection.

Low-Intensity Running and High-Intensity Swimming Exercises Differentially Improve Energy Metabolism in Mice With Mild Spinal Muscular Atrophy

Spinal Muscular Atrophy (SMA), an autosomal recessive neurodegenerative disease characterized by the loss of spinal-cord motor-neurons, is caused by mutations on Survival-of-Motor Neuron (SMN)-1 gene. The expression of SMN2, a SMN1 gene copy, partially compensates for SMN1 disruption due to exon-7 excision in 90% of transcripts subsequently explaining the strong clinical heterogeneity. Several alterations in energy metabolism, like glucose intolerance and hyperlipidemia, have been reported in SMA at both systemic and cellular level, prompting questions about the potential role of energy homeostasis and/or production involvement in disease progression. In this context, we have recently reported the tolerance of mild SMA-like mice (Smn^Δ7/Δ7; huSMN2^+/+) to 10 months of low-intensity running or high-intensity swimming exercise programs, respectively involving aerobic and a mix aerobic/anaerobic muscular metabolic pathways. Here, we investigated whether those exercise-induced benefits were associated with an improvement in metabolic status in mild SMA-like mice. We showed that untrained SMA-like mice exhibited a dysregulation of lipid metabolism with an enhancement of lipogenesis and adipocyte deposits when compared to control mice. Moreover, they displayed a high oxygen consumption and energy expenditure through β-oxidation increase yet for the same levels of spontaneous activity. Interestingly, both exercises significantly improved lipid metabolism and glucose homeostasis in SMA-like mice, and enhanced oxygen consumption efficiency with the maintenance of a high oxygen consumption for higher levels of spontaneous activity. Surprisingly, more significant effects were obtained with the high-intensity swimming protocol with the maintenance of high lipid oxidation. Finally, when combining electron microscopy, respiratory chain complexes expression and enzymatic activity measurements in muscle mitochondria, we found that (1) a muscle-specific decreased in enzymatic activity of respiratory chain I, II, and IV complexes for equal amount of mitochondria and complexes expression and (2) a significant decline in mitochondrial maximal oxygen consumption, were reduced by both exercise programs. Most of the beneficial effects were obtained with the high-intensity swimming protocol. Taking together, our data support the hypothesis that active physical exercise, including high-intensity protocols, induces metabolic adaptations at both systemic and cellular levels, providing further evidence for its use in association with SMN-overexpressing therapies, in the long-term care of SMA patients.

Chronic Pressure Overload Results in Deficiency of Mitochondrial Membrane Transporter ABCB7 Which Contributes to Iron Overload, Mitochondrial Dysfunction, Metabolic Shift and Worsens Cardiac Function

We examined the hitherto unexplored role of mitochondrial transporters and iron metabolism in advancing metabolic and mitochondrial dysfunction in the heart during long term pressure overload. We also investigated the link between mitochondrial dysfunction and fluctuation in mitochondrial transporters associated with pressure overload cardiac hypertrophy. Left ventricular hypertrophy (LVH) was induced in 3-month-old male Wistar rats by constriction of the aorta using titanium clips. After sacrifice at the end of 6 and 15 months after constriction, tissues from the left ventricle (LV) from all animals were collected for histology, biochemical studies, proteomic and metabolic profiling, and gene and protein expression studies. LV tissues from rats with LVH had a significant decrease in the expression of ABCB7 and mitochondrial oxidative phosphorylation (mt-OXPHOS) enzymes, an increased level of lipid metabolites, decrease in the level of intermediate metabolites of pentose phosphate pathway and elevated levels of cytoplasmic and mitochondrial iron, reactive oxygen species (ROS) and autophagy-related proteins. Knockdown of ABCB7 in H9C2 cells and stimulation with angiotensin II resulted in increased ROS levels, ferritin, and transferrin receptor expression and iron overload in both mitochondria and cytoplasm. A decrease in mRNA and protein levels of mt-OXPHOS specific enzymes, mt-dynamics and autophagy clearance and activation of IGF-1 signaling were also seen in these cells. ABCB7 overexpression rescued all these changes. ABCB7 was found to interact with mitochondrial complexes IV and V. We conclude that in chronic pressure overload, ABCB7 deficiency results in iron overload and mitochondrial dysfunction, contributing to heart failure.

p53 prevents doxorubicin cardiotoxicity independently of its prototypical tumor suppressor activities

Doxorubicin is a widely used chemotherapeutic agent that causes dose-dependent cardiotoxicity in a subset of treated patients, but the genetic determinants of this susceptibility are poorly understood. Here, we report that a noncanonical tumor suppressor activity of p53 prevents cardiac dysfunction in a mouse model induced by doxorubicin administered in divided low doses as in the clinics. While relatively preserved in wild-type (p53 ^+/+ ) state, mice deficient in p53 (p53 ^-/- ) developed left ventricular (LV) systolic dysfunction after doxorubicin treatment. This functional decline in p53 ^-/- mice was associated with decreases in cardiac oxidative metabolism, mitochondrial mass, and mitochondrial genomic DNA (mtDNA) homeostasis. Notably, mice with homozygous knockin of the p53 R172H (p53 ^172H/H ) mutation, which like p53 ^-/- state lacks the prototypical tumor suppressor activities of p53 such as apoptosis but retains its mitochondrial biogenesis capacity, showed preservation of LV function and mitochondria after doxorubicin treatment. In contrast to p53-null state, wild-type and mutant p53 displayed distinct mechanisms of transactivating mitochondrial transcription factor A (TFAM) and p53-inducible ribonucleotide reductase 2 (p53R2), which are involved in mtDNA transcription and maintenance. Importantly, supplementing mice with a precursor of NAD⁺ prevented the mtDNA depletion and cardiac dysfunction. These findings suggest that loss of mtDNA contributes to cardiomyopathy pathogenesis induced by doxorubicin administered on a schedule simulating that in the clinics. Given a similar mtDNA protection role of p53 in doxorubicin-treated human induced pluripotent stem cell (iPSC)-derived cardiomyocytes, the mitochondrial markers associated with cardiomyopathy development observed in blood and skeletal muscle cells may have prognostic utility.

Antioxidant and Cardioprotective Effects of EPA on Early Low-Severity Sepsis through UCP3 and SIRT3 Upholding of the Mitochondrial Redox Potential

Sepsis still causes death, often through cardiac failure and mitochondrial dysfunction. Dietary ω3 polyunsaturated fatty acids are known to protect against cardiac dysfunction and sepsis lethality. This study set out to determine whether early low-severity sepsis alters the cardiac mitochondrial function in animals fed a Western-type diet and whether dietary eicosapentaenoic acid (EPA) administration protects the myocardium against the deleterious effects of sepsis and if so to seek possible mechanisms for its effects. Rats were divided into two groups fed either an ω3 PUFA-deficient diet (“Western diet,” DEF group) or an EPA-enriched diet (EPA group) for 5 weeks. Each group was subdivided into two subgroups: sham-operated rats and rats subjected to cecal ligation and puncture (CLP). In vivo cardiac mechanical function was examined, and mitochondria were harvested to determine their functional activity. Oxidative stress was evaluated together with several factors involved in the regulation of reactive oxygen species metabolism. Sepsis had little effect on cardiac mechanical function but strongly depressed mitochondrial function in the DEF group. Conversely, dietary EPA greatly protected the mitochondria through a decreased oxidative stress of the mitochondrial matrix. The latter was probably due to an increased uncoupling protein-3 expression, already seen in the sham-operated animals. CLP rats in the EPA group also displayed increased mitochondrial sirtuin-3 protein expression that could reinforce the upholding of oxidative phosphorylation. Dietary EPA preconditioned the heart against septic damage through several modifications that protect mitochondrial integrity. This preconditioning can explain the cardioprotective effect of dietary EPA during sepsis.

Forms of extracellular mitochondria and their impact in health

Mitochondria play an important role as an intracellular energy plant and signaling organelle. However, mitochondria also exist outside cells where they could mediate cell-to-cell communication, repair and serve as an activator of the immune response. Their effects depend on the mitochondrial state or the form in which it is present, either as a whole functional structure as fragments or only as mitochondrial DNA. Herein, we provide evidence of why extracellular mitochondria and their varying forms are considered regenerative factors or pro-inflammatory activators. Understanding these aspects will provide the base of their use in therapy or as a biomarker of disease severity and prognosis.

Tortuous Paths of Insulin Signaling and Mitochondria in Alzheimer's Disease

Due to the exponential growth of aging population worldwide, neurodegenerative diseases became a major public health concern. Among them, Alzheimer's disease (AD) prevails as the most common in the elderly, rendering it a research priority. After several decades considering the brain as an insulin-insensitive organ, recent advances proved a central role for this hormone in learning and memory processes and showed that AD shares a high number of features with systemic conditions characterized by insulin resistance. Mitochondrial dysfunction has also been widely demonstrated to play a major role in AD development supporting the idea that this neurodegenerative disease is characterized by a pronounced metabolic dysregulation. This chapter is intended to discuss evidence demonstrating the key role of insulin signaling and mitochondrial anomalies in AD.

Lysosomes Mediate Benefits of Intermittent Fasting in Cardiometabolic Disease: The Janitor Is the Undercover Boss

Adaptive responses that counter starvation have evolved over millennia to permit organismal survival, including changes at the level of individual organelles, cells, tissues, and organ systems. In the past century, a shift has occurred away from disease caused by insufficient nutrient supply toward overnutrition, leading to obesity and diabetes, atherosclerosis, and cardiometabolic disease. The burden of these diseases has spurred interest in fasting strategies that harness physiological responses to starvation, thus limiting tissue injury during metabolic stress. Insights gained from animal and human studies suggest that intermittent fasting and chronic caloric restriction extend lifespan, decrease risk factors for cardiometabolic and inflammatory disease, limit tissue injury during myocardial stress, and activate a cardioprotective metabolic program. Acute fasting activates autophagy, an intricately orchestrated lysosomal degradative process that sequesters cellular constituents for degradation, and is critical for cardiac homeostasis during fasting. Lysosomes are dynamic cellular organelles that function as incinerators to permit autophagy, as well as degradation of extracellular material internalized by endocytosis, macropinocytosis, and phagocytosis. The last decade has witnessed an explosion of knowledge that has shaped our understanding of lysosomes as central regulators of cellular metabolism and the fasting response. Intriguingly, lysosomes also store nutrients for release during starvation; and function as a nutrient sensing organelle to couple activation of mammalian target of rapamycin to nutrient availability. This article reviews the evidence for how the lysosome, in the guise of a janitor, may be the "undercover boss" directing cellular processes for beneficial effects of intermittent fasting and restoring homeostasis during feast and famine. © 2018 American Physiological Society. Compr Physiol 8:1639-1667, 2018.