Myocardial Adenosine Triphosphate Research Articles

Integrated Functions of Cardiac Energetics, Mechanics, and Purine Nucleotide Metabolism.

Purine nucleotides play central roles in energy metabolism in the heart. Most fundamentally, the free energy of hydrolysis of the adenine nucleotide adenosine triphosphate (ATP) provides the thermodynamic driving force for numerous cellular processes including the actin-myosin crossbridge cycle. Perturbations to ATP supply and/or demand in the myocardium lead to changes in the homeostatic balance between purine nucleotide synthesis, degradation, and salvage, potentially affecting myocardial energetics and, consequently, myocardial mechanics. Indeed, both acute myocardial ischemia and decompensatory remodeling of the myocardium in heart failure are associated with depletion of myocardial adenine nucleotides and with impaired myocardial mechanical function. Yet there remain gaps in the understanding of mechanistic links between adenine nucleotide degradation and contractile dysfunction in heart disease. The scope of this article is to: (i) review current knowledge of the pathways of purine nucleotide depletion and salvage in acute ischemia and in chronic heart disease; (ii) review hypothesized mechanisms linking myocardial mechanics and energetics with myocardial adenine nucleotide regulation; and (iii) highlight potential targets for treating myocardial metabolic and mechanical dysfunction associated with these pathways. It is hypothesized that an imbalance in the degradation, salvage, and synthesis of adenine nucleotides leads to a net loss of adenine nucleotides in both acute ischemia and under chronic high-demand conditions associated with the development of heart failure. This reduction in adenine nucleotide levels results in reduced myocardial ATP and increased myocardial inorganic phosphate. Both of these changes have the potential to directly impact tension development and mechanical work at the cellular level. © 2024 American Physiological Society. Compr Physiol 14:5345-5369, 2024.

Assessment of left ventricular tissue mitochondrial bioenergetics in patients with stable coronary artery disease

Recurrent myocardial ischemia can lead to left ventricular (LV) dysfunction in patients with coronary artery disease (CAD). In this observational cohort study, we assessed for chronic metabolomic and transcriptomic adaptations within LV myocardium of patients undergoing coronary artery bypass grafting. During surgery, paired transmural LV biopsies were acquired on the beating heart from regions with and without evidence of inducible ischemia on preoperative stress perfusion cardiovascular magnetic resonance. From 33 patients, 63 biopsies were acquired, compared to analysis of LV samples from 11 donor hearts. The global myocardial adenosine triphosphate (ATP):adenosine diphosphate (ADP) ratio was reduced in patients with CAD as compared to donor LV tissue, with increased expression of oxidative phosphorylation (OXPHOS) genes encoding the electron transport chain complexes across multiple cell types. Paired analyses of biopsies obtained from LV segments with or without inducible ischemia revealed no significant difference in the ATP:ADP ratio, broader metabolic profile or expression of ventricular cardiomyocyte genes implicated in OXPHOS. Differential metabolite analysis suggested dysregulation of several intermediates in patients with reduced LV ejection fraction, including succinate. Overall, our results suggest that viable myocardium in patients with stable CAD has global alterations in bioenergetic and transcriptional profile without large regional differences between areas with or without inducible ischemia.

Neocryptotanshinone ameliorates insufficient energy production in heart failure by targeting retinoid X receptor alpha

Retinoid X receptor alpha (RXRα) is a nuclear transcription factor that extensively regulates energy metabolism in cardiovascular diseases. Identification of targeted RXRα drugs for heart failure (HF) therapy is urgently needed. Neocryptotanshinone (NCTS) is a component derived from Salvia miltiorrhiza Bunge, the effect and mechanism of which for treating HF have not been reported. The goal of this study was to explore the pharmacological effects of NCTS on energy metabolism to protect against HF post-acute myocardial infarction (AMI) via RXRα. We established a left anterior descending artery ligation-induced HF post-AMI model in mice and an oxygen-glucose deprivation-reperfusion-induced H9c2 cell model to investigate the cardioprotective effect of NCTS. Component–target binding techniques, surface plasmon resonance (SPR), microscale thermophoresis (MST) and small interfering RNA (siRNA) transfection were applied to explore the potential mechanism by which NCTS targets RXRα. The results showed that NCTS protects the heart against ischaemic damage, evidenced by improvement of cardiac dysfunction and attenuation of cellular hypoxic injury. Importantly, the SPR and MST results showed that NCTS has a high binding affinity for RXRα. Meanwhile, the critical downstream target genes of RXRα/PPARα, which are involved in fatty acid metabolism, including Cd36 and Cpt1a, were upregulated under NCTS treatment. Moreover, NCTS enhanced TFAM levels, promoted mitochondrial biogenesis and increased myocardial adenosine triphosphate levels by activating RXRα. In conclusion, we confirmed that NCTS improves myocardial energy metabolism, including fatty acid oxidation and mitochondrial biogenesis, by regulating the RXRα/PPARα pathway in mice with HF post-AMI.

Cyclocreatine Phosphate: A Novel Bioenergetic/Anti-Inflammatory Drug That Resuscitates Poorly Functioning Hearts and Protects against Development of Heart Failure

Irreversible myocardial injury causes the exhaustion of cellular adenosine triphosphate (ATP) contributing to heart failure (HF). Cyclocreatine phosphate (CCrP) was shown to preserve myocardial ATP during ischemia and maintain cardiac function in various animal models of ischemia/reperfusion. We tested whether CCrP administered prophylactically/therapeutically prevents HF secondary to ischemic injury in an isoproterenol (ISO) rat model. Thirty-nine rats were allocated into five groups: control/saline, control/CCrP, ISO/saline (85 and 170 mg/kg/day s.c. for 2 consecutive days), and ISO/CCrP (0.8 g/kg/day i.p.) either administrated 24 h or 1 h before ISO administration (prophylactic regimen) or 1 h after the last ISO injection (therapeutic regimen) and then daily for 2 weeks. CCrP protected against ISO-induced CK-MB elevation and ECG/ST changes when administered prophylactically or therapeutically. CCrP administered prophylactically decreased heart weight, hs-TnI, TNF-α, TGF-β, and caspase-3, as well as increased EF%, eNOS, and connexin-43, and maintained physical activity. Histology indicated a marked decrease in cardiac remodeling (fibrin and collagen deposition) in the ISO/CCrP rats. Similarly, therapeutically administered CCrP showed normal EF% and physical activity, as well as normal serum levels of hs-TnI and BNP. In conclusion, the bioenergetic/anti-inflammatory CCrP is a promising safe drug against myocardial ischemic sequelae, including HF, promoting its clinical application to salvage poorly functioning hearts.

Effects of preoperative intravenous glutamine administration on cardiac and renal functions in patients undergoing mitral valve replacement surgeries: A randomized double-blind controlled trial

ABSTRACT Background Preoperative poor nutrition greatly raises the risk of complications and increases length of stay (LOS). Glutamine deficiency may impair immune functions, reduce myocardial adenosine triphosphate–adenosine diphosphate (ATP-ADP) substrate and decrease myocardial glutathione level. We evaluated the effects of preoperative glutamine administration in patients undergoing mitral valve replacement surgery upon cardiac and renal outcomes or hospital/ICU LOS. Methods This prospective randomized double-blinded study included 60 patients above 18 up to 60 years undergoing mitral valve replacement. For 3 days preoperatively, Group N patients received glutamine intravenously 0.4 g/kg/day while Group C patients received intravenous normal saline as placebo. The primary outcome was to assess the effects of glutamine on cardiac function as reflected on proBNP (brain natriuretic peptide) during 4 postoperative days. Secondary outcomes included renal function, vasoactive inotropic score, duration of mechanical ventilation, and hospital/ICU stays. Results Postoperative proBNP was significantly lower in Group N during the entire period. It was significantly decreased on the first postoperative day in both groups in comparison to the preoperative values. No significant changes were recorded regarding renal functions, and duration of mechanical ventilation between groups. Also, there was signifiacant difference between the two studied groups regarding the vasoactive inotropic score at the 12th, 18th, 24th and 48th hours with lower scores in Group N. ICU and hospital stays were significantly lower in Group N than Group C. Conclusion Short term of preoperative intravenous glutamine 0.4 g/kg/day decreased the postoperative proBNP level and hospital/ICU stays in mitral valve replacement surgery. No significant implication was reported upon postoperative human NGAL level or kidney functions.

Abstract 9706: A Novel High Energy Phosphate Source Resuscitates Poorly Functioning Donor Hearts

Introduction: Over 60% of the time donor hearts cannot be utilized for transplant, mostly because of poor left ventricular ejection fraction (EF) of ≤40% due to stress cardiomyopathy (i.e., demand ischemia) with depletion of myocardial adenosine triphosphate (ATP). The bioenergetic cyclocreatine phosphate (CCrP) is an FDA Orphan Designated Drug for heart transplantation . When CCrP is given prophylactically in an isoprenaline (ISO) rat model of demand ischemia, it restored ATP and maintained contractility. Hypothesis: We hypothesized that administering CCrP therapeutically after ISO-induced myocardial dysfunction in rats (simulating rejected donor hearts), will prevent ischemic injury and sustain long-term restoration of EF. Methods: Wistar male rats (180-220 g) were injected SC with ISO (85 and 170 mg/kg/day) for two consecutive days. CCrP (n=6, 0.8 gm/kg/day ip) and saline control (n=4) were administered 1 hour after completing the course of ISO injections and then daily for 2 weeks. A negative control group was injected with saline (n=4). Serum CK-MB and ECG/ST were measured 24 hours after last ISO injection. Evidence of stress cardiomyopathy was assessed after 14 days by ECHO analysis for EF and levels of hs-Troponin I (TnI) and BNP. One-way ANOVA analysis was used. Results: Table I shows two main benefits of therapeutically administered CCrP in this stress cardiomyopathy model: 1) poor heart function was quickly restored in the acute phase (24 hours), as indicated by normal ECG/ST and CK-MB levels; and 2) the restoration of function was sustained over the long term (14 days), as indicated by normal EF% and levels of hs-TnI and BNP. Conclusions: The bioenergetic CCrP is a novel cardioprotective drug that appears to salvage cardiac dysfunction and restore normal EF% in a rat model of stress cardiomyopathy. If this benefit translates into clinical organ donors with poor heart function, CCrP could be used to increase heart utilization for transplantation.

Ketogenic diet modulates cardiac metabolic dysregulation in streptozocin-induced diabetic rats

The ketogenic diet (KD) might improve cardiac function in diabetic cardiomyopathy, but the mechanisms remain unclear. This study investigated the effects of KD on myocardial fatty acid (FA), glucose, and ketone metabolism in diabetic cardiomyopathy. Echocardiograms, biochemistry, and micro-positron emission tomography were performed to evaluate cardiac function and glucose uptake in control rats and streptozotocin-induced diabetes mellitus (DM) rats with normal diet (ND) or KD for 6 weeks. Histopathology, adenosine triphosphate measurement, and Western blot were performed in the ventricular myocytes to analyze fibrosis, FA, ketone body, and glucose utilization. The ND-fed DM rats exhibited impaired left ventricular systolic function and increased chamber dilatation, whereas control and KD-fed DM rats did not. The KD reduced myocardial fibrosis and apoptosis in the DM rats. Myocardial glucose uptake in the micro-positron emission tomography was similar between ND-fed DM rats and KD-fed DM rats and was substantially lower than the control rats. Compared with the control rats, ND-fed DM rats had increased phosphorylation of acetyl CoA carboxylase and higher expressions of CD-36, carnitine palmitoyltransferase-1β, tumor necrosis factor-α, interleukin-1β, interleukin6, PERK, and e-IF2α as well as more myocardial fibrosis and apoptosis (assessed by Bcl-2, BAX, and caspase-3 expression); these increases were attenuated in the KD-fed DM rats. Moreover, ND-fed DM rats had significantly lower myocardial adenosine triphosphate, BHB, and OXCT1 levels than the control and KD-fed DM rats. The KD may improve the condition of diabetic cardiomyopathy by suppressing FA metabolism, increasing ketone utilization, and decreasing endoplasmic reticulum stress and inflammation.

Mitochondrial ATP Synthase Tetramer Disassembly following Blood-Based or del Nido Cardioplegia during Neonatal Cardiac Surgery

Conservation of mitochondrial adenosine triphosphate (ATP) synthase proteins during ischemia is critical to preserve ATP supply and ventricular function. Following myocardial ischemia in adults, higher order ATP synthase tetramer proteins disassemble into simpler monomer units, reducing the efficiency of ATP production. However, it is unknown if myocardial ischemia following the use of cardioplegia results in tetramer disassembly in neonates, and whether it can be mitigated by cardioplegia if it does occur. We investigated myocardial ATP synthase tetramer disassembly in both a neonatal lamb cardiac surgery model and in neonatal children requiring cardiac surgery for the repair of congenital heart disease. Neonatal lambs (Ovis aries) were placed on cardiopulmonary bypass (CPB) and underwent cardioplegic arrest using a single dose of 30 mL/kg antegrade blood-based potassium cardioplegia (n = 4) or a single dose of 30 mL/kg antegrade del Nido cardioplegia (n = 6). Right ventricular biopsies were taken at baseline on CPB (n = 10) and after approximately 60 minutes of cardioplegic arrest before the cross clamp was released (n = 10). Human right ventricular biopsies (n = 3) were taken following 40.0 ± 23.1 minutes of ischemia after a single dose of antegrade blood-based cardioplegia. Protein complexes were separated on clear native gels and the tetramer to monomer ratio quantified. From the neonatal lamb model regardless of the cardioplegia strategy, the tetramer:monomer ratio decreased significantly during ischemia from baseline measurements (.6 ± .2 vs. .5 ± .1; p = .03). The del Nido solution better preserved the tetramer:monomer ratio when compared to the blood-based cardioplegia (Blood .4 ± .1 vs. del Nido .5 ± .1; p = .05). The tetramer:monomer ratio following the use of blood-based cardioplegia in humans aligned with the lamb data (tetramer:monomer .5 ± .2). These initial results suggest that despite cardioprotection, ischemia during neonatal cardiac surgery results in tetramer disassembly which may be limited when using the del Nido solution.

Mitochondrial ATP Synthase Tetramer Disassembly following Blood-Based or del Nido Cardioplegia during Neonatal Cardiac Surgery.

Conservation of mitochondrial adenosine triphosphate (ATP) synthase proteins during ischemia is critical to preserve ATP supply and ventricular function. Following myocardial ischemia in adults, higher order ATP synthase tetramer proteins disassemble into simpler monomer units, reducing the efficiency of ATP production. However, it is unknown if myocardial ischemia following the use of cardioplegia results in tetramer disassembly in neonates, and whether it can be mitigated by cardioplegia if it does occur. We investigated myocardial ATP synthase tetramer disassembly in both a neonatal lamb cardiac surgery model and in neonatal children requiring cardiac surgery for the repair of congenital heart disease. Neonatal lambs (Ovis aries) were placed on cardiopulmonary bypass (CPB) and underwent cardioplegic arrest using a single dose of 30 mL/kg antegrade blood-based potassium cardioplegia (n = 4) or a single dose of 30 mL/kg antegrade del Nido cardioplegia (n = 6). Right ventricular biopsies were taken at baseline on CPB (n = 10) and after approximately 60 minutes of cardioplegic arrest before the cross clamp was released (n = 10). Human right ventricular biopsies (n = 3) were taken following 40.0 ± 23.1 minutes of ischemia after a single dose of antegrade blood-based cardioplegia. Protein complexes were separated on clear native gels and the tetramer to monomer ratio quantified. From the neonatal lamb model regardless of the cardioplegia strategy, the tetramer:monomer ratio decreased significantly during ischemia from baseline measurements (.6 ± .2 vs. .5 ± .1; p = .03). The del Nido solution better preserved the tetramer:monomer ratio when compared to the blood-based cardioplegia (Blood .4 ± .1 vs. del Nido .5 ± .1; p = .05). The tetramer:monomer ratio following the use of blood-based cardioplegia in humans aligned with the lamb data (tetramer:monomer .5 ± .2). These initial results suggest that despite cardioprotection, ischemia during neonatal cardiac surgery results in tetramer disassembly which may be limited when using the del Nido solution.

Abstract 13311: Cyclocreatine Phosphate: A Novel Mechanism for Preventing Development of Heart Failure

Introduction: Demand ischemia causes irreversible myocardial injury (MI) through exhaustion of cellular adenosine triphosphate (ATP). We demonstrated that enhancing myocardial ATP stores during ischemia using Cyclocreatine Phosphate (CCrP), prevents myocardial injury and maintains cardiac contractility in a variety of models. The FDA has granted CCrP Orphan Drug Status with the designation of “ Prevention of Ischemic Injury to Enhance Cardiac Graft Recovery and Survival in Heart Transplantation ” . Hypothesis: CCrP administration will prevent ischemic injury and the subsequent development of heart failure in standard isoproterenol (ISO) rat model. Methods: 20 male Wistar rats (180-220 g) were used: ISO/saline (n=6), ISO/CCrP 0.8 gm/kg/day (n=5), control/saline (n=5), control/CCrP 0.8 gm/kg/day (n=4). Rats were injected S.C. with ISO for two consecutive days at doses of 85 and 170 mg/kg/day, respectively, then left for 2 weeks. CCrP and saline were injected IP (1 ml) 24 hours and 1 hour before ISO administration, then daily for 2 weeks. Serum CK-MB (U/L) measured 24 hours after last ISO injection. After 14 days, ECHO analysis for Ejection Fraction (EF%) was conducted, as well as heart weight (mg), fibrosis and deposition of collagen. Mean ± S.E.M and one-way ANOVA analysis were used. Results: Table I shows evidence of MI after 24 hours by high elevation of CK-MB in ISO rats, while significant protection was seen in ISO/CCrP rats. After 14 days, ISO/CCrP rats showed normal EF% and heart weight, while ISO/saline rats showed significant drop in EF% and an increase in heart weight. Blinded pathology indicated marked increase of fibrin and collagen deposition in ISO/saline rats, which were not seen in ISO/CCrP rats. Healthy rats treated with CCrP for 14 days, showed no toxicity in liver and renal function. Conclusions: The bioenergetic Cyclocreatine Phosphate is a promising first-in-class cardio-protective drug that prevents the development of heart failure due to ischemia.

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

AimHeart failure (HF) post-acute myocardial infarction (AMI) leads to a large number of hospitalizations and deaths worldwide. Danqi pill (DQP) is included in the 2015 national pharmacopoeia and widely applied in the treatment of HF in clinics in China. We examined whether DQP acted on glucose metabolism to protect against HF post-AMI via hypoxia inducible factor-1 alpha (HIF-1α)/peroxisome proliferator-activated receptor α co-activator (PGC-1α) pathway.Methods and ResultsIn this study, left anterior descending (LAD) artery ligation induced HF post-AMI rats and oxygen-glucose deprivation-reperfusion (OGD/R)-induced H9C2 cell model were structured to explore the efficacy and mechanism of DQP. Here we showed that DQP protected the heart against ischemic damage as evidenced by improved cardiac functions and attenuated inflammatory infiltration. The expressions of critical proteins involved in glucose intake and transportation such as GLUT4 and PKM2 were up-regulated, while negative regulatory proteins involved in oxidative phosphorylation were attenuated in the treatment of DQP. Moreover, DQP up-regulated NRF1 and TFAM, promoted mitochondrial biogenesis and increased myocardial adenosine triphosphate (ATP) level. The protection effects of DQP were significantly compromised by HIF-1α siRNA, suggesting that HIF-1α signaling pathway was the potential target of DQP on HF post-AMI.ConclusionsDQP exhibits the efficacy to improve myocardial glucose metabolism, mitochondrial oxidative phosphorylation and biogenesis by regulating HIF-1α/PGC-1α signaling pathway in HF post-AMI rats.

The intestine responds to heart failure by enhanced mitochondrial fusion through glucagon-like peptide-1 signalling.

Glucagon-like peptide-1 (GLP-1) is a neuroendocrine hormone secreted by the intestine. Its receptor (GLP-1R) is expressed in various organs, including the heart. However, the dynamics and function of the GLP-1 signal in heart failure remains unclear. We investigated the impact of the cardio-intestinal association on hypertensive heart failure using miglitol, an α-glucosidase inhibitor known to stimulate intestinal GLP-1 production. Dahl salt-sensitive (DS) rats fed a high-salt diet were assigned to miglitol, exendin (9-39) (GLP-1R blocker) and untreated control groups and treated for 11 weeks. Control DS rats showed marked hypertension and cardiac dysfunction with left ventricular dilatation accompanied by elevated plasma GLP-1 levels and increased cardiac GLP-1R expression as compared with age-matched Dahl salt-resistant (DR) rats. Miglitol further increased plasma GLP-1 levels, suppressed adverse cardiac remodelling, and mitigated cardiac dysfunction. In cardiomyocytes from miglitol-treated DS hearts, mitochondrial size was significantly larger with denser cristae than in cardiomyocytes from control DS hearts. The change in mitochondrial morphology reflected enhanced mitochondrial fusion mediated by protein kinase A activation leading to phosphorylation of dynamin-related protein 1, expression of mitofusin-1 and OPA-1, and increased myocardial adenosine triphosphate (ATP) content. GLP-1R blockade with exendin (9-39) exacerbated cardiac dysfunction and led to fragmented mitochondria with disarrayed cristae in cardiomyocytes and reduction of myocardial ATP content. In cultured cardiomyocytes, GLP-1 increased expression of mitochondrial fusion-related proteins and ATP content. When GLP-1 and exendin (9-39) were administered together, their effects cancelled out. Increased intestinal GLP-1 secretion is an adaptive response to heart failure that is enhanced by miglitol. This could be an effective strategy for treating heart failure through regulation of mitochondrial dynamics.

Metabolic management of heart disease

Alterations of cardiac metabolism occur with ischemia and heart failure (HF). This results in increased utilization of noncarbohydrate substrates for energy production and depletion of myocardial adenosine triphosphate, phosphocreatine, and creatine kinase with decreased efficiency of mechanical work. A direct approach to manipulate cardiac energy metabolism consists in modifying substrate utilization by the failing heart. The results of research suggest that shifting the energy substrate preference away from fatty acid metabolism and toward glucose metabolism could be an effective adjunctive treatment in patients with HF, in terms of left ventricular function and glucose metabolism improvement. In this paper, some of these concepts will be discussed, and the role of drugs such as trimetazidine will be discussed.

Deranged Cardiac Metabolism and the Pathogenesis of Heart Failure.

Activation of the neuro-hormonal system is a pathophysiological consequence of heart failure. Neuro-hormonal activation promotes metabolic changes, such as insulin resistance, and determines an increased use of non-carbohydrate substrates for energy production. Fasting blood ketone bodies as well as fat oxidation are increased in patients with heart failure, yielding a state of metabolic inefficiency. The net result is additional depletion of myocardial adenosine triphosphate, phosphocreatine and creatine kinase levels with further decreased efficiency of mechanical work. In this context, manipulation of cardiac energy metabolism by modification of substrate use by the failing heart has produced positive clinical results. The results of current research support the concept that shifting the energy substrate preference away from fatty acid metabolism and towards glucose metabolism could be an effective adjunctive treatment in patients with heart failure. The additional use of drugs able to partially inhibit fatty acids oxidation in patients with heart failure may therefore yield a significant protective effect for clinical symptoms and cardiac function improvement, and simultaneously ameliorate left ventricular remodelling. Certainly, to clarify the exact therapeutic role of metabolic therapy in heart failure, a large multicentre, randomised controlled trial should be performed.

Donor pretreatment with adenosine monophosphate-activated protein kinase activator protects cardiac grafts from cold ischaemia/reperfusion injury.

Adenosine monophosphate-activated protein kinase (AMPK) is a master regulator of energy metabolism and has been shown to be protective in ischaemia/reperfusion injury (IRI). We hypothesized that preactivation of AMPK with an activator before donor heart procurement could protect heart grafts from cold IRI. Donor Sprague-Dawley rats were injected intravenously with AMPK activator 5-amino-imidazole-4-carboxamide ribonucleotide (AICAR) or vehicle 30 min before heart procurement. Heart grafts were then preserved in histidine-tryptophan-ketoglutarate (HTK) solution at 4°C for 8 h. After preservation, grafts were immediately mounted on the Langendorff perfusion system and perfused with Krebs-Henseleit buffer at 37°C for 1 h. Adenosine triphosphate (ATP) and malondialdehyde (MDA) content in graft tissue were quantified post-preservation and post-reperfusion. After reperfusion, isolated heart function was assessed using a pressure transducer; cumulative release of creatine kinase (CK) and lactate dehydrogenase (LDH) into the perfusate was measured to assess cardiomyocyte necrosis; ultrastructural changes in the mitochondria of the grafts were examined using transmission electron microscopy (TEM). After preservation, myocardial ATP content in the pretreated hearts was significantly higher than in the control hearts (3.247 ± 0.3034 vs 1.817 ± 0.2533 µmol/g protein; P < 0.05). AICAR-pretreated heart grafts exhibited significantly higher coronary flow (9.667 ± 0.3159 vs 8.033 ± 0.2459 ml/min; P < 0.05) and left ventricular developing pressure (58.67 ± 2.894 vs 42.67 ± 3.333 mmHg; P < 0.05) than the vehicle treated after reperfusion. Cumulative release of CK (300.0 ± 25.30 vs 431.7 ± 42.39 U/l; P < 0.05) and LDH (228.0 ± 16.68 vs 366.8 ± 57.41 U/l; P < 0.05) in the perfusate was significantly lower in the AICAR-pretreated group than that in the control group. Myocardial MDA content was also reduced in the pretreated group (0.5167 ± 0.1046 vs 0.9333 ± 0.1333 nmol/mg protein; P < 0.05). TEM suggested that the mitochondrial structure of AICAR-pretreated hearts was much better preserved. Moreover, AICAR-pretreated hearts significantly diminished cytosolic cytochrome c release after reperfusion. This study demonstrates that pretreatment with AMPK activator AICAR significantly protects heart grafts from extended cold IRI. This novel protocol may be useful and feasible in clinical heart transplantation.

Diastolic Dysfunction Induced by a High-Fat Diet Is Associated with Mitochondrial Abnormality and Adenosine Triphosphate Levels in Rats.

BackgroundObesity is well-known as a risk factor for heart failure, including diastolic dysfunction. However, this mechanism in high-fat diet (HFD)-induced obese rats remain controversial. The purpose of this study was to investigate whether cardiac dysfunction develops when rats are fed with a HFD for 10 weeks; additionally, we sought to investigate the association between mitochondrial abnormalities, adenosine triphosphate (ATP) levels and cardiac dysfunction.MethodsWe examined myocardia in Wistar rats after 10 weeks of HFD (45 kcal% fat, n=6) or standard diet (SD, n=6). Echocardiography, histomorphologic analysis, and electron microscopy were performed. The expression levels of mitochondrial oxidative phosphorylation (OXPHOS) subunit genes, peroxisome-proliferator-activated receptor γ co-activator-1α (PGC1α) and anti-oxidant enzymes were assessed. Markers of oxidative stress damage, mitochondrial DNA copy number and myocardial ATP level were also examined.ResultsAfter 10 weeks, the body weight of the HFD group (349.6±22.7 g) was significantly higher than that of the SD group (286.8±14.9 g), and the perigonadal and epicardial fat weights of the HFD group were significantly higher than that of the SD group. Histomorphologic and electron microscopic images were similar between the two groups. However, in the myocardium of the HFD group, the expression levels of OXPHOS subunit NDUFB5 in complex I and PGC1α, and the mitochondrial DNA copy number were decreased and the oxidative stress damage marker 8-hydroxydeoxyguanosine was increased, accompanied by reduced ATP levels.ConclusionDiastolic dysfunction was accompanied by the mitochondrial abnormality and reduced ATP levels in the myocardium of 10 weeks-HFD-induced rats.

Low-Flow Hypothermic Crystalloid Perfusion Is Superior to Cold Storage During Prolonged Heart Preservation

BackgroundPreservation of donor hearts for transplantation has traditionally been performed with the use of static cold storage. We have developed and tested a novel gravity-powered system of cold crystalloid perfusion for prolonged donor heart preservation. MethodsGreyhounds were anesthetized; their hearts were arrested with cold cardioplegic solution and excised. Hearts were allocated to 12 hours of perfusion preservation (n = 6) or cold storage in ice (n = 5). Non-preserved hearts (n = 5) served as a normal reference group. Perfusion hearts were perfused (20 mL/min, 8–12°C) with a novel oxygenated nutrient-containing preservation solution. After preservation, the recovery of the hearts was assessed in a blood-perfused working heart rig over 2 hours in terms of function, blood lactate level, myocardial adenosine triphosphate, and histology. ResultsAfter 2 hours of reperfusion, in comparison with cold storage hearts, perfused heart function curves showed superior recovery of cardiac output (P = .001), power (P = .001), and efficiency (0.046 ± 0.01 vs 0.004 ± 0.003 joules/mL O2, P = .034). Myocardial adenosine triphosphate content (mmol/mg protein) was reduced significantly from the normal level of 26.5 (15.9, 55.8) to 5.08 (0.50, 10.4) (P = .049) in cold storage hearts but not in perfused hearts. Over a period of 2 hours, lactate levels in the blood perfusate were significantly lower in the perfusion group than in the cold storage group (P < .05). ConclusionsContinuous hypothermic crystalloid perfusion provides myocardial preservation superior to cold storage for long-term heart preservation, with potential applicability to marginal and donation after circulatory death hearts.

Effects of ischemic preconditioning with atorvastatin on heart ischemia-reperfusion injury and possible mechanism

Objective To investigate the effects of pretreatment with atorvastatin (Ator) on the heart ischemia-reperfusion injury (IRI) and the possible mechanism.Methods After establishment of IRI models,66 healthy male SD rats were divided into three experimental groups (n =22 each).In control group,the rats were given cardiac perfusion continuous buffer.In IRI group,myocardia of rats accepted 30 min global ischemia and 120 min reperfusion.In Ator group,the rats were given 1 μmol/L Ator befor ischemia,and perfused for 30 min,followed by IRI.The myocardial ultrastructure,infarct size,hemodynamic,serum lactate dehydrogenase levels,adenosine triphosphate (ATP) and nicotinamide adenine dinucleotide (NAD +) levels in three groups were observed.Results In IRI group and Ator group,arched upward ST segment elevation and T wave fusion after the anterior descending artery ligation were seen.The electrocardiogram (ECG) in the control group had no significant change after surgery.As compared with the IRI group,the myocardial infarction area in the Ator group was significantly decreased (P ＜ 0.05).Microstructure showed that there was significant difference in the cardiomyocytes edema,myofibril,mitochondrial structure and glycogen granules among the three groups.After ischemia-reperfusion,the left ventricular systolic pressure (LVSP),peak velocity of left ventricular pressure drop (dp/dtmin) and heart rate (HR) values in the IRI group were decreased significantly,and the left ventricle end-diastolic pressure (LVEDP) values increased significantly (P ＜ 0.05) as compared wiht the Ator group (P ＜ 0.05).The lactate dehydrogenase (LDH) levels in the control group,IRI group and Ator group were (164.32 ± 20.84),(3589.63 ± 133.25) and (1703.25 ± 155.80) U/L respectively.The LDH levels in the IRI group were lower than in the control group,and those in IRI group were higher than in the Ator group (P ＜ 0.05).The myocardial ATP and NAD + levels in the IRI group were decreased significantly as compared with the control group (P ＜ 0.05),and increased as compared with the Ator group (P ＜ 0.05).Conclusion Ischemic preconditioning with Ator for IRI can play an effective role in myocardial protection,which is achieved by activating the mitochondrial ATP-sensitive potassium channels and reducing lactic acid-mediated expression. Key words: Ischemic preconditioning; Ischemia reperfusion injury; Atorvastatin; Myocardial protection

Effect of L-arginine on Function of Mitochondria in Ischemia – Reperfusion Myocardial Cell in Rabbits

Objective: To investigate the effect of L-arginine (L-Arg) on the function of myocardial mitochondria during myocardia ischemia - reperfusion (IR). Methods: Dividing randomly the 30 rabbits into three groups (n=10): control group (C), myocardia ischemiareperfusion group (IR) and L-Arginine pretreatment group (L-Arg+IR). The relevant parameters, including myocardial mitochondria respiratory function, Ca2+ concentration ([Ca2+]), malondialdehyde (MDA) concentration, superoxide dismutase (SOD) activity, myocardial adenosine triphosphate (ATP), Adenosine diphosphate (ADP), adenosine monophosphate (AMP) content, the total amount of AMP (TAN, TAN=ATP+ADP+AMP) and energy charge (EC, EC=1/2ADP+ATP/TAN) were determined, respectively. Results: The mitochondria respiratory control rate (RCR), III state respiration rate (V3), and SOD in group L-Arg +IR were significantly higher than those in group IR, while IV state respiration rate (V4) , [Ca2+] m, and MDA were obviously lower than those of group IR, the levels of ATP, ADP, TNA and the EC of myocardium showed significantly higher than those in group IR. There were no significant differences in terms of V3, V4, SOD, MDA, AMP and TAN between group L-Arg+IR and group C. Conclusion: It indicated that L-arginine can reduce the level of the oxygen free radicals and partly attenuatecalcium overload to improve the function of myocardial mitochondria during myocardium ischemia reperfusion injury.

Endothelial Lipase Modulates Pressure Overload–Induced Heart Failure Through Alternative Pathway for Fatty Acid Uptake

Lipoprotein lipase has been considered as the only enzyme capable of generating lipid-derived fatty acids for cardiac energy. Endothelial lipase is another member of the triglyceride lipase family and hydrolyzes high-density lipoproteins. Although endothelial lipase is expressed in the heart, its function remains unclear. We assessed the role of endothelial lipase in the genesis of heart failure. Pressure overload-induced cardiac hypertrophy was generated in endothelial lipase(-/-) and wild-type mice by ascending aortic banding. Endothelial lipase expression in cardiac tissues was markedly elevated in the early phase of cardiac hypertrophy in wild-type mice, whereas lipoprotein lipase expression was significantly reduced. Endothelial lipase(-/-) mice showed more severe systolic dysfunction with left-ventricular dilatation compared with wild-type mice in response to pressure overload. The expression of mitochondrial fatty acid oxidation-related genes, such as carnitine palmitoyltransferase-1 and medium-chain acyl coenzyme A dehydrogenase, was significantly lower in the heart of endothelial lipase(-/-) mice than in wild-type mice. Also, endothelial lipase(-/-) mice had lower myocardial adenosine triphosphate levels than wild-type mice after aortic banding. In cultured cardiomyocytes, endothelial lipase was upregulated by inflammatory stimuli, whereas lipoprotein lipase was downregulated. Endothelial lipase-overexpression in cardiomyocytes resulted in an upregulation of fatty acid oxidation-related enzymes and intracellular adenosine triphosphate accumulation in the presence of high-density lipoprotein. Endothelial lipase may act as an alternative candidate to provide fatty acids to the heart and regulate cardiac function. This effect seemed relevant particularly in the diseased heart, where lipoprotein lipase action is downregulated.