Pioglitazone, a peroxisome proliferator-activated receptor-γ agonist, attenuates myocardial ischemia–reperfusion injury in mice with metabolic disorders

The Exercise Preconditioning Effect on Cardiac Tissue Injury following Induction of Myocardial Infarction in Male Rats

Materials and Methods

Twenty-four male rats were divided into 4 groups including MI, Sham, HIIT, and HIIT+MI (N = 6). HIIT and HIIT+MI which underwent high-intensity interval training (HIIT) for 4 weeks (5 days a week). The training protocol included 10 intervals of 1-minute running, with 2 minutes rest between each interval. The training intensity was different every week according to the peak treadmill running speed (v peak) percentage of each rat. Isoproterenol injection was used to induce myocardial infarction (MI). Expressions of creatine kinase-MB (CK-MB), PGC-1α troponin-I, mitochondrial transcription factor A (TFAM), vascular endothelial growth factor (VEGF), and microRNA 126 (miR-126) genes were measured. The variables were measured using biochemical and RT-PCR methods. The significance level (P value≤0.05) was analyzed using ANOVA test.

Results

The results showed that 4 weeks of HIIT training led to a significant increase in PGC-1α, TFAm, and VEGF levels in the MI, HIIT, and HIIT+MI groups compared to the sham group (P = 0.001). HIIT exercises increased miR-126 in the different groups compared to the sham group; however, it was not significant.

Conclusion

The results obtained showed that HIIT exercise exerts cardio-protective effects to reduce cardiac tissue injury and necrosis against MI. These effects increase mitochondrial biogenesis and angiogenesis by inducing the increased expression of VEGF, TFAM, PGC-1α, and miR-126 genes in the heart tissue. Therefore, HIIT training, as a preconditioning program, was able to protect the cardiac tissue against MI.

Diabetes mellitus — metabolic preconditioning in protecting the heart from ischemic damage?

The negative impact of diabetes mellitus (DM) on the cardiovascular system has been confirmed by numerous clinical studies. However, there are experimental studies that show an increase in the resistance of the heart to ischemic and reperfusion damage in animals with DM. This phenomenon is characterized by a smaller size of the infarct zone, better preservation of the contractile function of the myocardium, and a lower incidence of ischemic and reperfusion arrhythmias. It is assumed that at a certain stage in the development of DM, a “metabolic window” is formed, in which metabolic alterations at the cellular level trigger adaptive mechanisms that increase the viability of cardiomyocytes. Published data confirm that the magnitude of the protective effect induced by DM is comparable to, and in some cases even exceeds, the effect of the preconditioning phenomenon. It is recognized that the mechanisms that protect the heart from ischemic and reperfusion damage against the background of DM are universal and are associated with the modulation of the antioxidant system, apoptosis factors, pro-inflammatory cytokines, and signaling systems that ensure cell survival. The one of the main pathogenic factor in DM is hyperglycemia, but under stress it plays the role of an adaptive mechanism aimed at meeting the increased energy demand in pathological conditions. Probably, at a certain stage of DM, hyperglycemia becomes a trigger for the development of protective effects and activates not only signaling pathways, but also the restructuring of energy metabolism, which makes it possible to maintain ATP production at a sufficient level to maintain the vital activity of heart cells under ischemia/reperfusion conditions. It is possible that an increased level of glucose, accompanied by the activation of insulin-independent mechanisms of its entry into cells, as well as the availability of this energy substrate, will contribute to a better restoration of energy production in heart cells after a infarction, which, in turn, will significantly reduce the degree of myocardial damage and will help preserve the contractile function of the heart. Identification of the conditions and mechanisms of the cardioprotective phenomenon induced by DM will make it possible to simulate the metabolic state in which the protection of cardiomyocytes from damaging factors is realized.

Perspectives on mitochondrial relevance in cardiac ischemia/reperfusion injury

Cardiovascular disease is the most common cause of death worldwide and in particular, ischemic heart disease holds the most considerable position. Even if it has been deeply studied, myocardial ischemia-reperfusion injury (IRI) is still a side-effect of the clinical treatment for several heart diseases: ischemia process itself leads to temporary damage to heart tissue and obviously the recovery of blood flow is promptly required even if it worsens the ischemic injury. There is no doubt that mitochondria play a key role in pathogenesis of IRI: dysfunctions of these important organelles alter cell homeostasis and survival. It has been demonstrated that during IRI the system of mitochondrial quality control undergoes alterations with the disruption of the complex balance between the processes of mitochondrial fusion, fission, biogenesis and mitophagy. The fundamental role of mitochondria is carried out thanks to the finely regulated connection to other organelles such as plasma membrane, endoplasmic reticulum and nucleus, therefore impairments of these inter-organelle communications exacerbate IRI. This review pointed to enhance the importance of the mitochondrial network in the pathogenesis of IRI with the aim to focus on potential mitochondria-targeting therapies as new approach to control heart tissue damage after ischemia and reperfusion process.

The Role of PPAR-γ in Allergic Disease

PURPOSE OF REVIEW

The incidence of allergic diseases such as asthma, rhinitis and atopic dermatitis has risen at an alarming rate over the last century. Thus, there is a clear need to understand the critical factors that drive such pathologic immune responses. Peroxisome proliferator-activated receptor-γ (PPAR-γ) is a nuclear receptor that has emerged as an important regulator of multiple cell types involved in the inflammatory response to allergens; from airway epithelial cells to T Helper (TH) cells.

RECENT FINDINGS

Initial studies suggested that agonists of PPAR-γ could be employed to temper allergic inflammation, suppressing pro-inflammatory gene expression programs in epithelial cells. Several lines of work now suggest that PPAR-γ plays an essential in promoting 'type 2' immune responses that are typically associated with allergic disease. PPAR-γ has been found to promote the functions of TH2 cells, type 2 innate lymphoid cells, M2 macrophages and dendritic cells, regulating lipid metabolism and directly inducing effector gene expression. Moreover, preclinical models of allergy in gene-targeted mice have increasingly implicated PPAR-γ in driving allergic inflammation. Herein, we highlight the contrasting roles of PPAR-γ in allergic inflammation and hypothesize that the availability of environmental ligands for PPAR-γ may be at the heart of the rise in allergic diseases worldwide.

S. Ferreira KC, Neto JCR. Pharmacological Strategies for Insulin Sensitivity in Obesity and Cancer: Thiazolidinediones and Metformin

Background:

Chronic diseases, such as obesity and cancer, have high prevalence rates. Both diseases have hyperinsulinemia, hyperglycemia, high levels of IGF-1 and inflammatory cytokines in common. Therefore, these can be considered triggers for cancer development and growth. In addition, low-grade inflammation that modulates the activation of immune cells, cellular metabolism, and production of cytokines and chemokines are common in obesity, cancer, and insulin resistance. Pharmacological strategies are necessary when a change in lifestyle does not improve glycemic homeostasis. In this regard, thiazolidinediones (TZD) possess multiple molecular targets and regulate PPARγ in obesity and cancer related to insulin resistance, while metformin acts through the AMPK pathway.

Objective:

The aim of this study was to review TZD and metformin as pharmacological treatments for insulin resistance associated with obesity and cancer.

Conclusions:

Thiazolidinediones restored adiponectin secretion and leptin sensitivity, reduced lipid droplets in hepatocytes and orexigen peptides in the hypothalamus. In cancer cells, TZD reduced proliferation, production of reactive oxygen species, and inflammation by acting through the mTOR and NFκB pathways. Metformin has similar effects, though these are AMPK-dependent. In addition, both drugs can be efficient against certain side effects caused by chemotherapy.

Peroxisome proliferator-activated receptor-gamma targeting nanomedicine promotes cardiac healing after acute myocardial infarction by skewing monocyte/macrophage polarization in preclinical animal models

Aims

Monocyte-mediated inflammation is a major mechanism underlying myocardial ischaemia-reperfusion (IR) injury and the healing process after acute myocardial infarction (AMI). However, no definitive anti-inflammatory therapies have been developed for clinical use. Pioglitazone, a peroxisome proliferator-activated receptor-gamma (PPARγ) agonist, has unique anti-inflammatory effects on monocytes/macrophages. Here, we tested the hypothesis that nanoparticle (NP)-mediated targeting of pioglitazone to monocytes/macrophages ameliorates IR injury and cardiac remodelling in preclinical animal models.

Methods and results

We formulated poly (lactic acid/glycolic acid) NPs containing pioglitazone (pioglitazone-NPs). In a mouse IR model, these NPs were delivered predominantly to circulating monocytes and macrophages in the IR heart. Intravenous treatment with pioglitazone-NPs at the time of reperfusion attenuated IR injury. This effect was abrogated by pre-treatment with the PPARγ antagonist GW9662. In contrast, treatment with a pioglitazone solution had no therapeutic effects on IR injury. Pioglitazone-NPs inhibited Ly6Chigh inflammatory monocyte recruitment as well as inflammatory gene expression in the IR hearts. In a mouse myocardial infarction model, intravenous treatment with pioglitazone-NPs for three consecutive days, starting 6 h after left anterior descending artery ligation, attenuated cardiac remodelling by reducing macrophage recruitment and polarizing macrophages towards the pro-healing M2 phenotype. Furthermore, pioglitazone-NPs significantly decreased mortality after MI. Finally, in a conscious porcine model of myocardial IR, pioglitazone-NPs induced cardioprotection from reperfused infarction, thus providing pre-clinical proof of concept.

Conclusion

NP-mediated targeting of pioglitazone to inflammatory monocytes protected the heart from IR injury and cardiac remodelling by antagonizing monocyte/macrophage-mediated acute inflammation and promoting cardiac healing after AMI.

Pioglitazone alleviates oxygen and glucose deprivation-induced injury by up-regulation of miR-454 in H9c2 cells

OBJECTIVES

Pioglitazone, an anti-diabetic agent, has been widely used to treat type II diabetes. However, the effect of pioglitazone on myocardial ischemia reperfusion injury (MIRI) is still unclear. Herein, the objective of this study is to learn about the regulation and mechanism of pioglitazone effects on oxygen glucose deprivation (OGD)-induced myocardial cell injury.

MATERIALS AND METHODS

A cellular injury model of OGD-treated H9c2 cells in vitro was constructed to simulate ischemic/reperfusion (I/R) injury. Then, various concentrations of pioglitazone (0, 2.5, 5, 7.5 and 10 μM) were used for the treatment of H9c2 cells, and CCK-8, flow cytometry and western blot assays were performed to examine cell viability, apoptosis, and the protein levels of factors involved in cell cycle and apoptosis in OGD-treated cells. MiR-454 inhibitor was used to suppress miR-454 expression, and whether miR-454 was involved in regulating OGD-induced cell injury was studied. Two key signal pathways were examined to uncover the underlying mechanism.

RESULTS

OGD reduced cell proliferation and induced apoptosis in H9c2 cells (P<0.05, P<0.01 or P< 0.001). OGD-induced injury was significantly attenuated by pioglitazone at the concentration of 5 μM. Additionally, pioglitazone significantly up-regulated miR-454 expression in OGD-injured cells (P< 0.05 or P< 0.01). MiR-454 suppression declined the protective effect of pioglitazone on OGD-injured H9c2 cells (P<0.05 or P< 0.01). Besides, pioglitazone activated PI3K/AKT and ERK/MAPK pathways via up-regulating miR-454.

CONCLUSION

Pioglitazone protected H9c2 cells against OGD-induced injury through up-regulating miR-454, indicating a novel therapeutic strategy for treatment of MIRI.

Myocardial Expression of PPARγ and Exercise Capacity in Patients after Coronary Artery Bypass Surgery

Activation of PPARs may be involved in the development of heart failure (HF). We evaluated the relationship between expression of PPARγ in the myocardium during coronary artery bypass grafting (CABG) and exercise tolerance initially and during follow-up. 6-minute walking test was performed before CABG, after 1, 12, 24 months. Patients were divided into two groups (HF and non-HF) based on left ventricular ejection fraction and plasma proBNP level. After CABG, 67% of patients developed HF. The mean distance 1 month after CABG in HF was 397 ± 85 m versus 420 ± 93 m in non-HF. PPARγ mRNA expression was similar in both HF and non-HF groups. 6MWT distance 1 month after CABG was inversely correlated with PPARγ level only in HF group. Higher PPARγ expression was related to smaller LVEF change between 1 month and 1 year (R = 0.18, p < 0.05), especially in patients with HF. Higher initial levels of IL-6 in HF patients were correlated with longer distance in 6MWT one month after surgery and lower PPARγ expression. PPARγ expression is not related to LVEF before CABG and higher PPARγ expression in the myocardium of patients who are developing HF following CABG may have some protecting effect.

Myocardial susceptibility to ischaemia/reperfusion in obesity: a re-evaluation of the effects of age

Background

Reports on the effect of age and obesity on myocardial ischaemia/reperfusion (I/R) injury and ischaemic preconditioning are contradictory. The aim of this study was to re-evaluate the effects of age and diet-induced obesity (DIO) on myocardial I/R injury and preconditioning potential.

Methods

Four groups of Wistar male rats were used: age-matched controls (AMC) receiving standard rat chow for (i) 16 weeks and (ii) 16 months respectively; DIO rats receiving a sucrose-supplemented diet for (iii) 16 weeks and (iv) 16 months respectively. The ages of groups (i) and (iii) were 22 weeks (“young”) and groups (ii) and (iv) 17 months (“middle-aged”) at time of experimentation. Isolated perfused working hearts were subjected to 35 min regional ischaemia/1 h reperfusion. Endpoints were infarct size (tetrazolium staining) and functional recovery. Hearts were preconditioned by 3 × 5 min ischaemia/5 min reperfusion. Results were processed using GraphPad Prism statistical software.

Results

Age did not affect baseline heart function before induction of ischaemia and I/R damage as indicated by infarct size and similar values were obtained in hearts from both age groups. Age also had no effect on functional recovery of hearts during reperfusion after regional ischaemia in AMC rats, but cardiac output during reperfusion was better in hearts from middle-aged than young DIO rats.

The diet reduced infarct size in hearts from young rats (% of area at risk: AMC: 32.4 ± 3.6; DIO: 20.7 ± 2.9, p < 0.05), with no differences in hearts from middle-aged rats (AMC: 24.6 ± 4.6; DIO: 28.3 ± 13.5, p = NS). Compared to their respective AMC, diet-induced obesity had no significant effect on functional recovery of hearts from both age groups after exposure to regional ischaemia.

When exposed to the more severe stress of global ischaemia, the functional recovery potential of middle-aged DIO rats appeared to be impeded compared to hearts of young DIO rats, while age had no effect on the functional recovery of AMC hearts.

Preconditioning reduced infarct size in hearts from young control rats and both middle-aged groups, but not from young DIO rats. Age had a significant effect on functional recovery in preconditioning: it was improved in hearts from young control and DIO rats, but depressed in both middle-aged groups.

Conclusions

The data showed that middle-age and obesity had no effect on baseline myocardial function and did not increase susceptibility to I/R damage upon exposure to regional ischaemia. On the contrary, obesity reduced I/R damage in young rats. Preconditioned aging hearts showed a decreased infarct size, but a reduction in functional recovery.

Pioglitazone increases PGC1-α signaling within chronically ischemic myocardium

The peroxisome proliferator-activated receptor (PPAR)-γ drug pioglitazone (PIO) has been shown to protect tissue against oxidant stress. In a swine model of chronic myocardial ischemia, we tested whether PIO increases PGC1-α signaling and the expression of mitochondrial antioxidant peptides. Eighteen pigs underwent a thoracotomy with placement of a fixed constrictor around the LAD artery. At 8 weeks, diet was supplemented with either PIO (3 mg/kg) or placebo for 4 weeks. Regional myocardial function and blood flow were determined at the time of the terminal study. PGC1-α expression was quantified from nuclear membranes by gels and respiration, oxidant stress markers and proteomics by iTRAQ were determined from isolated mitochondria. In the chronically ischemic LAD region, wall thickening from the PIO and control groups was 42 ± 6 and 45 ± 5 %, respectively (NS) with no intergroup differences in basal blood flow (0.72 ± 0.04 versus 0.74 ± 0.04 ml/min g, respectively; NS). In the PIO group, the expression of nuclear bound PGC1-α was higher (11.3 ± 2.6 versus 4.4 ± 1.4 AU; P < 0.05) and the content of mitochondrial antioxidant peptides including superoxide dismutase 2, aldose reductase, glutathione S-transferase and thioredoxin reductase were greater than controls. Although isolated mitochondria from the PIO group showed lower state 3 respiration (102 ± 13 versus 161 ± 22 nmol/min mg; P < 0.05), no differences in oxidant stress were noted by protein carbonyl (1.7 ± 0.7 versus 1.1 ± 0.1 nmol/mg). Chronic pioglitazone does not reduce regional myocardial blood flow or function in a swine model of chronic myocardial ischemia, but may have an important role in increasing expression of antioxidant proteins through PGC1-α signaling.

The Influence of Diabetes Mellitus in Myocardial Ischemic Preconditioning

Ischemic preconditioning (IP) is a powerful mechanism of protection discovered in the heart in which ischemia paradoxically protects the myocardium against other ischemic insults. Many factors such as diseases and medications may influence IP expression. Although diabetes poses higher cardiovascular risk, the physiopathology underlying this condition is uncertain. Moreover, although diabetes is believed to alter intracellular pathways related to myocardial protective mechanisms, it is still controversial whether diabetes may interfere with ischemic preconditioning and whether this might influence clinical outcomes. This review article looks at published reports with animal models and humans that tried to evaluate the possible influence of diabetes in myocardial ischemic preconditioning.

PPARγ and the Innate Immune System Mediate the Resolution of Inflammation

The resolution of inflammation is an active and dynamic process, mediated in large part by the innate immune system. Resolution represents not only an increase in anti-inflammatory actions, but also a paradigm shift in immune cell function to restore homeostasis. PPARγ, a ligand activated transcription factor, has long been studied for its anti-inflammatory actions, but an emerging body of literature is investigating the role of PPARγ and its ligands (including thiazolidinediones, prostaglandins, and oleanolic acids) in all phases of resolution. PPARγ can shift production from pro- to anti-inflammatory mediators by neutrophils, platelets, and macrophages. PPARγ and its ligands further modulate platelet and neutrophil function, decreasing trafficking, promoting neutrophil apoptosis, and preventing platelet-leukocyte interactions. PPARγ alters macrophage trafficking, increases efferocytosis and phagocytosis, and promotes alternative M2 macrophage activation. There are also roles for this receptor in the adaptive immune response, particularly regarding B cells. These effects contribute towards the attenuation of multiple disease states, including COPD, colitis, Alzheimer's disease, and obesity in animal models. Finally, novel specialized proresolving mediators-eicosanoids with critical roles in resolution-may act through PPARγ modulation to promote resolution, providing another exciting area of therapeutic potential for this receptor.

Pharmacogenomics and pharmacogenetics of thiazolidinediones: role in diabetes and cardiovascular risk factors

The most important goal in the treatment of patients with diabetes is to prevent the risk of cardiovascular disease (CVD), the first cause of mortality in these subjects. Thiazolidinediones (TZDs), a class of antidiabetic drugs, act as insulin sensitizers increasing insulin-dependent glucose disposal and reducing hepatic glucose output. TZDs including pioglitazone, rosiglitazone and troglitazone, by activating PPAR-γ have shown pleiotropic effects in reducing vascular risk factors and atherosclerosis. However, troglitazone was removed from the market due to its hepatoxicity, and rosiglitazone and pioglitazone both have particular warnings due to being associated with heart diseases. Specific genetic variations in genes involved in the pathways regulated by TDZs have demonstrated to modify the variability in treatment with these drugs, especially in their side effects. Therefore, pharmacogenomics and pharmacogenetics are an important tool in further understand intersubject variability per se but also to assess the therapeutic potential of such variability in drug individualization and therapeutic optimization.

Roles of obese-insulin resistance and anti-diabetic drugs on the heart with ischemia-reperfusion injury

The incidence of obesity with insulin resistance is increasing worldwide. This condition is also known as a risk factor of coronary artery disease and associated with increased arrhythmias, impaired left ventricular function, and increased infarct size during cardiac ischemia-reperfusion (I/R) injury. The proposed mechanisms are due to impaired glucose utilization and pro-survival signaling molecules, and increased inflammatory cytokines, which have been demonstrated in the I/R hearts in various models of obese-insulin resistance. However, the cardiac effects of diets in the I/R heart are still unsettled since several studies reported that high-caloric diet consumption might protect the heart from I/R injury. Although several therapeutic strategies such as anti-diabetic drugs, natural compounds as well as treadmill exercise have been proposed to exert cardioprotection in the I/R heart in obese-insulin resistant animals, some interventions including ischemic post-conditioning failed to protect the heart from I/R injury. In this comprehensive review, reports from both genetic deletion and dietary-induced obese-insulin resistant animal models regarding the effects of obese-insulin resistance on metabolic parameters, cardiac function, infarct size, and molecular mechanisms under I/R injury are summarized. Moreover, the effects of anti-diabetic drugs and other pharmacological interventions on these parameters in an obese-insulin resistant model under I/R injury are also comprehensively summarized and discussed.

Type 2 diabetes mellitus and myocardial ischemic preconditioning in symptomatic coronary artery disease patients

Background

The influence of diabetes mellitus on myocardial ischemic preconditioning is not clearly defined. Experimental studies are conflicting and human studies are scarce and inconclusive.

Objectives

Identify whether diabetes mellitus intervenes on ischemic preconditioning in symptomatic coronary artery disease patients.

Methods

Symptomatic multivessel coronary artery disease patients with preserved systolic ventricular function and a positive exercise test underwent two sequential exercise tests to demonstrate ischemic preconditioning. Ischemic parameters were compared among patients with and without type 2 diabetes mellitus. Ischemic preconditioning was considered present when the time to 1.0 mm ST deviation and rate pressure-product were greater in the second of 2 exercise tests. Sequential exercise tests were analyzed by 2 independent cardiologists.

Results

Of the 2,140 consecutive coronary artery disease patients screened, 361 met inclusion criteria, and 174 patients (64.2 ± 7.6 years) completed the study protocol. Of these, 86 had the diagnosis of type 2 diabetes. Among diabetic patients, 62 (72 %) manifested an improvement in ischemic parameters consistent with ischemic preconditioning, whereas among nondiabetic patients, 60 (68 %) manifested ischemic preconditioning (p = 0.62). The analysis of patients who demonstrated ischemic preconditioning showed similar improvement in the time to 1.0 mm ST deviation between diabetic and nondiabetic groups (79.4 ± 47.6 vs 65.5 ± 36.4 s, respectively, p = 0.12). Regarding rate pressure-product, the improvement was greater in diabetic compared to nondiabetic patients (3011 ± 2430 vs 2081 ± 2139 bpm x mmHg, respectively, p = 0.01).

Conclusions

In this study, diabetes mellitus was not associated with impairment in ischemic preconditioning in symptomatic coronary artery disease patients. Furthermore, diabetic patients experienced an improvement in this significant mechanism of myocardial protection.

Blood PGC-1α Concentration Predicts Myocardial Salvage and Ventricular Remodeling After ST-segment Elevation Acute Myocardial Infarction

INTRODUCTION AND OBJECTIVES

Peroxisome proliferator-activated receptor gamma coactivator 1α (PGC-1α) is a metabolic regulator induced during ischemia that prevents cardiac remodeling in animal models. The activity of PGC-1α can be estimated in patients with ST-segment elevation acute myocardial infarction. The aim of the present study was to evaluate the value of blood PGC-1α levels in predicting the extent of necrosis and ventricular remodeling after infarction.

METHODS

In this prospective study of 31 patients with a first myocardial infarction in an anterior location and successful reperfusion, PGC-1α expression in peripheral blood on admission and at 72 hours was correlated with myocardial injury, ventricular volume, and systolic function at 6 months. Edema and myocardial necrosis were estimated using cardiac magnetic resonance imaging during the first week. At 6 months, infarct size and ventricular remodeling, defined as an increase > 10% of the left ventricular end-diastolic volume, was evaluated by follow-up magnetic resonance imaging. Myocardial salvage was defined as the difference between the edema and necrosis areas.

RESULTS

Greater myocardial salvage was seen in patients with detectable PGC-1α levels at admission (mean [standard deviation (SD)], 18.3% [5.3%] vs 4.5% [3.9%]; P = .04). Induction of PGC-1α at 72 hours correlated with greater ventricular remodeling (change in left ventricular end-diastolic volume at 6 months, 29.7% [11.2%] vs 1.2% [5.8%]; P = .04).

CONCLUSIONS

Baseline PGC-1α expression and an attenuated systemic response after acute myocardial infarction are associated with greater myocardial salvage and predict less ventricular remodeling.

Current cigarette smoking is an independent risk factor for subacute stent thrombosis in acute myocardial infarction patients

BACKGROUND

Acute myocardial infarction (AMI) is prevalent and has serious consequences including re-infarction and death. Cigarette smoking is a coronary risk factor for AMI, although a "smoker's paradox" for AMI has been reported in Western countries. On the other hand, some researchers have reported that smoking is associated with subacute stent thrombosis (SAST) after AMI. However, the occurrence of this condition is not well documented in Japan. The aim of this study was to clarify how prior smoking status may affect prognosis, including SAST, in Japanese patients with AMI.

METHODS

A total of 266 consecutive patients with AMI were enrolled retrospectively in the study if they had undergone emergency coronary intervention (bare metal stent) within 24h of symptom onset, and had a 5-10 month follow-up examination. The patients were divided into three groups based on their cigarette smoking status (non-smokers, past smokers, and current smokers).

RESULTS

Current smokers were significantly younger than the other two groups, although their levels of low density lipoprotein-cholesterol and triglyceride were significantly higher. White blood cell count and hemoglobin level on admission were also significantly higher in current smokers compared with the other two groups. The incidence of SAST was significantly higher in current smokers than in the other groups, although the occurrence of heart failure after AMI was similar in the three groups. On the other hand, improvement in left ventricular ejection fraction was observed in non-smokers and past smokers, but not in current smokers. Multiple logistic analysis revealed that current smoking was an independent risk factor for SAST (odds ratio 5.4; p<0.05). Current smokers were about five times more likely to have a SAST compared with non-smokers.

CONCLUSIONS

These findings indicate that current cigarette smoking predicts SAST after primary percutaneous coronary intervention for AMI in Japanese patients.

Use of pioglitazone in the treatment of diabetes: effect on cardiovascular risk

Pioglitazone and other thiazolidinediones (TZDs) initially showed great promise as unique receptor-mediated oral therapy for type 2 diabetes, but a host of serious side effects, primarily cardiovascular, have limited their utility. It is crucial at this point to perform a risk- benefit analysis to determine what role pioglitazone should play in our current treatment of type 2 diabetes and where the future of this class of drugs is headed. This review provides a comprehensive overview of the present literature. Clinical data currently available indicate that pioglitazone is an effective and generally well-tolerated treatment option for use in patients with type 2 diabetes. Pioglitazone can still reduce adverse cardiovascular risk.

Activation of Peroxisome Proliferator-Activated Receptor γ Prolongs Islet Allograft Survival

Exposing donor mice to carbon monoxide (CO) protects transplanted islet allografts from immune rejection after transplantation (referred as the “donor” effect). In an attempt to understand the mechanisms of the donor effect of CO, we found that donor treatment with CO upregulates expression of peroxisome proliferatoractivated receptor γ (PPARγ), a transcriptional regulator, in isolated islets. In this study, we evaluated whether PPARγ contributes to the survival and function of transplanted islets and whether PPARγ mediates the protective effect of CO in a major mismatch islet allogeneic transplantation model. BALB/c (H-2d) islets in which PPARγ activity was induced by its agonists, 15-deoxy-Δ12–14-prostaglandin J2 (15d-PGJ2) or troglitazone were transplanted into C57BL/6 (H-2b) recipients that had been rendered diabetic by streptozotocin (STZ). Blood glucose levels of recipients were monitored to determine the function of transplanted islets. Our data indicated that PPARγ activation in islets led to a high percentage of BALB/c islets survived long-term in C57BL/6 recipients. Activation of PPARγ in the donor suppresses expressions of proinflammatory cytokines including tumor necrosis factor-α (TNF-α) and inducible nitric oxide synthase (iNOS) in transplanted islets. Blocking PPARγ activity by its antagonist, GW9662, abrogated the donor effect of CO in vivo and in vitro. Our data demonstrate that PPARγ plays a critical role in the survival and function of transplanted islets after transplantation in the recipient. The protective effects of CO are at least in part mediated by PPARγ.

PGC-1α induction in pulmonary arterial hypertension

Idiopathic Pulmonary arterial hypertension (IPAH) is characterized by the obstructive remodelling of pulmonary arteries, and a progressive elevation in pulmonary arterial pressure (PAP) with subsequent right-sided heart failure and dead. Hypoxia induces the expression of peroxisome proliferator activated receptor γ coactivator-1α (PGC-1α) which regulates oxidative metabolism and mitochondrial biogenesis. We have analysed the expression of PGC-1α, cytochrome C (CYTC), superoxide dismutase (SOD), the total antioxidant status (TAS) and the activity of glutathione peroxidase (GPX) in blood samples of IPAH patients. Expression of PGC-1α was detected in IPAH patients but not in healthy volunteers. The mRNA levels of SOD were lower in IPAH patients compared to controls (3.93 ± 0.89 fold change). TAS and GPX activity were lower too in patients compared to healthy donors, (0.13 ± 0.027 versus 0.484 ± 0.048 mM and 56.034 ± 10.37 versus 165.46 ± 11.38 nmol/min/mL, resp.). We found a negative correlation between expression levels of PGC-1α and age, PAP and PVR, as well as a positive correlation with CI, PaO₂, mRNA levels of CYTC and SOD, TAS and GPX activity. These results taken together are indicative of the possible role of PGC-1α as a potential biomarker of the progression of IPAH.

Effects of diabetes on myocardial infarct size and cardioprotection by preconditioning and postconditioning

In spite of the current optimal therapy, the mortality of patients with ischemic heart disease (IHD) remains high, particularly in cases with diabetes mellitus (DM) as a co-morbidity. Myocardial infarct size is a major determinant of prognosis in IHD patients, and development of a novel strategy to limit infarction is of great clinical importance. Ischemic preconditioning (PC), postconditioning (PostC) and their mimetic agents have been shown to reduce infarct size in experiments using healthy animals. However, a variety of pharmacological agents have failed to demonstrate infarct size limitation in clinical trials. One of the possible reasons for the discrepancy between the results of animal experiments and clinical trials is that co-morbidities, including DM, modified myocardial responses to ischemia/reperfusion and to cardioprotective agents. Here we summarize observations of the effects of DM on myocardial infarct size and ischemic PC and PostC and discuss perspectives for protection of DM hearts.

Uncoupling protein-2 expression and effects on mitochondrial membrane potential and oxidant stress in heart tissue

Myocardial uncoupling protein (UCP)-2 is increased with chronic peroxisome proliferator-activated receptor γ (PPARγ) stimulation, but the effect on membrane potential and superoxide is unclear. Wild-type (WT) and UCP-2 knockout (KO) mice were given a 3-week diet of control (C) or the PPARγ agonist pioglitazone (PIO; 50 μg/g-chow per day). In isolated mitochondria, UCP-2 content by Western blots, membrane potential (ΔΨm) by tetraphenylphosphonium (TPP), and relative superoxide levels by dihydroethidium (DHE) were measured. Oxygen respiration was determined at baseline and after 10 min anoxia-reoxygenation. PIO induced a 2-fold increase in UCP-2 and nuclear-bound PGC1α in WT mice with no UCP-2 expression in KO mice. Mitochondrial ΔΨm from WT mice on C and PIO diets was -166±4 mV and -147±6 mV, respectively (P<0.05). These values were lower than in UCP-2 KO mice on C and PIO (-180±4 mV and -180±4 mV, respectively; P<0.05). Maximal complex III inhibitable superoxide from WT mice on C and PIO diets was 22.5±1.3 and 17.8±1.1 AU, respectively (P<0.05), and were lower than UCP-2 KO on C and PIO (32.9±2.3 and 29.2±1.9 AU, respectively; P<0.05). Postanoxia, the respiratory control index (RCI) in mitochondria from WT mice with and without PIO was 2.5±0.3 and 2.4±0.2, respectively, and exceeded that of UCP-2 KO mice on C and PIO (1.2±0.1 and 1.4±0.1, respectively; P<0.05). In summary, chronic PPARγ stimulation leads to depolarization of the inner membrane and reduced superoxide of isolated heart mitochondria, which was critically dependent on increased expression of UCP-2. Thus, UCP-2 expression affords resistance to brief anoxia-reoxygenation.

Protective effects of pioglitazone on renal ischemia-reperfusion injury in mice

BACKGROUND

Renal ischemia-reperfusion injury (IRI) is a complex pathophysiologic process involving cell apoptosis and oxidant damages that leads to acute renal failure in both native kidneys and renal allografts. Pioglitazone is a novel class of oral antidiabetic agents currently used to treat type 2 diabetes mellitus. Pioglitazone exerts protective effects on acute myocardial ischemia and acute cerebral ischemia. The aim of this study was to investigate the possible beneficial effects of pioglitazone on renal IRI in mice.

METHODS

IRI was induced by bilateral renal ischemia for 45 min followed by reperfusion. Fifty-five healthy male Balb/c mice were randomly assigned to one of the following groups: PBS + IRI, pioglitazone + IRI, PBS + sham IRI, pioglitazone + sham IRI. Kidney function tests, histopathologic examination, renal cell Bcl-2, and Bax expression were determined 24 h after reperfusion. Animals' survival was examined 7 days after operation.

RESULTS

Animals pretreated with pioglitazone had lower plasma levels of blood urea nitrogen and creatinine caused by IRI, lower histopathologic scores, and improved survival rates following IRI. Renal cell apoptosis induced by IRI was abrogated in kidneys of mice pretreated by pioglitazone, with an increase in Bcl-2 expression and a decrease in Bax expression. Furthermore, pioglitazone pretreatment protected against lethal renal IRI.

CONCLUSIONS

Peroxisome proliferator-activated receptor activation by pioglitazone exerts protective effects on renal IRI in mice by abrogating renal cell apoptosis. Thus, pioglitazone could be a novel therapeutic tool in renal IRI.

New insights into the role of peroxisome proliferator-activated receptors in regulating the inflammatory response after tissue injury

Major trauma results in a strong inflammatory response in injured tissue. This posttraumatic hyperinflammation has been implied in the adverse events leading to a breakdown of host defense mechanisms and ultimately to delayed organ failure. Ligands to peroxisome proliferator-activated receptors (PPARs) have recently been identified as potent modulators of inflammation in various acute and chronic inflammatory conditions. The main mechanism of action mediated by ligand binding to PPARs is the inhibition of the nuclear transcription factor NF-κB, leading to downregulation of downstream gene transcription, such as for genes encoding proinflammatory cytokines. Pharmacological PPAR agonists exert strong anti-inflammatory properties in various animal models of tissue injury, including central nervous system trauma, ischemia/reperfusion injury, sepsis, and shock. In addition, PPAR agonists have been shown to induce wound healing process after tissue trauma. The present review was designed to provide an up-to-date overview on the current understanding of the role of PPARs in the pathophysiology of the inflammatory response after major trauma. Therapeutic options for using recombinant PPAR agonists as pharmacological agents in the management of posttraumatic inflammation will be discussed.

Postischemic cardiac recovery in heme oxygenase-1 transgenic ischemic/reperfused mouse myocardium

Heme oxygenase-1 (HO-1) transgenic mice (Tg) were created using a rat HO-1 genomic transgene. Transgene expression was detected by RT-PCR and Western blots in the left ventricle (LV), right ventricle (RV) and septum (S) in mouse hearts, and its function was demonstrated by the elevated HO enzyme activity. Tg and non-transgenic (NTg) mouse hearts were isolated and subjected to ischemia/reperfusion. Significant post-ischemic recovery in coronary flow (CF), aortic flow (AF), aortic pressure (AOP) and first derivative of AOP (AOPdp/dt) were detected in the HO-1 Tg group compared to the NTg values. In HO-1 Tg hearts treated with 50 μmol/kg of tin protoporphyrin IX (SnPPIX), an HO enzyme inhibitor, abolished the post-ischemic cardiac recovery. HO-1 related carbon monoxide (CO) production was detected in NTg, HO-1 Tg and HO-1 Tg + SnPPIX treated groups, and a substantial increase in CO production was observed in the HO-1 Tg hearts subjected to ischemia/reperfusion. Moreover, in ischemia/reperfusion-induced tissue Na⁺ and Ca²⁺ gains were reduced in HO-1 Tg group in comparison with the NTg and HO-1 Tg + SnPPIX treated groups; furthermore K⁺ loss was reduced in the HO-1 Tg group. The infarct size was markedly reduced from its NTg control value of 37 ± 4% to 20 ± 6% (P < 0.05) in the HO-1 Tg group, and was increased to 47 ± 5% (P < 0.05) in the HO-1 knockout (KO) hearts. Parallel to the infarct size reduction, the incidence of total and sustained ventricular fibrillation were also reduced from their NTg control values of 92% and 83% to 25% (P < 0.05) and 8% (P < 0.05) in the HO-1 Tg group, and were increased to 100% and 100% in HO-1 KO^−/− hearts. Immunohistochemical staining of HO-1 was intensified in HO-1 Tg compared to the NTg myocardium. Thus, the HO-1 Tg mouse model suggests a valuable therapeutic approach in the treatment of ischemic myocardium.

Induction of PGC-1α expression can be detected in blood samples of patients with ST-segment elevation acute myocardial infarction

Following acute myocardial infarction (MI), cardiomyocyte survival depends on its mitochondrial oxidative capacity. Cell death is normally followed by activation of the immune system. Peroxisome proliferator activated receptor γ-coactivator 1α (PGC-1α) is a transcriptional coactivator and a master regulator of cardiac oxidative metabolism. PGC-1α is induced by hypoxia and facilitates the recovery of the contractile capacity of the cardiac muscle following an artery ligation procedure. We hypothesized that PGC-1α activity could serve as a good molecular marker of cardiac recovery after a coronary event. The objective of the present study was to monitor the levels of PGC-1α following an ST-segment elevation acute myocardial infarction (STEMI) episode in blood samples of the affected patients. Analysis of blood mononuclear cells from human patients following an STEMI showed that PGC-1α expression was increased and the level of induction correlated with the infarct size. Infarct size was determined by LGE-CMR (late gadolinium enhancement on cardiac magnetic resonance), used to estimate the percentage of necrotic area. Cardiac markers, maximum creatine kinase (CK-MB) and Troponin I (TnI) levels, left ventricular ejection function (LVEF) and regional wall motion abnormalities (RWMA) as determined by echocardiography were also used to monitor cardiac injury. We also found that PGC-1α is present and active in mouse lymphocytes where its expression is induced upon activation and can be detected in the nuclear fraction of blood samples. These results support the notion that induction of PGC-1α expression can be part of the recovery response to an STEMI and could serve as a prognosis factor of cardiac recovery.

The potential effects of anti-diabetic medications on myocardial ischemia-reperfusion injury

Heart disease and stroke account for 65% of the deaths in people with diabetes mellitus (DM). DM and hyperglycemia cause systemic inflammation, endothelial dysfunction, a hypercoagulable state with impaired fibrinolysis and increased platelet degranulation, and reduced coronary collateral blood flow. DM also interferes with myocardial protection afforded by preconditioning and postconditioning. Newer anti-diabetic agents should not only reduce serum glucose and HbA1c levels, but also improve cardiovascular outcomes. The older sulfonylurea agent, glyburide, abolishes the benefits of ischemic and pharmacologic preconditioning, but newer sulfonylurea agents, such as glimepiride, may not interfere with preconditioning. GLP-1 analogs and sitagliptin, an oral dipeptidyl peptidase IV inhibitor, limit myocardial infarct size in animal models by increasing intracellular cAMP levels and activating protein kinase A, whereas metformin protects the heart by activating AMP-activated protein kinase. Both thiazolidinediones (rosiglitazone and pioglitazone) limit infarct size in animal models. The protective effect of pioglitazone is dependent on downstream activation of cytosolic phospholipase A(2) and cyclooxygenase-2 with subsequent increased production of 15-epi-lipoxin A(4), prostacyclin and 15-d-PGJ(2). We conclude that agents used to treat DM have additional actions that have been shown to affect the ability of the heart to protect itself against ischemia-reperfusion injury in preclinical models. However, the effects of these agents in doses used in the clinical setting to minimize ischemia-reperfusion injury and to affect clinical outcomes in patients with DM have yet to be shown. The clinical implications as well as the mechanisms of protection should be further studied.

Pioglitazone attenuates acute cocaine toxicity in rat isolated heart: potential protection by metabolic modulation

BACKGROUND

The authors tested whether cocaine depresses mitochondrial acylcarnitine exchange and if a drug that enhances glucose metabolism could protect against cocaine-induced cardiac dysfunction.

METHODS

Oxygen consumption with and without cocaine was compared in rat cardiac mitochondria using octanoylcarnitine (lipid) or pyruvate (nonlipid) substrates. Isolated hearts from rats with or without a pioglitazone-supplemented diet were exposed to cocaine.

RESULTS

The 0.5 mM cocaine inhibited respiration supported by octanoylcarnitine (82 ± 10.4 and 45.7 ± 4.24 ngatomO min⁻¹ · mg⁻¹ · protein ± SEM, for control and cocaine treatment, respectively; P < 0.02) but not pyruvate-supported respiration (281 ± 12.5 and 267 ± 12.7 ngatomO min⁻¹ · mg⁻¹ · protein ± SEM; P = 0.45). Cocaine altered contractility, lusitropy, coronary resistance, and lactate production in isolated heart. These effects were each blunted in pioglitazone-treated hearts. The pioglitazone diet attenuated the drop in the rate-pressure product (P = 0.002), cocaine-induced diastolic dysfunction (P = 0.04), and myocardial vascular resistance (P = 0.05) compared with that of controls. Lactate production was higher in pretreated hearts (P = 0.008) and in ventricular myocytes cultured with pioglitazone (P = 0.0001).

CONCLUSIONS

Cocaine inhibited octanoylcarnitine-supported mitochondrial respiration. A pioglitazone diet significantly attenuated the effects of cocaine on isolated heart. The authors postulate that inhibition of acylcarnitine exchange could contribute to cocaine-induced cardiac dysfunction and that metabolic modulation warrants additional study.

The emergence of designed multiple ligands for neurodegenerative disorders

The incidence of neurodegenerative diseases has seen a constant increase in the global population, and is likely to be the result of extended life expectancy brought about by better health care. Despite this increase in the incidence of neurodegenerative diseases, there has been a dearth in the introduction of new disease-modifying therapies that are approved to prevent or delay the onset of these diseases, or reverse the degenerative processes in brain. Mounting evidence in the peer-reviewed literature shows that the etiopathology of these diseases is extremely complex and heterogeneous, resulting in significant comorbidity and therefore unlikely to be mitigated by any drug acting on a single pathway or target. A recent trend in drug design and discovery is the rational design or serendipitous discovery of novel drug entities with the ability to address multiple drug targets that form part of the complex pathophysiology of a particular disease state. In this review we discuss the rationale for developing such multifunctional drugs (also called designed multiple ligands or DMLs), and why these drug candidates seem to offer better outcomes in many cases compared to single-targeted drugs in pre-clinical studies for neurodegenerative diseases such as Alzheimer's and Parkinson's disease. Examples are drawn from the literature of drug candidates that have already reached the market, some unsuccessful attempts, and others that are still in the drug development pipeline.

Acute administration of cannabidiol in vivo suppresses ischaemia-induced cardiac arrhythmias and reduces infarct size when given at reperfusion

BACKGROUND AND PURPOSE

Cannabidiol (CBD) is a phytocannabinoid, with anti-apoptotic, anti-inflammatory and antioxidant effects and has recently been shown to exert a tissue sparing effect during chronic myocardial ischaemia and reperfusion (I/R). However, it is not known whether CBD is cardioprotective in the acute phase of I/R injury and the present studies tested this hypothesis.

EXPERIMENTAL APPROACH

Male Sprague-Dawley rats received either vehicle or CBD (10 or 50 microg kg(-1) i.v.) 10 min before 30 min coronary artery occlusion or CBD (50 microg kg(-1) i.v.) 10 min before reperfusion (2 h). The appearance of ventricular arrhythmias during the ischaemic and immediate post-reperfusion periods were recorded and the hearts excised for infarct size determination and assessment of mast cell degranulation. Arterial blood was withdrawn at the end of the reperfusion period to assess platelet aggregation in response to collagen.

KEY RESULTS

CBD reduced both the total number of ischaemia-induced arrhythmias and infarct size when administered prior to ischaemia, an effect that was dose-dependent. Infarct size was also reduced when CBD was given prior to reperfusion. CBD (50 microg kg(-1) i.v.) given prior to ischaemia, but not at reperfusion, attenuated collagen-induced platelet aggregation compared with control, but had no effect on ischaemia-induced mast cell degranulation.

CONCLUSIONS AND IMPLICATIONS

This study demonstrates that CBD is cardioprotective in the acute phase of I/R by both reducing ventricular arrhythmias and attenuating infarct size. The anti-arrhythmic effect, but not the tissue sparing effect, may be mediated through an inhibitory effect on platelet activation.

Are markers of inflammation more strongly associated with risk for fatal than for nonfatal vascular events?

BACKGROUND

Circulating inflammatory markers may more strongly relate to risk of fatal versus nonfatal cardiovascular disease (CVD) events, but robust prospective evidence is lacking. We tested whether interleukin (IL)-6, C-reactive protein (CRP), and fibrinogen more strongly associate with fatal compared to nonfatal myocardial infarction (MI) and stroke.

METHODS AND FINDINGS

In the Prospective Study of Pravastatin in the Elderly at Risk (PROSPER), baseline inflammatory markers in up to 5,680 men and women aged 70-82 y were related to risk for endpoints; nonfatal CVD (i.e., nonfatal MI and nonfatal stroke [n = 672]), fatal CVD (n = 190), death from other CV causes (n = 38), and non-CVD mortality (n = 300), over 3.2-y follow-up. Elevations in baseline IL-6 levels were significantly (p = 0.0009; competing risks model analysis) more strongly associated with fatal CVD (hazard ratio [HR] for 1 log unit increase in IL-6 1.75, 95% confidence interval [CI] 1.44-2.12) than with risk of nonfatal CVD (1.17, 95% CI 1.04-1.31), in analyses adjusted for treatment allocation. The findings were consistent in a fully adjusted model. These broad trends were similar for CRP and, to a lesser extent, for fibrinogen. The results were also similar in placebo and statin recipients (i.e., no interaction). The C-statistic for fatal CVD using traditional risk factors was significantly (+0.017; p<0.0001) improved by inclusion of IL-6 but not so for nonfatal CVD events (p = 0.20).

CONCLUSIONS

In PROSPER, inflammatory markers, in particular IL-6 and CRP, are more strongly associated with risk of fatal vascular events than nonfatal vascular events. These novel observations may have important implications for better understanding aetiology of CVD mortality, and have potential clinical relevance.

Oral glyburide, but not glimepiride, blocks the infarct-size limiting effects of pioglitazone

BACKGROUND

Many patients with type 2 diabetes mellitus receive several oral hypoglycemic agents, including sulfonylurea drugs. Intravenous glyburide (Glyb), a sulfonylurea agent, blocks the protective effects of "ischemic" and pharmacologic preconditioning in various animal models without affecting myocardial infarct size when administered alone. However, there are conflicting results when other sulfonylurea drugs are used. Pioglitazone (PIO) reduces infarct size in the rat. We asked whether oral Glyb and glimepiride (Glim) affect the infarct size-limiting effects of PIO.

METHODS

Sprague-Dawley rats received 3-day oral treatment with: PIO (5 mg/kg/day); PIO + Glyb (10 mg/kg/day); PIO + Glim (4 mg/kg/day) or water alone (experiment 1) or PIO (5 mg/kg/day) with or without 5-hydroxydecanoate (5HD, 10 mg/kg), a specific mitochondrial ATP-sensitive K+ channels inhibitor, administered intravenously 30 min before coronary artery ligation. PIO, Glyb and Glim were administered by oral gavage. Sugar 5% was added to water to prevent hypoglycemia. Rats underwent 30 min coronary artery occlusion and 4 h reperfusion (n = 6 in each group). Ischemic area at risk was assessed by blue dye and infarct size by triphenyl-tetrazolium-chloride.

RESULTS

Body weight and the size of the area at risk were comparable among groups. Infarct size (% of the area at risk) was significantly smaller in the PIO (14.3 +/- 1.1%; p < 0.001) and PIO + Glim (13.2 +/- 0.8%; p < 0.001) groups than in the control group (37.7 +/- 1.2%). Glyb completely blocked the effect of PIO (43.0 +/- 1.7%; p < 0.001). Glim did not affect the protective effect of PIO (p = 0.993). 5HD blocked the protective effect of PIO (infarct size 48.5 +/- 0.8% versus 14.8 +/- 0.6%, respectively; p < 0.0001). In conclusion, the infarct size limiting effects of PIO are dependent on activation of mitochondrial ATP-sensitive K+ channels. Oral Glyb, but not Glim, blocks the infarct size limiting effects of PIO. It is plausible that Glyb affects other pleiotropic effects of PIO and thus may attenuate favorable effects on cardiovascular outcomes. In contrast, Glim does not attenuate the protective effect of PIO.