The PPARalpha activator fenofibrate slows down the progression of the left ventricular dysfunction in porcine tachycardia-induced cardiomyopathy

Potential perioperative cardiovascular outcomes in cannabis/cannabinoid users. A call for caution

Background

Cannabis is one of the most widely used psychoactive substances. Its components act through several pathways, producing a myriad of side effects, of which cardiovascular events are the most life-threatening. However, only a limited number of studies address cannabis's perioperative impact on patients during noncardiac surgery.

Methods

Studies were identified by searching the PubMed, Medline, EMBASE, and Google Scholar databases using relevant keyword combinations pertinent to the topic.

Results

Current evidence shows that cannabis use may cause several cardiovascular events, including abnormalities in cardiac rhythm, myocardial infarction, heart failure, and cerebrovascular events. Additionally, cannabis interacts with anticoagulants and antiplatelet agents, decreasing their efficacy. Finally, the interplay of cannabis with inhalational and intravenous anesthetic agents may lead to adverse perioperative cardiovascular outcomes.

Conclusions

The use of cannabis can trigger cardiovascular events that may depend on factors such as the duration of consumption, the route of administration of the drug, and the dose consumed, which places these patients at risk of drug-drug interactions with anesthetic agents. However, large prospective randomized clinical trials are needed to further elucidate gaps in the body of knowledge regarding which patient population has a greater risk of perioperative complications after cannabis consumption.

Associations of omega-3 fatty acids vs. fenofibrate with adverse cardiovascular outcomes in people with metabolic syndrome: propensity matched cohort study

AIMS

Omega-3 fatty acids and fenofibrates have shown some beneficial cardiovascular effects; however, their efficacy has not been compared. This study aimed to compare the effectiveness of currently available omega-3 fatty acids and fenofibrate for reducing major adverse cardiovascular events (MACE).

METHODS AND RESULTS

From a nationwide population-based cohort in South Korea (2008-2019), individuals with metabolic syndrome (≥30 years) who received statin with omega-3 fatty acids and those receiving statin with fenofibrate were matched by propensity score (n = 39 165 in both groups). The primary outcome was MACE, including ischaemic heart disease (IHD), ischaemic stroke (IS), and death from cardiovascular causes. The risk of MACE was lower [hazard ratio (HR), 0.79; 95% confidence interval (CI), 0.74-0.83] in the fenofibrate group than in the omega-3 fatty acid group. Fenofibrate was associated with a lower incidence of IHD (HR, 0.72; 95% CI, 0.67-0.77) and hospitalization for heart failure (HR, 0.90; 95% CI, 0.82-0.97), but not IS (HR, 0.90; 95% CI, 0.81-1.00) nor death from cardiovascular causes (HR, 1.07; 95% CI, 0.97-1.17). The beneficial effect of fenofibrate compared to omega-3 fatty acids was prominent in patients with preexisting atherosclerotic cardiovascular disease and those receiving lower doses of omega-3 fatty acids (≤2 g per day).

CONCLUSION

In a real-world setting, fenofibrate use was associated with a lower risk of MACE compared with low-dose omega-3 fatty acids when added to statins in people with metabolic syndrome.

Qiliqiangxin: A multifaceted holistic treatment for heart failure or a pharmacological probe for the identification of cardioprotective mechanisms?

The active ingredients in many traditional Chinese medicines are isoprene oligomers with a diterpenoid or triterpenoid structure, which exert cardiovascular effects by signalling through nutrient surplus and nutrient deprivation pathways. Qiliqiangxin (QLQX) is a commercial formulation of 11 different plant ingredients, whose active compounds include astragaloside IV, tanshione IIA, ginsenosides (Rb1, Rg1 and Re) and periplocymarin. In the QUEST trial, QLQX reduced the combined risk of cardiovascular death or heart failure hospitalization (hazard ratio 0.78, 95% confidence interval 0.68-0.90), based on 859 events in 3119 patients over a median of 18.2 months; the benefits were seen in patients taking foundational drugs except for sodium-glucose cotransporter 2 (SGLT2) inhibitors. Numerous experimental studies of QLQX in diverse cardiac injuries have yielded highly consistent findings. In marked abrupt cardiac injury, QLQX mitigated cardiac injury by upregulating nutrient surplus signalling through the PI3K/Akt/mTOR/HIF-1α/NRF2 pathway; the benefits of QLQX were abrogated by suppression of PI3K, Akt, mTOR, HIF-1α or NRF2. In contrast, in prolonged measured cardiac stress (as in chronic heart failure), QLQX ameliorated oxidative stress, maladaptive hypertrophy, cardiomyocyte apoptosis, and proinflammatory and profibrotic pathways, while enhancing mitochondrial health and promoting glucose and fatty acid oxidation and ATP production. These effects are achieved by an action of QLQX to upregulate nutrient deprivation signalling through SIRT1/AMPK/PGC-1α and enhanced autophagic flux. In particular, QLQX appears to enhance the interaction of PGC-1α with PPARα, possibly by direct binding to RXRα; silencing of SIRT1, PGC-1α and RXRα abrogated the favourable effects of QLQX in the heart. Since PGC-1α/RXRα is also a downstream effector of Akt/mTOR signalling, the actions of QLQX on PGC-1α/RXRα may explain its favourable effects in both acute and chronic stress. Intriguingly, the individual ingredients in QLQX - astragaloside IV, ginsenosides, and tanshione IIA - share QLQX's effects on PGC-1α/RXRα/PPARα signalling. QXQL also contains periplocymarin, a cardiac glycoside that inhibits Na+ -K+ -ATPase. Taken collectively, these observations support a conceptual framework for understanding the mechanism of action for QLQX in heart failure. The high likelihood of overlap in the mechanism of action of QLQX and SGLT2 inhibitors requires additional experimental studies and clinical trials.

SGLT2 inhibitors: role in protective reprogramming of cardiac nutrient transport and metabolism

Sodium-glucose cotransporter 2 (SGLT2) inhibitors reduce heart failure events by direct action on the failing heart that is independent of changes in renal tubular function. In the failing heart, nutrient transport into cardiomyocytes is increased, but nutrient utilization is impaired, leading to deficient ATP production and the cytosolic accumulation of deleterious glucose and lipid by-products. These by-products trigger downregulation of cytoprotective nutrient-deprivation pathways, thereby promoting cellular stress and undermining cellular survival. SGLT2 inhibitors restore cellular homeostasis through three complementary mechanisms: they might bind directly to nutrient-deprivation and nutrient-surplus sensors to promote their cytoprotective actions; they can increase the synthesis of ATP by promoting mitochondrial health (mediated by increasing autophagic flux) and potentially by alleviating the cytosolic deficiency in ferrous iron; and they might directly inhibit glucose transporter type 1, thereby diminishing the cytosolic accumulation of toxic metabolic by-products and promoting the oxidation of long-chain fatty acids. The increase in autophagic flux mediated by SGLT2 inhibitors also promotes the clearance of harmful glucose and lipid by-products and the disposal of dysfunctional mitochondria, allowing for mitochondrial renewal through mitochondrial biogenesis. This Review describes the orchestrated interplay between nutrient transport and metabolism and nutrient-deprivation and nutrient-surplus signalling, to explain how SGLT2 inhibitors reverse the profound nutrient, metabolic and cellular abnormalities observed in heart failure, thereby restoring the myocardium to a healthy molecular and cellular phenotype.

Identification of shared fatty acid metabolism related signatures in dilated cardiomyopathy and myocardial infarction

Aim: It is to be elucidated the risk-predictive role of differentially expressed fatty acid metabolism related genes (DE-FRGs) in dilated cardiomyopathy (DCM) and myocardial infarction. Materials & methods: Four gene enrichment analyses defined DE-FRGs’ biological functions and pathways. Three strategies were applied to identify risk biomarkers and construct a nomogram. The 4-DE-FRG correlation with immune cell infiltration, drugs, and ceRNA was explored. Results: DE-FRGs were enriched in lipid metabolism. A risk nomogram was established by ACSL1, ALDH2, CYP27A1 and PPARA, demonstrating a good ability for DCM and myocardial infarction prediction. PPARA was positively correlated with adaptive immunocytes. Thirty-five drugs are candidate therapeutic targets. Conclusion: A nomogram and new biological targets for early diagnosis and treatment of DCM and myocardial infarction were provided.

PPAR Alpha Activation by Clofibrate Alleviates Ischemia/Reperfusion Injury in Metabolic Syndrome Rats by Decreasing Cardiac Inflammation and Remodeling and by Regulating the Atrial Natriuretic Peptide Compensatory Response

Metabolic syndrome (MetS) is a cluster of factors that increase the risk of developing diabetes, stroke, and heart failure. The pathophysiology of injury by ischemia/reperfusion (I/R) is highly complex and the inflammatory condition plays an important role by increasing matrix remodeling and cardiac apoptosis. Natriuretic peptides (NPs) are cardiac hormones with numerous beneficial effects mainly mediated by a cell surface receptor named atrial natriuretic peptide receptor (ANPr). Although NPs are powerful clinical markers of cardiac failure, their role in I/R is still controversial. Peroxisome proliferator-activated receptor α agonists exert cardiovascular therapeutic actions; however, their effect on the NPs’ signaling pathway has not been extensively studied. Our study provides important insight into the regulation of both ANP and ANPr in the hearts of MetS rats and their association with the inflammatory conditions caused by damage from I/R. Moreover, we show that pre-treatment with clofibrate was able to decrease the inflammatory response that, in turn, decreases myocardial fibrosis, the expression of metalloprotease 2 and apoptosis. Treatment with clofibrate is also associated with a decrease in ANP and ANPr expression.

How do phytocannabinoids affect cardiovascular health? An update on the most common cardiovascular diseases

Cardiovascular disease (CVD) causes millions of deaths worldwide each year. Despite the great progress in therapies available for patients with CVD, some limitations, including drug complications, still exist. Hence, the endocannabinoid system (ECS) was proposed as a new avenue for CVDs treatment. The ECS components are widely distributed through the body, including the heart and blood vessels, thus the action of its endogenous and exogenous ligands, in particular, phytocannabinoids play a key role in various pathological states. The cardiovascular action of cannabinoids is complex as they affect vasculature and myocardium directly via specific receptors and exert indirect effects through the central and peripheral nervous system. The growing interest in phytocannabinoid studies, however, has extended the knowledge about their molecular targets as well as therapeutical properties; nonetheless, some areas of their actions are not yet fully recognized. Researchers have reported various cannabinoids, especially cannabidiol, as a promising approach to CVDs; hence, the purpose of this review is to summarize and update the cardiovascular actions of the most potent phytocannabinoids and the potential therapeutic role of ECS in CVDs, including ischemic reperfusion injury, arrhythmia, heart failure as well as hypertension.

Pemafibrate Prevents Rupture of Angiotensin II-Induced Abdominal Aortic Aneurysms

Background

Abdominal aortic aneurysm (AAA) is a life-threatening disease that lacks effective preventive therapies. This study aimed to evaluate the effect of pemafibrate, a selective peroxisome proliferator-activated receptor alpha (PPARα) agonist, on AAA formation and rupture.

Methods

Experimental AAA was induced by subcutaneous angiotensin II (AngII) infusion in ApoE ^{- / -} mice for 4 weeks. Pemafibrate (0.1 mg/kg/day) was administered orally. Dihydroethidium staining was used to evaluate the reactive oxygen species (ROS).

Results

The size of the AngII-induced AAA did not differ between pemafibrate- and vehicle-treated groups. However, a decreased mortality rate due to AAA rupture was observed in pemafibrate-treated mice. Pemafibrate ameliorated AngII-induced ROS and reduced the mRNA expression of interleukin-6 and tumor necrosis factor-α in the aortic wall. Gelatin zymography analysis demonstrated significant inhibition of matrix metalloproteinase-2 activity by pemafibrate. AngII-induced ROS production in human vascular smooth muscle cells was inhibited by pre-treatment with pemafibrate and was accompanied by an increase in catalase activity. Small interfering RNA-mediated knockdown of catalase or PPARα significantly attenuated the anti-oxidative effect of pemafibrate.

Conclusion

Pemafibrate prevented AAA rupture in a murine model, concomitant with reduced ROS, inflammation, and extracellular matrix degradation in the aortic wall. The protective effect against AAA rupture was partly mediated by the anti-oxidative effect of catalase induced by pemafibrate in the smooth muscle cells.

Cardiac foetal reprogramming: a tool to exploit novel treatment targets for the failing heart

As the heart matures during embryogenesis from its foetal stages, several structural and functional modifications take place to form the adult heart. This process of maturation is in large part due to an increased volume and work load of the heart to maintain proper circulation throughout the growing body. In recent years, it has been observed that these changes are reversed to some extent as a result of cardiac disease. The process by which this occurs has been characterized as cardiac foetal reprogramming and is defined as the suppression of adult and re-activation of a foetal genes profile in the diseased myocardium. The reasons as to why this process occurs in the diseased myocardium are unknown; however, it has been suggested to be an adaptive process to counteract deleterious events taking place during cardiac remodelling. Although still in its infancy, several studies have demonstrated that targeting foetal reprogramming in heart failure can lead to substantial improvement in cardiac functionality. This is highlighted by a recent study which found that by modulating the expression of 5-oxoprolinase (OPLAH, a novel cardiac foetal gene), cardiac function can be significantly improved in mice exposed to cardiac injury. Additionally, the utilization of angiotensin receptor neprilysin inhibitors (ARNI) has demonstrated clear benefits, providing important clinical proof that drugs that increase natriuretic peptide levels (part of the foetal gene programme) indeed improve heart failure outcomes. In this review, we will highlight the most important aspects of cardiac foetal reprogramming and will discuss whether this process is a cause or consequence of heart failure. Based on this, we will also explain how a deeper understanding of this process may result in the development of novel therapeutic strategies in heart failure.

Reactivation of fatty acid oxidation by medium chain fatty acid prevents myocyte hypertrophy in H9c2 cell line

Metabolic shift is an important contributory factor for progression of hypertension-induced left ventricular hypertrophy into cardiac failure. Under hypertrophic conditions, heart switches its substrate preference from fatty acid to glucose. Prolonged dependence on glucose for energy production has adverse cardiovascular consequences. It was reported earlier that reactivation of fatty acid metabolism with medium chain triglycerides ameliorated cardiac hypertrophy, oxidative stress and energy level in spontaneously hypertensive rat. However, the molecular mechanism mediating the beneficial effect of medium chain triglycerides remained elusive. It was hypothesized that reduction of cardiomyocyte hypertrophy by medium chain fatty acid (MCFA) is mediated by modulation of signaling pathways over expressed in cardiac hypertrophy. The protective effect of medium chain fatty acid (MCFA) was evaluated in cellular model of myocyte hypertrophy. H9c2 cells were stimulated with Arginine vasopressin (AVP) for the induction of hypertrophy. Cell volume and secretion of brain natriuretic peptide (BNP) were used for assessment of cardiomyocyte hypertrophy. Cells were pretreated with MCFA (Caprylic acid) and metabolic modulation was assessed from the expression of medium-chain acyl-CoA dehydrogenase (MCAD), cluster of differentiation-36 (CD36) and peroxisome proliferator-activated receptor (PPAR)-α mRNA. The signaling molecules modified by MCFA was evaluated from protein expression of mitogen activated protein kinases (MAPK: ERK1/2, p38 and JNK) and Calcineurin A. Pretreatment with MCFA stimulated fatty acid metabolism in hypertrophic H9c2, with concomitant reduction of cell volume and BNP secretion. MCFA reduced activated ERK1/2, JNK and calicineurin A expression mediated by AVP. In conclusion, the beneficial effect of MCFA is possibly mediated by stimulation of fatty acid metabolism and modulation of MAPK and Calcineurin A.

Changes in Myocardial Metabolism Preceding Sudden Cardiac Death

Heart disease is widely recognized as a major cause of death worldwide and is the leading cause of mortality in the United States. Centuries of research have focused on defining mechanistic alterations that drive cardiac pathogenesis, yet sudden cardiac death (SCD) remains a common unpredictable event that claims lives in every age group. The heart supplies blood to all tissues while maintaining a constant electrical and hormonal feedback communication with other parts of the body. As such, recent research has focused on understanding how myocardial electrical and structural properties are altered by cardiac metabolism and the various signaling pathways associated with it. The importance of cardiac metabolism in maintaining myocardial function, or lack thereof, is exemplified by shifts in cardiac substrate preference during normal development and various pathological conditions. For instance, a shift from fatty acid (FA) oxidation to oxygen-sparing glycolytic energy production has been reported in many types of cardiac pathologies. Compounded by an uncoupling of glycolysis and glucose oxidation this leads to accumulation of undesirable levels of intermediate metabolites. The resulting accumulation of intermediary metabolites impacts cardiac mitochondrial function and dysregulates metabolic pathways through several mechanisms, which will be reviewed here. Importantly, reversal of metabolic maladaptation has been shown to elicit positive therapeutic effects, limiting cardiac remodeling and at least partially restoring contractile efficiency. Therein, the underlying metabolic adaptations in an array of pathological conditions as well as recently discovered downstream effects of various substrate utilization provide guidance for future therapeutic targeting. Here, we will review recent data on alterations in substrate utilization in the healthy and diseased heart, metabolic pathways governing cardiac pathogenesis, mitochondrial function in the diseased myocardium, and potential metabolism-based therapeutic interventions in disease.

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.

Therapeutic Effect of Targeting Branched-Chain Amino Acid Catabolic Flux in Pressure-Overload Induced Heart Failure

Background Branched-chain amino acid (BCAA) catabolic defect is an emerging metabolic hallmark in failing hearts in human and animal models. The therapeutic impact of targeting BCAA catabolic flux under pathological conditions remains understudied. Methods and Results BT2 (3,6-dichlorobenzo[b]thiophene-2-carboxylic acid), a small-molecule inhibitor of branched-chain ketoacid dehydrogenase kinase, was used to enhance BCAA catabolism. After 2 weeks of transaortic constriction, mice with significant cardiac dysfunctions were treated with vehicle or BT2. Serial echocardiograms showed continuing pathological deterioration in left ventricle of the vehicle-treated mice, whereas the BT2-treated mice showed significantly preserved cardiac function and structure. Moreover, BT2 treatment improved systolic contractility and diastolic mechanics. These therapeutic benefits appeared to be independent of impacts on left ventricle hypertrophy but associated with increased gene expression involved in fatty acid utilization. The BT2 administration showed no signs of apparent toxicity. Conclusions Our data provide the first proof-of-concept evidence for the therapeutic efficacy of restoring BCAA catabolic flux in hearts with preexisting dysfunctions. The BCAA catabolic pathway represents a novel and potentially efficacious target for treatment of heart failure.

Interrelationship between diabetes mellitus and heart failure: the role of peroxisome proliferator-activated receptors in left ventricle performance

Heart failure (HF) is a common cardiac syndrome, whose pathophysiology involves complex mechanisms, some of which remain unknown. Diabetes mellitus (DM) constitutes not only a glucose metabolic disorder accompanied by insulin resistance but also a risk factor for cardiovascular disease and HF. During the last years though emerging data set up, a bidirectional interrelationship between these two entities. In the case of DM impaired calcium homeostasis, free fatty acid metabolism, redox state, and advance glycation end products may accelerate cardiac dysfunction. On the other hand, when HF exists, hypoperfusion of the liver and pancreas, b-blocker and diuretic treatment, and autonomic nervous system dysfunction may cause impairment of glucose metabolism. These molecular pathways may be used as therapeutic targets for novel antidiabetic agents. Peroxisome proliferator-activated receptors (PPARs) not only improve insulin resistance and glucose and lipid metabolism but also manifest a diversity of actions directly or indirectly associated with systolic or diastolic performance of left ventricle and symptoms of HF. Interestingly, they may beneficially affect remodeling of the left ventricle, fibrosis, and diastolic performance but they may cause impaired water handing, sodium retention, and decompensation of HF which should be taken into consideration in the management of patients with DM. In this review article, we present the pathophysiological data linking HF with DM and we focus on the molecular mechanisms of PPARs agonists in left ventricle systolic and diastolic performance providing useful insights in the molecular mechanism of this class of metabolically active regiments.

Elucidating the Beneficial Role of PPAR Agonists in Cardiac Diseases

Peroxisome proliferator-activated receptors (PPARs) are nuclear hormone receptors that bind to DNA and regulate transcription of genes involved in lipid and glucose metabolism. A growing number of studies provide strong evidence that PPARs are the promising pharmacological targets for therapeutic intervention in various diseases including cardiovascular disorders caused by compromised energy metabolism. PPAR agonists have been widely used for decades as lipid-lowering and anti-inflammatory drugs. Existing studies are mainly focused on the anti-atherosclerotic effects of PPAR agonists; however, their role in the maintenance of cellular bioenergetics remains unclear. Recent studies on animal models and patients suggest that PPAR agonists can normalize lipid metabolism by stimulating fatty acid oxidation. These studies indicate the importance of elucidation of PPAR agonists as potential pharmacological agents for protection of the heart from energy deprivation. Here, we summarize and provide a comprehensive analysis of previous studies on the role of PPARs in the heart under normal and pathological conditions. In addition, the review discusses the PPARs as a therapeutic target and the beneficial effects of PPAR agonists, particularly bezafibrate, to attenuate cardiomyopathy and heart failure in patients and animal models.

The Effects of PPAR Stimulation on Cardiac Metabolic Pathways in Barth Syndrome Mice

Aim: Tafazzin knockdown (TazKD) in mice is widely used to create an experimental model of Barth syndrome (BTHS) that exhibits dilated cardiomyopathy and impaired exercise capacity. Peroxisome proliferator-activated receptors (PPARs) are a group of nuclear receptor proteins that play essential roles as transcription factors in the regulation of carbohydrate, lipid, and protein metabolism. We hypothesized that the activation of PPAR signaling with PPAR agonist bezafibrate (BF) may ameliorate impaired cardiac and skeletal muscle function in TazKD mice. This study examined the effects of BF on cardiac function, exercise capacity, and metabolic status in the heart of TazKD mice. Additionally, we elucidated the impact of PPAR activation on molecular pathways in TazKD hearts.

Methods: BF (0.05% w/w) was given to TazKD mice with rodent chow. Cardiac function in wild type-, TazKD-, and BF-treated TazKD mice was evaluated by echocardiography. Exercise capacity was evaluated by exercising mice on the treadmill until exhaustion. The impact of BF on metabolic pathways was evaluated by analyzing the total transcriptome of the heart by RNA sequencing.

Results: The uptake of BF during a 4-month period at a clinically relevant dose effectively protected the cardiac left ventricular systolic function in TazKD mice. BF alone did not improve the exercise capacity however, in combination with everyday voluntary running on the running wheel BF significantly ameliorated the impaired exercise capacity in TazKD mice. Analysis of cardiac transcriptome revealed that BF upregulated PPAR downstream target genes involved in a wide spectrum of metabolic (energy and protein) pathways as well as chromatin modification and RNA processing. In addition, the Ostn gene, which encodes the metabolic hormone musclin, is highly induced in TazKD myocardium and human failing hearts, likely as a compensatory response to diminished bioenergetic homeostasis in cardiomyocytes.

Conclusion: The PPAR agonist BF at a clinically relevant dose has the therapeutic potential to attenuate cardiac dysfunction, and possibly exercise intolerance in BTHS. The role of musclin in the failing heart should be further investigated.

Peroxisome proliferator-activated receptors as therapeutic targets for heart failure

Heart failure (HF) is a common clinical syndrome that affects more than 23 million individuals worldwide. Despite the marked advances in its management, the mortality rates in HF patients have remained unacceptably high. Peroxisome proliferator-activated receptors (PPARs) are nuclear transcription regulators, involved in the regulation of fatty acid and glucose metabolism. PPAR agonists are currently used for the treatment of type II diabetes mellitus and hyperlipidemia; however, their role as therapeutic agents for HF remains under investigation. Preclinical studies have shown that pharmacological modulation of PPARs can upregulate the expression of fatty acid oxidation genes in cardiomyocytes. Moreover, PPAR agonists were proven able to improve ventricular contractility and reduce cardiac remodelling in animal models through their anti-inflammatory, anti-oxidant, anti-fibrotic, and anti-apoptotic activities. Whether these effects can be replicated in humans is yet to be proven. This article reviews the interactions of PPARs with the pathophysiological mechanisms of HF and how the pharmacological modulation of these receptors can be of benefit for HF patients.

The PPAR pan-agonist bezafibrate ameliorates cardiomyopathy in a mouse model of Barth syndrome

BACKGROUND

The PGC-1α/PPAR axis has been proposed as a potential therapeutic target for several metabolic disorders. The aim was to evaluate the efficacy of the pan-PPAR agonist, bezafibrate, in tafazzin knockdown mice (TazKD), a mouse model of Barth syndrome that exhibits age-dependent dilated cardiomyopathy with left ventricular (LV) dysfunction.

RESULTS

The effect of bezafibrate on cardiac function was evaluated by echocardiography in TazKD mice with or without beta-adrenergic stress. Adrenergic stress by chronic isoproterenol infusion exacerbates the cardiac phenotype in TazKD mice, significantly depressing LV systolic function by 4.5 months of age. Bezafibrate intake over 2 months substantially ameliorates the development of LV systolic dysfunction in isoproterenol-stressed TazKD mice. Without beta-adrenergic stress, TazKD mice develop dilated cardiomyopathy by 7 months of age. Prolonged treatment with suprapharmacological dose of bezafibrate (0.5% in rodent diet) over a 4-month period effectively prevented LV dilation in mice isoproterenol treatment. Bezafibrate increased mitochondrial biogenesis, however also promoted oxidative stress in cardiomyocytes. Surprisingly, improvement of systolic function in bezafibrate-treated mice was accompanied with simultaneous reduction of cardiolipin content and increase of monolysocardiolipin levels in cardiac muscle.

CONCLUSIONS

Thus, we demonstrate that bezafibrate has a potent therapeutic effect on preventing cardiac dysfunction in a mouse model of Barth syndrome with obvious implications for treating the human disease. Additional studies are needed to assess the potential benefits of PPAR agonists in humans with Barth syndrome.

Fenofibrate increases cardiac autophagy via FGF21/SIRT1 and prevents fibrosis and inflammation in the hearts of Type 1 diabetic mice

Fenofibrate (FF) as a commonly-used lipid-lowering medicine in clinics was examined for its potentially repurposing to prevent the cardiac abnormalities in patients with type 1 diabetes. We demonstrated here that fenofibrate significantly prevented diabetes-induced cardiac dysfunction and remodeling in fibroblast growth factor 21 (FGF21)-dependent manner.

Mitochondrion as a Target for Heart Failure Therapy- Role of Protein Lysine Acetylation

Heart failure is a leading cause of death worldwide. Despite medical advances, the dismal prognosis of heart failure has not been improved. The heart is a high energy-demanding organ. Impairments of cardiac energy metabolism and mitochondrial function are intricately linked to cardiac dysfunction. Mitochondrial dysfunction contributes to impaired myocardial energetics and increased oxidative stress in heart failure, and the opening of mitochondrial permeability transition pore triggers cell death and myocardial remodeling. Therefore, there has been growing interest in targeting mitochondria and metabolism for heart failure therapy. Recent developments suggest that mitochondrial protein lysine acetylation modulates the sensitivity of the heart to stress and hence the propensity to heart failure. This article reviews the role of mitochondrial dysfunction in heart failure, with a special emphasis on the regulation of the nicotinamide adenine dinucleotide (NAD(+)/NADH) ratio and sirtuin-dependent lysine acetylation by mitochondrial function. Strategies for targeting NAD(+)-sensitive mechanisms in order to intervene in protein lysine acetylation and, thereby, improve stress tolerance, are described, and their usefulness in heart failure therapy is discussed.

Ligand specific variation in cardiac response to stimulation of peroxisome proliferator-activated receptor-alpha in spontaneously hypertensive rat

Left ventricular hypertrophy (LVH) is an independent risk factor for cardiac failure. Reduction of LVH has beneficial effects on the heart. LVH is associated with shift in energy substrate preference from fatty acid to glucose, mediated by down regulation of peroxisome proliferator-activated receptor-alpha (PPAR-α). As long-term dependence on glucose can promote adverse cardiac remodeling, it was hypothesized that, prevention of metabolic shift by averting down regulation of PPAR-α can reduce cardiac remodeling in spontaneously hypertensive rat (SHR). Cardiac response to stimulation of PPAR-α presumably depends on the type of ligand used. Therefore, the study was carried out in SHR, using two different PPAR-α ligands. SHR were treated with either fenofibrate (100 mg/kg/day) or medium-chain triglyceride (MCT) Tricaprylin (5% of diet) for 4 months. Expression of PPAR-α and medium-chain acylCoA dehydrogenase served as markers, for stimulation of PPAR-α. Both ligands stimulated PPAR-α. Decrease of blood pressure was observed only with fenofibrate. LVH was assessed from heart-weight/body weight ratio, histology and brain natriuretic peptide expression. As oxidative stress is linked with hypertrophy, serum and cardiac malondialdehyde and cardiac 3-nitrotyrosine levels were determined. Compared to untreated SHR, LVH and oxidative stress were lower on supplementation with MCT, but higher on treatment with fenofibrate. The observations indicate that reduction of blood pressure is not essentially accompanied by reduction of LVH, and that, progressive cardiac remodeling can be prevented with decrease in oxidative stress. Contrary to the notion that reactivation of PPAR-α is detrimental; the study substantiates that cardiac response to stimulation of PPAR-α is ligand specific.

Cardiac metabolism in hypertrophy and heart failure: implications for therapy

The heart consumes huge amounts of energy to fulfil its function as a relentless pump. A highly sophisticated system of energy generation based on flexibility of substrate use and efficient energy production, effective energy sensing and energy transfer ensures function of the healthy heart across a range of physiological situations. In left ventricular hypertrophy and heart failure, these processes become disturbed, leading as will be discussed to impaired cardiac energetic status and to further impairment of cardiac function. These metabolic disturbances form a potential target for therapy.

Cardiac metabolism and its interactions with contraction, growth, and survival of cardiomyocytes

The network for cardiac fuel metabolism contains intricate sets of interacting pathways that result in both ATP-producing and non-ATP-producing end points for each class of energy substrates. The most salient feature of the network is the metabolic flexibility demonstrated in response to various stimuli, including developmental changes and nutritional status. The heart is also capable of remodeling the metabolic pathways in chronic pathophysiological conditions, which results in modulations of myocardial energetics and contractile function. In a quest to understand the complexity of the cardiac metabolic network, pharmacological and genetic tools have been engaged to manipulate cardiac metabolism in a variety of research models. In concert, a host of therapeutic interventions have been tested clinically to target substrate preference, insulin sensitivity, and mitochondrial function. In addition, the contribution of cellular metabolism to growth, survival, and other signaling pathways through the production of metabolic intermediates has been increasingly noted. In this review, we provide an overview of the cardiac metabolic network and highlight alterations observed in cardiac pathologies as well as strategies used as metabolic therapies in heart failure. Lastly, the ability of metabolic derivatives to intersect growth and survival are also discussed.

Enhancing the metabolic substrate: PPAR-alpha agonists in heart failure

The prognosis for patients diagnosed with heart failure has significantly improved over the past three decades; however, the disease still confers a high degree of morbidity and mortality. Current treatments for chronic heart failure have focused primarily on blocking neurohormonal signaling and optimizing hemodynamic parameters. Although significant resources have been devoted toward the development of new pharmaceutical therapies for heart failure, few new drugs have been designed to target myocardial metabolic pathways despite growing evidence that on a fundamental level chronic heart failure can be characterized as an imbalance between myocardial energy demand and supply. Disruptions in myocardial energy pathways are evident as the myocardium is unable to generate sufficient amounts of ATP with advancing stages of heart failure. Down-regulation of fatty acid oxidation likely contributes to the phenotype of the "energy starved" heart. Fibrates are small molecule agonists of PPARα pathways that have been used to treat dyslipidemia. Although never used therapeutically in clinical heart failure, PPARα agonists have been shown to enhance fatty acid oxidation, improve endothelial cell function, and decrease myocardial fibrosis and hypertrophy in animal models of heart failure. In light of their excellent clinical safety profile, PPARα agonists may improve outcomes in patients suffering from systolic heart failure by augmenting myocardial ATP production in addition to targeting maladaptive hypertrophic pathways.

Dietary fat and heart failure: moving from lipotoxicity to lipoprotection

There is growing evidence suggesting that dietary fat intake affects the development and progression of heart failure. Studies in rodents show that in the absence of obesity, replacing refined carbohydrate with fat can attenuate or prevent ventricular expansion and contractile dysfunction in response to hypertension, infarction, or genetic cardiomyopathy. Relatively low intake of n-3 polyunsaturated fatty acids from marine sources alters cardiac membrane phospholipid fatty acid composition, decreases the onset of new heart failure, and slows the progression of established heart failure. This effect is associated with decreased inflammation and improved resistance to mitochondrial permeability transition. High intake of saturated, monounsaturated, or n-6 polyunsaturated fatty acids has also shown beneficial effects in rodent studies. The underlying mechanisms are complex, and a more thorough understanding is needed of the effects on cardiac phospholipids, lipid metabolites, and metabolic flux in the normal and failing heart. In summary, manipulation of dietary fat intake shows promise in the prevention and treatment of heart failure. Clinical studies generally support high intake of n-3 polyunsaturated fatty acids from marine sources to prevent and treat heart failure. Additional clinical and animals studies are needed to determine the optimal diet in terms of saturated, monounsaturated, and n-6 polyunsaturated fatty acids intake for this vulnerable patient population.

Mitochondrial protein phosphorylation as a regulatory modality: implications for mitochondrial dysfunction in heart failure

Phosphorylation of mitochondrial proteins has been recognized for decades, and the regulation of pyruvate- and branched-chain α-ketoacid dehydrogenases by an atypical kinase/phosphatase cascade is well established. More recently, the development of new mass spectrometry-based technologies has led to the discovery of many novel phosphorylation sites on a variety of mitochondrial targets. The evidence suggests that the major classes of kinase and several phosphatases may be present at the mitochondrial outer membrane, intermembrane space, inner membrane, and matrix, but many questions remain to be answered as to the location, timing, and reversibility of these phosphorylation events and whether they are functionally relevant. The authors review phosphorylation as a mitochondrial regulatory strategy and highlight its possible role in the pathophysiology of cardiac hypertrophy and failure.

Association of the peroxisome proliferator-activated receptor α gene L162V polymorphism with stage C heart failure

OBJECTIVE

To analyze whether genetic variants of PPARA are associated with the development of stage C heart failure.

METHODS

We analyzed the distribution of the rs1800206, rs4253778 and rs135551 polymorphisms in genomic DNA extracted from peripheral blood cells of 534 patients in different heart failure stages and 63 healthy individuals. The mRNA expression of the peroxisome proliferator-activated receptor (PPAR)α target genes long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) and medium-chain acyl-CoA dehydrogenase (MCAD) was measured in myocardial biopsies of a subgroup of stage B and C patients. Functional studies were performed in HL-1 cardiomyocytes.

RESULTS

The V162 allele of the rs1800206 polymorphism was more frequent in stage C patients than in stage A and B patients and healthy individuals. Patients with the V162 allele exhibited decreased myocardial LCHAD and MCAD mRNA expression as compared to L162 homozygote patients. In addition, stage C patients exhibited lower myocardial LCHAD and MCAD mRNA expression than stage B patients. Cardiomyocytes transfected with the V162 allele presented decreased PPARα transcriptional activity, LCHAD mRNA expression and ATP production compared to cardiomyocytes transfected with the L162 variant.

CONCLUSIONS

These findings suggest that the V162 allele of the human PPARA gene can be a new risk factor in the development of stage C heart failure, likely via depressed cardiac PPARα activity.

The PPARalpha-PGC-1alpha Axis Controls Cardiac Energy Metabolism in Healthy and Diseased Myocardium

The mammalian myocardium is an omnivorous organ that relies on multiple substrates in order to fulfill its tremendous energy demands. Cardiac energy metabolism preference is regulated at several critical points, including at the level of gene transcription. Emerging evidence indicates that the nuclear receptor PPARα and its cardiac-enriched coactivator protein, PGC-1α, play important roles in the transcriptional control of myocardial energy metabolism. The PPARα-PGC-1α complex controls the expression of genes encoding enzymes involved in cardiac fatty acid and glucose metabolism as well as mitochondrial biogenesis. Also, evidence has emerged that the activity of the PPARα-PGC-1α complex is perturbed in several pathophysiologic conditions and that altered activity of this pathway may play a role in cardiomyopathic remodeling. In this review, we detail the current understanding of the effects of the PPARα-PGC-1α axis in regulating mitochondrial energy metabolism and cardiac function in response to physiologic and pathophysiologic stimuli.

Modulating fatty acid oxidation in heart failure

In the advanced stages of heart failure, many key enzymes involved in myocardial energy substrate metabolism display various degrees of down-regulation. The net effect of the altered metabolic phenotype consists of reduced cardiac fatty oxidation, increased glycolysis and glucose oxidation, and rigidity of the metabolic response to changes in workload. Is this metabolic shift an adaptive mechanism that protects the heart or a maladaptive process that accelerates structural and functional derangement? The question remains open; however, the metabolic remodelling of the failing heart has induced a number of investigators to test the hypothesis that pharmacological modulation of myocardial substrate utilization might prove therapeutically advantageous. The present review addresses the effects of indirect and direct modulators of fatty acid (FA) oxidation, which are the best pharmacological agents available to date for 'metabolic therapy' of failing hearts. Evidence for the efficacy of therapeutic strategies based on modulators of FA metabolism is mixed, pointing to the possibility that the molecular/biochemical alterations induced by these pharmacological agents are more complex than originally thought. Much remains to be understood; however, the beneficial effects of molecules such as perhexiline and trimetazidine in small clinical trials indicate that this promising therapeutic strategy is worthy of further pursuit.

Myocardial fatty acid metabolism in health and disease

There is a constant high demand for energy to sustain the continuous contractile activity of the heart, which is met primarily by the beta-oxidation of long-chain fatty acids. The control of fatty acid beta-oxidation is complex and is aimed at ensuring that the supply and oxidation of the fatty acids is sufficient to meet the energy demands of the heart. The metabolism of fatty acids via beta-oxidation is not regulated in isolation; rather, it occurs in response to alterations in contractile work, the presence of competing substrates (i.e., glucose, lactate, ketones, amino acids), changes in hormonal milieu, and limitations in oxygen supply. Alterations in fatty acid metabolism can contribute to cardiac pathology. For instance, the excessive uptake and beta-oxidation of fatty acids in obesity and diabetes can compromise cardiac function. Furthermore, alterations in fatty acid beta-oxidation both during and after ischemia and in the failing heart can also contribute to cardiac pathology. This paper reviews the regulation of myocardial fatty acid beta-oxidation and how alterations in fatty acid beta-oxidation can contribute to heart disease. The implications of inhibiting fatty acid beta-oxidation as a potential novel therapeutic approach for the treatment of various forms of heart disease are also discussed.

Fenofibrate attenuates endothelial monocyte adhesion in chronic heart failure: an in vitro study

BACKGROUND

Inflammation is implicated in chronic heart failure (CHF). In this study, the potential inhibitory effect of peroxisome proliferator-activated receptor-alpha (PPARalpha) activator fenofibrate on monocyte adhesion in CHF patients was investigated in vitro.

MATERIALS AND METHODS

Isolated peripheral blood mononuclear cells (PBMCs) were collected from 36 patients (aged 65 +/- 8 years) with symptomatic CHF and from 12 healthy control subjects. The cultured human aortic endothelial cells (HAECs) were stimulated with or without 2 ng mL(-1) tumour necrosis factor-alpha (TNF-alpha) and the inhibitory effects of fenofibrate at 25, 50, 100 and 200 microM on endothelial mononuclear cell adhesion were tested. Furthermore, the HAECs were stimulated with 70% sera obtained from CHF patients and control individuals, respectively, with or without pretreatments with fenofibrate. The endothelial expression of vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) was then confirmed by mRNA expression and Western blot.

RESULTS

We found that the increased adhesion of PBMCs to TNF-alpha-stimulated HAECs in CHF patients was reduced when the HAECs were pretreated with fenofibrate (31% inhibition, P = 0.0121). However, pretreatment of the isolated PBMCs collected from CHF patients with fenofibrate failed to suppress their adherence to TNF-alpha-stimulated HAECs. Furthermore, stimulation of cultured HAECs with CHF patient sera significantly increased VCAM-1 and ICAM-1 expression, which could also be inhibited by fenofibrate.

CONCLUSIONS

The fenofibrate directly inhibits monocyte binding by TNF-alpha-activated HAECs, probably through preventing up-regulation of cell adhesion molecules by endothelial cells in response to inflammatory stimuli. This PPARalpha activator may have the potential to ameliorate vascular inflammation in patients with CHF.

The peroxisome proliferator-activated receptor-alpha (PPAR-alpha) agonist, AVE8134, attenuates the progression of heart failure and increases survival in rats

AIM

To investigate the efficacy of the peroxisome proliferator-activated receptor-alpha (PPARalpha) agonist, AVE8134, in cellular and experimental models of cardiac dysfunction and heart failure.

METHODS

In Sprague Dawley rats with permanent ligation of the left coronary artery (post-MI), AVE8134 was compared to the PPARgamma agonist rosiglitazone and in a second study to the ACE inhibitor ramipril. In DOCA-salt sensitive rats, efficacy of AVE8134 on cardiac hypertrophy and fibrosis was investigated. Finally, AVE8134 was administered to old spontaneously hypertensive rats (SHR) at a non-blood pressure lowering dose with survival as endpoint. In cellular models, we studied AVE8134 on hypertrophy in rat cardiomyocytes, nitric oxide signaling in human endothelial cells (HUVEC) and LDL-uptake in human MonoMac-6 cells.

RESULTS

In post-MI rats, AVE8134 dose-dependently improved cardiac output, myocardial contractility and relaxation and reduced lung and left ventricular weight and fibrosis. In contrast, rosiglitazone exacerbated cardiac dysfunction. Treatment at AVE8134 decreased plasma proBNP and arginine and increased plasma citrulline and urinary NOx/creatinine ratio. In DOCA rats, AVE8134 prevented development of high blood pressure, myocardial hypertrophy and cardiac fibrosis, and ameliorated endothelial dysfunction. Compound treatment increased cardiac protein expression and phosphorylation of eNOS. In old SHR, treatment with a low dose of AVE8134 improved cardiac and vascular function and increased life expectancy without lowering blood pressure. AVE8134 reduced phenylephrine-induced hypertrophy in adult rat cardiomyocytes. In HUVEC, Ser-1177-eNOS phosphorylation but not eNOS expression was increased. In monocytes, AVE8134 increased the expression of CD36 and the macrophage scavenger receptor 1, resulting in enhanced uptake of oxidized LDL.

CONCLUSION

The PPARalpha agonist AVE8134 prevents post-MI myocardial hypertrophy, fibrosis and cardiac dysfunction. AVE8134 has beneficial effects against hypertension-induced organ damages, resulting in decreased mortality. The compound exerts its protective properties by a direct effect on cardiomyocyte hypertrophy, but also indirectly via monocyte signaling and increased endothelial NO production.Acta Pharmacologica Sinica (2009) 30: 935-946; doi: 10.1038/aps.2009.58; published online 8 June 2009.

Fenofibrate inhibits aldosterone-induced apoptosis in adult rat ventricular myocytes via stress-activated kinase-dependent mechanisms

Aldosterone induces extracellular signal-regulated kinase (ERK)-dependent cardiac remodeling. Fenofibrate improves cardiac remodeling in adult rat ventricular myocytes (ARVM) partly via inhibition of aldosterone-induced ERK1/2 phosphorylation and inhibition of matrix metalloproteinases. We sought to determine whether aldosterone caused apoptosis in cultured ARVM and whether fenofibrate ameliorated the apoptosis. Aldosterone (1 microM) induced apoptosis by increasing terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL)-positive nuclei in ARVM. Spironolactone (100 nM), an aldosterone receptor antagonist, but not RU-486, a glucocorticoid receptor, inhibited aldosterone-mediated apoptosis, indicating that the mineralocorticoid receptor (MR) plays a role. SP-600125 (3 microM)-a selective inhibitor of c-Jun NH(2)-terminal kinase (JNK)-inhibited aldosterone-induced apoptosis in ARVM. Although aldosterone increased the expression of both stress-activated protein kinases, pretreatment with fenofibrate (10 microM) decreased aldosterone-mediated apoptosis by inhibiting only JNK phosphorylation and the aldosterone-induced increases in Bax, p53, and cleaved caspase-3 and decreases in Bcl-2 protein expression in ARVM. In vivo studies demonstrated that chronic fenofibrate (100 mg*kg body wt(-1)*day(-1)) inhibited myocardial Bax and increased Bcl-2 expression in aldosterone-induced cardiac hypertrophy. Similarly, eplerenone, a selective MR inhibitor, used in chronic pressure-overload ascending aortic constriction inhibited myocardial Bax expression but had no effect on Bcl-2 expression. Therefore, involvement of JNK MAPK-dependent mitochondrial death pathway mediates ARVM aldosterone-induced apoptosis and is inhibited by fenofibrate, a peroxisome proliferator-activated receptor (PPAR)alpha ligand. Fenofibrate mediates beneficial effects in cardiac remodeling by inhibiting programmed cell death and the stress-activated kinases.

PPAR transcriptional activator complex polymorphisms and the promise of individualized therapy for heart failure

The PPAR gene pathway consists of interrelated genes that encode transcription factors, enzymes, and downstream targets which coordinately act to regulate cellular processes central to glucose and lipid metabolism. The pathway includes the PPAR genes themselves, other class II nuclear hormone receptor transcription factors within the PPAR family, PPAR co-activators, PPAR co-repressors, and downstream metabolic gene targets. This review focuses on the transcription factors that comprise the PPAR transcriptional activator complex--the PPARs (PPARalpha, PPARbeta, or PPARgamma), PPAR heterodimeric partners, such as RXRalpha, and PPAR co-activators, such as PPARgamma coactivator 1alpha (PGC-1alpha) and the estrogen-related receptors (ERRalpha, ERRbeta, and ERRgamma). These transcription factors have been implicated in the development of myocardial hypertrophy and dilated cardiomyopathy as well as response to myocardial ischemia/infarction and, by association, ischemic cardiomyopathy. Human expression studies and animal data are presented as the background for a discussion of the emerging field of pharmacogenetics as it applies to these genes and the consequent implications for the individualization of therapy for patients with heart failure.

Metabolic remodelling of the failing heart: beneficial or detrimental?

The failing heart is characterized by alterations in energy metabolism, including mitochondrial dysfunction and a reduction in fatty acid (FA) oxidation rate, which is partially compensated by an increase in glucose utilization. Together, these changes lead to an impaired capacity to convert chemical energy into mechanical work. This has led to the concept that supporting cardiac energy conversion through metabolic interventions provides an important adjuvant therapy for heart failure. The potential success of such a therapy depends on whether the shift from FA towards glucose utilization should be considered beneficial or detrimental, a question still incompletely resolved. In this review, the current status of the literature is evaluated and possible causes of observed discrepancies are discussed. It is cautiously concluded that for the failing heart, from a therapeutic point of view, it is preferable to further stimulate glucose oxidation rather than to normalize substrate metabolism by stimulating FA utilization. Whether this also applies to the pre-stages of cardiac failure remains to be established.

Key pathways associated with heart failure development revealed by gene networks correlated with cardiac remodeling

Heart failure (HF) is the leading cause of morbidity and mortality in the industrialized world. While the transcriptomic changes in end-stage failing myocardium have received much attention, no information is available on the gene expression patterns associated with the development of HF in large mammals. Therefore, we used a well-controlled canine model of tachycardia-induced HF to examine global gene expression in left ventricular myocardium with Affymetrix canine oligonucleotide arrays at various stages after initiation of rapid ventricular pacing (days 3, 7, 14, and 21). The gene expression data were complemented with measurements of action potential duration, conduction velocity, and left ventricular end diastolic pressure, and dP/dt(max) over the time course of rapid ventricular pacing. As a result, we present a phenotype-centered gene association network, defining molecular systems that correspond temporally to hemodynamic and electrical remodeling processes. Gene Ontology analysis revealed an orchestrated regulation of oxidative phosphorylation, ATP synthesis, cell signaling pathways, and extracellular matrix components, which occurred as early as 3 days after the initiation of ventricular pacing, coinciding with the early decline in left ventricular pump function and prolongation of action potential duration. The development of clinically overt left ventricular dysfunction was associated with few additional changes in the myocardial transcriptome. We conclude that the majority of tachypacing-induced transcriptional changes occur early after initiation of rapid ventricular pacing. As the transition to overt HF is characterized by few additional transcriptional changes, posttranscriptional modifications may be more critical in regulating myocardial structure and function during later stages of HF.

Role of diet and fuel overabundance in the development and progression of heart failure

Under physiological conditions, the human heart derives energy from glucose, fatty acids, and/or lactate depending upon substrate availability, circulating hormone levels, and nutritional status. Circulating free fatty acid and glucose levels often exceed the normal range, as observed with type 2 diabetes, obesity, or physical inactivity. Chronic exposure of the heart to high plasma levels of free fatty acids may cause accumulation of toxic lipid intermediates within cardiomyocytes. Furthermore, suppression of glucose oxidation by increased fatty acid uptake shunts glucose into the oxidative pentose phosphate and hexosamine biosynthetic pathways, both of which yield potentially harmful products. Noxious derivatives of aberrant glucose and fatty acid oxidation can activate signalling cascades leading to myocyte dysfunction or death, processes termed 'glucotoxicity' and 'lipotoxicity'. This review discusses the effects of dietary extremes (e.g. high fat and high carbohydrate consumption) and substrate overabundance in the context of heart failure (HF) development and progression. Emerging data suggest that substrate excess leads to cardiac dysfunction and HF, which may be prevented or slowed by maintaining low body fat and high insulin sensitivity and consuming a diet of low glycaemic load that is high in mono- and polyunsaturated fatty acids.