Search

OBJECTIVES: To compare the efficacy and safety of the dual-therapy CD34 antibody-covered sirolimus-eluting Combo stent (DTS) and the sirolimus-eluting Orsiro stent (O-SES) in patients with and without acute coronary syndrome (ACS) included in the SORT OUT X study.BACKGROUND: The incidence of target lesion failure (TLF) after treatment with modern drug-eluting stents has been reported to be significantly higher in patients with ACS when compared to patients without ACS. Whether the results from the SORT OUT X study apply to patients with and without ACS remains unknown.METHODS: In total, 3146 patients were randomized to stent implantation with DTS (n = 1578; ACS: n = 856) or O-SES (n = 1568; ACS: n = 854). The primary end point, TLF, was a composite of cardiac death, target-lesion myocardial infarction (MI), or target lesion revascularization (TLR) within 1 year.RESULTS: At 1 year, the rate of TLF was higher in the DTS group compared to the O-SES group, both among patients with ACS (6.7% vs. 4.1%; incidence rate ratio: 1.65 [95% confidence interval, CI: 1.08-2.52]) and without ACS (6.0% vs. 3.2%; incidence rate ratio: 1.88 [95% CI: 1.13-3.14]). The differences were mainly explained by higher rates of TLR, whereas rates of cardiac death and target lesion MI did not differ significantly between the two stent groups in patients with or without ACS CONCLUSION: Compared to the O-SES, the DTS was associated with a higher risk of TLF at 12 months in patients with and without ACS. The differences were mainly explained by higher rates of TLR.

OBJECTIVES: To compare the efficacy and safety of the dual therapy CD34 antibody-covered sirolimus-eluting Combo stent (DTS) and the sirolimus-eluting Orsiro stent (SES) in patients with and without diabetes mellitus (DM) included in the Scandinavian Organization for Randomized Trials with Clinical Outcome (SORT OUT) X study.BACKGROUND: The incidence of target lesion failure (TLF) after treatment with modern drug-eluting stents has been reported to be significantly higher in patients with DM when compared to patients without DM. Thus, whether the results from the SORT OUT X study apply to patients with and without DM remains unknown.METHODS: In total 3146 patients were randomized to stent implantation with DTS (n = 1578; DM: n = 279) or SES (n = 1568; DM: n = 271). The primary end point, TLF, was a composite of cardiac death, target-lesion myocardial infarction (MI), or target lesion revascularization (TLR) within 1 year.RESULTS: At 1 year, the rate of TLF was increased in the DTS group compared to the SES group, both among patients with DM (9.3% vs. 4.8%; risk difference: 4.5%; incidence rate ratio: 1.99, 95% confidence interval [CI]: 1.02-3.90) and without DM (5.7% vs. 3.5%; incidence rate ratio: 1.67, 95% CI: 1.15-2.42). The differences were mainly explained by higher rates of TLR.CONCLUSION: Compared to the SES, the DTS was associated with an increased risk of TLF at 12 months in patients with and without DM. The differences were mainly explained by higher rates of TLR, whereas rates of cardiac death and target lesion MI did not differ significantly between the two stent groups in patients with or without DM.

Background: Target lesion failure remains an issue with contemporary drug-eluting stents. Thus, the dual-therapy sirolimus-eluting and CD34+ antibody–coated Combo stent (DTS) was designed to further improve early healing. This study aimed to investigate whether the DTS is noninferior to the sirolimus-eluting Orsiro stent (SES) in an all-comers patient population. Methods: The SORT OUT X (Combo Stent Versus Orsiro Stent) trial, was a large-scale, randomized, multicenter, single-blind, 2-arm, noninferiority trial with registry-based follow-up. The primary end point target lesion failure was a composite of cardiac death, myocardial infarction, or target lesion revascularization within 12 months, analyzed using intention-to-treat. The trial was powered for assessing target lesion failure noninferiority of the DTS compared with the SES with a predetermined noninferiority margin of 0.021. Results: A total of 3146 patients were randomized to treatment with the DTS (1578 patients; 2008 lesions) or SES (1568 patients; 1982 lesions). At 12 months, intention-to-treat analysis showed that 100 patients (6.3%) assigned the DTS and 58 patients (3.7%) assigned the SES met the primary end point (absolute risk difference, 2.6% [upper limit of 1-sided 95% CI, 4.1%]; P (noninferiority)=0.76). The SES was superior to the DTS (incidence rate ratios for target lesion failure, 1.74 [95% CI, 1.26–2.41]; P =0.00086). The difference was explained mainly by a higher incidence of target lesion revascularization in the DTS group compared with the SES group (53 [3.4%] vs. 24 [1.5%]; incidence rate ratio, 2.22 [95% CI, 1.37–3.61]; P =0.0012). Conclusions: The DTS did not confirm noninferiority to the SES for target lesion failure at 12 months in an all-comer population. The SES was superior to the DTS mainly because the DTS was associated with an increased risk of target lesion revascularization. However, rates of death, cardiac death, and myocardial infarction at 12 months did not differ significantly between the 2 stent groups. Registration: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT03216733.

A multitargeted strategy to treat the consequences of ischemia and reperfusion (IR) injury in acute myocardial infarction may add cardioprotection beyond reperfusion therapy alone. We investigated the cardioprotective effect of mild hypothermia combined with local ischemic preconditioning (IPC) or remote ischemic conditioning (RIC) on IR injury in isolated rat hearts. Moreover, we aimed to define the optimum timing of initiating hypothermia and evaluate underlying cardioprotective mechanisms. Compared to infarct size in normothermic controls (56 ± 4%), mild hypothermia during the entire or final 20 min of the ischemic period reduced infarct size (34 ± 2%, p

Ischemia reperfusion (IR) injury may be attenuated through succinate dehydrogenase (SDH) inhibition by dimethyl malonate (DiMAL). Whether SDH inhibition yields protection in diabetic individuals and translates into human cardiac tissue remain unknown. In isolated perfused hearts from 24 weeks old male Zucker diabetic fatty (ZDF) and age matched non-diabetic control rats and atrial trabeculae from patients with and without diabetes, we compared infarct size, contractile force recovery and mitochondrial function. The cardioprotective effect of a 10 minutes DiMAL administration prior to global ischemia and ischemic preconditioning (IPC) was evaluated. In non-diabetic hearts exposed to IR, DiMAL 0.1 mM reduced infarct size compared to IR (55 ± 7% vs. 69 ± 6%, p

Mitochondrial dysfunction plays a central role in ischemia-reperfusion (IR) injury. The pre-ischemic administration of aminooxyacetate (AOA), an inhibitor of the malate-aspartate shuttle (MAS), provides cardioprotection against IR injury, but the underlying mechanism remains unknown. We hypothesized that a transient inhibition of the MAS during ischemia and early reperfusion could preserve mitochondrial function at later phase of reperfusion in IR-injured heart to the same extent as ischemic preconditioning (IPC), which is a well-validated cardioprotective strategy against IR injury. Here we showed that a pre-ischemic administration of AOA preserved mitochondrial complex I-linked state 3 respiration and fatty acid oxidation during late reperfusion in IR-injured isolated rat hearts. The AOA treatment also attenuated the excessive emission of mitochondrial reactive oxygen species during state 3 with complex I-linked substrates during late reperfusion, which was consistent with reduced oxidative damage in IR-injured heart. As a result, the AOA treatment reduced infarct size after reperfusion. These protective effects of MAS inhibition on the mitochondria were similar to those of IPC. Intriguingly, the protection of mitochondrial function by AOA treatment seems different from that of IPC, since AOA treatment, but not IPC, downregulated myocardial tricarboxilic acid (TCA)-cycle intermediates at the onset of reperfusion. MAS inhibition thus preserved mitochondrial respiratory capacity and decreased mitochondrial oxidative stress during late reperfusion in IR-injured heart, at least in part, via metabolic regulation of TCA-cycle intermediates in the mitochondria at the onset of reperfusion. This article is protected by copyright. All rights reserved

Myocardial fibrosis (MF) contributes to the pathogenesis of cardiac hypertrophy secondary to energetic perturbation. Recent evidence suggests an increase of purine signalling upon energetic deficiency and specifically a role of adenosine signalling in tissue fibrosis. The specific objective of this study was to delineate adenosine A2A receptors in the development of MF. In vitro, isolated cardiac fibroblasts demonstrated a significant increase in collagen production upon A2A receptor stimulation. This was inhibited by addition of a specific A2A receptor inhibitor. In vivo, models of cardiac hypertrophy including the transverse aortic constriction (TAC) model and cardiac actin E99K transgenic mice (E99K mice) were investigated as murine models for MF. In E99K mice a reduced phosphocreatine/ATP ratio was demonstrated using magnetic resonance spectroscopy. Interstitial adenosine levels measured by microdialysis correlated with collagen content, showing energy deficiency and a correlation with MF. Crossbreeding of E99K and Adenosine A2A receptor knock out (A2A KO) mice resulted in a significant reduction of MF in E99K heterozygous A2A KO animals. A2A KO mice undergoing TAC demonstrated significantly less fibrosis formation compared to wild type mice upon measurement of myocardial collagen and on histology. This was associated with a significant rescue of cardiac function. Finally, pharmacologic adenosine A2A receptor inhibition using the antagonist ZM241385 demonstrated a partial rescue effect on MF in both TAC and E99K animals. This data indicates that signalling of energy deficiency via adenosine A2A receptors play a crucial role in the formation of MF and that this pathway is susceptible to pharmacologic modulation.

A 73-year old woman presented to our hospital with a few hours of chest pain. Her first troponin-I level was 705 ng/l. The electrocardiogram (ECG) showed normal sinus rhythm with a normal QRS axis and duration, and inverted T waves in leads V2 and V3. She was started on dual-antiplatelet

Background: The Sodium Glucose Transporter 2 (SGLT2)-inhibitor, empagliflozin, reduces death fromcardiovascular causes. We hypothesized that the mechanism involved direct protection against Ischemia-Reperfusion (IR) injury and improved post-ischemic mitochondrial function.Methods: We examined infarct size (series I) and mitochondrial respiration (series II) in four groups of isolatedperfused hearts from male Wistar rats: Sham-operated hearts (Sham group), IR-injured hearts (IR group), heartstreated with ischemic preconditioning (IPC) by 2 × 5 min. cycles of IR prior to sustained ischemia (IPC group), andhearts co-perfused with 2.14 mg/l of empagliflozin 10 min. prior to sustained ischemia (EMPA group).Results: In contrast to IPC, empagliflozin did not reduce infarct size compared to the IR group, when given 10min prior to the acute myocardial infarction. Empagliflozin improved post-ischemic complex I+II respiration comparedto the IR group. This improvement was similar to IPC. In contrast to the improved complex I respiration by IPC,empagliflozin mainly improved complex II respiration. Empagliflozin hearts had significantly higher respiration inoligomycin induced state 4 than the sham and IR group, indicating that empagliflozin modulates the innermitochondrial membrane.Conclusion: In conclusion, empagliflozin yielded no acute cardioprotection in the isolated perfused non-diabeticrat heart. Empagliflozin mainly improved complex II respiration and increased permeability of the inner membrane,providing a potential explanation for the positive long-term effects observed in post infarction myocardial dysfunction.

Udgivelsesdato: 2010-Dec-1 Research within the field of metabolite profiling has already illuminated our understanding of a variety of physiological and pathological processes. Microdialysis has added further refinement to previous models and has allowed the testing of new hypotheses. In the present study, a new ultra-performance liquid chromatography/electrospray-tandem mass spectrometry (UPLC-ESI-MS/MS) method for the simultaneous detection and quantification of intermediary energy metabolites in microdialysates was developed. The targeted metabolites were mainly from the citric acid cycle in combination with pyruvic acid, lactic acid, and the ATP (adenosine triphosphate) hydrolysis product adenosine along with metabolites of adenosine. This method was successfully applied to analyze the microdialysates obtained from an experimental animal study giving insight into the hitherto unknown concentration of many interstitial energy metabolites, such as succinic acid and malic acid. With a total cycle time of 3 min, injection to injection, this method permits analysis of a much larger number of samples in comparison with conventional high performance liquid chromatography/tandem mass spectrometry HPLC-MS/MS strategies. With this novel combination where microdialysis and high sensitivity UPLC-MS/MS technique is combined within cardiologic research, new insights into the intermediary energy metabolism during ischemia-reperfusion is now feasible.

We have found that cardioprotection by l-glutamate mimics protection by classical ischaemic preconditioning (IPC). We investigated whether the effect of IPC involves amino acid transamination and whether IPC modulates myocardial glutamate metabolism. In a glucose-perfused, isolated rat heart model subjected to 40 min global no-flow ischaemia and 120 min reperfusion, the effects of IPC (2 cycles of 5 min ischaemia and 5 min reperfusion) and continuous glutamate (20 mm) administration during reperfusion on infarct size and haemodynamic recovery were studied. The effect of inhibiting amino acid transamination was evaluated by adding the amino acid transaminase inhibitor amino-oxyacetate (AOA; 0.025 mm) during reperfusion. Changes in coronary effluent, interstitial (microdialysis) and intracellular glutamate ([GLUT](i)) concentrations were measured. Ischaemic preconditioning and postischaemic glutamate administration reduced infarct size to the same extent (41 and 40%, respectively; P < 0.05 for both), without showing an additive effect. Amino-oxyacetate abolished infarct reduction by IPC and glutamate, and increased infarct size in both control and IPC hearts in a dose-dependent manner. Ischaemic preconditioning increased [GLUT](i) before ischaemia (P < 0.01) and decreased the release of glutamate during the first 10 min of reperfusion (P = 0.03). A twofold reduction in [GLUT](i) from the preischaemic state to 45 min of reperfusion (P = 0.0001) suggested increased postischaemic glutamate utilization in IPC hearts. While IPC and AOA changed haemodynamics in accordance with infarct size, glutamate decreased haemodynamic recovery despite reduced infarct size. In conclusion, ischaemic cardioprotection of the normal and IPC-protected heart depends on amino acid transamination and activity of the malate-aspartate shuttle during reperfusion. Underlying mechanisms of IPC include myocardial glutamate metabolism.

The prevalence of Type 2 diabetes mellitus is increasing worldwide with obese diabetic patients constituting the majority of this population. Type 2 diabetes is associated with increased morbidity and mortality after acute myocardial infarction. Previous experimental studies of ischaemia-reperfusion tolerance in diabetes have only been performed in animal models of Type 1 diabetes mellitus, yielding conflicting data. The aim of the present study was to characterise and compare the tolerance to ischaemia and effects of ischaemic preconditioning (IPC) in hearts from obese Zucker diabetic fatty (ZDF) and lean Goto-Kakizaki (GK) Type 2 diabetic rats, using non-obese Zucker and Wistar rats as respective controls. The two rat strains were divided into 8 groups. The ZDF study (n=47) consisted of: Control −IPC, Control +IPC, ZDF −IPC and ZDF +IPC. The GK study (n=38) consisted of: Control −IPC, Control +IPC, GK −IPC and GK +IPC. Hearts, which were studied in a Langendorff preparation perfused with Krebs-Henseleit buffer, were subjected or not to IPC (+IPC, −IPC) before 50 minutes of regional ischaemia and 120 minutes reperfusion. Ischaemic reperfusion injury was smaller in obese (p

Objectives: Remote ischemic preconditioning (rIPC) reduces myocardial injury in adults and children undergoing cardiac surgery. We compared the effect of rIPC in adult and neonatal rabbits to investigate whether protection against ischemia-reperfusion injury can be achieved in the newborn heart by (1) in vivo rIPC and (2) dialysate from adult rabbits undergoing rIPC. Methods: Isolated hearts from newborn and adult rabbits were randomized into 3 subgroups (control, in vivo rIPC, and dialysate obtained from adult, remotely preconditioned rabbits). Remote preconditioning was induced by four 5-minute cycles of lower limb ischemia. Left ventricular (LV) function was assessed using a balloon-tipped catheter, glycolytic flux by tracer kinetics, and infarct size by tetrazolium staining. Isolated hearts underwent stabilization while perfused with standard Krebs-Henseleit buffer (control and in vivo rIPC) or Krebs-Henseleit buffer with added dialysate, followed by global no-flow ischemia and reperfusion. Results: Within the age groups, the baseline LV function was similar in all subgroups. In the adult rabbit hearts, rIPC and rIPC dialysate attenuated glycolytic flux and protected against ischemia-reperfusion injury, with better-preserved LV function compared with that of the controls. In contrast, in the neonatal hearts, the glycolytic flux was lower and LV function was better preserved in the controls than in the rIPC and dialysate groups. In the adult hearts, the infarct size was reduced in the rIPC and dialysate groups compared with that in the controls. In the neonatal hearts, the infarct size was smaller in the controls than in the rIPC and dialysate groups. Conclusions: Remote ischemic preconditioning does not protect against ischemia-reperfusion injury in isolated newborn rabbit hearts and might even cause deleterious effects. Similar adverse effects were induced by dialysate from remotely preconditioned adult rabbits. Copyright © 2014 by The American Association for Thoracic Surgery.

Background While remote ischemic preconditioning (rIPC) protects the mature heart against ischemia-reperfusion (IR) injury, the effect on the neonatal heart is not known. The neonatal heart relies almost solely on carbohydrate metabolism, which is modified by rIPC in the mature heart. We hypothesized that rIPC combined with metabolic support with glucose-insulin (GI) infusion improves cardiac function and reduces infarct size after IR injury in neonatal piglets in-vivo. Methods and results 32 newborn piglets were randomized into 4 groups: control, GI, GI + rIPC and rIPC. GI and GI + rIPC groups received GI infusion continuously from 40 min prior to ischemia. rIPC and GI + rIPC groups underwent four cycles of 5 min limb ischemia. Myocardial IR injury was induced by 40 min occlusion of the left anterior descending artery followed by 2 h reperfusion. Myocardial lactate concentrations were assessed in microdialysis samples analyzed by mass spectrometry. Infarct size was measured using triphenyltetrazolium chloride staining. Systolic recovery (dP/dtmax as % of baseline) after 2 h reperfusion was 68.5 ± 13.8% in control, 53.7 ± 11.2% in rIPC (p < 0.05), and improved in GI (83.6 ± 18.8%, p < 0.05) and GI + rIPC (87.0 ± 15.7%, p < 0.01). Conclusion rIPC + GI protects the neonatal porcine heart against IR injury in-vivo. rIPC alone has detrimental metabolic and functional effects that are abrogated by simultaneous GI infusion. © 2013 Elsevier Ireland Ltd.

Mitochondrial aldehyde dehydrogenase-2 (ALDH-2) is involved in preconditioning pathways, but its role in remote ischaemic preconditioning (rIPC) is unknown. We investigated its role in animal and human models of rIPC. (i) In a rabbit model of myocardial infarction, rIPC alone reduced infarct size [69 ± 5.8 % (n = 11) to 40 ± 6.5 % (n = 12), P = 0.019]. However, rIPC protection was lost after pre-treatment with the ALDH-2 inhibitor cyanamide (62 ± 7.6 % controls, n = 10, versus 61 ± 6.9 % rIPC after cyanamide, n = 10, P > 0.05). (ii) In a forearm plethysmography model of endothelial ischaemia-reperfusion injury, 24 individuals of Asian ethnic origin underwent combined rIPC and ischaemia-reperfusion (IR). 11 had wild-type (WT) enzyme and 13 carried the Glu504Lys (ALDH22) polymorphism (rendering ALDH-2 functionally inactive). In WT individuals, rIPC protected against impairment of response to acetylcholine (P = 0.9), but rIPC failed to protect carriers of Glu504Lys polymorphism (P = 0.004). (iii) In a second model of endothelial IR injury, 12 individuals participated in a double-blind placebo-controlled crossover study, receiving the ALDH-2 inhibitor disulfiram 600 mg od or placebo for 48 h prior to assessment of flow-mediated dilation (FMD) before and after combined rIPC and IR. With placebo, rIPC was effective with no difference in FMD before and after IR (6.18 ± 1.03 % and 4.76 ± 0.93 % P = 0.1), but disulfiram inhibited rIPC with a reduction in FMD after IR (7.87 ± 1.27 % and 3.05 ± 0.53 %, P = 0.001). This study demonstrates that ALDH-2 is involved in the rIPC pathway in three distinct rabbit and human models. This has potential implications for future clinical studies of remote conditioning. © 2013 Springer-Verlag Berlin Heidelberg.

Background: Inhibition of glucose oxidation during initial reperfusion confers protection against ischemia-reperfusion (IR) injury in the heart. Mitochondrial metabolism is altered with progression of type 2 diabetes (T2DM). We hypothesized that the metabolic alterations present at onset of T2DM induce cardioprotection by metabolic shutdown during IR, and that chronic alterations seen in late T2DM cause increased IR injury. Methods: Isolated perfused hearts from 6 (prediabetic), 12 (onset of T2DM) and 24 (late T2DM) weeks old male Zucker diabetic fatty rats (ZDF) and their age-matched heterozygote controls were subjected to 40 min ischemia/120 min reperfusion. IR injury was assessed by TTC-staining. Myocardial glucose metabolism was evaluated by glucose tracer kinetics (glucose uptake-, glycolysis- and glucose oxidation rates), myocardial microdialysis (metabolomics) and tissue glycogen measurements. Results: T2DM altered the development in sensitivity towards IR injury compared to controls. At late diabetes ZDF hearts suffered increased damage, while injury was decreased at onset of T2DM. Coincident with cardioprotection, oxidation of exogenous glucose was decreased during the initial and normalized after 5 minutes of reperfusion. Metabolomic analysis of citric acid cycle intermediates demonstrated that cardioprotection was associated with a reversible shutdown of mitochondrial glucose metabolism during ischemia and early reperfusion at onset of but not at late type 2 diabetes. Conclusions: The metabolic alterations of type 2 diabetes are associated with protection against IR injury at onset but detrimental effects in late diabetes mellitus consistent with progressive dysfunction of glucose oxidation. These findings may explain the variable efficacy of cardioprotective interventions in individuals with type 2 diabetes.

Summary The citric acid cycle (CAC) metabolite fumarate has been proposed to be cardioprotective; however, its mechanisms of action remain to be determined. To augment cardiac fumarate levels and to assess fumarate's cardioprotective properties, we generated fumarate hydratase (Fh1) cardiac knockout (KO) mice. These fumarate-replete hearts were robustly protected from ischemia-reperfusion injury (I/R). To compensate for the loss of Fh1 activity, KO hearts maintain ATP levels in part by channeling amino acids into the CAC. In addition, by stabilizing the transcriptional regulator Nrf2, Fh1 KO hearts upregulate protective antioxidant response element genes. Supporting the importance of the latter mechanism, clinically relevant doses of dimethylfumarate upregulated Nrf2 and its target genes, hence protecting control hearts, but failed to similarly protect Nrf2-KO hearts in an in vivo model of myocardial infarction. We propose that clinically established fumarate derivatives activate the Nrf2 pathway and are readily testable cytoprotective agents., Highlights ► Cardiac fumarase deletion (cFH1-KO) results in mice with elevated cardiac fumarate ► cFH1-KO is compensated for by amino acid influx into the citric acid cycle ► Nrf2 and its target genes are activated in the hearts of cFH1-KO mice ► Fumarate-related Nrf2 activation is cytoprotective and may be of therapeutic use

Efficacy of ischemic preconditioning is decreased in animal models of type 2 diabetes mellitus while the responses in humans with diabetes are contradictory. It is unknown whether attenuation is related to decreased release of a mediating humoral cardioprotective factor or reduced ability to respond in the target tissue. The aim of the present study was to investigate the release and effect of a circulating cardioprotective factor in type 2 diabetes mellitus patients. Blood samples were drawn from nine non-diabetic subjects, eight diabetic patients without peripheral neuropathy, and eight diabetic patients with peripheral neuropathy before (control) and after a remote ischemic preconditioning (rIPC) stimulus. Blood samples were dialyzed against Krebs-Henseleit buffer and the cardioprotective effects of the dialysates were tested in rabbit hearts mounted on a Langendorff model and subjected to 30-min global ischemia and 120-min reperfusion. rIPC dialysate from non-diabetic and diabetic subjects without peripheral neuropathy reduced infarct size and improved hemodynamic recovery compared to control dialysate from non-diabetic and diabetic subjects. However, in the subgroup of diabetic patients with neuropathy the cardioprotective effect was attenuated. These findings indicate that the release mechanism involves neural pathways.

Exercise protects against myocardial ischemia-reperfusion (I-R) injury but the mechanism remains unclear. Protection can be transferred from a remotely preconditioned human donor to an isolated perfused rabbit heart using a dialysate of plasma. We hypothesized that physical exercise preconditioning also confers cardioprotection through a humorally mediated effector dependent on opioid receptor activation. Thirteen male volunteers performed vigorous exercise (four 2-minute bouts of high-intensity exercise) and 1 week later they underwent remote ischemic preconditioning (four cycles of 5 min upper limb ischemia and reperfusion). Dialysates were prepared from blood collected before (control) and after the two interventions. Isolated rabbit hearts were perfused with the dialysates without and with co-administration of naloxone (opioid receptor antagonist) prior to 40 min regional ischemia and 2 h reperfusion. Exercise and remote ischemic preconditioning (rIPC) reduced infarct size from 60 ± 5 to 35 ± 5 % and from 57 ± 7 to 27 ± 3 % of the area at risk, respectively (p

The convergence of cardioprotective intracellular signalling pathways to modulate mitochondrial function as an end-target of cytoprotective stimuli is well described. However, our understanding of whether the complementary changes in mitochondrial energy metabolism are secondary responses or inherent mechanisms of ischaemic cardioprotection remains incomplete. In the heart, the malate-aspartate shuttle (MAS) constitutes the primary metabolic pathway for transfer of reducing equivalents from the cytosol into the mitochondria for oxidation. The flux of MAS is tightly linked to the flux of the tricarboxylic acid cycle and the electron transport chain, partly by the amino acid l-glutamate. In addition, emerging evidence suggests the MAS is an important regulator of cytosolic and mitochondrial calcium homeostasis. In the isolated rat heart, inhibition of MAS during ischaemia and early reperfusion by the aminotransferase inhibitor aminooxyacetate induces infarct limitation, improves haemodynamic responses, and modulates glucose metabolism, analogous to effects observed in classical ischaemic preconditioning. On the basis of these findings, the mechanisms through which MAS preserves mitochondrial function and cell survival are reviewed. We conclude that the available evidence is supportive of a down-regulation of mitochondrial respiration during lethal ischaemia with a gradual 'wake-up' during reperfusion as a pivotal feature of ischaemic cardioprotection. Finally, comments on modulating myocardial energy metabolism by the cardioprotective amino acids glutamate and glutamine are given.

Udgivelsesdato: 2010-Nov-21 AIMS/HYPOTHESIS: Sulfonylureas (SUs) may impair outcome in patients with acute coronary syndrome. Most experimental studies of the myocardial effects of SU treatment are performed in non-diabetic models. We compared the effect of two widely used SUs, glibenclamide (gb) and gliclazide (gc), with high and low myocardial K(ATP) channel affinity, respectively, at therapeutic concentrations on infarct size, left ventricular (LV) function and myocardial glycogen, lactate and alanine content before and after ischaemia/reperfusion (I/R). METHODS: Non-diabetic Wistar and diabetic Goto-Kakizaki rat hearts were investigated in a Langendorff preparation. Gb (0.1 μmol/l) and gc (1.0 μmol/l) were administrated throughout the study. Infarct size was evaluated after 120 min of reperfusion. Myocardial metabolite content was measured before and after ischaemia. RESULTS: Infarct size was smaller in diabetic hearts than in non-diabetic hearts (0.33 ± 0.03 vs 0.51 ± 0.05, p

Udgivelsesdato: 2010-Nov-1 AIMS: Preserved mitochondrial function is essential for protection against ischaemia-reperfusion (IR) injury. The malate-aspartate (MA) shuttle constitutes the principal pathway for transport of reducing cytosolic equivalents for mitochondrial oxidation. We hypothesized that a transient shut-down of the MA-shuttle by aminooxyacetate (AOA) during ischaemia and early reperfusion modulates IR injury by mechanisms comparable to ischaemic preconditioning (IPC). METHODS AND RESULTS: Isolated perfused rat hearts exposed to 40 min global no-flow ischaemia were studied in: (i) control, (ii) pre-ischaemic AOA (0.1 mM), (iii) IPC, and (iv) AOA+IPC hearts. IR injury was evaluated by infarct size and haemodynamic recovery. Tracer-estimated glucose oxidation and metabolic changes in glycogen, lactate, pyruvate, tricarboxylic acid (TCA) cycle intermediates, and ATP degradation products were measured. The effects of AOA on complex I respiration and reactive oxygen species (ROS) production were examined in isolated rabbit mitochondria. Treatment with AOA, IPC, or AOA+IPC induced significant infarct reduction; 28 ± 6, 30 ± 3, and 18 ± 1%, respectively, vs. 52 ± 5% of left ventricular (LV) mass for control (P < 0.01 for all). LV-developed pressure improved to 60 ± 3, 63 ± 5 and 53 ± 4 vs. 31 ± 5 mmHg (P < 0.01 for all) after 2 h reperfusion. Pre-ischaemic AOA administration inhibited glycolysis and increased glucose oxidation during post-ischaemic reperfusion similar to IPC, and suppressed complex I respiration and ROS production in the non-ischaemic heart. Changes in lactate, pyruvate, TCA intermediates, and ATP end products suggested an AOA inhibition of the MA-shuttle during late ischaemia and early reperfusion. CONCLUSION: Inhibition of the MA-shuttle during ischaemia and early reperfusion is proposed as a mechanism to reduce IR injury.

Udgivelsesdato: 2008-Mar-12 1. Previously, we found that administration of high-dose l-glutamate during postischaemic reperfusion improves haemodynamic recovery and enhances glycogen resynthesis. In the present study, we investigated whether the same effect occurs in an insulin-free model and whether glutamate administration reduces infarct size. Further, we studied whether the cardioprotective effect of glutamate depends on preserved glutamate transamination and K(ATP) channel activity. 2. In a rat isolated, insulin-free, perfused heart model, we compared the effects of administration of l-glutamate (10 mmol/L) during either 45 min no-flow regional ischaemia plus 120 min reperfusion or reperfusion alone on infarct size and left ventricular (LV) recovery. The effect of glutamate on glycogen metabolism was studied in a model of 30 min global no-flow ischaemia and 60 min reperfusion. In both models, the effects of inhibition of glutamate transamination and K(ATP) channel activity were examined by adding amino-oxyacetate (an aminotransferase inhibitor; 0.1 mmol/L) and glibenclamide (a K(ATP) blocker; 10 mmol/L), respectively. 3. Administration of l-glutamate reduced infarct size by 60% (P < 0.01) and improved postischaemic LV function (developed pressure and rate pressure product; P < 0.05). l-Glutamate increased glycogen content after 60 min reperfusion by 65% (P < 0.01). Amino-oxyacetate, as well as glibenclamide, abolished the glutamate-mediated reduction in infarct size, haemodynamic improvement and glycogen resynthesis during reperfusion. 4. In conclusion, l-glutamate administration from the start of postischaemic reperfusion exerts cardioprotective effects, including reduced infarct size, improved haemodynamic recovery and enhanced glycogen resynthesis. These effects depend on preserved transamination of glutamate and K(ATP) channel activity, but not on insulin administration.

1. L-Glutamate and glutamine have been suggested to have cardioprotective effects. However, the issue is controversial and the metabolic mechanisms underlying a beneficial effect are not well understood. 2. In the present study we investigated the effects of L-glutamate and glutamine on haemodynamic recovery, the rate of de novo glycogen synthesis and myocardial glucose uptake during postischaemic reperfusion. 3. Hearts from male Wistar rats (250-300 g) were divided into three groups as follows: (i) control (n = 12); (ii) L-glutamate (n = 12); and (iii) glutamine (n = 12). Hearts were mounted in a Langendorff preparation and perfused with oxygenated Krebs'-Henseleit solution at 80 mmHg and 37C. Global ischaemia for 20 min was followed by 15 min reperfusion, during which L-glutamate (50 mmol/L) or glutamine (20 mmol/L) were administered. Left ventricular developed pressure (LVDP), de novo synthesis of glycogen using [14C]-glucose and myocardial glucose uptake using D-[2-3H]-glucose were measured. 4. L-Glutamate and glutamine increased postischaemic LVDP (P < 0.01 vs control hearts for both). L-Glutamate and glutamine increased de novo glycogen synthesis by 78% (P < 0.001) and 55% (P < 0.01), respectively. At the end of reperfusion, total myocardial glycogen content was increased by both L-glutamate and glutamine (5.7 +/- 0.3 and 6.2 +/- 0.7 micromol/g wet weight, respectively; P < 0.05 and 0.01, respectively) compared with that in control hearts (3.6 +/- 0.4 micromol/g wet weight). Neither L-glutamate nor glutamine affected myocardial glucose uptake during reperfusion. 5. Improved postischaemic haemodynamic recovery after L-glutamate and glutamine supplementation during reperfusion is associated with increased de novo glycogen synthesis, suggesting a favourable modulation of intracellular myocardial carbohydrate metabolism.

Visual Abstract, Highlights • Pre-conditioning has emerged as a potentially powerful means of reducing ischemia-reperfusion injury. • Several animal models have implicated adenosine in pre-conditioning pathways, but its role in human physiology is unknown. • In human volunteers, the authors demonstrate that adenosine receptor activation in “trigger” tissue is an important step in initiating a pre-conditioning signal, but adenosine receptor blockade in “target” tissue does not block the protection afforded by pre-conditioning. • The authors also demonstrate that pre-conditioning elaborates a transferrable cardioprotective factor(s) into the serum. This elaboration is prevented by adenosine receptor blockade but can be mirrored by the infusion of exogenous adenosine. • An improved understanding of the physiological effectors of pre-conditioning may allow for better targeted clinical studies of pre-conditioning and pre-conditioning mimetics in the future., Summary Remote ischemic pre-conditioning (rIPC) has emerged as a potential mechanism to reduce ischemia-reperfusion injury. Clinical data, however, have been mixed, and its physiological basis remains unclear, although it appears to involve release of circulating factor(s) and/or neural pathways. Here, the authors demonstrate that adenosine receptor activation is an important step in initiating human pre-conditioning; that pre-conditioning liberates circulating cardioprotective factor(s); and that exogenous adenosine infusion is able to recapitulate release of this factor. However, blockade of adenosine receptors in ischemic tissue does not block the protection afforded by pre-conditioning. These data have important implications for defining the physiology of human pre-conditioning and its translation to future clinical trials.