Alterations In Myocardial Metabolism Research Articles

Pathological Changes and Metabolic Adaptation in the Myocardium of Rats in Response to Chronic Variable Mild Stress.

Chronic variable mild stress (CVS) in rats is a well-established paradigm for inducing depressive-like behaviors and has been utilized extensively to explore potential therapeutic interventions for depression. While the behavioral and neurobiological effects of CVS have been extensively studied, its impact on myocardial function remains largely unexplored. To induce the CVS model, rats were exposed to various stressors over 40 days. Behavioral assessments confirmed depressive-like behavior. Biochemical analyses revealed alterations in myocardial metabolism, including changes in NAD+ and NADP+, and NADPH concentrations. Free amino acid analysis indicated disturbances in myocardial amino acid metabolism. Evaluation of oxidative DNA damage demonstrated an increased number of abasic sites in the DNA of rats exposed to CVS. Molecular analysis showed significant changes in gene expression associated with glucose metabolism, oxidative stress, and cardiac remodeling pathways. Histological staining revealed minor morphological changes in the myocardium of CVS-exposed rats, including increased acidophilicity of cells, collagen deposition surrounding blood vessels, and glycogen accumulation. This study provides novel insights into the impact of chronic stress on myocardial function and metabolism, highlighting potential mechanisms linking depression and cardiovascular diseases. Understanding these mechanisms may aid in the development of targeted therapeutic strategies to mitigate the adverse cardiovascular effects of depression.

Molecular mechanisms of metabolic dysregulation in diabetic cardiomyopathy.

Diabetic cardiomyopathy (DCM), one of the most serious complications of diabetes mellitus, has become recognized as a cardiometabolic disease. In normoxic conditions, the majority of the ATP production (>95%) required for heart beating comes from mitochondrial oxidative phosphorylation of fatty acids (FAs) and glucose, with the remaining portion coming from a variety of sources, including fructose, lactate, ketone bodies (KB) and branched chain amino acids (BCAA). Increased FA intake and decreased utilization of glucose and lactic acid were observed in the diabetic hearts of animal models and diabetic patients. Moreover, the polyol pathway is activated, and fructose metabolism is enhanced. The use of ketones as energy sources in human diabetic hearts also increases significantly. Furthermore, elevated BCAA levels and impaired BCAA metabolism were observed in the hearts of diabetic mice and patients. The shift in energy substrate preference in diabetic hearts results in increased oxygen consumption and impaired oxidative phosphorylation, leading to diabetic cardiomyopathy. However, the precise mechanisms by which impaired myocardial metabolic alterations result in diabetes mellitus cardiac disease are not fully understood. Therefore, this review focuses on the molecular mechanisms involved in alterations of myocardial energy metabolism. It not only adds more molecular targets for the diagnosis and treatment, but also provides an experimental foundation for screening novel therapeutic agents for diabetic cardiomyopathy.

Redefining Diabetic Cardiomyopathy: Perturbations in Substrate Metabolism at the Heart of Its Pathology.

Cardiovascular disease represents the leading cause of death in people with diabetes, most notably from macrovascular diseases such as myocardial infarction or heart failure. Diabetes also increases the risk of a specific form of cardiomyopathy referred to as diabetic cardiomyopathy (DbCM), originally defined as ventricular dysfunction in the absence of underlying coronary artery disease and/or hypertension. Herein, we provide an overview on the key mediators of DbCM, with an emphasis on the role for perturbations in cardiac substrate metabolism. We discuss key mechanisms regulating metabolic dysfunction in DbCM, with additional focus on the role of metabolites as signalling molecules within the diabetic heart. Furthermore, we discuss the preclinical approaches to target these perturbations to alleviate DbCM. With several advancements in our understanding, we propose "diastolic dysfunction in the presence of altered myocardial metabolism in a person with diabetes, but absence of other known causes of cardiomyopathy and/or hypertension", as a new definition for, or approach to classify, DbCM. However, we recognize that no definition can fully explain the complexity of why some individuals with DbCM exhibit diastolic dysfunction, whereas others develop systolic dysfunction. Due to DbCM sharing pathological features with heart failure with preserved ejection fraction (HFpEF), the latter of which is more prevalent in the diabetic population, it is imperative to determine whether effective management of DbCM decreases HFpEF prevalence.

Effect of a specially formulated diet on progression of heart enlargement in dogs with subclinical degenerative mitral valve disease.

Previous studies in dogs with degenerative mitral valve disease (DMVD) have identified altered myocardial energy metabolism and oxidation, which might contribute to cardiac hypertrophy. Diets rich in medium chain fatty acids and antioxidants are a potential means of treatment. A previous clinical study found significantly smaller left atrial diameter (LAD) and left atrium-to-aorta diameter ratio (LA : Ao) in dogs with subclinical DMVD fed a specially formulated diet vs control diet for 6 months. A specially formulated diet will slow or arrest left heart enlargement in dogs with subclinical DMVD over 365 days. One hundred twenty-seven dogs with unmedicated subclinical DMVD; 101 dogs in the per protocol cohort. Randomized double-blinded controlled multicenter clinical trial. The study's primary composite outcome measure was the sum of percentage change in LAD and left ventricular internal dimension at end-diastole (LVIDd) at day 365. In the per protocol cohort, the outcome measure increased by 8.0% (95% confidence interval [CI], 2.9%-13.1%) in dogs receiving the test diet vs 8.8% (95% CI, 5.1%-12.5%) in dogs receiving control diet (P = .79). Neither component of the primary outcome measure was significantly different between groups (LAD, P = .65; LVIDd, P = .92). No difference was found in mitral valve E wave velocity (P = .36) or the proportion of dogs withdrawn from the study because of worsening DMVD and heart enlargement (P = .41). Feeding a specially formulated diet for 365 days was not associated with a significantly different rate of change of left heart size in dogs with subclinical DMVD as compared to control.

Transmission Electron Microscopic (TEM) analysis of STZ-diabetes induced Cardiac Structural changes in Rats.

Diabetes mellitus (DM) is a global health crisis, imposing a substantial burden on both healthcare systems and individuals due to its chronic nature and associated complications. Among these complications, cardiovascular diseases rank as the primary cause of morbidity and mortality in people with diabetes. Diabetic cardiomyopathy (DCM), a distinctive form of heart disease, is characterized by structural and functional abnormalities within the heart, independent of conventional cardiovascular risk factors. The multifaceted pathophysiology of DCM involves factors like hyperglycemia-induced oxidative stress, inflammation, altered myocardial metabolism, and fibrosis, collectively leading to cardiac tissue structural changes and impaired function. Streptozotocin (STZ), a compound derived from Streptomyces achromogenes, is commonly used to induce diabetes in animal models, particularly rodents, making it a valuable tool for simulating diabetes in laboratory settings. Transmission Electron Microscopy (TEM) provides a powerful means to investigate ultrastructural changes within cardiac tissues at the microscopic level, encompassing myofibrillar structure, mitochondrial integrity, sarcoplasmic reticulum, and interstitial components. Figure-1 illustrates the pathological changes caused by STZ-induced diabetes in experimental animals, showing structural alterations in cardiac and brain tissues. Notably, the use of a polyherbal extract containing Curcuma amada rhizome and Sida spinosa leaves appears to mitigate some of the detrimental effects of STZ-induced diabetes on cardiac cells, suggesting potential protective benefits.

CPAL, as a New Mediator of Cardiomyocyte Metabolic Alterations and Pyroptosis, Regulates Myocardial Infarction Injury in Mice

Myocardial infarction (MI), the most serious of the ischemic heart diseases, is accompanied by myocardial metabolic disorders and the loss of cardiomyocytes. Increasing evidence has shown that Long noncoding RNAs (lncRNAs) are involved in various pathological conditions such as cancer and cardiovascular diseases (CVDs), and are emerging as a novel biomarker for these disorders. This study aims to investigate the regulatory role and mechanisms of lncRNAs in myocardial remodeling in the setting of MI. We find that post-infarcted hearts exhibit a reduction of adenosine triphosphate (ATP) and an alteration of the glucose and lipid metabolism genes Cluster of differentiation 36 (CD36) , Hexokinase ( HK ), and Glucose transporter 4 (GLUT 4), accompanied by cardiomyocyte pyroptosis. We then identify a previously unknown conserved lncRNA, AK009126 (cardiomyocyte pyroptosis-associated lncRNA, CPAL), which is remarkably upregulated in the myocardial border zone of MI mice. Importantly, the Adeno-associated virus 9 (AAV9)-mediated silencing of endogenous CPAL by its short hairpin RNA (shRNA) partially abrogates myocardial metabolic alterations and cardiomyocyte pyroptosis during MI in mice. Mechanistically, CPAL is shown to bind directly to nuclear factor kappa B (NFκB) and to act as an activator of NFκB to induce NFκB phosphorylation in cardiomyocytes. We also find that CPAL upregulates caspase-1 expression at the transcriptional level and consequently promotes the release of interleukin (IL)-18 and IL-1β from cardiomyocytes. Collectively, our findings reveal the conserved lncRNA CPAL as a new regulator of cardiac metabolic abnormalities and cardiomyocyte pyroptosis in the setting of MI and suggest CPAL as a new therapeutic target to protect cardiomyocytes against ischemic injury in infarcted hearts.

Abstract 12182: Cardiac Transcriptome Remodeling and Impaired Bioenergetics in Single Ventricle Congenital Heart Disease

Introduction: Single Ventricle congenital heart disease (SV) encompasses a group of cardiac abnormalities where improper development of the heart results in only one functional pumping chamber. From a molecular standpoint, how the myocardium adapts to the chronic altered hemodynamic conditions of SV physiology, and the mechanisms implicated in the transition to heart failure (HF) which is common in the SV population, are poorly understood. Here, we test the hypothesis that metabolic remodeling represents a pathophysiologic mechanism of heart failure progression in SV. Methods: We performed comprehensive multi-omics analysis (transcriptomics, metabolomics, and lipidomics) of the SV myocardium from both failing (SVHF, N=15) and non-failing (SVNF, N=9) SV subjects, compared with biventricular non-failing controls (BVNF, N=4). Furthermore, we assessed functional components of mitochondrial bioenergetics in each of these populations. Results: Integrated multi-omics analysis demonstrated dysregulation of multiple metabolic pathways in the failing SV heart (A). Functional cardiac bioenergetics analysis revealed decreased mitochondrial carnitine palmitoyl transferase activity (B) and mitochondrial dysfunction (C), with corresponding decreases in tricarboxylic acid cycle metabolites, high energy phosphates, and lipid intermediates in the failing SV heart. Moreover, some of these bioenergetic perturbations precede the onset of overt failure, and are seen in the non-failing SV heart (B-C). Conclusions: Our findings indicate that SV physiology induces myocardial metabolic alterations that limit mitochondrial fatty acid β-oxidation and decrease cardiac energy generation. Together, these data suggest SV patients may be uniquely vulnerable to changes in energetic demand and may benefit from therapeutic strategies aimed at preserving cardiac bioenergetics and preventing cardiometabolic remodeling for the treatment or prevention of HF.

Multi-modality cardiac imaging in the management of diabetic heart disease.

Diabetic heart disease is a major healthcare problem. Patients with diabetes show an excess of death from cardiovascular causes, twice as high as the general population and those with diabetes type 1 and longer duration of the disease present with more severe cardiovascular complications. Premature coronary artery disease and heart failure are leading causes of morbidity and reduced life expectancy. Multimodality cardiac imaging, including echocardiography, cardiac computed tomography, nuclear medicine, and cardiac magnetic resonance play crucial role in the diagnosis and management of different pathologies included in the definition of diabetic heart disease. In this review we summarise the utility of multi-modality cardiac imaging in characterising ischaemic and non-ischaemic causes of diabetic heart disease and give an overview of the current clinical practice. We also describe emerging imaging techniques enabling early detection of coronary artery inflammation and the non-invasive characterisation of the atherosclerotic plaque disease. Furthermore, we discuss the role of MRI-derived techniques in studying altered myocardial metabolism linking diabetes with the development of diabetic cardiomyopathy. Finally, we discuss recent data regarding the use of artificial intelligence applied to large imaging databases and how those efforts can be utilised in the future in screening of patients with diabetes for early signs of disease.

Abstract P3049: Age-independent Cardiac Protection By Pharmacological Activation Of Beclin-1 During Endotoxemia And Its Association With Energy Metabolic Reprogramming In Myocardium-A Targeted Metabolomics Study

Background: We previously showed that Beclin-1-dependent autophagy is cardiac protective in a rodent model of endotoxemia using young adult mice. In this report, we compared the potential therapeutic effects of pharmacological Beclin-1 activating peptide, TB-peptide, on the cardiac outcomes of young adult and aged mice during endotoxemia. We further examined alterations in myocardial metabolism induced by lipopolysaccharide (LPS) challenge with and without the TB-peptide treatment. Methods: C57BL/6J mice of 10-week and 24-month-old were challenged by LPS at doses at which cardiac dysfunction occurred. Following the treatment of TB-peptide or control vehicle, heart contractility, circulating cytokines, and myocardial autophagy were evaluated. A targeted metabolomics assay was applied to analyze cardiac metabolism. Results: TB-peptide boosted autophagic response, attenuated cytokine production, and improved cardiac performance in both young and aged mice during endotoxemia. A targeted metabolomics assay was designed to detect a pool of 361 known metabolites, of which 156 were detected in at least one of the heart tissue samples. LPS-induced impairments were found in glucose and amino acid (AA) metabolisms in mice of all ages, and TB-peptide provided ameliorative effects to rescue these alterations. However, lipid metabolites were upregulated in the young group but moderately downregulated in the aged by LPS, suggesting an age-dependent response. TB-peptide mitigated LPS-mediated trend of lipids in the young mice but provided little effect on the aged ones. Conclusion: Pharmacological activation of Beclin-1 by TB-peptide protects the heart in both young and aged population during endotoxemia, suggest a therapeutic potential for sepsis-induced cardiomyopathy. Metabolomics analysis suggests that this age-independent protection by TB-peptide is associated with reprograming of energy production via glucose and AA metabolisms.

Age-Independent Cardiac Protection by Pharmacological Activation of Beclin-1 During Endotoxemia and Its Association With Energy Metabolic Reprograming in Myocardium-A Targeted Metabolomics Study.

Background We showed that Beclin-1-dependent autophagy protects the heart in young and adult mice that underwent endotoxemia. Herein, we compared the potential therapeutic effects of Beclin-1 activating peptide, TB-peptide, on endotoxemia-induced cardiac outcomes in young adult and aged mice. We further evaluated lipopolysaccharide (lipopolysaccharide)-induced and TB-peptide treatment-mediated alterations in myocardial metabolism. Methods and Results C57BL/6J mice that were 10 weeks and 24 months old were challenged by lipopolysaccharide using doses at which cardiac dysfunction occurred. Following the treatment of TB-peptide or control vehicle, heart contractility, circulating cytokines, and myocardial autophagy were evaluated. We detected that TB-peptide boosted autophagy, attenuated cytokines, and improved cardiac performance in both young and aged mice during endotoxemia. A targeted metabolomics assay was designed to detect a pool of 361 known metabolites, of which 156 were detected in at least 1 of the heart tissue samples. Lipopolysaccharide-induced impairments were found in glucose and amino acid metabolisms in mice of all ages, and TB-peptide ameliorated these alterations. However, lipid metabolites were upregulated in the young group but moderately downregulated in the aged by lipopolysaccharide, suggesting an age-dependent response. TB-peptide mitigated lipopolysaccharide-mediated trend of lipids in the young mice but had little effect on the aged. (Study registration: Project DOI: https://doi.org/10.21228/M8K11W). Conclusions Pharmacological activation of Beclin-1 by TB-peptide is cardiac protective in both young and aged population during endotoxemia, suggest a therapeutic potential for sepsis-induced cardiomyopathy. Metabolomics analysis suggests that an age-independent protection by TB-peptide is associated with reprograming of energy production via glucose and amino acid metabolisms.

Effect of elevated plasma ketones on cardiac efficiency

BackgroundThe mechanism(s) responsible for the cardiac benefits of SGLT2 inhibitors remain unknown. Specific AimTo examine the effect of increased plasma ketone concentration (with infusion of beta-hydroxybutyrate [BOHB]) on LV function and myocardial glucose uptake. MethodsTwo groups (6 per group) of T2DM with HFrEF (<45%) were studied. Group I (Age=59; BMI=31 kg/m2; A1c = 7.2%; EF=41%) received in random order a 6-hour BOHB infusion (Prime =1.5 mg/kg.min, then 0.75 mg/kg.min) or 6-hour HCO3 infusion with matching volume (control). Group II (Age=56; BMI=34 kg/m2; A1c=7.2%; EF=38%) received a 3-hour BOHB infusion at a higher rate (Prime=4.0 mg/kg.min, then 2.0 mg/kg.min). A cardiac MRI was performed before and after each infusion. Additionally, Group I underwent a PET study with 18F-2-DOG and 15O. ResultsGroups I and II achieved plasma ketone levels of 1.4 and 2.5 mmol/L, respectively. In Group II, BOHB infusion significantly (P<0.01) increased CO and EF, whereas in Group I the increase in CO and EF tend toward significance (p=0.06), suggesting a dose-dependent response to the increase in plasma ketone concentration. NaHCO3 infusion had no effect on any cardiac indices (Fig.1). Myocardial blood flow increased significantly (P<0.01) in both Group I and II. Myocardial glucose uptake was not altered by BOHB infusion. ConclusionIn patients with T2DM and HFrEF, a physiologic increase in plasma ketone concentration significantly increased LV function and myocardial blood flow without affecting cardiac glucose metabolism. These results suggest that altered myocardial substrate metabolism can be employed therapeutically to improve cardiac function in HFrEF.

Myocardial glucose and fatty acid metabolism is altered and associated with lower cardiac function in young adults with Barth syndrome

BackgroundBarth syndrome (BTHS) is a rare X-linked condition resulting in cardiomyopathy, however; the effects of BTHS on myocardial substrate metabolism and its relationships with cardiac high-energy phosphate metabolism and left ventricular (LV) function are unknown. We sought to characterize myocardial glucose, fatty acid (FA), and leucine metabolism in BTHS and unaffected controls and examine their relationships with cardiac high-energy phosphate metabolism and LV function. Methods/ResultsYoung adults with BTHS (n = 14) and unaffected controls (n = 11, Control, total n = 25) underwent bolus injections of 15O-water and 1-11C-glucose, palmitate, and leucine and concurrent positron emission tomography imaging. LV function and cardiac high-energy phosphate metabolism were examined via echocardiography and 31P magnetic resonance spectroscopy, respectively. Myocardial glucose extraction fraction (21 ± 14% vs 10 ± 8%, P = .03) and glucose utilization (828.0 ± 470.0 vs 393.2 ± 361.0 μmol·g−1·min−1, P = .02) were significantly higher in BTHS vs Control. Myocardial FA extraction fraction (31 ± 7% vs 41 ± 6%, P < .002) and uptake (0.25 ± 0.04 vs 0.29 ± 0.03 mL·g−1·min−1, P < .002) were significantly lower in BTHS vs Control. Altered myocardial metabolism was associated with lower cardiac function in BTHS. ConclusionsMyocardial substrate metabolism is altered and may contribute to LV dysfunction in BTHS.Clinical Trials #: NCT01625663.

Dynamic FDG PET Imaging to Probe for Cardiac Metabolic Remodeling in Adults Born Premature.

Individuals born very premature have an increased cardiometabolic and heart failure risk. While the structural differences of the preterm heart are now well-described, metabolic insights into the physiologic mechanisms underpinning this risk are needed. Here, we used dynamic fluorodeoxyglucose (FDG) positron emission tomography/magnetic resonance imaging (PET-MRI) in young adults born term and preterm during normoxic (N = 28 preterm; 18 term) and hypoxic exposure (12% O2; N = 26 preterm; 17 term) to measure the myocardial metabolic rate of glucose (MMRglc) in young adults born term (N = 18) and preterm (N = 32), hypothesizing that young adults born preterm would have higher rates of MMRglc under normoxic conditions and a reduced ability to augment glucose metabolism under hypoxic conditions. MMRglc was calculated from the myocardial and blood pool time-activity curves by fitting the measured activities to the 3-compartment model of FDG kinetics. MMRglc was similar at rest between term and preterm subjects, and decreased during hypoxia exposure in both groups (p = 0.02 for MMRglc hypoxia effect). There were no differences observed between groups in the metabolic response to hypoxia, either globally (serum glucose and lactate measures) or within the myocardium. Thus, we did not find evidence of altered myocardial metabolism in the otherwise healthy preterm-born adult. However, whether subtle changes in myocardial metabolism may preceed or predict heart failure in this population remains to be determined.

Myocardial iron depletion exacerbates end-stage heart failure by promoting adverse remodeling and worsening mitochondrial function

Abstract Background Heart failure (HF) is highly associated with systemic iron deficiency (ID) yet its association with myocardial iron depletion (MID) remains barely unveiled. Similarly, it has been unclear whether and how MID deteriorates the progression to advanced HF. Furthermore, neither the underlying pathophysiology nor the negative impact of unmet iron availability to the failing heart, at the molecular level, is elucidated. Purpose We aim to integrate clinical information and experimental data from human explanted heart tissues: 1) to establish the defining criterion of MID in advanced HF population; 2) to recapitulate the pathophysiological role MID plays in the progression of HF; and 3) to identify novel HF molecular signatures or potential cures to correct MID status underestimated in the failing hearts. Methods Adult failing hearts (N=143), including dilated (n=76) and ischemic (n=67) cardiomyopathies, and non-failing control hearts (NFC, N=46) were collected per Human Explanted Heart Program. Iron levels were measured directly from both ventricles, which were re-evaluated by cardiac magnetic resonance imaging (CMR) mapping sequences (e.g. T1, T2*, etc.). Mitochondrial metabolic, reactive oxygen species (ROS) and ROS-scavenging profiles were assessed spectrophotometrically. Tissue remodeling and ultrastructure characteristics were captured by confocal and electron microscopies respectively. Meanwhile, the patients' clinical profiles were integrated into the analysis of molecular regulatory mechanism. Results Myocardial iron content in LV was significantly lower in HF versus NFC [121.4 (88.1–150.3) vs. 137.4 (109.2–165.9) μg/g dry weight, p&amp;lt;0.05], while both RVs showed no difference. With a cutoff of 86.1 μg/g iron level in LV, it screened ∼23% HF patients with MID (HF-MID). Compared with non-MID HF patients, depleted iron store weakly correlated with systemic hemoglobin concentration (r=−0.27, p=0.13) but highly with T2* and magnetic susceptibility proving CMR as an exceptional surrogate for non-invasive diagnosis. And it was noted that MID independently predicted ominous endpoints as NYHA grade increased and LV dysfunctions worsened (all p&amp;lt;0.05). Cardiac respiratory chain enzymatic activities from complex I to V (except for COX III) were further suppressed in the iron-deficient failing hearts, indicating altered myocardial metabolism and excessive ROS production. Moreover, the whole anti-ROS defense were severely impaired, consistent with remarkably inverse tissue remodeling and ultrastructure disintegrity in HF-MID. Mechanistically, two iron-regulatory proteins (IRP-1/2) and following iron trafficking pathways were inactivated possibly determine the restricted iron availability to advanced failing hearts. Conclusions MID worsens HF progression primarily mediated by mitochondrial dysfunction and collapsed oxidative protection in LV, independently predicting an inferior prognosis. CMR demonstrates clinical potential to monitor MID. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): Canadian Institutes for Health Research (CIHR); Heart &amp; Stroke Foundation (HSF)

Metabolic Modulation to Treat Cardiac Diseases: Role for Membrane Substrate Transporters

There is growing recognition of the importance and multiple roles of substrate energy metabolism in both cardiac health and disease. Cardiac diseases are frequently accompanied by altered myocardial metabolism, while chronic changes in the type of myocardial substrate utilization are found to elicit cardiac contractile dysfunction. Examples are the increased glucose utilization, at the expense of fatty acids, in cardiac hypertrophy and ischemic heart failure, and the increased fatty acid utilization, at the expense of glucose, in obesity and diabetes-related cardiac dysfunction. Modulation of cardiac metabolism has emerged as a suitable therapeutic intervention in cardiac disease. Insights obtained during the past decade have revealed sarcolemmal substrate transport, facilitated by CD36 for fatty acids and by GLUT4 for glucose, to represent the main rate-governing kinetic step of substrate utilization, over-ruling intracellular sites of flux regulation. This suggests that manipulating the presence of substrate transporters in the sarcolemma may be an effective approach for metabolic modulation therapy. The present mini-review provides a short summary of the functioning of substrate transporters CD36 and GLUT4 in the heart, and discusses their application as targets for metabolic intervention.

Metabolic Alterations in Myocardial Metabolism during Ex Situ Heart Perfusion

Purpose Ex situ heart perfusion (ESHP) is a novel method for preservation of the donated heart in a semi-physiologic state and provides the opportunity to evaluate pre-transplant function. Because of the well-described extraordinary metabolic requirements of the heart, efficient metabolic support is critical for optimal preservation of function and viability. Our aim was to determine changes in energy metabolism/energy substrates during extended ex situ perfusion of hearts in two different perfusion modes, working mode (WM) and non-working mode (NWM). Methods 17 female domestic breed pigs (37-47 kg) were included. Hearts were perfused on a custom ESHP apparatus (12 hours, NWM n=6 and WM n=7) with insulin and glucose infusions for metabolic support. Cardiac function, and changes in myocardial oxidative metabolism, glucose utilization, lactate, free fatty acids (FFA) and triglycerides (TG) were evaluated during ESHP. The enzymatic activity of pyruvate kinase was assessed using immunoassay techniques. The results were compared with baseline values (in vivo, n=4). Results Cardiac function declined over time but it was better preserved in WM (cardiac index change, p=0.02). Glucose utilization increased overtime in both groups (WM p=0.04, NWM p=0.04). Venous and arteriovenous lactate did not change over time and were not different between WM and NWM. FFA concentrations declined considerably during ESHP in both groups (WM p Conclusion Our data suggests functional decline during ESHP has a metabolic basis and is therefore reversible. Furthermore, a strategy of insulin and glucose appears insufficient for maintenance of metabolic integrity during ESHP and there is decoupling of glycolysis and the TCA cycle at the level of pyruvate kinase. Further research is required to determine the causative factors underpinning these alterations and optimal methods to abrogate their effects to ensure optimal preservation of contractile function during ESHP.

The interplay between metabolic alterations, diastolic strain rate and exercise capacity in mild heart failure with preserved ejection fraction: a cardiovascular magnetic resonance study

BackgroundHeart failure (HF) is characterized by altered myocardial substrate metabolism which can lead to myocardial triglyceride accumulation (steatosis) and lipotoxicity. However its role in mild HF with preserved ejection fraction (HFpEF) is uncertain. We measured myocardial triglyceride content (MTG) in HFpEF and assessed its relationships with diastolic function and exercise capacity.MethodsTwenty seven HFpEF (clinical features of HF, left ventricular EF >50%, evidence of mild diastolic dysfunction and evidence of exercise limitation as assessed by cardiopulmonary exercise test) and 14 controls underwent 1H-cardiovascular magnetic resonance spectroscopy (1H-CMRS) to measure MTG (lipid/water, %), 31P-CMRS to measure myocardial energetics (phosphocreatine-to-adenosine triphosphate - PCr/ATP) and feature-tracking cardiovascular magnetic resonance (CMR) imaging for diastolic strain rate.ResultsWhen compared to controls, HFpEF had 2.3 fold higher in MTG (1.45 ± 0.25% vs. 0.64 ± 0.16%, p = 0.009) and reduced PCr/ATP (1.60 ± 0.09 vs. 2.00 ± 0.10, p = 0.005). HFpEF had significantly reduced diastolic strain rate and maximal oxygen consumption (VO2 max), which both correlated significantly with elevated MTG and reduced PCr/ATP. On multivariate analyses, MTG was independently associated with diastolic strain rate while diastolic strain rate was independently associated with VO2 max.ConclusionsMyocardial steatosis is pronounced in mild HFpEF, and is independently associated with impaired diastolic strain rate which is itself related to exercise capacity. Steatosis may adversely affect exercise capacity by indirect effect occurring via impairment in diastolic function. As such, myocardial triglyceride may become a potential therapeutic target to treat the increasing number of patients with HFpEF.

Myocardial metabolic alterations in mice with diet-induced atherosclerosis: linking sulfur amino acid and lipid metabolism

Atherosclerosis is a leading cause of cardiovascular disease (CVD), but the effect of diet on the atherosclerotic heart’s metabolism is unclear. We used an integrated metabolomics and lipidomics approach to evaluate metabolic perturbations in heart and serum from mice fed an atherogenic diet (AD) for 8, 16, and 25 weeks. Nuclear magnetic resonance (NMR)-based metabolomics revealed significant changes in sulfur amino acid (SAA) and lipid metabolism in heart from AD mice compared with heart from normal diet mice. Higher SAA levels in AD mice were quantitatively verified using liquid chromatography-mass spectrometry (LC/MS). Lipidomic profiling revealed that fatty acid and triglyceride (TG) levels in the AD group were altered depending on the degree of unsaturation. Additionally, levels of SCD1, SREBP-1, and PPARγ were reduced in AD mice after 25 weeks, while levels of reactive oxygen species were elevated. The results suggest that a long-term AD leads to SAA metabolism dysregulation and increased oxidative stress in the heart, causing SCD1 activity suppression and accumulation of toxic TGs with a low degree of unsaturation. These findings demonstrate that the SAA metabolic pathway is a promising therapeutic target for CVD treatment and that metabolomics can be used to investigate the metabolic signature of atherosclerosis.

Treatment strategies for the right heart in pulmonary hypertension.

The function of the right ventricle (RV) determines the prognosis of patients with pulmonary hypertension. While much progress has been made in the treatment of pulmonary hypertension, therapies for the RV are less well established. In this review of treatment strategies for the RV, first we focus on ways to reduce wall stress since this is the main determinant of changes to the ventricle. Secondly, we discuss treatment strategies targeting the detrimental consequences of increased RV wall stress. To reduce wall stress, afterload reduction is the essential. Additionally, preload to the ventricle can be reduced by diuretics, by atrial septostomy, and potentially by mechanical ventricular support. Secondary to ventricular wall stress, left-to-right asynchrony, altered myocardial energy metabolism, and neurohumoral activation will occur. These may be targeted by optimising RV contraction with pacing, by iron supplement, by angiogenesis and improving mitochondrial function, and by neurohumoral modulation, respectively. We conclude that several treatment strategies for the right heart are available; however, evidence is still limited and further research is needed before clinical application can be recommended.

Metabolic risk factors associated with sudden cardiac death (SCD) during acute myocardial ischemia

ABSTRACTSudden cardiac death (SCD) is the leading cause of death worldwide. Myocardial ischemia (MI) is the most common underlying causal disorder for SCD. Metabolic risks leading to SCD during acute MI are still not fully understood. Here, using tissue metabolomics, we aimed to investigate myocardial metabolic alterations relevant to SCD events in an acute MI rat model induced by coronary artery ligation (CAL). Thirty-four rats were successfully performed CAL, of which 13 developed lethal ventricular tachyarrhythmia (LVTA)-SCD and 7 developed severe atrioventricular block (AB)-SCD. Fourteen rats that survived within 70 min after the ligation were served as peer controls. The partial least squares-discriminant analysis plots demonstrated clear separations between the SCD rats and controls, indicating obvious differences in myocardial metabolome between these rats. The levels of isoleucine, lactate, glutamate choline, phosphorylcholine, taurine and asparagine in ischemic myocardia were positively associated with LVTA-SCD events; in contrast, the levels of alanine, urea, phenylalanine, linoleic acid, elaidic acid and stearic acid were inversely correlated with LVTA-SCD events. The levels of glutamate and urea were positively and negatively relevant to AB-SCD events, respectively. The dangerous metabolites indicated that lower levels of energy substrates, severe hypoxia, the inhibition of transamination and hyper sympathetic excitement and reactive oxygen species in myocardia were vulnerable to SCD during acute MI. The results suggest fatal metabolic alterations correlated with SCD events during acute MI, which could offer novel clues for the prevention or treatment of acute MI-related SCD.