Ten year mortality in relation to original size of myocardial infarct: results from the Gothenburg metoprolol study

Mitochondria-associated membrane-modulated Ca2+ transfer: A potential treatment target in cardiac ischemia reperfusion injury and heart failure

Effective Ca²⁺ dependent mitochondrial energy supply is imperative for proper cardiac contractile activity, while disruption of Ca²⁺ homeostasis participates in the pathogenesis of multiple human diseases. This phenomenon is particularly prominent in cardiac ischemia and reperfusion (I/R) and heart failure, both of which require strict clinical intervention. The interface between endoplasmic reticula (ER) and mitochondria, designated the mitochondria-associated membrane (MAM), is now regarded as a crucial mediator of Ca²⁺ transportation. Thus, interventions targeting this physical and functional coupling between mitochondria and the ER are highly desirable. Increasing evidence supports the notion that restoration, and maintenance, of the physiological contact between these two organelles can improve mitochondrial function, while inhibiting cell death, thereby sufficiently ameliorating I/R injury and heart failure development. A better understanding regarding the underlying mechanism of MAM-mediated transport will pave the way for identification of novel treatment approaches for heart disease. Therefore, in this review, we summarize the crucial functions and potential mechanisms of MAMs in the pathogenesis of I/R and heart failure.

Cardioprotective GLP-1 metabolite prevents ischemic cardiac injury by inhibiting mitochondrial trifunctional protein-α

Mechanisms mediating the cardioprotective actions of glucagon-like peptide 1 (GLP-1) were unknown. Here, we show in both ex vivo and in vivo models of ischemic injury that treatment with GLP-1(28-36), a neutral endopeptidase-generated (NEP-generated) metabolite of GLP-1, was as cardioprotective as GLP-1 and was abolished by scrambling its amino acid sequence. GLP-1(28-36) enters human coronary artery endothelial cells (caECs) through macropinocytosis and acts directly on mouse and human coronary artery smooth muscle cells (caSMCs) and caECs, resulting in soluble adenylyl cyclase Adcy10-dependent (sAC-dependent) increases in cAMP, activation of protein kinase A, and cytoprotection from oxidative injury. GLP-1(28-36) modulates sAC by increasing intracellular ATP levels, with accompanying cAMP accumulation lost in sAC-/- cells. We identify mitochondrial trifunctional protein-α (MTPα) as a binding partner of GLP-1(28-36) and demonstrate that the ability of GLP-1(28-36) to shift substrate utilization from oxygen-consuming fatty acid metabolism toward oxygen-sparing glycolysis and glucose oxidation and to increase cAMP levels is dependent on MTPα. NEP inhibition with sacubitril blunted the ability of GLP-1 to increase cAMP levels in coronary vascular cells in vitro. GLP-1(28-36) is a small peptide that targets novel molecular (MTPα and sAC) and cellular (caSMC and caEC) mechanisms in myocardial ischemic injury.

Early kinetics of serum Interleukine-17A and infarct size in patients with reperfused acute ST-elevated myocardial infarction

BACKGROUND

Recently, it was shown that interleukin-17A (IL-17A) is involved in the pathophysiology of reperfusion injury and associated with infarct size (IS) in experimental models of myocardial infarction. Our aim was to evaluate whether the IL-17A serum level and the IL-17A active fraction was correlated with IS in humans.

METHODS

101 patients presenting with a ST-elevated Myocardial Infarction (STEMI) referred for primary percutaneous coronary intervention (PPCI) and 10 healthy controls were included. For each participant, blood samples at admission (H0) and 4 hours after admission (H4) were collected. IL-17A serum levels were assessed using ELISA and the active fraction was assessed with a functional test. IS was determined by peak troponin and peak CK levels for every patient and by contrast-enhanced cardiac magnetic resonance (ce-CMR) for 20 patients.

RESULTS

The IL-17A serum level was significantly increased in STEMI patients compared to healthy controls, (0.9 pg/mL IQR [0.0-3.2] at H0 and 1.0 pg/mL IQR [0.2-2.8] at H4 versus 0.2 pg/mL IQR [0.0-0.7] for healthy controls; p<0.005). At either time points, IL-17A levels did not correlate with IS as measured by peak troponin, peak CK pr ce-CMR. Also, no correlation was found between the active fraction of IL-17A and IS.

CONCLUSION

Serum IL-17A level is significantly increased in patients at the early phase of acute MI compared to healthy controls. However, the level of IL-17A in the early hours after reperfusion does not correlate with IS.

Pharmacokinetics and safety of a single dose of the novel necrosis inhibitor LC28-0126 in healthy male subjects

AIMS

A novel necrosis inhibitor, LC28-0126, is expected to have a cellular protective effect from ischaemic reperfusion injury in acute myocardial infarction. The objective of this study was to investigate the safety, tolerability and pharmacokinetics of LC28-0126 after a single intravenous administration in healthy male subjects.

METHODS

The study was a dose-block-randomized, double-blind, placebo-controlled, single ascending dose, first-in-human trial. Subjects were randomly assigned to receive 0.3, 1, 3, 10, 25, 50, 100 or 200 mg of LC28-0126. LC28-0126 was infused for 30 min and 5 min in cohorts 1 and 2, respectively. An interim analysis to assess the tolerability and pharmacokinetics was conducted in each dose group. Blood samples were taken to determine plasma LC28-0126 concentrations from predose to 48 or 144 h postdose, and urine samples were taken from predose to 48 or 72 h postdose.

RESULTS

Overall, 89 subjects were randomly assigned to the dose groups of the two cohorts. LC28-0126 was well tolerated, and no serious adverse events were reported. LC28-0126 showed rapid disposition in the distribution phase. Overall, the fraction of unchanged LC28-0126 excreted during the 48 or 72 h after administration was below 5%. The systemic exposure of LC28-0126 tends to be increased in a dose-proportional manner in the dose range of 0.3-200 mg.

CONCLUSIONS

A single intravenous dose of LC28-0126 was safe and well tolerated up to 200 mg. Furthermore, LC28-0126 demonstrated a predictable pharmacokinetic profile after a single intravenous infusion of doses ranging from 0.3 to 200 mg.

Inhibition of myocardial reperfusion injury by ischemic postconditioning requires sirtuin 3-mediated deacetylation of cyclophilin D

RATIONALE

How ischemic postconditioning can inhibit opening of the mitochondrial permeability transition pore (PTP) and subsequent cardiac myocytes death at reperfusion remains unknown. Recent studies have suggested that de-acetylation of cyclophilin D (CyPD) by sirtuin 3 (SIRT3) can modulate its binding to the PTP.

OBJECTIVE

The aim of the present study was to examine whether ischemic postconditioning (PostC) might activate SIRT3 and consequently prevent lethal myocardial reperfusion injury through a deacetylation of CyPD.

METHODS AND RESULTS

Using hypoxia-reoxygenation (H/R) in H9C2 cells, we showed that SIRT3 overexpression prevented CyPD acetylation, limited PTP opening and reduced cell death by 24%. In vitro modification of the CyPD acetylation status in MEFs by site-directed mutagenesis altered capacity of PTP opening by calcium. Calcium Retention Capacity (CRC) was significantly decreased with CyPD-KQ that mimics acetylated protein compared with CyPD WT (871 ± 266 vs 1193 ± 263 nmoles Ca(2+)/mg protein respectively). Cells expressing non-acetylable CyPD mutant (CyPD-KR) displayed 20% decrease in cell death compared to cells expressing CyPD WT after H/R. Correspondingly, in mice we showed that cardiac ischemic postconditioning could not reduce infarct size and CyPD acetylation in SIRT3 KO mice, and was unable to restore CRC in mitochondria as it is observed in WT mice.

CONCLUSIONS

Our study suggests that the increased acetylation of CyPD following myocardial ischemia-reperfusion facilitates PTP opening and subsequent cell death. Therefore ischemic postconditioning might prevent lethal reperfusion injury through an increased SIRT3 activity and subsequent attenuation of CyPD acetylation at reperfusion.

Targeting reperfusion injury in acute myocardial infarction: a review of reperfusion injury pharmacotherapy

INTRODUCTION

Acute myocardial infarction (AMI) (secondary to lethal ischemia-reperfusion [IR]) contributes to much of the mortality and morbidity from ischemic heart disease. Currently, the treatment for AMI is early reperfusion; however, this itself contributes to the final myocardial infarct size, in the form of what has been termed 'lethal reperfusion injury'. Over the last few decades, the discovery of the phenomena of ischemic preconditioning and postconditioning, as well as remote preconditioning and remote postconditioning, along with significant advances in our understanding of the cardioprotective pathways underlying these phenomena, have provided the possibility of successful mechanical and pharmacological interventions against reperfusion injury.

AREAS COVERED

This review summarizes the evidence from clinical trials evaluating pharmacological agents as adjuncts to standard reperfusion therapy for ST-elevation AMI.

EXPERT OPINION

Reperfusion injury pharmacotherapy has moved from bench to bedside, with clinical evaluation and ongoing clinical trials providing us with valuable insights into the shortcomings of current research in establishing successful treatments for reducing reperfusion injury. There is a need to address some key issues that may be leading to lack of translation of cardioprotection seen in basic models to the clinical setting. These issues are discussed in the Expert opinion section.

Use of carvedilol in hypertension: an update

β-blockers are effective antihypertensive agents and, together with diuretics, have been the cornerstone of pioneering studies showing their benefits on cardiovascular morbidity and mortality as a consequence of blood pressure reduction in patients with hypertension. However, evidence from recent meta-analyses have demonstrated no benefit afforded by atenolol compared with placebo in risk of mortality, myocardial infarction, or stroke, and a higher risk of mortality and stroke with atenolol/propranolol compared with other antihypertensive drug classes. Thus, the effect of these agents on cardiovascular morbidity and mortality in hypertensive patients, especially their use in uncomplicated hypertension, has remained largely controversial. However, it is recognized that the clinical studies used in these meta-analyses were mainly based on the older second-generation β-blockers, such as atenolol and metoprolol. Actually, considerable heterogeneity in, eg, pharmacokinetic, pharmacological, and physicochemical properties exists across the different classes of β-blockers, particularly between the second-generation and newer third-generation agents. Carvedilol is a vasodilating noncardioselective third-generation β-blocker, without the negative hemodynamic and metabolic effects of traditional β-blockers, which can be used as a cardioprotective agent. Compared with conventional β-blockers, carvedilol maintains cardiac output, has a reduced prolonged effect on heart rate, and reduces blood pressure by decreasing vascular resistance. Studies have also shown that carvedilol exhibits favorable effects on metabolic parameters, eg, glycemic control, insulin sensitivity, and lipid metabolism, suggesting that it could be considered in the treatment of patients with metabolic syndrome or diabetes. The present report provides an overview of the main clinical studies concerning carvedilol administered as either monotherapy or in combination with another antihypertensive or more frequently a diuretic agent, with particular focus on the additional benefits beyond blood pressure reduction.

Beta-blockers in hypertension

Beta blockers have been used in the treatment of cardiovascular conditions for decades. Despite a long history and status as a guideline-recommended treatment option for hypertension, recent meta-analyses have brought into question whether β blockers are still an appropriate therapy given outcomes data from other antihypertensive drug classes. However, β blockers are a heterogenous class of agents with diverse pharmacologic and physiologic properties. Much of the unfavorable data revealed in the recent meta-analyses were gleaned from studies involving nonvasodilating, traditional β blockers, such as atenolol. However, findings with traditional β blockers may not be extrapolated to other members of the class, particularly those agents with vasodilatory activity. Vasodilatory β blockers (i.e., carvedilol and nebivolol) reduce blood pressure in large part through reducing systemic vascular resistance rather than by decreasing cardiac output, as is observed with traditional β blockers. Vasodilating ability may also ameliorate some of the concerns associated with traditional β blockade, such as the adverse effects on metabolic and lipid parameters, including an increased risk for new-onset diabetes. Furthermore, vasodilating ability is physiologically relevant and important in treating a condition with common co-morbidities involving metabolic and lipid abnormalities such as hypertension. In patients with hypertension and diabetes or coronary artery disease, vasodilating β blockers provide effective blood pressure control with neutral or beneficial effects on important parameters for the co-morbid disease. In conclusion, it is time for a reexamination of the clinical evidence for the use of β blockers in hypertension, recognizing that there are patients for whom β blockers, particularly those with vasodilatory actions, are an appropriate treatment option.

Which factors determine the long-term outcome among patients with a very small or unconfirmed AMI

AIM

To describe various factors associated with the very long-term prognosis for patients with a very small or an unconfirmed acute myocardial infarction (AMI).

METHODS

Patients below 76 years of age, hospitalized due to suspected AMI who either developed a very small AMI (enzyme elevation<twice upper normal limit and maximum serum (S) aspartate aminotransferase (S-ASAT)<1.4 ukat/l) or an unconfirmed AMI (a suspected ischemic event with no signs of myocardial necrosis) were evaluated at our out-patient clinic. The 10-year mortality was related to the clinical history, age and sex, metabolic factors, diagnosis at hospital discharge, various psychosocial factors, use of medication, current symptoms, underlying reason to the symptoms, maximal working capacity and other observations at bicycle exercise test including signs of myocardial ischemia.

RESULTS

In all, 714 patients (33% women) with a median age of 63 years were included in the analyses. The following appeared as independent risk indicators for 10-year mortality: S-gammaglutamyl transpeptidase (GT) (P<0.0001), age (P<0.0001), current smoking (P<0.0001), a history of previous AMI (P<0.0001), maximal working capacity at bicycle exercise test (P=0.002), and current treatment with digitalis (borderline significance; P=0.022).

CONCLUSION

Among patients with a suspected acute myocardial ischemic event with no or minimal myocardial necrosis, various factors reflecting their age, history of cardiac disease and smoking, liver function, working capacity and possibly use of medication affected their very long-term prognosis.