Amphipathic metabolites and membrane dysfunction in ischemic myocardium

L-Palmitoylcarnitine potentiates plasmin and tPA to inhibit thrombosis

L-Palmitoylcarnitine (L-PC) is an important endogenous fatty acid metabolite. Its classical biological functions are involved in the regulations of membrane molecular dynamics and the β-oxidation of fatty acids. Decreased plasma long-chain acylcarnitines showed the association of venous thrombosis, implying anticoagulant activity of the metabolites and inspiring us to investigate if and how L-PC, a long-chain acylcarnitine, takes part in coagulation. Here we show that L-PC exerted anti-coagulant effects by potentiating the enzymatic activities of plasmin and tissue plasminogen activator (tPA). L-PC directly interacts with plasmin and tPA with an equilibrium dissociation constant (KD) of 6.47 × 10-9 and 4.46 × 10-9 M, respectively, showing high affinities. In mouse model, L-PC administration significantly inhibited FeCl3-induced arterial thrombosis. It also mitigated intracerebral thrombosis and inflammation in a transient middle cerebral artery occlusion (tMCAO) mouse model. L-PC induced little bleeding complications. The results show that L-PC has anti-thrombotic function by potentiating plasmin and tPA.

Ameliorative effect of flavocoxid on cyclophosphamide-induced cardio and neurotoxicity via targeting the GM-CSF/NF-κB signaling pathway

Cyclophosphamide (Cyclo) is a chemotherapeutic agent used as an immunosuppressant and as a treatment for many cancerous diseases. Many previous pieces of literature proved the marked cardio and neurotoxicity of the drug. Thus, this research provides evidence on the alleviative effect of flavocoxid on the cardiac and brain toxicity of cyclophosphamide in mice and determines its underlying mechanisms. Flavocoxid (Flavo) is a potent antioxidant and anti-inflammatory agent that inhibits the peroxidase activity of cyclooxygenase (COX-1 and COX-2) enzymes and 5-lipooxygenase (5-LOX). Flavo was administered orally (20 mg/kg) for 2 weeks, followed by Cyclo (100 mg/kg, i.p.) on day 14. Higher heart and brain weight indices, serum lactate dehydrogenase (LDH), creatine kinase (CK-MB), and nitric oxide (NO) were mitigated following Flavo administration. Flavo modulated oxidative stress biomarkers (malonaldehyde (MDA), glutathione (GSH), and superoxide dismutase (SOD)), tumor necrosis factor-α (TNF-α), and interleukin (IL)-1β. Additionally, cardiac troponin I (cTn-I), nuclear factor kappa B (NF-κB), brain amyloid precursor protein (APP), and granulocyte macrophage colony-stimulating factor (GM-CSF) were decreased by Flavo administration. Moreover, Flavo ameliorated heart and brain histopathological changes and caspase-3 levels. Collectively, Flavo (20 mg/kg) for 14 days showed significant cardio and neuroprotective effects due to its antioxidant, anti-inflammatory, and antiapoptotic activities via modulation of oxidative stress, inflammation, and the GM-CSF/NF-κB signaling pathway.

Acylcarnitines: Nomenclature, Biomarkers, Therapeutic Potential, Drug Targets, and Clinical Trials

Acylcarnitines are fatty acid metabolites that play important roles in many cellular energy metabolism pathways. They have historically been used as important diagnostic markers for inborn errors of fatty acid oxidation and are being intensively studied as markers of energy metabolism, deficits in mitochondrial and peroxisomal β -oxidation activity, insulin resistance, and physical activity. Acylcarnitines are increasingly being identified as important indicators in metabolic studies of many diseases, including metabolic disorders, cardiovascular diseases, diabetes, depression, neurologic disorders, and certain cancers. The US Food and Drug Administration-approved drug L-carnitine, along with short-chain acylcarnitines (acetylcarnitine and propionylcarnitine), is now widely used as a dietary supplement. In light of their growing importance, we have undertaken an extensive review of acylcarnitines and provided a detailed description of their identity, nomenclature, classification, biochemistry, pathophysiology, supplementary use, potential drug targets, and clinical trials. We also summarize these updates in the Human Metabolome Database, which now includes information on the structures, chemical formulae, chemical/spectral properties, descriptions, and pathways for 1240 acylcarnitines. This work lays a solid foundation for identifying, characterizing, and understanding acylcarnitines in human biosamples. We also discuss the emerging opportunities for using acylcarnitines as biomarkers and as dietary interventions or supplements for many wide-ranging indications. The opportunity to identify new drug targets involved in controlling acylcarnitine levels is also discussed. SIGNIFICANCE STATEMENT: This review provides a comprehensive overview of acylcarnitines, including their nomenclature, structure and biochemistry, and use as disease biomarkers and pharmaceutical agents. We present updated information contained in the Human Metabolome Database website as well as substantial mapping of the known biochemical pathways associated with acylcarnitines, thereby providing a strong foundation for further clarification of their physiological roles.

Mycobacterium tuberculosis encodes a YhhN family membrane protein with lysoplasmalogenase activity that protects against toxic host lysolipids

The pathogen Mycobacterium tuberculosis (M.tb) resides in human macrophages, wherein it exploits host lipids for survival. However, little is known about the interaction between M.tb and macrophage plasmalogens, a subclass of glycerophospholipids with a vinyl ether bond at the sn-1 position of the glycerol backbone. Lysoplasmalogens, produced from plasmalogens by hydrolysis at the sn-2 carbon by phospholipase A2, are potentially toxic but can be broken down by host lysoplasmalogenase, an integral membrane protein of the YhhN family that hydrolyzes the vinyl ether bond to release a fatty aldehyde and glycerophospho-ethanolamine or glycerophospho-choline. Curiously, M.tb encodes its own YhhN protein (MtbYhhN), despite having no endogenous plasmalogens. To understand the purpose of this protein, the gene for MtbYhhN (Rv1401) was cloned and expressed in Mycobacterium smegmatis (M.smeg). We found the partially purified protein exhibited abundant lysoplasmalogenase activity specific for lysoplasmenylethanolamine or lysoplasmenylcholine (pLPC) (Vmax∼15.5 μmol/min/mg; Km∼83 μM). Based on cell density, we determined that lysoplasmenylethanolamine, pLPC, lysophosphatidylcholine, and lysophosphatidylethanolamine were not toxic to M.smeg cells, but pLPC and LPC were highly toxic to M.smeg spheroplasts, which are cell wall-deficient mycobacterial forms. Importantly, spheroplasts prepared from M.smeg cells overexpressing MtbYhhN were protected from membrane disruption/lysis by pLPC, which was rapidly depleted from the media. Finally, we found that overexpression of full-length MtbYhhN in M.smeg increased its survival within human macrophages by 2.6-fold compared to vector controls. These data support the hypothesis that MtbYhhN protein confers a growth advantage for mycobacteria in macrophages by cleaving toxic host pLPC into potentially energy-producing products.

iPLA2β Contributes to ER Stress-Induced Apoptosis during Myocardial Ischemia/Reperfusion Injury

Both calcium-independent phospholipase A2 beta (iPLA2β) and endoplasmic reticulum (ER) stress regulate important pathophysiological processes including inflammation, calcium homeostasis and apoptosis. However, their roles in ischemic heart disease are poorly understood. Here, we show that the expression of iPLA2β is increased during myocardial ischemia/reperfusion (I/R) injury, concomitant with the induction of ER stress and the upregulation of cell death. We further show that the levels of iPLA2β in serum collected from acute myocardial infarction (AMI) patients and in samples collected from both in vivo and in vitro I/R injury models are significantly elevated. Further, iPLA2β knockout mice and siRNA mediated iPLA2β knockdown are employed to evaluate the ER stress and cell apoptosis during I/R injury. Additionally, cell surface protein biotinylation and immunofluorescence assays are used to trace and locate iPLA2β. Our data demonstrate the increase of iPLA2β augments ER stress and enhances cardiomyocyte apoptosis during I/R injury in vitro and in vivo. Inhibition of iPLA2β ameliorates ER stress and decreases cell death. Mechanistically, iPLA2β promotes ER stress and apoptosis by translocating to ER upon myocardial I/R injury. Together, our study suggests iPLA2β contributes to ER stress-induced apoptosis during myocardial I/R injury, which may serve as a potential therapeutic target against ischemic heart disease.

Resorcinol as a highly efficient aromatic electron donor in bioelectrochemical system

Bioelectrochemical systems (BESs) have been known as a promising technology for accelerating aromatic contaminants degradation and energy recovery. However, most existing studies concentrate on aromatics metabolized through a benzoyl-CoA pathway while those metabolized through other pathways are limited. In this work, resorcinol, a typical aromatic contaminant as well as a key central intermediate (other than benzoyl-CoA) involved in aromatics anaerobic biodegradation, was studied in BESs. Unlike the general impression of the relatively poor organic-to-current performance in the aromatics driven BESs, high efficiencies for resorcinol-fed BESs were observed with a current density and coulombic efficiency of up to 0.26 ± 0.05 mAcm^-2 and 74.3 ± 10.7%, respectively. The higher performance likely correlates to the readily fermentable property of resorcinol. Analysis of microbial communities in the biofilm suggests a syntrophic interaction between resorcinol-degrading bacteria (RDB) and anode-respiring bacteria (ARB) was involved in current generation. Additional tests involving the removal of accumulated acetate through fast resorcinol feeding indicates that a mechanism based on direct utilization of resorcinol for current generation may also exist. This study extends the knowledge for the fate of aromatics in BESs and indicates that aromatics entering into the resorcinol metabolic pathway can be treated efficiently with good energy recovery efficiency in BESs.

Long-Chain Acylcarnitines and Cardiac Excitation-Contraction Coupling: Links to Arrhythmias

A growing number of metabolomic studies have associated high circulating levels of the amphiphilic fatty acid metabolites, long-chain acylcarnitines (LCACs), with cardiovascular disease (CVD) risk. These studies show that plasma LCAC levels can be correlated with the stage and severity of CVD and with indices of cardiac hypertrophy and ventricular function. Complementing these recent clinical associations is an extensive body of basic research that stems mostly from the twentieth century. These works, performed in cardiomyocyte and multicellular preparations from animal and cell models, highlight stereotypical derangements in cardiac electrophysiology induced by exogenous LCAC treatment that promote arrhythmic muscle behavior. In many cases, this is coupled with acute inotropic modulation; however, whether LCACs increase or decrease contractility is inconclusive. Linked to the electromechanical alterations induced by LCAC exposure is an array of effects on cardiac excitation-contraction coupling mechanisms that overload the cardiomyocyte cytosol with Na⁺ and Ca²⁺ ions. The aim of this review is to revisit this age-old literature and collate it with recent findings to provide a pathophysiological context for the growing body of metabolomic association studies that link circulating LCACs with CVD.

Intralipid Restoration of Myocardial Contractions Following Bupivacaine-Induced Asystole: Concentration- and Time-Dependence In Vitro

BACKGROUND

The concentration- and time-response relationships of lipid emulsion (LE; Intralipid) on the recovery of myocardial contractility following bupivacaine (BPV)-induced asystole are poorly defined.

METHODS

After achieving asystole by 500-μM BPV, varied concentrations of LE were applied to determine the recovery of stimulated contractile responses and contractions in the cardiac tissues of guinea pigs at a 1.2-Hz stimulation rate. These experiments were performed with LE in either a recirculating (2%-16%) or washout (nonrecirculating) condition (0.05%-12%) for 60 minutes. The effect of LE itself (0.05%-12%) was examined. Oxfenicine was used to evaluate the metabolic action of LE to reverse asystole. BPV concentrations in solution and myocardial tissues were measured.

RESULTS

In the recirculation condition, partial recovery of contractile forces was observed for 60 minutes at 4%, 8%, and 12% LE. A contracture followed after exposure to 16% LE in some asystolic muscles. In the washout experiments, following asystole, LE (0.05%-12%) had no effect on the recovery time of the first and regular contractile responses. LE (0.1%-8%) restored contractility to baseline levels after 45 minutes; partial recovery was shown with lower (0.05%) and higher (12%) concentrations. Oxfenicine did not alter the recovery of contractile forces. Contractile depression was observed with 12% LE alone. Concentration-related reduction of tissue BPV concentration by LE was observed in both circulating conditions.

CONCLUSIONS

LE induced time- and concentration-dependent recovery of stimulated myocardial contractions from BPV-induced asystole. The lipid uptake effect, along with other undefined mechanisms of LE, seems to contribute to the recovery of contractile function; however, the LE effect on myocardial metabolism is less likely involved at this concentration (500 μM) of BPV.

Myocardial Response to Pretreatment with L-Carnitine in Patients with Cardiac Valve Replacement

Twenty-one patients undergoing mitral valve replacement (MVR) with either isolated or combined valvular procedure were investigated to determine the ef fect of randomized and prospective administration of L-carnitine (car) chloride on myocardial function. Carnitine chloride (1800 mg/day, for seven consecu tive days just prior to MVR) was given orally to 9 patients (car-treated group) who were compared with 12 car-untreated patients (control group) subjected to the same procedure. Valve replacement was performed using the Bjork-Shiley mechanical prosthesis in aortic and mitral position and bioprosthesis in tricuspid position in both groups under cardiopulmonary bypass (CPB) associated with cold potassium-magnesium cardioplegia and systemic hypothermia. Preopera tive and intraoperative clinical profile (age, functional class, duration of aortic clamp and CPB, and level of hypothermia) was well matched in both groups. Free, short-chain acyl, long-chain acyl, and total Car were measured in the papil lary muscle excised adjacent to the free wall of the left ventricle at the time of valvular surgery. Heart rate and mean arterial pressure did not differ between the two groups. Cardiac index was 3.44 ± 0.08 and 3.82 ± 0.13 L/m2/min in the control and car-treated groups, respectively, (p < 0.05). Dobutamine (DOB) infusion rate was 8.55 ± 0.73 and 5.57 ± 0.95 μg/kg/min in the control and car-treated groups, respectively (p < 0.05). Left ventricular stroke work index (LVSWI)/DOB ratio was 4.50 ± 0.65 and 8.16 ± 1.72 g*m/m 2/beat/unit of DOB, in the control and car-treated groups, respectively (p < 0.05). Long-chain acyl carnitine was 0.224 ± 0.031 and 0.460 ± 0.096 nmoL/mg noncollagenous protein in the control and the car-treated groups, respectively (p<0.05). LVSWI/DOB ratio was well correlated with long-chain acyl carnitine in the tis sue, r = 0.74, n = 18, p<0.001.

These findings suggest that pretreatment with L-carnitine chloride appears to be effective in improving myocardial function in the early phase of reperfu sion following surgery and that long-chain acyl carnitine may play a key role in the enhancement of carnitine-meditated mitochondrial metabolic process.

Standardized Chinese Formula Xin-Ke-Shu inhibits the myocardium Ca(2+) overloading and metabolic alternations in isoproterenol-induced myocardial infarction rats

Xin-Ke-Shu (XKS) is a traditional Chinese patent medicine used for treatment of coronary heart diseases in China. However, its mechanism of action is still unclear. In this paper, the mediation of XKS on the isoproterenol (ISO)-induced myocardial infarction (MI) rat were evaluated based on a tissue-targeted metabonomics in vitro/vivo. The result indicated that twelve metabolic pathways were involved in the therapeutic effect of XKS in vivo, where seven pathways were associated with the Ca²⁺ overloading mechanism. In agreement with regulation on metabolic variations, XKS markedly reversed the over-expressions of three involved proteins including phospholipase A2 IIA (PLA2 IIA), calcium/calmodulin-dependent protein kinase II (CaMK II) and Pro-Caspase-3. The metabolic regulations of XKS on H9c2 cell also partially confirmed its metabolic effect. These metabolic characteristics in vitro/vivo and western blotting analysis suggested that XKS protected from MI metabolic perturbation major via inhibition of Ca²⁺ overloading mechanism. Furthermore, 11 active ingredients of XKS exerted steady affinity with the three proteins through the molecular docking study. Our findings indicate that the metabonomics in vitro/vivo combined with western blotting analysis offers the opportunity to gain insight into the comprehensive efficacy of TCMs on the whole metabolic network.

Long-chain acylcarnitines determine ischaemia/reperfusion-induced damage in heart mitochondria

The accumulation of long-chain fatty acids (FAs) and their CoA and carnitine esters is observed in the ischaemic myocardium after acute ischaemia/reperfusion. The aim of the present study was to identify harmful FA intermediates and their detrimental mechanisms of action in mitochondria and the ischaemic myocardium. In the present study, we found that the long-chain acyl-CoA and acylcarnitine content is increased in mitochondria isolated from an ischaemic area of the myocardium. In analysing the FA derivative content, we discovered that long-chain acylcarnitines, but not acyl-CoAs, accumulate at concentrations that are harmful to mitochondria. Acylcarnitine accumulation in the mitochondrial intermembrane space is a result of increased carnitine palmitoyltransferase 1 (CPT1) and decreased carnitine palmitoyltransferase 2 (CPT2) activity in ischaemic myocardium and it leads to inhibition of oxidative phosphorylation, which in turn induces mitochondrial membrane hyperpolarization and stimulates the production of reactive oxygen species (ROS) in cardiac mitochondria. Thanks to protection mediated by acyl-CoA-binding protein (ACBP), the heart is much better guarded against the damaging effects of acyl-CoAs than against acylcarnitines. Supplementation of perfusion buffer with palmitoylcarnitine (PC) before occlusion resulted in a 2-fold increase in the acylcarnitine content of the heart and increased the infarct size (IS) by 33%. A pharmacologically induced decrease in the mitochondrial acylcarnitine content reduced the IS by 44%. Long-chain acylcarnitines are harmful FA intermediates, accumulating in ischaemic heart mitochondria and inducing inhibition of oxidative phosphorylation. Therefore, decreasing the acylcarnitine content via cardioprotective drugs may represent a novel treatment strategy.

Inhibition of gene expression of carnitine palmitoyltransferase I and heart fatty acid binding protein in cyclophosphamide and ifosfamide-induced acute cardiotoxic rat models

This study investigated whether cyclophosphamide (CP) and ifosfamide (IFO) therapy alters the expression of the key genes engaged in long-chain fatty acid (LCFA) oxidation outside rat heart mitochondria, and if so, whether these alterations should be viewed as a mechanism during CP- and IFO-induced cardiotoxicity. Adult male Wistar albino rats were assigned to one of the six treatment groups: Rats in group 1 (control) and group 2 (L-carnitine) were injected intraperitoneal (i.p.) with normal saline and L-carnitine (200 mg/kg/day), respectively, for 10 successive days. Animals in group 3 (CP group) were injected i.p. with normal saline for 5 days before and 5 days after a single dose of CP (200 mg/kg, i.p.). Rats in group 4 (IFO group) received normal saline for 5 successive days followed by IFO (50 mg/kg/day, i.p.) for 5 successive days. Rats in group 5 (CP-carnitine supplemented) were given the same doses of L-carnitine as group 2 for 5 days before and 5 days after a single dose of CP as group 3. Rats in group 6 (IFO-carnitine supplemented) were given the same doses of L-carnitine as group 2 for 5 days before and 5 days concomitant with IFO as group 4. Immediately, after the last dose of the treatment protocol, blood samples were withdrawn and animals were killed for biochemical, histopathological and gene expression studies. Treatment with CP and IFO significantly decreased expression of heart fatty acid binding protein (H-FABP) and carnitine palmitoyltransferase I (CPT I) genes in cardiac tissues. Moreover, CP but not IFO significantly increased acetyl-CoA carboxylase2 mRNA expression. Conversely, IFO but not CP significantly decreased mRNA expression of malonyl-CoA decarboxylase. Both CP and IFO significantly increased serum lactate dehydrogenase, creatine kinase isoenzyme MB and malonyl-CoA content and histopathological lesions in cardiac tissues. Interestingly, carnitine supplementation completely reversed all the biochemical, histopathological and gene expression changes induced by CP and IFO to the control values, except CPT I mRNA, and protein expression remained inhibited by IFO. Data from the current study suggest, for the first time, that (1) CP and IFO therapy is associated with the inhibition of the expression of H-FABP and CPT I genes in cardiac tissues with the consequent inhibition of mitochondrial transport and oxidation of LCFA. (2) The progressive increase in cardiotoxicity enzymatic indices and the decrease in H-FABP and CPT I expression may point to the possible contribution of these genes to CP- and IFO-induced cardiotoxicity.

The YhhN protein of Legionella pneumophila is a Lysoplasmalogenase

Lysoplasmalogenase catalyzes hydrolytic cleavage of the vinyl-ether bond of lysoplasmalogen to yield fatty aldehyde and glycerophospho-ethanolamine or glycerophospho-choline. We recently purified lysoplasmalogenase from rat liver microsomes and identified the protein as TMEM86B, an integral membrane protein that is a member of the YhhN family found in numerous species of eukaryotes and bacteria. To test the hypothesis that bacterial YhhN proteins also function as lysoplasmalogenase enzymes, we cloned the Lpg1991 gene of Legionella pneumophila, which encodes a 216 amino acid YhhN protein (LpYhhN), and expressed it in Escherichia coli as a C-terminal-GFP-His8-fusion. Membranes were solubilized and the fusion protein was purified by nickel-affinity chromatography, cleaved with Tobacco Etch Virus protease, and subjected to a reverse nickel column to purify the un-tagged LpYhhN. Both the fusion protein and un-tagged LpYhhN exhibit robust lysoplasmalogenase activity, cleaving the vinyl-ether bond of lysoplasmalogen with a Vmax of 12 µmol/min/mg protein and a Km of 45 μM. LpYhhN has no activity on diradyl plasmalogen, 1-alkenyl-glycerol, and monoacylglycerophospho-ethanolamine or monoacylglycerophospho-choline; the pH optimum is 6.5-7.0. These properties are very similar to mammalian TMEM86B. Sequence analysis suggests that YhhN proteins contain eight transmembrane helices, an N-in/C-in topology, and about 5 highly conserved amino acid residues that may form an active site. This work is the first to demonstrate a function for a bacterial YhhN protein, as a vinyl ether bond hydrolase specific for lysoplasmalogen. Since L. pneumophila does not contain endogenous plasmalogens, we hypothesize that LpYhhN may serve to protect the bacterium from lysis by lysoplasmalogen derived from plasmalogens of the host.

Effects of fatty acid provision during severe hypoxia on routine and maximal performance of the in situ tilapia heart

The ability to maintain stable cardiac function during environmental hypoxia exposure is crucial for hypoxia tolerance in animals and depends upon the maintenance of cardiac energy balance as well as the state of the heart's extracellular environment (e.g., availability of metabolic fuels). Hypoxic depression of plasma [non-esterified fatty acids] (NEFA), an important cardiac aerobic fuel, is a common response in many species of hypoxia-tolerant fishes, including tilapia. We tested the hypothesis that decreased plasma [NEFA] is important for maintaining stable cardiac function during and following hypoxia exposure, based on the premise that continued reliance upon cardiac fatty acid metabolism under such conditions could impair cardiac function. We examined the effect of severe hypoxia exposure (PO2 < 0.2 kPa) on routine and maximum performance of the in situ perfused tilapia heart under conditions of routine (400 μmol L(-1)) and low (75 μmol L(-1)) [palmitate], which mimicked the in vivo levels of plasma [NEFA] found in normoxic and hypoxic tilapia, respectively. Under both concentrations of palmitate, the in situ tilapia heart showed exceptional hypoxic performance as a result of a high maximum glycolytic potential, confirming our previous results using a perfusate without fatty acids. We additionally provide evidence suggesting that non-contractile ATP demand is depressed in tilapia heart during hypoxia exposure. Cardiac performance during and following severe hypoxia exposure was unaffected by the level of palmitate. Thus, we conclude that hypoxic depression of plasma [NEFA] in fishes does not play a role in cardiac hypoxia tolerance.

Metformin rescues the myocardium from doxorubicin-induced energy starvation and mitochondrial damage in rats

Clinical use of doxorubicin (DOX) is limited by its cardiotoxic side effects. Recent studies established that metformin (MET), an oral antidiabetic drug, possesses an antioxidant activity. However, whether it can protect against DOX-induced energy starvation and mitochondrial damage has not been reported. Our results, in a rat model of DOX-induced cardiotoxicity, show that DOX treatment significantly increased serum levels of LDH and CK-MB, indicators of cardiac injury, and induced expression of hypertrophic gene markers. DOX also caused marked decreases in the cardiac levels of glutathione, CoA-SH and ATP, and mRNA expression of catalase and NQO-1. These biochemical changes were associated with myocardial histopathological and ultrastructural deteriorations, as observed by light and electron microscopy, respectively. Cotreatment with MET (500 mg/kg) eliminated all DOX-induced biochemical, histopathological, and ultrastructural changes. These findings demonstrate that MET successfully prevents DOX-induced cardiotoxicity in vivo by inhibiting DOX-induced oxidative stress, energy starvation, and depletion of intramitochondrial CoA-SH.

The effects of supplementation with omega-3 polyunsaturated Fatty acids on cardiac rhythm: anti-arrhythmic, pro-arrhythmic, both or neither? It depends…

Supplementation of omega-3 fatty acids (Ω-3) has been associated with a decreased cardiovascular risk, thereby concentrating attention on a potentially preventive effect regarding tachyarrhythmias and sudden cardiac death. However, recent randomized controlled trials challenge the efficacy of the additional application of Ω-3 and its anti-arrhythmic effect under certain clinical conditions. The present paper reflects the results of earlier and recent clinical studies with respect to the individual background conditions that may determine the clinical outcome of Ω-3 supplementation and thereby explain apparently conflicting clinical results. It is concluded that the efficacy of Ω-3 supplementation to prevent cardiac arrhythmias strongly depends on the underlying clinical and pharmacological conditions, a hypothesis that also is supported by data from experimental animal studies and by molecular interactions of Ω-3 at the cellular level.

Two free radical pathways mediate chemical hypoxia-induced glutamate release in synaptosomes from the prefrontal cortex

It has been known that the inhibition of mitochondrial cytochrome c oxidase is one of the earliest events occurring under hypoxia and this inhibition can lead to neuronal damages. Thus, the cytochrome c oxidase inhibitor sodium cyanide (NaCN) is widely used to produce a model of chemical hypoxia by inhibiting this enzyme. However, the downstream signaling pathways of the inhibition of the cytochrome c oxidase remain to be studied. In the present paper, we used sodium cyanide to mimic the inhibition of the mitochondrial cytochrome c oxidase and studied its effect on glutamate release in synaptosomes from the prefrontal cortex using on-line fluorimetry. We also further investigated the mechanisms underlying the enhancing effect of sodium cyanide on glutamate release using pharmacological approaches combined with other techniques. The results showed that sodium cyanide significantly increased glutamate release from synaptosomes of prefrontal cortex; the broad-spectrum free radical scavenger MnTBAP and melatonin completely abolished the effect of sodium cyanide on glutamate release; the H2O2-NMDA receptor pathway mediated one part, whereas the lipid peroxyl radicals-ATP synthase pathway mediated another part of the sodium cyanide-induced glutamate release; scavenging H2O2 and enhancing ATP synthase activity could completely abolish the sodium cyanide-induced glutamate release.

Deletion of the metabolic transcriptional coactivator PGC1β induces cardiac arrhythmia

AIMS

Peroxisome proliferator-activated receptor-γ coactivators PGC1α and PGC1β modulate mitochondrial biogenesis and energy homeostasis. The function of these transcriptional coactivators is impaired in obesity, insulin resistance, and type 2 diabetes. We searched for transcriptomic, lipidomic, and electrophysiological alterations in PGC1β(-/-) hearts potentially associated with increased arrhythmic risk in metabolic diseases.

METHODS AND RESULTS

Microarray analysis in mouse PGC1β(-/-) hearts confirmed down-regulation of genes related to oxidative phosphorylation and the electron transport chain and up-regulation of hypertrophy- and hypoxia-related genes. Lipidomic analysis showed increased levels of the pro-arrhythmic and pro-inflammatory lipid, lysophosphatidylcholine. PGC1β(-/-) mouse electrocardiograms showed irregular heartbeats and an increased incidence of polymorphic ventricular tachycardia following isoprenaline infusion. Langendorff-perfused PGC1β(-/-) hearts showed action potential alternans, early after-depolarizations, and ventricular tachycardia. PGC1β(-/-) ventricular myocytes showed oscillatory resting potentials, action potentials with early and delayed after-depolarizations, and burst firing during sustained current injection. They showed abnormal diastolic Ca(2+) transients, whose amplitude and frequency were increased by isoprenaline, and Ca(2+) currents with negatively shifted inactivation characteristics, with increased window currents despite unaltered levels of CACNA1C RNA transcripts. Inwardly and outward rectifying K(+) currents were all increased. Quantitiative RT-PCR demonstrated increased SCN5A, KCNA5, RYR2, and Ca(2+)-calmodulin dependent protein kinase II expression.

CONCLUSION

PGC1β(-/-) hearts showed a lysophospholipid-induced cardiac lipotoxicity and impaired bioenergetics accompanied by an ion channel remodelling and altered Ca(2+) homeostasis, converging to produce a ventricular arrhythmic phenotype particularly during adrenergic stress. This could contribute to the increased cardiac mortality associated with both metabolic and cardiac disease attributable to lysophospholipid accumulation.

Protective action of L-carnitine on cardiac mitochondrial function and structure against fatty acid stress

Cardiovascular risks are frequently accompanied by high serum fatty acid levels. Although recent studies have shown that fatty acids affect mitochondrial function and induce cell apoptosis, L-carnitine is essential for the uptake of fatty acids by mitochondria, and may attenuate the mitochondrial dysfunction and apoptosis of cardiocytes. This study aimed to elucidate the activity of L-carnitine in the prevention on fatty acid-induced mitochondrial membrane permeability transition and cytochrome c release using isolated cardiac mitochondria from rats. Palmitoyl-CoA-induced mitochondrial respiration that was observed with L-carnitine was inhibited with oligomycin. The palmitoyl-CoA-induced mitochondrial membrane depolarization and swelling were greatly inhibited by the presence of L-carnitine. In ultrastructural observations, terminally swollen and ruptured mitochondria with little or no distinguishable cristae structures were induced by treatment with palmitoyl-CoA. However, the severe morphological damage in cardiac mitochondria was dramatically inhibited by pretreatment with L-carnitine. Treatment with L-carnitine also attenuated 4-hydroxy-L-phenylglycine- and rotenone-induced mitochondrial swelling even when the L-carnitine could not protect against the decrease in oxygen consumption associated with these inhibitors. Furthermore, L-carnitine completely inhibited palmitoyl-CoA-induced cytochrome c release. We concluded that L-carnitine is essential for cardiac mitochondria to attenuate the membrane permeability transition, and to maintain the ultrastructure and membrane stabilization, in the presence of high fatty acid β-oxidation. Consequently, the cells may be protected against apoptosis by L-carnitine through inhibition of the fatty acid-induced cytochrome c release.

Purification, identification, and cloning of lysoplasmalogenase, the enzyme that catalyzes hydrolysis of the vinyl ether bond of lysoplasmalogen

Lysoplasmalogenase (EC 3.3.2.2 and EC 3.3.2.5) is an enzyme that catalyzes hydrolytic cleavage of the vinyl ether bond of lysoplasmalogen, forming fatty aldehyde and glycerophosphoethanolamine or glycerophosphocholine and is specific for the sn-2-deacylated form of plasmalogen. Here we report the purification, characterization, identification, and cloning of lysoplasmalogenase. Rat liver microsomal lysoplasmalogenase was solubilized with octyl glucoside and purified 500-fold to near homogeneity using four chromatography steps. The purified enzyme has apparent K(m) values of ∼50 μm for both lysoplasmenylcholine and lysoplasmenylethanolamine and apparent V(m) values of 24.5 and 17.5 μmol/min/mg protein for the two substrates, respectively. The pH optimum was 7.0. Lysoplasmalogenase was competitively inhibited by lysophosphatidic acid (K(i) ∼20 μm). The predominant band on a gel at ∼19 kDa was subjected to trypsinolysis, and the peptides were identified by mass spectrometry as Tmem86b, a protein of unknown function. Transient transfection of human embryonic kidney (HEK) 293T cells showed that TMEM86b cDNA yielded lysoplasmalogenase activity, and Western blot analyses confirmed the synthesis of TMEM86b protein. The protein was localized in the membrane fractions. The TMEM86b gene was also transformed into Escherichia coli, and its expression was verified by Western blot and activity analyses. Tmem86b is a hydrophobic transmembrane protein of the YhhN family. Northern blot analyses demonstrated that liver expressed the highest level of Tmem86b, which agreed with tissue distribution of activity. Overexpression of TMEM86b in HEK 293T cells resulted in decreased levels of plasmalogens, suggesting that the enzyme may be important in regulating plasmalogen levels in animal cells.

Early inflammatory reactions in atherosclerosis are induced by proline-rich tyrosine kinase/reactive oxygen species-mediated release of tumor necrosis factor-alpha and subsequent activation of the p21Cip1/Ets-1/p300 system

OBJECTIVE

Reactive oxygen species (ROS) are involved in the initial process of atherosclerosis, whereas it remains to be determined how atherogenic stimulus causes ROS-mediated proinflammatory reactions. Here, we focused on proline-rich tyrosine kinase (PYK2)-mediated ROS generation and examined how atherogenic stimulus causes early proinflammatory reactions.

METHODS AND RESULTS

PYK2-deficient (knockout [KO]) (PYK2-KO) mice were crossbred with apolipoprotein E (ApoE)-deficient (PYK2-KO/ApoE-KO) mice. PYK2-KO/ApoE-KO mice and endothelial cells (EC) were used for the study. Aortic atherogenic lesions in PYK2-KO/ApoE-KO mice were markedly decreased (55% versus ApoE-KO) after 8 weeks of a Western diet. Aortic PYK2 was activated as early as 7 days after the Western diet, when inflammatory cells were not yet activated. Addition of the proatherogenic oxidized phospholipid lysophosphatidylcholine caused activation of endothelial PYK2. Lysophosphatidylcholine-activated PYK2 induced NADPH oxidase-mediated ROS generation and ROS-mediated synthesis of tumor necrosis factor-α (TNFα), vascular cell adhesion molecule-1 (VCAM-1), monocyte chemotactic protein-1 (MCP-1), and p21Cip1/Ets-1. Neutralizing anti-TNFα antibody or knockdown of p21Cip1/Ets-1 system blocked the induction of VCAM-1 and MCP-1. PYK2 deficiency abolished these ROS-mediated proinflammatory reactions. Further analysis revealed that PYK2/ROS-mediated p21Cip1/Ets-1 activation upregulated the transcription of the MCP-1 gene in collaboration with p300 transcription coactivator.

CONCLUSIONS

PYK2 is a key tyrosine kinase activated by high cholesterol exposure, which causes ROS-mediated TNFα release and induces TNFα-dependent expression of proinflammatory molecules via the p21Cip1/Ets-1/p300 transcription system.

Lipid oxidation by hypochlorous acid: chlorinated lipids in atherosclerosis and myocardial ischemia

Leukocytes, containing myeloperoxidase (MPO), produce the reactive chlorinating species, HOCl, and they have important roles in the pathophysiology of cardiovascular disease. Leukocyte-derived HOCl can target primary amines, alkenes and vinyl ethers of lipids, resulting in chlorinated products. Plasmalogens are vinyl ether-containing phospholipids that are abundant in tissues of the cardiovascular system. The HOCl oxidation products derived from plasmalogens are α-chlorofatty aldehyde and unsaturated molecular species of lysophosphatidylcholine. α-chlorofatty aldehyde is the precursor of both α-chlorofatty alcohol and α-chlorofatty acid. Both α-chlorofatty aldehyde and α-chlorofatty acid accumulate in activated neutrophils and have disparate chemotactic properties. In addition, α-chlorofatty aldehyde increases in activated monocytes, human atherosclerotic lesions and rat infarcted myocardium. This article addresses the pathways for the synthesis of these lipids and their biological targets.

The washout rate of (123)I-BMIPP and the evolution of left ventricular function in patients with successfully reperfused ST-segment elevation myocardial infarction: comparisons with the echocardiography

The evolution of the oxidative metabolism of (11)C acetate parallels the recovery of left ventricular(LV) contraction following acute myocardial infarction(AMI). This study was designed to unravel, for the first time, the impact of the global washout rate(WR) of (123)I-beta-methyl-p-iodophenylpentadecanoic acid (BMIPP) on the recovery of LV function followingAMI, as evidenced from conventional echocardiography.Twenty consecutive patients (age: 58 +/- 13 years; 16 males and 4 females) with ST-segment elevation myocardial infarction (STEMI) were enrolled and all of them underwent successful percutaneous coronary intervention (PCI). (123)I-BMIPP cardiac scintigraphy was performed at 7 +/- 3 days after admission. The WR was calculated from the polar map and the regional BMIPP defect score was calculated using a 17 segment model. Echocardiography was performed within 24 h of admission and at 3 months to record the ejection fraction (EF), the wall motion score index (WMSI), the ratio of the mitralinflow velocity to the early diastolic velocity (E/E0)and the myocardial performance index (MPI). The mean global WR of the BMIPP was 22.12 +/- 7.22%, and it was significantly correlated with the improvement of the WMSI (r = 0.61, P\0.004). However,the relative changes of the EF, E/E0 and MPI were not correlated with the WR. The BMIPP defect score (18 +/- 10) was significantly correlated with the WMSI on admission (r = 0.74, P = 0.0002), but the defect score was not correlated with the relative changes of any of the echocardiographic parameters. We proved that the WR of the BMIPP is a promising indicator of improvement of the LV wall motion (WMSI) following ST-segment elevation myocardial infarction and successful reperfusion.

Effects of environmental hypoxia on cardiac energy metabolism and performance in tilapia

The ability of an animal to depress ATP turnover while maintaining metabolic energy balance is important for survival during hypoxia. In the present study, we investigated the responses of cardiac energy metabolism and performance in the hypoxia-tolerant tilapia (Oreochromis hybrid sp.) during exposure to environmental hypoxia. Exposure to graded hypoxia (> or =92% to 2.5% air saturation over 3.6 +/- 0.2 h) followed by exposure to 5% air saturation for 8 h caused a depression of whole animal oxygen consumption rate that was accompanied by parallel decreases in heart rate, cardiac output, and cardiac power output (CPO, analogous to ATP demand of the heart). These cardiac parameters remained depressed by 50-60% compared with normoxic values throughout the 8-h exposure. During a 24-h exposure to 5% air saturation, cardiac ATP concentration was unchanged compared with normoxia and anaerobic glycolysis contributed to ATP supply as evidenced by considerable accumulation of lactate in the heart and plasma. Reductions in the provision of aerobic substrates were apparent from a large and rapid (in <1 h) decrease in plasma nonesterified fatty acids concentration and a modest decrease in activity of pyruvate dehydrogenase. Depression of cardiac ATP demand via bradycardia and an associated decrease in CPO appears to be an integral component of hypoxia-induced metabolic rate depression in tilapia and likely contributes to hypoxic survival.

Combined thallium-201 and dynamic iodine-123 iodophenylpentadecanoic acid single-photon emission computed tomography in patients after acute myocardial infarction with effective reperfusion

BACKGROUND

Considerable derangements of energy metabolism are to be expected during ischemia and reperfusion. In ischemic myocardium, the oxidative degradation of carbohydrates is shifted toward the anaerobic production of lactate and the oxidation of fatty acids is suppressed.

HYPOTHESIS

The aim of this study was to examine the uptake and metabolism of iodine-123 (123I) iodophenylpentadecanoic acid (IPPA) in stunned myocardium.

METHODS

In 15 patients, SPECT with 201Tl and 123I IPPA as well as echocardiography with low-dose dobutamine stimulation were performed 12 +/- 5 days after myocardial infarction with reperfusion. Follow-up echocardiography was carried out 24 +/- 8 days later for documentation of functional improvement. Uptake of 201Tl and 123I IPPA were obtained in five left ventricular segments, and dynamic SPECT imaging was used for calculation of the fast and the slow components of the biexponential myocardial 123I IPPA clearance.

RESULTS

Wall motion improved in 14 of 26 dysfunctional segments (54%). Stunned segments were characterized by a reduced 123I IPPA extraction, a shorter half-life of the fast, and a longer half-life of the slow clearance component. All parameters of the combined 201Tl/123I IPPA study predicted functional recovery with similar accuracies (area under the receiver operator characteristic curves between 0.68 and 0.76; p = NS). Analysis of 201Tl uptake alone could not predict functional recovery in this study.

CONCLUSIONS

Stunned myocardium is characterized by a disturbance of fatty acid metabolism. For prediction of functional improvement, 123I IPPA imaging added significant diagnostic information.

Ischemic preconditioning accelerates the fatty acid oxidation of rat hearts

BACKGROUND

Ischemic preconditioning (IPC) reduced myocardial ATP depletion during sustained ischemia and has a powerful protective effect on the myocardium. The purpose of the present study was to clarify the effects of IPC on myocardial accumulation of fatty acid (FA) tracer and its intracellular metabolism.

METHODS

Myocardial ischemia-reperfusion (MI-R) injury was induced by the left coronary artery ligation for 15 min followed by reperfusion in Wistar rats. IPC was achieved with a single cycle of 5-minute coronary ligation followed by 5-minute reperfusion before MI-R. Three days after ischemia-reperfusion, FA metabolism was evaluated in rats with or without IPC using (131)I- and (125)I-15-(p-iodophenyl)-9-methylpentadecanoic acid (9MPA) and thin-layer chromatography.

RESULTS

IPC attenuated a reduction of 9MPA accumulation in ischemic region (IR). The metabolite fraction of 9MPA including both early and late metabolites was less in IR as compared to non-IR in rats without IPC. IPC increased the final metabolic product of 9MPA processed via alpha- and beta-oxidation in both IR and non-IR.

CONCLUSIONS

IPC accelerated fatty acid oxidation in both IR and non-IR. This alteration in fatty acid metabolism would inhibit an intracellular accumulation of detrimental fatty acid metabolites.

Modulation of hSlo BK current inactivation by fatty acid esters of CoA

Lipid metabolism influences membrane proteins, including ion channels, in health and disease. Fatty acid esters of CoA are important intermediates in fatty acid metabolism and lipid biosynthesis. In the present study, we examined the effect of acyl-CoAs on hSlo BK currents. Arachidonoyl-CoA (C(20)-CoA) induced beta2-dependent inhibition of hSlo-alpha current when applied intracellularly but not extracellularly. This action was also mimicked by other long-chain acyl-CoAs such as oleoyl-CoA (C(18)-CoA) and palmitoyl-CoA (C(16)-CoA), but not acetyl-CoA (C(2)-CoA, shorter chain), suggesting that the length of acyl chains, rather than CoA headgroups, is critical. When hSlo-alpha inactivation was induced by a free synthetic cationic beta2 NH2-terminus inactivation ball peptide, long-chain acyl-CoAs inhibited hSlo-alpha current and facilitated inactivation. The precursor fatty acids also facilitated the ball peptide-induced inactivation in a chain length-dependent manner, whereas sphingosine (positively charged) slowed this inactivation. When the beta2-induced inactivation was compared with that of the ball peptide, there was a negative shift in the steady state inactivation, slower recovery, and a reduced voltage-dependence of inactivation onset. These data suggest that electrostatic interactions with the cytosolic inactivation domain of beta2 mediate acyl-CoA modulation of BK currents. BK channel inactivation may be a specific target for lipid modulation in physiological and pathophysiological conditions.

Mitochondria and cardioprotection

Major factors linking mitochondrial dysfunction with myocardial injury are analyzed along with protective mechanisms elicited by endogenous processes and pharmacological treatments. In particular, a reduced rate of ATP hydrolysis and a slight increase in ROS formation appear to represent the prevailing components of self-defense mechanisms, especially in the case of ischemic preconditioning. These protective processes are activated by signaling pathways, which converge on mitochondria activating the mitochondrial K(ATP) channels and/or inhibiting the mitochondrial permeability transition pore. These pathways can also be stimulated by pharmacological treatments. Another major goal for cardioprotection is decreasing the burst in mitochondrial ROS formation that characterizes post-ischemic reperfusion. Finally, mitochondrial targets for therapeutic intervention may include the switch of substrate being utilized, because inhibition of fatty acid oxidation is associated with cardioprotective effects.

A compartment model analysis for investigation of myocardial fatty acid metabolism in patients with hypertrophic cardiomyopathy

OBJECTIVE

The purpose of this study was to investigate the myocardial fatty acid metabolism in patients with hypertrophic cardiomyopathy (HCM) from dynamic SPECT through a compartment model analysis.

METHODS

Twenty-four normal controls, seven patients with left ventricular hypertrophy (LVH) due to essential hypertension (eHT), and 30 patients with HCM were studied. 123I-BMIPP and 99mTc-tetrofosmin SPECT were performed. All the myocardium was divided into 13 segments, and a total of 390 segments of HCM were categorized into early, moderately and severely advanced HCM segments, based on these SPECT imaging. By using the myocardial and blood pool time-activity curves, BMIPP pharmacokinetics were analysed through a two-compartment model. We defined k1 and k2 as influx and outflux rate constants between blood and myocardial reversible component, and k3 as the specific uptake rate constant between myocardial reversible and irreversible compartments.

RESULTS

The averages of k3 in HCM were higher than in normal. In contrast, the averages of k1/k2 in HCM were lower than in normal, and gradually decreased with progression of HCM. There are no significant differences in these indexes between normal controls and patients with LVH due to eHT.

CONCLUSION

k3 might be a sensitive predictor for early detection of HCM, and k1/k2 could be a useful index to evaluate its progression. A mathematical compartment model analysis with a BMIPP SPECT study might be useful not only for identification of HCM in very early stage, but also for evaluation of the progression of HCM.

Mitochondrial permeability transition pore opening as an endpoint to initiate cell death and as a putative target for cardioprotection

In recent years, mitochondria have been recognized as regulators of cell death via both apoptosis and necrosis in addition to their essential role for cell survival. Cellular dysfunctions induced by intra- or extracellular insults converge on mitochondria and induce a sudden increase in permeability of the inner mitochondrial membrane, the so-called mitochondrial permeability transition. The mitochondrial permeability transition is caused by the opening of permeability transition pores (PTP) in the inner mitochondrial membrane with subsequent loss of ionic homeostasis, matrix swelling and outer membrane rupture. The detailed molecular mechanisms underlying the PTP-induced cellular dysfunction during cardiac pathology such as ischemia/reperfusion or post-infarction remodeling remain to be elucidated. However, a growing body of evidence supports the concept that pharmacological inhibition of the PTP is an effective and promising strategy for the protection of the heart against ischemia/reperfusion injury and for attenuation of the remodeling process which contributes to heart failure. This review summarizes and discusses current data on i) the structure and function of the PTP, ii) possible mechanisms and consequences of PTP opening and iii) the inhibition of PTP opening as a therapeutic approach for treatment of heart disease.

Delayed recovery of fatty acid metabolism after transient myocardial ischemia: a potential imaging target for "ischemic memory"

The myocardium preferentially oxidizes free fatty acids for energy production. However, the dependency of this metabolic pathway on oxygen makes this process vulnerable to ischemia. The energy requirements of the myocardium are subsequently met by the oxidation of carbohydrates, particularly glucose. Recovery of fatty acid metabolism lags behind restoration of perfusion, resulting in the phenomenon of metabolic stunning. This decrease of fatty acid utilization following ischemia can be imaged with fatty acid radiotracers, particularly beta-Methyl-p-(123)I-iodophenyl pentadecanoic acid (BMIPP), which demonstrates markedly limited metabolism via beta-oxidation, resulting in prolonged retention in the cardiomyocyte. Thus, in patients presenting with chest pain and no prior myocardial infarction, abnormal BMIPP uptake at rest reflects metabolic alteration caused by the preceding ischemia, also termed ischemic memory.

Effect of Lycopene on Doxorubicin-Induced Cardiotoxicity: An Echocardiographic, Histological and Morphometrical Assessment

Doxorubicin is an excellent chemotherapeutic agent utilized for several types of cancer but the irreversible doxorubicin-induced cardiac damage is the major limitation for its use. Oxidative stress seems to be associated with some phase of the toxicity mechanism process. To determine if lycopene protects against doxorubicin-induced cardiotoxicity, male Wistar rats were randomly assigned either to control, lycopene, doxorubicin or doxorubicin + lycopene groups. They received corn oil (control, doxorubicin) or lycopene (5 mg/kg body weight a day) (lycopene, doxorubicin + lycopene) by gavage for a 7-week period. They also received saline (control, lycopene) or doxorubicin (4 mg/kg) (doxorubicin, doxorubin + lycopene) intraperitoneally by week 3, 4, 5 and 6. Animals underwent echocardiogram and were killed for tissue analyses by week 7. Mean lycopene levels (nmol/kg) in liver were higher in the doxorubicin + lycopene group (5822.59) than in the lycopene group (2496.73), but no differences in lycopene were found in heart or plasma of these two groups. Lycopene did not prevent left ventricular systolic dysfunction induced by doxorubicin. However, morphologic examination revealed that doxorubicin-induced myocyte damage was significantly suppressed in rats treated with lycopene. Doxorubicin treatment was followed by increase of myocardium interstitial collagen volume fraction. Our results show that: (i) doxorubicin-induced cardiotoxicity was confirmed by echocardiogram and morphological evaluations; (ii) lycopene absorption was confirmed by its levels in heart, liver and plasma; (iii) lycopene supplementation provided myocyte protection without preventing interstitial collagen accumulation increase; (iv) doxorubicin-induced cardiac dysfunction was not prevented by lycopene supplementation; and (v) lycopene depletion was not observed in plasma and tissues from animals treated with doxorubicin.

Highly Purified Omega-3 Fatty Acids for Secondary Prevention of Sudden Cardiac Death After Myocardial Infarction—Aims and Methods of the OMEGA-Study

INTRODUCTION

During the last decades a large body of data has been accumulated indicating omega-3 fatty acids to exert beneficial effects on the prognosis of patients with cardiovascular disease. Especially, omega-3 fatty acids are regarded to be effective in reducing the risk of sudden cardiac death after acute myocardial infarction. However, treatment of acute myocardial infarction and secondary prevention considerably have been improved within the past years including early revascularization by PCI, the routine use of beta-blockers, statins and ACE-inhibitors as well as cardiac rehabilitation for improving life style measures. To date, there exists no controlled randomized trial testing the prognostic effect of omega-3 fatty acids after acute myocardial infarction in a double blind regimen under the conditions of modern treatment of myocardial infarction.

MATERIALS AND METHODS

The present study therefore evaluates the effect of highly purified omega-3 fatty acid ethylesters (omega-3-acid ethyl esters 90=Zodin) on the rate of sudden cardiac death within 1 year after acute myocardial infarction. Secondary endpoints are total mortality, non-fatal cardiovascular events, rhythm abnormalities in holter monitoring and depression score.

RESULT AND CONCLUSION

The recruitment-period started in October 2003 and is expected to last until December 2006. The results of the study are therefore expected for the beginning of 2008, when all patients will have completed the 12-months follow up-period.

Mildronate, a novel fatty acid oxidation inhibitor and antianginal agent, reduces myocardial infarct size without affecting hemodynamics

Mildronate is a fatty acid oxidation inhibitor approved as an antianginal drug in parts of Europe. We carried out the first study to determine whether a 10-day course of mildronate could reduce myocardial infarct size (IS) during acute myocardial ischemia. Sprague Dawley rats received 200 mg/kg/d of mildronate (treated group, n = 16) or sterile water (control group, n = 14) subcutaneously for 10 days before ischemia-reperfusion. Rats were then subjected to 45 minutes of left coronary artery occlusion and 2 hours of reperfusion. The 2 groups had identical areas at risk: treated 38 +/- 3%; controls 38 +/- 2%. The amount of necrosis was smaller in the mildronate group at 16 +/- 2% of the left ventricle versus controls, 22 +/- 2% (P = 0.05); and for any amount of risk >25%, necrosis was smaller in the treated group (P = 0.0035). Myocardial IS (% of risk zone) was 43+/-3% in the mildronate-treated rats, and 57+/-4% in controls (P = 0.004). During occlusion, there were no differences between the 2 groups in heart rate (216 +/- 12 bpm, mildronate and 210 +/- 9 bpm, control), in mean arterial pressure (60 +/- 2 mm Hg, mildronate and 64 +/- 3 mm Hg, control) or in the frequency of arrhythmias. Our study for the first time demonstrated that a 10-day treatment with mildronate reduced myocardial IS in an experimental model of acute myocardial ischemia, without any effect on hemodynamics.

Immediate no-flow ischemia decreases rat heart nonesterified fatty acid and increases acyl-CoA species concentrations

Tissues changes in FA metabolism can occur quite rapidly in response to ischemia and may require immediate microwave fixation to determine basal concentrations. The present study aimed to quantify the effects of immediate no-flow ischemia on concentrations of individual nonesterified FA (NEFA) and acyl-CoA species in the rat heart. Male CDF 344 rats were anesthetized and decapitated either 5 min prior to being microwaved (5.5 kW, 3.4 s, twice) to produce ischemia or microwaved prior to decapitation (nonischemic). Hearts were then removed and used to measure the concentrations of acyl-CoA species and FA in several lipid classes. The ischemic heart total NEFA concentration was significantly lower than that in the nonischemic heart (11.9 vs. 19.0 nmol/g). Several individual NEFA concentrations were decreased by 31-85%. Ischemic heart total long-chain acyl-CoA concentrations (21.0 nmol/g) were significantly higher than those in nonischemic hearts (11.4 nmol/g). Increased concentrations of individual acyl-CoA species occurred in palmitoyl-CoA, stearoyl-CoA, oleoyl-CoA, and linoleoyl-CoA. Concentrations of short-chain acetyl-CoA and beta-hydroxy-beta-methylglutaryl-CoA were also two- to three-fold higher in ischemic hearts than in nonischemic hearts. The FA concentration in TG and phospholipids generally did not differ between the groups. Decreases in concentrations of individual FA and increases in acyl-CoA species during no-flow ischemia occur very rapidly within the heart. Although it is not clear how these alterations contribute to the pathogenesis of ischemia, it is evident that future studies attempting to quantify basal levels of these metabolites could use microwave fixation.

Hypoxia-induced fatty acid transporter translocation increases fatty acid transport and contributes to lipid accumulation in the heart

Protein-mediated LCFA transport across plasma membranes is highly regulated by the fatty acid transporters FAT/CD36 and FABPpm. Physiologic stimuli (insulin stimulation, AMP kinase activation) induce the translocation of one or both transporters to the plasma membrane and increase the rate of LCFA transport. In the hypoxic/ischemic heart, intramyocardial lipid accumulation has been attributed to a reduced rate of fatty acid oxidation. However, since acute hypoxia (15 min) activates AMPK, we examined whether an increased accumulation of intramyocardial lipid during hypoxia was also attributable to an increased rate of LCFA uptake as a result AMPK-induced translocation of FAT/CD36 and FABPpm. In cardiac myocytes, hypoxia (15 min) induced the redistribution of FAT/CD36 from an intracellular pool (LDM) (-25%, P<0.05) to the plasma membranes (PM) (+54%, P<0.05). Hypoxia also induced an increase in FABPpm at the PM (+56%, P<0.05) and a concomitant FABPpm reduction in the LDM (-24%, P<0.05). Similarly, in intact, Langendorff perfused hearts, hypoxia induced the translocation of a both FAT/CD36 and FABPpm to the PM (+66% and +61%, respectively, P<0.05), with a concomitant decline in FAT/CD36 and FABPpm in the LDM (-24% and -23%, respectively, P<0.05). Importantly, the increased plasmalemmal content of these transporters was associated with increases in the initial rates of palmitate uptake into cardiac myocytes (+40%, P<0.05). Acute hypoxia also redirected palmitate into intracellular lipid pools, mainly to PL and TG (+48% and +28%, respectively, P<0.05), while fatty acid oxidation was reduced (-35%, P<0.05). Thus, our data indicate that the increased intracellular lipid accumulation in hypoxic hearts is attributable to both: (a) a reduced rate of fatty acid oxidation and (b) an increased rate of fatty acid transport into the heart, the latter being attributable to a hypoxia-induced translocation of fatty acid transporters.

Influence of fasting on the effects of dimethylamiloride and oxfenicine on ischaemic-reperfused rat hearts

To assess whether glycolysis, Na+-H+ exchange and oxidation of fatty acid derived from endogenous lipolysis are involved in the beneficial effects of 24-h fasting on the ischaemic - reperfused heart, it was studied the effects of inhibiting Na+ - H+ exchange using 10 muM dimethylamiloride and fatty acid oxidation using 2 mM oxfenicine, on the functional activity, lactate production and cell viability measured with tetrazolium stain. Since fasting accelerates heart fatty acid oxidation, data were compared to those from fed rats; using Langendorff perfused (glucose 10 mM) hearts of 250-350 g Wistar rats exposed to 25 min ischaemia - 30 min reperfusion. Fasting reduced the ischaemic rise of end diastolic pressure (contracture), improved recovery of contraction and lowered lactate production in comparison with the fed whereas cellular viability was similar in both groups. Dimethylamiloride improved the recovery of contraction (fed control 24 +/- 9%, fed treated 68 +/- 11%, P < 0.05 at the end of reperfusion), attenuated the contracture (fed control 40 +/- 9%, fed treated 24 +/- 11%, P < 0.05 at the beginning of reperfusion) and reduced lactate production in the fed group and increased cellular viability in both groups (fed control 21 +/- 6%, fed treated 69 +/- 7%, P < 0.05, and fasted control 18 +/- 7%, fasted treated 53 +/- 8%, P < 0.05). Oxfenicine reduced the recovery of contraction (fasted control 88 +/- 6%, fasted treated 60 +/- 11%, P < 0.05) and increased lactate production of fasted group and attenuated the contracture in the fed. These data suggest that beneficial effects of fasting owe, at least in part, to a lowered glycolysis probably secondary to the increased fatty acid oxidation and to the accumulation of energy supplying acyl esters. Dimethylamiloride slowing of glycolysis might explain functional improvement, whereas it seems unrelated to the protection on cell viability.

Influence of .BETA.-Adrenoceptor Blockade on the Myocardial Accumulation of Fatty Acid Tracer and Its Intracellular Metabolism in the Heart After Ischemia-Reperfusion Injury

BACKGROUND

Increases in sympathetic nerve activity during ischemia may increase intracellular fatty acid (FA) accumulation via enhanced FA uptake and inhibition of beta-oxidation. Therefore, the beneficial effects of beta-adrenoceptor blockade on myocardial ischemic injury might result from the suppression of FA accumulation.

METHODS AND RESULTS

Carvedilol (1 mg/kg) or propranolol (1 mg/kg) was injected 10 min before 15-min occlusion of coronary artery in rats. Myocardial FA accumulation and intracellular metabolites of FA tracer were determined 3 days after reperfusion using (125)I-and (131)I-9-metylpentadecanoic acid (9MPA). Carvedilol significantly decreased 9MPA accumulation in both the ischemic region (IR) and non-IR, as compared with vehicle, and increased its clearance. However, the non-metabolized 9MPA fraction was not different between carvedilol- and vehicle-treated rats. Consequently, the amount of non-metabolized 9MPA in the myocardium was lower in rats treated with carvedilol than in those given vehicle. These effects of carvedilol were not different from those of propranolol.

CONCLUSION

Beta-adrenoceptor blockade did not affect a visual assessment of the autoradiographic image of 9MPA in hearts subjected to ischemia-reperfusion, but it accelerated the clearance of 9MPA in both the IR and non-IR. The administration of beta-blockade before ischemia could accelerate the recovery from ischemia-reperfusion injury by inhibiting myocardial FA accumulation before beta-oxidation.

Membrane Effects of the n-3 Fish Oil Fatty Acids, which Prevent Fatal Ventricular Arrhythmias

Fish oil fatty acids are known to exert beneficial effects on the heart and vascular systems. We have studied the membrane effects on ion channel conductance by the n-3 fish oil fatty acids that account for these beneficial effects. We have confirmed that these fatty acids prevent fatal cardiac arrhythmias in a reliable dog model of sudden cardiac death. This finding was followed by experiments indicating that the n-3 fatty acids electrically stabilize heart cells and do so largely through modulation of the fast voltage-dependent Na(+) currents and the L-type Ca(2+) channels in a manner, which makes the heart cells resistant to arrhythmias. Others and we have demonstrated that these membrane effects on the heart can prevent fatal cardiac arrhythmias in humans.